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Blaustein MP, Hamlyn JM. Sensational site: the sodium pump ouabain-binding site and its ligands. Am J Physiol Cell Physiol 2024; 326:C1120-C1177. [PMID: 38223926 DOI: 10.1152/ajpcell.00273.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 12/22/2023] [Accepted: 01/10/2024] [Indexed: 01/16/2024]
Abstract
Cardiotonic steroids (CTS), used by certain insects, toads, and rats for protection from predators, became, thanks to Withering's trailblazing 1785 monograph, the mainstay of heart failure (HF) therapy. In the 1950s and 1960s, we learned that the CTS receptor was part of the sodium pump (NKA) and that the Na+/Ca2+ exchanger was critical for the acute cardiotonic effect of digoxin- and ouabain-related CTS. This "settled" view was upended by seven revolutionary observations. First, subnanomolar ouabain sometimes stimulates NKA while higher concentrations are invariably inhibitory. Second, endogenous ouabain (EO) was discovered in the human circulation. Third, in the DIG clinical trial, digoxin only marginally improved outcomes in patients with HF. Fourth, cloning of NKA in 1985 revealed multiple NKA α and β subunit isoforms that, in the rodent, differ in their sensitivities to CTS. Fifth, the NKA is a cation pump and a hormone receptor/signal transducer. EO binding to NKA activates, in a ligand- and cell-specific manner, several protein kinase and Ca2+-dependent signaling cascades that have widespread physiological effects and can contribute to hypertension and HF pathogenesis. Sixth, all CTS are not equivalent, e.g., ouabain induces hypertension in rodents while digoxin is antihypertensinogenic ("biased signaling"). Seventh, most common rodent hypertension models require a highly ouabain-sensitive α2 NKA and the elevated blood pressure is alleviated by EO immunoneutralization. These numerous phenomena are enabled by NKA's intricate structure. We have just begun to understand the endocrine role of the endogenous ligands and the broad impact of the ouabain-binding site on physiology and pathophysiology.
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Affiliation(s)
- Mordecai P Blaustein
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, United States
- Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland, United States
| | - John M Hamlyn
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, United States
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2
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Socha MW, Chmielewski J, Pietrus M, Wartęga M. Endogenous Digitalis-like Factors as a Key Molecule in the Pathophysiology of Pregnancy-Induced Hypertension and a Potential Therapeutic Target in Preeclampsia. Int J Mol Sci 2023; 24:12743. [PMID: 37628922 PMCID: PMC10454430 DOI: 10.3390/ijms241612743] [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: 07/15/2023] [Revised: 08/10/2023] [Accepted: 08/11/2023] [Indexed: 08/27/2023] Open
Abstract
Preeclampsia (PE), the most severe presentation of hypertensive disorders of pregnancy, is the major cause of morbidity and mortality linked to pregnancy, affecting both mother and fetus. Despite advances in prophylaxis and managing PE, delivery of the fetus remains the only causative treatment available. Focus on complex pathophysiology brought the potential for new treatment options, and more conservative options allowing reduction of feto-maternal complications and sequelae are being investigated. Endogenous digitalis-like factors, which have been linked to the pathogenesis of preeclampsia since the mid-1980s, have been shown to play a role in the pathogenesis of various cardiovascular diseases, including congestive heart failure and chronic renal disease. Elevated levels of EDLF have been described in pregnancy complicated by hypertensive disorders and are currently being investigated as a therapeutic target in the context of a possible breakthrough in managing preeclampsia. This review summarizes mechanisms implicating EDLFs in the pathogenesis of preeclampsia and evidence for their potential role in treating this doubly life-threatening disease.
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Affiliation(s)
- Maciej W. Socha
- Department of Perinatology, Gynecology and Gynecologic Oncology, Faculty of Health Sciences, Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University, Łukasiewicza 1, 85-821 Bydgoszcz, Poland
- Department of Obstetrics and Gynecology, St. Adalbert’s Hospital in Gdańsk, Copernicus Healthcare Entity, Jana Pawła II 50, 80-462 Gdańsk, Poland
| | - Jakub Chmielewski
- Department of Obstetrics and Gynecology, St. Adalbert’s Hospital in Gdańsk, Copernicus Healthcare Entity, Jana Pawła II 50, 80-462 Gdańsk, Poland
| | - Miłosz Pietrus
- Department of Gynecology and Obstetrics, Jagiellonian University Medical College, 31-501 Kraków, Poland
| | - Mateusz Wartęga
- Department of Pathophysiology, Faculty of Pharmacy, Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University, M. Curie- Skłodowskiej 9, 85-094 Bydgoszcz, Poland
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Carullo N, Fabiano G, D'Agostino M, Zicarelli MT, Musolino M, Presta P, Michael A, Andreucci M, Bolignano D, Coppolino G. New Insights on the Role of Marinobufagenin from Bench to Bedside in Cardiovascular and Kidney Diseases. Int J Mol Sci 2023; 24:11186. [PMID: 37446363 DOI: 10.3390/ijms241311186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Revised: 07/03/2023] [Accepted: 07/04/2023] [Indexed: 07/15/2023] Open
Abstract
Marinobufagenin (MBG) is a member of the bufadienolide family of compounds, which are natural cardiac glycosides found in a variety of animal species, including man, which have different physiological and biochemical functions but have a common action on the inhibition of the adenosine triphosphatase sodium-potassium pump (Na+/K+-ATPase). MBG acts as an endogenous cardiotonic steroid, and in the last decade, its role as a pathogenic factor in various human diseases has emerged. In this paper, we have collated major evidence regarding the biological characteristics and functions of MBG and its implications in human pathology. This review focused on MBG involvement in chronic kidney disease, including end-stage renal disease, cardiovascular diseases, sex and gender medicine, and its actions on the nervous and immune systems. The role of MBG in pathogenesis and the development of a wide range of pathological conditions indicate that this endogenous peptide could be used in the future as a diagnostic biomarker and/or therapeutic target, opening important avenues of scientific research.
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Affiliation(s)
- Nazareno Carullo
- Renal Unit, "Magna Graecia" University of Catanzaro, 88100 Catanzaro, Italy
| | - Giuseppe Fabiano
- Renal Unit, "Magna Graecia" University of Catanzaro, 88100 Catanzaro, Italy
| | - Mario D'Agostino
- Renal Unit, "Magna Graecia" University of Catanzaro, 88100 Catanzaro, Italy
| | | | - Michela Musolino
- Renal Unit, "Magna Graecia" University of Catanzaro, 88100 Catanzaro, Italy
| | - Pierangela Presta
- Renal Unit, "Magna Graecia" University of Catanzaro, 88100 Catanzaro, Italy
| | - Ashour Michael
- Renal Unit, "Magna Graecia" University of Catanzaro, 88100 Catanzaro, Italy
| | - Michele Andreucci
- Renal Unit, "Magna Graecia" University of Catanzaro, 88100 Catanzaro, Italy
| | - Davide Bolignano
- Renal Unit, "Magna Graecia" University of Catanzaro, 88100 Catanzaro, Italy
| | - Giuseppe Coppolino
- Renal Unit, "Magna Graecia" University of Catanzaro, 88100 Catanzaro, Italy
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Gambassi F, Lanzi C, Ricci Z, Duchini P, L'Erario M, Mannaioni G, Cini N, Bonari A, Saffirio C, Occupati B. Life-threatening pediatric poisoning due to ingestion of Bufo bufo toad eggs: A case report. Toxicon 2022; 217:13-16. [PMID: 35839868 DOI: 10.1016/j.toxicon.2022.07.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Revised: 07/07/2022] [Accepted: 07/08/2022] [Indexed: 11/27/2022]
Abstract
Bufo parotid glands and eggs contain cardiac glycosides also known as bufadienolides. This class of molecules can cause digoxin-like cardiac toxicity, as they can block the sodium potassium-adenosine triphosphatase (Na/K-ATPase) pump. Poisoning with these toxins is rare but carries a high mortality risk. There are only a few cases of toad poisoning that have been reported worldwide, mainly in the southern hemisphere. We will describe the case of a child on the autistic spectrum disorder who developed an acute and severe cardiac bradyarrhythmia soon after being in a mountain creek. The child ingested a large quantity of Bufo bufo toad eggs and developed bradycardia (35/min) associated with junctional rhythm with narrow QRS complexes. The poison control center (PCC) indicated the use of atropine on the way to the nearest hospital and the administration of antidotal therapy, i.e., anti-digoxine fragment antibodies (DigiFab), as soon as possible. The patient was transferred by air ambulance to the Regional Referral Pediatric Hospital (RRPH), tested for digoxin blood level by immuno-essay (0.68 ng/mL) and successfully treated with five vials of DigiFab, since atropine administration produced only a fleeting effect on the cardiac rhythm. Patient was discharged 48 hours after poisoning. The presence of bufadienolides in the toad eggs was also confirmed. To our knowledge, this is the first report of toad egg poisoning in Europe. The administration of Digifab helped to reverse the bufadienolide cardiac toxicity.
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Affiliation(s)
- Francesco Gambassi
- Medical Toxicology Unit and Poison Control Centre, Careggi University Hospital, Florence, Italy
| | - Cecilia Lanzi
- Medical Toxicology Unit and Poison Control Centre, Careggi University Hospital, Florence, Italy.
| | - Zaccaria Ricci
- Pediatric Intensive Care Unit, Meyer Children's Hospital, Italy
| | | | | | - Guido Mannaioni
- Medical Toxicology Unit and Poison Control Centre, Careggi University Hospital, Florence, Italy; Neurofarba, University of Florence, Italy
| | - Nicoletta Cini
- General Laboratory, Careggi University Hospital, Florence, Italy
| | | | - Claudia Saffirio
- Department of Emergency Medicine and Trauma Center, Meyer Children's Hospital, Italy
| | - Brunella Occupati
- Medical Toxicology Unit and Poison Control Centre, Careggi University Hospital, Florence, Italy
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Słabiak-Błaż N, Piecha G. Endogenous Mammalian Cardiotonic Steroids-A New Cardiovascular Risk Factor?-A Mini-Review. Life (Basel) 2021; 11:life11080727. [PMID: 34440471 PMCID: PMC8398695 DOI: 10.3390/life11080727] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Revised: 07/18/2021] [Accepted: 07/20/2021] [Indexed: 12/19/2022] Open
Abstract
The role of endogenous mammalian cardiotonic steroids (CTS) in the physiology and pathophysiology of the cardiovascular system and the kidneys has interested researchers for more than 20 years. Cardiotonic steroids extracted from toads or plants, such as digitalis, have been used to treat heart disease since ancient times. CTS, also called endogenous digitalis-like factors, take part in the regulation of blood pressure and sodium homeostasis through their effects on the transport enzyme called sodium–potassium adenosine triphosphatase (Na/K-ATPase) in renal and cardiovascular tissue. In recent years, there has been increasing evidence showing deleterious effects of CTS on the structure and function of the heart, vasculature and kidneys. Understanding the role of CTS may be useful in the development of potential new therapeutic strategies.
