Chemosensitivity analysis of tiger nuts (Cyperus esculentus L.) using ethyl methanesulfonate (EMS) and colchicine mutagens

Four hundred tubers of four genotypes, two brown and two black tiger nuts were subjected to Ethyl Methanesulfonate (EMS) and Colchicine treatments at concentrations of 0 %, 0.1 %, 0.25 %, 0.5 % and 1.0 % for 24 h. Each genotype had twenty tubers treated with each of the five different concentrations and were planted using Complete Randomized Design (CRD) in a greenhouse. Quantitative data was collected and LD50 and RD50 were analysed using Excell 2016 and Genstat 11.2. A general decreasing trend in percentage germination and plant height was observed with increasing concentrations of mutagens applied. An EMS treatment had LD50 and RD50 values of 0.97 % and 1.49 % for black and 0.63 % and 1.63 % for brown genotypes. Similarly, the percentage colchicine treatment had LD50 and RD50 values of 1.65 % and 19.51 % concentrations for black and 0.91 % and 1.71 % concentrations for brown genotypes.

Heterocyclic aromatic amines in meat: Formation mechanisms, toxicological implications, occurrence, risk evaluation, and analytical methods

Heterocyclic aromatic amines (HAAs) are detrimental substances can develop during the high-temperature cooking of protein-rich foods, such as meat. They are potent mutagens and carcinogens linked to an increased risk of various cancers. HAAs have complex structures with nitrogen-containing aromatic rings and are formed through chemical reactions between amino acids, creatin(in)e, and sugars during cooking. The formation of HAAs is influenced by various factors, such as food type, cooking temperature, time, cooking method, and technique. HAAs exert their toxicity through mechanisms like DNA adduct formation, oxidative stress, and inflammation. The research on HAAs is important for public health and food safety, leading to risk assessment and management strategies. It has also led to innovative approaches for reducing HAAs formation during cooking and minimizing related health risks. Understanding HAAs' chemistry and formation is crucial for developing effective ways to prevent their occurrence and protect human health. The current review presents an overview about HAAs, their formation pathways, and the factors influencing their formation. Additionally, it reviews their adverse health effects, occurrence, and the analytical methods used for measuring them.

Mutagens in commercial food processing and its microbial transformation

Mutagens are chemical molecules that have the ability to damage DNA. Mutagens can enter into our body upon consumption of improperly cooked or processed food products such as high temperature or prolonged cooking duration. Mutagens are found in the food products can be classified into N-nitroso derivatives, polycyclic aromatic hydrocarbons, and heterocyclic aromatic amines. Food products with high fat and protein content are more prone to mutagenic formation. Microorganisms were found to be a potent weapon in the fight against various mutagens through biotransformation. Therefore, searching for the microorganisms which have the ability to transform mutagens and the development of techniques for the identification as well as detection of mutagens in food products is much needed. In the future, methods for the identification and detection of these mutagens as well as the identification of new and more potent microorganisms which can transform mutagens into non-mutagens are much needed.

Causes of Clonal Hematopoiesis: a Review

PURPOSE OF REVIEW

Clonal hematopoiesis (CH) is an age-dependent process detectable using advanced sequencing technologies and is associated with multiple adverse health outcomes including cardiovascular disease and cancer. The purpose of this review is to summarize known causes of CH mutations and to identify key areas and considerations for future research on CH.

RECENT FINDINGS

Studies have identified multiple potential causes of CH mutations including smoking, cancer therapies, cardiometabolic disease, inflammation, and germline risk factors. Additionally, large-scale studies have facilitated the identification of gene-specific effects of CH mutation risk factors that may have unique downstream health implications. For example, cancer therapies and sources of environmental radiation appear to cause CH through their impact on DNA damage repair genes. There is a growing body of evidence defining risk factors for CH mutations. Standardization in the identification of CH mutations may have important implications for future research. Additional studies in underrepresented populations and their diverse environmental exposures are needed to facilitate broad public health impact of the study of CH mutations.

