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)： 雄激素通过鲜为人知的分子机制减少肌肉萎缩。在研究雄激素诺孕酮对神经切断瘫痪的肌肉萎缩的影响时，我们发现，当在神经切断后29天(35天)开始使用这种类固醇时，肌肉泛素连接酶MAFbx和MuRF1的表达减少，在开始使用诺洛酮后7天内萎缩的速度就会降低。相反，在神经切断后7天(7天)开始用药，并没有减缓萎缩或减少MAFbx或MuRF1的表达。我们认为，这个模型提供了一个独特的机会来理解诺龙减缓肌肉萎缩的分子机制，以及为什么肌肉在某些条件下对诺龙的有益影响具有抵抗力。令人感兴趣的是，基因图谱显示，在35天而不是7天时受到诺德隆影响的基因中，有可能能够调节肌肉大小的是FOXO1和RCAN2。RCAN2在骨骼肌中高水平表达，它通过激活转录因子NFAT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的过表达也降低了钙调神经磷酸酶的活性，可能是通过上调MAFbx[5-7]，这表明诺洛酮诱导的FOXO1和MAFbx水平的降低可能是第二种平行的机制，通过这种机制，诺洛酮可以增加失神经肌肉中的钙调神经磷酸酶活性。失神经肌肉在早期对诺龙的不敏感很可能反映了一种转录调节因子的表达，该转录调节因子阻止了诺龙的作用，或者是下调了对其必要的一种调节。我们发现，在失神经支配后7天和35天，去神经骨骼肌中几种转录辅助调节因子的表达水平存在很大差异，其中最大的变化是Ankrd2，下降了25倍。我们认为，分析这些转录辅助调节因子对雄激素敏感性的影响，将为了解肌肉对雄激素和其他雄激素的影响的分子决定因素提供新的见解，并解释一些病理生理条件下骨骼肌对雄激素耐药的有趣问题。这项建议的主要目的是，在失神经萎缩的大鼠模型中，确定：1)诺得龙是否增加失神经肌肉中钙调神经磷酸酶的活性，以及这种增加是否是由于依赖诺得龙的钙调神经磷酸酶、RCAN和钙调神经磷酸酶上游调节因子(FOXO1和MAFbx)水平的变化；2)特定的转录辅助调节因子是否介导了对诺洛酮的抵抗，以减轻萎缩和抑制MAFbx。 公共卫生相关性： 意义康复医学的主要目标是恢复急性病或损伤恢复者的功能，以及保留慢性病患者的功能以保持独立性。康复的一个重要障碍是瘫痪、制动、药物治疗和慢性病导致的肌肉萎缩。减少萎缩的方法侧重于治疗导致肌肉损失的潜在疾病，注重营养，以及各种形式的物理调节。这些方法并不直接调节导致肌肉丧失的生物过程。开发安全有效的药物，促进肌肉恢复，阻止肌肉丢失，或两者兼而有之，将是加快康复治疗和出院的一大步。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，以及关于这种保护的分子决定因素的新信息。除了扩展一般知识外，这些信息还具有改进未来安全防止肌肉萎缩的治疗方法的潜力。与VHA使命相关的是，肌肉损失会影响患有各种医疗条件的退伍军人，包括中风、脊髓损伤、慢性阻塞性肺病、哮喘和风湿病。它还影响受伤士兵从烧伤中恢复和/或因受伤而不能动弹。改善治疗以保护或恢复这些退伍军人的功能的知识有可能显著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合。