ABSTRACT
BACKGROUND AND OBJECTIVES: Oxygen radical scavengers and inhibitors are known to have protective functions (or roles) against hypoxia and noise exposure in the cochlea and brain. The purpose of this study was to examine the toxic effect of oxygen radicals (xanthine oxidase and hypoxanthine) on cultured mouse facial nerve Schwann cells, and determine if antioxidants (TPEN and DFO) might ptotect Schwann cells from oxidant-induced neurotoxicity. MATERIALS AND METHODS: Dissociated cell cultures were prepared from the facial nerve of a mouse. After dissociation of Schwann cells, isolated cells were washed, resuspended in feeding medium, and plated onto poly-L-lysine-coated Aclar plastic cover slips (12 mm diameter) in petri dishes or in 96 well multichambers at cell density of 2X105 ceIls/coverslip or lX10(5) ceIls/we11. The feeding medium consisted of Eagle's minimum essential medium (MEM) containing 5% horse serum, 5 mg/ml D-glucose, and 25 ng/ml gentamicin. Cultures were grown in 5% CO2/95% atmosphere at 37degreesC, and the medium was renewed twice a week. Cultures grown for 4-5 days were utilized for experiments. Oxygen radical exposure was done using XO and HX, and antioxidant pretreatment was carried out using tetrakis (2-pyridylmethyl) ethylenediamine (TPEN) and desferrioxamine (DFO). Cytotoxicity assay was performed by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide cytotoxic assay and inverted microscopy. RESULTS: Cell viability of cultured mouse Schwann cells treated with markedly decreased in a dose-dependent manner. Cultured mouse Schwann cells exposed to XO/HX for 4 hours showed degenerative changes such as the decrease of cell number and process. Pretreatment of 80 uM TPEN for 2 hours increased remarkably the cell viability of cultured Schwann cells exposed to 20 mU/ml XO/0.1 mM HX, while DFO did not show any protective effects on oxidant-induced neurotoxicity in these cultures. CONCLUSION: It is suggested that oxygen radicals induce neurotoxic effect on cultured mouse Schwann cells, and that selective antioxidants such as TPEN is very effective in blocking oxidant-induced neurotoxicity.