Mutagens in raw ewe milk in Orava region, northern Slovakia: metals

The aim of this work was to determine the concentrations of selected mutagenic elements (As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Se) in raw ewe milk from undisturbed environment in Orava region, northern Slovakia. There are possible sources of some of the analyzed metals which may be distributed from the metallurgical plants located in the Ostrava region, Czech Republic, and Katowice, Poland. In total, forty milk samples were analyzed in June and August using an inductively coupled plasma optical emission spectrometry. The differences in elements concentrations between the seasonal periods were not significant except of iron (p < 0.0001). The concentrations of most of the metals in ewe milk were low and under the permissible or recommended limits. However, arsenic and selenium concentrations were elevated and could pose a risk of the mutagenic effect, particularly in children. The frequency of element occurrence in June was as follows: Se > Fe > As > Cu > Mn > Ni > Co > Pb > Cr > Cd, and in August: Se > Fe = As > Cu > Mn > Pb > Co > Ni > Cr > Cd. The correlation analysis revealed very strong positive correlation between Cu:Pb (p < 0.05), very strong negative correlation between Fe:Se (p < 0.05). The strong correlations were also found between other elements. The present study showed that milk produced in the relatively undisturbed environment might contain various mutagenic elements. The relationships between the elements might result in the additive or synergistic effects of elements and increase the risk of their mutagenic effects even in low concentrations. Therefore, attention must be paid to the monitoring of metals in the areas where food sources destined especially for child nutrition are produced.

Unravelling the molecular mechanism of mutagenic factors impacting human health

Environmental mutagens are chemical and physical substances in the environment that has a potential to induce a wide range of mutations and generate multiple physiological, biochemical, and genetic modifications in humans. Most mutagens are having genotoxic effects on the following generation through germ cells. The influence of germinal mutations on health will be determined by their frequency, nature, and the mechanisms that keep a specific mutation in the population. Early prenatal lethal mutations have less public health consequences than genetic illnesses linked with long-term medical and social difficulties. Physical and chemical mutagens are common mutagens found in the environment. These two environmental mutagens have been associated with multiple neurological disorders and carcinogenesis in humans. Thus in this study, we aim to unravel the molecular mechanism of physical mutagens (UV rays, X-rays, gamma rays), chemical mutagens (dimethyl sulfate (DMS), bisphenol A (BPA), polycyclic aromatic hydrocarbons (PAHs), 5-chlorocytosine (5ClC)), and several heavy metals (Ar, Pb, Al, Hg, Cd, Cr) implicated in DNA damage, carcinogenesis, chromosomal abnormalities, and oxidative stress which leads to multiple disorders and impacting human health. Biological tests for mutagen detection are crucial; therefore, we also discuss several approaches (Ames test and Mutatox test) to estimate mutagenic factors in the environment. The potential risks of environmental mutagens impacting humans require a deeper basic knowledge of human genetics as well as ongoing research on humans, animals, and their tissues and fluids.

A perspective review on medicinal plant resources for their antimutagenic potentials

Mutagens present in the environment manifest toxic effects and are considered as serious threat for human health and healthcare. Recent reports reveal that medicinal plant resources are being explored for identifying potent antimutagenic as well as cancer preventing agents. There is mounting evidence that cancer and other mutation-related diseases can be prevented with the use of medicinal pant resources including crude extracts, active fractions, phytochemicals, and pure phytomolecules. These medicinal plant resources possessing antimutagenic potentials have been shown to target molecular mechanisms underlying the mutagenic impacts. Technological advents and high-throughput screening/activity methods have revolutionized this field, though several potent plants and their active principles have been reported as effective antimutagens. The translational success rate needs to be improved, but the trends are encouraging. In this review, we present the current understandings and updates on various mutagens in the environment, toxicities related/attributed to them, the resultant mutations (and cancer), and how medicinal plants come to the rescue. A perspective review has been presented on whether and how medicinal plant resources can be an effective approach for addressing mutagens in the environment. An account of medicinal plant resources used as antimutagenic agents has been given along with the underlying mechanism of action and their therapeutic potential in various models of cancer. Recent success stories, current challenges, and future prospects are discussed.

Effect of Mutagens on Yield and its Components of Two Varieties of Faba Bean (Vicia faba L.)

