MG132对肿瘤恶病质小鼠骨骼肌消耗及TRAF6表达的影响

Effect of protease inhibitor MG132 on skeletal muscle consumption and expression of TRAF6 in cancer cachexia in mice

目的探讨蛋白酶体抑制剂MGl32对肿瘤恶病质骨骼肌消耗和TRAF6及其所调节的自噬溶酶体途径和泛素蛋白酶体途径相关因子Beclin-1、MuRF1和MAFbx基因表达的影响。方法小鼠结肠腺癌C26细胞接种BALB/c小鼠诱导肿瘤恶病质模型。分为对照组(HC)、恶病质组(CC)和MG132治疗组(MG)。监测体质量和自发性活动,于接种后第12天,每天腹腔注射给予MG组小鼠0.1 mg/kg的MG132,HC和CC组小鼠给予等量0.9%氯化钠注射液,第19天处死小鼠。称量肿瘤、左侧腓肠肌重量,检测腓肠肌横切面积,RT-PCR和Western blot检测TRAF6、Beclin1、MuRF1和MAFbx的mRNA和蛋白水平。结果 CC组小鼠去瘤体质量、自发性活动、腓肠肌重量和横切面积均显著低于HC组(P<0.05),MG组小鼠这次指标均显著回升(P<0.05),但仍低于HC组(P<0.05)。CC组小鼠腓肠肌组织TRAF6、Beclin1、MAFbx和MuRF1的mRNA和蛋白水平均显著高于HC组(P<0.05),MG组小鼠这次指标均显著低于CC组(P<0.05)。结论 MG132改善肿瘤恶病质骨骼肌消耗可能与抑制腓肠肌TRAF6的表达,阻断自噬溶酶体途径和泛素蛋白酶体途径有关。

Objective To investigate the effect of protease inhibitor MG132 on skeletal muscle consumption and the expression of TRAF6, Beclin-1, MuRF1 and MAFbx in cancer cachexia. Methods Murine colon C26 adenocarci- noma cells were inoculated into male BALB/c mice to induce cancer cachexia. 24 male BALB/c mice were divided into 3 groups： healthy control group（HC） ;cancer cachexia group （CC）and MG132 treatment group （MG）. Body weight and spontaneous activity were examined. Equal amount of physiological saline and 0. 1 mg/kg doses of MG132 were given intraperitoneally daily to CC and MG groups, respectively, on day 12 after tumor inoculation. All mice were sacrificed on day 19. Tumor and the left gastrocnemius muscle were accurately weighed, crosscut area of gastrocnemius muscle were measured. MRNA and protein level of TRAF6, Beclinl, MuRF1 and MAFbx were detected by RT-PCR and Western blot, respectively. Results On-tumor body weight, spontaneous activity gastrocnemius muscle weight and crosscut area of CC group lower than HC group （P 〈0. 05）, these indexesbounced significantly of MG group （P 〈0. 05）, but still lower than that in HC group（P 〈0. 05）. The mRNA and protein expression of TRAF6, Beclinl, MuRF1 and MAFbx in the gastrocnemius muscle of CC group were significantly higher HC group （P 〈0. 05）, these indexes of MG group were significantly lower than those in CC group （P 〈0. 05）. Conclusions The improvement of skeletal muscle consumption in cancer cachexia by MG132 may be explaimed by its inhibition to TAF6 expression, thus suppressing autophagy-lysosome pathway and ubiquitin-proteasome pathway.