Green Tea-Derived Catechins Suppress the Acid Productions of Streptococcus mutans and Enhance the Efficiency of Fluoride

Green tea-derived catechins, which can be divided into galloylated (epicatechin gallate: ECG, epigallocatechin gallate: EGCG) and non-galloylated (catechin: C, epicatechin: EC, epigallocatechin: EGC) catechins, are considered to be the main contributors to the caries control potential of green tea. In this study, we intended to compare the antimicrobial effects of these representative green tea-derived catechins and their combined effects with fluoride on the acid production and aggregation of Streptococcus mutans. The effects of different catechins on the growth, aggregation and acid production of S. mutans, and the combined effect of catechins and potassium fluoride (2 mm at pH 7.0, 0.3 mm at pH 5.5) on S. mutans acid production were measured by anaerobic culture, turbidity changes due to aggregation, and pH-stat methods. Molecular docking simulations were also performed to investigate the interactions between catechins and membrane-embedded enzyme II complex (EIIC), a component of the phosphoenolpyruvate-dependent phosphotransferase system (sugar uptake-related enzyme). ECG or EGCG at 1 mg/mL significantly inhibited the growth of S. mutans, induced bacterial aggregation, and decreased glucose-induced acid production (p < 0.05). All catechins were able to bind to EIIC in silico, in the following order of affinity: EGCG, ECG, EGC, EC, and C. Furthermore, they enhanced the inhibitory effects of fluoride at pH 5.5 and significantly inhibited S. mutans acid production by 47.5-86.6% (p < 0.05). These results suggest that both galloylated and non-galloylated catechins exhibit antimicrobial activity, although the former type demonstrates stronger activity, and that the caries control effects of green tea may be due to the combined effects of multiple components, such as catechins and fluoride. The detailed mechanisms underlying these phenomena and the in vivo effect need to be explored further.

Profiling of the microbiota of breast milk before and after feeding with an artificial nipple

OBJECTIVES

Breast milk is a valuable and useful source of nutrition; however, surplus milk is routinely discarded for hygiene reasons despite an unclear scientific basis. Here, we profiled the microbiota of expressed breast milk before and after feeding with an artificial nipple and examined the bacterial survival in breast milk stored at 4°C.

METHODS

Eleven mother-baby pairs were included in the study. Samples of expressed breast milk were collected before and after feeding with an artificial nipple and examined both immediately (0 h) and after storage for 3 and 12 h at 4°C. Each sample was inoculated onto a blood agar plate and incubated anaerobically and aerobically at 37°C. Genomic DNA was extracted from individual bacterial colonies, which were identified by 16S rRNA gene sequencing.

RESULTS

Before feeding, the bacterial counts at 0 and 12 h were (1.4 ± 1.6) × 10⁵ colony-forming units (CFU)/mL and (1.4 ± 0.6) × 10⁵ CFU/mL, respectively. Staphylococcus (47.7% and 41.9%, respectively), Cutibacterium (20.7% and 36.0%, respectively), and Streptococcus (16.1% and 6.6%, respectively) were identified among the samples. In contrast, after feeding, the bacterial counts at 0 and 12 h were (2.7 ± 1.7) × 10⁵ CFU/mL and (2.1 ± 2.5) × 10⁵ CFU/mL, respectively. Staphylococcus (30.1% and 37.4%, respectively), Cutibacterium (11.7% and 31.7%, respectively), and Streptococcus (41.5% and 25.2%, respectively), were identified among the samples.

CONCLUSIONS

Bacteria were present in the breast milk before feeding. Although the main component of the microbiota shifted from Staphylococcus to Streptococcus species after feeding, these results suggest that surplus expressed breast milk may be preserved safely in a refrigerator for at least 12 h after feeding with an artificial nipple.

Rewired Cellular Metabolic Profiles in Response to Metformin under Different Oxygen and Nutrient Conditions

Metformin is a metabolic disruptor, and its efficacy and effects on metabolic profiles under different oxygen and nutrient conditions remain unclear. Therefore, the present study examined the effects of metformin on cell growth, the metabolic activities and consumption of glucose, glutamine, and pyruvate, and the intracellular ratio of nicotinamide adenine dinucleotide (NAD⁺) and reduced nicotinamide adenine dinucleotide (NADH) under normoxic (21% O₂) and hypoxic (1% O₂) conditions. The efficacy of metformin with nutrient removal from culture media was also investigated. The results obtained show that the efficacy of metformin was closely associated with cell types and environmental factors. Acute exposure to metformin had no effect on lactate production from glucose, glutamine, or pyruvate, whereas long-term exposure to metformin increased the consumption of glucose and pyruvate and the production of lactate in the culture media of HeLa and HaCaT cells as well as the metabolic activity of glucose. The NAD⁺/NADH ratio decreased during growth with metformin regardless of its efficacy. Furthermore, the inhibitory effects of metformin were enhanced in all cell lines following the removal of glucose or pyruvate from culture media. Collectively, the present results reveal that metformin efficacy may be regulated by oxygen conditions and nutrient availability, and indicate the potential of the metabolic switch induced by metformin as combinational therapy.

Hypoxically cultured cells of oral squamous cell carcinoma increased their glucose metabolic activity under normoxic conditions

Objective

The oxygen concentration within cancer tissue is known to be low, but is expected to increase rapidly when oxygen is supplied by angiogenesis and hematogenous metastasis, suggesting that rapid increases in oxygen levels might influence cancer cell physiology. Therefore, we investigated the effects of oxygen concentration fluctuations on the glucose metabolism of cancer cells.

Methods

The glucose metabolism of oral squamous cell carcinoma (HSC-2 and HSC-3) and normal epithelial (HaCaT) cells cultured under normoxic (21% oxygen) or hypoxic (1% oxygen) conditions was measured using a pH-stat system under normoxic or hypoxic conditions. The acidic end-products and reactive oxygen species (ROS) generated by glucose metabolism were also measured.

Results

Under normoxic conditions, the metabolic activity of hypoxically cultured cancer cells was significantly increased, and the production of acids other than lactate was upregulated, while the normal cells did not respond to rapid increases in oxygen levels. ROS production was higher in normoxic conditions in all cells, especially the hypoxically cultured HSC-3 cells.

Conclusions

Rapid increases in oxygen levels might enhance the glucose metabolism of hypoxically cultured cancer cells by mainly activating the TCA cycle and electron transport system, which might activate cancer cells through the ATP and ROS generation.

Profiling system of oral microbiota utilizing polymerase chain reaction-restriction fragment length polymorphism analysis

OBJECTIVES

Profiling of oral microbiota has traditionally been performed using conventional methods. These methods are relatively time-consuming and labor-intensive. Metagenomic analysis of oral microbiota using high-speed next-generation sequencing is a highly promising technology. However, it is expensive. This study sought to develop a simple and cost-effective profiling method for oral microbiota using 16S rRNA gene polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of PCR-amplified 16S ribosomal RNA genes.

METHODS

Oral isolates of 59 bacterial species from human saliva, including Streptococcus, Actinomyces, and Veillonella, were cultured anaerobically on CDC Anaerobe 5% sheep blood agar plates. Genomic DNA was extracted from single colonies and 16S rRNA genes were PCR-amplified using the 27F and 1492R universal primers. The PCR products were purified and characterized by single digestion with HpaII restriction endonuclease. 16S rRNA gene sequences were obtained from the GenBank database, and the expected restriction profiles were compared with the RFLP patterns obtained from agarose gel electrophoresis.

