Browsing by Author "Li, Mingyun"

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    Effect of Green Tea on Streptococcus mutans Metabolic Activity, Planktonic Growth, and Biofilm Activity in the Presence of Nicotine
    (Office of the Vice Chancellor for Research, 2013-04-05) Gardner, R.; Foltz, J.; Li, Mingyun; Huang, Ruijie; Gregory, Richard L.
    Streptococcus mutans is the main bacterial cause of dental caries, and it has been proven by previous research that its growth is affected by various concentrations of nicotine and other agents. The amount of S. mutans in the mouth is directly proportional to the number of dental cavities. Studies have shown that smokers have an increased amount of caries, much of which is due to the low concentrations of nicotine the mouth is exposed to. It is known that S. mutans thrives in low-moderate concentrations of nicotine, and that nicotine is a promoting agent for S. mutans. S. mutans has also been proven as a contributor to atherosclerosis, resulting from dental plaque entering the bloodstream. Green Tea is a commonly consumed beverage, which has been known to reduce the number of dental cavities. Previous research has concluded that green tea contains polyphenols, which have antimicrobial effects, including an inhibitory effect on S. mutans. The objective of this research is to observe how green tea affects S. mutans metabolic activity, as well as biofilm and planktonic growth, in the presence of nicotine. The experiments compared S. mutans treated with nicotine concentrations (0-8 mg/ml), and S. mutans treated with a 2.5 g/200 mL concentration of Sencha Jade Reserve Japanese green tea in conjunction with the various nicotine concentrations. The assays were performed in a microtiter plate; the XTT and biofilm assays measured absorbance, and the planktonic assay measured kinetic growth. The experiments conclude that green tea has an inhibitory effect on nicotine-treated S. mutans metabolic activity and planktonic growth, with higher concentrations of green tea inhibiting more effectively. It was also concluded that green tea increases biofilm formation. These conclusions provide evidence of the inhibitory effect green tea has on nicotine-treated S. mutans, and may indicate a way to reduce the incidence of caries and atherosclerosis.
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    Effect of nicotine on cariogenic virulence of Streptococcus mutans
    (Springer, 2016-11) Li, Mingyun; Huang, Ruijie; Zhou, Xuedong; Qiu, Wei; Xu, Xin; Gregory, Richard L.; Department of Biomedical and Applied Sciences, IU School of Dentistry
    Nicotine has well-documented effects on the growth and colonization of Streptococcus mutans. This study attempts to investigate the effects of nicotine on pathogenic factors of S. mutans, such as the effect on biofilm formation and viability, expression of pathogenic genes, and metabolites of S. mutans. The results demonstrated that addition of nicotine did not significantly influence the viability of S. mutans cells. The biofilms became increasingly compact as the concentrations of nicotine increased. The expression of virulence genes, such as ldh and phosphotransferase system (PTS)-associated genes, was upregulated, and nlmC was upregulated significantly, while ftf was downregulated. The lactate concentration of S. mutans grown in 1 mg/mL of nicotine was increased up to twofold over either biofilm or planktonic cells grown without nicotine. Changes in the metabolites involved in central carbon metabolism from sucrose indicated that most selected metabolites were detectable and influenced by increased concentrations of nicotine. This study demonstrated that nicotine can influence the pathogenicity of S. mutans and may lead to increased dental caries through the production of more lactate and the upregulation of virulence genes.
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    EFFECT OF TOBACCO-TREATED MG63 OSTEOBLAST ON HUMAN PULP CELLS
    (Office of the Vice Chancellor for Research, 2012-04-13) Gebreslassie, Seret; Huang, Ruijie; Li, Mingyun; Song, Fengeyu; Gregory, Richard L.
    Objective: The objective of this study is to determine the effects of to-bacco products on protein concentration and growth of MG63 osteoblasts and the effects of the bacterial cells and culture supernatants on human pulp cells. The study was designed to observe the effects of P.gingivalis grown in four different tobacco solutions such as CSC (cigarette smoked condensate), nicotine (chewing tobacco), and DST (dissolvable smokeless tobacco) strips, and in the media control only without tobacco products. Methods: MG63 os-teoblast was grown in BHI-YE (Bacteria Heart Infusion-Yeast Extract) and hemin-vitamin K. In addition, MG63 osteoblast was grown in BHI-Y-E con-taining nicotine, CSC, and DST. Human pulp cells were grown in media con-taining BGS (Bovine Growth Serum) and washed. The pulp cell cultures will be assayed for cytotoxicity and the supernatants will be assayed for cyto-kines and MMP expression. Results: The protein assays was performed us-ing a microplate spectrophometer and SoftMax Pro 5.2, and we observed that nicotine and DST treated cells had significantly less protein than control cells, however, CSC treated cells had significantly more protein. The undilut-ed control had significantly less protein than the tobacco-treated superna-tants. Conclusion: Based on the previous experiments, we speculate that the additional protein in the undiluted CSC cells and tobacco-treated super-natant may stimulate more effect on human pulp cells than the control, nico-tine or DST treated cells or the control supernatant.
