In vivo and in vitro studies on the genotoxicity of cadmium chloride in mice

Cytogenetic damage by vanadium(IV) and vanadium(III) on the bone marrow of mice

Vanadium is a strategic metal that has many important industrial applications and is generated by the use of burning fossil fuels, which inevitably leads to their release into the environment, mainly in the form of oxides. The wastes generated by their use represent a major health hazard. Furthermore, it has attracted attention because several genotoxicity studies have shown that some vanadium compounds can affect DNA; among the most studied compounds is vanadium pentoxide, but studies in vivo with oxidation states IV and III are scarce and controversial. In this study, the genotoxic and cytotoxic potential of vanadium oxides was investigated in mouse bone marrow cells using structural chromosomal aberration (SCA) and mitotic index (MI) test systems. Three groups were administered vanadium(IV) tetraoxide (V2O4) intraperitoneally at 4.7, 9.4 or 18.8 mg/kg, and three groups were administered vanadium(III) trioxide (V2O3) at 4.22, 8.46 or 16.93 mg/kg body weight. The control group was treated with sterile water, and the positive control group was treated with cadmium(II) chloride (CdCl2). After 24 h, all doses of vanadium compounds increased the percentage of cells with SCA and decreased the MI. Our results demonstrated that under the present experimental conditions and doses, treatment with V2O4 and V2O3 induces chromosomal aberrations and alters cell division in the bone marrow of mice.

Interlaboratory validation of the ToxTracker assay: An in vitro reporter assay for mechanistic genotoxicity assessment

ToxTracker is a mammalian cell reporter assay that predicts the genotoxic properties of compounds with high accuracy. By evaluating induction of various reporter genes that play a key role in relevant cellular pathways, it provides insight into chemical mode-of-action (MoA), thereby supporting discrimination of direct-acting genotoxicants and cytotoxic chemicals. A comprehensive interlaboratory validation trial was conducted, in which the principles outlined in OECD Guidance Document 34 were followed, with the primary objectives of establishing transferability and reproducibility of the assay and confirming the ability of ToxTracker to correctly classify genotoxic and non-genotoxic compounds. Reproducibility of the assay to predict genotoxic MoA was confirmed across participating laboratories and data were evaluated in terms of concordance with in vivo genotoxicity outcomes. Seven laboratories tested a total of 64 genotoxic and non-genotoxic chemicals that together cover a broad chemical space. The within-laboratory reproducibility (WLR) was up to 98% (73%-98% across participants) and the overall between-laboratory reproducibility (BLR) was 83%. This trial confirmed the accuracy of ToxTracker to predict in vivo genotoxicants with a sensitivity of 84.4% and a specificity of 91.2%. We concluded that ToxTracker is a robust in vitro assay for the accurate prediction of in vivo genotoxicity. Considering ToxTracker's robust standalone accuracy and that it can provide important information on the MoA of chemicals, it is seen as a valuable addition to the regulatory in vitro genotoxicity battery that may even have the potential to replace certain currently used in vitro battery assays.

Morin mitigates cadmium-induced testicular impairment by stimulating testosterone secretion and germ cell proliferation in mice

Cadmium (Cd) is one of the heavy metal pollutants present in the environment due to human intervention. It is well known that Cd causes toxicological effects on various organs, including the testes. Morin hydrate is a plant-derived bioflavonoid with antioxidant, anti-inflammatory, and anti-stress properties. Thus, the question can be raised as to whether Morin has an effect on Cd-intoxication-induced testicular impairment. Therefore, the aim of this study was to investigate the role of Morin on Cd-mediated disruption of testicular activity. Mice were divided into three groups: group 1 served as the control group, group 2 was given Cd (10 mg/kg) orally for 35 days, and group 3 was given Cd and Morin hydrate (100 mg/kg) for 35 days. To validate the in vivo findings, an in vitro study on testicular explants was also performed. The results of the in vivo study showed that Cd-intoxicated mice had testicular disorganization, reduced circulating testosterone levels, decreased sperm density, and elevated oxidative stress and sperm abnormality. The expression of the germ cell proliferation marker, germ cell nuclear acidic protein (GCNA), and adipocytokine visfatin were also downregulated. It was observed that Morin hydrate upregulated testicular visfatin and GCNA expression in Cd-intoxicated mice, along with improvement in circulating testosterone, testicular histology, and sperm parameters. Furthermore, the in vitro study showed that Cd-mediated downregulation of testicular visfatin and GCNA expression, along with the suppressed secretion of testosterone from testicular explants, was normalized by Morin treatment, whereas visfatin expression was not. Overall, these data indicate that environmental cadmium exposure impairs testicular activity through downregulation of visfatin and GCNA expression, and Morin might play a protective role against Cd-induced testicular toxicity.

Human serum elements' levels and leukemia: A first pilot study from an adult Greek cohort

BACKGROUND

The present study focuses on the evaluation of potential relationships between trace elements and acute and chronic types of leukemia, via the determination of their levels in human blood serum.

