synthesis matrix in research example

• Synthesis Matrix
• Synthesis Matrix - A Step-by-Step Guide

The Synthesis Matrix - How to begin

A Synthesis Matrix is a great tool to help you organize and synthesize your research. Essentially, it is a table or chart where you identify your main ideas along the first column and your sources along the top row. Once set up, you can enter your notes and quotes from each source that correspond to each of your main ideas.

• Synthesis Matrix tutorial
• Blank Synthesis Matrix (Google Docs) Use this Google Doc to set up your Synthesis Matrix. Make a copy of the document to enter your information.

Synthesis Matrix - Step 1 - Identify Themes

    What are your main ideas or concepts? 

Think about the assigned reading and the ideas that came up when discussing it in class. What are the ideas or themes that you found most interesting? Or that you are most curious about. Enter these themes or concepts into the first column of the Synthesis Matrix, putting each one in a different row.

These are the themes you will use to search for your secondary sources in the Library's databases.

Synthesis Matrix - Step 2 - Research the Themes

  Look for sources related to your themes

After identifying your main themes or concepts, take a moment to think about them. What are they? Are there other words you could use to describe them? What subject areas or disciplines would address those topics? Before you start searching in a Library database, record this information in your Synthesis Matrix under each theme.

If you are unsure of what words to use you could look up your terms in a dictionary or encyclopedia . You can also look online for ideas, Wikipedia is a good source for this part of your research. You will not use Wikipedia as a source but you can use it to identify keywords and related ideas. 

Search for sources

Use the keywords you identified to search for sources in the Library's databases . Try our SNAP! Search or some of the databases listed below.

Here are a few tips to help you out:

• Begin with a simple search 
• Only enter your concepts - don't enter your thesis statement, research question, or complete sentences
• Use the Advanced Search whenever possible
• Be persistent and flexible - if you're not finding what you need switch your keywords with ones that you identified on your Synthesis Matrix
• If you need help, let us know !

Here is an example of a search.

• SNAP! Search Our SNAP! Search makes finding information and credible sources a breeze. Search almost all of our databases at once with this powerful search. Here, you’ll find journals, books, videos, magazines, and more all in one search.
• Opposing Viewpoints in Context This link opens in a new window Informed viewpoints support learners in developing critical-thinking skills and drawing their own conclusions. Covers current social issues through viewpoints, reference articles, infographics, news, images, video, and audio.
• U.S. History in Context This link opens in a new window Find articles, statistics, images, videos, and other types of sources on the most significant people, events and topics in U.S. History.
• JSTOR This link opens in a new window JSTOR is an excellent source for scholarly, peer-reviewed articles, ebooks and images, covering literature, history, the arts, and more.
• CINAHL Complete This link opens in a new window Nursing and allied health literature. Find evidence based research articles/studies, evidence-based care sheets and practice guidelines.

Synthesis Matrix - Step 3 - Fill in the Matrix

    Read the articles and start filling in the Matrix

Review all the articles you found and choose the ones you would like to use. Read these articles thoroughly, take notes, and highlight passages that relate to your themes.

In this example, I have quotes from the Tom Tiede article that represent the experiences of doctors in the first column. In the next columns, I have quotes from the other articles I chose that represent the same idea - the experiences of medical personnel.

I don't have any quotes from the Horwitz book in this row. I didn't find anything in this source that discussed this aspect of my topic and that's fine. The Horwitz book had good information on PTSD and war that I can use. Not all of my sources will cover all of my topic. You will use your sources and the matrix to create a conversation about your topic, bringing in evidence from an array of sources.

The next rows of the matrix for the topics of War and PTSD are below.

The Synthesis Matrix - Examples and Help

• Blank Synthesis Matrix Use this Google Doc to set up your Synthesis Matrix. Make a copy of the document by clicking on "File" and "Make a Copy" to enter your information. You should be logged in to MyNorthShore to access this document.
• Synthesis Matrix Use this Word document to set up your Synthesis Matrix
• Synthesis Matrix for "Black Men and Public Spaces" This is an example of a Synthesis Matrix based on the article, "Black Men and Public Spaces" by Brent Staples.
• Synthesis Matrix for Story of an Hour
• Tom Tiede - Synthesis Matrix
• Synthesis Matrix for Black Men in Public Spaces Google Doc
• Tom Tiede Synthesis Matrix Example Google Doc
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• URL: https://library.northshore.edu/synthesis-matrix

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• Synthesizing Sources | Examples & Synthesis Matrix

Synthesizing Sources | Examples & Synthesis Matrix

Published on July 4, 2022 by Eoghan Ryan . Revised on May 31, 2023.

Synthesizing sources involves combining the work of other scholars to provide new insights. It’s a way of integrating sources that helps situate your work in relation to existing research.

Synthesizing sources involves more than just summarizing . You must emphasize how each source contributes to current debates, highlighting points of (dis)agreement and putting the sources in conversation with each other.

You might synthesize sources in your literature review to give an overview of the field or throughout your research paper when you want to position your work in relation to existing research.

Table of contents

Example of synthesizing sources, how to synthesize sources, synthesis matrix, other interesting articles, frequently asked questions about synthesizing sources.

Let’s take a look at an example where sources are not properly synthesized, and then see what can be done to improve it.

This paragraph provides no context for the information and does not explain the relationships between the sources described. It also doesn’t analyze the sources or consider gaps in existing research.

Research on the barriers to second language acquisition has primarily focused on age-related difficulties. Building on Lenneberg’s (1967) theory of a critical period of language acquisition, Johnson and Newport (1988) tested Lenneberg’s idea in the context of second language acquisition. Their research seemed to confirm that young learners acquire a second language more easily than older learners. Recent research has considered other potential barriers to language acquisition. Schepens, van Hout, and van der Slik (2022) have revealed that the difficulties of learning a second language at an older age are compounded by dissimilarity between a learner’s first language and the language they aim to acquire. Further research needs to be carried out to determine whether the difficulty faced by adult monoglot speakers is also faced by adults who acquired a second language during the “critical period.”

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To synthesize sources, group them around a specific theme or point of contention.

As you read sources, ask:

• What questions or ideas recur? Do the sources focus on the same points, or do they look at the issue from different angles?
• How does each source relate to others? Does it confirm or challenge the findings of past research?
• Where do the sources agree or disagree?

Once you have a clear idea of how each source positions itself, put them in conversation with each other. Analyze and interpret their points of agreement and disagreement. This displays the relationships among sources and creates a sense of coherence.

Consider both implicit and explicit (dis)agreements. Whether one source specifically refutes another or just happens to come to different conclusions without specifically engaging with it, you can mention it in your synthesis either way.

Synthesize your sources using:

• Topic sentences to introduce the relationship between the sources
• Signal phrases to attribute ideas to their authors
• Transition words and phrases to link together different ideas

To more easily determine the similarities and dissimilarities among your sources, you can create a visual representation of their main ideas with a synthesis matrix . This is a tool that you can use when researching and writing your paper, not a part of the final text.

In a synthesis matrix, each column represents one source, and each row represents a common theme or idea among the sources. In the relevant rows, fill in a short summary of how the source treats each theme or topic.

This helps you to clearly see the commonalities or points of divergence among your sources. You can then synthesize these sources in your work by explaining their relationship.

If you want to know more about ChatGPT, AI tools , citation , and plagiarism , make sure to check out some of our other articles with explanations and examples.

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Synthesizing sources means comparing and contrasting the work of other scholars to provide new insights.

It involves analyzing and interpreting the points of agreement and disagreement among sources.

You might synthesize sources in your literature review to give an overview of the field of research or throughout your paper when you want to contribute something new to existing research.

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a thesis, dissertation , or research paper , in order to situate your work in relation to existing knowledge.

Topic sentences help keep your writing focused and guide the reader through your argument.

In an essay or paper , each paragraph should focus on a single idea. By stating the main idea in the topic sentence, you clarify what the paragraph is about for both yourself and your reader.

At college level, you must properly cite your sources in all essays , research papers , and other academic texts (except exams and in-class exercises).

Add a citation whenever you quote , paraphrase , or summarize information or ideas from a source. You should also give full source details in a bibliography or reference list at the end of your text.

The exact format of your citations depends on which citation style you are instructed to use. The most common styles are APA , MLA , and Chicago .

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On This Page:

When you write a literature review or essay, you have to go beyond just summarizing the articles you’ve read – you need to synthesize the literature to show how it all fits together (and how your own research fits in).

Synthesizing simply means combining. Instead of summarizing the main points of each source in turn, you put together the ideas and findings of multiple sources in order to make an overall point.

At the most basic level, this involves looking for similarities and differences between your sources. Your synthesis should show the reader where the sources overlap and where they diverge.

Unsynthesized Example

Franz (2008) studied undergraduate online students. He looked at 17 females and 18 males and found that none of them liked APA. According to Franz, the evidence suggested that all students are reluctant to learn citations style. Perez (2010) also studies undergraduate students. She looked at 42 females and 50 males and found that males were significantly more inclined to use citation software ( p < .05). Findings suggest that females might graduate sooner. Goldstein (2012) looked at British undergraduates. Among a sample of 50, all females, all confident in their abilities to cite and were eager to write their dissertations.

Synthesized Example

Studies of undergraduate students reveal conflicting conclusions regarding relationships between advanced scholarly study and citation efficacy. Although Franz (2008) found that no participants enjoyed learning citation style, Goldstein (2012) determined in a larger study that all participants watched felt comfortable citing sources, suggesting that variables among participant and control group populations must be examined more closely. Although Perez (2010) expanded on Franz’s original study with a larger, more diverse sample…

Step 1: Organize your sources

After collecting the relevant literature, you’ve got a lot of information to work through, and no clear idea of how it all fits together.

Before you can start writing, you need to organize your notes in a way that allows you to see the relationships between sources.

One way to begin synthesizing the literature is to put your notes into a table. Depending on your topic and the type of literature you’re dealing with, there are a couple of different ways you can organize this.

Summary table

A summary table collates the key points of each source under consistent headings. This is a good approach if your sources tend to have a similar structure – for instance, if they’re all empirical papers.

Each row in the table lists one source, and each column identifies a specific part of the source. You can decide which headings to include based on what’s most relevant to the literature you’re dealing with.

For example, you might include columns for things like aims, methods, variables, population, sample size, and conclusion.

For each study, you briefly summarize each of these aspects. You can also include columns for your own evaluation and analysis.

The summary table gives you a quick overview of the key points of each source. This allows you to group sources by relevant similarities, as well as noticing important differences or contradictions in their findings.

Synthesis matrix

A synthesis matrix is useful when your sources are more varied in their purpose and structure – for example, when you’re dealing with books and essays making various different arguments about a topic.

Each column in the table lists one source. Each row is labeled with a specific concept, topic or theme that recurs across all or most of the sources.

Then, for each source, you summarize the main points or arguments related to the theme.

The purposes of the table is to identify the common points that connect the sources, as well as identifying points where they diverge or disagree.

Step 2: Outline your structure

Now you should have a clear overview of the main connections and differences between the sources you’ve read. Next, you need to decide how you’ll group them together and the order in which you’ll discuss them.

For shorter papers, your outline can just identify the focus of each paragraph; for longer papers, you might want to divide it into sections with headings.

There are a few different approaches you can take to help you structure your synthesis.

If your sources cover a broad time period, and you found patterns in how researchers approached the topic over time, you can organize your discussion chronologically .

That doesn’t mean you just summarize each paper in chronological order; instead, you should group articles into time periods and identify what they have in common, as well as signalling important turning points or developments in the literature.

If the literature covers various different topics, you can organize it thematically .

That means that each paragraph or section focuses on a specific theme and explains how that theme is approached in the literature.

Source Used with Permission: The Chicago School

If you’re drawing on literature from various different fields or they use a wide variety of research methods, you can organize your sources methodologically .

That means grouping together studies based on the type of research they did and discussing the findings that emerged from each method.

If your topic involves a debate between different schools of thought, you can organize it theoretically .

That means comparing the different theories that have been developed and grouping together papers based on the position or perspective they take on the topic, as well as evaluating which arguments are most convincing.

Step 3: Write paragraphs with topic sentences

What sets a synthesis apart from a summary is that it combines various sources. The easiest way to think about this is that each paragraph should discuss a few different sources, and you should be able to condense the overall point of the paragraph into one sentence.

This is called a topic sentence , and it usually appears at the start of the paragraph. The topic sentence signals what the whole paragraph is about; every sentence in the paragraph should be clearly related to it.

A topic sentence can be a simple summary of the paragraph’s content:

“Early research on [x] focused heavily on [y].”

For an effective synthesis, you can use topic sentences to link back to the previous paragraph, highlighting a point of debate or critique:

“Several scholars have pointed out the flaws in this approach.” “While recent research has attempted to address the problem, many of these studies have methodological flaws that limit their validity.”

By using topic sentences, you can ensure that your paragraphs are coherent and clearly show the connections between the articles you are discussing.

As you write your paragraphs, avoid quoting directly from sources: use your own words to explain the commonalities and differences that you found in the literature.

Don’t try to cover every single point from every single source – the key to synthesizing is to extract the most important and relevant information and combine it to give your reader an overall picture of the state of knowledge on your topic.

Step 4: Revise, edit and proofread

Like any other piece of academic writing, synthesizing literature doesn’t happen all in one go – it involves redrafting, revising, editing and proofreading your work.

Checklist for Synthesis

•   Do I introduce the paragraph with a clear, focused topic sentence?
•   Do I discuss more than one source in the paragraph?
•   Do I mention only the most relevant findings, rather than describing every part of the studies?
•   Do I discuss the similarities or differences between the sources, rather than summarizing each source in turn?
•   Do I put the findings or arguments of the sources in my own words?
•   Is the paragraph organized around a single idea?
•   Is the paragraph directly relevant to my research question or topic?
•   Is there a logical transition from this paragraph to the next one?

Further Information

How to Synthesise: a Step-by-Step Approach

Help…I”ve Been Asked to Synthesize!

Learn how to Synthesise (combine information from sources)

How to write a Psychology Essay

The Sheridan Libraries

• Write a Literature Review
• Sheridan Libraries
• Evaluate This link opens in a new window

Get Organized

• Lit Review Prep Use this template to help you evaluate your sources, create article summaries for an annotated bibliography, and a synthesis matrix for your lit review outline.

Synthesize your Information

Synthesize: combine separate elements to form a whole.

Synthesis Matrix

A synthesis matrix helps you record the main points of each source and document how sources relate to each other.

After summarizing and evaluating your sources, arrange them in a matrix or use a citation manager to help you see how they relate to each other and apply to each of your themes or variables.  

By arranging your sources by theme or variable, you can see how your sources relate to each other, and can start thinking about how you weave them together to create a narrative.

• Step-by-Step Approach
• Example Matrix from NSCU
• Matrix Template
• << Previous: Summarize
• Next: Integrate >>
• Last Updated: Jul 30, 2024 1:42 PM
• URL: https://guides.library.jhu.edu/lit-review

ED595 - Introduction to Research: Synthesis Matrix

• Introduction to Research Skills
• Database Search Tips
• Synthesis Matrix
• Managing Sources with Zotero
• Writing an Annotated Bibliography

What is a Synthesis Matrix?

A synthesis matrix is a tool that a researcher can use to help them organize and synthesize multiple sources of information. A synthesis matrix is often used when writing literature reviews because this kind of table can help you see how the sources relate and "communicate" with one another.

How Do You Make a Synthesis Matrix? 

The general idea behind a synthesis matrix is to create a table to organize your sources by theme/concept. This can take many shapes and be customized in whatever manner is most appropriate for your research project. A basic example (adapted from NC State University Writing and Speaking ) is provided below to illustrate what a synthesis matrix may look like.

Across the top row of the table, the author of each source is listed. Listed down the first column are the main concepts (or themes) the researcher will address in their project. If the source addresses a concept, notes and page numbers are added to the appropriate box in the matrix. However, remember that a source does not have to address every concept to be useful in your research. If a source does not address a topic, you would leave a gap in the matrix. This process allows you to see where your sources are similar or different and visualize the discussion around a topic.

Remember:   You create a synthesis matrix while you are conducting research , not afterward. 

Synthesis Matrix Template

• Synthesis Matrix Template This editable template can be used to create your synthesis matrix.

Synthesis Matrix Tutorial

Credit: Andrew Davis | Creative Commons Attribution License 

Online Resources

• Writing A Literature Review and Using a Synthesis Matrix This PDF document, created by North Carolina State University Writing and Speaking Tutorial Service Tutors, addresses what synthesis is and provides an example of a synthesis matrix.
• << Previous: Synthesizing Research Sources
• Next: Managing Sources with Zotero >>
• Last Updated: Aug 21, 2024 12:57 PM
• URL: https://centralmethodist.libguides.com/ed595

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Literature Review: A Self-Guided Tutorial for NUR 288

• Literature Reviews: A Recap
• Peer-Review
• Reading the Literature
• Developing Research Questions
• 2. Review discipline styles
• Super Searching
• Finding the Full Text
• Citation Searching
• Evaluating online information
• When to stop searching
• How to cite your sources following APA
• In-Text Citations
• Keeping track of your references
• Annotating Articles Tip
• 5. Critically analyze and evaluate
• How to review the literature

Using a synthesis matrix

• 7. Write literature review

Synthesize : combine separate elements to form a whole.

Why use a synthesis matrix? 

• A synthesis matrix helps you record the main points of each source and document how sources relate to each other.
• After summarizing and evaluating your sources, arrange them in a matrix or use a citation manager to help you see how they relate to each other and apply to each of your themes or variables.  
• By arranging your sources by theme or variable, you can see how your sources relate to each other, and can start thinking about how you weave them together to create a narrative.

A synthesis matrix visually represents your research by organizing your sources by themes:

Add each article citation to the Source column and begin to identify the theme(s) from the article. 

Use the Excel template below to help you evaluate your sources, create article summaries for an annotated bibliography, and a synthesis matrix for your lit review outline. From John Hopkins Sheridan Libraries.  

NOTE : There are several tabs at the bottom of the Excel spreadsheet to help guide you with this method.

• Literature Review Prep - with Synthesis Matrix
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• Next: 7. Write literature review >>
• Last Updated: Sep 20, 2024 9:37 AM
• URL: https://libguides.wccnet.edu/literature_review

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• Research Guides

How to Write a Literature Review

• 6. Synthesize
• Literature Reviews: A Recap
• Reading Journal Articles
• Does it Describe a Literature Review?
• 1. Identify the Question
• 2. Review Discipline Styles
• Searching Article Databases
• Finding Full-Text of an Article
• Citation Chaining
• When to Stop Searching
• 4. Manage Your References
• 5. Critically Analyze and Evaluate

Synthesis Visualization

Synthesis matrix example.

• 7. Write a Literature Review

• Synthesis Worksheet

About Synthesis

Approaches to Synthesis

You can sort the literature in various ways, for example:

How to Begin?

Read your sources carefully and find the main idea(s) of each source

Look for similarities in your sources – which sources are talking about the same main ideas? (for example, sources that discuss the historical background on your topic)

Use the worksheet (above) or synthesis matrix (below) to get organized

This work can be messy. Don't worry if you have to go through a few iterations of the worksheet or matrix as you work on your lit review!

Four Examples of Student Writing

In the four examples below, only ONE shows a good example of synthesis: the fourth column, or  Student D . For a web accessible version, click the link below the image.

Long description of "Four Examples of Student Writing" for web accessibility

• Download a copy of the "Four Examples of Student Writing" chart

Click on the example to view the pdf.

From Jennifer Lim

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• Next: 7. Write a Literature Review >>
• Last Updated: Aug 12, 2024 11:48 AM
• URL: https://researchguides.uoregon.edu/litreview

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Analysis and Synthesis

Using a synthesis matrix.

We have included a sample Synthesis Matrix below. You can create one using this image as a guideline:

Download a synthesis matrix template (.xlsx format)

As you can see, you can list trends (ideas that are repeated or shared) and gaps (ideas about which sources seem to differ or conflict, or which are simply not addressed) in the left hand column. Then, you can list paraphrases or direct quotations from the sources in the following columns; this will enable you to “see” where these sources overlap or differ. (Be careful to use quotation marks correctly in your matrix; if you are directly quoting from the source, leave yourself those clues that the material should be paraphrased later when you incorporate the ideas into your Literature Review.)

It is important to remember that a trend does not exist unless two or more sources support it. Also, a gap cannot exist unless two or more sources disagree, report conflicting data, or fail to address a particular idea. For this reason, each body paragraph needs to represent one trend or gap in your research, and contain evidence from two or more sources to demonstrate that this trend or gap exists.

research toolbox

For this research toolbox, use a synthesis matrix (like the one included on this page) to map out your sources. You will want to list at least four to six academic sources from your Annotated Bibliography, and locate at least two to three trends and/or gaps within the sources. Do note that each trend and/or gap should be supported by evidence from two or more sources. In other words, you do not need to include evidence from every source to support each trend and/or gap.

