Abstract
The protein phosphatase inhibitor okadaic acid (OA) dose-dependently induced apoptosis in CHP-100 neuroepithelioma cells when administered for 24 h at concentrations ranging from 10–100 nM. Apoptosis was largely, albeit not completely, dependent on cystein protease (caspase) activation. CPP32 processing and poly(ADP-ribose) polymerase (PARP) cleavage started to be observed only at 20 nM OA; moreover, the caspase inhibitor Z-Val-Ala-DL-Asp-fluoromethylketone (Z-VAD.fmk) (100 μM) had negligible effect on apoptosis induced by 10 nM OA, but rescued from death an increasing cell fraction as OA concentration was raised from 20–100 nM. Cell treatment for 24 h with OA induced ceramide accumulation; the phenomenon started to be evident at 20 nM OA and reached its maximum at 50–100 nM OA. In cells exposed to 50 nM OA, ceramide was already elevated by 5 h; at this time, however, PARP cleavage and apoptosis were not yet observed. Z-VAD.fmk (100 μM) had no effect on ceramide elevation induced by 50 nM OA within 5 h, but markedly reduced ceramide accumulation as the incubation was prolonged to 24 h. The latter phenomenon was accompanied by elevation of glucosylceramide levels, thus suggesting that a caspase-dependent reduction of glucosylceramide synthesis might contribute to late ceramide accumulation. Short-chain ceramide (30 μM) induced apoptosis in CHP-100 cells and its effect was additive with that evoked by OA (10–20 nM). These results suggest that ceramide generation might be an important mechanism through which sustained protein phosphatase inhibition induces caspase activation and apoptosis in CHP-100 cells.
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Spinedi, A., Di Bartolomeo, S., Di Sano, F. et al. Ceramide accumulation precedes caspase-dependent apoptosis in CHP-100 neuroepithelioma cells exposed to the protein phosphatase inhibitor okadaic acid. Cell Death Differ 6, 618–623 (1999). https://doi.org/10.1038/sj.cdd.4400533
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DOI: https://doi.org/10.1038/sj.cdd.4400533
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