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<journal-id journal-id-type="publisher-id">Front. Pharmacol.</journal-id>
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<journal-title>Frontiers in Pharmacology</journal-title>
<abbrev-journal-title abbrev-type="pubmed">Front. Pharmacol.</abbrev-journal-title>
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<issn pub-type="epub">1663-9812</issn>
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<article-id pub-id-type="publisher-id">1779345</article-id>
<article-id pub-id-type="doi">10.3389/fphar.2026.1779345</article-id>
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<subj-group subj-group-type="heading">
<subject>Original Research</subject>
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<title-group>
<article-title>PPAR-gamma regulates PFAS-mediated proinflammatory cytokines in lung epithelial cells </article-title>
<alt-title alt-title-type="left-running-head">Shaikh et al.</alt-title>
<alt-title alt-title-type="right-running-head">
<ext-link ext-link-type="uri" xlink:href="https://doi.org/10.3389/fphar.2026.1779345">10.3389/fphar.2026.1779345</ext-link>
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<contrib contrib-type="author" equal-contrib="yes">
<name>
<surname>Shaikh</surname>
<given-names>Sadiya Bi</given-names>
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<xref ref-type="aff" rid="aff1">
<sup>1</sup>
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<sup>&#x2021;</sup>
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<surname>Faizan</surname>
<given-names>Md Imam</given-names>
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<surname>Islam</surname>
<given-names>Khursheed Ul</given-names>
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<name>
<surname>Rehan</surname>
<given-names>Virender K.</given-names>
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<sup>2</sup>
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<surname>Rahman</surname>
<given-names>Irfan</given-names>
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<sup>1</sup>
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<aff id="aff1">
<label>1</label>
<institution>Department of Environmental Medicine, University of Rochester Medical Center</institution>, <city>Rochester</city>, <state>NY</state>, <country country="US">United States</country>
</aff>
<aff id="aff2">
<label>2</label>
<institution>Division of Neonatology, Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, David Geffen School of Medicine at UCLA</institution>, <city>Torrance</city>, <state>CA</state>, <country country="US">United States</country>
</aff>
<author-notes>
<corresp id="c001">
<label>&#x2a;</label>Correspondence: Irfan Rahman, <email xlink:href="mailto:irfan_rahman@urmc.rochester.edu">irfan_rahman@urmc.rochester.edu</email>
</corresp>
<fn fn-type="other" id="fn001">
<label>&#x2020;</label>
<p>ORCID: Irfan Rahman, <ext-link ext-link-type="uri" xlink:href="http://orcid.org/0000-0003-2274-2454">orcid.org/0000-0003-2274-2454</ext-link>, Md Imam Faizan, <ext-link ext-link-type="uri" xlink:href="http://orcid.org/0000-0002-3805-4608">orcid.org/0000-0002-3805-4608</ext-link>, Khursheed Ul Islam, <ext-link ext-link-type="uri" xlink:href="http://orcid.org/0000-0001-7363-5689">orcid.org/0000-0001-7363-5689</ext-link>
</p>
</fn>
<fn fn-type="equal" id="fn002">
<label>&#x2021;</label>
<p>These authors have contributed equally to this work</p>
</fn>
</author-notes>
<pub-date publication-format="electronic" date-type="pub" iso-8601-date="2026-02-03">
<day>03</day>
<month>02</month>
<year>2026</year>
</pub-date>
<pub-date publication-format="electronic" date-type="collection">
<year>2026</year>
</pub-date>
<volume>17</volume>
<elocation-id>1779345</elocation-id>
<history>
<date date-type="received">
<day>01</day>
<month>01</month>
<year>2026</year>
</date>
<date date-type="rev-recd">
<day>10</day>
<month>01</month>
<year>2026</year>
</date>
<date date-type="accepted">
<day>14</day>
<month>01</month>
<year>2026</year>
</date>
</history>
<permissions>
<copyright-statement>Copyright &#xa9; 2026 Shaikh, Faizan, Islam, Rehan and Rahman.</copyright-statement>
<copyright-year>2026</copyright-year>
<copyright-holder>Shaikh, Faizan, Islam, Rehan and Rahman</copyright-holder>
<license>
<ali:license_ref start_date="2026-02-03">https://creativecommons.org/licenses/by/4.0/</ali:license_ref>
<license-p>This is an open-access article distributed under the terms of the <ext-link ext-link-type="uri" xlink:href="https://creativecommons.org/licenses/by/4.0/">Creative Commons Attribution License (CC BY)</ext-link>. The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.</license-p>
