ENTR1 regulates periodontitis by modulating macrophage M1 polarization via AMPK activation

Aims: Periodontitis is a chronic inflammatory disorder arising from an imbalance between oral microbiota and the host's immune response, with macrophages as pivotal targets for prevention and treatment. Endosomeassociated Trafficking Regulator 1 (ENTR1) is indispensable for protein trafficking and implant osseointegration. However, its specific role in periodontitis has yet to be clarified. This research seeks to explore the effects of ENTR1 on macrophage polarization, elucidate its mechanisms, and evaluate its regulatory functions in the regeneration of periodontal tissues. Materials and methods: A ligature-induced periodontitis mouse model was established to investigate the correlation between macrophage polarization markers and ENTR1 expression. Techniques including qRT-PCR, Western blot, ELISA, flow cytometry, and immunofluorescence staining were utilized to evaluate the impact of ENTR1 on macrophage polarization under inflammatory stimuli. Micro-CT and histological staining were applied to assess periodontal bone resorption. The interaction between ENTR1 and AMP-activated protein kinase (AMPK) was explored through Western blot and co-immunoprecipitation, further validated by applying the AMPK inhibitor Compound C (CpC). Key findings: ENTR1 expression was down-regulated in the mice with periodontitis relative to healthy controls. Overexpressing ENTR1 suppressed macrophage M1 polarization and mitigated bone loss in periodontitis, while knocking down ENTR1 exacerbated these effects. ENTR1 directly interacted with AMPK, enhancing its phosphorylation. Furthermore, the inhibitory impact of ENTR1 on macrophage M1 polarization and inflammationinduced alveolar bone resorption were partially attenuated by CpC treatment. Significance: ENTR1 regulates periodontitis by suppressing macrophage M1 polarization through enhancing AMPK phosphorylation, presenting a promising therapeutic target for its prevention and management.