Attenuation of denervation atrophy by nandrolone: molecular mechanisms

诺龙减轻去神经萎缩：分子机制

• 批准号: 7750432
• 负责人: CHRISTOPHER P CARDOZO
• 金额: --
• 依托单位: JAMES J PETERS VA MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-01 至 2013-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7750432
• 关键词: Acute; Adenovirus Vector; Affect; Androgen Receptor; Androgens; Asthma; Atrophic; Binding; Biological Preservation; Biological Process; Burn injury; Calcineurin; Cell Culture Techniques; Chronic; Chronic Disease; Chronic Obstructive Airway Disease; Codon Nucleotides; Communities; Complex; DNA Fingerprinting; DNA Sequence; Denervation; Development; Disease; Down-Regulation; Failure; Future; Gene Expression; Genes; Goals; Hospitals; Immobilization; Injury; Knowledge; Mediating; Medical; Medicine; Methionine; Mission; Modeling; Molecular; Muscle; Muscular Atrophy; Nandrolone; Nerve; Oligonucleotide Microarrays; Outcome; Paralysed; Pharmaceutical Preparations; Pharmacologic Substance; Protein Dephosphorylation; Protein phosphatase; Quality of life; Rattus; Recovery; Rehabilitation therapy; Repression; Resistance; Role; Signal Transduction; Skeletal Muscle; Small Interfering RNA; Soldier; Speed; Spinal cord injury; Steroids; Stroke; Testing; Therapeutic; Time; Transcriptional Regulation; Veterans; activating transcription factor; attenuation; functional restoration; improved; inhibitor/antagonist; insight; interest; muscle hypertrophy; novel; nutrition; octamer transcription factor OTF-1; overexpression; physical conditioning; prevent; public health relevance; restoration; sciatic nerve; transcription factor; ubiquitin ligase

DESCRIPTION (provided by applicant): Androgenic steroids reduce muscle atrophy through molecular mechanisms that are poorly understood. In studies of the effects of the androgenic steroid nandrolone on atrophy of muscle paralyzed by nerve transection, we have found that rates of atrophy are reduced within 7 days after beginning nandrolone when this steroid is started at 29 days after nerve transection (35 days) associated with reduced expression of the muscle ubiquitin ligases MAFbx and MuRF1. By contrast, when nandrolone was begun at the time of nerve transection, it did not slow atrophy or reduce expression of MAFbx or MuRF1 7 days later (7 days). We believe that this model provides a unique opportunity to understand the molecular mechanisms by which nandrolone slows muscle atrophy, and to understand why muscle is resistant to the beneficial effects of nandrolone under some conditions. Of interest, gene profiling revealed that, among genes affected by nandrolone at 35 but not 7 days, and potentially capable of regulating muscle size, were FOXO1 and RCAN2. RCAN2 is expressed at high levels in skeletal muscle, where it inhibits calcineurin, a protein phosphatase involved in muscle hypertrophy by activating the transcription factor NFAT. Of interest, FOXO1 overexpression also reduces calcineurin activity, possibly by upregulating MAFbx [5-7], suggesting that nandrolone-induced reductions in FOXO1 and MAFbx levels may represent a second, parallel mechanism by which nandrolone may increase calcineurin activity in denervated muscle. The insensitivity of denervated muscle to nandrolone at early time points most likely reflects expression of a transcriptional regulator that blocks nandrolone action, or downregulation of one that is necessary for it. We found large differences in expression levels of several transcriptional coregulators in denervated skeletal muscle at 7 versus 35 days after denervation, with the greatest change, a 25-fold decrease, being for Ankrd2. We propose that analysis of effects of these transcriptional coregulators on nandrolone sensitivity will provide new insights into molecular determinants of muscle to effects of nandrolone and other androgens and explain the intriguing problem of resistance of skeletal muscle to androgens under some pathophysiological conditions. Major Aims of this proposal are, in a rat model of denervation atrophy, to determine: 1) whether nandrolone increases calcineurin activity in denervated muscle, and whether such increases are due to nandrolone-dependent changes in levels of calcineurin, RCAN2, and upstream regulators of calcineurin levels (FOXO1 and MAFbx); 2) whether specific transcriptional coregulators mediate resistance to effects of nandrolone to reduce atrophy and repress MAFbx. PUBLIC HEALTH RELEVANCE: Significance Restoration of function in those recovering from acute illness or injury, and preservation of function in those with chronic medical conditions to maintain independence are major goals in rehabilitation medicine. A significant impediment to rehabilitation is muscle atrophy as a consequence of paralysis, immobilization, medications, and chronic illness. Approaches to minimizing atrophy focus on treating the underlying disease causing muscle loss, on nutrition, and on various forms of physical conditioning. These approaches do not directly regulate the biological processes causing muscle loss. The development of safe and effective pharmaceuticals that promote muscle recovery, block muscle loss, or both would be a huge step forward in speeding up rehabilitation therapy and discharge from the hospital. The two major expected outcomes of our studies are greater insights into specific mechanisms by which androgens prevent muscle atrophy, and new information about the molecular determinants of such protection. In addition to expanding general knowledge, this information holds the potential to improve future therapeutics that safely prevent muscle atrophy. Relevance to the VHA Mission Muscle loss affects veterans with diverse medical conditions that include stroke, spinal cord injury, COPD, asthma and rheumatological disease. It also affects wounded soldiers during recovery from burns and/or immobilization resulting from their injuries. Knowledge that improves treatments to preserve or restore function of these veterans holds the potential to significantly improve the speed of their recovery, and, possibly, their quality of life and community function and integration.

