Neutrophil extracellular trap (NET) formation characterises stable and exacerbated COPD and correlates with airflow limitation

Abstract

BackgroundCOPD is a progressive disease of the airways that is characterized by neutrophilic inflammation, a condition known to promote the excessive formation of neutrophil extracellular traps (NETs). The presence of large amounts of NETs has recently been demonstrated for a variety of inflammatory lung diseases including cystic fibrosis, asthma and exacerbated COPD.ObjectiveWe test whether excessive NET generation is restricted to exacerbation of COPD or whether it also occurs during stable periods of the disease, and whether NET presence and amount correlates with the severity of airflow limitation.Patients, materials and methodsSputum samples from four study groups were examined: COPD patients during acute exacerbation, patients with stable disease, and smoking and non-smoking controls without airflow limitation. Sputum induction followed the ECLIPSE protocol. Confocal laser microscopy (CLSM) and electron microscopy were used to analyse samples. Immunolabelling and fluorescent DNA staining were applied to trace NETs and related marker proteins. CLSM specimens served for quantitative evaluation.ResultsSputum of COPD patients is clearly characterised by NETs and NET-forming neutrophils. The presence of large amounts of NET is associated with disease severity (p < 0.001): over 90 % in exacerbated COPD, 45 % in stable COPD, and 25 % in smoking controls, but less than 5 % in non-smokers. Quantification of NET-covered areas in sputum preparations confirms these results.ConclusionsNET formation is not confined to exacerbation but also present in stable COPD and correlates with the severity of airflow limitation. We infer that NETs are a major contributor to chronic inflammatory and lung tissue damage in COPD.

Histones as Mediators of Host Defense, Inflammation and Thrombosis

“…As noted, histones are major components of neutrophil NETs. NETs are found to contribute to adverse inflammatory responses in auto-immune diseases such as systemic lupus erythematosus [81][82][83] or respiratory impairment in cystic fibrosis [61,84,85] or chronic obstructive pulmonary disease [86]. Some studies have histones of 50 μg/ml or more have been found to induce death of endothelial and lung epithelial cells [87].…”

Aberrant function of neutrophils in asthma

“…As mentioned above in this review, NETs are associated with inflammation and disease severity in chronic airway diseases [34,35] . While glucocorticoid had no effect on the NETs formation in peripheral blood neutrophils induced by activation, phorbol myristate acetate (PMA), in vitro [107] .…”

“…NETs are an important component of innate immunity, but their role is ambiguous as causing severe host tissue damage in certain pathological conditions [33] . Accumulating evidences shown that NETs directly contributed to host cell death and chronic tissue damage when formed in excess or were insufficiently cleared by mechanisms that were still poorly understood [34] . Recently, several studies have detected increased NETs and NET components in neutrophils from airways or peripheral blood of patients with asthma, suggesting an involvement of NETs in asthma pathogenesis [35][36][37] .…”

Nonparametric Inference for Multivariate Data: The R Package npmv

“…Published applications of the package npmv can be found, for example, in Nardone et al (2014Nardone et al ( , 2015, and Grabcanovic-Musija et al (2015).…”