&lt;b&gt;Background and Objective:&lt;/b&gt; It is known that any genetic improvement depends on the presence of many genetic variations so that the plant breeder can choose the desired traits such as the trait of the crop or resistance to some diseases. Different or it can be used for selection, whether for yield, early maturity or other characteristics. This study aimed to use gamma irradiation and the chemical mutagen Dimethyl sulfoxide for the induction of genetic variation in two types of beans. &lt;b&gt;Materials and Methods:&lt;/b&gt; The Giza 429 and Misr 1 genotypes were treated with three different concentrations of dimethyl sulfur oxide (1000, 2000 and 3000 ppm) and gamma radiation doses (10, 15 and 20 kr) to perform mutagenesis treatments. &lt;b&gt;Results:&lt;/b&gt; In the first and second seasons of the study, all the mutations resulting from the radiological and chemical mutagenic treatments of the two Egyptian bean cultivars, Giza 429 and Misr 1, were highly significant for all treatments in the following traits: Number of branches/plant, plant height, number of pods/plant with the weight of 100 seeds (g) and seed yield/plant (g). &lt;b&gt;Conclusion:&lt;/b&gt; The benefit of this research was obtained from plants that outperformed the two cultivars Giza 429 and Misr 1 and are considered among the promising plants that can be used in mixed breeding programs or direct selection for high productivity.

Mutagen-induced telomere instability in human cells

Telomere instability is one of the main sources of genome instability and may result from chromosome end loss (due to chromosome breakage at one or both ends) or, more frequently, telomere dysfunction. Dysfunctional telomeres arise when they lose their end-capping function or become critically short, which causes chromosomal termini to behave like a DNA double-strand break. Telomere instability may occur at the chromosomal or at the molecular level, giving rise, respectively, to telomere-related chromosomal aberrations or the loss or modification of any of the components of the telomere (telomere DNA, telomere-associated proteins, or telomere RNA). Since telomeres play a fundamental role in maintaining genome stability, the study of telomere instability in cells exposed to mutagens is of great importance to understand the telomere-driven genomic instability present in those cells. In the present review, we will focus on the current knowledge about telomere instability induced by physical, chemical, and biological mutagens in human cells.

Metabolism and biomarkers of heterocyclic aromatic amines in humans

Heterocyclic aromatic amines (HAAs) form during the high-temperature cooking of meats, poultry, and fish. Some HAAs also arise during the combustion of tobacco. HAAs are multisite carcinogens in rodents, inducing cancer of the liver, gastrointestinal tract, pancreas, mammary, and prostate glands. HAAs undergo metabolic activation by N-hydroxylation of the exocyclic amine groups to produce the proposed reactive intermediate, the heteroaryl nitrenium ion, which is the critical metabolite implicated in DNA damage and genotoxicity. Humans efficiently convert HAAs to these reactive intermediates, resulting in HAA protein and DNA adduct formation. Some epidemiologic studies have reported an association between frequent consumption of well-done cooked meats and elevated cancer risk of the colorectum, pancreas, and prostate. However, other studies have reported no associations between cooked meat and these cancer sites. A significant limitation in epidemiology studies assessing the role of HAAs and cooked meat in cancer risk is their reliance on food frequency questionnaires (FFQ) to gauge HAA exposure. FFQs are problematic because of limitations in self-reported dietary history accuracy, and estimating HAA intake formed in cooked meats at the parts-per-billion level is challenging. There is a critical need to establish long-lived biomarkers of HAAs for implementation in molecular epidemiology studies designed to assess the role of HAAs in health risk. This review article highlights the mechanisms of HAA formation, mutagenesis and carcinogenesis, the metabolism of several prominent HAAs, and the impact of critical xenobiotic-metabolizing enzymes on biological effects. The analytical approaches that have successfully biomonitored HAAs and their biomarkers for molecular epidemiology studies are presented.

Protection of nuclear DNA by lifespan-extending compounds in the yeast Saccharomyces cerevisiae

DNA damage has been hypothesized to be a driving force of the aging process. At the same time, there exists multiple compounds that can extend lifespan in model organisms, such as yeast, worms, flies, and mice. One possible mechanism of action for these compounds is a protective effect against DNA damage. We investigated whether five of these lifespan-extending compounds, dinitrophenol, metformin, rapamycin, resveratrol, and spermidine, could protect nuclear DNA in the yeast Saccharomyces cerevisiae at the same doses under which they confer lifespan extension. We found that rapamycin and spermidine were able to decrease the spontaneous mutation rate at the CAN1 locus, whereas dinitrophenol, metformin, and resveratrol were able to protect yeast against CAN1 mutations induced by ethyl methanesulfonate (EMS). We also tested whether these compounds could enhance survival against EMS, ultraviolet (UV) light, or hydrogen peroxide (H₂O₂) insult. All five compounds conferred a protective effect against EMS, while metformin and spermidine protected yeast against UV light. Somewhat surprisingly, none of the compounds were able to afford a significant protection against H₂O₂, with spermidine dramatically sensitizing cells. We also examined the ability of these compounds to increase lifespan when growth-arrested by hydroxyurea; only spermidine was found to have a positive effect. Overall, our results suggest that lifespan-extending compounds may act in part by protecting nuclear DNA.

