Title : Circulating extracellular vesicles-containing P. gingivalis OMVs from periodontitis patients may penetrate in the brain and trigger the release of inflammatory markers and the amyloid-? peptide inducing neuroinflammation

Introduction: Periodontitis, a chronic inflammatory disease, and its key pathogen Porphyromonas gingivalis has been implicated in several systemic disorders, including Alzheimer's disease (AD). However, the underlying mechanisms linking this oral pathogen to neurodegenerative pathology remain poorly understood. This study aims to investigate the systemic dissemination of P. gingivalis and its contribution to Alzheimer's disease (AD) pathology through its outer membrane vesicles (OMVs). Specifically, we will identify P. gingivalis-derived OMVs (Pg-OMVs) in the plasma of periodontitis patients and assess their impact on microglial and neuronal cells.

Methods Circulating extracellular vesicles (cEVs) were isolated from the plasma of periodontitis patients using size-exclusion chromatography. The presence of Pg-OMVs in the cEVs sample was analyzed by the detection of the Kgp protease marker using capillary western blot analysis and TEM immunogold labeling. Biodistribution and brain entry of PKH-labelled cEVs were evaluated by their intravenous injection to the Tg(flk:EGFP zebrafish model. The effects of cEVs, and Pg-OMVs, on the secretion of inflammatory cytokines (IL-4, IL-6, IL8, IL-10, IL-1β, TNF-α) by the human microglial HMC3 cells were determined using ELISA-MSD. Their effects on the release of Aβ1-42 by the N2a-SW-APP neuronal cells were also measured using ELISA-MSD. The interaction between P. gingivalis and amyloid beta peptide was also investigated.

Results: Our results show that cEVs contain Pg-OMVs as confirmed by western blot and TEM immunogold labelling cEVs injected into zebrafish traversed the blood-brain barrier and were found in the brain three hours after the injection. These cEVs triggered the secretion of inflammatory cytokines by HMC3 cells and Aβ1-42 by N2a-SW cells. P.gingivalis behaved differentially in the presence Aβ1-42 depending on its physical state.

Conclusion: This study demonstrates that plasma derived-cEVs from periodontitis patients can trigger inflammation and the production of Aβ1-42. These results highlight the systemic spreading of Pg-OMVs and the contribution of cEVs containing Pg-OMVs to the development of neurodegenerative disorders by crossing the BBB. Thus, cEVs could be considered as critical tools to discover systemic markers of neurodegenerative disease in periodontitis patients.

Prof. TamasFulop M.D, PhD, FRCPC is an internist-geriatrician and senior researcher at the Research Center at the Université de Sherbrooke. He completed his medical studies at the faculty of medicine of the University of Geneva. He made his PhD at Hungary. He was a postdoctoral fellow at Paris XII. He moved to the Université de Sherbrooke in 1993. His main research field is immunology in aging and age-related diseases, especially neurodegenerative diseases. He authored more than 400 papers. He led the memory clinic for more than 10 years. He is Editor-in-Chief of Gerontology. He is a fellow of the Canadian Academy of Health Sciences, Fellow of the Gerontological Society of America and corresponding member of the French Medical Academy.