Genotoxic ability of cadmium, chromium and nickel salts studied by kinetochore staining in the cytokinesis-blocked micronucleus assay

The Roles of Histone Post-Translational Modifications in the Formation and Function of a Mitotic Chromosome

During mitosis, many cellular structures are organized to segregate the replicated genome to the daughter cells. Chromatin is condensed to shape a mitotic chromosome. A multiprotein complex known as kinetochore is organized on a specific region of each chromosome, the centromere, which is defined by the presence of a histone H3 variant called CENP-A. The cytoskeleton is re-arranged to give rise to the mitotic spindle that binds to kinetochores and leads to the movement of chromosomes. How chromatin regulates different activities during mitosis is not well known. The role of histone post-translational modifications (HPTMs) in mitosis has been recently revealed. Specific HPTMs participate in local compaction during chromosome condensation. On the other hand, HPTMs are involved in CENP-A incorporation in the centromere region, an essential activity to maintain centromere identity. HPTMs also participate in the formation of regulatory protein complexes, such as the chromosomal passenger complex (CPC) and the spindle assembly checkpoint (SAC). Finally, we discuss how HPTMs can be modified by environmental factors and the possible consequences on chromosome segregation and genome stability.

Genotoxicity of chromium (III) and cobalt (II) and interactions between them

Introduction. Chromium and cobalt are essential trace elements that are required only in a small amount, otherwise their excess can cause toxic effects.

Aim. The aim of this study was to determine the effects of chromium (III) and cobalt (II) and their combinations on genotoxicity in human fibroblasts cells (BJ).

Material and methods. In this work, comet and micronucleus assays were used. The BJ cells were exposed to chromium chloride and cobalt chloride at concentration ranges from 100 to 1400 µM. Mixtures of these elements were prepared so as to examine interactions between them.

Results. The present study shows the genotoxic effects of chromium (III) and cobalt (II) and their mixtures on BJ cells. In the comet assay, no comets were observed at the lowest concentrations; in the higher, a significant increase in their percentage was observed. In the other assay (formation of micronuclei), a statistically significant increase in the number of cells with micronuclei was observed in the BJ cells spiked with cobalt chloride and chromium chloride. In the case of simultaneous incubation of chromium chloride at 200 µM and cobalt chloride at 1000 µM in the BJ line, antagonism was observed. However, the interaction of chromium chloride at the 1000 µM and cobalt chloride at 200 µM leads to synergism between the studied elements.

Conclusions. Cobalt (II) and chromium (III) show genotoxic properties, they induce breaks in double and single-stranded DNA and they cause formation of AP-sites that do not have purine or pyrimidine bases.

Comparative Study of Cytotoxicity, DNA Damage and Oxidative Stress Induced by Heavy Metals Cd(II), Hg(II) and Cr(III) in Yeast

Wide range of applications of heavy metals and improperly discarded their castoffs possess serious threats to environment and human health. In this study, cytotoxicity, DNA damage and oxidative stress induced by Cd(II), Hg(II) and Cr(III) were comparatively studied in yeast Saccharomyces cerevisiae. Cd(II), Hg(II), and Cr(III) all produced strong cytotoxicity resulting in growth inhibition and cell mortality to varying degrees (Hg(II) > Cd(II) > Cr(III)). Hg(II) produced more oxidative stress. Cr(III) caused more serious DNA damage in vitro. Cd(II) also caused both obvious DNA damage and oxidative stress at higher concentration, but not as efficiently as Cd(II) and Hg(II). A further null mutation sensitivity assay showed that the relative sensitivity of rad1∆ to the metals was Cr(III) > Cd(II) > Hg(II), and that of trx1∆ to the metals was Hg(II) > Cd(II) > Cr(III). These data provide a clear evidence that the Cr(III) can cause significant DNA damage and potential genotoxicity; Hg(II) can strongly inhibit SOD activity, produce lipid peroxidation and cause serious membrane injury, suggesting these heavy metals can cause different toxic effects in different ways.

Measuring mutagenicity in ecotoxicology: A case study of Cd exposure in Chironomus riparius

Existing mutagenicity tests for metazoans lack the direct observation of enhanced germline mutation rates after exposure to anthropogenic substances, therefore being inefficient. Cadmium (Cd) is a metal described as a mutagen in mammalian cells and listed as a group 1 carcinogenic and mutagenic substance. But Cd mutagenesis mechanism is not yet clear. Therefore, in the present study, we propose a method coupling short-term mutation accumulation (MA) lines with subsequent whole genome sequencing (WGS) and a dedicated data analysis pipeline to investigate if chronic Cd exposure on Chironomus riparius can alter the rate at which de novo point mutations appear. Results show that Cd exposure did not affect the basal germline mutation rate nor the mutational spectrum in C. riparius, thereby arguing that exposed organisms might experience a range of other toxic effects before any mutagenic effect may occur. We show that it is possible to establish a practical and easily implemented pipeline to rapidly detect germ cell mutagens in a metazoan test organism. Furthermore, our data implicate that it is questionable to transfer mutagenicity assessments based on in vitro methods to complex metazoans.

Heavy metals modulate DNA compaction and methylation at CpG sites in the metal hyperaccumulator Arabidopsis halleri

Excess heavy metals affect plant physiology by inducing stress symptoms, however several species have evolved the ability to hyperaccumulate metals in above-ground tissues without phytotoxic effects. In this study we assume that at subcellular level, different strategies were adopted by hyperaccumulator versus the non-accumulator plant species to face the excess of heavy metals. At this purpose the comet assay was used to investigate the nucleoid structure modifications occurring in response to Zn and Cd treatments in the I16 and PL22 populations of the hyperaccumulator Arabidopsis halleri versus the nonaccumulator species Arabidopsis thaliana. Methy-sens comet assay and RT-qPCR were also performed to associate metal induced variations in nucleoids with possible epigenetic modifications. The comet assay showed that Zn induced a mild but non significant reduction in the tail moment in A. thaliana and in both I16 and PL22. Cd treatment induced an increase in DNA migration in nuclei of A. thaliana, whereas no differences in DNA migration was observed for I16, and a significant increase in nucleoid condensation was found in PL22 Cd treated samples. This last population showed higher CpG DNA methylation upon Cd treatment than in control conditions, and an up-regulation of genes involved in symmetric methylation and histone deacetylation. Our data support the hypothesis of a possible role of epigenetic modifications in the hyperaccumulation trait to cope with the high Cd shoot concentrations. In addition, the differences observed between PL22 and I16 could reinforce previous suggestions of divergent strategies for metals detoxification developing in the two metallicolous populations.

