Melatonin attenuates inflammation and cardiac dysfunction in myocardial infarction by regulating the miRNA-200b-3p/high mobility group box chromosomal protein 1 axis.

Melatonin confers protection against myocardial injury by reducing inflammation and inhibiting apoptosis. In the present study, we investigated whether melatonin regulates cardiomyocyte proliferation and improves cardiac function in rats with myocardial infarction (MI). Two MI models were established in vitro (H9c2 cells were cultured under hypoxia) and in vivo (the left anterior descending coronary artery of rats was surgically ligated). miR-200b-3p and high mobility group box 1 (HMGB1) levels were detected. Cell proliferation and apoptosis were analyzed in vitro, and cardiac function, inflammatory cytokines, and myocardial injury markers in vivo were tested. The experimental results reported that melatonin promoted proliferation and impaired apoptosis of H9c2 cells cultured in hypoxia. In vivo, melatonin improved cardiac function and inhibited the inflammation and myocardial injury of rats with MI. miR-200b-3p was downregulated and HMGB1 was upregulated in MI, while melatonin could upregulate miR-200b-3p and downregulate HMGB1. The HMGB1 was targeted by miR-200b-3p. Upregulating miR-200b-3p or downregulating HMGB1 could further promote the therapeutic effect of melatonin, and downregulating miR-200b-3p or upregulating HMGB1 could abolish the therapeutic effect of melatonin. In conclusion, melatonin alleviates inflammation and cardiac dysfunction after MI by regulating the miR-200b-3p/HMGB1 axis, offering a new therapeutic strategy for MI.