Although periodontal infection does affect the concentration of hs-CRP and IL-6 in serum, a subgroup of patients exist who are highly susceptible to an increased risk of CHD associated with periodontitis, suggesting that there may be subjects who have an elevated risk of CHD independent of susceptibility to periodontal tissue destruction per se.

SummaryThe balance between inflammatory mediators and their counter-regulatory molecules may be crucial for determining the outcome of immune pathology of periodontal diseases. Based on clinical and immunological findings, the immune response in stable gingivitis lesion is supposed to be in balance, whereas the response is skewed towards the predominance of proinflammatory reactivity in progressive periodontitis lesion. However, this hypothesis has not been verified. Therefore, the aim of this study was to compare the gene expression profile of inflammatory mediators including proinflammatory cytokines and other inflammatory molecules, and anti-inflammatory cytokines by using quantitative real-time polymerase chain reaction in gingivitis and periodontitis lesions showing distinct clinical entities. For inflammatory mediators, interleukin (IL)-1β β β β , interferon (IFN)-γ γ γ γ and receptor activator of nuclear factor (NF)-κ κ κ κ B ligand tended to be higher in periodontitis, whereas tumour necrosis factor (TNF)-α α α α and IL-12 p40 showed no difference. Heat-shock protein 60 (HSP60) expression was up-regulated significantly in periodontitis. For anti-inflammatory cytokines, transforming growth factor (TGF)-β β β β 1 expression tended to be higher in periodontitis compared with gingivitis, whereas no difference was observed for IL-10 and IL-4. These findings support further our previous finding that autoimmune response to HSP60 may exert in periodontitis lesion, and suggest that perhaps subtle differences in the balance of cytokines may result in different disease expression.

Increasing evidence suggests that distinct inflammatory cytokines convert forkhead box protein P3 (FOXP3(+)) regulatory T-cells (Tregs) into IL-17-producing cells (Th17 cells) in vitro. However, this functional plasticity has not been examined in the pathogenesis of periodontal disease. In this study, we analyzed the IL-17A(+)FOXP3(+) cells present in periodontitis lesions to determine the association between Treg conversion and the pathogenesis of periodontitis. The immunohistochemical analysis of gingival tissues demonstrated that the numbers of Th17 cells (IL-17A(+)FOXP3(-)) and Tregs (IL-17A(-)FOXP3(+)) were greater in periodontitis lesions than in gingivitis lesions. We further identified a small number of IL-17A(+)FOXP3(+) cells in periodontitis lesions but not in gingivitis lesions. The flow cytometry analysis of CD4(+) T-cell lines established from gingival tissues and the peripheral blood of periodontitis patients showed that the proportion of Tregs was reduced and the proportion of IL-17A(+)FOXP3(+) cells among all FOXP3(+) cells was elevated in gingival tissue T-cell lines relative to the proportions in peripheral blood T-cell lines. Our findings indicate that Treg-Th17 conversion may occur in periodontitis lesions. Further studies addressing the role of Treg conversion during inflammatory responses against periodontopathic bacteria are needed.

SummarySeveral reports have demonstrated a possible association of periodontal infections with coronary heart disease (CHD) by elevated antibody titre to periodontopathic bacteria in CHD patients compared with non-diseased controls. Although each periodontopathic bacterium may vary in virulence for periodontitis and atherosclerosis, antibody response to multiple bacteria in CHD patients has not been understood fully. Therefore, serum levels of antibody to 12 periodontopathic bacteria together with other atherosclerotic risk markers were compared among 51 patients with CHD, 55 patients with moderate to severe chronic periodontitis and 37 healthy individuals. The antibody response was the most prevalent for Porphyromonas gingivalis, a major causative organism, in CHD as well as periodontitis patients. However, antibody positivity was different between CHD and periodontitis if the response was analysed for two different strains of P. gingivalis, namely FDC381 and Su63. While periodontitis patients were positive for both P. gingivalis FDC381 and Su63, a high frequency of antibody positivity for P. gingivalis Su63 but not for FDC381 was observed in CHD patients. The results indicate that the presence of particular periodontopathic bacteria with high virulence may affect atherogenesis. Identifying the virulence factors of P. gingivalis Su63 may gain insight into the new therapeutic modality for infection-induced deterioration of atherosclerosis.

This is the first study to show that a variety of TLRs are up-regulated in periodontitis lesions compared with gingivitis lesions, suggesting that diverse microbial and possibly viral antigens are involved in the pathogenic mechanisms for periodontal diseases. However, the ligands recognized by the various TLRs in periodontal lesions remain to be determined.

The function of T cells infiltrating periodontitis lesions is complex and has not been fully elucidated. Here, we established T-cell clones from the gingival tissues of periodontitis patients and examined their gene expression. A total of 57 and 101 T-cell clones were established by means of immobilized anti-CD3 antibody and IL-2 from gingival tissues and peripheral blood, respectively. The gingival T-cell clones were derived from three patients, and the peripheral blood T-cell clones from two of these patients and a further patient whose gingival T-cell clones were not established. Gingival tissues were also obtained from a further 19 periodontitis patients. The expression of cytokines and molecules related to both regulatory function and tissue destruction were examined by means of reverse-transcription polymerase chain reaction. All the gingival T-cell clones expressed mRNA for TGF-beta1, CTLA-4, and CD25, and all the T-cell clones from peripheral blood expressed IFN-gamma and TGF-beta1 mRNAs. Most but not all the T-cell clones from gingival tissues and peripheral blood expressed mRNA for IFN-gamma and, CD25 and CTLA-4, respectively. The frequency of T-cell clones and gingival tissues expressing FOXP3, a possible master gene for mouse CD4(+)CD25(+) regulatory T cells, was very high (97%, 93%, and 100% for gingival T-cell clones, peripheral blood T-cell clones, and gingival tissues, respectively). Whereas the frequency of IL-4-expressing T-cell clones was lower for gingival T-cell clones (70% vs. 87%), the frequency of the gingival T-cell clones expressing IL-10 and IL-17 was higher than peripheral blood T-cell clones (75% vs. 62% for IL-10, 51% vs. 11% for IL-17). A similar expression profile was observed for gingival T-cell clones compared with gingival tissue samples with the exception of IL-4 expression, where the frequency of positive samples was lower in the gingival tissues (70% vs. 11%). These results suggest that the individual T cells infiltrating gingival lesions can express mRNA for both Th1 and Th2 cytokines as well as regulatory cytokines simultaneously.

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Our study makes it evident that most, if not all, of the FOXP3(+) T cells in periodontitis lesions can be considered to be effector T cells. The effector activity of the gingival T-cell clones could be attributable to the low level of membrane CD25 expression. Further studies are clearly needed to clarify the role of these T cells and their unique characteristics in the pathogenesis of periodontal disease.