The Mechanism Of Changes On Activity Of Ubiquitin Proteasome Pathway After Exercise In Rat Skeletal Muscle

Purpose:In this study,we investigated the effect of ubiquitin-proteasome pathway(UPP)activity with or without injection of PDTC or Trolox on proteolysis after an acute bout of physical exercise in rat skeletal muscle,and revealed roles of oxidative stress and NF-kB signal in UPP activity after exercise.Method:The male Sprague-Dawley rats run on the treadmill at 25 m/min, 5%grade,for 1 h after familiarization with the treadmill by 10-15 min on 3 days.In Study 1,six of thirty six rats were killed respectively at rest,immediately after half an hour and an hour exercise,and 1 h, 2h,6h post-an exercise.Changes of 3-MH content,ubiquitinated protein content,26S proteasome activity,and ubiquitin,MuRF1,MAFbx,26S proteasome C2 subunit mRNA expression were detected in gastrocnemius muscle.In study 2,sixty rats were divided into three groups,control group(n=24),PDTC and Trolox injection group(n=18,respectively).Six rats of control group were killed at rest,then six rats of the three groups separately were killed immediately,1 and 6 hours after exercise in the three groups.Besides of the indexs in study 1,IκBαprotein content in myofibrillar cytoplasm,activity of NF-κB binding DNA in nucleus,as well as MDA content in muscle and serum,serum CK dynamic changes were dfetected.Results:(1)3-MH content and 26S proteasome activity increased immediately after half an hour exercise and at 6h post-exercise in rat gastrocnemius muscle(P＜0.05).(2)Ubiquitined protein content increased significantly at 6h post-exercise(P＜0.01).(3)There was a increasing trend of expression of ubiquitin ligase MAFbx,MuRF1 mRNA after exercise (P＜0.05).(4)Expression of ubiquitin and 26S proteasome C2 subunit mRNA were low than the resting during and after exercise,but expression of C2 mRNA increased Sharply at 6h post-exercise(P＜0.01).(5)Trolox slowed down MDA content in gastrocnemius muscle and serum after exercise (P＜0.05).(6)PDTC and Trolox slowed down the degradation of IκBαin cytoplasm,and inhibited exercise-induced activation of NF-κB signal in nucleolus(P＜0.05).(7)PDTC and Trolox slowed down effects of exercise on 3-MH content,26S proteasome activity and gene expression of MAFbx, MuRF1,ubiquitin,C2 subunit(P＜0.05).Conclusions:(1)The increase of UPP activity enhanced contractile protein degradation in skeletal muscle during and after a strenuous exercise.(2)The increase of protein ubiquitination-related enzymes activity and 26S proteasome activity resulted in the increase of UPP activity during a strenuous exercise,and the increase of components gene expression in UPP resulted in the increase of its activity after a strenuous exercise.(3)Inhibition of exercise-induced oxidative stress in skeletal muscle could reduce the activation of NF-κB signal,and reduce the activity of UPP by regulation gene transcription of the components of UPP,which could reduce the contractile protein degradation.