1
|
The electrogenic sodium bicarbonate cotransporter and its roles in the myocardial ischemia-reperfusion induced cardiac diseases. Life Sci 2021; 270:119153. [PMID: 33539911 DOI: 10.1016/j.lfs.2021.119153] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 01/06/2021] [Accepted: 01/22/2021] [Indexed: 12/19/2022]
Abstract
Cardiac tissue ischemia/hypoxia increases glycolysis and lactic acid accumulation in cardiomyocytes, leading to intracellular metabolic acidosis. Sodium bicarbonate cotransporters (NBCs) play a vital role in modulating intracellular pH and maintaining sodium ion concentrations in cardiomyocytes. Cardiomyocytes mainly express electrogenic sodium bicarbonate cotransporter (NBCe1), which has been demonstrated to participate in myocardial ischemia/reperfusion (I/R) injury. This review outlines the structural and functional properties of NBCe1, summarizes the signaling pathways and factors that may regulate the activity of NBCe1, and reviews the roles of NBCe1 in the pathogenesis of I/R-induced cardiac diseases. Further studies revealing the regulatory mechanisms of NBCe1 activity should provide novel therapeutic targets for preventing I/R-induced cardiac diseases.
Collapse
|
2
|
Portal L, Morin D, Motterlini R, Ghaleh B, Pons S. The CO-releasing molecule CORM-3 protects adult cardiomyocytes against hypoxia-reoxygenation by modulating pH restoration. Eur J Pharmacol 2019; 862:172636. [PMID: 31491405 DOI: 10.1016/j.ejphar.2019.172636] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 08/26/2019] [Accepted: 09/02/2019] [Indexed: 01/18/2023]
Abstract
Several studies have reported that CORM-3, a water-soluble carbon monoxide releasing molecule, elicits cardioprotection against myocardial infarction but the mechanism remains to be investigated. Numerous reports indicate that inhibition of pH regulators, the Na+/H+ exchanger (NHE) and Na+/HCO3- symporter (NBC), protect cardiomyocytes from hypoxia/reoxygenation injury by delaying the intracellular pH (pHi) recovery at reperfusion. Our goal was to explore whether CORM-3-mediated cytoprotection involves the modulation of pH regulation. When added at reoxygenation, CORM-3 (50 μM) reduced the mortality of cardiomyocytes exposed to 3 h of hypoxia and 2 h of reoxygenation in HCO3--buffered solution. This effect was lost when using inactive iCORM-3, which is depleted of CO and used as control, thus implicating CO as the mediator of this cardioprotection. Interestingly, the cardioprotective effect of CORM-3 was abolished by switching to a bicarbonate-free medium. This effect of CORM-3 was also inhibited by 5-hydroxydecanoate, a mitochondrial ATP-dependent K+ (mKATP) channel inhibitor (500 μM) or PD098059, a MEK1/2 inhibitor (10 μM). In additional experiments and in the absence of hypoxia-reoxygenation, intracellular pH was monitored in cardiomyocytes exposed to cariporide to block NHE activity. CORM-3 inhibited alkalinisation and this effect was blocked by PD098059 and 5-HD. In conclusion, CORM-3 protects the cardiomyocyte against hypoxia-reoxygenation injury by inhibiting a bicarbonate transporter at reoxygenation, probably the Na+/HCO3- symporter. This cardioprotective effect of CORM-3 requires the activation of mKATP channels and the activation of MEK1/2.
Collapse
Affiliation(s)
- Lolita Portal
- U955-IMRB, Equipe 03, Inserm, UPEC, Ecole Nationale Vétérinaire d'Alfort, Créteil, France
| | - Didier Morin
- U955-IMRB, Equipe 03, Inserm, UPEC, Ecole Nationale Vétérinaire d'Alfort, Créteil, France
| | | | - Bijan Ghaleh
- U955-IMRB, Equipe 03, Inserm, UPEC, Ecole Nationale Vétérinaire d'Alfort, Créteil, France.
| | - Sandrine Pons
- U955-IMRB, Equipe 03, Inserm, UPEC, Ecole Nationale Vétérinaire d'Alfort, Créteil, France
| |
Collapse
|
3
|
Rinaldi L, Pozdniakova S, Jayarajan V, Troidl C, Abdallah Y, Aslam M, Ladilov Y. Protective role of soluble adenylyl cyclase against reperfusion-induced injury of cardiac cells. Biochim Biophys Acta Mol Basis Dis 2018; 1865:252-260. [PMID: 30044950 DOI: 10.1016/j.bbadis.2018.07.021] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2018] [Revised: 06/15/2018] [Accepted: 07/17/2018] [Indexed: 12/16/2022]
Abstract
AIMS Disturbance of mitochondrial function significantly contributes to the myocardial injury that occurs during reperfusion. Increasing evidence suggests a role of intra-mitochondrial cyclic AMP (cAMP) signaling in promoting respiration and ATP synthesis. Mitochondrial levels of cAMP are controlled by type 10 soluble adenylyl cyclase (sAC) and phosphodiesterase 2 (PDE2), however their role in the reperfusion-induced injury remains unknown. Here we aimed to examine whether sAC may support cardiomyocyte survival during reperfusion. METHODS AND RESULTS Adult rat cardiomyocytes or rat cardiac H9C2 cells were subjected to metabolic inhibition and recovery as a model of simulated ischemia and reperfusion. Cytosolic Ca2+, pH, mitochondrial cAMP (live-cell imaging), and cell viability were analyzed during a 15-min period of reperfusion. Suppression of sAC activity in cardiomyocytes and H9C2 cells, either by sAC knockdown, by pharmacological inhibition or by withdrawal of bicarbonate, a natural sAC activator, compromised cell viability and recovery of cytosolic Ca2+ homeostasis during reperfusion. Contrariwise, overexpression of mitochondria-targeted sAC in H9C2 cells suppressed reperfusion-induced cell death. Analyzing cAMP concentration in mitochondrial matrix we found that inhibition of PDE2, a predominant mitochondria-localized PDE isoform in mammals, during reperfusion significantly increased cAMP level in mitochondrial matrix, but not in cytosol. Accordingly, PDE2 inhibition attenuated reperfusion-induced cardiomyocyte death and improved recovery of the cytosolic Ca2+ homeostasis. CONCLUSION sAC plays an essential role in supporting cardiomyocytes viability during reperfusion. Elevation of mitochondrial cAMP pool either by sAC overexpression or by PDE2 inhibition beneficially affects cardiomyocyte survival during reperfusion.
Collapse
Affiliation(s)
- Laura Rinaldi
- Department of Cardiology and Angiology, Justus Liebig University, Giessen, Germany
| | | | | | - Christian Troidl
- Department of Cardiology and Angiology, Justus Liebig University, Giessen, Germany
| | - Yaser Abdallah
- Department of Cardiology and Angiology, Justus Liebig University, Giessen, Germany
| | - Muhammad Aslam
- Department of Cardiology and Angiology, Justus Liebig University, Giessen, Germany; DZHK (German Centre for Cardiovascular Research), partner site Rhein-Main, Bad Nauheim, Germany
| | - Yury Ladilov
- Center for Cardiovascular Research, Charité, Berlin, Germany; DZHK (German Centre for Cardiovascular Research), partner site Berlin, Berlin, Germany.
| |
Collapse
|
4
|
Sermersheim MA, Park KH, Gumpper K, Adesanya TMA, Song K, Tan T, Ren X, Yang JM, Zhu H. MicroRNA regulation of autophagy in cardiovascular disease. Front Biosci (Landmark Ed) 2017; 22:48-65. [PMID: 27814601 DOI: 10.2741/4471] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Autophagy, a form of lysosomal degradation capable of eliminating dysfunctional proteins and organelles, is a cellular process associated with homeostasis. Autophagy functions in cell survival by breaking down proteins and organelles and recycling them to meet metabolic demands. However, aberrant up regulation of autophagy can function as an alternative to apoptosis. The duality of autophagy, and its regulation over cell survival/death, intimately links it with human disease. Non-coding RNAs regulate mRNA levels and elicit diverse effects on mammalian protein expression. The most studied non-coding RNAs to-date are microRNAs (miRNA). MicroRNAs function in post-transcriptional regulation, causing profound changes in protein levels, and affect many biological processes and diseases. The role and regulation of autophagy, whether it is beneficial or harmful, is a controversial topic in cardiovascular disease. A number of recent studies have identified miRNAs that target autophagy-related proteins and influence the development, progression, or treatment of cardiovascular disease. Understanding the mechanisms by which these miRNAs work can provide promising insight and potential progress towards the development of therapeutic treatments in cardiovascular disease.
