DEVELOPMENTAL REGULATION OF OXYGEN SENSING IN THE LUNG

出生时，肺循环发生了巨大的变化。肺血流量增加8-10倍，肺动脉压下降。如果肺循环没有过渡到高流量，低压回路，那么新生儿持续性肺动脉高压（PPHN）的结果。PPHN的特点是肺血管张力和反应性增加，导致严重的中枢性低氧血症，对补充O2和其他血管扩张剂刺激的反应不完全。目前既无法预防，也无法治愈。由于对产后肺循环适应机制的不完全了解，治疗方案受到损害。虽然O2张力的急性升高显然是围产期肺血管舒张的必要生理刺激，但O2传感器的身份尚不清楚。因此，围产期肺血管感觉和血管舒张以响应急性氧张力升高的机制仍不完全清楚。由于缺乏治疗的分子靶点，治疗策略受到损害。本研究旨在确定肺血管系统对急性氧张力升高的反应能力是否受到发育调节，以及允许围产期肺循环血管舒张以应对氧张力升高的亚细胞机制。有证据表明，PA平滑肌细胞（SMC）中的钾（K+）通道起O2传感器的作用。我们实验室的工作表明，钙敏感的K+ (KCa)通道在介导围产期肺循环对急性氧张力升高的反应中起着核心作用。我们提出工作假说，氧气通过细胞内钙释放激活KCa通道，引起PA SMC Em超极化，有助于围产期肺血管舒张。具体目的是检验以下假设：目标1。KCa通道是孕晚期胎儿和新生儿PA SMC O2感知的主要组成部分，并受发育调节[2]。通过Ca2+火花激活PA SMC KCa通道有助于围产期肺血管舒张。为了验证这些假设，我们计划使用电生理学、动态钙成像、共聚焦显微镜、分子生物学、免疫细胞化学和全动物生理学进行实验。该实验将明确鉴定新生儿肺循环中可能受发育调节的O2传感器，并阐明导致其激活的亚细胞过程，从而为治疗新生儿肺血管疾病提供新的分子靶点。

At birth, the pulmonary circulation changes dramatically. Pulmonary blood flow increases 8-10 fold while pulmonary arterial (PA) pressure declines. If the pulmonary circulation does not make the transition to a high flow, low pressure circuit, then persistent pulmonary hypertension of the newborn (PPHN) results. PPHN is characterized by increased pulmonary vascular tone and reactivity, resulting in severe central hypoxemia that responds incompletely to the administration of supplemental O2 and other vasodilator stimuli. Neither prevention nor cure is currently available. Treatment options are compromised by incomplete understanding of the mechanisms responsible for postnatal adaptation of the pulmonary circulation. While the acute increase in O2 tension is clearly an essential physiologic stimulus for pulmonary vasodilation in the perinatal period, the identity of the O2 sensor remains unknown. Thus, the mechanism whereby the perinatal pulmonary vasculature senses and vasodilates in response to the acute increase in O2 tension remains incompletely understood. Treatment strategies are compromised by the lack of molecular targets for therapy. This proposal seeks to determine whether the ability of the pulmonary vasculature to respond to an acute increase in O2 tension is developmentally regulated and the subcellular mechanisms that allow the perinatal pulmonary circulation to vasodilate in response to an increase in O2 tension. Evidence suggests that potassium (K+) channels in PA smooth muscle cells (SMC) act as the O2 sensor. Work from our laboratory suggests that the calcium-sensitive K+ (KCa) channel plays a central role in mediating the response of the perinatal pulmonary circulation to an acute increase in O2 tension. We propose the working HYPOTHESIS that oxygen activates a KCa channel through intracellular calcium release to cause PA SMC Em hyperpolarization, contributing to perinatal pulmonary vasodilation. The specific aims are to test the following hypotheses: Aim 1. The KCa channel is a major component of PA SMC O2 sensing in the late-gestation fetus and newborn and is developmentally regulated Aim 2. Activation of the PA SMC KCa channel through Ca2+ sparks contributes to perinatal pulmonary vasodilation. To test these hypotheses, we plan experiments using electrophysiology, dynamic calcium imaging, confocal microscopy, molecular biology, immunocytochemistry, and whole animal physiology. The experiments will provide definitive identification of an O2 sensor in the neonatal pulmonary circulation that may be developmentally regulated and elucidate the subcellular processes that lead to its activation, thereby providing a novel molecular target to address neonatal pulmonary vascular disease.