Mutagenesis and comutagenesis by lead compounds

Health Risk Assessment for Potentially Toxic Elements Accumulation in Amaranthaceae Family Cultivars and their Correlation with Antioxidants and Antinutrients

Delhi's agricultural hub, nestled along the Yamuna floodplains, faces soil and water contamination issues. Utilizing organic waste composts is gaining traction to improve soil quality, but uncertainties remain about their efficacy in reducing harmful elements. The study examined three Amaranthaceae cultivars, comparing organic waste composts with chemical fertilizer to evaluate correlations between heavy metals, antioxidants, and antinutrients to assess their bioremediation potential. "Heavy metals" or "potentially toxic elements (PTE)" levels in soil and leaves were measured by ICP-MS, while antioxidants and antinutrients were analyzed with UV-VIS spectroscopy. The study revealed higher PTE levels in floodplain soil, with Cr, Ni, and Cd exceeding safe limits in all cultivars. Compost amendments reduced these pollutants by 28% compared to chemical fertilizers, decreasing bioaccumulation by 20%. Health risk assessments showed lower risks in compost-amended cultivars. Additionally, compost amendment displayed a stronger negative correlation between PTE and antioxidants, suggesting effective bioremediation. Overall, compost amendments offer promise for mitigating PTE in metropolitan floodplains.

Microsatellite Instability Assay as a Potential Approach to Evaluate Genotoxicity: Lead Exposure in a Nestling Passerine Bird at the Stage of Intensive Erythropoiesis

Although many avian studies have investigated the toxic effects of lead on important biochemical and physiological processes, organ and system function, and behavior, studies evaluating the specific genotoxic effects of exposure to lead are scarce. Nowadays, rapid technological advances can provide new molecular techniques in this regard. In this study, as a novel approach in bird studies, we used a panel of ten microsatellite loci to investigate the microsatellite instability (MSI) in response to experimental lead intoxication in a common hole-nesting species, the great tit Parus major. For this purpose, an experiment based on an intentional single supplementation of a lead (II) acetate trihydrate compound was conducted, with the use of two different doses, applied to randomly chosen great tit nestlings from randomly selected broods, being at the stage of intensive erythropoiesis. Although this preliminary study did not find any MSI in the seven microsatellite markers retained for the final comparison, it contributes to the examination of this molecular technique in field conditions as being potentially applicable in ecotoxicological bird studies. We believe that certain issues should be considered in finding an explanation for our result. First, the single doses of lead used in this study may have been too weak to induce genetic instability. Second, the panel of microsatellite markers studied may have been unsusceptible to lead genotoxicity in general. Third, the relatively short time interval (5 days) between the experimental procedure (lead exposure) and the sampling of post-exposure material (blood) for genetic analyses could have limited the effect of lead genotoxicity. Further analyzes are needed to verify these findings and to evaluate the scope of application of the MSI analysis in wild bird population studies.

Examining the Effect of a Chitosan Biopolymer on Alkali-Activated Inorganic Material for Aqueous Pb(II) and Zn(II) Sorption

Biopolymers and alkali-activated materials have attracted a great deal of attention as adsorbents for the removal of heavy metal contaminants from aqueous solutions. Both materials are sustainable and feature unique properties, but biopolymers are relatively more expensive or difficult to prepare and exhibit low mechanical and surface properties, a narrow pH range, and thermal stability. In this study, hybrid adsorbents were prepared from both types of material, by alkali activation of low-cost fly ash precursors accompanied by incorporation of 0-2%_mass chitosan biopolymer. Two types of alkaline activating solutions, NaOH and Na₂SiO₃, were employed to generate two sets of hybrid adsorbents with varying chitosan contents. The effect of the chitosan dosage on the aqueous Pb(II) and Zn(II) sorption efficiency was also investigated. The adsorbents exhibited 98-100% removal efficiencies for both metals, but the sorption of Zn(II) was generally higher than that of Pb(II). The addition of 0.1-2.0%_mass chitosan resulted in very little improvement in the overall efficiency of the adsorbents. In contrast, 0.05%_mass chitosan led to a decrease in the sorption efficiency; this was linked to the decrease in the adsorbents' ζ potential. The Na₂SiO₃-activated materials featured larger BET surface areas and better overall sorption performance, while the NaOH-activated materials showed the worst Pb(II) sorption performance and hence more noticeable improvement upon addition of chitosan. Mechanistic investigation shows that the sorption process follows second-order kinetics and is a chemisorption-driven process.

Analytic and chemometric assessments of the native probiotic bacteria and inulin effects on bioremediation of lead salts

BACKGROUND

Lead (Pb²⁺ ) is one of the most toxic heavy metals and can be found in various quantities in the environment. The five native probiotic bacteria and inulin were used to assess in vitro lead nitrate and lead acetate binding capacities, as well as removal potentials.

RESULTS

The highest decrease in media pH was seen for samples containing a combination of Lactobacillus paracasei IRBC-M 10784, lead nitrate and inulin (5.30 ± 0.012). The presence of inulin in the environment accelerated decreases in the pH of all samples with no significance. In all groups, lead nitrate-containing samples included maximum pH decreases. From the highest to the lowest, the ability of lead removal was linked to Lactobacillus acidophilus PTCC-1932 (88.48%), Bifidobacterium bifidum BIA-7 (85.32%), Bifidobacterium lactis BIA-6 (85.24%), Lactobacillus rhamnosus IBRC-M 10782 (83.18%) and L. paracasei IRBC-M 10784 (80.66%). Most species included the highest decrease in lead nitrate. Fourier-transform infrared spectroscopy (FTIR) analysis demonstrated that various functional groups (hydroxyl, carboxylic, carbonyl, amino and amide binds) on the bacterial cell wall were involved in lead ion binding during incubation. Principal component analysis of the FTIR results showed differences with respect to treated groups and control groups.

CONCLUSION

The results obtained in the present study reveal that the simultaneous use of native probiotics and inulin can be an effective and safe approach for removing various toxic substances, especially Pb. © 2021 Society of Chemical Industry.

Gut microbiota of animals living in polluted environments are a potential resource of anticancer molecules

Cancer is a prominent cause of morbidity and mortality worldwide, in spite of advances in therapeutic interventions and supportive care. In 2018 alone, there were 18·1 million new cancer cases and 9·6 million deaths indicating the need for novel anticancer agents. Plant-based products have often been linked with protective effects against communicable and non-communicable diseases. Recently, we have shown that animals such as crocodiles thrive in polluted environments and are often exposed to carcinogenic agents, but still benefit from prolonged lifespan. The protective mechanisms shielding them from cancer could be attributed to the immune system, and/or it is possible that their gut microbiota produce anticancer molecules. In support, several lines of evidence suggest that gut microbiota plays a critical role in the physiology of its host. Here, we reviewed the available literature to assess whether the gut microbiota of animals thriving in polluted environment possess anticancer molecules.

