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Islam S, Sarkar O, Mukherjee S, Kamila S, Bhowmik AD, Chattopadhyay A. Chronic low-dose chromium VI exposure induces oxidative stress and apoptosis with altered expressions of DNA repair genes and promoter hypermethylation in the liver of Swiss albino mice. J Appl Toxicol 2024. [PMID: 38523572 DOI: 10.1002/jat.4600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Revised: 02/23/2024] [Accepted: 03/04/2024] [Indexed: 03/26/2024]
Abstract
The present investigation dealt with harmful effects of hexavalent chromium (Cr [VI]) on liver of Swiss albino mice. This variant exhibited cytotoxicity, mutagenicity, and carcinogenicity. Our study focused on elucidating the hepatotoxic effects of chronic low-dose exposure to Cr (VI) (2, 5, and 10 ppm) administered via drinking water for 4 and 8 months. The observed elevation in SGPT, ALP, and SGOT and increased oxidative stress markers unequivocally confirmed the severe disruption of liver homeostasis at these low treatment doses. Noteworthy alterations in histoarchitecture, body weight, and water intake provided further evidences of the harmful effects of Cr (VI). Production of reactive oxygen species (ROS) during metabolism led to DNA damages. Immunohistochemistry and qRT-PCR analyses revealed that chronic low-dose exposure of Cr (VI) induced apoptosis in liver tissue. Our study exhibited alterations in the expression pattern of DNA repair genes (Rad51, Mutyh, Mlh1, and Ogg1), coupled with promoter hypermethylation of Mutyh and Rad51, leading to transcriptional inhibition. Our findings underscored the potential of low-dose Cr (VI) exposure on hepatotoxicity by the intricate interplay between apoptosis induction and epigenetic alterations of DNA repair genes.
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Affiliation(s)
- Shehnaz Islam
- Department of Zoology, Visva-Bharati, Santiniketan, West Bengal, India
| | - Olivia Sarkar
- Department of Zoology, Visva-Bharati, Santiniketan, West Bengal, India
| | - Sunanda Mukherjee
- Department of Zoology, Visva-Bharati, Santiniketan, West Bengal, India
| | - Sreejata Kamila
- Department of Zoology, Visva-Bharati, Santiniketan, West Bengal, India
| | - Arpan Dey Bhowmik
- Department of Zoology, Visva-Bharati, Santiniketan, West Bengal, India
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2
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Murthy MK, Khandayataray P, Padhiary S, Samal D. A review on chromium health hazards and molecular mechanism of chromium bioremediation. REVIEWS ON ENVIRONMENTAL HEALTH 2023; 38:461-478. [PMID: 35537040 DOI: 10.1515/reveh-2021-0139] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Accepted: 04/19/2022] [Indexed: 05/13/2023]
Abstract
Living beings have been devastated by environmental pollution, which has reached its peak. The disastrous pollution of the environment is in large part due to industrial wastes containing toxic pollutants. The widespread use of chromium (Cr (III)/Cr (VI)) in industries, especially tanneries, makes it one of the most dangerous environmental pollutants. Chromium pollution is widespread due to ineffective treatment methods. Bioremediation of chromium (Cr) using bacteria is very thoughtful due to its eco-friendly and cost-effective outcome. In order to counter chromium toxicity, bacteria have numerous mechanisms, such as the ability to absorb, reduce, efflux, or accumulate the metal. In this review article, we focused on chromium toxicity on human and environmental health as well as its bioremediation mechanism.
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Affiliation(s)
| | | | - Samprit Padhiary
- Department of Biotechnology, Academy of Management and Information Technology, Khordha, India
| | - Dibyaranjan Samal
- Department of Biotechnology, Academy of Management and Information Technology, Khordha, India
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3
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Krawic C, Zhitkovich A. Chemical mechanisms of DNA damage by carcinogenic chromium(VI). ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2022; 96:25-46. [PMID: 36858775 PMCID: PMC10069994 DOI: 10.1016/bs.apha.2022.07.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Hexavalent chromium is a firmly established human carcinogen with documented exposures in many professional groups. Environmental exposure to Cr(VI) is also a significant public health concern. Cr(VI) exists in aqueous solutions as chromate anion that is unreactive with DNA and requires reductive activation inside the cells to produce genotoxic and mutagenic effects. Reduction of Cr(VI) in cells is nonenzymatic and in vivo principally driven by ascorbate with a secondary contribution from nonprotein thiols glutathione and cysteine. In addition to its much faster rate of reduction, ascorbate-driven metabolism avoids the formation of Cr(V) which is the first intermediate in Cr(VI) reduction by thiols. The end-product of Cr(VI) reduction is Cr(III) which forms several types of Cr-DNA adducts that are collectively responsible for all mutagenic and genotoxic effects in Cr(VI) reactions with ascorbate and thiols. Some Cr(V) forms can react with H2O2 to produce DNA-oxidizing peroxo species although this genotoxic pathway is suppressed in cells with physiological levels of ascorbate. Chemical reactions of Cr(VI) with ascorbate or thiols lack directly DNA-oxidizing metabolites. The formation of oxidative DNA breaks in early studies of these reactions was caused by iron contamination. Production of Cr(III)-DNA adducts in cells showed linear dose-dependence irrespective of the predominant reduction pathway and their processing by mismatch repair generated more toxic secondary genetic lesions in euchromatin. Overall, Cr(III)-DNA adduction is the dominant pathway for the formation of genotoxic and mutagenic DNA damage by carcinogenic Cr(VI).
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Affiliation(s)
- Casey Krawic
- Department of Pathology and Laboratory Medicine, Legorreta Cancer Center, Brown University, Providence, RI, United States
| | - Anatoly Zhitkovich
- Department of Pathology and Laboratory Medicine, Legorreta Cancer Center, Brown University, Providence, RI, United States.
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Yang S, Liu JDH, Diem M, Wesseling S, Vervoort J, Oostenbrink C, Rietjens IMCM. Molecular Dynamics and In Vitro Quantification of Safrole DNA Adducts Reveal DNA Adduct Persistence Due to Limited DNA Distortion Resulting in Inefficient Repair. Chem Res Toxicol 2020; 33:2298-2309. [PMID: 32786539 DOI: 10.1021/acs.chemrestox.0c00097] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The formation and repair of N2-(trans-isosafrol-3'-yl)-2'-deoxyguanosine (S-3'-N2-dG) DNA adduct derived from the spice and herbal alkenylbenzene constituent safrole were investigated. DNA adduct formation and repair were studied in vitro and using molecular dynamics (MD) simulations. DNA adduct formation was quantified using liquid chromatography-mass spectrometry (LCMS) in wild type and NER (nucleotide excision repair) deficient CHO cells and also in HepaRG cells and primary rat hepatocytes after different periods of repair following exposure to safrole or 1'-hydroxysafrole (1'-OH safrole). The slower repair of the DNA adducts found in NER deficient cells compared to that in CHO wild type cells indicates a role for NER in repair of S-3'-N2-dG DNA adducts. However, DNA repair in liver cell models appeared to be limited, with over 90% of the adducts remaining even after 24 or 48 h recovery. In our further studies, MD simulations indicated that S-3'-N2-dG adduct formation causes only subtle changes in the DNA structure, potentially explaining inefficient activation of NER. Inefficiency of NER mediated repair of S-3'-N2-dG adducts points at persistence and potential bioaccumulation of safrole DNA adducts upon daily dietary exposure.
