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This paper investigates the mechanical behavior of carbon nanotube (CNT)-reinforced aluminum composites (CNT–Al composites) under a tensile loading condition using molecular dynamics (MD) simulations. A review of current computational and experimental studies highlights the benefits of CNT–Al composites from a structural point of view. However, quantitative and qualitative investigations on the improvements due to the inclusion of CNTs are still rare. This study shows that, compared to pure aluminum, the Young's moduli are improved by 31% for (4,4)CNT–Al, 33% for (6,6)CNT–Al, and 39% for (8,8)CNT–Al. Moreover, the corresponding toughness values are significantly enhanced by 37%, 72%, and 100%. Furthermore, the MD simulations provide insights into various fracture behaviors at the atomic scale, including lattice disordering, local changes in lattice structures due to stacking faults, and void nucleation/growth. The component analysis shows that the mechanical properties of CNT–Al composites improve significantly, even with a small amount of CNT, due to the considerable load-bearing capacity of CNT. [ABSTRACT FROM AUTHOR]

Abstract: Streptococcus mutans metabolize carbohydrates, such as glucose and sucrose, to produce acid and enhance biofilm formation with the early colonizing bacteria to induce dental caries. Xylitol has been used as a reliable substitute for carbohydrate to inhibit the acid production of S. mutans. However, long-term xylitol consumption leads to the emergence of xylitol-resistance in S. mutans. The aim of this study was to investigate the cariogenic trait of Xylitol-resistant (XR) S. mutans using biofilm formation and coaggregation of xylitol-sensitive (XS) and XR S. mutans with salivary bacteria and their glucosyltransferases expression. When XS or XR S. mutans were incubated in brain heart infusion broth with bacteria from human saliva, XR S. mutans exhibited reduction in biofilm formation in comparison to XS S. mutans. The coaggregation between XR S. mutans and S, gordonii, S. mitis, S. oralis or S. sanguinis was less pronounced than that of XS S. mutans in the presence of sucrose. However, there was no difference in the coaggregation between XR and XS S. mutans in the sucrose-free condition. The level of gtfB and gtfC mRNA expression of XR S. mutans was lower than that of XS S. mutans, whilst the level of gtfD mRNA expression did not differ between the two strains. The reduction of biofilm formation in XS S. mutans due to decrease in glucosyltransferases expression suggests that XR S. mutans may be less cariogenic than XS S. mutans. [Copyright &y& Elsevier]

Synaptotagmin-1 (Syt1) is a major Ca2+ sensor for synchronous neurotransmitter release, which requires vesicle fusion mediated by SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptors). Syt1 utilizes its diverse interactions with target membrane (t-) SNARE, SNAREpin, and phospholipids, to regulate vesicle fusion. To dissect the functions of Syt1, we apply a single-molecule technique, alternating-laser excitation (ALEX), which is capable of sorting out subpopulations of fusion intermediates and measuring their kinetics in solution. The results show that Syt1 undergoes at least three distinct steps prior to lipid mixing. First, without Ca2+, Syt1 mediates vesicle docking by directly binding to t-SNARE/phosphatidylinositol 4,5-biphosphate (PIP2) complex and increases the docking rate by 103 times. Second, synaptobrevin-2 binding to t-SNARE displaces Syt1 from SNAREpin. Third, with Ca2+, Syt1 rebinds to SNAREpin, which again requires PIP2. Thus without Ca2+, Syt1 may bring vesicles to the plasma membrane in proximity via binding to t-SNARE/PIP2 to help SNAREpin formation and then, upon Ca2+ influx, it may rebind to SNAREpin, which may trigger synchronous fusion. The results show that ALEX is a powerful method to dissect multiple kinetic steps in the vesicle fusion pathway. [ABSTRACT FROM AUTHOR]

Filifactor alocis, an asaccharolytic anaerobic Gram-positive rod (AAGPR), is an emerging marker of periodontitis. Severe periodontitis causes destruction of the alveolar bone that supports teeth and can even lead to tooth loss. Based on our previous report that F. alocis-derived extracellular vesicles (FA EVs) contain various effector molecules and have immunostimulatory activity, we investigated the effect of FA EVs on osteogenesis using mouse bone-derived mesenchymal stromal cells (BMSCs). FA EVs dramatically inhibited bone mineralization similar to whole bacteria and reduced the expression levels of osteogenic marker genes. The osteogenic differentiation of TLR2-deficient BMSCs was not inhibited by FA EVs, suggesting that their inhibitory effect on osteogenesis is dependent on TLR2 signaling. FA EVs effectively activated TLR2 downstream signaling of the MAPK and NF-κB pathways. In addition, FA EVs regulated RANKL and OPG gene expression, increasing the RANKL/OPG ratio in BMSCs in a TLR2-dependent manner. Our study suggests that F. alocis-derived EVs interfere with bone metabolism via TLR2 activation, providing insight into the pathogenesis of bone loss associated with periodontitis. [ABSTRACT FROM AUTHOR]

Traces a study which showed the cloning of the major sheath protein-encoding gene, mspA of the oral spirochete Treponema maltophilum ATCC 51939 by screening a genomic library with an anti-outer membrane fraction antibody. Nucleotide sequence analysis of the DNA region containing mspA locus; Analysis of the mspA peptide; Occurrence of the mspA gene-containing region in other treponeme species.

Filifactor alocis, a gram-positive, obligate anaerobic rod, is an emerging periodontal pathogen that is frequently isolated from patients with periodontitis, peri-implantitis, and apical periodontitis. Recent studies have shown that extracellular vesicles (EVs) from gram-negative periodontal pathogens, so-called outer membrane vesicles (OMVs), harbor various effector molecules responsible for inducing host inflammatory responses. However, there are no reports of EVs from F. alocis. In this study, we purified and characterized the protein profiles of EVs from F. alocis and investigated their immunostimulatory activity on human monocytic THP-1 and human oral keratinocyte HOK-16B cell lines. Highly pure EVs were obtained from F. alocis using density gradient ultracentrifugation. Nanoparticle tracking analysis and transmission electron microscopy showed that F. alocis EVs were between 50 and 270 nm in diameter. Proteome analysis identified 28 proteins, including lipoproteins, autolysins, F. alocis complement inhibitor (FACIN), transporter-related proteins, metabolism-related proteins, and ribosomal proteins. Human cytokine array analysis showed that F. alocis EVs remarkably induced the expression of CCL1, CCL2, MIP-1, CCL5, CXCL1, CXCL10, ICAM-1, IL-1β, IL-1ra, IL-6, IL-8, MIF, SerpinE, and TNF-α in THP-1 cells and CXCL1, G-CSF, GM-CSF, IL-6, and IL-8 in HOK-16B cells. The immunostimulatory activity of F. alocis EVs was similar to that of the whole bacterial cells. Our findings provide new insight into the role of EVs from gram-positive oral bacteria in periodontal diseases. [ABSTRACT FROM AUTHOR]

