Adverse effects of arecoline and nicotine on human periodontal ligament fibroblasts in vitro

Background, aims: The habit of betel nut chewing impinges on the daily live s of approximately 200 million people. Betel quid chewers have a higher pre valence of periodontal diseases than non-chewers. This study examined the p athobiological effects of arecoline, a major component of the betel nut alk aloids, on human periodontal ligament fibroblasts (PDLF) in vitro. Method: Cell viability, proliferation, protein synthesis, and cellular thio l levels were used to investigate the effects of human PDLF exposed to arec oline levels of 0 to 200 mug/ml. In addition, nicotine was added to test ho w it modulated the effects of arecoline. Results: Arecoline significantly inhibited cell proliferation in a dose-dep endent manner. At concentrations of 10 and 30 mug/ml, arecoline suppressed the growth of PDLF by 20% and 50% (p < 0.05), respectively. Arecoline also decreased protein synthesis in a dose-dependent manner during a 24-h cultur e period. A 100 <mu>g/ml concentration level of arecoline significantly inh ibited protein synthesis to only 50% of that in the untreated control (p < 0.05). Moreover, arecoline significantly depleted intracellular thiols in a dose-dependent manner. At concentrations of 25 <mu>g/ml and 100 mug/ml, ar ecoline depleted about 18% and 56% of thiols (p < 0.05), respectively. This suggests that arecoline itself might augment the destruction of periodonti um associated with betel nut use. Furthermore, the addition of nicotine act ed with a synergistic effect on the arecoline-induced cytotoxicity. At a co ncentration of 60 <mu>g/ml, arecoline suppressed the growth of PDLF by abou t 33%, and 5 mM nicotine enhanced the arecoline-induced cytotoxic response to cause about 66% cell death. Conclusion: During thiol depletion, arecoline may render human PDLF more vu lnerable to reactive agents within cigarettes. Taken together, people who c ombine habits of betel nut chewing with cigarette smoking could be more sus ceptible to periodontium damage than betel nut chewing alone.