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

The Use of Biomarkers as Alternatives to Current Animal Tests on Food Chemicals

Recent developments in biomarkers relating to the interrelationship of diet, disease and health were surveyed. Most emphasis was placed on biomarkers of deleterious effects, since these are of greatest relevance to the subject of this review. The area of greatest activity was found to be that relating to biomarkers of mutagenic, genotoxic and carcinogenic effects. This is also one of the major areas of concern in considerations of the beneficial and deleterious effects of dietary components, and also the area in which regulatory testing requires studies of the longest duration. A degree of progress has also been made in the identification and development of biomarkers relating to certain classes of target organ toxicity. Biomarkers for other types of toxicity, such as immunotoxicity, neurotoxicity, reproductive toxicity and developmental toxicity, are less developed, and further investigation in these areas is required before a comprehensive biomarker strategy can be established. A criticism that recurs constantly in the biomarker literature is the lack of standardisation in the methods used, and the lack of reference standards for the purposes of validation and quality control. It is encouraging to note the growing acknowledgement of the need for validation of biomarkers and biomarker assays. Some validation studies have already been initiated. This review puts forward proposals for criteria to be used in biomarker validation. More discussion on this subject is required. It is concluded that the use of biomarkers can, in some cases, facilitate the implementation of the Three Rs with respect to the testing of food chemicals and studies on the effects of diet on health. The greatest potential is seen to be in the refinement of animal testing, in which biomarkers could serve as early and sensitive endpoints, in order to reduce the duration of the studies and also reduce the number of animals required. Biomarkers could also contribute to establishing a mechanistic basis for in vitro test systems and to facilitating their validation and acceptance. Finally, the increased information that could result from the incorporation of biomarker determinations into population studies could reduce the need for supplementary animal studies. This review makes a number of recommendations concerning the prioritisation of future activities on dietary biomarkers in relation to the Three Rs. It is emphasised, however, that further discussions will be required among toxicologists, epidemiologists and others researching the relationship between diet and health.

Evaluation of urinary 1-hydroxypyrene,S-phenylmercapturic acid,trans,trans-muconic acid, 3-methyladenine, 3-ethyladenine, 8-hydroxy-2′-deoxyguanosine and thioethers as biomarkers of exposure to cigarette smoke

The objective was to evaluate the utility of urinary 1-hydroxypyrene (1-OHP), S-phenylmercapturic acid (S-PMA), trans,trans-muconic acid (t,t-MA), 3-methyladenine (3-MeAd), 3-ethyladenine (3-EtAd), 8-hydroxy-2'-deoxyguanosine (8-OHdG) and thioethers as biomarkers for assessing the exposure in adult smokers who switched from smoking conventional cigarettes to candidate potential reduced exposure products (PREP) or who stopped smoking. Two electrically heated smoking systems (EHCSS) were used as prototype cigarettes that have significant reductions in a number of mainstream smoke constituents as measured by smoking machines relative to those from conventional cigarettes. Urine samples were collected from a randomized, controlled, forced-switching study in which 110 adult smokers of a conventional cigarette brand (CC1) were randomly assigned to five study groups. The groups included the CC1 smoking group, a lower-tar conventional cigarette (CC2) smoking group, EHCSS1 group, EHCSS2 group and a no smoking group that were monitored for 8 days. Biomarkers were measured at baseline and day 8. The daily excretion levels of these biomarkers were compared among the groups before and after switching, and the relationships between the daily excretion levels of these biomarkers and cigarette smoking-related exposure were investigated using Pearson product-moment correlation and multiple regression analyses. It was concluded that under controlled study conditions: (1) 1-OHP, S-PMA and t,t-MA are useful biomarkers that could differentiate exposure between smoking conventional and EHCSS cigarettes or between smoking conventional cigarettes and no smoking; between S-PMA and t,t-MA, the former appeared to be more sensitive; (2) 3-MeAd could only differentiate between smoking conventional cigarettes and no smoking; the results for 3-EtAd were not conclusive because contradictory results were observed; (3) 8-OHdG had a questionable association with smoking and therefore the utility of this biomarker for smoking-related exposure could not be established; and (4) urinary excretion of thioethers as a biomarker lacked sensitivity to demonstrate a clear dose-response relationship in conventional cigarette smokers, although it could differentiate the excretion levels between those subjects who smoked a conventional cigarette and those who stopped smoking.