Advances in Understanding How Heavy Metal Pollution Triggers Gastric Cancer

With the development of industrialization and urbanization, heavy metals contamination has become a major environmental problem. Numerous investigations have revealed an association between heavy metal exposure and the incidence and mortality of gastric cancer. The mechanisms of heavy metals (lead, cadmium, mercury, chromium, and arsenic) contamination leading to gastric cancer are concluded in this review. There are four main potential mechanisms: (1) Heavy metals disrupt the gastric mucosal barrier by decreasing mucosal thickness, mucus content, and basal acid output, thereby affecting the function of E-cadherin and inducing reactive oxygen species (ROS) damage. (2) Heavy metals directly or indirectly induce ROS generation and cause gastric mucosal and DNA lesions, which subsequently alter gene regulation, signal transduction, and cell growth, ultimately leading to carcinogenesis. Exposure to heavy metals also enhances gastric cancer cell invasion and metastasis. (3) Heavy metals inhibit DNA damage repair or cause inefficient lesion repair. (4) Heavy metals may induce other gene abnormalities. In addition, heavy metals can induce the expression of proinflammatory chemokine interleukin-8 (IL-8) and microRNAs, which promotes tumorigenesis. The present review is an effort to underline the human health problem caused by heavy metal with recent development in order to garner a broader perspective.

Indels, structural variation, and recombination drive genomic diversity in Plasmodium falciparum

The malaria parasite Plasmodium falciparum has a great capacity for evolutionary adaptation to evade host immunity and develop drug resistance. Current understanding of parasite evolution is impeded by the fact that a large fraction of the genome is either highly repetitive or highly variable and thus difficult to analyze using short-read sequencing technologies. Here, we describe a resource of deep sequencing data on parents and progeny from genetic crosses, which has enabled us to perform the first genome-wide, integrated analysis of SNP, indel and complex polymorphisms, using Mendelian error rates as an indicator of genotypic accuracy. These data reveal that indels are exceptionally abundant, being more common than SNPs and thus the dominant mode of polymorphism within the core genome. We use the high density of SNP and indel markers to analyze patterns of meiotic recombination, confirming a high rate of crossover events and providing the first estimates for the rate of non-crossover events and the length of conversion tracts. We observe several instances of meiotic recombination within copy number variants associated with drug resistance, demonstrating a mechanism whereby fitness costs associated with resistance mutations could be compensated and greater phenotypic plasticity could be acquired.

DNA Damage, Cell Cycle Arrest, and Apoptosis Induction Caused by Lead in Human Leukemia Cells

In recent years, the industrial use of lead has been significantly reduced from paints and ceramic products, caulking, and pipe solder. Despite this progress, lead exposure continues to be a significant public health concern. The main goal of this research was to determine the in vitro mechanisms of lead nitrate [Pb(NO₃)₂] to induce DNA damage, apoptosis, and cell cycle arrest in human leukemia (HL-60) cells. To reach our goal, HL-60 cells were treated with different concentrations of Pb(NO₃)₂ for 24 h. Live cells and necrotic death cells were measured by the propidium idiode (PI) assay using the cellometer vision. Cell apoptosis was measured by the flow cytometry and DNA laddering. Cell cycle analysis was evaluated by the flow cytometry. The result of the PI demonstrated a significant (p < 0.05) increase of necrotic cell death in Pb(NO₃)₂-treated cells, indicative of membrane rupture by Pb(NO₃)₂ compared to the control. Data generated from the comet assay indicated a concentration-dependent increase in DNA damage, showing a significant increase (p < 0.05) in comet tail-length and percentages of DNA cleavage. Data generated from the flow cytometry assessment indicated that Pb(NO₃)₂ exposure significantly (p < 0.05) increased the proportion of caspase-3 positive cells (apoptotic cells) compared to the control. The flow cytometry assessment also indicated Pb(NO₃)₂ exposure caused cell cycle arrest at the G₀/G₁ checkpoint. The result of DNA laddering assay showed presence of DNA smear in the agarose gel with little presence of DNA fragments in the treated cells compared to the control. In summary, Pb(NO₃)₂ inhibits HL-60 cells proliferation by not only inducing DNA damage and cell cycle arrest at the G₀/G₁ checkpoint but also triggering the apoptosis through caspase-3 activation and nucleosomal DNA fragmentation accompanied by secondary necrosis. We believe that our study provides a new insight into the mechanisms of Pb(NO₃)₂ exposure and its associated adverse health effects.

Heavy metal toxicity and the environment

Heavy metals are naturally occurring elements that have a high atomic weight and a density at least five times greater than that of water. Their multiple industrial, domestic, agricultural, medical, and technological applications have led to their wide distribution in the environment, raising concerns over their potential effects on human health and the environment. Their toxicity depends on several factors including the dose, route of exposure, and chemical species, as well as the age, gender, genetics, and nutritional status of exposed individuals. Because of their high degree of toxicity, arsenic, cadmium, chromium, lead, and mercury rank among the priority metals that are of public health significance. These metallic elements are considered systemic toxicants that are known to induce multiple organ damage, even at lower levels of exposure. They are also classified as human carcinogens (known or probable) according to the US Environmental Protection Agency and the International Agency for Research on Cancer. This review provides an analysis of their environmental occurrence, production and use, potential for human exposure, and molecular mechanisms of toxicity, genotoxicity, and carcinogenicity.

Combined effect of cadmium, lead, and UV rays on Bacillus cereus using comet assay and oxidative stress parameters

Exposure to environmental chemicals and oxidative stress particularly at low dose levels may produce additive or synergistic interactions not seen in single component exposure. Exposure to cadmium, lead, and ultraviolet rays occurs in many occupational settings, such as pigment and battery production, galvanization, and recycling of electric tools. However, little is known about interactions between heavy metals and ultraviolet rays. This study aimed to evaluate the interactions of ultraviolet rays of 254 nm (UV-B) with cadmium or lead on Bacillus cereus. B. cereus was treated with different concentrations of cadmium or lead followed by exposure to UV-B radiation as combined effect. Photoirradiation of B. cereus with UV-B with exposure to cadmium or lead results in DNA damage, cytotoxicity, depletion of glutathione, and formation of lipid peroxidation. UV-B rays alone enhanced glutathione production which was depleted with lead and high doses of cadmium. Lead alone does not increase DNA breaking. The mechanism behind these interactions might be repair inhibition of oxidative DNA damage, since a decrease in repair capacity will increase susceptibility to reactive oxygen species generated by cadmium or lead. Lipid peroxidation was increased with exposure to UV-B and cadmium or lead. DNA, glutathione, and lipid peroxidation can be used as biomarkers to identify possible environmental contamination in bacteria. One conclusion from this model is the existence of more than multiplicative effects for co-exposures of cadmium or lead and UV rays.

