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Ehlers A, These A, Hessel S, Preiss-Weigert A, Lampen A. Active elimination of the marine biotoxin okadaic acid by P-glycoprotein through an in vitro gastrointestinal barrier. Toxicol Lett 2014; 225:311-7. [DOI: 10.1016/j.toxlet.2013.12.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Revised: 12/18/2013] [Accepted: 12/19/2013] [Indexed: 10/25/2022]
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Valdiglesias V, Prego-Faraldo MV, Pásaro E, Méndez J, Laffon B. Okadaic acid: more than a diarrheic toxin. Mar Drugs 2013; 11:4328-49. [PMID: 24184795 PMCID: PMC3853731 DOI: 10.3390/md11114328] [Citation(s) in RCA: 166] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Revised: 10/08/2013] [Accepted: 10/23/2013] [Indexed: 01/04/2023] Open
Abstract
Okadaic acid (OA) is one of the most frequent and worldwide distributed marine toxins. It is easily accumulated by shellfish, mainly bivalve mollusks and fish, and, subsequently, can be consumed by humans causing alimentary intoxications. OA is the main representative diarrheic shellfish poisoning (DSP) toxin and its ingestion induces gastrointestinal symptoms, although it is not considered lethal. At the molecular level, OA is a specific inhibitor of several types of serine/threonine protein phosphatases and a tumor promoter in animal carcinogenesis experiments. In the last few decades, the potential toxic effects of OA, beyond its role as a DSP toxin, have been investigated in a number of studies. Alterations in DNA and cellular components, as well as effects on immune and nervous system, and even on embryonic development, have been increasingly reported. In this manuscript, results from all these studies are compiled and reviewed to clarify the role of this toxin not only as a DSP inductor but also as cause of alterations at the cellular and molecular levels, and to highlight the relevance of biomonitoring its effects on human health. Despite further investigations are required to elucidate OA mechanisms of action, toxicokinetics, and harmful effects, there are enough evidences illustrating its toxicity, not related to DSP induction, and, consequently, supporting a revision of the current regulation on OA levels in food.
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Affiliation(s)
- Vanessa Valdiglesias
- Toxicology Unit, Department of Psychobiology, University of A Coruña, A Coruña E15071, Spain; E-Mails: (E.P.); (B.L.)
- Department of Cellular and Molecular Biology, University of A Coruna, A Coruña E15071, Spain; E-Mails: (M.V.P.-F.); (J.M.)
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +34-981167000; Fax: +34-981167172
| | - María Verónica Prego-Faraldo
- Department of Cellular and Molecular Biology, University of A Coruna, A Coruña E15071, Spain; E-Mails: (M.V.P.-F.); (J.M.)
| | - Eduardo Pásaro
- Toxicology Unit, Department of Psychobiology, University of A Coruña, A Coruña E15071, Spain; E-Mails: (E.P.); (B.L.)
| | - Josefina Méndez
- Department of Cellular and Molecular Biology, University of A Coruna, A Coruña E15071, Spain; E-Mails: (M.V.P.-F.); (J.M.)
| | - Blanca Laffon
- Toxicology Unit, Department of Psychobiology, University of A Coruña, A Coruña E15071, Spain; E-Mails: (E.P.); (B.L.)
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Liu L, Guo F, Crain S, Quilliam MA, Wang X, Rein KS. The structures of three metabolites of the algal hepatotoxin okadaic acid produced by oxidation with human cytochrome P450. Bioorg Med Chem 2012; 20:3742-5. [PMID: 22608922 DOI: 10.1016/j.bmc.2012.04.046] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Revised: 04/16/2012] [Accepted: 04/24/2012] [Indexed: 11/25/2022]
Abstract
Four metabolites of okadaic acid were generated by incubation with human recombinant cytochrome P450 3A4. The structures of two of the four metabolites have been determined by MS/MS experiments and 1D and 2D NMR methods using 94 and 133 μg of each metabolite. The structure of a third metabolite was determined by oxidation to a metabolite of known structure. Like okadaic acid, the metabolites are inhibitors of protein phosphatase PP2A. Although one of the metabolites does have an α,β unsaturated carbonyl with the potential to form adducts with an active site cysteine, all of the metabolites are reversible inhibitors of PP2A.
