Objective:In order to investigate whether the Atrogin-1 gene silence could alleviate myotube atrophy, the size of C2C12 myotube treated with dexamethasone (DEX) was observed, and the protein synthesis, degradation and the expression of Atrogin-1 was measured. Methodology :Cultured the mouse myofiber C2C12 cells and differentiated into myotube were established, then they were treated with DEX for 48h. The 3 H-Tyrosine incorporation into the myotube were measured to analyze the protein synthesis, and the 3H-Tyrosine released into the medium was to analyze the protein degradation. The myotube size was observed by microscope and calculated with software. The mRNA expression of Atrogin1 ( Muscle Atrophy Fbox-1 ) was detected by Northern blot. The myotube changes after silenced the Atrogin-1 gene used SiRNA technique was also investigated. Results:The tyrosine incorporation into myotube was decreased 17.4％, and the tyrosine released from myotube was increased 24. 7％ after treated with DEX (5 μ mol/L), and the myotube size became thinner and atrophy. The protein expression of Atrogin-1 was increased with DEX dose-dependent, and the mRNA expression was increased 3 folds in the dose of DEX 5 μ mol/L. But the myotube size was changed slightly after Atrogin-1 gene silenced. Conclusion: Glucorcoticoid caused myotube atrophy by accelerating protein degradation and inhibiting protein synthesis, which was alleviated by Atrogin-1 gene silence. Atrogin-1 maybe a gene target to reversed the muscle wasting which contributed to malnutrition.%目的:研究糖皮质激素地塞米松(dexamethasone,DEX)对体外培养肌管的形态、蛋白质合成/分解代谢及肌肉萎缩蛋白Fbox-1(Atrogin-1)的表达,Atrogin-1基因沉默是否可减轻肌管萎缩.方法:体外培养小鼠肌纤维细胞株C2C12细胞并分化为肌管后,用DEX处理48h,同位素3H-酪氨酸掺入法检测蛋白合成,3H-酪氨酸释放率检测蛋白分解代谢;荧光显微镜观察肌管形态并拍照;Northern blot检测Atrogin-1 mRNA水平;应用小分子干扰RNA片段(siRNA)技术使Atrogin-1基因沉默后,观察DEX作用下肌管形态的改变.结果:DEX 5μmol/L作用后,肌管酪氨酸(tyrosine)掺入率下降17.4%,同时tyrosine释放率升高24.7%,使肌管形态变细、萎缩;剂量依赖性地升高Atroign-1蛋白表达水平,使Atroign-1 mRNA表达升高3倍;Atrogin-1基因沉默可改善DEX引起的肌管萎缩. 结论:DEX促进肌管蛋白质分解代谢,并抑制蛋白合成代谢,导致肌肉萎缩;Atrogin-1基因沉默可改善DEX引起的肌肉萎缩,Atrogin-1基因可能是逆转肌肉消耗性营养不良的有效靶点.
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