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Su S, Wahl A, Rugis J, Suresh V, Yule DI, Sneyd J. A mathematical model of ENaC and Slc26a6 regulation by CFTR in salivary gland ducts. Am J Physiol Gastrointest Liver Physiol 2024; 326:G555-G566. [PMID: 38349781 DOI: 10.1152/ajpgi.00168.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Revised: 01/17/2024] [Accepted: 02/06/2024] [Indexed: 02/15/2024]
Abstract
Cystic fibrosis (CF) is a genetic disease caused by the mutations of cystic fibrosis transmembrane conductance regulator (CFTR), the cystic fibrosis transmembrane conductance regulator gene. Cftr is a critical ion channel expressed in the apical membrane of mouse salivary gland striated duct cells. Although Cftr is primarily a Cl- channel, its knockout leads to higher salivary Cl- and Na+ concentrations and lower pH. Mouse experiments show that the activation of Cftr upregulates epithelial Na+ channel (ENaC) protein expression level and Slc26a6 (a 1Cl-:2[Formula: see text] exchanger of the solute carrier family) activity. Experimentally, it is difficult to predict how much the coregulation effects of CFTR contribute to the abnormal Na+, Cl-, and [Formula: see text] concentrations and pH in CF saliva. To address this question, we construct a wild-type mouse salivary gland model and simulate CFTR knockout by altering the expression levels of CFTR, ENaC, and Slc26a6. By reproducing the in vivo and ex vivo final saliva measurements from wild-type and CFTR knockout animals, we obtain computational evidence that ENaC and Slc26a6 activities are downregulated in CFTR knockout in salivary glands.NEW & NOTEWORTHY This paper describes a salivary gland mathematical model simulating the ion exchange between saliva and the salivary gland duct epithelium. The novelty lies in the implementation of CFTR regulating ENaC and Slc26a6 in a CFTR knockout gland. By reproducing the experimental saliva measurements in wild-type and CFTR knockout glands, the model shows that CFTR regulates ENaC and Slc26a6 anion exchanger in salivary glands. The method could be used to understand the various cystic fibrosis phenotypes.
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Affiliation(s)
- Shan Su
- Department of Mathematics, University of Auckland, Auckland, New Zealand
| | - Amanda Wahl
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York, United States
| | - John Rugis
- Department of Mathematics, University of Auckland, Auckland, New Zealand
| | - Vinod Suresh
- Auckland Biomedical Engineering Institute, University of Auckland, Auckland, New Zealand
- Department of Engineering Science, University of Auckland, Auckland, New Zealand
| | - David I Yule
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York, United States
| | - James Sneyd
- Department of Mathematics, University of Auckland, Auckland, New Zealand
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2
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Wilson AD, Richards MA, Curtis MK, Gunadasa-Rohling M, Monterisi S, Loonat AA, Miller JJ, Ball V, Lewis A, Tyler DJ, Moshnikova A, Andreev OA, Reshetnyak YK, Carr C, Swietach P. Acidic environments trigger intracellular H+-sensing FAK proteins to re-balance sarcolemmal acid-base transporters and auto-regulate cardiomyocyte pH. Cardiovasc Res 2022; 118:2946-2959. [PMID: 34897412 PMCID: PMC9648823 DOI: 10.1093/cvr/cvab364] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Accepted: 12/08/2021] [Indexed: 11/12/2022] Open
Abstract
AIMS In cardiomyocytes, acute disturbances to intracellular pH (pHi) are promptly corrected by a system of finely tuned sarcolemmal acid-base transporters. However, these fluxes become thermodynamically re-balanced in acidic environments, which inadvertently causes their set-point pHi to fall outside the physiological range. It is unclear whether an adaptive mechanism exists to correct this thermodynamic challenge, and return pHi to normal. METHODS AND RESULTS Following left ventricle cryo-damage, a diffuse pattern of low extracellular pH (pHe) was detected by acid-sensing pHLIP. Despite this, pHi measured in the beating heart (13C NMR) was normal. Myocytes had adapted to their acidic environment by reducing Cl-/HCO3- exchange (CBE)-dependent acid-loading and increasing Na+/H+ exchange (NHE1)-dependent acid-extrusion, as measured by fluorescence (cSNARF1). The outcome of this adaptation on pHi is revealed as a cytoplasmic alkalinization when cells are superfused at physiological pHe. Conversely, mice given oral bicarbonate (to improve systemic buffering) had reduced myocardial NHE1 expression, consistent with a needs-dependent expression of pHi-regulatory transporters. The response to sustained acidity could be replicated in vitro using neonatal ventricular myocytes incubated at low pHe for 48 h. The adaptive increase in NHE1 and decrease in CBE activities was linked to Slc9a1 (NHE1) up-regulation and Slc4a2 (AE2) down-regulation. This response was triggered by intracellular H+ ions because it persisted in the absence of CO2/HCO3- and became ablated when acidic incubation media had lower chloride, a solution manoeuvre that reduces the extent of pHi-decrease. Pharmacological inhibition of FAK-family non-receptor kinases, previously characterized as pH-sensors, ablated this pHi autoregulation. In support of a pHi-sensing role, FAK protein Pyk2 (auto)phosphorylation was reduced within minutes of exposure to acidity, ahead of adaptive changes to pHi control. CONCLUSIONS Cardiomyocytes fine-tune the expression of pHi-regulators so that pHi is at least 7.0. This autoregulatory feedback mechanism defines physiological pHi and protects it during pHe vulnerabilities.
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Affiliation(s)
- Abigail D Wilson
- Department of Physiology, Anatomy & Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford OX1 3PT, UK
| | - Mark A Richards
- Department of Physiology, Anatomy & Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford OX1 3PT, UK
| | - M Kate Curtis
- Department of Physiology, Anatomy & Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford OX1 3PT, UK
| | - Mala Gunadasa-Rohling
- Department of Physiology, Anatomy & Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford OX1 3PT, UK
| | - Stefania Monterisi
- Department of Physiology, Anatomy & Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford OX1 3PT, UK
| | - Aminah A Loonat
- Department of Physiology, Anatomy & Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford OX1 3PT, UK
| | - Jack J Miller
- Department of Physiology, Anatomy & Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford OX1 3PT, UK
- Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR), Radcliffe Department of Medicine, Level 0, John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK
| | - Vicky Ball
- Department of Physiology, Anatomy & Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford OX1 3PT, UK
| | - Andrew Lewis
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR), Radcliffe Department of Medicine, Level 0, John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK
| | - Damian J Tyler
- Department of Physiology, Anatomy & Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford OX1 3PT, UK
- Oxford Centre for Clinical Magnetic Resonance Research (OCMR), Radcliffe Department of Medicine, Level 0, John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK
| | - Anna Moshnikova
- Physics Department, University of Rhode Island, 2 Lippitt Rd, Kingston, RI 02881, USA
| | - Oleg A Andreev
- Physics Department, University of Rhode Island, 2 Lippitt Rd, Kingston, RI 02881, USA
| | - Yana K Reshetnyak
- Physics Department, University of Rhode Island, 2 Lippitt Rd, Kingston, RI 02881, USA
| | - Carolyn Carr
- Department of Physiology, Anatomy & Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford OX1 3PT, UK
| | - Pawel Swietach
- Department of Physiology, Anatomy & Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford OX1 3PT, UK
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Hammers DE, Donahue DL, Tucker Z, Ashfeld BL, Ploplis VA, Castellino FJ, Lee SW. Streptolysin S targets the sodium-bicarbonate cotransporter NBCn1 to induce inflammation and cytotoxicity in human keratinocytes during Group A Streptococcal infection. Front Cell Infect Microbiol 2022; 12:1002230. [PMID: 36389147 PMCID: PMC9663810 DOI: 10.3389/fcimb.2022.1002230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2022] [Accepted: 09/29/2022] [Indexed: 11/30/2022] Open
Abstract
Group A <i>Streptococcus</i> (GAS, <i>Streptococcus pyogenes</i>) is a Gram-positive human pathogen that employs several secreted and surface-bound virulence factors to manipulate its environment, allowing it to cause a variety of disease outcomes. One such virulence factor is Streptolysin S (SLS), a ribosomally-produced peptide toxin that undergoes extensive post-translational modifications. The activity of SLS has been studied for over 100 years owing to its rapid and potent ability to lyse red blood cells, and the toxin has been shown to play a major role in GAS virulence <i>in vivo</i>. We have previously demonstrated that SLS induces hemolysis by targeting the chloride-bicarbonate exchanger Band 3 in erythrocytes, indicating that SLS is capable of targeting host proteins to promote cell lysis. However, the possibility that SLS has additional protein targets in other cell types, such as keratinocytes, has not been explored. Here, we use bioinformatics analysis and chemical inhibition studies to demonstrate that SLS targets the electroneutral sodium-bicarbonate cotransporter NBCn1 in keratinocytes during GAS infection. SLS induces NF-κB activation and host cytotoxicity in human keratinocytes, and these processes can be mitigated by treating keratinocytes with the sodium-bicarbonate cotransport inhibitor S0859. Furthermore, treating keratinocytes with SLS disrupts the ability of host cells to regulate their intracellular pH, and this can be monitored in real time using the pH-sensitive dye pHrodo Red AM in live imaging studies. These results demonstrate that SLS is a multifunctional bacterial toxin that GAS uses in numerous context-dependent ways to promote host cell cytotoxicity and increase disease severity. Studies to elucidate additional host targets of SLS have the potential to impact the development of therapeutics for severe GAS infections.
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Affiliation(s)
- Daniel E. Hammers
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, United States,Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, United States
| | - Deborah L. Donahue
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, United States,William Myron (W. M.) Keck Center for Transgene Research, University of Notre Dame, Notre Dame, IN, United States
| | - Zachary D. Tucker
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, United States
| | - Brandon L. Ashfeld
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, United States
| | - Victoria A. Ploplis
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, United States,William Myron (W. M.) Keck Center for Transgene Research, University of Notre Dame, Notre Dame, IN, United States
| | - Francis J. Castellino
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, United States,William Myron (W. M.) Keck Center for Transgene Research, University of Notre Dame, Notre Dame, IN, United States
| | - Shaun W. Lee
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, United States,Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, United States,William Myron (W. M.) Keck Center for Transgene Research, University of Notre Dame, Notre Dame, IN, United States,*Correspondence: Shaun W. Lee,
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Ring T, Rees SE, Frische S. Acid content and buffer-capacity: a charge-balance perspective. Scand J Clin Lab Invest 2022; 82:356-362. [PMID: 35792720 DOI: 10.1080/00365513.2022.2092903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Rational treatment and thorough diagnostic classification of acid-base disorders requires quantitative understanding of the mechanisms that generate and dissipate loads of acid and base. A natural precondition for this tallying is the ability to quantify the acid content in any specified fluid. Physical chemistry defines the pH-dependent charge on any buffer species, and also on strong ions on which, by definition, the charge is pH-invariant. Based, then, on the requirement of electroneutrality and conservation of mass, it was shown in 1914 that pH can be calculated and understood on the basis of the chemical composition of any fluid. Herein we first show that this specification for [H+] of the charge-balance model directly delivers the pH-dependent buffer-capacity as defined in the literature. Next, we show how the notion of acid transport as proposed in experimental physiology can be understood as a change in strong ion difference, ΔSID. Finally, based on Brønsted-Lowry theory we demonstrate that by defining the acid content as titratable acidity, this is equal to SIDref - SID, where SIDref is SID at pH 7.4. Thereby, any chemical situation is represented as a curve in a novel diagram with titratable acidity = SIDref - SID as a function of pH. For any specification of buffer chemistry, therefore, the change in acid content in the fluid is path invariant. Since constituents of SID and titratable acidity are additive, we thereby, based on first principles, have defined a new framework for modeling acid balance across a cell, a whole organ, or the whole-body.
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Affiliation(s)
- Troels Ring
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Stephen Edward Rees
- Respiratory and Critical Care Group, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
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Ji MJ, Son KH, Hong JH. Addition of oh8dG to Cardioplegia Attenuated Myocardial Oxidative Injury through the Inhibition of Sodium Bicarbonate Cotransporter Activity. Antioxidants (Basel) 2022; 11:antiox11091641. [PMID: 36139714 PMCID: PMC9495749 DOI: 10.3390/antiox11091641] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Revised: 08/19/2022] [Accepted: 08/23/2022] [Indexed: 11/28/2022] Open
Abstract
The biomarker 8-hydroxy-2′-deoxyguanosine (oh8dG) is derived from oxidized nucleic acids or products of oxidant-mediated DNA damage. Enhanced sodium bicarbonate cotransporter (NBC) activity is caused by reactive oxygen species (ROS) production in ventricular myocytes. Thus, we hypothesized that cardioplegia-solution-mediated ROS generation may be involved in the regulation of NBC activity in cardiomyocytes and that oh8dG treatment may modulate ROS and associated NBC activity. Langendorff-free cardioplegia-arrested cardiac strips and cardiomyocytes were isolated to determine the NBC activity and effects of oh8dG on oxidative-stress-mediated cardiac damage markers. We first determined the histidine-tryptophan-ketoglutarate (HTK) solution mediated NBC activity in cardiac strips and cells. The oh8dG treatment attenuated NBC activity in the electroneutral or electrogenic form of NBC. Additionally, exposure to HTK solution induced ROS, whereas co-administration of oh8dG attenuated ROS-mediated NBC activity, reduced ROS levels, and decreased the expression of apoptotic markers and fibrosis-associated proteins in cardiac cells. The oh8dG-administrated cardiac tissues were also protected from enhanced HTK-induced damage markers, heat shock protein 60 and polyADP-ribose. Our results show that oh8dG has a protective role against myocardial oxidative damage and provides a useful treatment strategy for restoring cardiac function.
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Affiliation(s)
- Min Jeong Ji
- Department of Health Sciences and Technology, Lee Gil Ya Cancer and Diabetes Institute, GAIHST, Gachon University, 155 Getbeolro, Yeonsu-gu, Incheon 21999, Korea
| | - Kuk Hui Son
- Department of Thoracic and Cardiovascular Surgery, Gachon University Gil Medical Center, Gachon University, Incheon 21565, Korea
- Correspondence: (K.H.S.); (J.H.H.); Tel.: +82-32-899-6682 (J.H.H.)
| | - Jeong Hee Hong
- Department of Health Sciences and Technology, Lee Gil Ya Cancer and Diabetes Institute, GAIHST, Gachon University, 155 Getbeolro, Yeonsu-gu, Incheon 21999, Korea
- Correspondence: (K.H.S.); (J.H.H.); Tel.: +82-32-899-6682 (J.H.H.)
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6
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Acute pH alterations do not impact cardiac mitochondrial respiration in naked mole-rats or mice. Comp Biochem Physiol A Mol Integr Physiol 2022; 268:111185. [PMID: 35278722 DOI: 10.1016/j.cbpa.2022.111185] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 03/06/2022] [Accepted: 03/06/2022] [Indexed: 01/04/2023]
Abstract
Energetically demanding conditions such as hypoxia and exercise favour anaerobic metabolism (glycolysis), which leads to acidification of the cellular milieu from ATP hydrolysis and accumulation of the anaerobic end-product, lactate. Cellular acidification may damage mitochondrial proteins and/or alter the H+ gradient across the mitochondrial inner membrane, which may in turn impact mitochondrial respiration and thus aerobic ATP production. Naked mole-rats are among the most hypoxia-tolerant mammals, and putatively experience intermittent environmental and systemic hypoxia while resting and exercising in their underground burrows. Previous studies in naked mole-rat brain, heart, and skeletal muscle mitochondria have demonstrated adaptations that favour improved efficiency in hypoxic conditions; however, the impact of cellular acidification on mitochondrial function has not been explored. We hypothesized that, relative to hypoxia-intolerant mice, naked mole-rat cardiac mitochondrial respiration is less sensitive to cellular pH changes. To test this, we used high-resolution respirometry to measure mitochondrial respiration by permeabilized cardiac muscle fibres from naked mole-rats and mice exposed in vitro to a pH range from 6.6 to 7.6. Surprisingly, we found that acute pH changes do not impact cardiac mitochondrial respiration or compromise mitochondrial integrity in either species. Our results suggest that acute alterations of cellular pH have minimal impact on cardiac mitochondrial respiration.
