Melatonin Alleviates Periodontitis by Suppressing Neutrophil Extracellular Traps–Dependent Neutrophil Recruitment

ABSTRACT Aim To investigate the impact of neutrophil extracellular traps (NETs) on periodontitis and the regulatory mechanisms by which melatonin alleviates the disease. Materials and Methods The expression of NET markers in periodontitis tissues was detected using multiple immunohistochemical staining. The effect of NETs on periodontitis was explored through in vivo and in vitro experiments. qPCR and transwell migration assay were used to assess neutrophil activation and recruitment. Flow cytometry, micro‐CT and histological staining were employed to evaluate neutrophil recruitment in gingiva and periodontitis progression in a ligature‐induced periodontitis (LIP) mouse model. Melatonin was then administered in vivo and in vitro to evaluate its effects on NET formation, neutrophil activation, neutrophil recruitment and periodontitis progression. Finally, Western blotting and qPCR were employed to elucidate the mechanisms underlying melatonin‐mediated regulation of NET formation. Results NETs were evident in gingival tissues from patients with periodontitis. After inhibiting NET formation, the expression levels of inflammatory cytokines (Il‐1β, Il‐6, Tnf‐α), neutrophil chemokines (Ccl2, Ccl4, Cxcl1) and neutrophil recruitment were found to decrease. Furthermore, melatonin treatment reduced NET formation, decreased neutrophil activation and recruitment and alleviated bone resorption in LIP mice. Mechanistically, melatonin suppresses NET formation through the NF‐κB signalling pathway. Conclusions Melatonin decreases neutrophil recruitment by suppressing NET formation, exerting a protective effect in periodontitis.