RESULTS

Sixty-five RFLP patterns were obtained from 27 genera and 59 species. The expected fragment sizes of these species were calculated based on GenBank 16S rRNA gene sequences. Fifty-nine patterns were obtained from the analysis of GenBank sequences. The RFLP patterns produced with HpaII distinguished many oral bacterial species. RFLP patterns enabling identification of oral bacteria were generated. The 16S rRNA gene PCR-RFLP analysis did not require expensive equipment and reagents and was cost-effective.

CONCLUSION

PCR-RFLP analysis based on 16S rRNA genes could be an alternative method for oral microbiota analysis in smaller laboratories.

Profiling of Microbiota at the Mouth of Bottles and in Remaining Tea after Drinking Directly from Plastic Bottles of Tea

It has been speculated that oral bacteria can be transferred to tea in plastic bottles when it is drunk directly from the bottles, and that the bacteria can then multiply in the bottles. The transfer of oral bacteria to the mouth of bottles and bacterial survival in the remaining tea after drinking directly from bottles were examined immediately after drinking and after storage at 37 °C for 24 h. Twelve healthy subjects (19 to 23 years of age) were asked to drink approximately 50 mL of unsweetened tea from a plastic bottle. The mouths of the bottles were swabbed with sterile cotton, and the swabs and the remaining tea in the bottles were analyzed by anaerobic culture and 16S rRNA gene sequencing. Metagenomic analysis of the 16S rRNA gene was also performed. The mean amounts of bacteria were (1.8 ± 1.7) × 10⁴ colony-forming units (CFU)/mL and (1.4 ± 1.5) × 10⁴ CFU/mL at the mouth of the bottles immediately after and 24 h after drinking, respectively. In contrast, (0.8 ± 1.6) × 10⁴ CFU/mL and (2.5 ± 2.6) × 10⁶ CFU/mL were recovered from the remaining tea immediately after and 24 h after drinking, respectively. Streptococcus (59.9%) were predominant at the mouth of the bottles immediately after drinking, followed by Schaalia (5.5%), Gemella (5.5%), Actinomyces (4.9%), Cutibacterium (4.9%), and Veillonella (3.6%); the culture and metagenomic analyses showed similar findings for the major species of detected bacteria, including Streptococcus (59.9%, and 10.711%), Neisseria (1.6%, and 24.245%), Haemophilus (0.6%, and 15.658%), Gemella (5.5%, and 0.381%), Cutibacterium (4.9%, and 0.041%), Rothia (2.6%, and 4.170%), Veillonella (3.6%, and 1.130%), Actinomyces (4.9%, and 0.406%), Prevotella (1.6%, and 0.442%), Fusobacterium (1.0%, and 0.461%), Capnocytophaga (0.3%, and 0.028%), and Porphyromonas (1.0%, and 0.060%), respectively. Furthermore, Streptococcus were the most commonly detected bacteria 24 h after drinking. These findings demonstrated that oral bacteria were present at the mouth of the bottles and in the remaining tea after drinking.

Green Tea-Derived Epigallocatechin Gallate Inhibits Acid Production and Promotes the Aggregation of Streptococcus mutans and Non-Mutans Streptococci

It has been suggested that green tea-derived epigallocatechin gallate (EGCG), which has antimicrobial properties, might help prevent dental caries. However, the detailed properties of EGCG remain unclear. In this study, the antimicrobial properties of EGCG were evaluated by examining its bactericidal activity, its inhibitory effects against bacterial growth, acid production, acidic end-product formation, and sugar uptake (phosphoenolpyruvate-dependent phosphotransferase system, PEP-PTS activity), and its effects on bacterial aggregation, using monocultured planktonic cells of Streptococcus mutans and non-mutans streptococci. Coincubating S. mutans with EGCG (1 mg/mL) for 4 h had no bactericidal effects, while it decreased the growth and acid production of S. mutans by inhibiting the activity of the PEP-PTS. EGCG (2 mg/mL) caused rapid bacterial cell aggregation and had reduced the optical density of S. mutans cell suspension by 86.7% at pH 7.0 and 90.7% at pH 5.5 after 2 h. EGCG also reduced the acid production of non-mutans streptococci, including S. sanguinis, S. gordonii, and S. salivarius, and promoted the aggregation of these non-mutans streptococci. Furthermore, these antimicrobial effects of short-term EGCG treatment persisted in the presence of saliva. These results suggest that EGCG might have short-term antibacterial effects on caries-associated streptococci in the oral cavity.

Bacterial concentration and composition in liquid baby formula and a baby drink consumed with an artificial nipple

OBJECTIVES

To clarify the characteristics and growth of bacteria that may infiltrate liquid baby formula during feeding and after storage for more than 3 h, the transfer of oral bacteria through artificial nipples, and bacterial survival in liquid baby formula and a baby drink were examined immediately after drinking and after storage at 4 °C for 12 h and 24 h.

METHODS

Thirteen human subjects (aged 19-24 years) were asked to drink approximately 50 mL of liquid baby formula and a baby drink, via the artificial nipple of a baby bottle. Samples of the remaining liquid after storage at 4 °C for 12 h and 24 h were inoculated onto blood agar plates and incubated anaerobically at 37 °C for 7 days. Genomic DNA was extracted from individual colonies, and the bacterial species were identified by 16S rRNA gene sequencing.

RESULTS

The mean concentrations of bacteria in the liquid baby formula were (2.6 ± 2.8) × 10⁴ and (4.1 ± 6.6) × 10⁴ colony-forming unit/mL after storage at 4 °C for 12 h and 24 h, respectively. Streptococcus (43.2%), Veillonella (9.3%), and Schaalia (8.2%) species were recovered from the remaining liquid baby formula after storage at 4 °C for 12 h. In contrast, no bacteria were detected in the remaining baby drink after storage at 37 °C for 24 h.

CONCLUSIONS

The levels of bacteria immediately after drinking and after storage at 4 °C for 12 h or 24 h were similar, suggesting that remaining liquid baby formula may be preserved safely in a refrigerator for more than 3 h.

The potential of a surface pre-reacted glass root canal dressing for treating apical periodontitis in rats

AIM

To evaluate the efficacy of a prototype root canal dressing containing surface pre-reacted glass-ionomer (S-PRG) fillers on repairing induced periapical lesions in a rat model. Calcium hydroxide [Ca(OH)₂ ] was applied as a comparison in the healing process.

METHODOLOGY

The pulp chambers of the maxillary first molars in 64 male Wistar rats aged 16 weeks were opened to induce periapical lesions. After 28 days, the mesial canal of each tooth was prepared, irrigated with 2.5% sodium hypochlorite only (control group: irrigation) or followed by the respective dressing [Ca(OH)₂ group, irrigation + Ca(OH)₂ ; S-PRG group, irrigation + S-PRG] and restored with composite resin for 3 or 7 days (10/group). Four rats with healthy molars were used as blank controls. Descriptive analysis of the periapical radiographs, haematoxylin and eosin staining and immunohistochemical observation was performed 3 and 7 days after treatment. The periapical grey value, CD68 macrophages and osteoclasts (cathepsin-K) were quantified and statistically analysed with Tukey's honest significant difference test. A significant difference was achieved when P values were <0.05.

RESULTS

S-PRG and Ca(OH)₂ dressings were associated with increased periapical grey values and inhibited osteoclast activity at 3 and 7 days; a significant difference in radiographic results and the number of osteoclasts was obtained at 3 and 7 days compared with the control group (P < 0.05). Reparative tissue was observed histologically in the space of the periapical resorbed necrotic area after S-PRG and Ca(OH)₂ treatment for 3 and 7 days. The number of macrophages was significantly decreased at 3 and 7 days in the S-PRG and Ca(OH)₂ specimens when compared with the controls (P < 0.05).

