Cytokines play an important role in regulating fibroblast function and is likely to play a key role in regulating the initiation and progression of scarring in any fibrotic disease. Interleukin-6 (IL-6) has been implicated in the development of a variety of fibrotic diseases. Objective: The aim of this study was to compare IL-6 expression in normal human buccal mucosa and oral submucous fibrosis (OSF) specimens and further explore the potential mechanism that may lead to induce IL-6 expression. Methods: The aims of this study were to investigate the relative levels of IL-6 in OSF compared with normal buccal mucosa and the effects of arecoline, the major areca nut alkaloid, on IL-6 expression in normal human buccal mucosa fibroblasts (BMFs) in vitro. To determine whether glutathione (GSH) levels were important in the induction of IL-6 by arecoline, we pretreated cells with 2-oxothiazolidine-4-carboxylic acid (OTZ) to boost GSH levels or buthionine sulfoximine (BSO) to deplete GSH. Results: OSF exhibited higher IL-6 gene expression than BMF in mRNA levels (p<0.05). The exposure of quiescent BMF to arecoline resulted in the elevation of IL-6 mRNA expression in a dose-dependent manner (p<0.05). IL-6 gene regulated by arecoline correlated with intracellular GSH levels in BMF. Arecoline at a concentration of 20 µg/ml induced about 2.7 fold IL-6 mRNA levels over the 6 h incubation period. However, BSO enhanced the IL-6 mRNA levels up to 3.9 fold (p<0.05). In addition, OTZ was found to marginally reduced the arecoline-induced IL-6 expression by lowering about 1.7 fold (p<0.05). Conclusion: Taken together, these results suggest that IL-6 expression is significantly upregulated in OSF tissues from areca quid chewers and arecoline may be responsible for the enhanced IL-6 expression in vivo. In addition, the regulation of IL-6 expression induced by arecoline is critically dependent on the intracellular GSH concentrations.