Ochratoxin A (OTA) is a widespread mycotoxin produced by several species of the genera Aspergillus and Penicillium. OTA exists in a variety of foods, including rice, oats, and coffee and is hepatotoxic, with a similar mode of action as aflatoxin B1. The precise mechanism of cytotoxicity is not yet known, but oxidative damage is suspected to contribute to its cytotoxic effects. In this study, human hepatocyte HepG2 cells were treated with various concentrations of OTA (5–500 nM) for 48 h. OTA triggered oxidative stress as demonstrated by glutathione depletion and increased reactive oxygen species, malondialdehyde level, and nitric oxide production. Apoptosis was observed with 500 nM OTA treatment. OTA increased both the mRNA and protein expression of phase I and II enzymes. The same results were observed in an in vivo study using ICR mice. Furthermore, the relationship between phase I and II enzymes was demonstrated by the knockdown of the aryl hydrocarbon receptor (AhR) and NF-E2-related factor 2 (Nrf2) with siRNA. Taken together, our results show that OTA induces oxidative stress through the phase I reaction regulated by AhR and induces apoptosis, and that the phase II reaction is activated by Nrf2 in the presence of oxidative stress.

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Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus and Penicillium, and it is found in many foods. Acrylamide (AA) can be produced in foods treated at high temperatures. In this study, we investigated the combined toxicity of OTA and AA against human renal and hepatic cells in vitro. The concentration at which the synergistic effect of OTA and AA occurs was determined using the combination index obtained from the cell viability results for OTA and AA individually or in combination. The synergistic toxicity of both substances was evaluated by cell viability and the production of reactive oxygen species. In addition, apoptosis-related markers were significantly upregulated by OTA and AA individually or in combination. To determine the combined toxic effects of OTA and AA on the cells, the levels of enzymes involved in the phase I reaction and apoptosis-related markers were determined using quantitative (q)PCR and Western blot. The expression levels of CYP enzymes CYP1A1 and CYP1A2 involved in the phase I reaction significantly increased when the cells were treated with OTA and AA in combination. The expression of apoptosis-related markers, Bcl2-associated X protein (Bax) and caspase 3, also increased when the cells were treated with OTA and AA in combination. Therefore, the synergistic toxicity of OTA and AA suggests that such effects may contribute to nephrotoxicity and hepatotoxicity.

Ochratoxin A (OTA) is a widespread mycotoxin produced by several species of the genera Aspergillus and Penicillium. Since OTA is mainly found in foods such as rice and oats consumed all over the world, there are many researches on the reduction of OTA. Benzo [a] pyrene (B[a]P) and acrylamide (AA) may occur during the heat treatment process to reduce the OTA present in rice. In this study, we tried to identify the combined toxicity of the three substances (OTA, B[a]P, AA) in the liver. The cell viability of OTA, B[a]P and AA was checked to determine the concentration of IC20. The toxicity of the combination of the three substances showed synergistic effects on cell viability and NO production. To further elucidate the mechanism of toxicity in liver, real‐time PCR was used to confirm mRNA expression levels of enzymes involved in phase I and II pathway. In the case of cytochrome P450 (CYP) families (CYP1A1, CYP1A2, and CYP3A4) belonging to Phase I, the mRNA expression levels were significantly increased when all three of them were mixed with each other than those treated with OTA, B[a]P and AA, respectively. The mRNA expression levels of heme oxygenase‐1 (HO‐1) and glutamate cysteine ligase catalytic subunit (GCLC) belonging to Phase II were also similar to those of Phase I. Therefore, in all experiments, the combined toxicity of OTA, B[a]P, and AA was confirmed, indicating synergistic effects on hepatotoxicity.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.