Plasminogen activator inhibitor‐1 (PAI‐1) is associated with nonalcoholic fatty liver disease (NAFLD) by lipid accumulation in the liver. In this study, we showed that extracellular vesicles (EVs) from the periodontal pathogens Filifactor alocis and Porphyromonas gingivalis induced steatosis by inducing PAI‐1 in the liver and serum of mice fed a low‐fat diet. PAI‐1 induction was not observed in TLR2−/− mice. When tested using HEK‐Blue hTLR2 cells, human TLR2 reporter cells, the TLR2‐activating ability of serum from NAFLD patients (n = 100) was significantly higher than that of serum from healthy subjects (n = 100). Correlation analysis confirmed that PAI‐1 levels were positively correlated with the TLR2‐activating ability of serum from NAFLD patients and healthy subjects. Amphiphilic molecules in EVs were involved in PAI‐1 induction. Our data demonstrate that the TLR2/PAI‐1 axis is important for hepatic steatosis by EVs of periodontal pathogens. [ABSTRACT FROM AUTHOR]

Interleukin-24 is a pleiotropic immunoregulatory cytokine and a member of the IL-20R subfamily of the IL-10 family. The aim of this study was to investigate the regulation of IL-24 in the human oral keratinocyte cell line HOK-16B following infection with Tannerella forsythia, a major periodontal pathogen. T. forsythia induced the expression of IL-24 mRNA and the secretion of glycosylated IL-24 in HOK-16B cells. Glycosylation of IL-24 is linked to its solubility and bioavailability. T. forsythia-stimulated reactive oxygen species (ROS) induced the expression of IL-24, which was regulated by IL-6. The ROS inhibitor N-acetylcysteine and MAPK inhibitors significantly reduced the expression of IL-6 and IL-24 induced by T. forsythia. Recombinant human IL-24 significantly enhanced the expression of IL-1α, IL-8, CXCL10, and MCP-1 in HOK-16B cells. Together, these results indicate that ROS, MAPKs, and IL-6 comprise the axis of IL-24 expression in HOK-16B cells stimulated with T. forsythia. Thus, IL-24 may be involved in inflammation in oral keratinocytes. [ABSTRACT FROM AUTHOR]

Periodontitis is a chronic inflammatory disease caused by periodontal pathogens in subgingival plaque and is associated with systemic inflammatory diseases. Extracellular vesicles (EVs) released from host cells and pathogens carry a variety of biological molecules and are of interest for their role in disease progression and as diagnostic markers. In the present study, we analysed the proteome and inflammatory response of EVs derived from macrophages infected with Tannerella forsythia, a periodontal pathogen. The EVs isolated from the cell conditioned medium of T. forsythia‐infected macrophages were divided into two distinct vesicles, macrophage‐derived EVs and T. forsythia‐derived OMVs, by size exclusion chromatography combined with density gradient ultracentrifugation. Proteome analysis showed that in T. forsythia infection, macrophage‐derived EVs were enriched with pro‐inflammatory cytokines and inflammatory mediators associated with periodontitis progression. T. forsythia‐derived OMVs harboured several known virulence factors, including BspA, sialidase, GroEL and various bacterial lipoproteins. T. forsythia‐derived OMVs induced pro‐inflammatory responses via TLR2 activation. In addition, we demonstrated that T. forsythia actively released OMVs when T. forsythia encountered macrophage‐derived soluble molecules. Taken together, our results provide insight into the characterisation of EVs derived from cells infected with a periodontal pathogen. [ABSTRACT FROM AUTHOR]

Objective The antimicrobial efficacy of zinc- (ZnCl 2 ) and cetylpyridinium-chloride (CPC) and their inhibition capacity on volatile sulfur compound (VSC) production by oral bacterial strains were investigated. Design Minimum inhibitory concentrations (MIC) and growth curves were determined for ZnCl 2 , CPC, and CPC with ZnCl 2 solutions against eight oral microorganisms ( Aggregatibacter actinomycetemcomitans , Fusobacterium nucleatum, Porphyromonas gingivalis , Prevotella intermedia , Treponema denticola , Tannerella forsythia , Staphylococcus aureus and Streptococcus mutans ) known to be involved in the pathophysiology of both halitosis and periodontal disease. Gas chromatography was applied to measure VSCs (H 2 S, CH 3 SH, (CH 3 ) 2 S) production levels of each strains following exposure to the solutions. Results ZnCl 2 and CPC effectively inhibited growth of all eight strains. ZnCl 2 was generally more effective than CPC in suppressing bacterial growth excluding A. actinomycetemcomitans , P. intermedia , and T. forsythia . Synergism between CPC and ZnCl 2 was shown in A. actinomycetemcomitans . The MIC for CPC was significantly lower than ZnCl 2 . VSC production was detected in five bacterial strains ( A. actinomycetemcomitans , F. nucleatum , P. gingivalis , T. denticola , and T. forsythia ). Each bacterial strain showed unique VSCs production profiles. H 2 S was produced by F. nucleatum , P. gingivalis , and T. denticola , CH 3 SH by all five strains and (CH 3 ) 2 S by A. actinomycetemcomitans , F. nucleatum , P. gingivalis , and T. denticola . Production of CH 3 SH, the most malodorous component among the three major VSCs from mouth air was evident in F. nucleatum and T. forsythia . Conclusion Both ZnCl 2 and CPC effectively inhibit bacterial growth causative of halitosis and periodontal disease, resulting in a direct decrease of bacterial VSCs production. [ABSTRACT FROM AUTHOR]

Extracellular fibronectin (Fn) can activate pro-inflammatory pathways and serves as an endogenous danger signalling molecule; thus, it has been suggested as a biomarker for several diseases. In the present study, we found that pathogen-derived activators of the inflammasomes induce the expression and secretion of Fn in macrophages through a mechanism involving adenosine triphosphate and caspase-1 activation. We also found that plasma Fn induces caspase-1 activation and cell death in macrophages, epithelial cells, and fibroblasts. Together, these results indicate that Fn plays a critical role in inflammasome-activated cells by amplifying caspase-1 activation and inducing inflammatory cell death. [ABSTRACT FROM AUTHOR]

