Perfluorooctanoic acid induces mitochondrial dysfunction in MC3T3-E1 osteoblast cells

Sodium p-perfluorous nonenoxybenzene sulfonate induces ROS-mediated necroptosis by directly targeting catalase in HepG2 cells

Sodium p-perfluorous nonenoxybenzene sulfonate (OBS) has been widely used as a substitute for perfluorooctane sulfonic acid (PFOS) because of its high surface activity and low cost, but the knowledge of its biological effects is still limited. In this study, we compared the toxic effects of OBS and PFOS on human hepatoma cells (HepG2). OBS resulted in lower cell viability, higher ROS levels, and more severe necrosis than PFOS, indicating that OBS caused higher cytotoxicity than PFOS. In this process, OBS induced a burst of ROS and downregulation of catalase (CAT). OBS-induced oxidative stress was recovered after the CAT overexpression, but the CAT levels were not reversed after N-acetylcysteine (NAC) pretreatment. This indicates that the downregulated CAT is an upstream signal of the ROS burst. Moreover, drug affinity targeting assay, spectroscopic analysis and molecular docking were conducted, showing that OBS directly targeted CAT and therefore downregulated CAT. In addition, we found that OBS-induced necrosis is RIP1/RIP3-dependent programmed necroptosis. In summary, OBS directly targets CAT to reduce CAT levels and induces oxidative stress and necroptosis. Our findings are helpful to understand the toxicity of OBS and to evaluate the safety of OBS as a substitute for PFOS.

Exposure to select PFAS and PFAS mixtures alters response to platinum-based chemotherapy in endometrial cancer cell lines

BACKGROUND

Exposure to per- and poly-fluoroalkyl substances (PFAS) has been associated with significant alterations in female reproductive health. These include changes in menstrual cyclicity, timing of menarche and menopause, and fertility outcomes, as well as increased risk of endometriosis, all of which may contribute to an increased risk of endometrial cancer. The effect of PFAS on endometrial cancer cells, specifically altered treatment response and biology, however, remains poorly studied. Like other gynecologic malignancies, a key contributor to lethality in endometrial cancer is resistance to chemotherapeutics, specifically to platinum-based agents that are used as the standard of care for patients with advanced-stage and/or recurrent disease.

OBJECTIVES

To explore the effect of environmental exposures, specifically PFAS, on platinum-based chemotherapy response and mitochondrial function in endometrial cancer.

METHODS

HEC-1 and Ishikawa endometrial cancer cells were exposed to sub-cytotoxic nanomolar and micromolar concentrations of PFAS/PFAS mixtures and were treated with platinum-based chemotherapy. Survival fraction was measured 48-h post-chemotherapy treatment. Mitochondrial membrane potential was evaluated in both cell lines following exposure to PFAS ± chemotherapy treatment.

RESULTS

HEC-1 and Ishikawa cells displayed differing outcomes after PFAS exposure and chemotherapy treatment. Cells exposed to PFAS appeared to be less sensitive to carboplatin, with instances of increased survival fraction, indicative of platinum resistance, observed in HEC-1 cells. In Ishikawa cells treated with cisplatin, PFAS mixture exposure significantly decreased survival fraction. In both cell lines, increases in mitochondrial membrane potential were observed post-PFAS exposure ± chemotherapy treatment.

DISCUSSION

Exposure of endometrial cancer cell lines to PFAS/PFAS mixtures had varying effects on response to platinum-based chemotherapies. Increased survival fraction post-PFAS + carboplatin treatment suggests platinum resistance, while decreased survival fraction post-PFAS mixture + cisplatin exposure suggests enhanced therapeutic efficacy. Regardless of chemotherapy sensitivity status, mitochondrial membrane potential findings suggest that PFAS exposure may affect endometrial cancer cell mitochondrial functioning and should be explored further.

