Interleukin-6 induces human heme oxygenase-1 expression via STAT3 phosphorylation. (A) HepG2 cells were treated with various concentrations of IL-6, as indicated, for 24 h. Expressions of STAT3 and phospho-STAT3 were determined by immunoblotting. (B) The HO-1 reporter vector (pHO1-KX) transfected HepG2 cells were treated with IL-6 (10 ng/mL), IL-1β ng/mL), and interferon γ (10 nM) for 24 h. Data are expressed as mean ± SE (n = 6) of luciferase activity relative to the control-treated group. HepG2 cells were treated with various doses of recombinant human INFγ (C) and IL-1β (D). Protein levels of HO-1, STAT3, phospho-STAT3, STAT1, phospho-STAT1, and β-Actin were analyzed using immunoblot assays. The quantitative data of INFγ (E) and IL-1β (F) treatments were expressed as the intensity of the protein band of the target gene/β-Actin or phosphorylation protein/total protein relative to the control solvent-treated group (n = 3). (**, p < 0.01).