The Comet assay for the detection of DNA damage in Mus spretus from Doñana National Park

Metalliferous Mining Pollution and Its Impact on Terrestrial and Semi-terrestrial Vertebrates: A Review

Metalliferous mining, a major source of metals and metalloids, has severe potential environmental impacts. However, the number of papers published in international peer-reviewed journals seems to be low regarding its effects in terrestrial wildlife. To the best of our knowledge, our review is the first on this topic. We used 186 studies published in scientific journals concerning metalliferous mining or mining spill pollution and their effects on terrestrial and semi-terrestrial vertebrates. We identified the working status of the mine complexes studied, the different biomarkers of exposure and effect used, and the studied taxa. Most studies (128) were developed in former mine sites and 46 in active mining areas. Additionally, although several mining accidents have occurred throughout the world, all papers about effects on terrestrial vertebrates from mining spillages were from Aznalcóllar (Spain). We also observed a lack of studies in some countries with a prominent mining industry. Despite >50% of the studies used some biomarker of effect, 42% of them only assessed exposure by measuring metal content in internal tissues or by non-invasive sampling, without considering the effect in their populations. Most studied species were birds and small mammals, with a negligible representation of reptiles and amphibians. The information gathered in this review could be helpful for future studies and protocols on the topic and it facilitates a database with valuable information on risk assessment of metalliferous mining pollution.

Chronic exposure to lead and cadmium pollution results in genomic instability in a model biomonitor species (Apodemus flavicollis Melchior, 1834)

Polymetal dust is a common industrial pollutant. While the use of remediation filters and equipment in lead smelters has reduced pollutant emission, surrounding areas remain contaminated due to the long-term transfer of heavy metals along the food chain. Here we assess the mutagenic potential of the lead-zinc smelter near Plovdiv (Bulgaria) situated in an area that has been contaminated with heavy metals for 60 years. We aimed to evaluate the genomic response of the yellow-necked mouse (A. flavicollis), a biomonitor species, in three sampling sites along the pollution gradient. Mice from Strandzha Natural Park were used as a negative control. The bioaccumulation rate of two non-essential heavy metals, lead (Pb) and cadmium (Cd), in liver tissues was determined by atomic absorption spectroscopy. Genetic alterations attributable to chronic exposure to trace levels of heavy metals were assessed in different blood cell populations using two independent methods: a micronucleus test was applied to evaluate the clastogenic and aneugenic alterations in erythrocytes, while a comet assay was used to assess DNA instability, as evidenced by single- and double-stranded breaks and alkali-labile sites, in leucocytes. We observed elevated levels of Pb and Cd in livers derived from mice from the impacted area: the mean Pb concentration (21.38 ± 8.77 μg/g) was two-fold higher than the lowest-observed-adverse-effect levels (LOAELs), while the mean Cd concentration (13.95 ± 9.79 μg/g) was extremely close to these levels. The mean levels of Pb and Cd in livers derived from mice from the impacted area were 31-fold and 63-fold higher, respectively, than the levels measured in mice from the control area. The mean frequency of micronuclei was significantly higher (four-fold) than that observed in the control animals. Furthermore, parameters measured by the comet assay, % tail DNA, tail length and tail moment, were significantly higher in the impact area, indicating the degree of genetic instability caused by exposure to heavy metals. In conclusion, this study shows that despite the reported reduction in lead and cadmium emissions in Bulgaria in recent years, A. flavicollis individuals inhabiting areas subject to long-term contamination exhibit significant signs of DNA damage.

