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Lee SG, Eom SY, Lim JA, Choi BS, Kwon HJ, Hong YS, Kim YD, Kim H, Park JD. Association between urinary arsenic concentration and genetic polymorphisms in Korean adults. Toxicol Res 2024; 40:179-188. [PMID: 38223675 PMCID: PMC10786758 DOI: 10.1007/s43188-023-00216-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 10/10/2023] [Accepted: 10/25/2023] [Indexed: 01/16/2024] Open
Abstract
Arsenic (As) is a human carcinogen widely distributed in the environment. This study evaluated the association between the urinary As concentration and single nucleotide polymorphisms (SNPs) in Korean adults to determine the genetic factors related to As concentration. The study included 496 participants for the genome-wide association study (GWAS) and 1483 participants for the candidate gene approach study. Participants were 19 years and older. The concentrations of total As (Tot As) and total As metabolites (Tmet As, the sum of inorganic As and their metabolites; arsenite, arsenate, monomethylarsonic, and dimethylarsinic acid) in the urine were analyzed. The GWAS identified four SNPs (rs1432523, rs3776006, rs11171747, and rs807573) associated with urinary Tot As and four SNPs (rs117605537, rs3776006, rs11171747, and rs148103384) significantly associated with urinary Tmet As concentration (P < 1 × 10-4). The candidate gene study identified two SNPs (PRDX2 rs10427027 and GLRX rs3822751) in genes related to the reduction reaction associated with urinary Tot As and Tmet As. This study suggests that genetic factors may play a role in regulating As metabolism in the human body, affecting both exposure levels and its potential health risks in the general Korean population, even at low exposure levels. Supplementary Information The online version contains supplementary material available at 10.1007/s43188-023-00216-x.
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Affiliation(s)
- Seul-Gi Lee
- Department of Preventive Medicine, College of Medicine, Chung-Ang University, 84 Heukseok-Ro, Dongjak-Gu, Seoul, 06974 Republic of Korea
| | - Sang-Yong Eom
- Department of Preventive Medicine, College of Medicine, Chungbuk National University, Cheongju, 28644 Republic of Korea
| | - Ji-Ae Lim
- Department of Preventive Medicine, College of Medicine, Dankook University, Cheonan, 16890 Republic of Korea
| | - Byung-Sun Choi
- Department of Preventive Medicine, College of Medicine, Chung-Ang University, 84 Heukseok-Ro, Dongjak-Gu, Seoul, 06974 Republic of Korea
| | - Ho-Jang Kwon
- Department of Preventive Medicine, College of Medicine, Dankook University, Cheonan, 16890 Republic of Korea
| | - Young-Seoub Hong
- Department of Preventive Medicine, College of Medicine, Dong-A University, Busan, 49201 Republic of Korea
| | - Yong-Dae Kim
- Department of Preventive Medicine, College of Medicine, Chungbuk National University, Cheongju, 28644 Republic of Korea
| | - Heon Kim
- Department of Preventive Medicine, College of Medicine, Chungbuk National University, Cheongju, 28644 Republic of Korea
| | - Jung-Duck Park
- Department of Preventive Medicine, College of Medicine, Chung-Ang University, 84 Heukseok-Ro, Dongjak-Gu, Seoul, 06974 Republic of Korea
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Shao J, Li X, Luo Y, Fang H, Lin F, Zhang G, Lu F, Guo L, Sun Y. Distribution of arsenic species and pathological characteristics of tissues of the mice fed with arsenic-supplemented food simulating rice. J Toxicol Sci 2021; 46:539-551. [PMID: 34719557 DOI: 10.2131/jts.46.539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The exposure and harm of arsenic have attracted wide attention. Rice is an arsenic-rich crop. The purpose of this study was to learn the distribution of arsenic species and the pathological changes in tissues of mice exposed to arsenic-supplemented food simulating rice. Test groups of mice were orally exposed with prepared arsenic feeds supplemented with four arsenic species (arsenite iAsIII, arsenate iAsV, monomethylarsonate MMA, and dimethylarsinate DMA) at three doses (total As concentration: 0.91, 9.1 and 30 μg/g), which simulated the arsenic species ratio in rice. After 112 days, the concentrations of the arsenic species in the spleen, thymus, heart, skin and hair were detected, and histopathology of the spleen, heart and skin was observed. Each arsenic species was detected and their total concentration increased in a dose-dependent manner with a few exceptions. One interesting phenomenon is that ratio of the organic arsenic to inorganic arsenic also increased in a dose-dependent manner. For the other, the order of tissues from high to low arsenic concentration was the same in the medium- and high-dose groups. The histopathological sections of the spleen, heart and skin showed dose-dependent debilitating alterations in tissue architecture. Hyperplasia, hyaline degeneration and sclerosis of fibrous connective tissue occurred in the spleen. Myocardial cell atrophy and interstitial edema occurred in the heart. Hyperpigmentation, hyperkeratosis and atypia of basal cells occurred in the skin. In summary, the long-term intake of high arsenic rice has a health risk. Further studies are needed to assess it.
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Affiliation(s)
- Junli Shao
- School of Public Health, Dongguan Key Laboratory of Environmental Medicine, Guangdong Medical University; School of Public Health, Institute of Environmental Health, Guangdong Medical University, China
| | - Xin Li
- School of Food and Biological Engineering, Guangdong Polytechnic of Science and Trade, China
| | - Yu Luo
- School of Public Health, Dongguan Key Laboratory of Environmental Medicine, Guangdong Medical University; School of Public Health, Institute of Environmental Health, Guangdong Medical University, China
| | - Heng Fang
- School of Public Health, Dongguan Key Laboratory of Environmental Medicine, Guangdong Medical University; School of Public Health, Institute of Environmental Health, Guangdong Medical University, China
| | - Fangyan Lin
- School of Public Health, Dongguan Key Laboratory of Environmental Medicine, Guangdong Medical University; School of Public Health, Institute of Environmental Health, Guangdong Medical University, China
| | - Guiwei Zhang
- Shenzhen Academy of Metrology and Quality Inspection, China
| | - Furong Lu
- School of Public Health, Dongguan Key Laboratory of Environmental Medicine, Guangdong Medical University; School of Public Health, Institute of Environmental Health, Guangdong Medical University, China
| | - Lianxian Guo
- School of Public Health, Dongguan Key Laboratory of Environmental Medicine, Guangdong Medical University; School of Public Health, Institute of Environmental Health, Guangdong Medical University, China
| | - Yanqin Sun
- Department of Pathology, Guangdong Medical University, China
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Mehta K, Kaur B, Pandey KK, Dhar P, Kaler S. Resveratrol protects against inorganic arsenic-induced oxidative damage and cytoarchitectural alterations in female mouse hippocampus. Acta Histochem 2021; 123:151792. [PMID: 34634674 DOI: 10.1016/j.acthis.2021.151792] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2021] [Revised: 09/13/2021] [Accepted: 09/16/2021] [Indexed: 01/04/2023]
Abstract
Prolonged inorganic arsenic (iAs) exposure is widely associated with brain damage particularly in the hippocampus via oxidative and apoptotic pathways. Resveratrol (RES) has gained considerable attention because of its benefits to human health. However, its neuroprotective potential against iAs-induced toxicity in CA1 region of hippocampus remains unexplored. Therefore, we investigated the neuroprotective efficacy of RES against arsenic trioxide (As2O3)-induced adverse effects on neuronal morphology, apoptotic markers and oxidative stress parameters in mouse CA1 region (hippocampus). Adult female Swiss albino mice of reproductive maturity were orally exposed to either As2O3 (2 and 4 mg/kg bw) alone or in combination with RES (40 mg/kg bw) for a period of 45 days. After animal sacrifice on day 46, the perfusion fixed brain samples were used for the observation of neuronal morphology and studying the morphometric features. While the freshly dissected hippocampi were processed for biochemical estimation of oxidative stress markers and western blotting of apoptosis-associated proteins. Chronic iAs exposure led to significant decrease in Stratum Pyramidale layer thickness along with reduction in cell density and area of Pyramidal neurons in contrast to the controls. Biochemical analysis showed reduced hippocampal GSH content but no change in total nitrite (NO) levels following iAs exposure. Western blotting showed apparent changes in the expression levels of Bax and Bcl-2 proteins following iAs exposure, however the change was statistically insignificant. Contrastingly, iAs +RES co-treatment exhibited substantial reversal in morphological and biochemical observations. Together, these findings provide preliminary evidence of neuroprotective role of RES on structural and biochemical alterations pertaining to mouse hippocampus following chronic iAs exposure.
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Affiliation(s)
- K Mehta
- Department of Anatomy, All India Institute of Medical Sciences (AIIMS), New Delhi 110029, India
| | - B Kaur
- Department of Anatomy, All India Institute of Medical Sciences (AIIMS), New Delhi 110029, India
| | - K K Pandey
- Department of Anatomy, All India Institute of Medical Sciences (AIIMS), New Delhi 110029, India
| | - P Dhar
- Department of Anatomy, All India Institute of Medical Sciences (AIIMS), New Delhi 110029, India
| | - S Kaler
- Department of Anatomy, All India Institute of Medical Sciences (AIIMS), New Delhi 110029, India.
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Li J, Chen B, Zhang X, Hao Z, Zhang X, Zhu Y. Arsenic transformation and volatilization by arbuscular mycorrhizal symbiosis under axenic conditions. JOURNAL OF HAZARDOUS MATERIALS 2021; 413:125390. [PMID: 33611032 DOI: 10.1016/j.jhazmat.2021.125390] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 09/27/2020] [Accepted: 02/09/2021] [Indexed: 06/12/2023]
Abstract
It is well known that arbuscular mycorrhizal (AM) fungi can enhance plant arsenic (As) resistance by influencing As uptake, translocation, and speciation; however, As transformation and volatilization by an entire plant inoculated with AM fungus remains uninvestigated. In the present study, AM symbiosis of Rhizophagus irregularis with unbroken Medicago sativa was successfully established in vitro. Afterwards, five concentrations of arsenate were applied to the culture media. The results showed that AM inoculation could methylate inorganic As into dimethylarsinic acid (DMA), dimethylarsine (DMAsH), and trimethylarsine (TMAs), which were detected in the plants, media, or air. Volatile As, accounting for a small proportion of total organic As, appeared under high arsenate exposure, accompanied by remarkable upregulation of root RiMT-11, an arsenite methyltransferase gene in R. irregularis. In addition, AM colonization significantly increased arsenite percentages in plant tissues and external media. Regardless of As species, AM inoculation tended to release the transformed As into the environment rather than transfer them to plant tissues. Our present study, for the first time, comprehensively verified As methylation, volatilization, and reduction by AM fungus associated with the entire plant under absolute axenic conditions and gained a deeper insight into As metabolism in AM symbionts.