Biochemical changes associated with ascorbic acid-cisplatin combination therapeutic efficacy and protective effect on cisplatin-induced toxicity in tumor-bearing mice

Cisplatin is one of the well-established anticancer drugs being used against a wide spectrum of cancers. However, full therapeutic efficacy of the drug is limited due to development of various toxicities in the host. This study examines the comparative therapeutic effectiveness and toxicities of cisplatin alone and in combination of dietary ascorbic acid (AA) in ascites Dalton's lymphoma-bearing mice. The findings show that the combination treatment of mice with ascorbic acid plus cisplatin has much better therapeutic efficacy against murine ascites Dalton's lymphoma (DL) in comparison to cisplatin alone and this may involve a decrease in reduced glutathione (GSH), catalase activity and increased lipid peroxidation (LPO) in Dalton's lymphoma tumor cells. At the same time, combination treatment indicates a protective role of ascorbic acid against cisplatin-induced tissue toxicities (side effects) in the hosts. Cisplatin-induced histopathological changes in liver, kidney and testes were decreased after combination treatment. The analysis of renal function test (RFT), liver function test (LFT) and sperm abnormalities also suggest an improvement in these parameters after combination treatment. Therefore, it may be concluded that the increased GSH level, catalase activity and decreased LPO in the tissues, i.e., liver, kidney and testes after combination treatment may be involved in its protective ability against cisplatin-induced tissue toxicities in the host.

Evaluation of mesenchymal stem cells in treatment of infertility in male rats

INTRODUCTION

The present study aimed to elucidate the therapeutic effects of mesenchymal stem cells (MSCs) derived from the bone marrow of rats (BM) against toxic effects of lead (Pb) on the male gonads of experimental rats.

METHODS

The experimental animals were exposed to lead in the form of lead nitrate (LN) one quarter of the LD50. The efficacy of MSCs to reduce gonado-totoxicity induced by lead nitrate at 21, 30 and 60 days, was evaluated experimentally in male rats.

RESULTS

The results showed that testosterone levels and semen quality ameliorated following treatment with MSCs. Also, superoxide dismutase, glutathione peroxidase and catalase levels were increased 21, 30 and 60 days post treatment of MSCs. Moreover, a decrease in genomic DNA alteration and percentage of fragmented DNA was recorded after MSCs treatment. Lead nitrate caused degeneration, necrosis, interstitial edema, and reduction in spermatogenic activity in some seminiferous tubules. The LN-induced changes in histopathologic findings of testis were partially reversed by treatment with MSCs. Histological examination of testis showed deformities in morphology of testis in test animals with gross damage within the seminiferous tubules in Lead nitrate group. The LN-induced changes in histopathologic findings of testis were partially reversed by treatment of MSCs.

CONCLUSIONS

It was concluded that lead is a gonadotoxic with a tendency of suppressing semen characteristics and testosterone levels of animals, the presence of MSCs was found to alleviate the toxic effects of lead. We conclude that MSCs derived from the bone marrow of rats can be an effective therapy of LN induced gonado toxicity, thus can contribute to the treatment of infertility.

Heavy metal toxicity and the environment

Heavy metals are naturally occurring elements that have a high atomic weight and a density at least five times greater than that of water. Their multiple industrial, domestic, agricultural, medical, and technological applications have led to their wide distribution in the environment, raising concerns over their potential effects on human health and the environment. Their toxicity depends on several factors including the dose, route of exposure, and chemical species, as well as the age, gender, genetics, and nutritional status of exposed individuals. Because of their high degree of toxicity, arsenic, cadmium, chromium, lead, and mercury rank among the priority metals that are of public health significance. These metallic elements are considered systemic toxicants that are known to induce multiple organ damage, even at lower levels of exposure. They are also classified as human carcinogens (known or probable) according to the US Environmental Protection Agency and the International Agency for Research on Cancer. This review provides an analysis of their environmental occurrence, production and use, potential for human exposure, and molecular mechanisms of toxicity, genotoxicity, and carcinogenicity.

Modified natural clinoptilolite detoxifies small mammal's organism loaded with lead II: genetic, cell, and physiological effects

The detoxification capacity of the clinoptilolite modification KLS-10-MA used as food additive in small mammals, chronically lead-exposed, was proven for the first time. The modified clinoptilolite was prepared based on natural Bulgarian clinoptilolite deposits. As a powder, it was mechanically mixed at 12.5% concentration with the conventional forage for small rodents. Lead in the form of aqueous solution of Pb(NO(3))(2) was diluted in the drinking water. In the ecotoxicological experiment covering 90 days, imprinting control region laboratory mice were used. They were allocated into four groups: group 1, (control): animals fed with conventional food for small rodents and water; group 2: animals fed with conventional food + clinosorbent KLS-10-MA and water; group 3: animals fed with conventional food and water + Pb(NO(3))(2); and group 4: animals fed with conventional food + KLS-10-MA and water + Pb(NO(3))(2). A group of non-exposed healthy animals was fed with conventional forage mixed with KLS-10-MA to prove eventual toxicity of the sorbent and influence on growth performance. The changes in the chromosome structure, mitotic index, erythrocyte form, erythropoiesis, and body weight gain were recorded. On day 90, the following relations were established: Pb-exposed and clinoptilolite-supplemented mice exhibited 2.3-fold lower chromosome aberrations frequency, 2.5-fold higher mitotic index, and 1.5-fold higher percentage normal erythrocytes 1.3-fold higher body weight compared to Pb-exposed and unsupplemented animals. The obtained data showed that the sorbent is practically non-toxic. The results of the present study encourage a further elaboration of a reliable drug based on the tested substance in the cases of chronic lead intoxication.

Peripheral blood signatures of lead exposure

BACKGROUND

Current evidence indicates that even low-level lead (Pb) exposure can have detrimental effects, especially in children. We tested the hypothesis that Pb exposure alters gene expression patterns in peripheral blood cells and that these changes reflect dose-specific alterations in the activity of particular pathways.

METHODOLOGY/PRINCIPAL FINDING

Using Affymetrix Mouse Genome 430 2.0 arrays, we examined gene expression changes in the peripheral blood of female Balb/c mice following exposure to per os lead acetate trihydrate or plain drinking water for two weeks and after a two-week recovery period. Data sets were RMA-normalized and dose-specific signatures were generated using established methods of supervised classification and binary regression. Pathway activity was analyzed using the ScoreSignatures module from GenePattern.

CONCLUSIONS/SIGNIFICANCE

The low-level Pb signature was 93% sensitive and 100% specific in classifying samples a leave-one-out crossvalidation. The high-level Pb signature demonstrated 100% sensitivity and specificity in the leave-one-out crossvalidation. These two signatures exhibited dose-specificity in their ability to predict Pb exposure and had little overlap in terms of constituent genes. The signatures also seemed to reflect current levels of Pb exposure rather than past exposure. Finally, the two doses showed differential activation of cellular pathways. Low-level Pb exposure increased activity of the interferon-gamma pathway, whereas high-level Pb exposure increased activity of the E2F1 pathway.