Collapse
Affiliation(s)
- Matthew A Sermersheim
- Department of Surgery, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio 43210, USA
| | - Ki Ho Park
- Department of Surgery, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio 43210, USA
| | - Kristyn Gumpper
- Department of Surgery, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio 43210, USA
| | - T M Ayodele Adesanya
- Department of Surgery, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio 43210, USA
| | - Kuncheng Song
- Department of Surgery, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio 43210, USA
| | - Tao Tan
- Department of Surgery, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio 43210, USA
| | - Xingcong Ren
- Department of Pharmacology, The Penn State Hershey Cancer Institute, The Pennsylvania State University, College of Medicine and Milton S. Hershey Medical Center, 500 University Drive, Hershey, PA 17033, USA
| | - Jin-Ming Yang
- Department of Pharmacology, The Penn State Hershey Cancer Institute, The Pennsylvania State University, College of Medicine and Milton S. Hershey Medical Center, 500 University Drive, Hershey, PA 17033, USA
| | - Hua Zhu
- Department of Surgery, Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, Ohio 43210, USA,
| |
Collapse
|
5
|
Cuomo O, Vinciguerra A, Cerullo P, Anzilotti S, Brancaccio P, Bilo L, Scorziello A, Molinaro P, Di Renzo G, Pignataro G. Ionic homeostasis in brain conditioning. Front Neurosci 2015; 9:277. [PMID: 26321902 PMCID: PMC4530315 DOI: 10.3389/fnins.2015.00277] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 07/23/2015] [Indexed: 12/26/2022] Open
Abstract
Most of the current focus on developing neuroprotective therapies is aimed at preventing neuronal death. However, these approaches have not been successful despite many years of clinical trials mainly because the numerous side effects observed in humans and absent in animals used at preclinical level. Recently, the research in this field aims to overcome this problem by developing strategies which induce, mimic, or boost endogenous protective responses and thus do not interfere with physiological neurotransmission. Preconditioning is a protective strategy in which a subliminal stimulus is applied before a subsequent harmful stimulus, thus inducing a state of tolerance in which the injury inflicted by the challenge is mitigated. Tolerance may be observed in ischemia, seizure, and infection. Since it requires protein synthesis, it confers delayed and temporary neuroprotection, taking hours to develop, with a pick at 1–3 days. A new promising approach for neuroprotection derives from post-conditioning, in which neuroprotection is achieved by a modified reperfusion subsequent to a prolonged ischemic episode. Many pathways have been proposed as plausible mechanisms to explain the neuroprotection offered by preconditioning and post-conditioning. Although the mechanisms through which these two endogenous protective strategies exert their effects are not yet fully understood, recent evidence highlights that the maintenance of ionic homeostasis plays a key role in propagating these neuroprotective phenomena. The present article will review the role of protein transporters and ionic channels involved in the control of ionic homeostasis in the neuroprotective effect of ischemic preconditioning and post-conditioning in adult brain, with particular regards to the Na+/Ca2+ exchangers (NCX), the plasma membrane Ca2+-ATPase (PMCA), the Na+/H+ exchange (NHE), the Na+/K+/2Cl− cotransport (NKCC) and the acid-sensing cation channels (ASIC). Ischemic stroke is the third leading cause of death and disability. Up until now, all clinical trials testing potential stroke neuroprotectants failed. For this reason attention of researchers has been focusing on the identification of brain endogenous neuroprotective mechanisms activated after cerebral ischemia. In this context, ischemic preconditioning and ischemic post-conditioning represent two neuroprotecive strategies to investigate in order to identify new molecular target to reduce the ischemic damage.
Collapse
Affiliation(s)
- Ornella Cuomo
- Division of Pharmacology, Department of Neuroscience, Reproductive and Dentistry Sciences, School of Medicine, Federico II University of Naples Naples, Italy
| | - Antonio Vinciguerra
- Division of Pharmacology, Department of Neuroscience, Reproductive and Dentistry Sciences, School of Medicine, Federico II University of Naples Naples, Italy
| | - Pierpaolo Cerullo
- Division of Pharmacology, Department of Neuroscience, Reproductive and Dentistry Sciences, School of Medicine, Federico II University of Naples Naples, Italy
| | | | - Paola Brancaccio
- Division of Pharmacology, Department of Neuroscience, Reproductive and Dentistry Sciences, School of Medicine, Federico II University of Naples Naples, Italy
| | - Leonilda Bilo
- Division of Neurology, Department of Neuroscience, Reproductive and Dentistry Sciences, School of Medicine, Federico II University of Naples Naples, Italy
| | - Antonella Scorziello
- Division of Pharmacology, Department of Neuroscience, Reproductive and Dentistry Sciences, School of Medicine, Federico II University of Naples Naples, Italy
| | - Pasquale Molinaro
- Division of Pharmacology, Department of Neuroscience, Reproductive and Dentistry Sciences, School of Medicine, Federico II University of Naples Naples, Italy
| | - Gianfranco Di Renzo
- Division of Pharmacology, Department of Neuroscience, Reproductive and Dentistry Sciences, School of Medicine, Federico II University of Naples Naples, Italy
| | - Giuseppe Pignataro
- Division of Pharmacology, Department of Neuroscience, Reproductive and Dentistry Sciences, School of Medicine, Federico II University of Naples Naples, Italy
| |
Collapse
|
6
|
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.
Collapse
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
| |
Collapse
|
7
|
Zhao H, Iwasaki M, Yang J, Savage S, Ma D. Hypoxia-inducible factor-1: A possible link between inhalational anesthetics and tumor progression? ACTA ACUST UNITED AC 2014; 52:70-6. [DOI: 10.1016/j.aat.2014.05.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Accepted: 02/07/2014] [Indexed: 01/10/2023]
|
8
|
Fantinelli JC, Orlowski A, Aiello EA, Mosca SM. The electrogenic cardiac sodium bicarbonate co-transporter (NBCe1) contributes to the reperfusion injury. Cardiovasc Pathol 2014; 23:224-30. [PMID: 24721237 DOI: 10.1016/j.carpath.2014.03.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Revised: 03/13/2014] [Accepted: 03/13/2014] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Although the participation of the electrogenic sodium/bicarbonate cotransporter (NBCe1) in the recovery from an intracellular acid load is recognized, its role in ischemia-reperfusion is still unclear. METHODS AND RESULTS Our objective was to assess the role of NBCe1 in reperfusion injury. We use selective functional antibodies against extracellular loop 3 (a-L3) and loop 4 (a-L4) of NBCe1. a-L3 inhibits and a-L4 stimulates NBCe1 activity. Isolated rat hearts were submitted to 40 min of coronary occlusion and 1 h of reperfusion. a-L3, a-L4 or S0859--selective Na(+)-HCO3(-) co-transport inhibitor--were administered during the initial 10 min of reperfusion. The infarct size (IS) was measured by triphenyltetrazolium chloride staining technique. Postischemic systolic and diastolic functions were also assessed. a-L3 and S0859 treatments decreased significantly (P < .05) the IS (16 ± 3% for a-L3 vs. 32 ± 5% in hearts treated with control nonimmune serum and 19 ± 3% for S0859 vs. 39 ± 2% in untreated hearts). Myocardial function during reperfusion improved after a-L3 treatment, but it was not modified by S0859. The infusion of a-L4 did not modify neither the IS nor myocardial function. CONCLUSIONS The NBCe1 hyperactivity during reperfusion leads to Na(+) and Ca(2+) loading, conducing to Ca(2+) overload and myocardial damage. Consistently, we have shown herein that the selective NBCe1 blockade with a-L3 exerted cardioprotection. This beneficial action strongly suggests that NBCe1 could be a potential target for the treatment of coronary disease.
Collapse
Affiliation(s)
- Juliana C Fantinelli
- Established Investigator of CONICET, Centro de Investigaciones Cardiovasculares, Universidad Nacional de La Plata, La Plata, Buenos Aires, Argentina
| | - Alejandro Orlowski
- Fellowship of Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Centro de Investigaciones Cardiovasculares, Universidad Nacional de La Plata, La Plata, Buenos Aires, Argentina
| | - Ernesto A Aiello
- Established Investigator of CONICET, Centro de Investigaciones Cardiovasculares, Universidad Nacional de La Plata, La Plata, Buenos Aires, Argentina
| | - Susana M Mosca
- Established Investigator of CONICET, Centro de Investigaciones Cardiovasculares, Universidad Nacional de La Plata, La Plata, Buenos Aires, Argentina.
| |
Collapse
|
9
|
Aiello EA, De Giusti VC. Regulation of the cardiac sodium/bicarbonate cotransporter by angiotensin II: potential Contribution to structural, ionic and electrophysiological myocardial remodelling. Curr Cardiol Rev 2013; 9:24-32. [PMID: 23116057 PMCID: PMC3584305 DOI: 10.2174/157340313805076340] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Revised: 08/15/2012] [Accepted: 09/13/2012] [Indexed: 12/15/2022] Open
Abstract
The sodium/ bicarbonate cotransporter (NBC) is, with the Na+/H+ exchanger (NHE), an important alkalinizing mechanism that maintains cellular intracellular pH (pHi). In the heart exists at least three isoforms of NBC, one that promotes the co-influx of 1 molecule of Na+ per 1molecule of HCO3-(electroneutral isoform; nNBC) and two others that generates the co-influx of 1 molecule of Na+ per 2 molecules of HCO3- (electrogenic isoforms; eNBC). In addition, the eNBC generates an anionic repolarizing current that modulate the cardiac action potential (CAP), adding to such isoforms the relevance to modulate the electrophysiological function of the heart. Angiotensin II (Ang II) is one of the main hormones that regulate cardiac physiology. The alkalinizing mechanisms (NHE and NBC) are stimulated by Ang II, increasing pHi and intracellular Na+ concentration, which indirectly, due to the stimulation of the Na+/Ca2+ exchanger (NCX) operating in the reverse form, leads to an increase in the intracellular Ca2+ concentration. Interestingly, it has been shown that Ang II exhibits an opposite effect on NBC isoforms: it activates the nNBC and inhibits the eNBC. This inhibition generates a CAP prolongation, which could directly increase the intracellular Ca2+ concentration. The regulation of the intracellular Na+ and Ca2+ concentrations is crucial for the cardiac cellular physiology, but these ions are also involved in the development of cardiac hypertrophy and the damage produced by ischemia-reperfusion, suggesting a potential role of NBC in cardiac diseases.
