Intracortical injection of immune checkpoint inhibitor promotes monocyte/macrophage infiltration and restores microglial function and neuronal activity in an AD mouse model
Alzheimer's disease (AD) involves complex neuroimmune interactions. However, the role of immune checkpoint pathways in regulating the glial and neuronal functions of the AD brain remains unclear. This study aims to investigate how the brain-specific modulation of the PD-1/PD-L1 axis affects glial and neuronal function in an AD mouse model, which is characterized by the significant upregulation of microglial PD-1 and astrocytic PD-L1. A single intracortical administration of anti-PD-L1 antibody reshaped the glial microenvironment, which was accompanied by the restoration of impaired microglial process convergence. Astrocyte-specific Pd-l1 knockdown using the pSico system validated the essential role of astrocytic PD-L1 in enhancing microglial responses. Notably, the blockade of the PD-1/PD-L1 signaling pathway increased the microglial P2RY12 expression, a key marker of microglial homeostasis, which likely contributed to the restoration of neuronal hyperactivity. Collectively, these findings confirmed the potential of targeting the astrocyte-microglia PD-1/PD-L1 axis to mitigate AD pathology.