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Lanceleur R, Gémin MP, Blier AL, Meslier L, Réveillon D, Amzil Z, Ternon E, Thomas OP, Fessard V. Toxic responses of metabolites produced by Ostreopsis cf. ovata on a panel of cell types. Toxicon 2024; 240:107631. [PMID: 38331106 DOI: 10.1016/j.toxicon.2024.107631] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 01/11/2024] [Accepted: 01/28/2024] [Indexed: 02/10/2024]
Abstract
Blooms of the dinoflagellate Ostreopsis cf. ovata are regularly associated with human intoxications that are attributed to ovatoxins (OVTXs), the main toxic compounds produced by this organism and close analogs to palytoxin (PlTX). Unlike for PlTX, information on OVTXs'toxicity are scarce due to the absence of commercial standards. Extracts from two cultures of Mediterranean strains of O. cf. ovata (MCCV54 and MCCV55), two fractions containing or not OVTXs (prepared from the MCCV54 extract) and OVTX-a and -d (isolated from the MCCV55 extract) were generated. These chemical samples and PlTX were tested on a panel of cell types from several organs and tissues (skin, intestine, lung, liver and nervous system). The MCCV55 extract, containing a 2-fold higher amount of OVTXs than MCCV54 extract, was shown to be more cytotoxic on all the cell lines and more prone to increase interleukin-8 (IL-8) release in keratinocytes. The fraction containing OVTXs was also cytotoxic on the cell lines tested but induced IL-8 release only in liver cells. Unexpectedly, the cell lines tested showed the same sensitivity to the fraction that does not contain OVTXs. With this fraction, a pro-inflammatory effect was shown both in lung and liver cells. The level of cytotoxicity was similar for OVTX-a and -d, except on intestinal and skin cells where a weak difference of toxicity was observed. Among the 3 toxins, only PlTX induced a pro-inflammatory effect mostly on keratinocytes. These results suggest that the ubiquitous Na+/K+ ATPase target of PlTX is likely shared with OVTX-a and -d, although the differences in pro-inflammatory effect must be explained by other mechanisms.
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Affiliation(s)
- Rachelle Lanceleur
- ANSES, Fougères Laboratory, Toxicology of Contaminants Unit, French Agency for Food, Environmental and Occupational Health & Safety, Fougères, 35 306, France
| | | | - Anne-Louise Blier
- ANSES, Fougères Laboratory, Toxicology of Contaminants Unit, French Agency for Food, Environmental and Occupational Health & Safety, Fougères, 35 306, France
| | - Lisa Meslier
- ANSES, Fougères Laboratory, Toxicology of Contaminants Unit, French Agency for Food, Environmental and Occupational Health & Safety, Fougères, 35 306, France
| | | | - Zouher Amzil
- IFREMER, PHYTOX, METALG Laboratory, 44000, Nantes, France
| | - Eva Ternon
- Sorbonne Université, CNRS, Laboratoire d'Océanographie de Villefranche, UMR 7093, BP 28, 06230, Villefranche-sur-Mer, France; Université Côte d'Azur, CNRS, OCA, IRD, Géoazur, 250 rue Albert Einstein, 06560, Valbonne, France
| | - Olivier P Thomas
- School of Biological and Chemical Sciences and Ryan Institute, University of Galway, University Road, H91TK33, Galway, Ireland
| | - Valérie Fessard
- ANSES, Fougères Laboratory, Toxicology of Contaminants Unit, French Agency for Food, Environmental and Occupational Health & Safety, Fougères, 35 306, France.
