title: Anticardiolipin antibody-positive serum enhances endothelial cell platelet-activating factor production.
abstract: Circulating antiphospholipids have been linked to recurrent pregnancy loss by a mechanism involving placental and decidual thrombosis. We hypothesized that platelet-activating factor, an autacoid synthesized by vascular endothelium, might mediate this phenomenon through its ability to promote platelet aggregation and fibrin deposition. Alternatively, antiphospholipid antibodies might exert a procoagulant effect by inhibiting the synthesis of prostacyclin. To evaluate these theories, endothelial cells (harvested from human umbilical veins) were grown to confluence and incubated for 48 hours with 20% concentrations of anticardiolipin antibody-positive and -negative human sera as well as fetal bovine serum. After incubation culture wells were stimulated with 10 mumol/ml calcium ionophore A23187 (an agonist of platelet-activating factor and prostacyclin synthesis). Intracellular platelet-activating factor was measured by tritiated acetate incorporation, phospholipid extraction, thin-layer chromatography, and scintillation spectrophotometry. Enhanced platelet-activating factor synthesis was identified in cultures incubated with anticardiolipin antibody-positive serum (25,544 +/- 2604 disintegrations per minute, mean +/- SD) when compared with anticardiolipin antibody-negative serum (18,600 +/- 3316 dpm) or fetal bovine serum (19,014 +/- 4233 dpm; analysis of variance, p = 0.033). In similar experiments, prostacyclin synthesis was determined by measuring its primary metabolite, 6-keto-prostaglandin F1 alpha, in culture supernatants. No differences between anticardiolipin antibody-positive and control cultures were observed (analysis of variance, p = 0.90). We conclude that in this endothelial cell model, anticardiolipin antibody-positive serum enhances ionophore-mediated platelet-activating factor synthesis but has no apparent effect on the production of prostacyclin. These findings suggest a potential role for platelet-activating factor in anticardiolipin antibody-mediated vascular thrombosis.
authors.affiliation: Division of Maternal-Fetal Medicine, Evanston Hospital, IL 60201.
authors.forename: R K
authors.initials: RK
authors.lastname: Silver
authors.forename: L
authors.initials: L
authors.lastname: Adler
authors.forename: A R
authors.initials: AR
authors.lastname: Hickman
authors.forename: J R
authors.initials: JR
authors.lastname: Hageman
mesh_terms: D015121:6-Ketoprostaglandin F1 alpha / Q000096:biosynthesis; D000906:Antibodies / Q000097:blood*; D016736:Antiphospholipid Syndrome / Q000097:blood; D000001:Calcimycin / Q000494:pharmacology; D002308:Cardiolipins / Q000276:immunology*; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000378:metabolism*; D006801:Humans; D010972:Platelet Activating Factor / Q000096:biosynthesis*; D014471:Umbilical Veins
chemical_list: D000906:Antibodies; D002308:Cardiolipins; D010972:Platelet Activating Factor; D000001:Calcimycin; D015121:6-Ketoprostaglandin F1 alpha