Evaluation of the individual and combined toxicity of perfluoroalkyl substances to human liver cells using biomarkers of oxidative stress

Critical new insights into the interactions of hexafluoropropylene oxide-dimer acid (GenX or HFPO-DA) with albumin at molecular and cellular levels

A key characteristic to be elucidated, to address the harmful health risks of environmental perfluorinated alkyl substances (PFAS), is their binding modes to serum albumin, the most abundant protein in blood. Hexafluoropropylene oxide-dimer acid (GenX or HFPO-DA) is a new industrial replacement for the widespread linear long-chain PFAS. However, the detailed interaction of new-generation short-chain PFAS with albumin is still lacking. Herein, the binding characteristics of bovine serum albumin (BSA) to GenX were explored at the molecular and cellular levels. It was found that this branched short-chain GenX could bind to BSA with affinity lower than that of legacy linear long-chain perfluorooctanoic acid (PFOA). Site marker competitive study and molecular docking simulation revealed that GenX interacted with subdomain IIIA to form BSA-GenX complex. Consistent with its weaker affinity to albumin protein, the cytotoxicity of branched short-chain GenX was less susceptible to BSA binding compared with that of the linear long-chain PFOA. In contrast to the significant effects of strong BSA-PFOA interaction, the weak affinity of BSA-GenX binding did not influence the structure of protein and the cytotoxicity of GenX. The detailed characterization and direct comparisons of serum albumin interaction with new generation short-chain GenX will provide a better understanding for the toxicological properties of this new alternative.

Early-life exposure to PCBs and PFAS exerts negative effects on the developing central nervous system

Persistent organic pollutants (POPs) are ubiquitous in the environment and display the capacity to bioaccumulate in living organisms, constituting a hazard to both wildlife and humans. Although restrictions have been applied to prohibit the production of several POPs since the 1960s, high levels of these compounds can still be detected in many environmental and biological matrices, due to their chemical properties and significantly long half-lives. Some POPs can be passed from mother to the fetus and can gain entry to the central nervous system (CNS), by crossing the blood-brain barrier (BBB), resulting in significant deleterious effects, including neurocognitive and psychiatric abnormalities, which may lead to long-term socio-economic burdens. A growing body of evidence obtained from clinical and experimental studies has increasingly indicated that these POPs may influence neurodevelopment through several cellular and molecular mechanisms. However, studies assessing their mechanisms of action are still incipient, requiring further research. Polychlorinated biphenyls (PCBs) and per- and polyfluoroalkyl substances (PFAS) are two of the main classes of POPs associated with disturbances in different human systems, mainly the nervous and endocrine systems. This narrative review discusses the main PCB and PFAS effects on the CNS, focusing on neuroinflammation and oxidative stress and their consequences for neural development and BBB integrity. Moreover, we propose which mechanisms could be involved in POP-induced neurodevelopmental defects. In this sense, we highlight potential cellular and molecular pathways by which these POPs can affect neurodevelopment and could be further explored to propose preventive therapies and formulate public health policies.

A prospective cohort study of persistent endocrine-disrupting chemicals and perceived stress

Persistent endocrine-disrupting chemicals (EDCs) can dysregulate the stress response. We evaluated associations between persistent EDCs and perceived stress among participants in the Study of Environment, Lifestyle, and Fibroids (n = 1394), a prospective cohort study of Black women. Participants completed the Perceived Stress Scale 4 (PSS-4) at baseline and every 20 months through 60 months (score range: 0-16); higher scores indicate higher stress. Endocrine-disrupting chemicals, including per- and polyfluoroalkyl substances, polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and organochlorine pesticides, were quantified in plasma samples at baseline. We fit bayesian kernel machine regression and linear mixed-effects models to estimate associations of EDCs (as a mixture and individually) with PSS-4 scores at baseline and at each follow-up visit, respectively. Increasing percentiles of the mixture were not strongly associated with PSS-4 scores at baseline, and no interactions were observed among EDCs. Several individual EDCs (eg, perfluorodecanoic acid, PCB 118, PBDE 99) were associated with higher PSS-4 scores at baseline or follow-up, and other EDCs (eg PCB 138/158) were associated with lower PSS-4 scores at baseline or follow-up. The directionality of associations for individual EDCs was inconsistent across follow-up visits. In conclusion, specific EDCs may be associated with perceived stress in Black women. This article is part of a Special Collection on Environmental Epidemiology.

Per- and polyfluoroalkyl substances (PFAS) and cancer: Detection methodologies, epidemiological insights, potential carcinogenic mechanisms, and future perspectives

Per- and polyfluoroalkyl substances (PFAS), known as "forever chemicals," are synthetic chemicals which have been used since the 1940s. Given their remarkable thermostability and chemical stability, PFAS have been widely utilized in commercial products, including textiles, surfactants, food packages, nonstick coatings, and fire-fighting foams. Thus, PFAS are widely distributed worldwide and have been detected in human urine, blood, breast milk, tissues and other substances. Growing concerns over the risks of PFAS, including their toxicity and carcinogenicity, have attracted people's attention. Recent reviews have predominantly emphasized advancements in the detection, adsorption, and degradation of PFAS through their chemical structures and toxic properties; however, further examination of the literature is needed to determine the link between PFAS exposure and cancer risk. Here, we introduced different PFAS detection methods based on sensors and liquid chromatography-mass spectrometry (LC-MS). Then, we discussed epidemiological investigations on PFAS levels and cancer risks in recent years, as well as the mechanisms underlying the carcinogenesis. Finally, we proposed the "4C principles" for ongoing exploration and refinement in this field. This review highlights PFAS-cancer associations to fill knowledge gaps and provide evidence-based strategies for future research.

PFAS exposure is associated with an unfavourable metabolic profile in infants six months of age

Exposure to perfluoroalkyl substances (PFAS) are reported to have numerous negative health effects and children are especially vulnerable. The aim of this study was to investigate whether maternal and infant PFAS burden have any impact on prenatal and postnatal growth, liver and lipid parameters in infants at age six months. Data on diet and growth parameters, as well as blood samples were collected from healthy pregnant women in week 18 and in the women and their infants at six months postpartum. The blood samples were analysed for liver enzymes, blood lipids and PFAS. Maternal perfluoroalkyl carboxylic acids (PFCA) and fish for dinner ≥ 3 days per week in pregnancy week 18 were associated with reduced birth weight and increased percent weight gain the first six months of life. Infant PFCA concentrations were positively associated with serum alanine aminotransferase and total- and LDL-cholesterol concentrations at six months of age. Our data demonstrate that prenatal and postnatal PFAS exposure are associated with an unfavourable metabolic profile at a very young age. This pattern is concerning as it may be linked to early conditioning of later metabolic disease. It is vital to reduce PFAS exposure in women of fertile age in order to prevent development of metabolic disease in the next generation.

An in-depth examination of Per- and Polyfluoroalkyl (PFAS) effects on transporters, with emphasis on the ABC superfamily: A critical review

Per- and polyfluoroalkyl (PFAS) substances are a type of chemical compound unique for their multiple carbon-fluorine bonds, imbuing them with strength and environmental permanence. While legacy substances have been phased out due to human health risks, short-chain and alternative PFAS remain omnipresent. However, a detailed explanation for the pathways through which PFAS interact on a cellular and molecular level is still largely unknown, and the human health effects remain mechanistically unexplained. Of particular interest when focusing on this topic are the interactions between these exogenous chemicals and plasma and membrane proteins. Such proteins include serum albumin which can transport PFAS throughout the body, solute carrier proteins (SLC) and ATP binding cassette (ABC) transporters which are able to move PFAS into and out of cells, and proteins and nuclear receptors which interact with PFAS intracellularly. ABC transporters as a family have little available human data despite being responsible for the export of endogenous substances and drugs throughout the body. The multifactorial regulation of these crucial transporters is affected directly and indirectly by PFAS. Changes, which can include alterations to membrane transport activity and differences in protein expression, vary greatly depending on the specific PFAS and protein of interest. Together, the myriad of changes caused by understudied PFAS exposure to a class of understudied proteins crucial to cellular function and drug treatments has not been fully explored regarding human health and presents room for further exploration. This critical work aims to provide a novel framework of existing human data on PFAS and ABC transporters, allowing for future advancement and investigation into human transporter activity, mechanisms of regulation, and interactions with emerging contaminants.

Hepatic transcriptomic assessment of Sprague Dawley rats in response to dietary perfluorobutane sulfonate (PFBS) ingestion

Perfluorobutane sulfonate is a short-chain PFAS that is a less toxic replacement for the rather more toxic long-chain perfluorooctane sulfonate. PFBS is widespread in the environment and has raised environmental and health concerns. The study goal was to investigate whether dietary ingestion of PFBS would induce hepatic damage. Sprague-Dawley rats were assigned to three PFBS treatment groups for 11 weeks followed by clinical markers analyses in the serum and liver. There was a significant increase in liver and body weights of PFBS rats. Total antioxidant capacity was significantly reduced in the PFBS-treated group. ALT levels increased based on concentration ingested. Close to 1000 gene transcripts were differentially expressed. Further, transmembrane transport and oxidation-reduction processes were the most up-regulated biological processes. Inflammatory genes were up-regulated in the exposed group and those associated with oxidative damage were down-regulated. In conclusion, PFBS ingestion produced mild effects in the liver of Sprague Dawley rats.

