TNF and Parkinson disease: Enteric inflammation occurs in PD, and it has been demonstrated by increased levels of inflammation markers in the gastrointestinal tract, such as glial fibrillary acidic protein (GFAP) and pro-inflammatory cytokines, including IL-1β, IL-6, TNF-α, and IFN-γ, further reinforcing the role of peripheral inflammation in the initiation and/or progression of PD [120].