Next, include at least one paraphrase or direct quotation from multiple sources to support your trend and/or gaps. This activity should help you properly analyze and synthesize your sources for the Literature Review.

• Complete a synthesis matrix using a spreadsheet.
• Include at least four to six academic sources from your Annotated Bibliography
• Locate and identify at least two to three trends and/or gaps in your sources
• Include at least one paraphrase or direct quotation from each source
• From Analysis to Synthesis. Authored by : Keith Boran and Sheena Boran. Provided by : University of Mississippi. Project : WRIT 250 Committee OER Project. License : CC BY-SA: Attribution-ShareAlike

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Chapter 7: Synthesizing Sources

Learning objectives.

At the conclusion of this chapter, you will be able to:

• synthesize key sources connecting them with the research question and topic area.

7.1 Overview of synthesizing

7.1.1 putting the pieces together.

Combining separate elements into a whole is the dictionary definition of synthesis.  It is a way to make connections among and between numerous and varied source materials.  A literature review is not an annotated bibliography, organized by title, author, or date of publication.  Rather, it is grouped by topic to create a whole view of the literature relevant to your research question.

Your synthesis must demonstrate a critical analysis of the papers you collected as well as your ability to integrate the results of your analysis into your own literature review.  Each paper collected should be critically evaluated and weighed for “adequacy, appropriateness, and thoroughness” ( Garrard, 2017 ) before inclusion in your own review.  Papers that do not meet this criteria likely should not be included in your literature review.

Begin the synthesis process by creating a grid, table, or an outline where you will summarize, using common themes you have identified and the sources you have found. The summary grid or outline will help you compare and contrast the themes so you can see the relationships among them as well as areas where you may need to do more searching. Whichever method you choose, this type of organization will help you to both understand the information you find and structure the writing of your review.  Remember, although “the means of summarizing can vary, the key at this point is to make sure you understand what you’ve found and how it relates to your topic and research question” ( Bennard et al., 2014 ).

As you read through the material you gather, look for common themes as they may provide the structure for your literature review.  And, remember, research is an iterative process: it is not unusual to go back and search information sources for more material.

At one extreme, if you are claiming, ‘There are no prior publications on this topic,’ it is more likely that you have not found them yet and may need to broaden your search.  At another extreme, writing a complete literature review can be difficult with a well-trod topic.  Do not cite it all; instead cite what is most relevant.  If that still leaves too much to include, be sure to reference influential sources…as well as high-quality work that clearly connects to the points you make. ( Klingner, Scanlon, & Pressley, 2005 ).

7.2 Creating a summary table

Literature reviews can be organized sequentially or by topic, theme, method, results, theory, or argument.  It’s important to develop categories that are meaningful and relevant to your research question.  Take detailed notes on each article and use a consistent format for capturing all the information each article provides.  These notes and the summary table can be done manually, using note cards.  However, given the amount of information you will be recording, an electronic file created in a word processing or spreadsheet is more manageable. Examples of fields you may want to capture in your notes include:

• Authors’ names
• Article title
• Publication year
• Main purpose of the article
• Methodology or research design
• Participants
• Measurement
• Conclusions

  Other fields that will be useful when you begin to synthesize the sum total of your research:

• Specific details of the article or research that are especially relevant to your study
• Key terms and definitions
• Strengths or weaknesses in research design
• Relationships to other studies
• Possible gaps in the research or literature (for example, many research articles conclude with the statement “more research is needed in this area”)
• Finally, note how closely each article relates to your topic.  You may want to rank these as high, medium, or low relevance.  For papers that you decide not to include, you may want to note your reasoning for exclusion, such as ‘small sample size’, ‘local case study,’ or ‘lacks evidence to support assertion.’

This short video demonstrates how a nursing researcher might create a summary table.

7.2.1 Creating a Summary Table

  Summary tables can be organized by author or by theme, for example:

For a summary table template, see http://blogs.monm.edu/writingatmc/files/2013/04/Synthesis-Matrix-Template.pdf

7.3 Creating a summary outline

An alternate way to organize your articles for synthesis it to create an outline. After you have collected the articles you intend to use (and have put aside the ones you won’t be using), it’s time to identify the conclusions that can be drawn from the articles as a group.

  Based on your review of the collected articles, group them by categories.  You may wish to further organize them by topic and then chronologically or alphabetically by author.  For each topic or subtopic you identified during your critical analysis of the paper, determine what those papers have in common.  Likewise, determine which ones in the group differ.  If there are contradictory findings, you may be able to identify methodological or theoretical differences that could account for the contradiction (for example, differences in population demographics).  Determine what general conclusions you can report about the topic or subtopic as the entire group of studies relate to it.  For example, you may have several studies that agree on outcome, such as ‘hands on learning is best for science in elementary school’ or that ‘continuing education is the best method for updating nursing certification.’ In that case, you may want to organize by methodology used in the studies rather than by outcome.

Organize your outline in a logical order and prepare to write the first draft of your literature review.  That order might be from broad to more specific, or it may be sequential or chronological, going from foundational literature to more current.  Remember, “an effective literature review need not denote the entire historical record, but rather establish the raison d’etre for the current study and in doing so cite that literature distinctly pertinent for theoretical, methodological, or empirical reasons.” ( Milardo, 2015, p. 22 ).

As you organize the summarized documents into a logical structure, you are also appraising and synthesizing complex information from multiple sources.  Your literature review is the result of your research that synthesizes new and old information and creates new knowledge.

7.4 Additional resources:

Literature Reviews: Using a Matrix to Organize Research / Saint Mary’s University of Minnesota

Literature Review: Synthesizing Multiple Sources / Indiana University

Writing a Literature Review and Using a Synthesis Matrix / Florida International University

 Sample Literature Reviews Grid / Complied by Lindsay Roberts

Select three or four articles on a single topic of interest to you. Then enter them into an outline or table in the categories you feel are important to a research question. Try both the grid and the outline if you can to see which suits you better. The attached grid contains the fields suggested in the video .

Literature Review Table  

Test Yourself

• Select two articles from your own summary table or outline and write a paragraph explaining how and why the sources relate to each other and your review of the literature.
• In your literature review, under what topic or subtopic will you place the paragraph you just wrote?

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Literature Reviews for Education and Nursing Graduate Students Copyright © by Linda Frederiksen is licensed under a Creative Commons Attribution 4.0 International License , except where otherwise noted.

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Learning about Synthesis Analysis

What D oes Synthesis and Analysis Mean?

Synthesis: the combination of ideas to

• show commonalities or patterns

Analysis: a detailed examination

• of elements, ideas, or the structure of something
• can be a basis for discussion or interpretation

Synthesis and Analysis: combine and examine ideas to

• show how commonalities, patterns, and elements fit together
• form a unified point for a theory, discussion, or interpretation
• develop an informed evaluation of the idea by presenting several different viewpoints and/or ideas

Key Resource: Synthesis Matrix

Synthesis Matrix

A synthesis matrix is an excellent tool to use to organize sources by theme and to be able to see the similarities and differences as well as any important patterns in the methodology and recommendations for future research. Using a synthesis matrix can assist you not only in synthesizing and analyzing,  but it can also aid you in finding a researchable problem and gaps in methodology and/or research.

Use the Synthesis Matrix Template attached below to organize your research by theme and look for patterns in your sources .Use the companion handout, "Types of Articles" to aid you in identifying the different article types for the sources you are using in your matrix. If you have any questions about how to use the synthesis matrix, sign up for the synthesis analysis group session to practice using them with Dr. Sara Northern!

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Building a Summary Table or Synthesis Matrix

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What a Summary Table or Synthesis Matrix looks like

Use the "Literature Review Matrix Template" as a guideline to help you sort through your thoughts, note important points and think through the similarities and differences: 

You are organizing the review by ideas and not by sources .  The literature review is not just a summary of the already published works.  Your synthesis should show how various articles are linked. 

A summary table is also called a synthesis matrix.  The table helps you organize and compare information for your systematic review, scholarly report, dissertation or thesis

Synthesis Matrix.

A summary table is also called a synthesis matrix . A summary table helps you record the main points of each source and document how sources relate to each other. After summarizing and evaluating your sources, arrange them in a matrix to help you see how they relate to each other, and apply to each of your themes or variables.

Faculty who typically guide students find it challenging to help students learn how to synthesize material (Blondy, Blakesless, Scheffer, Rubenfeld, Cronin, & Luster-Turner, 2016; Kearney, 2015) .  Writers  can easily summarize material but seem to struggle to adequately synthesize knowledge about their topic and express that in their writing. So, whether you are writing a student papers, dissertations, or scholarly report it is necessary to learn a few tips and tricks to organize your ideas.

Building a summary table and developing solid synthesis skills is important for nurses, nurse practitioners, and allied health researchers.  Quality evidence-based practice initiatives and nursing care and medicine are based on understanding and evaluating the resources and research available, identifying gaps, and building a strong foundation for future work.

Good synthesis is about putting the data gathered, references read, and literature analyzed together in a new way that shows connections and relationships. ( Shellenbarger, 2016 ). The Merriam-Webster dictionary defines synthesis as something that is made by combining different things or the composition or combination of parts or elements so as to form a whole (Synthesis, n.d.).  

In other words, building a summary table or synthesis matrix  involves taking information from a variety of sources, evaluating that information and forming new ideas or insights in an original way.  This can be a new and potentially challenging experience for students and researchers who are used to just repeating what is already in the literature.

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What is Synthesis?

How to synthesize, what is a synthesis matrix, example synthesis matrix.

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Synthesis is a core component of a strong research paper. It refers to the process of combining ideas and arguments from multiple sources and analyzing them to provide new insights.  This process involves more than simply summarizing a source or adding direct quotes from sources to your paper.  When done well, synthesis organizes information in such a way that helps the reader make sense of the sources and better understand how they overlap.

Effective synthesis requires you to emphasize how each source contributes to the known research about a given topic, highlighting points of agreement and disagreement.  In essence, you are putting sources in conversation with each other and thinking about the answers to these questions:

• Do any sources agree/disagree with other sources?
• Does one source extend (add to) the research of another source?
• Does any source raise new questions or ideas about the topic? 
• How does each source support or contradict my thesis?
• Read your sources carefully, skimming for big ideas and points that support your thesis.
• Reread each source and take detailed notes using a synthesis matrix (more on that below).
• Using the topics identified in your synthesis matrix, write complete sentences stating each of the supporting points you want to use to support your thesis. These will become topic sentences for your paragraphs
• Use specific facts, quotes, and paraphrases from your sources in order to expand and develop your paragraphs.
• Add your voice to the scholarly conversation by including an analysis of the topic at the end of each paragraph.

A synthesis matrix is a table that you can use when researching and writing your paper.  It is not part of the final text.  Synthesis matrices are used to show where there is overlap and differences between your sources.

In a synthesis matrix, each column represents one source, and each row represents a common theme or idea among the sources.  As you're reading a source, jot down ideas that support your thesis in the relevant rows.  Not every source will touch on every theme, so you will have some blank spot in your matrix.  That's OK!

When completed, a synthesis matrix will help you to clearly see the commonalities or points of divergence among your sources.  You can then use the information for each theme to explain a relationship between your sources and construct paragraphs.

Here is the basic structure for creating a synthesis matrix.  This structure can be expanded to accommodate any number of sources or common themes.

Topic : Can video games be considered art?

Additional Synthesis Matrix Examples:

• Anxiety in Graduate Students
• Dog Behavior
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Common Assignments: Literature Review Matrix

Literature review matrix.

As you read and evaluate your literature there are several different ways to organize your research. Courtesy of Dr. Gary Burkholder in the School of Psychology, these sample matrices are one option to help organize your articles. These documents allow you to compile details about your sources, such as the foundational theories, methodologies, and conclusions; begin to note similarities among the authors; and retrieve citation information for easy insertion within a document.

You can review the sample matrixes to see a completed form or download the blank matrix for your own use.

• Literature Review Matrix 1 This PDF file provides a sample literature review matrix.
• Literature Review Matrix 2 This PDF file provides a sample literature review matrix.
• Literature Review Matrix Template (Word)
• Literature Review Matrix Template (Excel)

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How I Made My Life Easier By Using A Synthesis Matrix

By Abbie, a Writing Center Coach

I’ve always enjoyed writing and thought myself quite good at it before getting to college. Of course, a lot of the writing you do then is for English class, reading one book and writing about it; you still have to work at figuring out your focus and how to support it, but the “research” aspect is limited. Stepping outside of a traditional English paper is another step, one that I was hit with when I first started college and had to write for other subjects.

To me, a research paper is one of the most daunting assignments I’ve ever received. Suddenly, I needed to look at more than just a single work of fiction. There are often semester-long steps to picking a question, finding sources, evaluating them, and synthesizing them. It’s easy for me to want to push those tasks until later or cherrypick evidence to support an easier answer. But that doesn’t result in the best research paper possible, and I might not even learn much along the way.

One of my favorite strategies for writing research papers is creating a synthesis matrix, which is essentially creating a research worksheet to fill out. They can look different depending on what I’m working on, but their main purpose is for taking research notes and seeing relationships across large numbers of sources and information categories. I’ve used both Microsoft Excel and Google Sheets to create synthesis matrices in the past.

The first time I ever created a synthesis matrix was for ENGL 402 , which I took to apply to work at the Writing Center. The assignment was a literature review where I had to pick any topic related to writing and explore what the literature said about it. I had no idea where to start, but this method helped me land on and deeply explore my topic.

While working on my literature review, I divided my synthesis matrix process into five steps: topic selection, source selection, matrix setup, reading and categorization, and usage of the matrix itself.

Step 1: Topic Selection

First, I decided to freewrite some topic ideas, a strategy I got from the Writing Center’s Brainstorming handout . I set a timer for 5 minutes and listed out every topic related to writing that came to mind. I came up with multiple ideas, but the one I chose was about writing motivation. As someone who has always loved writing, I wanted to explore people writing solely for a grade rather than because of genuine passion and interest in the topic. This helped me come up with keywords (writing, grades, motivation, rubrics) that I could then use in my initial research step when searching for sources.

Step 2: Source Selection

Once I had my keywords, I turned to the UNC Libraries website. I always begin with the “E-Research by Discipline” tool, which allows me to select databases of academic articles that are more likely to be related to my topic. For my initial ideas about writing motivation, I went to a database under the “English” discipline. The “Articles+” on the library site has more search filters under “Advanced Search” that I used to get more specific search results.

Through this research process, I landed on a topic: utility-value in writing . Using this topic to form my new keywords, I found multiple sources related to writing, learning, real world applications of course material, and connections between class content. One issue I ran into was that a lot of sources were about multilingual learners, while I just wanted to focus on general college writing (rather than language learning). Thankfully, I was able to use Boolean search logic to filter out language learning sources.

Step 3: Setting up the Matrices

Before looking through the sources I had gathered, I set up a Microsoft Excel sheet for note taking. This would become my synthesis matrix — all of my sources, along with the author, date, and citation, were listed in the left columns. The rest of the columns were broken into categories of information I thought I might use. The first few columns make it easy for me to find important information needed for parenthetical citations and references, as well as to remember the specific focus of a source. I was mostly using empirical studies, though other source types could have different categories, like a synopsis of a book from which a chapter had been pulled. I ended up with two separate sections of my sheet: one for sources related to utility value writing and another for sources related to Writing-To-Learn ( a learning pedagogy with some similarities).

With my matrix set up, I felt much better about my ability to take good notes on my sources rather than trying to tackle them with a blank document.

Step 4: Reading & Note-taking

Once I started reading, using the matrix felt like I had given myself a checklist of sources to get through along with boxes to fill in for each one. Because of this, I was able to get through my sources much more quickly, feeling a sense of accomplishment as I could see how much I had done. I also was already beginning to organize my notes because of the matrix setup. It initially seemed like a much more time-consuming method, but the organizational element was a huge time-saver when it came to actually putting my paper together. I was much more familiar with my evidence by the time it came to outline, so I didn’t have to dig through my notes as much to figure out what to say or where to say it.

As I read through my sources, I took notes in the matrix by copy and pasting quotes from my sources as well as paraphrasing information. I always made sure to add page numbers so I could easily go back and find where I got my information. Along the way, my categories molded to what I was reading. It was important for me to not only search for what I was originally looking for but reflect what was actually being discussed in my sources.

Step 5: Using the Matrix 

Once I had filled in the entire Excel sheet, I could see which sources overlapped where, compare and contrast what they said, and see areas of agreement and disagreement. My next step was to use this information to organize my paper. I decided to color-code the boxes based on where I thought they might fit; while this ended up largely following the column categories, there were a few that fit somewhere else, and the visual strategy helped remind me to include everything where I wanted it.

The last step was writing the actual paper. I found it to be a much easier and faster process with my synthesis matrix having already organized everything, and was able to sit down and write an entire 10 pages over just a couple days. I ended up satisfied with what I had written, and I know it would have been much harder without the synthesis matrix.

Reflections

If I were to go back and work on this matrix again, I might work on paraphrasing more than just pasting direct quotes in. While it was easier to just paste the original wording, I ended up having to work a lot on paraphrasing and evaluating my sources’ information when I was actually writing the paper. I think using more paraphrasing relative to quoting when I was filling in the matrix would have gotten me to try to better understand what I was reading when I was reading it, and probably would have saved some space since I ended up with a lot of blocks of long quotes. I also had a column for figures and diagrams that I didn’t fill in much and didn’t end up using what I had filled in at all, so I might reevaluate what forms of information I’m predominantly paying attention to in sources and whether other forms might add something of value to my paper, perhaps by listing out information I get without even looking at the main text.

I highly recommend trying this strategy out on your next research paper or literature review! I learned it from Dr. Gigi Taylor in ENGL 402, a class where you can try using this strategy and learn more about yourself and your writing style. I am very grateful to have found a method that works so well with my approach to writing, and I hope that it helps you as well.

This blog showcases the perspectives of UNC Chapel Hill community members learning and writing online. If you want to talk to a Writing and Learning Center coach about implementing strategies described in the blog, make an appointment with a writing coach , a peer tutor , or an academic coach today. Have an idea for a blog post about how you are learning and writing remotely? Contact us here .

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Synthesis: Home

Engaging in synthesis.

Synthesis requires you to make sense of all the relevant ideas in your sources and blend them together with your own thoughts and ideas. Watch this video to learn how to engage in synthesis in order to take research from multiple sources along with your own arguments and turn it into a research paper.

Synthesizing Your Research

Understanding your research.

1. Read through your sources carefully.

2. Identify common themes or sub-topics that keep appearing in the articles you’re reading.

The Research Matrix

• Blank Research Matrix Fill out this blank matrix.
• Blank Synthesis Matrix template (Google Docs)

The research matrix is a helpful tool you can use to synthesize your research along with your own voice. The blank research matrix above can help you organize your paper by main idea, identify connections between your sources, and add your own analysis.

Filling Out Your Matrix

1. Write your topic or research question above the matrix.

2. Write your main ideas for your paper on the left side of the matrix. Helpful Tip: Choose your main ideas AFTER you have read your sources!

3. Write the title, author, or citation of each source in the top row of the matrix.

4. Fill in the matrix boxes with a paraphrase or direct quote that represents how the source discussed that main idea. You do not need every source to address every main idea!

5. Don't forget to nclude your own analysis of the main idea and the sources in the last column on the matrix.

Identify Gaps in Your Research

1. There’s a high likelihood that you will have empty spaces on your research matrix and that’s okay! Small gaps show that there is room for your own voice to join the conversation.

2. Large gaps in your matrix are often a sign that you need to do more research on that main idea. As a rule of thumb you should have at least two sources for each main idea in order to create a meaningful dialogue. 

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When you look for areas where your sources agree or disagree and try to draw broader conclusions about your topic based on what your sources say, you are engaging in synthesis. Writing a research paper usually requires synthesizing the available sources in order to provide new insight or a different perspective into your particular topic (as opposed to simply restating what each individual source says about your research topic).

Note that synthesizing is not the same as summarizing.  

• A summary restates the information in one or more sources without providing new insight or reaching new conclusions.
• A synthesis draws on multiple sources to reach a broader conclusion.

There are two types of syntheses: explanatory syntheses and argumentative syntheses . Explanatory syntheses seek to bring sources together to explain a perspective and the reasoning behind it. Argumentative syntheses seek to bring sources together to make an argument. Both types of synthesis involve looking for relationships between sources and drawing conclusions.

In order to successfully synthesize your sources, you might begin by grouping your sources by topic and looking for connections. For example, if you were researching the pros and cons of encouraging healthy eating in children, you would want to separate your sources to find which ones agree with each other and which ones disagree.

