Preconditioning Improves Coronary Patency

描述(申请人提供)：我们实验室的证据显示 除了短暂的先天‘预适应’缺血之外， 限制梗死范围：(1)改善犬冠状动脉通畅性 模拟不稳定型心绞痛的一次止血；以及(2)提高速度和 犬凝血和持续性血栓模型的溶栓效果 血栓闭塞。我们的结果进一步证明了腺苷的释放 来自缺血/再灌流的心肌以及随后对血小板的刺激 腺苷A2受体在这一现象中起着关键作用。然而， 导致这些改善的特定的‘远端’分子机制 冠状动脉的通畅性尚不清楚。 血小板的黏附、激活--最终通过结合而聚集 相邻血小板上的纤维蛋白原与糖蛋白(GP)LLb/Ill受体的关系-- 代表复发性脑缺血的潜在“病理生理学”。 不稳定型心绞痛的设定。因此，我们的第一个假设是，改进后的 冠状动脉通畅性与短暂缺血/血小板A2受体的关系 刺激是通过下调黏附分子的表达来实现的 参与形成和稳定的分子和/或配体 血小板聚集物--特别是GP IIb/IIIa、P-选择素、von Willebrand 因子、PECAM和/或GP Ib。从一个不稳定的血小板‘塞子’到一个 永久性的含纤维蛋白的凝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“桥梁”)与纤维蛋白的结合， 凝血酶介导的凝血因子XIII及其后续因子的激活 XIII催化的纤维蛋白交联。因此，我们的第二个假设是 短暂的先天缺血/A2受体刺激引起--结果 血小板活化/聚集和黏附分子表达的变化 --凝血过程中凝血和纤维蛋白聚合的改变 促进裂解剂的渗透和结合的发展，从而 加速溶栓。 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，我们将采用犬不稳定型心绞痛的活体模型。 和持续性血栓形成来评估短暂性先兆缺血的影响 选择性；药理A2受体刺激作用：冠脉再通； 血小板黏附分子表达(用流式细胞术；血小板 聚集计量法)；和因子X11催化的纤维蛋白聚合(通过定量 光镜)在冠状动脉血栓演变中。第二，同时进行 研究中，我们将评估外源性A2受体刺激对IN的影响 血管通畅性的体外替代指标(体外血小板聚集； 体外血栓形成/溶栓)。最后，为了解决我们的第三个假设-- A2介导的信号转导的有利作用在我们的 实验模型具有潜在的临床相关性--我们将进行 血小板聚集与血栓形成/溶栓体外分析的一致性 取自人类志愿者的血液样本。这些假设，如果 证实，最终可能有助于设计新的治疗策略 旨在提高不稳定型心绞痛临床病例的血管通畅性 用于急性心肌梗死的再灌注治疗。

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.