The Effects Of Porphyromonas Gingivalis Periodontal Infection On The Cognitive Function Of Mice

Objective:Periodontal disease is a common oral chronic infectious disease mainly caused by bacterial plague.Induced damage grows from impairment on periodontal tissue to tooth loss,making periodontal disease the main pathogenic factor for tooth loss.Cognitive impairment is the cardinal symptom of Alzheimer's disease.With intensifying aging of the global population,the world is facing an increasing incidence of Alzheimer's disease.According to the recent researches,close connection between periodontal disease and systemic diseases including those related with central nervous system.But the correlation between periodontal disease and age-dependent cognitive dysfunction as well as their mechanism hasn't been clarified.In this experiment,it is mainly investigated whether P.gingivalis periodontal infection could cause cognitive dysfunction by causing age-related neuroinflammation in mice.Method:1.Thirty 4-week-old(young)female C57BL/6J mice were randomly divided into two groups,the control group and the experimental group.Thirty 12-month-old(middle-aged)were grouped as above.The mouth of the mice in the experimental group was infected with P.gingivalis.2.Morris water maze was performed to assess the learning and memory ability of mice.3.The expression levels of the pro-inflammatory cytokines TNF-?,IL-6,and IL-1? in the mice brain tissues were determined by immunohistochemistry.4.The expression levels of the pro-inflammatory cytokines TNF-?,IL-6,and IL-1? in the mice brain tissues were determined by ELISA.5.The m RNA expression levels of the pro-inflammatory cytokines TNF-?,IL-6,and IL-1? in the mice brain tissues were determined by q RT-PCR.Results:1.Both young P.gingivalis infected and control mice progressively saw a decreasing trend on the time of finding the platform,with the difference being more obvious on day 4 when compared to day 1.The escape latency of the middle-aged mice control group was gradually reduced,especially on day 4 compared to day 1.The escape latency of middle-aged P.gingivalis infected mice was not significantly reduced during the 4 successive days.There was no significant effect in the escape latency between the young P.gingivalis infected and the control mice on the same day.The escape latency of the middle-aged P. gingivalis infected mice was statistically different from the control group on day 2,day 3 and day 4.2.No significant variations in the number of crossing times were observed between the young P.gingivalis infected and the control mice.As for the middle-aged mice,the P.gingivalis infected mice crossed the area where the platform had been located less times than the control group.3.No significant effect on the m RNA levels of TNF-?,IL-6,IL-1? in the young mice group was observed.The m RNA expression levels of TNF-?,IL-6,IL-1? in the brain tissues of the middle-aged P.gingivalis infected mice was increased,in comparison to the control group.4.The levels of pro-inflammatory cytokines TNF-?,IL-6,and IL-1?were significantly higher in middle-aged P.gingivalis infected mice than in control mice.In contrast,the levels of TNF-?,IL-6,and IL-1?did not witness obvious deifferences within the young mice groups.Conclusion:Porphyromonas gingivalis periodontal infection may cause cognitive impairment via age-dependent neuroinflammation in mice.