</license>
</permissions>
<abstract>
<sec>
<title>Background</title>
<p>Per and polyfluoroalkyl substances (PFAS), including the legacy compound perfluorooctanesulfonic acid (PFOS), are persistent organic pollutants with long biological half-lives. Emerging evidence suggests a significant accumulation of PFAS/PFOS in the human lung, potentially contributing to inflammation and altered immune responses. However, the role of peroxisome proliferator-activated receptor gamma (PPAR&#x3b3;) signaling in PFAS/PFOS-induced pulmonary toxicity remains unclear.</p>
</sec>
<sec>
<title>Methods</title>
<p>Primary human bronchial epithelial (NHBE) cells were exposed to 15&#xa0;&#xb5;M binary PFAS mixture (PFOS &#x2b; PFOA) or quaternary mixture (PFOS, PFOA, PFHxS, GenX) with or without the PPAR&#x3b3; antagonist (15&#xa0;&#xb5;M) and/or the PPAR&#x3b3; agonists rosiglitazone (10&#xa0;&#xb5;M) or pioglitazone (10&#xa0;&#xb5;M) for 24&#xa0;h. BALB/c mice were orally administered PFOS (2&#xa0;mg/kg/day) or vehicle control for 2&#xa0;weeks.</p>
</sec>
<sec>
<title>Results</title>
<p>In NHBE cells, PFAS exposure significantly increased IL-6 and IL-8 secretion. Treatment with rosiglitazone or pioglitazone reversed these cytokine increases, whereas co-treatment with the PPAR&#x3b3; antagonist elevated IL-6 and IL-8 levels compared to PFAS exposure alone in epithelial cells. PFOS exposure in mice caused a reduction in lung PPAR&#x3b3; protein levels, while PPAR&#x3b1; expression remained unchanged.</p>
</sec>
<sec>
<title>Conclusion</title>
<p>These findings demonstrate that PFAS-induced pro-inflammatory cytokines is mediated, at least in part, through PPAR&#x3b3; signaling, and that pharmacological activation of PPAR&#x3b3; signaling can attenuate PFAS-triggered pro-inflammatory cytokine responses in lung epithelial cells.</p>
</sec>
</abstract>
<kwd-group>
<kwd>epithelial cells</kwd>
<kwd>inflammation</kwd>
<kwd>lungs</kwd>
<kwd>PFAS</kwd>
<kwd>PPAR&#x3b3;</kwd>
</kwd-group>
<funding-group>
<funding-statement>The author(s) declared that financial support was not received for this work and/or its publication.</funding-statement>
</funding-group>
<counts>
<fig-count count="4"/>
<table-count count="0"/>
<equation-count count="0"/>
<ref-count count="42"/>
<page-count count="7"/>
</counts>
<custom-meta-group>
<custom-meta>
<meta-name>section-at-acceptance</meta-name>
<meta-value>Respiratory Pharmacology</meta-value>
</custom-meta>
</custom-meta-group>
</article-meta>
</front>
<body>
<sec sec-type="intro" id="s1">
<title>Introduction</title>
<p>Per- and polyfluoroalkyl substances (PFAS), the so called &#x201c;forever chemicals&#x201d; are ubiquitous in the environment and throughout biological trophic levels, owing to their use in products, such as food-contact materials, non-stick cookware, firefighting foams, stain- and water-resistant fabrics, and personal-care items (<xref ref-type="bibr" rid="B40">Wei et al., 2018</xref>; <xref ref-type="bibr" rid="B6">Domingo, 2025</xref>; <xref ref-type="bibr" rid="B10">Gl et al., 2020</xref>). PFAS are classified by carbon-chain length: long-chain (C &#x3e; 6), short-chain (4 &#x3c; C &#x2264; 6), and ultra-short-chain (C &#x3d; 2&#x2013;3), in which nearly all hydrogens are replaced by strongly electronegative fluorine atoms. The resulting C&#x2013;F bond is the strongest covalent bond in organic chemistry, conferring exceptional chemical and thermal stability. Legacy PFAS, such as perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) contain eight carbons (C8), whereas more recently adopted short-chain congeners, including perfluorohexanesulfonic acid (PFHxS), perfluorohexanoic acid (PFHxA), and hexafluoropropylene-oxide dimer acid ammonium salt (HFPO-DA, &#x201c;Gen X&#x201d;), contain three to six fully fluorinated carbons (<xref ref-type="bibr" rid="B40">Wei et al., 2018</xref>; <xref ref-type="bibr" rid="B6">Domingo, 2025</xref>; <xref ref-type="bibr" rid="B10">Gl et al., 2020</xref>). PFAS mixtures, including binary combinations like PFOS &#x2b; PFOA and broader mixtures containing PFOS, PFOA, PFHxS, and PFNA, are commonly found in environmental samples and represent typical exposure scenarios (<xref ref-type="bibr" rid="B24">Post et al., 2024</xref>).</p>
