PFOS Inhibited Normal Functional Development of Placenta Cells via PPARγ Signaling

Associations of Serum Perfluoroalkyl Substances and Placental Human Chorionic Gonadotropin in Early Pregnancy, Measured in the UPSIDE Study in Rochester, New York

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are widely detected in pregnant women and associated with adverse outcomes related to impaired placental function. Human chorionic gonadotropin (hCG) is a dimeric glycoprotein hormone that can indicate placental toxicity.

OBJECTIVES

Our aim was to quantify the association of serum PFAS with placental hCG, measured as an intact molecule (hCG), as free alpha-(hCG α ) and beta-subunits (hCG β ), and as a hyperglycosylated form (h-hCG), and evaluate effect measure modification by social determinants and by fetal sex.

METHODS

Data were collected from 326 pregnant women enrolled from 2015 to 2019 in the UPSIDE study in Rochester, New York. hCG forms were normalized for gestational age at the time of blood draw in the first trimester [multiple of the median (MoM)]. Seven PFAS were measured in second-trimester maternal serum. Multivariate imputation by chained equations and inverse probability weighting were used to evaluate robustness of linear associations. PFAS mixture effects were estimated by Bayesian kernel machine regression.

RESULTS

Perfluorohexane sulfonic acid (PFHxS) [hCG β : 0.29 log MoM units per log PFHxS; 95% confidence interval (CI): 0.08, 0.51] and perfluorodecanoic acid (PFDA) (hCG: - 0.09 ; 95% CI: - 0.16 , - 0.02 ) were associated with hCG in the single chemical and mixture analyses. The PFAS mixture was negatively associated with hCG α and positively with hCG β . Subgroup analyses revealed that PFAS associations with hCG differed by maternal race/ethnicity and education. Perfluoropentanoic acid (PFPeA) was associated with hCG β only in Black participants (- 0.23 ; 95% CI: - 0.37 , - 0.09 ) and in participants with high school education or less (- 0.14 ; 95% CI: - 0.26 , - 0.02 ); conversely, perfluorononanoic acid (PFNA) was negatively associated with hCG α only in White participants (- 0.15 ; 95% CI: - 0.27 , - 0.03 ) and with hCG β only in participants with a college education or greater (- 0.19 ; 95% CI: - 0.36 , - 0.01 ). These findings were robust to testing for selection bias, confounding bias, and left truncation bias where PFAS detection frequency was < 100 % . Two associations were negative in male (and null in female) pregnancies: Perfluoroundecanoic acid (PFUnDA) with hCG α , and PFNA with h-hCG.

CONCLUSIONS

Evidence was strongest for the association between PFHxS and PFDA with hCG in all participants and for PFPeA and PFNA within subgroups defined by social determinants and fetal sex. PFAS mixture associations with hCG α and hCG β differed, suggesting subunit-specific types of toxicity and/or regulation. Future studies will evaluate the biological, clinical and public health significance of these findings. https://doi.org/10.1289/EHP12950.

Evidence of promoting effects of 6:2 Cl-PFESA on hepatocellular carcinoma proliferation in humans: An ideal alternative for PFOS in terms of environmental health?

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are synthetic chemicals, encompassing compounds like perfluorooctane sulfonate (PFOS), which have widespread applications across various industries, including food packaging and firefighting. In recent years, China has increasingly employed 6:2 Cl-PFESA as an alternative to PFOS. Although the association between PFAS exposure and hepatocellular carcinoma (HCC) has been demonstrated, the underlying mechanisms that promote HCC proliferation are uncleared. Therefore, we aimed to investigate the effects and differences of PFOS and 6:2 Cl-PFESA on HCC proliferation through in vivo and in vitro tumor models. Our results reveal that both PFOS and 6:2 Cl-PFESA significantly contribute to HCC proliferation in vitro and in vivo. Exposure led to reduced population doubling times, enlarged cell colony sizes, enhanced DNA synthesis efficiency, and a higher proportion of cells undergoing mitosis. Furthermore, both PFOS and 6:2 Cl-PFES) have been shown to activate the PI3K/AKT/mTOR signaling pathway and inhibit necroptosis. This action consequently enhances the proliferation of HCC cells. Our phenotypic assay findings suggest that the tumorigenic potential of 6:2 Cl-PFESA surpasses that of PFOS; in a subcutaneous tumor model using nude mice, the mean tumor weight for the 6:2 Cl-PFESA-treated cohort was 2.33 times that observed in the PFOS cohort (p < 0.01). Despite 6:2 Cl-PFESA being considered a safer substitute for PFOS, the pronounced effects of this chemical on HCC cell growth warrant a thorough assessment of hepatotoxicity risks linked to its usage.

