Mitogen-activated protein kinase phosphatase-1 negatively regulates the expression of interleukin-6, interleukin-8, and cyclooxygenase-2 in A549 human lung epithelial cells.
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-1beta, and interferon-gamma; 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.
Turpeinen
Tuija
T
The Immunopharmacology Research Group, Medical School, University of Tampere, FIN-33014 Tampere, Finland.
Nieminen
Riina
R
Moilanen
Eeva
E
Korhonen
Riku
R
D002460:Cell Line; D051546:Cyclooxygenase 2 / Q000096:biosynthesis*; D054638:Dual Specificity Phosphatase 1 / Q000502:physiology*; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D053583:Interleukin-1beta / Q000494:pharmacology; D015850:Interleukin-6 / Q000096:biosynthesis*; D016209:Interleukin-8 / Q000096:biosynthesis*; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D008168:Lung / Q000276:immunology / Q000378:metabolism*; D010766:Phosphorylation; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
D053583:Interleukin-1beta; D015850:Interleukin-6; D016209:Interleukin-8; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; D051546:Cyclooxygenase 2; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C517019:DUSP1 protein, human; D054638:Dual Specificity Phosphatase 1