After you have a good idea of what your sources are saying, you want to construct your body paragraphs in a way that acknowledges different sources and highlights where you can draw new conclusions.

As you continue synthesizing, here are a few points to remember:

• Don’t force a relationship between sources if there isn’t one. Not all of your sources have to complement one another.
• Do your best to highlight the relationships between sources in very clear ways.
• Don’t ignore any outliers in your research. It’s important to take note of every perspective (even those that disagree with your broader conclusions).

Example Syntheses

Below are two examples of synthesis: one where synthesis is NOT utilized well, and one where it is.

Parents are always trying to find ways to encourage healthy eating in their children. Elena Pearl Ben-Joseph, a doctor and writer for KidsHealth , encourages parents to be role models for their children by not dieting or vocalizing concerns about their body image. The first popular diet began in 1863. William Banting named it the “Banting” diet after himself, and it consisted of eating fruits, vegetables, meat, and dry wine. Despite the fact that dieting has been around for over a hundred and fifty years, parents should not diet because it hinders children’s understanding of healthy eating.

In this sample paragraph, the paragraph begins with one idea then drastically shifts to another. Rather than comparing the sources, the author simply describes their content. This leads the paragraph to veer in an different direction at the end, and it prevents the paragraph from expressing any strong arguments or conclusions.

An example of a stronger synthesis can be found below.

Parents are always trying to find ways to encourage healthy eating in their children. Different scientists and educators have different strategies for promoting a well-rounded diet while still encouraging body positivity in children. David R. Just and Joseph Price suggest in their article “Using Incentives to Encourage Healthy Eating in Children” that children are more likely to eat fruits and vegetables if they are given a reward (855-856). Similarly, Elena Pearl Ben-Joseph, a doctor and writer for Kids Health , encourages parents to be role models for their children. She states that “parents who are always dieting or complaining about their bodies may foster these same negative feelings in their kids. Try to keep a positive approach about food” (Ben-Joseph). Martha J. Nepper and Weiwen Chai support Ben-Joseph’s suggestions in their article “Parents’ Barriers and Strategies to Promote Healthy Eating among School-age Children.” Nepper and Chai note, “Parents felt that patience, consistency, educating themselves on proper nutrition, and having more healthy foods available in the home were important strategies when developing healthy eating habits for their children.” By following some of these ideas, parents can help their children develop healthy eating habits while still maintaining body positivity.

In this example, the author puts different sources in conversation with one another. Rather than simply describing the content of the sources in order, the author uses transitions (like "similarly") and makes the relationship between the sources evident.

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What is Synthesis?

Here are some ways to think about synthesis:

Synthesis blends claims, evidence, and your unique insights to create a strong, unified paragraph. Assertions act as the threads, evidence adds texture, and your commentary weaves them together, revealing the connections and why they matter.

Beyond the sum of its parts: Synthesis isn't just adding one and one. It's recognizing how multiple sources, through their connections and relationships, create a deeper understanding than any single one could achieve.

Synthesis isn't just about what sources say, it's about how they say it. By digging into assumptions, interpretations, and even speculations, you uncover hidden connections and build a more nuanced picture.

Whereas analyzing involves dismantling a whole to understand its parts and their relationships, synthesizing involves collecting diverse parts and weaving them together to form a novel whole. Reading is an automatic synthesis process, where we connect incoming information with our existing knowledge, constructing a new, expanded "whole" of our understanding in the subject area.

You've been doing synthesis for a long time, the key now is being aware and organized in the process.

• Sharpen your research direction: Be clear about your main objective. This guides your reading and analysis to make the most of your time.
• Build a strong foundation: Use trusted sources like peer-reviewed journals, academic books, and reputable websites. Diverse sources add strength and credibility to your research.

Then Organize your Research:

• Dig deep and connect the dots: While reading, highlight key ideas, arguments, and evidence. Mark potential links between sources, like overlaps or contrasting arguments.
• Organize ideas by neighborhood: Group sources with similar themes or angles on your topic. This will show you where sources agree or clash, helping you build a nuanced understanding.
• Build a mind map of your research: Create a table of key themes, listing key points from each source and how they connect. This visual map can reveal patterns and identify any missing pieces in your research.

Finally, Build your synthesis:

• Lay out the groundwork: Kick off each section with a clear claim or theme to guide your analysis.
• Weave sources together: Briefly explain what each source brings to the table, smoothly connecting their ideas with transitions and language.
• Embrace the debate: Don't tiptoe around differences. Point out where sources agree or clash, and explore possible reasons for these discrepancies.
• Dig deeper than surface facts: Don't just parrot findings. Explain what they mean and how they impact your topic.
• Add your voice to the mix: Go beyond reporting. Analyze, evaluate, and draw conclusions based on your synthesis. What does this research tell us?

Tips & Tricks:

• Let the evidence do the talking: Back up your claims with concrete details, quotes, and examples from your sources. No need for personal opinions, just let the facts speak for themselves.
• Play fair with opposing views: Be objective and present different perspectives without showing favoritism. Even if you disagree, let readers see the other side of the coin.
• Give credit where credit is due: Make sure your sources get the recognition they deserve with proper citations, following your chosen style guide consistently.
• Polish your masterpiece: Take some time to revise and proofread your work. Ensure your arguments are crystal clear, concise, and well-supported by the evidence.
• Embrace the growth mindset: Remember, research and synthesis are a journey, not a destination. Keep refining your analysis as you learn more and encounter new information. The more you explore, the deeper your understanding will become.

Demonstrates how two or more sources agree with one another.

The collaborative nature of writing tutorials has been discussed by scholars like Andrea Lunsford (1991) and Stephen North (1984). In these essays, they explore the usefulness and the complexities of collaboration between tutors and students in writing center contexts.

Demonstrates how two or more sources support a main point in different ways.

While some scholars like Berlin (1987) have primarily placed their focus on the histories of large, famous universities, other scholars like Yahner and Murdick (1991) have found value in connecting their local histories to contrast or highlight trends found in bigger-name universities.

Accumulation

Demonstrates how one source builds on the idea of another.

Although North’s (1984) essay is fundamental to many writing centers today, Lunsford (1991) takes his ideas a step further by identifying different writing center models and also expanding North’s ideas on how writing centers can help students become better writers.

Demonstrates how one source discusses the effects of another source’s ideas.

While Healy (2001) notes the concerns of having primarily email appointments in writing centers, he also notes that constraints like funding, resources, and time affect how online resources are formed. For writing centers, email is the most economical and practical option for those wanting to offer online services but cannot dedicate the time or money to other online tutoring methods. As a result, in Neaderheiser and Wolfe’s (2009) reveals that of all the online options available in higher education, over 91% of institutions utilize online tutoring through email, meaning these constraints significantly affect the types of services writing centers offer.

[Taken from University of Illinois, "Synthesizing Research "]

The Writing Center at University of Arizona showcases how to create and use a synthesis matrix when reading sources and taking notes. It is a great, organized way to synthesize your research.

You can find it here .

Creativity in researching begins with developing a thorough understanding of your research topic; this is fundamental to streamlining the process and enriching your findings. This entails delving into its intricacies—exploring both similarities and divergences with related subject areas. Consider the most appropriate sources (and types of sources) for your study, critically engaging with all perspectives, and acknowledging the complex interplay between its positives, negatives, and broader connections.

Embrace interdisciplinary exploration. Delve deeper through transdisciplinary analysis, venturing beyond the immediate field to parallel professions and diverse academic arenas. Consider comparative studies from other cultural contexts to add fresh perspectives.

For example, researching rule changes in the NFL demands a nuanced approach. One might investigate the link to Traumatic Brain Injury, analyze case studies of impacted players, and even examine rule adjustments in other sports, drawing insights from their rationale and outcomes.

Remember, librarians are invaluable partners in this process. Their expertise in creative thinking and resource navigation can unlock a wealth of information, guiding you towards fruitful discoveries.

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• Published: 25 September 2024

Gold-catalysed amine synthesis by reductive hydroamination of alkynes with nitroarenes

• Tongliang Zhou   ORCID: orcid.org/0000-0002-7334-7078 1 ,
• Pengcheng Gao   ORCID: orcid.org/0000-0003-4266-0616 1 ,
• Roger Lalancette   ORCID: orcid.org/0000-0002-3470-532X 1 ,
• Roman Szostak 2 &
• Michal Szostak   ORCID: orcid.org/0000-0002-9650-9690 1  

Nature Chemistry ( 2024 ) Cite this article

Metrics details

• Catalytic mechanisms
• Synthetic chemistry methodology

Amines are the most pivotal class of organic motifs in pharmaceutical compounds. Here we provide a blueprint for a general synthesis of amines by catalyst differentiation enabled by triple Au–H/Au + /Au–H relay catalysis. The parent catalyst is differentiated into a set of catalytically active species to enable triple cascade catalysis, where each catalytic species is specifically tuned for one catalytic cycle. This strategy enables the synthesis of biorelevant amine motifs by reductive hydroamination of alkynes with nitroarenes. Using this triple cascade approach, we have achieved exceptional functional group tolerance, enabling the use of bulk chemical feedstocks as coupling partners for the amination of both simple and complex alkynes (>100 examples), including those derived from pharmaceuticals, peptides and natural products (>30 examples). The isolation and full crystallographic characterization of gold hydride and hydride-bridged gold complexes has garnered insights into the catalyst differentiation process of fundamental organometallic gold hydride complexes.

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Data availability

Experimental procedures and characterization data are available within this article and its Supplementary Information . Crystallographic data for the structures reported in this article have been deposited at the Cambridge Crystallographic Data Centre under deposition numbers CCDC 2257337 ([(ImPyDippMes)AuCl]), 2257339 ([(ImPyDippMes)AuH]), 2257340 ({[(ImPyDippMes)Au] 2 (µ-H)} + BArF − ) and 2257341 ([(ImPyDippMes)Au(MeCN)] + BArF − ).

van Leeuwen, P. W. N. M. Homogeneous Catalysis: Understanding the Art (Springer, 2004).

Bhaduri, S. & Mukesh, D. Homogeneous Catalysis: Mechanisms and Industrial Applications 2nd edn (Wiley, 2014).

Cornils, B., Herrmann, W. A., Beller, M. & Paciello, R. Applied Homogeneous Catalysis with Organometallic Compounds: A Comprehensive Handbook in Four Volumes 3rd edn (Wiley-VCH, 2018).

Bender, T. A., Dabrowski, J. A. & Gagné, M. R. Homogeneous catalysis for the production of low-volume, high-value chemicals from biomass. Nat. Rev. Chem. 2 , 35–46 (2018).

Article   CAS   Google Scholar  

Lee, J. M., Na, Y., Han, H. & Chang, S. Cooperative multi-catalyst systems for one-pot organic transformations. Chem. Soc. Rev. 33 , 302–312 (2004).

Article   PubMed   CAS   Google Scholar  

Lohr, T. L. & Marks, T. J. Orthogonal tandem catalysis. Nat. Chem. 7 , 477–482 (2015).

Roughley, S. D. & Jordan, A. M. The medicinal chemist’s toolbox: an analysis of reactions used in the pursuit of drug candidates. J. Med. Chem. 54 , 3451–3479 (2011).

Cernak, T., Dykstra, K. D., Tyagarajan, S., Vachal, P. & Krska, S. W. The medicinal chemist’s toolbox for late stage functionalization of drug-like molecules. Chem. Soc. Rev. 45 , 546–576 (2016).

Blakemore, D. C. et al. Organic synthesis provides opportunities to transform drug discovery. Nat. Chem. 10 , 383–394 (2018).

Hili, R. & Yudin, A. K. Making carbon–nitrogen bonds in biological and chemical synthesis. Nat. Chem. Biol. 2 , 284–287 (2006).

Lawrence, S. A. Amines: Synthesis, Properties and Applications (Cambridge Univ. Press, 2004).

Ricci, A. Amino Group Chemistry: From Synthesis to the Life Sciences (Wiley-VCH, 2008).

Smith, M. B. & March, J. March’s Advanced Organic Chemistry: Reactions, Mechanisms, and Structure 6th edn (Wiley, 2007).

Ruiz-Castillo, P. & Buchwald, S. L. Applications of palladium-catalyzed C–N cross-coupling reactions. Chem. Rev. 116 , 12564–12649 (2016).

Article   PubMed   PubMed Central   CAS   Google Scholar  

Afanasyev, O. I., Kuchuk, E., Usanov, D. L. & Chusov, D. Reductive amination in the synthesis of pharmaceuticals. Chem. Rev. 119 , 11857–11911 (2019).

Irrgang, T. & Kempe, R. Transition-metal-catalyzed reductive amination employing hydrogen. Chem. Rev. 120 , 9583–9674 (2020).

Huang, L., Arndt, M., Gooßen, K., Heydt, H. & Gooßen, L. J. Late transition metal-catalyzed hydroamination and hydroamidation. Chem. Rev. 115 , 2596–2697 (2015).

Isaeva, V. I. & Kustov, L. M. Catalytic hydroamination of unsaturated hydrocarbons. Top. Catal. 59 , 1196–1206 (2016).

Liu, R. Y. & Buchwald, S. L. CuH-catalyzed olefin functionalization: from hydroamination to carbonyl addition. Acc. Chem. Res. 53 , 1229–1243 (2020).

Dow, N. W., Cabré, A. & MacMillan, D. W. C. A general N -alkylation platform via copper metallaphotoredox and silyl radical activation of alkyl halides. Chem. 7 , 1827–1842 (2021).

Severin, R. & Doyle, S. The catalytic hydroamination of alkynes. Chem. Soc. Rev. 36 , 1407–1420 (2007).

Gui, J. et al. Practical olefin hydroamination with nitroarenes. Science 348 , 886–891 (2015).

Jordan, A. J., Lalic, G. & Sadighi, J. P. Coinage metal hydrides: synthesis, characterization, and reactivity. Chem. Rev. 116 , 8318–8372 (2016).

Hashmi, A. S. K. Gold-catalyzed organic reactions. Chem. Rev. 107 , 3180–3211 (2007).

Hashmi, A. S. K. Introduction: gold chemistry. Chem. Rev. 121 , 8309–8310 (2021).

Nolan, S. P. N-Heterocyclic Carbenes: Effective Tools for Organometallic Synthesis (Wiley, 2014).

Gao, P. et al. L-shaped heterobidentate imidazo[1,5- a ]pyridin-3-ylidene (N,C)-ligands for oxidant-free Au I /Au III catalysis. Angew. Chem. Int. Ed. 62 , e202218427 (2023).

Zhou, T. et al. Well-defined, air- and moisture-stable palladium–imidazo[1,5- a ]pyridin-3-ylidene complexes: a versatile catalyst platform for cross-coupling reactions by L-shaped NHC ligands. Catal. Sci. Technol. 12 , 6581–6589 (2022).

Alcarazo, M., Stork, T., Anoop, A., Thiel, W. & Fürstner, A. Steering the surprisingly modular π-acceptor properties of N-heterocyclic carbenes: implications for gold catalysis. Angew. Chem. Int. Ed. 49 , 2542–2546 (2010).

Ma, X. et al. ‘Traceless’ directing group enables catalytic S N 2 glycosylation toward 1,2- cis -glycopyranosides. J. Am. Chem. Soc. 143 , 11908–11913 (2021).

Collado, A., Gomez-Suarez, A., Martin, A. R., Slawin, A. M. Z. & Nolan, S. P. Straightforward synthesis of [Au(NHC)X] (NHC = N-heterocyclic carbene, X = Cl, Br, I) complexes. Chem. Commun. 49 , 5541–5543 (2013).

Fructos, M. R. et al. A gold catalyst for carbene-transfer reactions from ethyl diazoacetate. Angew. Chem. Int. Ed. 44 , 5284–5288 (2005).

Falivene, L. et al. Towards the online computer-aided design of catalytic pockets. Nat. Chem. 11 , 872–879 (2019).

Heal, D. J., Smith, S. S., Gosden, J. & Nutt, D. J. Amphetamine, past and present—a pharmacological and clinical perspective. J. Psychopharmacol. 27 , 479–496 (2013).

Article   PubMed   PubMed Central   Google Scholar  

Boissier, J. R., Ratouis, R. & Dumont, C. New derivatives of phenylisopropylamine: synthesis and study of their anorexic activity. Ann. Pharm. Fr. 24 , 57–68 (1966).

PubMed   CAS   Google Scholar  

Baird, J. K. & Hoffman, S. L. Primaquine therapy for malaria. Clin. Infect. Dis. 39 , 1336–1345 (2004).

Tsui, E. Y., Müller, P. & Sadighi, J. P. Reactions of a stable monomeric gold(I) hydride complex. Angew. Chem. Int. Ed. 47 , 8937–8940 (2008).

Carroll, T. G., Ryan, D. E., Erickson, J. D., Bullock, R. M. & Tran, B. L. Isolation of a Cu–H monomer enabled by remote steric substitution of a N-heterocyclic carbene ligand: stoichiometric insertion and catalytic hydroboration of internal alkenes. J. Am. Chem. Soc. 144 , 13865–13873 (2022).

Phillips, N., Dodson, T., Tirfoin, R., Bates, J. I. & Aldridge, S. Expanded-ring N-heterocyclic carbenes for the stabilization of highly electrophilic gold(I) cations. Chem. Eur. J. 20 , 16721–16731 (2014).

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Acknowledgements

We gratefully acknowledge the NIH (R35GM133326, M.S.), the NSF (CAREER CHE-1650766, M.S.) and Rutgers University (M.S.) for generous financial support. The results presented herein are based on work supported by the National Science Foundation (grant no. 2018753, M.S.). Supplemental funding for this project was provided by the Rutgers University–Newark Chancellor’s Research Office (M.S.). We thank the Wroclaw Center for Networking and Supercomputing (grant no. WCSS159, R.S.).

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Department of Chemistry, Rutgers University, Newark, NJ, USA

Tongliang Zhou, Pengcheng Gao, Roger Lalancette & Michal Szostak

Department of Chemistry, Wroclaw University, Wroclaw, Poland

Roman Szostak

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Contributions

T.Z. and M.S. conceived the project. T.Z. developed the reaction and conducted the experiments. P.G. contributed to ligand design. R.L. conducted the crystallographic analyses. R.S. conducted DFT calculations. T.Z. and M.S. analysed the data and wrote the paper. M.S. directed the project.

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Correspondence to Michal Szostak .

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M.S. and T.Z. are listed on a patent application filed by Rutgers University on the ligands and precatalysts described in this paper (US 63/318481). The remaining authors declare no competing interests.

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Supplementary information

Supplementary information.

Supplementary discussion, experimental details, NMR spectra, Figs. 1–36 and Tables 1–19.

Supplementary Data 1

Crystallographic data of compound [ImPyDippMesAuCl]. CCDC reference 2257337 .

Supplementary Data 2

Crystallographic data of compound [ImPyDippMesAuH]. CCDC reference 2257339 .

Supplementary Data 3

Crystallographic data of compound [(ImPyDippMes)Au(MeCN)]BArF. CCDC reference 2257341 .

Supplementary Data 4

Crystallographic data of the [ImPyDippMesAuH] dimer. CCDC reference 2257340 .

Supplementary Data 5

Computational . xyz and .log files.

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Zhou, T., Gao, P., Lalancette, R. et al. Gold-catalysed amine synthesis by reductive hydroamination of alkynes with nitroarenes. Nat. Chem. (2024). https://doi.org/10.1038/s41557-024-01624-8

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DOI : https://doi.org/10.1038/s41557-024-01624-8

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Critical resolved shear stress and work hardening determination in hcp metals: application to zr single crystals.

1. Introduction

• Intrinsic anisotropy: This arises from the atomic structure, resulting in different critical resolved shear stresses (CRSSs) for deformation mechanisms and varying strain-hardening values, as the interactions between systems are unequal.
• Extrinsic anisotropy: This comes from the pronounced texture of HCP metals, which significantly affects their macroscopic properties. Current models better account for this anisotropy through texture measurements [ 2 , 3 , 6 ].

2. Methodology

2.1. slip/twin systems, 2.2. calculation of the coefficients of the work-hardening matrix, 3. experimental, 4.1. stage i: determination of some crsss, 4.2. stage ii: interaction with two or more systems.

Click here to enlarge figure

4.3. Influence of the Deformation Rate

5. discussion, 5.1. voce law and prismatic glide, 5.2. deformation rate, 6. conclusions, author contributions, data availability statement, acknowledgments, conflicts of interest, appendix a. calculation of slopes a, b, c, d, and e, appendix b. geometry of hcp crystal.

