CD300lf Regulates Neutrophil Aging and Periodontal Immune Homeostasis.

Immune alterations, such as neutrophil dysfunction, significantly affect the progression and outcome of periodontitis, a prevalent inflammatory disease. Despite this, the molecular mechanisms driving neutrophil dysregulation in periodontitis remain poorly understood. In this study, we demonstrate that CD300lf, a critical immune regulator, is markedly downregulated in neutrophils from a periodontitis mouse model and human patients. The loss of CD300lf accelerates neutrophil aging, as evidenced by increased reactive oxygen species production, the senescence-associated secretory phenotype with elevated IL-1β and S100A8/A9 levels, and heightened neutrophil extracellular trap formation. Mechanistically, CD300lf deficiency leads to MyD88 upregulation, indicating a shift toward a proinflammatory state. Inhibition of MyD88 effectively reduces periodontal inflammation in CD300lf-deficient mice. Furthermore, targeting CD300lf with its known ligand ceramide alleviates periodontitis and mitigates the aging phenotype of neutrophils. These findings underscore the critical role of the CD300lf/MyD88 axis in neutrophil homeostasis and suggest that modulation of CD300lf through ceramide presents a promising therapeutic strategy for periodontitis.