Masami Yoshioka

Effect of Inactivation of the Arg- and/or Lys-Gingipain Gene on Selected Virulence and Physiological Properties of Porphyromonas gingivalis

ABSTRACT Proteolytic enzymes produced by Porphyromonas gingivalis are thought to play critical roles in the pathogenesis of periodontitis. The aim of this study was to investigate the effect of gingipain cysteine proteinase gene inactivation on selected pathological and physiological functions of P. gingivalis. Our results showed that Arg- and Lys-gingipain activities are critical components for the efficient growth of P. gingivalis in human serum. However, when the serum was supplemented with peptides provided as pancreatic casein hydrolysate, the gingipains did not appear to be essential for growth. The effect of gingipain gene inactivation on the susceptibility of P. gingivalis to serum bactericidal activity was investigated using standardized human serum. The wild-type strain, P. gingivalis ATCC 33277, was largely unaffected by the bactericidal activity of human serum complement. On the other hand, mutants lacking Arg-gingipain A, Arg-gingipain B, or Lys-gingipain activity were susceptible to complement. Since gingipains are mostly located on the outer membrane of P. gingivalis, inactivation of the genes for these enzymes may modify cell surface properties. We showed that gingipain-deficient mutants differed in their capacities to assimilate radiolabeled amino acids, cause hemolysis, express adhesins, hemagglutinate, and form biofilms. Lastly, the gingipains, more specifically Arg-gingipains, were responsible for causing major cell damage to human gingival fibroblasts. In conclusion, our study indicated that, in addition to being critical in the pathogenic process, gingipains may play a variety of physiological roles in P. gingivalis, including controlling the expression and/or processing of virulence factors. Mutations in gingipain genes thus give rise to pleiotropic effects.

Relationship between Campylobacter rectus and periodontal status during pregnancy

INTRODUCTION In a previous study, we showed that the growth of Campylobacter rectus is stimulated by the presence of female sex hormones in the culture medium. In the present study, we examined the relationship between C. rectus levels in the saliva and the periodontal status of pregnant women. METHODS Unstimulated whole saliva was collected from 22 pregnant and 15 non-pregnant women. Periodontal pocket depth (PD) and bleeding on probing (BOP) were recorded. A quantitative real-time polymerase chain reaction was performed to determine the concentrations of suspected periodontopathogenic bacteria in the saliva samples. In addition, the concentration of estradiol in the saliva samples was measured by enzyme immunoassay. RESULTS The average age, number of teeth, and total number of bacteria in the saliva of subjects in both groups were similar. The percentage of sites with a PD = 4 mm and the salivary estradiol concentrations were significantly higher in pregnant women than in non-pregnant women. In addition, the percentage of BOP sites and the C. rectus levels in the saliva of the pregnant women tended to be higher than in non-pregnant women, although these differences were not statistically significant. There were positive correlations between C. rectus levels and estradiol concentrations, and between C. rectus levels and the percentage of sites with PD = 4 mm in the pregnant women. CONCLUSION These results indicate that C. rectus levels are higher in the oral flora of pregnant women and that this may be associated with increased salivary estradiol concentrations. This may contribute to periodontal disease progression during pregnancy.

Specific‐wavelength visible light irradiation inhibits bacterial growth of Porphyromonas gingivalis

BACKGROUND AND OBJECTIVE The effects of laser irradiation on Porphyromonas gingivalis have been reported, but the results are still controversial regarding the efficiency because of the differences of the light sources and irradiation conditions. The aim of this study was to determine the wavelength and irradiation conditions under which the most effective inhibitory effect on P. gingivalis growth was seen without any photosensitizers. MATERIAL AND METHODS Using an Okazaki large spectrograph, monochromatic light spectra ranging from 400 to 700 nm were evaluated to determine which spectra effectively inhibited bacterial growth. Moreover, using a monochromatic 405-nm irradiating device, the effects of various irradiating conditions on P. gingivalis growth were examined. RESULTS Growth of bacteria irradiated at 400 nm and 410 nm was significantly suppressed compared with a nonirradiated control, whereas wavelengths of 430 nm and longer produced no significant inhibition. A constant energy density of 15 J/cm2 was found to be enough to show an inhibitory effect. Significant inhibition of bacterial growth was found after only 1 min at 50 mW/cm2 irradiation. CONCLUSION These results indicate that P. gingivalis growth is specifically suppressed by 405-nm light irradiation, suggesting that visible blue light irradiation is a promising means for eradicating periodontopathogenic bacteria from periodontal lesions.

