BDNF and neurodegenerative disease: After TBI, several ligand–receptor interactions were significantly downregulated, including colony‐stimulating factor signaling, neurotrophic (NT) signaling (BDNF‐NTRK2 interaction, Figure S1A), and neuropeptide Y (NPY) signaling (Figure 2C), which generally play a neuroprotective role in TBI or neurodegenerative diseases.26, 27, 28