Outer membrane vesicles (OMVs) of bacteria harbor physiologically active molecules, and quorum sensing inhibitors (QSIs) are expected to regulate bacterial virulence. In this study, we analyzed the proinflammatory activity of OMVs of the periodontal pathogen Tannerella forsythia treated with d‐arabinose and d‐galactose as QSIs, which inhibit the biofilm formation of periodontal pathogens and autoinducer 2 activity. Compared to OMVs of nontreated T. forsythia (TF OMVs), OMVs released from QSI‐treated T. forsythia, designated TF ara‐OMVs and TF gal‐OMVs, showed reduced production of TNF‐α, IL‐1β, IL‐6, and IL‐8 in THP‐1 monocytes through decreased activation of NF‐κB/MAPKs. Using a human NF‐κB reporter cell line and bone marrow‐derived macrophages from TLR2−/− mice, TF ara‐OMVs and TF gal‐OMVs showed less activation of TLR2 than TF OMVs. These results demonstrated that QSIs provide a dual advantage against bacterial infection by inhibiting bacterial biofilm formation and generating OMVs with reduced proinflammatory activity. [ABSTRACT FROM AUTHOR]

Outer membrane vesicles (OMVs) released from gram-negative bacteria harbor diverse molecules to communicate with host cells. In this study, we evaluated the OMVs of periodontal pathogens for their effects on the activation of dendritic cells and CD4+ T cell differentiation. OMVs of Porphyromonas gingivalis ATCC 33277, Treponema denticola ATCC 33521, and Tannerella forsythia ATCC 43037 ('red complex' pathogens) were isolated by density gradient ultracentrifugation. Mouse bone marrow-derived dendritic cells (BMDCs) were treated with OMVs, and OMV-primed BMDCs were cocultured with naïve CD4+ T cells to analyze the polarization of effector helper T cells. The OMVs upregulated maturation markers, including MHC class II, CD80, CD86, and CD40, on BMDCs. OMVs of P. gingivalis and T. forsythia induced the expression of the proinflammatory cytokines IL-1β, IL-6, IL-23, and IL-12p70 in BMDCs. In T. denticola OMV-primed BMDCs, proinflammatory cytokines were poorly detected, which may be attributed to posttranslational degradation due to the highly proteolytic nature of OMVs. In cocultures of naïve CD4+ T cells with OMV-primed BMDCs, OMVs of P. gingivalis and T. denticola induced the differentiation of Th17 cells, whereas T. forsythia OMVs induced Th1 cell differentiation. These results demonstrate that OMVs derived from the 'red complex' periodontal pathogens induce maturation of BMDCs and differentiation of naïve CD4+ T cells to Th1 or Th17 cells. [ABSTRACT FROM AUTHOR]

P orphyromonas gingivalis utilizes its major proteases, Arg gingipains ( RgpA and RgpB) and Lys gingipain ( Kgp), for dysregulation of host immune systems. The aim of this study was to investigate the roles of gingipains in caspase-1 activation and its sequelae in P . gingivalis-infected macrophages. Infection with P . gingivalis at low multiplicity of infections ( MOIs), but not at high MOIs, resulted in low levels of interleukin-1β and lactate dehydrogenase without detectable active caspase-1 in the culture supernatants. The proteins released from caspase-1-activated cells were rapidly degraded by gingipains. However, P . gingivalis with gingipains induced higher intracellular caspase-1 activity in the infected cells than the gingipain-null mutant, which was associated with ATP release from the infected cells. In addition, growing the gingipain-null mutant with gingipains enhanced caspase-1 activation by the mutant. In contrast, inhibition of the protease activity of Kgp or Rgps increased the caspase-1-activating potential of wild-type P . gingivalis, indicating an inhibitory effect of the collaborative action of Kgp and Rgps. These results illuminate the contradictory roles of gingipains in the manipulation of host defence systems by P . gingivalis, as they act by both stimulating and inhibiting innate immune responses. [ABSTRACT FROM AUTHOR]

Dysbiosis of the oral microbiota plays an important role in the progression of periodontitis, which is characterized by chronic inflammation and alveolar bone loss, and associated with systemic diseases. Bacterial extracellular vesicles (EVs) contain various bioactive molecules and show diverse effects on host environments depending on the bacterial species. Recently, we reported that EVs derived from Filifactor alocis, a Gram-positive periodontal pathogen, had osteoclastogenic activity. In the present study, we analysed the osteoclastogenic potency and immunostimulatory activity of EVs derived from the Gram-negative periodontal pathogens Porphyromonas gingivalis and Tannerella forsythia, the oral commensal bacterium Streptococcus oralis, and the gut probiotic strain Lactobacillus reuteri. Bacterial EVs were purified by density gradient ultracentrifugation using OptiPrep (iodixanol) reagent. EVs from P. gingivalis, T. forsythia, and S. oralis increased osteoclast differentiation and osteoclstogenic cytokine expression in osteoclast precursors, whereas EVs from L. reuteri did not. EVs from P. gingivalis, T. forsythia, and S. oralis preferentially activated Toll-like receptor 2 (TLR2) rather than TLR4 or TLR9, and induced osteoclastogenesis mainly through TLR2. The osteoclastogenic effects of EVs from P. gingivalis and T. forsythia were reduced by both lipoprotein lipase and polymyxin B, an inhibitor of lipopolysaccharide (LPS), while the osteoclastogenic effects of EVs from S. oralis were reduced by lipoprotein lipase alone. These results demonstrate that EVs from periodontal pathogens and oral commensal have osteoclastogenic activity through TLR2 activation by lipoproteins and/or LPS. [ABSTRACT FROM AUTHOR]

Periodontitis is an inflammatory disease induced by local infection in tooth‐supporting tissue. Periodontitis is associated with systemic bone diseases, but little is known about the mechanism of the causal effect of periodontitis on systemic bone resorption. Bacteria‐derived extracellular vesicles (EVs) act as natural carriers of virulence factors that are responsible for systemic inflammation. In this study, we investigated the role of EVs derived from Filifactor alocis, a Gram‐positive, anaerobic periodontal pathogen, in systemic bone loss and osteoclast differentiation. F. alocis EVs accumulated in the long bones of mice after intraperitoneal administration. These EVs induced proinflammatory cytokines, osteoclastogenesis, and bone resorption via Toll‐like receptor 2 (TLR2). The phase separation of F. alocis EVs showed that amphiphilic molecules were responsible for the induced bone resorption and osteoclastogenesis. The osteoclastogenic effects of F. alocis EVs were reduced by lipoprotein lipase. Proteomic analysis of the amphiphilic molecules identified seven lipoproteins. Our results indicate that lipoprotein‐like molecules in F. alocis EVs may contribute to systemic bone loss via TLR2. [ABSTRACT FROM AUTHOR]

