Role of Histone Deacetylase 4 in Alcoholic Liver Disease

项目总结 酒精性肝病是世界范围内发病率和死亡率的主要原因。ALD排在第八位 美国常见的死亡原因，在所有胃肠道疾病中居第二位 疾病。酒精性肝炎(AH)是酒精性肝病的进展型，可进展为肝硬化和 肝细胞癌。因此，开发有效的治疗策略是一项尚未得到满足的需求 阿。有证据表明，组蛋白脱乙酰酶(HDAC)与酒精诱导的细胞损伤有关。然而， 关于每种HDAC亚型在AH发病机制中的作用，人们知之甚少。我们发现HDAC4mRNA 在酒精性肝硬变的人肝和小鼠中蛋白质水平显著增加 肝脏暴露在酒精中。此外，我们的初步数据表明，乙醇增加了HDAC4 在人肝细胞癌细胞系Huh-7中的表达。此外，乙醇诱导了该基因的表达 HDAC4伴随着巨噬细胞炎症和氧化应激的增加，这是 当HDAC4被敲除或被击倒时，其强度显著减弱。已知sirtuin 1(SIRT1)可预防 酒精相关的细胞损伤和肝脏损伤。一贯地，我们发现SIRT1抑制剂增加 白介素1b(IL1b)的表达，而SIRT1激活剂显著抑制乙醇诱导的 巨噬细胞中HDAC4和IL1b的表达。有趣的是，HDAC4缺乏增加了Sirt1 表达，而人HDAC4过表达在RAW 264.7中引起相反的效应 巨噬细胞。初步结果提示，HDAC4/SIRT1轴可能在 环境卫生的发展。基于上述强有力的前提，我们建立了一个中心假设 肝细胞或巨噬细胞中HDAC4的缺失通过改变肝脏来抑制AH的发展 包括SIRT1在内的与酒精引起的炎症和氧化密切相关的基因的表达 压力。我们将采用靶向方法(SIRT1途径)和非靶向方法(全基因组转录组 分析)使用在慢性狂欢下具有肝细胞或巨噬细胞特异性HDAC4缺失的新小鼠 乙醇喂养(NIAAA模型)与体内模型相同。我们将通过追求以下两个方面来检验这一假设 目的：1)明确肝细胞和巨噬细胞HDAC4在急性肝炎和急性胰腺炎发病中的作用。 评估HDAC4/SIRT1轴在AH发病中的作用；2)进行全基因组转录组研究 肝细胞和巨噬细胞中HDAC4调控的致病相关基因分析 用人肝标本和原代人肝细胞来证实这一发现 和巨噬细胞。这项探索性研究的发现将产生关于以下方面的急需的信息 肝细胞和巨噬细胞HDAC4在AH发病机制中的作用此外，这项研究将导致新的发现 基因/途径，可用于未来的治疗急性肝炎。因此，对公众产生重大影响 在完成这项研究后，预计会有健康状况。

PROJECT SUMMARY Alcoholic liver disease (ALD) is a major cause of morbidity and mortality worldwide. ALD is the eighth most common cause of mortality in the U.S. and the second leading cause of death among all gastrointestinal diseases. Alcoholic hepatitis (AH) is the progressive form of ALD, which can progress to cirrhosis and hepatocellular carcinoma. Therefore, there is an unmet need for developing effective therapeutic strategies for AH. Evidence suggests histone deacetylases (HDACs) are involved in alcohol-induced cell damages. However, little is known about the role of each HDAC isoform in the pathogenesis of AH. We found that HDAC4 mRNA and protein levels were markedly increased in the human liver with alcoholic cirrhosis and the mouse liver exposed to alcohol. Furthermore, our preliminary data indicate that ethanol increased HDAC4 expression in Huh-7 cells, a human hepatocellular carcinoma cell line. Also, ethanol induced the expression of Hdac4 with concomitant increases in inflammation and oxidative stress in macrophages, which was significantly attenuated when Hdac4 was knocked out or down. Sirtuin 1 (SIRT1) is known to prevent alcohol-related cell damages and liver injury. Consistently, we found that a SIRT1 inhibitor increased interleukin-1b (Il1b) expression, whereas a SIRT1 activator significantly abolished ethanol-induced Hdac4 and Il1b expression in macrophages. It is of interest that Hdac4 deficiency increased Sirt1 expression, while human HDAC4 overexpression elicited the opposite effects in RAW 264.7 macrophages. The preliminary results suggest the HDAC4/SIRT1 axis may play a crucial role in the development of AH. Based on the strong premise described above, we establish the central hypothesis that the deletion of Hdac4 in hepatocytes or macrophages inhibits the development of AH by altering hepatic expression of genes, including SIRT1, that are critically involved in alcohol-induced inflammation and oxidative stress. We will take both targeted (SIRT1 pathway) and untargeted approaches (genome-wide transcriptome analysis) using novel mice that have hepatocyte- or macrophage-specific deletion of Hdac4 under chronic-binge ethanol feeding (the NIAAA model) as in vivo models. We will test the hypothesis by pursuing the following two Specific Aims: 1) to determine the role of hepatocyte and macrophage HDAC4 in the development of AH and to evaluate the HDAC4/SIRT1 axis for the pathogenesis of AH; and 2) to conduct a genome-wide transcriptome analysis to identify HDAC4-regulated genes in hepatocytes and macrophages that mediate the pathogenic processes of AH and to corroborate the findings using human liver specimens and primary human hepatocytes and macrophages. The findings from this exploratory study will produce much-needed information on the role of hepatocyte and macrophage HDAC4 in the pathogenesis of AH. Also, this study will lead to the discovery of new genes/pathways, which can be exploited for future therapies for AH. Therefore, a significant impact on public health is anticipated upon completion of this study.