Ceramides that mediate apoptosis reduce glucose uptake and transporter affinity for glucose in human leukaemic cell lines but not in neutrophils

We have demonstrated that CD95-induced apoptosis in a human leukaemic T-cell line resulted in loss of glucose transporter function (Berridge ct al. 1996). To determine whether ceramide, a mediator of CD95 and tumour necrosis factor-a-induced apoptosis, has similar effects on glucose transport, the human leukaemic cell lines, Jurkat and U937, and human peripheral blood neutrophils were treated with ceramide or sphingomyelinase and the effects on glucose transport determined by measuring [H-3]-2-deoxyglucose uptake. We show that in U937 and Jurkat cells, the cell permeable ceramides, C-2 (N-acetylsphingosine) and C-6 (N-hexanoylsphingosine) inhibit glucose uptake within minutes of initiating ceramide treatment, 60- 70% inhibition bring observed within 2 hr. Loss of glucose transport correlated with loss of proliferative response, but metabolic activity as measured by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) reduction, was affected to a much lesser extent. With Jurkat and U937 cells, the inhibitory effects of ceramides on glucose transport were associated with reduced affinity of glucose transporters for glucose (K-m). Similar effects were observed with sphingomyelinase. With human peripheral blood neutrophils, C-2 and C-6-ceramides inhibited glucose uptake by 70-80% within 30 min. without affecting transporter affinity for glucose, but the maximum velocity of uptake (V-max) was reduced. These results show that acute regulation of glucose transport is an early effector mechanism of cell death induced by ceramides in human leukaemic cell lines and peripheral blood neutrophils. This is the first study which describes ceramide-induced early physiological/biochemical events leading to cell death in human cells.