Mutagenic activity of overnight urine from healthy non-smoking subjects

Urinary mutagenicity was evaluated in relation to environmental mutagen exposure (i.e., diet, indoor/outdoor activities, residential area etc.) on the day prior to sample collection, and also considering factors that contribute to the variability of Salmonella mutagenicity assay results. Overnight urine samples from 283 healthy non-smoking residents of northeast Italy (46% males, 20-62 years) were analyzed for mutagenicity on sensitive Salmonella typhimurium strain YG1024 with S9 mix employing the preincubation version of the plate incorporation assay (i.e., the Salmonella reverse mutation test). Urinary mutagenicity varied between 0.02 and 9.84 rev/ equiv. ml, and 7% of samples were positive (i.e., sample elicited a two-fold increase in revertants). There was an evident increase in mutagenicity in subjects with increased intake of mutagen-rich meals (n = 80) (P < 0.01 and positive urine 13% vs. 5%, P = 0.025). Indoor-exposed subjects (n = 65) also showed a higher percentage of positive urine (14% vs. 5%, P = 0.015). In particular, those subjects exposed to cooking fumes the previous evening (n = 28) revealed higher urinary mutagenicity (P = 0.035, positive urine 25% vs. 5%, P < 0.001) than non-indoor exposed. The sources of variability of the mutagenicity assay, mainly the histidine content of the urine concentrate (z = 4.06, P < 0.0001), and to a lesser extent bacterial inoculum size (z = 2.33, P = 0.019), also significantly influenced urinary mutagenicity values. In a linear multiple regression analysis, their effects were still significant (i.e., histidine content P = 0.026 and inoculum size P = 0.021), but the effects of diet, indoor exposure, and other environmental exposures (i.e., traffic and heating system exhausts, residential area) were not. It is concluded that the previous day's exposure to mutagen-rich meals and cooking fumes may influence the presence of mutagenic activity in the overnight urine of non-smoking subjects. This mutagenic activity, which remains in contact with bladder mucosa for several hours, could be considered risk factors for colorectal adenoma and possibly other cancers (i.e., bladder) in non-smokers. Accurate control of histidine content and bacterial inoculum size is strongly recommended when investigating the mutagenic activity of urine from non-smokers.

Influence of smoking charcoal filter tipped cigarettes on various biomarkers of exposure

Charcoal (CC) filters of cigarettes are known to significantly reduce a series of volatile constituents in mainstream smoke, including reactive alpha,beta-unsaturated aldehydes such as acrolein and crotonaldehyde. We performed a randomized, crossover, 2-wk brand-switching study with 39 smokers. Twenty of the subjects smoked cellulose acetate (CA) filter tipped cigarettes during wk 1 of the study; the remaining 19 subjects smoked CC filter tipped cigarettes during wk 1. In wk 2, the subjects switched to the corresponding brand with the other filter type, with similar smoking machine-derived tar and nicotine yields. Daily cigarette consumption, carbon monoxide in exhaled breath, salivary cotinine, and urinary nicotine equivalents (molar sum of nicotine plus five major metabolites) did not change significantly when switching to the cigarettes with the other filter type. Urinary excretion rates of 3-hydroxy-1-methylpropylmercapturic acid (metabolite of crotonaldehyde), monohydroxybutenylmercapturic acid (metabolite of 1,3-butadiene), and S-phenylmercapturic acid (metabolite of benzene) were significantly lower when smoking CC compared to CA filter tipped cigarettes. The reduction in amount of 3-hydroxypropylmercapturic acid (metabolite of acrolein) was of borderline significance. Other mercapturic acids and thioethers (the latter is a summary parameter that indicates the exposure to electrophilic compounds) were not or were only slightly reduced upon smoking CC filter tipped cigarettes. We conclude that smoking CC filter tipped cigarettes does not change the uptake of carbon monoxide and nicotine when compared to CA filter tipped cigarettes with similar tar and nicotine yields, but significantly reduces the exposure to toxicologically relevant smoke constituents such as acrolein, crotonaldehyde, 1,3-butadiene, and benzene.

