GENOTOXIC AND NONGENOTOXIC EFFECTS OF BETEL QUID INGREDIENTS ON ORAL MUCOSAL FIBROBLASTS IN-VITRO

To understand the role of betel quid (BQ) in the pathogenesis of oral submucous fibrosis (OSF) and oral cancer, we used DNA damage, cytotoxi city, and cell proliferation assays to study the pathobiological effec ts of aqueous extracts of three BQ constituents [betel nut (Areca cate chu, BN), inflorescence of Piper betle (IPB), and lime], one BN alkalo id (arecoline), and one BN polyphenol [(+)-catechin] on cultured oral mucosal fibroblasts. Extracts of BN and IPB induced DNA strand break f ormation in a dose-dependent manner. Extracts of BN and IPB, (+)-catec hin, and arecoline decreased cell survival and proliferation in a dose -dependent manner. However, aqueous extract of lime (50-800 mu g/mL) i ncreased cell proliferation by 20-40%. These results indicate that BQ contains not only genotoxic and cytotoxic agents, but also compounds w hich stimulate cell proliferation. These compounds may act synergistic ally in the pathogenesis of OSF and oral cancer in BQ chewers. In addi tion, five anti-oxidants [glutathione (GSH), cysteine, mannitol, catal ase, and superoxide dismutase (SOD)] were tested for their protective effects against the cytotoxicity of BQ constituents. GSH (1.95 and 2.6 mmol/L) and cysteine (4 and 8 mmol/L) prevented the arecoline-induced cytotoxicity. In contrast, mannitol, catalase, and SOD did not decrea se the arecoline-induced cytotoxicity. These results indicate that thi ol depletion, but not the attack of oxygen free radicals, could be the mechanism for arecoline cytotoxicity. GSH could also protect cells fr om the cytotoxicity of IPB extract. Increasing dietary intake of GSH-r ich foods or dietary supplements of GSH may have chemopreventive poten tial to reduce BQ-associated oral lesions.