Perfluoroalkyl Substance Exposure and the BDNF Pathway in the Placental Trophoblast

Sex-specific associations of per- and polyfluoroalkyl substances with brain-derived neurotrophic factors (BDNF) in cord serum

Peripheral Contribution of BDNF/TrkB signaling in Mediating Oral Cancer Pain

<p dir="ltr">Per- and polyfluoroalkyl substances (PFAS) are a group of synthetic chemicals, abundantly produced and with a wide range of applications. The partial or full fluorination of alkyl substances with varying functional groups, leads to physicochemical properties that are mainly characterised by persistence and amphiphilicity. While these properties are highly valuable for industrial- and consumer products, they pose major challenges in environmental pollution and health implications. Especially influences on the lipid metabolism have been frequently connected to PFAS exposures, yet lack deeper mechanistic understanding, and were, hence, the main investigated experimental subject of this thesis.</p><p dir="ltr">Regulatory efforts for PFAS have been made in the past and are currently underway. A harmonised approach for the assessment of human health effects, following PFAS exposure is, however, still needed. Dose-response assessment, through benchmark dose (BMD) modelling is the state of the science for hazard characterisation for risk assessment purposes. Specifically, the selection of a critical effect size (CES) - a threshold for adversity - of the assessed effect (response), is important in this context.</p><p dir="ltr">This thesis set out to tackle the outlined challenges in toxicological assessments of PFAS in three main approaches.</p><p dir="ltr">1) Testing contrasting ways to select the CESs in different BMD modelling approaches and assess the outcome metrics for select PFAS case-studies (Study I).</p><p dir="ltr">2) Utilise human cell models to gain insights into PFAS-effects on the human lipid metabolism. This was done by investigating PFAS (single and mixture) exposures and PPARa receptor activation, lipid metabolism-related gene expression and lipid accumulation in Study III. Further, PFAS (single) exposure was investigated with regards to affecting hepatocyte lipidomic profiles in Study II.</p><p dir="ltr">3) Assessing the meaningfulness of comparative relative potency factors (RPFs) for PFAS, through characterisation of RPFs, based on the endpoints in Study III.</p><p dir="ltr">The findings of Study I reveal that the CES choice alters the results of a dose- response assessment significantly for both, frequentist and Bayesian BMD modelling. Further, it became apparent that for the selected case-studies, the Bayesian BMD modelling - paired with flexible, effect-specific CES selection - led to more stable and biologically relevant results, supporting their use in regulatory decision-making.</p><p dir="ltr">Study II unveiled wide-range influences of PFAS exposures on the intracellular (hepatocyte) lipid profile. Legacy PFAS (e.g., PFOS and PFOA), as well as substitute PFAS (e.g., HFPO-DA and ADONA), were shown to have lipid profile-altering properties, with PFOS and PFOA having displayed the largest effects.</p><p dir="ltr">The cell-based assays in Study III confirmed PFAS influences in multiple mechanistic steps of the lipid metabolism. This further underscores the body of evidence for the investigated PFAS and PFAS mixtures to be involved in alterations of important lipid metabolic pathways with likely relevance to cardiovascular diseases and other metabolic conditions. With regards to their relative potencies, PFAS appeared to be endpoint-specific, with no unambiguous pattern of potency.</p><p dir="ltr">This thesis offers an assessment of the BMD methodology in chemical hazard characterisation within the context of assessing the risks from PFAS. Further, multi-endpoint assessment and exposures to single PFAS and PFAS mixtures of human relevance, highlighted the importance of the lipid metabolism as a major target system for PFAS toxicity. The use of RPFs to compare PFAS effects in an endpoint-specific manner, however, needs to be further investigated and a universal approach across endpoints appears to be very challenging.</p><h3>List of scientific papers</h3><p dir="ltr">I. BRUNKEN, L., Vieira Silva, A., & Öberg, M. (2025). Selection of the critical effect size alters hazard characterization - a retrospective analysis of key studies used for risk assessments of PFAS. Frontiers in Toxicology. 7. <a href="https://doi.org/10.3389/ftox.2025.1525089" rel="noreferrer" target="_blank">https://doi.org/10.3389/ftox.2025.1525089</a></p><p dir="ltr">II. Kashobwe, L.#, Sadrabadi, F.#, BRUNKEN, L.#, Coelho, A. C. M. F., Sandanger, T. M., Braeuning, A., Buhrke, T., Öberg, M., Hamers, T., & Leonards, P. E. G. (2024). Legacy and alternative per- and polyfluoroalkyl substances (PFAS) alter the lipid profile of HepaRG cells. Toxicology. 506, 153862. # Equally contributed. <a href="https://doi.org/10.1016/j.tox.2024.153862" rel="noreferrer" target="_blank">https://doi.org/10.1016/j.tox.2024.153862</a></p><p dir="ltr">III. BRUNKEN, L., Vieira Silva, A., & Öberg, M. Relative Potency of PFAS in Human Cell Models: Linking PPARa Activation, Gene Regulation, and Lipid Accumulation. [Manuscript]</p>

