Effects of perfluorooctanoic acid (PFOA) on gene expression profiles via nuclear receptors in HepaRG cells: Comparative study with in vitro transactivation assays

Perfluorooctanoic acid (PFOA), a synthetic perfluorinated eight-carbon organic chemical, induces hepatotoxicity in rodents, indicated increased liver weight, hepatocellular hypertrophy, necrosis, and peroxisome proliferation. Epidemiological studies have demonstrated the association between serum PFOA levels and various adverse effects. In this study, we investigated the gene expression profiles of human HepaRG cells exposed to 10 and 100 mu M PFOA for 24 h. Treatment with 10 and 100 mu M PFOA significantly modulated the expression of 190 and 996 genes, respectively. Genes upregulated or downregulated by 100 mu M PFOA included peroxisome proliferator-activated receptor (PPAR) signaling genes related to lipid metabolism, adipocyte differentiation, and gluconeogenesis. Moreover, we identified the Nuclear receptors-meta pathways following the activation of other nuclear receptors: constitutive androstane receptor (CAR), pregnane X receptor (PXR) and farnesoid X receptor (FXR), as well as the transcription factor nuclear factor E2-related factor 2 (Nrf2). The expression levels of some target genes (CYP4A11, CYP2B6, CYP3A4, CYP7A1, and GPX2) of these nuclear receptors and Nrf2 were confirmed using quantitative reverse transcription polymerase chain reaction. Next, we performed trans-activation assays using COS-7 and HEK293 cells to investigate whether these signaling-pathways were activated by the direct effects of PFOA on human PPAR alpha, CAR, PXR, FXR and Nrf2. PFOA concentration-dependently activated PPARa, but not CAR, PXR, FXR, or Nrf2. Taken together, these results suggest that PFOA affects the hepatic transcriptomic responses of HepaRG cells through the direct activation of PPARa and indirect activation of CAR, PXR, FXR, and Nrf2. Our finding indicates that PPARa activation in the Nuclear receptors-meta pathways functions as a molecular initiating event for PFOA, and indirect activation of alternative nuclear receptors and Nrf2 also induce important molecular mechanisms in PFOA-induced human hepatotoxicity.

Automated summary

This study investigated the gene expression profiles of human HepaRG cells exposed to PFOA. The results suggest that PFOA affects hepatic transcriptomic responses through direct activation of PPARa and indirect activation of CAR, PXR, FXR, and Nrf2. This finding reveals important molecular mechanisms in PFOA-induced human hepatotoxicity.