title: Up-regulation of cyclooxygenase-2 by cobalt chloride-induced hypoxia is mediated by phospholipase D isozymes in human astroglioma cells.
abstract: Cyclooxygenase-2 (COX-2) is an isoform of prostaglandin H synthase induced by hypoxia and has been implicated in the growth and progression of a variety of human cancers. In the present study, we investigated the role of phospholipase D (PLD) isozymes in cobalt chloride (CoCl(2))-induced hypoxia-driven COX-2 expression in U87 MG human astroglioma cells. CoCl(2) stimulated PLD activity and synthesis of COX-2 protein in a dose and time-dependent manner. Moreover, elevated expression of PLD1 and PLD2 increased hypoxia-induced COX-2 expression and prostaglandin E2 (PGE(2)) production. Pretreatment of cells with 1-butanol, but not 3-butanol, suppressed CoCl(2)-induced COX-2 expression and PGE(2) formation. In addition, evidence that PLD activity was involved in the stimulation of COX-2 expression was provided by the observations that overexpression of wild type PLD isozymes, but not catalytically inactive PLD isozymes, stimulated CoCl(2)-induced COX-2 expression and PGE(2) production. PLD1 enhanced COX-2 expression by CoCl(2) via reactive oxygen species (ROS), p38 MAPK kinase, PKC-delta, and PKA, but not ERK, whereas PLD2 enhanced CoCl(2)-induced COX-2 expression via ROS and p38 MAPK, but not ERK, PKC-delta, and PKA. Differential regulation of COX-2 expression mediated through PLD isozymes was comparable with that of CoCl(2)-induced PLD activity in these two PLD isozymes. Taken together, our results demonstrate for the first time that PLD1 and PLD2 isozymes enhance CoCl(2)-induced COX-2 expression through differential signaling pathways in astroglioma cells.
authors.affiliation: Cardiovascular Branch National Heart, Lung and Blood Institute (NHLBI), NIH Bldg 10/CRC 5-3288 10 Center Drive, Bethesda, MD 20892, USA.
authors.forename: Bong-Hyun
authors.initials: BH
authors.lastname: Ahn
authors.forename: Mi Hee
authors.initials: MH
authors.lastname: Park
authors.forename: Young Han
authors.initials: YH
authors.lastname: Lee
authors.forename: Taeg Kyu
authors.initials: TK
authors.lastname: Kwon
authors.forename: Do Sik
authors.initials: do S
authors.lastname: Min
mesh_terms: D001254:Astrocytoma / Q000201:enzymology* / Q000235:genetics*; D015687:Cell Hypoxia / Q000187:drug effects; D003035:Cobalt / Q000494:pharmacology*; D051546:Cyclooxygenase 2 / Q000235:genetics* / Q000378:metabolism; D015232:Dinoprostone / Q000096:biosynthesis; D004789:Enzyme Activation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D037342:Pertussis Toxin / Q000494:pharmacology; D010739:Phospholipase D / Q000378:metabolism*; D054467:Phospholipases A2 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D010738:Type C Phospholipases / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects*
chemical_list: D007527:Isoenzymes; D008070:Lipopolysaccharides; D003035:Cobalt; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D037342:Pertussis Toxin; D054467:Phospholipases A2; D010738:Type C Phospholipases; D010739:Phospholipase D; C018021:cobaltous chloride; D015232:Dinoprostone; D013755:Tetradecanoylphorbol Acetate