1
|
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: 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: 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.
Collapse
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
| |
Collapse
|
2
|
Hulikova A, Park KC, Loonat AA, Gunadasa-Rohling M, Curtis MK, Chung YJ, Wilson A, Carr CA, Trafford AW, Fournier M, Moshnikova A, Andreev OA, Reshetnyak YK, Riley PR, Smart N, Milne TA, Crump NT, Swietach P. Alkaline nucleoplasm facilitates contractile gene expression in the mammalian heart. Basic Res Cardiol 2022; 117:17. [PMID: 35357563 PMCID: PMC8971196 DOI: 10.1007/s00395-022-00924-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 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: 09/13/2021] [Revised: 03/04/2022] [Accepted: 03/11/2022] [Indexed: 01/31/2023]
Abstract
Cardiac contractile strength is recognised as being highly pH-sensitive, but less is known about the influence of pH on cardiac gene expression, which may become relevant in response to changes in myocardial metabolism or vascularization during development or disease. We sought evidence for pH-responsive cardiac genes, and a physiological context for this form of transcriptional regulation. pHLIP, a peptide-based reporter of acidity, revealed a non-uniform pH landscape in early-postnatal myocardium, dissipating in later life. pH-responsive differentially expressed genes (pH-DEGs) were identified by transcriptomics of neonatal cardiomyocytes cultured over a range of pH. Enrichment analysis indicated "striated muscle contraction" as a pH-responsive biological process. Label-free proteomics verified fifty-four pH-responsive gene-products, including contractile elements and the adaptor protein CRIP2. Using transcriptional assays, acidity was found to reduce p300/CBP acetylase activity and, its a functional readout, inhibit myocardin, a co-activator of cardiac gene expression. In cultured myocytes, acid-inhibition of p300/CBP reduced H3K27 acetylation, as demonstrated by chromatin immunoprecipitation. H3K27ac levels were more strongly reduced at promoters of acid-downregulated DEGs, implicating an epigenetic mechanism of pH-sensitive gene expression. By tandem cytoplasmic/nuclear pH imaging, the cardiac nucleus was found to exercise a degree of control over its pH through Na+/H+ exchangers at the nuclear envelope. Thus, we describe how extracellular pH signals gain access to the nucleus and regulate the expression of a subset of cardiac genes, notably those coding for contractile proteins and CRIP2. Acting as a proxy of a well-perfused myocardium, alkaline conditions are permissive for expressing genes related to the contractile apparatus.
Collapse
Affiliation(s)
- Alzbeta Hulikova
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK
| | - Kyung Chan Park
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK
| | - Aminah A Loonat
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK
| | - Mala Gunadasa-Rohling
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK
| | - M Kate Curtis
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK
| | - Yu Jin Chung
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK
| | - Abigail Wilson
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK
| | - Carolyn A Carr
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK
| | - Andrew W Trafford
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, University of Manchester, Manchester, UK
| | - Marjorie Fournier
- Department of Biochemistry, Advanced Proteomics Facility, University of Oxford, Oxford, 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
| | - Paul R Riley
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK
| | - Nicola Smart
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK
| | - Thomas A Milne
- MRC Molecular Haematology Unit, Radcliffe Department of Medicine, MRC Weatherall Institute of Molecular Medicine, NIHR Oxford Biomedical Research Centre Haematology Theme, University of Oxford, Oxford, UK
| | - Nicholas T Crump
- MRC Molecular Haematology Unit, Radcliffe Department of Medicine, MRC Weatherall Institute of Molecular Medicine, NIHR Oxford Biomedical Research Centre Haematology Theme, University of Oxford, Oxford, UK
| | - Pawel Swietach
- Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Road, Oxford, OX1 3PT, UK.
