Role of ascorbic acid on mercuric chloride-induced genotoxicity in human blood cultures

Genotoxicity of Mercury and Its Derivatives Demonstrated In Vitro and In Vivo in Human Populations Studies. Systematic Review

Beside partial coverage in three reviews so far (1994, 2009, 2019), there is no review on genotoxic studies dealing with mercury (Hg) and human exposure using the most usual genotoxic assays: sister chromatid exchanges (SCE), chromosomal aberrations (CA), cytochalasin B blocked micronucleus assay (CBMN), and single-cell gel electrophoresis (SCGE or alkaline comet assay). Fifty years from the first Hg genotoxicity study and with the Minamata Convention in force, the genotoxic potential of Hg and its derivatives is still controversial. Considering these antecedents, we present this first systematic literature overview of genotoxic studies dealing with Hg and human exposure that used the standard genotoxic assays. To date, there is not sufficient evidence for Hg human carcinogen classification, so the new data collections can be of great help. A review was made of the studies available (those published before the end of October 2021 on PubMed or Web of Science in English or Spanish language) in the scientific literature dealing with genotoxic assays and human sample exposure ex vivo, in vivo, and in vitro. Results from a total of 66 articles selected are presented. Organic (o)Hg compounds were more toxic than inorganic and/or elemental ones, without ruling out that all represent a risk. The most studied inorganic (i)Hg compounds in populations exposed accidentally, occupationally, or iatrogenically, and/or in human cells, were Hg chloride and Hg nitrate and of the organic compounds, were methylmercury, thimerosal, methylmercury chloride, phenylmercuric acetate, and methylmercury hydroxide.

The palliative effect of camel milk on hepatic CYP1A1 gene expression and DNA damage induced by fenpropathrin oral intoxication in male rats

The present study investigated the alleviating role of camel milk (CM) in the mitigation of fenpropathrin (FNP) type II pyrethroid induced oxidative stress, alterations of hepatic (CYP1A1) mRNA expression pattern, and DNA damage using the alkaline comet assay (SCGE) in male rats. Sixty male Sprague-Dawley rats were separated into six groups (n = 10): 1st control (C), 2nd corn oil (CO), 3rd (CM): gavaged CM 2ml/rat, 4th (FNP): gavaged FNP 7.09 mg/kg body weight (BW), 5th (FNP pro/co-treated): gavaged CM firstly for 15 days, then CM + FNP by the same mentioned doses and route, 6th (FNP + CM co-treated): gavaged FNP firstly followed by CM by the same mentioned doses and route. Rats were orally gavaged three times per week, day after day for 60 days. FNP exposure significantly reduced serum glutathione (GSH) levels, but significantly increased serum levels of superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), protein carbonyl (PCO), and 8hydroxy2deoxyguanosine (8OH2dG). Additionally, FNP exposure significantly up-regulated the mRNA expression levels of hepatic CYP1A1 and increased the SCGE indices in whole blood, liver, and spleen tissues of exposed male rats. Administration of CM significantly regulated the FNP induced oxidative stress, reduced hepatic CYP1A1 mRNA expression levels and values of comet assay indices particularly in the (CM + FNP pro/co-treated) group compared to the (FNP + CM co-treated) group. In conclusion, our results indicate, for the first time, that FNP retains an in vivo genotoxic potential at a dose of (1/10 LD₅₀) and up-regulated hepatic CYP1A1 mRNA expression in male rats. Additionally, CM supplements may improve the genotoxic outcomes, oxidative stress, and altered CYP1A1 mRNA expression induced by FNP particularly in the pro/concurrent-treatment compared to the concurrent treatment alone.

Toxicity of mercury: Molecular evidence

Minamata disease in Japan and the large-scale poisoning by methylmercury (MeHg) in Iraq caused wide public concerns about the risk emanating from mercury for human health. Nowadays, it is widely known that all forms of mercury induce toxic effects in mammals, and increasing evidence supports the concern that environmentally relevant levels of MeHg could impact normal biological functions in wildlife. The information of mechanism involved in mercurial toxicity is growing but knowledge gaps still exist between the adverse effects and mechanisms of action, especially at the molecular level. A body of data obtained from experimental studies on mechanisms of mercurial toxicity in vivo and in vitro points to that disruption of the antioxidant system may play an important role in the mercurial toxic effects. Moreover, the accumulating evidence indicates that signaling transduction, protein or/and enzyme activity, and gene regulation are involving in mediating toxic and adaptive response to mercury exposure. We conducted here a comprehensive review of mercurial toxic effects on wildlife and human, in particular synthesized key findings of molecular pathways involved in mercurial toxicity from the cells to human. We discuss the molecular evidence related mercurial toxicity to the adverse effects, with particular emphasis on the gene regulation. The further studies relying on Omic analysis connected to adverse effects and modes of action of mercury will aid in the evaluation and validation of causative relationship between health outcomes and gene expression.

Medicinal plants and natural products can play a significant role in mitigation of mercury toxicity

Mercury is a heavy metal of considerable toxicity. Scientific literature reveals various plants and plant derived natural products, i.e., phytochemicals, which can alleviate experimentally induced mercury toxicity in animals. The present review attempts to collate those experimental studies on medicinal plants and phytochemicals with ameliorative effects on mercury toxicity. A literature survey was carried out by using Google, Scholar Google, Scopus and Pub-Med. Only the scientific journal articles found in the internet for the last two decades (1998–2018) were considered. Minerals and semi-synthetic or synthetic analogs of natural products were excluded. The literature survey revealed that in pre-clinical studies 27 medicinal plants and 27 natural products exhibited significant mitigation from mercury toxicity in experimental animals. Clinical investigations were not found in the literature. Admissible research in this area could lead to development of a potentially effective agent from the plant kingdom for clinical management of mercury toxicity in humans.

Protective effects of phenolic acids on mercury-induced DNA damage in precision-cut kidney slices

Objective(s):

Precision-cut tissue slices are considered an organotypic 3D model widely used in biomedical research. The comet assay is an important screening test for early genotoxicity risk assessment that is mainly applied on in vitro models. The aim of the present study was to provide a 3D organ system for determination of genotoxicity using a modified method of the comet assay since the stromal components from the original tissue make this technique complicated.

Materials and Methods:

A modified comet assay technique was validated using precision-cut hamster kidney slices to analyze the antigenotoxic effect of the phenolic compounds caffeic acid, chlorogenic acid, and rosmarinic acid in tissue slices incubated with 15 µM HgCl₂. Cytotoxicity of the phenolic compounds was studied in Vero cells, and by morphologic analysis in tissue slices co-incubated with HgCl₂ and phenolic compounds.

Results:

A modification of the comet assay allows obtaining better and clear comet profiles for analysis. Non-cytotoxic concentrations of phenolic acids protected kidney tissue slices against mercury-induced DNA damage, and at the same time, were not nephrotoxic. The highest protection was provided by 3 µg/ml caffeic acid, although 6 µg/ml rosmarinic and 9 µg/ml chlorogenic acids also exhibited protective effects.