CONCLUSIONS

In a rat experimental model, the S-PRG root canal dressing was comparable to Ca(OH)₂ in promoting the healing of experimentally induced periapical lesions. S-PRG paste has the potential to be used as an alternative intracanal dressing in teeth with apical periodontitis.

Sugar Metabolism of Scardovia wiggsiae, a Novel Caries-Associated Bacterium

Scardovia wiggsiae has been detected from caries in children and adolescents and has been suggested to be a caries-associated microorganism. To investigate the cariogenic potential of S. wiggsiae, we examined carbohydrate metabolism and acid productivity, the fluoride sensitivity of carbohydrate metabolism and the mechanism by which fluoride inhibits carbohydrate metabolism, and the acid sensitivity of carbohydrate metabolism in this bacterium. S. wiggsiae metabolized glucose and reduced the environmental pH to 3.5. It mainly produced acetic acid from glucose, together with small amounts of lactic and formic acid. The 50% inhibitory concentration of fluoride for acid production was 8.0 mM at pH 7.0 and 1.5 mM at pH 5.5, which were much higher than those of representative caries-associated bacteria, such as Streptococcus mutans. Metabolomic profiles showed the accumulation of 3-phosphoglycerate and a marked reduction in the pyruvate concentration in the presence of fluoride, suggesting that fluoride inhibits the latter half of glycolysis, including enolase activity. Enolase activity was inhibited by fluoride in S. wiggsiae, but it was more fluoride-tolerant than the enolase activity of S. mutans. Unlike in S. mutans, lactic acid did not inhibit acid production by S. wiggsiae at acidic pH. These results indicate that S. wiggsiae exhibits high acid production and tolerance to fluoride and lactic acid. S. wiggsiae possesses a unique metabolic pathway, the F6PPK shunt, which might allow it to avoid the lactate-formate pathway, including fluoride-sensitive enolase activity, and enable metabolic flow to the fluoride-tolerant acetate pathway. The fluoride tolerance of S. wiggsiae's enolase activity also increases the fluoride tolerance of its carbohydrate metabolism. The lactic acid tolerance of S. wiggsiae's acid production might result in S. wiggsiae having high acidogenic and aciduric potential and make it ecologically competitive in acidic environments, such as caries lesions, where lactic acid predominates.

DNA methylation of GJA1, BMP2 and BMP4 in a human cementoblast cell line induced by lipopolysaccharide

AIM

To examine DNA methylation of GJA1, BMP2 and BMP4 in human cementoblasts (HCEM) induced by lipopolysaccharide (LPS).

METHODOLOGY

HCEM were cultured in osteoinduction medium. After 24 h, Escherichia coli LPS (1 μg/mL) was added to the medium, which was changed every 2-3 days. Untreated samples were used as controls. Messenger RNA was extracted after 4 weeks, and quantitative real-time polymerase chain reaction (qRT-PCR) for GJA1, BMP2, BMP4 and DNMT1 was performed. Genomic DNA was extracted after 4 weeks, and quantitative methylation-specific polymerase chain reaction was carried out for GJA1, BMP2 and BMP4. To detect mineralization, alizarin red and alkaline phosphatase staining were performed. The cells were also treated with the DNA methyltransferase inhibitor 5-Aza-2'-deoxycytidine (5Aza) and examined. The significance of differences amongst groups was assessed using a two-way analysis of variance (ANOVA) followed by Bonferroni's multiple comparison test with P < 0.05 being significant.

RESULTS

Decreased expression of mRNA was seen in GJA1, BMP2 and BMP4 after 4 weeks (P < 0.05). DNA hypermethylation was detected in GJA1, BMP2 and BMP4 (P < 0.05). Alizarin red staining and alkaline phosphatase staining revealed decreased mineralization levels in HCEM stimulated with LPS. 5Aza abolished the effects of DNA methylation in HCEM stimulated with LPS.

CONCLUSIONS

These results suggest that long-term LPS stimulation induces DNA methylation of GJA1, BMP2 and BMP4 in HCEM.

Control of protein function through oxidation and reduction of persulfidated states

Irreversible oxidation of Cys residues to sulfinic/sulfonic forms typically impairs protein function. We found that persulfidation (CysSSH) protects Cys from irreversible oxidative loss of function by the formation of CysSSO_1-3H derivatives that can subsequently be reduced back to native thiols. Reductive reactivation of oxidized persulfides by the thioredoxin system was demonstrated in albumin, Prx2, and PTP1B. In cells, this mechanism protects and regulates key proteins of signaling pathways, including Prx2, PTEN, PTP1B, HSP90, and KEAP1. Using quantitative mass spectrometry, we show that (i) CysSSH and CysSSO₃H species are abundant in mouse liver and enzymatically regulated by the glutathione and thioredoxin systems and (ii) deletion of the thioredoxin-related protein TRP14 in mice altered CysSSH levels on a subset of proteins, predicting a role for TRP14 in persulfide signaling. Furthermore, selenium supplementation, polysulfide treatment, or knockdown of TRP14 mediated cellular responses to EGF, suggesting a role for TrxR1/TRP14-regulated oxidative persulfidation in growth factor responsiveness.

Profiling of microbiota in liquid baby formula consumed with an artificial nipple

It is suspected that oral bacteria are transferred to the liquid baby formula through the artificial nipple and multiply in the bottle after feeding. In the present study, in order to understand the influence of bacteria on liquid baby formula after feeding, the transfer of oral bacteria through artificial nipples and their survival in liquid baby formula were examined immediately after drinking as well as after storage at 4°C for 3 h. Four healthy human subjects (20-23 years old) were asked to drink liquid baby formula (Aptamil^®, ca. 50 mL) from baby bottles using artificial nipples. Samples of the liquid baby formula (immediately after drinking and 3 h later) were inoculated onto blood agar plates and incubated anaerobically at 37°C for 7 days. Salivary samples from each subject and 6 newborn infants were also cultured. Genomic DNA was extracted from individual colonies, and bacterial species were identified by 16S rRNA gene sequencing. The mean amounts of bacteria (CFU/mL) were (3.2 ± 3.0) ×10⁴ and (3.4 ± 3.3) ×10⁴ immediately after drinking and 3 h later, respectively. Streptococcus (41.6 and 40.5%), Actinomyces (24.3 and 21.5%) and Veillonella (16.2 and 11.0%) were recovered from the samples immediately after drinking and 3 h later, respectively. On the other hand, Streptococcus (38.9%), Actinomyces (17.1%), Neisseria (9.1%), Prevotella (6.9%), Rothia (6.9%) and Gemella (5.1%) were predominant in the saliva of adult subjects, and Streptococcus (65.2%), Staphylococcus (18.5%), Gemella (8.2%) and Rothia (5.4%) were predominant in the saliva of infant subjects. From these findings, oral bacteria, e.g., Streptococcus, Gemella and Rothia, were found to transfer into the liquid baby formula through artificial nipples, and the bacterial composition in the remaining liquid baby formula was found to resemble that of human saliva. The bacterial levels were similar between immediately after drinking and when stored at 4°C for 3 h, suggesting that the remaining liquid baby formula may be preserved in a refrigerator for a specified amount of time.

