MECHANISMS OF NITRIC OXIDE PROTECTION IN REPERFUSION INJURY

在缺血和再灌流中观察到的许多微血管功能障碍 (L/R)的小肠已被归因于激活 附着于毛细血管后小静脉的中性粒细胞 然后移居到肠道间质中。静脉注射 给予某些酶类抗氧化剂(如超氧化物歧化酶、过氧化氢酶)或 针对中性粒细胞表面黏附糖蛋白的单抗 血管内皮细胞减轻中性粒细胞与血管内皮细胞的黏附 从而减弱微血管通透性的增加 这些数据表明，白细胞和/或内皮细胞- 衍生活性氧在促进中性粒细胞黏附中的作用 增加血管通透性的静脉内皮细胞。近期 包括我们自己在内的几个实验室的研究表明， 释放一氧化氮(NO)的化合物显著抑制这种I/R- 诱导中性粒细胞黏附和微血管功能障碍。假设：我们 提示NO可减轻中性粒细胞与缺血后细胞的黏附 通过抑制超氧化物(O2)和/或过氧化氢(H_2O_2)- 依赖的，铁催化的反应，促进合成 促炎症介质和增加黏附分子的表达 分子。为了检验这一假设，我们提出了以下建议 具体目标：1)表征O2、 氧化还原活性铁络合物存在或不存在时的过氧化氢和一氧化氮，2) 确定一氧化氮减轻缺氧/复氧的机制(S) (A/R)诱导静脉内皮细胞、中性粒细胞和/或 血小板，3)确定NO减弱A/R诱导的机制 无血小板或有血小板时PMN与内皮细胞的黏附 以及4)确定NO减弱应收账款诱导的机制 血管内皮细胞通透性增加 中性粒细胞和/或血小板。拟议的研究将增加我们对 在生物化学和细胞机制的基础上保护 一氧化氮在肠缺血再灌注损伤中的作用。 因为人们对使用NO释放化合物作为 治疗缺血性疾病的潜在药物，如闭塞剂 血管疾病和器官移植，数据从这些 研究可能被证明对设计新的治疗药物是有用的 这些疾病的治疗。

Much of the microvascular dysfunction observed in ischemia and reperfusion (L/R) of the small intestine has been attributed to activated polymorphonuclear leukocytes (PMNs) that adhere in postcapillary venules and subsequently emigrate into the intestinal interstitium. Intravenous administration of certain enzymatic antioxidants (e.g. SOD, catalase) or monoclonal antibodies directed against the adhesion glycoproteins on PMNS or endothelial cells attenuates adhesion of PMNs to the venular endothelium and consequently attenuates the increase in microvascular permeability induced by I/R. These data suggest that leukocyte and/or endothelial cell- derived reactive oxygen species play a role in promoting adhesion of PMNs to venular endothelium which increases vascular permeability. Recent studies from several laboratories, including our own, have demonstrated that nitric oxide (NO) releasing compounds dramatically inhibit this I/R- induced PMN adhesion and microvascular dysfunction. Hypothesis: We propose that NO attenuates adhesion of PMNs to the post-ischemic endothelium by inhibiting superoxide (O2)-and/or hydrogen peroxide (H2O2)- dependent, iron-catalyzed reactions that promote the synthesis of proinflammatory mediators and increase the expression of adhesion molecules. In order to test this hypothesis, we propose the following specific aims; 1) Characterize the biochemical interactions among O2, H2O2 and NO in the absence or presence of redox-active iron complexes, 2) Determine the mechanism(s) by which NO attenuates anoxia/reoxygenation (A/R)induced oxidant production by venular endothelial cells, PMNs and /or platelets, 3) Determine the mechanisms by which NO attenuates A/R-induced PMN adhesion to endothelial cells in the absence or presence of platelets and 4) Identify the mechanisms by which NO attenuates A/R-induced increases in endothelial cell permeability int eh absence or presence of PMNs and/or platlets. The proposed studies will increase our understanding of the biochemical and cellular mechanisms that underlie the protective effects of NO in ischemia and reperfusion-induced injury in the intestine. Because of the growing interest in the use of No-releasing compounds as a potential therapeutic agents for ischemic disorders, such as occlusive vascular disease and organ transplantation, data obtained from these studies may prove useful in the design of new therapeutic agents for the treatment of these disorders.