Effect of CSE exposure (24 h) on endothelial expression and distribution of ZO-1, Occludin and actin filaments. (A) Down-regulation of ZO-1 expression and disruption and cell-cell junctions were progressively more significant following exposure to 3R4F, NF and ultralow nicotine CSEs. Down-regulation and disruption at cell-cell contacts of occludin were also observed (B). Immunofluorescence analyses were confirmed by WB of corresponding membrane fractions (C). Loss of BBB integrity was further assessed by permeability measurements to dextran molecules ranging from 3 to 70 kDa (D) n = 3 biological replicates, *p < 0.05, **p < 0.01, ***p < 0.001 compared to controls.