Nicotinamide nucleotide transhydrogenase regulates redox balance in atherosclerosis

项目摘要 动脉粥样硬化是一种进行性慢性炎症性血管壁疾病，受氧化应激调节。 在疾病发展的整个过程中。内皮功能障碍是一个关键的启动步骤 动脉粥样硬化的发展和越来越多的证据表明线粒体活性氧物种 (ROS)是内皮功能障碍和血管炎症的重要因素。烟酰胺核苷酸 转氢酶(NNT)是调节线粒体NADPH水平的一种重要酶 它可以通过调节线粒体对许多代谢途径产生重大影响 氧化还原平衡。我们实验室的初步数据支持这一概念，证明了NNT的表达 与健康对照组相比，动脉粥样硬化患者的血管内皮细胞减少。这些数据是 与我们实验室以前发表的数据一致，表明AAV8-PCSK9和高脂饮食 治疗导致缺乏NNT的C57BL/6J小鼠的斑块负担增加。利用小发夹的最新研究 人主动脉内皮细胞中NNT的RNA敲除显示过氧化氢产生增加 与线粒体NADPH的减少和下游抗氧化酶的损伤有关 谷胱甘肽过氧化物酶和谷胱甘肽还原酶。此外，这些细胞中NNT的丢失也导致了 黏附分子表达增加和炎性细胞转运提示NNT在 调节线粒体平衡在调节动脉粥样硬化斑块的发展过程中起着至关重要的作用。我们 已经在体内用一种新型的内皮特异性基因敲除小鼠证实了这些观察到的丢失 NNT促进AAV8-PCSK9诱导的小鼠主动脉弓黏附分子表达增强 部分颈动脉结扎和高脂饮食诱导斑块形成的紊乱血流模型。建立在 这些发现，我们认为，NNT活性的丧失有助于促进线粒体的氧化 通过增强线粒体ROS而加剧动脉粥样硬化进展的表型 产生、内皮功能障碍和血管炎症。为了验证这一假设，有研究表明 提出将决定i)NNT是否抑制线粒体ROS的产生并保护线粒体 人血管内皮细胞的抗氧化活性和氧化代谢；II)NNT表达是否减少 线粒体ROS产生的增加刺激了NOx的活性，从而降低了NO的生物利用度 并促进内皮细胞激活；以及iii)内皮细胞NNT是否关键地调节线粒体氧化还原平衡 以及高脂饮食处理的小鼠的血管功能。拟议研究的数据将确定NNT是一种 线粒体功能和ROS产生的主要调节者的缺失加剧了糖尿病的发展 通过促进内皮功能障碍和血管炎症导致动脉粥样硬化，导致斑块增加 发展。

PROJECT ABSTRACT Atherosclerosis, a progressive chronic inflammatory disease of the vessel wall, is regulated by oxidant stress throughout the course of disease development. Endothelial dysfunction is a critical, initiating step in the development of atherosclerosis and increasing evidence implicates mitochondrial reactive oxygen species (ROS) as an important contributor to endothelial dysfunction and vascular inflammation. Nicotinamide nucleotide transhydrogenase (NNT) is emerging as an important enzyme in the regulation of mitochondrial NADPH levels which can have a significant impact on a number of metabolic pathways through the regulation of mitochondrial redox balance. Preliminary data from our laboratory supports this concept demonstrating that NNT expression is reduced in the endothelium of atherosclerotic patients when compared to healthy controls. These data are consistent with previously published data from our laboratory indicating that AAV8-PCSK9 and high fat diet treatment led to increased plaque burden in C57Bl/6J mice that lack NNT. Recent studies utilizing small hairpin RNA knockdown of NNT in human aortic endothelial demonstrates increased hydrogen peroxide production that is associated with reductions in mitochondrial NADPH and impairment of downstream antioxidant enzymes glutathione peroxidase and glutathione reductase. Furthermore, the loss of NNT in these cells also led to increased adhesion molecule expression and inflammatory cell trafficking suggesting that NNT’s role in regulating mitochondrial balance can play a critical role in modulating atherosclerotic plaque development. We have confirmed these observations in vivo using a novel endothelial specific knockout mouse where the loss of NNT promotes enhanced adhesion molecule expression in the aortic arch of mice subjected to AAV8-PCSK9, partial carotid ligation, and high fat diet in a model of disturbed flow induced plaque development. Building upon these findings, we propose that the loss of NNT activity contributes to a pro-oxidative mitochondrial phenotype that exacerbates the progression of atheroscelrosis by enhancing mitochondrial ROS production, endothelial dysfunction, and vascular inflammation . To test this hypothesis, studies are proposed that will determine i) if NNT inhibits mitochondrial ROS production and preserves mitochondrial antioxidant activity and oxidative metabolisim in human vascular endothelial cells; ii) if reduced NNT expression and increased mitochondrial ROS production stimulates Nox activity that contributes to reduced NO bioavailibilty and promotes endothelial activation; and iii) if endothelial NNT critically regulates mitochondrial redox balance and vascular function in mice treated with high fat diet. Data from the proposed studies will identify NNT as a master regulator of mitochondrial function and ROS production whose absence exacerbates the development of atherosclerosis by promoting endothelial dysfunction and vascular inflammation, leading to increased plaque development.