Inhibition of phosphatidylcholine synthesis precedes apoptosis induced by C-2-ceramide: protection by exogenous phosphatidylcholine

Cerebellar granule neurons in primary culture underwent apoptosis when expo sed to C-2-ceramide. Addition of exogenous phosphatidylcholine (PtdCho) res ulted in a dose-dependent full prevention of neuronal death. Exogenous PtdC ho also prevented apoptosis induced by farnesol, N-oleoylethanolamine, and sphingomyelinase, but did not prevent apoptosis induced after lowering the potassium concentration in the medium to non-depolarizing levels. Moreover, C-2-ceramide inhibited labeling of [P-32]PtdCho in cells incubated with [P -32]orthophosphate, with the same potency to that causing apoptosis. Althou gh cell viability did not decrease during the first few hours, inhibition o f PtdCho synthesis was already patent after a 1 h exposure to C-2-ceramide. Taken together, these results strongly suggest that inhibition of PtdCho s ynthesis constitutes one of the primary events by which C-2-ceramide trigge rs apoptosis in cerebellar granule neurons. NeuroReport 11:3103-3108 (C) 20 00 Lippincott Williams & Wilkins.