1
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He J, Liu W, Ge X, Wang GC, Desai V, Wang S, Mu W, Bhardwaj V, Seifert E, Liu LZ, Bhushan A, Peiper SC, Jiang BH. Arsenic-induced metabolic shift triggered by the loss of miR-199a-5p through Sp1-dependent DNA methylation. Toxicol Appl Pharmacol 2019; 378:114606. [PMID: 31170415 PMCID: PMC6788774 DOI: 10.1016/j.taap.2019.114606] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Revised: 05/21/2019] [Accepted: 05/31/2019] [Indexed: 12/23/2022]
Abstract
Inorganic arsenic is an environmental carcinogen that poses a major global public health risk. A high percentage of drinking water from wells in the U.S. contains higher-than-normal levels of arsenic, suggesting an increased risk of arsenic-induced deleterious effects. In addition to primary preventive measures, therapeutic strategies need to effectively address and integrate multiple molecular mechanisms underlying arsenic-induced carcinogenesis. We previously showed that the loss of miR-199a-5p in arsenic-transformed cells is pivotal to promote arsenic-induced angiogenesis and tumor growth in lung epithelial cells. In this study, we further showed that subacute or chronic exposure to arsenic diminished miR-199a-5p levels largely due to DNA methylation, which was achieved by increased DNA methyltransferase-1 (DNMT1) activity, mediated by the formation of specific protein 1 (Sp1)/DNMT1 complex. In addition to the DNA hypermethylation, arsenic exposure also repressed miR-199a transcription through a transcriptional repressor Sp1. We further identified an association between miR-199a-5p repression and the arsenic-mediated energy metabolic shift, as reflected by mitochondria defects and a switch to glycolysis, in which a glycolytic enzyme pyruvate kinase 2 (PKM2) was a functional target of miR-199a-5p. Taken together, the repression of miR-199a-5p through both Sp1-dependent DNA methylation and Sp1 transcriptional repression promotes an arsenic-mediated metabolic shift from mitochondria respiration to aerobic glycolysis via PKM2.
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Affiliation(s)
- Jun He
- Department of Pathology, Anatomy & Cell Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19107, United States of America.
| | - Weitao Liu
- Department of Pathology, Nanjing Medical University, Nanjing, China
| | - Xin Ge
- Department of Pathology, Nanjing Medical University, Nanjing, China
| | - Gao-Chan Wang
- Department of Pathology, Anatomy & Cell Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19107, United States of America
| | - Vilas Desai
- Department of Pharmaceutical Sciences, College of Pharmacy, Thomas Jefferson University, Philadelphia, PA 19107, United States of America
| | - Shaomin Wang
- Department of Pathology, Anatomy & Cell Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19107, United States of America
| | - Wei Mu
- School of Public Health, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Vikas Bhardwaj
- Department of Pharmaceutical Sciences, College of Pharmacy, Thomas Jefferson University, Philadelphia, PA 19107, United States of America
| | - Erin Seifert
- Department of Pathology, Anatomy & Cell Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19107, United States of America
| | - Ling-Zhi Liu
- Department of Pathology, Carver College of Medicine, University of Iowa, Iowa City, IW 52242, United States of America
| | - Alok Bhushan
- Department of Pharmaceutical Sciences, College of Pharmacy, Thomas Jefferson University, Philadelphia, PA 19107, United States of America
| | - Stephen C Peiper
- Department of Pathology, Anatomy & Cell Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19107, United States of America
| | - Bing-Hua Jiang
- Department of Pathology, Carver College of Medicine, University of Iowa, Iowa City, IW 52242, United States of America.
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Guo X, Chen X, Wang J, Liu Z, Gaile D, Wu H, Yu G, Mao G, Yang Z, Di Z, Guo X, Cao L, Chang P, Kang B, Chen J, Gao W, Ren X. Multi-generational impacts of arsenic exposure on genome-wide DNA methylation and the implications for arsenic-induced skin lesions. ENVIRONMENT INTERNATIONAL 2018; 119:250-263. [PMID: 29982128 PMCID: PMC6143427 DOI: 10.1016/j.envint.2018.06.024] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 06/18/2018] [Accepted: 06/19/2018] [Indexed: 05/19/2023]
Abstract
As a nonmutagenic human carcinogen, arsenic (As)'s carcinogenic activity is likely the result of epigenetic changes, particularly alterations in DNA methylation. While increasing studies indicate a potentially important role for timing of As exposure on DNA methylation patterns and the subsequent differential risks for As toxicity and carcinogenesis, there is a lack of research that tackles these critical questions, particularly in human based populations. Here we reported a family-based study including three generations, in which each generation living in the same household had a distinctive timing of As exposure: in adulthood, in utero and during early childhood, and in germlines exposure for grandparents, parents, and grandchildren, respectively. We generated genome-wide DNA methylation data for 18 As-exposed families, nine control families, as well as 18 arsenical skin lesion patients. Our analysis showed that As exposure may leave detectable DNA methylation changes even though exposure occurred decades ago, and the most significant changes of global DNA methylation were observed among patients afflicted with arsenical skin lesions. As exposure across generations shared common differentially methylated DNA loci and regions (744 DML and 15 DMRs) despite the distinctive exposure timing in each generation. Importantly, based on these DML, clustering analysis grouped skin lesion patients together with grandparents in exposed families in the same cluster, separated from grandparents in control families. Further analysis identified a number of DML and several molecular pathways that were significantly distinguished between controls, exposed populations, as well as skin lesion patients. Finally, our exploratory analysis suggested that some of these DML altered by As exposure, may have the potential to be inherited affecting not only those directly exposed but also later generations. Together, our results suggest that common DML and/or DMRs associated with an increased risk for disease development could be identified regardless of when exposure to As occurred during their life span, and thus may be able to serve as biomarkers for identifying individuals at risk for As-induced skin lesions and possible cancers.
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Affiliation(s)
- Xiaojuan Guo
- School of Public Health, Inner Mongolia Medical University, Hohhot, Inner Mongolia, China; School of Public Health & Management, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Xushen Chen
- Department of Epidemiology and Environmental Health, School of Public Health and Health Professions, University at Buffalo, Buffalo, NY, USA
| | - Jie Wang
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, USA
| | - Zhiyue Liu
- School of Public Health, Inner Mongolia Medical University, Hohhot, Inner Mongolia, China
| | - Daniel Gaile
- Department of Biostatistics, School of Public Health and Health Professions, University at Buffalo, Buffalo, NY, USA
| | - Hongmei Wu
- School of Public Health & Management, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Guan Yu
- Department of Biostatistics, School of Public Health and Health Professions, University at Buffalo, Buffalo, NY, USA
| | - Guangyun Mao
- School of Public Health & Management, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Zuopeng Yang
- Center for Disease Control and Prevention, Wuyuan County, Inner Mongolia, China
| | - Zhen Di
- Center for Disease Control and Prevention, Hangjinhouqi County, Inner Mongolia, China
| | - Xiuqing Guo
- School of Public Health, Inner Mongolia Medical University, Hohhot, Inner Mongolia, China
| | - Li Cao
- School of Public Health, Inner Mongolia Medical University, Hohhot, Inner Mongolia, China
| | - Peiye Chang
- School of Public Health, Inner Mongolia Medical University, Hohhot, Inner Mongolia, China
| | - Binxian Kang
- Center for Disease Control and Prevention, Wuyuan County, Inner Mongolia, China
| | - Jinyu Chen
- Center for Disease Control and Prevention, Wuyuan County, Inner Mongolia, China
| | - Wen Gao
- Center for Disease Control and Prevention, Wuyuan County, Inner Mongolia, China
| | - Xuefeng Ren
- School of Public Health, Inner Mongolia Medical University, Hohhot, Inner Mongolia, China; Department of Epidemiology and Environmental Health, School of Public Health and Health Professions, University at Buffalo, Buffalo, NY, USA.
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3
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Wang X, Zhao G, Wang H, Liang J, Xu S, Chen S, Xu A, Wu L. Assessment of the cytotoxic and mutagenic potential of the Jialu River and adjacent groundwater using human-hamster hybrid cells. J Environ Sci (China) 2018; 70:133-143. [PMID: 30037400 DOI: 10.1016/j.jes.2017.11.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 11/21/2017] [Accepted: 11/21/2017] [Indexed: 06/08/2023]
Abstract
The Jialu River in China has been seriously polluted by the direct discharge of industrial and domestic wastewater. The predominant contaminants of the Jialu River and its adjacent groundwater were recently investigated. However, the potential genotoxic impact of polluted water on human health remains to be clarified. Here, we used human-hamster hybrid (AL) cells, which are sensitive for detecting environmental mutagens. We found that the cytotoxicity and mutagenicity of the groundwater in the Jialu River basin were influenced by the infiltration of the Jialu River. Hydrological periods significantly affected the cytotoxicity, but not the mutagenic potential, of surface and groundwater. Further, the mutagenic potential of groundwater samples located <1km from the Jialu River (SM-2 water samples) was detected earlier than that of groundwater samples located approximately 20km from the Jialu River (SN water samples). Because of high cytotoxicity, the mutagenic potential of water samples from the Jialu River (SM-1 water samples) was not significantly enhanced compared with that of untreated controls. To further assess the mutagenic dispersion potential, an artificial neural network model was adopted. The results showed that the highest mutagenic potential of groundwater was observed approximately 10km from the Jialu River. Although further investigation of mutagenic spatial dispersion is required, our data are significant for advancing our understanding of the origin, dispersion, and biological effects of water samples from polluted areas.
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Affiliation(s)
- Xiaofei Wang
- Key Laboratory of High Magnetic Field and Ion Beam Physical Biology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China; Department of Biological and Environmental Engineering, Hefei University, Hefei 230601, China.
| | - Guoping Zhao
- Key Laboratory of High Magnetic Field and Ion Beam Physical Biology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China; Key Laboratory of Environmental Toxicology and Pollution Control Technology of Anhui Province, Hefei 230031, China
| | - Hongqiang Wang
- Institute of Intelligent Machines, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
| | - Junting Liang
- Key Laboratory of High Magnetic Field and Ion Beam Physical Biology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China; Key Laboratory of Environmental Toxicology and Pollution Control Technology of Anhui Province, Hefei 230031, China
| | - Shengmin Xu
- Key Laboratory of High Magnetic Field and Ion Beam Physical Biology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China; Key Laboratory of Environmental Toxicology and Pollution Control Technology of Anhui Province, Hefei 230031, China
| | - Shaopeng Chen
- Key Laboratory of High Magnetic Field and Ion Beam Physical Biology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China; Key Laboratory of Environmental Toxicology and Pollution Control Technology of Anhui Province, Hefei 230031, China
| | - An Xu
- Key Laboratory of High Magnetic Field and Ion Beam Physical Biology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China; Key Laboratory of Environmental Toxicology and Pollution Control Technology of Anhui Province, Hefei 230031, China.
| | - Lijun Wu
- Key Laboratory of High Magnetic Field and Ion Beam Physical Biology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China; Key Laboratory of Environmental Toxicology and Pollution Control Technology of Anhui Province, Hefei 230031, China; School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230026, China.