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7
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Swietach P, Despa S. Channelling protons out of the heart. J Physiol 2022; 600:2551-2552. [PMID: 35490392 PMCID: PMC9322403 DOI: 10.1113/jp283250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Accepted: 04/28/2022] [Indexed: 11/24/2022] Open
Affiliation(s)
- Pawel Swietach
- Department of Physiology Anatomy & Genetics Parks Road Oxford OX1 3PT UK
| | - Sanda Despa
- Department of Pharmacology and Nutritional Sciences University of Kentucky 900 S Limestone, CTW 465 Lexington KY 40536 USA
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8
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Di Mattía RA, Díaz Zegarra LA, Valverde CA, Blanco PG, Jaquenod De Giusti C, Portiansky EL, Aiello EA, Orlowski A. In vivo Overexpression of Electrogenic Sodium/Bicarbonate Cotransporter (NBCe1) by AAV9 Modifies the Cardiac Action Potential and the QT Interval in Mice. Front Cardiovasc Med 2022; 9:862118. [PMID: 35548416 PMCID: PMC9082548 DOI: 10.3389/fcvm.2022.862118] [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: 01/25/2022] [Accepted: 03/23/2022] [Indexed: 11/29/2022] Open
Abstract
Cardiac cells depend on specific sarcolemmal ion transporters to assure the correct intracellular pH regulation. The sodium/bicarbonate cotransporter (NBC) is one of the major alkalinizing mechanisms. In the heart two different NBC isoforms have been described: the electroneutral NBCn1 (1Na+:1HCO3-) and the electrogenic NBCe1 (1Na+:2HCO3-). NBCe1 generates an anionic repolarizing current that modulates the action potential duration (APD). In addition to regulating the pH, the NBC is a source of sodium influx. It has been postulated that NBC could play a role in the development of hypertrophy. The aim of this research was to study the contribution of NBCe1 in heart electrophysiology and in the development of heart hypertrophy in an in vivo mouse model with overexpression of NBCe1. Heart NBCe1 overexpression was achieved by a recombinant cardiotropic adeno-associated virus (AAV9) and was evidenced by western-blot and qPCR. AAV9-mCherry was used as a transduction control. NBCe1 overexpression fails to increase heart growth. Patch clamp and electrocardiogram were performed. We observed a reduction on both, ventricular myocytes APD and electrocardiogram QT interval corrected by cardiac rate, emphasizing for the first time NBCe1 relevance for the electrical activity of the heart.
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Affiliation(s)
- Romina A. Di Mattía
- Centro de Investigaciones Cardiovasculares “Dr. Horacio E. Cingolani, ” Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, La Plata, Argentina
| | - Leandro A. Díaz Zegarra
- Centro de Investigaciones Cardiovasculares “Dr. Horacio E. Cingolani, ” Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, La Plata, Argentina
| | - Carlos A. Valverde
- Centro de Investigaciones Cardiovasculares “Dr. Horacio E. Cingolani, ” Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, La Plata, Argentina
| | - Paula G. Blanco
- Centro de Fisiología Reproductiva y Métodos Complementarios de Diagnóstico, Facultad de Ciencias Veterinarias, Universidad Nacional de La Plata-CONICET, La Plata, Argentina
| | - Carolina Jaquenod De Giusti
- Centro de Investigaciones Cardiovasculares “Dr. Horacio E. Cingolani, ” Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, La Plata, Argentina
| | - Enrique L. Portiansky
- Laboratorio de Análisis de Imágenes, Facultad de Ciencias Veterinarias, Universidad Nacional de La Plata-CONICET, La Plata, Argentina
| | - Ernesto A. Aiello
- Centro de Investigaciones Cardiovasculares “Dr. Horacio E. Cingolani, ” Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, La Plata, Argentina
- *Correspondence: Ernesto A. Aiello
| | - Alejandro Orlowski
- Centro de Investigaciones Cardiovasculares “Dr. Horacio E. Cingolani, ” Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, La Plata, Argentina
- Alejandro Orlowski
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Lyu Y, Thai PN, Ren L, Timofeyev V, Jian Z, Park S, Ginsburg KS, Overton J, Bossuyt J, Bers DM, Yamoah EN, Chen-Izu Y, Chiamvimonvat N, Zhang XD. Beat-to-beat dynamic regulation of intracellular pH in cardiomyocytes. iScience 2022; 25:103624. [PMID: 35005560 PMCID: PMC8718820 DOI: 10.1016/j.isci.2021.103624] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 11/10/2021] [Accepted: 12/10/2021] [Indexed: 11/20/2022] Open
Abstract
The mammalian heart beats incessantly with rhythmic mechanical activities generating acids that need to be buffered to maintain a stable intracellular pH (pHi) for normal cardiac function. Even though spatial pHi non-uniformity in cardiomyocytes has been documented, it remains unknown how pHi is regulated to match the dynamic cardiac contractions. Here, we demonstrated beat-to-beat intracellular acidification, termed pHi transients, in synchrony with cardiomyocyte contractions. The pHi transients are regulated by pacing rate, Cl-/HCO3 - transporters, pHi buffering capacity, and β-adrenergic signaling. Mitochondrial electron-transport chain inhibition attenuates the pHi transients, implicating mitochondrial activity in sculpting the pHi regulation. The pHi transients provide dynamic alterations of H+ transport required for ATP synthesis, and a decrease in pHi may serve as a negative feedback to cardiac contractions. Current findings dovetail with the prevailing three known dynamic systems, namely electrical, Ca2+, and mechanical systems, and may reveal broader features of pHi handling in excitable cells.
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Affiliation(s)
- Yankun Lyu
- Department of Internal Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Phung N. Thai
- Department of Internal Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Lu Ren
- Department of Internal Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Valeriy Timofeyev
- Department of Internal Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Zhong Jian
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | - Seojin Park
- Department of Physiology and Cell Biology, University of Nevada, Reno, Reno, NV 89557, USA
| | - Kenneth S. Ginsburg
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | - James Overton
- Department of Internal Medicine, University of California, Davis, Davis, CA 95616, USA
| | - Julie Bossuyt
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | - Donald M. Bers
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | - Ebenezer N. Yamoah
- Department of Physiology and Cell Biology, University of Nevada, Reno, Reno, NV 89557, USA
| | - Ye Chen-Izu
- Department of Internal Medicine, University of California, Davis, Davis, CA 95616, USA
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
- Department of Biomedical Engineering, University of California, Davis, Davis, CA 95616, USA
| | - Nipavan Chiamvimonvat
- Department of Internal Medicine, University of California, Davis, Davis, CA 95616, USA
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
- Department of Veterans Affairs, Northern California Health Care System, Mather, CA 95655, USA
| | - Xiao-Dong Zhang
- Department of Internal Medicine, University of California, Davis, Davis, CA 95616, USA
- Department of Veterans Affairs, Northern California Health Care System, Mather, CA 95655, USA
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Chung YJ, Park KC, Tokar S, Eykyn TR, Fuller W, Pavlovic D, Swietach P, Shattock MJ. Off-target effects of sodium-glucose co-transporter 2 blockers: empagliflozin does not inhibit Na+/H+ exchanger-1 or lower [Na+]i in the heart. Cardiovasc Res 2021; 117:2794-2806. [PMID: 33135077 PMCID: PMC8683707 DOI: 10.1093/cvr/cvaa323] [Citation(s) in RCA: 78] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Revised: 09/28/2020] [Accepted: 11/02/2020] [Indexed: 12/17/2022] Open
Abstract
AIMS Emipagliflozin (EMPA) is a potent inhibitor of the renal sodium-glucose co-transporter 2 (SGLT2) and an effective treatment for type-2 diabetes. In patients with diabetes and heart failure, EMPA has cardioprotective effects independent of improved glycaemic control, despite SGLT2 not being expressed in the heart. A number of non-canonical mechanisms have been proposed to explain these cardiac effects, most notably an inhibitory action on cardiac Na+/H+ exchanger 1 (NHE1), causing a reduction in intracellular [Na+] ([Na+]i). However, at resting intracellular pH (pHi), NHE1 activity is very low and its pharmacological inhibition is not expected to meaningfully alter steady-state [Na+]i. We re-evaluate this putative EMPA target by measuring cardiac NHE1 activity. METHODS AND RESULTS The effect of EMPA on NHE1 activity was tested in isolated rat ventricular cardiomyocytes from measurements of pHi recovery following an ammonium pre-pulse manoeuvre, using cSNARF1 fluorescence imaging. Whereas 10 µM cariporide produced near-complete inhibition, there was no evidence for NHE1 inhibition with EMPA treatment (1, 3, 10, or 30 µM). Intracellular acidification by acetate-superfusion evoked NHE1 activity and raised [Na+]i, reported by sodium binding benzofuran isophthalate (SBFI) fluorescence, but EMPA did not ablate this rise. EMPA (10 µM) also had no significant effect on the rate of cytoplasmic [Na+]i rise upon superfusion of Na+-depleted cells with Na+-containing buffers. In Langendorff-perfused mouse, rat and guinea pig hearts, EMPA did not affect [Na+]i at baseline nor pHi recovery following acute acidosis, as measured by 23Na triple quantum filtered NMR and 31P NMR, respectively. CONCLUSIONS Our findings indicate that cardiac NHE1 activity is not inhibited by EMPA (or other SGLT2i's) and EMPA has no effect on [Na+]i over a wide range of concentrations, including the therapeutic dose. Thus, the beneficial effects of SGLT2i's in failing hearts should not be interpreted in terms of actions on myocardial NHE1 or intracellular [Na+].
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Affiliation(s)
- Yu Jin Chung
- British Heart Foundation Centre of Research Excellence, King’s College London, The Rayne Institute, St Thomas’ Hospital, Lambeth Palace Road, London SE1 7EH, UK
| | - Kyung Chan Park
- Department of Physiology, Anatomy and Genetics, Parks Road, Oxford, OX1 3PT, UK
| | - Sergiy Tokar
- British Heart Foundation Centre of Research Excellence, King’s College London, The Rayne Institute, St Thomas’ Hospital, Lambeth Palace Road, London SE1 7EH, UK
| | - Thomas R Eykyn
- British Heart Foundation Centre of Research Excellence, King’s College London, The Rayne Institute, St Thomas’ Hospital, Lambeth Palace Road, London SE1 7EH, UK
- School of Biomedical Engineering and Imaging Sciences, King’s College London, The Rayne Institute, St Thomas' Hospital, Lambeth Palace Road, London SE1 7EH, UK
| | - William Fuller
- Institute of Cardiovascular & Medical Sciences, Sir James Black Building, University of Glasgow, University Avenue, Glasgow G12 8QQ, UK
| | - Davor Pavlovic
- Institute for Cardiovascular Sciences, University of Birmingham, Wolfson Drive, Birmingham B15 2TT, UK
| | - Pawel Swietach
- Department of Physiology, Anatomy and Genetics, Parks Road, Oxford, OX1 3PT, UK
| | - Michael J Shattock
- British Heart Foundation Centre of Research Excellence, King’s College London, The Rayne Institute, St Thomas’ Hospital, Lambeth Palace Road, London SE1 7EH, UK
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11
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Alyu F, Olgar Y, Degirmenci S, Turan B, Ozturk Y. Interrelated In Vitro Mechanisms of Sibutramine-Induced Cardiotoxicity. Cardiovasc Toxicol 2021; 21:322-335. [PMID: 33389602 DOI: 10.1007/s12012-020-09622-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2020] [Accepted: 11/24/2020] [Indexed: 11/26/2022]
Abstract
Consumption of illicit pharmaceutical products containing sibutramine has been reported to cause cardiovascular toxicity problems. This study aimed to demonstrate the toxicity profile of sibutramine, and thereby provide important implications for the development of more effective strategies in both clinical approaches and drug design studies. Action potentials (APs) were determined from freshly isolated ventricular cardiomyocytes with whole-cell configuration of current clamp as online. The maximum amplitude of APs (MAPs), the resting membrane potential (RMP), and AP duration from the repolarization phases were calculated from original records. The voltage-dependent K+-channel currents (IK) were recorded in the presence of external Cd2+ and both inward and outward parts of the current were calculated, while their expression levels were determined with qPCR. The levels of intracellular free Ca2+ and H+ (pHi) as well as reactive oxygen species (ROS) were measured using either a ratiometric micro-spectrofluorometer or confocal microscope. The mechanical activity of isolated hearts was observed with Langendorff-perfusion system. Acute sibutramine applications (10-8-10-5 M) induced significant alterations in both MAPs and RMP as well as the repolarization phases of APs and IK in a concentration-dependent manner. Sibutramine (10 μM) induced Ca2+-release from the sarcoplasmic reticulum under either electrical or caffeine stimulation, whereas it depressed left ventricular developed pressure with a marked decrease in the end-diastolic pressure. pHi inhibition by sibutramine supports the observed negative alterations in contractility. Changes in mRNA levels of different IK subunits are consistent with the acute inhibition of the repolarizing IK, affecting AP parameters, and provoke the cardiotoxicity.
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Affiliation(s)
- Feyza Alyu
- Department of Pharmacology, Faculty of Pharmacy, Anadolu University, Yunus Emre Campus, 26470, Eskisehir, Turkey
| | - Yusuf Olgar
- Department of Biophysics, Faculty of Medicine, Ankara University, 06230, Ankara, Turkey
| | - Sinan Degirmenci
- Department of Biophysics, Faculty of Medicine, Ankara University, 06230, Ankara, Turkey
| | - Belma Turan
- Department of Biophysics, Faculty of Medicine, Ankara University, 06230, Ankara, Turkey
- Department of Biophysics, Faculty of Medicine, Lokman Hekim University, 06230, Ankara, Turkey
| | - Yusuf Ozturk
- Department of Pharmacology, Faculty of Pharmacy, Anadolu University, Yunus Emre Campus, 26470, Eskisehir, Turkey.
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12
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Wang J, Wang W, Wang H, Tuo B. Physiological and Pathological Functions of SLC26A6. Front Med (Lausanne) 2021; 7:618256. [PMID: 33553213 PMCID: PMC7859274 DOI: 10.3389/fmed.2020.618256] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 12/30/2020] [Indexed: 12/26/2022] Open
Abstract
Solute Carrier Family 26 (SLC26) is a conserved anion transporter family with 10 members in human (SLC26A1-A11, A10 being a pseudogene). All SLC26 genes except for SLC26A5 (prestin) are versatile anion exchangers with notable ability to transport a variety of anions. SLC26A6 has the most extensive exchange functions in the SLC26 family and is widely expressed in various organs and tissues of mammals. SLC26A6 has some special properties that make it play a particularly important role in ion homeostasis and acid-base balance. In the past few years, the function of SLC26A6 in the diseases has received increasing attention. SLC26A6 not only participates in the development of intestinal and pancreatic diseases but also serves a significant role in mediating nephrolithiasis, fetal skeletal dysplasia and arrhythmia. This review aims to explore the role of SLC26A6 in physiology and pathophysiology of relative mammalian organs to guide in-depth studies about related diseases of human.
