Endothelial BKCa Channels and Hypoxic Pulmonary Endothelial Dysfunction

描述（由申请人提供）： 肺动脉高压（PH）可使慢性阻塞性肺疾病（COPD）引起的缺氧复杂化，并与COPD的发病率和死亡率增加相关。低血压PH与肺内皮功能障碍有关，包括一氧化氮（NO）和前列环素（PGI2）产生减少、血管收缩以及内皮和血管平滑肌细胞增殖。大电导钙激活钾通道（BKCa）在内皮细胞（EC）中表达，并响应于细胞内Ca 2+而开放，导致K+流出和膜超极化。在EC中，超极化可引起细胞内Ca 2+进入增加，从而导致血管扩张剂如NO、PGI2和内皮源性超极化因子（EDHF）的释放;这些因子也影响细胞增殖。关于内皮K+通道在PH中的重要性的数据有限。缺氧导致内皮BKCa表达增加，但其活性降低。低氧肺内皮细胞中BKCa表达增加但活性降低的机制尚不清楚。此外，它是不知道是否增加内皮细胞BKCa活性可以改善缺氧肺内皮功能障碍，血管重塑和PH。我们的总体假设是，增加内皮细胞BKCa 1-亚基的表达和活性降低提供了一个现成的“超极化储备”在缺氧。因此，内皮BKCa的激活将改善缺氧时的内皮功能。具体目标：目标1：我们将检测肺微血管内皮细胞BKCa 1亚单位在缺氧反应中的表达，并探讨其机制。目的二：研究缺氧时肺微血管内皮细胞BKCa活性的变化，探讨其机制。目标3：我们将确定内皮细胞BKCa激活对内皮舒张功能、EC增殖和缺氧后血管重塑的影响。 公共卫生相关性： 内皮功能障碍是肺血管疾病的重要组成部分，包括缺氧相关的肺动脉高压（PH），这是退伍军人的常见疾病。肺动脉高压可使慢性阻塞性肺疾病（COPD）引起的缺氧复杂化，并与COPD的发病率和死亡率增加相关，这是退伍军人的一个重要问题。拟议的研究将调查的作用，内皮细胞BKCa通道在调节内皮功能的一般，特别是在缺氧环境。此外，拟议的研究将阐明内皮BKCa通道激活作为缺氧相关PH和COPD的新治疗靶点的潜力，通过改善缺氧时的内皮功能。

DESCRIPTION (provided by applicant): Pulmonary hypertension (PH) can complicate hypoxia due to chronic obstructive pulmonary disease (COPD), and is associated with increased morbidity and mortality in COPD. Hypoxic PH is associated with pulmonary endothelial dysfunction including decreased nitric oxide (NO) and prostacyclin (PGI2) production, vasoconstriction, and endothelial and vascular smooth muscle cell proliferation. Large-conductance Ca2+- activated potassium channels (BKCa) are expressed in endothelial cells (EC), and open in response to intracellular Ca2+, leading to K+ efflux and membrane hyperpolarization. In ECs, hyperpolarization can cause an increase in intracellular Ca2+ entry leading to the release of vasodilators, such as NO, PGI2 and endothelium-derived hyperpolarizing factor (EDHF); factors which also affect cellular proliferation. There is limited data on the importance of endothelial K+ channels in PH. Hypoxia causes an increase in endothelial BKCa expression, yet a decrease in their activity. The mechanism of increased BKCa expression, yet decreased activity, in hypoxic lung endothelial cells is not known. Also, it is not known whether increasing the endothelial BKCa activity can improve hypoxic pulmonary endothelial dysfunction, vascular remodeling and PH. Our overall hypothesis is that increased endothelial BKCa 1-subunit expression and decreased activity provides a readily available "hyperpolarization reserve" in hypoxia. Hence, activation of endothelial BKCa will improve endothelial function in hypoxia. SPECIFIC AIMS: Aim 1: We will determine the expression of lung microvascular endothelial BKCa 1- subunit in response to hypoxia and investigate the underlying mechanism. Aim 2: We will determine the activity of lung microvascular endothelial BKCa in response to hypoxia and investigate the underlying mechanism. Aim 3: We will determine the effect of endothelial BKCa activation on endothelial vasodilatory function, EC proliferation and vascular remodeling in response to hypoxia. PUBLIC HEALTH RELEVANCE: Endothelial dysfunction is an important component of pulmonary vascular diseases including pulmonary hypertension (PH) associated with hypoxia, a common disease among Veterans. Pulmonary hypertension can complicate hypoxia due to chronic obstructive pulmonary disease (COPD), and is associated with increased morbidity and mortality in COPD, a significant problem in Veterans. The proposed studies will investigate the role of endothelial BKCa channels in modulating endothelial function in general and specifically in hypoxic settings. Also, the proposed studies will elucidate the potential of endothelial BKCa channel activation as a novel therapeutic target in PH associated with hypoxia and COPD through the improvement of endothelial function in hypoxia.