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Banjac K, Obradovic M, Zafirovic S, Essack M, Gluvic Z, Sunderic M, Nedic O, Isenovic ER. The involvement of Akt, mTOR, and S6K in the in vivo effect of IGF-1 on the regulation of rat cardiac Na +/K +-ATPase. Mol Biol Rep 2024; 51:517. [PMID: 38622478 DOI: 10.1007/s11033-024-09451-3] [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: 12/01/2023] [Accepted: 03/15/2024] [Indexed: 04/17/2024]
Abstract
BACKGROUND We previously demonstrated that insulin-like growth factor-1 (IGF-1) regulates sodium/potassium adenosine triphosphatase (Na+/K+-ATPase) in vascular smooth muscle cells (VSMC) via phosphatidylinositol-3 kinase (PI3K). Taking into account that others' work show that IGF-1 activates the PI3K/protein kinase B (Akt) signaling pathway in many different cells, we here further questioned if the Akt/mammalian target of rapamycin (mTOR)/ribosomal protein p70 S6 kinase (S6K) pathway stimulates Na+/K+-ATPase, an essential protein for maintaining normal heart function. METHODS AND RESULTS There were 14 adult male Wistar rats, half of whom received bolus injections of IGF-1 (50 μg/kg) for 24 h. We evaluated cardiac Na+/K+-ATPase expression, activity, and serum IGF-1 levels. Additionally, we examined the phosphorylated forms of the following proteins: insulin receptor substrate (IRS), phosphoinositide-dependent kinase-1 (PDK-1), Akt, mTOR, S6K, and α subunit of Na+/K+-ATPase. Additionally, the mRNA expression of the Na+/K+-ATPase α1 subunit was evaluated. Treatment with IGF-1 increases levels of serum IGF-1 and stimulates Na+/K+-ATPase activity, phosphorylation of α subunit of Na+/K+-ATPase on Ser23, and protein expression of α2 subunit. Furthermore, IGF-1 treatment increased phosphorylation of IRS-1 on Tyr1222, Akt on Ser473, PDK-1 on Ser241, mTOR on Ser2481 and Ser2448, and S6K on Thr421/Ser424. The concentration of IGF-1 in serum positively correlates with Na+/K+-ATPase activity and the phosphorylated form of mTOR (Ser2448), while Na+/K+-ATPase activity positively correlates with the phosphorylated form of IRS-1 (Tyr1222) and mTOR (Ser2448). CONCLUSION These results indicate that the Akt/mTOR/S6K signalling pathway may be involved in the IGF-1 regulating cardiac Na+/K+-ATPase expression and activity.
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Affiliation(s)
- Katarina Banjac
- Department of Radiobiology and Molecular Genetics, "VINCA" Institute of Nuclear Sciences - National Institute of the Republic of Serbia, University of Belgrade, P.O.Box 522, Belgrade, 11000, Serbia
| | - Milan Obradovic
- Department of Radiobiology and Molecular Genetics, "VINCA" Institute of Nuclear Sciences - National Institute of the Republic of Serbia, University of Belgrade, P.O.Box 522, Belgrade, 11000, Serbia.
| | - Sonja Zafirovic
- Department of Radiobiology and Molecular Genetics, "VINCA" Institute of Nuclear Sciences - National Institute of the Republic of Serbia, University of Belgrade, P.O.Box 522, Belgrade, 11000, Serbia
| | - Magbubah Essack
- Computational Bioscience Research Center (CBRC), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Kingdom of Saudi Arabia
| | - Zoran Gluvic
- Clinic of Internal Medicine, School of Medicine, University Clinical-Hospital Centre Zemun-Belgrade, University of Belgrade, Vukova 9, Belgrade, 11080, Serbia
| | - Milos Sunderic
- Institute for the Application of Nuclear Energy, Department for Metabolism, University of Belgrade, Banatska 31b, Belgrade, Serbia
| | - Olgica Nedic
- Institute for the Application of Nuclear Energy, Department for Metabolism, University of Belgrade, Banatska 31b, Belgrade, Serbia
| | - Esma R Isenovic
- Department of Radiobiology and Molecular Genetics, "VINCA" Institute of Nuclear Sciences - National Institute of the Republic of Serbia, University of Belgrade, P.O.Box 522, Belgrade, 11000, Serbia
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Tokinoya K, Shirai T, Ota Y, Takemasa T, Takekoshi K. Denervation-induced muscle atrophy suppression in renalase-deficient mice via increased protein synthesis. Physiol Rep 2020; 8:e14475. [PMID: 32741114 PMCID: PMC7395909 DOI: 10.14814/phy2.14475] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Revised: 04/17/2020] [Accepted: 05/12/2020] [Indexed: 12/20/2022] Open
Abstract
Denervation-induced muscle atrophy increases signaling through both protein degradation and synthesis pathways. Renalase is a flavin adenine dinucleotide-dependent amine oxidase that inhibits apoptosis and inflammation and promotes cell survival. This study aimed to elucidate the effect of renalase on denervation-induced muscle atrophy. We used 7-week-old renalase knock-out (KO) mice (a model of denervation-induced muscle atrophy) and wild-type (WT) mice (KO: n = 6, weight = 20-26 g; WT: n = 5, weight = 19-23 g). After their left legs were denervated, these mice were killed 1 week later. KO mice had lighter muscle weight than the WT mice. We observed an increase in molecular signaling through protein degradation pathway as well as oxidative stress in denervated muscles compared with that in sham-operated muscles in both WT and KO mice. Additionally, we also observed the main effect of renalase in WT and KO mice. Mitochondrial oxidative phosphorylation protein content was lower in denervated muscles than in sham-operated muscles in both WT and KO mice. However, a significant difference was noted in the reaction with Akt and p70S6K (components of the protein synthesis pathway) between WT and KO mice. In conclusion, mice with renalase deficiency demonstrated an attenuation of denervation-induced muscle atrophy. This might be related to catecholamines because signaling through the protein synthesis pathway was increased following denervation in renalase KO mice compared with that in WT mice, despite showing no change in signaling through protein degradation pathways.