| |
Collapse
|
3
|
Ion Channels, Transporters, and Sensors Interact with the Acidic Tumor Microenvironment to Modify Cancer Progression. Rev Physiol Biochem Pharmacol 2021; 182:39-84. [PMID: 34291319 DOI: 10.1007/112_2021_63] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Solid tumors, including breast carcinomas, are heterogeneous but typically characterized by elevated cellular turnover and metabolism, diffusion limitations based on the complex tumor architecture, and abnormal intra- and extracellular ion compositions particularly as regards acid-base equivalents. Carcinogenesis-related alterations in expression and function of ion channels and transporters, cellular energy levels, and organellar H+ sequestration further modify the acid-base composition within tumors and influence cancer cell functions, including cell proliferation, migration, and survival. Cancer cells defend their cytosolic pH and HCO3- concentrations better than normal cells when challenged with the marked deviations in extracellular H+, HCO3-, and lactate concentrations typical of the tumor microenvironment. Ionic gradients determine the driving forces for ion transporters and channels and influence the membrane potential. Cancer and stromal cells also sense abnormal ion concentrations via intra- and extracellular receptors that modify cancer progression and prognosis. With emphasis on breast cancer, the current review first addresses the altered ion composition and the changes in expression and functional activity of ion channels and transporters in solid cancer tissue. It then discusses how ion channels, transporters, and cellular sensors under influence of the acidic tumor microenvironment shape cancer development and progression and affect the potential of cancer therapies.
Collapse
|
4
|
Zhang T, Guan YZ, Liu H. Association of Acidemia With Short-Term Mortality of Acute Myocardial Infarction: A Retrospective Study Base on MIMIC-III Database. Clin Appl Thromb Hemost 2021; 26:1076029620950837. [PMID: 32862673 PMCID: PMC7466881 DOI: 10.1177/1076029620950837] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Acute myocardial infarction (AMI) is a leading cause of death and not a few of these patients are combined with acidemia. This study aimed to detect the association of acidemia with short-term mortality of AMI patients. A total of 972 AMI patients were selected from the Medical Information Mart for Intensive Care (MIMIC) III database for analysis. Propensity-score matching (PSM) was used to reduce the imbalance. Kaplan-Meier survival analysis was used to compare the mortality, and Cox-proportional hazards model was used to detect related factors associated with mortality. After PSM, a total of 345 non-acidemia patients and 345 matched acidemia patients were included. The non-acidemia patients had a significantly lower 30-day mortality (20.0% vs. 28.7%) and lower 90-day mortality (24.9% vs. 31.9%) than the acidemia patients (P < 0.001 for all). The severe-acidemia patients (PH < 7.25) had the highest 30-day mortality (52.6%) and 90-day mortality (53.9%) than non-acidemia patients and mild-acidemia (7.25 ≤ PH < 7.35) patients (P < 0.001). In Cox-proportional hazards model, acidemia was associated with improved 30-day mortality (HR = 1.518; 95%CI = 1.110-2.076, P = 0.009) and 90-day mortality (HR = 1.378; 95%CI = 1.034 -1.837, P = 0.029). These results suggest that severe acidemia is associated with improved 30-day mortality and 90-day mortality of AMI patients.