Uric acid is a potential metabolite that serves as a danger‐associated molecular pattern (DAMP) and induces inflammatory responses in sterile environments. Porphyromonas gingivalis is a keystone periodontopathogen, and its gingipain proteases play a critical role in the pathogenesis of periodontitis. In this study, we demonstrate that P. gingivalis gingipains play a role in THP‐1 macrophage uric acid production by increasing the expression and activity of xanthine oxidoreductase (XOR). Uric acid sodium salt induces caspase‐1 activation, cell death, and the expression of proinflammatory cytokines, including IL‐1α, IL‐6, and IL‐8, in the human keratinocyte HOK‐16B cell line. Our results suggest that gingipain‐induced uric acid can mediate inflammation in periodontal tissue cells. [ABSTRACT FROM AUTHOR]

This study aimed to verify, in in vivo settings, whether quorum‐sensing inhibition molecules could attenuate alveolar bone loss induced by Porphyromonas gingivalis/Fusobacterium nucleatum co‐infection and reduce the bacterial colonization of periodontal tissues. In BALB/c mice, periodontitis was induced through oral inoculation with P. gingivalis and F. nucleatum six times during a 42‐d period. Quorum sensing inhibitors (a furanone compound and D‐ribose) were administered simultaneously with bacterial infection. Linear and volumetric modifications of interproximal alveolar bone levels were compared between groups using micro‐computed tomography. Total bacteria, and P. gingivalis and F. nucleatum DNA in periodontal tissues, were quantified using real‐time PCR. Radiographic linear measurements demonstrated a significant reduction of alveolar bone loss, of approximately 40%, in mice treated with quorum sensing inhibitors when compared with the co‐infection group. This was confirmed by a significant increase of residual bone volume in the test group. While total bacterial genes in the treatment group significantly decreased by 93% in periodontal tissue samples when quorum sensing inhibitors were administered, no significant differences of P. gingivalis DNA were found. Quorum sensing inhibitors reduced periodontal breakdown and bacterial infection in periodontal tissues after co‐infection with P. gingivalis and F. nucleatum. [ABSTRACT FROM AUTHOR]

Invasion of periodontal pathogens into periodontal tissues is an important step that can cause tissue destruction in periodontal diseases. Porphyromonas gingivalis is a keystone pathogen and its gingipains are key virulence factors. Fusobacterium nucleatum is a bridge organism that mediates coadhesion of disease-causing late colonizers such as P. gingivalis and early colonizers during the development of dental biofilms. The aim of this study was to investigate how P. gingivalis, in particular its gingipains, influences the invasion of coinfecting F. nucleatum into gingival epithelial cells. When invasion of F. nucleatum was analyzed after 4 h of infection, invasion of F. nucleatum was suppressed in the presence of P. gingivalis compared with during monoinfection. However, coinfection with a gingipain-null mutant of P. gingivalis did not affect invasion of F. nucleatum. Inhibition of PI3K reduced invasion of F. nucleatum. P. gingivalis inactivated the PI3K/AKT pathway, which was also dependent on gingipains. Survival of intracellular F. nucleatum was promoted by P. gingivalis with Arg gingipain mutation. The results suggest that P. gingivalis, in particular its gingipains, can affect the invasion of coinfecting F. nucleatum through modulating intracellular signaling of the host cells. [ABSTRACT FROM AUTHOR]

Bacterial behaviors such as virulence factor secretion and biofilm formation are critical for survival, and are effectively regulated through quorum sensing, a mechanism of intra- and interspecies communication in response to changes in cell density and species complexity. Many bacterial species colonize host tissues and form a defensive structure called a biofilm, which can be the basis of inflammatory diseases. Periodontitis, a chronic inflammatory disease affecting the periodontium, is caused by subgingival biofilms related to periodontopathogens. In particular, Fusobacterium nucleatum is a major co-aggregation bridge organism in the formation and growth of subgingival biofilms, linking the early and late colonizers in periodontal biofilms. According to our previous study, the intergeneric quorum-sensing signal molecule autoinducer-2 (AI-2) of F. nucleatum plays a key role in intra- and interspecies interactions of periodontopathogens, and may be a good target for periodontal biofilm inhibition. Recently, brominated furanones produced by the macroalga Delisea pulchra were shown to inhibit biofilm formation via AI-2, and have been investigated toward the goal of increasing the inhibition effect. In this study, we describe the synthesis of new bromofuranone analogs, i.e., 3-(dibromomethylene)isobenzofuran-1(3H)-one derivatives, and demonstrate their inhibitory activities against biofilm formation by periodontopathogens, including F. nucleatum, Porphyromonas gingivalis, and Tannerella forsythia. [ABSTRACT FROM AUTHOR]

Quorum sensing (QS) is a chemical communication between bacteria, with which bacteria sense the population of their own species. Autoinducer-2 ( AI-2) is a class of universal quorum-sensing molecules, which is used by both Gram-negative and Gram-positive bacteria. The inhibition of AI-2-mediated QS has various practical applications, including the prevention of the formation of biofilm in dental gums. In this work, we develop a computational protocol for developing AI-2 inhibitors. A challenging aspect of such an endeavor is that the receptor undergoes a large conformational change upon ligand binding. We combine several methods such as molecular docking with multiple conformations, molecular dynamics simulations, and molecular mechanics Poisson-Boltzmann computation, in order to estimate binding affinity of candidate molecules to a quorum-sensing receptor. We apply our method to rank the substances in a chemical library. We indeed find a molecule that has a higher affinity than previously known ligands, thus showing the feasibility of the protocol for the development of quorum-sensing inhibitors. [ABSTRACT FROM AUTHOR]