<p>Emerging evidence suggests a substantial burden of PFAS in the human lung, which may impact inflammation and allergic responses (<xref ref-type="bibr" rid="B21">Nielsen et al., 2024a</xref>; <xref ref-type="bibr" rid="B17">Lucas et al., 2022</xref>; <xref ref-type="bibr" rid="B18">Lucas et al., 2024a</xref>; <xref ref-type="bibr" rid="B19">Lucas et al., 2024b</xref>; <xref ref-type="bibr" rid="B9">Dragon et al., 2023</xref>; <xref ref-type="bibr" rid="B14">Kvalem et al., 2020</xref>; <xref ref-type="bibr" rid="B20">Luo et al., 2020</xref>; <xref ref-type="bibr" rid="B23">P&#xe9;rez et al., 2013</xref>; <xref ref-type="bibr" rid="B25">Qin et al., 2017</xref>; <xref ref-type="bibr" rid="B37">Sorli et al., 2019</xref>). We have recently shown that developmental PFAS exposure alters airway epithelial permeability and inflammatory-allergic responses in epithelial cells and mouse lungs (<xref ref-type="bibr" rid="B17">Lucas et al., 2022</xref>; <xref ref-type="bibr" rid="B18">Lucas et al., 2024a</xref>; <xref ref-type="bibr" rid="B19">Lucas et al., 2024b</xref>). PPAR&#x3b3;, a nuclear hormone receptor, regulates airway epithelial cell development, epithelial-mesenchymal interactions, and pulmonary inflammatory responses (<xref ref-type="bibr" rid="B23">P&#xe9;rez et al., 2013</xref>; <xref ref-type="bibr" rid="B25">Qin et al., 2017</xref>; <xref ref-type="bibr" rid="B37">Sorli et al., 2019</xref>; <xref ref-type="bibr" rid="B38">Stark et al., 2021</xref>). PPAR&#x3b3; is known to play an important role in lung development and maturation (<xref ref-type="bibr" rid="B27">Reddy et al., 2012</xref>; <xref ref-type="bibr" rid="B28">Rehan and Torday, 2012</xref>). PFAS may interact with PPAR&#x3b3;. However, the specific role of PPAR&#x3b3; signaling in regulating the inflammatory response to PFAS exposure remains unclear. Here, we show that lung PPAR&#x3b3; levels are reduced after PFAS/PFOS exposure both <italic>in vivo</italic> and <italic>in vitro</italic> models. Furthermore, <italic>in vitro</italic> studies demonstrate that a PPAR&#x3b3; agonist blocks PFAS-induced increase in inflammatory cytokines that were in turn in turn reversed by concurrent treatment with a PPAR&#x3b3; antagonist.</p>
</sec>
<sec sec-type="materials|methods" id="s2">
<title>Materials and methods</title>
<sec id="s2-1">
<title>Ethics approval statement: institutional biosafety and animal protocol approval</title>
<p>The University of Rochester&#x2019;s Institutional Biosafety Committee approved the laboratory protocols under Rahman/102054/09-167/07-186, with the identification code 07-186. The mouse study was reviewed and approved by the University Committee on Animal Research (UCAR) at the University of Rochester, Rochester, NY, under the UCAR protocol 102,204/UCAR-2007-070E.</p>
</sec>
<sec id="s2-2">
<title>Cell culture and treatments</title>
<p>Normal human bronchial epithelial cells (NHBE; Lonza CC-2541) were treated with 15&#xa0;&#xb5;M PFOS (Sigma, Cat &#x23; 77282), 10&#xa0;&#xb5;M rosiglitazone (ROSI) (Sigma, Cat&#x23; R2408), 10&#xa0;&#xb5;M pioglitazone hydrochloride (PIO) (Sigma, Cat &#x23;E6910), or 15&#xa0;&#xb5;M PPAR&#x3b3; antagonist III, G3335 (Sigma, Cat&#x23; 516566). PFAS treatments were also performed in combination exposures, including a binary mixture of PFOS and PFOA (5&#xa0;&#xb5;M each), and a quaternary mixture consisting of PFOS, PFOA, PFHxS (Cayman, CAS 355-46-4), and hexafluoropropylene oxide dimer acid (HFPO-DA or GenX) (Cayman, CAS 13252-13-6). Cells were exposed in a two-step sequence. First, cells were treated with PFOS (15&#xa0;&#x3bc;M) for 24&#xa0;h to induce an inflammatory response. After this initial exposure, cells were washed with PBS and then treated with either the PPAR&#x3b3; agonist (ROSI or PIO) or the PPAR&#x3b3; antagonist, and were harvested 48&#xa0;h after this second treatment. This PFOS and agonist/antagonist sequence was used to assess how modulation of PPAR&#x3b3; influences PFOS-induced cytokine release. Culture supernatants (cell-free media) were collected at the end of the treatment period and used to measure IL-6 and IL-8 levels by ELISA.</p>
</sec>
<sec id="s2-3">
<title>Animals and treatments</title>
<p>The University Committee on Animal Resources at the University of Rochester Medical Center (URMC) approved the study for all animal experiments. Both male and female mice were included in this study (<xref ref-type="bibr" rid="B18">Lucas et al., 2024a</xref>; <xref ref-type="bibr" rid="B19">Lucas et al., 2024b</xref>). All mice were housed at the University of Rochester Medical Center vivarium facility with a 12-h light/12-h dark cycle. Treatments were performed as previously described (<xref ref-type="bibr" rid="B18">Lucas et al., 2024a</xref>; <xref ref-type="bibr" rid="B19">Lucas et al., 2024b</xref>).</p>
</sec>
<sec id="s2-4">
<title>Quantification of pro-inflammatory cytokines by ELISA</title>
