Neuroprotective effects of copper/zinc-dependent superoxide dismutase against a wide variety of death-inducing stimuli and proapoptotic effect of familial amyotrophic lateral sclerosis mutations.

Superoxide dismutase plays a key role in cell protection against the damaging effects of superoxide. Mutations in the copper/zinc dependent intracellular form of superoxide dismutase (SOD1) are associated with a subset of cases of familial amyotrophic lateral sclerosis (FALS). In this study we have investigated the effects of over-expressing wild-type SOD1 and two mutant forms of SOD1 found in FALS, G93A and G93R, on cell survival using stably transfected neuronal cells. G93R is associated with early age of onset and severely reduced erythrocyte SOD1 enzyme activity. Overexpression of wild-type SOD1 in ND7 cells significantly enhanced cell survival and reduced apoptosis after serum deprivation. Conversely, cells expressing the G93R mutation of SOD1 exhibited significantly increased cell death and increased number of TUNEL-positive cells, having a more profound effect than G93A SOD1 expressing cells, thus reflecting the relative clinical severity of these mutations. The effects of three further apoptotic and nonapoptotic death-inducing paradigms were investigated, hypoxia with reperfusion, staurosporine and gamma-interferon induced cell death. With each paradigm, cell death was significantly reduced by overexpression of wild-type SOD1 and increased by overexpression of the SOD1 mutations G93A and G93R. We further used these SOD1 constructs to develop a virus expressing either wild type SOD1 or the SOD1 mutant G93R and found a similar protective effect against serum withdrawal following infection with an HSV vector expressing wild-type SOD1 which offers a potential tool for neuroprotective gene delivery in vivo.