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Sitprija V, Sitprija S. Marine toxins and nephrotoxicity:Mechanism of injury. Toxicon 2019; 161:44-49. [PMID: 30826470 DOI: 10.1016/j.toxicon.2019.02.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Revised: 02/21/2019] [Accepted: 02/24/2019] [Indexed: 02/06/2023]
Abstract
Marine toxins are known among several causes of toxin induced renal injury. Enzymatic mechanism by phospholipase A2 is responsible for acute kidney injury (AKI) in sea snake envenoming without any change in cardiac output and systemic vascular resistance. Cnidarian toxins form pores in the cell membrane with Ca influx storm resulting in cell death. Among plankton toxins domoic acid, palytoxin and maitotoxin cause renal injury by ion transport into the cell through ion channels resulting in renal cell swelling and lysis. Okadaic acid, calyculin A, microcystin LR and nodularin cause AKI by serine threonine phosphatase inhibition and hyperphosphorylation with increased activity of Ca2+/calmodulin - dependent protein kinase II, increased cytosolic Ca2+, reactive oxygen species, caspase and P53. Renal injury by plankons is mostly subclinical and requires sensitive biomarker for diagnosis. In this respect repeated consumption of plankton toxin contaminated seafood is a risk of developing chronic renal disease. The subject deserves more clinical study and scientific attention.
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Affiliation(s)
- Visith Sitprija
- Queen Saovabha Memorial Institute, Thai Red Cross Society, Rama 4 Road, Bangkok, 10330, Thailand.
| | - Siravit Sitprija
- Department of Biology, Mahidol University, Rama 6 Road, Bangkok, 10400, Thailand.
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Görögh T, Bèress L, Quabius ES, Ambrosch P, Hoffmann M. Head and neck cancer cells and xenografts are very sensitive to palytoxin: decrease of c-jun n-terminale kinase-3 expression enhances palytoxin toxicity. Mol Cancer 2013; 12:12. [PMID: 23409748 PMCID: PMC3585753 DOI: 10.1186/1476-4598-12-12] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Accepted: 02/06/2013] [Indexed: 02/01/2023] Open
Abstract
Objectives Palytoxin (PTX), a marine toxin isolated from the Cnidaria (zooanthid) Palythoa caribaeorum is one of the most potent non-protein substances known. It is a very complex molecule that presents both lipophilic and hydrophilic areas. The effect of PTX was investigated in a series of experiments conducted in head and neck squamous cell carcinoma (HNSCC) cell lines and xenografts. Materials and methods Cell viability, and gene expression of the sodium/potassium-transporting ATPase subumit alpha1 (ATP1AL1) and GAPDH were analyzed in HNSCC cells and normal epithelial cells after treatment with PTX using cytotoxicity-, clonogenic-, and enzyme inhibitor assays as well as RT-PCR and Northern Blotting. For xenograft experiments severe combined immunodeficient (SCID) mice were used to analyze tumor regression. The data were statistically analyzed using One-Way Annova (SPSS vs20). Results Significant toxic effects were observed in tumor cells treated with PTX (LD50 of 1.5 to 3.5 ng/ml) in contrast to normal cells. In tumor cells PTX affected both the release of LDH and the expression of the sodium/potassium-transporting ATPase subunit alpha1 gene suggesting loss of cellular integrity, primarily of the plasma membrane. Furthermore, strong repression of the c-Jun N-terminal kinase 3 (JNK3) mRNA expression was found in carcinoma cells which correlated with enhanced toxicity of PTX suggesting an essential role of the mitogen activated protein kinase (MAPK)/JNK signalling cascades pathway in the mechanisms of HNSCC cell resistance to PTX. In mice inoculated with carcinoma cells, injections of PTX into the xenografted tumors resulted within 24 days in extensive tumor destruction in 75% of the treated animals (LD50 of 68 ng/kg to 83 ng/kg) while no tumor regression occurred in control animals. Conclusions These results clearly provide evidence that PTX possesses preferential toxicity for head and neck carcinoma cells and therefore it is worth further studying its impact which may extend our knowledge of the biology of head and neck cancer.
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Affiliation(s)
- Tibor Görögh
- Department of Otorhinolaryngology- Head and Neck Surgery, Section of Experimental Oncology, University of Kiel Schleswig-Holstein, Kiel, 24105, Germany.
