Novel assays of thrombogenic pathogenicity in the antiphospholipid syndrome based on the detection of molecular oxidative modification of the major autoantigen β₂‐glycoprotein I

Abstract

ObjectiveBeta-2-glycoprotein I (β2GPI) constitutes the major autoantigen in the antiphospholipid syndrome (APS), a common acquired cause of arterial and venous thrombosis. We recently described the novel observation that β2GPI may exist in healthy individuals in a free thiol (biochemically reduced) form. The present study was undertaken to quantify the levels of total, reduced, and posttranslationally modified oxidized β2GPI in APS patients compared to various control groups.MethodsIn a retrospective multicenter analysis, the proportion of β2GPI with free thiols in serum from healthy volunteers was quantified. Assays for measurement of reduced as well as total circulating β2GPI were developed and tested in the following groups: APS (with thrombosis) (n = 139), autoimmune disease with or without persistent antiphospholipid antibodies (aPL) but without APS (n = 188), vascular thrombosis without APS or aPL (n = 38), and healthy volunteers (n = 91).ResultsTotal β2GPI was significantly elevated in patients with APS (median 216.2 μg/ml [interquartile range 173.3–263.8]) as compared to healthy subjects (median 178.4 μg/ml [interquartile range 149.4–227.5] [P < 0.0002]) or control patients with autoimmune disease or vascular thrombosis (both P < 0.0001). The proportion of total β2GPI in an oxidized form (i.e., lacking free thiols) was significantly greater in the APS group than in each of the 3 control groups (all P < 0.0001).ConclusionThis large retrospective multicenter study shows that posttranslational modification of β2GPI via thiol-exchange reactions is a highly specific phenomenon in the setting of APS thrombosis. Quantification of posttranslational modifications of β2GPI in conjunction with standard laboratory tests for APS may offer the potential to more accurately predict the risk of occurrence of a thrombotic event in the setting of APS.

Detection of Anti-Domain I β-2 Glycoprotein I Antibodies as New Potential Target in Antiphospholipid Syndrome Diagnosis

“…Evidence of the pathogenicity of anti-DI antibodies comes from both in-vitro and in-vivo studies. First, anti-DI antibodies were repeatedly observed to induce in-vitro prolongation of clotting time [3][4][5][6][7][8].…”

Successful pregnancy outcome in grade IV lupus nephritis and secondary antiphospholipid antibody syndrome with recurrent pregnancy failures - challenging achievement of motherhood

“…17 Many studies reported that antiplatelet agents, especially low to moderate doses of Aspirin, were used to prevent preeclampsia in high-risk patients. 18 Our patient was also started on a low dose of Aspirin (75mg/dl) as a preventive measure immediately after noting the fetal cardiac activity by USG but even then she developed PIH (probably due to the oral steroids) and thus started on anti-hypertensives.…”

The Pathophysiology of Antiphospholipid Syndrome

“…Additionally, monocytes from APS patients have an increased amount of intracellular reactive oxygen species [35]. In these conditions, disulphide bonds are formedand β2-GPI, becomes more immunogenic [36]. Evidence exists that patients with APS have a greater proportion of the oxidized versus the "free thiol form" than do patients with either other autoimmune diseases but without APS, patients with thrombosis without aPL or healthy volunteers (p<0,001 for all comparisons) [36].…”

“…In these conditions, disulphide bonds are formedand β2-GPI, becomes more immunogenic [36]. Evidence exists that patients with APS have a greater proportion of the oxidized versus the "free thiol form" than do patients with either other autoimmune diseases but without APS, patients with thrombosis without aPL or healthy volunteers (p<0,001 for all comparisons) [36]. In vitro studies showed that the "free thiol form" protects the endothelium from reactive oxygen species (ROS) [35] and that aPL promote formation of intracellular ROS.…”