NOS2 and Parkinson disease: Microglia in PD have been observed to grow densely in the striatum and SN with increased expression of proinflammatory mediators, including tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β) [16], IL-2, IL-4, IL-6, transforming growth factor-α (TGF-α), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) [14].