Method: We orally infected 62-week-old APP-Tg mice with P. gingivalis (strain ATCC 33277) to induce experimental periodontitis. Five weeks after infection, behavioral testing was performed for cognitive functional estimation. Mice were given another 5 weeks to breed, then brain and mandibular bone specimens were obtained. The level of periodontitis was determined using mandibular bone micro-CT analysis, while the levels of Aβ, IL-1β, and TNF-α in the brain were measured using an ELISA kit, and brain Aβ accumulation was assessed by immunostaining.
Result: P. gingivalis infected-APP-Tg mice showed significant bone resorption as compared to the non-infected control mice. Interestingly, we found that the infected mice also had reduced cognitive function as compared to the controls. Furthermore, areas of Aβ accumulation and the levels of Aβ in the hippocampus (test vs. control: 307.1 vs. 209.8 ng/mg of protein), and IL-1β (17.5 vs. 14.3 pg/mL) and TNF-α (60.2 vs 57.3 pg/mL) in the brain were significantly increased in the infected mice (p<0.01, p<0.01, p<0.01, and p<0.05, respectively).
Conclusion: Our findings suggest a possible relationship of periodontal disease with AD progression.