32P-Postlabeling Analysis of DNA Adducts

³²P-Postlabeling analysis is an ultra-sensitive method for the detection of DNA adducts, such as those formed directly by the covalent binding of carcinogens and mutagens to bases in DNA, and other DNA lesions resulting from modification of bases by endogenous or exogenous agents (e.g., oxidative damage). The procedure involves four main steps: enzymatic digestion of DNA sample; enrichment of the adducts; radiolabeling of the adducts by T4 kinase-catalyzed transference of ³²P-orthophosphate from [γ-³²P]ATP; chromatographic separation of labeled adducts, and detection and quantification by means of their radioactive decay. Using 10 μg of DNA or less, it is capable of detecting adduct levels as low as 1 adduct in 10⁹-10¹⁰ normal nucleotides. It is applicable to a wide range of investigations, including monitoring human exposure to environmental or occupational carcinogens, determining whether a chemical has genotoxic properties, analysis of the genotoxicity of complex mixtures, elucidation of the pathways of activation of carcinogens, and monitoring DNA repair.

Mode of action-based risk assessment of genotoxic carcinogens

The risk assessment of chemical carcinogens is one major task in toxicology. Even though exposure has been mitigated effectively during the last decades, low levels of carcinogenic substances in food and at the workplace are still present and often not completely avoidable. The distinction between genotoxic and non-genotoxic carcinogens has traditionally been regarded as particularly relevant for risk assessment, with the assumption of the existence of no-effect concentrations (threshold levels) in case of the latter group. In contrast, genotoxic carcinogens, their metabolic precursors and DNA reactive metabolites are considered to represent risk factors at all concentrations since even one or a few DNA lesions may in principle result in mutations and, thus, increase tumour risk. Within the current document, an updated risk evaluation for genotoxic carcinogens is proposed, based on mechanistic knowledge regarding the substance (group) under investigation, and taking into account recent improvements in analytical techniques used to quantify DNA lesions and mutations as well as "omics" approaches. Furthermore, wherever possible and appropriate, special attention is given to the integration of background levels of the same or comparable DNA lesions. Within part A, fundamental considerations highlight the terms hazard and risk with respect to DNA reactivity of genotoxic agents, as compared to non-genotoxic agents. Also, current methodologies used in genetic toxicology as well as in dosimetry of exposure are described. Special focus is given on the elucidation of modes of action (MOA) and on the relation between DNA damage and cancer risk. Part B addresses specific examples of genotoxic carcinogens, including those humans are exposed to exogenously and endogenously, such as formaldehyde, acetaldehyde and the corresponding alcohols as well as some alkylating agents, ethylene oxide, and acrylamide, but also examples resulting from exogenous sources like aflatoxin B1, allylalkoxybenzenes, 2-amino-3,8-dimethylimidazo[4,5-f] quinoxaline (MeIQx), benzo[a]pyrene and pyrrolizidine alkaloids. Additionally, special attention is given to some carcinogenic metal compounds, which are considered indirect genotoxins, by accelerating mutagenicity via interactions with the cellular response to DNA damage even at low exposure conditions. Part C finally encompasses conclusions and perspectives, suggesting a refined strategy for the assessment of the carcinogenic risk associated with an exposure to genotoxic compounds and addressing research needs.

Mechanistic formation of hazardous molecular heterocyclic amines from high temperature pyrolysis of model biomass materials: cellulose and tyrosine

Background

Research inventories on the co-pyrolysis of major biomass components such as cellulose with amino acid materials is scarce in literature despite the fact that such studies are critical in understanding toxic product relations from high temperature cooking, combustion of bio-fuels, cigarette smoking and forest fires. This paper explores, quantitatively, the yields of heterocyclic nitrogenated molecular reaction products of grave mutagenetic concern from the co-pyrolysis of model biomass materials; tyrosine and cellulose. Research has established that heterocyclic amines such as isocyanates are mutagens as well precursors for asthma, and other respiratory disorders.

