Fig. 1

a The levels of SIRT1 DNA methylation in cells treated with 50 μg/mL arecoline were significantly increased compared to that in control cells. b The expression levels of SIRT1 mRNA in cells treated with arecoline at 50 μg/mL was significantly decreased compared to that in control cells. c The production of SIRT1 protein (bands of 120 kDa) was reduced by arecoline treatment compared to controls. As a control, the levels of GAPDH (bands of 37 kDa) were similar in all cells. d The ratio of intensities of SIRT1 to GAPDH in control cells was considered to be 100%. The ratio of intensities of SIRT1/GAPDH in control cells and arecoline-treated cells was 100 ± 16.2% and 40.1 ± 3.3%, respectively. The SIRT1 protein levels were reduced by arecoline treatment. Each experiment was performed in triplicate and results with p values of < 0.05 were considered to be statistically significant. CTL, control; ARE, arecoline