Mechanism of perinatal-hyperoxic suppression of chemoreceptor function

描述（由申请人提供）：颈动脉体化学感受器是呼吸/心血管系统用于快速检测缺氧（低血氧）的主要传感器。它们的刺激引发了一系列保护性反射，包括呼吸的动力增加、从睡眠中唤醒和血压升高。先前发表的研究结果表明，在出生后的关键时期暴露于高氧（高血氧）会导致急性缺氧的通气反应受损，这种损害持续一生，尽管恢复到正常的氧气水平。我们提出的研究目的是确定高氧暴露导致化学受体功能受损的机制。我们实验室的研究表明，在正常缺氧和急性缺氧暴露期间，高氧暴露会导致传入神经活动的大量减少。氧感知受损是由于血管球细胞功能的改变引起的，血管球细胞是连接传入神经末梢的突触前细胞，通常被认为是缺氧转导的部位。基因芯片分析（并通过实时半定量PCR证实）表明，高氧降低了参与分泌颗粒合成的多个基因的表达，并降低了一些离子通道的表达，这些离子通道被认为参与缺氧介导的肾小球细胞去极化，特别是TASK-1和TASK-3。此外，高氧暴露降低了血管球细胞对急性缺氧的去极化和分泌反应。拟议的研究将检查遗传变化的时间过程，并将其与器官功能的变化联系起来，通过分泌（伏安法）、器官功能（单轴突上的尖峰活动）和血管球细胞缺氧的生物物理反应（去极化，钙反应）来评估。通过基因芯片分析、PCR和定量免疫组织化学鉴定对器官功能至关重要的基因和高氧改变的基因。将使用siRNA抑制候选基因来确认功能。预期的结果将确定围生期高氧改变的外周化学感受器内的关键元素。由于高氧在临床上广泛应用于新生儿，特别是早产儿，这些结果对于理解这种干预引起的生理改变很重要。

DESCRIPTION (provided by applicant): Carotid body chemoreceptors are the primary sensors of the respiratory/cardiovascular system for the rapid detection of hypoxia (low blood oxygen). Their stimulation initiates a number of protective reflexes, including an increase in drive to breathe, arousal from sleep and increased blood pressure. Previous, published results demonstrated that exposure to hyperoxia (high blood oxygen) during critical periods in the time immediately after birth results in an impaired ventilatory response to acute hypoxia, an impairment that lasts throughout life, despite a return to normal levels of oxygen. The purpose of our proposed study is to identify the mechanism by which hyperoxia exposure results in impaired chemoreceptor function. Work from our laboratories demonstrate that hyperoxia exposure results in a large decrease in afferent nerve activity during normoxia and during acute hypoxia exposure. The impaired oxygen sensing appears due to alterations in the function of glomus cells - cells presynaptic to the afferent nerve endings and which are generally believed to be the site of transduction of hypoxia. Gene chip analysis (and confirmation by real-time, semi-quantitative PCR) demonstrate that hyperoxia reduces expression of multiple genes involved in the synthesis of secretory granules and reduces expression of some ion channels which are proposed to be involved in hypoxia-mediated depolarization of glomus cells, specifically TASK-1 and TASK-3. Furthermore, the depolarization and secretory responses of glomus cells to acute hypoxia are reduced by hyperoxia exposure. The proposed studies will examine the time course of genetic changes and correlate this with changes in organ function as assessed by secretion (voltammetry), organ function (spiking activity on single axons) and biophysical responses to hypoxia of glomus cells (depolarization, calcium responses). Identification of genes critical for organ function and which are altered by hyperoxia will be assessed by gene chip analyses and confirmation by PCR and quantitative immunohistochemistry. Confirmation of function will be undertaken using siRNA suppression of candidate genes. The anticipated results will identify critical elements within peripheral chemoreceptors which are altered by perinatal hyperoxia. Since hyperoxia is extensively used clinically in newborn and, especially in premature infants, these results are important in understanding physiologic alterations caused by this intervention.