O2-CHEMOSENSING BY REATIVE OXYGEN SPECIES/NADPH OXIDASE

描述(申请人提供)：颈动脉小体的O2-感觉发生在神经外胚层来源的I型球体细胞中，低氧引起复杂的化学转导级联反应，涉及膜去极化、钙进入和兴奋性神经递质的释放。了解这些细胞对O2的敏感度的努力主要集中在PO2和K+通道活性之间的关系。目前的一个假说认为，局部PO2与K+通道的开闭状态之间的偶联是由一种类似吞噬细胞的多亚单位酶NADPH氧化酶介导的，该酶产生与PO2成比例的活性氧物种(ROS)。在肺神经上皮体(NEB)中的O2敏感细胞中，实验证实了缺氧时ROS水平降低，E-M和K+通道活性确实受NADPH氧化酶产生的ROS控制。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是化学转导的重要贡献者，但它们在I型细胞中的作用与NEB所利用的机制有根本的不同。我们建议检验这一假设，即在对缺氧的反应中，I型细胞中NADPH氧化酶的活性增加，并且进一步地，在低O2反应中产生的更高的ROS水平通过激活K+通道的子集来促进膜的复极化。此外，我们将检验一种假设，即非吞噬的NADPH氧化酶介导了颈动脉体慢性缺氧(CH)诱导的适应性形态和生理调节，慢性缺氧(CH)是临床上睡眠呼吸暂停和慢性阻塞性肺疾病(COPD)的一种情况。研究包括：1.研究I型细胞产生ROS的来源和机制；2.评价NADPH氧化酶和ROS在颈动脉小体对急性缺氧反应中的作用；3.NADPH氧化酶亚基在颈动脉小体中的表达；以及CH的作用；以及IV.NADPH氧化酶和ROS在颈动脉小体对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.