Porphyromonas gingivalis67-kDa fimbriae induced cytokine production and osteoclast differentiation utilizing TLR2

Abstract

Porphyromonas gingivalis, a major etiological agent of adult periodontitis, has two distinctly different types of fimbriae on the cell surface. The major fimbriae, which consist of a 41-kDa fimbrillin of P. gingivalis ATCC 33277, have been known to induce inflammatory cytokine production in murine peritoneal macrophages. In this study, we examined the effects of the minor fimbriae of P. gingivalis, composed of a 67-kDa fimbrillin, on cytokine production in murine peritoneal macrophages and the ability to induce osteoclast differentiation. Murine peritoneal macrophages were stimulated with P. gingivalis 67-kDa minor fimbriae for 24 h, then the levels of interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha and IL-6 production were determined by enzyme-linked immunosorbent assay (ELISA). To estimate osteoclast differentiation, mouse osteoclast precursors were placed on dentine slices, and cultured with or without P. gingivalis 67-kDa minor fimbriae for 7 days. P. gingivalis 67-kDa minor fimbriae clearly induced IL-1beta, TNF-alpha and IL-6 production in mouse macrophages. Furthermore, pit formations on the dentine slices were significantly extended when the osteoclast precursors were incubated with P. gingivalis 67-kDa minor fimbriae. Pretreatment with anti-Toll-like receptor 2 (TLR2) antibody significantly inhibited IL-1beta, TNF-alpha and IL-6 induction (P<0.05) in mouse macrophages and pit-forming activity of osteoclast precursor cells stimulated with P. gingivalis 67-kDa minor fimbriae. These results suggest that P. gingivalis 67-kDa minor fimbriae may provoke host inflammatory response and be involved in periodontal tissue breakdown.

Inflammatory osteolysis: a conspiracy against bone

“…Alveolar bone loss elicited by Porphyromonas gingivalis shares many features of lysis attending OM. Cytokine release (166) as well as induction of RANKL downstream of TLR2 and NOD2 are the prominent pathways leading to osteoclast activation in periodontitis (167,168). IL-17 is also markedly increased in periodontitis and appears to be an important factor in both inflammation and osteolysis of the periodontal tissue (169).…”

Bacterial Fimbriae Stimulate Proinflammatory Activation in the Endothelium through Distinct TLRs

“…The major (41-kDa) and minor (67-kDa) fimbriae are distinct types of fimbriae expressed simultaneously by this organism (14,15). The minor fimbriae of P. gingivalis has been reported to induce TNF (TNF-␣), IL-1␤, and IL-6 production in human monocytic cell lines and murine peritoneal macrophages (16,17), although the receptors required for this response have not been defined. The major fimbriae of P. gingivalis are composed of a single subunit protein (fimbrillin), which shares no amino acid sequence homology with any other type of fimbriae (18), and has been shown to be required for adhesion and invasion of fibroblasts and endothelial cells (19 -21).…”

Porphyromonas gingivalis Minor Fimbriae Are Required for Cell-Cell Interactions

“…Furthermore, major fimbriae interrupt the host immune system by inducing human peripheral macrophages and neutrophils to overproduce several proinflammatory cytokines such as interleukin-1 (IL-l), IL-6, and tumor necrosis factor alpha (12,13). Although the role of minor fimbriae in P. gingivalis virulence is less well understood, Hiramine et al (6) have shown that the 67-kDa fimbrial protein induces IL-1␣, IL-1␤, and tumor necrosis factor alpha expression in mouse peritoneal macrophages, suggesting their possible involvement in the inflammatory response during the development of periodontal disease. Recent research has shown that minor fimbriae are necessary for the development of P. gingivalis biofilms on streptococcal substrates (7).…”