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Affiliation(s)
- Jinglong Li
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Baodong Chen
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xin Zhang
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
| | - Zhipeng Hao
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Xuemeng Zhang
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yongguan Zhu
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
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Park D, Propper CR, Wang G, Salanga MC. Synonymous single nucleotide polymorphism in arsenic (+3) methyltransferase of the Western mosquitofish (Gambusia affinis) and its gene expression among field populations. ECOTOXICOLOGY (LONDON, ENGLAND) 2021; 30:711-718. [PMID: 33811567 PMCID: PMC8060185 DOI: 10.1007/s10646-021-02376-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 02/22/2021] [Indexed: 05/05/2023]
Abstract
Naturally occurring arsenic is toxic at extremely low concentrations, yet some species persist even in high arsenic environments. We wanted to test if these species show evidence of evolution associated with arsenic exposure. To do this, we compared allelic variation across 872 coding nucleotides of arsenic (+3) methyltransferase (as3mt) and whole fish as3mt gene expression from three field populations of Gambusia affinis, from water sources containing low (1.9 ppb), medium-low (3.3 ppb), and high (15.7 ppb) levels of arsenic. The high arsenic site exceeds the US EPA's Maximum Contamination Level for drinking water. Medium-low and high populations exhibited homozygosity, and no sequence variation across all animals sampled. Eleven of 24 fish examined (45.8%) in the low arsenic population harbored synonymous single nucleotide polymorphisms (SNPs) in exons 4 and/or 10. SNP presence in the low arsenic population was not associated with differences in as3mt transcript levels compared to fish from the medium-low site, where SNPs were noted; however, as3mt expression in fish from the high arsenic concentration site was significantly lower than the other two sites. Low sequence variation in fish populations from sites with medium-low and high arsenic concentrations suggests greater selective pressure on this allele, while higher variation in the low population suggests a relaxed selection. Our results suggest gene regulation associated with arsenic detoxification may play a more crucial role in influencing responses to arsenic than polymorphic gene sequence. Understanding microevolutionary processes to various contaminants require the evaluation of multiple populations across a wide range of pollution exposures.
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Affiliation(s)
- Daesik Park
- Division of Science Education, Kangwon National University, Chuncheon, Kangwon, 24341, South Korea
| | - Catherine R Propper
- Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, 86011, USA
| | - Guangning Wang
- Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, 86011, USA
| | - Matthew C Salanga
- Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, 86011, USA.
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Arsenic methylation - Lessons from three decades of research. Toxicology 2021; 457:152800. [PMID: 33901604 PMCID: PMC10048126 DOI: 10.1016/j.tox.2021.152800] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 04/05/2021] [Accepted: 04/19/2021] [Indexed: 01/26/2023]
Abstract
Between 1990 and 2020, our understanding of the significance of arsenic biomethylation changed in remarkable ways. At the beginning of this period, the conversion of inorganic arsenic into mono- and di-methylated metabolites was viewed primarily as a process that altered the kinetic behavior of arsenic. By increasing the rate of clearance of arsenic, the formation of methylated metabolites reduced exposure to this toxin; that is, methylation was detoxification. By 2020, it was clear that at least some of the toxic effects associated with As exposure depended on formation of methylated metabolites containing trivalent arsenic. Because the trivalent oxidation state of arsenic is associated with increased potency as a cytotoxin and clastogen, these findings were consistent with methylation-related changes in the dynamic behavior of arsenic. That is, methylation was activation. Our current understanding of the role of methylation as a modifier of kinetic and dynamic behaviors of arsenic is the product of research at molecular, cellular, organismic, and population levels. This information provides a basis for refining our estimates of risk associated with long term exposure to inorganic arsenic in environmental media, food, and water. This report summarizes the growth of our knowledge of enzymatically catalyzed methylation of arsenic over this period and considers the prospects for new discoveries.
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Stýblo M, Venkatratnam A, Fry RC, Thomas DJ. Origins, fate, and actions of methylated trivalent metabolites of inorganic arsenic: progress and prospects. Arch Toxicol 2021; 95:1547-1572. [PMID: 33768354 DOI: 10.1007/s00204-021-03028-w] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 03/11/2021] [Indexed: 12/16/2022]
Abstract
The toxic metalloid inorganic arsenic (iAs) is widely distributed in the environment. Chronic exposure to iAs from environmental sources has been linked to a variety of human diseases. Methylation of iAs is the primary pathway for metabolism of iAs. In humans, methylation of iAs is catalyzed by arsenic (+ 3 oxidation state) methyltransferase (AS3MT). Conversion of iAs to mono- and di-methylated species (MAs and DMAs) detoxifies iAs by increasing the rate of whole body clearance of arsenic. Interindividual differences in iAs metabolism play key roles in pathogenesis of and susceptibility to a range of disease outcomes associated with iAs exposure. These adverse health effects are in part associated with the production of methylated trivalent arsenic species, methylarsonous acid (MAsIII) and dimethylarsinous acid (DMAsIII), during AS3MT-catalyzed methylation of iAs. The formation of these metabolites activates iAs to unique forms that cause disease initiation and progression. Taken together, the current evidence suggests that methylation of iAs is a pathway for detoxification and for activation of the metalloid. Beyond this general understanding of the consequences of iAs methylation, many questions remain unanswered. Our knowledge of metabolic targets for MAsIII and DMAsIII in human cells and mechanisms for interactions between these arsenicals and targets is incomplete. Development of novel analytical methods for quantitation of MAsIII and DMAsIII in biological samples promises to address some of these gaps. Here, we summarize current knowledge of the enzymatic basis of MAsIII and DMAsIII formation, the toxic actions of these metabolites, and methods available for their detection and quantification in biomatrices. Major knowledge gaps and future research directions are also discussed.
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Affiliation(s)
- Miroslav Stýblo
- Department of Nutrition, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.
| | - Abhishek Venkatratnam
- Department of Nutrition, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
- Department of Environmental Science and Engineering, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Rebecca C Fry
- Department of Environmental Science and Engineering, Gillings School of Global Public Health, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - David J Thomas
- Chemical Characterization and Exposure Division, Center for Computational Toxicology and Exposure, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC, 27709, USA.
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Barguilla I, Peremartí J, Bach J, Marcos R, Hernández A. Role of As3mt and Mth1 in the genotoxic and carcinogenic effects induced by long-term exposures to arsenic in MEF cells. Toxicol Appl Pharmacol 2020; 409:115303. [DOI: 10.1016/j.taap.2020.115303] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 10/13/2020] [Accepted: 10/21/2020] [Indexed: 11/30/2022]
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Douillet C, Koller BH, Stýblo M. Metabolism of Inorganic Arsenic in Mice Lacking Genes Encoding GST-P, GST-M, and GST-T. Chem Res Toxicol 2020; 33:2043-2046. [PMID: 32700902 DOI: 10.1021/acs.chemrestox.0c00273] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
To investigate the role of glutathione transferases (GSTs) in the metabolism of inorganic arsenic (iAs), we compared the disposition of iAs and its metabolites in wild-type mice and mice lacking genes encoding GST-P, -M and -T after exposure to 100 ppb iAs in drinking water. We found no differences between the two genotypes in the concentrations of total arsenic or arsenic species in urine, liver, and kidneys. No genotype-dependent differences were found in proportions of arsenicals in the tissues, and only small differences were observed in the urine. Thus, under these conditions, GST-P, -M and -T did not play a significant role in iAs metabolism in mice.
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Xing C, Chen J, Zheng X, Chen L, Chen M, Wang L, Li X. Functional metagenomic exploration identifies novel prokaryotic copper resistance genes from the soil microbiome. Metallomics 2020; 12:387-395. [PMID: 31942889 DOI: 10.1039/c9mt00273a] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Functional metagenomics is a premise-free approach for exploring metal resistance genes, enabling more profound effects on the development of bioremediation tools than pure culture based selection. Six soil metagenomic libraries were screened for copper (Cu) resistance genes in the current study through conventional functional genomics. Clones from the six metagenomic libraries were randomly selected from solid medium supplied with Cu, resulting in 411 Cu resistance clones. Thirty-five clones with the strongest Cu resistance were sequenced and 12 unique sequences harboring 25 putative open reading frames were obtained. It is inferred by bioinformatic analysis that putative genes carried by these recombinant plasmids probably function in the pathways of responding to Cu stress, including energy metabolism, integral components of membrane, ion transport/chelation, protein/amino acid metabolism, carbohydrate/fatty acid metabolism, signal transduction and DNA binding. The sequenced clones were re-transformed into Escherichia coli strain DH5α, and the host's biomass and the metal sorption under Cu stress were subsequently determined. The results showed that the biomass of eight of the clones was significantly increased, whereas four of them were significantly reduced. A negative correlation (R = 0.86) was found between the biomass and Cu sorption capacity. The 12 positive clones were further transferred into a Cu-sensitive E. coli strain (ΔCopA), among which nine restored the host's Cu resistance substantially. The Cu resistant genes explored in this study by functional metagenomics possess a potential capacity for developing novel bioremediation strategies, and the findings imply a vast diversity of microbial Cu resistance genetic factors in soil yet to be discovered.
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Affiliation(s)
- Chao Xing
- Key Laboratory of Soil Ecology, Key Laboratory of Agricultural Water Resources, Centre for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Shijiazhuang 050021, China.
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Clemente MJ, Cimbalo A, Chiocchetti G, Devesa V, Vélez D. Dietary Compounds To Reduce In Vivo Inorganic Arsenic Bioavailability. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2019; 67:9032-9038. [PMID: 31334646 DOI: 10.1021/acs.jafc.9b03372] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
It is estimated that approximately 200 million people are exposed to arsenic levels above the World Health Organization provisional guideline value, and various agencies have indicated the need to reduce this exposure. In view of the difficulty of removing arsenic from water and food, one alternative is to reduce its bioavailability (the amount that reaches the systemic circulation after ingestion). In this study, dietary components [glutathione, tannic acid, and Fe(III)] were used to achieve this goal. As(III) or As(V) (1 mg/kg body weight) was administered daily to BALB/c mice, along with the dietary components, for 15 days. The results confirm the efficacy of Fe(III) and glutathione as reducers of arsenic bioavailability and tissue accumulation. Also, these treatments did not result in reductions of Ca, K, P, and Fe contents in the liver. These data suggest that use of these two compounds could be part of valid strategies for reducing inorganic arsenic exposure in chronically exposed populations.
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Affiliation(s)
- María Jesús Clemente
- Instituto de Agroquímica y Tecnología de Alimentos (IATA-CSIC) , Calle Agustín Escardino 7 , Paterna 46980 , Valencia , Spain
| | - Alessandra Cimbalo
- Instituto de Agroquímica y Tecnología de Alimentos (IATA-CSIC) , Calle Agustín Escardino 7 , Paterna 46980 , Valencia , Spain
| | - Gabriela Chiocchetti
- Instituto de Agroquímica y Tecnología de Alimentos (IATA-CSIC) , Calle Agustín Escardino 7 , Paterna 46980 , Valencia , Spain
| | - Vicenta Devesa
- Instituto de Agroquímica y Tecnología de Alimentos (IATA-CSIC) , Calle Agustín Escardino 7 , Paterna 46980 , Valencia , Spain
| | - Dinoraz Vélez
- Instituto de Agroquímica y Tecnología de Alimentos (IATA-CSIC) , Calle Agustín Escardino 7 , Paterna 46980 , Valencia , Spain
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Li J, Sun Y, Zhang X, Hu Y, Li T, Zhang X, Wang Z, Wu S, Wu Z, Chen B. A methyltransferase gene from arbuscular mycorrhizal fungi involved in arsenic methylation and volatilization. CHEMOSPHERE 2018; 209:392-400. [PMID: 29935468 DOI: 10.1016/j.chemosphere.2018.06.092] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Revised: 06/11/2018] [Accepted: 06/12/2018] [Indexed: 05/27/2023]
Abstract
Arbuscular mycorrhizal fungi (AMF), ubiquitous symbiotic fungi associated with the majority of terrestrial plants, were demonstrated to play important roles in arsenic (As) translocation and transformation in the plant-soil continuum, and substantially influence plant As tolerance. However, the direct involvement of AMF in As methylation and volatilization and their molecular mechanisms remain unsolved. Here, an arsenite methyltransferase gene RiMT-11 was identified and characterized from AM fungus Rhizophagus irregularis. Heterologous expression of RiMT-11 enhanced arsenite resistance of E. coli (Δars) through methylating As into monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and ultimately volatile trimethyl arsine (TMAs). In a two-compartment in vitro monoxenic cultivation system, methylated and volatile As were also detected from AM symbioses with arsenate addition, accompanied by strong up-regulation of RiMT-11 expression in extraradical hyphae. The present study provided direct evidence and illustrated an underlying mechanism of As methylation and volatilization by AMF, leading to a deeper insight into the role of AMF in As biogeochemical cycling.
