Exercise Pressor Reflex in Peripheral Artery Disease: Roles of Flow Limitation and Reperfusion

项目摘要/摘要 我们的目标是确定导致外周动脉疾病(Pad)心血管功能障碍的机制。 然后研究将减少这些病理生理过程的影响的治疗方法。我们有 显示PAD患者腿部运动时的运动加压反射(EPR)被夸大。这个 PAD患者EPR升高的机制尚未得到彻底研究。利用两个人 和动物研究，我们建议检查血流限制(BFR)和缺血-再灌注的作用 (IR)诱发夸大EPR的重音。我们预计，酸敏感离子通道(ASIC)的阻断 阿米洛利可减少PAD患者夸大的EPR，提高步行耐量。目标1： 确定BFR在诱发PAD过度EPR中的作用。我们假设BFR会导致 运动肌肉间质中较高的H/较低的pH，从而通过刺激增强EPR 亚瑟斯。我们建议使用健康受试者的BFR来模拟PAD中的BFR。我们推测BFR将会 在安慰剂试验中增加EPR和阿米洛利将减少EPR并增加运动时间/负荷 BFR条件。我们还推测，阿米洛利将在PAD患者中发挥同样的有益作用。在动物身上 研究表明，我们推测股动脉闭塞的BFR会增加间质H/降低pH。 通过ASIC亚型3(ASIC3)夸大EPR和长时间闭塞将上调ASIC3的表达 在PAD的肌肉传入神经中。目的2：探讨胰岛素抵抗在PAD诱发EPR增加中的作用。 我们假设IR有助于PAD中夸大的EPR，而阿米洛利减少夸大的EPR IR应激通过阻断ASIC诱导。健康受试者将在自由流动状态下进行足底屈曲练习 缺血20min后，再灌流20min。我们推测，IR压力将加剧 EPR。PAD患者在小腿血运重建前后还将进行足底屈曲训练。我们 推测阿米洛利可改善IR应激后受试者的EPR，增加运动时间/负荷。 PAD患者血运重建。在动物实验中，我们将在不同的时间检测IR大鼠的EPR 并推测IR大鼠满意的再灌流将减轻EPR和升压反应 由激活传入神经的ASIC3诱导。目的3：确定ASIC对老年人运动能力的影响 垫片和基本机构。我们推测阿米洛利会降低升压反应 并增加PAD患者的跛行起始时间和步行距离/时间。在动物研究中， 我们推测，在ASIC3基因敲除的大鼠中，IR引起的夸大的EPR将被减弱。我们会 缺血再灌注大鼠肌肉传入神经元ASIC3蛋白水平及其电流反应的比较 不同的时间进程和它们的对应物作为对照。我们推测ASIC3的表达和它的 肌肉传入神经元的电流反应在IR起始阶段被放大及IR的影响 将通过ASIC3基因敲除或有足够的再灌流时间而减少。

PROJECT SUMMARY/ABSTRACT Our goal is to identify the mechanisms responsible for cardiovascular disability in peripheral artery disease (PAD) and to then examine therapies that will reduce the impact of these pathophysiologic processes. We have demonstrated that the exercise pressor reflex (EPR) during leg exercise is exaggerated in PAD patients. The mechanisms for the exaggerated EPR in PAD patients have not been examined thoroughly. Utilizing both human and animal studies, we propose to examine the roles of blood flow restriction (BFR) and ischemia-reperfusion (IR) stress in inducing the exaggerated EPR. We anticipate that a blockade of acid sensing ion channels (ASICs) with amiloride will reduce the exaggerated EPR and enhance the walking tolerance in PAD patients. Aim 1: Determine the role of BFR in inducing the exaggerated EPR in PAD. We hypothesize that BFR leads to a greater H+/lower pH in the interstitium of exercising muscles and thereby accentuates the EPR via stimulating ASICs. We propose to employ BFR in healthy subjects to simulate the BFR in PAD. We speculate that BFR will augment the EPR in the placebo trial and amiloride will reduce the EPR and increase exercise time/load under BFR condition. We also speculate that amiloride will play the same beneficial role in PAD patients. In animal studies, we speculate that BFR by femoral artery occlusion will increase interstitial H+/decrease pH thereby exaggerating the EPR via ASIC subtype 3 (ASIC3) and prolonged occlusion will upregulate ASIC3 expression in muscle afferent nerves of PAD. Aim 2: Determine the role of IR in inducing the exaggerated EPR in PAD. We hypothesize that IR contributes to the exaggerated EPR in PAD and amiloride reduces the exaggerated EPR induced by IR stress via blocking ASICs. Healthy subjects will perform plantar flexion exercise under free flow conditions and after 20 min ischemia followed by 20 min reperfusion. We speculate that IR stress will accentuate the EPR. PAD patients before and after leg revascularization will also perform plantar flexion exercise. We speculate that amiloride will improve the EPR and increase exercise time/load in subjects after IR stress and in PAD patients with revascularization. In animal studies, we will examine the EPR in IR rats at different time courses and speculate that in IR rats satisfied reperfusion will alleviate the EPR and the pressor response induced by activation of afferent nerves’ ASIC3. Aim 3: Determine the effects of ASIC on exercise ability in PAD and fundamental mechanisms. We speculate that amiloride will decrease the pressor response to walking and increase the claudication onset time and walking distance/time in PAD patients. In animal studies, we speculate that exaggerated EPR induced by the IR will be attenuated in ASIC3 knockout rats. We will compare the protein levels of ASIC3 and its current response in muscle afferent neurons between IR rats at different time courses and their counterparts serving as controls. We speculate that ASIC3 expression and its current response in muscle afferent neurons will be amplified during the initiating IR stage and the effects of IR will be reduced by ASIC3 knockout or with sufficient time of reperfusion.