The genotoxicity of particulate and soluble chromate in sperm whale (physeter macrocephalus) skin fibroblasts

Hexavalent chromium is a marine pollutant of concern, both for the health of ocean ecosystems and for public health. Hexavalent chromium is known to induce genotoxicity in human and other terrestrial mammals. It is also known to be present in both water and air in the marine environment. However, currently there are limited data concerning both chromium levels and its toxicological effects in marine mammals. This study investigated the cytotoxic and genotoxic effects of soluble and particulate hexavalent chromium in sperm whale skin fibroblasts. Both forms of hexavalent chromium induced concentration-dependent increases in cytotoxicity and genotoxicity indicating that these compounds can be a health risk if the whales are exposed to them. These data support a hypothesis that chromium is a concern in the marine environment in general and for the health of sperm whales in particular.

Differences inHPRTmutant frequency among middle-aged Flemish women in association with area of residence and blood lead levels

Biomarkers were measured in residents of Wilrijk and Hoboken, industrial suburbs of the city of Antwerp, and of Peer, a rural municipality in Flanders, Belgium. Persons with known occupational exposures to toxic compounds or commuting over long distances were excluded. Here, we report the hypoxanthine phosphoribosyltransferase gene (HPRT) variant frequencies for 99 non-smoking women aged 50-65 years. HPRT values above the detection limit (V(fpos) values) were observed for 43 subjects (21 from Peer, 22 from Antwerp). The median (10th to 90th percentiles) HPRT variant frequency (V(fpos)) in peripheral lymphocytes was 9.59 (3.44-56.99) for Peer and 3.57 (1.57-13.96) for Antwerp. The V(fpos) value was significantly higher in Peer than in Antwerp, both in terms of crude data (p=0.011) and after correction for age, level of education, smoking status, serum level of selenium and body mass index through analysis of covariance (p=0.011). For the total study population, serum lead concentration showed a non-significant positive correlation with lnV(fpos). In addition, subjects with a blood lead concentration above the median tended to have higher V(fpos) values (9.45x10(-6) for 'high' group versus 5.21x10(-6) for 'low' group; p=0.077 after correction for confounding). Subjects with a serum selenium level above the median tended to have lower V(fpos) values (4.99x10(-6) for 'high' group versus 9.83x10(-6) for 'low' group; p=0.051 after correction for confounding). These data are consistent with an indirect genotoxic effect of lead and with an antimutagenic effect of selenium.

Cytotoxicity and genotoxicity of hexavalent chromium in human and North Atlantic right whale (Eubalaena glacialis) lung cells

Humans and cetaceans are exposed to a wide range of contaminants. In this study, we compared the cytotoxic and genotoxic effects of a metal pollutant, hexavalent chromium [Cr(VI)], which has been shown to cause damage in lung cells from both humans and North Atlantic right whales. Our results show that Cr induces increased cell death and chromosome damage in lung cells from both species with increasing intracellular Cr ion levels. Soluble Cr(VI) induced less of a cytotoxic and genotoxic effect based on administered dose in right whale (Eubalaena glacialis) cells than in human (Homo sapiens) cells. Whereas, particulate Cr(VI) induced a similar cytotoxic effect but less of a genotoxic effect based on administered dose in right whale cells than in human cells. Differences in chromium ion uptake explained soluble chromate-induced cell death but not all of the soluble chromate-induced chromosome damage. Uptake differences of lead ions could explain the differences in particulate chromate-induced toxicity. The data show that both forms of Cr(VI) are less genotoxic to right whale than human lung cells, and that soluble Cr(VI) induces a similar cytotoxic effect in both right whale and human cells, while particulate Cr(VI) is more cytotoxic to right whale lung cells.

A comparison of the effect of lead nitrate on rat liver chromatin, DNA and histone proteins in solution

Although lead is widely recognized as a toxic substance in the environment and directly damage DNA, no studies are available on lead interaction with chromatin and histone proteins. In this work, we have examined the effect of lead nitrate on EDTA-soluble chromatin (SE chromatin), DNA and histones in solution using absorption and fluorescence spectroscopy, thermal denaturation and gel electrophoresis techniques. The results demonstrate that lead nitrate binds with higher affinity to chromatin than to DNA and produces an insoluble complex as monitored at 400 nm. Binding of lead to DNA decreases its Tm, increases its fluorescence intensity and exhibits hypochromicity at 210 nm which reveal that both DNA bases and the backbone participate in the lead-DNA interaction. Lead also binds strongly to histone proteins in the absence of DNA. The results suggest that although lead destabilizes DNA structure, in the chromatin, the binding of lead introduces some sort of compaction and aggregation, and the histone proteins play a key role in this aspect. This chromatin condensation, upon lead exposure, in turn may decrease fidelity of DNA, and inhibits DNA and RNA synthesis, the process that introduces lead toxicity at the chromatin level.

Brain tumor epidemiology: consensus from the Brain Tumor Epidemiology Consortium

Epidemiologists in the Brain Tumor Epidemiology Consortium (BTEC) have prioritized areas for further research. Although many risk factors have been examined over the past several decades, there are few consistent findings, possibly because of small sample sizes in individual studies and differences between studies in patients, tumor types, and methods of classification. Individual studies generally have lacked samples of sufficient size to examine interactions. A major priority based on available evidence and technologies includes expanding research in genetics and molecular epidemiology of brain tumors. BTEC has taken an active role in promoting understudied groups, such as pediatric brain tumors; the etiology of rare glioma subtypes, such as oligodendroglioma; and meningioma, which, although it is not uncommon, has only recently been registered systematically in the United States. There also is a pressing need for more researchers, especially junior investigators, to study brain tumor epidemiology. However, relatively poor funding for brain tumor research has made it difficult to encourage careers in this area. In this report, BTEC epidemiologists reviewed the group's consensus on the current state of scientific findings, and they present a consensus on research priorities to identify which important areas the science should move to address.

Characterization of substrate specificity of dog CYP1A2 using CYP1A2-deficient and wild-type dog liver microsomes

Beagle dogs are commonly used for toxicological and pharmacological studies of drug candidates in the pharmaceutical industry. Recently, we reported a CYP1A2-deficient dog with a nonsense mutation (C1117T). In this study, using CYP1A2-deficient and wild-type dog liver microsomes, substrate specificity of dog CYP1A2 was investigated and compared with human CYP1A2. For this purpose, 11 cytochrome P450 assays were conducted in human or dog liver microsomes, genotyped for the CYP1A2 C1117T mutation. There was no statistical difference between C/C, C/T, and T/T dogs in activities of aminopyrine N-demethylase, aniline hydroxylase, bufuralol 1'-hydroxylase, and midazolam 1'-hydroxylase. On the other hand, activities of phenacetin O-deethylase, ethoxyresorufin O-deethylase, and tacrine 1-hydroxylase, which were catalyzed by human CYP1A2, were significantly lower in T/T dogs than C/C dogs, indicating that dog and human CYP1A2 was responsible for these activities. However, dog CYP1A2 was not involved in caffeine metabolism, a marker activity for human CYP1A2. As for endogenous substances, our results indicated that human CYP1A2, but not dog CYP1A2, is responsible for melatonin 6-hydroxylase, 9-cis-retinal oxidase, and estradiol 2-hydroxylase activity. In conclusion, tacrine, ethoxyresorufin, and phenacetin are probe substrates for CYP1A2 not only in humans but also in dogs. However, caffeine, melatonin, 9-cis-retinal, and estradiol, which are substrate for human CYP1A2, are not good substrates for dog CYP1A2. The finding that there are species differences in substrate specificity of CYP1A2 between humans and beagle dogs is an important issue and must be considered for preclinical studies using beagle dogs.