Collapse
Affiliation(s)
- Ernesto Alejandro Aiello
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, Calle 60 y 120, 1900, La Plata, Argentina.
| | | |
Collapse
|
10
|
Parker MD, Boron WF. The divergence, actions, roles, and relatives of sodium-coupled bicarbonate transporters. Physiol Rev 2013; 93:803-959. [PMID: 23589833 PMCID: PMC3768104 DOI: 10.1152/physrev.00023.2012] [Citation(s) in RCA: 197] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The mammalian Slc4 (Solute carrier 4) family of transporters is a functionally diverse group of 10 multi-spanning membrane proteins that includes three Cl-HCO3 exchangers (AE1-3), five Na(+)-coupled HCO3(-) transporters (NCBTs), and two other unusual members (AE4, BTR1). In this review, we mainly focus on the five mammalian NCBTs-NBCe1, NBCe2, NBCn1, NDCBE, and NBCn2. Each plays a specialized role in maintaining intracellular pH and, by contributing to the movement of HCO3(-) across epithelia, in maintaining whole-body pH and otherwise contributing to epithelial transport. Disruptions involving NCBT genes are linked to blindness, deafness, proximal renal tubular acidosis, mental retardation, and epilepsy. We also review AE1-3, AE4, and BTR1, addressing their relevance to the study of NCBTs. This review draws together recent advances in our understanding of the phylogenetic origins and physiological relevance of NCBTs and their progenitors. Underlying these advances is progress in such diverse disciplines as physiology, molecular biology, genetics, immunocytochemistry, proteomics, and structural biology. This review highlights the key similarities and differences between individual NCBTs and the genes that encode them and also clarifies the sometimes confusing NCBT nomenclature.
Collapse
Affiliation(s)
- Mark D Parker
- Dept. of Physiology and Biophysics, Case Western Reserve University School of Medicine, 10900 Euclid Ave., Cleveland, OH 44106-4970, USA.
| | | |
Collapse
|
11
|
Queliconi BB, Marazzi TBM, Vaz SM, Brookes PS, Nehrke K, Augusto O, Kowaltowski AJ. Bicarbonate modulates oxidative and functional damage in ischemia-reperfusion. Free Radic Biol Med 2013; 55:46-53. [PMID: 23195687 PMCID: PMC3995138 DOI: 10.1016/j.freeradbiomed.2012.11.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2012] [Revised: 11/01/2012] [Accepted: 11/13/2012] [Indexed: 11/25/2022]
Abstract
The carbon dioxide/bicarbonate (CO(2)/HCO(3)(-)) pair is the main biological pH buffer. However, its influence on biological processes, and in particular redox processes, is still poorly explored. Here we study the effect of CO(2)/HCO(3)(-) on ischemic injury in three distinct models (cardiac HL-1 cells, perfused rat heart, and Caenorhabditis elegans). We found that, although various concentrations of CO(2)/HCO(3)(-) do not affect function under basal conditions, ischemia-reperfusion or similar insults in the presence of higher CO(2)/HCO(3)(-) resulted in greater functional loss associated with higher oxidative damage in all models. Because the effect of CO(2)/HCO(3)(-) was observed in all models tested, we believe this buffer is an important determinant of oxidative damage after ischemia-reperfusion.
Collapse
Affiliation(s)
- Bruno B. Queliconi
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Thire B. M. Marazzi
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Sandra M. Vaz
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil
| | | | - Keith Nehrke
- University of Rochester Medical Center, Rochester, NY, USA
| | - Ohara Augusto
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Alicia J. Kowaltowski
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil
| |
Collapse
|
12
|
Boedtkjer E, Aalkjaer C. Intracellular pH in the resistance vasculature: regulation and functional implications. J Vasc Res 2012; 49:479-96. [PMID: 22907294 DOI: 10.1159/000341235] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Accepted: 06/20/2012] [Indexed: 12/18/2022] Open
Abstract
Net acid extrusion from vascular smooth muscle (VSMCs) and endothelial cells (ECs) in the wall of resistance arteries is mediated by the Na(+),HCO(3)(-) cotransporter NBCn1 (SLC4A7) and the Na(+)/H(+) exchanger NHE1 (SLC9A1) and is essential for intracellular pH (pH(i)) control. Experimental evidence suggests that the pH(i) of VSMCs and ECs modulates both vasocontractile and vasodilatory functions in resistance arteries with implications for blood pressure regulation. The connection between disturbed pH(i) and altered cardiovascular function has been substantiated by a genome-wide association study showing a link between NBCn1 and human hypertension. On this basis, we here review the current evidence regarding (a) molecular mechanisms involved in pH(i) control in VSMCs and ECs of resistance arteries at rest and during contractions, (b) implications of disturbed pH(i) for resistance artery function, and (c) involvement of disturbed pH(i) in the pathogenesis of vascular disease. The current evidence clearly implies that pH(i) of VSMCs and ECs modulates vascular function and suggests that disturbed pH(i) either consequent to disturbed regulation or due to metabolic challenges needs to be taken into consideration as a mechanistic component of artery dysfunction and disturbed blood pressure regulation.
Collapse
Affiliation(s)
- Ebbe Boedtkjer
- Department of Biomedicine and Water and Salt Research Center, Aarhus University, Aarhus, Denmark.
| | | |
Collapse
|
13
|
Garcia-Dorado D, Ruiz-Meana M, Inserte J, Rodriguez-Sinovas A, Piper HM. Calcium-mediated cell death during myocardial reperfusion. Cardiovasc Res 2012; 94:168-80. [PMID: 22499772 DOI: 10.1093/cvr/cvs116] [Citation(s) in RCA: 222] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Reperfusion may induce additional cell death in patients with acute myocardial infarction receiving primary angioplasty or thrombolysis. Altered intracellular Ca(2+) handling was initially considered an essential mechanism of reperfusion-induced cardiomyocyte death. However, more recent studies have demonstrated the importance of Ca(2+)-independent mechanisms that converge on mitochondrial permeability transition (MPT) and are shared by cardiomyocytes and other cell types. This article analyses the importance of Ca(2+)-dependent cell death in light of these new observations. Altered Ca(2+) handling includes increased cytosolic Ca(2+) levels, leading to activation of calpain-mediated proteolysis and sarcoplasmic reticulum-driven oscillations; this can induce hypercontracture, but also MPT due to the privileged Ca(2+) transfer between sarcoplasmic reticulum and mitochondria through cytosolic Ca(2+) microdomains. In the opposite direction, permeability transition can worsen altered Ca(2+) handling and favour hypercontracture. Ca(2+) appears to play an important role in cell death during the initial minutes of reperfusion, particularly after brief periods of ischaemia. Developing effective and safe treatments to prevent Ca(2+)-mediated cardiomyocyte death in patients with transient ischaemia, by targeting Ca(2+) influx, intracellular Ca(2+) handling, or Ca(2+)-induced cell death effectors, is an unmet challenge with important therapeutic implications and large potential clinical impact.
Collapse
|
14
|
De Giusti VC, Orlowski A, Villa-Abrille MC, de Cingolani GEC, Casey JR, Alvarez BV, Aiello EA. Antibodies against the cardiac sodium/bicarbonate co-transporter (NBCe1) as pharmacological tools. Br J Pharmacol 2012; 164:1976-89. [PMID: 21595652 DOI: 10.1111/j.1476-5381.2011.01496.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND AND PURPOSE Na(+) /HCO(3) (-) co-transport (NBC) regulates intracellular pH (pH(i) ) in the heart. We have studied the electrogenic NBC isoform NBCe1 by examining the effect of functional antibodies to this protein. EXPERIMENTAL APPROACH We generated two antibodies against putative extracellular loop domains 3 (a-L3) and 4 (a-L4) of NBCe1 which recognized NBCe1 on immunoblots and immunostaining experiments. pH(i) was monitored using epi-fluorescence measurements in cat ventricular myocytes. Transport activity of total NBC and of NBCe1 in isolation were evaluated after an ammonium ion-induced acidosis (expressed as H(+) flux, J(H) , in mmol·L(-1) min(-1) at pH(i) 6.8) and during membrane depolarization with high extracellular potassium (potassium pulse, expressed as ΔpH(i) ) respectively. KEY RESULTS The potassium pulse produced a pH(i) increase of 0.18 ± 0.006 (n= 5), which was reduced by the a-L3 antibody (0.016 ± 0.019). The a-L-3 also decreased J(H) by 50%. Surprisingly, during the potassium pulse, a-L4 induced a higher pH(i) increase than control,(0.25 ± 0.018) whereas the recovery of pH(i) from acidosis was faster (J(H) was almost double the control value). In perforated-patch experiments, a-L3 prolonged and a-L4 shortened action potential duration, consistent with blockade and stimulation of NBCe1-carried anionic current respectively. CONCLUSIONS AND IMPLICATIONS Both antibodies recognized NBCe1, but they had opposing effects on the function of this transporter, as the a-L3 was inhibitory and the a-L4 was excitatory. These antibodies could be valuable in studies on the pathophysiology of NBCe1 in cardiac tissue, opening a path for their potential clinical use.