<p>To assess the release of inflammatory cytokines by the treated and untreated cells, IL-6 (Cat&#x23; CHC1263, Invitrogen, Waltham, MA) and IL-8 (Cat&#x23; CHC1303, Invitrogen) levels were measured using ELISA according to the manufacturer&#x2019;s protocol.</p>
</sec>
<sec id="s2-5">
<title>Immunoblotting</title>
<p>Western blot analyses were performed as previously described (<xref ref-type="bibr" rid="B18">Lucas et al., 2024a</xref>; <xref ref-type="bibr" rid="B19">Lucas et al., 2024b</xref>). Briefly, lung tissue and cell lysates were prepared in RIPA lysis buffer (Sigma, Cat&#x23; 20-188). Homogenates were clarified by centrifugation at 13,000&#xa0;rpm for 30&#xa0;min at 4&#xa0;&#xb0;C, and the supernatants were collected for protein quantification using the BCA assay. Equal amounts of protein were resolved on 10% SDS-PAGE gels and transferred to PVDF membranes (Bio-Rad, Cat&#x23; 162-0177) using a wet transfer. Membranes were blocked in blocking buffer (Bio-Rad, Cat&#x23; 12010020) for 40&#xa0;min at room temperature, then incubated overnight at 4&#xa0;&#xb0;C with primary antibodies anti-PPAR&#x3b1; (mouse; Proteintech, Cat&#x23; 66826-1-Ig) and anti-PPAR&#x3b3; (rabbit; CST, Cat&#x23; 2435S), each at 1:1000 with gentle agitation. After washing in 1&#xd7; TBST, membranes were incubated with HRP-conjugated secondary antibodies (Bio-Rad, Cat&#x23; 1706515 and 1706516) at 1:10,000, washed, and developed using SuperSignal&#x2122; Femto ECL substrate (Thermo Fisher, Ref&#x23; 34096).</p>
</sec>
<sec id="s2-6">
<title>Statistical analysis</title>
<p>All experiments involving more than two groups were analyzed using one-way ANOVA. For each analysis, the overall between-group p-value is reported to indicate whether group differences were statistically significant. When pairwise comparisons were made, primarily between the vehicle control and individual treatment groups (PFOS, agonist, or antagonist conditions), we applied Tukey&#x2019;s Honest Significant Difference (HSD) <italic>post hoc</italic> test. All statistical analyses were performed using GraphPad Prism (version 10), and Data are presented as mean &#xb1; SEM. A <italic>p</italic>-value &#x3c;0.05 was considered statistically significant.</p>
</sec>
</sec>
<sec sec-type="results" id="s3">
<title>Results</title>
<sec id="s3-1">
<title>PFOS exposure reduces PPAR&#x3b3; abundance in mouse lungs and lung epithelial cells</title>
<p>PFOS exposure led to a significant reduction in PPAR&#x3b3; protein expression, without affecting PPAR&#x3b1; levels, in the whole lung tissue of exposed mice as demonstrated by Western blot analysis (<xref ref-type="fig" rid="F1">Figure 1A</xref>). Because PPAR&#x3b3; signaling is a key determinant of lung epithelial cell differentiation and function, and lung epithelial cells are affected by PFOS exposure (<xref ref-type="bibr" rid="B17">Lucas et al., 2022</xref>), we next examined the effect of PFOS on PPAR&#x3b3; expression in primary human lung epithelial cells. Consistent with our <italic>in vivo</italic> findings, PFOS exposure significantly reduced PPAR&#x3b3; abundance without altering PPAR&#x3b1; levels (<xref ref-type="fig" rid="F1">Figure 1B</xref>). These results indicate that legacy PFOS selectively downregulates PPAR&#x3b3; in both <italic>in vivo</italic> and <italic>in vitro</italic> models, implicating PPAR&#x3b3; signaling as a potential mediator of PFAS-induced pro-inflammatory responses.</p>
<fig id="F1" position="float">
<label>FIGURE 1</label>
<caption>
<p>PFOS Exposure Reduces PPAR&#x3b3; Abundance in Mouse Lungs and Lung Epithelial Cells <bold>(A)</bold> Developmental PFOS exposure (2&#xa0;mg/kg/day) reduces PPAR&#x3b3; protein expression in mouse lung tissue. Bar graphs represent the relative fold change of PPAR&#x3b3; and PPAR&#x3b1; protein levels normalized to &#x3b2;-actin. Data are presented as mean &#xb1; SEM (n &#x3d; 3 per group); &#x2a;p &#x3c; 0.05 vs. control. <bold>(B)</bold> Representative Western blots of PPAR&#x3b3; and PPAR&#x3b1; in primary human bronchial epithelial (NHBE) cells exposed to PFOS (15&#xa0;&#xb5;M). Quantification of band intensities normalized to &#x3b2;-actin is shown in bar graphs. Data are expressed as mean &#xb1; SEM (n &#x3d; 3); &#x2a;&#x2a;&#x2a;p &#x3c; 0.001 vs. control.</p>
</caption>
<graphic xlink:href="fphar-17-1779345-g001.tif">
<alt-text content-type="machine-generated">Comparison of PPAR-&#x3B3; and PPAR-&#x3B1; protein expression levels in mouse lungs and lung epithelial cells. Panel A shows decreased PPAR-&#x3B3; expression in PFOS-treated mouse lungs versus control. Panel B shows decreased PPAR-&#x3B3; and similar PPAR-&#x3B1; expression in PFOS-treated lung epithelial cells versus control. Each panel includes Western blot images and corresponding bar graphs, with graphs illustrating a significant reduction in PPAR-&#x3B3; expression in PFOS conditions. Protein levels are normalized to &#x3B2;-Actin, with molecular weights indicated.</alt-text>
