Inhibition of human erythroid colony formation by ceramide.
In previous studies, we have demonstrated that the inhibitory effects of tumor necrosis factor (TNF) and interleukin (IL)-1 on human erythroid colony formation are indirect and mediated by beta and gamma interferon (IFN), respectively, which act directly upon erythroid colony forming units (CFU-E). The in vitro inhibitory effect of gammaIFN but not betaIFN is reversed by exposure to high concentrations of recombinant human (rh) erythropoietin (EPO). Ceramide, a product of sphingomyelin hydrolysis, is a known mediator of apoptotic effects of TNF, IL-1, and gammaIFN. In this report, the effects of ceramide on CFU-E colony formation and its implication in the model described above are evaluated. Endogenous ceramide produced by exposure to bacterial sphingomyelinase (0.2-2.0 U/mL) and exogenous cell-permeable ceramide (C2-ceramide; 5 and 10 mM) significantly inhibited bone marrow CFU-E colony formation. This effect was reversed by the ceramide antagonist sphingosine-1-phosphate (S-1-P). Inhibition of CFU-E by rhgammaIFN, but not rhbetaIFN, was significantly reversed by S-1-P. rhEPO 10 U/mL reversed CFU-E inhibition by C2-ceramide 10 mM. Exposure of marrow cells to rhgammaIFN led to a 57% increase in ceramide content. The present study demonstrates that colony formation by human CFU-E is inhibited by endogenous and exogenous ceramide, and that inhibition by rhgammaIFN can be reversed by the ceramide antagonist S-1-P. Inhibition of CFU-E colony formation by ceramide and by are both reversed by high concentrations of rhEPO. These findings strongly suggest that ceramide mediates inhibition of human CFU-E colony formation by gammaIFN.
Dallalio
G
G
Department of Internal Medicine, Department of Veterans Affairs Medical Center and the University of Cincinnati College of Medicine, OH, USA.
North
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M
Worden
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BD
Means
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D017209:Apoptosis / Q000187:drug effects; D002518:Ceramides / Q000037:antagonists & inhibitors / Q000494:pharmacology* / Q000502:physiology; D003114:Colony-Forming Units Assay; D003864:Depression, Chemical; D015672:Erythroid Precursor Cells / Q000187:drug effects*; D004920:Erythropoiesis / Q000187:drug effects*; D004921:Erythropoietin / Q000037:antagonists & inhibitors / Q000494:pharmacology; D006801:Humans; D016899:Interferon-beta / Q000494:pharmacology; D007371:Interferon-gamma / Q000494:pharmacology; D008246:Lysophospholipids; D011994:Recombinant Proteins / Q000494:pharmacology; D013108:Sphingomyelin Phosphodiesterase / Q000494:pharmacology; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D019014:fas Receptor / Q000502:physiology
D002518:Ceramides; D008246:Lysophospholipids; C064769:N-acetylsphingosine; D011994:Recombinant Proteins; C109343:dihydroceramide; D019014:fas Receptor; D004921:Erythropoietin; C060506:sphingosine 1-phosphate; D016899:Interferon-beta; D007371:Interferon-gamma; D013108:Sphingomyelin Phosphodiesterase; D013110:Sphingosine