Genotoxic effect of Goeckerman regimen of psoriasis

Goeckerman regimen (GR) of psoriasis includes daily dermal application of crude coal tar (CCT) and dermal exposure to UV-A and UV-B radiation. Observed group consisted of 23 patients with psoriasis treated by GR. Therapeutic ointment contained 5% of CCT. The level of psoriasis area and severity index was significantly decreased after GR (P < 0.001) and confirms high efficiency of GR. High levels of selected metabolites of pyrene and phenanthrene indicated high level of dermal penetration. We found significantly increased urinary mutagenicity in samples collected in the middle and in the end of GR (TA98+S9, P < 0.01; YG1041-S9, P < 0.001; YG1041+S9, P < 0.001). Significant increasing of chromosomal aberrations in peripheral lymphocytes (CA) in blood samples collected in the end of GR (P < 0.001) and consecutive decreasing of CA in 78th day after the end of GR has been observed. Almost all results indicated that the patients could be endangered by a peak genotoxic exposure. Nevertheless, the genotoxic effect does not seem to be long lasting. Despite conflicting results from cancer epidemiological studies, it is evident that single GR can contribute to the total load of environmental mutagens in a group of treated patients.

Biomonitoring of inhaled complex mixtures--ambient air, diesel exhaust and cigarette smoke

Human biomonitoring comprises the determination of biomarkers in body-fluids, cells and tissues. Biomarkers are generally assigned to one of three classes, namely, biomarkers of exposure, effect or susceptibility. Since biomarkers represent steps in an exposure-disease continuum, their application in epidemiological studies ('molecular epidemiology') shows promise. However, to be a predictor of disease, a biomarker has to be validated. Validation criteria for a biomarker include intrinsic qualities such as specificity, sensitivity, knowledge of background in the population, existence of dose-response relationships, degree of inter- and intra-individual variability, knowledge of the kinetics, confounding and modifying factors. In addition, properties of the sampling and analytical procedures are of relevance, including constraints and non-invasiveness of sampling, stability of sample as well as simplicity, high sensitivity, specificity and speed of the analytical method. It is of particular importance to prove by suitable studies that the biomarker of exposure indicates the actual exposure, the biomarker of effect strongly predicts the actual risk of disease and the biomarker of susceptibility actually modifies the risk. Biomonitoring of the exposure to complex mixtures such as polluted ambient air, diesel exhaust or tobacco smoke is a particular challenge since these exposures have many constituents in common and many people were exposed to more than one of these mixtures. Data on the exposure to polycyclic aromatic hydrocarbons (PAH) and benzene from ambient air, diesel exhaust and tobacco smoke will be presented. In addition, some source-specific biomarkers such as nitro-arenes and nicotine metabolites as well as their application in population groups will be discussed. The second part of the presentation addresses the application of biomarkers for assessing so called 'potentially reduced exposure products' (PREPs). According to a recent report of the Institute of Medicine (USA), "reducing risk of disease by reducing exposure to tobacco toxicants is feasible" and "surrogate biological markers that are associated with tobacco-related diseases could be used to offer guidance as to whether or not PREPs are likely to be risk-reducing." In general, the same validation criteria apply as discussed above. In addition, it is suggested that a panel of biomarkers should be used, representing both smoke phases (gas and particulate phase) and the various chemical classes of smoke constituents (e.g., carbonyls, benzene, PAH, tobacco-specific nitrosamines, aromatic amines). Also, a panel of biomarkers of effect should cover the major known adverse effects of smoking (e.g., oxidative stress, inflammatory processes, lipid peroxidation, lipometabolic disorders, mutagenic effects). Biomarkers of nicotine and carbon monoxide uptake are of interest for evaluating the smoking and inhalation behavior, respectively. Finally, suitable study designs for evaluating PREPs are discussed. It is concluded that suitable biomarkers for assessing the exposure to complex mixtures such as ambient air, diesel exhaust and tobacco smoke as well as for evaluating the exposure-reducing properties of PREPs are already available. Future efforts should focus on the development and validation of biomarkers of effect.

