Differential responses of oligodendrocytes to tumor necrosis factor and other pro-apoptotic agents: role of ceramide in apoptosis.
Staurosporine induced apoptosis in a human oligodendroglioma cell line (HOG), neonatal rat oligodendrocyte (O2A(+)) precursors, and mature rat oligodendrocytes. In all three cell culture systems, the activation of caspase-3-like activity (CPP32) coincided with the increased formation of ceramide from sphingomyelin and the onset of DNA fragmentation. Further, the addition of exogenous C(2)-ceramide induced CPP32 activation and DNA fragmentation in all three culture systems. Raising endogenous ceramide levels by the addition of the ceramidase inhibitor, oleoylethanolamine, enhanced apoptosis in both a time- and concentration-dependent manner. Inhibitors of phosphatidylinositol 3-kinase (wortmannin and LY294002) also induced caspase-3 (CPP32) activation, increased ceramide formation, induced DNA fragmentation, and reduced cell viability. In contrast, cytokines such as tumor necrosis factor-alpha (TNF-alpha) had a differential effect on the three cell cultures. Thus, TNF-alpha (160 ng/ml) induced 70% apoptosis in 24 hr in freshly isolated rat brain O2A(+) precursor cells, 60% apoptosis in 24 hr in a human oligodendroglioma (HOG) cell line, but no apoptosis in mature neonatal rat oligodendrocytes. Interferon-gamma augmented the activation of CPP32 by TNF-alpha in HOG cells and O2A(+) oligodendrocyte precursor cells but had no effect on mature oligodendrocytes. Thus, the death pathway appears to be similar in the three cell lines but the lack of coupling between TNF-alpha receptors and the apoptotic pathway leads to a lack of response to cytokines in mature oligodendrocytes.
Scurlock
B
B
Committee on Neurobiology, Department of Pediatrics, University of Chicago, Chicago, Illinois 60637, USA.
Dawson
G
G
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D002518:Ceramides / Q000378:metabolism*; D053938:DNA Fragmentation; D004789:Enzyme Activation / Q000187:drug effects; D009836:Oligodendroglia / Q000187:drug effects / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051381:Rats; D013109:Sphingomyelins / Q000378:metabolism; D019311:Staurosporine / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism* / Q000494:pharmacology
D002518:Ceramides; D000081082:Phosphoinositide-3 Kinase Inhibitors; D013109:Sphingomyelins; D014409:Tumor Necrosis Factor-alpha; C505407:CASP3 protein, human; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D019311:Staurosporine