HGF and Signaling Pathways in Hepatic Tissue Assembly

HGF 和肝组织组装中的信号通路

• 批准号: 8081865
• 负责人: GEORGE K MICHALOPOULOS
• 金额: $ 29.42万
• 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/8081865
• 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; Prevention; Proto-Oncogene Protein c-met; Rattus; Receptor Protein-Tyrosine Kinases; Resected; Role; S Phase; 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）：这是一项修订后的续展拨款申请，现已进入第五年，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传递促有丝分裂信号的受体酪氨酸激酶（在无血清培养基中以及当给予整个动物、大鼠或小鼠时）。我们还表明，HGF/Met 和 EGFR 是仅有的两个能够促进培养中的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着。许多其他受体酪氨酸激酶在肝细胞中表达，它们的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。我们最近通过 ShRNA 对 HGF/Met 或 EGFR 进行短期敲低 (KD)，并证明两者对肝再生都有抑制作用，一种信号不能完全补偿另一种信号，而且影响的范围和复杂性不同。 EGFR KD 后，ErbB 家族其他成员代偿性增加，MET 上调。在每种情况下，促凋亡途径都有显着但非致命的激活。我们进一步在大鼠中扩展这些研究，并进行 HGF/Met 和 EGFR 的双重 KD，然后进行部分肝切除术 (PHx)。结果是完全肝衰竭，大多数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 KD 时，没有看到这种效应。拟议的研究旨在确定导致肝衰竭的信号，假设许多参与肝再生的细胞因子（例如 TNF 和 TGFb1）也可以在 EGFR 和 MET 的有丝分裂信号不起作用时充当导致肝细胞死亡和肝衰竭的因子。除实验研究外，我们还将分析从暴发性肝坏死病例获得的人肝脏材料中上述受体以及能够诱导肝细胞死亡和肝衰竭的细胞因子的表达和激活状态。最后，我们将评估 EGFR KD 后出现的代偿机制的重要性，并确定废除这些机制是否也能够导致肝衰竭。这些研究的结合可能使我们能够了解导致大规模肝坏死的机制，因为参与肝脏再生的早期信号的异常失调，并允许基于合理的机制方案设计预防大规模肝坏死的治疗干预措施。 公共健康相关性：拟议的研究旨在将从肝再生中获得的知识应用于阐明导致肝衰竭的途径。暴发性肝衰竭（FHF）仍然是最致命和最昂贵的人类疾病之一，只能通过肝移植治愈。肝脏再生失败和两种促有丝分裂受体（EGFR 和 MET）的潜在失败与参与再生的途径改变相结合，也可以诱导肝细胞凋亡（例如 TNF），很可能为治疗这一严重的临床问题提供合理的机制理解和治疗选择。