title: The influence of anti-endothelial/antiphospholipid antibodies on fibrin formation and lysis on endothelial cells.
abstract: The prothrombotic mechanisms associated with antiphospholipid antibodies remain incompletely defined. Antibody binding to endothelial cells in vitro is a feature of antiphospholipid antibody-positive sera. We hypothesised that impairment of endothelium-dependent fibrinolysis by antiphospholipid/anti-endothelial antibodies is a contributory factor in the pathogenesis of thrombosis. We also aimed to confirm the displacement of annexin-V from endothelial cells and enhanced fibrin formation. Binding of immunoglobulin (Ig) from antiphospholipid antibody-positive sera to endothelial cells was examined using a cell-based enzyme-linked immunosorbent assay. Effects on fibrin formation and lysis were examined on cultured endothelial cell monolayers. Plasminogen activator inhibitor-1 (PAI-1) was assayed in supernatants. We confirmed antibody binding to endothelial cells. With four of 14 antiphospholipid antibody-positive sera there was some prolongation of fibrin clot lysis time, consistent with impairment of endothelial fibrinolytic activity. Secretion of PAI-1 was significantly correlated with clot lysis time on endothelial cell monolayers incubated with antiphospholipid/anti-endothelial antibody-positive sera, but not with control sera. IgG from antiphospholipid antibody-positive sera had little effect on endothelial cell surface annexin-V expression. We conclude that impaired endothelial fibrinolysis is a potential prothrombotic mechanism in subjects with antiphospholipid antibodies. We were unable to confirm enhanced displacement of annexin-V from endothelium by antiphospholipid antibodies.
authors.affiliation: School of Medicine, University of Aberdeen, Foresterhill, Aberdeen, UK.
authors.forename: Angela M
authors.initials: AM
authors.lastname: Patterson
authors.forename: Isobel
authors.initials: I
authors.lastname: Ford
authors.forename: Audrey
authors.initials: A
authors.lastname: Graham
authors.forename: Nuala A
authors.initials: NA
authors.lastname: Booth
authors.forename: Mike
authors.initials: M
authors.lastname: Greaves
mesh_terms: D017304:Annexin A5 / Q000378:metabolism; D017152:Antibodies, Antiphospholipid / Q000276:immunology; D001323:Autoantibodies / Q000276:immunology*; D001777:Blood Coagulation / Q000276:immunology; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000276:immunology; D004730:Endothelium, Vascular / Q000166:cytology / Q000276:immunology*; D005337:Fibrin / Q000096:biosynthesis*; D005342:Fibrinolysis / Q000276:immunology*; D006801:Humans; D007124:Immunoenzyme Techniques; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism
chemical_list: D017304:Annexin A5; D017152:Antibodies, Antiphospholipid; D001323:Autoantibodies; D017395:Plasminogen Activator Inhibitor 1; D005337:Fibrin