Sinomenine reversed TBHP-induced apoptosis in rat NP cells. A, B. PI/Annexin V assays were performed to evaluate the apoptosis rate in NP cells treated with 3.33 mM sinomenine, 100 μM THBP or 3.33 mM sinomenine + 100 μM THBP, respectively. C-F. Western blotting assay was performed to measure the protein expressions of Bax, Bcl-2 and active caspase 3 in NP cells treated with 3.33 mM sinomenine, 100 μM THBP or 3.33 mM sinomenine + 100 μM THBP, respectively. N = 3, **P < 0.01 vs. control group. ##P < 0.01 vs. 100 μM THBP group.