FIG. 1.

KA is the primary tryptophan oxidation product that exhibits potent AHR agonist activity. (A) TCDD and the primary products of the IDO pathway were tested at 10μM for their ability after 4 h to activate the AHR in HepG2 40/6 reporter cell line. (B) Induction of CYP1A1 mRNA levels in HepG2 cells after 3-h exposure to increasing concentrations of KA. (C) Structures of the compounds utilized to determine the structural requirements necessary to mediate AHR activity. (D) Luciferase reporter assays were used to test the ability of quinoline and several derivatives at 10μM to activate the AHR in HepG2 40/6 cells. Experiments were performed in triplicate; error bars denote SD. ** or ***Significance at p < 0.01 or p < 0.001, as compared to respective control-treated samples.