Urinary Excretion Of Mutagens Research Articles

Effect of phenethyl isothiocyanate (PEITC) on the urinary excretion of mutagens in rats treated with IQ (2-amino-3-methyl-3H-imidazo[4,5-f] quinoline)

Effect of phenethyl isothiocyanate (PEITC) on the urinary excretion of mutagens in rats treated with IQ (2-amino-3-methyl-3H-imidazo[4,5-f] quinoline)

In vivo Antimutagenic Potential of Ginger on Formation and Excretion of Urinary Mutagens in Rats

In vivo Antimutagenic Potential of Ginger on Formation and Excretion of Urinary Mutagens in Rats

Inhibitory Efect of Uprocessed/Processed Aliums under in vitro/in vivo Conditions on Carcinogen Induced Mutagenesis Using Different Assays

Three experiments were carried out to assess the antimutagenic potential of garlic or onion This was tested in, in vitro/in vivo models where mutagenicity was induced either with benzo (a) pyrene (BP)/3-methyl-cholanthrene (3MC), using Ames test or the comet assay. Also the effects of cooking processes like boiling/frying on the antimutagenic potential of these alliums were tested by SOS inhibition assay using 4-nitroquinoline-N-oxide (4 NQO) as the mutagen. In the first experiment, onion feeding at 1 and 5% in the diet inhibited the formation and excretion of urinary mutagens in dose dependent manner as indicated by decreased frequency of revertants in strains TA 98 and TA100 in the presence of urine belonging to rats fed onion and exposed to BP or 3MC. In the second experiment using SOS induction assay, both processed or unprocessed garlic exhibited dose dependent inhibition of SOS induction. However with boiled/unboiled onion this was not statistically significant. Studies with DAS also showed a dose dependent inhibition of SOS induction. No significant differences were observed in inhibition of SOS responses with processing of onion/garlic. These results indicate that the antimutagenic principle in garlic is not destroyed on heat treatment during cooking processes. In the third experiment, BP treatment resulted in comet induction (as judged by the comet ratio¬diameter/length) significantly as compared to control, both in liver and kidney tissues (p<0.001). Allium vegetables fed groups showed values similar to control group. As was observed in the peripheral blood lymphocytes, a trend towards recovery from damage was noted both in liver and kidney tissue due to prior allium feeding. All these results show that alliums whether in the processed or unprocessed form can be used in diets to avert toxic effects of environmental carcinogens/genotoxicants and can be potent chemopreventive agents and cancer prevention is far more desirable alternative than treatment by surgery and drugs. The protection could be achieved even by very low intake level of allium in natural form through diet.

Black tea intake modulates the excretion of urinary mutagens in rats exposed to 6-aminochrysene: induction of cytochromes P450 by 6-aminochrysene in the rat

Rats were exposed to black tea (2.5% w/v) as their sole drinking liquid for either 1 day (short-term) or 1 month (long-term), while controls received water. After exposure, all animals received a single oral dose of 6-aminochrysene and urine was collected for 72 h. Urinary mutagenicity was determined in the Ames test using an activation system comprising hepatic cytosol from Aroclor 1254-induced rats and utilizing the Salmonella typhimurium O-acetylase overexpressing bacterial strain YG1024. Both tea treatments suppressed the urinary excretion of indirect acting mutagens; no direct acting mutagenic activity was detectable. Furthermore, both tea treatments induced hepatic CYP1A2 activity, as exemplified by the O-demethylation of methoxyresorufin, when compared with the corresponding controls; similarly, an increase in CYP1A2 apoprotein levels was observed. The O-depentylation of pentoxyresorufin was also induced by the long-term tea treatment only, but the effect was less pronounced. No significant changes were seen in glutathione S-transferase and glucuronosyl transferase activities. When rats were exposed to caffeine at a dose level corresponding to that in black tea, a marked decrease was observed in the urinary excretion of indirect acting mutagens following a single oral dose of 6-aminochrysene. It is concluded that even after short-term exposure, black tea enhances the metabolism of 6-aminochrysene and that this is probably related to the up-regulation of hepatic CYP1A2 by the caffeine present in black tea. Finally, 6-aminochrysene was a potent inducer of CYP1A1, as assessed by the O-deethylation of ethoxyresorufin and immunoblot analysis. The same treatment modestly increased glutathione S-transferase activity when assessed using 1-chloro-2,4-dinitrobenzene as the accepting substrate.

Short-term black tea intake modulates the excretion of urinary mutagens in rats treated with 2-amino-3-methylimidazo-[4,5-f]quinoline (IQ): role of CYP1A2 upregulation.

