Regulation of phospholipase D activity and ceramide production in daunorubicin-induced apoptosis in A-431 cells

We demonstrated here that daunorubicin induced apoptosis in A-431 cells, a human epidermoid carcinoma cell line. Treatment of cells with daunorubicin induced chromatin condensation, nuclear fragmentation, internucleosomal DNA degradation, and the proteolytic cleavage of PKC-delta and poly(ADP-ribose ) polymerase in A-431 cells. Daunorubicin, as well as sphingomyelinase (SMa st) and the exogenous cell-permeable ceramide analogue Cz-ceramide, inhibit ed phospholipase D activity stimulated by phorbol 12-myristate 13-acetate o r epidermal growth factor (EGF). Like ceramide, daunorubicin also decreased EGF-induced diacylglycerol generation. However, no increase in ceramide le vel was observed in daunorubicin-induced apoptosis in A-431 cells. Moreover , treatment of A-431 cells with exogenous cell-permeable C-2-ceramide or SM ase did not induce apoptosis. These results indicate that daunorubicin indu ces apoptosis in A-431 cells via a mechanism that does not involve increase d ceramide formation. (C) 2000 Elsevier Science B.V. All rights reserved.