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Affiliation(s)
- Shuo Yang
- Division of Toxicology, Wageningen University and Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands
| | - Jakob D H Liu
- Institute of Molecular Modeling and Simulation, Department of Material Sciences and Process Engineering, University of Natural Resources and Life Sciences, Muthgasse 18, 1190 Vienna, Austria
| | - Matthias Diem
- Institute of Molecular Modeling and Simulation, Department of Material Sciences and Process Engineering, University of Natural Resources and Life Sciences, Muthgasse 18, 1190 Vienna, Austria
| | - Sebastiaan Wesseling
- Division of Toxicology, Wageningen University and Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands
| | - Jacques Vervoort
- Division of Biochemistry, Wageningen University and Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands
| | - Chris Oostenbrink
- Institute of Molecular Modeling and Simulation, Department of Material Sciences and Process Engineering, University of Natural Resources and Life Sciences, Muthgasse 18, 1190 Vienna, Austria
| | - Ivonne M C M Rietjens
- Division of Toxicology, Wageningen University and Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands
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5
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Pavesi T, Moreira JC. Mechanisms and individuality in chromium toxicity in humans. J Appl Toxicol 2020; 40:1183-1197. [DOI: 10.1002/jat.3965] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Revised: 02/10/2020] [Accepted: 02/23/2020] [Indexed: 12/18/2022]
Affiliation(s)
- Thelma Pavesi
- Centro de Estudos da Saúde do Trabalhador e Ecologia HumanaEscola Nacional de Saúde Pública, Fundação Oswaldo Cruz Rio de Janeiro Brazil
| | - Josino Costa Moreira
- Centro de Estudos da Saúde do Trabalhador e Ecologia HumanaEscola Nacional de Saúde Pública, Fundação Oswaldo Cruz Rio de Janeiro Brazil
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Reduction of chromium-VI by chromium-resistant Escherichia coli FACU: a prospective bacterium for bioremediation. Folia Microbiol (Praha) 2020; 65:687-696. [DOI: 10.1007/s12223-020-00771-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2019] [Accepted: 01/16/2020] [Indexed: 01/04/2023]
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7
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Ferreira LMR, Cunha-Oliveira T, Sobral MC, Abreu PL, Alpoim MC, Urbano AM. Impact of Carcinogenic Chromium on the Cellular Response to Proteotoxic Stress. Int J Mol Sci 2019; 20:ijms20194901. [PMID: 31623305 PMCID: PMC6801751 DOI: 10.3390/ijms20194901] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 09/22/2019] [Accepted: 09/30/2019] [Indexed: 12/22/2022] Open
Abstract
Worldwide, several million workers are employed in the various chromium (Cr) industries. These workers may suffer from a variety of adverse health effects produced by dusts, mists and fumes containing Cr in the hexavalent oxidation state, Cr(VI). Of major importance, occupational exposure to Cr(VI) compounds has been firmly associated with the development of lung cancer. Counterintuitively, Cr(VI) is mostly unreactive towards most biomolecules, including nucleic acids. However, its intracellular reduction produces several species that react extensively with biomolecules. The diversity and chemical versatility of these species add great complexity to the study of the molecular mechanisms underlying Cr(VI) toxicity and carcinogenicity. As a consequence, these mechanisms are still poorly understood, in spite of intensive research efforts. Here, we discuss the impact of Cr(VI) on the stress response—an intricate cellular system against proteotoxic stress which is increasingly viewed as playing a critical role in carcinogenesis. This discussion is preceded by information regarding applications, chemical properties and adverse health effects of Cr(VI). A summary of our current understanding of cancer initiation, promotion and progression is also provided, followed by a brief description of the stress response and its links to cancer and by an overview of potential molecular mechanisms of Cr(VI) carcinogenicity.
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Affiliation(s)
- Leonardo M R Ferreira
- Department of Surgery and Diabetes Center and Sean N. Parker Autoimmune Research Laboratory, University of California, San Francisco, San Francisco, CA 94143, USA.
| | - Teresa Cunha-Oliveira
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, UC-Biotech, Biocant Park, 3060-197 Cantanhede, Portugal.
| | - Margarida C Sobral
- Department of Life Sciences, University of Coimbra, 3000-456 Coimbra, Portugal.
| | - Patrícia L Abreu
- Instituto de Medicina Molecular João Lobo Antunes, Faculty of Medicine, University of Lisbon, 1649-028 Lisbon, Portugal.
| | - Maria Carmen Alpoim
- Department of Life Sciences, Center of Investigation in Environment, Genetics and Oncobiology (CIMAGO) and CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3000-456 Coimbra, Portugal.
| | - Ana M Urbano
- Department of Life Sciences, Molecular Physical Chemistry Research Unit and Center of Investigation in Environment, Genetics and Oncobiology (CIMAGO), University of Coimbra, 3000-456 Coimbra, Portugal.
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8
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Luczak MW, Krawic C, Zhitkovich A. p53 activation by Cr(VI): a transcriptionally limited response induced by ATR kinase in S-phase. Toxicol Sci 2019; 172:11-22. [PMID: 31388677 PMCID: PMC6813752 DOI: 10.1093/toxsci/kfz178] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2019] [Revised: 07/19/2019] [Accepted: 07/26/2019] [Indexed: 01/30/2023] Open
Abstract
Cellular reduction of carcinogenic chromium(VI) causes several forms of Cr-DNA damage with different genotoxic properties. Chromate-treated cultured cells have shown a strong proapoptotic activity of the DNA damage-sensitive transcription factor p53. However, induction of p53 transcriptional targets by Cr(VI) in rodent lungs was weak or undetectable. We examined Cr(VI) effects on the p53 pathway in human cells with restored levels of ascorbate that acts as a principal reducer of Cr(VI) in vivo but is nearly absent in standard cell cultures. Ascorbate-restored H460 and primary human cells treated with Cr(VI) contained higher levels of p53 and its Ser15 phosphorylation, which were induced by ATR kinase. Cr(VI)-stimulated p53 phosphorylation occurred in S-phase by a diffusible pool of ATR that was separate from the chromatin-bound pool targeting DNA repair substrates at the sites of toxic mismatch repair of Cr-DNA adducts. Even when more abundantly present than after exposure to the radiomimetic bleomycin, Cr(VI)-stabilized p53 showed a much more limited activation of its target genes in two types of primary human cells. No increases in mRNA were found for nucleotide excision repair factors and a majority of proapoptotic genes. A weak transcription activity of Cr(VI)-upregulated p53 was associated with its low lysine acetylation in the regulatory C-terminal domain, resulting from the inability of Cr(VI) to activate ATM in ascorbate-restored cells. Thus, p53 activation by ascorbate-metabolized Cr(VI) represents a limited genome-protective response that is defective in upregulation of DNA repair genes and proapoptotic transcripts for elimination of damaged cells.
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Affiliation(s)
- Michal W Luczak
- Brown University, Department of Pathology and Laboratory Medicine, Providence, RI, USA
| | - Casey Krawic
- Brown University, Department of Pathology and Laboratory Medicine, Providence, RI, USA
| | - Anatoly Zhitkovich
- Brown University, Department of Pathology and Laboratory Medicine, Providence, RI, USA
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9
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Samavarchi Tehrani S, Mahmoodzadeh Hosseini H, Yousefi T, Abolghasemi M, Qujeq D, Maniati M, Amani J. The crosstalk between trace elements with DNA damage response, repair, and oxidative stress in cancer. J Cell Biochem 2019; 120:1080-1105. [PMID: 30378148 DOI: 10.1002/jcb.27617] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Accepted: 08/14/2018] [Indexed: 01/24/2023]
Abstract
DNA damage response (DDR) is a regulatory system responsible for maintaining genome integrity and stability, which can sense and transduce DNA damage signals. The severity of damage appears to determine DDRs, which can include damage repair, cell-cycle arrest, and apoptosis. Furthermore, defective components in DNA damage and repair machinery are an underlying cause for the development and progression of various types of cancers. Increasing evidence indicates that there is an association between trace elements and DDR/repair mechanisms. In fact, trace elements seem to affect mediators of DDR. Besides, it has been revealed that oxidative stress (OS) and trace elements are associated with cancer development. In this review, we discuss the role of some critical trace elements in the risk of cancer. In addition, we provide a brief introduction on DDR and OS in cancer. Finally, we will further review the interactions between some important trace elements including selenium, zinc, chromium, cadmium, and arsenic, and DDR, and OS in cancer.
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Affiliation(s)
- Sadra Samavarchi Tehrani
- Applied Microbiology Research Center, Systems Biology and Poisonings Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran
| | - Hamideh Mahmoodzadeh Hosseini
- Applied Microbiology Research Center, Systems Biology and Poisonings Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran
| | - Tooba Yousefi
- Student Research Committee, Babol University of Medical Sciences, Babol, Iran
| | - Maryam Abolghasemi
- Student Research Committee, Babol University of Medical Sciences, Babol, Iran
| | - Durdi Qujeq
- Department of Clinical Biochemistry, Babol University of Medical Sciences, Babol, Iran
| | - Mahmood Maniati
- English Department, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
| | - Jafar Amani
- Applied Microbiology Research Center, Systems Biology and Poisonings Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran
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10
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Long C, Liu J, Hu G, Feng H, Zhou D, Wang J, Zhai X, Zhao Z, Yu S, Wang T, Jia G. Modulation of homologous recombination repair gene polymorphisms on genetic damage in chromate exposed workers. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2019; 66:126-132. [PMID: 30677706 DOI: 10.1016/j.etap.2019.01.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 12/29/2018] [Accepted: 01/16/2019] [Indexed: 06/09/2023]
Abstract
Hexavalent chromium [Cr(VI)] is one of the most common environmental carcinogens, which is associated with DNA damage, genetic instability and increase the risk of cancer development. However, the mechanisms of genetic damage induced by Cr(VI) remains to be thoroughly illustrated. A molecular epidemiological study was conducted on 120 chromate exposed workers and 97 controls. Results indicated that,the rs12432907 of XRCC3 carrying T allele, the rs144848 of BRCA2 with C allele and the rs1805800 of NBS1 with genotype(TT) of individuals were associated with lower genetic damage, while the rs2295152 of XRCC3 carrying T allele, the rs13312986 (CC and CT genotypes) and the rs2697679 of NBS1 with A allele were associated with higher genetic damage in workers exposed to chromate. The interaction of chromate exposure with rs2295152 of XRCC3 had a significant effect on micronuclei frequency (MNF). The gene polymorphisms in homologous recombination repair pathway could modulate chromate-induced genetic damage.
