MiR-223-3p as a Novel MicroRNA Regulator of Expression of Voltage-Gated K+ Channel Kv4.2 in Acute Myocardial Infarction.
OBJECTIVE
Acute myocardial infarction (AMI) is a devastating cardiovascular disease with a high rate of morbidity and mortality, partly due to enhanced arrhythmogenicity. MicroRNAs (miRNAs) have been shown to participate in the regulation of cardiac ion channels and the associated arrhythmias. The purpose of this study was to test our hypothesis that miR-223-3p contributes to the electrical disorders in AMI via modulating KCND2, the gene encoding voltage-gated channel Kv4.2 that carries transient outward K+ current Ito.


METHODS
AMI model was established in male Sprague-Dawley (SD) rats by left anterior descending artery (LAD) ligation. Evans blue and TTC staining was used to measure infarct area. Ito was recorded in isolated ventricular cardiomyocytes or cultured neonatal rat ventricular cells (NRVCs) by whole-cell patch-clamp techniques. Western blot analysis was employed to detect the protein level of Kv4.2 and real-time RT-PCR to determine the transcript level of miR-223-3p. Luciferase assay was used to examine the interaction between miR-223-3p and KCND2 in cultured NRVCs.


RESULTS
Expression of miR-223-3p was remarkably upregulated in AMI relative to sham control rats. On the contrary, the protein level of Kv4.2 and Ito density were significantly decreased in AMI. Consistently, transfection of miR-223-3p mimic markedly reduced Kv4.2 protein level and Ito current in cultured NRVCs. Co-transfection of AMO-223-3p (an antisense inhibitor of miR-223-3p) reversed the repressive effect of miR-223-3p. Luciferase assay showed that miR-223-3p, but not the negative control, substantially suppressed the luciferase activity, confirming the direct binding of miR-223-3p to the seed site within the KCND2 sequence. Finally, direct intramuscular injection of AMO-223-3p into the ischemic myocardium to knockdown endogenous miR-223-3p decreased the propensity of ischemic arrhythmias.


CONCLUSIONS
Upregulation of miR-223-3p in AMI repressed the expression of KCND2/Kv4.2 resulting in reduction of Ito density that can cause APD prolongation and promote arrhythmias in AMI, and therefore knockdown of endogenous miR-223-3p might be considered a new approach for antiarrhythmic therapy of ischemic arrhythmias.
Department of Pharmacology (State-Province Key Laboratories of Biomedicine-Pharmaceutics of China, Key Laboratory of Cardiovascular Research, Ministry of Education), Harbin Medical University, Harbin, P.R. China.
Xue
X
Liu
Ying
Y
Zhang
Weijie
W
Du
Haihai
H
Liang
Hua
H
He
Lu
L
Zhang
Zhenwei
Z
Pan
Xuelian
X
Li
Chaoqian
C
Xu
Yuhong
Y
Zhou
Leimin
L
Wang
Ming
M
Qian
Tianyi
T
Liu
Hongli
H
Yin
Yanjie
Y
Lu
Baofeng
B
Yang
Hongli
H
Shan
D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D002478:Cells, Cultured; D005786:Gene Expression Regulation; D015640:Ion Channel Gating / Q000235:genetics / Q000502:physiology; D008297:Male; D008564:Membrane Potentials / Q000235:genetics / Q000502:physiology; D035683:MicroRNAs / Q000235:genetics*; D009203:Myocardial Infarction / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology; D032383:Myocytes, Cardiac / Q000378:metabolism / Q000502:physiology; D018408:Patch-Clamp Techniques; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051672:Shal Potassium Channels / Q000235:genetics* / Q000378:metabolism / Q000502:physiology
C000609258:MIRN223 microRNA, rat; D035683:MicroRNAs; D051672:Shal Potassium Channels