Rats were exposed to black tea (2.5% w/v) as their sole drinking liquid for either 1 day or 1 month, while controls were maintained on water. After this treatment period, all animals received a single oral dose IQ (2-amino-3-methylimidazo-[4,5-f]quinoline), and urine was collected for 48 h. Mutagenic activity of the urine was determined in the Ames test in the presence and absence of an activation system. The excretion of direct-acting mutagens was markedly reduced following tea intake, and was more pronounced after the 1-day treatment. Similarly, both tea treatments suppressed the excretion of indirect-acting mutagens. Furthermore, both tea treatments induced hepatic CYP1A2 activity and expression, but cytosolic glutathione S-transferase activity was only modestly induced in the group of animals receiving tea for 1 day, and only when DCNB (1,2-dichloro-4-nitrobenzene) was used as substrate; glucuronosyl activity was elevated modestly only in the animals receiving the tea for a month. It is concluded that even short-term exposure to black tea is capable of influencing the metabolic fate of IQ, and this is most likely related to the upregulation of CYP1A2.

Consumption of tea modulates the urinary excretion of mutagens in rats treated with IQ. Role of caffeine

The present study was undertaken to investigate whether the consumption of green tea and black tea influences the excretion of mutagens and promutagens in rats treated orally with the food carcinogen 2-amino-3-methylimidazo[4,5- f]quinoline (IQ). Rats were maintained on aqueous extracts (2.5%, w/v) of green tea, black tea or decaffeinated black tea as their sole drinking liquid. After 4 weeks, the animals received, by gastric intubation, a single dose of IQ (5 mg/kg), and urine was collected for 48 h. Direct and indirect mutagenicity, in the presence of an activation system derived from Aroclor 1254-treated rats, was determined in the urine samples using the Ames mutagenicity assay. Consumption of green tea and black tea, but not of decaffeinated black tea, markedly decreased the urinary excretion of mutagens and promutagens. In a further study, supplementation of decaffeinated black tea with caffeine suppressed the excretion of mutagens and promutagens in the urine of rats pretreated with IQ. It is concluded that both green tea and black tea modulate the bioactivation and metabolism of IQ, and that caffeine is largely responsible for this effect.

Reduction of urinary mutagen excretion in rats fed garlic.

Naturally occurring substances of plant origin are known to possess antimutagenic potential. Garlic (Allium sativum) was fed to rats in dried powdered form at 0.1%, 0.5% and 1% concentrations in their diet for 4 weeks. At the end of the experiment benzo[a]pyrene (1 mg/rat) was injected intraperitoneally and 24-h urine was collected from the rats. Urinary mutagens were quantitated by the Salmonella typhimurium assay. There was a significant reduction in the excretion of urinary mutagens by carcinogen-exposed rats fed garlic. Further, there was a stimulation in the activities of liver cytosolic glutathione-S-transferase and liver and lung quinone reductases. The study suggested that the antimutagenic potential of garlic may be mediated through induction of detoxification enzymes in target tissues.

Urinary mutagenicity and thioethers in nonsmokers: Role of environmental tobacco smoke (ETS) and diet

The urinary excretion of mutagens and thiothers was investigated in a controlled diet study and in two field studies. A diet containing charcoal-broiled meat and other items rich in mutagenic compounds increased the urinary mutagenicity as assessed in Salmonella typhimurium strain TA98 with metabolic activation ∼ 46-fold compared to a diet low in mutagens. The excretion of thiothers after ingestion of the diet rich in mutagens also increased significantly when compared to the diet low in mutagens. The increase was associated with the content of preformed thiothers in the diet. In the first field study with 21 nonsmokers, urinary mutagenicity as assessed in Salmonella typhimurium strain TA98 and excretion of thiothers showed no relation to either the self-reported exposure to environmental tobacco smoke (ETS) or to serum cotinine concentrations used as an objective marker for ETS exposure. In the second field study, urinary mutagenicity was determined with a tobacco-smoke sensitive Salmonella typhimurium strain YG1024 with metabolic activation. No correlation was found between the mutagenic activity in urine and ETS exposure duration, nicotine on the personal sampler, cotinine in saliva and cotinine in urine. Our results suggest that real-life ETS exposure does not measurably increase either urinary mutagen or urinary thioether excretion. Furthermore, diet seems to be the most important source for both urinary mutagen and thioether excretion in nonsmokers.

GSTM1 and NAT2 genotypes and urinary mutagens in coke oven workers.