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Affiliation(s)
- Juan Wang
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical University, Zunyi, China
| | - Wenkang Wang
- Department of Critical Care Medicine of the Third Affiliated Hospital (The First People's Hospital of Zunyi City), Zunyi Medical University, Zunyi, China
| | - Hui Wang
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical University, Zunyi, China
| | - Biguang Tuo
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical University, Zunyi, China
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13
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Medina AJ, Ibáñez AM, Diaz-Zegarra LA, Portiansky EL, Blanco PG, Pereyra EV, de Giusti VC, Aiello EA, Yeves AM, Ennis IL. Cardiac up-regulation of NBCe1 emerges as a beneficial consequence of voluntary wheel running in mice. Arch Biochem Biophys 2020; 694:108600. [PMID: 33007282 DOI: 10.1016/j.abb.2020.108600] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 09/17/2020] [Accepted: 09/23/2020] [Indexed: 11/30/2022]
Abstract
Physical training stimulates the development of physiologic cardiac hypertrophy (CH), being a key event in this process the inhibition of the Na+/H+ exchanger. However, the role of the sodium bicarbonate cotransporter (NBC) has not been explored yet under this circumstance. C57/Bl6 mice were allowed to voluntary exercise (wheel running) for five weeks. Cardiac mass was evaluated by echocardiography and histomorphometry detecting that training promoted the development of physiological CH (heart weight/tibia length ratio, mg/mm: 6.54 ± 0.20 vs 8.81 ± 0.24; interstitial collagen content, %: 3.14 ± 0.63 vs. 1.57 ± 0.27; and cross-sectional area of cardiomyocytes, μm2: 200.6 ± 8.92 vs. 281.9 ± 24.05; sedentary (Sed) and exercised (Ex) mice, respectively). The activity of the electrogenic isoform of the cardiac NBC (NBCe1) was estimated by recording intracellular pH under high potassium concentration and by measuring action potential duration (APD). NBCe1 activity was significantly increased in isolated cardiomyocytes of trained mice. Additionally, the APD was shorter and the alkalization due to high extracellular potassium-induced depolarization was greater in this group, indicating that the NBCe1 was hyperactive. These results are online with the observed myocardial up-regulation of the NBCe1 (Western Blot, %: 100 ± 13.86 vs. 202 ± 29.98; Sed vs. Ex, n = 6 each group). In addition, we detected a reduction in H2O2 production in the myocardium of trained mice. These results support that voluntary training induces the development of physiologic CH with up-regulation of the cardiac NBCe1 in mice. Furthermore, the improvement in the antioxidant capacity contributes to the beneficial cardiovascular consequences of physical training.
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Affiliation(s)
- Andrés J Medina
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E, Cingolani" Facultad de Ciencias Médicas UNLP-CONICET, Argentina
| | - Alejandro M Ibáñez
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E, Cingolani" Facultad de Ciencias Médicas UNLP-CONICET, Argentina
| | - Leandro A Diaz-Zegarra
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E, Cingolani" Facultad de Ciencias Médicas UNLP-CONICET, Argentina
| | - Enrique L Portiansky
- Laboratorio de Análisis de Imágenes, Facultad de Ciencias Veterinarias UNLP-CONICET, Argentina
| | - Paula G Blanco
- Servicio de Cardiología, Facultad de Ciencias Veterinarias, UNLP-CONICET, Argentina
| | - Erica V Pereyra
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E, Cingolani" Facultad de Ciencias Médicas UNLP-CONICET, Argentina
| | - Verónica C de Giusti
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E, Cingolani" Facultad de Ciencias Médicas UNLP-CONICET, Argentina
| | - Ernesto A Aiello
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E, Cingolani" Facultad de Ciencias Médicas UNLP-CONICET, Argentina
| | - Alejandra M Yeves
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E, Cingolani" Facultad de Ciencias Médicas UNLP-CONICET, Argentina
| | - Irene L Ennis
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E, Cingolani" Facultad de Ciencias Médicas UNLP-CONICET, Argentina.
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14
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Abstract
Although students initially learn of ionic buffering in basic chemistry, buffering and acid-base transport in biology often is relegated to specialized classes, discussions, or situations. That said, for physiology, nephrology, pulmonology, and anesthesiology, these basic principles often are critically important for mechanistic understanding, medical treatments, and assessing therapy effectiveness. This short introductory perspective focuses on basic chemistry and transport of buffers and acid-base equivalents, provides an outline of basic science acid-base concepts, tools used to monitor intracellular pH, model cellular responses to pH buffer changes, and the more recent development and use of genetically encoded pH-indicators. Examples of newer genetically encoded pH-indicators (pHerry and pHire) are provided, and their use for in vitro, ex vivo, and in vivo experiments are described. The continued use and development of these basic tools provide increasing opportunities for both basic and potentially clinical investigations.
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Affiliation(s)
- Michael F Romero
- Physiology and Biomedical Engineering, Nephrology and Hypertension, Mayo Clinic College of Medicine and Science, Rochester, MN.
| | - Adam J Rossano
- Physiology and Biomedical Engineering, Nephrology and Hypertension, Mayo Clinic College of Medicine and Science, Rochester, MN
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15
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Loh SH, Tsai YT, Huang SF, Yu TC, Kuo PC, Chao SC, Chou MF, Tsai CS, Lee SP. Effects of Andrographolide on Intracellular pH Regulation, Cellular Migration, and Apoptosis in Human Cervical Cancer Cells †. Cancers (Basel) 2020; 12:cancers12020387. [PMID: 32046125 PMCID: PMC7072207 DOI: 10.3390/cancers12020387] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 02/03/2020] [Accepted: 02/04/2020] [Indexed: 12/15/2022] Open
Abstract
Cancer cells have been characterized with alkaline intracellular pH (pHi) values (≥7.2) to enable cancer proliferation, migration, and progression. The aim of the present study was to explore the concentration-dependent effects of Andrographolide, an active diterpenoid compound of herb Andrographis paniculata, on Na+/H+ exchanger isoform 1 (NHE1), cellular migration and apoptosis in human cervical cancer cells (HeLa). The pHi was detected by microspectrofluorometry method, and intracellular acidification was induced by NH4Cl prepulse technique. Viability and protein expression were determined by MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and Western blot, respectively. Human normal endocervical cells (End1), ectocervical cells (Ect1), and HeLa were bought commercially. The resting pHi value of HeLa (≈7.47) was significantly higher than that of End1 and Ect1 (≈7.30), and shifted from alkaline to acidic following acid/base impacts. In HEPES (4-(2-Hydroxyethyl)piperazine-1-ethanesulfonic acid | N-(2-Hydroxyethyl)piperazine-N′-(2-ethanesulfonic acid) -buffered superfusate, NHE1 and V-ATPase co-existed functionally for acid extrusion in HeLa, while only NHE1 existed functionally in End/Ect1. Andrographolide (3–1000 μM) concentration-dependently inhibited NHE1 activity. Cell-migration and expressions of NHE1, V-ATPase, PARP (poly-ADP-ribose-polymerase), pro-Caspase-3, and Bcl-2 were significantly reduced by pretreating with Andrographolide (≥100 μM) for 24–48 h in HeLa. Andrographolide inhibited cell viability of End1-cells/Ect1 and HeLa (≥100 and ≥30 μM, respectively). The present findings implicate the promising clinical applications of Andrographolide on cervical cancer treatment.
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Affiliation(s)
- Shih-Hurng Loh
- Department of Clinical Pharmacy, Tri-Service General Hospital, National Defense Medical Center, Taipei 11490, Taiwan; (S.-H.L.); (S.-F.H.); (M.-F.C.)
- Department of Pharmacology, National Defense Medical Center, Taipei 11490, Taiwan; (T.-C.Y.); (P.-C.K.)
| | - Yi-Ting Tsai
- Division of Cardiovascular Surgery, Department of Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei 11490, Taiwan; (Y.-T.T.); (C.-S.T.)
| | - Shu-Fu Huang
- Department of Clinical Pharmacy, Tri-Service General Hospital, National Defense Medical Center, Taipei 11490, Taiwan; (S.-H.L.); (S.-F.H.); (M.-F.C.)
| | - Tien-Chieh Yu
- Department of Pharmacology, National Defense Medical Center, Taipei 11490, Taiwan; (T.-C.Y.); (P.-C.K.)
| | - Pei-Chun Kuo
- Department of Pharmacology, National Defense Medical Center, Taipei 11490, Taiwan; (T.-C.Y.); (P.-C.K.)
| | - Shih-Chi Chao
- Graduate Institute of Life Sciences, National Defense Medical Center, Taipei 11490, Taiwan;
| | - Mei-Fang Chou
- Department of Clinical Pharmacy, Tri-Service General Hospital, National Defense Medical Center, Taipei 11490, Taiwan; (S.-H.L.); (S.-F.H.); (M.-F.C.)
| | - Chien-Sung Tsai
- Division of Cardiovascular Surgery, Department of Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei 11490, Taiwan; (Y.-T.T.); (C.-S.T.)
| | - Shiao-Pieng Lee
- Department of Biomedical Engineering, National Defense Medical Center, Taipei 11490, Taiwan
- Department of Oral and Maxillofacial Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei 11490, Taiwan
- Correspondence:
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16
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Espejo MS, Orlowski A, Ibañez AM, Di Mattía RA, Velásquez FC, Rossetti NS, Ciancio MC, De Giusti VC, Aiello EA. The functional association between the sodium/bicarbonate cotransporter (NBC) and the soluble adenylyl cyclase (sAC) modulates cardiac contractility. Pflugers Arch 2019; 472:103-115. [PMID: 31754830 DOI: 10.1007/s00424-019-02331-x] [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: 06/26/2019] [Revised: 10/15/2019] [Accepted: 11/13/2019] [Indexed: 12/21/2022]
Abstract
The soluble adenylyl cyclase (sAC) was identified in the heart as another source of cyclic AMP (cAMP). However, its cardiac physiological function is unknown. On the other hand, the cardiac Na+/HCO3- cotransporter (NBC) promotes the cellular co-influx of HCO3- and Na+. Since sAC activity is regulated by HCO3-, our purpose was to investigate the potential functional relationship between NBC and sAC in the cardiomyocyte. Rat ventricular myocytes were loaded with Fura-2, Fluo-3, or BCECF to measure Ca2+ transient (Ca2+i) by epifluorescence, Ca2+ sparks frequency (CaSF) by confocal microscopy, or intracellular pH (pHi) by epifluorescence, respectively. Sarcomere or cell shortening was measured with a video camera as an index of contractility. The NBC blocker S0859 (10 μM), the selective inhibitor of sAC KH7 (1 μM), and the PKA inhibitor H89 (0.1 μM) induced a negative inotropic effect which was associated with a decrease in Ca2+i. Since PKA increases Ca2+ release through sarcoplasmic reticulum RyR channels, CaSF was measured as an index of RyR open probability. The generation of CaSF was prevented by KH7. Finally, we investigated the potential role of sAC activation on NBC activity. NBC-mediated recovery from acidosis was faster in the presence of KH7 or H89, suggesting that the pathway sAC-PKA is negatively regulating NBC function, consistent with a negative feedback modulation of the HCO3- influx that activates sAC. In summary, the results demonstrated that the complex NBC-sAC-PKA plays a relevant role in Ca2+ handling and basal cardiac contractility.
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Affiliation(s)
- María S Espejo
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, Calle 60 y 120, 1900, La Plata, Argentina
| | - Alejandro Orlowski
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, Calle 60 y 120, 1900, La Plata, Argentina
| | - Alejandro M Ibañez
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, Calle 60 y 120, 1900, La Plata, Argentina
| | - Romina A Di Mattía
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, Calle 60 y 120, 1900, La Plata, Argentina
| | - Fernanda Carrizo Velásquez
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, Calle 60 y 120, 1900, La Plata, Argentina
| | - Noelia S Rossetti
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, Calle 60 y 120, 1900, La Plata, Argentina
| | - María C Ciancio
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, Calle 60 y 120, 1900, La Plata, Argentina
| | - Verónica C De Giusti
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, Calle 60 y 120, 1900, La Plata, Argentina.
| | - Ernesto A Aiello
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, Calle 60 y 120, 1900, La Plata, Argentina.
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17
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Richards MA, Simon JN, Ma R, Loonat AA, Crabtree MJ, Paterson DJ, Fahlman RP, Casadei B, Fliegel L, Swietach P. Nitric oxide modulates cardiomyocyte pH control through a biphasic effect on sodium/hydrogen exchanger-1. Cardiovasc Res 2019; 116:1958-1971. [PMID: 31742355 PMCID: PMC7567331 DOI: 10.1093/cvr/cvz311] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Revised: 10/31/2019] [Accepted: 11/16/2019] [Indexed: 11/14/2022] Open
Abstract
AIMS When activated, Na+/H+ exchanger-1 (NHE1) produces some of the largest ionic fluxes in the heart. NHE1-dependent H+ extrusion and Na+ entry strongly modulate cardiac physiology through the direct effects of pH on proteins and by influencing intracellular Ca2+ handling. To attain an appropriate level of activation, cardiac NHE1 must respond to myocyte-derived cues. Among physiologically important cues is nitric oxide (NO), which regulates a myriad of cardiac functions, but its actions on NHE1 are unclear. METHODS AND RESULTS NHE1 activity was measured using pH-sensitive cSNARF1 fluorescence after acid-loading adult ventricular myocytes by an ammonium prepulse solution manoeuvre. NO signalling was manipulated by knockout of its major constitutive synthase nNOS, adenoviral nNOS gene delivery, nNOS inhibition, and application of NO-donors. NHE1 flux was found to be activated by low [NO], but inhibited at high [NO]. These responses involved cGMP-dependent signalling, rather than S-nitros(yl)ation. Stronger cGMP signals, that can inhibit phosphodiesterase enzymes, allowed [cAMP] to rise, as demonstrated by a FRET-based sensor. Inferring from the actions of membrane-permeant analogues, cGMP was determined to activate NHE1, whereas cAMP was inhibitory, which explains the biphasic regulation by NO. Activation of NHE1-dependent Na+ influx by low [NO] also increased the frequency of spontaneous Ca2+ waves, whereas high [NO] suppressed these aberrant forms of Ca2+ signalling. CONCLUSIONS Physiological levels of NO stimulation increase NHE1 activity, which boosts pH control during acid-disturbances and results in Na+-driven cellular Ca2+ loading. These responses are positively inotropic but also increase the likelihood of aberrant Ca2+ signals, and hence arrhythmia. Stronger NO signals inhibit NHE1, leading to a reversal of the aforementioned effects, ostensibly as a potential cardioprotective intervention to curtail NHE1 overdrive.
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Affiliation(s)
- Mark A Richards
- Department of Physiology, Anatomy and Genetics, Parks Road, Oxford OX1 3PT, UK
| | - Jillian N Simon
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, British Heart Foundation Centre for Research Excellence, John Radcliffe Hospital, Oxford OX3 9DU, UK
| | - Ruichong Ma
- Department of Physiology, Anatomy and Genetics, Parks Road, Oxford OX1 3PT, UK
| | - Aminah A Loonat
- Department of Physiology, Anatomy and Genetics, Parks Road, Oxford OX1 3PT, UK
| | - Mark J Crabtree
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, British Heart Foundation Centre for Research Excellence, John Radcliffe Hospital, Oxford OX3 9DU, UK
| | - David J Paterson
- Department of Physiology, Anatomy and Genetics, Parks Road, Oxford OX1 3PT, UK
| | - Richard P Fahlman
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Barbara Casadei
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, British Heart Foundation Centre for Research Excellence, John Radcliffe Hospital, Oxford OX3 9DU, UK
| | - Larry Fliegel
- Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Pawel Swietach
- Department of Physiology, Anatomy and Genetics, Parks Road, Oxford OX1 3PT, UK
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18
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Pedersen SF, Counillon L. The SLC9A-C Mammalian Na +/H + Exchanger Family: Molecules, Mechanisms, and Physiology. Physiol Rev 2019; 99:2015-2113. [PMID: 31507243 DOI: 10.1152/physrev.00028.2018] [Citation(s) in RCA: 103] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Na+/H+ exchangers play pivotal roles in the control of cell and tissue pH by mediating the electroneutral exchange of Na+ and H+ across cellular membranes. They belong to an ancient family of highly evolutionarily conserved proteins, and they play essential physiological roles in all phyla. In this review, we focus on the mammalian Na+/H+ exchangers (NHEs), the solute carrier (SLC) 9 family. This family of electroneutral transporters constitutes three branches: SLC9A, -B, and -C. Within these, each isoform exhibits distinct tissue expression profiles, regulation, and physiological roles. Some of these transporters are highly studied, with hundreds of original articles, and some are still only rudimentarily understood. In this review, we present and discuss the pioneering original work as well as the current state-of-the-art research on mammalian NHEs. We aim to provide the reader with a comprehensive view of core knowledge and recent insights into each family member, from gene organization over protein structure and regulation to physiological and pathophysiological roles. Particular attention is given to the integrated physiology of NHEs in the main organ systems. We provide several novel analyses and useful overviews, and we pinpoint main remaining enigmas, which we hope will inspire novel research on these highly versatile proteins.