Conclusion:

This is the first time that a modification of the comet assay technique is reported as a tool to visualize the comets from kidney tissue slices in a clear and simple way. The phenolic compounds tested in this study provided protection against mercury-induced genotoxic damage in precision-cut kidney slices.

Mercury disrupts redox status, up-regulates metallothionein and induces genotoxicity in respiratory tree of sea cucumber (Holothuria forskali)

Mercury (Hg) is among the most deleterious contaminant in the aquatic environment and presents a serious risk to humans and ecosystems. This study evaluated the effects of Hg on oxidative stress biomarkers, DNA integrity and histological structure of the respiratory tree of Holothuria forskali exposed to different concentrations of mercury chloride HgCl₂ (0.04, 0.08 and 0.16 mg L^-1) for 96 h. Exposure of H. forskali to Hg led to oxidative stress with an increase in Malondialdehyde (MDA), hydrogen peroxide (H₂O₂), advanced oxidation protein product (AOPP) and protein carbonyls (PCO) levels in the treated groups. Alteration of the antioxidant system was also confirmed by the significant increase in glutathione (GSH), nonprotein thiol (NPSH) and vitamin C contents. Moreover, the enzymatic activity of superoxide dismutase (SOD), Glutathione peroxidase (GPX) and Catalase (CAT) increased significantly. Our research revealed that total Metallothionein (MTs) content enhanced in a dose-dependent manner. Interestingly, the exposure to this metal provoked a decrease in Acetylcholinesterase (AChE) activity. Hg genotoxicity was further evidenced by a random DNA degradation that was observed in the treated groups. The histopathological findings confirmed the biochemical results. Overall, our results indicated that mercury-induced genotoxicity, oxidative damage and histopathological injuries in the respiratory tree of H. forskali.

Inorganic Hg toxicity in plants: A comparison of different genotoxic parameters

Inorganic Mercury (Hg) contamination persists an environmental problem, but its cyto- and genotoxicity in plants remains yet unquantified. To determine the extent of Hg-induced cyto- and genotoxicity, and assess most sensitive endpoints in plants, Pisum sativum L. seedlings were exposed for 14 days to different HgCl2 concentrations up to 100 μM. Shoots and roots from hydroponic exposure presented growth impairment and/or morphological disorders for doses >1 μM, being the roots more sensitive. Plant growth, ploidy changes, clastogenicity (HPCV), cell cycle dynamics (G1-S-G2), Comet-tail moment (TM), Comet-TD, Mitotic-index (MI) and cell proliferation index (CPI) were used to evaluate Hg-induced cyto/genotoxicity. Both leaf and root DNA-ploidy levels, assessed by flow cytometry (FCM), remained unaltered after exposure. Root cell cycle impairment occurred at lower doses (≥1 μM) than structural DNA damages (≥10 μM). Cytostatic effects depended on the Hg concentration, with delays during S-phase at lower doses, and arrests at G1 at higher ones. This arrest was paralleled with decreases of both mitotic index (MI) and cell proliferation index (CPI). DNA fragmentation, assessed by the Comet assay parameters of TD and TM, could be visualized for conditions ≥10 μM, while FCM-clastogenic parameter (FPCV) and micronuclei (MNC) were only altered in roots exposed to 100 μM. We demonstrate that inorganic-Hg induced cytostaticity is detectable even at 1 μM (a value found in contaminated sites), while structural DNA breaks/damage are only visualized in plants at concentrations ≥10 μM. We also demonstrate that among the different techniques tested for cyto- and genotoxicity, TD and TM Comet endpoints were more sensitive than FPCV or MNC. Regarding cytostatic effects, cell cycle analysis by FCM, including the difference in % cell cycle phases and CPI were more sensitive than MI or MNC frequency. Our data contribute to better understand Hg cyto- and genotoxicity in plants and to understand the information and sensitivity provided by each of the genotoxic techniques used.

Protective Effect of Leaf Ethanolic Extract Etlingera hemisphaerica Blume Against Mercuric Chloride Toxicity in Blood of Mice

This research was intended to investigate the protective effect of leaf ethanolic extract Etlingera hemisphaerica Blume (LE3H) against mercuric chloride (HgCl₂) toxicity in blood of mice (Mus musculus). The experimental animals, 95 male M. musculus, received drink and food ad libitum. Three materials were tested: LE3H (0.13, 0.26, 0.39 mg/g body weight [bw]) was administered by gavage; HgCl₂ (5 mg/kg bw) was administrated by gavage or intraperitoneal injection; and Imunos (the nutritional supplement to stimulate the immune system; 0.2 mg/g bw), as a positive control for LE3H treatment, was given by gavage. Blood samples were taken from the tails for determining number of blood cells. The animals were killed by cervical dislocation (CD), and then blood samples were collected from the hearts for protein electrophoresis. Results revealed the same number of leukocytes with LE3H (0.39 mg/g bw) treatment as with the Imunos treatment. HgCl₂ administration increased leukocytes and decreased erythrocytes; HgCl₂ administration followed by LE3H (0.39 mg/g bw) treatment protected the amount of blood cells as well as the control. HgCl₂ administration showed a new 125 kDa protein and caused overexpression of 48 kDa protein; this protein profile could be protected by LE3H (0.39 mg/g bw) treatment as in the control condition. We conclude that LE3H provides a protective effect against HgCl₂ toxicity in blood of M. musculus.

A multi-biomarker approach in scallop Chlamys farreri to assess the impact of contaminants in Qingdao coastal area of China

A multi-biomarker approach was carried out to classify the environmental quality and the adverse effects of contaminants on scallop Chlamys farreri. The scallops were collected from three sampling stations in Qingdao coastal area of China in March, May, August and October of 2015. A suite of environmental factors and biomarkers, including temperature, salinity, pH, the concentrations of polycyclic aromatic hydrocarbons (PAHs), tetrabromobisphenol A (TBBPA) and metals (Cr, Mn, Cu, Zn, Cd, Pb, As) in seawater and soft tissue, mRNA expression of aryl hydrocarbon receptor (AhR) and P-glycoprotein (P-gp), 7-ethoxyresorufin O-deethylase (EROD), glutathione-S-transferase (GST), uridine-diphosphate-glucuronyl-transferase (UGT), sulfotransferase (SULT), metallothionein (MT), Superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), lipid peroxidation (LPO) and protein carbonyl (PC) contents and DNA strand breaks, were measured in the gill and digestive gland. The results showed that S2 was the most polluted while S1 was identified the least polluted. Despite the differentiation of pollution levels and environmental parameters the selected biomarkers responded efficiently to contaminants. Principal component analysis (PCA) revealed that EROD for PAHs, AhR for TBBPA, MT for Cr, Pb and Mn, LPO and PC for Zn were the effective biomarkers respectively. This study demonstrated that the application of multi-biomarker approach in conjunction with the traditional analysis of environmental parameters and contaminants provided valuable information in environmental risk assessment.

