Dipotassium glycyrrhizate prevents oral dysbiosis caused by Porphyromonas gingivalis in an in vitro saliva-derived polymicrobial biofilm model.

OBJECTIVES: Oral microbiome dysbiosis prevention is important to avoid the onset and progression of periodontal disease. Dipotassium glycyrrhizate (GK2) is a licorice root extract with anti-inflammatory effects, and its associated mechanisms have been well-reported. However, their effects on the oral microbiome have not been investigated. This study aimed to elucidate the effects of GK2 on the oral microbiome using an in vitro polymicrobial biofilm model. METHODS: An in vitro saliva-derived polymicrobial biofilm model was used to evaluate the effects of GK2 on the oral microbiome. One-week anaerobic culture was performed, in which GK2 was added to the medium. Subsequently, microbiome analysis was performed based on the V1-V2 region of the 16S rRNA gene, and pathogenicity indices were assessed. We investigated the effects of GK2 on various bacterial monocultures by evaluating its inhibitory effects on cell growth, based on culture turbidity. RESULTS: GK2 treatment altered the microbiome structure and decreased the relative abundance of periodontal pathogenic bacteria, including Porphyromonas. Moreover, GK2 treatment reduced the DPP4 activity -a pathogenicity index of periodontal disease. Specifically, GK2 exhibited selective antibacterial activity against periodontal pathogenic bacteria. CONCLUSIONS: These findings suggest that GK2 has a selective antibacterial effect against periodontal pathogenic bacteria; thus, preventing oral microbiome dysbiosis. Therefore, GK2 is expected to contribute to periodontal disease prevention by modulating the oral microbiome toward a state with low inflammatory potential, thereby utilizing its anti-inflammatory properties on the host.

Efficacy of hard gummy candy chewing in improving masticatory function in Japanese children aged 6-12 years: a clinical trial.

OBJECTIVES: Japanese children have been shown to exhibit decreased masticatory function; however, limited evidence is available regarding the efficacy of certain food items in improving this issue. Therefore, this study examined the effects of chewing hard gummy candy on the masticatory function of Japanese children aged 6-12 years. METHODS: The study included 26 participants (10 boys and 16 girls; mean age ± standard error = 9.3 ± 0.3 years) who were asked to chew hard gummy candy twice daily for 4 weeks at home. The lip-closing force, occlusal force, and masticatory performance of the participants were recorded before commencement (T1), 4 weeks after commencement (T2), and 4 weeks after completion (T3) of the training. Statistical analyses were performed using the Wilcoxon rank-sum test or the Wilcoxon signed-rank test with Bonferroni correction. RESULTS: No correlation was observed between masticatory function and sex at T1. The lip-closing and right occlusal forces increased significantly after 4 weeks of exercise, and the effects persisted for another 4 weeks after completion. The masticatory performance also improved after training, although these effects did not persist and deteriorated substantially 4 weeks after completion of the training. CONCLUSIONS: Habitual mastication training using hard gummy candy markedly enhances masticatory function (e.g., lip-closing force, occlusal force, and masticatory performance) in Japanese children.

Dipotassium glycyrrhizate and hinokitiol enhance macrophage efferocytosis by regulating recognition, uptake, and metabolism of apoptotic cells in vitro.

BACKGROUND AND OBJECTIVE: Efferocytosis is a process whereby macrophages remove apoptotic cells, such as neutrophils, that have accumulated in tissues, which is required for resolution of inflammation. Efferocytosis is impaired in individuals with increasing age and in those with various systemic diseases. Recently, efferocytosis has been reported to be related to the pathogenesis and progression of periodontitis, and enhancement of efferocytosis, especially in the subjects with impaired efferocytosis, was suggested to lead to periodontitis prevention and care. Various anti-inflammatory ingredients are used in oral care products, but their effect on efferocytosis is unclear. Here, we aimed to identify ingredients contained in oral care products that are effective for efferocytosis regulation. METHODS: The ability of dead cells to induce inflammation in human gingival fibroblast (HGF) cells were evaluated by measuring IL-6 secretion. Six ingredients in oral care products used as anti-inflammatory agents were evaluated for their effect on efferocytosis using flow cytometry. The expression of various efferocytosis-related molecules, such as MERTK and LRP1 involved in recognition, and LXRα and ABCA1 that function in metabolism, were measured in RAW264.7 cells with or without ingredient treatment. Rac1 activity, which is related to the uptake of dead cells, was measured using the G-LISA kit. RESULTS: Dead cells elicited IL-6 secretion in HGF cells. Among the six ingredients, GK2 and hinokitiol enhanced efferocytosis activity. GK2 and hinokitiol significantly increased the expression of MERTK and LRP1, and also enhanced LXRα and ABCA1 expression after efferocytosis. Furthermore, they increased Rac1 activity in the presence of dead cells. CONCLUSION: Among the six ingredients tested, GK2 and hinokitiol promoted efferocytosis by regulating apoptotic cell recognition, uptake, and metabolism-related molecules. Efferocytosis upregulation may be one of the mechanisms of GK2 and hinokitiol in the treatment of inflammatory diseases, such as periodontitis.

