Daunorubicin- and mitoxantrone-triggered phosphatidylcholine hydrolysis: Implication in drug-induced ceramide generation and apoptosis

Several studies have suggested that diacylglycerol can affect the induction of apoptosis induced by toxicants and ceramide. The present study demonstr ates that clinically relevant concentrations of the chemotherapeutic drugs daunorubicin and mitoxantrone (0.2-1 mu M) transiently stimulated concurren tly with sphingomyelin-derived ceramide generation and diacylglycerol and p hosphorylcholine production within 4 to 10 min via phospholipase C hydrolys is of phosphatidylcholine. Pretreatment of cells with the xanthogenate comp ound D609, a potent inhibitor of phosphatidylcholine-phospholipase C, led t o significant inhibition of drug triggered diacylglycerol and phosphorylcho line production and to a sustained increase in ceramide levels for a period up to 2 h. Moreover, D609 pretreatment induced both cell death and ceramid e generation at daunorubicin and mitoxantrone concentrations previously sho wn to be ineffective (i.e., 0.1 mu M). These results underline the importan ce of diacylglycerol in the regulation of programmed cell death and strongl y argue for a balance between apoptotic (ceramide) and survival (diacylglyc erol) signal transducers.