Fluorinated Organic Polymers for Cancer Drug Delivery

In the realm of cancer therapy, the spotlight is on nanoscale pharmaceutical delivery systems, especially polymer-based nanoparticles, for their enhanced drug dissolution, extended presence in the bloodstream, and precision targeting achieved via surface engineering. Leveraging the amplified permeation and retention phenomenon, these systems concentrate therapeutic agents within tumor tissues. Nonetheless, the hurdles of systemic toxicity, biological barriers, and compatibility with living systems persist. Fluorinated polymers, distinguished by their chemical idiosyncrasies, are poised for extensive biomedical applications, notably in stabilizing drug metabolism, augmenting lipophilicity, and optimizing bioavailability. Material science heralds the advent of fluorinated polymers that, by integrating fluorine atoms, unveil a suite of drug delivery merits: the hydrophobic traits of fluorinated alkyl chains ward off lipid or protein disruption, the carbon-fluorine bond's stability extends the drug's lifecycle in the system, and a lower alkalinity coupled with a diminished ionic charge bolsters the drug's ability to traverse cellular membranes. This comprehensive review delves into the utilization of fluorinated polymers for oncological pharmacotherapy, elucidating their molecular architecture, synthetic pathways, and functional attributes, alongside an exploration of their empirical strengths and the quandaries they encounter in both experimental and clinical settings.

Per- and polyfluoroalkyl substances (PFAS), perceived stress, and depressive symptoms in a prospective cohort study of black women

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are endocrine-disrupting chemicals with neurotoxic properties. PFAS have been associated with depressive symptoms among women in some studies, but little research has evaluated the effects of PFAS mixtures. Further, no study has investigated interactions of PFAS-depression associations by perceived stress, which has been shown to modify the effects of PFAS on other health outcomes.

OBJECTIVE

In a prospective cohort study of reproductive-aged Black women, we investigated associations between PFAS and depressive symptoms and the extent to which perceived stress modified these associations.

METHODS

We analyzed data from 1499 participants (23-35 years) in the Study of Environment, Lifestyle, and Fibroids. We quantified concentrations of nine PFAS in baseline plasma samples using online solid-phase extraction-liquid chromatography-isotope dilution tandem mass spectrometry. Participants reported perceived stress via the Perceived Stress Scale (PSS-4; range = 0-16) at baseline and depressive symptoms via the Center for Epidemiologic Studies Depression Scale (CESD; range = 0-44) at the 20-month follow-up visit. We used Bayesian Kernel Machine Regression to estimate associations between PFAS concentrations, individually and as a mixture, and depressive symptoms, and to assess effect modification by PSS-4 scores, adjusting for confounders.

RESULTS

Baseline perfluorodecanoic acid concentrations were associated with greater depressive symptoms at the 20-month follow-up, but associations for other PFAS were null. The PFAS were not associated with depressive symptoms when evaluated as a mixture. The association between the 90th percentile (vs. 50th percentile) of the PFAS mixture with CES-D scores was null at the 10th (β = 0.03; 95 % CrI = 0.20, 0.25), 50th (β = 0.02; 95 % CrI = -0.16, 0.19), and 90th (β = 0.01; 95 % CrI = 0.18, 0.20) percentiles of PSS-4 scores, suggesting perceived stress did not modify the PFAS mixture.

CONCLUSION

In this prospective cohort study, PFAS concentrations-assessed individually or as a mixture-were not appreciably associated with depressive symptoms, and there was no evidence of effect modification by perceived stress.

Exposure to per- and polyfluoroalkyl substances in lung cancer patients and their associations with clinical health indicators

Per- and polyfluoroalkyl substances (PFASs) have potential carcinogenicity, immunotoxicity, and hepatotoxicity. Research has been conducted on PFAS exposure in people to discuss their potential health effects, excluding lung cancer. In this study, we recruited participants (n = 282) with lung cancer from Heilongjiang Province, northeast China. The PFAS concentrations were measured in their serum to fill the data gap of exposure, and relationships were explored in levels between PFASs and clinical indicators of tumor, immune and liver function. Ten PFASs were found in over 80 % of samples and their total concentrations were 5.27-152 ng/mL, with the highest level for perfluorooctanesulfonate (median: 12.4 ng/mL). Long-chain PFASs were the main congeners and their median concentration (20.5 ng/mL) was nearly three times to that of short-chain PFASs (7.61 ng/mL). Significantly higher concentrations of perfluorobutanoic acid, perfluorononanoic acid and perfluorohexanesulfonate were found in males than in females (p < 0.05). Serum levels of neuro-specific enolase were positively associated with perfluoropentanoic acid in all participants and were negatively associated with perfluorononanesulfonate in females (p < 0.05, multiple linear regression models). Exposure to PFAS mixture was significantly positively associated with the lymphocytic absolute value (difference: 0.224, 95% CI: 0.018, 0.470; p < 0.05, quantile g-computation models) and serum total bilirubin (difference: 2.177, 95% CI: 0.0335, 4.33; p < 0.05). Moreover, PFAS exposure can affect γ-glutamyl transpeptidase through several immune markers (p < 0.05, mediating test). Our results suggest that exposure to certain PFASs could interfere with clinical indicators in lung cancer patients. To our knowledge, this is the first study to detect serum PFAS occurrence and check their associations with clinical indicators in lung cancer patients.

In vitro toxicity of Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) on Human Renal and Hepatoma Cells

We evaluate the cytotoxicity, intracellular redox conditions, apoptosis, and methylation of DNMTs/TETs upon exposure to LiTFSI, a novel Per and Polyfluoroalkyl Substances (PFAS) commonly found in lithium-ion batteries, on human renal carcinoma cells (A498) and hepatoma cells (HepG2). The MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay showed both Perfluorooctane sulfonate (PFOS) and Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) had a dose-dependent effect on A498 and HepG2, with LiTFSI being less toxic. Intracellular redox conditions were assessed with a microplate reader and confocal, which showed a significant decrease in Reactive Oxygen Species (ROS) levels and an increase in Superoxide dismutase (SOD) content in both cells. Exposure to LiTFSI enhanced cell apoptosis, with HepG2 being more susceptible than A498. Quantitative analysis of mRNA expression levels of 19 genes associated with kidney injury, methylation, lipid metabolism and transportation was performed. LiTFSI exposure impacted kidney function by downregulating smooth muscle alpha-actin (Acta2) and upregulating transforming growth factor beta 1 (Tgfb1), B-cell lymphoma 2-like 1) Bcl2l1, hepatitis A virus cellular receptor 1 (Harvcr1), nuclear factor erythroid 2-like 2 (Nfe2l2), and hairy and enhancer of split 1 (Hes1) expression. LiTFSI exposure also affected the abundance of transcripts associated with DNA methylation by the expression of ten-eleven translocation (TET) and DNA methyltransferase (DNMT) genes. Furthermore, LiTFSI exposure induced an increase in lipid anabolism and alterations in lipid catabolism in HepG2. Our results provide new insight on the potential role of a new contaminant, LiTFSI in the regulation of oxidative stress, apoptosis and methylation in human renal carcinoma and hepatoma cells.

Prenatal exposure to per- and polyfluoroalkyl substances (PFAS) and associations with hypertensive disorders of pregnancy in the Atlanta African American Maternal-Child cohort

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are man-made chemicals that are slow to break down in the environment and widely detected in humans. Epidemiological evidence suggests that prenatal exposure to perfluorooctanoic acid (PFOA), a legacy PFAS, is linked to gestational hypertension and preeclampsia. However, the relationship between other PFAS, which are structurally similar, and these outcomes remains largely understudied, despite biologic plausibility. Here, we examined associations between serum PFAS mixtures in relation to hypertensive disorders of pregnancy within a birth cohort of African Americans.

METHODS

Participants in the present study were enrolled in the Atlanta African American Maternal-Child cohort between 2014 and 2020 (n = 513). Serum samples collected between 8 and 14 weeks gestation were analyzed for four PFAS. Logistic regression was used to assess associations between individual natural log transformed PFAS and specific hypertensive disorders of pregnancy (preeclampsia, gestational hypertension), while quantile g-computation was used to estimate mixture effects. Preeclampsia and gestational hypertension were treated as separate outcomes in individual models. All models were adjusted for maternal education, maternal age, early pregnancy body mass index, parity, and any alcohol, tobacco, or marijuana use.

