1
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Leslie TK, Tripp A, James AD, Fraser SP, Nelson M, Sajjaboontawee N, Capatina AL, Toss M, Fadhil W, Salvage SC, Garcia MA, Beykou M, Rakha E, Speirs V, Bakal C, Poulogiannis G, Djamgoz MBA, Jackson AP, Matthews HR, Huang CLH, Holding AN, Chawla S, Brackenbury WJ. A novel Na v1.5-dependent feedback mechanism driving glycolytic acidification in breast cancer metastasis. Oncogene 2024:10.1038/s41388-024-03098-x. [PMID: 39048659 DOI: 10.1038/s41388-024-03098-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 06/29/2024] [Accepted: 07/04/2024] [Indexed: 07/27/2024]
Abstract
Solid tumours have abnormally high intracellular [Na+]. The activity of various Na+ channels may underlie this Na+ accumulation. Voltage-gated Na+ channels (VGSCs) have been shown to be functionally active in cancer cell lines, where they promote invasion. However, the mechanisms involved, and clinical relevance, are incompletely understood. Here, we show that protein expression of the Nav1.5 VGSC subtype strongly correlates with increased metastasis and shortened cancer-specific survival in breast cancer patients. In addition, VGSCs are functionally active in patient-derived breast tumour cells, cell lines, and cancer-associated fibroblasts. Knockdown of Nav1.5 in a mouse model of breast cancer suppresses expression of invasion-regulating genes. Nav1.5 activity increases ATP demand and glycolysis in breast cancer cells, likely by upregulating activity of the Na+/K+ ATPase, thus promoting H+ production and extracellular acidification. The pH of murine xenograft tumours is lower at the periphery than in the core, in regions of higher proliferation and lower apoptosis. In turn, acidic extracellular pH elevates persistent Na+ influx through Nav1.5 into breast cancer cells. Together, these findings show positive feedback between extracellular acidification and the movement of Na+ into cancer cells which can facilitate invasion. These results highlight the clinical significance of Nav1.5 activity as a potentiator of breast cancer metastasis and provide further evidence supporting the use of VGSC inhibitors in cancer treatment.
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Affiliation(s)
- Theresa K Leslie
- Department of Biology, University of York, York, UK
- York Biomedical Research Institute, University of York, York, UK
| | - Aurelien Tripp
- Division of Cancer Biology, Institute of Cancer Research, London, UK
| | - Andrew D James
- Department of Biology, University of York, York, UK
- York Biomedical Research Institute, University of York, York, UK
| | - Scott P Fraser
- Department of Life Sciences, Imperial College London, London, UK
| | - Michaela Nelson
- Department of Biology, University of York, York, UK
- York Biomedical Research Institute, University of York, York, UK
| | - Nattanan Sajjaboontawee
- Department of Biology, University of York, York, UK
- York Biomedical Research Institute, University of York, York, UK
| | - Alina L Capatina
- Department of Biology, University of York, York, UK
- York Biomedical Research Institute, University of York, York, UK
| | - Michael Toss
- Department of Pathology, School of Medicine, University of Nottingham, Nottingham, UK
| | - Wakkas Fadhil
- Department of Pathology, School of Medicine, University of Nottingham, Nottingham, UK
| | | | - Mar Arias Garcia
- Division of Cancer Biology, Institute of Cancer Research, London, UK
| | - Melina Beykou
- Division of Cancer Biology, Institute of Cancer Research, London, UK
- Department of Electrical and Electronic Engineering, Imperial College London, London, UK
| | - Emad Rakha
- Department of Pathology, School of Medicine, University of Nottingham, Nottingham, UK
| | - Valerie Speirs
- Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | - Chris Bakal
- Division of Cancer Biology, Institute of Cancer Research, London, UK
| | | | - Mustafa B A Djamgoz
- Department of Life Sciences, Imperial College London, London, UK
- Biotechnology Research Centre, Cyprus International University, Haspolat, TRNC, Mersin, Turkey
| | - Antony P Jackson
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Hugh R Matthews
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Christopher L-H Huang
- Department of Biochemistry, University of Cambridge, Cambridge, UK
- Physiological Laboratory, University of Cambridge, Cambridge, UK
| | - Andrew N Holding
- Department of Biology, University of York, York, UK
- York Biomedical Research Institute, University of York, York, UK
| | - Sangeeta Chawla
- Department of Biology, University of York, York, UK
- York Biomedical Research Institute, University of York, York, UK
| | - William J Brackenbury
- Department of Biology, University of York, York, UK.
- York Biomedical Research Institute, University of York, York, UK.
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2
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Michaels AM, Zoccarato A, Hoare Z, Firth G, Chung YJ, Kuchel PW, Shah AM, Shattock MJ, Southworth R, Eykyn TR. Disrupting Na + ion homeostasis and Na +/K + ATPase activity in breast cancer cells directly modulates glycolysis in vitro and in vivo. Cancer Metab 2024; 12:15. [PMID: 38783368 PMCID: PMC11119389 DOI: 10.1186/s40170-024-00343-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2024] [Accepted: 05/16/2024] [Indexed: 05/25/2024] Open
Abstract
BACKGROUND Glycolytic flux is regulated by the energy demands of the cell. Upregulated glycolysis in cancer cells may therefore result from increased demand for adenosine triphosphate (ATP), however it is unknown what this extra ATP turnover is used for. We hypothesise that an important contribution to the increased glycolytic flux in cancer cells results from the ATP demand of Na+/K+-ATPase (NKA) due to altered sodium ion homeostasis in cancer cells. METHODS Live whole-cell measurements of intracellular sodium [Na+]i were performed in three human breast cancer cells (MDA-MB-231, HCC1954, MCF-7), in murine breast cancer cells (4T1), and control human epithelial cells MCF-10A using triple quantum filtered 23Na nuclear magnetic resonance (NMR) spectroscopy. Glycolytic flux was measured by 2H NMR to monitor conversion of [6,6-2H2]D-glucose to [2H]-labelled L-lactate at baseline and in response to NKA inhibition with ouabain. Intracellular [Na+]i was titrated using isotonic buffers with varying [Na+] and [K+] and introducing an artificial Na+ plasma membrane leak using the ionophore gramicidin-A. Experiments were carried out in parallel with cell viability assays, 1H NMR metabolomics of intracellular and extracellular metabolites, extracellular flux analyses and in vivo measurements in a MDA-MB-231 human-xenograft mouse model using 2-deoxy-2-[18F]fluoroglucose (18F-FDG) positron emission tomography (PET). RESULTS Intracellular [Na+]i was elevated in human and murine breast cancer cells compared to control MCF-10A cells. Acute inhibition of NKA by ouabain resulted in elevated [Na+]i and inhibition of glycolytic flux in all three human cancer cells which are ouabain sensitive, but not in the murine cells which are ouabain resistant. Permeabilization of cell membranes with gramicidin-A led to a titratable increase of [Na+]i in MDA-MB-231 and 4T1 cells and a Na+-dependent increase in glycolytic flux. This was attenuated with ouabain in the human cells but not in the murine cells. 18FDG PET imaging in an MDA-MB-231 human-xenograft mouse model recorded lower 18FDG tumour uptake when treated with ouabain while murine tissue uptake was unaffected. CONCLUSIONS Glycolytic flux correlates with Na+-driven NKA activity in breast cancer cells, providing evidence for the 'centrality of the [Na+]i-NKA nexus' in the mechanistic basis of the Warburg effect.
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Affiliation(s)
- Aidan M Michaels
- School of Biomedical Engineering and Imaging Sciences, King's College London, St Thomas' Hospital, London, SE1 7EH, UK
| | - Anna Zoccarato
- School of Cardiovascular and Metabolic Medicine and Sciences, King's College London, London, UK
| | - Zoe Hoare
- School of Cardiovascular and Metabolic Medicine and Sciences, King's College London, London, UK
| | - George Firth
- School of Biomedical Engineering and Imaging Sciences, King's College London, St Thomas' Hospital, London, SE1 7EH, UK
| | - Yu Jin Chung
- School of Cardiovascular and Metabolic Medicine and Sciences, King's College London, London, UK
| | - Philip W Kuchel
- School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, 2006, Australia
| | - Ajay M Shah
- School of Cardiovascular and Metabolic Medicine and Sciences, King's College London, London, UK
| | - Michael J Shattock
- School of Cardiovascular and Metabolic Medicine and Sciences, King's College London, London, UK
| | - Richard Southworth
- School of Biomedical Engineering and Imaging Sciences, King's College London, St Thomas' Hospital, London, SE1 7EH, UK
| | - Thomas R Eykyn
- School of Biomedical Engineering and Imaging Sciences, King's College London, St Thomas' Hospital, London, SE1 7EH, UK.
