Figure 1.
Effect of zearalenone and apigenin on estrogen receptor (ER) activation. MCF-7 cells were transfected with an estrogen-responsive element-thymidine kinase (ERE-TK)-luciferase reporter plasmid and a cytomegalo virus (CMV)-β galactosidase plasmid as a control for transfection efficiency. Then, cells were treated with solvent as a negative control (white), 10−9 M E2 as a positive control (blue) or various doses of zearalenone (red) (A) or apigenin (green) (B) for 24 h. The results are expressed as the percentage of luciferase activity attained with E2 treatment and are the means ± standard error of the mean (SEM) of three to four independent experiments. Cells were treated with solvent as a negative control (white), 10-9 M E2 as a positive control (blue), 10−8 M zearalenone (red) or 10−5 M apigenin (green) for 1 h, 3 h, 6 h, 16 h and 24 h (C). The results are expressed as the percentage of luciferase activity attained with E2 treatment at 24 h and are the means ± SEM of three independent experiments. (D) To confirm the estrogenic effects of apigenin and zearalenone, transfected cells were cotreated with 10−6 M ICI182,780 and either 10−9 M E2 (blue) or 10−8 M zearalenone (red) or 10−5 M apigenin (green). *** indicates a p-value < 0.001 by one-way analysis of variance (ANOVA) followed by Dunnett’s post hoc test for comparison of the control treatment with the other treatments.