title: Loss of the miR-144/451 cluster impairs ischaemic preconditioning-mediated cardioprotection by targeting Rac-1.
abstract: OBJECTIVE
  While a wealth of data has uncovered distinct microRNA (miR) expression alterations in hypertrophic and ischaemic/reperfused (I/R) hearts, little is known about miR regulation and response to ischaemic preconditioning (IPC).
  
  
  RESULTS
  We analysed miRs in murine hearts preconditioned with six cycles of 4 min ischaemia via coronary artery occlusion, followed by 4 min reperfusion in vivo. Both miRs within the miR-144/451 cluster were the most elevated among a cohort of 21 dysregulated miRs in preconditioned hearts, compared with shams. To investigate the significance of this finding, we examined IPC-mediated cardioprotection within a miR-144/451-knockout (KO) mouse model. Wild-type (WT) hearts exposed to IPC followed by I/R (30 min/24 h) showed a smaller infarction size compared with mice treated with I/R alone. In contrast, IPC failed to protect miR-144/451-KO hearts against infarct caused by I/R treatment. Thus, the miR-144/451 cluster is required for IPC-elicited cardioprotection. Rac-1, a key component of NADPH oxidase, was mostly up-regulated in KO hearts among three bona fide targets (Rac-1, 14-3-3ζ, and CUGBP2) for both miR-144 and miR-451. Accordingly, reactive oxygen species (ROS) levels were markedly increased in KO hearts upon IPC, compared with IPC-WT hearts. Pre-treatment of KO hearts with a Rac-1 inhibitor NSC23766 (20 mg/kg, ip) reduced IPC-triggered ROS levels and restored IPC-elicited cardioprotection. Using antagomiRs, we showed that miR-451 was largely responsible for IPC-mediated cardioprotection.
  
  
  CONCLUSIONS
  Loss of the miR-144/451 cluster limits IPC cardioprotection by up-regulating Rac-1-mediated oxidative stress signalling.
authors.affiliation: Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0575, USA.
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Wang
authors.forename: Hongyan
authors.initials: H
authors.lastname: Zhu
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Zhang
authors.forename: Yong
authors.initials: Y
authors.lastname: Liu
authors.forename: Jing
authors.initials: J
authors.lastname: Chen
authors.forename: Mario
authors.initials: M
authors.lastname: Medvedovic
authors.forename: Hongliang
authors.initials: H
authors.lastname: Li
authors.forename: Mitchell J
authors.initials: MJ
authors.lastname: Weiss
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Ren
authors.forename: Guo-Chang
authors.initials: GC
authors.lastname: Fan
mesh_terms: D000818:Animals; D015153:Blotting, Western; D019157:Ischemic Preconditioning, Myocardial / Q000379:methods*; D051379:Mice; D018345:Mice, Knockout; D035683:MicroRNAs / Q000378:metabolism*; D009203:Myocardial Infarction / Q000378:metabolism* / Q000517:prevention & control; D015428:Myocardial Reperfusion Injury / Q000378:metabolism* / Q000517:prevention & control; D009206:Myocardium / Q000378:metabolism*; D018384:Oxidative Stress / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism*
chemical_list: C551064:MIRN144 microRNA, mouse; D035683:MicroRNAs; C550758:Mirn451 microRNA, mouse; D017382:Reactive Oxygen Species