Dipyridamole activation of mitogen-activated protein kinase phosphatase-1 mediates inhibition of lipopolysaccharide-induced cyclooxygenase-2 expression in RAW 264.7 cells.
Dipyridamole is a nucleoside transport inhibitor and a non-selective phosphodiesterase inhibitor. However, the mechanisms by which dipyridamole exerts its anti-inflammatory effects are not completely understood. In the present study, we investigated the role of mitogen-activated kinase phosphatase-1 (MKP-1) in dipyridamole's anti-inflammatory effects. We show that dipyridamole inhibited interleukin-6 and monocyte chemoattractant protein-1 secretion, inducible nitric oxide synthase protein expression, nitrite accumulation, and cyclooxygenase-2 (COX-2) induction in lipopolysaccharide (LPS)-activated RAW 264.7 macrophages. Dipyridamole inhibited the nuclear factor kappa B (NF-kappaB) signaling pathway as demonstrated by inhibition of the inhibitor of NF-kappaB (IkappaB) phosphorylation, IkappaB degradation, p65 translocation from the cytosol to the nucleus, and transcription of the reporter gene. Dipyridamole also inhibited LPS-stimulated p38 mitogen-activated protein kinase (p38 MAPK) and IkappaB kinase-beta (IKK-beta) activities in RAW 264.7 cells. A p38 MAPK inhibitor, SB 203580, inhibited LPS-stimulated COX-2 expression and IKK-beta activation suggesting that LPS may activate the NF-kappaB signaling pathway via upstream p38 MAPK activation. Furthermore, dipyridamole stimulated transient activation of MKP-1, a potent inhibitor of p38 MAPK function. Knockdown of MKP-1 by transfecting MKP-1 siRNA or inhibition of MKP-1 by the specific inhibitor, triptolide, significantly reduced the inhibitory effects of dipyridamole on COX-2 expression induced by LPS. Taken together, these data suggest that dipyridamole exerts its anti-inflammatory effect via activation of MKP-1, which dephosphorylates and inactivates p38 MAPK. Inactivation of p38 MAPK in turn inhibits IKK-beta activation and subsequently the NF-kappaB signaling pathway that mediates LPS-induced cyclooxygenase-2 expression in RAW 264.7 cells.
Chen
Tso-Hsiao
TH
Department of Internal Medicine, Taipei Medical University, Wan-Fang Hospital, Taiwan.
Kao
Yuan-Chung
YC
Chen
Bing-Chang
BC
Chen
Cheng-Hsien
CH
Chan
Paul
P
Lee
Horng-Mo
HM
D000818:Animals; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D052246:Cyclooxygenase 2 Inhibitors / Q000494:pharmacology; D004176:Dipyridamole / Q000494:pharmacology*; D054638:Dual Specificity Phosphatase 1; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D004797:Enzyme-Linked Immunosorbent Assay; D005455:Fluorescent Antibody Technique; D020868:Gene Silencing; D017874:Immediate-Early Proteins / Q000235:genetics / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects* / Q000201:enzymology; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D016328:NF-kappa B / Q000096:biosynthesis; D009569:Nitric Oxide / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D054645:Protein Phosphatase 1; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D018797:Cell Cycle Proteins; D052246:Cyclooxygenase 2 Inhibitors; D017874:Immediate-Early Proteins; D008070:Lipopolysaccharides; D016328:NF-kappa B; D010726:Phosphodiesterase Inhibitors; D009569:Nitric Oxide; D004176:Dipyridamole; D052247:Nitric Oxide Synthase Type II; D051546:Cyclooxygenase 2; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054638:Dual Specificity Phosphatase 1; C517020:Dusp1 protein, mouse; D017027:Protein Tyrosine Phosphatases