DEVELOPMENTAL REGULATION OF OXYGEN SENSING IN THE LUNG

出生时，肺循环会发生剧烈变化。肺血流量增加8-10倍，而肺动脉(PA)压力下降。如果肺循环没有过渡到高流量、低压力回路，则会导致新生儿持续性肺动脉高压(PPHN)。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管理不完全反应。目前既不能预防也不能治愈。由于对肺循环出生后适应机制的不完全了解，治疗方案受到影响。虽然氧气压力的急剧升高显然是围产期肺血管扩张的基本生理刺激，但氧气传感器的身份仍不清楚。因此，围产期肺血管感觉和血管扩张对氧分压急剧升高的反应机制仍不完全清楚。治疗策略因缺乏治疗的分子靶点而受到影响。这一建议旨在确定肺血管系统对氧分压急剧增加的反应能力是否受到发育调节，以及允许围产期肺循环对氧分压增加做出反应的亚细胞机制。有证据表明，PA平滑肌细胞(SMC)上的钾(K)通道是O2的感受器。我们实验室的研究表明，钙敏感钾(Kca)通道在调节围产期肺循环对氧气浓度急剧升高的反应中起着核心作用。我们提出的工作假设是氧气通过细胞内钙释放激活KCA通道，引起PA-SMC-Em超极化，从而促进围产期肺血管扩张。目的1.Kca通道是妊娠晚期胎儿和新生儿PA-SMC O2感觉的主要组成部分，是发育调节的；2.通过钙火花激活PA-SMC-KCA通道有助于围产期肺血管扩张。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、免疫细胞化学和整个动物生理学进行实验。这些实验将确定新生儿肺循环中可能受到发育调节的氧气传感器，并阐明导致其激活的亚细胞过程，从而为解决新生儿肺血管疾病提供一个新的分子靶点。

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.