301
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Puerto M, Pichardo S, Jos Á, Cameán AM. Microcystin-LR induces toxic effects in differentiated and undifferentiated Caco-2 cells. Arch Toxicol 2010; 84:405-10. [DOI: 10.1007/s00204-010-0513-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2009] [Accepted: 01/14/2010] [Indexed: 11/28/2022]
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302
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Campos A, Vasconcelos V. Molecular mechanisms of microcystin toxicity in animal cells. Int J Mol Sci 2010; 11:268-287. [PMID: 20162015 PMCID: PMC2821003 DOI: 10.3390/ijms11010268] [Citation(s) in RCA: 340] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Revised: 01/11/2010] [Accepted: 01/12/2010] [Indexed: 12/31/2022] Open
Abstract
Microcystins (MC) are potent hepatotoxins produced by the cyanobacteria of the genera Planktothrix, Microcystis, Aphanizomenon, Nostoc and Anabaena. These cyclic heptapeptides have strong affinity to serine/threonine protein phosphatases (PPs) thereby acting as an inhibitor of this group of enzymes. Through this interaction a cascade of events responsible for the MC cytotoxic and genotoxic effects in animal cells may take place. Moreover MC induces oxidative stress in animal cells and together with the inhibition of PPs, this pathway is considered to be one of the main mechanisms of MC toxicity. In recent years new insights on the key enzymes involved in the signal-transduction and toxicity have been reported demonstrating the complexity of the interaction of these toxins with animal cells. Key proteins involved in MC up-take, biotransformation and excretion have been identified, demonstrating the ability of aquatic animals to metabolize and excrete the toxin. MC have shown to interact with the mitochondria. The consequences are the dysfunction of the organelle, induction of reactive oxygen species (ROS) and cell apoptosis. MC activity leads to the differential expression/activity of transcriptional factors and protein kinases involved in the pathways of cellular differentiation, proliferation and tumor promotion activity. This activity may result from the direct inhibition of the protein phosphatases PP1 and PP2A. This review aims to summarize the increasing data regarding the molecular mechanisms of MC toxicity in animal systems, reporting for direct MC interacting proteins and key enzymes in the process of toxicity biotransformation/excretion of these cyclic peptides.
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Affiliation(s)
- Alexandre Campos
- Centro Interdisciplinar de Investigação Marinha e Ambiental, CIIMAR/CIMAR, Rua dos Bragas 289, 4050-123 Porto, Portugal; E-Mail:
- Author to whom correspondence should be addressed; E-Mail:
; Tel.: +351-223-401-813; Fax: +351-223-390-608
| | - Vitor Vasconcelos
- Centro Interdisciplinar de Investigação Marinha e Ambiental, CIIMAR/CIMAR, Rua dos Bragas 289, 4050-123 Porto, Portugal; E-Mail:
- Departamento de Biologia, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, 4069-007 Porto, Portugal
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303
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Svircev Z, Baltić V, Gantar M, Juković M, Stojanović D, Baltić M. Molecular aspects of microcystin-induced hepatotoxicity and hepatocarcinogenesis. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART C, ENVIRONMENTAL CARCINOGENESIS & ECOTOXICOLOGY REVIEWS 2010; 28:39-59. [PMID: 20390967 DOI: 10.1080/10590500903585382] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
It is known that microcystin (MC) is a cyanotoxin that is a potent environmental inhibitor of eucariotic protein serine/threonine phosphatase 1 and 2A, both in vitro and in vivo. Consequently, these cyanobacterial toxins (MC-IARC group 2B carcinogen, MC extracts-group 3) are potent tumor promoters and there is an indication that they may also act as tumor initiators. The ability of microcystin-LR (MC-LR) to act as a tumor initiator is based on fact that it can induce DNA damage either by direct interaction with DNA or by indirect mechanisms through formation of reactive oxygen species (ROS). Both acute and chronic exposures, to either low or high doses of MC-LR, can activate apoptotic pathways. Chronic exposure to low concentrations of MC-LR contributes to increased risk for cancer development. Epidemiological studies, in certain areas of China, have suggested that MC is one of the risk factors for the high incidence of primary liver cancer (PLC). Recently, we have reported a correlation between PLC and cyanobacterial "blooms" in reservoirs used as a source for drinking water supply in central Serbia. It appears that the combination of acute and chronic exposures to both high and low doses of MC can lead to PLC initiation and promotion. Based on this, we propose that the requirement for the co-factors such as aflatoxin B1 and other mycotoxins, HBV, HCV, alcohol, etc. is not needed for initiation and promotion of PLC by MC-LR as was suggested earlier. The possible mechanisms of the genotoxicity of MC and its role as a hepatocarcinogen are outlined in this review. Furthermore, we show that the exposure of hepatocytes to MC can lead either to malignant proliferation or apoptosis.
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Affiliation(s)
- Z Svircev
- Department of Biology and Ecology, Faculty of Sciences, University of Novi Sad, Serbia.
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304
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Daily A, Monks NR, Leggas M, Moscow JA. Abrogation of microcystin cytotoxicity by MAP kinase inhibitors and N-acetyl cysteine is confounded by OATPIB1 uptake activity inhibition. Toxicon 2009; 55:827-37. [PMID: 19944114 DOI: 10.1016/j.toxicon.2009.11.019] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2009] [Revised: 10/12/2009] [Accepted: 11/18/2009] [Indexed: 10/20/2022]
Abstract
Solute transporters that are selectively expressed on tumor cell membranes could be targeted with small molecule toxins that are selective substrates for these transporters. HeLa cells transfected to express the solute transporter OATP1B1 are exquisitely sensitive in vitro to microcystin LR (MCLR) and its analogs, and undergo rapid morphologic changes after exposure to MCLR. Immunoblot analyses revealed HSP27 phosphorylation increased prior to the rapid MCLR-induced morphologic changes. However, transfection of OATP1B1-expressing cells with HSP27 dominant negative mutants did not reverse MCLR toxicity. Although the MAP kinase p38 inhibitor SB202190 partially reversed MCLR cytotoxicity, the control molecule, SB202474, had similar effects. Unexpectedly, both SB202190 and SB202474 inhibited OATP1B1 uptake activity, indicating an alternative explanation for cytotoxicity reversal that did not involve p38 MAP kinase. Similarly, although the potassium chloride co-transporter (KCC) inhibitor (dihydro-indenyl)oxyalkanoic acid (DIOA), and the anti-oxidant, N-acetyl cysteine (NAC) both reversed MCLR cytotoxicity, both were also found to be unexpected OATP1B1 transport inhibitors. Therefore, the mechanism of MCLR-induced cytotoxicity is obscured by the inhibition of OATP1B1 uptake activity by MAP kinase inhibitors, DIOA, and NAC. Finally, growth of OATP1B1-expressing HeLa xenografts was inhibited by MCLR, suggesting that MCLR structural analogs selected for a broader therapeutic index could target OATP-expressing tumors.
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Affiliation(s)
- Abigail Daily
- Department of Pediatrics, College of Medicine, University of Kentucky, Lexington, KY 40536, USA.
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305
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Huang DY, Mock M, Hagenbuch B, Chan S, Dmitrovic J, Gabos S, Kinniburgh D. Dynamic cytotoxic response to microcystins using microelectronic sensor arrays. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2009; 43:7803-7809. [PMID: 19921897 DOI: 10.1021/es901189c] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Microcystins are bioactive metabolites produced by cyanobacteria in water. These cyclic heptapeptides have caused public health concern worldwide. By interfering with cellular phosphorylation and signaling, microcystins can cause acute and chronic liver diseases. Therefore, the World Health Organization (WHO) has set the provisional drinking water guideline value at 1.0 microg/L for microcystin-LR (free plus cell-bound). Microcystins do not readily cross cell membranes in in vitro cell-based assays, except for those using freshly isolated hepatocytes. However, the sensitivity of in vitro cell-based assays is not adequate for testing samples at low environmental concentrations. Hence, there is a need to develop a sensitive and stable cytotoxicity assay for use in environmental studies. On the basis of the observation that microcystin-LR can be transported by the liver-specific members of the organic anion transporting polypeptides (OATPs), we investigated the potential of using an OATP1B3-expressing cell line in a cytotoxicity assay for microcystins. Using a novel cell electronic sensing system (RT-CES), we were able to monitor the real-time, dynamic cytotoxic response to microcystins at microgram per liter concentrations. We demonstrated that the cytotoxicity of the most common microcystins, -LR, -YR, -RR, -LF, and -LW, was mediated by OATP1B3 transporters. Microcystin-LF is the most potent toxin among the five congeners. In conclusion, we have established a highly automated, real-time, sensitive, and stable assay for measuring microcystin cytoxicity.