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Affiliation(s)
- Jinglong Li
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yuqing Sun
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xin Zhang
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
| | - Yajun Hu
- Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, Hunan 410125, China
| | - Tao Li
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Xuemeng Zhang
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhi Wang
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; College of Forestry, Jiangxi Agricultural University, Nanchang, Jiangxi 330045, China
| | - Songlin Wu
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Zhaoxiang Wu
- Jiangxi Engineering and Technology Research Center for Ecological Remediation of Heavy Metal Pollution, Institute of Biology and Resources, Jiangxi Academy of Sciences, Nanchang, Jiangxi 330096, China
| | - Baodong Chen
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
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Twaddle NC, Vanlandingham M, Churchwell MI, Doerge DR. Metabolism and disposition of arsenic species from controlled oral dosing with sodium arsenite in adult female CD-1 mice. I. Pilot study to determine dosing, analytical measurements, and sampling strategies. Food Chem Toxicol 2017; 111:482-493. [PMID: 29217265 DOI: 10.1016/j.fct.2017.12.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Revised: 11/07/2017] [Accepted: 12/02/2017] [Indexed: 12/21/2022]
Abstract
Arsenic (As) is ubiquitous in the earth's crust, with typical dietary intake in developed countries <1 μg/kg bw/d, and atypical groundwater exposures in developing countries approaching 50 μg/kg bw/d. Arsenic exposures are linked with human diseases and doses of toxicological concern are similar to typical dietary intake estimates. The methylation of arsenite by arsenite-3-methyltransferase (As3MT) promotes the clearance of arsenic as pentavalent species, but also generates reactive trivalent intermediates. This study measured inorganic arsenic and its metabolites in pentavalent and trivalent states in blood, tissues, and excreta after oral administration of arsenite (50-200 μg/kg bw). While liver was a major site for clearance of arsenite and formation of methylated species, it also had extensive binding of trivalent intermediates; however, thiol exchange and oxidation reactions of trivalent arsenic were facile since dimethylarsinic acid (DMAV) was the predominant species in blood and urine. Consistent evidence was observed for a non-linear relationship between doses above 50 μg/kg bw and levels of bound trivalent As metabolites. The abundance of protein-bound trivalent arsenic within target tissues should correlate with disruption of critical cellular processes, which rely on defined interactions of thiol functional groups, and could provide dose-response relationships from animal models for human risk assessment.
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Affiliation(s)
- Nathan C Twaddle
- Division of Biochemical Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR 72079, United States
| | - Michelle Vanlandingham
- Division of Biochemical Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR 72079, United States
| | - Mona I Churchwell
- Division of Biochemical Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR 72079, United States
| | - Daniel R Doerge
- Division of Biochemical Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR 72079, United States.
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14
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Li J, Pawitwar SS, Rosen BP. The organoarsenical biocycle and the primordial antibiotic methylarsenite. Metallomics 2017; 8:1047-1055. [PMID: 27730229 DOI: 10.1039/c6mt00168h] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Arsenic is the most pervasive environmental toxic substance. As a consequence of its ubiquity, nearly every organism has genes for resistance to inorganic arsenic. In bacteria these genes are found largely in bacterial arsenic resistance (ars) operons. Recently a parallel pathway for synthesis and degradation of methylated arsenicals has been identified. The arsM gene product encodes the ArsM (AS3MT in animals) As(iii) S-adenosylmethionine methyltransferase that methylates inorganic trivalent arsenite in three sequential steps to methylarsenite MAs(iii), dimethylarsenite (DMAs(iii) and trimethylarsenite (TMAs(iii)). MAs(iii) is considerably more toxic than As(iii), and we have proposed that MAs(iii) was a primordial antibiotic. Under aerobic conditions these products are oxidized to nontoxic pentavalent arsenicals, so that methylation became a detoxifying pathway after the atmosphere became oxidizing. Other microbes have acquired the ability to regenerate MAs(v) by reduction, transforming it again into toxic MAs(iii). Under this environmental pressure, MAs(iii) resistances evolved, including the arsI, arsH and arsP genes. ArsI is a C-As bond lyase that demethylates MAs(iii) back to less toxic As(iii). ArsH re-oxidizes MAs(iii) to MAs(v). ArsP actively extrudes MAs(iii) from cells. These proteins confer resistance to this primitive antibiotic. This oscillation between MAs(iii) synthesis and detoxification is an essential component of the arsenic biogeocycle.
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Affiliation(s)
- Jiaojiao Li
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, 11200 S.W. 8 Street, Miami, FL 33199 USA
| | - Shashank S Pawitwar
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, 11200 S.W. 8 Street, Miami, FL 33199 USA
| | - Barry P Rosen
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, 11200 S.W. 8 Street, Miami, FL 33199 USA
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15
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Shen L, Jiang X, Chen Z, Fu D, Li Q, Ouyang T, Wang Y. Chemical reactive features of novel amino acids intercalated layered double hydroxides in As(III) and As(V) adsorption. CHEMOSPHERE 2017; 176:57-66. [PMID: 28259079 DOI: 10.1016/j.chemosphere.2017.02.100] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Revised: 12/27/2016] [Accepted: 02/19/2017] [Indexed: 06/06/2023]
Abstract
Layered double hydroxides (LDHs) intercalated with amino acids such as methionine (Met) were synthesized as new adsorbents to remediate arsenic-polluted water. This Zn2Al-Met-LDHs, identified with the formula of Zn0.7Al0.3(OH)2(Met)0.3·0.32H2O, has good thermal stability. Adsorption experiments with Zn2Al-Met-LDHs showed that the residual arsenic in solution could be reduced below the regulation limit, and this adsorption process fitted Langmuir isotherm and the pseudo-second-order kinetics well. A remarkably high removal efficiency and the maximum adsorption capacity for As(III) were achieved, 96.7% and 94.1 mg/g, respectively, at 298 K. The desorption efficiency of As(III) from the arsenic-saturated Zn2Al-Met-LDHs (<8.7%), far less than that of As(V), promises a specific and reliable uptake of As(III) in sorts of solutions. More importantly, a complete and in-depth spectra analysis through FTIR, XPS and NMR was conducted to explain the excellent performance of Zn2Al-Met-LDHs in arsenic removal. Herein, two special chemical reactions were proposed as the dominant mechanisms, i.e., hydrogen bonding between the carboxyl group of the host Met and the hydroxyl group of As(III) or As(V), and the formation of a chelate ring between the guest As(III) and the S, N bidentate ligands of the intercalated Met in the LDHs.
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Affiliation(s)
- Liang Shen
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, The Key Laboratory for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen, 361005, PR China
| | - Xiuli Jiang
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, The Key Laboratory for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen, 361005, PR China; Department of Environment Engineering, College of the Environment and Ecology, and The Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystem, Xiamen University, Xiamen, 361102, PR China; School of Environmental Science & Engineering, South University of Science and Technology of China, Shenzhen, 518055, PR China
| | - Zheng Chen
- Department of Environment Engineering, College of the Environment and Ecology, and The Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystem, Xiamen University, Xiamen, 361102, PR China
| | - Dun Fu
- Department of Environment Engineering, College of the Environment and Ecology, and The Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystem, Xiamen University, Xiamen, 361102, PR China
| | - Qingbiao Li
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, The Key Laboratory for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen, 361005, PR China; Department of Environment Engineering, College of the Environment and Ecology, and The Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystem, Xiamen University, Xiamen, 361102, PR China; College of Chemistry and Life Science, Quanzhou Normal University, Quanzhou, 362000, PR China
| | - Tong Ouyang
- Department of Environment Engineering, College of the Environment and Ecology, and The Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystem, Xiamen University, Xiamen, 361102, PR China.
| | - Yuanpeng Wang
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, The Key Laboratory for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen, 361005, PR China.
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16
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Strain differences in arsenic-induced oxidative lesion via arsenic biomethylation between C57BL/6J and 129X1/SvJ mice. Sci Rep 2017; 7:44424. [PMID: 28303940 PMCID: PMC5355880 DOI: 10.1038/srep44424] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 02/07/2017] [Indexed: 12/11/2022] Open
Abstract
Arsenic is a common environmental and occupational toxicant with dramatic species differences in its susceptibility and metabolism. Mouse strain variability may provide a better understanding of the arsenic pathological profile but is largely unknown. Here we investigated oxidative lesion induced by acute arsenic exposure in the two frequently used mouse strains C57BL/6J and 129X1/SvJ in classical gene targeting technique. A dose of 5 mg/kg body weight arsenic led to a significant alteration of blood glutathione towards oxidized redox potential and increased hepatic malondialdehyde content in C57BL/6J mice, but not in 129X1/SvJ mice. Hepatic antioxidant enzymes were induced by arsenic in transcription in both strains and many were higher in C57BL/6J than 129X1/SvJ mice. Arsenic profiles in the liver, blood and urine and transcription of genes encoding enzymes involved in arsenic biomethylation all indicate a higher arsenic methylation capacity, which contributes to a faster hepatic arsenic excretion, in 129X1/SvJ mice than C57BL/6J mice. Taken together, C57BL/6J mice are more susceptible to oxidative hepatic injury compared with 129X1/SvJ mice after acute arsenic exposure, which is closely associated with arsenic methylation pattern of the two strains.
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17
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Xue XM, Ye J, Raber G, Francesconi KA, Li G, Gao H, Yan Y, Rensing C, Zhu YG. Arsenic Methyltransferase is Involved in Arsenosugar Biosynthesis by Providing DMA. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:1224-1230. [PMID: 28076949 DOI: 10.1021/acs.est.6b04952] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Arsenic is an ubiquitous toxic element in the environment, and organisms have evolved different arsenic detoxification strategies. Studies on arsenic biotransformation mechanisms have mainly focused on arsenate (As(V)) reduction, arsenite (As(III)) oxidation, and arsenic methylation; little is known, however, about the pathway for the biosynthesis of arsenosugars, which are significant arsenic transformation products. Here, the involvement of As(III) S-Adenosylmethionine methyltransferase (ArsM) in arsenosugar synthesis is demonstrated for the first time. Synechocystis sp. PCC 6803 incubated with As(III) or monomethylarsonic acid (MMA(V)) produced dimethylarsinic acid (DMA(V)) and arsenosugars, as determined by high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC/ICPMS). Arsenosugars were also detected in the cells when they were exposed to DMA(V). A mutant strain Synechocystis ΔarsM was constructed by disrupting arsM in Synechocystis sp. PCC 6803. Methylation of arsenic species was not observed in the mutant strain after exposure to arsenite or MMA(V); when Synechocystis ΔarsM was incubated with DMA(V), arsenosugars were detected in the cells. These results suggest that ArsM is a required enzyme for the methylation of inorganic arsenicals, but not required for the synthesis of arsenosugars from DMA, and that DMA is the precursor of arsenosugar biosynthesis. The findings will stimulate more studies on the biosynthesis of complex organoarsenicals, and lead to a better understanding of the bioavailability and function of the organoarsenicals in biological systems.
