Role of Gap Junction in Hypoxia-induced Pulmonary Hypertension

项目摘要/摘要 低氧通过增加平滑肌收缩和减弱而导致肺血管收缩 内皮依赖性松弛(EDR)。持续性肺血管收缩和随后的血管 远端小动脉重塑是肺血管增多的主要原因 缺氧性肺动脉高压患者的抵抗力。与内皮功能障碍有牵连 在许多心血管疾病的发展过程中，包括高血压和糖尿病。EDR通过不同的途径进行调节 小的远端动脉和大的近端动脉的机制。近端大动脉的血管扩张主要是由 内皮源性一氧化氮(NO)和/或前列环素(PGI2)，而远端小动脉的血管扩张 突出表现为内皮源性超极化(EDH)。间隙连接(GJ)是一种细胞间连接 传输小分子并将电信号(例如，超极化)传播到相邻细胞。GJ是更多 远端小动脉较近端大动脉丰富。我们最近报告说，糖尿病小鼠 表现出对HPH的敏感性显著增加，糖尿病患者对HPH的敏感性更高 出现肺血管异常。然而，目前尚不清楚血管内皮细胞功能是否发生改变 糖尿病与决定HPH的严重程度有关。这项研究的目标是调查a)如果以及如何 由于内皮细胞(ECs)中的GJ功能障碍，导致小动脉远端的内皮功能障碍 与HPH的发展和进展有关，以及b)糖尿病相关的GJ功能障碍是否以及如何加剧 HPH。我们的初步数据表明：1)远端(4-5级)较小，近端(1-2级)不大 PAS，表现出强烈的EDH依赖的松弛，可被低氧减弱；ii)肺内皮细胞来自 HPH小鼠的连接蛋白40(Cx40，GJ的一种成分)的蛋白水平低于正常氧小鼠的内皮细胞； 低氧降低肺内皮细胞GJ活性，IV)Cx40过表达增强EDH依赖的松弛 并降低HPH小鼠的右室收缩压；v)缺氧性糖尿病小鼠表现为EDR减弱 与低氧对照组小鼠相比，小鼠(第4-5只)的PAS；和vi)糖尿病小鼠的肺内皮细胞较低 Cx40基因的表达水平高于对照组小鼠内皮细胞。根据这些初步数据，我们假设a)慢性 低氧下调Cx40表达，减弱GJ功能，损害小鼠EDH依赖的松弛 (4-5)PAS，并最终诱发HPH；和b)糖尿病增加HPH的易感性，因为 GJ活动。其具体目的是：1)确定慢性缺氧减轻的分子机制 2)探讨Cx40在HPH发生发展中的作用。 3)研究2型糖尿病对HPH发生的影响，特别是内皮细胞的影响 GJ函数。这项拟议研究的完成将为开发个性化的治疗方法带来巨大的启发 生活在高海拔地区和/或患有缺氧性心肺疾病的糖尿病患者。

Project Summary/Abstract Hypoxia induces pulmonary vasoconstriction by increasing smooth muscle contraction and attenuating endothelium-dependent relaxation (EDR). Sustained pulmonary vasoconstriction and subsequent vascular remodeling in small distal pulmonary artery (PA) are the major causes for the increased pulmonary vascular resistance in patients with hypoxia-induced pulmonary hypertension (HPH). Endothelial dysfunction is implicated in the development of many cardiovascular diseases including HPH and diabetes. EDR is mediated via different mechanisms in small distal and large proximal arteries. Vasodilation in large proximal artery is mainly caused by endothelium-derived nitric oxide (NO) and/or prostacyclin (PGI2), while vasodilation in small distal artery is due prominently to endothelium-derived hyperpolarization (EDH). Gap junction (GJ) is an intercellular junction that transfers small molecules and propagates electric signals (e.g., hyperpolarization) to adjacent cells. GJ is more abundant in small distal artery compared to large proximal artery. We recently reported that diabetic mice exhibited significantly increased sensitivity to develop HPH and diabetic patients have higher susceptibility to develop pulmonary vascular abnormalities. It is, however, unknown whether alteration of endothelial function in diabetes is involved in determining severity of HPH. The goal of this study is to investigate a) if and how endothelial dysfunction in small distal PAs, as a result of dysfunctional GJ in endothelial cells (ECs), contributes to the development and progression of HPH and b) if and how diabetes-associated GJ dysfunction exacerbates HPH. Our preliminary data demonstrate that: i) small distal (4th-5th order) PAs, but not large proximal (1st-2nd order) PAs, exhibit great EDH-dependent relaxation that can be attenuated by hypoxia; ii) pulmonary ECs from HPH mice show lower protein level of connexin 40 (Cx40, a component of GJ) than ECs from normoxic mice; iii) hypoxia attenuates GJ activity in pulmonary ECs, iv) Cx40 overexpression enhances EDH-dependent relaxation and decreases right ventricular systolic pressure in HPH mice; v) hypoxic diabetic mice exhibit attenuated EDR in small (4th-5th) PAs compared to hypoxic control mice; and vi) pulmonary ECs from diabetic mice show lower Cx40 mRNA level than ECs from control mice. Based on these preliminary data, we hypothesize that a) chronic hypoxia downregulates Cx40 expression, attenuates GJ function, impairs EDH-dependent relaxation in small (4th-5th) PAs and, ultimately, induces HPH; and b) diabetes increases the susceptibility to HPH due to decreased GJ activity. The specific aims are 1) to identify the molecular mechanisms by which chronic hypoxia attenuates endothelial function in small distal PAs, 2) to investigate the pathogenic role of Cx40 in the development of HPH, and 3) to examine the effect of type 2 diabetes on the development of HPH with a special focus on endothelial GJ function. Completion of the proposed study will shed great lights into developing personalized therapies for diabetic patients living at high altitude and/or have hypoxic cardiopulmonary diseases.