Interestingly, both SOD1 and SOD2 transgenic mice have been demonstrated to be resistant to MPTP-induced neurotoxicity, providing evidence that some of the deleterious effects of MPTP could be mediated by superoxide radicals and strongly supporting the possibility that these radical species could play a significant role in the aetiology of PD [76, 77]. This evidence concerns the gene SOD1 and Parkinson disease.