Interleukin-1 alpha stimulates prostaglandin biosynthesis in serum-activated mesangial cells by induction of a non-pancreatic (type II) phospholipase A2.
Enhanced prostaglandin (PG) biosynthesis is a hallmark of inflammation, and interleukin-1 (IL), a proinflammatory cytokine, is a potent stimulus of PG production. We investigated the mechanisms of IL-1 alpha-enhanced PG synthesis in serum-stimulated mesangial cells. The rIL-1-stimulated increase in PGE2 synthesis was dose- and time-dependent and inhibited by both cycloheximide and actinomycin D. Phospholipase (PL) activity was increased 5- to 10-fold in acid extracts of rIL-1-treated cells as measured by arachidonate release from exogenous [14C]arachidonyl-phosphatidyl-ethanolamine. This induced phospholipase activity was Ca(2+)-dependent and inhibited by the PLA2 inhibitors, aristocholic acid, 7,7-dimethyl-5,8-eicosadienoic acid, and p-bromophenacylbromide, but not by the 1,2-diacylglycerol lipase inhibitor RHC 80267. The rIL-1-stimulated PLA2 had an alkaline pH optimum, and phosphatidylethanolamine was preferred over phosphatidylcholine as substrate. The PLA2 activity increased by rIL-1 was inhibited in cells coincubated with cycloheximide and was measurable after 6 h. A sensitive and specific solution hybridization assay demonstrated a coordinate time-dependent induction of non-pancreatic PLA2 mRNA expression which was increased at least 6-fold by 24 h. In whole cells, IL-1 had no effect on basal [3H]arachidonic acid release but vasopressin (1 microM)-stimulated release was potentiated 2- to 3-fold, suggesting that IL-1 may prime cells for increased PG synthesis via increased PLA2 activity. Thus IL-1 directly stimulates, as well as primes cells for, enhanced PG synthesis, in part, by increasing PLA2 activity through new synthesis of a non-pancreatic (Type II) PLA2.
Nakazato
Y
Y
Department of Medicine, School of Medicine, Case Western Reserve University, Cleveland, Ohio.
Simonson
M S
MS
Herman
W H
WH
Konieczkowski
M
M
Sedor
J R
JR
D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism; D015152:Blotting, Northern; D002455:Cell Division; D002478:Cells, Cultured; D015232:Dinoprostone / Q000096:biosynthesis; D004790:Enzyme Induction; D015870:Gene Expression; D005920:Glomerular Mesangium / Q000378:metabolism*; D066298:In Vitro Techniques; D007375:Interleukin-1 / Q000494:pharmacology*; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D054467:Phospholipases A2; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D011453:Prostaglandins / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D011994:Recombinant Proteins
D001095:Arachidonic Acids; D007375:Interleukin-1; D011453:Prostaglandins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D016718:Arachidonic Acid; D011451:Prostaglandin-Endoperoxide Synthases; D010741:Phospholipases A; D054467:Phospholipases A2; D015232:Dinoprostone