Biofilm formation on dental implant surfaces can cause peri-implant mucositis and peri-implantitis. Lectins are involved in interactions between bacteria or between bacteria and their hosts. Disrupting these interactions via specific sugars can result in reduced adhesion and biofilm formation. The purpose of this study was to identify sugars that function as antiadhesion or antibiofilm agents on titanium discs. Of the sugars tested, the sugars that did not affect the planktonic growth of Streptococcus oralis , Fusobacterium nucleatum , and Porphyromonas gingivalis were selected. The selected sugars were assessed for their ability to inhibit biofilm formation of bacteria in single and consortium species by crystal violet staining, confocal laser scanning microscopy after live/dead staining, and scanning electron microscopy. The sugars were evaluated for their ability to inhibit activity of the quorum sensing molecule autoinducer 2 (AI-2) by bioluminescence assay. Biofilm formation of single bacteria or consortia of S. oralis , F. nucleatum , and P. gingivalis on titanium discs was significantly inhibited in the presence of d -arabinose. Pretreating titanium discs with d -arabinose for 3 min inhibited biofilm formation at a level comparable to that observed when d -arabinose was present over the entire period, suggesting that d -arabinose had initial anti-adhesive activity. In addition, d -arabinose inhibited the activity of AI-2. d -Arabinose may be a good candidate for application as an antibiofilm agent and AI-2 inhibitor. • d -Arabinose inhibited biofilm formation of S. oralis , F. nucleatum , and P. gingivalis on titanium discs. • Pretreatment of titanium discs with d -arabinose for 3 min resulted in significantly reduced biofilm formation. • d -Arabinose inhibited the activity of autoinducer 2, a quorum sensing molecule. [ABSTRACT FROM AUTHOR]

Abstract: Autoinducer 2 (AI-2) is a quorum sensing molecule and plays an important role in dental biofilm formation, mediating interspecies communication and virulence expression of oral bacteria. Fusobacterium nucleatum connects early colonizing commensals and late colonizing periodontopathogens. F. nucleatum AI-2 and quorum sensing inhibitors (QSIs) can manipulate dental biofilm formation. In this study, we evaluated the effect of F. nucleatum AI-2 and QSIs on biofilm formation of Streptococcus gordonii and Streptococcus oralis, which are initial colonizers in dental biofilm. F. nucleatum AI-2 significantly enhanced biofilm growth of S. gordonii and attachment of F. nucleatum to preformed S. gordonii biofilms. By contrast, F. nucleatum AI-2 reduced biofilm growth of S. oralis and attachment of F. nucleatum to preformed S. oralis biofilms. The QSIs, (5Z)-4-bromo-5-(bromomethylene)-2(5H)-furanone and d-ribose, reversed the stimulatory and inhibitory effects of AI-2 on S. gordonii and S. oralis, respectively. In addition, co-culture using a two-compartment system showed that secreted molecules of F. nucleatum had the same effect on biofilm growth of the streptococci as AI-2. Our results demonstrate that early colonizing bacteria can influence the accretion of F. nucleatum, a secondary colonizer, which ultimately influences the binding of periodontopathogens. [Copyright &y& Elsevier]

Abstract: Periodontitis is initiated by bacteria in subgingival biofilms, which are composed mostly of Gram-negative anaerobes. Autoinducer 2 (AI-2) is a universal quorum sensing (QS) molecule that mediates intergeneric signalling in multispecies bacterial communities and may induce biofilm formation. As Fusobacterium nucleatum is the major coaggregation bridge organism that links early colonising commensals and late pathogenic colonisers in dental biofilms via the accretion of periodontopathogens, we hypothesised that AI-2 of F. nucleatum contributes to this interspecies interaction, and interruption of this signalling could result in the inhibition of biofilm formation of periodontopathogens. To test this hypothesis, we evaluated the effect of partially purified F. nucleatum AI-2 on monospecies biofilm as well as mutualistic interactions between F. nucleatum and the so-called ‘red complex’ (Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia). Then we tested the effect of two QS inhibitors (QSIs), (5Z)-4-bromo-5-(bromomethylene)-2(5H)-furanone (furanone compound) and d-ribose, on AI-2-induced biofilm formation and coaggregation. F. nucleatum AI-2 remarkably induced biofilm growth of single and dual species and coaggregation between F. nucleatum and each species of the ‘red complex’, all of which were inhibited by the QSIs. F. nucleatum AI-2 induced the expression of the representative adhesion molecules of the periodontopathogens, which were inhibited by the QSIs. Our results demonstrate that F. nucleatum AI-2 plays an important role in inter- and intraspecies interactions between periodontopathogens via enhanced expression of adhesion molecules and may be a target for the inhibition of pathogenic dental biofilm formation. [Copyright &y& Elsevier]

Summary: Integrins are cell-surface heterodimeric glycoproteins composed of alpha and beta subunits that mediate cell-cell, cell-extracellular matrix, and cell-pathogen interactions. In this study, we report a specific role of integrin α5β1 in NLRP3 inflammasome activation in macrophages stimulated by Td92, a surface protein of the periodontopathogen, Treponema denticola. The direct interaction of Td92 with the cell membrane integrin α5β1 resulted in ATP release and K+ efflux, which are the main events in NLRP3 activation. This interaction was arginine-glycine-aspartate (RGD)-independent, and Td92 internalization was not required for the activity. An integrin α5β1 antibody and oxATP, an ATP receptor antagonist, inhibited NLRP3 expression, caspase-1 activation, interleukin-1β (IL-1β) secretion, and proIL-1β synthesis, all of which were regulated by NF-κB activation. Therefore, our data has identified the integrin α5β1 as a principal cell membrane receptor for both NLRP3 inflammasome activation and IL-1β transcription by a bacterial protein, which could exaggerate inflammation, a characteristic of periodontitis. [ABSTRACT FROM AUTHOR]

Abstract: Aim of the study: Our previous research has showed that rhizome of Atractylodes japonica Koidz (Compositae) exhibits an increase in the spontaneous contractility of distal colon in rats. The aims of this study are to identify the phytochemical(s), which stimulate(s) the colonic contractility, contained in Atractylodes japonica and to evaluate the pharmacological mechanism responsible for the colonic muscle contraction. Materials and methods: Based on the stimulatory activity-guided fractionation on the isometric contraction of rat distal colonic strips, atractylodiol (ATD) and diacetyl-atractylodiol (DATD) were isolated from the CHCl3 fractions of Atractylodes japonica. Results: ATD and DATD dose-dependently increased both tension and amplitude of distal colon longitudinal muscle (DCLM), but they stimulated only amplitude in the distal colon circular muscle. The ED50 values of ATD and DATD to stimulate the amplitude of DCLM were revealed as 9.1×10−9 M and 1.8×10−8 M, respectively. l-NAME (0.1mM) significantly increased the ADT (1μM)-induced contraction of DCLM, whereas SNAP (0.1mM) markedly reduced the stimulatory effects of ATD on DCLM contractility. The combined effects of SNAP and atropine (0.5μM) on the ATD-induced contraction of DCLM were similar to the inhibitory effects of SNAP alone. Suramin (0.1mM) significantly enhanced the increase of ATD-induced DCLM contraction, whereas ADPβS (0.1mM) markedly abolished the stimulatory effects of ATD on the spontaneous contractility of DCLM. Conclusions: The present results demonstrate that acetylene compounds, ATD and DATD, are the effective phytochemical of Atractylodes japonica to stimulate the motility of distal colon in rats, and ATD possibly enhances the spontaneous contractility of distal colon through inhibiting the mechanism of nitrergic–purinergic relaxation. [ABSTRACT FROM AUTHOR]