Metabolic property of acetaldehyde production from ethanol and glucose by oral Streptococcus and Neisseria

Acetaldehyde is known to be carcinogenic and produced by oral bacteria. Thus, bacterial acetaldehyde production might contribute to oral cancer. Therefore, we examined bacterial acetaldehyde production from ethanol and glucose under various conditions mimicking the oral cavity and clarified the metabolic pathways responsible for bacterial acetaldehyde production. Streptococcus mitis, S. salivarius, S. mutans, Neisseria mucosa and N. sicca were used. The bacterial metabolism was conducted at pH 5.0–8.0 under aerobic and anaerobic conditions. The production of acetaldehyde and organic acids was measured with gas chromatography and HPLC, respectively. Bacterial enzymes were also assessed. All of the bacteria except for S. mutans exhibited their greatest acetaldehyde production from ethanol at neutral to alkaline pH under aerobic conditions. S. mutans demonstrated the greatest acetaldehyde from glucose under anaerobic conditions, although the level was much lower than that from ethanol. Alcohol dehydrogenase and NADH oxidase were detected in all of the bacteria. This study revealed that oral indigenous bacteria, Streptococcus and Neisseria can produce acetaldehyde, and that such acetaldehyde production is affected by environmental conditions. It was suggested that alcohol dehydrogenase and NADH oxidase are involved in ethanol-derived acetaldehyde production and that the branched-pathway from pyruvate is involved in glucose-derived acetaldehyde production.

Acidogenic Potential of Oral Bifidobacterium and Its High Fluoride Tolerance

Bifidobacterium is frequently detected in early childhood caries and white spot lesions, indicating that it is a novel caries-associated bacterium. Bifidobacterium is known to possess a unique metabolic pathway, the “bifid shunt,” which might give it cariogenic potential by increasing its acid production. Thus, we evaluated the acid-producing activity of Bifidobacterium and its sensitivity to fluoride, a caries preventive reagent. Bifidobacterium longum, Bifidobacterium dentium, and Streptococcus mutans were used. Acid-producing activity was measured using a pH-stat in the absence and presence of fluoride under anaerobic conditions. Furthermore, metabolomic analysis was performed to elucidate the mechanism underlying the inhibitory effects of fluoride. The acid production of Bifidobacterium at pH 5.5 was as high as that seen at pH 7.0, indicating that Bifidobacterium has high cariogenic potential, although it produced less acid than S. mutans. In addition, Bifidobacterium produced acid in the absence of extracellular carbohydrates, suggesting that it can store intracellular polysaccharides. Bifidobacterium produced more acid from lactose than from glucose. Bifidobacterium mainly produced acetate, whereas S. mutans mainly produced lactate. The 50% inhibitory concentration (IC₅₀) of fluoride for acid production was 6.0–14.2 times higher in Bifidobacterium than in S. mutans. Fluoride inhibited enolase in the glycolysis, resulting in the intracellular accumulation of 3-phosphoenolpyruvate, glucose 6-phosphate, and erythrose 4-phosphate. However, the bifid shunt provides a bypass pathway that can be used to produce acetate, suggesting that Bifidobacterium is able to metabolize carbohydrates in the presence of fluoride. It is suggested that its exclusive acetate production contributes to the pathogenesis of dental caries.

Inhibitory effect of resin composite containing S-PRG filler on Streptococcus mutans glucose metabolism

OBJECTIVES

Resin composites containing surface pre-reacted glass-ionomer (S-PRG) fillers have been reported to inhibit Streptococcus mutans growth on their surfaces, and their inhibitory effects were attributed to BO₃^3- and F^- ions. The aim of this study was to evaluate S. mutans acid production through glucose metabolism on resin composite containing S-PRG fillers and assess inhibitory effects of BO₃^3- and F^- on S. mutans metabolic activities.

METHODS

The pH change through S. mutans acid production on experimental resin composite was periodically measured after the addition of glucose. Inhibitory effects of BO₃^3- or F^- solutions on S. mutans metabolism were evaluated by XTT assays and measurement of the acid production rate.

RESULTS

The pH of experimental resin containing S-PRG fillers was significantly higher than that of control resin containing silica fillers (p < 0.05). OD₄₅₀ values by XTT assays and S. mutans acid production rates significantly decreased in the presence of BO₃^3- and F^- compared with the absence of these ions (p < 0.05).

CONCLUSIONS

pH reduction by S. mutans acid production was inhibited on resin composite containing S-PRG fillers. Moreover, S. mutans glucose metabolism and acid production were inhibited in the presence of low concentrations of BO₃^3- or F^-.

CLINICAL SIGNIFICANCE

BO₃^3- or F^- released from resin composite containing S-PRG fillers exhibits inhibitory effects on S. mutans metabolism at concentrations lower than those which inhibit bacterial growth.

Characterization of Treponema denticola mutants defective in the major antigenic proteins, Msp and TmpC

Treponema denticola, a gram-negative and anaerobic spirochete, is associated with advancing severity of chronic periodontitis. In this study, we confirmed that two major antigenic proteinswere Msp and TmpC, and examined their physiological and pathological roles using gene-deletion mutants. Msp formed a large complex that localized to the outer membrane, while TmpC existed as a monomer and largely localized to the inner membrane. However, TmpC was also detected in the outer membrane fraction, but its cell-surface exposure was not detected. Msp defects increased cell-surface hydrophobicity and secretion of TNF-α from macrophage-like cells, whereas TmpC defects decreased autoagglutination and chymotrypsin-like protease activities. Both mutants adhered to gingival epithelial cells similarly to the wild-type and showed slightly decreased motility. In addition, in Msp-defective mutants, the TDE1072 protein, which is a major membrane protein, was abolished; therefore, phenotypic changes in the mutant can be, at least in part, attributed to the loss of the TDE1072 protein. Thus, the major antigenic proteins, Msp and TmpC, have significant and diverse impacts on the characteristics of T. denticola, especially cell surface properties.

Major membrane protein TDE2508 regulates adhesive potency in Treponema denticola

The cultivation and genetic manipulation of Treponema denticola, a Gram-negative oral spirochaeta associated with periodontal diseases, is still challenging. In this study, we formulated a simple medium based on a commercially available one, and established a transformation method with high efficiency. We then analyzed proteins in a membrane fraction in T. denticola and identified 16 major membrane-associated proteins, and characterized one of them, TDE2508, whose biological function was not yet known. Although this protein, which exhibited a complex conformation, was presumably localized in the outer membrane, we did not find conclusive evidence that it was exposed on the cell surface. Intriguingly, a TDE2508-deficient mutant exhibited significantly increased biofilm formation and adherent activity on human gingival epithelial cells. However, the protein deficiency did not alter autoaggregation, coaggregation with Porphyromonas gingivalis, hemagglutination, cell surface hydrophobicity, motility, or expression of Msp which was reported to be an adherent molecule in this bacteria. In conclusion, the major membrane protein TDE2508 regulates biofilm formation and the adhesive potency of T. denticola, although the underlying mechanism remains unclear.

Genetic and antigenic analyses of Porphyromonas gingivalis FimA fimbriae

The periodontal pathogen Porphyromonas gingivalis generally expresses two distinct fimbriae, FimA and Mfa1, which play a role in biofilm formation. The fimA gene that encodes FimA fimbrilin is polymorphic, and polymerase chain reaction analysis has identified six genotypes called types I-V and Ib. We found recently that fimbriae exhibit antigenic heterogeneity among the genotypes. In the present study, we analysed the fimA DNA sequences of 84 strains of P. gingivalis and characterized the antigenicity of FimA fimbriae. Strains analysed here comprised 10, 16, 29, 13, 10 and 6 strains of types I, Ib, II, III, IV and V, respectively. DNA sequencing revealed that type Ib does not represent a single cluster and that type II sequences are remarkably diverse. In contrast, the fimA sequences of the other types were relatively homogeneous. Antigenicity was investigated using antisera elicited by pure FimA fimbriae of types I-V. Antigenicity correlated generally with the respective genotype. Type Ib strains were recognized by type I antisera. However, some strains showed cross-reactivity, especially, many type II strains reacted with type III antisera. The levels of fimbrial expression were highly variable, and expression was positively correlated with ability of biofilm formation on a saliva-coated plate. Further, two strains without FimA and Mfa1 fimbriae expressed fimbrial structures, suggesting that the strains produce other types of fimbriae.

