Proinflammatory signals from microglia, for example, TNF- α, INF- γ, IL-1β are elevated in PD as are levels of ROS associated with the increased expression of inducible nitric oxide synthase (iNOS) and nicotinamide adenine dinucleotide phosphate oxidase (Mogi et al. 1994; Hunot et al. 1996; Muller et al. 1998; Knott et al. 2000; Nagatsu et al. 2000; Gao et al. 2003a; Wu et al. 2003). Here, NOS2 is linked to Parkinson disease.