Gene expression profiling in the lung and liver of PFOA-exposed mouse fetuses

Integrative transcriptomics analysis reveals convergent toxicological effects of perfluorooctanoic acid and perfluorooctane sulfonate on human liver: Evidence from multiple models

Perfluorooctanoic acid and perfluorooctane sulfonate are well-known eight-carbon per- and polyfluoroalkyl substances (8C-PFAS) potentially toxic for the human liver. However, direct experimental evidence demonstrating their toxicity on the human liver remains limited. Consequently, this study aimed to extrapolate the 8C-PFAS liver toxicity mechanisms by leveraging omics data to integrate mouse and human findings. Through integration analyses of nine datasets (one human, six murine, and two rat), we identified 199 genes with known biological functions that are commonly affected by 8C-PFAS across species. We delineated a comprehensive regulatory network of 8C-PFAS toxicity, demonstrating that 8C-PFAS may trigger fatty liver disease by up-regulating CD36 and PPARα pathway; dysregulate xenobiotic metabolism by disrupting CAR and CYP family genes; and induce cancer by dysregulating WNT, TGFβ, FGF21, and P53 pathways. We also identified ATF3, EGR1, ESR1, NFATC4, SNAI2, TP53, and EZH2 as transcriptionally regulated by 8C-PFAS, along with PPARα, RXRα, FGFR1, TCF3, and SMAD3 as potentially functionally impacted. Collectively, these factors account for over 90 % of 8C-PFAS-affected key genes. This study not only developed a novel method for extrapolating human toxicity risks by integrating scattered toxicity evidence based on transcriptomics data, but also proposes new mechanisms by which 8C-PFAS contributes to fatty liver disease and cancer.

Exploring maternal and developmental toxicity of perfluoroalkyl ether acids PFO4DA and PFO5DoA using hepatic transcriptomics and serum metabolomics

Production of per- and polyfluoroalkyl substances (PFAS) has shifted from long-chain perfluoroalkyl acids to short-chain compounds and those with ether bonds in the carbon chain. Next-generation perfluoroalkylether PFAS include HFPO-DA ("GenX chemicals"), Nafion Byproducts, and the PFOx homologous series that includes perfluoro-3,5,7,9-butaoxadecanoic acid (PFO4DA) and perfluoro-3,5,7,9,11-pentaoxadodecanoic acid (PFO5DoA). PFO4DA and PFO5DoA have been detected in serum and/or tissues from humans and wildlife proximal to contamination point sources. However, toxicity data are extremely limited, with no in vivo developmental toxicology data. To address these data gaps, pregnant Sprague-Dawley rats were exposed via oral gavage to vehicle, PFO4DA, or PFO5DoA across a series of doses (0.1 to 62.5 mg/kg/day) from gestation day (GD) 18-22. Hepatic transcriptomics were assayed in dams and fetuses, and serum metabolomics in dams. These data were overlaid with serum PFO4DA and PFO5DoA concentrations to perform dose-response modeling. Both dams and fetuses exhibited dose-responsive disruption of hepatic gene expression in response to PFO4DA or PFO5DoA, with fetal expression disrupted at lower doses than dams. Several differentially expressed genes were upregulated by every dose of PFO5DoA in both maternal and fetal samples, including genes encoding enzymes that hydrolyze acyl-coA to free fatty acids. Maternal serum metabolomics revealed PFO4DA exposure did not induce significant changes at any tested dose, whereas PFO5DoA exposure resulted in dose-dependent differential metabolite abundance for 149 unique metabolites. Multi-omics pathway analyses of integrated maternal liver transcriptomics and serum metabolomics revealed significant convergent changes as low as 3 mg/kg/d PFO4DA and 0.3 mg/kg/d PFO5DoA exposure. Overall, transcriptomic and metabolomic effects of PFO4DA and PFO5DoA appear consistent with other carboxylic acid PFAS, with primary changes related to lipid metabolism, bile acids, cholesterol, and cellular stress. Importantly, PFO5DoA exposure more potently induced changes in maternal and fetal hepatic gene expression and maternal circulating metabolites, despite high structural similarity. Further, we report in vitro PPARα and PPARγ receptor activation for both compounds as putative molecular mechanisms. This work demonstrates the potential developmental toxicity of alternative moiety perfluoroethers and highlights the developing liver as particularly vulnerable to transcriptomic disruption. Synopsis: Developmental exposure to fluoroether carboxylic acids PFO4DA and PFO5DoA result in differential impacts on hepatic transcriptome in dams and offspring and circulating metabolome in dams, with PFO5DoA exhibiting higher potency than PFO4DA.

Sex and obesity influence the relationship between perfluoroalkyl substances and lean body mass: NHANES 2011-2018

Objective

Polyfluoroalkyl substances (PFAS) are known endocrine disruptors, that have been the subject of limited research regarding their impact on human lean body mass. The aim of this study was to investigate the effects of PFAS exposure on lean body mass.

Methods

We performed a cross-sectional data analysis involving 1022 adolescents and 3274 adults from the National Health and Nutrition Examination Survey (NHANES) 2011-2018, whose lean body mass was measured by dual-energy X-ray absorptiometry. The lean mass index (LMI) was calculated as lean body mass dividing by the square of height. The association between PFAS and LMI was examined through a multivariate-adjusted weighted generalized linear model. Moreover, weighted quantile sum (WQS) regression models were employed to futher examine the relationship between the mixture of PFAS and LMI.

Results

Regression analyses revealed an inverse correlation between PFAS exposure and LMI after adjusting for potential covariates. Adults with higher serum PFAS concentrations manifested a reduction in whole LMI ( β  = -0.193, 95 % confidence interval (CI): -0.325 to -0.06). Notably, this correlation was particularly significant in adult females and individuals with obesity, and it was observed across diverse anatomical regions, including lower limbs, right arm, trunk, and whole lean body mass. In adult females, the association between PFAS and whole LMI was statistically significant ( β  = -0.294, 95 % CI: -0.495 to -0.094), and a similar trend was found in obese individuals ( β  = -0.512, 95 % CI: -0.762 to -0.261). WQS regression analyses supported the results obtained from weighted linear regression analyses.

Conclusions

Our study suggests that exposure to PFAS, whether individually or in combination, is associated with decreased lean body mass in specific body areas, with sex and obesity serving as major influencing factors.

Effects of PFAS on human liver transporters: implications for health outcomes

Per- and polyfluoroalkyl substances (PFAS) have become internationally recognized over the past three decades as persistent organic pollutants used in the production of various consumer and industrial goods. Research efforts continue to gauge the risk that historically used, and newly produced, PFAS may cause to human health. Numerous studies report toxic effects of PFAS on the human liver as well as increased serum cholesterol levels in adults. A major concern with PFAS, also dubbed "forever chemicals," is that they accumulate in the liver and kidney and persist in serum. The mechanisms responsible for their disposition and excretion in humans are poorly understood. A better understanding of the interaction of PFAS with liver transporters, as it pertains to the disposition of PFAS and other xenobiotics, could provide mechanistic insight into human health effects and guide efforts toward risk assessment of compounds in development. This review summarizes the current state of the literature on the emerging relationships (eg, substrates, inhibitors, modulators of gene expression) between PFAS and specific hepatic transporters. The adaptive and toxicological responses of hepatocytes to PFAS that reveal linkages to pathologies and epidemiological findings are highlighted. The evidence suggests that our understanding of the molecular landscape of PFAS must improve to determine their impact on the expression and function of hepatocyte transporters that play a key role in PFAS or other xenobiotic disposition. From here, we can assess what role these changes may have in documented human health outcomes.

Systematic transcriptome-wide meta-analysis across endocrine disrupting chemicals reveals shared and unique liver pathways, gene networks, and disease associations

Cardiometabolic disorders (CMD) are a growing public health problem across the world. Among the known cardiometabolic risk factors are compounds that induce endocrine and metabolic dysfunctions, such as endocrine disrupting chemicals (EDCs). To date, how EDCs influence molecular programs and cardiometabolic risks has yet to be fully elucidated, especially considering the complexity contributed by species-, chemical-, and dose-specific effects. Moreover, different experimental and analytical methodologies employed by different studies pose challenges when comparing findings across studies. To explore the molecular mechanisms of EDCs in a systematic manner, we established a data-driven computational approach to meta-analyze 30 human, mouse, and rat liver transcriptomic datasets for 4 EDCs, namely bisphenol A (BPA), bis(2-ethylhexyl) phthalate (DEHP), tributyltin (TBT), and perfluorooctanoic acid (PFOA). Our computational pipeline uniformly re-analyzed pre-processed quality-controlled microarray data and raw RNAseq data, derived differentially expressed genes (DEGs) and biological pathways, modeled gene regulatory networks and regulators, and determined CMD associations based on gene overlap analysis. Our approach revealed that DEHP and PFOA shared stable transcriptomic signatures that are enriched for genes associated with CMDs, suggesting similar mechanisms of action such as perturbations of peroxisome proliferator-activated receptor gamma (PPARγ) signaling and liver gene network regulators VNN1 and ACOT2. In contrast, TBT exhibited highly divergent gene signatures, pathways, network regulators, and disease associations from the other EDCs. In addition, we found that the rat, mouse, and human BPA studies showed highly variable transcriptomic patterns, providing molecular support for the variability in BPA responses. Our work offers insights into the commonality and differences in the molecular mechanisms of various EDCs and establishes a streamlined data-driven workflow to compare molecular mechanisms of environmental substances to elucidate the underlying connections between chemical exposure and disease risks.