Collapse
Affiliation(s)
- Tang Zhang
- Department of Cardiology, The Second Affiliated Hospital, 74626Guangxi Medical University, Nanning, Guangxi, People's Republic of China
| | - Yao-Zong Guan
- Department of Cardiology, Institute of Cardiovascular Diseases, The First Affiliated Hospital, 74626Guangxi Medical University, Nanning, Guangxi, People's Republic of China
| | - Hao Liu
- Department of Cardiology, The Second Affiliated Hospital, 74626Guangxi Medical University, Nanning, Guangxi, People's Republic of China
| |
Collapse
|
5
|
Cost-Effective Real-Time Metabolic Profiling of Cancer Cell Lines for Plate-Based Assays. CHEMOSENSORS 2021. [DOI: 10.3390/chemosensors9060139] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
A fundamental phenotype of cancer cells is their metabolic profile, which is routinely described in terms of glycolytic and respiratory rates. Various devices and protocols have been designed to quantify glycolysis and respiration from the rates of acid production and oxygen utilization, respectively, but many of these approaches have limitations, including concerns about their cost-ineffectiveness, inadequate normalization procedures, or short probing time-frames. As a result, many methods for measuring metabolism are incompatible with cell culture conditions, particularly in the context of high-throughput applications. Here, we present a simple plate-based approach for real-time measurements of acid production and oxygen depletion under typical culture conditions that enable metabolic monitoring for extended periods of time. Using this approach, it is possible to calculate metabolic fluxes and, uniquely, describe the system at steady-state. By controlling the conditions with respect to pH buffering, O2 diffusion, medium volume, and cell numbers, our workflow can accurately describe the metabolic phenotype of cells in terms of molar fluxes. This direct measure of glycolysis and respiration is conducive for between-runs and even between-laboratory comparisons. To illustrate the utility of this approach, we characterize the phenotype of pancreatic ductal adenocarcinoma cell lines and measure their response to a switch of metabolic substrate and the presence of metabolic inhibitors. In summary, the method can deliver a robust appraisal of metabolism in cell lines, with applications in drug screening and in quantitative studies of metabolic regulation.
Collapse
|
6
|
Kopylova GV, Matyushenko AM, Berg VY, Levitsky DI, Bershitsky SY, Shchepkin DV. Acidosis modifies effects of phosphorylated tropomyosin on the actin-myosin interaction in the myocardium. J Muscle Res Cell Motil 2021; 42:343-353. [PMID: 33389411 DOI: 10.1007/s10974-020-09593-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 12/05/2020] [Indexed: 12/15/2022]
Abstract
Phosphorylation of α-tropomyosin (Tpm1.1), a predominant Tpm isoform in the myocardium, is one of the regulatory mechanisms of the heart contractility. The Tpm 1.1 molecule has one site of phosphorylation, Ser283. The degree of the Tpm phosphorylation decreases with age and also changes in heart pathologies. Myocardial pathologies, in particular ischemia, are usually accompanied by pH lowering in the cardiomyocyte cytosol. We studied the effects of acidosis on the structural and functional properties of the pseudo-phosphorylated form of Tpm1.1 with the S283D substitution. We found that in acidosis, the interaction of the N- and C-ends of the S283D Tpm molecules decreases, whereas that of WT Tpm does not change. The pH lowering increased thermostability of the complex of F-actin with S283D Tpm to a greater extent than with WT Tpm. Using an in vitro motility assay with NEM- modified myosin as a load, we assessed the effect of the Tpm pseudo-phosphorylation on the force of the actin-myosin interaction. In acidosis, the force generated by myosin in the interaction with thin filaments containing S283D Tpm was higher than with those containing WT Tpm. Also, the pseudo-phosphorylation increased the myosin ability to resist a load. We conclude that ischemia changes the effect of the phosphorylated Tpm on the contractile function of the myocardium.
Collapse
Affiliation(s)
- Galina V Kopylova
- Institute of Immunology and Physiology, Russian Academy of Sciences, 620049, Yekaterinburg, Russia.
| | - Alexander M Matyushenko
- Research Center of Biotechnology, A.N. Bach Institute of Biochemistry, Russian Academy of Sciences, 119071, Moscow, Russia
| | - Valentina Y Berg
- Institute of Immunology and Physiology, Russian Academy of Sciences, 620049, Yekaterinburg, Russia
| | - Dmitrii I Levitsky
- Research Center of Biotechnology, A.N. Bach Institute of Biochemistry, Russian Academy of Sciences, 119071, Moscow, Russia
| | - Sergey Y Bershitsky
- Institute of Immunology and Physiology, Russian Academy of Sciences, 620049, Yekaterinburg, Russia
| | - Daniil V Shchepkin
- Institute of Immunology and Physiology, Russian Academy of Sciences, 620049, Yekaterinburg, Russia
| |
Collapse
|
7
|
Maltsev AV, Kokoz YM. Cardiomyocytes generating spontaneous Ca2+-transients as tools for precise estimation of sarcoplasmic reticulum Ca2+ transport. Arch Biochem Biophys 2020; 693:108542. [DOI: 10.1016/j.abb.2020.108542] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 07/19/2020] [Accepted: 08/07/2020] [Indexed: 01/05/2023]
|
8
|
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.
