Role of autophagy and apoptosis in atrophic epithelium in oral submucous fibrosis

Oral submucous fibrosis (OSF) is a serious, potentially malignant oral disorder. It is histopathologically characterized by chronic inflammation and atrophic epithelium accompanied by the accumulation of collagen fibers in the lamina propria. The molecular mechanisms leading to atrophic epithelium remain poorly understood. Therefore, the present study investigated the role of autophagy and apoptosis in atrophic epithelium in OSF. The expression of Caspase-3 and autophagy-related proteins (LC3 and P62) in OSF epithelial tissues was quantified by immunohis-tochemistry. The analysis demonstrated that, compared with normal oral mucosal tissues, autophagy and apoptosis increased with the progression of OSF. Flow cytometry and Western blotting showed that arecoline induces apoptosis in human oral keratinocytes (HOKs) in a time-dependent manner in vitro. Arecoline-induced autophagy was confirmed by transmission electron microscopy and Western blotting. When chloroquine was used as an inhibitor of autophagy, the apoptosis rate and Caspase-3 expression decreased compared with the use of arecoline alone. Thus, autophagy and apoptosis may be involved in atrophic epithelium in OSF, and arecoline-induced autophagy promotes apoptosis in HOKs.