Homocysteine, ER Stress and Alcoholic Liver Injury.

描述(申请人提供)：我们已经证明，灌胃酒精喂养的小鼠会出现高同型半胱氨酸血症、内质网应激和脂肪性肝炎。喂食甜菜碱可以防止酒精的所有这些影响。在我们以前研究的基础上，我们制定了五个具体目标来检验同型半胱氨酸诱导的内质网应激在酒精性肝病发病机制中起关键作用的假说：目的1.确定肝脏特异性缺失GRP78对酒精或高蛋氨酸低叶酸(HMLF)喂养所致肝损伤的易感性的影响：这项工作包括条件基因敲除小鼠的培育和表型鉴定，以及GRP78缺失的体内外研究；目的2.确定分子伴侣在抑制酒精和同型半胱氨酸诱导的内质网应激和脂肪性肝炎中的有效性：这项工作包括作为保护作用的原理证明的体外研究和体内研究。目的3.研究JNK在内质网应激诱导的肝损伤中的作用：这些研究将在酒精和HMLF模型中评估JNK1、2或两者的反义在体外的作用。前三个目的是在胃内小鼠模型中检验内质网应激是酒精性肝病严重程度的主要决定因素的假设。目的4.通过验证内质网应激诱导的Insig-1异常调节导致SREBP激活所致酒精性脂肪肝的假说，确定内质网应激在肝脏脂质蓄积中的机制和作用。目的5.通过检验BHMT的反应是高同型半胱氨酸血症和随后的内质网应激下游激活导致脂肪变性和损伤的关键因素这一假说，确定BHMT在酒精性肝损伤中的作用；这项工作将包括BHMT转录调控的物种差异(小鼠和大鼠)，核因子-kB在抑制BHMT中的作用，同型半胱氨酸和甜菜碱诱导BHMT的机制，以及通过给予CBHcy抑制BHMT的效果，以测试是否可以克服对酒精性肝病的抵抗。这项工作将导致预防或治疗酒精性肝病的新方法，并将扩大我们对肝脏内质网应激的原因和影响的了解。 公共卫生相关性：在美国，长期过量饮酒导致的脂肪肝和损伤导致的肝硬变是肝脏相关死亡和移植的主要原因。我们已经在动物模型中确定了肝病和酒精引起的同型半胱氨酸水平升高之间的联系。因此，了解酒精如何增加同型半胱氨酸水平，以及同型半胱氨酸水平升高如何导致肝脏损害，将为预防和治疗由酒精和其他原因引起的肝病开辟新的途径。

DESCRIPTION (provided by applicant): We have demonstrated that the intragastric alcohol fed mouse develops hyperhomocysteinemia, ER stress and steatohepatitis. Feeding betaine prevents all of these effects of alcohol. Based upon our previous studies we have developed five specific aims which test the hypothesis that ER stress induced by homocysteine plays a key role in the pathogenesis of alcoholic liver disease: Aim 1. Determine the effect of liver specific deletion of Grp78 on the susceptibility to liver injury from alcohol or high methionine low folate (HMLF) feeding: this work includes breeding and phenotyping conditional knockout mice, and in vitro and in vivo studies of the effect of deletion of Grp78; Aim 2. Determine the effectiveness of molecular chaperones in inhibiting alcohol and homocysteine-induced ER stress and steatohepatitis: this work includes in vitro studies as proof of principle and in vivo studies of the protective effect. Aim 3. Examine the contribution of JNK in ER stress-induced liver injury: these studies will assess the effects of antisense to JNK1, 2, or both in vitro in proof of principle studies and in vivo studies in the alcohol and HMLF models. The first three aims test the hypothesis that ER stress is a major determinant of the severity of alcohol liver disease in the intragastric mouse model. Aim 4. Determine the mechanism and role of ER stress in hepatic lipid accumulation by testing the hypothesis that alcoholic fatty liver is caused by ER stress induced dysregulation of Insig-1 leading to SREBP activation. Aim 5. Determine the role of BHMT in alcohol-induced liver injury by testing the hypothesis that the response of BHMT is a critical factor in the development of hyperhomocysteinemia and subsequent downstream activation of ER stress resulting in steatosis and injury; this work will include studies of the species differences (mouse versus rat) in the transcriptional regulation of BHMT, the role of NF-kB in repression of BHMT, the mechanism of induction of BHMT by homocysteine and betaine, and the effect of inhibiting BHMT by feeding CBHcy with alcohol in the rat model to test if the resistance to alcoholic liver disease can be overcome. This work will lead to new approaches to prevent or treat alcoholic liver disease and will expand our knowledge of the causes and effects of ER stress in the liver. PUBLIC HEALTH RELEVANCE: Fatty liver and injury leading to cirrhosis as a consequence of chronic excessive alcohol use is a leading cause of liver-related death and transplantation in the United States. We have identified a link between liver disease and elevated homocysteine levels caused by alcohol in animal models. Therefore, understanding how alcohol increase homocysteine levels and how increased levels of homocysteine contribute to liver damage will open new avenues for preventing and treating liver disease due to alcohol and other causes.