Cytochrome P4501A induction caused by the imidazole derivative Prochloraz in a rainbow trout cell line

A variety of aquatic pollutants are able to induce cytochrome P4501A (CYP1A) in fish by ligand binding to the aryl hydrocarbon receptor (AhR). High-affinity AhR ligands are planar aromatic polycyclic molecules such as the prototypical ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The present work investigates the ability of the imidazole derivative, Prochloraz (PRO), to induce CYP1A. Computational studies on the molecular structure of PRO indicated that it is highly unlikely for PRO to have both aromatic rings of the molecule, i.e. the imidazole and the benzene ring, in the same plane. Thus, the possible conformers do not take planar structures, in contrast to the typically planar AhR ligands. Experimentally, the capability of PRO to induce CYP1A was assessed using the rainbow trout liver cell line, RTL-W1, as in vitro model. PRO increased in a concentration-dependent way the catalytic activity of CYP1A (determined as 7-ethoxyresorufin-O-deethylase, EROD, activity) in RTL-W1 cells. The potency of PRO was lower than that of a reference AhR-ligand, β-naphthoflavone (βNF). In addition to the catalytic level, PRO activated CYP1A also at the transcriptional level as determined by RT-PCR analysis of CYP1A mRNA. These results indicate that PRO, although its structure is not corresponding to the typical features of CYP1A-inducing AhR ligands, still is able to activate CYP1A expression.