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Affiliation(s)
- Changmao Long
- Department of Occupational and Environmental Health Sciences, School of Public Health, Peking University, Beijing, 100191, PR China
| | - Jiaxing Liu
- Department of Medical Record, Third Hospital of Peking University, Beijing, 100191, PR China
| | - Guiping Hu
- Department of Occupational and Environmental Health Sciences, School of Public Health, Peking University, Beijing, 100191, PR China
| | - Huimin Feng
- Department of Occupational and Environmental Health Sciences, School of Public Health, Peking University, Beijing, 100191, PR China
| | - Di Zhou
- Department of Occupational and Environmental Health Sciences, School of Public Health, Peking University, Beijing, 100191, PR China
| | - Jing Wang
- Yima Center for Disease Control and Prevention, Sanmenxia City, Henan Province, 472300, PR China
| | - Xinxia Zhai
- Yima Center for Disease Control and Prevention, Sanmenxia City, Henan Province, 472300, PR China
| | - Zuchang Zhao
- Sanmenxia Municipal Center for Disease Control and Prevention, Sanmenxia, Henan Province, 472000, PR China
| | - Shanfa Yu
- Institute of Occupational Disease Prevention, Zhengzhou City, Henan Province, 450052, PR China
| | - Tiancheng Wang
- Department of Clinical Laboratories, Third Hospital of Peking University, Beijing 100191, PR China
| | - Guang Jia
- Department of Occupational and Environmental Health Sciences, School of Public Health, Peking University, Beijing, 100191, PR China.
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11
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Tdp1 processes chromate-induced single-strand DNA breaks that collapse replication forks. PLoS Genet 2018; 14:e1007595. [PMID: 30148840 PMCID: PMC6128646 DOI: 10.1371/journal.pgen.1007595] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Revised: 09/07/2018] [Accepted: 07/26/2018] [Indexed: 01/20/2023] Open
Abstract
Hexavalent chromium [Cr(VI)] damages DNA and causes cancer, but it is unclear which DNA damage responses (DDRs) most critically protect cells from chromate toxicity. Here, genome-wide quantitative functional profiling, DDR measurements and genetic interaction assays in Schizosaccharomyces pombe reveal a chromate toxicogenomic profile that closely resembles the cancer chemotherapeutic drug camptothecin (CPT), which traps Topoisomerase 1 (Top1)-DNA covalent complex (Top1cc) at the 3’ end of single-stand breaks (SSBs), resulting in replication fork collapse. ATR/Rad3-dependent checkpoints that detect stalled and collapsed replication forks are crucial in Cr(VI)-treated cells, as is Mus81-dependent sister chromatid recombination (SCR) that repairs single-ended double-strand breaks (seDSBs) at broken replication forks. Surprisingly, chromate resistance does not require base excision repair (BER) or interstrand crosslink (ICL) repair, nor does co-elimination of XPA-dependent nucleotide excision repair (NER) and Rad18-mediated post-replication repair (PRR) confer chromate sensitivity in fission yeast. However, co-elimination of Tdp1 tyrosyl-DNA phosphodiesterase and Rad16-Swi10 (XPF-ERCC1) NER endonuclease synergistically enhances chromate toxicity in top1Δ cells. Pnk1 polynucleotide kinase phosphatase (PNKP), which restores 3’-hydroxyl ends to SSBs processed by Tdp1, is also critical for chromate resistance. Loss of Tdp1 ameliorates pnk1Δ chromate sensitivity while enhancing the requirement for Mus81. Thus, Tdp1 and PNKP, which prevent neurodegeneration in humans, repair an important class of Cr-induced SSBs that collapse replication forks. Hexavalent chromium is a carcinogen that is found at toxic waste sites and in some groundwater supplies. Cellular metabolism converts chromium into DNA-damaging chromate, but it is unclear which types of chromate-DNA lesions are most dangerous, and which cellular mechanisms most critically prevent chromium toxicity. This study uses whole-genome profiling to identify DNA repair pathways that are crucial for chromate resistance in fission yeast. The resulting ‘toxicogenomic’ profile of chromate closely matches camptothecin, a natural product representing a class of chemotherapeutic drugs that cause replication fork collapse by poisoning Topoisomerase 1 (Top1), which relaxes supercoiled DNA by creating and resealing single-strand breaks (SSBs). Genetic interaction analyses uncover important roles for Tdp1 tyrosyl-DNA phosphodiesterase and Pnk1 polynucleotide 5’-kinase 3’-phosphatase (PNKP), which repair camptothecin-induced SSBs and prevent neurological disease in humans. However, chromium toxicity does not involve Top1. As Tdp1 and Pnk1 repair SSBs with 3’-blocked termini, these data suggest that Top1-independent 3’-blocked SSBs contribute to the carcinogenic and mutagenic properties of chromium.
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Tian X, Patel K, Ridpath JR, Chen Y, Zhou YH, Neo D, Clement J, Takata M, Takeda S, Sale J, Wright FA, Swenberg JA, Nakamura J. Homologous Recombination and Translesion DNA Synthesis Play Critical Roles on Tolerating DNA Damage Caused by Trace Levels of Hexavalent Chromium. PLoS One 2016; 11:e0167503. [PMID: 27907204 PMCID: PMC5132242 DOI: 10.1371/journal.pone.0167503] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Accepted: 11/15/2016] [Indexed: 12/17/2022] Open
Abstract
Contamination of potentially carcinogenic hexavalent chromium (Cr(VI)) in the drinking water is a major public health concern worldwide. However, little information is available regarding the biological effects of a nanomoler amount of Cr(VI). Here, we investigated the genotoxic effects of Cr(VI) at nanomoler levels and their repair pathways. We found that DNA damage response analyzed based on differential toxicity of isogenic cells deficient in various DNA repair proteins is observed after a three-day incubation with K2CrO4 in REV1-deficient DT40 cells at 19.2 μg/L or higher as well as in TK6 cells deficient in polymerase delta subunit 3 (POLD3) at 9.8 μg/L or higher. The genotoxicity of Cr(VI) decreased ~3000 times when the incubation time was reduced from three days to ten minutes. TK mutation rate also significantly decreased from 6 day to 1 day exposure to Cr(VI). The DNA damage response analysis suggest that DNA repair pathways, including the homologous recombination and REV1- and POLD3-mediated error-prone translesion synthesis pathways, are critical for the cells to tolerate to DNA damage caused by trace amount of Cr(VI).
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Affiliation(s)
- Xu Tian
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Keyur Patel
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - John R. Ridpath
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Youjun Chen
- Department of Neurology, UNC Neuroscience center, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Yi-Hui Zhou
- Bioinformatics Research Center, North Carolina State University, Raleigh, North Carolina
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina
| | - Dayna Neo
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Jean Clement
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Minoru Takata
- Laboratory of DNA Damage Signaling, Department of Late Effects Studies, Radiation Biology Center, Kyoto University, Kyoto, Japan
| | - Shunichi Takeda
- Department of Radiation Genetics Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Julian Sale
- Medical Research Council Laboratory of Molecular Biology, Cambridge, United Kingdom
| | - Fred A. Wright
- Bioinformatics Research Center, North Carolina State University, Raleigh, North Carolina
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina
- Department of Statistics, North Carolina State University, Raleigh, North Carolina
- * E-mail: (JN); (FW)
| | - James A. Swenberg
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
- Curriculum in Toxicology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Jun Nakamura
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
- * E-mail: (JN); (FW)
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Chandra S, Khatoon R, Pandey A, Saini S, Vimal D, Singh P, Chowdhuri DK. Dme-miR-314-3p modulation in Cr(VI) exposed Drosophila affects DNA damage repair by targeting mus309. JOURNAL OF HAZARDOUS MATERIALS 2016; 304:360-369. [PMID: 26590872 DOI: 10.1016/j.jhazmat.2015.10.075] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Revised: 10/20/2015] [Accepted: 10/29/2015] [Indexed: 06/05/2023]
Abstract
microRNAs (miRNAs) as one of the major epigenetic modulators negatively regulate mRNAs at post transcriptional level. It was therefore hypothesized that modulation of miRNAs by hexavalent Chromium [Cr(VI)], a priority environmental chemical, can affect DNA damage. In a genetically tractable model, Drosophila melanogaster, role of maximally up-regulated miRNA, dme-miR-314-3p, on DNA damage was examined by exposing the third instar larvae to 5.0-20.0 μg/ml Cr(VI) for 24 and 48 h. mus309, a Drosophila homologue of human Bloom's syndrome and predicted as one of the potential targets of this miRNA, was confirmed as its target by 5'RLM-RACE assay. A significant down-regulation of mus309 was observed in dme-miR-314-3p overexpression strain (myo-gal4>UAS-miR-314-3p) as compared with that in parental strains (myo-gal4 and UAS-miR-314-3p) and in w(1118). A significant increase in DNA damage including double strand breaks generation was observed in exposed myo-gal4>UAS-miR-314 and mus309 mutants as compared with that in parental strain and in unexposed control. A significant down-regulation of cell cycle regulation genes (CycA, CycB and cdc2) was observed in these exposed genotypes. Collectively, the study demonstrates that dme-miR-314-3p can mediate the downregulation of repair deficient gene mus309 leading to increased DNA damage and cell cycle arrest in exposed organism which may affect Cr(VI) mediated carcinogenesis.