METHODS

A total of 199 serum samples from a Greek cohort were examined, including both leukemia cases and controls. Elements' analysis was carried out using inductively coupled plasma mass spectrometry (ICP-MS) and demographic features such as age, gender, smoking habits and area of residence were recorded and statistically treated applying Shapiro-Wilk, Kolmogorov-Smirnov, Mann Whitney and Kruskal Wallis tests (p < 0.05). Spearman correlation and principal component analysis (PCA) were also performed to investigate possible associations.

RESULTS

The results demonstrated significantly higher (p < 0.05) trace elements concentrations in cases' serum compared to that of controls excluding Ba, with Cu (median concentration 1295 μg L^-1) being the most abundant in cases. Additionally, concentration of toxic Pb and Cd were found at seven and four fold higher concentrations in cases, respectively. Among the trace elements examined, only Rb (164 μg L^-1) was detected in higher concentrations in controls. Ba, Cd and Co presented the lowest concentrations (lower than 1 μg L^-1). PCA was performed for overall and classified data, indicating a stronger relation among the toxic As, Cd, Ni and Pb in cases than controls, particularly referring to smokers and industrial sites' residents. Hematological parameters and factors such as age and gender did not present any significant outcome or correlation.

CONCLUSIONS

The findings from this pilot study suggest a potential relationship between metals and leukemia, especially concerning the toxic ones. Results from the employed source apportionment tools imply that smoking and atmospheric degradation may be positively related with higher metal serum levels in leukemia patients.

Metal-metal interaction and metal toxicity: a comparison between mammalian and D. melanogaster

1. Non-essential heavy metals such as mercury (Hg), arsenic (As), cadmium (Cd), and aluminium (Al) are useless to organisms and have shown extensive toxic effects. Previous studies show that two main molecular mechanisms of metal toxicity are oxidative stress and metal-metal interaction which can disrupt metal homeostasis.2. In this paper, we mainly illustrate metal toxicity and metal-metal interaction through examples in mammalians and D. melanogaster (fruit fly).3. We describe the interference of metal homeostasis by metal-metal interactions in three aspects including replacement, cellular transporter competition, and disruption of the regulation mechanism, and elaborate the mechanisms of metal toxicity to better deal with the challenges of heavy metal pollution and related health problems.

A heavy metal baseline score predicts outcome in acute myeloid leukemia

Despite abundant epidemiological data linking metals to leukemia and other cancers, baseline values of toxic and essential metals in patients with leukemia and the clinical impact of these metals remain unknown. Thus, we sought to quantify metal values in untreated patients with acute myeloid leukemia (AML) and controls and determine the impact of metal values on AML patients' survival. Serum samples from patients with untreated AML and controls at Hospices Civils de Lyon were analyzed and compared for trace metals and copper isotopic abundance ratios with inductively coupled plasma mass spectrometry. Survival analysis was performed as a function of metal values, and a multi-metal score was developed for patients with AML. Serum samples were collected from 67 patients with untreated AML and 94 controls. Most patients had intermediate-risk cytogenetics (63.1%) without FLT3 internal tandem duplication mutations (75.6%) or NPM1 mutations (68.1%). Most metal values differed significantly between AML and control groups. Patients with lower magnesium and higher cadmium values had the worst survival rates, with only 36% surviving at 6 months (P = .001). The adverse prognostic effect of this combination was maintained on multivariate analysis. Based on this, we developed a novel metal score, which accounts for multiple relative abnormalities in the values of five toxic and five essential metals. Patients with a higher metal score had significantly worse survival, which was maintained on multivariate analysis (P = .03). This baseline metal scoring system was also prognostic when we applied it to a separate population of front-line AML patients.

Genotoxicity of yellow shammah (smokeless tobacco) in murine bone marrow cells in vivo

Shammah is a traditional form of smokeless tobacco (ST) that is manufactured and used locally by people of Middle East with highest usage in Saudi Arabia, Yemen and Sudan. In Saudi Arabia, shammah comes in three variants: white, brown and yellow. In the present study, we investigated the genotoxicity of yellow shammah (YS) on bone marrow (BM) cells in vivo using mice. Bone marrow (BM) chromosomal aberration (CA) and micronucleus (MN) assay were performed and hepatic markers of oxidative stress were determined. Swiss albino mice were divided into five groups (n = 6) including negative control (NC) and positive control (PC) groups. The three treated groups included YS-100, 200 and 300 mg/kg, doses freshly prepared in 0.5% carboxymethyl cellulose (CMC) and administered orally once a day for 2 weeks. PC animals were administered cyclophosphamide (CP) at a dose of 40 mg/kg body weight, 24 h before termination. Two weeks continuous treatment of YS induced a dose dependent and significant increase in aberrant metaphases (AM), CA per cell and depression in mitotic activity. In micronucleus assay, YS treatment increased the percentage of micronucleated polychromatic erythrocytes (MNPCE) frequency and showed statistically significant reduction in polychromatic erythrocyte/normochromatic erythrocyte ratio at all doses, as compared to NC. YS also markedly inhibited the activities of superoxide dismutase, reduced glutathione and increased malondialdehyde content. CP was used as clastogen (positive control) and yielded the expected positive results. Therefore, it may be concluded that YS has genotoxic and cytotoxic effects for BM cells of mice in vivo.

