Preconditioning improves coronary patency

描述（由申请人提供）：预适应（PC）是一种描述良好的现象，即短暂的心肌缺血发作使心肌细胞对后来持续的缺血损伤具有抵抗力。然而，我们小组的证据表明，在模拟急性缺血性综合征临床实例的复发性血栓模型中，PC对维持血管通畅有辅助的有利作用。在之前的研究中，我们假设：(1)PC缺血导致的血管通畅增强是由于PC诱导的血小板激活-聚集的一个或多个分子指标的衰减；(2)在PC刺激过程中释放的腺苷，以及由此产生的血小板表面腺苷A2A受体的刺激，是改善通畅的触发因素。第一个概念得到了新证据的支持，即pc诱导血小板p选择素表达、血小板-纤维蛋白原结合和中性粒细胞-血小板聚集物（NPAs）形成的显著下调。然而，血小板反应性分子指标的这种有利衰减并不能完全由血小板- a2a受体刺激来解释。因此，我们在这一竞争性更新中的目标是扩展血小板- a2a受体范式，并研究由PC缺血引发的血管开放改善是多个触发因素（即腺苷和缓激素）在多个位点（中性粒细胞和血小板上的受体）之间复杂相互作用的结果。我们将对复发性血栓形成的多种体内模型（从大鼠到转基因小鼠再到狗）的生理和分子细胞终点进行综合分析，以质疑两个主要假设：(1)中性粒细胞（即npa的形成和中性粒细胞L-选择素的激活）有助于复发性血栓形成的病理生理学。此外，在PC缺血时，腺苷的释放有助于通过a2a介导的中性粒细胞l -选择素激活的下调来改善血管通畅的维持。（II） PC缺血时缓激肽的释放及其快速分解和稳定缓激肽代谢物的产生，通过刺激血小板PAR4受体，有助于PC诱导动脉通畅的增强。此外，我们提出，预先的PC缺血的有利影响并不局限于预处理策略；相反：（III）在复发性血栓形成后应用基于“PC”的治疗，可以改善急性冠状动脉综合征模型的动脉通畅。我们建议的最终目标是获得新的机制见解，这可能在未来被用于设计新的治疗方法，用于有血栓形成事件风险的患者。公共卫生相关性：在急性缺血性综合征患者中，不能维持冠状动脉通畅可引发多种有害后果，包括延长住院时间，增加介入手术的需要，最值得注意的是，死亡率增加2倍。现有旨在降低血栓事件发生概率的治疗方法（最显著的是预防性给予阿司匹林和氯吡格雷）对估计5-40%的患者无效。因此，从所提出的实验中获得的见解-即确定预适应缺血和腺苷A2A受体刺激的短暂发作改善血管通畅的机制-可能在未来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.