Antimicrobial effect of photodynamic therapy using high-power blue light-emitting diode and red-dye agent on Porphyromonas gingivalis

BACKGROUND AND OBJECTIVE

Antimicrobial photodynamic therapy (a-PDT) using a combination of red-colored laser/light-emitting diode (LED) and blue dye has been employed for periodontal therapy and the antimicrobial effect seems promising. Blue light, which has favorable wavelength properties, would be more effective as a light source for a-PDT because blue light itself possesses an antimicrobial effect. This study aimed to investigate the effect of a-PDT using a novel combination of high-power blue LED and red-dye agent on Porphyromonas gingivalis in vitro.

MATERIAL AND METHODS

Porphyromonas gingivalis ATCC 33277 suspension was irradiated with blue LED (BL) (425-470 nm) or red LED (RL) (625-635 nm) at 30-90 J/cm(2) , or was mixed with erythrosine (ER), phloxine B (PB) or rose bengal (RB) with or without BL irradiation (30 J/cm(2) ). RL (30 J/cm(2) ) in combination with toluidine blue was employed as positive control. All the suspensions of P. gingivalis were serially diluted, plated and incubated anaerobically, and the numbers of colony-forming units (CFUs) were counted on day 7.

RESULTS

BL irradiation at 60 and 90 J/cm(2) demonstrated a significant reduction in the numbers of CFUs. ER, PB and RB solutions at 160 μg/mL showed almost no or only a minimal reduction in the numbers of CFUs. BL at 30 J/cm(2) combined with ER, PB or RB at 160 μg/mL resulted in a log reduction of 0.9, 1.0 and 7.1, respectively, in the numbers of CFUs; 30 J/cm(2) BL with RB at 1.6, 16 and 160 μg/mL demonstrated a log reduction of 6.3, 8.0 and 5.5, respectively; and a log reduction of 5.2 was obtained after 30 J/cm(2) RL with 16 μg/mL TB.

CONCLUSION

Within the limits of this study, BL was found to have an antimicrobial/growth-inhibiting effect on P. gingivalis, and a-PDT using a combination of BL and RB shows promise as a new technical modality for bacterial elimination in periodontal therapy.

Assessment of the Plasma/Serum IgG Test to Screen for Periodontitis

Chronic periodontitis is a silent infectious disease prevalent worldwide and affects lifestyle-related diseases. Therefore, efficient screening of patients is essential for general health. This study was performed to evaluate prospectively the diagnostic utility of a blood IgG antibody titer test against periodontal pathogens. Oral examination was performed, and IgG titers against periodontal pathogens were measured by ELISA in 1,387 individuals. The cut-off value of the IgG titer was determined in receiver operating characteristic curve analysis, and changes in periodontal clinical parameters and IgG titers by periodontal treatment were evaluated. The relationships between IgG titers and severity of periodontitis were analyzed. The best cut-off value of IgG titer against Porphyromonas gingivalis for screening periodontitis was 1.682. Both clinical parameters and IgG titers decreased significantly under periodontal treatment. IgG titers of periodontitis patients were significantly higher than those of healthy controls, especially in those with sites of probing pocket depth over 4 mm. Multiplied cut-off values were useful to select patients with severe periodontitis. A blood IgG antibody titer test for Porphyromonas gingivalis is useful to screen hitherto chronic periodontitis patients (ClinicalTrials.gov number NCT01658475).

Characterization of human-type monoclonal antibodies against reduced form of hemin binding protein 35 from Porphyromonas gingivalis

BACKGROUND AND OBJECTIVE

The gram-negative anaerobe Porphyromonas gingivalis has been implicated as an important pathogen in the development of adult periodontitis, and its colonization of subgingival sites is critical in the pathogenic process. We previously identified a 35 kDa surface protein (hemin binding protein 35; HBP35) from P. gingivalis that exhibited coaggregation activity, while additional analysis suggested that this protein possessed an ability to bind heme molecules. For development of passive immunotherapy for periodontal diseases, human-type monoclonal antibodies have been prepared using HBP35 as an antigen in TransChromo mice. In the present study, we focused on a single antibody, TCmAb-h13, which is known to inhibit heme binding to recombinant HBP35. The aim of our investigation was to clarify the redox-related function of HBP35 and consider the benefits of human-type monoclonal antibodies.

MATERIAL AND METHODS

To examine the antigen recognition capability of TCmAbs with immunoblotting and Biacore techniques, we used the native form as well as several Cys-to-Ser variants of recombinant HBP35.

RESULTS

We found that the redox state of recombinant HBP35 was dependent on two Cys residues, (48) C and (51) C, in the thioredoxin active center (WCGxCx). Furthermore, TCmAb-h13 recognized the reduced forms of recombinant HBP35, indicating its inhibitory effect on P. gingivalis growth.

CONCLUSION

Hemin binding protein 35 appears to be an important molecule involved in recognition of the redox state of environmental conditions. In addition, TCmAb-h13 had an inhibitory effect on heme binding to recombinant HBP35, thereby interfering with P. gingivalis growth.

Transcriptome analysis of β-TCP implanted in dog mandible

Beta-tricalcium phosphate (β-TCP) is widely used in clinical orthopedic surgery due to its high biodegradability, osteoconductivity, easy manipulation and lack of histotoxicity. However, little is known about the molecular mechanisms responsible for the beneficial effects of β-TCP in bone formation. In this study, β-TCP was implanted in dog mandibles, after which the gene expression profiles and signaling pathways were monitored using microarray and Ingenuity Pathways Analysis (IPA). Following the extraction of premolars and subsequent bone healing, β-TCP was implanted into the artificial osseous defect. Histological evaluation (H-E staining) was carried out 4, 7 and 14 days after implantation. In addition, total RNA was isolated from bone tissues and gene expression profiles were examined using microarray analysis coupled with Ingenuity Pathways Analysis (IPA). Finally, real-time PCR was used to confirm mRNA levels. It was found that β-TCP implantation led to a two-fold change in 3409 genes on day 4, 3956 genes on day 7, and 6899 genes on day 14. Among them, the expression of collagen type I α1 (COL1A1), alkaline phosphatase (ALP) and transforming growth factor (TGF)-β2 was increased on day 4, the expression of receptor activator of NF-kappaB ligand (RANKL) and interferon-γ (IFN-γ) was decreased on day 7, and the expression of osteoprotegerin (OPG) was decreased on day 14, affecting the bone morphogenetic protein (BMP), Wnt/β-catenin and nuclear factor-kappaB (NF-κB) signaling pathways in osteoblasts and osteoclasts. Simultaneously, vascular cell adhension molecule (VCAM)-1 expression was increased on day 4 and stromal cell-derived factor (SDF)-1 expression was increased on days 4 and 14. Taken together, these findings shed light on some of the cellular events associated with bone formation, bioresorption, regeneration and healing of β-TCP following its implantation. The results suggest that β-TCP enhances bone healing processes and stimulates the coordinated actions of osteoblasts and osteoclasts, leading to bone regeneration.

