Critical role of COX-1 in prostacyclin production by human endothelial cells under modification of hydroperoxide tone.
We aimed at evaluating the relative contribution of cyclooxygenase (COX) -1 and COX-2 to the synthesis of prostacyclin in endothelial cells under static conditions in the presence or absence of exogenous arachidonic acid and/or altered intracellular redox balance. Selective inhibitors of either COX-1 (SC560 and FR122047) or COX-2 (SC236) concentration dependently (1-300 nM) reduced basal and interleukin (IL) -1beta-induced prostacyclin production in human umbilical vein endothelial cells by 70% or more; compound selectivity was confirmed using a whole-blood assay (IC(50) COX-1/COX-2: 13 nM/930 nM for SC-560; 9 microM/457 nM for SC-236). The observed concomitant formation of isoprostane appeared to be associated with COX enzyme activity, while formation of COX-1/COX-2 heterodimers was detected by immunoprecipitation. In the presence of arachidonic acid and 12-hydroperoxy-eicosatetraenoic acid, either exogenous or provided by platelet activation, or after glutathione depletion, COX-1 inhibition but not COX-2 inhibition concentration dependently decreased prostacyclin production. Both isoforms appear to contribute to basal prostacyclin production by endothelial cells, with COX-2 providing the hydroperoxide tone required for COX-1 activity. Conversely, in the case of intracellular glutathione depletion or enhanced availability of arachidonic acid and hydroperoxides, selective COX-2 inhibition did not significantly affect the production of endothelial prostacyclin. These findings contribute to a better understanding of the effects of cyclooxygenase inhibitors on prostacyclin production.
Department of Pharmacological Sciences, University of Milan, Via Balzaretti 9, 20133 Milan, Italy.
Chiara
C
Bolego
Carola
C
Buccellati
Alberto
A
Prada
Rosa Maria
RM
Gaion
Giancarlo
G
Folco
Angelo
A
Sala
D016718:Arachidonic Acid / Q000494:pharmacology; D002478:Cells, Cultured; D051545:Cyclooxygenase 1 / Q000378:metabolism*; D051546:Cyclooxygenase 2 / Q000378:metabolism; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism*; D011464:Epoprostenol / Q000096:biosynthesis*; D005978:Glutathione / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism; D015289:Leukotrienes / Q000494:pharmacology; D055503:Protein Multimerization
D016861:Cyclooxygenase Inhibitors; D007527:Isoenzymes; D015289:Leukotrienes; D016718:Arachidonic Acid; C021201:12-HPETE; D006861:Hydrogen Peroxide; D011464:Epoprostenol; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D005978:Glutathione