Investigation of coffee in sister chromatid exchange and micronucleus tests in vivo

Coffee consumption protects human lymphocytes against oxidative and 3-amino-1-methyl-5H-pyrido[4,3-b]indole acetate (Trp-P-2) induced DNA-damage: Results of an experimental study with human volunteers

Aim of the study was to investigate the impact of coffee on DNA-stability in humans. DNA-damage was monitored in lymphocytes of eight individuals with single cell gel electrophoresis assays before and after consumption of 600 ml coffee (400 ml paper filtered and 200 ml metal filtered/d) for five days. Under standard conditions, no alteration of DNA-migration was seen, but a strong reduction of DNA-migration attributable to endogenous formation of oxidised purines and pyrimidines was detected with restriction enzymes; furthermore DNA-damage caused by reactive oxygen radicals (H2O2 treatment) and by the heterocyclic aromatic amine 3-amino-1-methyl-5H-pyrido[4,3-b]indole-acetate was significantly reduced after coffee consumption by 17% and 35%, respectively. Also in in vitro experiments, inhibition of H2O2 induced DNA-damage was observed with coffee at low concentrations (<or= 25 microl/ml) whereas the diterpenoids cafestol and kahweol caused only marginal effects indicating that the effects of coffee are due to scavenging effects of other constituents. Enzyme measurements showed that additionally induction of antioxidant enzymes may play a role: while the activity of glutathione peroxidase was only marginally increased after coffee consumption, a significant (38%) increase of superoxide dismutase activity was detected. Comparisons with results of earlier studies suggest that coffee consumption may prevent oxidative DNA-damage to a higher extent as diets enriched in fruits and vegetables.

Genotoxicity of instant coffee: possible involvement of phenolic compounds

Instant coffee exhibits direct genotoxic activity in the tester strains TA 98, 100, 102, 104 and YG 1024. In the Ames tester strain TA 100, the presence of S9 mix, S100 mix, S9 mix without cofactors led to a significant decrease of the genotoxicity observed. The decrease observed in the presence of S9 mix seems to be highly correlated with the catalase content of S9 mix. The genotoxicity of instant coffee detected in strain TA 100 was dependent on the pH, with higher genotoxic effects at pH values above neutrality. Also, dependent on the pH was the ability of some phenolic molecules present in coffee promoting the degradation of deoxyribose in the presence of Fe3+/EDTA. These results suggest that apart from other molecules present in instant coffee responsible for their genotoxicity in several short term assays, phenolic molecules could also be implicated in the genotoxicity of coffee, via reactive oxygen species arising from its auto-oxidation.

Potential genotoxic, mutagenic and antimutagenic effects of coffee: a review

Coffee and caffeine are mutagenic to bacteria and fungi, and in high concentrations they are also mutagenic to mammalian cells in culture. However, the mutagenic effects of coffee disappear when bacteria or mammalian cells are cultured in the presence of liver extracts which contain detoxifying enzymes. In vivo, coffee and caffeine are devoid of mutagenic effects. Coffee and caffeine are able to interact with many other mutagens and their effects are synergistic with X-rays, ultraviolet light and some chemical agents. Caffeine seems to potentiate rather than to induce chromosomal aberrations and also to transform sublethal damage of mutagenic agents into lethal damage. Conversely, coffee and caffeine are also able to inhibit the mutagenic effects of numerous chemicals. These antimutagenic effects depend on the time of administration of coffee as compared to the acting time of the mutagenic agent. In that case, caffeine seems to be able to restore the normal cycle of mitosis and phosphorylation in irradiated cells. Finally, the potential genotoxic and mutagenic effects of the most important constituents of coffee are reviewed. Mutagenicity of caffeine is mainly attributed to chemically reactive components such as aliphatic dicarbonyls. The latter compounds, formed during the roasting process, are mutagenic to bacteria but less to mammalian cells. Hydrogen peroxide is not very active but seems to considerably enhance mutagenic properties of methylglyoxal. Phenolic compounds are not mutagenic but rather anticarcinogenic. Benzopyrene and mutagens formed during pyrolysis are not mutagenic whereas roasting of coffee beans at high temperature generates mutagenic heterocyclic amines. In conclusion, the mutagenic potential of coffee and caffeine has been demonstrated in lower organisms, but usually at doses several orders of magnitude greater than the estimated lethal dose for caffeine in humans. Therefore, the chances of coffee and caffeine consumption in moderate to normal amounts to induce mutagenic effects in humans are almost nonexistent.

