Prostaglandin endoperoxide synthase-2 contributes to the endothelin/sarafotoxin-induced prostaglandin E2 synthesis in mouse osteoblastic cells (MC3T3-E1): evidence for a protein tyrosine kinase-signaling pathway and involvement of protein kinase C.
Endothelin (ET) peptides are potent growth factors binding to G protein-coupled receptors. Sarafotoxins (S6) isolated from Atractaspis engaddensis are highly homologous to endothelins. In this study, we have investigated the effects of endothelin/sarafotoxin peptides on the prostaglandin synthesizing system in an osteoblast-like cell line, MC3T3-E1. ET-1, ET-2, beta-ET, and S6b rapidly stimulated prostaglandin E2 production within 5 min, whereas ET-3, S6a, and S6c did not. ET-1, ET-2, beta-ET, S6b, and S6a induced prostaglandin synthesis after 3 h of incubation. Antagonizing these effects with BQ-123, PD 142893, BQ-788, and S6c suggests signaling through an ET(A) receptor subtype in osteoblasts. Long-term prostaglandin synthesis was blocked by NS-398, and reduced to short-term levels by cycloheximide and actinomycin D, indicating induction of PGHS-2. There was only minor enhancement of cAMP accumulation by the agonists, which had no effect on prostaglandin synthesis. Induction of PGHS-2 was furthermore demonstrated by Northern blot analysis of PGHS-2 messenger RNA. Depletion of protein kinase C with TPA largely blunted the response. Genistein, an inhibitor of protein tyrosine kinases, also blocked long-term prostaglandin E2 formation. We conclude that in osteoblast-like MC3T3-E1 cells, ET-1, ET-2, beta-ET, S6b, and S6a peptides induce PGHS-2 through a protein tyrosine kinase-dependent and protein kinase C-dependent pathway, signaling through ET(A) receptor occupancy.
Leis
H J
HJ
University Children's Hospital, Department of Biochemical Analysis and Mass Spectrometry, University of Graz, Austria. hans.leis@kfunigraz.ac.at
Zach
D
D
Huber
E
E
Windischhofer
W
W
D016475:3T3 Cells; D000818:Animals; D000242:Cyclic AMP / Q000096:biosynthesis; D015232:Dinoprostone / Q000096:biosynthesis*; D016232:Endothelins / Q000494:pharmacology*; D051379:Mice; D009578:Nitrobenzenes / Q000494:pharmacology; D010006:Osteoblasts / Q000378:metabolism*; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics / Q000502:physiology*; D011493:Protein Kinase C / Q000502:physiology*; D011505:Protein-Tyrosine Kinases / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D017466:Receptors, Endothelin / Q000502:physiology; D013449:Sulfonamides / Q000494:pharmacology; D014757:Viper Venoms / Q000494:pharmacology*
D016232:Endothelins; D009578:Nitrobenzenes; D012333:RNA, Messenger; D017466:Receptors, Endothelin; D013449:Sulfonamides; D014757:Viper Venoms; C057354:sarafotoxins s6; C080955:N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide; D000242:Cyclic AMP; D011451:Prostaglandin-Endoperoxide Synthases; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; D015232:Dinoprostone