NOS2 and Parkinson disease: Studies have shown that the oxidative stress factors leading to PD mainly include the following aspects (Zhu et al., 2019): Firstly, mitochondrial dysfunction, impaired mitochondrial complex I activity substantially increases ROS generation; Secondly, neuroimmune inflammatory responses induce the massive release of pro-inflammatory cytokines (e.g., TNF-α, IL-1β, IL-2), enhances iNOS activities, promoting ROS and ONOO- formation (Przedborski and Dawson, 2001).