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Affiliation(s)
- Katsuyuki Tokinoya
- Doctoral Program in Sports MedicineGraduate School of Comprehensive Human SciencesUniversity of TsukubaTsukubaJapan
- Research Fellow of the Japan Society for the Promotion of ScienceTokyoJapan
| | - Takanaga Shirai
- Graduate School of Comprehensive Human SciencesUniversity of TsukubaTsukubaJapan
| | - Yuya Ota
- Graduate School of Comprehensive Human SciencesUniversity of TsukubaTsukubaJapan
| | - Tohru Takemasa
- Faculty of Health and Sport SciencesUniversity of TsukubaTsukubaJapan
| | - Kazuhiro Takekoshi
- Division of Clinical MedicineFaculty of MedicineUniversity of TsukubaTsukubaJapan
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Sharma S, Mazumder AG, Rana AK, Patial V, Singh D. Spontaneous Recurrent Seizures Mediated Cardiac Dysfunction via mTOR Pathway Upregulation: A Putative Target for SUDEP Management. CNS & NEUROLOGICAL DISORDERS-DRUG TARGETS 2019; 18:555-565. [DOI: 10.2174/1871527318666190801112027] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 05/02/2019] [Accepted: 05/08/2019] [Indexed: 12/13/2022]
Abstract
Background:Alteration in electrophysiology, leading to cardiac dysfunction and subsequently a nontraumatic death is a complication of epilepsy known as “SUDEP” (Sudden Unexpected Death in Epilepsy).Aims:The present study was designed to understand the molecular changes and cardiac parameters during different phases of epileptogenesis in lithium-pilocarpine (Li-pilo) rat model of epilepsy.Methods:The animals were exposed to Li-pilo to induce Spontaneous Recurrent Seizures (SRS). Noninvasive blood pressure and electrocardiography was recorded at 7th, 28th and 75th day following pilocarpine administration, considered as latent, initial and late SRS phases, respectively. The serum biochemistry, cardiac histopathology, protein and mRNA expressions were studied, following electrocardiography on day 75.Results:The mean arterial pressure decreased during the latent phase, thereafter it progressively increased during the initial and the late SRS phases, as compared to the basal and the latent phase. Histopathological analysis of the heart sections indicated hypertrophy, degenerative changes and fibrous tissue deposition in epileptic animals, along with increased levels of lactate dehydrogenase and creatine kinase-MB in the serum. The expression of HIF-1α, phospho-S6, phospho-mTOR, TGF-β, collagen I and Na+/K+-ATPase α1 proteins, and mRNA levels of HIF-1α, mTOR, Rps6, Scn1b, Scn3b, Nav1.5 and TGF-β were increased in the cardiac tissue of epileptic animals, as compared to control.Conclusion:Our results conclusively showed that Li-pilo-induced SRS leads to cardiac dysfunction via mTOR pathway upregulation, thus suggested the regulatory control of mTOR pathway as a potential target for SUDEP management.
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Affiliation(s)
- Supriya Sharma
- Pharmacology and Toxicology Laboratory, CSIR-Institute of Himalayan Bioresource Technology, Palampur-176061, Himachal Pradesh, India
| | - Arindam G. Mazumder
- Pharmacology and Toxicology Laboratory, CSIR-Institute of Himalayan Bioresource Technology, Palampur-176061, Himachal Pradesh, India
| | - Anil K. Rana
- Pharmacology and Toxicology Laboratory, CSIR-Institute of Himalayan Bioresource Technology, Palampur-176061, Himachal Pradesh, India
| | - Vikram Patial
- Pharmacology and Toxicology Laboratory, CSIR-Institute of Himalayan Bioresource Technology, Palampur-176061, Himachal Pradesh, India
| | - Damanpreet Singh
- Pharmacology and Toxicology Laboratory, CSIR-Institute of Himalayan Bioresource Technology, Palampur-176061, Himachal Pradesh, India
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4
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Hamacher J, Hadizamani Y, Borgmann M, Mohaupt M, Männel DN, Moehrlen U, Lucas R, Stammberger U. Cytokine-Ion Channel Interactions in Pulmonary Inflammation. Front Immunol 2018; 8:1644. [PMID: 29354115 PMCID: PMC5758508 DOI: 10.3389/fimmu.2017.01644] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Accepted: 11/10/2017] [Indexed: 12/12/2022] Open
Abstract
The lungs conceptually represent a sponge that is interposed in series in the bodies’ systemic circulation to take up oxygen and eliminate carbon dioxide. As such, it matches the huge surface areas of the alveolar epithelium to the pulmonary blood capillaries. The lung’s constant exposure to the exterior necessitates a competent immune system, as evidenced by the association of clinical immunodeficiencies with pulmonary infections. From the in utero to the postnatal and adult situation, there is an inherent vital need to manage alveolar fluid reabsorption, be it postnatally, or in case of hydrostatic or permeability edema. Whereas a wealth of literature exists on the physiological basis of fluid and solute reabsorption by ion channels and water pores, only sparse knowledge is available so far on pathological situations, such as in microbial infection, acute lung injury or acute respiratory distress syndrome, and in the pulmonary reimplantation response in transplanted lungs. The aim of this review is to discuss alveolar liquid clearance in a selection of lung injury models, thereby especially focusing on cytokines and mediators that modulate ion channels. Inflammation is characterized by complex and probably time-dependent co-signaling, interactions between the involved cell types, as well as by cell demise and barrier dysfunction, which may not uniquely determine a clinical picture. This review, therefore, aims to give integrative thoughts and wants to foster the unraveling of unmet needs in future research.