Activation of protein kinase Calpha signaling prevents cytotoxicity and mutagenicity following lead acetate in CL3 human lung cancer cells

Protein kinase C (PKC) family of serine/threonine protein kinases is sensitive signaling transducers in response to lead acetate (Pb) that could transmit phosphorylation cascade for proliferation and de-differentiation of neural cells. However, little is known as to the impact of PKC on Pb genotoxicity. Here we investigate whether Pb activates the conventional/classical subfamily of PKC (cPKC) signaling to affect cytotoxicity and mutagenicity in CL3 human non-small-cell lung adenocarcinoma cells. Pb specifically promoted membrane localization of the alpha isoform of PKC in CL3 cells. Pb also elicited Raf-1 activation as measured by the induction of phospho-Raf-1S338 and the dissociation from the Raf-1 kinase inhibitor protein. Inhibition of cPKC activity using Gö6976 or depletion of PKCalpha by introducing specific small interfering RNA blocked the induction of phospho-Raf-1S338, phospho-MKK1/2 and phospho-ERK1/2 in cells exposed to Pb. Intriguingly, declining PKCalpha enhanced the Pb cytotoxicity and revealed the Pb mutagenicity at the hprt gene. The results suggest that PKCalpha is obligatory for activation of the Raf-1-MKK1/2-ERK1/2 signaling module and plays a defensive role against cytotoxicity and mutagenicity following Pb exposure. Results obtained in this study also support our previous report showing that ERK1/2 activity is involved in preventing Pb genotoxicity.

A study on metals content in patients with colorectal polyps

Data on metals involvement in colorectal polyps are scarce and fragmentary. The aim of this study was to examine whether the level of metals could be associated with risk of colorectal polyp development. The concentration of 15 chemical elements (Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg Mg, Mn, Pb, Se, Sr, and Zn) in 17 colorectal biopsies of healthy individuals, in 15 polypotic and corresponding nonpolypotic biopsies taken from the same individual, was evaluated. Concentration in polyps of metals such as Al, Ca, Mg, Mn, Pb, Sr, and Zn was unchanged both in unpaired and paired samples; elements such as Ba, Cd, and Hg were significantly lower and Fe was significantly higher both in individual and paired tissues. Cobalt, Cr, and Cu were significantly different only between polyps and the adjacent normal tissue area; Se showed a significant accumulation comparing polyps versus healthy tissues. The difference found in some elements between polyps and a control tissue provides an indication about the role of essential and nonessential elements in the early stage (polyps) in the colon carcinogenic process and encourages further studies to confirm the involvement of such elements in neoplastic processes.

Role of extracellular signal-regulated kinase (ERK) signaling in nucleotide excision repair and genotoxicity in response to As(III) and Pb(II)

Arsenic and lead can induce genetic injuries and epigenetic signaling pathways in cultured mammalian cells. To test whether signaling pathways affect the extent of genetic injuries, we explored the impacts of extracellular signal-regulated kinase 1 and 2 (ERK) on nucleotide excision repair (NER), cytotoxicity, and genotoxicity following sodium arsenite [As(III)] and lead acetate [Pb(II)]. Sustained ERK activation was observed in human cells exposed to As(III) and Pb(II). As(III) inhibited the cellular NER synthesis capability; conversely, Pb(II) stimulated it. ERK activation contributed to the As(III)-induced NER inhibition and micronucleus formation. In contrast, this signal was required for inducing cellular NER activity and preventing mutagenesis following Pb(II). ERK activation by Pb(II) was dependent on protein kinase C (PKCα) that also exhibited anti-mutagenicity. Enforced expression of ERK signaling markedly elevated the cellular NER activity, which was suppressed by As(III). Nonetheless, ERK activation could counteract the cytotoxicity caused by these two metals. Together, the results indicate that pro-survival ERK signaling exhibits dual and opposing impacts on NER process following As(III) and Pb(II) exposures. The findings also suggest that ERK is an important epigenetic signaling in the determination of metal genotoxicity.

Lead contamination results in late and slowly repairable DNA double-strand breaks and impacts upon the ATM-dependent signaling pathways

Despite a considerable amount of data, evaluation of the potential genotoxicity and cancer proneness of lead compounds remains unclear, probably due to the plethora of experimental procedures, biological endpoints and cellular models used. In parallel, the understanding in DNA damage formation, repair and signaling has considerably progressed all along these last years, notably for DNA double-strand breaks (DSBs). Here, were examined DNA damage formation and repair in human cells exposed to lead nitrate (Pb(NO(3))(2)) and their consequences upon the ATM-dependent stress signaling, cell cycle progression and cell death. As observed with anti-pH2AX immunofluorescence, exposure to Pb(NO(3))(2) results in formation of late DSBs, that would not originate from conversion of nucleotide damage but likely by a direct production of single-strand breaks. Lead contamination inhibits non-homologous end-joining repair process by preventing the DNA-PK kinase activity whereas the MRE11-dependent repair pathway is exacerbated. Lead contamination triggers successive synchronization of cells in G2/M phase in which the RAD51-dependent homologous recombination was found to be activated. Altogether, our findings support that lead contamination generates late unrepairable DSBs that impact upon the ATM-dependent stress signaling pathway by favoring propagation of errors. Such findings should help to consider more carefully the biological action of lead compounds in the frame of public and occupational exposures.

Lead, genetic susceptibility, and risk of adult brain tumors

BACKGROUND

Although few etiologic factors for brain tumors have been identified, limited data suggest that lead may increase the risk of brain tumors, particularly meningioma. The ALAD G177C polymorphism affects the toxicokinetics of lead and may confer genetic susceptibility to adverse effects of lead exposure.

METHODS

We examined occupational exposure to lead and risk of brain tumors in a multisite, hospital-based, case-control study of 489 patients with glioma, 197 with meningioma, and 799 non-cancer controls frequency matched on hospital, age, sex, race/ethnicity, and residential proximity to hospital. ALAD genotype was assessed by a Taqman assay for 355 glioma patients, 151 meningioma patients, and 505 controls. Exposure to lead was estimated using a rigorous questionnaire-based exposure assessment strategy incorporating lead measurement and other occupational data abstracted from published articles and reports.

