Ovarian disrupting effects of per-and polyfluoroalkyl substances (PFAS) on gonadotropin-dependent folliculogenesis and ovulation

PROJECT SUMMARY The per- and polyfluoroalkyl substances (PFAS) are human-made organic compounds that are widely used in consumer and industrial products. The strong C-F bonds of PFAS make them highly resistant to environmental degradation and thus earn PFAS the name “Forever Chemicals. Humans can be exposed to high levels of PFAS through drinking water and foods in areas near the contaminated sites. PFAS are rarely metabolized once absorbed, with half-lives as long as 8-9 years. Epidemiological evidence revealed associations between PFAS and female ovarian disorders, such as premature ovarian failure (POF), irregular menstrual cycles, and infertility, but the underlying mechanisms remain elusive. So far, nearly all studies focused on perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), two long-chain legacy PFAS that have been phased out. The ovarian toxicity (ovotoxicity) of other widely used long-chain PFAS such as perfluorononanoic acid (PFNA) are rarely studied, despite some may have similar or even higher contamination levels. In the real world, humans are exposed to PFAS mixtures, but their ovarian impacts are poorly characterized. Our recently published studies and preliminary data support ovotoxicity of PFAS. (1) A cross-sectional epidemiological analysis of the NHANES dataset revealed positive associations between serum concentrations of long-chain PFAS and long-term amenorrhea in women of reproductive age; (2) In an in vivo mouse exposure model, PFNA accumulated in the ovary to levels observed in women, and PFNA dose-dependently inhibited ovulation; (3) In an in vitro mouse ovarian follicle culture system, PFNA concentration-dependently inhibited follicle maturation and ovulation; and (4) A selective antagonist of peroxisome proliferator-activated receptor gamma (PPARγ) rescued PFNA-blocked ovulation in both in vitro and in vivo models. With these findings, we will test our central hypothesis that: (1) at environmentally high but human-relevant exposure levels, PFNA acts primarily as a PPARγ agonist, as the molecular initiating event (MIE), in follicular granulosa cells to interfere with folliculogenesis, leading to impaired ovarian functions and female reproduction; (2) also via PPARγ-mediated MIEs, PFAS of major public health concern and their mixtures produce similar ovotoxic effects but with different potentials. We will integrate in vivo, in vitro, and in silico models to test our hypotheses in three Specific Aims. In Aim 1, we will use a mouse model of natural ovarian cycles and human-relevant doses and duration of PFNA exposure via drinking water to investigate ovarian disrupting effects of PFNA and female reproductive outcomes. In Aim 2, we will study the mechanistic and causal roles of PPARγ in PFNA-induced ovarian follicle maturation and ovulation defects. In Aim 3, we will use experimental and computational models to determine the ovotoxicity of PFAS singles and mixtures of major health concern. This research is highly innovative and significant given the emerging concern of PFAS on female reproduction. Elucidating the ovotoxicity of PFAS will enable us to speed up the development of prevention, mitigation, and remediation methods to protect female reproductive health and fertility.