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Affiliation(s)
- Jürg Hamacher
- Internal Medicine and Pneumology, Lindenhofspital, Bern, Switzerland.,Internal Medicine V - Pneumology, Allergology, Respiratory and Environmental Medicine, Faculty of Medicine, Saarland University, Saarbrücken, Germany.,Lungen- und Atmungsstiftung Bern, Bern, Switzerland
| | - Yalda Hadizamani
- Internal Medicine and Pneumology, Lindenhofspital, Bern, Switzerland.,Lungen- und Atmungsstiftung Bern, Bern, Switzerland
| | - Michèle Borgmann
- Internal Medicine and Pneumology, Lindenhofspital, Bern, Switzerland.,Lungen- und Atmungsstiftung Bern, Bern, Switzerland
| | - Markus Mohaupt
- Internal Medicine, Sonnenhofspital Bern, Bern, Switzerland
| | | | - Ueli Moehrlen
- Paediatric Visceral Surgery, Universitäts-Kinderspital Zürich, Zürich, Switzerland
| | - Rudolf Lucas
- Department of Pharmacology and Toxicology, Vascular Biology Center, Medical College of Georgia, Augusta, GA, United States
| | - Uz Stammberger
- Lungen- und Atmungsstiftung Bern, Bern, Switzerland.,Novartis Institutes for Biomedical Research, Translational Clinical Oncology, Novartis Pharma AG, Basel, Switzerland
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DiNuzzo M, Giove F, Maraviglia B, Mangia S. Monoaminergic Control of Cellular Glucose Utilization by Glycogenolysis in Neocortex and Hippocampus. Neurochem Res 2015; 40:2493-504. [PMID: 26168779 DOI: 10.1007/s11064-015-1656-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Revised: 04/23/2015] [Accepted: 06/30/2015] [Indexed: 01/01/2023]
Abstract
Brainstem nuclei are the principal sites of monoamine (MA) innervation to major forebrain structures. In the cortical grey matter, increased secretion of MA neuromodulators occurs in response to a wealth of environmental and homeostatic challenges, whose onset is associated with rapid, preparatory changes in neural activity as well as with increases in energy metabolism. Blood-borne glucose is the main substrate for energy production in the brain. Once entered the tissue, interstitial glucose is equally accessible to neurons and astrocytes, the two cell types accounting for most of cellular volume and energy metabolism in neocortex and hippocampus. Astrocytes also store substantial amounts of glycogen, but non-stimulated glycogen turnover is very small. The rate of cellular glucose utilization in the brain is largely determined by hexokinase, which under basal conditions is more than 90 % inhibited by its product glucose-6-phosphate (Glc-6-P). During rapid increases in energy demand, glycogen is a primary candidate in modulating the intracellular level of Glc-6-P, which can occur only in astrocytes. Glycogenolysis can produce Glc-6-P at a rate higher than uptake and phosphorylation of glucose. MA neurotransmitter are released extrasinaptically by brainstem neurons projecting to neocortex and hippocampus, thus activating MA receptors located on both neuronal and astrocytic plasma membrane. Importantly, MAs are glycogenolytic agents and thus they are exquisitely suitable for regulation of astrocytic Glc-6-P concentration, upstream substrate flow through hexokinase and hence cellular glucose uptake. Conforming to such mechanism, Gerald A. Dienel and Nancy F. Cruz recently suggested that activation of noradrenergic locus coeruleus might reversibly block astrocytic glucose uptake by stimulating glycogenolysis in these cells, thereby anticipating the rise in glucose need by active neurons. In this paper, we further develop the idea that the whole monoaminergic system modulates both function and metabolism of forebrain regions in a manner mediated by glycogen mobilization in astrocytes.
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Affiliation(s)
- Mauro DiNuzzo
- Magnetic Resonance for Brain Investigation Laboratory, Museo Storico della Fisica e Centro di Studi e Ricerche "Enrico Fermi", Rome, Italy. .,Magnetic Resonance for Brain Investigation Laboratory, Via Ardeatina 306, 00179, Rome, Italy.
| | - Federico Giove
- Magnetic Resonance for Brain Investigation Laboratory, Museo Storico della Fisica e Centro di Studi e Ricerche "Enrico Fermi", Rome, Italy.,Dipartimento di Fisica, Sapienza Università di Roma, Rome, Italy
| | - Bruno Maraviglia
- Magnetic Resonance for Brain Investigation Laboratory, Museo Storico della Fisica e Centro di Studi e Ricerche "Enrico Fermi", Rome, Italy.,Fondazione Santa Lucia IRCCS, Rome, Italy
| | - Silvia Mangia
- Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, USA
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Abstract
Pulmonary oedema (PO) is a common manifestation of acute heart failure (AHF) and is associated with a high-acuity presentation and with poor in-hospital outcomes. The clinical picture of PO is dominated by signs of pulmonary congestion, and its pathogenesis has been attributed predominantly to an imbalance in Starling forces across the alveolar-capillary barrier. However, recent studies have demonstrated that PO formation and resolution is critically regulated by active endothelial and alveolar signalling. PO represents a medical emergency and treatment should be individually tailored to the urgency of the presentation and acute haemodynamic characteristics. Although, the majority of patients admitted with PO rapidly improve as result of conventional intravenous (IV) therapies, treatment of PO remains largely opinion based as there is a general lack of good evidence to guide therapy. Furthermore, none of these therapies showed simultaneous benefit for symptomatic relief, haemodynamic improvement, increased survival and end-organ protection. Future research is required to develop innovative pharmacotherapies capable of relieving congestion while simultaneously preventing end-organ damage.
