HGF and Signaling Pathways in Hepatic Tissue Assembly

HGF 和肝组织组装中的信号通路

• 批准号: 7996306
• 负责人: GEORGE K MICHALOPOULOS
• 金额: $ 30.33万
• 依托单位: UNIVERSITY OF PITTSBURGH AT PITTSBURGH
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-04-01 至 2015-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7996306
• 关键词: Acute Liver Failure; Animals; Apoptosis; Apoptotic; Automobile Driving; Bile Acids; Biliary; Cell Death; Cessation of life; Clinical; Epidermal Growth Factor Receptor; Epithelial Cells; ErbB Receptor Family Protein; Event; Failure; Family; Financial compensation; Grant; Hepatectomy; Hepatic Tissue; Hepatocyte; Human; Investigation; Knowledge; Lead; Ligands; Literature; Liver; Liver Failure; Liver Regeneration; Liver parenchyma; Massive Hepatic Necrosis; Mus; Natural regeneration; Necrosis; Partial Hepatectomy; Pathway interactions; Phase; Prevention; Proto-Oncogene Protein c-met; Rattus; Receptor Protein-Tyrosine Kinases; Resected; Role; Scheme; Serum-Free Culture Media; Signal Pathway; Signal Transduction; System; TNF gene; TNFSF10 gene; Therapeutic; Therapeutic Intervention; Transplantation; Up-Regulation; Ursidae Family; base; cytokine; design; hepatic necrosis; human disease; knock-down; liver transplantation; meetings; member; pro-apoptotic protein; public health relevance; receptor; receptor coupling; regenerative; research study; transdifferentiation

DESCRIPTION (provided by applicant): This is a revised renewal application for a grant, now in its 5th year, aiming to understand the role of HGF and signaling pathways in hepatic tissue assembly. Our recent studies have demonstrated that HGF and its receptor Met, as well as EGF receptor and the EGFR associated ligands) constitute the only two receptor tyrosine kinases capable of delivering a mitogenic signal to hepatocytes (in serum-free media and when administered to the whole animal, rat or mouse). We have also showed that HGF/Met and EGFR are the only two signaling systems capable of promoting transdifferentiation of hepatocytes to biliary epithelial cells in culture. These unique effects of HGF/Met and EGFR are highly significant. Many other receptor tyrosine kinases are expressed in hepatocytes and their ligands are capable of activating the cognate receptor, yet mitogenic signals are limited to HGF/Met and EGFR. We have recently applied short term knock down (KD) of either HGF/Met or EGFR by ShRNA and demonstrated that both have inhibitory effects on liver regeneration, that the one signal cannot compensate totally for the other, and that the effects are different in scope and complexity. KD of EGFR was followed by compensatory increases in other members of the ErbB family and upregulation of MET. In each instance, there was significant but not lethal activation of pro-apoptotic pathways. We further extend these studies in rats and performed a double KD of both HGF/Met and EGFR followed by partial hepatectomy (PHx). The result was complete liver failure, with massive apoptosis and necrosis of most hepatocytes and collapse of the hepatic parenchyma. This effect was not seen when double KD was performed without PHx. The proposed study will aim to determine the signals that lead to liver failure under the hypothesis that many cytokines involved in liver regeneration (e.g. TNF and TGFb1) can also function as agents that bring hepatocyte death and liver failure when the mitogenic signals of both EGFR and MET fail to function. In addition to the experimental studies, we will also analyze expression and status of activation of the above receptors as well cytokines capable of inducing hepatocyte death and liver failure in human liver material obtained from cases of fulminant hepatic necrosis. Finally we will assess the importance of the compensatory mechanisms emerging after KD of EGFR and determine whether abrogation of these mechanisms is capable to also lead to liver failure by itself. The combination of these studies may allow us to understand the mechanisms that lead to massive hepatic necrosis as an aberrant dis-coordination of the early signals involved in liver regeneration and allow design of therapeutic interventions for prevention of massive hepatic necrosis based on rational mechanistic schemes. PUBLIC HEALTH RELEVANCE: The proposed studies aim to bring to bear the knowledge gained from liver regeneration to the elucidation of the pathways leading to liver failure. Fulminant hepatic failure (FHF) remains as one of the most lethal and costly human diseases curable only by liver transplantation. The failure of the liver to regenerate and the potential failure of the two mitogenic receptors (EGFR and MET) in combination with altered pathways involved in regeneration that can also induce hepatocyte apoptosis (e.g. TNF) are very likely to provide rational mechanistic understanding and therapeutic options in management of this serious clinical problem.

描述（由申请人提供）：这是一份修订后的授权续期申请，目前已进入第5年，旨在了解HGF和信号通路在肝组织组装中的作用。我们最近的研究表明，HGF及其受体Met，以及EGF受体和EGFR相关配体构成了仅有的两种能够向肝细胞递送促有丝分裂信号的受体酪氨酸激酶（在无血清培养基中和当施用于整个动物、大鼠或小鼠时）。我们还发现，HGF/Met和EGFR是仅有的两种能够促进培养物中肝细胞向胆管上皮细胞转分化的信号系统。HGF/Met和EGFR的这些独特作用非常显著。许多其他受体酪氨酸激酶在肝细胞中表达，其配体能够激活同源受体，但促有丝分裂信号仅限于HGF/Met和EGFR。我们最近应用了通过shRNA对HGF/Met或EGFR的短期敲低（KD），并证明两者对肝再生具有抑制作用，一种信号不能完全补偿另一种信号，并且作用的范围和复杂性不同。EGFR KD之后是ErbB家族其他成员的代偿性增加和MET的上调。在每种情况下，都存在显著但非致死性的促凋亡途径激活。我们在大鼠中进一步扩展了这些研究，并进行了HGF/Met和EGFR的双KD，然后进行部分肝切除术（PHx）。结果是完全肝衰竭，大部分肝细胞大量凋亡和坏死，肝实质塌陷。当在没有PHx的情况下进行双重KD时，未观察到这种效应。拟议的研究将旨在确定导致肝衰竭的信号，假设当EGFR和MET的促有丝分裂信号都无法发挥作用时，参与肝再生的许多细胞因子（例如TNF和TGF β 1）也可以作为导致肝细胞死亡和肝衰竭的因子发挥作用。除了实验研究外，我们还将分析上述受体的表达和激活状态以及能够诱导肝细胞死亡和肝衰竭的细胞因子，这些细胞因子是从暴发性肝坏死病例中获得的人肝脏材料中获得的。最后，我们将评估EGFR KD后出现的代偿机制的重要性，并确定这些机制的废除是否也能够导致肝衰竭本身。这些研究的结合可能使我们能够理解导致大面积肝坏死的机制，即肝再生早期信号的异常不协调，并允许基于合理的机制方案设计预防大面积肝坏死的治疗干预措施。 公共卫生关系：拟议的研究旨在利用从肝再生中获得的知识来阐明导致肝衰竭的途径。暴发性肝功能衰竭（FHF）是人类最致命、最昂贵的疾病之一，只能通过肝移植治疗。肝脏再生的失败和两种促有丝分裂受体（EGFR和MET）的潜在失败与再生中涉及的也可诱导肝细胞凋亡（例如TNF）的改变的途径相结合，很可能为这一严重临床问题的管理提供合理的机制理解和治疗选择。