Collapse
Affiliation(s)
- Verónica C De Giusti
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | | | | | | | | | | | | |
Collapse
|
15
|
Inserte J, Ruiz-Meana M, Rodríguez-Sinovas A, Barba I, Garcia-Dorado D. Contribution of delayed intracellular pH recovery to ischemic postconditioning protection. Antioxid Redox Signal 2011; 14:923-39. [PMID: 20578958 DOI: 10.1089/ars.2010.3312] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Ischemic postconditioning (PoCo) has been proven to be a feasible approach to attenuate reperfusion injury and enhance myocardial salvage in patients with acute myocardial infarction, but its mechanisms have not been completely elucidated yet. Recent studies demonstrate that PoCo may delay the recovery of intracellular pH during initial reperfusion, and that its ability to limit infarct size critically depends on this effect. Prolongation of postischemic intracellular acidosis inhibits hypercontracture, mitochondrial permeability transition, calpain-mediated proteolysis, and gap junction-mediated spread of injury during the first minutes of reflow. This role of prolonged acidosis does not exclude the participation of other pathways in PoCo-induced cardioprotection. On the contrary, it may allow these pathways to act by preventing immediate reperfusion-induced cell death. Moreover, the existence of interactions between intracellular acidosis and endogenous protection signaling cannot be excluded and needs to be investigated. The role of prolonged acidosis in PoCo cardioprotection has important implications in the design of optimal PoCo protocols and in the translation of cardioprotective strategies to patients with on-going myocardial infarction receiving coronary reperfusion.
Collapse
Affiliation(s)
- Javier Inserte
- Department of Cardiology, Vall d'Hebron University Hospital and Research Institute, Universitat Autònoma de Barcelona, Barcelona, Spain
| | | | | | | | | |
Collapse
|
16
|
Inserte J, Barrabes JA, Hernando V, Garcia-Dorado D. Orphan targets for reperfusion injury. Cardiovasc Res 2009; 83:169-78. [DOI: 10.1093/cvr/cvp109] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
|
17
|
Prasad V, Bodi I, Meyer JW, Wang Y, Ashraf M, Engle SJ, Doetschman T, Sisco K, Nieman ML, Miller ML, Lorenz JN, Shull GE. Impaired cardiac contractility in mice lacking both the AE3 Cl-/HCO3- exchanger and the NKCC1 Na+-K+-2Cl- cotransporter: effects on Ca2+ handling and protein phosphatases. J Biol Chem 2008; 283:31303-14. [PMID: 18779325 PMCID: PMC2581574 DOI: 10.1074/jbc.m803706200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Revised: 08/27/2008] [Indexed: 12/27/2022] Open
Abstract
To analyze the cardiac functions of AE3, we disrupted its gene (Slc4a3) in mice. Cl(-)/HCO3(-) exchange coupled with Na+-dependent acid extrusion can mediate pH-neutral Na+ uptake, potentially affecting Ca2+ handling via effects on Na+/Ca2+ exchange. AE3 null mice appeared normal, however, and AE3 ablation had no effect on ischemia-reperfusion injury in isolated hearts or cardiac performance in vivo. The NKCC1 Na+-K+-2Cl(-) cotransporter also mediates Na+ uptake, and loss of NKCC1 alone does not impair contractility. To further stress the AE3-deficient myocardium, we combined the AE3 and NKCC1 knock-outs. Double knock-outs had impaired contraction and relaxation both in vivo and in isolated ventricular myocytes. Ca2+ transients revealed an apparent increase in Ca2+ clearance in double null cells. This was unlikely to result from increased Ca2+ sequestration, since the ratio of phosphorylated phospholamban to total phospholamban was sharply reduced in all three mutant hearts. Instead, Na+/Ca2+ exchanger activity was found to be enhanced in double null cells. Systolic Ca2+ was unaltered, however, suggesting more direct effects on the contractile apparatus of double null myocytes. Expression of the catalytic subunit of protein phosphatase 1 was increased in all mutant hearts. There was also a dramatic reversal, between single null and double null hearts, in the carboxymethylation and localization to the myofibrillar fraction, of the catalytic subunit of protein phosphatase 2A, which corresponded to the loss of normal contractility in double null hearts. These data show that AE3 and NKCC1 affect Ca2+ handling, PLN regulation, and expression and localization of major cardiac phosphatases and that their combined loss impairs cardiac function.
Collapse
Affiliation(s)
- Vikram Prasad
- Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267-0524, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
18
|
Ch'en FFT, Villafuerte FC, Swietach P, Cobden PM, Vaughan-Jones RD. S0859, an N-cyanosulphonamide inhibitor of sodium-bicarbonate cotransport in the heart. Br J Pharmacol 2008; 153:972-82. [PMID: 18204485 DOI: 10.1038/sj.bjp.0707667] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND AND PURPOSE Intracellular pH (pH(i)) in heart is regulated by sarcolemmal H(+)-equivalent transporters such as Na(+)-H(+) exchange (NHE) and Na(+)-HCO(3) (-) cotransport (NBC). Inhibition of NBC influences pH(i) and can be cardioprotective in animal models of post-ischaemic reperfusion. Apart from a rabbit polyclonal NBC-antibody, a selective NBC inhibitor compound has not been studied. Compound S0859 (C(29)H(24)ClN(3)O(3)S) is a putative NBC inhibitor. Here, we provide the drug's chemical structure, test its potency and selectivity in ventricular cells and assess its suitability for experiments on cardiac contraction. EXPERIMENTAL APPROACH pH(i) recovery from intracellular acidosis was monitored using pH-epifluorescence (SNARF-fluorophore) in guinea pig, rat and rabbit isolated ventricular myocytes. Electrically evoked cell shortening (contraction) was measured optically. With CO(2)/HCO(3) (-)-buffered superfusates containing 30 muM cariporide (to inhibit NHE), pH(i) recovery is mediated by NBC. KEY RESULTS S0859, an N-cyanosulphonamide compound, reversibly inhibited NBC-mediated pH(i) recovery (K (i)=1.7 microM, full inhibition at approximately 30 microM). In HEPES-buffered superfusates, NHE-mediated pH(i) recovery was unaffected by 30 microM S0859. With CO(2)/HCO(3) (-) buffer, pH(i) recovery from intracellular alkalosis (mediated by Cl(-)/HCO(3) (-) and Cl(-)/OH(-) exchange) was also unaffected. Selective NBC-inhibition was not due to action on carbonic anhydrase (CA) enzymes, as 100 microM acetazolamide (a membrane-permeant CA-inhibitor) had no significant effect on NBC activity. pH(i) recovery from acidosis was associated with increased contractile-amplitude. The time course of recovery of pH(i) and contraction was slowed by S0859, confirming that NBC is a significant controller of contractility during acidosis. CONCLUSIONS AND IMPLICATIONS Compound S0859 is a selective, high-affinity generic NBC inhibitor, potentially important for probing the transporter's functional role in heart and other tissues.
Collapse
Affiliation(s)
- F F-T Ch'en
- Burdon Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, Division of Medical Sciences, Oxford University, Oxford, UK
| | | | | | | | | |
Collapse
|
19
|
Xue J, Zhou D, Yao H, Haddad GG. Role of transporters and ion channels in neuronal injury under hypoxia. Am J Physiol Regul Integr Comp Physiol 2007; 294:R451-7. [PMID: 17977915 DOI: 10.1152/ajpregu.00528.2007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aims of the current study were to 1) examine the effects of hypoxia and acidosis on cultured cortical neurons and 2) explore the role of transporters and ion channels in hypoxic injury. Cell injury was measured in cultured neurons or hippocampal slices following hypoxia (1% O(2)) or acidosis (medium pH 6.8) treatment. Inhibitors of transporters and ion channels were employed to investigate their roles in hypoxic injury. Our results showed that 1) neuronal damage was apparent at 5-7 days of hypoxia exposure, i.e., 36-41% of total lactate dehydrogenase was released to medium and 2) acidosis alone did not lead to significant injury compared with nonacidic, normoxic controls. Pharmacological studies revealed 1) no significant difference in neuronal injury between controls (no inhibitor) and inhibition of Na(+)-K(+)-ATP pump, voltage-gated Na(+) channel, ATP-sensitive K(+) channel, or reverse mode of Na(+)/Ca(2+) exchanger under hypoxia; however, 2) inhibition of NBCs with 500 microM DIDS did not cause hypoxic death in either cultured cortical neurons or hippocampal slices; 3) in contrast, inhibition of Na(+)/H(+) exchanger isoform 1 (NHE1) with either 10 microM HOE-642 or 2 microM T-162559 resulted in dramatic hypoxic injury (+95% for HOE-642 and +100% for T-162559 relative to normoxic control, P < 0.001) on treatment day 3, when no death occurred for hypoxic controls (no inhibitor). No further damage was observed by NHE1 inhibition on treatment day 5. We conclude that inhibition of NHE1 accelerates hypoxia-induced neuronal damage. In contrast, DIDS rescues neuronal death under hypoxia. Hence, DIDS-sensitive mechanism may be a potential therapeutic target.