• Tenckhoff, E. Deformation Mechanisms, Texture, and Anisotropy in Zirconium and Zircaloy ; ASTM International: West Conshohocken, PA, USA, 1988; Volume 966. [ Google Scholar ] [ CrossRef ]
• Proust, G.; Tomé, C.; Kaschner, G. Modeling texture, twinning and hardening evolution during deformation of hexagonal materials. Acta Mater. 2007 , 55 , 2137–2148. [ Google Scholar ] [ CrossRef ]
• Van Houtte, P. The effect of strain path on texture: Theoretical and experimental considerations. In Strength of Metals and Alloys (ICSMA 7) ; Elsevier: Amsterdam, The Netherlands, 1986; pp. 1701–1725. [ Google Scholar ] [ CrossRef ]
• Akhtar, A. Prismatic slip in zirconium single crystals at elevated temperatures. Metall. Trans. A 1975 , 6 , 1217–1222. [ Google Scholar ] [ CrossRef ]
• Naka, S.; Lasalmonie, A. Cross-slip on the first order pyramidal plane (10 1) of a-type dislocations [1 10] in the plastic deformation of α -titanium single crystals. J. Mater. Sci. 1983 , 18 , 2613–2617. [ Google Scholar ] [ CrossRef ]
• Tome, C.N.; Lebensohn, R.A. Material Modeling with the Visco-Plastic Self-Consistent (VPSC) Approach: Theory and Practical Applications ; Elsevier: Amsterdam, The Netherlands, 2023. [ Google Scholar ] [ CrossRef ]
• Legrand, B. Relation between the electronic structure and ease of gliding in hexagonal close-packed metals. Philos. Mag. B. 1984 , 49 , 171–184. [ Google Scholar ] [ CrossRef ]
• Clouet, E. Screw dislocation in zirconium: An ab initio study. Phys. Rev. B—Condensed Matter Mater. Phys. 2012 , 86 , 144104. [ Google Scholar ] [ CrossRef ]
• Trojanová, Z.; Lukáč, P. Thermally activated deformation of alpha zirconium. Cryst. Res. Technol. 1984 , 19 , 401–405. [ Google Scholar ] [ CrossRef ]
• Miyada-Naborikawa, L.; De Batisi, R.; Delavignette, P. Transmission electron microscopy observations of dislocations and twins in polycrystalline zirconium. Phys. Status Solidi (a) 1985 , 89 , 521–531. [ Google Scholar ] [ CrossRef ]
• Rapperport, E. Room temperature deformation processes in zirconium. Acta Metall. 1959 , 7 , 254–260. [ Google Scholar ] [ CrossRef ]
• MacEwen, S.; Fleck, R.; Ho, E.; Woo, O. Deformation of α -zirconium in the vicinity of 0.5 Tm. Metall. Trans. A 1981 , 12 , 1751–1759. [ Google Scholar ] [ CrossRef ]
• Crépin, J. Etude des Mécanismes de Déformation et D’endommagement du Zirconium Grade 702 Traité beta: Application aux Cordons de Soudure. Ph.D. Thesis, Ecole Polytechnique, Palaiseau, France, 1995. [ Google Scholar ]
• Onchi, T.; Kayano, H.; Higashiguchi, Y.; Narui, M. Effects of temperature, strain rate, and specimen orientation on localized plastic deformation of irradiated zircaloy-2. J. Nucl. Sci. Technol. 1980 , 17 , 848–856. [ Google Scholar ] [ CrossRef ]
• Kaschner, G.; Tomé, C.; Beyerlein, I.; Vogel, S.; Brown, D.; McCabe, R. Role of twinning in the hardening response of zirconium during temperature reloads. Acta Mater. 2006 , 54 , 2887–2896. [ Google Scholar ] [ CrossRef ]
• Murty, K.; Adams, B. Multiaxial creep of textured Zircaloy-4. In Mechanical Testing for Deformation Model Development ; ASTM International: West Conshohocken, PA, USA, 1982. [ Google Scholar ] [ CrossRef ]
• Murty, K.L.; Charit, I. Texture development and anisotropic deformation of zircaloys. Prog. Nucl. Energy 2006 , 48 , 325–359. [ Google Scholar ] [ CrossRef ]
• Akhtar, A. Compression of zirconium single crystals parallel to the c-axis. J. Nucl. Mater. 1973 , 47 , 79–86. [ Google Scholar ] [ CrossRef ]
• Akhtar, A.; Teghtsoonian, A. Plastic deformation of zirconium single crystals. Acta Metall. 1971 , 19 , 655–663. [ Google Scholar ] [ CrossRef ]
• Dickson, J.; Craig, G. Room-temperature basal slip in zirconium. J. Nucl. Mater. 1971 , 40 , 346–348. [ Google Scholar ] [ CrossRef ]
• Caillard, D.; Gaumé, M.; Onimus, F. Glide and cross-slip of a-dislocations in Zr and Ti. Acta Mater. 2018 , 155 , 23–34. [ Google Scholar ] [ CrossRef ]
• Knezevic, M.; Beyerlein, I.J.; Nizolek, T.; Mara, N.A.; Pollock, T.M. Anomalous basal slip activity in zirconium under high-strain deformation. Mater. Res. Lett. 2013 , 1 , 133–140. [ Google Scholar ] [ CrossRef ]
• Akhtar, A. Basal slip in zirconium. Acta Metall. 1973 , 21 , 1–11. [ Google Scholar ] [ CrossRef ]
• Li, Y.; Po, G.; Cui, Y.; Ghoniem, N. Prismatic-to-basal plastic slip transition in zirconium. Acta Mater. 2023 , 242 , 118451. [ Google Scholar ] [ CrossRef ]
• Kaschner, G.; Gray, G. The influence of crystallographic texture and interstitial impurities on the mechanical behavior of zirconium. Metall. Mater. Trans. A 2000 , 31 , 1997–2003. [ Google Scholar ] [ CrossRef ]
• Devincre, B.; Kubin, L.; Lemarchand, C.; Madec, R. Mesoscopic simulations of plastic deformation. Mater. Sci. Eng. A 2001 , 309 , 211–219. [ Google Scholar ] [ CrossRef ]
• Soo, P.; Higgins, G. The deformation of zirconium-oxygen single crystals. Acta Metall. 1968 , 16 , 177–186. [ Google Scholar ] [ CrossRef ]
• Ferrer, F.; Barbu, A.; Bretheau, T.; Crépin, J.; Willaime, F.; Charquet, D. The effect of small concentrations of sulfur on the plasticity of zirconium alloys at intermediate temperatures. In ECCOMAS 2002-Zirconium in the Nuclear Industry: Thirteenth International Symposium ; ASTM International: West Conshohocken, PA, USA, 2001; Volume STP11420S, pp. 863–887. [ Google Scholar ] [ CrossRef ]
• Allais, L.; Bornert, M.; Bretheau, T.; Caldemaison, D. Experimental characterization of the local strain field in a heterogeneous elastoplastic material. Acta Metall. Mater. 1994 , 42 , 3865–3880. [ Google Scholar ] [ CrossRef ]
• Fundenberger, J.J.; Morawiec, A.; Bouzy, E.; Lecomte, J.S. System for creating orientation maps using TEM. Mater. Chem. Phys. 2003 , 81 , 535–537. [ Google Scholar ] [ CrossRef ]
• Fundenberger, J.J.; Morawiec, A.; Bouzy, E. Advances in automatic TEM based orientation mapping. Solid State Phenom. 2005 , 105 , 37–42. [ Google Scholar ] [ CrossRef ]
• Bunge, H. Texture Analysis in Materials Science ; Butterworth-Heinemann: Oxford, UK, 1982; Volume 11, p. L0. [ Google Scholar ] [ CrossRef ]
• Edington, J.W.; Edington, J. Electron Diffraction in the Electron Microscope ; Springer: Berlin/Heidelberg, Germany, 1975. [ Google Scholar ] [ CrossRef ]
• Zhang, Y.; Wang, S.; Esling, C.; Lecomte, J.S.; Schuman, C.; Zhao, X.; Zuo, L. A method to identify dislocations in a known crystal structure by transmission electron microscopy. J. Appl. Crystallogr. 2011 , 44 , 1164–1168. [ Google Scholar ] [ CrossRef ]
• Bachmann, F.; Hielscher, R.; Schaeben, H. Grain detection from 2d and 3d EBSD data—Specification of the MTEX algorithm. Ultramicroscopy 2011 , 111 , 1720–1733. [ Google Scholar ] [ CrossRef ]
• Beausir, B.; Fundenberger, J. Analysis Tools for Electron and X-ray diffraction, ATEX-software. Univ. De Lorraine-Metz 2017 , 2017 . [ Google Scholar ]
• Fisher, E.; Renken, C. Single-crystal elastic moduli and the hcp→ bcc transformation in Ti, Zr, and Hf. Phys. Rev. 1964 , 135 , A482. [ Google Scholar ] [ CrossRef ]
• Knezevic, M.; Zecevic, M.; Beyerlein, I.J.; Bingert, J.F.; McCabe, R.J. Strain rate and temperature effects on the selection of primary and secondary slip and twinning systems in HCP Zr. Acta Mater. 2015 , 88 , 55–73. [ Google Scholar ] [ CrossRef ]
• An, X.; Zhang, H.; Ni, S.; Ou, X.; Liao, X.; Song, M. Effects of temperature and alloying content on the phase transformation and {101 ¯ 1} twinning in Zr during rolling. J. Mater. Sci. Technol. 2020 , 41 , 76–80. [ Google Scholar ] [ CrossRef ]
• Pujol, C. Etude des Mecanismes de Deformation en Traction et Fluage du zr Alpha Entre 20 et 300c. Ph.D. Thesis, ENMP, Paris, France, 1994. [ Google Scholar ]
• Skippon, T.; Mareau, C.; Daymond, M. On the determination of single-crystal plasticity parameters by diffraction: Optimization of a polycrystalline plasticity model using a genetic algorithm. J. Appl. Crystallogr. 2012 , 45 , 627–643. [ Google Scholar ] [ CrossRef ]
• Gong, J.; Britton, T.B.; Cuddihy, M.A.; Dunne, F.P.; Wilkinson, A.J. <a> Prismatic, <a> basal, and <c + a> slip strengths of commercially pure Zr by micro-cantilever tests. Acta Mater. 2015 , 96 , 249–257. [ Google Scholar ] [ CrossRef ]
• Monnet, G.; Devincre, B.; Kubin, L. Dislocation study of prismatic slip systems and their interactions in hexagonal close packed metals: Application to zirconium. Acta Mater. 2004 , 52 , 4317–4328. [ Google Scholar ] [ CrossRef ]
• Kelly, A.; Knowles, K.M. Crystallography and Crystal Defects ; John Wiley & Sons: Hoboken, NJ, USA, 2020. [ Google Scholar ] [ CrossRef ]

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Lecomte, J.-S.; Crépin, J.; Barberis, P. Critical Resolved Shear Stress and Work Hardening Determination in HCP Metals: Application to Zr Single Crystals. Metals 2024 , 14 , 1101. https://doi.org/10.3390/met14101101

Lecomte J-S, Crépin J, Barberis P. Critical Resolved Shear Stress and Work Hardening Determination in HCP Metals: Application to Zr Single Crystals. Metals . 2024; 14(10):1101. https://doi.org/10.3390/met14101101

Lecomte, Jean-Sébastien, Jérôme Crépin, and Pierre Barberis. 2024. "Critical Resolved Shear Stress and Work Hardening Determination in HCP Metals: Application to Zr Single Crystals" Metals 14, no. 10: 1101. https://doi.org/10.3390/met14101101

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Synthesis and Characterization of Biocomposite Food Packaging Composite Film Using Waste Orange Peel Bio-Plasticizer and PLA(Poly Lactic Acid) /PCL (Polycaprolactone) Blend

• Original Paper
• Published: 23 September 2024

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• Anbhazhagan Nallathambi 1 ,
• T. Thendral Thiyaku 1 &
• R. S. M. Vijay Aravinthan 2  

This research aims to synthesis and characterization of biocomposite films for food packaging application using orange peel essential oil (OEO) as green plasticizer and PCL (Polycaprolactone), is biodegradable polyester and PLA (Poly Lactic Acid) is a renewable plastic made from food starches was blends as matrix. The bio-based composite films were prepared using polylacticacid, polycaprolactone and orange peel essential oil via a simple solvent casting technique. The PLA is initially blended with chloroform to make films as non-biocompatible sample preparation protocol at lab scale level and to obtain optimum blends. Once the optimum blends ratios obtained the biocompatible solvents could be used for large scale production with safe food packing concerns. The PLA/PCL formulations of varying compositions were further mixed with 5, 10, and 15% weight of orange peel oil, at mixing ratios of 90/10, 85/10, 80/10, and 75/10 respectively. A variety of characterisation approaches, including film colour, opacity, surface hydrophobicity, mechanical behaviour and anti-microbial activity were performed on all PLA/PCL blended films. Results revealed that the film’s opacity and hydrophobicity values gradually increased upon addition of orange peel oil. Similarly, the mechanical properties demonstrated an increased elongation at break for 15wt. % addition of orange peel oil into PLA/PCL blends. Moreover, the wettability and flexibility of the developed bio-based films were found to have improved by the use of orange peel oil in the PLA/PCL matrix. Apparently, the orange peel oil incorporated bio-based PLA/PCL blended films exhibited excellent antibacterial behaviour against S. aureus and E. coli microorganisms. The exploratory findings demonstrate that the polylacticacid, polycaprolactone and orange peel essential oil blended films could be recommended for usage in food packaging applications requiring high flexibility, thermal stability, barrier resistance, low water absorption and repellent to microbial attack.

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Hongdilokkul, K., Keeratipinit, S., Chawthai, B., Hararak, M., Seadan, Suttiruengwong, S.: IOP Publishing Ltd, vol. 87, (2015)

Zhu, G., et al.: Polym.-Plast. Technol. Eng. 51 (15), 1562–1566 (2012)

Article   Google Scholar  

Ahmad Sawpan, M., Islam, M.R., Beg, M.D.H., Pickering, K.: J. Polym. Environ. 27 , 942–955 (2019)

Akindoyo, J.O., Beg, M.D.H., Ghazali, S.B., Islam, M.R., Mamun, A.A.: Polym.-Plast. Technol. Eng. 54 (13), 1321–1333 (2015). https://doi.org/10.1080/03602559.2015.1010219

Mina, M.F., Beg, M.D.H., Islam, M.R., Nizam, A., Alam, A.K., M. M., Yunus, R.M.: Polym. Eng. Sci. 54 (2), 317–326 (2014). https://doi.org/10.1002/pen.23564

Gao, C., Chen, P., Ma, Y., Sun, L., Yan, Y., Ding, Y., Sun, L.: Int. J. Biol. Macromol. 253 , 126494 (2023). https://doi.org/10.1016/j.ijbiomac.2023.126494

Noori, N., Khanjari, A., Rezaeigolestani, M., Karabagias, I.K., Mokhtari, S.: Polymers. 13 (21), 3791 (2021). https://doi.org/10.3390/polym13213791

Akindoyo, J.O., Beg, M.D.H., Ghazali, S., Islam, M.R.: J. Appl. Polym. Sci., 132 (45). (2015)

Thakur, M., Majid, I., Hussain, S., Nanda, V.: Packaging Technol. Sci. 34 (8), 449–461 (2021). https://doi.org/10.1002/pts.2572

Deshmukh, K., Basheer Ahamed, M., Deshmukh, R.R., Khadheer Pasha, S.K., Chidambaram, K.: Pundlik Rambhau Bhagat, Biopolymer Composites in Electronics, pp. 27–128, (2017)

Jantrawut, P., Boonsermsukcharoen, K., Thipnan, K., Chaiwarit, T., Hwang, K.M., Park, E.S.: Nanomaterials, (2018)

Jarine Amaral do Evangelho: Guilherme da Silva Dannenberg,Barbara Biduski,Shanise Lisie Mello el Halal,Dianini Hüttner Kringel,Marcia Arocha Gularte,Angela Maria Fiorentini,Elessandra da Rosa Zavareze, Carbohydrate Polymers, vol. 222, no. 114981, (2019)

Eom, Y.: Bulim Choi, and Su-il Park. J. Polym. Environ. 27 , 256–262 (2019)

Anuar, H., Nur Fatin Izzati, A.B., Nurul Inani, S., Siti Nur, S.M., Munirah Salimah, E.M.A.S., Ali, A.B., F. B., Manshor, M.R.: J. Packaging Technol. Res. 1 , 149–156 (2017). https://doi.org/10.1007/s41783-017-0022-1

Ghoroghi, M., Estaji, S., Tayouri, M.I., Jahanmardi, R., Nobre, M.A., Khonakdar, H.A.: Arab. J. Chem. (2024). 105928 https://doi.org/10.1016/j.arabjc.2024.105928

Adamska, K., Voelkel, A.: Berlińska J. Pharm. Biomedical Anal. 127 , 202–206 (2016)

Ai, X., et al.: The properties of chemical cross-linked poly (lactic acid) by bis (tert-butyl dioxy isopropyl) benzene. Polym. Bull. 76 , 575–594 (2019)

Sikdar, D.C., Menon, R., Duseja, K., Kumar, P., Swami, P.: Int. J. Tech. Res. Appl. 4 (3), 341–346 (2016)

Google Scholar  

Akindoyo, J.O., Beg, H., Ghazali, M.D., S., Islam, M.R.: J. Polym. Eng. 36 (5), 489–497 (2016)

Ostafinska, A., Fortelny, I., Nevoralova, M., Hodan, J., Kredatusova, J., Slouf, M.: RSC Adv. 5 (120), 98971–98982 (2015)

Fortelny, I., Ujcic, A., Fambri, L., Slouf, M.: Phase structure, compatibility, and toughness of PLA/PCL blends: A review. Front. Mater. 6 , 206 (2019)

Li, Y., Tang, C., He, Q.: Effect of orange (Citrus sinensis L.) peel essential oil on characteristics of blend films based on chitosan and fish skin gelatin. Food Bioscience, 41 , (2021)

Hao, F., Wu, Q., Lou, J.E.S.S.-N., Ho, C.-T.: J. Food Drug Anal. 23 (1), 30–39 (2015)

Sajed Amjadi, H., Almasi, A., Ghadertaj, L., Mehryar: Food Processing and Preservation, vol. 45, no. 2, (2021)

Thiyagu, T.T., Prasanna Kumar, S., Gurusamy, J.V., Sathiyamoorthy, P.V., Maridurai, T., Arun Prakash, V.R.: Biomass Conversion and Bio refinery, (2021)

Saha, D., et al.: Preparation and characterization of poly (lactic acid)/poly (ethylene oxide) blend film: Effects of poly (ethylene oxide) and poly (ethylene glycol) on the properties. Polym. Int. 68 (1), 164–172 (2019)

Maria do Socorro Rocha Bastos, Kim, S., Biswas, A., Cheng, H.N.: Larissa Da Silva Laurentino, Kirley Marques Canuto, Luana Guabiraba Mendes, Camila Mota Martins, Sarah Maria Frota Silva, Roselayne Ferro Furtado. Polym. Test. 49 , 156–161 (2016)

Arun Prakash, V.R., Xavier, J.F., Ramesh, G., et al.: Biomass Conv Bioref. 12 , 5451–5461 (2022). https://doi.org/10.1007/s13399-020-00938-0

Marc Delgado-Aguilar, Rita Puig, IlijaSazdovski, Pere Fullana-i-Palmer. Mater. Sci., (2020)

Singh, S., et al.: Rheological aspects and film processability of poly (lactic acid)/linear low-density polyethylene blends. Polym. Eng. Sci. 61 (1), 85–94 (2021)

Article   MathSciNet   Google Scholar  

Rajadurai, A.: Appl. Surf. Sci. 384 , 99–106 (2016). https://doi.org/10.1016/j.apsusc.2016.04.185

Indrarti, L.: Incorporation of citrus Essential oils into Bacterial Cellulosebased Edible Films and Assessment of Their Physical Properties. IOP Publishing (2017)

Arrieta, M.P., López, J., Ferrándiz, S., Peltzer, M.A.: Characterization of PLA-limonene blends for food packaging applications. Polym. Test. 32 (4), 760–768 (2013)

Thiyagu, T.T., Gokilakrishnan, G., Uvaraja, V.C., Maridurai, T., Prakash, V.R.: Silicon. 14 (7), 3795–3808 (2022)

Yan, D., Wang, Z., Guo, Z., Ma, Y., Wang, C., Tan, H., Zhang, Y.: J. Mater. Res. Technol. 9 (5), 11895–11904 (2020)

Sitompul, J.P., et al.: Improvement of properties of Poly (L-lactic acid) through solution blending of biodegradable polymers. J. Eng. Technological Sci. 48 .4 (2016)

Takkalkar, P., et al.: J. Taiwan Inst. Chem. Eng. 104 , 293–300 (2019)

Wei, Y., et al.: Toughened transparent poly (L-lactic acid)/poly (D-lactide)-b-poly (butadiene)-b-poly (D-lactide) blended film with balanced strength. Polymer. 267 , 125695 (2023)

Yahyaoui, M., Gordobil, O., Díaz, R.H., Abderrabba, M., Labidi, J.: Reactive Funct. Polym. 109 , 1–8 (2016)

Ben Samuel, J., Julyes Jaisingh, S., Sivakumar, K., et al.: Visco-Elastic Silicon. 13 , 1703–1712 (2021). https://doi.org/10.1007/s12633-020-00569-0

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Nallathambi, A., Thiyaku, T. & Aravinthan, R. Synthesis and Characterization of Biocomposite Food Packaging Composite Film Using Waste Orange Peel Bio-Plasticizer and PLA(Poly Lactic Acid) /PCL (Polycaprolactone) Blend. Waste Biomass Valor (2024). https://doi.org/10.1007/s12649-024-02724-9

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It takes two peroxisome proliferator-activated receptors (PPAR-β/δ and PPAR-γ) to tango idiopathic pulmonary fibrosis

• Eistine Boateng 1   nAff8 ,
• Rocio Bonilla-Martinez 1 ,
• Barbara Ahlemeyer 1 ,
• Vannuruswamy Garikapati 1 , 6   nAff9 ,
• Mohammad Rashedul Alam 1 ,
• Omelyan Trompak 2 ,
• Gani Oruqaj 1   nAff10 ,
• Natalia El-Merhie 1   nAff11 ,
• Michael Seimetz 3 ,
• Clemens Ruppert 3 , 4 ,
• Andreas Günther 3 , 5 ,
• Bernhard Spengler 6 ,
• Srikanth Karnati 1   na1   nAff7 &
• Eveline Baumgart-Vogt 1   na1  

Respiratory Research volume  25 , Article number:  345 ( 2024 ) Cite this article

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Idiopathic pulmonary fibrosis (IPF) is characterized by aberrant lung epithelial phenotypes, fibroblast activation, and increased extracellular matrix deposition. Transforming growth factor-beta (TGF-β)1-induced Smad signaling and downregulation of peroxisomal genes are involved in the pathogenesis and can be inhibited by peroxisome proliferator-activated receptor (PPAR)-α activation. However, the three PPARs, that is PPAR-α, PPAR-β/δ, and PPAR-γ, are known to interact in a complex crosstalk.

