Roles of cytochromes P450 and ribosome inhibition in the interaction between two preoccupying mycotoxins, aflatoxin B1 and deoxynivalenol.

Mycotoxins are a threat to human and animal health. Climate change increases their occurrence and our dietary exposure. Although humans and animals are concomitantly exposed to several mycotoxins, their combined effects are poorly characterised. This study investigated the interaction between aflatoxin B1 (AFB1), the most potent natural carcinogen, and deoxynivalenol (DON), which is among the most prevalent mycotoxins. AFB1 is associated with hepatocellular carcinoma through its bioactivation by cytochrome P450 (CYP450) enzymes; while DON induces ribotoxic stress leading to an alteration of intestinal, immune and hepatic functions. Analysis of DNA damage biomarkers γ-H2AX and 53BP1 revealed that DON reduces the genotoxicity of AFB1. This effect was mimicked with cycloheximide (CHX), another ribosome inhibitor; moreover DOM-1, a DON-derivative lacking ribosome inhibition, did not affect DNA damage. Exposure to DON, alone or in combination with AFB1, decreased the protein levels and/or activities of CYP1A2 and CYP3A4 in a time- and dose-dependent manner. A similar reduction of CYP1A2 and CYP3A4 activities was also observed with CHX. Altogether, these results revealed an original interaction between DON and AFB1, DON inhibiting the genotoxicity of AFB1. The underlying mechanism involves ribosome inhibition by DON and the subsequent impairment of CYP450s, responsible for the bioactivation of AFB1. This work highlights the importance of studying mycotoxins not only individually but also in mixture and of considering food contaminants as part of the exposome.