DDAH1 effects on endogenous NOS inhibitors and vascular endothelial function

内源性NO合成酶（NOS）抑制剂不对称二甲基精氨酸（ADMA）和ng -单甲基- l-精氨酸（L-NMMA）的积累是高血压、冠状动脉疾病、中风、糖尿病和动脉粥样硬化等心血管疾病的主要危险因素。这些内源性NOS抑制剂与l -精氨酸竞争抑制NOS产生NO。ADMA和L-NMMA主要由二甲基精氨酸二甲氨基水解酶（DDAH）消除，肾脏排泄的贡献很小。据报道，ADMA和L-NMMA都被DDAH1和DDAH2降解，但DDAH1和DDAH2的相对贡献一直存在争议。此外，DDAH1是否能在调节NO生成之外对血管功能产生影响尚不清楚。通过我们实验室培育的新型组织特异性DDAH1基因缺陷小鼠和全局DDAH1基因缺陷小鼠，我们的初步数据表明，DDAH1在降解内源性NOS抑制剂中起着至关重要的作用，分布在内皮细胞中的DDAH1在调节血管内皮NO生成和内皮细胞生长及损伤修复中起着重要作用。最有趣的是，我们的初步数据进一步表明，DDAH1还通过一种不依赖内源性NOS抑制剂降解的新型分子途径调节内皮细胞功能。基于这些新发现，我们提出验证两个假设。首先，我们假设DDAH1是降解ADMA和L-NMMA的主要酶。其次，我们假设DDAH1在调节血管内皮细胞生长和损伤修复的ADMA和L-NMMA降解作用之外还发挥了其他作用。为了验证这些假设，我们已经产生了一种新的组织特异性内皮-DDAH1 KO （endodo -DDAH1 KO）小鼠品系和一种全局DDAH1 KO小鼠品系。本研究将利用体外和体内方法，为内源性NOS抑制剂的功能以及DDAH1维持血管内皮细胞生长和损伤修复的新分子机制提供新的见解。

DESCRIPTION (provided by applicant): Accumulation of the endogenous NO synthase (NOS) inhibitors asymmetric dimethyl arginine (ADMA) and Ng-monomethyl-L-arginine (L-NMMA) is a major risk factor for cardiovascular diseases including hypertension, coronary artery disease, stroke, diabetes and atherosclerosis. These endogenous NOS inhibitors compete with L-arginine to inhibit NO production by NOS. ADMA and L-NMMA are eliminated principally by dimethylarginine dimethylaminohydrolase (DDAH) with a small contribution from renal excretion. It is reported that ADMA and L-NMMA are degraded by both DDAH1 and DDAH2, but the relative contributions of DDAH1 and DDAH2 have been controversial. Furthermore, whether DDAH1 can exert effects on vascular function beyond regulation of NO production is unknown. Using novel tissue specific DDAH1 deficient mice and global DDAH1 gene deficient mice generated in our laboratory, our preliminary data demonstrate that DDAH1 plays an essential role in degrading the endogenous NOS inhibitors, and that DDAH1 distributed in endothelial cells plays an important role in regulating vascular endothelial NO production and endothelial cell growth and injury repair. Most interestingly, our preliminary data further demonstrated that DDAH1 also regulates endothelial cell function through a novel molecular pathway independent of degradation the of endogenous NOS inhibitors. Based on these new findings, we propose to test two hypotheses. First, we hypothesize that DDAH1 is the principal enzyme responsible for degrading ADMA and L-NMMA. Second, we hypothesize that DDAH1 exerts additional actions beyond its role in degrading ADMA and L-NMMA that regulate vascular endothelial cell growth and injury repair. To test these hypotheses, we have generated a novel tissue specific endothelial-DDAH1 KO (endo-DDAH1 KO) mouse strain and a global DDAH1 KO mouse strain. The proposed studies will utilize in vitro and in vivo approaches to provide new insight into the function of the endogenous NOS inhibitors, as well as novel molecular mechanisms by which DDAH1 acts to maintain vascular endothelial cell growth and injury repair. PUBLIC HEALTH RELEVANCE: Accumulation of the endogenous nitric oxide synthase (NOS) inhibitors asymmetric dimethyl arginine (ADMA) and Ng-monomethyl-L-arginine (L-NMMA) is a major risk factor for cardiovascular diseases including hypertension, coronary artery disease, stroke, diabetes and atherosclerosis. DDAH1 degrades ADMA and L-NMMA to increase nitric oxide production. The proposed studies will integrate in vitro and in vivo approaches to provide new insight into the function of the endogenous NOS inhibitors, as well as novel molecular mechanisms by which DDAH1 acts to maintain vascular endothelial cell growth and injury repair.