Abstract: Aim of the study: Our previous research has showed that rhizome of Atractylodes japonica Koidz (Compositae) exhibits an increase in the spontaneous contractility of distal colon in rats. The aims of this study are to identify the phytochemical(s), which stimulate(s) the colonic contractility, contained in Atractylodes japonica and to evaluate the pharmacological mechanism responsible for the colonic muscle contraction. Materials and methods: Based on the stimulatory activity-guided fractionation on the isometric contraction of rat distal colonic strips, atractylodiol (ATD) and diacetyl-atractylodiol (DATD) were isolated from the CHCl3 fractions of Atractylodes japonica. Results: ATD and DATD dose-dependently increased both tension and amplitude of distal colon longitudinal muscle (DCLM), but they stimulated only amplitude in the distal colon circular muscle. The ED50 values of ATD and DATD to stimulate the amplitude of DCLM were revealed as 9.1×10−9 M and 1.8×10−8 M, respectively. l-NAME (0.1mM) significantly increased the ADT (1μM)-induced contraction of DCLM, whereas SNAP (0.1mM) markedly reduced the stimulatory effects of ATD on DCLM contractility. The combined effects of SNAP and atropine (0.5μM) on the ATD-induced contraction of DCLM were similar to the inhibitory effects of SNAP alone. Suramin (0.1mM) significantly enhanced the increase of ATD-induced DCLM contraction, whereas ADPβS (0.1mM) markedly abolished the stimulatory effects of ATD on the spontaneous contractility of DCLM. Conclusions: The present results demonstrate that acetylene compounds, ATD and DATD, are the effective phytochemical of Atractylodes japonica to stimulate the motility of distal colon in rats, and ATD possibly enhances the spontaneous contractility of distal colon through inhibiting the mechanism of nitrergic–purinergic relaxation. [Copyright &y& Elsevier]

Aim of the study: Poncirus trifoliata (L.) Raf. (Rutaceae, PT) has been commonly used for treating gastrointestinal (GI) disorders in Korean traditional medicine, but its pharmacological roles in the regulation of colonic motility have not been clarified. This study investigated the regulatory effects of PT on the colonic motility. Materials and methods: Immature fruits of PT were sequentially partitioned with MeOH, n-hexane, CHCl3, EtOAc, n-BuOH and H2O, and the effects of PT extracts on the contractility of colonic strips and colonic luminal transit in rats were measured in vitro and in vivo, respectively. Results: Among six different extracts, only hexane extract of PT (PTHE) dose-dependently increased the low frequency contraction of longitudinal muscle in distal colonic strips, and the ED50 value was revealed to be 0.71μg/ml. The contractile patterns induced by PTHE were remarkably different from those caused by acetylcholine (ACh) and serotonin (5-HT). The stimulatory effects of PTHE on the whole distal colonic strips were more prominent than on the mucosa/submucosa-denuded segments. The M2 receptor-preferring, methoctramine (0.5μM), and M3 receptor-preferring antagonist, 4-DAMP (0.5μM) significantly blocked the PTHE (1μg/ml)-induced contraction of distal colon longitudinal muscles, whereas the 5-HT receptor antagonists (1.0μM, alone or in combination) selective for 5-HT3 (ondansetron), 5-HT4 (GR113808) and 5-HT1, 2, 5–7 (methysergide) receptors did not change the PTHE (1μg/ml)-induced contractility of distal colon longitudinal muscles. SNAP (0.1mM), a NO donor, enhanced the stimulatory effects of PTHE on the longitudinal muscle of distal colon, but l-NAME (0.1mM), a NO synthesis inhibitor, had no effects. PTHE (10–100mg/kg) caused a dose-dependent increase of colonic luminal transit. Conclusions: Collectively, these findings suggest that PTHE specifically acts on the longitudinal muscle of distal colon in rats, and these stimulatory effects are likely mediated, at least, by activation of acetylcholinergic M2 and M3 receptors. [Copyright &y& Elsevier]

Abstract: In this study, we investigated the antibacterial activity of eight antimicrobial peptides (AMPs), comprising four human β-defensins (HBDs), three human neutrophil defensins (HNPs) and the cathelicidin LL-37, against two representative periodontopathogens, Prevotella intermedia and Tannerella forsythia. The neutralising effect of these AMPs on expression of interleukin (IL)-1β, IL-8 and intercellular adhesion molecule 1 (ICAM-1) induced by lipopolysaccharide (LPS) from P. intermedia and T. forsythia was also tested in THP-1 cells and human gingival fibroblasts. Prevotella intermedia was susceptible to HBD-3 and LL-37 but was resistant to HBD-1, HBD-2, HBD-4, HNP-1, HNP-2 and HNP-3 at concentrations up to 10μM. However, all of the AMPs except HNP-2 at 5μM significantly inhibited the expression of IL-1β, IL-8 and ICAM-1 induced by P. intermedia LPS. Tannerella forsythia showed marked susceptibility to the AMPs tested in the following order: LL-37, HBD-3, HBD-2, HBD-1, HNP-1 and HBD-4. All of the AMPs except HNP-3 had significant neutralising effects on T. forsythia LPS activity. The AMPs showing LPS-neutralising activity inhibited LPS binding to the cells. These results suggest that AMPs may be considered as preventive and therapeutic agents against mixed bacterial infections such as periodontitis by eliminating the pathogens themselves as well as reducing the activity of LPS. [Copyright &y& Elsevier]

