Abstract
Synthetic glucocorticoids (GCs) remain among the most effective agents for the management of chronic inflammatory diseases. However, major side effects severely limit their therapeutic use. Physiologic and therapeutic activities of GCs are mediated by a nuclear receptor belonging to a superfamily of ligand-inducible transcription factors that, in addition to directly regulating their cognate gene programs, can also mutually interfere with other signaling pathways. We recently identified selective ligands of the glucocorticoid receptor that dissociate transactivation from activator protein 1 transrepression, and most importantly retain in vivo anti-inflammatory activity. To further document the mechanisms of action sustaining the observed in vivo activity, we report here on the interference of dissociated GCs with nuclear factor κB (NF-κB)-driven gene activation. We show that dissociated GCs repress tumor necrosis factor-induced interleukin-6 gene expression by an NF-κB-dependent mechanism, without changing the expression level of inhibitor κB. The DNA-binding activity of induced NF-κB also remained unchanged after stimulation of cells with the various compounds. Evidence for a direct nuclear mechanism of action was obtained by analysis of cell lines constitutively expressing a fusion protein between the DNA-binding domain of the yeast Gal4 protein and the transactivating p65 subunit of NF-κB, which was able to efficiently repress a Gal4-dependent luciferase reporter gene upon addition of the dissociated compounds. We therefore conclude that, in addition to dissociating transactivation from activator protein 1 transrepression, dissociated GCs mediate inhibition of NF-κB signaling by a mechanism that is independent of inhibitor κB induction.
Footnotes
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Send reprint requests to: Dr. Michèle Resche-Rigon, Hoechst Marion Roussel, Molecular and Cellular Biology, Bone Disease Group, 102, route de Noisy, 93235 Romainville Cedex, France. E-mail:michele.resche-rigon{at}hmrag.com
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1 This work was supported by the Interuniversitaire Attractiepolen. G.H. is a Research Director with the Fonds voor Wetenschappelijk Onderzoek—Vlaanderen. K.D. holds a fellowship from the Vlaams Instituut voor de Bevordering van het Wetenschappelijk-Technologisch Onderzoek in de Industrie.
- Abbreviations:
- GC
- glucocorticoid
- DBD
- DNA-binding domain
- DEX
- dexamethasone
- HTC
- hepatoma cell
- I-κB
- inhibitor κB
- NF-κB
- nuclear factor κB
- TNF
- tumor necrosis factor
- IL
- interleukin
- TRE
- tumor-promoting agent-responsive element
- GR
- glucocorticoid receptor
- NR
- nuclear receptor
- DMEM
- Dulbecco’s modified Eagle’s medium
- FCS
- fetal calf serum
- TBS
- Tris-buffered saline
- ELISA
- enzyme-linked immunosorbant assay
- ERK
- extracellular signal receptor-activated kinase
- MAPK
- mitogen-activated protein kinase
- AP-1
- activator protein 1
- GRE
- glucocorticoid-responsive element
- MMTV
- mouse mammary tumor virus
- ERK
- extracellular signal-regulated kinase
- Received April 7, 1999.
- Accepted June 24, 1999.
- The American Society for Pharmacology and Experimental Therapeutics
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