title: Involvement of suppressor of cytokine signaling-3 as a mediator of the inhibitory effects of IL-10 on lipopolysaccharide-induced macrophage activation.
abstract: Previous studies have shown that IL-10 can induce the expression of the suppressor of cytokine signaling 3 (SOCS-3) mRNA in human monocytes and neutrophils, suggesting that the capacity of IL-10 to inhibit the expression of LPS-inducible proinflammatory genes may depend on SOCS-3 induction. However, no direct experimental evidence has been provided to support such hypothesis. Herein, we show that stable transfection of SOCS-3 into the mouse macrophage cell line J774 resulted in an inhibition of NO, TNF-alpha, IL-6, and GM-CSF secretion in response to LPS at levels similar to those exerted by IL-10 in LPS-stimulated wild-type J774. Constitutive SOCS-3 expression also down-regulated the mRNA expression of inducible NO synthase and IL-6 and impaired the production of TNF-alpha, mainly at a post-transcriptional level. In addition, SOCS-3-transfected cells displayed a constitutive expression of the IL-1R antagonist gene, consistent with the observation that IL-10 enhances IL-1R antagonist mRNA in LPS-stimulated wild-type cells. Furthermore, in peritoneal macrophages harvested from mice carrying heterozygous disruption of the SOCS-3 gene, IL-10 was less effective in repressing LPS-stimulated TNF-alpha and NO production. Taken together, our data show that SOCS-3 inhibits LPS-induced macrophage activation, strongly supporting the idea that it plays a role in the molecular mechanism by which IL-10 down-modulates the effector functions of LPS-activated macrophages. Finally, we show that forced expression of SOCS-3 significantly suppresses the ability of IL-10 to trigger tyrosine phosphorylation of STAT3. Therefore, SOCS-3 functions both as an LPS signal inhibitor and as a negative feedback regulator of IL-10/STAT3 signaling.
authors.affiliation: Department of Pathology, Section of General Pathology, University of Verona, Verona, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Berlato
authors.forename: Marco A
authors.initials: MA
authors.lastname: Cassatella
authors.forename: Ichiko
authors.initials: I
authors.lastname: Kinjyo
authors.forename: Luana
authors.initials: L
authors.lastname: Gatto
authors.forename: Akihiko
authors.initials: A
authors.lastname: Yoshimura
authors.forename: Flavia
authors.initials: F
authors.lastname: Bazzoni
mesh_terms: D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D053590:Interleukin 1 Receptor Antagonist Protein; D016753:Interleukin-10 / Q000494:pharmacology* / Q000502:physiology; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism; D008070:Lipopolysaccharides / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000276:immunology; D008262:Macrophage Activation / Q000235:genetics / Q000276:immunology*; D008264:Macrophages / Q000276:immunology / Q000378:metabolism; D017737:Macrophages, Peritoneal / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism; D017472:Receptors, Interleukin-1 / Q000037:antagonists & inhibitors; D012097:Repressor Proteins; D050796:STAT3 Transcription Factor; D012795:Sialoglycoproteins / Q000096:biosynthesis / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology*; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D015534:Trans-Activators / Q000037:antagonists & inhibitors / Q000378:metabolism; D014157:Transcription Factors; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics; D015854:Up-Regulation / Q000235:genetics / Q000276:immunology; D000093242:Interleukin-6 Inhibitors
chemical_list: D004268:DNA-Binding Proteins; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D053590:Interleukin 1 Receptor Antagonist Protein; D016753:Interleukin-10; D015850:Interleukin-6; D008070:Lipopolysaccharides; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D011506:Proteins; D012333:RNA, Messenger; D017472:Receptors, Interleukin-1; D012097:Repressor Proteins; D050796:STAT3 Transcription Factor; D012795:Sialoglycoproteins; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D000093242:Interleukin-6 Inhibitors; C507763:IL1RN protein, human; C507764:Il1rn protein, mouse; C106644:SOCS3 protein, human; C491411:Socs3 protein, mouse; C494087:Stat3 protein, mouse; C496317:Nos2 protein, mouse