Long-chain PFAS potently disrupt renal carboxylesterase activity and exacerbate nephrotoxicity: an investigation of the chain length-dependent nephrotoxicity of PFAS

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are recognized as critical environmental health hazards, however, their toxicity mechanisms in specific organ systems remain poorly characterized. This study systematically investigated the chain length-dependent nephrotoxicity of PFAS and their inhibitory effects on renal carboxylesterase (CES) activity. In vitro experiments revealed that PFAS were cytotoxic to Human Kidney-2 (HK-2) cells in a dose-dependent and chain length-dependent manner. Furthermore, functional group modification significantly affected the toxicity, perfluoroalkyl carboxylic acids (PFCA) showed the strongest toxic effects compared to fluorotelomer alcohols (FTOH) and perfluoroiodides of the same carbon chain length. PFAS inhibited CES activity in a concentration-dependent manner, with stronger inhibitory effects observed at higher concentrations. PFCA showed the strongest inhibition of CES activity and chain length-dependent manner. Molecular simulations indicated that the PFAS easily bind to CES, suggesting PFAS may affect the activity by affecting secondary structure of CES. In vivo experiments revealed that exposure to perfluorocapric acid (PFDA) in C57BL/6 mice significantly suppressed renal CES activity and induced kidney injury, whereas perfluorohexanoic acid (PFHxA) exerted negligible effects. In addition, kidney weight was positively correlated with CES activity, suggesting a potential causal relationship between CES and PFAS-induced nephrotoxicity. Overall, this study not only provides new insights into the toxicological mechanisms of PFAS-laying a scientific foundation for the safety assessment of alternative compounds and the formulation of risk management strategies-but also validates the reliability of in vitro cell-based assays for the early screening of PFAS biotoxicity.