Cigarette smokers have been reported to void urine which is more mutagenic, as measured in the Ames assay, than urine voided by non-smokers. Condensate from the mainstream smoke of a cigarette which primarily heats tobacco (test cigarette) has shown significantly reduced mutagenicity in a battery of in vitro genotoxicity assays compared with tobacco-burning cigarettes. The objective of this study was to determine whether the reduction in mutagenic activity observed in the in vitro assays would be reflected in the urine of smokers of the test cigarette. Twenty smokers were enrolled in a 4-week crossover study, with each smoker consuming test cigarettes ad libitum for a week and their usual brand of tobacco-burning cigarettes the other 3 weeks. Diet was strictly controlled throughout the study, and broiled and pan-fried meat was not served to minimize ingestion of mutagenic protein pyrolysis products. There was no statistically significant difference (p = 0.06) in consumption of tobacco-heating and tobacco-burning cigarettes. There were no statistically significant differences (p = 0.22) in salivary cotinine concentrations for smokers when smoking either tobacco-burning or tobacco-heating cigarettes. Urinary nicotine (ng/mg creatinine) was not different (p = 0.31) for smokers when smoking either tobacco-burning or tobacco-heating cigarettes. Urinary cotinine (ng/mg creatinine) was 32% lower (p = 0.0004) when smoking tobacco-heating cigarettes as compared with smoking tobacco-burning cigarettes. Twenty-four-hour urine samples were collected twice weekly, concentrated using XAD-2 resin and tested in Ames strains TA98 and YG1024 with metabolic activation. Tobacco-burning cigarette smokers experienced a 79% reduction in urinary mutagenicity as measured in strain YG1024 and a 72% reduction as measured in strain TA98 during the week that they smoked the tobacco-heating cigarette while maintaining a fixed dietary regimen. The results of this study indicate that smokers of tobacco-heating cigarettes void urine which is significantly less mutagenic than urine voided by smokers of tobacco-burning cigarettes.
Increased consumption of green vegetables in the diet has been associated with protection against carcinogenic effects and related mutagenic and clastogenic (chromosome breaking) activity of genotoxic agents. Chlorophyll, present in all green plant parts, has been suggested to be a major protective factor in the process. We have, however, observed that while a crude aqueous extract of Indian spinach leaf significantly reduced genotoxic effects, chlorophyll alone was ineffective. On the other hand, chlorophyll, both as an aqueous extract from the leaf and in a purified commercial form, induced a significantly high frequency of chromosome breaks in bone marrow cells of mice on oral administration. The crude aqueous extract of the leaf was non-toxic. The protective activity of the crude leaf extract may be attributed to the total effect of the interaction between different components, in which the clastogenicity of chlorophyll has been neutralized.
Involvement of human CYP2E1 expressed in genetically engineered cells in the metabolic activation of promutagens and procarcinogens was studied, An expression plasmid containing an insert of CYP2E1 cDNA and SR alpha promoter was constructed and transfected into the cultured cell line CR-119 which had previously been established by introducing a cDNA coding for NADPH-cytochrome P450 reductase. Among newly established cell lines, ER-181 showed the highest expression of CYP2E1 mRNA. Production of the CYP2E1 protein was confirmed by Western blot analysis using anti-rat CYP2E1 antibodies. Assay of 7-ethoxycoumarin O-deethylase activity demonstrated that ER-181 cells acquired the catalytic function of CYP2E1. ER-181 cells showed higher sensitivity to N,N-dimethylnitorosamine (DMN) in cytotoxicity assays as compared to parental CR-119 cells. Hypersensitivity to DMN of ER-181 cells was completely suppressed by 3-amino-1,2,4-triazole, a known inhibitor of CYP2E1. These results indicate that ER-181 cells which express human CYP2E1 are a useful tool to investigate toxicological functions of the cytochrome.