Investigation of soy sauce treated with nitrite in the chromosomal aberration test in vitro and the micronucleus test in vivo

Soy sauce pretreated with 2300 ppm nitrite caused no more aberrations than did untreated soy sauce in the chromosomal aberration test in vitro using a Chinese hamster fibroblast cell line with or without S9 mixture. The aberration induction by soy sauce is likely to be caused by the 17% sodium chloride it contains. Soy sauce with or without pretreatment with 2300 ppm nitrite was orally given to ICR mice at a dose of 14 ml/kg body weight once or 6 ml/kg body weight/day for 5 consecutive days. This oral administration did not induce any significant increase in micronuclei in the micronucleus test in vivo.

Inhibitory effects of coffee on the genotoxicity of carcinogens in mice

The mouse bone marrow micronucleus test was carried out to evaluate the possible inhibitory effects of 3 doses (125, 250 and 500 mg/kg) of standard instant coffee on the in vivo genotoxicity of 7,12-dimethylbenz[a]anthracene (DMBA), benzo[a]pyrene (BP), aflatoxin B1 (AFB1) and urethane (UR). Coffee was orally administered twice, 2 and 20 h before the carcinogens were injected intraperitoneally. From the results obtained, it was evident that the administration of 250 and 500 mg coffee/kg body weight could significantly inhibit the in vivo genotoxicity of these carcinogens. A linear dose response was observed for the inhibitory effect of coffee. Furthermore, inhibition of genotoxicity by coffee was observed in bone marrow cells which were sampled at 6-h intervals (48, 54, 60, 66 and 72 h) from the time of peak induction of micronuclei by DMBA.

Inhibition of in vivo genotoxicity by coffee

The possible role of coffee in modulating the in vivo genotoxicity of the well established genotoxic chemicals, mitomycin C, cyclophosphamide, procarbazine and adriamycin, was evaluated. Coffee was administered orally to mice that received the genotoxic chemicals ip. Genotoxicity was assessed in the bone-marrow micronucleus test. Doses of coffee in the range 225 to 1125 mg (dry weight)/kg body weight caused significant reductions in the in vivo genotoxicity of mitomycin C, cyclophosphamide and procarbazine but not adriamycin. The inhibitory effect was significant when the coffee was given about 2 hr before the genotoxin; there was a lesser effect when coffee was given together with the genotoxin but there was no inhibition when coffee was given 2-4 hr after the genotoxin. An experiment with mitomycin C demonstrated that the reduction in genotoxicity was dependent on the coffee dose. The inhibition of genotoxicity by coffee was observed in bone-marrow cells sampled 24, 48 or 68 hr after injecting cyclophosphamide. Freshly brewed coffee extract, standard instant coffee, decaffeinated instant coffee and freeze-dried home-brew coffee all exerted inhibitory effects.

Contribution of coffee aroma constituents to the mutagenicity of coffee

About 40 coffee aroma constituents belonging to the classes of dicarbonyls, sulphur-containing compounds, furfuryls, N-heterocyclics and others were systematically evaluated in three Ames tester strains. Only aliphatic dicarbonyl compounds showed notable direct mutagenic activity, which mainly affected 'base-pair substitution' in Ames tester strains TA100 and TA102. Very weak effects were also seen with some N-heterocyclics, mainly affecting frameshift tester strain TA98 upon metabolic activation. However, it was shown that these N-heterocyclics do not contribute substantially to the mutagenicity in coffee. The hydrogen peroxide and methylglyoxal contents of coffee were determined up to 26 hr after preparation. Their concentrations tended to decrease whereas mutagenic activity decreased significantly with time in tester strains TA100 and TA102. It is concluded that several highly labile coffee constituents contribute to the bacterial mutagenicity and also that the synergism between hydrogen peroxide and methylglyoxal is not the main factor. The absence of coffee mutagenicity/carcinogenicity in rodents with these highly reactive coffee aroma compounds can be explained in part by detoxification of microsomal enzyme systems.