PFOS Impairs Mitochondrial Biogenesis and Dynamics and Reduces Oxygen Consumption in Human Trophoblasts

Perfluorooctane sulfonate (PFOS), a synthetic chemical used in various commercial applications and industrial settings, has led to contamination of drinking water and has been detected in the bloodstream of pregnant women with gestational complications. Recent investigations have indicated that PFOS disrupts placental function; however, the mechanism remains elusive. Given the significant abundance of mitochondria in the placenta, which play a pivotal role in fulfilling the heightened energy requirements of pregnancy, our research aimed to examine the repercussions of PFOS exposure on mitochondrial dynamics within placental trophoblasts. Specifically, human trophoblasts (HTR-8/SVneo) were exposed to environmentally relevant concentrations of PFOS ranging from 0.1 to 50 μM for 48 hours. Findings revealed that PFOS exposure elicited a concentration-dependent decrease in basal, maximal, and ATP-linked respiration. PFOS inhibited the activity of electron transport complexes I, II, and III, resulting in diminished ATP production. Furthermore, PFOS reduced mitochondrial DNA copy number, indicating less mitochondrial content. Concurrently, there was a downregulation in the expression of mitochondrial biogenesis-related genes, including PGC-1α, NRF1, and NRF2. Notably, PFOS perturbed mitochondrial dynamics by suppressing the expression of fission-related genes (FIS1 and DRP1) and fusion-related genes (MFN1 and MFN2). In summary, our findings suggest that PFOS exposure leads to a decline in mitochondrial content and compromises the bioenergetic capacity of trophoblasts by impairing cellular respiration. This reduction in mitochondrial biogenesis and alterations in fission/fusion dynamics induced by PFOS may contribute to mitochondrial dysfunction in trophoblasts. Consequently, strategies that preserve mitochondrial function in trophoblasts may mitigate PFOS-induced impairment of placental energy metabolism.

Restoring Angiotensin Type 2 Receptor Function Reverses PFOS-Induced Vascular Hyper-Reactivity and Hypertension in Pregnancy

Perfluorooctane sulfonic acid (PFOS) exposure during pregnancy induces hypertension with decreased vasodilatory angiotensin type-2 receptor (AT2R) expression and impaired vascular reactivity and fetal weights. We hypothesized that AT2R activation restores the AT1R/AT2R balance and reverses gestational hypertension by improving vascular mechanisms. Pregnant Sprague-Dawley rats were exposed to PFOS through drinking water (50 μg/mL) from gestation day (GD) 4-20. Controls received drinking water with no detectable PFOS. Control and PFOS-exposed rats were treated with AT2R agonist Compound 21 (C21; 0.3 mg/kg/day, SC) from GD 15-20. In PFOS dams, blood pressure was higher, blood flow in the uterine artery was reduced, and C21 reversed these to control levels. C21 mitigated the heightened contraction response to Ang II and enhanced endothelium-dependent vasorelaxation in uterine arteries of PFOS dams. The observed vascular effects of C21 were correlated with reduced AT1R levels and increased AT2R and eNOS protein levels. C21 also increased plasma bradykinin production in PFOS dams and attenuated the fetoplacental growth restriction. These data suggest that C21 improves the PFOS-induced maternal vascular dysfunction and blood flow to the fetoplacental unit, providing preclinical evidence to support that AT2R activation may be an important target for preventing or treating PFOS-induced adverse maternal and fetal outcomes.

