Multi-Level Analysis of Gut Microbiome Extracellular Vesicles-Host Interaction Reveals a Connection to Gut-Brain Axis Signaling

Microbiota-released extracellular vesicles (MEVs) have emerged as a key player in intercellular signaling. However, their involvement in the gut-brain axis has been poorly investigated. In this study, we aimed to investigate the cargo capacity of MEVs for bioactive metabolites and their interactions with the host. Metabolomics analysis identified various neuro-related compounds encapsulated within the 28 MEVs, such as arachidonyl-dopamine, gabapentin, glutamate, and N-acylethanolamines. 29 Metaproteomics unveiled an enrichment of enzymes involved in neuronal metabolism, primarily in the glutamine/glutamate/GABA pathway. The detected neuro-related proteins and metabolites were correlated with Bacteroides spp. A GABA-producing Bacteroides isolate, B. finegoldii, released EVs with a high GABA content (4 µM) as opposed to a low GABA-producing isolate, Phocaeicola massiliensis. MEVs exhibited a dose-dependent paracellular transport and were endocytosed by Caco-2 and hCMEC/D3 cells. RNA-Seq analyses showed that MEVs stimulate several immune pathways while suppressing cell apoptosis process. The in vivo biodistribution confirmed the presence of MEVs in the brain, liver, stomach, and spleen. Overall, our results highlight the ability of MEVs to cross the intestinal and blood-brain barriers to deliver their cargoes to distant organs, including the brain, where it may modulate the organ functionalities. MEVs could be an integral part of microbiome-host communications, with potential implication for the gut-brain axis.