IFNG and Parkinson disease: Accumulation of reactive oxygen species (ROS), inflammatory-associated factors including cycloxygenase-2 (COX-2) and inducible-nitric oxide synthase (iNOS)-derived NO, and pro-inflammatory cytokines (including TNF-α, IL-1β and IFN-γ) in the SN of PD patients further support that a state of chronic inflammation characterizes PD brain [5,22-26].