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Affiliation(s)
- Xi-Mei Xue
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences , Xiamen 361021, China
| | - Jun Ye
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences , Xiamen 361021, China
| | - Georg Raber
- Institute of Chemistry, University of Graz , Graz, Austria
| | | | - Gang Li
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences , Xiamen 361021, China
| | - Hong Gao
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences , Wuhan, China
| | - Yu Yan
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences , Xiamen 361021, China
| | - Christopher Rensing
- College of Resources and Environment, Fujian Agriculture and Forestry University , Fuzhou, China
| | - Yong-Guan Zhu
- Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences , Xiamen 361021, China
- State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , Beijing, China
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18
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Verma S, Verma PK, Meher AK, Dwivedi S, Bansiwal AK, Pande V, Srivastava PK, Verma PC, Tripathi RD, Chakrabarty D. A novel arsenic methyltransferase gene of Westerdykella aurantiaca isolated from arsenic contaminated soil: phylogenetic, physiological, and biochemical studies and its role in arsenic bioremediation. Metallomics 2016; 8:344-53. [PMID: 26776948 DOI: 10.1039/c5mt00277j] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Elevated arsenic concentration in the environment and agricultural soil is a serious concern to crop production and human health. Among different detoxification mechanisms, the methylation of arsenic is a widespread phenomenon in nature. A number of microorganisms are able to methylate arsenic, but less is known about the arsenic metabolism in fungi. We identified a novel arsenic methyltransferase (WaarsM) gene from a soil fungus, Westerdykella aurantiaca. WaarsM showed sequence homology with all known arsenic methyltransferases having three conserved SAM binding motifs. The expression of WaarsM enhanced arsenic resistance in E. coli (Δars) and S. cerevisiae (Δacr2) strains by biomethylation and required endogenous reductants, preferably GSH, for methyltransferase activity. The purified WaarsM catalyzes the production of methylated arsenicals from both AsIII and AsV, and also displays AsV reductase activity. It displayed higher methyltransferase activity and lower KM 0.1945 ± 0.021 mM and KM 0.4034 ± 0.078 mM for AsIII and AsV, respectively. S. cerevisiae (Δacr2) cells expressing WaarsM produced 2.2 ppm volatile arsenic and 0.64 ppm DMA(v) with 0.58 ppm volatile arsenicals when exposed to 20 ppm AsV and 2 ppm AsIII, respectively. Arsenic tolerance in rice after co-culture with genetically engineered yeast suggested its potential role in arsenic bioremediation. Thus, characterization of WaarsM provides a potential strategy to reduce arsenic concentration in soil with reduced arsenic accumulation in crops grown in arsenic contaminated areas, and thereby alleviating human health risks.
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Affiliation(s)
- Shikha Verma
- Genetics and Molecular Biology Division, CSIR-National Botanical Research Institute, India. and Department of Biotechnology, Kumaun University, India
| | - Pankaj Kumar Verma
- Genetics and Molecular Biology Division, CSIR-National Botanical Research Institute, India. and Department of Biotechnology, Kumaun University, India
| | - Alok Kumar Meher
- Environmental Material Division, CSIR-National Environmental Engineering Research Institute, India
| | - Sanjay Dwivedi
- Plant Ecology and Environmental Science Division, CSIR-National Botanical Research Institute, India
| | - Amit Kumar Bansiwal
- Environmental Material Division, CSIR-National Environmental Engineering Research Institute, India
| | - Veena Pande
- Department of Biotechnology, Kumaun University, India
| | - Pankaj Kumar Srivastava
- Plant Ecology and Environmental Science Division, CSIR-National Botanical Research Institute, India
| | - Praveen Chandra Verma
- Genetics and Molecular Biology Division, CSIR-National Botanical Research Institute, India.
| | - Rudra Deo Tripathi
- Plant Ecology and Environmental Science Division, CSIR-National Botanical Research Institute, India
| | - Debasis Chakrabarty
- Genetics and Molecular Biology Division, CSIR-National Botanical Research Institute, India.
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19
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Heavy Metals and Human Health: Mechanistic Insight into Toxicity and Counter Defense System of Antioxidants. Int J Mol Sci 2015; 16:29592-630. [PMID: 26690422 PMCID: PMC4691126 DOI: 10.3390/ijms161226183] [Citation(s) in RCA: 475] [Impact Index Per Article: 52.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Revised: 12/01/2015] [Accepted: 12/03/2015] [Indexed: 02/07/2023] Open
Abstract
Heavy metals, which have widespread environmental distribution and originate from natural and anthropogenic sources, are common environmental pollutants. In recent decades, their contamination has increased dramatically because of continuous discharge in sewage and untreated industrial effluents. Because they are non-degradable, they persist in the environment; accordingly, they have received a great deal of attention owing to their potential health and environmental risks. Although the toxic effects of metals depend on the forms and routes of exposure, interruptions of intracellular homeostasis include damage to lipids, proteins, enzymes and DNA via the production of free radicals. Following exposure to heavy metals, their metabolism and subsequent excretion from the body depends on the presence of antioxidants (glutathione, α-tocopherol, ascorbate, etc.) associated with the quenching of free radicals by suspending the activity of enzymes (catalase, peroxidase, and superoxide dismutase). Therefore, this review was written to provide a deep understanding of the mechanisms involved in eliciting their toxicity in order to highlight the necessity for development of strategies to decrease exposure to these metals, as well as to identify substances that contribute significantly to overcome their hazardous effects within the body of living organisms.
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Sumi D, Tsurumoto M, Yoshino Y, Inoue M, Yokobori T, Kuwano H, Himeno S. High accumulation of arsenic in the esophagus of mice after exposure to arsenite. Arch Toxicol 2015; 89:1751-8. [PMID: 25092181 DOI: 10.1007/s00204-014-1326-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Accepted: 07/21/2014] [Indexed: 11/28/2022]
Abstract
Arsenic-induced toxicity appears to be dependent on the tissue- or cell-specific accumulation of this metalloid. An early study showed that arsenic was retained in the esophagus as well as the liver, kidney cortex and skin of marmosets after intraperitoneal administration of (74)As-arsenite. However, there is little available information regarding the distribution of arsenic in the esophagus. Here, we compared the retention of arsenic in the esophagus, liver, lung, kidney and heart in mice intraperitoneally administered 1 or 5 mg/kg sodium arsenite (As(III)) daily for 3 or 7 days. The results showed that the arsenic concentration was highest in the esophagus. We compared the mRNA levels of aquaglyceroporin (AQP) 3, AQP7 and AQP9, which are responsible for arsenic influx, and those of multidrug-resistance protein (MRP) 1 and MRP2, which are responsible for arsenic efflux. The levels of AQP3 mRNA in the esophagus were much higher than those in liver, lung and heart, while the mRNA levels of MRP2 were very low in the esophagus. In addition, we found extremely low expression of Nrf2 in the esophagus at the basal and under the activated conditions, which might have resulted in low levels of glutamyl-cysteine ligase catalytic and modulatory subunits, and subsequently in the low levels of glutathione. Thus, the highest retention of arsenic was detected in the esophagus after intraperitoneal administration of As(III) to mice, and this appeared to result from multiple factors, including high expression of AQP3, low expression of MRP2, low capacity of glutathione synthesis and low activation of Nrf2.
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Affiliation(s)
- Daigo Sumi
- Laboratory of Molecular Nutrition and Toxicology, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Yamashiro-cho, Tokushima, 770-8514, Japan
| | - Miyu Tsurumoto
- Laboratory of Molecular Nutrition and Toxicology, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Yamashiro-cho, Tokushima, 770-8514, Japan
| | - Yuri Yoshino
- Laboratory of Molecular Nutrition and Toxicology, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Yamashiro-cho, Tokushima, 770-8514, Japan
| | - Masahisa Inoue
- Laboratory of Functional Morphology, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Yamashiro-cho, Tokushima, 770-8514, Japan
| | - Takehiko Yokobori
- Department of General Surgical Science, Graduate School of Medicine, Gunma University, Showa-cho, Maebashi-city, Gunma, 371-8511, Japan
| | - Hiroyuki Kuwano
- Department of General Surgical Science, Graduate School of Medicine, Gunma University, Showa-cho, Maebashi-city, Gunma, 371-8511, Japan
| | - Seiichiro Himeno
- Laboratory of Molecular Nutrition and Toxicology, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Yamashiro-cho, Tokushima, 770-8514, Japan.
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22
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Dheeman DS, Packianathan C, Pillai JK, Rosen BP. Pathway of human AS3MT arsenic methylation. Chem Res Toxicol 2014; 27:1979-89. [PMID: 25325836 PMCID: PMC4237493 DOI: 10.1021/tx500313k] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
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A synthetic gene encoding human As(III) S-adenosylmethionine
(SAM) methyltransferase (hAS3MT) was expressed, and the purified enzyme
was characterized. The synthetic enzyme is considerably more active
than a cDNA-expressed enzyme using endogenous reductants thioredoxin
(Trx), thioredoxin reductase (TR), NADPH, and reduced glutathione
(GSH). Each of the seven cysteines (the four conserved residues, Cys32,
Cys61, Cys156, and Cys206, and nonconserved, Cys72, Cys85, and Cys250)
was individually changed to serine. The nonconserved cysteine derivates
were still active. None of the individual C32S, C61S, C156S, and C206S
derivates were able to methylate As(III). However, the C32S and C61S
enzymes retained the ability to methylate MAs(III). These observations
suggest that Cys156 and Cys206 play a different role in catalysis
than that of Cys32 and Cys61. A homology model built on the structure
of a thermophilic orthologue indicates that Cys156 and Cys206 form
the As(III) binding site, whereas Cys32 and Cys61 form a disulfide
bond. Two observations shed light on the pathway of methylation. First,
binding assays using the fluorescence of a single-tryptophan derivative
indicate that As(GS)3 binds to the enzyme much faster than
inorganic As(III). Second, the major product of the first round of
methylation is MAs(III), not MAs(V), and remains enzyme-bound until
it is methylated a second time. We propose a new pathway for hAS3MT
catalysis that reconciles the hypothesis of Challenger ((1947) Sci. Prog., 35, 396–416) with the
pathway proposed by Hayakawa et al. ((2005) Arch. Toxicol., 79, 183–191). The products are the more
toxic and more carcinogenic trivalent methylarsenicals, but arsenic
undergoes oxidation and reduction as enzyme-bound intermediates.
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Affiliation(s)
- Dharmendra S Dheeman
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University , Miami, Florida 33199 United States
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23
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Tokumoto M, Kutsukake N, Yamanishi E, Katsuta D, Anan Y, Ogra Y. Arsenic (+3 oxidation state) methyltransferase is a specific but replaceable factor against arsenic toxicity. Toxicol Rep 2014; 1:589-595. [PMID: 28962272 PMCID: PMC5598430 DOI: 10.1016/j.toxrep.2014.08.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 08/22/2014] [Accepted: 08/23/2014] [Indexed: 01/31/2023] Open
Abstract
AS3MT catalyzed the methylation of arsenic. Selenium and tellurium were not methylated in the presence of AS3MT. AS3MT knockdown had no effect on the cytotoxicity of arsenic.
Inorganic metalloids, such as arsenic (As), antimony (Sb), selenium (Se), and tellurium (Te), are methylated in biota. In particular, As, Se, and Te are methylated and excreted in urine. The biomethylation is thought to be a means to detoxify the metalloids. The methylation of As is catalyzed by arsenic (+3 oxidation state) methyltransferase (AS3MT). However, it is still unclear whether AS3MT catalyzes the methylation of the other metalloids. It is also unclear whether other factors catalyze the As methylation instead of AS3MT. Recombinant human AS3MT (rhAS3MT) was prepared and used in the in vitro methylation of As, Se, and Te. As, but not Se and Te, was specifically methylated in the presence of rhAS3MT. Then, siRNA targeting AS3MT was introduced into human hepatocarcinoma (HepG2) cells. Although AS3MT protein expression was completely silenced by the gene knockdown, no increase in As toxicity was found in the HepG2 cells transfected with AS3MT-targeting siRNA. We conclude that AS3MT catalyzes the methylation of As and not other biomethylatable metalloids, such as Se and Te. We speculate that other methylation enzyme(s) also catalyze the methylation of As in HepG2 cells.
