MODULATION OF VASCULAR FUNCTION BY HYPOXEMIA/ISCHEMIA

低氧血症/组织缺氧（H）长期以来与促凝血事件相关，特别是静脉血栓形成，这是发病率和死亡率的主要原因。 实验性肢体制动导致血氧张力快速下降，同时静脉瓣袋中纤维蛋白沉积，从而为血栓形成提供了病灶。 在常压缺氧模型中，我们提供了缺氧触发凝血途径的第一个轮廓：缺氧上调单核吞噬细胞（MP）中的组织因子和纤溶酶原激活物抑制剂（派）-1，最终导致血管纤维蛋白沉积。 我们假设，有两个关键的和意想不到的事件，在这个H-触发的途径，这两个都是独立的缺氧诱导因子（HIF）-1：蛋白激酶C亚型β II（PKC β II）的激活和转录因子Egr-1的激活。 缺氧MP中的组织因子诱导是由于启动子中Egr-1位点的转录增加，并且缺氧的Egr-1缺失小鼠显示缺乏组织因子诱导和血管纤维蛋白沉积。 我们的体外研究已经将最终导致Egr-1转录的H相关途径追溯到PKC β II：缺氧激活PKC β II，后者触发raf和MEK依赖性途径激活MAP激酶和Elk-1;并且，激活的Elk-1与血清应答因子协同诱导Egr-1的转录。 我们的基本概念是，在缺氧的最早阶段发生的事件，PKC β II和Egr-1激活（每一个都在缺氧后几分钟内观察到），对低氧血管内血栓形成病灶的形成至关重要。 我们的首要目标是使用PKC β O小鼠评估PKC β在H相关血管纤维蛋白形成中的作用，并通过分析PKC β O和Egr-10小鼠的反应将H诱导的血管扰动的概念扩展到肺缺血模型。 我们的第二个目标解决的假设，即激活的PKC β II在MP是一个关键事件驱动的促凝血机制，以及其他途径，有助于缺血性组织损伤，通过制作和分析转基因小鼠有针对性的抑制或激活的PKC β II在MP。 我们的总体目标是确定PKC β II和Egr-1是否是在低氧血症和缺血性应激反应中保持血管稳态的潜在治疗靶点。

Hypoxemia/tissue hypoxia (H) has long been associated with procoagulant events, especially venous thrombosis, a major cause of morbidity and mortality. Experimental limb immobilization leads to a rapid fall in blood oxygen tension in parallel with fibrin deposition in venous valve pockets, thereby providing a nidus for thrombus formation. In a model of normobaric hypoxia, we have provided the first outline of a pathway through which oxygen deprivation triggers coagulation: hypoxia upregulates tissue factor and plasminogen activator inhibitor (PAI)-1 in mononuclear phagocytes (MPs), ultimately causing vascular fibrin deposition. We hypothesize that there are two pivotal and unexpected events in this H-triggered pathway, both of which are independent of hypoxia-inducible factor (HIF)-1: activation of protein kinase C isoform betaII (PKCbetaII) and activation of the transcription factor Egr-1. Tissue factor induction in hypoxic MPs is due to increased transcription at Egr-1 sites in the promoter, and Egr-1 null mice subject to oxygen deprivation display absence of tissue factor induction and vascular fibrin deposition. Our in vitro studies have traced the H-associated pathway culminating in Egr-1 transcription back to PKCbetaII: hypoxia activates PKCbetaII, the latter triggers a raf- and MEK-dependent pathway activating MAP kinases and Elk-1; and, activated Elk-1, in concert with Serum Response Factor, induces transcription of Egr-1. Our underlying concept is that events occurring at the earliest stage of oxygen deprivation, PKCbetaII and Egr-1 activation (each seen within minutes of H), are critical to the formation of thrombogenic foci within hypoxemic vasculature. Our first aim is to evaluate the role of PKCbeta in H-associated vascular fibrin formation using PKCbeta O mice, and to extend our concept of H-induced vascular perturbation to a model of lung ischemia by analyzing the response of PKCbeta O and Egr-10 mice. Our second aim addresses the hypothesis that activation of PKCbetaII in MPs is a key event driving the procoagulant mechanism, as well as other pathways contributing to ischemic tissue injury, by making and analyzing transgenic mice with targeted suppression or activation of PKCbetaII in Mps. Our overall goal is to determine if PKCbetaII and Egr-1 are potential therapeutic targets for preserving vascular homeostasis in response to hypoxemic and ischemic stress.