[Effect of different electrical current intensities of electroacupuncture preconditioning on cardiac function and macrophage polarization in mice with acute myocardial ischemia].

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 C57BL/6J 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 CD11b+F480+CD206, M2 macrophages were labeled with CD11b+F480+CD206 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 (<0.000 1), number of cardiac macrophages and percentage of M1 type macrophages (<0.000 1), and the expression levels of myocardial IL-1β, TNF-α, TLR4 proteins (<0.001, <0.01), and a remarkable decrease in the levels of EF, FS and the percentage of M2 type macrophages (<0.000 1). In contrast to those of the model group, the area of myocardial infarction (<0.000 1, <0.01), expression levels of myocardial IL-1β, TNF-α, TLR4 proteins (<0.01, <0.05, <0.001) in the 0.5 mA, 1 mA and 3 mA groups, number of macrophages and percentage of M1 macrophages (<0.05) in the 1 mA group were significantly decreased, while the levels of EF and FS (<0.000 1, <0.05, <0.001) in the 3 EA groups, and percentage of M2 macrophage (<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 (<0.01, <0.001), and in down-regulating the area of infarct myocardium (<0.01, <0.000 1), and the expression of TLR4 protein (<0.01), and 0.5 mA group in the expression of IL-1β and TNF-α proteins (<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.