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Affiliation(s)
- Dorothy Yu Huang
- Alberta Centre for Toxicology, Department of Physiology and Pharmacology, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada.
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306
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Herfindal L, Kasprzykowski F, Schwede F, Łankiewicz L, Fladmark KE, Łukomska J, Wahlsten M, Sivonen K, Grzonka Z, Jastorff B, Døskeland SO. Acyloxymethyl esterification of nodularin-R and microcystin-LA produces inactive protoxins that become reactivated and produce apoptosis inside intact cells. J Med Chem 2009; 52:5758-62. [PMID: 19705870 DOI: 10.1021/jm900502e] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report the esterification of the carboxyl groups of the cyclic peptide toxins nodularin-R and microcystin-LA to produce stable diacetoxymethyl and dipropionyloxymethyl ester derivatives. The derivatives had no activity but were reactivated upon esterase treatment. When injected into cells, the acyloxymethyl moieties were cleaved off and apoptosis induced. Linking the acyloxymethyl-ester moiety of these potent toxins to carriers destined for endocytosis paves the way for selective apoptosis induction in target (e.g., cancer) cells.
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Affiliation(s)
- Lars Herfindal
- Translational Signaling Group, Department of Biomedicine, University of Bergen, Jonas Lies Vei 91, N-5009 Bergen, Norway.
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307
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Labine M, Minuk G. Cyanobacterial toxins and liver diseaseThis article is one of a selection of papers published in a special issue celebrating the 125th anniversary of the Faculty of Medicine at the University of Manitoba. Can J Physiol Pharmacol 2009; 87:773-88. [DOI: 10.1139/y09-081] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Blue-green algae, also known as cyanobacteria, produce a variety of toxins, some of which have been implicated in the pathogenesis of severe and potentially life-threatening diseases in humans. As the growth of cyanobacteria within freshwater lakes increases worldwide, it is important to review our present understanding of their toxicity and potential carcinogenicity to gain insight into how these organisms impact human health. This review addresses each of these topics, with special emphasis given to cyanobacterial hepatotoxins within freshwater environments.
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Affiliation(s)
- M.A. Labine
- Section of Hepatology, Department of Medicine, and Pharmacology and Therapeutics, University of Manitoba, 715 McDermot Avenue, Winnipeg, MB R3E 3P4, Canada
| | - G.Y. Minuk
- Section of Hepatology, Department of Medicine, and Pharmacology and Therapeutics, University of Manitoba, 715 McDermot Avenue, Winnipeg, MB R3E 3P4, Canada
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308
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Urquhart BL, Kim RB. Blood−brain barrier transporters and response to CNS-active drugs. Eur J Clin Pharmacol 2009; 65:1063-70. [DOI: 10.1007/s00228-009-0714-8] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2009] [Accepted: 07/28/2009] [Indexed: 10/20/2022]
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309
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Morphological and ultrastructural effects of microcystin-LR from Microcystis aeruginosa extract on a kidney cell line. Toxicon 2009; 54:283-94. [DOI: 10.1016/j.toxicon.2009.04.014] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2009] [Revised: 04/13/2009] [Accepted: 04/14/2009] [Indexed: 11/21/2022]
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310
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Malécot M, Mezhoud K, Marie A, Praseuth D, Puiseux-Dao S, Edery M. Proteomic study of the effects of microcystin-LR on organelle and membrane proteins in medaka fish liver. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2009; 94:153-161. [PMID: 19628287 DOI: 10.1016/j.aquatox.2009.06.012] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2009] [Revised: 06/16/2009] [Accepted: 06/19/2009] [Indexed: 05/28/2023]
Abstract
The microcystin-leucine-arginine toxin (MC-LR) is produced by cyanobacteria that sometimes bloom in water reservoirs. It targets the liver, thus posing potential health risks to human and animals. Microcystin inhibits the protein phosphatases PP1 and PP2A, leading to diverse cellular deregulation processes. A proteomic approach was applied to the medaka fish (Oryzias latipes) to obtain an overview of the effects of MC-LR on the liver. As membrane and organelle proteins are major structural and functional components of several cell signalling pathways, we decided to investigate here the membrane and organelle-enriched fractions from the livers of control and MC-LR treated medaka fish. Seventeen proteins were identified by proteomic analysis as being modulated in response to MC-LR treatment. This is the first time for eight of them to be reported as being involved in MC-LR effects: prohibitin, fumarylacetoacetase, protein disulfide isomerase A4 and A6, glucose regulated protein 78kDa, 40S ribosomal protein SA, cytochrome b5, and ATP synthase mitochondrial d subunit. These proteins are involved in protein maturation or in the response to oxidative stress highlighting the role of organelles in protein processing and the complex cooperation associated with oxidative stress.
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Affiliation(s)
- Mélodie Malécot
- CNRS, FRE 3206 Molécules de communication et adaptation des microorganismes, and MNHN, USM 505 Cyanobactéries, cyanotoxines et environnement, Département Régulations, développement et diversité moléculaire, Muséum national d'Histoire naturelle, Paris Cedex 05, France
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311
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Oxidative stress induced by microcystin-LR on PLHC-1 fish cell line. Toxicol In Vitro 2009; 23:1445-9. [PMID: 19720136 DOI: 10.1016/j.tiv.2009.08.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Revised: 07/23/2009] [Accepted: 08/25/2009] [Indexed: 11/22/2022]
Abstract
Increasing evidences suggest that oxidative stress may play a significant role in microcystins (MCs) toxicity not only in mammals, but also in fish. In this regard, many in vivo studies have been performed but little is still known about the alteration of oxidative stress biomarkers on fish cell lines so far. In this study, the toxic effects of MC-LR were investigated in the fish cell line PLHC-1, derived from a hepatocellular carninoma of the topminnow Poeciliosis lucida, after 48 h of exposure. The different response of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione-S-transferase (GST), as well as lipid peroxidation (LPO) as a biomarker of oxygen-mediated toxicity, were assessed in PLHC-1 cells. The increases in the antioxidant enzymatic activities (SOD, GPx, and GST) as well as in LPO values observed evidenced the oxidative stress induced by MC-LR exposure. Moreover, the enhancements of these enzymes could suggest an adaptative response to combat oxidative injure induced by MC-LR, confirming that this mechanism is involved in the damage induced by MCs on fish cells.
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312
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Comparison of the toxicity induced by microcystin-RR and microcystin-YR in differentiated and undifferentiated Caco-2 cells. Toxicon 2009; 54:161-9. [DOI: 10.1016/j.toxicon.2009.03.030] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2009] [Revised: 03/27/2009] [Accepted: 03/30/2009] [Indexed: 11/22/2022]
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313
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Meyer zu Schwabedissen HE, Ware JA, Tirona RG, Kim RB. Identification, Expression, and Functional Characterization of Full-Length and Splice Variants of Murine Organic Anion Transporting Polypeptide 1b2. Mol Pharm 2009; 6:1790-7. [DOI: 10.1021/mp900030w] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- Henriette E. Meyer zu Schwabedissen
- Division of Clinical Pharmacology, Department of Medicine,
University of Western Ontario, London, Ontario, Canada, Department
of Physiology and Pharmacology, University of Western Ontario, London,
Ontario, Canada, Pfizer Global Research and Development, Ann Arbor,
Michigan, and Genentech Inc., San Francisco, California
| | - Joseph A. Ware
- Division of Clinical Pharmacology, Department of Medicine,
University of Western Ontario, London, Ontario, Canada, Department
of Physiology and Pharmacology, University of Western Ontario, London,
Ontario, Canada, Pfizer Global Research and Development, Ann Arbor,
Michigan, and Genentech Inc., San Francisco, California
| | - Rommel G. Tirona
- Division of Clinical Pharmacology, Department of Medicine,
University of Western Ontario, London, Ontario, Canada, Department
of Physiology and Pharmacology, University of Western Ontario, London,
Ontario, Canada, Pfizer Global Research and Development, Ann Arbor,
Michigan, and Genentech Inc., San Francisco, California
| | - Richard B. Kim
- Division of Clinical Pharmacology, Department of Medicine,
University of Western Ontario, London, Ontario, Canada, Department
of Physiology and Pharmacology, University of Western Ontario, London,
Ontario, Canada, Pfizer Global Research and Development, Ann Arbor,
Michigan, and Genentech Inc., San Francisco, California
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314
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Franke RM, Scherkenbach LA, Sparreboom A. Pharmacogenetics of the organic anion transporting polypeptide 1A2. Pharmacogenomics 2009; 10:339-44. [PMID: 19290786 DOI: 10.2217/14622416.10.3.339] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The solute carrier, human organic anion transporting polypeptide 1A2 (OATP1A2, OATP-A, OATP1 and OATP) is highly expressed in the intestine, kidney, cholangiocytes and the blood-brain barrier. This localization suggests that OATP1A2 may be vitally important in the absorption, distribution and excretion of a broad array of clinically important drugs. Several nonsynonymous polymorphisms have been identified in the gene encoding OATP1A2, SLCO1A2 (SLC21A3), with some of these variants demonstrating functional changes in the transport of OATP1A2 substrates.
