鹅去氧胆酸通过激活法尼醇 X 受体诱导细胞解毒酶表达是通过 AMP 激活的蛋白激酶和细胞外信号调节激酶 1/2 磷酸化 CCAAT/增强子结合蛋白 β 实现的。

Farnesoid X receptor activation by chenodeoxycholic acid induces detoxifying enzymes through AMP-activated protein kinase and extracellular signal-regulated kinase 1/2-mediated phosphorylation of CCAAT/enhancer binding protein β.

机构信息

Interdisciplinary Program of Clinical Pharmacology, College of Pharmacy, Seoul National University, Seoul, South Korea.

出版信息

Drug Metab Dispos. 2011 Aug;39(8):1451-9. doi: 10.1124/dmd.111.038414. Epub 2011 May 19.

Abstract

Farnesoid X receptor (FXR) regulates redox homeostasis and elicits a cytoprotective effect. CCAAT/enhancer binding protein-β (C/EBPβ) plays a role in regulating the expression of hepatocyte-specific genes and contributes to hepatocyte protection and liver regeneration. In view of the role of FXR in xenobiotic metabolism and hepatocyte survival, this study investigated the potential of FXR to activate C/EBPβ for the induction of detoxifying enzymes and the responsible regulatory pathway. Chenodeoxycholic acid (CDCA), a major component in bile acids, activates FXR. In HepG2 cells, CDCA treatment activated C/EBPβ, as shown by increases in its phosphorylation, nuclear accumulation, and expression. 3-(2,6-Dichlorophenyl)-4-(3'-carboxy-2-chlorostilben-4-yl-)oxymethyl-5-isopropyl-isoxazole (GW4064), a synthetic FXR ligand, had similar effects. In addition, CDCA enhanced luciferase gene transcription from the construct containing -1.65-kb GSTA2 promoter, which contained C/EBP response element (pGL-1651). Moreover, CDCA treatment activated AMP-activated protein kinase (AMPK), which led to extracellular signal-regulated kinase 1/2 (ERK1/2) activation, as evidenced by the results of experiments using a dominant-negative mutant of AMPKα and chemical inhibitor. The activation of ERK1/2 was responsible for the activating phosphorylation of C/EBPβ. FXR knockdown attenuated the ability of CDCA to activate AMPK and ERK1/2 and phosphorylate C/EBPβ. Consistently, enforced expression of FXR promoted the phosphorylation of AMPKα, ERK1/2, and C/EBPβ, verifying that C/EBPβ phosphorylation elicited by CDCA results from the activation of AMPK and ERK1/2 by FXR. In mice, CDCA treatment activated C/EBPβ with the induction of detoxifying enzymes in the liver. Our results demonstrate that CDCA induces antioxidant and xenobiotic-metabolizing enzymes by activating C/EBPβ through AMPK-dependent ERK1/2 pathway downstream of FXR.

摘要

法尼醇 X 受体 (FXR) 调节氧化还原平衡并发挥细胞保护作用。CCAAT/增强子结合蛋白-β (C/EBPβ) 在调节肝细胞特异性基因的表达中发挥作用,并有助于肝细胞保护和肝脏再生。鉴于 FXR 在异生物质代谢和肝细胞存活中的作用,本研究探讨了 FXR 激活 C/EBPβ 诱导解毒酶的潜力及其负责的调节途径。鹅脱氧胆酸 (CDCA),胆汁酸中的主要成分,激活 FXR。在 HepG2 细胞中,CDCA 处理激活了 C/EBPβ,表现为其磷酸化、核积累和表达增加。合成 FXR 配体 3-(2,6-二氯苯基)-4-(3'-羧基-2-氯二苯乙烯-4-基)-氧甲基-5-异丙基异恶唑 (GW4064) 也有类似的作用。此外,CDCA 增强了包含-1.65-kb GSTA2 启动子的构建体中的荧光素酶基因转录,该启动子包含 C/EBP 反应元件 (pGL-1651)。此外,CDCA 处理激活了 AMP 激活的蛋白激酶 (AMPK),这导致细胞外信号调节激酶 1/2 (ERK1/2) 的激活,这可以通过使用 AMPKα的显性负突变体和化学抑制剂的实验结果证明。ERK1/2 的激活负责 C/EBPβ 的激活磷酸化。FXR 敲低减弱了 CDCA 激活 AMPK 和 ERK1/2 并磷酸化 C/EBPβ 的能力。一致地,强制表达 FXR 促进了 AMPKα、ERK1/2 和 C/EBPβ 的磷酸化,验证了 CDCA 引起的 C/EBPβ 磷酸化是由 FXR 激活的 AMPK 和 ERK1/2 引起的。在小鼠中,CDCA 处理激活了 C/EBPβ,并在肝脏中诱导了解毒酶。我们的结果表明,CDCA 通过 FXR 下游的 AMPK 依赖性 ERK1/2 途径激活 C/EBPβ 诱导抗氧化和异生物质代谢酶。

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