SIRT3 expression protects cells from doxorubicin-mediated cell death. (A) Cell death monitored by TUNEL (green) staining for cardiomyocytes overexpressing either adenoviral vector (Ad.Vector) or SIRT3-adenovirus (Ad.SIRT3) and treated with doxorubicin or vehicle for 24 h. Nuclei are marked with DAPI staining (blue). Scale bar, 10 μm. (B) Quantification of TUNEL-positive cells shown in panel A. Values are means ± SEM, n = 4. *, P < 0.001. (C) IB showing acetylated OPA1 immunoprecipitated from neonatal rat cardiomyocytes treated with 300 nM doxorubicin. The right lane shows that overexpressed SIRT3 binds to and deacetylates endogenous OPA1. Veh., vehicle; vect., vector.