Inhibition of phosphatidylcholine synthesis precedes apoptosis induced by C2-ceramide

Abstract

Cerebellar granule neurons in primary culture underwent apoptosis when exposed to C₂-ceramide. Addition of exogenous phosphatidylcholine (PtdCho) resulted in a dose-dependent full prevention of neuronal death. Exogenous PtdCho 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, C₂-ceramide inhibited labeling of [³²P]PtdCho in cells incubated with [³²P]orthophosphate, with the same potency to that causing apoptosis. Although cell viability did not decrease during the first few hours, inhibition of PtdCho synthesis was already patent after a 1 h exposure to C₂-ceramide. Taken together, these results strongly suggest that inhibition of PtdCho synthesis constitutes one of the primary events by which C₂-ceramide triggers apoptosis in cerebellar granule neurons.