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4
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Ge Y, Zhu J, Wang X, Zheng N, Tu C, Qu J, Ren X. Mapping dynamic histone modification patterns during arsenic-induced malignant transformation of human bladder cells. Toxicol Appl Pharmacol 2018; 355:164-173. [PMID: 29966674 DOI: 10.1016/j.taap.2018.06.029] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 06/14/2018] [Accepted: 06/28/2018] [Indexed: 01/17/2023]
Abstract
Arsenic is a known potent risk factor for bladder cancer. Increasing evidence suggests that epigenetic alterations, e.g., DNA methylation and histones posttranslational modifications (PTMs), contribute to arsenic carcinogenesis. Our previous studies have demonstrated that exposure of human urothelial cells (UROtsa cells) to monomethylarsonous acid (MMAIII), one of arsenic active metabolites, changes the histone acetylation marks across the genome that are correlated with MMAIII-induced UROtsa cell malignant transformation. In the current study, we employed a high-resolution and high-throughput liquid chromatography tandem mass spectrometry (LC-MS/MS) to identify and quantitatively measure various PTM patterns during the MMAIII-induced malignant transformation. Our data showed that MMAIII exposure caused a time-dependent increase in histone H3 acetylation on lysine K4, K9, K14, K18, K23, and K27, but a decrease in acetylation on lysine K5, K8, K12, and K16 of histone H4. Consistent with this observation, H3K18ac was increased while H4K8ac was decreased in the leukocytes collected from people exposed to high concentrations of arsenic compared to those exposed to low concentrations. MMAIII was also able to alter histone methylation patterns: MMAIII transformed cells experienced a loss of H3K4me1, and an increase in H3K9me1 and H3K27me1. Collectively, our data shows that arsenic exposure causes dynamic changes in histone acetylation and methylation patterns during arsenic-induced cancer development. Exploring the genomic location of the altered histone marks and the resulting aberrant expression of genes will be of importance in deciphering the mechanism of arsenic-induced carcinogenesis.
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Affiliation(s)
- Yichen Ge
- Department of Epidemiology and Environmental Health, School of Public Health and Health Professions, The State University of New York, Buffalo, NY 14214, USA
| | - Jinqiu Zhu
- Department of Epidemiology and Environmental Health, School of Public Health and Health Professions, The State University of New York, Buffalo, NY 14214, USA
| | - Xue Wang
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, The State University of New York, Buffalo, NY 14214, USA
| | - Nina Zheng
- Department of Pharmacology and Toxicology, School of Biomedical Sciences, The State University of New York, Buffalo, NY 14214, USA
| | - Chengjian Tu
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, The State University of New York, Buffalo, NY 14214, USA
| | - Jun Qu
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, The State University of New York, Buffalo, NY 14214, USA
| | - Xuefeng Ren
- Department of Epidemiology and Environmental Health, School of Public Health and Health Professions, The State University of New York, Buffalo, NY 14214, USA; Department of Pharmacology and Toxicology, School of Biomedical Sciences, The State University of New York, Buffalo, NY 14214, USA.
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5
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Tu W, Liu Y, Xie C, Zhou X. Arsenite downregulates H3K4 trimethylation and H3K9 dimethylation during transformation of human bronchial epithelial cells. J Appl Toxicol 2017; 38:480-488. [DOI: 10.1002/jat.3555] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 09/29/2017] [Indexed: 12/19/2022]
Affiliation(s)
- Wei Tu
- Department of Occupational and Environmental Health, Key Laboratory of Environment and Health, Ministry of Education, School of Public Health, Tongji Medical College; Huazhong University of Science and Technology; Wuhan Hubei 430030 People's Republic of China
| | - Yin Liu
- Department of Occupational and Environmental Health, Key Laboratory of Environment and Health, Ministry of Education, School of Public Health, Tongji Medical College; Huazhong University of Science and Technology; Wuhan Hubei 430030 People's Republic of China
| | - Chengfeng Xie
- Department of Occupational and Environmental Health, Key Laboratory of Environment and Health, Ministry of Education, School of Public Health, Tongji Medical College; Huazhong University of Science and Technology; Wuhan Hubei 430030 People's Republic of China
| | - Xue Zhou
- Department of Occupational and Environmental Health, Key Laboratory of Environment and Health, Ministry of Education, School of Public Health, Tongji Medical College; Huazhong University of Science and Technology; Wuhan Hubei 430030 People's Republic of China
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6
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Zhu J, Wang J, Chen X, Tsompana M, Gaile D, Buck M, Ren X. A time-series analysis of altered histone H3 acetylation and gene expression during the course of MMAIII-induced malignant transformation of urinary bladder cells. Carcinogenesis 2017; 38:378-390. [PMID: 28182198 DOI: 10.1093/carcin/bgx011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Accepted: 01/26/2017] [Indexed: 01/05/2023] Open
Abstract
Our previous studies have shown that chronic exposure to low doses of monomethylarsonous acid (MMAIII) causes global histone acetylation dysregulation in urothelial cells (UROtsa cells) during the course of malignant transformation. To reveal the relationship between altered histone acetylation patterns and aberrant gene expression, more specifically, the carcinogenic relevance of these alterations, we performed a time-course analysis of the binding patterns of histone 3 lysine 18 acetylation (H3K18ac) across the genome and generated global gene-expression profiles from this UROtsa cell malignant transformation model. We showed that H3K18ac, one of the most significantly upregulated histone acetylation sites following MMAIII exposure, was enriched at gene promoter-specific regions across the genome and that MMAIII-induced upregulation of H3K18ac led to an altered binding pattern in a large number of genes that was most significant during the critical window for MMAIII-induced UROtsa cells' malignant transformation. Some genes identified as having a differential binding pattern with H3K18ac, acted as upstream regulators of critical gene networks with known functions in tumor development and progression. The altered H3K18ac binding patterns not only led to changes in expression of these directly affected upstream regulators but also resulted in gene-expression changes in their regulated networks. Collectively, our data suggest that MMAIII-induced alteration of histone acetylation patterns in UROtsa cells led to a time- and malignant stage-dependent aberrant gene-expression pattern, and that some gene regulatory networks were altered in accordance with their roles in carcinogenesis, probably contributing to MMAIII-induced urothelial cell malignant transformation and carcinogenesis.
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Affiliation(s)
- Jinqiu Zhu
- Department of Epidemiology and Environmental Health
| | | | - Xushen Chen
- Department of Epidemiology and Environmental Health
| | | | | | | | - Xuefeng Ren
- Department of Epidemiology and Environmental Health.,Department of Pharmacology and Toxicology, The State University of New York, Buffalo, NY, USA
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7
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Wang D, Ma Y, Yang X, Xu X, Zhao Y, Zhu Z, Wang X, Deng H, Li C, Gao F, Tong J, Yamanaka K, An Y. Hypermethylation of the Keap1 gene inactivates its function, promotes Nrf2 nuclear accumulation, and is involved in arsenite-induced human keratinocyte transformation. Free Radic Biol Med 2015; 89:209-19. [PMID: 26409248 DOI: 10.1016/j.freeradbiomed.2015.07.153] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Revised: 07/14/2015] [Accepted: 07/28/2015] [Indexed: 12/13/2022]
Abstract
It is well known that long-term exposure to arsenite leads to human skin cancer, but the underlying mechanisms of carcinogenesis remain obscure. The transcription factor Nrf2-mediated antioxidant response represents a critical cellular defense mechanism; however, emerging data suggest that constitutive activation of Nrf2 is associated with cancer development and chemotherapy resistance. The reasons Nrf2 continuously accumulates in cancer cells remain to be fully understood. By establishing transformed human keratinocyte cells via chronic arsenite treatment, we observed a continuous reduction in reactive oxygen species levels and enhanced levels of Nrf2 and its target antioxidant enzymes in the later stage of arsenite-induced cell transformation. We also revealed that hypermethylation of the Keap1 gene promoter region induced by DNA methyltransferase-3 leading to inactivation of its function was responsible for constitutive activation of Nrf2 and its target enzymes. To validate these observations, the expression of Keap1 protein was restored in arsenite-transformed cells by treatment with a DNA methyltransferase inhibitor, 5-aza-2'-deoxycytidine (5-Aza-dC), and protein levels of Nrf2 and colony formation were then determined after these treatments. Results showed that enhancement of Keap1 expression by 5-Aza-dC significantly reduced Nrf2 and its target antioxidant enzyme levels, and that in turn suppressed cell proliferation and colony formation of the transformed cells. Taken together, the present study strongly suggests that loss of Keap1 function by hypermethylation of its promoter region leading to Nrf2 nuclear accumulation appears to play a role in arsenite-induced human keratinocyte transformation.
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Affiliation(s)
- Dapeng Wang
- Department of Toxicology, School of Public Health, Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, Medical College of Soochow University, Suzhou, Jiangsu 215123, People's Republic of China; Department of Toxicology, School of Public Health, Guizhou Medical University, Guiyang, Guizhou 550025, People's Republic of China
| | - Yuan Ma
- Department of Toxicology, School of Public Health, Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, Medical College of Soochow University, Suzhou, Jiangsu 215123, People's Republic of China
| | - Xu Yang
- Department of Toxicology, School of Public Health, Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, Medical College of Soochow University, Suzhou, Jiangsu 215123, People's Republic of China
| | - Xiguo Xu
- Department of Toxicology, School of Public Health, Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, Medical College of Soochow University, Suzhou, Jiangsu 215123, People's Republic of China
| | - Yingying Zhao
- Department of Toxicology, School of Public Health, Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, Medical College of Soochow University, Suzhou, Jiangsu 215123, People's Republic of China
| | - Zhen Zhu
- Department of Toxicology, School of Public Health, Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, Medical College of Soochow University, Suzhou, Jiangsu 215123, People's Republic of China
| | - Xiaojuan Wang
- Department of Toxicology, School of Public Health, Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, Medical College of Soochow University, Suzhou, Jiangsu 215123, People's Republic of China
| | - Hanyi Deng
- Department of Toxicology, School of Public Health, Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, Medical College of Soochow University, Suzhou, Jiangsu 215123, People's Republic of China
| | - Chunchun Li
- Department of Toxicology, School of Public Health, Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, Medical College of Soochow University, Suzhou, Jiangsu 215123, People's Republic of China
| | - Fenfang Gao
- Department of Toxicology, School of Public Health, Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, Medical College of Soochow University, Suzhou, Jiangsu 215123, People's Republic of China
| | - Jian Tong
- Department of Toxicology, School of Public Health, Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, Medical College of Soochow University, Suzhou, Jiangsu 215123, People's Republic of China
| | - Kenzo Yamanaka
- Laboratory of Environmental Toxicology and Carcinogenesis, School of Pharmacy, Nihon University, Chiba, Japan
| | - Yan An
- Department of Toxicology, School of Public Health, Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, Medical College of Soochow University, Suzhou, Jiangsu 215123, People's Republic of China.
