title: Vitamin E (alpha-tocopherol) attenuates cyclo-oxygenase 2 transcription and synthesis in immortalized murine BV-2 microglia.
abstract: One of the immediate early microglial genes that are up-regulated in response to proinflammatory stimuli is cyclo-oxygenase 2 (COX-2). In the present study, we have investigated the effects of alpha-tocopherol (alpha TocH), an essential constituent of the nervous system, on the activation of COX-2 in lipopolysaccharide (LPS)-stimulated mouse BV-2 microglia. In unstimulated BV-2 cells, COX-2 mRNA and protein were almost undetectable but were strongly up-regulated in response to LPS. Activation of COX-2 protein synthesis in LPS-stimulated BV-2 cells involved activation of the extracellular-signal-regulated kinase 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (MAPK) pathway and was sensitive to the protein kinase C (PKC) inhibitors staurosporine and chelerythrine, and the MAP kinase/ERK kinase 1/2 inhibitors PD98059 and U0126. Supplementation of BV-2 cells with alpha TocH before LPS stimulation resulted in pronounced up-regulation of protein phosphatase 2A (PP2A) activity, down-regulation of PKC activity, ERK1/2 phosphorylation and nuclear factor kappa B (NF kappa B) activation. As a result, COX-2 protein levels and prostaglandin E(2) production were significantly lower in alpha TocH-supplemented cells. The effects of alpha TocH on PKC activity could be reverted by calyculin A and okadaic acid, two PP inhibitors. In summary, our results suggest that alpha TocH activates microglial PP2A activity and thereby silences an LPS-activated PKC/ERK/NF kappa B signalling cascade resulting in significantly attenuated COX-2 protein synthesis. These in vitro results imply that alpha TocH could induce quiescence to pathways that are associated with acute or chronic inflammatory conditions in the central nervous system.
authors.affiliation: Institute of Medical Biochemistry and Molecular Biology, University Graz, Harrachgasse 21, 8010 Graz, Austria.
authors.forename: Tamara
authors.initials: T
authors.lastname: Egger
authors.forename: Rufina
authors.initials: R
authors.lastname: Schuligoi
authors.forename: Andrea
authors.initials: A
authors.lastname: Wintersperger
authors.forename: Rainer
authors.initials: R
authors.lastname: Amann
authors.forename: Ernst
authors.initials: E
authors.lastname: Malle
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Sattler
mesh_terms: D000818:Animals; D002461:Cell Line, Transformed; D051546:Cyclooxygenase 2; D015232:Dinoprostone / Q000378:metabolism; D004789:Enzyme Activation / Q000502:physiology; D007527:Isoenzymes / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics*; D008070:Lipopolysaccharides / Q000378:metabolism; D051379:Mice; D017628:Microglia / Q000187:drug effects / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics*; D054648:Protein Phosphatase 2; D014810:Vitamin E / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D007527:Isoenzymes; D008070:Lipopolysaccharides; D016328:NF-kappa B; D014810:Vitamin E; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D020928:Mitogen-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D015232:Dinoprostone