内毒素在慢性阻塞性肺疾病大鼠骨骼肌蛋白分解代谢中的作用机制

Effect of Lipopolysaccharide on metabolism of skeletal muscle protein in rats with chronic obstructive pulmonary disease and its underlying mechanism

目的 研究内毒素脂多糖（LPS）在慢性阻塞性肺疾病（COPD）大鼠骨骼肌蛋白高分解代谢中的作用机制.方法 SD大鼠随机分为空白对照组、COPD组、COPD＋ LPS组,每组15只,COPD组和COPD＋ LPS组大鼠用单纯熏香烟法制成COPD大鼠动物模型,分离其伸趾长肌,分别给予含或不含有LPS（4 mg/L）的孵育液进行离体有氧孵育.利用实时定量PCR和Western blot技术检测泛素和C2亚基在转录和蛋白水平的变化.结果 COPD组和COPD＋ LPS组泛素mRNA表达是正常对照组的1.93倍和3.12倍（P＜0.01）；COPD组和COPD＋ LPS组C2亚基mRNA表达是正常对照组的1.74倍和2.04倍（P ＜0.01）；COPD组泛素蛋白表达（0.95±0.12）和COPD＋ LPS组泛素蛋白表达（1.56±0.16）也高于正常对照组（0.63±0.12）（P＜0.05,P＜0.01）；COPD组和COPD＋ LPS组C2亚基蛋白表达分别为1.24±0.18和1.55±0.21,也高于正常对照组（0.91±0.l0）（P＜0.05,P＜0.01）.结论 COPD患者难以纠正的骨骼肌蛋白降解增加可能是由于LPS激活泛素-蛋白酶体途径所致.

Objective To study the effect of Lipopolysaccharide （LPS） on hypermetabolism of skeletal muscle protein in rats with chronic obstructive pulmonary disease （COPD） and evaluate its mechanism.Methods The SD rats were randomly divided into normal control group,COPD group and COPD＋LPS group,with 15 rats in each group.To establish rat COPD models by passive cigarette smoking in COPD group and COPD＋ LPS group.After dissecting and isolating the extensor digitorium longus muscles （EDL）,the in vitro muscle incubation system with adequate oxygen supply.The EDL were either cultured with media containing 4 mg/L recombinant rat LPS or without LPS.The subsequent changes in ubiquitin and proteasome subunit C2 mRNA and protein levels were determined by real-time quantitative PCR and Western blot,respectively.Results The expression of the ubiquitin mRNA of the COPD group and COPD＋LPS group were higher than that of normal control group,up to 1.93 fold and 3.12 fold,respectively （all P 〈0.01）.The expression of the proteasome subunit C2 mRNA of the COPD group and COPD＋LPS group were higher than that of normal control group,up to 1.74 fold and 2.04fold,respectively （all P 〈0.01）.The expressions of the ubiquitin protein of the COPD group （0.95±0.12） and COPD＋ LPS group （1.56 ± 0.16） were higher than that of normal control group （0.63 ±0.12） （P 〈0.05,P 〈0.01,respectively）.The expressions of the proteasome subunit C2of the COPD group （1.24±0.18） and COPD＋ LPS group （1.55 ± 0.21） were higher than that of normal control group （0.91±0.10） （P 〈0.05,P 〈0.01,respectively）.Conclusions LPS could directly strengthen the function of ubiquitin dependent proteolytic system in COPD.