RESULTS

The geometric mean of PFOS and PFHxS was slightly lower among those with preeclampsia relative to those without a hypertensive disorder (e.g., geometric mean for PFOS was 1.89 and 1.94, respectively). Serum concentrations of PFAS were not strongly associated with gestational hypertension or preeclampsia in single pollutant or mixture models. For example, using quantile g-computation, a simultaneous one quartile increase in all PFAS was not associated with odds of gestational hypertension (odds ratio = 0.86, 95% CI = 0.60, 1.23), relative to those without a hypertensive disorder of pregnancy.

CONCLUSIONS

In this birth cohort of African Americans, there was no association between serum PFAS measured in early pregnancy and hypertensive disorders of pregnancy, which may be reflective of the fairly low PFAS levels in our study population.

Association of per- and polyfluoroalkyl substances with constipation: The National Health and Nutrition Examination Survey (2005-2010)

BACKGROUND

The impact of per- and polyfluoroalkyl substances (PFAS) on constipation, as mediated through gastrointestinal absorption and perturbations to the intestinal microecology, remains poorly understood.

OBJECTIVE

This study seeks to explain the relationship between PFAS and constipation.

METHODS

A total of 2945 adults from the National Health and Nutrition Examination Survey (NHANES) 2005-2010 were included in this study. Constipation was defined using the Bristol Stool Form Scale (BSFS) based on stool consistency. The relationship between PFAS and constipation was evaluated using weighted logistic regression and restricted cubic spline (RCS) analysis, while adjusting for confounding variables.

RESULTS

The weighted median concentration of total PFAS (ΣPFAS) was significantly lower in individuals with constipation (19.01 μg/L) compared to those without constipation (23.30 μg/L) (p < 0.0001). Subgroup analysis revealed that the cumulative effect of PFAS was more pronounced in the elderly, men, individuals with obesity, high school education or equivalent, and high-income individuals (p < 0.05). After adjusting for confounding factors, multivariable analysis demonstrated an inverse association between PFOA [OR (95% CI), 0.666(0.486,0.914)] and PFHxS [OR (95% CI), 0.699(0.482,1.015)], and constipation. None of the personal and lifestyle factors showed a significant correlation with this negative association, as confirmed by subgroup analysis and interaction testing (p for interaction > 0.05). The RCS analysis demonstrated a linear inverse relationship between PFAS levels and constipation.

CONCLUSION

The findings of this study provide evidence of a significant inverse correlation between serum concentrations of PFAS, particularly PFOA and PFHxS, and constipation.

Dietary exposure to per- and polyfluoroalkyl substances: Potential health impacts on human liver

Per- and polyfluoroalkyl substances (PFAS), dubbed "forever chemicals", are widely present in the environment. Environmental contamination and food contact substances are the main sources of PFAS in food, increasing the risk of human dietary exposure. Numerous epidemiological studies have established the link between dietary exposure to PFAS and liver disease. Correspondingly, PFAS induced-hepatotoxicity (e.g., hepatomegaly, cell viability, inflammation, oxidative stress, bile acid metabolism dysregulation and glycolipid metabolism disorder) observed from in vitro models and in vivo rodent studies have been extensively reported. In this review, the pertinent literature of the last 5 years from the Web of Science database was researched. This study summarized the source and fate of PFAS, and reviewed the occurrence of PFAS in food system (natural and processed food). Subsequently, the characteristics of human dietary exposure PFAS (population characteristics, distribution trend, absorption and distribution) were mentioned. Additionally, epidemiologic evidence linking PFAS exposure and liver disease was alluded, and the PFAS-induced hepatotoxicity observed from in vitro models and in vivo rodent studies was comprehensively reviewed. Lastly, we highlighted several critical knowledge gaps and proposed future research directions. This review aims to raise public awareness about food PFAS contamination and its potential risks to human liver health.

Interaction between Per- and Polyfluorinated Substances (PFAS) and Acetaminophen in Disease Exacerbation-Focusing on Autism and the Gut-Liver-Brain Axis

This review presents a new perspective on the exacerbation of autism spectrum disorder (ASD) by per- and polyfluoroalkyl substances (PFAS) through the gut-liver-brain axis. We have summarized evidence reported on the involvement of the gut microbiome and liver inflammation that led to the onset and exacerbation of ASD symptoms. As PFAS are toxicants that particularly target liver, this review has comprehensively explored the possible interaction between PFAS and acetaminophen, another liver toxicant, as the chemicals of interest for future toxicology research. Our hypothesis is that, at acute dosages, acetaminophen has the ability to aggravate the impaired conditions of the PFAS-exposed liver, which would further exacerbate neurological symptoms such as lack of social communication and interest, and repetitive behaviors using mechanisms related to the gut-liver-brain axis. This review discusses their potential interactions in terms of the gut-liver-brain axis and signaling pathways that may contribute to neurological diseases.

The interaction of perfluorooctane sulfonate with hemoproteins and its relevance to molecular toxicology

Perfluorooctane sulfonate (PFOS), a representative of perfluorinated compounds in industrial and commercial products, has posed a great threat to animals and humans via environmental exposure and dietary consumption. Herein, we investigated the effects of PFOS binding on the redox state and stability of two hemoproteins (hemoglobin (Hb) and myoglobin (Mb)). Fluorescence spectroscopy, circular dichroism and UV-vis absorption spectroscopy demonstrated that PFOS could induce the conformational changes of proteins along with the exposure of heme cavity and generation of hemichrome, which resulted in the increased release of free hemin. After that, free hemin liberated from hemoproteins led to reactive oxygen species formation, lipid peroxidation, cell membrane damage and loss of cell viability in vascular endothelial cells, while neither Hb nor Mb did show cytotoxicity. Chemical inhibitors of ferroptosis effectively mitigated hemin-caused toxicity, identifying the hemin-dependent ferroptotic cell death mechanisms. These data demonstrated that PFOS posed a potential threat of toxicity through a mechanism which involved its binding to hemoproteins, decreased oxygen transporting capacity, and increased hemin release. Altogether, our findings elucidate the binding mechanisms of PFOS with two hemoproteins, as well as possible risks on vascular endothelial cells, which would have important implications for the human and environmental toxicity of PFOS.

Serum albumin mitigated perfluorooctane sulfonate-induced cytotoxicity by affecting the cellular responses

During the wide applications of perfluorinated materials such as perfluorooctane sulfonate (PFOS) in commercial and industrial products, the potential toxicity of these engineered compounds has attracted more and more attention. As a typical environmental pollutant, PFOS could preferentially bind to albumin protein in vivo. However, the role of protein-PFOS interactions in the cytotoxicity of PFOS was not stressed enough. Herein, we investigated the interactions of PFOS with human serum albumin (HSA, the most abundant protein in human plasma) using both experimental and theoretical approaches. It was demonstrated that PFOS could mainly bind to the Sudlow site I of HSA to generate HSA-PFOS complex through hydrogen bonds and van der Waals forces. Toxicity assays with endothelial cells illustrated that the binding of HSA could significantly attenuate the intracellular uptake and subcellular distribution of PFOS, thereby inhibiting the formation of reactive oxygen species and toxicity for those HSA-bound PFOS. Similarly, the presence of fetal bovine serum in the cell culture media greatly reduced PFOS-caused cytotoxicity. Conclusively, our study reveals that the binding of albumin protein to PFOS could mitigate its toxicity by the modulation of cellular responses. The formation of protein-complexed contaminants would significantly reduce the bioavailability of these chemicals and subsequently mitigate their environmental toxicology to the human health.

Evaluation of the Effect of Perfluorohexane Sulfonate on the Proliferation of Human Liver Cells

Perfluorohexane sulfonate (PFHxS) is a widely detected replacement for legacy long-chain perfluoroalkyl substances (PFAS) in the environment and human blood samples. Its potential toxicity led to its recent classification as a globally regulated persistent organic pollutant. Although animal studies have shown a positive association between PFHxS levels and hepatic steatosis and hepatocellular hypertrophy, the link with liver toxicity, including end-stage liver cancer, remains inconclusive. In this study, we examined the effects of PFHxS on the proliferation of Hep3B (human hepatocellular carcinoma) and SK-Hep1 (human liver sinusoidal endothelial cells). Cells were exposed to different PFHxS concentrations for 24-48 h to assess viability and 12-14 days to measure colony formation. The viability of both cell lines increased at PFHxS concentrations <200 μM, decreased at >400 μM, and was highest at 50 μM. Colony formation increased at <300 μM and decreased at 500 μM PFHxS. Consistent with the effect on cell proliferation, PFHxS increased the expression of proliferating cell nuclear antigen (PCNA) and cell-cycle molecules (CDK2, CDK4, cyclin E, and cyclin D1). In summary, PFHxS exhibited a biphasic effect on liver cell proliferation, promoting survival and proliferation at lower concentrations and being cytotoxic at higher concentrations. This suggests that PFHxS, especially at lower concentrations, might be associated with HCC development and progression.

Maternal co-exposure to mercury and perfluoroalkyl acid isomers and their associations with child neurodevelopment in a Canadian birth cohort

BACKGROUND

Perfluoroalkyl acids (PFAAs) within the broader class of per- and polyfluoroalkyl substances (PFAS) are present in human serum as isomer mixtures, but epidemiological studies have yet to address isomer-specific associations with child development and behavior.