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Affiliation(s)
| | | | | | | | | | - Yasumitsu Ogra
- Corresponding author. Tel.: +81 42 721 1563; fax: +81 42 721 1563
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Niedzwiecki MM, Hall MN, Liu X, Slavkovich V, Ilievski V, Levy D, Alam S, Siddique AB, Parvez F, Graziano JH, Gamble MV. Interaction of plasma glutathione redox and folate deficiency on arsenic methylation capacity in Bangladeshi adults. Free Radic Biol Med 2014; 73:67-74. [PMID: 24726863 PMCID: PMC4111991 DOI: 10.1016/j.freeradbiomed.2014.03.042] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Revised: 03/28/2014] [Accepted: 03/30/2014] [Indexed: 11/19/2022]
Abstract
Inorganic arsenic(As) is metabolized through a series of methylation reactions catalyzed by arsenic(III)-methyltransferase (AS3MT), resulting in the generation of monomethylarsonic (MMAs) and dimethylarsinic acids (DMAs). AS3MT activity requires the presence of the methyl donor S-adenosylmethionine, a product of folate-dependent one-carbon metabolism, and a reductant. Although glutathione (GSH), the primary endogenous antioxidant, is not required for As methylation, GSH stimulates As methylation rates in vitro. However, the relationship between GSH redox and As methylation capacity in humans is unknown. We wished to test the hypothesis that a more oxidized plasma GSH redox status is associated with decreased As methylation capacity and examine whether these associations are modified by folate nutritional status. Concentrations of plasma GSH and GSSG, plasma folate, total blood As (bAs), total urinary As (uAs), and uAs metabolites were assessed in a cross-sectional study of n=376 Bangladeshi adults who were chronically exposed to As in drinking water. We observed that a decreased plasma GSH/GSSG ratio (reflecting a more oxidized redox state) was significantly associated with increased urinary %MMA, decreased urinary %DMA, and increased total bAs in folate-deficient individuals (plasma folate ≤ 9.0 nmol/L). Concentrations of plasma GSH and GSSG were independently associated with increased and decreased As methylation capacity, respectively. No significant associations were observed in folate-sufficient individuals, and interactions by folate status were statistically significant. Our findings suggest that GSH/GSSG redox regulation might contribute to the large interindividual variation in As methylation capacity observed in human populations.
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Affiliation(s)
- Megan M Niedzwiecki
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, NY 10032, USA
| | - Megan N Hall
- Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, NY 10032, USA
| | - Xinhua Liu
- Department of Biostatistics, Mailman School of Public Health, Columbia University, New York, NY 10032, USA
| | - Vesna Slavkovich
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, NY 10032, USA
| | - Vesna Ilievski
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, NY 10032, USA
| | - Diane Levy
- Department of Biostatistics, Mailman School of Public Health, Columbia University, New York, NY 10032, USA
| | - Shafiul Alam
- Columbia University Arsenic Project in Bangladesh, Dhaka, Bangladesh
| | - Abu B Siddique
- Columbia University Arsenic Project in Bangladesh, Dhaka, Bangladesh
| | - Faruque Parvez
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, NY 10032, USA
| | - Joseph H Graziano
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, NY 10032, USA
| | - Mary V Gamble
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, NY 10032, USA.
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25
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Sun HJ, Rathinasabapathi B, Wu B, Luo J, Pu LP, Ma LQ. Arsenic and selenium toxicity and their interactive effects in humans. ENVIRONMENT INTERNATIONAL 2014; 69:148-58. [PMID: 24853282 DOI: 10.1016/j.envint.2014.04.019] [Citation(s) in RCA: 229] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Revised: 04/29/2014] [Accepted: 04/29/2014] [Indexed: 05/15/2023]
Abstract
Arsenic (As) and selenium (Se) are unusual metalloids as they both induce and cure cancer. They both cause carcinogenesis, pathology, cytotoxicity, and genotoxicity in humans, with reactive oxygen species playing an important role. While As induces adverse effects by decreasing DNA methylation and affecting protein 53 expression, Se induces adverse effects by modifying thioredoxin reductase. However, they can react with glutathione and S-adenosylmethionine by forming an As-Se complex, which can be secreted extracellularly. We hypothesize that there are two types of interactions between As and Se. At low concentration, Se can decrease As toxicity via excretion of As-Se compound [(GS3)2AsSe](-), but at high concentration, excessive Se can enhance As toxicity by reacting with S-adenosylmethionine and glutathione, and modifying the structure and activity of arsenite methyltransferase. This review is to summarize their toxicity mechanisms and the interaction between As and Se toxicity, and to provide suggestions for future investigations.
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Affiliation(s)
- Hong-Jie Sun
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, Jiangsu 210046, China
| | - Bala Rathinasabapathi
- Horticultural Sciences Department, University of Florida, Gainesville, FL 32611, United States
| | - Bing Wu
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, Jiangsu 210046, China
| | - Jun Luo
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, Jiangsu 210046, China
| | - Li-Ping Pu
- Suzhou Health College, Suzhou, Jiangsu 215000, China
| | - Lena Q Ma
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, Jiangsu 210046, China; Soil and Water Science Department, University of Florida, Gainesville, FL 32611, USA.
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26
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Lawley SD, Yun J, Gamble MV, Hall MN, Reed MC, Nijhout HF. Mathematical modeling of the effects of glutathione on arsenic methylation. Theor Biol Med Model 2014; 11:20. [PMID: 24885596 PMCID: PMC4041632 DOI: 10.1186/1742-4682-11-20] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Accepted: 04/30/2014] [Indexed: 02/06/2023] Open
Abstract
Background Arsenic is a major environmental toxin that is detoxified in the liver by biochemical mechanisms that are still under study. In the traditional metabolic pathway, arsenic undergoes two methylation reactions, each followed by a reduction, after which it is exported and released in the urine. Recent experiments show that glutathione plays an important role in arsenic detoxification and an alternative biochemical pathway has been proposed in which arsenic is first conjugated by glutathione after which the conjugates are methylated. In addition, in rats arsenic-glutathione conjugates can be exported into the plasma and removed by the liver in the bile. Methods We have developed a mathematical model for arsenic biochemistry that includes three mechanisms by which glutathione affects arsenic methylation: glutathione increases the speed of the reduction steps; glutathione affects the activity of arsenic methyltranferase; glutathione sequesters inorganic arsenic and its methylated downstream products. The model is based as much as possible on the known biochemistry of arsenic methylation derived from cellular and experimental studies. Results We show that the model predicts and helps explain recent experimental data on the effects of glutathione on arsenic methylation. We explain why the experimental data imply that monomethyl arsonic acid inhibits the second methylation step. The model predicts time course data from recent experimental studies. We explain why increasing glutathione when it is low increases arsenic methylation and that at very high concentrations increasing glutathione decreases methylation. We explain why the possible temporal variation of the glutathione concentration affects the interpretation of experimental studies that last hours. Conclusions The mathematical model aids in the interpretation of data from recent experimental studies and shows that the Challenger pathway of arsenic methylation, supplemented by the glutathione effects described above, is sufficient to understand and predict recent experimental data. More experimental studies are needed to explicate the detailed mechanisms of action of glutathione on arsenic methylation. Recent experimental work on the effects of glutathione on arsenic methylation and our modeling study suggest that supplements that increase hepatic glutathione production should be considered as strategies to reduce adverse health effects in affected populations.
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Affiliation(s)
| | | | | | | | - Michael C Reed
- Department of Mathematics, Duke University, Durham, NC 27708, USA.
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27
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Affiliation(s)
- William R. Cullen
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z1
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28
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Li X, Geng Z, Chang J, Wang S, Song X, Hu X, Wang Z. Identification of the third binding site of arsenic in human arsenic (III) methyltransferase. PLoS One 2013; 8:e84231. [PMID: 24391919 PMCID: PMC3877260 DOI: 10.1371/journal.pone.0084231] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Accepted: 11/21/2013] [Indexed: 01/15/2023] Open
Abstract
Arsenic (III) methyltransferase (AS3MT) catalyzes the process of arsenic methylation. Each arsenite (iAs3+) binds to three cysteine residues, methylarsenite (MMA3+) binds to two, and dimethylarsenite (DMA3+) binds to one. However, only two As-binding sites (Cys156 and Cys206) have been confirmed on human AS3MT (hAS3MT). The third As-binding site is still undefined. Residue Cys72 in Cyanidioschyzon merolae arsenite S-adenosylmethyltransferase (CmArsM) may be the third As-binding site. The corresponding residue in hAS3MT is Cys61. Functions of Cys32, Cys61, and Cys85 in hAS3MT are unclear though Cys32, Cys61, and Cys85 in rat AS3MT have no effect on the enzyme activity. This is why the functions of Cys32, Cys61, and Cys85 in hAS3MT merit investigation. Here, three mutants were designed, C32S, C61S, and C85S. Their catalytic activities and conformations were determined, and the catalytic capacities of C156S and C206S were studied. Unlike C85S, mutants C32S and C61S were completely inactive in the methylation of iAs3+ and active in the methylation of MMA3+. The catalytic activity of C85S was also less pronounced than that of WT-hAS3MT. All these findings suggest that Cys32 and Cys61 markedly influence the catalytic activity of hAS3MT. Cys32 and Cys61 are necessary to the first step of methylation but not to the second. Cys156 and Cys206 are required for both the first and second steps of methylation. The SC32 is located far from arsenic in the WT-hAS3MT-SAM-As model. The distances between SC61 and arsenic in WT-hAS3MT-As and WT-hAS3MT-SAM-As models are 7.5 Å and 4.1 Å, respectively. This indicates that SAM-binding to hAS3MT shortens the distance between SC61 and arsenic and promotes As-binding to hAS3MT. This is consistent with the fact that SAM is the first substrate to bind to hAS3MT and iAs is the second. Model of WT-hAS3MT-SAM-As and the experimental results indicate that Cys61 is the third As-binding site.
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Affiliation(s)
- Xiangli Li
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, PR China
| | - Zhirong Geng
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, PR China
- * E-mail: (ZW); (ZG)
| | - Jiayin Chang
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, PR China
| | - Shuping Wang
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, PR China
| | - Xiaoli Song
- School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou, PR China
| | - Xin Hu
- Modern Analysis Center of Nanjing University, Nanjing, PR China
| | - Zhilin Wang
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, PR China
- * E-mail: (ZW); (ZG)
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29
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Dai W, Yang X, Chen H, Xu W, He Z, Ma M. Phytotoxicities of inorganic arsenic and dimethylarsinic acid to Arabidopsis thaliana and Pteris vittata. BULLETIN OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 2013; 91:652-5. [PMID: 24084979 DOI: 10.1007/s00128-013-1115-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Accepted: 09/18/2013] [Indexed: 05/09/2023]
Abstract
The mechanisms by which Pteris vittata (L.) hyperaccumulates arsenic (As) have not been fully elucidated. To investigate how P. vittata tolerates high concentrations of arsenite, we compared the toxicities of various As compounds to P. vittata and Arabidopsis thaliana (L.). The phytotoxicities of As species were found to be in the order of arsenite > arsenate > dimethylarsinic acid (DMAA) in A. thaliana, and in the order of DMAA > arsenate > arsenite in P. vittata. P. vittata calli displayed a weaker ability to absorb arsenite than arsenate. These results demonstrate that P. vittata possesses mechanisms of As accumulation and detoxification.
