1
|
Adlung A, Licht C, Reichert S, Özdemir S, Mohamed SA, Samartzi M, Fatar M, Gass A, Prost EN, Schad LR. Quantification of tissue sodium concentration in the ischemic stroke: A comparison between external and internal references for 23Na MRI. J Neurosci Methods 2022; 382:109721. [PMID: 36202191 DOI: 10.1016/j.jneumeth.2022.109721] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Revised: 09/28/2022] [Accepted: 09/30/2022] [Indexed: 11/06/2022]
Affiliation(s)
- Anne Adlung
- Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Germany.
| | - Christian Licht
- Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Germany
| | - Simon Reichert
- Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Germany
| | - Safa Özdemir
- Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Germany
| | - Sherif A Mohamed
- Department of Neuroradiology, Medical Faculty Mannheim, Heidelberg University, Germany; Clinic for Diagnostic and Interventional Radiology, University Hospital Heidelberg, Germany
| | - Melina Samartzi
- Department of Neurology, Medical Faculty Mannheim and Mannheim Center of Translational Neurosciences (MCTN), Heidelberg University, Germany
| | - Marc Fatar
- Department of Neurology, Medical Faculty Mannheim and Mannheim Center of Translational Neurosciences (MCTN), Heidelberg University, Germany
| | - Achim Gass
- Department of Neurology, Medical Faculty Mannheim and Mannheim Center of Translational Neurosciences (MCTN), Heidelberg University, Germany
| | - Eva Neumaier Prost
- Department of Neuroradiology, Medical Faculty Mannheim, Heidelberg University, Germany
| | - Lothar R Schad
- Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Germany
| |
Collapse
|
2
|
Platonova A, Koltsova S, Maksimov GV, Grygorczyk R, Orlov SN. The death of ouabain-treated renal epithelial C11-MDCK cells is not mediated by swelling-induced plasma membrane rupture. J Membr Biol 2011; 241:145-54. [PMID: 21584679 DOI: 10.1007/s00232-011-9371-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Accepted: 05/05/2011] [Indexed: 10/18/2022]
Abstract
This study examined the role of cell volume modulation in plasma membrane rupture and death documented in ouabain-treated renal epithelial cells. Long-term exposure to ouabain caused massive death of C11-MDCK (Madin-Darby canine kidney) epithelial cells, documented by their detachment, chromatin cleavage and complete loss of lactate dehydrogenase (LDH), but did not affect the survival of vascular smooth muscle cells (VSMCs) from the rat aorta. Unlike the distinct impact on cell survival, 2-h exposure to ouabain led to sharp elevation of the [Na⁺](i)/[K⁺](i) ratio in both cell types. A similar increment of Na⁺(i) content was evoked by sustained inhibition of Na⁺,K⁺-ATPase in K⁺-free medium. However, in contrast to ouabain, C11-MDCK cells survived perfectly during 24-h exposure to K⁺-free medium. At 3 h, the volume of ouabain-treated C11-MDCK cells and VSMCs, measured by the recently developed dual-image surface reconstruction technique, was increased by 16 and 12%, respectively, whereas 5-10 min before the detachment of ouabain-treated C11-MDCK cells, their volume was augmented by ~30-40%. To examine the role of modest swelling in the plasma membrane rupture of ouabain-treated cells, we compared actions of hypotonic medium on volume and LDH release. We observed that LDH release from hypoosmotically swollen C11-MDCK cells was triggered when their volume was increased by approximately fivefold. Thus, our results showed that the rupture of plasma membranes in ouabain-treated C11-MDCK cells was not directly caused by cell volume modulation evoked by Na⁺,K⁺-ATPase inhibition and inversion of the [Na⁺](i)/[K⁺](i) ratio.
Collapse
Affiliation(s)
- Alexandra Platonova
- Research Centre, Centre Hospitalier de l'Université de Montréal (CRCHUM)-Technopôle Angus, 2901 Rachel Est, Montreal, QC H1W4A4, Canada
| | | | | | | | | |
Collapse
|
3
|
The cytolytic and cytotoxic activities of palytoxin. Toxicon 2011; 57:449-59. [DOI: 10.1016/j.toxicon.2010.12.013] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2010] [Revised: 12/15/2010] [Accepted: 12/20/2010] [Indexed: 11/18/2022]
|
4
|
Palytoxin toxicology: Animal studies. Toxicon 2011; 57:470-7. [DOI: 10.1016/j.toxicon.2010.10.003] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Revised: 09/02/2010] [Accepted: 10/04/2010] [Indexed: 11/17/2022]
|
5
|
Satoh E, Iwasaki R. Experimental diabetes attenuates calcium mobilization and proliferative response in splenic lymphocytes from mice. J Physiol Sci 2011; 61:23-30. [PMID: 20972743 PMCID: PMC10717575 DOI: 10.1007/s12576-010-0117-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Accepted: 09/30/2010] [Indexed: 11/27/2022]
Abstract
The present study was conducted to investigate the effects of the diabetic condition on cytosolic free Ca(2+) concentration, [Ca(2+)](i), and the proliferation of splenic lymphocytes from mice. Diabetes was induced in mice by intraperitoneal injection of alloxan. [Ca(2+)](i) and the proliferation ex vivo of splenic lymphocytes isolated from mice were examined using fura-2 and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide, respectively. Diabetes caused a significant increase in resting [Ca(2+)](i) and significantly reduced the ability of concanavalin A (Con A; a T-lymphocyte-selective mitogen) to increase [Ca(2+)](i), but not that of lipopolysaccharide (LPS; a B-lymphocyte-selective mitogen). In addition, diabetes significantly reduced Con A-stimulated but not LPS-stimulated lymphocyte proliferation. Verapamil (an L-type Ca(2+) channel blocker) inhibited Con A-induced increases in [Ca(2+)](i) and proliferation in lymphocytes from control and diabetic mice to a similar extent, respectively. These results suggest that diabetes attenuates Con A-stimulated T-lymphocyte proliferation by decreasing [Ca(2+)](i) via reduction of Ca(2+) entry through L-type Ca(2+) channels.
