BACKGROUND A possible relationship between periodontitis and Alzheimer's disease (AD) has been reported. However, there is limited information on the association between the Porphyromonas gingivalis (P. gingivalis) periodontal infection and the pathological features of AD. The hypothesis that P. gingivalis periodontal infection may cause cognitive impairment via age-dependent neuroinflammation was tested. RESULTS Thirty 4-week-old (young) female C57BL/6 J 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. Morris water maze(MWM) was performed to assess the learning and memory ability of mice after 6 weeks. Moreover, the expression levels of the pro-inflammatory cytokines TNF-α, IL-6, and IL-1β in the mice brain tissues were determined by Quantitative real-time polymerase chain reaction (qRT-PCR), Enzyme Linked Immunosorbent Assay(ELISA) and immunohistochemistry. Our results showed that the learning and memory abilities of the middle-aged P. gingivalis infected mice were impaired. Moreover, the expression levels of the pro-inflammatory cytokines TNF-α, IL-6, and IL-1β in the brain tissues of the middle-aged P. gingivalis infected mice were increased. CONCLUSIONS These results suggest that P. gingivalis periodontal infection may cause cognitive impairment via the release of the pro-inflammatory cytokines TNF-α, IL-6, and IL-1β in the brain tissues of middle-aged mice.

中文翻译：

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牙龈卟啉单胞菌是一种引起牙周炎的细菌，可在小鼠中诱发记忆障碍和年龄依赖性神经炎症。

背景已经报道了牙周炎和阿尔茨海默病(AD)之间的可能关系。然而，关于牙龈卟啉单胞菌（P. gingivalis）牙周感染与 AD 病理特征之间关联的信息有限。检验了牙龈卟啉单胞菌牙周感染可能通过年龄依赖性神经炎症引起认知障碍的假设。结果 30只4周龄(幼)雌性C57BL/6 J小鼠随机分为对照组和实验组两组。三十个 12 个月大（中年）按上述分组。实验组小鼠口腔感染了牙龈卟啉单胞菌。6周后进行Morris水迷宫(MWM)评估小鼠的学习记忆能力。而且，采用定量实时聚合酶链反应（qRT-PCR）、酶联免疫吸附试验（ELISA）和免疫组织化学。我们的研究结果表明，中年感染牙龈卟啉单胞菌的小鼠的学习和记忆能力受损。此外，中年牙龈卟啉菌感染小鼠脑组织中促炎细胞因子TNF-α、IL-6和IL-1β的表达水平升高。结论 这些结果表明，牙龈卟啉单胞菌牙周感染可能通过中年小鼠脑组织中促炎细胞因子TNF-α、IL-6和IL-1β的释放引起认知障碍。通过定量实时聚合酶链反应（qRT-PCR）、酶联免疫吸附试验（ELISA）和免疫组织化学测定小鼠脑组织中的IL-1β和IL-1β。我们的研究结果表明，中年感染牙龈卟啉单胞菌的小鼠的学习和记忆能力受损。此外，中年牙龈卟啉菌感染小鼠脑组织中促炎细胞因子TNF-α、IL-6和IL-1β的表达水平升高。结论 这些结果表明，牙龈卟啉单胞菌牙周感染可能通过中年小鼠脑组织中促炎细胞因子TNF-α、IL-6和IL-1β的释放引起认知障碍。通过定量实时聚合酶链反应（qRT-PCR）、酶联免疫吸附试验（ELISA）和免疫组织化学测定小鼠脑组织中的IL-1β和IL-1β。我们的研究结果表明，中年感染牙龈卟啉单胞菌的小鼠的学习和记忆能力受损。此外，中年牙龈卟啉菌感染小鼠脑组织中促炎细胞因子TNF-α、IL-6和IL-1β的表达水平升高。结论 这些结果表明，牙龈卟啉单胞菌牙周感染可能通过中年小鼠脑组织中促炎细胞因子TNF-α、IL-6和IL-1β的释放引起认知障碍。我们的研究结果表明，中年感染牙龈卟啉单胞菌的小鼠的学习和记忆能力受损。此外，中年牙龈卟啉菌感染小鼠脑组织中促炎细胞因子TNF-α、IL-6和IL-1β的表达水平升高。结论 这些结果表明，牙龈卟啉单胞菌牙周感染可能通过中年小鼠脑组织中促炎细胞因子TNF-α、IL-6和IL-1β的释放引起认知障碍。我们的研究结果表明，中年感染牙龈卟啉单胞菌的小鼠的学习和记忆能力受损。此外，中年牙龈卟啉菌感染小鼠脑组织中促炎细胞因子TNF-α、IL-6和IL-1β的表达水平升高。结论 这些结果表明，牙龈卟啉单胞菌牙周感染可能通过中年小鼠脑组织中促炎细胞因子TNF-α、IL-6和IL-1β的释放引起认知障碍。