Abstract 15477: MicroRNA-494 Targeting both Pro-apoptotic and Anti-apoptotic Proteins Protects against Ischemia/Reperfusion-Induced Cardiac Injury
Background: microRNAs (miRs) have been implicated in many cardiac pathophysiological processes including ischemia/reperfusion (I/R)-induced cardiac injury. Recently, we and others observed that miR-494 was downregulated in I/R injured mouse and human hearts. However, the functional consequence of miR-494 in response to I/R remains unknown.
Methods and Results: To further elucidate the functional role of miR-494 in both ex vivo and in vivo I/R-induced cardiac injury, we generated a mouse model with cardiac-specific overexpression of miR-494. Transgenic (TG) hearts and wild-type (WT) hearts from multiple lines were subjected to global no-flow I/R using the Langendorff system. We observed that TG hearts exhibited improved recovery of contractile performance over the reperfusion period. This improvement was accompanied by remarkable decreases in both lactate dehydrogenase release and the extent of apoptosis (DNA fragmentation and TUNEL-positive nuclei), compared to WTs (p<0.05, n=6–11). Furthermore, in vivo experiments of 30 min myocardial ischemia, via coronary artery occlusion, followed by 24 h reperfusion, showed that myocardial infarction size was significantly reduced by ∼70% in TGs, versus WTs (p<0.01, n=11). Moreover, in vivo knockdown of miR-494 by three consecutive daily tail vein injection of cholesterol-modified antagomiR-494 (3x40 mg/kg) significantly increased I/R-triggered cardiac apoptosis by ∼30% and infarction size by ∼40%, relative to the administration of mutant antagomiR-494 and saline controls (p<0.05, n=6). Using Target-Scan software, luciferase reporter assay and western-blot analysis, we identified three pro-apoptotic proteins (PTEN, ROCK1 and CaMKIIδ) and two anti-apoptotic proteins (FGFR2 and LIF) were authentic targets for miR-494. Nonetheless, the Akt-mitochondrial signaling pathway was activated in miR-494-overexpressing myocytes.
Conclusion: our findings indicate that although miR-494 targets both pro-apoptotic and anti-apoptotic proteins, the ultimate consequence is activation of the Akt pathway, contributing to its cardioprotective effects against I/R-induced injury. Thus, miR-494 may constitute a new therapeutic agent for the treatment of ischemic heart disease.
- © 2010 by American Heart Association, Inc.