Effects of PFOS and its substitute PFHxS on steroid hormone secretion, uptake, and transport in BeWo cells

Perfluorooctane sulfonate (PFOS) and perfluorohexanesulfonic acid (PFHxS) are environmental contaminants, yet their transplacental transport and developmental toxicity remain unclear. This study investigated the placental transfer of PFOS and PFHxS and their effects on steroid hormone secretion using BeWo cells. Cytotoxicity, steroid hormone secretion, and the expression of steroidogenic enzymes were assessed, while LC-MS/MS was used to quantify PFOS/PFHxS concentrations. Cellular uptake and apparent permeability were evaluated under different concentrations, exposure times, and transporter inhibitor treatments. Molecular docking was performed to predict interactions with five transporters (P-gp, BCRP, MRP, OAT, and OCT). The results demonstrated that PFOS and PFHxS showed no cytotoxicity within 0.1-100 μM. PFOS significantly inhibited pregnenolone secretion and downregulated CYP11A1 expression (P < 0.05); PFOS and PFHxS promoted estradiol secretion and upregulated HSD17β1 expression (P < 0.05). Molecular docking suggested potential interactions between the compounds and all transporters (binding energies < 0 kcal/mol). Cellular uptake increased with rising concentration and prolonged exposure time. OAT/OCT inhibition significantly reduced PFOS uptake (P < 0.05). In the Transwell model, transporter inhibitors significantly altered the apparent permeability coefficients of PFOS and PFHxS (P < 0.05), indicating the involvement of both passive diffusion and active transport in transplacental transfer. These findings suggest that PFOS and PFHxS can cross the placental barrier and disrupt steroid hormone homeostasis, highlighting their potential risks to fetal development and providing new insights into maternal-fetal exposure to PFAS.