Heavy metal accumulation and genotoxic effects in levant vole (Microtus guentheri) collected from contaminated areas due to mining activities

Heavy metal contamination is a serious environmental problem commonly monitored in various organisms. Small wild rodents are ideal biological monitors to show the extent of environmental pollution. The aim of this study was to evaluate the adverse effects of marble and stone quarries on the Levant vole, Microtus guentheri, inhabiting some polluted sites. In this context, Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used to analyze distribution of thirteen heavy metals (Fe, Al, Zn, Cu, Cr, Mn, Ni, B, Pb, As, Co, Cd, and Hg) in the organs (skins, bones, muscles, livers and kidneys) of the biological specimens, and the comet assay revealed DNA damage in blood lymphocytes for the first time. This study was conducted at close to the marble and stone quarries at Korkuteli, Antalya-Turkey during spring, summer, autumn (2017) and winter (2018) seasons. In spring and summer, genetic damage in blood lymphocytes from all polluted sites (sites 1-5) was significantly higher than that of controls, while in autumn it was higher in samples from three sites (sites 3-5). In terms of heavy metal distribution in organs, we found depositions of Fe, Al, Zn, Ni, Mn, Cr, Co, As and Pb primarily in the skin with its derivatives, Cu and Cd deposits in the kidney, Cu, Cd and B deposits in the liver, and As and Pb depositions in the bones. The study shows that certain organs (especially skin with its derivatives) and blood lymphocytes of Levant vole can be used as ideal indicators of heavy metal pollution. Our results suggest that the Korkuteli area could already be under the threat of heavy metal pollution.

The comet assay in animal models: From bugs to whales - (Part 2 Vertebrates)

The comet assay has become one of the methods of choice for the evaluation and measurement of DNA damage. It is sensitive, quick to perform and relatively affordable for the evaluation of DNA damage and repair at the level of individual cells. The comet assay can be applied to virtually any cell type derived from different organs and tissues. Even though the comet assay is predominantly used on human cells, the application of the assay for the evaluation of DNA damage in yeast, plant and animal cells is also quite high, especially in terms of biomonitoring. The present extensive overview on the usage of the comet assay in animal models will cover both terrestrial and water environments. The first part of the review was focused on studies describing the comet assay applied in invertebrates. The second part of the review, (Part 2) will discuss the application of the comet assay in vertebrates covering cyclostomata, fishes, amphibians, reptiles, birds and mammals, in addition to chordates that are regarded as a transitional form towards vertebrates. Besides numerous vertebrate species, the assay is also performed on a range of cells, which includes blood, liver, kidney, brain, gill, bone marrow and sperm cells. These cells are readily used for the evaluation of a wide spectrum of genotoxic agents both in vitro and in vivo. Moreover, the use of vertebrate models and their role in environmental biomonitoring will also be discussed as well as the comparison of the use of the comet assay in vertebrate and human models in line with ethical principles. Although the comet assay in vertebrates is most commonly used in laboratory animals such as mice, rats and lately zebrafish, this paper will only briefly review its use regarding laboratory animal models and rather give special emphasis to the increasing usage of the assay in domestic and wildlife animals as well as in various ecotoxicological studies.

Transcriptome signatures of p,p´-DDE-induced liver damage in Mus spretus mice

The use of DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl) ethane) in some countries, although regulated, is contributing to an increased worldwide risk of exposure to this organochlorine pesticide or its derivative p,p'-DDE [1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene]. Many studies have associated p,p'-DDE exposure to type 2 diabetes, obesity and alterations of the reproductive system, but their molecular mechanisms of toxicity remain poorly understood. We have addressed this issue by using commercial microarrays based on probes for the entire Mus musculus genome to determine the hepatic transcriptional signatures of p,p'-DDE in the phylogenetically close mouse species Mus spretus. High-stringency hybridization conditions and analysis assured reliable results, which were also verified, in part, by qRT-PCR, immunoblotting and/or enzymatic activity. Our data linked 198 deregulated genes to mitochondrial dysfunction and perturbations of central signaling pathways (kinases, lipids, and retinoic acid) leading to enhanced lipogenesis and aerobic glycolysis, inflammation, cell proliferation and testosterone catabolism and excretion. Alterations of transcript levels of genes encoding enzymes involved in testosterone catabolism and excretion would explain the relationships established between p,p´-DDE exposure and reproductive disorders, obesity and diabetes. Further studies will help to fully understand the molecular basis of p,p´-DDE molecular toxicity in liver and reproductive organs, to identify effective exposure biomarkers and perhaps to design efficient p,p'-DDE exposure counteractive strategies.