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Affiliation(s)
- S F Pedersen
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark; and Université Côte d'Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, LP2M, France, and Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
| | - L Counillon
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark; and Université Côte d'Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, LP2M, France, and Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
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19
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Feng HZ, Jin JP. Transgenic expression of carbonic anhydrase III in cardiac muscle demonstrates a mechanism to tolerate acidosis. Am J Physiol Cell Physiol 2019; 317:C922-C931. [PMID: 31390226 DOI: 10.1152/ajpcell.00130.2019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Carbonic anhydrase III (CAIII) is abundant in liver, adipocytes, and skeletal muscles, but not heart. A cytosolic enzyme that catalyzes conversions between CO2 and HCO3- in the regulation of intracellular pH, its physiological role in myocytes is not fully understood. Mouse skeletal muscles lacking CAIII showed lower intracellular pH during fatigue, suggesting its function in stress tolerance. We created transgenic mice expressing CAIII in cardiomyocytes that lack endogenous CAIII. The transgenic mice showed normal cardiac development and life span under nonstress conditions. Studies of ex vivo working hearts under normal and acidotic conditions demonstrated that the transgenic and wild-type mouse hearts had similar pumping functions under normal pH. At acidotic pH, however, CAIII transgenic mouse hearts showed significantly less decrease in cardiac function than that of wild-type control as shown by higher ventricular pressure development, systolic and diastolic velocities, and stroke volume via elongating the time of diastolic ejection. In addition to the effect of introducing CAIII into cardiomyocytes on maintaining homeostasis to counter acidotic stress, the results demonstrate the role of carbonic anhydrases in maintaining intracellular pH in muscle cells as a potential mechanism to treat heart failure.
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Affiliation(s)
- Han-Zhong Feng
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
| | - J-P Jin
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan
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20
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Lagadic-Gossmann D, Hardonnière K, Mograbi B, Sergent O, Huc L. Disturbances in H + dynamics during environmental carcinogenesis. Biochimie 2019; 163:171-183. [PMID: 31228544 DOI: 10.1016/j.biochi.2019.06.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Accepted: 06/16/2019] [Indexed: 12/24/2022]
Abstract
Despite the improvement of diagnostic methods and anticancer therapeutics, the human population is still facing an increasing incidence of several types of cancers. According to the World Health Organization, this growing trend would be partly linked to our environment, with around 20% of cancers stemming from exposure to environmental contaminants, notably chemicals like polycyclic aromatic hydrocarbons (PAHs). PAHs are widespread pollutants in our environment resulting from incomplete combustion or pyrolysis of organic material, and thus produced by both natural and anthropic sources; notably benzo[a]pyrene (B[a]P), i.e. the prototypical molecule of this family, that can be detected in cigarette smoke, diesel exhaust particles, occupational-related fumes, and grilled food. This molecule is a well-recognized carcinogen belonging to group 1 carcinogens. Indeed, it can target the different steps of the carcinogenic process and all cancer hallmarks. Interestingly, H+ dynamics have been described as key parameters for the occurrence of several, if not all, of these hallmarks. However, information regarding the role of such parameters during environmental carcinogenesis is still very scarce. The present review will thus mainly give an overview of the impact of B[a]P on H+ dynamics in liver cells, and will show how such alterations might impact different aspects related to the finely-tuned balance between cell death and survival processes, thereby likely favoring environmental carcinogenesis. In total, the main objective of this review is to encourage further research in this poorly explored field of environmental molecular toxicology.
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Affiliation(s)
- Dominique Lagadic-Gossmann
- Univ Rennes, Inserm, EHESP, Irset (Institut de recherche en santé, environnement et travail), UMR_S 1085, F-35000, Rennes, France.
| | - Kévin Hardonnière
- Univ Rennes, Inserm, EHESP, Irset (Institut de recherche en santé, environnement et travail), UMR_S 1085, F-35000, Rennes, France
| | - Baharia Mograbi
- Institute of Research on Cancer and Ageing of Nice (IRCAN), INSERM U1081, CNRS UMR7284, 2. Université de Nice-Sophia Antipolis, Faculté de Médecine, Centre Antoine Lacassagne, Nice, F-06107, France
| | - Odile Sergent
- Univ Rennes, Inserm, EHESP, Irset (Institut de recherche en santé, environnement et travail), UMR_S 1085, F-35000, Rennes, France
| | - Laurence Huc
- INRA, ToxAlim (Research Centre in Food Toxicology), Université de Toulouse, INRA, ENVT, INP-Purpan, UPS, Toulouse, France
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21
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Ibañez AM, Espejo MS, Zavala MR, Villa-Abrille MC, Lofeudo JM, Aiello EA, De Giusti VC. Regulation of Intracellular pH is Altered in Cardiac Myocytes of Ovariectomized Rats. J Am Heart Assoc 2019; 8:e011066. [PMID: 30917747 PMCID: PMC6509710 DOI: 10.1161/jaha.118.011066] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Background It is well known that after menopause women are exposed to a greater cardiovascular risk, but the intracellular modifications are not properly described. The sodium/proton exchanger (NHE) and the sodium/bicarbonate cotransporter (NBC) regulate the intracellular pH and, indirectly, the intracellular sodium concentration ([Na+]). There are 2 isoforms of NBC in the heart: the electrogenic (1Na+/2[Formula: see text]; NBCe1) and the electroneutral (1Na+/1[Formula: see text]; NBCn1). Because NHE and NBCn1 hyperactivity as well as the NBCe1 decreased activity have been associated with several cardiovascular pathologies, the aim of this study was to investigate the potential alterations of the alkalinizing transporters during the postmenopausal period. Methods and Results Three-month ovariectomized rats (OVX) were used. The NHE activity and protein expression are significantly increased in OVX. The NBCe1 activity is diminished, and the NBCn1 activity becomes predominant in OVX rats. p-Akt levels showed a significant diminution in OVX. Finally, NHE activity in platelets from OVX rats is also higher in comparison to sham rats, resulting in a potential biomarker of cardiovascular diseases. Conclusions Our results demonstrated for the first time that in the cardiac ventricular myocytes of OVX rats NHE and NBC isoforms are altered, probably because of the decreased level of p-Akt, compromising the ionic intracellular homeostasis.
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Affiliation(s)
- Alejandro Martín Ibañez
- 1 Centro de Investigaciones Cardiovasculares Facultad de Ciencias Médicas Universidad Nacional de La Plata-CONICET La Plata Argentina
| | - María Sofía Espejo
- 1 Centro de Investigaciones Cardiovasculares Facultad de Ciencias Médicas Universidad Nacional de La Plata-CONICET La Plata Argentina
| | - Maite Raquel Zavala
- 1 Centro de Investigaciones Cardiovasculares Facultad de Ciencias Médicas Universidad Nacional de La Plata-CONICET La Plata Argentina
| | - María Celeste Villa-Abrille
- 1 Centro de Investigaciones Cardiovasculares Facultad de Ciencias Médicas Universidad Nacional de La Plata-CONICET La Plata Argentina
| | - Juan Manuel Lofeudo
- 1 Centro de Investigaciones Cardiovasculares Facultad de Ciencias Médicas Universidad Nacional de La Plata-CONICET La Plata Argentina
| | - Ernesto Alejandro Aiello
- 1 Centro de Investigaciones Cardiovasculares Facultad de Ciencias Médicas Universidad Nacional de La Plata-CONICET La Plata Argentina
| | - Verónica Celeste De Giusti
- 1 Centro de Investigaciones Cardiovasculares Facultad de Ciencias Médicas Universidad Nacional de La Plata-CONICET La Plata Argentina
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22
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Díaz RG, Escudero DS, Brea MS, Morgan PE, Pérez NG. p38 mitogen activated protein kinase mediates cardiac Na +/H + exchanger inhibition induced by Sildenafil. Eur J Pharmacol 2019; 849:96-105. [PMID: 30721701 DOI: 10.1016/j.ejphar.2019.01.070] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Revised: 01/11/2019] [Accepted: 01/21/2019] [Indexed: 10/27/2022]
Abstract
Since the original description as potent antianginal compounds, phosphodiesterase 5A inhibitors have continuously increased their possible therapeutic applications. In the heart, Sildenafil was shown to protect against an ischemic insult by decreasing cardiac Na+/H+ exchanger (NHE1) activity, action that was mediated by protein kinase G. p38 mitogen activated protein kinase (p38MAPK) activation was described in cardiac ischemia, but its precise role remains elusive. It has been shown that p38MAPK is activated by protein kinase G (PKG) in certain non-cardiac tissues, while in others modulates NHE1 activity. Current study was aimed to seek the role of p38MAPK in the Sildenafil-triggered pathway leading to NHE1 inhibition in myocardium. Rat isolated papillary muscles were used to evaluate NHE1 activity during intracellular pH recovery from an acidic load. Protein kinases phosphorylation (activation) was determined by western blot. Sustained acidosis promoted NHE1 hyperactivity by enhancing Ser703 phosphorylation, effect that was blunted by Sildenafil. p38MAPK inhibition reversed the effect of Sildenafil on NHE1. Activation of p38MAPK, by Sodium Arsenite or Anisomycin, mimicked the inhibitory effect of Sildenafil on the exchanger. Consistently, Sildenafil induced p38MAPK phosphorylation/activation during acidosis. Neither Sildenafil nor p38MAPK inhibition affected extracellular signal-regulated kinases 1/2 phosphorylation, kinases upstream NHE1. Furthermore, inhibition of NHE1 after p38MAPK activation was precluded by preventing the activation of protein phosphatase 2A with Okadaic Acid. Taken together, these results suggest that activation of p38MAPK is a necessary step to trigger the inhibitory effect of Sildenafil on cardiac NHE1 activity, thorough a mechanism that involves protein phosphatase 2A-mediated exchanger dephosphorylation.
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Affiliation(s)
- Romina G Díaz
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Calle 60 y 120, 1900 La Plata, Argentina
| | - Daiana S Escudero
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Calle 60 y 120, 1900 La Plata, Argentina
| | - María S Brea
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Calle 60 y 120, 1900 La Plata, Argentina
| | - Patricio E Morgan
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Calle 60 y 120, 1900 La Plata, Argentina.
| | - Néstor G Pérez
- Centro de Investigaciones Cardiovasculares "Dr. Horacio E. Cingolani", Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Calle 60 y 120, 1900 La Plata, Argentina.
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23
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Chao SC, Wu GJ, Huang SF, Dai NT, Huang HK, Chou MF, Tsai YT, Lee SP, Loh SH. Functional and molecular mechanism of intracellular pH regulation in human inducible pluripotent stem cells. World J Stem Cells 2018; 10:196-211. [PMID: 30613313 PMCID: PMC6306555 DOI: 10.4252/wjsc.v10.i12.196] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Revised: 11/14/2018] [Accepted: 12/05/2018] [Indexed: 02/06/2023] Open
Abstract
AIM To establish a functional and molecular model of the intracellular pH (pHi) regulatory mechanism in human induced pluripotent stem cells (hiPSCs).
METHODS hiPSCs (HPS0077) were kindly provided by Dr. Dai from the Tri-Service General Hospital (IRB No. B-106-09). Changes in the pHi were detected either by microspectrofluorimetry or by a multimode reader with a pH-sensitive fluorescent probe, BCECF, and the fluorescent ratio was calibrated by the high K+/nigericin method. NH4Cl and Na-acetate prepulse techniques were used to induce rapid intracellular acidosis and alkalization, respectively. The buffering power (β) was calculated from the ΔpHi induced by perfusing different concentrations of (NH4)2SO4. Western blot techniques and immunocytochemistry staining were used to detect the protein expression of pHi regulators and pluripotency markers.
RESULTS In this study, our results indicated that (1) the steady-state pHi value was found to be 7.5 ± 0.01 (n = 20) and 7.68 ± 0.01 (n =20) in HEPES and 5% CO2/HCO3--buffered systems, respectively, which were much greater than that in normal adult cells (7.2); (2) in a CO2/HCO3--buffered system, the values of total intracellular buffering power (β) can be described by the following equation: βtot = 107.79 (pHi)2 - 1522.2 (pHi) + 5396.9 (correlation coefficient R2 = 0.85), in the estimated pHi range of 7.1-8.0; (3) the Na+/H+ exchanger (NHE) and the Na+/HCO3- cotransporter (NBC) were found to be functionally activated for acid extrusion for pHi values less than 7.5 and 7.68, respectively; (4) V-ATPase and some other unknown Na+-independent acid extruder(s) could only be functionally detected for pHi values less than 7.1; (5) the Cl-/ OH- exchanger (CHE) and the Cl-/HCO3- anion exchanger (AE) were found to be responsible for the weakening of intracellular proton loading; (6) besides the CHE and the AE, a Cl--independent acid loading mechanism was functionally identified; and (7) in hiPSCs, a strong positive correlation was observed between the loss of pluripotency and the weakening of the intracellular acid extrusion mechanism, which included a decrease in the steady-state pHi value and diminished the functional activity and protein expression of the NHE and the NBC.
CONCLUSION For the first time, we established a functional and molecular model of a pHi regulatory mechanism and demonstrated its strong positive correlation with hiPSC pluripotency.