Collapse
Affiliation(s)
- Jin Xue
- Department of Pediatrics, University of California-San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0735, USA
| | | | | | | |
Collapse
|
20
|
Wei GZ, Zhou JJ, Wang B, Wu F, Bi H, Wang YM, Yi DH, Yu SQ, Pei JM. Diastolic Ca2+ overload caused by Na+/Ca2+ exchanger during the first minutes of reperfusion results in continued myocardial stunning. Eur J Pharmacol 2007; 572:1-11. [PMID: 17822695 DOI: 10.1016/j.ejphar.2007.05.065] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2007] [Revised: 05/22/2007] [Accepted: 05/24/2007] [Indexed: 10/23/2022]
Abstract
The pathogenesis of myocardial stunning caused by brief ischemia and reperfusion remains unclear. The aim of the present study was to investigate the underlying mechanism of myocardial stunning. An isolated cell model of myocardial stunning was firstly established in isolated rat ventricular myocytes exposed to 8 min of simulated ischemia and 30 min of reperfusion, the cardiomyocyte contractile function was used to evaluate myocardial stunning. A diastolic Ca(2+) overload without significant changes in systolic Ca(2+) and the amplitude of Ca(2+) transient during the first 10 min of reperfusion played an important role in the occurrence of myocardial stunning. Decreasing Ca(2+) entry into myocardial cells with low Ca(2+) reperfusion was a very efficient way to prevent myocardial stunning. Diastolic Ca(2+) overload was closely related to the reverse mode of Na(+)/Ca(2+) exchanger (NCX) rather than L-type Ca(2+) channel. The activity of the reverse mode of NCX was found significantly higher at the initial time of reperfusion, and KB-R7943, a selective inhibitor of the reverse mode of NCX, administered at first 10 min of reperfusion rather than at the time of ischemia significantly attenuated myocardial stunning. In addition, NCX inhibition also attenuated the Ca(2+) oscillation and cardiac dysfunction when field stimulus was stopped at first 10 min of reperfusion. These data suggest that one of the important mechanisms of triggering myocardial stunning is diastolic Ca(2+) overload caused by activation of the reverse mode of NCX of cardiomyocytes during the initial period of reperfusion following brief ischemia.
Collapse
Affiliation(s)
- Geng-Ze Wei
- Department of Physiology, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, PR China
| | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Lequerica JL, O'Connor JE, Such L, Alberola A, Meseguer I, Dolz M, Torreblanca M, Moya A, Colom F, Soria B. A halocin acting on Na+/H+ exchanger of haloarchaea as a new type of inhibitor in NHE of mammals. J Physiol Biochem 2007; 62:253-62. [PMID: 17615951 DOI: 10.1007/bf03165754] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
The capability of halocin H6 (a bacteriocin-like protein produced by haloarchaea Haloferax gibbonsii) to inhibit Na+/H+ exchanger (NHE) in mammalian cells and its cardio-protective efficacy on the ischemic and reperfused myocardium were evaluated in the present study. H6 inhibits NHE activity (measured by a flow cytometry method) in a dose-dependent form of cell lines of mammalian origin (HEK293, NIH3T3, Jurkat and HL-1) as well as in primary cell culture from human skeletal muscle (myocytes and fibroblasts). In vivo, an ischemia-reperfusion model in dogs by coronary arterial occlusion was used (two hours of regional ischemia and three hours of reperfusion). In animals treated with halocin H6 there was a significant reduction of premature ventricular ectopic beats and infarct size, whereas blood pressure and heart rate remained unchanged. Up to date, halocin H6 is the only described biological molecule that exerts a specific inhibitory activity in NHE of eukaryotic cells.
Collapse
Affiliation(s)
- J L Lequerica
- Instituto de Biomedicina, Spanish Council for Scientific Research CSIC, Valencia.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
22
|
Saini HK, Elimban V, Ozcelikay AT, Dhalla NS. Mechanisms of cardiodepression by an Na+-H+ exchange inhibitor methyl-N-isobutyl amiloride (MIA) on the heart: lack of beneficial effects in ischemia-reperfusion injury. Can J Physiol Pharmacol 2007; 85:67-78. [PMID: 17487246 DOI: 10.1139/y06-099] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Although Na+-H+ exchange (NHE) inhibitors such as methyl-N-isobutyl amiloride (MIA) are known to depress the cardiac function, the mechanisms of their negative inotropic effect are not completely understood. In this study, isolated rat hearts were perfused with MIA to study its action on cardiac performance, whereas isolated subcellular organelles such as sarcolemma, myofibrils, sarcoplasmic reticulum, and mitochondria were treated with MIA to determine its effect on their function. The effect of MIA on intracellular Ca2+ mobilization was examined in fura-2-AM-loaded cardiomyocytes. MIA was observed to depress cardiac function in a concentration-dependent manner in HCO3- -free buffer. On the other hand, MIA had an initial positive inotropic effect followed by a negative inotropic effect in HCO3-containing buffer. MIA increased the basal concentration of intracellular Ca2+ ([Ca2+]i) and augmented the KCl-mediated increase in [Ca2+]i. MIA did not show any direct effect on myofibrils, sarcolemma, and sarcoplasmic reticulum ATPase activities; however, this agent was found to decrease the intracellular pH, which reduced the myofibrils Ca2+-stimulated ATPase activity. MIA also increased Ca2+ uptake by mitochondria without having any direct effect on sarcoplasmic reticulum Ca2+ uptake. In addition, MIA did not protect the hearts subjected to mild Ca2+ paradox as well as ischemia-reperfusion-mediated injury. These results suggest that the increase in [Ca2+]i in cardiomyocytes may be responsible for the initial positive inotropic effect of MIA, but its negative inotropic action may be due to mitochondrial Ca2+ overloading as well as indirect depression of myofibrillar Ca2+ ATPase activity. Thus the accumulation of [H+]i as well as occurrence of intracellular and mitochondrial Ca2+ overload may explain the lack of beneficial effects of MIA in preventing the ischemia-reperfusion-induced myocardial injury.
Collapse
Affiliation(s)
- Harjot K Saini
- Institute of Cardiovascular Sciences, St. Boniface General Hospital Research Centre, and Department of Physiology, Faculty of Medicine, University of Manitoba, 351 Tache Avenue, Winnipeg, MB R2H 2A6, Canada
| | | | | | | |
Collapse
|
23
|
Yamamoto T, Shirayama T, Sakatani T, Takahashi T, Tanaka H, Takamatsu T, Spitzer KW, Matsubara H. Enhanced activity of ventricular Na+-HCO3- cotransport in pressure overload hypertrophy. Am J Physiol Heart Circ Physiol 2007; 293:H1254-64. [PMID: 17416604 DOI: 10.1152/ajpheart.00964.2006] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The Na(+)-HCO(3)(-) cotransporter (NBC) plays a key role in intracellular pH (pH(i)) regulation in normal ventricular muscle. However, the state of NBC in nonischemic hypertrophied hearts is unresolved. In this study, we examined functional and molecular properties of NBC in adult rat ventricular myocytes. The cells were enzymatically isolated from both normal and hypertrophied hearts. Ventricular hypertrophy was induced by pressure overload created by suprarenal abdominal aortic constriction of 50% for 7 wk. pH(i) was measured in single cells using the fluorescent pH indicator 2',7'-bis(2-carboxyethyl)5-(6)carboxyfluorescein. Real-time PCR analysis was used to quantitatively assess expression of NBC-encoding mRNA, including SLC4A4 (encoding electrogenic NBC, NBCe1) and SLC4A7 (electroneutral NBC, NBCn1). Our results demonstrate that: 1) mRNA levels of both the electrogenic NBCe1 (SLC4A4) and electroneutral NBCn1 (SLC4A7) forms of NBC were increased by aortic constriction, 2) the onset of NBC upregulation occurred within 3 days after constriction, 3) normal and hypertrophied ventricles displayed regional differences in NBC expression, 4) acid extrusion via NBC (J(NBC)) was increased significantly in hypertrophied myocytes, 5) although acid extrusion via Na(+)/H(+) exchange was also increased in hypertrophied myocytes, the relative enhancement of J(NBC) was larger, 6) membrane depolarization markedly increased J(NBC) in hypertrophied myocytes, and 7) losartan, an ANG II AT(1) receptor antagonist, significantly attenuated the upregulation of both NBCs induced by 3 wk of aortic constriction. Enhanced NBC activity during hypertrophic development provides a mechanism for intracellular Na(+) overload, which may render the ventricles more vulnerable to Ca(2+) overload during ischemia-reperfusion.
