title: Phospholipase D isozymes mediate epigallocatechin gallate-induced cyclooxygenase-2 expression in astrocyte cells.
abstract: Little is known about the effect of epigallocatechin-3 gallate (EGCG), a major constituent of green tea, on the expression of cyclooxygenase (COX)-2. Here, we studied the role of phospholipase D (PLD) isozymes in EGCG-induced COX-2 expression. Stimulation of human astrocytoma cells (U87) with EGCG induced formation of phosphatidylbutanol, a specific product of PLD activity, and synthesis of COX-2 protein and its product, prostaglandin E(2) (PGE(2)). Pretreatment of cells with 1-butanol, but not 3-butanol, suppressed EGCG-induced COX-2 expression and PGE synthesis. Furthermore, evidence that PLD was involved in EGCG-induced COX-2 expression was provided by the observations that COX-2 expression was stimulated by overexpression of PLD1 or PLD2 isozymes and treatment with phosphatidic acid (PA), and that prevention of PA dephosphorylation by 1-propranolol significantly potentiated COX-2 expression induced by EGCG. EGCG induced activation of p38 mitogen-activated protein kinase (p38 MAPK), and specific inhibition of p38 MAPK dramatically abolished EGCG-induced PLD activation, COX-2 expression, and PGE(2) formation. Moreover, protein kinase C (PKC) inhibition suppressed EGCG-induced p38 MAPK activation, COX-2 expression, and PGE(2) accumulation. The same pathways as those obtained (2)in the astrocytoma cells were active in primary rat astrocytes, suggesting the relevance of the findings. Collectively, our results demonstrate for the first time that PLD isozymes mediate EGCG-induced COX-2 expression through PKC and p38 in immortalized astroglial line and normal astrocyte cells.
authors.affiliation: Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 137-701, Korea.
authors.forename: Shi Yeon
authors.initials: SY
authors.lastname: Kim
authors.forename: Bong-Hyun
authors.initials: BH
authors.lastname: Ahn
authors.forename: Kyoung-Jin
authors.initials: KJ
authors.lastname: Min
authors.forename: Young Han
authors.initials: YH
authors.lastname: Lee
authors.forename: Eun-Hye
authors.initials: EH
authors.lastname: Joe
authors.forename: Do Sik
authors.initials: DS
authors.lastname: Min
mesh_terms: D020001:1-Butanol / Q000494:pharmacology; D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D001254:Astrocytoma / Q000378:metabolism; D015153:Blotting, Western; D002227:Carbazoles / Q000494:pharmacology; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D051546:Cyclooxygenase 2; D015232:Dinoprostone / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007527:Isoenzymes / Q000096:biosynthesis*; D008565:Membrane Proteins; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010712:Phosphatidic Acids / Q000378:metabolism / Q000494:pharmacology; D010739:Phospholipase D / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D010766:Phosphorylation; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis*; D020033:Protein Isoforms; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D002227:Carbazoles; D004791:Enzyme Inhibitors; D007211:Indoles; D007527:Isoenzymes; D008565:Membrane Proteins; D010712:Phosphatidic Acids; D020033:Protein Isoforms; C081021:Go 6976; D020001:1-Butanol; D002392:Catechin; C045651:epigallocatechin gallate; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C105606:phospholipase D2; D010739:Phospholipase D; C106801:phospholipase D1; D015232:Dinoprostone