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Treas J, Roy P, Singh KP. Chronic coexposure to arsenic and estrogen potentiates genotoxic estrogen metabolic pathway and hypermethylation of DNA glycosylase MBD4 in human prostate epithelial cells. Prostate 2022; 82:1273-1283. [PMID: 35747940 DOI: 10.1002/pros.24401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Revised: 05/14/2022] [Accepted: 06/01/2022] [Indexed: 11/10/2022]
Abstract
BACKGROUND Previously we reported that arsenic and estrogen cause synergistic effects in the neoplastic transformation of human prostate epithelial cells. In addition to receptor-mediated pathways, DNA-reactive estrogen metabolites have also been shown to play a critical role in mutagenicity and carcinogenicity. Both estrogen and arsenic are known prostate carcinogens, however, the effect of coexposure to these two chemicals on genes involved in estrogen metabolism is not known. Therefore, the objective of this study was to evaluate the role of arsenic and estrogen coexposure on the expression of estrogen receptors and estrogen metabolism-associated genes. Earlier, we also reported the synergistic effect of arsenic and estrogen on decreased expression of MBD4 genes that play an important role in DNA repair through its DNA glycosylase activity. To further understand the mechanism, the promoter methylation of this gene was also analyzed. METHODS Total RNA and protein were isolated from RWPE-1 human prostate epithelial cells that were coexposed to arsenic and estrogen for a chronic duration (6 months). The expression of estrogen receptors, estrogen metabolism associated phase I genes (CYP 1A1, 1A2, 3A4, and 1B1) and phase II gene catechol-O-methyltransferase (COMT), as well as antioxidant MnSOD, were analyzed either at the RNA level by quantitative reverse transcriptase-polymerase chain reaction or at the protein level by western blot. Promoter methylation of MBD4 was analyzed by pyrosequencing. RESULTS Expression of MnSOD and phase I genes that convert E2 into genotoxic metabolites 2-OH-E2 and 4-OH-E2 were significantly increased, whereas the expression of phase II gene COMT that detoxifies estrogen metabolites was significantly decreased in arsenic and estrogen coexposed cells. MBD4 promoter was hypermethylated in arsenic and estrogen coexposed cells. Coexposure to arsenic and estrogen has synergistic effects on the expression of these genes as well as in MBD4 promoter hypermethylation. CONCLUSIONS These novel findings suggest that coexposure to arsenic and estrogen acts synergistically in the activation of not only the estrogen receptors but also the genes associated with genotoxic estrogen metabolism and epigenetic inactivation of DNA glycosylase MBD4. Together, these genetic and epigenetic aberrations provide the molecular basis for the potentiation of carcinogenicity of arsenic and estrogen coexposure in prostate epithelial cells.
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Affiliation(s)
- Justin Treas
- Department of Internal Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Priti Roy
- Department of Internal Medicine, University of California San Francisco, San Francisco, California, USA
| | - Kamaleshwar P Singh
- Department of Environmental Toxicology, The Institute of Environmental and Human Health (TIEHH), Texas Tech University, Lubbock, Texas, USA
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Fernández-Bertólez N, Costa C, Bessa MJ, Park M, Carriere M, Dussert F, Teixeira JP, Pásaro E, Laffon B, Valdiglesias V. Assessment of oxidative damage induced by iron oxide nanoparticles on different nervous system cells. Mutat Res Genet Toxicol Environ Mutagen 2018; 845:402989. [PMID: 31561889 DOI: 10.1016/j.mrgentox.2018.11.013] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 11/02/2018] [Accepted: 11/29/2018] [Indexed: 12/30/2022]
Abstract
Iron oxide nanoparticles (ION) have received much attention for their utility in biomedical applications, such as magnetic resonance imaging, drug delivery and hyperthermia, but concerns regarding their potential harmful effects are also growing. Even though ION may induce different toxic effects in a wide variety of cell types and animal systems, there is a notable lack of toxicological data on the human nervous system, particularly important given the increasing number of applications on this specific system. An important mechanism of nanotoxicity is reactive oxygen species (ROS) generation and oxidative stress. On this basis, the main objective of this work was to assess the oxidative potential of silica-coated (S-ION) and oleic acid-coated (O-ION) ION on human SH-SY5Y neuronal and A172 glial cells. To this aim, ability of ION to generate ROS (both in the absence and presence of cells) was determined, and consequences of oxidative potential were assessed (i) on DNA by means of the 8-oxo-7,8-dihydroguanine DNA glycosylase (OGG1)-modified comet assay, and (ii) on antioxidant reserves by analyzing ratio of reduced glutathione (GSH) to oxidized glutathione (GSSG). Conditions tested included a range of concentrations, two exposure times (3 and 24 h), and absence and presence of serum in the cell culture media. Results confirmed that, even though ION were not able to produce ROS in acellular environments, ROS formation was increased in the neuronal and glial cells by ION exposure, and was parallel to induction of oxidative DNA damage and, only in the case of neuronal cells treated with S-ION, to decreases in the GSH/GSSG ratio. Present findings suggest the production of oxidative stress as a potential action mechanism leading to the previously reported cellular effects, and indicate that ION may pose a health risk to human nervous system cells by generating oxidative stress, and thus should be used with caution.
