Zinc amplifies mSOD1-mediated toxicity in a transgenic mouse model of amyotrophic lateral sclerosis.

Transgenic mice overexpressing the human mutated form (G93A) of Cu,Zn-superoxide dismutase (mSOD1) develop motor neuron degeneration resembling amyotrophic lateral sclerosis. In vitro studies have shown that mSOD1-induced, reactive oxygen species-mediated apoptosis of motor neurons depends on the presence of copper and the relative absence of zinc. Oral intake of zinc sulphate induces the expression of metallothioneins, enzymes that decrease oxidative stress, and leads to higher serum zinc, and lower copper levels. We therefore tested the effect of chronic oral administration of zinc sulfate (0.075 and 0.375 g/kg) on disease onset and survival of mSOD1 transgenic mice. We observed that zinc sulfate, rather than prolonging survival, decreased survival. We conclude that zinc sulfate amplifies the mSOD1 transgenic mouse phenotype. This finding may shed more light on the role of zinc in mSOD1-mediated toxicity.