Arginase and the Aging Cardiovascular System

描述(由申请人提供)：血管内皮细胞异常无扩张剂机制导致老化心血管系统的心血管风险增加。一氧化氮合酶底物L-精氨酸改善内皮依赖性血管扩张的机制未知(S)，因为细胞内L-精氨酸的浓度远远超过一氧化氮合酶的Kd。观察到，即使在细胞内L-精氨酸水平明显充足的情况下，给予L-精氨酸也能增加NO的合成并增强内皮功能，这一观察结果被称为“L-精氨酸悖论”。精氨酸酶是尿素循环中的一种酶，也使用L-精氨酸作为底物，存在于心血管组织中。我们的初步数据表明，L-精氨酸代谢酶精氨酸酶相互调节血管内皮细胞一氧化氮合酶活性，并直接影响大鼠血管松弛。此外，衰老大鼠血管中精氨酸酶活性和表达增加，抑制精氨酸酶活性可减轻老年大鼠血管组织中产生的活性氧自由基(ROS)的增加。我们假设：1)内皮细胞精氨酸酶通过竞争细胞内的L-精氨酸，限制内皮细胞NO的产生，从而限制内皮依赖性血管扩张；2)衰老的血管内皮细胞功能障碍与内皮细胞精氨酸酶的表达增加有关，抑制精氨酸酶使NO依赖的信号和内皮功能恢复到年轻表型的水平；3)相关底物(L-精氨酸)缺乏通过改变NO和02-之间的平衡而增加ROS的产生，进一步损害内皮功能；4)长期抑制精氨酸酶将恢复精氨酸反应性，增强NO信号，减少ROS的产生，从而将改变的心血管综合参数(血管和心室僵直增加，室动脉偶联改变)恢复到年轻表型的水平。我们将研究精氨酸酶在正常内皮功能和NO信号中的调节作用，以及它在与衰老相关的内皮功能障碍的病理生理中的作用。这些实验将为NO信号通路的调节以及NO和内皮功能中02-in之间的平衡提供新的见解，对以内皮功能障碍为特征的各种疾病具有重要的治疗意义。

DESCRIPTION (provided by applicant): Abnormal endothelial NO vasodilator mechanisms contribute to increased cardiovascular risk in the aging cardiovascular system. L-arginine, the NO synthase substrate, improves endothelial dependent vasodilatation by unknown mechanism(s), since intracellular concentrations of L-arginine far exceed the Kd for nitric oxide synthase (NOS). The observation that L-arginine administration increases NO synthesis and enhances endothelial function even in the setting of apparently adequate L-arginine levels in the cell has come to be called the "L-arginine paradox". Arginase, an enzyme of the urea cycle also uses L-arginine as a substrate and is present in cardiovascular tissue. Our preliminary data demonstrate that the L-arginine metabolizing enzyme, arginase, reciprocally regulates vascular endothelial NOS activity, and directly influences vascular relaxation in rats. Furthermore, arginase activity and expression are increased in agingrat vessels, and arginase inhibition attenuates the increased reactive oxygen species (ROS) produced in old rat vascular tissue. We hypothesize that: 1) endothelial arginase limits endothelial NO production and thus, endothelial-dependent vasodilatation, by competing for intracellular L-arginine; 2) vascular endothelial dysfunction of aging is associated with increased expression of endothelial arginase, and inhibition of arginase restores NO-dependent signaling and endothelial function to that of the young phenotype; 3) relative substrate (L-arginine) deficiency enhances ROS production further compromising endothelial function by altering the balance between NO and 02-; and 4) chronic arginase inhibition will restore Larginine reponsiveness, enhance NO signaling, and decrease ROS production thereby restoring altered integrated cardiovascular parameters (increased vascular and ventricular stiffness and altered ventriculararterial coupling) to that of the young phenotype. We will study the regulatory role of arginase in normal endothelial function and NO signaling, as well as its role in the pathophysiology of endothelial dysfunction associated with aging. These experiments will offer novel insights into regulation of the NO signaling pathway, and the balance between NO and 02- in endothelial function, with important therapeutic implications for a wide variety of disorders characterized by endothelial dysfunction.