IRAKM and Mincle in ALD

 描述（由申请人提供）：酒精性肝病（ALD）是酒精相关发病率和死亡率的主要来源。据估计，10- 15%的酗酒者会发展成纤维化、肝硬化和肝细胞癌。炎症反应是疾病进展的关键因素。炎症增加的一个重要途径是肠道通透性增加和细菌菌群的变化，导致枯否细胞上Toll样受体4（TLR 4）的激活。然而，乙醇也直接损伤肝细胞;我们的初步数据表明，来自受损肝细胞的信号对肝巨噬细胞的活化也至关重要。本提案的总体目标是研究TLR依赖性炎症反应与酒精诱导的肝细胞损伤如何协同导致ALD的发病机制。TLR通过接头分子MyD 88和IL-1 R相关激酶（IRAK）家族的成员（包括IRAK 1、IRAK 2、IRAKM和IRAK 4）传递信号。上游激酶IRAK 4直接与MyD 88相互作用。虽然MyD 88-IRAK 4-IRAK 1介导TAK 1依赖性NF κ B B活化，但MyD 88-IRAK 4-IRAK 2对于转录后控制是关键的。虽然IRAKM与MyD 88-IRAK 4相互作用以介导MEKK 3依赖性第二波NF κ B B活化，但其与IRAK 2相互作用以抑制细胞因子和趋化因子的翻译。因此，IRAKM对炎症反应发挥总体抑制作用。令人惊讶的是，我们发现IRAKM缺陷小鼠免受乙醇诱导的肝损伤。阵列分析使我们对一种特定的TLR 4诱导的IRAKM依赖性基因Mincle感兴趣，Mincle是一种C型凝集素受体，它能感知非稳态细胞死亡，从而诱导促炎细胞因子和趋化因子的产生。在ALD患者的肝脏中和在IRAKM依赖性途径中乙醇喂养后的小鼠中诱导Mincle表达。此外，Mincle缺陷型小鼠可免受乙醇诱导的肝损伤。由于Mincle是细胞死亡的传感器，其表达是IRAKM依赖性的，我们假设TLR诱导的IRAKM依赖性Mincle在枯否细胞中的上调提供了酒精诱导的细胞死亡和炎症反应发生之间的关键联系，有助于ALD的发病机制。为了验证这一假设，我们提出了以下目的：目的1研究ALD中TLR介导的IRAKM依赖性通路的机制：我们将研究（1）低剂量TLR配体诱导的TLR-MyD 88-IRAKM-MEKK 3依赖性通路的分子机制;（2）ALD中TLR-MyD 88-IRAKM-MEK 3依赖性通路的致病作用机制。目的2探讨Mincle介导的信号通路在ALD发病中的作用机制：我们将研究（1）Mincle介导的炎性小体激活的分子机制;（2）Mincle依赖的信号通路在ALD发病中的细胞机制。这些结合的分子/细胞和临床前研究将确定TLR-IRAK-M-Mincle信号传导在ALD中的作用的关键要素，从而改进用于预防和治疗ALD的疗法。

 DESCRIPTION (provided by applicant): Alcoholic liver disease (ALD) is a major source of alcohol-related morbidity and mortality. It is estimated that 10-15 percent of alcoholics develop fibrosis, cirrhosis and hepatocellular carcinoma. Inflammatory responses are critical contributors to disease progression. One important pathway to increased inflammation results from increased intestinal permeability and changes in bacterial microflora, resulting in activation of Toll-like receptor 4 (TLR4) on Kupffer cells. However, ethanol also directly injures hepatocytes; our preliminary data indicate that signals from injured hepatocytes are also critical to the activation of hepatic macrophages. The overall objective of this proposal is to investigate how TLR-dependent inflammatory responses, in combination with alcohol-induced hepatocellular injury, coordinately lead to pathogenesis of ALD. TLRs transduce their signals through the adaptor molecule MyD88 and members of the IL-1R-associated kinase (IRAK) family, including IRAK1, IRAK2, IRAKM and IRAK4. IRAK4, the upstream kinase, directly interacts with MyD88. While MyD88- IRAK4-IRAK1 mediates TAK1-dependent NFB activation, MyD88-IRAK4-IRAK2 is critical for post- transcriptional control. While IRAKM interacts with MyD88-IRAK4 to mediate a MEKK3-dependent second wave NFB activation, it interacts with IRAK2 to inhibit translation of cytokines and chemokines. Thus, IRAKM exerts an overall inhibitory effect on inflammatory responses. Surprisingly, we found IRAKM-deficient mice were protected from ethanol-induced liver injury. Array analysis led us to be interested in one particular TLR4-induced IRAKM-dependent gene, Mincle, a C-type lectin receptor, that senses non-homeostatic cell death, thereby inducing pro-inflammatory cytokine and chemokine production. Mincle expression was induced in liver of ALD patients and in mice after ethanol feeding in an IRAKM-dependent pathway. Further, Mincle-deficient mice were protected from ethanol-induced liver injury. Since Mincle is a sensor for cell death and its expression is IRAKM-dependent, we hypothesize that TLR-induced IRAKM-dependent Mincle up-regulation in Kupffer cells provides a critical link between alcohol-induced cell death and onset of inflammatory responses, contributing to the pathogenesis of ALD. To test this hypothesis, we propose the following Aims: Aim 1 Investigate the mechanism for TLR-mediated IRAKM-dependent pathway in ALD: we will investigate (1) The molecular mechanism for the TLR-MyD88-IRAKM-MEKK3-dependent pathway induced by low dose of TLR ligands; (2) The mechanism for the pathogenic role of the TLR-MyD88-IRAKM-MEKK3-dependent pathway in ALD. Aim 2 Investigate the mechanism by which Mincle-mediated signaling contributes to ALD: We will investigate (1) The molecular mechanism for Mincle-mediated inflammasome activation; (2) The cellular mechanism for the pathogenic role of the Mincle-dependent pathway in ALD. These combined molecular/cellular and pre-clinical studies will identify critical elements in the role of the TLR-IRAK-M-Mincle signaling in ALD, leading to improved therapeutics for prevention and treatment of ALD.