In utero exposures to perfluoroalkyl substances and the human fetal liver metabolome in Scotland: a cross-sectional study

BACKGROUND

Perfluoroalkyl and polyfluoroalkyl substances are classed as endocrine disrupting compounds but continue to be used in many products such as firefighting foams, flame retardants, utensil coatings, and waterproofing of food packaging. Perfluoroalkyl exposure aberrantly modulates lipid, metabolite, and bile acid levels, increasing susceptibility to onset and severity of metabolic diseases, such as diabetes and metabolic dysfunction-associated steatotic liver disease. To date, most studies in humans have focused on perfluoroalkyl-exposure effects in adults. In this study we aimed to show if perfluoroalkyls are present in the human fetal liver and if they have metabolic consequences for the human fetus.

METHODS

In this cross-sectional study, human fetal livers from elective termination of pregnancies at the Aberdeen Pregnancy Counselling Service, Aberdeen, UK, were analysed by both targeted (bile acids and perfluoroalkyl substances) and combined targeted and untargeted (lipids and polar metabolites) mass spectrometry based metabolomic analyses, as well as with RNA-Seq. Only fetuses from normally progressing pregnancies (determined at ultrasound scan before termination), terminated for non-medical reasons, from women older than 16 years, fluent in English, and between 11 and 21 weeks of gestation were collected. Women exhibiting considerable emotional distress or whose fetuses had anomalies identified at ultrasound scan were excluded. Stringent bioinformatic and statistical methods such as partial correlation network analysis, linear regression, and pathway analysis were applied to this data to investigate the association of perfluoroalkyl exposure with hepatic metabolic pathways.

FINDINGS

Fetuses included in this study were collected between Dec 2, 2004, and Oct 27, 2014. 78 fetuses were included in the study: all 78 fetuses were included in the metabolomics analysis (40 female and 38 male) and 57 fetuses were included in the RNA-Seq analysis (28 female and 29 male). Metabolites associated with perfluoroalkyl were identified in the fetal liver and these varied with gestational age. Conjugated bile acids were markedly positively associated with fetal age. 23 amino acids, fatty acids, and sugar derivatives in fetal livers were inversely associated with perfluoroalkyl exposure, and the bile acid glycolithocholic acid was markedly positively associated with all quantified perfluoroalkyl. Furthermore, 7α-hydroxy-4-cholesten-3-one, a marker of bile acid synthesis rate, was strongly positively associated with perfluoroalkyl levels and was detectable as early as gestational week 12.

INTERPRETATION

Our study shows direct evidence for the in utero effects of perfluoroalkyl exposure on specific key hepatic products. Our results provide evidence that perfluoroalkyl exposure, with potential future consequences, manifests in the human fetus as early as the first trimester of gestation. Furthermore, the profiles of metabolic changes resemble those observed in perinatal perfluoroalkyl exposures. Such exposures are already linked with susceptibility, initiation, progression, and exacerbation of a wide range of metabolic diseases.

FUNDING

UK Medical Research Council, Horizon Europe Program of the European Union, Seventh Framework Programme of the European Union, NHS Grampian Endowments grants, European Partnership for the Assessment of Risks from Chemicals, Swedish Research Council, Formas, Novo Nordisk Foundation, and the Academy of Finland.

Dose additive maternal and offspring effects of oral maternal exposure to a mixture of three PFAS (HFPO-DA, NBP2, PFOS) during pregnancy in the Sprague-Dawley rat

Simultaneous exposure to multiple per- and polyfluoroalkyl substances (PFAS) is common in humans across the globe. Individual PFAS are associated with adverse health effects, yet the nature of mixture effects after exposure to two or more PFAS remains unclear. Previously we reported that oral administration of hexafluoropropylene oxide-dimer acid (HFPO-DA, or GenX), Nafion byproduct 2 (NBP2), or perfluorooctane sulfonate (PFOS) individually during pregnancy produced maternal and F1 effects. Here, we hypothesized that responses to the combined exposure to these three PFAS would be dose additive. Pregnant Sprague-Dawley rats were exposed to a fixed-ratio equipotent mixture where the top dose contained each PFAS at their ED50 for neonatal mortality (100 % dose = PFOS 3 mg/kg; NBP2 10 mg/kg; HFPO-DA 110 mg/kg), followed by a dilution series (33.3, 10, 3.3, and 1 %) and vehicle controls (0 % dose). Consistent with the single chemical studies, dams were exposed from gestation day (GD)14-18 or from GD8-postnatal day (PND2). Fetal and maternal livers on GD18 displayed multiple significantly upregulated genes associated with lipid and carbohydrate metabolism at all dose levels, while dams displayed significantly increased liver weight (≥3.3 % dose) and reduced serum thyroid hormones (≥33.3 % dose). Maternal exposure from GD8-PND2 significantly reduced pup bodyweights at birth (≥33.3 % dose) and PND2 (all doses), increased neonatal liver weights (≥3.3 % dose), increased pup mortality (≥3.3 % dose), and reduced maternal bodyweights and weight gain at the top dose. Echocardiography of adult F1 males and females identified significantly increased left ventricular anterior wall thickness (~10 % increase), whereas other cardiac morphological, functional, and transcriptomic measures were unaffected. Mixture effects in maternal and neonatal animals conformed to dose addition using a relative potency factor (RPF) analysis. Results support dose addition-based cumulative assessment approaches for estimating combined effects of PFAS co-exposure.

Mediating effect of endocrine hormones on association between per- and polyfluoroalkyl substances exposure and birth size: Findings from sheyang mini birth cohort study

BACKGROUND

Prenatal exposure to per- and polyfluoroalkyl substances (PFAS) has been reported to affect fetus growth, but current results were inconsistent and their mechanism remained unclear.

OBJECTIVES

We aimed to evaluate the associations of prenatal exposure to single and/or multiple PFAS with birth size and to elucidate whether thyroid hormones and reproductive hormones mediate these associations.

METHODS

A total of 1087 mother-newborn pairs from Sheyang Mini Birth Cohort Study were included in the present cross-sectional analysis. 12 PFAS, 5 thyroid hormones and 2 reproductive hormones were measured in cord serum. Multiple linear regression models and Bayesian kernel machine regression (BKMR) models were used to examine the associations of PFAS with either birth size or endocrine hormones. One-at-a-time pairwise mediating effect analysis was applied to estimate the mediating effect of single hormone in the association between individual chemical and birth size. High-dimensional mediation approach including elastic net regularization and Bayesian shrinkage estimation were further performed to reduce exposure dimension and figure out the global mediation effects of joint endocrine hormones.

RESULTS

Perfluorononanoic acid (PFNA) exposure was positively associated to weight for length z score [WLZ, per log10-unit: regression coefficient (β) = 0.26, 95% confidence intervals (CI): 0.04, 0.47] and ponderal index (PI, β = 0.56, 95% CI: 0.09, 1.02), and PFAS mixture results fit by BKMR model showed consistent consequences. High-dimensional mediating analyses revealed that thyroid stimulating hormone (TSH) explained 6.7% of the positive association between PFAS mixtures exposure and PI [Total effect (TE) = 1.499 (0.565, 2.405); Indirect effect (IE) = 0.105 (0.015, 0.231)]. Besides, 7.3% of the PI variance was indirectly explained by 7 endocrine hormones jointly [TE = 0.810 (0.802, 0.819); IE = 0.040 (0.038, 0.041)].

CONCLUSIONS

Prenatal PFAS mixtures exposure, especially PFNA, was positively associated to birth size. Such associations were partly mediated by cord serum TSH.

Perfluoroalkyl Substance Serum Concentrations and Cholesterol Absorption-Inhibiting Medication Ezetimibe

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are human-made compounds with a widespread presence in human blood and other organs. PFAS have been associated with multiple health effects, including higher serum cholesterol and LDL cholesterol.

OBJECTIVE

Potential population differences in serum PFAS attributable to ezetimibe, a medication that inhibits cholesterol absorption, are of interest for several reasons. The "C8" Health Project survey data from six contaminated water districts in the mid-Ohio Valley of the United States provide a wide enough range of serum PFAS and a sufficient number of ezetimibe takers to explore this topic.

METHODS

A total of 44,126 adult participants of the C8 Health Survey were included in the community-based study. The status of taking (1075) or non-taking of ezetimibe, alone or in combination with another lipid-lowering agent, was acquired. The geometric mean serum concentrations of the four most commonly detected serum PFAS were compared based on the status of ezetimibe use.