Blockade of metabotropic glutamate receptor 5 protects against DNA damage in a rotenone-induced Parkinson's disease model

Glutamate excitotoxicity contributes to the development of Parkinson's disease (PD) and pharmacological blockade of metabotropic glutamate receptor 5 (mGluR5) has beneficial anti-akinetic effects in animal models of PD; however, the mechanism by which these antagonists alleviate PD symptoms is largely unknown. In our study, the effects of mGluR5 inhibition on DNA damage were investigated in a rotenone-induced model of PD. We first found that the selective mGluR5 antagonist, 2-methyl-6- (phenylethynyl) pyridine, prevented rotenone-induced DNA damage in MN9D dopaminergic neurons through a mechanism involving the downregulation of intracellular calcium release which was associated with a reduction in endoplasmic reticulum stress and reactive oxygen species (ROS)-related mitochondrial dysfunction. Interestingly, the ROS-related mitochondrial dysfunction was accompanied by an increase in expression of the antioxidant protein, Trx2. Treatment of cells with the calcium chelating agent 1,2-bis-(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid or the ROS scavenger N-acetyl-L-cysteine, also reduced rotenone-induced DNA damage, while transfection of a dominant-negative form of Trx2 increased it. In addition, mGluR5 inhibition altered the expression profiles of proteins involved in DNA repair activity. Specifically, the expression of phosphorylated ERK (p-ERK) and CREB, as well as APE1 and Rad51 were elevated after rotenone stimulation and were subsequently downregulated following blockade of mGluR5. These findings were confirmed in vivo in a rotenone-induced rat model of PD. Inhibition of mGluR5 protected against neurotoxicity by mitigating oxidative stress-related DNA damage associated with 8-hydroxy-2'-deoxyguanosine production and also reduced p-ERK activity and Trx2 expression. These findings provide a novel link between mGluR5 and DNA damage in a model of PD, and reveal a potential mechanism by which mGluR5 mediates DNA damage in neurodegenerative diseases.

The Comet Assay and its applications in the field of ecotoxicology: a mature tool that continues to expand its perspectives

Since Singh and colleagues, in 1988, launched to the scientific community the alkaline Single Cell Gel Electrophoresis (SCGE) protocol, or Comet Assay, its uses and applications has been increasing. The thematic areas of its current employment in the evaluation of genetic toxicity are vast, either in vitro or in vivo, both in the laboratory and in the environment, terrestrial or aquatic. It has been applied to a wide range of experimental models: bacteria, fungi, cells culture, arthropods, fishes, amphibians, reptiles, mammals, and humans. This document is intended to be a comprehensive review of what has been published to date on the field of ecotoxicology, aiming at the following main aspects: (i) to show the most relevant experimental models used as bioindicators both in the laboratory and in the field. Fishes are clearly the most adopted group, reflecting their popularity as bioindicator models, as well as a primary concern over the aquatic environment health. Amphibians are among the most sensitive organisms to environmental changes, mainly due to an early aquatic-dependent development stage and a highly permeable skin. Moreover, in the terrestrial approach, earthworms, plants or mammalians are excellent organisms to be used as experimental models for genotoxic evaluation of pollutants, complex mix of pollutants and chemicals, in both laboratory and natural environment. (ii) To review the development and modifications of the protocols used and the cell types (or tissues) used. The most recent developments concern the adoption of the enzyme linked assay (digestion with lesion-specific repair endonucleases) and prediction of the ability to repair of oxidative DNA damage, which is becoming a widespread approach, albeit challenging. For practical/technical reasons, blood is the most common choice but tissues/cells like gills, sperm cells, early larval stages, coelomocytes, liver or kidney have been also used. (iii) To highlight correlations with other biomarkers. (iv) To build a constructive criticism and summarize the needs for protocol improvements for future test applications within the field of ecotoxicology. The Comet Assay is still developing and its potential is yet underexploited in experimental models, mesocosmos or natural ecosystems.