The influence of the metabolic genotypes GSTM1 and NAT2 on the urinary excretion of mutagens in 46 coke oven workers (27 of them smokers) was studied. Exposure to polycyclic aromatic hydrocarbons (PAH) was estimated from urinary 1-pyrenol levels, which varied from 0.23 to 5.59 micromol/mol creatinine. Fourteen urine samples (30.4%), all but one belonging to smokers, were positive for mutagenic activity (i.e. at least one of the assayed doses was able to double the number of spontaneous revertants). Nine of the urine-positive subjects were both GSTM1-null and NAT2-ss (64.3%), while the same combination of genotypes was found in nine out of 31 urine-negative subjects (29.0%) (P < 0.05). Significantly more smoking workers with the genotype combination GSTM1-null/NAT2-ss showed positive urine mutagenicity than the other subjects (75.0 versus 28.6%, P < 0.05). Smokers with the slow acetylator genotype showed a significantly higher frequency of positive urine samples than smoking fast acetylators (64.7 versus 22.2%, P < 0.05). Our results suggest that smoking coke oven workers with genotypes unfavourable for detoxification of aromatic amines (NAT2-ss) and PAH (GSTM1-null) may have an increased risk of developing bladder cancer.

Smokers and urinary genotoxins: Implications for selection of cohorts and modulation of endpoints in chemoprevention trials

Urinary genotoxicity assays measure the internal dose of genotoxic carcinogens, thereby providing a particularly sensitive endpoint for selecting cohorts of individuals exposed to cigarette smoke or other mutagens excreted with urines, as well as for evaluating the modulation of this parameter after administration of chemopreventive agents. Mutagenicity of urines was investigated in smoking Italian volunteers, who received oral N-acetylcysteine (NAC) at the same doses which are usually prescribed for the long-term treatment of chronic bronchitis. The daily excretion of mutagens, concentrated on XAD-2 columns and tested in Salmonella typhimurium YG1024 with S9 mix, was significantly and remarkably decreased by NAC in the majority of the subjects examined so far. Time-course experiments showed that this effect starts since the first day of drug administration and reverses when treatment is withdrawn. In addition, NAC administration almost totally prevented urinary genotoxicity in one subject whose concentrated urines induced a differential lethality in Escherichia coli strains having distinctive DNA repair capacities. The decrease of urinary genotoxicity produced by NAC in the majority of smokers correlates with the ability of this thiol to prevent tumors and to affect a variety of intermediate biomarkers in animal models. Modulation of the urinary excretion of mutagens is one of the biomarkers evaluated in two ongoing Phase II chemoprevention trials. One study involves the oral administration of NAC in Dutch smokers. The pretreatment urine samples of all the subjects so far recruited are clearly mutagenic. The other study involves the oral administration of the dithiolethione oltipraz to individuals living in the Qidong County of the People's Republic of China, an area of high endemy for HBV infection and of high exposure to aflatoxins. Additionally, a large proportion of the recruited male subjects are smokers. A total of 500 urine specimens will be assayed from 240 subjects according to a complex protocol arranged in three consecutive phases.

95/06630 Urinary excretion of mutagens in coke oven workers

95/06630 Urinary excretion of mutagens in coke oven workers

Potentiation of 2,6‐dinitrotoluene genotoxicity in fischer 344 rats by pretreatment with coal tar creosote

Pretreatment of male Fischer 344 rats for 5 wk with coal tar creosote, a coal distillation product that is widely used as a wood preservative, potentiated the excretion of urinary mutagens in 2,6-dinitrotoluene (DNT) treated rats. Creosote increased the bioactivation of DNT to significantly greater levels of urinary genotoxic metabolites and/or formed DNA adducts in the liver. A significant increase in the excretion of mutagenic DNT metabolites was observed after the first week of creosote treatment, peaked at wk 3, and then decreased by 33% after 5 wk of treatment. Nevertheless, there was a significant increase (66%) in the formation of DNT-derived DNA adducts in the livers of rats treated with DNT plus creosote at wk 5. Increased cecal beta-glucuronidase activity and reduced small intestinal nitroreductase activity may play roles in the bioactivation of DNT. The excretion of mutagenic DNT metabolites supplies useful information about the bioactivation of DNT; it does not provide a useful index of DNT-derived hepatic DNA adduct formation. Such interactions could be important to predictive risk assessment because the overall cancer risk of such chemical mixtures may exceed the sum of the component risks.

Urinary excretion of mutagens in coke oven workers.