RESULTS

There is no significant difference in serum concentrations of perfluorohexanesulfonic acid (PFHxS), perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), and perfluorononanoic acid (PFNA) between ezetimibe users and non-users after adjustment for age, sex, body mass index, estimated glomerular filtration rate (eGFR), cigarette smoking, education, and average household income.

CONCLUSION

The sterol absorption-inhibiting medication ezetimibe does not appear to affect serum PFAS concentrations. We sought but did not find direct evidence that ezetimibe could inhibit PFAS uptake nor inferential evidence that inter-individual differences in sterol absorption could provide a confounding factor explanation for the association of serum total- and LDL-cholesterol with serum PFAS.

Perfluorooctanoic Acid-Disturbed Serum and Liver Lipidome in C57BL/6 Mice

Perfluorooctanoic acid is a manufactured material extensively utilized in industrial and consumer products. As a persistent organic pollutant, perfluorooctanoic acid has raised increasing public health concerns recently. Although perfluorooctanoic acid is known to induce lipid accumulation in the liver, the impact of perfluorooctanoic acid on different lipid classes has not been fully evaluated. In this study, we performed untargeted lipidomics analysis to investigate the impact of perfluorooctanoic acid on the lipid homeostasis in C57BL/6 male mice. Perfluorooctanoic acid disturbed the lipid profiles in serum and liver, with a variety of lipid classes significantly altered. Greater impacts were observed in the liver lipidome than the serum lipidome. In particular, some lipid clusters in the liver were altered by both high- and low-dose perfluorooctanoic acid exposure, including the increase of unsaturated triglycerides and the decrease of sphingomyelins, saturated phosphatidylcholines, saturated lysophosphatidylcholines, and phospholipid ethers. In parallel with an increase in the liver, a decrease of saturated phosphatidylcholines was found in the serum of high-dose perfluorooctanoic acid-treated mice. The findings from this study are helpful to improve the understanding of perfluorooctanoic acid-induced dysregulation of lipid metabolism and perfluorooctanoic acid-associated health effects in liver.

Transcriptional pathways linked to fetal and maternal hepatic dysfunction caused by gestational exposure to perfluorooctanoic acid (PFOA) or hexafluoropropylene oxide-dimer acid (HFPO-DA or GenX) in CD-1 mice

Per- and polyfluoroalkyl substances (PFAS) comprise a diverse class of chemicals used in industrial processes, consumer products, and fire-fighting foams which have become environmental pollutants of concern due to their persistence, ubiquity, and associations with adverse human health outcomes, including in pregnant persons and their offspring. Multiple PFAS are associated with adverse liver outcomes in adult humans and toxicological models, but effects on the developing liver are not fully described. Here we performed transcriptomic analyses in the mouse to investigate the molecular mechanisms of hepatic toxicity in the dam and its fetus after exposure to two different PFAS, perfluorooctanoic acid (PFOA) and its replacement, hexafluoropropylene oxide-dimer acid (HFPO-DA, known as GenX). Pregnant CD-1 mice were exposed via oral gavage from embryonic day (E) 1.5-17.5 to PFOA (0, 1, or 5 mg/kg-d) or GenX (0, 2, or 10 mg/kg-d). Maternal and fetal liver RNA was isolated (N = 5 per dose/group) and the transcriptome analyzed by Affymetrix Array. Differentially expressed genes (DEG) and differentially enriched pathways (DEP) were obtained. DEG patterns were similar in maternal liver for 5 mg/kg PFOA, 2 mg/kg GenX, and 10 mg/kg GenX (R2: 0.46-0.66). DEG patterns were similar across all 4 dose groups in fetal liver (R2: 0.59-0.81). There were more DEGs in fetal liver compared to maternal liver at the low doses for both PFOA (fetal = 69, maternal = 8) and GenX (fetal = 154, maternal = 93). Upregulated DEPs identified across all groups included Fatty Acid Metabolism, Peroxisome, Oxidative Phosphorylation, Adipogenesis, and Bile Acid Metabolism. Transcriptome-phenotype correlation analyses demonstrated > 1000 maternal liver DEGs were significantly correlated with maternal relative liver weight (R2 >0.92). These findings show shared biological pathways of liver toxicity for PFOA and GenX in maternal and fetal livers in CD-1 mice. The limited overlap in specific DEGs between the dam and fetus suggests the developing liver responds differently than the adult liver to these chemical stressors. This work helps define mechanisms of hepatic toxicity of two structurally unique PFAS and may help predict latent consequences of developmental exposure.

Cumulative maternal and neonatal effects of combined exposure to a mixture of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) during pregnancy in the Sprague-Dawley rat

Globally, biomonitoring data demonstrate virtually all humans carry residues of multiple per- and polyfluoroalkyl substances (PFAS). Despite pervasive co-exposure, limited mixtures-based in vivo PFAS toxicity research has been conducted. Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) are commonly detected PFAS in human and environmental samples and both produce adverse effects in laboratory animal studies, including maternal and offspring effects when orally administered during pregnancy and lactation. To evaluate the effects of combined exposure to PFOA and PFOS, we orally exposed pregnant Sprague-Dawley rats from gestation day 8 (GD8) to postnatal day 2 (PND2) to PFOA (10-250 mg/kg/d) or PFOS (0.1-5 mg/kg/d) individually to characterize effects and dose response curve parameters, followed by a variable-ratio mixture experiment with a constant dose of PFOS (2 mg/kg/d) mixed with increasing doses of PFOA (3-80 mg/kg/d). The mixture study design was intended to: 1) shift the PFOA dose response curves for endpoints shared with PFOS, 2) allow comparison of dose addition (DA) and response addition (RA) model predictions, 3) conduct relative potency factor (RPF) analysis for multiple endpoints, and 4) avoid overt maternal toxicity. Maternal serum and liver concentrations of PFOA and PFOS were consistent between the individual chemical and mixture experiments. Combined exposure with PFOS significantly shifted the PFOA dose response curves towards effects at lower doses compared to PFOA-only exposure for multiple endpoints and these effects were well predicted by dose addition. For endpoints amenable to mixture model analyses, DA produced equivalent or better estimates of observed data than RA. All endpoints evaluated were accurately predicted by RPF and DA approaches except for maternal gestational weight gain, which produced less-than-additive results in the mixture. Data support the hypothesis of cumulative effects on shared endpoints from PFOA and PFOS co-exposure and dose additive approaches for predictive estimates of mixture effects.

In vitro activity of a panel of per- and polyfluoroalkyl substances (PFAS), fatty acids, and pharmaceuticals in peroxisome proliferator-activated receptor (PPAR) alpha, PPAR gamma, and estrogen receptor assays

Data demonstrate numerous per- and polyfluoroalkyl substances (PFAS) activate peroxisome proliferator-activated receptor alpha (PPARα), however, additional work is needed to characterize PFAS activity on PPAR gamma (PPARγ) and other nuclear receptors. We utilized in vitro assays with either human or rat PPARα or PPARγ ligand binding domains to evaluate 16 PFAS (HFPO-DA, HFPO-DA-AS, NBP2, PFMOAA, PFHxA, PFOA, PFNA, PFDA, PFOS, PFBS, PFHxS, PFOSA, EtPFOSA, and 4:2, 6:2 and 8:2 FTOH), 3 endogenous fatty acids (oleic, linoleic, and octanoic), and 3 pharmaceuticals (WY14643, clofibrate, and the metabolite clofibric acid). We also tested chemicals for human estrogen receptor (hER) transcriptional activation. Nearly all compounds activated both PPARα and PPARγ in both human and rat ligand binding domain assays, except for the FTOH compounds and PFOSA. Receptor activation and relative potencies were evaluated based on effect concentration 20% (EC20), top percent of max fold induction (pmaxtop), and area under the curve (AUC). HFPO-DA and HFPO-DA-AS were the most potent (lowest EC20, highest pmaxtop and AUC) of all PFAS in rat and human PPARα assays, being slightly less potent than oleic and linoleic acid, while NBP2 was the most potent in rat and human PPARγ assays. Only PFHxS, 8:2 and 6:2 FTOH exhibited hER agonism >20% pmax. In vitro measures of human and rat PPARα and PPARγ activity did not correlate with oral doses or serum concentrations of PFAS that induced increases in male rat liver weight from the National Toxicology Program 28-d toxicity studies. Data indicate that both PPARα and PPARγ activation may be molecular initiating events that contribute to the in vivo effects observed for many PFAS.

