title: Neutrophil elastase-deficient mice form neutrophil extracellular traps in an experimental model of deep vein thrombosis.
abstract: ESSENTIALS: Neutrophil elastase (NE) plays a role in extracellular trap formation (NETosis) triggered by microbes. The contribution of NE was evaluated in mouse NETosis models of sterile inflammation and thrombosis. NE is not required for mouse neutrophil NET production in vitro with non-infectious stimuli. NE deficiency had no significant effect on thrombosis in the inferior vena cava stenosis model.
  
  
  CONCLUSIONS
  
  
  
  BACKGROUND
  Neutrophil serine proteases have been implicated in coagulation and neutrophil extracellular trap (NET) formation. In human neutrophils, neutrophil elastase (NE) translocates to the nucleus during NETosis and cleaves histones, thus aiding in chromatin decondensation. NE(-/-) mice were shown not to release NETs in response to microbes. However, mouse studies evaluating the role of NE in NET formation in sterile inflammation and thrombosis are lacking.
  
  
  OBJECTIVE
  We wished to establish if neutrophils from NE(-/-) mice have a defect in NETosis, similar to peptidylarginine deiminase 4 (PAD4(-/-)) mice, and how this might have an impact on venous thrombosis, a model where NETs are produced and are crucial to thrombus development.
  
  
  METHODS
  We performed in vitro NET assays using neutrophils from wild-type (WT), NE(-/-), SerpinB1 (SB1)(-/-) and NE(-/-) SB1(-/-) mice. We compared WT and NE(-/-) animals using the inferior vena cava stenosis model of deep vein thrombosis (DVT).
  
  
  RESULTS
  Neutrophil elastase deficiency resulted in a small reduction in ionomycin-induced NET formation in vitro without affecting histone citrullination. However, NET production in response to phorbol 12-myristate 13-acetate or platelet activating factor was normal in neutrophils from two independent NE-deficient mouse lines, and in NE(-/-) SB1(-/-) as compared with SB1(-/-) neutrophils. NE deficiency or inhibition did not prevent NETosis in vivo or DVT outcome.
  
  
  CONCLUSIONS
  Neutrophil elastase is not required for NET formation in mice. NE(-/-) mice, which form pathological venous thrombi containing NETs, do not phenocopy PAD4(-/-) mice in in vitro NETosis assays or experimental venous thrombosis. Our study suggests that NET-targeted therapies need to be highly effective to have an impact on DVT.
authors.affiliation: Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA.|Department of Pediatrics, Harvard Medical School, Boston, MA, USA.
authors.forename: K
authors.initials: K
authors.lastname: Martinod
authors.affiliation: Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA.|Department of Pediatrics, Harvard Medical School, Boston, MA, USA.
authors.forename: T
authors.initials: T
authors.lastname: Witsch
authors.affiliation: Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA.|Department of Pediatrics, Harvard Medical School, Boston, MA, USA.
authors.forename: K
authors.initials: K
authors.lastname: Farley
authors.affiliation: Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA.
authors.forename: M
authors.initials: M
authors.lastname: Gallant
authors.affiliation: Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA.|Department of Pediatrics, Harvard Medical School, Boston, MA, USA.|Division of Hematology/Oncology, Boston Children's Hospital, Boston, MA, USA.
authors.forename: E
authors.initials: E
authors.lastname: Remold-O'Donnell
authors.affiliation: Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA.|Department of Pediatrics, Harvard Medical School, Boston, MA, USA.|Division of Hematology/Oncology, Boston Children's Hospital, Boston, MA, USA.
authors.forename: D D
authors.initials: DD
authors.lastname: Wagner
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004195:Disease Models, Animal; D065206:Extracellular Traps / Q000378:metabolism*; D005838:Genotype; D015759:Ionomycin / Q000494:pharmacology; D019272:Leukocyte Elastase / Q000172:deficiency* / Q000235:genetics; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018375:Neutrophil Activation; D009504:Neutrophils / Q000187:drug effects / Q000201:enzymology*; D010641:Phenotype; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D020246:Venous Thrombosis / Q000097:blood / Q000201:enzymology* / Q000235:genetics
chemical_list: D015759:Ionomycin; D019272:Leukocyte Elastase; D013755:Tetradecanoylphorbol Acetate
keywords: eukocyte elastase; extracellular traps; neutrophils; serine proteases; venous thrombosis