Imazalil modulates CYPs 1A1 and 3A4 activities in the human Caco-2 cells as an intestinal model to assess food safety

Abstract

There are increasing evidences that ingestion of contaminated food provokes interactions at the intestinal level of major concern for food safety and appearance of drug interactions. We currently use human intestinal Caco-2 cells to evaluate interactions between chemicals and intestinal xenobiotic-metabolizing enzymes, mainly CYPs 1A1 and 3A4 isoforms, as well as apical efflux transporters. Imazalil (IMA) is a widely used post-harvest fungicide and, as such, a relevant food contaminant. IMA strongly induced CYP1A1 activity in a dose- and time-dependent manner. At low, but realistic intestinal concentrations (25 ppb), CYP1A1 activity increased rapidly, but only transiently, suggesting IMA biotransformation and/or (intralysosomal) accumulation by Caco-2 cells. In these cells, IMA was not an aryl hydrocarbon receptor (AhR) agonist, as revealed by reporter gene assay. In TCDD-induced cells, IMA showed no antagonistic effect towards CYP1A1 activity. Finally, some polyphenols reduced the IMA-induced CYP1A1 activity, whereas an additive effect was observed upon coincubation of IMA with benzo(a)pyrene. IMA also appeared as a CYP3A4 inhibitor as potent as ketoconazole, a classical pharmacological inhibitor. In addition, IMA seems to be without effect on either PgP or MRP-2 efflux pumps. HPLC analyses were carried out in order to evaluate IMA absorption by Caco-2 cells. These data reveal that IMA is a potent inducer of CYP1A1 activity in human intestinal Caco-2 cells, occurring by an AhR-independent mechanism, as well as a potent inhibitor of CYP3A4. These CYPs interactions may potentially cause adverse effects on human health by activating procarcinogenic food contaminants or by modulating drug bioavailability.