<p dir="ltr">Per- and polyfluoroalkyl substances (PFAS) are a group of synthetic chemicals, abundantly produced and with a wide range of applications. The partial or full fluorination of alkyl substances with varying functional groups, leads to physicochemical properties that are mainly characterised by persistence and amphiphilicity. While these properties are highly valuable for industrial- and consumer products, they pose major challenges in environmental pollution and health implications. Especially influences on the lipid metabolism have been frequently connected to PFAS exposures, yet lack deeper mechanistic understanding, and were, hence, the main investigated experimental subject of this thesis.</p><p dir="ltr">Regulatory efforts for PFAS have been made in the past and are currently underway. A harmonised approach for the assessment of human health effects, following PFAS exposure is, however, still needed. Dose-response assessment, through benchmark dose (BMD) modelling is the state of the science for hazard characterisation for risk assessment purposes. Specifically, the selection of a critical effect size (CES) - a threshold for adversity - of the assessed effect (response), is important in this context.</p><p dir="ltr">This thesis set out to tackle the outlined challenges in toxicological assessments of PFAS in three main approaches.</p><p dir="ltr">1) Testing contrasting ways to select the CESs in different BMD modelling approaches and assess the outcome metrics for select PFAS case-studies (Study I).</p><p dir="ltr">2) Utilise human cell models to gain insights into PFAS-effects on the human lipid metabolism. This was done by investigating PFAS (single and mixture) exposures and PPARa receptor activation, lipid metabolism-related gene expression and lipid accumulation in Study III. Further, PFAS (single) exposure was investigated with regards to affecting hepatocyte lipidomic profiles in Study II.</p><p dir="ltr">3) Assessing the meaningfulness of comparative relative potency factors (RPFs) for PFAS, through characterisation of RPFs, based on the endpoints in Study III.</p><p dir="ltr">The findings of Study I reveal that the CES choice alters the results of a dose- response assessment significantly for both, frequentist and Bayesian BMD modelling. Further, it became apparent that for the selected case-studies, the Bayesian BMD modelling - paired with flexible, effect-specific CES selection - led to more stable and biologically relevant results, supporting their use in regulatory decision-making.</p><p dir="ltr">Study II unveiled wide-range influences of PFAS exposures on the intracellular (hepatocyte) lipid profile. Legacy PFAS (e.g., PFOS and PFOA), as well as substitute PFAS (e.g., HFPO-DA and ADONA), were shown to have lipid profile-altering properties, with PFOS and PFOA having displayed the largest effects.</p><p dir="ltr">The cell-based assays in Study III confirmed PFAS influences in multiple mechanistic steps of the lipid metabolism. This further underscores the body of evidence for the investigated PFAS and PFAS mixtures to be involved in alterations of important lipid metabolic pathways with likely relevance to cardiovascular diseases and other metabolic conditions. With regards to their relative potencies, PFAS appeared to be endpoint-specific, with no unambiguous pattern of potency.</p><p dir="ltr">This thesis offers an assessment of the BMD methodology in chemical hazard characterisation within the context of assessing the risks from PFAS. Further, multi-endpoint assessment and exposures to single PFAS and PFAS mixtures of human relevance, highlighted the importance of the lipid metabolism as a major target system for PFAS toxicity. The use of RPFs to compare PFAS effects in an endpoint-specific manner, however, needs to be further investigated and a universal approach across endpoints appears to be very challenging.</p><h3>List of scientific papers</h3><p dir="ltr">I. BRUNKEN, L., Vieira Silva, A., & Öberg, M. (2025). Selection of the critical effect size alters hazard characterization - a retrospective analysis of key studies used for risk assessments of PFAS. Frontiers in Toxicology. 7. <a href="https://doi.org/10.3389/ftox.2025.1525089" rel="noreferrer" target="_blank">https://doi.org/10.3389/ftox.2025.1525089</a></p><p dir="ltr">II. Kashobwe, L.#, Sadrabadi, F.#, BRUNKEN, L.#, Coelho, A. C. M. F., Sandanger, T. M., Braeuning, A., Buhrke, T., Öberg, M., Hamers, T., & Leonards, P. E. G. (2024). Legacy and alternative per- and polyfluoroalkyl substances (PFAS) alter the lipid profile of HepaRG cells. Toxicology. 506, 153862. # Equally contributed. <a href="https://doi.org/10.1016/j.tox.2024.153862" rel="noreferrer" target="_blank">https://doi.org/10.1016/j.tox.2024.153862</a></p><p dir="ltr">III. BRUNKEN, L., Vieira Silva, A., & Öberg, M. Relative Potency of PFAS in Human Cell Models: Linking PPARa Activation, Gene Regulation, and Lipid Accumulation. [Manuscript]</p>

