Neutrophil extracellular traps are associated with disease severity and microbiota diversity in patients with chronic obstructive pulmonary disease

Alison J Dicker,Megan L Crichton,Eleanor G Pumphrey,Andrew J Cassidy,Guillermo Suarez-Cuartin,Oriol Sibila,Elizabeth Furrie,Christopher J Fong,Wasyla Ibrahim,Gill Brady,Gisli G Einarsson,J Stuart Elborn,Stuart Schembri,Sara E Marshall,Colin N.A Palmer,James D Chalmers

doi:10.1016/j.jaci.2017.04.022

Abstract

BackgroundNeutrophil extracellular traps (NETs) have been observed in the airway in patients with chronic obstructive pulmonary disease (COPD), but their clinical and pathophysiologic implications have not been defined.ObjectiveWe sought to determine whether NETs are associated with disease severity in patients with COPD and how they are associated with microbiota composition and airway neutrophil function.MethodsNET protein complexes (DNA-elastase and histone-elastase complexes), cell-free DNA, and neutrophil biomarkers were quantified in soluble sputum and serum from patients with COPD during periods of disease stability and during exacerbations and compared with clinical measures of disease severity and the sputum microbiome. Peripheral blood and airway neutrophil function were evaluated by means of flow cytometry ex vivo and experimentally after stimulation of NET formation.ResultsSputum NET complexes were associated with the severity of COPD evaluated by using the composite Global Initiative for Obstructive Lung Disease scale (P < .0001). This relationship was due to modest correlations between NET complexes and FEV1, symptoms evaluated by using the COPD assessment test, and higher levels of NET complexes in patients with frequent exacerbations (P = .002). Microbiota composition was heterogeneous, but there was a correlation between NET complexes and both microbiota diversity (P = .009) and dominance of Haemophilus species operational taxonomic units (P = .01). Ex vivo airway neutrophil phagocytosis of bacteria was reduced in patients with increased sputum NET complexes. Consistent results were observed regardless of the method of quantifying sputum NETs. Failure of phagocytosis could be induced experimentally by incubating healthy control neutrophils with soluble sputum from patients with COPD.ConclusionNET formation is increased in patients with severe COPD and associated with more frequent exacerbations and a loss of microbiota diversity.

Highlights

Neutrophil extracellular traps (NETs) have been observed in the airway in patients with chronic obstructive pulmonary disease (COPD), but their clinical and pathophysiologic implications have not been defined
When stratified by the presence of greater than 40% Haemophilus species operational taxonomic units (OTUs) at the genus level, there was a clear relationship between Haemophilus species dominance and NET formation, as measured based on histone-elastase complexes (P < .0001) and DNA-elastase complexes (P 5 .01; Fig 3, C)
Markers of platelet activation were significantly increased in sera from patients with COPD (CD40 ligand [Fig 5, B] and P-selectin); analysis of sputum by means of flow cytometry showed the presence of neutrophilplatelet aggregates (Fig 5, A), but we found no evidence of a correlation between the degree of platelet activation and NET

Summary

Introduction

Neutrophil extracellular traps (NETs) have been observed in the airway in patients with chronic obstructive pulmonary disease (COPD), but their clinical and pathophysiologic implications have not been defined. Objective: We sought to determine whether NETs are associated with disease severity in patients with COPD and how they are associated with microbiota composition and airway neutrophil function. Methods: NET protein complexes (DNA-elastase and histoneelastase complexes), cell-free DNA, and neutrophil biomarkers were quantified in soluble sputum and serum from patients with COPD during periods of disease stability and during. S.E.M. is an employee of the Wellcome Trust

Objectives

Methods

Results

Conclusion