title: Multiple transcription factors regulating the IL-6 gene are activated by cAMP in cultured Caco-2 cells.
abstract: Mucosal and enterocyte IL-6 production is increased during sepsis and endotoxemia. Recent studies suggest that cAMP potentiates IL-6 production in endotoxin- or IL-1beta-stimulated enterocytes, but the molecular mechanisms are not known. We examined the role of the transcription factors NF-kappaB, activator protein (AP)-1, CCAAT/enhancer binding protein (C/EBP), and cAMP response element-binding protein (CREB) in cAMP-induced IL-6 production in cultured Caco-2 cells, a human intestinal epithelial cell line. In addition, the role of the protein kinase A (PKA), protein kinase C (PKC), and mitogen-activated protein (MAP) kinase signaling pathways was examined. Treatment of the cells with IL-1beta increased IL-6 production and activated the IL-6 promoter in cells transfected with a luciferase reporter plasmid containing a wild-type IL-6 promoter. These effects of IL-1beta were significantly potentiated by cAMP. When the binding sites for the individual transcription factors in the IL-6 promoter were mutated, results indicated that all four transcription factors may be involved in the cAMP-induced activation of the IL-6 gene. Treatment of the Caco-2 cells with cAMP increased the DNA binding activity of CREB, C/EBP, and AP-1, but not NF-kappaB. By using specific blockers, evidence was found that both PKA and p38 MAP kinase (but not PKC or p42/44 MAP kinase) may be involved in the cAMP-induced potentiation of IL-6 production. The present results suggest that cAMP activates multiple transcription factors involved in the regulation of the IL-6 gene and that the activation of these transcription factors may at least in part explain why cAMP potentiates IL-6 production in stimulated enterocytes.
authors.affiliation: Department of Surgery, University of Cincinnati, Cincinnati, Ohio 45267, USA.
authors.forename: Dan D
authors.initials: DD
authors.lastname: Hershko
authors.forename: Bruce W
authors.initials: BW
authors.lastname: Robb
authors.forename: Guangju
authors.initials: G
authors.lastname: Luo
authors.forename: Per-Olof
authors.initials: PO
authors.lastname: Hasselgren
mesh_terms: D015153:Blotting, Western; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics; D018938:Caco-2 Cells; D002470:Cell Survival / Q000502:physiology; D002712:Chlorides / Q000378:metabolism; D002766:Cholecystokinin / Q000378:metabolism; D000242:Cyclic AMP / Q000494:pharmacology*; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics; D005768:Gastrointestinal Hormones / Q000378:metabolism; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics*; D007413:Intestinal Mucosa / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000235:genetics; D015398:Signal Transduction / Q000502:physiology; D018808:Transcription Factor AP-1 / Q000235:genetics; D014157:Transcription Factors / Q000502:physiology*; D014162:Transfection
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; D002712:Chlorides; D017362:Cyclic AMP Response Element-Binding Protein; D005768:Gastrointestinal Hormones; D015850:Interleukin-6; D016328:NF-kappa B; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D002766:Cholecystokinin; D000242:Cyclic AMP; D008156:Luciferases; D020928:Mitogen-Activated Protein Kinases