Glucocorticoids inhibit IL-1beta-induced GM-CSF expression at multiple levels: roles for the ERK pathway and repression by MKP-1.

Newton, Robert and King, Elizabeth M. and Gong, Wei and Rider, Christopher F. and Staples, Karl J. and Holden, Neil S. and Bergmann, Martin W. (2010) Glucocorticoids inhibit IL-1beta-induced GM-CSF expression at multiple levels: roles for the ERK pathway and repression by MKP-1. The Biochemical Journal, 427 (1). pp. 113-24. ISSN 0264-6021

Full content URL: http://www.biochemj.org/bj/427/bj4270113.htm

Documents
Glucocorticoids inhibit IL-1beta-induced GM-CSF expression at multiple levels: roles for the ERK pathway and repression by MKP-1

Request a copy
[img] PDF
__ddat02_staffhome_jpartridge_4270113.pdf - Whole Document
Restricted to Repository staff only

950kB
Item Type:Article
Item Status:Live Archive

Abstract

In the present study, IL (interleukin)-1beta 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-1beta 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-1beta-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-1beta-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-1beta-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.

Keywords:Corticosteroid, dual-specificity phosphatase 1 (DUSP1), Epithelial cells, granulocyte/macrophage colony-stimulating factor (GM-CSF), Inflammation, Mitogen-Activated Protein Kinases
Subjects:C Biological Sciences > C741 Medical Biochemistry
Divisions:College of Science > School of Life Sciences
ID Code:15120
Deposited On:23 Oct 2014 11:37

Repository Staff Only: item control page