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Lemongrass - an anticlastogenic agent against arsenic. THE NUCLEUS 2015. [DOI: 10.1007/s13237-015-0141-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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9
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Chanda S, Dasgupta UB, Mazumder DG, Saha J, Gupta B. Human GMDS gene fragment hypermethylation in chronic high level of arsenic exposure with and without arsenic induced cancer. SPRINGERPLUS 2013; 2:557. [PMID: 24255851 PMCID: PMC3825097 DOI: 10.1186/2193-1801-2-557] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Accepted: 09/26/2013] [Indexed: 12/31/2022]
Abstract
Arsenic, though a poor mutagen, is an accepted environmental carcinogen. Perturbation of DNA methylation pattern leading to aberrant gene expression has been hypothesized as the mechanism for arsenic induced carcinogenesis. We had earlier demonstrated the hypermethylation of promoter region of p53 and p16 genes in persons exposed to different doses of arsenic. Till now no genomic hot spot has been identified which is frequently hypermethylated or hypomethylated in persons chronically exposed to environmental arsenic. In the present work, we have identified one hypermethylated sequence by methyl-sensitive arbitrarily primed polymerase chain reaction in the peripheral blood leukocyte DNA of chronically arsenic exposed persons with and without arsenic induced skin cancer. The sequence is from GMDS gene responsible for fucose metabolism. Southern hybridization of the sequence to the amplification products of methyl sensitive restriction enzyme digested genome of persons exposed to different doses of arsenic indicated that methylation increased in a dose dependent manner.
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Affiliation(s)
- Sarmishtha Chanda
- Department of Biophysics, Molecular biology & Genetics, University of Calcutta, Kolkata, West Bengal 700092 India ; Department of Physiology, Presidency University, Kolkata, West Bengal 700073 India
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10
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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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11
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Patlolla AK, Todorov TI, Tchounwou PB, van der Voet G, Centeno JA. Arsenic-induced biochemical and genotoxic effects and distribution in tissues of Sprague-Dawley rats. Microchem J 2012; 105:101-107. [PMID: 23175155 PMCID: PMC3500913 DOI: 10.1016/j.microc.2012.08.013] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Arsenic (As) is a well documented human carcinogen. However, its mechanisms of toxic action and carcinogenic potential in animals have not been conclusive. In this research, we investigated the biochemical and genotoxic effects of As and studied its distribution in selected tissues of Sprague-Dawley rats. Four groups of six male rats, each weighing approximately 60 ± 2 g, were injected intraperitoneally, once a day for 5 days with doses of 5, 10, 15, 20 mg/kg bw of arsenic trioxide. A control group was also made of 6 animals injected with distilled water. Following anaesthetization, blood was collected and enzyme analysis was performed by spectrophotometry following standard protocols. At the end of experimentation, the animals were sacrificed, and the lung, liver, brain and kidney were collected 24 h after the fifth day treatment. Chromosome and micronuclei preparation was obtained from bone marrow cells. Arsenic exposure significantly increased (p<0.05) the activities of plasma alanine aminotransferase-glutamate pyruvate transaminase (ALT/GPT), and aspartate aminotransferase-glutamate oxaloacetate transaminase (AST/GOT), as well as the number of structural chromosomal aberrations (SCA) and frequency of micronuclei (MN) in the bone marrow cells. In contrast, the mitotic index in these cells was significantly reduced (p<0.05). These findings indicate that aminotransferases are candidate biomarkers for arsenic-induced hepatotoxicity. Our results also demonstrate that As has a strong genotoxic potential, as measured by the bone marrow SCA and MN tests in Sprague-Dawley rats. Total arsenic concentrations in tissues were measured by inductively coupled plasma mass spectrometry (ICP-MS). A dynamic reaction cell (DRC) with hydrogen gas was used to eliminate the ArCl interference at mass 75, in the measurement of total As. Total As doses in tissues tended to correlate with specific exposure levels.
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Affiliation(s)
- Anita K. Patlolla
- NIH-RCMI Center for Environmental Health, Jackson State University, Jackson, MS, USA
| | - Todor I. Todorov
- Crustal Geophysics and Geochemistry Science Center, US Geological Survey, Denver, CO, USA
| | - Paul B. Tchounwou
- NIH-RCMI Center for Environmental Health, Jackson State University, Jackson, MS, USA
| | - Gijsbert van der Voet
- Biophysical Toxicology Laboratory, The Joint Pathology Center, Silver Spring, MD 20910-1290
| | - Jose A. Centeno
- Biophysical Toxicology Laboratory, The Joint Pathology Center, Silver Spring, MD 20910-1290
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Ren X, McHale CM, Skibola CF, Smith AH, Smith MT, Zhang L. An emerging role for epigenetic dysregulation in arsenic toxicity and carcinogenesis. ENVIRONMENTAL HEALTH PERSPECTIVES 2011; 119:11-9. [PMID: 20682481 PMCID: PMC3018488 DOI: 10.1289/ehp.1002114] [Citation(s) in RCA: 172] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2010] [Accepted: 08/02/2010] [Indexed: 05/08/2023]
Abstract
BACKGROUND Exposure to arsenic, an established human carcinogen, through consumption of highly contaminated drinking water is a worldwide public health concern. Several mechanisms by which arsenical compounds induce tumorigenesis have been proposed, including oxidative stress, genotoxic damage, and chromosomal abnormalities. Recent studies have suggested that epigenetic mechanisms may also mediate toxicity and carcinogenicity resulting from arsenic exposure. OBJECTIVE We examined the evidence supporting the roles of the three major epigenetic mechanisms-DNA methylation, histone modification, and microRNA (miRNA) expression-in arsenic toxicity and, in particular, carcinogenicity. We also investigated future research directions necessary to clarify epigenetic and other mechanisms in humans. DATA SOURCES AND SYNTHESIS We conducted a PubMed search of arsenic exposure and epigenetic modification through April 2010 and summarized the in vitro and in vivo research findings, from both our group and others, on arsenic-associated epigenetic alteration and its potential role in toxicity and carcinogenicity. CONCLUSIONS Arsenic exposure has been shown to alter methylation levels of both global DNA and gene promoters; histone acetylation, methylation, and phosphorylation; and miRNA expression, in studies analyzing mainly a limited number of epigenetic end points. Systematic epigenomic studies in human populations exposed to arsenic or in patients with arsenic-associated cancer have not yet been performed. Such studies would help to elucidate the relationship between arsenic exposure, epigenetic dysregulation, and carcinogenesis and are becoming feasible because of recent technological advancements.
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Affiliation(s)
- Xuefeng Ren
- Division of Environmental Health Sciences, School of Public Health, University of California–Berkeley, Berkeley, California 94720, USA.
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13
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Chakraborty T, De M. Clastogenic effects of inorganic arsenic salts on human chromosomesin vitro. Drug Chem Toxicol 2009; 32:169-73. [DOI: 10.1080/01480540802594509] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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14
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Jensen TJ, Wozniak RJ, Eblin KE, Wnek SM, Gandolfi AJ, Futscher BW. Epigenetic mediated transcriptional activation of WNT5A participates in arsenical-associated malignant transformation. Toxicol Appl Pharmacol 2008; 235:39-46. [PMID: 19061910 DOI: 10.1016/j.taap.2008.10.013] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2008] [Revised: 10/16/2008] [Accepted: 10/21/2008] [Indexed: 10/21/2022]
Abstract
Arsenic is a human carcinogen with exposure associated with cancer of the lung, skin, and bladder. Many potential mechanisms have been implicated as playing a role in the process of arsenical-induced malignancy including the perturbation of signaling pathways and aberrant epigenetic regulation. We initiated studies to examine the role of a member of the non-canonical WNT signaling pathway, WNT5A, in UROtsa cells and arsenite [URO-ASSC] and monomethylarsonous acid [URO-MSC] malignantly transformed variants. We present data herein that suggest that WNT5A is transcriptionally activated during arsenical-induced malignant transformation. This WNT5A transcriptional activation is correlated with the enrichment of permissive histone modifications and the reduction of repressive modifications in the WNT5A promoter region. The epigenetic activation of WNT5A expression and acetylation of its promoter remain after the removal of the arsenical, consistent with the maintenance of an anchorage independent growth phenotype in these cells. Additionally, treatment with epigenetic modifying drugs supports a functional role for these epigenetic marks in controlling gene expression. Reduction of WNT5A using lentiviral shRNA greatly attenuated the ability of these cells to grow in an anchorage independent fashion. Extension of our model into human bladder cancer cell lines indicates that each of the cell lines examined also express WNT5A. Taken together, these data suggest that the epigenetic remodeling of the WNT5A promoter is correlated with its transcriptional activation and this upregulation likely participates in arsenical-induced malignant transformation.
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Affiliation(s)
- Taylor J Jensen
- Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, 1515 N. Campbell, Levy Bldg 3925, Tucson, AZ 85724, USA
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15
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Jensen TJ, Novak P, Eblin KE, Gandolfi AJ, Futscher BW. Epigenetic remodeling during arsenical-induced malignant transformation. Carcinogenesis 2008; 29:1500-8. [PMID: 18448484 DOI: 10.1093/carcin/bgn102] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Humans are exposed to arsenicals through many routes with the most common being in drinking water. Exposure to arsenic has been associated with an increase in the incidence of cancer of the skin, lung and bladder. Although the relationship between exposure and carcinogenesis is well documented, the mechanisms by which arsenic participates in tumorigenesis are not fully elucidated. We evaluated the potential epigenetic component of arsenical action by assessing the histone acetylation state of 13 000 human gene promoters in a cell line model of arsenical-mediated malignant transformation. We show changes in histone H3 acetylation occur during arsenical-induced malignant transformation that are linked to the expression state of the associated gene. DNA hypermethylation was detected in hypoacetylated promoters in the select cases analyzed. These epigenetic changes occurred frequently in the same promoters whether the selection was performed with arsenite [As(III)] or with monomethylarsonous acid, suggesting that these promoters were targeted in a non-random fashion, and probably occur in regions important in arsenical-induced malignant transformation. Taken together, these data suggest that arsenicals may participate in tumorigenesis by altering the epigenetic terrain of select genes.
