Tomoyuki Honda

Balance of inflammatory response in stable gingivitis and progressive periodontitis lesions

The 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, interferon (IFN)‐γ and receptor activator of nuclear factor (NF)‐κB ligand tended to be higher in periodontitis, whereas tumour necrosis factor (TNF)‐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)‐β1 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.

Relationship of periodontal infection to serum antibody levels to periodontopathic bacteria and inflammatory markers in periodontitis patients with coronary heart disease

Several 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.

Elevated expression of IL-17 and IL-12 genes in chronic inflammatory periodontal disease

BACKGROUND A number of different theories have been postulated to explain the progression of gingivitis to periodontitis in the context of the Th1/Th2 paradigm. However, no consistent results have been obtained. Th17, a new T-cell subset producing IL-17, which is implicated in many aspect of inflammatory tissue destruction, overcomes many of the discrepant findings in the studies related to the Th1/Th2 hypothesis. We compared the gene expression profile of Th17-related molecules in gingivitis and periodontitis lesions showing distinct clinical entities. METHODS Gingival tissue samples were obtained from 23 gingivitis and 24 periodontitis tissues. The gene expression was measured by using quantitative real-time PCR for IL-17A, IL-17F, CCR4, CCR6, IL-12 p35 and IL-23 p19. The difference of gene expressions between gingivitis and periodontitis was analyzed by Mann-Whitney U-test. Correlations between each gene expression were also analyzed. RESULTS The expression level of IL-17A was higher than that of IL-17F and a significant difference in expression between gingivitis and periodontitis was observed only for IL-17A. CCR4 and CCR6 tended to be higher in periodontitis compared with gingivitis, although the differences were not statistically significant. Whereas the gene expression of IL-12 p35 was significantly higher in periodontitis compared with gingivitis, that of IL-23 p19 was not different between the two diseases. CONCLUSION This study demonstrates the elevated expression of IL-17 and IL-12 in periodontitis, i.e., the tissue destruction form of periodontal diseases, as compared with gingivitis, and provides new insight into the T-cell mediated immunopathogenesis of periodontal disease.

The Presence of IL-17+/FOXP3+ Double-positive Cells in Periodontitis

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.

Characterization of CD4+ FOXP3+ T-cell clones established from chronic inflammatory lesions.

INTRODUCTION Our previous study demonstrated that the gene expression of FOXP3, a characteristic marker for CD4(+) CD25(+) regulatory T cells in mice, is upregulated more in periodontitis than in gingivitis at the messenger RNA (mRNA) level. Furthermore, most of the T-cell clones established from periodontitis lesions expressed FOXP3 mRNA. However, role of the FOXP3(+) gingival T cells has not been elucidated. METHODS The phenotype of FOXP3-expressing cells in periodontitis lesions was determined immunohistochemically. CD4(+) FOXP3(+) gingival T-cell clones were established from three patients with advanced periodontitis by using immunomagnetic beads. Gene expression and phenotype analyses were performed by reverse-transcription polymerase chain reactions and flow cytometry, respectively. The effect of CD4(+) FOXP3(+) T-cell clones on the proliferative response of CD4(+) CD25(-) T cells was examined by [(3)H]thymidine incorporation. RESULTS FOXP3 expression was found in some CD4(+) T cells and CD25(+) cells but not in CD8(+) T cells by immunohistochemistry. In spite of a substantial expression of the CD25 gene, the expression level of membrane CD25 on the CD4(+) FOXP3(+) gingival T-cell clones was low. While peripheral blood CD4(+) CD25(+) FOXP3(+) cells suppressed the proliferation of CD4(+) CD25(-) T cells, the CD4(+) CD25(low) FOXP3(+) gingival T-cell clones enhanced the proliferation significantly. CONCLUSION 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.

Early and preferential induction of IL-1 receptor-associated kinase-M in THP-1 cells by LPS derived from Porphyromonas gingivalis

LPS of Porphyromonas gingivalis (P. gingivalis) is suggested to be a virulence factor in periodontitis, stimulating host cells to produce proinflammatory mediators. However, P. gingivalis LPS has been reported to show lower biological activity compared with Escherichia coli (E. coli) LPS. Although differences in the chemical structure of lipid A and the receptor conferring LPS signaling are thought to account for these characteristics, the precise reason is unknown. Here, we demonstrate that P. gingivalis LPS up‐regulates IL‐1R‐associated kinase (IRAK)‐M, a negative regulator of the TLR signaling pathway, in a THP‐1‐derived macrophage more robustly than E. coli LPS. Although down‐regulation of IRAK‐M by small interfering (si)RNA augmented transcription and translation of TNF‐α, IL‐6, and IL‐12 p40 in LPS‐stimulated macrophages, the effect of siRNA was more prominent in P. gingivalis LPS‐stimulated cells. Degradation of IRAK‐1 was more obvious in E. coli LPS‐stimulated macrophages than the cells stimulated with P. gingivalis LPS, suggesting that P. gingivalis LPS‐induced IRAK‐M suppressed dissociation of IRAK‐1 from the receptor complex, resulting in escape from subsequent degradation. This activity may be involved in the chronic infection of this bacterium in periodontal tissue by serving as an escape mechanism from immune surveillance.

