LPS binding to TLR4 regulates hepatic stellate cell activation and fibrosis

LPS 与 TLR4 结合调节肝星状细胞活化和纤维化

• 批准号: 8223187
• 负责人: EKIHIRO SEKI
• 金额: $ 33.67万
• 依托单位: UNIVERSITY OF CALIFORNIA, SAN DIEGO
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-02-15 至 2016-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8223187
• 关键词: Activins; Adaptor Signaling Protein; Address; Affect; Agonist; Alcohol abuse; Alcoholic Liver Cirrhosis; Antisense Oligonucleotides; Autoimmune Diseases; Binding; Blood Circulation; Bone Marrow; Bone Morphogenetic Proteins; CCL2 gene; CCR1 gene; CCR5 gene; CX3CL1 gene; Cells; Chemotaxis; Chronic; Cirrhosis; Clinical; Complex; Deposition; Down-Regulation; Endotoxins; Extracellular Matrix; Extracellular Matrix Proteins; Fibrosis; Fractalkine; Genes; Genetic Transcription; Goals; Healthcare; Heavy Drinking; Hepatic; Hepatic Stellate Cell; Hepatitis B; Hepatitis C; Hepatocyte; Infection; Inflammation; Inflammatory; Inflammatory Response; Injury; Intestines; Kupffer Cells; Link; Lipopolysaccharides; Liver; Liver Failure; Liver Fibrosis; MAP3K7 gene; MAPK8 gene; Macrophage Inflammatory Protein-1; Malignant Neoplasms; Mediating; Membrane; Molecular; Morbidity - disease rate; Mus; Mutate; Pathway interactions; Patients; Pattern recognition receptor; Phosphotransferases; Play; Population; Portal Hypertension; Prevention strategy; Prevention therapy; Primary carcinoma of the liver cells; Production; Promoter Regions; Protein Biosynthesis; RANTES; Recruitment Activity; Regulation; Repression; Resistance; Role; Signal Transduction; Staging; Symptoms; System; Testing; Transcription Factor AP-1; Viral hepatitis; base; care burden; chemokine; chemokine receptor; cytokine; design; gene induction; gut microflora; inhibitor/antagonist; liver transplantation; macrophage; migration; mortality; nonalcoholic steatohepatitis; novel therapeutic intervention; overexpression; promoter; public health relevance; receptor; response; toll-like receptor 4; transcription factor

DESCRIPTION (provided by applicant): Liver fibrosis caused by excessive alcohol consumption, viral hepatitis, autoimmune diseases, and non- alcoholic steatohepatitis (NASH), can progress to cirrhosis, liver failure, portal hypertension, and hepatocellular carcinoma. Hepatic fibrosis is characterized by the excessive deposition of extracellular matrix, mainly produced by activated hepatic stellate cells (HSCs), and is highly associated with chronic liver inflammation. However, the precise link between inflammation and hepatic fibrosis is still unknown. Thus, understanding the molecular mechanisms of hepatic fibrosis may help to design strategies for the prevention and treatment of liver injury and fibrosis. Patients with cirrhosis show increased systemic levels of endotoxin (lipopolysaccharide, LPS). We have previously shown that Toll-like receptor 4 (TLR4), a pattern recognition receptor for LPS, plays a critical role in hepatic fibrosis. Gut microflora-derived LPS entering into the portal circulation directly activates HSCs through TLR4, but not Kupffer cells. Activation of the LPS/TLR4 pathway enhances signaling by TGF-2, the most potent fibrogenic agonist, by downregulating bone morphogenetic protein and Activin membrane bound inhibitor (Bambi), a transmembrane suppressor of TGF-2 signaling. Based on our findings, we propose to further characterize the role of TLR4 in the activation of HSCs and in hepatic fibrosis. We hypothesize that gut intestinal microflora-derived LPS binds to the TLR4 receptor in HSCs. Activated TLR4 signaling results in the formation and the release of an intracellular signaling complex. The resulting intracellular signaling activates genes including chemokines and leads to hepatic inflammation and hepatic fibrosis. The TGF-2 signaling modulator Bambi is regulated by TLR4 signaling at the promoter level in HSCs. Based on these hypotheses, we will determine the distinct roles of MyD88 and TRIF between HSCs and Kupffer cells, and TLR4-dependent receptor-associated signaling complex in HSCs (Aim 1). We will determine the regulation of Bambi at the signaling and promoter levels by LPS in HSCs (Aim 2). Moreover, we will address the role of TLR4-induced chemokines in hepatic fibrosis (Aim 3). The pursuit of these three aims will elucidate the crucial role of TLR4 signaling in HSC activation and hepatic fibrosis. The long-term goal of this project is to provide a novel therapeutic approach targeting TLR4 signaling in the prevention and therapy of liver fibrosis. PUBLIC HEALTH RELEVANCE: Hepatic fibrosis and its end stage, cirrhosis, represent a massive health care burden worldwide. The goal of this study is to investigate whether lipopolysaccharide and its receptor TLR4 affect hepatic fibrosis through TLR4 intracellular signaling, TGF-2 signaling, and chemokine/receptor systems. The results from this study might establish TLR4 and its related functions as targets for the therapy of hepatic fibrosis.

描述（由申请人提供）：由过量饮酒、病毒性肝炎、自身免疫性疾病和非酒精性脂肪性肝炎（NASH）引起的肝纤维化，可发展为肝硬化、肝功能衰竭、门脉高压和肝细胞癌。肝纤维化以细胞外基质过度沉积为特征，主要由活化的肝星状细胞（HSCs）产生，与慢性肝脏炎症高度相关。然而，炎症和肝纤维化之间的确切联系尚不清楚。因此，了解肝纤维化的分子机制可能有助于设计预防和治疗肝损伤和纤维化的策略。肝硬化患者表现出全身内毒素（脂多糖，LPS）水平升高。我们之前已经证明toll样受体4 （TLR4）是LPS的一种模式识别受体，在肝纤维化中起关键作用。肠道菌群来源的LPS通过TLR4直接激活hsc，但不激活Kupffer细胞。LPS/TLR4通路的激活通过下调骨形态发生蛋白和激活素膜结合抑制剂（Bambi） （TGF-2信号的跨膜抑制因子）来增强TGF-2信号传导，TGF-2是最有效的纤维化激动剂。基于我们的研究结果，我们建议进一步表征TLR4在造血干细胞激活和肝纤维化中的作用。我们假设肠道菌群来源的LPS与造血干细胞中的TLR4受体结合。激活的TLR4信号导致细胞内信号复合体的形成和释放。由此产生的细胞内信号激活包括趋化因子在内的基因，导致肝脏炎症和肝纤维化。在造血干细胞中，TGF-2信号调节器Bambi在启动子水平上受TLR4信号的调控。基于这些假设，我们将确定MyD88和TRIF在造血干细胞和Kupffer细胞之间的不同作用，以及tlr4依赖性受体相关信号复合物在造血干细胞中的不同作用（目的1）。我们将在hsc中确定LPS在信号和启动子水平上对Bambi的调节（目的2）。此外，我们将探讨tlr4诱导的趋化因子在肝纤维化中的作用（目的3）。对这三个目标的追求将阐明TLR4信号在HSC激活和肝纤维化中的关键作用。该项目的长期目标是为肝纤维化的预防和治疗提供一种新的靶向TLR4信号的治疗方法。