Impacts of fullerene C60 and virgin olive oil on cadmium-induced genotoxicity in rats

Currently, cadmium is considered to be one of the major environmental pollutants. Environmentally, cadmium is released in various forms e.g. oxide, chloride and sulphide. The aim of the present study was to examine the genotoxic impact of fullerene nanoparticles C₆₀ (C₆₀) and virgin olive oil (VOO) on cadmium chloride (CdCl₂)-induced genotoxicity in rats. To evaluate these effects on DNA damage and chromosomal frequency, 25 albino rats were randomly assigned to 5 groups (n=5 per group): Group 1 served as a control; Group 2 received a single intraperitoneal dose of CdCl₂ (3.5mg/kg); Group 3 animals were treated with C₆₀ (4mg/kg, orally) every other day for 20days; Group 4 received a single intraperitoneal dose of CdCl₂ (3.5mg/kg) and an oral dose of C₆₀ (4mg/kg); and Group 5 received a single intraperitoneal dose of CdCl₂ (3.5mg/kg) and oral doses of VOO every other day for 20 consecutive days. Genotoxic and anti-genotoxic effects of C₆₀ and VOO were evaluated in the liver, kidney and bone marrow using molecular and cytogenetic assays. As expected, CdCl₂ and C₆₀ administration was associated with band number alterations in both liver and kidney; however, C₆₀ pretreatment recovered to approximately basal number. Surprisingly, C₆₀ and VOO significantly attenuated the genotoxic effects caused by CdCl₂ in livers and kidneys. In bone marrow, in addition to a reduction in the chromosomal number, several chromosomal aberrations were caused by CdCl₂. These chromosomal alterations were also reversed by C₆₀ and VOO. In conclusion, molecular and cytogenetic studies showed that C₆₀ and VOO exhibit anti-genotoxic agents against CdCl₂-induced genotoxicity in rats. Further studies are needed to investigate the optimal conditions for potential biomedical applications of these anti-genotoxic agents.

Effects of Spirulina platensis on DNA damage and chromosomal aberration against cadmium chloride-induced genotoxicity in rats

Todays, bioactive compounds extracted from Spirulina platensis have been intensively studied for their therapeutical values. Therefore, in the present study, we aimed to evaluate the effects of S. platensis extract on DNA damage and chromosomal aberrations induced by cadmium in rats. Four groups of male albino rats (n = 7 rats) were used. The first group served as a control group and received distilled water. The second group was exposed intraperitoneally to cadmium chloride (CdCl₂) (3.5 mg/kg body weight dissolved in 2 ml distilled water). The third group included the rats that were orally treated with S. platensis extract (1 g/kg dissolved in 5 ml distilled water, every other day for 30 days). The fourth group included the rats that were intraperitoneally and orally exposed to cadmium chloride and S. platensis, respectively. The experiment in all groups was extended for 60 days. The results of cadmium-mediated toxicity revealed significant genetic effects (DNA fragmentation, deletion or disappearance of some base pairs of DNA, and appearance of few base pairs according to ISSR-PCR analysis). Moreover, chromosomes showed structural aberrations such as reduction of chromosomal number, chromosomal ring, chromatid deletions, chromosomal fragmentations, and dicentric chromosomes. Surprisingly, S. platensis extract plus CdCl₂-treated group showed less genetic effects compared with CdCl₂ alone. Further, S. platensis extract upon CdCl₂ toxicity was associated with less chromosomal aberration number and nearly normal appearance of DNA fragments as indicated by the bone marrow and ISSR-PCR analysis, respectively. In conclusion, the present novel study showed that co-treatment with S. platensis extract could reduce the genotoxic effects of CdCl₂ in rats.

Genotoxicity of 11 heavy metals detected as food contaminants in two human cell lines

Heavy metals, such as arsenic (As), antimony (Sb), barium (Ba), cadmium (Cd), cobalt (Co), germanium (Ge), lead (Pb), nickel (Ni), tellurium (Te), and vanadium (V) are widely distributed in the environment and in the food chain. Human exposure to heavy metals through water and food has been reported by different international agencies. Although some of these heavy metals are essential elements for human growth and development, they may also be toxic at low concentrations due to indirect mechanisms. In this study, the genotoxic and cytotoxic properties of 15 different oxidation statuses of 11 different heavy metals were investigated using high-throughput screening (γH2AX assay) in two human cell lines (HepG2 and LS-174T) representative of target organs (liver and colon) for food contaminants. Base on their lowest observed adverse effect concentration, the genotoxic potency of each heavy metal in each cell line was ranked in decreasing order, NaAsO₂  > CdCl₂  > PbCl₂ (only in LS-174T cells) > As₂ O₅  > SbCl₃  > K₂ TeO₃  > As₂ O₃ . No significant genotoxicity was observed with the other heavy metals tested. Cell viability data indicate that several heavy metals (As, Cd, Co, Ni, Sb, and Te) induce cytotoxicity at high concentrations, whereas an increase in the number of cells was observed for lead concentrations >100 µM in both cell lines tested, suggesting that lead stimulates cell growth. All these results highlight the possible human health hazards associated with the presence of heavy metals present in food. Environ. Mol. Mutagen. 59:202-210, 2018. © 2017 Wiley Periodicals, Inc.