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Affiliation(s)
- Natalia Fernández-Bertólez
- Universidade da Coruña, DICOMOSA Group, Department of Psychology, Area of Psychobiology, Edificio de Servicios Centrales de Investigación, Campus Elviña s/n, 15071-A Coruña, Spain; Universidade da Coruña, Department of Cell and Molecular Biology, Facultad de Ciencias, Campus A Zapateira s/n, 15071-A Coruña, Spain
| | - Carla Costa
- Portuguese National Institute of Health, Department of Environmental Health, Rua Alexandre Herculano, 321, 4000-055 Porto, Portugal; Universidade do Porto, EPIUnit - Instituto de Saúde Pública, Rua das Taipas, 135, 4050-600 Porto, Portugal
| | - Maria João Bessa
- Portuguese National Institute of Health, Department of Environmental Health, Rua Alexandre Herculano, 321, 4000-055 Porto, Portugal; Universidade do Porto, EPIUnit - Instituto de Saúde Pública, Rua das Taipas, 135, 4050-600 Porto, Portugal
| | - Margriet Park
- Centre for Health Protection, National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands
| | - Marie Carriere
- Univ. Grenoble-Alpes, CEA, CNRS, INAC-SyMMES, Chimie Interface Biologie pour l'Environnement, la Santé et la Toxicologie (CIBEST), 38000 Grenoble, France
| | - Fanny Dussert
- Univ. Grenoble-Alpes, CEA, CNRS, INAC-SyMMES, Chimie Interface Biologie pour l'Environnement, la Santé et la Toxicologie (CIBEST), 38000 Grenoble, France
| | - João Paulo Teixeira
- Portuguese National Institute of Health, Department of Environmental Health, Rua Alexandre Herculano, 321, 4000-055 Porto, Portugal; Universidade do Porto, EPIUnit - Instituto de Saúde Pública, Rua das Taipas, 135, 4050-600 Porto, Portugal
| | - Eduardo Pásaro
- Universidade da Coruña, DICOMOSA Group, Department of Psychology, Area of Psychobiology, Edificio de Servicios Centrales de Investigación, Campus Elviña s/n, 15071-A Coruña, Spain
| | - Blanca Laffon
- Universidade da Coruña, DICOMOSA Group, Department of Psychology, Area of Psychobiology, Edificio de Servicios Centrales de Investigación, Campus Elviña s/n, 15071-A Coruña, Spain.