To mimic the pathogenesis of lung fibrosis, primary lung fibroblasts from control and IPF patients with comparable levels of all three PPARs were treated with TGF-β1 for 24 h, followed by the addition of PPAR ligands either alone or in combination for another 24 h. Fibrosis markers (intra- and extracellular collagen levels, expression and activity of matrix metalloproteinases) and peroxisomal biogenesis and metabolism (gene expression of peroxisomal biogenesis and matrix proteins, protein levels of PEX13 and catalase, targeted and untargeted lipidomic profiles) were analyzed after TGF-β1 treatment and the effects of the PPAR ligands were investigated.

TGF-β1 induced the expected phenotype; e.g. it increased the intra- and extracellular collagen levels and decreased peroxisomal biogenesis and metabolism. Agonists of different PPARs reversed TGF-β1-induced fibrosis even when given 24 h after TGF-β1. The effects included the reversals of (1) the increase in collagen production by repressing COL1A2 promoter activity (through PPAR-β/δ activation); (2) the reduced activity of matrix metalloproteinases (through PPAR-β/δ activation); (3) the decrease in peroxisomal biogenesis and lipid metabolism (through PPAR-γ activation); and (4) the decrease in catalase protein levels in control (through PPAR-γ activation) and IPF (through a combined activation of PPAR-β/δ and PPAR-γ) fibroblasts. Further experiments to explore the role of catalase showed that an overexpression of catalase protein reduced collagen production. Additionally, the beneficial effect of PPAR-γ but not of PPAR-β/δ activation on collagen synthesis depended on catalase activity and was thus redox-sensitive.

Our data provide evidence that IPF patients may benefit from a combined activation of PPAR-β/δ and PPAR-γ.

IPF is a severe restrictive interstitial lung disease with patient median survival of 2.5–3.5 years [ 1 ]. Concerning the pathogenesis of IPF, it is being discussed that an excessive injury response results in persistent overproduction of extracellular matrix (ECM) components by activated and proliferating fibroblasts. In addition, oxidative stress remains a major mechanism associated with the progression of this disease [ 2 ]. Today, only limited treatment options for IPF are available. Evidence-based recommendations for the pharmacological management of the disease are the tyrosine kinase inhibitor nintedanib [ 3 , 4 ] and pirfenidone [ 4 , 5 ], an inhibitor of TGF-β1-stimulated collagen synthesis. Both drugs increase quality of life, attenuate symptoms and slow down IPF progression, but only nintedanib influences mortality. Some of the novel medications targeted pentraxin (involved in endogenous tissue repair), lysophosphatidic acid, or connective tissue growth factor (mediates TGF-β1 downstream signaling), but failed the clinical endpoints [ 6 , 7 ]. Other substances in the pipeline are nerandomilast (a tyrosine kinase inhibitor) which successfully completed phase II clinical trials [ 8 ] and inhaled treprostinil, a prostacyclin analogue. Treprostinil showed beneficial effects in the initial INCREASE trial [ 9 ] and ongoing TETON study [ 10 ] and has meanwhile been approved for the therapy of WHO group 1 pulmonary hypertension with an additional positive impact in IPF. Nevertheless, extensive research is still required to develop new therapeutic modalities.

To find therapeutic interventions for IPF, several studies explored the anti-fibrotic potentials of natural and synthetic PPAR ligands. For example, PPAR-α activation was demonstrated to attenuate fibrosis in the liver [ 11 ], heart [ 12 ] and lung [ 13 , 14 ], while PPAR-β agonists exhibited anti-proliferative effects [ 15 ], but increased the secretion of TGF-β1 and ECM [ 16 ]. Ligands of PPAR-γ are most promising [ 17 , 18 , 19 , 20 ] and were thought to inhibit fibroblast trans-differentiation [ 21 , 22 ] and to strengthen the anti-oxidative defense system [ 23 ]. In addition, pan-PPAR agonists, such as lanifibranor [ 24 ] and IVA337 [ 25 ] attenuated fibrosis. In all these studies, however, the anti-fibrotic mechanism of PPAR agonists remained unclear and was supposed to be mainly due to their anti-inflammatory activities [ 26 ]. Another drawback was the time schedule of the drug treatment. Typically, drugs were added before or together with TGF-β1, but these approaches do not reflect the patient situation where drugs can be given only after the diagnosis of the disease, years after its initiation. In two studies, PPAR-γ agonists were applied after bleomyin-induced lung injury in the mouse. Zeng et al. [ 27 ] added the PPARγ ligand asarinin 15–28 days after bleomycin administration, which reduced the severity of fibrosis. Speca et al. [ 22 ] applied GED-0507, a PPARγ modulator with strong anti-inflammatory effects, to mice on day 14 after bleomycin administration and reported resolution of fibrosis with 50% mortality rate. This post-treatment schedule reduced collagen deposition, but to a lesser extent than in the prevention approach used in the same study. Thus, we thought that a post-treatment with a combination of PPAR ligands may further increase the anti-fibrotic effect. Moreover, we aimed to use a human model and human cultured fibroblasts as the latter in vitro model better guaranties the drug availability and allows a selective (biochemical) analysis of changes in fibroblasts, the main players in fibrosis.

In this study, we investigated whether activation of each of the three PPARs alone or in various combinations influenced collagen synthesis and release of lung fibroblasts from control and IPF patients when given 24 h after TGF-β1, the endogenous stimulator of fibrosis. Moreover, we attempted to explore the mechanism of the anti-fibrotic effect of PPAR agonists by analyzing changes in members of matrix metalloproteinases (MMPs) [ 28 ], biogenesis and metabolism of peroxisomes [ 13 , 14 ], and the protein level and activity of catalase, the major anti-oxidative enzyme in peroxisomes [ 29 ] with the highest turnover numbers of all enzymes [ 30 ].

Study approval

Biospecimen collection (i.e. lung tissues and fibroblasts from organ donors) was approved by the Ethics Committee of the Justus Liebig University Giessen (Az58/15 and Az111/08, JLU).

Cell culture and drug treatment

Lung fibroblasts from control and IPF patients (Additional file: Table S1) and catalase-deficient fibroblast cell lines were cultured in Dulbecco´s Modified Eagle Medium (DMEM) with penicillin/streptomycin or puromycin, respectively. For the experiments, cells were serum-starved for 3 h, stimulated with vehicle or rhTGF-β1 for 24 h (except for Figs. 2 B, C, E, 3 B), followed by the addition of vehicle or drugs either alone or in combinations for another 24 h.

Knockdown of catalase in human lung fibroblasts

Knockdown of catalase was done with CAT siRNA using ScreenFectA transfection reagent. Stable catalase knockdown was achieved by transduction with pGIPZ-shCatalase and pGIPZ-non-silencing control lentivirus vectors as described earlier [ 31 ].

Overexpression of catalase in human lung fibroblasts

Transfection with catalase overexpression plasmid (pGL 4.14- Catalase ) and promoter reporter plasmids COL1A2 -luc and PPAR response element ( PPRE) -luc were done as described earlier [ 13 , 32 ]. Data from pRL-SV40 vector served to normalize results of the luciferase reporter plasmid.

Human TGF-β1 immunoassay and sircol collagen assay

The collected culture media of control and IPF fibroblasts were used for Sircol collagen assays and TGF-β1 ELISA assay according to the manufacturers´ instructions.

Measurements of catalase activity, hydrogen peroxide (H 2 O 2 ) production and cell proliferation

Determination of catalase activity with a redox dye assay kit based on the degradation of H 2 O 2 . H 2 O 2 produced by cultured cells was quantified using a fluorometric detection kit. The incorporation of BrdU into proliferating cells was detected with an ELISA kit. For all the aforementioned kits, we followed the manufacturers´ instructions.

Western blotting

Proteins of total cell lysates were separated on 10% SDS-PAGE gels and blotted on polyvinylidene difluoride membranes. Specific proteins were detected using primary and horseradish peroxidase (HRP)-labelled secondary antibodies followed by chemiluminescent detection of the HRP substrate. ImageJ was used for semi-quantitative analysis of signal intensities.

Immunofluorescence staining

Thin sections of paraffin-embedded lung tissues were incubated with primary and secondary fluorophore-labelled antibodies. Immunofluorescence images were acquired by confocal laser scanning microscopy.

Isolation of total RNA and RT-qPCR

Total RNA was isolated using RNAzol and mRNA levels were analyzed by RT-qPCR.

Targeted quantification of fatty acids

Arachidonic acid (AA), docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA) were analyzed in the culture medium by solid phase extraction and a targeted liquid chromatography tandem mass spectrometry (LC–MS/MS) approach as described previously [ 32 ].

Untargeted lipidomics

Lipids were extracted from cell lysates using a biphasic methyl- tert -butyl ether (MTBE) extraction protocol [ 33 ] and analyzed using an untargeted LC–MS/MS method as described previously [ 34 ].

Analysis was done using GraphPad Prism software. Data were expressed as means ± SEM. For comparisons between two groups, the F-test was applied to compare their variances followed by Mann–Whitney U test (unequal variances) or unpaired t -test (equal variances). For multiple comparisons, ANOVA was used with post-hoc Tukey´s multiple comparisons test. P values < 0.05 were considered as statistically significant.

Characterization of the fibrosis markers COL1 and α-SMA, as well as of PPARs in lung tissues and cultured fibroblasts from control and IPF patients

The fibrosis marker collagen type I (COL1) and myofibroblast marker α-smooth muscle actin (α-SMA) were first assessed in lung biopsy samples from control and IPF patients. Lung tissues from IPF patients showed comparatively higher levels of COL1 and α-SMA than those from control subjects (Fig.  1 A). Although increased mRNA levels of COL1A1 and ACTA2 were detected in cultured lung fibroblasts from IPF compared to control patients (Additional file: Fig. S1A, B), their protein levels and that of transforming growth factor-beta receptor 1 (TGFBR1) were higher in most cases in fibroblasts from control compared to IPF patients (Additional file: Fig. S1C, Table  1 ). Although unexpected at first glance, it is noteworthy that IPF lung tissue contains a much higher number of fibroblasts than controls. Probably, the higher number of fibroblasts in the lungs of IPF patients and to a minor extent their individual properties contribute to the differences in tissue pathology. Moreover, the reduced level of TGFBR1 in IPF fibroblasts suggests that they are less sensitive to TGF-β1 presumably due to their chronic exposure to the cytokine in vivo. Accordingly, analysis of extracellular collagen revealed no significant difference between control and IPF fibroblasts (Fig.  1 B, Additional file: Fig. S1D). IPF is characterized by elevated levels of TGF-β1 mRNA and protein in the lung tissues of patients [ 35 , 36 ]. Interestingly, the amount of released active TGF-β1 was higher in the culture media from control than IPF fibroblasts (Fig.  1 C). We demonstrated an anti-fibrotic role of peroxisomes in the progression of IPF via PPAR-α signaling [ 13 , 14 ]. Since all three PPARs crosstalk with each other [ 37 ], we next analyzed their protein levels in fibroblasts from control and IPF patients at basal conditions (no treatment in vitro). Collectively, IPF fibroblasts showed increased mRNA and protein levels of PPAR-α, but not of the ones of PPAR-β/δ and PPAR-γ compared to control fibroblasts (Fig.  1 D, Table  1 , Additional file: Fig. S1E).

Characterization of the fibrosis markers COL1 and α-SMA, and PPARs in lung tissue and cultured fibroblasts from control and IPF patients. A Lung tissue sections from control (left side) and IPF (right side) patients were incubated with antibodies to detect collagen (COL1, green) and α-SMA (red), and counterstained with DAPI (blue). Negative controls (NC) were done by omitting the primary antibody . B There was no difference in the release of collagen between fibroblasts from control and IPF patients. The release of collagen into culture media was measured using Sircol assay. Data represent 5 control and 5 IPF patients across six independent fibroblast cultures. C The release of active TGF-β1 is higher in control than in IPF fibroblasts. The amount of active human TGF-β1 was analyzed in the culture media of fibroblasts from 5 controls and 7 IPF patients by ELISA. D The protein levels of PPAR-α were higher in IPF compared to control fibroblasts, whereas there was no difference with regard to PPAR-β/δ and PPAR-γ. Cultured fibroblasts from 5 control and 7 IPF patients were collected and their protein levels were analyzed by Western blot analysis with GAPDH as reference protein

TGF-β1 induced a fibrotic response in fibroblasts from control and IPF patients. A TGF-β1 induced proliferation in control and IPF fibroblasts. Fibroblasts were serum-starved for 3 h and then incubated for 24 h with vehicle or TGF-β1. Thereafter, proliferation was analyzed using BrdU cell proliferation assay. B Treatment with different concentrations of TGF-β1 showed no difference between control and IPF fibroblasts with regard to the release of collagen into culture media. Control and IPF fibroblasts were serum-starved for 3 h and then treated with vehicle (Control) or 2.5, 5, 10 and 20 ng/ml TGF-β1 for 24 h. Cell culture media were collected and extracellular collagen was analyzed using Sircol assay. C , D TGF-β1 increased the level of intracellular COL1 in control and IPF fibroblasts in a time-dependent manner. Control and IPF fibroblasts were serum-starved for 3 h and then treated with vehicle or 5 ng/ml TGF-β1 for 12, 24, 36 and 48 h. Cell lysates were used to detect COL1 and α-SMA by Western blot analysis using GAPDH as reference protein ( C ). Data for a time period of 24 h from 5 control (patients A–E) and 5 IPF (patients F–J) patients is shown in ( D ). E TGF-β1 increased the protein level of PPAR-β/δ, whereas the ones of the other PPARs remained unchanged. Control and IPF fibroblasts were treated for 24, 48 and 72 h with TGF-β1 (5 ng/ml) or vehicle. Cell lysates were used for Western blot analysis of the PPARs using GAPDH as reference protein

Activation of PPAR-β/δ induced anti-fibrotic responses in TGF-β1-stimulated fibroblasts from control and IPF patients

As already noted, the number of fibroblasts in the lungs of IPF patients might be crucial for the disease progression. To confirm this, we analyzed the proliferation of vehicle- and TGF-β1-treated control and IPF fibroblasts since the cytokine was used to mimic part of the disease condition in vitro. As expected, TGF-β1 stimulated cell proliferation in control and IPF fibroblasts (Fig.  2 A). Next, we analyzed time-dependent changes in α-SMA and COL1 protein levels of control and IPF fibroblasts treated with TGF-β1. Control and IPF fibroblasts did not show differences after stimulation with different concentrations of TGF-β1 (2.5–20 ng/ml; Fig.  2 B) in the extracellular collagen released into the culture media. Though 2.5 ng/ml of TGF-β1 was already sufficient to reach the maximal effect for collagen values 24 h after treatment (Fig.  2 B), 5 ng/ml TGF-β1 was used to obtain maximal effects in all following experiments with distinct parameters. TGF-β1 increased intracellular COL1 and α-SMA protein levels from 12 to 48 h in control fibroblasts and from 24 h up to 48 h in IPF fibroblasts (Fig.  2 C). Moreover, the treatment with TGFβ-1 for 24 h in control and IPF fibroblasts from 10 different patients showed a homogenous and stable increase in the protein levels of COL1, but an inconsistent reaction in the case of α-SMA (Fig.  2 D, Table  1 ). To investigate the role of peroxisomes in IPF, their proliferation was induced using different PPAR ligands. Interestingly, TGF-β1 upregulated the protein level of PPAR-β/δ especially after 48 h of treatment (Fig.  2 E). Following 24 h TGF-β1 stimulation, treatment with PPAR-β/δ agonist alone or in combination with the two other members of the PPAR protein family inhibited the TGF-β1-mediated increase in COL1 and—to a lesser extent—α-SMA protein levels in control and IPF fibroblasts (Fig.  3 A). As already noted, anti-fibrotic properties of PPAR-γ have been reported in the past. In our study, the post-treatment with a PPAR-β/δ agonist (GW0742) alone or combined with a PPAR-γ agonist (rosiglitazone) strongly decreased the amount of TGF-β1-mediated increase in intracellular COL1 (Fig.  3 A–C) by affecting COL1A2 promotor activity (Fig.  3 D) as well as extracellular collagen (Fig.  3 E) in both, fibroblasts from control and IPF patients. Lesser effects were observed in the case of activation of PPAR-γ alone (Fig.  3 A, C, E). The decrease in the amount of COL1 as a result of the dual treatment of PPAR-β/δ and PPAR-γ agonists was stable over time (Fig.  3 B) and between patients (Fig.  3 C). Furthermore, the anti-fibrotic effects of a combined activation of PPAR-β/δ and PPAR-γ were blocked in the presence of PPAR-β/δ (GSK0660) and PPAR-γ (GW9662) antagonists (Fig.  3 F). In addition, we thought to use the compound STK 648389 (ZINC ID: 31,775,965), a putative dual agonist for PPAR-β/δ and PPAR-γ. However, analysis of the STK 648389 for its effect on collagen showed adverse effects and even increased extracellular collagen levels released by control and IPF fibroblasts after TGF-β1 exposure (Additional file: Fig. S2). Altogether, these findings suggest that although TGF-β1 increases the PPAR-β/δ protein as a protective adaptive mechanism, endogenous PPAR-β/δ activating ligands are probably diminished to prevent fibrosis in patients.

