Secretory phospholipase A2 mediates cooperative prostaglandin generation by growth factor and cytokine independently of preceding cytosolic phospholipase A2 expression in rat gastric epithelial cells.
Transforming growth factor (TGF)-alpha and interleukin (IL)-1beta are responsible for the healing of gastric lesions through, in part, prostaglandin (PG) generation. We examined the contribution of cytosolic and secretory phospholipase A(2)s (cPLA(2) and sPLA(2)) to the PG generation by rat gastric epithelial cells in response to both stimuli. Stimulation with TGF-alpha for 24 h increased cPLA(2) and cyclooxygenase (COX)-2 markedly, PGE(2) slightly, and type IIA sPLA(2) and COX-1 not at all, whereas IL-1beta increased sPLA(2) only. Both stimuli synergistically increased PGE(2), sPLA(2), and the two COXs but not cPLA(2). The onset of the PGE(2) generation paralleled the sPLA(2) release but was apparently preceded by increases in cPLA(2) and the two COXs. The increase in PGE(2) was impaired by inhibitors for sPLA(2) and COX-2 but not COX-1. cPLA(2) inhibitors suppressed PGE(2) generation by TGF-alpha alone but not augmentation of PGE(2) generation or sPLA(2) release by IL-1beta in combination with TGF-alpha. Furthermore, despite an increase in cPLA(2) including its phosphorylated form (phosphoserine), -induced arachidonic acid liberation was impaired in the TGF-alpha/IL-1beta-stimulated cells, in which p11, a putative cPLA(2) inhibitory molecule, was also increased and co-immunoprecipitated with cPLA(2). These results suggest that synergistic stimulation of sPLA(2) and COX-2 expression by TGF-alpha and IL-1beta results in an increase in PGE(2). Presumably, the preceding cPLA(2) expression is not involved in the PGE(2) generation, because of impairment of its hydrolytic activity in the stimulated cells.
Akiba
S
S
Department of Pathological Biochemistry, Kyoto Pharmaceutical University, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan. akiba@mb.kyoto-phu.ac.jp
Hatazawa
R
R
Ono
K
K
Kitatani
K
K
Hayama
M
M
Sato
T
T
D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D002461:Cell Line, Transformed; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D015232:Dinoprostone / Q000378:metabolism; D005753:Gastric Mucosa / Q000166:cytology / Q000201:enzymology*; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008565:Membrane Proteins; D010741:Phospholipases A / Q000235:genetics / Q000378:metabolism*; D054467:Phospholipases A2; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D011994:Recombinant Proteins / Q000494:pharmacology*; D016211:Transforming Growth Factor alpha / Q000494:pharmacology*
D007375:Interleukin-1; D007527:Isoenzymes; D008565:Membrane Proteins; D011994:Recombinant Proteins; D016211:Transforming Growth Factor alpha; D016718:Arachidonic Acid; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; C496511:PTGS1 protein, human; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; C496513:Ptgs1 protein, rat; D010741:Phospholipases A; D054467:Phospholipases A2; D015232:Dinoprostone