The influence of occupational exposure to polycyclic aromatic hydrocarbons (PAHs) on urinary mutagenic activity was assessed in 75 coke oven workers, using a highly sensitive bacterial mutagen technique (extraction with C18 resin and liquid micro-preincubation test on strain TA98 of Salmonella typhimurium in the presence of metabolizing and deconjugating enzymes). Exposure to PAHs was assessed according to the urinary excretion of 1-pyrenol; the main confounding factors were checked by the number of cigarettes smoked per day and the levels of nicotine and its metabolites in urine, or by ascertaining whether recommended dietary restrictions had been followed. Of the 20 urine samples which turned out to be positive (producing at least double the number of spontaneous revertants), 19 (95%) belonged to smokers. Only one non-smoker had obvious urinary mutagenic activity, and was highly exposed occupationally to PAHs (urinary 1-pyrenol of 3.930 mumol/mol of creatinine). Of the five urine samples from subjects who had not followed the recommended diet, two (40%) were clearly mutagenic. Multiple regression analysis (n = 67) showed that the presence of samples positive for urinary mutagenic activity depended only on smoking habits, if this confounding factor was assessed according to the number of cigarettes smoked per day, while the significant influence of exposure to PAH could be shown when the confounding factor was objectively estimated according to the urinary levels of nicotine and its metabolites. Assessment of the mutagenic potency of urinary extracts (net revertants/mmol creatinine) confirmed the strong influence of smoking habits on urinary mutagenic activity (all smokers 2156 +/- 2691 versus non-smokers 939 +/- 947 net revertants/mmol creatinine; Mann-Whitney test: P < 0.01). In smokers highly exposed to PAHs, greater excretion of mutagens with respect to low-exposure smokers was revealed (3548 +/- 4009 versus 1552 +/- 1227 net revertants/mmol creatinine; Mann-Whitney test: P < 0.01). Multiple regression analysis showed that the mutagenic potency of urinary extracts of coke oven workers depended on exposure to PAHs, tobacco smoking habits, and consumption of fried, grilled or barbecued meat. Increased urinary mutagenic activity strengthens epidemiological evidence of the increased risk of renal and urinary tract tumours in these workers. The presence of mutagenic metabolites in urine as a result of occupational exposure to PAH may be demonstrated only by using highly sensitive techniques for assessing urinary mutagenic activity in studies which include careful checking of the main confounding factors.

Urinary excretion of mutagens and covalent DNA damage induced in the bladder and kidney after passive smoking in rats.

Using 32P-postlabeling assay, we studied the effect of sidestream smoke of cigarettes, so-called passive smoking, on the covalent DNA adduct formation in an animal model. Urine samples of 18 rats, 9 male and 9 female, before smoking resulted in an average of 2.4 adducts per 1 x 10(7) nucleotides per 24-h urine of a rat in the target plasmid DNA after incubation for 2 h in vitro. Urine samples of 4 out of 6 rats after exposure to sidestream smoke induced additional adducts in the target DNA. The incidence increased to 17.5 adducts per 1 x 10(7) nucleotides per 24-h urine of a rat. Without exposure to smoke, no increase in the adduct formation was observed. Adduct formations similar to those induced in vitro were detected in the bladder and kidney DNA, but not in the testicular DNA, of the four rats exposed to sidestream smoke. These observations suggest that passive smoking causes covalent DNA damage of the cells in the bladder and kidney by excreting chemicals in urine. Passive smoking as well as active smoking might contribute to the bladder and renal carcinogenic process.

Evaluation of exposure reducing measures on parameters of genetic risk in a population occupationally exposed to coal fly ash

In a previous study we found increased SCE frequencies in peripheral blood lymphocytes (PBLs) of workers occupationally exposed in a coal fly ash processing industry, as compared to a non-exposed control population. Shortly after this study, measures were taken in this plant to reduce fly ash levels. The objective of the present study, conducted 2 years later in the same plants, was to evaluate the effect of these measures with respect to genotoxic risk. A group of 18 male workers of the coal fly ash processing industry agreed to participate in the study. The control population consisted of 18 male workers from a flour processing industry, who were matched for age and smoking behavior. In contrast to our previous study, no increased SCE frequencies were found in PBLs of workers potentially exposed to coal fly ash when compared to the control group (mean SCEs: 6.4 ± 1.2 and 7.0 ± 0.9, respectively). In addition, no differences were observed between the exposed and control groups for frequencies of gene mutations at the hypoxanthine guanine phosphoribosyltransferase ( hprt) locus in PBLs, for micronucleus frequencies using the cytokinesis block method, or for urinary mutagen excretion measured with Salmonella typhimurium tester strains TA98 and TA97 with and without metabolic activation. In smokers, however, SCE frequencies in PBLs were significantly increased in comparison to non-smokers (7.1 ± 1.1 vs. 6.1 ± 0.5; P < 0.005), as was 24-h urinary mutagen excretion measured with strain TA98 with S9 mix (2373 ± 1870 vs. 156 ± 211; P < 0.001) and with TA98 with S9 mix and β-glucuronidase/arylsulfatase (2361 ± 1958 vs. 538 ± 396; P < 0.005). In addition, hprt variant frequencies in PBLs were higher in smokers than in non-smokers (15.0 ± 23.5 × 10 −66 vs. 2.6 ± 2.8 × 10 −6; P < 0.05). No differences were observed for micronucleus induction between smokers and non-smokers.