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Affiliation(s)
- Li Liu
- Department of Chemistry and Biochemistry, Florida International University, 11200 SW 8th Street, Miami, FL 33199, USA
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Fieber LA, Greer JB, Guo F, Crawford DC, Rein KS. GENE EXPRESSION PROFILING OF HUMAN LIVER CARCINOMA (HepG2) CELLS EXPOSED TO THE MARINE TOXIN OKADAIC ACID. TOXICOLOGICAL AND ENVIRONMENTAL CHEMISTRY 2012; 24:1805-1821. [PMID: 23172983 PMCID: PMC3500632 DOI: 10.1080/02772248.2012.730199] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The marine toxin, okadaic acid (OA) is produced by dinoflagellates of the genera Prorocentrum and Dinophysis and is the causative agent of the syndrome known as diarrheic shellfish poisoning (DSP). In addition, OA acts as both a tumor promoter, attributed to OA-induced inhibition of protein phosphatases as well as an inducer of apoptosis. To better understand the potentially divergent toxicological profile of OA, the concentration dependent cytotoxicity and alterations in gene expression on the human liver tumor cell line HepG2 upon OA exposure were determined using RNA microarrays, DNA fragmentation, and cell proliferation assays as well as determinations of cell detachment and cell death in different concentrations of OA. mRNA expression was quantified for approximately 15,000 genes. Cell attachment and proliferation were both negatively correlated with OA concentration. Detached cells displayed necrotic DNA signatures but apoptosis also was broadly observed. Data suggest that OA has a concentration dependent effect on cell cycle, which might explain the divergent effects that at low concentration OA stimulates genes involved in the cell cycle and at high concentrations it stimulates apoptosis.
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Affiliation(s)
- Lynne A. Fieber
- Division of Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, 4600 Rickenbacker Cswy, Miami, FL, USA 33149
| | - Justin B. Greer
- Division of Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, 4600 Rickenbacker Cswy, Miami, FL, USA 33149
| | - Fujiang Guo
- Department of Chemistry and Biochemistry, 11200 SW 8 St, Florida International University, Miami, FL, USA33199
| | - Douglas C. Crawford
- Division of Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, 4600 Rickenbacker Cswy, Miami, FL, USA 33149
| | - Kathleen S. Rein
- Department of Chemistry and Biochemistry, 11200 SW 8 St, Florida International University, Miami, FL, USA33199
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Ehlers A, Scholz J, These A, Hessel S, Preiss-Weigert A, Lampen A. Analysis of the passage of the marine biotoxin okadaic acid through an in vitro human gut barrier. Toxicology 2011; 279:196-202. [DOI: 10.1016/j.tox.2010.11.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2010] [Revised: 11/03/2010] [Accepted: 11/09/2010] [Indexed: 10/18/2022]
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Dominguez HJ, Paz B, Daranas AH, Norte M, Franco JM, Fernández JJ. Dinoflagellate polyether within the yessotoxin, pectenotoxin and okadaic acid toxin groups: Characterization, analysis and human health implications. Toxicon 2010; 56:191-217. [DOI: 10.1016/j.toxicon.2009.11.005] [Citation(s) in RCA: 104] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2008] [Revised: 10/11/2009] [Accepted: 11/09/2009] [Indexed: 11/26/2022]
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7
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Guo F, An T, Rein KS. The algal hepatoxoxin okadaic acid is a substrate for human cytochromes CYP3A4 and CYP3A5. Toxicon 2009; 55:325-32. [PMID: 19699225 DOI: 10.1016/j.toxicon.2009.08.007] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2009] [Revised: 08/11/2009] [Accepted: 08/14/2009] [Indexed: 11/28/2022]
Abstract
The hepatotoxin okadaic acid (OA) was incubated with nine human recombinant cytochrome P450s (1A1, 1A2, 2C8, 2C9, 2C19, 2D6, 2E1, 3A4 and 3A5). Both CYP3A4 and CYP3A5 converted OA to a mixture of the same four metabolites, but incubation with CYP3A4 resulted in higher levels of conversion. Michaelis-Menten parameters, K(m) (73.4 microM) and V(max) (7.23 nmol of metabolitesnmol(-1)min(-1)) for CYP3A4 were calculated by analyzing double-reciprocal plots. LC-MS(n) analysis and chemical interconversion indicate that metabolites 2 and 3 are the 11S-hydroxy and 11R-hydroxy okadaic acid respectively, while metabolite 4 is 11-oxo okadaic acid. LC-MS(n) analysis of metabolite 1 shows a molecular ion which corresponds to an addition of 16 amu to OA, also suggesting hydroxylation, but the specific site has not been identified. The same four metabolites were produced upon incubation of okadaic acid with pooled human liver microsomes. This transformation could be completely inhibited with ketokonazole, and inhibitor of the CYP3A family of enzymes. The metabolites were determined to be only slightly less potent inhibitors of serine threonine protein phosphatase 2A (PP2A) when compared to OA. As PP2A is the principle molecular target for OA, these oxidative transformations may not effectively detoxify OA.
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Affiliation(s)
- Fujiang Guo
- Department of Chemistry and Biochemistry, Florida International University, 11200 SW 8th St., Miami, FL 33199, USA
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Marine biotoxins in shellfish - okadaic acid and analogues - Scientific Opinion of the Panel on Contaminants in the Food chain. EFSA J 2008. [DOI: 10.2903/j.efsa.2008.589] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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Pinto-Silva CRC, Creppy EE, Matias WG. Micronucleus test in mussels Perna perna fed with the toxic dinoflagellate Prorocentrum lima. Arch Toxicol 2005; 79:422-6. [PMID: 15692819 DOI: 10.1007/s00204-004-0645-1] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2004] [Accepted: 12/20/2004] [Indexed: 10/25/2022]
Abstract
Micronucleus (MN) and other nuclear abnormalities have been measured in the hemocytes of mussels Perna perna to verify whether feeding mussels with different concentrations of Prorocentrum lima results in accumulation of levels of okadaic acid (OA) capable of inducing genotoxic effects at the chromosome level, as evidenced by micronuclei and nuclear abnormalities. Four groups of 12 mussels housed individually in aquaria containing filtered seawater were fed with different concentrations of P. lima. Another group collected directly from the production area served as outdoor control. A significantly higher frequency of MN and nuclear lesions was observed in hemocytes from the groups fed P. lima.
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Affiliation(s)
- C R Carvalho Pinto-Silva
- Department of Environmental Engineering, Toxicological Laboratory of the Federal University of Santa Catarina, Brazil
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Huynh-Delerme C, Fessard V, Kiefer-Biasizzo H, Puiseux-Dao S. Characteristics of okadaic acid--induced cytotoxic effects in CHO K1 cells. ENVIRONMENTAL TOXICOLOGY 2003; 18:383-394. [PMID: 14608608 DOI: 10.1002/tox.10140] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
This article reports the results of investigations into the process of cell death induced in the Chinese hamster ovary cell K1 subclone (CHO K1) by okadaic acid (OA), a hydrophobic polyether produced by marine dinoflagellates. The IC50 was about 13 nM OA after 24 h of treatment, as determined using neutral red. With the MTT assay, the IC50 was 25 nM, although in this case 25% of the initial staining was still observed at 100 nM. Hoechst staining showed that mitotic figures accumulated at 12 nM OA after a 24- or 48-h treatment. In experiments limited to a 3-day treatment without changing the medium, CHO K1 cells were engaged in the death process at 50 nM OA after about 20 h and at 10 nM OA after 48 h. In many cells nuclear fragmentation that resulted in the apparent appearance of vesicles correlated with increasing cellular volume. But additional cell fragmentation was not observed with any treatment, and the chromatin material seemed to progressively disappear inside the cells. DNA fragmentation was analyzed by electrophoresis and with the TUNEL technique. With both techniques, the DNA was fragmented by 48 h in both 25 and 50 nM OA. Electrophoresis showed that both adherent and nonadherent cells were affected. Annexin-positive/ propidium iodide (PI)-negative cells were rarely observed after OA treatment. Some were seen under the scanning cytometer after 20 h at 50 nM OA or after 48 h at 10 nM OA, but they were never detected by flow cytometry. Most of the time scanning cytometry showed either unstained cells or PI-positive (annexin-positive or -negative) cells (48 h, 50 nM, or 72 h, 10 nM). Flow cytometry cytograms showed two cell subpopulations: one composed of a majority of smaller cells, the other of larger cells. The larger cells markedly decreased with time and OA treatment (50 and 100 nM). Stained-cell counting showed that all cells that stained were both annexin- and PI positive and that most PI-positive cells were smaller. Ki67 antigen labeling showed the proliferative activity of CHO K1 cultures but also demonstrated the loss of this activity in smaller cells treated with 50 nM OA for 48 h. We concluded that in our culture conditions the main OA target within CHO K1 cultures was dividing cells. Our results suggest that cells with disturbed metaphase-anaphase enter apoptosis, leading to necrotic daughter cells.
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Affiliation(s)
- C Huynh-Delerme
- USM 505, Laboratoire de Cryptogamie, Muséum National d'Histoire Naturelle, 12 rue Buffon, 75231 Paris cedex 05, France
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Carvalho Pinto-Silva CR, Ferreira JF, Costa RHR, Belli Filho P, Creppy EE, Matias WG. Micronucleus induction in mussels exposed to okadaic acid. Toxicon 2003; 41:93-7. [PMID: 12467666 DOI: 10.1016/s0041-0101(02)00214-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Some toxins present in the marine environment are capable of inducing mutagenicity and/or carcinogenicity. Among these toxins, okadaic acid (OA) is gaining considerable interest since it induces DNA based modifications at low concentrations and accumulates in filter-feeding marine animals, including those used for human consumption. This study aims to evaluate the genotoxicity of OA in the haemocytes of the mussel Perna perna, using the micronucleus assay. Fifty-four mussels were separated into three groups of 18 animals. One group received 0.3 microg of OA diluted in 10 microl of ethanol and ultrapure water while the other groups were considered as controls and were exposed to a solvent plus seawater mixture. A significantly higher frequency of micronuclei was observed in haemocytes from the OA-exposed group. There were no statistical differences between the two control groups.
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Affiliation(s)
- C R Carvalho Pinto-Silva
- Department of Environmental Engineering, Toxicological Laboratory of the Federal University of Santa Catarina, Brazil
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12
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Janssens V, Goris J. Protein phosphatase 2A: a highly regulated family of serine/threonine phosphatases implicated in cell growth and signalling. Biochem J 2001; 353:417-39. [PMID: 11171037 PMCID: PMC1221586 DOI: 10.1042/0264-6021:3530417] [Citation(s) in RCA: 924] [Impact Index Per Article: 40.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Protein phosphatase 2A (PP2A) comprises a family of serine/threonine phosphatases, minimally containing a well conserved catalytic subunit, the activity of which is highly regulated. Regulation is accomplished mainly by members of a family of regulatory subunits, which determine the substrate specificity, (sub)cellular localization and catalytic activity of the PP2A holoenzymes. Moreover, the catalytic subunit is subject to two types of post-translational modification, phosphorylation and methylation, which are also thought to be important regulatory devices. The regulatory ability of PTPA (PTPase activator), originally identified as a protein stimulating the phosphotyrosine phosphatase activity of PP2A, will also be discussed, alongside the other regulatory inputs. The use of specific PP2A inhibitors and molecular genetics in yeast, Drosophila and mice has revealed roles for PP2A in cell cycle regulation, cell morphology and development. PP2A also plays a prominent role in the regulation of specific signal transduction cascades, as witnessed by its presence in a number of macromolecular signalling modules, where it is often found in association with other phosphatases and kinases. Additionally, PP2A interacts with a substantial number of other cellular and viral proteins, which are PP2A substrates, target PP2A to different subcellular compartments or affect enzyme activity. Finally, the de-regulation of PP2A in some specific pathologies will be touched upon.
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Affiliation(s)
- V Janssens
- Afdeling Biochemie, Faculteit Geneeskunde, Katholieke Universiteit Leuven, Herestraat 49, B-3000 Leuven, Belgium
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Masuzawa N, Urata Y, Yagi K, Ashihara T. Constrained, Random, and Independent Motion of Texas-Red-labeled Chromatin in Living Interphase PtK2 Cells. Acta Histochem Cytochem 2000. [DOI: 10.1267/ahc.33.419] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Affiliation(s)
- Naoko Masuzawa
- First Department of Pathology, Kyoto Prefectural University of Medicine
| | - Yoji Urata
- First Department of Pathology, Kyoto Prefectural University of Medicine
| | - Katsumi Yagi
- Department of Mathematics, Kyoto Prefectural University of Medicine
| | - Tsukasa Ashihara
- First Department of Pathology, Kyoto Prefectural University of Medicine
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Katahira M, Fukuda H, Kawasumi H, Sugimura T, Nakagama H, Nagao M. Intramolecular quadruplex formation of the G-rich strand of the mouse hypervariable minisatellite Pc-1. Biochem Biophys Res Commun 1999; 264:327-33. [PMID: 10529363 DOI: 10.1006/bbrc.1999.1521] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The minisatellite Pc-1, isolated from the mouse genome consisting of a tandem repeat of d(GGCAG), is hypervariable with a mutation rate of 0.15/generation. Here we describe a structural characterization of the G-rich strand of Pc-1 by biochemical and physicochemical methods. It was found to be comparatively resistant to both single-stranded DNA-binding protein binding and digestion by single-stranded DNA-specific nuclease and to cause arrest of DNA synthesis. The guanine imino proton NMR signals observed on the Pc-1 G-rich strand and their slow (1)H/(2)H exchange profiles pointed to a quadruplex structure with guanine quartets. The melting temperature of the quadruplex determined by CD was not dependent on DNA concentration. These results indicate that the G-rich strand of Pc-1 forms an intramolecular folded-back quadruplex structure under physiological conditions. Possible mechanisms of the Pc-1 mutations implicated with the formation of the quadruplex structure are discussed.
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Affiliation(s)
- M Katahira
- Department of Chemistry and Biotechnology, Faculty of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama, 240, Japan
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Nakagama H, Kaneko S, Shima H, Inamori H, Fukuda H, Kominami R, Sugimura T, Nagao M. Induction of minisatellite mutation in NIH 3T3 cells by treatment with the tumor promoter okadaic acid. Proc Natl Acad Sci U S A 1997; 94:10813-6. [PMID: 9380716 PMCID: PMC23496 DOI: 10.1073/pnas.94.20.10813] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Okadaic acid (OA) is a strong tumor promoter of mouse skin carcinogenesis and also a potent inhibitor of serine/threonine protein phosphatases. OA induces various genetic alterations in cultured cells, such as diphtheria-toxin-resistance mutations, sister chromatid exchange, exclusion of exogenous transforming oncogenes, and gene amplification. The present study revealed that it caused minisatellite mutation (MSM) at a high frequency in NIH 3T3 cells, although no microsatellite mutation was found. Nine of 31 clones (29%) exhibited MSM after 6 days of OA treatment, as opposed to only 1 of 30 clones (3%) without OA exposure. Moreover, NIH 3T3 cells treated with OA acquired tumorigenicity in nude mice, giving rise to 7 tumors within 25 weeks in 20 sites where 3 x 10(6) cells were injected. In contrast, the same numbers of untreated cells gave rise to only one tumor, and the tumor grew much slower. All of three OA-induced tumors examined manifested the MSM. The findings thus point to a molecular mechanism by which OA could function as a tumor promoter, and also the biological relevance of the induction of MSM in the tumorigenic process by OA.