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Gross NB, Abad N, Lichtstein D, Taron S, Aparicio L, Fonteh AN, Arakaki X, Cowan RP, Grant SC, Harrington MG. Endogenous Na+, K+-ATPase inhibitors and CSF [Na+] contribute to migraine formation. PLoS One 2019; 14:e0218041. [PMID: 31173612 PMCID: PMC6555523 DOI: 10.1371/journal.pone.0218041] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2019] [Accepted: 05/24/2019] [Indexed: 12/24/2022] Open
Abstract
There is strong evidence that neuronal hyper-excitability underlies migraine, and may or may not be preceded by cortical spreading depression. However, the mechanisms for cortical spreading depression and/or migraine are not established. Previous studies reported that cerebrospinal fluid (CSF) [Na+] is higher during migraine, and that higher extracellular [Na+] leads to hyper-excitability. We raise the hypothesis that altered choroid plexus Na+, K+-ATPase activity can cause both migraine phenomena: inhibition raises CSF [K+] and initiates cortical spreading depression, while activation raises CSF [Na+] and causes migraine. In this study, we examined levels of specific Na+, K+-ATPase inhibitors, endogenous ouabain-like compounds (EOLC), in CSF from migraineurs and controls. CSF EOLC levels were significantly lower during ictal migraine (0.4 nM +/- 0.09) than from either controls (1.8 nM +/- 0.4) or interictal migraineurs (3.1 nM +/- 1.9). Blood plasma EOLC levels were higher in migraineurs than controls, but did not differ between ictal and interictal states. In a Sprague-Dawley rat model of nitroglycerin-triggered central sensitization, we changed the concentrations of EOLC and CSF sodium, and measured aversive mechanical threshold (von Frey hairs), trigeminal nucleus caudalis activation (cFos), and CSF [Na+] (ultra-high field 23Na MRI). Animals were sensitized by three independent treatments: intraperitoneal nitroglycerin, immunodepleting EOLC from cerebral ventricles, or cerebroventricular infusion of higher CSF [Na+]. Conversely, nitroglycerin-triggered sensitization was prevented by either vascular or cerebroventricular delivery of the specific Na+, K+-ATPase inhibitor, ouabain. These results affirm our hypothesis that higher CSF [Na+] is linked to human migraine and to a rodent migraine model, and demonstrate that EOLC regulates them both. Our data suggest that altered choroid plexus Na+, K+-ATPase activity is a common source of these changes, and may be the initiating mechanism in migraine.
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Affiliation(s)
- Noah B. Gross
- Huntington Medical Research Institutes, Pasadena, California, United States of America
| | - Nastaren Abad
- Department of Chemical & Biomedical Engineering, FAMU-FSU College of Engineering, Florida State University, Tallahassee, Florida, United States of America
- Center for Interdisciplinary Magnetic Resonance, National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida, United States of America
| | - David Lichtstein
- Department of Medical Neurobiology, Institute for Medical Research, Israel-Canada, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Shiri Taron
- Department of Medical Neurobiology, Institute for Medical Research, Israel-Canada, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Lorena Aparicio
- Huntington Medical Research Institutes, Pasadena, California, United States of America
| | - Alfred N. Fonteh
- Huntington Medical Research Institutes, Pasadena, California, United States of America
| | - Xianghong Arakaki
- Huntington Medical Research Institutes, Pasadena, California, United States of America
| | - Robert P. Cowan
- Department of Neurology, Stanford University, Palo Alto, California, United States of America
| | - Samuel C. Grant
- Department of Chemical & Biomedical Engineering, FAMU-FSU College of Engineering, Florida State University, Tallahassee, Florida, United States of America
- Center for Interdisciplinary Magnetic Resonance, National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida, United States of America
| | - Michael G. Harrington
- Huntington Medical Research Institutes, Pasadena, California, United States of America
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Lichtstein D, Ilani A, Rosen H, Horesh N, Singh SV, Buzaglo N, Hodes A. Na⁺, K⁺-ATPase Signaling and Bipolar Disorder. Int J Mol Sci 2018; 19:E2314. [PMID: 30087257 PMCID: PMC6121236 DOI: 10.3390/ijms19082314] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2018] [Revised: 07/25/2018] [Accepted: 07/26/2018] [Indexed: 02/07/2023] Open
Abstract
Bipolar disorder (BD) is a severe and common chronic mental illness characterized by recurrent mood swings between depression and mania. The biological basis of the disease is poorly understood and its treatment is unsatisfactory. Although in past decades the "monoamine hypothesis" has dominated our understanding of both the pathophysiology of depressive disorders and the action of pharmacological treatments, recent studies focus on the involvement of additional neurotransmitters/neuromodulators systems and cellular processes in BD. Here, evidence for the participation of Na⁺, K⁺-ATPase and its endogenous regulators, the endogenous cardiac steroids (ECS), in the etiology of BD is reviewed. Proof for the involvement of brain Na⁺, K⁺-ATPase and ECS in behavior is summarized and it is hypothesized that ECS-Na⁺, K⁺-ATPase-induced activation of intracellular signaling participates in the mechanisms underlying BD. We propose that the activation of ERK, AKT, and NFκB, resulting from ECS-Na⁺, K⁺-ATPase interaction, modifies neuronal activity and neurotransmission which, in turn, participate in the regulation of behavior and BD. These observations suggest Na⁺, K⁺-ATPase-mediated signaling is a potential target for drug development for the treatment of BD.
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Affiliation(s)
- David Lichtstein
- Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel.
| | - Asher Ilani
- Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel.
| | - Haim Rosen
- Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel.
| | - Noa Horesh
- Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel.
| | - Shiv Vardan Singh
- Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel.
| | - Nahum Buzaglo
- Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel.
| | - Anastasia Hodes
- Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel.
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Role of endogenous digitalis-like factors in the clinical manifestations of severe preeclampsia: a sytematic review. Clin Sci (Lond) 2018; 132:1215-1242. [PMID: 29930141 DOI: 10.1042/cs20171499] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 04/26/2018] [Accepted: 05/08/2018] [Indexed: 12/18/2022]
Abstract
Endogenous digitalis-like factor(s), originally proposed as a vasoconstrictor natriuretic hormone, was discovered in fetal and neonatal blood accidentally because it cross-reacts with antidigoxin antibodies (ADAs). Early studies using immunoassays with ADA identified the digoxin-like immuno-reactive factor(s) (EDLF) in maternal blood as well, and suggested it originated in the feto-placental unit. Mammalian digoxin-like factors have recently been identified as at least two classes of steroid compounds, plant derived ouabain (O), and several toad derived bufodienolides, most prominent being marinobufagenin (MBG). A synthetic pathway for MBG has been identified in mammalian placental tissue. Elevated maternal and fetal EDLF, O and MBG have been demonstrated in preeclampsia (PE), and inhibition of red cell membrane sodium, potassium ATPase (Na, K ATPase (NKA)) by EDLF is reversed by ADA fragments (ADA-FAB). Accordingly, maternal administration of a commercial ADA-antibody fragment (FAB) was tested in several anecdotal cases of PE, and two, small randomized, prospective, double-blind clinical trials. In the first randomized trial, ADA-FAB was administered post-partum, in the second antepartum. In the post-partum trial, ADA-FAB reduced use of antihypertensive drugs. In the second trial, there was no effect of ADA-FAB on blood pressure, but the fall in maternal creatinine clearance (CrCl) was prevented. In a secondary analysis using the pre-treatment maternal level of circulating Na, K ATPase (NKA) inhibitory activity (NKAI), ADA-FAB reduced the incidence of pulmonary edema and, unexpectedly, that of severe neonatal intraventricular hemorrhage (IVH). The fall in CrCl in patients given placebo was proportional to the circulating level of NKAI. The implications of these findings on the pathophysiology of the clinical manifestations PE are discussed, and a new model of the respective roles of placenta derived anti-angiogenic (AAG) factors (AAGFs) and EDLF is proposed.
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Lenaerts C, Bond L, Tuytten R, Blankert B. Revealing of endogenous Marinobufagin by an ultra-specific and sensitive UHPLC-MS/MS assay in pregnant women. Talanta 2018; 187:193-199. [PMID: 29853035 DOI: 10.1016/j.talanta.2018.05.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2018] [Revised: 05/02/2018] [Accepted: 05/04/2018] [Indexed: 01/24/2023]
Abstract
Marinobufagenin (MBG) is a bufadienolide cardiac inotrope implicated in volume expansion-mediated hypertensive states including essential hypertension and preeclampsia (PE). Endogenous MBG is an inhibitor of the α1-isoform of Na+,K+-ATPase with vasoconstrictive and cardiotonic properties, causing hypertension and natriuresis. Elevated endogenous MBG-like material levels have been described by immunoassays in salt-sensitive pregnant and preeclamptic rats as well as in preeclamptic human patients. The rise of endogenous MBG-like material appears prior the development of the main symptoms of PE, leading us to consider MBG as one of the potential biomarkers for PE. The weak specificity and the high variability of the published immunoassays gives no certification about endogenous MBG existence. This led us to set-up a highly specific and sensitive analytical method to detect MBG in plasma at low levels relying on liquid chromatography combined to mass spectrometry (UHPLC-MS/MS) with recording of 7 highly specific MRM transitions for MBG. Pure MBG standard used in the method development was obtained by purification from the Bufo marinus toad venom. d3-25-hydroxyvitamin D3 was used as internal standard. An increasing organic gradient with mobile phase A and B composed of 97:3 (v/v) H2O: MeOH and 50:45:5 (v/v/v) MeOH:IPA:H2O at pH 4.5 respectively was used on a Pursuit 3 PFP column (100 mm × 3 mm; 3 µm) to allow elution and separation of the plasmatic compounds. Chromatographic analyses of plasma samples were preceded by a precipitation of proteins pretreatment. The developed UHPLC-MS/MS assay has been applied to early-pregnant women plasma samples allowing us to investigate MBG plasma levels. Thanks to the high specificity of the assay we were able to authenticate and certify the presence of endogenous MBG in early-pregnant women plasma with the use of the 7 selected specific mass transitions. These pioneering preliminary results are giving a promising perspective for early preeclampsia risk assessment in pregnant women.
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Affiliation(s)
- Charline Lenaerts
- Laboratory of Pharmaceutical Analysis, Faculty of medicine and pharmacy, Research Institute for Health Sciences and Technology, University of Mons, Place du Parc 20, 7000 Mons, Belgium
| | - Liz Bond
- Metabolomic Diagnostics, Little Island, Cork, Ireland
| | - Robin Tuytten
- Metabolomic Diagnostics, Little Island, Cork, Ireland
| | - Bertrand Blankert
- Laboratory of Pharmaceutical Analysis, Faculty of medicine and pharmacy, Research Institute for Health Sciences and Technology, University of Mons, Place du Parc 20, 7000 Mons, Belgium.
