Cellular responses to PFOS and PFOA in rainbow trout cell lines: Implications for aquatic ecotoxicology

Per- and polyfluoroalkyl substances (PFAS), including perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), are highly persistent contaminants of global concern due to their accumulation in aquatic ecosystems and potential to disrupt fish health. Despite extensive environmental detection, mechanistic understanding of their cellular impacts in ecologically relevant models remains limited. Here, we investigated cytotoxic and oxidative stress responses to PFOS and PFOA in two rainbow trout (Oncorhynchus mykiss) cell lines: RTg-2 (gonadal) and RTgill-W1 (gill epithelial), representing sensitive reproductive and respiratory tissues. A 24-h exposure to increasing concentrations (0–30 mg/L) significantly reduced cell viability, elevated reactive oxygen species (ROS), and disrupted antioxidant defenses. While superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GR) were upregulated, glutathione peroxidase (GPx) and glutathione-S-transferase (GST) were suppressed, coinciding with glutathione (GSH) depletion and lipid peroxidation. Apoptosis was triggered through both intrinsic and extrinsic pathways, as shown by activation of caspase-3, -8, and -9. Importantly, PFOS and PFOA also stimulated mitogen-activated protein kinase (MAPK) signaling, with phosphorylation of ERK and p38, linking oxidative stress to downstream cell death signaling. By integrating oxidative, apoptotic, and signaling endpoints, this study provides novel mechanistic evidence of how PFOS and PFOA compromise vital fish cell types, highlighting their ecological hazard and reinforcing concerns over their persistence in aquatic environments.