Methods

An equimassic mixture of tyrosine and cellulose (50 ± 2 mg) by weight were pyrolyzed in a tubular quartz reactor in flowing nitrogen at 1 atm. Besides, varying combinations of tyrosine and cellulose in the ratios 3:1 and 1:3 were also explored for comparison. The reaction time was set at 2 s so as to simulate combustions events in nature. The pyrolysate was collected over 5 mL dichloromethane and characterized using a gas chromatograph coupled to a mass spectrometer detector.

Results

Evidently, it was noted that 1-methylindazole was released in high yields at 300 °C, constituting ~ 300 µg in the entire pyrolysis temperature range (200–700 °C). Nonetheless, isoindazole gave the highest yield ~ 730 µg while 1-naphthyl isocyanate gave a total yield of ~ 336 µg in the same temperature range. Remarkably, the change in char yield between 300 and 450 °C for the pyrolysis of 25% tyrosine in 75% cellulose was found to be ~ 48% whereas the change in char yield for the pyrolysis of 75% tyrosine in 25% cellulose was 49%.

Conclusion

The char and tar yields considered important residues of biomass burning have been reported in this study and found to be consistent with other research output in literature. The striking similarities of % yield of char across all temperatures for various combinations was the most significant observation in this investigation—char yield was independent of the mixing ratio during pyrolysis. From a mechanistic standpoint, it was noted that tyrosine inhibited cellulose based nitrogenated products. Thus N-products dominated the O-products.

A comparison of transgenic rodent mutation and in vivo comet assay responses for 91 chemicals

A database of 91 chemicals with published data from both transgenic rodent mutation (TGR) and rodent comet assays has been compiled. The objective was to compare the sensitivity of the two assays for detecting genotoxicity. Critical aspects of study design and results were tabulated for each dataset. There were fewer datasets from rats than mice, particularly for the TGR assay, and therefore, results from both species were combined for further analysis. TGR and comet responses were compared in liver and bone marrow (the most commonly studied tissues), and in stomach and colon evaluated either separately or in combination with other GI tract segments. Overall positive, negative, or equivocal test results were assessed for each chemical across the tissues examined in the TGR and comet assays using two approaches: 1) overall calls based on weight of evidence (WoE) and expert judgement, and 2) curation of the data based on a priori acceptability criteria prior to deriving final tissue specific calls. Since the database contains a high prevalence of positive results, overall agreement between the assays was determined using statistics adjusted for prevalence (using AC1 and PABAK). These coefficients showed fair or moderate to good agreement for liver and the GI tract (predominantly stomach and colon data) using WoE, reduced agreement for stomach and colon evaluated separately using data curation, and poor or no agreement for bone marrow using both the WoE and data curation approaches. Confidence in these results is higher for liver than for the other tissues, for which there were less data. Our analysis finds that comet and TGR generally identify the same compounds (mainly potent mutagens) as genotoxic in liver, stomach and colon, but not in bone marrow. However, the current database content precluded drawing assay concordance conclusions for weak mutagens and non-DNA reactive chemicals.

Rationale for Environmental Hygiene towards global protection of fetuses and young children from adverse lifestyle factors

BACKGROUND

The regulatory management of chemicals and toxicants in the EU addresses hundreds of different chemicals and health hazards individually, one by one. An issue is that, so far, the possible interactions among chemicals or hazards are not considered as such. Another issue is the anticipated delay of several decades before effective protection of public health by regulatory decisions due to a time consuming process. Prenatal and early postnatal life is highly vulnerable to environmental health hazards with lifelong consequences, and a priority period for reduction of exposure. There are some initiatives regarding recommendations for pregnant women aiming at protection against one or another category of health hazard, however not validated by intervention studies.

HYPOTHESIS

Here, we aim at strengthening the management of exposure to individual health hazards during pregnancy and lactation, with protective measures in a global strategy of Environmental Hygiene. We hypothesize that such a strategy could reduce both the individual effects of harmful agents in complex mixtures and the possible interactions among them. A panel of experts should develop and endorse implementable measures towards a protective behavior. Their application is meant to be preferably as a package of measures in order to maximize protection and minimize interactions in causing adverse effects. Testing our hypothesis requires biomonitoring studies and longitudinal evaluation of health endpoints in the offspring. Favorable effects would legitimate further action towards equal opportunity access to improved environmental health.

CONCLUSION

Environmental Hygiene is proposed as a global strategy aiming at effective protection of pregnant women, unborn children and infants against lifelong consequences of exposure to combinations of adverse lifestyle factors.

