Abstract 10291: MicroRNA-210 is Upregulated by Akt Through a Hypoxia Inducible Factor-Independent Mechanism And By P53 Through a Hypoxia Inducible Factor-Dependent Mechanism
microRNA-210 (miR-210) is highly upregulated in hypoxic cardiomyocytes and exerts cytoprotective effects; however less well understood is regulation of this microRNA by factors other than hypoxia-inducible factor (HIF). Given the roles Akt and p53 play in hypoxia, we assessed whether these molecules induce miR-210 and the dependence of any induction on HIF. Hypoxic miR-210 induction is decreased by 55 ± 14% in Akt knockout mouse embryonic fibroblasts (MEFs) and 72 ± 8% in p53 knockout MEFs as compared to wildtype MEFs, indicating that both Akt and p53 are involved in miR-210 regulation. Treatment of H9c2 cardiomyoblasts with Akt inhibitor or neonatal rat cardiomyocytes (NRCM) with the PI3 kinase inhibitors LY29004 and wortmannin suppressed miR-210 induction upon exposure to hypoxia, while treatment of both cell lines with insulin, an upstream activator of Akt, increased miR-210 levels. Taken together, these data indicate that Akt induces miR-210. To assess whether Akt induction of miR-210 is independent of HIF, further experiments were performed in cells lacking intact HIF signaling, aryl hydrocarbon receptor nuclear translocator (ARNT) knockout MEFs. Transfection of constitutively active Akt plasmid into ARNT knockout MEFs increased miR-210 levels by 4.1 ± 0.4 fold, a level of induction comparable to that in wildtype MEFs (4.3 ± 1.0 fold). In addition, wortmannin and LY29004 suppressed the hypoxic induction of miR-210 in ARNT knockout MEFs. Taken together, these data demonstrate that Akt activates miR-210 through a HIF-independent mechanism. To assess whether p53-mediated induction of miR-210 is HIF-dependent, we transfected wildtype MEFs and ARNT knockout MEFs with p53 plasmid. Though a 3.8 ± 0.2 fold increase in miR-210 levels was seen in wildtype MEFs, no miR-210 induction was seen in ARNT knockout MEFs. Furthermore, overexpression of p53 dominant-negative plasmid in ARNT knockout MEFs did not blunt the hypoxic induction of miR-210. Taken together, these data demonstrate that p53 activation of miR-210 is HIF-dependent. In summary, microRNA-210 is upregulated in hypoxic cardiomyocytes, in part through Akt via a HIF-independent pathway, and p53 via a HIF-dependent pathway.
- © 2011 by American Heart Association, Inc.