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Abstract
Studies in the early 1990s suggested that a hormone identical to ouabain or an isomer of ouabain is secreted by the adrenal glands into the circulation and plays a role in the regulation of arterial pressure and cardiac and renal function. This hormone, known as endogenous ouabain (EO), was claimed to contribute to the pathophysiology of a number of disorders including heart failure, renal failure, pregnancy-induced, and essential hypertension. However, some research groups have been unable to confirm the presence of EO in the human circulation and the issue remains in dispute. In that the implications are of considerable importance to clinicians who, like the authors, lack biochemical expertise, it would be useful if the dispute could be addressed by disinterested scientists with long-standing and acknowledged expertise in analytical chemistry who could opine as to whether the evidence is, or is not, sufficient to state categorically that EO does (or does not) exist in the circulation in man. This brief review does not present new data but, rather, recommends that adjudication is needed regarding this important issue. © 2018 BioFactors, 44(3):219-221, 2018.
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Affiliation(s)
- Risto J Kaaja
- Institute of Clinical Medicine, Internal Medicine, University of Turku and Turku University Hospital, Finland
| | - M Gary Nicholls
- Christchurch Hospital, University of Otago-Christchurch, Christchurch, New Zealand
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11
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Blaustein MP. The pump, the exchanger, and the holy spirit: origins and 40-year evolution of ideas about the ouabain-Na + pump endocrine system. Am J Physiol Cell Physiol 2017; 314:C3-C26. [PMID: 28971835 DOI: 10.1152/ajpcell.00196.2017] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Two prescient 1953 publications set the stage for the elucidation of a novel endocrine system: Schatzmann's report that cardiotonic steroids (CTSs) are all Na+ pump inhibitors, and Szent-Gyorgi's suggestion that there is an endogenous "missing screw" in heart failure that CTSs like digoxin may replace. In 1977 I postulated that an endogenous Na+ pump inhibitor acts as a natriuretic hormone and simultaneously elevates blood pressure (BP) in salt-dependent hypertension. This hypothesis was based on the idea that excess renal salt retention promoted the secretion of a CTS-like hormone that inhibits renal Na+ pumps and salt reabsorption. The hormone also inhibits arterial Na+ pumps, elevates myocyte Na+ and promotes Na/Ca exchanger-mediated Ca2+ gain. This enhances vasoconstriction and arterial tone-the hallmark of hypertension. Here I describe how those ideas led to the discovery that the CTS-like hormone is endogenous ouabain (EO), a key factor in the pathogenesis of hypertension and heart failure. Seminal observations that underlie the still-emerging picture of the EO-Na+ pump endocrine system in the physiology and pathophysiology of multiple organ systems are summarized. Milestones include: 1) cloning the Na+ pump isoforms and physiological studies of mutated pumps in mice; 2) discovery that Na+ pumps are also EO-triggered signaling molecules; 3) demonstration that ouabain, but not digoxin, is hypertensinogenic; 4) elucidation of EO's roles in kidney development and cardiovascular and renal physiology and pathophysiology; 5) discovery of "brain ouabain", a component of a novel hypothalamic neuromodulatory pathway; and 6) finding that EO and its brain receptors modulate behavior and learning.
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Affiliation(s)
- Mordecai P Blaustein
- Departments of Physiology and Medicine, University of Maryland School of Medicine , Baltimore, Maryland
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12
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Dmitrieva RI, Cranford SM, Doris PA. Genetic Control of Serum Marinobufagenin in the Spontaneously Hypertensive Rat and the Relationship to Blood Pressure. J Am Heart Assoc 2017; 6:JAHA.117.006704. [PMID: 28982675 PMCID: PMC5721872 DOI: 10.1161/jaha.117.006704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND We have investigated serum levels of immunoreactive marinobufagenin (MBG) in 16- to 20-week-old spontaneously hypertensive rats (SHRs)-A3 and in the normotensive Wistar-Kyoto (WKY) rat strain in the absence of salt loading, and we have investigated the genetic control of serum MBG. METHODS AND RESULTS We genotyped the F2 progeny of an SHR-A3×WKY intercross using a genome-wide panel of 253 single-nucleotide polymorphism markers that were dimorphic between SHR-A3 and WKY and measured serum MBG by ELISA. Serum MBG levels were lower in SHR-A3 than WKY rats (0.39±0.07 and 1.27±0.40 nmol/L, respectively), suggesting that MBG may not play a role in the markedly divergent blood pressure measured by telemetry in rats of these 2 strains (SHR-A3 and WKY, 198.3±4.43 and 116.8±1.51 mm Hg, respectively). The strain difference in serum MBG was investigated to determine whether genomic regions influencing MBG might be identified by genetic mapping. Quantitative trait locus mapping indicated a single locus influencing serum MBG in the region of chromosome 6q12. Homozygosity of WKY alleles at this locus was associated with increased serum MBG levels. We surveyed whole genome sequences from our SHR-A3 and WKY lines, seeking coding sequence variation between SHR-A3 and WKY within the mapped locus that might explain the inherited strain difference in serum MBG. CONCLUSIONS We identified amino acid substitution in the sterol transport protein Abcg5, present in SHR-A3, but absent in WKY, that is a potential mechanism influencing MBG levels.
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Affiliation(s)
- Renata I Dmitrieva
- Institute of Molecular Medicine, University of Texas Health Science Center at Houston, TX
| | - Stacy M Cranford
- Institute of Molecular Medicine, University of Texas Health Science Center at Houston, TX
| | - Peter A Doris
- Institute of Molecular Medicine, University of Texas Health Science Center at Houston, TX
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Hodes A, Lichtstein D. Natriuretic hormones in brain function. Front Endocrinol (Lausanne) 2014; 5:201. [PMID: 25506340 PMCID: PMC4246887 DOI: 10.3389/fendo.2014.00201] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Accepted: 11/12/2014] [Indexed: 01/11/2023] Open
Abstract
Natriuretic hormones (NH) include three groups of compounds: the natriuretic peptides (ANP, BNP and CNP), the gastrointestinal peptides (guanylin and uroguanylin), and endogenous cardiac steroids. These substances induce the kidney to excrete sodium and therefore participate in the regulation of sodium and water homeostasis, blood volume, and blood pressure (BP). In addition to their peripheral functions, these hormones act as neurotransmitters or neuromodulators in the brain. In this review, the established information on the biosynthesis, release and function of NH is discussed, with particular focus on their role in brain function. The available literature on the expression patterns of each of the NH and their receptors in the brain is summarized, followed by the evidence for their roles in modulating brain function. Although numerous open questions exist regarding this issue, the available data support the notion that NH participate in the central regulation of BP, neuroprotection, satiety, and various psychiatric conditions, including anxiety, addiction, and depressive disorders. In addition, the interactions between the different NH in the periphery and the brain are discussed.
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Affiliation(s)
- Anastasia Hodes
- Faculty of Medicine, Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - David Lichtstein
- Faculty of Medicine, Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, The Hebrew University of Jerusalem, Jerusalem, Israel
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Lewis LK, Yandle TG, Hilton PJ, Jensen BP, Begg EJ, Nicholls MG. Endogenous ouabain is not ouabain. Hypertension 2014; 64:680-3. [PMID: 25001271 DOI: 10.1161/hypertensionaha.114.03919] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Lynley K Lewis
- From the Christchurch Heart Institute (L.K.L., T.G.Y.) and Department of Medicine (E.J.B., M.G.N.), University of Otago-Christchurch, Christchurch, New Zealand; Department of Medicine, St Thomas' Hospital, London, United Kingdom (P.J.H.); and Division of Toxicology, Canterbury Health Laboratories, Christchurch, New Zealand (B.P.J.)
| | - Timothy G Yandle
- From the Christchurch Heart Institute (L.K.L., T.G.Y.) and Department of Medicine (E.J.B., M.G.N.), University of Otago-Christchurch, Christchurch, New Zealand; Department of Medicine, St Thomas' Hospital, London, United Kingdom (P.J.H.); and Division of Toxicology, Canterbury Health Laboratories, Christchurch, New Zealand (B.P.J.)
| | - Philip J Hilton
- From the Christchurch Heart Institute (L.K.L., T.G.Y.) and Department of Medicine (E.J.B., M.G.N.), University of Otago-Christchurch, Christchurch, New Zealand; Department of Medicine, St Thomas' Hospital, London, United Kingdom (P.J.H.); and Division of Toxicology, Canterbury Health Laboratories, Christchurch, New Zealand (B.P.J.)
| | - Berit P Jensen
- From the Christchurch Heart Institute (L.K.L., T.G.Y.) and Department of Medicine (E.J.B., M.G.N.), University of Otago-Christchurch, Christchurch, New Zealand; Department of Medicine, St Thomas' Hospital, London, United Kingdom (P.J.H.); and Division of Toxicology, Canterbury Health Laboratories, Christchurch, New Zealand (B.P.J.)
| | - Evan J Begg
- From the Christchurch Heart Institute (L.K.L., T.G.Y.) and Department of Medicine (E.J.B., M.G.N.), University of Otago-Christchurch, Christchurch, New Zealand; Department of Medicine, St Thomas' Hospital, London, United Kingdom (P.J.H.); and Division of Toxicology, Canterbury Health Laboratories, Christchurch, New Zealand (B.P.J.)
| | - M Gary Nicholls
- From the Christchurch Heart Institute (L.K.L., T.G.Y.) and Department of Medicine (E.J.B., M.G.N.), University of Otago-Christchurch, Christchurch, New Zealand; Department of Medicine, St Thomas' Hospital, London, United Kingdom (P.J.H.); and Division of Toxicology, Canterbury Health Laboratories, Christchurch, New Zealand (B.P.J.).
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15
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Kerek F, Voicu VA. Spherical Oligo-Silicic Acid SOSA Disclosed as Possible Endogenous Digitalis-Like Factor. Front Endocrinol (Lausanne) 2014; 5:233. [PMID: 25667581 PMCID: PMC4304351 DOI: 10.3389/fendo.2014.00233] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Accepted: 12/16/2014] [Indexed: 11/15/2022] Open
Abstract
The Na(+)/K(+)-ATPase is a membrane ion-transporter protein, specifically inhibited by digitalis glycosides used in cardiac therapy. The existence in mammals of some endogenous digitalis-like factors (EDLFs) as presumed ATPase ligands is generally accepted. But the chemical structure of these factors remained elusive because no weighable amounts of pure EDLFs have been isolated. Recent high-resolution crystal structure data of Na(+)/K(+)-ATPase have located the hydrophobic binding pocket of the steroid glycoside ouabain. It remained uncertain if the EDLF are targeting this steroid-receptor or another specific binding site(s). Our recently disclosed spherical oligo-silicic acids (SOSA) fulfill the main criteria to be identified with the presumed EDL factors. SOSA was found as a very potent inhibitor of the Na(+)/K(+)-ATPase, Ca(2+)-ATPase, H(+)/K(+)-ATPase, and of K-dp-ATPase, with IC50 values between 0.2 and 0.5 μg/mL. These findings are even more astonishing while so far, neither monosilicic acid nor its poly-condensed forms have been remarked biologically active. With the diameter ϕ between 1 and 3 nm, SOSA still belong to molecular species definitely smaller than silica nano-particles with ϕ > 5 nm. In SOSA molecules, almost all Si-OH bonds are displayed on the external shell, which facilitates the binding to hydrophilic ATPase domains. SOSA is stable for long term in solution but is sensitive to freeze-drying, which could explain the failure of countless attempts to isolate pure EDLF. There is a strong resemblance between SOSA and vanadates, the previously known general inhibitors of P-type ATPases. SOSA may be generated endogenously by spherical oligomerization of the ubiquitously present monosilicic acid in animal fluids. The structure of SOSA is sensitive to the concentration of Na(+), K(+), Ca(2+), Mg(2+), and other ions suggesting a presumably archaic mechanism for the regulation of the ATPase pumps.
