Synergistic effects of peroxynitrite on arecoline-induced cytotoxicity in human buccal mucosal fibroblasts

Epidemiological studies have demonstrated a clear association between betel nut chewing and an increased risk for oral mucosal lesions. Arecoline, the most abundant betel alkaloid, is considered the most important etiologic f actor in betel nuts. In addition, most betel nut chewers are also smokers. In order to elucidate the potential toxicological implications of interacti ons of arecoline and peroxynitrite (a reaction product of cigarette smoking ), cell viability, and cellular levels of glutathione (GSH) were investigat ed, using cultured human buccal mucosal fibroblasts. At a concentration hig her than 0.8 mM, arecoline was cytotoxic to buccal mucosal fibroblasts in a concentration- and time-dependent manner. Arecoline also depleted intracel lular GSH in a dose-dependent manner (P < 0.05). The addition of extracellu lar peroxynitrite acted as a synergistic effect on the arecoline-induced cy totoxicity (P < 0.05). Furthermore, at a concentration of 0.8 mM. arecoline depleted intracellular GSH by about 42%, while 2 mM peroxynitrite enhanced the arecoline-depleted GSH level further to 86% as compared with the contr ol. During GSH depletion, arecoline may render the human buccal mucosal fib roblasts more vulnerable to other reactive agents within cigarette smoking. Taken together, we suggest that people who combine the habits of betel nut chewing with cigarette smoking could be more susceptible to oral mucosal d amage than betel quid chewing alone. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.