1
|
Cai F, Liu J, Li C, Wang J. Intracellular Calcium Plays a Critical Role in the Microcystin-LR-Elicited Neurotoxicity Through PLC/IP3 Pathway. Int J Toxicol 2015; 34:551-8. [PMID: 26395499 DOI: 10.1177/1091581815606352] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Neurotoxicity of microcystin-leucine-arginine (MCLR) has been widely reported. However, the mechanism is not fully understood. Using primary hippocampal neurons, we tested the hypothesis that MCLR-triggered activation in intracellular free calcium concentration ([Ca(2+)](i)) induces the death of neurons. Microcystin-leucine-arginine inhibited cell viability at a range of 0.1 to 30 μmol/L and caused a dose-dependent increase in [Ca(2+)](i). This increase in [Ca(2+)](i) was observed in Ca(2+)-free media and blocked by an endoplasmic reticulum Ca(2+) pump inhibitor, suggesting intracellular Ca(2+) release. Moreover, pretreatment of hippocampal neurons with intracellular Ca(2+) chelator (O,O'-bis (2-aminophenyl) ethyleneglycol-N,N,N',N'-tetraacetic acid, tetraacetoxy-methyl ester) and inositol 1,4,5-trisphosphate receptor antagonist (2-aminoethoxydiphenyl borate) could block both the Ca(2+) mobilization and the neuronal death following MCLR exposure. In contrast, the ryanodine receptor inhibitor (dantrolene) did not ameliorate the effect of MCLR. In conclusion, MCLR disrupts [Ca(2+)](i) homeostasis in neurons by releasing Ca(2+) from intracellular stores, and this increase in [Ca(2+)](i) may be a key determinant in the mechanism underlying MCLR-induced neurotoxicity.
Collapse
Affiliation(s)
- Fei Cai
- Department of Pharmacology, Hubei University of Science and Technology, Xianning, China
| | - Jue Liu
- Department of Pharmacy, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Cairong Li
- Hubei Province Key Laboratory on Cardiovascular, Cerebrovascular, and Metabolic Disorders, Hubei University of Science and Technology, Xianning, Hubei, China
| | - Jianghua Wang
- Fisheries College, Huazhong Agricultural University, Wuhan, China
| |
Collapse
|
2
|
Mechanisms of microcystin-LR-induced cytoskeletal disruption in animal cells. Toxicon 2015; 101:92-100. [DOI: 10.1016/j.toxicon.2015.05.005] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2015] [Revised: 05/06/2015] [Accepted: 05/12/2015] [Indexed: 12/31/2022]
|
3
|
Zhao Y, Xie P, Tang R, Zhang X, Li L, Li D. In vivo studies on the toxic effects of microcystins on mitochondrial electron transport chain and ion regulation in liver and heart of rabbit. Comp Biochem Physiol C Toxicol Pharmacol 2008; 148:204-10. [PMID: 18590982 DOI: 10.1016/j.cbpc.2008.05.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2008] [Revised: 05/19/2008] [Accepted: 05/20/2008] [Indexed: 11/24/2022]
Abstract
This study examined the toxic effects of microcystins on mitochondria of liver and heart of rabbit in vivo. Rabbits were injected i.p. with extracted microcystins (mainly MC-RR and -LR) at two doses, 12.5 and 50 MC-LReq. microg/kg bw, and the changes in mitochondria of liver and heart were studied at 1, 3, 12, 24 and 48 h after injection. MCs induced damage of mitochondrial morphology and lipid peroxidation in both liver and heart. MCs influenced respiratory activity through inhibiting NADH dehydrogenase and enhancing succinate dehydrogenase (SDH). MCs altered Na(+)-K(+)-ATPase and Ca(2+)-Mg(2+)-ATPase activities of mitochondria and consequently disrupted ionic homeostasis, which might be partly responsible for the loss of mitochondrial membrane potential (MMP). MCs were highly toxic to mitochondria with more serious damage in liver than in heart. Damage of mitochondria showed reduction at 48 h in the low dose group, suggesting that the low dose of MCs might have stimulated a compensatory response in the rabbits.
