Histone Methyltransferase G9a Regulates Expression of Nuclear Receptors and Cytochrome P450 Enzymes in HepaRG Cells at Basal Level and in Fatty Acid Induced Steatosis
Histone Methyltransferase G9a Regulates Expression of Nuclear Receptors and Cytochrome P450 Enzymes in HepaRG Cells at Basal Level and in Fatty Acid Induced Steatosis
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DOI：
10.1124/dmd.120.000195
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发表时间：
2020-10
影响因子：
3.9
通讯作者：
Parimal Pande;Xiao-bo Zhong;W. Ku
中科院分区：
文献类型：
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作者：
Parimal Pande;Xiao-bo Zhong;W. Ku
肥胖和非酒精性脂肪性肝病（NAFLD）影响细胞色素P450基因（P450）的表达和功能。炎性细胞因子的表达增加是NAFLD中P450表达下调的主要驱动因素。P450表达降低可能导致药物相互作用、药物药理作用无效或肝毒性。已知可增加组蛋白3赖氨酸9甲基化的表观遗传修饰剂组蛋白3赖氨酸9甲基转移酶（G9 a）在饮食诱导的肥胖动物模型中下调。在肝脏特异性G9 a基因敲除动物模型中，P450的表达下调。目前，G9 a在脂肪变性中调节P450的作用尚不清楚。我们的假设是，在脂肪变性中，G9 a在P450表达的下调中起作用。在这项研究中，我们使用HepaRG细胞诱导脂肪变性，使用游离脂肪酸油酸和棕榈酸的组合。分别使用小干扰RNA和腺病毒介导的方法敲低和过表达G9 a。在不存在脂肪变性的情况下，G9 a的敲低和过表达分别降低和增加了核受体组成型雄烷受体（CAR）、雄烷X受体、小异源二聚体伴侣和CYP 2B 6、2 E1、2C 8、2C 9和3A 4的表达。在脂肪变性条件下，G9 a的过表达阻止了脂肪酸介导的CAR、CYP 2C 19、2C 8、7A 1和3A 4的表达降低。我们目前的研究表明，G9 a可能作为一个关键的调节P450表达在基础水平和早期脂肪变性条件。G9 a单核苷酸多态性导致功能丧失/获得，可能导致慢代谢型或超快代谢型表型。本研究表明，组蛋白修饰酶G9 a参与调节基础条件下和脂肪酸诱导的脂肪变性细胞模型中的核受体组成型雄烷受体、雄烷X受体和小异源二聚体伴侣以及药物代谢细胞色素P450（P450）的表达。组蛋白3赖氨酸9甲基化应与组蛋白3赖氨酸4和组蛋白3赖氨酸27甲基化一起被认为是控制P450基因表达的表观遗传机制。
Obesity and nonalcoholic 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 downregulation 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, histone 3 lysine 9 methyl transferase enzyme (G9a), known to increase histone 3 lysine 9 methylation, is downregulated in diet-induced obesity animal models. In a liver-specific G9a knockout animal model, expression of P450s was downregulated. Currently, the role of G9a in regulation of P450s in steatosis is unknown. Our hypothesis is that in steatosis G9a plays a role in downregulation 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 small interfering RNA and adenovirus mediated approaches, respectively. Knockdown and overexpression of G9a in the absence of steatosis decreased and increased expression of nuclear receptors constitutive androstane receptor (CAR), pregnane X receptor, small heterodimer partner, and 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. Single nucleotide polymorphism of G9a leading to loss/gain of function could lead to the poor metabolizer or ultrarapid metabolizer phenotypes. SIGNIFICANCE STATEMENT The current study demonstrates that histone modification enzyme G9a is involved in the regulation of expression of nuclear receptors constitutive androstane receptor, pregnane X receptor, and small heterodimer partner as well as drug-metabolizing cytochrome P450s (P450s) at basal conditions and in fatty acid induced cellular model of steatosis. Histone 3 lysine 9 methylation should be considered together with histone 3 lysine 4 and histone 3 lysine 27 methylation as the epigenetic mechanisms controlling gene expression of P450s.