Nitric oxide protects blood-brain barrier in vitro from hypoxia/reoxygenation-mediated injury

A cell culture model of blood-brain barrier (BBB, coculture of rat brain endothelial cells with rat astrocytes) was used to investigate the effect of nitric oxide (^.NO) on the damage of the BBB induced by hypoxia/reoxygenation (H/R). Permeability coefficient of fluorescein across the endothelium was used as a marker of BBB tightness. The permeability coefficient increased 5.2 times after H/R indicating strong disruption of the BBB. The presence of the ^.NO donor S-nitroso-N-acetylpenicillamine (SNAP, 30 μM), authentic ^.NO (6 μM) or superoxide dismutase (50 units/ml) during H/R attenuated H/R-induced increase in permeability. 30 μM SNAP or 6 μM ^.NO did not influence the function of BBB during normoxia, however, severe disruption was observed using 150 μM of SNAP and more than 24 μM of ^.NO. After H/R of endothelial cells, the content of malondialdehyde (MDA) increased 2.3 times indicating radical-induced peroxidation of membrane lipids. 30 μM SNAP or 6 μM authentic ^.NO completely prevented MDA formation. The results show that ^.NO may effectively scavenge reactive oxygen species formed during H/R of brain capillary endothelial cells, affording protection of BBB at the molecular and functional level.