Oxidative stress induces persistent telomeric DNA damage responsible for nuclear morphology change in mammalian cells

One main function of telomeres is to maintain chromosome and genome stability. The rate of telomere shortening can be accelerated significantly by chemical and physical environmental agents. Reactive oxygen species are a source of oxidative stress and can produce modified bases (mainly 8-oxoG) and single strand breaks anywhere in the genome. The high incidence of guanine residues in telomeric DNA sequences makes the telomere a preferred target for oxidative damage. Our aim in this work is to evaluate whether chromosome instability induced by oxidative stress is related specifically to telomeric damage. We treated human primary fibroblasts (MRC-5) in vitro with hydrogen peroxide (100 and 200 µM) for 1 hr and collected data at several time points. To evaluate the persistence of oxidative stress-induced DNA damage up to 24 hrs after treatment, we analysed telomeric and genomic oxidative damage by qPCR and a modified comet assay, respectively. The results demonstrate that the genomic damage is completely repaired, while the telomeric oxidative damage persists. The analysis of telomere length reveals a significant telomere shortening 48 hrs after treatment, leading us to hypothesise that residual telomere damage could be responsible for the telomere shortening observed. Considering the influence of telomere length modulation on genomic stability, we quantified abnormal nuclear morphologies (Nucleoplasmic Bridges, Nuclear Buds and Micronuclei) and observed an increase of chromosome instability in the same time frame as telomere shortening. At subsequent times (72 and 96 hrs), we observed a restoration of telomere length and a reduction of chromosome instability, leaving us to conjecture a correlation between telomere shortening/dysfunction and chromosome instability. We can conclude that oxidative base damage leads to abnormal nuclear morphologies and that telomere dysfunction is an important contributor to this effect.

Effect of mining activities in biotic communities of Villa de la Paz, San Luis Potosi, Mexico

Mining is one of the most important industrial activities worldwide. During its different stages numerous impacts are generated to the environment. The activities in the region have generated a great amount of mining residues, which have caused severe pollution and health effects in both human population and biotic components. The aim of this paper was to assess the impact of mining activities on biotic communities within the district of Villa de la Paz. The results showed that the concentrations of As and Pb in soil were higher than the national regulations for urban or agricultural areas. The bioavailability of these metals was certified by the presence of them in the roots of species of plants and in kidneys and livers of wild rodents. In regard to the community analysis, the sites that were located close to the mining district of Villa de la Paz registered a lower biological diversity, in both plants and wild rodents, aside from showing a change in the species composition of plant communities. The results of this study are evidence of the impact of mining on biotic communities, and the need to take into account the wildlife in the assessment of contaminated sites.

Geno- and cyto-toxicity in free-living rodent Mus spretus exposed to simulated onshore oil spill

This study investigated geno- and cyto-toxic damage in the free-living rodent, Mus spretus after exposure to a simulated spill of crude oil on soil. The results revealed increased mutagenicity and cytotoxicity in bone marrow cells and increased DNA damage in blood cells. Exposure to crude oil increased sperm abnormalities, with lasso-like folds being the most common. These results point to the value of this rodent in serving as a sentinel species for the monitoring and prediction of environmental hazards.

