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

摘要： 杜氏肌营养不良症 (DMD) 是一种严重的进行性肌肉疾病，影响 肌肉和骨骼。迄今为止，DMD 的有效治疗方法有限。研究表明 神经元一氧化氮继发性损失导致一氧化氮 (NO) 生物利用度降低 在缺乏抗肌营养不良蛋白的情况下，氧化合酶（nNOS）是疾病进展的关键因素。 通过饮食中的亚硝酸盐和硝酸盐恢复 NO 稳态是一种新的治疗方法 方法，因为它能够在低氧和缺血状态下转化为 NO， 绕过 nNOS。本研究的目的是测试无机亚硝酸盐的功效并探讨其 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-肌营养不良蛋白/肌营养不良蛋白双敲除） 破坏营养不良性肌肉中的 NO 稳态，更令人兴奋的是，口服 亚硝酸盐显着改善营养不良者的寿命和一系列病理变化 小鼠的骨骼肌和骨组织。这些背后的机制 值得进一步研究改进，以提供重要的临床前和机制 用于识别新治疗靶点的信息。我们假设无机亚硝酸盐 通过增强 NO 信号传导改善 DMD 中的肌肉和骨骼病理学 营养不良性肌肉中的途径并通过调节骨的表达和分泌 调节肌因子。我们将在三个具体目标上检验这一假设。目标 1：测试 假设无机亚硝酸盐可以恢复营养不良小鼠的硝酸盐/亚硝酸盐库并改善 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： 检验以下假设：除了增加机械负荷外，亚硝酸盐还会影响骨骼 通过调节骨调节肌因子的表达和分泌来实现体内平衡 营养不良的肌肉。我们预计这些发现将提供一种新颖、安全且低成本的方法 对于目前无法治疗的 DMD，这种治疗方法对肌肉和骨骼都有好处。 完成这些目标将增进我们对新机制的了解 DMD 骨异常的发病机制还通过骨调节肌因子进行；其中 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 不仅对 DMD 具有转化意义，而且对其他缺乏的神经肌肉疾病也有转化意义 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.