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Affiliation(s)
- Franz Kerek
- SiNatur GmbH, Martinsried, Germany
- *Correspondence: Franz Kerek, SiNatur GmbH, Am Klopferspitz 19, IZB, 82152 Munich, Germany e-mail:
| | - Victor A. Voicu
- Department of Clinical Pharmacology, Toxicology and Psychopharmacology, Carol Davila University of Medicine and Pharmacy, Bucharest, Romania
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Lenaerts C, Demeyer M, Gerbaux P, Blankert B. Analytical aspects of marinobufagenin. Clin Chim Acta 2013; 421:193-201. [DOI: 10.1016/j.cca.2013.02.028] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Revised: 02/21/2013] [Accepted: 02/22/2013] [Indexed: 11/30/2022]
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Hiyoshi H, Abdelhady S, Segerström L, Sveinbjörnsson B, Nuriya M, Lundgren TK, Desfrere L, Miyakawa A, Yasui M, Kogner P, Johnsen JI, Andäng M, Uhlén P. Quiescence and γH2AX in neuroblastoma are regulated by ouabain/Na,K-ATPase. Br J Cancer 2012; 106:1807-15. [PMID: 22531632 PMCID: PMC3364115 DOI: 10.1038/bjc.2012.159] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Background: Cellular quiescence is a state of reversible proliferation arrest that is induced by anti-mitogenic signals. The endogenous cardiac glycoside ouabain is a specific ligand of the ubiquitous sodium pump, Na,K-ATPase, also known to regulate cell growth through unknown signalling pathways. Methods: To investigate the role of ouabain/Na,K-ATPase in uncontrolled neuroblastoma growth we used xenografts, flow cytometry, immunostaining, comet assay, real-time PCR, and electrophysiology after various treatment strategies. Results: The ouabain/Na,K-ATPase complex induced quiescence in malignant neuroblastoma. Tumour growth was reduced by >50% when neuroblastoma cells were xenografted into immune-deficient mice that were fed with ouabain. Ouabain-induced S-G2 phase arrest, activated the DNA-damage response (DDR) pathway marker γH2AX, increased the cell cycle regulator p21Waf1/Cip1 and upregulated the quiescence-specific transcription factor hairy and enhancer of split1 (HES1), causing neuroblastoma cells to ultimately enter G0. Cells re-entered the cell cycle and resumed proliferation, without showing DNA damage, when ouabain was removed. Conclusion: These findings demonstrate a novel action of ouabain/Na,K-ATPase as a regulator of quiescence in neuroblastoma, suggesting that ouabain can be used in chemotherapies to suppress tumour growth and/or arrest cells to increase the therapeutic index in combination therapies.
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Affiliation(s)
- H Hiyoshi
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm SE-17177, Sweden
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Ma J, Esplin MS, Adair CD, Mason LA, Graves SW. Increasing evidence for and regulation of a human placental endogenous digitalis-like factor. Reprod Sci 2012; 19:437-48. [PMID: 22344738 DOI: 10.1177/1933719111424441] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Endogenous digitalis-like factors (EDLFs) appear to be hypertensiogenic and increased in the serum and placenta of women with preeclampsia (PE), a complication of pregnancy. Digibind, an anti-digoxin antibody Fab fragment, reverses in vitro effects of EDLF and in vivo features of PE. We used Digibind in a radioimmunoassay to measure EDLF and compared this to a bio-functional assay of EDLF with good agreement. These methods confirmed that human placenta was a source of EDLF, synthesizing and releasing EDLF into the media of cultured human placental tissue. Ketoconazole, a steroid synthesis inhibitor, and 17-OH progesterone, a possible substrate of steroid synthesis, were shown to inhibit or increase EDLF release respectively, suggesting overlap of synthetic pathways. Abnormalities of PE such as placental hypoxia, increased reactive oxygen species and increased pro-inflammatory cytokines were demonstrated to increase placental EDLF release. These findings strongly support placental production of EDLF with increased release due to features of PE.
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Affiliation(s)
- Jie Ma
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, USA
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Jacobs BE, Liu Y, Pulina MV, Golovina VA, Hamlyn JM. Normal pregnancy: mechanisms underlying the paradox of a ouabain-resistant state with elevated endogenous ouabain, suppressed arterial sodium calcium exchange, and low blood pressure. Am J Physiol Heart Circ Physiol 2012; 302:H1317-29. [PMID: 22245773 DOI: 10.1152/ajpheart.00532.2011] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Endogenous cardiotonic steroids (CTS) raise blood pressure (BP) via vascular sodium calcium exchange (NCX1.3) and transient receptor-operated channels (TRPCs). Circulating CTS are superelevated in pregnancy-induced hypertension and preeclampsia. However, their significance in normal pregnancy, where BP is low, is paradoxical. Here we test the hypothesis that vascular resistance to endogenous ouabain (EO) develops in normal pregnancy and is mediated by reduced expression of NCX1.3 and TRPCs. We determined plasma and adrenal levels of EO and the impact of exogenous ouabain in pregnancy on arterial expression of Na(+) pumps, NCX1.3, TRPC3, and TRPC6 and BP. Pregnant (embryonic day 4) and nonpregnant rats received infusions of ouabain or vehicle. At 14-16 days, tissues and plasma were collected for blotting and EO assay by radioimmunoassay (RIA), liquid chromatography (LC)-RIA, and LC-multidimensional mass spectrometry (MS3). BP (-8 mmHg; P < 0.05) and NCX1.3 expression fell (aorta -60% and mesenteric artery -30%; P < 0.001) in pregnancy while TRPC expression was unchanged. Circulating EO increased (1.14 ± 0.13 nM) vs. nonpregnant (0.6 ± 0.08 nM; P < 0.05) and was confirmed by LC-MS3 and LC-RIA. LC-MS3 revealed two previously unknown isomers of EO; one increased ∼90-fold in pregnancy. Adrenal EO but not isomers were increased in pregnancy. In nonpregnant rats, similar infusions of ouabain raised BP (+24 ± 3 mmHg; P < 0.001). In ouabain-infused rats, impaired fetal and placental growth occurred with no BP increase. In summary, normal pregnancy is an ouabain-resistant state associated with low BP, elevated circulating levels of EO, two novel steroidal EO isomers, and increased adrenal mass and EO content. Ouabain raises BP only in nonpregnant animals. Vascular resistance to the chronic pressor activity of endogenous and exogenous ouabain is mediated by suppressed NCX1.3 and reduced sensitivity of events downstream of Ca(2+) entry. The mechanisms of EO resistance and the impaired fetal and placental growth due to elevated ouabain may be important in pregnancy-induced hypertension (PIH) and preeclampsia (PE).
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Affiliation(s)
- Brandiese E Jacobs
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, USA
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Dvela M, Rosen H, Ben-Ami HC, Lichtstein D. Endogenous ouabain regulates cell viability. Am J Physiol Cell Physiol 2011; 302:C442-52. [PMID: 22031604 DOI: 10.1152/ajpcell.00336.2011] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The endogenous cardiac steroid-like compounds, endogenous ouabain (EO) in particular, are present in the human circulation and are considered putative ligands of the inhibitory binding site of the plasma membrane Na(+)-K(+)-ATPase. A vast amount of data shows that, when added to cell cultures, these steroids promote the growth of cardiac, vascular, and epithelial cells. However, the involvement of the endogenous compounds in the regulation of cell viability and proliferation has never been addressed experimentally. In this study, we show that EO is present in mammalian sera and cerebral spinal fluid, as well as in commercial bovine and horse sera. The lowering of serum EO concentration by the addition of specific anti-ouabain antibodies caused a decrease in the viability of several cultured cell lines. Among these, neuronal NT2 cells were mostly affected, whereas no reduction in viability was seen in rat neuroendocrine PC12 and monkey kidney COS-7 cells. The anti-ouabain antibody-induced reduction in NT2 cell viability was significantly attenuated by the addition of ouabain and was not observed in cells growing in serum-free media. Furthermore, the addition to the medium of low concentrations (nM) of the cardenolide ouabain, but not of the bufadienolide bufalin, increased NT2 and PC12 cell viability and proliferation. In addition, at these concentrations both ouabain and bufalin caused the activation of ERK1/2 in the NT2 cells. The specific ERK1/2 inhibitor U0126 inhibited both the ouabain-induced activation of the enzyme and the increase in cell viability. Furthermore, anti-ouabain antibodies attenuated serum-stimulated ERK1/2 activity in NT2 but not in PC12 cells. Cumulatively, our results suggest that EO plays a significant role in the regulation of cell viability. In addition, our findings support the notion that activation of the ERK1/2 signaling pathway is obligatory but not sufficient for the induction of cell viability by EO.
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Affiliation(s)
- Moran Dvela
- Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, Hebrew University-Hadassah Medical School, Jerusalem, Israel
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Hilton PJ, McKinnon W, Gravett EC, Peron JMR, Frampton CM, Nicholls MG, Lord G. Selective inhibition of the cellular sodium pump by emicymarin and 14ß anhydroxy bufadienolides. Steroids 2010; 75:1137-45. [PMID: 20688094 DOI: 10.1016/j.steroids.2010.07.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2009] [Revised: 06/30/2010] [Accepted: 07/22/2010] [Indexed: 10/19/2022]
Abstract
Partial inhibition of the sodium pump (Na/K-ATP-ase) by a circulating inhibitor is known to occur in humans. The objectives of this study were to determine the effects of novel bufadienolides lacking an oxygen at C14 on sodium pumps in human erythrocytes and leucocytes, dog kidney and pig brain and to document the importance of the stereochemistry at C17 on the ability to inhibit these sodium pumps. 14α bufadienolides were weak inhibitors of all preparations studied. 3ß-OH,5ß,14ß bufadienolide produced near-total inhibition of dog kidney and pig brain Na/K-ATP-ase. Over the same concentration range, it maximally inhibited the sodium pump of erythrocytes by 70% and leucocytes by 47%. The inhibition profile induced in the leucocyte sodium pump deviated significantly from the simple sigmoidal relationship present in the other preparations over the 3×10(-5) to 1×10(-7) mol/l concentration range. Allo-emicymarin (17α) was confirmed to be a weak inhibitor of the sodium pump/ATP-ase compared with emicymarin (17ß) but both were weaker inhibitors of the leucocyte sodium pump than that of the other preparations. Molecules with the C14 in the ß configuration are more efficacious than in the α configuration. In the case of emicymarin, the attachment of the furone at C17 in the α configuration results in substantially weaker inhibitory activity than in the beta configuration, seen in most cardenolides and bufadienolides. Unlike ouabain and bufalin that show no specificity of action in these preparations, 3ß- OH,5ß,14ß bufadienolide selectively inhibits the activity of at least one low-prevalence subset of the leucocyte Na/K-ATP-ase.
