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)：这是一份修订后的基金续期申请，现已进入第5个年头，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)是仅有的两种能够向肝细胞传递有丝分裂信号的受体酪氨酸激酶(在无血清介质中，当给药到整个动物、大鼠或小鼠时)。我们还发现，HGF/Met和EGFR是目前仅有的两个能促进肝细胞转分化为胆管上皮细胞的信号系统。HGF/Met和EGFR的这些独特作用是非常显著的。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，但有丝分裂信号仅限于HGF/Met和EGFR。我们最近用shRNA对HGF/Met或EGFR进行了短期敲除(KD)，并证明了两者都对肝再生有抑制作用，一个信号不能完全补偿另一个信号，并且影响的范围和复杂性不同。在EGFR的KD之后，ErbB家族其他成员的代偿性增加和MET的上调。在每一种情况下，促凋亡通路都有显著的激活，但不是致命的。我们在大鼠身上进一步扩展了这些研究，并在部分肝切除(PHX)之后进行了HGF/Met和EGFR的双重KD。结果是完全肝功能衰竭，大部分肝细胞大量凋亡和坏死，肝实质塌陷。在不使用PHX的情况下进行双KD手术时，这种影响不明显。这项拟议的研究旨在确定导致肝功能衰竭的信号，假设许多参与肝脏再生的细胞因子(如肿瘤坏死因子和转化生长因子b1)也可以在EGFR和MET的有丝分裂信号均失效时导致肝细胞死亡和肝功能衰竭。除了实验研究外，我们还将分析上述受体以及能够诱导肝细胞死亡和肝功能衰竭的细胞因子在暴发性肝坏死病例中的表达和激活状态。最后，我们将评估EGFR KD后出现的代偿机制的重要性，并确定这些机制的取消是否能够本身导致肝功能衰竭。这些研究的结合可能使我们能够理解导致大量肝坏死的机制是参与肝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。 公共卫生相关性：拟议的研究旨在利用从肝脏再生中获得的知识来阐明导致肝功能衰竭的途径。暴发性肝功能衰竭(FHF)仍然是人类最致命和最昂贵的疾病之一，只有通过肝移植才能治愈。肝再生的失败和两种有丝分裂原受体(EGFR和MET)的潜在失效，再加上参与再生的通路的改变，也可以诱导肝细胞凋亡(如肿瘤坏死因子)，很可能为解决这一严重的临床问题提供合理的机制理解和治疗选择。