HYPOXIA INCREASES THE SUSCEPTIBILITY TO OXIDANT STRESS AND THE PERMEABILITY OF THE BLOOD-BRAIN-BARRIER ENDOTHELIAL-CELL MONOLAYER

Using a cell culture model of the blood-brain barrier (BBB), we invest igated the brain capillary endothelial cell (EC) response to hypoxia. The activities of antioxidant enzymes such as glutathione peroxidase, glutathione reductase, catalase, and superoxide dismutase and the GSH level of brain capillary ECs alone or in coculture with astrocytes, as well as those of pericytes, were compared with those obtained with fr eshly isolated microvessels. These results demonstrated that brain cap illary ECs cocultured with astrocytes and used in the presence of a co culture-conditioned medium provided a relevant in vitro model for stud ying the effect of hypoxia-reoxygenation at the BBB level. The effect of hypoxia on antioxidant enzymes, GSH, and ATP levels was studied, as well as the modification of the permeability to small weight molecule s. A decrease in all enzymes and the GSH level could explain an increa se in the susceptibility of the brain capillary ECs to further oxidant injury. Second, profound rearrangements of F-actin filaments of the E Cs and a decrease in the ATP level could be associated with an increas e in the permeability of the monolayer. Furthermore, an apoptotic proc ess was detected by in situ end labeling of DNA. These results indicat e that hypoxia distorts the function of ECs and that these cells in cu lture provide a valuable tool for exploring mechanisms after hypoxia-r eoxygenation.