Effect of resveratrol and oxyresveratrol on deferoxamine-induced cancer stem cell marker expression in human head and neck squamous cell carcinoma.

Objectives: Resveratrol and oxyresveratrol, a resveratrol derivative, possess various pharmacological activities, including anti-cancer activities. Because cancer stem cells play an important role in cancer recurrence, the aims of this study were to investigate whether resveratrol or oxyresveratrol can inhibit the expression of cancer stem cell markers under hypoxia. Materials and methods: Deferoxamine was used to mimic the hypoxic condition. The mRNA expression of cancer stem cell markers was analyzed by Real-time PCR. Flow cytometry was used to determine the number of CD-44 + and CD-105 + cells. Results: Deferoxamine dose-dependently induced the expression of cancer stem cell markers; Oct-4, Nanog, CD-44, CD-105, and CD-133. The induction of these cancer stem cells markers was inhibited when the cells were treated with either resveratrol or oxyresveratrol. Moreover, we found that resveratrol also reduced the number of CD-44 + and CD-105 + cells after deferoxamine treatment. Conclusions: Resveratrol and oxyresveratrol inhibit the expression of cancer stem cell markers and might target cancer stem cells in a hypoxia-associated tumor.

Optimal concentration of potassium iodide to reduce the black staining of silver diamine fluoride.

BACKGROUND/PURPOSE: Potassium iodide (KI) is used for reducing the degree of black staining occurred after silver diamine fluoride (SDF) application. However, the optimal KI concentration remains unknown. This study aimed to identify the optimal concentration of KI that effectively reduces black staining after SDF application. MATERIALS AND METHODS: Twenty-four extracted teeth with similar pattern of carious lesions were assigned into 6 groups as follows: 1) SDF only, 2) SDF+7.5%KI, 3) SDF+10%KI, 4) SDF+15%KI, 5) SDF+20%KI, and 6) SDF+saturated KI. The KI solution was applied immediately after SDF application. Tooth images were obtained for color measurement at different time points as followed; before SDF application, immediately after SDF application, immediately after KI application, 1, 3, 7 and 14 days after SDF+KI application. The photographs were analyzed for mean gray value using the ImageJ program. RESULTS: The KI groups demonstrated a dose-dependent significant immediate reduction in black staining after KI application, except the saturated KI group. The teeth in the 20% KI group had the highest Δ mean gray value compared with other groups immediately after KI application, whereas a reduction in black staining in the saturated KI group appeared 1 day after KI application. The Δ mean gray value in all groups decreased over time. After 7 and 14 days, the reduction in black staining was not clearly different between KI groups. CONCLUSION: KI application was able to reduce the degree of black staining in a dose-dependent manner, but the subsequent color change was minimal over the period of 14 days.

Effect of mixed chlorhexidine and hydrogen peroxide mouthrinses on developing plaque and stain in gingivitis patients: a randomized clinical trial.

AIMS: To evaluate the effects of mixed chlorhexidine (CHX)/hydrogen peroxide (H2O2) mouthrinses compared with CHX mouthrinse alone on plaque, tooth stain, and gingivitis. MATERIALS AND METHODS: This study was a double-blind, randomized two group parallel experiment, using a 14-day non-brushing half-mouth model. The test group was randomly assigned to the mixed 0.12% CHX and 1.5% H2O2 mouthrinse, whereas the control group used 0.12% CHX. Sixty healthy volunteers were enrolled in the study and received scaling and polishing 2 weeks prior to the experiment and then rinsed with the allocated mouthrinses twice daily for 2 weeks. The plaque, stain, and gingivitis scores were evaluated and recorded by a calibrated investigator. RESULTS: Fifty-two subjects completed the study (CHX + H2O2n = 25/CHX n = 27). There were significant differences between the control and test groups for plaque index (CHX 0.64 ± 0.41 vs. CHX + H2O2 0.46 ± 0.36, p = 0.035) and stain intensity at proximal areas (CHX 0.26 ± 0.36 vs. CHX + H2O2 0.09 ± 0.14, p = 0.019) at the end of the experimental non-brushing side. However, the gingival indices did not differ significantly (CHX 0.61 ± 0.34 vs. CHX + H2O2 0.62 ± 0.31, p = 0.938) between groups. CONCLUSIONS: In the absence of oral hygiene practice, the mixed CHX + H2O2 mouthrinse was slightly superior in reducing plaque scores and stain compared with CHX alone. CLINICAL RELEVANCE: The clinical effectiveness of CHX + H2O2 is comparable with CHX mouthwash alone. Therefore, the use of the mixed mouthrinse is beneficial compared with CHX for minimizing biofilm and tooth staining.

Managing knowledge for health care quality: An investigation of rational antibiotic use among Thai dentists.

OBJECTIVES: Because of the irrational use of antibiotics, antimicrobial resistance is now a global concern that requires developing effective strategies against. The aim of this study was to assess the knowledge gap that causes the irrational use of antibiotics among Thai dentists. METHODS: Thai dentists were asked to complete an online questionnaire regarding their knowledge, perception, and attitude towards rationale antibiotic use. The survey was conducted during November to December 2018. RESULTS: Online questionnaires were completed by 588 dentists. Most respondents had a positive perception and were aware of the rational use of antibiotics. However, the use of antibiotics without proper indication and the lack of pharmacological knowledge were found. A mobile application was considered the most preferable approach to manage knowledge for rational drug use. CONCLUSION: Irrational drug use among Thai dentists can be caused by lack of knowledge, attitude, and the perception of each dentist. Policy makers should promote self-learning through knowledge management strategies that can complement the pharmacology courses taught in dental school.

Perception of Thai dental students on becoming innovative healthcare professionals.

OBJECTIVES: This study investigated the perception of dental students on becoming innovative healthcare professionals. The specific objective was to identify aspects of innovative healthcare development that could spur their interest in becoming more involved in healthcare research and new product development. METHODS: Survey research was conducted via questionnaires using a five-point Likert scale response. Based on the innovation science literature, each questionnaire comprised three sets of questions that might foster dental students' interest in healthcare innovation development. Data were obtained from 265 students from years 2, 4 and 6. RESULTS: Three critical dimensions of dental student's preferences were revealed. First, socially related goals were identified as important for developing healthcare innovation. Second, non-traditional learning activities, especially lectures from experienced innovators or an industrial trip were suggested to foster interest in healthcare innovation. Third, the students thought it was important to learn about the research process that translates scientific findings into healthcare innovation. CONCLUSIONS: This study identifies potential ways to develop dental clinicians' interest in becoming innovative professionals who are involved in healthcare product development. This is especially true for Thailand where commercially based innovation has not yet flourished.

Hydrogen peroxide masks the bitterness of chlorhexidine mouthwash without affecting its antibacterial activity.

BACKGROUND: Chlorhexidine (CHX) is an antiseptic mouthwash widely used as the gold standard for inhibiting plaque formation. However, the bitter taste of CHX limits patient compliance. We developed a 0.12% CHX and 1.5% hydrogen peroxide (H2O2) mouthwash that masked the bitter taste of CHX. This study evaluated the antibacterial activity and subject satisfaction of the developed mouthwash. MATERIALS AND METHODS: Three mouthwashes were used as follows: (1) a commercial 0.12% CHX mouthwash, (2) a prepared 0.12% CHX mouthwash containing 1.5% H2O2, and (3) a prepared 0.12% CHX mouthwash. A disc diffusion assay was performed to determine the antibacterial activity of each mouthwash against Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans. To assess subject satisfaction with each mouthwash, a satisfaction questionnaire was completed immediately after rinsing with each mouthwash. RESULTS: The antibacterial activities of the three mouthwashes were similar. Moreover, the questionnaire results revealed that the level of satisfaction was significantly higher for the 0.12% CHX/1.5% H2O2 mouthwash compared with the other mouthwashes. CONCLUSION: The 0.12% CHX/1.5% H2O2 mouthwash revealed a similar antibacterial activity as the CHX standard against periodontal disease pathogens. In addition, the subjects were more satisfied with the new formula compared with 0.12% CHX alone. These data suggest that the 0.12% CHX/1.5% H2O2 formulation is an alternative antibacterial mouthwash to avoid the unpleasant CHX side effects.

Cobalt Chloride Enhances the Stemness of Human Dental Pulp Cells.

INTRODUCTION: Hypoxia is a factor in controlling stem cell stemness. We investigated if cobalt chloride (CoCl2), a chemical agent that mimics hypoxia in vitro, affected human dental pulp cell (hDPC) stemness by examining cell proliferation, stem cell marker expression, and osteogenic differentiation. METHODS: hDPCs were cultured with or without 25 or 50 µmol/L CoCl2. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was used to determine cell proliferation. The number of STRO-1+ cells was determined by flow cytometry. The messenger RNA expression of the stem cell markers REX1, OCT4, SOX2, and NANOG and the osteogenic-associated genes ALP, COLI, and RUNX2 were evaluated using reverse transcription polymerase chain reaction or real-time polymerase chain reaction. Osteogenic differentiation was assessed by alkaline phosphatase (ALP) activity and mineralization assays. RESULTS: Although 25 and 50 µmol/L CoCl2 suppressed hDPC proliferation, 50 µmol/L CoCl2 increased the number of STRO-1+ cells. Moreover, CoCl2 dose dependently induced stem cell marker expression. Additionally, CoCl2 treatment suppressed osteogenic-associated gene expression, ALP activity, and calcium deposition. The addition of apigenin, a hypoxia-inducible factor 1-alpha inhibitor, reversed the inhibitory effect of CoCl2 on ALP activity. CONCLUSIONS: This study indicated that CoCl2 may enhance hDPC stemness.

Apigenin inhibited hypoxia induced stem cell marker expression in a head and neck squamous cell carcinoma cell line.

OBJECTIVE: Cancer stem cells contribute to tumor recurrence, and a hypoxic environment is critical for maintaining cancer stem cells. Apigenin is a natural product with anticancer activity. However, the effect of apigenin on cancer stem cells remains unclear. Our aim was to investigate the effect of apigenin on cancer stem cell marker expression in head and neck squamous cell carcinoma cells under hypoxia. DESIGN: We used three head and neck squamous cell carcinoma cell lines; HN-8, HN-30, and HSC-3. The mRNA expression of cancer stem cell markers was determined by semiquantitative RT-PCR and Real-time PCR. The cytotoxic effect of apigenin was determined by MTT colorimetric assay. Flow cytometry was used to reveal the number of cells expressing cancer stem cell surface markers. RESULTS: HN-30 cells, a cancer cell line from the pharynx, showed the greatest response to hypoxia by increasing their expression of CD44, CD105, NANOG, OCT-4, REX-1, and VEGF. Apigenin significantly decreased HN-30 cell viability in dose- and time-dependent manners. In addition, 40µM apigenin significantly down-regulated the mRNA expression of CD44, NANOG, and CD105. Consistent with these results, the hypoxia-induced increase in CD44+ cells, CD105+ cells, and STRO-1+ cells was significantly abolished by apigenin. CONCLUSION: Apigenin suppresses cancer stem cell marker expression and the number of cells expressing cell surface markers under hypoxia.

Cobalt chloride supplementation induces stem-cell marker expression and inhibits osteoblastic differentiation in human periodontal ligament cells.

OBJECTIVE: Low oxygen tension is one of the crucial factors of the stem-cell niche. However, the long-term hypoxic culture of stem cells is difficult and requires special equipment. In this study, we investigated whether mimicking hypoxia using cobalt chloride (CoCl2) could maintain human periodontal ligament (HPDL) cell stemness. METHODS: HPDL cells were treated with either 50 or 100 µM CoCl2. Cell proliferation was determined by an MTT assay. The mRNA expression of stem-cell marker and osteogenic associated genes were analyzed by RT-PCR and Real-time PCR. Osteogenic differentiation was determined by assaying alkaline phosphatase activity and in vitro mineralization. RESULTS: The results showed that the CoCl2 supplementation had no effect on cell proliferation. CoCl2 treatment increased the mRNA expression of the embryonic stem-cell markers REX1 and OCT4. Culturing HDPL cells in osteogenic medium containing CoCl2 resulted in a decrease in alkaline phosphatase activity, down-regulation of osteogenic associated gene expression, and suppression of mineralization. The use of Apigenin, an HIF-1α inhibitor, indicated that CoCl2 might inhibit osteogenic differentiation through an HIF-1α- dependent mechanism. CONCLUSION: This study shows that CoCl2 treatment can induce stem-cell marker expression and inhibit the osteoblastic differentiation of HPDL cells. These findings suggest the potential application of CoCl2 for maintaining the stem-cell state in the laboratory.

Thermal stimulation of TRPV1 up-regulates TNFα expression in human periodontal ligament cells.

OBJECTIVE: We previously demonstrated that the activation of transient receptor potential vanilloid 1 (TRPV1), a nociceptive ion channel receptor, by capsaicin led to the up-regulation of the osteoprotegerin (OPG)/receptor activator of nuclear factor kappa B ligand (RANKL) ratio in human periodontal ligament (HPDL) cells. Since TRPV1 is recognised as one of the thermo-sensitive cation channels, this study investigated the response of TRPV1 to thermal stimulation in HPDL cells. METHODS: HPDL cells were incubated at 45°C for thermal stimulation. The mRNA expression of OPG, RANKL, tumour necrosis factor α (TNFα), and interleukin-1 ß (IL-1ß) was determined by using RT-PCR. OPG secretion and RANKL protein expression were analysed by ELISA and Western blot analysis, respectively. The mechanisms of heat-induced TNFα expression were studied using several TRPV1 inhibitors. RESULTS: In contrast to capsaicin, thermal stimulation had no effect on OPG or RANKL expression. Interestingly, the mRNA expression of TNFα, but not IL-1ß, was increased by heat. Using TRPV1 antagonists, we confirmed that TNFα up-regulation was mediated by TRPV1. Phospholipase C (PLC) was previously shown to be involved in capsaicin-induced OPG expression. However, we found that protein kinase C, not PLC, was required for heat-induced TNFα expression. Additionally, the use of cytochalasin D, an inhibitor of actin polymerisation, revealed that cytoskeleton rearrangement might be an important mechanism for cellular sensing of thermal stimuli. CONCLUSION: Our results indicate that TRPV1 plays a multi-functional role in HPDL cells depending on the stimuli. In response to heat, TRPV1 activation leads to the induction of TNFα expression.