</graphic>
</fig>
</sec>
<sec id="s3-2">
<title>PPAR&#x3b3; agonists suppress PFOS-induced IL-6 and IL-8 secretion by lung epithelial cells</title>
<p>Human bronchial epithelial cells were exposed to PFOS with or without the PPAR&#x3b3; agonists ROSI or PIO. PFOS exposure markedly increased the secretion of the inflammatory cytokines IL-6 and IL-8 by primary lung epithelial cells, as measured by ELISA. Co-treatment with ROSI significantly reduced PFOS-induced increases in IL-6 and IL-8 levels compared with PFOS alone. Interestingly, ROSI treatment alone produced a modest but insignificant increase in cytokine levels (<xref ref-type="fig" rid="F2">Figure 2A</xref>). Similar effects were observed with PIO, where co-treatment significantly decreased PFOS-induced cytokine secretion, and PIO alone treatment showed the same trend as seen with ROSI (<xref ref-type="fig" rid="F2">Figure 2B</xref>). Overall, both ROSI and PIO attenuated PFOS-induced inflammatory responses, indicating that PPAR&#x3b3; activation mitigates PFOS-triggered cytokine release, highlighting the potential anti-inflammatory role of PPAR&#x3b3; agonists in blocking PFOS-associated lung injury.</p>
<fig id="F2" position="float">
<label>FIGURE 2</label>
<caption>
<p>PPAR&#x3b3; Agonists Attenuate PFOS-Induced Inflammatory Cytokines: Primary lung epithelial cells were treated with PFOS (15&#xa0;&#xb5;M), rosiglitazone, or pioglitazone HCl (10&#xa0;&#xb5;M). <bold>(A)</bold> IL-6 and IL-8 levels measured by ELISA following PFOS and rosiglitazone treatments. <bold>(B)</bold> IL-6 and IL-8 levels measured by ELISA following PFOS and pioglitazone treatments. &#x2a;&#x2a;&#x2a;p &#x3c; 0.001, &#x2a;&#x2a;p &#x3c; 0.01, &#x2a;p &#x3c; 0.05 vs. control; <sup>&#x23;&#x23;&#x23;</sup>p &#x3c; 0.001, <sup>&#x23;&#x23;</sup>p &#x3c; 0.01, <sup>&#x23;</sup>p &#x3c; 0.05 vs. PFOS; <sup>$$</sup>p &#x3c; 0.01 vs. rosiglitazone; <sup>&#x2b;&#x2b;&#x2b;</sup>p &#x3c; 0.001 vs. pioglitazone.</p>
</caption>
<graphic xlink:href="fphar-17-1779345-g002.tif">
<alt-text content-type="machine-generated">Bar graphs illustrate IL-6 and IL-8 levels in different experimental groups. Panel A shows Control, PFOS, PFOS plus Rosi, and Rosi treatments. Panel B compares Control, PFOS, PFOS plus Pio, and Pio treatments. Bars show significant differences using symbols such as asterisks and hashes.</alt-text>
</graphic>
</fig>
</sec>
<sec id="s3-3">
<title>PPAR&#x3b3; antagonism exacerbates PFOS-induced IL-6 and IL-8 secretion in lung epithelial cells</title>
<p>Having observed that PPAR&#x3b3; agonists attenuate PFOS-induced inflammatory responses, we next examined whether blocking PPAR&#x3b3; would exacerbate these responses and negate the protective effects of PPAR&#x3b3; agonists. As above, human bronchial epithelial cells were exposed to PFOS with or without the PPAR&#x3b3; agonists ROSI or PIO, and with or without a PPAR&#x3b3; antagonist (antagonist III, G3335). PFOS exposure significantly increased IL-6 and IL-8 secretion. Co-treatment with ROSI or PIO suppressed these PFOS-induced increases; however, this protective effect was completely abolished by co-treatment with the PPAR&#x3b3; antagonist (<xref ref-type="fig" rid="F3">Figures 3A&#x2013;D</xref>). suggesting a key role of PPAR&#x3b3; signaling in regulating the inflammatory response of bronchial epithelial cells.</p>
<fig id="F3" position="float">
<label>FIGURE 3</label>
<caption>
<p>PPAR&#x3b3; Antagonism Exacerbates PFOS-Induced IL-6 and IL-8 Secretion in Lung Epithelial Cells: <bold>(A)</bold> Primary lung epithelial cells were treated with PFOS (15&#xa0;&#xb5;M), rosiglitazone, or pioglitazone HCl (10&#xa0;&#xb5;M) and PPAR&#x3b3; Antagonist (15&#xa0;&#xb5;M). <bold>(A,B)</bold> IL-6 and IL-8 levels measured by ELISA following PFOS and rosiglitazone treatments. <bold>(C,D)</bold> IL-6 and IL-8 levels measured by ELISA following PFOS and pioglitazone treatments. &#x2a;&#x2a;&#x2a;p &#x3c; 0.001, &#x2a;&#x2a;p &#x3c; 0.01, &#x2a;p &#x3c; 0.05 vs. control; &#x23;&#x23;&#x23;p &#x3c; 0.001, &#x23;&#x23;p &#x3c; 0.01, <sup>&#x23;</sup>p &#x3c; 0.05 vs. PFOS; <sup>$$$</sup>p &#x3c; 0.001 vs. rosiglitazone; <sup>&#x2b;&#x2b;&#x2b;</sup>p &#x3c; 0.001 vs. pioglitazone.</p>
</caption>
<graphic xlink:href="fphar-17-1779345-g003.tif">