Activation of PPAR-β/δ induced anti-fibrotic responses in TGF-β1-stimulated fibroblasts. A – C , E Control and IPF fibroblasts were serum-starved for 3 h, treated with TGF-β1 (5 ng/ml) for 24 h, followed by the addition of the PPAR-α agonist WY14643 (100 μM, α; A ), PPAR-β/δ agonist GW0742 (10 μM, β; A–C , E ), and PPAR-γ agonist rosiglitazone (10 μM, γ; A – C , E ) either for 24 h ( A , C , E) or different time periods (12, 24, 36 and 48 h; B ). A PPAR-β/δ activation reversed TGF-β1-induced increase in COL1. Cell lysates were used to detect COL1 and α-SMA by Western blot analysis using GAPDH as reference protein. B , C Reverse of fibrosis phenotype by PPAR-β/δ and PPAR-γ activation was stable for up to 48 h. Cell lysates at 12 to 24 h ( B ) and 48 h from two other control and IPF patients ( C ) were used for Western blot analysis using β-actin (β-ACTIN) as reference protein. D Combined activation of PPAR-β/δ and PPAR-γ abolished TGF-β1-induced increase in COL1A2 promoter activity. IPF fibroblasts were transfected with a plasmid containing the luciferase firefly reporter gene adjacent to COL1A2 promoter and Renilla luciferase as second reporter for normalization. At 72 h after transfection, cells were treated with vehicle (Vector) or TGF-β1 (5 ng/ml) for 24 h followed by the addition of the PPAR-β/δ agonist GW0742 (10 μM, β) combined with the PPAR-γ agonist rosiglitazone (10 μM, γ) or vehicle for another 24 h. Cells were lysed and collected for dual luciferase activity measurements. E Ligand activation of PPAR-β/δ together with PPAR-γ strongly decreased the release of collagen produced by TGF-β1-stimulation in control and IPF fibroblasts. Culture media were collected and extracellular collagen was analyzed using Sircol assay. F Combined activation of PPAR-β/δ and PPAR-γ decreased TGF-β1-stimulated release of collagen by control and IPF fibroblasts—this effect was blocked using the respective antagonists. Cells were serum-starved for 3 h, stimulated with vehicle (Control) or TGF-β1 (5 ng/ml) for 24 h, followed by the addition of the PPAR-β/δ agonist GW0742 (10 μM, β) and PPAR-γ agonist rosiglitazone (10 μM, γ) either combined with vehicle or the PPAR-β/δ antagonist GSK0660 (10 nM, β ant) and PPAR-γ antagonist GW9662 (10 μM, γ ant) for another 24 h. Culture media were collected and extracellular collagen was analyzed by Sircol assay

PPAR-β/δ triggers anti-fibrotic responses by activating MMP-1 in control and IPF fibroblasts

Extracellular collagen is degraded by proteinases, e.g. MMPs. The mRNA levels of selected MMPs in control fibroblasts at basal condition (without treatment) were measured, showing the highest value for MMP1 in comparison to the lower mRNA values for MMP2 , MMP3 , MMP10 , and MMP16 (Fig.  4 A). Interestingly, the mRNA level of MMP7 which is associated with disease severity [ 28 ] was below detectable levels in our samples of control and IPF fibroblasts (ct values > 35). Comparing the mRNA levels between control and IPF fibroblasts, no differences were observed in the case of MMP1 and MMP16 (Fig.  4 B, F), but higher levels were found for MMP2 , MMP3 and MMP10 (Fig.  4 C–E). Individual mRNA values for MMP1 , but also for MMP3 and MMP10 , varied strongly within the IPF sample group (Fig.  4 B, D, E). Due to the much higher mRNA levels for MMP1 compared to the other MMPs (Fig.  4 A), we analyzed MMP-1 protein as the dominant enzyme for collagen degradation in subsequent experiments. As expected, the protein level of active MMP-1 was reduced by TGF-β1 and restored in the presence of PPAR-β/δ agonist alone or in combination with PPAR-α or PPAR-γ agonists (Fig.  4 G). This suggests that PPAR-β/δ might be a key regulator of the protein level of active MMP-1. Therefore, we analyzed the effect of the PPAR-β/δ agonist in TGF-β1-stimulated fibroblasts at the mRNA levels of all detectable MMPs . The mRNA levels of MMP1 in IPF fibroblast were increased (> fivefold) by the PPAR-β/δ agonist in comparison to TGF-β1 stimulation alone (Fig.  4 H). The MMP16 mRNA levels were elevated > fivefold in both types of fibroblasts and that of MMP10 about threefold in control fibroblasts only (Additional file: Fig. S3). To explore the anti-fibrotic potential of increased levels of MMP s , we used a broad-spectrum inhibitor for MMPs, primarily influencing the amount of extracellular collagen. Simultaneous treatment with the MMP inhibitor and PPAR-β/δ agonist after TGF-β1 stimulation increased extracellular collagen in the culture media released by control fibroblasts, but not in the case of IPF fibroblasts (Fig.  4 I). Since the MMP inhibitor only partly blocked the effect of the PPAR-β/δ agonist, we speculate that activated PPAR-β/δ also regulates other proteins involved in fibrosis attenuation.

PPAR-β/δ triggers anti-fibrotic responses by activating MMP-1 in control and IPF fibroblasts. A The transcript of MMP1 is the highest among the different MMPs in control fibroblasts. Analysis of MMP1, MMP2, MMP3, MMP10 and MMP16 of control fibroblasts was done using isolated total RNA and RT-qPCR with HPRT1 as reference gene. B – F Comparative gene expression profile of MMPs was done by RT-qPCR with HPRT1 as reference gene. G PPAR-β/δ attenuated TGF-β1-induced decrease in the amount of active MMP-1. Control and IPF fibroblasts were serum-starved for 3 h, treated with vehicle or TGF-β1 (5 ng/ml) for 24 h, followed by the addition of the PPAR-α agonist WY14643 (100 μM, α), PPAR-β/δ agonist GW0742 (10 μM, β), and PPAR-γ agonist rosiglitazone (10 μM, γ) as well as various combinations thereof for another 24 h. Cell lysates were used to detect active MMP-1 by Western blot analysis using β-actin (β-ACTIN) as reference protein. H Ligand activation of PPAR-β/δ strongly increased the mRNA level of MMP1 in TGF-β1-treated control and IPF fibroblasts. Cells were serum-starved, treated with vehicle (Control) or TGF-β1 (5 ng/ml) for 24 h followed by the addition of the PPAR-β/δ agonist GW0742 (10 μM, β) or vehicle for another 24 h. The mRNA levels were measured by RT-qPCR with HPRT1 as reference gene. I Inhibition of MMPs increased TGF-β1-induced release of collagen. Control and IPF fibroblasts were serum-starved for 3 h, treated with vehicle or TGF-β1 (5 ng/ml) for 24 h, followed by the addition of the PPAR-β/δ agonist GW0742 (10 μM, β) and MMP inhibitor (MMP inh., 4-aminobenzoyl-Gly-Pro-D-Leu-D-Ala hydroxamic acid, 20 μM) for another 24 h. The release of collagen into the culture media was measured by Sircol assay

Activation of PPAR-β/δ and PPAR-γ in TGF-β1-treated fibroblasts increased peroxisomal biogenesis and lipid metabolism, and the inhibited fibrotic response

Previously, we showed that pretreatment with PPAR-α agonists could inhibit fibrosis phenotypes [ 13 , 14 ]. In the present study, we treated control and IPF fibroblasts with TGF-β1 before the addition of agonists of all three PPARs, an experimental setup that more accurately recapitulates the clinical setting. We first investigated the mRNA levels of several peroxisomal genes involved in the organelle biogenesis ( PEX13, PEX14 ), plasmalogen synthesis ( AGPS, GNPAT ), and fatty acid β-oxidation ( ACOX1, ACAA1 ) in control and IPF fibroblasts. The mRNA levels of PEX13 , ACOX1 and AGPS were higher in IPF compared to control fibroblasts, whereas those of PEX14, ACAA1 and GNPAT were not significantly different (Additional file: Fig. S4A–F). Next, we stimulated peroxisomal proliferation with different PPAR agonists (alone or in combination) in TGF-β1-treated control and IPF fibroblasts. Combined activation of PPAR-β/δ and PPAR-γ increased mRNA (Additional file: Fig. S4G) and protein levels (Fig.  5 A) of PEX13 in TGF-β1-stimulated control and IPF fibroblasts compared to TGF-β1 treatment only. Since the combined activation of PPAR-β/δ and PPAR-γ reversed the TGF-β1-induced trans-differentiation of fibroblasts into myofibroblasts (as indicated by changes in the level of α-SMA, Fig.  3 A–C), decreased the protein level of COL1 (Fig.  3 A–C) and increased PEX13 (Fig.  5 A), we focused on these two PPAR agonists in the following experiments. First, the intracellular lipidomic profile was assessed in control and IPF fibroblasts to ascertain possible differences in the lipid metabolism under basal conditions and after treatments with TGF-β1 alone and PPAR-β/δ and PPAR-γ agonists. In total, 1003 lipid ion species covering 5 major lipid categories (glycerophospholipids, sphingolipids, glycerolipids, fatty acyls, and sterols) belonging to 22 lipid classes were identified based on high mass accuracy (5 ppm) and their fragmentation patterns (Additional file: Fig. S5A). Basal levels of all classes of lipids analyzed were lower in IPF fibroblasts except for the triglycerides (TG; Fig.  5 B). TGF-β1 decreased the levels of phosphatidylcholine (PC), phosphatidylethanolamine (PE), sphingomyelin (SM) and TG in IPF fibroblasts. The levels of PC, SM and TG were partially restored by a post-treatment with PPAR-β/δ and PPAR-γ agonists (Fig.  5 B). Furthermore, activation of PPAR-β/δ and PPAR-γ strongly increased the synthesis of peroxisome-derived AA, DHA, and EPA (Fig.  5 C), which are all endogenous activators of PPARs. In the absence of TGF-β1, PPAR agonists either increased or decreased the levels of PC in control and IPF fibroblasts (Additional file: Fig. S5B) and increased the levels of AA, DHA and EPA with PPAR-γ exhibiting the strongest effect on DHA (Additional file: Fig. S5C). This suggests that, the PPAR-γ agonist was the driving factor for the increase and release of AA, DHA and EPA in fibroblasts treated with TGF-β1 followed by combined PPAR-β/δ and PPAR-γ agonists treatment (Fig.  5 C). Collectively, activation of PPAR-β/δ and PPAR-γ potentially regulates the fibrosis phenotype by modulating peroxisomal lipid metabolism, but differently in control and IPF fibroblasts.

Activation of PPAR-β/δ and PPAR-γ in TGF-β1-treated fibroblasts increased peroxisomal biogenesis and lipid metabolism. A - C Control and IPF fibroblasts were serum-starved for 3 h, treated with vehicle or TGF-β1 (5 ng/ml) for 24 h, followed by the addition of the PPAR-α agonist WY14643 (100 μM, α; A ), PPAR-β/δ agonist GW0742 (10 μM, β; A – C ), and PPAR-γ agonist rosiglitazone (10 μM, γ; A-C ) as well as various combinations thereof for another 24 h. A Activation of PPAR-β/δ and PPAR-γ reversed TGF-β1-induced decrease in the protein levels of the peroxisomal biogenesis protein PEX13. Cell lysates were used for Western blot analysis of PEX13 using GAPDH as reference protein. B Heatmap of the lipidomic profile of control and IPF fibroblasts. Cells were collected in PBS for lipid analysis using LC–MS/MS. C Activation of PPAR-β/δ and PPAR-γ increased the synthesis of endogenous activators of these receptors in line with a positive feedback loop. Fibroblasts from control and IPF patients were serum-starved for 3 h, treated with vehicle (Control) or TGF-β1 (5 ng/ml) for 24 h, followed by the addition of vehicle or the PPAR-β/δ agonist GW0742 (10 μM, β) combined with the PPAR-γ agonist rosiglitazone (10 μM, γ) for another 24 h. The releases of AA, DHA, and EPA were analyzed in the culture media by LC–MS/MS

Activation of PPAR-β/δ in combination with PPAR-γ restored TGF-β1-induced decrease in catalase mRNA and protein levels

Though not significant, TGF-β1 decreased CAT mRNA level in control and IPF fibroblasts, which was restored by the combined activation of PPAR-β/δ and PPAR-γ (Additional file: Fig. S4G). We therefore speculated that this anti-oxidative enzyme might be involved in regulation of fibrogenesis. We first analyzed catalase and glutathione peroxidase (GPX)1/2 in human lung tissue samples. The protein level of catalase was markedly decreased in alveolar epithelial type II cells in the lungs of IPF compared to control patients (Fig.  6 A), whereas that of GPX1/2 was increased (Fig.  6 B), probably to compensate catalase deficiency. Moreover, we detected a gradual decrease in catalase protein level in mouse lungs after bleomycin-induced fibrosis, remarkably from day 14 after treatment (Additional file: Fig. S6A). When we analyzed the fibroblasts from control and IPF patients, we found no differences in the mRNA levels of CAT and GPX1/2 (Additional file: Fig. S6B, C). Protein level of catalase was lower in IPF compared to control fibroblasts (isolated from 5 patients each, Fig.  6 C, Table  1 ). Apart from catalase and GPX1/2, peroxiredoxins (PRDXs) were measured as they also support the anti-oxidant defense system. The mRNA levels of different peroxiredoxin family members varied strongly (Additional file: Fig. S6D) with PRDX6 showing the highest and PRXD2 and PRXD3 the lowest gene expression levels. Only the mRNA levels of PRDX4 and PRDX6 were significantly higher in IPF compared to control fibroblasts (Additional file: Fig. S6E–J). To confirm the regulatory effects of TGF-β1 on catalase, we treated control and IPF fibroblasts with TGF-β1 at various concentrations. Increasing concentrations of TGF-β1 gradually decreased the protein level of catalase in both fibroblast groups (Fig.  6 D). Catalase activity was reduced by TGF-β1 in control and IPF fibroblasts, but not in the same manner since IPF fibroblasts were less sensitive towards lower concentrations of TGF-β1 (2.5 and 5 ng/ml; Fig.  6 E). Activation of PPAR-γ increased the protein level of catalase in the absence of TGF-β1 (Additional file: Fig. S6K) and reversed the TGF-β1-induced decrease in catalase in control fibroblasts (Fig.  6 F). The level of catalase increased in both groups when PPAR-β/δ and PPAR-γ were activated 24 h after TGF-β1 treatment (Fig.  6 F), but not when added together with TGF-β1 (Fig.  6 G).

TGF-β1 caused a decrease in catalase mRNA and protein levels. A , B The immunoreactivity of catalase was lower, and that of GPX1/2 higher in IPF (right) compared to control (left) lung tissues. Immunofluorescence staining was performed using antibodies to detect catalase ( A , red) and GPX1/2 ( B , red) and DAPI to counterstain nuclei. C The protein level of catalase is lower in IPF than in control fibroblasts. Cell lysates of fibroblasts from 5 control and 5 IPF patients were used for Western blot analysis of catalase (CAT) with β-actin (β-ACTIN) as reference protein. D TGF-β1 decreased catalase protein levels in control and IPF fibroblasts. Cells were serum-starved for 3 h, and treated with various concentrations of TGF-β1 or vehicle for 48 h. Cell lysates were used for Western blot analysis of catalase with GAPDH as reference protein. E – G Activation of PPAR-β/δ in combination with PPAR-γ restored TGF-β1-induced decrease in catalase protein levels and activity. E TGF-β1 decreased catalase activity in control and IPF fibroblasts. Cells were serum-starved for 3 h, and treated with vehicle (Control) or various concentrations of TGF-β1 for 12 h. Cell lysates were used for measuring catalase activity. F , G Activation of PPAR-β/δ in combination with PPAR-γ inhibited TGF-β1-induced decrease in catalase protein levels in control and IPF fibroblasts. Cells were serum-starved for 3 h, stimulated with vehicle ( F , G ) or TGF-β1 (5 ng/ml, F , G ) or for 24 h, followed by the addition of the PPAR-β/δ agonist GW0742 (10 μM, β) and the PPAR-γ agonist rosiglitazone (10 μM, γ) for another 24 h ( F ). In ( G ), the PPAR agonists were added together with TGF-β1 for 48 h. Cell lysates were used to detect catalase (CAT) by Western blot analysis using α-tubulin (α-TUB) as reference protein

Catalase contributes to collagen reduction in pulmonary fibrosis

To confirm the anti-fibrotic role of catalase in IPF, we intended to generate stable catalase-deficient fibroblast cell lines by RNAi using two independent shRNAs against catalase (CAT sh1 RNA and CAT sh2 RNA). Knockdown efficiency of catalase was high and stable in control fibroblasts, whereas IPF fibroblasts died after a few passages probably because the catalase protein level was already low prior to shRNA transduction (see Fig.  6 C) and a further decrease in this protein was detrimental. Successful reduction of catalase is shown on the protein (Fig.  7 A) and activity (Fig.  7 B) levels, resulting in an increase in H 2 O 2 concentration (Fig.  7 C). The decrease in catalase protein in control fibroblasts expressing either of the two independent catalase shRNAs was accompanied with increased extracellular collagen (Fig.  7 D) and intracellular COL1 (Fig.  7 A) levels. Using siRNA technology, a transient catalase knockdown was achieved in control and IPF fibroblasts (Additional file: Fig. S7A). In IPF fibroblasts, we detected higher levels of collagen released into the culture medium compared to those transfected with scrambled control siRNA (Additional file: Fig. S7B). Moreover, catalase overexpression in control and IPF fibroblasts decreased COL1 and α-SMA protein levels even after TGF-β1 stimulation (Fig.  7 E). Lastly, we analyzed whether the reduction in collagen synthesis by activation of PPAR-β/δ and PPAR-γ depends on catalase activity. In both fibroblast cell lines, the reduction in collagen by the PPAR-γ agonist, but not by PPAR-β/δ was reversed in the presence of 3-amino-1,2,4-triazole (AT, Fig.  7 F, lane 5 versus lanes 7 and 8). Interestingly, AT inhibited the beneficial effect of a combined activation of PPAR-β/δ and PPAR-γ in control, but not in IPF fibroblasts (Fig.  7 F, lane 5 versus lane 6). We suggest that during TGF-β1 treatment either the protein level, sensitivity or signaling of PPAR-β/δ dominates in IPF and that of PPAR-γ in control fibroblasts with regard to catalase protein content and its activity.

Catalase contributes to collagen reduction in pulmonary fibrosis. A , B Stable knockdown of catalase decreased catalase protein and activity. Cell lines transfected with catalase shRNA (CAT sh1, CAT sh2) were serum-starved for 3 h. Cell lysates were used for measuring catalase (CAT), COL1 and α-SMA protein levels by Western blot analysis using GAPDH as reference protein ( A ) and catalase activity by catalase activity assay kit ( B ). C , D Stable knockdown of catalase increased the cellular H 2 O 2 production and extracellular collagen levels. Culture media from catalase-deficient (CAT sh1, CAT sh2) and mock-transfected (CAT sc) control fibroblasts were used to detect the release of H 2 O 2 using the hydrogen peroxide assay ( C ) and of extracellular collagen by Sircol assay ( D ). E Overexpression of catalase decreased the protein level of COL1 in control and IPF fibroblasts under basal condition (no treatment) and after TGF-β1 treatment. Control and IPF fibroblasts were transfected with pGL 4.14-Catalase (CAT overexpr.) or a mock vector for 48 h, followed by the addition of vehicle or TGF-β1 (5 ng/ml) for another 48 h. Cell lysates were analyzed for catalase (CAT), α-SMA, and COL1 protein levels by Western blot analysis using GAPDH as reference protein. F The catalase activity inhibitor AT does not increase COL1 in control and IPF fibroblasts. Cells were serum-starved for 3 h, treated with vehicle or TGF-β1 (5 ng/ml) or for 24 h, followed by the addition of the PPAR-β/δ agonist GW0742 (10 μM, β), the PPAR-γ agonist rosiglitazone (10 μM, γ) and AT (25 µM) as well as various combinations thereof for another 24 h. Cell lysates were used to analyze catalase (CAT), COL1, and α-SMA protein levels by Western blot analysis using GAPDH as reference protein

In the present study, cultured human lung fibroblasts were treated with TGF-β1 to mimic fibrosis and were then analyzed to evaluate the role of PPARs during disease progression. Human lung tissue samples from control and IPF patients (Figs. 1 , 6 ) were used in parallel. Traditional animal models of experimental lung fibrosis were carried out by radiation or intratracheal administration of asbestosis fibers and silica, but the latter two induce rather asbestosis and silicosis than fibrosis [ 38 ]. Since high levels of TGF-β1 were shown to initiate and support fibrosis [ 35 , 36 ], a rat model of adenoviral overexpression of TGF-β1 has been established, however, the adenovirus vector itself already induced fibrosis [ 38 , 39 ]. Most commonly, mice were treated with bleomycin which induced a rapid fibrosis within 2–4 weeks via intra-tracheal instillation or 4–12 weeks by systemic administration [ 38 ]. The injury first triggers an inflammatory response which leads to wound healing. The infiltrating immune cells produce pro-fibrotic cytokines, e.g. TGF-β1, which stimulates fibroblast-to-myofibroblast transition. A dysregulated wound healing process could moreover lead to excessive deposition of ECM and finally resulting in fibrosis. However, this mouse model does not represent all aspects of the histopathological phenotype of the disease as observed in humans, for example, honeycomb pattern, thick scars at the alveolar region and fibroblastic foci [ 40 , 41 , 42 ], probably because these features take time to develop in humans. In addition, bleomycin-induced fibrosis is often reversible and contains a strong inflammatory component in the beginning which is not true for the disease in humans [ 38 ].