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3
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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 PMCID: PMC11193536 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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4
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Forouzandehmehr M, Paci M, Hyttinen J, Koivumäki JT. In silico study of the mechanisms of hypoxia and contractile dysfunction during ischemia and reperfusion of hiPSC cardiomyocytes. Dis Model Mech 2024; 17:dmm050365. [PMID: 38516812 PMCID: PMC11073514 DOI: 10.1242/dmm.050365] [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: 06/21/2023] [Accepted: 03/15/2024] [Indexed: 03/23/2024] Open
Abstract
Interconnected mechanisms of ischemia and reperfusion (IR) has increased the interest in IR in vitro experiments using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). We developed a whole-cell computational model of hiPSC-CMs including the electromechanics, a metabolite-sensitive sarcoplasmic reticulum Ca2+-ATPase (SERCA) and an oxygen dynamics formulation to investigate IR mechanisms. Moreover, we simulated the effect and action mechanism of levosimendan, which recently showed promising anti-arrhythmic effects in hiPSC-CMs in hypoxia. The model was validated using hiPSC-CM and in vitro animal data. The role of SERCA in causing relaxation dysfunction in IR was anticipated to be comparable to its function in sepsis-induced heart failure. Drug simulations showed that levosimendan counteracts the relaxation dysfunction by utilizing a particular Ca2+-sensitizing mechanism involving Ca2+-bound troponin C and Ca2+ flux to the myofilament, rather than inhibiting SERCA phosphorylation. The model demonstrates extensive characterization and promise for drug development, making it suitable for evaluating IR therapy strategies based on the changing levels of cardiac metabolites, oxygen and molecular pathways.
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Affiliation(s)
| | - Michelangelo Paci
- Department of Electrical, Electronic, and Information Engineering ‘Guglielmo Marconi’, University of Bologna, 47522 Cesena, Italy
| | - Jari Hyttinen
- Faculty of Medicine and Health Technology, Tampere University, 33520 Tampere, Finland
| | - Jussi T. Koivumäki
- Faculty of Medicine and Health Technology, Tampere University, 33520 Tampere, Finland
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5
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Longden TA, Lederer WJ. Electro-metabolic signaling. J Gen Physiol 2024; 156:e202313451. [PMID: 38197953 PMCID: PMC10783436 DOI: 10.1085/jgp.202313451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 10/27/2023] [Accepted: 12/14/2023] [Indexed: 01/11/2024] Open
Abstract
Precise matching of energy substrate delivery to local metabolic needs is essential for the health and function of all tissues. Here, we outline a mechanistic framework for understanding this critical process, which we refer to as electro-metabolic signaling (EMS). All tissues exhibit changes in metabolism over varying spatiotemporal scales and have widely varying energetic needs and reserves. We propose that across tissues, common signatures of elevated metabolism or increases in energy substrate usage that exceed key local thresholds rapidly engage mechanisms that generate hyperpolarizing electrical signals in capillaries that then relax contractile elements throughout the vasculature to quickly adjust blood flow to meet changing needs. The attendant increase in energy substrate delivery serves to meet local metabolic requirements and thus avoids a mismatch in supply and demand and prevents metabolic stress. We discuss in detail key examples of EMS that our laboratories have discovered in the brain and the heart, and we outline potential further EMS mechanisms operating in tissues such as skeletal muscle, pancreas, and kidney. We suggest that the energy imbalance evoked by EMS uncoupling may be central to cellular dysfunction from which the hallmarks of aging and metabolic diseases emerge and may lead to generalized organ failure states-such as diverse flavors of heart failure and dementia. Understanding and manipulating EMS may be key to preventing or reversing these dysfunctions.
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Affiliation(s)
- Thomas A. Longden
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA
- Laboratory of Neurovascular Interactions, Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - W. Jonathan Lederer
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA
- Laboratory of Molecular Cardiology, Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD, USA
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6
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Desousa BR, Kim KKO, Jones AE, Ball AB, Hsieh WY, Swain P, Morrow DH, Brownstein AJ, Ferrick DA, Shirihai OS, Neilson A, Nathanson DA, Rogers GW, Dranka BP, Murphy AN, Affourtit C, Bensinger SJ, Stiles L, Romero N, Divakaruni AS. Calculation of ATP production rates using the Seahorse XF Analyzer. EMBO Rep 2023; 24:e56380. [PMID: 37548091 PMCID: PMC10561364 DOI: 10.15252/embr.202256380] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 07/05/2023] [Accepted: 07/14/2023] [Indexed: 08/08/2023] Open
Abstract
Oxidative phosphorylation and glycolysis are the dominant ATP-generating pathways in mammalian metabolism. The balance between these two pathways is often shifted to execute cell-specific functions in response to stimuli that promote activation, proliferation, or differentiation. However, measurement of these metabolic switches has remained mostly qualitative, making it difficult to discriminate between healthy, physiological changes in energy transduction or compensatory responses due to metabolic dysfunction. We therefore present a broadly applicable method to calculate ATP production rates from oxidative phosphorylation and glycolysis using Seahorse XF Analyzer data and empirical conversion factors. We quantify the bioenergetic changes observed during macrophage polarization as well as cancer cell adaptation to in vitro culture conditions. Additionally, we detect substantive changes in ATP utilization upon neuronal depolarization and T cell receptor activation that are not evident from steady-state ATP measurements. This method generates a single readout that allows the direct comparison of ATP produced from oxidative phosphorylation and glycolysis in live cells. Additionally, the manuscript provides a framework for tailoring the calculations to specific cell systems or experimental conditions.
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Affiliation(s)
- Brandon R Desousa
- Department of Molecular and Medical PharmacologyUniversity of California, Los AngelesLos AngelesCAUSA
| | - Kristen KO Kim
- Department of Molecular and Medical PharmacologyUniversity of California, Los AngelesLos AngelesCAUSA
| | - Anthony E Jones
- Department of Molecular and Medical PharmacologyUniversity of California, Los AngelesLos AngelesCAUSA
| | - Andréa B Ball
- Department of Molecular and Medical PharmacologyUniversity of California, Los AngelesLos AngelesCAUSA
| | - Wei Y Hsieh
- Department of Microbiology, Immunology, and Molecular GeneticsUniversity of California, Los AngelesLos AngelesCAUSA
| | | | - Danielle H Morrow
- Department of Molecular and Medical PharmacologyUniversity of California, Los AngelesLos AngelesCAUSA
| | | | | | - Orian S Shirihai
- Department of MedicineUniversity of California, Los AngelesLos AngelesCAUSA
| | | | - David A Nathanson
- Department of Molecular and Medical PharmacologyUniversity of California, Los AngelesLos AngelesCAUSA
| | | | | | | | | | - Steven J Bensinger
- Department of Microbiology, Immunology, and Molecular GeneticsUniversity of California, Los AngelesLos AngelesCAUSA
| | - Linsey Stiles
- Department of Molecular and Medical PharmacologyUniversity of California, Los AngelesLos AngelesCAUSA
- Department of MedicineUniversity of California, Los AngelesLos AngelesCAUSA
| | | | - Ajit S Divakaruni
- Department of Molecular and Medical PharmacologyUniversity of California, Los AngelesLos AngelesCAUSA
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7
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Chen L, Yu D, Ling S, Xu JW. Mechanism of tonifying-kidney Chinese herbal medicine in the treatment of chronic heart failure. Front Cardiovasc Med 2022; 9:988360. [PMID: 36172573 PMCID: PMC9510640 DOI: 10.3389/fcvm.2022.988360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Accepted: 08/22/2022] [Indexed: 12/04/2022] Open
Abstract
According to traditional Chinese medicine (TCM), chronic heart failure has the basic pathological characteristics of “heart-kidney yang deficiency.” Chronic heart failure with heart- and kidney-Yang deficiency has good overlap with New York Heart Association (NYHA) classes III and IV. Traditional Chinese medicine classical prescriptions for the treatment of chronic heart failure often take “warming and tonifying kidney-Yang” as the core, supplemented by herbal compositions with functions of “promoting blood circulation and dispersing blood stasis.” Nowadays, there are still many classical and folk prescriptions for chronic heart failure treatment, such as Zhenwu decoction, Bushen Huoxue decoction, Shenfu decoction, Sini decoction, as well as Qili Qiangxin capsule. This review focuses on classical formulations and their active constituents that play a key role in preventing chronic heart failure by suppressing inflammation and modulating immune and neurohumoral factors. In addition, given that mitochondrial metabolic reprogramming has intimate relation with inflammation, cardiac hypertrophy, and fibrosis, the regulatory role of classical prescriptions and their active components in metabolic reprogramming, including glycolysis and lipid β-oxidation, is also presented. Although the exact mechanism is unknown, the classical TCM prescriptions still have good clinical effects in treating chronic heart failure. This review will provide a modern pharmacological explanation for its mechanism and offer evidence for clinical medication by combining TCM syndrome differentiation with chronic heart failure clinical stages.
