title: Short-term treatment of RAW264.7 macrophages with adiponectin increases tumor necrosis factor-alpha (TNF-alpha) expression via ERK1/2 activation and Egr-1 expression: role of TNF-alpha in adiponectin-stimulated interleukin-10 production.
abstract: Adiponectin is an adipokine with potent anti-inflammatory properties. However, the mechanisms by which adiponectin suppresses macrophage function are not well understood. Treatment of RAW264.7 macrophages with adiponectin for 18 h decreased lipopolysaccharide (LPS)-stimulated tumor necrosis factor-alpha (TNF-alpha) production. Here we demonstrate that globular adiponectin (gAcrp) initially increased TNF-alpha expression in RAW264.7 macrophages; this TNF-alpha then contributed to increased expression of interleukin-10, which in turn was required for the development of tolerance to subsequent LPS exposure. gAcrp-mediated increases in TNF-alpha mRNA accumulation were associated with increased TNF-alpha promoter activity. gAcrp increased the DNA binding activity of both Egr-1 and NFkappaB; mutation of either the Egr-1 or NFkappaB binding sites in the TNF-alpha promoter decreased gAcrp-stimulated promoter activity. Further, co-transfection with either dominant negative Egr-1 or the IkappaB super-repressor prevented gAcrp-stimulated TNF-alpha promoter activity. gAcrp also increased Egr-1 promoter activity, mRNA accumulation, and DNA binding activity. Inhibition of ERK1/2 with U0126 potently suppressed gAcrp-stimulated Egr-1 promoter activity, as well as TNF-alpha promoter activity. In summary, these data demonstrate that adiponectin initially increases TNF-alpha production by macrophages via ERK1/2-->Egr-1 and NFkappaB-dependent mechanisms; these increases in TNF-alpha in turn lead to increased expression of interleukin-10 and an eventual dampening of LPS-mediated cytokine production in macrophages.
authors.affiliation: Department of Pathobiology, Cleveland Clinic Foundation, Cleveland, OH 44195, USA.
authors.forename: Pil-Hoon
authors.initials: PH
authors.lastname: Park
authors.forename: Megan R
authors.initials: MR
authors.lastname: McMullen
authors.forename: Honglian
authors.initials: H
authors.lastname: Huang
authors.forename: Varsha
authors.initials: V
authors.lastname: Thakur
authors.forename: Laura E
authors.initials: LE
authors.lastname: Nagy
mesh_terms: D052242:Adiponectin / Q000494:pharmacology*; D000818:Animals; D002460:Cell Line; D016207:Cytokines / Q000096:biosynthesis; D017931:DNA Primers; D051766:Early Growth Response Protein 1 / Q000235:genetics*; D004789:Enzyme Activation; D017930:Genes, Reporter; D016753:Interleukin-10 / Q000096:biosynthesis*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008156:Luciferases / Q000235:genetics; D008264:Macrophages / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D010766:Phosphorylation; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics*
chemical_list: D052242:Adiponectin; D016207:Cytokines; D017931:DNA Primers; D051766:Early Growth Response Protein 1; C486109:Egr1 protein, mouse; D008070:Lipopolysaccharides; D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D008156:Luciferases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3