Protective effects of Brussels sprouts towards B[a]P-induced DNA damage: a model study with the single-cell gel electrophoresis (SCGE)/Hep G2 assay

Cruciferous Vegetable Intake and Bulky DNA Damage within Non-Smokers and Former Smokers in the Gen-Air Study (EPIC Cohort)

Epidemiologic studies have indicated that cruciferous vegetables can influence the cancer risk; therefore, we examined with a cross-sectional approach the correlation between the frequent consumption of the total cruciferous vegetables and the formation of bulky DNA damage, a biomarker of carcinogen exposure and cancer risk, in the Gen-Air study within the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. DNA damage measurements were performed in the peripheral blood of 696 of those apparently healthy without cancer controls, including 379 never-smokers and 317 former smokers from seven European countries by the 32P-postlabeling assay. In the Gen-Air controls, the median intake of cruciferous vegetables was 6.16 (IQR 1.16−13.66) g/day, ranging from 0.37 (IQR 0−6.00) g/day in Spain to 11.34 (IQR 6.02−16.07) g/day in the UK. Based on this information, participants were grouped into: (a) high consumers (>20 g/day), (b) medium consumers (3−20 g/day) and (c) low consumers (<3.0 g/day). Overall, low cruciferous vegetable intake was correlated with a greater frequency of bulky DNA lesions, including benzo(a)pyrene, lactone and quinone-adducts and bulky oxidative lesions, in the adjusted models. Conversely, a high versus low intake of cruciferous vegetables was associated with a reduction in DNA damage (up to a 23% change, p = 0.032); this was particularly evident in former smokers (up to a 40% change, p = 0.008). The Generalized Linear Regression models indicated an overall Mean Ratio between the high and the low consumers of 0.78 (95% confidence interval, 0.64−0.97). The current study suggests that a higher intake of cruciferous vegetables is associated with a lower level of bulky DNA adducts and supports the potential for cancer prevention strategies through dietary habit changes aimed at increasing the consumption of cruciferous vegetables.

Assessment of DNA damage and repair in adults consuming allyl isothiocyanate or Brassica vegetables

Allyl isothiocyanate (AITC) is a dietary component with possible anticancer effects, though much information about AITC and cancer has been obtained from cell studies. To investigate the effect of AITC on DNA integrity in vivo, a crossover study was conducted. Adults (n=46) consumed AITC, AITC-rich vegetables [mustard and cabbage (M/C)] or a control treatment with a controlled diet for 10 days each. On day 11, volunteers provided blood and urine before and after consuming treatments. Volunteers were characterized for genotype for GSTM1 and GSTT1 (glutathione S-transferases) and XPD (DNA repair). DNA integrity in peripheral blood mononuclear cells was assessed by single-cell gel electrophoresis. Urine was analyzed for 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and creatinine. Ten-day intake of neither AITC nor M/C resulted in statistically significant differences in DNA strand breaks [least squares mean (LSmean) % DNA in tail±S.E.M.: 4.8±0.6 for control, 5.7±0.7 for AITC, 5.3±0.6 for M/C] or urinary 8-oxodG (LSmean μg 8-oxodG/g creatinine±S.E.M.: 2.95±0.09 for control, 2.88±0.09 for AITC, 3.06±0.09 for M/C). Both AITC and M/C increased DNA strand breaks 3 h postconsumption (LSmean % DNA in tail±S.E.M.: 3.2±0.7 for control, 8.3±1.7 for AITC, 8.0±1.7 for M/C), and this difference disappeared at 6 h (4.2±0.9 for control, 5.7±1.2 for AITC, 5.5±1.2 for M/C). Genotypes for GSTM1, GSTT1 and XPD were not associated with treatment effects. In summary, DNA damage appeared to be induced in the short term by AITC and AITC-rich products, but that damage disappeared quickly, and neither AITC nor AITC-rich products affected DNA base excision repair.

