Nicotine promotes Streptococcus mutans extracellular polysaccharide synthesis, cell aggregation and overall lactate dehydrogenase activity

Abstract

Several epidemiology studies have reported a positive relationship between smoking and dental caries. Nicotine, an alkaloid component of tobacco, has been demonstrated to stimulate biofilm formation and metabolic activity of Streptococcus mutans, one of the most important pathogens of dental caries. The first aim of the present study was to explore the possible mechanisms leading to increased biofilm by nicotine treatment from three aspects, extracellular polysaccharides (EPS) synthesis, glucosyltransferase (Gtf) synthesis and glucan-binding protein (Gbp) synthesis at the mRNA and protein levels. The second aim was to investigate how nicotine affects S. mutans virulence, particular in lactate dehydrogenase (LDH) activity. Confocal laser scanning microscopy results demonstrated that both biofilm bacterial cell numbers and EPS were increased by nicotine. Gtf and GbpA protein expression of S. mutans planktonic cells were upregulated while GbpB protein expression of biofilm cells were downregulated by nicotine. The mRNA expression trends of those genes were mostly consistent with results on protein level but not statistically significant, and gtfD and gbpD of biofilm cells were inhibited. Nicotine was not directly involved in S. mutans LDH activity. However, since it increases the total number of bacterial cells in biofilm, the overall LDH activity of S. mutans biofilm is increased. In conclusion, nicotine stimulates S. mutans planktonic cell Gtf and Gbp expression. This leads to more planktonic cells attaching to the dental biofilm. Increased cell numbers within biofilm results in higher overall LDH activity. This contributes to caries development in smokers.

Number of <i>Streptococcus mutans</i> and <i>Lactobacillus</i> in saliva versus the status of cigarette smoking, considering duration of smoking and number of cigarettes smoked daily

“…Studies conducted by Huang et al [18] revealed that nicotine increases the formation of biofilm by the action of SM bacteria, and its metabolic activity on teeth surfaces which suggests the possibility of increased risk of dental caries in smokers.…”

Nicotine Enhances Staphylococcus epidermidis Biofilm Formation by Altering the Bacterial Autolysis, Extracellular DNA Releasing, and Polysaccharide Intercellular Adhesin Production

“…Furthermore, several studies have demonstrated a positive relationship between nicotine, the major addictive component of tobacco smoke, and bacterial biofilm formation. For example, Huang et al reported that nicotine could stimulate Streptococcus mutans biofilm formation and its metabolic activity ( Huang et al, 2012 ; Li et al, 2014 ; Huang et al, 2015 ). They also found that nicotine could enhance Streptococcus gordonii biofilm formation, aggregation, and gene expression of binding proteins ( Huang et al, 2014 ).…”

In vitro Cariostatic effects of cinnamon water extract on nicotine-induced Streptococcus mutans biofilm

“…An overnight culture of S. mutans was placed in 96-well microtiter plates with TSBS to stimulate S. mutans growth and biofilm formation. Nicotine was added to both study and control groups to increase biofilm formation as this was confirmed in previous studies [5,6,20,25].…”

“…A positive correlation has also been found between nicotine and S. mutans biofilm. Nicotine upregulates certain S. mutans virulence genes including GTF and glucan binding protein (GbpA) expression, and Ldh, nlmC, and phosphotransferase system (PTS)-associated genes, which eventually leads to more lactic acid production [5,6]. A recent in-vivo study indicates that caries was higher in Wistar rats infected with S. mutans and treated with nicotine compared with a nicotine-untreated group [7].…”