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Affiliation(s)
- Swati Chandra
- Embryotoxicology Laboratory, Environmental Toxicology Group, CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Mahatma Gandhi Marg, Lucknow 226001, Uttar Pradesh, India; Academy of Scientific Innovation & Research (AcSIR), CSIR-IITR Campus, Lucknow, India
| | - Rehana Khatoon
- Embryotoxicology Laboratory, Environmental Toxicology Group, CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Mahatma Gandhi Marg, Lucknow 226001, Uttar Pradesh, India
| | - Ashutosh Pandey
- Embryotoxicology Laboratory, Environmental Toxicology Group, CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Mahatma Gandhi Marg, Lucknow 226001, Uttar Pradesh, India
| | - Sanjay Saini
- Embryotoxicology Laboratory, Environmental Toxicology Group, CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Mahatma Gandhi Marg, Lucknow 226001, Uttar Pradesh, India
| | - Divya Vimal
- Embryotoxicology Laboratory, Environmental Toxicology Group, CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Mahatma Gandhi Marg, Lucknow 226001, Uttar Pradesh, India; Academy of Scientific Innovation & Research (AcSIR), CSIR-IITR Campus, Lucknow, India
| | - Pallavi Singh
- Embryotoxicology Laboratory, Environmental Toxicology Group, CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Mahatma Gandhi Marg, Lucknow 226001, Uttar Pradesh, India; Academy of Scientific Innovation & Research (AcSIR), CSIR-IITR Campus, Lucknow, India
| | - D Kar Chowdhuri
- Embryotoxicology Laboratory, Environmental Toxicology Group, CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Mahatma Gandhi Marg, Lucknow 226001, Uttar Pradesh, India; Academy of Scientific Innovation & Research (AcSIR), CSIR-IITR Campus, Lucknow, India.
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14
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Fang Z, Zhao M, Zhen H, Chen L, Shi P, Huang Z. Genotoxicity of tri- and hexavalent chromium compounds in vivo and their modes of action on DNA damage in vitro. PLoS One 2014; 9:e103194. [PMID: 25111056 PMCID: PMC4128586 DOI: 10.1371/journal.pone.0103194] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2014] [Accepted: 06/26/2014] [Indexed: 12/19/2022] Open
Abstract
Chromium occurs mostly in tri- and hexavalent states in the environment. Hexavalent chromium [Cr(VI)] compounds are extensively used in diverse industries, and trivalent chromium [Cr(III)] salts are used as micronutrients and dietary supplements. In the present work, we report that they both induce genetic mutations in yeast cells. They both also cause DNA damage in both yeast and Jurkat cells and the effect of Cr(III) is greater than that of Cr(VI). We further show that Cr(III) and Cr(VI) cause DNA damage through different mechanisms. Cr(VI) intercalates DNA and Cr(III) interferes base pair stacking. Based on our results, we conclude that Cr(III) can directly cause genotoxicity in vivo.
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Affiliation(s)
- Zhijia Fang
- College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai, China
| | - Min Zhao
- College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai, China
| | - Hong Zhen
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, China
| | - Lifeng Chen
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, China
| | - Ping Shi
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, China
| | - Zhiwei Huang
- College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai, China
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15
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Wilson J, Zuniga MC, Yazzie F, Stearns DM. Synergistic cytotoxicity and DNA strand breaks in cells and plasmid DNA exposed to uranyl acetate and ultraviolet radiation. J Appl Toxicol 2014; 35:338-49. [PMID: 24832689 DOI: 10.1002/jat.3015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Revised: 03/03/2014] [Accepted: 03/14/2014] [Indexed: 11/08/2022]
Abstract
Depleted uranium (DU) has a chemical toxicity that is independent of its radioactivity. The purpose of this study was to explore the photoactivation of uranyl ion by ultraviolet (UV) radiation as a chemical mechanism of uranium genotoxicity. The ability of UVB (302 nm) and UVA (368 nm) radiation to photoactivate uranyl ion to produce single strand breaks was measured in pBR322 plasmid DNA, and the presence of adducts and apurinic/apyrimidinic sites that could be converted to single strand breaks by heat and piperidine was analyzed. Results showed that DNA lesions in plasmid DNA exposed to UVB- or UVA-activated DU were only slightly heat reactive, but were piperidine sensitive. The cytotoxicity of UVB-activated uranyl ion was measured in repair-proficient and repair-deficient Chinese hamster ovary cells and human keratinocyte HaCaT cells. The cytotoxicity of co-exposures of uranyl ion and UVB radiation was dependent on the order of exposure and was greater than co-exposures of arsenite and UVB radiation. Uranyl ion and UVB radiation were synergistically cytotoxic in cells, and cells exposed to photoactivated DU required different DNA repair pathways than cells exposed to non-photoactivated DU. This study contributes to our understanding of the DNA lesions formed by DU, as well as their repair. Results suggest that excitation of uranyl ion by UV radiation can provide a pathway for uranyl ion to be chemically genotoxic in populations with dermal exposures to uranium and UV radiation, which would make skin an overlooked target organ for uranium exposures.
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Affiliation(s)
- Janice Wilson
- Department of Chemistry and Biochemistry, Northern Arizona University, Flagstaff, AZ, USA
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16
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Comparative Studies of Tri- and Hexavalent Chromium Cytotoxicity and Their Effects on Oxidative State of Saccharomyces cerevisiae Cells. Curr Microbiol 2013; 68:448-56. [DOI: 10.1007/s00284-013-0496-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2013] [Accepted: 10/23/2013] [Indexed: 12/22/2022]
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17
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Morse JL, Luczak MW, Zhitkovich A. Chromium(VI) causes interstrand DNA cross-linking in vitro but shows no hypersensitivity in cross-link repair-deficient human cells. Chem Res Toxicol 2013; 26:1591-8. [PMID: 24059640 DOI: 10.1021/tx400293s] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Hexavalent chromium is a human carcinogen activated primarily by direct reduction with cellular ascorbate and to a lesser extent, by glutathione. Cr(III), the final product of Cr(VI) reduction, forms six bonds allowing intermolecular cross-linking. In this work, we investigated the ability of Cr(VI) to cause interstrand DNA cross-links (ICLs) whose formation mechanisms and presence in human cells are currently uncertain. We found that in vitro reduction of Cr(VI) with glutathione showed a sublinear production of ICLs, the yield of which was less than 1% of total Cr-DNA adducts at the optimal conditions. Formation of ICLs in fast ascorbate-Cr(VI) reactions occurred during a short reduction interval and displayed a linear dose dependence with the average yield of 1.3% of total adducts. In vitro production of ICLs was strongly suppressed by increasing buffer molarity, indicating inhibitory effects of ligand-Cr(III) binding on the formation of cross-linking species. The presence of ICLs in human cells was assessed from the impact of ICL repair deficiencies on Cr(VI) responses. We found that ascorbate-restored FANCD2-null and isogenic FANCD2-complemented cells showed similar cell cycle inhibition and toxicity by Cr(VI). XPA-null cells are defective in the repair of Cr-DNA monoadducts, but stable knockdowns of ERCC1 or XPF in these cells with extended time for the completion of cross-linking reactions did not produce any sensitization to Cr(VI). Our results together with chemical and steric considerations of Cr(III) reactivity suggest that ICL generation by chromate is probably an in vitro phenomenon occurring at conditions permitting the formation of Cr(III) oligomers.
