In vitro testing of the responses of human gingival fibroblasts and L-929 cells to nicotine

Tobacco smoke is considered to be a major risk factor in the development of cardiac diseases and lung cancer. It has also been shown that periodontiti s is more prevalent and more severe in smokers than in non-smokers. Nicotin e, the major pyridine alkaloid in tobacco, has been shown to participate in periodontal disease, exerting both local and systemic effects. In the pres ent study, the effects of nicotine (6 mu g/ml, 60 mu g/ml and 600 mu g/ml) on human gingival fibroblasts (HGF) were assessed by using various exposure protocols. The responses of HGF cultures obtained from smokers and non-smo kers were compared to those found when using a continuous cell line (L-929) . Neutral red uptake (NRU) and the measurement of DNA content with bis-benz imide dye were used to assess cell viability and cell number, respectively. NRU was the most sensitive technique for the detection of cytotoxic effect s. L-929 cells were found to be affected by nicotine in the NRU assay, with a strong cytotoxic effect with 600 mu g/ml nicotine, and a "response" with 60 mu g/ml nicotine when prolonged or double challenge was applied. Nonsmo ker HGF and smoker HGF reacted to nicotine in different ways, depending on the concentrations and the exposure times used, but had identical reactions following double exposure. With the Hoechst DNA assay, 600 mu g/ml nicotin e was found to affect the growth of non-smoker HGF after long or repeated e xposure, while smoker HGF were affected only by repeated exposure; growth o f L-929 cells was not affected. It was concluded that HGF from smokers are able to sustain higher concentrations of nicotine without adverse effects t han are non-smoker HGF and L-929 cells. If this occurs in vivo, nicotine wo uld not be considered to be a major toxicant to HGF in smokers.