Nicotine-Treated Fusobacterium nucleatum Binding to Collagen, Fibrinogen, and Fibronectin

Objectives: Fusobacterium nucleatum, a gram-negative anaerobic bacterium found in dental plaque, causes periodontal diseases. Smoking is one of the risk factors that can increase periodontal problems and atherosclerosis. Atherosclerosis is initiated by oral bacteria (i.e., F. nucleatum) binding to surface proteins of endothelial cells, such as collagen, fibrinogen, and fibronectin. The main objective for this study was to test the binding of F. nucleatum to collagen, fibrinogen, and fibronectin under the effect of different concentrations of nicotine.
Methods: F. nucleatum was grown overnight in brain-heart infusion (BHI) supplemented with yeast extract and 5% vitamin-K/hemin. Biofilm was grown for 48 hours in 0, 0.25, 0.5, 1, and 2 mg/mL of nicotine. Then, the biofilm cells were labeled with biotin, fixed with 10% formaldehyde and coated in a high-binding 96-well microtiter plate with 1 µg/mL of collagen, fibrinogen, or fibronectin.
Results: Collagen, fibrinogen, and fibronectin binding assays demonstrated significantly higher absorbance (p<0.05) with 2 mg/mL nicotine-treated F. nucleatum cells compared to untreated cells. Regarding collagen, absorbance at 2 mg/mL of nicotine had 7 fold increase compared to the negative control while cells coated with fibrinogen had 5 fold increase. On the other hand, cells coated with fibronectin showed 3 fold increase compared to the 0 mg/mL of nicotine. The results indicated that an increase in nicotine concentration leads to an increase in F. nucleatum binding to collagen, fibrinogen, and fibronectin.
Conclusions: This means that smokers may have an increased risk for atherosclerosis.