MicroRNA-320 is involved in the regulation of cardiac ischemia/reperfusion injury by targeting heat-shock protein 20.
BACKGROUND
Recent studies have identified critical roles for microRNAs (miRNAs) in a variety of cellular processes, including regulation of cardiomyocyte death. However, the signature of miRNA expression and possible roles of miRNA in the ischemic heart have been less well studied.


RESULTS
We performed miRNA arrays to detect the expression pattern of miRNAs in murine hearts subjected to ischemia/reperfusion (I/R) in vivo and ex vivo. Surprisingly, we found that only miR-320 expression was significantly decreased in the hearts on I/R in vivo and ex vivo. This was further confirmed by TaqMan real-time polymerase chain reaction. Gain-of-function and loss-of-function approaches were employed in cultured adult rat cardiomyocytes to investigate the functional roles of miR-320. Overexpression of miR-320 enhanced cardiomyocyte death and apoptosis, whereas knockdown was cytoprotective, on simulated I/R. Furthermore, transgenic mice with cardiac-specific overexpression of miR-320 revealed an increased extent of apoptosis and infarction size in the hearts on I/R in vivo and ex vivo relative to the wild-type controls. Conversely, in vivo treatment with antagomir-320 reduced infarction size relative to the administration of mutant antagomir-320 and saline controls. Using TargetScan software and proteomic analysis, we identified heat-shock protein 20 (Hsp20), a known cardioprotective protein, as an important candidate target for miR-320. This was validated experimentally by utilizing a luciferase/GFP reporter activity assay and examining the expression of Hsp20 on miR-320 overexpression and knockdown in cardiomyocytes.


CONCLUSIONS
Our data demonstrate that miR-320 is involved in the regulation of I/R-induced cardiac injury and dysfunction via antithetical regulation of Hsp20. Thus, miR-320 may constitute a new therapeutic target for ischemic heart diseases.
Ren
Xiao-Ping
XP
Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH 45267.
Wu
Jinghai
J
Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH 45267.
Wang
Xiaohong
X
Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH 45267.
Sartor
Maureen A
MA
Department of Environmental Health, University of Cincinnati College of Medicine, Cincinnati, OH 45267.
Jones
Keith
K
Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH 45267.
Qian
Jiang
J
Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH 45267.
Nicolaou
Persoulla
P
Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH 45267.
Pritchard
Tracy J
TJ
Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH 45267.
Fan
Guo-Chang
GC
Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH 45267.
D000818:Animals; D002316:Cardiotonic Agents; D016923:Cell Death; D002478:Cells, Cultured; D020869:Gene Expression Profiling; D050886:HSP20 Heat-Shock Proteins / Q000235:genetics*; D051379:Mice; D008822:Mice, Transgenic; D035683:MicroRNAs / Q000235:genetics / Q000502:physiology*; D015428:Myocardial Reperfusion Injury / Q000235:genetics*; D032383:Myocytes, Cardiac
D002316:Cardiotonic Agents; D050886:HSP20 Heat-Shock Proteins; D035683:MicroRNAs; C541056:Mirn320 microRNA, mouse