Genotoxicity of environmental tobacco smoke: a review

Environmental tobacco smoke (ETS), or second-hand smoke, is a widespread contaminant of indoor air in environments where smoking is not prohibited. It is a significant source of exposure to a large number of substances known to be hazardous to human health. Numerous expert panels have concluded that there is sufficient evidence to classify involuntary smoking (or passive smoking) as carcinogenic to humans. According to the recent evaluation by the International Agency for Research on Cancer, involuntary smoking causes lung cancer in never-smokers with an excess risk in the order of 20% for women and 30% for men. The present paper reviews studies on genotoxicity and related endpoints carried out on ETS since the mid-1980s. The evidence from in vitro studies demonstrates induction of DNA strand breaks, formation of DNA adducts, mutagenicity in bacterial assays and cytogenetic effects. In vivo experiments in rodents have shown that exposure to tobacco smoke, whole-body exposure to mainstream smoke (MS), sidestream smoke (SS), or their mixture, causes DNA single strand breaks, aromatic adducts and oxidative damage to DNA, chromosome aberrations and micronuclei. Genotoxicity of transplacental exposure to ETS has also been reported. Review of human biomarker studies conducted among non-smokers with involuntary exposure to tobacco smoke indicates presence of DNA adducts, urinary metabolites of carcinogens, urinary mutagenicity, SCEs and hypoxanthine-guanine phosphoribosyltransferase (HPRT) gene mutations (in newborns exposed through involuntary smoking of the mother). Studies on human lung cancer from smokers and never-smokers involuntarily exposed to tobacco smoke suggest occurrence of similar kinds of genetic alterations in both groups. In conclusion, these overwhelming data are compatible with the current knowledge on the mechanisms of carcinogenesis of tobacco-related cancers, occurring not only in smokers but with a high biological plausibility also in involuntary smokers.

Carcinogen derived biomarkers: applications in studies of human exposure to secondhand tobacco smoke

OBJECTIVE

To review the literature on carcinogen derived biomarkers of exposure to secondhand tobacco smoke (SHS). These biomarkers are specifically related to known carcinogens in tobacco smoke and include urinary metabolites, DNA adducts, and blood protein adducts.

METHOD

Published reviews and the current literature were searched for relevant articles.

RESULTS

The most consistently elevated biomarker in people exposed to SHS was 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and its glucuronides (NNAL-Gluc), urinary metabolites of the tobacco specific lung carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). The tobacco specificity of this biomarker as well as its clear relation to an established lung carcinogen are particularly appropriate for its application in studies of SHS exposure.

CONCLUSION

The results of the available carcinogen derived biomarker studies provide biochemical data which support the conclusion, based on epidemiologic investigations, that SHS causes lung cancer in non-smokers.

Biomonitoring of urine mutagenicity with the Ames test: improvement of the extraction/concentration method

Comparative extraction efficiency of the pre-packed Bakerbond-spe-SDB-1 resin and of Amberlite-AD2 (XAD-2) resin, for the preparation of urine extracts in biomonitoring studies. Urine extracts were prepared in parallel with the Bakerbond column and with the classical XAD-2 resin from urines (1) spiked with mutagenic chemicals, (2) collected from patients after chemotherapy, and (3) from smokers. Mutagenic activities were evaluated on Salmonella typhimurium tester strains TA97a, TA98, TA100 and TA102 with and without S9 mix. Mutagenic activities obtained with Bakerbond extracts were almost always higher or at least equivalent to those prepared on XAD-2 resin. Similar results were observed for the three urine sample groups. When fully validated, the use of the pre-packed columns will be more convenient and time-saving for large population studies.