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Affiliation(s)
- Philip J Hilton
- Renal Laboratory, St Thomas' Hospital, London, United Kingdom. address:
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Hopoate-Sitake ML, Adair CD, Mason LA, Torres C, Kipikasa J, Graves SW. Digibind Reverses Inhibition of Cellular Rb+ Uptake Caused by Endogenous Sodium Pump Inhibitors Present in Serum and Placenta of Women with Preeclampsia. Reprod Sci 2010; 18:190-9. [DOI: 10.1177/1933719110385133] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
| | - C. David Adair
- Department Obstetrics and Gynecology, University of Tennessee College of Medicine, Baroness Erlanger Hospital, Chattanooga, TN, USA
| | - Lorrie A. Mason
- Department Obstetrics and Gynecology, University of Tennessee College of Medicine, Baroness Erlanger Hospital, Chattanooga, TN, USA
| | - Carlos Torres
- Department Obstetrics and Gynecology, University of Tennessee College of Medicine, Baroness Erlanger Hospital, Chattanooga, TN, USA
| | - Joseph Kipikasa
- Department Obstetrics and Gynecology, University of Tennessee College of Medicine, Baroness Erlanger Hospital, Chattanooga, TN, USA
| | - Steven W. Graves
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, USA
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Cunha-Filho GA, Resck IS, Cavalcanti BC, Pessoa CÓ, Moraes MO, Ferreira JR, Rodrigues FA, dos Santos ML. Cytotoxic profile of natural and some modified bufadienolides from toad Rhinella schneideri parotoid gland secretion. Toxicon 2010; 56:339-48. [DOI: 10.1016/j.toxicon.2010.03.021] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2009] [Revised: 03/13/2010] [Accepted: 03/23/2010] [Indexed: 11/24/2022]
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Puschett JB, Agunanne E, Uddin MN. Emerging Role of the Bufadienolides in Cardiovascular and Kidney Diseases. Am J Kidney Dis 2010; 56:359-70. [DOI: 10.1053/j.ajkd.2010.01.023] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Accepted: 01/05/2010] [Indexed: 01/11/2023]
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Fedorova OV, Shapiro JI, Bagrov AY. Endogenous cardiotonic steroids and salt-sensitive hypertension. Biochim Biophys Acta Mol Basis Dis 2010; 1802:1230-6. [PMID: 20347967 DOI: 10.1016/j.bbadis.2010.03.011] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2010] [Revised: 03/18/2010] [Accepted: 03/20/2010] [Indexed: 12/12/2022]
Abstract
Endogenous cardiotonic steroids (CTS), also called digitalis like factors, have been postulated to play important roles in pathogenesis of hypertension for nearly half of a century. For the past 50 years biomedical scientists have been in quest of an unidentified factor or hormone that both increases blood pressure and renal sodium excretion; this "natriuretic hormone" was, in fact, postulated to interact with the Na/K-ATPase. Recent discoveries have led to the identification of steroid molecules which are present in humans, rodents and amphibians, and which, in a complex manner, interact with each other and with the other systems that regulate renal salt handling and contribute to the salt-sensitivity of blood pressure. Recent findings include the specific identification of endogenous cardenolide (endogenous ouabain) and bufadienolide (marinobufagenin) CTS in humans along with the delineation of mechanisms by which CTS can signal through the Na/K-ATPase. Although CTS were first considered important in the regulation of renal sodium transport and arterial pressure, more recent work implicates these hormones in the central regulation of blood pressure and regulation of cell growth, and development of cardiovascular and renal fibrosis in particular.
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Affiliation(s)
- Olga V Fedorova
- National Institute on Aging, National Institutes of Health, Baltimore, MD, USA
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Abstract
BACKGROUND Preeclampsia is a major cause of maternal and fetal mortality, and its pathogenesis is not fully understood. Endogenous digitalis-like cardiotonic steroids (CTS) have been implicated in the pathophysiology of preeclampsia; this is illustrated by clinical observations that Digibind, a therapeutic digoxin antibody fragment which binds CTS, lowers blood pressure and reverses Na/K-ATPase inhibition in patients with preeclampsia. Recently we reported that plasma levels of marinobufagenin (MBG), a bufadienolide vasoconstrictor CTS, are increased four-fold in patients with severe preeclampsia. METHODS In the present study, we compared levels of MBG in normal and preeclamptic placentae, as well as the interactions of Digibind and antibodies against MBG and ouabain with material purified from preeclamptic placentae using high-performance liquid chromatography (HPLC). RESULTS Levels of endogenous MBG, but not that of endogenous ouabain, exhibited a four-fold elevation in preeclamptic placentae vs. normal placentae (13.6 +/- 2.5 and 48.6 +/- 7.0 nmoles/g tissue; P < 0.01). The elution time of endogenous placental MBG-like immunoreactive material from reverse-phase HPLC column was identical to that of authentic MBG. A competitive immunoassay based on Digibind exhibited reactivity to HPLC fractions having retention times similar to that seen with MBG and other bufadienolides, but not to ouabain-like immunoreactive material. CONCLUSIONS Our results suggest that elevated levels of endogenous bufadienolide CTS represent a potential target for immunoneutralization in patients with preeclampsia.
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Puschett JB, Agunanne E, Uddin MN. Marinobufagenin, resibufogenin and preeclampsia. Biochim Biophys Acta Mol Basis Dis 2010; 1802:1246-53. [PMID: 20167272 DOI: 10.1016/j.bbadis.2010.02.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2009] [Revised: 01/15/2010] [Accepted: 02/06/2010] [Indexed: 11/18/2022]
Abstract
The bufodienolides are cardiac glycosides which have the ability to inhibit the enzyme, Na(+)/K(+) ATPase (sodium potassium adenosine triphosphatase). They are cardiac inotropes, cause vasoconstriction (and, potentially, hypertension) and are natriuretic. Evidence has accrued over time which supports the view that they are mechanistically involved in volume expansion-mediated hypertension. In this communication, the authors summarize data which support the view that the bufodienolides and, in particular, marinobufagenin (MBG) are involved in the pathogenesis of preeclampsia. In a rat model of the syndrome, MBG causes hypertension, proteinuria, intrauterine growth restriction and increased weight gain. All of these phenotypic characteristics are prevented by an antagonist to MBG, resibufogenin (RBG). The "preeclamptic" animals also develop a vascular leak syndrome, resulting in hemoconcentration. Abnormalities in the MAPK (mitogen-activated protein kinase) system play a role in the mechanism by which MBG produces the abnormalities in the pregnant rat. Studies to discover the relevance of these findings to human preeclampsia are currently underway in several laboratories and clinics.
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Affiliation(s)
- J B Puschett
- Department of Medicine, Texas A&M Health Science Center, Temple, TX 76508, USA.
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Adair CD, Luper A, Rose JC, Russell G, Veille JC, Buckalew VM. The hemodynamic effects of intravenous digoxin-binding fab immunoglobulin in severe preeclampsia: a double-blind, randomized, clinical trial. J Perinatol 2009; 29:284-9. [PMID: 19148110 DOI: 10.1038/jp.2008.224] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVE An endogenous digitalis-like factor (EDLF) has been implicated in the pathophysiology of preeclampsia (PE). This hypothesis is supported by two cases of preeclampsia in which administration of digoxin immune Fab (DIF) reduced mean arterial pressure (MAP). STUDY DESIGN To study this observation further, we performed a double-blind, placebo-controlled, randomized clinical trial to examine the effects on MAP of intravenous DIF given after delivery in 26 subjects with severe preeclampsia. Treating obstetricians were blinded to subject assignment and were allowed to use standard antihypertensive drugs during the trial. RESULTS The primary outcome, a significant difference in blood pressure between the two groups over the 24-h period of observation after the intervention, was not supported. However, mean MAP was significantly lower in the DIF-treated subjects for the first 4 h after therapy as compared with controls (P=0.05). Six subjects (46.2%) in the placebo arm were given conventional antihypertensive medications by their obstetrician for blood pressure >160 mm Hg systolic or >110 mm Hg diastolic, compared with zero subjects in the treatment arm (P=0.01). A trend towards increased creatinine clearance was observed in DIF-treated subjects (137.6+/-42.6 versus 104.1+/-43.4, P=0.07). CONCLUSION These results support the hypothesis that EDLF contributes to the elevated blood pressure in preeclampsia and suggests a possible role for DIF as a treatment for this condition.
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Affiliation(s)
- C D Adair
- Department of Obstetrics and Gynecology, Section of Maternal Fetal Medicine, Wake Forest University School of Medicine, Winston-Salem, NC, USA.
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Bagrov AY, Shapiro JI, Fedorova OV. Endogenous cardiotonic steroids: physiology, pharmacology, and novel therapeutic targets. Pharmacol Rev 2009; 61:9-38. [PMID: 19325075 PMCID: PMC2763610 DOI: 10.1124/pr.108.000711] [Citation(s) in RCA: 383] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Endogenous cardiotonic steroids (CTS), also called digitalis-like factors, have been postulated to play important roles in health and disease for nearly half a century. Recent discoveries, which include the specific identification of endogenous cardenolide (endogenous ouabain) and bufadienolide (marinobufagenin) CTS in humans along with the delineation of an alternative mechanism by which CTS can signal through the Na(+)/K(+)-ATPase, have increased the interest in this field substantially. Although CTS were first considered important in the regulation of renal sodium transport and arterial pressure, more recent work implicates these hormones in the regulation of cell growth, differentiation, apoptosis, and fibrosis, the modulation of immunity and of carbohydrate metabolism, and the control of various central nervous functions and even behavior. This review focuses on the physiological interactions between CTS and other regulatory systems that may be important in the pathophysiology of essential hypertension, preeclampsia, end-stage renal disease, congestive heart failure, and diabetes mellitus. Based on our increasing understanding of the regulation of CTS as well as the molecular mechanisms of these hormone increases, we also discuss potential therapeutic strategies.
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Affiliation(s)
- Alexei Y Bagrov
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, 5600 Nathan Shock Dr., Baltimore, MD 21224, USA.