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Affiliation(s)
- Shih-Chi Chao
- Graduate Institute of Life Sciences, National Defense Medical Center, Taipei 11490, Taiwan
| | - Gwo-Jang Wu
- Department of Obstetrics and Gynecology, Tri-Service General Hospital, National Defense Medical Center, Taipei 11490, Taiwan
| | - Shu-Fu Huang
- Department of Pharmacy Practice, Tri-Service General Hospital, National Defense Medical Center, Taipei 11490, Taiwan
| | - Niann-Tzyy Dai
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei 11490, Taiwan
| | - Hsu-Kai Huang
- Division of Chest Surgery, Department of Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei 11490, Taiwan
| | - Mei-Fang Chou
- Department of Pharmacy Practice, Tri-Service General Hospital, National Defense Medical Center, Taipei 11490, Taiwan
| | - Yi-Ting Tsai
- Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei 11490, Taiwan
- Division of Cardiovascular Surgery, Department of Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei 11490, Taiwan
| | - Shiao-Pieng Lee
- Division of Oral and Maxillofacial Surgery, Department of Dentistry, School of Dentistry, Tri-Service General Hospital and National Defense Medical Center, Taipei 11490, Taiwan
| | - Shih-Hurng Loh
- Graduate Institute of Life Sciences, National Defense Medical Center, Taipei 11490, Taiwan
- Department of Pharmacy Practice, Tri-Service General Hospital, National Defense Medical Center, Taipei 11490, Taiwan
- Department of Pharmacology, National Defense Medical Center, Taipei 11490, Taiwan
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24
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Şimşek G, Vaughan-Jones RD, Swietach P, Kandilci HB. Recovery from hypoxia-induced internalization of cardiac Na + /H + exchanger 1 requires an adequate intracellular store of antioxidants. J Cell Physiol 2018; 234:4681-4694. [PMID: 30191998 DOI: 10.1002/jcp.27268] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Accepted: 07/24/2018] [Indexed: 11/07/2022]
Abstract
The heart is highly active metabolically but relatively underperfused and, therefore, vulnerable to ischemia. In addition to acidosis, a key component of ischemia is hypoxia that can modulate gene expression and protein function as part of an adaptive or even maladaptive response. Here, using cardiac-derived HL-1 cells, we investigate the effect of various hypoxic stimuli on the expression and activity of Na+ /H + exchanger 1 (NHE1), a principal regulator of intracellular pH. Acute (10 min) anoxia produced a reversible decrease in the sarcolemmal NHE1 activity attributable to NHE1 internalization. Treatment with either 1% O 2 or dimethyloxaloylglycine (DMOG; 1 mM) for 48-hr stabilized hypoxia-inducible factor 1 and reduced the sarcolemmal NHE1 activity by internalization, but without a change in total NHE1 immunoreactivity or message levels of the coding gene ( SLC9A1) determined in whole-cell lysates. Unlike the effect of DMOG, which was rapidly reversed on washout, reoxygenation after a prolonged period of hypoxia did not reverse the effects on NHE1, unless media were also supplemented with a membrane-permeant derivative of glutathione (GSH). Without a prior hypoxic episode, GSH supplementation had no effect on the NHE1 activity. Thus, posthypoxic NHE1 reinsertion can only take place if cells have a sufficient reservoir of a reducing agent. We propose that oxidative stress under prolonged hypoxia depletes intracellular GSH to an extent that curtails NHE1 reinsertion once the hypoxic stimulus is withdrawn. This effect may be cardioprotective, as rapid postischaemic restoration of the NHE1 activity is known to trigger reperfusion injury by producing an intracellular Na + -overload, which is proarrhythmogenic.
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Affiliation(s)
- Gül Şimşek
- Department of Biophysics, Faculty of Medicine, Ankara University, Ankara, Turkey
| | | | - Pawel Swietach
- Department of Physiology, Anatomy, and Genetics, Oxford University, Oxford, UK
| | - H Burak Kandilci
- Department of Biophysics, Faculty of Medicine, Ankara University, Ankara, Turkey
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25
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Chen GS, Lee SP, Huang SF, Chao SC, Chang CY, Wu GJ, Li CH, Loh SH. Functional and molecular characterization of transmembrane intracellular pH regulators in human dental pulp stem cells. Arch Oral Biol 2018. [PMID: 29524788 DOI: 10.1016/j.archoralbio.2018.02.018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
OBJECTIVE Homeostasis of intracellular pH (pHi) plays vital roles in many cell functions, such as proliferation, apoptosis, differentiation and metastasis. Thus far, Na+-H+ exchanger (NHE), Na+-HCO3- co-transporter (NBC), Cl-/HCO3- exchanger (AE) and Cl-/OH- exchanger (CHE) have been identified to co-regulate pHi homeostasis. However, functional and biological pHi-regulators in human dental pulp stem cells (hDPSCs) have yet to be identified. DESIGN Microspectrofluorimetry technique with pH-sensitive fluorescent dye, BCECF, was used to detect pHi changes. NH4Cl and Na+-acetate pre-pulse were used to induce intracellular acidosis and alkalosis, respectively. Isoforms of pHi-regulators were detected by Western blot technique. RESULTS The resting pHi was no significant difference between that in HEPES-buffered (nominal HCO3--free) solution or CO2/HCO3-buffered system (7.42 and 7.46, respectively). The pHi recovery following the induced-intracellular acidosis was blocked completely by removing [Na+]o, while only slowed (-63%) by adding HOE694 (a NHE1 specific inhibitor) in HEPES-buffered solution. The pHi recovery was inhibited entirely by removing [Na+]o, while adding HOE 694 pulse DIDS (an anion-transporter inhibitor) only slowed (-55%) the acid extrusion. Both in HEPES-buffered and CO2/HCO3-buffered system solution, the pHi recovery after induced-intracellular alkalosis was entirely blocked by removing [Cl-]o. Western blot analysis showed the isoforms of pHi regulators, including NHE1/2, NBCe1/n1, AE1/2/3/4 and CHE in the hDPSCs. CONCLUSIONS We demonstrate for the first time that resting pHi is significantly higher than 7.2 and meditates functionally by two Na+-dependent acid extruders (NHE and NBC), two Cl--dependent acid loaders (CHE and AE) and one Na+-independent acid extruder(s) in hDPSCs. These findings provide novel insight for basic and clinical treatment of dentistry.
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Affiliation(s)
- Gunng-Shinng Chen
- Division of Orthodontic, Dentofacial Orthopedic & Pediatric Dentistry, Department of Dentistry, School of Dentistry, Tri-Service General Hospital and National Defense Medical Center, Taipei 114, Taiwan
| | - Shiao-Pieng Lee
- Division of Oral and Maxillofacial Surgery, Department of Dentistry, School of Dentistry, Tri-Service General Hospital and National Defense Medical Center, Taipei 114, Taiwan
| | - Shu-Fu Huang
- Department of Clinical Pharmacy, Tri-Service General Hospital, National Defense Medical Center, Taipei 114, Taiwan
| | - Shih-Chi Chao
- Graduate Institute of Life Sciences, National Defense Medical Center, Taipei 114, Taiwan; Department of Pharmacology, National Defense Medical Center, Taipei 114, Taiwan
| | - Chung-Yi Chang
- Heart Center and Department of General Surgery, Cheng Hsin General Hospital, Taipei 112, Taiwan
| | - Gwo-Jang Wu
- Department of Obstetrics and Gynecology, Tri-Service General Hospital, National Defense Medical Center, Taipei 114, Taiwan
| | - Chung-Hsing Li
- Division of Orthodontic, Dentofacial Orthopedic & Pediatric Dentistry, Department of Dentistry, School of Dentistry, Tri-Service General Hospital and National Defense Medical Center, Taipei 114, Taiwan
| | - Shih-Hurng Loh
- Graduate Institute of Life Sciences, National Defense Medical Center, Taipei 114, Taiwan; Department of Pharmacology, National Defense Medical Center, Taipei 114, Taiwan.
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26
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Parker MD. Mouse models of SLC4-linked disorders of HCO 3--transporter dysfunction. Am J Physiol Cell Physiol 2018; 314:C569-C588. [PMID: 29384695 DOI: 10.1152/ajpcell.00301.2017] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The SLC4 family Cl-/[Formula: see text] cotransporters (NBCe1, NBCe2, NBCn1, and NBCn2) contribute to a variety of vital physiological processes including pH regulation and epithelial fluid secretion. Accordingly, their dysfunction can have devastating effects. Disorders such as epilepsy, hemolytic anemia, glaucoma, hearing loss, osteopetrosis, and renal tubular acidosis are all genetically linked to SLC4-family gene loci. This review summarizes how studies of Slc4-modified mice have enhanced our understanding of the etiology of SLC4-linked pathologies and the interpretation of genetic linkage studies. The review also surveys the novel disease signs exhibited by Slc4-modified mice which could either be considered to presage their description in humans, or to highlight interspecific differences. Finally, novel Slc4-modified mouse models are proposed, the study of which may further our understanding of the basis and treatment of SLC4-linked disorders of [Formula: see text]-transporter dysfunction.
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Affiliation(s)
- Mark D Parker
- Department of Physiology and Biophysics, The State University of New York: The University at Buffalo , Buffalo, New York.,Department of Ophthalmology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo: The State University of New York , Buffalo, New York.,State University of New York Eye Institutes, University at Buffalo: The State University of New York , Buffalo, New York
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27
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Garciarena CD, Malik A, Swietach P, Moreno AP, Vaughan-Jones RD. Distinct moieties underlie biphasic H + gating of connexin43 channels, producing a pH optimum for intercellular communication. FASEB J 2018; 32:1969-1981. [PMID: 29183963 PMCID: PMC5893178 DOI: 10.1096/fj.201700876r] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Most mammalian cells can intercommunicate via connexin-assembled, gap-junctional channels. To regulate signal transmission, connexin (Cx) channel permeability must respond dynamically to physiological and pathophysiological stimuli. One key stimulus is intracellular pH (pHi), which is modulated by a tissue’s metabolic and perfusion status. Our understanding of the molecular mechanism of H+ gating of Cx43 channels—the major isoform in the heart and brain—is incomplete. To interrogate the effects of acidic and alkaline pHi on Cx43 channels, we combined voltage-clamp electrophysiology with pHi imaging and photolytic H+ uncaging, performed over a range of pHi values. We demonstrate that Cx43 channels expressed in HeLa or N2a cell pairs are gated biphasically by pHivia a process that consists of activation by H+ ions at alkaline pHi and inhibition at more acidic pHi. For Cx43 channel–mediated solute/ion transmission, the ensemble of these effects produces a pHi optimum, near resting pHi. By using Cx43 mutants, we demonstrate that alkaline gating involves cysteine residues of the C terminus and is independent of motifs previously implicated in acidic gating. Thus, we present a molecular mechanism by which cytoplasmic acid–base chemistry fine tunes intercellular communication and establishes conditions for the optimal transmission of solutes and signals in tissues, such as the heart and brain.—Garciarena, C. D., Malik, A., Swietach, P., Moreno, A. P., Vaughan-Jones, R. D. Distinct moieties underlie biphasic H+ gating of connexin43 channels, producing a pH optimum for intercellular communication.
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Affiliation(s)
- Carolina D Garciarena
- Department of Physiology, Anatomy and Genetics, Burdon Sanderson Cardiac Science Centre, University of Oxford, Oxford, United Kingdom.,Irish Centre for Vascular Biology, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Akif Malik
- Department of Physiology, Anatomy and Genetics, Burdon Sanderson Cardiac Science Centre, University of Oxford, Oxford, United Kingdom
| | - Pawel Swietach
- Department of Physiology, Anatomy and Genetics, Burdon Sanderson Cardiac Science Centre, University of Oxford, Oxford, United Kingdom
| | - Alonso P Moreno
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, Utah, USA
| | - Richard D Vaughan-Jones
- Department of Physiology, Anatomy and Genetics, Burdon Sanderson Cardiac Science Centre, University of Oxford, Oxford, United Kingdom
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28
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Danes VR, Anthony J, Rayani K, Spitzer KW, Tibbits GF. pH recovery from a proton load in rat cardiomyocytes: effects of chronic exercise. Am J Physiol Heart Circ Physiol 2017; 314:H285-H292. [PMID: 29101173 DOI: 10.1152/ajpheart.00405.2017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The ability of cardiomyocytes to recover from a proton load was examined in the hearts of exercise-trained and sedentary control rats in CO2/[Formula: see text]-free media. Acidosis was created by the NH4Cl prepulse technique, and intracellular pH (pHi) was determined using fluorescence microscopy on carboxy-SNARF-1 AM-loaded isolated cardiomyocytes. CO2-independent pHi buffering capacity (βi) was measured by incrementally reducing the extracellular NH4Cl concentration in steps of 50% from 20 to 1.25 mM. βi increased as pHi decreased in both exercise-trained and sedentary control groups. However, the magnitude of increase in βi as a function of pHi was found to be significantly ( P < 0.001) greater in the exercise-trained group compared with the sedentary control group. The rate of pHi recovery from an imposed proton load was found to not be different between the exercise-trained and control groups. The Na+/H+ exchanger-dependent H+ extrusion rate during the recovery from an imposed proton load, however, was found to be significantly greater in the exercise-trained group compared with the control group. By increasing βi and subsequently the Na+/H+ exchanger-dependent H+ extrusion rate, exercise training may provide cardiomyocytes with the ability to better handle an intracellular excess of H+ generated during hypoxia/ischemic insults and may serve in a cardioprotective role. These data may be predictive of two positive outcomes: 1) increased exercise tolerance by the heart and 2) a protective mechanism that limits the degree of myocardial acidosis and subsequent damage that accompanies ischemia-reperfusion stress. NEW & NOTEWORTHY The enhanced ability to deal with acidosis conferred by exercise training is likely to improve exercise tolerance and outcomes in response to myocardial ischemia-reperfusion injury.
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Affiliation(s)
- Vennetia R Danes
- Molecular Cardiac Physiology Group, Simon Fraser University , Burnaby, British Columbia , Canada
| | - Josephine Anthony
- Molecular Cardiac Physiology Group, Simon Fraser University , Burnaby, British Columbia , Canada
| | - Kaveh Rayani
- Molecular Cardiac Physiology Group, Simon Fraser University , Burnaby, British Columbia , Canada
| | - Kenneth W Spitzer
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah , Salt Lake City, Utah
| | - Glen F Tibbits
- Molecular Cardiac Physiology Group, Simon Fraser University , Burnaby, British Columbia , Canada.,Cardiovascular Sciences, BC Research Institute for Children's and Women's Health , Vancouver, British Columbia , Canada
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29
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Chao PC, Butt AG. cAMP-dependent secretagogues stimulate the NaHCO 3 cotransporter in the villous epithelium of the brushtail possum, Trichosurus vulpecula. J Comp Physiol B 2017; 187:1019-1028. [PMID: 28247055 DOI: 10.1007/s00360-017-1063-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2016] [Revised: 01/30/2017] [Accepted: 02/05/2017] [Indexed: 12/22/2022]
Abstract
In the ileum of the brushtail possum, Trichosurus vulpecula, fluid secretion appears to be driven by electrogenic HCO3- secretion. Consistent with this, the cystic fibrosis transmembrane conductance regulator is expressed in the apical membrane of the ileal epithelial cells and the pancreatic or secretory variant of the NaHCO3 cotransporter in the basolateral membrane. This suggests that in the possum ileum, electrogenic HCO3- secretion is driven by basolateral NaHCO3 cotransporter (NBC) activity. To determine if the NBC contributes to HCO3- secretion in the possum ileum, intracellular pH (pHi) measurements in isolated villi were used to demonstrate NBC activity in the ileal epithelial cells and investigate the effect of cAMP-dependent secretagogues. In CO2/HCO3--free solutions, recovery of the epithelial cells from an acid load was Na+-dependent and ≈80% inhibited by ethyl-isopropyl-amiloride (EIPA, 10 µmol L-1), indicative of the presence of an Na+/H+ exchanger, most likely NHE1. However, in the presence of CO2/HCO3-, EIPA only inhibited ≈ 50% of the recovery, the remainder was inhibited by 4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid (DIDS, 500 µmol L-1), indicative of NBC activity. Under steady-state conditions, NHE1 inhibition by EIPA had little effect on pHi in the presence or absence of secretagogues, but NBC inhibition with DIDS resulted in a rapid acidification of the cells, which was increased fivefold by secretagogues. These data demonstrate the functional activity of an NaHCO3 cotransporter in the ileal epithelial cells. Furthermore, the stimulation of NBC activity by secretagogues is consistent with the involvement of an NaHCO3 cotransporter in electrogenic HCO3- secretion.
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Affiliation(s)
- Pin-Chun Chao
- Department of Physiology, School of Biomedical Sciences, University of Otago, PO Box 56, Dunedin, 9054, New Zealand
| | - A Grant Butt
- Department of Physiology, School of Biomedical Sciences, University of Otago, PO Box 56, Dunedin, 9054, New Zealand.
