Vitamin E (alpha-tocopherol) attenuates cyclo-oxygenase 2 transcription and synthesis in immortalized murine BV-2 microglia.
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.
Egger
Tamara
T
Institute of Medical Biochemistry and Molecular Biology, University Graz, Harrachgasse 21, 8010 Graz, Austria.
Schuligoi
Rufina
R
Wintersperger
Andrea
A
Amann
Rainer
R
Malle
Ernst
E
Sattler
Wolfgang
W
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
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