Gene (HPRT) and chromosomal (MN) mutations of nickel metal powder in V79 Chinese hamster cells

Nickel metal is a naturally occurring element used in many industrial and consumer applications. Human epidemiological data and animal cancer bioassays indicate that nickel metal is not likely to be a human carcinogen. Yet, nickel metal is classified as a suspected human carcinogen (CLP) and possibly carcinogenic to humans (IARC). There are no reliable studies on the potential for nickel metal to induce gene and micronucleus (MN) mutations. To fill these datagaps and increase our understanding of the mechanisms underlying the lack of nickel metal carcinogenicity, gene and micronucleus mutation studies were conducted with nickel metal powder (N36F) in V79 Chinese Hamster cells following OECD 476 and 487 guidelines, respectively, under GLP. Gene mutation at the hprt locus was tested, with and without metabolic activation, after 4-h treatment with 0.05-2.5 mM nickel metal powder. Cytokinesis-block MN frequency following exposure to 0.25-1.5 mM nickel metal was tested after 4-h treatment, with and without metabolic activation, followed by a 24-h treatment without metabolic activation. In the gene mutation assay, there were modest increases in hprt mutants observed at some test concentrations, not exceeding 2.2-fold, which were either within the historical control values and/or showed no concentration-response trend. The positive controls showed increases of at least 7-fold. Likewise, no increases in the MN frequency exceeding 1.5-fold were observed with nickel metal, with no concentration-response trends. Taking these results together, it can be concluded that nickel metal is non-mutagenic and does not cause gene nor chromosomal mutations.

Micronucleus cytome assay in the differential assessment of cytotoxicity and genotoxicity of cadmium and lead in Amietophrynus regularis

Amphibians are increasingly being used as bio-indicator of contamination in ecosystems due to their sensitivity to xenobiotics in the environment. Cadmium and lead compounds, ubiquitous mutagens and carcinogens, are capable of eliciting genome instability in adult toads which may enhance amphibian decline. Micronucleus cytome (MN-cyt) assay, a comprehensive cytogenetic test for the assessment of genome instability induced by xenobiotics in organisms, was utilized in the differential cytogenotoxic evaluation of Cd and Pb in adult Amietophrynus regularis. A. regularis was exposed to six concentrations (8 - 512 mg/L) of the metal solutions to determine 96 h acute toxicity. Four toads per group were exposed to five sub-lethal concentrations (5 - 75 %) of the 96 h LC50 of the metals for 14 days. At post exposure, bone marrow and peripheral erythrocytes were collected for MN-cyt analysis. The metals induced differential concentration and time-dependent increase in mortality with 96 h LC50 of 36.36 mg/L (Cd) and 112.06 mg/L (Pb). No observable effective concentrations (NOEC); Cd=8 and Pb=32 (mg/L) and Lowest observable effective concentrations (LOEC); Cd=16 and Pb=64 (mg/L) were recorded for the metals. Derived toxicity factor (TF) showed that Cd was 3.08 times more toxic to the toads than Pb. The metal solutions induced significant (p<0.05) increase in frequencies of MN, binucleated, nuclear bud, notch, lobe, vacuolated erythrocytes, apoptosis and necrosis compared to the negative control. Cd elicited 1.42 and 3.26 folds increase in MN and NAs respectively, than Pb. MN-cyt assay is a suitable cytogenetic tool for assessing genome instability in A. regularis. Increased genetic instability induced by Cd and Pb may be associated with genetic related syndromes; neoplasms, reproductive dysfunctions and mortality. This suggests threat to amphibian health and may enhance population decline.

Metal toxicity assessment by sentinel species of mangroves: In situ case study integrating chemical and biomarkers analyses

Globally, there is a lack of knowledge about tropical ecotoxicology dealing with the potential impact of metal contamination in mangrove ecosystem. This habitat is considered a nursery for several animal species, among them the "uçá"-crab (Ucides cordatus), known as a key species due to its biological and economical importance. This study evaluated the association involving metal contamination (Cd, Cu, Pb, Cr, Mn and Hg) in water, sediment, red-mangrove vegetation (Rhizophora mangle) and tissues of uçá crab, together with its geno-cytotoxic responses, based on micronucleated hemocytes frequency and the retention time of neutral red in lysosomes. We assessed six mangrove areas with distinct pollution levels in São Paulo State, Brazil, where the water and sediment contamination by metals were associated with accumulation of these pollutants in biotic compartments (mangrove leaves and crab). In U. cordatus, metal accumulation was best explained by metal concentration found in leaves of R. mangle than in the water or sediment, indicating that feeding drives metal exposure in this organism. Mercury (Hg) concentration in sediment, copper (Cu) concentration in hepatopancreas of U. cordatus and lead (Pb) in water and green leaves of R. mangle showed a significant correlation with genotoxic impact in U. cordatus. However, copper concentration (in green/senescent leaves and hepatopancreas) and lead (in sediment), were the major metals affecting lysosomal membrane integrity. Therefore, representatives of all compartments were associated with cyto and genotoxicity in this species, thus requiring a holistic approach to issues related to sublethal damage. Probability estimates of cytogenetic impacts related to metal concentration in abiotic compartments (significantly correlated with known biomarkers: Hg in sediment; and Pb in water and sediment) are also presented. Our results highlight the need for environmental restoration of mangroves areas contaminated with metals, responsible for cytogenetic injuries and revealing a pre-pathological condition in this sentinel species, in addition to ecological disturbances.

Gene 33/Mig6 inhibits hexavalent chromium-induced DNA damage and cell transformation in human lung epithelial cells

Hexavalent Chromium [Cr(VI)] compounds are human lung carcinogens and environmental/occupational hazards. The molecular mechanisms of Cr(VI) carcinogenesis appear to be complex and are poorly defined. In this study, we investigated the potential role of Gene 33 (ERRFI1, Mig6), a multifunctional adaptor protein, in Cr(VI)-mediated lung carcinogenesis. We show that the level of Gene 33 protein is suppressed by both acute and chronic Cr(VI) treatments in a dose- and time-dependent fashion in BEAS-2B lung epithelial cells. The inhibition also occurs in A549 lung bronchial carcinoma cells. Cr(VI) suppresses Gene 33 expression mainly through post-transcriptional mechanisms, although the mRNA level of gene 33 also tends to be lower upon Cr(VI) treatments. Cr(VI)-induced DNA damage appears primarily in the S phases of the cell cycle despite the high basal DNA damage signals at the G2M phase. Knockdown of Gene 33 with siRNA significantly elevates Cr(VI)-induced DNA damage in both BEAS-2B and A549 cells. Depletion of Gene 33 also promotes Cr(VI)-induced micronucleus (MN) formation and cell transformation in BEAS-2B cells. Our results reveal a novel function of Gene 33 in Cr(VI)-induced DNA damage and lung epithelial cell transformation. We propose that in addition to its role in the canonical EGFR signaling pathway and other signaling pathways, Gene 33 may also inhibit Cr(VI)-induced lung carcinogenesis by reducing DNA damage triggered by Cr(VI).

