title: Neutrophil depletion reduces edema formation and tissue loss following traumatic brain injury in mice.
abstract: BACKGROUND
  Brain edema as a result of secondary injury following traumatic brain injury (TBI) is a major clinical concern. Neutrophils are known to cause increased vascular permeability leading to edema formation in peripheral tissue, but their role in the pathology following TBI remains unclear.
  
  
  METHODS
  In this study we used controlled cortical impact (CCI) as a model for TBI and investigated the role of neutrophils in the response to injury. The outcome of mice that were depleted of neutrophils using an anti-Gr-1 antibody was compared to that in mice with intact neutrophil count. The effect of neutrophil depletion on blood-brain barrier function was assessed by Evan's blue dye extravasation, and analysis of brain water content was used as a measurement of brain edema formation (24 and 48 hours after CCI). Lesion volume was measured 7 and 14 days after CCI. Immunohistochemistry was used to assess cell death, using a marker for cleaved caspase-3 at 24 hours after injury, and microglial/macrophage activation 7 days after CCI. Data were analyzed using Mann-Whitney test for non-parametric data.
  
  
  RESULTS
  Neutrophil depletion did not significantly affect Evan's blue extravasation at any time-point after CCI. However, neutrophil-depleted mice exhibited a decreased water content both at 24 and 48 hours after CCI indicating reduced edema formation. Furthermore, brain tissue loss was attenuated in neutropenic mice at 7 and 14 days after injury. Additionally, these mice had a significantly reduced number of activated microglia/macrophages 7 days after CCI, and of cleaved caspase-3 positive cells 24 h after injury.
  
  
  CONCLUSIONS
  Our results suggest that neutrophils are involved in the edema formation, but not the extravasation of large proteins, as well as contributing to cell death and tissue loss following TBI in mice.
authors.affiliation: Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Ellinor
authors.initials: E
authors.lastname: Kenne
authors.forename: Anna
authors.initials: A
authors.lastname: Erlandsson
authors.forename: Lennart
authors.initials: L
authors.lastname: Lindbom
authors.forename: Lars
authors.initials: L
authors.lastname: Hillered
authors.forename: Fredrik
authors.initials: F
authors.lastname: Clausen
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology / Q000627:therapeutic use*; D000950:Antigens, Ly / Q000276:immunology / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D001812:Blood-Brain Barrier / Q000187:drug effects; D001929:Brain Edema / Q000209:etiology / Q000473:pathology / Q000628:therapy*; D001930:Brain Injuries / Q000150:complications / Q000473:pathology*; D053148:Caspase 3 / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism / Q000473:pathology; D004195:Disease Models, Animal; D004334:Drug Administration Schedule; D005070:Evans Blue; D037502:Galectin 3 / Q000378:metabolism; D006624:Hippocampus / Q000378:metabolism / Q000473:pathology; D008262:Macrophage Activation / Q000187:drug effects; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D017628:Microglia / Q000187:drug effects / Q000473:pathology; D020556:Neutrophil Infiltration / Q000187:drug effects; D009504:Neutrophils / Q000187:drug effects / Q000473:pathology*; D013997:Time Factors; D014867:Water / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D000950:Antigens, Ly; D037502:Galectin 3; C480309:Ly6G antigen, mouse; D014867:Water; D005070:Evans Blue; D053148:Caspase 3