PFAS Exposures and the Human Metabolome: A Systematic Review of Epidemiological Studies

Purpose of Review

There is a growing interest in understanding the health effects of exposure to per- and polyfluoroalkyl substances (PFAS) through the study of the human metabolome. In this systematic review, we aimed to identify consistent findings between PFAS and metabolomic signatures. We conducted a search matching specific keywords that was independently reviewed by two authors on two databases (EMBASE and PubMed) from their inception through July 19, 2022 following PRISMA guidelines.

Recent Findings

We identified a total of 28 eligible observational studies that evaluated the associations between 31 different PFAS exposures and metabolomics in humans. The most common exposure evaluated was legacy long-chain PFAS. Population sample sizes ranged from 40 to 1,105 participants at different stages across the lifespan. A total of 19 studies used a non-targeted metabolomics approach, 7 used targeted approaches, and 2 included both. The majority of studies were cross-sectional (n = 25), including four with prospective analyses of PFAS measured prior to metabolomics.

Summary

Most frequently reported associations across studies were observed between PFAS and amino acids, fatty acids, glycerophospholipids, glycerolipids, phosphosphingolipids, bile acids, ceramides, purines, and acylcarnitines. Corresponding metabolic pathways were also altered, including lipid, amino acid, carbohydrate, nucleotide, energy metabolism, glycan biosynthesis and metabolism, and metabolism of cofactors and vitamins. We found consistent evidence across studies indicating PFAS-induced alterations in lipid and amino acid metabolites, which may be involved in energy and cell membrane disruption.

Pre-differentiation GenX exposure induced neurotoxicity in human dopaminergic-like neurons

GenX, also known as hexafluoropropylene oxide dimer acid (HFPO) was introduced as a safer alternative to perfluorooctanoic acid (PFOA) in 2009. After nearly two decades of applications there are increasing safety concerns about GenX due to its association with various organ damages. Few studies, however, have systematically assessed the molecular neurotoxicity of low-dose GenX exposure. Here, we evaluated the effects of pre-differentiation exposure of GenX on dopaminergic (DA) -like neurons using SH-SY5Y cell line; and assessed changes in epigenome, mitochondrion, and neuronal characteristics. Low dose GenX exposure at 0.4 and 4 μg/L prior to differentiation induces persistent changes in nuclear morphology and chromatin arrangements, manifested specifically in the facultative repressive marker H3K27me3. We also observed impaired neuronal network, increased calcium activity along with alterations in Tyrosine hydroxylase (TH) and α-Synuclein after prior exposure to GenX. Collectively, our results identified neurotoxicity of low-dose GenX exposure in human DA-like neurons following a developmental exposure scheme. The observed changes in neuronal characteristics suggest GenX as a potential neurotoxin and risk factor for Parkinson's disease.

Association between perfluoroalkyl and polyfluoroalkyl internal exposure and serum α-Klotho levels in middle-old aged participants

Purpose

Exposure to perfluoroalkyl and polyfluoroalkyl substances causes oxidative stress, which is strongly associated with adverse health effects. Klotho protein plays an anti-aging role via antioxidation activity.

Methods

We investigated the levels of serum α-Klotho and PFAS exposure in adults who participated in the National Health and Nutrition Examination Survey from 2013 to 2016. A nationally representative subsample of 1,499 adults aged 40-79 years was analyzed for the associations of serum α-Klotho levels with serum PFAS exposures by correlation analysis and multiple general linear models. Of note, the potential confounding factors including age and gender were adjusted. Quantile-based g-computation models were used to assess the effects of mixed PFAS exposure on serum α-Klotho levels.

Results

The weighted geometric mean of serum α-Klotho was 791.38 pg/mL for the subjects during 2013-2016. After adjusting for potential confounders, serum Klotho levels showed a statistically significant downward trend with increasing quartiles of PFOA and PFNA. Multivariate adjusted general linear regression analysis showed that increased exposure to PFNA was substantially associated with lower serum levels of α-Klotho, and each 1-unit increase in PFNA concentration was accompanied by a 20.23 pg/mL decrease in α-Klotho level; while no significant association was observed between other PFAS exposures and serum α-Klotho levels. It was negatively correlated between α-Klotho and Q4 for PFNA relative to the lowest quartile (Q1) of exposure (P = 0.025). It was found that the strongest negative correlation between PFNA exposure and serum α-Klotho levels was in the middle-aged (40-59 years) female participants. Furthermore, the mixture of the four PFAS substances showed an overall inverse association with serum α-Klotho concentrations, with PFNA being the major contributor.