Levels of salivary stress markers in patients with anxiety about halitosis

OBJECTIVE To investigate the relationship between salivary stress markers and mental stress states in patients complaining of oral malodour. The utility of the salivary stress markers in assessment of mental conditions of those patients was also investigated. DESIGN The study population included 74 patients, aged 20-59 years, who complained of oral malodour and were referred to the Breath Odor Clinic at Tokushima University Hospital. Patients were classified into two groups, genuine halitosis (GH) and psychosomatic halitosis (PH), according to the results of organoleptic rating measurement. All patients were subjected to examination by the Cornell Medical Index (CMI) Health Questionnaire. Resting saliva was collected and levels of salivary IgA, cortisol and chromogranin A were determined by ELISA. Twenty-three volunteers not complaining of halitosis were included as the control group. Kruskal-Wallis test and Mann-Whitneys U-test were used for statistical analysis. RESULTS A significant increase was observed in the concentrations of salivary cortisol in the PH group as compared with GH and control groups (p<0.05). Concentrations of IgA and chromogranin A in saliva were not significantly different among the three groups. In addition, higher salivary cortisol concentrations were found in CMI scale III and IV (tendency towards neurosis) than in scale I and II (normal) (p<0.05). Since salivary cortisol reflects a status of chronic stress condition, psychosomatic halitosis might be closely related to this state of chronic stress. CONCLUSIONS Determination of cortisol levels in saliva may provide useful information for evaluating the mental status of patients complaining of halitosis.

Effects of Japanese traditional herbal medicines (Kampo) on growth and virulence properties of Porphyromonas gingivalis and viability of oral epithelial cells.

Abstract Context: Kampos, commonly used in Japanese traditional medicine, are standardized herbal mixtures that have been used for centuries to treat a variety of ailments. We hypothesized that Kampos may have unidentified properties that may be beneficial in periodontitis, an inflammatory disease affecting the tooth-supporting tissues. Objective: The aim of our study was to investigate various Kampos and their natural ingredients for their effects on Porphyromonas gingivalis growth, adherence to epithelial cells and proteinase activity. In addition, their effects on oral epithelial cell viability were evaluated. Materials and methods: Growth inhibition of P. gingivalis by various Kampos and their natural ingredients was evaluated by a microdilution broth assay method. Their effects on P. gingivalis proteinase activity and adherence to oral epithelial cells were determined by fluorometric assays. The cytotoxicity of test compounds towards oral epithelial cells was evaluated by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] test. Results: Of the 27 Kampos tested, 7 were found to inhibit the growth of P. gingivalis. The lowest minimal inhibitory concentration (MIC) (250 µg/ml) was obtained with TJ-113. Analysis of the composition of the seven active Kampos showed that they contain Chinese rhubarb as a common ingredient. Therefore, additional growth inhibitory assays on P. gingivalis were carried out with purified anthraquinones known to be present in rhubarb. Aloe-emodin and rhein possessed the strongest antibacterial effects towards P. gingivalis with an MIC of 0.78 µg/ml. The seven Kampos containing rhubarb and purified anthraquinones also exhibited the capacity to decrease the adherence of P. gingivalis to oral epithelial cells and to reduce its proteinase activity. The most important anti-adherence effect of Kampo was obtained with TJ-126; at 250 µg/ml it reduced adherence of P. gingivalis to epithelial cells by 83%. Purified anthraquinones were found to be less active than Kampos. Kampo TJ-113 was found to be the most effective for inhibition of gelatin degradation (49% inhibition at 62.5 µg/ml). Again, purified anthraquinones inhibited gelatin degradation to a lesser extent. Lastly, none of the tested compounds showed cytotoxicity towards oral epithelial cells at the effective concentrations. Conclusion: Kampos containing rhubarb and its anthraquinone derivatives may represent promising molecules for controlling periodontal diseases through their capacity to inhibit P. gingivalis growth and virulence properties.