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Affiliation(s)
- Taylor J Jensen
- Department of Pharmacology and Toxicology, College of Pharmacy, Arizona Cancer Center, University of Arizona, Tucson, AZ 85724, USA
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Lee JJ, Jang CS, Wang SW, Liu CW. Evaluation of potential health risk of arsenic-affected groundwater using indicator kriging and dose response model. THE SCIENCE OF THE TOTAL ENVIRONMENT 2007; 384:151-62. [PMID: 17628636 DOI: 10.1016/j.scitotenv.2007.06.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2007] [Revised: 05/30/2007] [Accepted: 06/08/2007] [Indexed: 05/16/2023]
Abstract
This study analyzed the potential health risk associated with the ingestion of arsenic-affected groundwater in the arseniasis-endemic Lanyang plain of northeastern Taiwan. Indicator kriging was used to estimate arsenic concentrations in groundwater. Target cancer risk (TR) and dose response functions were adopted to evaluate the potential health risk based on the estimated arsenic concentration distributions. The estimated arsenic concentrations in groundwater reveal that arsenic concentrations (>50 microg/L) in well water are high in six townships - JiaoSi, YiLan, JhungWei, WuJie, DonShan and LouDon. Highest arsenic concentrations (70.32 microg/L) are in the YiLan and the JhungWei townships. The estimated TR values at the arsenic-affected townships are ten times more than an acceptable standard (10(-6)). The largest TR values are 145.5 and 91.2 times higher than an acceptable standard for males and females, respectively. The estimated annual mortalities by arsenic-induced internal cancers occur in the YiLan township (ten cases), LouDon (five cases), WuJie (three cases), JhungWei (two cases) and DonShan (one case). The highest number of mortalities per year in the study area is 24. Residents of the six townships with high arsenic-affected groundwater should use tap water as drinking water and use groundwater only for other purpose. The well water in other townships in the Lanyang plain has no adverse effects on human health.
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Affiliation(s)
- Jin-Jing Lee
- Department of Bioenvironmental Systems Engineering, National Taiwan University, Taipei, 106, Taiwan ROC
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17
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Chanda S, Dasgupta UB, Guhamazumder D, Gupta M, Chaudhuri U, Lahiri S, Das S, Ghosh N, Chatterjee D. DNA Hypermethylation of Promoter of Gene p53 and p16 in Arsenic-Exposed People with and without Malignancy. Toxicol Sci 2005; 89:431-7. [PMID: 16251483 DOI: 10.1093/toxsci/kfj030] [Citation(s) in RCA: 177] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Chronic arsenic exposure is known to produce arsenicosis and cancer. To ascertain whether perturbation of methylation plays a role in such carcinogenesis, the degree of methylation of p53 and p16 gene in DNA obtained from blood samples of people chronically exposed to arsenic and skin cancer subjects was studied. Methylation-specific restriction endonuclease digestion followed by polymerase chain reaction (PCR) of gene p53 and bisulfite treatment followed by methylation-sensitive PCR of gene p16 have been carried out to analyze the methylation status of the samples studied. Significant DNA hypermethylation of promoter region of p53 gene was observed in DNA of arsenic-exposed people compared to control subjects. This hypermethylation showed a dose-response relationship. Further, hypermethylation of p53 gene was also observed in arsenic-induced skin cancer patients compared to subjects having skin cancer unrelated to arsenic, though not at significant level. However, a small subgroup of cases showed hypomethylation with high arsenic exposure. Significant hypermethylation of gene p16 was also observed in cases of arsenicosis exposed to high level of arsenic. In man, arsenic has the ability to alter DNA methylation patterns in gene p53 and p16, which are important in carcinogenesis.
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Affiliation(s)
- Sarmishtha Chanda
- Department of Biophysics, Molecular Biology and Genetics, University of Calcutta, 92, APC Road, Kolkata- 700009, India
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18
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Patlolla AK, Tchounwou PB. Cytogenetic evaluation of arsenic trioxide toxicity in Sprague-Dawley rats. Mutat Res 2005; 587:126-33. [PMID: 16213187 DOI: 10.1016/j.mrgentox.2005.08.007] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2004] [Revised: 08/12/2005] [Accepted: 08/18/2005] [Indexed: 11/24/2022]
Abstract
Acute exposure to arsenic trioxide has been reported to induce death and/or multiple organ damage with symptoms including nausea, vomiting, diarrhea, gastrointestinal hemorrhage, cerebral edema, tachycardia, dysrhythmias and hypovolemic shock. Its toxic effects are due to its ability to bind to sulfhydryl groups of proteins and to inhibit energy production. Although the chronic exposure to arsenic trioxide has been linked to various types of cancer, such as skin, liver, lung, bladder and kidney neoplasms, studies of its carcinogenic potential in animals have not been conclusive. In this study, we investigated the genotoxic potential of arsenic trioxide in bone-marrow cells obtained from Sprague-Dawley rats; using chromosomal aberrations (CA), mitotic index (MI) and micronuclei (MN) formation as the toxicological endpoints. Four groups of six male rats each, weighing approximately 60+/-2 g per rat, were injected intraperitoneally, once a day for 5 days with doses of 5, 10, 15 and 20 mg/kg body weight (BW) of arsenic trioxide dissolved in distilled water. A control group was also made of six animals injected with distilled water without chemical. All the animals were sacrificed at the end of the treatment period. Chromosome and micronuclei preparation was obtained from bone-marrow cells following standard protocols. Arsenic trioxide exposure significantly increased the number of structural chromosomal aberrations, the frequency of micronucleated cells and decreased the mitotic index in treated groups when compared with the control group. Our results demonstrate that arsenic trioxide has a clastogenic/genotoxic potential as measured by the bone-marrow CA and MN tests in Sprague-Dawley rats.
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Affiliation(s)
- Anita K Patlolla
- Molecular Toxicology Research Laboratory, NIH - Center for Environmental Health, College of Science, Engineering, and Technology, Jackson State University, Jackson, MS, USA
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19
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Ni Dhubhghaill OM, Sadler PJ. The structure and reactivity of arsenic compounds: Biological activity and drug design. STRUCTURE AND BONDING 2005. [DOI: 10.1007/3-540-54261-2_3] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/13/2023]
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20
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Tchounwou PB, Centeno JA, Patlolla AK. Arsenic toxicity, mutagenesis, and carcinogenesis--a health risk assessment and management approach. Mol Cell Biochem 2004; 255:47-55. [PMID: 14971645 DOI: 10.1023/b:mcbi.0000007260.32981.b9] [Citation(s) in RCA: 234] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A comprehensive analysis of published data indicates that arsenic exposure induces cardiovascular diseases, developmental abnormalities, neurologic and neurobehavioral disorders, diabetes, hearing loss, hematologic disorders, and various types of cancer. Although exposure may occur via the dermal, and parenteral routes, the main pathways of exposure include ingestion, and inhalation. The severity of adverse health effects is related to the chemical form of arsenic, and is also time- and dose-dependent. Recent reports have pointed out that arsenic poisoning appears to be one of the major public health problems of pandemic nature. Acute and chronic exposure to arsenic has been reported in several countries of the world where a large proportion of drinking water (groundwater) is contaminated with high concentrations of arsenic. Research has also pointed significantly higher standardized mortality rates for cancers of the bladder, kidney, skin, liver, and colon in many areas of arsenic pollution. There is therefore a great need for developing a comprehensive health risk assessment (RA) concept that should be used by public health officials and environmental managers for an effective management of the health effects associated with arsenic exposure. With a special emphasis on arsenic toxicity, mutagenesis, and carcinogenesis, this paper is aimed at using the National Academy of Science's RA framework as a guide, for developing a RA paradigm for arsenic based on a comprehensive analysis of the currently available scientific information on its physical and chemical properties, production and use, fate and transport, toxicokinetics, systemic and carcinogenic health effects, regulatory and health guidelines, analytical guidelines and treatment technologies.
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Affiliation(s)
- Paul B Tchounwou
- Molecular Toxicology Research Laboratory, NIH-Center for Environmental Health, School of Science and Technology, Jackson State University, Jackson, MS 39217, USA.
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21
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Tchounwou PB, Patlolla AK, Centeno JA. Carcinogenic and systemic health effects associated with arsenic exposure--a critical review. Toxicol Pathol 2004; 31:575-88. [PMID: 14585726 DOI: 10.1080/01926230390242007] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Arsenic and arsenic containing compounds are human carcinogens. Exposure to arsenic occurs occupationally in several industries, including mining, pesticide, pharmaceutical, glass and microelectronics, as well as environmentally from both industrial and natural sources. Inhalation is the principal route of arsenic exposure in occupational settings, while ingestion of contaminated drinking water is the predominant source of significant environmental exposure globally. Drinking water contamination by arsenic remains a major public health problem. Acute and chronic arsenic exposure via drinking water has been reported in many countries of the world, where a large proportion of drinking water is contaminated with high concentrations of arsenic. General health effects that are associated with arsenic exposure include cardiovascular and peripheral vascular disease, developmental anomalies, neurologic and neurobehavioural disorders, diabetes, hearing loss, portal fibrosis, hematologic disorders (anemia, leukopenia and eosinophilia) and multiple cancers: significantly higher standardized mortality rates and cumulative mortality rates for cancers of the skin, lung, liver, urinary bladder, kidney, and colon in many areas of arsenic pollution. Although several epidemiological studies have documented the sources of exposure and the global impact of arsenic contamination, the mechanisms by which arsenic induces health effects, including cancer, are not well characterized. Further research is needed to provide a better understanding of the pathobiology of arsenic-induced diseases and to better define the toxicologic pathology of arsenic in various organ systems. In this review, we provide and discuss the underlying pathology and nature of arsenic-induced lesions. Such information is critical for understanding the magnitude of health effects associated with arsenic exposure throughout the world.
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Affiliation(s)
- Paul B Tchounwou
- Molecular Toxicology Research Laboratory, NIH-Center for Environmental Health, School of Science and Technology, Jackson State University, Jackson, Mississippi 39217, USA.
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23
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Abstract
As inorganic arsenic is a proven human carcinogen, significant effort has been made in recent decades in an attempt to understand arsenic carcinogenesis using animal models, including rodents (rats and mice) and larger mammals such as beagles and monkeys. Transgenic animals were also used to test the carcinogenic effect of arsenicals, but until recently all models had failed to mimic satisfactorily the actual mechanism of arsenic carcinogenicity. However, within the past decade successful animal models have been developed using the most common strains of mice or rats. Thus dimethylarsinic acid (DMA), an organic arsenic compound which is the major metabolite of inorganic arsenicals in mammals, has been proven to be tumorigenic in such animals. Reports of successful cancer induction in animals by inorganic arsenic (arsenite and arsenate) have been rare, and most carcinogenetic studies have used organic arsenicals such as DMA combined with other tumor initiators. Although such experiments used high concentrations of arsenicals for the promotion of tumors, animal models using doses of arsenicals species closed to the exposure level of humans in endemic areas are obviously the most significant. Almost all researchers have used drinking water or food as the pathway for the development of animal model test systems in order to mimic chronic arsenic poisoning in humans; such pathways seem more likely to achieve desirable results.