Conclusions

Taken together, in a representative sample of the U.S. middle-aged and elderly populations, serum concentrations of PFAS, especially PFNA, have been negatively associated with serum levels of α-Klotho, which is strongly associated with cognition and aging. It was important to note that the majority of associations were limited to middle-aged women. It will be meaningful to clarify the causal relationship and the pathogenic mechanisms of PFAS exposure and α-Klotho levels, which is helpful to aging and aging-related diseases.

An Experimental Study on Antioxidant Enzyme Gene Expression in Trematomus newnesi (Boulenger, 1902) Experimentally Exposed to Perfluoro-Octanoic Acid

Antarctica is the continent with the lowest local human impact; however, it is susceptible to pollution from external sources. Emerging pollutants such as perfluoroalkyl substances pose an increasing threat to this environment and therefore require more in-depth investigations to understand their environmental fate and biological impacts. The present study focuses on expression analysis at the transcriptional level of genes coding for four antioxidant enzymes (sod1, sod2, gpx1, and gpx4) in the liver and kidney of an Antarctic fish species, Trematomus newnesi (Boulenger, 1902). mRNA levels were also assessed in fish exposed to 1.5 μg/L of perfluoro-octanoic acid for 10 days. The kidney showed a higher level of expression than the liver in wildlife specimens. In the liver, the treatment induced an increase in gene expression for all the considered enzymes, whereas in the kidney, it induced a general decrease. The obtained results advance the scientific community's understanding of how the potential future presence of anthropogenic contaminants in the Southern Ocean can affect the antioxidant system of Antarctic fishes. The presence of pollutants belonging to the perfluoroalkyl substances in the Southern Ocean needs to be continuously monitored in parallel with this type of research.

Adverse PFAS effects on mouse oocyte in vitro maturation are associated with carbon-chain length and inclusion of a sulfonate group

OBJECTIVES

Per- and polyfluoroalkyl substances (PFAS) are man-made chemicals that are widely used in various products. PFAS are characterized by their fluorinated carbon chains that make them hard to degrade and bioaccumulate in human and animals. Toxicological studies have shown PFAS toxic effects: cytotoxicity, immunotoxicity, neurotoxicity, and reproductive toxicity. However, it is still unclear how the structures of PFAS, such as carbon-chain length and functional groups, determine their reproductive toxicity.

METHODS AND RESULTS

By using a mouse-oocyte-in-vitro-maturation (IVM) system, we found the toxicity of two major categories of PFAS, perfluoroalkyl carboxylic acid (PFCA) and perfluoroalkyl sulfonic acid (PFSA), is elevated with increasing carbon-chain length and the inclusion of the sulfonate group. Specifically, at 600 μM, perfluorohexanesulfonic acid (PFHxS) and perfluorooctanesulfonic acid (PFOS) reduced the rates of both germinal-vesicle breakdown (GVBD) and polar-body extrusion (PBE) as well as enlarged polar bodies. However, the shorter PFSA, perfluorobutanesulfonic acid (PFBS), and all PFCA did not show similar adverse cytotoxicity. Further, we found that 600 μM PFHxS and PFOS exposure induced excess reactive oxygen species (ROS) and decreased mitochondrial membrane potential (MMP). Cytoskeleton analysis revealed that PFHxS and PFOS exposure induced chromosome misalignment, abnormal F-actin organization, elongated spindle formation, and symmetric division in the treated oocytes. These meiotic defects compromised oocyte developmental competence after parthenogenetic activation.

CONCLUSIONS

Our study provides new information on the structure-toxicity relationship of PFAS.

