• Xiaohui Wang, Tuanzhu Ha, Jianghuan Zou, Danyang Ren, Li Liu, Xia Zhang, John Kalbfleisch, Xiang Gao, David Williams, and Chuanfu Li.
• Department of Surgery, James H. Quillen College of Medicine, East Tennessee State University, Campus Box 70575, Johnson City, TN 37614-0575, USA.
• Cardiovasc. Res. 2014 Jun 1; 102 (3): 385-95.

AimsThe present study examined the role of microRNA-125b (miR-125b) in myocardial ischaemia/reperfusion (I/R) injury. We constructed lentivirus-expressing miR-125b (LmiR-125b) and developed transgenic mice with overexpression of miR-125b.Methods And ResultsLmiR-125b was transfected into mouse hearts through the right common carotid artery. Lentivirus vector (LmiR-Con) served as vector control. Untreated mice served as I/R control. Sham operation served as sham control. Seven days after transfection, the hearts were subjected to ischaemia (45 min) followed by reperfusion (4 h). Myocardial infarct size was analysed by 2,3,5-triphenyltetrazolium chloride staining. In separate experiments, hearts were subjected to ischaemia (45 min) followed by reperfusion for up to 7 days. Cardiac function was measured by echocardiography before, as well as 3 and 7 days after myocardial I/R. Increased expression of miR-125b significantly decreased I/R-induced myocardial infarct size by 60% and prevented I/R-induced decreases in ejection fraction (EF%) and fractional shortening (%FS). Transgenic mice with overexpression of miR-125b also showed the protection against myocardial I/R injury. Increased expression of miR-125b attenuated I/R-induced myocardial apoptosis and caspase-3/7 and -8 activities. Western blot showed that increased expression of miR-125b suppresses p53 and Bak1 expression in the myocardium. In addition, transfection of LmiR-125b decreased the levels of TNF receptor-associated factor 6 (TRAF6) and prevented I/R-induced NF-κB activation.ConclusionmiR-125 protects the myocardium from I/R injury by preventing p53-mediated apoptotic signalling and suppressing TRAF6-mediated NF-κB activation.Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2014. For permissions please email: journals.permissions@oup.com.

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