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Affiliation(s)
- Jessica L Morse
- Department of Pathology and Laboratory Medicine, Brown University , 70 Ship Street, Providence, Rhode Island 02912, United States
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18
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Calderón-Garcidueñas L, Serrano-Sierra A, Torres-Jardón R, Zhu H, Yuan Y, Smith D, Delgado-Chávez R, Cross JV, Medina-Cortina H, Kavanaugh M, Guilarte TR. The impact of environmental metals in young urbanites' brains. EXPERIMENTAL AND TOXICOLOGIC PATHOLOGY : OFFICIAL JOURNAL OF THE GESELLSCHAFT FUR TOXIKOLOGISCHE PATHOLOGIE 2013; 65:503-11. [PMID: 22436577 PMCID: PMC3383886 DOI: 10.1016/j.etp.2012.02.006] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Revised: 01/16/2012] [Accepted: 02/21/2012] [Indexed: 01/22/2023]
Abstract
Air pollution exposures are linked to cognitive and olfaction deficits, oxidative stress, neuroinflammation and neurodegeneration including frontal hyperphosphorylated tau and diffuse amyloid plaques in Mexico City children and young adults. Mexico City residents are chronically exposed to fine particulate matter (PM(2.5)) concentrations (containing toxic combustion and industrial metals) above the annual standard (15 μg/m(3)) and to contaminated water and soil. Here, we sought to address the brain-region-specific effects of metals and key neuroinflammatory and DNA repair responses in two air pollution targets: frontal lobe and olfactory bulb from 12 controls vs. 47 Mexico City children and young adults average age 33.06±4.8 SE years. Inductively coupled plasma mass spectrometry (metal analysis) and real time PCR (for COX2, IL1β and DNA repair genes) in target tissues. Mexico City residents had higher concentrations of metals associated with PM: manganese (p=0.003), nickel and chromium (p=0.02) along with higher frontal COX2 mRNA (p=0.008) and IL1β (p=0.0002) and COX2 (p=0.005) olfactory bulb indicating neuroinflammation. Frontal metals correlated with olfactory bulb DNA repair genes and with frontal and hippocampal inflammatory genes. Frontal manganese, cobalt and selenium increased with age in exposed subjects. Together, these findings suggest PM-metal neurotoxicity causes brain damage in young urbanites, the olfactory bulb is a target of air pollution and participates in the neuroinflammatory response and since metal concentrations vary significantly in Mexico City urban sub-areas, place of residency has to be integrated with the risk for CNS detrimental effects particularly in children.
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19
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Yu H, Zhao H, Wang LE, Liu Z, Li D, Wei Q. Correlation between base-excision repair gene polymorphisms and levels of in-vitro BPDE-induced DNA adducts in cultured peripheral blood lymphocytes. PLoS One 2012; 7:e40131. [PMID: 22792228 PMCID: PMC3390316 DOI: 10.1371/journal.pone.0040131] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Accepted: 06/02/2012] [Indexed: 01/08/2023] Open
Abstract
In vitro benzo[a]pyrene diol epoxide (BPDE)-induced DNA adducts in cultured peripheral lymphocytes have been shown to be a phenotypic biomarker of individual’s DNA repair phenotype that is associated with cancer risk. In this study, we explored associations between genotypes of base-excision repair genes (PARP1 Val762Ala, APEX1 Asp148Glu, and XRCC1 Arg399Gln) and in vitro BPDE-induced DNA adducts in cultured peripheral blood lymphocytes in 706 cancer-free non-Hispanic white subjects. We found that levels of BPDE-induced DNA adducts were significantly higher in ever smokers than in never smokers and that individuals with the Glu variant genotypes (i.e., Asp/Glu and Glu/Glu) exhibited lower levels of BPDE-induced DNA adducts than did individuals with the common Asp/Asp homozygous genotype (median RAL levels: 32.0 for Asp/Asp, 27.0 for Asp/Glu, and 17.0 for Glu/Glu, respectively; Ptrend = 0.030). Further stratified analysis showed that compared with individuals with the common APEX1-148 homozygous Asp/Asp genotype, individuals with the APEX1-148Asp/Glu genotype or the Glu/Glu genotype had a lower risk of having higher-level adducts (adjusted OR = 0.60, 95% CI: 0.36–0.98 and adjusted OR = 0.47, 95% CI: 0.26–0.86, respectively; Ptrend = 0.012) among smokers. Such an effect was not observed in non-smokers. However, there was no significant interaction between the APEX1 Asp148Glu polymorphism and smoking exposure in this study population (P = 0.512). Additional genotype-phenotype analysis found that the APEX1-148Glu allele had significantly increased expression of APEX1 mRNA in 270 Epstein-Barr virus-transformed lymphoblastoid cell lines, which is likely associated with more active repair activity. Our findings suggest that the functional APEX1-148Glu allele is associated with reduced risk of having high levels of BPDE-induced DNA adducts mediated with high levels of mRNA expression.
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Affiliation(s)
- Hongping Yu
- Department of Epidemiology and Biostatistics, School of Public Health, Guiling Medical University, Guilin, China
- Department of Epidemiology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, United States of America
- * E-mail: (HY); (QW)
| | - Hui Zhao
- Department of Epidemiology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, United States of America
| | - Li-E Wang
- Department of Epidemiology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, United States of America
| | - Zhensheng Liu
- Department of Epidemiology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, United States of America
| | - Donghui Li
- Department of Gastrointestinal Medical Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, United States of America
| | - Qingyi Wei
- Department of Epidemiology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, United States of America
- * E-mail: (HY); (QW)
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20
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Reynolds M, Armknecht S, Johnston T, Zhitkovich A. Undetectable role of oxidative DNA damage in cell cycle, cytotoxic and clastogenic effects of Cr(VI) in human lung cells with restored ascorbate levels. Mutagenesis 2012; 27:437-43. [PMID: 22241526 DOI: 10.1093/mutage/ger095] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Cultured human cells are invaluable biological models for mechanistic studies of genotoxic chemicals and drugs. Continuing replacement of animals in toxicity testing will further increase the importance of in vitro cell systems, which should accurately reproduce key in vivo characteristics of toxicants such as their profiles of metabolites and DNA lesions. In this work, we examined how a common severe deficiency of cultured cells in ascorbate (Asc) impacts the formation of oxidative DNA damage by hexavalent chromium (chromate). Cr(VI) is reductively activated inside the cells by both Asc and small thiols but with different rates and spectra of intermediates and DNA adducts. We found that Cr(VI) exposure of H460 human lung epithelial cells in standard culture (<0.01 mM cellular Asc) induced biologically significant amounts of oxidative DNA damage. Inhibition of oxidative damage repair in these cells by stable XRCC1 knockdown strongly enhanced cytotoxic effects of Cr(VI) and led to depletion of cells from G(1) and accumulation in S and G(2) phases. However, restoration of physiological levels of Asc (≈ 1 mM) completely eliminated Cr(VI) hypersensitivity of XRCC1 knockdown. The induction of chromosomal breaks assayed by the micronucleus test in Asc-restored H460, primary human lung fibroblasts, and CHO cells was also unaffected by the XRCC1 status. Centromere-negative (clastogenic) micronuclei accounted for 80-90% of all Cr(VI)-induced micronuclei. Consistent with the micronuclei results, Asc-restored cells also showed no increase in the levels of poly(ADP-ribose), which is a biochemical marker of single-stranded breaks. Asc had no effect on cytotoxicity of O(6)-methylguanine, a lesion produced by direct DNA alkylation. Overall, our results indicate that the presence of physiological levels of Asc strongly suppresses pro-oxidant pathways in Cr(VI) metabolism and that the use of standard cell cultures creates a distorted profile of its genotoxic properties.
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Affiliation(s)
- Mindy Reynolds
- Department of Pathology and Laboratory Medicine, Brown University, Providence, RI 02912, USA
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21
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Wu F, Sun H, Kluz T, Clancy HA, Kiok K, Costa M. Epigallocatechin-3-gallate (EGCG) protects against chromate-induced toxicity in vitro. Toxicol Appl Pharmacol 2011; 258:166-75. [PMID: 22079256 DOI: 10.1016/j.taap.2011.10.018] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Revised: 10/20/2011] [Accepted: 10/27/2011] [Indexed: 12/11/2022]
Abstract
Hexavalent chromium [Cr(VI)] is a human carcinogen that results in the generation of reactive oxygen species (ROS) and a variety of DNA lesions leading to cell death. Epigallocatechin-3-gallate (EGCG), the major polyphenol present in green tea, possesses potent antioxidative activity capable of protecting normal cells from various stimuli-induced oxidative stress and cell death. Here we demonstrated that co-treatment with EGCG protected human normal bronchial epithelial BEAS-2B cells from Cr(VI)-induced cell death in a dose-dependent manner. Cr(VI) induces apoptosis as the primary mode of cell death. Co-treatment of BEAS-2B cells with EGCG dose-dependently suppressed Cr(VI)-induced apoptosis. Fluorescence microscopic analyses and quantitative measurement revealed that EGCG significantly decreased intracellular levels of ROS induced by Cr(VI) exposure. Using a well-established K(+)/SDS precipitation assay, we further showed that EGCG was able to dose-dependently reduce DNA-protein cross-links (DPC), lesions that could be partially attributed to Cr(VI)-induced oxidative stress. Finally, analyses of Affymetrix microarray containing 28,869 well-annotated genes revealed that, among the 3412 genes changed more than 1.5-fold by Cr(VI) treatment, changes of 2404 genes (70%) were inhibited by pretreatment of EGCG. Real-time PCR confirmed the induction of 3 genes involved in cell death and apoptosis by Cr(VI), which was eliminated by EGCG. In contrast, Cr(VI) reduced the expression of 3 genes related to cellular defense, and this reduction was inhibited by EGCG. Our results indicate that EGCG protects BEAS-2B cells from Cr(VI)-induced cytotoxicity presumably by scavenging ROS and modulating a subset of genes. EGCG, therefore, might serve as a potential chemopreventive agent against Cr(VI) carcinogenesis.
