NO-Mediated Pulmonary Vasodilation After Chronic Hypoxia

描述（由申请人提供）：与各种肺部疾病相关的慢性缺氧（CH）导致肺动脉高压。适应性反应，包括增强的一氧化氮（NO）介导的血管舒张，可以减轻缺氧性肺动脉高压的严重程度。然而，无论是CH后改变NO依赖性反应的机制，还是导致NO介导的肺血管舒张的信号通路都没有很好的理解。蛋白激酶G（PKG）是NO信号转导的重要靶点，通过降低细胞内游离钙离子浓度（[Ca 2+]i）和降低收缩器官对Ca 2+的敏感性来促进血管平滑肌（VSM）的舒张。PKG引起Ca 2+脱敏的后一种作用在很大程度上是不确定的，尽管研究已经暗示了RhoA-Rho激酶信号级联在这种反应中的失活作用。有趣的是，初步实验表明，CH减弱PKG依赖性的VSM [Ca 2+]i下降，同时矛盾地增强PKG介导的血管舒张。因此，本研究将探讨中心假设，CH损害PKG依赖性调节[Ca 2 +]i在肺VSM和介导的PKG信号的代偿性转变，以促进脱敏的收缩装置[Ca 2+]。将通过以下具体目标解决该假设：具体目标#1：建立CH损害PKG依赖性肺VSM [Ca 2 +]i降低的机制。为此目的的工作假设是CH通过干扰Ca 2+内流和螯合机制的调节来减少PKG介导的VSM [Ca 2 +]i的降低。具体目标#2：确定CH增强PKG介导的肺VSM Ca 2+脱敏的机制。我们假设，增强PKG介导的肺血管舒张后CH是VSM钙脱敏通过抑制RhoA-Rho激酶途径的功能。拟议的研究将采用一种创新的方法来解决CH改变肺VSM中PKG信号传导的机制，包括同时测量对照组和CH大鼠分离的加压小肺动脉中的血管反应性和VSM [Ca 2 +]i。研究结果有望从根本上推进我们对PKG调节肺血管张力的信号转导机制以及肺循环对CH的适应性反应的理解。

DESCRIPTION (provided by applicant): Chronic hypoxia (CH) associated with various lung diseases leads to pulmonary hypertension. Adaptive responses, including enhanced nitric oxide (NO)-mediated vasodilation, may diminish the severity of hypoxic pulmonary hypertension. However, neither the mechanism of altered NO-dependent reactivity following CH, nor the signaling pathways leading to NO-mediated pulmonary vasodilation are well understood. Protein kinase G (PKG) is a prominent target of NO signaling that elicits relaxation of vascular smooth muscle (VSM) by decreasing the concentration of intracellular free calcium ([Ca 2+]i)as well as desensitization of the contractile apparatus to Ca 2+ . This latter effect of PKG to cause Ca2+-desensitization is largely undefined, although studies have implicated a role for inactivation of the RhoA-Rho kinase-signaling cascade in this response. Interestingly, pilot experiments suggest that CH attenuates PKG-dependent decreases in VSM [Ca 2+]i while paradoxically augmenting PKG-mediated vasodilation. Therefore, the proposed studies will investigate the central hypothesis that CH impairs PKG-dependent regulation of [Ca2+]i in pulmonary VSM and mediates a compensatory shift in PKG signaling to promote desensitization of the contractile apparatus to [Ca 2+]. This hypothesis will be addressed by the following specific aims: Specific Aim #1: Establish the mechanism by which CH impairs PKG-dependent reduction of pulmonary VSM [Ca2+]i. The working hypothesis for this aim is that CH diminishes PKG-mediated decreases in VSM [Ca2+]i by interfering with regulation of Ca 2+ influx and sequestration mechanisms. Specific Aim #2: Identify the mechanism by which CH augments PKG-mediated pulmonary VSM Ca2+-desensitization. We hypothesize that enhanced PKG-mediated pulmonary vasodilation following CH is a function of VSM Ca2+-desensitization through inhibition of the RhoA-Rho kinase pathway. The proposed studies will employ an innovative approach to address mechanisms by which CH alters PKG-signaling in pulmonary VSM, including simultaneous measurement of vasoreactivity and VSM [Ca2+]i in isolated, pressurized small pulmonary arteries from control and CH rats. Findings from studies are expected to fundamentally advance our understanding of signal transduction mechanisms by which PKG regulates pulmonary vascular tone, as well as adaptive responses of the pulmonary circulation to CH.