Effect of nicotine on streptococcus mutans

Indiana University-Purdue University Indianapolis (IUPUI)Streptococcus mutans is a key contributor to dental caries. Smokers have increased caries, but the association between tobacco, nicotine, caries and S. mutans growth is little investigated. In the first section, seven S. mutans strains were used for screening. The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and minimum biofilm inhibitory concentration (MBIC) were 16 mg/ml (0.1 M), 32 mg/ml (0.2 M), and 16 mg/ml (0.1 M), respectively, for most of the S. mutans strains. Growth of planktonic S. mutans cells was significantly repressed by 2.0-8.0 mg/ml nicotine concentrations. Biofilm formation and metabolic activity of S. mutans was increased in a nicotine-dependent manner up to 16.0 mg/ml. Scanning electron microscopy (SEM) revealed higher nicotine-treated S. mutans had thicker biofilm and more spherical bacterial cells than lower concentrations of nicotine. In the second section, confocal laser scanning microscopy (CLSM) results demonstrated that both biofilm bacterial cell numbers and extracellular polysaccharide (EPS) synthesis were increased by nicotine. Glucosyltransferase (Gtf) and glucan binding protein A (GbpA) protein expression of S. mutans planktonic cells were upregulated, while GbpB protein expression of biofilm cells were downregulated by nicotine. The mRNA expression of those genes were mostly consistent with their protein results. Nicotine was not directly involved in S. mutans LDH activity. However, since it increased the total number of bacterial cells in biofilm; total LDH activity of S. mutans biofilm was increased. In the third section, a PCR-based multiple species cell counting (PCR-MSCC) method was designed to investigate the effect of nicotine on S. mutans in a ten mixed species culture. The absolute S. mutans number in mixed biofilm culture was increased but the percentage of S. mutans in the total number of bacterial cells was not changed. In conclusion, nicotine enhanced biofilm formation and biofilm metabolism of S. mutans, through stimulating S. mutans planktonic cell Gtfs and Gbps expression. This leads to more planktonic cells attaching to dental biofilm. Increased S. mutans cell numbers, in biofilms of single species or ten mixed species, resulted in higher overall LDH activity. More lactic acid may be generated and contribute to caries development in smokers

Volatile Sulfur Compounds and their Effects on Streptococcus mutans Biofilm

poster abstractVolatile sulfur compounds (VSC) are produced by certain anaerobic bacteria known to cause halitosis in the oral cavity. Porphyromonas gingivalis produces VSC and causes halitosis and periodontal disease. Streptococcus mutans is a facultative anaerobic bacterium that is most commonly known for causing dental caries in the oral cavity. No research has been reported indicating a connection between S. mutans and VSC. An observation was made by Dr. Richard Gregory and Ph.D. student Ruijie Huang that when an S. mutans culture was left in an anaerobic environment with P. gingivalis, the growth of S. mutans appeared to be inhibited. This study explored that observation using not only P. gingivalis culture supernatant containing VSC but also other VSC, such as DTT, and 2ME to demonstrate that VSC inhibit the growth of S. mutans biofilm using total growth and biofilm formation after crystal violet staining. The results were read using a spectrophotometer to read the total growth and biofilm formation. These results indicate that S. mutans total growth and biofilm is significantly inhibited (p<0.05) by the presence of VSC. Results also establish that different VSC inhibit S. mutans depending on the amount of sulfur in each agent; however, each agent greatly reduced the amount of S. mutans biofilm. Due to these results, one can conclude that there is an inhibitory relationship between VSC and S. mutans. A person with a major case of halitosis or a person who has periodontal disease would most likely have little to no evidence of dental caries at that time

Nicotine Regulates Streptococcus mutans Extracellular Polysaccharide and Related Protein Expression

poster abstractStreptococcus 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

Association between periodontal disease and prostate cancer:a systematic review and meta-analysis

