This study strongly demonstrated the critical role of microglia in neuroinflammation and neurodegeneration during P. gingivalis infection and pointed out that IL-8 released from stimulated microglia and astrocytes is the major neurotoxic cytokine in P. gingivalis infection, which contributes to the understanding of the role of the mouth-brain axis in AD. Here, CXCL8 is linked to Alzheimer disease.