Attenuation of denervation atrophy by nandrolone: molecular mechanisms

诺龙减轻去神经萎缩：分子机制

• 批准号: 8837614
• 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 2012-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8837614
• 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; Methionine; Mission; Modeling; Molecular; Muscle; Muscular Atrophy; Nandrolone; Nerve; Oligonucleotide Microarrays; Outcome; Paralysed; Pharmaceutical Preparations; Pharmacologic Substance; Physical Medicine; 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; restoration; sciatic nerve; transcription factor; ubiquitin ligase

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.

雄激素类固醇通过分子机制减少肌肉萎缩， 明白在研究雄激素类固醇诺龙对肌肉萎缩的影响时， 由于神经切断而瘫痪，我们发现在神经切断后7天内萎缩率降低， 在神经切断后29天开始使用诺龙（35天） 与肌肉泛素连接酶MAFbx和MuRF 1的表达减少有关。相比之下， 当在神经切断时开始使用诺龙时， 7天后（7天）MAFbx或MuRF 1的表达。我们认为，这种模式提供了一种独特的 有机会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情况下对诺龙的有益作用有抵抗力， 条件有趣的是，基因分析显示，在35岁时受诺龙影响的基因中， 不是7天，并且可能能够调节肌肉大小的是FOXO 1和RCAN 2。RCAN 2是 在骨骼肌中高水平表达，抑制钙调神经磷酸酶，一种蛋白磷酸酶 通过激活转录因子NFAT参与肌肉肥大。感兴趣的，FOXO 1 过表达还可能通过上调MAFbx降低钙调神经磷酸酶活性[5-7]，提示 诺龙诱导的FOXO 1和MAFbx水平的降低可能代表了第二个平行的 诺龙可能增加失神经肌肉中钙调磷酸酶活性的机制。 失神经肌肉在早期时间点对诺龙的不敏感性最可能反映了 阻断诺龙作用的转录调节因子的表达，或下调阻断诺龙作用的转录调节因子的表达， 我们发现在几种转录因子的表达水平上存在很大的差异， 在去神经支配后7天与35天，去神经支配骨骼肌中的协同调节因子， 变化，减少了25倍，是Ankrd 2。我们建议，分析这些影响， 转录辅助调节子对诺龙敏感性的影响将为分子生物学提供新的见解。 肌肉的决定因素对诺龙和其他雄激素的影响，并解释了有趣的 在某些病理生理条件下骨骼肌对雄激素的抵抗问题。 该建议的主要目的是，在大鼠去神经萎缩模型中，确定：1）是否 诺龙增加失神经肌肉中的钙调磷酸酶活性，以及这种增加是否是由于 钙调神经磷酸酶、RCAN 2和上游调节因子水平的诺龙依赖性变化 钙调神经磷酸酶水平（FOXO 1和MAFbx）; 2）特定的转录辅助调节因子是否介导 对诺龙减少萎缩和抑制MAFbx的作用的抗性。