Myeloperoxidase and NO signaling in the vasculature

描述（由申请人提供）：血红素蛋白髓过氧化物酶（MPO） 在宿主防御反应中起着重要作用。髓过氧化物酶催化 在过氧化氢中加入氯化物，导致形成 氯化物质次氯酸（HOCI）次氯酸反应 与包括硫醇、胺、核苷酸和 不饱和脂肪酸最近的证据表明，MPO和HOCI有助于 心血管疾病的发病机制。在本申请中，我们提出 数据表明，MPO衍生的HOCI有助于发展 通过降低一氧化氮（NO）的生物利用度来降低内皮功能障碍。MPO 有效地与动脉壁结合， 组织酶活性增加。体外研究结果显示， MPO衍生的HOCI损害乙酰胆碱诱导的舒张，但不影响 由NO供体诱导的弛豫。这些数据表明，内皮细胞是一个 MPO依赖性损伤的靶点。HOCI介导MPO的抑制作用 由于加入HOC可以预防内皮功能障碍， 清除剂L-蛋氨酸。内皮细胞NO有几种成分， 可能被HOCI修饰的合成途径，包括NO合酶（NOS III） 活性、L-精氨酸底物和NOS III依赖性辅因子。在这 建议，我们将确定潜在的抑制作用的机制， MPO衍生的HOCI对NO生物利用度的影响：1）定义MPO对 内皮NO信号传导过程; 2）表征L-精氨酸的作用 衍生的N-氯胺在MPO依赖性内皮细胞损伤中的作用;以及3）通过 确定MPO抑制剂是否能预防血管内皮功能障碍， 啮齿动物缺血-再灌注模型。HOCI依赖性修饰 L-精氨酸可能代表了一种常见的致病机制， 多种心血管疾病中的功能障碍。

DESCRIPTION (provided by the applicant): The heme protein myeloperoxidase (MPO) plays an important role in the host defense response. Myeloperoxidase catalyzes the addition of chloride to hydrogen peroxide, resulting in the formation of the chlorinating species hypochlorous acid (HOCI) Hypochlorous acid reacts avidly with numerous cellular targets including thiols, amines, nucleotides and unsaturated fatty acids. Recent evidence suggests that MPO and HOCI contribute to the pathogenesis of cardiovascular disease. In this application, we present data suggesting that MPO-derived HOCI contributes to the development of endothelial dysfunction by reducing nitric oxide (NO) bioavailability. MPO effectively binds to the arterial wall and is associated with a significant increase in tissue enzymatic activity. Results of in vitro studies showed that MPO-derived HOCI impairs acetylcholine-induced relaxation but does not affect relaxation induced by an NO donor. These data suggest that the endothelium is a target of MPO-dependent injury. HOCI mediates the inhibitory effects of MPO since endothelial dysfunction could be prevented by addition of the HOC scavenger L-methionine. There are several components of the endothelial NO synthetic pathway that may be modified by HOCI including NO synthase (NOS III) activity, L-arginine substrate and NOS Ill-dependent cofactors. In this proposal, we will identify mechanisms underlying the inhibitory effects of MPO-derived HOCI on NO bioavailability by 1) defining the effects of MPO on endothelial NO signaling processes; 2) characterizing the role of L-arginine derived N-chloramines in MPO-dependent endothelial cell injury; and 3) by determining whether inhibitors of MPO prevent endothelial dysfunction in a rodent model of ischemia-reperfusion. The HOCI-dependent modification of L-arginine may represent a common pathogenic mechanism underlying endothelial dysfunction in diverse cardiovascular diseases.