| | - Vanessa Valdiglesias
- Universidade da Coruña, DICOMOSA Group, Department of Psychology, Area of Psychobiology, Edificio de Servicios Centrales de Investigación, Campus Elviña s/n, 15071-A Coruña, Spain; Universidade do Porto, EPIUnit - Instituto de Saúde Pública, Rua das Taipas, 135, 4050-600 Porto, Portugal
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Kumari B, Sinha KK, DAS P. Complex interplay of lesion-specific DNA repair enzyme on bistranded clustered DNA damage harboring Tg:G mismatch in nucleosome core particles. J Biosci 2018; 43:575-583. [PMID: 30207305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
5,6-Dihydroxy-5,6-dihydrothymine (thymine glycol) and 7,8-dihydro-8-oxo-20-deoxyguanosine (8-oxodG) are major DNA damage lesions produced by endogenous oxidative stress, as well as inflicted by carcinogens and ionizing radiation. The processing of Tg:G mismatch and 8-oxodG in close proximity of each other in a bistranded clustered environment in DNA oligomer duplexes as well as in a nucleosome core particle (NCP) model are reported here. The processing of the lesions was evaluated by purified enzyme cocktails of hNTH1 and hOGG1 as well as with a HeLa cell extract. Interestingly, the yield of double-strand breaks (DSBs) resulting from the processing of the bistranded lesions are appreciably lower when the DNA is treated with the HeLa cell extract compared with the relevant purified enzyme cocktail in both models. Clustered bistranded lesions become more repair refractive when reconstituted as an NCP. This indicates a complex interplay between the repair enzymes that influence the processing of the bistranded cluster damage positively to avoid the formation of DSBs under cellular conditions. In addition to position and orientation of the lesions, the type of the lesions in the cluster environment in DNA along with the relative abundance of the lesion-specific enzymes in the cells strongly prevents the processing of the oxidized nucleobases.
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Affiliation(s)
- Bhavini Kumari
- Department of Chemistry, Indian Institute of Technology Patna, Bihta, Bihar 801 103, India
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Harrison JF, Rinne ML, Kelley MR, Druzhyna NM, Wilson GL, Ledoux SP. Altering DNA base excision repair: use of nuclear and mitochondrial-targeted N-methylpurine DNA glycosylase to sensitize astroglia to chemotherapeutic agents. Glia 2007; 55:1416-25. [PMID: 17674369 PMCID: PMC2706656 DOI: 10.1002/glia.20556] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Primary astrocyte cultures were used to investigate the modulation of DNA repair as a tool for sensitizing astrocytes to genotoxic agents. Base excision repair (BER) is the principal mechanism by which mammalian cells repair alkylation damage to DNA and involves the processing of relatively nontoxic DNA adducts through a series of cytotoxic intermediates during the course of restoring normal DNA integrity. An adenoviral expression system was employed to target high levels of the BER pathway initiator, N-methylpurine glycosylase (MPG), to either the mitochondria or nucleus of primary astrocytes to test the hypothesis that an alteration in BER results in increased alkylation sensitivity. Increasing MPG activity significantly increased BER kinetics in both the mitochondria and nuclei. Although modulating MPG activity in mitochondria appeared to have little effect on alkylation sensitivity, increased nuclear MPG activity resulted in cell death in astrocyte cultures treated with methylnitrosourea (MNU). Caspase-3 cleavage was not detected, thus indicating that these alkylation sensitive astrocytes do not undergo a typical programmed cell death in response to MNU. Astrocytes were found to express relatively high levels of antiapoptotic Bcl-2 and Bcl-XL and very low levels of proapoptotic Bad and Bid suggesting that the mitochondrial pathway of apoptosis may be blocked making astrocytes less vulnerable to proapoptotic stimuli compared with other cell types. Consequently, this unique characteristic of astrocytes may be responsible, in part, for resistance of astrocytomas to chemotherapeutic agents.