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Pagliara P, Caroppo C. Toxicity assessment of Amphidinium carterae, Coolia cfr. monotis and Ostreopsis cfr. ovata (Dinophyta) isolated from the northern Ionian Sea (Mediterranean Sea). Toxicon 2012; 60:1203-14. [DOI: 10.1016/j.toxicon.2012.08.005] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Revised: 08/07/2012] [Accepted: 08/09/2012] [Indexed: 11/17/2022]
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Rossini GP, Bigiani A. Palytoxin action on the Na(+),K(+)-ATPase and the disruption of ion equilibria in biological systems. Toxicon 2010; 57:429-39. [PMID: 20932855 DOI: 10.1016/j.toxicon.2010.09.011] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2010] [Revised: 09/03/2010] [Accepted: 09/24/2010] [Indexed: 11/29/2022]
Abstract
Palytoxin-group toxins (PlTX) exert their potent biological activity by altering mechanisms of ion homeostasis in excitable and non-excitable tissues. This review will describe major aspects that led to the relatively early identification of the Na(+),K(+)-ATPase as the molecular target and receptor of the toxin in sensitive systems. The importance of this pump in the normal functioning of animal cells has driven extensive investigative efforts. The recognized molecular mechanism of action of PlTX involves its binding to the extracellular portion of alpha subunit of this plasma membrane protein, which converts an enzyme carrying ions against their concentration gradients at the expense of chemical energy (ATP) into a non-selective cation channel, allowing passive flow of ions following their concentration gradients. More recent findings have indicated that PlTX would interfere with the normal strict coupling between inner and outer gates of the pump controlling the ion access to the Na(+),K(+)-ATPase, allowing the gates to be simultaneously open. The ability of PlTX to make internal portions of the Na(+),K(+)-ATPase accessible to relatively large molecules has been exploited to characterize the structure-function relationship of the pump, leading to a better understanding of its ion translocation pathway. Thus, forty years from the isolation of this potent marine biotoxin, a considerable understanding of its mode of action and of its potential as a research tool have been achieved and are the basis for promising future advancement in the characterization of biological systems and their alteration by PlTX.
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Affiliation(s)
- Gian Paolo Rossini
- Dipartimento di Scienze Biomediche, Università di Modena e Reggio Emilia, Via G. Campi 287, I-41125 Modena, Italy.
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Abstract
Palytoxin is a marine toxin originally isolated from the zoantharians of the genus Palythoa, but now is found in marine organisms ranging from dinoflagellates to fishes. With a MW of 2680, it is one of the largest nonpolymeric natural products ever found. Its complex structure has been elucidated and total synthesis has been achieved. With an LD(50) of 25 ng/kg for rabbits (the most sensitive species), it is one of the most lethal marine toxins. It binds to the Na,K-ATPase specifically with a K(D) of 20 pM. It has a unique action on the Na,K-ATPase, converting the pump into an ion channel and resulting in K(+) efflux, Na(+) influx and membrane depolarization. As a result palytoxin causes a wide spectrum of secondary pharmacological actions. By acting like a key to unlock the internal structure of the Na,K-ATPase, palytoxin holds promise as a useful tool for investigation of the pump molecule.
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Affiliation(s)
- Chau H Wu
- Department of Molecular Pharmacology and Biological Chemistry, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611-3008, USA.
