Regulation of transporters by perfluorinated carboxylic acids in HepaRG cells

Perfluorinated carboxylic acids (PFCAs) are environmental pollutants for which human exposure has been documented. PFCAs at high doses were known regulate xenobiotic transporters partly through PPARα and CAR in rodents. Less is known regarding how various PFCAs at a lower concentration modulate transporters for endogenous substrates such as amino acids in human hepatocytes. Such studies are of particular importance because amino acids are involved in chemical detoxification and their transport system may serve as promising therapeutic targets for structurally similar xenobiotics. The focus of this study was to further elucidate how PFCAs modulate transporters involved in intermediary metabolism and xenobiotic biotransformation. We tested the hepatic transcriptomic response of HepaRG cells exposed to 45 µM PFOA, PFNA, or PFDA in triplicates for 24 h (vehicle: 0.1% DMSO), as well as the prototypical ligands for PPARα (WY-14643, 45 µM) and CAR (CITCO, 2 µM). PFCAs with increasing carbon chain lengths (C8-C10) regulated more liver genes, with amino acid metabolism and transport ranked among the top enriched pathways and PFDA ranked as the most potent PFCA tested. Genes encoding amino acid transporters, which are essential for protein synthesis, were novel inducible targets by all 3 PFCAs, suggesting a potentially protective mechanism to reduce further toxic insults. None of the transporter regulations appeared to be through PPARα or CAR but potential involvement of Nrf2 is noted for all 3 PFCAs. In conclusion, PFCAs with increasing carbon chain lengths up-regulate amino acid transporters and modulate xenobiotic transporters to limit further toxic exposures in HepaRG cells. Little is known regarding how various PFCAs modulate the transporters for endogenous substrates in human liver cells. Using HepaRG cells, this study is among the first to show that PFCAs with increasing carbon chain lengths up-regulate amino acid transporters, which are essential for protein synthesis, and modulate xenobiotic transporters to limit further toxic exposures at concentrations lower than what was used in literature.