title: Neutrophil apoptosis is delayed in an equine model of colitis: Implications for the development of systemic inflammatory response syndrome.
abstract: BACKGROUND
  Horses that develop colitis invariably exhibit signs of a systemic inflammatory response syndrome (SIRS). A significant contributor to the development of SIRS in human subjects is delayed neutrophil apoptosis, but this has not been specifically studied in horses.
  
  
  OBJECTIVE
  To determine the occurrence of ex vivo neutrophil apoptosis and its contribution to the development of SIRS in an equine colitis model.
  
  
  METHODS
  Experiment using a colitis model.
  
  
  METHODS
  Neutrophils were isolated before and after the induction of colitis using an oligofructose overdose model, placed into culture for 12 h or 24 h with or without lipopolysaccharide (LPS) at various concentrations, and assessed for the occurrence of apoptosis using Annexin V and propidium iodide staining with flow cytometric quantification. Levels of caspase-3, -8 and -9 activity were measured after 12 h of incubation in neutrophil lysates.
  
  
  RESULTS
  Ex vivo neutrophil apoptosis was significantly delayed in neutrophils isolated after the induction of colitis (12-h incubation: P = 0.004; 24-h incubation: P = 0.003) with concomitant reductions in caspase-3, -8 and -9 activity (caspase-3: P = 0.004; caspase-8: P = 0.02; caspase-9: P = 0.02). Neutrophils isolated after the induction of colitis were refractory to LPS-delayed apoptosis. Neutrophil apoptosis was delayed with increasing cell concentration in vitro.
  
  
  CONCLUSIONS
  The main limitation of the study is the that the exact mechanism for delayed neutrophil apoptosis following the induction of colitis was not fully elucidated.
  
  
  CONCLUSIONS
  The data show that neutrophil apoptosis is delayed in horses following the induction of colitis as a result of interference with the intrinsic and extrinsic apoptotic pathways, which may contribute to the development of equine SIRS. Concurrent development of neutrophilia may contribute to a prolonged neutrophil lifespan through a concentration-dependent delay in apoptosis.
authors.affiliation: Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada.
authors.forename: S L
authors.initials: SL
authors.lastname: Anderson
authors.affiliation: Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada.
authors.forename: B
authors.initials: B
authors.lastname: Singh
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D003092:Colitis / Q000139:chemically induced / Q000378:metabolism / Q000662:veterinary*; D006734:Horse Diseases / Q000473:pathology*; D006736:Horses; D009504:Neutrophils / Q000502:physiology*; D009844:Oligosaccharides / Q000633:toxicity; D018746:Systemic Inflammatory Response Syndrome / Q000662:veterinary*
chemical_list: D009844:Oligosaccharides; C120489:oligofructose
keywords: horse; systemic inflammatory response syndrome