Evidence for a dual mechanism for IL-10 suppression of TNF-alpha production that does not involve inhibition of p38 mitogen-activated protein kinase or NF-kappa B in primary human macrophages.
IL-10 is a potent anti-inflammatory cytokine and inhibitor of TNF-alpha production. The molecular pathways by which IL-10 inhibits TNF-alpha production are obscure, with diverse mechanisms having been published. In this study, a new approach has been taken for the study of human cells. Adenovirus was used to deliver TNF-alpha promoter-based luciferase reporter genes to primary human monocytic cells. The reporter genes were highly responsive to macrophage activation and appeared to mirror the behavior of the endogenous TNF-alpha gene. When added, either with or after the stimulus, IL-10 required the 3' untranslated region of the TNF-alpha gene to inhibit luciferase mRNA and protein expression, indicating a posttranscriptional mechanism. However, if macrophages were incubated with IL-10 before activation, inhibition of gene expression was also mediated by the 5' promoter, suggesting a transcriptional mechanism. To our knowledge, this is the first time that a dual mechanism for IL-10 function has been demonstrated. Studies to elucidate the mechanisms underlying the inhibition of TNF-alpha production addressed the effect of IL-10 on the activation of p38 mitogen-activated protein kinase and NF-kappaB. However, these studies could demonstrate no requirement for the inhibition of p38 mitogen-activated protein kinase or NF-kappaB activation as potential mechanisms. Overall, these results may explain the diversity previously ascribed to the complex mechanisms of IL-10 anti-inflammatory activity.
Denys
Agnes
A
Kennedy Institute of Rheumatology Division, Imperial College Faculty of Medicine, Charing Cross Campus, 1 Aspenlea Road, London, United Kingdom.
Udalova
Irina A
IA
Smith
Clive
C
Williams
Lynn M
LM
Ciesielski
Cathleen J
CJ
Campbell
Jamie
J
Andrews
Caroline
C
Kwaitkowski
Dominic
D
Foxwell
Brian M J
BM
D020413:3' Untranslated Regions / Q000502:physiology; D020121:5' Untranslated Regions / Q000502:physiology; D000256:Adenoviridae / Q000235:genetics / Q000276:immunology; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000276:immunology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000276:immunology; D017930:Genes, Reporter / Q000276:immunology; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D016753:Interleukin-10 / Q000494:pharmacology*; D008070:Lipopolysaccharides / Q000037:antagonists & inhibitors / Q000494:pharmacology; D008264:Macrophages / Q000201:enzymology* / Q000276:immunology* / Q000378:metabolism / Q000821:virology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000276:immunology; D020871:RNA Stability / Q000276:immunology; D012333:RNA, Messenger / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics; D015054:Zymosan / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases
D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D004791:Enzyme Inhibitors; D007166:Immunosuppressive Agents; D008070:Lipopolysaccharides; D016328:NF-kappa B; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D015054:Zymosan; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases