| Myocardial ischemic disease is the leading killer threatening humans life and health.Therefore,it is particularly important to reduce the injury caused by heart ischemia.Ischemic injury is fast and multidimensional.Mitochondria occupy approximately more than 40% of the total cell volume,and are key organelles determining myocardial metabolism.Mitochondrial dynamic networks(fusion and fission)play an important role in maintaining mitochondrial structure and function.Trimetazidine(TMZ),a clinically effective anti-ischemic drug,is conventionally used for patients with coronary heart disease.Although a large body of evidence demonstrates that trimetazidine plays an important role in modulating mitochondrial energy metabolism during myocardial ischaemia reperfusion,the effects of trimetazidine on mitochondria dynamic networks(fusion and fission)durning acute myocardial ischemia remains to be identified definitively.Therefore,the aim of the present study was to reveal the regulation mechanism of oral treatment of trimetazidine on mitochondria in acute myocardial ischemic rats.For this purpose,firstly,we established an in vivo rat model of acute myocardial ischemia by ligation of left coronary artery,and then confirming that ischemia has been effectively generated by monitoring the changes of electrocardiogram(ECG),hemodynamics,infarct size and ventricular arrhythmia.Then,the in vivo rat model of acute myocardial ischemia was used to evaluate the protective effects of TMZ on heart ischemia.Finally,we determined mitochondrial respiratory activity,complexes activity,the mRNA and protein expression of mitochondria dynamics.The research was divided into two parts:Part Establishment of acute myocardial ischemic model in rats?Methods: Male rats were randomised into two groups,sham group(S group)and ischemic group(I group).Following left thoractomy,a 5.0 silk suture was used to permanetly ligate the left coronary artery in I group.Sutures for rats in S group were encircled without tying.Durning ischemia,the heart rate(HR),ST-segment,mean arterial pressure(MAP),rate-pressure product(RPP)and ventricular arrhythmia were monitored continuously.30 min after ischemia,rats in each group were randomly divided into subgroup A and subgroup B.In subgroup A,the area at risk(AAR)and infarct size(IS)were stained and quantified by Evans blue(EB)and 2,3,5-Triphenyltetrazolium chloride(TTC).In subgroup B,histological changes were observed by HE staining.Main results: The rats' weight and temperature did not differ significantly between the two groups(P>0.05).Compared to S group,ischemia induced in I group resulted in a comparable increase in HR and ST-segment,and decrease in MAP and RPP(P<0.05).Besides,ventricular arrhythmia,such as ventricular premature beat(VPB),ventricular tachycardia(VT)and ventricular fibrillation(VF),were obseved during ischemia.EB and TTC staining confirmed ischemic injury in rats.Under the light microscope,lots of pathological changes,such as wavy phenomenon,irregular arrangement of myocardial fibers,increased eosin-ophilic staining and stripe slur,were observed in I group.Part ?Effects of TMZ on mitochondra function,biogenisis and dynamic networks(fusion and fission)in acute myocardial ischemic ratMethods: Male rats were randomised into three groups,sham group(S group),ischemic group(I group)and trimetazidine(TMZ group).Rats in TMZ group were orally treated by gavage with TMZ at the dose of 10 mg/kg/d,and rats in the other two groups were only given the same quantity of tap water.7 days after oral administration,a 5.0 silk suture was used to permanetly ligate the left coronary artery in I group and TMZ group.Sutures for rats in S group were encircled without tying.Durning ischemia,the same parameters were monitored continuously as described in part?.30 min after ischemia,rats in each group were randomly divided into five subgroups.In subgroup A,the area at risk(AAR)and infarct size(IS)were stained and quantified by EB and TTC.In subgroup B,histological changes were observed by HE staining.In subgroup C,mitochondrial respiratory activity and mitochondrial enzyme activity were detected using an oxygraph.In subgroup D,the mRNA and protein expression of mitochondrial dynamics were assessed by the real time quantitative polymerase chain reaction and western blotting respectively.In subgroup E,mitochondrial structure was performed by electron microscopy.Main results:1.Trimetazidine significantly improved acute myocardial ischemic injury.Compared to S group,the changes of HR,ST-segment,MAP,RPP,ventricular arrhythmia,infarct size staining and pathological changes under the light microscope were the same as part?.Compared to I group,TMZ significantly decreased the total number of ventricular ectopic beats,the incidence of VT/VF,arrhythmia score and infact size.Besides,the detrimental changes was attenuated by TMZ,as evidenced by decreases in wavy phenomenon,irregular arrangement of myocardial fibers and stripe slur.2.Acute myocardial ischemia impaired mitochondrial structure and function,and trimetazidine can help restore its function and structure.Compared to S group,state 3,RCR and complex I activity were significantly decreased in I group.TMZ significantly prevented mitochondrial alteration from the deleterious effect of ischemia,as as evidenced by increasing in state 3,RCR and complex I activity.State 4 and complex ?activity were not significantly changed among groups.Besides,periods of ischemia of 30 mins' duration produced striking ultrastructural changes including swelling mitochondria,disorganization of cristae,an increase in matrix space in I group,and the detrimental changes was attenuated by TMZ.3.Acute myocardial ischemia broke mitochondrial dynamics,and trimetazidine can help restore its dynamics.Compared to S group,the mRNA and protein expression of mfn1,opa1 and drp1 were significantly lower in I group.Besides,the protein expression of mfn2 were significantly lower in I group.TMZ significantly prevented mitochondrial alteration by increasing the mRNA and protein expression of mfn1,opa1,drp1 and mfn2.Conclusions:1.The in vivo rat model of acute myocardial ischemia,showing infarcted myocardium,occurred arrhythmia and cardiac dysfunction,was established successfully in the experiment.2.Trimetazidine significantly improved acute myocardial ischemic injury by decreasing the total number of ventricular ectopic beats,incidence of VT/VF,arrhythmia score,infact size and pathological damage.3.Trimetazidine demonstrated cardioprotective effects through activating mitochondrial respiratory performance,fixing mitochondrial ultrastructure damage,rebalancing mitochondrial dynamic network. |
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