Collapse
Affiliation(s)
- Eiki Satoh
- Research Center for Animal Hygiene and Food Safety, Obihiro University of Agriculture and Veterinary Medicine, Obihiro 080-8555, Japan.
| | | |
Collapse
|
6
|
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.
Collapse
Affiliation(s)
- Gian Paolo Rossini
- Dipartimento di Scienze Biomediche, Università di Modena e Reggio Emilia, Via G. Campi 287, I-41125 Modena, Italy.
| | | |
Collapse
|
7
|
Panayiotidis MI, Franco R, Bortner CD, Cidlowski JA. Ouabain-induced perturbations in intracellular ionic homeostasis regulate death receptor-mediated apoptosis. Apoptosis 2010; 15:834-49. [PMID: 20422450 DOI: 10.1007/s10495-010-0494-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Apoptosis is defined by specific morphological and biochemical characteristics including cell shrinkage (termed apoptotic volume decrease), a process that results from the regulation of ion channels and plasma membrane transporter activity. The Na(+)-K(+)-ATPase is the predominant pump that controls cell volume and plasma membrane potential in cells and alterations in its function have been suggested to be associated with apoptosis. We report here that the Na(+)-K(+)-ATPase inhibitor ouabain, potentiates apoptosis in the human lymphoma Jurkat cells exposed to Fas ligand (FasL) or tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) but not other apoptotic agents such as H(2)O(2), thapsigargin or UV-C implicating a role for the Na(+)-K(+)-ATPase in death receptor-induced apoptosis. Interestingly, ouabain also potentiated perturbations in cell Ca(2+) homeostasis only in conjunction with the apoptotic inducer FasL but not TRAIL. Ouabain did not affect alterations in the intracellular Ca(2+) levels in response to H(2)O(2), thapsigargin or UV-C. FasL-induced alterations in Ca(2+) were not abolished in Ca(2+)-free medium but incubation of cells with BAPTA-AM inhibited both Ca(2+) perturbations and the ouabain-induced potentiation of FasL-induced apoptosis. Our data suggest that the impairment of the Na(+)-K(+)-ATPase activity during apoptosis is linked to perturbations in cell Ca(2+) homeostasis that modulate apoptosis induced by the activation of Fas by FasL.
Collapse
Affiliation(s)
- Mihalis I Panayiotidis
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences (NIEHS), National Institutes of Health, Research Triangle Park, NC, 27709, USA.
| | | | | | | |
Collapse
|
8
|
Akimova OA, Tremblay J, Van Huysse JW, Hamet P, Orlov SN. Cardiotonic steroid-resistant alpha1-Na+,K+-ATPase rescues renal epithelial cells from the cytotoxic action of ouabain: evidence for a Nai+,Ki+ -independent mechanism. Apoptosis 2010; 15:55-62. [PMID: 19949978 DOI: 10.1007/s10495-009-0429-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mechanisms underlying the tissue-specific impact of cardiotonic steroids (CTS) on cell survival and death remain poorly understood. This study examines the role of Na(+),K(+)-ATPase alpha subunits in death of Madin-Darby canine kidney (MDCK) cells evoked by 24-h exposure to ouabain. MDCK cells expressing a variant of the alpha1 isoform, CTS-sensitive alpha1S, were stably transfected with a cDNA encoding CTS-resistant alpha1R-Na(+),K(+)-ATPase, whose expression was confirmed by RT-PCR. In mock-transfected and alpha1R-cells, maximal inhibition of (86)Rb influx was observed at 10 and 1000 muM ouabain, respectively, thus confirming high abundance of alpha1R-Na(+),K(+)-ATPase in these cells. Six-hour treatment of alpha1R-cells with 1000 muM ouabain led to the same elevation of the [Na(+)](i)/[K(+)](i) ratio that was detected in mock-transfected cells treated with 3 muM ouabain. However, in contrast to the massive death of mock-transfected cells exposed to 3 muM ouabain, alpha1R-cells survived after 24-h incubation with 1000 muM ouabain. Inversion of the [Na(+)](i)/[K(+)](i) ratio evoked by Na(+),K(+)-ATPase inhibition in K(+)-free medium did not affect survival of alpha1R-cells but increased their sensitivity to ouabain. Our results show that the alpha1R subunit rescues MDCK cells from the cytotoxic action of CTS independently of inhibition of Na(+),K(+)-ATPase-mediated Na(+) and K(+) fluxes and inversion of the [Na(+)](i)/[K(+)](i) ratio.
Collapse
Affiliation(s)
- Olga A Akimova
- Centre de Recherche, Centre Hospitalier de l'Université de Montréal, Technopôle Angus, 2901 Rachel Est, Montreal, QC H1W 4A4, Canada.
| | | | | | | | | |
Collapse
|
9
|
Death of ouabain-treated renal epithelial cells: evidence for p38 MAPK-mediated Na (i) (+) /K (i) (+) -independent signaling. Apoptosis 2010; 14:1266-73. [PMID: 19784777 DOI: 10.1007/s10495-009-0404-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Recent studies demonstrate that cytotoxic actions of ouabain and other cardiotonic steroids (CTS) on renal epithelial cells (REC) are triggered by their interaction with the Na(+),K(+)-ATPase alpha-subunit but not the result of inhibition of Na(+),K(+)-ATPase-mediated ion fluxes and inversion of the [Na(+)](i)/[K(+)](i) ratio. This study examined the role of mitogen-activated protein kinases (MAPK) in the death of ouabain-treated REC. Exposure of C7-MDCK cells that resembled principal cells from canine kidney to 3 microM ouabain led to phosphorylation of p38 without significant impact on phosphorylation of ERK and JNK MAPK. Maximal increment of p38 phosphorylation was observed at 4 h followed by cell death at 12 h of ouabain addition. In contrast to ouabain, neither cell death nor p38 MAPK phosphorylation were affected by elevation of the [Na(+)](i)/[K(+)](i) ratio triggered by Na(+),K(+)-ATPase inhibition in K(+)-free medium. p38 phosphorylation was noted in all other cell types exhibiting death in the presence of ouabain, such as intercalated cells from canine kidney and human colon rectal carcinoma cells. We did not observe any action of ouabain on p38 phosphorylation in ouabain-resistant smooth muscle cells from rat aorta and endothelial cells from human umbilical vein. Both p38 phosphorylation and death of ouabain-treated C7-MDCK cells were suppressed by p38 inhibitor SB 202190 but were resistant to its inactive analogue SB 202474. Our results demonstrate that death of CTS-treated REC is triggered by Na (i) (+) ,K (i) (+) -independent activation of p38 MAPK.
