NADPH oxidase 5 promotes adhesion and infiltration of immune cells in the brain. Implications in ischemic stroke

Blood-brain barrier (BBB) disruption and immune cell infiltration increase the pathological outcomes present in aging, neurodegenerative diseases, and stroke. NADPH oxidase 5 (NOX5) is a ROS-producing enzyme that promotes BBB-permeability in vivo by altering the endothelial junctions (EJs). The aim of this project was to elucidate the mechanisms by which NOX5 dysregulates EJs in endothelial cells and whether it increases immune infiltrates in a systemic inflammatory condition, using a murine model of ischemic stroke. A brain microvascular endothelial cell line (hCMEC/D3) and HUVECs infected with a NOX5 overexpressing adenovirus were used to study the effects of this protein on EJs, endothelial phenotype, and immune cell adhesion and infiltration in vitro. An endothelial NOX5 knock-in mouse was used to study EJs expression in the brain. Finally, in an experimental model of ischemic stroke induced by FeCl₃ we analyzed the potential effects of NOX5 on the infiltration of immune cells to the brain. NOX5 overexpression dysregulated EJs and increased permeability in hCMEC/D3 cells. In HUVECs, overexpression of NOX5 promoted the remodeling of the cytoskeleton and increased inflammatory cell adhesion and infiltration. Under inflammatory conditions, such as those present in ischemic stroke, mice expressing endothelial NOX5 exhibited an increase in the infiltration of immune cells in the brain across the vasculature of the non-infarcted (contralateral) hemisphere and increased inflammatory markers in the infarcted (ipsilateral) hemisphere. NOX5 promotes the dysregulation of EJs and cytoskeletal changes in endothelial cells, which leads to an increased immune cell infiltration in the brain at proinflammatory situations.