OBJECTIVES

To examine associations between prenatal exposure to 25 PFAAs, including perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) isomers, and child neurodevelopment among 490 mother-child pairs in a prospective Canadian birth cohort, the Alberta Pregnancy Outcomes and Nutrition (APrON) study. To consider the influence of a classic neurotoxicant, total mercury (THg), based on its likelihood of co-exposure with PFAAs from common dietary sources.

METHODS

Maternal blood samples were collected in the second trimester and child neurodevelopment was assessed at 2 years of age using the Bayley Scales of Infant and Toddler Development, 3rd Edition (Bayley-III). Linear or curvilinear multiple regression models were used to examine associations between exposures and neurodevelopment outcomes.

RESULTS

Select PFAAs were associated with lower Cognitive composite scores, including perfluoroheptanoate (PFHpA) (β = -0.88, 95% confidence interval (CI): -1.7, -0.06) and perfluorododecanoate (PFDoA) (β = -2.0, 95% CI: -3.9, -0.01). Non-linear relationships revealed associations of total PFOS (β = -4.4, 95% CI: -8.3, -0.43), and linear-PFOS (β = -4.0, 95% CI: -7.5, -0.57) and 1m-PFOS (β = -1.8, 95% CI: -3.3, -0.24) isomers with lower Language composite scores. Although there was no effect modification, including THg interaction terms in PFAA models revealed negative associations between perfluorononanoate (PFNA) and Motor (β = -3.3, 95% CI: -6.2, -0.33) and Social-Emotional (β = -3.0, 95% CI: -5.6, -0.40) composite scores.

DISCUSSION

These findings reinforce previous reports of adverse effects of maternal PFAA exposure during pregnancy on child neurodevelopment. The unique hazards posed from isomers of PFOS justify isomer-specific analysis in future studies. To control for possible confounding, mercury co-exposure may be considered in studies of PFAAs.

Effects of short-chain per- and polyfluoroalkyl substances (PFAS) on human cytochrome P450 (CYP450) enzymes and human hepatocytes: An in vitro study

Short-chain per- and polyfluoroalkyl substances (PFAS) have been developed as alternatives to legacy long-chain PFAS, but they may still pose risks due to their potential to interact with biomolecules. Cytochrome P450 (CYP450) enzymes are essential for xenobiotic metabolism, and disruptions of these enzymes by PFAS can have significant human health implications. The inhibitory potential of two legacy long-chain (PFOA and PFOS) and five short-chain alternative PFAS (PFBS, PFHxA, HFPO-DA, PFHxS, and 6:2 FTOH) were assessed in recombinant CYP1A2, - 2B6, -2C19, -2E1, and -3A4 enzymes. Most of the short-chain PFAS, except for PFHxS, tested did not result in significant inhibition up to 100 μM. PFOS inhibited recombinant CYP1A2, -2B6, -2C19, and -3A4 enzymes. However, concentrations where inhibition occurred, were all higher than the averages reported in population biomonitoring studies, with IC50 values higher than 10 µM. We also evaluated the activities of CYP1A2 and CYP3A4 in HepaRG monolayers following 48 h exposures of the short-chain PFAS at two concentrations (1 nM or 1 µM) and with or without an inducer (benzo[a]pyrene, BaP, for CYP1A2 and rifampicin for CYP3A4). Our findings suggest that both 1 nM and 1 µM exposures to short-chain PFAS can modulate the CYP1A2 activity induced by BaP. Except for PFHxS, the short-chain PFAS appear to have little effect on CYP3A4 activity. Understanding the effects of PFAS exposure on biotransformation can shed light on the mechanisms of PFAS toxicity and aid in developing effective strategies for managing chemical risks, enabling regulators to make more informed decisions.

Cross-Species Transcriptomics Analysis Highlights Conserved Molecular Responses to Per- and Polyfluoroalkyl Substances

In recent decades, per- and polyfluoroalkyl substances (PFASs) have garnered widespread public attention due to their persistence in the environment and detrimental effects on the health of living organisms, spurring the generation of several transcriptome-centered investigations to understand the biological basis of their mechanism. In this study, we collected 2144 publicly available samples from seven distinct animal species to examine the molecular responses to PFAS exposure and to determine if there are conserved responses. Our comparative transcriptional analysis revealed that exposure to PFAS is conserved across different tissues, molecules and species. We identified and reported several genes exhibiting consistent and evolutionarily conserved transcriptional response to PFASs, such as ESR1, HADHA and ID1, as well as several pathways including lipid metabolism, immune response and hormone pathways. This study provides the first evidence that distinct PFAS molecules induce comparable transcriptional changes and affect the same metabolic processes across inter-species borders. Our findings have significant implications for understanding the impact of PFAS exposure on living organisms and the environment. We believe that this study offers a novel perspective on the molecular responses to PFAS exposure and provides a foundation for future research into developing strategies for mitigating the detrimental effects of these substances in the ecosystem.

Binding of serum albumin to perfluorooctanoic acid reduced cytotoxicity

With the ubiquitous applications of perfluorinated compounds such as perfluorooctanoic acid (PFOA) in industrial and commercial products, the toxicity of these engineered materials in environmental and public health is received growing attention. As a typical organic pollutant, PFOA has been extensively found in wildlife and human bodies, and can preferentially bind to serum albumin in vivo. However, the importance of protein-PFOA interactions on the cytotoxicity of PFOA could not be stressed enough. In this study, we used both experimental and theoretical approaches, to investigate the interactions of PFOA with bovine serum albumin (BSA, the most abundant protein in blood). It was found that PFOA could mainly interact with Sudlow site I of BSA to form BSA-PFOA complex, in which van der Waals forces and hydrogen bonds played dominant roles. Moreover, the strong binding of BSA could greatly alter the cellular uptake and distribution of PFOA in human endothelial cells, and result in the decreases of reactive oxygen species formation and cytotoxicity for these BSA-coated PFOA. Consistently, the addition of fetal bovine serum into cell culture medium also significantly mitigated PFOA-induced cytotoxicity, which was attributed to the extracellular complexation between PFOA and serum proteins. Altogether, our study demonstrates that the binding of serum albumin to PFOA could reduce its toxicity by affecting the cellular responses.

Newborn metabolomic signatures of maternal per- and polyfluoroalkyl substance exposure and reduced length of gestation

Marginalized populations experience disproportionate rates of preterm birth and early term birth. Exposure to per- and polyfluoroalkyl substances (PFAS) has been reported to reduce length of gestation, but the underlying mechanisms are unknown. In the present study, we characterized the molecular signatures of prenatal PFAS exposure and gestational age at birth outcomes in the newborn dried blood spot metabolome among 267 African American dyads in Atlanta, Georgia between 2016 and 2020. Pregnant people with higher serum perfluorooctanoic acid and perfluorohexane sulfonic acid concentrations had increased odds of an early birth. After false discovery rate correction, the effect of prenatal PFAS exposure on reduced length of gestation was associated with 8 metabolomic pathways and 52 metabolites in newborn dried blood spots, which suggested perturbed tissue neogenesis, neuroendocrine function, and redox homeostasis. These mechanisms explain how prenatal PFAS exposure gives rise to the leading cause of infant death in the United States.

Perfluoroalkyl substances promote breast cancer progression via ERα and GPER mediated PI3K/Akt and MAPK/Erk signaling pathways

Perfluoroalkyl substances (PFASs) are a classic environmental endocrine disruptor with carcinogenic risk. Epidemiological studies have shown that PFASs contamination is associated with breast cancer development, but the mechanism remains largely unknown. This study first obtained complex biological information about PFASs-induced breast cancer through the comparative toxicogenomics database (CTD). The Protein-Protein Interaction (PPI) network, Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) analysis were utilized to investigate molecular pathways. The ESR1 and GPER expression levels at different pathological stages and the prognosis of Breast Cancer patients were confirmed using the Cancer Genome Atlas (TCGA) database. Furthermore, we verified this by cellular experiments and the results showed breast cancer cell migration and invasion were promoted by PFOA. Two estrogen receptors (ER), ERα and G protein-coupled estrogen receptor (GPER), mediated the promoting effects of PFOA by activating MAPK/Erk and PI3K/Akt signaling pathways. These pathways were regulated by ERα and GPER in MCF-7 cells or independently by GPER in MDA-MB-231 cells. Overall, our study provides a better overview of the mechanisms associated with PFASs-induced breast cancer development and progression.