Collapse
Affiliation(s)
- Yanyan Zhao
- Fisheries College of Huazhong Agricultural University; Key Lab of Agricultural Animal Genetics, Breeding and Reproduction of Ministry of Education, Wuhan 430070, People's Republic of China
| | | | | | | | | | | |
Collapse
|
4
|
Zurawell RW, Chen H, Burke JM, Prepas EE. Hepatotoxic cyanobacteria: a review of the biological importance of microcystins in freshwater environments. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART B, CRITICAL REVIEWS 2005; 8:1-37. [PMID: 15762553 DOI: 10.1080/10937400590889412] [Citation(s) in RCA: 303] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Cyanobacteria possess many adaptations to develop population maxima or "blooms" in lakes and reservoirs. A potential consequence of freshwater blooms of many cyanobacterial species is the production of potent toxins, including the cyclic hepatotoxins, microcystins (MCs). Approximately 70 MC variants have been isolated. Their toxicity to humans and other animals is well studied, because of public health concerns. This review focuses instead on the production and degradation of MCs in freshwater environments and their effects on aquatic organisms. Genetic research has revealed the existence of MC-related genes, yet the expression of these genes seems to be regulated by complex mechanisms and is influenced by environmental factors. In natural water bodies, the species composition of cyanobacterial communities and the ratio of toxic to nontoxic species and strains are largely responsible for total toxin production. Cyanobacteria play vital roles in aquatic food webs, yet production, accumulation, and toxicity patterns of MCs within aquatic food webs remain obscure.
Collapse
Affiliation(s)
- Ronald W Zurawell
- Department of Biological Sciences, Biological Sciences Building, University of Alberta, Edmonton, Alberta, Canada
| | | | | | | |
Collapse
|
5
|
Ding WX, Shen HM, Ong CN. Calpain activation after mitochondrial permeability transition in microcystin-induced cell death in rat hepatocytes. Biochem Biophys Res Commun 2002; 291:321-31. [PMID: 11846407 DOI: 10.1006/bbrc.2002.6453] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Previous studies have shown that microcystin-LR (MLR), a specific hepatotoxin, induces onset of mitochondrial permeability transition (MPT) and apoptosis in cultured rat hepatocytes. Here we attempted to investigate the downstream events after the onset of MPT in MLR-treated hepatocytes. Various mitochondrial electron transport chain (ETC) inhibitors effectively prevented the onset of MPT, suggesting that the mitochondrial ETC plays an important role in MLR-induced MPT. MLR also induced mitochondrial cytochrome c release, which can be prevented by a specific MPT inhibitor (cyclosporin A, CsA), and by various ETC inhibitors. Interestingly, the release of cytochrome c did not activate caspase-9 and -3, the main caspases involved in apoptosis. Instead, MLR activated calpain in rat hepatocytes, probably through the increase of intracellular Ca(2+) released from mitochondria. Both ALLN and ALLM, two calpain inhibitors, significantly blocked MLR-induced calpain activation and subsequent cell death. CsA also prevented MLR-induced calpain activation and cell death, suggesting that the activation of calpain may be a post-mitochondrial event. These data demonstrate for the first time that calpain rather than caspases plays an important role in MLR-induced apoptosis.
Collapse
Affiliation(s)
- Wen-Xing Ding
- Center for Environmental and Occupational Health, Department of Community, Occupational, and Family Medicine, Faculty of Medicine, National University of Singapore, Singapore 117597, Singapore
| | | | | |
Collapse
|
6
|
McDermott CM, Nho CW, Howard W, Holton B. The cyanobacterial toxin, microcystin-LR, can induce apoptosis in a variety of cell types. Toxicon 1998; 36:1981-96. [PMID: 9839682 DOI: 10.1016/s0041-0101(98)00128-7] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Cyanobacterial toxins, especially the microcystins (MCYST), are found in eutrophied waters throughout the world. These toxins cause hepatocyte damage by inhibiting protein phosphatases 1 and 2A, resulting in hyperphosphorylation of cytoskeletal proteins. Acute intoxication of animals and humans has been reported following MCYST exposure. Okadaic acid, a marine biotoxin, has a similar mechanism of action to MCYST and has been shown to cause apoptosis, a form of programmed cell death, in a variety of cell types. In this study, primary rat hepatocytes (in suspension and monolayer culture), human fibroblasts, human endothelial cells, human epithelial cells, and rat promyelocytes were observed following treatment with MCYST for morphological and biochemical changes typical of apoptosis. Hepatocytes underwent cell membrane blebbing, cell shrinkage, organelle redistribution, and chromatin condensation as early as 30 min following MCYST application (0.8 microM). Other cell types treated with MCYST (100 microM) also showed these morphological changes, but required a longer period of treatment. DNA fragmentation and "ladder" formation occurred in most cell types exposed to MCYST. These observations demonstrate that MCYST causes apoptosis in a variety of mammalian cells.
Collapse
Affiliation(s)
- C M McDermott
- Department of Biology and Microbiology, Halsey Science Center, University of Wisconsin Oshkosh, 54901, USA
| | | | | | | |
Collapse
|
7
|
Lakshmana Rao PV, Bhattacharya R, Parida MM, Jana AM, Bhaskar AS. Freshwater cyanobacterium Microcystis aeruginosa (UTEX 2385) induced DNA damage in vivo and in vitro. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 1998; 5:1-6. [PMID: 21781844 DOI: 10.1016/s1382-6689(97)00022-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/1996] [Revised: 05/21/1997] [Accepted: 05/29/1997] [Indexed: 05/31/2023]
Abstract
Microcystins are a family of potent hepatotoxins and liver tumor promoters produced by several genera of cyanobacteria including Microcystis, Nodularia, Anabena, Nostoc, etc. They are chemically very stable and represent a public health threat when they occur in water used for human consumption. We investigated the DNA damage effects of M. aeruginosa UTEX 2385 in mouse liver in vivo and also in mammalian cells in vitro. The DNA damage effect is compared with purified toxin microcystin-LR (MCLR) in non-hepatic cells viz. baby hamster kidney cells (BHK-21) and mouse embryo fibroblasts primary cells (MEF). Cell-free extracts of UTEX 2385 induced significant DNA fragmentation at 0.5, 1 and 2 LD(50) (32.7, 65.4 and 130.8 mg/kg, respectively) and it was also time dependent. M. aeruginosa UTEX 2385 and MCLR induced significant DNA fragmentation in BHK-21 and MEF cells at 100 and 1.0 μg/ml concentration. Electrophoretic analysis revealed necrotic DNA damage by UTEX 2385 in vivo. Both the toxins caused smear in agarose gel electrophoresis indicating the necrotic DNA damage in MEF cells, whereas, multiple DNA fragments in BHK-21 cells. The DNA damage effect of the toxin is supported by data on hepatotoxicity in vivo and cytotoxicity in vitro.
Collapse
Affiliation(s)
- P V Lakshmana Rao
- Division of Pharmacology and Toxicology, Defence Research and Development Establishment, Gwalior-474002, India
| | | | | | | | | |
Collapse
|
8
|
Wickstrom ML, Khan SA, Haschek WM, Wyman JF, Eriksson JE, Schaeffer DJ, Beasley VR. Alterations in microtubules, intermediate filaments, and microfilaments induced by microcystin-LR in cultured cells. Toxicol Pathol 1995; 23:326-37. [PMID: 7659955 DOI: 10.1177/019262339502300309] [Citation(s) in RCA: 93] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Microcystin-LR (MCLR) is a cyanobacterial hepatotoxin that inhibits intracellular serine/threonine protein phosphatases causing disruption of actin microfilaments (MFs) and intermediate filaments (IFs) in hepatocytes. This study compared the effects of MCLR on the organization of MFs, IFs, and microtubules (MTs) in hepatocytes and nonhepatocyte cell lines and determined the sequence of toxin-induced changes in these cytoskeletal components. Rat renal epithelial cells and fibroblasts were incubated with MCLR at 100 or 200 microM for 6-18 hr. Rat hepatocytes in primary culture were exposed to the toxin at 1 or 10 microM for 2-64 min. Cells were fixed and incubated with primary antibodies against beta-tubulin, actin, and vimentin or cytokeratin IFs, followed by gold-labeled secondary antibodies with silver enhancement of the gold probe. The fraction of fibroblasts and hepatocytes with altered cytoskeletal morphology was evaluated as a function of MCLR dose and exposure time to assess the sequence of changes in cytoskeletal components. Changes in fibroblasts and some hepatocytes were characterized initially by disorganization of IFs, followed rapidly by disorganization of MTs, with the progressive collapse of both cytoskeletal components around cell nuclei. Many hepatocytes exhibited MT changes prior to effects on IF structure. Alterations in MFs occurred later and included initial aggregation of actin under the plasma membrane, followed by condensation into rosette-like structures and eventual complete collapse into a dense perinuclear bundle. The similarity of effects among different cell types suggests a common mechanism of action, but the independent kinetics of IF and MT disruption in hepatocytes suggests that there may be at least 2 sites of phosphorylation that lead to cytoskeletal alterations.
Collapse
Affiliation(s)
- M L Wickstrom
- Department of Veterinary Biosciences, University of Illinois, Urbana 61801, USA
| | | | | | | | | | | | | |
Collapse
|
9
|
Khan SA, Ghosh S, Wickstrom M, Miller LA, Hess R, Haschek WM, Beasley VR. Comparative pathology of microcystin-LR in cultured hepatocytes, fibroblasts, and renal epithelial cells. NATURAL TOXINS 1995; 3:119-28. [PMID: 7648020 DOI: 10.1002/nt.2620030302] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The cyanobacterial toxin microcystin-LR (MCLR) is a potent inhibitor of protein phosphatases 1 and 2A, and is selectively toxic to the liver in vivo and to isolated hepatocytes in vitro. This selectivity is believed to be due to toxin uptake via bile acid carriers. We investigated at the light and ultrastructural levels the effects of high concentrations of MCLR and long incubation times to determine in vitro whether fibroblasts and kidney cells (non-target cells) respond in the same manner as do hepatocytes (target cells) at low concentrations and short incubation times. Cultured rat skin fibroblasts (ATCC 1213) and rat kidney epithelial cells (ATCC 1571) were incubated with with MCLR at 133 microM for 1-24 hr. Lesions in these cells were compared with those in cultured hepatocytes incubated MCLR at 13.3 microM from 1 to 32 min. Lesions in hepatocytes, kidney cells, and fibroblasts were noted at 4 min, 1 hr, and 8 hr, respectively, after initial exposure to MCLR. Lesions in all three cell types progressed and included plasma membrane blebbing, loss of cell-to-cell contact, clumping and rounding of cells, cytoplasmic vacuolization, and redistribution of cytoplasmic organelles. Loss of microvilli, whorling of rough endoplasmic reticulum, dense staining and dilated cristae in mitochondria, and pinching off of membrane blebs were noted only in hepatocytes. Nuclear changes typical of apoptosis were observed only in fibroblasts and kidney cells. Similarities in responses of different cell types to MCLR exposure probably reflect a common biochemical mechanism of action, i.e., inhibition of protein phosphatases 1 and 2A as described by others.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
Affiliation(s)
- S A Khan
- Department of Veterinary Biosciences, College of Veterinary Medicine, University of Illinois, Urbana 61801, USA
| | | | | | | | | | | | | |
Collapse
|
10
|
Thompson W, Pace J. Substances that protect cultured hepatocytes from the toxic effects of microcystin-LR. Toxicol In Vitro 1992; 6:579-87. [DOI: 10.1016/0887-2333(92)90071-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/1991] [Revised: 03/31/1992] [Indexed: 11/26/2022]
|
11
|
Sepulveda MS, Rojas M, Zambrano F. Inhibitory effect of a Microcystis sp (cyanobacteria) toxin on development of preimplantation mouse embryos. ACTA ACUST UNITED AC 1992; 102:549-53. [PMID: 1360361 DOI: 10.1016/0742-8413(92)90157-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
1. A soluble toxin, purified from the algae bloom of an eutrophic lake dominated by Microcystis, is a very effective inhibitor of early embryo development in a dose-response relationship. 2. Two- and 8-cell mouse embryos under the influence of Microcystis toxin do not reach the developmental stages of morula and blastocyst, respectively. 3. Actin cortex is disorganized without change in the microtubules structure. 4. Results are discussed in terms of the possible mechanisms by which the toxin arrests development considering, specifically, effects on the cytoskeleton and/or on voltage-insensitive transmembrane Ca2+ channels.
Collapse
Affiliation(s)
- M S Sepulveda
- Departamento de Biologia, Facultad de Ciencias, Universidad de Chile
| | | | | |
Collapse
|
12
|
Falconer IR, Yeung DS. Cytoskeletal changes in hepatocytes induced by Microcystis toxins and their relation to hyperphosphorylation of cell proteins. Chem Biol Interact 1992; 81:181-96. [PMID: 1370395 DOI: 10.1016/0009-2797(92)90033-h] [Citation(s) in RCA: 169] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The heptapeptide toxins produced by the blue-green alga (cyanobacterium) Microcystis aeruginosa are selectively hepatotoxic in mammals. The characteristic post-mortem pathology of the liver is extensive lobular disruption due to sinusoidal breakdown, leakage of blood into the tissue and hepatocyte disintegration. Isolated hepatocytes incubated with toxin show severe structural deformity and surface blebbing. This paper demonstrates the effects of Microcystis toxins on the contraction and aggregation of actin microfilaments, and on the relocation and breakdown of cytokeratin intermediate filaments, in cultured hepatocytes. Earlier work did not show changes in the assembly/disassembly of actin; however, this paper demonstrates the change in cytokeratin from intermediate filaments to distributed granules in the cytoplasm of toxin-affected cells. Acrylamide gel electrophoresis of cytoskeletal fractions from hepatocytes did not show changes in total cytokeratins; however, marked changes in the immunogenicity of cytokeratins at 52 and 58 kDa were seen on toxin exposure of cells. Measurement of 32P-phosphorylation of proteins in toxin-affected cells incubated with [32P]orthophosphate showed a dramatic increase compared to control incubations. This is in agreement with research elsewhere describing phosphatase inhibition in vitro by Microcystis toxins. The data indicate that phosphorylated cytokeratin is a major component of cytoplasmic fraction phosphorylated protein after toxin exposure to hepatocytes. It is concluded that the mechanism of Microcystis toxicity to the hepatocyte is through cytoskeletal damage leading to loss of cell morphology, cell to cell adhesion and finally cellular necrosis. The underlying biochemical lesion is likely to be phosphatase inhibition causing hyperphosphorylation of a number of hepatocyte proteins, including those cytokeratins responsible for microfilament orientation and intermediate filament integrity.