DNA replication after mutagenic treatment in Hordeum vulgare

The temporal and spatial properties of DNA replication in plants related to DNA damage and mutagenesis is poorly understood. Experiments were carried out to explore the relationships between DNA replication, chromatin structure and DNA damage in nuclei from barley root tips. We quantitavely analysed the topological organisation of replication foci using pulse EdU labelling during the S phase and its relationship with the DNA damage induced by mutagenic treatment with maleic hydrazide (MH), nitroso-N-methyl-urea (MNU) and gamma ray. Treatment with mutagens did not change the characteristic S-phase patterns in the nuclei; however, the frequencies of the S-phase-labelled cells after treatment differed from those observed in the control cells. The analyses of DNA replication in barley nuclei were extended to the micronuclei induced by mutagens. Replication in the chromatin of the micronuclei was rare. The results of simultanous TUNEL reaction to identify cells with DNA strand breaks and the labelling of the S-phase cells with EdU revealed the possibility of DNA replication occurring in damaged nuclei. For the first time, the intensity of EdU fluorescence to study the rate of DNA replication was analysed.

Different sensitivities of cultured mammalian cells towards aphidicolin-enhanced DNA effects in the comet assay

The comet assay in combination with the polymerase inhibitor aphidicolin (APC) has been used to measure DNA excision repair activity, DNA repair kinetics and individual DNA repair capacity. Since APC can enhance genotoxic effects of mutagens measured by the comet assay, this approach has been proposed for increasing the sensitivity of the comet assay in human biomonitoring. The APC-modified comet assay has mainly been performed with human blood and it was shown that it not only enhances the detection of DNA damage repaired by nucleotide excision repair (NER) but also damage typically repaired by base excision repair (BER). Recently, we reported that in contrast to blood leukocytes, A549 cells (a human lung adenocarcinoma cell line) seem to be insensitive towards the repair-inhibiting action of APC. To further elucidate the general usefulness of the APC-modified comet assay for studying repair in cultured mammalian cells, we comparatively investigated further cell lines (HeLa, TK6, V79). DNA damage was induced by BPDE (benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide) and MMS (methyl methanesulfonate) in the absence and presence of APC (3 or 15μM). APC was either added for 2h together with the mutagen or cells were pre-incubated for 30min with APC before the mutagen was added. The results indicate that the cell lines tested differ fundamentally with regard to their sensitivity and specificity towards the repair-inhibiting effect of APC. The actual cause for these differences is still unclear but potential molecular explanations are discussed. Irrespective of the underlying mechanism(s), our study revealed practical limitations of the use of the APC-modified comet assay.

Long-term methadone intake and genotoxicity in addicted patients

Background:

It is well known that contact with some physical, chemical or biological compounds can increase the incidence of mutation. Among these compounds, are pharmaceuticals that meet long duration of use and potentially could be misused and taken more than the ordered dosage.

Objectives:

The aim of this study was to evaluate mutagenic effect of methadone in addicted patients referred to Imam Khomeini Hospital in Ahvaz by single cell gel electrophoresis technic or comet assay.

Patients and Methods:

In this study, 90 subjects were divided into dichromate treated group, no treated healthy volunteers group and test group. Each group included 30 subjects. Screening was performed according to questionnaire and qualified subjects were entered the study. Blood samples were collected and lymphocytes were isolated, mixed with low melting point agarose for slide preparation according to standard method. Slides were analyzed using fluorescence microscope and comet patterns were assessed.

Results:

The mutagenicity index in addicted group was robustly higher than healthy volunteers. Fortunately, this significant difference was lower than positive control.

Conclusions:

Genome instability in addicted patients was demonstrated in this study. Controversially, considering incoherent results of previous studies and our data, more studies in longer duration of methadone use are needed to elucidate the consequence.

