In PD, the excessive extracellular release of toxic oligomers of α-synuclein, as well as neuromelanin from dying neurons, activate microglia, resulting in the subsequent secretion of pro-inflammatory cytokines such as interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) [144,145]. This evidence concerns the gene TNF and Parkinson disease.