O-GlcNAcylation reprograms microglial inflammatory states and attenuates Alzheimer's disease pathology

Chronic neuroinflammation, primarily driven by microglia, is a hallmark and key contributor to Alzheimer's disease (AD) progression. O-GlcNAcylation, a nutrient-sensitive post-translational modification, has emerged as a key regulator of cellular stress and inflammation, yet its role in microglial activation in AD remains unclear. We observed that hippocampal tissue from AD patients exhibits a marked reduction in O-GlcNAcylation, accompanied by enhanced pro-inflammatory M1 microglial polarization, elevated NF-κB signaling, and NLRP3 inflammasome activation. In an LPS-induced neuroinflammation model exhibiting AD-relevant inflammatory and cognitive features, as well as in in vitro microglial cultures, LPS exposure led to a pronounced decrease in O-GlcNAcylation, particularly within Iba1-positive microglia. Systemic or in vitro treatment with glucosamine (GlcN) effectively restored O-GlcNAc levels, suppressed M1-associated inflammatory pathways, and promoted an anti-inflammatory M2 phenotype. Mechanistically, GlcN enhanced O-GlcNAcylation of NF-κB subunits p65 and c-Rel, limiting their nuclear translocation and downstream pro-inflammatory gene expression. Notably, GlcN treatment ameliorated LPS-induced memory deficits and neuronal loss in mice. Collectively, these findings suggest that O-GlcNAcylation acts as a modulatory regulator of microglial activation and neuroinflammation in AD, and that enhancing O-GlcNAcylation may represent a potential therapeutic strategy to preserve immune homeostasis and neuronal integrity.