Agonistic and potentiating effects of perfluoroalkyl substances (PFAS) on the Atlantic cod (Gadus morhua) peroxisome proliferator-activated receptors (Ppars)

Toxicity mediated by per- and polyfluoroalkyl substances (PFAS), and especially perfluoroalkyl acids (PFAAs), has been linked to activation of peroxisome proliferator-activated receptors (Ppar) in many vertebrates. Here, we present the primary structures, phylogeny, and tissue-specific distributions of the Atlantic cod (Gadus morhua) gmPpara1, gmPpara2, gmPparb, and gmPparg, and demonstrate that the carboxylic acids PFHxA, PFOA, PFNA, as well as the sulfonic acid PFHxS, activate gmPpara1 in vitro, which was also supported by in silico analyses. Intriguingly, a binary mixture of PFOA and the non-activating PFOS produced a higher activation of gmPpara1 compared to PFOA alone, suggesting that PFOS has a potentiating effect on receptor activation. Supporting the experimental data, docking and molecular dynamics simulations of single and double-ligand complexes led to the identification of a putative allosteric binding site, which upon binding of PFOS stabilizes an active conformation of gmPpara1. Notably, binary exposures of gmPpara1, gmPpara2, and gmPparb to model-agonists and PFAAs produced similar potentiating effects. This study provides novel mechanistic insights into how PFAAs may modulate the Ppar signaling pathway by either binding the canonical ligand-binding pocket or by interacting with an allosteric binding site. Thus, individual PFAAs, or mixtures, could potentially modulate the Ppar-signaling pathway in Atlantic cod by interfering with at least one gmPpar subtype.

Integrative omics analysis reveals the protective role of vitamin C on perfluorooctanoic acid-induced hepatoxicity

Introduction

Perfluorooctanoic acid (PFOA) is a compound used as an industrial surfactant in chemical processes worldwide. Population and cross-sectional studies have demonstrated positive correlations between PFOA levels and human health problems.

Objectives

Many studies have focused on the hepatotoxicity and liver problems caused by PFOA, with little attention to remediation of these problems. As an antioxidant, vitamin C is frequently utilized as a supplement for hepatic detoxification.

Methods

In this study, we use a mouse model to study the possible role of vitamin C in reducing PFOA-induced liver damage. Based on comparative transcriptomic and metabolomic analysis, we elucidate the mechanisms underlying the protective effect of vitamin C.

Results

Our results show that vitamin C supplementation reduces signs of PFOA-induced liver damage including total cholesterol and triglyceride levels increase, liver damage markers aspartate, transaminase, and alanine aminotransferase elevation, and liver enlargement. Further, we show that the protective role of vitamin C is associated with signaling networks control, suppressing linoleic acid metabolism, reducing thiodiglycolic acid, and elevating glutathione in the liver.

Conclusion

The findings in this study demonstrate, for the first time, the utility of vitamin C for preventing PFOA-induced hepatotoxicity.

Exposure to legacy and novel perfluoroalkyl substance disturbs the metabolic homeostasis in pregnant women and fetuses: A metabolome-wide association study

BACKGROUND

Perfluoroalkyl substances (PFASs) exist extensively and several of these have been verified to be toxic. Prenatal exposure to PFASs has attracted much attention. Metabolome-wide association analyses can be used to explore the toxicity mechanisms of PFASs by identifying associated biomarkers.

OBJECTIVES

To evaluate associations between the metabolites in maternal and cord serum and internal exposure to several common PFASs.

METHODS

Paired maternal and cord serum samples were collected from 84 pregnant women who gave birth between 2015 and 2016. Seven legacy and two novel PFASs were measured. A nontarget metabolomic method and an iterative metabolite annotation based on metabolic pathways were applied to characterize the metabolic profiles. Linear regression adjusted with the false discovery rate and covariates was used to indicate the associations.

RESULTS

A total of 279 features in maternal serum and 338 features in cord serum were identified as metabolites associated with PFAS exposure. Perfluorooctanoic acid (PFOA) and perfluorohexane sulfonic acid (PFHxS) were two PFASs associated with more metabolites, while the two novel chlorinated polyfluorinated ether sulfonic acids (Cl-PFESAs) showed less relevance to the metabolome. With pathway enrichment analysis, we found that three fatty acid metabolisms and retinol metabolism were correlated with PFAS exposure in maternal blood, and that sterol metabolism showed the correlation in both maternal serum and cord serum.

CONCLUSIONS

We identified metabolites and pathways in pregnant women and fetuses associated with the exposure to several PFAS, indicating a promising application for metabolome-wide association studies. Additional research is needed to confirm causation.

Transcriptional effects of binary combinations of PFAS in FaO cells

Per- and polyfluoroalkyl substances (PFAS) represent a large class of structurally diverse chemicals of increasing public concern, mostly due to their chemical stability and undetermined toxicity profiles. In laboratory animals, adverse effects implicated for certain PFAS, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in particular, include liver toxicity and the associated metabolic dysregulation, immune and thyroid alterations, reproductive toxicity, and selected tumors. The broad commercialization and environmental distribution of PFAS has drawn attention to the need for understanding risks associated with combined exposure to multiple PFAS in complex mixtures. The purpose of this investigation is to determine whether binary combinations of PFAS elicit a molecular response that is either greater than or less than the sum of the individual responses. Exposure of FaO rat hepatoma cells for 24 h to 25 μM-200 μM of the 4- and 8-carbon perfluorocarboxylic acids (PFBA and PFOA) or the 4, 6, and 8-carbon perfluorosulfonic acids (PFBS, PFHxS, and PFOS, respectively) individually caused a dose-dependent increase in PPARα-regulated expression of peroxisomal bifunctional enzyme (Ehhadh). Potency increased with carbon number, with the carboxylates eliciting a greater transcriptional response than the corresponding sulfonates. Combined exposure to PFOA and PFBA produced an effect that was significantly less than the sum of the individual responses. The response to the combination of PFOA and PFOS produced a summative effect at concentrations that were not cytotoxic. Combined exposures to PFOS and either PFBS or PFHxS at low noncytotoxic concentrations produced a transcriptional effect that was significantly less than the sum of the individual effects. The results demonstrate that among the five structurally related perfluoroalkyl acids included in this investigation, PPARα transcriptional activation in response to combined binary exposures is consistently at or below that predicted by the sum of the individual effects.

Non-targeted metabolomics of multiple human cells revealing differential toxic effects of perfluorooctanoic acid

Differences in toxic effects of contaminants among human cells are essential for evaluating their health risks to humans. In this study, non-targeted metabolomics of multiple human cell lines (A549 (lung), DLD-1 (intestine) and L-02 (liver) cells) was used to address the differential toxicity of perfluorooctanoic acid (PFOA). The number of differential metabolites (DMs) identified in the PFOA-treated A549 cells (67) was highest, followed by DLD-1 (12) and L-02 cells (10). The categorization of DMs was almost uniquely specific to each of cell lines. PFOA significantly promoted linoleic acid metabolism in L-02 cells whereas this metabolism was inhibited in the PFOA-treated A549 cells. The levels of interleukin (IL)-1β, IL-6, IL-8 and IL-13 were about 1.5 times higher in the PFOA-treated A549 and L-02 cells than in the controls. PFOA stimulated the biosynthesis of arginine and the metabolism of vitamin B6 in A549 cells. Arginine and vitamin B6 supplemented into cell culture effectively decreased the levels of IL-6 and IL-8. The inhibition of purine metabolism by PFOA resulted in the arrestation of DLD-1 cells at the G₀/G₁-phase. Our results suggest that the differential toxicity of PFOA related to exposure pathways could be elucidated by metabolic profiles specific to various human cells.

Prenatal exposure of female mice to perfluorononanoic acid delays pubertal activation of the reproductive endocrine axis through enhanced hepatic FGF21 production

The developmental toxicity of perfluorononanoic acid (PFNA), a ubiquitous environmental contaminant, has been associated with the activation of PPARα. This study investigated influence of prenatal exposure to PFNA in pubertal activation of reproductive endocrine axis in female mice and explored underlying molecular mechanisms. Herein, we show that when PFNA (3 mg kg^-1 body weight) was orally administered during gestational days 1-18, dams showed an increase in liver weight and hepatic FGF21 synthesis via PPARα activation, and their female offspring (PFNA mice) showed an increase in liver weight and hepatic FGF21 synthesis from postnatal day (PND) 1 to PND21, which were corrected by the administration of the PPARα antagonist GW6471 from PND1-14 (pup-GW). Expression of vasopressin (VAP) in the hypothalamic suprachiasmatic nucleus (SCN) was reduced in PND14-30 PFNA mice, and could be rescued by pup-GW. Pubertal activation of kisspeptin neurons in anteroventral periventricular nucleus (AVPV) and hypothalamic GnRH neurons in PND21-30 PFNA mice was obviously suppressed, but were recovered by pup-GW or PND21-30 application of VAP. The times of vaginal opening and first estrus were delayed in PFNA mice with a decrease in ovary size and the numbers of primary, secondary and antral follicles, and corpora lutea, which were relieved by pup-GW or application of VAP. The findings indicate that prenatal exposure to PFNA through increased FGF21 production in postnatal female offspring impedes postnatal activation of SCN-VAP neurons, which suppresses pubertal onset in AVPV-kisspeptin neurons and reproductive endocrine axis, leading to delayed puberty and dysfunction of ovaries.

Prenatal exposure to per- and polyfluoroalkyl substances (PFAS) and neurobehavior in US children through 8 years of age: The HOME study

BACKGROUND

Studies of prenatal per- and polyfluoroalkyl substances (PFAS) and attention deficit hyperactivity disorder (ADHD)-related behaviors in children are inconsistent.

OBJECTIVES

To examine associations between maternal serum PFAS concentrations and child behavior in 241 mother-child dyads within the Health Outcomes and Measures of the Environment (HOME) Study.