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Affiliation(s)
- Jason F. Harrison
- Department of Cell Biology and Neuroscience, University of South Alabama, Mobile, Alabama
| | - Mikael L. Rinne
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana
| | - Mark R. Kelley
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana
- Department of Pediatrics, Herman B. Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana
| | - Nadiya M. Druzhyna
- Department of Cell Biology and Neuroscience, University of South Alabama, Mobile, Alabama
| | - Glenn L. Wilson
- Department of Cell Biology and Neuroscience, University of South Alabama, Mobile, Alabama
| | - Susan P. Ledoux
- Department of Cell Biology and Neuroscience, University of South Alabama, Mobile, Alabama
- Correspondence to: Susan P. LeDoux, Department of Cell Biology and Neuroscience, University of South Alabama, 307 University Blvd MSB 1200, Mobile, AL 36688, USA. E-mail:
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Wang D, Zhong ZY, Zhang QH, Li ZP, Kelley MR. [Effect of adenoviral N-methylpurine DNA glycosylase overexpression on chemosensitivity of human osteosarcoma cells]. Zhonghua Bing Li Xue Za Zhi 2006; 35:352-6. [PMID: 16834910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
OBJECTIVE The overexpression of N-methylpurine DNA glycosylase (MPG) may imbalance the DNA base excision repair (BER) to sensitize tumor cells to current DNA damage chemotherapy. In an effort to improve the efficacy of cancer chemotherapy, we have constructed adenoviral vector of MPG, to study its ability to sensitize human osteosarcoma cell HOS to DNA damage agents. METHODS The adenoviral infection and MPG expression, as well as enzyme activity were determined by flow cytometry, Western blot, and HEX labeled oligonucleotide-based assay respectively. The cell survival/proliferation was measured using MTS, SRB, and [(3)H] thymidine incorporation assay. Apoptosis cell death was assayed by flow cytometry after treatment using phycoerythin (PE)-conjugated Annexin V and 7-amino-actinomycin (7-AAD). RESULTS A 10 MOI of recombinant nonreplicating adenovirus was found to infect more than 90% of HOS cells within 24 hours by EGFP fluorescence, in which the MPG overexpression and MPG enzyme activity were also detected. The MPG overexpression HOS cells were significantly more sensitive to the DNA damage agents, including MMS, MNNG, and TMZ, with changes in the IC50 of 6.0, 4.5, and 2.5 fold respectively. CONCLUSIONS These data establish transient MPG overexpression as a potential therapeutic approach for increasing HOS cellular sensitivity to DNA damage agent chemotherapy.
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Affiliation(s)
- Dong Wang
- Cancer Center and Department of Pathology, Daping Hospital, Third Military Medical University, Chongqing 400042, China.
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Hu YC, Ahrendt SA. hOGG1 Ser326Cys polymorphism and G:C-to-T:A mutations: no evidence for a role in tobacco-related non small cell lung cancer. Int J Cancer 2005; 114:387-93. [PMID: 15551330 DOI: 10.1002/ijc.20730] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Human 8-oxoguanine DNA glycosylase 1 (hOGG1) plays a major role in the repair of 8-hydroxyguanine, one of the major forms of DNA damage generated by reactive oxygen species in tobacco smoke. If left unrepaired by hOGG1, 8-hydroxyguanine can produce G:C-to-T:A transversions. Recent studies have suggested that the hOGG1 Ser326Cys polymorphism is associated with both a decrease in enzyme activity and an increased risk of lung cancer. To define the interaction between tobacco carcinogens, hOGG1-mediated DNA repair and DNA damage, we examined the role of the hOGG1 Ser326Cys polymorphism in mutation of the p53 gene in non small cell lung cancer (NSCLC). Tumor and nonneoplastic DNA were collected from 141 cigarette smokers with NSCLC. p53 mutations were detected by direct dideoxy sequencing and/or the GeneChip p53 assay in 74 of the 141 (52%) tumors. hOGG1 codon 326 polymorphisms were identified by polymerase chain reaction-restriction fragment length polymorphism analysis. The distribution of hOGG1 codon 326 genotypes was Ser/Ser, 90 of 141 (64%); Ser/Cys, 45 of 141 (32%); and Cys/Cys, 6 of 141 (4%). p53 mutations were significantly (p = 0.04) less common in NSCLC from patients with codon 326 Ser/Cys or Cys/Cys genotypes (21 of 51; 41%) than in NSCLC from Ser/Ser homozygotes (53 of 90; 59%). The decrease in p53 mutation frequency among carriers of the Cys allele was more evident in lung squamous cell cancer [7 of 17 (41%) for Cys/Cys and Ser/Cys vs. 27 of 38 (71%) for Ser/Ser; p = 0.04] than in nonbronchoalveolar adenocarcinoma [11 of 26 (42%) for Cys/Cys and Ser/Cys vs. 20 of 35 (57%) for Ser/Ser; p = 0.25]. The prevalence of G:C-to-T:A transversions was similar among hOGG1 codon 326 genotypes. In summary, the hOGG1 codon 326 Cys allele was associated with a decrease in p53 mutations and no effect on G:C-to-T:A transversions in NSCLC. This decrease in p53 mutations in vivo is not consistent with a decrease in the repair of 8-hydroxyguanine among carriers of the hOGG1 codon 326 Cys allele in vitro.
