Preconditioning Improves Coronary Patency

描述（由申请人提供）：我们实验室的证据显示 短暂的前期“预处理”缺血，除了 限制梗死面积：（1）改善犬模型的冠状动脉通畅性， 模拟不稳定型心绞痛的主要止血;和（2）提高速度和 在犬凝血和持续性血栓形成模型中溶栓的有效性 血栓性闭塞我们的研究结果进一步暗示了腺苷的释放 缺血/再灌注心肌，随后刺激血小板 腺苷A2受体，在这种现象中起着关键作用。然而，在这方面， 负责这些改善的特定“远端”分子机制 冠状动脉通畅率未知。 血小板粘附，活化，最终通过结合 纤维蛋白原与相邻血小板上的糖蛋白（GP）IIb/III受体结合-- 代表了脑缺血再发的潜在“病理生理学”， 不稳定型心绞痛的情况。因此，我们的第一个假设是， 冠状动脉通畅性与短暂的先行缺血/血小板A2受体 通过下调粘附分子的表达来实现刺激 分子和/或配体参与的形成和稳定 血小板聚集体--特别是GP IIb/IIIa、P-选择素、血管性血友病 因子、PECAM和/或GP Ib。从不稳定的血小板“栓塞”到 一个持久的，含纤维蛋白的血块涉及凝血酶催化的转化 纤维蛋白原（血小板聚集体中的分子“桥”）与纤维蛋白的结合， 凝血酶介导的因子XIII和后续因子的活化 XIII催化的纤维蛋白交联。因此，我们的第二个假设是， 短暂的先行缺血/A2受体刺激增强--结果 血小板活化/聚集和粘附分子表达的变化 --在凝块过程中凝血和纤维蛋白聚合的变化 促进溶解剂的渗透和结合的发展， 加速血栓溶解。 这些概念将通过体内和体内的综合分析进行测试。 体外终点。首先，我们将采用在体犬模型的不稳定型心绞痛 和持续性血栓形成，以评估短暂的先行缺血的影响 和选择性;药理学A2受体刺激：冠状动脉通畅; 血小板粘附分子表达（流式细胞术;血小板 凝血因子XIII-催化的纤维蛋白聚合（通过定量测定） 光学显微镜下）在不断发展的冠状动脉血栓。第二，同时 研究中，我们将评估外源性A2受体刺激对 体外，血管通畅性的替代指标（体外血小板聚集; 体外血栓形成/血栓溶解）。最后，为了解决我们的第三个假设-- 在我们的研究中观察到的A2介导的信号传导的有利作用， 实验模型具有潜在的临床相关性-我们将进行一项 血小板聚集和血栓形成/血栓溶解相同体外分析 从人类志愿者身上获得的血液样本。这些假设，如果 证实，可能最终有助于设计新的治疗策略， 旨在增强不稳定型心绞痛临床病例中的血管通畅性， 再灌注治疗急性心肌梗死。

DESCRIPTION (provided by applicant): Evidence from our laboratory has revealed that brief episodes of antecedent 'preconditioning' ischemia, in addition to limiting infarct size: (1) improve coronary artery patency in a canine model of primary hemostasis mimicking unstable angina; and (2) enhance the speed and efficacy of thrombolysis in a canine model of coagulation and persistent thrombotic occlusion. Our results have further implicated release of adenosine from ischemic/reperfused myocardium, and subsequent stimulation of platelet adenosine A2 receptors, as playing a pivotal role in this phenomenon. However, the specific 'distal' molecular mechanisms responsible for these improvements in coronary patency are unknown. Platelet adhesion, activation -- and, ultimately, aggregation via the binding of fibrinogen to glycoprotein (GP) llb/lll receptors on adjacent platelets -- represents the underlying 'pathophysiology' of recurrent ischemia in the setting of unstable angina. Thus, our first hypothesis is that the improved coronary patency seen with brief antecedent ischemia/platelet A2 receptor stimulation is achieved by a down-regulation in the expression of adhesion molecules and/or ligands involved in the formation and stabilization of platelet aggregates -- specifically, GP IIb/IIIa, P-selectin, von Willebrand Factor, PECAM and/or GP Ib. The evolution from an unstable platelet 'plug' to a persistent, fibrin-containing clot involves the thrombin-catalyzed conversion of fibrinogen (the molecular 'bridge' in platelet aggregates) to fibrin, thrombin-mediated activation of Factor XIII and subsequent Factor XIII-catalyzed fibrin cross-linking. Accordingly, our second hypothesis is that brief antecedent ischemia/A2 receptor stimulation elicits -- as a consequence of changes in platelet activation/aggregation and adhesion molecule expression -- modifications in coagulation and thus fibrin polymerization during clot development that facilitate penetration and binding of the lytic agent and thus accelerate thrombolysis. These concepts will be tested via an integrated analysis of both in vivo and in vitro endpoints. First, we will employ in viva canine models of unstable angina and persistent thrombosis to evaluate the effects of brief antecedent ischemia and selective; pharmacologic A2 receptor stimulation on: coronary patency; platelet adhesion molecule expression (by flow cytometry; platelet aggregometry); and Factor XlIl-catalyzed fibrin polymerization (by quantitative light microscopy) in the evolving coronary thrombus. Second, in concurrent studies, we will assess the effects of exogenous A2 receptor stimulation on in vitro, surrogate indices of vessel patency (in vitro platelet aggregation; in vitro thrombosis/thrombolysis). Finally, to address our third hypothesis -- that the favorable effects of A2-mediated signaling observed in our experimental models have potential clinical relevance -- we will conduct an identical in vitro analysis of platelet aggregation and thrombosis/thrombolysis on blood samples obtained from human volunteers. These hypotheses, if confirmed, may ultimately aid in the design of novel therapeutic strategies aimed at enhancing vessel patency in clinical instances of unstable angina and reperfusion for the treatment of acute myocardial infarction.