In the present study, IL (interleukin)-1β increased GM-CSF (granulocyte/macrophage colony-stimulating factor) expression from pulmonary A549 cells and primary HBE (human bronchial epithelial) cells. These responses were repressed by the glucocorticoid dexamethasone, allowing the use of A549 cells as a relevant model. IL-1β induced GM-CSF release into the culture medium by 6 h and in cell lysates (cytosolic) at 2 h. These effects were profoundly inhibited by dexamethasone, yet IL-1β-induced GM-CSF mRNA and unspliced nRNA (nuclear RNA; a surrogate of transcription rate) were modestly inhibited by dexamethasone at times up to 2 h. Although this indicates an effect on protein synthesis, actinomycin D chase experiments also indicated post-transcriptional repression by dexamethasone. Dexamethasone-dependent mRNA repression increased with time and was prevented by translational blockade. In addition, dexamethasone and the dissociated steroid RU24858 repressed GM-CSF release in an actinomycin D-sensitive manner, thereby implicating glucocorticoid-induced gene expression. At 2 h, IL-1β-induced expression of GM-CSF protein, but not mRNA, was sensitive to the MEK [MAPK (mitogen-activated protein kinase)/ERK (extracellular-signal-regulated kinase) kinase] inhibitors PD098059 and U0126. Although this indicates a role for the MEK/ERK pathway in GM-CSF translation, PD098059 subsequently destabilized GM-CSF mRNA. Dexamethasone and RU24858 both reduced IL-1β-induced ERK phosphorylation and increased MKP-1 (MAPK phosphatase-1) expression. Inhibition of ERK phosphorylation was reproduced by MKP-1 overexpression and prevented by MKP-1-targeting siRNA (small interfering RNA). Since MKP-1 prevented GM-CSF expression by transcriptional, post-transcriptional and translational processes, we propose that glucocorticoids induce MKP-1 expression to reduce both MEK/ERK activation and GM-CSF protein synthesis. Thus de novo gene expression, particularly of MKP-1, is involved in the repressive effects of glucocorticoids.
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Research Article|
March 15 2010
Glucocorticoids inhibit IL-1β-induced GM-CSF expression at multiple levels: roles for the ERK pathway and repression by MKP-1
Robert Newton;
Robert Newton
1
*Airways Inflammation Research Group, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada T2N 4N1
1To whom correspondence should be addressed (email rnewton@ucalgary.ca).
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Elizabeth M. King;
Elizabeth M. King
*Airways Inflammation Research Group, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada T2N 4N1
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Wei Gong;
Wei Gong
†Department of General Surgery, Xinhua Hospital, Jiaotong University, School of Medicine, Shanghai, People's Republic of China
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Christopher F. Rider;
Christopher F. Rider
*Airways Inflammation Research Group, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada T2N 4N1
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Karl J. Staples;
Karl J. Staples
‡Division of Infection, Inflammation and Immunity, University of Southampton, Southampton, U.K.
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Neil S. Holden;
Neil S. Holden
*Airways Inflammation Research Group, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada T2N 4N1
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Martin W. Bergmann
Martin W. Bergmann
§Department of Cardiology, Franz Volhard Clinic, Charité Campus Buch, Berlin, Germany
∥Max Delbrück Center for Molecular Medicine, Berlin, Germany
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Publisher: Portland Press Ltd
Received:
July 09 2009
Revision Received:
January 09 2010
Accepted:
January 26 2010
Accepted Manuscript online:
January 26 2010
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© The Authors Journal compilation © 2010 Biochemical Society
2010
Biochem J (2010) 427 (1): 113–124.
Article history
Received:
July 09 2009
Revision Received:
January 09 2010
Accepted:
January 26 2010
Accepted Manuscript online:
January 26 2010
Citation
Robert Newton, Elizabeth M. King, Wei Gong, Christopher F. Rider, Karl J. Staples, Neil S. Holden, Martin W. Bergmann; Glucocorticoids inhibit IL-1β-induced GM-CSF expression at multiple levels: roles for the ERK pathway and repression by MKP-1. Biochem J 1 April 2010; 427 (1): 113–124. doi: https://doi.org/10.1042/BJ20091038
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