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)引起的低氧复杂化，并与COPD的发病率和死亡率增加有关。缺氧性PH与肺内皮细胞功能障碍有关，包括一氧化氮(NO)和前列环素(PGI2)的产生减少，血管收缩，内皮和血管平滑肌细胞增殖。大电导钙激活钾通道(BKCa)在血管内皮细胞(EC)中表达，并在细胞内钙离子作用下开放，导致钾离子外流和膜超极化。在内皮细胞中，超极化可导致细胞内钙离子内流增加，导致血管扩张剂释放，如NO、PGI2和内皮衍生超极化因子(EDHF)等，这些因素也影响细胞增殖。关于内皮K通道在PH中的重要性的数据有限。缺氧导致内皮细胞BKCa表达增加，但活性降低。低氧肺内皮细胞BKCa表达增加而活性降低的机制尚不清楚。此外，增加内皮细胞BKCa活性是否能改善缺氧性肺内皮细胞功能障碍、血管重构和PH也尚不清楚。我们的总体假设是，内皮细胞BKCa1亚单位表达增加，活性降低，在缺氧时提供了一种现成的“超极化储备”。因此，激活内皮细胞BKCa可改善缺氧状态下的内皮功能。具体目的：目的1：检测低氧对肺微血管内皮细胞BKCa1亚单位表达的影响，并探讨其机制。目的：检测低氧对肺微血管内皮细胞BKCa活性的影响，并探讨其作用机制。目的：探讨低氧条件下内皮细胞BKCa激活对内皮血管扩张功能、内皮细胞增殖及血管重塑的影响。 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，包括退伍军人常见的缺氧性肺高压(PH)。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发病率和死亡率的增加有关，COPD是退伍军人的一个重要问题。这项拟议的研究将调查内皮BKCa通道在调节内皮功能中的作用，特别是在低氧环境下。此外，这些研究还将阐明内皮BKCa通道激活作为一种新的治疗靶点的潜力，通过改善缺氧时的内皮功能来治疗与缺氧和COPD相关的PH。

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.