NPCs were divided into five groups. As a control, group A was treated with vehicle mixture (ethanol and DMSO, <0.1%; ethanol was the solvent of E2 and DMSO was the solvent of RSV). Group B was treated with 75 ng/ml IL-1β. Group C was treated with 75 ng/ml IL-1β with the pretreatment of 1 μM E2 for 30 min. Group D was treated with 75 ng/ml IL-1β with the pretreatment of 200 μM RSV for 30 min. Group E was treated with 75 ng/ml IL-1β with the pretreatment of 1 μM E2 and 200 μM RSV for 30 min. All groups were incubated for 24 h in the serum-free medium without phenol red. Caspase-3 activity was determined using a caspase-3 activity kit (Beyotime, Shanghai, China). Caspase-3 activity is expressed as the fold change in enzyme activity over control. * p < 0.05, by one-way analysis of variance (ANOVA) accompanied by pairwise comparison using SNK-q test. NPCs, nucleus pulposus cells; IL-1β, interleukin-1β; E2, 17β-estradiol; RSV, resveratrol; mean ± SD (standard deviation); n = 6.