Nitronyl nitroxides, a novel group of protective agents against oxidative stress in endothelial cells forming the blood−brain barrier

Abstract

Nitronyl nitroxides (NN) effectively decompose free radicals ( Haseloff, Zoellner, Kirilijuk, Grigoriev, Reszka, Bernhardt, Mertsch, Roloff and Blasig, 1997a Free Radical Research 26, 7–17) . As brain endothelium, forming the blood-brain barrier (BBB), is both the main source and the target of reactive species during cerebral oxidative stress, we studied the effect of NN on brain endothelial cells injured by the mediator of oxidative stress H 2O 2 ( Kondo, Kinouchi, Kawase and Yoshimoto, 1996. Neuroscience Letters 215, 103–106) . H 2O 2 caused hydroxyl radical generation, lipid peroxidation, membrane dysfunction, membrane leak and cell death, concentration dependently. Due to 0.5 mM H 2O 2, oxy-radical-induced membrane phospholipid peroxidation (malondialdehyde) increased to 0.61±0.04 nmol/mg protein vs control (0.32±0.03, p<0.05), cells lost cytosolic proteins into the medium and viability decreased to 28±2% of control ( p<0.05). Permeability through the endothelial monolayer (measure for the tightness of the BBB) rose to 250±40% after 0.15 mM H 2O 2 ( p<0.001). Addition of 10 μM of the NN 5,5-dimethyl-2,4-diphenyl-4-methoxy-2-imidazoline-3-oxide-1-oxyl (NN-2), 1 mM phenylbutyl nitrone (PBN), or 10 μM of the lazaroid U83836E improved cell viability during incubation with 0.5 mM H 2O 2 to 57±1%, 49±2%, and 42±3% ( p<0.05, vs drug-free H 2O 2 group). The permeability enhancement by 0.15 mM H 2O 2 was reduced to 171±21%, 170±25%, and 118±32% ( p<0.05 vs drug-free H 2O 2 group). Generally, the assumption is supported that during cerebral oxidative stress the protection should also be directed to the cells of the BBB, which can be provided by antioxidative approaches. NN represent a new group of antioxdatively acting cytoprotectiva improving the survival and function of the endothelium against oxidative stress.