title: Cyclooxygenase-1 and -2 of endothelial cells utilize exogenous or endogenous arachidonic acid for transcellular production of thromboxane.
abstract: The presence of prostaglandin (PG) H2 in the supernatant of human umbilical vein endothelial cells (HUVEC) stimulated by thrombin restores the capacity of aspirin-treated platelets to generate thromboxane (TX) B2. Induction of cyclooxygenase-2 (Cox-2) by interleukin (IL)-1alpha or a phorbol ester increases this formation. HUVEC treated with aspirin lost their capacity to generate PGs but recovery occurred after 3- or 6-h induction of Cox-2 with phorbol ester or IL-1alpha. Enzyme activity of the newly synthesized Cox-2 in aspirin-treated cells, evaluated after immunoprecipitation, was similar to untreated cells but after 18 h of cell stimulation only 50-60% recovery of Cox-1 was observed. The use of SC58125, a selective Cox-2 inhibitor, confirmed these findings in intact cells. Cyclooxygenase activity was related to the amount of Cox proteins present in the cells, but after induction of Cox-2, contribution of the latter to PG production was 6-8-fold that of Cox-1. Aspirin-treated or untreated cells were incubated in the absence or presence of SC58125 and stimulated by thrombin, the ionophore A23187, or exogenous arachidonic acid. The production of endogenous (6-keto-PGF1alpha, PGE2, PGF2alpha) versus transcellular (TXB2) metabolites was independent of the inducer, the source of arachidonic acid and the Cox isozyme. However, in acetylsalicylic acid-treated cells, after 6-h stimulation with IL-1alpha, newly synthesized Cox-2 produced less TXB2 than 6-keto-PGF1alpha compared to untreated cells. At later times (>18 h), there was no metabolic difference between the cells. These studies suggest that in HUVEC, Cox compartmentalization occurring after short-term activation may selectively affect transcellular metabolism, but not constitutive production, of PGs.
authors.affiliation: U348 INSERM, Institut Fédératif de Recherche Biologie de la Circulation-Lariboisière, Hôpital Laribosière, Paris, France.
authors.forename: S
authors.initials: S
authors.lastname: Karim
authors.forename: A
authors.initials: A
authors.lastname: Habib
authors.forename: S
authors.initials: S
authors.lastname: Lévy-Toledano
authors.forename: J
authors.initials: J
authors.lastname: Maclouf
mesh_terms: D016718:Arachidonic Acid / Q000378:metabolism*; D001241:Aspirin / Q000494:pharmacology; D001792:Blood Platelets / Q000378:metabolism*; D002450:Cell Communication; D002478:Cells, Cultured; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000502:physiology*; D008565:Membrane Proteins; D044262:Prostaglandin H2; D011451:Prostaglandin-Endoperoxide Synthases / Q000502:physiology*; D011463:Prostaglandins H / Q000096:biosynthesis; D013917:Thrombin / Q000494:pharmacology; D013931:Thromboxanes / Q000096:biosynthesis*
chemical_list: D007527:Isoenzymes; D008565:Membrane Proteins; D011463:Prostaglandins H; D013931:Thromboxanes; D016718:Arachidonic Acid; D044262:Prostaglandin H2; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; C496511:PTGS1 protein, human; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D013917:Thrombin; D001241:Aspirin