Purpose: Doxorubicin (DOX) is a widely prescribed chemotherapeutic. The hypothesis for the present study is that DOX-induced myocyte apoptosis involves mitochondrial dysfunction that is a consequence of nuclear DOX effects. Methods: H9c2 myoblasts were incubated with 0, 0.5 and 1 μM DOX and nuclear and mitochondrial alterations were determined. Results: Doxorubicin accumulation in the nucleus was detected after 3 h treatment, followed by an increase in p53 and a decrease in mitochondrial membrane potential. Apoptotic markers, such as caspase activation and chromatin condensation were detected after 24 h of DOX treatment. Bax and p53 translocation to mitochondria as well as the formation of Bax clusters in the cytosol were observed. Importantly, pifithrin-alpha, a p53 inhibitor, protected against DOX-induced mitochondrial depolarization, caspase activation and cell death. Conclusion: Mitochondrial dysfunction in H9c2 myoblasts treated with DOX is a consequence of nuclear p53 activation rather than a direct effect of the drug on mitochondria.
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Acknowledgments This work was supported by NIH grant HL 58016 and FCT SAU-OSM-64084-2006. Vilma A. Sardão is supported by grants from the Portuguese Foundation for Science and Technology, SFRH/BD/10251/2002 and SFRH/BPD/31549/2006. We acknowledge Ana Filipa Branco for excellent technical assistance. We also acknowledge Dr. Marc Fariss (University of Colorado, Denver) for providing vitamin E-succinate.
- H9c2 myoblast
- Oxidative stress