Following the pattern of other neurodegenerative diseases, microglia in PD become overactive and contribute to a chronic, deleterious cycle of neuroinflammation via secretion of TNFα, IL-6, IL-1β, IFN-γ and free radicals (ROS, NO) which stimulate NF-κB cell-death pathways (183). This evidence concerns the gene TNF and Parkinson disease.