CERAMIDE MEDIATES TUMOR-NECROSIS-FACTOR EFFECTS ON P450-AROMATASE ACTIVITY IN CULTURED GRANULOSA-CELLS

In [H-3]serine-labelled granulosa cells treatment with TNF alpha (10 n g/ml) resulted in a transient decrease in cellular [H-3]sphingomyelin and generation of [H-3]ceramide that remained elevated 60 min later. I n cells labelled with [methyl-C-14]choline, TNF alpha induced a simila r reduction in [C-14]sphingomyelin content that was accompanied by a s ustained elevation in [C-14]phosphorylcholine levels. In FSH-primed ce lls, TNF alpha inhibited P450-AROM activity in a dose-dependent manner , an effect that was also observed in cells treated with bacterial sph ingomyelinase (SMase 0.003-0.3 U/ml) or increasing concentrations (0.1 -10 mu M) of N-acetylsphingosine (C2-cer) a membrane-permeable analogu e of ceramide. These results support the notion that sphingomyelin deg radation to a bioeffector molecule ceramide, may be an early event inv olved in TNF alpha-induced signal transduction in granulosa cells.