Intrauterine chronic hypoxia and ryanodine receptors in fetal pulmonary arteries

描述（由申请人提供）：宫内应激可引起长期的功能变化，使胎儿终生易患疾病。由于高海拔生活、胎盘功能不全和吸烟导致的母亲低氧血症使某些人群的婴儿有发生肺动脉高压、高原肺水肿的风险，并增加了以后发生特发性肺动脉高压的风险。高海拔妊娠可导致胎羊肺血管畸形，包括内皮依赖性松弛抑制、心肌细胞生长改变和反应性改变，使胎羊在出生后有患高血压的风险。的确，高海拔妊娠和分娩会加重缺氧引起的2周龄绵羊肺血管收缩，并导致肺动脉高压的显著渗透。因此，绵羊是理解与肺血管疾病胎儿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再现了人类发现的疾病。基本的焦点是，ryanodine受体（RyR）是响应急性肺泡缺氧的肺动脉收缩过程的核心，这可能在肺动脉高压患者中失调。已知有三种RyR亚型，这三种亚型对肺动脉急性缺氧时的内在血管收缩反应至关重要。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，高海拔妊娠会抑制RyR介导的局部Ca2+“火花”和由于急性缺氧引起的全局Ca2+反应，这些反应将通过RyR表达的减少来表现。我们提出这种平衡机制会增加急性缺氧时血管收缩。这将有助于减少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。特异性Aim 1将确定高海拔妊娠是否抑制三种RyR亚型的表达。特异性Aim 2将确定急性缺氧时RyR介导的Ca2+反应和肺血管收缩的相应减少。这些假设将通过对足月胎儿羔羊的肺动脉进行分子、组织化学和功能研究来检验。关于预期结果，本研究旨在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RyRs与肺血管疾病联系起来，从根本上推动肺血管生物学领域的发展。这些结果将提供重要的积极影响，因为ryr极有可能为治疗肺血管疾病的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.