Muscle Wasting in Burns: Pivotal Role of Akt/PKB

烧伤中的肌肉萎缩：Akt/PKB 的关键作用

• 批准号: 6794551
• 负责人: RONALD GARY TOMPKINS
• 金额: $ 16.44万
• 依托单位: MASSACHUSETTS GENERAL HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-04-01 至 2009-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6794551
• 关键词: apoptosis; atrophy; biological signal transduction; burns; cysteine endopeptidases; disease /disorder etiology; enzyme activity; genetically modified animals; insulin; laboratory mouse; membrane potentials; mitochondrial disease /disorder; mitochondrial membrane; mitogen activated protein kinase; molecular pathology; muscle cells; muscle function; neuromuscular disorder; nitric oxide; nuclear magnetic resonance spectroscopy; oxidoreductase inhibitor; posttranslational modifications; protease inhibitor; protein biosynthesis; serine threonine protein kinase; striated muscles; tissue /cell culture; trauma

The important functional change in skeletal muscle following thermal injury is muscle weakness, which is associated with loss of muscle mass (atrophy) resulting in hypoventilation, difficulty in weaning off respirators, and decreased mobilization. A recognized pathway for accelerated muscle protein breakdown is the activation of ubiquitin-proteosome system. Apoptosis or programmed cell death is a relatively recently described mechanism of loss of parenchymal tissue and can be initiated by many factors, including growth factor withdrawal. Recent studies following burn injury have confirmed apoptotic changes in skeletal muscles. Insulin is a key growth factor, which, via downstream Akt/PKB signaling pathway, plays a key role in protein synthesis, mitochondrial function, and anti-apoptosis. Insulin resistance with decreased signaling via PI3-K/AktJPKB pathway, is a concomitant feature of burns. The hypothesis tested is that the decreased growth factor (insulin) signaling, specifically via Akt/PKB leads to apoptotic changes in muscle with mitochondria playing a central role. It is also postulated that the burn injury results in the activation of inducible nitric oxide synthase (iNOS) with release of reactive nitric oxide (NO), which alters Akt/PKB by post translational modifications. Thus, the proposed studies, using muscle cell cultures, and rodents with thermal injury, will critically evaluate the role of NO in decreased Akt/PKB activation, mitochondrial function, and in the apoptotic changes seen in muscle. The hypothesis that burn-induced mitochondrial, apoptotic and functional (tension) changes in muscle can be attenuated by either infection/over-expression of constitutively active Akt/PKB, highly specific iNOS inhibitors, or by inhibition of pro-apoptotic caspases will also be tested. The proposed studies, using morphologic, biochemical and molecular pharmacological approaches, together with functional (tension studies), and protein kinetic analyses would characterize the effects of burn injury on local and distant muscle apoptosis, and their relationship to neuromuscular dysfunction. Our studies on the effectiveness of iNOS inhibitor, and use of iNOS knockout mice, and the use of caspase inhibitors will thus provide significant insights into the pathogenesis of muscle wasting, and furnish novel therapeutic armamentaria and/or strategies to treat burn-induced neuromuscular dysfunction in humans. Information obtained from these mechanistic studies will provide a scientific basis and rationale for therapeutic maneuvers to prevent and/or rectify neuromuscular complications of burns in humans.

热损伤后骨骼肌的重要功能变化是肌肉无力，这与肌肉质量的丧失(萎缩)导致的换气不足、难以撤除呼吸器和活动减少有关。一个公认的加速肌肉蛋白质分解的途径是激活泛素-蛋白小体系统。细胞凋亡或程序性细胞死亡是最近被描述的一种实质组织丧失的机制，可由许多因素启动，包括生长因子停用。烧伤后的最新研究证实了骨骼肌细胞凋亡的变化。胰岛素是一种关键的生长因子，通过Akt/PKB下游信号通路，在蛋白质合成、线粒体功能和抗细胞凋亡等方面发挥关键作用。胰岛素抵抗，通过PI3-K/AktJPKB途径信号转导减少，是烧伤的伴随特征。假设是生长因子(胰岛素)信号的减少，特别是通过Akt/PKB导致了肌肉细胞的凋亡变化，线粒体起着中心作用。还推测烧伤导致诱导型一氧化氮合酶(INOS)激活，释放反应性一氧化氮合酶(NO)，通过翻译后修饰改变Akt/PKB。因此，拟议中的研究，使用肌肉细胞培养，以及患有烫伤的啮齿动物，将进行严格的评估。 NO在降低Akt/PKB活性、线粒体功能和肌肉细胞凋亡变化中的作用。烧伤引起的肌肉线粒体、凋亡和功能(张力)变化可以通过感染/过度表达固有活性的Akt/PKB、高度特异的iNOS抑制剂或抑制促凋亡的caspase来减弱的假说也将得到检验。这些拟议的研究将利用形态、生化和分子药理学方法，以及功能(张力研究)和蛋白质动力学分析，来表征烧伤对局部和远端肌肉细胞凋亡的影响，以及它们与神经肌肉功能障碍的关系。因此，我们对iNOS抑制剂的有效性、iNOS基因敲除小鼠的使用以及caspase抑制剂的使用的研究将为肌肉萎缩的发病机制提供重要的见解，并为治疗烧伤引起的神经肌肉疾病提供新的治疗手段和/或策略。 人类的功能障碍。从这些机制研究中获得的信息将为预防和/或矫正人类烧伤的神经肌肉并发症的治疗操作提供科学基础和理论基础。