TGR5通过抑制Kupffer细胞炎性应答缓解淤胆型肝硬化的机制研究

Cholestatic liver cirrhosis is a complex pathophysiological process, characterized by diffuse liver injury caused by long-term cholestasis. The intrahepatic resident macrophages, also named as Kupffer cells, play an essential role in the pathogenesis of cholestatic liver cirrhosis by pro-inflammatory activation. Recent studies have shown the critical functions of TGR5 in various liver diseases involved with inflammation. Our group found that TGR5 (plasma membrane-bound G protein–coupled bile acid receptor) was induced in the liver tissues of cholestatic liver cirrhosis. Furthermore, TGR5 knock out enhanced macrophage pro-inflammatory activation, leading to enhanced cholestatic liver cirrhosis. Thus, we hypothesize that TGR5 could alleviate cholestatic liver cirrhosis through downregulating pro-inflammatory activation of Kupffer cells. We plan to take advantages of TGR5 knock out mice and the TGR5 agonist to further define the functional significance of TGR5 in regulating the macrophage activation during cholestatic liver cirrhosis. To further define the underlying mechanisms, signaling pathways including AKT-GSK3β and NRF2/HO-1 will be tested by the in vitro macrophage activation studies. Finally, we will further confirmed these findings by analyzing liver tissues from patients with cholestatic liver cirrhosis. Studies on how TGR5 in regulation of macrophage activation during cholestatic liver cirrhosis will not only help to illustrate the mechanism involved in cholestatic liver cirrhosis, but also provide novel therapeutic target and related theoretical basis.

淤胆型肝硬化是长期胆汁淤积导致的慢性肝损害肝内Kupffer细胞介导的慢性炎症在其中扮演重要的角色，但其具体机制仍不清楚。近期研究发现TGR5（G蛋白偶联胆汁酸膜受体）与肝损伤的关系密切。本组研究证实了淤胆型肝硬化肝脏组织中TGR5表达显著增高，而敲除TGR5基因后肝内Kupffer产生大量炎性因子，促进了淤胆型肝硬化的发生。由此提出本假说：TGR5信号可能通过抑制Kupffer细胞免疫反应，阻止淤胆型肝硬化的进展。本课题拟采用TGR5敲除小鼠和TGR5激动剂，通过建立小鼠淤胆型肝硬化模型，验证TGF5与Kupffer在淤胆型肝硬化中的作用机制。进一步分析TGR5抑制Kupffer细胞活化的下游信号通路是否与AKT-GSK3β和NRF2/HO-1有关。最后，通过淤胆型肝硬化患者的临床标本进一步验证。本课题研究有助于深入了解淤胆型肝硬化的发生发展的机制，为临床干预治疗提供新的靶点和理论依据。

淤胆性肝病(CLD)以存在炎症，纤维化和胆管增生为特征，可影响任何年龄组的人。Takeda G蛋白偶联受体(TGR5)通过Toll样受体4(TLR4)和核因子kappa B（NF-kB）参与炎症抑制。枯否细胞及其M1极化通过产生促炎细胞因子在炎症和淤胆性肝损伤中发挥重要作用。然而，TGR5信号转导在CLD中的作用仍不清楚。在这里，我们发现胆汁淤积性肝硬化患者血清胆汁酸和TGR5水平升高。TGR5基因敲除通过增加氧化应激，促进枯否细胞以M1为主的极化和升高血清炎性细胞因子水平，显著增加胆管结扎(BDL)引起的肝损伤。相反，TGR5的激活抑制了ROS的产生，促炎性细胞因子的分泌，以及枯否细胞M1占优势的极化。结果表明，TGR5可能通过抑制NF-kB信号通路和激活核因子2(Nrf2)/HO-1信号通路而发挥作用。最后，在体内证实了TGR5对淤胆性肝损伤的作用。总之，TGR5的激活通过抑制NF-kB途径抑制炎症反应和通过激活NRF2/HO-1信号途径减少ROS的产生而保护BDL诱导的CLD。这些发现表明TGR5在CLD中的重要性，并为CLD的治疗策略提供了新的见解。