Figure 1. SIRT6 expression is inhibited in endothelial cells during oxidative stress-induced or replicative senescence. (A) Representative image of SA β-gal-positive HUVECs 10 d after the addition of H2O2 (200 μM). (B) The percentage of SA β-gal-positive senescent HUVECs that were treated with 200 μM H2O2 for 1 h and then cultured for the indicated time to generate oxidative stress-induced senescence. The data represent the mean percentage ± SD (n = 3). *P < 0.01 vs. control. (C) Western blot images to analyze the expression of SIRT1, SIRT2, SIRT3, SIRT5, and SIRT6 in HUVECs at 1, 3, 5, or 10 d after addition of H2O2 (200 μM). (D) SA β-gal staining images for young (PDL8) and old (PDL36) cells. (E) The percentage of SA β-gal-positive HUVECs that were passaged to induce replicative senescence. The data are shown as the mean ± SD (n = 3). *P < 0.01 vs. young cells. (F) The expression of SIRTs in young and old HUVECs. An antibody recognizing β-actin was used as a loading control.