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Marcoline FV, Ishida Y, Mindell JA, Nayak S, Grabe M. A mathematical model of osteoclast acidification during bone resorption. Bone 2016; 93:167-180. [PMID: 27650914 PMCID: PMC5077641 DOI: 10.1016/j.bone.2016.09.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/12/2016] [Revised: 08/16/2016] [Accepted: 09/09/2016] [Indexed: 12/01/2022]
Abstract
Bone resorption by osteoclasts occurs through the creation of a sealed extracellular compartment (ECC), or pit, adjacent to the bone that is subsequently acidified through a complex biological process. The low pH of the pit dissolves the bone mineral and activates acid proteases that further break down the bone matrix. There are many ion channels, transporters, and soluble proteins involved in osteoclast mediated resorption, and in the past few years, there has been an increased understanding of the identity and properties of some key proteins such as the ClC-7 Cl-/H+ antiporter and the HV1 proton channel. Here we present a detailed mathematical model of osteoclast acidification that includes the influence of many of the key regulatory proteins. The primary enzyme responsible for acidification is the vacuolar H+-ATPase (V-ATPase), which pumps protons from the cytoplasm into the pit. Unlike the acidification of small lysosomes, the pit is so large that protons become depleted from the cytoplasm. Hence, proton buffering and production in the cytoplasm by carbonic anhydrase II (CAII) is potentially important for proper acidification. We employ an ordinary differential equations (ODE)-based model that accounts for the changes in ionic species in the cytoplasm and the resorptive pit. Additionally, our model tracks ionic flow between the cytoplasm and the extracellular solution surrounding the cell. Whenever possible, the properties of individual channels and transporters are calibrated based on electrophysiological measurements, and physical properties of the cell, such as buffering capacity, surface areas, and volumes, are estimated based on available data. Our model reproduces many of the experimental findings regarding the role of key proteins in the acidification process, and it allows us to estimate, among other things, number of active pumps, protons moved, and the influence of particular mutations implicated in disease.
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Affiliation(s)
- Frank V Marcoline
- Cardiovascular Research Institute, University of California, San Francisco, CA 94158, USA; Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94158, USA
| | - Yoichi Ishida
- Department of Philosophy, Ohio University, Athens, OH 45701, USA
| | - Joseph A Mindell
- Membrane Transport Biophysics Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - Smita Nayak
- Swedish Center for Research and Innovation, Swedish Health Services, Seattle, WA 98122, USA
| | - Michael Grabe
- Cardiovascular Research Institute, University of California, San Francisco, CA 94158, USA; Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94158, USA.
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31
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Rossano AJ, Kato A, Minard KI, Romero MF, Macleod GT. Na + /H + exchange via the Drosophila vesicular glutamate transporter mediates activity-induced acid efflux from presynaptic terminals. J Physiol 2016; 595:805-824. [PMID: 27641622 DOI: 10.1113/jp273105] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 09/14/2016] [Indexed: 01/26/2023] Open
Abstract
KEY POINTS Intracellular pH regulation is vital to neurons as nerve activity produces large and rapid acid loads in presynaptic terminals. Rapid clearance of acid loads is necessary to maintain control of neurotransmission, but neuronal acid clearance mechanisms remain poorly understood. Glutamate is loaded into synaptic vesicles via the vesicular glutamate transporter (VGLUT), a mechanism conserved across phyla, and this study reports a previously unknown role for VGLUT as an acid-extruding protein when deposited in the plasmamembrane during exocytosis. The finding was made in Drosophila (fruit fly) larval motor neurons through a combined pharamacological and genetic dissection of presynaptic pH homeostatic mechanisms. A dual role for VGLUT serves to integrate neuronal activity and pH regulation in presynaptic nerve terminals. ABSTRACT Neuronal activity can result in transient acidification of presynaptic terminals, and such shifts in cytosolic pH (pHcyto ) probably influence mechanisms underlying forms of synaptic plasticity with a presynaptic locus. As neuronal activity drives acid loading in presynaptic terminals, we hypothesized that the same activity might drive acid efflux mechanisms to maintain pHcyto homeostasis. To better understand the integration of neuronal activity and pHcyto regulation we investigated the acid extrusion mechanisms at Drosophila glutamatergic motorneuron terminals. Expression of a fluorescent genetically encoded pH indicator, named 'pHerry', in the presynaptic cytosol revealed acid efflux following nerve activity to be greater than that predicted from measurements of the intrinsic rate of acid efflux. Analysis of activity-induced acid transients in terminals deficient in either endocytosis or exocytosis revealed an acid efflux mechanism reliant upon synaptic vesicle exocytosis. Pharmacological and genetic dissection in situ and in a heterologous expression system indicate that this acid efflux is mediated by conventional plasmamembrane acid transporters, and also by previously unrecognized intrinsic H+ /Na+ exchange via the Drosophila vesicular glutamate transporter (DVGLUT). DVGLUT functions not only as a vesicular glutamate transporter but also serves as an acid-extruding protein when deposited on the plasmamembrane.
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Affiliation(s)
- Adam J Rossano
- School of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
| | - Akira Kato
- Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, 226-8503, Japan.,Physiology & Biomedical Engineering and Nephrology & Hypertension, Mayo Clinic College of Medicine, Rochester, MN, 55905, USA
| | - Karyl I Minard
- Biological Sciences & Wilkes Honors College, Florida Atlantic University, Jupiter, FL, 33431, USA
| | - Michael F Romero
- Physiology & Biomedical Engineering and Nephrology & Hypertension, Mayo Clinic College of Medicine, Rochester, MN, 55905, USA
| | - Gregory T Macleod
- Biological Sciences & Wilkes Honors College, Florida Atlantic University, Jupiter, FL, 33431, USA
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Hladky SB, Barrand MA. Fluid and ion transfer across the blood-brain and blood-cerebrospinal fluid barriers; a comparative account of mechanisms and roles. Fluids Barriers CNS 2016; 13:19. [PMID: 27799072 PMCID: PMC5508927 DOI: 10.1186/s12987-016-0040-3] [Citation(s) in RCA: 168] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Accepted: 09/01/2016] [Indexed: 12/24/2022] Open
Abstract
The two major interfaces separating brain and blood have different primary roles. The choroid plexuses secrete cerebrospinal fluid into the ventricles, accounting for most net fluid entry to the brain. Aquaporin, AQP1, allows water transfer across the apical surface of the choroid epithelium; another protein, perhaps GLUT1, is important on the basolateral surface. Fluid secretion is driven by apical Na+-pumps. K+ secretion occurs via net paracellular influx through relatively leaky tight junctions partially offset by transcellular efflux. The blood-brain barrier lining brain microvasculature, allows passage of O2, CO2, and glucose as required for brain cell metabolism. Because of high resistance tight junctions between microvascular endothelial cells transport of most polar solutes is greatly restricted. Because solute permeability is low, hydrostatic pressure differences cannot account for net fluid movement; however, water permeability is sufficient for fluid secretion with water following net solute transport. The endothelial cells have ion transporters that, if appropriately arranged, could support fluid secretion. Evidence favours a rate smaller than, but not much smaller than, that of the choroid plexuses. At the blood-brain barrier Na+ tracer influx into the brain substantially exceeds any possible net flux. The tracer flux may occur primarily by a paracellular route. The blood-brain barrier is the most important interface for maintaining interstitial fluid (ISF) K+ concentration within tight limits. This is most likely because Na+-pumps vary the rate at which K+ is transported out of ISF in response to small changes in K+ concentration. There is also evidence for functional regulation of K+ transporters with chronic changes in plasma concentration. The blood-brain barrier is also important in regulating HCO3- and pH in ISF: the principles of this regulation are reviewed. Whether the rate of blood-brain barrier HCO3- transport is slow or fast is discussed critically: a slow transport rate comparable to those of other ions is favoured. In metabolic acidosis and alkalosis variations in HCO3- concentration and pH are much smaller in ISF than in plasma whereas in respiratory acidosis variations in pHISF and pHplasma are similar. The key similarities and differences of the two interfaces are summarized.
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Affiliation(s)
- Stephen B. Hladky
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD UK
| | - Margery A. Barrand
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD UK
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Orlowski A, De Giusti VC, Ciancio MC, Espejo MS, Aiello EA. The cardiac electrogenic sodium/bicarbonate cotransporter (NBCe1) is activated by aldosterone through the G protein-coupled receptor 30 (GPR 30). Channels (Austin) 2016; 10:428-434. [PMID: 27249584 DOI: 10.1080/19336950.2016.1195533] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The sodium/bicarbonate cotransporter (NBC) transports extracellular Na+ and HCO3- into the cytoplasm upon intracellular acidosis, restoring the acidic pHi to near neutral values. Two different NBC isoforms have been described in the heart, the electroneutral NBCn1 (1Na+:1HCO3-) and the electrogenic NBCe1 (1Na+:2HCO3-). Certain non-genomic effects of aldosterone (Ald) were due to an orphan G protein-couple receptor 30 (GPR30). We have recently demonstrated that Ald activates GPR30 in adult rat ventricular myocytes, which transactivates the epidermal growth factor receptor (EGFR) and in turn triggers a reactive oxygen species (ROS)- and PI3K/AKT-dependent pathway, leading to the stimulation of NBC. The aim of this study was to investigate the NBC isoform involved in the Ald/GPR30-induced NBC activation. Using specific NBCe1 inhibitory antibodies (a-L3) we demonstrated that Ald does not affect NBCn1 activity. Ald was able to increase NBCe1 activity recorded in isolation. Using immunofluorescence and confocal microscopy analysis we showed in this work that both NBCe1 and GPR30 are localized in t-tubules. In conclusion, we have demonstrated that NBCe1 is the NBC isoform activated by Ald in the heart.
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Affiliation(s)
- Alejandro Orlowski
- a Centro de Investigaciones Cardiovasculares "Dr. Horacio Cingolani" , Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET , La Plata , Buenos Aires , Argentina
| | - Verónica C De Giusti
- a Centro de Investigaciones Cardiovasculares "Dr. Horacio Cingolani" , Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET , La Plata , Buenos Aires , Argentina
| | - María C Ciancio
- a Centro de Investigaciones Cardiovasculares "Dr. Horacio Cingolani" , Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET , La Plata , Buenos Aires , Argentina
| | - María S Espejo
- a Centro de Investigaciones Cardiovasculares "Dr. Horacio Cingolani" , Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET , La Plata , Buenos Aires , Argentina
| | - Ernesto A Aiello
- a Centro de Investigaciones Cardiovasculares "Dr. Horacio Cingolani" , Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET , La Plata , Buenos Aires , Argentina
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Clancy CE, Chen-Izu Y, Bers DM, Belardinelli L, Boyden PA, Csernoch L, Despa S, Fermini B, Hool LC, Izu L, Kass RS, Lederer WJ, Louch WE, Maack C, Matiazzi A, Qu Z, Rajamani S, Rippinger CM, Sejersted OM, O'Rourke B, Weiss JN, Varró A, Zaza A. Deranged sodium to sudden death. J Physiol 2015; 593:1331-45. [PMID: 25772289 DOI: 10.1113/jphysiol.2014.281204] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 10/14/2014] [Indexed: 12/19/2022] Open
Abstract
In February 2014, a group of scientists convened as part of the University of California Davis Cardiovascular Symposium to bring together experimental and mathematical modelling perspectives and discuss points of consensus and controversy on the topic of sodium in the heart. This paper summarizes the topics of presentation and discussion from the symposium, with a focus on the role of aberrant sodium channels and abnormal sodium homeostasis in cardiac arrhythmias and pharmacotherapy from the subcellular scale to the whole heart. Two following papers focus on Na(+) channel structure, function and regulation, and Na(+)/Ca(2+) exchange and Na(+)/K(+) ATPase. The UC Davis Cardiovascular Symposium is a biannual event that aims to bring together leading experts in subfields of cardiovascular biomedicine to focus on topics of importance to the field. The focus on Na(+) in the 2014 symposium stemmed from the multitude of recent studies that point to the importance of maintaining Na(+) homeostasis in the heart, as disruption of homeostatic processes are increasingly identified in cardiac disease states. Understanding how disruption in cardiac Na(+)-based processes leads to derangement in multiple cardiac components at the level of the cell and to then connect these perturbations to emergent behaviour in the heart to cause disease is a critical area of research. The ubiquity of disruption of Na(+) channels and Na(+) homeostasis in cardiac disorders of excitability and mechanics emphasizes the importance of a fundamental understanding of the associated mechanisms and disease processes to ultimately reveal new targets for human therapy.
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Affiliation(s)
- Colleen E Clancy
- Department of Pharmacology, University of California, Davis, Genome Building Rm 3503, Davis, CA, 95616-8636, USA
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35
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Loh SH, Lee CY, Chen GS, Wu CH, Tsao CJ, Shih SJ, Chou CC, Tsai CS, Tsai YT. The Effect and Underlying Mechanism of Ethanol on Intracellular H(+) -Equivalent Membrane Transporters in Human Aorta Smooth Muscle Cells. Alcohol Clin Exp Res 2015; 39:2302-12. [PMID: 26577834 DOI: 10.1111/acer.12892] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2015] [Accepted: 08/31/2015] [Indexed: 01/28/2023]
Abstract
BACKGROUND The presence of intracellular pH (pHi ) regulators, including Na(+) -H(+) exchanger (NHE), Na(+) -HCO3- co-transporter (NBC), Cl(-) /OH(-) exchanger (CHE), and Cl(-) /HCO3- exchanger (AE), have been confirmed in many mammalian cells. Alcohol consumption is associated with increased risk of cardiovascular disorder. The aims of the study were to identify the possible transmembrane pHi regulators and to explore the effects of ethanol (EtOH) (10 to 300 mM) on the resting pHi and pHi regulators in human aorta smooth muscle cells (HASMCs). METHODS HASMCs were obtained from patients undergoing heart transplant. The pHi was measured by microspectrofluorimetry with the pH-sensitive dye, BCECF-AM. RESULTS The following results are obtained. (i) In cultured HASMCs, the resting pHi was 7.19 ± 0.04 and 7.13 ± 0.02 for HEPES- and CO2 /HCO3--buffered solution, respectively. (ii) Two different Na(+) -dependent acid-equivalent extruders, including NHE and Na(+) -coupled HCO3- transporter, functionally coexisted. (iii) Two different Cl(-) -dependent acid loaders (CHE and AE) were functionally identified. (iv) EtOH induced a biphasic, concentration-dependent change in resting pHi (+0.25 pH unit at 100 mM but only +0.05 pH unit at 300 mM) in bicarbonate-buffered solution, while caused a concentration-dependent decrease in resting pHi (-0.06 pH unit at 300 mM) in HEPES-buffered solution. (v) The effect of EtOH on NHE activity was also biphasic: increase of 40% at lower concentration of 10 mM, followed by decrease of 30% at higher concentration of 300 mM. (vi) The increase in Na(+) -coupled HCO3- transporter activity by EtOH was concentration dependent. (vii) The effect of EtOH on CHE and AE activities was both biphasic: increase of ~25% at 30 mM, followed by decrease of 10 to 25% at 100 mM, and finally increase of 15 to 20% at 300 mM. CONCLUSIONS This study demonstrated that 2 acid extruders and 2 acid loaders coexisted functionally in HASMCs and that EtOH induced a biphasic, concentration-dependent change in resting pHi by altering the activity of the 2 acid extruders, NHE and Na(+) -coupled HCO3- transporter, and the 2 acid loaders, CHE and AE.