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Affiliation(s)
- Ovidiu Chioncel
- Institute of Emergency for Cardiovascular Diseases 'Prof. C.C. Iliescu', University of Medicine and Pharmacy Carol Davila, Bucuresti, Romania
| | - Sean P Collins
- Department of Emergency Medicine, Vanderbilt University, Nashville, Tennessee, US
| | | | - Mihai Gheorghiade
- Center for Cardiovascular Innovation, Northwestern University Feinberg School of Medicine, Chicago, Illinois, US
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7
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Uhlig C, Silva PL, Ornellas D, Santos RS, Miranda PJ, Spieth PM, Kiss T, Kasper M, Wiedemann B, Koch T, Morales MM, Pelosi P, de Abreu MG, Rocco PR. The effects of salbutamol on epithelial ion channels depend on the etiology of acute respiratory distress syndrome but not the route of administration. Respir Res 2014; 15:56. [PMID: 24886221 PMCID: PMC4026154 DOI: 10.1186/1465-9921-15-56] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Accepted: 04/24/2014] [Indexed: 02/06/2023] Open
Abstract
Introduction We investigated the effects of intravenous and intratracheal administration of salbutamol on lung morphology and function, expression of ion channels, aquaporin, and markers of inflammation, apoptosis, and alveolar epithelial/endothelial cell damage in experimental pulmonary (p) and extrapulmonary (exp) mild acute respiratory distress syndrome (ARDS). Methods In this prospective randomized controlled experimental study, 56 male Wistar rats were randomly assigned to mild ARDS induced by either intratracheal (n = 28, ARDSp) or intraperitoneal (n = 28, ARDSexp) administration of E. coli lipopolysaccharide. Four animals with no lung injury served as controls (NI). After 24 hours, animals were anesthetized, mechanically ventilated in pressure-controlled mode with low tidal volume (6 mL/kg), and randomly assigned to receive salbutamol (SALB) or saline 0.9% (CTRL), intravenously (i.v., 10 μg/kg/h) or intratracheally (bolus, 25 μg). Salbutamol doses were targeted at an increase of ≈ 20% in heart rate. Hemodynamics, lung mechanics, and arterial blood gases were measured before and after (at 30 and 60 min) salbutamol administration. At the end of the experiment, lungs were extracted for analysis of lung histology and molecular biology analysis. Values are expressed as mean ± standard deviation, and fold changes relative to NI, CTRL vs. SALB. Results The gene expression of ion channels and aquaporin was increased in mild ARDSp, but not ARDSexp. In ARDSp, intravenous salbutamol resulted in higher gene expression of alveolar epithelial sodium channel (0.20 ± 0.07 vs. 0.68 ± 0.24, p < 0.001), aquaporin-1 (0.44 ± 0.09 vs. 0.96 ± 0.12, p < 0.001) aquaporin-3 (0.31 ± 0.12 vs. 0.93 ± 0.20, p < 0.001), and Na-K-ATPase-α (0.39 ± 0.08 vs. 0.92 ± 0.12, p < 0.001), whereas intratracheal salbutamol increased the gene expression of aquaporin-1 (0.46 ± 0.11 vs. 0.92 ± 0.06, p < 0.001) and Na-K-ATPase-α (0.32 ± 0.07 vs. 0.58 ± 0.15, p < 0.001). In ARDSexp, the gene expression of ion channels and aquaporin was not influenced by salbutamol. Morphological and functional variables and edema formation were not affected by salbutamol in any of the ARDS groups, regardless of the route of administration. Conclusion Salbutamol administration increased the expression of alveolar epithelial ion channels and aquaporin in mild ARDSp, but not ARDSexp, with no effects on lung morphology and function or edema formation. These results may contribute to explain the negative effects of β2-agonists on clinical outcome in ARDS.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | - Marcelo Gama de Abreu
- Laboratory of Pulmonary Investigation, Carlos Chagas Filho Biophysics Institute, Federal University of Rio de Janeiro, Av, Carlos Chagas Filho s/n, Bloco G-014, Rio de Janeiro, RJ 21941-902, Brazil.
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Blagosklonny MV. Common drugs and treatments for cancer and age-related diseases: revitalizing answers to NCI's provocative questions. Oncotarget 2013; 3:1711-24. [PMID: 23565531 PMCID: PMC3681506 DOI: 10.18632/oncotarget.890] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
In 2011, The National Cancer Institute (NCI) has announced 24 provocative questions on cancer. Some of these questions have been already answered in “NCI's provocative questions on cancer: some answers to ignite discussion” (published in Oncotarget, 2011, 2: 1352.) The questions included “Why do many cancer cells die when suddenly deprived of a protein encoded by an oncogene?” “Can we extend patient survival by using approaches that keep tumors static?” “Why are some disseminated cancers cured by chemotherapy alone?” “Can we develop methods to rapidly test interventions for cancer treatment or prevention?” “Can we use our knowledge of aging to enhance prevention or treatment of cancer?” “What is the mechanism by which some drugs commonly and chronically used for other indications protect against cancer?” “How does obesity contribute to cancer risk?” I devoted a single subchapter to each the answer. As expected, the provocative questions were very diverse and numerous. Now I choose and combine, as a single problem, only three last questions, all related to common mechanisms and treatment of age-related diseases including obesity and cancer. Can we use common existing drugs for cancer prevention and treatment? Can we use some targeted “cancer-selective” agents for other diseases and … aging itself.
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Affiliation(s)
- Mikhail V Blagosklonny
- Department of Cell Stress Biology, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY, USA.
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Wu X, Cao Y, Nie J, Liu H, Lu S, Hu X, Zhu J, Zhao X, Chen J, Chen X, Yang Z, Li X. Genetic and pharmacological inhibition of Rheb1-mTORC1 signaling exerts cardioprotection against adverse cardiac remodeling in mice. THE AMERICAN JOURNAL OF PATHOLOGY 2013; 182:2005-14. [PMID: 23567640 DOI: 10.1016/j.ajpath.2013.02.012] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Revised: 02/04/2013] [Accepted: 02/07/2013] [Indexed: 10/27/2022]
Abstract
A previous study indicated that Rheb1 is required for mammalian target of TOR complex 1 (mTORC1) signaling in the brain. However, the function of Rheb1 in the heart is still elusive. In the present study, we deleted Rheb1 specifically in cardiomyocytes and found that reduced Rheb1 levels conferred cardioprotection against pathologic remodeling in myocardial infarction (MI) and pressure overload (transverse aortic constriction) mouse models. Cardiomyocyte apoptosis was reduced and mTORC1 activity was suppressed in cardiomyocyte Rheb1-deletion mice, suggesting that Rheb1 regulates mTORC1 activation in myocardium. Furthermore, we demonstrated that astragaloside IV (As-IV) could inhibit mTORC1, and As-IV treatment displayed similar protection against MI and transverse aortic constriction as Rheb1 genetic inhibition. This study indicates that Rheb1 is essential for mTORC1 activation in cardiomyocytes and suggests that targeting Rheb1-mTORC1 signaling, such as by As-IV treatment, may be an effective therapeutic method for treating patients with adverse cardiac remodeling after MI and hypertrophy.