Human urinary carcinogen metabolites: biomarkers for investigating tobacco and cancer

Measurement of human urinary carcinogen metabolites is a practical approach for obtaining important information about tobacco and cancer. This review presents currently available methods and evaluates their utility. Carcinogens and their metabolites and related compounds that have been quantified in the urine of smokers or non-smokers exposed to environmental tobacco smoke (ETS) include trans,trans-muconic acid (tt-MA) and S-phenylmercapturic acid (metabolites of benzene), 1- and 2-naphthol, hydroxyphenanthrenes and phenanthrene dihydrodiols, 1-hydroxypyrene (1-HOP), metabolites of benzo[a]pyrene, aromatic amines and heterocyclic aromatic amines, N-nitrosoproline, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol and its glucuronides (NNAL and NNAL-Gluc), 8-oxodeoxyguanosine, thioethers, mercapturic acids, and alkyladenines. Nitrosamines and their metabolites have also been quantified in the urine of smokeless tobacco users. The utility of these assays to provide information about carcinogen dose, delineation of exposed vs. non-exposed individuals, and carcinogen metabolism in humans is discussed. NNAL and NNAL-Gluc are exceptionally useful biomarkers because they are derived from a carcinogen- 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)- that is specific to tobacco products. The NNAL assay has high sensitivity and specificity, which are particularly important for studies on ETS exposure. Other useful assays that have been widely applied involve quantitation of 1-HOP and tt-MA. Urinary carcinogen metabolite biomarkers will be critical components of future studies on tobacco and human cancer, particularly with respect to new tobacco products and strategies for harm reduction, the role of metabolic polymorphisms in cancer, and further evaluation of human carcinogen exposure from ETS.

Environmental tobacco smoke interference in the assessment of the health impact of a municipal waste incinerator on children through urinary thioether assay

The urinary elimination of thioethers urinary thioethers (UT) was studied in 83 schoolchildren living in two different areas of the city of Mataró, with special attention paid to the influence of a waste incinerator and of the smoking habits of their parents. The mean UT values were 8.79+/-3.23 and 7.52+/-3.23 mmol/mol creatinine in the area close to the incinerator (A1) and in the area far away from it (A2) respectively (statistically n.s.). Children exposed to environmental tobacco smoke (ETS) at home presented increased levels of UT (8.60+/-3.11 vs 5.93+/-3.22 mmol/mol creatinine; P=0.002). Considering the two exposures together (waste incinerator and ETS), no differences were found between the two areas studied (A1 and A2) in non-exposed (ETS) children, whereas slight differences were found when comparing highest ETS exposed children from the two areas (10. 18+/-2.70 vs 8.00+/-3.42 mmol/mol creatinine; P=0.04). Exposure to ETS could affect health more than pollutants from a waste incinerator and may interfere with non-selective assays such as urinary thioethers.

Biomonitoring exposure to environmental tobacco smoke (ETS): a critical reappraisal

1 The most frequently used biomarkers for exposure to environmental tobacco smoke (ETS) are cotinine and thiocyanate in body fluids, carboxyhaemoglobin in red blood cells (COHb) and carbon monoxide in the expired air. Although not ideal, cotinine in blood, saliva or urine is an established biomarker for ETS exposure within the past 1-3 days. Comparison with cotinine concentrations in cigarette smokers reveals that passive smokers take up less than 1/100 of the nicotine dose of smokers. 2 Biomonitoring data available for the ETS-related exposure to genotoxic substances comprise uptake of benzene, polycyclic aromatic hydrocarbons (PAH), aromatic amines, tobacco-specific nifrosamines (TSNA), electrophilic compounds giving rise to urinary thioethers, mutagens causing urinary mutagenic activity and the formation of various DNA adducts. With the exception of TSNA, these biomarkers are related to chemicals occurring ubiquitously in the environment and in the food. As a consequence, the background levels in unexposed nonsmokers are high compared to the observed increases (if any) associated with ETS exposure. 3 Some markers of biological effects, which, by definition, are non-specific with regard to the underlying exposure, have also been investigated in relation to ETS exposure. These markers comprise cytogenetic effects, aryl hydrocarbon hydroxylase (AHH) induction, urinary hydroxyproline excretion and various factors indicative of cardiovascular risks. The available data suggest that passive smoking is associated with a small induction of placental AHH and also with effects on cardiovascular risk markers. The latter findings in particular may be confounded by other risk factors, which have been observed to be more frequent in passive smokers than in unexposed nonsmokers.