RESULTS

Increased risk of meningioma with occupational lead exposure (estimated by odds ratios and 95% confidence intervals) was most apparent in individuals with the ALAD2 variant allele, for whom risk increased from 1.1 (0.3-4.5) to 5.6 (0.7-45.5) and 12.8 (1.4-120.8) for estimated cumulative lead exposures of 1 to 49 microg/m3-y, 50 to 99 microg/m3-y, and >or=100 microg/m3-y, respectively, compared with unexposed individuals (two-sided P trend = 0.06). This relationship became stronger after excluding occupational lead exposures characterized by a low confidence level or occurring in the 10 years before meningioma diagnosis. Occupational lead exposure was not associated with glioma risk.

CONCLUSIONS

Although our results indicate that lead may be implicated in meningioma risk in genetically susceptible individuals, these results need to be interpreted with caution given the small numbers of exposed cases with a variant genotype.

Human lung cell growth is not stimulated by lead ions after lead chromate-induced genotoxicity

Chromate compounds are known human lung carcinogens. Water solubility is an important factor in the carcinogenicity of these compounds with the most potent carcinogenic compounds being water-insoluble or 'particulate'. Previously we have shown that particulate chromates dissolve extracellularly releasing chromium (Cr) and lead (Pb) ions and only the Cr ions induce genotoxicity. Pb ions have been considered to have epigenetic effects and it is thought that these may enhance the carcinogenic activity of lead chromate, perhaps by stimulating Cr-damaged cells to divide. However, this possibility has not been directly tested. Accordingly, we investigated the ability of Pb ions to stimulate human lung cells and possibly force lead chromate-damaged cells to grow. We found that at concentrations of lead chromate that induced damage, human lung cells exhibited cell cycle arrest and growth inhibition that were very similar to those observed for sodium chromate. Moreover, we found that soluble Pb ions were not growth stimulatory to human lung cells and in fact induced progressive mitotic arrest. These data indicate that lead chromate-generated Cr ions cause growth inhibition and cell cycle arrest and that Pb does not induce epigenetic effects that stimulate chromate-damaged cells to grow.

Comparison of the mutagenic potential of 17 physical and chemical agents analyzed by the flow cytometry mutation assay

Several methods to assess genotoxicity of physical and chemical agents have been developed, most of which depend on growing colonies in selective medium. We recently published a new method for detecting mutations in the CD59 gene in a Chinese hamster ovary cell line that contains a single copy of human chromosome 11 (CHO A(L)). The assay is based on detecting the surface expression of CD59 with monoclonal antibodies using flow cytometry. The capabilities of this flow cytometry mutation assay (FCMA) to detect mutations from a wide variety of genotoxic agents are described here. There was a 400-fold separation between CD59- and CD59+ populations based on fluorescence intensity. Small numbers of negative cells mixed in with positive cells were detected in a highly linear fashion. Mutation dose response curves over a dose range yielding 80% to 20% survival are shown for ethyl methane sulfonate (EMS), mitomycin C (MMC) and lead acetate. EMS and lead acetate exhibited a threshold in response while MMC had a linear dose response over the full dose range. The mutant fraction was measured over time periods ranging up to 35 days following treatment. The mutant fraction peaked at different times ranging from 6 to 12 days after treatment. An additional 14 chemical and physical agents including point mutagens, heavy metals, ionizing and UV radiation, and DNA intercalators and cross linkers, were analyzed for mutagenic potential after doses giving 80% to 20% survival. The results presented here demonstrate the sensitivity and broad-ranging capability of the FCMA to detect mutations induced by a variety of genotoxic agents.

Lead-induced genotoxicity in lymphocytes from peripheral blood samples of humans: in vitro studies

Lead is a known toxicant that has been implicated in encephalopathy in children and may affect the gastrointestinal and hematopoietic and other systems in adults. In fact, lead has been shown to compete with calcium for entry into the synaptosome and induce toxic effects. The aim of the current study was to evaluate the cytotoxic and genotoxic effects of lead by using lymphocytes from human peripheral blood in vitro. The LC50 for lead nitrate as determined by Trypan blue dye exclusion technique was found to be 3.14 mM. Chromosomal aberration frequency at sublethal doses (1/10 of LC50) as determined by examining the metaphase chromosomes (karyotyping) did not show significant aberrations except for some aneuploidy and about 2-4% gaps, breaks (3-4%), and about 5% satellite associations. However, significant DNA damage was determined by SCGE (Comet assay). The comet tail length proportionately increased with increasing lead nitrate concentration. Thus, Pb can induce single-strand DNA breaks, possibly by competing with metal binding sites.

Assessment of Lead Ecotoxicity in Water using the Amphibian Larvae (Xenopus laevis) and Preliminary Study of its Immobilization in Meat and Bone Meal Combustion Residues

Lead (Pb) is a major chemical pollutant of the environment. It has been associated with human activities for the last 6000 years. Quite rightly, it remains a public health concern today. The present investigation evaluates the toxic potential of Pb in larvae of the toad Xenopus laevis after 12 days exposure in lab conditions. Acute toxicity, genotoxicity and Pb bioaccumulation were analyzed. The genotoxic effects were analyzed in the circulating blood from the levels of micronucleus induction according to the French standard micronucleus assay (AFNOR 2000 Association française de normalization. Norme NFT 90-325. Qualité de l'Eau. Evaluation de la génotoxicité au moyen de larves d'amphibien (Xenopus laevis, Pleurodeles waltl)). Lead bioaccumulation was analyzed in the liver of larvae at the end of exposure. Moreover, the toxic potential of lead, in aquatic media, was investigated in the presence of meat and bone meal combustion residues (MBMCR) known to be rich in phosphates and a potential immobiliser of lead. Previously, acute toxicity and genotoxicity of MBMCR alone were evaluated using Xenopus larvae. The results obtained in the present study demonstrated: (i) that lead is acutely toxic and genotoxic to amphibian larvae from 1 mg Pb/l and its bioaccumulation is significant in the liver of larvae from the lowest concentration of exposure (1 microg Pb/l), (ii) MBMCR were not acutely toxic nor genotoxic in Xenopus larvae, (iii) lead in presence of MBMCR induced inhibition or reduction of the toxic and genotoxic potential of lead in water at concentrations that do not exceed the capacity of MBMCR of Pb-binding (iv) Pb accumulation in larvae exposed to lead with MBMCR in water was lower than Pb-accumulation in larvae exposed to lead alone except at the concentration of 0.01 mg Pb/l suggesting complex mechanisms of MBMCR interaction in organisms. The results confirm the high toxicity and genotoxicity of lead in the aquatic compartment and suggest the potential utility of MBMCR for use in remediation.

