CCL2 and Cognitive impairment: The sera, MGCs, and brain regions of the SNCA mouse model of PD have shown overexpression of different species of α-syn and pro-inflammatory cytokines (e.g., IFNγ, TNFα, IL-1α, IL-1β, IL-6, IL-10, TGFβ, CCL2, CCL3, CCL5, CXCL10, and ICAM-1) as well as their link to neuronal cell death and cognitive defects (Table 4A).