METHODS

We quantified perfluorooctanoate (PFOA), perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS), and perfluorononanoate (PFNA) in maternal serum collected during pregnancy or at delivery. We evaluated a total of 17 outcomes of child behavior using the Behavioral Assessment System for Children-2 (BASC-2) at 5 and 8 years (n = 240) and ADHD diagnostic symptoms and criteria with the Diagnostic Interview Schedule for Children-Young Child (DISC-YC) at 5 years (n = 190). We used linear mixed models and logistic regression with generalized estimating equations to assess associations between PFAS and continuous or dichotomous "at risk" BASC-2 scores; negative binomial regression to calculate incident rate ratios for counts of ADHD symptoms; and Poisson regression with robust standard errors to calculate relative risks of meeting ADHD diagnostic criteria.

RESULTS

Each ln-unit increase in PFOS, PFHxS, and PFNA was associated with higher BASC-2 scores and increased odds of "at-risk" scores for externalizing behaviors, including hyperactivity (PFOS: odds ratio [OR] 2.7, 95% confidence interval [CI] 1.2, 5.9; PFHxS: OR 2.5, 95% CI 1.5, 4.3; PFNA: OR 3.2, 95% CI 1.3, 8.0). PFHxS was also associated with internalizing problems (OR 2.0, 95% CI 1.1, 3.4) and somatization (OR 2.2, 95% CI 1.2, 4.0). PFOS and PFNA were significantly associated with 50-80% more DISC-YC symptoms and diagnostic criteria related to hyperactive-impulsive type ADHD. Prenatal PFNA was associated with increased risk of any-type ADHD.

CONCLUSIONS

Prenatal PFOS and PFNA were consistently associated with measures related to hyperactive-impulsive type ADHD across two validated assessment instruments. PFHxS was associated with increased problems with both externalizing and internalizing behaviors. No associations were noted between PFOA and child neurobehavior.

Early life exposure to per- and polyfluoroalkyl substances (PFAS) and latent health outcomes: A review including the placenta as a target tissue and possible driver of peri- and postnatal effects

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous drinking water contaminants of concern due to mounting evidence implicating adverse health outcomes associated with exposure, including reduced kidney function, metabolic syndrome, thyroid disruption, and adverse pregnancy outcomes. PFAS have been produced in the U.S. since the 1940s and now encompass a growing chemical family comprised of diverse chemical moieties, yet the toxicological effects have been studied for relatively few compounds. Critically, exposures to some PFAS in utero are associated with adverse outcomes for both mother and offspring, such as hypertensive disorders of pregnancy (HDP), including preeclampsia, and low birth weight. Given the relationship between HDP, placental dysfunction, adverse health outcomes, and increased risk for chronic diseases in adulthood, the role of both developmental and lifelong exposure to PFAS likely contributes to disease risk in complex ways. Here, evidence for the role of some PFAS in disrupted thyroid function, kidney disease, and metabolic syndrome is synthesized with an emphasis on the placenta as a critical yet understudied target of PFAS and programming agent of adult disease. Future research efforts must continue to fill the knowledge gap between placental susceptibility to environmental exposures like PFAS, subsequent perinatal health risks for both mother and child, and latent health effects in adult offspring.

Exposure of female mice to perfluorooctanoic acid suppresses hypothalamic kisspeptin-reproductive endocrine system through enhanced hepatic fibroblast growth factor 21 synthesis, leading to ovulation failure and prolonged dioestrus

Perfluorooctanoic acid (PFOA) is widely used in household applications. High-dose exposure to PFOA has been associated with increased risks of infertility and premature ovarian insufficiency in woman. PFOA can alter hepatic gene expression by activating peroxisome proliferator-activated receptor α (PPARα). The present study investigated whether exposure to PFOA via PPARα activation alters the synthesis of hepatic fibroblast growth factor 21 (FGF21) to disturb female neuroendocrine and reproductive function. In the present study, we show that the oral administration of PFOA (2 or 5 mg kg^-1 ) in adult female mice (PFOA mice) caused prolonged dioestrous, a reduction in the number of corpora lutea and decreased levels of hypothalamic gonadotrophin-releasing hormone, serum progesterone and luteinising hormone (LH). Exposure to PFOA decreased the expression of vasopressin in the suprachiasmatic nucleus (SCN) and kisspeptin in the anteroventral periventricular nucleus (AVPV) with deficits in preovulation or oestrogen-induced LH surge. PFOA via activation of PPARα increased dose-dependently hepatic FGF21 expression, leading to elevated serum and hypothalamic FGF21 concentrations. Treatment of PFOA mice with the PPARα antagonist GW6471 or the FGF21 inhibitor PD173074 rescued SCN vasopressin and AVPV-kisspeptin expression. Either administration of GW6471 and PD173074 or treatment with vasopressin and the G protein coupled receptor 54 agonist kisspeptin-10 in PFOA-mice was able to recover the regular oestrous cycle, ovulation ability, LH surge production and reproductive hormone levels. The present study provides in vivo evidence that exposure to PFOA (≥2 mg kg^-1 ) in mice causes down-regulation of the kisspeptin-reproductive endocrine system by enhancing PPARα-mediated hepatic FGF21 expression. The liver-brain reproductive endocrine disorder caused by PFOA exposure may lead to prolonged dioestrous and ovulation failure.

Adverse effects of perfluoroalkyl acids on fish and other aquatic organisms: A review

Perfluoroalkyl acids (PFAAs) have been widely used in many industrial and consumer products. They have been detected ubiquitously in ambient water along with other environmental matrices, and their adverse effects on aquatic organisms have been a subject of active investigation. Here, we intended to summarize and synthesize the existing body of knowledge on PFAA toxicity through an extensive literature review, and shed light on areas where further research is warranted. PFAA toxicity appears to be influenced by the sex and developmental stages of aquatic organisms, but not significantly by exposure route. PFAA-induced aquatic toxicity could be classified as metabolism disturbance, reproduction disruption, oxidative stress, developmental toxicity, thyroid disruption, etc. At the molecular level, these responses can be initiated by key events, such as nuclear receptor activation, reactive oxygen species induction, or interaction with a membrane, followed by a cascade of downstream responses. PFAA-induced toxicity involves diverse metabolic processes, and therefore elucidating crosstalk or interactions among diverse metabolic pathways is a challenging task. In the presence of other chemicals, PFAAs can function as agonists or antagonists, resulting in different directions of combined toxicity. Therefore, mixture toxicity with other groups of chemicals is another research opportunity. Experimental evidence supports the trans-generational toxicity of PFAAs, suggesting that their long-term consequences for aquatic ecosystems should become of concern. A recent global ban of several PFAAs resulted in an increasing dependence on PFAA alternatives. The lack of sufficient toxicological information on this emerging group of chemicals warrant caution and rigorous toxicological assessments.

Perfluorooctanoic acid-induced toxicities in chicken embryo primary cardiomyocytes: Roles of PPAR alpha and Wnt5a/Frizzled2

Perfluorooctanoic acid (PFOA) is a widespread persistent organic pollutant and may induce developmental toxicities, including developmental cardiotoxicity. To explore the potential mechanism of developmental cardiotoxicity induced by PFOA exposure, chicken embryo primary cardiomyocytes were extracted either from chicken embryos pretreated with PFOA (2 mg/kg), or from untreated embryos and then directly exposed cells to PFOA (1, 10, 30 or 100 μg/ml) in culture. Additionally, peroxisome proliferator activated receptor alpha (PPAR alpha) silencing lentivirus was applied to the embryos on embryonic day (ED2). Cell viability was measured with CCK-8 kit, morphology was assessed with hematoxylin and eosin staining, and intracellular Ca²⁺ concentrations were determined with Fluo-4 AM probe. Western blotting was utilized to confirm PPAR alpha silencing efficiency and the protein abundance of Wnt5a and Frizzled2. The results indicated that both PFOA pretreatment and direct exposure decreased primary cardiomyocyte viability, altered cell morphology and increased intracellular Ca²⁺ concentrations. While l-carnitine co-treatment effectively abolished such changes, PPAR alpha silencing only abolished most of the changes in PFOA pretreatment group, but not in cells directly exposed to relatively high doses of PFOA. The protein abundance of Wnt5a and Frizzled2 was increased by PFOA pretreatment, while direct exposure to PFOA increased Frizzled2 abundance but decreased Wnt5a abundance. PPAR alpha silencing resulted in over 50% decrease of PPAR alpha expression level, which abolished the Wnt5a/Frizzled2 expression alterations following PFOA exposure. In conclusion, PFOA-induced primary cardiomyocyte toxicity is associated with PPAR alpha and Wnt5a/Frizzled2, in which PPAR alpha seems to play regulatory roles towards Wnt5a/Frizzled2.

