Ischemic Postconditioning-Regulated miR-499 Protects the Rat Heart Against Ischemia/Reperfusion Injury by Inhibiting Apoptosis through PDCD4

BACKGROUND: Here, we determined miR-499 involvement in the protective effect of ischemic postconditioning (IPC) against myocardial ischemia/reperfusion (I/R) injury and identified the underlying mechanisms. METHODS: To investigate the cardioprotective effect of IPC-induced miR-499, rats were divided into the following five groups: sham, I/R, IPC, IPC + scramble, and IPC + antagomiR-499. Hemodynamic indexes were measured by carotid-artery intubation to assess left ventricular function . Ischemia and infarction areas of rat hearts were determined by Evans blue and triphenyltetrazolium chloride staining, and cardiomyocyte apoptosis was detected by terminal deoxynucleotidyl transferase dUTP nick-end-labeling assay. RESULTS: IPC attenuated I/R-induced infarct size of the left ventricle (45.28 ± 5.40% vs. 23.56 ± 6.20%, P < 0.05), myocardial apoptosis, and decreased creatine kinase (1867.31 ± 242.41% vs. 990.21 ± 172.39%, P < 0.05), lactate dehydrogenase (2257.50 ± 305.11% vs. 1289.11 ± 347.28%, P < 0.05), and malondialdehyde levels (7.18 ± 1.63% vs. 4.85 ± 1.52%, P < 0.05). Additionally, left ventricular systolic pressure, +dp/dtmax, and -dp/dtmax were elevated, and left ventricular end diastolic pressure was significantly reduced in the IPC group. Furthermore, IPC-mediated cardiac protection against I/R injury was inhibited in vivo and in vitro by knockdown of cardiac miR-499, suggesting that miR-499 may participate in the protective function of IPC against I/R injury through targeting programmed cell death 4 (PDCD4). CONCLUSION: Our data revealed that IPC-regulated miR-499 plays an important role in IPC-mediated cardiac protection against I/R injury by targeting PDCD4.