Role of AMP-activated protein kinase α1 in 17α-ethinylestradiol-induced cholestasis in rats.
Li Xiaojiaoyang,Liu Runping,Luo Lan,Yu Linxi,Chen Xin,Sun Lixin,Wang Tao,Hylemon Phillip B,Zhou Huiping,Jiang Zhenzhou,Zhang Luyong
Archives of toxicology
Estrogen-induced cholestasis occurs in many women who are susceptible due to pregnancy or hormone replacement therapy for postmenopausal syndrome. 17α-Ethinylestradiol (EE), as a synthetic estrogen, has been widely used to study the underlying mechanisms of estrogen-induced cholestasis. Recent studies have also reported that liver kinase B1 (LKB1)-mediated activation of AMP-activated protein kinase (AMPK) plays a critical role in the regulation of canalicular network formation. However, the role of AMPK in EE-induced cholestasis remains to be determined. In this study, the effects of EE (1-100 µM) on AMPK activation and the expression of farnesoid X receptor (FXR) and hepatic bile acid transporters were examined in in vitro using 3D-cultured rat primary hepatocytes and in in vivo using rat cholestasis models. We also used specific chemical agonist and antagonist of AMPK, AMPK subunit-specific antibodies and lentiviral shRNAs for AMPKα1 and AMPKα2 to delineate the role of AMPK in EE-induced cholestasis and potential cellular mechanisms. We found that EE-induced phosphorylation of AMPKα1 via extracellular signal-regulated kinases-LKB1-mediated signaling pathways and subsequent nuclear translocation accounted for the down-regulation of FXR and bile acid transporters and disruption of bile acid homeostasis. Inhibition of AMPK activation using an AMPK antagonist Compound C (2 µM) or down-regulation of AMPKα1 using gene-specific shRNA attenuated EE-induced cholestasis both in in vitro and in in vivo. In conclusion, these results revealed that activation of cAMP-ERK-LKB1-AMPKα1 signaling pathway plays a critical role in EE-mediated dysregulation of the expression of FXR and bile acid transporters. AMPKα1 may represent an important therapeutic target for estrogen-induced cholestasis.
Protective effect of dioscin against thioacetamide-induced acute liver injury via FXR/AMPK signaling pathway in vivo.
Zheng Lingli,Yin Lianhong,Xu Lina,Qi Yan,Li Hua,Xu Youwei,Han Xu,Liu Kexin,Peng Jinyong
Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie
Our previous works showed that dioscin, a natural product, could protect liver from acute liver damages induced by dimethylnitrosamine, ethanol, carbon tetrachloride and acetaminophen. However, the effect of dioscin on thioacetamide (TAA)-induced acute liver injury still remained unknown. The purpose of this study was to investigate whether dioscin confers a protective effect against TAA-induced acute liver injury in rats and mice. The results showed that dioscin decreased the serum levels of ALT, AST, and rehabilitated histopathological changes compared with the model groups. In addition, dioscin obviously increased the levels of GSH, GSH-Px, SOD, and significantly reduced MDA levels compared with the model groups. Mechanistic study showed that dioscin significantly up-regulated the expression levels of FXR, p-AMPKα, and then increased the expression levels of Nrf2, HO-1, NQO-1, GCLM and GST. Furthermore, dioscin obviously down-regulated the expression levels of NF-κB (p65), ICAM-1, HMGB1, COX-2, TNF-α, IL-1β and IL-6. Taken together, dioscin showed protective effect against TAA-induced acute liver injuries in rats and mice and the effects might be obtained through inhibiting oxidative stress and inflammation via FXR/AMPK signal pathway. These findings provided a new insight on the role of doscin in the treatment of acute liver injury.
Alpha-naphthylisothiocyanate impairs bile acid homeostasis through AMPK-FXR pathways in rat primary hepatocytes.
Li Xiaojiaoyang,Liu Runping,Yu Linxi,Yuan Zihang,Sun Rong,Yang Hang,Zhang Luyong,Jiang Zhenzhou
Alpha-naphthylisothiocyanate (ANIT) is widely used to induce cholestasis in basic researches. Although direct damage induced by ANIT to bile duct epithelial cells has been documented in previous studies, few works investigated ANIT-induced effects on hepatocytes. Our previous study indicated that activated AMP-activated protein kinase (AMPK) inhibited farnesoid X receptor (FXR) expression and further participated in the pathogenesis of estrogen-induced cholestasis. However, whether ANIT has effects on bile acid homeostasis in hepatocytes, and the role of AMPK-FXR pathway played in these effects remain unclear. In this study, our results showed that ANIT induced intracellular bile acid accumulation without obvious cellular toxicity in sandwich cultured rat primary hepatocytes (SCRHs), accompanied with significant decreased expression of FXR and bile acid transporters. AMPK activation via ERK1/2-LKB1 pathway was critical for ANIT-induced effects on hepatocytes. Compound C, specific AMPK inhibitor, blocked ANIT-regulated gene expression, decreased bile acid accumulation and recovered bile canalicular structure both in vitro and in vivo. Furthermore, the expression of A adenosine receptor (AAR), a potential cholestatic target, was relatively low in hepatocytes compared with expression in rat whole livers. Consistent with these findings, DPCPX, a classic antagonist of AAR, had no effect on ANIT-induced hepatocytes injury. In summary, our results indicate that AMPK-FXR signaling is critical for ANIT-induced toxic effects on hepatocytes, provide new insights into the pathogenesis of ANIT-induced cholestasis, and suggest AMPK-FXR pathway as a potential therapeutic target for cholestasis.