Potential of an in vitro toolbox combined with exposure data as a first step for the risk assessment of dietary chemical contaminants

in Food Additives & Contaminants (2011), 28(9), 1136-1158

In vitro risk assessment of dietary contaminants has become a priority in human food safety. This paper proposes an in vitro approach associating different complementary tools in an original toolbox and ... [more ▼]

In vitro risk assessment of dietary contaminants has become a priority in human food safety. This paper proposes an in vitro approach associating different complementary tools in an original toolbox and aims to improve the assessment of the toxicological impact of dietary contaminants at realistic human exposure levels, with a special focus on the intestinal compartment. The system is based on the use of four complementary cellular tools, namely stress gene induction in transgenic strains of Escherichia coli, modulation of the activity of key biotransformation enzymes (cytochrome P-450 (CYP) 1A1 and 3A4) in a human intestinal cell line, and activation of aryl hydrocarbon receptor (AhR) and oestrogenic receptor (ER)-dependent genes in agonistic and antagonistic assays with luciferase reporter cells. It was applied to four chosen model molecules: ochratoxin A (OTA) and deoxynivalenol (DON), two common food-borne mycotoxins, and imazalil (IMA) and benomyl (BEN), two fungicides widely occurring in foodstuffs. All these assays were performed at or around a realistic intestinal concentration, determined through a deterministic approach based on the calculation of a theoretical maximum daily intake (TMDI). Using the four model molecules, it is clearly highlighted that induction of CYP1A1 activity and inhibition of CYP3A4 activity occurred in Caco-2 cells at a realistic intestinal concentration of IMA. Furthermore, some bacterial stress genes were induced in a range of realistic concentrations, following exposure to DON and IMA. In addition, BEN clearly provoked an ER agonistic activity in a human oestrogen sensitive reporter cell line. All these results are in accordance with the literature, suggesting that the in vitro toolbox constitutes an interesting approach in order to obtain a first 'fingerprint' of dietary contaminants at realistic human exposure for further risk assessment. [less ▲]

Reporter gene assays as screening tools to assess the endocrine disrupting potencies of 20 pesticides

Poster (2009, May 20)

CYP1A1 induction and CYP3A4 inhibition by the fungicide imazalil in the human intestinal Caco-2 cells-Comparison with other conazole pesticides

in Toxicology Letters (2009), 184(3), 159-168

Imazalil (IMA) is a widely used imidazole-antifungal pesticide and. therefore. a food contaminant. This compound is also used as a drug (enilconazole). As intestine is the first site of exposure to ... [more ▼]

Imazalil (IMA) is a widely used imidazole-antifungal pesticide and. therefore. a food contaminant. This compound is also used as a drug (enilconazole). As intestine is the first site of exposure to ingested drugs and pollutants, we have investigated the effects of IMA, at realistic intestinal concentrations, on xenobiotic-metabolizing enzymes and efflux pumps by using Caco-2 cells, as a validated in vitro model of the human intestinal absorptive epithelium. For comparison, other conazole fungicides, i.e. ketoconazole, propiconazole and tebuconazole. were also studied. IMA induced cytochrome P450 (CYP) 1A1 activity to the same extent as benzo(a)pyrene (B(a)P) or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), in a dose-and time-dependent manner. Cell-free aryl hydrocarbon receptor (AhR) binding assay and reporter gene assay suggested that IMA is not an AhR-ligand, implying that IMA-mediated induction should involve an AhR-independent pathway. Moreover, IMA strongly inhibited the CYP3A4 activity in 1,25-vitamin D-3-induced Caco-2 cells. The other fungicides had weak or nil effects on CYP activities. Study of the apical efflux pump activities revealed that ketoconazole inhibited both P-glycoprotein (Pgp) and multidrug resistance-associated protein 2 (MRP-2) or breast cancer resistance protein (BCRP), whereas IMA and other fungicides did not. Our results imply that coingestion of IMA-contaminated food and CYP3A4- or CYP1A1-metabolizable drugs or chemicals could lead to drug bioavailability modulation or toxicological interactions, with possible adverse effects for human health. (C) 2008 Elsevier Ireland Ltd. All rights reserved. [less ▲]

Imazalil is an aryl hydrocarbon receptor (AhR) antagonist in AhR-dependent reporter human and rat hepatoma cells

in Toxicology Letters (2007), 172

New experimental approach of identification and characterization of emerging risks in food safety (EMRISK).

Report (2007)