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Affiliation(s)
- Jian Ping Wang
- National Research Center for Environmental Toxicology, University of Queensland, 39 Kessels Road, Coopers Plains, Brisbane, Qld 4108, Australia
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Peng B, Sharma R, Mass MJ, Kligerman AD. Induction of genotoxic damage is not correlated with the ability to methylate arsenite in vitro in the leukocytes of four mammalian species. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2002; 39:323-332. [PMID: 12112384 DOI: 10.1002/em.10080] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Arsenic is a natural drinking water contaminant that impacts the health of large populations of people throughout the world; however, the mode or mechanism by which arsenic induces cancer is unclear. In a series of in vitro studies, we exposed leukocytes from humans, mice, rats, and guinea pigs to a range of sodium arsenite concentrations to determine whether the lymphocytes from these species showed differential sensitivity to the induction of micronuclei (MN) assessed in cytochalasin B-induced binucleate cells. We also determined the capacity of the leukocytes to methylate arsenic by measuring the production of MMA [monomethylarsinic acid (MMA(V)) and monomethylarsonous acid (MMA(III))] and DMA [dimethylarsinic acid (DMA(V)) and dimethylarsonous acid (DMA(III))]. The results indicate that cells treated for 2 hr at the G(0) stage of the cell cycle with sodium arsenite showed only very small to negligible increases in MN after mitogenic stimulation. Treatment of actively cycling cells produced induction of MN with increasing arsenite concentration, with the human, rat, and mouse lymphocytes being much more sensitive to MN induction than those of the guinea pig. These data gave an excellent fit to a linear model. The leukocytes of all four species, including the guinea pig (a species previously thought not to methylate arsenic), were able to methylate arsenic, but there was no clear correlation between the ability to methylate arsenic and the induction of MN.
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Affiliation(s)
- B Peng
- Environmental Carcinogenesis Division MD-68, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA
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Jessen BA, Qin Q, Phillips MA, Phillips DL, Rice RH. Keratinocyte differentiation marker suppression by arsenic: mediation by AP1 response elements and antagonism by tetradecanoylphorbol acetate. Toxicol Appl Pharmacol 2001; 174:302-11. [PMID: 11485391 DOI: 10.1006/taap.2001.9227] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Culture models of target cells are anticipated to help elucidate the mechanism by which inorganic arsenic acts as a carcinogen in humans. Present work characterizes the response of human keratinocytes, a target cell type, to arsenic suppression of their differentiation program. Four representative differentiation marker mRNAs (involucrin, keratinocyte transglutaminase, small proline-rich protein 1, and filaggrin) were suppressed by both arsenate and arsenite in normal, spontaneously immortalized (premalignant), and malignant keratinocytes with EC50 values in the low micromolar range. The suppression was almost completely reversed 9 days after removal of arsenate from the culture medium. In the case of the involucrin gene, suppression was mediated primarily by two functional AP1 response elements in the gene promoter. Both glucocorticoid and serum stimulation of differentiation occurred to a similar extent in the presence and absence of arsenic, indicating neither stimulation was a specific target of arsenic action and neither agent could overcome arsenic suppression. In contrast, 12-O-tetradecanoylphorbol-13-acetate prevented the suppression of keratinocyte transglutaminase, suggesting that arsenic acts upstream of protein kinase C.
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Affiliation(s)
- B A Jessen
- Department of Environmental Toxicology, University of California, One Shields Avenue, Davis, California, 95616-8588, USA
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26
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Saleha Banu B, Danadevi K, Jamil K, Ahuja YR, Visweswara Rao K, Ishaq M. In vivo genotoxic effect of arsenic trioxide in mice using comet assay. Toxicology 2001; 162:171-7. [PMID: 11369113 DOI: 10.1016/s0300-483x(01)00359-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Although arsenic has been the subject of toxicological research, acute in vivo genotoxic studies using relevant animal models and uniform methodology are lacking. Hence, the present study aims to study DNA damage caused by arsenic trioxide in mice in in vivo using alkaline single cell gel electrophoresis (Comet) assay. Mice were administered orally 0,0.13,0.27,0.54,1.08,2.15,4.3 and 6.45 mg/kg body weight of arsenic trioxide dissolved in distilled water. The samples of whole blood were collected at 24,48,72 h, first and second week post-treatment and the assay was carried out to determine DNA damage as represented by comet tail-length. All the doses induced significant increase in comet tail-length at 24 h post-treatment (P<0.05) showing a clear dose dependent increase from 0.13 to 2.15 mg/kg b.wt. and a dose dependent decrease in higher doses (4.3-6.45 mg/kg b.wt). At 48 h post-treatment all the doses showed a significant increase (P<0.05) in comet tail-length when compared to 24 h post-treatment. A gradual decrease in the comet tail-length was observed for all the doses from 72 h post-treatment onwards indicating a gradual repair in DNA damage. This indicates a non-linear dose and time response between DNA damage and different doses of arsenic trioxide at different time-intervals. A significant increase in comet tail-length at all the doses clearly gives evidence that arsenic trioxide cause DNA damage effectively. The study indicates that the alkaline comet assay is a reliable and effective method to detect DNA damage caused by metals.
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Affiliation(s)
- B Saleha Banu
- Department of Genetics, Osmania University, Hyderabad, Andhra Pradesh, India.
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27
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Liu SX, Athar M, Lippai I, Waldren C, Hei TK. Induction of oxyradicals by arsenic: implication for mechanism of genotoxicity. Proc Natl Acad Sci U S A 2001; 98:1643-8. [PMID: 11172004 PMCID: PMC29310 DOI: 10.1073/pnas.98.4.1643] [Citation(s) in RCA: 304] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2000] [Indexed: 01/12/2023] Open
Abstract
Although arsenic is a well-established human carcinogen, the mechanisms by which it induces cancer remain poorly understood. We previously showed arsenite to be a potent mutagen in human-hamster hybrid (A(L)) cells, and that it induces predominantly multilocus deletions. We show here by confocal scanning microscopy with the fluorescent probe 5',6'-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate that arsenite induces, within 5 min after treatment, a dose-dependent increase of up to 3-fold in intracellular oxyradical production. Concurrent treatment of cells with arsenite and the radical scavenger DMSO reduced the fluorescent intensity to control levels. ESR spectroscopy with 4-hydroxy-2,2,6,6-tetramethyl-1-hydroxypiperidine (TEMPOL-H) as a probe in conjunction with superoxide dismutase and catalase to quench superoxide anions and hydrogen peroxide, respectively, indicates that arsenite increases the levels of superoxide-driven hydroxyl radicals in these cells. Furthermore, reducing the intracellular levels of nonprotein sulfhydryls (mainly glutathione) in A(L) cells with buthionine S-R-sulfoximine increases the mutagenic potential of arsenite by more than 5-fold. The data are consistent with our previous results with the radical scavenger DMSO, which reduced the mutagenicity of arsenic in these cells, and provide convincing evidence that reactive oxygen species, particularly hydroxyl radicals, play an important causal role in the genotoxicity of arsenical compounds in mammalian cells.
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Affiliation(s)
- S X Liu
- Center for Radiological Research, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
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28
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Induction of oxyradicals by arsenic: implication for mechanism of genotoxicity. Proc Natl Acad Sci U S A 2001. [PMID: 11172004 PMCID: PMC29310 DOI: 10.1073/pnas.031482998] [Citation(s) in RCA: 201] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Although arsenic is a well-established human carcinogen, the mechanisms by which it induces cancer remain poorly understood. We previously showed arsenite to be a potent mutagen in human-hamster hybrid (A(L)) cells, and that it induces predominantly multilocus deletions. We show here by confocal scanning microscopy with the fluorescent probe 5',6'-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate that arsenite induces, within 5 min after treatment, a dose-dependent increase of up to 3-fold in intracellular oxyradical production. Concurrent treatment of cells with arsenite and the radical scavenger DMSO reduced the fluorescent intensity to control levels. ESR spectroscopy with 4-hydroxy-2,2,6,6-tetramethyl-1-hydroxypiperidine (TEMPOL-H) as a probe in conjunction with superoxide dismutase and catalase to quench superoxide anions and hydrogen peroxide, respectively, indicates that arsenite increases the levels of superoxide-driven hydroxyl radicals in these cells. Furthermore, reducing the intracellular levels of nonprotein sulfhydryls (mainly glutathione) in A(L) cells with buthionine S-R-sulfoximine increases the mutagenic potential of arsenite by more than 5-fold. The data are consistent with our previous results with the radical scavenger DMSO, which reduced the mutagenicity of arsenic in these cells, and provide convincing evidence that reactive oxygen species, particularly hydroxyl radicals, play an important causal role in the genotoxicity of arsenical compounds in mammalian cells.
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29
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Pott WA, Benjamin SA, Yang RS. Pharmacokinetics, metabolism, and carcinogenicity of arsenic. REVIEWS OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 2001; 169:165-214. [PMID: 11330077 DOI: 10.1007/978-1-4613-0107-3_3] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The carcinogenicity of arsenic in humans has been unambiguously demonstrated in a variety of epidemiological studies encompassing geographically diverse study populations and multiple exposure scenarios. Despite the abundance of human data, our knowledge of the mechanism(s) responsible for the carcinogenic effects of arsenic remains incomplete. A deeper understanding of these mechanisms is highly dependent on the development of appropriate experimental models, both in vitro and in vivo, for future mechanistic investigations. Suitable in vitro models would facilitate further investigation of the critical chemical species (arsenate/arsenite/MMA/DMA) involved in the carcinogenic process, as well as the evaluation of the generation and role of ROS. Mechanisms underlying the clastogenic effects of arsenic, its role in modulating DNA methylation, and the phenomenon of inducible tolerance could all be more completely investigated using in vitro models. The mechanisms involved in arsenic's inhibition of ubiquitin-mediated proteolysis demand further attention, particularly with respect to its effects on cell proliferation and DNA repair. Exploration of the mechanisms responsible for the protective or anticarcinogenic effects of arsenic could also enhance our understanding of the cellular and molecular interactions that influence its carcinogenicity. In addition, appropriate in vivo models must be developed that consider the action of arsenic as a promoter and/or progressor. In vivo models that allow further investigation of the comutagenic effects of arsenic are also especially necessary. Such models may employ initiation-promotion-progression bioassays or transgenic animals. Both in vitro and in vivo models have the potential to greatly enhance our current understanding of the cellular and molecular interactions of arsenic and its metabolites in target tissues. However, refinement of our knowledge of the mechanistic aspects of arsenic carcinogenicity is not alone sufficient; an understanding of the pharmacokinetics and target tissue doses of the critical chemical species is essential. Additionally, a more thorough characterization of species differences in the tissue kinetics of arsenic and its methylated metabolites would facilitate the development of more accurate and relevant PBPK models. Improved models could be used to further investigate the existence of a methylation threshold for arsenic and its relevance to arsenic carcinogenicity in humans. The significance of alterations in relative tissue concentrations of SAM and SAH deserves further attention, particularly with respect to their role in modulating methyltransferases involved in arsenic metabolism and DNA methylation. The importance of genetic polymorphisms and nutrition in influencing methyltransferase activities must not be overlooked. In vivo models are necessary to evaluate these factors; transgenic or knockout models would be particularly useful in the investigation of methylation polymorphisms. Further evaluation of methylation polymorphisms in human populations is also warranted. Other in vivo models incorporating dietary manipulation could provide valuable insight into the role of nutrition in the carcinogenicity of arsenic. With more complete knowledge of the pharmacokinetics of arsenic metabolism and the mechanisms associated with its carcinogenic effects, development of more reliable risk assessment strategies are possible. Integration of data, both pharmacokinetic and mechanistic in nature, will lead to more accurate descriptions of the interactions that occur between the active chemical species and cellular constituents which lead to the development of cancer. This knowledge, in turn, will facilitate the development of more accurate and reliable risk assessment strategies for arsenic.