PFOS, PFOA, estrogen homeostasis, and birth size in Chinese infants

Laboratory studies have suggested that perfluoroalkyl substances (PFASs) could affect fetal growth by disrupting estrogen homeostasis, but there are limited data for human. For this, 424 mother-infant pairs were selected from a cohort established in Hebei Province of North China in 2013. Two typical PFASs, perfluorooctyl sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), and three typical estrogens, estrone (E₁), β-estradiol (E₂), and estriol (E₃), were measured in cord serum. After adjusted for important covariates, serum PFOS was positively related to E₁ and E₃, but negatively related to E₂. Serum PFOA was positively related to serum E₁ and negatively related to head circumference at birth. Serum E₂ was negatively related to head circumference, body weight, and body length at birth and serum E₃ was positively related to body weight. Serum E₃ mediated the relationship between serum PFOS and body weight. There were sex-specific differences for the associations between PFOS/PFOA and estrogens/birth size. These findings suggested that exposure to PFASs could affect estrogen homeostasis and fetal growth during pregnancy and that estrogens might mediate the association between exposure to PFASs and fetal growth.

Biphasic effects of perfluorooctanoic acid on steroidogenesis in mouse Leydig tumour cells

Perfluorooctanoic acid (PFOA) is a persistent organic pollutant, which may possess endocrine disrupting properties. Herein, we investigated the possible mechanism(s) of toxicity and steroidogenesis in mouse Leydig cells. MLTC-1 (mouse Leydig tumour cells) cells were exposed to 0, 50, 100 or 200 μM PFOA for 48 h to ascertain their effects on the nuclear (membrane) receptor responses, steroidogenesis pathway and related regulated gene expression and steroid hormone secretion profiles. Our results reveal that nuclear receptors PXR, SR-B1 and LHR are sensitive to PFOA exposure. PFOA can accumulate in mitochondria and alter cholesterol precursor (fatty acid) mitochondrial transport process-related gene expression and thus inhibit steroid hormone precursor (cholesterol) production. In particular, PFOA exhibits biphasic effects on testosterone and progesterone production at differing levels of exposure. These findings indicate the potential endocrine-related effects of PFOA on steroid hormone secretion in Leydig cells and point to a novel disruption model.

PFOA-induced metabolism disturbance and multi-generational reproductive toxicity in Oryzias latipes

The aims of this study were to examine multi-generational reproductive toxicity and metabolism disturbances in Oryzias latipes exposed to 0.3, 3, and 30mg/L PFOA for 259-day. The highest concentration of PFOA suppressed fecundity over three generations from F0 to F2 and sac-fry survival rate in F2 generation, indicating that PFOA resulted in multi-generational reproductive toxicity (p<0.05). Histologically, in F1 and F2 generations, O. latipes exposed to 30mg/L PFOA revealed accelerated gonad development, and the atrophy and degeneration of thyroid follicular cell. Glucose content showed the highest increase in both genders in all metabolites. However, alanine, glutamine, threonine, and lactate content, which are converted into glucose showed decline tendency, suggesting that PFOA led to gluconeogenesis. Change of osmolyte content affecting osmosis such as a decrease of male myo-inositol (m-Ino), an increase of female trimethylamine N-oxide (TMAO) and an increase of male dimethylamine (DMA) suggest that PFOA might affect osmoregulation of O. latipes. Oxaloacetate of male fish and succinate of female fish showed significant alterations, indicating that PFOA may affect energy metabolism differently by sex. These findings will help elucidate the toxicity of PFOA in diverse biological responses including metabolism change.

Perfluoroalkyl Substances during Pregnancy and Offspring Weight and Adiposity at Birth: Examining Mediation by Maternal Fasting Glucose in the Healthy Start Study

BACKGROUND

Certain perfluoroalkyl and polyfluoroalkyl substances (PFAS) are widespread, persistent environmental contaminants. Prenatal PFAS exposure has been associated with lower birth weight; however, impacts on body composition and factors responsible for this association are unknown.

OBJECTIVES

We aimed to estimate associations between maternal PFAS concentrations and offspring weight and adiposity at birth, and secondarily to estimate associations between PFAS concentrations and maternal glucose and lipids, and to evaluate the potential for these nutrients to mediate associations between PFAS and neonatal outcomes.

METHODS

Within the Healthy Start prospective cohort, concentrations of 11 PFAS, fasting glucose, and lipids were measured in maternal mid-pregnancy serum (n=628). Infant body composition was measured using air displacement plethysmography. Associations between PFAS and birth weight and adiposity, and between PFAS and maternal glucose and lipids, were estimated via linear regression. Associations were decomposed into direct and indirect effects.

RESULTS

Five PFAS were detectable in >50% of participants. Maternal perfluorooctanoate (PFOA) and perfluorononanoate (PFNA) concentrations were inversely associated with birth weight. Adiposity at birth was approximately 10% lower in the highest categories of PFOA, PFNA, and perfluorohexane sulfonate (PFHxS) compared to the lowest categories. PFOA, PFNA, perfluorodecanoate (PFDeA), and PFHxS were inversely associated with maternal glucose. Up to 11.6% of the effect of PFAS on neonatal adiposity was mediated by maternal glucose concentrations. Perfluorooctane sulfonate (PFOS) was not significantly associated with any outcomes studied.

CONCLUSIONS

Follow-up of offspring will determine the potential long-term consequences of lower weight and adiposity at birth associated with prenatal PFAS exposure. https://doi.org/10.1289/EHP641.

Analysis of Sub-Lethal Toxicity of Perfluorooctane Sulfonate (PFOS) to Daphnia magna Using ¹H Nuclear Magnetic Resonance-Based Metabolomics

¹H nuclear magnetic resonance (NMR)-based metabolomics was used to characterize the response of Daphnia magna after sub-lethal exposure to perfluorooctane sulfonate (PFOS), a commonly found environmental pollutant in freshwater ecosystems. Principal component analysis (PCA) scores plots showed significant separation in the exposed samples relative to the controls. Partial least squares (PLS) regression analysis revealed a strong linear correlation between the overall metabolic response and PFOS exposure concentration. More detailed analysis showed that the toxic mode of action is metabolite-specific with some metabolites exhibiting a non-monotonic response with higher PFOS exposure concentrations. Our study indicates that PFOS exposure disrupts various energy metabolism pathways and also enhances protein degradation. Overall, we identified several metabolites that are sensitive to PFOS exposure and may be used as bioindicators of D. magna health. In addition, this study also highlights the important utility of environmental metabolomic methods when attempting to elucidate acute and sub-lethal pollutant stressors on keystone organisms such as D. magna.

Perfluoroalkyl Substances, Sex Hormones, and Insulin-like Growth Factor-1 at 6-9 Years of Age: A Cross-Sectional Analysis within the C8 Health Project

BACKGROUND

Exposure to some perfluoroalkyl substances (PFAS), such as perfluorohexane sulfonate (PFHxS), perfluorooctanoate (PFOA), perfluorooctane sulfonate (PFOS), and perfluorononanoic acid (PFNA), may alter levels of sex hormones and insulin-like growth factor-1 (IGF-1) in animals. Human studies on this topic are scarce, and none have been conducted in young children.

OBJECTIVES

We investigated the relationship between levels of PFAS and estradiol, total testosterone, and IGF-1 in 2,292 children (6-9 years of age) from the C8 Health Project who lived near a chemical plant in the Mid-Ohio Valley (USA) with local contamination from PFOA.

METHODS

Serum samples were collected in 2005-2006 and analyzed for PFAS, sex hormones, and IGF-1. Results from regression models were expressed as the adjusted percentage difference (95% CI) per sex-specific interquartile range (IQR) increment of each PFAS serum concentration. Analyses by PFAS quartiles were also conducted.

RESULTS

Median concentrations of PFHxS, PFOA, PFOS, and PFNA were 8, 35, 22, and 1.7 ng/mL in boys and 7, 30, 21, and 1.7 ng/mL in girls. In boys, PFOA concentrations were significantly associated with testosterone levels (-4.9%; 95% CI: -8.7, -0.8%); PFOS with estradiol (-4.0%; 95% CI: -7.7, -0.1%), testosterone (-5.8%; 95% CI: -9.4, -2.0%), and IGF-1 (-5.9%; 95% CI: -8.3, -3.3%); and PFNA with IGF-1 (-3.5%; 95% CI: -6.0, -1.0%). In girls, significant associations were found between PFOS and testosterone (-6.6%; 95% CI: -10.1, -2.8%) and IGF-1 (-5.6%; -8.2, -2.9%); and PFNA and IGF-1 (-3.8%; 95% CI: -6.4, -1.2%). In both sexes, the magnitudes of the associations decreased monotonically across quartiles for both testosterone and IGF-1 in relation to PFOS, and for IGF-1 and PFNA in girls.

CONCLUSIONS

To our knowledge, this is the first study suggesting that PFAS are associated with lower levels of IGF-1 and sex hormones in young children.

CITATION

Lopez-Espinosa MJ, Mondal D, Armstrong BG, Eskenazi B, Fletcher T. 2016. Perfluoroalkyl substances, sex hormones, and insulin-like growth factor-1 at 6-9 years of age: a cross-sectional analysis within the C8 Health Project. Environ Health Perspect 124:1269-1275; http://dx.doi.org/10.1289/ehp.1509869.