Brassica oleracea L. Var. costata DC and Pieris brassicae L. aqueous extracts reduce methyl methanesulfonate-induced DNA damage in V79 hamster lung fibroblasts

Brassica oleracea L. var. costata DC leaves and Pieris brassicae L. larvae aqueous extracts were assayed for their potential to prevent/induce DNA damage. None of them was mutagenic at the tested concentrations in the Ames test reversion assay using Salmonella His(+) TA98 strains, with and without metabolic activation. In the hypoxanthine-guanine phosphoribosyltransferase mutation assay using mammalian V79 fibroblast cell line, extracts at 500 μg/mL neither induced mutations nor protected against the mutagenicity caused by methyl methanesulfonate (MMS). In the comet assay, none of the extracts revealed to be genotoxic by itself, and both afforded protection, more pronounced for larvae extracts, against MMS-induced genotoxicity. As genotoxic/antigenotoxic effects of Brassica vegetables are commonly attributed to isothiocyanates, the extracts were screened for these compounds by headspace-solid-phase microextraction/gas chromatography-mass spectrometry. No sulfur compound was detected. These findings demonstrate that both extracts could be useful against damage caused by genotoxic compounds, the larvae extract being the most promising.

Mass spectrometry imaging of glucosinolates in Arabidopsis flowers and siliques

Glucosinolates are multi-functional plant secondary metabolites which play a vital role in plant defence and are, as dietary compounds, important to human health and livestock well-being. Knowledge of the tissue-specific regulation of their biosynthesis and accumulation is essential for plant breeding programs. Here, we report that in Arabidopsis thaliana, glucosinolates are accumulated differentially in specific cells of reproductive organs. Using matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI), distribution patterns of three selected compounds, 4-methylsulfinylbutyl (glucoraphanin), indol-3-ylmethyl (glucobrassicin), and 4-benzoyloxybutyl glucosinolates, were mapped in the tissues of whole flower buds, sepals and siliques. The results show that tissue localization patterns of aliphatic glucosinolate glucoraphanin and 4-benzoyloxybutyl glucosinolate were similar, but indole glucosinolate glucobrassicin had different localisation, indicating a possible difference in function. The high resolution images obtained by a complementary approach, cryo-SEM Energy Dispersive X-ray analysis (cryo-SEM-EDX), confirmed increased concentration of sulphur in areas with elevated amounts of glucosinolates, and allowed identifying the cell types implicated in accumulation of glucosinolates. High concentration of sulphur was found in S-cells adjacent to the phloem in pedicels and siliques, indicating the presence of glucosinolates. Moreover, both MALDI MSI and cryo-SEM-EDX analyses indicated accumulation of glucosinolates in cells on the outer surface of the sepals, suggesting that a layer of glucosinolate-accumulating epidermal cells protects the whole of the developing flower, in addition to the S-cells, which protect the phloem. This research demonstrates the high potential of MALDI MSI for understanding the cell-specific compartmentation of plant metabolites and its regulation.

Anti-proliferative activity and chemoprotective effects towards DNA oxidative damage of fresh and cooked Brassicaceae

Epidemiological evidence shows that regular consumption of Brassicaceae is associated with a reduced risk of cancer and heart disease. Cruciferous species are usually processed before eating and the real impact of cooking practices on their bioactive properties is not fully understood. We have evaluated the effect of common cooking practices (boiling, microwaving, and steaming) on the biological activities of broccoli, cauliflower and Brussels sprouts. Anti-proliferative and chemoprotective effects towards DNA oxidative damage of fresh and cooked vegetable extracts were evaluated by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium and Comet assays on HT-29 human colon carcinoma cells. The fresh vegetable extracts showed the highest anti-proliferative and antioxidant activities on HT-29 cells (broccoli>cauliflower = Brussels sprouts). No genotoxic activity was detected in any of the samples tested. The cooking methods that were applied influenced the anti-proliferative activity of Brassica extracts but did not alter considerably the antioxidant activity presented by the raw vegetables. Raw, microwaved, boiled (except broccoli) and steamed vegetable extracts, at different concentrations, presented a protective antioxidative action comparable with vitamin C (1 mm). These data provide new insight into the influence of domestic treatment on the quality of food, which could support the recent epidemiological studies suggesting that consumption of cruciferous vegetables, mainly cooked, may be related to a reduced risk of developing cancer.