Safety Evaluation of Potential Toxic Metals Exposure from Street Foods Consumed in Mid-West Nigeria

Objective. Street-vended foods offer numerous advantages to food security; nevertheless, the safety of street food should be considered. This study has investigated the level of potential toxic metal (Pb, Cd, Hg, Sb, Mn, and Al) contamination among street-vended foods in Benin City and Umunede. Methods. Twenty street food samples were purchased from vendors at bus stops. Metals were analyzed with atomic absorption spectrophotometry. The methods developed by the US EPA were employed to evaluate the potential health risk of toxic metals. Results. The concentrations of the toxic metals in mg/kg were in the range of Pb (0.014-1.37), Cd (0.00-0.00017), Hg (0.00-0.00014), Sb (0.00-0.021), Mn (0.00-0.012), and Al (0.00-0.22). All the toxic metals except Pb were below permissible limit set by WHO, EU, and USEPA. The daily intake, hazard quotient, and hazard index of all toxic metals except for Pb in some street foods were below the tolerable daily intake and threshold value of 1, indicating an insignificant health risk. Total cancer risk was within the priority risk level of 1.0E - 04 but higher than the acceptable risk level of 1E - 06. Conclusion. Consumption of some of these street foods is of public health concern.

The detoxification responses, damage effects and bioaccumulation in the scallop Chlamys farreri exposed to single and mixtures of benzo[a]pyrene and chrysene

This study aimed to investigate the detoxification responses, damage effects and biotransformation in scallop Chlamys farreri exposed to benzo[a]pyrene (BaP) (0.1, 1μg/L), chrysene (CHR) (0.1, 1μg/L) and BaP+CHR (0.1+0.1, 1+1μg/L) for 15days. Results demonstrated that BaP and CHR concentration (BaP<CHR) in tissues increased rapidly in a time and dose effect. The mRNA expression of aryl hydrocarbon receptor (AhR), cytochrome P450 1A1 (CYP1A1), CYP1B1, multidrug resistance protein 1 (MRP1/ABCC1), breast cancer resistance protein (BCRP/ABCG2) and P-glycoprotein (P-gp) were induced especially in the mixtures of BaP and CHR. Heat shock protein 90 (HSP90) and aryl hydrocarbon receptor nuclear translocator (ARNT) mRNA expression was significantly elevated at days 1, 10 and 15. Detoxification enzymes of 7-ethoxyresorufin O-deethylase (EROD), uridine-diphosphate-glucuronyl-transferase (UGT) and sulfotransferase (SULT) were significantly induced and then became stable gradually while glutathione-S-transferase (GST) was inhibited in the mixtures of BaP and CHR at days 10 and 15. Superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT) and glutathione (GSH) were all stimulated especially in the mixtures of BaP and CHR. The levels of DNA strand breaks, lipid peroxidation (LPO) and protein carbonyl (PC) contents showed damage effects exposed BaP and CHR. All the results indicated that BaP and CHR have similar induced effect and a majority of the biomarkers pointed to a more toxic effect when BaP and CHR were mixed. These will provide a solid foundation for the study of PAHs detoxification mechanism in bivalves and valuable information for marine pollution monitoring.

Dietary vitamin C reduced mercury contents in the tissues of juvenile olive flounder (Paralichthys olivaceus) exposed with and without mercury

A 2×3 factorial design was employed to evaluate the effects of dietary vitamin C (l-ascorblyl-2-monophosphate, C2MP) levels on growth and tissue mercury (Hg) accumulations in juvenile olive flounder, Paralichthys olivaceus. Six experimental diets with two levels of mercuric chloride (0 or 20mg HgCl2/kg diet) and three levels of vitamin C (0, 100, or 200mg C2MP/kg diet) were added to the basal diet. At the end of 6 weeks feeding trial, in presence or absence of dietary Hg, fish body weight gain, specific growth rate, feed efficiency, protein efficiency ratio and whole body lipid content were increased in a dose-dependent manner as dietary vitamin C level increased in the diets. Interestingly, fish fed 100 or 200mg C2MP/kg diets showed significant interactive effects on reducing Hg content in kidney tissue. These results revealed that dietary vitamin C as 100 or 200mg C2MP/kg diet had protective effect against Hg accumulation in juvenile olive flounder.

Results of micronucleus assays with individuals who are occupationally and environmentally exposed to mercury, lead and cadmium

Millions of humans are exposed occupationally and environmentally to lead, mercury and cadmium compounds. Mercury compounds are less abundant but some of them belong to the most toxic chemicals which are known. We evaluated the literature to find out if these metals act in humans as genotoxic carcinogens and if their health effects can be predicted by use of micronucleus (MN) assays with lymphocytes and/or with other genotoxicity tests. Numerous studies showed that lead and mercury induce cancer in humans and also in animals, in vitro experiments with cultured cells indicate that they cause DNA damage via different molecular mechanisms including release of reactive oxygen species and interactions with DNA repair processes. Also in most human studies, positive results were obtained in MN tests with lymphocytes (all 15 occupational studies with lead yielded positive results, with mercury 6 out of 7 investigations were positive). For cadmium, there is clear evidence that it causes cancer in humans; however, induction of chromosomal damage was only seen in high dose experiments with mammalian cells while results of animal and human studies yielded conflicting results (only in 2 of 5MN trials with humans positive findings were reported). Possibly, non-genotoxic mechanisms such as inhibition of apoptosis and interaction with signaling pathways account for the carcinogenic properties of cadmium species. The findings of MN studies with lead and mercury are in excellent agreement with results which were obtained with other endpoints (e.g. chromosomal aberrations and comet formations) and it is evident that this approach can be used for occupational and environmental monitoring of exposed individuals. Important future tasks will be the realization of larger studies with a uniform standardized protocol, the additional evaluation of anomalies other than MN (nuclear buds and bridges) and the combination of such trials with investigations which allow to define the molecular mechanisms relevant for exposed humans.

Methylmercury inhibits prolactin release in a cell line of pituitary origin

Heavy metals, such as methylmercury, are key environmental pollutants that easily reach human beings by bioaccumulation through the food chain. Several reports have demonstrated that endocrine organs, and especially the pituitary gland, are potential targets for mercury accumulation; however, the effects on the regulation of hormonal release are unclear. It has been suggested that serum prolactin could represent a biomarker of heavy metal exposure. The aim of this study was to evaluate the effect of methylmercury on prolactin release and the role of the nitrergic system using prolactin secretory cells (the mammosomatotroph cell line, GH3B6). Exposure to methylmercury (0-100 μM) was cytotoxic in a time- and concentration-dependent manner, with an LC₅₀ higher than described for cells of neuronal origin, suggesting GH3B6 cells have a relative resistance. Methylmercury (at exposures as low as 1 μM for 2 h) also decreased prolactin release. Interestingly, inhibition of nitric oxide synthase by N-nitro-L-arginine completely prevented the decrease in prolactin release without acute neurotoxic effects of methylmercury. These data indicate that the decrease in prolactin production occurs via activation of the nitrergic system and is an early effect of methylmercury in cells of pituitary origin.