Effect of turmeric on urinary mutagens in smokers.

Curcumin, the active principle of turmeric, is known to act as an anti-oxidant, anti-mutagen and anti-carcinogen in experimental animals. In the present study, anti-mutagenic effects of turmeric were assessed in 16 chronic smokers. It was observed that turmeric, given in doses of 1.5 g/day for 30 days, significantly reduced the urinary excretion of mutagens in smokers. In contrast, in six non-smokers, who served as control, there was no change in the urinary excretion of mutagens after 30 days. Turmeric had no significant effect on serum aspartate aminotransferase and alanine aminotransferase, blood glucose, creatinine and lipid profile. These results indicate that dietary turmeric is an effective anti-mutagen and it may be useful in chemoprevention.

Effect of Lactobacillus acidophilus Supplements on Mutagen Excretion in Faeces and Urine in Humans

Lactic acid bacteria have been reported to have antimutagenic properties in vitro . In order to investigate whether Lactobacillus acidophilus supplements have antimutagenic effects in humans, 11 healthy subjects on a standardised diet consumed fried beef patties twice daily for 3 d. The diets were supplemented with ordinary Lactococcus fermented milk (phase 1) and thereafter with L. acidophilus fermented milk (phase 2), whereby the excretion of mutagenic activity was determined in urine and faeces. In both faeces and urine high levels of mutagenicity were detected during phase 1. There was an increase in lactobacilli in the intestinal microflora in seven of 11 subjects by the L. acidophilus supplement (phase 2), and the mutagenic activity in urine was 72 per cent lower on day 2 ( P < 0.01) and 55 per cent lower on day 3 ( P < 0.05) compared to days 2 and 3 in phase 1. The total faecal and urinary mutagen excretion on day 3 during phase 2 was 47 per cent lower compared to day 3, phase 1 ( P < 0.02). Thus, L. acidophilus given together with fried meat lowered mutagen excretion in humans. Keywords: Lactobacillus acidophilus ; Mutagens; Human faecal flora; Faeces; Urine.

Mutagenic activity in gastric juice and urine of subjects with chronic atrophic gastritis, gastric epithelial dysplasia and gastric cancer

Gastric juice and urine samples from consecutive patients who underwent endoscopy for upper GI tract complaints were examined for the presence of mutagens. Patients endoscopically and histologically diagnosed as having either chronic atrophic gastritis (CAG) or gastric cancer (GC) had higher than normal levels of mutagens in their gastric juice and urine. The gastric juice pH of these patients was also elevated and, in the case of the CAG patients, contained detectable levels of nitrites. No correlation was however found between gastric mutagen levels and urinary mutagen excretion in the individuals examined.

Urinary excretion of mutagens, thioethers and D-glucaric acid in workers exposed to bitumen fumes.

The authors carried out biological monitoring of the mutagenic/carcinogenic hazards associated with exposure to bitumen fumes during paving operations, analysing some biological parameters in the urine of a group of exposed workers. The urine samples were studied for mutagenicity by the Ames test and for thioethers concentration. D-Glucaric acid urine excretion was also determined to investigate the enzymatic induction potential of bitumens. Even though, in a previous environmental monitoring phase, a low content of mutagenic/carcinogenic compounds was found in bitumen and air samples, urinary mutagenicity data of exposed workers were statistically higher than those of a group of unexposed subjects. The urinary mutagenicity increased further if exposure to bitumens was associated with cigarette smoking. Thioethers were higher only in subjects exposed simultaneously to bitumens and cigarettes. D-Glucaric acid excretion did not increase significantly. The authors think that this type of coupled environmental and biological monitoring is a valid tool for a better evaluation of the mutagenic/carcinogenic exposure to bitumens or similar complex mixtures.

Relationship between the urinary mutagen excretion and the induction of metabolic activation, in the liver of rats pretreated with two dipyridoimidazole derivatives

Relationship between the urinary mutagen excretion and the induction of metabolic activation, in the liver of rats pretreated with two dipyridoimidazole derivatives