CX3CR1: a potential microglia-specific PET imaging target in Alzheimer’s and Parkinson’s diseases

Microglia are the resident immune cells of the central nervous system (CNS), playing a crucial role in maintaining brain homeostasis and mediating neuroimmune responses. The chemokine receptor CX3CR1, predominantly expressed on microglia, regulates microglial function via interactions with its neuronal ligand CX3CL1. The CX3CR1-CX3CL1 signaling exhibits complex, context-dependent roles in neurodegenerative diseases. In Alzheimer's disease (AD) and Parkinson's disease (PD) animal models, CX3CR1 deficiency shows paradoxical outcomes, attenuating or exacerbating amyloid-β (Aβ) and tau pathologies in AD, while consistently worsening α-synuclein-induced neurodegeneration in PD. Although CX3CR1 emerges as a promising therapeutic and diagnostic target, its complex role in microglial dynamics remains incompletely understood. Positron emission tomography (PET) imaging provides a powerful, noninvasive method for investigating biological processes <i>in vivo</i>. There is an urgent need to develop and validate new PET tracers targeting microglial CX3CR1 in the CNS, further offering new opportunities for the diagnosis and treatment of neuroinflammation-associated neurodegenerative diseases.