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Affiliation(s)
- Fen Wu
- Department of Environmental Medicine, New York University School of Medicine, Tuxedo, NY 10987, USA
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22
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Abstract
Drinking water supplies in many geographic areas contain chromium in the +3 and +6 oxidation states. Public health concerns are centered on the presence of hexavalent Cr that is classified as a known human carcinogen via inhalation. Cr(VI) has high environmental mobility and can originate from anthropogenic and natural sources. Acidic environments with high organic content promote the reduction of Cr(VI) to nontoxic Cr(III). The opposite process of Cr(VI) formation from Cr(III) also occurs, particularly in the presence of common minerals containing Mn(IV) oxides. Limited epidemiological evidence for Cr(VI) ingestion is suggestive of elevated risks for stomach cancers. Exposure of animals to Cr(VI) in drinking water induced tumors in the alimentary tract, with linear and supralinear responses in the mouse small intestine. Chromate, the predominant form of Cr(VI) at neutral pH, is taken up by all cells through sulfate channels and is activated nonenzymatically by ubiquitously present ascorbate and small thiols. The most abundant form of DNA damage induced by Cr(VI) is Cr-DNA adducts, which cause mutations and chromosomal breaks. Emerging evidence points to two-way interactions between DNA damage and epigenetic changes that collectively determine the spectrum of genomic rearrangements and profiles of gene expression in tumors. Extensive formation of DNA adducts, clear positivity in genotoxicity assays with high predictive values for carcinogenicity, the shape of tumor-dose responses in mice, and a biological signature of mutagenic carcinogens (multispecies, multisite, and trans-sex tumorigenic potency) strongly support the importance of the DNA-reactive mutagenic mechanisms in carcinogenic effects of Cr(VI). Bioavailability results and kinetic considerations suggest that 10-20% of ingested low-dose Cr(VI) escapes human gastric inactivation. The directly mutagenic mode of action and the incompleteness of gastric detoxification argue against a threshold in low-dose extrapolation of cancer risk for ingested Cr(VI).
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Affiliation(s)
- Anatoly Zhitkovich
- Department of Pathology and Laboratory Medicine, Brown University, 70 Ship Street, Providence, RI 02912, United States.
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23
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Mishra M, Sharma A, Negi MPS, Dwivedi UN, Chowdhuri DK. Tracing the tracks of genotoxicity by trivalent and hexavalent chromium in Drosophila melanogaster. Mutat Res 2011; 722:44-51. [PMID: 21382505 DOI: 10.1016/j.mrgentox.2011.02.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2010] [Revised: 02/14/2011] [Accepted: 02/27/2011] [Indexed: 01/08/2023]
Abstract
Mutagen sensitive strains (mus) in Drosophila are known for their hypersensitivity to mutagens and environmental carcinogens. Accordingly, these mutants were grouped in pre- and post-replication repair pathways. However, studying mutants belonging to one particular repair pathway may not be adequate for examining chemical-induced genotoxicity when other repair pathways may neutralize its effect. To test whether both pre-and post-replication pathways are involved and effect of Cr(III)- and Cr(VI)-induced genotoxicity in absence or presence of others, we used double mutant approach in D. melanogaster. We observed DNA damage as evident by changes in Comet assay DNA migration in cells of larvae of Oregon R(+) and single mutants of pre- (mei-9, mus201 and mus210) and post- (mei-41, mus209 and mus309) replication repair pathways and also in double mutants of different combinations (pre-pre, pre-post and post-post replication repair) exposed to increasing concentrations of Cr(VI) (0.0, 5.0, 10.0 and 20.0 μg/ml) for 48 h. The damage was greater in pre-replication repair mutants after exposure to 5.0 μg/ml Cr(VI), while effects on Oregon R(+) and post replication repair mutants were insignificant. Post-replication repair mutants revealed significant DNA damage after exposure to 20.0 μg/ml Cr(VI). Further, double mutants generated in the above repair categories were examined for DNA damage following Cr(VI) exposure and a comparison of damage was studied between single and double mutants. Combinations of double mutants generated in the pre-pre replication repair pathways showed an indifferent interaction between the two mutants after Cr(VI) exposure while a synergistic interaction was evident in exposed post-post replication repair double mutants. Cr(III) (20.0 μg/ml) exposure to these strains did not induce any significant DNA damage in their cells. The study suggests that both pre- and post-replication pathways are affected in Drosophila by Cr(VI) leading to genotoxicity, which may have consequences for metal-induced carcinogenesis.
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Affiliation(s)
- Manish Mishra
- Embryotoxicology Section, Indian Institute of Toxicology Research, Lucknow 226 001, India
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24
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Hazane-Puch F, Benaraba R, Valenti K, Osman M, Laporte F, Favier A, Anderson RA, Roussel AM, Hininger-Favier I. Chromium III histidinate exposure modulates gene expression in HaCaT human keratinocytes exposed to oxidative stress. Biol Trace Elem Res 2010; 137:23-39. [PMID: 19902159 DOI: 10.1007/s12011-009-8557-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2009] [Accepted: 10/21/2009] [Indexed: 11/25/2022]
Abstract
While the toxicity of hexavalent chromium is well established, trivalent chromium is an essential nutrient involved in insulin and glucose homeostasis. To study the antioxidant effects of Cr(III)His, cDNA arrays were used to investigate the modulation of gene expression by trivalent chromium histidinate (Cr(III)His) in HaCaT human keratinocytes submitted to hydrogen peroxide (H2O2). Array was composed by a set of 81 expressed sequences tags (ESTs) essentially represented by antioxidant and DNA repair genes. HaCaT were preincubated for 24 h with 50 microM Cr(III)His and were treated with 50 muM H2O2. Total RNAs were isolated immediately or 6 h after the stress. In Cr(III)His preincubated cells, transcripts related to antioxidant family were upregulated (glutathione synthetase, heme oxygenase 2, peroxiredoxin 4). In Cr(III)His preincubated cells and exposed to H2O2, increased expressions of polymerase delta 2 and antioxidant transcripts were observed. Biochemical methods performed in parallel to measure oxidative stress in cells showed that Cr(III)His supplementation before H2O2 stress protected HaCaT from thiol groups decrease and thiobarbituric acid reactive substances increase. In summary, these results give evidence of antioxidant gene expression and antioxidant protection in HaCaT preincubated with Cr(III)His and help to explain the lack of toxicity reported for Cr(III)His.
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Affiliation(s)
- Florence Hazane-Puch
- Département de Biologie Intégrée, Biologie Nutritionnelle, Centre Hospitalier Universitaire, BP 217, 38043, Grenoble Cedex 09, France
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25
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Zecevic A, Hagan E, Reynolds M, Poage G, Johnston T, Zhitkovich A. XPA impacts formation but not proteasome-sensitive repair of DNA-protein cross-links induced by chromate. Mutagenesis 2010; 25:381-8. [PMID: 20410141 DOI: 10.1093/mutage/geq017] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
DNA-protein cross-links (DPCs) are caused by a large number of human carcinogens and anti-cancer drugs. However, cellular processes involved in decreasing a burden of these genotoxic lesions remain poorly understood. Here, we examined the impact of nucleotide excision repair (NER), which is a principal repair pathway for bulky DNA adducts, and the main cellular reducers on removal of chromium(VI)-induced DPC. We found that standard and ascorbate-restored cultures of isogenic XPA-null (NER deficient) and XPA-complemented human fibroblasts had very similar repair of Cr-DPC (60-65% average DPC removal after 24 h). However, XPA absence caused depletion of G1 and accumulation of G2 cells at low Cr(VI) doses, suggesting that Cr-DPC were not a significant cause of cell cycle perturbations. Interestingly, although pro-oxidant metabolism of Cr(VI) in glutathione-depleted cells generated significantly fewer DPC, they were repair resistant irrespective of the NER status of cells. Inhibition of proteasome activity by MG132 abolished DPC repair in both XPA-null and XPA-complemented cells. XPA loss caused two to three times higher initial DPC formation, demonstrating the importance of NER in removal of the precursor lesions. Our results indicate that human NER is not involved in removal of Cr-DPC containing non-histone proteins but it acts as a defence mechanism against these large lesions by preventing their formation. Therefore, individual differences in NER activity are expected to alter sensitivity but not persistence of DPC as a biomarker of hexavalent Cr.