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Ouabain, a circulating hormone secreted by the adrenals, is pivotal in cardiovascular disease. Fact or fantasy? J Hypertens 2009; 27:3-8. [DOI: 10.1097/hjh.0b013e32831101d1] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Bagrov AY, Shapiro JI. Endogenous digitalis: pathophysiologic roles and therapeutic applications. NATURE CLINICAL PRACTICE. NEPHROLOGY 2008; 4:378-92. [PMID: 18542120 PMCID: PMC2574729 DOI: 10.1038/ncpneph0848] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2008] [Accepted: 04/29/2008] [Indexed: 12/22/2022]
Abstract
Endogenous digitalis-like factors, also called cardiotonic steroids, have been thought for nearly half a century to have important roles in health and disease. The endogenous cardiotonic steroids ouabain and marinobufagenin have been identified in humans, and an effector mechanism has been delineated by which these hormones signal through the sodium/potassium-transporting ATPase. These findings have increased interest in this field substantially. Although cardiotonic steroids were first considered important in the regulation of renal sodium transport and arterial pressure, subsequent work has implicated these hormones in the control of cell growth, apoptosis and fibrosis, among other processes. This Review focuses on the role of endogenous cardiotonic steroids in the pathophysiology of essential hypertension, congestive heart failure, end-stage renal disease and pre-eclampsia. We also discuss potential therapeutic strategies that have emerged as a result of the increased understanding of the regulation and actions of cardiotonic steroids.
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Affiliation(s)
- Alexei Y Bagrov
- Hypertension Unit at Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, NIH, Baltimore 21224, MD, USA.
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Pullen MA, Harpel MR, Danoff TM, Brooks DP. Comparison of non-digitalis binding properties of digoxin-specific Fabs using direct binding methods. J Immunol Methods 2008; 336:235-41. [PMID: 18555269 DOI: 10.1016/j.jim.2008.05.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2008] [Revised: 04/01/2008] [Accepted: 05/08/2008] [Indexed: 11/30/2022]
Abstract
Digibind and DigiFab are commercial formulations of polyclonal, ovine, digoxin-specific Fabs in clinical use for treatment of digoxin intoxication. Of interest for extending its use to other clinical indications, Digibind has also been reported to neutralize the effect of endogenous digoxin-like molecules, including ouabain, that are linked to clinical disorders ranging from preeclampsia to congestive heart failure. Although Digibind and DigiFab are equivalent in their digoxin-binding activity, the antigens used to produce these Fabs are different. We therefore explored, using native (3)H-digoxin and (3)H-ouabain in four different types of solution-phase binding methods, whether they might exhibit different profiles with respect to ouabain and other digoxin-like factors. Consistent with previous results, both Fab preparations bound digoxin with the same affinities and capacities. However, (3)H-ouabain was found to bind with high affinity only to Fab sub-populations present in both products. Interestingly, this sub-population was twice as large for Digibind compared to DigiFab. Competition experiments also showed differences in specificity within Fab sub-populations. Therefore, the equivalence in digoxin-binding activity of the two Fab preparations does not extend to ouabain-binding capacity and Fab specificity, with implications for clinical differentiation between the preparations in treatment of disorders related to control of non-digoxin cardenolides. The existence of a small but perhaps clinically relevant sub-population of antibodies was detected using specific radioligands. This sub-population could not have been detected nor quantified using standard cross-reactivity in an ELISA assay.
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Affiliation(s)
- Mark A Pullen
- Department of Biochemistry, Cardiovascular and Urogenital Center of Excellence for Drug Discovery, GlaxoSmithKline Pharmaceuticals, 709 Swedeland Road, King of Prussia, PA 19406, USA.
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Dvela M, Rosen H, Feldmann T, Nesher M, Lichtstein D. Diverse biological responses to different cardiotonic steroids. ACTA ACUST UNITED AC 2007; 14:159-66. [PMID: 17964766 DOI: 10.1016/j.pathophys.2007.09.011] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Cardiotonic steroids (CS) such as ouabain, digoxin and bufalin, are steroidal drugs prepared from the seeds and dried leaves of the genus Digitalis, and the skin and parotid gland of amphibians, are used as a cardiac stimulant. Steroids similar or identical to the cardiotonic steroids were identified in human tissues. The available literature unequivocally supports the notion that these endogenous CS function as hormones in mammals. Recent studies show that although similar in structure, the different CS exhibit diverse biological responses. This was shown at the molecular, cellular, tissue and whole animal levels. This review summarizes these diversities, raises a possible explanation for their presence and discusses their implication on the physiological role of the different steroids.
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Affiliation(s)
- Moran Dvela
- Department of Physiology and Institute of Microbiology, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
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Mijatovic T, Van Quaquebeke E, Delest B, Debeir O, Darro F, Kiss R. Cardiotonic steroids on the road to anti-cancer therapy. Biochim Biophys Acta Rev Cancer 2007; 1776:32-57. [PMID: 17706876 DOI: 10.1016/j.bbcan.2007.06.002] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2007] [Revised: 06/19/2007] [Accepted: 06/21/2007] [Indexed: 01/04/2023]
Abstract
The sodium pump, Na(+)/K(+)-ATPase, could be an important target for the development of anti-cancer drugs as it serves as a versatile signal transducer, it is a key player in cell adhesion and its aberrant expression and activity are implicated in the development and progression of different cancers. Cardiotonic steroids, known ligands of the sodium pump have been widely used for the treatment of heart failure. However, early epidemiological evaluations and subsequent demonstration of anti-cancer activity in vitro and in vivo have indicated the possibility of developing this class of compound as chemotherapeutic agents in oncology. Their development to date as anti-cancer agents has however been impaired by a narrow therapeutic margin resulting from their potential to induce cardiovascular side-effects. The review will thus discuss (i) sodium pump structure, function, expression in diverse cancers and its chemical targeting and that of its sub-units, (ii) reported in vitro and in vivo anti-cancer activity of cardiotonic steroids, (iii) managing the toxicity of these compounds and the limitations of existing preclinical models to adequately predict the cardiotoxic potential of new molecules in man and (iv) the potential of chemical modification to reduce the cardiovascular side-effects and improve the anti-cancer activity of new molecules.
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Nesher M, Shpolansky U, Rosen H, Lichtstein D. The digitalis-like steroid hormones: new mechanisms of action and biological significance. Life Sci 2007; 80:2093-2107. [PMID: 17499813 DOI: 10.1016/j.lfs.2007.03.013] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2007] [Revised: 03/08/2007] [Accepted: 03/14/2007] [Indexed: 12/25/2022]
Abstract
Digitalis-like compounds (DLC) are a family of steroid hormones synthesized in and released from the adrenal gland. DLC, the structure of which resembles that of plant cardiac glycosides, bind to and inhibit the activity of the ubiquitous cell surface enzyme Na(+), K(+)-ATPase. However, there is a large body of evidence suggesting that the regulation of ion transport by Na(+), K(+)-ATPase is not the only physiological role of DLC. The binding of DLC to Na(+), K(+)-ATPase induces the activation of various signal transduction cascades that activate changes in intracellular Ca(++) homeostasis, and in specific gene expression. These, in turn, stimulate endocytosis and affect cell growth and proliferation. At the systemic level, DLC were shown to be involved in the regulation of major physiological parameters including water and salt homeostasis, cardiac contractility and rhythm, systemic blood pressure and behavior. Furthermore, the DLC system has been implicated in several pathological conditions, including cardiac arrhythmias, hypertension, cancer and depressive disorders. This review evaluates the evidence for the different aspects of DLC action and delineates open questions in the field.
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Affiliation(s)
- Maoz Nesher
- Department of Physiology, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Uri Shpolansky
- Department of Physiology, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Haim Rosen
- The Kuvin Center for the Study of Infectious and Tropical Diseases, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - David Lichtstein
- Department of Physiology, The Hebrew University-Hadassah Medical School, Jerusalem, Israel.
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Goldstein I, Levy T, Galili D, Ovadia H, Yirmiya R, Rosen H, Lichtstein D. Involvement of Na(+), K(+)-ATPase and endogenous digitalis-like compounds in depressive disorders. Biol Psychiatry 2006; 60:491-9. [PMID: 16712803 DOI: 10.1016/j.biopsych.2005.12.021] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2005] [Revised: 11/17/2005] [Accepted: 12/05/2005] [Indexed: 11/29/2022]
Abstract
BACKGROUND Sodium and potassium-activated adenosine triphosphatase (Na(+), K(+)-ATPase) and endogenous digitalis-like compounds (DLC) in the brain have been implicated in the pathogenesis of mood disorders. This hypothesis was examined by the determination of Na(+), K(+)-ATPase/DLC system in parietal cortex of patients with different mood disorders and two animal models of depression. METHODS Na(+), K(+)-ATPase concentrations in human brain synaptosomal fractions, from patients with mood disorders, schizophrenia, and normal individuals, were determined by (3)H-ouabain binding assay. Alpha isoforms were quantified by Western blotting. Brain DLC were measured using sensitive enzyme linked immunosorbant assay (ELISA). The effects of ouabain and ouabain-antibodies on behavior were determined in two animal models of depression. RESULTS (3)H-ouabain binding in bipolar patients was significantly lower than in major depressed and schizophrenic patients. Na(+), K(+)-ATPase alpha isoforms in synaptosomal fractions were not different among the groups. DLC levels in the parietal cortex of bipolar patients were significantly higher than in normal individuals and depressed patients. Injection of lipopolysaccharide (intraperitoneally) to rats elicited depression-like symptoms, which were significantly attenuated by pre-injection of ouabain-antibodies. Injection of ouabain and ouabain-antibodies (intracerebroventricular) reduced depression-like symptoms in the forced swimming test in rats. CONCLUSIONS The results support the possibility that Na(+), K(+)-ATPase and endogenous DLC participate in the pathogenesis of depressive disorders.
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Affiliation(s)
- Inbal Goldstein
- Department of Physiology, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
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Haddy FJ. Role of dietary salt in hypertension. Life Sci 2006; 79:1585-92. [PMID: 16828490 DOI: 10.1016/j.lfs.2006.05.017] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2005] [Revised: 05/10/2006] [Accepted: 05/23/2006] [Indexed: 11/16/2022]
Abstract
Certain things have not changed since my colleague and I last reviewed the role of dietary salt in hypertension [Haddy, F.J., Pamnani, M.B., 1995. Role of dietary salt in hypertension. Journal of the American College of Nutrition 14, 428-438]. Over half of hypertensives are still salt sensitive, i.e., they respond to a high NaCl intake with a rise in blood pressure. This can be ameliorated by restricting NaCl intake, supplementing potassium intake, and consuming diuretics. Some things have changed. We now have more insight into mechanism; we suspected that volume expansion and endogenous Na(+),K(+)-ATPase inhibitors were the connection between excessive salt intake and the hypertension, but we were not certain as to the nature of the inhibitors. Now it appears that the inhibitors are steroids released from the adrenal gland and are members of the cardenolide family, e.g., ouabain, and the bufadienolide family, e.g., marinobufagenin. This presents new possibilities in therapy, including antibodies to these agents and competitive inhibitors to their binding to Na(+),K(+)-ATPase.
