Angiopoietin-1 reduces vascular endothelial growth factor-induced brain endothelial permeability via upregulation of ZO-2.

Brain microvessels possess barrier structures comprising tight junctions which are critical for the maintenance of central nervous system homeostasis. Brain vascular diseases, such as ischemic stroke damage to blood-brain barrier, increase the vascular permeability, and then lead to vasogenic brain edema. Herein, we examined whether angiopoietin-1 (Ang-1) could regulate zonula occludens-2 (ZO-2) expression and counteract vascular endothelial growth factor (VEGF)-induced vascular permeability. When we treated brain microvascular endothelial cells with Ang-1, Ang-1 caused a time- and dose-dependent increase of ZO-2 and down-regulation in endothelial permeability. VEGF, one of the key regulators of ischemia-induced vascular permeability, increased endothelial cell permeability in vitro, whereas, Ang-1 reversed this VEGF effect by up-regulating ZO-2 expression. Additionally, the recovery effect of Ang-1 on permeability was strongly blocked by siRNA against ZO-2. Collectively, our results suggest that Ang-1 shows anti-permeability activity through up-regulation of ZO-2.