Many studies have suggested that NADPH oxidase has been linked to microglia-derived OS after a variety of PD-related neurotoxin, for example, 6-OHDA (Rodriguez-Pallares et al., 2007), rotenone (Gao et al., 2002), paraquat (Wu et al., 2005), and α-synuclein (Zhang et al., 2005), which suggest that microglia are the major NOX2-expressing cells in PD and in PD experimental models. This evidence concerns the gene FMO5 and Parkinson disease.