NOS2 and Parkinson disease: In this regard, various PD toxin-base mouse models, such as 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), 6-hydroxydopamine, and rotenone, as well as mutant α-syn transgenic models of PD (M7KO, M83KO and SYNKO), have also demonstrated microgliosis with elevated levels of inflammatory cytokines IL-1β, IL-2, IL-4, IL-6, IFN-γ, and TNF-α, high levels of enzymes related to inflammation such as COX-1, COX-2, and iNOS, and reduced levels of neurotrophins, such as nerve growth factor and brain-derived neurotrophic factor (BDNF; Liu et al., 2019).