A review of metal-catalyzed molecular damage: protection by melatonin

Metal exposure is associated with several toxic effects; herein, we review the toxicity mechanisms of cadmium, mercury, arsenic, lead, aluminum, chromium, iron, copper, nickel, cobalt, vanadium, and molybdenum as these processes relate to free radical generation. Free radicals can be generated in cells due to a wide variety of exogenous and endogenous processes, causing modifications in DNA bases, enhancing lipid peroxidation, and altering calcium and sulfhydryl homeostasis. Melatonin, an ubiquitous and pleiotropic molecule, exerts efficient protection against oxidative stress and ameliorates oxidative/nitrosative damage by a variety of mechanisms. Also, melatonin has a chelating property which may contribute in reducing metal-induced toxicity as we postulate here. The aim of this review was to highlight the protective role of melatonin in counteracting metal-induced free radical generation. Understanding the physicochemical insights of melatonin related to the free radical scavenging activity and the stimulation of antioxidative enzymes is of critical importance for the development of novel therapeutic strategies against the toxic action of these metals.

Antioxidant responses in clam Venerupis philippinarum exposed to environmental pollutant hexabromocyclododecane

The objective of this study was to assess the potential toxic effects of hexabromocyclododecane (HBCD) on tissues of clam Venerupis philippinarum using parameters of antioxidant defenses and oxidative stress. Antioxidant biomarkers including ethoxyresorufin-O-deethylase (EROD), glutathione S-transferase (GST), superoxide dismutase (SOD), and glutathione (GSH), as well as DNA damage and lipid peroxidation (LPO) in gills and digestive glands of V. philippinarum, were analyzed after a 1-, 3-, 6-, 10-, and 15-day exposure to seawater containing HBCD at environmentally related concentrations, respectively. The results showed that the activity of most antioxidant enzymes increased, and different trends were detected with exposure time extending. The oxidative stress could be obviously caused in the gills and digestive glands under the experimental conditions. This could provide useful information for toxic risk assessment of environmental pollutant HBCD.

Toxicity assessment of environmental pollutant phenanthrene in clam Venerupis philippinarum using oxidative stress biomarkers

The objective of this study was to assess potential toxic effects of phenanthrene (PHE) on tissues of clam Venerupis philippinarum using parameters of antioxidant defenses and oxidative stress. Antioxidant biomarkers including ethoxyresorufin-O-deethylase (EROD), glutathione S-transferase (GST), superoxide dismutase (SOD), and glutathione (GSH), as well as DNA damage and lipid peroxidation (LPO) in gills and digestive glands of V. philippinarum, were analyzed after a 1-, 3-, 6-, 10- and 15-day exposure to seawater containing PHE at concentrations of 2, 10, 50 μg/L. The results showed that the activity of most antioxidant enzymes was induced throughout the exposure period, and different trends were detected with time of exposure. The oxidative stress could be obviously caused in the gills and digestive glands under the experimental conditions. Overall, our results show that digestive glands are more sensitive to marine environmental stressors than gills, and GSH is proposed as potential useful biomarker as it showed good correlation with the target contaminant. This could provide useful information for toxic risk assessment of environmental pollutant PHE.

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

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

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.

Role of aqueous Bryoria capillaris (Ach.) extract as a genoprotective agent on imazalil-induced genotoxicity in vitro

In recent years, a number of studies have suggested that lichens might be the easily accessible sources of natural drugs that could be used as a possible food supplement. Extensive research is being carried out to explore the importance of lichen species, which are known to contain a variety of pharmacological active compounds. On the other hand, imazalil (IMA), a commonly used fungicide in both agricultural and clinical domains, is suspected to produce very serious toxic effects in vertebrates. In this context, the antigenotoxic effect of aqueous Bryoria capillaris (Ach.) extract (BCE) was studied against the genotoxic damage induced by IMA on cultured human lymphocytes using chromosomal aberrations (CA) and micronucleus (MN) as cytogenetic parameters. Human peripheral lymphocytes were treated in vitro with varying concentrations of BCE (5, 10, 25, 50 and 100 µg/mL), tested in combination with IMA (336 µg/mL). BCE alone was not genotoxic, and when combined with IMA treatment, it reduced the frequency of CAs and the rates of MN. A clear dose-dependent decrease in the genotoxic damage of IMA was observed, suggesting a genoprotective role of BCE. The results of the present study suggest that this plant extract per se do not have genotoxic potential, but can modulate the genotoxicity of IMA on peripheral human lymphocytes in vitro. In conclusion, our findings may have an important application in the protection of cultured human lymphocyte from the genetic damage and side effects induced by agricultural and medical chemicals that are hazardous to people.

Oxoguanine glycosylase 1 (OGG1) protects cells from DNA double-strand break damage following methylmercury (MeHg) exposure

Methylmercury (MeHg) is a potent neurotoxin, teratogen, and probable carcinogen, but the underlying mechanisms of its actions remain unclear. Although MeHg causes several types of DNA damage, the toxicological consequences of this macromolecular damage are unknown. MeHg enhances oxidative stress, which can cause various oxidative DNA lesions that are primarily repaired by oxoguanine glycosylase 1 (OGG1). Herein, we compared the response of wild-type and OGG1 null (Ogg1(-/-)) murine embryonic fibroblasts to environmentally relevant, low micromolar concentrations of MeHg by measuring clonogenic efficiency, cell cycle arrest, DNA double-strand breaks (DSBs), and activation of the DNA damage response pathway.Ogg1(-/-) cells exhibited greater sensitivity to MeHg than wild-type controls, as measured by the clonogenic assay, and showed a greater propensity for MeHg-initiated apoptosis. Both wild-type and Ogg1(-/-) cells underwent cell cycle arrest when exposed to micromolar concentrations of MeHg; however, the extent of DSBs was exacerbated in Ogg1(-/-) cells compared with that in wild-type controls. Pretreatment with the antioxidative enzyme catalase reduced levels of DSBs in both wild-type and Ogg1(-/-) cells but failed to block MeHg-initiated apoptosis at micromolar concentrations. Our findings implicate reactive oxygen species mediated DNA damage in the mechanism of MeHg toxicity; and demonstrate for the first time that impaired DNA repair capacity enhances cellular sensitivity to MeHg. Accordingly, the genotoxic properties of MeHg may contribute to its neurotoxic and teratogenic effects, and an individual's response to oxidative stress and DNA damage may constitute an important determinant of risk.

Role of non-enzymatic antioxidants on the bivalves' adaptation to environmental mercury: Organ-specificities and age effect in Scrobicularia plana inhabiting a contaminated lagoon

This study aimed to investigate the role of non-enzymatic antioxidants on adaptive skills over time in the bivalve Scrobicularia plana environmentally exposed to mercury. Inter-age (2(+), 3(+), 4(+), 5(+) year old) and organ-specific (gills, digestive gland) approaches were applied in bivalves collected from moderately and highly contaminated sites at Ria de Aveiro (Portugal). S. plana's adaptive skills were dependent on the contamination extent; under moderate contamination scenario, the intervention of the different antioxidants took place harmoniously, evidencing an adjustment capacity increasing with the age. Under higher contamination degree, S. plana failed to cope with mercury threat, showing an age-dependent deterioration of the defense abilities. In organ-specific approach, the differences were particularly evident for thiol-compounds, since only gills displayed the potential to respond to moderate levels by increasing non-protein thiols and total glutathione. Under high contamination degree, both organs were unable to increase thiol-compounds, which were compensated by the ascorbic acid elevation.

