Neurodegeneration in PD may be accompanied by an inflammatory reaction, characterized by activation of microglia, which leads to production of a number of inflammatory mediators (e.g., NF-κB, interleukin-1 (IL-1), IL-6, IL-1β, cyclooxygenase-2 (COX-2), tumoral necrosis factor-α (TNF-α), inducible nitric oxide synthase (iNOS), interferon-γ) and increased expression of different proinflammatory cytokines by glial cells. This evidence concerns the gene NOS2 and Parkinson disease.