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Affiliation(s)
- Xiangqi Wu
- Department of Cardiology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, China
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O’Donnell J, Zeppenfeld D, McConnell E, Pena S, Nedergaard M. Norepinephrine: a neuromodulator that boosts the function of multiple cell types to optimize CNS performance. Neurochem Res 2012; 37:2496-512. [PMID: 22717696 PMCID: PMC3548657 DOI: 10.1007/s11064-012-0818-x] [Citation(s) in RCA: 222] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2012] [Revised: 05/16/2012] [Accepted: 05/26/2012] [Indexed: 12/23/2022]
Abstract
Norepinephrine (NE) is a neuromodulator that in multiple ways regulates the activity of neuronal and non-neuronal cells. NE participates in the rapid modulation of cortical circuits and cellular energy metabolism, and on a slower time scale in neuroplasticity and inflammation. Of the multiple sources of NE in the brain, the locus coeruleus (LC) plays a major role in noradrenergic signaling. Processes from the LC primarily release NE over widespread brain regions via non-junctional varicosities. We here review the actions of NE in astrocytes, microglial cells, and neurons based on the idea that the overarching effect of signaling from the LC is to maximize brain power, which is accomplished via an orchestrated cellular response involving most, if not all cell types in CNS.
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Affiliation(s)
- John O’Donnell
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, University of Rochester, 601 Elmwood Avenue, Rochester, NY 14642, USA
| | - Douglas Zeppenfeld
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, University of Rochester, 601 Elmwood Avenue, Rochester, NY 14642, USA
| | - Evan McConnell
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, University of Rochester, 601 Elmwood Avenue, Rochester, NY 14642, USA
| | - Salvador Pena
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, University of Rochester, 601 Elmwood Avenue, Rochester, NY 14642, USA
| | - Maiken Nedergaard
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, University of Rochester, 601 Elmwood Avenue, Rochester, NY 14642, USA
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Abstract
National Cancer Institute has announced 24 provocative questions on cancer. Here I try to answer some of them by linking the dots of existing knowledge.
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Affiliation(s)
- Mikhail V Blagosklonny
- Department of Cell Stress Biology, Roswell Park Cancer Institute, BLSC, L3-312, Elm and Carlton Streets, Buffalo, NY 14263, USA.
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12
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Ma X, Song Y, Chen C, Fu Y, Shen Q, Li Z, Zhang Y. Distinct actions of intermittent and sustained β-adrenoceptor stimulation on cardiac remodeling. SCIENCE CHINA-LIFE SCIENCES 2011; 54:493-501. [DOI: 10.1007/s11427-011-4183-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Accepted: 05/10/2011] [Indexed: 02/02/2023]
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13
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Davis PJ, Davis FB, Lin HY. Roles and controls of mTOR in the heart. Focus on “mTOR attenuates the inflammatory response in cardiomyocytes and prevents cardiac dysfunction in pathological hypertrophy”. Am J Physiol Cell Physiol 2010; 299:C1250-2. [DOI: 10.1152/ajpcell.00410.2010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Paul J. Davis
- Ordway Research Institute,
- Albany Medical College, and
- Albany College of Pharmacy, Albany, New York
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Rahman MS, Gandhi S, Otulakowski G, Duan W, Sarangapani A, O'Brodovich H. Long-term terbutaline exposure stimulates alpha1-Na+-K+-ATPase expression at posttranscriptional level in rat fetal distal lung epithelial cells. Am J Physiol Lung Cell Mol Physiol 2009; 298:L96-L104. [PMID: 19880505 DOI: 10.1152/ajplung.00158.2009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Transepithelial Na(+) transport through epithelial Na(+) channels (ENaC) on the apical membrane and Na(+)-K(+)-ATPase activity on the basolateral membrane of distal lung epithelial cells are critical for alveolar fluid clearance. Acute exposure to beta-adrenergic agonists stimulates lung fluid clearance by increasing Na(+) transport. We investigated the effects of chronic exposure to the beta(2)-adrenergic agonist terbutaline on the transepithelial Na(+) transport in rat fetal distal lung epithelia (FDLE). FDLE monolayers exposed to 10(-4) M terbutaline for 48 h had significantly increased propanolol-blockable transepithelial total and amiloride-sensitive short-circuit current (I(sc)); however, when these chronically exposed monolayers were acutely exposed to additional beta-agonists and intracellular cAMP upregulators, there was no further increase in I(sc). Monolayers exposed to terbutaline for >48 h had I(sc) similar to control cells. Ouabain-sensitive Na(+)-K(+)-ATPase activity was increased in 48-h terbutaline-exposed FDLE whose apical membranes were permeabilized with nystatin. In contrast, terbutaline did not increase amiloride-sensitive apical membrane I(sc) in FDLE whose basolateral membranes were permeabilized with nystatin. Terbutaline treatment did not affect alpha-, beta-, or gamma-ENaC mRNA or alpha-ENaC protein steady-state levels, but increased total cellular levels and rate of synthesis of alpha(1)-Na(+)-K(+)-ATPase protein in FDLE in the absence of any change in alpha(1)-Na(+)-K(+)-ATPase mRNA. Total cellular beta(1)-Na(+)-K(+)-ATPase mRNA and protein levels were not affected by terbutaline. These data suggest that FDLE have different responses from adult type II epithelial cells when chronically exposed to terbutaline, and their increased transepithelial Na(+) transport occurs via a posttranscriptional increase in alpha(1)-Na(+)-K(+)-ATPase expression.
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Affiliation(s)
- Muhammad S Rahman
- Program in Physiology and Experimental Medicine, Hospital for Sick Children Research Institute, 555 Univ. Ave., Toronto, Ontario, Canada M5G 1X8
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15
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Hochberg I, Abassi Z, Azzam ZS. Patterns of alveolar fluid clearance in heart failure. Int J Cardiol 2008; 130:125-30. [PMID: 18579236 DOI: 10.1016/j.ijcard.2008.03.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2007] [Revised: 02/19/2008] [Accepted: 03/01/2008] [Indexed: 11/17/2022]
Abstract
Alveolar fluid clearance (AFC) is important in keeping the airspaces free of edema. This process is accomplished via passive and active transport of Na(+) across the alveolo-capillary barrier mostly by apical Na(+) channels and basolateral Na,K-ATPases, respectively. Patterns of alveolar fluid clearance were found to be decreased in acutely elevated left atrial pressures, possibly due to the inhibition of alveolar epithelial active sodium transport. On the other hand, chronic elevation of pulmonary capillary pressure, such as seen in experimental and clinical congestive heart failure, increases alveolar fluid clearance most likely secondary to upregulation of active sodium transport.
