The aflatoxin B1-fumonisin B1 toxicity in BRL-3A hepatocytes is associated to induction of cytochrome P450 activity and arachidonic acid metabolism

Human oral exposure to aflatoxin B-1 (AFB(1)) and fumonisin B-1 (FB1) is associated with increased hepatocellular carcinoma. Although evidence suggested interactive AFB(1)-FB1 hepatotoxicity, the underlying mechanisms remain mostly unidentified. This work was aimed at evaluating the possible AFB(1)-FB1 interplay to induce genetic and cell cycle toxicities in BRL-3A rat hepatocytes, reactive oxygen species (ROS) involvement, and the AFB(1) metabolizing pathways cytochrome P450 (CYP) and arachidonic acid (ArAc) metabolism as ROS contributors. Flow cytometry of stained BRL-3A hepatocytes was used to study the cell cycle (propidium iodide), ROS intracellular production (DCFH-DA, HE, DAF-2 DA), and phospholipase A activity (staining with bis-BODIPY FL C11-PC). The CYP1A activity was assessed by the 7-ethoxyresorufin-O-deethylase (EROD) assay. Despite a 48-h exposure to FB1 (30 mu M) not being genotoxic, the AFB(1) (20 mu M)-induced micronucleus frequency was overcome by the AFB(1)-FB1 mixture (MIX), presumably showing toxin interaction. The mycotoxins blocked G1/S-phase, but only MIX caused cell death. Overall, the oxidative stress led these alterations as the pretreatment with N-acetyl-l-cysteine reduced such toxic effects. While AFB(1) had a major input to the MIX pro-oxidant activity, with CYP and ArAc metabolism being ROS contributors, these pathways were not involved in the FB1-elicited weak oxidative stress. The MIX-induced micronucleus frequency in N-acetyl-L-cysteine pretreated cells was greater than that caused by AFB(1) without antioxidants, suggesting enhanced AFB(1) direct genotoxicity probably owing to the higher CYP activity and ArAc metabolism found in MIX. The metabolic pathways modulation by AFB(1)-FB1 mixtures could raise its hepatocarcinogenic properties.