Thioredoxin and Endothelial Cell Function

描述(申请人提供)：在美国，冠状动脉粥样硬化引起的心肌梗死仍然是主要的死亡原因。细胞/系统氧化还原状态的改变，导致炎症(如肿瘤坏死因子)和活性氧物种(ROS)的增加，是动脉粥样硬化的常见致病机制。主要限制炎症和动脉粥样硬化过程的血管细胞是内皮细胞(EC)。ROS诱导的NO生物利用度的降低和EC凋亡的增加导致动脉粥样硬化形成。越来越多的证据支持，血管内线粒体产生的ROS在EC功能障碍和动脉粥样硬化进展中起重要作用。此外，最近的数据表明，线粒体通常在所有细胞器中产生最强的还原环境，并且线粒体特别容易受到包括促炎细胞因子在内的应激刺激的氧化。线粒体氧化还原的关键系统是线粒体特异性硫氧还蛋白(Trx2)系统，它由Trx2、Trx2还原酶(TrxR2)和Trx2依赖的过氧化物酶(Prx3)组成。线粒体Trx2系统在血管系统中的作用知之甚少。我们的数据表明，线粒体Trx2可能在维持线粒体还原状态，防止ROS诱导的EC功能障碍中发挥关键作用。具体地说，我们使用了EC特异的转基因和基因敲除小鼠，并证明了Trx2通过增加NO生物活性来调节内皮功能的关键作用。我们还表明，Trx2通过蛋白质-蛋白质相互作用抑制促凋亡蛋白激酶ASK1的活性，保护EC免受肿瘤坏死因子和ROS诱导的细胞凋亡。我们认为Trx2通过两条不同和协同的途径来预防ROS诱导的EC功能障碍：Trx2维持EC线粒体的减少状态，减少ROS的产生，增加NO的生物活性；Trx2通过直接与ASK1结合来保护ROS诱导的EC凋亡。我们进一步假设，增加NO生物活性和减少凋亡反应可以防止EC功能障碍和动脉粥样硬化的发展。为了探索这些假说，我们提出了以下具体目标：1)确定Trx2没有生物活性和EC功能的机制。2)确定Trx2抑制线粒体ASK1介导的细胞凋亡的机制。3)在小鼠模型中确定Trx2在预防EC功能障碍和动脉粥样硬化发生/进展中的作用。这项建议使用体外和体内模型来确定Trx2在对抗ROS诱导的EC功能障碍和动脉粥样硬化发展/进展中的作用。如果这些研究成功，将有助于开发新的治疗方法来控制动脉粥样硬化进展和心肌梗死。项目简介：动脉狭窄导致的心肌梗死表现为血流减少，在美国仍然是主要的死亡原因。我们将研究抗氧化蛋白质硫氧还蛋白对血管内皮细胞的影响。我们的工作可能会为动脉粥样硬化患者带来更好的测试和治疗。

DESCRIPTION (provided by applicant): Myocardial infarction due to atherosclerosis of coronary arteries remains the leading cause of death in the United States. It has become clear that changes of cellular/systemic redox state, resulting in increases in inflammation (e.g., TNF) and reactive oxygen species (ROS), represent a common pathogenic mechanism for atherosclerosis. The vascular cell that primarily limits the inflammatory and atherosclerotic process is the endothelial cell (EC). ROS-induced reduction in NO bioavailability and increase of EC apoptosis results in a proatherogenic state. Increasing evidence supports that ROS generated from mitochondria in vasculature significantly contribute to EC dysfunction and atherosclerotic progression. Furthermore, recent data suggest that mitochondria normally produce the strongest reducing environment among all cellular organelles, and mitochondria are especially vulnerable to oxidation in response to stress stimuli including proinflammatory cytokines. A key system regulating mitochondria redox is mitochondria-specific thioredoxin (Trx2) system, consisting of Trx2, Trx2 reductase (TrxR2) and Trx2-depndent peroxidase (Prx3). Little is known for the role of mitochondrial Trx2 system in vasculature. Our data suggest that mitochondrial Trx2 may play critical roles in maintaining mitochondria reduced state, preventing ROS-induced EC dysfunction. Specifically, we have used both EC-specific transgenic and knockout mice, and demonstrated a critical role of Trx2 in regulating endothelium functions by increasing NO bioactivity. We also show that Trx2 inhibits the activity of proapoptotic protein kinase ASK1 through protein-protein interactions, protecting EC from TNF and ROS- induced apoptosis. We propose that Trx2 prevents ROS-induced EC dysfunction through two distinct and cooperative pathways: Trx2 maintains a reduced state of mitochondria in EC, reducing ROS generation leading and increasing NO bioactivity; Trx2 protects ROS-induced EC apoptosis by directly binding to ASK1. We further hypothesize that increased NO bioactivity and decreased apoptotic responses prevent EC dysfunction and atherosclerotic development. To explore these hypotheses, we propose the following specific aims: 1) Determine the mechanisms by which Trx2 preserves NO bioactivity and EC function. 2) Determine the mechanisms by which Trx2 inhibits mitochondrial ASK1-mediated apoptosis. 3) Determine the role of Trx2 in preventing EC dysfunction and atherosclerosis development/progression in a mouse model. This proposal uses both in vitro and in vivo models to determine the roles of Trx2 in protection against ROS- induced EC dysfunction and atherosclerosis development/progression. These studies, if successful, will facilitate the development of new therapeutic approaches to control atherosclerosis progression and myocardial infarction. Project Narrative: Myocardial infarction due to narrowing of arteries manifesting as decreased blood flow remains the leading cause of death in the United States. We will study the effects of a antioxidant protein thioredoxin, on vascular endothelium. Our work may lead to better tests and treatments for atherosclerosis patients.