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Coca R, Soler F, Fernández-Belda F. Characterization of the palytoxin effect on Ca2+-ATPase from sarcoplasmic reticulum (SERCA). Arch Biochem Biophys 2008; 478:36-42. [PMID: 18675777 DOI: 10.1016/j.abb.2008.07.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2008] [Revised: 07/16/2008] [Accepted: 07/17/2008] [Indexed: 10/21/2022]
Abstract
The effect of palytoxin was studied in a microsomal fraction enriched in longitudinal tubules of the sarcoplasmic reticulum membrane. Half-maximal effect of palytoxin on Ca(2+)-ATPase activity yielded an apparent inhibition constant of approx. 0.4 microM. The inhibition process exhibited the following characteristics: (i) the degree of inhibition was dependent on membrane protein concentration; (ii) no protection was observed when the ATP concentration was raised; (iii) dependence on Ca(2+) concentration with a decreased maximum catalytic rate; (iv) it occurred in the absence of Ca(2+) ionophoric activity. Likewise, the inhibition mechanism was linked to: (i) rapid enzyme phosphorylation from ATP in the presence of Ca(2+) but lower steady-state levels of phosphoenzyme; (ii) more drastic effect on phosphoenzyme levels when the toxin was added to the enzyme in the absence of Ca(2+); (iii) decreased phosphoenzyme levels at saturating Ca(2+) concentrations; (iv) no effect on kinetics of phosphoenzyme decomposition. The palytoxin effect is related with lock of the enzyme in the Ca(2+)-free conformation so that progression of the catalytic cycle is impeded.
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Affiliation(s)
- Ramón Coca
- Departamento de Bioquímica y Biología Molecular A, Universidad de Murcia, Campus de Espinardo, 30071 Espinardo, Murcia, Spain
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Zies DL, Gumz ML, Wingo CS, Cain BD. The renal H+, K+-ATPases as therapeutic targets. Expert Opin Ther Targets 2007; 11:881-90. [PMID: 17614757 DOI: 10.1517/14728222.11.7.881] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The kidney is an important regulatory organ responsible for maintaining constant blood volume and composition despite wide variations in the intake of food and water. Throughout the nephron, the functional unit of the kidney, there is a wide variety of proteins that function to add additional waste products and to recover needed materials from the lumen filtrate. The collecting duct of the nephron is the primary renal location for the H+, K+-ATPases, a group of ion pumps that function in both acid/base balance and potassium homeostasis. This review summarizes the present understanding of the structure and functions for the different subtypes of the H+, K+-ATPases under specific physiologic conditions. The obstacles in determining the pharmacologic properties of the different subtypes are considered and future directions for the inhibition and/or stimulation of the H+, K+-ATPases are evaluated.
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Affiliation(s)
- Deborah L Zies
- University of Mary Washington, Department of Biology, Fredericksburg, VA 22401, USA
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Guennoun-Lehmann S, Fonseca JE, Horisberger JD, Rakowski RF. Palytoxin acts on Na(+),K (+)-ATPase but not nongastric H(+),K (+)-ATPase. J Membr Biol 2007; 216:107-16. [PMID: 17639367 PMCID: PMC2396460 DOI: 10.1007/s00232-007-9040-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2007] [Accepted: 05/14/2007] [Indexed: 10/23/2022]
Abstract
Palytoxin (PTX) opens a pathway for ions to pass through Na,K-ATPase. We investigate here whether PTX also acts on nongastric H,K-ATPases. The following combinations of cRNA were expressed in Xenopus laevis oocytes: Bufo marinus bladder H,K-ATPase alpha(2)- and Na,K-ATPase beta(2)-subunits; Bufo Na,K-ATPase alpha(1)- and Na,K-ATPase beta(2)-subunits; and Bufo Na,K-ATPase beta(2)-subunit alone. The response to PTX was measured after blocking endogenous Xenopus Na,K-ATPase with 10 microM ouabain. Functional expression was confirmed by measuring (86)Rb uptake. PTX (5 nM: ) produced a large increase of membrane conductance in oocytes expressing Bufo Na,K-ATPase, but no significant increase occurred in oocytes expressing Bufo H,K-ATPase or in those injected with Bufo beta(2)-subunit alone. Expression of the following combinations of cDNA was investigated in HeLa cells: rat colonic H,K-ATPase alpha(1)-subunit and Na,K-ATPase beta(1)-subunit; rat Na,K-ATPase alpha(2)-subunit and Na,K-ATPase beta(2)-subunit; and rat Na,K-ATPase beta(1)- or Na,K-ATPase beta(2)-subunit alone. Measurement of increases in (86)Rb uptake confirmed that both rat Na,K and H,K pumps were functional in HeLa cells expressing rat colonic HKalpha(1)/NKbeta(1) and NKalpha(2)/NKbeta(2). Whole-cell patch-clamp measurements in HeLa cells expressing rat colonic HKalpha(1)/NKbeta(1) exposed to 100 nM PTX showed no significant increase of membrane current, and there was no membrane conductance increase in HeLa cells transfected with rat NKbeta(1)- or rat NKbeta(2)-subunit alone. However, in HeLa cells expressing rat NKalpha(2)/NKbeta(2), outward current was observed after pump activation by 20 mM K(+) and a large membrane conductance increase occurred after 100 nM PTX. We conclude that nongastric H,K-ATPases are not sensitive to PTX when expressed in these cells, whereas PTX does act on Na,K-ATPase.
