Glycyrrhizic acid-loaded biomimetic hybrid liposomes targeting inflammatory cascades and PD-1/PD-L1 pathway to reverse neuroinflammation-driven cognitive decline.

Neuroinflammation is a key pathogenic process in multiple central nervous system (CNS) disorders. It can lead to neuronal injury and cognitive decline through excessive glial activation and aberrant engagement of the programmed cell death protein-1/programmed death-ligand 1 (PD-1/PD-L1) checkpoint axis. To address these pathologies, we engineered a PD-1-enriched macrophage-membrane, lactoferrin-modified, PEGylated, glycyrrhizic-acid-loaded biomimetic hybrid liposome (PMLpGL) for dual, precise modulation of the neuroinflammatory microenvironment. PMLpGL alleviates neuronal inhibitory signaling by reversibly sequestering excess PD-L1 via membrane-anchored PD-1, while its cargo GA suppresses high-mobility group box-1 (HMGB1)-driven inflammatory cascades, thereby returning inducible PD-1/PD-L1 expression and glial activation toward homeostasis. Physicochemical characterization showed a hydrodynamic diameter of 165 ± 3 nm and a zeta potential of -10.2 ± 0.2 mV. Engineered macrophage membranes displayed marked PD-1 overexpression, and ligand-depletion saturation assays demonstrated specific, saturable PD-1/PD-L1 binding. In a Transwell blood-brain barrier (BBB) model, PMLpGL achieved a 24-h permeability of 22.86 ± 0.14 %, indicating robust in-vitro BBB traversal. In vivo fluorescence imaging showed peak brain accumulation at 24 h with retention to 48 h; liquid chromatography-tandem mass spectrometry further confirmed brain targeting and persistence-at 12 h, brain GA with PMLpGL was ∼48-fold higher than free drug and remained quantifiable at 48 h. Pharmacodynamic evaluations in cells and mice demonstrated that PMLpGL suppresses glial activation and normalizes inducible checkpoint expression; reshapes the cytokine milieu by lowering IL-6, IL-1β, TNF-α, and HMGB1 while increasing IL-10, TGF-β, and brain-derived neurotrophic factor; and restores the synaptic protein synapsin-1. Correspondingly, PMLpGL significantly improved cognition in open-field, novel object recognition, and Morris water maze tests. Collectively, PMLpGL combines PD-1 decoy sequestration with GA-mediated upstream immunomodulation to attenuate neuroinflammatory cascades, protect neurons, and reverse cognitive deficits. By pairing BBB compatibility with microenvironment-precise regulation, this platform offers a promising therapeutic strategy for CNS diseases associated with cognitive decline.