CCL2 and Cognitive impairment: The MGCs, Mφs, and sera of the PARK2 mouse model displayed decreased expression of parkin and its link to the increased generation of pro-inflammatory cytokines and chemokines (e.g., IFNβ1, TNFα, IL-1β, IL-12, IL-13, IL-17, CCL2, and CXCL1), loss of DA neurons, and cognitive defects in PD (Table 5A).