PRECONDITIONING--PMN ADHESION AND MICROVASCULAR INJURY

我们实验室和其他实验室的最新研究表明， 需要粘附于血管内皮以产生微血管 缺血后骨骼肌功能障碍和肌细胞坏死。 对这一事实的认识导致了一项主要的研究工作， 评价抑制白细胞粘附作为一种新的 再灌注损伤的治疗方法。 的初步数据 我们的实验室表明，缺血预处理（IPC，一种现象， 其中使组织抵抗以下物质的有害作用： 通过预先暴露于短暂的、重复的 血管闭塞期）通过以下方式预防I/R诱导的肌肉坏死： 抑制再灌注期间白细胞粘附和移出。 的 本申请中概述的项目的总体目标是确定 IPC减弱白细胞粘附的机制 通过毛细血管后微静脉的迁移，微血管屏障破坏， 毛细血管无复流，随后骨骼肌中的肌细胞坏死 暴露于延长的缺血和再灌注（I/R）。 我们的工作 假设IPC将减轻微血管功能障碍， 缺血后骨骼肌中的肌细胞坏死， 在IPC期间和IPC期间， 再灌注后，延长缺血。 为了解决这个问题，我们建议 确定：1）IPC是否会减弱白细胞粘附， 移行、毛细血管无流动、微静脉蛋白渗漏和肌细胞 I/R引起的坏死; 2）腺苷在I/R过程中产生的作用 预处理期的IPC的保护作用，成为 在长时间缺血后的再灌注期间明显; 3）是否 IPC期间腺苷A/1受体激活的有益作用 周期通过涉及激活ATP敏感的 钾通道; 4）IPC诱导的5'- 持续性脑缺血再灌注时核苷酸酶活性的变化 IPC的保护作用; 5）腺苷的产生是否 在预处理骨骼肌再灌注期间增加， 促进了IPC提供的保护行动， 腺苷A/2受体。 为了实现这些目标，我们将利用 活体显微镜方法定量白细胞粘附， 小鼠的移行、微静脉蛋白渗漏和毛细血管无复流 提睾肌 缺血预处理对I/-诱导心肌细胞坏死的影响 也将被审查。 组织腺苷水平将通过高 高效液相色谱法。 研究报告不仅要 大大提高我们对IPC机制的理解， 减少骨骼肌微血管功能障碍和肌细胞坏死 经受随后的长时间缺血和再灌注， 也应该为药物治疗提供理论依据， 以I/R为特征的疾病。

Recent studies from our laboratory and others indicate that neutrophil adherence to vascular endothelium is required to produce microvascular dysfunction and myocyte necrosis in postischemic skeletal muscle. Recognition of this fact has led to a major research effort directed at evaluating the potential for inhibition of leukocyte adhesion as a novel approach to the treatment of reperfusion injury. Preliminary data from our laboratory indicates that ischemic preconditioning (IPC, a phenomenon n which a tissue is rendered resistant to the deleterious effects of prolonged ischemia and reperfusion by prior exposure to brief, repeated periods of vascular occlusion) prevents muscle necrosis induced by I/R by inhibiting leukocyte adherence and emigration during reperfusion. The overall goal of the projects outlined in this application is to determine the mechanisms by which IPC attenuates leukocyte adhesion to and emigration across postcapillary venules, microvascular barrier disruption, capillary no-reflow, and myocyte necrosis in skeletal muscles subsequently exposed to prolonged ischemia and reperfusion (I/R). Our working hypothesis is that IPC will attenuate microvascular dysfunction and myocyte necrosis in postischemic skeletal muscles via a mechanism that involves adenosine receptor activation during the period of IPC and during reperfusion after prolonged ischemia. To address this issue, we propose to determine: 1) whether IPC will attenuate leukocyte adhesion and emigration, capillary no-flow, venular protein leakage, and myocyte necrosis induced by I/R; 2) the role of adenosine produced during the preconditioning period in the protective effects of IPC that become apparent during reperfusion after prolonged ischemia; 3) whether the beneficial effects of adenosine A/1-receptor activation during the IPC period occur by a mechanism that involves activation of ATP-sensitive potassium channels; 4) the role of IPC-induced increases in 5'- nucleotidase activity during reperfusion after sustained ischemia in the protective actions of IPC; and 5) whether adenosine production is increased during reperfusion of preconditioned skeletal muscles and contributed to the protective actions afforded by IPC by activating adenosine A/2-receptors. To accomplish these aims, we will utilize intravital microscopic approaches to quantitate leukocyte adhesion and emigration, venular protein leakage, and capillary no-reflow in the mouse cremaster muscle. The influence of IPC on I/-induced myocyte necrosis will also be examined. Tissue adenosine levels will be measured by high performance liquid chromatography. The proposed studies should not only substantially improve our understanding of the mechanisms whereby IPC reduces microvascular dysfunction and myocyte necrosis in skeletal muscles subjected to subsequent prolonged periods of ischemia and reperfusion but should also provide a rationale for the pharmacologic treatment of disorders characterized by I/R.