Chelerythrine rapidly induces apoptosis through generation of reactive oxygen species in cardiac myocytes

The role of protein kinase C (PKC) inhibition in cardiac myocyte apoptosis has not been well understood. We investigated the mechanism, by which chele rythrine, a commonly used PKC inhibitor. induces potent myocyte death. Chel erythrine (6-30 muM) rapidly induced pyknosis, shrinkage and subsequent cel l death in cardiac myocytes. Chelerythrine-induced myocyte death was accomp anied by nuclear fragmentation and activation of caspase-3 and -9, while it was prevented by XIAP. suggesting that the cell death is due to apoptosis. Higher concentrations of chelerythrine caused necrotic cell death where ne ither cell shrinkage nor caspase activation was observed. Intravenous injec tion of chelerythrine (5 mg/kg) also increased apoptosis in adult rat heart s in vivo. Downregulation of the phorbol 12-myristate 13-acetate (PMA)-sens itive PKC failed to affect chelerythrine-induced apoptosis, while anti-oxid ants, including N-acetyl-L-cysteine (NAC) and glutathione, inhibited it. su ggesting that generation of reactive oxygen species (ROS) rather than inhib ition of PMA-sensitive PKC mediates chelerythrine-induced cardiac myocyte a poptosis. Chelerythrine caused cytochrome c release from mitochondria. whic h was significantly inhibited in the presence of NAC, suggesting that ROS m ediates chelerythrine-induced cytochrome c release. Partial inhibition of c ytochrome c release by Bcl-X-L significantly reduced chelerythrine-induced apoptosis. These results suggest that chelerythrine rapidly induces cardiac myocyte apoptosis and that production of ROS, possibly H2O2, and subsequen t cytochrome c release from mitochondria play an important role in mediatin g chelerythrine-induced rapid cardiac myocyte apoptosis, (C), 2001 Academic Press.