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8
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Numata S, McDermott JP, Blanco G. Genetic Ablation of Na,K-ATPase α4 Results in Sperm Energetic Defects. Front Cell Dev Biol 2022; 10:911056. [PMID: 35693932 PMCID: PMC9178190 DOI: 10.3389/fcell.2022.911056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 05/03/2022] [Indexed: 11/13/2022] Open
Abstract
The Na,K-ATPase alpha 4 isoform (NKAα4) is expressed specifically in the male germ cells of the testes and is particularly abundant in mature spermatozoa. Genetic deletion of NKAα4 in mice (NKAα4 KO mice) results in complete infertility of male, but not female mice. The reduced fecundity of NKAα4 KO male mice is due to a series of defects, including a severe impairment in total and hyperactive sperm motility. In this work, we show that deletion of NKAα4 also leads to major defects in sperm metabolism and energetics. Thus, compared to wild-type sperm, sperm from NKAα4 KO mice display a significant reduction in the extracellular acidification rate (ECAR), indicative of impaired glycolytic flux. In addition, mitochondrial function is disrupted in sperm lacking NKAα4, as indicated by a reduction in the mitochondrial membrane potential and lower oxygen consumption rate (OCR). Moreover, the ratio between the oxidized and reduced forms of nicotinamide adenine dinucleotide (NAD/NADH) is increased in NKAα4 KO sperm, indicating a shift in the cellular redox state. These metabolic changes are associated with augmented reactive oxygen species (ROS) production and increased lipid peroxidation in NKAα4 KO sperm. Altogether, these findings reveal a novel link between NKAα4 activity and sperm energetics, highlighting the essential role of this ion transporter in sperm physiology.
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9
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Simionato G, Rabe A, Gallego-Murillo JS, van der Zwaan C, Hoogendijk AJ, van den Biggelaar M, Minetti G, Bogdanova A, Mairbäurl H, Wagner C, Kaestner L, van den Akker E. In Vitro Erythropoiesis at Different pO 2 Induces Adaptations That Are Independent of Prior Systemic Exposure to Hypoxia. Cells 2022; 11:cells11071082. [PMID: 35406648 PMCID: PMC8997720 DOI: 10.3390/cells11071082] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Revised: 03/20/2022] [Accepted: 03/22/2022] [Indexed: 12/23/2022] Open
Abstract
Hypoxia is associated with increased erythropoietin (EPO) release to drive erythropoiesis. At high altitude, EPO levels first increase and then decrease, although erythropoiesis remains elevated at a stable level. The roles of hypoxia and related EPO adjustments are not fully understood, which has contributed to the formulation of the theory of neocytolysis. We aimed to evaluate the role of oxygen exclusively on erythropoiesis, comparing in vitro erythroid differentiation performed at atmospheric oxygen, a lower oxygen concentration (three percent oxygen) and with cultures of erythroid precursors isolated from peripheral blood after a 19-day sojourn at high altitude (3450 m). Results highlight an accelerated erythroid maturation at low oxygen and more concave morphology of reticulocytes. No differences in deformability were observed in the formed reticulocytes in the tested conditions. Moreover, hematopoietic stem and progenitor cells isolated from blood affected by hypoxia at high altitude did not result in different erythroid development, suggesting no retention of a high-altitude signature but rather an immediate adaptation to oxygen concentration. This adaptation was observed during in vitro erythropoiesis at three percent oxygen by a significantly increased glycolytic metabolic profile. These hypoxia-induced effects on in vitro erythropoiesis fail to provide an intrinsic explanation of the concept of neocytolysis.
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Affiliation(s)
- Greta Simionato
- Department of Experimental Physics, University Campus, Building E2.6, Saarland University, 66123 Saarbrücken, Germany; (A.R.); (C.W.); (L.K.)
- Department of Experimental Surgery, Campus University Hospital, Building 65, Saarland University, 66421 Homburg, Germany
- Correspondence: (G.S.); (E.v.d.A.)
| | - Antonia Rabe
- Department of Experimental Physics, University Campus, Building E2.6, Saarland University, 66123 Saarbrücken, Germany; (A.R.); (C.W.); (L.K.)
| | - Joan Sebastián Gallego-Murillo
- Sanquin Research, Landsteiner Laboratory, Department of Hematopoiesis, Amsterdam UMC, University of Amsterdam, 1066 CX Amsterdam, The Netherlands;
- Department of Biotechnology, Faculty of Applied Sciences, Delft University of Technology, 2629 HZ Delft, The Netherlands
| | - Carmen van der Zwaan
- Sanquin Research, Landsteiner Laboratory, Department of Molecular Hematology, Amsterdam UMC, University of Amsterdam, 1066 CX Amsterdam, The Netherlands; (C.v.d.Z.); (A.J.H.); (M.v.d.B.)
| | - Arie Johan Hoogendijk
- Sanquin Research, Landsteiner Laboratory, Department of Molecular Hematology, Amsterdam UMC, University of Amsterdam, 1066 CX Amsterdam, The Netherlands; (C.v.d.Z.); (A.J.H.); (M.v.d.B.)
| | - Maartje van den Biggelaar
- Sanquin Research, Landsteiner Laboratory, Department of Molecular Hematology, Amsterdam UMC, University of Amsterdam, 1066 CX Amsterdam, The Netherlands; (C.v.d.Z.); (A.J.H.); (M.v.d.B.)
| | - Giampaolo Minetti
- Department of Biology and Biotechnology “L. Spallanzani”, Laboratories of Biochemistry, University of Pavia, I-27100 Pavia, Italy;
| | - Anna Bogdanova
- Red Blood Cell Research Group, Institute of Veterinary Physiology, University of Zurich, CH-8057 Zurich, Switzerland;
| | - Heimo Mairbäurl
- University Hospital Heidelberg, Medical Clinic VII, Sports Medicine, 69120 Heidelberg, Germany;
- Translational Lung Research Centre Heidelberg (TLRC), Part of the German Centre for Lung Research (DZL), 69120 Heidelberg, Germany
- Translational Pneumology, University Hospital Heidelberg, 69120 Heidelberg, Germany
| | - Christian Wagner
- Department of Experimental Physics, University Campus, Building E2.6, Saarland University, 66123 Saarbrücken, Germany; (A.R.); (C.W.); (L.K.)
- Physics and Materials Science Research Unit, University of Luxembourg, L-1511 Luxembourg City, Luxembourg
| | - Lars Kaestner
- Department of Experimental Physics, University Campus, Building E2.6, Saarland University, 66123 Saarbrücken, Germany; (A.R.); (C.W.); (L.K.)
- Theoretical Medicine and Biosciences, Campus University Hospital, Building 61.4, Saarland University, 66421 Homburg, Germany
| | - Emile van den Akker
- Sanquin Research, Landsteiner Laboratory, Department of Hematopoiesis, Amsterdam UMC, University of Amsterdam, 1066 CX Amsterdam, The Netherlands;
- Correspondence: (G.S.); (E.v.d.A.)
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10
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Li J, Fang Y, Wu D. Mechanical forces and metabolic changes cooperate to drive cellular memory and endothelial phenotypes. CURRENT TOPICS IN MEMBRANES 2021; 87:199-253. [PMID: 34696886 DOI: 10.1016/bs.ctm.2021.07.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Endothelial cells line the innermost layer of arterial, venous, and lymphatic vascular tree and accordingly are subject to hemodynamic, stretch, and stiffness mechanical forces. Normally quiescent, endothelial cells have a hemodynamic set point and become "activated" in response to disturbed hemodynamics, which may signal impending nutrient or gas depletion. Endothelial cells in the majority of tissue beds are normally inactivated and maintain vessel barrier functions, are anti-inflammatory, anti-coagulant, and anti-thrombotic. However, under aberrant mechanical forces, endothelial signaling transforms in response, resulting cellular changes that herald pathological diseases. Endothelial cell metabolism is now recognized as the primary intermediate pathway that undergirds cellular transformation. In this review, we discuss the various mechanical forces endothelial cells sense in the large vessels, microvasculature, and lymphatics, and how changes in environmental mechanical forces result in changes in metabolism, which ultimately influence cell physiology, cellular memory, and ultimately disease initiation and progression.
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Affiliation(s)
- Jin Li
- Committee on Molecular Metabolism and Nutrition, Biological Sciences Division, University of Chicago, Chicago, IL, United States; Department of Medicine, Biological Sciences Division, University of Chicago, Chicago, IL, United States
| | - Yun Fang
- Committee on Molecular Metabolism and Nutrition, Biological Sciences Division, University of Chicago, Chicago, IL, United States; Department of Medicine, Biological Sciences Division, University of Chicago, Chicago, IL, United States
| | - David Wu
- Committee on Molecular Metabolism and Nutrition, Biological Sciences Division, University of Chicago, Chicago, IL, United States; Department of Medicine, Biological Sciences Division, University of Chicago, Chicago, IL, United States.
