O2-CHEMOSENSING BY REATIVE OXYGEN SPECIES/NADPH OXIDASE

描述（由申请人提供）：颈动脉体内的o2感应发生在神经外胚来源的I型血管球细胞中，其中缺氧引起复杂的化学转导级联，包括膜去极化、ca2 +进入和兴奋性神经递质的释放。了解这些细胞对o2敏感的努力主要集中在PO2和K+通道活性之间的关系上。目前的一种假设认为，局部PO2和K+通道的开闭状态之间的耦合是由一种吞噬细胞样的多亚基酶NADPH氧化酶介导的，该酶产生活性氧（ROS）与普遍存在的PO2成比例。在肺神经上皮小体（NEB）中含有的o2敏感细胞中，实验证实缺氧时ROS水平降低，并且NADPH氧化酶产生的ROS确实控制着E - M和K+通道活性。然而，我们实验室最近的研究表明，由非吞噬形式的NADPH氧化酶产生的ROS是化学转导的重要参与者，但它们在I型细胞中的作用与NEB所利用的机制根本不同。我们建议验证一种假设，即在缺氧的反应中，NADPH氧化酶活性在I型细胞中增加，并且进一步。在低氧条件下产生的ROS水平的增加通过激活一部分K+通道促进了膜的再极化。此外，我们将研究非吞噬性NADPH氧化酶介导颈动脉体暴露于慢性缺氧（CH）诱导的适应性形态和生理调节的假设，慢性缺氧是临床上发生在睡眠呼吸暂停和慢性阻塞性肺疾病（COPD）中的一种情况。研究将包括：1 .对I型细胞中ROS产生的来源和机制的研究；NADPH氧化酶和ROS在颈动脉急性缺氧机体反应中的作用3。NADPH氧化酶亚基在颈动脉组织中的表达以及CH的影响；4 . NADPH氧化酶和ROS在颈动脉机体对CH的适应中的作用。

DESCRIPTION (provided by applicant): O2-sensing in the carotid body occurs in neuroectoderm-derived type I glomus cells where hypoxia elicits a complex chemotransduction cascade involving membrane depolarization, Ca 2+ entry and the release of excitatory neurotransmitters. Efforts to understand the exquisite O2-sensitivity of these cells focus primarily on the relationship between PO2 and the activity of K+-channels. A current hypothesis proposes that coupling between local PO2 and the open-closed state of K+-channels is mediated by a phagocytic-like multisubunit enzyme, NADPH oxidase, which produces reactive oxygen species (ROS) in proportion to the prevailing PO2. In O2-sensitive cells contained in lung neuroepithelial bodies (NEB), experiments have confirmed that ROS levels decrease in hypoxia, and that E M and K+-channel activity are indeed controlled by ROS produced by NADPH oxidase. However, recent studies in our laboratory suggest that ROS generated by a non-phagocytic form of NADPH oxidase, are important contributors to chemotransduction, but that their role in type I cells differs fundamentally from the mechanism utilized by NEB. We propose to test the hypothesis that in response to hypoxia, NADPH oxidase activity is increased in type I cells, and further, that increased ROS levels generated in response to low-O2 facilitate membrane re-polarization via the activation of a subset of K+-channels. In addition, we will examine the hypothesis that a non-phagocytic NADPH oxidase mediates adaptive morphological and physiological adjustments induced by exposure of the carotid body to chronic hypoxia (CH), a condition that occurs clinically in sleep apnea and chronic obstructive pulmonary disease (COPD). Studies will include: I. An examination of the sources and mechanisms of ROS production in type I cells, II. Evaluation of the involvement of NADPH oxidase and ROS in the carotid body response to acute hypoxia; III. The expression of NADPH oxidase subunits in the carotid body; and the effects of CH; and IV. The role of NADPH oxidase and ROS in carotid body adaptation to CH.