Peroxide mediated prothrombotic effects of aging

 描述（由申请人提供）：血栓性并发症，如心血管疾病和中风，是我们老龄化人群发病率和死亡率的主要原因。尽管衰老和血栓形成之间存在很强的临床相关性，但老年人血栓形成的机制还不清楚。在最近的一项研究中，我们证明了老年小鼠对血栓形成的易感性增加。我们的研究结果还显示，老年小鼠血小板内过氧化氢（H2O2）水平升高，血小板活性亢进（整合素α IIb β 3活化增加）。重要的是，消除H2O2的遗传方法可以防止老年小鼠的血小板过度活跃，这表明H2O2是一种关键的介质。重要的是，我们在人类受试者中的初步研究表明，来自老年人的血小板表现出过氧化物介导的活性亢进。本申请的目的是鉴定导致H2O2在血小板中积累的上游机制，并确定预防H2O2介导的血小板活性亢进是否降低与衰老相关的血栓形成易感性增加。我们的中心假设是，衰老导致动脉和静脉血栓形成的易感性增加，通过增强血小板活化的途径，包括产生超氧化物的含Nox2的NADPH氧化酶，然后通过超氧化物歧化酶1（SOD 1）的超氧化物转化为H2O2，导致H2O2诱导的血小板活化增强。这一假设的基本原理是，含Nox 2的NADPH氧化酶是血小板活性氧的主要来源，我们最近的研究表明，老年小鼠血小板中NADPH氧化酶和SOD 1的上调。目的1探讨NADPH氧化酶和SOD 1在衰老过程中血小板活化中的作用机制。目的2将确定是否抑制H2O2介导的血小板过度活跃是足以降低血栓形成的易感性与老化。研究将利用一种新的小鼠模型，其中内源性血小板在从老年或年轻小鼠转移血小板之前被免疫耗竭，允许在不存在宿主血小板的潜在混杂效应的情况下评估供体血小板对动脉闭塞和静脉血栓形成的影响。目的3将评估老年人血小板活性亢进及其血栓形成的后果。了解血小板活化与衰老的机制有助于血栓形成的易感性，有可能揭示新的治疗策略，以尽量减少老年人的血管下降。

 DESCRIPTION (provided by applicant): Thrombotic complications such as cardiovascular diseases and stroke are a leading cause of morbidity and mortality in our aging population. Despite the strong clinical association between aging and thrombosis, the mechanisms of thrombosis in the elderly are not well understood. In a recent study we demonstrated that aged mice display increased susceptibility to thrombosis. Our findings also revealed that aged mice develop increased intra-platelet hydrogen peroxide (H2O2) levels and platelet hyperactivity (increased integrin aIIbß3 activation). Importantly, genetic approaches to eliminate H2O2 prevented platelet hyperactivity in aged mice, suggesting that H2O2 is a critical mediator. Importantly, our pilot studies in human subjects demonstrate that platelets from aged humans exhibit peroxide mediated hyperactivity The objectives of this application are to identify the upstream mechanism leading to accumulation of H2O2 in platelets and to determine whether prevention of H2O2-mediated platelet hyperactivity decreases aging-associated increased thrombotic susceptibility. Our central hypothesis is that aging results in increased arterial and venous thrombotic susceptibility via enhanced platelet activation in a pathway that includes generation of superoxide by a Nox2- containing NADPH oxidase, followed by conversion of superoxide to H2O2 by superoxide dismutase1 (SOD1), leading to H2O2-induced enhancement of platelet activation. The rationale for this hypothesis is that Nox2- containing NADPH oxidase is the major source of platelet reactive oxygen species, and our recent study demonstrated upregulation of NADPH oxidase and SOD1 in platelets from aged mice. Aim 1 will determine the mechanistic roles of NADPH oxidase and SOD1 in platelet hyperactivation in aging. Aim 2 will determine whether inhibition of H2O2-mediated platelet hyperactivity is sufficient to decrease thrombotic susceptibility with aging. Studies will utilize a novel mouse model in which endogenous platelets are immunodepleted prior to transfer of platelets from aged or young mice, allowing assessment of the effects of donor platelets on arterial occlusion and venous thrombosis in the absence of potential confounding effects of host platelets. Aim 3 will evaluate hyperactivity of platelets from aged humans and its thrombotic consequences. Understanding the mechanism by which platelet activation with aging contributes to thrombotic susceptibility has the potential to reveal new therapeutic strategies to minimize vascular decline in the elderly.