Preconditioning improves coronary patency

描述（由申请人提供）：预处理（PC）是一种描述充分的现象，心肌缺血的短暂发作使心肌细胞对随后的持续缺血损伤具有抵抗力。然而，来自我们小组的证据表明，在模拟急性缺血综合征临床病例的复发性血栓形成模型中，PC对维持血管通畅性具有辅助、有利的作用。在我们之前的申请中，我们假设：（1）PC缺血时观察到的增强的通畅性是由于PC诱导的血小板活化-聚集的一种或多种分子指标的衰减;和（2）PC刺激期间释放的腺苷，以及血小板表面上腺苷A2 A受体的最终刺激，作为改善通畅性的触发因素。第一个概念得到了新的证据的支持，一个显着的，PC诱导的血小板P-选择素表达，血小板-纤维蛋白原结合，并形成嗜血小板聚集体（NPA）的下调。然而，这种有利的衰减血小板反应性的分子指数不能解释仅仅由血小板A2 A受体刺激。因此，我们在这种竞争性更新中的目的是扩展血小板-A2 A受体范例，并研究PC缺血引发的改善的血管通畅性是多种触发因素之间复杂相互作用的结果（即，腺苷和缓激肽）作用于多个位点（中性粒细胞以及血小板上的受体）。我们将在复发性血栓形成的多个体内模型（从大鼠到转基因小鼠再到狗）中使用生理和分子细胞终点的综合分析来询问两个主要假设：（I）中性粒细胞（即，NPA的形成和嗜中性粒细胞L-选择素的活化）有助于复发性血栓形成的病理生理学。此外，PC缺血期间腺苷的释放有助于通过A2 A介导的中性粒细胞L-选择素活化的下调来改善血管通畅性的维持。(II)PC缺血期间缓激肽的释放及其快速分解和稳定的缓激肽代谢产物的产生有助于通过刺激血小板PAR 4受体来增强PC诱导的动脉通畅性。此外，我们建议，前PC缺血的有利影响并不局限于预处理策略，而是：（III）“PC”为基础的治疗，适用于复发性血栓形成后，改善动脉通畅性在我们的模型急性冠状动脉综合征。我们的建议的最终目标是获得新的机制的见解，在未来，可能会被用于设计新的治疗方案，为患者的风险发展血栓事件。公共卫生相关性：在急性缺血综合征患者中，未能维持冠状动脉通畅可导致多种有害后果，包括住院时间延长、介入手术需求增加，以及最显著的死亡率增加约2倍。旨在降低血栓形成事件概率的现有疗法（最值得注意的是，预防性给予阿司匹林和氯吡格雷）在估计5-40%的患者中无效。因此，从拟议的实验中获得的见解-即，确定短暂的预处理缺血和腺苷A2 A受体刺激改善血管通畅性的机制，将来可能会用于设计新的抗血小板策略。

DESCRIPTION (provided by applicant): Preconditioning (PC) is the well-described phenomenon whereby brief episodes of myocardial ischemia render cardiomyocytes resistant to a later, sustained ischemic insult. However, evidence from our group has shown that PC has an ancillary, favorable effect on the maintenance of vessel patency in models of recurrent thrombosis mimicking clinical instances of acute ischemic syndromes. We hypothesized, in our previous application, that: (1) the enhanced patency seen with PC ischemia is due to a PC-induced attenuation in one or more molecular indices of platelet activation-aggregation; and (2) adenosine liberated during the PC stimulus, and resultant stimulation of adenosine A2A receptors on the platelets' surface, serves as the trigger for the improved patency. The first concept was supported by novel evidence of a significant, PC-induced down-regulation of platelet P-selectin expression, platelet-fibrinogen binding, and formation of neutrophil-platelet aggregates (NPAs). However, this favorable attenuation in molecular indices of platelet reactivity was not explained solely by platelet-A2A receptor stimulation. Accordingly, our aim in this competitive renewal is to expand on the platelet-A2A receptor paradigm and investigate the concept that the improved vessel patency initiated by PC ischemia is a consequence of a complex interplay among multiple triggers (i.e., adenosine and bradykinin) acting at multiple sites (receptors on neutrophils as well as platelets). We will use an integrated analysis of physiologic and molecular-cellular endpoints, in multiple in vivo models of recurrent thrombosis (ranging from rats to genetically modified mice to dogs), to interrogate two primary hypotheses: (I) Neutrophils (i.e., formation of NPAs and activation of neutrophil L- selectin) contribute to the pathophysiology of recurrent thrombosis. Moreover, release of adenosine during PC ischemia contributes to the improved maintenance of vessel patency by an A2A-mediated down- regulation of neutrophil L-selectin activation. (II) Release of bradykinin during PC ischemia, and its rapid breakdown and production of stable bradykinin metabolites, contribute to the PC-induced augmentation of arterial patency via stimulation of platelet PAR4 receptors. Furthermore, we propose that the favorable effects of antecedent PC ischemia are not confined to a pretreatment strategy; rather: (III) 'PC'-based therapies, applied after the onset of recurrent thrombosis, improve arterial patency in our models of acute coronary syndromes. The ultimate goal of our proposal is to obtain novel mechanistic insights that may, in future, be exploited for the design of new treatments for patients at risk of developing thrombotic events. PUBLIC HEALTH RELEVANCE: In patients with acute ischemic syndromes, failure to maintain coronary patency can precipitate multiple deleterious consequences, including prolonged hospitalization, an increased need for interventional procedures, and, most notably, a ~2-fold increase in mortality. Existing therapies aimed at reducing the probability of thrombotic events (most notably, prophylactic administration of aspirin and clopidogrel) are ineffective in an estimated 5-40% of patients. Thus, insights gained from the proposed experiments - i.e., identification of the mechanisms by which brief episodes of preconditioning ischemia and adenosine A2A receptor stimulation improve vessel patency - may, in future, be exploited in the design of novel anti-platelet strategies.