HGF/HGFR Axis and Fatty Liver Disease

HGF/HGFR 轴与脂肪肝疾病

• 批准号: 9077861
• 负责人: Reza Zarnegar
• 金额: $ 34.65万
• 依托单位: UNIVERSITY OF PITTSBURGH AT PITTSBURGH
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-04-01 至 2020-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9077861
• 关键词: Albumins; Alcoholic Hepatitis; Automobile Driving; Biological; Cell Death; Cell Survival; Cells; Cessation of life; Cirrhosis; Clinical; Coupled; Data; Defect; Disease; Event; Fatty Liver; Fatty acid glycerol esters; Fibrosis; Glucose; Growth Factor Receptors; HGF gene; Hepatic; Hepatocyte; High Fat Diet; Homeostasis; Human; In Vitro; Inflammation; Inflammatory; Insulin; Insulin Receptor; Insulin Resistance; Liver; Liver Failure; Liver diseases; MET gene; Malignant neoplasm of liver; Mediating; Mediator of activation protein; Metabolic; Metabolic syndrome; Metabolism; Modification; Molecular; Mus; Necrosis; Non-Insulin-Dependent Diabetes Mellitus; Pathology; Pathway interactions; Phosphotransferases; Play; Process; Proteasome Inhibition; Protein Kinase; Protein Tyrosine Kinase; Public Health; RIPK1 gene; Regulation; Resistance; Role; Series; Signal Transduction; Site-Directed Mutagenesis; System; Testing; Transgenic Mice; Tyrosine; Up-Regulation; base; cancer type; cell growth; feeding; gain of function; glucose metabolism; hepatic necrosis; in vivo Model; insight; lipid metabolism; liver inflammation; liver injury; loss of function; meetings; mouse model; non-alcoholic; non-alcoholic fatty liver; nonalcoholic steatohepatitis; novel; prevent; public health relevance; receptor function; research study; response; restoration

 DESCRIPTION (provided by applicant): Fatty Liver Disease (FLD) is a leading public health problem in the U.S. and elsewhere. Liver parenchymal cells (hepatocytes) play an essential role in regulating glucose and fat homeostasis which is believed to be achieved by the proper action of the Insulin-Insulin Receptor (I-IR) axis. Dysregulation of this pathway in Type 2 Diabetes (T2D) can result in non-alcoholic FLD (NAFLD) - a disorder showing a spectrum of pathologies from hepatocyte fat accumulation (steatosis), inflammation and necrosis of steatotic hepatocytes (NASH), fibrosis, cirrhosis and liver cancer that are not well understood at the molecular level. Hepatic insulin resistance is believed to be a driver of this process and results from lack of optimum insulin receptor (IR) function in hepatocytes. Recently, we established that the Hepatocyte Growth Factor (HGF)-MET signaling axis controls hepatic glucose and fat metabolism and is essential for optimum hepatic insulin response. Given the fact that the HGF-MET signaling axis not only controls metabolism but also modulates cell growth and survival (i.e. suppression of cell death), we propose that diminished HGF-MET signalling (that is, "HGF Resistance") in the liver acts as a double-edged sword causing a vicious cycle of hepatocyte metabolic derangement coupled with an inability to overcome (or survive) liver damage provoked by insults such as lipotoxicity. RIPK1 (Receptor Interacting Protein Kinase 1) has emerged as the master switch that dictates inflammation and necrosis. Based on our groundbreaking preliminary data examining the impact of the HGF- MET axis on RIPK1 in hepatocytes, we hypothesize that, under normal conditions in hepatocytes, the HGF-MET axis negatively regulates RIPK1 enzymatic activity through directly tyrosine phosphorylating RIPK1 promoting RIPK1 proteosomal degradation in order to protect hepatocytes from RIPK1's pro- inflammatory and pro-necrotic actions, and that, in the setting of hepatocyte lipotoxicity and NAFLD, reduced and defective HGF-MET signaling results in escape of RIPK1 from HGF-MET-mediated negative regulation unleashing RIPK1-dependent hepatocyte inflammation and necrotic cell death. We propose that restoration of HGF-MET signaling will negate this effect. We outline three specific aims to test this novel hypothesis. Aim 1 - we will investigate the functional consequences of tyrosine phoshorylation of RIPK1 by MET using site directed mutagenesis and in vitro hepatocytic cell cuture systems to establish that this modification results in inhibition of RIPK1 enzymatic activity and promotes its proteosomal degradation - hence, RIPK1 mediated inflammation and necrosis are prevented. We will also test the hypothesis that disruption of MET signaling results in uncontrolled RIPK1 activity unleashing RIPK1- mediated hepatocyte death. The molecular mechanisms that regulate RIPK1 are not well understood. We have discovered that MET directly tyrosine phosphorylates RIPK1 on Tyr384 downregulating RIPK1 kinase activity and marking it for proteosomal degradation. Thus, studies under this aim will decipher the molecular regulation of RIPK1 by the tyrosine kinase growth factor receptor MET. Aim 2 - we will directly test our hypothesis that HGF-MET mediated regulation of RIPK1 has biological and pathological implications to liver homeostasis in the setting of fatty liver disease using loss- and gain-of-function mouse models. We believe that HGF-MET insufficiency caused by lipotoxicity exacerbates RIPK1-induced liver inflammation and necrosis and that restoration of HGF-MET signaling will negate this effect. We have discovered that RIPK1 is upregulated and HGF/MET are downregulated in human and mouse fatty liver. The molecular mechanisms that drive progression of fatty liver disease are not well understood. We propose that reduced HGF/MET signaling in fatty hepatocytes causes RIPK1 to escape MET-mediated negative regulation driving RIPK1-induced hepatocyte necrosis. We will induce fatty liver disease (by feeding a high fat diet) in liver specific loss-of function (using LMETKO and LRIPK1 KO) and gain- of-function (Albumin-HGF Transgenic) mouse models. Aim 3 - we will determine the molecular basis of RIPK1 upregulation in hepatocytes by lipotoxicity. We hypothesize that any defect in HGF/MET signaling provoked by lipotoxicity will promote RIPK1 accumulation. Liptoxicity may also stabilizes RIPK1 via direct inhibition of the proteasome. We will perform a series of comprehensive experiments using a hepatocyte culture system and in vivo models to test if one or both of these pathways are active to define the molecular bases of RIPK1 dysregulation in fatty liver disease. The proposed studies will establish a new paradigm by which tyrosine kinase growth factor receptor systems like HGF-Met prevent hepatic inflammation and necrosis by downmodulating the pro-inflammatory and pro- death activity of RIPK1. Our studies will provide rationale for manipulating these key mediators (HGF-MET and RIPK1) in the clinical setting of inflammatory hepatic conditions such as NASH or alcoholic hepatitis.

