Expression of tissue factor mRNA in thrombosis associated with antiphospholipid syndrome.

Tissue factor (TF) is a procoagulant protein associated with increased risk of thrombotic events in antiphospholipid syndrome (t-APS). The mechanisms by which TF levels are increased in APS have not yet been established. The aim of this study was to investigate whether TF mRNA expression is associated with TF levels and thrombosis in APS. We compared levels of circulating TF and high sensitivity C-reactive protein (hs-CRP) between t-APS and controls (individuals without thrombosis). The association between TF mRNA expression, quantified by real time quantitative polymerase chain reaction, and t-APS was accessed using regression analysis. We included 41 controls and 42 t-APS patients, mean age was 41 years old (SD 14) in both groups. Hs-CRP and TF levels were higher in t-APS patients (mean hs-CRP levels 0.81 mg/dL [SD 1.88] and median TF levels 249.0 pg/mL [IQR 138.77-447.61]) as compared to controls (mean hs-CRP levels 0.24 mg/dL [SD 0.26] and median TF levels 113.0 pg/mL [IQR 81.17-161.53]; P = 0.02 and P < 0.0001, respectively). There was no correlation between TF mRNA expression and TF levels in t-APS (r - 0.209, P = 0.19). TF mRNA expression was not associated with t-APS (adjusted OR 1.16; 95%CI 0.72-1.87). Despite circulating TF levels being higher in patients with t-APS than in controls, TF mRNA expression was similar between groups. The results demonstrate that TF mRNA expression is not associated with levels of circulating TF and hypercoagulability in t-APS.

Association between neutrophil extracellular traps (NETs) and thrombosis in antiphospholipid syndrome.

BACKGROUND: The release of neutrophil extracellular traps (NETs) is the basis of immune-mediated thrombosis. Data on the clinical relevance of NETs in antiphospholipid syndrome-related thrombosis are scarce. OBJECTIVE: The aim of this study was to evaluate whether the NET regulator proteins PADI4, ELANE, and MPO are associated with thrombosis in APS. METHODS: A total of 152 thrombotic APS (t-APS) patients and 123 individuals without thrombosis (controls) were included. The following markers of NETs were evaluated: PADI4, ELANE, and MPO gene expression by qPCR and circulating levels of citrullinated histone H3 (H3cit) and myeloperoxidase-DNA complexes (MPO-DNA) by ELISA. RESULTS: The levels of circulating MPO-DNA and MPO mRNA expression and PADI4 mRNA expression were higher in t-APS patients than in controls. The mean differences were 0.05 OD (95% CI 0.01 to 0.09) in MPO-DNA levels, 1.07 AU (95% CI 0.20 to 1.93) for MPO mRNA and 0.20 AU (95% CI 0.03 to 0.36) in PADI4 mRNA fold-change. These differences were more pronounced in triple-positive patients, who had 56% increased levels of MPO-DNA, 44% increased MPO mRNA expression and 69% increased PADI4 mRNA expression compared to controls. Additionally, circulating MPO-DNA levels and MPO mRNA expression were higher in patients with recurrent thrombosis than in patients with incident thrombosis and controls. In recurrent thrombosis, levels of MPO-DNA were 43.8% higher and MPO mRNA expression was 2-fold higher than in controls. Levels of circulating MPO-DNA and PADI4 mRNA expression did not differ substantially between primary and secondary APS. CONCLUSION: Thrombotic APS was associated with increased NET formation, which was more pronounced among patients with poorer prognosis, such as those with triple antiphospholipid positivity and recurrent thrombosis. Our results provide evidence on the association of NETs and the severity of APS-related thrombosis.