Involvement of Yes-associated protein 1 (YAP1) in doxorubicin-induced cytotoxicity in H9c2 cardiac cells.

Cardiac cell death is one of the major events implicated in doxorubicin-induced cardiotoxicity, which leads to heart failure. We recently reported that Yes-associated protein 1 (YAP1) regulates cell survival and apoptosis. However, it is unclear whether YAP1 regulates doxorubicin-induced cell death in cardiomyocytes. We investigated whether YAP1 is involved in doxorubicin-induced cell death using H9c2 cardiac cells and mouse heart. In an in vivo study, YAP1 protein expression was significantly decreased in hearts of doxorubicin-treated mice with increased caspase-3 activation. Doxorubicin also caused cell death by increasing caspase-3 activation in H9c2 cells. Doxorubicin reduced YAP1 protein expression and messenger RNA expression accompanied by increased phosphorylation of YAP1 at Ser127. Doxorubicin further increased cell death with increased caspase-3/7 activation in the absence of YAP1 when compared with doxorubicin or siYAP1 treatment alone. Overexpression of constitutively active YAP1 (YAP1-5SA) using an adenovirus gene transfer technique significantly reversed doxorubicin-induced cell death by decreasing caspase-3/7 activation in H9c2 cells. Akt, a potential prosurvival factor, decreased in doxorubicin- and YAP1 short interfering RNA (siRNA)-treated cells. Doxorubicin further significantly decreased Akt protein expression when YAP1 was silenced. Overexpression of YAP1 canceled decreased Akt protein expression induced by doxorubicin treatment in H9c2 cells. In conclusion, these results suggest that doxorubicin-induced cardiac cell death is mediated in part by down-regulation of YAP1 and YAP1-targeted gene, Akt. Modulating YAP1 and its related Hippo pathway on local cardiomyocytes may be a promising therapeutic approach for doxorubicin-induced cardiotoxicity.