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STRESS‐Responsive Deacetylase SIRT3 is Up‐Regulated by Areca Nut Extract‐Induced Oxidative Stress in Human Oral Keratinocytes

Areca chewing is an important environmental risk factor for development of oral premalignant lesions and cancer. Epidemiological evidence indicates that areca chewing is tightly linked to oral carcinogenesis. However, the pathogenetic impacts of areca nut extract (ANE) on normal human oral keratinocytes (HOKs) are unclear and possibly involve oxidative stress via redox imbalance. Sirtuin 3 (SIRT3) is a member of the sirtuin family of proteins that play an important role in regulating cellular reactive oxygen species (ROS) production. Recent studies have confirmed that ANE and other areca ingredients can induce ROS. In this study, we examined the role of SIRT3 in the regulation of ANE‐induced ROS in HOK cells. We examined HOK cell viability following treatment with various ANE concentrations. ANE‐induced cytotoxicity increased in a dose‐dependent manner and was approximately 48% at a concentration of 50 μg/ml after 24 h. SIRT3 expression and enzyme activity were up‐regulated in HOK cells by ANE‐induced oxidative stress. Additionally, we identified that SIRT3 controls the enzymatic activity of mitochondrial proteins, such as forkhead box O3a (Foxo3a) transcription factor and antioxidant‐encoding gene superoxide dismutase 2 (SOD2), by deacetylation in HOK cells. Moreover, SIRT3‐mediated deacetylation and activation of Foxo3a promotes nuclear localization in vivo. These findings suggest that SIRT3 is an endogenous negative regulator in response to ANE‐induced oxidative stress and demonstrate an essential role for redox balance in HOK cells. J. Cell. Biochem. 115: 328–339, 2014. © 2013 Wiley Periodicals, Inc.