Abstract
Mitogen-activated protein kinase phosphatase (MKP)-1 is a protein phosphatase that regulates the activity of p38 mitogen-activated protein (MAP) kinase and c-Jun NH2-terminal kinase (JNK) and, to lesser extent, p42/44 extracellular signal-regulated kinase. Studies with MKP-1(−/−) mice show that MKP-1 is a regulating factor suppressing excessive cytokine production and inflammatory response. The data on the role of MKP-1 in the regulation of inflammatory gene expression in human cells are much more limited. In the present study, we investigated the effect of MKP-1 on the expression of interleukin (IL)-6, IL-8 and cyclooxygenase (COX)-2 in response to stimulation with cytokines (tumor necrosis factor, IL-1β, and interferon-γ; 10 ng/ml each) in A549 human lung epithelial cells. Cytokines enhanced p38 and JNK phosphorylation and MKP-1 expression. p38 MAP kinase inhibitors 4-[4-(4-fluorophenyl)-5-(4-pyridinyl)-1H-imidazol-2-yl] phenol (SB202190) and 1-(5-tert-butyl-2-p-tolyl-2H-pyrazol-3-yl)-3(4-(2-morpholin-4-yl-ethoxy)naphthalen-1-yl)urea (BIRB 796) inhibited cytokine-induced phosphorylation of p38 substrate MAP kinase-activated protein kinase 2 and expression of IL-6, IL-8, and COX-2. An aminopyridine-based JNK inhibitor, N-(4-amino-5-cyano-6-ethoxypyridin-2-yl)-2-(2,5-dimethoxyphenyl)acetamide (JNK inhibitor VIII), inhibited phosphorylation of a JNK substrate c-Jun but did not have any effect on IL-6, IL-8, or COX-2 expression. Down-regulation of MKP-1 with small interfering RNA enhanced p38 and JNK phosphorylation and increased IL-6, IL-8, and COX-2 expression in A549 cells. In conclusion, cytokine-induced MKP-1 expression was found to negatively regulate p38 phosphorylation and the expression of IL-6, IL-8, and COX-2 in human pulmonary epithelial cells. Our results suggest that MKP-1 is an important negative regulator of inflammatory gene expression in human pulmonary epithelial cells, and compounds that enhance MKP-1 may have anti-inflammatory effects and control inflammatory response in the human lung.
Footnotes
- Received June 22, 2009.
- Accepted January 19, 2010.
This work was supported by competitive research funding of the Pirkanmaa Hospital District, Finland [Grants MK6008, 9J045] (to R.K.), [Grants 9K079, 9J066] (to E.M.), and Tampere Tuberculosis Foundation, Finland (to R.K. and E.M.).
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
doi:10.1124/jpet.109.157438.
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ABBREVIATIONS:
- MAP
- mitogen-activated protein
- ERK
- extracellular signal-regulated-kinase
- TNF
- tumor necrosis factor
- IL
- interleukin
- COX
- cyclooxygenase
- Th
- T helper
- IFN
- interferon
- MKP
- mitogen-activated protein kinase phosphatase
- DUSP
- dual-specificity phosphatase
- LPS
- lipopolysaccharide
- GRO-α
- growth-related oncogene protein-α
- SB202190
- 4-[4-(4-fluorophenyl)-5-(4-pyridinyl)-1H-imidazol-2-yl] phenol
- BIRB 796
- 1-(5-tert-butyl-2-p-tolyl-2H-pyrazol-3-yl)-3(4-(2-morpholin-4-yl-ethoxy)naphthalen-1-yl)urea
- JNK
- c-Jun NH2-terminal kinase
- JNK inhibitor VIII
- N-(4-amino-5-cyano-6-ethoxypyridin-2-yl)-2-(2,5-dimethoxyphenyl)acetamide
- RT-PCR
- reverse transcription-polymerase chain reaction
- MK2
- mitogen-activated protein kinase-activated protein kinase 2
- FAM
- 5-carboxyfluorescein
- TAMRA
- 5-carboxytetramethylrhodamine
- GAPDH
- glyceraldehyde-3-phosphate dehydrogenase
- siRNA
- small interfering RNA
- ELISA
- enzyme-linked immunosorbent assay
- ANOVA
- analysis of variance
- SB203580
- 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)lH-imidazole.
- Copyright © 2010 by The American Society for Pharmacology and Experimental Therapeutics
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