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Affiliation(s)
- Ryan M Franke
- Department of Pharmaceutical Sciences, St Jude Children's Hospital, 332 North Lauderdale, DTRC, Mail Stop 313, Room I5308, Memphis, TN 38105, USA
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315
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Kujbida P, Hatanaka E, Vinolo MAR, Waismam K, Cavalcanti DMDH, Curi R, Farsky SHP, Pinto E. Microcystins -LA, -YR, and -LR action on neutrophil migration. Biochem Biophys Res Commun 2009; 382:9-14. [PMID: 19360947 DOI: 10.1016/j.bbrc.2009.02.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Microcystins (MCs) produced by some freshwater cyanobacterial species possess potent liver toxicity as evidenced by acute neutrophil infiltration. Here, we investigate the ability of three structurally distinct toxins (MC-LA, MC-LR, and MC-YR) to evoke neutrophil recruitment per se and their effects on migration pathways. Intravital microscopic studies showed that topical application of only MC-LR enhanced the numbers of rolling and adhered leukocytes in the endothelium of postcapillary mesenteric venules. The latter effects may be dependent upon induction of the synthesis and expression of L-selectin and beta2-integrin in neutrophils, as assessed by flow cytometry and RT-PCR, respectively. Conversely, the three toxins promoted direct locomotion of neutrophils and enhanced their migration in response to fMLP, as measured by Boyden chamber assays, and increased intracellular calcium, a messenger in the chemotaxic process. In conclusion, our results show that MCs act on specific pathways of neutrophil recruitment, indicating their potential effect on neutrophils activation.
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Affiliation(s)
- Paula Kujbida
- Department of Clinical and Toxicological Analyses, Faculty of Pharmaceutical Sciences, University of São Paulo, Avenida Prof. Lineu Prestes, 580 bloco 13 B, 05508-900 Butanta, São Paulo, SP, Brazil
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316
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Dias E, Andrade M, Alverca E, Pereira P, Batoréu M, Jordan P, Silva MJ. Comparative study of the cytotoxic effect of microcistin-LR and purified extracts from Microcystis aeruginosa on a kidney cell line. Toxicon 2009; 53:487-95. [DOI: 10.1016/j.toxicon.2009.01.029] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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317
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Amado LL, Garcia ML, Ramos PB, Freitas RF, Zafalon B, Ferreira JLR, Yunes JS, Monserrat JM. A method to measure total antioxidant capacity against peroxyl radicals in aquatic organisms: application to evaluate microcystins toxicity. THE SCIENCE OF THE TOTAL ENVIRONMENT 2009; 407:2115-23. [PMID: 19095287 DOI: 10.1016/j.scitotenv.2008.11.038] [Citation(s) in RCA: 263] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2008] [Revised: 09/09/2008] [Accepted: 11/14/2008] [Indexed: 05/20/2023]
Abstract
Determination of total antioxidant capacity, instead of the measurements of limited number of antioxidants, is very important for the understanding of how antioxidants interact with reactive oxygen species (ROS). Several techniques already exist with this propose, although some of them are extremely time-consuming. A new methodology is proposed, based on the detection of ROS by fluorometry (ex/em: 485/520 nm) employing 2',7'-dichlorofluorescein diacetate (H(2)DCF-DA) as substrate. Supernatant of homogenized samples from different organs (gill, muscle, liver, and brain) of the teleost fish Jenynsia multidentata (Anaplebidae) were exposed to peroxyl radicals generated by thermal (35 degrees C) decomposition of 2,2'-azobis (2 methylpropionamidine) dihydrochloride (ABAP, 4 mM). Different protein concentrations (0.5, 1, 2 and 8 mg/ml) were assayed to get the best signal and curve fitting of fluorescence data over time (30 min). Total antioxidant capacity against peroxyl radicals was estimated as the difference in ROS area with and without ABAP, relative to the fluorescence registered without ABAP. For application of this methodology, J. multidentata specimens were exposed for 24 h to microcystins, cyanotoxins known to induce oxidative stress. Almost all organs showed a lower antioxidant capacity (p<0.05) in samples with 8 mg proteins/ml, when compared to protein content of 1-2 mg/ml. In liver samples, higher (p<0.05) free iron content was determined in samples with 8 mg proteins/ml. Sensitivity test employing GSH spiked in homogenized samples showed the protocol efficiency in detecting total antioxidant capacity. In the test with microcystins a dose-dependent decrease (p<0.05) of antioxidant competence in gills and brain and an inverse result with liver samples were observed. The use of antioxidant defenses was efficient in avoiding oxidative damage, as the content of oxidized proteins was not altered. Data obtained show the potential of this new methodology to be used in ecotoxicological studies.
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Affiliation(s)
- Lílian Lund Amado
- Universidade Federal do Rio Grande - FURG, Instituto de Ciências Biológicas, Rio Grande, RS, Brazil
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318
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Oatp-associated uptake and toxicity of microcystins in primary murine whole brain cells. Toxicol Appl Pharmacol 2009; 234:247-55. [DOI: 10.1016/j.taap.2008.10.011] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2008] [Revised: 10/17/2008] [Accepted: 10/20/2008] [Indexed: 02/08/2023]
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319
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Li Y, Ye H, Du M, Zhang Y, Ye B, Pu Y, Wang D. Induction of chemotaxis to sodium chloride and diacetyl and thermotaxis defects by microcystin-LR exposure in nematode Caenorhabditis elegans. J Environ Sci (China) 2009; 21:971-979. [PMID: 19862965 DOI: 10.1016/s1001-0742(08)62370-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Apart from the liver disruption, embryotoxicity and genotoxicity, microcystin (MC)-LR also could cause neurotoxicity. Nematode Caenorhabditis elegans was explored as a model to study the neurotoxicity. In the present study, we provided evidence to indicate the neurotoxicity on chemotaxis to NaCl and diacetyl, and thermotaxis from MC-LR exposure to C. elegans. As a result, higher concentrations of MC-LR caused significantly severe defects of chemotaxis to NaCl and diacetyl, and thermotaxis. The neurotoxicity on chemotaxis to NaCl and diacetyl, and thermotaxis from MC-LR exposure might be largely mediated by the damage on the corresponding sensory neurons (ASE, AWA, and AFD) and interneuron AIY The expression levels of che-1 and odr-7 were significantly decreased (P < 0.01) in animals exposed to MC-LR at concentrations lower than 10 microg/L, whereas the expression levels of ttx-1 and ttx-3 could be significantly (P < 0.01) lowered in animals even exposed to 1 microg/L of MC-LR. Moreover, both the chemotaxis to NaCl and diacetyl and the thermotaxis were more significantly reduced in MC-LR exposed mutants of che-1(p674), odr-7(ky4), ttx-1(p767), and ttx-3(ks5) than those in exposed wild-type N2 animals at the same concentrations.
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Affiliation(s)
- Yunhui Li
- Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, Nanjing 210009, China.
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320
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Hagenbuch B, Gui C. Xenobiotic transporters of the human organic anion transporting polypeptides (OATP) family. Xenobiotica 2008; 38:778-801. [PMID: 18668430 DOI: 10.1080/00498250801986951] [Citation(s) in RCA: 299] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
1. The organic anion transporting polypeptides (humans OATP; other species Oatp) belong to the SLCO gene superfamily of transporters and are twelve transmembrane domain glycoproteins expressed in various epithelial cells. Some OATPs/Oatps are expressed in a single organ, while others are expressed ubiquitously. 2. The functionally characterized members mediate sodium-independent transport of a variety of structurally independent, mainly amphipathic organic compounds, including bile salts, hormones and their conjugates, toxins, and various drugs. 3. This review summarizes the general features and the substrates of the eleven human OATPs. Furthermore, it reviews what is known about the mechanism of their multispecificity, their predicted structure, their role in drug-food interactions, and their role in cancer. 4. Finally, some open questions are raised that need to be addressed to advance OATP research in the near future.
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Affiliation(s)
- B Hagenbuch
- The University of Kansas Medical Center, Pharmacology, Toxicology and Therapeutics, Kansas City, KS 66160, USA.
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321
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Nies AT, Schwab M, Keppler D. Interplay of conjugating enzymes with OATP uptake transporters and ABCC/MRP efflux pumps in the elimination of drugs. Expert Opin Drug Metab Toxicol 2008; 4:545-68. [PMID: 18484914 DOI: 10.1517/17425255.4.5.545] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
BACKGROUND Biliary excretion is a major elimination route of many drugs and their metabolites. Hepatobiliary elimination is a vectorial process involving uptake transporters in the basolateral hepatocyte membrane, possibly Phase I and Phase II metabolizing enzymes, and ATP-dependent efflux pumps in the apical hepatocyte membrane. OBJECTIVES Because many drugs and their metabolites are anions, this review focuses on transporters involved in their hepatocellular uptake (members of the organic anion transporting polypeptide (OATP) family) and biliary elimination (apical conjugate efflux pump ABCC2/MRP2). METHODS The molecular and functional characteristics of the human OATP and ABCC/MRP transporters are presented, including a detailed overview of endogenous and drug substrates. Examples illustrate the interplay of transporters with Phase II conjugating enzymes. Model systems to study the vectorial transport of organic anions are also discussed. RESULTS/CONCLUSIONS OATP uptake transporters, conjugating enzymes, and ABCC2/MRP2 work in concert to enable the hepatobiliary elimination of anionic drugs and their metabolites. It is increasingly important to understand how genetic variants of these transporters and enzymes influence the interindividual variability of drug elimination.
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Affiliation(s)
- Anne T Nies
- Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology, Stuttgart and University of Tübingen, Auerbachstrasse 112, 70376 Stuttgart, Germany.
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322
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Funari E, Testai E. Human Health Risk Assessment Related to Cyanotoxins Exposure. Crit Rev Toxicol 2008; 38:97-125. [DOI: 10.1080/10408440701749454] [Citation(s) in RCA: 267] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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323
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Xing ML, Wang XF, Xu LH. Alteration of proteins expression in apoptotic FL cells induced by MCLR. ENVIRONMENTAL TOXICOLOGY 2008; 23:451-458. [PMID: 18214937 DOI: 10.1002/tox.20355] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Microcystins (MCs) are a family of monocyclic heptapeptide hepatotoxins produced by freshwater species of cyanobacteria. Microcystin-LR (MCLR) is the most frequently studied and most toxic in over 80 MC congeners. Great deals of studies have demonstrated that MCLR can induce apoptosis in a wide variety of cell types. Although much evidence indicates that mitochondria play a pivotal role in MCLR-induced apoptosis, the complicated apoptosis mechanisms induced by MCLR have not been completely characterized. It is possible that there are other apoptotic pathways existing in MCLR-induced apoptosis. The present study was undertaken to determine the expression of PP2A, CHOP, Bax, Bcl-2, and p53 proteins in MCLR-induced apoptosis in FL cells. The results showed that MCLR could induce apoptosis in FL cells and the process was accompanied with the upregulation of PP2A, Bax, and p53 proteins and the downregulation of Bcl-2 proteins. In addition, the CHOP protein was upregulated at most treatment groups and decreased at the highest concentration group. These results, especially the alteration of PP2A and CHOP proteins might provide new insights into MCLR-induced apoptosis.
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Affiliation(s)
- Ming-Luan Xing
- Department of Biochemistry and Genetics, School of Medicine, Zhejiang University, 388 Yu Hang Tang Road, Hangzhou 310058, China
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324
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Dose-dependent antioxidant responses and pathological changes in tenca (Tinca tinca) after acute oral exposure to Microcystis under laboratory conditions. Toxicon 2008; 52:1-12. [PMID: 18588906 DOI: 10.1016/j.toxicon.2008.05.009] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2008] [Revised: 05/20/2008] [Accepted: 05/20/2008] [Indexed: 12/28/2022]
Abstract
The effects of cyanobacterial cells containing microcystins (MCs), toxins from cyanobacteria, on oxidative stress biomarkers from liver and kidney of Tenca fish (Tinca tinca) were investigated under laboratory conditions. Moreover, a histopathological study of liver, kidney, heart and intestine tissues was performed. Fish were orally exposed to cyanobacterial cells dosing 0, 5, 11, 25 and 55 microg MC-LR/fish mixed with the food. Results showed a dose-dependent decrease of superoxide dismutase (SOD) activity, and also of catalase (CAT) in the liver. Glutathione levels and protein oxidation, however, were not altered by the exposure to the cyanobacterial material. The microscopic study revealed tissue alterations even at the lower cyanobacterial cells doses. Onion-like hepatocytes in the liver, glomerulopathy in the kidney, loss of myofibrils in the heart and vacuolated enterocytes in the gastrointestinal tract were the main changes observed. These findings suggest that this fresh water fish can be adversely affected by cyanobacterial blooms in their natural habitats.
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325
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Wase NV, Wright PC. Systems biology of cyanobacterial secondary metabolite production and its role in drug discovery. Expert Opin Drug Discov 2008; 3:903-29. [DOI: 10.1517/17460441.3.8.903] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Nishikant V Wase
- The University of Sheffield, Biological and Environmental Systems Group, Department of Chemical and Process Engineering, Mappin St., Sheffield, S1 3JD, UK ;
| | - Phillip C Wright
- The University of Sheffield, Biological and Environmental Systems Group, Department of Chemical and Process Engineering, Mappin St., Sheffield, S1 3JD, UK ;
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326
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Pasková V, Adamovský O, Pikula J, Skocovská B, Band'ouchová H, Horáková J, Babica P, Marsálek B, Hilscherová K. Detoxification and oxidative stress responses along with microcystins accumulation in Japanese quail exposed to cyanobacterial biomass. THE SCIENCE OF THE TOTAL ENVIRONMENT 2008; 398:34-47. [PMID: 18423819 DOI: 10.1016/j.scitotenv.2008.03.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2007] [Revised: 03/04/2008] [Accepted: 03/04/2008] [Indexed: 05/26/2023]
Abstract
The cyanobacterial exposure has been implicated in mass mortalities of wild birds, but information on the actual effects of cyanobacteria on birds in controlled studies is missing. Effects on detoxification and antioxidant parameters as well as bioaccumulation of microcystins (MCs) were studied in birds after sub-lethal exposure to natural cyanobacterial biomass. Four treatment groups of model species Japanese quail (Coturnix coturnix japonica) were exposed to controlled doses of cyanobacterial bloom during acute (10 days) and sub-chronic (30 days) experiment. The daily doses of cyanobacterial biomass corresponded to 0.2-224.6 ng MCs/g body weight. Significant accumulation of MCs was observed in the liver for both test durations and slight accumulation also in the muscles of the highest treatment group from acute test. The greatest accumulation was observed in the liver of the highest treatment group in the acute test reaching average concentration of 43.7 ng MCs/g fresh weight. The parameters of detoxification metabolism and oxidative stress were studied in the liver, heart and brain. The cyanobacterial exposure caused an increase of activity of cytochrome P-450-dependent 7-ethoxyresorufin O-deethylase representing the activation phase of detoxification metabolism. Also the conjugation phase of detoxification, namely the activity of glutathione-S-transferase, was altered. Cyanobacterial exposure also modulated oxidative stress responses including the level of glutathione and activities of glutathione-related enzymes and caused increase in lipid peroxidation. The overall pattern of detoxification parameters and oxidative stress responses clearly separated the control and the lowest exposure group from all the higher exposed groups. This is the first controlled study documenting the induction of oxidative stress along with MCs accumulation in birds exposed to natural cyanobacterial biomass. The data also suggest that increased activities of detoxification enzymes could lead to greater biotransformation and elimination of the MCs at the longer exposure time.