Collapse
|
10
|
Ares IR, Cagide E, Louzao MC, Espiña B, Vieytes MR, Yasumoto T, Botana LM. Ostreocin-D impact on globular actin of intact cells. Chem Res Toxicol 2009; 22:374-81. [PMID: 19154108 DOI: 10.1021/tx800273f] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ostreocin-D, discovered in the past decade, is a marine toxin produced by dinoflagellates. It shares structure with palytoxin, a toxic compound responsible for the seafood intoxication named clupeotoxism. At the cellular level, the action sites and pharmacological effects for ostreocin-D are still almost unknown. Previously, we demonstrated that these toxins change the filamentous actin cytoskeleton, which is essential for multiple cellular functions. However, nothing has yet been reported about what happens with the unpolymerized actin pool. Here (i) the effects induced by ostreocin-D on unpolymerized actin, (ii) the Ca2+ role in such a process, and (iii) the cytotoxic activity of ostreocin-D on the human neuroblastoma BE(2)-M17 cell line are shown for the first time. Fluorescently labeled DNase I was used for staining of monomeric actin prior to detection with both laser-scanning cytometry and confocal microscopy techniques. Cellular viability was tested through a microplate metabolic activity assay. Ostreocin-D elicited a rearrangement of monomeric actin toward the nuclear region. This event was not accompanied by changes in its content. In addition, the presence or absence of external Ca2+ did not change these results. This toxin was also found to cause a decrease in the viability of neuroblastoma cells, which was inhibited by the specific blocker of Na+/K+-ATPase, ouabain. All these responses were comparable to those obtained with palytoxin under identical conditions. The data suggest that ostreocin-D modulates the unassembled actin pool, activating signal transduction pathways not related to Ca2+ influx in the same way as palytoxin.
Collapse
Affiliation(s)
- Isabel R Ares
- Departamento de Farmacología, Facultad de Veterinaria, Universidad de Santiago de Compostela, Campus de Lugo, 27002 Lugo, Spain
| | | | | | | | | | | | | |
Collapse
|
11
|
Abstract
The mechanisms of cell death signaling triggered by cardiotonic steroids are poorly understood. Based on massive detachment of ouabain-treated Madin-Darby canine kidney (MDCK) cells, it may be proposed that the cytotoxic action of these compounds is mediated by anoikis, i.e. a particular mode of death occurring in cells lacking cell-to-extracellular matrix interactions. We tested this hypothesis. Six hour incubation of MDCK cells with ouabain, marinobufagenin or K+-free medium almost completely blocked Na+,K+-ATPase, increased Na (i) + content by approximately 10-fold and suppressed cell attachment to regular-plastic-plates by up to 5-fold. In contrast, the death of attached cells was observed after 24-h incubation with ouabain but not in the presence of marinobufagenin or K+-free medium. Cells treated with ouabain and undergoing anoikis on ultra-low attachment plates exhibited different cell volume behaviour, i.e. swelling and shrinkage, respectively. The pan-caspase inhibitor z-VAD.fmk and the protein kinase C activator PMA rescued MDCK cells from anoikis but did not influence the survival of ouabain-treated cells, whereas medium acidification from pH 7.2 to 6.7 almost completely abolished the cytotoxic action of ouabain, but did not significantly affect anoikis. Our results show that the Na (i) + ,K (i) + -independent mode of MDCK cell death evoked by ouabain is not mediated by anoikis.
Collapse
|
12
|
Valverde I, Lago J, Vieites JM, Cabado AG. In vitro approaches to evaluate palytoxin-induced toxicity and cell death in intestinal cells. J Appl Toxicol 2008; 28:294-302. [PMID: 17604342 DOI: 10.1002/jat.1278] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Palytoxin isolated from the genus Palythoa is the most potent marine toxin known. The aim of the present study was to quantify palytoxin-induced cellular injury in the human intestinal cell line Caco-2. Cellular damage was measured by evaluating cell proliferation, cell membrane permeability, cell morphology and apoptotic markers. Furthermore, changes in F-actin were studied after exposure of cells to increasing amounts of palytoxin. The results show that cell proliferation decreased in a concentration-dependent manner with a mean IC(50) value of about 0.1 nM. A noticeable increase of cell detachment correlated with cell rounding and F-actin depolymerization was observed in palytoxin-treated cells. Moreover LDH was released from the cells in a dose and time dependent manner, although under these conditions there was no propidium iodide uptake. On the other hand, palytoxin impaired mitochondrial activity but other apoptotic markers, such as DNA fragmentation or caspases activation, were not observed. The results obtained in this paper suggest that the effects of palytoxin in Caco-2 cells were very potent and unspecific, since a primary necrosis and a secondary apoptosis seem to occur under these conditions.
