Formation of estrogenic metabolites of benzo[a]pyrene and chrysene by cytochrome P450 activity and their combined and supra-maximal estrogenic activity

BaP itself exhibited estrogenicity in the ER-CALUX assay due to bio-activation into estrogenic metabolites, probably via aryl hydrocarbon receptor (AhR) induced CYP activity. Furthermore, 2-hydroxy-CHN (2-OHCHN) induced supra-maximal (400%) estrogenic effects in the ER-CALUX assay. This effect was entirely ER-mediated, since the response was completely blocked with the ER-antagonist ICI182,780. We showed that 2-OHCHN increased ER-concentration, using ELISA techniques, which may explain the observed supra-maximal effects. Co-treatment with the AhR-antagonist 3′,4′-dimethoxyflavone (DMF) enhanced ER-signaling, possibly via blockage of AhR-ER inhibitory cross-talk.