Critical role of neutrophil extracellular traps (NETs) in patients with Behcet’s disease

Abstract

ObjectivesBehçet’s disease (BD) is a chronic systemic vasculitis. Thrombosis is a frequent and life-threatening complication. The pathogenesis of BD is poorly understood and evidence supporting a role for primed neutrophils in BD-associated thrombotic risk is scant. To respond to inflammatory insults, neutrophils release web-like structures, known as neutrophil extracellular traps (NETs), which are prothrombotic. We evaluated the role of NETs and markers of NETs in BD.MethodsBlood samples were collected from patients with BD, according to the International Study Group Criteria for Behçet's disease, and healthy donors (HD). NET components, including cell-free DNA (CfDNA) and neutrophil enzymes myeloperoxidase (MPO), were assessed in serum or in purified neutrophils from patients with BD and HD.ResultsPatients with active BD had elevated serum cfDNA levels and MPO-DNA complexes compared with patients with inactive BD and to HD. In addition, levels of cfDNA and MPO-DNA complexes were significantly higher in patients with BD with vascular involvement compared with those without vascular symptoms. Purified neutrophils from patients with BD exhibited spontaneous NETosis compared with HD. Thrombin generation in BD plasma was significantly increased and positively correlated with the levels of MPO-DNA complexes and cfDNA. Importantly, DNAse treatment significantly decreased thrombin generation in BD plasma but not in HD plasma. In addition, biopsy materials obtained from patients with BD showed NETs production in areas of vasculitic inflammation and thrombosis.ConclusionsOur data show that NETs and markers of NETS levels are elevated in patients with BD and contribute to the procoagulant state. Targeting NETs may represent a potential therapeutic target for the reduction or prevention of BD-associated thrombotic risk.

Neutrophil-mediated Thrombosis and NETosis in Behçet's Disease: a Hypothesis

“…We know that colchicine, anti-TNF (tumor necrosis factor), and anti-interleukin 6 drugs, which have been already used in BD treatment, cause a decrease in NET formation. 10 Potential other medicines such as N-acetyl-cysteine, PAD4 inhibitor, or DNase I that directly target circulating NETs could also be tried. 31 32 33 However, the efficacy and safety data for novel NET inhibitors are deficient.…”

“…Venous inflammation and neutrophil hyperfunction are the hallmarks of BD pathogenesis. 9 10 11 Veins are a primary location for inflammation in BD patients, although the etiology of venous predilection remains unknown. Both Seyahi et al 11 and Alibaz-Oner et al 9 demonstrated that vein wall thickness increased among BD patients, even in the absence of evident vascular involvement.…”

“… 16 Neutrophils from BD patients were shown to be more prone to NETosis even in the absence of stimuli in vitro, and the amount of NETs was higher in BD patients with vascular involvement compared to the ones without vascular involvement. 10 In their in-vitro model of thrombin generation, Le Joncour et al 10 have shown that platelet-thrombin-NETs axis promotes intravascular coagulation and vascular dysfunction. In addition to promoting the thrombin generation, NETs also cause endothelial dysfunction via decreasing cell proliferation and increasing apoptosis.…”

“…The velocity of thrombin generation has also been shown to increase in BD patients. 10 20 Le Joncour et al 10 have shown that the velocity and peak of thrombin generation are positively correlated with NET markers in serum, and these are decreased with the addition of a NET-disrupting enzyme, DNAase, to the medium. In other diseases such as sepsis, NETs are also key triggers of thrombus.…”

Neutrophil elastase and endogenous inhibitors in Behçet's disease saliva

“…The controlled mechanism of NE delivery consists of either the release of granules into a phagolysosome where microbes are degraded or exocytosis of the azurophil into extracellular spaces [20]. Uncontrolled release of NE can also be due to necrosis and/or NET activation and release (NETosis) [20,21]. Neutrophil degranulation can be triggered by various inflammatory factors or direct contact with the extracellular matrix (ECM) [22], and increased neutrophil recruitment can extend the duration of inflammation [23].…”