MAT1A NULL MOUSE: MODEL FOR ALCOHOLIC TISSUE INJURY

MAT1A 空鼠标：酒精组织损伤模型

• 批准号: 6711048
• 负责人: Shelly Chi-Loo Lu
• 金额: $ 37.02万
• 依托单位: UNIVERSITY OF SOUTHERN CALIFORNIA
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-03-01 至 2008-02-29
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6711048
• 关键词: CD14 molecule; S adenosylmethionine; cytochrome P450; disease /disorder model; enzyme linked immunosorbent assay; ethanol; gene expression; gene targeting; gene therapy; genetically modified animals; high performance liquid chromatography; immunocytochemistry; injury; laboratory mouse; liver; macrophage; methionine adenosyltransferase; microarray technology; nonhuman therapy evaluation; northern blottings; oxidative stress; pancreas; polymerase chain reaction; tissues; tumor necrosis factor alpha; western blottings

DESCRIPTION (provided by applicant): Methionine adenosyltransferase (MAT) is a critical enzyme responsible for the biosynthesis of S-adenosylmethionine (SAM). Of the two genes (MAT1A, MAT2A) that encode MAT, MAT1A is mainly expressed in adult liver. Due to differences in kinetics and regulatory properties, cells expressing MAT1A have much higher SAM levels than cells expressing MAT2A. Cirrhotic patients have decreased hepatic MAT activity and SAM biosynthesis. SAM has been used therapeutically but the molecular targets remain unclear. Recently we showed the importance of MAT1A in maintaining a normal liver phenotype using the MAT1A null mice. Three-month old MAT1A null mice have reduced hepatic SAM and GSH levels, hyperplasia, spontaneous oxidative stress, increased cytochrome P4502E1 (CYP2E1) expression and are prone to liver injury. On a normal diet, MAT1A null mice develop non-alcoholic steatohepatitis by 8 months and hepatocellular carcinoma by 18 months. Further, we discovered that the once thought to be liver-specific MAT1A is highly expressed in normal pancreas and pancreatic acini. MAT expression undergoes dramatic changes and pancreatic SAM level fall in female mice fed a choline-deficient ethionine supplemented diet (a model of necrotizing pancreatitis). SAM supplementation prevented pancreatic injury in this model and ameliorated injury due to cerulein infusion, a more acute model of pancreatitis. Although pancreatic injury is normally absent in rodents fed ethanol, they are more susceptible to cerulein-induced injury. Pancreatic SAM levels fell during ethanol feeding and may sensitize the organ to further injury. Given these provocative results, we hypothesize that MAT1A null and heterozygous mice are more susceptible to ethanol-induced tissue injury and may serve as a novel model to study the pathogenesis and treatment of these diseases. The aims of the proposal are: 1) examine the effect of SAM depletion and treatment in ethanol-induced liver injury-examine whether SAM depletion predisposes to ethanol-induced injury and whether SAM is effective therapeutically in the absence of MAT1A; 2) examine the effect of SAM depletion and treatment in ethanol-induced pancreatic injury-examine whether SAM depletion predisposes to ethanol-induced pancreatic injury and the effect of SAM treatment; 3) elucidate the mechanisms of SAM depiction's sensitizing effect on liver injury-examine the role of CYP2E1, mitochondrial GSH and hepatic macrophage activation in SAM depletion s sensitizing effect; 4) identify the molecular targets of SAM's therapeutic effect in alcoholic liver injury-identify targets of SAM using genomics and proteomics.

描述（由申请人提供）： 甲硫氨酸腺苷转移酶（MAT）是S-腺苷甲硫氨酸（SAM）生物合成的关键酶。在编码MAT的两个基因（MAT 1A、MAT 2A）中，MAT 1A主要在成人肝脏中表达。由于动力学和调节特性的差异，表达MAT 1A的细胞具有比表达MAT 2A的细胞高得多的SAM水平。肝硬化患者肝脏MAT活性和SAM生物合成降低。SAM已被用于治疗，但分子靶点仍不清楚。最近，我们使用MAT 1A缺失小鼠显示了MAT 1A在维持正常肝脏表型中的重要性。三个月大的MAT 1A缺失小鼠具有降低的肝脏SAM和GSH水平、增生、自发氧化应激、增加的细胞色素P4502 E1（CYP 2 E1）表达，并且易于发生肝损伤。在正常饮食下，MAT 1A基因敲除小鼠在8个月时发生非酒精性脂肪性肝炎，在18个月时发生肝细胞癌。此外，我们发现，曾经被认为是肝脏特异性的MAT 1A在正常胰腺和胰腺腺泡中高度表达。MAT表达经历了显着的变化和胰腺SAM水平下降的雌性小鼠喂养胆碱缺乏乙醇补充饮食（坏死性胰腺炎模型）。SAM补充防止胰腺损伤，在这个模型中，并改善损伤由于雨蛙肽输注，更急性胰腺炎模型。虽然胰腺损伤通常是不存在的啮齿动物喂食乙醇，他们更容易受到雨蛙素诱导的损伤。胰腺SAM水平在乙醇喂养期间下降，并可能使器官对进一步损伤敏感。鉴于这些挑衅性的结果，我们假设MAT 1A无效和杂合子小鼠更容易受到乙醇诱导的组织损伤，并可能作为一种新的模型来研究这些疾病的发病机制和治疗。该提案的目的是：1）检查SAM消耗和治疗对乙醇诱导的肝损伤的影响-检查SAM消耗是否容易导致乙醇诱导的损伤，以及在没有MAT 1A的情况下，SAM是否具有治疗效果; 2）检查SAM消耗和治疗在乙醇诱导的胰腺损伤中的作用-检查SAM消耗是否易患乙醇-本研究的主要目的是：1）探讨SAM对胰腺损伤的增敏作用及其治疗效果; 2）阐明SAM对肝损伤增敏作用的机制--探讨CYP 2 E1、线粒体GSH和肝巨噬细胞活化在SAM耗竭增敏作用中的作用; 3）确定SAM对胰腺损伤增敏作用的分子靶点， SAM对酒精性肝损伤的治疗作用--利用基因组学和蛋白质组学鉴定SAM的作用靶点。