ROS in Episodic Hypoxia-Induced Cardiovascular Dysfunct*

描述(由申请人提供)： 睡眠呼吸暂停是一种常见的呼吸障碍，经常与神经和心血管并发症有关。然而，导致睡眠呼吸暂停患者心血管功能障碍的分子机制仍不清楚。睡眠中慢性间歇性低氧(CIH)是人类睡眠呼吸暂停的标志。强有力的证据表明，睡眠呼吸暂停会增加心血管疾病的发病率和死亡率。目前研究的主要目的是阐明在睡眠呼吸暂停期间脑出血导致的神经介导的心血管功能障碍的ROS产生增加的分子机制。目前应用的工作假设是，CIH期间氧浓度的波动模拟了缺血(缺氧)/复氧过程，因此将增加细胞ROS的产生。脑出血后ROS的产生增加是导致压力感受性反射敏感性减弱、心脏轴突变性，进而导致心血管功能障碍的早期和主要事件。相反，增加抗氧化剂或抗氧化酶活性，有效地抑制ROS介导的氧化应激的启动和传播，可能会减少或预防CIH诱导的心血管功能障碍。我们提出了以下特定的目标来验证这一假说，即增加ROS的产生/抗氧化酶的表达可以促进/预防CIH引起的神经介导的心血管功能障碍。1.建立并鉴定模拟人类睡眠呼吸暂停的脑出血致心血管功能障碍小鼠模型。具体地说，我们将首先定义诱导心血管功能障碍所需的缺氧程度、周期频率和暴露时间，表现为血压升高、压力反射敏感性减弱和脑心连接减少。2.鉴定和分析CIH诱导的ROS生成增加在心血管功能障碍中的分子事件。具体地说，我们将结合自由基化学、生物化学和分子生物学技术来确定特定的ROS产生(氧化应激传播)，它可能导致脑干神经细胞损伤，导致小鼠模型和细胞培养系统中的心血管功能障碍。3.明确ROS产生/抗氧化酶表达增强在心血管功能障碍的贡献/预防中的基础作用。具体地说，我们将利用转基因和基因敲除小鼠的方法来检验增强/降低抗氧化酶的表达是否会减弱/促进先前定义的由脑出血引起的心血管功能障碍。由于睡眠呼吸暂停是心血管功能障碍的重要危险因素，而慢性间歇性低氧是睡眠呼吸暂停的基本因素，分析ROS介导的心血管功能障碍的分子过程可能有助于开发有效的治疗方法来降低与睡眠呼吸暂停相关的心血管疾病的风险。

DESCRIPTION (provided by applicant): Sleep apnea is a common breathing disorder that is frequently associated with neurological and cardiovascular complications. However, the molecular mechanisms resulting in the cardiovascular dysfunction in sleep apnea remain largely unknown. Chronic intermittent hypoxia (CIH) during sleep is a hallmark of human sleep apnea. Strong evidence suggests that sleep apnea can increase cardiovascular morbidity and mortality. The major objective of the current research application is to delineate the molecular mechanisms of enhanced reactive oxygen species (ROS) production that result in the neural-mediated cardiovascular dysfunction induced by CIH during sleep apnea. The working hypothesis of the current application is that the oscillations in oxygen concentration during CIH mimic the ischemia (hypoxia)/re-oxygenation process and therefore will increase cellular ROS generation. Enhanced ROS production by CIH is the early and cardinal event that will attenuate baroreflex sensitivity, induce cardiac axonal degeneration, and consequently contribute to the cardiovascular dysfunction. Conversely, increasing antioxidants or antioxidant enzymatic activity that effectively inhibits ROS-mediated oxidative stress initiation and propagation may reduce or prevent CIH-induced cardiovascular dysfunction. The following specific aims are proposed to test the hypothesis that increased ROS production/antioxidant enzyme expression can facilitate/prevent neural-mediated cardiovascular dysfunction by CIH. 1. To establish and characterize a mouse model of CIH-induced cardiovascular dysfunction mimicking human sleep apnea. Specifically, we will first define the magnitude of hypoxia, cycle frequency, and exposure duration required for induction of cardiovascular dysfunction, as evidenced by elevated blood pressure, attenuated baroreflex sensitivity, and reduced brain-heart connections. 2. To identify and analyze molecular events of enhanced ROS production induced by CIH on the cardiovascular dysfunction. Specifically, we will combine free radical chemistry, biochemistry and molecular biology techniques to identify specific ROS production (oxidative stress propagation) that potentially contributes to brainstem neuronal cell damage leading to the cardiovascular dysfunction in the mouse model and in cell culture systems. 3. To define the fundamental roles of enhanced ROS production/antioxidant enzyme expression in the contribution/prevention of cardiovascular dysfunction. Specifically, we will utilize transgenic and knockout mouse approaches to examine whether enhanced/decreased antioxidant enzyme expression will attenuate/facilitate the previously defined cardiovascular dysfunctions induced by CIH. Since sleep apnea is a significant risk factor for cardiovascular dysfunction and chronic intermittent hypoxia is the essential element of sleep apnea, analysis of the molecular processes of ROS-mediated cardiovascular dysfunction may contribute significantly to the development of effective therapeutic approaches to reduce the risks of cardiovascular diseases associated with sleep apnea.