BMAL1: A Novel Regulator For Inflammatory Liver Injury

描述（申请人提供）：酒精性肝病（ALD）是世界范围内主要的慢性肝病之一，由过量饮酒引起。ALD包括一系列肝脏疾病，从单纯性脂肪肝到酒精性肝炎、肝硬化和肝衰竭。目前对酒精性肝炎等严重ALD的治疗是有限的，缺乏长期疗效。因此，迫切需要开发新的治疗方法来阻止或延缓最终的器官衰竭，并降低巨大的医疗费用。ALD的主要病理特征之一是肝脏内存在长期和低度的炎症反应。内毒素水平升高激活肝巨噬细胞（库普弗细胞）产生氧化应激，产生多种促炎细胞因子，导致肝细胞凋亡增加，细胞外基质蛋白过量产生，纤维化。因此，巨噬细胞和肝细胞之间的复杂相互作用可能会促进慢性乙醇消耗存在的未解决的炎症。更好地了解如何抑制肝脏炎症和细胞凋亡将有助于开发有效的治疗和预防ALD。BMAL1作为一种关键的生物钟蛋白，在肝细胞中高度表达，调节昼夜节律基因以及脂质和糖代谢相关基因的振荡。我们发现Bmal1缺乏会加重脂多糖（LPS）或急性酒精中毒引起的小鼠肝损伤。Bmal1-/-小鼠肝损伤的严重程度与炎症和细胞凋亡的增加有关，这表明在肝损伤治疗中，正常的Bmal1蛋白表达或功能是保护肝细胞免于凋亡和抑制炎症的必要条件。基于这些新的初步数据，我们假设BMAL1通过促进肝细胞存活和减轻慢性肝脏炎症在酒精性肝病的进展中发挥关键作用。我们将在两个具体目标中检验这一假设。在Aim 1中，我们将确定肝细胞特异性Bmal1缺乏是否足以在酒精喂养期间增强肝脏炎症和损伤。在Aim 2中，我们将确定BMAL1缺乏是否通过激活促凋亡转录因子fox01使肝细胞对乙醇诱导的凋亡敏感。我们将确定抑制FOXO1对Bmal1-/-敲除小鼠肝损伤的影响。该应用程序的成功完成将对酒精性肝损伤产生新的见解，并确定治疗ALD的新策略。

DESCRIPTION (provided by applicant): Caused by excessive alcohol drinking, alcoholic liver disease (ALD) is one of the leading chronic liver diseases worldwide. ALD includes a spectrum of liver disorders ranging from simple fatty liver to alcoholic hepatitis, cirrhosis, and liver faiure. Current treatment for severe ALD such as alcoholic hepatitis is limited and lacks long-term efficacy. Therefore, there is an urgent need for developing new therapeutics to block or delay the eventual organ failure and reduce the huge medical costs. One of the main pathological features in ALD is the presence of prolonged and low-grade inflammatory response within liver. Activation of hepatic macrophages (Kupffer cells) by elevated endotoxin levels generates oxidative stress and produces a variety of pro-inflammatory cytokines, which result in increased apoptosis of hepatocytes, excessive production of extracellular matrix proteins, and fibrosis. Thus, a complex interaction between macrophages and hepatocytes might promote unsolved inflammation in the presence of chronic ethanol consumption. A better understanding of how to restrain inflammation and apoptosis in the liver will shed light on developing effective treatment and prevention of ALD. As a key circadian clock protein, highly expressed in hepatocytes, BMAL1 regulates oscillations of circadian genes as well as genes involved in lipid and glucose metabolism. We discovered that Bmal1 deficiency exacerbates liver injury induced by either lipopolysaccharide (LPS) or acute alcohol intoxication in mice. The severity of liver injury in Bmal1-/- mice is associated with increased inflammation and cell apoptosis, suggesting that normal BMAL1 protein expression or function is required to protect hepatocytes from apoptosis and suppress inflammation in response to liver injury treatment. Based on these novel preliminary data, we hypothesize that BMAL1 plays a critical role during the progression of alcohol liver disease by promoting hepatocyte survival and alleviating chronic hepatic inflammation. We will test the hypothesis in two specific aims. In Aim 1, we will determine whether hepatocyte-specific Bmal1 deficiency is sufficient to enhance liver inflammation and injury during alcohol feeding. In Aim 2, we will determine whether BMAL1 deficiency sensitizes hepatocyte to ethanol-induced apoptosis via activating pro-apoptotic transcription factor FOXO1. We will determine the effects of inhibition of FOXO1 on liver injury in Bmal1-/- knockout mice. Successful completion of the application will yield new insights on alcohol-induced liver injury and identify new strategies for the treatment of ALD.