OBJECTIVE To observe the changes of cardiac function, local inflammation level and macrophage M2 polarization in mice with acute myocardial infarction (AMI) after electroacupuncture preconditioning at the Neiguan point, and to explore the possible mechanisms from the perspective of regulating the DNA-PK/Rictor/Myc signaling pathway.
METHODS Male C57BL/6J mice were randomly divided into sham group, model group and electroacupuncture group, with 10 mice in each group. The electroacupuncture group received bilateral electroacupuncture interventions at the Neiguan points, sparse-dense wave, 2/15 Hz, 1 mA, 20 min/time, once a day for 3 consecutive days, and AMI models were performed 0.5 h after the electroacupuncture interventions. The myocardial ischemia model was prepared by ligating the left anterior descending branch. Echocardiography was used to detect cardiac ejection fraction (EF) and fractional shortening (FS) to evaluate cardiac function; HE and TUNEL staining were used to observe the pathological morphology of myocardium and apoptosis of cardiomyocytes, and immunohistochemistry and ELISA were used to detect IL-1β, TNF-α and NLRP3 in infarcted myocardium and peripheral blood to evaluate the level of inflammation; flow cytometry was used to detect cardiac macrophage polarization status, and Western blot method to detect the protein expression levels of DNA-PK, p-DNA-PK, Rictor and Myc in infarcted myocardium.
RESULTS Compared with the sham group, the model group showed significantly lower EF and FS (P < 0.000 1), significant inflammatory cell infiltration, significantly higher cardiomyocyte apoptotic index (P < 0.001), up-regulated expression of IL-1β, NLRP3 and TNF-α in the myocardium and serum (P < 0.01, P < 0.001), a significant increase in the percentage of macrophages (P < 0.001), a decrease in the percentage of cardiac M2-type macrophages (P < 0.000 1), and a significant decrease in the expression levels of p-DNA-PK, Rictor and Myc proteins in myocardium (P < 0.05, P < 0.000 1). Compared with the model group, EF and FS were significantly higher in the electroacupuncture group (P < 0.000 1), inflammatory cell infiltration was reduced, cardiomyocyte apoptotic index was decreased (P < 0.01), and the expression of IL-1β, NLRP3 and TNF-α was down-regulated in myocardium and serum (P < 0.05, P < 0.01, P < 0.001); the macrophage percentage was decreased (P < 0.05), cardiac M2-type macrophage percentage was increased (P < 0.01), and p-DNA-PK, Rictor and Myc protein expression was enhanced in myocardium (P < 0.05, P < 0.01, P < 0.000 1).
CONCLUSION Electroacupuncture preconditioning may promote macrophage M2 polarization, attenuate local inflammation, and reduce cardiomyocyte apoptosis by modulating the DNA-PK/Rictor/Myc signaling pathway, thus improving cardiac function and achieving myocardial protective effects.
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