Low-Dose Dioxin Reduced Glucose Uptake in C2C12 Myocytes: The Role of Mitochondrial Oxidative Stress and Insulin-Dependent Calcium Mobilization

Chronic exposure to some environmental polluting chemicals (EPCs) is strongly associated with metabolic syndrome, and insulin resistance is a major biochemical abnormality in the skeletal muscle in patients with metabolic syndrome. However, the causal relationship is inconsistent and little is known about how EPCs affect the insulin signaling cascade in skeletal muscle. Here, we investigated whether exposure to 100 pM of 2,3,7,8-tetrachlorodibenzodioxin (TCDD) as a low dose of dioxin induces insulin resistance in C2C12 myocytes. The treatment with TCDD inhibited the insulin-stimulated glucose uptake and translocation of glucose transporter 4 (GLUT4). The low-dose TCDD reduced the expression of insulin receptor β (IRβ) and insulin receptor substrate (IRS)-1 without affecting the phosphorylation of Akt. The TCDD impaired mitochondrial activities, leading to reactive oxygen species (ROS) production and the blockage of insulin-induced Ca2+ release. All TCDD-mediated effects related to insulin resistance were still observed in aryl hydrocarbon receptor (AhR)-deficient myocytes and prevented by MitoTEMPO, a mitochondria-targeting ROS scavenger. These results suggest that low-dose TCDD stress may induce muscle insulin resistance AhR-independently and that mitochondrial oxidative stress is a novel therapeutic target for dioxin-induced insulin resistance.

Select Per- and Polyfluoroalkyl Substances (PFAS) Induce Resistance to Carboplatin in Ovarian Cancer Cell Lines

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous environmental contaminants associated with adverse reproductive outcomes including reproductive cancers in women. PFAS can alter normal ovarian function, but the effects of PFAS on ovarian cancer progression and therapy response remain understudied. Ovarian cancer is the most lethal gynecologic malignancy, and a major barrier to effective treatment is resistance to platinum-based chemotherapy. Platinum resistance may arise from exposure to external stimuli such as environmental contaminants. This study evaluated PFAS and PFAS mixture exposures to two human ovarian cancer cell lines to evaluate the ability of PFAS exposure to affect survival fraction following treatment with carboplatin. This is the first study to demonstrate that, at sub-cytotoxic concentrations, select PFAS and PFAS mixtures increased survival fraction in ovarian cancer cells following carboplatin treatment, indicative of platinum resistance. A concomitant increase in mitochondrial membrane potential, measured by the JC-1 fluorescent probe, was observed in PFAS-exposed and PFAS + carboplatin-treated cells, suggesting a potential role for altered mitochondrial function that requires further investigation.

Association between perfluoroalkyl substances concentration and bone mineral density in the US adolescents aged 12-19 years in NHANES 2005-2010

BACKGROUND

Reports on the association of perfluoroalkyl substances (PFASs) exposure with adolescent bone health are scarce, and studies have primarily targeted maternal serum.

OBJECTIVE

We evaluated the relationship between autologous serum perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorohexane sulfonic acid (PFHxS) and perfluorononanoic acid (PFNA) levels and bone mineral density (BMD) in adolescents.

METHODS

We analyzed data from 1228 adolescents aged 12-19 years in the National Health and Nutrition Examination Survey (NHANES) 2005-2010 and used multiple regression analysis to identify the relationship between serum PFOA, PFOS, PFHxS, and PFNA concentrations and total femur, femoral neck, and lumbar spine BMD, in addition to multiple stratified subgroup analyses.

