Effects of various compounds on transactivation of canine PXR.
HepG2 cells were transfected with canine PXR or empty expression vector and luciferase reporter construct harboring the CYP3A4 proximal and distal promoter regions and seeded in 96-well assay plates as described in Materials and Methods. (A) Cells were treated with panel of 19 compounds for 48 h before detection of fluorescence for cell viability and luminescence for transcriptional activation. All luminescence values were normalized for cell viability. Data for each compound and concentration represents the mean ± SE from three independent experiments in triplicate expressed as fold activation above vehicle control treated cells. All data is normalized against fold activation values from transactivation assays with an empty expression vector. An asterisk denotes compounds exhibiting significant difference from their respective vehicle control at a level of p < 0.01. (B) The graph represents a SR12812 dose-response curve for canine PXR. Cells in triplicate wells were treated with 0.1, 1, 2.5, 5, 10, 20 and 30 μM SR12813 for 48h before luminescence was detected and normalized against cell viability (fluorescence values). Results are expressed as fold activation above 0.1% DMSO treated cells. Data represents the mean ± SE from three independent experiments in triplicate. EC50 and EMAX values were calculated using nonlinear regression of a typical log dose-response curve.
