AhR/ROS-mediated endoplasmic reticulum stress contributes to PFOSA-induced cardiac defects.

Perfluorooctane sulfonamide (PFOSA), an immediate precursor of perfluorooctane sulfonate (PFOS), is widely detected in the environment. Recent studies have indicated that the aryl hydrocarbon receptor (AhR) mediates PFOSA-induced cardiac defects; however, the precise mechanisms remain unclear. Given that genes involved in endoplasmic reticulum stress (ERS) are enriched in zebrafish larvae following PFOSA exposure, we hypothesized that AhR mediates PFOSA-induced cardiac defects through ERS. In this study, we observed a dose-dependent increase in the ERS markers Grp78 and Chop in the hearts of zebrafish larvae exposed to PFOSA. Furthermore, PFOSA-induced ERS activated the PERK branch of the unfolded protein response (UPR), while inhibition of either AhR or reactive oxygen species (ROS) significantly attenuated PFOSA-triggered ERS and PERK branch activation. The results further demonstrated that PFOSA-induced ERS and PERK activation led to 1) mitochondrial calcium overload through the Ip3r/Grp75/Vdac1 complex, and 2) downregulation of PGC-1α resulting from CHOP overexpression. Collectively, these events resulted in apoptosis in the zebrafish embryonic heart. AhR/ROS-dependent ERS, PERK branch activation, and mitochondrial damage were also observed in rat embryonic cardiomyocytes exposed to PFOSA. In conclusion, our findings indicate that PFOSA induces ERS and activates the PERK branch through the AhR/ROS axis, leading to mitochondrial damage via calcium overload and PGC-1α suppression, ultimately resulting in apoptosis and cardiac defects. Overall, these results highlight the fundamental role of ERS in the cardiac developmental toxicity of PFOSA.