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Affiliation(s)
- Veronika Pasková
- Centre for Cyanobacteria and Their Toxins (Institute of Botany, The Academy of Sciences of the Czech Republic & RECETOX, Masaryk University), Brno, Czech Republic
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327
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Zegura B, Volcic M, Lah TT, Filipic M. Different sensitivities of human colon adenocarcinoma (CaCo-2), astrocytoma (IPDDC-A2) and lymphoblastoid (NCNC) cell lines to microcystin-LR induced reactive oxygen species and DNA damage. Toxicon 2008; 52:518-25. [PMID: 18657565 DOI: 10.1016/j.toxicon.2008.06.026] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2008] [Revised: 06/26/2008] [Accepted: 06/30/2008] [Indexed: 10/21/2022]
Abstract
Microcystins, which are hepatotoxins produced by cyanobacteria, have been reported to be potent tumour promoters, and there is an indication that they can also act as tumour initiators. They thus constitute a potential threat to human and animal health, at concentrations that do not cause acute hepatotoxic effects. The main target organ of microcystin toxicity is the liver; however, several studies have shown that other organs and tissues may also be affected. We have investigated the effect of non-cytotoxic concentrations of microcystin-LR (MCLR) on the generation of intracellular reactive oxygen species (ROS) and on DNA damage in human colon adenocarcinoma CaCo-2, human astrocytoma IPDDC-A2 and human B-lymphoblastoid NCNC cell lines. The viability of CaCo-2 cells exposed to 10 microg/MCLR for 24 and 48 h was reduced by about 40%, while that of NCNC and IPDDC-2A cells was not affected. Intracellular ROS production was increased in CaCo-2 and IPDDC-2A, but not NCNC, cells. Using the comet assay, it was shown that MCLR, at non-cytotoxic concentrations, induced a time and dose dependent increase of DNA damage in CaCo-2 cells, but not significantly in IPDDC-2A and NCNC cells. Thus, CaCo-2 cells were the most sensitive. Their sensitivity is comparable to that observed in our previous study with human hepatoma HepG2 cells. These results indicate that, in addition to liver cells, colon cells should also be considered as a target for microcystin toxicity, and that exposure to low doses of microcystins may affect intestinal tissue.
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Affiliation(s)
- Bojana Zegura
- National Institute of Biology, Department for Genetic Toxicology and Cancer Biology, Vecna Pot 111, 1000 Ljubljana, Slovenia.
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328
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Dietrich DR, Fischer A, Michel C, Hoeger SJ. Toxin mixture in cyanobacterial blooms--a critical comparison of reality with current procedures employed in human health risk assessment. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 619:885-912. [PMID: 18461795 DOI: 10.1007/978-0-387-75865-7_39] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Cyanobacteria are the oldest life forms on earth known to produce a broad spectrum of secondary metabolites. The functions/advantages of most of these secondary metabolites (peptides and alkaloids) are unknown, however, some of them have adverse effects in humans and wildlife, especially when ingested, inhaled or upon dermal exposure. Surprisingly, some of these cyanobacteria are ingested voluntarily. Indeed, for centuries mankind has used cyanobacteria as a protein source, primarily Spirulina species. However, recently also Aphanizomenon flos-aquae are used for the production of so called blue green algae supplements (BGAS), supposedly efficacious for treatment of various diseases and afflictions. Unfortunately, traces of neurotoxins and protein phosphatases (inhibiting compounds) have been detected in BGAS, making these health supplements a good example for human exposure to a mixture of cyanobacterial toxins in a complex matrix. The discussion of this and other possible exposure scenarios, e.g. drinking water, contact during recreational activity, or consumption of contaminated food, can provide insight into the question of whether or not our current risk assessment schemes for cyanobacterial blooms and the toxins contained therein suffice for protection of human health.
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329
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Nong Q, Komatsu M, Izumo K, Indo HP, Xu B, Aoyama K, Majima HJ, Horiuchi M, Morimoto K, Takeuchi T. Involvement of reactive oxygen species in Microcystin-LR-induced cytogenotoxicity. Free Radic Res 2008; 41:1326-37. [PMID: 17963120 DOI: 10.1080/10715760701704599] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Microcystin-LR (MCLR) is a potent hepatotoxin. Oxidative stress is thought to be implicated in the cytotoxicity of MCLR, but the mechanisms by which MCLR produces reactive oxygen species (ROS) are still unclear. This study investigated the role and possible sources of ROS generation in MCLR-induced cytogenotoxicity in HepG2, a human hepatoma cell line. MCLR increased DNA strand breaks, 8-hydroxydeoxiguanosine formation, lipid peroxidation, as well as LDH release, all of which were inhibited by ROS scavengers. ROS scavengers partly suppressed MCLR-induced cytotoxicity determined by the MTT assay. MCLR induced the generation of ROS, as confirmed by confocal microscopy with 2-[6-(4'-hydroxy)phenoxy-3H-xanthen-3-on-9-yl]benzoic acid, and upregulated the expression of CYP2E1 mRNA. In addition, CYP2E1 inhibitors chlormethiazole and diallyl dulphide inhibited both ROS generation and cytotoxicity induced by MCLR. The results suggest that ROS contribute to MCLR-induced cytogenotoxicity. CYP2E1 might be a potential source responsible for ROS generation by MCLR.
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Affiliation(s)
- Qingqing Nong
- Department of Environmental Medicine, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
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330
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Atencio L, Moreno I, Prieto AI, Moyano R, Molina AM, Cameán AM. Acute Effects of Microcystins MC-LR and MC-RR on Acid and Alkaline Phosphatase Activities and Pathological Changes in Intraperitoneally Exposed Tilapia Fish (Oreochromis sp.). Toxicol Pathol 2008; 36:449-58. [DOI: 10.1177/0192623308315356] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Microcystins (MC) are frequently present in cyanobacterial blooms in rivers and lakes, increasing the risk of toxicity to both animals and humans. There more than eighty reported microcystins, and the present study was undertaken to determine whether MC-LR and MC-RR can induce different enzyme alterations and histopathological changes in tilapia fish ( Oreochromis sp.) exposed to a single intraperitoneal (i.p.) injection of the pure standards (MC-LR and MC-RR) at a dose of 500 μg/kg; the tilapia fish were then observed for seven days. The two MC variants caused significant changes in the activities of acid and alkaline phosphatases (ACP and ALP) in vital organs, showing a different response pattern. The livers and kidneys of fish injected with MC-LR were particularly affected. MC-RR induced a very pronounced increase of ACP in the kidney and a significant increase of ALP in the liver. Both MC variants caused pathological lesions in hepatic tissues, such as megalocytosis, necrotic process, and microvesicular steatosis, particularly in fish treated with MC-LR, and degenerative renal changes, glomerulopathy, were more severe in tilapias exposed to MC-RR. In addition, both microcystins also caused significant myopathy in the heart. In contrast, the gills did not show any change in enzyme activity or histopathological injury.
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Affiliation(s)
- Loyda Atencio
- Área de Toxicología, Facultad de Farmacia, Universidad de Sevilla, 41012 Sevilla, Spain
| | - Isabel Moreno
- Área de Toxicología, Facultad de Farmacia, Universidad de Sevilla, 41012 Sevilla, Spain
| | - Ana I. Prieto
- Área de Toxicología, Facultad de Farmacia, Universidad de Sevilla, 41012 Sevilla, Spain
| | - Rosario Moyano
- Dpto. Farmacología, Toxicología, Medicina Legal y Forense, Universidad de Córdoba, 14071 Córdoba, Spain
| | - Ana M. Molina
- Dpto. Farmacología, Toxicología, Medicina Legal y Forense, Universidad de Córdoba, 14071 Córdoba, Spain
| | - Ana M. Cameán
- Área de Toxicología, Facultad de Farmacia, Universidad de Sevilla, 41012 Sevilla, Spain
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331
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Billam M, Mukhi S, Tang L, Gao W, Wang JS. Toxic response indicators of microcystin-LR in F344 rats following a single-dose treatment. Toxicon 2008; 51:1068-80. [DOI: 10.1016/j.toxicon.2008.01.014] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2007] [Revised: 01/20/2008] [Accepted: 01/28/2008] [Indexed: 10/22/2022]
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332
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Pegram RA, Nichols T, Etheridge S, Humpage A, LeBlanc S, Love A, Neilan B, Pflugmacher S, Runnegar M, Thacker R. Cyanotoxins Workgroup report. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 619:317-81. [PMID: 18461775 DOI: 10.1007/978-0-387-75865-7_15] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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333
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Toxin types, toxicokinetics and toxicodynamics. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 619:383-415. [DOI: 10.1007/978-0-387-75865-7_16] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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334
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Lu H, Choudhuri S, Ogura K, Csanaky IL, Lei X, Cheng X, Song PZ, Klaassen CD. Characterization of organic anion transporting polypeptide 1b2-null mice: essential role in hepatic uptake/toxicity of phalloidin and microcystin-LR. Toxicol Sci 2008; 103:35-45. [PMID: 18296417 DOI: 10.1093/toxsci/kfn038] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The liver-specific importer organic anion transporting polypeptide 1b2 (Oatp1b2, Slco1b2, also known as Oatp4 and Lst-1) and its human orthologs OATP1B1/1B3 transport a large variety of chemicals. Oatp1b2-null mice were engineered by homologous recombination and their phenotype was characterized. Oatp1b2 protein was absent in livers of Oatp1b2-null mice. Oatp1b2-null mice develop normally and breed well. However, adult Oatp1b2-null mice had moderate conjugated hyperbilirubinemia. Compared with wild-types, Oatp1b2-null mice had similar hepatic messenger RNA expression of most transporters examined except a higher Oatp1a4 but lower organic anion transporter 2. Intra-arterial injection of the mushroom toxin phalloidin (an Oatp1b2-specific substrate identified in vitro) caused cholestasis in wild-type mice but not in Oatp1b2-null mice. Hepatic uptake of fluorescence-labeled phalloidin was absent in Oatp1b2-null mice. Three hours after administration of microcystin-LR (a blue-green algae toxin), the binding of microcystin-LR to hepatic protein phosphatase 1/2a was much lower in Oatp1b2-null mice compared with wild-type mice. In contrast, Oatp1b2-null mice were transiently protected from decrease in bile flow induced by estradiol-17beta-D-glucuronide, a common substrate for Oatps. Oatp1b2-null mice were completely resistant to the hepatotoxicity induced by phalloidin and microcystin-LR, but were similarly sensitive to alpha-amanitin-induced hepatotoxicity compared with wild-type mice. In conclusion, Oatp1b2-null mice display altered basic physiology and markedly decreased hepatic uptake/toxicity of phalloidin and microcystin-LR. Oatp1b2-null mice are useful in elucidating the role of Oatp1b2 and its human orthologs OATP1B1/1B3 in hepatic uptake and systemic disposition of toxic chemicals and therapeutic drugs.
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Affiliation(s)
- Hong Lu
- Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, KS 66160-7417, USA
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335
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Sex-specific extraction of organic anions by the rat liver. Life Sci 2008; 82:436-43. [DOI: 10.1016/j.lfs.2007.12.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2007] [Revised: 11/18/2007] [Accepted: 12/04/2007] [Indexed: 12/12/2022]
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336
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Abstract
Cyanobacteria are responsible for poisoning numerous cases of livestock and other animals, but sometimes they induce serious problems in humans. Mass occurrence and blooms of cyanobacteria were studied in rivers, canals, lakes, and accu?mulations that had been examined in Serbia during period 1980-2002. Because of massive blooming of cyanobacteria, when they produce cyanotoxins, which could be responsible for poisoning, and damage of organs, studies are steered to better understanding cyanotoxins effects on human health. The investigation on microcystins, as one of many cyanotoxins, is increas?ing due to the related ecological and public health risks. There is evidence that microcystins have a tumor promoting activity and microcystin-LRcould be tumor initiator and possibly cancerogenic to humans. Epidemiological studies have suggested that there is connection between primary liver cancer (PLC) and microcystins, as one of risk factor for high incidence rate of PLC in Serbia.
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337
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Gaudin J, Huet S, Jarry G, Fessard V. In vivo DNA damage induced by the cyanotoxin microcystin-LR: comparison of intra-peritoneal and oral administrations by use of the comet assay. Mutat Res 2007; 652:65-71. [PMID: 18282792 DOI: 10.1016/j.mrgentox.2007.10.024] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2006] [Revised: 05/10/2007] [Accepted: 10/15/2007] [Indexed: 12/13/2022]
Abstract
Microcystin-LR (MC-LR), involved in human and animal poisonings by cyanobacteria, has been shown to be both a potent tumour promoter in rat liver and an inhibitor of serine/threonine protein phosphatases, specifically PP1 and PP2A. The research on the genotoxic potential of MC-LR counts only few in vivo studies. In order to determine the target organs for DNA-damage induction by MC-LR, the single-cell gel electrophoresis (SCGE) or comet assay was performed in mice. Following a single oral administration of 2 and 4mg/kg bw of MC-LR, a statistically significant induction of DNA damage in blood cells was obtained after 3h. However, after an intra-peritoneal injection (ip), DNA lesions were mainly induced in the liver, but were also reported in the kidney, the intestine and the colon. The sensitivity of the ip route compared to the oral route suggested a difference in the bio-disponibility of the toxin. In any case, DNA damage was induced by MC-LR irrespective of the administration route. Among the target organs, the DNA damage induced in the intestinal tissues (ileum and colon) may contribute to an increased cancer risk.
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Affiliation(s)
- Julien Gaudin
- Agence Française de Sécurité Sanitaire des Aliments, Laboratoire d'Etudes et de Recherches sur les Médicaments Vétérinaires et les Désinfectants, Unité de Toxicologie Génétique des Contaminants Alimentaires, Fougères, France.
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338
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Prieto AI, Pichardo S, Jos Á, Moreno I, Cameán AM. Time-dependent oxidative stress responses after acute exposure to toxic cyanobacterial cells containing microcystins in tilapia fish (Oreochromis niloticus) under laboratory conditions. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2007; 84:337-345. [PMID: 17669513 DOI: 10.1016/j.aquatox.2007.06.012] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2007] [Revised: 06/20/2007] [Accepted: 06/22/2007] [Indexed: 05/16/2023]
Abstract
Microcystins (MCs) have been reported to induce oxidative stress in aquatic organisms including fish. The effect of acute exposure to toxic cyanobacterial material containing MCs on antioxidant enzymes and lipid peroxidation has been studied in liver, kidney and gills of tilapia fish (Oreochromis niloticus). Fish were orally exposed to a single dose of cyanobacterial cells containing 120 microg/fish MC-LR and sacrificed at 24 and 72 h. The activities of glutathione peroxidase (GPx), glutathione reductase (GR), superoxide dismutase (SOD) and catalase (CAT) enzymes in the studied organs decreased in general 24 and 72 h after the dose application, although elevation of CAT and GR was found in liver at 72 h post exposure in comparison to 24h values. In contrast, the lipid peroxidation level increased significantly in all the studied organs with the liver (3.6-fold) proving to be the most affected. Protein oxidation was also increased 1.5-fold in the liver. However, recovery in these parameters was observed in liver 72 h after exposure. The results show that an acute dose of MCs does not induce an adaptative response of the antioxidant enzymes, as a sub-chronic exposure to MCs in tilapia fish does, but a general decrease in them with an initial recovery of the oxidative damage after 72 h, expressed as enhancement of CAT and GR activities and a reduction of LPO and protein oxidation in comparison to 24h values.
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Affiliation(s)
- Ana I Prieto
- Area of Toxicology, Faculty of Pharmacy, University of Seville, Profesor García González no. 2, 41012 Seville, Spain
| | - Silvia Pichardo
- Area of Toxicology, Faculty of Pharmacy, University of Seville, Profesor García González no. 2, 41012 Seville, Spain
| | - Ángeles Jos
- Area of Toxicology, Faculty of Pharmacy, University of Seville, Profesor García González no. 2, 41012 Seville, Spain.
| | - Isabel Moreno
- Area of Toxicology, Faculty of Pharmacy, University of Seville, Profesor García González no. 2, 41012 Seville, Spain
| | - Ana M Cameán
- Area of Toxicology, Faculty of Pharmacy, University of Seville, Profesor García González no. 2, 41012 Seville, Spain
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339
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Hilborn ED, Carmichael WW, Soares RM, Yuan M, Servaites JC, Barton HA, Azevedo SMFO. Serologic evaluation of human microcystin exposure. ENVIRONMENTAL TOXICOLOGY 2007; 22:459-63. [PMID: 17696142 DOI: 10.1002/tox.20281] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Microcystins are among the most commonly detected toxins associated with cyanobacteria blooms worldwide. Two episodes of intravenous microcystin exposures occurred among kidney dialysis patients during 1996 and 2001. Analysis of serum samples collected during these episodes suggests that microcystins are detectable as free and bound forms in human serum. Our goal was to characterize the biochemical evidence for human exposure to microcystins, to identify uncertainties associated with interpretation of these observed results, and to identify research needs. We analyzed serum samples using enzyme-linked immunosorbent assay (ELISA) methods to detect free microcystins, and gas chromatography/mass spectrometry (GC/MS) to detect 2-methyl-3-methoxy-4-phenylbutyric acid (MMPB). MMPB is derived from both free and protein-bound microcystins by chemical oxidation, and it appears to represent total microcystins present in serum. We found evidence of free microcystins in patient serum for more than 50 days after the last documented exposure. Serum concentrations of free microcystins were consistently lower than MMPB quantification of total microcystins: free microcystins as measured by ELISA were only 8-51% of total microcystin concentrations as detected by the GC/MS method. After intravenous exposure episodes, we found evidence of microcystins in human serum in free and protein-bound forms, though the nature of the protein-bound forms is uncertain. Free microcystins appear to be a small but variable subset of total microcystins present in human serum. Research is needed to elucidate the human toxicokinetics of microcystins, in part to determine how observed serum concentrations can be used to estimate previous microcystin exposure.