RESULTS

The mean age of participants was 15 years, males had higher serum PFAS concentrations than females. The results of multiple regression analysis showed that the natural log(ln)-transformed serum PFOA, PFOS, and PFNA concentrations were negatively correlated with total femur, femoral neck, and lumbar spine BMD (all p < 0.05), and ln-PFHxS was positively correlated with total femur and femoral neck BMD (all p< 0.05). In males, ln-PFOA was negatively associated with total femur and lumbar spine BMD (all p< 0.05), ln-PFOS was associated with the reduced total femur, femoral neck, and lumbar spine BMD (all p< 0.05), while ln-PFHxS and ln-PFNA were not observed to correlate with BMD at these three sites. In females, both ln-PFOA and ln-PFOS were negatively correlated with total femur and lumbar spine BMD (all p< 0.05), ln-PFHxS is associated with the increased total femur and femoral neck BMD (all p< 0.05), and ln-PFNA was negatively correlated with total femur and femoral neck BMD (all p< 0.05), most of the associations were confined to females. The associations of ln-PFOS with femoral neck BMD and ln-PFNA with total femur BMD were more significant in those who were overweight/obese and had anemia, respectively (all p for interaction < 0.05).

CONCLUSIONS

In this representative sample of US adolescents aged 12-19 years, certain PFAS were associated with lower bone mineral density, and most of the associations were confined to females. The negative effect of PFAS on BMD is more pronounced in those who are overweight/obese and have anemia. However, further studies are needed to confirm this finding.

Perfluorooctanoic acid induces cytotoxicity in spermatogonial GC-1 cells

Perfluorooctane acid (PFOA), a typical perfluorinated chemical, has been suggested to interfere with male reproductive function. In this study, mouse spermatogonial GC-1 cells were in vitro treated with PFOA (250, 500 or 750 μM) for 24 h to investigate the cytotoxicity of PFOA and its underlying mechanisms. Our results indicated that exposure to intermediate and high doses of PFOA suppressed the viability of GC-1 cells in a concentration-dependent manner. Furthermore, PFOA treatment markedly enhanced the generation of reactive oxygen species and malondialdehyde, with diminished activity of superoxide dismutase. Particularly, PFOA exposure evoked a decline in mitochondrial membrane potential and ATP production. Furthermore, the apoptotic index and caspase-3 activity were significantly elevated after treatment with PFOA. In addition, PFOA incubation caused an increase in LC3B-II/LC3B-I ratio. Meanwhile, PFOA resulted in an excessive accumulation of autophagosomes in the cytoplasm. Taken together, exposure to PFOA can elicit cytotoxicity to spermatogonial GC-1 cells in vitro, which may be link to the mitochondrial oxidative damage and induction of apoptosis and autophagy.

Comparative toxicometabolomics of perfluorooctanoic acid (PFOA) and next-generation perfluoroalkyl substances

Owing to environmental health concerns, a number of per- and polyfluoroalkyl substances (PFAS) have been phased-out, and increasingly replaced by various chemical analogs. Most prominent among these replacements are numerous perfluoroether carboxylic acids (PFECA). Toxicity, and environmental health concerns associated with these next-generation PFAS, however, remains largely unstudied. The zebrafish embryo was employed, in the present study, as a toxicological model system to investigate toxicity of a representative sample of PFECA, alongside perfluorooctanoic acid (PFOA) as one of the most widely used, and best studied, of the "legacy" PFAS. In addition, high-resolution magic angle spin (HRMAS) NMR was utilized for metabolic profiling of intact zebrafish embryos in order to characterize metabolic pathways associated with toxicity of PFAS. Acute embryotoxicity (i.e., lethality), along with impaired development, and variable effects on locomotory behavior, were observed for all PFAS in the zebrafish model. Median lethal concentration (LC₅₀) was significantly correlated with alkyl chain-length, and toxic concentrations were quantitatively similar to those reported previously for PFAS. Metabolic profiling of zebrafish embryos exposed to selected PFAS, specifically including PFOA and two representative PFECA (i.e., GenX and PFO3TDA), enabled elaboration of an integrated model of the metabolic pathways associated with toxicity of these representative PFAS. Alterations of metabolic profiles suggested targeting of hepatocytes (i.e., hepatotoxicity), as well as apparent modulation of neural metabolites, and moreover, were consistent with a previously proposed role of mitochondrial disruption and peroxisome proliferator-activated receptor (PPAR) activation as reflected by dysfunctions of carbohydrate, lipid and amino acid metabolism, and consistent with a previously proposed contribution of PFAS to metabolic syndrome. Taken together, it was generally concluded that toxicity of PFECA is quantitatively and qualitatively similar to PFOA, and these analogs, likewise, represent potential concerns as environmental toxicants.

