Role of Hypoxia Inducible Factor-1 in Inflammation

描述（由申请人提供）：在缺血后血管系统中发生的生物过程通常会引发内源性炎症系统衰竭，加速血管和实质器官损伤的事件。缺氧诱导因子-1 （Hypoxia Inducible Factor-1, HIF-1）是一种由α和β亚基组成的异二聚体蛋白，在缺氧时在血管内皮中被激活，在缺血环境中调节细胞生存所必需的基因（即诱导性一氧化氮合酶和血红素加氧酶-1）的表达。迄今为止，很少有研究确定HIF-1在调节缺血后血管系统中发生的炎症事件中的作用。提交此修订申请的新研究表明，HIF-1 α亚基的稳定性可显著减少缺血后兔和小鼠心脏的梗死面积和多形核中性粒细胞浸润，白细胞介素-8 (IL-8)，一种与缺血后血管损伤和器官损伤相关的促炎趋化因子，在我们的研究中被HIF-1激活显著抑制。利用人微血管内皮细胞进行的体外实验表明，HIF-1分别通过诱导一氧化氮合酶（NO）和血红素加氧酶-1 （HO-1）基因产生一氧化氮（NO）和一氧化碳（CO）间接调节IL-8的分泌。我们推测：缺氧诱导因子-1单独或协同关键效应基因调控微血管内皮再氧化趋化因子的表达。在这个应用中提出了四个目的：(1)确定HIF-1激活在缺血/再灌注后心脏趋化因子生成衰减中的作用；(2)探讨NO和CO在再氧微血管内皮中调节IL-8表达中的相互依赖关系；(3)评价HIF-1在ho -1诱导的IL-8生成中的调节作用；(4)确定HIF-1结合IL-8启动子在微血管内皮中的功能意义。这里提出的研究将产生大量的新知识，确定HIF-1是调节炎症事件的关键分子。此外，这项工作的结果将开启一个理解趋化因子诱导炎症调节的新时代，并允许合理设计专门用于减轻缺血后血管损伤的工具。

DESCRIPTION (provided by applicant): Biological processes occurring in post-ischemic vasculature commonly initiate events that produce failure of endogenous inflammatory systems, precipitating vascular and parenchymal organ injury. Hypoxia Inducible Factor-1 (HIF-1), a heterodimeric protein consisting of alpha and beta subunits activated in vascular endothelium during hypoxia, modulates expression of genes essential for cell survival (i.e., inducible nitric oxide synthase and heme oxygenase-1) in ischemic environments. Little research to date has established a role for HIF-1 in modulating inflammatory events that occur in post ischemic vasculature. New research leading to submission of this revised application reveals that stabilization of the alpha subunit of HIF-1 dramatically reduces infarct size and polymorphonuclear neutrophil infiltration in post-ischemic rabbit and murine hearts, lnterleukin-8 (IL-8), a pro-inflammatory chemokine consistently associated with post-ischemic vascular injury and organ damage was strikingly repressed by HIF-1 activation in our studies. In vitro experiments using human microvascular endothelial cells suggest that HIF-1 modulates secretion of IL-8 acting directly at a transcriptional level or indirectly through generation of nitric oxide (NO) and carbon monoxide (CO) following induction of nitric oxide synthase and heme oxygenase-1 (HO-1) genes respectively. We hypothesize that: Hypoxia inducible factor-1 acting independently or in concert with key effector genes regulates chemokine expression in reoxygenating microvascular endothelium. Four aims are proposed in this application: (1) To determine the role of HIF-1 activation in attenuation of cardiac chemokine generation following ischemia/reperfusion; (2) To examine molecular interdependency between NO and CO in regulation of IL-8 expression in reoxygenating microvascular endothelium; (3) To evaluate the role of HIF-1 in modulating HO-1-induced IL-8 generation; (4) To determine the functional significance of IL-8 promoter binding by HIF-1 in microvascular endothelium. The research proposed here will produce substantial new knowledge, establishing HIF-1 as a pivotal molecule in modulation of inflammatory events. Further, the results of this work will open a new era of understanding of the regulation of chemokine induced inflammation and permit the rational design of tools targeted specifically to attenuate post-ischemic vascular injury.