Effects of areca nut, inflorescence piper betle extracts and arecoline on cytotoxicity, total and unscheduled DNA synthesis in cultured gingival keratinocytes

Betel quid (BQ) chewing has a strong correlation with oral leukoplakia, sub mucous fibrosis and oral cancer. For elucidation of its pathogenesis, we in vestigated the effects of areca nut (AN) and inflorescence piper betle (IPB ) extracts and arecoline on the growth, total DNA synthesis (TDS) and unsch eduled DNA synthesis (UDS) of cultured human gingival keratinocytes (GK). A recoline and AN extract suppressed the growth of GK over 5 days of incubati on in a dose-dependent fashion. At concentrations of 100, 200 and 400 mu g/ ml, AN extract suppressed the growth of GK by 31%, 46% and 90%, respectivel y The IPB extracts exerted less inhibitory effect on the growth of GE;. IPB extract (200-400 mu g/ml) decreased cell numbers by 20-40% over 5 days of incubation. Moreover, at a concentration of 0.1, 0.2 and 0.4 mM, arecoline suppressed cell growth by 44%, 77% and 96%, respectively. However, only AN extract induced TDS and UDS in cultured GK within 6 h of exposure. Inductio n of UDS by AN extract was concomitant with the presence of apparent intrac ellular vacuolization. Arecoline was also toxic to GK. but did not induce i ntracellular vacuolization. At a concentration range of 200-1600 mu g/ml, A N extract induced TDS by 2.1- to 6.5-fold. Furthermore, at a concentration of 400-1600 mu g/ml, AN extract elevated the UDS by 2.4- to 5.5-fold more t han that of untreated control. On the contrary, IPB extract (200-1600 mu g/ ml) and arecoline (0.2-1.6 mM) inhibited the TDS and UDS of GK to a differe nt extent. Simultaneous exposure of confluent GK to AN extract. IPB extract and arecoline for 1 to 5 days led to different degrees of cytotoxicity tha t was dose- and time-dependent. These results indicate that AN, IPB and are coline take part in the pathogenesis of BQ chewing-related oral mucosal les ions, possibly through both genotoxic and non-genotoxic mechanisms.