Metal bioaccumulation, genotoxicity and gene expression in the European wood mouse (Apodemus sylvaticus) inhabiting an abandoned uranium mining area

Genotoxic effects caused by the exposure to wastes containing metals and radionuclides were investigated in the European wood mice (Apodemus sylvaticus). The animals were captured in the surroundings of an abandoned uranium mining site. DNA damage was assessed by comet assay; gene expression and single nucleotide polymorphisms (SNPs) were assessed, respectively, by Real-Time PCR and melt curve analysis. The bioaccumulation of metals in the liver, kidney and bones was also determined to help clarify cause-effect relationships. Results confirmed the bioaccumulation of cadmium and uranium in organisms exposed to uranium mining wastes. P53 gene was found to be significantly up-regulated in the liver of those organisms and SNPs in the Rb gene were also detected in the kidney. Our results showed that uranium mining wastes caused serious DNA damage resulting in genomic instability, disclosed by the significant increase in DNA strand breaks and P53 gene expression disturbance. These effects can have severe consequences, since they may contribute for the emergence of serious genetic diseases. The fact that mice are often used as bioindicator species for the evaluation of risks of environmental exposure to humans, raises concerns on the risks for human populations living near uranium mining areas.

Evaluation of the trypanocidal, cytotoxic and genotoxic activity of styrylquinoline analogs

Styrylquinolines isolated from Galipea longiflora have shown leishmanicidal, trypanocidal, nematocidal and antimalarial activity. Here, we propose to use analogs of these styrylquinolines to enhance the activity against Trypanosoma cruzi. Three compounds in a reduced and oxidized state were synthesized, and the activity against epimastigotes and trypomastigotes was evaluated. in addition, the cytotoxic activity and genotoxic effect were also determined. The results indicated that epimastigotes from different T. cruzi I stocks were highly sensitive to the three compounds. The PQM4 compound presented promising activity against trypomastigotes and low cytotoxic and genotoxic effects. Finally, we observed that the doublebond reduction of the lateral chain of the three carbons made on these compounds improved the activity and substantially diminished the toxicity of the compounds.

Wild rodents (Dipodomys merriami) used as biomonitors in contaminated mining sites

Mining is one of the most important industrial activities globally; however, mining processes have critical environmental impacts, as mining is a major source of metals and metalloids that contribute significantly to the pollution of soil, sediment, water and air. Heavy metals can impact the health of exposed human populations and nonhuman receptors. This study focused on arsenic because its genotoxicity is well-known. Previously, we proposed a methodology to evaluate and integrate risk from a single source affecting different biologic receptors. Here, we propose an alternative approach estimating arsenic exposure in children and kangaroo rats using probabilistic simulation with Monte Carlo modeling. The estimates are then associated to measured DNA damage and compared to both populations of children and rodents living in contaminated and in reference areas. Finally, based on the integrated analysis of the generated information, we evaluate the potential use of wild rodents (Dipodomys merriami) as a biomonitor at mining sites. Results indicate that the variation of genotoxicity in children of the reference site is approximately 2 units when compared to the children of the contaminated site. In the rodents we observed a variation of approximately 4 units between those of the reference site when compared to those living on the contaminated site. We propose that D. merriami can be used as a biomonitor organism in sites with mining activity, and that a non-lethal test can be used to evaluate risk from metal exposure.

Metals in liver and kidneys and the effects of chronic exposure to pyrite mine pollution in the shrew Crocidura russula inhabiting the protected wetland of Doñana

Historically impacted by anthropogenic activities, the nature reserve of Doñana (SW Spain) was affected by an unprecedented spillage of mud and acidic water from the Aznalcóllar pyrite mine in April 1998. Although several studies have addressed the influence of this spill on soils, water, and biota, there is little information on mammals, especially carnivorous species. We measured the concentrations of Fe, Mg, Pb, Hg, Cd, Zn, Cu, Mn, Mo, Co, and Cr in specimens of the greater white-toothed shrew, Crocidura russula, inhabiting the protected area affected by the mine spillage. We also examined other parameters to approach at the physiological effects of pollution. We found an increase in non-essential metals (Pb, Cd, and Hg), and morphometric, histological and genotoxic alterations. Age and gender were two significant factors explaining metal bioaccumulation: adults had higher Hg and Cd levels than juveniles, whereas males bioaccumulated more Pb and Co and less Mo than females. The micronucleus frequencies in blood erythrocytes were significantly higher in specimens from the polluted site than animals from the control site. Shrews from the impacted area also had hepatic alterations, namely increased liver-body ratio, focal necrosis, and signs of apoptosis in hepatocytes. Due to the relevance of small mammals in the diet of endangered species such as carnivorous birds and mammals, the findings of our study are of practical use for the management of the Doñana wildlife reserve and other protected Mediterranean wetlands.

