Enhanced expression of let-7f after ischemic preconditioning in rat heart is cardioprotective

microRNAs (miRNA) have been established to play vital roles in cardiovascular diseases such as cardiac hypertrophy and atherosclerosis. The present study was performed to elucidate the effect of microRNAs during cardiac ischemic preconditioning in rats. microArray screening revealed that compared with sham-operated rats, 4 miRNAs in ischemic reperfusion area of rat hearts undergoing 3 cycles of 5 min ischemia intermitted with 5 min reperfusion were upregulated and 5 were downregulated. The expression changes were more significant in nonischemic area of IP hearts in comparison with sham-operated hearts, with 23 microRNAs upregulated and 9 downregulated. qRT-PCR identification showed that of all the abberant expressed microRNAs after IPC, let-7f demonstrated most significant change, which was 6 times more abundant than control hears. Transfection of let-7f alleviated H2O2 induced cell damage in neonatal cardiac myocytes in MTT assay and TUNEL staining. These results showed that miRNAs are important regulators of IPC, which are possibly to be developed into novel agents in treating cardiac ischemia reperfusion damage. Further studies are needed to identify the gene targets by which miRNA produce protective action.