The Kampo Medicine Rokumigan Possesses Antibiofilm, Anti-Inflammatory, and Wound Healing Properties

Periodontal diseases, which are inflammatory diseases of bacterial origin affecting the tooth-supporting tissues, are characterized by inflammation and destruction of gingival connective tissue and alveolar bone, and may lead to tooth loss. The aim of the study was to investigate Rokumigan, a Kampo Japanese traditional medicine made of six different plants, for its capacity to prevent biofilm formation by Fusobacterium nucleatum, to inhibit interleukin-6 (IL-6) and interleukin-8 (IL-8) secretion by mucosal cells, and to promote wound healing in a fibroblast model. Using a microplate colorimetric assay, Rokumigan prevented biofilm formation by F. nucleatum, while it had no effect on bacterial growth. Rokumigan inhibited IL-6 secretion in both epithelial cells and fibroblasts stimulated with lipopolysaccharide. However, it caused no significant inhibition of IL-8 secretion by both cell types. Rokumigan significantly increased proliferation and migration of gingival fibroblasts in a wound healing assay. In conclusion, the Kampo formulation Rokumigan, through suppression of biofilm formation by F. nucleatum, inhibition of IL-6 secretion by gingival epithelial cells and fibroblasts, and promotion of wound healing in a fibroblast model, may have potential application for periodontal diseases.

PKR plays a positive role in osteoblast differentiation by regulating GSK-3β activity through a β-catenin-independent pathway.

Double-stranded RNA-dependent protein kinase (PKR) is involved in various cellular functions. We previously reported that PKR regulates osteoblast differentiation, but the specific mechanisms by which this occurs remain unclear. In this study, we investigated the role of PKR in Glycogen synthase kinase 3β (GSK-3β) regulation of osteoblast differentiation. Lithium chloride (LiCl), a GSK-3β inhibitor, increased GSK-3β phosphorylation in MC3T3-E1 and MG-63 cells. LiCl also inhibited Runx2 and expression of its regulated genes, causing inhibition of Alkaline phosphatase activity and mineralization. LiCl injection to the calvaria in mice suppressed bone formation. Further, GSK-3β phosphorylation was increased in osteoblasts, by Akt-independent mechanisms, in which PKR was constitutively inactivated. A PKR inhibitor, 2-aminopurine, also induced GSK-3β phosphorylation in MC3T3-E1 and MG-63 cells. Further, Runx2 and its regulated genes were inhibited in PKR-inactivated osteoblasts, and differentiation was suppressed through a β-catenin-independent pathway. PKR positively regulates the differentiation of osteoblasts by mediating GSK-3β activity through a β-catenin-independent pathway.

Interaction between PKR and PACT mediated by LPS‐inducible NF‐κB in human gingival cells

The double‐stranded RNA‐dependent protein kinase (PKR) is a serine/threonine kinase expressed constitutively in mammalian cells. PKR is activated upon virus infection by double‐stranded RNA (dsRNA), and plays a critical role in host antiviral defense mechanisms. PKR is also known to regulate various biological responses, including cell differentiation and apoptosis. However, whether PKR is involved in the progress of periodontitis is not clear. The present study explained the phosphorylation of PKR by LPS in the human gingival cell line, Sa3. Expression of genes encoding LPS receptors was detected in Sa3 cells and treatment of cells with 1 µg/mL LPS for 6 h caused PKR phosphorylation. LPS elevated the expression of the protein activator of PKR (PACT) mRNA and protein, followed by the enhanced association between PACT and PKR within 3 h. In addition, LPS treatment induced the translocation of NF‐κB to the nucleus after 30 min, and inhibition of NF‐κB decreased the PACT–PKR interaction induced by LPS. The level of pro‐inflammatory cytokine mRNA, including interleukin‐6 (IL‐6) and tumor necrosis factor alpha (TNFα), appeared within 45 min and reached at the maximal levels by 90 min after the addition of LPS. This induction of pro‐inflammatory cytokines was not affected by RNAi‐mediated silencing of PKR and a pharmacological inhibitor of PKR, whereas the inhibition of NF‐κB decreased it. These results indicated that LPS induces PKR phosphorylation and the PACT–PKR association in Sa3 cells. Our results also suggest that NF‐κB is involved in the PACT–PKR interaction and the production of pro‐inflammatory cytokines in periodontitis. J. Cell. Biochem. 113: 165–173, 2012.