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Affiliation(s)
- Wentao Dai
- Key Laboratory of Plant Resources, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, People's Republic of China
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30
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Affiliation(s)
- Shengwen Shen
- Department
of Laboratory Medicine
and Pathology, 10-102 Clinical Sciences Building, University
of Alberta, Edmonton, Alberta, Canada, T6G 2G3
| | - Xing-Fang Li
- Department
of Laboratory Medicine
and Pathology, 10-102 Clinical Sciences Building, University
of Alberta, Edmonton, Alberta, Canada, T6G 2G3
| | - William R. Cullen
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver,
British Columbia, Canada, V6T 1Z1
| | - Michael Weinfeld
- Department of Oncology, Cross
Cancer Institute, University of Alberta, 11560 University Avenue, Edmonton, Alberta, Canada, T6G 1Z2
| | - X. Chris Le
- Department
of Laboratory Medicine
and Pathology, 10-102 Clinical Sciences Building, University
of Alberta, Edmonton, Alberta, Canada, T6G 2G3
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31
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Residues in human arsenic (+3 oxidation state) methyltransferase forming potential hydrogen bond network around S-adenosylmethionine. PLoS One 2013; 8:e76709. [PMID: 24124590 PMCID: PMC3790734 DOI: 10.1371/journal.pone.0076709] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 08/27/2013] [Indexed: 11/19/2022] Open
Abstract
Residues Tyr59, Gly78, Ser79, Met103, Gln107, Ile136 and Glu137 in human arsenic (+3 oxidation state) methyltransferase (hAS3MT) were deduced to form a potential hydrogen bond network around S-adenosylmethionine (SAM) from the sequence alignment between Cyanidioschyzon merolae arsenite S-adenosylmethyltransferase (CmArsM) and hAS3MT. Herein, seven mutants Y59A, G78A, S79A, M103A, Q107A, I136A and E137A were obtained. Their catalytic activities and conformations were characterized and models were built. Y59A and G78A were completely inactive. Only 7.0%, 10.6% and 13.8% inorganic arsenic (iAs) was transformed to monomethylated arsenicals (MMA) when M103A, Q107A and I136A were used as the enzyme. The Vmax (the maximal velocity of the reaction) values of M103A, Q107A, I136A and E137A were decreased to 8%, 22%, 15% and 50% of that of WT-hAS3MT, respectively. The KM(SAM) (the Michaelis constant for SAM) values of mutants M103A, I136A and E137A were 15.7, 8.9 and 5.1 fold higher than that of WT-hAS3MT, respectively, indicating that their affinities for SAM were weakened. The altered microenvironment of SAM and the reduced capacity of binding arsenic deduced from KM(As) (the Michaelis constant for iAs) value probably synergetically reduced the catalytic activity of Q107A. The catalytic activity of S79A was higher than that of WT despite of the higher KM(SAM), suggesting that Ser79 did not impact the catalytic activity of hAS3MT. In short, residues Tyr59 and Gly78 significantly influenced the catalytic activity of hAS3MT as well as Met103, Ile136 and Glu137 because they were closely associated with SAM-binding, while residue Gln107 did not affect SAM-binding regardless of affecting the catalytic activity of hAS3MT. Modeling and our experimental results suggest that the adenine ring of SAM is sandwiched between Ile136 and Met103, the amide group of SAM is hydrogen bonded to Gly78 in hAS3MT and SAM is bonded to Tyr59 with van der Waals, cation-π and hydrogen bonding contacts.
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32
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Cohen SM, Arnold LL, Beck BD, Lewis AS, Eldan M. Evaluation of the carcinogenicity of inorganic arsenic. Crit Rev Toxicol 2013; 43:711-52. [DOI: 10.3109/10408444.2013.827152] [Citation(s) in RCA: 123] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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33
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Chen B, Lu X, Shen S, Arnold LL, Cohen SM, Le XC. Arsenic Speciation in the Blood of Arsenite-Treated F344 Rats. Chem Res Toxicol 2013; 26:952-62. [DOI: 10.1021/tx400123q] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Baowei Chen
- Division of Analytical and Environmental
Toxicology, Department of Laboratory Medicine and Pathology, Faculty
of Medicine and Dentistry, University of Alberta, Edmonton, Alberta T6G 2G3, Canada
| | - Xiufen Lu
- Division of Analytical and Environmental
Toxicology, Department of Laboratory Medicine and Pathology, Faculty
of Medicine and Dentistry, University of Alberta, Edmonton, Alberta T6G 2G3, Canada
| | - Shengwen Shen
- Division of Analytical and Environmental
Toxicology, Department of Laboratory Medicine and Pathology, Faculty
of Medicine and Dentistry, University of Alberta, Edmonton, Alberta T6G 2G3, Canada
| | - Lora L. Arnold
- Department of Pathology and
Microbiology, University of Nebraska Medical Center, Omaha, Nebraska 68198-3135, United States
| | - Samuel M. Cohen
- Department of Pathology and
Microbiology, University of Nebraska Medical Center, Omaha, Nebraska 68198-3135, United States
| | - X. Chris Le
- Division of Analytical and Environmental
Toxicology, Department of Laboratory Medicine and Pathology, Faculty
of Medicine and Dentistry, University of Alberta, Edmonton, Alberta T6G 2G3, Canada
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34
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Li X, Geng Z, Wang S, Song X, Hu X, Wang Z. Functional evaluation of Asp76, 84, 102 and 150 in human arsenic(III) methyltransferase (hAS3MT) interacting with S-adenosylmethionine. FEBS Lett 2013; 587:2232-40. [PMID: 23742935 DOI: 10.1016/j.febslet.2013.05.052] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 05/23/2013] [Accepted: 05/23/2013] [Indexed: 11/26/2022]
Abstract
We prepared eight mutants (D76P, D76N, D84P, D84N, D102P, D102N, D150P and D150N) to investigate the functions of residues Asp76, 84, 102 and 150 in human arsenic(III) methyltransferase (hAS3MT) interacting with the S-adenosylmethionine (SAM)-binding. The affinity of all the mutants for SAM were weakened. All the mutants except for D150N completely lost their methylation activities. Residues Asp76, 84, 102 and 150 greatly influenced hAS3MT catalytic activity via affecting SAM-binding or methyl transfer. Asp76 and 84 were located in the SAM-binding pocket, and Asp102 significantly affected SAM-binding via forming hydrogen bonds with SAM.
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Affiliation(s)
- Xiangli Li
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, PR China
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35
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Currier J, Saunders RJ, Ding L, Bodnar W, Cable P, Matoušek T, Creed JT, Stýblo M. Comparative oxidation state specific analysis of arsenic species by high-performance liquid chromatography-inductively coupled plasma-mass spectrometry and hydride generation-cryotrapping-atomic absorption spectrometry. JOURNAL OF ANALYTICAL ATOMIC SPECTROMETRY 2013; 28:843-852. [PMID: 23687401 PMCID: PMC3655785 DOI: 10.1039/c3ja30380b] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The formation of methylarsonous acid (MAsIII) and dimethylarsinous acid (DMAsIII) in the course of inorganic arsenic (iAs) metabolism plays an important role in the adverse effects of chronic exposure to iAs. High-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) and hydride generation-cryotrapping-atomic absorption spectrometry (HG-CT-AAS) have been frequently used for the analysis of MAsIII and DMAsIII in biological samples. While HG-CT-AAS has consistently detected MAsIII and DMAsIII, HPLC-ICP-MS analyses have provided inconsistent and contradictory results. This study compares the capacities of both methods to detect and quantify MAsIII and DMAsIII in an in vitro methylation system consisting of recombinant human arsenic (+3 oxidation state) methyltransferase (AS3MT), S-adenosylmethionine as a methyl donor, a non-thiol reductant tris(2-carboxyethyl)phosphine, and arsenite (iAsIII) or MAsIII as substrate. The results show that reversed-phase HPLC-ICP-MS can identify and quantify MAsIII and DMAsIII in aqueous mixtures of biologically relevant arsenical standards. However, HPLC separation of the in vitro methylation mixture resulted in significant losses of MAsIII, and particularly DMAsIII with total arsenic recoveries below 25%. Further analyses showed that MAsIII and DMAsIII bind to AS3MT or interact with other components of the methylation mixture, forming complexes that do not elute from the column. Oxidation of the mixture with H2O2 which converted trivalent arsenicals to their pentavalent analogs prior to HPLC separation increased total arsenic recoveries to ~95%. In contrast, HG-CT-AAS analysis found large quantities of methylated trivalent arsenicals in mixtures incubated with either iAsIII or MAsIII and provided high (>72%) arsenic recoveries. These data suggest that an HPLC-based analysis of biological samples can underestimate MAsIII and DMAsIII concentrations and that controlling for arsenic species recovery is essential to avoid artifacts.
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Affiliation(s)
- Jenna Currier
- Curriculum in Toxicology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7461, USA
| | - R. Jesse Saunders
- Department of Nutrition, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7461, USA
| | - Lan Ding
- Department of Nutrition, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7461, USA
| | - Wanda Bodnar
- Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7461, USA
| | - Peter Cable
- Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7461, USA
| | - Tomáš Matoušek
- Institute of Analytical Chemistry of the ASCR, v.v.i., Veveří 97, 602 00 Brno, Czech Republic
| | - John T. Creed
- Microbiological and Chemical Exposure Assessment Research Division, NERL, US EPA, Cincinnati, OH 45628, USA
| | - Miroslav Stýblo
- Curriculum in Toxicology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7461, USA
- Department of Nutrition, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7461, USA
- Corresponding Author: Tel: (+1) 919-966-5721; Fax: (+1) 919-843-0776;
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36
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Sumi D, Himeno S. Role of arsenic (+3 oxidation state) methyltransferase in arsenic metabolism and toxicity. Biol Pharm Bull 2013; 35:1870-5. [PMID: 23123458 DOI: 10.1248/bpb.b212015] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The metabolism of arsenicals, including their reduction and methylation has been extensively studied, and both classical and novel pathways of arsenic methylation are proposed. Arsenic methylation has been considered to be a detoxification process of inorganic arsenicals, although recent studies have indicated that trivalent methylated arsenicals, the intermediate products of arsenic methylation, are more toxic than inorganic arsenicals. In 2002, arsenite (+3 oxidation state) methyltransferase (As3MT) was discovered to be an enzyme responsible for arsenic methylation. This review focuses on current information on the function, genetic polymorphism, and alternative splicing of As3MT, all of which contribute to arsenic metabolism and toxicity.
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Affiliation(s)
- Daigo Sumi
- Laboratory of Molecular Nutrition and Toxicology, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Tokushima, Japan.
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37
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Differential toxicity and gene expression in Caco-2 cells exposed to arsenic species. Toxicol Lett 2013; 218:70-80. [PMID: 23353816 DOI: 10.1016/j.toxlet.2013.01.013] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2012] [Revised: 01/12/2013] [Accepted: 01/15/2013] [Indexed: 12/17/2022]
Abstract
Inorganic arsenic [As(V)+As(III)] and its metabolites, especially the trivalent forms [monomethylarsonous acid, MMA(III), and dimethylarsinous acid, DMA(III)], are considered the forms of arsenic with the highest degree of toxicity, linked to certain types of cancer and other pathologies. The gastrointestinal mucosa is exposed to these forms of arsenic, but it is not known what toxic effect these species may have on it. The aim of the present work was to evaluate the toxicity and some mechanisms of action of inorganic arsenic and its metabolites [monomethylarsonic acid, MMA(V), dimethylarsinic acid, DMA(V), MMA(III) and DMA(III)] in intestinal epithelial cells, using the Caco-2 human cell line as a model. The results show that the pentavalent forms do not produce toxic effects on the intestinal monolayer, but the trivalent species have a different degree of toxicity. As(III) induces death mainly by necrosis, whereas only apoptotic cells are detected after exposure to MMA(III), and for DMA(III) the percentages of apoptosis and necrosis are similar. The three forms produce reactive oxygen species, accompanied by a reduction in intracellular GSH and lipid peroxidation, the latter being especially notable in the dimethylated form. They also alter the enzyme activity of glutathione peroxidase and catalase and induce expression of stress proteins and metallothioneins. The results indicate that the trivalent forms of arsenic can affect cell viability of intestinal cells by mechanisms related to the induction of oxidative stress. Further studies are needed to evaluate how the effects observed in this study affect the structure and functionality of the intestinal epithelium.
