Brief report on differential toxicity of legacy and second-generation PFAS on dopaminergic neurons and mitochondria

Per/polyfluoroalkyl substances (PFAS) are anthropogenic chemicals that have shown extensive usage. Owing to widespread use and resistance to environmental degradation, they have become a hazard with respect to the environment and human health. While the legacy PFAS are being phased out, they are being replaced by second-generation PFAS that are considered safer alternatives. However, the lack of information pertaining to the underlying mechanisms for legacy and especially second-generation PFAS exacerbates the risk. This study investigates legacy and second-generation PFAS to determine their individual effects on neurotoxicity and mitochondrial respiration. Legacy PFAS, perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), and second-generation PFAS, GenX, and ADONA were employed, and studies were conducted using Caenorhabditis elegans and mitochondria isolated from Rat brain for Complex I to IV. It was found that legacy PFAS, PFNA, and PFDA were neurotoxic, with neurotoxicity proportional to chain length. PFOA, PFNA, and PFDA also exhibited significant inhibition to most of the mitochondrial complexes. Whereas in the case of second-generation PFAS ADONA, and GenX, it was only limited to the inhibition of Complex IV. GenX only exhibited neurodegeneration at very high doses. Our findings conclude that the legacy and second-generation PFAS might have significant neurotoxic implications. While the targets are similar to some extent, the mechanisms between the two classes are distinct. Our study the sets the stage to evaluate further the combined effect of PFAS (legacy and emergent) to fill in informational gaps pertaining to their safety.