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Affiliation(s)
| | - James E. Fonseca
- School of Electrical Engineering & Computer Science, Ohio University, Athens, OH 45701 USA
| | - Jean-Daniel Horisberger
- Dept. of Pharmacology and Toxicology of the University of Lausanne, Rue du Bugnon 27, CH-1005 Lausanne, Switzerland
| | - Robert F. Rakowski
- Department of Biological Sciences, Ohio University, Athens, OH 45701 USA
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Wattenberg EV. Palytoxin: exploiting a novel skin tumor promoter to explore signal transduction and carcinogenesis. Am J Physiol Cell Physiol 2006; 292:C24-32. [PMID: 16855216 PMCID: PMC1769420 DOI: 10.1152/ajpcell.00254.2006] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Palytoxin is a novel skin tumor promoter, which has been used to help probe the role of different types of signaling mechanisms in carcinogenesis. The multistage mouse skin model indicates that tumor promotion is an early, prolonged, and reversible phase of carcinogenesis. Understanding the molecular mechanisms underlying tumor promotion is therefore important for developing strategies to prevent and treat cancer. Naturally occurring tumor promoters that bind to specific cellular receptors have proven to be useful tools for investigating important biochemical events in multistage carcinogenesis. For example, the identification of protein kinase C as the receptor for the prototypical skin tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) (also called phorbol 12-myristate 13-acetate, PMA) provided key evidence that tumor promotion involves the aberrant modulation of signaling cascades that govern cell fate and function. The subsequent discovery that palytoxin, a marine toxin isolated from zoanthids (genus Palythoa), is a potent skin tumor promoter yet does not activate protein kinase C indicated that investigating palytoxin action could help reveal new aspects of tumor promotion. Interestingly, the putative receptor for palytoxin is the Na(+),K(+)-ATPase. This review focuses on palytoxin-stimulated signaling and how palytoxin has been used to investigate alternate biochemical mechanisms by which important targets in carcinogenesis can be modulated.
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Affiliation(s)
- Elizabeth V Wattenberg
- Division of Environmental Health Sciences, School of Public Health, University of Minnesota, Mayo Mail Code #807, 420 Delaware Street SE, Minneapolis, MN 55455, USA.
