NOS2 and Parkinson disease: Overactivation of microglia leads to excess production of pro-inflammatory factors including inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), tumor necrosis factor-α (TNFα), prostaglandin E2 (PGE2), interleukin-6 (IL-6), and nitric oxide (NO) [9], which lead to DA neuronal death in PD [10].