Regulation of Hepatic Ischemia/Reperfusion Injury

描述(由申请人提供)： 肝脏缺血再灌注(I/R)损伤是创伤手术、肝移植和肝切除手术以及失血性休克的主要并发症。这一建议的长期目标是确定肝脏I/R导致炎性肝损伤的诱导和传播的分子和细胞机制。目的1将解决的假设是，核因子-kB活化发生在缺血期库普弗细胞，这是导致炎症级联反应的初始事件。这一点，以及再灌注后肝细胞中核因子-kappaB的激活可能是促进肝脏恢复和修复的保护机制的相反观点，将在原代肝细胞分离株以及我们的整个动物模型中进行研究，使用包含突变形式的核因子-kappaB抑制蛋白IkappaBalpha的新型融合蛋白结构。目的2提出的假设是，核受体和转录因子PPARpha和PPARGamma分别是启动炎症和调节氧化剂诱导的肝细胞损伤的中枢调节因子。我们提供的证据表明，PPARGamma在缺血期失活，这可能有助于核因子-kappaB的反式激活。我们将确定PPARGamma被缺血下调的机制，以及PPARGamma的激动性调节是否可以抑制I/R损伤。我们的数据表明，PPARa调节肝细胞诱导型一氧化氮合酶(INOS)的表达。我们将确定PPARpha在再灌注后被激活的机制以及它控制iNOS基因表达的方式。目的3阐明IL-12在肝脏I/R后的作用机制。我们的实验室发现，肝脏缺血时产生IL-12，IL-12是产生肿瘤坏死因子α和促进中性粒细胞依赖性肝损伤所必需的。我们将确定IL-12的细胞来源(S)和靶点(S)，以及IL-12在肝细胞中发挥作用的信号机制。目的4将提出这样的假设，即肝脏在再灌流早期对CD4T细胞的募集是随后中性粒细胞募集和肝细胞损伤的先决条件。我们将确定CD4T细胞在再灌流后被招募到肝脏的机制，以及这些细胞如何促进中性粒细胞的招募。这些研究将极大地促进我们对肝脏I/R损伤的病理生理学的认识，并可能确定一些潜在的治疗靶点。

DESCRIPTION (provided by applicant): Hepatic ischemia/reperfusion (I/R) injury is a major complication of trauma surgery, liver transplantation and resectional surgery, and hemorrhagic shock. The long-term goal of this proposal is to determine the molecular and cellular mechanisms by which hepatic I/R leads to induction and propagation of inflammatory liver injury. Aim 1 will address the hypothesis that NF-kB activation occurs in Kupffer cells during the ischemic period and that this is the initial event leading to the inflammatory cascade. This, along with the converse notion that NF-kappaB activation in hepatocytes after reperfusion may be a protective mechanism that promotes liver recovery and repair, will be studied with primary liver cell isolates as well as our whole animal model using novel fusion protein constructs containing mutant forms of the NF-kappaB inhibitory protein, IkappaBalpha. Aim 2 will address the hypothesis that the nuclear receptors and transcription factors, PPARalpha and PPARgamma, are central regulatory factors for the initiation of inflammation and regulation of oxidant-induced hepatocyte injury, respectively. We provide evidence that PPARgamma is deactivated during the ischemic period and that this may facilitate transactivation of NF-kappaB. We will determine the mechanisms by which PPARgamma is down-regulated by ischemia and whether agonistic modulation of PPARgamma can suppress I/R injury. Our data suggest that PPARa modulates hepatocyte expression of inducible nitric oxide synthase (iNOS). We will determine the mechanisms by which PPARalpha is activated after reperfusion and the manner in which it controls iNOS gene expression. Aim 3 will delineate the mechanism of action of IL-12 in the liver after I/R. Our laboratory discovered that IL-12 is Produced in the liver during hepatic ischemia and that IL-12 is required for the production of TNF alpha and the promotion of neutrophil-dependent liver injury. We will determine the cellular source(s) and target(s) of IL-12 as well as the signaling mechanism by which IL-12 functions in liver cells. Aim 4 will address the hypothesis that liver recruitment of CD4 T cells during early reperfusion is prerequisite for the subsequent recruitment of neutrophils and hepatocellular injury. We will determine the mechanisms by which CD4 T cells are recruited into the liver after reperfusion and how these cells promote the recruitment of neutrophils. These studies will greatly advance our knowledge of the pathophysiology of hepatic I/R injury and may identify several potential therapeutic targets.