Metabolic mechanisms underlying bronchopulmonary dysplasia-associated pulmonary hypertension

总结 支气管肺发育不良（BPD）是早产儿的一种慢性肺部疾病，由机械性肺损伤引起。 通气和高氧等因素。30%的BPD婴儿会出现肺部疾病， 高血压（PH），其特征在于肺血管（PV）重构。没有治愈的疗法， 这种疾病。我的长期目标是开发新的靶向疗法来治疗BPD相关PH（BPD-PH）。 肺静脉重塑的特征是肺动脉中层增厚增加。这是由于 血管平滑肌细胞（SMC）增殖，或从内皮细胞（EC）转分化为SMC (i.e.,内皮-间充质转化，EndoMT）。我们已经证明，新生小鼠体内的高氧， 早产羔羊的机械通气引起肺静脉重塑，导致PH，这与增加 EndoMT。我们初步表明，EndoMT也观察到在肺的早产儿，需要 机械通气阻断EndoMT可防止新生儿高氧诱导的PV进展 提示EndoMT在诱导PH中起致病作用。我们观察到， 在高氧暴露的小鼠中，EdU掺入SMC的增加，表明这些细胞的增殖确实 我们最近报道，新生儿高氧会导致持续性肺静脉重构， 内皮肉毒碱棕榈酰转移酶1a（Cpt 1a）的减少，肉毒碱的限速酶 穿梭系统负责将长链脂肪酸转运到线粒体中用于脂肪代谢过程中的β-氧化 酸氧化我们的初步数据表明，肺Cpt 1a基因表达也减少，机械 通气的早产羔羊和早产人类婴儿。此外，Cpt 1a的内皮缺失增加 新生小鼠暴露于高氧后的EndoMT和PV重塑。此外，药理学 Cpt 1a的上调在体外减弱EndoMT并防止新生小鼠中PV重塑， 高氧。新生儿高氧和机械通气是否降低内皮细胞Cpt 1a，导致PH， 尚未确定。中心假设是新生儿高氧和机械通气导致 EndoMT通过下调内皮Cpt 1a水平，从而导致PV重塑和PH。我们将测试 这三个具体目标的假设。目的1将确定Cpt 1a 下调有助于EndoMT。在目标2中，我们将定义内皮细胞Cpt 1a减少的作用。 BPD-PH和EndoMT。在目标3中，我们将评估内皮Cpt 1a作为BPD-PH的治疗靶点， 羔羊和小鼠模型。临床相关的羔羊和小鼠模型与我们新的 产生的EC特异性Cpt 1a KO小鼠和新的EC靶向纳米颗粒递送系统提供了一种新的治疗方法。 创新的方法来揭示Cpt 1a下调介导EndoMT及其 这一贡献是重要的，因为它可能导致新的治疗方法 特异性靶向新生儿内皮Cpt 1a或EndoMT治疗BPD-PH。

SUMMARY Bronchopulmonary dysplasia (BPD) is a chronic lung disease in premature infants, caused by mechanical ventilation and hyperoxia amongst other factors. Thirty percent of infants with BPD develop pulmonary hypertension (PH), characterized by pulmonary vascular (PV) remodeling. There are no curative therapies for this disease. My long-term goal is to develop novel targeted therapies to treat BPD associated PH (BPD-PH). PV remodeling is characterized by increased pulmonary arterial media layer thickening. This results from proliferation of vascular smooth muscle cells (SMCs), or transdifferentiation from endothelial cells (ECs) to SMCs (i.e., endothelial-mesenchymal transition, EndoMT). We have shown that hyperoxia in newborn mice and mechanical ventilation in preterm lambs cause PV remodeling resulting in PH, which is associated with increased EndoMT. We preliminarily show that EndoMT is also observed in the lung of premature human infants requiring mechanical ventilation. Blocking EndoMT prevents the progression of neonatal hyperoxia-induced PV remodeling and PH in mice, suggesting that EndoMT plays a causative role in inducing PH. We observed no increase in EdU incorporation into SMCs in hyperoxia-exposed mice, suggesting proliferation in these cells does not contribute to PV remodeling in BPD-PH. We recently reported that neonatal hyperoxia causes a persistent reduction of endothelial carnitine palmitoyltransferase 1a (Cpt1a), the rate-limiting enzyme of the carnitine shuttle system responsible for transporting long-chain fatty acids into mitochondria for β-oxidation during fatty acid oxidation. Our preliminary data show that lung Cpt1a gene expression is also reduced in mechanically ventilated preterm lambs and premature human infants. Additionally, endothelial deletion of Cpt1a increases EndoMT and PV remodeling in neonatal mice after exposure to hyperoxia. Furthermore, pharmacological upregulation of Cpt1a attenuates EndoMT in vitro and prevents PV remodeling in neonatal mice in response to hyperoxia. Whether neonatal hyperoxia and mechanical ventilation reduce endothelial Cpt1a, leading to PH is yet to be determined. The central hypothesis is that neonatal hyperoxia and mechanical ventilation cause EndoMT by downregulating endothelial Cpt1a levels, thereby resulting in PV remodeling and PH. We will test this hypothesis in three Specific Aims. Aim 1 will determine the molecular mechanisms by which Cpt1a downregulation contributes to EndoMT. In Aim 2, we will define the contribution of endothelial Cpt1a reduction to BPD-PH and EndoMT. In Aim 3, we will evaluate endothelial Cpt1a as a therapeutic target for BPD-PH using both lamb and mouse models. The combination of clinically relevant lamb and mouse models with our newly generated EC-specific Cpt1a KO mice and the novel EC-targeted nanoparticle delivery system provides an innovative approach to uncover the mechanisms by which Cpt1a downregulation mediates EndoMT and its significant roles in BPD-PH. This contribution is significant because it is likely to result in new therapies specifically targeting endothelial Cpt1a or EndoMT in neonates to treat BPD-PH.