BACKGROUND AND AIM: Non-targeted metabolomics has been incorporated into recent epidemiological studies to investigate metabolic mechanisms underlying adverse health effects of per-fluoroalkyl and polyfluoroalkyl substances (PFAS) exposure. The purpose of this review is to summarize the application of non-targeted metabolomics in epidemiological studies that assessed metabolite and metabolic pathway alterations associated with PFAS exposure. METHODS: We performed a scoping review of human studies that conducted non-targeted metabolomics and PFAS analyses including original articles published in PubMed before March 1, 2021. We summarized the study characteristics and the metabolites and metabolic pathways reported to be associated with PFAS exposure. RESULTS:Nine human studies published between 2018 to 2021 were identified. The study sample ranged from 40 to 965 participants, including children and adolescents (n=3), adults (n=3), or pregnant women (n=3). Health outcomes involved included non-alcoholic liver, type 2 diabetes and other cardiometabolic outcomes. Liquid chromatography–mass spectrometry was the primary analytical platform for PFAS measurement and non-targeted metabolomics. PFAS levels were measured in plasma (n=5) or serum (n=4), while the metabolomic profiles were generated in plasma (n=5), serum (n=3), or urine (n=1). The most studied PFAS compounds were PFOS (n=9), PFOA (n=8), PFHxS (n=8), PFNA (n=5), and PFAS mixtures (n=4). Among seven studies that conducted pathway enrichment analysis, the most commonly reported metabolic pathways affected by multiple PFAS compounds were lipid metabolism, including glycerophospholipid, glycosphingolipid, and linoleate metabolism, followed by amino acid-related pathways, such as urea cycle/amino group metabolism, alanine and aspartate metabolism, and beta-alanine metabolism. Other reported metabolomics alterations possibly associated with PFAS include carbohydrate-related metabolism, xenobiotic (drug) related metabolism, and vitamin metabolism. CONCLUSIONS:Multiple PFAS exposures were associated with alterations to lipid- or amino acid-related metabolism in human studies that used non-targeted metabolomics. Whether these PFAS-associated biological changes lead to adverse health risks requires further research. KEYWORDS: PFAS, Metabolomics, Chemical exposures, Obesity and metabolic disorders

Sexual dimorphism in BDNF signaling after neonatal hypoxia–ischemia and treatment with necrostatin-1

