AG490 and luteolin block the activation of Interleukin-6 in heme oxygenase-1 expression through the downregulation of STAT3 phosphorylation. (A) HepG2 cells were co-treated by recombinant human IL-6 (10 ng/mL) and various doses of AG490, as indicated, for 16 h. The expression of HO-1, STAT3, and phospho-STAT3, JAK, phospho-JAK, and β-Actin were determined by immunoblot assays. (B) HepG2 cells were co-treated with recombinant human IL-6 (10 ng/mL) with or without luteolin (20 μM) for 16 h. Protein levels of HO-1, STAT3, phospho-STAT3, AKT, phospho-AKT, or β-Actin were analyzed using immunoblot assays. The quantitative data of IL-6 and/or AG490 (C) and IL-6 and/or luteolin (D) 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). (E) The HO-1 reporter vector (pHO1-KX) of transfected HepG2 cells was treated with IL-6 (10 ng/mL), AG490 (20 μM), and/or luteolin (20 μM) for 16 h. Data are expressed as mean percent ± SE (n = 6) of luciferase activity relative to the solvent-treated group. (*, p < 0.05; **, p < 0.01).