Objective To observe the effect of different intensities of electroacupuncture(EA) preconditioning on car-diac function and polarization state of macrophages in mice with acute myocardial ischemia(AMI)

so as to explore its possible mechanism underlying improvement of AMI. Methods A total of 50 male C57 BL/6 J mice were randomly divided into sham ope-ration

AMI model

and EA pretreatment groups(0.5 mA

1 mA

3 mA subgroups)

with 10 mice in each group/subgroup. The mice in the EA pretreatment groups were subjected to EA stimulation of bilateral “Neiguan”(PC6) with 0.5

1.0 and 3 mA respectively and frequency of 2 Hz/15 Hz for 20 min

once a day

for 3 days. The acute myocardial ischemia model was established by ligating the anterior descending branch(ADB) of the left coronary artery

while the sham operation only had a surgical suture trans-passed below the ADB but without ligation. The myocardial infarction area was measured after TTC staining

and the cardiac function [left ventricular ejection fraction(EF)

short-axis contraction rate(FS)] was detected by using echocardiography. The M1 macrophages were labeled with CD11 b+F480+CD206

(low)

M2 macrophages were labeled with CD11 b+F480+CD206(low)

M2 macrophages were labeled with CD11 b+F480+CD206

(high)

and detected by using flow cytometry

and the expression levels of myocardial interleukin-1β(IL-1β)

tumor necrosis factor-α(TNF-α)

Toll-like receptor-4(TLR4) proteins were detected by using Western blot. Results Compared with the sham operation group

the model group had a significant increase in the infarction area(P

<

0.000 1)

number of cardiac macrophages and percentage of M1 type macrophages(P

<

0.000 1)

and the expression levels of myocardial IL-1β

TNF-α

TLR4 proteins(P

<

0.001

P

<

0.01)

and a remarkable decrease in the levels of EF

FS and the percentage of M2 type macrophages(P

<

0.000 1). In contrast to those of the model group

the area of myocardial infarction(P

<

0.000 1

P

<

0.01)

expression levels of myocardial IL-1β

TNF-α

TLR4 proteins(P

<

0.01

P

<

0.05

P

<

0.001) in the 0.5 mA

1 mA and 3 mA groups

number of macrophages and percentage of M1 macrophages(P

<

0.05) in the 1 mA group were significantly decreased

while the levels of EF and FS(P

<

0.000 1

P

<

0.05

P

<

0.001) in the 3 EA groups

and percentage of M2 macrophage(P

<

0.05) in the 1 mA group were significantly increased. Comparison among the 3 EA groups displayed that the effects of 1 mA group were significantly superior to those of 0.5 and 3 mA groups in up-regulating EF and FS(P

<

0.01

P

<

0.001)

and in down-regulating the area of infarct myocardium(P

<

0.01

P

<

0.000 1)

and the expression of TLR4 protein(P

<

0.01)

and 0.5 mA group in the expression of IL-1β and TNF-α proteins(P

<

0.05). Conclusion EA preconditioning with electrical current intensities of 0.5 mA

1 mA and 3 mA can effectively reduce myocardial infarction size

improve cardiac function in mice with AMI

which may be related with its effects in reducing the number of cardiac macrophages and down-regulating the expression of myocardial IL-1β

TNF-α and TLR4 proteins. The therapeutic effect of 1 mA is better than that of 0.5 and 3 mA.