Neutrophil Activation Promotes Fibrinogen Oxidation and Thrombus Formation in Behçet's Disease

BACKGROUND: -Behçet disease (BD) is a systemic vasculitis with a broad range of organ involvement, characterized by a multisystemic, immune-inflammatory disorder involving vessels of all sizes and often complicated by thrombosis. Systemic redox imbalance and circulating neutrophil hyperactivation have been observed in BD patients and are thought to be responsible for impaired coagulation. We here focused on the pathogenetic mechanisms potentially linking immune cell activation and thrombosis, and specifically examined whether neutrophil activation can affect fibrinogen modifications and consequently elicit thrombosis. METHODS AND RESULTS: -Blood samples were collected from 98 consecutive BD patients attending our dedicated Center and from 70 age and sex-matched healthy controls; in all patients fibrinogen function and structure, fibrin susceptibility to plasmin-lysis, plasma redox status, leucocyte oxidative stress markers and possible ROS sources were examined. Thrombin-catalyzed fibrin formation and fibrin susceptibility to plasmin-induced lysis were significantly impaired in BD patients (p<0.001). These findings were associated to increased plasma oxidative stress markers (p<0.001) and to a marked carbonylation of fibrinogen (p<0.001) whose secondary structure appeared deeply modified. Neutrophils displayed an enhanced NADPH oxidase activity and increased ROS production (p<0.001), which significantly correlated with fibrinogen carbonylation level (r2=0.33 p<0.0001), residual β-band intensity (r2=0.07 p<0.01) and fibrinogen clotting ability (r2=0.073 p<0.01) CONCLUSIONS: -In BD patients, altered fibrinogen structure and impaired fibrinogen function are associated with neutrophil activation and enhanced ROS production whose primary source is represented by neutrophil NADPH oxidase.