title: Calcineurin inhibitors down-regulate iNOS expression by destabilizing mRNA.
abstract: In inflammation, bacterial products and pro-inflammatory cytokines induce the expression of inducible nitric oxide synthase (iNOS) and formation of high amounts of nitric oxide (NO). In a number of inflammatory diseases NO has pro-inflammatory and cytotoxic effects. The aim of the present study was to investigate the effects of immunosuppressive drugs cyclosporin A (CsA), tacrolimus (FK-506) and pimecrolimus on NO production through iNOS pathway in activated macrophages and fibroblasts. Calcineurin inhibitors (CsA, FK-506 and pimecrolimus) inhibited NO production and iNOS expression in a concentration-dependent manner, CsA being more potent than FK-506 and pimecrolimus. No effect on the activation or activity of the transcription factors nuclear factor-kappaB (NF-kappaB) and signal transducer and activator of transcription 1 (STAT-1) was found. CsA, FK-506 and pimecrolimus did not reduce iNOS mRNA levels when measured 6-8 h after the inflammatory stimulus, but significantly lower levels of iNOS mRNA were found after 24 h incubation. Also, in cells transfected with a luciferase gene under the control of 3' untranslated region (3'UTR) of iNOS, CsA reduced luciferase activity. In conclusion, the results suggest that calcineurin inhibitors cyclosporin A, tacrolimus (FK-506) and pimecrolimus inhibit iNOS expression and NO production in response to inflammatory stimuli by enhancing the decay of iNOS mRNA by a 3'UTR-dependent manner. The findings add our knowledge on the anti-inflammatory effects of CsA, FK-506 and pimecrolimus, and suggest that calcineurin may have a role in the regulation of iNOS expression.
authors.affiliation: The Immunopharmacology Research Group, University of Tampere Medical School and Tampere University Hospital, Research Unit, Tampere, Finland. mari.j.hamalainen@uta.fi
authors.forename: Mari
authors.initials: M
authors.lastname: Hämäläinen
authors.forename: Riku
authors.initials: R
authors.lastname: Korhonen
authors.forename: Eeva
authors.initials: E
authors.lastname: Moilanen
mesh_terms: D000818:Animals; D065095:Calcineurin Inhibitors; D002352:Carrier Proteins / Q000276:immunology / Q000378:metabolism; D002460:Cell Line; D016572:Cyclosporine / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D050832:Interferon-Stimulated Gene Factor 3 / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008156:Luciferases / Q000235:genetics; D008264:Macrophages / Q000187:drug effects / Q000201:enzymology; D051379:Mice; D016328:NF-kappa B / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D009363:Neoplasm Proteins / Q000276:immunology / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors* / Q000378:metabolism; D020871:RNA Stability; D012333:RNA, Messenger / Q000187:drug effects*; D016559:Tacrolimus / Q000031:analogs & derivatives* / Q000494:pharmacology*; D051996:Transcription Factor RelA
chemical_list: D065095:Calcineurin Inhibitors; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D007166:Immunosuppressive Agents; D050832:Interferon-Stimulated Gene Factor 3; D008070:Lipopolysaccharides; D016328:NF-kappa B; D009363:Neoplasm Proteins; D012333:RNA, Messenger; C498144:Rela protein, mouse; D051996:Transcription Factor RelA; C079868:gamma interferon activation factor; D009569:Nitric Oxide; C117268:pimecrolimus; D016572:Cyclosporine; D008156:Luciferases; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D016559:Tacrolimus