Collapse
Affiliation(s)
- I R Falconer
- Department of Biochemistry, Microbiology and Nutrition, University of New England, Armidale, N.S.W., Australia
| | | |
Collapse
|
13
|
Bøe R, Gjertsen BT, Vintermyr OK, Houge G, Lanotte M, Døskeland SO. The protein phosphatase inhibitor okadaic acid induces morphological changes typical of apoptosis in mammalian cells. Exp Cell Res 1991; 195:237-46. [PMID: 1647324 DOI: 10.1016/0014-4827(91)90523-w] [Citation(s) in RCA: 238] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Okadaic acid, a specific and potent inhibitor of protein phosphatases 2A and 1, was tested for its effect on the morphology of a number of cell types: freshly isolated rat hepatocytes in suspension or in primary culture, the human mammary carcinoma cell line MCF-7, the human neuroblastoma cell line SK-N-SH, rat pituitary adenoma GH3 cells, and rat promyelocytic IPC-81 cells. All the cell types reacted within a few hours to okadaic acid in the concentration range 0.1 to 1 microM with profound morphological alterations. Among the changes noted were: condensation of chromatin, shedding of cell contents via surface bleb formation, redistribution and compacting of cytoplasmic organelles, formation of cytoplasmic vacuoles, and hyperconvolution of the nuclear membrane. In some cells nuclear fragmentation was noted. In addition, cells growing as monolayers rounded up and detached from the substratum. The treated cells had no swollen mitochondria and retained the ability to exclude trypan blue until the final stage of dissolution, supporting the hypothesis that the changes were apoptotic rather than necrotic. In hepatocytes the action of okadaic acid was mimicked by another phosphatase inhibitor, microcystin, and was accompanied by shrinkage of the cell volume, as judged by Coulter counter analysis. The action of phosphatase inhibitor was not abolished by protein synthesis inhibitors, Ca(2+)-depleted medium, or phorbol ester. Although hepatocyte DNA replication was very sensitive to inhibition by okadaic acid, DNA fragmentation was less pronounced in response to okadaic acid than other agents inducing the morphological appearance of apoptosis.
Collapse
Affiliation(s)
- R Bøe
- Department of Anatomy, University of Bergen, Norway
| | | | | | | | | | | |
Collapse
|
14
|
Mereish KA, Bunner DL, Ragland DR, Creasia DA. Protection against microcystin-LR-induced hepatotoxicity by Silymarin: biochemistry, histopathology, and lethality. Pharm Res 1991; 8:273-7. [PMID: 1902564 DOI: 10.1023/a:1015868809990] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Microcystin-LR, a cyclic heptapeptide synthesized by the blue-green algae, Microcystis aeruginosa, is a potent hepatotoxin. Pathological examination of livers from mice and rats that received microcystin-LR revealed severe, peracute, diffuse, centrilobular hepatocellular necrosis, and hemorrhage. These changes were correlated with increased serum activities of sorbitol dehydrogenase, alanine aminotransferase, and lactate dehydrogenase. Pretreatment of either rats or mice with a single dose of silymarin, a flavonolignane isolated from the wild artichoke (Silybum marianum L. Gaertn), completely abolished the lethal effects, pathological changes, and significantly decreased the levels of serum enzymes induced by microcystin-LR intoxication.
Collapse
Affiliation(s)
- K A Mereish
- Medical Division, U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, Maryland 21702-5011
| | | | | | | |
Collapse
|
15
|
Runnegar MT, Gerdes RG, Falconer IR. The uptake of the cyanobacterial hepatotoxin microcystin by isolated rat hepatocytes. Toxicon 1991; 29:43-51. [PMID: 1903001 DOI: 10.1016/0041-0101(91)90038-s] [Citation(s) in RCA: 94] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Microcystin-YM a cyclic heptapeptide hepatotoxin isolated from the cyanobacterium Microcystis aeruginosa was radiolabeled with 125I, and used to investigate the uptake of the toxin by freshly isolated rat hepatocytes. The uptake was temperature dependent with apparent activation energy of 18 kcal/mole (77 kJ/mole) for the initial rate of uptake. Uptake of non-toxic (10-20 nM) doses of microcystin by hepatocytes continued with time, the intracellular to extracellular distribution ratio for the toxin was 70 at 60 min for 10(6) cells/ml. Uptake of higher doses of microcystin (100 nM and more) stopped when the cells blebbed: a toxic response of hepatocytes to microcystin. Uptake of microcystin by hepatocytes was inhibited 70-80% by the addition of 10 microM sodium deoxycholate or bromsulphthlein, compounds that protect hepatocytes from the toxic effects of microcystin.
Collapse
Affiliation(s)
- M T Runnegar
- Department of Biochemistry, Microbiology, and Nutrition, University of New England, Armidale, NSW, Australia
| | | | | |
Collapse
|
16
|
Hermansky SJ, Stohs SJ, Markin RS, Murray WJ. Hepatic lipid peroxidation, sulfhydryl status, and toxicity of the blue-green algal toxin microcystin-LR in mice. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH 1990; 31:71-91. [PMID: 2120461 DOI: 10.1080/15287399009531438] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Microcystin-LR (MCLR), a cyclic heptapeptide produced by the blue-green algae Microcystis aeruginosa, produces death in female mice treated with 100 micrograms MCLR/kg. Kupffer-cell hyperplasia was observed histologically after treatment with 50 or 100 micrograms MCLR/kg. No other changes or lethality were observed with the 50 micrograms MCLR/kg, while 100% lethality occurred in less than 2 h in mice treated with 100 micrograms/kg. In these animals liver weights increased by 45% and hepatic hemoglobin content increased 106% at 60 min posttreatment. Liver histology showed loss of hepatic architecture and necrosis 30 min after treatment, and congestion with blood became evident at 45 min after treatment. Serum enzymes were significantly increased 45 min posttreatment. Hepatic nonprotein sulfhydryl content decreased 19% when calculated on the basis of cytosolic protein and 39% when based upon the total protein content, respectively. The sulfhydryl content of the liver cytoskeletal fraction decreased 26% by 30 min after treatment. Decreased enzyme-mediated and increased non-enzyme-mediated lipid peroxidation were observed in hepatic microsomes following both in vivo and in vitro exposure of hepatic microsomes to MCLR. The toxicity of MCLR may be related to alterations in the sulfhydryl content of the cytoskeletal protein. Furthermore, MCLR may either directly or indirectly affect microsomes, suggesting alterations in structure and function of smooth endoplasmic reticulum.
Collapse
Affiliation(s)
- S J Hermansky
- Department of Pharmaceutical Science, University of Nebraska Medical Center, Omaha
| | | | | | | |
Collapse
|
17
|
Eriksson JE, Grönberg L, Nygård S, Slotte JP, Meriluoto JA. Hepatocellular uptake of 3H-dihydromicrocystin-LR, a cyclic peptide toxin. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1025:60-6. [PMID: 2369577 DOI: 10.1016/0005-2736(90)90190-y] [Citation(s) in RCA: 136] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The cellular uptake of microcystin-LR, a cyclic heptapeptide hepatotoxin from the cyanobacterium Microcystis aeruginosa, was studied by means of a radiolabelled derivative of the toxin. 3H-dihydromicrocystin-LR. The uptake of 3H-dihydromicrocystin-LR was shown to be specific for freshly isolated rat hepatocytes whereas the uptake in the human hepatocarcinoma cell line Hep G2 as well as the mouse fibroblast cell line NIH-3T3, and the human neuroblastoma cell line SH-SY5Y, was negligible. By means of a surface barostat technique it was shown that the membrane penetrating capacity (surface activity) of microcystin-LR was low, indicating that the toxin requires an active uptake mechanism. The hepatocellular uptake of microcystin-LR could be inhibited in the presence of bile acid transport inhibitors such as antamanide (5 microM), sulfobromophthalein (50 microM) and rifampicin (30 microM). The uptake was also reduced in a concentration dependent manner when the hepatocytes were incubated in the presence the bile salts cholate and taurocholate. A complete inhibition of the hepatocellular uptake was achieved by 100 microM of either bile salt. The overall results indicate that the uptake of microcystin-LR is through the multispecific transport system for bile acids. This mechanism of cell entry would explain the previously observed cell specificity and organotropism of microcystin-LR.
