title: Interleukin 10 (IL-10) regulation of tumour necrosis factor alpha (TNF-alpha) from human alveolar macrophages and peripheral blood monocytes.
abstract: BACKGROUND
  Regulation of the inflammatory response within the human lung is essential to prevent this important part of the normal host defence response becoming a pathological process. Tumour necrosis factor alpha (TNF-alpha) is a cytokine involved in the pathogenesis of shock and in granuloma formation, tissue necrosis, and fibrosis in many organ systems including the lung. Interleukin 10 (IL-10) has been proposed as having an inhibitory effect on the production of several inflammatory cytokines including TNF-alpha.
  
  
  METHODS
  The effect of IL-10 administration on TNF-alpha production was explored in human alveolar macrophages and peripheral blood monocytes from matched individuals. The effects of IL-10 on TNF-alpha protein production were determined by sandwich enzyme linked immunosorbant assay (ELISA), whereas the TNF-alpha mRNA response was established by Northeren blotting using a TNF-alpha specific oligonucleotide probe. The protein synthesis inhibitors actinomycin D and cyclohexamide were utilised to monitor IL-10 effects on mRNA degradation and de novo protein synthesis, respectively.
  
  
  RESULTS
  The lipopolysaccharide-mediated TNF-alpha production in alveolar macrophages was reduced from 3.508 (0.629) to 2.035 (0.385) ng/ml by 100 U/ml IL-10. Lipopolysaccharide-induced TNF-alpha production in peripheral blood monocytes was reduced from 2.035 (0.284) to 0.698 (0.167) ng/ml. TNF-alpha gene expression was also inhibited in both alveolar macrophages and peripheral blood monocytes; lipopolysaccharide-induced TNF-alpha mRNA was reduced by 47.8 (15.2)% and 83.1 (4.2)%, respectively, by IL-10. The IL-10 mediated suppression of TNF-alpha mRNA was unaffected by addition of cyclohexamide, suggesting that de novo protein synthesis was not required for TNF-alpha inhibition. mRNA stability experiments indicated no acceleration in lipopolysaccharide-induced TNF-alpha mRNA degradation in response to IL-10.
  
  
  CONCLUSIONS
  These findings suggest that IL-10 is a potent inhibitor of TNF-alpha expression and release from alveolar macrophages and peripheral blood monocytes, and thus it may have an important role in the cytokine network of the pulmonary immune response.
authors.affiliation: Department of Medicine, Medical School Unit, Southmead Hospital, Westbury on Trym, Bristol, UK.
authors.forename: L
authors.initials: L
authors.lastname: Armstrong
authors.forename: N
authors.initials: N
authors.lastname: Jordan
authors.forename: A
authors.initials: A
authors.lastname: Millar
mesh_terms: D000328:Adult; D015152:Blotting, Northern; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D066298:In Vitro Techniques; D016753:Interleukin-10 / Q000494:pharmacology*; D008070:Lipopolysaccharides / Q000494:pharmacology; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000378:metabolism*; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism*; D011994:Recombinant Proteins / Q000494:pharmacology; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D008070:Lipopolysaccharides; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10