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Induction of cytosolic phospholipase A 2 and prostaglandin H 2 synthase‐2 by ipopolysaccharide in human polymorphonuclear leukocytes
Author(s) -
Zaitsu Masafumi,
Hamasaki Yuhei,
Matsuo Muneaki,
Miyazaki Michiko,
Hayasaki Rika,
Muro Eriko,
Yamamoto Shuichi,
Kobayashi Ikuko,
Ichimaru Tomohiro,
Miyazaki Sumio
Publication year - 1999
Publication title -
european journal of haematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.904
H-Index - 84
eISSN - 1600-0609
pISSN - 0902-4441
DOI - 10.1111/j.1600-0609.1999.tb01122.x
Subject(s) - phospholipase a2 , thromboxane a2 , arachidonic acid , lipopolysaccharide , prostaglandin , thromboxane a synthase , prostaglandin e2 , enzyme , chemistry , atp synthase , microbiology and biotechnology , biochemistry , biology , endocrinology , receptor
Polymorphonuclear leukocytes (PMNs) produce arachidonic acid (AA) metabolites including thromboxane A 2 (TXA 2 ). These cells are the first line of defense against bacterial invasion, which often causes endotoxin shock. TXA 2 which plays an important role in the pathogenesis of endotoxin shock is synthesized by three consecutive enzyme activation, cytosolic phospholipase A 2 (cPLA 2 ), prostaglandin H 2 synthase (PHS type 1 and type 2) and TXA 2 synthase. Among them, cPLA 2 ‐ and PHS‐2 activity is known to be transcriptionally and/or post‐transcriptionally up‐regulated by various bioactive substances including lipopolysaccharide (LPS), a bacterial endotoxin, in many cell types. We investigated the action of LPS on TXA 2 synthesis in human PMNs. A23187‐stimulated production of thromboxane B 2 (TXB 2 , a stable metabolite of TXA 2 ), assayed by specific radioimmunoassay (RIA), was significantly increased from 566.7±44.1 pg/10 6 cells to 966.7±44.1 pg/10 6 cells ( p <0.05) after 6 h‐exposure to LPS at the concentration of 100 ng/ml. Messenger RNA for PHS‐2, PHS‐1, TXA 2 synthase and cPLA 2 , which was assessed by reverse transcription‐polymerase chain reaction (RT‐PCR), was expressed in PMNs without LPS stimulation. Although PHS‐2 was putatively an inducible enzyme, abundance of mRNA for PHS‐2 in PMNs without LPS stimulation was detectable. Messenger RNA abundance for PHS‐2 and cPLA 2 , but not for PHS‐1 and TXA 2 synthase, was enhanced by LPS‐treatment, indicating that the increased production of TXB 2 was attributable to the up‐regulation of cPLA 2 and PHS‐2. We conclude that (1) PHS‐2 plays a more important role than PHS‐1 in the production of TXA 2 in human PMNs and (2) TXA 2 synthesis in human PMNs is transcriptionally up‐regulated by new induction of cPLA 2 as well as PHS‐2, when the cells encounter endotoxin producing bacteria.