The possible mutagenicity of the water-soluble contents of cigarette smoke (WSCS) was evaluated by using the Vicia faba root tip micronucleus test. The results showed significant changes in micronucleus frequency which were caused by each different concentration of WSCS. This indicates that the Vicia faba root tip micronucleus test might be used as one kind of mutagenic detection method for cigarette smoke. A comparative evaluation on the mutagenicity of 10 brands of cigarettes was carried out. Results confirmed that various degrees of mutagenicity were found for all of the brand cigarettes, among them, Huaihai was the highest, while Camellia was the lowest. The micronucleus frequencies were reduced by adding tea polyphenol, nicotinamide adenine, vitamin C and sodium selenite to the WSCS. The results suggest that these added substances might reduce the genetic injury induced by cigarette smoke.
The frequency of chromosomal aberrations was evaluated in more than 500 liquidators of the Chernobyl accident. The 'sarcophagus' builders and the dosimetrists showed the highest frequency of aberrations per 100 cells: 3.24 +/- 0.25 and 3.11 +/- 0.43. For Chernobyl Atomic Power Station staff members the mean frequencies of aberrations per 100 cells was 2.37 +/- 0.20. The mean yields of aberrations in the other groups was between 1.31 and 1.47 per 100 cells. If the mean frequencies of aberrations are converted into equivalent whole body doses, values between 136 and 414 mGy are obtained. Especially in the group of 'sarcophagus' builders, the yields of aberrations varied interindividually and corresponded to equivalent whole body doses of up to about 2 Gy.
Nitropyrenes are a group of widespread environmental pollutants, some of which are highly potent as bacterial and mammalian cell mutagens and as animal carcinogens. A quantitative bacterial forward mutation assay, based on resistance to 8-azaguanine (8-AG) in Salmonella typhimurium TM677, was employed as an alternative to reversion assays to reexamine the mutagenicity of 1-, 2-, and 4-nitropyrene (1-, 2-, and 4-NP) and 1,3-, 1,6-, and 1,8-dinitropyrene (1,3-, 1,6-, and 1,8-DNP) in the presence and absence of rat liver postmitochondrial supernatant (PMS). The major finding is that 2-NP, reported as a potent mutagen in the absence of PMS in bacterial reversion assays, was inactive in the absence of PMS in this assay. However, 2-NP was mutagenic in the presence of PMS. The implications of this observation with respect to sample purity and the metabolism of 2-NP are discussed. Without PMS the following minimum detectable mutagen concentration (MDMC) potency series expressed as nmol/ml was obtained: 1,8-DNP (0.5 × 10−3), 1,6-DNP (1.2 × 10−3), 1,3-DNP (2.3 × 10−3), 4-NP (0.2), 1-NP (0.2), 2-NP (> 1200), pyrene (> 1500). With PMS the potency series was: 1,6-DNP (0.7), 1,8-DNP (2.1), 4-NP (2.2), 2-NP (2.6), 1,3-DNP (3.7), 1-NP (4.6), pyrene (> 1500). With the exception of 2-NP, all the nitropyrenes were more mutagenic without PMS than with PMS. The greatest difference was observed with the dinitropyrenes, which were three orders of magnitude less potent in the presence of PMS. Pyrene, often reported as a bacterial mutagen in the presence of PMS, was nonmutagenic in this assay when a purified sample was tested.
The genotoxic effect of ofloxacin was significantly decreased by standard antimutagens (sodium selenite, ascorbic acid, butylated hydroxyanisole and butylated hydroxytoluene) in the unicellular flagellate Euglena gracilis. The antiofloxacin activity of sodium selenite was also documented by a bacterial test in which the repair-proficient strain Salmonella typhimurium TA102 was used.
