title: Hypothermia Does Not Reverse Cellular Responses Caused by Lipopolysaccharide in Neonatal Hypoxic-Ischaemic Brain Injury.
abstract: BACKGROUND
  Bacterial lipopolysaccharide (LPS) injection prior to hypoxia-ischaemia significantly increases hypoxia-ischaemic brain injury in 7-day-old (P7) rats. In addition, therapeutic hypothermia (HT) is not neuroprotective in this setting. However, the mechanistic aspects of this therapeutic failure have yet to be elucidated. This study was designed to investigate the underlying cellular mechanisms in this double-hit model of infection-sensitised hypoxia-ischaemic brain injury.
  
  
  METHODS
  P7 rat pups were injected with either vehicle or LPS, and after a 4-hour delay were exposed to left carotid ligation followed by global hypoxia inducing a unilateral stroke-like hypoxia-ischaemic injury. Pups were randomised to the following treatments: (1) vehicle-treated pups receiving normothermia treatment (NT) (Veh-NT; n = 40), (2) LPS-treated pups receiving NT treatment (LPS-NT; n = 40), (3) vehicle-treated pups receiving HT treatment (Veh-HT; n = 38) and (4) LPS-treated pups receiving HT treatment (LPS-HT; n = 35). On postnatal day 8 or 14, Western blot analysis or immunohistochemistry was performed to examine neuronal death, apoptosis, astrogliosis and microglial activation.
  
  
  RESULTS
  LPS sensitisation prior to hypoxia-ischaemia significantly exacerbated apoptotic neuronal loss. NeuN, a neuronal biomarker, was significantly reduced in the LPS-NT and LPS-HT groups (p = 0.008). Caspase-3 activation was significantly increased in the LPS-sensitised groups (p < 0.001). Additionally, a significant increase in astrogliosis (glial fibrillary acidic expression, p < 0.001) was seen, as well as a trend towards increased microglial activation (Iba 1 expression, p = 0.051) in LPS-sensitised animals. Treatment with HT did not counteract these changes.
  
  
  CONCLUSIONS
  LPS-sensitised hypoxia-ischaemic brain injury in newborn rats is mediated through neuronal death, apoptosis, astrogliosis and microglial activation. In this double-hit model, treatment with HT does not ameliorate these changes.
authors.affiliation: Department of Physiology, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.
authors.forename: Damjan
authors.initials: D
authors.lastname: Osredkar
authors.forename: Hemmen
authors.initials: H
authors.lastname: Sabir
authors.forename: Mari
authors.initials: M
authors.lastname: Falck
authors.forename: Thomas
authors.initials: T
authors.lastname: Wood
authors.forename: Elke
authors.initials: E
authors.lastname: Maes
authors.forename: Torun
authors.initials: T
authors.lastname: Flatebø
authors.forename: Maja
authors.initials: M
authors.lastname: Puchades
authors.forename: Marianne
authors.initials: M
authors.lastname: Thoresen
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D004195:Disease Models, Animal; D005260:Female; D005911:Gliosis / Q000378:metabolism*; D007036:Hypothermia, Induced / Q000379:methods*; D020925:Hypoxia-Ischemia, Brain / Q000276:immunology / Q000378:metabolism / Q000628:therapy*; D008070:Lipopolysaccharides / Q000276:immunology*; D008297:Male; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar
chemical_list: D008070:Lipopolysaccharides; D053148:Caspase 3