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[Electroacupuncture and moxibustion pretreatments reduce cardiomyocyte apoptosis and autophagy in rats with myocardial ischemia/reperfusion injury].

OBJECTIVE
To observe the effect of "Neiguan" (PC6)-electroacupuncture (EA) or moxibustion (Moxi) pretreatment on myocardial apoptosis and expression of autophagy related proteins light chain (LC) 3-Ⅰ and LC3-Ⅱ in rats with myocardial ischemia/reperfusion injury (MIRI), so as to explore their mechanisms underlying improvement of MIRI.


METHODS
Forty SD rats (half male and half female) were randomly divided into sham operation, model, ischemic preconditioning (IP), EA and Moxi groups (n＝8 in each group). EA (10 Hz/50 Hz, 1 mA) or Moxi (ignited moxa stick) was respectively applied to bilateral "Neiguan" (PC6) for 20 min, once daily for 7 days. The MIRI model was established by occlusion of the anterior descending branch of the left coronary artery for 40 min, followed by reperfusion for 60 min. The ultrastructural changes and autophagy of myocardial cells were observed by electron microscopy (EM), and the myocardial cellular apoptosis [apoptotic index ＝ (number of apoptotic cells/total number of cardiomyocytes)×100%] was detected by the terminal deoxyribonucleotidyl transferase mediated dUTP nick end labelling (TUNEL) method. The expressions of LC3-Ⅰ and LC3-Ⅱ proteins (markers for autophagy) in myocardial tissue were detected by Western blot.


RESULTS
Following MI, EM observation revealed a vague structure of cardiomyocytes and muscular horizontal grain, dissolution of myofibers, mitochondrial swelling, some autophagic vacuoles and autophagic lysosomes at different degrees and surrounded by a double membrane in the model group, these situations were apparently milder in the EA and Moxi groups. The apoptosis index, myocardial LC3-Ⅰ and LC3-Ⅱ protein expression levels, and the ratio of LC3-Ⅱ/Ⅰ were significantly increased in the model group relevant to the sham operation group (P<0.05). After the treatment, the apoptosis index, the expression level of myocardial LC3-Ⅱ protein and the ratio of LC3-Ⅱ/Ⅰ were considerably down-regulated in the IP, EA and Moxi groups in comparison with those in the model group (P<0.05). The effect of EA was obviously superior to those of IP and Moxi in down-regulating the apoptosis index (P<0.05), but obviously inferior to those of IP and Moxi in down-regulating the levels of LC3-Ⅱ and LC3-Ⅱ/Ⅰ (P<0.05). No significant changes were found in the expression of LC3-Ⅰ after IP, EA and Moxi interventions in comparison with the model group (P>0.05), and no significant differences were observed in the apoptosis index and levels of LC3-Ⅱ and LC3-Ⅱ/Ⅰ between the IP and Moxi groups (P>0.05)．.


CONCLUSION
Both EA and moxibustion pretreatments, similar to IP, have a positive role in reducing myocardiocyte apoptosis and regulating autophagy-related protein expression in MIRI rats, which maybe contribute to their protective effects on ischemic myocardium.