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Affiliation(s)
- Shih-Hurng Loh
- Department of Pharmacology, National Defense Medical Center, Taipei, Taiwan
| | - Chung-Yi Lee
- Department of Surgery, Division of Cardiovascular Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Gunng-Shinng Chen
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan.,Department of Dentistry, Division of Orthodontics & Dentofacial Orthopedics and Pedodontics, Tri-Service General Hospital, Taipei, Taiwan.,School of Dentistry, National Defense Medical Center, Taipei, Taiwan
| | - Ching-Hsia Wu
- Department of Pharmacology, National Defense Medical Center, Taipei, Taiwan
| | - Chan-Jun Tsao
- Department of Pharmacology, National Defense Medical Center, Taipei, Taiwan
| | - Shou-Jou Shih
- Department of Pharmacology, National Defense Medical Center, Taipei, Taiwan
| | - Chi-Chung Chou
- Department of Pharmacology, National Defense Medical Center, Taipei, Taiwan
| | - Chien-Sung Tsai
- Department of Surgery, Division of Cardiovascular Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan.,Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei, Taiwan
| | - Yi-Ting Tsai
- Department of Surgery, Division of Cardiovascular Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan.,Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei, Taiwan.,School of Medicine, National Defense Medical Center, Taipei, Taiwan
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36
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Abstract
Carbon dioxide (CO2) is an end product of aerobic cellular respiration. In healthy persons, PaCO2 is maintained by physiologic mechanisms within a narrow range (35-45 mm Hg). Both hypercapnia and hypocapnia are encountered in myriad clinical situations. In recent years, the number of hypercapnic patients has increased by the use of smaller tidal volumes to limit lung stretch and injury during mechanical ventilation, so-called permissive hypercapnia. A knowledge and appreciation of the effects of CO2 in the heart are necessary for optimal clinical management in the perioperative and critical care settings. This article reviews, from a historical perspective: (1) the effects of CO2 on coronary blood flow and the mechanisms underlying these effects; (2) the role of endogenously produced CO2 in metabolic control of coronary blood flow and the matching of myocardial oxygen supply to demand; and (3) the direct and reflexogenic actions of CO2 on myocardial contractile function. Clinically relevant issues are addressed, including the role of increased myocardial tissue PCO2 (PmCO2) in the decline in myocardial contractility during coronary hypoperfusion and the increased vulnerability to CO2-induced cardiac depression in patients receiving a β-adrenergic receptor antagonist or with otherwise compromised inotropic reserve. The potential use of real-time measurements of PmO2 to monitor the adequacy of myocardial perfusion in the perioperative period is discussed.
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Affiliation(s)
- George J Crystal
- From the Department of Anesthesiology, Advocate Illinois Masonic Medical Center, Chicago, Illinois; and Departments of Anesthesiology and of Physiology and Biophysics, University of Illinois College of Medicine, Chicago, Illinois
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37
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De Giusti VC, Orlowski A, Ciancio MC, Espejo MS, Gonano LA, Caldiz CI, Vila Petroff MG, Villa-Abrille MC, Aiello EA. Aldosterone stimulates the cardiac sodium/bicarbonate cotransporter via activation of the g protein-coupled receptor gpr30. J Mol Cell Cardiol 2015; 89:260-7. [PMID: 26497404 DOI: 10.1016/j.yjmcc.2015.10.024] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Revised: 10/07/2015] [Accepted: 10/20/2015] [Indexed: 12/22/2022]
Abstract
Some cardiac non-genomic effects of aldosterone (Ald) are reported to be mediated through activation of the classic mineralocorticoid receptor (MR). However, in the last years, it was proposed that activation of the novel G protein-coupled receptor GPR30 mediates certain non-genomic effects of Ald. The aim of this study was to elucidate if the sodium/bicarbonate cotransporter (NBC) is stimulated by Ald and if the activation of GPR30 mediates this effect. NBC activity was evaluated in rat cardiomyocytes perfused with HCO3(-)/CO2 solution in the continuous presence of HOE642 (sodium/hydrogen exchanger blocker) during recovery from acidosis using intracellular fluorescence measurements. Ald enhanced NBC activity (% of ΔJHCO3(-); control: 100±5.82%, n=7 vs Ald: 151.88±11.02%, n=5; P<0.05), which was prevented by G15 (GPR30 blocker, 90.53±7.81%, n=7). Further evidence for the involvement of GPR30 was provided by G1 (GPR30 agonist), which stimulated NBC (185.13±18.28%, n=6; P<0.05) and this effect was abrogated by G15 (124.19±10.96%, n=5). Ald- and G1-induced NBC stimulation was abolished by the reactive oxygen species (ROS) scavenger MPG and by the NADPH oxidase inhibitor apocynin. In addition, G15 prevented Ald- and G1-induced ROS production. Pre-incubation of myocytes with wortmannin (PI3K-AKT pathway blocker) prevented Ald- or G1-induced NBC stimulation. In summary, Ald stimulates NBC by GPR30 activation, ROS production and AKT stimulation.
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Affiliation(s)
- Verónica C De Giusti
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, La Plata, Argentina
| | - Alejandro Orlowski
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, La Plata, Argentina
| | - María C Ciancio
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, La Plata, Argentina
| | - María S Espejo
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, La Plata, Argentina
| | - Luis A Gonano
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, La Plata, Argentina
| | - Claudia I Caldiz
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, La Plata, Argentina
| | - Martín G Vila Petroff
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, La Plata, Argentina
| | - María C Villa-Abrille
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, La Plata, Argentina
| | - Ernesto A Aiello
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata-CONICET, La Plata, Argentina
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38
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Abstract
Cation-coupled HCO3(-) transport was initially identified in the mid-1970s when pioneering studies showed that acid extrusion from cells is stimulated by CO2/HCO3(-) and associated with Na(+) and Cl(-) movement. The first Na(+)-coupled bicarbonate transporter (NCBT) was expression-cloned in the late 1990s. There are currently five mammalian NCBTs in the SLC4-family: the electrogenic Na,HCO3-cotransporters NBCe1 and NBCe2 (SLC4A4 and SLC4A5 gene products); the electroneutral Na,HCO3-cotransporter NBCn1 (SLC4A7 gene product); the Na(+)-driven Cl,HCO3-exchanger NDCBE (SLC4A8 gene product); and NBCn2/NCBE (SLC4A10 gene product), which has been characterized as an electroneutral Na,HCO3-cotransporter or a Na(+)-driven Cl,HCO3-exchanger. Despite the similarity in amino acid sequence and predicted structure among the NCBTs of the SLC4-family, they exhibit distinct differences in ion dependency, transport function, pharmacological properties, and interactions with other proteins. In epithelia, NCBTs are involved in transcellular movement of acid-base equivalents and intracellular pH control. In nonepithelial tissues, NCBTs contribute to intracellular pH regulation; and hence, they are crucial for diverse tissue functions including neuronal discharge, sensory neuron development, performance of the heart, and vascular tone regulation. The function and expression levels of the NCBTs are generally sensitive to intracellular and systemic pH. Animal models have revealed pathophysiological roles of the transporters in disease states including metabolic acidosis, hypertension, visual defects, and epileptic seizures. Studies are being conducted to understand the physiological consequences of genetic polymorphisms in the SLC4-members, which are associated with cancer, hypertension, and drug addiction. Here, we describe the current knowledge regarding the function, structure, and regulation of the mammalian cation-coupled HCO3(-) transporters of the SLC4-family.
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Affiliation(s)
- Christian Aalkjaer
- Department of Biomedicine, and the Water and Salt Research Center, Aarhus University, Aarhus, Denmark; Department of Physiology, Emory University School of Medicine, Atlanta, USA
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Hulikova A, Swietach P. Nuclear proton dynamics and interactions with calcium signaling. J Mol Cell Cardiol 2015; 96:26-37. [PMID: 26183898 PMCID: PMC4915819 DOI: 10.1016/j.yjmcc.2015.07.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Revised: 06/02/2015] [Accepted: 07/07/2015] [Indexed: 01/14/2023]
Abstract
Biochemical signals acting on the nucleus can regulate gene expression. Despite the inherent affinity of nucleic acids and nuclear proteins (e.g. transcription factors) for protons, little is known about the mechanisms that regulate nuclear pH (pHnuc), and how these could be exploited to control gene expression. Here, we show that pHnuc dynamics can be imaged using the DNA-binding dye Hoechst 33342. Nuclear pores allow the passage of medium-sized molecules (calcein), but protons must first bind to mobile buffers in order to gain access to the nucleoplasm. Fixed buffering residing in the nucleus of permeabilized cells was estimated to be very weak on the basis of the large amplitude of pHnuc transients evoked by photolytic H+-uncaging or exposure to weak acids/bases. Consequently, the majority of nuclear pH buffering is sourced from the cytoplasm in the form of mobile buffers. Effective proton diffusion was faster in nucleoplasm than in cytoplasm, in agreement with the higher mobile-to-fixed buffering ratio in the nucleus. Cardiac myocyte pHnuc changed in response to maneuvers that alter nuclear Ca2 + signals. Blocking Ca2 + release from inositol-1,4,5-trisphosphate receptors stably alkalinized the nucleus. This Ca2 +-pH interaction may arise from competitive binding to common chemical moieties. Competitive binding to mobile buffers may couple the efflux of Ca2 +via nuclear pores with a counterflux of protons. This would generate a stable pH gradient between cytoplasm and nucleus that is sensitive to the state of nuclear Ca2 + signaling. The unusual behavior of protons in the nucleus provides new mechanisms for regulating cardiac nuclear biology. Facilitated diffusion aboard mobile buffers is the only means by which protons enter the nucleus. The relative scarcity of fixed buffers residing in the nucleus accelerates proton diffusivity. Nuclear Ca2 + signals can regulate nuclear pH and generate stable gradients relative to cytoplasm.
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Affiliation(s)
- Alzbeta Hulikova
- Burdon Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, Parks Road, Oxford OX1 3PT, United Kingdom
| | - Pawel Swietach
- Burdon Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, Parks Road, Oxford OX1 3PT, United Kingdom.
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Thornell IM, Bevensee MO. Regulators of Slc4 bicarbonate transporter activity. Front Physiol 2015; 6:166. [PMID: 26124722 PMCID: PMC4464172 DOI: 10.3389/fphys.2015.00166] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 05/15/2015] [Indexed: 12/11/2022] Open
Abstract
The Slc4 family of transporters is comprised of anion exchangers (AE1-4), Na+-coupled bicarbonate transporters (NCBTs) including electrogenic Na/bicarbonate cotransporters (NBCe1 and NBCe2), electroneutral Na/bicarbonate cotransporters (NBCn1 and NBCn2), and the electroneutral Na-driven Cl-bicarbonate exchanger (NDCBE), as well as a borate transporter (BTR1). These transporters regulate intracellular pH (pHi) and contribute to steady-state pHi, but are also involved in other physiological processes including CO2 carriage by red blood cells and solute secretion/reabsorption across epithelia. Acid-base transporters function as either acid extruders or acid loaders, with the Slc4 proteins moving HCO−3 either into or out of cells. According to results from both molecular and functional studies, multiple Slc4 proteins and/or associated splice variants with similar expected effects on pHi are often found in the same tissue or cell. Such apparent redundancy is likely to be physiologically important. In addition to regulating pHi, a HCO−3 transporter contributes to a cell's ability to fine tune the intracellular regulation of the cotransported/exchanged ion(s) (e.g., Na+ or Cl−). In addition, functionally similar transporters or splice variants with different regulatory profiles will optimize pH physiology and solute transport under various conditions or within subcellular domains. Such optimization will depend on activated signaling pathways and transporter expression profiles. In this review, we will summarize and discuss both well-known and more recently identified regulators of the Slc4 proteins. Some of these regulators include traditional second messengers, lipids, binding proteins, autoregulatory domains, and less conventional regulators. The material presented will provide insight into the diversity and physiological significance of multiple members within the Slc4 gene family.
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Affiliation(s)
- Ian M Thornell
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham Birmingham, AL, USA
| | - Mark O Bevensee
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham Birmingham, AL, USA ; Nephrology Research and Training Center, University of Alabama at Birmingham Birmingham, AL, USA ; Center of Glial Biology in Medicine, University of Alabama at Birmingham Birmingham, AL, USA ; Civitan International Research Center, University of Alabama at Birmingham Birmingham, AL, USA
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41
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Bahrenburg S, Karow AR, Garidel P. Buffer-free therapeutic antibody preparations provide a viable alternative to conventionally buffered solutions: From protein buffer capacity prediction to bioprocess applications. Biotechnol J 2015; 10:610-22. [DOI: 10.1002/biot.201400531] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Revised: 12/03/2014] [Accepted: 01/27/2015] [Indexed: 12/12/2022]
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Loh SH, Chen GS, Wu CH, Liau CC, Hsu CC, Liu JY, Wu GJ, Chou CC. Physiological and pharmacological characterization of transmembrane acid extruders in cultured human umbilical artery smooth muscle cells. JOURNAL OF MEDICAL SCIENCES 2015. [DOI: 10.4103/1011-4564.167775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
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Swietach P, Spitzer KW, Vaughan-Jones RD. Na⁺ ions as spatial intracellular messengers for co-ordinating Ca²⁺ signals during pH heterogeneity in cardiomyocytes. Cardiovasc Res 2014; 105:171-81. [PMID: 25514933 PMCID: PMC4297422 DOI: 10.1093/cvr/cvu251] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Aims Contraction of the heart is regulated by electrically evoked Ca2+ transients (CaTs). H+ ions, the end products of metabolism, modulate CaTs through direct interactions with Ca2+-handling proteins and via Na+-mediated coupling between acid-extruding proteins (e.g. Na+/H+ exchange, NHE1) and Na+/Ca2+ exchange. Restricted H+ diffusivity in cytoplasm predisposes pH-sensitive Ca2+ signalling to becoming non-uniform, but the involvement of readily diffusible intracellular Na+ ions may provide a means for combatting this. Methods and results CaTs were imaged in fluo3-loaded rat ventricular myocytes paced at 2 Hz. Cytoplasmic [Na+] ([Na+]i) was imaged using SBFI. Intracellular acidification by acetate exposure raised diastolic and systolic [Ca2+] (also observed with acid-loading by ammonium prepulse or CO2 exposure). The systolic [Ca2+] response correlated with a rise in [Na+]i and sarcoplasmic reticulum Ca2+ load, and was blocked by the NHE1 inhibitor cariporide (CO2/HCO3−-free media). Exposure of one half of a myocyte to acetate using dual microperfusion (CO2/HCO3−-free media) raised diastolic [Ca2+] locally in the acidified region. Systolic [Ca2+] and CaT amplitude increased more uniformly along the length of the cell, but only when NHE1 was functional. Cytoplasmic Na+ diffusivity (DNa) was measured in quiescent cells, with strophanthidin present to inhibit the Na+/K+ pump. With regional acetate exposure to activate a local NHE-driven Na+-influx, DNa was found to be sufficiently fast (680 µm2/s) for transmitting the pH–systolic Ca2+ interaction over long distances. Conclusions Na+ ions are rapidly diffusible messengers that expand the spatial scale of cytoplasmic pH–CaT interactions, helping to co-ordinate global Ca2+ signalling during conditions of intracellular pH non-uniformity.
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Affiliation(s)
- Pawel Swietach
- Burdon Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, Oxford, UK
| | - Kenneth W Spitzer
- Nora Eccles Harrison Cardiovascular Research and Training Institute, Salt Lake City, UT, USA
| | - Richard D Vaughan-Jones
- Burdon Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, Oxford, UK
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Peetz J, Barros LF, San Martín A, Becker HM. Functional interaction between bicarbonate transporters and carbonic anhydrase modulates lactate uptake into mouse cardiomyocytes. Pflugers Arch 2014; 467:1469-1480. [PMID: 25118990 DOI: 10.1007/s00424-014-1594-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Revised: 07/30/2014] [Accepted: 08/04/2014] [Indexed: 11/26/2022]
Abstract
Blood-derived lactate is a precious energy substrate for the heart muscle. Lactate is transported into cardiomyocytes via monocarboxylate transporters (MCTs) together with H(+), which couples lactate uptake to cellular pH regulation. In this study, we have investigated how the interplay between different acid/base transporters and carbonic anhydrases (CA), which catalyze the reversible hydration of CO2, modulates the uptake of lactate into isolated mouse cardiomyocytes. Lactate transport was estimated both as lactate-induced acidification and as changes in intracellular lactate levels measured with a newly developed Förster resonance energy transfer (FRET) nanosensor. Recordings of intracellular pH showed an increase in the rate of lactate-induced acidification when CA was inhibited by 6-ethoxy-2-benzothiazolesulfonamide (EZA), while direct measurements of lactate flux demonstrated a decrease in MCT transport activity, when CA was inhibited. The data indicate that catalytic activity of extracellular CA increases lactate uptake and counteracts intracellular lactate-induced acidification. We propose a hypothetical model, in which HCO3 (-), formed from cell-derived CO2 at the outer surface of the cardiomyocyte plasma membrane by membrane-anchored, extracellular CA, is transported into the cell via Na(+)/HCO3 (-) cotransport to counteract intracellular acidification, while the remaining H(+) stabilizes extracellular pH at the surface of the plasma membrane during MCT activity to enhance lactate influx into cardiomyocytes.
