Transendothelial permeability changes induced by free radicals in an in vitro model of the blood-brain barrier

In the present study, we investigated the changes in blood-brain barrier (B BB) permeability following brain endothelial cell exposure to different xen obiotics able to promote free radical generation during their metabolism. O ur in vitro BBB model consisted of confluent monolayers of immortalized rat brain capillary endothelial cells (RBE4) grown on collagen-coated filters in the presence of C6 glioma cells grown in the lower compartment. We have recently shown that a range of xenobiotics, including menadione, nitrofuraz one, and methylviologen (paraquat) may undergo monoelectronic redox cycling in isolated brain capillaries, giving rise to reactive oxygen species. In this study, addition of 100 mu M menadione to the culture medium for 30 min significantly increased the permeability of endothelial cell monolayers to radiolabeled sucrose, The effect on endothelial permeability induced by me nadione was dose-dependent and reversible. These permeability changes prece ded the onset of cell death, as assessed by the Trypan blue exclusion metho d. Pre-incubation with superoxide dismutase and catalase blocked changes in sucrose permeability to control levels in a dose-dependent manner, suggest ing the involvement of reactive oxygen species in menadione-induced BBB ope ning. (C) 1999 Elsevier Science Inc.