Gut microbiota mediated bile acid alterations in hepatic carcinogenesis

 描述(由申请人提供)：慢性肝损伤长期以来一直与进行性肝病发展成脂肪性肝炎和随后增加的肝细胞癌(肝细胞癌)风险有关。胆汁酸(BA)代谢改变也与肝损伤密切相关。然而，到目前为止，bas在肝脏发病机制中的作用尚不清楚。脱氧胆酸(DCA)、石胆酸(LCA)和牛磺酸脱氧胆酸(TDCA)等疏水性胆碱的细胞内蓄积是胆汁淤积性肝损伤的机制之一。这些肠道微生物代谢的化合物，当积聚在肝细胞中时，会导致线粒体损伤，细胞膜破裂，产生活性氧，最终导致细胞凋亡或坏死。在这项研究中，我们假设肠道微生物区系介导的bas在肝内的积聚是导致随后的肝纤维化和恶性肿瘤发展的关键因素。该项目还旨在提供直接证据，证明调节BA代谢作为治疗肝损伤、防止肝硬化和癌症发展的有效性。本文设计了四个具体的目标来检验上述假设。该项目的目标1是确定肠道微生物群对宿主BA谱的影响。小鼠模型和细胞系将被用来解决两个问题：(1)肠道微生物群在介导肝脏和外周BA变化中起什么作用？(2)随着脂肪性肝炎从脂肪肝发展到肝细胞癌，肠道微生物区系和肝脏BA谱如何变化？该项目的目标2是确定bas在FXR调节肝脏损伤和癌变中的作用。体外模型以及FXR基因敲除的小鼠模型将被用来解决以下问题：(1)bas如何影响促炎细胞因子的产生；(2)bas能否在体外诱导正常肝细胞恶性转化？(3)bas的改变是否会影响肝bas的功能 以及(4)肝脏FXR-胆汁酸相互作用如何影响BA转运体、药物滞留和肝损伤？目标3是建立肠道微生物组和宿主BA代谢组之间的统计关系。目的4探讨BAS肝脏毒性的分子机制及BA动态平衡治疗的改善作用。

 DESCRIPTION (provided by applicant): Chronic liver injury has long been associated with progressive liver disease toward the development of steatohepatitis and the subsequent increased risk of hepatocellular carcinoma (HCC). Altered bile acid (BA) metabolism has also been associated closely with liver injury. However, the mechanistic role of BAs in hepatic pathogenesis has, so far, remained unclear. Intracellular accumulation of hydrophobic BAs such as deoxycholic acid (DCA), lithocholic acid (LCA), and taurodeoxycholic acid (TDCA), which appear to be the most cytotoxic species among BAs, has been proposed as a mechanism of cholestatic liver injury. These gut microbe - metabolized compounds, when accumulated in hepatocytes, result in mitochondrial damage, disruption of cell membranes, and production of reactive oxygen species, ultimately leading to apoptosis or necrosis. In this study, we hypothesize that gut microbiota mediated intrahepatic accumulation of BAs critically mediates sustained hepatocellular injury responsible for the subsequent development of fibrosis and malignancy. The project is also intended to provide direct evidence to demonstrate the efficacy of regulating BA metabolism as a treatment for liver injury, protecting against the development of cirrhosis and cancer. Four Specific Aims are designed to test the above hypothesis. The Aim 1 of the project is to determine the impact of gut microbiome on host BA profiles. Mouse models and cell lines will be used to address two questions: (1) what is the role of gut microbiome in mediating hepatic and peripheral BA alteration? (2) how do gut microbiota and hepatic BA profile change as steatohepatitis progresses from fatty liver to HCC? The Aim 2 of the project is to determine the role of BAs in FXR regulation in liver injury and carcinogenesis. In vitro models as well as a FXR-knock-out mouse model will be used to address the following questions, (1) how do BAs impact the production of proinflammatory cytokines, (2) can BAs induce malignant transformation of normal liver cell in vitro? (3) can altered BAs influence functions of hepatic BA transporters, and (4) how does hepatic FXR-bile acid interaction impact BA transporters, drug retention, and liver injury? The Aim 3 is to establish a statistical correlation between gut microbiome and host BA metabolome. The Aim 4 is to explore the molecular mechanisms of hepatic toxicity of BAs and the ameliorative effect of BA homeostasis therapies.