Figure 4.

Morphine-induced HMGB1 release requires HO-1.

(A) Morphine increased HO-1 expression in the supernatants of SH-SY5Y cells (50, 100, 200 μM), as assessed by western blot. (B) Znpp downregulated HMGB1 expression by SH-SY5Y cells. The cells were treated with Znpp (HO-1 inhibitor, 2 μM) for 12 hours before morphine administration, and the results were analyzed by western blot. (C) Transfection with HO-1 siRNA downregulated HO-1 expression in SH-SY5Y cells. (D) HO-1 siRNA decreased morphine-induced HMGB1 expression, as assessed by western blot. Data were normalized to the control group and are expressed as mean ± SD. *P < 0.05, **P < 0.01, ***P < 0.001 vs. control group; #P < 0.05, ##P < 0.01, ###P < 0.001, vs. morphine group (A: one-sample t-test; B–D: one-way analysis of variance followed by Tukey’s multiple-comparison test). HMGB1: High mobility group box 1; HO-1: heme oxygenase-1; siRNA: small interfering RNA; Znpp: Zinc protoporphyrin IX.