title: Interleukin-10 upregulates tumor necrosis factor receptor type-II (p75) gene expression in endotoxin-stimulated human monocytes.
abstract: Interferon-gamma (IFN-gamma) upregulates expression of certain genes in monocytes, including cell-surface molecules such as HLA class II, B7, and ICAM-1. IFN-gamma also potentiates production of cytokines such as tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and IL-12. Conversely, IL-10 downregulates expression of many of these same genes and often antagonizes the effects of IFN-gamma. IL-10 is known to inhibit TNF-alpha production in lipopolysaccharide (LPS)-stimulated monocytes; however, the effects of IL-10 on TNF receptor (TNF-R) expression are not well defined. We examined the effects of IL-10 on production of both membrane-associated (m) and soluble (s) TNF-R type II (sTNF-RII) by purified human CD14(+) monocytes. We also compared the effects of IFN-gamma and IL-10 on production of TNF-alpha and sTNF-RII by these cells. Monocytes constitutively expressed low levels of TNF-RII mRNA and mTNF-RII protein. LPS stimulation induced rapid, but transient loss (shedding) of mTNF-RII molecules and a delayed, but marked increase in TNF-RII mRNA levels. IL-10 increased expression of both mTNF-RII and sTNF-RII by LPS-stimulated monocytes, whereas IFN-gamma decreased their expression. The increased levels of sTNF-RII in cultures of IL-10-treated monocytes correlated directly with increased levels of TNF-RII mRNA and inversely with the levels of TNF-alpha mRNA. The ability of IL-10 to upregulate TNF-RII gene expression was transcriptionally mediated because actinomycin D blocked this effect. Furthermore, IL-10 treatment did not alter the half-life of TNF-RII mRNA transcripts in LPS-stimulated monocytes. To further examine the mechanism by which IL-10 potentiates TNF-RII gene expression, a 1.8-kb fragment of the human TNF-RII promoter cloned into a luciferase expression vector (pGL2-basic) was transfected into the IL-10-responsive macrophage cell line, RAW264.7. Although IL-10 alone induced only minimal promoter activity in these cells, it markedly increased the LPS-induced response, providing further evidence that the ability of IL-10 to amplify TNF-RII gene expression is transcriptionally controlled. Together, these findings demonstrate that IL-10 coordinately downregulates expression of TNF-alpha and upregulates expression of TNF-RII, particularly the soluble form of this receptor, in monocytes.
authors.affiliation: Division of Cytokine Biology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD, USA.
authors.forename: H L
authors.initials: HL
authors.lastname: Dickensheets
authors.forename: S L
authors.initials: SL
authors.lastname: Freeman
authors.forename: M F
authors.initials: MF
authors.lastname: Smith
authors.forename: R P
authors.initials: RP
authors.lastname: Donnelly
mesh_terms: D015815:Cell Adhesion Molecules / Q000096:biosynthesis / Q000235:genetics; D002478:Cells, Cultured; D004731:Endotoxins / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D016753:Interleukin-10 / Q000494:pharmacology*; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism*; D018124:Receptors, Tumor Necrosis Factor / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D015815:Cell Adhesion Molecules; D004731:Endotoxins; D018124:Receptors, Tumor Necrosis Factor; D016753:Interleukin-10