title: Inhibition of IL-10 expression by IFN-gamma up-regulates transcription of TNF-alpha in human monocytes.
abstract: Stimulation of human monocytes with LPS induces expression of multiple cytokines, including TNF-alpha, IL-1 beta, IL-6, and IL-10, IL-10 expression is delayed relative to that of TNF-alpha, IL-1 beta, and IL-6. Furthermore, IL-10 feedback inhibits expression of TNF-alpha, IL-1 beta, and IL-6, thus providing an efficient autocrine mechanism for controlling proinflammatory cytokine production in monocytes. The Th1-type lymphokine, IFN-gamma, markedly up-regulates TNF-alpha production in monocytes. However, the precise mechanism by which IFN-gamma mediates this effect is unknown. We examined the effects of IFN-gamma on IL-10 expression in LPS-stimulated monocytes, and the relationship between IL-10 and TNF-alpha production in these cells. LPS stimulation induced rapid, ordered expression of multiple cytokines. Steady-state mRNA levels for TNF-alpha increased rapidly, reached maximal levels by 2 to 3 h poststimulation, and then declined sharply. IL-1 beta and IL-6 mRNA levels also increased markedly following stimulation with LPS, but decreased more slowly than did TNF-alpha. Down-regulation of mRNA for TNF-alpha, IL-1 beta, and IL-6 coincided with a delayed and more gradual increase in IL-10 mRNA levels. Furthermore, neutralization of IL-10 with anti-IL-10 Abs prolonged TNF-alpha mRNA expression, and significantly increased net TNF-alpha production. IFN-gamma suppressed expression of IL-10 mRNA and protein in a dose-dependent manner. Moreover, inhibition of IL-10 production correlated with a marked increase in both the magnitude and duration of TNF-alpha expression. Thus, potentiation of TNF-alpha production by IFN-gamma in monocytes is coupled to inhibition of endogenous IL-10 expression.
authors.affiliation: Division of Cytokine Biology, Food and Drug Administration, Bethesda, MD 20892, USA.
authors.forename: R P
authors.initials: RP
authors.lastname: Donnelly
authors.forename: S L
authors.initials: SL
authors.lastname: Freeman
authors.forename: M P
authors.initials: MP
authors.lastname: Hayes
mesh_terms: D002478:Cells, Cultured; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D016753:Interleukin-10 / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D007378:Interleukins / Q000096:biosynthesis / Q000235:genetics; D008070:Lipopolysaccharides / Q000494:pharmacology; D009000:Monocytes / Q000187:drug effects* / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D007378:Interleukins; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D007371:Interferon-gamma