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Affiliation(s)
- Irit Hochberg
- Internal Medicine B, Rambam: Human Health Care Campus, Haifa, Israel
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16
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Abstract
beta(2)-adrenergic receptors are present throughout the lung, including the alveolar airspace, where they play an important role for regulation of the active Na(+) transport needed for clearance of excess fluid out of alveolar airspace. beta(2)-adrenergic receptor signaling is required for up-regulation of alveolar epithelial active ion transport in the setting of excess alveolar edema. The positive, protective effects of beta(2)-adrenergic receptor signaling on alveolar active Na(+) transport in normal and injured lungs provide substantial support for the use of beta-adrenergic agonists to accelerate alveolar fluid clearance in patients with cardiogenic and noncardiogenic pulmonary edema. In this review, we summarize the role of beta(2)-adrenergic receptors in the alveolar epithelium with emphasis on their role in the regulation of alveolar active Na(+) transport in normal and injured lungs.
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Affiliation(s)
- Gökhan M Mutlu
- Northwestern University Feinberg School of Medicine, Pulmonary and Critical Care Medicine, 240 E. Huron Street, McGaw M-300, Chicago, IL 60611, USA.
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17
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Vadász I, Raviv S, Sznajder JI. Alveolar epithelium and Na,K-ATPase in acute lung injury. Intensive Care Med 2007; 33:1243-1251. [PMID: 17530222 PMCID: PMC7095466 DOI: 10.1007/s00134-007-0661-8] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2006] [Accepted: 03/05/2007] [Indexed: 01/11/2023]
Abstract
Active transport of sodium across the alveolar epithelium, undertaken in part by the Na,K-adenosine triphosphatase (Na,K-ATPase), is critical for clearance of pulmonary edema fluid and thus the outcome of patients with acute lung injury. Acute lung injury results in disruption of the alveolar epithelial barrier and leads to impaired clearance of edema fluid and altered Na,K-ATPase function. There has been significant progress in the understanding of mechanisms regulating alveolar edema clearance and signaling pathways modulating Na,K-ATPase function during lung injury. The accompanying review by Morty et al. focuses on intact organ and animal models as well as clinical studies assessing alveolar fluid reabsorption in alveolar epithelial injury. Elucidation of the mechanisms underlying regulation of active Na+ transport, as well as the pathways by which the Na,K-ATPase regulates epithelial barrier function and edema clearance, are of significance to identify interventional targets to improve outcomes of patients with acute lung injury.
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Affiliation(s)
- István Vadász
- Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, 240 E. Huron Street, McGaw 2300, 60611, Chicago, IL, USA
| | - Stacy Raviv
- Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, 240 E. Huron Street, McGaw 2300, 60611, Chicago, IL, USA
| | - Jacob I Sznajder
- Division of Pulmonary and Critical Care Medicine, Feinberg School of Medicine, Northwestern University, 240 E. Huron Street, McGaw 2300, 60611, Chicago, IL, USA.
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18
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Schoner W, Scheiner-Bobis G. Endogenous and exogenous cardiac glycosides: their roles in hypertension, salt metabolism, and cell growth. Am J Physiol Cell Physiol 2007; 293:C509-36. [PMID: 17494630 DOI: 10.1152/ajpcell.00098.2007] [Citation(s) in RCA: 341] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Cardiotonic steroids (CTS), long used to treat heart failure, are endogenously produced in mammals. Among them are the hydrophilic cardenolide ouabain and the more hydrophobic cardenolide digoxin, as well as the bufadienolides marinobufagenin and telecinobufagin. The physiological effects of endogenous ouabain on blood pressure and cardiac activity are consistent with the "Na(+)-lag" hypothesis. This hypothesis assumes that, in cardiac and arterial myocytes, a CTS-induced local increase of Na(+) concentration due to inhibition of Na(+)/K(+)-ATPase leads to an increase of intracellular Ca(2+) concentration ([Ca(2+)](i)) via a backward-running Na(+)/Ca(2+) exchanger. The increase in [Ca(2+)](i) then activates muscle contraction. The Na(+)-lag hypothesis may best explain short-term and inotropic actions of CTS. Yet all data on the CTS-induced alteration of gene expression are consistent with another hypothesis, based on the Na(+)/K(+)-ATPase "signalosome," that describes the interaction of cardiac glycosides with the Na(+) pump as machinery activating various signaling pathways via intramembrane and cytosolic protein-protein interactions. These pathways, which may be activated simultaneously or selectively, elevate [Ca(2+)](i), activate Src and the ERK1/2 kinase pathways, and activate phosphoinositide 3-kinase and protein kinase B (Akt), NF-kappaB, and reactive oxygen species. A recent development indicates that new pharmaceuticals with antihypertensive and anticancer activities may be found among CTS and their derivatives: the antihypertensive rostafuroxin suppresses Na(+) resorption and the Src-epidermal growth factor receptor-ERK pathway in kidney tubule cells. It may be the parent compound of a new principle of antihypertensive therapy. Bufalin and oleandrin or the cardenolide analog UNBS-1450 block tumor cell proliferation and induce apoptosis at low concentrations in tumors with constitutive activation of NF-kappaB.
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Affiliation(s)
- Wilhelm Schoner
- Institut für Biochemie und Endokrinologie, Fachbereich Veterinärmedizin, Justus-Liebig-Universität Giessen, Frankfurter Str 100, Giessen, Germany.
