Immune Checkpoint PD-L1 Modulates Retinal Microglial Activation to Alleviate Vascular Leakage in Choroidal Neovascularization via ERK.

Neovascular age-related macular degeneration (NVAMD) is a common retinal disease causing vision loss in the elderly. Neuroinflammation significantly contributes to NVAMD's etiology. This study explores the role of Programmed cell death ligand 1 (PD-L1), an immune checkpoint (ICP) in microglia, known for limiting neuroinflammation in neurodegenerative diseases, and its potential function in NVAMD. This work finds increased PD-L1 expression in retinal microglia following laser injury. PD-L1 knockout (KO) or inhibitory PD-L1 antibody treatment worsens vascular leakage and neoangiogenesis in a laser-induced NVAMD mouse model, effects reversible by microglia depletion with PLX5622. This study underscores that choroidal neovascularization (CNV) may be regulated by multiple mechanisms, with PD-L1 modulation representing one of these pathways. Blocking PD-L1 elevated proinflammatory factors and p-ERK levels, indicating microglial overactivation in NVAMD. Conversely, enhancing PD-L1 signaling reduced neuroinflammation and neovascularization via ERK. These findings highlight PD-L1's role in neoangiogenesis and neuroinflammation in NVAMD, suggesting its potential as a target for immunomodulatory treatment in NVAMD.