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38
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Abstract
Arsenic has received considerable attention in the world, since it can lead to a multitude of toxic effects and has been recognized as a human carcinogen causing cancers. Here, we focus on the current state of knowledge regarding the proposed mechanisms of arsenic biotransformation, with a little about cellular uptake, toxicity and clinical utilization of arsenicals. Since pentavalent methylated metabolites were found in animal urine after exposure to iAs(III), methylation was considered to be a detoxification process, but the discovery of methylated trivalent intermediates and thioarsenicals in urine has diverted the view and gained much interest regarding arsenic biotransformation. To further investigate the partially understood phenomena relating to arsenic toxicity and the uses of arsenic as a drug, it is important to elucidate the exact pathways involved in metabolism of this metalloid, as the toxicity and the clinical uses of arsenic can be best recognized in context of its biotransformation. Thereby, in this perspective, we have focused on arsenic metabolic pathways including three proposed mechanisms: a classic pathway by Challenger in 1945, followed by a new metabolic pathway proposed by Hayakawa in 2005 involving arsenic-glutathione complexes, while the third is a new reductive methylation pathway that is proposed by our group involving As-protein complexes. According to previous and present in vivo and in vitro experiments, we conclude that the methylation reaction takes place with simultaneous reductive rather than stepwise oxidative methylation. In addition, production of pentavalent methylated arsenic metabolites are suggested to be as the end product of metabolism, rather than intermediates.
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Affiliation(s)
- Kanwal Rehman
- Department of Pharmacology, Toxicology, and Biochemical Pharmaceutics, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, Zhejiang, 310561, China
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39
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Calatayud M, Vélez D, Devesa V. Metabolism of Inorganic Arsenic in Intestinal Epithelial Cell Lines. Chem Res Toxicol 2012; 25:2402-11. [DOI: 10.1021/tx300385y] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- M. Calatayud
- Instituto de Agroquímica y Tecnología de Alimentos (IATA-CSIC), Avenida Agustín Escardino
No. 7, 46980 Paterna, Valencia, Spain
| | - D. Vélez
- Instituto de Agroquímica y Tecnología de Alimentos (IATA-CSIC), Avenida Agustín Escardino
No. 7, 46980 Paterna, Valencia, Spain
| | - V. Devesa
- Instituto de Agroquímica y Tecnología de Alimentos (IATA-CSIC), Avenida Agustín Escardino
No. 7, 46980 Paterna, Valencia, Spain
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40
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Ding L, Saunders RJ, Drobná Z, Walton FS, Xun P, Thomas DJ, Stýblo M. Methylation of arsenic by recombinant human wild-type arsenic (+3 oxidation state) methyltransferase and its methionine 287 threonine (M287T) polymorph: Role of glutathione. Toxicol Appl Pharmacol 2012; 264:121-30. [PMID: 22868225 PMCID: PMC3439589 DOI: 10.1016/j.taap.2012.07.024] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Revised: 07/19/2012] [Accepted: 07/21/2012] [Indexed: 01/11/2023]
Abstract
Arsenic (+3 oxidation state) methyltransferase (AS3MT) is the key enzyme in the pathway for methylation of arsenicals. A common polymorphism in the AS3MT gene that replaces a threonyl residue in position 287 with a methionyl residue (AS3MT/M287T) occurs at a frequency of about 10% among populations worldwide. Here, we compared catalytic properties of recombinant human wild-type (wt) AS3MT and AS3MT/M287T in reaction mixtures containing S-adenosylmethionine, arsenite (iAs(III)) or methylarsonous acid (MAs(III)) as substrates and endogenous or synthetic reductants, including glutathione (GSH), a thioredoxin reductase (TR)/thioredoxin (Trx)/NADPH reducing system, or tris (2-carboxyethyl) phosphine hydrochloride (TCEP). With either TR/Trx/NADPH or TCEP, wtAS3MT or AS3MT/M287T catalyzed conversion of iAs(III) to MAs(III), methylarsonic acid (MAs(V)), dimethylarsinous acid (DMAs(III)), and dimethylarsinic acid (DMAs(V)); MAs(III) was converted to DMAs(III) and DMAs(V). Although neither enzyme required GSH to support methylation of iAs(III) or MAs(III), addition of 1mM GSH decreased K(m) and increased V(max) estimates for either substrate in reaction mixtures containing TR/Trx/NADPH. Without GSH, V(max) and K(m) values were significantly lower for AS3MT/M287T than for wtAS3MT. In the presence of 1mM GSH, significantly more DMAs(III) was produced from iAs(III) in reactions catalyzed by the M287T variant than in wtAS3MT-catalyzed reactions. Thus, 1mM GSH modulates AS3MT activity, increasing both methylation rates and yield of DMAs(III). AS3MT genotype exemplified by differences in regulation of wtAS3MT and AS3MT/M287T-catalyzed reactions by GSH may contribute to differences in the phenotype for arsenic methylation and, ultimately, to differences in the disease susceptibility in individuals chronically exposed to inorganic arsenic.
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Affiliation(s)
- Lan Ding
- Department of Nutrition, Gillings School of Global Public Health, 2302 MHRC, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7461, USA
| | - R. Jesse Saunders
- Department of Nutrition, Gillings School of Global Public Health, 2302 MHRC, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7461, USA
| | - Zuzana Drobná
- Department of Nutrition, Gillings School of Global Public Health, 2302 MHRC, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7461, USA
| | - Felecia S. Walton
- Department of Nutrition, Gillings School of Global Public Health, 2302 MHRC, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7461, USA
| | - Pencheng Xun
- Department of Nutrition, Gillings School of Global Public Health, 2302 MHRC, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7461, USA
| | - David J. Thomas
- Department of Nutrition, Gillings School of Global Public Health, 2302 MHRC, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7461, USA
| | - Miroslav Stýblo
- Department of Nutrition, Gillings School of Global Public Health, 2302 MHRC, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7461, USA
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41
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Tsang V, Fry RC, Niculescu MD, Rager JE, Saunders J, Paul DS, Zeisel SH, Waalkes MP, Stýblo M, Drobná Z. The epigenetic effects of a high prenatal folate intake in male mouse fetuses exposed in utero to arsenic. Toxicol Appl Pharmacol 2012; 264:439-50. [PMID: 22959928 DOI: 10.1016/j.taap.2012.08.022] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Revised: 08/20/2012] [Accepted: 08/21/2012] [Indexed: 12/17/2022]
Abstract
Inorganic arsenic (iAs) is a complete transplacental carcinogen in mice. Previous studies have demonstrated that in utero exposure to iAs promotes cancer in adult mouse offspring, possibly acting through epigenetic mechanisms. Humans and rodents enzymatically convert iAs to its methylated metabolites. This reaction requires S-adenosylmethionine (SAM) as methyl group donor. SAM is also required for DNA methylation. Supplementation with folate, a major dietary source of methyl groups for SAM synthesis, has been shown to modify iAs metabolism and the adverse effects of iAs exposure. However, effects of gestational folate supplementation on iAs metabolism and fetal DNA methylation have never been thoroughly examined. In the present study, pregnant CD1 mice were fed control (i.e. normal folate, or 2.2 mg/kg) or high folate diet (11 mg/kg) from gestational day (GD) 5 to 18 and drank water with 0 or 85 ppm of As (as arsenite) from GD8 to 18. The exposure to iAs significantly decreased body weight of GD18 fetuses and increased both SAM and S-adenosylhomocysteine (SAH) concentrations in fetal livers. High folate intake lowered the burden of total arsenic in maternal livers but did not prevent the effects of iAs exposure on fetal weight or hepatic SAM and SAH concentrations. In fact, combined folate-iAs exposure caused further significant body weight reduction. Notably, iAs exposure alone had little effect on DNA methylation in fetal livers. In contrast, the combined folate-iAs exposure changed the CpG island methylation in 2,931 genes, including genes known to be imprinted. Most of these genes were associated with neurodevelopment, cancer, cell cycle, and signaling networks. The canonical Wnt-signaling pathway, which regulates fetal development, was among the most affected biological pathways. Taken together, our results suggest that a combined in utero exposure to iAs and a high folate intake may adversely influence DNA methylation profiles and weight of fetuses, compromising fetal development and possibly increasing the risk for early-onset of disease in offspring.
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Affiliation(s)
- Verne Tsang
- Department of Nutrition, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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Ajees AA, Marapakala K, Packianathan C, Sankaran B, Rosen BP. Structure of an As(III) S-adenosylmethionine methyltransferase: insights into the mechanism of arsenic biotransformation. Biochemistry 2012; 51:5476-85. [PMID: 22712827 DOI: 10.1021/bi3004632] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Enzymatic methylation of arsenic is a detoxification process in microorganisms but in humans may activate the metalloid to more carcinogenic species. We describe the first structure of an As(III) S-adenosylmethionine methyltransferase by X-ray crystallography that reveals a novel As(III) binding domain. The structure of the methyltransferase from the thermophilic eukaryotic alga Cyanidioschyzon merolae reveals the relationship between the arsenic and S-adenosylmethionine binding sites to a final resolution of ∼1.6 Å. As(III) binding causes little change in conformation, but binding of SAM reorients helix α4 and a loop (residues 49-80) toward the As(III) binding domain, positioning the methyl group for transfer to the metalloid. There is no evidence of a reductase domain. These results are consistent with previous suggestions that arsenic remains trivalent during the catalytic cycle. A homology model of human As(III) S-adenosylmethionine methyltransferase with the location of known polymorphisms was constructed. The structure provides insights into the mechanism of substrate binding and catalysis.
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Affiliation(s)
- A Abdul Ajees
- Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, 33199, United States
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43
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Nutritional manipulation of one-carbon metabolism: effects on arsenic methylation and toxicity. J Toxicol 2012; 2012:595307. [PMID: 22523489 PMCID: PMC3317163 DOI: 10.1155/2012/595307] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Revised: 12/20/2011] [Accepted: 12/21/2011] [Indexed: 01/30/2023] Open
Abstract
Exposure to arsenic (As) through drinking water is a substantial problem worldwide. The methylation of As, a reactive metalloid, generates monomethyl- (MMA) and dimethyl-arsenical (DMA) species. The biochemical pathway that catalyzes these reactions, one-carbon metabolism, is regulated by folate and other micronutrients. Arsenic methylation exerts a critical influence on both its urinary elimination and chemical reactivity. Mice having the As methyltransferase null genotype show reduced urinary As excretion, increased As retention, and severe systemic toxicity. The most toxic As metabolite in vitro is MMAIII, an intermediate in the generation of DMAV, a much less toxic metabolite. These findings have raised the question of whether As methylation is a detoxification or bioactivation pathway. Results of population-based studies suggest that complete methylation of inorganic As to DMA is associated with reduced risk for As-induced health outcomes, and that nutrients involved in one-carbon metabolism, such as folate, can facilitate As methylation and elimination.