Accumulation of chromium and nickel metals in lung tumors from lung cancer patients in Taiwan

Metallic carcinogenicity is generally thought to generate of free radicals, and thus some metals were reported to play a role in lung tumorigenesis. In order to verify the role of heavy metals in the development of Taiwanese lung cancer, a case-control study was conducted to compare heavy metal contents between 60 tumor and 42 normal lung tissues surgically resected from lung cancer and noncancer patients. The tissue concentration of heavy metals, including cadmium (Cd), chromium (Cr), cobalt (Co), lead (Pb), and nickel (Ni), was measured using by atomic absorption spectrometry (AAS). Our results indicated that Cr and Ni contents in lung tumors of lung cancer patients were significantly higher than those in normal lung tissue of noncancer controls, but Co content was markedly lower in lung tumors. Additionally, Pb content in lung tumors was associated with nodal involvement, and Co amounts in squamous-cell carcinomas were relatively higher than those in adenocarcinomas. Data suggest that accumulation of Cr and Ni in lung tumors may play a role, at least in part, in the development of lung cancer in Taiwan.

Lipids, lipid peroxidation and 7-ketocholesterol in workers exposed to lead

The study population included healthy men and hypertensive employees of zinc and lead steelworks in the south of Poland. Workers exposed to lead (n=137) were divided into two groups: the first included employees with low exposure to lead (LL) with mean blood lead (PbB) 25-40 microg/dL and the second one with PbB over 40 microg/dL (HL group). The administration workers (n=35) were the control group. Evaluation of lipids and oxidative changes of cholesterol and lipids were estimated in blood samples. No significant changes in concentration of 7-ketocholesterol and blood lipids (cholesterol, HDL, LDL, triglycerides) were found. Lipid peroxidation (LP) was significantly higher in both exposed groups in plasma and in the HL group in erythrocytes when compared with control. There can be two independent sources of LP increase: the first is connected with the direct effect of lead's ions on erythrocytes, the second is the prooxidative effect of delta-aminolevulinic acid. Hypertension in the HL group when compared with people with PbB below 40 microg/dL (OR 4.4, 95%CI 1.4-14.5) was found more often. LP significantly increased by about 71% and concentration of 7-ketocholesterol by about 122% in hypertensives when compared with normotensives in the HL group.

Proteomic analysis of beryllium-induced genotoxicity in anEscherichia coli mutant model system

Beryllium is the second lightest metal, has a high melting point and high strength-to-weight ratio, and is chemically stable. These unique chemical characteristics make beryllium metal an ideal choice as a component material for a wide variety of applications in aerospace, defense, nuclear weapons, and industry. However, inhalation of beryllium dust or fumes induces significant health effects, including chronic beryllium disease and lung cancer. In this study, the mutagenicity of beryllium sulfate (BeSO(4)) and the comutagenicity of beryllium with a known mutagen 1-methyl-3-nitro-1-nitrosoguanidine (MNNG) were evaluated using a forward mutant detection system developed in Escherichia coli. In this system, BeSO(4) was shown to be weakly mutagenic alone and significantly enhanced the mutagenicity of MNNG up to 3.5-fold over MNNG alone. Based on these results a proteomic study was conducted to identify the proteins regulated by BeSO(4). Using the techniques of 2-DE and oMALDI-TOF MS, we successfully identified 32 proteins being differentially regulated by beryllium and/or MNNG in the E. coli test system. This is the first study to describe the proteins regulated by beryllium in vitro, and the results suggest several potential pathways for the focus of further research into the mechanisms underlying beryllium-induced genotoxicity.

Chemopreventive activity of glycyrrhizin on lead acetate mediated hepatic oxidative stress and its hyperproliferative activity in Wistar rats

Lead is a pervasive environmental pollutant with no beneficial biological role and its toxicity continues to be a major health problem due to its interference with natural environment. In the present study we have evaluated the chemopreventive effect of glycyrrhizin on lead acetate mediated hepatic oxidative stress, toxicity and tumor promotion related alterations in rats. Lead acetate (100mg/kg bwt., i.p.) enhanced lipid peroxidation with concomitant reduction in glutathione, glutathione reductase, glutathione-S-transferase and glutathione peroxidase activities. There was an increase in the levels of transaminase enzymes and LDH. Lead acetate treatment also enhanced ornithine decarboxylase (ODC) activity and [(3)H] thymidine incorporation into hepatic DNA. Pretreatment of rats orally with glycyrrhizin (150 and 300 mg/kg bwt., orally) resulted in a significant decrease in hepatic microsomal lipid peroxidation (P<0.001) and increase in the level of GSH content (P<0.001) and its dependent enzyme. There was significant reduction in the levels of SGPT, SGOT and LDH (P<0.001). A significant inhibition in ODC activity and DNA synthesis (P<0.001) was also observed. On the basis of the above results it can be hypothesized that glycyrrhizin is a potent chemopreventive compound against lead acetate mediated hepatic oxidative stress, toxicity and tumor promotion related responses in rats.

Lead ions do not cause human lung cells to escape chromate-induced cytotoxicity

Hexavalent chromium (Cr (VI)) compounds are established human lung carcinogens. Solubility plays a key role in Cr (VI) carcinogenicity, with the most potent carcinogens being water-insoluble or 'particulate'. Lead chromate is used as the prototypical particulate Cr (VI) compound since it is the most insoluble of these compounds. Previous work in our laboratory showed that lead chromate particles dissolve outside cells to produce chromium (Cr) and lead (Pb) ions and that the Cr ions were genotoxic. Pb has been hypothesized to play an epigenetic role in the carcinogenic activity of lead chromate, perhaps by allowing Cr-damaged cells to survive, however, this possibility has not been investigated. Accordingly, we determined the functional role of Pb and Cr ions in lead chromate-induced clonogenic survival. We found that vitamin C co-treatment eliminated Cr ion uptake, had only a slight effect on Pb ion levels, and eliminated lead chromate cytotoxicity. These data indicate that Cr ions caused the cytotoxicity. We found that lead chromate and soluble Cr (VI) induced similar amounts of cytotoxicity indicating that Pb does not play an epigenetic role and cause Cr-damaged cells to survive.

Micronuclei in peripheral blood lymphocytes of workers exposed to lead

Lead plays an important role in many industrial processes. Although highly useful to man, lead has various types of toxic effects. There is constantly growing evidence of a relationship between the induction of chromosome breaks and an increased risk of onset of cancer. However, available data about the possible genotoxic and carcinogenic action of lead are conflicting. In this report we present the results of studies on lead concentrations in blood and the respective micronucleus frequencies in peripheral blood lymphocytes from workers employed in the recycling of automotive batteries in the surroundings of Porto Alegre, Brazil. We observed that in the occupationally exposed group, both lead concentration in peripheral blood and micronucleus frequency in lymphocytes were significantly higher compared to control (Z=6.35, P<0.0001 and Z=4.47, P<0.0001). The nuclear division index (NDI) values were significantly higher in the control group than in the exposed group (Z=2.13, P=0.0330), indicating a possible effect of Pb on nuclear proliferation. We also detected a negative correlation between micronuclei and progression of nuclear division (tau=-0.312, P=0.0129). There were no changes in micronucleus frequency between smoking and non-smoking workers exposed to lead (Z=0.03, P=0.9790). The only difference found between the groups of smokers and non-smokers was with respect to NDI, whose values were significantly higher among non-smokers (Z=1.98, P=0.0481).

