Role of Adenosine Receptors in Tissue Protection

描述（由申请人提供）：A3腺苷受体（AR）是最近鉴定的嘌呤核苷腺苷受体亚型，其生理功能，特别是心血管系统中的生理功能仍不清楚。在以前的研究中，我们已经证明，给予A3 AR的选择性激动剂有效地减少了心肌缺血和再灌注的多种不同临床前动物模型中的损伤。我们在研究中观察到的A3 AR治疗的主要优点之一是这些药物在不产生不良血流动力学效应的剂量下有效。该提案的目标是通过完成三个高度整合的具体目标，进一步扩大我们对A3 AR心脏保护作用的了解。在具体目标#1中，我们将扩展我们正在进行的研究，以探索A3 AR激活提供缺血/再灌注损伤保护的潜在机制。在前一个资助周期获得的信息的基础上，我们将测试A3 AR激活通过抑制炎症和嗜中性粒细胞介导的组织损伤来减弱致死性再灌注损伤的假设。将使用允许在小鼠中性粒细胞中特异性缺失A3 AR的新型遗传工具来测试该假设。具体目标#2的结果将提供重要信息，进一步探索A3 AR激动剂治疗缺血性心脏病的转化潜力。我们将确定MI后用A3 AR激动剂治疗是否能长期保持心脏功能，以及A3 AR激活是否能直接减少适应不良的重塑反应。最终高度创新的具体目标将测试最近开发的新A3 AR配体的心脏保护功效。我们将研究一系列新的嘌呤激动剂的有效性，这些嘌呤激动剂具有经修饰的（N）-甲烷碳环结构代替核糖，我们已将其鉴定为不依赖于物种的高选择性A3 AR激动剂。该实验被独特地设计为检查将化合物缀合至聚合物树枝状聚合物是否会通过促进协同配体-受体相互作用来增加其心脏保护效力和功效。最后，我们将研究变构增强剂对A3 AR的有用性。这些试剂作用于A3 AR蛋白的不同结合位点，其增加作用于腺苷直立结合位点的激动剂的亲和力。理论上，变构增强剂提供了靶向患病组织的机会，其中腺苷的产生增加，同时避免了由其他器官中受体的激活引起的潜在副作用。总的来说，本提案的中心目标是研究心肌缺血/再灌注损伤期间A3 AR在心血管和免疫系统中的病理生理作用。如果我们的假设是正确的，我们将证明A3 AR激活通过抗炎机制减少致死性再灌注损伤，并且除了梗死面积减小之外，用A3 AR激动剂治疗将提供减少梗死后适应不良重塑的额外益处。完成这项工作将重要地增加我们对A3 AR基础生物学的理解，并有可能导致开发用于治疗缺血性心脏病患者的新型药理学策略。 公共卫生相关性：缺血性心脏病是美国和其他工业化国家的主要死亡原因。这项研究将可能导致开发新的药物治疗急性心肌梗死患者。这项研究还将增加我们对腺苷及其受体在心血管和免疫系统中的生物学的理解。

DESCRIPTION (provided by applicant): The A3 adenosine receptor (AR) is the most recently identified subtype of receptor for the purine nucleoside adenosine, which remains poorly characterized in terms of its physiological function, particularly in the cardiovascular system. In previous studies, we have demonstrated that administering selective agonists of the A3AR effectively reduces injury in multiple different preclinical animal models of myocardial ischemia and reperfusion. One of the major advantages of A3AR therapy we have observed in our studies is that these agents are effective at doses that exert no adverse hemodynamic effects. The goal of this proposal is to further expand our knowledge of the cardioprotective actions of the A3AR by completing three highly integrated specific aims. In Specific Aim #1, we will extend our ongoing studies to explore potential mechanisms by which A3AR activation provides protection from ischemia/reperfusion injury. Building off of information gained during the previous grant cycle, we will test the hypothesis that A3AR activation attenuates lethal reperfusion injury by suppressing inflammation and neutrophil-mediated tissue injury. This hypothesis will be tested using novel genetic tools allowing for specific deletion of the A3AR in neutrophils in mice. The results of Specific Aim #2 will provide important information that will further explore the translational potential of A3AR agonists for treating ischemic heart disease. We will determine whether or not treating with A3AR agonists post-MI produces long-term preservation in cardiac performance and whether or not A3AR activation directly diminishes maladaptive remodeling responses. The final highly innovative specific aim will test the cardioprotective efficacy of new A3AR ligands that have recently been developed. We will examine the effectiveness of members of a new series of purine agonists with a modified (N)-methanocarba ring structure in place of the ribose, which we have identified as species-independent, highly selective A3AR agonists. The experiments are uniquely designed to examine whether conjugating the compound to a polymeric dendrimer will increase its cardioprotective potency and efficacy by promoting cooperative ligand-receptor interactions. Finally, we will examine the usefulness of allosteric enhancers for the A3AR. These agents act on a distinct binding site of the A3AR protein that increases the affinity of agonists acting at the orthostatic binding site for adenosine. Theoretically, allosteric enhancers offer the opportunity to target diseased tissues where the production of adenosine is increased while avoiding potential side effects caused by activation of receptors in other organs. Overall, the central objective of this proposal is to investigate the pathophysiological role of the A3AR in the cardiovascular and immune systems during myocardial ischemia/reperfusion injury. If our hypotheses are correct, we will demonstrate that A3AR activation reduces lethal reperfusion injury through anti- inflammatory mechanisms and that treating with A3AR agonists will provide, in addition to infarct size reduction, an added benefit to reduce post-infarction maladaptive remodeling. Completing this work will importantly increase our understanding of the basic biology of the A3AR and has the potential to lead to the development of novel new pharmacological strategies for treating patients with ischemic heart disease. PUBLIC HEALTH RELEVANCE: Ischemic heart disease is the leading cause of death in the U.S. and other industrialized nations. This research will potentially lead to the development of new drug therapies for treating patients with acute myocardial infarction. This research will also increase our understanding of the biology of adenosine and its receptors in the cardiovascular and immune systems.