Combinations of genotoxic tests for the evaluation of group 1 IARC carcinogens

Many of the known human carcinogens are potent genotoxins that are efficiently detected as carcinogens in human populations but certain types of compounds such as immunosuppressants, sex hormones, etc. act via non-genotoxic mechanism. The absence of genotoxicity and the diversity of modes of action of non-genotoxic carcinogens make predicting their carcinogenic potential extremely challenging. There is evidence that combinations of different short-term tests provide a better and efficient prediction of human genotoxic and non-genotoxic carcinogens. The purpose of this study is to summarize the in vivo and in vitro comet assay (CMT) results of group 1 carcinogens selected from the International Agency for Research on Cancer and to discuss the utility of the comet assay along with other genotoxic assays such as Ames, in vivo micronucleus (MN), and in vivo chromosomal aberration (CA) test. Of the 62 agents for which valid genotoxic data were available, 38 of 61 (62.3%) were Ames test positive, 42 of 60 (70%) were in vivo MN test positive and 36 of 45 (80%) were positive for the in vivo CA test. Higher sensitivity was seen in in vivo CMT (90%) and in vitro CMT (86.9%) assay. Combination of two tests has greater sensitivity than individual tests: in vivo MN + in vivo CA (88.6%); in vivo MN + in vivo CMT (92.5%); and in vivo MN + in vitro CMT (95.6%). Combinations of in vivo or in vitro CMT with other tests provided better sensitivity. In vivo CMT in combination with in vivo CA provided the highest sensitivity (96.7%).

A study on the investigation of cadmium chloride genotoxicity in rat bone marrow using micronucleus test and chromosome aberration analysis

In this study, we investigated the genotoxic and cytotoxic potential of cadmium chloride (CdCl2)in Wistar rat tibia bone marrow cells, using the structural chromosomal aberration (SCA) and micronucleus (MN) test systems. CdCl2 was administered to adult female rats as repeated i.p. doses of 0.5 mg/kg b.w. for 18 week (four months) at 48 h intervals. Mitomycin C (MMC) was used as a positive control (2 mg/kg b.w.). This study shows that cadmium chloride treatment significantly induced the frequency of micronucleus in polychromatic erythrocytes in tibia bone marrow. This increase in micronucleus frequency shows that cadmium has a genotoxic effect on bone marrow at this level. Also, in order to determine cytotoxicity in bone marrow, the ratio of polychromatic erythrocytes to normochromatic erythrocytes was calculated in bone marrow. The results of this study indicate that CdCl2 decreased this ratio. The decrease of this ratio in bone marrow shows CdCl2 may lead to cytotoxicity. We have reported that 0.5 mg/kg-level chronic exposure to cadmium (Cd) has an injurious effect on bone marrow. Our findings indicate that CdCl2 has a cytotoxic and genotoxic effect on rat bone marrow at chronic exposure.

Recent advances in in vivo genotoxicity testing: prediction of carcinogenic potential using comet and micronucleus assay in animal models

Genotoxic events have been known as crucial step in the initiation of cancer. To assess the risk of cancer, genotoxicity assays, including comet, micronucleus (MN), chromosomal aberration, bacterial reverse, and sister chromatid exchange assay, can be performed. Compared with in vitro genotoxicity assay, in vivo genotoxicity assay has been used to verify in vitro assay result and definitely provide biological significance for certain organs or cell types. The comet assay can detect DNA strand breaks as markers of genotoxicity. Methods of the in vivo comet assay have been established by Japanese Center for the Validation of Alternative Methods (JaCVAM) validation studies depending on tissue and sample types. The MN can be initiated by segregation error and lagging acentric chromosome fragment. Methods of the in vivo MN assay have been established by Organization for Economic Co-operation and Development (OECD) test guidelines and many studies. Combining the in vivo comet and MN assay has been regarded as useful methodology for evaluating genetic damage, and it has been used in the assessment of potential carcinogenicity by complementarily presenting two distinct endpoints of the in vivo genotoxicity individual test. Few studies have investigated the quantitative relation between in vivo genotoxicity results and carcinogenicity. Extensive studies emphasizes that positive correlation is detectable. This review summarizes the results of the in vivo comet and MN assays that have investigated the genotoxicity of carcinogens as classified by the International Agency for Research on Cancer (IARC) carcinogenicity database. As a result, these genotoxicity data may provide meaningful information for the assessment of potential carcinogenicity and for implementation in the prevention of cancer.

