Objective To observe the effect of electroacupuncture(EA)at different time-points on the injured myocardium and expression of myocardial Bax/Bcl-2 and Lc 3Ⅱ/Ⅰ proteins in acute myocardial ischemia-reperfusion injury(MIRI)rats so as to explore its mechanisms underlying myocardial protective effect via reducing cardiomyocyte autophagy and apoptosis.Methods A total of 66 adult SD rats were randomly divided into sham operation(sham)

model

EA-R 0 min(R=reperfusion)

EA-R30 min

EA-R 60 min

and EA-R 120 mingroups

with 6 rats being in the sham group and 12 rats being in each of the other 5 groups.The MIRI model was prepared by ligating the anterior descending branch(ADB)of the left coronary artery for 30 min followed by reperfusion for 4 h.In the sham group

the ADB was only threaded without ligation.EA was applied to bilateral"Neiguan"(PC 6)for 20 min at 0

30

60

and 120 min when reperfusion.Evans Blue-triphenyltetrazolium chloride(TTC)double staining was performed to determine the myocardial infarction area(MIA)and the ratio of the infarct size of the area at risk(IS/AAR).ELISA was performed to measure serum cardiac troponin 1(cTn-Ⅰ)content

and Western blot was used to measure the expression of apoptosis-related proteins Bax and Bcl-2 and autophagy related proteins Lc 3 Ⅱ and Lc 3 Ⅰin the left cardiac ventricle tissue.Results Compared with the model group

the percentages of MIA in the EA-R 30 min

EA-R 60 min

and EA-R 120 mingroups

and the IS/AAR in the EA-R 0 min

EA-R 30 min

EA-R 60 minand EA-R 120 mingroups were significantly reduced(P<0.05

P<0.01).Comparison among the 4 EA groups showed that the percentages of MIA and the IS/AAR were considerably lower in the EA-R 30 min

EA-R60 min

and EA-R 120 mingroups than in the EA-R 0 mingroup(P<0.05

except IS/AAR in the EA-R 120 mingroup)

but significantly higher in the EA-R 60 minand EA-R 120 mingroups than in the EA-R 30 mingroup(P<0.05

P<0.01)

suggesting a better therapeutic effect of EA intervention at 30 min of MIRI in improving MI.In comparison with the sham group

myocardial cTn-Ⅰ content and Bax/Bcl-2 and Lc 3Ⅱ/Ⅰlevels in the model group were significantly increased(P<0.01).After EA intervention

the increased cTn-Ⅰ content and Bax/Bcl-2 and Lc 3 Ⅱ/Ⅰlevels in the EA-R 0 min

EA-R 30 min

EA-R 60 min

and EA-R 120 mingroups were significantly reduced(P<0.05

P<0.01).The cTn-Ⅰ content was obviously lower at EA-R 30 min

but markedly increased at EAR 120 minthan at EA-R 0 min(P<0.05).The expression of Bcl-2 was obviously higher at EA-R 30 minthan at EA-R 0 min(P<0.05).No significant differences were found among the 4 EA intervention time-points in the levels of Bax/Bcl-2 and Lc 3Ⅱ/Ⅰ(P>0.05).Conclusion EA intervention can reduce MIA in MIRI rats

which is possibly closely related to its effects in reducing apoptosis and autophagy.The best intervention time is at 30 min after MI reperfusion

but the difference of effects of EA at different timepoints is independent of Bax/Bcl-2 and Lc 3 Ⅱ/Ⅰ expression.