Pulmonary Vasoreactivity Following Chronic Hypoxia

描述（由申请人提供）：与阻塞性肺病和睡眠呼吸暂停相关的慢性缺氧（CH）导致肺动脉高压。升高的基础血管平滑肌（VSM）张力和增强的血管收缩反应性在介导CH诱导的肺动脉高压中起着重要作用。然而，CH引起这些血管收缩反应的机制尚不清楚。初步研究揭示了CH通过RhoA/Rho激酶依赖性Ca 2+敏化途径在肺VSM中促进肌源性张力和增强血管收缩反应性的新作用。这些研究进一步表明，CH诱导的VSM膜去极化刺激RhoA/Rho激酶的VSM游离Ca 2+水平的变化无关，并提供有趣的证据NADPH氧化酶（NOX）衍生的活性氧（ROS）的主要贡献，这种反应。因此，所提出的研究将调查中心假设，CH诱导的VSM膜去极化介导NOX依赖性刺激RhoA/Rho激酶途径，导致肌源性和激动剂诱导的肌丝Ca 2+敏感性增加。这一假设将解决以下具体目标：具体目标#1：确定细胞内信号转导机制负责升高肌源性和激动剂依赖性收缩后CH。我们假设CH增强肺动脉肌源性紧张度和激动剂介导的收缩通过RhoA/ROK诱导VSM Ca 2+敏化。具体目标#2：确定膜去极化的贡献增加基础和激动剂诱导的肺动脉收缩后CH。基于下面列出的试点数据，工作假设这一目标是CH诱导的VSM膜去极化刺激RhoA/Rho激酶途径，导致增加基础和激动剂诱导的肌丝Ca 2+敏感性。具体目标#3：建立NOX衍生的ROS在CH后介导增强的肌源性和激动剂依赖性肺血管收缩反应性中的作用。我们假设NOX去极化诱导的ROS产生上调CH后肺VSM中基础和激动剂诱导的RhoA/Rho激酶信号传导。拟议的研究将采用整个动物，离体肺，分离的血管和分子的方法，以建立一个新的机制之间的联系VSM膜去极化，NOX衍生的ROS的产生，和RhoA/ROK信号在高血压肺循环。总的来说，这些结果有望从根本上推进我们对ROK调节血管张力的信号机制以及有助于肺动脉高压发展的血管收缩机制的理解。 公共卫生相关性：慢性阻塞性肺病（COPD）如肺气肿和慢性支气管炎是美国死亡率和发病率的主要原因。COPD目前是美国第四大死因，预计到2020年将成为第三大死因（Sin，D. D.和Man，S.F. Proc Am Thorac Soc 2：8-11，2005）。本研究的目的是确定在COPD大鼠模型中导致肺动脉高压发展的因素。这种疾病状态导致血液氧合不良（缺氧），并且由此产生的肺动脉高压导致人类右心衰竭和死亡。

DESCRIPTION (provided by applicant): Chronic hypoxia (CH) associated with obstructive lung diseases and sleep apnea leads to pulmonary hypertension. Elevated basal vascular smooth muscle (VSM) tone and enhanced vasoconstrictor reactivity play a prominent role in mediating CH-induced pulmonary hypertension. However, the mechanisms by which CH elicits these vasoconstrictor responses are not understood. Pilot studies have revealed a novel effect of CH to promote myogenic tone and enhance vasoconstrictor reactivity through a RhoA/Rho kinase-dependent Ca2+-sensitization pathway in pulmonary VSM. These studies further suggest that CH-induced VSM membrane depolarization stimulates RhoA/Rho kinase independent of changes in VSM free Ca2+ levels, and provide intriguing evidence for a major contribution of NADPH oxidase (NOX)-derived reactive oxygen species (ROS) to this response. Therefore, the proposed studies will investigate the central hypothesis that CH- induced VSM membrane depolarization mediates NOX-dependent stimulation the RhoA/Rho kinase pathway leading to increased myogenic and agonist-induced myofilament Ca2+ sensitivity. This hypothesis will be addressed by the following specific aims: Specific Aim #1: Identify the intracellular signaling mechanism responsible for elevated myogenic and agonist-dependent constriction following CH. We hypothesize that CH augments pulmonary arterial myogenic tone and agonist-mediated constriction via RhoA/ROK-induced VSM Ca2+ sensitization. Specific Aim #2: Determine the contribution of membrane depolarization to increased basal and agonist-induced pulmonary arterial constriction following CH. Based on pilot data outlined below, the working hypothesis for this aim is that CH-induced VSM membrane depolarization stimulates the RhoA/Rho kinase pathway leading to increased basal and agonist-induced myofilament Ca2+ sensitivity. Specific Aim #3: Establish the role of NOX-derived ROS in mediating enhanced myogenic and agonist-dependent pulmonary vasoconstrictor reactivity following CH. We hypothesize that depolarization-induced ROS-generation by NOX upregulates basal and agonist-induced RhoA/Rho kinase signaling in pulmonary VSM following CH. The proposed research will employ whole animal, isolated lung, isolated vessel and molecular approaches to establish a novel mechanistic link between VSM membrane depolarization, NOX-derived ROS generation, and RhoA/ROK signaling in the hypertensive pulmonary circulation. Collectively, these outcomes are expected to fundamentally advance our understanding of signaling mechanisms by which ROK regulates vascular tone, as well as vasoconstrictor mechanisms that contribute to the development of pulmonary hypertension. PUBLIC HEALTH RELEVANCE: Chronic obstructive pulmonary diseases (COPD) such as emphysema and chronic bronchitis are established major causes of mortality and morbidity in the U.S. COPD is currently the fourth leading cause of death in the U.S. and is predicted to be the third leading cause of death by 2020 (Sin, D.D. and Man, S.F. Proc Am Thorac Soc 2:8-11, 2005). The aim of this study is to determine the factors responsible for the development of pulmonary hypertension in a rat model of COPD. Such disease states cause poor oxygenation of the blood (hypoxia), and the resultant pulmonary hypertension leads to right heart failure and mortality in humans.