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11
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Hafner S, Schmiech M, Lang SJ. The Cardenolide Glycoside Acovenoside A Interferes with Epidermal Growth Factor Receptor Trafficking in Non-Small Cell Lung Cancer Cells. Front Pharmacol 2021; 12:611657. [PMID: 34025398 PMCID: PMC8133365 DOI: 10.3389/fphar.2021.611657] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 04/21/2021] [Indexed: 11/13/2022] Open
Abstract
Cardenolide glycosides are natural compounds known to inhibit the ion pumping function of the Na+/K+-ATPase in cellular systems. Interestingly, various cancer cell types are highly susceptible to cardenolide glycosides. Herein, we explore the cardenolide glycoside Acovenoside A (AcoA) with respect to its influences on human A549 non-small cell lung cancer (NSCLC) cells. We found that exposure to AcoA, digoxin and ouabain increases intracellular sodium and ATP levels indicating that the ion pumping function of the transmembrane Na+/K+-ATPase is effectively inhibited. Like digoxin and ouabain, AcoA inhibits transcription factor NF-κB activation and induces apoptotic cell death in NSCLC cells. This was confirmed by a preclinical in vivo model in which AcoA treatment of NSCLC xenografts grown on chick chorioallantoic membranes inhibited the expression of proliferation antigen Ki-67 and induced apoptotic DNA strand breaks. We aimed to elucidate the underlying mechanisms. The Na+/K+-ATPase transmembrane complex contains Src kinase and epidermal growth factor receptor (EGFR). Indeed, we found that AcoA activates Src kinase in A549 cells, but not in a cell-free assay using recombinant Src kinase. Src kinase is a downstream target of EGFR, and correlation analysis using the NCI60 database pointed to a role of EGFR in cardenolide glycoside-induced cancer cell death. Accordingly, NSCLC cells expressing hyperphosphorylated EGFRmut exhibited resistance to AcoA. To investigate the interaction between cardenolide glycosides and EGFR in detail, we performed immunoblotting studies: Whereas ligand binding and EGFR phosphorylation were not significantly affected, ubiquitinated EGFR accumulated after prolonged incubation with AcoA. To visualize EGFR trafficking we used A549 cells transfected with a fluorescent biosensor which binds to activated EGFR. Pretreatment with AcoA and digoxin induced accumulation of EGFR in endosomal compartments thus inhibiting EGF-induced EGFR degradation comparable to the Na+ ionophore monensin, a known inducer of EGFR endosomal arrest. Intracellular Na+ concentrations regulate EGFR trafficking and signaling. Na+ homeostasis is maintained by the Na+/K+-ATPase, which might account for its close interaction with the EGFR. Cardenolide glycosides inhibit the ATP-dependent Na+/K+ exchange through the Na+/K+-ATPase resulting in higher intracellular Na+ levels. Our data provide first evidence that this impedes efficient EGFR trafficking at the endosomal compartment.
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Affiliation(s)
- Susanne Hafner
- Institute of Pharmacology of Natural Products and Clinical Pharmacology, Ulm University, Ulm, Germany
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12
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Birkeland ES, Koch LM, Dechant R. Another Consequence of the Warburg Effect? Metabolic Regulation of Na +/H + Exchangers May Link Aerobic Glycolysis to Cell Growth. Front Oncol 2020; 10:1561. [PMID: 32974190 PMCID: PMC7462004 DOI: 10.3389/fonc.2020.01561] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Accepted: 07/20/2020] [Indexed: 12/13/2022] Open
Abstract
To adjust cell growth and proliferation to changing environmental conditions or developmental requirements, cells have evolved a remarkable network of signaling cascades that integrates cues from cellular metabolism, growth factor availability and a large variety of stresses. In these networks, cellular information flow is mostly mediated by posttranslational modifications, most notably phosphorylation, or signaling molecules such as GTPases. Yet, a large body of evidence also implicates cytosolic pH (pHc) as a highly conserved cellular signal driving cell growth and proliferation, suggesting that pH-dependent protonation of specific proteins also regulates cellular signaling. In mammalian cells, pHc is regulated by growth factor derived signals and responds to metabolic cues in response to glucose stimulation. Importantly, high pHc has also been identified as a hall mark of cancer, but mechanisms of pH regulation in cancer are only poorly understood. Here, we discuss potential mechanisms of pH regulation with emphasis on metabolic signals regulating pHc by Na+/H+-exchangers. We hypothesize that elevated NHE activity and pHc in cancer are a direct consequence of the metabolic adaptations in tumor cells including enhanced aerobic glycolysis, generally referred to as the Warburg effect. This hypothesis not only provides an explanation for the growth advantage conferred by a switch to aerobic glycolysis beyond providing precursors for accumulation of biomass, but also suggests that treatments targeting pH regulation as a potential anti-cancer therapy may effectively target the result of altered tumor cell metabolism.
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Affiliation(s)
- Eivind Salmorin Birkeland
- Institute of Biochemistry, Department of Biology, ETH Zürich, Zurich, Switzerland.,Life Science Zurich, Ph.D. Program for Molecular Life Sciences, Zurich, Switzerland
| | - Lisa Maria Koch
- Institute of Biochemistry, Department of Biology, ETH Zürich, Zurich, Switzerland.,Life Science Zurich, Ph.D. Program for Molecular Life Sciences, Zurich, Switzerland
| | - Reinhard Dechant
- Institute of Biochemistry, Department of Biology, ETH Zürich, Zurich, Switzerland
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13
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Takeuchi A, Matsuoka S. Integration of mitochondrial energetics in heart with mathematical modelling. J Physiol 2020; 598:1443-1457. [DOI: 10.1113/jp276817] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Accepted: 01/23/2020] [Indexed: 11/08/2022] Open
Affiliation(s)
- Ayako Takeuchi
- Department of Integrative and Systems PhysiologyFaculty of Medical Sciencesand Life Science Innovation CenterUniversity of Fukui Fukui 910‐1193 Japan
| | - Satoshi Matsuoka
- Department of Integrative and Systems PhysiologyFaculty of Medical Sciencesand Life Science Innovation CenterUniversity of Fukui Fukui 910‐1193 Japan
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14
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Jensen R, Nielsen J, Ørtenblad N. Inhibition of glycogenolysis prolongs action potential repriming period and impairs muscle function in rat skeletal muscle. J Physiol 2020; 598:789-803. [PMID: 31823376 DOI: 10.1113/jp278543] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Accepted: 12/06/2019] [Indexed: 12/22/2022] Open
Abstract
KEY POINTS Muscle glycogen content is associated with muscle function, but the physiological link between the two is poorly understood. This study investigated the effects of inhibiting glycogenolysis, while maintaining high overall energy status, on different aspects of muscle function. We demonstrate here that Na+ ,K+ -ATPase activity depends on glycogenolytically derived ATP regardless of high global ATP, with a decrease in activity leading to reduced force production and accelerated fatigue development. The results support the concept of compartmentalized energy transfer with glycogen metabolism playing a crucial role in intramuscular ATP resynthesis and ion regulation. This study gives specific insights into muscular function and may help towards a better understanding of glycogen storage diseases and muscle fatigue. ABSTRACT Skeletal muscle glycogen content is associated with muscle function and fatigability. However, little is known about the physiological link between glycogen content and muscle function. Here we aimed to investigate the importance of glycogenolytically derived ATP per se on muscle force and action potential (AP) repriming period, i.e. the time before a second AP can be produced (indicative of Na+ ,K+ -ATPase activity). Single fibres from rat extensor digitorum longus muscles were isolated and mechanically skinned in order to investigate force production and the AP repriming period while global ATP and PCr concentrations were kept high. The importance of glycogenolytically derived ATP was studied by inhibition of glycogen phosphorylase (1,4-dideoxy-1,4-imino-d-arabinitol (DAB; 2 mm) or CP-316,819 (CP; 10 µm)) or glycogen removal (amyloglucosidase, 20 U ml-1 ). Tetanic force decreased by (mean (SD)) 21 (15)% (P < 0.001) and 76 (28)% (DAB) or 94 (6)% (CP, P < 0.001) in well-polarized and partially depolarized fibres, respectively. In depolarized fibres, twitch force decreased by 16 (10)% and 55 (26)% with DAB and CP, respectively, with no effect in well-polarized fibres (84 (10)%, P = 0.14). There was no effect of glycogen phosphorylase inhibition on repriming period in well-polarized fibres (median (25th, 75th percentile): 5 (4, 5) vs. 4 (4, 5) ms, P = 0.26), while the repriming period was prolonged from 6 (5, 7) to 8 (7, 10) ms (P = 0.01) in partially depolarized fibres. In line with this, glycogen removal increased repriming period from 5 (5, 6) to 6 (5, 7) ms (P = 0.003) in depolarized fibres. Together, these data strongly indicate that blocking glycogenolysis attenuates Na+ ,K+ -ATPase activity, which in turn increases the repriming period and reduces force, demonstrating a functional link between glycogenolytically derived ATP and force production.
