Ceramide generation by two distinct pathways in tumor necrosis factor alpha-induced cell death

Ceramide accumulation in the cell can occur from either hydrolysis of sphin gomyelin or by de novo synthesis. In this study, we found that blocking de novo ceramide synthesis significantly inhibits ceramide accumulation and su bsequent cell death in response to tumor necrosis factor alpha. When cells were pre-treated with glutathione, a proposed cellular regulator of neutral sphingomyelinase, inhibition of ceramide accumulation at early time points was achieved with attenuation of cell death. Inhibition of both pathways a chieved near-complete inhibition of ceramide accumulation and cell death in dicating that both pathways of ceramide generation are stimulated. This ill ustrates the complexity of ceramide generation in cytokine action. (C) 2001 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.