PFOA and PFOS promote diabetic renal injury in vitro by impairing the metabolisms of amino acids and purines

BACKGROUND

Environmental pollutants, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), are common surfactants in various consumer products. Epidemiological studies have demonstrated the association of diabetic kidney diseases with PFOA and PFOS. However, mechanisms of metabolic alterations involved are still unclear.

METHODS

Considering their involvement of glomerular hemodynamics, rat mesangial cells (MCs) are used as an in vitro model of diabetic kidney diseases for exposure to PFOS/PFOA under diabetic condition. Non-targeted metabolomics studies based on liquid chromatography-high resolution mass spectrometry were conducted to determine how PFOA/PFOS promoted fibrotic and proinflammatory responses in the MCs under diabetic condition.

RESULTS

Exposure of PFOA/PFOS (10 μM) increased oxidative stress and the levels of fibrotic and proinflammatory markers in MCs under diabetic condition. We demonstrated for the first time that PFOA and PFOS altered amino acid biosynthesis, citrate cycle, and purine metabolism in MCs under diabetic condition. Compared with diabetic condition, the exposure of PFOA and PFOS under diabetic condition more significantly altered the levels of 13 intracellular metabolites, including L-tyrosine, L-phenylalanine, L-arginine, L-tryptophan, AMP, ADP, UMP, inosine, and hypoxanthine, which have been reported to be related to kidney injury. In addition, PFOA/PFOS treatment significantly altered the expression levels of key enzymes involved in these metabolisms. Treatment with L-tyrosine, L-phenylalanine, L-arginine, and L-tryptophan reduced the levels of fibrotic and inflammatory markers induced by PFOA/PFOS.

CONCLUSION

Our results suggest that under diabetic condition, exposure of PFOA or PFOS aggravated diabetic kidney injury in vitro by impairing metabolisms of amino acids and purines to induce more fibrosis and inflammation in MCs.

Maternal exposure causes mitochondrial dysfunction in brain, liver, and heart of mouse fetus: An explanation for perfluorooctanoic acid induced abortion and developmental toxicity

Perfluorooctanoic acid (PFOA) is an octanoic acid and is found in wildlife and humans. We have investigated mitochondrial toxicity in isolated mitochondria from, placenta, brain, liver, and heart after oral exposure with PFOA in mice during gestational days (7-15). Histopathological examination and mitochondrial toxicity parameters were assayed. Results indicated that PFOA decreased the weight of the fetus and placenta, the length of the fetus and the diameter of the placenta, dead fetuses and dead macerated fetuses in treated mice with 25 mg/kg. Histopathological examination showed that PFOA induced pathological abnormalities in liver, brain, heart, and placenta. Also, PFOA induced mitochondria toxicity in brain, liver, heart of mouse fetus. Our results indicate that PFOA up to 20 mg/kg exposure adversely affect embryofetal/developmental because for mitochondria dysfunction. These results suggested that mitochondrial dysfunction induced by PFOA in liver, heart, and brain lead to developmental toxicity and abnormality in tissues.

Exposure to Environmental Pollutants and Their Association with Biomarkers of Aging: A Multipollutant Approach