描述（由申请人提供）： 雄激素类固醇通过人们知之甚少的分子机制减少肌肉萎缩。在雄激素类固醇诺龙对因神经横断而麻痹的肌肉萎缩的影响的研究中，我们发现，如果在神经横断后 29 天（35 天）开始使用这种类固醇，则在开始使用诺龙后 7 天内，萎缩率会降低。肌肉泛素连接酶 MAFbx 和 MuRF1 的表达减少。相比之下，当神经横断时开始使用诺龙时，7天后（7天）并没有减缓萎缩或减少MAFbx或MuRF1的表达。我们相信，该模型提供了一个独特的机会来了解诺龙减缓肌肉萎缩的分子机制，并了解为什么肌肉在某些条件下对诺龙的有益作用具有抵抗力。有趣的是，基因分析显示，在 35 天而非 7 天时受诺龙影响且可能能够调节肌肉大小的基因包括 FOXO1 和 RCAN2。 RCAN2 在骨骼肌中高水平表达，它通过激活转录因子 NFAT 来抑制钙调神经磷酸酶（一种参与肌肉肥大的蛋白磷酸酶）。有趣的是，FOXO1 过度表达还可能通过上调 MAFbx 来降低钙调磷酸酶活性 [5-7]，这表明诺龙诱导的 FOXO1 和 MAFbx 水平降低可能代表诺龙可能增加去神经肌肉中钙调磷酸酶活性的第二种平行机制。 去神经肌肉在早期时间点对诺龙不敏感很可能反映了阻断诺龙作用的转录调节因子的表达，或者其所必需的转录调节因子的下调。我们发现去神经后7天和35天，去神经骨骼肌中几种转录共调节因子的表达水平存在很大差异，其中变化最大的是Ankrd2，降低了25倍。我们建议，分析这些转录共调节因子对诺龙敏感性的影响将为了解肌肉对诺龙和其他雄激素影响的分子决定因素提供新的见解，并解释在某些病理生理条件下骨骼肌对雄激素的抵抗这一有趣的问题。该提案的主要目的是在去神经萎缩大鼠模型中确定：1）诺龙是否会增加去神经肌肉中的钙调神经磷酸酶活性，以及​​这种增加是否是由于诺龙依赖性的钙调神经磷酸酶、RCAN2 和上游调节因子水平的变化所致钙调神经磷酸酶水平（FOXO1 和 MAFbx）； 2)特定的转录共调节因子是否介导对诺龙作用的抵抗以减少萎缩并抑制MAFbx。 公共卫生相关性： 意义 从急性疾病或损伤中恢复的人的功能恢复，以及患有慢性疾病的人保留功能以保持独立是康复医学的主要目标。康复的一个重大障碍是由于瘫痪、行动不便、药物和慢性病而导致的肌肉萎缩。减少肌肉萎缩的方法重点是治疗导致肌肉损失的潜在疾病、营养和各种形式的身体调理。这些方法并不直接调节导致肌肉损失的生物过程。开发安全有效的药物来促进肌肉恢复、阻止肌肉损失或两者兼而有之，将是加速康复治疗和出院的一大进步。我们研究的两个主要预期结果是更深入地了解雄激素防止肌肉萎缩的具体机制，以及有关这种保护的分子决定因素的新信息。除了扩展常识之外，这些信息还有可能改善未来安全预防肌肉萎缩的疗法。与 VHA 使命的相关性 肌肉损失会影响患有多种疾病的退伍军人，包括中风、脊髓损伤、慢性阻塞性肺病、哮喘和风湿病。它还会影响正在从烧伤和/或因受伤而无法行动的受伤士兵中恢复。改善治疗以保留或恢复这些退伍军人功能的知识有可能显着提高他们的康复速度，并可能提高他们的生活质量以及社区功能和融入。