Invited Perspective: Challenges in Evaluating the Effect of Per- and Polyfluoroalkyl Substance Mixtures on Polycystic Ovarian Syndrome

We investigated the role of the neurotrophin BDNF signalling via the TrkB receptor in rat adrenomedullary chromaffin cells (AMCs) exposed to normoxia (Nox; 21% O2) and chronic hypoxia (CHox; 2% O2) in vitro for ∼ 48 h. TrkB receptor expression was upregulated in primary AMCs and in immortalized chromaffin (MAH) cells exposed to CHox; this effect was absent in MAH cells deficient in the transcription factor, hypoxia inducible factor (HIF)-2α. Relative to normoxic controls, activation of the TrkB receptor in chronically hypoxic AMCs led to a marked increase in membrane excitability, intracellular [Ca(2+)], and catecholamine secretion. The BDNF-induced rise of intracellular [Ca(2+)] in CHox cells was sensitive to the selective T-type Ca(2+) channel blocker TTA-P2 and tetrodotoxin (TTX), suggesting key roles of low threshold T-type Ca(2+) and voltage-gated Na(+) channels in the signalling pathway. Environmental stressors, including chronic hypoxia, enhance the ability of adrenomedullary chromaffin cells (AMCs) to secrete catecholamines; however, the underlying molecular mechanisms remain unclear. Here, we investigated the role of brain-derived neurotrophic factor (BDNF) signalling in rat AMCs exposed to chronic hypoxia. In rat adrenal glands, BDNF and its tropomyosin-related kinase B (TrkB) receptor are highly expressed in the cortex and medulla, respectively. Exposure of AMCs to chronic hypoxia (2% O2; 48 h) in vitro caused a significant increase to TrkB mRNA expression. A similar increase was observed in an immortalized chromaffin cell line (MAH cells); however, it was absent in MAH cells deficient in the transcription factor HIF-2α. A specific TrkB agonist, 7,8-dihydroxyflavone (7,8-DHF), stimulated quantal catecholamine secretion from chronically hypoxic (CHox; 2% O2) AMCs to a greater extent than normoxic (Nox; 21% O2) controls. Activation of TrkB by BDNF or 7,8-DHF increased intracellular Ca(2+) ([Ca(2+)]i), an effect that was significantly larger in CHox cells. The 7,8-DHF-induced [Ca(2+)]i rise was sensitive to the tyrosine kinase inhibitor K252a and nickel (2 mm), but not the Ca(2+) store-depleting agent cyclopiazonic acid. Blockade of T-type calcium channels with TTA-P2 (1 μm) or voltage-gated Na(+) channels with TTX inhibited BDNF-induced [Ca(2+)]i increases. BDNF also induced a dose-dependent enhancement of action potential firing in CHox cells. These data demonstrate that during chronic hypoxia, enhancement of BDNF-TrkB signalling increases voltage-dependent Ca(2+) influx and catecholamine secretion in chromaffin cells, and that T-type Ca(2+) channels play a key role in the signalling pathway.

