肿瘤坏死因子α对慢性阻塞性肺疾病大鼠模型呼吸肌蛋白质分解代谢的影响

目的研究肿瘤坏死因子α（TNF-α）对慢性阻塞性肺疾病（COPD）模型大鼠呼吸肌蛋白质分解代谢率的影响。方法成年雄性Wistar大鼠90只，分为模型组70只，对照组20只，采用反复熏香烟和气管内注入猪胰弹性蛋白酶的方法建立COPD大鼠模型，模型建立成功2周后，以低于对照组大鼠平均体重的90％作为判断发生营养不良的标准，随机抽取已出现营养不良的大鼠10只，采用尾静脉注射TNF-α单克隆抗体0．1mg／kg进行干预，连续干预4d，继续饲养动物10d，处死全部动物。酶联免疫吸附测定法测定膈肌及肋间内肌匀浆中TNF-α含量；反相高效液相色谱荧光法测定膈肌和肋间内肌匀浆中3-甲基组氨酸（3-MH）及酪氨酸含量。结果营养不良组大鼠膈肌和肋间内肌的TNF-α含量[（125±11）和（119±11）pg／g]显著高于对照组[（64±5）和（59±5）pg／g]，营养不良组大鼠膈肌和肋间内肌匀浆中3-MH含量[（7．1±0．6）和（7．4±0．6）nmol／g]和酪氨酸含量[（639±24）和（660±25）nmol／g]均显著高于对照组[（4．0±0．5）、（4．2±0．3）和（557±24）、（579±26）nmol／g]，膈肌和肋间内肌TNF-α含量与蛋白质分解代谢率呈阴显正相关（r=0．854。P〈0．01）。TNF-α单克隆抗体干预后，蛋白质分解代谢率降低。结论COPD大鼠模型呼吸肌蛋白质分解代谢率增高，这种现象在COPD大鼠模型中发生营养不良的大鼠表现更为明显。TNF-α是引起COPD大鼠呼吸肌蛋白质分解代谢率增高的因素之一。

Effects of tumor necrosis factor alpha on proteolysis of respiratory muscles in rats with chronic obstructive pulmonary disease

OBJECTIVE: To investigate the impact of tumor necrosis factor alpha (TNF-alpha) on proteolysis of respiratory muscles in rats with chronic obstructive pulmonary disease (COPD). METHODS: Ninety healthy male adult Wistar rats were randomly divided into two groups: a normal control group (n = 20) and a model group (n = 70). The COPD rat model was established by intratracheal instillation of porcine pancreatic elastase and exposure to cigarette smoke for 60 days. Malnutrition was defined as the weight of the rats in the model group lower than 90% of the mean body weight of the control group. Two weeks after the establishment of the COPD model, 10 rats were randomly chosen in the malnutrition group, and received 4 days' therapy of intravenous injection of TNF-alpha monoclonal antibody (McAb) 0.1 mg/kg. The concentrations of TNF-alpha in the homogenates of respiratory muscles were measured by ELISA, and the contents of 3-methylhistidine, tyrosine in homogenates of respiratory muscle were measured by high performance liquid chromatography. RESULTS: The levels of TNF-alpha in the homogenates of diaphragmatic muscle of the malnutrition group [(125 +/- 11) pg/g] were significantly higher than that of the control group [(64 +/- 5) pg/g]; The levels of TNF-alpha in the homogenates of internal intercostal muscle of the malnutrition group [(119 +/- 11) pg/g] were significantly higher than that of the control group [(59 +/- 5) pg/g]. The contents of 3-methylhistidine in homogenates of diaphragmatic muscle [(7.1 +/- 0.6) nmol/g] and internal intercostal muscle [(7.4 +/- 0.6) nmol/g] of the malnutrition group were significantly higher than that of the control group [(4.0 +/- 0.5) nmol/g]. The contents of tyrosine in homogenates of diaphragmatic muscle [(639 +/- 24) nmol/g] and internal intercostal muscle [(660 +/- 25) nmol/g] of the malnutrition group were significantly higher than that of the control group [(579 +/- 26) nmol/g]. TNF-alpha in the respiratory muscle showed a strong positive correlation with proteolysis of respiratory muscle (r = 0.854, P < 0.01). CONCLUSION: An increase of proteolysis of respiratory muscles was found in COPD rats, more significant in the malnutrition rats. TNF-alpha is one of the causes for the increase of proteolysis of respiratory muscles.