Ceramide initiates NFkappaB-mediated caspase activation in neuronal apoptosis

The objective of the present study was to evaluate the role of ceramide in mediating apoptosis of dorsal root ganglion neurons induced by either nerve growth factor withdrawal or treatment with the chemotherapeutic agents suramin and cisplatin. Measurement of ceramide accumulation by mass spectrometry and the diacylglycerol kinase assay revealed elevation of intracellular ceramide only in suramin treated cultures. Ceramide-mediated neuronal cell death was inhibited by the caspase inhibitor zVAD.fmk. In these experimental models, ceramide accumulation mediated activation and nuclear translocation of the transcription factor NFkappaB and cyclin D1 protein expression. Specific inhibition of NFkappaB using a molecular decoy strategy resulted in increased cell viability accompanied by diminished caspase activity and cyclin D1 expression. Inhibition of NFkappaB did not alter intracellular ceramide levels. Our study suggests that ceramide generation occurs upstream of NFkappaB activation, cell cycle reentry, and caspase activation in the neuronal death pathway.