Collapse
Affiliation(s)
- I Valverde
- ANFACO-CECOPESCA, Campus Univ de Vigo, Vigo 36310, Spain
| | | | | | | |
Collapse
|
13
|
Valverde I, Lago J, Reboreda A, Vieites JM, Cabado AG. Characteristics of palytoxin-induced cytotoxicity in neuroblastoma cells. Toxicol In Vitro 2008; 22:1432-9. [PMID: 18550326 DOI: 10.1016/j.tiv.2008.04.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2007] [Revised: 04/14/2008] [Accepted: 04/14/2008] [Indexed: 10/22/2022]
Abstract
Cation fluxes appear to play a key role in palytoxin-induced signal. There are other cellular targets that have not been described as well as the biochemical signaling cascades that transmit palytoxin-stimulated signals remain to be clarified. Since modifications of cations, mainly calcium, are generally associated to cell death or apoptosis, we wanted to further evaluate the effect of palytoxin on cell death. Then, in vitro cytotoxic effects of palytoxin were characterized on human neuroblastoma cells. By using several techniques, we studied markers of cell death and apoptosis, such as cell detachment, mitochondrial membrane potential, caspases, DNA damage, LDH leakage, propidium iodide uptake, F-actin depolymerization and inhibition of cellular proliferation. Results show that palytoxin triggers a series of toxic responses; it inhibits cell proliferation, induces cell rounding, detachment from the substratum and F-actin disruption. Among the apoptotic markers studied we only detected fall in mitochondrial membrane potential. Neither caspases activation nor chromatin condensation or DNA fragmentation were observed in palytoxin-treated cells.
Collapse
Affiliation(s)
- I Valverde
- Microbiology and Biotoxins Area, ANFACO-CECOPESCA, Campus Univ de Vigo, Vigo, Spain
| | | | | | | | | |
Collapse
|
14
|
Akimova OA, Hamet P, Orlov SN. [Na+]i/[K+]i -independent death of ouabain-treated renal epithelial cells is not mediated by Na+,K+ -ATPase internalization and de novo gene expression. Pflugers Arch 2007; 455:711-9. [PMID: 17622553 DOI: 10.1007/s00424-007-0283-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2007] [Accepted: 05/02/2007] [Indexed: 10/23/2022]
Abstract
The cytotoxic effect of long-term exposure of renal epithelial cells to ouabain and other cardiotonic steroids (CTS) is mediated by the interaction of these compounds with Na(+),K(+)-ATPase but is independent of the inhibition of Na(+),K(+)-ATPase-mediated ion fluxes. Sustained application of CTS also leads to Na(+),K(+)-ATPase endocytosis and its translocation into the nuclei that might trigger the cell death machinery via the regulation of gene expression. This study examines the role of Na(+),K(+)-ATPase internalization and de novo gene expression in the death of ouabain-treated C7-Madin-Darby canine kidney (MDCK) cells derived from distal tubules of the MDCK. In these cells, 6-h exposure to 3 microM ouabain led to the internalization of approximately 50% of plasmalemmal Na(+),K(+)-ATPase. Prolonged incubation in a K(+)-free medium abolished ouabain-induced Na(+),K(+)-ATPase internalization but did not affect the cytotoxic action of ouabain seen after 18-h incubation. Previously, it was shown that CTS-induced Na(+),K(+)-ATPase internalization is mediated by its interaction with Src within caveolae. Neither caveolae damage by cholesterol depletion with methyl-beta-cyclodextrin nor Src inhibition with 4-amino-5(4-chlorophenyl)-7-(t-butyl)pyrazol[3,4-d]pyridine affected the death of ouabain-treated C7-MDCK cells. Actinomycin D at the 0.1-microg/ml concentration almost completely abolished ribonucleic acid synthesis but did not protect C7-MDCK cells from the cytotoxic action of ouabain. Our results show that neither Na(+),K(+)-ATPase endocytosis nor de novo gene expression contributes to Na(+)(i), K(+)(i)-independent cell death signaling evoked by prolonged exposure to CTS.
Collapse
Affiliation(s)
- Olga A Akimova
- Research Centre, Centre Hospitalier de l'Université de Montréal, Technôpole Angus, 2901 Rachel East, Montreal, Quebec H1W 4A4, Canada
| | | | | |
Collapse
|
15
|
Satoh E, Satoh K. Monensin causes transient calcium ion influx into mouse splenic lymphocytes in a sodium ion-independent fashion. Eur J Pharmacol 2007; 561:39-45. [PMID: 17336959 DOI: 10.1016/j.ejphar.2007.01.042] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2006] [Revised: 01/11/2007] [Accepted: 01/11/2007] [Indexed: 11/16/2022]
Abstract
Monensin, a Na(+) ionophore, can increase cytosolic free Ca(2+) concentration ([Ca(2+)](i)) in many cell types, but no studies have investigated the mechanism underlying a monensin-induced increase in [Ca(2+)](i) in immune cells. In view of this, we investigated the effect of monensin on [Ca(2+)](i) and cytosolic free Na(+) concentration ([Na(+)](i)) in mouse splenic lymphocytes using a fluorescence Ca(2+) indicator, fura-2, and a fluorescence Na(+) indicator, sodium-binding benzofuran isophthalate (SBFI), respectively. Monensin (1-100 microM) caused transient and sustained increases in [Ca(2+)](i) and [Na(+)](i), respectively, in a concentration-dependent manner. The monensin-induced increase in [Ca(2+)](i) was abolished by the omission of extracellular Ca(2+) or 1-[beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole hydrochloride (SKF-96365, 100-150 microM), and was largely inhibited by Ni(2+) (2-5 mM). The omission of extracellular Na(+) failed to inhibit the monensin-induced increases in [Ca(2+)](i). Furthermore, tetrodotoxin (1-10 microM), 5-(N,N-dimethyl)-amiloride (DMA, 10-20 microM), 2-[4-[(2,5-difluorophenyl)methoxy]phenoxy]-5-ethoxyaniline (SEA0400, 3-10 microM), verapamil (10-200 microM), nifedipine (10-200 microM), omega-agatoxin IVA (0.2-10 microM), omega-conotoxin GVIA (1-10 microM), omega-conotoxin MVIIC (0.5-10 microM), and nordihydroguaiaretic acid (NDGA, 1-10 microM) had no effect on the increases in [Ca(2+)](i). Monensin-induced Mn(2+) influx into splenic lymphocytes. The Mn(2+) influx was completely inhibited by SKF-96365. These results suggest that monensin transiently increases [Ca(2+)](i) in mouse splenic lymphocytes by stimulating Ca(2+) entry via non-selective cation channels in a Na(+)-independent manner.
