Pulmonary Vasoreactivity Following Chronic Hypoxia

描述(申请人提供)：慢性低氧(CH)与阻塞性肺疾病和睡眠呼吸暂停相关，可导致肺动脉高压。基础血管平滑肌(VSM)张力升高和血管收缩反应性增强在CH诱导的肺动脉高压中起重要作用。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激酶依赖的钙敏化途径在肺VSM中促进肌源性张力和增强血管收缩反应的新作用。这些研究进一步表明，CH诱导的VSM膜去极化刺激RhoA/Rho激酶不依赖于VSM游离钙水平的变化，并为NADPH氧化酶(NOX)衍生的活性氧物种(ROS)在这一反应中的主要贡献提供了有趣的证据。因此，建议的研究将探讨一个中心假设，即CH诱导的VSM膜去极化介导了NOX依赖的刺激RhoA/Rho激酶途径，导致肌源性和激动剂诱导的肌丝钙敏感性增加。这一假说将通过以下特定目标来解决：特定目标#1：确定导致脑出血后肌源性和激动剂依赖性收缩升高的细胞内信号机制。我们推测，CH通过RhoA/ROK诱导的VSM钙敏化而增强肺动脉肌源性张力和激动剂介导的收缩。具体目标#2：确定膜去极化对CH后基础和激动剂诱导的肺动脉收缩增加的贡献。基于下面概述的先导数据，这一目的的工作假设是CH诱导的VSM膜去极化刺激RhoA/Rho激酶途径，导致基础和激动剂诱导的肌丝钙敏感性增加。具体目标#3：确定NOX衍生的ROS在介导CH后增强的肌源性和激动剂依赖的肺血管收缩反应中的作用。我们推测，在CH后肺VSM中，NOX去极化诱导的ROS生成上调了基础和激动剂诱导的RhoA/Rho激酶信号。这项研究将采用全动物、离体肺、离体血管和分子方法，在高血压性肺循环中VSM膜去极化、NOX产生的ROS和RhoA/ROK信号之间建立新的机制联系。总的来说，这些结果有望从根本上促进我们对韩国调节血管张力的信号机制以及导致肺动脉高压发展的血管收缩机制的理解。 公共卫生相关性：肺气肿和慢性支气管炎等慢性阻塞性肺疾病(COPD)是美国死亡和发病率的主要原因。COPD目前是美国第四大死亡原因，预计到2020年将成为第三大死亡原因(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慢性阻塞性肺疾病大鼠模型中导致肺动脉高压的因素。这种疾病状态会导致血液氧合不良(缺氧)，由此产生的肺动脉高压会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.