Arginase 1 in age-dependent muscle and bone loss

摘要 衰老与肌肉量减少（肌肉减少症）和骨质差有关 （骨质疏松症），它们一起增加了福尔斯和骨折的发生率。人们普遍 我们认识到，衰老会引发全身性氧化应激，从而损害骨骼和肌肉 干细胞存活和分化;然而，这些年龄的基本机制- 相关的退行性变化还不清楚。我们的初步研究表明 （1）肌肉和骨骼中活性氧（ROS）水平显著增加 组织老化，2）抗氧化酶抑制剂治疗可防止氧化应激依赖性升高 萎缩相关的肌因子（例如，肌肉生长抑制素），细胞过早衰老和支持 肌管形成，3）抑制磷酸化酶防止膜蛋白Caveolin 3的损失 （4）抑制腺苷三磷酸酶可增强肌管的分化， 成骨基因（RUNX 2）在骨髓基质细胞（BMSC）中的表达。基于我们 新的和已发表的研究结果，我们的中心假设是，在骨和 肌肉细胞引起一氧化氮合成（NOS）的解偶联，减少NO的形成， 进一步增加ROS形成的负担并导致骨骼和肌肉失衡 体内平衡此外，阻断ARG 1活性或表达可以防止或减少骨形成。 和肌肉损失。这一假设将通过三个独立但相关的目标进行检验。 具体目的1：检验以下假设：在细胞中抑制β-内酰胺酶或缺乏表达， 肌肉和骨骼可以有效地防止或减少年龄依赖性肌肉和骨骼损失。我们 将使用肌肉和骨骼特异性（BMSC和成骨细胞）ARG 1基因敲除小鼠来检查 ARG 1在肌肉骨骼功能年龄依赖性丧失中的作用。具体目标2：测试 假设年龄相关的β-淀粉酶活性增加直接影响关键的细胞事件， 肌肉和骨骼的固定和固定。我们将使用原代人类和小鼠成肌细胞 和骨细胞（BMSC）来验证这一假设。具体目标3：确定分子 ARG 1调节肌肉和骨骼稳态的机制。我们将测试 假设ARG 1失调影响（a）肌肉中一氧化氮-卵泡抑素轴，（B） 影响肌肉修复/重塑通过改变膜蛋白（CAV 3，DYSF）的表达， 肌肉和（c）骨祖细胞中的一氧化氮-RUNX 2轴。我们的申请将有助于 ARG 1抑制作为一种新的治疗策略， 相关的肌肉和骨质流失。

Abstract Aging is associated with reduced muscle mass (sarcopenia) and poor bone quality (osteoporosis) which together increase the incidence of falls and bone fractures. It is widely appreciated that aging triggers systemic oxidative stress which can impair bone and muscle stem cell survival and differentiation; yet, the basic mechanisms underlying these age- associated degenerative changes are not well understood. Our preliminary studies demonstrate that (1) levels of reactive oxygen species (ROS) increase significantly in muscle and bone tissues with aging, 2) arginase inhibitor treatment prevents oxidative stress-dependent elevation of atrophy-associated myokines (e.g., myostatin), premature cell senescence and supports myotube formation, 3) arginase inhibition prevents loss of membrane proteins Caveolin 3 (CAV3) and Dysferlin (DYSF) in differentiating myotube, 4) arginase inhibition enhances the expression of osteogenic genes (RUNX2) in bone marrow stromal cells (BMSCs). Based on our new and published findings, our central hypothesis is that elevated levels of ARG1 in bone and muscle cells cause uncoupling of nitric oxide synthesis (NOS), reducing NO formation and further increasing the burden of ROS formation and resulting in imbalanced bone and muscle homeostasis. Furthermore, blocking ARG1 activity or expression can prevent or reduce bone and muscle loss. This hypothesis will be tested with three independent but related aims. Specific Aim 1: Test the hypothesis that inhibition of arginase or lack of expression in muscle and bone can effectively prevent or reduce age dependent muscle and bone loss. We will use muscle- and bone-specific (BMSCs, and osteoblast) ARG1 knockout mice to examine the role of ARG1 in age-dependent loss in musculoskeletal function. Specific Aim 2: Test the hypothesis that age-related increases in arginase activity directly impact key cellular events in muscle and bone anabolism and catabolism. We will use primary human and mouse myoblast and bone cells (BMSC) to test this hypothesis. Specific Aim 3: Determine the molecular mechanisms by which ARG1 modulates muscle and bone homeostasis. We will test the hypothesis that dysregulation of ARG1 affects (a) nitric oxide-follistatin axis in muscle, (b) affects muscle repair/remodeling by altering membrane proteins (CAV3, DYSF) expression in muscles and (c) nitric oxide-RUNX2 axis in bone progenitor cells. Our application will facilitate the successful preclinical translation of ARG1 inhibition as a novel therapeutic strategy for age- related muscle and bone loss.