BPA-free? Exploring the reproductive toxicity of BPA substitutes BPS and BPF on endometrial decidualization

Bisphenol A (BPA) exposure is linked to multiple adverse health outcomes, prompting the rise of "BPA-free" products. However, substitutes like Bisphenol S (BPS) and Bisphenol F (BPF) are equally prevalent, with detection frequencies and concentrations rivaling BPA. Our research previously identified BPA as an endocrine disruptor affecting reproductive and developmental systems. This study explores the impact of BPA, BPS, and BPF on endometrial decidualization and receptivity. We detected these bisphenols in serum samples from infertile women undergoing assisted reproductive technology (ART) treatment whose average age was 31.58 years. Human endometrial stromal cells were exposed to varying concentrations (0, 1 nM, 10 nM, 100 nM, and 1 µM) of BPA, BPS, and BPF, following hormonal induction of decidualization (10 nM E2 (Estradiol) + 0.5 mM cAMP (Cyclic adenosine monophosphate) + 1 µM MPA (Medroxyprogesterone acetate) for 6 days). Methods including CCK-8, RT-qPCR, untargeted metabolomics, and transcriptome sequencing assessed cell proliferation, molecular markers, gene expression, and metabolites. BPS levels in the serum of infertile patients were significantly higher than BPA (14.52 vs. 2.58 ng/mL) and even more pronounced in the recurrent implantation failure (RIF) group compared to the Control group (23.46 vs. 5.57 ng/mL). Findings revealed that BPA and its substitutes inhibited endometrial stromal cell proliferation and reduced decidualization markers. Differential metabolites (25, 66, 104) and gene expressions (3260, 9686, 10357) were observed with BPA, BPF, and BPS exposure, respectively. Enriched pathways included glutathione metabolism, arginine biosynthesis, ABC transporters, cAMP signaling, and glucagon signaling. Metabolomics and transcriptome analyses unveiled the reproductive toxic effects of BPA and its substitutes, suggesting significant impacts on endometrial decidualization through diverse signaling pathways.