Levodopa therapy reduces DNA damage in peripheral blood cells of patients with Parkinson's disease

Oxidative stress seems to play a major role in the pathogenesis of neurodegeneration. In Parkinson's disease (PD) patients, the dopaminergic neurons are subjected to oxidative stress resulting from reduced levels of antioxidant defenses such as glutathione and high amount of intracellular iron. Levodopa (LD) is widely used for the symptomatic treatment of PD, but its role in oxidative damage control is still unclear. The aim of this study was to analyze the presence of DNA damage in peripheral blood lymphocytes (PBL) of PD patients, during a washout and a controlled LD dosage and to evaluate the oxidative damage fluctuation after LD intake. The standard and the Fpg-modified version of Comet assay were applied in analyzing DNA damage in PBL from blood samples of nine PD patients and nine matched controls. Due to the limited number of patients we cannot reach definite conclusions even if our data confirm the accumulation of DNA lesions in PD patients; these lesions decrease after LD intake.

Genotoxicity detected in wild mice living in a highly polluted wetland area in south western Spain

A field study was carried out in the south of the Iberian Peninsula in an industrial area in the neighbourhood of Huelva city, SW Spain, and in a natural area (Doñana National Park) for comparison, to estimate the genetic risk induced by environmental pollution in wild mice. Genotoxic effects in a sentinel organism, the Algerian mice (Mus spretus) free living in the industrial area were compared with animals of the same species living in the natural protected area. The single cell gel electrophoresis, or Comet assay, was performed as a genotoxicity test in peripheral blood of mice. Our results clearly show that mice free living in the contaminated area bear a high burden of genetic damage as compared with control individuals. The results suggest that the assessing of genotoxicity levels by the Comet assay in wild mice can be used as a valuable test in pollution monitoring and environmental conservation.

Cell-cycle protein modifications in the kidney of Mus spretus from Doñana National Park

On April 1998 a tailing dam of the Aznalcollar pyrite mine partially collapsed and released to the Guadiamar river acidic water and mud containing toxic metals threatening the Doñana National Park, a Spanish wildlife reserve located near the estuary of Guadalquivir river. To assess the possible biological effects on terrestrial ecosystems, biochemical markers were assayed in the kidneys of Algerian mice (Mus spretus) collected in several areas of Doñana and Guadiamar river. Biomarkers assayed are proteins involved in cell cycle regulation, in particular cyclins and their associated kinases, and some cell cycle inhibitors. Moreover Mitogen Activated Protein Kinases (MAPK), a signal transduction system involved in cell division, p53, a protein involved in growth arrest after DNA damage, and HSP70, an early stress-induced protein, were assayed. The kidneys of animals collected one year after the ecological disaster had increased levels of PCNA (proliferating cell nuclear antigen), indicating an increased number of cells in the S phase of cell cycle. This shift of cells from G0 to S phase is due to increased levels of cyclins D1, E, and A, to decreased levels of p21 and p27 cdk inhibitors, and to activation of MAPK cascade. On the other hand, p53 and HSP70 levels are not changed. These data demonstrate that the presence of toxic metals after ecological disaster provoked the induction of kidney cell proliferation interpretable as a compensatory cell growth after tissue damage and apoptosis, and that could lead to the genomic instability characteristic of cancer cell.