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Affiliation(s)
- Francis J Haddy
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN 55901, USA.
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Pridjian G, Pridjian C, Danchuk S, Ianosi-Irimie M, Vu HV, Puschett JB. Beneficial Effects of Metolazone in a Rat Model of Preeclampsia. J Pharmacol Exp Ther 2006; 318:1027-32. [PMID: 16717105 DOI: 10.1124/jpet.106.104901] [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] [Indexed: 11/22/2022] Open
Abstract
Preeclampsia is a disorder that continues to exact a significant toll with respect to maternal morbidity and mortality as well as fetal wastage. Furthermore, the treatment of this disorder has not changed significantly in 50 years and is unsatisfactory. The use of diuretics in this syndrome is controversial because there is a concern related to potential baleful effects of volume contraction leading to a possible further decrement in the perfusion of the maternal-fetal unit. Metolazone is a diuretic/antihypertensive agent, which has a therapeutic effect on blood pressure (BP) in human essential hypertension without causing a natriuresis. We administered the drug in nondiuretic doses in a rat model of preeclampsia previously developed in this laboratory. The drug reduced BP without an accompanying natriuresis. Although there was a trend toward an improvement in intrauterine growth restriction, as determined by litter size and the number of pups demonstrating malformations, the values did not reach statistical significance. We conclude that metolazone, in low dosage, is an effective antihypertensive in this rat model. These studies have implications for the treatment of the human disorder.
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Affiliation(s)
- Gabriella Pridjian
- Department of Obstetrics and Gynecology, Tulane University School of Medicine, New Orleans, LA 70112-2699, USA.
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Deutsch J, Jang HG, Mansur N, Ilovich O, Shpolansky U, Galili D, Feldman T, Rosen H, Lichtstein D. 4-(3‘α15‘β-Dihydroxy-5‘β-estran-17‘β-yl)furan-2-methyl Alcohol: An Anti-Digoxin Agent with a Novel Mechanism of Action. J Med Chem 2005; 49:600-6. [PMID: 16420045 DOI: 10.1021/jm0505819] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The synthesis and some pharmacological properties of 4-(3'alpha-15'beta-dihydroxy-5beta-estran-17'beta-yl)furan-2-methyl alcohol (16) have been described. The compound was synthesized by reacting a synthetic 3alpha- benzyloxy-5beta-estr-15-en-17-one with the ethylene acetal of 4-bromo-2-furancarboxyaldehyde, followed by hydrolysis of the ethylene acetal and reduction of the aldehyde. Despite its resemblance to the structure of cardiac steroids (CS), 16 does not bind to the CS receptor on Na(+),K(+)-ATPase and does not increase the force of contraction of heart muscle. However, 16 inhibited the digoxin-induced increase in the force of contraction and arrhythmias in guinea pig papillary muscle and human atrial appendages. The steroid also inhibited digoxin-induced alteration in endocytosed membrane traffic, indicating a novel mechanism of action.
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Affiliation(s)
- Joseph Deutsch
- Department of Medicinal Chemistry, School of Pharmacy, The Hebrew University-Hadassah Medical School, Jerusalem, Israel.
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Vu HV, Ianosi-Irimie MR, Pridjian CA, Whitbred JM, Durst JM, Bagrov AY, Fedorova OV, Pridjian G, Puschett JB. Involvement of marinobufagenin in a rat model of human preeclampsia. Am J Nephrol 2005; 25:520-8. [PMID: 16179779 DOI: 10.1159/000088461] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2005] [Accepted: 07/25/2005] [Indexed: 11/19/2022]
Abstract
BACKGROUND Preeclampsia is a potentially devastating disorder of hypertension in pregnancy for which there is currently no definitive treatment short of delivery. The bufadienolide, marinobufagenin (MBG), an inhibitor of Na(+)/K(+) ATPase, has been found to be elevated in extracellular fluid volume-expanded hypertensive patients, a condition similar to preeclampsia. Thus, these studies sought to examine the role of MBG in our rat model of preeclampsia. METHODS AND RESULTS Pregnant female rats were injected intraperitoneally with deoxycorticosterone acetate (DOCA) and given 0.9% saline as drinking water for the duration of their pregnancy. Urinary MBG was measured using a DELFIA immunoassay. Blood pressure was measured via the tail-cuff method. Injections of anti-MBG antibody were given intraperitoneally or intravenously to hypertensive pregnant rats. MBG was given intraperitoneally to pregnant rats. Uterine arterioles were dissected free and their diameters were measured before and after perfusion of MBG, ouabain, or digoxin. MBG was found to be elevated in the pregnant + DOCA + saline (PDS) rats compared to normal pregnant animals. In addition, when PDS rats were injected with anti-MBG antibody, there was a subsequent reduction in blood pressure. Administration of MBG in normal pregnant rats caused an elevation in blood pressure equivalent to the PDS model. Also, uterine vessel measurements showed an increased vasoconstrictive reactivity to MBG in the PDS animals vs. the normal pregnant controls; while no changes were observed with perfusion of digoxin or ouabain at the same concentration. CONCLUSION These results suggest a relationship between MBG and a syndrome in rats resembling preeclampsia. Armed with these promising results, it would seem logical to further examine the role of MBG in human preeclampsia.
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Affiliation(s)
- Hop V Vu
- Department of Medicine, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA 70112-2699, USA
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Fedorova OV, Kolodkin NI, Agalakova NI, Namikas AR, Bzhelyansky A, St-Louis J, Lakatta EG, Bagrov AY. Antibody to marinobufagenin lowers blood pressure in pregnant rats on a high NaCl intake. J Hypertens 2005; 23:835-42. [PMID: 15775789 DOI: 10.1097/01.hjh.0000163153.27954.33] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE The pathogenesis of pre-eclampsia (PE), a major cause of maternal and fetal mortality, is not fully understood. Digitalis-like sodium pump ligands (SPLs) are believed to be implicated in PE, as illustrated by clinical observations that DIGIBIND, a digoxin antibody that binds SPLs, lowers blood pressure (BP) in PE. We recently reported that plasma levels of marinobufagenin (MBG), a vasoconstrictor SPL, are increased four-fold in patients with PE. In the present study, we tested whether a polyclonal antibody to MBG can lower BP in rats with pregnancy-associated hypertension. METHODS Systolic BP (SBP), 24-h renal excretion of MBG and endogenous ouabain (EO), and sodium pump activity in the thoracic aortae were measured in virgin and pregnant Sprague-Dawley rats without and with NaCl supplementation (drinking 1.8% NaCl solution). RESULTS NaCl supplementation of virgin rats stimulated renal excretion of MBG by 60%, but not that of EO, and did not change the BP. Compared with virgin rats, the last week of pregnancy in non-NaCl-loaded rats was associated with a decrease in SBP (106 +/- 2 versus 117 +/- 2 mmHg); a moderate increase in renal excretion of MBG (97.6 +/- 4.9 versus 57.4 +/- 7.0 pmoles/24 h) and EO (36.2 +/- 4.3 versus 24.1 +/- 3.2 pmoles/24 h). NaCl-loaded pregnant rats exhibited elevation in SBP (139 +/- 3 mmHg; P < 0.01 versus non-NaCl-loaded pregnant rats), in renal excretion of MBG (160.0 +/- 17.5 pmoles/24 h; P < 0.01 versus non-NaCl-loaded pregnant rats), but not in EO, and showed fetal growth retardation. Administration of the anti-MBG antibody to NaCl-loaded pregnant rats lowered SBP (111 +/- 2 mmHg; P < 0.01) and increased aortic sodium pump activity (144 +/- 3 versus 113 +/- 5 nmol Rb/g per min; P < 0.01 versus non-NaCl-loaded pregnant rats). CONCLUSIONS These observations provide evidence that MBG contributes to BP elevation in pregnant rats rendered hypertensive by NaCl supplementation.
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Affiliation(s)
- Olga V Fedorova
- Laboratory of Cardiovascular Science, National Institute on Aging, NIH, Baltimore Maryland, USA
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Applied Suzuki cross-coupling reaction for syntheses of biologically active compounds. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/s0169-3158(06)80004-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Pullen MA, Brooks DP, Edwards RM. Characterization of the neutralizing activity of digoxin-specific Fab toward ouabain-like steroids. J Pharmacol Exp Ther 2004; 310:319-25. [PMID: 14982968 DOI: 10.1124/jpet.104.065250] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Digoxin-specific Fab (Digibind) is a mixture of antidigoxin Fab fragments prepared from sheep sera and is used as a treatment for digoxin poisoning. Digoxin-specific Fab has been shown to neutralize an endogenous Na+/K+ ATPase inhibitor (endogenous digoxin-like Na+/K+ ATPase regulatory factor; EDLF) in rats and humans and to lower blood pressure. Although the exact structure of EDLF is unknown, compounds identical to or structurally related to ouabain, bufalin, and marinobufagenin have been detected in mammalian plasma. In this study, some structural characteristics of EDLF were inferred from the ability of digoxin-specific Fab to neutralize the Na+/K+ ATPase inhibitory activity of several known cardenolides and bufodienolides. Additional structural information was obtained from [3H]ouabain binding and enzyme-linked immunosorbent assay experiments. Digoxin-specific Fab had the ability to interact to some extent with all of the cardenolides and bufodienolides tested. However, digoxin-specific Fab was more than 20-fold more potent in neutralizing ouabain and bufalin than marinobufagenin. The antihypertensive effect of digoxin-specific Fab seen in preeclampsia and animal models of hypertension may therefore be due to a molecule identical to or structurally similar to ouabain or bufalin.
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Affiliation(s)
- Mark A Pullen
- Department of Renal Biology, GlaxoSmithKline Pharmaceuticals, King of Prussia, Pennsylvania, USA.
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Rosen H, Glukhman V, Feldmann T, Fridman E, Lichtstein D. Cardiac steroids induce changes in recycling of the plasma membrane in human NT2 cells. Mol Biol Cell 2004; 15:1044-54. [PMID: 14718569 PMCID: PMC363072 DOI: 10.1091/mbc.e03-06-0391] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Cardiac steroids (CSs) are specific inhibitors of Na+, K(+)-ATPase activity. Although the presence of CS-like compounds in animal tissues has been established, their physiological role is not evident. In the present study, treatment of human NT2 cells with physiological concentrations (nanomolar) of CSs caused the accumulation of large vesicles adjacent to the nucleus. Experiments using N-(3-triethylammonium propyl)-4-(dibutilamino)styryl-pyrodinum dibromide, transferrin, low-density lipoprotein, and selected anti-transferrin receptor and Rab protein antibodies revealed that CSs induced changes in endocytosis-dependent membrane traffic. Our data indicate that the CS-induced accumulation of cytoplasmic membrane components is a result of inhibited recycling within the late endocytic pathway. Furthermore, our results support the notion that the CS-induced changes in membrane traffic is mediated by the Na+, K(+)-ATPase. These phenomena were apparent in NT2 cells at nanomolar concentrations of CSs and were observed also in other human cell lines, pointing to the generality of this phenomenon. Based on these observations, we propose that the endogenous CS-like compounds are physiological regulators of recycling of endocytosed membrane proteins and cargo.