Collapse
Affiliation(s)
- Eiki Satoh
- Research Center for Animal Hygiene and Food Safety, Obihiro University of Agriculture and Veterinary Medicine, Obihiro 080-8555, Japan.
| | | |
Collapse
|
16
|
Satoh E, Edamatsu H, Omata Y. Acute restraint stress enhances calcium mobilization and proliferative response in splenic lymphocytes from mice. Stress 2006; 9:223-30. [PMID: 17175508 DOI: 10.1080/10253890601095794] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Calcium (Ca2+ ) plays an essential role in lymphocyte activation and maturation. Acute and chronic stress has been shown to modulate the lymphocyte immune response; but the relationship between cytosolic free Ca2+ concentration ([Ca2+ ]i) and the immune response in lymphocytes following exposure to stress has not been examined. In the present study, we investigated the effects of acute restraint stress on [Ca2+ ]i and the proliferation of splenic lymphocytes from mice. We observed that 2 h of restraint significantly increased plasma corticosterone levels in mice. On examining [Ca2+ ]i and the proliferation ex vivo of splenic lymphocytes isolated from restraint-stressed mice using fura-2 and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide, respectively, we found that acute restraint stress caused a significant increase in resting [Ca2+ ]i and significantly enhanced the ability of concanavalin A (Con A; a T-cell-selective mitogen) to increase [Ca2+ ]i but not that of lipopolysaccharide (LPS; a B-cell-selective mitogen). In addition, acute restraint stress significantly enhanced Con A-stimulated but not LPS-stimulated lymphocyte proliferation. Overall, there was a positive correlation between [Ca2+ ]i and T-cell proliferation following acute restraint stress. The enhancements of [Ca2+ ]i and T-cell proliferation were completely suppressed by verapamil (a Ca2+ channel blocker). These results suggest that acute restraint stress enhances Con A-stimulated T-cell proliferation by increasing [Ca2+ ]i via stimulation of Ca2+ entry.
Collapse
Affiliation(s)
- Eiki Satoh
- Department of Pathobiological Science, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, 080-8555, Japan.
| | | | | |
Collapse
|
17
|
Orlov SN, Hamet P. Intracellular monovalent ions as second messengers. J Membr Biol 2006; 210:161-72. [PMID: 16909338 DOI: 10.1007/s00232-006-0857-9] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2005] [Revised: 02/08/2006] [Indexed: 01/03/2023]
Abstract
It is generally accepted that electrochemical gradients of monovalent ions across the plasma membrane, created by the coupled function of pumps, carriers and channels, are involved in the maintenance of resting and action membrane potential, cell volume adjustment, intracellular Ca(2+ )handling and accumulation of glucose, amino acids, nucleotides and other precursors of macromolecular synthesis. In the present review, we summarize data showing that side-by-side with these classic functions, modulation of the intracellular concentration of monovalent ions in a physiologically reasonable range is sufficient to trigger numerous cellular responses, including changes in enzyme activity, gene expression, protein synthesis, cell proliferation and death. Importantly, the engagement of monovalent ions in regulation of the above-listed cellular responses occurs at steps upstream of Ca(2+) (i) and other key intermediates of intracellular signaling, which allows them to be considered as second messengers. With the exception of HCO (3) (-) -sensitive soluble adenylyl cyclase, the molecular origin of sensors involved in the function of monovalent ions as second messengers remains unknown.
Collapse
Affiliation(s)
- S N Orlov
- Centre de recherche, Centre hospitalier de l'Université de Montréal, (CHUM)-Hôtel-Dieu, Montreal, Quebec, Canada.
| | | |
Collapse
|
18
|
Orlov SN, Hamet P. The death of cardiotonic steroid-treated cells: evidence of Na+i,K+i-independent H+i-sensitive signalling. Acta Physiol (Oxf) 2006; 187:231-40. [PMID: 16734760 DOI: 10.1111/j.1748-1716.2006.01546.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Na/K-ATPase is the only known target of cardiotonic steroids (CTS) identified in plants, amphibians and later on in several mammalian species, including human. We focus our review on recent data implicating CTS in the tissue-specific regulation of cell survival and death. In vascular smooth muscle cells, CTS inhibited cell death triggered by apoptotic stimuli via a novel Na+i-mediated, Ca2+i-independent mechanism of expression of antiapoptotic genes, including mortalin. In contrast, exposure to CTS in vascular endothelial and renal epithelial cells led to cell death, showing combined markers of apoptosis and necrosis. This mode of cell death, termed oncosis, is caused by CTS interaction with Na/K-ATPase but is independent of the inhibition of Na/K-ATPase-mediated ion fluxes and inversion of the [Na+]i/[K+]i ratio. The intermediates of intracellular signalling involved in Na+i, K+i-independent oncosis of CTS-treated cells remain unknown. Recently, we found that this mode of cell death can be protected by modest intracellular acidification via the expression of H+i-sensitive genes. The molecular origin of intracellular Na+ and H+ sensor involvement in the development of apoptosis and oncosis is currently under investigation.
Collapse
Affiliation(s)
- S N Orlov
- Centre de recherche, Centre hospitalier de l'Université de Montréal (CHUM)-Hôtel-Dieu, Montreal, Quebec, Canada.
