Elevated expression of NF-κB in oral submucous fibrosis - Evidence for NF-κB induction by safrole in human buccal mucosal fibroblasts

Nuclear factor-kappa B (NF-κB) is considered to be important in many inflammatory and immune responses. The aim of this study was to compare NF-κB expression in normal human buccal mucosa and oral submucous fibrosis (OSF) specimens and further explore the potential mechanism that may lead to induction of NF-κB expression. Seventeen OSF and six normal buccal mucosa specimens were examined by immunohistochemistry. Primary human buccal mucosal fibroblasts (BMFs) were established and challenged with safrole, a major polyphenolic compound in the influorescence of Piper betel, by cytotoxicity and western blot assays. Furthermore, glutathione precursor N-acetyl-l-cysteine (NAC), extracellular signal-regulated protein kinase (ERK) inhibitor PD98059, cyclooxygenase-2 (COX-2) inhibitor NS-398, dexamethasone, and cyclosporin A were added to find the possible mechanism. NF-κB expression was significantly higher in OSF specimens and expressed mainly by fibroblasts, endothelial cells, and inflammatory cells. Safrole was cytotoxic to BMFs in a dose-dependent manner (p < 0.05). Western blot demonstrated highly elevated NF-κB protein expression in BMFs stimulated by safrole (p < 0.05). In addition, pretreatment with pharmacological agents markedly inhibited the safrole induced-NF-κB expression (p < 0.05). The result suggests that chewing areca quid may activate NF-κB expression that may be involved in the pathogenesis of OSF. NF-κB expression induced by safrole in fibroblasts may be mediated by ERK activation and COX-2 signal transduction pathway.