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Affiliation(s)
- W A Pott
- Center for Environment Toxicology and Technology, Department of Environmental Health, Colorado State University, Fort Collins, CO 80523-1680, USA
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Harrington-Brock K, Cabrera M, Collard DD, Doerr CL, McConnell R, Moore MM, Sandoval H, Fuscoe JC. Effects of arsenic exposure on the frequency of HPRT-mutant lymphocytes in a population of copper roasters in Antofagasta, Chile: a pilot study. Mutat Res 1999; 431:247-57. [PMID: 10635991 DOI: 10.1016/s0027-5107(99)00167-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
A pilot biomarker study was conducted to investigate the feasibility of using the hypoxanthine guanine phosphoribosyltransferase (HPRT) gene in peripheral blood lymphocytes as a biomarker for detecting genetic effects of arsenic exposure. Blood and urine samples were obtained from workers highly exposed to arsenic in a copper roasting plant in Antofagasta, Chile. Individuals were classified according to their job titles into three potential exposure groups: high, medium, and low. To confirm exposure, arsenic concentration was determined in urine samples. The HPRT mutant frequencies were measured in lymphocytes from 15 individuals ranging in age from 24 to 66 years. The mean mutant frequencies for the three exposure groups were: low (9 x 10(-6)), medium (11 x 10(-6)), and high (24 x 10(-6)). An increased mutant frequency was observed in the highly exposed group, but the response was so slight that it is not likely that this assay will be capable of providing dose-response information across a range of lower, more typical environmental arsenic levels.
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Affiliation(s)
- K Harrington-Brock
- Environmental Carcinogenesis Division, US Environmental Protection Agency, Research Triangle Park, NC 27711, USA
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31
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Porter AC, Fanger GR, Vaillancourt RR. Signal transduction pathways regulated by arsenate and arsenite. Oncogene 1999; 18:7794-802. [PMID: 10618720 DOI: 10.1038/sj.onc.1203214] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Arsenate and arsenite activate c-Jun N-terminal kinase (JNK), however, the mechanism by which this occurs is not known. By expressing inhibitory mutant small GTP-binding proteins, p21-activated kinase (PAK) and mitogen-activated protein kinase/extracellular signal-regulated kinase kinase kinases (MEKKs), we have identified specific proteins that are involved in arsenate- and arsenite-mediated activation of JNK. We observe a distinct difference between arsenate and arsenite signaling, which demonstrates that arsenate and arsenite are capable of activating unique proteins. Both arsenate and arsenite activation of JNK requires Rac and Rho. Neither arsenate nor arsenite signaling was inhibited by a dominant-negative mutant of Cdc42 or Ras. Arsenite stimulation of JNK requires PAK, whereas arsenate-mediated activation of JNK was unaffected by inhibitory mutant PAK. Of the four MEKKs tested, only MEKK3 and MEKK4 are involved in arsenate-mediated activation of JNK. In contrast, arsenite-mediated JNK activation requires MEKK2, MEKK3 and MEKK4. These results better define the mechanisms by which arsenate and arsenite activate JNK and demonstrate differences in the regulation of signal transduction pathways by these inorganic arsenic species.
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Affiliation(s)
- A C Porter
- Department of Pharmacology, College of Pharmacy, The University of Arizona, Tucson, Arizona, AZ 85721-0207, USA
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Arnold LL, Cano M, St John M, Eldan M, van Gemert M, Cohen SM. Effects of dietary dimethylarsinic acid on the urine and urothelium of rats. Carcinogenesis 1999; 20:2171-9. [PMID: 10545422 DOI: 10.1093/carcin/20.11.2171] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Dimethylarsinic acid (DMA), fed to rats for 2 years, produced bladder hyperplasia and tumors at doses of 40 and 100 p.p.m., more in females than males. No urothelial proliferation was seen in mice. Our objectives were to investigate the mode of action of bladder tumor formation, evaluate the dose-response and the role of diet and to determine if the urothelial effects were reversible. The study included groups of female F344 rats fed DMA in Purina 5002 diet at doses of 0, 2, 10, 40 or 100 p.p.m. for 10 weeks; two groups of females fed DMA (0 and 100 p.p.m.) in Altromin 1321 for 10 weeks; two groups of males fed DMA (0 and 100 p.p.m.) in Purina 5002 for 10 weeks; a female high-dose recovery group (100 p.p.m. in Purina 5002 diet for 10 weeks followed by control diet for 10 weeks); and two female groups (0 and 100 p.p.m.) in Purina diet for 20 weeks. Urothelial toxicity and hyperplasia were detected by light and scanning electron microscopy (SEM), and the bromodeoxyuridine labeling index was increased in the female 40 and 100 p.p.m. groups. The effects were less in males, but were similar in females fed DMA in Altromin 1321. SEM detected no abnormal urinary solids related to treatment in any group. Urinary calcium was increased in the females fed 40 and 100 p.p.m. in Purina diet, despite overall urinary dilution. Calcification was increased in kidneys of female rats fed Purina diet. The urothelial effects of DMA were reversible. The findings support a non-DNA reactive mechanism for DMA rat bladder carcinogenicity related to urothelial toxicity and regeneration. The toxicity is probably not due to urinary solids. The toxicity and regeneration are produced in a dose-responsive manner in female rats, are greater in female than in male rats, and are reversible.
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Affiliation(s)
- L L Arnold
- Department of Pathology and Microbiology and the Eppley Institute, University of Nebraska Medical Center, Omaha, NE 68198-3135, USA
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Tchounwou PB, Wilson B, Ishaque A. Important considerations in the development of public health advisories for arsenic and arsenic-containing compounds in drinking water. REVIEWS ON ENVIRONMENTAL HEALTH 1999; 14:211-229. [PMID: 10746734 DOI: 10.1515/reveh.1999.14.4.211] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Drinking water contamination by arsenic remains a major public health problem. Acute and chronic arsenic exposure via drinking water has been reported in many countries of the world; especially in Argentina, Bangladesh, India, Mexico, Thailand, and Taiwan, where a large proportion of drinking water (ground water) is contaminated with a high concentration of arsenic. Research has also pointed out significantly higher standardized mortality ratios and cumulative mortality rates for cancers of the bladder, kidney, skin, liver, and colon in many areas of arsenic pollution. General health effects that are associated with arsenic exposure include cardiovascular and peripheral vascular disease, developmental anomalies, neurologic and neurobehavioral disorders, diabetes, hearing loss, portal fibrosis of the liver, lung fibrosis, hematologic disorders (anemia, leukopenia, and eosinophilia), and carcinoma. Although, the clinical manifestations of arsenic poisoning appear similar, the toxicity of arsenic compounds depends largely u[on the chemical species and the form of arsenic involved. On the basis of its high degree of toxicity to humans, and the non-threshold dose-response assumption, a zero level exposure is recommended for arsenic, even though this level is practically non-attainable. In this review, we provide and discuss important information on the physical and chemical properties, production and use, fate and transport, toxicokinetics, systemic and carcinogenic health effects, regulatory and health guidelines, analytical methods, and treatment technologies that are applied to arsenic pollution. Such information is critical in assisting the federal, state and local officials who are responsible for protecting public health in dealing with the problem of drinking water contamination by arsenic and arsenic-containing compounds.
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Affiliation(s)
- P B Tchounwou
- NIH-Center for Environmental Health, School of Science and Technology, Jackson State University, Mississippi 39217-0940, USA.
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Salazar AM, Ostrosky-Wegman P, Menéndez D, Miranda E, García-Carrancá A, Rojas E. Induction of p53 protein expression by sodium arsenite. Mutat Res 1997; 381:259-65. [PMID: 9434882 DOI: 10.1016/s0027-5107(97)00207-8] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Arsenic is carcinogen for humans and has been shown to act as an enhancer in initiated animal models. In a previous work we found impairment of lymphocyte proliferation in arsenic-exposed individuals and in vitro we obtained dose-related inhibition of mitotic response and lymphocyte proliferation. Intrigued by these effects and based on the role of p53 on cell proliferation, we tested different concentrations of sodium arsenite for their ability to induce the expression of tumor suppressor gene p53 in different cell lines (HeLa, C-33A. Jurkat) and a lymphoblast cell line transformed with Epstein-Barr virus (LCL-EBV). We also evaluated changes in their viability after 24 h arsenic treatment; C-33A cells showed the higher sensitivity to arsenic treatment while HeLa, Jurkat and LCL-EBV cells showed similar cytotoxicity curves. Immunoblots showed an increased expression of p53 gene with 1 microM sodium arsenite in Jurkat cells and 10 microM sodium arsenite in HeLa and LCL-EBV cells. In addition, we transfected Jurkat cells and human lymphocytes with wild-type and mutated p53 genes; lymphocytes and Jurkat cells that received the mutated p53 showed increased sensitivity to arsenic cytotoxicity. Data obtained indicate that arsenic induces p53 expression and that cells with a functional p53 contend better with damage induced by this metalloid.