Collapse
Affiliation(s)
- J E Eriksson
- Department of Biology, Abo Akademi University, Turku, Finland
| | | | | | | | | |
Collapse
|
18
|
MacKintosh C, Beattie KA, Klumpp S, Cohen P, Codd GA. Cyanobacterial microcystin-LR is a potent and specific inhibitor of protein phosphatases 1 and 2A from both mammals and higher plants. FEBS Lett 1990; 264:187-92. [PMID: 2162782 DOI: 10.1016/0014-5793(90)80245-e] [Citation(s) in RCA: 1098] [Impact Index Per Article: 32.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The cyclic heptapeptide, microcystin-LR, inhibits protein phosphatases 1 (PP1) and 2A (PP2A) with Ki values below 0.1 nM. Protein phosphatase 2B is inhibited 1000-fold less potently, while six other phosphatases and eight protein kinases tested are unaffected. These results are strikingly similar to those obtained with the tumour promoter okadaic acid. We establish that okadaic acid prevents the binding of microcystin-LR to PP2A, and that protein inhibitors 1 and 2 prevent the binding of microcystin-LR to PP1. We discuss the possibility that inhibition of PP1 and PP2A accounts for the extreme toxicity of microcystin-LR, and indicate its potential value in the detection and analysis of protein kinases and phosphatases.
Collapse
Affiliation(s)
- C MacKintosh
- Department of Biochemistry, University of Dundee, Scotland
| | | | | | | | | |
Collapse
|
19
|
Mereish KA, Solow R. Effect of antihepatotoxic agents against microcystin-LR toxicity in cultured rat hepatocytes. Pharm Res 1990; 7:256-9. [PMID: 2339099 DOI: 10.1023/a:1015822028414] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Primary cultures of adult rat hepatocytes were used to investigate the effects of two putative therapeutic agents, dithioerythritol and silymarin on microcystin-LR-induced hepatotoxicity. Cell injury was assessed by the extent of cellular [14C]adenine nucleotides and lactate dehydrogenase (LDH) release into the medium and the extent of hepatocyte detachment from monolayers. Microcystin-LR (1 microM) induced a significant release of both 14C-labeled nucleotides and LDH from hepatocytes as well as significant detachment of cells from monolayers. Although both dithioerythritol (0.63-5 mM) and silymarin (25-200 microM) reduced the amount of marker release and cell detachment from microcystin-LR-treated wells, silymarin provided significantly greater protection than dithioerythritol at one-tenth the concentration. Furthermore, silymarin and dithioerythritol treatment prevented morphological deformations and detachment of cells.
Collapse
Affiliation(s)
- K A Mereish
- Pathophysiology Division, U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, Maryland 21701-5011
| | | |
Collapse
|
20
|
Meriluoto JA, Nygård SE, Dahlem AM, Eriksson JE. Synthesis, organotropism and hepatocellular uptake of two tritium-labeled epimers of dihydromicrocystin-LR, a cyanobacterial peptide toxin analog. Toxicon 1990; 28:1439-46. [PMID: 2128565 DOI: 10.1016/0041-0101(90)90157-3] [Citation(s) in RCA: 63] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Two tritium-labeled epimers of dihydromicrocystin-LR, a derivative of the cyanobacterial peptide hepatotoxin microcystin-LR, were synthesized by reduction with sodium boro[3H]hydride and purified with reversed-phase liquid chromatography. The epimers were hepatotoxic in mice; the i.p. LD50 was 120-135 micrograms/kg. They were concentrated in the liver and to some extent in the intestine and the kidney after an i.v. injection. Freshly isolated rat hepatocytes showed a rapid uptake of both epimers. The cellular uptake of the epimers was almost complete within 5 min at concentrations 1 microM (0.5 microM dihydromicrocystin-LR + 0.5 microM microcystin-LR) and 4 microM (0.5 microM + 3.5 microM). The uptake of the earlier eluting epimer was about three times higher than that of the later eluting epimer.