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Vale C, Alfonso A, Suñol C, Vieytes MR, Botana LM. Modulation of calcium entry and glutamate release in cultured cerebellar granule cells by palytoxin. J Neurosci Res 2006; 83:1393-406. [PMID: 16547972 DOI: 10.1002/jnr.20841] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
A channel open on the membrane can be formed by palytoxin (PTX). Ten nanomolar PTX caused an irreversible increase in the cytosolic calcium concentration ([Ca(2+)](c)), which was abolished in the absence of external calcium. The increase was eliminated by saxitoxin (STX) and nifedipine (NIF). Calcium rise is secondary to the membrane depolarization. PTX effect on calcium was dependent on extracellular Na(+). Li(+) decreased the PTX-evoked rise in [Ca(2+)](c); replacement of Na(+) by N-methyl-D-glucamine (NMDG) abolished PTX-induced calcium increase. [Ca(2+)](c) increase by PTX was strongly reduced after inhibition of the reverse operation of the Na(+)/Ca(2+) exchanger, in the presence of antagonists of excitatory amino acid (EAA) receptors, and by inhibition of neurotransmitter release. PTX did not modify calcium extrusion by the plasma membrane Ca(2+)-ATPase (PMCA), because blockade of the calcium pump increased rather than decreased the PTX-induced calcium influx. Extracellular levels of glutamate and aspartate were measured by HPLC and exocytotic neurotransmitter release by determination of synaptic vesicle exocytosis using total internal reflection fluorescence microscopy (TIRFM). PTX caused a concentration-dependent increase in EAA release to the culture medium. Ten nanomolar PTX decreased cell viability by 30% within 5 min. PTX-induced calcium influx involves three pathways: Na(+)-dependent activation of voltage-dependent sodium channels (VDSC) and voltage-dependent calcium channels (VDCC), reverse operation of the Na(+)/Ca(2+) exchanger, and indirect activation of EAA receptors through glutamate release. The neuronal injury produced by the toxin could be partially mediated by the PTX-induced overactivation of EAA receptors, VDSC, VDCC and the glutamate efflux into the extracellular space.
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Affiliation(s)
- Carmen Vale
- Departamento de Farmacología, Facultad de Veterinaria, USC, Campus Universitario, Lugo, Spain
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Fiddian-Green R. Clostridium difficile colitis: a marker for ischemic colitis? CMAJ 2004; 171:1325-6; author reply 1326-7. [PMID: 15557572 PMCID: PMC527310 DOI: 10.1503/cmaj.1041677] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
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Ai J, Du J, Wang N, Du ZM, Yang BF. Inhibition of small-intestinal sugar absorption mediated by sodium orthovanadate Na 3VO 4 in rats and its mechanisms. World J Gastroenterol 2004; 10:3612-5. [PMID: 15534916 PMCID: PMC4612002 DOI: 10.3748/wjg.v10.i24.3612] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
AIM: To investigate the inhibitory effects of sodium orthovanadate on small-intestinal glucose and maltose absorption in rats and its mechanism.
METHODS: Normal Wistar rats were lavaged with sodium orthovanadate (16 mg/kg, 4 mg/kg and 1 mg/kg) for 6 d. Blood glucose values were measured after fasting and 0.5, 1, 1.5 and 2 h after glucose and maltose feeding with oxidation-enzyme method. α-glucosidase was abstracted from the upper small intestine, and its activity was examined. mRNA expression of α-glucosidase and glucose-transporter 2 (GLUT2) in epithelial cells of the small intestine was observed by in situ hybridization.
RESULTS: Sodium orthovanadate could delay the increase of plasma glucose concentration after glucose and maltose loading, area under curve (AUC) in these groups was lower than that in control group. Sodium orthovanadate at dosages of 10 μmol/L, 100 μmol/L and 1000 μmol/L could suppress the activity of α-glucosidase in the small intestine of normal rats, with an inhibition rate of 68.18%, 87.22% and 91.91%, respectively. Sodium orthovanadate reduced mRNA expression of α-glucosidase and GLUT2 in epithelial cells of small intestine.
CONCLUSION: Sodium orthovanadate can reduce and delay the absorption of glucose and maltose. The mechanism may be that it can inhibit the activity and mRNA expression of α-glucosidase, as well as mRNA expression of GLUT2 in small intestine.