Collapse
MESH Headings
- Angiotensin II Type 1 Receptor Blockers/pharmacology
- Animals
- Aorta, Abdominal/surgery
- Disease Models, Animal
- Heart Ventricles/metabolism
- Hydrogen-Ion Concentration
- Hypertension/complications
- Hypertension/genetics
- Hypertension/metabolism
- Hypertrophy, Left Ventricular/etiology
- Hypertrophy, Left Ventricular/genetics
- Hypertrophy, Left Ventricular/metabolism
- Ligation
- Losartan/pharmacology
- Male
- Membrane Potentials
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/metabolism
- RNA, Messenger/metabolism
- Rats
- Rats, Wistar
- Sodium-Bicarbonate Symporters/genetics
- Sodium-Bicarbonate Symporters/metabolism
- Sodium-Potassium-Exchanging ATPase/metabolism
- Time Factors
- Transcription, Genetic/drug effects
- Up-Regulation
Collapse
Affiliation(s)
- Taku Yamamoto
- Department of Cardiology and Vascular Regenerative Medicine, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto 602-8566, Japan.
| | | | | | | | | | | | | | | |
Collapse
|
24
|
Vila-Petroff M, Salas MA, Said M, Valverde CA, Sapia L, Portiansky E, Hajjar RJ, Kranias EG, Mundiña-Weilenmann C, Mattiazzi A. CaMKII inhibition protects against necrosis and apoptosis in irreversible ischemia-reperfusion injury. Cardiovasc Res 2006; 73:689-98. [PMID: 17217936 DOI: 10.1016/j.cardiores.2006.12.003] [Citation(s) in RCA: 184] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2006] [Revised: 11/14/2006] [Accepted: 12/04/2006] [Indexed: 11/30/2022] Open
Abstract
OBJECTIVES Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) has been implicated in the regulation of cardiac excitation-contraction coupling (ECC) as well as in apoptotic signaling and adverse remodeling. The goal of the present study is to investigate the role of CaMKII in irreversible ischemia and reperfusion (I/R) injury. METHODS Isovolumic Langendorff perfused rat hearts were subjected to global no-flow I/R (45 min/120 min), and isolated myocytes were subjected to a protocol of simulated I/R (45 min simulated ischemia/60 min reoxygenation) either in the absence or presence of CaMKII inhibition [KN-93 (KN) or the CaMKII inhibitory peptide (AIP)]. RESULTS In I/R hearts, an increase in CaMKII activity at the beginning of reperfusion was confirmed by the significantly increased phosphorylation of the Thr(17) site of phospholamban. In the presence of KN, contractile recovery at the end of reperfusion was almost double that of I/R hearts. This recovery was associated with a significant decrease in the extent of infarction, lactate dehydrogenase release (necrosis), TUNEL-positive cells, caspase-3 activity, and an increase in the Bcl-2/Bax ratio (apoptosis). In isolated myocytes, both KN and AIP prevented simulated I/R-induced spontaneous contractile activity and cell mortality. Similar results were obtained when inhibiting the reverse mode Na(+)/Ca(2+) exchanger (NCX) with KB-R7943, sarcoplasmic reticulum (SR) function with ryanodine and thapsigargin, or SR Ca(2+) release with tetracaine. In contrast, overexpression of CaMKII decreased cell viability from 52+/-3% to 26+/-2%. CONCLUSIONS Taken together, the present findings are the first to establish CaMKII as a fundamental component of a cascade of events integrating the NCX, the SR, and mitochondria that promote cellular apoptosis and necrosis in irreversible I/R injury.
Collapse
Affiliation(s)
- Martin Vila-Petroff
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, 60 y 120, (1900) La Plata, Argentina
| | | | | | | | | | | | | | | | | | | |
Collapse
|
25
|
Villa-Abrille MC, Petroff MGV, Aiello EA. The electrogenic Na+/HCO3- cotransport modulates resting membrane potential and action potential duration in cat ventricular myocytes. J Physiol 2006; 578:819-29. [PMID: 17138608 PMCID: PMC2151338 DOI: 10.1113/jphysiol.2006.120170] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Perforated whole-cell configuration of patch clamp was used to determine the contribution of the electrogenic Na+/HCO3- cotransport (NBC) on the shape of the action potential in cat ventricular myocytes. Switching from Hepes to HCO3- buffer at constant extracellular pH (pH(o)) hyperpolarized resting membrane potential (RMP) by 2.67 +/- 0.42 mV (n = 9, P < 0.05). The duration of action potential measured at 50% of repolarization time (APD50) was 35.8 +/- 6.8% shorter in the presence of HCO3- than in its absence (n = 9, P < 0.05). The anion blocker SITS prevented and reversed the HCO3- -induced hyperpolarization and shortening of APD. In addition, no HCO3- -induced hyperpolarization and APD shortening was observed in the absence of extracellular Na+. Quasi-steady-state currents were evoked by 8 s duration voltage-clamped ramps ranging from -130 to +30 mV. A novel component of SITS-sensitive current was observed in the presence of HCO3-. The HCO3- -sensitive current reversed at -87 +/- 5 mV (n = 7), a value close to the expected reversal potential of an electrogenic Na+/HCO3- cotransport with a HCO3-:Na+ stoichiometry ratio of 2: 1. The above results allow us to conclude that the cardiac electrogenic Na+/HCO3- cotransport has a relevant influence on RMP and APD of cat ventricular cells.
Collapse
Affiliation(s)
- María C Villa-Abrille
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, 60 y 120, La Plata 1900, Argentina
| | | | | |
Collapse
|
26
|
Dolz M, O'Connor JE, Lequerica JL. Flow cytometric kinetic assay of the activity of Na+/H+ antiporter in mammalian cells. Cytometry A 2005; 61:99-104. [PMID: 15382148 DOI: 10.1002/cyto.a.20077] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
BACKGROUND The Na(+)/H(+) exchanger (NHE) of mammalian cells is an integral membrane protein that extrudes H(+) ion in exchange for extracellular Na(+) and plays a crucial role in the regulation of intracellular pH (pHi). Thus, when pHi is lowered, NHE extrudes protons at a rate depending of pHi that can be expressed as pH units/s. METHODS To abolish the activity of other cellular pH-restoring systems, cells were incubated in bicarbonate-free Dulbecco's modified Eagle's medium buffered with HEPES. Flow cytometry was used to determine pHi with 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein acetoxymethyl ester or 5-(and-6)-carboxy SNARF-1 acetoxymethyl ester acetate, and the appropriate fluorescence ratios were measured. The calibration of fluorescence ratios versus pHi was established by using ionophore nigericin. The activity of NHE was calculated by a kinetic flow cytometric assay as the slope at time 0 of the best-fit curve of pHi recovery versus time after intracellular acidification with a pulse of exogenous sodium propionate. RESULTS The kinetic method allowed determination of the pHi-dependent activity of NHE in cell lines and primary cell cultures. NHE activity values were demonstrated to be up to 0.016 pH units/s within the pHi range of 7.3 to 6.3. The inhibition of NHE activity by the specific inhibitor ethyl isopropyl amiloride was easily detected by this method. CONCLUSIONS The assay conditions can be used to relate variations in pHi with the activity of NHE and provide a standardized method to compare between different cells, inhibitors, models of ischemia by acidification, and other relevant experimental or clinical situations.
Collapse
Affiliation(s)
- María Dolz
- Unidad de Investigaciones Cardíacas, Departamento de Biología y Terapia Molecular y Celular, Instituto de Biomedicina de Valencia, Consejo Superior de Investigaciones Científicas, Valencia, Spain
| | | | | |
Collapse
|
27
|
Ten Hove M, Nederhoff MGJ, Van Echteld CJA. Relative contributions of Na+/H+exchange and Na+/HCO3−cotransport to ischemic Nai+overload in isolated rat hearts. Am J Physiol Heart Circ Physiol 2005; 288:H287-92. [PMID: 15319198 DOI: 10.1152/ajpheart.01102.2003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Na+/H+exchanger (NHE) and/or the Na+/HCO3−cotransporter (NBC) were blocked during ischemia in isolated rat hearts. Intracellular Na+concentration ([Na+]i), intracellular pH (pHi), and energy-related phosphates were measured by using simultaneous23Na and31P NMR spectroscopy. Hearts were subjected to 30 min of global ischemia and 30 min of reperfusion. Cariporide (3 μM) or HCO3−-free HEPES buffer was used, respectively, to block NHE, NBC, or both. End-ischemic [Na+]iwas 320 ± 18% of baseline in HCO3−-perfused, untreated hearts, 184 ± 6% of baseline when NHE was blocked, 253 ± 19% of baseline when NBC was blocked, and 154 ± 6% of baseline when both NHE and NBC were blocked. End-ischemic pHiwas 6.09 ± 0.06 in HCO3−-perfused, untreated hearts, 5.85 ± 0.02 when NHE was blocked, 5.81 ± 0.05 when NBC was blocked, and 5.70 ± 0.01 when both NHE and NBC were blocked. NHE blockade was cardioprotective, but NBC blockade and combined blockade were not, the latter likely due to a reduction in coronary flow, because omission of HCO3−under conditions of NHE blockade severely impaired coronary flow. Combined blockade of NHE and NBC conserved intracellular H+load during reperfusion and led to massive Na+influx when blockades were lifted. Without blockade, both NHE and NBC mediate acid-equivalent efflux in exchange for Na+influx during ischemia, NHE much more than NBC. Blockade of either one does not affect the other.
