CD95/Apo-1/Fas: independent cell death induced by doxorubicin in normal cultured cardiomyocytes

Doxorubicin is a commonly used cytotoxic drug for effective treatment of both solid tumors and leukemias, which may cause severe cardiac adverse effects leading to heart failure. In certain tumor cells, doxorubicin-induced cell death is mediated by death receptors such as CD95/Apo-1/Fas. Here we studied the role of death receptors for doxorubicin-induced cell death in primary neonatal rat cardiomyocytes and the embryonic cardiomyocytic cell line H9c2.1. Doxorubicin-induced cell death of cardiomyocytes was associated with cleavage of caspases 3 and 8, a drop in mitochondrial transmembrane potential, and release of cytochrome c. Doxorubicin-treated cardiomyocytes secreted death-inducing ligands into the culture supernatant, but remained resistant toward cell death induction by death receptor triggering. In contrast to the chelator dexrazoxane, blockade of death receptor signaling by stable overexpression of transdominant negative adapter molecule FADD did not inhibit doxorubicin-induced cell death. Our data suggest that cultured cardiomyocytes secrete death-inducing ligands, but undergo death receptor-independent cell death upon exposure to doxorubicin.