Cytotoxic and clastogenic activity of CdCl2 in human lymphocytes from different donors

The sensitivity of human lymphocytes from different donors to CdCl2 using a complex of methods for determination of cytotoxicity and genotoxicity was studied. As endpoints for cytotoxicity the mitotic index (MI) and apoptosis were evaluated. To indicate genotoxicity chromosome aberrations test (CA) was used. The results indicate an individual sensitivity of lymphocytes to CdCl2-induced damage, which is directly depending on the concentration (10(-6), 10(-5), 5×10(-5), 10(-4)mol/l) applied. The assessment of the toxic and genotoxic effect using various endpoints allows more complete risk estimation for organisms exposed to heavy metals. The results have direct practical significance for threat evaluation in humans.

Histopathology and cytotoxicity as biomarkers in treated rats with cadmium and some therapeutic agents

The present study aimed to investigate the protective role of ascorbic acid (vitamin C) and zinc (Zn) against cadmium (Cd) induced histopathological changes in tissues of liver, kidney, lung and testis of rats as well as chromosomal aberrations. For this purpose, 60 male albino rats were divided into six groups; each group contained 10 animals. The first group served as control and was given only distilled water. The second and third groups received distilled water supplemented with 2 g ascorbic acid/l and 500 mg Zn/l, respectively. The fourth group received a daily oral dose containing 3 mg Cd/kg b.w. (1/30 LD50). The fifth group received Cd + ascorbic acid (3 mg Cd/kg b.w. + 2 g ascorbic acid/l), while the sixth group received Cd + Zn (3 mg Cd/kg b.w. +500 mg Zn/l). The treatment in all groups lasted for 90 consecutive days. Rats exposed to cadmium showed severe histopathological changes in the liver, kidney, lung and testicular tissues as well as chromosomal aberrations such as: break, ring, centromeric separation and polyploidy. Co-treatment with zinc partially improved the histopathological changes and chromosomal aberrations while co-treatment with vitamin C exhibited a more protective role and markedly reduced tissues damage induced by Cd.

The identification of apolipoprotein C-I in rare minnow (Gobiocypris rarus) and its expression following cadmium exposure

Cadmium (Cd) is a ubiquitous environment contaminant that has been detected in a variety of terrestrial and aquatic organisms. In our study, rare minnow were exposed to 0.4 mg/L Cd(2+) solution, fish tissues including gill, intestine, kidney, liver, muscle, and spleen were collected at 1, 6, 12, 24 and 48 h after exposure. Differential expression sequence tags (ESTs) were screened and an EST similar to Hemibarbus mylodon apolipoprotein C-I (ApoC-I) was identified. The ApoC-I cDNA had been obtained with the sequence of 583 bp, which can code 84 amino acids. The transcription expression patterns of ApoC-I were compared after Cd exposure with the real-time PCR in the above tissues. ApoC-I regulation was prominent in spleen, muscle, gill and liver and moderate in kidney and intestine. This suggests a complex transcriptional regulation of ApoC-I expression following Cd exposure.

Cadmium-induced lipid peroxidation and changes in antioxidant defense system in the rat testes: protective role of coenzyme Q(10) and vitamin E

The aim of this study was to investigate the protective role of coenzyme Q(10) (CoQ(10), 20mg/kg) and Vitamin E (Vit E, 20 IU/kg) alone or in combination against cadmium (Cd, 0.4 mg/kg) induced lipid peroxidation and changes in antioxidant defense system in the rat testes. The obtained results showed that Cd increased lipid peroxidation in the testes, suggesting that Cd-induced oxidative stress, while CoQ(10) and Vit E treatment reversed this change to control values. Acute intoxication with Cd was followed by significantly decreased activity of antioxidant enzymes (SOD, CAT, GSH-Px, GR and GST). Vitamins C and E concentrations also significantly declined in Cd-exposed rat testes. Treatment with CoQ(10) and Vit E reversed Cd-induced alterations of antioxidant defense system and significantly prevented Cd-induced testes damage. These results suggest that both CoQ(10) and Vit E function as a potent antioxidant in protection of rats testes against the oxidative stress induced by Cd.

Role of α-tocopherol in cadmium-induced oxidative stress in Wistar rat's blood, liver and brain

Cadmium (Cd) a highly toxic metal is considered to be a multitarget toxicant, and it accumulates principally in the liver and kidney after absorption. In vivo studies of mouse and rat liver have shown that apoptosis plays a primary role in Cd-induced hepatotoxicity. However, the detailed mechanisms by which toxic metals such as Cd produce their effects are still largely unknown. The present study aimed at investigating the consequences of exposure to Cd, alpha-tocopherol and their combination on stress biochemical parameters (lipoperoxidation and protein carbonyls levels). Male albino Wistar rats (1 month old) were treated intravenously with cadmium (2 mg CdCl(2)/kg body weight/day), and alpha-tocopherol (100 mg/kg body weight/day), or with alpha-tocopherol+Cd (100 mg Vit E/kg body weight, 2 mg CdCl(2)/kg). The lipoperoxidation was measured by the thiobarbituric acid reactive substances (TBARS) method and oxidatively generated damage to proteins by determining carbonyl (DNPH) levels. Among the hematological parameters measured the haematocrit value and haemoglobin concentration were significantly decreased in the blood of Cd-treated rats. A significant increase was observed in the level of malondialdehyde (MDA) and protein carbonyls in the cadmium exposed group compared to control group (p<0.001), and these values were decreased after administration of alpha-tocopherol (group 4). The activity of lactate dehydrogenase in rat liver and brain showed a significant increase as compared to that found in the control group and significant decrease of catalase and superoxide dismutase activities. In the liver of the Cd-treated group the contents of reduced glutathione were decreased. Our results suggest that cadmium induces an oxidation of cellular lipids and proteins and that administration of alpha-tocopherol can reduce Cd-induced oxidative stress and improve the glutathione level together with other biochemical parameters.

