Abstract
Introduction: Poldip2 is a novel regulator of cerebral vascular permeability involved in aggravating blood-brain barrier disruption following ischemic stroke; however, the underlying mechanisms are incompletely understood. Tight junctions are crucial for the formation of endothelial barriers and are composed of transmembrane proteins and adaptor proteins such as ZO-1. Cerebral ischemia and inflammation lead to ZO-1 redistribution resulting in vascular permeability. Hypothesis: We hypothesized that Poldip2 may mediate ZO-1 phosphorylation and promote brain endothelial monolayer permeability following cerebral ischemia. Methods: Cerebral ischemia was induced in endothelial-specific Poldip2 knockout and control mice. Vascular permeability was assessed by Evans blue dye extravasation. For in vitro analysis, primary rat brain microvascular endothelial cells were used to investigate the effect of Poldip2 depletion by siRNA on TNF-α-induced permeability and trans-endothelial electrical resistance (TEER). Immunocytochemistry was carried out to investigate the effects of Poldip2 depletion or overexpression on ZO-1 localization. Results: Endothelial-specific Poldip2 deletion abolished Evans blue dye extravasation after cerebral ischemia induction (p<0.05). Poldip2 knockdown in vitro suppressed TNF-α-induced endothelial cell (EC) monolayer permeability (FITC-dextran and biotin-avidin assays, p<0.05 and p<0.001) and prevented decreases in TEER (p<0.01). Poldip2 depletion prevented TNF-α-induced ZO-1 disruption at interendothelial junctions (p<0.05). Poldip2 overexpression increased endothelial permeability (p<0.05), decreased TEER (p<0.05), reduced ZO-1 localization at cell-cell junctions (p<0.0001) and enhanced reactive oxygen species (ROS) production (p<0.05). Treatment with the antioxidant N-acetyl cysteine (NAC) abrogated Poldip2-induced ZO-1 disruption (p<0.0001). Immunoprecipitation studies demonstrated that Poldip2 overexpression induced tyrosine phosphorylation of ZO-1 (p<0.0001), an effect prevented by NAC treatment (p<0.01). Conclusions: Poldip2 induces ROS-mediated tyrosine phosphorylation of the TJ protein ZO-1 and promotes EC permeability following cerebral ischemia
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