Periodontal disease is a chronic infectious disease caused by bacterial infection which may lead to various systematic diseases. Recently, increasing studies have explored the correlation of periodontal disease with the risk of prostate cancer. However, the findings were inconsistent. Hence, this study aims to investigate the association between periodontal disease and the risk of prostate cancer by a meta-analysis. PubMed, EMBASE, and Cochrane were searched for publications up to July 17, 2020. Cohort and case-control studies evaluating the risk of prostate cancer in patients with periodontal disease were included. A fixed or random-effect model was used to calculate the summary relative risk (RR) along with 95% confidence interval (CI). All analyses were conducted using Stata 12.0 software. Seven studies were included in the final analysis. The pooled estimates showed that periodontal disease was significantly associated with the risk of prostate cancer (RR = 1.17; 95% CI = 1.07-1.27; P = 0.001). Findings of sensitivity analyses proved that the overall results were robust. Periodontal disease may be considered as a potential risk factor for prostate cancer. Although it?s a possibility, males should be more aware of their oral health and implement effective measures to prevent and treat periodontal disease

Accuracy versus time frontiers of semi-supervised and self-supervised learning on medical images

For many applications of classifiers to medical images, a trustworthy label for each image can be difficult or expensive to obtain. In contrast, images without labels are more readily available. Two major research directions both promise that additional unlabeled data can improve classifier performance: self-supervised learning pretrains useful representations on unlabeled data only, then fine-tunes a classifier on these representations via the labeled set; semi-supervised learning directly trains a classifier on labeled and unlabeled data simultaneously. Recent methods from both directions have claimed significant gains on non-medical tasks, but do not systematically assess medical images and mostly compare only to methods in the same direction. This study contributes a carefully-designed benchmark to help answer a practitioner's key question: given a small labeled dataset and a limited budget of hours to spend on training, what gains from additional unlabeled images are possible and which methods best achieve them? Unlike previous benchmarks, ours uses realistic-sized validation sets to select hyperparameters, assesses runtime-performance tradeoffs, and bridges two research fields. By comparing 6 semi-supervised methods and 5 self-supervised methods to strong labeled-only baselines on 3 medical datasets with 30-1000 labels per class, we offer insights to resource-constrained, results-focused practitioners: MixMatch, SimCLR, and BYOL represent strong choices that were not surpassed by more recent methods. After much effort selecting hyperparameters on one dataset, we publish settings that enable strong methods to perform well on new medical tasks within a few hours, with further search over dozens of hours delivering modest additional gains.Comment: Semi-supervised Learning; Self-supervised Learning; Medical Imagin

Enantiodivergent α-Amino C–H Fluoroalkylation Catalyzed by Engineered Cytochrome P450s

The introduction of fluoroalkyl groups into organic compounds can significantly alter pharmacological characteristics. One enabling but underexplored approach for the installation of fluoroalkyl groups is selective C(sp^3)–H functionalization due to the ubiquity of C–H bonds in organic molecules. We have engineered heme enzymes that can insert fluoroalkyl carbene intermediates into α-amino C(sp3)–H bonds and enable enantiodivergent synthesis of fluoroalkyl-containing molecules. Using directed evolution, we engineered cytochrome P450 enzymes to catalyze this abiological reaction under mild conditions with total turnovers (TTN) up to 4070 and enantiomeric excess (ee) up to 99%. The iron-heme catalyst is fully genetically encoded and configurable by directed evolution so that just a few mutations to the enzyme completely inverted product enantioselectivity. These catalysts provide a powerful method for synthesis of chiral organofluorine molecules that is currently not possible with small-molecule catalysts

Effect of Green Tea on Streptococcus mutans Metabolic Activity, Planktonic Growth, and Biofilm Activity in the Presence of Nicotine

poster abstractStreptococcus 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

EFFECT OF TOBACCO-TREATED MG63 OSTEOBLAST ON HUMAN PULP CELLS

poster abstractObjective: 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