Effect of nicotine-treated epithelial cells on the proliferation and collagen production of gingival fibroblasts

Background, aims: Several in vitro and in vivo studies have indicated that tobacco smoking may be an important risk factor for the development and sev erity of inflammatory periodontal disease. Method: In the present study, we developed an in vitro model to study the i nteractions between nicotine-treated epithelial cells (EC) and gingival fib roblasts (GF) derived from the same patient. EC were treated with nicotine concentrations varying from 1 mug/ml to 500 mug/ml and their effect on diff erent functions of GF was studied. The proliferation of GF was evaluated by the incorporation of H-3-thymidine. A dose-dependent inhibition was observ ed with nicotine concentrations greater than or equal to 100 mug/ml. Simila r results were observed when studying the total protein synthesis of GF by incorporation of H-3-proline into non-dialyzable material. Results: When collagen production was evaluated by H-3-proline incorporatio n into collagenase-sensitive protein, a dose-dependent reduction was observ ed: the degree of inhibition varied from 25% with 50 mug/ml nicotine, to al most 60% with 500 mug/ml. Interestingly, the production of non-collagenous proteins decreased by almost 50% only when EC were treated with the highest concentration of nicotine. Conclusions: The results suggest that epithelial cells, acting as mechanica l barrier, can reduce but not completely eliminate the deleterious effect o f nicotine on gingival fibroblasts.