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Affiliation(s)
- E D Hilborn
- United States Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Research Triangle Park, North Carolina, USA
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340
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Pichardo S, Jos A, Zurita JL, Salguero M, Cameán AM, Repetto G. Acute and subacute toxic effects produced by microcystin-YR on the fish cell lines RTG-2 and PLHC-1. Toxicol In Vitro 2007; 21:1460-7. [PMID: 17706912 DOI: 10.1016/j.tiv.2007.06.012] [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] [Received: 03/14/2007] [Revised: 06/01/2007] [Accepted: 06/11/2007] [Indexed: 10/23/2022]
Abstract
Approximately 80 microcystins (MCs) variants have been isolated in surface water worldwide. The toxicity of the most frequently MCs are encountered, MC-LR and MC-RR, has been extensively studied in humans and animals. However, studies dealing with MC-YR toxicity are still scarce. In this work, the toxic effects of MC-YR were investigated in the fish cell line PLHC-1, derived from a hepatocellular carcinoma of the topminnow Poeciliopsis lucida, and RTG-2 fibroblast-like cells derived from the gonads of rainbow trout Oncorhynchus mykiss. After 48 h, morphological and biochemical changes (total protein content, neutral red uptake and methylthiazol tetrazolium salt metabolization) were determined. The most sensitive endpoint for both cell lines was the reduction of total protein content, with EC(50) values of 35 microM for PLHC-1 cells and 67 microM for the RTG-2 cell line. Lysosomal function and methylthiazol tetrazolium salt metabolization were stimulated at low concentrations, while they decreased at high doses. Increase of piknotic cells, rounding effects, reduction in cell number and cell size, hydropic degeneration, and death mainly by necrosis but also by apoptosis were observed in the morphological study. Furthermore, PLHC-1 cells are more sensitive than RTG-2 cells to MC-YR exposure. These results were similar to those obtained when both cell lines were exposed for 24h to a Microcystis aeruginosa isolated strain extract containing MC-LR.
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Affiliation(s)
- S Pichardo
- Area of Toxicology, Faculty of Pharmacy, University of Seville, 41012 Seville, Spain
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341
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Abstract
Several transporter families that can transport thyroid hormones have been identified. One of these is represented by the organic anion transporting polypeptide (OATP) gene superfamily, classified within the solute carrier family SLCO. In humans, eleven different OATPs are expressed in various tissues, including the liver, kidney, brain, lung, intestine and placenta. They mediate sodium-independent transport of a variety of amphipathic organic compounds, including thyroid hormones, bile acids, steroid hormones and their conjugates, linear and cyclic peptides, prostaglandins, numerous drugs and other xenobiotics. OATP1C1, which is expressed in the blood-brain barrier and testes, is the thyroid hormone transporter with the highest apparent affinity, with K(m) values of 90.4nM for thyroxine (T(4)) and 127.7nM for reverse T(3) (rT(3)) transport, and could be essential for thyroid hormone delivery to the developing brain. OATP4A1 is expressed in the placenta and could be important for maternal thyroid hormone transport to the developing fetus.
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Affiliation(s)
- Bruno Hagenbuch
- Department of Pharmacology, Toxicology and Therapeutics, The University of Kansas Medical Center, Kansas City, KS 66160, USA.
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342
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Hoeger SJ, Schmid D, Blom JF, Ernst B, Dietrich DR. Analytical and functional characterization of microcystins [Asp3]MC-RR and [Asp3,Dhb7]MC-RR: consequences for risk assessment? ENVIRONMENTAL SCIENCE & TECHNOLOGY 2007; 41:2609-16. [PMID: 17438823 DOI: 10.1021/es062681p] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The microcystin (MC) producing P. rubescens occurs in pre-alpine lakes and may impact fishery success, bathing, and raw water quality. P. rubescens extracts, characterized via LC-MS, contained the two MC-RR variants [Asp3]MC-RR and [Asp3,Dhb7]MC-RR. The protein-phosphatase-inhibition assay (cPPIA with phosphatases 1 and 2A) in its capability to quantify [Asp3]MC-RR, [Asp3,Dhb7]MC-RR, and MC-RR was compared to HPLC-DAD and anti-Adda-ELISA. The IC50 values (PP1 and PP2A) determined for MC-LR, MC-RR, and [Asp3]MC-RR were in the same range (1.9-3.8 and 0.45-0.75 nM). A 50-fold higher concentration of [Asp3,Dhb7]MC-RR (29.8 nM) was necessary to inhibit the PP2A by 50%. The PP1-IC50 of [Asp3,Dhb7]MC-RR was 22-fold higher (56.4 nM) than those of the other MCs, suggesting that specific structural characteristics are responsible for its weaker PPI capacity. Western blots demonstrated that [Asp3,Dhb7]MC-RR does not covalently bind to PP1. [Asp3,Dhb7]MC-RR has comparable in vivo LD50 values to MC-RR, despite a far lower PP-inhibiting capacity, suggesting that toxicodynamic and toxicokinetic characteristics of [Asp3,Dhb7]MC-RR are responsible for its high in vivo toxicity. The data demonstrate that cPPIA analysis of [Asp3,Dhb7]MC-RR-containing samples prevent reliable MC determination and lead to underestimation of potential toxicity.
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Affiliation(s)
- S J Hoeger
- Environmental Toxicology, University of Konstanz, Germany
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343
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Westholm DE, Rumbley JN, Salo DR, Rich TP, Anderson GW. Organic anion-transporting polypeptides at the blood-brain and blood-cerebrospinal fluid barriers. Curr Top Dev Biol 2007; 80:135-70. [PMID: 17950374 DOI: 10.1016/s0070-2153(07)80004-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Organic anion-transporting polypeptides (Oatps) are solute carrier family members that exhibit marked evolutionary conservation. Mammalian Oatps exhibit wide tissue expression with an emphasis on expression in barrier cells. In the brain, Oatps are expressed in the blood-brain barrier endothelial cells and blood-cerebrospinal fluid barrier epithelial cells. This expression profile serves to illustrate a central role for Oatps in transporting endo- and xenobiotics across brain barrier cells. This chapter will detail the expression patterns and substrate specificities of Oatps expressed in the brain, and will place special emphases on the role of Oatps in prostaglandin synthesis and in the transport of conjugated endobiotics.
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Affiliation(s)
- Daniel E Westholm
- College of Pharmacy, University of Minnesota, Duluth, Minnesota 55812, USA
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344
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Meier-Abt F, Hammann-Hänni A, Stieger B, Ballatori N, Boyer JL. The organic anion transport polypeptide 1d1 (Oatp1d1) mediates hepatocellular uptake of phalloidin and microcystin into skate liver. Toxicol Appl Pharmacol 2006; 218:274-9. [PMID: 17198718 DOI: 10.1016/j.taap.2006.11.015] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2006] [Revised: 10/27/2006] [Accepted: 11/10/2006] [Indexed: 11/20/2022]
Abstract
Organic anion transporting polypeptides (rodent Oatp; human OATP) mediate cellular uptake of numerous organic compounds including xenobiotic toxins into mammalian hepatocytes. In the little skate Leucoraja erinacea a liver-specific Oatp (Oatp1d1, also called sOatp) has been identified and suggested to represent an evolutionarily ancient precursor of the mammalian liver OATP1B1 (human), Oatp1b2 (rat), and OATP1B3 (human). The present study tested whether Oatp1d1 shares functional transport activity of the xenobiotic oligopeptide toxins phalloidin and microcystin with the mammalian liver Oatps/OATPs. The phalloidin analogue [(3)H]-demethylphalloin was taken up into skate hepatocytes with high affinity (Km approximately 0.4 microM), and uptake could be inhibited by phalloidin and a variety of typical Oatp/OATP substrates such as bromosulfophthalein, bile salts, estrone-3-sulfate, cyclosporine A and high concentrations of microcystin-LR (Ki approximately 150 microM). When expressed in Xenopus laevis oocytes Oatp1d1 increased uptake of demethylphalloin (Km approximately 2.2 microM) and microcystin-LR (Km approximately 27 microM) 2- to 3-fold over water-injected oocytes, whereas the alternative skate liver organic anion transporter, the dimeric Ostalpha/beta, exhibited no phalloidin and only minor microcystin-LR transport. Also, the closest mammalian Oatp1d1 orthologue, the human brain and testis OATP1C1, did not show any phalloidin transport activity. These results demonstrate that the evolutionarily ancient Oatp1d1 is able to mediate uptake of cyclic oligopeptide toxins into skate liver. The findings support the notion that Oatp1d1 is a precursor of the liver-specific mammalian Oatps/OATPs and that its transport properties are closely associated with certain forms of toxic liver injury such as for example protein phosphatase inhibition by the water-borne toxin microcystin.
