Abstract TP133: GSNO Pre- and Post-Conditioning Blocks Blood-Brain Barrier Disruption and Improves Endothelial Function in a Mouse Model of Cerebral Ischemia and Reperfusion

Abstract

Background: Endothelial dysfunction is a major risk factor of stroke, and stroke injury itself causes endothelial dysfunction. Endothelial pathology following stroke blocks the mechanisms of neuroprotection and brain repair. Aberrant endothelial nitric oxide synthase (eNOS) activity and its consequent disturbed nitric oxide (NO) metabolome are mainly responsible for endothelial dysfunction. The major NO metabolite S-nitrosoglutathione (GSNO) maintains endothelial function via S-nitrosylation and invokes neuroprotection via activation of Akt. We investigated whether exogenous administration of GSNO mimics beneficial functions of eNOS-derived NO in protecting the neurovascular unit using wild-type and eNOS-deficient mouse models of stroke. Methods: Transient cerebral ischemic injury was induced by middle cerebral artery occlusion (MCAO) for 60 minutes in male adult wild-type and eNOS-null mice. GSNO (0.1 mg/kg bw, iv) and GSNO reductase inhibitor N6022 (5mg/kg bw, iv) were administered 30 minutes before MCAO in pre-injury studies and at reperfusion in post-injury studies. Brain infarctions, edema, and neurobehavioral functions were evaluated 24 h after reperfusion. Akt activity was determined by Western blot and immunohistochemistry. Results: eNOS-null mice had a higher degree (p<0.05) of injury than wild-type. Pre-MCAO treatment with GSNO significantly reduced infarct volume, decreased edema and improved neurological score, and increased tactile strength in both wild-type and eNOS-null mice compared with untreated, injured animals. Post-ischemic injury GSNO treatment also significantly reduced infarct volume and improved neurological score. N6022 also had effects similar to exogenously administered GSNO. Conclusions: Reduced brain infarction and edema, and improved neurobehavioral function by pre-injury exogenous/endogenous GSNO treatment indicate that GSNO-mediated pre-conditioning protects against IR, likely by mimicking the eNOS-derived NO-dependent functions involving Akt activity. Neurovascular protection by GSNO and N6022 in both pre- and post-ischemic injury events support GSNO and/or N6022 as a promising candidate to be evaluated for prevention and protection of humans from stroke injury.