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Affiliation(s)
- Rasmus Jensen
- Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
| | - Joachim Nielsen
- Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
| | - Niels Ørtenblad
- Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
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15
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Hilgemann DW. Control of cardiac contraction by sodium: Promises, reckonings, and new beginnings. Cell Calcium 2019; 85:102129. [PMID: 31835176 DOI: 10.1016/j.ceca.2019.102129] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 11/20/2019] [Accepted: 11/20/2019] [Indexed: 12/12/2022]
Abstract
Several generations of cardiac physiologists have verified that basal cardiac contractility depends strongly on the transsarcolemmal Na gradient, and the underlying molecular mechanisms that link cardiac excitation-contraction coupling (ECC) to the Na gradient have been elucidated in good detail for more than 30 years. In brief, small increases of cytoplasmic Na push cardiac (NCX1) Na/Ca exchangers to increase contractility by increasing the myocyte Ca load. Accordingly, basal cardiac contractility is expected to be physiologically regulated by pathways that modify the cardiac Na gradient and the function of Na transporters. Assuming that this expectation is correct, it remains to be elucidated how in detail signaling pathways affecting the cardiac Na gradient are controlled in response to changing cardiac output requirements. Some puzzle pieces that may facilitate progress are outlined in this short review. Key open issues include (1) whether the concept of local Na gradients is viable, (2) how in detail Na channels, Na transporters and Na/K pumps are regulated by lipids and metabolic processes, (3) the physiological roles of Na/K pump inactivation, and (4) the possibility that key diffusible signaling molecules remain to be discovered.
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Affiliation(s)
- Donald W Hilgemann
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX, 75235, USA.
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16
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Lamarre SG, MacCormack TJ, Bourloutski É, Callaghan NI, Pinto VD, Andrade JP, Sykes AV, Driedzic WR. Interrelationship Between Contractility, Protein Synthesis and Metabolism in Mantle of Juvenile Cuttlefish ( Sepia officinalis). Front Physiol 2019; 10:1051. [PMID: 31507433 PMCID: PMC6716058 DOI: 10.3389/fphys.2019.01051] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Accepted: 07/31/2019] [Indexed: 11/13/2022] Open
Abstract
Young juvenile cuttlefish (Sepia officinalis) can grow at rates as high as 12% body weight per day. How the metabolic demands of such a massive growth rate impacts muscle performance that competes for ATP is unknown. Here, we integrate aspects of contractility, protein synthesis, and energy metabolism in mantle of specimens weighing 1.1 g to lend insight into the processes. Isolated mantle muscle preparations were electrically stimulated and isometric force development monitored. Preparations were forced to contract at 3 Hz for 30 s to simulate a jetting event. We then measured oxygen consumption, glucose uptake and protein synthesis in the hour following the stimulation. Protein synthesis was inhibited with cycloheximide and glycolysis was inhibited with iodoacetic acid in a subset of samples. Inhibition of protein synthesis impaired contractility and decreased oxygen consumption. An intact protein synthesis is required to maintain contractility possibly due to rapidly turning over proteins. At least, 41% of whole animal ṀO2 is used to support protein synthesis in mantle, while the cost of protein synthesis (50 μmol O2 mg protein–1) in mantle was in the range reported for other aquatic ectotherms. A single jetting challenge stimulated protein synthesis by approximately 25% (2.51–3.12% day–1) over a 1 h post contractile period, a similar response to that which occurs in mammalian skeletal muscle. Aerobic metabolism was not supported by extracellular glucose leading to the contention that at this life stage either glycogen or amino acids are catabolized. Regardless, an intact glycolysis is required to support contractile performance and protein synthesis in resting muscle. It is proposed that glycolysis is needed to maintain intracellular ionic gradients. Intracellular glucose at approximately 3 mmol L–1 was higher than the 1 mmol L–1 glucose in the bathing medium suggesting an active glucose transport mechanism. Octopine did not accumulate during a single physiologically relevant jetting challenge; however, octopine accumulation increased following a stress that is sufficient to lower Arg-P and increase free arginine.
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Affiliation(s)
- Simon G Lamarre
- Département de Biologie, Université de Moncton, Moncton, NB, Canada
| | - Tyson J MacCormack
- Department of Chemistry and Biochemistry, Mount Allison University, Sackville, NB, Canada
| | | | - Neal I Callaghan
- Faculty of Applied Science and Engineering, Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada.,Translational Biology and Engineering Program, Ted Rogers Centre for Heart Research, Toronto, ON, Canada
| | - Vanessa D Pinto
- Centro de Ciências do Mar do Algarve, Campus de Gambelas, Universidade do Algarve, Faro, Portugal
| | - José P Andrade
- Centro de Ciências do Mar do Algarve, Campus de Gambelas, Universidade do Algarve, Faro, Portugal
| | - Antonio V Sykes
- Centro de Ciências do Mar do Algarve, Campus de Gambelas, Universidade do Algarve, Faro, Portugal
| | - William R Driedzic
- Department of Ocean Sciences, Memorial University, St. John's, NL, Canada
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17
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Respiration of permeabilized cardiomyocytes from mice: no sex differences, but substrate-dependent changes in the apparent ADP-affinity. Sci Rep 2019; 9:12592. [PMID: 31467353 PMCID: PMC6715638 DOI: 10.1038/s41598-019-48964-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Accepted: 08/12/2019] [Indexed: 11/17/2022] Open
Abstract
Sex differences in cardiac physiology are getting increased attention. This study assessed whether isolated, permeabilized cardiomyocytes from male and female C57BL/6 mice differ in terms of their respiration with multiple substrates and overall intracellular diffusion restriction estimated by the apparent ADP-affinity of respiration. Using respirometry, we recorded 1) the activities of respiratory complexes I, II and IV, 2) the respiration rate with substrates fuelling either complex I, II, or I + II, and 3) the apparent ADP-affinity with substrates fuelling complex I and I + II. The respiration rates were normalized to protein content and citrate synthase (CS) activity. We found no sex differences in CS activity (a marker of mitochondrial content) normalized to protein content or in any of the respiration measurements. This suggests that cardiomyocytes from male and female mice do not differ in terms of mitochondrial respiratory capacity and apparent ADP-affinity. Pyruvate modestly lowered the respiration rate, when added to succinate, glutamate and malate. This may be explained by intramitochondrial compartmentalization caused by the formation of supercomplexes and their association with specific dehydrogenases. To our knowledge, we show for the first time that the apparent ADP-affinity was substrate-dependent. This suggests that substrates may change or regulate intracellular barriers in cardiomyocytes.
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18
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Rosenstein PG, Tennent-Brown BS, Hughes D. Clinical use of plasma lactate concentration. Part 1: Physiology, pathophysiology, and measurement. J Vet Emerg Crit Care (San Antonio) 2018. [PMID: 29533512 DOI: 10.1111/vec.12708] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
OBJECTIVE To review the current literature with respect to the physiology, pathophysiology, and measurement of lactate. DATA SOURCES Data were sourced from veterinary and human clinical trials, retrospective studies, experimental studies, and review articles. Articles were retrieved without date restrictions and were sourced primarily via PubMed, Scopus, and CAB Abstracts as well as by manual selection. HUMAN AND VETERINARY DATA SYNTHESIS Lactate is an important energy storage molecule, the production of which preserves cellular energy production and mitigates the acidosis from ATP hydrolysis. Although the most common cause of hyperlactatemia is inadequate tissue oxygen delivery, hyperlactatemia can, and does occur in the face of apparently adequate oxygen supply. At a cellular level, the pathogenesis of hyperlactatemia varies widely depending on the underlying cause. Microcirculatory dysfunction, mitochondrial dysfunction, and epinephrine-mediated stimulation of Na+ -K+ -ATPase pumps are likely important contributors to hyperlactatemia in critically ill patients. Ultimately, hyperlactatemia is a marker of altered cellular bioenergetics. CONCLUSION The etiology of hyperlactatemia is complex and multifactorial. Understanding the relevant pathophysiology is helpful when characterizing hyperlactatemia in clinical patients.
