Kim Sangsoo Daniel, Morgan Larry, Hargreaves Elyse, Zhang Xiaoying, Jiang Zhihui, Antenos Monica, Li Ben, Kirby Gordon M
Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada.
Chinese-German Joint Institute for Natural Product Research, College of Biological Science and Engineering, Shaanxi University of Technology, Hanzhong, China.
Front Pharmacol. 2021 Nov 22;12:730416. doi: 10.3389/fphar.2021.730416. eCollection 2021.
Jaundice is a potentially fatal condition resulting from elevated serum bilirubin levels. For centuries, herbal remedies containing Thunb including the compound 6,7-dimethylesculetin (DE) have been used in Asia to prevent and treat jaundice in neonates. DE activates an important regulator of bilirubin metabolism, the constitutive androstane receptor (CAR), and increases bilirubin clearance. In addition, murine cytochrome P450 2a5 (Cyp2a5) is known to be involved in the oxidative metabolism of bilirubin. Moreover, treatment of mice with phenobarbital, a known inducer of both CAR and Cyp2a5, increases expression of Cyp2a5 suggesting a potential relationship between CAR and Cyp2a5 expression. The aim of this study is to investigate the influence of and DE on the expression and regulatory control of Cyp2a5 and the potential involvement of CAR. Treatment of mouse hepatocytes in primary culture with DE (50 μM) significant increased Cyp2a5 mRNA and protein levels. In mice, and DE treatment also increased levels of hepatic Cyp2a5 protein. Luciferase reporter assays showed that CAR increases gene transcription through a CAR response element in the gene promoter. Moreover, DE caused nuclear translocation of CAR in primary mouse hepatocytes and increased Cyp2a5 transcription in the presence of CAR. These results identify a potential CAR-mediated mechanism by which DE regulates gene expression and suggests that DE may enhance bilirubin clearance by increasing Cyp2a5 levels. Understanding this process could provide an opportunity for the development of novel therapies for neonatal and other forms of jaundice.
黄疸是一种由血清胆红素水平升高导致的潜在致命病症。几个世纪以来，亚洲一直使用含有滨蒿的草药疗法（包括化合物6,7 - 二甲基七叶亭（DE））来预防和治疗新生儿黄疸。DE可激活胆红素代谢的一个重要调节因子——组成型雄甾烷受体（CAR），并增加胆红素清除率。此外，已知小鼠细胞色素P450 2a5（Cyp2a5）参与胆红素的氧化代谢。而且，用苯巴比妥（一种已知的CAR和Cyp2a5诱导剂）处理小鼠会增加Cyp2a5的表达，这表明CAR和Cyp2a5表达之间可能存在关联。本研究的目的是调查DE对Cyp2a5表达和调控的影响以及CAR的潜在作用。用DE（50 μM）处理原代培养的小鼠肝细胞可显著增加Cyp2a5 mRNA和蛋白水平。在小鼠中，DE处理也会增加肝脏Cyp2a5蛋白水平。荧光素酶报告基因检测表明，CAR通过基因启动子中的CAR反应元件增加基因转录。此外，DE可导致原代小鼠肝细胞中CAR的核转位，并在有CAR存在的情况下增加Cyp2a5转录。这些结果确定了一种潜在的CAR介导机制，通过该机制DE调节基因表达，并表明DE可能通过增加Cyp2a5水平来增强胆红素清除率。了解这一过程可为开发针对新生儿黄疸及其他形式黄疸的新疗法提供契机。
