LncRNA MALAT1 protects cardiomyocytes from isoproterenol‐induced apoptosis through sponging miR‐558 to enhance ULK1‐mediated protective autophagy

Investigating the molecular mechanisms of myocardial infarction (MI) and subsequent heart failure have gained considerable attention worldwide. Long noncoding RNA (lncRNA) metastasis‐associated lung adenocarcinoma transcript 1 (MALAT1) has been previously demonstrated to regulate the proliferation and metastasis of several tumors. However, little is known about the effects of MALAT1 in MI and in regulating the cell date after MI. In our study, first, it was shown that the expression levels of MALAT1 were increased in the MI samples compared with normal tissues using quantitative reverse‐transcription polymerase chain reaction. Then, MALAT1 knock- down could significantly decrease the cell viability and increase the apoptotic rates in isoproterenol (ISO)‐treated H9C2 cells. In addition, we screened the possible target and found that miR‐558 is its direct target using dual luciferase reporter assay, indicating that MALAT1 functioned as decoys sponging miR‐558. Transfection of miR‐ 558 mimic decreased the cell viability and enhanced the apoptosis. Furthermore, we revealed that miR‐558 could downregulate ULK1 expression and suppressed ISO‐ induced protective autophagy. Activation of MALAT1/miR‐558/ULK1 pathway protected H9C2 cells from ISO‐induced mitochondria‐dependent apoptosis. Finally, we used MALAT1‐knockout mice to further demonstrated that MALAT1 protected cardiomyocytes from apoptosis and partially improved the cardiac functions upon ISO treatment. In conclusion, we elucidated that lncRNA MALAT1 protected cardiomyo- cytes from ISO‐induced apoptosis by sponging miR‐558 thus promoting ULK1‐ dependent autophagy. Targeting lncRNA MALAT1 might become a potential strategy in protecting cardiomyocytes during MI.