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Intracellular signaling complexes of the innate immune system orchestrate the development of inflammation. Porphyromonas gingivalis is a commensal bacterium that induces periodontal pyroptosis. The transcription factor Dec1 can regulate the expression of inflammatory molecules. In this study, we investigated whether a deficiency of Dec1 activates/represses Caspase-1 and/or Gasdermin-D in periodontal pyroptosis, resulting in the release of the proinflammatory mediator interleukin-1β. Dec1 expression in human periodontal ligament fibroblasts (HPDLFs) treated with P. gingivalis lipopolysaccharide (LPS) was assessed and pyroptosis activation was determined by microscopy, qRT-PCR and Western blot analysis. Moreover, a siRNA targeting Dec1 was introduced into HPDLFs to determine the function of Dec1 in periodontal pyroptosis and a Dec1-deficient experimental mouse model of periodontitis was used. Treatment of HPDLFs with P. gingivalis LPS-stimulated levels of cleaved-Caspase-1 and cleaved-GSDMD and increased levels of phosphorylated NF-κB and interleukin-1β. In contrast, Dec1 knockdown maintained cellular homeostasis with low levels of pyroptosis. Treatment with P. gingivalis alleviated periodontal pyroptosis in PDLFs of wild-type mice and a Dec1 deficiency subsequently repressed the inflammatory effect of P. gingivalis. These results reveal for the first time the novel function of Dec1 in periodontal pyroptosis, suggesting that Dec1 is a crucial target to prevent periodontal inflammation. [ABSTRACT FROM AUTHOR]