MAT1A NULL MOUSE: MODEL FOR ALCOHOLIC TISSUE INJURY

MAT1A 空鼠标：酒精组织损伤模型

• 批准号: 6555520
• 负责人: Shelly Chi-Loo Lu
• 金额: $ 38.52万
• 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/6555520
• 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)： 蛋氨酸腺苷转移酶(MAT)是S-腺苷蛋氨酸(SAM)合成的关键酶。在编码MAT的两个基因(MAT1A、MAT2A)中，MAT1A主要在成人肝脏中表达。由于动力学和调节特性的不同，表达MAT1A的细胞比表达MAT2A的细胞具有更高的SAM水平。肝硬变患者肝组织MAT活性降低，SAM生物合成减少。SAM已被用于治疗，但其分子靶点仍不清楚。最近，我们利用MAT1A缺失的小鼠证明了MAT1A在维持正常肝脏表型方面的重要性。三个月龄的Mat1a基因缺失小鼠肝脏SAM和GSH水平降低，肝组织增生，自发氧化应激，细胞色素P4502E1(CYP2E1)表达增加，容易发生肝损伤。在正常饮食中，Mat1a基因缺失的小鼠在8个月后患上非酒精性脂肪性肝炎，在18个月后患上肝细胞癌。此外，我们发现，曾经被认为是肝脏特异性的MAT1A在正常胰腺和胰腺腺泡中高度表达。喂饲缺乏胆碱的乙硫氨酸饲料的雌性小鼠(坏死性胰腺炎模型)的MAT表达发生了戏剧性的变化，胰腺SAM水平下降。在这一模型中，补充SAM可预防胰腺损伤，并改善由于注射更急性的胰腺炎模型--蓝蓝蛋白而造成的损伤。尽管饮用乙醇的啮齿动物通常不会出现胰腺损伤，但它们更容易受到雨蓝蛋白诱导的损伤。在酒精喂养期间，胰腺SAM水平下降，可能会使器官对进一步的损伤敏感。鉴于这些具有挑衅性的结果，我们假设Mat1a基因缺失和杂合子的小鼠更容易受到乙醇诱导的组织损伤，并可能成为研究这些疾病的发病机制和治疗的新模型。本研究的目的是：1)研究SAM耗竭和治疗在酒精性肝损伤中的作用--研究SAM耗竭是否易导致酒精性肝损伤，以及在没有MAT1A的情况下，SAM是否具有治疗作用；2)研究SAM耗竭和治疗在酒精性胰腺损伤中的作用--研究SAM耗竭是否易诱发酒精性胰腺损伤以及SAM治疗的效果；3)阐明SAM描述对肝损伤的增敏作用的机制--检测细胞色素P2 E1、线粒体GSH和肝巨噬细胞激活在SAM耗竭增敏作用中的作用；4)确定SAM耗竭致敏效应的分子靶点 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确定SAM的靶点。