Glucocorticoids inhibit IL-1beta-induced GM-CSF expression at multiple levels: roles for the ERK pathway and repression by MKP-1
Glucocorticoids inhibit IL-1beta-induced GM-CSF expression at multiple levels: roles for the ERK pathway and repression by MKP-1
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.
113-124
Newton, Robert
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King, Elizabeth M.
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Gong, Wei
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Rider, Christopher F.
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Staples, K arl J.
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Holden, Neil S.
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Bergmann, Martin W.
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1 April 2010
Newton, Robert
4a2c2a99-b7ad-4373-8840-96fbb5b5313e
King, Elizabeth M.
cf72612d-3af1-4d82-90b4-3c53f328aa40
Gong, Wei
d01e6a8e-67ac-4eba-b159-8e0f213dd2a6
Rider, Christopher F.
9ae565b0-226e-4d71-bac7-180416836501
Staples, K arl J.
e0e9d80f-0aed-435f-bd75-0c8818491fee
Holden, Neil S.
4250cf94-47c7-4685-956a-fbc062c43b73
Bergmann, Martin W.
569898b9-1e22-497d-964b-85bb6741f48c
Newton, Robert, King, Elizabeth M., Gong, Wei, Rider, Christopher F., Staples, K arl J., 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.
Biochemical Journal, 427 (1), .
(doi:10.1042/BJ20091038).
(PMID:20100175)
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.
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Published date: 1 April 2010
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Local EPrints ID: 185843
URI: http://eprints.soton.ac.uk/id/eprint/185843
ISSN: 1470-8728
PURE UUID: 6a2236d1-0f25-4085-a531-9bf12169987a
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Date deposited: 11 May 2011 10:41
Last modified: 15 Mar 2024 03:27
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Author:
Robert Newton
Author:
Elizabeth M. King
Author:
Wei Gong
Author:
Christopher F. Rider
Author:
Neil S. Holden
Author:
Martin W. Bergmann
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