title: Antiphospholipid antibody-mediated effects in an arterial model of thrombosis are dependent on Toll-like receptor 4.
abstract: Patients with antiphospholipid syndrome (APS) produce antiphospholipid antibodies (aPL) and develop vascular thrombosis that may occur in large or small vessels in the arterial or venous beds. On the other hand, many individuals produce aPL and yet never develop thrombotic events. Toll-like receptor 4 (TLR4) appears to be necessary for aPL-mediated prothrombotic effects in venous and microvascular models of thrombosis, but its role in arterial thrombosis has not been studied. Here, we propose that aPL alone are insufficient to cause thrombotic events in an arterial model of APS, and that a concomitant trigger of innate immunity (e.g. TLR4 activation) is required. We show specifically that anti-β2-glycoprotein I (anti-β2GPI) antibodies, a subset of aPL, accelerated thrombus formation in C57BL/6 wild-type, but not TLR4-deficient, mice in a ferric chloride-induced carotid artery injury model. These aPL bound to arterial and venous endothelial cells, particularly in the presence of β2GPI, and to human TLR4 by enzyme-linked immunoassay. Arterial endothelium from aPL-treated mice had enhanced leukocyte adhesion, compared to control IgG-treated mice. In addition, aPL treatment of mice enhanced expression of tissue factor (TF) in leukocytes induced by the TLR4 ligand lipopolysaccharide (LPS). aPL also enhanced LPS-induced TF expression in human leukocytes in vitro. Our findings support a mechanism in which aPL enhance TF expression by leukocytes, as well as augment adhesion of leukocytes to the arterial endothelium. The activation of TLR4 in aPL-positive individuals may be required to trigger thrombotic events.
authors.affiliation: Division of Rheumatology, Department of Medicine, Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada Current affiliation: Centre Hospitalier de l'Université de Montréal (CHUM) Research Center, Montreal, Quebec, Canada.
authors.forename: P
authors.initials: P
authors.lastname: Laplante
authors.affiliation: Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA Current affiliation: Cato Research Ltd., Durham, NC.
authors.forename: R
authors.initials: R
authors.lastname: Fuentes
authors.affiliation: Division of Rheumatology, Department of Medicine, Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada.
authors.forename: D
authors.initials: D
authors.lastname: Salem
authors.affiliation: Division of Rheumatology, Department of Medicine, Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada.
authors.forename: R
authors.initials: R
authors.lastname: Subang
authors.affiliation: Montreal Heart Institute, Université de Montréal, Montreal Heart Institute, Montreal, Quebec, Canada.
authors.forename: M-A
authors.initials: MA
authors.lastname: Gillis
authors.affiliation: Montreal Heart Institute, Université de Montréal, Montreal Heart Institute, Montreal, Quebec, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Hachem
authors.affiliation: Montreal Heart Institute, Université de Montréal, Montreal Heart Institute, Montreal, Quebec, Canada Current affiliation: Pharsight, a Certara™ Company, Montreal, Quebec, Canada.
authors.forename: N
authors.initials: N
authors.lastname: Farhat
authors.affiliation: Department of Critical Care and Department of Medicine, Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada.
authors.forename: S T
authors.initials: ST
authors.lastname: Qureshi
authors.affiliation: Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Fletcher
authors.affiliation: Division of Rheumatology, Allergy, and Immunology, Department of Medicine and Thurston Arthritis Research Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: R A S
authors.initials: RA
authors.lastname: Roubey
authors.affiliation: Montreal Heart Institute, Université de Montréal, Montreal Heart Institute, Montreal, Quebec, Canada.
authors.forename: Y
authors.initials: Y
authors.lastname: Merhi
authors.affiliation: Montreal Heart Institute, Université de Montréal, Montreal Heart Institute, Montreal, Quebec, Canada.
authors.forename: É
authors.initials: É
authors.lastname: Thorin
authors.affiliation: Section of Nephrology, Department of Medicine, University of Illinois at Chicago, and Section of Nephrology, Department of Medicine, Jesse Brown Veterans Affairs Medical Center, Chicago, IL, USA.
authors.forename: J S
authors.initials: JS
authors.lastname: Levine
authors.affiliation: Division of Hematology/Oncology, Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: N
authors.initials: N
authors.lastname: Mackman
authors.affiliation: Division of Rheumatology, Department of Medicine, Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada joyce.rauch@mcgill.ca.
authors.forename: J
authors.initials: J
authors.lastname: Rauch
mesh_terms: D000818:Animals; D017152:Antibodies, Antiphospholipid / Q000276:immunology*; D058846:Antibodies, Monoclonal, Murine-Derived / Q000276:immunology; D016736:Antiphospholipid Syndrome / Q000276:immunology; D002448:Cell Adhesion / Q000502:physiology; D004730:Endothelium, Vascular / Q000378:metabolism; D005260:Female; D006801:Humans; D007113:Immunity, Innate; D007962:Leukocytes / Q000276:immunology; D008070:Lipopolysaccharides / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D013925:Thromboplastin / Q000276:immunology; D013927:Thrombosis / Q000276:immunology*; D051197:Toll-Like Receptor 4 / Q000276:immunology*; D053482:beta 2-Glycoprotein I / Q000037:antagonists & inhibitors / Q000276:immunology
chemical_list: D017152:Antibodies, Antiphospholipid; D058846:Antibodies, Monoclonal, Murine-Derived; D008070:Lipopolysaccharides; D051197:Toll-Like Receptor 4; D053482:beta 2-Glycoprotein I; D013925:Thromboplastin
keywords: Antiphospholipid syndrome; Toll-like receptor 4; anti-β2-glycoprotein I antibodies; murine models; thrombosis; tissue factor