title: The role of p38 mitogen-activated kinase (MAPK) in the mechanism regulating cyclooxygenase gene expression in equine leukocytes.
abstract: The goal of this study was to define the role for p38 mitogen-activated kinase (MAPK) in the signaling mechanism regulating pro-inflammatory cyclooxygenase (COX) gene expression in lipopolysaccharide (LPS)-activated equine leukocytes for the purposes of identifying novel targets for anti-inflammatory therapy in endotoxemic horses. The p38 MAPK has been shown to positively regulate inflammatory gene expression in human leukocytes and can be activated by a variety of stimuli including LPS, TNF-alpha, and IL-1. Activation-associated phosphorylated p38 MAPK has been implicated in the up-regulation of several inflammatory genes, including COX-2 which ultimately results in the production of prostanoids that are responsible for the pathophysiology associated with endotoxemia. Our hypothesis is that activation of p38 MAPK is essential for LPS-induced COX-2 expression in equine peripheral blood leukocytes. We tested our hypothesis by investigating the effects of the specific p38 MAPK inhibitors SB203580 and SB202190 on LPS-induced COX-2 protein expression and PGE(2) production in equine leukocytes. LPS stimulation activated p38 MAPK and increased COX-2 expression in a dose-dependent manner with maximal activation observed after 30min and 4h, respectively, at a concentration of 10 ng/ml LPS. In contrast, LPS stimulation did not affect COX-1 protein expression. Pretreatment with SB203580 or SB202190 significantly inhibited LPS-induced activation-associated p38 MAPK phosphorylation, COX-2 mRNA and protein levels, and PGE(2) production in equine leukocytes. Maximal inhibition of LPS-induced COX-2 protein expression was achieved at a concentration of 10 microM SB203580. We concluded that p38 MAPK is essential for LPS-induced COX-2 expression suggesting that p38 MAPK is a potential target for anti-inflammatory therapy during equine endotoxemia.
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27607, USA.
authors.forename: Rachael E
authors.initials: RE
authors.lastname: Eckert
authors.forename: Laura E
authors.initials: LE
authors.lastname: Neuder
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Bell
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Trujillo
authors.forename: Samuel L
authors.initials: SL
authors.lastname: Jones
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D051546:Cyclooxygenase 2 / Q000235:genetics* / Q000378:metabolism*; D004789:Enzyme Activation; D011464:Epoprostenol / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D006736:Horses / Q000097:blood / Q000235:genetics; D007093:Imidazoles / Q000494:pharmacology; D007962:Leukocytes / Q000378:metabolism*; D011453:Prostaglandins / Q000235:genetics / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D007093:Imidazoles; D011453:Prostaglandins; D011725:Pyridines; D012333:RNA, Messenger; D011464:Epoprostenol; D051546:Cyclooxygenase 2; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole