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Gambhir N, Kamvar ZN, Higgins R, Amaradasa BS, Everhart SE. Spontaneous and Fungicide-Induced Genomic Variation in Sclerotinia sclerotiorum. PHYTOPATHOLOGY 2021; 111:160-169. [PMID: 33320026 DOI: 10.1094/phyto-10-20-0471-fi] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Stress from exposure to sublethal fungicide doses may cause genomic instability in fungal plant pathogens, which may accelerate the emergence of fungicide resistance or other adaptive traits. In a previous study, five strains of Sclerotinia sclerotiorum were exposed to sublethal doses of four fungicides with different modes of action, and genotyping showed that such exposure induced mutations. The goal of the present study was to characterize genome-wide mutations in response to sublethal fungicide stress in S. sclerotiorum and study the effect of genomic background on the mutational repertoire. The objectives were to determine the effect of sublethal dose exposure and genomic background on mutation frequency/type, distribution of mutations, and fitness costs. Fifty-five S. sclerotiorum genomes were sequenced and aligned to the reference genome. Variants were called and quality filtered to obtain high confidence calls for single nucleotide polymorphisms (SNPs), insertions/deletions (INDELs), copy number variants, and transposable element (TE) insertions. Results suggest that sublethal fungicide exposure significantly increased the frequency of INDELs in two strains from one genomic background (P value ≤ 0.05), while TE insertions were generally repressed for all genomic backgrounds and under all fungicide exposures. The frequency and/or distribution of SNPs, INDELs, and TE insertions varied with genomic background. A propensity for large duplications on chromosome 7 and aneuploidy of this chromosome were observed in the S. sclerotiorum genome. Mutation accumulation did not significantly affect the overall in planta strain aggressiveness (P value > 0.05). Understanding factors that affect pathogen mutation rates can inform disease management strategies that delay resistance evolution.
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Affiliation(s)
- Nikita Gambhir
- Department of Plant Pathology, University of Nebraska, Lincoln, NE 68583
| | - Zhian N Kamvar
- Department of Plant Pathology, University of Nebraska, Lincoln, NE 68583
| | - Rebecca Higgins
- Department of Plant Pathology, University of Nebraska, Lincoln, NE 68583
| | | | - Sydney E Everhart
- Department of Plant Pathology, University of Nebraska, Lincoln, NE 68583
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Younes M, Aquilina G, Castle L, Engel KH, Fowler P, Fürst P, Gürtler R, Gundert-Remy U, Husøy T, Mennes W, Moldeus P, Oskarsson A, Shah R, Waalkens-Berendsen I, Wölfle D, Boon P, Crebelli R, Di Domenico A, Filipič M, Mortensen A, Van Loveren H, Woutersen R, Giarola A, Lodi F, Riolo F, Frutos Fernandez MJ. Re-evaluation of hydrochloric acid (E 507), potassium chloride (E 508), calcium chloride (E 509) and magnesium chloride (E 511) as food additives. EFSA J 2019; 17:e05751. [PMID: 32626371 PMCID: PMC7009240 DOI: 10.2903/j.efsa.2019.5751] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The Panel on Food Additives and Flavourings added to Food (FAF) provided a scientific opinion re-evaluating the safety of chlorides (E 507-509, E 511) as food additives. Chlorides are authorised food additives in the EU in accordance with Annex II and III to Regulation (EC) No 1333/2008. In the non- brand-loyal scenario, mean exposure to chlorides (E 507-509, E 511) as food additives ranged from 2 mg/kg body weight (bw) per day in the elderly to 42 mg/kg bw per day in toddlers. The 95th percentile of exposure ranged from 5 mg/kg bw per day in the elderly to 71 mg/kg bw per day in toddlers. Chloride is an essential nutrient and after absorption is distributed to organs and tissues. The Panel considered chlorides to be of low acute oral toxicity and there is no concern with respect to genotoxicity and carcinogenicity. No effects were reported in developmental toxicity studies in rats following administration of magnesium chloride hexahydrate at 800 mg/kg bw per day. Some animal studies suggested a role of chloride in increasing blood pressure but based on the toxicological database available the Panel considered human data more appropriate to identify a level of chloride intake which does not raise a safety concern. The Panel identified a human dose of 40 mg chloride/kg bw per day as a reference value for the assessment. Mean levels of exposure in all age groups were below or at this reference value, which indicates no safety concern. In some age groups (toddlers, children and adolescents), the 95th percentile exposure estimates were slightly above this reference value. The Panel concluded that the exposure to chloride from hydrochloric acid and its potassium, calcium and magnesium salts (E 507, E 508, E 509 and E 511) does not raise a safety concern at the reported use and use levels.
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Ragu S, Dardalhon M, Sharma S, Iraqui I, Buhagiar-Labarchède G, Grondin V, Kienda G, Vernis L, Chanet R, Kolodner RD, Huang ME, Faye G. Loss of the thioredoxin reductase Trr1 suppresses the genomic instability of peroxiredoxin tsa1 mutants. PLoS One 2014; 9:e108123. [PMID: 25247923 PMCID: PMC4172583 DOI: 10.1371/journal.pone.0108123] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Accepted: 08/25/2014] [Indexed: 11/19/2022] Open
Abstract
The absence of Tsa1, a key peroxiredoxin that scavenges H2O2 in Saccharomyces cerevisiae, causes the accumulation of a broad spectrum of mutations. Deletion of TSA1 also causes synthetic lethality in combination with mutations in RAD51 or several key genes involved in DNA double-strand break repair. In the present study, we propose that the accumulation of reactive oxygen species (ROS) is the primary cause of genome instability of tsa1Δ cells. In searching for spontaneous suppressors of synthetic lethality of tsa1Δ rad51Δ double mutants, we identified that the loss of thioredoxin reductase Trr1 rescues their viability. The trr1Δ mutant displayed a Can(R) mutation rate 5-fold lower than wild-type cells. Additional deletion of TRR1 in tsa1Δ mutant reduced substantially the Can(R) mutation rate of tsa1Δ strain (33-fold), and to a lesser extent, of rad51Δ strain (4-fold). Loss of Trr1 induced Yap1 nuclear accumulation and over-expression of a set of Yap1-regulated oxido-reductases with antioxidant properties that ultimately re-equilibrate intracellular redox environment, reducing substantially ROS-associated DNA damages. This trr1Δ -induced effect was largely thioredoxin-dependent, probably mediated by oxidized forms of thioredoxins, the primary substrates of Trr1. Thioredoxin Trx1 and Trx2 were constitutively and strongly oxidized in the absence of Trr1. In trx1Δ trx2Δ cells, Yap1 was only moderately activated; consistently, the trx1Δ trx2Δ double deletion failed to efficiently rescue the viability of tsa1Δ rad51Δ. Finally, we showed that modulation of the dNTP pool size also influences the formation of spontaneous mutation in trr1Δ and trx1Δ trx2Δ strains. We present a tentative model that helps to estimate the respective impact of ROS level and dNTP concentration in the generation of spontaneous mutations.