Nanominerals, fullerene aggregates, and hazardous elements in coal and coal combustion-generated aerosols: An environmental and toxicological assessment

Studies on coal-derived nanoparticles as well as nano-minerals are important in the context of the human health and the environment. The coal combustion-generated aerosols also affect human health and environmental quality aspects in any coal-fired station. In this study, the feed coals and their combustion-generated aerosols from coal-fired boilers of two tea industry facilities were investigated for the presence of nanoparticles/nano minerals, fullerene aggregates, and potentially hazardous elements (PHEs). The samples were characterized by using X-ray diffraction (XRD), Time-of-flight secondary ion mass spectroscopy (TOF-SIMS), High resolution-transmission electron microscopy/energy dispersive spectroscopy (HR-TEM/EDS) and Ultra Violet-visible spectroscopy (UV-Vis) to know their extent of environmental risks to the human health when present in coals and aerosols. The feed coals contain mainly clay minerals, whilst glass fragments, spinel, quartz, and other minerals occur in lesser quantities. The PM samples contain potentially hazardous elements (PHEs) like As, Pb, Cd and Hg. Enrichment factor of the trace elements in particulate matters (PMs) was calculated to determine their sources. The aerosol samples were also found to contain nanomaterials and ultrafine particles. The fullerene aggregates along with potentially hazardous elements were also detected in the aerosol samples. The cytotoxicity studies on the coal combustion-generated PM samples show their potential risk to the human health. This detailed investigation on the inter-relationship between the feed coals and their aerosol chemistry will be useful for understanding the extent of environmental hazards and related human health risk.

Cytotoxic and genotoxic potential of Cr(VI), Cr(III)-nitrate and Cr(III)-EDTA complex in human hepatoma (HepG2) cells

Chromium (Cr) and ethylenediaminetetraacetate (EDTA) are common environmental pollutants and can be present in high concentrations in surface waters at the same time. Therefore, chelation of Cr with EDTA can occur and thereby stable Cr(III)-EDTA complex is formed. Since there are no literature data on Cr(III)-EDTA toxicity, the aim of our work was to evaluate and compare Cr(III)-EDTA cytotoxic and genotoxic activity with those of Cr(VI) and Cr(III)-nitrate in human hepatoma (HepG2) cell line. First the effect of Cr(VI), Cr(III)-nitrate and Cr(III)-EDTA on cell viability was studied in the concentration range from 0.04 μg mL(-1) to 25 μg mL(-1) after 24 h exposure. Further the influence of non-cytotoxic concentrations of Cr(VI), Cr(III)-nitrate and Cr(III)-EDTA on DNA damage and genomic stability was determined with the comet assay and cytokinesis block micronucleus cytome assay, respectively. Cell viability was decreased only by Cr(VI) at concentrations above 1.0 μg mL(-1). Cr(VI) at ≥0.2 μg mL(-1) and Cr(III) at ≥1.0 μg mL(-1) induced DNA damage, while after Cr(III)-EDTA exposure no formation DNA strand breaks was determined. Statistically significant formation of micronuclei was induced only by Cr(VI) at ≥0.2 μg mL(-1), while no influence on the frequency of nuclear buds nor nucleoplasmic bridges was observed at any exposure. This study provides the first evidence that Cr(III)-EDTA did not induce DNA damage and had no influence on the genomic stability of HepG2 cells.

Genotoxicity and cytotoxicity of chromium, copper, manganese and lead, and their mixture in WIL2-NS human B lymphoblastoid cells is enhanced by folate depletion

Heavy metal exposure or dietary deficiency is associated with increased genetic damage, cancer and age-related diseases. Folate (vitamin B9) required for DNA repair and synthesis may increase cellular susceptibility to metal induced genotoxicity. This study investigated the interactive effects of folic acid deficiency and sufficiency on genome instability and cytotoxicity induced by chromium (VI), copper (II), manganese (II), lead (IV), and their mixture (CCMP) in WIL2-NS human B lymphoblastoid cells. WIL2-NS cells were cultured in folic acid deficient (20 nM) and replete (2000 nM) RPMI 1640 medium treated with different concentrations (0.00-1000 μM) of the metals and CCMP for 48 h. Chromosomal damage and cytotoxicity were measured using the Cytokinesis-block Micronucleus Cytome assay. CCMP, Cr, Pb, Cu and Mn induced concentration dependent, increases in cells with chromosome damage (micronuclei, nucleoplasmic bridges, nuclear buds) and necrotic cells and decreased nuclear division index. The metals exhibited different cytotoxic and genotoxic potentials (CCMP>Cr>Pb>Cu>Mn) in both folate deficient and sufficient cells, with the cytogenotoxic effects being greater in folate deficient cells. Significant interaction between the metals and folic acid suggests that folic acid deficiency exacerbated cell proliferation inhibition and genome instability induced by metals. Folate deficiency, increasing metal concentration, and their interactions explained 3-11%, 74-92% and 4-12% of the variance of DNA damage biomarkers. In conclusion, exposure to the tested metals (0.01-1000 μM) increased chromosomal DNA damage in WIL2-NS cells and this was exacerbated by folate deficiency.

Metal-on-polyethylene versus metal-on-metal bearing surfaces in total hip arthroplasty

The long term biological effects of wear products following total hip arthroplasty (THA) are unclear. However, the indications for THA are expanding, with increasingly younger patients undergoing the procedure.

This prospective, randomised study compared two groups of patients undergoing THA after being randomised to receive one of two different bearing surfaces: metal-on-polyethylene (MoP) n = 22 and metal-on-metal (MoM) n = 23. We investigated the relationship between three variables: bearing surface (MoP vs MoM), whole blood levels of chromium (Cr) and cobalt (Co) and chromosomal aberrations in peripheral lymphocyte pre-operatively and at one, two and five years post-surgery.