Antenatal Exposure to Plastic Pollutants: Study of the Bisphenols and Perfluoroalkyls Effects on Human Stem Cell Models

Endocrine disruptors (EDs), such as Bisphenols (BPs) and Perfluoroalkyls (PFs), are a class of plastic pollutants widely used in industrial applications. Human exposure to these molecules usually occurs through ingestion of contaminated food and water. Once entered the human body they can interfere with endogenous hormone signaling, leading to a wide spectrum of diseases. It has been reported that BPs and PFs can cross the placental barrier accumulating in the fetal serum, but the detrimental consequences for human development remain to be clarified. Here we analyze the effects of different doses of bisphenol A and S (BPA, BPS) perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) on proliferation and mitochondrial health on different types of stem cells: through an integrated approach that combines data from pluripotent stem cells (hiPSCs) with that from the “environment” in which the embryo develops (fetal annexes-derived perinatal stem cells) we verified the potential developmental toxicity of the in utero EDs exposure. Data obtained showed that overall, BPs, and PFs tended to increase the proliferation rate of perinatal stem cells; a similar response was observed in hiPSCs exposed to very low doses of BPs and PFs, while at higher concentrations these chemicals were toxic; in addition, both the BPs and the PFs exerted a mitotoxic effects hiPSCs at all the concentration studied. All these data suggest that antenatal exposure to BPs and PFs, also at very low concentrations, may modify the biological characteristics of stem cells present in both the developing fetus and the fetal annexes, thus perturbing normal human development.

Predicting Exposure to Perfluorinated Alkyl Substances (PFAS) among US Infants

PFASs have been detected in nearly every serum sample collected over the last two decades from US adults as part of the National Health and Nutrition Examination Survey (NHANES) and are commonly found in other data sets from around the world. However, less is known about infant PFAS exposures, primarily because the collection of infant serum samples is less common and frequently avoided. Cord blood samples are often preferred for chemical exposure assessments because this is thought to provide a good representation of infant serum concentrations, at least at the time of birth. In this paper, we will provide a statistical and probabilistic analysis of what can be expected for infants living in the US using NHANES from 2007 to 2008, which contains a rare subset of infant data. Regulatory efforts that require estimation of exposures among the very youth can be challenging, both because of a lack of data in general and because variability among this most vulnerable population can be uncertain. We report that US infant exposures are extremely common and that serum concentrations remain fairly constant, despite infant growth rates and relatively high caloric and fluid intake, with the possible exception of PFOS. Infant serum PFOS concentrations between months 1 and 3 are consistently higher than at less than one month, even though healthy infants at 1 and 2 months weigh more than they did at birth. This suggests that the babies are exposed to greater concentrations of PFOS after birth or that excretion kinetics differ for this PFAS.

A High-Throughput Toxicity Screen of 42 Per- and Polyfluoroalkyl Substances (PFAS) and Functional Assessment of Migration and Gene Expression in Human Placental Trophoblast Cells

