Intrauterine chronic hypoxia and ryanodine receptors in fetal pulmonary arteries

描述（由申请人提供）：宫内应激可诱导功能的长期变化，使胎儿一生中易患疾病。由于高海拔生活、胎盘功能不全和吸烟引起的母体低氧血症使某些人群的婴儿处于发展肺动脉高压、高海拔肺水肿的风险中，并增加了在以后生活中发展特发性肺动脉高压的风险。在高海拔地区妊娠会导致胎羊发生各种肺血管畸形，包括内皮依赖性舒张功能抑制、肌细胞生长改变和反应性，这些都使胎羊在出生后有发生高血压的风险。事实上，高海拔妊娠和出生加剧了2周龄绵羊缺氧诱导的肺血管收缩，并导致肺动脉高压的显著渗透。因此，绵羊是了解与胎儿肺血管疾病起源相关的新途径和机制的相关模型，因为高海拔妊娠引起的低氧血症重现了人类中发现的疾病。其基本焦点是兰尼碱受体（RyR）是肺动脉收缩过程中对急性肺泡缺氧的反应的中心，其可在肺动脉高压个体中失调。三种RyR亚型是已知的，并且所有三种对于肺动脉中急性缺氧的固有血管收缩反应都是至关重要的。RyR通道病变积极参与神经元、骨骼肌、心脏和血管疾病的发病机制，但其在肺血管疾病的胎儿编程中的作用尚不清楚。该项目的中心假设是，高海拔妊娠将抑制RyR介导的局部Ca2+“火花”和全球Ca2+反应，由于急性缺氧，这些反应将表现为RyR表达的减少。我们提出这种平衡机制，将增加血管收缩急性缺氧。这将有助于减少由于长期宫内缺氧引起的肺动脉高压的程度。中心假设是基于已发表的和对足月胎羊进行的初步研究。我们计划通过追求两个具体目标来检验我们的中心假设。具体目标1将确定是否高海拔妊娠抑制三个RyR亚型的表达。具体目标2将确定响应于急性缺氧的RyR介导的Ca2+反应和肺血管收缩的相应减少。将通过对足月胎羊肺动脉进行分子、组织化学和功能研究来检验这些假设。关于预期的结果，提出的工作预计将确定长期宫内缺氧对胎儿RyR功能的影响。这些研究有望通过将RyR与肺血管疾病联系起来，从根本上推进肺血管生物学领域。这样的结果将提供重要的积极影响，因为RyR极有可能为肺血管疾病的治疗干预提供新的靶点。 公共卫生相关性：我们提出的研究有助于为长期宫内缺氧在新生儿肺动脉高压发展中的作用提供机制基础。这些研究的目的是将兰尼碱受体与疾病的发病机制联系起来。这样的结果将提供重要的积极影响，因为兰尼碱受体极有可能为治疗干预提供新的靶点。

DESCRIPTION (provided by applicant): Intrauterine stress can induce long-lived changes in function that predispose the fetus for disease throughout life. Maternal hypoxemia due to high altitude living, placental insufficiency, and smoking puts infants of certain populations at risk o developing pulmonary hypertension, high altitude pulmonary edema, and increases the risk for development of idiopathic pulmonary hypertension later in life. Gestation at high altitude causes a variety of pulmonary vascular malformations in fetal sheep including suppressed endothelium dependent relaxation, altered myocyte growth, and reactivity that place them at risk of developing hypertension after birth. Indeed, high altitude gestation and birth exaggerates hypoxia induced pulmonary vasoconstriction in 2 week old sheep and results in significant penetration of pulmonary hypertension. Sheep are therefore a relevant model for understanding novel pathways and mechanisms associated with fetal origins of pulmonary vascular disease because hypoxemia due to high altitude gestation recapitulates disease found in humans. The fundamental focus is that ryanodine receptors (RyR) are central to the process of pulmonary arterial constriction in response to acute alveolar hypoxia, which can be dysregulated in individuals with pulmonary hypertension. Three RyR isoforms are known, and all three are vital to the intrinsic vasoconstrictor response to acute hypoxia in pulmonary arteries. RyR channelopathies actively participate in the pathogenesis of neuronal, skeletal muscle, cardiac, and vascular diseases and yet their role in fetal programming of pulmonary vascular disease is unknown. The central hypothesis of this project is that high altitude gestation will suppress RyR-mediated local Ca2+ "sparks" and global Ca2+ responses due to acute hypoxia and that these responses will be manifested by reductions in RyR expression. We propose this counterbalances mechanisms that would increase vascular contraction to acute hypoxia. This would help reduce the extent of pulmonary hypertension due to long-term intrauterine hypoxia. The central hypothesis is based on published and preliminary studies performed with full-term fetal sheep. We plan to test our central hypothesis by pursuing two Specific Aims. Specific Aim 1 will determine whether high altitude gestation suppresses the expression of the three RyR isoforms. Specific Aim 2 will determine the corresponding reduction in RyR mediated Ca2+ responses and pulmonary vasoconstriction in response to acute hypoxia. The hypotheses will be examined by performing molecular, histochemical, and functional studies in pulmonary arteries from term-fetal lambs. With regards to the expected outcomes, the work proposed is expected to identify the influence of long-term intrauterine hypoxia on RyR function in the fetus. These studies are expected to fundamentally advance the field of pulmonary vascular biology by associating RyRs with pulmonary vascular disease. Such results will provide an important positive impact, because RyRs are highly likely to provide novel targets for therapeutic interventions in the treatment of pulmonary vascular disease. PUBLIC HEALTH RELEVANCE: The investigations we propose help provide a mechanistic basis for the role of long-term intrauterine hypoxia in the development of pulmonary hypertension in the newborn. The goal of these studies is to associate ryanodine receptors with disease pathogenesis. Such results will provide an important positive impact, because ryanodine receptors are highly likely to provide novel targets for therapeutic interventions.