Fig. 4.

Effects of SIRT1 siRNA transfection on apoptosis of degenerative human NP cells. Cells were transfected with negative control siRNA (NC-siRNA) or SIRT1-specific siRNA. Transfected degenerative NP cells were left untreated or treated with tumor necrosis factor-α (TNFα; 12 ng/ml) at 48 h after transfection. a The amounts of SIRT1 proteins were evaluated by Western blot analysis of total cell lysates. b–d The apoptotic percentage of degenerative NP cells determined by flow cytometry. Data represents mean ± SD of three independent experiments. Asterisk: significant difference with respect to NC-siRNA (p < 0.05)