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Affiliation(s)
- Jing Ai
- Department of Pharmacology, Harbin Medical University, Bio-Pharmaceutical Key Laboratory of Heilongjiang Province-Incubator of State Key Laboratory, Harbin 150086, Heilongjiang Province, China
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Kockskämper J, Ahmmed GU, Zima AV, Sheehan KA, Glitsch HG, Blatter LA. Palytoxin disrupts cardiac excitation-contraction coupling through interactions with P-type ion pumps. Am J Physiol Cell Physiol 2004; 287:C527-38. [PMID: 15084477 DOI: 10.1152/ajpcell.00541.2003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Palytoxin is a coral toxin that seriously impairs heart function, but its effects on excitation-contraction (E-C) coupling have remained elusive. Therefore, we studied the effects of palytoxin on mechanisms involved in atrial E-C coupling. In field-stimulated cat atrial myocytes, palytoxin caused elevation of diastolic intracellular Ca2+ concentration ([Ca2+]i), a decrease in [Ca2+]i transient amplitude, Ca2+ alternans followed by [Ca2+]i waves, and failures of Ca2+ release. The decrease in [Ca2+]i transient amplitude occurred despite high sarcoplasmic reticulum (SR) Ca2+ load. In voltage-clamped myocytes, palytoxin induced a current with a linear current-voltage relationship (reversal potential ∼5 mV) that was blocked by ouabain. Whole cell Ca2+ current and ryanodine receptor Ca2+ release channel function remained unaffected by the toxin. However, palytoxin significantly reduced Ca2+ pumping of isolated SR vesicles. In current-clamped myocytes stimulated at 1 Hz, palytoxin induced a depolarization of the resting membrane potential that was accompanied by delayed afterdepolarizations. No major changes of action potential configuration were observed. The results demonstrate that palytoxin interferes with the function of the sarcolemmal Na+-K+ pump and the SR Ca2+ pump. The suggested mode of palytoxin toxicity in the atrium involves the conversion of Na+-K+ pumps into nonselective cation channels as a primary event followed by depolarization, Na+ accumulation, and Ca2+ overload, which, in turn, causes arrhythmogenic [Ca2+]i waves and delayed afterdepolarizations.
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Affiliation(s)
- Jens Kockskämper
- Department of Physiology, Loyola University-Chicago, 2160 S. First Avenue, Maywood, IL 60153, USA
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Ito K, Toyoda I, Higashiyama M, Uemura D, Sato MH, Yoshimura SH, Ishii T, Takeyasu K. Channel induction by palytoxin in yeast cells expressing Na+,K+-ATPase or its chimera with sarco/endoplasmic reticulum Ca2+-ATPase. FEBS Lett 2003; 543:108-12. [PMID: 12753915 DOI: 10.1016/s0014-5793(03)00418-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Palytoxin (PTX) induces a cation channel through interaction with Na(+),K(+)-ATPase. It is unclear how this action relates to the enzyme catalytic activity. We examined whether the action of PTX depends on the catalytic domain specific for Na(+),K(+)-ATPase. Wild-type Na(+),K(+)-ATPase alpha-subunit (NNN) or its chimera (NCN), in which the catalytic domain was replaced with that of sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase, was co-expressed with beta-subunit in the yeast Saccharomyces cerevisiae. PTX (0.1-100 nM) increased K(+) efflux in NNN- or NCN-transfected cells to a similar degree but not in non-transfected cells. When ouabain-resistant NNN and NCN were expressed, PTX also increased K(+) efflux. Ouabain inhibited the effect of PTX in NNN or NCN cells but not in ouabain-resistant cells. These data suggest that the channel-forming action of PTX does not depend on the catalytic domain species.
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Affiliation(s)
- Katsuaki Ito
- Department of Veterinary Pharmacology, Faculty of Agriculture, Miyazaki University, 889-2192, Miyazaki, Japan.
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Affiliation(s)
- Donald W Hilgemann
- Department of Physiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9040, USA.
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