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Affiliation(s)
- A M Salazar
- Departamento de Genética y Toxicología Ambiental, U.N.A.M., México, Mexico
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Gómez-Arroyo S, Armienta MA, Cortés-Eslava J, Villalobos-Pietrini R. Sister chromatid exchanges in Vicia faba induced by arsenic-contaminated drinking water from Zimapan, Hidalgo, Mexico. Mutat Res 1997; 394:1-7. [PMID: 9434837 DOI: 10.1016/s1383-5718(97)00117-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Sister chromatid exchanges (SCE) in Vicia faba root tips were used to examine well water containing high levels of arsenic. The increased amount of arsenic was contained in well water from different towns of Zimapan, Hidalgo, Mexico. Treatments of 3 h were applied followed by the differential staining technique of Tempelaar et al. (Mutation Res. 103 (1982) 321-326). Concentrations of arsenic from 0.267 up to 1.070 mg/l were determined by colorimetry in the polluted samples used for this study. These values were above the permissible limit of 0.05 mg/l in drinking water. In all cases, except one in which the As concentration was 0.021, the arsenic-contaminated water produced significant increases of SCE compared with the control (p < 0.001) and a concentration-response relationship was observed. The SCE potency factor of 33 per mg/l of arsenic was calculated as the slope of a common regression line, pooling data previously obtained in the Comarca Lagunera and the results observed in Zimapan.
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Affiliation(s)
- S Gómez-Arroyo
- Laboratorios de Citogenética y Mutagénesis Ambientales, Centro de Ciencias de la Atmósfera, Universidad Nacional Autónoma de México, Coyoacán, México.
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Zhao CQ, Young MR, Diwan BA, Coogan TP, Waalkes MP. Association of arsenic-induced malignant transformation with DNA hypomethylation and aberrant gene expression. Proc Natl Acad Sci U S A 1997; 94:10907-12. [PMID: 9380733 PMCID: PMC23527 DOI: 10.1073/pnas.94.20.10907] [Citation(s) in RCA: 335] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Inorganic arsenic, a human carcinogen, is enzymatically methylated for detoxication, consuming S-adenosyl-methionine (SAM) in the process. The fact that DNA methyltransferases (MeTases) require this same methyl donor suggests a role for methylation in arsenic carcinogenesis. Here we test the hypothesis that arsenic-induced initiation results from DNA hypomethylation caused by continuous methyl depletion. The hypothesis was tested by first inducing transformation in a rat liver epithelial cell line by chronic exposure to low levels of arsenic, as confirmed by the development of highly aggressive, malignant tumors after inoculation of cells into Nude mice. Global DNA hypomethylation occurred concurrently with malignant transformation and in the presence of depressed levels of S-adenosyl-methionine. Arsenic-induced DNA hypomethylation was a function of dose and exposure duration, and remained constant even after withdrawal of arsenic. Hyperexpressibility of the MT gene, a gene for which expression is clearly controlled by DNA methylation, was also detected in transformed cells. Acute arsenic or arsenic at nontransforming levels did not induce global hypomethylation of DNA. Whereas transcription of DNA MeTase was elevated, the MeTase enzymatic activity was reduced with arsenic transformation. Taken together, these results indicate arsenic can act as a carcinogen by inducing DNA hypomethylation, which in turn facilitates aberrant gene expression, and they constitute a tenable theory of mechanism in arsenic carcinogenesis.
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Affiliation(s)
- C Q Zhao
- Inorganic Carcinogenesis Section, Laboratory of Comparative Carcinogenesis, National Cancer Institute/National Institute on Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
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Abstract
Inorganic arsenic is considered a human carcinogen based principally on epidemiological evidence. Unlike most initiating chemicals, arsenic is inactive or extremely weak in its ability to directly induce gene mutations. Arsenite has been shown, however, to enhance mutagenicity when present with other agents such as UV radiation. Synergistic potentiation of chromosomal damage has been shown with co-treatment with DNA-crosslinking agents. Arsenite at low concentrations is known to be highly selective in reacting with closely spaced (vicinal) dithiol groups in proteins. Poly(ADP-ribose) polymerase (PARP) is known to contain such vicinal dithiol groups. Stimulation of PARP is an immediate response of eukaryotic cells to DNA strand breaks and has been implicated in DNA repair. The effect of treatment with sodium arsenite on PARP activity was assessed as follows: Molt-3 cells (a human T-cell lymphoma-derived cell line) in culture were treated for 24 h with concentrations of sodium arsenite ranging from 2.5 up to 25 microM. Speciation of inorganic arsenic and cell viability were determined. Cell cycle kinetics were measured by flow cytometry. Poly(ADP-ribose) synthesis was assayed using a palindromic decameric deoxynucleotide to stimulate enzyme activity. Results show that arsenite decreases PARP activity in a dose-dependent manner with an approximately 50% decrease in enzyme activity at 10 microM arsenite and 80% viability. The percent of cells in S-phase increases with increasing concentration of arsenite. These results provide further indication that arsenite may potentiate genetic damage through reaction with dithiols in DNA repair proteins such as PARP, perhaps resulting in interference with normal repair function.
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Affiliation(s)
- J W Yager
- Environment Group, Electric Power Research Institute, Palo Alto, CA 94303, USA
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Tice RR, Yager JW, Andrews P, Crecelius E. Effect of hepatic methyl donor status on urinary excretion and DNA damage in B6C3F1 mice treated with sodium arsenite. Mutat Res 1997; 386:315-34. [PMID: 9219569 DOI: 10.1016/s1383-5742(97)00004-5] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
This study evaluated the effect of hepatic methyl donor status on the ability of sodium arsenite (2.5, 5.0 and 10.0 mg/kg) administered by gavage once or on four consecutive days to induce DNA damage in male B6C3F1 mice. Maintenance on a choline-deficient (CD) diet prior to treatment resulted in mice with hepatic methyl donor deficiency (HMDD) and altered arsenical metabolism, as demonstrated by a decreased total urinary excretion of inorganic and organic arsenicals. The alkaline (pH > 13) Single Cell Gel (SCG) assay was used to evaluate for the induction of DNA damage (single strand breaks, alkali labile sites, DNA crosslinking) in blood leukocytes, liver parenchymal cells, and cells sampled from bladder, lung, and skin, while the bone marrow erythrocyte micronucleus (MN) assay was used to assess for the induction of chromosomal damage in bone marrow cells. Treatment with sodium arsenite once or four times induced a significant decrease in DNA migration (indicative of DNA crosslinking) in bladder and liver parenchymal cells of hepatic methyl donor sufficient (HMDS) mice, but in skin cells of HMDD mice. Both HMDD and HMDS mice exhibited a significant increase in the frequency of micronucleated polychromatic erythrocytes (MN-PCE) in bone marrow following four, but not following one, treatments. However, the positive response occurred at a lower dose for HMDS mice and, in these mice, bone marrow toxicity, as demonstrated by a significant reduction in the percentage of PCE, was present also. These results indicate that hepatic methyl donors deficiency significantly decreases the total urinary excretion of orally administered sodium arsenite and markedly modulates target organ arsenic-induced DNA damage, with an apparent shift from liver and bladder to skin.
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Affiliation(s)
- R R Tice
- Integrated Laboratory Systems, Research Triangle Park, NC 27709, USA
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Gonsebatt ME, Vega L, Salazar AM, Montero R, Guzmán P, Blas J, Del Razo LM, García-Vargas G, Albores A, Cebrián ME, Kelsh M, Ostrosky-Wegman P. Cytogenetic effects in human exposure to arsenic. Mutat Res 1997; 386:219-28. [PMID: 9219560 DOI: 10.1016/s1383-5742(97)00009-4] [Citation(s) in RCA: 127] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The cytogenetic effects of arsenic exposure were studied among rural populations that live in the same geographical area and have similar socioeconomic status, but different degree of exposure to inorganic arsenic (As) via drinking water. A group of inhabitants of Santa Ana (408.17 micrograms/l of As in drinking water) were considered the exposed individuals and a group of inhabitants of Nazareno (29.88 micrograms/l) were considered as controls. Blood and urine samples were obtained from volunteers. Past and current exposure, health, and nutritional status as well as the presence of arsenic skin lesions were ascertained in study participants through questionnaires and physical examination. The frequencies and types of chromosomal aberrations in first-division metaphases were studied in whole blood lymphocyte cultures while the presence of micronuclei (MN) was studied in exfoliated epithelial cells obtained from the oral mucosa and from urine samples. Total arsenic (TAs) content, and the relative proportions of inorganic arsenic (IAs), and the metabolites monomethylarsonic (MMA) and dimethylarsinic (DMA) acid were determined in urine samples. Exposed individuals showed a significant increase in the frequency of chromatid and isochromatid deletions in lymphocytes and of MN in oral and urinary epithelial cells. Males were more affected than females, and a higher number of micronucleated oral cells were found among those individuals with skin lesions. The type of cytogenetic damage observed gives evidence of arsenic as a clastogenic/aneugenic carcinogen.
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Affiliation(s)
- M E Gonsebatt
- Departamento de Genética y Toxicología Ambiental, UNAM, Ciudad Universitario, México, México
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Moore MM, Harrington-Brock K, Doerr CL. Relative genotoxic potency of arsenic and its methylated metabolites. Mutat Res 1997; 386:279-90. [PMID: 9219565 DOI: 10.1016/s1383-5742(97)00003-3] [Citation(s) in RCA: 120] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Arsenic is one of the few identified human carcinogens that has yet to be shown to cause cancer in rodents when the standard bioassay protocols are used. The reasons for this apparent interspecies difference are unclear but may be related to differences between humans and rodents in their detoxification capabilities. Detoxification of arsenic may occur through a methylation pathway. If, in fact, methylation does detoxify arsenic, one would predict that the methylated arsenicals might be less genotoxic than the inorganic arsenicals. To evaluate the hypothesis that the inorganic arsenicals are more mutagenic than the organic arsenicals, we tested sodium arsenite, sodium arsenate, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) for their relative mutagenic and clastogenic potentials. We used the L5178Y/TK+/- mouse lymphoma assay which allows the detection of chemicals inducing a broad spectrum of different types of genetic damage. Sodium arsenite and sodium arsenate were active at concentrations of 1-2 micrograms/ml and 10-14 micrograms/ml, respectively. MMA was active between 2500-5000 micrograms/ml; while DMA required almost 10000 micrograms/ml to induce a genotoxic response. The organic arsenicals are thus much less potent as mutagenic agents than the inorganic arsenicals. All four of these arsenicals appear to act by mechanisms that cause chromosomal mutations.
