title: Neutrophil extracellular traps are associated with inflammation in chronic airway disease.
abstract: OBJECTIVE
  Neutrophil extracellular traps (NETs) are web-like structures comprising DNA and antimicrobial proteins, expelled from neutrophils during NETosis. Persistence of NETs can be pro-inflammatory, yet their role in respiratory disease remains unclear. This study aimed to investigate the presence of NETs in sputum from patients with asthma and COPD, and the relationship of NETs with inflammatory phenotype and disease severity.
  
  
  METHODS
  Induced sputum was collected from healthy controls, asthma and COPD patients. Extracellular DNA (eDNA) was quantified by PicoGreen. LL-37, α-defensins1-3, NE, IL-1β and CXCL8 were quantified by ELISA. PAD4 and NLRP3 gene expression was performed using qPCR. NETs were imaged in sputum smears using immunofluorescence microscopy.
  
  
  RESULTS
  Sputum eDNA and NET neutrophil antimicrobial proteins were significantly elevated in asthma and COPD compared with healthy controls. Levels of eDNA and NET components were significantly higher in neutrophilic versus non-neutrophilic asthma and COPD. NETs were clearly visualized in sputum smears. PAD4 mRNA was upregulated in neutrophilic COPD. The level of eDNA was higher in severe asthma. High eDNA levels were associated with heightened innate immune responses, including elevated CXCL8 and IL-1β, and NLRP3 gene expression in both COPD and asthma. Antimicrobial proteins and eDNA were positively correlated with airway neutrophils, and negatively correlated with lung function and symptoms.
  
  
  CONCLUSIONS
  NETs are present in the airways of subjects with asthma and COPD. Accumulation of excessive NETs was associated with activation of innate immune responses contributing to disease pathogenesis in chronic airway disease.
authors.affiliation: Priority Research Centre for Asthma and Respiratory Diseases, Hunter Medical Research Institute, The University of Newcastle, New Lambton Heights, New South Wales, Australia.
authors.forename: Thomas K
authors.initials: TK
authors.lastname: Wright
authors.affiliation: Priority Research Centre for Asthma and Respiratory Diseases, Hunter Medical Research Institute, The University of Newcastle, New Lambton Heights, New South Wales, Australia.|Department of Respiratory and Sleep Medicine, John Hunter Hospital, New Lambton, New South Wales, Australia.
authors.forename: Peter G
authors.initials: PG
authors.lastname: Gibson
authors.affiliation: Priority Research Centre for Asthma and Respiratory Diseases, Hunter Medical Research Institute, The University of Newcastle, New Lambton Heights, New South Wales, Australia.|Department of Respiratory and Sleep Medicine, John Hunter Hospital, New Lambton, New South Wales, Australia.
authors.forename: Jodie L
authors.initials: JL
authors.lastname: Simpson
authors.affiliation: Priority Research Centre for Asthma and Respiratory Diseases, Hunter Medical Research Institute, The University of Newcastle, New Lambton Heights, New South Wales, Australia.|Department of Respiratory and Sleep Medicine, John Hunter Hospital, New Lambton, New South Wales, Australia.
authors.forename: Vanessa M
authors.initials: VM
authors.lastname: McDonald
authors.affiliation: Priority Research Centre for Asthma and Respiratory Diseases, Hunter Medical Research Institute, The University of Newcastle, New Lambton Heights, New South Wales, Australia.|Department of Respiratory and Sleep Medicine, John Hunter Hospital, New Lambton, New South Wales, Australia.
authors.forename: Lisa G
authors.initials: LG
authors.lastname: Wood
authors.affiliation: Priority Research Centre for Asthma and Respiratory Diseases, Hunter Medical Research Institute, The University of Newcastle, New Lambton Heights, New South Wales, Australia.|Department of Respiratory and Sleep Medicine, John Hunter Hospital, New Lambton, New South Wales, Australia.
authors.forename: Katherine J
authors.initials: KJ
authors.lastname: Baines
mesh_terms: D000368:Aged; D002908:Chronic Disease; D065206:Extracellular Traps / Q000378:metabolism*; D005260:Female; D006801:Humans; D007113:Immunity, Innate; D007249:Inflammation / Q000378:metabolism* / Q000473:pathology; D016209:Interleukin-8 / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009504:Neutrophils / Q000473:pathology; D012140:Respiratory Tract Diseases / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D013183:Sputum / Q000166:cytology / Q000378:metabolism*
chemical_list: C508606:CXCL8 protein, human; D016209:Interleukin-8
keywords: asthma; chronic obstructive pulmonary disease; extracellular deoxyribonucleic acid; neutrophil; neutrophil extracellular trap