Methionine Adenosyltransferase as a Therapeutic Target for Liver Fibrosis

项目概述：肝纤维化是许多慢性肝病的结果，如病毒性肝炎和自身免疫性肝炎，以及饮酒和胆道梗阻。长期的肝损伤触发肝星状细胞（HSC）的激活和炎症细胞的募集进入肝脏。在分子水平上，这些变化涉及基因组关键转录调节因子的表达或活性的调节。蛋氨酸腺苷基转移酶（Methionine adenosyl transferases， MAT）是催化主要的生物甲基供体s -腺苷基蛋氨酸（SAMe）形成的必需酶。已知MAT中的两个基因MAT2A和MAT2p与肝细胞增殖和恶性变性密切相关。最近，我们发现MAT2A和MAT2P基因对于由众所周知的促纤维化因子瘦素介导的肝癌细胞增殖至关重要。这些新发现使我们假设MAT基因的表达在HSC激活过程中被诱导，这可能是纤维形成过程中的一个重要事件。因此，我们计划使用生化和分子生物学技术来解决四个具体目标：1)评估MAT基因在体外和体内大鼠HSC激活过程中的表达，确定其是否为激活所必需的；2)确定MAT信号通路中的代谢物SAMe和甲基硫代腺苷（MTA）是否可以改变MAT基因的表达和HSC的激活；3)检查已知的促纤维化因子瘦素和血小板衍生生长因子（PDGF）对大鼠HSC中MAT基因表达的影响，以及SAMe和MTA是否可以阻断这种反应。4)评估人HSC细胞系在响应促纤维化信号、瘦素和血小板衍生生长因子（PDGF）激活过程中MAT基因的表达，进一步了解人肝分离HSC中MAT基因表达的机制。我们将在指导阶段启动前两个目标，我将在奖项的独立阶段进一步发展后续目标。我的长期计划是成为人类肝纤维化和肝硬化领域的独立研究者。相关性（见说明书）：拟议的实验将更好地了解肝纤维化及其相关并发症的机制，并将有助于开发治疗人类肝纤维化的治疗策略。

DESCRIPTION (provided by applicant): Project Summary: Hepatic fibrosis is an outcome of many chronic liver diseases, such as viral and autoimmune hepatitis, and of alcohol consumption and biliary obstruction. Prolonged liver injury triggers activation of hepatic stellate cells (HSC) and recruitment of inflammatory cells into the liver. At the molecular level, these changes involve modulation of the expression or activity of key transcriptional regulators of the genome. Methionine adenosyl transferases (MAT) are essential enzymes that catalyze the formation of the principle biological methyl donor, S-adenosylmethionine (SAMe). Two of the MAT genes, MAT2A and MAT2p are known to be strongly associated with liver cell proliferation and malignant degeneration. Recently we discovered that MAT2A and MAT2P genes are essential for proliferation of liver cancer cells mediated by a well known pro-fibrogenic factor, leptin. These novel findings led us to hypothesize that the expression of MAT genes is induced during HSC activation and this may be an important event during fibrogenesis. Thus, we plan to use biochemical and molecular biology techniques to address four specific aims: 1) to evaluate the expression of MAT genes during activation of rat HSCs in vitro and in vivo and to determine whether they are required for activation, 2) to establish whether the metabolites in the MAT signaling pathway, SAMe and methylthioadenosine (MTA) can alter MAT gene expression and HSC activation, 3) to examine whether known pro-fibrogenic factors, leptin and platelet-derived growth factor (PDGF) can influence MAT gene expression in rat HSCs and whether SAMe and MTA can block this response and 4) to evaluate the expression of MAT genes in human HSC cell lines during activation in response to pro-fibrogenic signals, leptin and platelet-derived growth factor (PDGF) and further understand these mechanisms in HSCs isolated from human liver. We will initiate the first two aims during the mentored phase and I will further develop the subsequent aims during the independent phase of the award. My long term plan is to establish myself as an independent investigator in the field of human liver fibrosis and cirrhosis. RELEVANCE (Seeinstructions): The proposed experiments will provide a better understanding of the mechanisms underlying hepatic fibrosis its associated complications and will be useful in the development of therapeutic strategies for treatment of human liver fibrosis.