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Affiliation(s)
- Patricia G Rosenstein
- Department of Veterinary Clinical Sciences, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Werribee, Victoria, Australia
| | - Brett S Tennent-Brown
- Department of Veterinary Clinical Sciences, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Werribee, Victoria, Australia
| | - Dez Hughes
- Department of Veterinary Clinical Sciences, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Werribee, Victoria, Australia
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19
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Hilgemann DW, Dai G, Collins A, Lariccia V, Magi S, Deisl C, Fine M. Lipid signaling to membrane proteins: From second messengers to membrane domains and adapter-free endocytosis. J Gen Physiol 2018; 150:211-224. [PMID: 29326133 PMCID: PMC5806671 DOI: 10.1085/jgp.201711875] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Hilgemann et al. explain how lipid signaling to membrane proteins involves a hierarchy of mechanisms from lipid binding to membrane domain coalescence. Lipids influence powerfully the function of ion channels and transporters in two well-documented ways. A few lipids act as bona fide second messengers by binding to specific sites that control channel and transporter gating. Other lipids act nonspecifically by modifying the physical environment of channels and transporters, in particular the protein–membrane interface. In this short review, we first consider lipid signaling from this traditional viewpoint, highlighting innumerable Journal of General Physiology publications that have contributed to our present understanding. We then switch to our own emerging view that much important lipid signaling occurs via the formation of membrane domains that influence the function of channels and transporters within them, promote selected protein–protein interactions, and control the turnover of surface membrane.
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Affiliation(s)
- Donald W Hilgemann
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Gucan Dai
- Department of Physiology and Biophysics, University of Washington, Seattle, WA
| | - Anthony Collins
- Saba University School of Medicine, The Bottom, Saba, Dutch Caribbean
| | - Vincenzo Lariccia
- Department of Biomedical Sciences and Public Health, School of Medicine, University "Politecnica delle Marche," Ancona, Italy
| | - Simona Magi
- Department of Biomedical Sciences and Public Health, School of Medicine, University "Politecnica delle Marche," Ancona, Italy
| | - Christine Deisl
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX
| | - Michael Fine
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX
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20
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Koronowski KB, Khoury N, Saul I, Loris ZB, Cohan CH, Stradecki-Cohan HM, Dave KR, Young JI, Perez-Pinzon MA. Neuronal SIRT1 (Silent Information Regulator 2 Homologue 1) Regulates Glycolysis and Mediates Resveratrol-Induced Ischemic Tolerance. Stroke 2017; 48:3117-3125. [PMID: 29018134 PMCID: PMC5654689 DOI: 10.1161/strokeaha.117.018562] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Revised: 09/06/2017] [Accepted: 09/13/2017] [Indexed: 12/13/2022]
Abstract
BACKGROUND AND PURPOSE Resveratrol, at least in part via SIRT1 (silent information regulator 2 homologue 1) activation, protects against cerebral ischemia when administered 2 days before injury. However, it remains unclear if SIRT1 activation must occur, and in which brain cell types, for the induction of neuroprotection. We hypothesized that neuronal SIRT1 is essential for resveratrol-induced ischemic tolerance and sought to characterize the metabolic pathways regulated by neuronal Sirt1 at the cellular level in the brain. METHODS We assessed infarct size and functional outcome after transient 60 minute middle cerebral artery occlusion in control and inducible, neuronal-specific SIRT1 knockout mice. Nontargeted primary metabolomics analysis identified putative SIRT1-regulated pathways in brain. Glycolytic function was evaluated in acute brain slices from adult mice and primary neuronal-enriched cultures under ischemic penumbra-like conditions. RESULTS Resveratrol-induced neuroprotection from stroke was lost in neuronal Sirt1 knockout mice. Metabolomics analysis revealed alterations in glucose metabolism on deletion of neuronal Sirt1, accompanied by transcriptional changes in glucose metabolism machinery. Furthermore, glycolytic ATP production was impaired in acute brain slices from neuronal Sirt1 knockout mice. Conversely, resveratrol increased glycolytic rate in a SIRT1-dependent manner and under ischemic penumbra-like conditions in vitro. CONCLUSIONS Our data demonstrate that resveratrol requires neuronal SIRT1 to elicit ischemic tolerance and identify a novel role for SIRT1 in the regulation of glycolytic function in brain. Identification of robust neuroprotective mechanisms that underlie ischemia tolerance and the metabolic adaptations mediated by SIRT1 in brain are crucial for the translation of therapies in cerebral ischemia and other neurological disorders.
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Affiliation(s)
- Kevin B Koronowski
- From the Cerebral Vascular Disease Research Laboratories (K.B.K., N.K., I.S., C.H.C., H.M.S.-C., K.R.D., M.A.P.-P.), Department of Neurology (K.B.K., N.K., I.S., C.H.C., H.M.S.-C., K.R.D., M.A.P.-P.), The Miami Project to Cure Paralysis (Z.B.L.), Department of Neurological Surgery (Z.B.L.), John P. Hussman Institute for Human Genomics (J.I.Y.) and Department of Human Genetics (J.I.Y.), University of Miami Leonard M. Miller School of Medicine, FL
| | - Nathalie Khoury
- From the Cerebral Vascular Disease Research Laboratories (K.B.K., N.K., I.S., C.H.C., H.M.S.-C., K.R.D., M.A.P.-P.), Department of Neurology (K.B.K., N.K., I.S., C.H.C., H.M.S.-C., K.R.D., M.A.P.-P.), The Miami Project to Cure Paralysis (Z.B.L.), Department of Neurological Surgery (Z.B.L.), John P. Hussman Institute for Human Genomics (J.I.Y.) and Department of Human Genetics (J.I.Y.), University of Miami Leonard M. Miller School of Medicine, FL
| | - Isabel Saul
- From the Cerebral Vascular Disease Research Laboratories (K.B.K., N.K., I.S., C.H.C., H.M.S.-C., K.R.D., M.A.P.-P.), Department of Neurology (K.B.K., N.K., I.S., C.H.C., H.M.S.-C., K.R.D., M.A.P.-P.), The Miami Project to Cure Paralysis (Z.B.L.), Department of Neurological Surgery (Z.B.L.), John P. Hussman Institute for Human Genomics (J.I.Y.) and Department of Human Genetics (J.I.Y.), University of Miami Leonard M. Miller School of Medicine, FL
| | - Zachary B Loris
- From the Cerebral Vascular Disease Research Laboratories (K.B.K., N.K., I.S., C.H.C., H.M.S.-C., K.R.D., M.A.P.-P.), Department of Neurology (K.B.K., N.K., I.S., C.H.C., H.M.S.-C., K.R.D., M.A.P.-P.), The Miami Project to Cure Paralysis (Z.B.L.), Department of Neurological Surgery (Z.B.L.), John P. Hussman Institute for Human Genomics (J.I.Y.) and Department of Human Genetics (J.I.Y.), University of Miami Leonard M. Miller School of Medicine, FL
| | - Charles H Cohan
- From the Cerebral Vascular Disease Research Laboratories (K.B.K., N.K., I.S., C.H.C., H.M.S.-C., K.R.D., M.A.P.-P.), Department of Neurology (K.B.K., N.K., I.S., C.H.C., H.M.S.-C., K.R.D., M.A.P.-P.), The Miami Project to Cure Paralysis (Z.B.L.), Department of Neurological Surgery (Z.B.L.), John P. Hussman Institute for Human Genomics (J.I.Y.) and Department of Human Genetics (J.I.Y.), University of Miami Leonard M. Miller School of Medicine, FL
| | - Holly M Stradecki-Cohan
- From the Cerebral Vascular Disease Research Laboratories (K.B.K., N.K., I.S., C.H.C., H.M.S.-C., K.R.D., M.A.P.-P.), Department of Neurology (K.B.K., N.K., I.S., C.H.C., H.M.S.-C., K.R.D., M.A.P.-P.), The Miami Project to Cure Paralysis (Z.B.L.), Department of Neurological Surgery (Z.B.L.), John P. Hussman Institute for Human Genomics (J.I.Y.) and Department of Human Genetics (J.I.Y.), University of Miami Leonard M. Miller School of Medicine, FL
| | - Kunjan R Dave
- From the Cerebral Vascular Disease Research Laboratories (K.B.K., N.K., I.S., C.H.C., H.M.S.-C., K.R.D., M.A.P.-P.), Department of Neurology (K.B.K., N.K., I.S., C.H.C., H.M.S.-C., K.R.D., M.A.P.-P.), The Miami Project to Cure Paralysis (Z.B.L.), Department of Neurological Surgery (Z.B.L.), John P. Hussman Institute for Human Genomics (J.I.Y.) and Department of Human Genetics (J.I.Y.), University of Miami Leonard M. Miller School of Medicine, FL
| | - Juan I Young
- From the Cerebral Vascular Disease Research Laboratories (K.B.K., N.K., I.S., C.H.C., H.M.S.-C., K.R.D., M.A.P.-P.), Department of Neurology (K.B.K., N.K., I.S., C.H.C., H.M.S.-C., K.R.D., M.A.P.-P.), The Miami Project to Cure Paralysis (Z.B.L.), Department of Neurological Surgery (Z.B.L.), John P. Hussman Institute for Human Genomics (J.I.Y.) and Department of Human Genetics (J.I.Y.), University of Miami Leonard M. Miller School of Medicine, FL
| | - Miguel A Perez-Pinzon
- From the Cerebral Vascular Disease Research Laboratories (K.B.K., N.K., I.S., C.H.C., H.M.S.-C., K.R.D., M.A.P.-P.), Department of Neurology (K.B.K., N.K., I.S., C.H.C., H.M.S.-C., K.R.D., M.A.P.-P.), The Miami Project to Cure Paralysis (Z.B.L.), Department of Neurological Surgery (Z.B.L.), John P. Hussman Institute for Human Genomics (J.I.Y.) and Department of Human Genetics (J.I.Y.), University of Miami Leonard M. Miller School of Medicine, FL.
