NITRIC OXIDE-INDUCED PERTURBATIONS IN A CELL-CULTURE MODEL OF THE BLOOD-BRAIN-BARRIER

The actions of an intracellular nitric oxide generator compound on the properties of a co-culture model of the blood-brain barrier are descr ibed. Addition of the iron-sulphur cluster nitrosyl Roussin's black sa lt (RBS, heptanitrosyl-tri-mu 3-thioxotetraferrate (1-)) resulted in a rapid and dose-dependent (50-250 mu M) decline in the electrical resi stance displayed by co-cultures of vascular endothelial cells and C6 g lioma cells. The breach in barrier integrity elicited by RBS (250 mu M ) could be prevented by either haemoglobin (100 mu M), methylene blue (200 mu M), or by photon-induced inactivation of RBS. In contrast, the nitric oxide synthase inhibitor nitro-L-arginine methyl ester (250 mu M) caused no inhibition in the decline in resistance of RBS-exposed c ultures. Addition of 8-bromo-guanosine-cyclic monophosphate (500 mu M) did not mimic the actions of RBS. Exposure to intense light of co-cul tures manifesting a high transcellular electrical resistance resulted in a reduction in tissue resistance which could be prevented by the pr esence of haemoglobin (100 mu M). We conclude that nitric oxide libera ted from RBS results in a reversible diminution in the integrity of th e endothelial cell barrier in the co-culture system, and we suggest th at light-sensitive endogenous nitric oxide generator compounds may be present in intact cells. Possible roles of nitric oxide in blood-brain -barrier function are considered. (C) 1996 Wiley-Liss Inc.