title: Inhibition of NF-kappaB-dependent transcription by MKP-1: transcriptional repression by glucocorticoids occurring via p38 MAPK.
abstract: Acting via the glucocorticoid receptor (GR), glucocorticoids exert potent anti-inflammatory effects partly by repressing inflammatory gene transcription occurring via factors such as NF-kappaB. In the present study, the synthetic glucocorticoid, dexamethasone, induces expression of MKP-1 (mitogen-activated protein kinase (MAPK) phosphatase-1) in human bronchial epithelial (BEAS-2B) and pulmonary (A549) cells. This correlates with reduced TNFalpha-stimulated p38 MAPK phosphorylation. Since NF-kappaB-dependent transcription and IL-8 protein, mRNA, and unspliced RNA (a surrogate of transcription rate) are sensitive to p38 MAPK inhibitors (SB203580 and SB239063), we explored the role of MKP-1 in repression of these outputs. Repression of TNFalpha-induced p38 MAPK phosphorylation, NF-kappaB-dependent transcription, and IL-8 expression by dexamethasone are sensitive to transcriptional or translational inhibitors. This indicates a role for de novo gene synthesis. Adenoviral expression of MKP-1 profoundly reduces p38 MAPK phosphorylation and IL-8 expression. Similarly, NF-kappaB-dependent transcription is significantly reduced to levels consistent with maximal p38 MAPK inhibition. Thus, MKP-1 attenuates TNFalpha-dependent activation of p38 MAPK, induction of IL-8 expression, and NF-kappaB-dependent transcription. Small interfering RNA knockdown of dexamethasone-induced MKP-1 expression partially reverses the repression of TNFalpha-activated p38 MAPK, demonstrating that MKP-1 participates in the dexamethasone-dependent repression of this pathway. In the presence of MKK6 (MAPK kinase 6), a p38 MAPK activator, dexamethasone dramatically represses TNFalpha-induced NF-kappaB-dependent transcription, and this is significantly reversed by MKP-1-targeting small interfering RNA. This reveals an important and novel role for transcriptional activation (transactivation) of MKP-1 in the repression of NF-kappaB-dependent transcription by glucocorticoids. We conclude that GR transactivation is essential to the anti-inflammatory properties of GR ligands.
authors: Airways Inflammation Group, Faculty of Medicine, University of Calgary, Calgary, Alberta T2N 4N1, Canada.
authors: Elizabeth M
authors: EM
authors: King
authors: Neil S
authors: NS
authors: Holden
authors: Wei
authors: W
authors: Gong
authors: Christopher F
authors: CF
authors: Rider
authors: Robert
authors: R
authors: Newton
mesh_terms: D015153:Blotting, Western; D002460:Cell Line; D045744:Cell Line, Tumor; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D054638:Dual Specificity Phosphatase 1 / Q000235:genetics* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D005938:Glucocorticoids / Q000494:pharmacology; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D016209:Interleukin-8 / Q000235:genetics / Q000378:metabolism; D016328:NF-kappa B / Q000235:genetics* / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011725:Pyridines / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic / Q000187:drug effects*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D005938:Glucocorticoids; D007093:Imidazoles; D016209:Interleukin-8; D016328:NF-kappa B; D011725:Pyridines; D011743:Pyrimidines; D014409:Tumor Necrosis Factor-alpha; D003609:Dactinomycin; D003907:Dexamethasone; D003513:Cycloheximide; D048051:p38 Mitogen-Activated Protein Kinases; C517019:DUSP1 protein, human; D054638:Dual Specificity Phosphatase 1; C406525:SB 239063; C093642:SB 203580