This study aimed to examine the functional role of microRNA-20 (miR-20) and its potential target, Kir6.1, in ischemic myocardiocytes. The expression of miR-20 was detected by real-time PCR. Myocardiocytes were stained with terminal deoxynucleotidyl transferase dUTP nick end labeling (TU-NEL) reagent for apoptosis evaluation. Western blotting was used to detect the Kir6.1 protein in ischemic myocardiocytes transfected with miR-20 mimics or inhibitors. Luciferase reporter gene assay was performed to confirm the targeting effect of miR-20 on KCNJ8. The results showed that miR-20 was remarkably down-regulated, while the KATP subunit Kir6.1 was significantly up-regulated, during myocardial ischemia. The miR-20 overexpression promoted the apoptosis of ischemic myocardiocytes, but showed no such effect on normal cells. Under ischemic condition, myocardiocytes transfected with miR-20 mimics expressed less Kir6.1. On the contrary, inhibiting miR-20 increased the expression of Kir6.1 in the cells. Co-transfection of miR-20 mimics with the KCNJ8 3'-UTR plasmid into HEK293 cells consistently produced less luciferase activity than transfection of the plasmid alone. It was concluded that miR-20 may regulate myocardiac ischemia by targeting KATP subunit Kir6.1 to accelerate the cell apoptosis. Therefore miR-20 may serve as a therapeutic target for myocardial ischemic disease.
Keywords: KATP; Kir6.1; miR-20; myocardiac ischemia.