<alt-text content-type="machine-generated">Bar graphs labeled A, B, C, and D display levels of IL-6 and IL-8 in different conditions. Each graph compares control, PFOS, various combinations with Rosiglitazone or Pioglitazone, and PPAR gamma antagonist treatments. Significant increases in IL levels are noted with PFOS and PPAR gamma antagonist. Statistical significance is indicated by asterisks and symbols.</alt-text>
</graphic>
</fig>
</sec>
<sec id="s3-4">
<title>PPAR&#x3b3; agonist reduces inflammatory cytokine release caused by PFAS mixtures in lung epithelial cells</title>
<p>Primary human bronchial epithelial cells were exposed to binary (PFOS &#x2b; PFOA) and quaternary (PFOS, PFOA, PFHxS, GenX) PFAS mixtures, both of which significantly increased IL-6 and IL-8 secretion compared with controls. As shown in <xref ref-type="fig" rid="F4">Figure 4A</xref>, both mixtures markedly elevated IL-6 production, with the quaternary mixture inducing the highest levels. Co-treatment with the PPAR&#x3b3; agonist ROSI significantly reduced IL-6 secretion under both exposure conditions, although levels remained above control values. A similar pattern was observed for IL-8 (<xref ref-type="fig" rid="F4">Figure 4B</xref>), where the quaternary mixture again elicited a slightly higher response than the binary mixture. ROSI co-treatment though attenuated IL-6 levels but had no effect on IL-8 release.</p>
<fig id="F4" position="float">
<label>FIGURE 4</label>
<caption>
<p>PPAR&#x3b3; Agonist Modulates Cytokine Responses to PFAS in Primary Human Bronchial Epithelial (NHBE): Primary NHBE cells were seeded and treated with various combinations of PFAS and a PPAR&#x3b3; agonist (rosiglitazone). PFAS exposures included a binary mixture (PFOS &#x2b; PFOA) and a quaternary mixture (PFOS, PFOA, PFHxS, and GenX), designed to mimic environmental co-exposures. Treatments were applied at 0&#xa0;h and repeated at 24&#xa0;h. Supernatants were collected at 48&#xa0;h for ELISA-based quantification of pro-inflammatory cytokines. <bold>(A,B)</bold> Bar graphs show levels of IL-6 and IL-8 under different treatment conditions in response to binary PFAS and quaternary PFAS, and IL-8 secretion under the same respective conditions. Rosiglitazone treatment partially attenuated IL-6 and IL-8 responses, particularly under quaternary exposure condition. Data are presented as mean &#xb1; SEM. &#x2a;&#x2a;&#x2a;p &#x3c; 0.001, &#x2a;&#x2a;p &#x3c; 0.01, &#x2a;p &#x3c; 0.05 vs. control; <sup>&#x23;&#x23;&#x23;</sup>p &#x3c; 0.001, <sup>&#x23;&#x23;</sup>p &#x3c; 0.01, vs. Rosi.</p>
</caption>
<graphic xlink:href="fphar-17-1779345-g004.tif">
<alt-text content-type="machine-generated">Bar graphs labeled A and B compare IL-6 and IL-8 concentrations in different treatments: Control (DMSO), Binary, Quaternary, Rosi, Binary+Rosi, and Quaternary+Rosi. The y-axes denote IL-6 and IL-8 concentrations in picograms per milliliter. Orange bars represent treatments with significant levels, noted with asterisks and pound signs indicating varying significance levels.</alt-text>
</graphic>
</fig>
</sec>
</sec>
<sec sec-type="discussion" id="s4">
<title>Discussion</title>
<p>PFAS, including PFOS, have been widely detected in human serum, and several reports indicate their accumulation in lung tissue (<xref ref-type="bibr" rid="B23">P&#xe9;rez et al., 2013</xref>). Epidemiologic studies have linked PFAS exposure to heightened asthma risk (<xref ref-type="bibr" rid="B2">Calafat et al., 2007</xref>; <xref ref-type="bibr" rid="B11">Jackson-Browne et al., 2020</xref>; <xref ref-type="bibr" rid="B42">Zeng et al., 2019</xref>; <xref ref-type="bibr" rid="B8">Dong et al., 2013</xref>), with serum PFAS concentrations correlating with asthma incidence (<xref ref-type="bibr" rid="B42">Zeng et al., 2019</xref>; <xref ref-type="bibr" rid="B8">Dong et al., 2013</xref>). In rodent models, PFAS exposure elevates Th2 cytokines, augments eosinophilic inflammation (<xref ref-type="bibr" rid="B41">Yang et al., 2021</xref>; <xref ref-type="bibr" rid="B7">Dong et al., 2011</xref>), and amplifies ovalbumin-induced allergic airway inflammation (<xref ref-type="bibr" rid="B41">Yang et al., 2021</xref>; <xref ref-type="bibr" rid="B15">Lee et al., 2018</xref>). PFAS exposure disrupts epithelial and immune homeostasis through both direct and systemic mechanisms. Recently, we demonstrated the sex-dependent effects of developmental PFOS exposure on airway allergic responses in mice (<xref ref-type="bibr" rid="B18">Lucas et al., 2024a</xref>; <xref ref-type="bibr" rid="B19">Lucas et al., 2024b</xref>). Together, these observations underscore the clinical relevance of elucidating PFAS-driven mechanisms underlying aberrant lung development and immune modulation (<xref ref-type="bibr" rid="B10">Gl et al., 2020</xref>; <xref ref-type="bibr" rid="B34">Sevelsted et al., 2023</xref>; <xref ref-type="bibr" rid="B26">Rafiee et al., 2024</xref>; <xref ref-type="bibr" rid="B36">Solan and Park, 2024</xref>; <xref ref-type="bibr" rid="B35">Shi et al., 2023</xref>; <xref ref-type="bibr" rid="B3">Chen et al., 2024</xref>; <xref ref-type="bibr" rid="B13">Kornher et al., 2025</xref>). However, the exact mechanisms by which PFAS induce pulmonary toxicity, particularly their impact on PPAR&#x3b3; signaling, a key pathway involved in lung development and inflammation regulation, remain poorly understood.</p>
