NOS2 and Parkinson disease: Recruitment of activated microglia to the SNpc in PD therefore leads to an upregulation and secretion of proinflammatory cytokines, such as Tumour Necrosis Factor α (TNFα), Interleukin 6 (IL6) and Interleukin 1β (IL1β), and activation of inducible Nitric Oxide Synthase (iNOS) resulting in production of nitric oxide (NO) [23], which in turn are thought to exacerbate degeneration of dopaminergic SNpc neurons [11].