| | | |
Collapse
|
19
|
Akimova OA, Lopina OD, Hamet P, Orlov SN. Search for intermediates of Na+,K+-ATPase-mediated [Na+]i/[K+]i-independent death signaling triggered by cardiotonic steroids. PATHOPHYSIOLOGY 2005; 12:125-35. [PMID: 16023561 DOI: 10.1016/j.pathophys.2005.03.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2005] [Revised: 03/08/2005] [Accepted: 03/10/2005] [Indexed: 11/22/2022] Open
Abstract
Previously, we reported that ouabain and other cardiotonic steroids (CTS) kill renal epithelial and vascular endothelial cells via their interaction with the Na+,K+-ATPase alpha-subunit, but independently of elevation of the [Na+]i/[K+]i ratio. In distinct cell types, side-by-side with inhibition of Na+,K+-ATPase-mediated ion fluxes, CTS trigger [Ca2+]i oscillation, activation of Ras, mitogen-activated protein kinases (MAPK), phosphoinositide-3 kinase (PI3K), and protein kinase C as well as the production of reactive oxygen species and cytoskeleton reorganization. This study examined the potential involvement of the above-listed intermediates in death signaling triggered by ouabain in C7-Madin-Darby canine kidney cells. In these cells, twofold decreased staining with dimethylthiazol diphenyltetrazolium (MTT) and detachment of up to 80% of dead cells were detected in 6 and 24 h of ouabain addition, respectively. We did not observe any effect of extra- (EGTA) and intracellular (BAPTA) Ca2+-chelators, [Ca2+]i-raising compounds (thapsigargin, ATP), inhibitors of Ras signaling (alpha-hydroxyfarnesyl-sulphosphoric acid), PI3K (wortmannin), MAPK ERK1/2 kinase (PD98059), tyrosine kinases (genistein) as well as activators (4beta-PMA, 8-Br-cAMP, 8-Br-cGMP, forskolin) and inhibitors (calphostin) of serine-threonine kinases on MTT staining and death of ouabain-treated cells. Ouabain did not affect cellular redox state and the production of superoxide anion and hydroperoxide. Neither N-acetylcysteine nor reduced gluthatione suppressed the death of ouabain-treated cells. Thus, our results show that none of the above-listed signaling systems plays a major role in the development of Nai+,Ki+-independent death machinery triggered by CTS interaction with the Na+,K+-ATPase alpha-subunit.
Collapse
Affiliation(s)
- Olga A Akimova
- Centre de Recherche, Centre hospitalier de l'Université de Montréal (CHUM-Hôtel-Dieu), Montreal, Que., H2W 1T7, Canada
| | | | | | | |
Collapse
|
20
|
Akimova OA, Pchejetski D, Hamet P, Orlov SN. Modest intracellular acidification suppresses death signaling in ouabain-treated cells. Pflugers Arch 2005; 451:569-78. [PMID: 16052351 DOI: 10.1007/s00424-005-1493-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2005] [Accepted: 07/05/2005] [Indexed: 10/25/2022]
Abstract
The signaling cascade resulting in the death of several types of cells treated with ouabain or other cardiotonic steroids (CTS) remains poorly understood. Recently, we observed that ouabain kills epithelial and endothelial cells via its interaction with Na(+), K(+) -ATPase, but independently of inhibition of Na(+), K(+) -ATPase-mediated ion fluxes and inversion of the [Na(+)](i)/[K(+)](i) ratio. Here, we report that the death of ouabain-treated epithelial cells from the Madin-Darby canine kidney (C7-MDCK) and endothelial cells from porcine aortae is suppressed by acidification of medium from pH 7.4 to 7.0, i.e. under conditions when pH(i) was decreased from approximately 7.2 to 6.9. The rescue of ouabain-treated C7-MDCK cells was also detected under selective intracellular acidification caused by inhibition of Na(+)/H(+) exchanger. In these cells, neither Na(+), K(+) pump activity nor [(3)H]-ouabain binding was significantly affected by modest acidification. The death of ouabain-treated cells was independent of inhibition of RNA and protein synthesis with actinomycin D and cycloheximide. In contrast, both compounds sharply attenuated the protective action of acidified medium. Thus, our results show that very modest intracellular acidification is sufficient to inhibit the Na(+) (i)/K(+) (i)-independent death signal triggered in epithelial and endothelial cells by CTS. They also suggest that the protective action of acidification is mediated by de novo expression of genes involved in inhibition of the cell death machinery.
Collapse
Affiliation(s)
- Olga A Akimova
- Centre de recherche, Centre hospitalier de l'Université de Montréal, CHUM - Hôtel-Dieu, Montreal, Canada
| | | | | | | |
Collapse
|
21
|
Satoh E, Ishii T, Nishimura M. Palytoxin-induced increase in cytosolic-free Ca(2+) in mouse spleen cells. Eur J Pharmacol 2003; 465:9-13. [PMID: 12650827 DOI: 10.1016/s0014-2999(03)01459-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The effect of palytoxin (C(129)H(223)N(3)O(54)) on Ca(2+) homeostasis in immune cells has not been studied. Therefore, we investigated the effect of palytoxin on the cytosolic-free Ca(2+) concentration ([Ca(2+)](i)) in mouse spleen cells using a fluorescence Ca(2+) indicator, fura-2. Palytoxin (0.1-100 nM) increased [Ca(2+)](i) in a concentration-dependent manner. The palytoxin-induced increase in [Ca(2+)](i) was abolished by the omission of extracellular Ca(2+) or 1-[beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole hydrochloride (SKF-96365, 100 microM), and was greatly inhibited by Ni(2+) (2 mM). Ouabain (0.5-1 mM) partially inhibited the palytoxin-induced response. There was no effect of decreased extracellular Na(+) (6.2 mM), tetrodotoxin (1 microM), verapamil (10 microM), nifedipine (10 microM), omega-agatoxin IVA (200 nM), omega-conotoxin GVIA (1 microM), omega-conotoxin MVIIC (500 nM), or La(3+) (100 microM). These results suggest that palytoxin increases [Ca(2+)](i) in mouse spleen cells by stimulating Ca(2+) entry through an SKF-96365-, Ni(2+)-sensitive pathway.
Collapse
Affiliation(s)
- Eiki Satoh
- Department of Pathobiological Science, Obihiro University of Agriculture and Veterinary Medicine, Obihiro 080-8555, Japan.
| | | | | |
Collapse
|
22
|
Pchejetski D, Taurin S, Der Sarkissian S, Lopina OD, Pshezhetsky AV, Tremblay J, deBlois D, Hamet P, Orlov SN. Inhibition of Na+,K+-ATPase by ouabain triggers epithelial cell death independently of inversion of the [Na+]i/[K+]i ratio. Biochem Biophys Res Commun 2003; 301:735-44. [PMID: 12565842 DOI: 10.1016/s0006-291x(02)03002-4] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Treatment with ouabain led to massive death of principal cells from collecting ducts (C7-MDCK), indicated by cell swelling, loss of mitochondrial function, an irregular pattern of DNA degradation, and insensitivity to pan-caspase inhibitor. Equimolar substitution of extracellular Na(+) by K(+) or choline(+) sharply attenuated the effect of ouabain on intracellular Na(+) and K(+) content but did not protect the cells from death in the presence of ouabain. In contrast to ouabain, inhibition of the Na(+)/K(+) pump in K(+)-free medium increased Na(+)(i) content but did not affect cell survival. In control and K(+)-free medium, ouabain triggered half-maximal cell death at concentrations of approximately 0.5 and 0.05 microM, respectively, which was consistent with elevation of Na(+)/K(+) pump sensitivity to ouabain in K(+)-depleted medium. Our results show for the first time that the death of ouabain-treated renal epithelial cells is independent of the inhibition of Na(+)/K(+) pump-mediated ion fluxes and the [Na(+)](i)]/[K(+)](i) ratio.
