Abstract 3592: Acute Doxorubicin Cardiotoxicity is Associated With miR-146a-induced Inhibition of the Neureglin-ErbB4 Pathway
Backgrounds: Doxorubicin is used to treat childhood and adult cancer. Doxorubicin treatment is associated with both acute and chronic cardiotoxicity. The cardiotoxic effects of doxorubicin are cumulative, which limits its chemotherapeutic dose. Free radical generation and p53-dependent apoptosis are thought to contribute to doxorubicin-induced cardiotoxicity. We hypothesized that miRNA-mediated pathway is involved in acute doxorubicin cardiotoxicity.
Results: Under stimulation with doxorubicin, miR-146a was up-regulated in neonatal cardiomyocytes. The computational miRNA target prediction algorithm showed that ErbB4 is one of the targets by miR-146a. There are three potential miR-146a binding sites within the ErbB4 3’UTR. By luciferase reporter assay, we confirmed that miR-146a targets the ErbB4 3’UTR. Over-expression of miR-146a reduced the expression of ErbB4 and neureglin-1β mediated Akt activation. Under doxorubicin treatment, overexpression of miR-146a as well as that of siRNA against ErbB4 induced more apoptotic cells in cardiomyocytes, which was confirmed by the reducition of membrane potential, elevated cleaved caspase-3, and reduced bcl-2 expression. Re-expression of ectopic ErbB4 in miR-146a over-expressed cardiomyocytes suppressed the increase of doxorubicin-induced apoptosis. To examine the loss of miR-146a function, we constructed ‘decoy’ genes that had tandem complementary sequences of miR-146a at the 3’UTR of luciferase gene under the control of CMV promoter. When miR-146a ‘decoy’ genes were introduced into cardiomyocytes, the expression of ErbB4 was up-regulated and a reduction in doxorubicin-induced apoptosis was observed. Finally, we analyzed the hearts of mice after a single intra-peritoneal injection of doxorubicin (20mg/g). The expression of ErbB4 decreased at 12hrs and further decreased at 24hrs after the doxorubicin injection, while, the expression of miR-146a increased.
Conclusions: These findings suggest that the up-regulated expression of miR-146a after doxorubicin treatment is involved in acute doxorubicin cardiotoxicity by targeting ErbB4.