Poly(lactic-co-glycolic acid) immunomodulatory nanoparticles attenuate neuroinflammation and Alzheimer’s disease-related pathology in 5xFAD mice

Alzheimer’s disease is characterized by progressive cognitive decline, amyloid-β deposition, neuroinflammation, and neurodegeneration, yet effective and well-tolerated therapies remain limited. Because dysregulated myeloid responses are increasingly recognized as important drivers of disease progression, we investigated the therapeutic potential of poly(lactic-co-glycolic acid) immunomodulatory nanoparticles in the 5xFAD mouse model of amyloid-driven neurodegeneration. Poly(lactic-co-glycolic acid) immunomodulatory nanoparticles and fluorescently labeled particles displayed the expected size range and negative surface charge. After intraperitoneal administration, fluorescent particles were preferentially associated with myeloid cells in the blood, spleen, and brain, with greater uptake by brain myeloid populations in 5xFAD mice than in wild-type controls. Therapeutic treatment of 6.5-month-old 5xFAD mice, a stage at which behavioral abnormalities are already established, resulted in significant improvement in elevated plus maze behavior and a more modest improvement in Barnes maze performance. Flow cytometric analysis performed 9 weeks after the final treatment demonstrated persistent changes in brain immune composition, with the most prominent effects observed in P2RY12 ⁺ microglial populations, particularly the CD11c ⁺ subset, and comparatively limited sustained effects in CD11b ⁺ P2RY12 ^- myeloid cells. These changes were accompanied by reduced expression of activation- and disease-associated markers and lower pro-inflammatory cytokine production within microglial populations. Histological analysis further showed reduced cortical amyloid plaque burden, decreased CD68 immunoreactivity, and reduced neurodegeneration in treated 5xFAD mice. Together, these findings show that systemically administered poly(lactic-co-glycolic acid) immunomodulatory nanoparticles produce durable behavioral, immunological, and pathological benefits in 5xFAD mice and support further investigation of this biodegradable myeloid-targeted platform as a therapeutic strategy for Alzheimer’s disease.