Alteration of the daunorubicin-triggered sphingomyelin-ceramide pathway and apoptosis in MDR cells: Influence of drug transport abnormalities
✍ Scribed by Marie-George Côme; Ali Bettaieb; Andrzej Skladanowski; Annette K. Larsen; Guy Laurent
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- French
- Weight
- 163 KB
- Volume
- 81
- Category
- Article
- ISSN
- 0020-7136
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✦ Synopsis
We have previously shown that in myeloid leukemic cells, daunorubicin (DNR) induces apoptosis via the activation of the sphingomyelin-ceramide pathway. We have now investigated sphingomyelin (SM) hydrolysis, ceramide generation, and apoptosis in vincristine-selected multidrug resistant (MDR) HL-60 cells (HL-60/Vinc), compared with their parental counterparts. We show that DNR triggers the SM cycle (stimulation of neutral sphingomyelinase, SM hydrolysis, and ceramide generation) and apoptosis in both parental and MDR cells, when used at isotoxic doses (i.e., 1 and 100M for HL-60 and HL-60/Vinc, respectively). However, in MDR cells treated with either 10M DNR or 1µM DNR in association with the P-glycoprotein (P-gp) blocker verapamil (treatment conditions which yield an intracellular DNR concentration similar to that achieved with 1M in the parental cells), we were unable to detect SM hydrolysis, ceramide generation and apoptosis. This implies that inhibition of the DNRinduced SM cycle in MDR cells is not directly related to P-gp. We have also investigated the influence of intracellular drug localization on the DNR-induced SM-cycle in HL-60/Vinc cells. In these cells, DNR at 10M is mainly localized in cytoplasmic vesicles, while the drug is diffusely distributed when used at 100M. A diffuse distribution pattern was also observed when MDR cells were treated with 1M DNR in association with the cyclosporine derivative PSC-833, but not with verapamil. In parallel, PSC-833, but not verapamil, restored the induction of the SM cycle and the apoptotic potential of DNR, and markedly increased drug cytotoxicity in MDR cells. Our results suggest that altered intracellular drug transport plays an important role in limiting ceramide generation and cell death in MDR cells.