Abstract
By repressing inflammatory gene expression, glucocorticoids are the most effective treatment for chronic inflammatory diseases such as asthma. However, in some patients with severe disease, or who smoke or suffer from chronic obstructive pulmonary disease, glucocorticoids are poorly effective. Although many investigators focus on defects in the repression of inflammatory gene expression, glucocorticoids also induce (transactivate) the expression of numerous genes to elicit anti-inflammatory effects. Using human bronchial epithelial (BEAS-2B) and pulmonary (A549) cells, we show that cytokines [tumor necrosis factor α (TNFα) and interleukin 1β], mitogens [fetal calf serum (FCS) and phorbol ester], cigarette smoke, and a Gq-linked G protein-coupled receptor agonist attenuate simple glucocorticoid response element (GRE)-dependent transcription. With TNFα and FCS, this effect was not overcome by increasing concentrations of dexamethasone, budesonide, or fluticasone propionate. Thus, the maximal ability of the glucocorticoid to promote GRE-dependent transcription was reduced, and this was shown additionally for the glucocorticoid-induced gene p57KIP2. The long-acting β2-adrenoceptor agonists (LABAs) formoterol fumarate and salmeterol xinafoate enhanced simple GRE-dependent transcription to a level that could not be achieved by glucocorticoid alone. In the presence of TNFα or FCS, which repressed glucocorticoid responsiveness, these LABAs restored glucocorticoid-dependent transcription to levels that were achieved by glucocorticoid alone. Given the existence of genes, such as p57KIP2, which may mediate anti-inflammatory actions of glucocorticoids, we propose that repression of transactivation represents a mechanism for glucocorticoid resistance and for understanding the clinical benefit of LABAs as an add-on therapy in asthma and chronic obstructive pulmonary disease.
Footnotes
This research was supported by a grant from AstraZeneca (to R.N. and M.A.G.); operating grants from the Canadian Institutes of Health Research [Grant 68828] (to R.N.); a studentship from the Lung Association of Alberta and Northwest Territories (to C.F.R.); studentships from Alberta Innovates-Health Solutions (to C.F.R. and E.M.K.); and an Izaak Walton Killam postdoctoral Fellowship (to N.S.H.). A grant from the Canadian Fund for Innovation and the Alberta Science and Research Authority provided equipment and infrastructure for conducting real-time PCR. R.N. and M.A.G. also are supported by grants from Gilead Sciences and GlaxoSmithKline.
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
doi:10.1124/jpet.111.181016.
↵ The online version of this article (available at http://jpet.aspetjournals.org) contains supplemental material.
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ABBREVIATIONS:
- ICS
- inhaled corticosteroid
- ANOVA
- analysis of variance
- AP-1
- activator protein 1
- Bud
- budesonide
- CSE
- cigarette smoke extract
- Dex
- dexamethasone
- DMSO
- dimethyl sulfoxide
- FCS
- fetal calf serum
- Form
- formoterol
- FP
- fluticasone propionate
- GILZ
- glucocorticoid-induced leucine zipper
- GR
- glucocorticoid receptor
- GRE
- glucocorticoid response element
- HDAC
- histone deacetylase
- IL
- interleukin
- JNK
- c-Jun N-terminal kinase
- LABA
- long-acting β2-adrenoceptor agonist
- MAPK
- mitogen-activated protein kinase
- MTT
- 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide
- OD
- optical density
- PCR
- polymerase chain reaction
- U46619
- 9,11-dideoxy-11a,9a-epoxymethano-prostaglandin F2α
- PMA
- phorbol 12-myristate 13-acetate
- Salm
- salmeterol
- TNFα
- tumor necrosis factor α.
- Received February 24, 2011.
- Accepted May 23, 2011.
- Copyright © 2011 by The American Society for Pharmacology and Experimental Therapeutics
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