Synergistic effects of nicotine on arecoline-induced cytotoxicity in humanbuccal mucosal fibroblasts

Areca quid chewing has been linked to oral submucous fibrosis and oral canc er. Arecoline, a major areca nut alkaloid, is considered to be the most imp ortant etiologic factor in the areca nut. In order to elucidate the pathobi ological effects of arecoline, cytotoxicity assays, cellular glutathione S- transferase (GST) activity and lipid peroxidation assay were employed to in vestigate cultured human buccal mucosal fibroblasts. To date, there is a la rge proportion of areca quid chewers who are also smokers. Furthermore, nic otine, the major product of cigarette smoking, was added to test how it mod ulated the cytotoxicity of arecoline. At a concentration higher than 50 mug /ml, arecoline was shown to be cytotoxic to human buccal fibroblasts in a d ose-dependent manner by the alamar blue dye colorimetric assay (P < 0.05). In addition, arecoline significantly decreased GST activity in a dose-depen dent manner (P < 0.05). At concentrations of 100 mug/ml and 400 mug/ml, are coline reduced GST activity about 21% and 46%, respectively, during a 24 h incubation period. However, arecoline at any test dose did not increase lip id peroxidation in the present human buccal fibroblast test system. The add ition of extracellular nicotine acted synergistically on the arecoline-indu ced cytotoxicity. Arecoline at a concentration of 50 mug/ml caused about 30 % of cell death over the 24 h incubation period. However, 2.5 mM nicotine e nhanced the cytotoxic response and caused about 50% of cell death on 50 mug /ml arecoline-induced cytotoxicity. Taken together, arecoline may render hu man buccal mucosal fibroblasts more vulnerable to other reactive agents in cigarettes via GST reduction. The compounds of tobacco products may act syn ergistically in the pathogenesis of oral mucosal lesions in areca quid chew ers. The data presented here may partly explain why patients who combined t he habits of areca quid chewing and cigarette smoking are at greater risk o f contracting oral cancer.