Our results demonstrated significantly higher mean cobalt and chromium (Co and Cr) blood levels in the MoM group at all follow-up points following surgery (p < 0.01), but there were no significant differences in the chromosomal aberration indices between MoM and MoP at two or five years (two years: p = 0.56, p = 0.08, p = 0.91, p = 0.51 and five years: p = 0.086, p = 0.73, p = 0.06, p = 0.34) for translocations, breaks, loss and gain of chromosomes respectively. Regression analysis showed a strong linear relationship between Cr levels and the total chromosomal aberration indices in the MoM group (R2 = 0.90016), but this was not as strong for Co (R2 = 0.68991). In the MoP group, the analysis revealed a poor relationship between Cr levels and the total chromosomal aberration indices (R2 = 0.23908) but a slightly stronger relationship for Co (R2 = 0.64292). Across both groups, Spearman’s correlation detected no overall association between Co and Cr levels and each of the studied chromosomal aberrations. There remains no clear indication which THA bearing couple is the most biocompatible, especially in young active patients. While THA continues to be very successful at alleviating pain and restoring function, the long-term biological implications of the procedure still require further scrutiny.

Cite this article: Bone Joint J 2015;97-B:1183–91.

Assessment of the mode of action for hexavalent chromium-induced lung cancer following inhalation exposures

Inhalation of hexavalent chromium [Cr(VI)] is associated with increased lung cancer risk among workers in several industries, most notably chromate production workers exposed to high concentrations of Cr(VI) (≥100 μg/m(3)), for which clear exposure-response relationships and respiratory irritation and tissue damage have been reported. Data from this industry are used to assess lung cancer risk associated with environmental and current occupational exposures, occurring at concentrations that are significantly lower. There is considerable uncertainty in the low dose extrapolation of historical occupational epidemiology data to assess risk at current exposures because no published or well recognized mode of action (MOA) for Cr(VI)-induced lung tumors exists. We conducted a MOA analysis for Cr(VI)-induced lung cancer evaluating toxicokinetic and toxicological data in humans and rodents and mechanistic data to assess plausibility, dose-response, and temporal concordance for potential MOAs. Toxicokinetic data support that extracellular reduction of Cr(VI), which limits intracellular absorption of Cr(VI) and Cr(VI)-induced toxicity, can be overwhelmed at high exposure levels. In vivo genotoxicity and mutagenicity data are mostly negative and do not support a mutagenic MOA. Further, both chronic bioassays and the epidemiologic literature support that lung cancer occurs at exposures that cause tissue damage. Based on this MOA analysis, the overall weight of evidence supports a MOA involving deposition and accumulation of particulate chromium in the bifurcations of the lung resulting in exceedance of clearance mechanisms and cellular absorption of Cr(VI). Once inside the cell, reduction of Cr(VI) results in oxidative stress and the formation of Cr ligands. Subsequent protein and DNA damage lead to tissue irritation, inflammation, and cytotoxicity. These effects, concomitant with increased cell proliferation, result in changes to DNA sequences and/or methylation status that can lead to tumorigenesis. This MOA supports the use of non-linear approaches when extrapolating lung cancer risk occurring at high concentration occupational exposures to environmentally-relevant exposures.

Testing the genotoxicity, cytotoxicity, and oxidative stress of cadmium and nickel and their additive effect in male mice

The present study was aimed to investigate the ability of cadmium (Cd) and nickel (Ni) to induce genotoxicity, cytotoxicity, and oxidative stress in bone marrow cells of male mice. Aneuploidy and chromosomal aberrations (CA) showed that Cd is a stronger mutagen than Ni. Cd and Ni increased significantly the incidences of micronucleated polychromatic erythrocytes (PCEs). Also, the ratio of polychromatic erythrocytes to normochromatic erythrocytes (PCE/NCE) suggests that treatment with higher doses of the two metals increased the cytotoxicity. Numerical chromosomal aberrations increased hypoploidy with the treatment which reached two to three times of the frequency of hyperploidy. The results showed that both Cd and Ni are aneugenic that act on kinetochores and cause malsegregation of chromosomes as well as being clastogenic. Both Cd and Ni increased single-break aberrations and also Cd and Ni were found to induce significant DNA damage in mouse bone marrow cells as assessed by the comet assay. In addition to the cytotoxicity results, biochemical analysis in bone marrow revealed a dose-dependent increase of oxidative stress markers. According to the results obtained, genotoxicity and cytotoxicity effects of cadmium and nickel in vivo are dose-dependent and are associated with oxidative stress and their combined effect is less than their expected additive effect, and it could be concluded that there are no synergistic effects resulting from the combined application of both metals.

In vitro studies on protective effect of Glycyrrhiza glabra root extracts against cadmium-induced genetic and oxidative damage in human lymphocytes

Cadmium is a modern environmental contaminant that is toxic and carcinogenic. Glycyrrhiza glabra is a traditional medicinal herb which grows in the various parts of the World. Recent studies demonstrated that G. glabra has antifungal, antimicrobial, antioxidant, and powerful antiinflammatory features. The purpose of this study was to investigate the genetic safety of extracts from G. glabra and its effects on cadmium (as CdCl2) induced genotoxicity. Therefore we evaluated the capability of G. glabra extract to inhibit the rate of micronucleus (MN), sister chromatid exchange (SCE) formations induced by CdCl2. Moreover, to assess the effects of G. glabra on cell viability and oxidative status, we performed 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and total antioxidant capacity (TAC) assays. Our results showed that there were significant increases (P < 0.05) in both SCE and MN frequencies of cultures treated with CdCl2 (5 ppm) as compared to controls. However, co-application of G. glabra extract (5, 10 and 20 ppm) and CdCl2 resulted in decreases of MN and SCE rates as compared to the group treated with CdCl2 alone. Again, the results of MTT and TAC assays clearly indicated dose dependent ameliorative effects of G. glabra extracts against CdCl2 toxicity. In conclusion, this study demonstrated for the first time that G. glabra extracts provided increased resistance of DNA against CdCl2 induced genetic and oxidative damage in human lymphocytes. So, the risk on target tissues of CdCl2 could be reduced and ensured early recovery from its toxicity.

Cell cycle alterations induced by urban PM2.5 in bronchial epithelial cells: characterization of the process and possible mechanisms involved

BACKGROUND

This study explores and characterizes cell cycle alterations induced by urban PM2.5 in the human epithelial cell line BEAS-2B, and elucidates possible mechanisms involved.

METHODS

The cells were exposed to a low dose (7.5 μg/cm(2)) of Milan winter PM2.5 for different time points, and the cell cycle progression was analyzed by fluorescent microscopy and flow cytometry. Activation of proteins involved in cell cycle control was investigated by Western blotting and DNA damage by (32)P-postlabelling, immunostaining and comet assay. The formation of reactive oxygen species (ROS) was quantified by flow cytometry. The role of PM organic fraction versus washed PM on the cell cycle alterations was also examined. Finally, the molecular pathways activated were further examined using specific inhibitors.