Reduction of saliva-derived droplet diffusion by mouth-closed tooth brushing in the era of COVID-19.

PURPOSE: To clarify the effect of mouth-closed tooth brushing on the suppression of droplet generation in comparison with ordinary (mouth-open) tooth brushing and to investigate the difference in plaque removal efficacy between mouth-open and mouth-closed tooth brushing. METHODS: Fourteen adults participated in the study. The labial/buccal, lingual, and occlusal surfaces of each sextant were brushed with the mouth open and closed, and a high-sensitivity camera and a high-power light source were used to measure the number of generated droplets. The plaque removal efficacy of each type of tooth brushing was evaluated according to the O'Leary Plaque Control Record. RESULTS: Significantly more droplets were generated by mouth-open brushing than by mouth-closed brushing. The number of droplets was highest when the lingual surfaces of the upper anterior sextants were brushed with the mouth open. In mouth-closed brushing, almost no droplets were observed from any region. The plaque removal rate with each type of brushing did not differ significantly among any regions except the lingual surfaces of the upper left sextant. CONCLUSION: Mouth-closed tooth brushing almost completely suppressed droplet generation and did not reduce the plaque removal efficacy. Therefore, mouth-closed tooth brushing is beneficial as an oral hygiene method during coronavirus disease 2019 outbreaks.

The inhibitory effects of toothpaste and mouthwash ingredients on the interaction between the SARS-CoV-2 spike protein and ACE2, and the protease activity of TMPRSS2 in vitro.

SARS-CoV-2 enters host cells when the viral spike protein is cleaved by transmembrane protease serine 2 (TMPRSS2) after binding to the host angiotensin-converting enzyme 2 (ACE2). Since ACE2 and TMPRSS2 are expressed in the tongue and gingival mucosa, the oral cavity is a potential entry point for SARS-CoV-2. This study evaluated the inhibitory effects of general ingredients of toothpastes and mouthwashes on the spike protein-ACE2 interaction and the TMPRSS2 protease activity using an in vitro assay. Both assays detected inhibitory effects of sodium tetradecene sulfonate, sodium N-lauroyl-N-methyltaurate, sodium N-lauroylsarcosinate, sodium dodecyl sulfate, and copper gluconate. Molecular docking simulations suggested that these ingredients could bind to inhibitor-binding site of ACE2. Furthermore, tranexamic acid exerted inhibitory effects on TMPRSS2 protease activity. Our findings suggest that these toothpaste and mouthwash ingredients could help prevent SARS-CoV-2 infection.

Avalanche-like fluidization of a non-Brownian particle gel.

We report on the fluidization dynamics of an attractive gel composed of non-Brownian particles made of fused silica colloids. Extensive rheology coupled to ultrasonic velocimetry allows us to characterize the global stress response together with the local dynamics of the gel during shear startup experiments. In practice, after being rejuvenated by a preshear, the gel is left to age for a time tw before being subjected to a constant shear rate [small gamma, Greek, dot above]. We investigate in detail the effects of both tw and [small gamma, Greek, dot above] on the fluidization dynamics and build a detailed state diagram of the gel response to shear startup flows. The gel may display either transient shear banding towards complete fluidization or steady-state shear banding. In the former case, we unravel that the progressive fluidization occurs by successive steps that appear as peaks on the global stress relaxation signal. Flow imaging reveals that the shear band grows until complete fluidization of the material by sudden avalanche-like events which are distributed heterogeneously along the vorticity direction and correlated to large peaks in the slip velocity at the moving wall. These features are robust over a wide range of tw and [small gamma, Greek, dot above] values, although the very details of the fluidization scenario vary with [small gamma, Greek, dot above]. Finally, the critical shear rate [small gamma, Greek, dot above]* that separates steady-state shear-banding from steady-state homogeneous flow depends on the width of the shear cell and exhibits a nonlinear dependence with tw. Our work brings about valuable experimental data on transient flows of attractive dispersions, highlighting the subtle interplay between shear, wall slip and aging whose modeling constitutes a major challenge that has not been met yet.

Indirect measurement of interfacial melting from macroscopic ice observations.

Premelted water that is adsorbed to particle surfaces and confined to capillary regions remains in the liquid state well below the bulk melting temperature and can supply the segregated growth of ice lenses. Using macroscopic measurements of ice-lens initiation position in step-freezing experiments, we infer how the nanometer-scale thicknesses of premelted films depend on temperature depression below bulk melting. The interfacial interactions between ice, liquid, and soda-lime glass particles exhibit a power-law behavior that suggests premelting in our system is dominated by short-range electrostatic forces. Using our inferred film thicknesses as inputs to a simple force-balance model with no adjustable parameters, we obtain good quantitative agreement between numerical predictions and observed ice-lens thickness. Macroscopic observations of lensing behavior have the potential as probes of premelting behavior in other systems.