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Affiliation(s)
- H Nakagama
- Biochemistry, National Cancer Center Research Institute, 1-1, Tsukiji 5, Chuo-ku, Tokyo 104, Japan
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Fessard V, Grosse Y, Pfohl-Leszkowicz A, Puiseux-Dao S. Okadaic acid treatment induces DNA adduct formation in BHK21 C13 fibroblasts and HESV keratinocytes. Mutat Res 1996; 361:133-41. [PMID: 8980699 DOI: 10.1016/s0165-1161(96)90248-4] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Okadaic acid (OA), a toxin involved in diarrhetic shellfish poisoning (DSP), has been shown to be a potent tumor promoter in mouse skin and glandular stomach. However, more recent studies tended to show that OA can also act as a genotoxic. In this study, using the 32P-postlabelling method, DNA adduct formation was obtained in two cell lines (BHK21 C13 fibroblasts and HESV keratinocytes) after treatment by OA for 24 h with a dose range between 0.01 and 5 nM. Nineteen adducts were observed with BHK21 C13 cells and 15 with HESV ones. Low doses did not show adduct formation. Intermediate doses have given the most important number of adducts and with higher doses, the number of adducts decreased dose dependently. Ten adducts were similar in the two strains while 9 were specific of BHK21 C13 cell line and 5 of HESV one. The highest total DNA adduct level from origin parts was estimated at 95.6 adducts/10(9) nucleotides for BHK21 C13 fibroblasts (1 nM OA treatment) and 31.1 adducts/10(9) nucleotides for HESV keratinocytes (0.5 nM OA treatment). In this case, the major adduct (number 3) represented 20% for the fibroblastic cell line and 30% for the keratinocytic strain. The genotoxic effect of OA showed in this study should lead to a more careful survey of DSP outbreaks.
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Affiliation(s)
- V Fessard
- Laboratoire de Toxicologie Marine, Faculté de Médecine, Nice, France
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Shima H, Tohda H, Aonuma S, Nakayasu M, DePaoli-Roach AA, Sugimura T, Nagao M. Characterization of the PP2A alpha gene mutation in okadaic acid-resistant variants of CHO-K1 cells. Proc Natl Acad Sci U S A 1994; 91:9267-71. [PMID: 7937753 PMCID: PMC44793 DOI: 10.1073/pnas.91.20.9267] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Okadaic acid (OA)-resistant variants of Chinese hamster ovary cells, clones CHO/OAR6-6 and CHO/OAR2-3, were isolated from a CHO-K1 culture. These variant cells were 17- to 26-fold more resistant to OA than the parental cells. The phosphorylase phosphatase activity of the variant cell extracts was 2- to 4-fold more resistant to OA than that of the parental cells in the presence of inhibitor 2, a specific inhibitor of type 1 protein serine/threonine phosphatase (PP1). Nucleotide sequencing of PP2A alpha (an isotype of PP2A catalytic subunit) cDNA demonstrated that both variants have a T-->G transversion at the first base of codon 269 (805 nt), which results in substitution of glycine for cysteine. We expressed in COS-1 cells a mutant PP2A alpha tagged with the influenza hemagglutinin epitope. The recombinant mutant PP2A alpha protein immunoprecipitated with an anti-influenza hemagglutinin antibody was more resistant than the wild type to OA, their IC50 values being 0.65 nM and 0.15 nM, and their IC80 values being 4.0 nM and 0.45 nM, respectively. The cysteine at residue 269 present only in highly OA-sensitive protein serine/threonine phosphatase catalytic subunit isozymes, PP2A alpha, PP2A beta, and PPX, is suggested to be involved in the binding of OA. CHO/OAR6-6 and CHO/OAR2-3 cells also overexpressed the P-glycoprotein, and the efflux of OA was more rapid. It is suggested that the PP2A alpha mutation in cooperation with a high level of P-glycoprotein makes the CHO-K1 variants highly resistant to OA.
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Affiliation(s)
- H Shima
- Carcinogenesis Division, National Cancer Center Research Institute, Tokyo, Japan
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