To mimic fibrosis in vitro, pro-fibrotic cytokines were added to cultured lung fibroblasts such as platelet-derived growth factor, connective tissue growth factor, interleukin-1β, tumor necrosis factor-α (TNF-α) and TGF-β1 [ 43 ]. Interleukin-1β and growth factors induced a marked inflammation and fibrosis with aberrant wound healing, TNF-α induced a strong inflammation and mild fibrosis, and TGF-β1 solely caused minor inflammation together with a marked fibrosis. Thus, TGF-β1-induced changes reflected the pathogenesis found in human IPF patients and was therefore used in our experiments. In vitro models, as an advantage, allow drug treatments to block TGF-β1-induced fibrosis signaling pathways and cell transfection to knockdown proteins of interest, which is difficult to establish in vivo. On the other hand, analysis of cultured lung fibroblasts neglects the in vivo situation where they interact with themselves and other cell types such as alveolar epithelial cells type I and type II, endothelial cells and macrophages. Interestingly, alveolar epithelial type II cells restrict the number of fibroblasts [ 44 ], and thus, control fibroblasts in vitro (and in the absence of alveolar epithelial type II cells) might re-start proliferation together with an increased collagen synthesis reaching similar levels as found in IPF fibroblasts. Moreover, TGF-β1 in IPF is mainly produced by macrophages [ 45 ]. Therefore, TGF-β1 (at least 5 ng/ml) had to be added to induce fibrosis in cultures of pure fibroblasts (which secrete 0.15 ng/ml TGF-β1, Fig.  1 C). In this study, tissues and an in vitro model established with fibroblasts from control and IPF patients were used in parallel.

To study the pathophysiology of lung fibrosis, we measured the two fibrosis markers associated with IPF such as collagen [ 46 , 47 , 48 ], and α-SMA, although the latter has been currently debated as a sole marker for studying fibrosis [ 49 ] as its expression doesn´t mean that a cell produces high amounts of collagen [ 50 ]. Interestingly, IPF is characterized by excessive accumulation of collagen-rich ECM produced by activated fibroblasts and myofibroblasts [ 51 , 52 ]; thus the degree of fibrosis is strongly dependent on their number and proliferation. Our data showed that fibroblasts from control and IPF patients were not different with regard to (1) the intracellular level of α-SMA and ω-fatty acids such as AA, DHA and EPA; (2) the release of collagen into the extracellular space; (3) the activity of collagen-degrading enzyme MMP-1; and (4) cell proliferation rate under basal conditions. Instead, fibroblasts from IPF compared to control patients showed significantly lower protein levels of PEX13, catalase, and of the TGFBR1 and are thus less sensitive towards TGF-β1. They secrete less active TGF-β1 into the culture medium. Contrarily, higher protein levels were found in IPF compared to control fibroblasts for intracellular GPX1/2 and PPAR-α. For IPF, the number and proliferation of fibroblasts/myofibroblasts are directly and the level of catalase indirectly related to the disease progression. Nonetheless, individual fibroblasts from control and IPF patients differ strongly even within the group (Figs. 1 D, 6 C , Additional file: Fig. S1A–C). This phenomenon might probably be due to the recently reported spatial heterogeneity of fibroblasts in fibrotic foci containing multiple subtypes such as lipofibroblasts, myofibroblasts, EBF1 + fibroblasts, intermediate fibroblasts, and mesothelial cells, all expressing different amounts of collagen under healthy conditions and during IPF progression [ 50 ]. In addition, the patients differ either with regard to the disease (acute exacerbation versus chronic stages, slow versus rapid decline of lung function), to co-morbidities (hypertension, viral infection, chronic aspiration of gastric content) or to other trigger factors such as age (age-related mitochondrial and peroxisomal dysfunction leading to oxidative stress), environmental exposures, smoking, and genetic factors [ 53 ]. Interestingly, differences between patients in our experiments were mainly observed for protein levels of PPAR-α (Fig.  1 D), PPAR-γ (Fig.  1 D), MMP-1 (Additional file: Fig. S1C) and catalase (Fig.  6 C), whereas the protein levels of PPAR-β/δ (Fig.  1 D), catalase activity (Fig.  6 E), the level of intracellular and secreted collagen with and without TGF-β1 (Figs.  1 B,   2 B–D, Additional file: Fig. S1D) as well as the collagen-reducing effect of a combined treatment with PPAR-β/δ and PPAR-γ agonists (Fig.  3 A–F) were less variable. This gives hope that the observed beneficial effect of PPAR-β/δ and PPAR-γ agonists is applicable to a broad spectrum of IPF patients. However, the strong heterogeneity of the target, namely the fibroblasts of IPF, but also of control patients, will limit the global use of any drug for IPF. Clinical trials discriminating between different subsets of patients may help to find the right drug in this regard.

We demonstrated that among the three PPARs, PPAR-β/δ might be a strong target for lung fibrosis resolution compared to PPAR-α (minor effect) and PPAR-γ (additive effect with PPAR-β/δ under these experimental conditions, Table  2 ). Focusing first on fibrosis pathways, we detected no differences between control and IPF fibroblasts with regard to the synthesis and release of collagen as well as gene expression and activity of MMP-1 (the dominant MMP, Fig.  4 A) either when treated or untreated with TGF-β1, and PPAR-β and PPAR-γ agonists . However, MMPs differ between the diverse lung cell types such as alveolar epithelial type I and type II cells, alveolar macrophages and endothelial cells [ 54 , 55 ]. In addition, MMP-1, -2, -3, -7, -13, -14, and -19, exhibit either anti- or pro-fibrotic [ 28 ] activities. MMP-2, as an example for the latter one, cleaves elastin which is deleterious for the lung. Interestingly, PPAR-β stimulation decreased the secretion of MMP-2 and increased the elastin level in human skin fibroblasts [ 56 ].

Next, we observed a TGF-β1-induced decrease in the peroxisomal biogenesis protein PEX13 which is reversed by stimulation of PPAR-γ. This was accompanied by changes in peroxisomal lipid metabolism, e.g. TGF-β1 increased the level of phosphatidylcholine in control, but decreased it in IPF fibroblasts with no additional effects of the PPAR drugs. The levels of AA, DHA and EPA were not significantly changed by TGF-β1, but increased strongly upon treatment with the PPAR-γ agonist. Metabolites from AA oxidation have been described to mediate inflammatory responses, and DHA is known to be anti-inflammatory [ 57 , 58 ]. A balance between the fatty acids will essentially determine the direction of the drug interventions. The production of DHA was more than that of AA in control and IPF fibroblasts following PPAR-γ activation, whereas the activation of PPAR-β/δ increased levels of AA to a higher extent compared to DHA in control and IPF fibroblasts. However, the strong anti-fibrotic effects of PPAR-β/δ support the combined activation of both receptors during treatments. Thus, with regard to peroxisomes, PPAR-β/δ and PPAR-γ agonists increased the peroxisomal biogenesis protein PEX13, as well as peroxisome lipid metabolism, and the resulting metabolites may further activate PPARs, establishing a positive activation loop [ 59 , 60 ].

Furthermore, the TGF-β1-induced decrease in the protein level and activity of catalase was reversed upon stimulation of PPAR-γ and PPAR-β/δ. Interestingly, in control fibroblasts the anti-fibrotic effect is mediated mainly via the maintenance of catalase protein through a reactive oxygen species (ROS)-dependent stimulation of PPAR-γ, because the effect is blocked by the specific catalase inhibitor AT in the combined treatment group by sustaining catalase levels. In IPF fibroblasts, the anti-fibrotic effect is mainly caused by a combined activation of PPAR-β/δ and PPAR-γ. The collagen-reducing effect is not inhibited by AT and thus ROS-independent. A decreased catalase level has been found in lung homogenates (and especially in the bronchial epithelium) of patients with IPF [ 61 ]. In acatalasemic mice, bleomycin induced a much higher invasion of pro-inflammatory cells together with increased levels of TGF-β1 and collagen and thus a higher degree of fibrosis [ 29 ], suggesting a beneficial role of high catalase levels in IPF disease progression. Interestingly, catalase (low affinity, high turnover) together with PRDX1 and PRDX5 (high affinity, low turnover), breakdown H 2 O 2 generated by multiple pathways inside peroxisomes. While catalase is crucial for safeguarding the organelle at excessive H 2 O 2 , PRDX1 and PRDX5 function as a redox-regulator in cell signaling and H 2 O 2 redox relay factor at low levels of H 2 O 2 , respectively [ 62 ]. In addition, catalase impedes ROS-induced inhibition of peroxisomal β-oxidation including the synthesis of the anti-inflammatory DHA [ 61 ]. With regard to PPARs, the catalase gene promotor region contains PPRE binding sites, e.g. for PPAR-γ (located at nucleotides − 1027 to − 1014; [ 63 ]) and an additional PPAR-γ binding site in humans only (located at nucleotides − 11,710 to − 11,698, [ 64 ]). Activation of PPAR-γ [ 23 ], but also of PPAR-β/δ (at the direct repeat 1 response element, [ 65 ]) increased catalase protein levels [ 65 , 66 ]. We assume that the observed increase in catalase protein in our experiments by PPAR-β/δ and PPAR-γ was similarly due to an induction of the catalase promotor activity. The additive effect by the combined treatment with PPAR-β/δ and PPAR-γ ligands in IPF fibroblasts suggests an importance of the additional human-specific PPRE binding sites and demonstrates that human models are required to analyze the role of PPARs in fibrosis.

We would like to emphasize that in contrast to most of the previous publications we performed a post-treatment (to mimic the clinical situation) with a combination of PPAR-β/δ and PPAR-γ agonists to reverse the TGF-β1-induced fibrotic phenotype of IPF fibroblasts. It is well known that activated PPAR-γ alone is potentially anti-fibrotic [ 17 , 18 , 19 , 20 ]. With regard to PPAR-β/δ, to the best of our knowledge, only one review described an inhibition of the proliferation of normal human lung fibroblasts by its stimulation [ 26 ]. The question arises how an activation of PPAR-β/δ can support PPAR-γ or vice-versa. One possibility is that stimulation of one PPAR might increase the protein level of itself and of the other receptors. For example, agonists for PPAR-α and PPAR-β/δ, but not PPAR-γ, have been shown to increase the protein levels of PPAR-β/δ and PPAR-γ in osteoblasts [ 37 ]. Thus, especially PPAR-β/δ stimulation can end up in a positive activation loop as it increased its own as well as the PPAR-γ receptor [ 60 ]. This offers the possibility for a post-treatment schedule starting with the PPAR-β/δ agonist to increase PPAR-γ levels so that the later given PPAR-γ agonist can work more efficiently. Interestingly, after 48 h treatment with TGF-β1, we observed increases in the protein levels of PPAR-γ and PPAR-β/δ in control and IPF fibroblasts although with varying degrees (Fig.  2 E, Table  1 ). This might explain why the post-treatment with PPAR-β/δ and PPAR-γ agonists is even more beneficial than direct treatment. Moreover, we demonstrated that the test compound STK 648389 (ZINC ID: 31,775,965), which has been suggested to be a dual PPAR-β/δ/PPAR-γ agonist by structure-based virtual screening [ 67 ], did not elicit anti-fibrotic effects (Additional file: Fig. S2). We hypothesized that the dual agonist (which is a single molecule) might be less specific for both receptors than the respective individual agonists and must be applied at a higher concentration which could induce more side effects in lung fibroblasts. Indeed, luciferase transactivation assays have shown EC50 values of 132 µM for PPAR-β/δ and 18 µM for PPAR-γ [ 67 ], and thus STK 648389 activated PPAR-γ only (see Fig.  3 E showing no reduction of the extracellular collagen using 10 µM of the specific PPARγ agonist troglitazone).

In summary, combined activation of PPAR-β/δ and PPAR-γ exerts strong anti-fibrotic effects. Catalase, which is decreased during treatment with TGF-β1, is inverse proportionally involved in collagen production. Catalase protein level and activity can be increased by stimulation of PPAR-β/δ and PPAR-γ in control and IPF human lung fibroblasts. For IPF patients (to refer to the clinical situation), the most beneficial anti-fibrotic effects could possibly be achieved by a combined local treatment with PPAR-β/δ and PPAR-γ agonists via aerosol inhalation.

Availability of data and materials

Raw data of the lipid analyses are available upon request to the corresponding author.

Abbreviations

α-Smooth muscle actin

Arachidonic acid

3-Amino-1,2,4-triazole

Collagen type 1

Dulbecco’s Modified Eagle Medium

Docosahexaenoic acid

Extracellular matrix

Eicosapentaenoic acid

Glutathione peroxidase 1/2

Horse radish peroxidase

• Idiopathic pulmonary fibrosis

Liquid chromatography tandem mass spectrometry

Matrix metalloproteinase

Methyl- tert -butyl ether

Phosphatidylcholine

Phosphatidylethanolamine

Peroxisomal biogenesis protein, peroxin

Peroxisome proliferator-activated receptor

Peroxiredoxin

PPAR response element

Reactive oxygen species

Quantitative reverse transcription polymerase chain reaction

Sphingomyelin

Solid phase extraction

Triglycerides

Transforming growth factor-beta 1

Transforming growth factor-beta receptor 1

Tumor necrosis factor-α

Maher TM. Interstitial lung disease: a review. JAMA. 2024;331:1655–65. https://doi.org/10.1001/jama.2024.3669 .

Article   PubMed   CAS   Google Scholar  

Cheresh P, Kim SJ, Tulasiram S, Kamp DW. Oxidative stress and pulmonary fibrosis. Biochim Biophys Acta. 2013;1832:1028–40. https://doi.org/10.1016/j.bbadis.2012.11.021 .

Richeldi L, du Bois RM, Raghu G, Azuma A, Brown KK, Costabel U, Cottin V, Flaherty KR, Hansell DM, Inoue Y, Kim DS, Kolb M, Nicholson AG, Noble PW, Selman M, Taniguchi H, Brun M, Le Maulf F, Girard M, Stowasser S, Schlenker-Herceg R, Disse B, Collard HR, INPULSIS Trial Investigators. Efficacy and safety of nintedanib in idiopathic pulmonary fibrosis. N Engl J Med. 2014;370:2071–82. https://doi.org/10.1056/NEJMoa1402584 .

Raghu G, Remy-Jardin M, Richeldi L, Thomson CC, Inoue Y, Johkoh T, Kreuter M, Lynch DA, Maher TM, Martinez FJ, Molina-Molina M, Myers JL, Nicholson AG, Ryerson CJ, Strek ME, Troy LK, Wijsenbeek M, Mammen MJ, Hossain T, Bissell BD, Herman DD, Hon SM, Kheir F, Khor YH, Macrea M, Antoniou KM, Bouros D, Buendia-Roldan I, Caro F, Crestani B, Ho L, Morisset J, Olson AL, Podolanczuk A, Poletti V, Selman M, Ewing T, Jones S, Knight SL, Ghazipura M, Wilson KC. Idiopathic pulmonary fibrosis (an update) and progressive pulmonary fibrosis in adults: an official ATS/ERS/JRS/ALAT clinical practice guideline. Am J Respir Crit Care Med. 2022;205:e18–47. https://doi.org/10.1164/rccm.202202-0399ST .

Article   PubMed   PubMed Central   Google Scholar  

King TE Jr, Bradford WZ, Castro-Bernardini S, Fagan EA, Glaspole I, Glassberg MK, Gorina E, Hopkins PM, Kardatzke D, Lancaster L, Lederer DJ, Nathan SD, Pereira CA, Sahn SA, Sussman R, Swigris JJ, Noble PW, ASCEND Study Group. A phase 3 trial of pirfenidone in patients with idiopathic pulmonary fibrosis. N Engl J Med. 2014;370:2083–92. https://doi.org/10.1056/NEJMoa1402582 .

Sofia C, Comes A, Sgalla G, Richeldi L. Promising advances in treatments for the management of idiopathic pulmonary fibrosis. Expert Opin Pharmacother. 2024;25:717–25. https://doi.org/10.1080/14656566.2024.2354460 .

Bonella F, Spagnolo P, Ryerson C. Current and future treatment landscape for idiopathic pulmonary fibrosis. Drugs. 2023;83:1581–93. https://doi.org/10.1007/s40265-023-01950-0 .

Richeldi L, Azuma A, Cottin V, Hesslinger C, Stowasser S, Valenzuela C, Wijsenbeek MS, Zoz DF, Voss F, Maher TM, 1305-0013 Trial Investigators. Trial of a preferential phosphodiesterase 4B inhibitor for idiopathic pulmonary fibrosis. N Engl J Med. 2022;386:2178–87. https://doi.org/10.1056/NEJMoa2201737 .

Waxman A, Restrepo-Jaramillo R, Thenappan T, Engel P, Bajwa A, Ravichandran A, Feldman J, Hajari Case A, Argula RG, Tapson V, Smith P, Deng C, Shen E, Nathan SD. Long-term inhaled treprostinil for pulmonary hypertension due to interstitial lung disease: INCREASE open-label extension study. Eur Respir J. 2023;61:2202414. https://doi.org/10.1183/13993003.02414-2022 .

Article   PubMed   PubMed Central   CAS   Google Scholar  

Nathan SD, Behr J, Cottin V, Lancaster L, Smith P, Deng CQ, Pearce N, Bell H, Peterson L, Flaherty KR. Study design and rationale for the TETON phase 3, randomised, controlled clinical trials of inhaled treprostinil in the treatment of idiopathic pulmonary fibrosis. BMJ Open Respir Res. 2022;9: e001310. https://doi.org/10.1136/bmjresp-2022-001310 .

Toyama T, Nakamura H, Harano Y, Yamauchi N, Morita A, Kirishima T, Minami M, Itoh Y, Okanoue T. PPARalpha ligands activate antioxidant enzymes and suppress hepatic fibrosis in rats. Biochem Biophys Res Commun. 2004;324:697–704. https://doi.org/10.1016/j.bbrc.2004.09.110 .

Ogata T, Miyauchi T, Sakai S, Irukayama-Tomobe Y, Goto K, Yamaguchi I. Stimulation of peroxisome-proliferator-activated receptor alpha (PPAR alpha) attenuates cardiac fibrosis and endothelin-1 production in pressure-overloaded rat hearts. Clin Sci (Lond). 2002;103:S284–8. https://doi.org/10.1042/CS103S284S .

Article   Google Scholar  

Oruqaj G, Karnati S, Vijayan V, Kotarkonda LK, Boateng E, Zhang W, Ruppert C, Günther A, Shi W, Baumgart-Vogt E. Compromised peroxisomes in idiopathic pulmonary fibrosis, a vicious cycle inducing a higher fibrotic response via TGF-beta signaling. Proc Natl Acad Sci USA. 2015;112:2048–57. https://doi.org/10.1073/pnas.1415111112 .

Article   CAS   Google Scholar  

Oruqaj G, Karnati S, Kotarkonda LK, Boateng E, Bartkuhn M, Zhang W, Ruppert C, Günther A, Bartholin L, Shi W, Baumgart-Vogt E. Transforming growth factor-b1 regulates peroxisomal genes/proteins via Smad signaling in idiopathic pulmonary fibrosis fibroblasts and transgenic mouse models. Am J Pathol. 2023;193:259–74. https://doi.org/10.1016/j.ajpath.2022.11.006 .

Foreman JE, Sharma AK, Amin S, Gonzalez FJ, Peters JM. Ligand activation of peroxisome proliferator-activated receptor-beta/delta (PPARbeta/delta) inhibits cell growth in a mouse mammary gland cancer cell line. Cancer Lett. 2010;288:219–25. https://doi.org/10.1016/j.canlet.2009.07.006 .

Ham SA, Kim HJ, Kim HJ, Kang ES, Eun SY, Kim GH, Park MH, Woo IS, Kim HJ, Chang KC, Lee JH, Seo HG. PPARdelta promotes wound healing by up-regulating TGF-beta1-dependent or -independent expression of extracellular matrix proteins. J Cell Mol Med. 2010;14:1747–59. https://doi.org/10.1111/j.1582-4934.2009.00816.x .

Burgess HA, Daugherty LE, Thatcher TH, Lakatos HF, Ray DM, Redonnet M, Phipps RP, Sime PJ. PPARgamma agonists inhibit TGF-beta induced pulmonary myofibroblast differentiation and collagen production: implications for therapy of lung fibrosis. Am J Physiol Lung Cell Mol Physiol. 2005;288:L1146–53. https://doi.org/10.1152/ajplung.00383.2004 .

Milam JE, Keshamouni VG, Phan SH, Hu B, Gangireddy SR, Hogaboam CM, Standiford TJ, Thannickal VJ. Reddy RC PPAR-gamma agonists inhibit profibrotic phenotypes in human lung fibroblasts and bleomycin-induced pulmonary fibrosis. Am J Physiol Lung Cell Mol Physiol. 2008;294:L891–901. https://doi.org/10.1152/ajplung.00333.2007 .