Gene expression profile changes in Eisenia fetida chronically exposed to PFOA

Eisenia fetida is a terrestrial organism, which can be used to diagnose sub-lethal concentrations of PFOA by using molecular biomarkers. In order to identify potential molecular biomarkers, we have exposed E. fetida to 10 mg/kg of PFOA in soil for 8 months. The mRNA isolation, sequencing, transcriptome assembly followed by differential gene expression studies have revealed that genes that are involved in apoptotic process, reproduction, calcium signalling, neuronal development and lipid metabolism are predominantly affected. Highly specific genes that are altered by PFOA can be further validated and used as biomarker to detect sub-lethal concentrations of PFOA in the soil.

Programming of metabolic effects in C57BL/6JxFVB mice by in utero and lactational exposure to perfluorooctanoic acid

Perfluorooctanoic acid (PFOA) is known to cause developmental toxicity and is a suggested endocrine disrupting compound (EDC). Early life exposure to EDCs has been implicated in programming of the developing organism for chronic diseases later in life. Here we study perinatal metabolic programming by PFOA using an experimental design relevant for human exposure. C57BL/6JxFVB hybrid mice were exposed during gestation and lactation via maternal feed to seven low doses of PFOA at and below the NOAEL used for current risk assessment (3-3000 µg/kg body weight/day). After weaning, offspring were followed for 23-25 weeks without further exposure. Offspring showed a dose-dependent decrease in body weight from postnatal day 4 to adulthood. Growth under high fat diet in the last 4-6 weeks of follow-up was increased in male and decreased in female offspring. Both sexes showed increased liver weights, hepatic foci of cellular alterations and nuclear dysmorphology. In females, reductions in perigonadal and perirenal fat pad weights, serum triglycerides and cholesterol were also observed. Endocrine parameters, such as glucose tolerance, serum insulin and leptin, were not affected. In conclusion, our study with perinatal exposure to PFOA in mice produced metabolic effects in adult offspring. This is most likely due to disrupted programming of metabolic homeostasis, but the assayed endpoints did not provide a mechanistic explanation. The BMDL of the programming effects in our study is below the current point of departure used for calculation of the tolerable daily intake.

Molecular impacts of perfluorinated chemicals (PFASs) in the liver and testis of male largemouth bass (Micropterus salmoides) in Minnesota Lakes

Perfluorinated chemicals (PFASs) stem from a wide range of sources and have been detected in aquatic ecosystems worldwide, including the upper Midwest and the state of Minnesota in the USA. This study investigated whether fish with high body burden levels of PFASs in the Twin Cities Metro Areas showed any evidence of adverse effects at the level of the transcriptome. We hypothesized that fish with higher body burden levels of PFASs would exhibit molecular responses in the liver and testis that were suggestive of oxidative and general stress, as well as impaired reproduction. Concentrations of PFASs in largemouth bass varied significantly across the sampled lakes, with the lowest concentrations of PFASs found in fish from Steiger and Upper Prior Lakes and the highest concentrations found in fish from Calhoun and Twin Lakes. Largemouth bass with high PFAS concentrations exhibited changes in the expression of genes related to lipid metabolism, energy production, RNA processing, protein production/degradation and contaminant detoxification, all of which are consistent with biomarker responses observed in other studies with PFASs. However, given the wide range of genes that were differentially expressed across the lakes and the variability observed in the mechanisms through which biological processes were affected, it is unlikely that PFASs are the only stressors affecting largemouth bass in the Twin Cities Metro Areas lakes. Indeed, Twin Lake is affected by the Joslyn superfund site which contains polycyclic aromatic hydrocarbons, pentachlorophenol, polychlorinated biphenyls, and dioxins. These compounds are also expected to drive the transcriptomics responses observed, but to what degree is difficult to ascertain at this time.

Prenatal Exposure to Perfluoroalkyl Acids and Serum Testosterone Concentrations at 15 Years of Age in Female ALSPAC Study Participants

BACKGROUND

Exposure to perfluorooctane sulfonic acid (PFOS) or to perfluorooctanoic acid (PFOA) increases mouse and human peroxisome proliferator-activated receptor alpha (PPARα) subtype activity, which influences lipid metabolism. Because cholesterol is the substrate from which testosterone is synthesized, exposure to these substances has the potential to alter testosterone concentrations.

OBJECTIVES

We explored associations of total testosterone and sex hormone-binding globulin (SHBG) concentrations at age 15 years with prenatal exposures to PFOS, PFOA, perfluorohexane sulfonic acid (PFHxS), and perfluoronanoic acid (PFNA) in females.

METHODS

Prenatal concentrations of the perfluoroalkyl acids (PFAAs) were measured in serum collected from pregnant mothers at enrollment (1991-1992) in the Avon Longitudinal Study of Parents and Children (ALSPAC). The median gestational age when the maternal blood sample was obtained was 16 weeks (interquartile range, 11-28 weeks). Total testosterone and SHBG concentrations were measured in serum obtained from their daughters at 15 years of age. Associations between prenatal PFAAs concentrations and reproductive outcomes were estimated using linear regression models (n = 72).

RESULTS

Adjusted total testosterone concentrations were on average 0.18-nmol/L (95% CI: 0.01, 0.35) higher in daughters with prenatal PFOS in the upper concentration tertile compared with daughters with prenatal PFOS in the lower tertile. Adjusted total testosterone concentrations were also higher in daughters with prenatal concentrations of PFOA (β = 0.24; 95% CI: 0.05, 0.43) and PFHxS (β = 0.18; 95% CI: 0.00, 0.35) in the upper tertile compared with daughters with concentrations in the lower tertile. We did not find evidence of associations between PFNA and total testosterone or between any of the PFAAs and SHBG.

CONCLUSIONS

Our findings were based on a small study sample and should be interpreted with caution. However, they suggest that prenatal exposure to some PFAAs may alter testosterone concentrations in females.

Prenatal exposures to perfluoroalkyl acids and serum lipids at ages 7 and 15 in females

BACKGROUND

In some cross-sectional epidemiologic studies the shape of the association between serum concentrations of perfluoroalkyl acids (PFAAs) and lipids suggests departures from linearity.

OBJECTIVES

We used statistical approaches allowing for non-linearity to determine associations of prenatal exposures of perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) with lipid concentrations.

METHODS

PFAAs were measured in serum from pregnant women collected in 1991-1992 at enrollment in the Avon Longitudinal Study of Parents and Children and lipids in serum from their daughters at ages 7 (n=111) and 15 (n=88). The associations of PFAAs with lipids were first explored by cubic splines, followed by piecewise linear regressions by tertiles to obtain regression coefficients (β) and their 95% confidence limits (95% CL) (in mg/dL per 1ng/mL).

RESULTS

At age 7, total cholesterol was positively associated with prenatal PFOA concentrations in the lower tertile (β=15.01; 95% CL=2.34, 27.69) but not with PFOA concentrations in the middle (β=-3.63; 95% CL=-17.43, 10.16) and upper (β=-1.58; 95% CL=-4.58, 1.42) tertiles. At age 15, a similar pattern was noted as well. Positive associations between LDL-C and prenatal PFOA concentration in the lower tertile were observed in daughters at ages 7 (β=14.91; 95% CL=3.53, 28.12) and 15 (β=13.93; 95% CL=0.60, 27.26). LDL-C was not associated with PFOA concentrations in the middle or upper tertile at any age. Neither HDL-C nor triglycerides was associated with prenatal PFOA exposure. Non-linear patterns of association of total cholesterol and LDL-C with prenatal PFOS were less consistently noted.

CONCLUSION

Exposure to low levels of PFOA during prenatal development may alter lipid metabolism later in life. Given the small sample size further replication of the association in large independent cohorts is important.

Role of Endoplasmic reticulum apoptotic pathway in testicular Sertoli cells injury induced by Carbon disulfide

The exposure of Carbon disulfide (CS2) is associated with germ cell injury and male infertility in animals and humans. However, the molecular mechanism is currently unknown. This study show here that CS2-induced Sertoli cells injury via Endoplasmic reticulum (ER) apoptotic pathway. SD male rats were exposed to doses of CS2 (0, 50, 250, 1250mgm(-3)) for 4weeks. After treatment, loose structures of seminiferous tubules and disordered cell arrangements were observed by light microscopy. Ultrastructural lesions, deformed chromatins and vacuoles formed from swollen ER were observed by electron microscopy. After primary culture of Sertoli cells, a dose-dependent increased apoptosis were found. The increased activity of Caspase 3, accumulation of intracellular Ca(2+), up-regulation of mRNA and protein expressions of ER apoptotic relative molecules (Calpain 2, Cleaved-Caspase 12, GRP78 and CHOP) were also found in this study. Altogether, our findings indicated that ER apoptotic pathway played an important role in CS2-induced Sertoli cell impairment.