Structural requirements for mutation formation from polycyclic aromatic hydrocarbon dihydrodiol epoxides in their interaction with food chemopreventive compounds

Chinese hamster V79 cells were used to investigate the protective effect of four known antimutagens present in food, chlorophyllin (CHL), ellagic acid (EA), epigallocathechingallate (EGCG) and benzylisothiocyanate (BITC), against potent mutagenic polycyclic aromatic hydrocarbon diol epoxides (PAH-DE) derived from benzo[a]pyrene (BP), dibenzo[a,h]anthracene (DBA), dibenzo[a,l]pyrene (DBP), and benzo[c]phenanthrene (BPh) known to be deposited on crops from polluted ambient air or formed during food processing. As fjord-region PAH-DE are more toxic and mutagenic than bay-region PAH-DE, we adjusted the concentrations of PAH-DE to induce approximately the same levels of adducts. The studies were performed using an assay indicating toxicity in terms of reduced cell proliferation together with the V79 Hprt assay for monitoring mutant frequencies. CHL significantly increased the survival and showed a protective effect against the mutagenicity of all PAH-DE. A significant protective effect of EA was found towards the mutagenicity of BPDE, DBPDE and BPhDE and with EGCG for BPDE and BPhDE. BITC had a slight positive effect on the mutagenicity of DBADE and BPhDE. Taken together, a novel and unexpected finding was that the antimutagenic activity could differ as much as by a factor of 7 towards four carcinogenic PAH metabolites being relatively similar in structure and genotoxic activity.

Effect of allyl isothiocyanate (AITC) in both nitrite- and nitrosamine-induced cell death, production of reactive oxygen species, and DNA damage by the single-cell gel electrophoresis (SCGE): does it have any protective effect on HepG2 cells?

The current study was designed to investigate possible protective effect of allyl isothiocyanate (AITC) in nitrite- and nitrosamine-treated human hepatoma cells (HepG2) with the evaluation by cytotoxic effects and genotoxic effects determined by the single-cell gel electrophoresis (SCGE). Allyl isothiocyanate treatment enhanced cell viability and reduced intracellular reactive oxygen species (ROS) production in both nitrite- and nitrosamine-treated cells significantly. In SCGE, when compared to untreated control cells, all of the treated groups caused increases in the tail intensity (%) such as nitrite at 17%, N-nitrosodimethylamine (NDMA) at 279%, N-nitrosodiethylamine (NDEA) at 324%, and N-nitrosomorpholine (NMOR) at 288%. Allyl isothiocyanate reduced the tail intensity caused by nitrite 36%, by NDMA 36%, by NDEA 49%, and by NMOR 32%, respectively, when compared to each individual toxic compound-treated group. In conclusion, AITC protected HepG2 cells against cytotoxic and genotoxic effects caused by nitrite and the nitrosamines.

Evaluation of protective effects of sulforaphane on DNA damage caused by exposure to low levels of pesticide mixture using comet assay

The objective of the study was to evaluate the potential risk of DNA damage due to exposure to a mixture of the most widely used pesticides, namely endosulfan, chlorpyriphos and thiram at an environmentally relevant concentration (5 microM each) and the DNA protective capacity of sulforaphane (SFN) (10-30 microg/mL). DNA damage in human lymphocytes was ascertained with Single Cell Gel Electrophoresis (SCGE), also called Comet Assay. For positive control, H(2)O(2) at 100 mM was used. The pesticide mixture produced DNA damage at the concentration used in the lymphocytes. SFN was able to offer a statistically significant (P < 0.01), concentration-dependant protection to DNA damage between 10-20 microg/mL in both the pre-incubation and co-incubation strategies. The results indicate that exposure to low levels of these pesticide mixtures can induce DNA damage, and the presence of SFN in diet may reduce the incidence of genetic damage, especially in farm workers. However, it is not clear whether SFN is involved in quenching of the free radicals generated by the pesticide mixture or it is involved in DNA repair mechanism.

