PT  - JOURNAL ARTICLE
AU  - Parimal Pande
AU  - Xiao-bo Zhong
AU  - Warren W. Ku
TI  - Histone Methyltransferase G9a Regulates Expression of Nuclear Receptors and Cytochrome P450 Enzymes in HepaRG Cells at Basal Level and in Fatty Acid Induced Steatosis.
AID  - 10.1124/dmd.120.000195
DP  - 2020 Jan 01
TA  - Drug Metabolism and Disposition
PG  - DMD-AR-2020-000195
4099  - http://dmd.aspetjournals.org/content/early/2020/10/18/dmd.120.000195.short
4100  - http://dmd.aspetjournals.org/content/early/2020/10/18/dmd.120.000195.full
AB  - Obesity and non-alcoholic fatty liver disease (NAFLD) affect expression and function of cytochrome P450 genes (P450s). The increased expression of inflammatory cytokines is a major driver of the down regulation of P450 expression in NAFLD. Decrease in P450 expression could potentially lead to drug-drug interaction, inefficient pharmacological effect of a drug or hepatotoxicity. An epigenetic modifier, a histone methyl transferase enzyme G9a, known to increase histone 3 lysine 9 (H3K9) methylation, is down regulated in diet induced obesity animal models. In a liver specific G9a knockout animal model, expression of P450s was down regulated. Currently, the role of G9a in regulation of P450s in steatosis is unknown. Our hypothesis is that, in steatosis G9a plays a role in down regulation of P450 expression. In this study, we used HepaRG cells to induce steatosis using a combination of free fatty acids oleic acid and palmitic acid. The G9a was knocked down and overexpressed using siRNA and adenovirus mediated approaches, respectively. Knockdown and overexpression of G9a in the absence of steatosis decreased and increased expression of CAR, PXR, SHP, CYP2B6, 2E1, 2C8, 2C9, and 3A4, respectively. In steatotic conditions, overexpression of G9a prevented fatty acid mediated decreased expression of CAR, CYP2C19, 2C8, 7A1 and 3A4. Our current study suggests that G9a might serve as a key regulator of P450 expression at both the basal level and in early steatotic conditions. SNPs of G9a leading to loss/ gain of function could lead to the poor metabolizer or ultra-rapid metabolizer phenotypes. Significance Statement The current study demonstrates that histone modification enzyme G9a is involved in the regulation of expression of NRs CAR, PXR, and SHP as well as drug-metabolizing P450s at basal conditions and in FA induced cellular model of steatosis. H3K9 methylation should be considered together with H3K4 and H3K27 methylation as the epigenetic mechanisms controlling gene expression of P450s.