Skeletal muscle protein degradation mechanism in COPD rats and relationship with IL-10

Abstract

Objective To investigate the expressions of ubiquitin-proteasome markers, including E2-14K, MAFbx, Ub, tumor necrosis factor-α (INF-α), in skeletal muscle of COPD rats, and their relationship with IL-10 level in diaphragm and serum in order to elucidate the potential mechanism of diaphragm atrophy. Methods Forty-five adult male SD rats were randomly divided into a COPD model group(n=30)and a normal control group(n=15). The COPD rat model was established by instillation of lipopolysaccharide (LPS) and exposure to cigarette smoke for 28 days.The protein levels of E2-14K, MAFbx, Ub in diaphragm, gastrocnemius and intercostal muscle were measured by western blot.The concentration of IL-10 and TNF-α in serum, diaphragm, gastrocnemius and intercostal muscle was measured by ELISA. Results In the model group, the protein expressions of E2-14K, MAFbx, Ub protein in diaphragm, intercostal muscle, gastrocnemius increased significantly.In the model group, the serum and skeletal muscle of TNF-α increased significantly compared with the control group, but the expression of IL-10 decreased[serum (44.68±8.67) vs (75.96±10.59), diaphragm (50.55±7.41) vs (80.06±9.22), intercostal muscle (47.47±8.98) vs (78.10±7.21), gastrocnemius (48.60±10.88) vs (76.77±8.92), respectively, P<0.01]. The level of IL-10 in diaphragm, intercostal muscle and gastrocnemius was negatively correlated with TNF-α(serum r=-0.67, diaphragm r=-0.78, intercostal muscle r=-0.80, gastrocnemius r=-0.77, P<0.05). The level of IL-10 in diaphragm, intercostal muscle and gastrocnemius was negatively correlated with the percentage of neutrophils, levels of E2-14K, MAFbx, Ub(serum r=-0.80, r=-0.73, r=-0.69, r=-0.81; diaphragm r=-0.83, r=-0.81, r=-0.75, r=-0.79; intercostal muscle r=-0.81, r=-0.80, r=-0.74, r=-0.54, gastrocnemius r=-0.74, r=-0.69, r=-0.71, r=-0.62; P<0.05). The IL-10 levels in serum and skeletal muscle were also positively correlated each other (diaphragm r=0.83, intercostal muscle r=0.80, gastrocnemius r=0.73, P<0.01). Conclusions In COPD rats, down regulation of IL-10 plays an important role in inflammation, may be involved in skeletal muscle protein ubiquitin-proteasome degradation pathway of degradation mechanism of regulation. Key words: Chronic obstructive pulmonary disease; Skeletal muscle; Ubiquitin-proteasom pathway; Interleukin-10; Tumor necrosis factor-x03B1