Collapse
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
| |
Collapse
|
9
|
Loonat AA, Curtis MK, Richards MA, Nunez-Alonso G, Michl J, Swietach P. A high-throughput ratiometric method for imaging hypertrophic growth in cultured primary cardiac myocytes. J Mol Cell Cardiol 2019; 130:184-196. [PMID: 30986378 PMCID: PMC6520438 DOI: 10.1016/j.yjmcc.2019.04.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 03/14/2019] [Accepted: 04/04/2019] [Indexed: 12/21/2022]
Abstract
Maladaptive hypertrophy of cardiac myocytes increases the risk of heart failure. The underlying signaling can be triggered and interrogated in cultured neonatal ventricular myocytes (NRVMs) using sophisticated pharmacological and genetic techniques. However, the methods for quantifying cell growth are, by comparison, inadequate. The lack of quantitative, calibratable and computationally-inexpensive high-throughput technology has limited the scope for using cultured myocytes in large-scale analyses. We present a ratiometric method for quantifying the hypertrophic growth of cultured myocytes, compatible with high-throughput imaging platforms. Protein biomass was assayed from sulforhodamine B (SRB) fluorescence, and image analysis calculated the quotient of signal from extra-nuclear and nuclear regions. The former readout relates to hypertrophic growth, whereas the latter is a reference for correcting protein-independent (e.g. equipment-related) variables. This ratiometric measure, when normalized to the number of cells, provides a robust quantification of cellular hypertrophy. The method was tested by comparing the efficacy of various chemical agonists to evoke hypertrophy, and verified using independent assays (myocyte area, transcripts of markers). The method's high resolving power and wide dynamic range were confirmed by the ability to generate concentration-response curves, track the time-course of hypertrophic responses with fine temporal resolution, describe drug/agonist interactions, and screen for novel anti-hypertrophic agents. The method can be implemented as an end-point in protocols investigating hypertrophy, and is compatible with automated plate-reader platforms for generating high-throughput data, thereby reducing investigator-bias. Finally, the computationally-minimal workflow required for obtaining measurements makes the method simple to implement in most laboratories. Maladaptive hypertrophy of myocytes can lead to heart failure. Common methods for tracking growth in cultured myocytes are inadequate. We design and test a method for tracking myocyte hypertrophy in vitro. The method provides a ratiometric index of growth for high throughput analyses. Using the method, we characterize further details of (anti)hypertrophic responses.
Collapse
Affiliation(s)
- Aminah A Loonat
- University of Oxford, Department of Physiology, Anatomy & Genetics, Parks Road, Oxford OX1 3PT, United Kingdom
| | - M Kate Curtis
- University of Oxford, Department of Physiology, Anatomy & Genetics, Parks Road, Oxford OX1 3PT, United Kingdom
| | - Mark A Richards
- University of Oxford, Department of Physiology, Anatomy & Genetics, Parks Road, Oxford OX1 3PT, United Kingdom
| | - Graciela Nunez-Alonso
- University of Oxford, Department of Physiology, Anatomy & Genetics, Parks Road, Oxford OX1 3PT, United Kingdom
| | - Johanna Michl
- University of Oxford, Department of Physiology, Anatomy & Genetics, Parks Road, Oxford OX1 3PT, United Kingdom
| | - Pawel Swietach
- University of Oxford, Department of Physiology, Anatomy & Genetics, Parks Road, Oxford OX1 3PT, United Kingdom.
| |
Collapse
|
10
|
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.
Collapse
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
| |
Collapse
|