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疾病，通常与神经和心血管并发症有关。然而，导致睡眠呼吸暂停心血管功能障碍的分子机制仍然很大程度上未知。睡眠期间慢性间歇性缺氧（CIH）是人类睡眠呼吸暂停的一个标志。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。当前研究应用的主要目标是阐明活性氧 (ROS) 产生增强的分子机制，从而导致睡眠呼吸暂停期间 CIH 引起的神经介导的心血管功能障碍。当前应用的工作假设是 CIH 期间氧浓度的波动模拟缺血（缺氧）/再氧合过程，因此会增加细胞 ROS 的生成。 CIH 增加的 ROS 产生是早期的主要事件，会减弱压力反射敏感性，诱导心脏轴突变性，从而导致心血管功能障碍。相反，增加抗氧化剂或抗氧化酶活性，有效抑制 ROS 介导的氧化应激的引发和传播，可能会减少或预防 CIH 诱导的心血管功能障碍。提出以下具体目标来检验以下假设：增加 ROS 产生/抗氧化酶表达可以促进/预防 CIH 引起的神经介导的心血管功能障碍。 1. 建立模仿人类睡眠呼吸暂停的 CIH 诱发心血管功能障碍的小鼠模型并对其进行表征。具体来说，我们将首先定义诱发心血管功能障碍所需的缺氧程度、周期频率和暴露持续时间，如血压升高、压力反射敏感性减弱和脑心连接减少所证明的那样。 2. 识别和分析CIH诱导的ROS产生增强对心血管功能障碍的分子事件。具体来说，我们将结合自由基化学、生物化学和分子生物学技术来识别特定的 ROS 产生（氧化应激传播），这种产生可能导致脑干神经元细胞损伤，从而导致小鼠模型和细胞培养系统中的心血管功能障碍。 3. 确定增强的ROS产生/抗氧化酶表达在促进/预防心血管功能障碍中的基本作用。具体来说，我们将利用转基因和基因敲除小鼠方法来检查抗氧化酶表达的增强/减少是否会减弱/促进先前定义的由 CIH 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，而慢性间歇性缺氧是睡眠呼吸暂停的基本要素，因此对ROS介导的心血管功能障碍的分子过程的分析可能有助于开发有效的治疗方法，以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.