Premium
C 2 ‐ceramide and C 6 ‐ceramide inhibited priming for enhanced release of superoxide in monocytes, but had no effect on the killing of leukaemic cells by monocytes
Author(s) -
NAKABO Y.,
PABST M. J.
Publication year - 1997
Publication title -
immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.297
H-Index - 133
eISSN - 1365-2567
pISSN - 0019-2805
DOI - 10.1046/j.1365-2567.1997.d01-2189.x
Subject(s) - ceramide , lipopolysaccharide , monocyte , microbiology and biotechnology , lipid signaling , superoxide , cytokine , tumor necrosis factor alpha , thp1 cell line , secretion , biology , chemistry , biochemistry , cell culture , apoptosis , immunology , enzyme , genetics
Ceramide acts as an intracellular second messenger in cellular signal transduction. We examined the effects of two cell‐permeable ceramides, C 2 ‐ceramide and C 6 ‐ceramide, on human monocyte functions. After monocytes were primed with lipopolysaccharide (LPS) or interferon‐ γ (IFN‐ γ ) for 18 hr in suspension culture, they produced a high amount of superoxide (O− 2 ) when triggered by phorbol myristate acetate. C 2 ‐ or C 6 ‐ceramide inhibited O− 2 release from monocytes primed with LPS (1 ng/ml) or IFN‐ γ (100 U/ml), but did not affect unprimed monocytes. An analogue, C 2 ‐dihydroceramide, was inactive. C 2 ‐ceramide was most effective at 6 μm , and C 6 ‐ceramide at 60 μm . C 2 ‐ or C 6 ‐ceramide at these concentrations was not toxic for monocytes, as assessed by trypan blue exclusion and by the 3‐[4,5‐dimethylthiazol‐2‐yl]‐2,5 diphenyl tetrazolium bromide (MTT) assay which measures the ability of live cells to produce formazan. C 2 ‐ceramide (20 μm ) had no effect on the killing of leukaemic cells (HL‐60 and K562 cells) by monocytes treated with IFN‐ γ , LPS, or both for 18 hr, with killing assessed by an 111 Indium‐releasing assay. C 2 ‐ceramide (20 μm ) induced secretion of low amounts of tumour necrosis factor‐ α (TNF‐ α ) and interleukin‐1 β (IL‐1 β ) from the monocytes. But C 2 ‐ceramide did not alter the higher secretion of TNF‐ α or IL‐1 β from monocytes treated with IFN‐ γ or LPS. Thus, the cell‐permeable ceramides acted like antagonists of LPS, rather than analogues of LPS, as has been proposed. The results here showed that the signal transduction pathway for O− 2 release by monocytes differed from that for the cytolysis of leukaemic cells, and confirmed that oxygen radicals are not involved in cytolysis.