Mitochondrial DNA (mtDNA) content and telomere length are putative aging biomarkers and are sensitive to environmental stressors, including pollutants. Our objective was to identify, from a set of environmental exposures, which exposure is associated with leukocyte mtDNA content and telomere length in adults. This study includes 175 adults from 50 to 65 years old from the cross-sectional Flemish Environment and Health study, of whom leukocyte telomere length and mtDNA content were determined using qPCR. The levels of exposure of seven metals, 11 organohalogens, and four perfluorinated compounds (PFHxS, PFNA, PFOA, PFOS) were measured. We performed sparse partial least-squares regression analyses followed by ordinary least-squares regression to assess the multipollutant associations. While accounting for possible confounders and coexposures, we identified that urinary cadmium (6.52%, 95% confidence interval, 1.06, 12.28), serum hexachlorobenzene (2.89%, 018, 5.68), and perfluorooctanesulfonic acid (11.38%, 5.97, 17.08) exposure were positively associated ( p < 0.05) with mtDNA content, while urinary copper (-9.88%, -14.82, -4.66) and serum perfluorohexanesulfonic acid (-4.75%, -8.79, -0.54) exposure were inversely associated with mtDNA content. Urinary antimony (2.69%, 0.45, 4.99) and mercury (1.91%, 0.42, 3.43) exposure were positively associated with leukocyte telomere length, while urinary copper (-3.52%, -6.60, -0.34) and serum perfluorooctanesulfonic acid (-3.64%, -6.60, -0.60) showed an inverse association. Our findings support the hypothesis that environmental pollutants interact with molecular hallmarks of aging.

Environmental and human relevant PFOS and PFOA doses alter human mesenchymal stem cell self-renewal, adipogenesis and osteogenesis

PFOS and PFOA are two of the most abundant perfluorinated compounds (PFCs) in the environment. Previous studies have reported they have a long half-life (up to five years) once they enter into the human body. Moreover, they can potentially promote the adipogenic process by activating PPARγ. However, little is known about PFOS and PFOA chronic health impacts on humans. In this study, we employed primary human mesenchymal stem cells (hMSCs) and demonstrated that PFOS and PFOA exerted acute cytotoxicity and affected adipogenesis and osteogenesis at environmental and human relevant doses. In fact, PFOS and PFOA impaired the proper expression of CD90 (a surface antigen highly enriched in undifferentiated hMSCs) and promoted adipogenesis, presumably via their interaction with PPARγ. Moreover, PFOA partly disturbed osteogenesis. Thus, our findings not only validated the health risks of PFOS and PFOA, but also revealed new potential long-term PFOS/PFOA impacts on humans.

Per- and polyfluoroalkyl substances impact human spermatogenesis in a stem-cell-derived model

Per- and polyfluoroalkyl substances (PFASs) represent a highly ubiquitous group of synthetic chemicals used in products ranging from water and oil repellents and lubricants to firefighting foam. These substances can enter and accumulate in multiple tissue matrices in up to 100% of people assessed. Though animal models strongly identify these compounds as male reproductive toxicants, with exposed rodents experiencing declines in sperm count, alterations in hormones, and DNA damage in spermatids, among other adverse outcomes, human studies report conflicting conclusions as to the reproductive toxicity of these chemicals. Using an innovative, human stem-cell-based model of spermatogenesis, we assessed the effects of the PFASs perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and a mixture of PFOS, PFOA, and PFNA for their impacts on human spermatogenesis in vitro under conditions relevant to the general and occupationally exposed populations. Here, we show that PFOS, PFOA, PFNA, and a mixture of PFOS, PFOA, and PFNA do not decrease in vitro germ cell viability, consistent with reports from human studies. These compounds do not affect mitochondrial membrane potential or increase reactive oxygen species generation, and they do not decrease cell viability of spermatogonia, primary spermatocytes, secondary spermatocytes, or spermatids in vitro under the conditions examined. However, exposure to PFOS, PFOA, and PFNA reduces expression of markers for spermatogonia and primary spermatocytes. While not having direct effects on germ cell viability, these effects suggest the potential for long-term impacts on male fertility through the exhaustion of the spermatogonial stem cell pool and abnormalities in primary spermatocytes.

ABBREVIATIONS

CDC: Centers for Disease Control; DMSO: dimethyl sulfoxide; GHR: growth hormone receptor; hESCs: human embryonic stem cells; PFASs: per- and polyfluoroalkyl substances; PFCs: perfluorinated compounds; PFNA: perfluorononanoic acid; PFOS: perfluorooctanesulfonic acid; PFOA: perfluorooctanoic acid; PLZF: promyelocytic leukemia zinc finger; ROS: reactive oxygen species; HILI: RNA-mediated gene silencing 2; SSC: spermatogonial stem cell.