Role of Gap Junction in Hypoxia-induced Pulmonary Hypertension

项目总结/摘要 缺氧通过增加平滑肌收缩和减弱肺动脉收缩而引起肺血管收缩 内皮依赖性舒张（EDR）。持续的肺血管收缩和随后的血管 远端小肺动脉（PA）的重构是肺血管扩张的主要原因 缺氧性肺动脉高压（HPH）患者的阻力。内皮功能障碍与 在许多心血管疾病的发展中，包括HPH和糖尿病。EDR通过不同的 小的远端和大的近端动脉中的机制。近端大动脉的血管舒张主要是由 内皮源性一氧化氮（NO）和/或前列环素（PGI 2），而小远端动脉的血管舒张是由于 内皮源性超极化（EDH）。间隙连接（GJ）是细胞间连接， 转移小分子并传播电信号（例如，超极化）到相邻细胞。GJ更多 与近端大动脉相比，远端小动脉丰富。我们最近报道糖尿病小鼠 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，尚不清楚内皮功能的改变是否会影响血管内皮细胞的功能。 糖尿病参与决定HPH的严重程度。本研究的目的是调查a）是否以及如何 由于内皮细胞（EC）的GJ功能障碍，远端小PA的内皮功能障碍有助于 和B）糖尿病相关的GJ功能障碍是否以及如何恶化 HPH。我们的初步数据表明：i）远端（4 - 5阶）PA较小，但近端（1 - 2阶）PA不大 顺序）PA，表现出很大的EDH依赖性舒张，可以通过缺氧减弱; ii）肺EC从 HPH小鼠显示出比来自常氧小鼠的EC更低的连接蛋白40（Cx40，GJ的组分）的蛋白质水平; iii） 缺氧减弱肺EC中GJ活性，iv）Cx40过表达增强EDH依赖性舒张 并降低HPH小鼠的右心室收缩压; v）缺氧糖尿病小鼠表现出减弱的EDR 与缺氧对照小鼠相比，在较小的（第4-第5）PA中;和vi）来自糖尿病小鼠的肺EC显示出较低的 Cx40 mRNA水平高于对照组。基于这些初步数据，我们假设a）慢性 缺氧下调Cx40表达，减弱GJ功能，损害EDH依赖性舒张， （4 - 5）PA，并最终诱导HPH;和B）糖尿病增加了对HPH的易感性，这是由于降低了 GJ活动具体目标是：1）确定慢性缺氧减弱的分子机制 远端小PA的内皮功能，2）研究Cx40在HPH发生中的致病作用， 和3）检查2型糖尿病对HPH发展的影响，特别关注内皮细胞 GJ函数。完成拟议的研究将为开发个性化治疗提供很大的启发， 生活在高海拔地区的糖尿病患者和/或患有缺氧性心肺疾病的患者。

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.