Targeting Nitrate-Nitrite-NO pathway for Ameliorating Muscle and Bone Comorbidities in Duchenne Muscular Dystrophy

摘要： Duchenne肌营养不良症(DMD)是一种严重的进行性肌肉疾病，影响 肌肉和骨骼都有。到目前为止，治疗DMD的有效疗法有限。研究表明， 一氧化氮(NO)生物利用度的降低是由于神经元一氧化氮的继发性丧失造成的 在缺乏dystrophin的情况下，一氧化氮合酶(NNOS)是疾病进展的关键因素。 通过饮食亚硝酸盐和硝酸盐恢复体内非稳态是一种新的治疗方法 由于其在低氧和缺血状态下能够转化为NO，因此可以 绕过nNOS。本研究的目的是测试无机亚硝酸盐的功效，并探索其 对骨骼肌和骨骼的作用机制。我们的初步数据，基于 严重营养不良小鼠模型(dKO-dystrophin/utroin双重敲除)，演示 没有破坏营养不良肌肉的动态平衡，更令人兴奋的是，口服 亚硝酸盐显著改善营养不良患者的寿命和一系列病理变化 小鼠，在骨骼肌和骨组织中。这些问题背后的机制 改进值得进一步研究，以提供重要的临床前和机制 用于识别新的治疗靶点的信息。我们假设无机亚硝酸盐 给药通过增强NO信号转导改善DMD的肌肉和骨骼病理 营养不良肌肉中的通路以及通过调节骨的表达和分泌- 调节肌动蛋白。我们将在三个具体目标上检验这一假设。目标1：测试 无机亚硝酸盐恢复营养不良小鼠硝酸盐/亚硝酸库的假说及其改进 肌肉/骨骼病理，并保留肌肉功能。目标2：检验假设 亚硝酸盐通过肌红蛋白介导的NO-cGMP信号通路影响骨骼肌。目标3：实现 验证这样一种假设：除了机械负荷增加外，亚硝酸盐还会影响骨骼 通过调控骨调节肌动蛋白的表达和分泌实现动态平衡 营养不良的肌肉。我们期待这些发现将提供一种新颖、安全和低成本的 对目前无法治疗的DMD采取肌肉和骨骼兼得的治疗方法。 完成这些目标将促进我们对新机制的了解 DMD骨异常的发病机制也是通过骨调节肌动蛋白实现的 可能会发现新的潜在治疗靶点。重要的是，我们的发现可能具有深远的意义 翻译不仅对DMD，而且对其他缺乏 NO信号通路功能正常。

Abstract: Duchenne Muscular Dystrophy (DMD) is a severe, progressive muscular disease that affects both muscle and bone. To date, effective therapies for DMD are limited. Studies have shown that reduced nitric oxide (NO) bioavailability resulted from secondary loss of neuronal nitric oxide synthase (nNOS) in the absence of dystrophin is a key contributor to disease progression. Restoring NO homeostasis via dietary nitrite and nitrate representing a novel therapeutic approach due to its ability to be converted to NO in low oxygen and ischemic states that can bypass nNOS. The purpose of this study is to test the efficacy of inorganic nitrite and explore its mechanism of action on both skeletal muscle and bone. Our preliminary data, based on a severe dystrophic mouse model (dKO-dystrophin/utrophin double knock out), demonstrated disrupted NO homeostasis in dystrophic muscle and more excitingly, oral administration of nitrite significantly improved the life span and a series of pathological changes in dystrophic mice, both in skeletal muscle and bone tissues. The mechanisms underlying these improvements deserve further investigation to provide important preclinical and mechanistic information for identifying novel therapeutic targets. We hypothesize that inorganic nitrite administration improves both muscle and bone pathologies in DMD by enhancing NO signaling pathways in dystrophic muscle and by modulating the expression and secretion of bone- regulating myokines. We will test this hypothesis in three specific aims. Aim 1: To test the hypothesis that inorganic nitrite restores nitrate/nitrite pool in dystrophic mice and improves muscle/bone pathologies and preserves muscle function. Aim 2: To test the hypothesis that nitrite affects skeletal muscle via myoglobin-mediated NO-cGMP signaling pathway. Aim 3: To test the hypothesis that in addition to increased mechanical loading, nitrite affects bone homeostasis via modulating the expression and secretion of bone-regulating myokines from dystrophic muscle. We anticipate that these findings will provide a novel, safe and low-cost therapeutic approach benefiting both muscle and bone for the currently untreatable DMD. Completion of these aims will advance our knowledge of novel mechanisms for the pathogenesis of bone abnormalities in DMD through bone-regulating myokines as well; which may uncover new potential therapeutic targets. Importantly, our findings may have profound translational implications not only to DMD but also to other neuromuscular diseases that lack normal NO signaling pathway function.