| Objective:To observe the expressions of Ubiquitin mRNA and proteasome 20S subunit C2 mRNA of Ubiquitin-Proteasome Pathway(UPP) in the skeletal muscle protein degradation of Chronic Obstructive Pulmonary Disease(COPD) rats with malnutrition; and to explore the influence of indomethacin(IND) intervention on this pathway to select a right dose of IND for providing experimental evidence of the treatment for COPD with malnutrition.Methods:100 healthy male Wistar rats were divided randomly into two groups:the model group (n=80) and the control group (n=20). COPD model was established through being smoked and useing intratracheal instillation of Porcine Pancreatic Elastase (PPE) in the model group; the control group with no smoking cigarettes, was intratracheal instillation with isotonic physiologic saline while the model group was accepted to PPE.8 days after modeling success, malnutrition rats were selected from the model group according to the standard:body weight less than 90% of the average weight of rats in the control group, and were divided into four groups by randomized block design:COPD malnourished non-intervention group and COPD malnutrition IND intervention groups: 1,2 and 3. The rest rats of the model group was grouped as COPD normal nutrition group. Three IND intervention groups were continuously treated with different doses of IND, respectively 0.5mg/kg-d, 1.0mg/kg·d, and 2.0mg/kg·d, through stomach instillation for 14 days. The other three groups were treated with isotonic physiologic saline by the same way for 14 days. After the intervention, rats were continually feeding for 14 days. Recording the rats' weight in each groups, implementing pulmonary function tests and lung histopathology, and recording the wet weight of diaphragm and extensor digitorum longus muscle(EDL); the expression of Ubiquitin mRNA, proteasome 20S subunit C2 mRNA in diaphragm and EDL were measured by RT-PCR method.Results:1). Weight comparison:Before and after intervention, the growth of weight in IND intervention group 2 was higher than in IND group 1,3 and non-intervention group, and there were significantly different (all P<0.05). There was no significant difference between intervention group 1 and group 3 (P>0.05). The intervention group 1 or group 3 was slightly higher than non-intervention group, but lower than the control group or COPD normal nutrition group, and there all have significant difference (all P＜0.05).2). Wet weight of diaphragm and extensor digitorum longus(EDL) comparison:Each IND intervention group was higher than non-intervention group, especially the IND intervention group 2 with the significant statistical difference(all P＜0.05). There was no significant difference between IND intervention group 1 and group 3. All the four groups were lower than the control group and COPD normal nutrition group (all P＜0.05).3). Expression of ubiquitin mRNA and proteasome 20S C2 subunit mRNA in diaphragm and EDL comparison:the IND intervention group 2 was lower than that of IND intervention group 1, group 3, non-intervention group and COPD normal nutrition group but higher than the control group, there has statistical differences (all P＜0.05); IND intervention group 1 or group 3 was higher than non-intervention group, COPD normal nutrition group and the control group, with significant difference(all P＜0.05), while it showed no significant statistical difference between the two groups(P>0.05).4). The expression of Ubiquitin mRNA in diaphragm or EDL was negatively correlatated with the wet weight of diaphragm or EDL, (respectively, R=-0.865, P＜0.01; R=-0.849, P＜0.01). The proteasome 20S subunit C2 mRNA expression of the diaphragm or EDL was negatively correlated with the wet weight of the diaphragm or EDL, (respectively, R=-0.814, P＜0.01;R=-0.856, P＜0.01).Conclusions:1). The expression of ubiquitin mRNA and proteasome C2 subunit mRNA increased in the diaphragm or EDL of COPD model rats with malnutrition; the level of expression was negatively correlated with the wet weight of diaphragm or EDL muscle, respectively.2). Different doses of indomethacin affected on the ubiquitin mRNA and proteasome C2 subunit mRNA expressions in rats leading to different results; it suggested that in some degree, IND maybe increase or reduce the degradation amount of muscle protein through the ubiquitin-proteasome pathway. It can be considered that the appropriate dose of indomethacin can against malnutrition caused by muscle protein degradation.3).The appropriate dose of IND may improve body weight and skeletal muscle of COPD malnourished rats through inhibiting the ubiquitin-proteasome pathway.
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