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Affiliation(s)
- Sandrine Ragu
- Centre National de la Recherche Scientifique, UMR3348, Orsay, France
- Institut Curie, Centre de Recherche, Orsay, France
| | - Michèle Dardalhon
- Centre National de la Recherche Scientifique, UMR3348, Orsay, France
- Institut Curie, Centre de Recherche, Orsay, France
| | - Sushma Sharma
- Department of Medical Biochemistry and Biophysics, Umea University, Umea, Sweden
| | - Ismail Iraqui
- Centre National de la Recherche Scientifique, UMR3348, Orsay, France
- Institut Curie, Centre de Recherche, Orsay, France
| | - Géraldine Buhagiar-Labarchède
- Centre National de la Recherche Scientifique, UMR3348, Orsay, France
- Institut Curie, Centre de Recherche, Orsay, France
| | - Virginie Grondin
- Centre National de la Recherche Scientifique, UMR3348, Orsay, France
- Institut Curie, Centre de Recherche, Orsay, France
| | - Guy Kienda
- Centre National de la Recherche Scientifique, UMR3348, Orsay, France
- Institut Curie, Centre de Recherche, Orsay, France
| | - Laurence Vernis
- Centre National de la Recherche Scientifique, UMR3348, Orsay, France
- Institut Curie, Centre de Recherche, Orsay, France
| | - Roland Chanet
- Centre National de la Recherche Scientifique, UMR3348, Orsay, France
- Institut Curie, Centre de Recherche, Orsay, France
| | - Richard D. Kolodner
- Ludwig Institute for Cancer Research, University of California School of Medicine San Diego, La Jolla, California, United States of America
| | - Meng-Er Huang
- Centre National de la Recherche Scientifique, UMR3348, Orsay, France
- Institut Curie, Centre de Recherche, Orsay, France
| | - Gérard Faye
- Centre National de la Recherche Scientifique, UMR3348, Orsay, France
- Institut Curie, Centre de Recherche, Orsay, France
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Shor E, Fox CA, Broach JR. The yeast environmental stress response regulates mutagenesis induced by proteotoxic stress. PLoS Genet 2013; 9:e1003680. [PMID: 23935537 PMCID: PMC3731204 DOI: 10.1371/journal.pgen.1003680] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 06/13/2013] [Indexed: 12/26/2022] Open
Abstract
Conditions of chronic stress are associated with genetic instability in many organisms, but the roles of stress responses in mutagenesis have so far been elucidated only in bacteria. Here, we present data demonstrating that the environmental stress response (ESR) in yeast functions in mutagenesis induced by proteotoxic stress. We show that the drug canavanine causes proteotoxic stress, activates the ESR, and induces mutagenesis at several loci in an ESR-dependent manner. Canavanine-induced mutagenesis also involves translesion DNA polymerases Rev1 and Polζ and non-homologous end joining factor Ku. Furthermore, under conditions of chronic sub-lethal canavanine stress, deletions of Rev1, Polζ, and Ku-encoding genes exhibit genetic interactions with ESR mutants indicative of ESR regulating these mutagenic DNA repair processes. Analyses of mutagenesis induced by several different stresses showed that the ESR specifically modulates mutagenesis induced by proteotoxic stress. Together, these results document the first known example of an involvement of a eukaryotic stress response pathway in mutagenesis and have important implications for mechanisms of evolution, carcinogenesis, and emergence of drug-resistant pathogens and chemotherapy-resistant tumors. Cellular capability to mutate its DNA plays an important role in evolution and impinges on medical issues, including acquisition of mutator phenotypes by cancer cells and emergence of drug-resistant pathogens. Whether and how the environment affects rates of mutation has been studied predominantly in the context of environmental agents that damage DNA (e.g. UV and γ-rays). However, it has been observed that conditions of chronic non-DNA-damaging stress (e.g. starvation or heat shock) also increase mutagenesis. It has been shown that in bacteria, activation of the general stress response activates a pro-mutagenic pathway and thus promotes mutagenesis during periods of stress. However, in eukaryotes, so far there has been no evidence of a stress response regulating mutagenesis. In this manuscript we demonstrate that in budding yeast, a model eukaryote, the general environmental stress response (ESR) regulates mutagenesis induced by proteotoxic stress (accumulation of unfolded proteins) at several loci. We also identify two pro-mutagenic DNA metabolic pathways that contribute to this mutagenesis and present genetic data showing that the ESR regulates these pathways. Together, these data advance our understanding of how cellular sensing and responding to environmental cues affect cellular capability for mutagenesis.
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Affiliation(s)
- Erika Shor
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, United States of America
| | - Catherine A. Fox
- Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin, United States of America
| | - James R. Broach
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, United States of America
- Department of Biochemistry and Molecular Biology, Penn State College of Medicine, Hershey, Pennsylvania, United States of America
- * E-mail:
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Alao JP, Sunnerhagen P. Rad3 and Sty1 function in Schizosaccharomyces pombe: an integrated response to DNA damage and environmental stress? Mol Microbiol 2008; 68:246-54. [DOI: 10.1111/j.1365-2958.2008.06147.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Kayraldiz A, Kaya FF, Canimoĝlu S, Rencüzoĝullari E. Mutagenicity of five food additives in Ames/Salmonella/microsome test. ANN MICROBIOL 2006. [DOI: 10.1007/bf03174993] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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BLOMBERG ANDERS. The Osmotic Hypersensitivity of the YeastSaccharomyces cerevisiae is Strain and Growth Media Dependent: Quantitative Aspects of the Phenomenon. Yeast 1997. [DOI: 10.1002/(sici)1097-0061(199705)13:6%3c529::aid-yea103%3e3.0.co;2-h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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Blomberg A. The osmotic hypersensitivity of the yeast Saccharomyces cerevisiae is strain and growth media dependent: quantitative aspects of the phenomenon. Yeast 1997; 13:529-39. [PMID: 9178504 DOI: 10.1002/(sici)1097-0061(199705)13:6<529::aid-yea103>3.0.co;2-h] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Osmotic hypersensitivity is manifested as cellular death at magnitudes of osmotic stress that can support growth. Cellular capacity for survival when plated onto high NaCl media was examined for a number of laboratory and industrial strains of Saccharomyces cerevisiae. During respiro-fermentative growth in rich medium with glucose as energy and carbon source, the hypersensitivity phenomenon was fairly strain invariant with a threshold value of about 1 M-NaCl; most strains fell within a 300 mM range in LD10 values (lethal dose yielding 10% survival). Furthermore, all but one of the strains displayed similar differential death responses above the threshold value, i.e. ten-fold decreased viability for every 250 mM increase in salinity. Addition of small amounts of salt to the growth medium drastically improved tolerance and shifted the hypersensitivity threshold to higher NaCl concentrations. This salt-instigated tolerance could partly be reversed by washing in water. The washing procedure depleted cells of the glycerol that they had accumulated under saline growth, and the contribution from glycerol to the improved tolerance was about 50% in the two strains examined. Growth on derepressing carbon sources like galactose, ethanol or glycerol gave strain-dependent responses. The laboratory strain X2180-1A drastically improved tolerance while the bakers' yeast strain Y41 did so only marginally. It was concluded that all strains of S. cerevisiae display the osmotic hypersensitivity phenomenon in qualitative terms while the quantitative values differ. It was also proposed that growth rate does not dictate the level of osmotic hypersensitivity of S. cerevisiae.
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Affiliation(s)
- A Blomberg
- Department of General and Marine Microbiology, University of Göteborg Sweden
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Cohen AJ, Roe FJ. Evaluation of the aetiological role of dietary salt exposure in gastric and other cancers in humans. Food Chem Toxicol 1997; 35:271-93. [PMID: 9146740 DOI: 10.1016/s0278-6915(96)00114-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The findings in laboratory and epidemiological studies relevant to the assessment of salt for carcinogenic potential are reviewed. Associations between the high consumption of certain highly salted foodstuffs, particularly in some oriental countries, and increased risk of cancer of the stomach do not incriminate salt per se. Some highly spiced foods contain potent genotoxic carcinogens, irrespective of whether they also contain salt. There is evidence in laboratory animals that high concentrations of salt may increase the incidence of gastric cancer caused by such carcinogens. This may well be attributable to a marked and sustained regenerative response in the gastric mucosa of laboratory animals chronically exposed to the cytotoxicity of hyperosmolar concentrations of salt, such a mitogenic response favouring the progression towards neoplasia. However, there is no laboratory evidence whatsoever to indicate that salt per se is a carcinogen for any site in the body; neither is there any reliable epidemiological evidence to indicate that dietary salt affects the incidence of gastric or other cancers. A particular problem in the interpretation of epidemiological studies is that the consumption of diets containing highly salted, spicy foods is often associated with low intakes of fruit and green vegetables, which contain cancer-protective antioxidants. In Western countries the incidence of cancer of the stomach has been falling for some 50 years. The consensus view is that this fall is attributable to improved food hygiene and increasingly available facilities for refrigeration. There are no grounds for supposing that the fall is attributable to a decreasing intake of salt. A high dietary salt intake does not necessarily entail exposure to salt in concentrations high enough to damage the gastric mucosa. The typical Western diet would not be expected to provide such high salt concentrations. It is concluded that there are no grounds for believing that a reduction in the average daily salt intake in the Western diet would have any effect on the risk of developing any form of cancer.