Hepatic Mitochondrial Alteration in CD-1 Mice Associated with Prenatal Exposures to Low Doses of Perfluorooctanoic Acid (PFOA)

Perfluorooctanoic acid (PFOA) is a perfluoroalkyl acid primarily used as an industrial surfactant. It persists in the environment and has been linked to potentially toxic and/or carcinogenic effects in animals and people. As a known activator of peroxisome proliferator-activated receptors (PPARs), PFOA exposure can induce defects in fatty acid oxidation, lipid transport, and inflammation. Here, pregnant CD-1 mice were orally gavaged with 0, 0.01, 0.1, 0.3, and 1 mg/kg of PFOA from gestation days (GD) 1 through 17. On postnatal day (PND) 21, histopathologic changes in the livers of offspring included hepatocellular hypertrophy and periportal inflammation that increased in severity by PND 91 in an apparent dose-dependent response. Transmission electron microscopy (TEM) of selected liver sections from PND 91 mice revealed PFOA-induced cellular damage and mitochondrial abnormalities with no evidence of peroxisome proliferation. Within hypertrophied hepatocytes, mitochondria were not only increased in number but also exhibited altered morphologies suggestive of increased and/or uncontrolled fission and fusion reactions. These findings suggest that peroxisome proliferation is not a component of PFOA-induced hepatic toxicity in animals that are prenatally exposed to low doses of PFOA.

Bioaccumulation of perfluorinated alkyl acids: observations and models

In this review, we consider the two prevailing hypotheses for the mechanisms that control the bioaccumulation of perfluorinated alkyl acids (PFAAs). The first assumes that partitioning to membrane phospholipids, which have a higher affinity for charged species than neutral storage lipids, can explain the high bioaccumulation potential of these compounds. The second assumes that interactions with proteins--including serum albumin, liver fatty acid binding proteins (L-FABP), and organic anion transporters--determine the distribution, accumulation and half-lives of PFAAs. We consider three unique phenomena to evaluate the two models: (1) observed patterns of tissue distribution in the laboratory and field, (2) the relationship between perfluorinated chain length and bioaccumulation, and (3) species- and gender-specific variation in elimination half-lives. Through investigation of these three characteristics of PFAA bioaccumulation, we show the strengths and weaknesses of the two modeling approaches. We conclude that the models need not be mutually exclusive, but that protein interactions are needed to explain some important features of PFAA bioaccumulation. Although open questions remain, further research should include perfluorinated alkyl substances (PFASs) beyond the long-chain PFAAs, as these substances are being phased out and replaced by a wide variety of PFASs with largely unknown properties and bioaccumulation behavior.

Endocrine disruption of the epigenome: a breast cancer link

The heritable component of breast cancer accounts for only a small proportion of total incidences. Environmental and lifestyle factors are therefore considered to among the major influencing components increasing breast cancer risk. Endocrine-disrupting chemicals (EDCs) are ubiquitous in the environment. The estrogenic property of EDCs has thus shown many associations between ongoing exposures and the development of endocrine-related diseases, including breast cancer. The environment consists of a heterogenous population of EDCs and despite many identified modes of action, including that of altering the epigenome, drawing definitive correlations regarding breast cancer has been a point of much discussion. In this review, we describe in detail well-characterized EDCs and their actions in the environment, their ability to disrupt mammary gland formation in animal and human experimental models and their associations with exposure and breast cancer risk. We also highlight the susceptibility of early-life exposure to each EDC to mediate epigenetic alterations, and where possible describe how these epigenome changes influence breast cancer risk.

Associations between serum perfluoroalkyl acids and LINE-1 DNA methylation

Perfluoroalkyl acids (PFAAs) are persistent, synthetic compounds that are used in a number of consumer products. Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) have been associated with cardiovascular risk factors, and changes in gene expression and DNA methylation in animals and cellular systems. However, whether PFAA exposure is associated with LINE-1 DNA methylation, a potential marker of cardiovascular risk, in humans remains unknown. We sought to evaluate the cross-sectional associations between serum PFAAs and LINE-1 DNA methylation in a population highly exposed to PFOA. We measured serum PFAAs twice four to five years apart in 685 adult participants (47% male, mean age±SD=42±11years). We measured percent LINE-1 DNA methylation in peripheral blood leukocytes at the second time point (follow-up), and estimated absolute differences in LINE-1 methylation associated with an interquartile (IQR) shift in mean PFAA serum levels. IQR increases in mean serum PFOA, PFOS, perfluorononanoic acid (PFNA), and perfluorohexane sulfonate (PFHxS) were associated with differences of -0.04 (p=0.16), 0.20 (p=0.001), 0.06 (p=0.19), and 0.02 (p=0.57), respectively, in % LINE-1 methylation at follow-up after adjustment for potential confounders. We observed a monotonic increase in LINE-1 DNA methylation across tertiles of PFOS and PFNA (ptrend=0.02 for both associations), but not across tertiles of PFOA or PFHxS (ptrend=0.71 and 0.44, respectively). In summary, serum PFOS was associated with LINE-1 methylation, while serum PFOA, PFHxS, and PFNA were not. Additional research is needed to more precisely determine whether these compounds are epigenetically active.

Particulate matter from Saudi Arabia induces genes involved in inflammation, metabolic syndrome and atherosclerosis

Airborne particulate matter (PM) exposure is a major environmental health concern and is linked to metabolic disorders, such as cardiovascular diseases (CVD) and diabetes, which are on the rise in the Kingdom of Saudi Arabia. This study investigated changes in mouse lung gene expression produced by administration of PM10 collected from Jeddah, Saudi Arabia. FVB/N mice were exposed to 100 μg PM10 or water by aspiration and euthanized 24 h later. The bronchoalveolar lavage fluid (BALF) was collected and analyzed for neutrophil concentration and tumor necrosis factor (TNF)-α and interleukin (IL)-6 levels. RNA was extracted from lungs and whole transcript was analyzed using Affymetrix Mouse Gene 1.0 ST Array. Mice exposed to PM10 displayed an increase in neutrophil concentration and elevated TNF-α and IL-6 levels. Gene expression analysis revealed that mice exposed to PM10 displayed 202 genes that were significantly upregulated and 40 genes that were significantly downregulated. PM10 induced genes involved in inflammation, cholesterol and lipid metabolism, and atherosclerosis. This is the first study to demonstrate that Saudi Arabia PM10 increases in vivo expression of genes located in pathways associated with diseases involving metabolic syndrome and atherosclerosis.

Perfluorooctanoic acid induces apoptosis through the p53-dependent mitochondrial pathway in human hepatic cells: a proteomic study

Perfluorooctanoic acid (PFOA) is one of the most commonly used perfluorinated compounds, and exposure to it has been associated with a number of adverse health effects. However, the molecular mechanisms involved in PFOA toxicity are still not well characterized. In the present study, flow cytometry analysis revealed that PFOA induced oxidative stress, cell cycle arrest and apoptosis in human non-tumor hepatic cells (L-02). Furthermore, we investigated the alterations in protein profile within L-02 cells exposed to PFOA, aiming to explore the mechanisms underlying PFOA hepatotoxicity on the proteome level. Of the 28 proteins showing significant differential expression in response to PFOA, 24 were down-regulated and 4 were up-regulated. This proteomic study proposed that the inhibition of some proteins, including GRP78, HSP27, CTSD and hnRNPC may be involved in the activation of p53, which consequently triggered the apoptotic process in L-02 cells. Induction of apoptosis via the p53-dependent mitochondrial pathway is further suggested as one of the key toxicological events occurring in L-02 cells under PFOA stress. We hope these data will shed new light on the molecular mechanisms responsible for PFOA-mediated toxicity in human liver cells, and from such studies useful biomarkers indicative of PFOA exposure could be developed.

Neurobehavioral effects, c-Fos/Jun expression and tissue distribution in rat offspring prenatally co-exposed to MeHg and PFOA: PFOA impairs Hg retention

Exposure to methylmercury (MeHg) and perfluorooctanoic acid (PFOA) can occur simultaneously as both contaminants are found in the same food sources, especially fish, seafood, marine mammals and milk. The aim of this study was to assess the effects of exposure to MeHg (10 μg mL(-1) in drinking water) and PFOA (10 μg mL(-1) in drinking water) from gestational day 1 to postnatal day (PND) 21, alone and in combination, on neurobehavioral development and the expression of c-Fos/Jun in different brain regions in the offspring. Our findings showed that exposure to MeHg alone, and exposure to MeHg combined with PFOA significantly induced cliff avoidance reflexes and negative geotaxis reflexes. And these effects appeared to be greater following exposure to MeHg alone. MeHg and/or PFOA exposure did not significantly impair motor coordination functions, or cause significant changes in c-Fos expression in the hippocampus and cerebellum, and spatial learning tests were similar to those in the controls, thus it was impossible to determine whether combined exposure to MeHg and PFOA had any additional effects on both hippocampus and cerebellum regions. However, a significant increase in the frequency of line crossing was observed in rats treated with MeHg or PFOA alone, and there were no significant differences between the MeHg+PFOA-treated group and the controls, suggesting that PFOA was antagonistic to MeHg toxicity in the locomotor activity test. Co-exposure to MeHg and PFOA decreased all tissue Hg concentrations in pups compared to the group exposed to MeHg only, suggesting that PFOA impaired Hg retention in different tissues.