The aryl hydrocarbon receptor (AhR) regulates expression of genes encoding drug/xenobiotic metabolizing enzymes. Cytochrome P450 (CYP) 3A5 is involved in drug metabolism. However, regulation of CYP3A5 gene expression is not yet well understood. In this study, we aimed to investigate the effect of the ligands of AhR on CYP3A5 gene expression. CYP3A5 mRNA expression was induced by the polycyclic aromatic hydrocarbons (PAHs) such as 3-methylcholanthrene (3MC) and benzo[a]pyrene in HepG2 cells. To determine whether the PAHs induced CYP3A5 gene expression via AhR, we generated AhR knockout (AhR KO) HepG2 cells. CYP3A5 mRNA expression was not induced by 3MC treatment in AhR KO cells. In addition, we generated AhR rescue cells from AhR KO cells and evaluated CYP3A5 mRNA expression. We found that CYP3A5 mRNA expression was induced by 3MC treatment in AhR rescue cells. Taken together, these results demonstrated that CYP3A5 mRNA expression was induced by PAHs via AhR in HepG2 cells. Our findings suggest that ligand-activated AhR affects CYP3A5-mediated drug metabolism.
Keywords: Aryl hydrocarbon receptor; CYP3A5; Polycyclic aromatic hydrocarbons.