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Daunorubicin-induced apoptosis: triggering of ceramide generation through sphingomyelin hydrolysis
J P Jaffrézou1, T Levade, A Bettaïeb
1CJF INSERM 9503, Centre Claudius Régaud, France.
Abstract:
The nature of the signaling pathway(s) which initiate drug-triggered apoptosis remains largely unknown and is of fundamental importance in understanding cell death induced by chemotherapeutic agents. Here we show that in the leukemic cell lines U937 and HL-60, daunorubicin, at concentrations which trigger apoptosis, stimulated two distinct cycles of sphingomyelin hydrolysis (approximately 20% decrease at 1 microM) within 4-10 min and 60-75 min with concomitant ceramide generation. We demonstrate that the increase in ceramide levels, which precedes apoptosis, is mediated by a neutral sphingomyelinase and not by ceramide synthase. Indeed, potent ceramide synthase inhibitors such as fumonisin B1 did not affect daunorubicin-triggered sphingomyelin hydrolysis, ceramide generation or apoptosis. In conclusion, we provide evidence that daunorubicin-triggered apoptosis is mediated by a signaling pathway which is initiated by an early sphingomyelin-derived ceramide production.
Insights
Daunorubicin triggers apoptosis in leukemia cells by initiating sphingomyelin hydrolysis and ceramide generation. This early ceramide production, mediated by neutral sphingomyelinase, is key to the cell death signaling pathway.
Area of Science:
- Cell Biology
- Biochemistry
- Pharmacology
Background:
- The precise signaling mechanisms initiating drug-induced apoptosis are crucial for understanding chemotherapy.
- Chemotherapeutic agents like daunorubicin induce programmed cell death, but the upstream pathways remain largely undefined.
Purpose of the Study:
- To elucidate the signaling pathway responsible for daunorubicin-induced apoptosis in leukemia cells.
- To investigate the role of sphingomyelin hydrolysis and ceramide generation in this process.
Main Methods:
- Treatment of U937 and HL-60 leukemic cell lines with daunorubicin.
- Measurement of sphingomyelin hydrolysis and ceramide levels over time.
- Assessment of the involvement of neutral sphingomyelinase and ceramide synthase using specific inhibitors.
Main Results:
- Daunorubicin induced two distinct cycles of sphingomyelin hydrolysis and ceramide generation within minutes and up to 75 minutes.
- Increased ceramide levels preceded apoptosis and were mediated by neutral sphingomyelinase, not ceramide synthase.
- Ceramide synthase inhibitors did not block daunorubicin-induced sphingomyelin hydrolysis, ceramide generation, or apoptosis.
Conclusions:
- Daunorubicin-triggered apoptosis is initiated by a signaling pathway involving early sphingomyelin-derived ceramide production.
- Neutral sphingomyelinase activation is critical for ceramide generation and subsequent apoptosis induction by daunorubicin.