RESULTS

Winter PM2.5 induced marked cell cycle alteration already after 3 h of exposure, represented by an increased number of cells (transient arrest) in G2. This effect was associated with an increased phosphorylation of Chk2, while no changes in p53 phosphorylation were observed at this time point. The increase in G2 was followed by a transient arrest in the metaphase/anaphase transition point (10 h), which was associated with the presence of severe mitotic spindle aberrations. The metaphase/anaphase delay was apparently followed by mitotic slippage at 24 h, resulting in an increased number of tetraploid G1 cells and cells with micronuclei (MN), and by apoptosis at 40 h. Winter PM2.5 increased the level of ROS at 2 h and DNA damage (8-oxodG, single- and double stand breaks) was detected after 3 h of exposure. The PM organic fraction caused a similar G2/M arrest and augmented ROS formation, while washed PM had no such effects. DNA adducts were detected after 24 h. Both PM-induced DNA damage and G2 arrest were inhibited by the addition of antioxidants and α-naphthoflavone, suggesting the involvement of ROS and reactive electrophilic metabolites formed via a P450-dependent reaction.

CONCLUSIONS

Milan winter PM2.5 rapidly induces severe cell cycle alterations, resulting in increased frequency of cells with double nuclei and MN. This effect is related to the metabolic activation of PM2.5 organic chemicals, which cause damages to DNA and spindle apparatus.

Genotoxicity evaluation of individual cigarette smoke toxicants using the in vitro γH2AX assay by high content screening

Cigarette smoke is a complex mixture consisting of more than 5600 identified chemical constituents of which approximately 150 have been identified so far as "tobacco smoke toxicants". Proposals made by the World Health Organisation Framework Convention on Tobacco Control mandate the lowering of nine tobacco smoke priority toxicants, including 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), N-nitrosonornicotine (NNN), and benzo[a]pyrene (B[a]P) and monitoring the levels of a further nine including cadmium. Here, we evaluated the genotoxic potential in human bronchial epithelial BEAS-2B cells of four cigarette smoke toxicants; NNK, NNN, B[a]P and cadmium using the novel in vitro γH2AX assay by High Content Screening (HCS). We also examined the genotoxicity of binary mixtures of NNK and NNN reporting their relative contribution to the genotoxic end-point. The results of this preliminary assessment showed that the in vitro γH2AX assay by HCS could be used as a pre-screening tool to detect and quantify the genotoxicity effect of cigarette smoke toxicants individually and in binary mixture. Moreover, the data produced could contribute to the prioritisation of toxicant reduction research in modified tobacco products.

Habitat monitoring and genotoxicity in Ucides cordatus (Crustacea: Ucididae), as tools to manage a mangrove reserve in southeastern Brazil

In Brazil, the state of São Paulo contains both preserved areas (Juréia-Itatins Ecological Station) and extremely impacted ones (Cubatão Municipality). This study evaluated the concentrations of five metals (Cu, Cd, Cr, Pb, and Hg) in two mangroves with different levels of anthropogenic impact and the apparent genotoxicity to Ucides cordatus. Water and sediment samples were obtained, and metal concentrations were determined with an atomic absorption spectrophotometer. The genotoxic impact was quantified based on the number of micronucleated cells per 1,000 analyzed (MN‰), using hemolymph slides stained with Giemsa. Metal concentrations in water were below the detection limit, except for lead, although no significant difference was observed between the areas (P > 0.05). Sediment from Cubatão had higher concentrations of Cd, Pb, Cr, and Cu than sediment from Juréia-Itatins (P < 0.05), but no significant differences in metal concentrations were detected among depth strata of the sediment (P > 0.05). Crabs from Cubatão had a 2.6 times higher mean frequency of micronucleated cells (5.2 ± 1.8 MN‰) than those from Juréia-Itatins (2.0 ± 1.0 MN‰; P < 0.0001). The more-polluted conditions found in the mangrove sediments of Cubatão were reflected in the micronucleus assay, demonstrating their genotoxic effect; however, genetic damage should be attributed to a synergistic effect with other kinds of pollutants previously recorded in different environments of Cubatão. U. cordatus proved to be an excellent bioindicator of mangrove pollution. This study established, for the first time, the normal frequency of MN‰ in a population of this species within an ecological station.

Alteration of Th1/Th2/Th17 cytokine profile and humoral immune responses associated with chromate exposure

BACKGROUND

The role of chromate exposure in the deregulation of total lymphocyte and other immune factors is largely unclear.

OBJECTIVES

We aimed to examine alteration of the Th1/Th2/Th17 cytokine profile and humoral indicators caused by occupational chromate exposure.

METHODS

A cross-sectional study was conducted in two similar workshops (groups 1 and 2) with 106 male occupational workers and 50 matched local controls. Environmental and biological exposures were assessed by measuring chromium concentrations in workplace air, and in whole blood and urine samples of the workers. Cytokines in serum (IL-2, IL-4, IL-6, IL-10, TNF-α, IFN-γ, IL-17A) were determined by CBA assay, while immunoglobin (IgA, IgM, IgG, IgE) and complement (C3, C4) were evaluated by immunonephelometric and ELISA methods. Micronucleus analysis was also used to explore the relationship between genotoxicity and immunotoxicity.

RESULTS

Compared with the control group, environmental chromate exposure in groups 1 and 2 was much higher, and the mean values of IL-6, IL-10, IFN-γ, IL-17A and IFN-γ/IL-4 were significantly decreased in group 1. In group 2, IgA and IgG levels were reduced, while C3 and C4 were increased. Levels of IFN-γ, IgG and IgA were all inversely associated with whole blood chromium, while C3 and C4 were positively associated with whole blood chromium (p<0.05). Both IL-10 and IL-17A were inversely associated with urine chromium. Correlations were also found between IL-10, IL-17A and micronucleus (r=-0.329, r=-0.312, respectively).

CONCLUSIONS

Occupational exposure to chromate could downregulate the cellular and humoral factors of the immune system.