Molecular targets of nutraceuticals derived from dietary spices: potential role in suppression of inflammation and tumorigenesis

Despite the fact cancer is primarily a preventable disease, recent statistics indicate cancer will become the number one killer worldwide in 2010. Since certain cancers are more prevalent in the people of some countries than others, suggests the role of lifestyle. For instance cancer incidence among people from the Indian subcontinent, where most spices are consumed, is much lower than that in the Western World. Spices have been consumed for centuries for a variety of purposes-as flavoring agents, colorants, and preservatives. However, there is increasing evidence for the importance of plant-based foods in regular diet to lowering the risk of most chronic diseases, so spices are now emerging as more than just flavor aids, but as agents that can not only prevent but may even treat disease. In this article, we discuss the role of 41 common dietary spices with over 182 spice-derived nutraceuticals for their effects against different stages of tumorigenesis. Besides suppressing inflammatory pathways, spice-derived nutraceuticals can suppress survival, proliferation, invasion, and angiogenesis of tumor cells. We discuss how spice-derived nutraceuticals mediate such diverse effects and what their molecular targets are. Overall our review suggests "adding spice to your life" may serve as a healthy and delicious way to ward off cancer and other chronic diseases.

Allyl isothiocyanate influences cell adhesion, migration and metalloproteinase gene expression in SK-Hep1 cells

Allyl isothiocyanate (AITC) has been reported to exhibit antimetastatic activity, but the mechanism remains unclear. The objective of this study was to determine the effect of AITC on cell adhesion, migration, and metalloproteinase gene expression in SK-Hep1 human hepatoma cells. The gene expression profiles of SK-Hep1 cells were obtained by using the HG-U133A Affymetrix GeneChip human genome array containing 14,500 human genes. Twenty antimetastatic genes including COL4A3, ADAMDEC1, CAPN10, CD14, and ITGB1BP3 were over expressed, while the expression of 35 genes such as COL8A1, MYBPC1, ST14, and SOS2 were down-regulated. Semiquantitative RT-PCR confirmed these results in mRNA levels. Based on these in vitro results, it can be concluded that AITC might be potentially useful in suppressing tumor cell migration and MMP expression.

Protective effects of isothiocyanates alone or in combination with vitamin C towardsN-nitrosodibutylamine orN-nitrosopiperidine-induced oxidative DNA damage in the single-cell gel electrophoresis (SCGE)/HepG2 assay

The aim of this study was to investigate the protective effect of isothiocyanates alone or in combination with vitamin C towards N-nitrosodibutylamine (NDBA) or N-nitrosopiperidine (NPIP)-induced oxidative DNA damage in the single cell gel electrophoresis (SCGE)/HepG2 assay. Phenethyl isothiocyanate (PEITC) and indole-3-carbinol (I3C) alone showed a weak protective effect towards NDBA (0.1 microm, 26-27%, respectively) or NPIP (1 microm, 26-28%, respectively)-induced oxidative DNA damage. Allyl isothiocyanate (AITC) alone did not attenuate the genotoxic effect provoked by NDBA or NPIP. In contrast, HepG2 cells simultaneously treated with PEITC, I3C and AITC in combination with vitamin C showed a stronger inhibition of oxidative DNA-damage induced by NDBA (0.1 microm, 67%, 42%, 32%, respectively) or NPIP (1 microm, 50%, 73%, 63%, respectively) than isothiocyanates (ITCs) alone. One feasible mechanism by which ITCs alone or in combination with vitamin C exert their protective effects towards N-nitrosamine-induced oxidative DNA damage could be by the inhibition of their cytochrome P450 dependent bioactivation. PEITC and I3C strongly inhibited the p-nitrophenol hydroxylation (CYP2E1) activity (0.1 microm, 66-50%, respectively), while the coumarin hydroxylase (CYP2A6) activity was slightly reduced (0.1 microm, 25-37%, respectively). However, the ethoxyresorufin O-deethylation (CYP1A1) activity was only inhibited by PEITC (1 microm, 55%). The results indicate that PEITC and I3C alone or PEITC, I3C and AITC in combination with vitamin C protects human-derived cells against the oxidative DNA damaging effects of NDBA and NPIP, two food carcinogenic compounds.

