Enantioselective disruption of human steroidogenesis in vitro by the azole fungicides imazalil, miconazole, and ketoconazole.

Racemic mixtures of azoles such as imazalil, miconazole and ketoconazole are widely used as fungicides on food crops indirectly affecting humans or directly in humans as treatment of fungal infections. We investigated the potency of individual enantiomers (R- and S-imazalil, R- and S-miconazole and RS- and SR-ketoconazole), to disrupt human steroidogenesis in vitro. Effects of individual enantiomers and racemic mixtures on the canonical steroidogenic pathway were examined in the OECD standardized H295R steroidogenesis assay. Results indicate that disruption of steroidogenesis by the studied azoles is a highly enantioselective process, the degree of stereoselectivity being strongly dependent on the compound and the steroidogenic pathway. Results from the cell assay are supported by recombinant enzyme assays, where inhibition of CYP17A1-hydroxylase and -lyase as well as CYP19A1-aromatase activity was investigated. To shed light on the potential binding modes of the azoles, the enantiomers were also docked to CYP11A1, CYP17A1, CYP19A1 and CYP21A2 and selected poses subjected to molecular dynamics simulations, indicating differences in binding affinities but high potentials for endocrine disruption for all investigated enantiomers.