Cytokines induce an early steroid resistance in airway smooth muscle cells: novel role of interferon regulatory factor-1.
We have previously shown that long-term treatment of airway smooth muscle (ASM) cells with a combination of TNF-alpha and IFN-gamma impaired steroid anti-inflammatory action through the up-regulation of glucocorticoid receptor beta isoform (GRbeta) (Mol Pharmacol 2006;69:588-596). We here found that steroid actions could also be suppressed by short-term exposure of ASM cells to TNF-alpha and IFN-gamma (6 h) as shown by the abrogated glucocorticoid responsive element (GRE)-dependent gene transcription; surprisingly, neither GRalpha nuclear translocation nor GRbeta expression was affected by cytokine mixture. The earlier induction of CD38, a molecule recently involved in asthma, seen with TNF-alpha and IFN-gamma combination but not with cytokine alone, was also completely insensitive to steroid pretreatment. Chromatin-immunoprecipitation (IP) and siRNA strategies revealed not only increased binding of interferon regulatory factor 1 (IRF-1) transcription factor to CD38 promoter, but also its implication in regulating CD38 gene transcription. Interestingly, the capacity of fluticasone to completely inhibit TNF-alpha-induced IRF-1 expression, IRF-1 DNA binding, and transactivation activities was completely lost in cells exposed to TNF-alpha and IFN-gamma in combination. This early steroid dysfunction seen with cytokine combination could be reproduced by enhancing IRF-1 cellular levels using constitutively active IRF-1, which dose-dependently inhibited GRE-dependent gene transcription. Consistently, reducing IRF-1 cellular levels using siRNA approach significantly restored steroid transactivation activities. Collectively, our findings demonstrate for the first time that IRF-1 is a novel alternative GRbeta-independent mechanism mediating steroid dysfunction induced by pro-asthmatic cytokines, in part via the suppression of GRalpha activities.
Tliba
Omar
O
Pulmonary, Allergy, and Critical Care Division, University of Pennsylvania, 125 South 31st Street, TRL Suite 1200, Room 1214, Philadelphia, PA 19104-3403, USA. omartlib@mail.med.upenn.edu
Damera
Gautam
G
Banerjee
Audreesh
A
Gu
Su
S
Baidouri
Hasna
H
Keslacy
Stefan
S
Amrani
Yassine
Y
D051997:ADP-ribosyl Cyclase 1 / Q000235:genetics / Q000378:metabolism; D000730:Androstadienes / Q000494:pharmacology*; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D004351:Drug Resistance / Q000187:drug effects*; D000068298:Fluticasone; D006801:Humans; D050856:Interferon Regulatory Factor-1 / Q000378:metabolism*; D007371:Interferon-gamma / Q000494:pharmacology*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D011965:Receptors, Glucocorticoid / Q000235:genetics / Q000378:metabolism; D012137:Respiratory System / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D015533:Transcriptional Activation / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D000730:Androstadienes; C494257:IRF1 protein, human; D050856:Interferon Regulatory Factor-1; D011965:Receptors, Glucocorticoid; D014409:Tumor Necrosis Factor-alpha; C411470:glucocorticoid receptor alpha; C121943:glucocorticoid receptor beta; D007371:Interferon-gamma; D000068298:Fluticasone; D051997:ADP-ribosyl Cyclase 1