Protective effects of xanthohumol against the genotoxicity of benzo(a)pyrene (BaP), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and tert-butyl hydroperoxide (t-BOOH) in HepG2 human hepatoma cells

Xanthohumol is the major prenylated flavonoid present in the hop plant Humulus lupulus L. (Cannabinaceae) and a common ingredient of beer. Recently, xanthohumol has gained considerable interest due to its potential cancer chemo-preventive effect. The aim of this study was to reveal the possible anti-genotoxic activity of xanthohumol in metabolically competent human hepatoma HepG2 cells, by use of the comet assay. Xanthohumol by itself was neither cytotoxic nor genotoxic to the cells at concentrations below 10microM. However, a significant protective effect against the pro-carcinogens benzo(a)pyrene (BaP) and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) was observed at concentrations as low as 0.01microM. In cells treated with xanthohumol in combination with tert-butyl hydroperoxide (t-BOOH) - an inducer of reactive oxygen species (ROS) - no protective effect was observed and xanthohumol also showed no significant scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals. On the other hand, HepG2 cells pre-treated with xanthohumol showed significantly reduced levels of t-BOOH-induced DNA strand breaks, indicating that its protective effect is mediated by induction of cellular defence mechanisms against oxidative stress. As xanthohumol is known to be an effective inhibitor of cytochrome P450 enzymes and an inducer of NAD(P)H: quinone reductase (QR), our findings can be explained by an inhibition of metabolic activation of pro-carcinogens and/or by induction of carcinogen-detoxifying and anti-oxidative enzymes by xanthohumol. These results provide evidence that xanthohumol displays anti-genotoxic activity in metabolically competent human cells.

Protective effects of isothiocyanates towards N-nitrosamine-induced DNA damage in the single-cell gel electrophoresis (SCGE)/HepG2 assay

The aim of this study was to investigate the protective effect of isothiocyanates towards N-nitrosamine-induced DNA damage in the single-cell gel electrophoresis (SCGE)/HepG2 assay. None of the isothiocyanates (ITCs) concentrations tested in the presence or absence of formamidopyrimidine-DNA glycosylase (Fpg) caused DNA damage per se. Combined treatments of HepG2 cells with phenethyl isothiocyanate (PEITC), allyl isothiocyanate (AITC) or indol-3-carbinol (I3C) and N-nitrosopyrrolidine (NPYR) or N-nitrosodimethylamine (NDMA) reduced the genotoxic effects of the N-nitrosamines in a dose-dependent manner. The protective effect of the three ITCs tested was higher towards NPYR-induced oxidative DNA damage than against NDMA. The greatest protective effect towards NPYR-induced oxidative DNA damage was shown by I3C (1 microM, 79%) and by PEITC (1 microM, 67%) and I3C (1 microM, 61%) towards NDMA (in presence of Fpg enzyme). However, in absence of Fpg enzyme, AITC (1 microM, 72%) exerted the most drastic reduction towards NPYR-induced oxidative DNA damage, and PEITC (1 microM, 55%) towards NDMA. Our results indicate that ITCs protect human-derived cells against the DNA damaging effect of NPYR and NDMA, two carcinogenic compounds that occur in the environment.

Assessment of the DNA damaging potency and chemopreventive effects towards BaP-induced genotoxicity in human derived cells by Monimiastrum globosum, an endemic Mauritian plant

Naturally occurring compounds have protective effects towards mutagens and carcinogens. The leaf extract of Monimiastrum globosum (Bois de Clous), a Mauritian endemic plant from the Myrtaceae family, was studied for its potency to induce DNA damage in human HepG2 hepatoma cells using DNA migration as a biological endpoint in the alkaline single cell gel electrophoresis (SCGE) assay. This was contrasted with the ability to modulate the benzo[a]pyrene (BaP)-dependent DNA damage in human hepatoma cells. M. globosum caused genotoxicity in HepG2 cells at concentrations exceeding 3mg fresh weight (FW) per ml cell culture in the absence of cytotoxicity. Pre-treatment of the cells with 12.2 microg FW/ml to 1.56 mg FW/ml led to a pronounced antigenotoxic effect towards BaP-induced DNA damage. DNA migration (OTM) was reduced by 66%, 81.5% and 74% for 49, 98 and 195 microg FW/ml, respectively. A U-shaped dose-response curve was derived for M. globosum indicating genotoxic effects in high doses and antigenotoxic effects in low doses. M. globosum extract had total phenolics (15 mg/g FW) with flavonoids (aglycones and conjugates: 8 mg/g FW) and proanthocyanidins (3mg/g FW) as major phenolic subclasses. The hydrolysis of conjugated flavonoids yielded the aglycones quercetin (606 microg/g FW) and kaempferol (117.8 microg/g FW) while HPLC-MS/MS analysis of the total extract revealed free flavonoids such as quercetin (19.2 microg/g FW) and myricetin (2.5 microg/g FW). The antioxidant activity of the extract of M. globosum, assessed by the FRAP and TEAC assays yielded values of 275+/-3.82 micromol/g FW and 346+/-4.2 micromol/g FW, respectively.

