title: Suppression of tumor necrosis factor alpha production by cAMP in human monocytes: dissociation with mRNA level and independent of interleukin-10.
abstract: BACKGROUND
  Elevation of cellular cAMP inhibits lipopolysaccharide(LPS)-stimulated tumor necrosis factor alpha (TNF-alpha) production and increases the expression of interleukin (IL)-10 in mononuclear cells. TNF-alpha gene expression obligates activation of the transcription factor nuclear factor kappaB (NF-kappaB). Exogenous IL-10 inhibits NF-kappaB in monocytes and thus attenuates TNF-alpha production. We examined the role of endogenous IL-10 in the regulation of NF-kappaB activation and TNF-alpha production in human monocytes by cAMP.
  
  
  METHODS
  Human monocytes were stimulated with Escherichia coli LPS (100 ng/ml) with and without forskolin (FSK, 50 microM) or dibutyryl cyclic AMP (dbcAMP, 100 microM). Cytokine (TNF-alpha and IL-10) release was measured by immunoassay. TNF-alpha mRNA was measured by reverse transcription polymerase chain reaction, and NF-kappaB DNA binding activity was assessed by gel mobility shift assay.
  
  
  RESULTS
  cAMP-elevating agents inhibited LPS-stimulated TNF-alpha release (0.77 +/- 0.13 ng/10(6) cells in LPS + dbcAMP and 0.68 +/- 0.19 ng/10(6) cells in LPS + FSK, both P < 0.05 vs 1.61 +/- 0.34 ng/10(6) cells in LPS alone). Conversely, cAMP enhanced LPS-stimulated IL-10 release (100 +/- 21.5 pg/10(6) cells in LPS + dbcAMP and 110 +/- 25.2 pg/10(6) cells in LPS + FSK, both P < 0.05 vs 53.3 +/- 12.8 pg/10(6) cells in LPS alone). Neither TNF-alpha mRNA expression nor NF-kappaB activation stimulated by LPS was inhibited by the cAMP-elevating agents. Neutralization of IL-10 with a specific antibody did not attenuate the effect of cAMP-elevating agents on TNF-alpha production.
  
  
  CONCLUSIONS
  The results indicate that cAMP inhibits LPS-stimulated TNF-alpha production through a posttranscriptional mechanism that is independent of endogenous IL-10.
authors.affiliation: Department of Surgery, University of Colorado Health Sciences Center, 4200 East Ninth Avenue, Denver, CO 80262, USA.
authors.forename: B D
authors.initials: BD
authors.lastname: Shames
authors.forename: R C
authors.initials: RC
authors.lastname: McIntyre
authors.forename: D D
authors.initials: DD
authors.lastname: Bensard
authors.forename: E J
authors.initials: EJ
authors.lastname: Pulido
authors.forename: C H
authors.initials: CH
authors.lastname: Selzman
authors.forename: L L
authors.initials: LL
authors.lastname: Reznikov
authors.forename: A H
authors.initials: AH
authors.lastname: Harken
authors.forename: X
authors.initials: X
authors.lastname: Meng
mesh_terms: D000906:Antibodies / Q000494:pharmacology; D003994:Bucladesine / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects / Q000276:immunology; D006801:Humans; D016753:Interleukin-10 / Q000235:genetics* / Q000276:immunology; D008070:Lipopolysaccharides / Q000494:pharmacology; D009000:Monocytes / Q000502:physiology*; D016328:NF-kappa B / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics*
chemical_list: D000906:Antibodies; D008070:Lipopolysaccharides; D016328:NF-kappa B; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D005576:Colforsin; D003994:Bucladesine; D000242:Cyclic AMP