Role of C5a versus C5b-9 in Myocardial Ischemia and Reperfusion Injury

描述(由申请人提供)：数十年的研究表明，补体激活有助于心肌缺血和再灌注(MI/R)后的组织损伤。我们研究的长期目标是了解心肌缺血时补体激活的组织损伤方面，并开发治疗策略来调节MI/R后补体的激活。补体诱导的损伤的确切机制尚不清楚，但包括炎症细胞在局部的募集，介导组织损伤的过敏性毒素的产生，以及由于过量的膜攻击复合体(MAC)沉积导致细胞坏死而可能造成的组织损伤。最近使用抗C5治疗(Pexelizumab)的临床试验，既能抑制C5a过敏性毒素的形成，又能抑制MAC的形成，尽管抗C5治疗在动物模型中成功地用于预防损伤，但在预防心肌梗死大小方面并不成功。最近的研究表明，形成亚溶血量的MAC激活了细胞周期和生存信号通路。这项研究的初步数据表明，与C6充足的动物相比，C6缺乏会增加心肌损伤。根据这些报道和初步数据，我们推测低浓度的MAC可能在MI/R损伤中起到保护作用。为了验证这一假设，我们将研究这些特定的目标：1.确定C5a和C5b-9在氧化应激后心肌细胞死亡中的作用。2.探讨C5a、C5b-9在体内介导心肌缺血/再灌注损伤中的作用。这些目标将通过使成年大鼠心室肌细胞(ARVM)在野生型动物或缺乏C6的动物的大鼠血清存在下缺氧和复氧来实现，因此无法形成MAC。为了解决C5a的作用，我们将测试一种针对ARVM损伤的C5a受体的药理抑制剂。我们还将使用大鼠和小鼠的MI/R活体模型来确定C5a和C5b-9在组织损伤和炎症中的作用。C6缺乏的大鼠和小鼠，以及C5a受体的药理抑制将被调查。这些研究将证明C5裂解产物C5a和C5b-9在介导MI/R后的组织损伤和炎症中的重要性。本研究的结果将为抑制心脏病发作后形成的生物活性补体分子提供一个合理的方案。目前可用的药物可能更好地用于保护心脏免受心脏病发作后的损害。

DESCRIPTION (provided by applicant): Decades of research have shown that complement activation contributes to tissue injury following myocardial ischemia and reperfusion (MI/R). The long term objectives of our research are to understand the tissue injurious aspect of complement activation in myocardial ischemia and develop therapeutic strategies to regulate complement activation following MI/R. The precise mechanisms of complement-induced injury are unknown, but include recruitment of inflammatory cells to the site, production of anaphylatoxins that mediate tissue damage, and possible tissue damage due to excessive membrane attack complex (MAC) deposition leading to cell necrosis. Recent clinical trials using anti-C5 therapy (pexelizumab), which inhibits the formation of both C5a anaphylatoxin and MAC, were unsuccessful in preventing the size of myocardial infarctions, despite the successful use of anti-C5 therapies in preventing injury in animal models. Recent studies have shown that formation of sublytic amounts of MAC activates cell cycle and survival signaling pathways. Preliminary data in this fellowship demonstrate that C6 deficiency increases myocardial injury compared C6 sufficient animals. In light of these reports and preliminary data, we hypothesize that low concentrations of the MAC may act as a protective agent in MI/R injury. To test this hypothesis, we will investigate these specific aims: 1. Establish the roles of C5a and C5b-9 in cardiomyocyte cell death following oxidative stress. 2. Investigate the roles of C5a and C5b-9 in mediating myocardial ischemia/reperfusion injury in vivo. These aims will be addressed by subjecting adult rat ventricular myocytes (ARVM) to anoxia and reoxygenation in the presence of rat serum from wild type animals or animals lacking C6 and are therefore unable to form the MAC. To address the role of C5a, we will test a pharmacological inhibitor of the C5a receptor on ARVM damage. We will also use in vivo models of MI/R in rats and mice to determine contributions of C5a and C5b-9 in tissue injury and inflammation. Rats and mice deficient in C6, as well as pharmacologic inhibition of the C5a receptor will be investigated. These studies will demonstrate the importance of C5 cleavage products, C5a and C5b-9, in mediating tissue injury and inflammation following MI/R. The results from this study will provide a rational plan for the inhibition of biologically active complement molecules formed following a heart attack. Drugs currently available may be better used to protect the heart from damage following a heart attack.