Association between maternal exposure to per- and polyfluoroalkyl substances and serum markers of liver function during pregnancy in China: A mixture-based approach

Previous studies have shown that per- and polyfluoroalkyl substances (PFAS) may have hepatotoxic effects in animals. However, epidemiological evidence in humans, especially pregnant women, is limited. This study aimed to assess the association of single and multiple PFAS exposure with serum markers of liver function in pregnant women. A total of 420 pregnant women from the Guangxi Zhuang Birth Cohort were enrolled from June 2015 to April 2019. Nine PFAS were measured in the maternal serum in early pregnancy. Data for liver function biomarkers, namely, alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyltransferase (GGT), total bilirubin (TBIL), direct bilirubin (DBIL), and indirect bilirubin (IBIL), were obtained from medical records. In generalized linear model (GLM), there was a positive association of perfluorooctane sulfonate (PFOS) with ALT, perfluorodecanoic acid (PFDA) and perfluorobutanesulfonic acid (PFBS) with GGT, and perfluorohexane sulfonate (PFHxS) with TBIL and IBIL. In contrast, there was a negative association of perfluoroheptanoic acid (PFHpA) with TBIL. There were inverse U-shaped relationships of PFUnA with ALT and AST and PFDA with ALT by restricted cubic spline. The weighted quantile sum (WQS) regression model revealed the positive effects of the PFAS mixture on GGT, TBIL, DBIL, and IBIL. Bayesian kernel machine regression (BKMR) analysis confirmed that the PFAS mixture was positively associated with GGT, and PFBS was the main contributor. In addition, the BKMR model showed a positive association of individual PFBS with GGT, individual PFHxS with TBIL and IBIL, and a negative association of individual PFHpA with TBIL. Our findings provide evidence of an association between individual PFAS, PFAS mixture and maternal serum markers of liver function during pregnancy. Additionally, these findings also enhance concerns over PFAS exposure on maternal liver function and PFAS monitoring in pregnancy, reducing the effect of maternal liver dysfunction on maternal and infant health.

Short-chain per- and polyfluoralkyl substances (PFAS) effects on oxidative stress biomarkers in human liver, kidney, muscle, and microglia cell lines

Long-chain per- and polyfluoralkyl substances (PFAS) are ubiquitous contaminants implicated in the induction of intracellular reactive oxygen species (ROS), compromising antioxidant defense mechanisms in vitro and in vivo. While a handful of studies have assessed oxidative stress effects by PFAS, few specifically address short-chain PFAS. We conducted an evaluation of oxidative stress biomarkers in vitro following exposures to low (1 nM) and high (1 μM) concentrations of five short-chain PFAS compounds: perfluorobutanesulfonic acid (PFBS), perfluorohexanoic acid (PFHxA), [undecafluoro-2-methyl-3-oxahexanoic acid (HFPO-DA)], 6:2 fluorotelomer alcohol (6:2 FTOH) and perfluorohexanesulfonic acid (PFHxS). We conducted experiments in human kidney (HEK293-hTLR2), liver (HepaRG), microglia (HMC-3), and muscle (RMS-13) cell lines. Fluorescence microscopy measurements in HepaRG cells indicated ROS generation in cells exposed to PFBS and PFHxA for 24 h. Antioxidant enzyme activities were determined following 24 h short-chain PFAS exposures in HepaRG, HEK293-hTLR2, HMC-3, and RMS-13. Notably, exposure to PFBS for 24 h increased the activity of GPX in all four cell types at 1 μM and 1 nM in HepaRG and RMS-13 cells. Every short-chain PFAS evaluated, except for PFHxS, increased the activity of at least one antioxidant enzyme. To our knowledge, this is the first study of its kind to explore antioxidant defense alterations to microglia and muscle cell lines by PFAS. The findings of this study hold great potential to contribute to the limited understanding of short-chain PFAS mechanisms of toxicity and provide data necessary to inform the human health risk assessment process.

Radiolabelling and in vivo radionuclide imaging tracking of emerging pollutants in environmental toxicology: A review

Emerging pollutants (EPs) have become a global concern, attracting tremendous attention because of serious threats to human and animal health. EP diversity emanates from their behaviour and ability to enter the body via multiple pathways and exhibit completely different distribution, transport, and excretion. To better understand the in vivo behaviour of EPs, we reviewed radiolabelling and in vivo radionuclide imaging tracking of various EPs, including micro- and nano-plastics, perfluoroalkyl substances, metal oxides, pharmaceutical and personal care products, and so on. Because this accurate and quantitative imaging approach requires the labelling of radionuclides onto EPs, the main strategies for radiolabelling were reviewed, such as synthesis with radioactive precursors, element exchange, proton beam activation, and modification. Spatial and temporal biodistribution of various EPs was summarised in a heat map, revealing that the absorption, transport, and excretion of EPs are markedly related to their type, size, and pathway into the body. These findings implicate the potential toxicity of diverse EPs in organs and tissues. Finally, we discussed the potential and challenges of radionuclide imaging tracking of EPs, which can be considered in future EPs studies.

Firefighters' exposure to per-and polyfluoroalkyl substances (PFAS) as an occupational hazard: A review

The term "firefighter" and "cancer" have become so intertwined in the past decade that they are now nearly inseparable. Occupational exposure of firefighters to carcinogenic chemicals may increase their risk of developing different types of cancer. PFAS are one of the major classes of carcinogenic chemicals that firefighters are exposed to as occupational hazard. Elevated levels of PFAS have been observed in firefighters' blood serum in recent studies. Possible sources of occupational exposure to PFAS include turnout gear, aqueous film-forming foam, and air and dust at both the fire scene and fire station. Preliminary discussion on PFAS includes definition, classification, and chemical structure. The review is then followed by identifying the sources of PFAS that firefighters may encounter as an occupational hazard. The structural properties of the PFAS used in identified sources, their degradation, and exposure pathways are reviewed. The elevated level of PFAS in the blood serum and how this might associate with an increased risk of cancer is discussed. Our review shows a significant amount of PFAS on turnout gear and their migration to untreated layers, and how turnout gear itself might be a potential source of PFAS exposure. PFAS from aqueous film-forming foams (AFFF), air, and dust of fire stations have been already established as potential exposure sources. Studies on firefighters' cancer suggest that firefighters have a higher cancer risk compared to the general population. This review suggests that increased exposure to PFAS as an occupational hazard could be a potential cancer risk for firefighters.

Associations between concentrations of serum α-klotho and selected urinary monohydroxy metabolites of polycyclic aromatic hydrocarbons: data for US adults aged 40-79 years

For the first time, the associations between urinary concentrations of oxidant polycyclic aromatic hydrocarbon (PAH) metabolites and serum concentrations of anti-oxidant α-klotho were estimated for US adults aged 40-79 years. Multivariate regression models with α-klotho as dependent variable and one of the urinary metabolite of PAH as independent variables were fitted. In the absence of albuminuria and normal (eGFR > 90 mL/min/1.73 m²) kidney function, 10% increases in concentrations of 2-hydroxynaphthalene, 9-hydroxyfluorene, and ∑PAH were associated with 0.25%, 0.32%, and 0.19% decreases in serum α-klotho concentrations. In the absence of albuminuria and near normal (60 <  = eGFR < 90 mL/min/1.73 m²) kidney function, 10% increases in concentrations of 1-hydroxynaphthalene, 9-hydroxyfluorene, 1-hydroxyphenanthrene, and ∑PAH were associated with 0.17%, 0.38%, 0.34%, and 0.18% decreases in serum α-klotho concentrations. To what degree, these mild decreases in α-klotho are a matter of concern, is a subject ripe for discussion and additional investigations. When kidney function was normal or near normal but albuminuria was present, the associations between α-klotho and different metabolites of PAH were, more or less, randomly positive or negative and none reached statistical significance. To conclude, exposure to polycyclic aromatic hydrocarbons may result in reduced concentrations of α-klotho, an antiaging protein.

Recent advances in the remediation of perfluoroalkylated and polyfluoroalkylated contaminated sites

Per- and polyfluoroalkyl substances (PFASs) are compounds used since 1940 in various formulations in the industrial and consumer sectors due to their high chemical and thermal stability. In recent years, PFASs have caused global concern due to their presence in different water and soil matrices, which threatens the environment and human health. These compounds have been reported to be linked to the development of serious human diseases, including but not limited to cancer. For this reason, PFASs have been considered as persistent organic compounds (COPs) and contaminants of emerging concern (CECs). Therefore, this work aims to present the advances in remediation of PFASs-contaminated soil and water by addressing the current literature. The performance and characteristics of each technique were addressed deeply in this work. The reviewed literature found that PFASs elimination studies in soil and water were carried out at a laboratory and pilot-scale in some cases. It was found that ball milling, chemical oxidation and thermal desorption are the most efficient techniques for the removal of PFASs in soils, however, phyto-microbial remediation is under study, which claims to be a promising technique. For the remediation of PFASs-contaminated water, the processes of electrocoagulation, membrane filtration, ozofractionation, catalysis, oxidation reactions - reduction, thermolysis and destructive treatments with plasma have presented the best results. It is noteworthy that hybrid treatments have also proved to be efficient techniques in the removal of these contaminants from soil and water matrices. Therefore, the improvisation and implication of existing techniques on a field-scale are greatly warranted to corroborate the yields obtained on a pilot- and laboratory-scale.

