title: Normobaric hyperoxia delays perfusion/diffusion mismatch evolution, reduces infarct volume, and differentially affects neuronal cell death pathways after suture middle cerebral artery occlusion in rats.
abstract: Normobaric hyperoxia (NBO) has been shown to extend the reperfusion window after focal cerebral ischemia. Employing diffusion (DWI)- and perfusion (PWI)-weighted magnetic resonance imaging (MRI), the effect of NBO (100% started at 30 mins after middle cerebral artery occlusion (MCAO)) on the spatiotemporal evolution of ischemia during and after permanent (pMCAO) and transient suture middle cerebral artery occlusion (tMCAO) was investigated (experiment 3). In two additional experiments, time window (experiment 1) and cell death pathways (experiment 2) were investigated in the pMCAO model. In experiment 1, NBO treatment reduced infarct volume at 24 h after pMCAO by 10% when administered for 3 h (P>0.05) and by 44% when administered for 6 h (P<0.05). In experiment 2, NBO acutely (390 mins, P<0.05) reduced in situ end labeling (ISEL) positivity in the ipsilesional penumbra but increased contralesional necrotic as well as caspase-3-mediated apoptotic cell death. In experiment 3, CBF characteristics and CBF-derived lesion volumes did not differ between treated and untreated animals, whereas the apparent diffusion coefficient (ADC)-derived lesion volume essentially stopped progressing during NBO treatment, resulting in a persistent PWI/DWI mismatch that could be salvaged by delayed (3 h) reperfusion. In conclusion, NBO (1) acutely preserved the perfusion/diffusion mismatch without altering CBF, (2) significantly extended the time window for reperfusion, (3) induced lasting neuroprotection in permanent ischemia, and (4) although capable of reducing cell death in hypoperfused tissue it also induced cell death in otherwise unaffected areas. Our data suggest that NBO may represent a promising strategy for acute stroke treatment.
authors.affiliation: Department of Neurology, University of Massachusetts Medical School, Worcester, Massachusetts, USA. Nils.Henninger@umassmed.edu
authors.forename: Nils
authors.initials: N
authors.lastname: Henninger
authors.forename: James
authors.initials: J
authors.lastname: Bouley
authors.forename: Julia M
authors.initials: JM
authors.lastname: Nelligan
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Sicard
authors.forename: Marc
authors.initials: M
authors.lastname: Fisher
mesh_terms: D000818:Animals; D001921:Brain / Q000098:blood supply / Q000473:pathology; D002545:Brain Ischemia / Q000473:pathology / Q000628:therapy*; D016923:Cell Death / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology; D018496:Hyperoxia; D020244:Infarction, Middle Cerebral Artery / Q000473:pathology / Q000628:therapy*; D008279:Magnetic Resonance Imaging; D008297:Male; D009474:Neurons / Q000473:pathology*; D010102:Oxygen Inhalation Therapy; D051381:Rats; D017207:Rats, Sprague-Dawley