Epigenetic toxicity of PFOA and GenX in HepG2 cells and their role in lipid metabolism

Perfluorooctanoic acid (PFOA), an extremely persistent perfluoroalkyl substance (PFAS), and 2,3,3,3-Tetrafluoro-2-(heptafluoropropoxy) propanoic acid (GenX), its shorter chain alternative, have been implicated in hepatocellular damage with unusual fat deposit and liver enlargement. In this study we explored the underlying mechanisms of PFOA and GenX induced hepatocellular damage. Liver hepatocellular carcinoma cell line HepG2 was used as a model to study induced liver inflammation in vitro at the cellular, genetic, and epigenetic levels. HepG2 cells were exposed to PFOA or GenX for 48 h and the DNA and RNA were extracted and analyzed. mRNA expression analysis of PFOA exposed cells showed that cell cycle homeostasis genes were affected significantly, as well as the ten-eleven translocation methylcytosine dioxygenases (TETs) and the essential lipid metabolism genes. GenX did not have as significant an effect. Global methylation levels of HepG2 cells were found to be inversely proportional to PFOA exposure levels. With GenX, the global methylation level decreased and then increased. Our work points to the fact that PFOA may contribute to higher overall epigenetic toxicity than GenX, and its induced epigenetic changes may play a major role in lipid metabolism gene regulation and fat deposits.