Ferguson HE, Kulkarni A, Lehmann GM, Garcia-Bates TM, Thatcher TH, Huxlin KR, Phipps RP, Sime PJ. Electrophilic peroxisome proliferator-activated receptor-gamma ligands have potent antifibrotic effects in human lung fibroblasts. Am J Respir Cell Mol Biol. 2009;41:722–30. https://doi.org/10.1165/rcmb.2009-0006OC .

Lin Q, Fang LP, Zhou WW, Liu XM. Rosiglitazone inhibits migration, proliferation, and phenotypic differentiation in cultured human lung fibroblasts. Exp Lung Res. 2010;36:120–8. https://doi.org/10.3109/01902140903214659 .

El Agha E, Moiseenko A, Kheirollahi V, De Langhe S, Crnkovic S, Kwapiszewska G, Szibor M, Kosanovic D, Schwind F, Schermuly RT, Henneke I, MacKenzie B, Quantius J, Herold S, Ntokou A, Ahlbrecht K, Braun T, Morty RE, Günther A, Seeger W, Bellusci S. Two-way conversion between lipogenic and myogenic fibroblastic phenotypes marks the progression and resolution of lung fibrosis. Cell Stem Cell. 2017;20:261-73.e3. https://doi.org/10.1016/j.stem.2016.10.004 .

Speca S, Dubuquoy C, Rousseaux C, Chavatte P, Desreumaux P, Spagnolo P. GED-0507 attenuates lung fibrosis by counteracting myofibroblast transdifferentiation in vivo and in vitro. PLoS ONE. 2021;16: e0257281. https://doi.org/10.1371/journal.pone.0257281 .

Korbecki J, Bobiński R, Dutka M. Self-regulation of the inflammatory response by peroxisome proliferator-activated receptors. Inflamm Res. 2019;68:443–58. https://doi.org/10.1007/s00011-019-01231-1 .

Derrett-Smith E, Clark KEN, Shiwen X, Abraham DJ, Hoyles RK, Lacombe O, Broqua P, Junien JL, Konstantinova I, Ong VH, Denton CP. The pan-PPAR agonist lanifibranor reduces development of lung fibrosis and attenuates cardiorespiratory manifestations in a transgenic mouse model of systemic sclerosis. Arthritis Res Ther. 2021;23:234. https://doi.org/10.1186/s13075-021-02592-x .

Avouac J, Konstantinova I, Guignabert C, Pezet S, Sadoine J, Guilbert T, Cauvet A, Tu L, Luccarini JM, Junien JL, Broqua P, Allanore Y. Pan-PPAR agonist IVA337 is effective in experimental lung fibrosis and pulmonary hypertension. Ann Rheum Dis. 2017;76:1931–40. https://doi.org/10.1136/annrheumdis-2016-210821 .

Lakatos HF, Thatcher TH, Kottmann RM, Garcia TM, Phipps RP, Sime PJ. The role of PPARs in lung fibrosis. PPAR Res. 2007;2007:71323. https://doi.org/10.1155/2007/71323 .

Zeng Q, Zhou TT, Huang WJ, Huang XT, Huang L, Zhang XH, Sang XX, Luo YY, Tian YM, Wu B, Liu L, Luo ZQ, He B, Liu W, Tang SY. Asarinin attenuates bleomycin-induced pulmonary fibrosis by activating PPARgamma. Sci Rep. 2023;13:14706. https://doi.org/10.1038/s41598-023-41933-5 .

Craig VJ, Zhang L, Hagood JS, Owen CA. Matrix metalloproteinases as therapeutic targets for idiopathic pulmonary fibrosis. Am J Respir Cell Mol Biol. 2015;53:585–600. https://doi.org/10.1165/rcmb.2015-0020TR .

Odajima N, Betsuyaku T, Nagai K, Moriyama C, Wang DH, Takigawa T, Ogino K, Nishimura M. The role of catalase in pulmonary fibrosis. Respir Res. 2010;11:183. https://doi.org/10.1186/1465-9921-11-183 .

Smejkal GB, Kakumanu S. Enzymes and their turnover numbers. Expert Rev Proteomics. 2019;16:543–4. https://doi.org/10.1080/14789450.2019.1630275 .

Filatova A, Seidel S, Böğürcü N, Gräf S, Garvalov BK, Acker T. Acidosis acts through HSP90 in a PHD/VHL-independent manner to promote HIF function and stem cell maintenance in glioma. Cancer Res. 2016;76:5845–56. https://doi.org/10.1158/0008-5472.CAN-15-2630 .

Vijayan V, Srinu T, Karnati S, Garikapati V, Linke M, Kamalyan L, Mali SR, Sudan K, Kollas A, Schmid T, Schulz S, Spengler B, Weichhart T, Immenschuh S, Baumgart-Vogt E. A new immunomodulatory role for peroxisomes in macrophages activated by the TLR4 ligand lipopolysaccharide. J Immunol. 2017;198:2414–25. https://doi.org/10.4049/jimmunol.1601596 .

Matyash V, Liebisch G, Kurzchalia TV, Shevchenko A, Schwudke D. Lipid extraction by methyl-tert-butyl ether for high-throughput lipidomics. J Lipid Res. 2008;49:1137–46. https://doi.org/10.1194/jlr.D700041-JLR200 .

Garikapati V, Colasante C, Baumgart-Vogt E, Spengler B. Sequential lipidomic, metabolomic, and proteomic analyses of serum, liver, and heart tissue specimens from peroxisomal biogenesis factor 11a knockout mice. Anal Bioanal Chem. 2022;414:2235–50. https://doi.org/10.1007/s00216-021-03860-0 .

Khalil N, O’Connor RN, Unruh HW, Warren PW, Flanders KC, Kemp A, Bereznay OH, Greenberg AH. Increased production and immunohistochemical localization of transforming growth factor-beta in idiopathic pulmonary fibrosis. Am J Respir Cell Mol Biol. 1991;5:155–62. https://doi.org/10.1165/ajrcmb/5.2.155 .

Bergeron A, Soler P, Kambouchner M, Loiseau P, Milleron B, Valeyre D, Hance AJ, Tazi A. Cytokine profiles in idiopathic pulmonary fibrosis suggest an important role for TGF-beta and IL-10. Eur Respir J. 2003;22:69–76. https://doi.org/10.1183/09031936.03.00014703 .

Qian G, Fan W, Ahlemeyer B, Karnati S, Baumgart-Vogt E. Peroxisomes in different skeletal cell types during intramembranous and endochondral ossification and their regulation during osteoblast differentiation by distinct peroxisome proliferator-activated receptors. PLoS ONE. 2015;10: e0143439. https://doi.org/10.1371/journal.pone.0143439 .

Moore BB, Lawson WE, Tim Oury TD, Sisson TH, Raghavendran K, Hogaboam CM. Animal models of fibrotic lung disease. Am J Respir Cell Mol Biol. 2013;49:167–79. https://doi.org/10.1165/rcmb.2013-0094TR .

Sime PJ, Xing Z, Graham FL, Csaky KG, Gauldie J. Adenovector-mediated gene transfer of active transforming growth factor-beta1 induces prolonged severe fibrosis in rat lung. J Clin Invest. 1997;100:768–76. https://doi.org/10.1172/JCI119590 .

Fukuda Y, Basset F, Ferrans VJ, Yamanaka N. Significance of early intra-alveolar fibrotic lesions and integrin expression in lung biopsy specimens from patients with idiopathic pulmonary fibrosis. Hum Pathol. 1995;26:53–61. https://doi.org/10.1016/0046-8177(95)90114-0 .

Cavazza A, Rossi G, Carbonelli C, Spaggiari L, Paci M, Roggeri A. The role of histology in idiopathic pulmonary fibrosis: an update. Respir Med. 2010;104:S11-22. https://doi.org/10.1016/j.rmed.2010.03.013 .

Article   PubMed   Google Scholar  

Jones MG, et al. Three-dimensional characterization of fibroblast foci in idiopathic pulmonary fibrosis. JCI Insight. 2016;1: e86375. https://doi.org/10.1172/jci.insight.86375 .

Kelly M, Kolb M, Bonniaud P, Gauldie J. Re-evaluation of fibrogenic cytokines in lung fibrosis. Curr Pharm Des. 2003;9:39–49. https://doi.org/10.2174/1381612033392341 .

Cerny L, Torday JS, Rehan VK. Prevention and treatment of bronchopulmonary dysplasia: contemporary status and future outlook. Lung. 2008;186:75–89. https://doi.org/10.1513/pats.201203-023AW .

Fernandez IE, Eickelberg O. The impact of TGF-beta on lung fibrosis: from targeting to biomarkers. Proc Am Thorac Soc. 2012;9:111–6. https://doi.org/10.1513/pats.201203-023AW .

Nakos G, Adams A, Andriopoulos N. Antibodies to collagen in patients with idiopathic pulmonary fibrosis. Chest. 1993;103:1051–8. https://doi.org/10.1378/chest.103.4.1051 .

Ramos C, Montaño M, García-Alvarez J, Ruiz V, Uhal BD, Selman M, Pardo A. Fibroblasts from idiopathic pulmonary fibrosis and normal lungs differ in growth rate, apoptosis, and tissue inhibitor of metalloproteinases expression. Am J Respir Cell Mol Biol. 2001;24:591–8. https://doi.org/10.1165/ajrcmb.24.5.4333 .

Su Y, Gu H, Weng D, Zhou Y, Li Q, Zhang F, Zhang Y, Shen L, Hu Y, Li H. Association of serum levels of laminin, type IV collagen, procollagen III N-terminal peptide, and hyaluronic acid with the progression of interstitial lung disease. Medicine (Baltimore). 2017;96: e6617. https://doi.org/10.1097/MD.0000000000006617 .

Sun KH, Chang Y, Reed NI, Sheppard D. alpha-Smooth muscle actin is an inconsistent marker of fibroblasts responsible for force-dependent TGFbeta activation or collagen production across multiple models of organ fibrosis. Am J Physiol Lung Cell Mol Physiol. 2016;310:L824–36. https://doi.org/10.1152/ajplung.00350.2015 .

Liu X, Dai K, Zhang X, Huang G, Lynn H, Rabata A, Liang J, Noble PW, Jiang D. Multiple fibroblast subtypes contribute to matrix deposition in pulmonary fibrosis. Am J Respir Cell Mol Biol. 2023;69:45–56. https://doi.org/10.1165/rcmb.2022-0292OC .

Zhang K, Rekhter MD, Gordon D, Phan SH. Myofibroblasts and their role in lung collagen gene expression during pulmonary fibrosis. A combined immunohistochemical and in situ hybridization study. Am J Pathol. 1994;145:114–25.

PubMed   PubMed Central   CAS   Google Scholar  

Zhang B, Berger J, Zhou G, Elbrecht A, Biswas S, White-Carrington S, Szalkowski D, Moller DE. Insulin- and mitogen-activated protein kinase-mediated phosphorylation and activation of peroxisome proliferator-activated receptor gamma. J Biol Chem. 1996;271:31771–4. https://doi.org/10.1074/jbc.271.50.31771 .

Gandhi S, Tonelli R, Murray M, Samarelli AV, Spagnolo P. Environmental causes of idiopathic pulmonary fibrosis. Int J Mol Sci. 2023;24:16481. https://doi.org/10.3390/ijms242216481 .

Wallace AM, Sandford AJ, English JC, Burkett KM, Li H, Finley RJ, Müller NL, Coxson HO, Paré PD, Abboud RT. Matrix metalloproteinase expression by human alveolar macrophages in relation to emphysema. COPD. 2008;5:13–23. https://doi.org/10.1080/15412550701817789 .

Garcia-de-Alba C, Buendia-Roldán I, Salgado A, Becerril C, Ramírez R, González Y, Checa M, Navarro C, Ruiz V, Pardo A, Selman M. Expression of matrix metalloproteases by fibrocytes: possible role in migration and homing. Am J Respir Crit Care Med. 2010;182:1144–52. https://doi.org/10.1164/rccm.201001-0028OC .

Ham SA, Yoo T, Hwang JS, Kang ES, Lee WJ, Paek KS, Park C, Kim JH, Do JT, Lim DS, Seo HG. Ligand-activated PPARδ modulates the migration and invasion of melanoma cells by regulating Snail expression. Am J Cancer Res. 2014;4:674–82.

PubMed   PubMed Central   Google Scholar  

Tallima H, El Ridi R. Arachidonic acid: physiological roles and potential health benefits—a review. J Adv Res. 2018;11:33–41. https://doi.org/10.1016/j.jare.2017.11.004 .

Meital LT, Windsor MT, Perissiou M, Schulze K, Magee R, Kuballa A, Golledge J, Bailey TG, Askew CD, Russell FD. Omega-3 fatty acids decrease oxidative stress and inflammation in macrophages from patients with small abdominal aortic aneurysm. Sci Rep. 2019;9:12978. https://doi.org/10.1038/s41598-019-49362-z .

Kliewer SA, Forman BM, Blumberg B, Ong ES, Borgmeyer U, Mangelsdorf DJ, Umesono K, Evans RM. Fatty acids and eicosanoids regulate gene expression through direct interactions with peroxisome proliferator-activated receptors alpha and gamma. Proc Natl Acad Sci USA. 1997;94:4318–23. https://doi.org/10.1073/pnas.94.9.4318 .

Colasante C, Chen J, Ahlemeyer B, Baumgart-Vogt E. Peroxisomes in cardiomyocytes and the peroxisome/peroxisome proliferator-activated receptor-loop. Thromb Haemost. 2015;113:452–63. https://doi.org/10.1160/TH14-06-0497 .

Hashimoto F, Hayashi H. Significance of catalase in peroxisomal fatty acyl-CoA beta-oxidation: NADH oxidation by acetoacetyl-CoA and H 2 O 2 . J Biochem. 1990;108:426–31. https://doi.org/10.1093/oxfordjournals.jbchem.a123217 .

Fransen M, Lismont C. Peroxisomal hydrogen peroxide signalling: a new chapter in intracellular communication research. Curr Opin Chem Biol. 2024;78:102426. https://doi.org/10.1016/j.cbpa.2024.102426 .

Girnun GD, Domann FE, Moore SA, Robbins ME. Identification of a functional peroxisome proliferator-activated receptor response element in the rat catalase promoter. Mol Endocrinol. 2002;16:2793–801. https://doi.org/10.1210/me.2002-0020 .

Okuno Y, Matsuda M, Miyata Y, Fukuhara A, Komuro R, Shimabukuro M, Shimomura I. Human catalase gene is regulated by peroxisome proliferator activated receptor-gamma through a response element distinct from that of mouse. Endocr J. 2010;57:303–9. https://doi.org/10.1507/endocrj.k09e-113 .

Hur J, Kang ES, Hwang JS, Lee WJ, Won JP, Lee HG, Kim E, Seo HG. Peroxisome proliferator-activated receptor-delta-mediated upregulation of catalase helps to reduce ultraviolet B-induced cellular injury in dermal fibroblasts. J Dermatol Sci. 2021;103:167–75. https://doi.org/10.1016/j.jdermsci.2021.08.003 .

Hwang JS, Kim E, Lee HG, Lee WJ, Won JP, Hur J, Fujii J, Seo HG. Peroxisome proliferator-activated receptor δ rescues xCT-deficient cells from ferroptosis by targeting peroxisomes. Biomed Pharmacother. 2021;143: 112223. https://doi.org/10.1016/j.biopha.2021.112223 .

Maltarollo VG, Togashi M, Nascimento AS, Honorio KM. Structure-based virtual screening and discovery of new PPARd/g dual agonist and PPARd and g agonists. PLoS ONE. 2015;10: e0118790. https://doi.org/10.1371/journal.pone.0118790 .

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Acknowledgements

Many thanks to Petra Hahn-Kohlberger, Bianca Pfeiffer, Andrea Textor and Susanne Pfreimer for their outstanding technical assistance. Sincere gratitude to Dr. Eunsum Jung (Biospectrum Life Science Institute) and Prof. Marc Fransen (Université catholique de Louvain, Belgium) for providing the COL1A2 luciferase and catalase overexpression plasmids, respectively.

Open Access funding enabled and organized by Projekt DEAL. This work was supported by funding from the German Academic Exchange Service (Government of Ghana DAAD, grant number 50015294) to EB, collaborative grant of the German Academic Exchange Service (DAAD) for granting the Graduate School Scholarship Programme "Lipids in Nutrition and Metabolism" (DAAD-GSSP-2015) to EBV, VG is a doctoral scholarship holder within this programme (Personal reference no 91566181), and performance-related resource allocation-funds of the Medical Faculty of the Justus Liebig University Giessen, so-called “ L eistungs o rientierte M ittel” (LOM) to EBV.

Author information

Srikanth Karnati

Present address: Institute for Anatomy and Cell Biology, Julius Maximilians University, 97070, Würzburg, Germany

Eistine Boateng

Present address: Department of Medical Education, College of Medicine and Life Sciences, University of Toledo, Toledo, OH, 43614, USA

Vannuruswamy Garikapati

Present address: Max Planck Institute of Molecular Cell Biology and Genetics, 01307, Dresden, Germany

Gani Oruqaj

Present address: Department of Internal Medicine II, Member of the German Center for Lung Research (DZL), Universities of Giessen and Marburg Lung Center (UGMLC), Justus Liebig University, 35392, Giessen, Germany

Natalia El-Merhie

Present address: Institute for Lung Health (ILH), Member of the German Center for Lung Research (DZL), Universities of Giessen and Marburg Lung Center (UGMLC), Justus Liebig University, 35392, Giessen, Germany

Srikanth Karnati and Eveline Baumgart-Vogt share senior authorship.

Authors and Affiliations

Institute for Anatomy and Cell Biology, Division of Medical Cell Biology, Justus Liebig University, Aulweg 123, 35392, Giessen, Germany

Eistine Boateng, Rocio Bonilla-Martinez, Barbara Ahlemeyer, Vannuruswamy Garikapati, Mohammad Rashedul Alam, Gani Oruqaj, Natalia El-Merhie, Srikanth Karnati & Eveline Baumgart-Vogt

Department of Internal Medicine VIII, Eberhard Karls University, 72076, Tübingen, Germany

Omelyan Trompak

Excellence Cluster Cardio-Pulmonary System, German Center for Lung Research (DZL), Universities of Giessen and Marburg Lung Center, 35392, Giessen, Germany

Michael Seimetz, Clemens Ruppert & Andreas Günther

UGMLC Giessen Biobank, Universities of Giessen and Marburg Lung Center, 35392, Giessen, Germany

Clemens Ruppert

Center for Interstitial and Rare Lung Diseases, Department of Internal Medicine, German Center for Lung Research, Universities of Giessen and Marburg Lung Center, 35392, Giessen, Germany

Andreas Günther

Institute of Inorganic and Analytical Chemistry, Justus Liebig University, 35392, Giessen, Germany

Vannuruswamy Garikapati & Bernhard Spengler

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Contributions

E.B.-V., S.K. and E.B. conceived and designed the research studies; E.B., R.B, B.A., O.T., V.G. and M.R.A. conducted the experiments; E.B.-V., B.A., B.S., S.K., R.B., V.G., N.E-M. and E.B. acquired and analyzed the data analyzed; E.B.-V., S.K., M.S., B.S., C.R., G.O., and A.G. provided reagents and materials; and E.B.-V., B.A., R.B. and E.B. wrote the manuscript. All authors reviewed the manuscript.

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Correspondence to Eveline Baumgart-Vogt .

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Protocol, data collection and analysis of the human material (isolated lung fibroblasts, lung tissues) were approved by the Local Ethics Committee of the Justus Liebig University Giessen (Az58/15 and Az111/08, JLU).

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Eistine Boateng, Vannuruswamy Garikapati, Gani Oruqaj, Natalia El-Merhie, Srikanth Karnati: All experimental work has been done at Institute for Anatomy and Cell Biology, Division of Medical Cell Biology, Justus Liebig University, Aulweg 123, 35392, Giessen, Germany. Vannuruswamy Garikapati: The experimental work has been done in a cooperative project at two places at the JLU Giessen (Institute for Anatomy and Cell Biology, Division of Medical Cell Biology, Justus Liebig University and Institute of Inorganic and Analytical Chemistry, Justus Liebig University).

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Boateng, E., Bonilla-Martinez, R., Ahlemeyer, B. et al. It takes two peroxisome proliferator-activated receptors (PPAR-β/δ and PPAR-γ) to tango idiopathic pulmonary fibrosis. Respir Res 25 , 345 (2024). https://doi.org/10.1186/s12931-024-02935-7

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Received : 03 May 2024

Accepted : 01 August 2024

Published : 23 September 2024

DOI : https://doi.org/10.1186/s12931-024-02935-7

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