Figure 1
Flavonoids activate PXR-mediated CYP3A4 gene expression. HepG2 cells (2 × 104/well) stably transfected with PXR and CYP3A4-luc [9] were seeded in 384-well plates and treated with indicated compounds for 24 h before the luciferase assay. CYP3A4 promoter activity induced by compound was expressed as a percentage of activation (% Act) by normalizing with luciferase activity from 2 μM rifampicin. Compounds were tested at 11 concentrations starting at 40 μM (leftmost for each compound), 1:1.5 (A) or 1:3 (B) serial dilutions. In (A), the concentrations for each compound tested were 40, 26.667, 17.778, 11.852, 7.901, 5.267, 3.512, 2.341, 1.561, 1.040 and 0.694 μM (from left to right). In (B), the concentrations for each compound tested were 40, 13.333, 4.444, 1.481, 0.494, 0.165, 0.055, 0.018, 0.006, 0.002 and 0.0007 μM (from left to right). Compounds were tested in quadruplicate. The bars denote the standard deviation.