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Affiliation(s)
- Jan Peetz
- Division of Zoology/Membrane Transport, FB Biologie, TU Kaiserslautern, P.O. Box 3049, 67653, Kaiserslautern, Germany
| | | | | | - Holger M Becker
- Division of Zoology/Membrane Transport, FB Biologie, TU Kaiserslautern, P.O. Box 3049, 67653, Kaiserslautern, Germany.
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Neuhof C, Neuhof H. Calpain system and its involvement in myocardial ischemia and reperfusion injury. World J Cardiol 2014; 6:638-652. [PMID: 25068024 PMCID: PMC4110612 DOI: 10.4330/wjc.v6.i7.638] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/26/2013] [Revised: 01/26/2014] [Accepted: 05/29/2014] [Indexed: 02/06/2023] Open
Abstract
Calpains are ubiquitous non-lysosomal Ca2+-dependent cysteine proteases also present in myocardial cytosol and mitochondria. Numerous experimental studies reveal an essential role of the calpain system in myocardial injury during ischemia, reperfusion and postischemic structural remodelling. The increasing Ca2+-content and Ca2+-overload in myocardial cytosol and mitochondria during ischemia and reperfusion causes an activation of calpains. Upon activation they are able to injure the contractile apparatus and impair the energy production by cleaving structural and functional proteins of myocytes and mitochondria. Besides their causal involvement in acute myocardial dysfunction they are also involved in structural remodelling after myocardial infarction by the generation and release of proapoptotic factors from mitochondria. Calpain inhibition can prevent or attenuate myocardial injury during ischemia, reperfusion, and in later stages of myocardial infarction.
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Hulikova A, Swietach P. Rapid CO2 permeation across biological membranes: implications for CO2 venting from tissue. FASEB J 2014; 28:2762-74. [PMID: 24652949 DOI: 10.1096/fj.13-241752] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The degree to which cell membranes are barriers to CO2 transport remains controversial. Proteins, such as aquaporins and Rh complex, have been proposed to facilitate CO2 transport, implying that the nonchannel component of membranes must have greatly reduced CO2 permeability. To determine whether membrane CO2 permeation is rate limiting for gas transport, the spread of CO2 across multicellular tissue growths (spheroids) was measured using intracellular pH as a spatial readout. Colorectal HCT116 cells have basal water and NH3 permeability, indicating the functional absence of aquaporins and gas channels. However, CO2 diffusivity in HCT116 spheroids was only 24 ± 4% lower than in pure water, which can be accounted for fully by volume exclusion due to proteins. Diffusivity was unaffected by blockers of aquaporins and Rh complex (Hg(2+), p-chloromercuribenzoic acid, and 4,4'-diisothiocyano-2,2'-stilbene-disulfonic acid) but decreased under hypertonic conditions (by addition of 300 mOsm mannitol), which increases intracellular protein crowding. Similar CO2 diffusivity was measured in spheroids of T47D breast cells (basal water permeability) and NHDF-Ad fibroblasts (aquaporin-facilitated water permeability). In contrast, diffusivity of NH3, a smaller but less lipophilic gas, was considerably slower than in pure water, as expected from rate-limiting membrane permeation. In conclusion, membranes, even in the functional absence of proposed gas channels, do not restrict CO2 venting from tissue growths.-Hulikova, A., Swietach, P. Rapid CO2 permeation across biological membranes: implications for CO2 venting from tissue.
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Affiliation(s)
- Alzbeta Hulikova
- Department of Physiology, Anatomy, and Genetics, University of Oxford, Oxford, United Kingdom
| | - Pawel Swietach
- Department of Physiology, Anatomy, and Genetics, University of Oxford, Oxford, United Kingdom
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Tsai YT, Lee CY, Hsu CC, Chang CY, Hsueh MK, Huang EYK, Tsai CS, Loh SH. Effects of urotensin II on intracellular pH regulation in cultured human internal mammary artery smooth muscle cells. Peptides 2014; 56:173-82. [PMID: 24768794 DOI: 10.1016/j.peptides.2014.04.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Revised: 04/15/2014] [Accepted: 04/15/2014] [Indexed: 12/18/2022]
Abstract
The Na(+)-H(+) exchanger (NHE) and the Na(+)-HCO3(-) co-transporter (NBC) have been confirmed as two major active acid extruders in many mammalian cells. Whether the NHE and NBC functional co-exist in human internal mammary artery smooth muscle cells (HIMASMCs) remains unclear. The aims of the present study were to investigate the acid-extruding mechanisms and to explore the effects of urotensin-II (U-II), a powerful vasoconstrictor, on pHi regulators in HIMASMCs. We investigated the changes of pHi by BCECF-fluorescence in HIMASMCs. We found that (a) two Na(+)-dependent acid extruders, i.e. NHE and NBC, functionally co-exist; (b) U-II (3-100 nM) induced a concentration-dependent intracellular acidosis; and (c) U-II (3-100 nM) caused a concentration-dependent increase on NHE activity, while decrease on NBC activity. In summary, we demonstrate for the first time that two acid-extruders, NHE and NBC, functionally co-exist in HIMASMCs. Moreover, U-II induces a concentration-dependent intracellular acidosis through the balanced effect of its effect on increasing NHE activity and decreasing NBC activity.
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Affiliation(s)
- Yi-Ting Tsai
- Department of Cardiovascular Surgery, Tri-Service General Hospital, Taipei, Taiwan
| | - Chung-Yi Lee
- Department of Cardiovascular Surgery, Tri-Service General Hospital, Taipei, Taiwan
| | - Chih-Chin Hsu
- Department of Pharmacology, National Defense Medical Center, Taipei City 114, Taiwan
| | - Chung-Yi Chang
- Department of General Surgery, Cheng-Hsieng General Hospital, Taipei, Taiwan
| | - Ming-Kai Hsueh
- Department of Pharmacology, National Defense Medical Center, Taipei, Taiwan
| | - Eagle Yi-Kung Huang
- Department of Pharmacology, National Defense Medical Center, Taipei City 114, Taiwan
| | - Chien-Sung Tsai
- Department of Cardiovascular Surgery, Tri-Service General Hospital, Taipei, Taiwan; Department of Pharmacology, National Defense Medical Center, Taipei City 114, Taiwan
| | - Shih-Hurng Loh
- Department of Pharmacology, National Defense Medical Center, Taipei City 114, Taiwan.
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Loh SH, Tsai YT, Lee CY, Chang CY, Tsai CS, Cheng TH, Lin CI. Antiarrhythmic effects of dehydroevodiamine in isolated human myocardium and cardiomyocytes. JOURNAL OF ETHNOPHARMACOLOGY 2014; 153:753-762. [PMID: 24680993 DOI: 10.1016/j.jep.2014.03.043] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Revised: 02/28/2014] [Accepted: 03/08/2014] [Indexed: 06/03/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Dehydroevodiamine alkaloid (DeHE), a bioactive component of the Chinese herbal medicine Wu-Chu-Yu (Evodiae frutus), exerted antiarrhythmic effect in guinea-pig ventricular myocytes. We further characterize the electromechanical effects of DeHE in the human atrial and ventricular tissues obtained from hearts of patients undergoing corrective cardiac surgery or heart transplantation. MATERIALS AND METHODS The transmembrane potentials of human myocardia were recorded with a traditional microelectrode technique while sarcolemmal Na(+) and Ca(2+) currents in single human cardiomyocytes were measured by a whole-cell patch-clamp technique. The intracellular pH (pHi) and Na(+)-H(+) exchanger (NHE) activity were determined using BCECF-fluorescence in human atria. RESULTS In human atria, DeHE (0.1-0.3 μM) depressed upstroke velocity, amplitude of action potential, and contractile force, both in slow and fast response action potential. Moreover, the similar depressant effects of DeHE were found in human ventricular myocardium. Both in isolated human atrial and ventricular myocytes, DeHE (0.1-1 μM) reversibly, concentration-dependently decreased the Na(+) and Ca(2+)currents. Moreover, DeHE (0.1 and 0.3 μM) suppressed delayed afterdepolarizations and aftercontractions, induced by epinephrine and high [Ca(2+)]o in atria. In human ventricular myocardium, the strophanthidin-induced triggered activities were attenuated by pretreating DeHE (0.3 μM). The resting pHi and NHE activity were also significantly increased by DeHE (0.1-0.3 μM). CONCLUSIONS We concluded for the first time that, in the human hearts, DeHE could antagonize triggered arrhythmias induced by cardiotonic agents through a general reduction of the Na(+) and Ca(2+) inward currents, while increase of resting pHi and NHE activity.
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Affiliation(s)
- Shih-Hurng Loh
- Department of Pharmacology, Tri-Service General Hospital, National Defense Medical Center, No. 161, Ming-Chuan E. Rd., Sect. 6, Nei-Hu District, Taipei 114, Taiwan, ROC.
| | - Yi-Ting Tsai
- Department of Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei 114, Taiwan, ROC
| | - Chung-Yi Lee
- Department of Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei 114, Taiwan, ROC
| | - Chung-Yi Chang
- Department of General Surgery, Cheng-Hsieng General Hospital, Taipei 114, Taiwan, ROC
| | - Chien-Sung Tsai
- Department of Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei 114, Taiwan, ROC
| | - Tzu-Hurng Cheng
- Department of Biological Science and Technology, China Medical University, Taichung 420, Taiwan, ROC
| | - Cheng-I Lin
- Department of Physiology, Tri-Service General Hospital, National Defense Medical Center, Taipei 114, Taiwan, ROC
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Loh SH, Lee CY, Tsai YT, Shih SJ, Chen LW, Cheng TH, Chang CY, Tsai CS. Intracellular Acid-extruding regulators and the effect of lipopolysaccharide in cultured human renal artery smooth muscle cells. PLoS One 2014; 9:e90273. [PMID: 24587308 PMCID: PMC3931831 DOI: 10.1371/journal.pone.0090273] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Accepted: 01/31/2014] [Indexed: 12/25/2022] Open
Abstract
Homeostasis of the intracellular pH (pHi) in mammalian cells plays a pivotal role in maintaining cell function. Thus far, the housekeeping Na(+)-H(+) exchanger (NHE) and the Na(+)-HCO3(-) co-transporter (NBC) have been confirmed in many mammalian cells as major acid extruders. However, the role of acid-extruding regulators in human renal artery smooth muscle cells (HRASMCs) remains unclear. It has been demonstrated that lipopolysaccharide (LPS)-induced vascular occlusion is associated with the apoptosis, activating calpain and increased [Ca(2+)]i that are related to NHE1 activity in endothelia cells. This study determines the acid-extruding mechanisms and the effect of LPS on the resting pHi and active acid extruders in cultured HRASMCs. The mechanism of pHi recovery from intracellular acidosis (induced by NH4Cl-prepulse) is determined using BCECF-fluorescence in cultured HRASMCs. It is seen that (a) the resting pHi is 7.19 ± 0.03 and 7.10 ± 0.02 for HEPES- and CO2/HCO3(-)- buffered solution, respectively; (b) apart from the housekeeping NHE1, another Na(+)-coupled HCO3(-) transporter i.e. NBC, functionally co-exists to achieve acid-equivalent extrusion; (c) three different isoforms of NBC: NBCn1 (SLC4A7; electroneutral), NBCe1 (SLC4A4; electrogenic) and NBCe2 (SLC4A5), are detected in protein/mRNA level; and (d) pHi and NHE protein expression/activity are significantly increased by LPS, in both a dose- and time- dependent manner, but NBCs protein expression is not. In conclusion, it is demonstrated, for the first time, that four pHi acid-extruding regulators: NHE1, NBCn1, NBCe1 and NBCe2, co-exist in cultured HRASMCs. LPS also increases cellular growth, pHi and NHE in a dose- and time-dependent manner.
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Affiliation(s)
- Shih-Hurng Loh
- Department of Pharmacology, National Defense Medical Center, Taipei City, Taiwan
- * E-mail:
| | - Chung-Yi Lee
- Department of Cardiovascular Surgery, Tri-Service General Hospital, Taipei, Taiwan
| | - Yi-Ting Tsai
- Department of Cardiovascular Surgery, Tri-Service General Hospital, Taipei, Taiwan
| | - Shou-Jou Shih
- Department of Pharmacology, National Defense Medical Center, Taipei City, Taiwan
| | - Li-Wei Chen
- Department of Pharmacology, National Defense Medical Center, Taipei City, Taiwan
| | - Tzu-Hurng Cheng
- Department of Biological Science and Technology, College of Life Sciences, China Medical University, Taichung, Taiwan
| | - Chung-Yi Chang
- Department of General Surgery, Cheng-Hsieng General Hospital, Taipei, Taiwan
| | - Chein-Sung Tsai
- Department of Cardiovascular Surgery, Tri-Service General Hospital, Taipei, Taiwan
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50
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Swietach P, Leem CH, Spitzer KW, Vaughan-Jones RD. Pumping Ca2+ up H+ gradients: a Ca2(+)-H+ exchanger without a membrane. J Physiol 2014; 592:3179-88. [PMID: 24514908 DOI: 10.1113/jphysiol.2013.265959] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Cellular processes are exquisitely sensitive to H+ and Ca2+ ions because of powerful ionic interactions with proteins. By regulating the spatial and temporal distribution of intracellular [Ca2+] and [H+], cells such as cardiac myocytes can exercise control over their biological function. A well-established paradigm in cellular physiology is that ion concentrations are regulated by specialized, membrane-embedded transporter proteins. Many of these couple the movement of two or more ionic species per transport cycle, thereby linking ion concentrations among neighbouring compartments. Here, we compare and contrast canonical membrane transport with a novel type of Ca(2+)-H+ coupling within cytoplasm, which produces uphill Ca2+ transport energized by spatial H+ ion gradients, and can result in the cytoplasmic compartmentalization of Ca2+ without requiring a partitioning membrane. The mechanism, demonstrated in mammalian myocytes, relies on diffusible cytoplasmic buffers, such as carnosine, homocarnosine and ATP, to which Ca2+ and H+ ions bind in an apparently competitive manner. These buffer molecules can actively recruit Ca2+ to acidic microdomains, in exchange for the movement of H+ ions. The resulting Ca2+ microdomains thus have the potential to regulate function locally. Spatial cytoplasmic Ca(2+)-H+ exchange (cCHX) acts like a 'pump' without a membrane and may be operational in many cell types.
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Affiliation(s)
- Pawel Swietach
- Burdon Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, Oxford, UK
| | - Chae-Hun Leem
- Department of Physiology, University of Ulsan College of Medicine, Seoul, Republic of Korea
| | - Kenneth W Spitzer
- Nora Eccles Harrison Cardiovascular Research and Training Institute, Salt Lake City, UT, USA
| | - Richard D Vaughan-Jones
- Burdon Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, Oxford, UK
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