Increased sister chromatid exchange associated with smoking and coffee consumption

Sister chromatid exchange (SCE) is a very sensitive cytogenetic assay for detecting exposure to chemical mutagens and carcinogens. One application of SCE is the monitoring of populations believed to be exposed to such agents. We have, however, relatively little knowledge about common lifestyle factors that may influence SCE and therefore complicate any study designed to examine the effects of exposure to genotoxins. In this study, we assessed the effect of cigarette smoking and coffee consumption on SCE. Smoking was associated with an increase of approximately 2 SCEs per cell and a decrease in cell proliferation. A positive linear relationship between SCE and coffee consumption was also observed. This effect was similar for smokers and nonsmokers. Additionally, the folic acid content of cell culture medium seemed to affect neither SCE nor cell proliferation.

Mutagenicity of instant coffee and its interaction with dimethylnitrosamine in the micronucleus test

The mutagenicity of instant coffee and its interaction with dimethylnitrosamine (DMN) were examined in mice using the micronucleus test. Although neither a single nor multiple administration of instant coffee by gavage induced a significant rise in micronucleated cells over the dose range tested (100-2500 mg/kg), there was a tendency for the number of micronucleated cells to increase in a dose-related fashion. When coffee was administered with DMN, the difference in the frequency of micronucleated cells was small in comparison to a single treatment with DMN alone, thus indicating a lack of synergism between coffee and DMN.

Investigation of coffee in Drosophila genotoxicity tests

Two preparations of coffee (instant coffee and freeze-dried home-brew coffee) were tested in different mutagenicity assays in germ cells as well as in somatic cells of Drosophila melanogaster. The three end-points assayed in germ cells were sex-linked recessive lethals (mainly gene mutations and small chromosome aberrations), dominant lethals (cytotoxic effects as well as genotoxic effects) and sex-chromosome losses (chromosome breakage and non-disjunction). The aqueous coffee solutions were fed either to adult male flies for 3 days or to growing larvae during the whole larval development. Treated males were crossed with appropriately marked females, and the different genetic end-points were analysed in the F1 or F2 generation. The test concentrations (instant coffee 4% (w/v), home-brew coffee 3%) were acutely toxic in adult males (killing approximately 75 and 90% of the exposed flies, respectively). No increase in deaths was caused in larvae by the same concentrations. Only cytotoxic effects were observed in the test for dominant lethals. No conclusive genotoxic effects could be detected in any of the three germ cell assays. The coffee preparations were also tested for induction of mutation and mitotic recombination in somatic cells of the wing imaginal disc. Larvae trans-heterozygous for two recessive wing hair markers were fed high concentrations of the coffees for varying periods of time. Wings of surviving adult flies were analysed for mosaic spots. Twin spots exhibiting both mutant phenotypes are produced by mitotic recombination; single spots showing one or the other phenotype are the result of somatic mutation, such as gene mutation or deletion, or of mitotic recombination. Both coffees had weak effects on normal (repair-proficient) cells as well as on excision repair-defective cells in this assay. Additional experiments with pure caffeine and decaffeinated coffee show that these weak effects in somatic cells were most probably caused by the caffeine present in the two coffees.

Instant and brewed coffees in the in vitro human lymphocyte mutagenicity test

Incubation of instant and 'home brew' coffees (caffeinated and decaffeinated) and of coffee aroma with cultured human lymphocytes in the presence and absence of S-9 increased the number of total aberrations. However, the increase was smaller in the presence of S-9 than in its absence. Pure caffeine tested with or without S-9 at doses equivalent to levels in caffeine-containing coffee did not give statistically significant increases of any type of aberration when compared with controls. In all in vitro test systems used to date, coffee and coffee aroma or their reactive compounds were metabolically deactivated in the presence of S-9. This could explain the negative results obtained in mutagenicity assays in vivo.