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)的治疗方法，这些婴儿患有与持续性和间歇性低氧相关的慢性心肺疾病。为了做到这一点，我们开发了一种新生猪的CPPH模型。我们已经证明，在慢性缺氧3天后，出现了肺动脉高压，肺血管产生的血管扩张剂NO是完整的。当低氧暴露延长到10天时，肺动脉高压恶化，并伴随着肺血管NO产生的减少。因此，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这一假设，即口服L-瓜氨酸，L-精氨酸和NO的前体，增加肺血管NO的产生，并改善慢性缺氧性肺动脉高压的进行性发展。本研究的目的是：1)评价L-瓜氨酸增加肺血管NO生成的能力及其机制；2)评价口服L-瓜氨酸对慢性缺氧性肺动脉高压的疗效和安全性。治疗从放置在低氧的当天开始，持续3或10天，总的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，并在随后的7天内继续治疗，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，将进行研究，以解决目前我们对L了解的空白-瓜氨酸的来源、可获得性和加工。这将包括研究以确定慢性缺氧是否降低了L-瓜氨酸的血浆(细胞外)或细胞内水平，减少了中性氨基酸(L-瓜氨酸)转运体的表达，改变了L-瓜氨酸的摄取，和/或损害了L-瓜氨酸在细胞内充分生成/再循环所需的酶和辅助前体(天冬氨酸)的数量、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少)。作为第二个目标的一部分，我们将进行L-瓜氨酸口服的药代动力学研究，以优化治疗方案。我们将确定优化的L-瓜氨酸疗法是否改善了因慢性缺氧而受到干扰的NO信号参数。这些研究将提供关于抵消和恢复受损的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，用于治疗患有慢性心肺疾病和部分由缺氧引起的CPPH的婴儿。 公共卫生相关性：肺动脉高压是公认的慢性肺病和心脏病婴儿的并发症。目前，治疗这些婴儿的好选择寥寥无几。这个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慢性或间歇性低氧的肺和心脏疾病的婴儿会出现进行性肺动脉高压，确定疾病发展过程中肺血管的变化，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.