THE INFLUENCE OF OXYGEN-FREE RADICALS ON THE PERMEABILITY OF THE MONOLAYER OF CULTURED BRAIN ENDOTHELIAL-CELLS

Free radicals have been implicated in the pathogenesis of vasogenic br ain edema caused by ischemic or traumatic injury. It has been reported that in transgenic mice overexpressing the human CuZn-superoxide dism utase, brain edema is decreased in many cerebral disorders. To investi gate the effects of free radicals on the permeability of the blood-bra in barrier, we established an in vitro model system of the blood-brain barrier using brain endothelial cells cultivated from transgenic mice and non-transgenic mice. The blood-brain barrier model is originated by a monolayer of brain endothelial cells cultured on a membrane which has 0.45-mu m pores. Electrical resistance across the cell monolayer, which reflects the paracellular flux of ionic molecules, was measured . The blood-brain barrier models were incubated with menadione (vitami n K-3, an intracellular O-2(-) producing agent), and segmental changes in the electrical resistance across the monolayer were compared betwe en the transgenic and the non-transgenic mice. Superoxide dismutase ac tivity of the cultured brain endothelial cells was 1.7 times higher in the transgenic than in the non-transgenic mice (n = 3, P < 0.001). Th e electrical resistance was reduced by menadione in the transgenic but not in the non-transgenic mice (n = 7, P < 0.05) in the early stage. Moreover, desferroxamine mesylate (Fe2+ chelating agent) inhibited the menadione-induced early decrease in electrical resistance in the tran sgenic mice (n = 7, P < 0.05). These results suggest that the permeabi lity of the blood-brain barrier may be affected by hydroxyl radicals a nd/or peroxynitrite rather than the O-2(-) itself. Copyright (C) 1996 Elsevier-Science Ltd.