Role of Histone Deacetylase 4 in Alcoholic Liver Disease

项目摘要 酒精性肝病（ALD）是世界范围内发病率和死亡率的主要原因。ALD是第八大 是美国常见的死亡原因，也是所有胃肠道疾病中的第二大死亡原因。 疾病酒精性肝炎（AH）是ALD的进行性形式，可进展为肝硬化， 肝细胞癌因此，对于开发有效的治疗策略， 啊有证据表明组蛋白去乙酰化酶（HDAC）参与酒精诱导的细胞损伤。然而，在这方面， 关于每种HDAC同种型在AH发病机制中的作用知之甚少。我们发现HDAC4 mRNA 在酒精性肝硬化的人肝和小鼠肝中， 肝脏暴露在酒精中此外，我们的初步数据表明，乙醇增加HDAC4 在Huh-7细胞（一种人肝细胞癌细胞系）中表达。此外，乙醇诱导表达 Hdac4的表达，同时伴随着巨噬细胞中炎症和氧化应激的增加， 当Hdac4被敲除或下调时显著减弱。Sirtuin 1（SIRT1）是一种预防 酒精相关的细胞损伤和肝脏损伤。一致地，我们发现SIRT1抑制剂增加了 白细胞介素-1b（IL-1b）表达，而SIRT 1激活剂显著消除乙醇诱导的 巨噬细胞中的Hdac4和Illb表达。有趣的是，Hdac 4缺乏增加了Sirt 1， 表达，而人HDAC4过表达在RAW 264.7中引起相反的作用。 巨噬细胞初步结果表明HDAC4/SIRT1轴可能在细胞凋亡中起着至关重要的作用。 发展AH。基于上述强有力的前提，我们建立了中心假设， 肝细胞或巨噬细胞中Hdac4的缺失通过改变肝细胞或巨噬细胞中Hdac4的表达来抑制AH的发展。 包括SIRT1在内的基因表达，这些基因与酒精诱导的炎症和氧化应激密切相关。 应力我们将采用靶向（SIRT1途径）和非靶向（全基因组转录组）方法 分析）使用在慢性暴食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）作为体内模型。我们将通过以下两个方面来检验这一假设 具体目的：1）确定肝细胞和巨噬细胞HDAC 4在AH发展中的作用， 评估HDAC4/SIRT1轴在AH发病机制中的作用; 2）进行全基因组转录组 分析以鉴定肝细胞和巨噬细胞中HDAC4调节的基因，这些基因介导致病性 AH的过程，并使用人肝标本和原代人肝细胞证实结果 和巨噬细胞。这项探索性研究的结果将提供急需的信息， 肝细胞和巨噬细胞HDAC4在AH发病机制中的作用。此外，这项研究将导致发现新的 基因/途径，这可以用于未来的治疗AH。对公众产生重大影响 预期在完成本研究后健康状况良好。

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.