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Affiliation(s)
- Ying Chuan Hu
- Department of Surgery, University of Rochester Medical School, Rochester, NY 14642, USA
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Arabski M, Kazmierczak P, Wisniewska-Jarosinska M, Poplawski T, Klupinska G, Chojnacki J, Drzewoski J, Blasiak J. Interaction of amoxicillin with DNA in human lymphocytes and H. pylori-infected and non-infected gastric mucosa cells. Chem Biol Interact 2005; 152:13-24. [PMID: 15766919 DOI: 10.1016/j.cbi.2005.01.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2004] [Revised: 01/10/2005] [Accepted: 01/10/2005] [Indexed: 01/23/2023]
Abstract
Amoxicillin is a penicillin derivative belonging to a group of beta-lactam antibiotics used in Helicobacter pylori eradication. Clinical application of amoxicillin is underlined by its antibacterial activity, but little is known about its interaction with DNA of human cells. Using the alkaline comet assay we investigated the genotoxicity of amoxicillin in human peripheral blood lymphocytes as well as in H. pylori-infected and non-infected human gastric mucosa cells. To assess the role of reactive oxygen species in the genotoxicity of amoxicillin we employed a set of antioxidant and free radical scavengers, including Vitamins C and E, melatonin and the nitrone spin trap N-tert-butyl-alpha-phenyl-nitrone (PBN). Amoxicillin-induced DNA damage was completely repaired after 60 min. The vitamins, melatonin and the spin trap decreased the extent of the damage. The cells exposed to amoxicillin and treated with endonuclease III and 3-methyladenine-DNA glycosylase II, the enzymes recognizing oxidized bases displayed greater extent of DNA damage than those not treated with these enzymes. H. pylori non-infected gastric mucosa cells exposed to hydrogen peroxide repaired their DNA in a 60 min incubation, but the infected cells were not able to do so. The action of DNA repair enzymes, the vitamins, melatonin and PBN indicated that amoxicillin-induced oxidative DNA damage. The drug did not induce DNA strand breaks in isolated pUC19 plasmid DNA. Our results suggest that amoxicillin can induce DNA damage in human lymphocytes and gastric mucosa cells and this effect may follow from the production of reactive oxygen species. Cellular activation of the drug is needed to induce DNA damage. Free radical scavengers and antioxidants may be used to assist H. pylori eradication with amoxicillin to protect DNA of the host cells. Our results suggest also that H. pylori infection may alter gastric mucosa cells response to DNA-damaging agents and in this way contribute to initiation/promotion of cancer transformation of these cells induced by external or internal carcinogens.