Periodontal pathogen Aggregatibacter actinomycetemcomitans LPS induces mitochondria-dependent-apoptosis in human placental trophoblasts

OBJECTIVE

Increasing evidence suggests an association between periodontal disease and low birthweight (LBW); however the underlying molecular mechanisms are yet to be fully elucidated. In this study, we performed a microarray analysis to observe the human placental trophoblast-like BeWo cells response to lipopolysaccharide (LPS) from periodontopathogen Aggregatibacter actinomycetemcomitans (Aa), in order to investigate the molecular basis of mechanisms for periodontitis-associated LBW. In vivo pregnant rats were also used to confirm the in vitro results.

STUDY DESIGN

The effects of Aa-LPS on cultured human placental trophoblast-like BeWo cells were studied using a DNA microarray, Ingenuity Pathway Analysis, real-time PCR and poly-caspase staining. The in vivo effects of Aa-LPS in pregnant rats were examined using TUNEL assays.

RESULTS

In BeWo cells, Aa-LPS increased levels of cytochrome c, caspase 2, caspase 3, caspase 9 and BCL2-antagonist/killer 1 mRNA, decreased those of B-cell CLL/lymphoma 2, BCL2-like 1 and catalase mRNA and increased poly-caspase activity, all of which are consistent with activation of the mitochondria-dependent apoptotic pathway. TUNEL assays confirmed the increased incidence of apoptosis in placentas of Aa-LPS-treated rats (p < 0.001).

CONCLUSION

Aa-LPS induces apoptosis in human trophoblasts via the mitochondria-dependent pathway, and this effect may contribute to the pathogenesis of periodontitis-associated LBW.

TGF-β Signaling in Gingival Fibroblast-Epithelial Interaction

The underlying mechanism and the therapeutic regimen for the transition of reversible gingivitis to irreversible periodontitis are unclear. Since transforming growth factor (TGF)-β has been implicated in differentially regulated gene expression in gingival fibroblasts, we hypothesized that TGF-β signaling is activated in periodontitis-affected gingiva, along with enhanced collagen degradation, that is reversed by TGF-β inhibition. A novel three-dimensional (3D) gel-culture system consisting of primary human gingival fibroblasts (GF) and gingival epithelial (GE) cells in collagen gels was applied. GF populations from patients with severe periodontitis degraded collagen gels, which was reduced by TGF-β-receptor kinase inhibition. Up-regulation of TGF-β-responsive genes was evident in GF/GE co-cultures. Furthermore, the TGF-β downstream transducer Smad3C was highly phosphorylated in periodontitis-affected gingiva and 3D cultures. These results imply that TGF-β signaling is involved in fibroblast-epithelial cell interaction in periodontitis, and suggest that the 3D culture system is a useful in vitro model for therapeutic drug screening for periodontitis.

Profiling of subgingival plaque biofilm microflora from periodontally healthy subjects and from subjects with periodontitis using quantitative real-time PCR

BACKGROUND AND OBJECTIVE

Qualitative and quantitative changes of the subgingival plaque biofilm microflora in periodontal pockets are thought to be associated with the development and progression of periodontitis. The aims of the present study were to quantify the proportions of nine periodontitis-associated bacterial species and four Streptococcus species in subgingival plaque, and to evaluate their relationship with periodontitis quantitatively.

MATERIAL AND METHODS

Subgingival plaque samples were obtained from 12 periodontally healthy subjects and from 28 patients with periodontitis. The amounts of total and target bacteria were measured by quantitative real-time PCR using universal and species-specific primers, respectively.

RESULTS

The proportion of total obligate anaerobes was found to be higher in subjects with periodontitis than in periodontally healthy subjects (p < 0.05). Among obligate anaerobes, Tannerella forsythia (2.04 +/- 5.27%, p < 0.05), Porphyromonas gingivalis (0.54 +/- 1.41%) and Eubacterium saphenum (0.30 +/- 0.96%) were detected at high proportions in subjects with periodontitis, but not in periodontally healthy subjects. By contrast, the proportion of total streptococci was lower in subjects with periodontitis (p < 0.05). Specifically, the proportion of T. forsythia, P. gingivalis or E. saphenum increased (>or= 2.78%) and the proportion of Streptococcus species decreased to virtually undetectable levels, in subjects with periodontitis.

CONCLUSION

Obligate anaerobes, including T. forthysia, P. gingivalis and E. saphenum, were identified predominantly in microflora from subjects with periodontitis, whereas Streptococcus species were identified predominantly in microflora from periodontally healthy subjects, suggesting a change in the subgingival environment that resulted in conditions more suitable for the survival of obligate anaerobes. The proportion of these obligate anaerobes in the subgingival plaque of subjects with periodontitis appears to be associated with the status of human periodontitis.

Proteome analysis of Porphyromonas gingivalis cells placed in a subcutaneous chamber of mice

INTRODUCTION

Porphyromonas gingivalis, an oral anaerobic bacterium, is considered a major pathogen for chronic periodontitis. Pathogenic bacteria usually upregulate or downregulate gene expression to combat the protective responses of their hosts.

METHODS

To determine what protein is regulated when P. gingivalis cells invade host tissues, we analyzed the proteome of P. gingivalis cells that were placed in a mouse subcutaneous chamber by two-dimensional gel electrophoresis and mass spectrometry.

RESULTS

Fourteen proteins were upregulated, while four proteins were downregulated. We focused on three upregulated proteins, PG1089 (DNA-binding response regulator RprY), PG1385 (TPR domain protein), and PG2102 (immunoreactive 61-kDa antigen), and constructed mutant strains that were defective in these proteins. Mouse abscess model experiments revealed that the mutant strain defective in PG1385 was clearly less virulent than the wild-type parent strain.

CONCLUSION

These results indicate that the PG1385 protein is involved in P. gingivalis virulence and that the method used here is useful when investigating the P. gingivalis proteins responsible for virulence.

DNA microarray analyses of genes expressed differentially in 3T3-L1 adipocytes co-cultured with murine macrophage cell line RAW264.7 in the presence of the toll-like receptor 4 ligand bacterial endotoxin

Recent studies have suggested that macrophages were integrated into adipose tissues to interact with adipocytes, thereby exacerbating inflammatory responses. Furthermore, both adipocytes and macrophages appear to express toll-like receptor-4 (TLR-4), and free fatty acids may stimulate cells through TLR-4. Herein, we analyzed genes differentially expressed in adipocytes when co-cultured with macrophages in the presence of a ligand for TLR-4, bacterial lipopolysaccharide (LPS). RAW264.7, a murine macrophage cell line and differentiated 3T3-L1 adipocytes were co-cultured using a transwell system. Genes differentially expressed in adipocytes were analyzed by the DNA microarray method following 4, 8, 12 and 24 h stimulation with 1 ng ml(-1) of Escherichia coli LPS. Randomly selected genes with high expressions were confirmed by quantitative methods at both the gene and the protein level. Co-culture of macrophages and adipocytes with a low LPS concentration (1 ng ml(-1)) markedly upregulated gene expressions associated with inflammation and/or angiogenesis, such as those of interleukin-6 (IL-6), MCP-1, RANTES and CXCL1/KC, in adipocytes. Furthermore, several genes associated with insulin resistance were differentially expressed. Upregulations of genes encoding MCP-1, RANTES and CXC/KC were confirmed by quantitative methods. These results suggest that ligands for TLR-4 stimulate both adipocytes and macrophages to upregulate the expressions of many genes associated with inflammation and/or angiogenesis.