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Bhattacharjee R, Li T, Koshy S, Beard LL, Sharma K, Carter EP, Garat C, Folkesson HG. Stimulation of MAP kinase pathways after maternal IL-1beta exposure induces fetal lung fluid absorption in guinea pigs. Respir Res 2007; 8:27. [PMID: 17386088 PMCID: PMC1847817 DOI: 10.1186/1465-9921-8-27] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2006] [Accepted: 03/26/2007] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND We tested the hypothesis that maternal interleukin-1beta (IL-1beta) pretreatment and induction of fetal cortisol synthesis activates MAP kinases and thereby affects lung fluid absorption in preterm guinea pigs. METHODS IL-1beta was administered subcutaneously daily to timed-pregnant guinea pigs for three days. Fetuses were obtained by abdominal hysterotomy and instilled with isosmolar 5% albumin into the lungs and lung fluid movement was measured over 1 h by mass balance. MAP kinase expression was measured by western blot. RESULTS Lung fluid absorption was induced at 61 days (D) gestation and stimulated at 68D gestation by IL-1beta. Maternal IL-1beta pretreatment upregulated ERK and upstream MEK expression at both 61 and 68D gestation, albeit being much more pronounced at 61D gestation. U0126 instillation completely blocked IL-1beta-induced lung fluid absorption as well as IL-1beta-induced/stimulated ERK expression. Cortisol synthesis inhibition by metyrapone attenuated ERK expression and lung fluid absorption in IL-1beta-pretreated fetal lungs. JNK expression after maternal IL-1beta pretreatment remained unaffected at either gestation age. CONCLUSION These data implicate the ERK MAP kinase pathway as being important for IL-1beta induction/stimulation of lung fluid absorption in fetal guinea pigs.
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Affiliation(s)
- Reshma Bhattacharjee
- Department of Physiology and Pharmacology, Northeastern Ohio Universities College of Medicine, Rootstown, OH 44272-0095, USA
| | - Tianbo Li
- Department of Physiology and Pharmacology, Northeastern Ohio Universities College of Medicine, Rootstown, OH 44272-0095, USA
| | - Shyny Koshy
- Department of Physiology and Pharmacology, Northeastern Ohio Universities College of Medicine, Rootstown, OH 44272-0095, USA
| | - LaMonta L Beard
- Department of Physiology and Pharmacology, Northeastern Ohio Universities College of Medicine, Rootstown, OH 44272-0095, USA
| | - Kapil Sharma
- Department of Physiology and Pharmacology, Northeastern Ohio Universities College of Medicine, Rootstown, OH 44272-0095, USA
| | - Ethan P Carter
- S/M Cardiovascular Pulmonary Research, University of Colorado Health Science Center, Denver, CO 80262, USA
| | - Chrystelle Garat
- S/M Cardiovascular Pulmonary Research, University of Colorado Health Science Center, Denver, CO 80262, USA
| | - Hans G Folkesson
- Department of Physiology and Pharmacology, Northeastern Ohio Universities College of Medicine, Rootstown, OH 44272-0095, USA
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20
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Abstract
Cardiac glycosides have been used for decades to treat congestive heart failure. The recent identification of cardiotonic steroids such as ouabain, digoxin, marinobufagenin, and telocinobufagin in blood plasma, adrenal glands, and hypothalamus of mammals led to exciting new perspectives in the pathology of heart failure and arterial hypertension. Biosynthesis of ouabain and digoxin occurs in adrenal glands and is under the control of angiotensin II, endothelin, and epinephrine released from cells of the midbrain upon stimulation of brain areas sensing cerebrospinal Na(+) concentration and, apparently, the body's K(+) content. Rapid changes of endogenous ouabain upon physical exercise may favor the economy of the heart by a rise of intracellular Ca(2)(+) levels in cardiac and atrial muscle cells. According to the sodium pump lag hypothesis, this may be accomplished by partial inhibition of the sodium pump and Ca(2+) influx via the Na(+)/Ca(2+) exchanger working in reverse mode or via activation of the Na(+)/K(+)-ATPase signalosome complex, generating intracellular calcium oscillations, reactive oxygen species, and gene activation via nuclear factor-kappaB or extracellular signal-regulated kinases 1 and 2. Elevated concentrations of endogenous ouabain and marinobufagenin in the subnanomolar concentration range were found to stimulate proliferation and differentiation of cardiac and smooth muscle cells. They may have a primary role in the development of cardiac dysfunction and failure because (i) offspring of hypertensive patients evidently inherit elevated plasma concentrations of endogenous ouabain; (ii) such elevated concentrations correlate positively with cardiac dysfunction, hypertrophy, and arterial hypertension; (iii) about 40% of Europeans with uncomplicated essential hypertension show increased concentrations of endogenous ouabain associated with reduced heart rate and cardiac hypertrophy; (iv) in patients with advanced arterial hypertension, circulating levels of endogenous ouabain correlate with BP and total peripheral resistance; (v) among patients with idiopathic dilated cardiomyopathy, high circulating levels of endogenous ouabain and marinobufagenin identify those individuals who are predisposed to progressing more rapidly to heart failure, suggesting that endogenous ouabain (and marinobufagenin) may contribute to toxicity upon digoxin therapy. In contrast to endogenous ouabain, endogenous marinobufagenin may act as a natriuretic substance as well. It shows a higher affinity for the ouabain-insensitive alpha(1) isoform of Na(+)/K(+)-ATPase of rat kidney tubular cells and its levels are increased in volume expansion and pre-eclampsia. Digoxin, which is synthesized in adrenal glands, seems to counteract the hypertensinogenic action of ouabain in rats, as do antibodies against ouabain, for example, (Digibind) and rostafuroxin (PST 2238), a selective ouabain antagonist. It lowers BP in ouabain- and adducin-dependent hypertension in rats and is a promising new class of antihypertensive medication in humans.
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Affiliation(s)
- Wilhelm Schoner
- Institute of Biochemistry and Endocrinology, Justus-Liebig-University Giessen, Giessen, Germany.
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Azzam ZS, Adir Y, Welch L, Chen J, Winaver J, Factor P, Krivoy N, Hoffman A, Sznajder JI, Abassi Z. Alveolar fluid reabsorption is increased in rats with compensated heart failure. Am J Physiol Lung Cell Mol Physiol 2006; 291:L1094-100. [PMID: 16815890 DOI: 10.1152/ajplung.00180.2005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Alveolar fluid reabsorption (AFR) is important in keeping the air spaces free of edema. This process is accomplished via active transport of Na+across the alveolo-capillary barrier mostly by apical Na+channels and basolateral Na+-K+-ATPases. Recently, we have reported that acute elevation of left atrial pressures is associated with decreased AFR in isolated rat lungs. However, the effect of chronic elevation of pulmonary capillary pressure, such as seen in patients with congestive heart failure (CHF), on AFR is unknown. CHF was induced by creating an aorto-caval fistula (ACF) in Sprague-Dawley male rats. Seven days after the placement of the fistula, AFR was studied in the isolated perfused rat lung model. AFR in control rats was 0.49 ± 0.02 ml/h (all values are means ± SE) and increased by ∼40% (0.69 ± 0.03 ml/h) in rats with chronic CHF ( P < 0.001). The albumin flux from the pulmonary circulation into the air spaces did not increase in the experimental groups, indicating that lung permeability for large solutes was not increased. Na+-K+-ATPase activity and protein abundance at the plasma membrane of distal alveolar epithelial tissue were significantly increased in CHF rats compared with controls. These changes were associated with increased plasma norepinephrine levels in CHF rats compared with controls. We provide evidence that in a rat model of chronic compensated CHF, AFR is increased, possibly due to increased endogenous norepinephrine upregulating active sodium transport and protecting against alveolar flooding.