Xanthoria elegans (Link) (lichen) extract counteracts DNA damage and oxidative stress of mitomycin C in human lymphocytes

Several lichen species have been used for medicinal purposes throughout the ages, and they are reported to be effective in the treatment of different disorders including ulcer and cancer. It is revealed that lichens may be easily accessible sources of natural drugs and possible food supplements after their safety evaluations. The main objective in this study was to evaluate the roles of aqueous extracts of Xanthoria elegans (at 25, 50 and 100 μg/ml) upon mitomycin C (MMC; at 10(-7) M) induced genotoxic and oxidative damages in cultured human lymphocytes. X. elegans were collected from the Erzurum and Artvin provinces (in Turkey) during August 2010. After the application of MMC and X. elegans extract (XEE), separate and together, human whole blood cultures were assessed by four genotoxicity end-points including chromosomal aberration, micronucleus, sister chromatid exchange (SCE) and 8-oxo-2-deoxyguanosine (8-OH-dG) assays. In addition, biochemical parameters [total antioxidant capacity (TAC) and total oxidative stress (TOS)] were examined to determine oxidative effects. According to our results, the frequencies of cytogenetic endpoints and 8-OH-dG levels were significantly increased by MMC compared with controls in human peripheral lymphocytes. MMC caused oxidative stress by altering TAC and TOS levels. On the contrary, XEE led to increases of TAC level without changing TOS level. XEE had no genotoxic effect. Furthermore, our findings revealed that MMC induced increases in the mean frequencies of four genotoxic indices were diminished by XEE in dose dependent manner, indicating its protective role towards cells from MMC exerted injury. In conclusion, the results obtained in the present study indicate for the first time that XEE is a potential source of natural antigenotoxicants.

The Effects of Taurine on Permethrininduced Cytogenetic and Oxidative Damage in Cultured Human Lymphocytes

Permethrin (PM) is a common pyrethroid pesticide used to control pests in agriculture, forestry, horticulture, health care, homes, and textile industry. It is confirmed as a strong mutagen in animals and humans. Taurine (TA) is an amino acid found in mammalian tissues that protects the cell against DNA damage. In this study, we investigated whether supplementation of human lymphocyte cultures with TA (in the concentrations of 25 μg mL-1, 50 μg mL-1and 100 μg mL-1) provided any protection against PM toxicity applied in the concentration of 200 μg mL-1. Genotoxicity was assessed using the micronucleus (MN) and sister chromatid exchanges (SCE) tests. In addition, we measured the total antioxidant capacity (TAC) and total oxidative stress (TOS) levels in the plasma to determine oxidative effects. PM increased SCE and MN levels and altered TAC and TOS levels. TA alone did not affect SCE and MN levels compared to controls, regardless of the concentration applied. In addition, it increased TAC levels without changing TOS levels. Moreover, it significantly buffered the negative cytogenetic and oxidative effects induced by PM in a clear dose-dependent manner. In conclusion, this study is the first to evidence the beneficial effects of TA against PM-induced DNA and oxidative damagesin vitro.

Anti-genotoxic role of eicosapentaenoic acid against imazalil-induced DNA damage in vitro

Eicosapentaenoic acid (EPA) is a polyunsaturated n-3 fatty acid and is essential to the health of mammals. Recent data show that EPA can act as anti-mutagenic agent. On the other hand, pesticides comprise a new and important class of environmental pollutants nowadays. Imazalil (IMA), a commonly used fungicide in both agricultural and clinical domains is suspected to produce very serious toxic effects in vertebrates. The present study investigated the anti-genotoxic effect of EPA against the genotoxic damage induced by IMA on cultured human lymphocytes using chromosomal aberration (CA) and micronucleus (MN) tests as cytogenetic endpoints. Peripheral blood cells were treated in vitro with varying concentrations of EPA (2.5, 5, 10, 20 and 40 μg/ml), tested in combination with IMA (336 μg/ml). Our results revealed that the rates of CAs and MNs in lymphocytes were significantly (p < 0.05) increased by IMA as compared to the controls. The results also showed that EPA alone was not genotoxic. Moreover, when combined with IMA treatment, EPA reduced the frequencies of CAs and MNs. A clear dose-dependent decrease in the genotoxic damage of IMA was observed, suggesting a genoprotective role of EPA. In conclusion, our data may have an important application for the protection of cultured human lymphocyte from the genetic damage and repercussions induced by agricultural and industrial chemicals hazardous in people.

Advances in carcinogenic metal toxicity and potential molecular markers

Metal compounds such as arsenic, cadmium, chromium, cobalt, lead, mercury, and nickel are classified as carcinogens affecting human health through occupational and environmental exposure. However, the underlying mechanisms involved in tumor formation are not well clarified. Interference of metal homeostasis may result in oxidative stress which represents an imbalance between production of free radicals and the system's ability to readily detoxify reactive intermediates. This event consequently causes DNA damage, lipid peroxidation, protein modification, and possibly symptomatic effects for various diseases including cancer. This review discusses predominant modes of action and numerous molecular markers. Attention is paid to metal-induced generation of free radicals, the phenomenon of oxidative stress, damage to DNA, lipid, and proteins, responsive signal transduction pathways with major roles in cell growth and development, and roles of antioxidant enzymatic and DNA repair systems. Interaction of non-enzymatic antioxidants (carotenoids, flavonoids, glutathione, selenium, vitamin C, vitamin E, and others) with cellular oxidative stress markers (catalase, glutathione peroxidase, and superoxide dismutase) as well as certain regulatory factors, including AP-1, NF-κB, Ref-1, and p53 is also reviewed. Dysregulation of protective pathways, including cellular antioxidant network against free radicals as well as DNA repair deficiency is related to oncogenic stimulation. These observations provide evidence that emerging oxidative stress-responsive regulatory factors and DNA repair proteins are putative predictive factors for tumor initiation and progression.

Modulatory effects of Thymbra spicata L. different extracts against the mercury induced genotoxicity in human lymphocytes in vitro

Mercury, a xenobiotic metal, is a highly deleterious environmental pollutant. Moreover, in any form mercury is reported to be toxic. On the other hand, Thymbra spicata L., a member of the Lamiaceae family, has long been investigated popularly of biological roles; mainly antimicrobial and antioxidant activities. However, there are very scarce data on the cytogenetic effects of thyme species. The purpose of this study was to investigate the genetic safety of different extracts from T. spicata (water extract, methanol extract, and ethanol extract) and the effects of T. spicata on mercury (as HgCl(2)) induced genotoxicity. Sister chromatid exchange (SCE) and micronucleus (MN) assays were performed to assess DNA damages in cultured human lymphocytes (n = 5). Our results clearly revealed that, the SCE and MN rates induced by HgCl(2) were alleviated by the presence of T. spicata. As conclusion, this study demonstrated for the first time that the T. spicata provided increased resistance of DNA against HgCl(2) induced genetic damage in human lymphocytes. Based on the results of this study, it may be concluded that the T. spicata is a nontoxic material that could be used as a suppressor of heavy metal-induced genotoxicity.

The protective role of ascorbic acid on imazalil-induced genetic damage assessed by the cytogenetic tests

Ascorbic acid (AA), known as vitamin C, has important antioxidant and metabolic functions, making its incorporation into the human diet essential. On the other hand, imazalil (IMA), a commonly used fungicide in both agricultural and clinical domains is suspected to produce very serious toxic effects in vertebrates. In this study, the antigenotoxic effects of AA were studied against the genotoxic damage induced by IMA on cultured human lymphocytes using chromosomal aberration (CA) and sister chromatid exchange (SCE) as genetic end points. Human peripheral lymphocytes were treated in vitro with varying concentrations of AA (25, 50, 100, 200, and 400 μg/ml), tested in combination with IMA (336 mg/L). AA alone was not genotoxic and when combined with IMA treatment, reduced the frequencies of CAs and SCEs. A clear dose-dependent decrease in the genotoxic damage of IMA was observed, suggesting a genoprotective role of AA. In conclusion, the preventive role of AA in alleviating IMA-induced DNA damage was indicated for the first time in the present study.

Role of Peltigera rufescens (Weis) Humb. (a lichen) on imazalil-induced genotoxicity: analysis of micronucleus and chromosome aberrations in vitro

Imazalil (IMA), a commonly used fungicide in both agricultural and clinical domains, is suspected to produce very serious toxic effects on vertebrates. On the other hand, in recent years, a number of studies have suggested that lichens might be easily accessible sources of natural drugs that could be used as a possible food supplement. Extensive research is being carried out to explore the importance of lichen species, which are known to contain a variety of pharmacological active compounds. In this context, the anti-genotoxic effects of aqueous Peltigera rufescens (Weis) Humb. extracts (PREs) were studied against the genotoxic damage induced by IMA on cultured human lymphocytes using chromosomal aberrations (CAs) and micronucleus (MN) as cytogenetic parameters. Human peripheral lymphocytes were treated in vitro with varying concentrations of PREs (0, 5, 10, 25, 50 and 100 mg/L), tested in combination with IMA (336 mg/L). PREs alone were not genotoxic and when combined with IMA treatment, reduced the frequency of CAs and the rates of MNs. A clear dose-dependent decrease in the genotoxic damage of IMA was observed, suggesting a genoprotective role of P. rufescens extract. The results of the present study indicate that this plant extract per se do not have genotoxic potential but can minimize the genotoxicity of IMA on human lymphocytes in vitro. In conclusion our findings may have an important application for the protection of human lymphocyte from the genetic damage and side effects induced by agricultural and medical chemicals hazardous in people.

A modulator against mercury chloride-induced genotoxic damage: Dermatocarpon intestiniforme (L.)

Mercury has been used in many domains of human activities for many years, although in any form mercury is reported to be toxic. On the other hand, lichens have been used in the treatment of several diseases such as tuberculosis, hemorrhoids, ulcer, dysentery and cancer. Animal investigations on some common lichen species have demonstrated their antioxidant and antimutagenic activity. However, there is very scarce data on the medical or biologic effects of specific lichen species. Therefore, in the present study, we assessed the cyotogenetic effects of mercuric chloride (HgCl2) and the role of aqueous Dermatocarpon intestiniforme lichen extracts in mercury-treated human blood cultures ( n = 3). The sister chromatid exchange (SCE) and micronucleus (MN) assays were performed to assess DNA damages in lymphocytes. Our results clearly revealed that the SCE and MN rates induced by HgCl2 were alleviated by the presence of D. intestiniforme. In conclusion, the results of the present study revealed for the first time that the lichen D. intestiniforme provided increased resistance of DNA against HgCl2-induced genetic damage on human lymphocytes.

Antigenotoxic and anticytotoxic effect of camel milk in mice treated with cisplatin

Camel milk (CM) has good nutritive value, in addition to its antigenotoxic and anticytotoxic effects. Therefore the aim of this investigation was to evaluate the capacity of CM to inhibit the micronucleated polychromatic erythrocytes (MnPCEs) in the bone marrow and improve the mitotic activity produced by cisplatin. Cisplatin is one of the most widely used antineoplastic drugs in the treatment of cancer. The 70 adult male Swiss albino mice were divided into seven groups:Gr. I: treated with distilled water and considered as a control group.Gr. II: treated with camel milk (33 ml/kg, b.w).Gr. III: treated previously with cisplatin (0.5 mg/kg, b.w).Gr. IV: treated with camel milk and followed after 2 h. with cisplatin (33 ml/kg → 0.5 mg/kg, b.w).Gr. V: treated with camel milk and cisplatin at the same time (33 ml/kg + 0.5 mg/kg, b.w).Gr. VI: treated with an acute single dose of cisplatin (2.5 mg/kg, b.w).Gr. VII: treated with camel milk prior and followed with an acute single dose of cisplatin (33 ml/kg → 2.5 mg /kg, b.w). The animals were sacrificed 24 h after cisplatin injection. The pretreatment with CM dose caused a significant decrease (P < 0.001) in the frequency of MnPCEs and increase (P < 0.001) in the mitotic index (MI) induced by cisplatin when compared with the groups treated with cisplatin alone. The possible explanation for the antigenotoxic and anticytotoxic effects observed in the pretreatment with CM is ascribed to its contents. In conclusion, from the findings we suggest that this milk has some antioxidant effect, and the antigenotoxic mechanism of this milk needs to be explored further before their use during cisplatin chemotherapy.

Antioxidant defenses and oxidative stress parameters in tissues of mud crab (Scylla serrata) with reference to changing salinity

The effects of salinity (10, 17 and 35 ppt) on O(2) consumption, CO(2) release and NH(3) excretion by crabs and oxidative stress parameters and antioxidant defenses of its tissues were reported. An increase in salinity caused a decrease in O(2) consumption and CO(2) release and an increase in ammonia excretion by crabs. Lipid peroxidation, protein carbonyl, H(2)O(2) levels and total antioxidant capacity of the tissues elevated significantly at 35 ppt salinity except in abdominal muscle where H(2)O(2) content was low. Ascorbic acid content of tissues was higher at 17 ppt salinity than at 10 and 35 ppt salinities. With increasing salinity, a gradual decrease in SOD, an increase in catalase, no change in GPx and a decrease followed by an increase in GR activities were recorded for abdominal muscle. While for hepatopancreas, an increase followed by a decrease in SOD and catalase, decrease in GPx and GR activities were noticed with increasing salinity. In the case of gills, a decrease followed by an increase in SOD, a decrease in catalase and GPx and an increase in GR activities were noted when the salinity increased from 10 ppt to 35 ppt. These results suggest that salinity modulation of oxidative stress and antioxidant defenses in Scylla serrata is tissue specific.

Effects of BSO, GSH, Vit-C and DMPS on the nephrotoxicity of mercury

OBJECTIVE

To study the effects of BSO, GSH, Vit-C and DMPS on the nephrotoxicity of mercury.

METHODS

The rats in groups 1, 2 and 3 were sc injected with 0.75, 1.5 and 2.5 mg/kg HgCl2, respectively. Fourth group rats were ip injected with 0.5 mmol/kg BSO and 4h later sc administrated with 0.75 mg/kg HgCl2. The rats in groups 5, 6 and 7 were ip injected with 3 mmol/kg GSH, 4 mmol/kg Vit-C, 200 micromol/kg DMPS, respectively, and 2 h later sc administrated with 2.5 mg/kg HgCl2. Eighth group rats were sc injected with saline as a control. Mercury concentrations in the liver, renal cortex and urine, urinary NAG, ALP, LDH activities, protein and BUN contents were determined.

