Adams Volker, Mangner Norman, Gasch Alexander, Krohne Christian, Gielen Stephan, Hirner Stephanie, Thierse Hermann-Josef, Witt Christian C, Linke Axel, Schuler Gerhard, Labeit Siegfried
Heart Center Leipzig, University Leipzig, Strümpellstrasse 39, D-04289 Leipzig, Germany.
J Mol Biol. 2008 Dec 5;384(1):48-59. doi: 10.1016/j.jmb.2008.08.087. Epub 2008 Sep 11.
Humoral circulating inflammatory cytokines such as tumor necrosis factor alpha (TNF-alpha) can impair skeletal muscle contractility. Furthermore, TNF-alpha expression correlates with elevated levels of atrogin-like muscle-specific ubiquitin E3 ligases, which are presumed to mediate muscle protein breakdown and atrophy. However, the casual relationships between MuRF1 and TNF-alpha and their relative contributions to muscle function impairment are not known.
TNF-alpha or saline was injected into either C57Bl6 or MuRF1(-/-) mice. After 16-24 h, the expression of MuRF1 in skeletal muscle was quantified by quantitative reverse transcription-PCR and Western blot analysis. Muscle function was measured in an organ bath. To obtain a broader overview on potential alterations, two-dimensional gel electrophoresis was performed.
Wild-type animals injected with TNF-alpha had higher MuRF1 mRNA expression (saline versus TNF-alpha: 56.6+/-12.1 versus 133.6+/-30.3 arbitrary units; p<0.05) and protein expression (saline versus TNF-alpha: 0.38+/-0.11 versus 1.07+/-0.25 arbitrary units; p<0.05) as compared to saline-injected littermates. Furthermore, TNF-alpha reduced force development at 150 Hz by 25% in C57Bl6 animals (saline versus TNF-alpha: 2412+/-120 versus 1799+/-114 g/cm(2); p<0.05), but not in MuRF1(-/-) mice (saline versus TNF-alpha: 2424+/-198 versus 2431+/-180 g/cm(2); p=NS). Proteome analysis revealed a significant down-regulation of fast skeletal muscle troponin T in wild-type animals treated with TNF-alpha as compared to MuRF1(-/-) mice that received TNF-alpha.
The results of this study demonstrate for the first time that TNF-alpha-induced reduction in skeletal muscle force development depends on the induction of the atrophy-related E3 ubiquitin ligase MuRF1. A link for the reduction in muscle force may be the TNF-alpha/MuRF1-mediated down-regulation of fast skeletal muscle troponin T.
诸如肿瘤坏死因子α（TNF-α）等体液循环炎症细胞因子可损害骨骼肌收缩力。此外，TNF-α的表达与atrogin样肌肉特异性泛素E3连接酶水平升高相关，这些酶被认为介导肌肉蛋白分解和萎缩。然而，MuRF1与TNF-α之间的因果关系及其对肌肉功能损害的相对作用尚不清楚。
将TNF-α或生理盐水注射到C57Bl6或MuRF1基因敲除（-/-）小鼠体内。16 - 24小时后，通过定量逆转录PCR和蛋白质免疫印迹分析对骨骼肌中MuRF1的表达进行定量。在器官浴中测量肌肉功能。为了更全面地了解潜在变化，进行了二维凝胶电泳。
与注射生理盐水的同窝小鼠相比，注射TNF-α的野生型动物的MuRF1 mRNA表达更高（生理盐水组与TNF-α组：56.6±12.1与133.6±30.3任意单位；p<0.05），蛋白质表达也更高（生理盐水组与TNF-α组：0.38±0.11与1.07±0.25任意单位；p<0.05）。此外，TNF-α使C57Bl6动物在150 Hz时的肌力发展降低了25%（生理盐水组与TNF-α组：2412±120与1799±114 g/cm²；p<0.05），但在MuRF1（-/-）小鼠中未出现这种情况（生理盐水组与TNF-α组：2424±198与2431±180 g/cm²；p=无显著性差异）。蛋白质组分析显示，与接受TNF-α的MuRF1（-/-）小鼠相比，用TNF-α处理的野生型动物中快骨骼肌肌钙蛋白T显著下调。
本研究结果首次表明，TNF-α诱导的骨骼肌肌力发展降低依赖于萎缩相关的E3泛素连接酶MuRF1的诱导。肌肉力量降低的一个联系可能是TNF-α/MuRF1介导的快骨骼肌肌钙蛋白T的下调。
