RESUMO
ObjectiveThis study was designed to explore the effect of MG53 on cardiac function affected by acute doxorubicin （DOX）-induced cardiotoxicity （DIC） in mice and its possible mechanism. MethodsIn vivo， C57BL/6 mice were injected intraperitoneally with twenty mg/kg DOX for one week to induce the acute DIC. In vitro， neonatal rat cardiomyocytes （NRCs） were treated with 1 μmol/L DOX to induce DIC. A small animal ultrasound imaging system was used to evaluate cardiac function， and the left ventricular changes in ejection fraction （EF） and fraction shortening （FS） were measured. qPCR technology was used to evaluate cardiac remodeling related factors ANP， BNP and α-MHC， autophagy-related factors Beclin1 and LC3， and apoptosis-related factor CASPASE3. Autophagy-related protein levels of Beclin1， LC3 and apoptosis-related protein levels of caspase3 were assessed by Western Blot. Transmission electron microscopy （TEM） was used to detect autophagosomes in heart tissues. TUNEL assay kit was used to detect apoptosis in neonatal murine cardiomyocytes. ResultsThe small animal ultrasound imaging revealed cardiac function was significantly reduced by doxorubicin in the DOX group and DOX+AAV9-NC group compared with the sham group （EF： Sham： 86.06 ± 2.08 vs. DOX：58.97 ± 1.62， P < 0.000 1； Sham： 86.06 ± 2.08 vs. DOX+AAV9-NC： 59.00 ± 1.86， P < 0.000 1. FS： Sham： 45.47 ± 1.95 vs. DOX：30.68 ± 1.21， P < 0.000 1； Sham： 45.47 ± 1.95 vs. DOX+AAV9-NC： 30.79 ± 1.13， P < 0.000 1）. However， the overexpression of MG53 with adeno-associated virus9 （AAV9） ameliorated cardiac dysfunction （EF： DOX+AAV9-MG53： 66.93 ± 1.78 vs. DOX+AAV9-NC： 59.00 ± 1.86， P < 0.000 1. FS： DOX+AAV9-MG53： 36.35 ± 1.33 vs. DOX+AAV9-NC： 30.79 ± 1.13， P < 0.000 1）. TEM showed autophagosomes were increased in the DOX+AAV9-MG53 group compared with the DOX group and DOX+AAV9-NC. qPCR results suggested that MG53 down-regulated the mRNA expression of cardiac remodeling related genes. Additionally， Western blot results confirmed that the protein level of caspases3 was decreased and Beclin1 and LC3 expression was increased in the DOX+AAV9-MG53 group compared with those in the DOX group and DOX+AAV9-NC group （caspase： DOX+AAV9-MG53： 1.49 ± 0.13 vs. DOX+AAV9-NC： 2.49 ± 0.46， P = 0.000 2； Beclin-1： DOX+AAV9-MG53：0.82 ± 0.02 vs. DOX+AAV9-NC： 0.62 ± 0.05， P < 0.000 1； LC3： DOX+AAV9-MG53： 0.83 ± 0.04 vs. DOX+AAV9-NC： 0.40 ± 0.05， P < 0.000 1）. In contrast， knockdown of MG53 significantly up-regulated the protein level of Caspase3 and significantly down-regulated the protein level of Beclin1 and LC3 （caspase： DOX+si-MG53： 4.52 ± 0.28 vs. DOX+si-NC： 3.37 ± 0.08， P < 0.000 1； Beclin-1： DOX+si-MG53： 0.34 ± 0.06 vs. DOX+si-NC： 0.54 ± 0.07， P = 0.026 2； LC3： DOX+si-MG53： 0.41 ± 0.12 vs. DOX+si-NC： 0.70 ± 0.07， P = 0.001 5）. TUNEL analysis showed overexpression of MG53 significantly inhibited the apoptosis of cardiomyocytes （DOX+Ad-MG53： 9.41 ± 0.53 vs. DOX+Ad-NC： 29.34 ± 7.29， P < 0.000 1）， and knockdown of MG53 significantly facilitate the apoptosis of cardiomyocytes （DOX+si-MG53： 71.34 ± 5.90 vs. DOX+si-NC： 32.19 ± 9.91， P < 0.000 1）. ConclusionMG53 inhibits cardiac apoptosis and enhances autophagy， which delays cardiac remodeling and ameliorates cardiac dysfunction.