INTRACELLULAR CALCIUM DISTRIBUTION IN APOPTOSIS OF HL-60 CELLS INDUCED BY HARRINGTONINE - INTRANUCLEAR ACCUMULATION AND REGIONALIZATION

Harringtonine (HT), an anticancer drug with high chemotherapeutic effi ciency to human chronic granulocytic/myelomonocytic leukemia, has been reported to rapidly induce apoptosis in HL-60 cells in a wide scope/r ange of dosage by investigators from our lab and others. In the presen t studies, by using video enhancement contrast (VEC) microscopy, we dy namically analyzed changes in intracellular calcium distribution in a single HL-60 cell over the period from the initiation of apoptosis to the obvious appearance of chromatin condensation. The results from thi s paper demonstrated the striking distinction of intracellular calcium distribution at different time points after treatment with HT. Before treatment in normal HL-60 cells the highest [Ca2+](i) accumulation wa s observed in the peri-nuclear area and the lowest was observed in the nucleus; after treatment with 1 mu g/ml HT for 30 min intracellular c alcium diffused all over the cell compartments, while intranuclear cal cium increased comparatively and significantly. The phenomenon of intr anuclear calcium accumulation was further confirmed by using laser sca nning confocal microscopy (LSCM). In addition, co-localization of the highest calcium region with condensed chromatin in apoptotic HL-60 cel ls was also observed by LSCM. Our results suggest that two sequential alterations of intracellular calcium distribution occurred in apoptoti c HL-60 cells induced by HT, i.e. (a) accumulation of calcium in the n ucleus and (b) regionalization in a specific nuclear region. (C) 1998 Elsevier Science Ireland Ltd.