Background and aims Antiphospholipid syndrome (APS) is a systemic autoimmune disease characterised by thrombosis, obstetric complications and the presence of anti-phospholipid antibodies such as anti-β2GPI-Abs. These antibodies may set off the coagulation cascade via several mechanisms, including the induction of tissue factor (TF) expression. Vitamin D has recently emerged as an immunomodulator that might exert an anti-thrombotic effect. Therefore, we studied serum vitamin D levels in a cohort of APS patients, as well as the effect of vitamin D in an in vitro model of APS-mediated thrombosis.
Methods Serum vitamin D levels were measured in 179 European APS patients and 141 healthy controls using the LIAISON chemiluminescent immunoassay, and the levels were evaluated in conjunction with a wide spectrum of clinical manifestations. In an vitro model, anti-β2GPI antibodies were purified from four patients with APS to evaluate the expression of TF in activated starved human umbilical vein endothelial cells. The effect of vitamin D (1,25-dihydroxyvitamin D, 10 nm) on anti-β2GPI-Abs mediated TF expression was analysed by immunoblot.
Results Vitamin D deficiency (serum level ≤15 ng/ml) was documented in 49.5% of our APS patients versus 30% of controls (p<0.001) and was significantly correlated with thrombosis (58% vs 42%; p<0.05), neurological and ophthalmic manifestations, pulmonary hypertension, livedo reticularis and skin ulcerations. In vitro vitamin D inhibited the expression of TF induced by anti-β2GPI-antibodies.
Conclusions Vitamin D deficiency is common among APS patients and is associated with clinically defined thrombotic events. Vitamin D inhibits anti-β2GPI-mediated TF expression in vitro. Thus, vitamin D deficiency might be associated with decreased inhibition of TF expression and increased coagulation in APS. Evaluation of vitamin D status and vitamin D supplementation in APS patients should be considered.
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Competing interests None.
Patient consent Obtained.
Ethics approval This study was conducted with the approval of the Sheba Medical Center, Israel, and fulfilled the ethical guidelines of the Declaration of Helsinki (Edinburgh, 2000).
Provenance and peer review Not commissioned; externally peer reviewed.