Association between Alzheimer's disease and Porphyromonas gingivalis products in murine models: A systematic review

Alzheimer's disease is a neurodegenerative dementia characterized by accumulation of β-amyloid plaques, tau hyperphosphorylation, and neuroinflammation. Recent research has highlighted a potential relationship between chronic oral infections and neurodegeneration, particularly the involvement of Porphyromonas gingivalis (P. gingivalis), a key pathogen in periodontitis. Experimental mouse models have been used to explore how P. gingivalis products contribute to neuroinflammatory and degenerative processes. However, a comprehensive synthesis of these findings is lacking. This systematic review evaluates the role of P. gingivalis-derived factors in triggering Alzheimer's-like pathology, with an emphasis on bacterial products and host immune responses. We hypothesize that P. gingivalis products exacerbate neuroinflammation and pathology in mouse models of Alzheimer's disease.

To link gingival P. gingivalis bacteria-associated products with the onset and progression of Alzheimer's disease-like pathology in mouse models.

This systematic review followed the 2020 PRISMA guidelines. A comprehensive search was conducted in five databases (PubMed, Scopus, ScienceDirect, Sage, SpringerLink) for original studies between 2014 and 2024. Studies included mouse models to evaluate the effect of P. gingivalis or its products on Alzheimer's-like pathologies. Exclusion criteria were in vitro, human, or review studies. Twenty-three studies met the inclusion criteria. Bacterial components and activated host factors were extracted, categorized, and analyzed using narrative synthesis and descriptive statistics.

In 24 studies, lipopolysaccharides (54.84%) and gingipains (25.81%) were the most frequently reported P. gingivalis products. These factors activated toll-like receptors (TLR2/TLR4), microglia, and astrocytes, increasing levels of interleukin 1 beta, tumor necrosis factor-alpha, and other proinflammatory cytokines. The host response included β-amyloid accumulation, Tau hyperphosphorylation, and changes in blood-brain barrier permeability. Glial cells were the most frequently mentioned host factors (n = 15), followed by proteins (n = 13) and cytokines (n = 11). These interactions promoted cognitive impairment, synaptic dysfunction, and neurodegeneration in mouse models, supporting a role for P. gingivalis in Alzheimer's-like pathology.

P. gingivalis products induce neuroinflammatory responses and Alzheimer's-like pathology in mouse models, supporting their role as contributors to neurodegeneration and potential targets for preventive strategies.