Methylarginines and Vascular Injury

描述(申请人提供)：这项建议的长期目标是建立二甲基精氨酸二甲氨基水解酶(DDAH)，负责甲基精氨酸(MA)代谢的酶，作为血管功能和损伤反应的关键调节因子。一氧化氮(NO)生物合成的改变与再狭窄损伤的发病机制有关，内源性一氧化氮合酶抑制剂ADMA和NMMA的积聚似乎是在这些条件下观察到的NO生成减少的原因。我们已经证明，在球囊介导的再狭窄损伤的兔和大鼠模型中，血管DDAH的表达显著减少，伴随着细胞MA水平的增加。这一建议的总体假设是，DDAH表达/活性的丧失导致MA积聚，并降低了NO的生物利用度，从而丧失了NO提供给血管壁的抗增殖、抗动脉粥样硬化的特性。为了验证这一假设，我们将追求以下目标。在目标1中，我们将定义DDAH的调节如何影响甲基精氨酸水平以及随后由NOS产生的NO和超氧化物的产生。在目标2中，我们将确定DDAH在血管损伤中的调节及其在动脉重塑中的作用。这些研究将考察DDAH表达缺失对血管细胞增殖、迁移和内皮再生的影响。此外，利用携带DDAH基因的AAV载体，我们将确定DDAH过表达是否可以调节血管重塑过程，改善血管功能。最终目标将确定甲基精氨酸在动脉粥样硬化形成中的作用。由于DDAH受低密度脂蛋白的调节，我们将研究在高脂血症状态下DDAH过度表达对动脉粥样硬化发生和发展的影响。我们相信，该项目将使DDAH成为血管损伤反应中的关键成分，并可能成为治疗血管增生性疾病的新靶点。

DESCRIPTION (provided by applicant): The long term objective of this proposal is to establish Dimethylarginine Dimethylaminohydrolase (DDAH), the enzyme responsible for methylarginine (MA) metabolism, as a key regulator of vascular function and the response to injury. Altered nitric oxide (NO) biosynthesis has been implicated in the pathogenesis of restenosis injury and it appears that accumulation of the endogenous nitric oxide synthase inhibitors, ADMA and NMMA, are responsible for the reduced NO generation observed in these conditions. We have shown that in both rabbit and rat models of balloon- mediated restenosis injury, vascular DDAH expression is significantly decreased with a concomitant increase in cellular MA levels. The overall hypothesis of this proposal is that the loss of DDAH expression/activity results in MA accumulation and decreased NO bioavailabilty with subsequent loss of the anti-proliferative anti-atherogenic properties afforded to the vascular wall by NO. To test this hypothesis we will pursue the following aims. In aim 1, we will define how modulation of DDAH affects methylarginine levels and subsequent NOS-derived NO and superoxide generation. In aim 2, we will determine the modulation of DDAH in vascular injury and its role in arterial remodeling. These studies will examine the effects of loss of DDAH expression on smooth muscle cell proliferation, migration and endothelial regeneration. In addition, using an AAV vector carrying the DDAH gene, we will determine whether DDAH over expression can modulate the vascular remodeling process and improve vascular function. The final aim will determine the role methylarginines in atherogenesis. Because DDAH is regulated by LDL, we will study the effects of DDAH over expression on the initiation and progression of atherosclerosis in the hyperlipidemic state. We believe that this project will establish DDAH as a critical component in the vascular response to injury and may serve as a novel therapeutic target in the treatment of vasculoproliferative disorders.