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Infect. Immun., 05 1995, 1863-1869, Vol 63, No. 5
H Fahmi, D Charon, M Mondange and R Chaby
Refractoriness (tolerance) to endotoxin effects, such as induction of tumor
necrosis factor alpha (TNF-alpha) secretion, can be elicited in vitro in
macrophages by preexposure of cells to endotoxin (lipopolysaccharide [LPS])
itself. The aim of this study was to determine whether this phenomenon is
due to negative feedback mediated by the free radical nitric oxide (NO)
produced by cells when they are activated by LPS. Among several efficient
inhibitors of NO production, NG-monomethyl-L-arginine did not induce
concomitant inhibition of TNF- alpha secretion. Mouse macrophages that were
exposed to LPS in the presence of NG-monomethyl-L-arginine partially
maintained the ability to secrete TNF-alpha in response to a second LPS
stimulation, compared with cells preexposed to LPS alone, thus suggesting
that NO is involved in part in LPS-induced desensitization of cells.
Furthermore, direct exposure of cells to the NO-generating compounds sodium
nitroprusside and S-nitroso-N-acetylpenicillamine mimicked LPS-induced
desensitization. However, low concentrations of a synthetic lipid (lipid
M4) that is structurally analogous to the reducing end of the lipid A
moiety of LPS induced desensitization of mouse macrophages without
concomitant production of NO. Taken together, these data suggest that
although NO actually takes part in LPS-induced desensitization of mouse
macrophages, additional and yet unknown mechanisms must also exist.
Copyright © 1995, American Society for Microbiology
Endotoxin-induced desensitization of mouse macrophages is mediated in part by nitric oxide production
Laboratory of Immunology, Faculty of Science, Universite Sidi Mohamed Ben Abdellah, Fes, Morocco.
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