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善患有与持续性和间歇性缺氧相关的慢性心肺疾病的婴儿的慢性进行性肺动脉高压（CPPH）的治疗。为此，我们在新生猪中开发了CPPH模型。我们已经表明，经过3天的慢性缺氧，肺动脉高压的发展和肺血管生产的血管扩张剂NO是完整的。当低氧暴露延长至10天时，肺动脉高压加重，并伴有肺血管NO产生减少。因此，抵消或恢复NO信号传导的损伤可以改善CPPH。我们的实验设计将检验以下假设：口服L-瓜氨酸（L-精氨酸和NO的前体）治疗可增加肺血管NO的产生并改善慢性缺氧诱导的肺动脉高压的进展。本提案的目的是：1）评价L-瓜氨酸增加肺血管NO生成的能力和机制; 2）评价口服L-瓜氨酸改善慢性缺氧性肺动脉高压的有效性和安全性。在置于低氧中的当天开始治疗并持续整个3天或10天的总低氧暴露将确定预防肺动脉高压的能力。在缺氧第3天结束时开始并持续随后7天缺氧的治疗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，将开展研究，以解决我们目前对L-瓜氨酸来源、可用性和加工的认识差距。这将包括研究，以确定是否慢性缺氧减少血浆（细胞外）或细胞内水平的L-瓜氨酸，减少中性氨基酸的表达（L-瓜氨酸）转运蛋白，改变L-瓜氨酸摄取，和/或损害量，酶和共前体的活性或复合L-瓜氨酸的充分细胞内生成/再循环所需的（天冬氨酸）（例如，eNOS和L-瓜氨酸与L-精氨酸再循环酶、氨基琥珀酸和氨基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信号传导参数。这些研究将提供有关抵消和恢复受损的NO信号通路的宝贵信息，这些信息最终可以转化为重要的临床试验，以治疗部分由于缺氧而患有慢性心肺疾病和CPPH的婴儿。 公共卫生相关性：肺动脉高压是婴儿慢性肺和心脏疾病的公认并发症。目前，治疗这些婴儿的好方法很少。该项目的目标是使用相关的动物模型来帮助我们了解为什么患有与慢性或间歇性缺氧相关的肺和心脏疾病的婴儿会发展为进行性肺动脉高压，确定疾病发展过程中肺血管中发生了什么，并开发这种疾病的治疗方法。

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.