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Affiliation(s)
- F Meier-Abt
- Mount Desert Island Biological Laboratories (MDIBL), Salsbury Cove, Maine 04672, USA
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345
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Abstract
Drug-induced liver injury is an important clinical problem with significant morbidity and mortality. Whereas for most hepatocellular forms of drug-induced hepatic injury the underlying pathophysiological mechanism is poorly understood, there is increasing evidence that cholestatic forms of drug-induced liver damage result from a drug- or metabolite-mediated inhibition of hepatobiliary transporter systems. In addition to their key role in determining hepatic drug exposure and clearance, the coordinated action of these transport systems is essential for bile formation and the biliary secretion of cholephilic compounds and xenobiotics. Any drug-mediated functional disturbance of these processes can lead to an intracellular accumulation of potentially harmful bile constituents and result in the development of cholestatic liver cell damage. In addition to direct drug-mediated inhibition of hepatocellular transport, function of these transporters can be altered by pre-existing hepatic disease and genetic factors, which contribute to the development of drug-induced cholestasis in susceptible individuals. This review summarizes current knowledge about the function of hepatobiliary uptake and efflux systems and discusses factors that might predispose to drug-induced cholestasis.
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Affiliation(s)
- Christiane Pauli-Magnus
- Division of Clinical Pharmacology and Toxicology, University Hospital Zurich, Zurich, Switzerland.
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346
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Huber RD, Gao B, Sidler Pfändler MA, Zhang-Fu W, Leuthold S, Hagenbuch B, Folkers G, Meier PJ, Stieger B. Characterization of two splice variants of human organic anion transporting polypeptide 3A1 isolated from human brain. Am J Physiol Cell Physiol 2006; 292:C795-806. [PMID: 16971491 DOI: 10.1152/ajpcell.00597.2005] [Citation(s) in RCA: 123] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
In the present study we isolated two splice variants of organic anion transporting polypeptide 3A1 (OATP3A1_v1 and OATP3A1_v2) from human brain. OATP3A1_v2 lacks 18 amino acids (aa) at the COOH-terminal end (692 aa) but is otherwise similar in sequence to OATP3A1_v1 (710 aa). OATP3A1_v1 exhibits a wide tissue distribution, with expression in testis, various brain regions, heart, lung, spleen, peripheral blood leukocytes, and thyroid gland, whereas OATP3A1_v2 is predominantly expressed in testis and brain. On the cellular and subcellular levels OATP3A1_v1 could be immunolocalized in testicular germ cells, the basolateral plasma membrane of choroid plexus epithelial cells, and neuroglial cells of the gray matter of human frontal cortex. Immunolocalization of OATP3A1_v2 included Sertoli cells in testis, apical and/or subapical membranes in choroid plexus epithelial cells, and neurons (cell bodies and axons) of the gray and white matter of human frontal cortex. The rodent ortholog Oatp3a1 was also widely distributed in rat brain, and its localization included somatoneurons as well as astroglial cells. Transport studies in cRNA-injected Xenopus laevis oocytes and in stably transfected Chinese hamster ovary FlpIn cells revealed a similar broad substrate specificity for both splice variants. Transported substrates include prostaglandin (PG)E(1) and PGE(2), thyroxine, and the cyclic oligopeptides BQ-123 (endothelin receptor antagonist) and vasopressin. These studies provide further evidence for the involvement of OATPs in oligopeptide transport. They specifically suggest that OATP3A1 variants might be involved in the regulation of extracellular vasopressin concentration in human brain and thus might influence the neuromodulation of neurotransmission by cerebral neuropeptides such as vasopressin.
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Affiliation(s)
- Robert D Huber
- Univ. Hospital, Dept. of Internal Medicine, Institute of Clinical Pharmacology and Toxicology, 8091 Zurich, Switzerland
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347
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Smith NF, Figg WD, Sparreboom A. Role of the liver-specific transporters OATP1B1 and OATP1B3 in governing drug elimination. Expert Opin Drug Metab Toxicol 2006; 1:429-45. [PMID: 16863454 DOI: 10.1517/17425255.1.3.429] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Members of the organic anion transporting polypeptide (OATP) family are responsible for the cellular uptake of a broad range of endogenous compounds and xenobiotics in multiple tissues. This review focuses on OATP1B1 and -1B3, which are specifically expressed in the liver and considered to be of particular importance for hepatic drug elimination and drug pharmacokinetics. Recent literature has indicated that inhibition of these transporters may result in drug-drug interactions. Furthermore, genetic polymorphisms in the genes encoding OATP1B1 and -1B3 have been described that increase or decrease transport in vitro and in vivo. Alteration of transporter function by either of these mechanisms may contribute to interindividual variability in drug disposition and response. In this review an update of this rapidly emerging field is provided.
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Affiliation(s)
- Nicola F Smith
- National Cancer Institute, Molecular Pharmacology Section, Medical Oncology Branch, Center for Cancer Research, 9000 Rockville Pike, Bethesda, MD 20892, USA.
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348
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349
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Meier-Abt F, Mokrab Y, Mizuguchi K. Organic anion transporting polypeptides of the OATP/SLCO superfamily: identification of new members in nonmammalian species, comparative modeling and a potential transport mode. J Membr Biol 2006; 208:213-27. [PMID: 16648940 DOI: 10.1007/s00232-005-7004-x] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2005] [Revised: 12/05/2005] [Indexed: 01/28/2023]
Abstract
Organic anion-transporting polypeptides (human, OATPs; other animals, Oatps; gene symbol, SLCO/Slco) form a transport protein superfamily that mediates the translocation of amphipathic substrates across the plasma membrane of animal cells. So far, OATPs/Oatps have been identified in human, rat and mouse tissues. In this study, we used bioinformatic tools to detect new members of the OATP/SLCO superfamily in nonmammalian species and to build models for the three-dimensional structure of OATPs/Oatps. New OATP/SLCO superfamily members, some of which form distinct novel families, were identified in chicken, zebrafish, frog, fruit fly and worm species. The lack of OATP/SLCO superfamily members in plants, yeast and bacteria suggests the emergence of an ancient Oatp protein in an early ancestor of the animal kingdom. Structural models were generated for the representative members OATP1B3 and OATP2B1 based on the known structures of the major facilitator superfamily of transport proteins. A model was also built for the large extracellular region between transmembrane helices 9 and 10, following the identification of a novel homology with the Kazal-type serine protease inhibitors. Along with the electrostatic potential and the conservation of key amino acid residues, we propose a common transport mechanism for all OATPs/Oatps, whereby substrates are translocated through a central, positively charged pore in a rocker-switch type of mechanism. Several amino acid residues were identified that may play crucial roles in the proposed transport mechanism.
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Affiliation(s)
- Fabienne Meier-Abt
- Department of Biochemistry, University of Cambridge, Old Addenbrookes Site, 80 Tennis Court Road, Cambridge, CB1 1GA, United Kingdom
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350
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König J, Seithel A, Gradhand U, Fromm MF. Pharmacogenomics of human OATP transporters. Naunyn Schmiedebergs Arch Pharmacol 2006; 372:432-43. [PMID: 16525793 DOI: 10.1007/s00210-006-0040-y] [Citation(s) in RCA: 253] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2005] [Accepted: 01/23/2006] [Indexed: 01/27/2023]
Abstract
Organic anion transporting polypeptides (OATPs) mediate the uptake of a broad range of compounds into cells. Substrates for members of the OATP family include bile salts, hormones, and steroid conjugates as well as drugs like the HMG-CoA-reductase inhibitors (statins), cardiac glycosides, anticancer agents like methotrexate, and antibiotics like rifampicin. OATPs are expressed in a variety of different tissues, including intestine, liver, kidney, and brain, suggesting that they play a critical role in drug absorption, distribution, and excretion. The identification and functional characterisation of naturally occurring variations in genes encoding human OATP (SLCO) family members is in the focus of transporter research. As a result of their broad substrate spectrum and their wide tissue distribution, altered transport characteristics or protein localisation can contribute significantly to interindividual variations of drug effects. The analysis of the consequences of genetic variations in genes encoding transport proteins may, therefore, contribute to a better understanding of interindividual differences in drug effects and to individualise treatment regimens with drugs that are substrates for human OATP proteins. In this review, we summarise the current knowledge on genetic variations in transporter genes encoding human OATP family members and their functional consequences analysed by in vitro and in vivo studies.
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Affiliation(s)
- Jörg König
- Institute for Experimental and Clinical Pharmacology and Toxicology, Friedrich-Alexander-University Erlangen-Nuremberg, Fahrstr. 17, 91054, Erlangen, Germany.
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