Evidence on cognitive function in relation to per- and polyfluoroalkyl substances (PFAS) exposure in firefighters is scarce. We conducted a pilot study aiming to explore the associations of individual PFAS analyte and PFAS mixture with domain-specific cognitive performance in firefighters. Firefighters (n = 65), who were actively serving four cities in Central Texas 2003-2025, were assessed for global cognition and processing speed measured by the NIH Toolbox Cognition Battery. Whole blood samples were collected from these participants and analyzed by liquid chromatography-tandem mass spectrometry for 24 PFAS analytes. Linear regression models were used to evaluate associations between cognitive performance and both individual PFAS analytes and the overall 24-PFAS mixture. Additionally, quantile g-computation and Bayesian Kernel Machine Regression (BKMR) were applied to investigate associations between 6-PFAS mixture and cognitive performance, with adjustment for potential covariates. Six PFAS analytes including potassium perfluoro-1-octanesulfonate (PFOS), perfluoro-n-octanoic acid (PFOA), perfluoro-n-heptanoic acid (PFHpA), perfluoro-n-nonanoic acid (PFNA), perfluoro-n-decanoic acid (PFDA), and potassium perfluoro-1-hexanesulfonate (PFHxS) were detected in the least 70% of participants. PFOS was negatively associated with scores of processing speed (ß = -0.58 p < 0.001). Neither the 6-PFAS mixture nor the 24-PFAS mixture was associated with either cognitive domain. These preliminary findings may inform future research seeking to clarify the biological pathways linking PFAS exposure to cognitive outcomes and to explore possible modifiable factors related to cognitive health in firefighters. They might also underscore the potential value of continued effort to minimize workplace PFAS exposure for this occupational group. Our study provides the first data on PFAS exposure and cognitive performance for firefighters. Our analysis revealed that PFOS was the primary contributor among the PFAS mixture (consisting of PFOS, PFOA, PFHxS, PFHpA, PFNA, and PFDA) linked to reduced processing speed scores in firefighters. Our findings pave the way for future, larger studies that observe firefighters for longer duration to develop confident estimates of cognitive health in relation to PFAS exposure. These data could inform analyses in support of workplace exposure reduction efforts and revision of preventive health care for first responders.

The antidepressant-like effects of glutamatergic drugs ketamine and AMPA receptor potentiator LY 451646 are preserved in bdnf+/− heterozygous null mice

Vol. 129, No. 12 Science SelectionOpen AccessA Measure of Strength: Developmental PFAS Exposures and Bone Mineral Content in Adolescenceis accompanied byAssociations of Maternal Serum Perfluoroalkyl Substances Concentrations with Early Adolescent Bone Mineral Content and Density: The Health Outcomes and Measures of the Environment (HOME) Study Charles W. Schmidt Charles W. Schmidt Search for more papers by this author Published:17 December 2021CID: 124002https://doi.org/10.1289/EHP10551AboutSectionsPDF ToolsDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmail AbstractThe amount of bone mass that accumulates during early childhood and adolescence is a significant factor governing skeletal strength and the risk of osteoporosis in older adults.1,2 Growing evidence suggests developing bone may be damaged by exposures to per- and polyfluoroalkyl substances (PFAS).3 A new study in Environmental Health Perspectives4 associates higher concentrations of PFAS in maternal blood during pregnancy with lower measures of bone strength in adolescent children. The study was led by Jessie Buckley, an associate professor of environmental health and engineering at the Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland.Resistance to bone diseases such as osteoporosis depends on maximizing bone mass during critical growth periods, which include adolescence. A new study reports associations between higher prenatal PFAS exposures and lower measures of bone strength in 12-year-olds, with potential implications for adult bone health. Image: © Sergey Novikov/Shutterstock.Commonly described as “forever chemicals” because they are exceedingly resistant to degradation, PFAS have been used as stain, oil, and water repellents and as surfactants in fire-fighting foam.5 Certain PFAS are being phased out of production, but other novel formulations are being introduced to take their place.6Buckley and colleagues analyzed data collected by the Health Outcomes and Measures of the Environment (HOME) study, which enrolled pregnant women from Cincinnati, Ohio, and the surrounding areas between 2003 and 2006. This ongoing study aims to assess how fetal and early-life chemical exposures affect children’s growth and development.7 The women provided blood samples at 16 and 26 weeks of pregnancy and within a day of their child’s delivery. For the current study, the investigators measured PFAS in one sample per participant, with all three sampling points represented in the study.Buckley’s team analyzed data for 206 children from the HOME cohort who had also undergone dual-energy X-ray absorptiometry bone scans at 12 years of age. These scans measure inorganic bone mineral, which gives the skeleton its strength.8 Using those data, the researchers calculated two bone measurements: bone mineral content (BMC) and bone mineral density (BMD). The team then looked at how BMC and BMD measures varied with maternal blood concentrations of four PFAS: perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorohexane sulfonic acid (PFHxS), and perfluorooctane sulfonic acid.Higher concentrations of PFOA and PFNA individually and of all four PFAS assessed as a mixture were associated with lower z-scores for BMC and BMD in the forearm and hip. The lower z-scores suggest that children with higher PFAS exposures had lower average bone mass compared with individuals of the same age, sex, and ancestry. “The mixture’s relationship with bone outcomes was stronger than the relationship [of any single] PFAS,” Buckley says. “This is important, since in the real world people tend to be exposed to mixtures of different PFAS all at once.”Abby Fleisch, a pediatric endocrinologist at Maine Medical Center in Portland, who was not involved in the research, says the study has several strengths. “It identifies gestation as a possible vulnerable window for PFAS exposures to impact bone health later in life,” she says. Furthermore, prospective data gathered so far have been limited to females, whereas Buckley and colleagues studied both sexes. Indeed, higher maternal PFOA concentrations were generally associated with lower z-scores in males compared with females. However, a key limitation, Buckley says, is that small sample sizes resulting from losses during follow-up made it difficult to assess sex-related differences.Still, the study addresses “important questions regarding prenatal exposure to both individual and mixtures of PFAS,” says Meghan Lynch, an environmental epidemiologist and PFAS expert at Abt Associates, an environmental consulting company headquartered in Rockville, Maryland. “Decreases in BMD in childhood are linked to an increase in fractures and the development of osteoporosis,” she says. “More research is needed to understand if this [association with PFAS] persists and if it is exacerbated by ongoing exposure to PFAS through adolescence and beyond.”Charles W. Schmidt, MS, is an award-winning journalist in Portland, ME, whose work has appeared in Scientific American, Nature, Science, Discover Magazine, Undark, the Washington Post, and many other publications.