Porphyromonas gingivalis gingipains cause G(1) arrest in osteoblastic/stromal cells

INTRODUCTION

The program for mammalian cell growth and division consists of four successive phases; G(1), S, G(2), and M. Porphyromonas gingivalis may manipulate the host cell cycle to benefit bacterial virulence expression, which likely causes the cell and tissue tropism observed in chronic periodontal infections. We examined P. gingivalis for its effects on cell-cycle modulation in mouse ST2 osteoblastic/stromal cells.

METHODS

Synchronized ST2 cells were infected with P. gingivalis ATCC33277 (wild-type, WT), gingipain-mutants [KDP136 (DeltargpADeltargpBDeltakgp), KDP129 (DeltargpADeltargpB), and KDP133 (Deltakgp)], and a fimbria-deficient mutant (KDP150) for 24 h, then the cell cycle was evaluated using flow cytometry. Cell-cycle-related molecule expression was examined with a microarray, as well as with quantitative real-time polymerase chain reaction and Western blotting assays.

RESULTS

Both the WT and KDP150 strains significantly inhibited cellular proliferation and arrested the cell cycle in the G(0)/G(1) phase, while the expression levels of the cell-cycle regulatory molecules cyclin D and cyclin E were also decreased. In contrast, KDP136 did not show any effects. G(1) arrest was also clearly induced by KDP129 and KDP133, with KDP129 being more effective.

CONCLUSION

The present findings suggest that P. gingivalis gingipains reduce cyclin expression and cause early G(1) arrest, leading to the inhibition of cellular proliferation.

Morphology of Malassez's epithelial rest-like cells in the cementum: transmission electron microscopy, immunohistochemical, and TdT-mediated dUTP-biotin nick end labeling studies

BACKGROUND AND OBJECTIVE

It is known that epithelial islands are embedded in the cementum during tooth root formation, but details of this process remain unknown. The purpose of this study was to investigate the dynamic characteristics of Malassez's epithelial rest cells in the cementum during tooth root formation in pigs in vivo.

MATERIAL AND METHODS

The first molars of 6-mo-old pigs were used in this study. Specimens were decalcified before being embedded in paraffin. Paraffin sections were investigated using TdT-mediated dUTP-biotin nick end labeling (TUNEL), immunohistochemical, and ultrastructural techniques.

RESULTS

Malassez's epithelial rest cells were located close to the root surface at the apical one-third of the periodontal ligament, and epithelial clusters surrounded by distinct lamina cementia were sometimes observed in the cementum. TUNEL-positive cells were detected only in the cementum. Malassez's epithelial rest cells in the periodontal ligament were completely surrounded by basement membranes, but epithelial clusters in the cementum were only intermittently surrounded by such membranes. Cytokeratin-positive cells in the superstratum of the cementum were directly connected by cementocytes and by desmosome-like structures. However, organelles were scarce in the cytokeratin-positive cells in the substratum of the cementum, and the matrix of the cementum was deposited in the cells.

CONCLUSION

These results suggest that the majority of the fragmented Hertwig's root sheath remains in the periodontal ligament and that some cells, which are connected to cementoblasts, are embedded in the cementum and progress to apoptosis.

Beta defensin-3 engineered epidermis shows highly protective effect for bacterial infection

Defensins are small cationic proteins that harbor broad-spectrum microbicidal activity against bacteria, fungi and viruses. This study examines the effects on pathogens of the epidermis engineered to express human beta-defensin 3 (HBD3) to combat bacterial infections. First, we examined the localization of HBD3 in the epidermis and observed HBD3 in the intercellular spaces and lamellar bodies of the upper epidermal layers. This result showed HBD3 expressed and assembled in the outer layers of the epidermis was suspected to counter the invading microorganisms. Next, we established a keratinocyte cell line that stably expressed HBD3 and found that the culture medium showed antibacterial activity. Furthermore, we prepared an epidermal sheet of these cells with the HBD3 gene and grafted this onto a dermal wound on a nude rat. The HBD3 engineered epidermis demonstrated significant antimicrobial activity. Skin ulcers without epidermis are constantly exposed to invading microorganisms. Biopsy samples of re-epithelizing epidermis from patients with skin ulcers were collected, and HBD3 mRNA level measured in the epidermis. The epidermal samples from the ulcer skin expressed 2.5 times higher levels of HBD3 transcript than those in the control skin. These results, taken together, indicate that the therapeutic introduction of the HBD3 gene into somatic cells may provide a new gene therapy strategy for intractable infectious diseases.

A searchable database for proteomes of oral microorganisms

An online database of proteomes for two-dimensional electrophoresis (2DE) gel data was constructed and it is now freely accessible through a web-based interface. Proteins from three oral bacteria, Streptococcus mutans UA159, Actinobacillus actinomycetemcomitans HK1651, and Porphyromonas gingivalis W83, whose genome databases are freely available, were separated by 2DE, and protein spots were analyzed by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) and identified. About 1000 spots from the gels of P. gingivalis W83 were extracted and analyzed by MALDI-TOF, and 330 proteins were identified. In addition, 160 of 240 spots of A. actinomycetemcomitans and 158 of 356 spots of S. mutans were identified. Information such as spot coordinates on the gels, protein names (predicted functions), molecular weights, isoelectroric points, and links to online databases, including Oral Pathogen Sequence Databases of the Los Alamos National Laboratory Bioscience Division (ORALGEN) and National Center for Biotechnology Information (NCBI) or The Institute Genomic Research (TIGR), were stored in tables accessible through the relational database management system MySQL on an Apache web server. To test for functionality of this database system, responses of S. mutans to environmental changes were analyzed using the database and 21 spots on the gel were identified as proteins whose expression had been increased or decreased by environmental pH change without in-gel trypsin digestion, protein extraction, or MALDI-TOF/TOF-MS (mass spectrometer) analysis. The identified proteins are agreement with those reported in previous papers on acid tolerance of S. mutans, demonstrating the usefulness of the system. This database is available at http://www.myamagu.dent.kyushu-u.ac.jp/~bioinformatics/index.html or http://www.bipos.mascat.nihon-u.ac.jp/index.html.

Interleukin-1beta increases RANTES gene expression and production in synovial fibroblasts from human temporomandibular joint

BACKGROUND

Synovial fibroblasts of temporomandibular joint (TMJ) are poorly characterized, although they have important roles in progression of temporomandibular disorders (TMD). In this study, we investigated responses of synovial fibroblasts to interleukin (IL)-1beta.

METHODS

We examined gene expression profiles of synovial fibroblasts in response to IL-1beta, using Affymetrix GeneChip. Regulated upon activation normal T-cell expressed and secreted (RANTES) gene expression was confirmed by polymerase chain reaction (PCR) and real-time PCR. RANTES protein levels were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The RANTES was preferentially up-regulated in synovial fibroblasts by IL-1beta. The increase in RANTES gene expression in response to IL-1beta was confirmed by PCR and real-time PCR. Protein level of RANTES in synovial fibroblasts was also increased by IL-1beta.

CONCLUSIONS

The RANTES, a cc-type chemokine, has chemotactic effects on lymphocytes and monocytes. Increased gene expression and protein production of RANTES in synovial fibroblasts, in response to IL-1beta, may play an important role in recruitment of inflammatory cells into synovium and progression of synovitis in TMD.

