Nitric oxide coupling and BH4 availability roles in muscle dysfunction with COPD

描述(申请人提供)：慢性阻塞性肺疾病(COPD)是美国第三大死亡原因，2011年，估计有1270万美国成年人患有COPD。这种疾病的特点是炎症导致的气流受限、实质破坏和其他全身症状的进行性发展。认识到“以肺为中心”的治疗方案进展有限，尤其令人感兴趣的是，骨骼肌功能障碍是COPD常见的和临床相关的全身性后果，它预测发病率和死亡率，独立于肺功能损害的严重程度。COPD患者肌肉功能障碍的发生与多种因素有关，但氧化应激被认为起主要作用。在其他以慢性氧化应激(如衰老和心血管疾病)为特征的疾病状态中，外周O2转运和肌肉代谢障碍与四氢生物蝶呤(BH4)缺乏导致的一氧化氮(NO)生物利用度降低和一氧化氮合酶(NOS)解偶联有关。然而，尽管作为一种新的治疗靶点，BH4缺陷诱导的一氧化氮合酶解偶联在慢性阻塞性肺疾病周围功能障碍发生中的作用仍然缺乏证据。因此，本项目的目标是通过阐明BH4的生物利用度和一氧化氮合酶偶联对COPD患者外周O2运输和肌肉代谢的作用来填补现有知识的空白，以期补充BH4可能能够恢复肌肉功能并改善这些患者的生活质量。因此，在这个项目的K99阶段，我们将阐明COPD患者在运动期间通过几个指标(血流/代谢匹配、肢体血流、体内和通透性纤维中的线粒体功能以及收缩效率)评估的外周功能障碍的严重程度是否与氧化应激水平以及BH4和无生物利用度(目标1)有关。然后，我们将研究急性(目标2)和长期(目标3)补充BH4对肌肉和血管中一氧化氮合酶偶联、氧化应激水平和NO生物利用度的影响，最终目标是恢复这些患者的骨骼肌功能和功能能力。为了实现这些目标，我们将使用一种综合的方法，结合体内近红外光谱(NIRS)、多普勒超声、动脉自旋标记(ASL)和31P-MRS测量运动肌肉中O2的运输和肌肉代谢，并在体外利用分子技术评估氧化应激水平，并使用通透性纤维进一步询问线粒体呼吸。在这些研究的结论中，我们将扩大我们对COPD患者肌肉功能障碍潜在机制的了解，或许更重要的是，从临床角度来看，我们将为这种疾病的潜在新疗法提供洞察力。

DESCRIPTION (provided by applicant): Chronic obstructive pulmonary disease (COPD) is the third leading cause of death in America, and, in 2011, 12.7 million US adults were estimated to have COPD. This disease is characterized by the progressive development of inflammation-induced airflow limitation, parenchymal destruction, and other systemic manifestations. Recognizing the limited advances in "lung focused" treatment options, it is of particular interest that skeletal muscle dysfunction is a frequent and clinically relevant systemic consequences of COPD that predicts morbidity and mortality, independently from the severity of lung function impairement. Several factors have been implicated in the development of muscle dysfunction with COPD, but oxidative stress has been suggested to play a major role. In other diseased states, also characterized by chronic oxidative stress (e.g. aging and cardiovascular disease), dysfunctional O2 transport and muscle metabolism in the periphery have been linked to both a lower nitric oxide (NO) bioavailability and nitric oxide synthase (NOS) uncoupling induced by a deficit in tetrahydrobiopterin (BH4). However, despite its potential as a novel target for therapeutic treatment, evidence of BH4 deficit-induced NOS uncoupling on the development of peripheral dysfunction with COPD is still lacking. Therefore, the goal of this project is to addres this gap in existing knowledge by elucidating the role of BH4 bioavailabiity and NOS coupling on peripheral O2 transport and muscle metabolism in patients suffering from COPD, with the prospective that BH4 supplemetation may be able to restore muscle function and improve the quality of life of these patients . Accordingly, during the K99 phase of this project, we will explre whether the severity of peripheral dysfunction assessed by several indices (perfusion/metabolism matching, limb blood flow, mitochondrial function in vivo and in permeabilized fibers, and contractile efficiency) during exercise in patients with COPD is related to the level of oxidative stress, as well as BH4 and NO bioavailability (Aim 1). We will then examine the effects of acute (Aim 2) and chronic (Aim 3) supplementations of BH4 on NOS coupling, the level of oxidative stress and NO bioavailability in the muscle and the vasculature, with the ultimate goal to restore skeletal muscle function and the functionnal capacity of these patients. To achieve these aims, we will use a comprehensive approach combining in vivo Near-Infrared Spectroscopy (NIRS), Doppler Ultrasound, Arterial Spin Labeling (ASL), and 31P-MRS measurements of O2 transport and muscle metabolism in exercising muscle, and in vitro methods utilizing molecular techniques to assess the level of oxidative stress, and permeabilized fibers to further interrogate mitochondrial respiration. At the conclusion of these studies, we will have expanded our knowledge of the mechanisms underlying muscle dysfunction in patients suffering from COPD, and, perhaps more important from a clinical perspective, provided insight into a potential novel therapeutic treatment for this disease.