Preventive Effect of Daiokanzoto (TJ-84) on 5-Fluorouracil-Induced Human Gingival Cell Death through the Inhibition of Reactive Oxygen Species Production

Daiokanzoto (TJ-84) is a traditional Japanese herbal medicine (Kampo formulation). While many Kampo formulations have been reported to regulate inflammation and immune responses in oral mucosa, there is no evidence to show that TJ-84 has beneficial effects on oral mucositis, a disease resulting from increased cell death induced by chemotherapeutic agents such as 5-fluorouracil (5-FU). In order to develop effective new therapeutic strategies for treating oral mucositis, we investigated (i) the mechanisms by which 5-FU induces the death of human gingival cells and (ii) the effects of TJ-84 on biological events induced by 5-FU. 5-FU-induced lactate dehydrogenase (LDH) release and pore formation in gingival cells (Sa3 cell line) resulted in cell death. Incubating the cells with 5-FU increased the expression of nucleotide-binding domain and leucine-rich repeat containing PYD-3 (NLRP3) and caspase-1. The cleavage of caspase-1 was observed in 5-FU-treated cells, which was followed by an increased secretion of interleukin (IL)-1β. The inhibition of the NLRP3 pathway slightly decreased the effects of 5-FU on cell viability and LDH release, suggesting that NLRP3 may be in part involved in 5-FU-induced cell death. TJ-84 decreased 5-FU-induced LDH release and cell death and also significantly inhibited the depolarization of mitochondria and the up-regulation of 5-FU-induced reactive oxygen species (ROS) and nitric oxide (NO) production. The transcriptional factor, nuclear factor-κB (NF-κB) was not involved in the 5-FU-induced cell death in Sa3 cells. In conclusion, we provide evidence suggesting that the increase of ROS production in mitochondria, rather than NLRP3 activation, was considered to be associated with the cell death induced by 5-FU. The results also suggested that TJ-84 may attenuate 5-FU-induced cell death through the inhibition of mitochondrial ROS production.

The Daiokanzoto (TJ-84) Kampo Formulation Reduces Virulence Factor Gene Expression in Porphyromonas gingivalis and Possesses Anti-Inflammatory and Anti-Protease Activities.

Kampo formulations used in Japan to treat a wide variety of diseases and to promote health are composed of mixtures of crude extracts from the roots, bark, leaves, and rhizomes of a number of herbs. The present study was aimed at identifying the beneficial biological properties of Daiokanzoto (TJ-84), a Kampo formulation composed of crude extracts of Rhubarb rhizomes and Glycyrrhiza roots, with a view to using it as a potential treatment for periodontal disease. Daiokanzoto dose-dependently inhibited the expression of major Porphyromonas gingivalis virulence factors involved in host colonization and tissue destruction. More specifically, Daiokanzoto reduced the expression of the fimA, hagA, rgpA, and rgpB genes, as determined by quantitative real-time PCR. The U937-3xκB-LUC monocyte cell line transfected with a luciferase reporter gene was used to evaluate the anti-inflammatory properties of Daiokanzoto. Daiokanzoto attenuated the P. gingivalis-mediated activation of the NF-κB signaling pathway. It also reduced the secretion of pro-inflammatory cytokines (IL-6 and CXCL8) by lipopolysaccharide-stimulated oral epithelial cells and gingival fibroblasts. Lastly, Daiokanzoto, dose-dependently inhibited the catalytic activity of matrix metalloproteinases (-1 and -9). In conclusion, the present study provided evidence that Daiokanzoto shows potential for treating and/or preventing periodontal disease. The ability of this Kampo formulation to act on both bacterial pathogens and the host inflammatory response, the two etiological components of periodontal disease, is of high therapeutic interest.