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.
Subject(s)
Animals , Mice , Hypoxia , Antioxidants , Atmosphere , Brain , Cell Count , Cell Culture Techniques , Cell Survival , Cochlea , Deferoxamine , Facial Nerve , Gentamicins , Glucose , Horses , Microscopy , Noise , Oxidoreductases , Oxygen , Plastics , Reactive Oxygen Species , Schwann CellsABSTRACT
Relationships between recovery of vestibuloocular reflex and expression of c-fos immunoreactive cells in the medial vestibular nuclei following unilateral labyrinthectomy(ULX) were investigated in rats. Frequency of spontaneous nystagmus, velocity of eye movement induced by sinusoidal rotation of the whole body at frequencies of 0.1, 0.2, 0.5Hz, and the number of c-fos immunoreactive cells in the medial vestibular nuclei were measured for 72 hours after ULX. Frequency of spontaneous nystagmus was 3.9+/-0.5 beats/sec(M+/-SD) immediately after ULX and disappeared completely within 48 hours. On sinusoidal rotation, eye movement induced by rotation toward the lesioned side recovered normal pattern within 24 hours at 0.1Hz rotation, and 12 hours at 0.2, 0.5Hz. Directional preponderance which represents the symmetry of bilateral vestibular functions decreased to less than 20% at 72 hours, but did not recover normal limit. The number of c-fos immunoreactive cells in the bilateral medial vestibular nuclei was severe asymmetry till 24 hours of ULX. However, the symmetry was recovered after 48 hours. These results indicate that the recovery of vestibuloocular reflex correlates with the expression of c-Fos immunoreactive cells of the medial vestibular nuclei in the early stage of vestibular compensation following ULX. Therefore, the vestibular nuclei may play a key role in vestibular compensation.