title: P38 mitogen-activated protein kinase inhibitor SB203580 has a bi-directional effect on iNOS expression and NO production.
abstract: In the present study, the mediator role of p38 kinase, a member of the mitogen-activated protein kinase (MAPK) family, was studied in lipopolysaccharide-induced inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) production in J774 mouse macrophages and T-84 human colon epithelial cells. Two pyridinyl imidazole inhibitors of p38 MAPK, 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)-imidazole (SB203580) and 4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)-imidazole (SB202190), stimulated NO production at low drug concentrations, maximal stimulation occurring at 1 microM drug concentration. In contrast, higher concentrations inhibited NO production, which was>90% at 30 microM drug concentration. The bi-directional effect was found in both cell types tested. Negative control compound SB202474, which is structurally related but does not inhibit p38, did not stimulate NO production but inhibited it at 30 microM concentration. A chemically different p38 inhibitor 2-methyl-4-phenyl-5-(4-pyridyl)oxazole (SC68376) had only a stimulatory action on NO production. Western blotting and reverse transcriptase polymerase chain reaction (RT-PCR) analysis of iNOS showed that both stimulatory and inhibitory effects of SB203580 occurred at the level of iNOS expression. SB203580 did not alter lipopolysaccharide-induced NF-kappaB activation as detected by electrophoretic mobility shift assay (EMSA). The data show that pyridinyl imidazoles SB203580 and SB202190 have a bi-directional effect on NO production through iNOS pathway depending on the drug concentration used. The inhibitory effect was unrelated to inhibition of p38 MAPK, whereas the stimulatory effect is most likely mediated by p38 MAPK dependent mechanism, suggesting a novel mechanism for regulation of iNOS expression, which is common for murine and human cells.
authors.affiliation: The Immunopharmacological Research Group, Department of Pharmacology, Medical School, University of Tampere and Tampere University Hospital, FIN-33014 Tampere, Finland.
authors.forename: Aleksi
authors.initials: A
authors.lastname: Lahti
authors.forename: Hannu
authors.initials: H
authors.lastname: Kankaanranta
authors.forename: Eeva
authors.initials: E
authors.lastname: Moilanen
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000494:pharmacology*; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction / Q000187:drug effects / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D052247:Nitric Oxide Synthase Type II; D011725:Pyridines / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D002352:Carrier Proteins; D007093:Imidazoles; D047908:Intracellular Signaling Peptides and Proteins; D011725:Pyridines; C015482:protein kinase modulator; D009569:Nitric Oxide; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580