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

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.

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Related in: MedlinePlus

Analysis of cell viability using the WST-1 assay after a 72 h treatment with unsaturated (A) aromatic nitriles (B), methylthioalkylnitriles (C) and benzyl-ITC (D). Control: solvent control, 0–30% double distilled sterile water (A–C), 0.1% DMSO (D). Bars are mean + SEM, n = 3. *P < 0.05; asterisks indicate a significant difference between the sample and the solvent control.
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f2: Analysis of cell viability using the WST-1 assay after a 72 h treatment with unsaturated (A) aromatic nitriles (B), methylthioalkylnitriles (C) and benzyl-ITC (D). Control: solvent control, 0–30% double distilled sterile water (A–C), 0.1% DMSO (D). Bars are mean + SEM, n = 3. *P < 0.05; asterisks indicate a significant difference between the sample and the solvent control.

Mentions: As there is only limited information about secondary and tertiary cancer chemopreventive effects, cytotoxicity of unsaturated aliphatic, aromatic, and methylthioalkylnitriles (Fig. 1) against human liver cancer (HepG2) cells was studied. Keeping the toxicity of the related ITC in mind1718, first investigations of the cytotoxicity of nitriles were carried out using concentrations ranging from 0.1 to 100 μM. However, these concentrations did not impact cell viability (data not shown). Thus, a concentration range between 0.3 to 30 mM was tested. Due to a limited solubility of nitriles in purified water, no higher concentrations than 30 mM were achieved. Treatment of HepG2 cells with unsaturated aliphatic nitriles (allyl-CN, 3-but-CN and 4-pent-CN) for 72 h did not result in significant changes in cell viability. In contrast, aromatic nitriles and methylthioalkylnitriles induced a loss of viability at concentrations exceeding 10 mM (Fig. 2). However, a significant reduction of cell viability was detected only at the highest concentration tested. The cytotoxic potential of the two aromatic nitriles was similar and lead to IC50 values of 19.95 mM (benzyl-CN) and 18.21 mM (2-phenylethyl-CN), respectively (Table 2). Comparative investigations with benzyl-ITC resulted in a 1000-fold stronger cytotoxic potency with an IC50 of 15.75 μM. Using methylthioalkylnitriles, a structure dependent increase in cytotoxicity could be observed with increasing chain length, with the lowest IC50 at 8.15 mM for 6-MTH-CN. The IC50 for 3-MTP-CN, 4-MTB-CN, and 5-MTP-CN are given in Table 2. Figure 1 shows the structural differences of these nitriles.


Cytotoxic and genotoxic potential of food-borne nitriles in a liver in vitro model
Analysis of cell viability using the WST-1 assay after a 72 h treatment with unsaturated (A) aromatic nitriles (B), methylthioalkylnitriles (C) and benzyl-ITC (D). Control: solvent control, 0–30% double distilled sterile water (A–C), 0.1% DMSO (D). Bars are mean + SEM, n = 3. *P < 0.05; asterisks indicate a significant difference between the sample and the solvent control.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2: Analysis of cell viability using the WST-1 assay after a 72 h treatment with unsaturated (A) aromatic nitriles (B), methylthioalkylnitriles (C) and benzyl-ITC (D). Control: solvent control, 0–30% double distilled sterile water (A–C), 0.1% DMSO (D). Bars are mean + SEM, n = 3. *P < 0.05; asterisks indicate a significant difference between the sample and the solvent control.
Mentions: As there is only limited information about secondary and tertiary cancer chemopreventive effects, cytotoxicity of unsaturated aliphatic, aromatic, and methylthioalkylnitriles (Fig. 1) against human liver cancer (HepG2) cells was studied. Keeping the toxicity of the related ITC in mind1718, first investigations of the cytotoxicity of nitriles were carried out using concentrations ranging from 0.1 to 100 μM. However, these concentrations did not impact cell viability (data not shown). Thus, a concentration range between 0.3 to 30 mM was tested. Due to a limited solubility of nitriles in purified water, no higher concentrations than 30 mM were achieved. Treatment of HepG2 cells with unsaturated aliphatic nitriles (allyl-CN, 3-but-CN and 4-pent-CN) for 72 h did not result in significant changes in cell viability. In contrast, aromatic nitriles and methylthioalkylnitriles induced a loss of viability at concentrations exceeding 10 mM (Fig. 2). However, a significant reduction of cell viability was detected only at the highest concentration tested. The cytotoxic potential of the two aromatic nitriles was similar and lead to IC50 values of 19.95 mM (benzyl-CN) and 18.21 mM (2-phenylethyl-CN), respectively (Table 2). Comparative investigations with benzyl-ITC resulted in a 1000-fold stronger cytotoxic potency with an IC50 of 15.75 μM. Using methylthioalkylnitriles, a structure dependent increase in cytotoxicity could be observed with increasing chain length, with the lowest IC50 at 8.15 mM for 6-MTH-CN. The IC50 for 3-MTP-CN, 4-MTB-CN, and 5-MTP-CN are given in Table 2. Figure 1 shows the structural differences of these nitriles.

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.


Related in: MedlinePlus