Collapse
Affiliation(s)
- Michiel Ten Hove
- Interuniversity Cardiology, Institute of the Netherlands, Utrecht, The Netherlands
| | | | | |
Collapse
|
28
|
Yamamoto T, Swietach P, Rossini A, Loh SH, Vaughan-Jones RD, Spitzer KW. Functional diversity of electrogenic Na+-HCO3- cotransport in ventricular myocytes from rat, rabbit and guinea pig. J Physiol 2004; 562:455-75. [PMID: 15550467 PMCID: PMC1665517 DOI: 10.1113/jphysiol.2004.071068] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The Na(+)-HCO(3)(-) cotransporter (NBC) is an important sarcolemmal acid extruder in cardiac muscle. The characteristics of NBC expressed functionally in heart are controversial, with reports suggesting electroneutral (NBCn; 1HCO(3)(-) : 1Na(+); coupling coefficient N= 1) or electrogenic forms of the transporter (NBCe; equivalent to 2HCO(3)(-) : 1Na(+); N= 2). We have used voltage-clamp and epifluorescence techniques to compare NBC activity in isolated ventricular myocytes from rabbit, rat and guinea pig. Depolarization (by voltage clamp or hyperkalaemia) reversibly increased steady-state pH(i) while hyperpolarization decreased it, effects seen only in CO(2)/HCO(3)(-)-buffered solutions, and blocked by S0859 (cardiac NBC inhibitor). Species differences in amplitude of these pH(i) changes were rat > guinea pig approximately rabbit. Tonic depolarization (-140 mV to -0 mV) accelerated NBC-mediated pH(i) recovery from an intracellular acid load. At 0 mV, NBC-mediated outward current at resting pH(i) was +0.52 +/- 0.05 pA pF(-1) (rat, n= 5), +0.26 +/- 0.05 pA pF(-1) (guinea pig, n= 5) and +0.10 +/- 0.03 pA pF(-1) (rabbit, n= 9), with reversal potentials near -100 mV, consistent with N= 2. The above results indicate a functionally active voltage-sensitive NBCe in these species. Voltage-clamp hyperpolarization negative to the reversal potential for NBCe failed, however, to terminate or reverse NBC-mediated pH(i)-recovery from an acid load although it was slowed significantly, suggesting electroneutral NBC may also be operational. NBC-mediated pH(i) recovery was associated with a rise of [Na(+)](i) at a rate approximately 25% of that mediated via NHE, and consistent with an apparent NBC stoichiometry between N= 1 and N= 2. In conclusion, NBCe in the ventricular myocyte displays considerable functional variation among the three species tested (greatest in rat, least in rabbit) and may coexist with some NBCn activity.
Collapse
Affiliation(s)
- Taku Yamamoto
- Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT 84112, USA.
| | | | | | | | | | | |
Collapse
|
29
|
Castellá M, Buckberg GD, Saleh S, Tan Z, Ignarro LJ. A new role for cardioplegic buffering: should acidosis or calcium accumulation be counteracted to salvage jeopardized hearts? J Thorac Cardiovasc Surg 2003; 126:1442-8. [PMID: 14666017 DOI: 10.1016/s0022-5223(03)00599-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES Thirty minutes of unprotected ischemia produced a jeopardized heart that was treated with a blood cardioplegic solution containing the natural erythrocyte and protein buffers. Cardioplegic pH was changed to 7.7 (buffered) or 7.2 (nonbuffered), and this was tested alone and after pretreatment with Na(+)-H(+) exchange blockade (cariporide) to define their protective effects. METHODS Twenty-four Yorkshire-Duroc pigs (27-34.5 kg) underwent 30 minutes of normothermic global ischemia, followed by 30 minutes of aortic clamping during protection with buffered (n = 12) or nonbuffered (n = 12) glutamate-aspartate-enriched blood cardioplegic solution. Twelve hearts (6 buffered and 6 nonbuffered) were pretreated with intravenous cariporide (5 mg/kg) 15 minutes before ischemia. RESULTS Severe and comparable left ventricle dysfunction followed buffered or nonbuffered cardioplegia: Preload recruitable stroke work recovered to 56% +/- 21% and 45% +/- 20% of baseline levels; creatine kinase MB, conjugated dienes, and myeloperoxidase activity markedly increased; moderate myocardial edema occurred; and endothelin-1 increased 2-fold more than baseline values. Cariporide pretreatment caused a similar return of preload recruitable stroke work to 86% +/- 9% and 90% +/- 6% after buffered or nonbuffered cardioplegia (P <.05 vs nonpretreated groups), allowed only minor creatine kinase MB and conjugated diene changes, and reduced endothelin-1 release 3-fold compared with hearts without sodium-hydrogen exchange blockage. CONCLUSIONS The severe ischemia-reperfusion injury of 30 minutes of normothermic ischemia is not altered by an acidic or alkalotic pH cardioplegic solution. Correction of damage is achieved by adding Na(+)-H(+) exchange blocker therapy before treatment with buffered and nonbuffered solutions; thus, sodium-hydrogen exchange inhibition plays a more vital role in recovery than pH management.
Collapse
Affiliation(s)
- Manuel Castellá
- Department of Surgery, Division of Cardiothoracic Surgery, University of California, Los Angeles, School of Medicine, USA
| | | | | | | | | |
Collapse
|
30
|
Ch'en FFT, Dilworth E, Swietach P, Goddard RS, Vaughan-Jones RD. Temperature dependence of Na+-H+ exchange, Na+-HCO3- co-transport, intracellular buffering and intracellular pH in guinea-pig ventricular myocytes. J Physiol 2003; 552:715-26. [PMID: 12923205 PMCID: PMC2343456 DOI: 10.1113/jphysiol.2003.051888] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 07/24/2003] [Accepted: 08/15/2003] [Indexed: 12/14/2022] Open
Abstract
Almost all aspects of cardiac function are sensitive to modest changes of temperature. We have examined the thermal sensitivity of intracellular pH regulation in the heart. To do this we determined the temperature sensitivity of pHi, intracellular buffering capacity, and the activity of sarcolemmal acid-extrusion proteins, Na+-H+ exchange (NHE) and Na+-HCO3- co-transport (NBC) in guinea-pig isolated ventricular myocytes. pHi was recorded fluorimetrically with acetoxymethyl (AM)-loaded carboxy-SNARF-1 at either 27 or 37 degrees C. At 27 degrees C, intrinsic (non-CO2-dependent) buffering power (betai) was approximately 60% of that at 37 degrees C. Acid-extrusion (Je) through NHE was approximately 50% slower than at 37 degrees C, consistent with a Q10 of approximately 2. In 5% CO2/HCO3--buffered conditions, in the presence of 30 microM cariporide to inhibit NHE, acid extrusion via NBC was also slowed at 27 degrees C, suggestive of a comparable Q10. Resting pHi at 27 degrees C was similar in Hepes- or 5% CO2/HCO3--buffered superfusates but, in both cases, was approximately 0.1 pH units lower at 37 degrees C. The higher the starting pHi, the larger was the thermally induced fall of pHi, consistent with a mathematical model where intrinsic buffers with a low principal pKa (e.g. close to 6.0) are less temperature-sensitive than those with a higher pKa. The high temperature sensitivity of pHi regulation in mammalian cardiac cells has implications for experimental work conducted at room temperature. It also has implications for the ability of intracellular acidosis to generate intracellular Na+ and Ca2+ overload, cardiac injury and arrhythmia in the heart.
Collapse
Affiliation(s)
- Frederick F-T Ch'en
- Burdon Sanderson Cardiac Science Centre, University Laboratory of Physiology, University of Oxford, Parks Road, Oxford OX1 3PT, UK
| | | | | | | | | |
Collapse
|
31
|
ten Hove M, van Emous JG, van Echteld CJA. Na+ overload during ischemia and reperfusion in rat hearts: comparison of the Na+/H+ exchange blockers EIPA, cariporide and eniporide. Mol Cell Biochem 2003; 250:47-54. [PMID: 12962142 DOI: 10.1023/a:1024985931797] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Intracellular myocardial Na+ overload during ischemia is an important cause of reperfusion injury via reversed Na+/Ca2+ exchange. Prevention of this Na+ overload can be accomplished by blocking the different Na+ influx routes. In this study the effect of ischemic inhibition of the Na+/H+ exchanger (NHE) on [Na+]i, pH, and post-ischemic contractile recovery was tested, using three different NHE-blockers: EIPA, cariporide and eniporide. pHi and [Na+]i were measured using simultaneous 31P and 23Na NMR spectroscopy, respectively, in paced (5 Hz) isolated, Langendorff perfused rat hearts while contractility was assessed by an intraventricular balloon. NHE-blockers (3 microM) were administered during 5 min prior to 30 min of global ischemia followed by 30 min drug-free reperfusion. NHE blockade markedly reduced ischemic Na+ overload; after 30 min of ischemia [Na+]i had increased to 293 +/- 26, 212 +/- 6, 157 +/- 5 and 146 +/- 6% of baseline values in untreated and EIPA (p < 0.01 vs. untreated), cariporide (p < 0.01 vs. untreated) and eniporide (p < 0.01 vs. untreated) treated hearts, respectively. Ischemic acidosis did not differ significantly between groups. During reperfusion, however, recovery of pH, was significantly delayed in treated hearts. The rate pressure product recovered to 12.0 +/- 1.9, 12.1 +/- 2.1, 19.5 +/- 2.8 and 20.4 +/- 2.5 x 10(3) mmHg/min in untreated and EIPA, cariporide (p < 0.01 vs. untreated) and eniporide (p < 0.01 vs. untreated) treated hearts, respectively. In conclusion, blocking the NHE reduced ischemic Na+ overload and improved post-ischemic contractile recovery. EIPA, however, was less effective and exhibited more side effects than cariporide and eniporide in the concentrations used.