Abstract: This study examined the pharmacological property of magnolol, a phenolic compound purified from Magnolia officinalis, on the GI motility using the rat isolated gastrointestinal (GI) strips. Magnolol (0.3–30μM) dose-dependently stimulated the tone and amplitude of spontaneous contractions in ileum longitudinal muscles. Magnolol at 3μM significantly increased the contractions of jejunum longitudinal and colon circular muscles, but not the longitudinal muscle contractions in fundus, antrum and colon. Pretreatment of ileum strips with either atropine (0.5μM) or 4-diphenyllacetoxy-N(2-chloriethyl)-piperidine (4-DAMP, 0.5μM) dramatically inhibited the acetylcholine (ACh, 0.1μM)- and magnolol (3μM)-induced longitudinal muscle contractions, but they were not affected by methoctramine (0.5μM) and hexamethonium (0.5μM). Ondansetron (0.1μM) and GR113808 (2μM) significantly reduced the tone of ileum longitudinal muscle contractions stimulated by 5-HT (10μM), but not the amplitude. Magnolol (3μM)-induced ileum longitudinal muscle contractions, both tone and amplitude, were significantly blocked by GR113808, but not by ondansetron. Taken together, magnolol differently regulates the spontaneous GI motility according to the region of GI tracts and orientation of smooth muscles, and magnolol-induced regulation of smooth muscle contractions in rat GI strips is likely to be mediated, at least in part, by activation of ACh and 5-HT receptors, possibly the M3 and/or 5-HT4 receptors. [Copyright &y& Elsevier]

Abstract: Abrupt proliferation of glomerular mesangial cells (GMCs) is a common feature in the early stage of diabetic glomerulopathy, and ganglioside GM3 (NeuAcα3Galβ4Glcβ1Cer) is thought to regulate the proliferation of many cell types. Recently, we have reported ganglioside GM3 as a modulator of glomerular hypertrophy in streptozotocin-induced diabetic rats [Kwak, D.H., Rho, Y.I., kwon, O.D., Ahn, S.H., Song, J.H., Choo, Y.K., Kim, S.J., Choi, B.K., Jung, K.Y., 2003. Decreases of ganglioside GM3 in streptozotocin-induced diabetic glomeruli of rats. Life Sciences 72, 1997-2006]. This study examined whether modulation of cellular ganglioside GM3 could regulate the high glucose- and transforming growth factor-β1 (TGF-β1)-induced proliferation of GMCs. To pharmacologically modulate the cellular ganglioside GM3, GMCs originated from rat kidneys were cultured with exogenous ganglioside GM3 or d-threo-PDMP, an inhibitor of ganglioside synthesis, in the RPMI 1640 media containing normal (5.6 mM, NG) or high (25 mM, HG) glucose. HG, TGF-β1 (10 ng/ml) and d-threo-PDMP (20 μM) significantly stimulated the mesangial cell proliferation, whereas these increments were remarkable attenuated by exogenous ganglioside mixture (0.1–0.2 mg/ml) or GM3 (20–100 μM) in a dose-dependent manner. The mesangial cell proliferation caused by HG, TGF-β1 and d-threo-PDMP was closely correlated with decreases in both cellular sialic acid contents and ganglioside GM3 synthase activity. Based upon the mobility on high-performance thin-layer chromatography (HPTLC), GMCs showed a complex pattern of ganglioside expression that consisted, at least, of five different components of gangliosides, mainly ganglioside GM3. HG, TGF-β1 and d-threo-PDMP induced a significant reduction of ganglioside expression with apparent changes in the composition of ganglioside GM3, and semi-quantitative analysis by HPTLC showed that ganglioside GM3 expression reduced to about 35–54% of control. These results provide a pathophysiological link between mesangial cell proliferation and ganglioside GM3 expression, indicating that exogenously added ganglioside GM3 inhibits the high-ambient glucose- and TGF-β1-induced proliferation of cultured GMCs. [Copyright &y& Elsevier]

Abstract: Previously, we reported the expression and function of system L amino acid transporter in KB human oral epidermoid carcinoma cells. In the present study, therefore, we investigated the expression and function of system L amino acid transporter in human normal oral keratinocytes (HNOK) and compared the expressions and functions of system L amino acid transporters in HNOK and KB cells. The HNOK expressed L-type amino acid transporter 1 (LAT1) and L-type amino acid transporter 2 (LAT2) with their subunit 4F2hc in the plasma membrane but the expression of LAT1 was very weak, which is in contrast to the KB cells expressing LAT1 but not LAT2 with the 4F2hc in the plasma membrane. The [14C] l-leucine uptake by HNOK, as well as KB cells, was inhibited by the system L selective inhibitor BCH. The majority of [14C] l-leucine uptake was, therefore, mainly mediated by LAT2 in the HNOK and by LAT1 in the KB cells. These results suggest that the transport of neutral amino acids including several essential amino acids into the HNOK and KB cells are mainly mediated by LAT2 and LAT1, respectively. The specific inhibition of LAT1 in oral cancer cells could be a new rationale for anti-cancer therapy. [Copyright &y& Elsevier]

We recently identified ganglioside GM3 as a modulator of glomerular hypertrophy in streptozotocin-induced diabetic rats (Life Sci., 72: 1997–2006, 2003). This study examined whether alteration of ganglioside GM3 expression could modulate the high glucose-induced proliferation of glomerular mesangial cells (GMCs). GMCs isolated from rat kidneys were cultured under normal (5.6 mM) or high (25 mM) glucose condition for 24–72 hrs. Cell proliferation was predominantly stimulated when GMCs were cultured with high glucose as well as 20 μM of d-threo-PDMP, an inhibitor of ganglioside biosynthesis, for 24 hrs, whereas raising ambient glucose significantly reduced the mesangial sialic acid contents. Based upon mobility on high-performance thin-layer chromatography (HPTLC), GMCs showed a complex pattern of ganglioside expression that consisted of three major components of gangliosides, mainly GM3. High glucose induced a significant reduction of ganglioside expression with apparent changes in the composition of major ganglioside GM3, and semi-quantitative analysis by HPTLC showed that ganglioside GM3 was reduced to 62% of GMCs cultured under normal glucose condition. A prominent immunofluorescence microscopy using anti-GM3 monoclonal antibody also showed a dramatic disappearance of immunoreactivity in high glucose-treated GMCs. Moreover, high glucose significantly lowered the Km values of GM3 synthase (16 μM vs. 49 μM), but did not change the Vmax. These results provide the pathophysiological relationship between the high glucose-induced proliferation of GMCs and the decreased expression of ganglioside GM3, indicating a mechanism for the negative regulation of mesangial proliferation by ganglioside GM3. This mechanism may play an important role in the development of diabetic glomerulopathy. [Copyright &y& Elsevier]

