Characterization of a new synthetic AHR agonist (PB502). (A) Chemical structure of PB502. (B) Modeling of a docking site on AHR for PB502. (C) Western blot analysis of AHR in nuclear and cytoplasmic extracts of A549 cells cultured for 4 hours in the presence of PB502 (2 μM) or L-Kyn (100 μM). (D) A549 cells were cultured in the presence of PB502 or L-Kyn for 2 hours. Chromatin immunoprecipitation (ChIP) assays were performed to assess the binding of AHR to a xenobiotic response element site in the Cyp1b1 promoter. (E-F) A549 cells were cultured in the presence of PB502 with or without CH-223191 for 4 (E) or 24 (F) hours. (E) Levels of Cyp1b1 expression were measured by real-time polymerase chain reaction (PCR). (F) The enzymatic activity of CYP1A1 was measured using EROD assays. (G) A549 cells were cultured in the presence of PB502 (1 μM) with or without CH-223291 (10 μM) for 48 hours, and IL-1β was added and further cultured for 24 hours. Levels of Jund and Il6 expression were measured by real-time PCR. (H-I) A549 cells were stimulated with IL-1β for 1 hour, and PB502 or L-Kyn was added for 2 hours. Immunoprecipitation with anti-AHR antibody was performed in cell lysates, and AHR, STAT1, and JunD were detected by western blot analysis. (I) ChIP assays were performed to assess binding of STAT1 (left) and JunD (right) to the Jund promoter. Results are representative of 2 (H-I) or ≥ 4 (C-G) independent experiments with similar results. Data represent mean ± SEM. One-way analysis of variance was performed (D-G,I). *P < .05, **P < .01, ***P < .001. mRNA, messenger RNA.