Quercetin exerts anti-inflammatory effects via inhibiting tumor necrosis factor-α-induced matrix metalloproteinase-9 expression in normal human gastric epithelial cells

Figure 7 Quercetin suppresses tumor necrosis factor-α-induced tumor necrosis factor-α antagonist-c-Src–extracellular-signal-regulated kinase 1/2–nuclear factor kappa B (p65) activation in normal human gastric mucosa epithelial cells. A: Normal human gastric mucosa epithelial cells (GES-1) were either untreated or treated with BAY (0, 5, 10, or 20 mM) for 0, 16, or 24 h; compounds were added 1 h before the addition of tumor necrosis factor-α (TNF-α) (30 ng/mL) as described in the Materials and Methods section. Matrix metallopeptidase-9 zymogen activity was measured by gelatin zymography. B and C: Cells were either untreated or treated with quercetin (B; 0 or 1 mM), PP1 (C; 0 or 1 mM), U0126 (0 or 1 mM), BAY (0 or 10 mM), or TNF-α antagonist (1 mM) for 1 h before the addition of TNF-α (30 ng/mL) and incubated for 0, 16, or 24 h. Nuclear factor kappa B (NF-κB) phosphorylation was examined by Western blot analysis; D and E: GES-1 cells were treated with 30 ng/mL TNF-α for 0, 5, 10, 15, 30, or 60 min (D) or quercetin (1 mM), PP1 (1 mM), U0126 (1 mM), or BAY (10 mM) for 1 h (E) before exposure to TNF-α (30 ng/mL) for 30 min; F: GES-1 cells were transfected with the human NF-κB–Luc response element reporter plasmids containing the dual-luciferase reporter system. The cells were then pretreated with PP1 (0 or 1 mM), U0126 (0 or 1 mM), BAY (0 or 10 mM), quercetin (1 mM), or TNF-α antagonist (1 mM) for 1 h and exposed to TNF-α for 1 h. Then, luciferase activity was measured. Firefly luciferase activity was standardized to that of Renilla luciferase. One-way ANOVA was used for comparisons among different treatment time points (^aP < 0.05, ^bP < 0.01 vs control cells in 0 h). One-way ANOVA was used for comparisons among different treatments simultaneously (^cP < 0.05, ^dP < 0.01 vs TNF-α-stimulated cells). Data are expressed as the mean ± SEM of three independent experiments. ERK: Extracellular-signal-regulated kinase; GAPDH: Glyceraldehyde-3-phosphate dehydrogenase; GES-1: Normal human gastric mucosa epithelial cell line; MMP-9: Matrix metallopeptidase-9; NF-κB: Nuclear factor kappa B; Q: Quercetin; TNF-α: Tumor necrosis factor-α.