Induction and repair of DNA damage measured by the comet assay in human T lymphocytes separated by immunomagnetic cell sorting

The comet assay is widely used in human biomonitoring to measure DNA damage in whole blood or isolated peripheral blood mononuclear cells (PBMC) as a marker of exposure to genotoxic agents. Cytogenetic assays with phytohemagglutinin (PHA)-stimulated cultured T lymphocytes are also frequently performed in human biomonitoring. Cytogenetic effects (micronuclei, chromosome aberrations, sister chromatid exchanges) may be induced in vivo but also occur ex vivo during the cultivation of lymphocytes as a consequence of DNA damage present in lymphocytes at the time of sampling. To better understand whether DNA damage measured by the comet assay in PBMC is representative for DNA damage in T cells, we comparatively investigated DNA damage and its repair in PBMC and T cells obtained by immunomagnetic cell sorting. PBMC cultures and T cell cultures were exposed to mutagens with different modes of genotoxic action and DNA damage was measured by the comet assay after the end of a 2h exposure and after 18h post-incubation. The mutagens tested were methyl methanesulfonate (MMS), (±)-anti-B[a]P-7,8-dihydrodiol-9,10-epoxide (BPDE), 4-nitroquinoline-1-oxide (4NQO), styrene oxide and potassium bromate. MMS and potassium bromate were also tested by the modified comet assay with formamido pyrimidine glycosylase (FPG) protein. The results indicate that the mutagens tested induce DNA damage in PBMC and T cells in the same range of concentrations and removal of induced DNA lesions occurs to a comparable extent. Based on these results, we conclude that the comet assay with PBMC is suited to predict DNA damage and its removal in T cells.

The mutagenicity analysis of imidapril hydrochloride and its degradant, diketopiperazine derivative, nitrosation mixtures by in vitro Ames test with two strains of Salmonella typhimurium

AIM

The evaluation of mutagenic properties of imidapril hydrochloride (IMD) and its degradation impurity, diketopiperazine derivative (DKP), nitrosation mixtures was conducted in order to analyze the carcinogenic risk of IMD long-term treatment in patients. In this study an in vitro Ames test with Salmonella enterica serovar Typhimurium TA 98 and TA 100 strains was used.

BACKGROUND

IMD and DKP contain nitrogen atoms, which makes them theoretically vulnerable to in vivo nitrosation with the production of N-nitroso compounds (NOC). NOC, in turn, are known animal mutagens indicating that their endogenous production from nitrosable drugs constitutes a carcinogenic hazard.

MATERIALS AND METHODS

Pure IMD sample was exposed to forced degradation conditions of increased temperature and dry air in order to achieve a DKP sample. Both samples were then treated with a nitrosating agent and the obtained nitrosation mixtures were subjected to mutagenicity analysis by the Ames test with S. typhimurium TA 98 and TA 100 strains in the presence and absence of metabolic activation system (S9 mix) using a commercial Ames MPF 98/100 microplate format mutagenicity assay kit.

RESULTS

None of the six concentrations of the investigated nitrosation mixtures exhibited any mutagenic potential in both S. typhimurium strains. The addition of S9 mix did not alter the non-mutagenic properties of the studied compounds.

CONCLUSIONS

The nitrite treatment of both studied compounds has no impact on their mutagenic properties under the conditions of the present studies. Hence, IMD and DKP nitrosation mixtures are classified as non-mutagens in this test.

Circular dichroism study of the interaction between mutagens and bilirubin bound to different binding sites of serum albumins

Although recent investigations have shown that bilirubin not only has a negative role in the organism but also exhibits significant antimutagenic properties, the mechanisms of interactions between bilirubin and mutagens are not clear. In this study, interaction between bilirubin bound to different binding sites of mammalian serum albumins with structural analogues of the mutagens 2-aminofluorene, 2,7-diaminofluorene and mutagen 2,4,7-trinitrofluorenone were investigated by circular dichroism and absorption spectroscopy. Homological human and bovine serum albumins were used as chiral matrices, which preferentially bind different conformers of bilirubin in the primary binding sites and make it observable by circular dichroism. These molecular systems approximated a real system for the study of mutagens in blood serum. Differences between the interaction of bilirubin bound to primary and to secondary binding sites of serum albumins with mutagens were shown. For bilirubin bound to secondary binding sites with low affinity, partial displacement and the formation of self-associates were observed in all studied mutagens. The associates of bilirubin bound to primary binding sites of serum albumins are formed with 2-aminofluorene and 2,4,7-trinitrofluorenone. It was proposed that 2,7-diaminofluorene does not interact with bilirubin bound to primary sites of human and bovine serum albumins due to the spatial hindrance of the albumins binding domains. The spatial arrangement of the bilirubin bound to serum albumin along with the studied mutagens was modelled using ligand docking, which revealed a possibility of an arrangement of the both bilirubin and 2-aminofluorene and 2,4,7-trinitrofluorenone in the primary binding site of human serum albumin.