title: Delayed production of arachidonic acid contributes to the delay of proteinase-activated receptor-1 (PAR1)-triggered prostaglandin E2 release in rat gastric epithelial RGM1 cells.
abstract: Proteinase-activated receptor-1 (PAR1), upon activation, exerts prostanoid-dependent gastroprotection, and increases prostaglandin E(2) (PGE(2)) release through cyclooxygenase-2 (COX-2) upregulation in rat gastric mucosal epithelial RGM1 cells. However, there is a big time lag between the PAR1-triggered PGE(2) release and COX-2 upregulation in RGM1 cells; that is, the former event takes 18 h to occur, while the latter rapidly develops and reaches a plateau in 6 h. The present study thus aimed at clarifying mechanisms for the delay of PGE(2) release after PAR1 activation in RGM1 cells. Although a PAR1-activating peptide, TFLLR-NH(2), alone caused PGE(2) release at 18 h, but not 6 h, TFLLR-NH(2) in combination with arachidonic acid dramatically enhanced PGE(2) release even for 1-6 h. TFLLR-NH(2) plus linoleic acid caused a similar rapid response. CP-24879, a Δ(5)/Δ(6)-desaturase inhibitor, abolished the PGE(2) release induced by TFLLR-NH(2) plus linoleic acid, but not by TFLLR-NH(2) alone. The TFLLR-NH(2)-induced PGE(2) release was not affected by inhibitors of cytosolic phospholipase A(2) (cPLA(2)), Ca(2+)-independent PLA(2) (cPLA(2)) or secretory PLA(2) (sPLA(2)), but was abolished by their mixture or a pan-PLA(2) inhibitor. Among PLA(2) isozymes, mRNA of group IIA sPLA(2) (sPLA(2)-IIA) was upregulated following PAR1 stimulation for 6-18 h, whereas protein levels of PGE synthases were unchanged. These data suggest that the delay of PGE(2) release after COX-2 upregulation triggered by PAR1 is due to the poor supply of free arachidonic acid at the early stage in RGM1 cells, and that plural isozymes of PLA(2) including sPLA(2)-IIA may complementarily contribute to the liberation of free arachidonic acid.
authors.affiliation: Division of Pharmacology and Pathophysiology, Kinki University School of Pharmacy, 3-4-1 Kowakae, Higashi-Osaka 577-8502, Japan.
authors.forename: Fumiko
authors.initials: F
authors.lastname: Sekiguchi
authors.forename: Ai
authors.initials: A
authors.lastname: Ohi
authors.forename: Yuma
authors.initials: Y
authors.lastname: Maeda
authors.forename: Kaori
authors.initials: K
authors.lastname: Takaoka
authors.forename: Teruki
authors.initials: T
authors.lastname: Sekimoto
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Nishikawa
authors.forename: Atsufumi
authors.initials: A
authors.lastname: Kawabata
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000096:biosynthesis*; D001095:Arachidonic Acids / Q000494:pharmacology; D002460:Cell Line; D051546:Cyclooxygenase 2 / Q000378:metabolism; D000090943:Delta-5 Fatty Acid Desaturase; D015232:Dinoprostone / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000378:metabolism*; D044943:Fatty Acid Desaturases / Q000378:metabolism; D005753:Gastric Mucosa / Q000166:cytology / Q000378:metabolism*; D019746:Intramolecular Oxidoreductases / Q000378:metabolism; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics; D009842:Oligopeptides / Q000494:pharmacology; D064801:Phospholipase A2 Inhibitors; D054467:Phospholipases A2 / Q000235:genetics; D000071876:Prostaglandin-E Synthases; D051381:Rats; D044463:Receptor, PAR-1 / Q000378:metabolism*; D013230:Stearoyl-CoA Desaturase / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D001095:Arachidonic Acids; D000090943:Delta-5 Fatty Acid Desaturase; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D009842:Oligopeptides; C462999:PAR-1-activating peptide; D064801:Phospholipase A2 Inhibitors; D044463:Receptor, PAR-1; C081565:arachidonyltrifluoromethane; D016718:Arachidonic Acid; D044943:Fatty Acid Desaturases; D013230:Stearoyl-CoA Desaturase; C474452:delta 6-desaturase, rat; D051546:Cyclooxygenase 2; D054467:Phospholipases A2; D019746:Intramolecular Oxidoreductases; D000071876:Prostaglandin-E Synthases; D015232:Dinoprostone