Regulation of bovine brain microvascular endothelial tight junction assembly and barrier function by laminar shear stress

Blood-brain barrier (BBB) controls paracellular solute diffusion into the brain microenvironment and is maintained primarily by tight junctions between adjacent microvascular endothelial cells. Studies implicate blood flow-associated shear stress as a pathophysiological mediator of BBB function, although detailed biochemical data are scarce. We hypothesize that shear stress upregulates BBB function via direct modulation of expression and properties of pivotal tight-junction proteins occludin and zonula occludens-1 (ZO-1). Bovine brain microvascular endothelial cells (BBMvECs) were exposed to either steady or pulsatile shear stress (10 and 14 dyn/[cm.sup.2], respectively) for 24 h. Sheared BBMvECs were monitored for occludin-ZO-1 expression, association, and subcellular localization, and transendothelial permeability of BBMvECs to FITC-dextran and [sup.14][C]sucrose was assessed. Actin reorganization and BBMvEC realignment were observed following steady shear stress for 24 h. Substantial increases in occludin mRNA and protein expression (2.73 [+ or -] 0.26- and 1.83 [+ or -] 0.03-fold) and in occludin-ZO-1 association (2.12 [+ or -] 0.15-fold) were also observed. Steady shear stress also induced clear relocalization of both proteins to the cell-cell border in parallel with reduced transendothelial permeability to FITC-dextran (but not sucrose). Following pulsatile shear stress, increased protein levels for both occludin and ZO-1 (2.15 [+ or -] 0.02- and 1.67 [+ or -] 0.21-fold) and increased occludin-ZO-1 association (2.91 [+ or -] 0.14-fold) were observed in parallel with a reduction in transendothelial permeability to [sup.14][C]sucrose. Shear stress upregulates BBMvEC barrier function at the molecular level via modulation of expression, association, and localization of occludin and ZO-1. The pulsatile shear model appeared to give the most profound biochemical responses. blood-brain barrier; occludin; zonula occludens-1 doi:10.1152/ajpheart.01177.2006