Microvascular Aging and eNOS Uncoupling

心血管系统是人体氧化代谢和有氧能力的主要决定因素； 因此，成功的心血管衰老对于老年人保持积极、独立的生活方式至关重要。 个人。心血管系统的老化导致进行性内皮功能障碍，这与 心血管疾病的风险增加，骨骼肌功能丧失。内皮细胞 老年大鼠骨骼肌阻力动脉功能障碍主要由一氧化氮减少所致 氧化(NO)信号；然而，年龄对调节NO信号的细胞机制的影响仍然是 要下定决心。最近的证据表明，四氢生物蝶呤(BH4)的可用性是一种必要的辅因子 老年大鼠骨骼肌阻抗动脉NO生成量减少。不足之处 BH4的可获得性可导致内皮型一氧化氮合酶(ENOS)生化解偶联和 NO的合成减少。此外，未偶联的eNOS会产生超氧阴离子(021a活性氧 可以限制NO信号并对细胞造成损害的物种。这项提案的首要目标是 1)确定衰老是否导致eNOS解偶联和骨骼中生物可利用的NO减少 肌肉阻力动脉，以及2)确定干预策略，包括有氧运动 训练可以扭转与年龄有关的BH4供应不足和eNOS解偶联的情况，增加NO 骨骼肌阻力动脉的生物利用度。在目标1中，NO和O2-将直接测量到 确定衰老是否导致大鼠比目鱼肌阻力动脉eNOS解偶联 降低了NO的生物利用度，增加了细胞毒性O2-的产生。在AIM 2中，内皮特异性 腺病毒基因转移将用于确定是否通过过度表达BH4来恢复BH4的可用性 GTP环水解酶(GTPCH)逆转增龄相关eNOS去偶联，增加NO的生物利用度和 降低比目鱼肌阻力动脉中的O2-。GTPCH的shRNAi敲除也将用于减少 BH4在比目鱼肌阻力动脉中的可用性和促进eNOS解偶联。目标3的目的是 确定慢性有氧运动训练是否减少氧化应激并增加GTPCH 从而增加BH4的可获得性并逆转eNOS和NO的年龄相关性解偶联 大鼠比目鱼肌阻力动脉的生物利用度。这些研究将增加我们对 骨骼肌阻力血管形成中年龄相关性内皮功能障碍的机制 并指出旨在提高BH4可用性的特定干预措施是否可以改善内皮细胞 老年功能障碍

The cardiovascular system is a major determinant of the body's oxidative metabolism and aerobic capacity; thus, successful cardiovascular aging is critical to maintenance of an active, independent lifestyle in elderly individuals. Aging of the cardiovascular system results in progressive endothelial dysfunction that is associated with increased risk for cardiovascular disease and a loss of skeletal muscle performance. The endothelial dysfunction present in skeletal muscle resistance arteries of aged rats results primarily from reduced nitric oxide (NO) signaling; however, the effects of age on cellular mechanisms that regulate NO signaling remain to be determined. Recent evidence indicates that the availability of tetrahydrobiopterin (BH4), a necessary cofactor in NO production, is decreased in skeletal muscle resistance arteries of aged rats. Inadequate availability of BH4 can result in biochemical uncoupling of endothelial nitric oxide synthase (eNOS) and reduced synthesis of NO. Furthermore, uncoupled eNOS produces superoxide anion (021 a reactive oxygen species which can limit NO signaling and contribute to cellular damage. The overarching goals of this proposal are 1) to determine whether aging results in uncoupling of eNOS and reduction of bioavailable NO in skeletal muscle resistance arteries, and 2) to determine whether interventional strategies, including aerobic exercise training, can reverse age-related deficiencies in BH4 availability and uncoupling of eNOS, increasing NO bioavailability in skeletal muscle resistance arteries. In Aim 1 NO and O2- will be measured directly to determine whether aging produces uncoupling of eNOS in resistance arteries from rat soleus muscle leading to reduced NO bioavailability, and increased production of cytotoxic O2-. In Aim 2, endothelium-specific adenoviral gene transfer will be used to determine whether restoration of BH4 availability by overexpression of GTP cyclohydrolase (GTPCH) reverses age-related uncoupling of eNOS, increasing NO bioavailability and reducing O2- in soleus muscle resistance arteries. shRNAi knockdown of GTPCH will also be used to reduce BH4 availability and promote eNOS uncoupling in soleus muscle resistance arteries. The purpose of Aim 3 is to determine whether chronic aerobic exercise training reduces oxidant stress and increases GTPCH expression thereby increasing BH4 availability and reversing age-related uncoupling of eNOS and NO bioavailability in resistance arteries from rat soleus muscle. These studies will increase our understanding of mechanisms that contribute to age-related endothelial dysfunction in resistance vasculature of skeletal muscle and indicate whether specific interventions designed to improve BH4 availability can ameliorate endothelial dysfunction in old age