Molecular biomonitoring of a population of nurses handling antineoplastic drugs

Many antineoplastic drugs have been found to have carcinogenic, mutagenic and teratogenic activity and so hospital personnel handling these substances are potentially exposed to health risk. Understanding this risk derived from protracted occupational exposure has great relevance even if the workers normally adopt individual and environmental protective measures. To address this question we have studied the presence of DNA and chromosome damage in a population of nurses employed in Italian oncology units and in matched controls. We used the comet assay to evidence the presence of DNA strand breaks, due to both acute and chronic exposure, and the micronucleus (MN) test, which is a measure of clastogenic and aneugenic events. Furthermore, since the individual response to the exogenous insults may be genetically determined, we studied the possible influence of single nucleotide polymorphism in XRCC1 and XRCC3 DNA repair genes on induced genetic damage. We also considered the effects of confounding factors like smoking, age and gender. The results indicated that the exposed subjects had significantly high levels of genetic damage. Age and gender were associated with increased values in MN, both in control and in exposed groups; the smoking habit affects MN frequency in controls, but not in workers. Furthermore we found that exposed subjects bearing at least one XRCC1 variant allele (399Gln) show higher values of MN. The present data provide the evidence to show that occupational exposure to antineoplastic drugs, even if in safety controlled conditions, represents a serious health risk. Furthermore we have shown that the presence of XRCC1 genetic polymorphism could contribute to increase the genetic damage in susceptible individuals who are occupationally exposed to dangerous substances.

Transfer and accumulation of metals in a soil-diet-wood mouse food chain along a metal pollution gradient

We studied the accumulation and transfer of As, Cd, Cu, Pb and Zn in the compartments of a soil-diet-wood mouse (Apodemus sylvaticus) food chain at five sites located along a metal pollution gradient. We observed a clear gradient in metal exposure at increasing distance from the smelter in all compartments of the food chain for the non-essential metals. The gradient was less clear or absent for the essential metals in acorn and mice target tissues. Regression analysis showed overall strong relationships within the soil-diet and diet-wood mouse compartments for the non-essential metals, while relationships for the essential metals were weak or absent. Total metal in soil appeared as a better predictor for the diet metal content than the available metal fraction. Our results suggest a more important transfer of non-essential elements through the food chain than essential elements, which is probably a consequence of homeostatic control of the latter group.

DNA damage repair and genetic polymorphisms: Assessment of individual sensitivity and repair capacity

PURPOSE

To study the repair capacity after X-ray irradiation in human peripheral blood cells of healthy subjects, in relation to their genotypes.

METHODS AND MATERIALS

The peripheral blood of 50 healthy subjects was irradiated in vitro with 2 Gy of X rays and the induced DNA damage was measured by Comet assay immediately after irradiation. DNA repair was detected by analyzing the cells at defined time intervals after the exposure. Furthermore, all subjects were genotyped for XRCC1, OGG1, and XPC genes.

RESULTS

After X-ray irradiation, persons bearing XRCC1 homozygous variant (codon 399) genotype exhibited significantly lower Tail DNA values than those bearing wild-type and heterozygous genotypes. These results are also confirmed at 30 and 60 min after irradiation. Furthermore, XPC heterozygous subjects (variant codon 939) showed lower residual DNA damage 60 min after irradiation compared with wild-type and homozygous genotypes.

CONCLUSION

The results of the present study show that polymorphisms in DNA repair genes could influence individual DNA repair capacity.

Absolute transcript expression signatures of Cyp and Gst genes in Mus spretus to detect environmental contamination

