CELLULAR MECHANISM OF GUT-DERIVED AMYLOID-Β PROPAGATION TO THE BRAIN

Alzheimer’s disease is a progressive neurodegenerative disorder classically defined by cerebral accumulation of amyloid-beta (Aβ), yet increasing evidence suggests that peripheral systems, particularly the gut, may contribute to early disease pathogenesis. However, the cellular mechanisms enabling Aβ transfer from the gut to the brain remain poorly understood. In this study, we investigated gut-to-brain Aβ trafficking using an integrated in vitro co-cultured transwell system and microfluidic platform comprising intestinal epithelial and neuronal cells to model transcellular transport pathways. Barrier integrity was validated using transepithelial electrical resistance measurements, Dextran-FITC permeability assays, and ZO-1 immunostaining, confirming preserved tight junction architecture and functional epithelial integrity. We further examined the role of extracellular vesicles (EVs) as mediators of long-range Aβ transport. Our results demonstrate that Aβ is predominantly propagated to neurons via EVs. Neurons directly exposed to free Aβ exhibited significantly higher reactive oxygen species production and cytotoxicity compared to neurons receiving EV-associated Aβ through the co-culture system, indicating distinct biological effects based on transport modality. In vivo imaging in zebrafish larvae further confirmed that gut-administered Aβ migrates to the brain, providing direct evidence of gut-to-brain transport in a living system. Together, these findings identify extracellular vesicles as critical mediators of peripheral-to-central amyloid propagation and uncover a previously underappreciated biological pathway linking gut pathology to early neurodegenerative processes. This gut-centric framework provides new mechanistic insight into Alzheimer’s disease pathogenesis and highlights EV-mediated transport pathways as promising targets for early therapeutic intervention.