Protective effect of zinc supplementation on blood antioxidant defense system in rats exposed to cadmium

The aim of this study was to assess the effects of subchronic exposure to cadmium (Cd) on the antioxidant defense system of red blood cells (RBCs) and lipid peroxide concentration in the plasma, as well as the possible protective role of zinc (Zn). For this purpose, 60 male Wistar rats (8 weeks old) were divided into three groups: the first group was exposed to Cd in the form of CdCl(2), administered in five doses (each of 0.4mg Cd/kg BW) on days 5, 10, 15, 20 and 25, giving a total dose of 2mg Cd/kg BW, i.p.; the second group was simultaneously exposed to Zn and Cd with the same timeline and the same doses of Cd as the first group but with, in addition, injections of Zn in the form of ZnCl(2), administered in doses of 0.8mg Zn/kg BW, giving a total dose of 4mg Zn/kg BW, i.p.; a control group received 0.5mL of physiological saline in an identical manner. It was shown that exposure to Cd induced a significant decrease (p<0.05) in superoxide dismutase (Zn/Cu SOD) and catalase (CAT) activities in RBCs. Increased lipid peroxide concentration, measured by thiobarbituric acid reactive substances (TBARS), was also observed in the plasma of cadmium-exposed rats. Cd had no effect on glutathione peroxidase (GSH-Px) activity. Zn administration had a beneficial effect on the Cd-induced decrease in Zn/Cu SOD activity (p<0.05) but not on CAT activity. Animals receiving Cd and Zn simultaneously had significantly (p<0.05) lower concentrations of lipid peroxides than rats exposed to Cd alone. Our results indicate that Cd causes oxidative stress and that Zn supply in conditions of exposure to Cd can partially protect against Cd-induced oxidative stress.

The in vitro immune modulation by cadmium depends on the way of cell activation

Among environmental contaminants known for their toxicity and worldwide distribution, heavy metals are of primary concern. Although the toxicology of cadmium (Cd) has been extensively studied, little information is available on the immunomodulation driven by exposure to low doses of Cd. We aimed to evaluate the immunomodulatory effects elicited by short-term exposure of human immunocompetent cells to low biologically relevant doses of Cd in two activation models. Human peripheral blood mononuclear cells, activated either by bacterial antigens (heat-killed Salmonella Enteritidis) or monoclonal antibodies (mAb: anti-CD3/anti-CD28/anti-CD40), were exposed to Cd acetate for 24h. Cell vitality was determined by MTT assay, cytokine release by ELISA, and cytokine gene expression by real-time RT-PCR. The results demonstrated that, in addition to the known toxic effects of Cd, doses from 0.013 to 13.3 microM exert differential effects on cytokine production. In the case of mAb-activation, secretion of interleukin (IL)-1 beta, tumour necrosis factor (TNF)-alpha and interferon (IFN)-gamma was greatly inhibited at low Cd doses compared to production of IL-4 and IL-10. This indicates a type-2-biased immune response. Under stimulation by bacterial antigens, release of IL-10 was highly suppressed compared to that of IFN-gamma and TNF-alpha; IL-4 was undetectable. These results imply that low Cd doses exert immunomodulatory effects and the direction of this modulation depends on the pathway to cell activation. Overall, Cd polarizes the immune response toward type-2 in cells stimulated via T cell receptors. However, a polarized type-1 response induced by bacterial antigens could not be overwhelmed by the effects of Cd.

Cadmium-induced genotoxicity, cytotoxicity and lipid peroxidation in Allium sativum and Vicia faba

Cadmium (Cd) is one of the most toxic environmental pollutants affecting cytogenetically the various organisms. The cytogenetic damage in root tip cells exposed to cadmium nitrate (CdNO3) solutions at four different concentrations (1, 10, 100 and 200 microM) was evaluated with biological tests based on micronucleus (MN) assay in two plant species, Allium sativum and Vicia faba. Additionally to the cytogenetic analysis, lipid peroxidation analyses were performed in both A.sativum and V.faba roots. Cd enhanced the MN frequency in both A.sativum and V.faba root tip cells, but no dose-dependent. Induction of MN is not depending on CdNO3 concentrations. Besides, high concentrations of Cd decreased the mitotic index and caused the delay in mitosis stages in both plants, mainly in V.faba. On the other hand, lipid peroxidation was significantly enhanced with external Cd in V.faba. The results clearly indicate that high concentrations of cadmium induce the lipid peroxidation resulting in oxidative stress that may contribute to the genotoxicity and cytotoxicity of Cd ions.