Assessment of the mode of action underlying development of rodent small intestinal tumors following oral exposure to hexavalent chromium and relevance to humans

Abstract Chronic exposure to high concentrations of hexavalent chromium (Cr(VI)) in drinking water causes intestinal adenomas and carcinomas in mice, but not in rats. Cr(VI) causes damage to intestinal villi and crypt hyperplasia in mice after only one week of exposure. After two years of exposure, intestinal damage and crypt hyperplasia are evident in mice (but not rats), as are intestinal tumors. Although Cr(VI) has genotoxic properties, these findings suggest that intestinal tumors in mice arise as a result of chronic mucosal injury. To better understand the mode of action (MOA) of Cr(VI) in the intestine, a 90-day drinking water study was conducted to collect histological, biochemical, toxicogenomic and pharmacokinetic data in intestinal tissues. Using MOA analyses and human relevance frameworks proposed by national and international regulatory agencies, the weight of evidence supports a cytotoxic MOA with the following key events: (a) absorption of Cr(VI) from the intestinal lumen, (b) toxicity to intestinal villi, (c) crypt regenerative hyperplasia and (d) clonal expansion of mutations within the crypt stem cells, resulting in late onset tumorigenesis. This article summarizes the data supporting each key event in the MOA, as well as data that argue against a mutagenic MOA for Cr(VI)-induced intestinal tumors.

Mechanistic Insights from the NTP Studies of Chromium

Hexavalent chromium (Cr(VI)) is a contaminant of water and soil and is a human lung carcinogen. Trivalent chromium (Cr(III)), a proposed essential element, is ingested by humans in the diet and in dietary supplements such as chromium picolinate (CP). The National Toxicology Program (NTP) demonstrated that Cr(VI) is also carcinogenic in rodents when administered in drinking water as sodium dichromate dihydrate (SDD), inducing neoplasms of the oral cavity and small intestine in rats and mice, respectively. In contrast, there was no definitive evidence of toxicity or carcinogenicity following exposure to Cr(III) administered in feed as CP monohydrate (CPM). Cr(VI) readily enters cells via nonspecific anion channels, in contrast to Cr(III), which cannot easily pass through the cell membrane. Extracellular reduction of Cr(VI) to Cr(III), which occurs primarily in the stomach, is considered a mechanism of detoxification, while intracellular reduction is thought to be a mechanism of genotoxicity and carcinogenicity. Tissue distribution studies in additional groups of male rats and female mice demonstrated higher Cr concentrations in tissues following exposure to Cr(VI) compared to controls and Cr(III) exposure at a similar external dose, indicating that some of the Cr(VI) escaped gastric reduction and was distributed systemically. The multiple potential pathways of Cr-induced genotoxicity will be discussed.

Cytogenetic response of Scots pine (Pinus sylvestris Linnaeus, 1753) (Pinaceae) to heavy metals

We studied cytogenetic reactions of Scots pine seedlings to heavy metals - lead, cupric and zinc nitrates applied at concentrations 0.5 to 2000 µM. We determined the range of concentrations of heavy metals that causes mutagenic effect. Lead was found to cause the strongest genotoxicity as manifested by significant increase in the frequency of pathological mitosis, occurrence of fragmentations and agglutinations of chromosomes, various types of bridges, and a significant number of the micronuclei which were absent in the control. Possible cytogenetic mechanisms of the cytotoxic action of heavy metals are discussed.

The role of cadmium and nickel in estrogen receptor signaling and breast cancer: metalloestrogens or not?

During the past half-century, incidences of breast cancer have increased globally. Various factors--genetic and environmental--have been implicated in the initiation and progression of this disease. One potential environmental risk factor that has not received a lot of attention is the exposure to heavy metals. While several mechanisms have been put forth describing how high concentrations of heavy metals play a role in carcinogenesis, it is unclear whether chronic, low-level exposure to certain heavy metals (i.e., cadmium and nickel) can directly result in the development and progression of cancer. Cadmium and nickel have been hypothesized to play a role in breast cancer development by acting as metalloestrogens--metals that bind to estrogen receptors and mimic the actions of estrogen. Since the lifetime exposure to estrogen is a well-established risk factor for breast cancer, anything that mimics its activity will likely contribute to the etiology of the disease. However, heavy metals, depending on their concentration, are capable of binding to a variety of proteins and may exert their toxicities by disrupting multiple cellular functions, complicating the analysis of whether heavy metal-induced carcinogenesis is mediated by the estrogen receptor. The purpose of this review is to discuss the various epidemiological, in vivo, and in vitro studies that show a link between the heavy metals, cadmium and nickel, and breast cancer development. We will particularly focus on the studies that test whether these two metals act as metalloestrogens in order to assess the strength of the data supporting this hypothesis.

Airborne urban particles (Milan winter-PM2.5) cause mitotic arrest and cell death: Effects on DNA, mitochondria, AhR binding and spindle organization

Airborne particulate matter (PM) is considered to be an important contributor to lung diseases. In the present study we report that Milan winter-PM2.5 inhibited proliferation in human bronchial epithelial cells (BEAS-2B) by inducing mitotic arrest. The cell cycle arrest was followed by an increase in mitotic-apoptotic cells, mitotic slippage and finally an increase in "classical" apoptotic cells. Exposure to winter-PM10 induced only a slight effect which may be due to the presence of PM2.5 in this fraction while pure combustion particles failed to disturb mitosis. Fewer cells expressing the mitosis marker phospho-histone H3 compared to cells with condensed chromosomes, suggest that PM2.5 induced premature mitosis. PM2.5 was internalized into the cells and often localized in laminar organelles, although particles without apparent plasma membrane covering were also seen. In PM-containing cells mitochondria and lysosomes were often damaged, and in mitotic cells fragmented chromosomes often appeared. PM2.5 induced DNA strands breaks and triggered a DNA-damage response characterized by increased phosphorylation of ATM, Chk2 and H2AX; as well as induced a marked increase in expression of the aryl hydrocarbon receptor (AhR)-regulated genes, CYP1A1, CYP1B1 and AhRR. Furthermore, some disturbance of the organization of microtubules was indicated. It is hypothesized that the induced mitotic arrest and following cell death was due to a premature chromosome condensation caused by a combination of DNA, mitochondrial and spindle damage.

Aneuploidy as an early mechanistic event in metal carcinogenesis

Aneuploidy has recently been proposed as an initiating event for carcinogenesis. There is significant evidence that carcinogenic metals induce aneuploidy. Here we review the mechanisms for how carcinogenic metals may induce aneuploidy and the evidence that carcinogenic metals induce an aneugenic effect which can destabilize the genome leading to genomic instability and cancer.

