Effects of Nicotine and Polyphenols on Streptococcus mutans Binding Endothelium

Cardiovascular disease is the leading cause of death in the United States. Streptococcus mutans has a role in the pathogenesis of cardiovascular disease, and it can contribute to atherosclerosis by utilizing antigen I/II adhesion to bind to fibronectin found on the surface of endothelial cells. In the presence of nicotine, the expression of several S. mutans virulence factors, including I/II, are enhanced. The purpose of this research was to determine if tea polyphenols (EGCG) would reduce the nicotine-induced expression of these surface adhesins to fibronectin. Objective: To investigate binding of S. mutans exposed to various concentrations of nicotine and tea polyphenols to fibronectin. S. mutans UA159 was incubated in various nicotine dilutions with and without 0.25 mg/ml of EGCG in order to analyze the binding of the bacterial cells to fibronectin. Methods: S. mutans UA159 was cultured in tryptic soy broth (TSB), supplemented with different nicotine concentrations (0-32mg/ml) and nicotine plus EGCG dilutions, and biotinylated. Microtiter plates were then coated with fibronectin and the biotinylated bacterial cells added followed by extra-avidin-peroxidase and O-phenylenediamine (OPD). The binding was measured by absorbance using a spectrophotometer at 490 nm. Results: Universally nicotine only dilutions incubated with S. mutans demonstrated significantly more (p<0.05) adhesion to fibronectin than nicotine/EGCG dilutions with S. mutans. As the concentration of nicotine was reduced, EGCG caused a 1.7 fold average decrease adhesion to fibronectin compared to the control. Conclusion: Nicotine up-regulates the adhesion of S. mutans to fibronectin. EGCG inhibited this increased adhesion.  Since the presence of EGCG demonstrated a decrease in bacterial adhesion to fibronectin, these results may suggest a therapeutic role for tea in people who have cardiovascular disease and smoke.