The Emerging Role of Microbial Extracellular Vesicles in Neuroinflammation and Neurodegeneration

ABSTRACT Neurodegenerative and neuropsychiatric disorders are increasingly viewed as systemic conditions shaped by interactions among peripheral immunity, microbiota, and the central nervous system. However, the mechanisms linking microbial activity to neuroinflammation and neurodegeneration remain poorly defined. Emerging evidence suggests that microbial extracellular vesicles (MEVs) act as key mediators of microbiota–brain communication by crossing biological barriers and modulating neuroimmune responses. In this perspective, we propose a conceptual framework in which MEVs link microbial dysbiosis to central nervous system pathology. We highlight unresolved mechanistic questions and biologically plausible pathways relevant to Alzheimer's disease, Parkinson's disease, and mood disorders, aiming to stimulate interdisciplinary research in this emerging field.