Elevated levels of cyclooxygenase-2 in antigen-stimulated mast cells is associated with minimal activation of p38 mitogen-activated protein kinase.
We have investigated possible factors that underlie changes in the production of eicosanoids after prolonged exposure of mast cells to Ag. Ag stimulation of cultured RBL-2H3 mast cells resulted in increased expression of cyclooxygenase (COX-2) protein and message. Other eicosanoid-related enzymes, namely COX-1, 5-lipoxygenase, and cytosolic phospholipase A(2) were not induced. Activation of extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38 mitogen-activated protein (MAP) kinase preceded the induction of COX-2, whereas phosphatidylinositol 3' kinase and its substrate, Akt, were constitutively activated in RBL-2H3 cells. Studies with pharmacologic inhibitors indicated that of these kinases, only p38 MAP kinase regulated expression of COX-2. The induction of COX-2 was blocked by the p38 MAP kinase inhibitor SB202190, even when added 12-16 h after stimulation with Ag when p38 MAP kinase activity had returned to near basal, but still minimally elevated, levels. Interestingly, expression of COX-2 as well as cytosolic phospholipase A(2) and 5-lipoxygenase were markedly reduced by SB202190 in unstimulated cells. Collectively, the results imply that p38 MAP kinase regulates expression of eicosanoid-related enzymes, passively or actively, at very low levels of activity in RBL-2H3 cells. Also, comparison with published data suggest that different MAP kinases regulate induction of COX-2 in inflammatory cells of different and even similar phenotype and suggest caution in extrapolating results from one type of cell to another.
Hundley
T R
TR
Laboratory of Molecular Immunology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Prasad
A R
AR
Beaven
M A
MA
D000818:Animals; D000941:Antigens / Q000276:immunology*; D001094:Arachidonate 5-Lipoxygenase / Q000096:biosynthesis; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D003907:Dexamethasone / Q000494:pharmacology; D004140:Dinitrophenols / Q000276:immunology; D004306:Dose-Response Relationship, Immunologic; D004789:Enzyme Activation / Q000276:immunology; D004790:Enzyme Induction / Q000276:immunology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D048031:JNK Mitogen-Activated Protein Kinases; D016859:Lipoxygenase Inhibitors; D020935:MAP Kinase Signaling System / Q000276:immunology; D008407:Mast Cells / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology*; D008565:Membrane Proteins; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D010766:Phosphorylation; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis*; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D012710:Serum Albumin, Bovine / Q000276:immunology; D014407:Tumor Cells, Cultured; D048051:p38 Mitogen-Activated Protein Kinases
D000941:Antigens; D004140:Dinitrophenols; D004791:Enzyme Inhibitors; D007093:Imidazoles; D007527:Isoenzymes; D016859:Lipoxygenase Inhibitors; D008565:Membrane Proteins; D011725:Pyridines; C034638:dinitrophenyl-bovine serum albumin; D012710:Serum Albumin, Bovine; D003907:Dexamethasone; D001094:Arachidonate 5-Lipoxygenase; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; C496513:Ptgs1 protein, rat; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D010741:Phospholipases A; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole