Hoi-Soon Lim

EGCG induces apoptosis in human laryngeal epidermoid carcinoma Hep2 cells via mitochondria with the release of apoptosis-inducing factor and endonuclease G

(-)-Epigallocatechin-3-gallate (EGCG), a major green tea polyphenol, was tested for in vitro cytotoxicity against human laryngeal epidermoid carcinoma of the larynx Hep2 cells. EGCG-induced apoptotic cell death accompanied by a change in the cell cycle. However, EGCG did not result in caspase activation, nor did a caspase inhibitor block cell death. Furthermore, EGCG caused no change in the intracellular levels of reactive oxygen species (ROS). The levels of p53 were increased in the EGCG-treated cells, with a corresponding decrease in Bcl-2 and Bid protein levels as well as an increase in the Bax level. In addition, EGCG induced the cytoplasmic release of cytochrome c from the mitochondria accompanied by a decreased mitochondrial membrane potential, and subsequently upregulated translocation of apoptosis-inducing factor (AIF) and endonuclease G (EndoG) into the nucleus during the apoptotic process. Taken together, these findings indicate that the p53-mediated mitochondrial pathway and the nuclear translocation of AIF and EndoG play a crucial role in EGCG-induced apoptosis of human laryngeal epidermoid carcinoma Hep2 cells, which proceeds through a caspase-independent pathway.

Inhibitory effect of Lactobacillus reuteri on periodontopathic and cariogenic bacteria

The interaction between Lactobacillus reuteri, a probiotic bacterium, and oral pathogenic bacteria have not been studied adequately. This study examined the effects of L. reuteri on the proliferation of periodontopathic bacteria including Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum, Porphyromonas gingivalis, and Tannerella forsythia, and on the formation of Streptococcus mutans biofilms. Human-derived L. reuteri strains (KCTC 3594 and KCTC 3678) and rat-derived L. reuteri KCTC 3679 were used. All strains exhibited significant inhibitory effects on the growth of periodontopathic bacteria and the formation of S. mutans biofilms. These antibacterial activities of L. reuteri were attributed to the production of organic acids, hydrogen peroxide, and a bacteriocin-like compound. Reuterin, an antimicrobial factor, was produced only by L. reuteri KCTC 3594. In addition, L. reuteri inhibited the production of methyl mercaptan by F. nucleatum and P. gingivalis. Overall, these results suggest that L. reuteri may be useful as a probiotic agent for improving oral health.

Xylitol Inhibits Inflammatory Cytokine Expression Induced by Lipopolysaccharide from Porphyromonas gingivalis

ABSTRACT Porphyromonas gingivalis is one of the suspected periodontopathic bacteria. The lipopolysaccharide (LPS) of P. gingivalis is a key factor in the development of periodontitis. Inflammatory cytokines play important roles in the gingival tissue destruction that is a characteristic of periodontitis. Macrophages are prominent at chronic inflammatory sites and are considered to contribute to the pathogenesis of periodontitis. Xylitol stands out and is widely believed to possess anticaries properties. However, to date, little is known about the effect of xylitol on periodontitis. The aim of the present study was to determine tumor necrosis factor alpha (TNF-α) and interleukin-1β (IL-1β) expression when RAW 264.7 cells were stimulated with P. gingivalis LPS (hereafter, LPS refers to P. gingivalis LPS unless stated otherwise) and the effect of xylitol on the LPS-induced TNF-α and IL-1β expression. The kinetics of TNF-α and IL-1β levels in culture supernatant after LPS treatment showed peak values at 1 h (TNF-α) and 2 to 4 h (IL-1β), respectively. NF-κB, a transcription factor, was also activated by LPS treatment. These cytokine expressions and NF-κB activation were suppressed by pretreatment with pyrrolidine dithiocarbamate (an inhibitor of NF-κB). Pretreatment with xylitol inhibited LPS-induced TNF-α and IL-1β gene expression and protein synthesis. LPS-induced mobilization of NF-κB was also inhibited by pretreatment with xylitol in a dose-dependent manner. Xylitol also showed inhibitory effect on the growth of P. gingivalis. Taken together, these findings suggest that xylitol may have good clinical effect not only for caries but also for periodontitis by its inhibitory effect on the LPS-induced inflammatory cytokine expression.

Effects of methyl gallate and gallic acid on the production of inflammatory mediators interleukin-6 and interleukin-8 by oral epithelial cells stimulated with Fusobacterium nucleatum

Interactions between periodontal bacteria and human oral epithelial cells can lead to the activation and expression of a variety of inflammatory mediators in epithelial cells. Fusobacterium nucleatum is a filamentous human pathogen that is strongly associated with periodontal diseases. This study examined the effects of methyl gallate (MG) and gallic acid (GA) on the production of inflammatory mediators, interleukin (IL)-6 and IL-8, by oral epithelial cells stimulated by F. nucleatum. In a real-time reverse transcription-polymerase chain reaction and an enzyme-linked immunosorbent assay, live F. nucleatum induced high levels of gene expression and protein release of IL-6 and IL-8. The effects of MG and GA were examined by treating KB oral epithelial cells with MG and GA and stimulating them with F. nucleatum. MG and GA inhibited significantly the increases in the IL-6 and IL-8 gene and protein levels in a dose-dependent manner. These Compounds also inhibited the growth of F. nucleatum. No visible effects of MG and GA on the adhesion and invasion of KB cells by F. nucleatum were observed. In conclusion, both MG and GA inhibit IL-6 and IL-8 production from F. nucleatum-activated KB cells.

Change of lip-line cant after 1-jaw orthognathic surgery in patients with mandibular asymmetry

INTRODUCTION The purpose of this study was to investigate the change of lip-line cant (LLC) after 1-jaw orthognathic surgery in mandibular asymmetry patients. METHODS Preoperative and postoperative data of 22 patients having 1-jaw orthognathic surgery, with menton deviation over 2 degrees before the surgery, were our subjects. LLC was measured in the preoperative and postoperative frontal photographs, and its change was correlated with various craniofacial measurements obtained from preoperative and postoperative frontal cephalograms and maxillofacial 3-dimensional computed tomography images. RESULTS Although these subjects had 2.4 degrees of LLC on average before surgery, LLC improved to 0.5 degrees after surgery, and the change (1.9 degrees ) was statistically significant. In the correlation analysis, preoperative LLC showed positive correlations with menton deviation and mandibular anterior occlusal plane cant. In the correlation analysis of LLC change, it had positive correlations with preoperative LLC and mandibular anterior occlusal plane cant and preoperative and postoperative change of menton deviation. CONCLUSIONS These results suggest that LLC is present with chin deviation, even without significant maxillary canting, and can be improved considerably by 1-jaw surgery alone.

Inhibition of mitochondria-dependent apoptosis by 635-nm irradiation in sodium nitroprusside-treated SH-SY5Y cells

Nitric oxide (NO) is a major factor contributing to the loss of neurons in ischemic stroke, demyelinating diseases, and other neurodegenerative disorders. NO not only functions as a direct neurotoxin, but also combines with superoxide (O(2)(-)) by a diffusion-controlled reaction to form peroxynitrite (ONOO(-)), a species that contributes to oxidative signaling and cellular apoptosis. However, the mechanism by which ONOO(-) induces apoptosis remains unclear, although subsequent formation of reactive oxygen species (ROS) has been suggested. The aim of this study was to further investigate the triggers of the apoptotic pathway using O(2)(-) scavenging with light irradiation to block ONOO(-) production. Antiapoptotic effects of light irradiation in sodium nitroprusside (SNP)-treated SH-SY5Y cells were assayed by reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, DNA fragmentation, flow cytometry, Western blot, and caspase activity assays. In addition, NO, total ROS, O(2)(-), and ONOO(-) levels were measured to observe changes in NO and its possible involvement in radical induction. Cell survival was reduced to approximately 40% of control levels by SNP treatment, and this reduction was increased to 60% by low-level light irradiation. Apoptotic cells were observed in the SNP-treated group, but the frequency of these was reduced in the irradiation group. NO, O(2)(-), total ROS, and ONOO(-) levels were increased after SNP treatment, but O(2)(-), total ROS, and ONOO(-) levels were decreased after irradiation, despite the high NO concentration induced by SNP treatment. Cytochrome c was released from mitochondria of SNP-treated SH-SY5Y cells, but not of irradiated cells, resulting in a decrease in caspase-3 and -9 activity in SNP-treated cells. Finally, these results show that 635-nm irradiation, by promoting the scavenging of O(2)(-), protected against neuronal death through blocking the mitochondrial apoptotic pathway induced by ONOO(-) synthesis.

Effect of Lactobacillus reuteri on the proliferation of Propionibacterium acnes and Staphylococcus epidermidis.

While it is generally accepted that Propionibacterium acnes is involved in the development of acne, other bacteria including Staphylococcus epidermidis have also been isolated from the acne lesion. The interaction between Lactobacillus reuteri, a probiotic bacterium, and acnegenic bacteria is unclear. This study examined the effects of L. reuteri on the proliferation of P. acnes and S. epidermidis. Human-derived L. reuteri strains (KCTC 3594 and KCTC 3678) and rat-derived L. reuteri KCTC 3679 were used. All strains exhibited significant inhibitory effects on the growth of P. acnes and S. epidermidis. The proliferation of P. acnes was decreased by 2-log scales after incubation with L. reuteri for 24 h. In addition, the proliferation of S. epidermidis was decreased by 3-log scales after incubation with L. reuteri for 24 h, whereas the growth of L. reuteri was unaffected by P. acnes or S. epidermidis. Among the L. reuteri strains examined, L. reuteri KCTC 3679 had the strongest inhibitory effect on the growth of P. acnes and S. epidermidis, followed by L. reuteri KCTC 3594 and L. reuteri KCTC 3678. Interestingly, reuterin, an antimicrobial factor, was produced only by L. reuteri KCTC 3594. The most pronounced the antibacterial activities of L. reuteri were attributed to the production of organic acids. Overall, these results suggest that L. reuteri may be a useful probiotic agent to control the growth of bacteria involved in acne inflammation and prevent acne.

Potentiation of bacterial killing activity of zinc chloride by pyrrolidine dithiocarbamate.

Zinc has antimicrobial activity and zinc salts including zinc chloride (ZnCl2) have been used for the control of oral malodor. In this study, we hypothesized that pyrrolidine dithiocarbamate (PDTC), a zinc ionophore, may enhance antimicrobial efficacy of ZnCl2. The bactericidal effectiveness of ZnCl2 alone (0.5–8 mM) or in combination with PDTC (1 or 10 μM) was evaluated by in vitro short (1 h) time-killing assays against Fusobacterium nucleatum and Porphyromonas gingivalis. Only a slight viability decrease was observed with ZnCl2 or PDTC alone after 1-h incubation. By contrast, combination of ZnCl2 and PDTC could achieve a more than 100-fold viability reduction compared with ZnCl2 or PDTC alone in F. nucleatum and P. gingivalis. Therefore, PDTC greatly enhanced the bactericidal activity of ZnCl2 against the oral malodor-producing bacteria. These results suggest that use of PDTC may be useful for enhancing bactericidal activity of antimalodor regimens of zinc salts.

Comparison of Temperature and Additives Affecting the Stability of the Probiotic Weissella cibaria

Daily use of probiotic chewing gum might have a beneficial effect on oral health, and it is important that the viability of the probiotics be maintained in this food product. In this study, we examined the stability of probiotic chewing gum containing Weissella cibaria. We evaluated the effects of various factors, including temperature and additives, on the survival of freeze-dried probiotic W. cibaria powder. No changes in viability were detected during storage at 4℃ for 5 months, whereas the viability of bacteria stored at 20℃ decreased. The stability of probiotic chewing gum decreased steadily during storage at 20℃ for 4 weeks. The viability of the freeze-dried W. cibaria mixed with various additives, such as xylitol, sorbitol, menthol, sugar ester, magnesium stearate, and vitamin C, was determined over a 4-week storage period at 20℃. Most of the freeze-dried bacteria except for those mixed with menthol and vitamin C were generally stable during a 3-week storage period. Overall, our study showed that W. cibaria was more stable at 4℃ than that at 20℃. In addition, menthol and vitamin C had a detrimental effect on the storage stability of W. cibaria. This is the first study to examine the effects of various chewing gum additives on the stability of W. cibaria. Further studies will be needed to improve the stability of probiotic bacteria for developing a novel probiotic W. cibaria gum.

Dichloromethane fraction from Gardenia jasminoides: DNA topoisomerase 1 inhibition and oral cancer cell death induction.

Context: A growing body of evidence shows that compounds of plant origin have the ability to prevent cancer. The fruit of gardenia, Gardenia jasminoides Ellis (Rubiaceae), has long been used as a food additive and herbal medicine, and its pharmacological actions, such as protective activity against oxidative damage, cytotoxic effect, and anti-inflammatory and anti-tumor activity, have already been reported. Objective: The purpose of the present study was to investigate the presence of DNA topoisomerase 1 inhibitor in various solvent fractions of Gardenia extract and examine the induction of oral cancer cell death upon treatment with Gardenia extract. Materials and methods: The methanol extract of Gardenia was partitioned with n-hexane, dichloromethane, ethyl acetate, n-butanol, and water. Results: In the DNA topoisomerase 1 assay, n-hexane and dichloromethane fractions inhibited topoisomerase 1 and led to a decrease in the cell viability of KB cells. The dichloromethane fraction (0.1 mg/mL) also showed 77% inhibition of cell viability in KB cells compared with HaCaT cells. Treatment with dichloromethane fraction led to apoptotic cell death as evidenced by flow cytometric analysis and morphological changes. In addition, treatment with Gardenia extract dichloromethane fraction led to the partial increase of caspase-3, caspase-8 and caspase-9 activities and the cleavage of poly (ADP-ribose) polymerase. Conclusion: Taken together, these results suggest that the dichloromethane fraction from Gardenia extract induces apoptotic cell death by DNA topoisomerase 1 inhibition in KB cells. These findings suggest the possibility that Gardenia extract could be developed as an anticancer modality.