We evaluated whether quantitation of mRNA molecules of key genes is a reliable biomonitoring end-point. We examined the Mus spretus expression levels of 19 transcripts encoding different cytochrome-P450s and glutathione transferases. Mice dwelling at the Doñana Biological Reserve were compared to those from an industrial settlement (PS). Metal biomonitoring indicated that PS animals sustained a heavier pollutant burden than those from the reference site. Transcript quantitations showed the following: (i) gender-related differences in the expression of most Cyp and Gst genes; (ii) one PS female displaying much smaller/larger transcript amounts than the remaining females; (iii) the concomitant up-regulation of Cyp1a2, Cyp2a5, Cyp2e1, Cyp4a10, Gsta1, Gsta2, Gstm1, and Gstm2 mRNAs in liver of PS males; and (iv) outstanding qualitative and quantitative differences between the hepatic expression signature of PS males and that promoted by paraquat. We conclude that (i) absolute amounts of transcripts encoding biotransformation enzymes are more potent biomarkers in males than in females, and in liver than in kidney; (ii) individual quantitations prevent biased interpretations by specimens with abnormal expression levels; and (iii)transcript expression signature of PS males is consistent with exposure to a complex profile of organic pollutants, other than oxidative stressors.

Rufloxacin induced photosensitization in bio-models of increasing complexity

Rufloxacin belongs to the class of fluoroquinolones that act mainly as specific inhibitors of bacterial Topoisomerase II. These drugs are widely known to be involved in various diseases ranging from cutaneous reactions to aging. The type II photosensitizing activity of Rufloxacin has been already demonstrated on calf thymus DNA and free nucleosides. The aim of this study is to examine in control untreated and UVA irradiated human fibroblasts the modifications on DNA status induced by Rufloxacin added in the culture medium. This allows to investigate the photosensitizing activity of Rufloxacin in a more complex cell model. Fibroblasts, either in the presence or in the absence of Rufloxacin, were exposed to UVA irradiation for different times. An experimental protocol was followed in order to evaluate the amount of single-strand breaks (SSB) and double-strand breaks (DSB) DNA fragmentation by comet assay, and plasmid photocleavage. The presence of oxidized bases was also evaluated using the 8-OH-dGuo test. The comet assay test was also employed to assess cellular repair capacity. The intracellular drug concentration was verified by HPLC-MS. The results confirming the role of Rufloxacin as photosensitizer were: (i) a time-dependent increase in DNA fragmentation when fibroblasts were irradiated in the presence of Rufloxacin; (ii) the efficiency of the cellular repair machinery to be exhaustive after 2 h (whereas no correlation between irradiation time and DNA damage repair was observed with a higher level of DNA fragmentation after shorter irradiation times); (iii) the increased number of cells exhibiting high DNA fragmentation, seen as comets with long tails, was not accompanied by a similar large extent of oxidised DNA base formation, as measured by 8-OH-dGuo analysis; (iv) the double helix SSB, formed in plasmid photosensitization, agreed with the comet assay results, pointing out a good correlation among the cell system and the simpler models used.

Comparative evaluation of background micronucleus frequencies in domestic mammals

Exposure of human alimentation-destined animals to toxic substances can be an important risk factor for human health. Mutagenicity tests represent a good method for genotoxic effect evaluation of environmental pollutants. The micronucleus frequency in peripheral blood and bone marrow erythrocytes has been evaluated in four domestic Ungulate species (ox, sheep, swine and horse). For each species two or three groups of animals coming from Italy and other European countries were analysed and the results indicate a relatively low mean frequency of micronucleated erythrocytes (ME), both in peripheral blood and bone marrow. The comparison between these two frequencies in the four species studied shows that the ME frequency in sheep and horse is significantly higher in peripheral blood than in bone marrow, whereas in bovines it is higher in the bone marrow, and in swine the difference is not significant. These results could indicate that in ox and swine the spleen is involved in ME removal from the peripheral circulation, as is known for other species including man. Nevertheless, it cannot be excluded that the same occurs in the other two species, since they exhibit a relatively low peripheral blood ME frequency as well. Further studies on domestic mammals are needed to clarify the spleen function and verify the use of the peripheral blood micronucleus test for genotoxic biomonitoring. At present, the application of the micronucleus test to the bone marrow seems a more suitable method, but, being invasive, it can be used only as a control system of animal hygiene and health, in addition to the routine tests, rather than for biomonitoring.