| Objetives:To investigate the protective effect of intermittent exercise with or without inflammatory factor TNF-a inhibitor Etanercept to inhibit the expression of E3 ubiquitin ligase muscle ring finger 1(MuRF1)on cardiac function and skeletal muscle protein degradation in rats with myocardial infarction.Methods:55 Male Sprague-Dawley rats were randomly divided into sham operation group(S),myocardial infarction group(MI),myocardial infarction +intermittent exercise group(ME),myocardial infarction + intermittent exercise +normal saline group(MES),myocardial infarction + intermittent exercise + TNF-a inhibitor group(MET),10 rats per group.Rats in MET group were injected Etanercept intraperitoneally 1.2?g per g of body weight before 3 days of ligation of the left anterior descending(LAD),1 time per 3-day x 4wk after LAD.Rats in MES group were injected with the same amount of normal saline as control.Rat treadmill was used to perform intermittent exercise.Rats in ME,MES and MET groups were subjected to exercise training after a week of LAD,the speed of the first week is(15 m/min,30mins/d x 5d),followed by intermittent exercise[25 m/min(85%?90%VO2max)×7 mins and 15m/min(50%?60%VO2max)× 3mins alternately],60min/time × 1 time/d,5d/wk x 4wk.After 4 weeks of training,the hemodynamics parameters were measured to evaluate the cardiac function.Then heart and skeletal muscle tissues were stripped on ice cubes at 0?-4?.HE staining,masson staining and immunofluorescence staining were used to detect and measure the cross-sectional area of the tibialis anterior muscle cells,the percentage of collagen volume fraction(CVF)of cardiac muscle,and the expression of a-actinin,Myosin and HSP70.The expression of MuRF1,MAFbx,TNF-a,NF-?B,cTn I,Myosin,a-actinin and HSP70 protein were detected by western blot.The expression of MuRF1 and MAFbx mRNA were detected by RT=qPCR.Results:(1)Myocardial infarction resulted in the increase of the expression of MuRF1 and MAFbx in cardic muscle of rats with myocardial infarction.Intermittent exercise with or without TNF-? inhibitor Etanercept could down-regulated the expression of MuRF1 and MAFbx,and intermittent exercise combined with Etanercept showed a better effect.(2)Myocardial infarction resulted in the increase of the expression of inflammatory factor TNF-a and nuclear transcription factor NF-?B(pp65)in cardiac muscle.Intermittent exercise with or without TNF-? inhibitor Etanercept could down-regulated the expression of TNF-? and NF-?B,and intermittent exercise combined with Etanercept showed a better effect.(3)Compared with Sham group,the expression of cTn I and a-actinin down-regulated,a-actinin structural disordered,collagen fibers hyperplasia and the CVF increased,cardiac function was significantly impaired in MI rats.Compared with MI rats,4 weeks of intermittent exercise with or without TNF-a inhibitor Etanercept up-regulated the expression of cTn I and a-actinin significantly,improved the a-actinin structural disorder,reduced CVF and promoted heart function.Intermittent exercise combined with Etanercept showed better effects.(4)Myocardial infarction resulted in the decrease of the ratio of tibial anterior muscle weight/tibial length,the cross-sectional area of tibialis anterior muscle cells,and the expression of Myosin and a-actinin.Intermittent exercise with or without Etanercept significantly improved the ratio of tibial anterior muscle weight/tibial length,the cross-sectional area of tibialis anterior muscle cells,and the expression of Myosin and a-actinin,and intermittent exercise combined with Etanercept showed better effects.(5)Myocardial infarction resulted in the increase of the protein and mRNA expression of MuRF1 and MAFbx in tibial anterior muscle.Intermittent exercise with or without Etanercept could significantly down-regulated the expression of MuRF1 and MAFbx,and intermittent exercise combined with Etanercept could give better effects.(6)Myocardial infarction resulted in the increase of the protein expression of TNF-? and NF-?B(pp65)in tibial anterior muscle.Intermittent exercise with or without Etanercept could down-regulated the expression of TNF-a and NF-?B(pp65),and intermittent exercise combined with Etanercept could give better effects.(7)Myocardial infarction resulted in the increase of the protein expression of HSP70 and MuRF1 in the cytoplasm and nucleus of the tibialis anterior muscle cells.Intermittent exercise could increase the expression of HSP70 and decrease the expression of MuRF1 protein in the cytoplasm and nucleus.(8)Myocardial infarction increased the activity of chymotrypsin in tibial anterior muscle which could be decreased by intermittent exercise.(9)Intermittent exercise inhibit the degradation of skeletal muscle protein in rats with myocardial infarction by reducing the expression of TNF-a and MuRF1,increasing the expression of endogenous HSP70,inhibiting the phosphorylation of NF-?B and the activity of chymotrypsin.Conclusions:(1)Myocardial infarction resulted in decreasing expression of myocardial contractile protein cTn I,increasing the myocardial collagen fiber hyperplasia and CVF,reducing the skeletal muscle mass,decreasing the expression of skeletal muscle contractile protein Myosin and muscle cell cross-sectional area.Intermittent exercise with or without Etanercept could significantly increase the expression of myocardial contractile protein cTn I,reduce CVF,improve heart function and increase skeletal muscle mass and cell cross-sectional area,up-regulated the expression of contractile protein Myosin,inhibit degradation of skeletal muscle protein,and intermittent exercise combined with Etanercept could give better effects.(2)The Cardiac function was closely related to the expression of MuRF1;intermittent exercise-improved cardiac function in MI rats may be related to the suppression of TNF-?/NF-?B/MuRF1 signaling pathway in myocardium.(3)Intermittent exercise inhibit skeletal muscle protein degradation in rats with myocardial infarction by reducing the expression of TNF-a and MuRF1,increasing the expression of endogenous HSP70,inhibit the phosphorylation of NF-?B and the activity of chymotrypsin. |
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