Taurine protects against perfluorooctanoic acid-induced hepatotoxicity via inhibition of oxidative stress, inflammatory, and apoptotic pathways

We are constantly encountering with low doses of chemicals in everyday life rather than toxic doses at a time. So, ongoing low-dose exposures of environmental chemicals commonly encountered are very likely to cause an adverse health effects. Perfluorooctanoic acid (PFOA) is frequently used for production of an array of consumer products and industrial processes. The present study evaluated the underlying mechanisms of PFOA-induced liver damage and also potential protection by taurine. Male Wistar rats were exposed to PFOA alone and in combination with taurine (25, 50, and 100 mg/kg/day) by gavage for 4 weeks. Liver function tests as well as histopathological examinations were studied. Also, oxidative stress markers, mitochondrial function, and nitric oxide (NO) production in liver tissues were measured. In addition, the expression of apoptosis-related genes (caspase-3, Bax, and Bcl-2), inflammation-associated genes (TNF-α, IL-6, NF-B), and c-Jun-N-terminal kinase (JNK) were evaluated. Taurine significantly reversed serum biochemical and histopathological alterations in the liver tissue following exposure to PFOA (10 mg/kg/day). Similarly, taurine alleviated mitochondrial oxidative damage-induced by PFOA in the liver tissue. An increased Bcl2: Bax ratio with decrees in the expression level of caspase-3, and decreased expression of inflammatory markers (TNF-α and IL-6), NF-B, and JNK were also observed following the administration of taurine. These findings suggest a protective role of taurine against PFOA-induced hepatotoxicity via the inhibition of oxidative stress, inflammation, and apoptosis.

Sublethal Exposure of Per- and Polyfluoroalkyl Substances of Varying Chain Length and Polar Functionality Results in Distinct Metabolic Responses in Daphnia magna

Per- and polyfluoroalkyl substances (PFAS) are a class of persistent organic pollutants used in industrial applications because of their physicochemical properties, which results in their ubiquitous presence across environmental matrices. To date, legacy PFAS have been well studied; however, the concentration of alternative PFAS may exceed the concentration of legacy pollutants, and more information is needed regarding the sublethal toxicity at the molecular level of aquatic model organisms, such as Daphnia magna. Perfluorobutanoic acid (PFBA), perfluorohexanoic acid (PFHxA), perfluorohexanesulfonic acid (PFHxS), and perfluorononanoic acid (PFNA) are four widely detected PFAS alternatives of varying chain length and polar functionality that are quantified in aquatic environments. The present study examines the metabolic perturbations of PFAS with varying chemistries to D. magna using targeted mass spectrometry-based metabolomics. Daphnia were acutely exposed to sublethal concentrations of PFBA, PFHxA, PFHxS, and PFNA before the polar metabolite profile was extracted from single organisms. Multivariate analysis demonstrated significant separation between the sublethal concentrations of PFHxA, PFHxS, and PFNA relative to the controls; in sum, longer chain lengths demonstrated greater overall perturbations to the extracted metabolic profiles. Univariate statistics revealed significant perturbations in the concentrations of several amino acids, nucleotides/nucleosides, and neurotransmitters with exposure to PFAS. These metabolic perturbations are consistent with disruptions in energy metabolism (pantothenate and coenzyme A metabolism, histidine metabolism) and protein synthesis (aminoacyl-transfer RNA biosynthesis and amino acid metabolism), which were identified through biochemical pathway analysis. These results provide evidence that although PFAS chemistry (chain length and polar functional group) invokes unique metabolic responses, there is also an underlying toxic mode of action that is common with select PFAS exposure. Overall, the present study highlights the capabilities of environmental metabolomics to elucidate the molecular-level perturbations of pollutants within the same chemical class to model aquatic organisms, which can be used to prioritize risk assessment of substituted PFAS alternatives. Environ Toxicol Chem 2023;42:242-256. © 2022 SETAC.

Associations of serum perfluoroalkyl substances with concentrations of blood manganese and selenium

The aim of this study was to estimate the associations of blood manganese and selenium with serum concentrations of selected perfluoroalkyl substances (PFAS). The presence or absence of this association is important because PFAS have documented pro-oxidant properties, whereas manganese and selenium are critical to antioxidant responses. For this purpose, the data from NHANES for US adults aged ≥ 20 years (N = 3982), adolescents aged 12-19 years (N = 1524), and children aged 3-11 years (N = 639) were analyzed. Among adults, concentrations of blood manganese were found to be inversely associated with serum concentrations of perfluorooctanoic acid or PFOA (β =  - 0.04204, p < 0.01), perfluorononanoic acid or PFNA (β =  - 0.02700, p < 0.01), perfluorohexane sulfonate or PFHxS (β =  - 0.04306, p < 0.01), and perfluorooctane sulfonate or PFOS (β =  - 0.04494, p < 0.01). Blood concentrations of selenium were found to be positively associated with PFHxS only among adults (β = 0.000678, p = 0.047) and adolescents (β = 0.01377, p = 0.02). The Mn results but not the less consistent Se associations were robust to adjustments for serum albumin. Possible reasons for the inverse association of PFOA, PFHxS, PFNA, and PFOS with Mn among US adults are discussed. The finding raises concerns about manganese's diminished ability to mount antioxidant responses to PFAS exposure.

Associations of per- and polyfluoroalkyl substances (PFAS) and their mixture with oxidative stress biomarkers during pregnancy

BACKGROUND

Oxidative stress from excess reactive oxygen species (ROS) is a hypothesized contributor to preterm birth. Per- and polyfluoroalkyl substances (PFAS) exposure is reported to generate ROS in laboratory settings, and is linked to adverse birth outcomes globally. However, to our knowledge, the relationship between PFAS and oxidative stress has not been examined in the context of human pregnancy.

OBJECTIVE

To investigate the associations between prenatal PFAS exposure and oxidative stress biomarkers among pregnant people.

METHODS

Our analytic sample included 428 participants enrolled in the Illinois Kids Development Study and Chemicals In Our Bodies prospective birth cohorts between 2014 and 2019. Twelve PFAS were measured in second trimester serum. We focused on seven PFAS that were detected in >65 % of participants. Urinary levels of 8-isoprostane-prostaglandin-F_2α, prostaglandin-F_2α, 2,3-dinor-8-iso-PGF_2α, and 2,3-dinor-5,6-dihydro-8-iso-PGF_2α were measured in the second and third trimesters as biomarkers of oxidative stress. We fit linear mixed-effects models to estimate individual associations between PFAS and oxidative stress biomarkers. We used quantile g-computation and Bayesian kernel machine regression (BKMR) to assess associations between the PFAS mixture and averaged oxidative stress biomarkers.

RESULTS

Linear mixed-effects models showed that an interquartile range increase in perfluorooctane sulfonic acid (PFOS) was associated with an increase in 8-isoprostane-prostaglandin-F_2α (β = 0.10, 95 % confidence interval = 0, 0.20). In both quantile g-computation and BKMR, and across all oxidative stress biomarkers, PFOS contributed the most to the overall mixture effect. The six remaining PFAS were not significantly associated with changes in oxidative stress biomarkers.

CONCLUSIONS

Our study is the first to investigate the relationship between PFAS exposure and biomarkers of oxidative stress during human pregnancy. We found that PFOS was associated with elevated levels of oxidative stress, which is consistent with prior work in animal models and cell lines. Future research is needed to understand how prenatal PFAS exposure and maternal oxidative stress may affect fetal development.

Associations of single and multiple perfluoroalkyl substances exposure with folate among adolescents in NHANES 2007-2010

BACKGROUND

The accumulation of perfluoroalkyl substances (PFAS) in human body has raised concerns about the potential health impacts on children and adolescents. However, no study has evaluated the associations of PFAS exposure with folate concentrations among adolescents.

METHODS

In the present study, we mainly used three statistical approaches, namely multiple linear regression, Bayesian Kernel Machine Regression (BKMR), and quantile-based g-computation (Q-gcomp) models, to evaluate associations of individual PFAS and their mixtures with serum and red blood cell (RBC) folate concentrations in a sample of 721 adolescents from the NHANES 2007-2010.

RESULTS

In multiple linear regression models, for per unit increase in ln-transformed perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), and perfluorononanoic acid (PFNA), and perfluorodecanoic acid (PFDA) concentrations, RBC folate concentrations decreased by 72.4 (95% confidence interval (CI): -112.7, -32.2), 58.3 (95% CI: -115.0, -1.6), 60.7 (95% CI: -107.5, -13.8), and 76.5 (95% CI: -119.0, -33.9) nmol/L, respectively. A similar significant inverse association was also observed between ln-transformed PFDA and serum folate. BKMR models further confirmed inverse associations of serum PFOS and PFDA with RBC folate, and serum PFDA with serum folate. However, the inverse associations of PFOA and PFNA with RBC folate shown in multiple linear regression model were not observed or less evident in BKMR analyses. We observed interactions of PFOA with PFOS, PFNA, and PFDA on RBC folate in BKMR models, with the negative slopes for PFOS, PFNA, and PFDA increased when PFOA concentration increased from the 10th percentile to the 90th percentile. Both BKMR and Q-gcomp models suggested that the mixtures of five PFAS showed inverse overall associations with RBC folate concentration.