Collapse
Affiliation(s)
- J A Meriluoto
- Abo Akademi University, Department of Biochemistry and Pharmacy, Turku, Finland
| | | | | | | |
Collapse
|
21
|
Eriksson JE, Paatero GI, Meriluoto JA, Codd GA, Kass GE, Nicotera P, Orrenius S. Rapid microfilament reorganization induced in isolated rat hepatocytes by microcystin-LR, a cyclic peptide toxin. Exp Cell Res 1989; 185:86-100. [PMID: 2806414 DOI: 10.1016/0014-4827(89)90039-6] [Citation(s) in RCA: 124] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The cyclic heptapeptide hepatotoxin microcystin-LR from the cyanobacterium Microcystis aeruginosa induces rapid and characteristic deformation of isolated rat hepatocytes. We investigated the mechanism(s) responsible for cell shape changes (blebbing). Our results show that the onset of blebbing was accompanied neither by alteration in intracellular thiol and Ca2+ homeostasis nor by ATP depletion. The irreversible effects were insensitive to protease and phospholipase inhibitors and also to thiol-reducing agents, excluding the involvement of enhanced proteolysis, phospholipid hydrolysis, and thiol modification in microcystin-induced blebbing. In contrast, the cell shape changes were associated with a remarkable reorganization of microfilaments as visualized both by electron microscopy and by fluorescent staining of actin with rhodamine-conjugated phalloidin. The morphological effects and the microfilament reorganization were specific for microcystin-LR and could not be induced by the microfilament-modifying drugs cytochalasin D or phalloidin. Using inhibition of deoxyribonuclease I as an assay for monomeric actin, we found that the microcystin-induced reorganization of hepatocyte microfilaments was not due to actin polymerization. On the basis of the rapid microfilament reorganization and the specificity of the effects, it is suggested that microcystin-LR constitutes a novel microfilament-perturbing drug with features that are clearly different from those of cytochalasin D and phalloidin.
Collapse
Affiliation(s)
- J E Eriksson
- Department of Biology, Abo Akademi University, Turku, Finland
| | | | | | | | | | | | | |
Collapse
|
22
|
Meriluoto JA, Sandström A, Eriksson JE, Remaud G, Craig AG, Chattopadhyaya J. Structure and toxicity of a peptide hepatotoxin from the cyanobacterium Oscillatoria agardhii. Toxicon 1989; 27:1021-34. [PMID: 2508270 DOI: 10.1016/0041-0101(89)90153-0] [Citation(s) in RCA: 106] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A peptide hepatotoxin was isolated by reversed phase liquid chromatography from the cyanobacterium Oscillatoria agardhii and characterized structurally and toxicologically. Amino acid analyses, proton nuclear magnetic resonance and fast atom bombardment mass spectrometry showed that the toxin is a cyclic heptapeptide (mol. wt 1023.5) with the structure cyclo-(Ala-Arg-Asp-Arg-Adda-Glu-N-methyldehydroAla) (Adda: 3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid). In mice the toxic effects were restricted mainly to the liver where the toxin induced massive hemorrhages and a disruption of the lobular and sinusoidal structure. The i.p. LD50 of the toxin was 250 micrograms/kg. The structural and toxic properties of this peptide are very close to those of microcystins, cyclic peptide toxins produced by the cyanobacterium Microcystis aeruginosa.
Collapse
Affiliation(s)
- J A Meriluoto
- Department of Biochemistry and Pharmacy, Abo Akademi, Finland
| | | | | | | | | | | |
Collapse
|
23
|
Carmichael WW, He JW, Eschedor J, He ZR, Juan YM. Partial structural determination of hepatotoxic peptides from Microcystis aeruginosa (cyanobacterium) collected in ponds of central China. Toxicon 1988; 26:1213-7. [PMID: 3149051 DOI: 10.1016/0041-0101(88)90307-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Waterbloom samples of the colonial cyanobacterium Microcystis aeruginosa, collected in fish ponds at the Hydrobiological Institute, Wuhan, People's Republic of China, were hepatotoxic to mice. Lyophilized cells had an LD50 (i.p. mouse; 40 mg/kg) and signs of poisoning similar to that reported for other cyanobacterial hepatotoxic peptides. Two toxins, with an LD50 (i.p. mouse) of 40 and 150 micrograms/kg, were isolated using gel filtration and high performance liquid chromatography. The amino acid composition and mol. wt (994) of the 40 micrograms/kg toxin was the same as that for microcystin-LR, while the 150 micrograms/kg toxin had an amino acid composition and mol. wt (1048) different from any of the reported cyanobacteria heptapeptide toxins reported to date.
Collapse
Affiliation(s)
- W W Carmichael
- Department of Biological Sciences, Wright State University, Dayton, OH 45435
| | | | | | | | | |
Collapse
|