Chronic progressive hypoxia-induced pulmonary hypertension in newborns

描述（由申请人提供）：我们的长期目标是改进慢性进行性肺动脉高压（CPPH）婴儿慢性心肺疾病伴持续性和偶发性缺氧的治疗方法。为此，我们在新生猪中建立了CPPH模型。我们的研究表明，慢性缺氧3天后，肺动脉高压发生，肺血管中血管扩张剂NO的生成完好无损。当缺氧暴露时间延长至10天时，肺动脉高压加重，并伴有肺血管NO生成减少。由此可见，抵消或恢复NO信号的损伤可以改善CPPH。我们的实验设计将验证口服l -瓜氨酸（l -精氨酸和一氧化氮的前体）治疗可以增加肺血管一氧化氮的产生并改善慢性缺氧引起的肺动脉高压的进行性发展的假设。本研究的目的是：1)评估l -瓜氨酸增加肺血管NO生成的能力和机制2)评估口服l -瓜氨酸改善慢性缺氧性肺动脉高压的有效性和安全性。治疗开始于低氧放置当天，持续3天或10天的全低氧暴露将决定预防肺动脉高压的能力。在缺氧第3天结束时开始治疗并持续缺氧7天，将评估阻止或逆转肺动脉高压进展的能力。作为第一个目标的一部分，将进行研究，以解决目前我们对l -瓜氨酸来源、可用性和加工的知识差距。这将包括确定慢性缺氧是否会降低血浆（细胞外）或细胞内L-瓜氨酸水平，减少中性氨基酸（L-瓜氨酸）转运蛋白的表达，改变L-瓜氨酸摄取和/或损害其量的研究。细胞内生成/循环L-瓜氨酸所需的酶和共前体（天冬氨酸）的活性或络合（例如，eNOS和L-瓜氨酸与L-精氨酸循环酶、精氨酸琥珀酸和精氨酸琥珀酸裂解酶的相互作用减弱）。作为第二个目标的一部分，我们将进行口服l -瓜氨酸的药代动力学研究，以优化治疗方案。我们将确定优化的l -瓜氨酸治疗是否能改善因暴露于慢性缺氧而受到干扰的NO信号参数。这些研究将为抵消和恢复受损的NO信号通路提供宝贵的信息，这些信息最终可以转化为重要的临床试验，以治疗部分由缺氧引起的慢性心肺疾病和CPPH婴儿。

DESCRIPTION (provided by applicant): Our long-term objective is to improve therapies for chronic progressive pulmonary hypertension (CPPH) in infants suffering from chronic cardiopulmonary disorders associated with persistent and episodic hypoxia. To do this, we developed a model of CPPH in newborn pigs. We have shown that after 3 days of chronic hypoxia, pulmonary hypertension develops and pulmonary vascular production of the vasodilator NO is intact. When hypoxic exposure is extended to 10 days, pulmonary hypertension worsens and is accompanied by reduced pulmonary vascular NO production. It follows that counteracting or restoring impairments in NO signaling could ameliorate CPPH. Our experimental design will test the hypothesis that treatment with oral L-citrulline, a precursor for L-arginine and NO, increases pulmonary vascular NO production and ameliorates the progressive development of chronic hypoxia-induced pulmonary hypertension. The aims of this proposal are to: 1) evaluate the ability of and mechanisms by which L-citrulline increases pulmonary vascular NO production 2) evaluate the efficacy and safety of oral L-citrulline to ameliorate chronic hypoxia-induced pulmonary hypertension. Treatments started on the day of placement in hypoxia and continued throughout 3 or 10 days total hypoxic exposure will determine the ability to prevent pulmonary hypertension. Treatments started at the end of the 3rd day of hypoxia and continued for the subsequent 7 days of hypoxia will evaluate the ability to arrest or reverse the progression of pulmonary hypertension. As part of the first aim, studies will be performed to address current gaps in our knowledge about L-citrulline sources, availability, and processing. This will include studies to determine whether chronic hypoxia reduces plasma (extracellular) or intracellular levels of L- citrulline, diminishes the expression of neutral amino acid (L-citrulline) transporters, alters L-citrulline uptake, and/or impairs the amounts, activities or complexing of the enzymes and co-precursors (aspartate) needed for adequate intracellular generation/recycling of L-citrulline (e.g. diminished interaction of eNOS and the L- citrulline to L-arginine recycling enzymes, argininosuccinate and argininosuccinate lyase). As part of the second aim, we will perform pharmacokinetic studies of oral L-citrulline to optimize the therapeutic regimen. We will determine if optimized L-citrulline therapy improves the parameters of NO signaling that are perturbed with exposure to chronic hypoxia. These studies will provide invaluable information about offsetting and restoring impaired NO signaling pathways that can ultimately be translated into important clinical trials to treat infants with chronic cardiopulmonary conditions and CPPH due in part to hypoxia. PUBLIC HEALTH RELEVANCE: Pulmonary hypertension is a well recognized complication of infants with chronic lung and heart disorders. Currently there are few good options for treating these infants. The goal of this project is to use a relevant animal model to help us understand why infants with lung and heart disorders associated with chronic or intermittent hypoxia develop progressive pulmonary hypertension, determine what happens in the lung blood vessels during disease development, and develop treatments for this disease.