Changes in plasma müllerian-inhibiting substance and brain-derived neurotrophic factor after chemotherapy in premenopausal women

Plasma brain-derived neurotrophic factor in women after bariatric surgery: a pilot study

Prenatal exposure to PFAS, associations with child cognitive ability and modification by maternal Vitamin D status: The MABC study.

Background:Per- and poly-fluoroalkyl substances (PFAS) exposure can occur through ingestion of contaminated food and water, and inhalation of indoor air contaminated with these chemicals from consumer and industrial products. Prenatal PFAS exposures may confer risk for pregnancy-related outcomes such as hypertensive and metabolic disorders, preterm birth, and impaired fetal development through intermediate metabolic and inflammation pathways.Objective:Estimate associations between maternal pregnancy PFAS exposure (individually and as a mixture) and bioactive lipids.Methods:Our study included pregnant women in the Environmental influences on Child Health Outcomes Program: Chemicals in our Bodies cohort (CiOB, n=73), Illinois Kids Developmental Study (IKIDS, n=287), and the ECHO-PROTECT cohort (n=54). We measured twelve PFAS in serum and 50 plasma bioactive lipids (parent fatty acids and eicosanoids derived from cytochrome p450, lipoxygenase, and cyclooxygenase) during pregnancy (median 17 gestational weeks). Pairwise associations across cohorts were estimated using linear mixed models and meta-analysis. Associations between the PFAS mixture and individual bioactive lipids were estimated using quantile g-computation.Results:PFDeA, PFOA, and PFUdA were associated (p<0.05) with changes in bioactive lipid levels in all three enzymatic pathways (cyclooxygenase [n=6 signatures]; cytochrome p450 [n=5 signatures]; lipoxygenase [n=7 signatures]) in at least one combined cohort analysis. The strongest signature indicated that a doubling in PFOA corresponded with a 24.3% increase (95% CI [7.3%, 43.9%]) in PGD2 (cyclooxygenase pathway) in the combined cohort. In the mixtures analysis, we observed nine positive signals across all pathways associated with the PFAS mixture. The strongest signature indicated that a quartile increase in the PFAS mixture was associated with a 34% increase in PGD2 (95% CI [8%, 66%]), with PFOS contributing most to the increase.Conclusions:Bioactive lipids were revealed as biomarkers of PFAS exposure and could provide mechanistic insights into PFAS’ influence on pregnancy outcomes, informing more precise risk estimation and prevention strategies.