Neutrophil extracellular traps aggravate periodontitis by disturbing regulatory T-cell differentiation

Excessive neutrophil extracellular traps (NETs) induce an intense inflammatory response in periodontitis. Recently, Tregs were shown to be essential for attenuating inflammation-driven bone resorption. However, the regulation of Tregs differentiation by NETs in periodontitis is still unclear and needs further investigation. In this study, a murine experimental periodontitis model was established either without or with NETs depletion via DNase I. Firstly, we revealed that NETs accumulated significantly in both periodontal tissues and sera of mice models with periodontitis, while the depletion of NETs alleviated alveolar bone resorption. Moreover, RNA sequencing and bioinformatics analysis revealed that NETs depletion regulated the immune response of gingival tissue, especially affecting T-cell differentiation, and identified potential regulatory pathways. Subsequently, we verified that inhibition of NETs promoted the infiltration of Tregs and increased expression levels of IL-10 and TGF-β in periodontal tissue. Furthermore, in vitro studies demonstrated that NETs produced by P. g-LPS-stimulated neutrophils impeded the differentiation of co-cultured naive CD4⁺ T cells into Tregs, which could be restored by DNase I-mediated digestion of NETs. In conclusion, excessive NETs could exacerbate alveolar bone resorption in periodontitis by interfering with the differentiation of Tregs, and DNase I provides a novel targeted strategy for the immunotherapy of periodontitis.