In the substantia nigra of PD patients and in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) models of PD, key enzymes involved in reactive oxygen species (ROS) production, such as microglia NAPDH oxidase, are upregulated in damaged areas and contribute to DA neuronal cell death [6]. This evidence concerns the gene FMO5 and Parkinson disease.