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Cytotoxic and genotoxic potential of food-borne nitriles in a liver in vitro model

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ABSTRACT

Isothiocyanates are the most intensively studied breakdown products of glucosinolates from Brassica plants and well recognized for their pleiotropic effects against cancer but also for their genotoxic potential. However, knowledge about the bioactivity of glucosinolate-borne nitriles in foods is very poor. As determined by GC-MS, broccoli glucosinolates mainly degrade to nitriles as breakdown products. The cytotoxicity of nitriles in human HepG2 cells and primary murine hepatocytes was marginal as compared to isothiocyanates. Toxicity of nitriles was not enhanced in CYP2E1-overexpressing HepG2 cells. In contrast, the genotoxic potential of nitriles was found to be comparable to isothiocyanates. DNA damage was persistent over a certain time period and CYP2E1-overexpression further increased the genotoxic potential of the nitriles. Based on actual in vitro data, no indications are given that food-borne nitriles could be relevant for cancer prevention, but could pose a certain genotoxic risk under conditions relevant for food consumption.

No MeSH data available.


Analysis of cell viability of CYP2E1 transfected HepG2 cells and vector cells after treatment with nitriles.Cells were treated with allyl-CN (A), 3-but-CN (B), benzyl-CN (C) and 4-MTB-CN (D) for 72 hours and viability was analyzed using WST-1 assay. Bars are mean + SEM, n = 3. *P ≤ 0.05, asterisks indicate a significant difference between the sample and the solvent control: medium. CYP2E1: HepG2-CYP2E1, vector: HepG2-vector.
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f3: Analysis of cell viability of CYP2E1 transfected HepG2 cells and vector cells after treatment with nitriles.Cells were treated with allyl-CN (A), 3-but-CN (B), benzyl-CN (C) and 4-MTB-CN (D) for 72 hours and viability was analyzed using WST-1 assay. Bars are mean + SEM, n = 3. *P ≤ 0.05, asterisks indicate a significant difference between the sample and the solvent control: medium. CYP2E1: HepG2-CYP2E1, vector: HepG2-vector.

Mentions: Recently, a study showed that the cytochrome-P450 isoform CYP2E1 is involved in the allyl-CN induced lethality of mice14. In contrast to normal human hepatocytes, the HepG2 cell line expresses only very low amounts of CYP2E1. This was verified by the present study using qPCR. Consequently and in order to assess whether the presence of CYP2E1 could further elevate the toxicity of the food-borne nitriles, the compounds were tested again using CYP2E1-overexpressing HepG2 cells. In comparison to wildtype HepG2 cells, the CYP2E1 expression in HepG2-CYP2E1 cells was 300 times higher. Results from two unsaturated aliphatic nitriles (allyl-CN, 3-but-CN), the aromatic nitrile benzyl-CN, and the methylthioalkylnitrile 4-MTB-CN are shown in Fig. 3. Only 10 mM 4-MTB-CN showed a significant difference in cytotoxicity between CYP2E1-overexpressing and vector control cells. To the best of our knowledge, there are no other proteins described in the literature that have an influence on the cytotoxicity of nitriles other than CYP2E1.


Cytotoxic and genotoxic potential of food-borne nitriles in a liver in vitro model
Analysis of cell viability of CYP2E1 transfected HepG2 cells and vector cells after treatment with nitriles.Cells were treated with allyl-CN (A), 3-but-CN (B), benzyl-CN (C) and 4-MTB-CN (D) for 72 hours and viability was analyzed using WST-1 assay. Bars are mean + SEM, n = 3. *P ≤ 0.05, asterisks indicate a significant difference between the sample and the solvent control: medium. CYP2E1: HepG2-CYP2E1, vector: HepG2-vector.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5121622&req=5

f3: Analysis of cell viability of CYP2E1 transfected HepG2 cells and vector cells after treatment with nitriles.Cells were treated with allyl-CN (A), 3-but-CN (B), benzyl-CN (C) and 4-MTB-CN (D) for 72 hours and viability was analyzed using WST-1 assay. Bars are mean + SEM, n = 3. *P ≤ 0.05, asterisks indicate a significant difference between the sample and the solvent control: medium. CYP2E1: HepG2-CYP2E1, vector: HepG2-vector.
Mentions: Recently, a study showed that the cytochrome-P450 isoform CYP2E1 is involved in the allyl-CN induced lethality of mice14. In contrast to normal human hepatocytes, the HepG2 cell line expresses only very low amounts of CYP2E1. This was verified by the present study using qPCR. Consequently and in order to assess whether the presence of CYP2E1 could further elevate the toxicity of the food-borne nitriles, the compounds were tested again using CYP2E1-overexpressing HepG2 cells. In comparison to wildtype HepG2 cells, the CYP2E1 expression in HepG2-CYP2E1 cells was 300 times higher. Results from two unsaturated aliphatic nitriles (allyl-CN, 3-but-CN), the aromatic nitrile benzyl-CN, and the methylthioalkylnitrile 4-MTB-CN are shown in Fig. 3. Only 10 mM 4-MTB-CN showed a significant difference in cytotoxicity between CYP2E1-overexpressing and vector control cells. To the best of our knowledge, there are no other proteins described in the literature that have an influence on the cytotoxicity of nitriles other than CYP2E1.

View Article: PubMed Central - PubMed

ABSTRACT

Isothiocyanates are the most intensively studied breakdown products of glucosinolates from Brassica plants and well recognized for their pleiotropic effects against cancer but also for their genotoxic potential. However, knowledge about the bioactivity of glucosinolate-borne nitriles in foods is very poor. As determined by GC-MS, broccoli glucosinolates mainly degrade to nitriles as breakdown products. The cytotoxicity of nitriles in human HepG2 cells and primary murine hepatocytes was marginal as compared to isothiocyanates. Toxicity of nitriles was not enhanced in CYP2E1-overexpressing HepG2 cells. In contrast, the genotoxic potential of nitriles was found to be comparable to isothiocyanates. DNA damage was persistent over a certain time period and CYP2E1-overexpression further increased the genotoxic potential of the nitriles. Based on actual in vitro data, no indications are given that food-borne nitriles could be relevant for cancer prevention, but could pose a certain genotoxic risk under conditions relevant for food consumption.

No MeSH data available.