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Affiliation(s)
- Haim Rosen
- The Kuvin Center for the Study of Infectious and Tropical Diseases, Institute of Microbiology, Jerusalem, Israel.
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Kajimura S, Hirano T, Moriyama S, Vakkuri O, Leppäluoto J, Grau EG. Changes in plasma concentrations of immunoreactive ouabain in the tilapia in response to changing salinity: is ouabain a hormone in fish? Gen Comp Endocrinol 2004; 135:90-9. [PMID: 14644648 DOI: 10.1016/j.ygcen.2003.08.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Ouabain, a cardiac glycoside and inhibitor of Na(+), K(+)-ATPase, is now believed to be a steroid hormone in mammals, involved in blood pressure and volume regulation and possibly acting as a natriuretic hormone. We have identified ouabain-like immunoreactivity in the plasma and tissues of a euryhaline teleost, the tilapia (Oreochromis mossambicus), by means of solid-phase extraction followed by a specific radioimmunoassay. Plasma concentrations of immunoreactive ouabain were 5-20pg/ml. Ouabain immunoreactivity was detected in all the tissues examined, with highest concentrations in the head kidney followed by intestine and body kidney. When the fish in fresh water were transferred to seawater, plasma osmolality increased significantly after 2, 4, 8, and 24h. Significant increases were observed in plasma ouabain immunoreactivity after 4 and 24h, and a significant correlation was seen between ouabain immunoreactivity and plasma osmolality. There was also a significant correlation between the plasma osmolality and cortisol concentrations. Upon transfer from seawater to fresh water, significant increases were seen in plasma cortisol after 4 and 8h and in immunoreactive ouabain after 4h. When the correlation was analyzed using all the data obtained during the two transfer experiments, plasma ouabain immunoreactivity and cortisol were significantly correlated with plasma osmolality, whereas there was a significant negative correlation between plasma prolactin and osmolality. A significant positive correlation was also seen between plasma cortisol and ouabain immunoreactivity. These results suggest that immunoreactive ouabain may be involved, together with cortisol, in the maintenance of hydromineral balance in the tilapia.
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Affiliation(s)
- S Kajimura
- Hawaii Institute of Marine Biology, University of Hawaii, P.O. Box 1346, Kaneohe, HI 96744, USA.
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McKinnon W, Lord GA, Forni LG, Hilton PJ. Circulating sodium pump inhibitors in five volume-expanded humans. J Hypertens 2003; 21:2315-21. [PMID: 14654752 DOI: 10.1097/00004872-200312000-00020] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND We have previously reported the isolation from human placentas of an inhibitor of the sodium pump (Na/K ATP-ase) of molecular weight 370 Da, which is considered to have a dihydropyrone-substituted steroid (bufenolide) structure. OBJECTIVE To examine if this inhibitor is present outside of the pregnant state. METHODS We examined the plasma ultrafiltrate of patients who were clinically volume-expanded. During the period of this study five such patients were identified. One was receiving haemofiltration for acute renal failure and four were being treated by plasma exchange. High performance liquid chromatograph (HPLC) purified fractions obtained from each of these five patients inhibited the human leucocyte sodium pump in vitro. RESULTS Each of the purified fractions that inhibited the leucocyte ATP-ase in vitro contained a compound of mass 370 Da, the same mass as that found previously in placental extracts. This inhibitory factor was absent from HPLC purified fractions of plasma ultrafiltrate obtained from fifty-five patients who were clinically normovolaemic. Negative ion mass spectrometry (MS)/MS of the inhibitory material produced the fragmentation pattern characteristic of the placenta-derived pump inhibitor in only one of the five samples. The other four samples, although having the same mass, exhibited a different fragmentation pattern. CONCLUSION The results suggest that an inhibitor of the sodium pump, identical in mass to that obtained from human placentas, circulates in the plasma of volume-expanded patients. The fragmentation pattern observed in negative ion mass spectrometry in the majority of the volume expanded patients may represent the presence of an isomer of the sodium pump inhibitor previously described in placental material.
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Kerek F, Stimac R, Apell HJ, Freudenmann F, Moroder L. Characterization of the macrocyclic carbon suboxide factors as potent Na,K-ATPase and SR Ca-ATPase inhibitors. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1567:213-20. [PMID: 12488055 DOI: 10.1016/s0005-2736(02)00609-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Recently discovered macrocyclic carbon suboxide (MCS) factors with the general formula (C(3)O(2))(n) were found to strongly inhibit rabbit and rat Na,K-ATPase as well as SR Ca-ATPase. Highly active MCS factors were obtained by a base/acid treatment of their lipophilic precursor isolated from plants. In the ESI-MS spectra, the dominant molar mass ion of 431 Da corresponds to a 1:1 complex of the carbon suboxide hexamer (n=6; M(r)=408 Da) with a Na(+) ion. Additional mass ions identified in positive and negative ion mode were assigned as complexes of the MCS hexamer (n=6) and octamer (n=8) with Na(+) or with TFA(-) in various ratios. The dominant mass ion values of these active MCS factors from plants are also found in mass spectra of previously described endogenous digitalis-like factors (EDLF) from animals. This would suggest that ubiquitously distributed MCS factors may function as putative endogenous regulatory substances of Na,K-ATPase and possibly of other ATPases. With the symmetric display of several equivalent carbonyl or hydroxy groups, the structure of MCS factors is particularly suited for interactions with proteins and other bio-molecules. This could explain the high biological activity and the unusual properties of the MCS factors.
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Affiliation(s)
- Franz Kerek
- AG Bioorganic Chemistry, Max-Planck-Institute for Biochemistry, Am Klopferspitz 18, D-82152 Martinsried, Munich, Germany.
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Abstract
Preeclampsia-eclampsia is still one of the leading causes of maternal and fetal morbidity and mortality. Despite active research for many years, the etiology of this disorder exclusive to human pregnancy is an enigma. Recent evidence suggests there may be several underlying causes or predispositions leading to the signs of hypertension, proteinuria, and edema, findings that allow us to make the diagnosis of the "syndrome" of preeclampsia. Despite improved prenatal care, severe preeclampsia and eclampsia still occur. Although understanding of the pathophysiology of these disorders has improved, treatment has not changed significantly in over 50 years. Although postponement of delivery in selected women with severe preeclampsia improves fetal outcome to a degree, this is not done without risk to the mother. In the United States, magnesium sulfate and hydralazine are the most commonly used medications for seizure prophylaxis and hypertension in the intrapartum period. The search for the underlying cause of this disorder and for a clinical marker to predict those women who will develop preeclampsia-eclampsia is ongoing, with its prevention the ultimate goal. This review began with the clinical and pathophysiologic aspects of preeclampsia-eclampsia (Part 1). Now, in Part 2, the experimental observations, the search for predictive factors, and the genetics of this disorder are reviewed.
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Affiliation(s)
- Gabriella Pridjian
- Department of Obstetrics & Gynecology, Tulane University Medical School, New Orleans, Louisiana 70112, USA.
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Kashkin VA, Bagrov AY, Fedorova OV, Bagrov YY, Agalakova NI, Patkina NA, Zvartau EE. Marinobufagenin (MBG) suppression of ethanol-seeking behavior is associated with inhibition of brain cortex Na/K-ATPase in mice. Eur Neuropsychopharmacol 2002; 12:217-23. [PMID: 12007673 DOI: 10.1016/s0924-977x(02)00026-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
In the present study the hypothesis was tested that sodium pump ligands (SPL) can modulate alcohol-seeking behavior and that this effect is related to changes in Na/K-ATPase activity in the central nervous system. Mice were tested for initiation of ethanol intravenous self-administration (IVSA) following i.p. pretreatment with vehicle or the endogenous SPL, marinobufagenin (MBG). Drug- and experimentally-naive mice acquired IVSA of 2% ethanol during a single 30-min session. MBG was found to dose-dependently attenuate (1.25-2.5 microg/kg) initiation of ethanol IVSA producing a decrease in the ratio and in the difference between operant responses of response-dependent and yoked animals as well as a decrease in percentage of mice demonstrating ethanol-seeking behavior. Attenuation of the reinforcing effect of ethanol resulting from MBG was associated with brain levels of this steroid capable of concurrently inhibiting Na/K-ATPase in the brain cortex. We hypothesize that endogenous digitalis-like factors could modulate the reinforcing effect of ethanol.
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Affiliation(s)
- Vladimir A Kashkin
- Department of Psychopharmacology, Valdman Institute of Pharmacology, Pavlov Medical University, 6/8 Lev Tolstoy Street, St. Petersburg 197089, Russia
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Schoner W. Endogenous cardiac glycosides, a new class of steroid hormones. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:2440-8. [PMID: 12027881 DOI: 10.1046/j.1432-1033.2002.02911.x] [Citation(s) in RCA: 258] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The search for endogenous digitalis has led to the isolation of ouabain as well as several additional cardiotonic steroids of the cardenolide and bufadienolide type from blood, adrenals, and hypothalamus. The concentration of endogenous ouabain is elevated in blood upon increased Na(+) uptake, hypoxia, and physical exercise. Changes in blood levels of ouabain upon physical exercise occur rapidly. Adrenal cortical cells in tissue culture release ouabain upon addition of angiotensin II and epinephrine, and it is thought that ouabain is released from adrenal cortex in vivo. Ouabain levels in blood are elevated in 50% of Caucasians with low-renin hypertension. Infusion over several weeks of low concentrations of ouabain, but not of digoxin, induces hypertension in rats. A digoxin-like compound, which has been isolated from human urine and adrenals, as well various other endogenous cardiac glycosides may counterbalance their actions within a regulatory framework of water and salt metabolism. Marinobufagenin, for instance, whose concentration is increased after cardiac infarction, may show natriuretic properties because it inhibits the alpha1 isoform of Na(+)/K(+)-ATPase, the main sodium pump isoform of the kidney, much better than other sodium pump isoforms. In analogy to other steroid hormones, cardiotonic steroid hormones in blood are bound to a specific cardiac glycoside binding globulin. The discovery of ouabain as a new adrenal hormone affecting Na(+) metabolism and the development of the new ouabain antagonist PST 2238 allows for new possibilities for the therapy of hypertension and congestive heart failure. This will lead in turn to a better understanding of the disease on a physiological and endocrinological level and of the action of ouabain on the cellular level as a signal that is transduced to the plasma membrane as well as to the cell nucleus.
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Affiliation(s)
- Wilhelm Schoner
- Institut für Biochemie und Endokrinologie, Justus-Liebig-Universität Giessen, Germany
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