Oxidative stress in pulmonary circulation during birth related transition

描述（由申请方提供）：胎儿的肺血管阻力（PVR）在出生时急剧下降，以促进出生后的气体交换。出生时暴露于较高的氧分压在这种适应中起着重要作用。内皮型一氧化氮合酶（eNOS）调节PVR的转变，并直接受到氧的刺激，间接受到氧化磷酸化和ATP释放增加的刺激。氧化磷酸化也产生超氧化物（O27-）作为副产物。然而，在这个过渡期调节胎儿肺动脉线粒体氧化应激的机制仍不清楚。出生时PVR未能降低会导致新生儿持续性肺动脉高压（PPHN），这是一种与肺动脉氧化应激增加相关的疾病。识别氧化应激的来源对于开发纠正PPHN血管功能障碍的特异性治疗至关重要。在胎羊肺动脉内皮细胞（PAEC）的研究表明，暴露于ATP，NOS激动剂，或过渡到出生后的氧张力刺激协会eNOS与线粒体外膜蛋白，孔蛋白。NOS激动剂增加胎儿PAEC线粒体NO释放。我们提出了一种新的假设，即eNOS靶向线粒体外膜调节率的氧化磷酸化和O27的产生在PAEC有针对性的NO释放在出生相关的过渡。拟议研究的广泛具体目的是（1）研究eNOS -线粒体相互作用是否在PAEC中与出生相关的转变期间调节线粒体O27-，并确定这种靶向机制，以及（2）确定eNOS-线粒体相互作用是否调节对出生后适应至关重要的内皮功能：NO、PGI 2和内皮素-1的合成以及出生后肺血管舒张。将在PAEC和完整胎羊中进行研究。将开发细胞生物学工具以（A）将eNOS靶向至胎儿PAEC中的特定亚细胞区室和（B）抑制eNOS与参与线粒体靶向的客户蛋白-hsp 90和孔蛋白的相互作用。这些研究将探讨出生时氧暴露过程中线粒体氧化应激的新调控机制。PAEC中这种新的氧化应激来源的鉴定可能导致更特异性的治疗，例如线粒体靶向抗氧化剂以恢复PPHN中的肺血管舒张和氧合。 公共卫生相关性：出生时胎儿肺暴露于氧气介导了肺血流量的增加，这是出生后建立气体交换所必需的。氧增加线粒体中的代谢，这反过来又可以增加自由基的产生。拟议的研究将调查一种新的机制，调节自由基的形成，在这种适应。

DESCRIPTION (provided by applicant): Pulmonary vascular resistance (PVR) in the fetus undergoes a dramatic decrease at birth to facilitate gas exchange during postnatal life. Exposure to higher oxygen tension at birth plays a major role in this adaptation. Endothelial nitric oxide synthase (eNOS) regulates the transition in PVR and is stimulated directly by oxygen and indirectly by an increase in oxidative phosphorylation and ATP release. Oxidative phosphorylation also generates superoxide (O27-) as a byproduct. However, the mechanisms that regulate mitochondrial oxidative stress in the fetal pulmonary arteries during this transition remain unclear. Failure of PVR to decrease at birth leads to persistent pulmonary hypertension of the newborn (PPHN), a condition associated with increased oxidative stress in pulmonary arteries. Identification of the sources of oxidative stress is critical to the development of specific therapies to correct the vascular dysfunction in PPHN. Studies in fetal lamb pulmonary artery endothelial cells (PAEC) demonstrated that exposure to ATP, a NOS agonist, or transition to postnatal oxygen tension stimulate the association of eNOS with the mitochondrial outer membrane protein, porin. NOS agonists increase mitochondrial NO release in fetal PAEC. We propose to investigate the novel hypothesis that targeting of eNOS to the mitochondrial outer membrane regulates the rate of oxidative phosphorylation and O27- generation in PAEC by targeted NO release during birth- related transition. The broad specific aims of the proposed studies are to (1) Investigate whether eNOS - mitochondrial interactions regulate the mitochondrial O27- during birth related transition in PAEC and to define the mechanism of this targeting and (2) determine whether eNOS-mitochondrial interactions regulate the endothelial functions critical to postnatal adaptation: synthesis of NO, PGI2 and endothelin-1 and postnatal pulmonary vasodilation. Studies will be done in PAEC and intact fetal lambs. Cell biology tools will be developed to (A) target eNOS to specific sub-cellular compartments in fetal PAEC and (B) to inhibit the interactions of eNOS with the client proteins involved in mitochondrial targeting - hsp90 and porin. The proposed studies will investigate a new regulatory mechanism for the mitochondrial oxidative stress during oxygen exposure at birth. Identification of this new source of oxidative stress in PAEC may lead to more specific therapies, such as mitochondrial targeted anti- oxidants to restore pulmonary vasodilation and oxygenation in PPHN. PUBLIC HEALTH RELEVANCE: Exposure of the fetal lung to oxygen at birth mediates the increase in pulmonary blood flow which is necessary to establish gas exchange during postnatal life. Oxygen increases the metabolism in mitochondria which in turn can increase free radical production. The proposed studies will investigate a new mechanism that regulates the formation of free radicals during this adaptation.