A core in vitro genotoxicity battery comprising the Ames test plus the in vitro micronucleus test is sufficient to detect rodent carcinogens and in vivo genotoxins

In vitro genotoxicity testing needs to include tests in both bacterial and mammalian cells, and be able to detect gene mutations, chromosomal damage and aneuploidy. This may be achieved by a combination of the Ames test (detects gene mutations) and the in vitro micronucleus test (MNvit), since the latter detects both chromosomal aberrations and aneuploidy. In this paper we therefore present an analysis of an existing database of rodent carcinogens and a new database of in vivo genotoxins in terms of the in vitro genotoxicity tests needed to detect their in vivo activity. Published in vitro data from at least one test system (most were from the Ames test) were available for 557 carcinogens and 405 in vivo genotoxins. Because there are fewer publications on the MNvit than for other mammalian cell tests, and because the concordance between the MNvit and the in vitro chromosomal aberration (CAvit) test is so high for clastogenic activity, positive results in the CAvit test were taken as indicative of a positive result in the MNvit where there were no, or only inadequate data for the latter. Also, because Hprt and Tk loci both detect gene-mutation activity, a positive Hprt test was taken as indicative of a mouse-lymphoma Tk assay (MLA)-positive, where there were no data for the latter. Almost all of the 962 rodent carcinogens and in vivo genotoxins were detected by an in vitro battery comprising Ames+MNvit. An additional 11 carcinogens and six in vivo genotoxins would apparently be detected by the MLA, but many of these had not been tested in the MNvit or CAvit tests. Only four chemicals emerge as potentially being more readily detected in MLA than in Ames+MNvit--benzyl acetate, toluene, morphine and thiabendazole--and none of these are convincing cases to argue for the inclusion of the MLA in addition to Ames+MNvit. Thus, there is no convincing evidence that any genotoxic rodent carcinogens or in vivo genotoxins would remain undetected in an in vitro test battery consisting of Ames+MNvit.

In vivo cytogenetic studies on rat's bone-marrow cells of structurally related Schiff base complexes

The in vivo interactions of structurally-related Ni(II) and Fe(III) Schiff base complexes based on N-(8-quinolyl)salicylaldimine (HL(1)) and N-(8-quinolyl)napthaldimine (HL(2)) ligands with DNA molecules in the bone-marrow cells of rats were demonstrated using chromosomal aberrations (CAs) assay. The complexes differ by one aromatic group on the aldehyde site of the Schiff base (basicity or lipophilicity), or by the type of the central metal ions (Ni(II) or Fe(III)). Animals were injected intraperitoneally (i.p) with different concentrations of each drug, and CAs were examined in bone-marrow cells, 15 hours later. A significant increase in the frequency of CAs was induced upon treatment with 15 mg / kg weight of L(1) complexes (P < 0.001), and not with L(2) complexes (P > 0.05). Also, the magnitude of aberrations induced by L(1)-Ni(II) was higher than that induced by L(1)-Fe(III) (P < 0.01). The binding data, estimated using UV-Visible absorption technique, showed that the metal binding of HL(1) was much greater than that of HL(2) and that the affinity of HL(1) towards Ni(II) is higher than that for Fe(III) ions. Thus, the trends in the presented in vivo results signify the important role of complex stability in predicting the clastogenicity of metal-ion-chelating Schiff base drugs.

Genotoxic analysis in aquatic environment under influence of cyanobacteria, metal and radioactivity

The micronucleus (MN) and nuclear abnormality (NA) tests were employed to evaluate the genotoxic potential of the Lucrecia dam (RN, Brazil) located in a semi-arid region and influenced by crop irrigation and irregular rainfall. The analyses of these water samples demonstrated the presence of several cyanobacteria as well as metals and radioactivity. The Nile Tilapia (Oreochromis niloticus) was used for micronucleus and nuclear abnormality assays and analysis of metal concentrations in gills and liver samples. Genotoxic assays in source water fish showed a significant increase in the frequency of nuclear damage (MN and NA) in relation to the negative control group. In conclusion, the results obtained with water surface and biological samples from the Lucrecia dam suggest that this important water resource contains a number of chemical and microbiological pollutants with genotoxic potential and that these substances may be compromising the species inhabiting this ecosystem. Particular care must be taken to prevent further degradation of this water supply. Capsule: A battery of assay was successfully applied to assess the water quality of Lucrecia dam from a Northeastern region of Brazil.

Effect of Ni2+ and Cd2+ ions on thermally induced conformational transitions in poly(dA)-poly(dT) system

Effects of Ni(2+) and Cd(2+) ions on thermally induced conformational transitions in the poly(dA)·poly(dT) polynucleotide duplex and poly(dA)·2poly(dT) triplex under near physiological ionic conditions were studied by measurement of UV absorption melting curves and static light scattering intensity. The diagrams of conformational transitions in poly(dA)-poly(dT)-Me(2+) systems were plotted. An aggregation in these polynucleotide systems arises at certain values of the metal ions concentration and the temperature after the polymer dissociation into single strands. The phenomenon is conditioned by the aggregation of poly(dA) via the interstrand cross-linking by the dication bridges. Unlike Ni(2+), Cd(2+) induces formation of very stable aggregates which did not disintegrate even upon cooling up to room temperature.

Metal-on-metal total hip arthroplasty

The effects of elevated levels of metal ions in patients who have undergone metal-on-metal total hip arthroplasty are not fully understood. The effects of femoral head size on serum metal-ion levels have been the subject of conflicting reports, and further investigation is needed to evaluate the impact of acetabular and femoral component alignment. The conduct of clinical trials of metal-on-metal total hip arthroplasties has been inadequate as few investigators have used a randomized controlled design to compare metal-on-metal bearings with other bearing surfaces. Additional clinical research needs to include appropriate validated patient-reported outcome measures, activity monitoring, and health economics.

The genotoxicity of physiological concentrations of chromium (Cr(III) and Cr(VI)) and cobalt (Co(II)): an in vitro study

Humans are exposed to chromium and cobalt in industry, from the environment and after joint replacement surgery from the CoCr alloy in the implant. In this study we have investigated whether Cr(III), Cr(VI), Co(II) and Cr in combination with Co could induce chromosome aberrations in human fibroblasts in vitro at the same concentrations that have been found in the peripheral blood of exposed humans. We used 24 colour M-FISH as a sensitive way to detect translocations and aneuploidy and examined the effects of a 24-h exposure and its consequences up to 30 days after the exposure in order to record genomic instability and/or repair. At these physiological doses the metals induced predominantly numerical rather than structural aberrations. Co was the least reactive and Cr(VI) especially in combination with Co the most. All metals at the highest physiological doses caused simple (gain or loss of 3 or less chromosomes) and complex (more than 49 chromosomes) aneuploidy. All metals at the lowest physiological dose caused a significant increase of total aberrations. Cr(VI) was much more effective than Cr(III) in causing chromosome fragments, which were only induced at the highest doses. There was a slow resolution of aneuploidy with time after exposure. This involved a reduction in the proportion of aneuploid cells and a reduction of the number of chromosomes within cells showing complex aneuploidy. We conclude that these metal ions can cause chromosome aberrations at physiological concentrations and that their main effect is aneugenic.

