Aryl hydrocarbon receptor-mediated and estrogenic activities of oxygenatedpolycyclic aromatic hydrocarbons and azaarenes originally identified in extracts of river sediments

Reproductive dysfunction in wildlife populations can be a result of environ mental contaminants binding to aryl hydrocarbon receptor (AhR) or estrogeni c receptors. Signaling by both types of receptors can be affected by polycy clic aromatic hydrocarbons (PAHs), which are potential endocrine disruptors . However, our knowledge regarding the effects of oxygenated (oxy)PAHs and azaarenes on AhR-mediated and estrogenic activities is incomplete. In the p resent study, we have identified 9-fluorenone, anthrone, anthraquinone, ben zanthrone, benz[a]anthracene-7,12-dione, benz[c]acridine, and dibenz[a.h]ac ridine as prevalent oxy-PAHs and azaarenes found in river sediments. Their concentrations in sediment samples ranged from 2.1 to 165.2 ng g(-1) for ox y-PAHs and up to 27.3 ng g(-1) for azaarenes. Their relative AhR-inducing a nd estrogenic potencies were quantified in vitro using two cell lines that were stably transfected with a luciferase reporter gene system and expresse d as induction equivalency factors (IEFs). The only oxy-PAHs with detectabl e levels of in vitro AhR-mediated activity were benzanthrone and benz[a]ant hracene7,12-dione. However, their IEFs were approximately three to four ord ers of magnitude lower than those of benzo[a]pyrene. On the other hand, aza arenes showed a strong AhR-mediated activity, with dibenzo[a,h]acridine bei ng a far more potent inducer of activity than benzo[a]pyrene. Benzanthrone, bent[a]anthracene-7,12-dione, anthraquinone. and benz[a]acridine were weak inducers of in vitro estrogenic activity, with IEFs similar to that of ben zo[a]pyrene. Based on concentrations and relative potencies, our results su ggest that dibenzo[a,h]acridine can significantly contribute to the overall AhR-mediated activity in river sediments, whereas the remaining compounds do not. No studied compound was found to contribute significantly to estrog en receptor-mediated activity in vitro,