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Affiliation(s)
- Zaher S Azzam
- Department of Physiology and Biophysics, Ruth & Bruce Rappaport Faculty of Medicine, Technion, Israel Institute of Technology.
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22
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Abstract
The mechanisms of pulmonary edema resolution are different from those regulating edema formation. Absorption of excess alveolar fluid is an active process that involves vectorial transport of Na+out of alveolar air spaces with water following the Na+osmotic gradient. Active Na+transport across the alveolar epithelium is regulated via apical Na+and chloride channels and basolateral Na-K-ATPase in normal and injured lungs. During lung injury, mechanisms regulating alveolar fluid reabsorption are inhibited by yet unclear pathways and can be upregulated by pharmacological means. Better understanding of the mechanisms that regulate edema clearance may lead to therapeutic interventions to improve the ability of lungs to clear fluid, which is of clinical significance.
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Affiliation(s)
- Gökhan M Mutlu
- Pulmonary and Critical Care Medicine, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA
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Otulakowski G, Rafii B, Harris M, O'Brodovich H. Oxygen and glucocorticoids modulate alphaENaC mRNA translation in fetal distal lung epithelium. Am J Respir Cell Mol Biol 2005; 34:204-12. [PMID: 16210692 DOI: 10.1165/rcmb.2005-0273oc] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Glucocorticoid hormones play an important role in fetal lung maturation. It is unknown how they interact with changes in O2 tension, which play an important role in converting the lung from a fluid-secreting to a fluid-absorbing organ at birth. Airspace fluid absorption arises from active transepithelial Na+ transport with the amiloride-sensitive epithelial Na channel (ENaC), consisting of alpha, beta, and gamma subunits, representing the rate-limiting step under nonpathologic conditions. We investigated the individual and combined effects of dexamethasone (DEX) and PO2 on alphaENaC mRNA levels, rate of alphaENaC protein synthesis, and amiloride-sensitive short-circuit current in primary cultures of rat fetal distal lung epithelial cells. DEX significantly induced alphaENaC mRNA in fetal (3%) and postnatal (21%) O2, but increases in alphaENaC protein synthesis and function occurred only when epithelia were grown under a postnatal PO2. Sucrose density gradient analyses showed that DEX treatment of cells cultured at 3% O2 decreased the association of alphaENaC mRNA with large polysomes and enhanced the association with small polysomes. Conversely, incubation of DEX-treated cells in 21% O2 restored alphaENaC mRNA association with large polysomes. No significant changes were seen in the overall polyribosome profiles or in the distribution of mRNAs encoding beta and gamma subunits of ENaC or cytokeratin 18, indicating specific modulation of alphaENaC mRNA translation. These data suggest that postnatal O2 exposure may be important for efficient translation of the alphaENaC mRNA.
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Affiliation(s)
- Gail Otulakowski
- Programme in Lung Biology Research, Hospital for Sick Children Research Institute, 555 University Avenue, Toronto, Ontario, Canada M5G 1X8.
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24
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Affiliation(s)
- Gökhan M Mutlu
- Northwestern University Feinberg School of Medicine, Pulmonary and Critical Care Medicine, Chicago, IL 60611, USA.
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Mutlu GM, Sznajder JI. beta(2)-Agonists for treatment of pulmonary edema: ready for clinical studies? Crit Care Med 2004; 32:1607-8. [PMID: 15241111 DOI: 10.1097/01.ccm.0000130825.84691.e2] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Otulakowski G, Rafii B, O'Brodovich H. Differential translational efficiency of ENaC subunits during lung development. Am J Respir Cell Mol Biol 2003; 30:862-70. [PMID: 14672917 DOI: 10.1165/rcmb.2003-0381oc] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The amiloride-sensitive epithelial Na(+) channel (ENaC), the rate-limiting step in epithelial Na(+) transport, consists of three subunits: alpha, beta, and gamma. The abundance of mRNA encoding the alpha-subunit far surpasses the amount for other subunits, and considerably exceeds the predicted subunit protein stoichiometry. We evaluated 5'-untranslated region (UTR) expression and found that fetal rat lung uses alternative 5'UTRs for alpha-ENaC during development. Sucrose density gradient analysis of postnuclear supernatants from fetal rat lung homogenates demonstrated that all three ENaC subunits were associated with high molecular weight polysomes, indicating active translation of the mRNAs, but translational efficiency was much lower for the alpha-subunit. Sucrose density gradient distributions were comparable for the endogenously expressed alpha-ENaC 5'UTRs in rat lung at Fetal Day 20 or Postnatal Day 1 using Northern analysis. Although birth resulted in a global decrease in lung mRNA translation, the loading of ribosomes on ENaC subunit mRNAs was largely unaffected. Evaluation of cytokeratin 18 and vimentin mRNAs in these gradients suggested a cell-specific effect. We conclude that there are different translational efficiencies for ENaC subunits and that perinatal processes globally modulate lung mRNA translation.
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Affiliation(s)
- Gail Otulakowski
- CIHR Group in Lung Development, Research Institute of the Hospital for Sick Children, Programme in Lung Biology Research, 555 University Avenue, Toronto, ON, M5G 1X8 Canada.
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27
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Berthiaume Y. Long-term stimulation of alveolar epithelial cells by beta-adrenergic agonists: increased Na+ transport and modulation of cell growth? Am J Physiol Lung Cell Mol Physiol 2003; 285:L798-801. [PMID: 12959925 DOI: 10.1152/ajplung.00166.2003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
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