Carcinogenicity assessment of water-soluble nickel compounds

IARC is reassessing the human carcinogenicity of nickel compounds in 2009. To address the inconsistencies among results from studies of water-soluble nickel compounds, we conducted a weight-of-evidence analysis of the relevant epidemiological, toxicological, and carcinogenic mode-of-action data. We found the epidemiological evidence to be limited, in that some, but not all, data suggest that exposure to soluble nickel compounds leads to increased cancer risk in the presence of certain forms of insoluble nickel. Although there is no evidence that soluble nickel acts as a complete carcinogen in animals, there is limited evidence that suggests it may act as a tumor promoter. The mode-of-action data suggest that soluble nickel compounds will not be able to cause genotoxic effects in vivo because they cannot deliver sufficient nickel ions to nuclear sites of target cells. Although the mode-of-action data suggest several possible non-genotoxic effects of the nickel ion, it is unclear whether soluble nickel compounds can elicit these effects in vivo or whether these effects, if elicited, would result in tumor promotion. The mode-of-action data equally support soluble nickel as a promoter or as not being a causal factor in carcinogenesis at all. The weight of evidence does not indicate that soluble nickel compounds are complete carcinogens, and there is only limited evidence that they could act as tumor promoters.

Aerosols near by a coal fired thermal power plant: chemical composition and toxic evaluation

Industrial processes discharge fine particulates containing organic as well as inorganic compounds into the atmosphere which are known to induce damage to cell and DNA, both in vitro and in vivo. Source and area specific studies with respect to the chemical composition, size and shape of the particles, and toxicity evaluations are very much limited. This study aims to investigate the trace elements associated with the aerosol particles distributed near to a coal burning thermal power plant and to evaluate their toxicity through Comet assay. PM(10) (particles determined by mass passing an inlet with a 50% cut-off efficiency having a 10-microm aerodynamic diameter) samples were collected using respirable dust samplers. Twelve elements (Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb, Se, Hg, and As) were analyzed using ICP-AES. Comet assay was done with the extracts of aerosols in phosphate buffered saline (PBS). Results show that Fe and Zn were found to be the predominant elements along with traces of other analyzed elements. Spherical shaped ultrafine particles of <1 microm aerodynamic diameter were detected through scanning electron microscope. PM(10) particles near to the coal burning power plant produced comets indicating their potential to induce DNA damage. DNA damage property is found to be depending upon the chemical characteristics of the components associated with the particles besides the physical properties such as size and shape.

Exposure of Vicia faba and Pisum sativum to copper-induced genotoxicity

The potential genotoxicity of Cu(2+) was investigated in Vicia faba and Pisum sativum seedlings in hydroponic culture conditions. Cu(2+) caused a dose-dependent increase in micronuclei frequencies in both plant models. Cytological analysis of root tips cells showed clastogenic and aneugenic effects of this heavy metal on V. faba root meristems. Cu(2+) induced chromosomal alterations at the lowest concentration used (2.5 mM) when incubated for 42 h, indicating the potent mutagenic effect of this ion. A spectrum of chromosomal abnormalities was observed in V. faba root meristems, illustrating the genotoxic events leading to micronuclei formation.

DNA-damage induction by eight metal compounds in TK6 human lymphoblastoid cells: results obtained with the alkaline Comet assay

Metal compounds are long-lived and can react with different macromolecules, producing a wide range of biological effects, including DNA damage. Since their reactivity is associated with their chemical structure, it is important to obtain information on more than one compound from the same metal. In this study, the DNA-damaging potential of two mercury compounds (mercury chloride and methyl mercury chloride), two nickel compounds (nickel chloride and potassium hexafluoronickelate), two palladium compounds (ammonium tetrachloropalladate and ammonium hexachloropalladate), and two tellurium compounds (sodium tellurite and sodium tellurate) was evaluated in human lymphoblastoid TK6 cells by use of the alkaline version of the Comet assay. As the use of computerized image-analysis systems to collect comet data has increased, the metric used for quantifying DNA damage was the Olive tail moment. Treatments lasted for 3h and the range of concentrations tested was different for each metal compound, depending on its toxicity. Both mercury agents produced DNA damage in TK6 cells, with mercury chloride producing considerably more DNA damage than methyl mercury chloride. Of the two nickel compounds, only nickel chloride (a Ni(II) compound) induced DNA breaks. Similarly, of the two palladium compounds, only the Pd(II) compound (ammonium tetrachloropalladate) was positive in the assay. Sodium tellurite was clearly positive, producing concentration-related increases in DNA damage, while sodium tellurate gave a negative response. In conclusion, the ability of inducing DNA damage by the selected metal compounds in human TK6 cells, when measured with the Comet assay, was dependent on the chemical form and, in general, compounds containing the metal in the lower valence state displayed the greater DNA-damaging ability.

Bioaccumulation of metals and effects of a landfill in small mammals. Part II. The wood mouse, Apodemus sylvaticus

We assess the bioaccumulation of metals (Pb, Hg, Cd, Fe, Mg, Zn, Cu, Mn, Mo, Cr) and effects of landfill leachates on morphological (RI, relative weights), plasma (GPT, GOT, creatinine), and genotoxic (MNT) parameters in wood mice, Apodemus sylvaticus, inhabiting close the Garraf landfill site (NE Spain). Due to the high age- and sex-dependent variation in wild populations, we also studied the effect of these biotic factors on the parameters studied. Wood mice from the landfill site, sited in a partially protected area, showed more Cd, Fe, Zn, Cu, Mn, Mo, and Cr than specimens from the reference site. Moreover, mice near the landfill registered low RI and high relative renal weight, GPT, and MN frequency, which indicate that the landfill affects the health of wild mice. In contrast to sympatric shrews from a previous study, wood mice showed lower bioaccumulation of metals and lower variation caused by biotic factors. Moreover, the morphological and physiological alterations demonstrated that they were also more sensitive at environmental pollution. Given the contribution of small mammals to ecosystem function and the scarce ecotoxicological data on the effects of landfill pollution on wild terrestrial mammals, we consider that our study can be used to improve the management of this protected area.