Effect of low-level laser irradiation on osteoglycin gene expression in osteoblasts

Many studies have attempted to elucidate the mechanism of the biostimulatory effects of low-level laser irradiation (LLLI), but the molecular basis of these effects remains obscure. We investigated the stimulatory effect of LLLI on bone formation during the early proliferation stage of cultured osteoblastic cells. A mouse calvaria-derived osteoblastic cell line, MC3T3-E1, was utilised to perform a cDNA microarray hybridisation to identify genes that induced expression by LLLI at the early stage. Among those genes that showed at least a twofold increased expression, the osteoglycin/mimecan gene was upregulated 2.3-fold at 2 h after LLLI. Osteoglycin is a small leucine-rich proteoglycan (SLRP) of the extracellular matrix which was previously called the osteoinductive factor. SLRP are abundantly contained in the bone matrix, cartilage cells and connective tissues, and are thought to regulate cell proliferation, differentiation and adhesion in close association with collagen and many other growth factors. We investigated the time-related expression of this gene by LLLI using a reverse transcription polymerase chain reaction (RT-PCR) method, and more precisely with a real-time PCR method, and found increases of 1.5-2-fold at 2-4 h after LLLI compared with the non-irradiated controls. These results suggest that the increased expression of the osteoglycin gene by LLLI in the early proliferation stage of cultured osteoblastic cells may play an important role in the stimulation of bone formation in concert with matrix proteins and growth factors.

Caffeine enhances the expression of the angiotensin II Type 2 receptor mRNA in BeWo cell culture and in the rat placenta

Although chronic caffeine exposure during pregnancy has been shown to affect fetal growth, adverse effects of caffeine on embryogenesis are not only well understood, but also controversial. We have used gene chip technology in an attempt to identify to what extent, if any, caffeine could possibly alter gene expressions in the cytotrophoblast-like cell line BeWo. Few down-regulated genes were found; most of the genes were up-regulated, suggesting that chronic caffeine exposure during the gestational period could exert certain influences on embryogenesis. The highest up-regulated gene expression of BeWo cells by caffeine was angiotensin II type 2 (AT(2)) receptor gene. We focused the genes of the renin-angiotensin system (RAS), angiotensin II type 1 (AT(1)) and AT(2)receptors and angiotensin I converting enzyme, for study on caffeine's responsive gene expression in BeWo cells and in the placentae of pregnant rats that were fed a diet supplemented with caffeine (2 mg/100 g body weight) during gestation, and analysed the gene expressions using RT-PCR and LightCycler system. A significantly increased AT(2)receptor gene expression and a slight decreased AT(1)receptor gene expression demonstrated the caffeine's effect to the placental RAS.

Production of monoclonal antibody inhibiting dipeptidylaminopeptidase IV activity of Porphyromonas gingivalis

Porphyromonas gingivalis is a Gram-negative anaerobic bacterial species implicated as an important pathogen in the development of adult periodontitis. We previously cloned a gene encoding dipeptydilaminopeptidase IV (DAPIV) from P. gingivalis. In the present study, for immunological diagnosis and development of passive immunization, we produced a mouse monoclonal antibody (MAb) capable of inhibiting the DAPIV activity of P. gingivalis using highly purified recombinant DAPIV as an immunogen. The constructed MAb, designated as MAb-Pg-DAP-1, significantly inhibited DAPIV activity in P. gingivalis, as well as slightly inhibited that in other gram-negative bacteria such as Porphyromonas endodontalis and Prevotella loesheii, whereas no inhibition was seen in the gram-positive bacteria Streptococcus mutans and Actinomyces viscosus. Furthermore, the MAb did not inhibit DAPIV enzyme activity in human serum. This novel MAb may be useful for the development of immunological diagnosis capability and in passive immunization.

Microarray analysis of gene expression changes in aging in mouse submandibular gland

Little is known about the effect of salivary gland function during aging based on gene expression. Recently emerged DNA array technology provides a sensitive, quantitative, rapid approach to the monitoring of the global pattern of gene expression. In this study, we used high-density oligonucleotide arrays to monitor the changes of gene expression levels in the submandibular gland (SMG) by comparing adult mice with elderly adult mice. Of the 1328 genes screened, 160 genes (12.0%) showed more than two-fold changes; 154 (96.3%) of these genes, associated with transcription regulation, transport, signal transduction, and enzymes in the elderly mice, exhibited decreased expression levels. The remaining 6 genes (3.7%) in the elderly mice showed increased expression levels. In mouse SMG, analysis of these data suggests that aging may lead the gene expression to decrease than increase. Thus, DNA array technology can be a powerful tool for the identification of age-associated candidate genes for further analysis in aging.

Passive immunization against dental caries and periodontal disease: development of recombinant and human monoclonal antibodies

Indigenous micro-organisms in the oral cavity can cause two major diseases, dental caries and periodontal diseases. There is neither agreement nor consensus as to the actual mechanisms of pathogenesis of the specific virulence factors of these micro-organisms. The complexity of the bacterial community in dental plaque has made it difficult for the single bacterial agent of dental caries to be determined. However, there is considerable evidence that Streptococcus mutans is implicated as the primary causative organism of dental caries, and the cell-surface protein antigen (SA I/II) as well as glucosyltransferases (GTFs) produced by S. mutans appear to be major colonization factors. Various forms of periodontal diseases are closely associated with specific subgingival bacteria. Porphyromonas gingivalis has been implicated as an important etiological agent of adult periodontitis. Adherence of bacteria to host tissues is a prerequisite for colonization and one of the important steps in the disease process. Bacterial coaggregation factors and hemagglutinins likely play major roles in colonization in the subgingival area. Emerging evidence suggests that inhibition of these virulence factors may protect the host against caries and periodontal disease. Active and passive immunization approaches have been developed for immunotherapy of these diseases. Recent advances in mucosal immunology and the introduction of novel strategies for inducing mucosal immune responses now raise the possibility that effective and safe vaccines can be constructed. In this regard, some successful results have been reported in animal experimental models. Nevertheless, since the public at large might be skeptical about the seriousness of oral diseases, immunotherapy must be carried out with absolute safety. For this goal to be achieved, the development of safe antibodies for passive immunization is significant and important. In this review, salient advances in passive immunization against caries and periodontal diseases are summarized, and the biotechnological approaches for developing recombinant and human-type antibodies are introduced. Furthermore, our own attempts to construct single-chain variable fragments (ScFv) and human-type antibodies capable of neutralizing virulence factors are discussed.

Cell death of osteocytes occurs in rat alveolar bone during experimental tooth movement

The purpose of this study was to examine the morphological changes in alveolar bone osteocytes on the pressure side during experimental tooth movement, using quantitative evaluation on hematoxylin and eosin-stained sections, the TUNEL method, confocal laser scanning microscopy (CLSM), and transmission electron microscopy. In 8-week-old Wistar rats, the left first molar was forced to move mesially with an average load of 10 g by a nickel-titanium superelastic wire. After 6 hours, nuclear condensation and fragmentation appeared in osteocytes adjacent to the hyalinized periodontal ligament (PDL). These cells showed TUNEL-positive reaction. The number of osteocytes with apoptosis progressively increased up to 1 day. At 1 and 2 days, cytoplasmic and nuclear destruction and distribution within the lacunae occurred and increased up to 4 days. The proportion of necrotic osteocytes and near empty lacunae peaked at 2 and 4 days, respectively. At 7 days, necrotic osteocyte and empty lacunae numbers returned to the level of control bone, probably due to resorption of the alveolar bone containing apoptotic and necrotic osteocytes. Ultrastructually, the osteocytes showed apoptotic morphology at 6 and 12 hours and 1 day; at 2 and 4 days, several osteocytes exhibited characteristics of necrosis and destructive images of the surrounding bone matrix, which resulted in enlargement of the lacunae. The present results demonstrate that osteocytes in alveolar bone adjacent to the hyalinized PDL underwent cell death via apoptosis and "secondary necrosis" during orthodontic tooth movement, which may be associated with the subsequent bone resorption.