Collapse
Affiliation(s)
- Dimitri Pchejetski
- Centre de recherche, Centre hospitalier de l'Université de Montréal, Hôtel-Dieu, PQ, Canada
| | | | | | | | | | | | | | | | | |
Collapse
|
23
|
Mann CL, Bortner CD, Jewell CM, Cidlowski JA. Glucocorticoid-induced plasma membrane depolarization during thymocyte apoptosis: association with cell shrinkage and degradation of the Na(+)/K(+)-adenosine triphosphatase. Endocrinology 2001; 142:5059-68. [PMID: 11713198 DOI: 10.1210/endo.142.12.8516] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Multiple signaling pathways are known to induce apoptosis in thymocytes through mechanisms that include the loss of mitochondrial membrane potential, cell shrinkage, caspase activation, and DNA degradation but little is known about the consequences of apoptosis on the properties of the plasma membrane. We have previously shown that apoptotic signals, including survival factor withdrawal and glucocorticoids, induce plasma membrane depolarization during rat thymocyte apoptosis, but the mechanisms involved in this process are unknown. We report here that inhibition of the Na(+)/K(+)-adenosine triphosphatase (Na(+)/K(+)-ATPase) with ouabain similarly depolarized control thymocytes and enhanced glucocorticoid-induced membrane depolarization, suggesting a link between Na(+)/K(+)-ATPase and plasma membrane depolarization of thymocytes. To determine whether repression of Na(+)/K(+)-ATPase levels within cells can account for the loss of plasma membrane potential, we assessed protein levels of the Na(+)/K(+)-ATPase in apoptotic thymocytes. Spontaneously dying thymocytes had decreased levels of both catalytic and regulatory subunits of Na(+)/K(+)-ATPase, and glucocorticoid treatment enhanced the loss of Na(+)/K(+)-ATPase protein. The pan caspase inhibitor (z-VAD) blocked both cellular depolarization and repression of Na(+)/K(+)-ATPase in both spontaneously dying and glucocorticoid-treated thymocytes; however, specific inhibitors of caspase 8, 9, and caspase 3 did not. Interestingly, glucocorticoid treatment simultaneously induced cell shrinkage and depolarization. Furthermore, depolarization and the loss of Na(+)/K(+)-ATPase protein were limited to the shrunken population of cells. The data indicate an important role for Na(+)/K(+)-ATPase in both spontaneous and glucocorticoid-induced apoptosis of rat thymocytes.
Collapse
Affiliation(s)
- C L Mann
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
| | | | | | | |
Collapse
|
24
|
Terness P, Navolan D, Dufter C, Kopp B, Opelz G. Exquisitely small amounts of nonglucocorticoid natural steroids suppress the human allogeneic T-cell response. Transplant Proc 2001; 33:547-8. [PMID: 11266951 DOI: 10.1016/s0041-1345(00)02135-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- P Terness
- Department of Transplantation Immunology, Institute of Immunology, University of Heidelberg, Heidelberg, Germany
| | | | | | | | | |
Collapse
|
25
|
Terness P, Navolan D, Dufter C, Kopp B, Opelz G. The T-cell suppressive effect of bufadienolides: structural requirements for their immunoregulatory activity. Int Immunopharmacol 2001; 1:119-34. [PMID: 11367509 DOI: 10.1016/s0162-3109(00)00264-2] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Many studies indicate that substances similar to cardenolides and bufadienolides naturally occur in mammals. The majority of previous studies focused on their cardiovascular, renal, and central nervous action. We analyzed the immunoregulatory property of 52 bufadienolides. Human T-cells were stimulated "in vitro" with mitogens or alloantigens in the presence of bufadienolides. The most active compound totally inhibited T-cell activity at a concentration of 0.75 pmol/10(5) cells. This effect is 16,384 x stronger than that of cortisol and 256 x stronger than that of cyclosporin A or tacrolimus. Preactivated T cells were downregulated and, most importantly, suppressed viable T cells could not be restimulated. Lack of the 17 beta-lactone ring dramatically reduced the activity of bufadienolides. Substitution at C3 also affected their function: components with a 3-OH group were up to 1000 x stronger than those without. The replacement of 14 beta-OH with an epoxy-group slightly decreased the activity. Because there is evidence that the latter change abolishes the cardiac activity, this finding is relevant for therapeutic applications in which immunosuppression without the risk of cardiotoxicity is attempted. One of the substances analyzed in this study was Proscillaridin A. A similar bufadienolide occurs naturally in mammals. We speculate that bufadienolides represent an important bioregulatory link between the cardiovascular, nervous and immune systems.