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    EFFECTS OF NICOTINE ON QUORUM SENSING IN STREPTOCOCCUS MUTANS
    (Office of the Vice Chancellor for Research, 2012-04-13) Bikormana, Emmanuel; Huang, Ruijie; Li, Mingyun; Gregory, Richard L.
    Streptococcus mutans is gram-positive cocci, facultative anaerobic bacterium commonly found in the human oral cavity, and significantly contributes to caries. The quorum sensing system plays an important role in microbial cell-cell interactions that leads to development of dental plaque. S. mutans produces glucosyltransferases together with the glucan binding proteins in order to facilitate the adherence of glucans to the tooth surface, thereby forming biofilms. Moreover, previous studies indicate that in the presence or absence of sucrose, a cell surface protein called antigen I/II plays an important role in the adherence process of S. mutans. There is a relationship between smoking and dental caries, in which the smoking population has a higher incidence of dental caries than a non-smoking population. Nicotine is one of the most important components in tobacco. In this study we investigated the effects of nicotine on quorum sensing in S. mutans. An S. mutans wild type UA159 and its knockout mutants defective in comC, comD and comE were used to investigate planktonic cell growth, the biofilm formation and biofilm metabolism at different concentrations of nicotine (0-32 mg/ml). The effects of nicotine on quorum sensing for S. mutans’ biofilm formation was evaluated using sucrose-dependent and sucrose-independent assays. The results indicate that S. mutans UA159 and its knockout mutants had no substantial differences in planktonic cell growth. In the presence of sucrose, the comC mutant was unable to produce biofilms, whereas the biofilm formation and biofilm metabolism of the comD and comE mutants were enhanced with increased nicotine concentration as with UA159 up to 8 mg/mL of nicotine. However, in the absence of sucrose, it was observed that the ComC mutant formed biofilms relatively similar to UA159. Biofilm formation in the comD and comE mutants was also enhanced with the increase of nicotine concentration up to 4 and 2 mg/mL, respectively. The results suggest that nicotine enhances the adherence process in S. mutans by antigen I/II through the comDE signaling pathway. However, the fact that the comC mutant produced biofilm in the absence of sucrose, but not in the presence of sucrose, indicates that the activity of antigen I/II is activated through different cell-cell signaling pathways depending on the amount of sucrose present.
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    Nicotine Regulates Streptococcus mutans Extracellular Polysaccharide and Related Protein Expression
    (Office of the Vice Chancellor for Research, 2013-04-05) Huang, Ruijie; Li, Mingyun; Gregory, Richard L.
    Streptococcus mutans, a gram-positive facultatively anaerobic bacterium, is considered as the primary contributor to caries due to its high acidogenicity and aciduricity. Smoking is one of the risk factors of periodontal disease and dental caries. Nicotine is one of the alkaloid pharmacologically active agents in tobacco. Previous studies indicated nicotine stimulated S. mutans biofilm formation and metabolism. However, the detailed mechanism is still unknown. Thus, the aim of this study is to investigate how nicotine facilitates S. mutans biofilm formation focused on extracellular polysaccharide synthesis. S. mutans UA159 (ATCC 700610) was used in the present study. Confocal laser scanning microscopy (CLSM) was used to investigate the effect of 0, 1, 2 and 4 mg/ml nicotine on 24 h S. mutans biofilm extracellular polysaccharide (EPS) expression (red fluorescentlabeled) and nucleic acid expression (green fluorescent-labeled). Western blot assays were used to investigate the effect of 0, 1, 2 and 4 mg/ml nicotine on the expression of glucosyltransferase (Gtfs), glucan-binding protein A (Gbp-A) and Gbp-B in 24 h S. mutans biofilm cells. CLSM results indicated nicotine increased both EPS and nucleic acid, and the ratio of EPS/nucleic acid was also increased. It implied EPS synthesis in single S. mutans cells was stimulated by nicotine treatment. Biofilm thickness was thicker in nicotine-treated groups than the non-treated group. Western blot assay results indicated that nicotine stimulated GtfC, Gbp-A and Gbp-B expression, but decreased GtfB expression. In conclusion, nicotine stimulates S. mutans cell proliferation and EPS synthesis partially by increasing GtfC, Gbp-A and Gbp-B.