RESULTS

Urinary NAG, ALP activities, protein and BUN contents in the rats of BSO pretreatment group were significantly higher than that of 0.75 mg/kg HgCl2 alone group and control group. As compared with 2.5 mg/kg HgCl2 alone group, urinary NAG, ALP, LDH activities, urinary protein and BUN contents decreased significantly.

CONCLUSION

BSO pretreatment could enhance the renal toxicity of mercury and GSH, Vit-C and DMPS pretreatment had antagonistic effects on nephrotoxicity of mercury.

Mercury exposure and antioxidant defenses in women: a comparative study in the Amazon

Mercury is a hazardous metal that has become an important issue of environmental contamination in Amazon areas. Human intoxication by mercury causes sensory deficits, motor dysfunction, delayed psychomotor development, genotoxicity, and several other health problems. One of the major cellular mechanisms of mercury toxicity is the oxidative stress which may lead to membrane peroxidation and generation of reactive oxygen species. The antioxidant defense, which includes scavenger compounds such as glutathione and antioxidant enzymes such as catalase, might prevent these injuries to occur. Thus, the objective of this work was to evaluate hair mercury levels and the strength of antioxidant defenses, evaluated by glutathione levels and catalase activity in the blood of exposed and non-exposed women living in Amazon populations. For each location, no statistically significant difference (P<0.05) was detected for age versus mercury content. However, women from populations under the influence of gold mining activity exhibit high mercury levels in hair samples, above the tolerance limit accepted by the World Health Organization. In addition, a significant correlation was found between high mercury content, high glutathione level, and lower catalase activity. These data suggest that chronic mercury intoxication may deplete antioxidant enzymatic activity, which can be used as an important peripheral marker. Knowledge originated by this monitoring will better assist the development of preventive strategies and governmental actions against the problem of mercury contamination.

Modulation of antioxidant defences in digestive gland of Perna viridis (L.), on mercury exposures

Sub-lethal effects of mercury exposure (110th of LC(50), i.e. 0.045 mg l(-1)) for 5, 10 and 15 d was investigated on oxidative stress parameters and antioxidant defences in digestive gland of Perna viridis. In addition to this an in vitro effect of mercury single and supplemented with reduced glutathione on lipid peroxidation was studied. Increased lipid peroxidation (during first 10 days and also during in vitro exposures), protein carbonyl and hydrogen peroxides (from 5th till last day of exposure) indicate the resultant oxidative stress in the mercury exposed specimen. DNA damage (F-value) response although less distinct on 5th and 15th d, its low values on 10th d and significant correlation with hydrogen peroxide suggests the toxic role of free radicals towards DNA integrity. Superoxide dismutase, which remains low initially (5th d) and increases later suggests its immediate response against superoxide radical. Higher activities of catalase, glutathione peroxidase and glutathione reductase on 15th d and glutathione-S-tranferase from 10th d onwards suggests the adaptive behaviour of the tissue against oxyradicals. Increasing levels of non-enzymatic antioxidant molecules, such as reduced glutathione and ascorbic acid indicated its involvement in counteracting oxidative damage. Further role of reduced glutathione in reducing Hg toxicity is evident in in vitro experiments where lipid peroxidation remains low in mercury concentrations supplemented with reduced glutathione. The elevated levels of metallothionein from 5th to 10th d suggest involvement of this protein in detoxification of reactive oxygen species and toxic metal. The above results suggest that both enzymatic and non-enzymatic antioxidants play an important role in protecting cell against Hg toxicity, which can be used as a biomarker of metal contamination in aquatic environment.

Epidemiologic confirmation that fruit consumption influences mercury exposure in riparian communities in the Brazilian Amazon

Since deforestation has recently been associated with increased mercury load in the Amazon, the problem of mercury exposure is now much more widespread than initially thought. A previous exploratory study suggested that fruit consumption may reduce mercury exposure. The objectives of the study were to determine the effects of fruit consumption on the relation between fish consumption and bioindicators of mercury (Hg) exposure in Amazonian fish-eating communities. A cross-sectional dietary survey based on a 7-day recall of fish and fruit consumption frequency was conducted within 13 riparian communities from the Tapajós River, Brazilian Amazon. Hair samples were collected from 449 persons, and blood samples were collected from a subset of 225, for total and inorganic mercury determination by atomic absorption spectrometry. On average, participants consumed 6.6 fish meals/week and ate 11 fruits/week. The average blood Hg (BHg) was 57.1 +/- 36.3 microg/L (median: 55.1 microg/L), and the average hair-Hg (HHg) was 16.8 +/- 10.3 microg/g (median: 15.7 microg/g). There was a positive relation between fish consumption and BHg (r = 0.48; P<0.0001), as well as HHg (r =0.34; P<0.0001). Both fish and fruit consumption entered significantly in multivariate models explaining BHg (fish: beta = 5.6, P<0.0001; fruit: beta = -0.5, P = 0.0011; adjusted model R2 = 36.0%) and HHg levels (fish: beta = 1.2, P<0.0001; fruit: beta = -0.2, P = 0.0002; adjusted model R2 = 21.0%). ANCOVA models showed that for the same number of fish meals, persons consuming fruits more frequently had significantly lower blood and HHg concentrations. For low fruit consumers, each fish meal contributed 9.8 microg/L Hg increase in blood compared to only 3.3 microg/L Hg increase for the high fruit consumers. In conclusion, fruit consumption may provide a protective effect for Hg exposure in Amazonian riparians. Prevention strategies that seek to maintain fish consumption while reducing Hg exposure in fish-eating communities should be pursued.

Mercuric dichloride induces DNA damage in human salivary gland tissue cells and lymphocytes

Amalgam is still one of the most frequently used dental filling materials. However, the possible adverse effects especially that of the mercuric component have led to continued controversy. Considering that mercury may be released from amalgam fillings into the oral cavity and also reach the circulating blood after absorption and resorption, it eventually may contribute to tumorigenesis in a variety of target cells. The present investigation focuses on genotoxic effects below a cytotoxic dose level of mercuric dichloride (HgCl(2)) in human samples of salivary glands and lymphocytes to elucidate a possible role in tumor initiation. DNA migration due to single strand breaks, alkali labile sites and incomplete excision repair was quantified with the aid of the single cell microgel electrophoresis (Comet) assay. The concepts of Olive Tail Moment, percentage of DNA in the Tail and Tail Length were used as measures of DNA damage. To control for cytotoxic effects, the trypan blue exclusion test was applied. Human samples of the parotid salivary gland and lymphocytes of ten donors were exposed to HgCl(2)concentrations from 1 to 50 microM. N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and dimethyl sulfoxide (DMSO) served as controls. Increasing dose-dependent DNA migration could be demonstrated after exposure to HgCl(2) in cells of the salivary glands and lymphocytes. In both cell types a significant increase in DNA migration could be shown starting from HgCl(2)concentrations of 5 microM in comparison to the negative control. The viability of the cell systems was not affected except at the highest concentration (50 microM) tested. These data indicate genotoxic effects of mercuric dichloride in human salivary glands and lymphocytes at concentrations not leading to cytotoxic effects or cell death. Consequently, a contributory role in oral salivary gland tumor initiation warrants further investigation.