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21
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Driedzic WR. Low plasma glucose limits glucose metabolism by RBCs and heart in some species of teleosts. Comp Biochem Physiol B Biochem Mol Biol 2017; 224:204-209. [PMID: 28803129 DOI: 10.1016/j.cbpb.2017.08.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Revised: 08/02/2017] [Accepted: 08/03/2017] [Indexed: 12/28/2022]
Abstract
Within teleosts there is a species range in plasma glucose levels from undetectable to 20mM. At low plasma glucose levels the gradient from the extracellular to the intracellular space is decreased. The impact of this on glucose metabolism by RBCs and heart from species with different steady state levels of plasma glucose (Atlantic cod ~5mM; Atlantic salmon ~5mM, cunner ~1mM, lumpfish <1mM; short-horned sculpin <1mM) is the subject of this review. Under normoxia, at physiological levels of extracellular glucose, RBCs and heart produce lactate although the contribution of anaerobic metabolism to ATP production is small. Sustained lactate production from extracellular glucose appears to be the primary fate of extracellular glucose. In many cases, glycogen is not mobilized and the rate of glucose metabolism=two times the rate of lactate production. As such, alternative metabolic sources are required to fuel oxidative metabolism. Under hypoxia, hearts from Atlantic cod and rainbow trout increase rates of both glucose metabolism and lactate production, partially supported by glycogen reserves. But in lumpfish and short-horned sculpin hearts there is no change in rates of glucose metabolism. The most likely explanation is that glucose uptake is compromised in lumpfish and short-horned sculpin hearts due to a low diffusion gradient. Under these conditions rates of lactate production are well below that of Atlantic cod or rainbow trout. Energy demand must be reduced under hypoxia in lumpfish and short-horned sculpin hearts in order to maintain ATP balance.
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Affiliation(s)
- William R Driedzic
- Department of Ocean Sciences, Memorial University, St. John's, N.L. A1C 1S7, Canada.
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22
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Lu FM, Hilgemann DW. Na/K pump inactivation, subsarcolemmal Na measurements, and cytoplasmic ion turnover kinetics contradict restricted Na spaces in murine cardiac myocytes. J Gen Physiol 2017; 149:727-749. [PMID: 28606910 PMCID: PMC5496509 DOI: 10.1085/jgp.201711780] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Accepted: 05/23/2017] [Indexed: 11/20/2022] Open
Abstract
The Na/K pump exports cytoplasmic Na ions while importing K ions, and its activity is thought to be affected by restricted intracellular Na diffusion in cardiac myocytes. Lu and Hilgemann find instead that the pump can enter an inactivated state and that inactivation can be relieved by cytoplasmic Na. Decades ago, it was proposed that Na transport in cardiac myocytes is modulated by large changes in cytoplasmic Na concentration within restricted subsarcolemmal spaces. Here, we probe this hypothesis for Na/K pumps by generating constitutive transsarcolemmal Na flux with the Na channel opener veratridine in whole-cell patch-clamp recordings. Using 25 mM Na in the patch pipette, pump currents decay strongly during continuous activation by extracellular K (τ, ∼2 s). In contradiction to depletion hypotheses, the decay becomes stronger when pump currents are decreased by hyperpolarization. Na channel currents are nearly unchanged by pump activity in these conditions, and conversely, continuous Na currents up to 0.5 nA in magnitude have negligible effects on pump currents. These outcomes are even more pronounced using 50 mM Li as a cytoplasmic Na congener. Thus, the Na/K pump current decay reflects mostly an inactivation mechanism that immobilizes Na/K pump charge movements, not cytoplasmic Na depletion. When channel currents are increased beyond 1 nA, models with unrestricted subsarcolemmal diffusion accurately predict current decay (τ ∼15 s) and reversal potential shifts observed for Na, Li, and K currents through Na channels opened by veratridine, as well as for Na, K, Cs, Li, and Cl currents recorded in nystatin-permeabilized myocytes. Ion concentrations in the pipette tip (i.e., access conductance) track without appreciable delay the current changes caused by sarcolemmal ion flux. Importantly, cytoplasmic mixing volumes, calculated from current decay kinetics, increase and decrease as expected with osmolarity changes (τ >30 s). Na/K pump current run-down over 20 min reflects a failure of pumps to recover from inactivation. Simulations reveal that pump inactivation coupled with Na-activated recovery enhances the rapidity and effectivity of Na homeostasis in cardiac myocytes. In conclusion, an autoregulatory mechanism enhances cardiac Na/K pump activity when cytoplasmic Na rises and suppresses pump activity when cytoplasmic Na declines.
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Affiliation(s)
- Fang-Min Lu
- Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX
| | - Donald W Hilgemann
- Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX
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23
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Béland-Millar A, Larcher J, Courtemanche J, Yuan T, Messier C. Effects of Systemic Metabolic Fuels on Glucose and Lactate Levels in the Brain Extracellular Compartment of the Mouse. Front Neurosci 2017; 11:7. [PMID: 28154523 PMCID: PMC5243849 DOI: 10.3389/fnins.2017.00007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Accepted: 01/04/2017] [Indexed: 01/11/2023] Open
Abstract
Classic neuroenergetic research has emphasized the role of glucose, its transport and its metabolism in sustaining normal neural function leading to the textbook statement that it is the necessary and sole metabolic fuel of the mammalian brain. New evidence, including the Astrocyte-to-Neuron Lactate Shuttle hypothesis, suggests that the brain can use other metabolic substrates. To further study that possibility, we examined the effect of intraperitoneally administered metabolic fuels (glucose, fructose, lactate, pyruvate, ß-hydroxybutyrate, and galactose), and insulin, on blood, and extracellular brain levels of glucose and lactate in the adult male CD1 mouse. Primary motor cortex extracellular levels of glucose and lactate were monitored in freely moving mice with the use of electrochemical electrodes. Blood concentration of these same metabolites were obtained by tail vein sampling and measured with glucose and lactate meters. Blood and extracellular fluctuations of glucose and lactate were monitored for a 2-h period. We found that the systemic injections of glucose, fructose, lactate, pyruvate, and ß-hydroxybutyrate increased blood lactate levels. Apart for a small transitory rise in brain extracellular lactate levels, the main effect of the systemic injection of glucose, fructose, lactate, pyruvate, and ß-hydroxybutyrate was an increase in brain extracellular glucose levels. Systemic galactose injections produced a small rise in blood glucose and lactate but almost no change in brain extracellular lactate and glucose. Systemic insulin injections led to a decrease in blood glucose and a small rise in blood lactate; however brain extracellular glucose and lactate monotonically decreased at the same rate. Our results support the concept that the brain is able to use alternative fuels and the current experiments suggest some of the mechanisms involved.
