Enhanced release of neutrophil extracellular traps from peripheral blood neutrophils in patients with rheumatoid arthritis. (22nd February 2012) - Papadaki, Garyfalia
Abstract : Background/objectives: Neutrophils are the most abundant cell type identified in joints from patients with rheumatoid arthritis (RA), with a key role in inflammation and cartilage damage. Activated neutrophils may form extracellular traps (NETs), with potent pro-inflammatory and immunostimulatory activity. The authors sought to assess the role of NET release in RA pathogenesis. Materials/methods: Peripheral blood neutrophils from RA patients (n=3) (DAS28>5.1) and control subjects (n=7) were isolated. NET formation from RA neutrophils and control neutrophils treated with RA serum (n=7) or synovial fluid (n=2) was assessed by immunofluoresence microscopy, using co-staining with myeloperoxidase and DAPI. The percentage of NET releasing cells was determined by examining 200 cells per sample in a double blind fashion. Time course experiments revealed optimal NET release at 3 h. Results: Freshly isolated RA neutrophils underwent spontaneous NET release at higher rates compared to normal controls (11.67±2.1% vs 3.21±0.9%, p<0.05). Treatment of control neutrophils with RA serum increased NET release compared to cells treated with normal serum (16±2.5%, p<0.005). Increased NET formation (approximately 3-fold induction) was observed in control neutrophils incubated with RA synovial fluid. Inhibition studies in progress address the impact of inflammatory cytokines and/or immune complexes in NET production as well as the impact of NETs on dendritic and T cell activation. Conclusions: Neutrophil activation in RA is associated with enhanced NET formation, driven by soluble factors found in RA sera and synovial fluid. Whether NETs are involved in the cross-talk between neutrophils and adaptive immune responses in RA is under investigation.