基于核受体PXR通路胆汁酸代谢调控的五味子醇乙抗胆汁淤积新机制

Cholestasis is a clinical syndrome with systemic and intrahepatic retention of excessive toxic bile acids that causes a variety of liver diseases. Currently, ursodeoxycholic acid (UDCA) is the only FDA-approved drug to treat cholestasis whereas its efficacy is limited to early stages of primary biliary cirrhosis. Thus, it is necessary to develop more effective therapeutic drugs for cholestasis treatment. Schisandrol B (SolB) is an active constituent of Schisandra sphenanthera which has been demonstrated to protect against different chemical-induced hepatoxicity. Recently, we proved the protection effect of Sol B on lithocholic acid (LCA)-induced intraphepatic cholestasis and bile duct ligation (BDL)-induced extrahepatic cholestasis in mice. RT-qPCR and western blot analysis showed that hepatic expression of Cyp3a11, Ugt1a1 and Oatp2 which are PXR targeted genes were significantly increased by SolB treatment. Further metabolomic analysis showed that SolB significantly reversed the abnormal metabolic map of bile acids induced by LCA. These results indicate that PXR axis and bile acids regulation may play an important role in hepatoprotection of SolB against cholestasis and the involved mechanisms need to be further elucidated. . Here, for the first time, we will assess the role of PXR axis in SolB-induced hepatoprotection against cholestasis and elucidate its molecular role in regulation of PXR axis and the homeostasis of bile acids. In this study, targeted metabolomics of bile acids in serum, intestinal content, bile, liver, and intestine tissue samples will be used to confirm the regulational effect of SolB on the disposition of bile acids. In silico molecular docking will be used to predict the binding activity of SolB with PXR’s ligand binding district (LBD). Meanwhile, electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) assay will be chosen to identify putative PXR binding elements. Effect of SolB on PXR activation will be also examined using luciferase reporter assay in HepG2 cells transiently transfected with PXR reporter genes. Furthermore, PXR knock-out mice will be used to confirm that SolB exerts hepatoprotection against cholestasis via activation of PXR pathway. Finally, the studies will provide a new insight into the importance of PXR axis and regulation of bile acids homeostasis in SolB-induced hepatoprotection against cholestasis, and then suggest SolB might be a novel potential drug target for the therapy of cholestasis.

胆汁淤积会导致严重肝胆疾病，目前胆汁淤积治疗药物非常匮乏；核受体PXR在胆汁酸代谢调控和胆汁淤积中起重要作用。我们前期发现，五味子醇乙显著抵抗石胆酸（LCA）所致胆汁淤积，且上调PXR通路胆汁酸代谢调控相关基因；代谢组学数据显示，五味子醇乙能逆转LCA所致的异常胆汁酸代谢谱。基于此，我们提出五味子醇乙调控PXR通路影响胆汁酸代谢从而抗胆汁淤积的科学假设。项目拟应用代谢组学研究胆汁酸代谢谱的变化，全面表征五味子醇乙对胆汁酸稳态的调控；并在计算机及细胞分子水平通过分子模拟、EMSA、ChIP、报告基因检测等手段，证明五味子醇乙对PXR结合和转录活性的影响及激动作用；最后采用Pxr基因敲除小鼠，证实五味子醇乙通过调控PXR通路抗胆汁淤积，从而全面获得五味子醇乙调控PXR通路影响胆汁酸代谢从而抗胆汁淤积的直接证据，为其抗胆汁淤积的护肝机制提供新思路，推进其作为抗胆汁淤积药物的研究。

胆汁淤积会导致严重肝胆疾病，目前胆汁淤积治疗药物非常匮乏；核受体PXR在胆汁酸代谢调控和胆汁淤积中起重要作用。我们前期发现，五味子醇乙显著抵抗石胆酸（LCA）所致胆汁淤积，且上调PXR通路胆汁酸代谢调控相关基因；代谢组学数据显示，五味子醇乙能逆转LCA所致的异常胆汁酸代谢谱。基于此，我们提出五味子醇乙调控PXR通路影响胆汁酸代谢从而抗胆汁淤积的科学假设。我们应用代谢组学研究胆汁酸代谢谱的变化，全面表征五味子醇乙对胆汁酸稳态的调控，结果表明SolB可促进毒性胆汁酸代谢而且SolB可促进肝脏淤积的毒性胆汁酸由肝脏和血液向肠道转移和排泄。在计算机及细胞分子水平通过分子模拟、报告基因检测等手段，我们证明了五味子醇乙对PXR结合和转录活性的影响及激动作用。最后采用Pxr基因敲除小鼠，证实SolB抗胆汁淤积的作用是经由PXR通路发挥的、是PXR依赖性的。综上所述，本研究全面获得五味子醇乙调控PXR通路影响胆汁酸代谢从而抗胆汁淤积的直接证据，为其抗胆汁淤积的护肝机制提供新思路，推进其作为抗胆汁淤积药物的研究。