CONCLUSIONS

The present study revealed that adolescent exposure to PFAS might affect serum and RBC folate concentrations.

Toxicity assessment of historical aqueous film-forming foams (AFFFs) using cell-based assays

Aqueous film-forming foam (AFFF) has historically contained high concentrations of long-chain per-and polyfluoroalkyl substances (PFAS), which have been linked with adverse health outcomes. However, the toxicity of historical AFFFs remains largely unknown, presenting uncertainties in their risk assessment. This study assessed the toxicity of historical AFFFs by exposing human liver cells (HepG2) to various dilutions of 3M Light Water AFFF or Ansulite AFFF (0.001%, 0.002%, 0.005%, 0.009%, 0.019%, 0.038%, 0.075%, 0.15%, and 0.3%) for 24 h. The effects of the two AFFF formulations on the cell viability, intracellular reactive oxygen species (ROS) production, Nrf2-ARE activity, and DNA damage were assessed by CellTiter 96® Aq_ueous One Solution Cell Proliferation Assay (MTS kit), dichlorofluorescein diacetate assay, luciferase assay, and alkaline Comet assay, respectively. The results revealed that the two brands of AFFFs tested were toxic to HepG2 cells at dilutions lower than the recommended 3% application formulation. Specifically, exposure to 3M Light Water AFFF or Ansulite AFFF induced a dilution-dependent decrease in cell viability, increased intracellular ROS production, and increased Nrf2-ARE activity. However, except for the highest concentration (lowest dilution) of 3M Light Water AFFF tested (0.038%.), both 3M Light Water AFFF and Ansulite AFFF did not significantly induce cellular DNA damage. Overall, 3M Light Water AFFF was more toxic than Ansulite AFFF. The findings from this study provided valuable in vitro toxicity data that may better inform the health risk assessment of these historical AFFFs.

Associations between the concentrations of α-klotho and selected perfluoroalkyl substances in the presence of eGFR based kidney function and albuminuria: Data for US adults aged 40-79 years

Exposures to per- and polyfluoroalkyl substances (PFAS) cause oxidative stress, a risk factor for tissue damage leading to kidney and cardiovascular diseases. The antiaging protein klotho is known to act as an anti-oxidative agent, and how klotho homeostasis interacts with PFAS has not been reported. This study among 3981 US adults aged 40-79 years old evaluated relationships of internal PFAS contamination to α-klotho across stages of estimated glomerular filtration rate or eGFR-based kidney function and albuminuria defined as urinary albumin creatinine ratio of >30 mg/g creatinine. In the absence of albuminuria and when eGFR based kidney function was in stage GF-1 (eGFR ≥ 90 mL/min/1.73 m²), statistically significant inverse associations between α-klotho and PFNA (β = -0.04930, p < 0.01), PFDA (β = -0.03307, p = 0.02), and PFUnDA (β = -0.03451, p = 0.01), PFHxS (β = -0.03011, p = 0.04) and PFOS (β = -0.03126, p = 0.03) were noted. No associations between α-klotho and PFAS were observed when kidney function was in stages GF-2 (60 ≤ eGFR < 90 mL/min/1.73 m²) or GF-3A (45 ≤ eGFR < 60 mL/min/1.73 m²) in the presence or absence of albuminuria. Unexpectedly, however, in the absence of albuminuria, with kidney function in stage GF-3B/4 (15 ≤ eGFR < 45 mL/min/1.73 m²), associations were positive between α-klotho and PFOA (β = 0.20989, p < 0.01), PFNA (β = 0.18373, p < 0.1), PFDA (β = 0.20413, p < 0.01), PFUnDA (β = 0.17660, p < 0.01), and PFOS (β = 0.14267, p < 0.01). The inverse relationship of PFAS to the antioxidant protein α-klotho in those with healthy kidney function has not been previously reported and should be evaluated in other populations.

Health-related toxicity of emerging per- and polyfluoroalkyl substances: Comparison to legacy PFOS and PFOA

Per- and polyfluoroalkyl substances (PFAS) are highly persistent, manufactured chemicals used in various manufacturing processes and found in numerous commercial products. With over 9000 compounds belonging to this chemical class, there is increasing concern regarding human exposure to these compounds due to their persistent, bioaccumulative, and toxic nature. Human exposure to PFAS may occur from a variety of exposure sources, including, air, food, indoor dust, soil, water, from the transfer of PFAS from non-stick wrappers to food, use of cosmetics, and other personal care products. This critical review presents recent research on the health-related impacts of PFAS exposure, highlighting compounds other than Perfluorooctanoic acid (PFOA) and Perfluoroctane sulfonate (PFOS) that cause adverse health effects, updates the current state of knowledge on PFAS toxicity, and, where possible, elucidates cause-and-effect relationships. Recent reviews identified that exposure to PFAS was associated with adverse health impacts on female and male fertility, metabolism in pregnancy, endocrine function including pancreatic dysfunction and risk of developing Type 2 diabetes, lipid metabolism and risk of childhood adiposity, hepatic and renal function, immune function, cardiovascular health (atherosclerosis), bone health including risk for dental cavities, osteoporosis, and vitamin D deficiency, neurological function, and risk of developing breast cancer. However, while cause-and-effect relationships for many of these outcomes were not able to be clearly elucidated, it was identified that 1) the evidence derived from both animal models and humans suggested that PFAS may exert harmful impacts on both animals and humans, however extrapolating data from animal to human studies was complicated due to differences in exposure/elimination kinetics, 2) PFAS precursor kinetics and toxicity mechanism data are still limited despite ongoing exposures, and 3) studies in humans, which provide contrasting results require further investigation of the long-term-exposed population to better evaluate the biological toxicity of chronic exposure to PFAS.

Comparative cytotoxicity of seven per- and polyfluoroalkyl substances (PFAS) in six human cell lines

Human exposures to perfluoroalkyl and polyfluoroalkyl substances (PFAS) have been linked to several diseases associated with adverse health outcomes. Animal studies have been conducted, though these may not be sufficient due to the inherent differences in metabolic processes between humans and rodents. Acquiring relevant data on the health effects of short-chain PFAS can be achieved through methods supported by in vitro human cell-based models. Specifically, cytotoxicity assays are the crucial first step to providing meaningful information used for determining safety and providing baseline information for further testing. To this end, we exposed human cell lines representative of six different tissue types, including colon (CaCo-2), liver (HepaRG), kidney (HEK293), brain (HMC-3), lung (MRC-5), and muscle (RMS-13) to five short-chain PFAS and two legacy PFAS. The exposure of the individual PFAS was assessed using a range of concentrations starting from a low concentration (10^-11 M) to a high concentration of (10^-4 M). Our results indicated that CaCo-2 and HEK293 cells were the least sensitive to PFAS exposure, while HMC-3, HepaRG, MRC-5, and RMS-13 demonstrated significant decreases in viability in a relatively narrow range (EC₅₀ ranging from 1 to 70 µM). The most sensitive cell line was the neural HMC-3 for all short- and long-chain PFAS (with EC₅₀ ranging from 1.34 to 2.73 µM). Our data suggest that PFAS do not exert toxicity on all cell types equally, and the cytotoxicity estimates we obtained varied from previously reported values. Overall, this study is novel because it uses human cell lines that have not been widely used to understand human health outcomes associated with PFAS exposure.

Framework for risk assessment of PFAS utilizing experimental studies and in-silico models

Perfluoroalkyl substances (PFAS), especially PFOS and PFOA, are two widely used synthetic chemicals that can impact human health based on evidence from animal and epidemiologic studies. In this paper, we have reviewed and summarized the influence of PFAS exposure on health, pointing the quality of evidence, and applied translational techniques to integrate evidence for PFAS policy making. This is the first review where highly referred articles on PFAS used for policymaking by several regulatory agencies were collected and evaluated based on the review guidelines developed by the US National Toxicology Program's Office of Health Assessment and Translation (OHAT) review guidelines. Several limitations were observed, including co-exposure to multiple chemicals and limited measurement of primary and secondary outcomes related to specific toxicity. However, data from all the studies provided a moderate to strong level of confidence for link between PFAS exposure and different adverse outcomes. Secondly, for translating the risk to humans, an in-silico model and scaling approach was utilized. Physiologically based pharmacokinetic model (PBPK) was used to calculate the human equivalent dose (HED) from two widely accepted studies and compared with tolerable daily intakes (TDIs) established by various regulatory agencies. Inter-species dose extrapolation was done to compare with human the relevance of dosing scenarios used in animals. Overall, a framework for translation of risk was proposed based on the conclusions of this review with the goal of improving policymaking. The current paper can improve the methodological protocols for PFAS experimental studies and encourage the utilization of in-silico models for translating risk.