Protective effects of garlic sulfur compounds against DNA damage induced by direct- and indirect-acting genotoxic agents in HepG2 cells

The aim of this study was to assess the antigenotoxic activity of several garlic organosulfur compounds (OSC) in the human hepatoma cell line HepG2, using comet assay. The OSC selected were allicin (DADSO), diallyl sulfide (DAS), diallyl disulfide (DADS), S-allyl cysteine (SAC) and allyl mercaptan (AM). To explore their potential mechanisms of action, two approaches were performed: (i) a pre-treatment protocol which allowed study of the possible modulation of drug metabolism enzymes by OSC before treatment of the cells with the genotoxic agent; (ii) a co-treatment protocol by which the ability of OSC to scavenge direct-acting compounds was assessed. Preliminary studies showed that, over the concentration range tested (5-100 microM), the studied OSC neither affected cell viability nor induced DNA damage by themselves. In the pre-treatment protocol, aflatoxin B1 genotoxicity was significantly reduced by all the OSC tested except AM. DADS was the most efficient OSC in reducing benzo(a)pyrene genotoxicity. SAC and AM significantly decreased DNA breaks in HepG2 cells treated with dimethylnitrosamine. Additionally, all the OSC studied were shown to decrease the genotoxicity of the direct-acting compounds, hydrogen peroxide and methyl methanesulfonate. This study demonstrated that garlic OSC displayed antigenotoxic activity in human metabolically competent cells.

Retracted: Protective effects of isothiocyanates towardsN-nitrosamine-induced DNA damage in the single-cell gel electrophoresis (SCGE)/HepG2 assay

The aim of this study was to investigate the protective effect of isothiocyanates towards N-nitrosamine-induced DNA damage in the single-cell gel electrophoresis (SCGE)/HepG2 assay. None of the isothiocyanates (ITCs) concentrations tested in the presence or absence of formamidopyrimidine-DNA glycosylase (Fpg), caused DNA damage per se. Combined treatments of HepG2 cells with phenethyl isothiocyanate (PEITC), allyl isothiocyanate (AITC) or indol-3-carbinol (I3C) and N-nitrosopyrrolidine (NPYR) or N-nitrosodimethylamine (NDMA) reduced the genotoxic effects of the N-nitrosamines in a dose-dependent manner. The protective effect of the three ITCs tested was higher towards NPYR-induced oxidative DNA damage than against NDMA. The greatest protective effect towards NPYR-induced oxidative DNA damage was shown by I3C (1 microm, 79%) and by PEITC (1 microm, 67%) and I3C (1 microm, 61%) towards NDMA (in the presence of Fpg enzyme). However, in the absence of Fpg enzyme, AITC (1 microm, 72%) exerted the most drastic reduction towards NPYR-induced oxidative DNA damage, and PEITC (1 microm, 55%) towards NDMA. The results indicate that ITCs protect human-derived cells against the DNA damaging effect of NPYR and NDMA, two carcinogenic compounds which occur in the environment.

Effect of glutathione-S-transferase polymorphisms on the cancer preventive potential of isothiocyanates: an epidemiological perspective

Isothiocyanates (ITCs) are widely distributed in cruciferous vegetables and are biologically active against chemical carcinogenesis due to their ability to induce phase II conjugating enzymes. Among these is the glutathione-S-transferase (GST) family of enzymes, which in turn catalyzes the metabolism of ITCs, for which it has high substrate specificity. A recent body of epidemiologic data on the inverse association between cruciferous vegetable/ITC intake and cancers of the colo-rectum, lung and breast, also support that this protective effect is greater among individuals who possess the GSTM1 or T1 null genotype, and who would be expected to accumulate higher levels of ITC at the target tissue level, a pre-requisite for their enzyme-inducing effects. The association between ITC and cancer, and its modification by GST status, is most consistent for lung cancer and appears to be strongest among current smokers. Within limits, a comparison between groups which have been stratified by GST genotype may be less susceptible to confounding by other variables, given the random assortment of genes in gametogenesis. While a more complete understanding of the overall effects on health will need to take into account other components such as indoles and anti-oxidants, the interaction between ITC intake and GST genotype may provide a firmer basis to support a biologically significant role for ITC in cruciferous vegetables.

