Dual Orexin Receptor Antagonism with Lemborexant Enhances Microglial Clearance of β-Amyloid in Mice

Methods

APP/PS1 mice were treated with lemborexant (10 or 30mg/kg daily) or doxepin (35mg/kg daily) for 3 months, starting just before the onset of amyloid plaque accumulation, or for 1 month after plaque pathology was established. Sleep was measured using a piezoelectric system, and amyloid pathology and glial responses were quantified by immunohistochemistry and confocal microscopy, as well as single cell RNAseq of isolated microglia.

Amyloid plaques were labeled with methoxy-X04 to monitor plaque growth, and microglial plaque phagocytosis was assessed by flow cytometry. Microglial elimination was performed using the CSF1r inhibitor PLX3397. Results: Despite equivalent total sleep enhancement, LEM more effectively prevented formation of and slowed growth of both fibrillar and diffuse Aβ plaques.

LEM enhanced peri-plaque microglial activation and enhanced microglial amyloid phagocytosis in vivo. Single-cell microglial transcriptomics showed a LEM-mediated shift toward pro-phagocytic and antigen-presentation gene signatures. Depleting microglia via CSF1R inhibition abolished LEM’s anti-amyloid effects, underscoring microglia as essential mediators.

Conclusions: These results demonstrate that dual orexin receptor antagonism with lemborexant can augment microglial function to mitigate AD pathology.