Aerobic-exercise-induced Activation of PI3K-Akt-PKG-1/p-PLN-SERCA2a Pathway Inhibits Myocardial Cell Apoptosis and Improves Cardiac Function in Myocardial Infarction Rats

To investigate the effect of aerobic exercise on cardiac function in myocardial infarction rats, SD male rats were randomly divided into normal group (C group), sham operation group (S group), myocardial infarction group (MI group), normal+exercise group (CE group) and myocardial infarction+exercise group (ME group) after 1 week of adaptive feeding. Then, an MI model was established by ligating the left anterior descending coronary artery and group S only threading without ligation. One week after surgery, animals were randomly assigned to receive 4 weeks of no training or training (1 h/d, 5 d/week on a treadmill). In detail, the training consisted of two 10-minute sessions at speed of 10 m/min and 13 m/min, and the remaining 40 min at speed of 16 m/min. The next day after the training, blood flow mechanics was used to detect cardiac function. A single cell visual moving edge detection system (Ion Optix) was used to determine [Ca2+](i) amplitude, [Ca2+](i) fluorescence ratio, departure velocity, time to peak(TTP), time to peak50%(TTP50%), time to baseline50%(TTB50%), return velocity, ratio amplitude, maximum contraction and diastolic rate of sarcomere(+/- dl/dtmax), sarcomere length(SL), peak twitch amplitude(PTA) and SL shortening%. The related proteins of PI3K-AKT-PKG-1/p-PLN-SERCA2a signaling pathway and apoptosis were detected by PI3K-AKT-PKG-1/p-PLN-SERCA2a signaling pathway and apoptosis related proteins were detected by Western blotting. Compared with group S, in group MI, PI3K-Akt-PKG-1/pPLN-SERCA2a signaling pathway is significantly inhibited, apoptosis and left ventricular end-diastolic pressure (LVEDP) are significantly increased, left ventricular systolic pressure (LVSP) and maximum pressure increasing and decreasing rate(+/- dp/dtmax), [Ca2+](i) amplitude, [Ca2+](i) ratio amplitude, departure velocity and return velocity all significantly reduce, and TTB50%, TTP and TTP50% both significantly increase. The myocardial cells were significantly reduced at the SL shortening%, PTA, +/- dp/dtmax. Compared with MI group, PI3K-Akt-PKG-1/pPLN-SERCA2a signaling pathway in ME group is significantly activated, apoptosis and LVEDP are significantly reduced, LVSP and +/- dp/dtmax are significantly increased, ratio amplitude, [Ca2+](i) amplitude, ratio velocity and departure velocity are significantly increased, and TB50%, TTP and TTP50% are significantly shortened. The myocardial cells were significantly inaeased at the SL shortening%, PTA, +/- dp/dtmax. It can be concluded that aerobic exercise improves the calcium transient and myocardial systolic function in peripheral infarction area of MI rats, activates the PI3K-Akt-PKG-1/p-PLN-SERCA2a signal, inhibits the apoptosis of myocardial cells, and improves myocardial infarction function. Moreover, the improvement of myocardial infarction function is closely related to the activation of PI3K-Akt-PKG-1/p-PLN-SERCA2a signaling pathway and the inhibition of myocardial cell apoptosis.