Coffee diterpenes prevent the genotoxic effects of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and N-nitrosodimethylamine in a human derived liver cell line (HepG2)

Aim of the present experiments was to study the genotoxic effects of coffee diterpenoids, namely cafestol palmitate and a mix of cafestol and kahweol (C+K) in human derived hepatoma (HepG2) cells. Furthermore, we investigated the potential protective properties of these substances towards carcinogens contained in the human diet, namely N-nitrosodimethylamine (NDMA) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). C+K and cafestol palmitate were tested over a broad dose range in micronucleus (MN) assays and no indication for genotoxic effects was seen. In combination experiments with PhIP (300 microM), pronounced inhibition (approximately 1.7-fold) of MN formation was observed with C+K and cafestol palmitate at dose levels > or = 0.9 and 1.7 microg/ml, respectively. Enzyme measurements indicate that the protection is due to inhibition of sulfotransferase, an enzyme involved in the activation of the amine, and/or to induction of UDP-glucuronosyltransferase which detoxifies the DNA-reactive metabolites of PhIP. Furthermore, a significant increase of glutathione-S-transferase was seen, whereas the activities of cytochrome P-450 1A1 and N-acetyltransferase 1 were not significantly altered. Also in combination experiments with C+K and NDMA, strong protective effects (50% reduction of genotoxicity) were seen at low dose levels (> or = 0.3 microg/ml). Since inhibition of MN was also observed when C+K were added after incubation with NDMA, it is likely that the chemoprotective effects are due to induction of DNA repair enzymes. Comparison of data on the effects of C+K on the cholesterol metabolism, which was investigated in earlier in vivo studies, with the present findings suggests that DNA-protective effects take place at exposure levels which are substantially lower than those which cause hypercholesterolemia.

Genotoxic effects of dietary and lifestyle related carcinogens in human derived hepatoma (HepG2, Hep3B) cells

Aim of the study was to investigate the usefulness of two human derived hepatoma cell lines (HepG2 and Hep3B) for the detection of dietary and lifestyle related DNA-reactive carcinogens. Comparisons of the sensitivity of HepG2 cells of different origin towards benzo[a]pyrene (B(a)P) showed that strong differences exist in the induction of micronuclei (MN). The most sensitive was used for all further experiments, in which we investigated the effects of aflatoxin B(1) (AFB(1)), B(a)P, As(2)O(3), CdCl(2), 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), N-nitrosodimethylamine (NDMA), N-nitrosopyrrolidine (NPYR), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), ethanol, acetaldehyde and caffeic acid in micronucleus (MN) tests. Dose dependent effects were detected in HepG2 with AFB(1) (0.2microM), CdCl(2) (2.2microM), As(2)O(3) (8.1microM), B(a)P (22.7microM), PhIP (35.7microM), NDMA (22.7mM), acetaldehyde (11.2mM) and ethanol (442.2mM). Numbers in parentheses indicate the C(D) values (concentration that induced a two-fold increase over the background). NNK and caffeic acid gave negative results under all conditions. In Hep3B cells, the effects were generally weaker. With PhIP, As(2)O(3) and NDMA negative results were obtained; with caffeic acid and NPYR marginal but significant induction of MN was observed. Enzyme measurements showed that both cell lines possess CYP1A1, glutathione-S-transferase (three-fold higher in HepG2) as well as N-acetyltransferase (NAT) 1 and sulfotransferases (SULT1A1 and SULT1A3; two- and seven-fold higher in HepG2); other cytochrome P450 enzymes (CYP1A2, 2B1, 2E1) and NAT2 were not detectable. The differences in the activities of the various enzymes may explain the contrasting results obtained in the MN experiments. Overall, our results indicate that the HepG2 line is more sensitive towards dietary genotoxins than Hep3B, and support the assumption that the HepG2/MN assay enables the detection of genotoxic carcinogens which give negative results in other currently used in vitro assays.

