刷牙和老年痴呆看似两个风马牛不相及的事情，实际上它们之间有很紧密的关联，洁净的牙齿可预防老年痴呆的发生是真的，呵呵。近日，Science Advance期刊发表了题名为“Porphyromonas gingivalis in Alzheimer's disease brains: Evidence for disease causation and treatment with small-molecule inhibitors”文章，研究发现牙龈疾病与阿尔茨海默病之间存在关联，科学家从阿尔茨海默病的病人大脑中发现了牙龈素，说明导致牙龈炎的细菌（牙龈卟啉菌）可从移动到大脑，其产生的蛋白质可破坏大脑的神经细胞，导致阿尔茨海默氏症的发生。因此，刷牙有助于预防阿尔兹海默症的发生（文章原文见：https://advances.sciencemag.org/content/5/1/eaau3333/tab-pdf）。

Porphyromonas gingivalis, the keystone pathogen in chronic periodontitis, was identified in the brain of Alzheimer’s disease patients. Toxic proteases from the bacterium called gingipains were also identified in the brain of Alzheimer’s patients, and levels correlated with tau and ubiquitin pathology. Oral P. gingivalis infection in mice resulted in Ab_1-42, a component of amyloid plaques. Further, gingipains were b brain colonization and increased production of A neurotoxic in vivo and in vitro, exerting detrimental effects on tau, a protein needed for normal neuronal function. To block this neurotoxicity, we designed and synthesized small-molecule inhibitors targeting gingipains. Ab_1-42 production, b Gingipain inhibition reduced the bacterial load of an established P. gingivalis brain infection, blocked A reduced neuroinflammation, and rescued neurons in the hippocampus. These data suggest that gingipain inhibitors could be valuable for treating P. gingivalis brain colonization and neurodegeneration in Alzheimer’s disease.