Roseburia intestinalis Offers Vagus-Dependent Neuroprotection Against Parkinson's Disease.

Parkinson's disease (PD) is characterized by dopaminergic neurodegeneration and increasingly associated with gut microbiota alterations. Roseburia intestinalis (R. intestinalis) is consistently reduced in PD; however, its functional contribution remains unknown. We performed two complementary mouse experiments using a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD model. In the primary intervention experiment, mice received live or heat-killed R. intestinalis, followed by behavioral assessments and multi-layer analyses, including immunofluorescence, western blotting, enzyme-linked immunosorbent assay, quantitative polymerase chain reaction, 16S rRNA sequencing, metabolomics, and transcriptomics. In a separate mechanistic experiment, subdiaphragmatic vagotomy was introduced to interrogate vagus-dependent gut-brain communication, with key behavioral and inflammatory endpoints assessed. Live R. intestinalis improved rotarod, pole, and grip strength performance and preserved tyrosine hydroxylase-positive neurons in the substantia nigra; however, these effects were not observed in the heat-killed group. Live R. intestinalis treatment also reduced glial reactivity, restored brain-derived neurotrophic factor expression, and maintained blood-brain barrier integrity. Systemically, R. intestinalis lowered serum lipopolysaccharide, tumor necrosis factor-α, and interleukin-6 levels; preserved colonic structure; and restored mucin-secreting goblet cell function. MPTP-induced dysbiosis was partially corrected. Metabolomic profiling revealed restoration of several acyl-carnitines and higher acetic acid levels. Transcriptomic analysis showed increased immediate early genes after MPTP, and the elevated c-Fos in the substantia nigra was partially normalized by R. intestinalis. Importantly, vagotomy abolished the central neuroprotective and anti-inflammatory effects but did not affect peripheral cytokine suppression, indicating both vagus-dependent and vagus-independent pathways. R. intestinalis supplementation alleviated motor impairments, reduced neuroinflammation, preserved dopaminergic neurons, and improved intestinal and metabolic alterations in mice with an MPTP-induced PD model. Its protective actions may involve both central and peripheral mechanisms, potentially including gut-brain communication pathways. R. intestinalis may be a promising candidate for microbiota-based strategies against PD.