Effect of periodontal treatment on the serum antibody levels to heat shock proteins

We have shown previously that both humoral and cellular immune responses to heat shock protein 60 (HSP60) are elevated in chronic periodontitis patients compared with non‐diseased subjects. The aim of the present study was to determine whether periodontal treatment could influence the level of serum antibodies to human HSP60 and Porphyromonas gingivalis GroEL, a bacterial homologue of human HSP60. Sera were obtained from 21 patients with moderate to advanced chronic periodontitis at the baseline examination and again after completion of treatment. Antibody levels were determined using an enzyme‐linked immunosorbent assay. The mean anti‐P. gingivalis GroEL antibody levels were down‐regulated significantly by periodontal treatment when recombinant P. gingivalis GroEL was used as an antigen, whereas antibody levels to P. gingivalis GroEL‐specific peptide were significantly elevated following successful periodontal therapy. The mean level of anti‐human HSP60 antibody remained unchanged although individual levels of antibody either increased or decreased after periodontal treatment, suggesting that synthesis of these antibodies might be regulated independently during the course of periodontal infection. Although their regulatory mechanisms in chronic infection are not understood, further study would provide insight not only into the role of these antibodies in the pathogenesis of periodontitis but also into the possible link between periodontitis and systemic diseases such as coronary heart disease.

Up-regulation of the endoplasmic reticulum stress-response in periodontal disease.

BACKGROUND Endoplasmic reticulum (ER) stress is the cell response by activation of the unfolded protein response (UPR) pathway in a variety of conditions such as infection and aging. The UPR may be associated with the pathogenesis of periodontal disease because of the induction of apoptosis and activation of nuclear factor-kappaB (NF-kappaB), a transcription factor for pro-inflammatory cytokines. However, the relationship between ER stress and periodontal disease is yet to be determined. METHODS The expression of UPR-related molecules was analyzed by real-time polymerase chain reaction and immunohistochemistry, respectively and compared between gingivitis and periodontitis. The gene expressions were also analyzed for macrophages stimulated with lipopolysaccharides (LPS) from Escherichia coli (E. coli), and Porphyromonas gingivalis (P. gingivalis) or IFN-gamma. RESULTS The expression levels of UPR-related genes and HSP60 were significantly higher in periodontitis compared with gingivitis lesions. However, LPS from P. gingivalis but not E. coli or IFN-gamma failed to up-regulate the gene expression in macrophage. CONCLUSIONS An inflammatory response may have profound effect on the UPR response, particularly in periodontitis patients. Considering the histological nature of periodontitis and the link between UPR and inflammatory responses via NF-kappaB, ER stress in B cells could be another pathological mechanism underlying periodontal disease.

Porphyromonas gingivalis antigens and interleukin-6 stimulate the production of monocyte chemoattractant protein-1 via the upregulation of early growth response-1 transcription in human coronary artery endothelial cells.

Background: Individuals with periodontitis have elevated serum levels of IL-6 and C-reactive protein and have been reported to have a significantly increased risk of developing cardiovascular disease. The transcription factor early growth response factor 1 (Egr-1) has been shown to play an important role in the development and progression of atherosclerosis. However, it is not known whether periodontal infection affects the expression of Egr-1 and subsequent endothelial cells expression of monocyte chemoattractant protein (MCP)-1, a key molecule of leukocyte chemoattraction into vessels. Methods: Human coronary artery endothelial cells (HCAECs) were stimulated with either sonicated extracts from Porphyromonas gingivalis strains 381 or SU63, or a combination of IL-6 and soluble IL-6 receptor (IL-6/sIL-6R). The expression of Egr-1, and subsequently MCP-1, was then analyzed. The role of Egr-1 on MCP-1 expression was analyzed by siRNA transfection. Results: Both P. gingivalis antigens and IL-6/sIL-6R stimulations upregulated the expression of Egr-1, with a more robust effect by IL-6/sIL-6R. Increased expression of Egr-1 coincided with MCP-1 production, and Egr-1 downregulation by siRNA suppressed this effect. Conclusion: These results clearly suggest that periodontal infection has the potential to affect HCAECs and hence contribute to the development of subsequent atherosclerosis.

Endoplasmic reticulum stress response and bone loss in experimental periodontitis in mice.

BACKGROUND AND OBJECTIVE Endoplasmic reticulum (ER) stress is the cell response that activates the unfolded protein response (UPR) pathway in a variety of conditions, such as inflammation and bone metabolism. The UPR may be associated with the pathogenesis of periodontal disease because the disease is inflammatory in nature, and alveolar bone resorption is a characteristic feature of the disease. However, the relationship between ER stress and alveolar bone resorption observed in periodontal disease remains elusive. MATERIAL AND METHODS C57BL/6 mice were orally administered Porphyromonas gingivalis, a representative periodontopathic bacterium, in the presence or absence of a chemical chaperone, 4-phenylbutyrate (4-PBA). The gene expression of UPR-related molecules and cytokines in gingival tissues were analyzed using real-time polymerase chain reaction, and alveolar bone resorption and osteoclast numbers were evaluated histologically. The in vitro effect of 4-PBA on the differentiation of mouse bone marrow cells induced by receptor activator of nuclear factor-κB ligand in the presence of macrophage colony-stimulating factor was analyzed. RESULTS The gene expression levels of UPR-related molecules and proinflammatory cytokines and alveolar bone resorption were significantly increased in P. gingivalis-administered mice. UPR-related gene expression and alveolar bone resorption were significantly suppressed by the administration of 4-PBA. However, no effect of 4-PBA was observed for proinflammatory cytokine expression in gingival tissues. Osteoclastic differentiation of bone marrow cells was also suppressed by 4-PBA with a concomitant reduction in the gene expression of cathepsin K and tartrate-resistant alkaline phosphatase genes. CONCLUSION ER stress induced by oral administration of P. gingivalis is involved in alveolar bone resorption independent of inflammatory cytokines in mice.