Mechanism of perinatal-hyperoxic suppression of chemoreceptor function

描述(申请人提供)：颈动脉小体化学感受器是呼吸/心血管系统的主要传感器，用于快速检测缺氧(低血氧)。它们的刺激启动了一些保护性反射，包括增加呼吸的动力，从睡眠中唤醒和升高血压。先前发表的结果表明，在出生后紧随其后的关键时期暴露于高氧(高血氧)会导致对急性缺氧的呼吸反应受损，这种损害持续终生，尽管氧气恢复到正常水平。我们提出的研究的目的是确定高氧暴露导致化学感受器功能受损的机制。我们实验室的工作表明，在常氧和急性低氧暴露期间，高氧暴露会导致传入神经活性大幅下降。氧感觉受损是由于球体细胞功能的改变，球体细胞是与传入神经末梢相连的突触前细胞，通常被认为是缺氧的转导部位。基因芯片分析(并通过实时、半定量聚合酶链式反应证实)表明，高氧减少了参与分泌颗粒合成的多个基因的表达，并减少了一些离子通道的表达，这些离子通道被认为参与了低氧介导的球体细胞去极化，特别是TASK-1和TASK-3。此外，高氧暴露降低了球体细胞对急性缺氧的去极化和分泌反应。拟议的研究将检验遗传变化的时间进程，并将其与通过分泌(伏安法)、器官功能(单个轴突上的尖峰活动)和球体细胞对缺氧的生物物理反应(去极化、钙反应)评估的器官功能变化相关联。将通过基因芯片分析来评估对器官功能至关重要并被高氧改变的基因的鉴定，并通过聚合酶链式反应和定量免疫组织化学进行确认。功能的确认将通过抑制候选基因的siRNA来进行。预期的结果将确定围产期高氧改变的外周化学感受器内的关键成分。由于高氧血症在临床上广泛应用于新生儿，尤其是早产儿，这些结果对于理解这种干预引起的生理变化很重要。

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.