Ganglioside GM3 (NeuAcα3Galβ4Glcβ1Cer) is known to regulate the proliferation of many cell types and to maintain the charge-selective filtration barrier of glomeruli. Based on these, this study examined whether altered expression of ganglioside GM3 was pathologically related with glomerular hypertrophy and proteinuria occurring in diabetic human and rat kidneys. Diabetic rats were produced by intraperitoneal injection of streptozotocin (80 mg/kg, I.P.). At 15 days after the induction of diabetes, glomerular volume and fibrotic matrix were dramatically elevated, whereas glomerular sialic acid contents were significantly reduced compared with control. Based upon mobility on high-performance thin-layer chromatography (HPTLC) and reactivity to anti-GM3 monoclonal antibody, normal glomeruli showed a complex ganglioside pattern that consisted of six different components of gangliosides, mainly GM3, and diabetes caused a severe reduction of these gangliosides with apparent changes in the composition of major ganglioside GM3. Semi-quantitative analysis by HPTLC showed that ganglioside GM3 was reduced to 57% of control in diabetic glomeruli. A prominent immunofluorescence microscopy showed a dramatic disappearance of GM3 expression in diabetic glomeruli. These results indicate that diabetic glomeruli can be characterized by decreases of glomerular sialic acid content and ganglioside GM3 expression, which may cause loss of charge-selective filtration barrier in renal glomeruli. These changes may be account, at least in part, for the development of glomerular hypertrophy and proteinuria seen in the early stage of diabetic glomerulopathy. [Copyright &y& Elsevier]

This study investigated the anti-angiogenic activities of Cnidium officinale Makino and Tabanus bovinus by using cultured glomerular capillary endothelial cells (GECs), chorioallantoic membrane (CAM) and rat cornea. Treatment of GECs with several concentrations (5–50 μg/ml) of C. officinale Makino and T. bovinus extracts for 24 h inhibited angiotensin II (10−8 M)-induced increases of [3H]thymidine uptake and cell numbers in a concentration-dependent manner. The extent of inhibitory rate of [3H]thymidine incorporation by C. officinale Makino and T. bovinus at 50 μg/ml was a similar to that by 10−5 M of retinoic acid. Herbal extracts also conspicuously inhibited the neovascularization. In contrast to the normal branching of vascular vessels, blood vessel patterns in CAMs treated with extracts (50 μg per egg) of C. officinale Makino and T. bovinus were ran parallel to each other without much branching. Moreover, oral administration of herbal extracts (20 mg/kg per day) for 4 weeks significantly inhibited the rat corneal neovascularization induced by suture, and the length of blood vessels in herbal medicine-treated rat cornea was conspicuously lower than that in control animals. A similar inhibitory effect to these was also observed in the rat cornea treated with thalidomide (200 mg/kg per day). These findings indicate that the anti-angiogenic properties of C. officinale Makino and T. bovinus may be one of the pharmacological mechanisms underlying the anti-tumor and anti-metastatic activities of herbal extracts tested in this study. [Copyright &y& Elsevier]

This study was performed to elucidate the possible involvement of organic anion transporter 3 (OAT3) in cephaloridine (CER)-induced nephrotoxicity and compare the substrate specificity between rOAT3 and rat OAT1 (rOAT1) for various cephalosporin antibiotics, using proximal tubule cells stably expressing rOAT3 (S2 rOAT3) and rOAT1 (S2 rOAT1). S2 rOAT3 exhibited a CER uptake and a higher susceptibility to CER cytotoxicity than did mock, which was recovered by probenecid. Various cephalosporin antibiotics significantly inhibited both estrone sulfate uptake in S2 rOAT3 and para-aminohippuric acid uptake in S2 rOAT1. The Ki values of CER, cefoperazone, cephalothin and cefazolin for rOAT3- and rOAT1-mediated organic anion transport ranged from 0.048 to 1.14 mM and from 0.48 to 1.32 mM, respectively. These results suggest that rOAT3, at least in part, mediates CER uptake and CER-induced nephrotoxicity as rOAT1. There was some difference of affinity between rOAT3 and rOAT1 for cephalosporin antibiotics. [Copyright &y& Elsevier]

The gene encoding a major surface protein (MspTL) of Treponema lecithinolyticum, a periodontopathogen, was cloned and sequenced. The mspTL gene has a 1770-bp open reading frame (ORF) encoding a protein of 590 amino acids with a predicted molecular mass of 65 kDa which had a typical prokaryotic signal sequence (19 amino acids). MspTL showed a high level of homology with major sheath protein (MspA) of Treponema maltophilum, phylogenetically the closest relative of T. lecithinolyticum. Southern blot analysis indicated that the mspTL gene exists in a single copy and Northern blot analysis showed that the mspTL transcript is monocistronic. Another ORF located downstream of mspTL was in the same orientation and encoded a putative protein, in which the first N-terminal 291 amino acids were identified. The homologous region of this protein is also a part on the T. maltophilum mspA locus. [Copyright &y& Elsevier]

• d -Galactose reduced biofilm formation of Streptococcus mutans. • d -Galactose increased biofilm formation of commensal oral streptococci. • d -Galactose inhibited the gene expression of S. mutans glucosyltransferases. • d -Galactose can be a valuable candidate substance for the development of oral hygiene products to prevent caries. In the oral microbial community, commensals can compete with pathogens and reduce their colonization in the oral cavity. A substance that can inhibit harmful bacteria and enrich beneficial bacteria is required to maintain oral health. The purpose of this study was to examine the effect of d -galactose on the biofilm formation of the cariogenic bacteria Streptococcus mutans and oral commensal streptococci and to evaluate their use in solution and in paste form. Biofilms of S. mutans , Streptococcus oralis , and Streptococcus mitis were formed on saliva-coated glass slips in the absence or presence of d -galactose and evaluated by staining with 1 % crystal violet. d -Galactose significantly inhibited the biofilm formation of S. mutans at concentrations ranging from 2 μM to 200 mM but increased the biofilm formation of S. oralis and S. mitis at concentrations of 2–200 mM. d -Galactose significantly inhibited three glucosyltransferase genes, gtfB , gtfC , and gtfD. The effect of d -galactose in the form of solution and paste was evaluated using bovine teeth. Pretreatment with 100 mM d -galactose on bovine teeth resulted in significantly reduced S. mutans biofilm formation. Our results suggest that d -galactose can be a candidate substance for the development of oral hygiene products to prevent caries by inhibiting the biofilm formation of S. mutans and simultaneously increasing the biofilm formation of commensal oral streptococci. [ABSTRACT FROM AUTHOR]