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44
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Li Y, Gao Y, Zhao L, Wei Y, Feng H, Wang C, Wei W, Ding Y, Sun D. Changes in serum thioredoxin among individuals chronically exposed to arsenic in drinking water. Toxicol Appl Pharmacol 2012; 259:124-32. [DOI: 10.1016/j.taap.2011.12.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2011] [Revised: 12/03/2011] [Accepted: 12/13/2011] [Indexed: 11/27/2022]
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Currier JM, Svoboda M, Matoušek T, Dědina J, Stýblo M. Direct analysis and stability of methylated trivalent arsenic metabolites in cells and tissues. Metallomics 2011; 3:1347-54. [PMID: 22015847 DOI: 10.1039/c1mt00095k] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Chronic ingestion of water containing inorganic arsenic (iAs) has been linked to a variety of adverse health effects, including cancer, hypertension and diabetes. Current evidence suggests that the toxic methylated trivalent metabolites of iAs, methylarsonous acid (MAs(III)) and dimethylarsinous acid (DMAs(III)) play a key role in the etiology of these diseases. Both MAs(III) and DMAs(III) have been detected in urine of subjects exposed to iAs. However, the rapid oxidation of DMAs(III) and, to a lesser extent, MAs(III) in oxygen-rich environments leads to difficulties in the analysis of these metabolites in samples of urine collected in population studies. Results of our previous work indicate that MAs(III) and DMAs(III) are relatively stable in a reducing cellular environment and can be quantified in cells and tissues. In the present study, we used the oxidation state-specific hydride generation-cryotrapping-atomic absorption spectroscopy (HG-CT-AAS) to examine the presence and stability of these trivalent metabolites in the liver of mice and in UROtsa/F35 cells exposed to iAs. Tri- and pentavalent metabolites of iAs were analyzed directly (without chemical extraction or digestion). Liver homogenates prepared in cold deionized water and cell culture medium and lysates were stored at either 0 °C or -80 °C for up to 22 days. Both MAs(III) and DMAs(III) were stable in homogenates stored at -80 °C. In contrast, DMAs(III) in homogenates stored at 0 °C began to oxidize to its pentavalent counterpart after 1 day; MAs(III) remained stable for at least 3 weeks under these conditions. MAs(III) and DMAs(III) generated in UROtsa/F35 cultures were stable for 3 weeks when culture media and cell lysates were stored at -80 °C. These results suggest that samples of cells and tissues represent suitable material for the quantitative, oxidation state-specific analysis of As in laboratory and population studies examining the metabolism or toxic effects of this metalloid.
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Affiliation(s)
- Jenna M Currier
- Curriculum in Toxicology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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46
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Hughes MF, Beck BD, Chen Y, Lewis AS, Thomas DJ. Arsenic exposure and toxicology: a historical perspective. Toxicol Sci 2011; 123:305-32. [PMID: 21750349 PMCID: PMC3179678 DOI: 10.1093/toxsci/kfr184] [Citation(s) in RCA: 692] [Impact Index Per Article: 53.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Accepted: 06/30/2011] [Indexed: 12/23/2022] Open
Abstract
The metalloid arsenic is a natural environmental contaminant to which humans are routinely exposed in food, water, air, and soil. Arsenic has a long history of use as a homicidal agent, but in the past 100 years arsenic, has been used as a pesticide, a chemotherapeutic agent and a constituent of consumer products. In some areas of the world, high levels of arsenic are naturally present in drinking water and are a toxicological concern. There are several structural forms and oxidation states of arsenic because it forms alloys with metals and covalent bonds with hydrogen, oxygen, carbon, and other elements. Environmentally relevant forms of arsenic are inorganic and organic existing in the trivalent or pentavalent state. Metabolism of arsenic, catalyzed by arsenic (+3 oxidation state) methyltransferase, is a sequential process of reduction from pentavalency to trivalency followed by oxidative methylation back to pentavalency. Trivalent arsenic is generally more toxicologically potent than pentavalent arsenic. Acute effects of arsenic range from gastrointestinal distress to death. Depending on the dose, chronic arsenic exposure may affect several major organ systems. A major concern of ingested arsenic is cancer, primarily of skin, bladder, and lung. The mode of action of arsenic for its disease endpoints is currently under study. Two key areas are the interaction of trivalent arsenicals with sulfur in proteins and the ability of arsenic to generate oxidative stress. With advances in technology and the recent development of animal models for arsenic carcinogenicity, understanding of the toxicology of arsenic will continue to improve.
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Affiliation(s)
- Michael F Hughes
- Office of Research and Development, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA.
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Jungwirth U, Kowol CR, Keppler BK, Hartinger CG, Berger W, Heffeter P. Anticancer activity of metal complexes: involvement of redox processes. Antioxid Redox Signal 2011; 15:1085-127. [PMID: 21275772 PMCID: PMC3371750 DOI: 10.1089/ars.2010.3663] [Citation(s) in RCA: 365] [Impact Index Per Article: 28.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Cells require tight regulation of the intracellular redox balance and consequently of reactive oxygen species for proper redox signaling and maintenance of metal (e.g., of iron and copper) homeostasis. In several diseases, including cancer, this balance is disturbed. Therefore, anticancer drugs targeting the redox systems, for example, glutathione and thioredoxin, have entered focus of interest. Anticancer metal complexes (platinum, gold, arsenic, ruthenium, rhodium, copper, vanadium, cobalt, manganese, gadolinium, and molybdenum) have been shown to strongly interact with or even disturb cellular redox homeostasis. In this context, especially the hypothesis of "activation by reduction" as well as the "hard and soft acids and bases" theory with respect to coordination of metal ions to cellular ligands represent important concepts to understand the molecular modes of action of anticancer metal drugs. The aim of this review is to highlight specific interactions of metal-based anticancer drugs with the cellular redox homeostasis and to explain this behavior by considering chemical properties of the respective anticancer metal complexes currently either in (pre)clinical development or in daily clinical routine in oncology.
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Affiliation(s)
- Ute Jungwirth
- Department of Medicine I, Institute of Cancer Research, Medical University Vienna, Vienna, Austria
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48
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Wen W, Wen J, Lu L, Liu H, Yang J, Cheng H, Che W, Li L, Zhang G. Metabolites of arsenic and increased DNA damage of p53 gene in arsenic plant workers. Toxicol Appl Pharmacol 2011; 254:41-7. [DOI: 10.1016/j.taap.2011.04.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2011] [Revised: 04/18/2011] [Accepted: 04/21/2011] [Indexed: 10/18/2022]
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Watanabe T, Ohta Y, Mizumura A, Kobayashi Y, Hirano S. Analysis of arsenic metabolites in HepG2 and AS3MT-transfected cells. Arch Toxicol 2011; 85:577-88. [PMID: 21537954 DOI: 10.1007/s00204-011-0710-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Accepted: 04/12/2011] [Indexed: 11/29/2022]
Abstract
It has been suggested that arsenic (+3 oxidation state) methyltransferase (AS3MT) plays a critical role in methylation of arsenic, and that arsenic-glutathione conjugate is a substrate for AS3MT-catalyzed methylation of arsenic. However, the mechanism of arsenic methylation in cells is not fully understood. Here, we have constructed T-REx-CHO-hAS3MTtr cells that transiently overexpress human AS3MT in response to tetracycline. The decreases in cell viability after exposure to sodium arsenite were greater in tetracycline-treated cells (tet(+) cells) than in untreated cells (tet(-) cells). Concentration of total cellular arsenic was significantly higher in tet(+) cells than in tet(-) cells. Speciation analyses of arsenic metabolites in whole cell lysates and cell culture medium were performed using both HepG2 cells and T-REx-CHO-hAS3MTtr cells. Speciation analyses of arsenic metabolites in lysates of T-REx-CHO-hAS3MTtr cells revealed that dimethylated arsenicals were the predominant arsenic metabolites in tet(+) cells, while methylated metabolites were not found in tet(-) cells. In contrast, less amount of methylated arsenic metabolites were found in the HepG2 cell lysates, and monomethylated trivalent arsenicals were the predominant methylated arsenic metabolites. Arsenate was found in the culture medium after 24 h culture with arsenite. A larger amount of arsenate was found in the culture medium of tet(+) or tet(-) cells compared to HepG2 cells. These findings indicated that AS3MT expression enhanced the cytotoxic effect of arsenite in tet(+) cells because these cells accumulated more arsenic metabolites than did the tet(-) cells, and accordingly, the tet(+) cells were more susceptible to arsenic than were the tet(-) cells. Oxidation--reduction of arsenic may be implicated in the toxic effects of arsenite.
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Affiliation(s)
- Takayuki Watanabe
- Graduate School of Pharmaceutical Sciences, Chiba University, Yayoi, Inage, Chiba, 263-8522, Japan
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Stamatelos SK, Brinkerhoff CJ, Isukapalli SS, Georgopoulos PG. Mathematical model of uptake and metabolism of arsenic(III) in human hepatocytes - Incorporation of cellular antioxidant response and threshold-dependent behavior. BMC SYSTEMS BIOLOGY 2011; 5:16. [PMID: 21266075 PMCID: PMC3302683 DOI: 10.1186/1752-0509-5-16] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Accepted: 01/25/2011] [Indexed: 08/29/2023]
Abstract
Background Arsenic is an environmental pollutant, potent human toxicant, and oxidative stress agent with a multiplicity of health effects associated with both acute and chronic exposures. A semi-mechanistic cellular-level toxicokinetic (TK) model was developed in order to describe the uptake, biotransformation and clearance of arsenical species in human hepatocytes. Notable features of this model are the incorporation of arsenic-glutathione complex formation and a "switch-like" formulation to describe the antioxidant response of hepatocytes to arsenic exposure. Results The cellular-level TK model applies mass action kinetics in order to predict the concentrations of trivalent and pentavalent arsenicals in hepatocytes. The model simulates uptake of arsenite (iAsIII) via aquaporin isozymes 9 (AQP9s), glutathione (GSH) conjugation, methylation by arsenic methyltransferase (AS3MT), efflux through multidrug resistant proteins (MRPs) and the induced antioxidant response via thioredoxin reductase (TR) activity. The model was parameterized by optimization of model estimates for arsenite (iAsIII), monomethylated (MMA) and dimethylated (DMA) arsenicals concentrations with time-course experimental data in human hepatocytes for a time span of 48 hours, and dose-response data at 24 hours for a range of arsenite concentrations from 0.1 to 10 μM. Global sensitivity analysis of the model showed that at low doses the transport parameters had a dominant role, whereas at higher doses the biotransformation parameters were the most significant. A parametric comparison of the TK model with an analogous model developed for rat hepatocytes from the literature demonstrated that the biotransformation of arsenite (e.g. GSH conjugation) has a large role in explaining the variation in methylation between rats and humans. Conclusions The cellular-level TK model captures the temporal modes of arsenical accumulation in human hepatocytes. It highlighted the key biological processes that influence arsenic metabolism by explicitly modelling the metabolic network of GSH-adducts formation. The parametric comparison with the TK model developed for rats suggests that the variability in GSH conjugation could have an important role in inter-species variability of arsenical methylation. The TK model can be incorporated into larger-scale physiologically based toxicokinetic (PBTK) models of arsenic for improving the estimates of PBTK model parameters.
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Affiliation(s)
- Spyros K Stamatelos
- Environmental and Occupational Health Sciences Institute (EOHSI), a joint institute of UMDNJ-Robert Wood Johnson Medical School and Rutgers University, 170 Frelinghuysen Rd, Piscataway, NJ 08854, USA
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