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）：由过度饮酒、病毒性肝炎、自身免疫性疾病和非酒精性脂肪性肝炎（NASH）引起的肝纤维化可进展为肝硬化、肝衰竭、门静脉高压和肝细胞癌。肝纤维化的特征是细胞外基质过度沉积，主要由活化的肝星状细胞（HSC）产生，并且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仍然是未知的。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。肝硬化患者显示内毒素（脂多糖，LPS）的全身水平增加。我们以前已经表明，Toll样受体4（TLR 4），LPS的模式识别受体，在肝纤维化中起着关键作用。肠道菌群来源的LPS进入门静脉循环直接激活HSC通过TLR 4，但不是库普弗细胞。LPS/TLR 4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信号传导的跨膜抑制剂）增强TGF-2（最有效的纤维化激动剂）的信号传导。基于我们的研究结果，我们建议进一步表征TLR 4在HSC活化和肝纤维化中的作用。我们推测肠道菌群来源的LPS与HSC中的TLR 4受体结合。激活的TLR 4信号传导导致细胞内信号复合物的形成和释放。由此产生的细胞内信号激活包括趋化因子在内的基因，并导致肝脏炎症和肝纤维化。TGF-2信号调节剂Bambi在HSC中受TLR 4信号在启动子水平的调节。基于这些假设，我们将确定MyD 88和TRIF在HSC和Kupffer细胞之间的不同作用，以及HSC中TLR 4依赖性受体相关信号传导复合物（Aim 1）。我们将在HSC中确定LPS在信号和启动子水平对Bambi的调节（目的2）。此外，我们将讨论TLR 4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TLR 4信号在HSC活化和肝纤维化中的关键作用。本项目的长期目标是提供一种新的治疗方法，靶向TLR 4信号转导在预防和治疗肝纤维化。 公共卫生相关性：肝纤维化及其终末期肝硬化是全球范围内巨大的卫生保健负担。本研究的目的是探讨脂多糖及其受体TLR 4是否通过TLR 4细胞内信号、TGF-2信号和趋化因子/受体系统影响肝纤维化。本研究结果可能为TLR 4及其相关功能作为肝纤维化治疗的靶点奠定基础。