DECREASED ENDOTHELIAL-CELL GLUTATHIONE AND INCREASED SENSITIVITY TO OXIDATIVE STRESS IN AN IN-VITRO BLOOD-BRAIN-BARRIER MODEL SYSTEM

Using a cell culture model of the blood-brain barrier (BBB) we have ev aluated the role of endothelial cell glutathione in protecting barrier integrity against nitric oxide (NO)-induced oxidative stress. The co- culture of human umbilical vein endothelial cells (ECV304) with rat (C 6) glioma cells, or incubation with glioma cell or primary astrocytic conditioned medium, resulted in a decline in endothelial cell glutathi one. Exposure to a single addition of NO gas induced a rapid breakdown in model barrier integrity in endothelial/glioma co-cultures. Additio n of NO gas or tumour necrosis factor-alpha (TNF-alpha) also resulted in a loss of membrane integrity, as measured by an enhanced release of lactate dehydrogenase, only from endothelial cells treated with gliom a conditioned medium. Furthermore, assessment of viability in endothel ial cells grown alone or treated with glioma conditioned medium, by pr opidium iodide labelled flow cytometry, demonstrated no difference in the number of positively stained cells after NO exposure. These result s indicate that when enhanced endothelial monolayer barrier formation occurs via astrocytic-endothelial interactions, cellular glutathione l evels are decreased. This renders the barrier cells, under these condi tions, more susceptible to oxidative stress but does not necessarily l ead to greater cell death. (C) 1998 Elsevier Science B.V. All rights r eserved.