A decisive role of mitochondria in defining rate and intensity of apoptosis induction by different alkaloids

Sanguinarine, chelerythrine and chelidonine possess prominent apoptotic effects towards cancer cells. In this study, we found that sanguinarine and chelerythrine induce apoptosis in human CEM T-leukemia cells, and that is accompanied by an early increase in cytosolic cytochrome c that precedes caspases-8, -9 and -3 processing. During apoptosis induction by sanguinarine and chelerythrine, reactive oxygen species (ROS) was rapidly generated and ΔΨmt dissipated, while Bax, Bcl-2 and Bcl-X(L/S) proteins’ content in the mitochondrial fraction did not change significantly. Caspase-3 activation and DNA fragmentation were considerably inhibited by N-acetyl-cysteine (NAC). Chelidonine induced only a slight release of cytochrome c (12 h), parallel to caspase-3 activation. Effect of sanguinarine or chelerythrine towards mitochondria was confirmed by marked changes in morphology of this organelle (3 h), while chelidonine did not affect mitochondria intactness. Sanguinarine or chelerythrine also caused an intensive DNA damage in cells in 1 h, however a massive increase in number of such impaired cells occurred in 6 h, while chelidonine induced intensive DNA damage in 15–20% cells only in 24 h. Thus, our results demonstrated that rapid cytochrome c release in CEM T-leukemia cells exposed to sanguinarine or chelerythrine was not accompanied by changes in Bax, Bcl-2 and Bcl-X(L/S) proteins in the mitochondrial fraction, and preceded activation of the initiator caspase-8.