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Ischemia/reperfusion (I/R) injury after middle cerebral artery occlusion (MCAO) induces detrimental processes such as oxidative stress, inflammation, and apoptosis. All parts of the neurovascular unit are involved in these pathological processes. Fibulin-5 is a 66-kD glycoprotein secreted by various vascular cells, including vascular smooth muscle cells (SMCs), fibroblasts, and endothelial cells. As an extracellular matrix protein involved in cell adhesion, fibulin-5 has been widely studied in tumor growth and invasion. However, the effects of fibulin-5 on brain injury following ischemia/reperfusion have not been reported. In this study, we examined the effect of overexpressed fibulin-5 on reactive oxygen species (ROS) production. Fibulin-5 overexpression attenuated ROS expression, which in turn decreased apoptosis and blood-brain barrier (BBB) permeability following MCAO and reperfusion. Fibulin-5 also improved neurological deficits but had no effect on infarction volume. T2-weighted MRI and electron microscopy further confirmed brain edema reduction and decreased BBB disruption in fibulin-5 overexpression recombinant adenovirus (Ad-FBLN) treated rats. In addition, tight junction protein occludin was significantly degraded and matrix metalloproteinase 9 (MMP-9) immunoreactivity was significantly increased. Fibulin-5-mediated ROS decrease was not due to increased total superoxide dismutase levels but was instead correlated with the activation of Rac-1 pathway. The findings highlight the importance of antioxidant mechanism underlying cerebral ischemia/reperfusion.

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