Collapse
Affiliation(s)
- P Terness
- Institute of Immunology, Department of Transplantation Immunology, INF 305, University of Heidelberg, 69120 Heidelberg, Germany.
| | | | | | | | | |
Collapse
|
26
|
Anner BM, Volet B. Uptake of reconstituted Na,K-ATPase vesicles by isolated lymphocytes measured by FACS, confocal microscopy and spectrofluorometry. Cell Biochem Biophys 1999; 30:437-54. [PMID: 10403060 DOI: 10.1007/bf02738123] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Na,K-ATPase (EC 3.6.1.37, Na,K-ATPase) is a fundamental vital membrane transport and receptor system which, after biosynthesis, is exported to the plasma membrane in inside-out vesicles. Na,K-ATPase can be extracted form the natural membrane and inserted into artificially formed phosphatidylcholine vesicles (liposomes). The ultrastructure of the reconstituted vesicles has been fully described. In the present work, the Na,K-ATPase-vesicles were labeled with fluorescent tracers either in their water or membrane phase, incubated with freshly isolated human lymphocytes, and the resulting cellular fluorescence measured with fluorescence activated cell sorting (FACS), confocal microscopy and spectrofluorometry. The FACS data show that all lymphocytes take up Na,K-ATPase-vesicles in a dose- and temperature-dependent fashion. Three-dimensional analysis of the fluorescence by confocal microscopy reveals that the fluorescence is contained within the cells. Quantitative determination by spectrofluorometry indicates that depending on the vesicle/cell ratio, a single lymphocyte takes up 650 to 36,500 vesicles within 30 min at 37 degrees C together with up to about 200,000 renal Na,K-ATPase molecules.
Collapse
Affiliation(s)
- B M Anner
- Department of Pharmacology, Geneva University Medical School, Switzerland.
| | | |
Collapse
|
27
|
Anner BM. Transposing results from an artificial minicell to a real cell. Experimental evidence for a working hypothesis linking Na,K-ATPase permeability states to specific alterations of cell life. Ann N Y Acad Sci 1997; 834:367-71. [PMID: 9405826 DOI: 10.1111/j.1749-6632.1997.tb52273.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The present work sets in parallel data obtained with the Na,K-ATPase in artificial vesicular membranes (artificial minicells) and in peripheral human lymphocytes ex vivo. The Na,K-ATPase was purified and reconstituted into single-walled, tight liposomes filled with a reservoir of ATP and Na in which the Na,K-ATPase functions as in cells, that is, the receptor is accessible on the liposome surface (artificial minicells). In this system, an E2-ouabain state impermeable to Rb ions and an Na,K-ATPase-palytoxin state leaky for Rb ions were characterized. The tight E2-ouabain form preserves the viability of isolated lymphocytes, whereas the leaky Na,K-ATPase-palytoxin induces rapid cell bursting and death by a ouabain-sensitive mechanism. Thus, the effect of Na,K-ATPase inhibitors on lymphocyte survival can be predicted from permeability measurements in artificial minicells as verified also with the leak-inducing metals mercury and silver.
Collapse
Affiliation(s)
- B M Anner
- Department of Pharmacology, Geneva University Medical School, CMU, Switzerland.
| |
Collapse
|
28
|
Lau CO, Ng FH, Khoo HE, Yuen R, Tan CH. Inhibition of sodium-dependent uptake processes in purified rat brain synaptosomes by Lophozozymus pictor toxin and palytoxin. Neurochem Int 1996; 28:385-90. [PMID: 8740445 DOI: 10.1016/0197-0186(95)00107-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
To get an insight into the mechanism of neurotoxicity exhibited by Lophozozymus pictor toxin (LPTX) and the toxin isolated from P.caribaeorum (C-PTX) studies were carried out on the effect of these toxins on the uptake of selected substrates (neurotransmitters, amino acids and glucose) in isolated nerve endings. The toxins were found to inhibit the uptake of gamma-aminobutyric acid (GABA), noradrenaline, choline, L-leucine and 2-deoxy-D-glucose in rat brain synaptosomes. LPTX- or C-PTX-induced inhibition of synaptosomal uptake was reduced in the absence of Na+ in the assay medium. Synaptosomes exposed to LPTX and C-PTX release K+ in a dose-dependent manner. Ouabain, a selective inhibitor of the plasma membrane Na+, K(+)-ATPase could inhibit LPTX- and C-PTX-induced K+ efflux from synaptosomes and alleviate the toxin-induced inhibition of synaptosomal GABA uptake. It appears that the induction of ionic flux is the primary cause of toxicity by these toxins leading to the inhibition of Na(+)-dependent uptake processes in synaptosomes. The antagonistic action of ouabain suggests the involvement of the membrane sodium pump in the development of cytotoxicity.
Collapse
Affiliation(s)
- C O Lau
- Department of Biochemistry, Faculty of Medicine, National University of Singapore, Republic of Singapore
| | | | | | | | | |
Collapse
|
29
|
Anner BM, Lacotte D, Anner RM, Moosmayer M. Interaction of hypothalamic Na,K-ATPase inhibitor with isolated human peripheral blood mononuclear cells. Biosci Rep 1994; 14:231-42. [PMID: 7772716 DOI: 10.1007/bf01209728] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
A ligand for the digitalis receptor located on the membrane-embedded Na,K-ATPase (NKA; EC 3.6.1.37) has been isolated from bovine hypothalamus (hypothalamic inhibitory factor; HIF) and identified as isomeric ouabain (Tymiak et al., 1993, Proc. Natl. Acad. Sci. 90: 8189-8193). In analogy to cardioactive steroids (CS) derived from plants or from toad, HIF inhibits the Na/K-exchange process and the ATPase activity of isolated Na,K-ATPase although by a different molecular action mechanism. In the present work we show that, as plant-derived ouabain, HIF inhibits 86Rb-uptake by isolated human lymphocytes with an IC50 of about 20 nM; above this concentration HIF reduces cell viability in contrast to ouabain. The decrease in cell viability by excess HIF is accompanied by discrete morphological alterations (mitochondrial swelling) visible by transmission electron microscopy of ultra-thin sectioned peripheral blood mononuclear cells. Taken together the results show that the hypothalamic NKA inhibitor blocks NKA of isolated human lymphocytes with high potency at nanomolar concentrations without toxicity; concentrations exceeding the ones required to block 86Rb-uptake reduce cell viability, probably due to leak formation across the NKA molecule. Thus, lymphocytes constitute a potential target for HIF action and by their altered NKA status a possible messenger between the nervous and the immune system.
Collapse
Affiliation(s)
- B M Anner
- Department of Pharmacology, Geneva University Medical School, Switzerland
| | | | | | | |
Collapse
|