Neutrophil Activation Promotes Fibrinogen Oxidation and Thrombus Formation in Behçet Disease

Abstract

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, leukocyte oxidative stress markers, and possible reactive oxygen species 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 with increased plasma oxidative stress markers (P<0.001) and with a marked carbonylation of fibrinogen (P<0.001), whose secondary structure appeared deeply modified. Neutrophils displayed an enhanced NADPH oxidase activity and increased reactive oxygen species production (P<0.001), which significantly correlated with fibrinogen carbonylation level (r 2 =0.33, P<0.0001), residual β-band intensity (r 2 =0.07, P<0.01), and fibrinogen clotting ability (r 2 =0.073, P<0.01) Conclusions-In BD patients, altered fibrinogen structure and impaired fibrinogen function are associated with neutrophil activation and enhanced reactive oxygen species production whose primary source is represented by neutrophil NADPH oxidase. Becatti et al Role of Neutrophils in Thrombus Formation 303for the management of BD suggest that thrombosis should be treated with immunosuppression rather than anticoagulation, 17 as an inflammation-induced thrombosis. Recent studies have provided evidence that fibrinogen plays a multifaceted role in inflammatory responses and autoimmunity. 18,19 The ability of fibrinogen to participate in the inflammatory response depends on its specific interaction with integrins, the leukocyte cell surface adhesion receptors. M2 (CD11b/CD18, Mac-1) and X2 (CD11c/CD18, p150,95) are the main fibrinogen receptors and are expressed on neutrophils, monocytes, macrophages and several subsets of lymphocytes. 20 In BD, endothelial cell dysfunction, increased reactive oxygen species (ROS) production, 21 and neutrophil hyperfunction have been reported, 15 together with an impaired fibrinolysis. 22 In this study, to highlight the mechanisms of inflammation-induced thrombosis, we investigated fibrinogen modifications, fibrin susceptibility to plasmin-lysis, plasma redox status, leukocyte oxidative stress, and possible ROS sources in a population of BD patients. Moreover, we explored fib...

CSF/serum matrix metallopeptidase‐9 ratio discriminates neuro Behçet from multiple sclerosis

“…In NBD CSF, TNF α and IL6 levels were higher in respect to MS ones; overall, the measured levels of CXCL8, IL6, and TNF α confirm the inflammatory response, previously described in NBD and in Behçet disease 20, 21. We know that neutrophils are important in Behçet disease inflammation 22 and the presence of CXCL8 in CSF suggests their involvement in the neuronal form too. In the NBD periphery, where MMP9 is increased compared to MS, we investigated the possible MMP9 source between circulating mononuclear cells.…”

Behçet’s syndrome as a tool to dissect the mechanisms of thrombo-inflammation: clinical and pathogenetic aspects

“…In this context the results of our recent investigation, performed on a large cohort of BS patients, highlighted a new mechanism in thrombus formation in this condition .…”

A low balance between microparticles expressing tissue factor pathway inhibitor and tissue factor is associated with thrombosis in Behçet’s Syndrome

“…The activation of trapped MP-associated TF by disulphide isomerase released locally may then increase the probability of clot propagation and overt thrombosis, as happens in preclinical models161718. A further mechanism enhancing clot propagation in BS may be the recently described oxidative injury to fibrinogen, which makes clots more resistant to lysis43.…”