Neuronal injury in
ischemic stroke is partly mediated by cytotoxic
reactive oxygen species. Although the
antioxidant ascorbic acid (AA) or
vitamin C does not penetrate the blood-brain barrier (BBB), its oxidized form,
dehydroascorbic acid (DHA), enters the brain by means of facilitative transport. We hypothesized that i.v. DHA would improve outcome after
stroke because of its ability to cross the BBB and augment brain
antioxidant levels. Reversible or permanent focal
cerebral ischemia was created by intraluminal
middle cerebral artery occlusion in mice treated with vehicle, AA, or DHA (40, 250, or 500 mg/kg), either before or after
ischemia. Given before
ischemia, DHA caused dose-dependent increases in postreperfusion cerebral blood flow, with reductions in neurological deficit and mortality. In reperfused
cerebral ischemia, mean
infarct volume was reduced from 53% and 59% in vehicle- and AA-treated animals, respectively, to 15% in 250 mg/kg DHA-treated animals (P < 0.05). Similar significant reductions occurred in nonreperfused
cerebral ischemia. Delayed postischemic DHA administration after 15 min or 3 h also mediated improved outcomes. DHA (250 mg/kg or 500 mg/kg) administered at 3 h postischemia reduced
infarct volume by 6- to 9-fold, to only 5% with the highest DHA dose (P < 0.05). In contrast, AA had no effect on
infarct volumes, mortality, or neurological deficits. No differences in the incidence of
intracerebral hemorrhage occurred. Unlike exogenous AA, DHA confers in vivo, dose-dependent neuroprotection in reperfused and nonreperfused
cerebral ischemia at clinically relevant times. As a naturally occurring interconvertible form of AA with BBB permeability, DHA represents a promising pharmacological
therapy for
stroke based on its effects in this model of
cerebral ischemia.