BDNF and Parkinson disease: Research has shown an inverse correlation of Netrin-1 and BDNF (brain-derived neurotrophic factor) with inflammatory cytokines-activated transcription factor CCAAT/enhancer binding protein β (C/EBPβ) in PD patient brains and colons resulting from binding of C/EBPβ to the promoters of Netrin-1 and BDNF genes to inhibit their mRNA expression (Ahn et al., 2020a, 2021).