Cadmium at a non-toxic dose alters gene expression in mouse testes

The testes are important targets of cadmium (Cd)-induced toxicity and carcinogenicity in rodents. Exposure to Cd at environmentally relevant low levels is a significant human health concern, but the effects of Cd on the rodent testes at doses that do not cause overt lesions are poorly defined. We used cDNA microarray and quantitative real-time RT-PCR assays to determine gene expression profiles in the testes of CD-1 mice 12-72 h after a single s.c. injection of 5 micromol/kg CdCl2. This dose of Cd did not produce overt histopathological changes, but clearly altered the expression of some genes that are likely to be important in toxicity responses. The most significant changes in gene expression occurred 24 h after treatment, corresponding to when the highest level of Cd was detected in the testes. Increased expression of the C-myc and Egr1 genes strongly suggests acute stress responses. Repressed expression of cell cycle-regulated cyclin B1 and CDC2 proteins indicates a potential for causing G2/M arrest and disturbance of meiosis. Decreased expression of pro-apoptotic genes, particularly Casp3, and DNA repair genes possibly contributes to Cd-induced carcinogenesis. These results indicate that changes in gene expression occur well before overt effects of Cd-induced testicular toxicity and carcinogenicity are apparent.

Biomonitoring results and cytogenetic markers among harbour workers with potential exposure to river silt aerosols

BACKGROUND

Workers on dredgers and lighters on rivers are potentially exposed to a variety of substances.

AIMS

To determine the internal load of heavy metals and arsenic as well as levels of cytogenetic markers in workers exposed to river silt aerosols.

METHODS

One hundred exposed workers were examined up to eight times within three years. Additionally, 100 control workers were studied once. Blood samples were analysed for lead, mercury, and cadmium. Additionally, micronuclei frequency and sister chromatid exchange (SCE) rates were determined. Urinary samples were analysed for cadmium, mercury, nickel, chromium, and arsenic. Information on potential confounders, such as smoking habits and consumption of fish were assessed.

RESULTS

Apart from some increased concentrations of mercury in blood (maximum 14.6 microg/l) and arsenic in urine (maximum 356.5 microg/l) all measurements were within reference values. None of the exposure and effect markers were found to be significantly increased in exposed workers compared to non-exposed controls. In multiple linear regression models, mercury levels in blood as well as the concentration of arsenic in urine were strongly related to fish consumption. Cadmium levels in blood as well as urinary cadmium concentrations were strongly related to smoking habits. After adjusting for smoking habits, SCE rates were associated with cadmium levels in blood.

CONCLUSION

Increased exposure levels or enhanced levels of cytogenetic markers were not found in workers exposed to river silt aerosols. However, cadmium exposure in blood was related to SCE frequency.

Genotoxicity modulation by cadmium treatment: studies in the Drosophila wing spot test

The genotoxic activity of cadmium chloride (CC) has been evaluated in the somatic mutation and recombination test (SMART) in Drosophila melanogaster. In addition, its possible modulating effect on the genotoxicity of two known mutagenic agents, potassium dichromate (PDC) and ethyl methanesulfonate (EMS), was investigated. Three different types of combined treatments of CC with the two genotoxins were performed: pretreatment, cotreatment, and posttreatment. The SMART assay is based on the principle that loss of heterozygosity for the recessive markers, multiple wing hairs (mwh) and flare-3 (flr(3)), leads to the formation of mutant clones in the imaginal disks of larvae, which are expressed as mutant spots on the wings of adult flies. Thus, after adult emergence, the wings of the adult flies were scored for the presence of single and/or twin spots. Our results show that CC alone was not effective in increasing the frequency of any of the three categories of spots (small, large, and twin). In the cotreatment experiments, CC increased the genotoxicity of PDC but it decreased the genotoxicity of EMS. No effects of CC were observed in the pretreatment or posttreatment experiments; however, only low concentrations of CC, PDC, and EMS were tested in the pretreatment assays due to the high toxicity of the treatment. Although our results with PDC are consistent with the hypothesis that cadmium can interfere with repair mechanisms, the EMS data suggest that other modulating mechanisms are also involved in the genotoxicity of this metal.

A systematic review of cytogenetic studies conducted in human populations exposed to cadmium compounds

BACKGROUND

Exposure to cadmium fumes or dusts has been associated with an increased risk of lung cancer and the characterisation of the genotoxic potential of cadmium compounds is, among other possible mechanisms, an important element in the assessment of the carcinogenic hazard of the element. While there is some evidence that in experimental systems, cadmium compounds may exert genotoxic effects, the results of the epidemiological studies having examined cytogenetic endpoints in humans exposed to cadmium appear conflicting. Therefore, a systematic review was undertaken to assess whether a cytogenetic effect of cadmium exposure is supported by the studies with the strongest design.