Integration of Toxicogenomics and Physiologically Based Pharmacokinetic Modeling in Human Health Risk Assessment of Perfluorooctane Sulfonate

Toxicogenomics and physiologically based pharmacokinetic (PBPK) models are useful approaches in chemical risk assessment, but the methodology to incorporate toxicogenomic data into a PBPK model to inform risk assessment remains to be developed. This study aimed to develop a probabilistic human health risk assessment approach by integrating toxicogenomic dose-response data and PBPK modeling using perfluorooctane sulfonate (PFOS) as a case study. Based on the available human in vitro and mouse in vivo toxicogenomic data, we identified the differentially expressed genes (DEGs) at each exposure paradigm/duration. Kyoto Encyclopedia of Genes and Genomes and disease ontology enrichment analyses were conducted on the DEGs to identify significantly enriched pathways and diseases. The dose-response data of DEGs were analyzed using the Bayesian benchmark dose (BMD) method. Using a previously published PBPK model, the gene BMDs were converted to human equivalent doses (HEDs), which were summarized to pathway and disease HEDs and then extrapolated to reference doses (RfDs) by considering an uncertainty factor of 30 for mouse in vivo data and 10 for human in vitro data. The results suggested that the median RfDs at different exposure paradigms were similar to the 2016 U.S. Environmental Protection Agency's recommended RfD, while the RfDs for the most sensitive pathways and diseases were closer to the recent European Food Safety Authority's guidance values. In conclusion, genomic dose-response data and PBPK modeling can be integrated to become a useful alternative approach in risk assessment of environmental chemicals. This approach considers multiple endpoints, provides toxicity mechanistic insights, and does not rely on apical toxicity endpoints.

Combined effects of mixed per- and polyfluoroalkyl substances on the Nrf2-ARE pathway in ARE reporter-HepG2 cells

Although the Nrf2-ARE pathway plays a critical role in cellular protection against toxicity and oxidative stress from environmental chemical stressors, the association between exposure to per- and polyfluoroalkyl substances (PFAS) mixtures and the changes of Nrf2-ARE pathway remains largely unexplored. This study evaluated the potential of PFAS to induce the Nrf2-ARE pathway as individual compounds and as binary, ternary, and multicomponent mixtures in the ARE reporter-HepG2 cells and compared the mixture toxicity data to the predictions by concentration addition (CA) model. The toxicological interactions between PFAS mixture components were also determined by the model deviation ratio (MDR) between the CA predicted and mixture toxicity values. The induction of the Nrf2-ARE pathway was quantified using the luciferase system, and the endpoint assessed was the concentration that induced an induction ratio (IR) of 1.5 (EC_IR1.5). The results showed that exposures to both individual and mixed PFAS induced the Nrf2-ARE pathway in ARE reporter-HepG2 cells. Based on the MDRs, the combinations with PFOS showed synergistic interactive effects, while the combinations with PFOA showed additive effects. These results indicate that the CA model underestimated the mixture toxicity of PFAS with PFOS co-exposures and may have health risk assessment implications.

The use of in vitro methods in assessing human health risks associated with short-chain perfluoroalkyl and polyfluoroalkyl substances (PFAS)

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are a large class of industrial chemicals with a ubiquitous and persistent presence in the environment. Of the thousands of PFAS used by consumers and industry, very few have been thoroughly characterized for potential adverse effects. This is especially true for the novel short-chain (C < 8) alternatives that replaced legacy PFAS. Perfluoroalkyl and polyfluoroalkyl substances have revealed inconsistencies in the toxicokinetics predicted by animal models and empirical findings in humans. To adequately assess the possible health effects of short-chain PFAS, there is a need for robust aggregated data sets on the mechanistic underpinnings and physiochemical properties of these alternatives. Acquiring relevant data on the health effects of short-chain PFAS can be achieved through high-throughput methods supported by in vitro human cell-based models. This review briefly summarizes some of the toxicity data obtained using human cells in vitro, discusses the advantages and limitations of cell-based models, and provides insights on potential solutions to challenges presented with the use of these methods for use in safety assessments.

Per- and Polyfluoroalkyl Substance Exposure Combined with High-Fat Diet Supports Prostate Cancer Progression

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals utilized in various industrial settings and include products such as flame retardants, artificial film-forming foams, cosmetics, and non-stick cookware, among others. Epidemiological studies suggest a link between increased blood PFAS levels and prostate cancer incidence, but the mechanism through which PFAS impact cancer development is unclear. To investigate the link between PFAS and prostate cancer, we evaluated the impact of metabolic alterations resulting from a high-fat diet combined with PFAS exposure on prostate tumor progression. We evaluated in vivo prostate cancer xenograft models exposed to perfluorooctane sulfonate (PFOS), a type of PFAS compound, and different diets to study the effects of PFAS on prostate cancer progression and metabolic activity. Metabolomics and transcriptomics were used to understand the metabolic landscape shifts upon PFAS exposure. We evaluated metabolic changes in benign or tumor cells that lead to epigenomic reprogramming and altered signaling, which ultimately increase tumorigenic risk and tumor aggressiveness. Our studies are the first in the field to provide new and clinically relevant insights regarding novel metabolic and epigenetic states as well as to support the future development of effective preventative and therapeutic strategies for PFAS-induced prostate cancers. Our findings enhance understanding of how PFAS synergize with high-fat diets to contribute to prostate cancer development and establish an important basis to mitigate PFAS exposure.

PFOS facilitates liver inflammation and steatosis: An involvement of NLRP3 inflammasome-mediated hepatocyte pyroptosis

Perfluorooctane sulfonate (PFOS) is a fluorinated organic pollutant with substantial accumulation in mammalian liver tissues. However, the impact of chronic PFOS exposure on liver disease progression and the underlying molecular mechanisms remain elusive. Herein, we for the first time revealed that micromolar range of PFOS exposure initiates the activation of NLR pyrin domain containing 3 (NLRP3) inflammasome to drive hepatocyte pyroptosis. We showed that 5 mg/kg/day PFOS exposure may exacerbated liver inflammation and steatosis in high-fat diet (HFD)-fed mice with concurrently elevated expression of NLRP3 and caspase-1. PFOS exposure resulted in viability impairment and LDH release in BRL-3A rat liver cells. 25-100 μM concentrations of PFOS exposure activated the NLRP3 inflammasome, leading to consequent GSDMD cleavage, IL-1β release and the initiation of pyroptosis in a dose-dependent manner, whereas treatment with 10 μM NLRP3 inhibitor MCC950 abrogated this effect. Moreover, pretreatment of 5 mM ROS scavenger N-acetyl-L-cysteine (NAC) ameliorated PFOS-induced NLRP3 inflammasome activation and pyroptosis. Collectively, our data highlight a pivotal role of pyroptotic death in PFOS-mediated liver inflammation and metabolic disorder.

Antioxidant defense system responses, lysosomal membrane stability and DNA damage in earthworms (Eisenia fetida) exposed to perfluorooctanoic acid: an integrated biomarker approach to evaluating toxicity

Perfluorooctanoic acid (PFOA) is one of the most representative perfluoroalkyl substances and has garnered intense human and ecological health concerns due to its ubiquity in the environment, bio-accumulative nature and potential toxicological effects. In this study, an artificial soil containing PFOA was used to evaluate the biological toxicity of PFOA to earthworms Eisenia fetida. Six kinds of oxidative stress biomarkers, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST), reduced glutathione (GSH) and lipid peroxidation (LPO), as well as lysosomal membrane stability (LMS) and DNA damage in earthworms were detected after exposure to 0, 10, 20, 40, 80 and 120 mg kg⁻¹ PFOA in the soil for 3, 7, 14, 28, and 42 days. The results of multi-biomarker responses indicated that PFOA can induce various adverse effects on earthworms, including growth inhibition, oxidative stress and genotoxicity, resulting in lipid membrane peroxidation, decreased lysosomal membrane stability and DNA damage. LPO, LMS and DNA damage all presented dose- and time-dependent relationships. An integrated biomarker response (IBR) index was applied to summarize the multi-biomarker responses to star plots, and the IBR value was calculated as the area of the plots to indicate the integrated stress of PFOA on earthworms. The IBR index showed that the integrated stress induced by PFOA increased markedly throughout the exposure period, exhibiting a concentration-related and exposure time-related effect. The graphical changing trend of the IBR star plots, along with the multi-biomarker responses, suggested that the biomarkers of the antioxidant defense system in earthworms are sufficiently sensitive for short-term PFOA biomonitoring programs, while the bioindicators that indicate actual damage in organisms are more suitable to be employed in long-term monitoring programs for the risk assessment of PFOA. This is the first study evaluating the biological toxicity of PFOA by using an integrated biomarker approach. Our results showed that PFOA can potentially damage soil ecosystems, which provides valuable information for chemical risk assessment of PFOA in the soil environment and early warning bioindicators of soils contaminated by PFOA.

The integrated biomarker response (IBR) index was calculated to evaluate the integrated toxicological effects of PFOA on earthworm Eisenia fetida.