<p>We found that PFOS exposure (a legacy PFAS) decreases PPAR&#x3b3; protein levels in mouse lungs, while there was no change in the abundance of PPAR&#x3b1; protein levels between treated and control groups. To investigate whether PPAR&#x3b3; regulates PFOS-induced epithelial inflammation, we modulated this pathway in lung epithelial cells.</p>
<p>PPAR&#x3b3; agonists (ROSI, PIO) prevented the PFOS-driven increases in IL-6 and IL-8, whereas co-treatment with a PPAR&#x3b3; antagonist further exacerbated these cytokine levels relative to PFOS alone. Together, these data identify PPAR&#x3b3; signaling as a central attenuator of PFOS-induced inflammatory responses in lung epithelium. We then examined the effects of mixture of environmentally relevant, medium-to long-chain PFAS commonly found in the environment, including PFOA, PFHxS, PFOS, and HFPO-DA GenX, an industrial replacement for the legacy PFAS- PFOA. We studied the effects of a mixture of medium to long-chain PFAS found in the environment, i.e., PFOA, PFHxS, PFOS, and HFPO-DA(Gen-X, an industrial replacement for the straight-chain PFAS and PFOA). Both binary and quaternary PFAS mixtures robustly induced pro-inflammatory cytokine release by lung epithelial cells, and that PPAR&#x3b3; agonists partially mitigated this effect, particularly for IL-6, highlighting the role for PPAR&#x3b3; signaling in modulating PFAS-induced inflammation. These results are consistent with prior reports of PFOS-mediated lung inflammation (<xref ref-type="bibr" rid="B17">Lucas et al., 2022</xref>; <xref ref-type="bibr" rid="B18">Lucas et al., 2024a</xref>; <xref ref-type="bibr" rid="B19">Lucas et al., 2024b</xref>) and the anti-inflammatory actions of ROSI and related analogs (<xref ref-type="bibr" rid="B12">Kang et al., 2011</xref>; <xref ref-type="bibr" rid="B39">Ward et al., 2006</xref>; <xref ref-type="bibr" rid="B29">Rehan et al., 2006</xref>; <xref ref-type="bibr" rid="B33">Sakurai et al., 2018</xref>; <xref ref-type="bibr" rid="B16">Lee et al., 2020</xref>; <xref ref-type="bibr" rid="B1">Anderson et al., 2016</xref>). IL-6 and IL-8 are regulated through distinct pathways. IL-6 primarily via STAT3 and IL-8 through NF-&#x3ba;B and PPAR&#x3b3; agonists differentially modulate these signals (<xref ref-type="bibr" rid="B30">Ricote et al., 1998</xref>; <xref ref-type="bibr" rid="B31">Ryoo et al., 2004</xref>; <xref ref-type="bibr" rid="B5">Cronin et al., 2016</xref>). This explains why ROSI/PIO produce stronger suppression of IL-8 (NF-&#x3ba;B&#x2013;dependent), but may have a more variable effect on IL-6 due to PPAR&#x3b3;-STAT3 interactions (<xref ref-type="bibr" rid="B5">Cronin et al., 2016</xref>). Given the evolving PFAS landscape, our findings underscore the need to examine the effects of ultrashort-chain PFAS, which are increasingly replacing legacy PFAS (PFOS) in the real world, on lung immune-inflammatory responses (<xref ref-type="bibr" rid="B4">Cheng et al., 2026</xref>), especially in the developing lung (e.g., during various stages of lung development), as well as from mother to child.</p>
<p>This study has several limitations., e.g., all experiments were performed in primary NHBE cells, which model proximal airway responses but do not represent the full heterogeneity of lung cell populations, such as structural alveolar epithelial cells, fibroblasts, and immune cells (involving various T- and B-subsets). It examines PFOS exposure in combination with PPAR&#x3b3; agonists and antagonists in a controlled <italic>in vitro</italic> system, and does not account for chronic or mixed PFAS exposures common in environmental settings. An PPAR&#x3b3; antagonist-only exposure condition was not included in our experimental design; therefore, the independent effects of PPAR&#x3b3; inhibition without PFOS exposure could not be segregated. A single PFOS concentration and exposure sequence were used, limiting broader dose-response and temporal interpretations. Furthermore, it may also be important to assess