METHODS

The relevant literature was identified through several databases and assessed with a check-list by two reviewers. Causes of heterogeneity between studies were looked for. Results were extracted and the strength of the evidence was evaluated with causality criteria.

RESULTS

No studies met the criteria for being considered as very convincing. Several factors were identified that could explain contradictory findings (small sample size, selection bias, insufficient characterisation of exposure, lack of consideration of confounders) but their actual impact could not be conclusively assessed with the published information. Importantly, it should be recognised that the absence of a clear mechanism for the cytogenetic action of cadmium compounds did not allow to select the most appropriate endpoint to be examined.

CONCLUSIONS

No clear association between cadmium exposure and cytogenetic endpoint appeared but no definite conclusion can be drawn from the existing studies in humans. Future research efforts should mainly focus on experimental studies to understand how cadmium compounds could produce genotoxic/carcinogenic effects, in order to target the most relevant endpoint to be examined in humans.

In vivo genotoxic effect of cadmium chloride in mice leukocytes using comet assay

The alkaline single cell gel electrophoresis (SCGE) or "comet" assay under alkaline conditions was used to measure DNA damage in the leukocytes of Swiss Albino male mice exposed to cadmium chloride (CdCl(2)). The effect of CdCl(2) was studied after a single acute oral administration of a range of doses starting from 0.5 to 128.0 mg/kg b.wt of CdCl(2). The samples of whole blood were collected from each mouse at 24, 48, 72, and 96 h post-treatment to study single/double strand breaks in DNA. A significant increase in mean comet tail length indicating DNA damage was observed with CdCl(2) at 24 h post-treatment (P<0.05) with CdCl(2) when compared to controls. A gradual decrease in the mean tail length was observed at 48 h post-treatment indicating repair of the damaged DNA. The mean tail length showed a dose-related increase and time-dependent decrease after treatment with CdCl(2) when compared to controls. The study also confirms that the comet assay is a sensitive and rapid method to detect DNA damage caused by heavy metal like Cadmium (Cd).

Effect of fetal calf serum on the cadmium clastogenicity

Inconsistent results among reports on cadmium genotoxicity revealed that certain confounding factors might significantly influence the outcomes of assessment. In Chinese hamster ovary (CHO-W8) cells, chromosome aberration induced by six different cadmium compounds was found positively associated with intracellular cadmium concentration. A parallel association was also observed among different CHO strains treated with same cadmium compound, the cadmium acetate. Both the cadmium-induced chromosome aberration and cadmium uptake were influenced by the presence of fetal calf serum (FCS). The presence of 10% FCS during the 2h treatment period greatly retarded the cellular cadmium uptake, and concurrently reduced the chromosome aberration induction. Other factors such as specific cadmium anion involved and the duration of cadmium treatment period in the investigation also influenced the assessment results of cadmium-induced chromosome aberration. In the protocol with a 2h pulse treatment, cadmium acetate, chloride and sulfate induced more chromosome aberration than cadmium nitrate, carbonate and oxide. When cadmium was present in the culture of the entire treatment period for 18 h, the results went the opposite way. Cadmium nitrate, carbonate and oxide induced significant chromosome aberration, while other three cadmium compounds gave negative results. Cadmium compounds did not induce significant SCE at the same dose level that yielded significant chromosome aberration induction, either in the protocol with the short pulse or long treatment period.

Genotoxic effects after in vivo exposure of vegetable extracts containing heavy metals from the Dhapa area of Calcutta, India. I. Effects of cauliflower, spinach and radish

Several reports have indicated that the sewage-fed vegetables of the Dhapa area, near the city of Calcutta, contain a very high amount of heavy metals. Currently 800 ha of land is being utilised throughout the year to cultivate more than eight types of vegetables, with a production of about 147 tonnes per day. A major population of Calcutta consumes these vegetables grown in the Dhapa area. Recently there has been huge pressure on the State Government to ban vegetables grown in the Dhapa area for human consumption. For this reason, we have studied the genotoxic effects of some of the most commonly used vegetable extracts from the Dhapa area after in vivo acute exposure in mice as measured by chromosomal aberrations (CA) and sister chromatid exchanges (SCE) to find out the minimum threshold dose to induce CA and SCE. Three different concentrations of the three most commonly used vegetable extracts (cauliflower, spinach, radish) were fed by gavage to mice for the study of CA and SCE. A significant increase in CA was observed only at the highest concentration of all the vegetable extract-treated groups when compared with the solvent control. A significant increase in SCE were observed in the middle and high doses of spinach and only the high dose of cauliflower and radish extract-treated series when compared with distilled water control. The lowest dose was equivalent to approximately 1 kg of vegetables consumed by a human (60 kg body weight) in a day. The middle and high doses of each vegetable extract were much higher than the normal amount of vegetables that a human can consume per day. So the minimum dose for inducing SCE and CA was much higher than the amount a human can consume in a day. Therefore this study indicates that these vegetables are safe for human consumption up to a certain limit, and attention should be given to reducing the heavy metal contents in the soil and sewage of the Dhapa area to thus reduce the heavy metal concentrations in the vegetables.