Stana Flavia, Vujovic Marija, Mayaki Dominique, Leduc-Gaudet Jean-Philippe, Leblanc Philippe, Huck Laurent, Hussain Sabah N A
All authors: Meakins-Christie Laboratories and Translational Research in Respiratory Diseases Program, Department of Medicine, Research Institute of the McGill University Health Centre, Montréal, QC, Canada and Department of Critical Care, McGill University Health Centre, Montréal, QC, Canada.
Crit Care Med. 2017 Sep;45(9):e971-e979. doi: 10.1097/CCM.0000000000002520.
Skeletal muscle fiber atrophy develops in response to severe sepsis, but it is unclear as to how the proteolytic pathways that are involved in its development are differentially regulated. We investigated the link between sepsis-induced fiber atrophy and activation of the proteasome and autophagy pathways and whether the degree of activation is more severe and sustained in limb muscles than it is in the diaphragm.
Randomized controlled experiment.
Animal research laboratory.
Adult male C57/BL6 mice.
Two groups of animals were studied. The sepsis group was subjected to a cecal ligation and perforation technique, whereas the control (sham) group was subjected to abdominal surgery without cecal ligation and perforation. Measurements for both groups were performed 24, 48, and 96 hours after the surgical procedure.
Atrophy was quantified in the diaphragm and tibialis anterior by measuring fiber diameter. Autophagy was evaluated using electron microscopic detection of autophagosomes and by measuring LC3B protein lipidation and autophagy-related protein expressions. Proteasomal degradation was quantified by measuring chymotrypsin-like activity of the 26S proteasome and messenger RNA expressions of muscle-specific E3 ligases. Sepsis triggered transient fiber atrophy in the diaphragm that lasted for 24 hours and prolonged atrophy in the tibialis anterior that persisted for 96 hours. The autophagy and proteasome pathways were activated in both muscles at varying intensities over the time course of sepsis. Activation was more pronounced in the tibialis anterior than in the diaphragm. Sepsis inhibited the V-Akt thymoma viral oncogene homolog 1 and complex 1 of the mammalian target of rapamycin pathways and stimulated the AMP-activated protein kinase pathway in both muscles.
Sepsis triggers more severe and sustained muscle fiber atrophy in limb muscles when compared with respiratory muscle. This response is associated with enhanced proteasomal and autophagic proteolytic pathway activities and is triggered by inhibition of the AKT and complex 1 of the mammalian target of rapamycin pathways and activation of the AMPK pathway.
骨骼肌纤维萎缩是对严重脓毒症的反应，但尚不清楚参与其发展的蛋白水解途径是如何被差异调节的。我们研究了脓毒症诱导的纤维萎缩与蛋白酶体和自噬途径激活之间的联系，以及肢体肌肉中激活程度是否比膈肌更严重和持续。
随机对照实验。
动物研究实验室。
成年雄性C57/BL6小鼠。
研究两组动物。脓毒症组采用盲肠结扎穿孔技术，而对照组（假手术组）进行无盲肠结扎穿孔的腹部手术。两组均在手术后24、48和96小时进行测量。
通过测量纤维直径对膈肌和胫前肌的萎缩进行量化。使用电子显微镜检测自噬体以及测量LC3B蛋白脂化和自噬相关蛋白表达来评估自噬。通过测量26S蛋白酶体的胰凝乳蛋白酶样活性和肌肉特异性E3连接酶的信使核糖核酸表达来量化蛋白酶体降解。脓毒症引发膈肌短暂的纤维萎缩，持续24小时，而胫前肌的萎缩延长，持续96小时。在脓毒症病程中，自噬和蛋白酶体途径在两块肌肉中均以不同强度被激活。胫前肌中的激活比膈肌更明显。脓毒症抑制了V-Akt胸腺瘤病毒癌基因同源物1和雷帕霉素哺乳动物靶标复合物1途径，并在两块肌肉中刺激了AMP激活的蛋白激酶途径。
与呼吸肌相比，脓毒症引发肢体肌肉更严重和持续的肌纤维萎缩。这种反应与蛋白酶体和自噬蛋白水解途径活性增强有关，并由AKT和雷帕霉素哺乳动物靶标复合物1途径的抑制以及AMPK途径的激活触发。
