Early oxygen therapy does not protect the brain from vasogenic edema following acute ischemic stroke in adult male rats

Brain edema aggravates primary brain injury and increases its mortality rate after ischemic stroke. It is believed that normobaric oxygen therapy (NBO) may produce neuroprotective effects against ischemic stroke; however, reports have been controversial, and its effects on vasogenic brain edema as a major complication of brain ischemia have not been clarified. The present study investigates the effects of NBO on cerebral edema and blood – brain barrier integrity using rat model of ischemic stroke. Transient focal cerebral ischemia was induced in adult male Sprague-Dawley rats by left middle cerebral artery occlusion (MCAO) for 90 min followed by 24 h reperfusion. Early NBO supplementation was started 15 min after MCAO and continued for 90 min. The results of the present study show that early oxygen therapy following acute ischemic stroke does not reduce vasogenic brain edema, nor does it protect against oxidative stress-induced BBB destruction. Additionally, cerebral edema formation occurs in conjunction with an increased mortality rate, serious brain injury, and impairment of brain antioxidant power. These findings suggest that further experimental studies should be carried out to clarify the beneficial effects and potential side effects of early oxygen therapy in acute ischemic stroke before its clinical use.