Figure 2. NecB treatment reduced SA-β-gal activity and senescence marker expression in old HDFs. (A) Young (Y) and old (O) HDFs were treated with vehicle or 10−20 μg/mL NecB for 2 days and stained with X-gal to examine the activity of SA-β-gal. The stained cells were photographed under an inverted microscope (100× magnification). (B) The number of SA-β-gal-stained cells in A was counted and its percentage was plotted as the mean ± SEM. **P < 0.01, ***P < 0.001, compared with vehicle-treated control. (C) The protein levels in vehicle-treated (N0), 10 and 20 μg/mL NecB-treated (N10 and N20, respectively) young and old HDFs were compared by western blot analysis for senescence markers, including caveolin-1, P-Ser15-p53, p53, p21waf1, p16ink4a, p27kip1, and cyclin D1. β-actin was used as an internal control. (D) The band density was examined by densitometry and normalized to β-actin. The relative protein levels were calculated and plotted as the mean ± SEM.