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Affiliation(s)
- A J Cohen
- Toxicology Advisory Services, Sutton, Surrey, UK
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Bianchi L, Zannoli A, Pizzala R, Stivala LA, Chiesara E. Genotoxicity assay of five pesticides and their mixtures in Saccharomyces cerevisiae D7. Mutat Res 1994; 321:203-11. [PMID: 7515158 DOI: 10.1016/0165-1218(94)90071-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Four organophosphorus pesticides (azinphos-methyl, diazinone, dimethoate, and pirimiphos-methyl), and one carbamate (benomyl) were tested for cytotoxicity, reverse mutation and gene conversion in Saccharomyces cerevisiae D7, with and without the S9 metabolic system. Furthermore, two mixtures of the above compounds, namely benomyl + pirimiphos-methyl (6/1 ratio) and dimethoate + diazinone + azinphos-methyl (10/4/6 ratio) were tested in the same experimental model. Azinphos-methyl, benomyl, and pirimiphos-methyl alone did not induce any genotoxic effect, whereas azinphos-methyl and diazinone were active in inducing reversion and gene conversion. The benomyl + pirimiphos-methyl mixture did not show any genotoxic activity. The dimethoate + diazinone + azimphos-methyl mixture was genotoxic, although an antagonistic effect between the components was observed. The addition of S9 post-mitochondrial liver fraction decreased the activity of both single and mixed genotoxic agents.
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Affiliation(s)
- L Bianchi
- Istituto di Patologia Generale, Università di Pavia, Italy
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Affiliation(s)
- A Blomberg
- Department of General and Marine Microbiology, University of Göteborg, Sweden
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Abstract
Arsenic is a human carcinogen that in small amounts is widely distributed in food and water. It has been regulated for almost 100 years worldwide and in the United States, on the judgment of the Royal Commission on Arsenic that a classical threshold of toxicity exists and that a daily intake of 400 micrograms/day is safe. Modern regulatory thinking in the United States has not accepted safe levels for carcinogens and is thus in conflict with the arsenic standard. Recent epidemics of arsenicism have quantitatively confirmed that threshold not only for the non-cancerous arsenical skin lesions but also for arsenical skin and internal cancers. Research shows that arsenic is a general gene inducer. Genes induced are involved in proliferation, recombination, amplification and the activation of viruses. This characterizes arsenic as an indirect carcinogen and provides a molecular basis for risk assessment and the observed threshold dose response. In the United States at present, about 300 cases of occupational arsenical cancer, declining in numbers, are known. Background arsenic below the drinking water standard is not known to have produced disease. The conspicuous nature of arsenical skin disease presents an unusual opportunity for a simplified survey of arsenical skin disease to support regulatory standards for arsenic.