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Affiliation(s)
- Alma Zecevic
- Department of Pathology and Laboratory Medicine, Brown University, Providence, RI 02912, USA
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O'Brien TJ, Witcher P, Brooks B, Patierno SR. DNA polymerase zeta is essential for hexavalent chromium-induced mutagenesis. Mutat Res 2009; 663:77-83. [PMID: 19428373 DOI: 10.1016/j.mrfmmm.2009.01.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2008] [Revised: 01/21/2009] [Accepted: 01/27/2009] [Indexed: 11/29/2022]
Abstract
Translesion synthesis (TLS) is a unique DNA damage tolerance mechanism involved in the replicative bypass of genetic lesions in favor of uninterrupted DNA replication. TLS is critical for the generation of mutations by many different chemical and physical agents, however, there is no information available regarding the role of TLS in carcinogenic metal-induced mutagenesis. Hexavalent chromium (Cr(VI))-containing compounds are highly complex genotoxins possessing both mutagenic and clastogenic activities. The focus of this work was to determine the impact that TLS has on Cr(VI)-induced mutagenesis in Saccharomyces cerevisiae. Wild-type yeast and strains deficient in TLS polymerases (i.e. Polzeta (rev3), Poleta (rad30)) were exposed to Cr(VI) and monitored for cell survival and forward mutagenesis at the CAN1 locus. In general, TLS deficiency had little impact on Cr(VI)-induced clonogenic lethality or cell growth. rad30 yeast exhibited higher levels of basal and induced mutagenesis compared to Wt and rev3 yeast. In contrast, rev3 yeast displayed attenuated Cr(VI)-induced mutagenesis. Moreover, deletion of REV3 in rad30 yeast (rad30 rev3) resulted in a significant decrease in basal and Cr(VI) mutagenesis relative to Wt and rad30 single mutants indicating that mutagenesis primarily depended upon Polzeta. Interestingly, rev3 yeast were similar to Wt yeast in susceptibility to Cr(VI)-induced frameshift mutations. Mutational analysis of the CAN1 gene revealed that Cr(VI)-induced base substitution mutations accounted for 83.9% and 100.0% of the total mutations in Wt and rev3 yeast, respectively. Insertions and deletions comprised 16.1% of the total mutations in Cr(VI) treated Wt yeast but were not observed rev3 yeast. This work provides novel information regarding the molecular mechanisms of Cr(VI)-induced mutagenesis and is the first report demonstrating a role for TLS in the fixation of mutations induced by a carcinogenic metal.
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Affiliation(s)
- Travis J O'Brien
- Department of Pharmacology and Physiology, The George Washington University, Washington, DC 20037, USA.
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Tamblyn L, Li E, Sarras H, Srikanth P, Hande MP, McPherson JP. A role for Mus81 in the repair of chromium-induced DNA damage. Mutat Res 2008; 660:57-65. [PMID: 19026666 DOI: 10.1016/j.mrfmmm.2008.10.013] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2008] [Revised: 10/09/2008] [Accepted: 10/14/2008] [Indexed: 01/11/2023]
Abstract
Hexavalent chromium (Cr[VI]) is a toxic environmental contaminant that is capable of producing a broad spectrum of DNA damage. The ability of Cr[VI] to induce mutagenesis and neoplastic transformation has been attributed to its genotoxic action, however our understanding of molecular mechanisms involved in the repair of Cr[VI]-induced DNA damage remains incomplete. Here, we report that Mus81, an enzyme that participates with Eme1 in the resolution of replication fork damage caused by certain lesions, is involved in the repair of Cr[VI]-induced DNA damage. Mus81-deficient cells were found to be more susceptible to Cr[VI]-induced proliferation arrest and more sensitive to the long-term cytotoxic effects of Cr[VI] than isogenic wild-type cells. Following Cr[VI] exposure, Mus81-deficient cells displayed a lag in the disappearance of Rad51 foci, exhibited elevated replication-associated gamma-H2AX and showed an increased incidence of chromosomal instability compared to wild-type cells. Our findings support a role for Mus81 in the resolution of replication-associated DNA damage associated with this genotoxic agent, by converting Cr[VI]-DNA lesions into a form more amenable for homologous recombination.
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Affiliation(s)
- Laura Tamblyn
- Department of Pharmacology, University of Toronto, Toronto, Ontario, Canada M5S 1A8
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Bypass of hexavalent chromium-induced growth arrest by a protein tyrosine phosphatase inhibitor: enhanced survival and mutagenesis. Mutat Res 2008; 660:40-6. [PMID: 19013184 DOI: 10.1016/j.mrfmmm.2008.10.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2008] [Revised: 10/03/2008] [Accepted: 10/08/2008] [Indexed: 11/22/2022]
Abstract
Although the consequences of genotoxic injury include cell cycle arrest and apoptosis, cell survival responses after genotoxic injury can produce intrinsic death-resistance and contribute to the development of a transformed phenotype. Protein tyrosine phosphatases (PTPs) are integral components of key survival pathways, and are responsible for their inactivation, while PTP inhibition is often associated with enhanced cell proliferation. Our aim was to elucidate signaling events that modulate cell survival after genotoxin exposure. Diploid human lung fibroblasts (HLF) were treated with Cr(VI) (as Na(2)CrO(4)), the soluble oxyanionic dissolution product of certain particulate chromates, which are well-documented human respiratory carcinogens. In vitro soluble Cr(VI) induces a wide spectrum of DNA damage, in both the presence and absence of a broad-range PTP inhibitor, sodium orthovanadate (SOV). Notably, SOV abrogated Cr(VI)-induced clonogenic lethality. The enhanced survival of Cr(VI)-exposed cells after SOV treatment was predominantly due to a bypass of cell cycle arrest, as there was no effect of the PTP inhibitor on Cr-induced apoptosis. Moreover, the SOV effect was not due to decreased Cr uptake as evidenced by unchanged Cr-DNA adduct burden. Additionally, the bypass of Cr-induced growth arrest by SOV was accompanied by a decrease in Cr(VI)-induced expression of cell cycle inhibiting genes, and an increase in Cr(VI)-induced expression of cell cycle promoting genes. Importantly, SOV resulted in an increase in forward mutations at the HPRT locus, supporting the hypothesis that PTP inhibition in the presence of certain types of DNA damage may lead to increased genomic instability, via bypass of cell cycle checkpoints.
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Brooks B, O'Brien TJ, Ceryak S, Wise JP, Wise SS, Wise JP, Defabo E, Patierno SR. Excision repair is required for genotoxin-induced mutagenesis in mammalian cells. Carcinogenesis 2008; 29:1064-9. [PMID: 18332048 DOI: 10.1093/carcin/bgn058] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Certain hexavalent chromium [Cr(VI)] compounds are human lung carcinogens. Although much is known about Cr-induced DNA damage, very little is known about mechanisms of Cr(VI) mutagenesis and the role that DNA repair plays in this process. Our goal was to investigate the role of excision repair (ER) pathways in Cr(VI)-mediated mutagenesis in mammalian cells. Repair-proficient Chinese hamster ovary cells (AA8), nucleotide excision repair (NER)-deficient (UV-5) and base excision repair (BER)-inhibited cells were treated with Cr(VI) and monitored for forward mutation frequency at the hypoxanthine-guanine phosphoribosyltransferase (HPRT) locus. BER was inhibited using methoxyamine hydrochloride (Mx), which binds to apurinic/apyrimidinic sites generated during BER. Notably, we found that both NER-deficient (UV-5 and UV-41) and BER-inhibited (AA8 + Mx) cells displayed attenuated Cr(VI) mutagenesis. To determine whether this was unique to Cr(VI), we included the alkylating agent, methylmethane sulfonate (MMS) and ultraviolet (UV) radiation (260 nm) in our studies. Similar to Cr(VI), UV-5 cells exhibited a marked attenuation of MMS mutagenesis, but were hypermutagenic following UV exposure. Moreover, UV-5 cells expressing human xeroderma pigmentosum complementation group D displayed similar sensitivity to Cr(VI) and MMS-induced mutagenesis as AA8 controls, indicating that the genetic loss of NER was responsible for attenuated mutagenesis. Interestingly, Cr(VI)-induced clastogenesis was also attenuated in NER-deficient and BER-inhibited cells. Taken together, our results suggest that NER and BER are required for Cr(VI) and MMS-induced genomic instability. We postulate that, in the absence of ER, DNA damage is channeled into an error-free system of DNA repair or damage tolerance.
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Affiliation(s)
- Bradford Brooks
- Department of Pharmacology and Physiology, The George Washington University Medical Center, 2300 Eye Street Northwest, Washington, DC 20037, USA
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Salnikow K, Zhitkovich A. Genetic and epigenetic mechanisms in metal carcinogenesis and cocarcinogenesis: nickel, arsenic, and chromium. Chem Res Toxicol 2008; 21:28-44. [PMID: 17970581 PMCID: PMC2602826 DOI: 10.1021/tx700198a] [Citation(s) in RCA: 561] [Impact Index Per Article: 35.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Chronic exposure to nickel(II), chromium(VI), or inorganic arsenic (iAs) has long been known to increase cancer incidence among affected individuals. Recent epidemiological studies have found that carcinogenic risks associated with chromate and iAs exposures were substantially higher than previously thought, which led to major revisions of the federal standards regulating ambient and drinking water levels. Genotoxic effects of Cr(VI) and iAs are strongly influenced by their intracellular metabolism, which creates several reactive intermediates and byproducts. Toxic metals are capable of potent and surprisingly selective activation of stress-signaling pathways, which are known to contribute to the development of human cancers. Depending on the metal, ascorbate (vitamin C) has been found to act either as a strong enhancer or suppressor of toxic responses in human cells. In addition to genetic damage via both oxidative and nonoxidative (DNA adducts) mechanisms, metals can also cause significant changes in DNA methylation and histone modifications, leading to epigenetic silencing or reactivation of gene expression. In vitro genotoxicity experiments and recent animal carcinogenicity studies provided strong support for the idea that metals can act as cocarcinogens in combination with nonmetal carcinogens. Cocarcinogenic and comutagenic effects of metals are likely to stem from their ability to interfere with DNA repair processes. Overall, metal carcinogenesis appears to require the formation of specific metal complexes, chromosomal damage, and activation of signal transduction pathways promoting survival and expansion of genetically/epigenetically altered cells.