Polymerase chain reaction (PCR)-based screening methods were used to classify mutations arising in vivo at the hypoxanthine guanine phosphoribosyl-transferase (hprt) locus in small samples of human T-lymphocyte clones (< 5 x 10(4) cells) from 29 bus maintenance workers exposed to diesel exhaust, and 14 control individuals. All subjects were healthy, non-smoking males. Among 462 T-cell mutants studied by multiplex-PCR of genomic DNA, only 12 (2.6%) deletions were found: three total deletions, five partial exon deletions and four mutants with one or two exons deleted. Point mutations were classified in 323 mutants using reverse transcriptase-PCR amplification: 74 (22.9%) of these had splice site mutations and 241 (74.6%) had coding errors. Splice mutation was more frequent among the garage workers (24.8%) as compared to the controls (19.5%), possibly reflecting a polycyclic aromatic hydrocarbon-specific mutation induction in these workers. Our results also show that both gene deletion and splice mutation at the hprt-locus in T-cells of healthy non-smokers could be less frequent than previously reported.
The mutations and DNA adducts produced by the environmental pollutant 2-nitropyrene were examined in Salmonella typhimurium tester strains. 2-Nitropyrene was a stronger mutagen than its extensively studied structural isomer 1-nitropyrene in strains TA96, TA97, TA98, TA100, TA102, TA104 and TA1538. Both 1- and 2-nitropyrene were essentially inactive in TA1535. The mutagenicity of 1- and 2-nitropyrene in TA98 was much higher than in TA98NR and the activity of these compounds in TA100 was much higher than in TA100NR. While 1-nitropyrene exhibited similar mutagenicity in strains TA98 and TA98/1,8-DNP6, the mutagenicity of 2-nitropyrene in TA98/1,8-DNP6 was much lower than in TA98. Analysis of DNA from TA96 and TA104 incubated with 2-nitropyrene indicated the presence of two adducts, N-(deoxyguanosin-8-yl)-2-aminopyrene and N-deoxyadenosin-8-yl)-2-aminopyrene. The results suggest that 2-nitropyrene is metabolized by bacterial nitroreductase(s) to N-hydroxy-2-aminopyrene, and possibly by activation to a highly mutagenic O-acetoxy ester. DNA adduct formation with deoxyguanosine and deoxyadenosine correlates with the mutagenicity of 2-nitropyrene in tester strains possessing both G:C and A:T mutational targets.
The clinical use of an immunosuppressive cyclosporine A (CsA) is limited by its serious nephrotoxic effect. Evidences have suggested the role of oxidative stress in its pathogenesis. Shallot (Allium ascalonicum L.) has recently been shown to possess antioxidative and free radical scavenging abilities. The present study was undertaken to investigate the possible beneficial effect of shallot extract on renal injury caused by CsA. Male Wistar rats were treated orally with vehicle, CsA (25 mg/kg), shallot extract (1 g/kg), and CsA plus shallot extract for 21 days. Renal function, histopathology, tissue malondialdehyde (MDA) and glutathione (GSH) levels were evaluated 24 h after the last treatment. CsA-induced nephrotoxicity was evidenced by increased blood urea nitrogen and serum creatinine, but decreased urea and creatinine clearance. The kidney of CsA treated rats exhibited severe vacuolations and tubular necrosis. CsA also induced oxidative stress, as indicated by increased renal MDA and reduced GSH concentrations. Administration of shallot extract along with CsA counteracted the deleterious effects of CsA on renal dysfunction, oxidative stress markers, and morphological changes. These data indicate the protective potential of shallot extract against CsA nephrotoxicity and suggest a significant contribution of its antioxidant property to this beneficial effect.
The mutagenicity in the Ames Salmonella-microsome test of four protein pyrolysate products, formed during the cooking of meat. (Trp-P-1, Trp-P-2, Glu-P-1 and Glu-P-2) was found to be inhibited by the addition of vitamin A in vitro in the form of retinol. The effect is interpreted as an inhibition of the metabolic activation of the mutagens to their respective ultimate mutagenic forms since retinol has been shown to have no effect on the survival of the Salmonella cells, no effect on directly acting mutagens and no effect on the formation of NADPH in the test system. The results demonstrate the need for an increased understanding of the interaction of dietary components in evaluating mutagenic/ carcinogenic risks from processed food.
