EFFECT OF BSO AND ETANIDAZOLE ON NEUROFILAMENT DEGRADATION IN NEONATAL RAT SPINAL-CORD CULTURES

Peripheral neuropathy is the major dose-limiting toxicity of the hypox ic cell sensitiser, etanidazole. Previous work from this laboratory us ing cultured neuronal cell lines suggested that nitroimidazole-induced degradation of neurofilament proteins might be the critical biologica l event mediating: this neurotoxicity. The purpose of the present stud y was to develop the neurofilament degradation assay in an organotypic spinal cord culture system with the goal of developing strategies for optimising sensitiser efficacy as well as ameliorating nitroimidazole -induced neurotoxicity. Spinal cord cultures were treated with etanida zole and neurofilament protein degradation was analysed by immunoblot analysis. Spinal cord cultures exposed to etanidazole exhibited a dose -dependent loss of parent neurofilament proteins, with concomitant app earance of low molecular weight degradation products. The potential ne urotoxic effect of L, S-buthionine sulphoximine (BSO), a compound that enhances the radiosensitising effectiveness of 2-nitroimidazoles, was also screened in this assay system. BSO alone, at concentrations up t o 100 mu M, did not promote neurofilament degradation. BSO (20 mu M) e nhanced the effect of etanidazole on neurofilament degradation by a do se-modifying factor of 1.6 +/- 0.5. Since 20 mu M BSO is expected to e nhance etanidazole radiosensitisation of hypoxic cells by a larger fac tor, this suggests that a therapeutic gain could be achieved using BSO in combination with etanidazole in radiation therapy.