Hypoxia and reoxygenation of brain endothelial cells in vitro: a comparison of biochemical and morphological response.

Reactive oxygen species are thought to be important for a variety of pathological processes in the brain. Endothelial cells have been proposed as both a significant source of oxidants and targets of oxidative damage. Therefore, lipid peroxidation (LPO) was investigated and compared to biochemical and morphological alterations in cultured pig brain capillary endothelial cells after hypoxia (120 min. 95% N2/5% CO2) and reoxygenation (30 min. 95% O2/5% CO2). The content of thiobarbituric acid reactive substances (TBARS) representing radical-induced LPO was 2.50 +/- 0.46 after hypoxia and 5.92 +/- 0.54 nmol/mg protein after reoxygenation (p < 0.05 each, vs. normoxic control 1.79 +/- 0.21). During hypoxia, ATP content decreased to 7.9 +/- 1.6 nmol/mg protein; lactate dehydrogenase activity in the incubation solution increased to 0.17 +/- 0.03 U/mg protein; (p < 0.05 vs. control 15.7 +/- 3.1 and 0.09 +/- 0.02, respectively). After hypoxia, morphological changes in lysosomes, multivesicular bodies and vacuoles were observed in contrast to normoxic cells. During reoxygenation, the ATP values were normalized; electron micrographs showed increasing amounts of lysosomes, multivesicular bodies, vacuoles, blebs and lipofuscin granula and lyzed cells. Comparing the biochemical and morphological observations, a sequence of disturbances occurred, in which energy depletion was accompanied and followed, respectively, by membrane destruction, cellular disintegration and an increase in LPO products. These results support the assumption that the damage of brain endothelial cells caused by hypoxia and reoxygenation is accompanied by peroxidation of membrane lipids.