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Affiliation(s)
- Michal Arabski
- Department of Molecular Genetics, University of Lodz, Banacha 12/16, 90-237 Lodz, Poland
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Blasiak J, Gloc E, Wozniak K, Czechowska A. Genotoxicity of acrylamide in human lymphocytes. Chem Biol Interact 2004; 149:137-49. [PMID: 15501435 DOI: 10.1016/j.cbi.2004.08.002] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2004] [Revised: 08/06/2004] [Accepted: 08/06/2004] [Indexed: 11/26/2022]
Abstract
Acrylamide is used in the industry and can be a by-product in a high-temperature food processing. It is reported to interact with DNA, but the mechanism of this interaction is not fully understood. In the present study, we investigated the DNA-damaging potential of acrylamide (ACM) in normal human lymphocytes using the alkaline-, neutral- and 12.1 versions of the comet assay and pulsed-field gel electrophoresis. We also investigated effect of acrylamide on caspase-3 activity as well as its influence on the repair process of hydrogen peroxide-induced DNA damage. Acrylamide at 0.5-50 microM induced mainly alkali-labile sites. This damage was repaired during a 60-min repair incubation. Post-treatment of the damaged DNA with repair enzymes: thymine glycol DNA N-glycosylase (Nth) and formamidopyrimidine-DNA glycosylase (Fpg), recognizing oxidized DNA bases, as well as 3-methyladenine-DNA glycosylase II (Alk A), recognizing alkylated bases, caused an increase in the extent of DNA damage, indicating the induction of oxidative and alkylative DNA base modifications by acrylamide. Pre-treatment of the lymphocytes with N-tert-butyl-alpha-phenylnitrone (PBN), a spin trap, as well as vitamins C and E decreased the DNA-damaging effect of acrylamide, which suggest that free radicals/reactive oxygen species may be involved in this effect. Acrylamide impaired the repair of DNA damaged by hydrogen peroxide and increased the activity of caspase-3, which may indicate its potential to induce apoptosis. Our results suggest that acrylamide may exert a wide spectrum of diverse effects on DNA of normal cells, including mostly DNA base modifications and apoptosis. Acrylamide may also impair DNA repair. Free radicals may underline these effects and some dietary antioxidants can be considered as protective agents against genotoxic action of acrylamide. As normal lymphocytes contain cyp2e1 and P450, engaged in the bioactivation of ACM to glicidamide it is uncertain whether acrylamide causes all of measured effect per se or this is the result of the action of its metabolites.
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Affiliation(s)
- Janusz Blasiak
- Department of Molecular Genetics, University of Lodz, Banacha 12/16, 90-237 Lodz, Poland.
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Møller P, Vogel U, Pedersen A, Dragsted LO, Sandström B, Loft S. No effect of 600 grams fruit and vegetables per day on oxidative DNA damage and repair in healthy nonsmokers. Cancer Epidemiol Biomarkers Prev 2003; 12:1016-22. [PMID: 14578137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/27/2023] Open
Abstract
In several epidemiological studies, high intakes of fruits and vegetables have been associated with a lower incidence of cancer. Theoretically, intake of antioxidants by consumption of fruits and vegetables should protect against reactive oxygen species and decrease the formation of oxidative DNA damage. We set up a parallel 24-day dietary placebo-controlled intervention study in which 43 subjects were randomized into three groups receiving an antioxidant-free basal diet and 600 g of fruits and vegetables, or a supplement containing the corresponding amounts of vitamins and minerals, or placebo. Blood and urine samples were collected before, once a week, and 4 weeks after the intervention period. The level of strand breaks, endonuclease III sites, formamidopyrimidine sites, and sensitivity to hydrogen peroxide was assessed in mononuclear blood cells by the comet assay. Excretion of 7-hydro-8-oxo-2'-deoxyguanine was measured in urine. The expressions of oxoguanine glycosylase 1 and excision repair cross complementing 1 DNA repair genes, determined by real-time reverse transcription-PCR of mRNAs, were investigated in leukocytes. Consumption of fruits and vegetables or vitamins and minerals had no effect on oxidative DNA damage measured in mononuclear cell DNA or urine. Hydrogen peroxide sensitivity, detected by the comet assay, did not differ between the groups. Expression of excision repair cross complementing 1 and oxoguanine glycosylase 1 in leukocytes was not related to the diet consumed. Our results show that after 24 days of complete depletion of fruits and vegetables, or daily ingestion of 600 g of fruit and vegetables, or the corresponding amount of vitamins and minerals, the level of oxidative DNA damage was unchanged. This suggests that the inherent antioxidant defense mechanisms are sufficient to protect circulating mononuclear blood cells from reactive oxygen species.
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Affiliation(s)
- Peter Møller
- Institute of Public Health, University of Copenhagen, DK-2200 Copenhagen N, Denmark.
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