Abstract 19386: Adaptive Upregulation of MicroRNA-146b Following Surgical Ischemia-Reperfusion Attenuates Myocardial Inflammation
Introduction: Using a comparative biology approach we prioritized microRNAs (miRs) deregulated by surgical myocardial I/R. We hypothesized that in vitro overexpression of miR-146b is cardioprotective following simulated I/R through attenuation of NF-kB mediated inflammation. Finally, we compared two delivery methods of miR modulators - chemical transfection versus nanoparticle-bound.
Methods: 1) miR expression analysis - microarray of myocardium from 2 models of I/R: a) rats - cardioplegic arrest (CA) or deep hypothermic circulatory arrest (DHCA) and 24h reperfusion, or sham; 2 rat strains with different susceptibilities to myocardial I/R used - Brown Norway (BN) and Dahl Salt Sensitive (DSS); b) pigs - CA or DHCA and 6h reperfusion, or sham (N=4/group). Deregulated miRs (FDR <0.1) validated by qPCR. 2) miR-146b functional analysis- ARVCs transfected with miR-146b mimics or inhibitors, subjected to 2h OGD - 6h reoxygenation; target gene expression IRAK1 and TRAF6 qPCR and Western; necrosis and apoptosis assays. 3) Nanoparticle delivery - chemical or nanoparticle-mediated ARVC transfection monitored as above plus Cy3-miR. Nanoparticle-bound Cy3-miR administered to rats in cardioplegia; biodistribution by fluorescence microscopy.
Results: Robust post I/R miR-146b upregulation conserved across species, experimental conditions, and reperfusion timepoints (Fig, A). Different miR-146b expression between rat strains (BN vs DSS) corresponded to severity of myocardial injury. miR-146b overexpression attenuated IRAK 1, TRAF6 and NF-kB p65 upregulation following simulated I/R (Fig, B), resulting in improved cardiomyocyte viability (Fig, C). Nanoparticles show superior transfection efficiency to chemical methods in vitro, and early extravascular myocardial distribution.
Conclusion: miR-146b may exert inhibitory feedback on NF-kB activation through effects on key regulatory elements IRAK1 and TRAF6 with potential cardioprotective roles.
- © 2012 by American Heart Association, Inc.