PPAR&#x3b3; responses independent of receptor ligand binding. Finally, while we focused on PPAR&#x3b3; protein and cytokine outputs, other relevant mechanisms, including transcriptional changes and cross-talk with additional PPAR isoforms, were not examined. Future studies will expand to <italic>in vivo</italic> models including PPAR&#x3b3; deficient mouse, multiple lung cell types, and the inclusion of all pharmacologic controls (as well as the use of PPAR&#x3b3;/PPAR-&#x3b1; mutant cells) to more comprehensively define PFAS-mediated airway toxicity including their deposition/toxicity in other organs (kidney, liver, and spleen), which have now been well documented (<xref ref-type="bibr" rid="B22">Nielsen et al., 2024b</xref>; <xref ref-type="bibr" rid="B32">Ryu et al., 2024</xref>). Nevertheless, our findings show that PFAS-mediated pro-inflammatory cytokines is mediated, at least in part, through PPAR&#x3b3; signaling in lung epithelial cells.</p>
</sec>
</body>
<back>
<sec sec-type="data-availability" id="s5">
<title>Data availability statement</title>
<p>The original contributions presented in the study are included in the article/<xref ref-type="sec" rid="s12">Supplementary Material</xref>, further inquiries can be directed to the corresponding author.</p>
</sec>
<sec sec-type="ethics-statement" id="s6">
<title>Ethics statement</title>
<p>The animal study was approved by The University Committee on Animal Resources at the University of Rochester Medical Center (URMC). The study was conducted in accordance with the local legislation and institutional requirements.</p>
</sec>
<sec sec-type="author-contributions" id="s7">
<title>Author contributions</title>
<p>SS: Formal Analysis, Writing &#x2013; review and editing, Methodology, Data curation, Investigation, Writing &#x2013; original draft, Visualization. MF: Methodology, Investigation, Writing &#x2013; review and editing, Software, Formal Analysis, Writing &#x2013; original draft. KI: Validation, Methodology, Data curation, Writing &#x2013; review and editing, Writing &#x2013; original draft, Investigation. VR: Writing &#x2013; original draft, Project administration, Supervision, Writing &#x2013; review and editing. IR: Project administration, Conceptualization, Supervision, Writing &#x2013; review and editing, Writing &#x2013; original draft, Funding acquisition, Resources.</p>
</sec>
<sec sec-type="COI-statement" id="s9">
<title>Conflict of interest</title>
<p>The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.</p>
<p>The author IR declared that they were an editorial board member of Frontiers at the time of submission. This had no impact on the peer review process and the final decision.</p>
</sec>
<sec sec-type="ai-statement" id="s10">
<title>Generative AI statement</title>
<p>The author(s) declared that generative AI was not used in the creation of this manuscript.</p>
<p>Any alternative text (alt text) provided alongside figures in this article has been generated by Frontiers with the support of artificial intelligence and reasonable efforts have been made to ensure accuracy, including review by the authors wherever possible. If you identify any issues, please contact us.</p>
</sec>
<sec sec-type="disclaimer" id="s11">
<title>Publisher&#x2019;s note</title>
<p>All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.</p>
</sec>
<sec sec-type="supplementary-material" id="s12">
<title>Supplementary material</title>
<p>The Supplementary Material for this article can be found online at: <ext-link ext-link-type="uri" xlink:href="https://www.frontiersin.org/articles/10.3389/fphar.2026.1779345/full#supplementary-material">https://www.frontiersin.org/articles/10.3389/fphar.2026.1779345/full&#x23;supplementary-material</ext-link>
</p>
<supplementary-material xlink:href="DataSheet1.pdf" id="SM1" mimetype="application/pdf" xmlns:xlink="http://www.w3.org/1999/xlink"/>
</sec>
<fn-group>
<fn fn-type="custom" custom-type="edited-by">
<p>
<bold>Edited by:</bold> <ext-link ext-link-type="uri" xlink:href="https://loop.frontiersin.org/people/19557/overview">Paolo Montuschi</ext-link>, Catholic University of the Sacred Heart, Italy</p>
</fn>
<fn fn-type="custom" custom-type="reviewed-by">
<p>
<bold>Reviewed by:</bold> <ext-link ext-link-type="uri" xlink:href="https://loop.frontiersin.org/people/3337093/overview">Venkatesan Narayanan</ext-link>, McGill University, Canada</p>
<p>
<ext-link ext-link-type="uri" xlink:href="https://loop.frontiersin.org/people/3338977/overview">Robert Foronjy</ext-link>, Downstate Health Sciences University, United States</p>
</fn>
</fn-group>
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