Increases in IL-33 production by fimbriae and lipopeptide from Porphyromonas gingivalis in mouse bone marrow-derived dendritic cells via toll-like receptor 2

Interleukin-33 (IL-33) is an IL-1 cytokine family member that is involved in the development of chronic inflammatory diseases and the initiation of allergic inflammation in response to pathogens. Porphyromonas gingivalis is a primary pathogen that is involved in chronic periodontitis and its bacterial components induce inflammatory responses. Dendritic cells (DCs) recognize pathogenassociated molecular patterns by expression of pattern-recognition receptors, such as Toll-like receptors (TLRs). DCs play an essential role in resistance to infection and maintenance of mucosal immune system. In this study, we investigated whether P. gingivalis increases the expression of IL-33 in mouse bone marrow-derived DCs (BMDCs). BMDCs exhibited an increased expression of IL-33 mRNA upon stimulation with P. gingivalis whole cells. Furthermore, fimbriae and lipopeptide derived from P. gingivalis exhibited higher IL-33 mRNA expression than P. gingivalis whole cells. In contrast, lipopolysaccharide derived from P. gingivalis did not induce IL-33 mRNA expression in BMDCs. The IL-33 mRNA expression after stimulation with fimbriae or lipopeptide was up-regulated in BMDCs from wild-type mice but not from TLR2-deficient (TLR2^-/-) mice. IL-33 production induced by fimbriae and lipopeptide accumulated in the cytoplasm of BMDCs from wild-type mice, but not from TLR2^-/- mice. These findings suggested that IL-33 production induced by P. gingivalis fimbriae and lipopeptide is recognized by TLR2 and may modulate DC function in periodontal diseases.