Abstract 17091: MicroRNA-20a Controls Biomechanical Stress-Induced Cardiomyocyte Apoptosis via Its Novel Target Egln-3/PHD3
Biomechanical stress and ischemia/hypoxia are known stimuli of cardiomyocyte apoptosis. In an effort to identify novel mediators of cardiac apoptosis, we have shown that biomechanical stretch induces a characteristic gene and microRNA expression pattern. MiR-20a, which is part of the miR-17∼92 cluster, was markedly upregulated by both biomechanical stress and hypoxia. On a functional level, adenoviral overexpression of miR-20a (AdVmiR-20a) inhibited hypoxia-mediated apoptosis in a dose-dependent fashion, while antimirs against miR-20a led to an increased rate of programmed cell death. In order to identify novel targets of miR-20a mediating its antiapoptotic properties, we used 3’UTR luciferase assays to validate predictions obtained from current databases. Besides known targets such as the E2F family, we could detect and confirm the prolyl hydroxylase Egln-3/PHD3 as a previously unknown target of miR-20a. To further analyze the functional role of Egln-3 downstream of miR-20a in cardiomyocytes, we generated adenoviral constructs for knockdown of Egln-3. Phasic biaxial stretch (+15%, 24 h) was applied to neonatal rat cardiomyocytes (NRCMs), causing a significant increase of apoptosis (+53% of cleaved/total caspase 3-ratio/+40% of cleaved/total caspase-7 ratio, both p<0.05). Simultaneous knockdown of Egln-3 completely prevented the stretch-mediated induction of apoptosis (as measured by cleaved/total caspase 3 and 7-ratios, n=3 each, both p<0.05). Similar results could be obtained using adenovirally overexpressed miR-20a. Stretch led to a 47% increase of the cleaved/total caspase 3- (p<0.05) as well as 113% increase of cleaved/total caspase 7-ratio. In line with the results obtained from Egln-3 knockdown, AdVmiR-20a completely inhibited programmed cell death caused by biomechanical stress as measured by cleaved/total caspase 3 and 7-ratios (n=3 each, both p<0.001). In conclusion, the miR-20a/Egln-3-axis is a novel regulator of stretch-induced apoptosis in cardiomyocytes. Perspectively, therapeutic manipulation of this pathway might offer new options in treating adverse cardiac remodeling.
- © 2012 by American Heart Association, Inc.