The Effect of Cruciferous and Leguminous Sprouts on Genotoxicity, In vitro and In vivo

Vegetable consumption is associated with a reduced risk of colorectal cancer, which is the second most common cancer after lung/breast cancer within Europe. Some putative protective phytochemicals are found in higher amounts in young sprouts than in mature plants.

The effect of an extract of mixed cruciferous and legume sprouts on DNA damage induced by H2O2 was measured in HT29 cells using single cell microgelelectrophoresis (comet). Significant antigenotoxic effect (P ≤ 0.05) was observed when HT29 cells were pre-incubated with the extract (100 and 200 μL/mL) for 24 hours and then challenged with H2O2. A parallel design intervention study was carried out on 10 male and 10 female healthy adult volunteers (mean age = 25.5 years) fed 113 g of cruciferous and legume sprouts daily for 14 days. The effect of the supplementation was measured on a range of parameters, including DNA damage in lymphocytes (comet), the activity of various detoxifying enzymes (glutathione S-transferase, glutathione peroxidase, and superoxide dismutase), antioxidant status using the ferric reducing ability of plasma assay, plasma antioxidants (uric acid, ascorbic acid, and α-tocopherol), blood lipids, plasma levels of lutein, and lycopene. A significant antigenotoxic effect against H2O2-induced DNA damage was shown in peripheral blood lymphocytes of volunteers who consumed the supplemented diet when compared with the control diet (P = 0.04). No significant induction of detoxifying enzymes was observed during the study, neither were plasma antioxidant levels or activity altered. The results support the theory that consumption of cruciferous vegetables is linked to a reduced risk of cancer via decreased damage to DNA.

Use of a human-derived liver cell line for the detection of cytoprotective, antigenotoxic and cogenotoxic agents

In this paper, we reviewed the data on the use of HepG2 cells to detect cytoprotective, antigenotoxic and cogenotoxic agents. Owing to their intact and inducible phase I and phase II enzymes, HepG2 cells are able to activate and detoxify xenobiotics and therefore reflect the metabolism of xenobiotics in the human body better than other metabolically incompetent cells used in conventional in vitro assays. Several dietary and non-dietary agents were found to be protective against different groups of cytotoxic and DNA-damaging xenobiotics in HepG2 cells and the mechanism of protection includes scavenging of electrophiles, reactive oxygen species and peroxides, inhibition of phase I activating enzymes, induction of phase II detoxifying enzymes and interactions with DNA-repair and/or replication processes. Additionally, certain non-mutagenic substances were found to enhance the effect of genotoxic agents in HepG2 cells by increasing the metabolic activation of the latter. In conclusion, HepG2 cells are of great relevance to detect cytotoxic and genotoxic substances and by extension cytoprotective, antigenotoxic and cogenotoxic agents.

Hydrolysis of glucosinolates to isothiocyanates after ingestion of raw or microwaved cabbage by human volunteers

Cabbage contains the glucosinolate sinigrin, which is hydrolyzed by myrosinase to allyl isothiocyanate. Isothiocyanates are thought to inhibit the development of cancer cells by a number of mechanisms. The effect of cooking cabbage on isothiocyanate production from glucosinolates during and after their ingestion was examined in human subjects. Each of 12 healthy human volunteers consumed three meals, at 48-h intervals, containing either raw cabbage, cooked cabbage, or mustard according to a cross-over design. At each meal, watercress juice, which is rich in phenethyl isothiocyanate, was also consumed to allow individual and temporal variation in postabsorptive isothiocyanate recovery to be measured. Volunteers recorded the time and volume of each urination for 24 h after each meal. Samples of each urination were analyzed for N-acetyl cysteine conjugates of isothiocyanates as a measure of entry of isothiocyanates into the peripheral circulation. Excretion of isothiocyanates was rapid and substantial after ingestion of mustard, a source of preformed allyl isothiocyanate. After raw cabbage consumption, allyl isothiocyanate was again rapidly excreted, although to a lesser extent than when mustard was consumed. On the cooked cabbage treatment, excretion of allyl isothiocyanate was considerably less than for raw cabbage, and the excretion was delayed. The results indicate that isothiocyanate production is more extensive after consumption of raw vegetables but that isothiocyanates still arise, albeit to a lesser degree, when cooked vegetables are consumed. The lag in excretion on the cooked cabbage treatment suggests that the colon microflora catalyze glucosinolate hydrolysis in this case.