Per- and polyfluoroalkyl substances (PFAS) have become ubiquitous environmental contaminants that have been associated with adverse pregnancy outcomes in women and experimental research models. Adverse developmental and reproductive outcomes have been investigated for relatively few PFAS, and such studies are not scalable to address the thousands of unique chemical structures. As the placenta has been reported as a PFAS target tissue, the human placental trophoblast JEG-3 cell line was employed in a high-throughput toxicity screen (HTTS) to evaluate the effects of 42 unique PFAS on viability, proliferation, and mitochondrial membrane potential (MMP). HTTS concentration-response curve fitting determined EC50 values for 79% of tested compounds for at least one of the three endpoints. Trophoblast migratory potential was evaluated for a subset of six prioritized PFAS using a scratch wound assay. Migration, measured as the percent of wound closure after 72 h, was most severely inhibited by exposure to 100 µM perfluorooctanoic acid (PFOA; 72% closure), perfluorooctanesulfonic acid (PFOS; 57% closure), or ammonium perfluoro-2-methyl-3-oxahexanoate (GenX; 79% closure). PFOA and GenX were subsequently evaluated for disrupted expression of 46 genes reported to be vital to trophoblast health. Disrupted regulation of oxidative stress was suggested by altered expression of GPEX1 (300 µM GenX and 3 µM GenX), GPER1 (300 µM GenX), and SOD1 and altered cellular response to xenobiotic stress was indicated by upregulation of the placental efflux transporter, ABCG2 (300 µM GenX, 3 µM GenX, and 100 µM PFOA). These findings suggest the placenta is potentially a direct target of PFAS exposure and indicate that trophoblast cell gene expression and function are disrupted at PFAS levels well below the calculated cytotoxicity threshold (EC50). Future work is needed to determine the mechanism(s) of action of PFAS towards placental trophoblasts.

LncRNA MEG3 alleviates PFOS induced placental cell growth inhibition through its derived miR-770 targeting PTX3

Perfluorooctane sulfonic acid (PFOS) is a persistent environmental pollutant. Exposure to PFOS has been associated with abnormal fetal development. The long non-coding RNA (lncRNA) has been showed to play a role in fetal growth restriction (FGR), preeclampsia (PE) and other pregnancy complications. Whether the lncRNA contributes to PFOS-induced toxicity in the placenta remains unknown. In this study, we investigated the function of lncRNA MEG3 and its derived miR-770 in PFOS-induced placental toxicity. Pregnant mice received gavage administration of different concentrations of PFOS (0.5, 2.5, and 12.5 mg/kg/day) from GD0 to GD17, and HTR-8/SVneo cells were treated with PFOS in the concentrations of 0, 10^-1, 1, 10 μM. We found that expression levels of miR-770 and its host gene MEG3 were reduced in mice placentas and HTR-8/SVneo cells with exposure of PFOS. A significant hypermethylation was observed at MEG3 promoter in placentas of mice gestational-treated with PFOS. We also confirmed that MEG3 and miR-770 overexpression alleviated the cell growth inhibition induced by PFOS. Furthermore, PTX3 (Pentraxin 3) was identified as the direct target of miR-770 and it was enhanced after PFOS exposure. In summary, our results suggested that MEG3 alleviate PFOS-induced placental cell inhibition through MEG3/miR-770/PTX3 axis.

PPARγ Regulates Triclosan Induced Placental Dysfunction

Exposure to the antibacterial agent triclosan (TCS) is associated with abnormal placenta growth and fetal development during pregnancy. Peroxisome proliferator-activated receptor γ (PPARγ) is crucial in placenta development. However, the mechanism of PPARγ in placenta injury induced by TCS remains unknown. Herein, we demonstrated that PPARγ worked as a protector against TCS-induced toxicity. TCS inhibited cell viability, migration, and angiogenesis dose-dependently in HTR-8/SVneo and JEG-3 cells. Furthermore, TCS downregulated expression of PPARγ and its downstream viability, migration, angiogenesis-related genes HMOX1, ANGPTL4, VEGFA, MMP-2, MMP-9, and upregulated inflammatory genes p65, IL-6, IL-1β, and TNF-α in vitro and in vivo. Further investigation showed that overexpression or activation (rosiglitazone) alleviated cell viability, migration, angiogenesis inhibition, and inflammatory response caused by TCS, while knockdown or inhibition (GW9662) of PPARγ had the opposite effect. Moreover, TCS caused placenta dysfunction characterized by the significant decrease in weight and size of the placenta and fetus, while PPARγ agonist rosiglitazone alleviated this damage in mice. Taken together, our results illustrated that TCS-induced placenta dysfunction, which was mediated by the PPARγ pathway. Our findings reveal that activation of PPARγ might be a promising strategy against the adverse effects of TCS exposure on the placenta and fetus.