Onion (Allium cepa) extract attenuates brain edema.

OBJECTIVE

This study investigated the potential beneficial effects of onion extract on brain ischemia-induced edema and blood-brain barrier (BBB) dysfunction. The possible underlying mechanisms are investigated, especially those linked to the antioxidant effects of the onion extract.

METHODS

Brain ischemia was induced by middle cerebral artery occlusion (MCAO) for 2 h followed by reperfusion in mice. Mice were treated intravenously with onion extract 30 min before MCAO. Brain edema and BBB hyperpermeability were evaluated by the measurement of the brain water content and Evans blue extravasation, respectively. The disruption of tight junction proteins was examined by immunohistochemical staining. The level of malondialdehyde was determined using the thiobarbituric acid method. The activities of glutathione peroxidase and catalase were determined by spectrophotometric assay.

RESULTS

Brain water content in the ischemic hemisphere was significantly reduced by treatment with onion extract. Onion extract also had a significant effect on both the decrease in Evans blue extravasation and the inhibition of zonula occludens-1 and occludin disruption caused by brain ischemia. In addition, onion extract significantly prevented brain ischemia-induced reduction in catalase and glutathione peroxidase activities and elevation of malondialdehyde level in the brain tissue.

CONCLUSIONS

The results from this study demonstrate that onion extract prevents brain edema, BBB hyperpermeability, and tight junction proteins disruption, possibly through its antioxidant effects in the mouse MCAO model. This study suggests that onion extract may be a beneficial nutrient for the prevention of BBB function during brain ischemia.