Hydrodynamic transitions with changing particle size that control ice lens growth.

Ice lenses are formed during soil freezing by the migration and solidification of premelted water that is adsorbed to ice-particle interfaces and confined to capillary regions. We develop a model of ice lens growth that clearly illustrates how the freezing rate dependence on particle size and soil microstructure changes in response to changes in the relative importance of permeable flow and thin-film flow in governing the water supply. The growth of an ice lens in fine-grained porous media is primarily constrained by low permeability in the unfrozen region. In contrast, the constraints offered by the film flow decrease the lens growth rate adjacent to larger particles. The trade-off between resistance to permeable flow and film flow causes the growth rate for ice lenses to be maximized for particles of intermediate size. Moreover, because film flow along particle surfaces adjacent to a growing lens is not strongly affected by the microstructure of the pore space, our analysis predicts that lensing in coarse-grained porous media is insensitive to the pore microstructure and porosity, but the permeable flow that governs lens formation in fine-grained porous media causes their growth to be much more affected by these details.

Effects of Hura crepitans and its active ingredient, daphne factor F3, on dihydrotestosterone-induced neurotrophin-4 activation and hair retardation.

Neurotrophin (NT)-4 is known to be an inducer of catagen in the hair cycle, but little is known of its role in the pathogenesis of androgenetic alopecia (AGA). We previously studied the gene expression of dermal papilla cells from AGA patients and controls and found that NT-4 was up-regulated in the AGA patients. In the present study, the etiological relationship between NT-4 and androgen, which is one of the causes of AGA, and the effect of an NT-4 inhibitor on hair growth were investigated. We established a NT-4 luciferase reporter assay system using a roughly 2-kb region upstream of the NT-4 transcriptional start site and investigated an accelerating effect of androgen on NT-4 transcription. We also screened for a NT-4 inhibitor by using the NT-4 reporter assay and evaluated the effects of NT-4 inhibitors on hair growth by using dihydrotestosterone (DHT)-implanted mice. The results show that transcriptional activity of NT-4 was accelerated by androgen, and extract of Hura crepitans L. inhibited the DHT-induced NT-4 transcriptional activation and ameliorated the retardation of hair regrowth by DHT-implanted mice. We also isolated the active ingredient in H. crepitans and found its structure to be that of 6,7-epoxy-5-hydroxyresiniferonol-14-(2,4-tetradecadienoate), i.e., daphne factor F3. These findings demonstrated that NT-4 activity accelerated by androgen might contribute to the pathogenesis of AGA and indicated that NT-4 inhibitors such as H. crepitans and daphne factor F3 might have a salutary effect on AGA.

Acoustic waveform of continuous bubbling in a non-Newtonian fluid.

We study experimentally the acoustic signal associated with a continuous bubble bursting at the free surface of a non-Newtonian fluid. Due to the fluid rheological properties, the bubble shape is elongated, and, when bursting at the free surface, acts as a resonator. For a given fluid concentration, at constant flow rate, repetitive bubble bursting occurs at the surface. We report a modulation pattern of the acoustic waveform through time. Moreover, we point out the existence of a precursor acoustic signal, recorded on the microphone array, previous to each bursting. The time delay between this precursor and the bursting signal is well correlated with the bursting signal frequency content. Their joint modulation through time is driven by the fluid rheology, which strongly depends on the presence of small satellite bubbles trapped in the fluid due to the yield stress.

Suppression of progressive loss of coat color in microphthalmia-vitiligo mutant mice.

The coat color of C57BL/6-Mitfvit/vit mice whitens with age, because of a one-nucleotide mutation in the DNA-binding region of the microphthalmia-associated transcription factor (MITF), which plays an important role in melanocyte growth and differentiation. To investigate the signals regulating MITF function, we prepared transgenic mice expressing three of the external signals that are important for melanocyte development, i.e., hepatocyte growth factor (HGF), stem cell factor (SCF), and endothelin-3 (ET3), and crossed these mice with Mitfvit/vit mice. We found that the age-dependent coat color whitening of the Mitfvit/vit mice was completely suppressed by the overexpression of HGF or SCF in the skin, but not by that of ET3. Moreover, HGF, but not ET3, promoted the proliferation of Mitfvit/vit mice-derived melanocytes in culture. These results suggest that the signals from exogenous HGF and SCF rescued the mi-vitiligo mutation and also that ET3 does not stimulate the common signal transduction pathway for MITF activation shared by HGF and SCF.