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Affiliation(s)
| | - Jeremy Larcher
- School of Psychology, University of Ottawa Ottawa, ON, Canada
| | | | - Tina Yuan
- School of Psychology, University of Ottawa Ottawa, ON, Canada
| | - Claude Messier
- School of Psychology, University of Ottawa Ottawa, ON, Canada
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24
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Rueda EM, Johnson JE, Giddabasappa A, Swaroop A, Brooks MJ, Sigel I, Chaney SY, Fox DA. The cellular and compartmental profile of mouse retinal glycolysis, tricarboxylic acid cycle, oxidative phosphorylation, and ~P transferring kinases. Mol Vis 2016; 22:847-85. [PMID: 27499608 PMCID: PMC4961465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2016] [Accepted: 07/21/2016] [Indexed: 10/26/2022] Open
Abstract
PURPOSE The homeostatic regulation of cellular ATP is achieved by the coordinated activity of ATP utilization, synthesis, and buffering. Glucose is the major substrate for ATP synthesis through glycolysis and oxidative phosphorylation (OXPHOS), whereas intermediary metabolism through the tricarboxylic acid (TCA) cycle utilizes non-glucose-derived monocarboxylates, amino acids, and alpha ketoacids to support mitochondrial ATP and GTP synthesis. Cellular ATP is buffered by specialized equilibrium-driven high-energy phosphate (~P) transferring kinases. Our goals were twofold: 1) to characterize the gene expression, protein expression, and activity of key synthesizing and regulating enzymes of energy metabolism in the whole mouse retina, retinal compartments, and/or cells and 2) to provide an integrative analysis of the results related to function. METHODS mRNA expression data of energy-related genes were extracted from our whole retinal Affymetrix microarray data. Fixed-frozen retinas from adult C57BL/6N mice were used for immunohistochemistry, laser scanning confocal microscopy, and enzymatic histochemistry. The immunoreactivity levels of well-characterized antibodies, for all major retinal cells and their compartments, were obtained using our established semiquantitative confocal and imaging techniques. Quantitative cytochrome oxidase (COX) and lactate dehydrogenase (LDH) activity was determined histochemically. RESULTS The Affymetrix data revealed varied gene expression patterns of the ATP synthesizing and regulating enzymes found in the muscle, liver, and brain. Confocal studies showed differential cellular and compartmental distribution of isozymes involved in glucose, glutamate, glutamine, lactate, and creatine metabolism. The pattern and intensity of the antibodies and of the COX and LDH activity showed the high capacity of photoreceptors for aerobic glycolysis and OXPHOS. Competition assays with pyruvate revealed that LDH-5 was localized in the photoreceptor inner segments. The combined results indicate that glycolysis is regulated by the compartmental expression of hexokinase 2, pyruvate kinase M1, and pyruvate kinase M2 in photoreceptors, whereas the inner retinal neurons exhibit a lower capacity for glycolysis and aerobic glycolysis. Expression of nucleoside diphosphate kinase, mitochondria-associated adenylate kinase, and several mitochondria-associated creatine kinase isozymes was highest in the outer retina, whereas expression of cytosolic adenylate kinase and brain creatine kinase was higher in the cones, horizontal cells, and amacrine cells indicating the diversity of ATP-buffering strategies among retinal neurons. Based on the antibody intensities and the COX and LDH activity, Müller glial cells (MGCs) had the lowest capacity for glycolysis, aerobic glycolysis, and OXPHOS. However, they showed high expression of glutamate dehydrogenase, alpha-ketoglutarate dehydrogenase, succinate thiokinase, GABA transaminase, and ~P transferring kinases. This suggests that MGCs utilize TCA cycle anaplerosis and cataplerosis to generate GTP and ~P transferring kinases to produce ATP that supports MGC energy requirements. CONCLUSIONS Our comprehensive and integrated results reveal that the adult mouse retina expresses numerous isoforms of ATP synthesizing, regulating, and buffering genes; expresses differential cellular and compartmental levels of glycolytic, OXPHOS, TCA cycle, and ~P transferring kinase proteins; and exhibits differential layer-by-layer LDH and COX activity. New insights into cell-specific and compartmental ATP and GTP production, as well as utilization and buffering strategies and their relationship with known retinal and cellular functions, are discussed. Developing therapeutic strategies for neuroprotection and treating retinal deficits and degeneration in a cell-specific manner will require such knowledge. This work provides a platform for future research directed at identifying the molecular targets and proteins that regulate these processes.
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Affiliation(s)
- Elda M. Rueda
- College of Optometry, University of Houston, Houston TX
| | - Jerry E. Johnson
- Department of Natural Sciences, University of Houston-Downtown, Houston TX
- Department of Biology and Biochemistry, University of Houston, Houston TX
| | - Anand Giddabasappa
- Department of Biology and Biochemistry, University of Houston, Houston TX
| | | | | | - Irena Sigel
- College of Optometry, University of Houston, Houston TX
| | - Shawnta Y. Chaney
- Department of Biology and Biochemistry, University of Houston, Houston TX
| | - Donald A. Fox
- College of Optometry, University of Houston, Houston TX
- Department of Biology and Biochemistry, University of Houston, Houston TX
- Department of Pharmacology and Pharmaceutical Sciences, University of Houston, Houston TX
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25
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Simson P, Jepihhina N, Laasmaa M, Peterson P, Birkedal R, Vendelin M. Restricted ADP movement in cardiomyocytes: Cytosolic diffusion obstacles are complemented with a small number of open mitochondrial voltage-dependent anion channels. J Mol Cell Cardiol 2016; 97:197-203. [PMID: 27261153 DOI: 10.1016/j.yjmcc.2016.04.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 04/19/2016] [Indexed: 12/17/2022]
Abstract
Adequate intracellular energy transfer is crucial for proper cardiac function. In energy starved failing hearts, partial restoration of energy transfer can rescue mechanical performance. There are two types of diffusion obstacles that interfere with energy transfer from mitochondria to ATPases: mitochondrial outer membrane (MOM) with voltage-dependent anion channel (VDAC) permeable to small hydrophilic molecules and cytoplasmatic diffusion barriers grouping ATP-producers and -consumers. So far, there is no method developed to clearly distinguish the contributions of cytoplasmatic barriers and MOM to the overall diffusion restriction. Furthermore, the number of open VDACs in vivo remains unknown. The aim of this work was to establish the partitioning of intracellular diffusion obstacles in cardiomyocytes. We studied the response of mitochondrial oxidative phosphorylation of permeabilized rat cardiomyocytes to changes in extracellular ADP by recording 3D image stacks of NADH autofluorescence. Using cell-specific mathematical models, we determined the permeability of MOM and cytoplasmatic barriers. We found that only ~2% of VDACs are accessible to cytosolic ADP and cytoplasmatic diffusion barriers reduce the apparent diffusion coefficient by 6-10×. In cardiomyocytes, diffusion barriers in the cytoplasm and by the MOM restrict ADP/ATP diffusion to similar extents suggesting a major role of both barriers in energy transfer and other intracellular processes.
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Affiliation(s)
- Päivo Simson
- Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology, Akadeemia Rd 21, 12618 Tallinn, Estonia
| | - Natalja Jepihhina
- Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology, Akadeemia Rd 21, 12618 Tallinn, Estonia
| | - Martin Laasmaa
- Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology, Akadeemia Rd 21, 12618 Tallinn, Estonia
| | - Pearu Peterson
- Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology, Akadeemia Rd 21, 12618 Tallinn, Estonia
| | - Rikke Birkedal
- Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology, Akadeemia Rd 21, 12618 Tallinn, Estonia
| | - Marko Vendelin
- Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology, Akadeemia Rd 21, 12618 Tallinn, Estonia.
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26
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Birkedal R, Laasmaa M, Vendelin M. The location of energetic compartments affects energetic communication in cardiomyocytes. Front Physiol 2014; 5:376. [PMID: 25324784 PMCID: PMC4178378 DOI: 10.3389/fphys.2014.00376] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Accepted: 09/10/2014] [Indexed: 01/08/2023] Open
Abstract
The heart relies on accurate regulation of mitochondrial energy supply to match energy demand. The main regulators are Ca2+ and feedback of ADP and Pi. Regulation via feedback has intrigued for decades. First, the heart exhibits a remarkable metabolic stability. Second, diffusion of ADP and other molecules is restricted specifically in heart and red muscle, where a fast feedback is needed the most. To explain the regulation by feedback, compartmentalization must be taken into account. Experiments and theoretical approaches suggest that cardiomyocyte energetic compartmentalization is elaborate with barriers obstructing diffusion in the cytosol and at the level of the mitochondrial outer membrane (MOM). A recent study suggests the barriers are organized in a lattice with dimensions in agreement with those of intracellular structures. Here, we discuss the possible location of these barriers. The more plausible scenario includes a barrier at the level of MOM. Much research has focused on how the permeability of MOM itself is regulated, and the importance of the creatine kinase system to facilitate energetic communication. We hypothesize that at least part of the diffusion restriction at the MOM level is not by MOM itself, but due to the close physical association between the sarcoplasmic reticulum (SR) and mitochondria. This will explain why animals with a disabled creatine kinase system exhibit rather mild phenotype modifications. Mitochondria are hubs of energetics, but also ROS production and signaling. The close association between SR and mitochondria may form a diffusion barrier to ADP added outside a permeabilized cardiomyocyte. But in vivo, it is the structural basis for the mitochondrial-SR coupling that is crucial for the regulation of mitochondrial Ca2+-transients to regulate energetics, and for avoiding Ca2+-overload and irreversible opening of the mitochondrial permeability transition pore.
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Affiliation(s)
- Rikke Birkedal
- Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology Tallinn, Estonia
| | - Martin Laasmaa
- Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology Tallinn, Estonia
| | - Marko Vendelin
- Laboratory of Systems Biology, Institute of Cybernetics, Tallinn University of Technology Tallinn, Estonia
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