Collapse
Affiliation(s)
- Michiel ten Hove
- Interuniversity Cardiology Institute of The Netherlands, Utrecht
| | | | | |
Collapse
|
32
|
Abstract
As of yet, only a few strategies to prevent myocardial reperfusion injury have been tested clinically. In the first minutes of reperfusion, the myocardium can be damaged by contracture development, causing mechanical stiffness, tissue necrosis, and the "stone heart" phenomenon. Reperfusion-induced contracture can have two different causes, namely, Ca2+overload-induced contracture or rigor-type contracture. Ca2+ contracture results from rapid re-energization of contractile cells with a persistent Ca2+ overload. Strategies to prevent this type of injury are directed at cytosolic Ca2+ control or myofibrillar Ca2+ sensitivity. Rigor-contracture occurs when re-energization proceeds very slowly. It does not depend on Ca2+ overload. It may be prevented by strategies improving early mitochondrial reactivation
Collapse
Affiliation(s)
- H Michael Piper
- Physiologisches Institut, Justus-Liebig-Universität, Giessen, Germany.
| | | | | |
Collapse
|
33
|
Abstract
Exacerbation of hypoxic injury after restoration of oxygenation (reoxygenation) is an important mechanism of cellular injury in transplantation and in myocardial, hepatic, intestinal, cerebral, renal, and other ischemic syndromes. Cellular hypoxia and reoxygenation are two essential elements of ischemia-reperfusion injury. Activated neutrophils contribute to vascular reperfusion injury, yet posthypoxic cellular injury occurs in the absence of inflammatory cells through mechanisms involving reactive oxygen (ROS) or nitrogen species (RNS). Xanthine oxidase (XO) produces ROS in some reoxygenated cells, but other intracellular sources of ROS are abundant, and XO is not required for reoxygenation injury. Hypoxic or reoxygenated mitochondria may produce excess superoxide (O) and release H(2)O(2), a diffusible long-lived oxidant that can activate signaling pathways or react vicinally with proteins and lipid membranes. This review focuses on the specific roles of ROS and RNS in the cellular response to hypoxia and subsequent cytolytic injury during reoxygenation.
Collapse
Affiliation(s)
- Chuanyu Li
- Department of Veterans Affairs Medical Center, Birmingham 35233, USA
| | | |
Collapse
|
34
|
Salameh A, Dhein S, Beuckelmann DJ. Role of the cardiac Na(+)/H(+)exchanger in [Ca(2+)](i)and [Na(+)](i)handling during intracellular acidosis. Effect of cariporide (Hoe 642). Pharmacol Res 2002; 45:35-41. [PMID: 11820859 DOI: 10.1006/phrs.2001.0908] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Intracellular acidosis is one of the alterations occurring in cardiac ischemia and has been discussed to be important in altering excitation--contraction coupling. The aim of this study was to determine how intracellular acidosis may affect intracellular sodium and calcium handling. Cardiomyocytes were isolated from the hearts of adult male guinea-pigs by standard techniques and superfused with modified Tyrode's solution at room temperature, either HEPES buffered containing 10 mM NaHCO(3)or HEPES buffered without NaHCO(3), in order to examine a possible interaction with the sodium bicarbonate symport. The whole cell voltage clamp technique was used utilizing 3 M Omega pipettes filled with (mM): Cs aspartate 120, CsCl 20, MgCl(2)1, NaCl 5, Mg-ATP 2, HEPES 10 and either 100 microM Fura-2 or 100 microM SBFI. The pH of the pipette solution was either 7.2 or 6.5. Cells were kept at a holding potential of -80 mV and after a pre-pulse to -40 mV the membrane was continuously clamped to potentials from -30 to +80 mV in 10 mV steps. Intracellular Ca(2+)or Na(+)were estimated using the Fura-2 or SBFI technique (impermeable salt), respectively. The cardiac Na(+)/H(+)exchanger was inhibited using the Na(+)/H(+)- exchange inhibitor cariporide (Hoe 642) (1 microM), when indicated. In NaHCO(3)-free experiments we found an increase in intracellular sodium reflected by a rise in the SBFI ratio of 0.326 +/- 0.01 upon intracellular acidification, in contrast to cells perfused at pH = 7.2 (no significant increase in intracellular Na(+)) (P< 0.05). There was no difference in intracellular calcium handling between cells perfused with solutions of pH = 7.2 or 6.5 (Fura-2 Delta ratio: 0.79 +/- 0.10 vs 0.82 +/- 0.07, n.s.). The l -type calcium current also remained unchanged. Blockade of the Na(+)/H(+)exchanger by Hoe 642 had no influence on cells perfused at pH = 7.2 but inhibited the increase in intracellular Na(+)at pH = 6.5 (0.023 +/- 0.026 in the presence of Hoe 642 vs 0.326 +/- 0.01 without Hoe 642, P< 0.05) without affecting [Ca(2+)](i)or the L-type calcium current. In cells superfused with a Tyrode solution containing NaHCO(3), the increase in intracellular sodium concentration was even more pronounced. Under these conditions Hoe 642 also antagonized this increase in intracellular sodium but without reaching the control level. We conclude that under these experimental conditions intracellular acidification causes an increase in [Na(+)](i)without changing intracellular Ca(2+)or the L-type calcium current. In addition in bicarbonate-buffered systems the acidosis-induced increase in sodium is enhanced which may involve the Na(+)/HCO(3)(minus sign)symport. The effect of cariporide (Hoe 642) in intracellular acidosis seems to be based on antagonization of the rise in intracellular sodium rather than calcium in this model.
Collapse
Affiliation(s)
- Aida Salameh
- Medizinische Klinik I, Abt. Kardiologie, Universität Leipzig, Johannisallee 32, 04103 Leipzig, Germany.
| | | | | |
Collapse
|
35
|
Sharikabad MN, Ostbye KM, Brørs O. Increased [Mg2+]o reduces Ca2+ influx and disruption of mitochondrial membrane potential during reoxygenation. Am J Physiol Heart Circ Physiol 2001; 281:H2113-23. [PMID: 11668073 DOI: 10.1152/ajpheart.2001.281.5.h2113] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Increase in extracellular Mg2+ concentration ([Mg2+]o) reduces Ca2+ accumulation during reoxygenation of hypoxic cardiomyocytes and exerts protective effects. The aims of the present study were to investigate the effect of increased [Mg(2+)](o) on Ca2+ influx and efflux, free cytosolic Ca2+ ([Ca2+]i) and Mg2+ concentrations ([Mg2+]i), Ca2+ accumulation in the presence of inhibitors of mitochondrial or sarcoplasmatic reticulum Ca2+ transport, and finally mitochondrial membrane potential (Delta(psi)m). Isolated adult rat cardiomyocytes were exposed to 1 h of hypoxia and subsequent reoxygenation. Cell Ca2+ was determined by 45Ca2+ uptake, and the levels of [Mg2+]i and [Ca2+]i were determined by flow cytometry as the fluorescence of magnesium green and fluo 3, respectively. Ca2+ influx rate was significantly reduced by approximately 40%, whereas Ca2+ efflux was not affected by increased [Mg2+]o (5 mM) during reoxygenation. [Ca2+]i and [Mg2+]i were increased at the end of hypoxia, fell after reoxygenation, and were unaffected by increased [Mg2+]o. Clonazepam, a selective mitochondrial Na+/Ca2+ exchange inhibitor (100 microM), significantly reduced Ca2+ accumulation by 70% and in combination with increased [Mg2+]o by 90%. Increased [Mg2+]o, clonazepam, and the combination of both attenuated the hypoxia-reoxygenation-induced reduction in Delta(psi)m, determined with the cationic dye JC-1 by flow cytometry. A significant inverse correlation was observed between Delta(psi)m and cell Ca2+ in reoxygenated cells treated with increased [Mg2+]o and clonazepam. In conclusion, increased [Mg2+]o (5 mM) inhibits Ca2+ accumulation by reducing Ca2+ influx and preserves Delta(psi)m without affecting [Ca2+]i and [Mg2+]i during reoxygenation. Preservation of mitochondria may be an important effect whereby increased [Mg2+]o protects the postischemic heart.
Collapse
Affiliation(s)
- M N Sharikabad
- Division of Clinical Pharmacology and Toxicology, Clinical Chemistry Department, Ullevaal University Hospital, N-0407 Oslo, Norway.
| | | | | |
Collapse
|