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Affiliation(s)
- G Stöhrer
- Washington Institute, Washington, DC 20036
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Scott D, Galloway SM, Marshall RR, Ishidate M, Brusick D, Ashby J, Myhr BC. International Commission for Protection Against Environmental Mutagens and Carcinogens. Genotoxicity under extreme culture conditions. A report from ICPEMC Task Group 9. Mutat Res 1991; 257:147-205. [PMID: 2005937 DOI: 10.1016/0165-1110(91)90024-p] [Citation(s) in RCA: 159] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- D Scott
- Cancer Research Campaign Laboratories, Paterson Institute for Cancer Research, Manchester, Great Britain
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Parker KR, von Borstel RC. Antimutagenesis in yeast by sodium chloride, potassium chloride, and sodium saccharin. BASIC LIFE SCIENCES 1990; 52:367-71. [PMID: 2183776 DOI: 10.1007/978-1-4615-9561-8_34] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Aqueous salt solutions containing NaCl, KCl, MgCl2, Na2SO4, CaCl2, NH4Cl, or sodium saccharin are mutagenic in yeast when logarithmic growth of cells is interrupted by exposure to a 0.5-2.0 M salt solution. Stationary-phase cells are not mutated by this treatment. When placed in an enriched medium with the salt, the stationary-phase cells grow after a prolonged lag period. The compounds tested (NaCl, KCl, and sodium saccharin), under conditions in which growth in medium can take place, exhibit an antimutagenic response as measured by the compartmentalization test. The antimutagenic action of salt solutions in yeast is concentration-dependent. Unlike the mutagenic action of these compounds, which approximates an osmolality-dependent response, the antimutagenic action seems to be correlated with toxicity as measured by growth rate reduction at increasing concentrations of the compounds. For example, sodium saccharin and NaCl exhibit almost identical osmolalities; however, 0.3 M sodium saccharin reduces the growth rate much more than does 0.3 M NaCl. At these same molar concentrations, the spontaneous mutation rate for histidine prototrophy is, for the control, 6.2 x 10(-8) mutations/cell/-generation, 3.5 x 10(-8) with 0.3 M NaCl, and 1.7 x 10(-8) with 0.3 M sodium saccharin.
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Affiliation(s)
- K R Parker
- Department of Genetics, University of Alberta, Edmonton, Canada
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Abstract
Almost from its discovery in 1879, the use of saccharin as an artificial, non-nutritive sweetener has been the center of several controversies regarding potential toxic effects, most recently focusing on the urinary bladder carcinogenicity of sodium saccharin in rats when fed at high doses in two-generation studies. No carcinogenic effect has been observed in mice, hamsters, or monkeys, and numerous epidemiological studies provide no clear or consistent evidence to support the assertion that sodium saccharin increases the risk of bladder cancer in the human population. Mechanism of action studies in the one susceptible species, the rat, continue to provide information useful in assessing potential risk to the human from saccharin consumption. Unlike typical carcinogens which interact with DNA, sodium saccharin is not genotoxic, but leads to an increase in cell proliferation of the urothelium, the only target tissue. It also appears that the effect of saccharin is modified by the salt form in which it is administered, despite equivalent concentrations of saccharin in the urine. The chemical form of saccharin in the urine is unaffected, and there is no evidence for a specific cell receptor for the saccharin molecule. Changes in several urinary parameters, such as pH, sodium, protein, silicates, volume, and others, appear to influence the reaction of the urothelium to sodium saccharin administration. Silicon-containing precipitate and/or crystals appear to be generated in the urine under specific circumstances, acting as microabrasive, cytotoxic material. Using a mathematical model of carcinogenesis, which encompasses the temporal dynamics and complexity of the process at a cellular level, including spontaneous genetic transitions, it has been shown that the effects of sodium saccharin can be explained entirely in terms of its non-genotoxic influence on cell proliferation. In interpreting these analytical studies in the human context, particularly as they pertain to the urinary milieu which appears to be pivotal in the effect of sodium saccharin, we are led to the conclusion that there is a threshold effect in male rats and that an effect on the human urothelium is unlikely at even the highest levels of human consumption.
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Affiliation(s)
- R L Anderson
- Procter and Gamble Company, Miami Valley Laboratory, Cincinnati, OH 45239-8707
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