STING-TBK1信号通路在非酒精性脂肪性肝病肝脏炎症中的机制研究

The prevalence of non-alcoholic fatty liver disease (NAFLD) is increasing gradually, and its natural history includes non-alcoholic fatty liver (NAFL), non-alcoholic steatohepatitis (NASH), liver fibrosis and hepatocellular carcinoma (HCC). So human health will be endangered seriously in the process from NASH to HCC. At present, the pathogenesis of NAFLD is not clear completely. Inflammation is the major feature of NASH that is different from steatosis, and inflammation of NASH is associated with steatosis. Studies have shown that STING-TBK1 signaling pathway is involved in the inflammatory response of infected and immune-related diseases, and STING-TBK1 signaling pathway is related to the regulation of fat metabolism. Our previous study found that STING-TBK1 signaling pathway is involved in liver inflammation and long-chain fatty acid synthesis in mouse NAFLD. But the important role of STING-TBK1 signaling pathway in the pathogenesis of NAFLD inflammation and lipid metabolism is not clear completely. In this study, we will illustrate and verify the relationship between the key mechanisms of STING-TBK1 signaling pathway and the occurrence, development and regression of hepatic steatosis and inflammation in NAFLD mouse model and NAFLD population, it may propose a new mechanism for the occurrence and development of NAFLD.

非酒精性脂肪性肝病（NAFLD）的流行率逐年升高，其自然史包括非酒精性脂肪肝（NAFL）、非酒精性脂肪性肝炎（NASH）、并可能经过肝脏纤维化最终进展成肝硬化和肝细胞癌（HCC），严重危害人类健康。炎症是NASH有别于肝脏脂肪变的主要标志，而NASH的炎症与脂肪变有关。研究表明STING-TBK1信号通路参与了感染和免疫相关疾病的炎症反应，同时STING-TBK1信号通路参与了脂肪代谢的调节。我们的前期研究发现STING-TBK1信号通路蛋白分子参与了小鼠NAFLD肝脏炎症和长链脂肪酸的合成。但是关于该通路在NAFLD肝脏炎症和脂肪变的具体分子机制尚不清楚。本研究拟通过NAFLD动物模型和NAFLD人群肝组织来研究和验证STING-TBK1信号通路的关键机制与NAFLD肝脏脂肪变及炎症发生、发展和消退的相关性, 可能会提出NAFLD发生发展的新机制。

非酒精性脂肪性肝病（NAFLD）的流行率逐年升高，其自然史包括非酒精性脂肪肝（NAFL.）、非酒精性脂肪性肝炎（NASH）、并可能经过肝脏纤维化最终进展成肝硬化和肝细胞癌（HCC），严重危害人类健康。天然免疫在NAFLD的发病机制中占有重要地位。干扰素基因激活蛋白（STING）是天然免疫的重要分子，研究表明STING参与了感染和免疫性疾病时机体的炎症反应和脂肪代谢。本研究通过检测NAFLD小鼠模型和患者肝脏中STING表达，分析STING与NAFLD进展的关系并探讨STING-TBK1信号参与NAFLD发生发展的可能机制。研究发现，与正常饮食小鼠肝组织相比，MCD小鼠模型肝组织中STING mRNA及蛋白水平显著升高，并且与肝脏炎症和纤维化程度呈正相关。与健康对照肝组织相比，NASH患者肝组织样本中STING+细胞数显著增加。STING主要在巨噬细胞表达，包括单核细胞来源的巨噬细胞（MoMFs，CCR2+, S100A9+），Kupffer细胞（CD68+）和CD163+巨噬细胞。与健康对照相比，NASH纤维化患者肝组织中STING+/CCR2+细胞和STING+/S100A9+细胞数显著增加，且与肝脏炎症水平和纤维化程度呈正相关。STING+/CD68+和STING+/CD163+细胞数仅在NASH严重纤维化肝组织中增加，且仅与肝纤维化程度呈正相关。与健康对照肝组织相比，NASH患者肝组织中STING+/p-TBK1+细胞数显著增加。为了解STING是否通过激活TBK1参与NASH进展，体外实验将THP-1巨噬细胞和LX2肝星状细胞共培养发现，THP-1巨噬细胞中p-TBK1的表达及IL1β和IL6的mRNAs水平显著升高。当THP-1巨噬细胞中STING激活后，共培养体系中LX2细胞的α-SMA的表达水平及Col1a1、纤维连接蛋白和TGFβ1的mRNAs水平显著升高，共培养上清中细胞因子IL1β的水平显著升高。总之，肝组织中STING的表达与NAFLD进展相关。STING+巨噬细胞，尤其是STING+MoMFs与NAFLD患者肝组织炎症和纤维化进展成正相关，且有可能是通过巨噬细胞中STING-TBK1信号通路的激活来调控炎症和纤维化进展。因此，MoMFs中STING表达增加可能是NAFLD进展的诱导因素，将来有可能成为NAFLD诊断治疗的新靶点。