Influence of smoking on bacterial adhesion to primary epithelial cells

Objectives: Smoking is one of the most significant risk factors in the development and progression of periodontitis. Adhesion of periodontopathogens to epithelial cells is considered as a crucial first stage in the induction of this infectious disease. This study investigated the effects of nicotine and its primary metabolite cotinine, the 2 most prevalent components in cigarette smoke, on the adhesion of Actinobacillus actinomycetemcomitans (Aa) and Porphyromonas gingivalis (Pg) to primary epithelial cells. Methods: Primary epithelial cells were cultured from biopsies after periodontal surgery. When confluency was reached, cells were inoculated with nicotine or cotinine. Afterwards, culture based adhesion experiments (2h) were preformed with Aa and Pg. In a first set of experiments, the influence of physiological serum concentrations of cotinine (non-/smokers: 0.2/203 ng/ml) and nicotine (non-/smokers: 0.2/12 ng/ml) for 24h and 48h were evaluated. In a subsequent set of experiments, the influence of inoculation time (0.5, 1, 2, 4, 6, 24h) was assessed using higher doses (1 µg/ml). Results: Inoculation of primary epithelial cells for 24 and 48h with physiological concentrations of nicotine and cotinine did not make the cells more prone for bacterial colonization. The second experiment showed a moderate time but a species specific effect on adhesion. Incubation with nicotine altered the susceptibility of the cells to colonisation significantly for short incubation times (up to 2h), while cotinine only altered the susceptibility after 6h of incubation (p< 0.05). Incubation with nicotine and cotinine, increased the susceptibility of cells to colonization by Aa, but lowered it for Pg. Cotinine had no significant influence on the susceptibility of cells to adhesion of Pg. Conclusions: The results suggested an influence of cotinine and nicotine on epithelial adhesion of Aa and Pg. As the observed changes were moderate, the clinical relevance of such variations is questionable. (Supported by DentAid, GABA, KUL-OT, nFWO)