Zymosan-induced glycerylprostaglandin and prostaglandin synthesis in resident peritoneal macrophages: roles of cyclo-oxygenase-1 and -2.
COX [cyclo-oxygenase; PG (prostaglandin) G/H synthase] oxygenates AA (arachidonic acid) and 2-AG (2-arachidonylglycerol) to endoperoxides that are converted into PGs and PG-Gs (glycerylprostaglandins) respectively. In vitro, 2-AG is a selective substrate for COX-2, but in zymosan-stimulated peritoneal macrophages, PG-G synthesis is not sensitive to selective COX-2 inhibition. This suggests that COX-1 oxygenates 2-AG, so studies were carried out to identify enzymes involved in zymosan-dependent PG-G and PG synthesis. When macrophages from COX-1-/- or COX-2-/- mice were treated with zymosan, 20-25% and 10-15% of the PG and PG-G synthesis observed in wild-type cells respectively was COX-2 dependent. When exogenous AA and 2-AG were supplied to COX-2-/- macrophages, PG and PG-G synthesis was reduced as compared with wild-type cells. In contrast, when exogenous substrates were provided to COX-1-/- macrophages, PG-G but not PG synthesis was reduced. Product synthesis also was evaluated in macrophages from cPLA(2alpha) (cytosolic phospholipase A2alpha)-/- mice, in which zymosan-induced PG synthesis was markedly reduced, and PG-G synthesis was increased approx. 2-fold. These studies confirm that peritoneal macrophages synthesize PG-Gs in response to zymosan, but that this process is primarily COX-1-dependent, as is the synthesis of PGs. They also indicate that the 2-AG and AA used for PG-G and PG synthesis respectively are derived from independent pathways.
Rouzer
Carol A
CA
Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232-0146, USA.
Tranguch
Susanne
S
Wang
Haibin
H
Zhang
Hao
H
Dey
Sudhansu K
SK
Marnett
Lawrence J
LJ
D000818:Animals; D002478:Cells, Cultured; D051545:Cyclooxygenase 1 / Q000235:genetics / Q000378:metabolism*; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D054513:Group IV Phospholipases A2; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D010741:Phospholipases A / Q000235:genetics / Q000378:metabolism; D011453:Prostaglandins / Q000096:biosynthesis*; D013379:Substrate Specificity; D015054:Zymosan / Q000494:pharmacology*
D011453:Prostaglandins; D015054:Zymosan; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D010741:Phospholipases A; D054513:Group IV Phospholipases A2