Glucosamine-Producing Engineered Probiotics Enhance the Immune Function of Microglia

Abstract Dysregulated microglial activation underlies both neuroinflammation and neurodegenerative pathology. GlcN has well-documented anti-inflammatory activity across multiple cell types, yet whether it acts on microglia in any meaningful way has not been directly tested. Here we show that GlcN shifts microglia toward an M2 anti-inflammatory state by altering their metabolic program, an effect accompanied by a clear improvement in immune function. A practical barrier complicates direct translation of this finding, oral GlcN is rapidly cleared and reaches target tissues at concentrations too low to be therapeutically useful. We therefore repurposed Escherichia coli Nissle 1917 (EcN) as a living production platform, introducing targeted genetic modifications to generate EcN-GlcN, a strain that continuously synthesizes GlcN within the gut lumen. In co-culture, EcN-GlcN drove the same M2 shift in microglia as exogenous GlcN. After oral gavage in mice, the strain established stable intestinal colonization and kept systemic GlcN concentrations detectable for at least 72 h. The work positions GlcN as an underappreciated neuroimmune regulator and offers a practical route to its long-term delivery through a living bacterial system.