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Affiliation(s)
- Konstantin Salnikow
- Konstantin Salnikow, National Cancer Institute, Bldg. 538, Room 205 E, Frederick, MD 21702, Phone: 301-846-5623, Fax: 301-846-5946, E-mail:
| | - Anatoly Zhitkovich
- Anatoly Zhitkovich, Brown University, Center for Genomics and Proteomics, Department of Pathology and Laboratory Medicine, 70 Ship Street, Providence RI 02912, Phone: 401-863-2912, Fax: 401-863-9008, E-mail:
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Wise SS, Holmes AL, Wise JP. Hexavalent chromium-induced DNA damage and repair mechanisms. REVIEWS ON ENVIRONMENTAL HEALTH 2008; 23:39-57. [PMID: 18557597 DOI: 10.1515/reveh.2008.23.1.39] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Hexavalent chromium is a commonly used industrial metal that has been shown to induce lung cancer in workers having long term exposure. In the particulate form, Cr(VI) dissolves slowly in vivo, leading to an extended exposure of lung cells. Hexavalent chromium is taken into the cell and rapidly reduced to Cr(V), Cr(IV), Cr(III), and reactive oxygen species. Cells treated with Cr(VI) are subject to several types of DNA damage resulting from this reduction, including base modification, single-strand breaks, double-strand breaks, Cr-DNA adducts, DNA-Cr-DNA adducts, and protein-Cr-DNA adducts. These types of damage, if left unrepaired or are misrepaired, can lead to growth arrest, cytotoxicity, and apoptosis, as well as mutations leading to neoplastic transformation and ultimately tumorigenesis. Here we review the current literature on Cr-induced DNA damage and its repair.
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Affiliation(s)
- Sandra S Wise
- Wise Laboratory of Environmental and Genetic Toxicology, Maine Center for Toxicology and Environmental Health, University of Southern Maine, Portland, Maine 04104-9300, USA
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Barak Y, Ackerley DF, Dodge CJ, Banwari L, Alex C, Francis AJ, Matin A. Analysis of novel soluble chromate and uranyl reductases and generation of an improved enzyme by directed evolution. Appl Environ Microbiol 2007; 72:7074-82. [PMID: 17088379 PMCID: PMC1636143 DOI: 10.1128/aem.01334-06] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Most polluted sites contain mixed waste. This is especially true of the U.S. Department of Energy (DOE) waste sites which hold a complex mixture of heavy metals, radionuclides, and organic solvents. In such environments enzymes that can remediate multiple pollutants are advantageous. We report here evolution of an enzyme, ChrR6 (formerly referred to as Y6), which shows a markedly enhanced capacity for remediating two of the most serious and prevalent DOE contaminants, chromate and uranyl. ChrR6 is a soluble enzyme and reduces chromate and uranyl intracellularly. Thus, the reduced product is at least partially sequestered and nucleated, minimizing the chances of reoxidation. Only one amino acid change, (Tyr)128(Asn), was responsible for the observed improvement. We show here that ChrR6 makes Pseudomonas putida and Escherichia coli more efficient agents for bioremediation if the cellular permeability barrier to the metals is decreased.
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Affiliation(s)
- Y Barak
- Department of Microbiology and Immunology, 299 Campus Drive West, Sherman Fairchild D317, Stanford University, Stanford, CA 94305-5124, USA
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O'Brien TJ, Jiang G, Chun G, Mandel HG, Westphal CS, Kahen K, Montaser A, States JC, Patierno SR. Incision of trivalent chromium [Cr(III)]-induced DNA damage by Bacillus caldotenax UvrABC endonuclease. Mutat Res 2006; 610:85-92. [PMID: 16890479 DOI: 10.1016/j.mrgentox.2006.06.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/05/2006] [Indexed: 10/24/2022]
Abstract
Some hexavalent chromium [Cr(VI)]-containing compounds are lung carcinogens. Once within cells, Cr(VI) is reduced to trivalent chromium [Cr(III)] which displays an affinity for both DNA bases and the phosphate backbone. A diverse array of genetic lesions is produced by Cr including Cr-DNA monoadducts, DNA interstrand crosslinks (ICLs), DNA-Cr-protein crosslinks (DPCs), abasic sites, DNA strand breaks and oxidized bases. Despite the large amount of information available on the genotoxicity of Cr, little is known regarding the molecular mechanisms involved in the removal of these lesions from damaged DNA. Recent work indicates that nucleotide excision repair (NER) is involved in the processing of Cr-DNA adducts in human and rodent cells. In order to better understand this process at the molecular level and begin to identify the Cr-DNA adducts processed by NER, the incision of CrCl(3) [Cr(III)]-damaged plasmid DNA was studied using a thermal-resistant UvrABC NER endonuclease from Bacillus caldotenax (Bca). Treatment of plasmid DNA with Cr(III) (as CrCl(3)) increased DNA binding as a function of dose. For example, at a Cr(III) concentration of 1 microM we observed approximately 2 Cr(III)-DNA adducts per plasmid. At this same concentration of Cr(III) we found that approximately 17% of the plasmid DNA contained ICLs ( approximately 0.2 ICLs/plasmid). When plasmid DNA treated with Cr(III) (1 microM) was incubated with Bca UvrABC we observed approximately 0.8 incisions/plasmid. The formation of endonuclease IV-sensitive abasic lesions or Fpg-sensitive oxidized DNA bases was not detected suggesting that the incision of Cr(III)-damaged plasmid DNA by UvrABC was not related to the generation of oxidized DNA damage. Taken together, our data suggest that a sub-fraction of Cr(III)-DNA adducts is recognized and processed by the prokaryotic NER machinery and that ICLs are not necessarily the sole lesions generated by Cr(III) that are substrates for NER.
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Affiliation(s)
- Travis J O'Brien
- Department of Pharmacology and Physiology, The George Washington University, Washington, DC 20037, United States.
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O'Brien TJ, Mandel HG, Sugden KD, Komarov AM, Patierno SR. Hypoxia impedes the formation of chromium DNA-adducts in a cell-free system. Biochem Pharmacol 2005; 70:1814-22. [PMID: 16242673 DOI: 10.1016/j.bcp.2005.09.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2005] [Revised: 09/19/2005] [Accepted: 09/20/2005] [Indexed: 10/25/2022]
Abstract
The metabolic reduction of hexavalent chromium [Cr(VI)] in the presence of DNA generates several lesions which impede DNA replication and gene transcription. However, the relative contribution of molecular oxygen to Cr-induced genetic damage is unclear. To elucidate the role of dioxygen in Cr genotoxicity, we studied the formation of Cr-induced lesions in DNA treated with either Cr(VI) and the physiological reductant, ascorbic acid (Asc), or Cr(III), under ambient and hypoxic (<1% oxygen) conditions. We found that hypoxia did not impede the reduction of Cr(VI) by Asc throughout a 2 h treatment. In contrast, Cr-DNA binding under these conditions was reduced up to 70% by hypoxia, and a 50-90% decrease in the frequency of Cr-induced Taq polymerase-arresting DNA adducts was also observed. In the presence of Cr(VI)/Asc, formation of Cr-DNA interstrand crosslinks (ICLs) under hypoxia was 50% or less of that under ambient conditions. Kinetic studies found that hypoxia reduced the rate at which Cr interacted with DNA, but not the ultimate steady state level of Cr-DNA binding. The inhibitory effect of hypoxia on Cr(VI)/Asc genotoxicity could not be explained solely by alterations in the reactivity of intermediate Cr(V) species because Cr(III)-DNA binding and Cr(III)-induced ICL formation were also impaired by hypoxia. Moreover, Cr(V) was generated to similar levels in ambient and hypoxic reactions. Hypoxia did not affect ICL formation by the inorganic chemotherapeutic agent cisplatin, suggesting that these effects were specific for Cr(III). Taken together, these results support a role for dioxygen in facilitating the formation of Cr-DNA coordination complexes.
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Affiliation(s)
- Travis J O'Brien
- Department of Pharmacology and Physiology, The George Washington University Medical Center, 2300 Eye Street NW, Washington, DC 20037, USA
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