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Affiliation(s)
- M M Moore
- Genetics and Cellular Toxicology Branch, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, USA
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Cooney RV, Harwood PJ. Effects of Arsenic Compounds on Proliferation and Nitric Oxide Synthesis in C3H 10T 1/2 Murine Fibroblasts. Appl Organomet Chem 1997. [DOI: 10.1002/(sici)1099-0739(199705)11:5<397::aid-aoc594>3.0.co;2-t] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Byrd DM, Roegner ML, Griffiths JC, Lamm SH, Grumski KS, Wilson R, Lai S. Carcinogenic risks of inorganic arsenic in perspective. Int Arch Occup Environ Health 1996; 68:484-94. [PMID: 8891790 DOI: 10.1007/bf00377874] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Induction of cancer by inorganic arsenic occurs inconsistently between species and between routes of exposure, and it exhibits different dose-response relationships between different target organs. Inhaled or ingested arsenic causes cancer in humans but not in other species. Inhaled arsenic primarily induces lung cancer, whereas ingested arsenic induces cancer at multiple sites, including the skin and various other organs. Cancer potency appears to vary by route of exposure (ingestion or inhalation) and by organ site, and increases markedly at higher exposures in some instances. To understand what might explain these inconsistencies, we reviewed several hypotheses about the mechanism of cancer induction by arsenic. Arsenic disposition does not provide satisfactory explanations. Induction of cell proliferation by arsenic is a mechanism of carcinogenesis that is biologically plausible and compatible with differential effects for species or differential dose rates for organ sites. The presence of other carcinogens, or risk modifiers, at levels that correlate with arsenic in drinking water supplies, may be a factor in all three inconsistencies: interspecies specificity, organ sensitivity to route of administration, and organ sensitivity to dose rate.
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Affiliation(s)
- D M Byrd
- Risk Assessment and Product Safety, Washington, DC 20005, USA
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Kochhar TS, Howard W, Hoffman S, Brammer-Carleton L. Effect of trivalent and pentavalent arsenic in causing chromosome alterations in cultured Chinese hamster ovary (CHO) cells. Toxicol Lett 1996; 84:37-42. [PMID: 8597176 DOI: 10.1016/0378-4274(95)03536-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Sodium salts of trivalent and pentavalent arsenic were tested for their effect in inducing chromosome aberrations and sister-chromatid exchange (SCE) in cultured Chinese hamster ovary (CHO) cells. It was discovered that arsenite (As 3) produced excessive endoreduplication of the chromosomes at higher levels. No endoreduplication was observed with arsenate (As 5) treatment. These agents also elevated the frequencies of SCE, but less so compared to aberrations. The results obtained indicate that arsenic may be carcinogenic in animal system.
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Affiliation(s)
- T S Kochhar
- Division of Mathematics and Sciences, Kentucky State University, Franfort, KY 40601, USA
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Hsueh YM, Cheng GS, Wu MM, Yu HS, Kuo TL, Chen CJ. Multiple risk factors associated with arsenic-induced skin cancer: effects of chronic liver disease and malnutritional status. Br J Cancer 1995; 71:109-14. [PMID: 7819025 PMCID: PMC2033480 DOI: 10.1038/bjc.1995.22] [Citation(s) in RCA: 156] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
In order to evaluate the prevalence and multiple risk factors of arsenic-induced skin cancer among residents in Taiwanese villages in which chronic arseniasis is hyperendemic, a total of 1571 subjects aged 30 or more years were recruited between September 1988 and March 1989. All of them were interviewed personally by a public health nurse using a structured questionnaire, and 1081 interviewed study subjects, including 468 men and 613 women, participated in physical examination, giving a participation rate of 68.8%. The overall prevalence of skin cancer was as high as 6.1%, showing an increase with age in both men and women. There was a significant dose-response relation between skin cancer prevalence and chronic arsenic exposure as indexed by duration of residence in the endemic area, duration of consumption of high-arsenic artesian well water, average arsenic exposure in parts per million (p.p.m.) and cumulative arsenic exposure in p.p.m.-years. Chronic carriers of hepatitis B surface antigen with liver dysfunction had an increased prevalence of skin cancer. Undernourishment, indexed by a high consumption of dried sweet potato as a staple food, was also significantly associated with an increased prevalence of arsenic-induced skin cancer. All these risk factors remained statistically significant in the multiple logistic regression analysis. Consistent with animal experiments, the findings imply that liver function and nutritional status may affect the metabolism of inorganic arsenic and the development of subsequent skin cancers.
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Affiliation(s)
- Y M Hsueh
- Department of Public Health School of Medicine, Taipei Medical College, Taiwan, Republic of China
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Abstract
While carcinogenic metal ions are mostly non-mutagenic in bacteria, different types of cellular damage have been observed in mammalian cells, which may account for their carcinogenic potential. Two modes of action seem to be predominant: the induction of oxidative DNA damage, best established for chromium compounds, and the interaction with DNA repair processes, leading to an enhancement of genotoxicity in combination with a variety of DNA damaging agents. In the case of Cd(II), Ni(II), Co(II), Pb(II) and As(III), DNA repair processes are disturbed at low, non-cytotoxic concentrations of the respective metal compounds. Even though different steps in DNA repair are affected by the diverse metals, one common mechanism might be the competition with essential metal ions.
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Affiliation(s)
- A Hartwig
- Department of Biology and Chemistry, University of Bremen, Germany
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46
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Hsieh LL, Chen HJ, Hsieh JT, Jee SH, Chen GS, Chen CJ. Arsenic-related Bowen's disease and paraquat-related skin cancerous lesions show no detectable ras and p53 gene alterations. Cancer Lett 1994; 86:59-65. [PMID: 7954356 DOI: 10.1016/0304-3835(94)90180-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We have investigated point mutations of codons 12, 13, and 61 in H-, K-, and N-ras oncogenes as well as p53 tumour suppressor gene exon 5 through exon 9 by PCR-SSCP analysis in 26 skin biopsy tissues from 16 arsenic-related Bowen's disease patients and 6 skin samples from 4 paraquat manufacturing workers. No mutation was found. These results are different from findings with UV associated skin cancers. Interestingly, a silent change at codon 27 of H-ras in one allele was detected in all 4 paraquat manufacturing workers and in 2 of 16 arsenic-related Bowen's disease patients. It is likely that the molecular mechanisms involved in arsenic and paraquat induced skin cancers differ from sunlight-related skin malignancies.
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Affiliation(s)
- L L Hsieh
- Department of Public Health, Chang Gung Medical College, Taiwan, R.O.C
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47
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Faroon OM, Williams M, O'Connor R. A review of the carcinogenicity of chemicals most frequently found at National Priorities List sites. Toxicol Ind Health 1994; 10:203-30. [PMID: 7855869 DOI: 10.1177/074823379401000309] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Several studies have shown that numerous National Priorities List (NPL) sites have been contaminated with arsenic (747), cadmium (791), chloroform (596), or nickel (664). The National Toxicology Program (NTP, 1991) has classified these substances as known human carcinogens (arsenic and certain arsenic compounds) or as substances that may reasonably be anticipated to be carcinogens (cadmium and certain cadmium compounds, chloroform, and nickel and certain nickel compounds). The general population is probably exposed to low levels of these hazardous substances through drinking water, eating food, or inhaling contaminated air. People working or living near industries and facilities that manufacture and use chloroform, nickel, arsenic, or cadmium may be exposed to higher than background levels of these hazardous substances. Multiple pathways of exposure may exist for populations near hazardous waste sites. For example, high levels of chloroform (1,890 ppb) were found in well water near a waste site; high levels of cadmium exposure may exist for individuals living near cadmium-contaminated waste sites.
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Affiliation(s)
- O M Faroon
- Division of Toxicology, U.S. Department of Health and Human Services Atlanta, Georgia
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48
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Abstract
Effects of arsenic on DNA synthesis in human lymphocytes were biphasic: either trivalent (arsenic trioxide and sodium arsenite) or pentavalent (sodium arsenate) arsenic compounds at very low concentrations enhanced DNA synthesis in human lymphocytes stimulated by phytohemagglutinin (PHA), whereas higher concentrations inhibited DNA synthesis. There were differences among individual susceptibilities to arsenic-induced DNA synthesis. Either stimulating or inhibiting effects of trivalent arsenic on DNA synthesis in PHA-stimulated lymphocytes were always stronger than those of pentavalent arsenic. It was also shown that both trivalent and pentavalent arsenic could be rapidly taken up into the human lymphocytes, and immediately stimulated or inhibited DNA synthesis. A possible dual effect of arsenic at very low concentrations as both comutagen and inhibitor of mutagenesis is discussed.
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Affiliation(s)
- Z Meng
- Department of Environmental Science, Shanxi University, Taiyuan, China
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49
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Smith AH, Hopenhayn-Rich C, Warner M, Biggs ML, Moore L, Smith MT. Rationale for selecting exfoliated bladder cell micronuclei as potential biomarkers for arsenic genotoxicity. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH 1993; 40:223-34. [PMID: 8230298 DOI: 10.1080/15287399309531790] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Biomarkers of effect have important potential in epidemiology, since they may enable ascertainment of exposure-effect associations in relatively inexpensive cross-sectional studies, with confirmation by short follow-up after cessation of exposure. Arsenic is known to cause human skin and lung cancer, and may also cause various internal cancers including bladder, kidney, and liver cancer. The strongest epidemiological association between arsenic ingestion and an internal cancer is that with bladder cancer. Epidemiological studies of a Taiwanese population exposed to high levels of arsenic from drinking water reported relative risks for bladder cancer well above any other known environmental carcinogen. Populations at increased risk for bladder cancer from other exposures, such as smoking and schistosomiasis infection, have elevated frequencies of micronuclei in exfoliated bladder cells. We have therefore proposed that the bladder cell micronucleus assay could be an appropriate biological marker of genotoxic effect of arsenic exposure. In this paper, we present the rationale for choosing the bladder cell micronucleus assay as a potential biomarker of effect for arsenic. We also briefly describe the studies we are conducting using this biomarker in currently exposed populations.
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Affiliation(s)
- A H Smith
- School of Public Health, University of California, Berkeley 94720
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50
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Gonsebatt ME, Vega L, Herrera LA, Montero R, Rojas E, Cebrián ME, Ostrosky-Wegman P. Inorganic arsenic effects on human lymphocyte stimulation and proliferation. Mutat Res 1992; 283:91-5. [PMID: 1381494 DOI: 10.1016/0165-7992(92)90139-9] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Lymphocyte cultures from individuals exposed to high levels of hydroarsenicism showed a slower cell cycle kinetics than cultures from low-exposed individuals. Since this difference in proliferation could be due to chronic arsenic exposure, the in vitro effects of inorganic arsenic in human whole blood lymphocyte cultures were investigated. When lymphocytes were exposed to concentrations of arsenite and arsenate similar to those found in the blood of exposed subjects (10(-7), 10(-8) and 10(-9) M) during the last 24 h before harvesting, a dose-related inhibition of proliferation was observed. Cultures were also treated with 10(-9) M of arsenite and arsenate for 2, 6 and 24 h at the beginning of the cultures in the presence or absence of phytohemagglutinin (PHA). Inhibition of stimulation and proliferation was directly related to the length of treatment. The results show that, at the concentrations tested, arsenite and arsenate impair lymphocyte stimulation and proliferation and confirm the fact that chronic arsenic exposure can affect the proliferation of whole blood lymphocytes.
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Affiliation(s)
- M E Gonsebatt
- Instituto de Investigaciones Biomédicas, UNAM, Mexico D.F
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