Detection of lead-induced oxidative stress in the rat epididymis by chemiluminescence

It has been shown that lead (Pb) is able to induce lipid peroxidation, one of the main manifestations of oxidative stress. In this study we examined the relationship between chronic Pb exposure and level of reactive oxygen species (ROS) in reproductive system tissues of sexually mature male Wistar rats. One group of animals (control, K) was allowed to drink distilled water, the second group (Pb) was allowed to drink freely 1% aqueous solution of lead acetate. Another groups had a following supplements: rats were allowed to drink distilled water containing vitamin C (vit C) at concentration of 500 mg/l or Trolox (a vitamin E analog) at concentration of 48 mg/l or vit C (500 mg/l) + Trolox (48 mg/l). The similar groups among Pb-treated animals were examined after treatment with the same vitamins and using the same vitamin doses, dissolved in 1% aqueous solution of lead acetate. In all cases the time of drinking was 6 months. It was found that lead content in samples of tissues from testis, epididymis and in a whole blood in Pb- and Pb with antioxidants treated rats was significantly elevated. Chemiluminescence (CL) emitted by the Pb-treated tissues was significantly higher when compared to the light emission by tissues isolated from the animals of control group. The increase in the CL caused by lead occurs in the following increasing order within the studied tissues: cauda of epididymis < testis < caput of epididymis (19%, 39% and 51%, respectively). Dietary vit C supplementation to the Pb-treated rats for 6 months period decreased the CL from caput of epididymis, cauda of epididymis and testis (by 43%, 24%, 39%, respectively) more effectively in comparison to the control group (35%, 17%, 33%, respectively). Also stronger quenching effect on the light emission from the above mentioned tissues after Trolox supplementation was observed in the Pb-treated group (42%, 21%, 35%, respectively) than in the control group (23%, 13%, 13% respectively). The combination of both antioxidants treatments (vit C and Trolox) did not give a higher significant quenching effect compared to the treatment with the vitamins separately. No ultrastructural changes were found in the seminiferous epithelium of Pb-treated animals. However, we found abnormalities in ultrastructure of epididymal epithelial cells and epididymal spermatozoa in rats of Pb-treated groups. These findings provide ex vivo evidence that Pb causes oxidative cellular damage in reproductive system tissues of adult male rats, which may be closely associated with the ROS production.

Protective action of vitamins on the spermatogenesis in lead-treated Swiss mice

The protective action of vitamins C and E against lead acetate-induced reduced sperm count and sperm abnormalities in Swiss mice has been studied. Intraperitoneal injection of lead acetate (10mg/kg body weight) in the present study stimulates lipid peroxidation in the testicular tissue, indicated by a significant increase in malondialdehyde content in the experimental mice group. This is associated with an increased generation of noxious reactive oxygen species (ROS). Significantly reduced sperm count associated with increased sperm abnormality percentage in the lead-injected mice group compared to controls substantially proves the ongoing damaging effects of lead-induced ROS on developing germ cells. However, intraperitoneal administration of vitamin C (Vit C) at a concentration equivalent to the human therapeutic dose (10 mg/kg body weight) was able to minimize significantly the testicular malondialdehyde content with a concomitant increase in sperm count and significant decrease in the percentage of abnormal sperm population. Vitamin E (Vit E) (100 mg/kg body weight) treatment of a batch of lead-injected mice had a similar effect as Vit C but with a comparatively lower efficacy. On the other hand, coadministration of both vitamins (Vit C + Vit E) at the above mentioned doses to lead-treated mice led to the most significant decline in malondialdehyde content along with elevated sperm count and reduction in the percentage of abnormal sperm population. The protective action and the synergistic action of both vitamins (C and E) against lead-induced genotoxicity are discussed.

Role of vitamin C on lead acetate induced spermatogenesis in swiss mice

In the present study significantly increased lipid peroxidation value (LPP) after a single intraperitioneal injection of lead acetate (LA) (100 mg/kg b.w.) indicated enormous generation of Reactive Oxygen Species (ROS). Lead-induced ROS has a direct inhibitory effect on the growth and differentiation of the spermatogonial cells showing a significant decline in sperm count. Chromosomal analysis of the primary spermatocytes at week 4 post-treatment in lead-treated mice revealed significantly higher no of aberrant cells including chromosomal deficiency, autosomal and XY-asynapsis plates compared to untreated control mice, Sperm morphology studies at week 1-4 and at week 8 post-treatment, indicated higher percentage of deformed sperm population compared to vehicle injected groups of mice. Supplementation of vitamin C (Vit C) at a dose of 10 mg/kg body weight to lead-treated mice groups, however, significantly reduced the LPP with a concomitant increase in sperm count, marked decrease in the no of aberrant cells and significant decline in the percentage of morphologically abnormal sperm population. Protective role of Vit C in combating lead-induced oxidative stress in mice testicular cells, has been discussed.

Lead induced DNA strand breaks in lymphocytes of exposed workers: role of reactive oxygen species and protein kinase C

Lead and lead compounds play a significant role in modern industry; a wide variety of population is at risk of occupational exposure and lead is suspected to be a human carcinogen. The biochemical and molecular mechanisms of lead toxicity are poorly understood, but emerging data suggest that some of the effects of lead may be due to its interference with calcium in the activation of protein kinase C (PKC) and/or through production of reactive oxygen species (ROS). Many of these results are conducted in vitro on cell lines or ex vivo on human lymphocytes treated in vitro. We, therefore, performed a study on the induction of DNA damage, using the alkaline comet assay, in lymphocytes of battery plant workers. To elucidate in vivo the mechanism(s) responsible for this effect, we determined ROS production, and glutathione (GSH) levels in living cells using the fluorescent probe (2',7'-dichlorofluorescein and monochlorobimane, respectively). Subcellular fractions were obtained from sonicated lymphocytes; cytosolic and membrane expression of PKC isoforms (alpha, and zeta) was evaluated after electrophoresis by immunoblot analysis. The results indicate that lead-exposed workers have significantly elevated levels of DNA breaks compared to the unexposed group. A multivariate analysis of variance (ANOVA) shows that the most common confounding factors (smoking, drinking and age) have no synergistic effects with lead-exposure on the comet parameters or on GSH levels and ROS production. The logistic regression analysis distinguishing the exposed and non-exposed indicates that only GSH with tail moment are selected as significant risk factors. There is a significant positive correlation with ROS production and negative correlation with GSH levels. The content of PKC alpha in cytosol and membranes is decreased 40% (indicating a down-regulation of protein), whereas PKC zeta isoform is not modified in an evident manner. Our results suggest that lead-exposure induces an increase of DNA breakage with an alternate cellular redox state and a significant down-regulation of PKC alpha, suggesting that this metal may act as a tumor promoter.