Methylmercury genotoxicity: a novel effect in human cell lines of the central nervous system

Methylmercury is an important source of environmental contamination and the central nervous system (CNS) is one of the main target organs. Methylmercury genotoxicity was already demonstrated in peripherical tissues but was never detected in the brain. Thus, the objective of this work was to verify its genotoxic effect using brain cell lines. Glioblastoma (U373) and neuroblastoma (B103) human cell lines were exposed to methylmercury (0-10 microM). By measuring cellular viability, concentrations inducing <20% of cellular death (P<0.05) were selected: 1 and 0.1 microM. To detect micronuclei, 200,000 cells were treated with methylmercury for 24 h, and then incubated with cytochalasin B (2 microg/ml) for 72 h (U373) or 48 h (B103). The binucleation index, frequency of micronucleated cells, micronucleation index, metaphasic index and index of nucleoplasmic bridges were determined. Statistical analysis showed indices and percentages significantly higher (P<0.05) in methylmercury-treated cells. Each cell line was shown to be differently sensitive to each biomarker of genotoxic damage, which seems to indicate the existence of different mechanisms of toxicity. This work demonstrates, for the first time, MeHg ability to provoke genotoxicity in cells of brain origin with relatively low levels of exposure.

Low dose mercury toxicity and human health

Post Minamata incident there has been awareness about mercury toxicity even among the general public. Previous researches contributed a vast amount of data regarding acute mercury exposure, but gradually information about the low dose [Ninomiya, T., Ohmori, H., Hashimoto, K., Tsuruta, K., Ekino, S., 1995. Expansion of methylmercury poisoning outside minamata: an epidemiological study on chronic methylmercury poisoninig outside of Minamata. Environ. Res. 70 (1) 47-50; Lebel, J., Mergler, D., Lucotte, M., Amorim, M., Dolbec, J., Miranda, D., Arantes, G., Rheault, I., Pichet, P., 1996. Evidence of early nervous system dysfunction in Amazonian populations exposed to low-levels of methylmercury. Neurotoxicology 17 (1) 157-167] of mercury toxicity has been trickling in. With mercury contaminating rain-, ground- and sea-water no one is safe. Polluted water leads to mercury laced fish, meat and vegetable. In aquatic environments, inorganic mercury is microbiologically transformed into lipophilic organic compound 'methylmercury'. This transformation makes mercury more prone to biomagnification in food chains. Consequently, populations with traditionally high dietary intake of food originating from fresh or marine environment have highest dietary exposure to mercury. Extensive research done on locals across the globe have already established this, persons who routinely consume fish or a particular species of fish are at an increased risk of methylmercury poisoning. The easy access of the toxicant to man through multiple pathways air, water, food, cosmetic products and even vaccines increase the exposure. Foetus and children are more susceptible towards mercury toxicity. Mothers consuming diet containing mercury pass the toxicant to foetus and to infants through breast milk. Decreased performance in areas of motor function and memory has been reported among children exposed to presumably safe mercury levels. Similarly, disruption of attention, fine motor function and verbal memory was also found in adults on exposure to low mercury levels. It is an occupational hazard for dental staff, chloralkali factory workers and goldminers, etc. Mercury has been found to be a causative agent of various sorts of disorders, including neurological, nephrological, immunological, cardiac, motor, reproductive and even genetic. Recently heavy metal mediated toxicity has been linked to diseases like Alzeihemer's, Parkinson's, Autism, Lupus, Amyotrophic lateral sclerosis, etc. Besides this, it poses danger to wildlife. Therefore, it becomes imperative to spread the information regarding the threat of mercury exposure amongst the scientists and masses.

Genotoxicity of inorganic mercury salts based on disturbed microtubule function

This study investigated the hypothesis that the chromosomal genotoxicity of inorganic mercury results from interaction(s) with cytoskeletal proteins. Effects of Hg2+ salts on functional activities of tubulin and kinesin were investigated by determining tubulin assembly and kinesin-driven motility in cell-free systems. Hg2+ inhibits microtubule assembly at concentrations above 1 microM, and inhibition is complete at about 10 microM. In this range, the tubulin assembly is fully (up to 6 microM) or partially (~6-10 microM) reversible. The inhibition of tubulin assembly by mercury is independent of the anion, chloride or nitrate. The no-observed-effect-concentration for inhibition of microtubule assembly in vitro was 1 microM Hg2+, the IC50 5.8 microM. Mercury(II) salts at the IC50 concentrations partly inhibiting tubulin assembly did not cause the formation of aberrant microtubule structures. Effects of mercury salts on the functionality of the microtubule motility apparatus were studied with the motor protein kinesin. By using a "gliding assay" mimicking intracellular movement and transport processes in vitro, HgCl2 affected the gliding velocity of paclitaxel-stabilised microtubules in a clear dose-dependent manner. An apparent effect is detected at a concentration of 0.1 microM and a complete inhibition is reached at 1 microM. Cytotoxicity of mercury chloride was studied in V79 cells using neutral red uptake, showing an influence above 17 microM HgCl2. Between 15 and 20 microM HgCl2 there was a steep increase in cell toxicity. Both mercury chloride and mercury nitrate induced micronuclei concentration-dependently, starting at concentrations above 0.01 microM. CREST analyses on micronuclei formation in V79 cells demonstrated both clastogenic (CREST-negative) and aneugenic effects of Hg2+, with some preponderance of aneugenicity. A morphological effect of high Hg2+ concentrations (100 microM HgCl2) on the microtubule cytoskeleton was verified in V79 cells by immuno-fluorescence staining. The overall data are consistent with the concept that the chromosomal genotoxicity could be due to interaction of Hg2+ with the motor protein kinesin mediating cellular transport processes. Interactions of Hg2+ with the tubulin shown by in vitro investigations could also partly influence intracellular microtubule functions leading, together with the effects on the kinesin, to an impaired chromosome distribution as shown by the micronucleus test.

Inhibitory effects of ascorbic acid and folinic acid on chromosome aberrations induced by pyrimethamine in vitro

In this study, the anticlastogenic effects of ascorbic acid and the protective effect of folinic acid against the formation of chromosomal aberrations in humans by pyrimethamine were investigated. Pyrimethamine is a folic acid antagonist used for the treatment of malaria and toxoplasmosis. In this study, 18 different healthy people, who do not drink alcohol and are non-smokers, were chosen as an experimental group; 0.025 mg/ml pyrimethamine was given to the lymphocyte culture, which had been prepared with the peripheral blood taken from this group. After that each of the following doses were given to the same culture: 20, 40, and 80 mM of ascorbic acid and 25, 50, and 100 mM of folinic acid. The results of the cytogenetic evaluation showed that the aberrations due to pyrimethamine in the chromosomes were reduced by ascorbic acid and folinic acid significantly, depending on the given dose.