Transcriptional and non-transcriptional functions of IRF3 in ALD

摘要 酒精消费是全世界可预防的发病率和死亡率的主要原因。慢性酗酒 是酒精性肝病（ALD）发病机制的基础，包括一系列病理学， 从脂肪变性到更严重的肝损伤，包括酒精性肝炎（AH）、纤维化和肝硬化。 人们越来越认识到先天免疫系统在疾病进展中的动态和复杂作用。 以及肝细胞损伤和纤维化的解决。控制和适当的解决方案 炎症是先天免疫反应的基本特征。这种受伤和受伤之间的动态相互作用 修复至少部分是由驻留组织巨噬细胞的巨大可塑性介导的， 浸润单核细胞，因为它们响应其微环境内的信号。 通过IRF 3的信号传导是在细胞凋亡中促存活与促死亡途径的动态调节中的重要因素。 免疫细胞虽然有几项研究表明IRF 3参与了ALD的进展，但其机制仍有待进一步研究。 IRF 3对肝损伤的贡献还不清楚。传统上，IRF 3被称为转录因子 对诱导干扰素-γ（IFN-γ）和抗病毒基因至关重要。最近，我们的团队成员发现 除了其转录功能外，IRF 3还直接触发称为RIG-I的促凋亡途径。 类受体（RLR）诱导的IRF-3介导的凋亡途径（RIPA）通过非转录 机制在IRF 3介导的细胞凋亡中，IRF 3通过两个赖氨酸残基上的线性泛素化被激活， 导致IRF 3与促凋亡蛋白Bax相互作用。然后IRF 3/BAX复合物易位 到线粒体中引发细胞凋亡。为了研究这一途径，我们创造了一种新的 表达仅表现出非转录功能的IRF 3蛋白的敲入小鼠。 重要的是，在初步实验中，我们发现IRF 3介导的先天免疫细胞凋亡 在高酒精暴露的反应中被招募到肝脏，动态地加剧炎症， 导致小鼠酒精性肝炎（mAH）。在这里，我们建议调查的机制， IRF 3的非转录活性有助于mAH模型中的肝脏炎症和纤维化， SA 1）确定IRF 3的非转录功能在介导纤维化中的贡献， 在mAH的Gao-binge模型和通过肝纤维化加速的小鼠模型中， 乙醇和SA 2）研究mAH或纤维化期间免疫细胞中IRF 3活化的机制。在 总之，我们的研究将揭示IRF 3的非转录活性在加剧先天性免疫缺陷中的新作用。 对酒精的免疫反应，以及确定潜在的治疗靶点， ALD患者炎症和纤维化的消退。

ABSTRACT Alcohol consumption is a leading cause of preventable morbidity and mortality worldwide. Chronic alcohol abuse underlies the pathogenesis of alcoholic liver disease (ALD), encompassed by a spectrum of pathologies, ranging from steatosis, to more severe forms of liver injury, including alcoholic hepatitis (AH), fibrosis, and cirrhosis. There is a growing appreciation of a dynamic and complex role of the innate immune system in the progression of ALD, as well as the resolution of hepatocellular injury and fibrosis. The controlled and appropriate resolution of inflammation is an essential feature of the innate immune response. This dynamic interplay between injury and repair is mediated, at least in part, by the tremendous plasticity of resident tissue macrophages and infiltrating monocytes as they respond to signals within their microenvironment. Signaling via IRF3 is an important element in the dynamic regulation of pro-survival vs pro-death pathways in immune cells. While several studies have implicated IRF3 in the progression of ALD, the mechanisms by which IRF3 contributes to liver injury are not well understood. Classically, IRF3 is known as a transcription factor essential for the induction of interferon- (IFN-) and antiviral genes. Recently, members of our team discovered that, in addition to its transcriptional functions, IRF3 directly triggers a pro-apoptotic pathway, termed RIG-I- like receptors (RLR)-induced IRF-3-mediated pathway of apoptosis (RIPA) via a non-transcriptional mechanism. In IRF3-mediated apoptosis, IRF3 is activated by linear ubiquitination on two lysine residues, resulting in the interaction of IRF3 with the pro-apoptotic protein Bax. The IRF3/BAX complex then translocates to the mitochondria where it triggers apoptosis. In order to study this pathway, we have generated a novel knock-in mouse that expresses an IRF3 protein that only exhibits non-transcriptional functions. Importantly, in preliminary experiments, we discovered that IRF3-mediated apoptosis of innate immune cells recruited to the liver in response to Gao-binge ethanol exposure dynamically exacerbates inflammation and contributes to murine alcoholic hepatitis (mAH). Here we propose to investigate the mechanisms by which the non-transcriptional activity of IRF3 contributes to both hepatic inflammation and fibrosis in models of mAH and fibrosis in 2 specific aims: SA1) Determine the contribution of the non-transcriptional function of IRF3 in mediating ethanol-induced liver injury in the Gao-binge model of mAH and a murine model of acceleration of fibrosis by ethanol and SA2) Investigate the mechanisms of IRF3 activation in immune cells during mAH or fibrosis. In summary, our studies will reveal novel roles for the non-transcriptional activity of IRF3 in exacerbating innate immune responses to alcohol, as well as identify potential therapeutic targets that would prevent and/or improve the resolution of inflammation and fibrosis in patients with ALD.