The Changes Of MuRF1, MAFbx And Pax7 In Rat Skeletal Muscles During Exhaustive Exercise And Blunt Contusion And Its Mechanism

Objective:This article detected the contents of NF-kappaB,MuRF1,MAFbx and Pax7 of skeletal muscle at immediate time,24 and 48 hours after exhaustive exercise and blunt contusion,and investigated the mechanism of skeletal muscle injury and repair induced by one-time exhaustive exercise and blunt contusion rats model.Methods:Forty-two 6-8 weeks old male Wistar rats were randomly divided into 7 groups,and each group has 6 rats:The control group(C),immediately group after exhaustive exercise(E0),24h group after exhaustive exercise(E24)and 48h group after exhaustive exercise(E48),immediately group after blunt contusion(DO),24h after blunt contusion group(D24)and 48h after blunt contusion group(D48).The control group sampling:Wistar rats were narcotized by intraperitoneal injection and killed.Left gastrocnemius muscle was divided into three parts:one for ELISA,one for Western blot and another for real-time fluorescence quantitative PCR.Exhaustive exercise groups and contusion groups sampling:Wistar rats were sampled with the similar steps at immediately or 24 and 48 hours after exhaustive exercise and blunt contusion.Results:(1)The experimental results of MuRF1:Compared with group C,MuRF1 protein expression of rats skeletal muscle in group E0,E24 increased significantly(p<0.05),MuRF1mRNA expression in group EO was also up-regulated significantly(p<0.05),but MuRF1mRNAexpression in group E48 decreased significantly(p<0.05).MuRF1mRNA in group E24 and MuRF1 protein in group E48 had no significant change(p>0.05).On the other hand,compared with group C,MuRF1mRNA and MuRF1 protein in group DO had no significant change,but MuRF1mRNA expression of rats skeletal muscle in group D24 increased significantly(p<0.01),then MuRF1mRNA in group D48 decreased significantly(p<0.01).MuRF1 proteins expression in group D24,D48 were down-regulated significantly(p<0.05,p<0.01).(2)The experimental results of MAFbx:Compared with group C,MAFbxmRNA expression of rats skeletal muscle in group E24,E48decreased significantly(p<0.01),but MAFxmRNA expression in group D24,D48 increased significantly(p<0.05,p<0.01).MAFbxmRNA in group E0,DO had no significant change(p>0.05).(3)The experimental results of Pax7:Compared with group C,Pax7 mRNA expression of rats skeletal muscle in group EO increased significantly(p<0.05),but Pax7 mRNA expression in group E24 decreased significantly(p<0.05).Pax7 mRNA in group E48 had no significant change(p>0.05).At the same time,Pax7 mRNA expression in group D0,D24 were significantly down-regulated(p<0.05).Pax7 mRNA in group D48 had no significant change(p>0.05).On the other hand,Pax7 protein expression of rats skeletal muscle in all exhaustive groups had no significant change(p>0.05),but Pax7 protein expression in all contusion groups(D0,D24,D48)were significantly down-regulated(p<0.05).(4)The experimental results of NF-kappaB:Compared with group C,NF-kappaB protein expression of rats skeletal muscle in group E48 decreased significantly(p<0.05),but NF-kappaB protein expression in group E0,E24 had no significant change(p>0.05).On the other hand,NF-kappaB protein in all contusion groups(D0,D24,D48)decreased significantly(p<0.05).Conclusion:(1)The expression of MuRFl gene and protein were significantly increased in the early stage of exhaustive exercise and blunt contusion.NP-?B/MuRF1 signal pathway may be activated at this time which induced the up-regulation of MuRFl mRNA and protein,and the degradation of muscle protein may also be enhanced.After 24 hours of injury,the expression of NF-?B and MuRF1 was gradually down-regulated,which may cause the decrease of skeletal muscle protein degradation.(2)Immediately after exhaustive exercise and contusion,MAFbx mRNA expression increased,then it gradually decreased after 24 hours of exhaustive exercise.But MAFbx mRNA continued to increase at 24 hours and at 48 hours after contusion.Due to the more severe injury caused by blunt contusion,the stimulatory effect on MAFbx mRNA was stronger,and the degree of skeletal muscle protein degradation caused by blunt contusion was also larger.(3)After one-time exhaustive exercise,the change trend of Pax7 mRNA showed first increase and then decrease,whereas Pax7 protein did not change significantly.It showed that the activation of satellite cells in skeletal muscle of rats may occur in early stage after exhaustive exercise,then myogenic differentiation occured.Otherwise;Pax7 gene and protein decreased at various phases after blunt contusion,which may be related to the severity of the injury,and is still in the Pax7 depletion phase.The comprehensive verification of more indicators is needed for the activation and differentiation of satellite cells.