 描述（由适用提供）：脂肪肝病（FLD）是美国和其他地方的主要公共卫生问题。肝副细胞（肝细胞）在调节葡萄糖和脂肪稳态中起着至关重要的作用，据信这是通过胰岛素 - 胰岛素受体（I-IR）轴的适当作用来实现的。该途径在2型糖尿病（T2D）中的失调可能会导致非酒精性FLD（NAFLD） - 一种疾病，显示出肝细胞脂肪积累（脂肪变性），炎症，炎症和坏死性肝细胞（NASH），纤维化（NASH），纤维化，CIREC注意到型摩尔氏症和糖尿病的疾病。据信肝细胞抗性是该过程的驱动力，并且是由于肝细胞缺乏最佳胰岛素受体（IR）功能而导致的。最近，我们确定了肝细胞生长因子（HGF）的信号轴控制肝葡萄糖和脂肪代谢，对于最佳肝胰岛素反应至关重要。 Given the fact that the HGF-MET signaling axis not only controls metabolism but also modulates cell growth and survival (i.e. suppression of cell death), we propose that diminished HGF-MET signaling (that is, "HGF Resistance") in the liver acts as a double-edged sword causing a vicious cycle of hepatocyte metabolic evolution coupled with an inability to overcome (or survive)诸如脂肪毒性等侮辱引起的肝损害。 RIPK1（受体相互作用蛋白激酶1）已成为决定感染和坏死的主开关。根据我们的开创性初步数据，研究了HGF- MET轴对肝细胞中RIPK1的影响，我们假设在肝细胞的正常情况下，HGF-met轴负调节RIPK1通过直接促进Ripk1 proveration Ripk1 proteRADING RIPK1蛋白质促进RIPK1蛋白质的RIPK1 hepatocytes from RIPK1's pro-inflammatory and pro-necrotic actions, and that, in the setting of hepatocyte lipotoxicity and NAFLD, reduced and defective HGF-MET signaling results in escape of RIPK1 from HGF-MET-mediated negative regulation unleashing RIPK1-dependent hepatocyte inflammation and necrotic cell death.我们建议恢复HGF-MET信号传导将否定这种效果。我们概述了三个特定的目标，以检验这一新假设。 AIM 1-我们将通过使用站点定向诱变和体外肝细胞切口系统对RIPK1酪氨酸磷酸的功能后果，以确定这种修饰会导致RIPK1酶促活性的抑制，并促进其蛋白质体去降解 - 因此，RIPK1介导的介导的注射和Necried necrise和Necrosis是预防的。我们还将检验以下假设：MET信号传导的破坏会导致不受控制的RIPK1活性释放RIPK1介导的肝细胞死亡。调节RIPK1的分子机制尚不清楚。我们发现，在Tyr384上直接抑制了酪氨酸磷酸化RIPK1，从而下调RIPK1激酶活性并将其标记为蛋白质体降解。这是该目标下的研究将通过酪氨酸激酶生长因子受体Met解解RIPK1的分子调节。 AIM 2-我们将直接检验我们的假设，即HGF-MET介导的RIPK1调节在使用损失和功能性小鼠模型的情况下，在脂肪肝病的情况下，对肝稳态具有生物学和病理意义。我们认为，由脂肪毒性引起的HGF-MET不足加剧了RIPK1诱导的肝感染和坏死，并且HGF-MET信号的恢复将否定这种效果。我们已经发现RIPK1被上调，HGF/MET在人和小鼠脂肪肝中被下调。驱动脂肪肝病进展的分子机制尚不清楚。我们提出，脂肪肝细胞中的HGF/MET信号降低会导致RIPK1逃脱MET介导的负调控，驱动RIPK1诱导的肝细胞坏死。我们将在肝脏特异性丧失中诱导脂肪肝病（通过喂养高脂肪饮食） 功能（使用LMETKO和LRIPK1 KO）和功能获得（白蛋白-HGF转基因）小鼠模型。 AIM 3-我们将通过脂肪毒性确定肝细胞中RIPK1上调的分子基础。我们假设脂肪毒性引起的HGF/MET信号传导中的任何缺陷都将促进RIPK1积累。 Liptoxicity还可以通过直接抑制蛋白酶体来稳定RIPK1。我们将使用肝细胞培养系统和体内模型进行一系列全面的实验，以测试其中一种或两种途径是否有效，以定义脂肪肝病中RIPK1失调的分子碱基。拟议的研究将建立一个新的范式，酪氨酸激酶生长因子受体系统（如HGF-MET）通过减少RIPK1的促炎和促染色活性来防止肝感染和坏死。我们的研究将为操纵这些关键介质（HGF-MET和RIPK1）在炎症性肝炎（例如NASH或酒精性肝炎）的临床环境中提供理由。