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Cheng H, Kong CHT, James AF, Cannell MB, Hancox JC. Modulation of Spontaneous Action Potential Rate by Inositol Trisphosphate in Myocytes from the Rabbit Atrioventricular Node. Cells 2024; 13:1455. [PMID: 39273026 PMCID: PMC11394215 DOI: 10.3390/cells13171455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2024] [Revised: 08/08/2024] [Accepted: 08/26/2024] [Indexed: 09/15/2024] Open
Abstract
The atrioventricular node (AVN) is a key component of the cardiac conduction system and takes over pacemaking of the ventricles if the sinoatrial node fails. IP3 (inositol 1,4,5 trisphosphate) can modulate excitability of myocytes from other regions of the heart, but it is not known whether IP3 receptor (IP3-R) activation modulates AVN cell pacemaking. Consequently, this study investigated effects of IP3 on spontaneous action potentials (APs) from AVN cells isolated from rabbit hearts. Immunohistochemistry and confocal imaging demonstrated the presence of IP3-R2 in isolated AVN cells, with partial overlap with RyR2 ryanodine receptors seen in co-labelling experiments. In whole-cell recordings at physiological temperature, application of 10 µM membrane-permeant Bt3-(1,4,5)IP3-AM accelerated spontaneous AP rate and increased diastolic depolarization rate, without direct effects on ICa,L, IKr, If or INCX. By contrast, application via the patch pipette of 5 µM of the IP3-R inhibitor xestospongin C led to a slowing in spontaneous AP rate and prevented 10 µM Bt3-(1,4,5)IP3-AM application from increasing the AP rate. UV excitation of AVN cells loaded with caged-IP3 led to an acceleration in AP rate, the magnitude of which increased with the extent of UV excitation. 2-APB slowed spontaneous AP rate, consistent with a role for constitutive IP3-R activity; however, it was also found to inhibit ICa,L and IKr, confounding its use for studying IP3-R. Under AP voltage clamp, UV excitation of AVN cells loaded with caged IP3 activated an inward current during diastolic depolarization. Collectively, these results demonstrate that IP3 can modulate AVN cell pacemaking rate.
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Affiliation(s)
- Hongwei Cheng
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol BS8 1TD, UK
| | - Cherrie H T Kong
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol BS8 1TD, UK
| | - Andrew F James
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol BS8 1TD, UK
| | - Mark B Cannell
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol BS8 1TD, UK
| | - Jules C Hancox
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol BS8 1TD, UK
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2
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Seidinger A, Roberts R, Bai Y, Müller M, Pfeil E, Matthey M, Rieck S, Alenfelder J, König GM, Pfeifer A, Kostenis E, Klinke A, Fleischmann BK, Wenzel D. Pharmacological Gq inhibition induces strong pulmonary vasorelaxation and reverses pulmonary hypertension. EMBO Mol Med 2024; 16:1930-1956. [PMID: 38977926 PMCID: PMC11319782 DOI: 10.1038/s44321-024-00096-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 05/28/2024] [Accepted: 06/05/2024] [Indexed: 07/10/2024] Open
Abstract
Pulmonary arterial hypertension (PAH) is a life-threatening disease with limited survival. Herein, we propose the pharmacological inhibition of Gq proteins as a novel concept to counteract pulmonary vasoconstriction and proliferation/migration of pulmonary artery smooth muscle cells (PASMCs) in PAH. We demonstrate that the specific pan-Gq inhibitor FR900359 (FR) induced a strong vasorelaxation in large and small pulmonary arteries in mouse, pig, and human subjects ex vivo. Vasorelaxation by FR proved at least as potent as the currently used triple therapy. We also provide in vivo evidence that local pulmonary application of FR prevented right ventricular systolic pressure increase in healthy mice as well as in mice suffering from hypoxia (Hx)-induced pulmonary hypertension (PH). In addition, we demonstrate that chronic application of FR prevented and also reversed Sugen (Su)Hx-induced PH in mice. We also demonstrate that Gq inhibition reduces proliferation and migration of PASMCs in vitro. Thus, our work illustrates a dominant role of Gq proteins for pulmonary vasoconstriction as well as remodeling and proposes direct Gq inhibition as a powerful pharmacological strategy in PH.
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Affiliation(s)
- Alexander Seidinger
- Institute of Physiology, Department of Systems Physiology, Medical Faculty, Ruhr University of Bochum, Bochum, Germany
| | - Richard Roberts
- Pharmacology Research Group, University Hospital of Nottingham, Nottingham, UK
| | - Yan Bai
- Division of Neonatology and Newborn Medicine, Department of Pediatrics, Massachusetts General Hospital and Harvard Medical School, Boston, USA
| | - Marion Müller
- Clinic for General and Interventional Cardiology/Angiology, Herz- und Diabeteszentrum NRW, University Hospital of the Ruhr University of Bochum, Bad Oeynhausen, Germany
- Agnes Wittenborg Institute for Translational Cardiovascular Research, Herz- und Diabeteszentrum NRW, University Hospital of the Ruhr University of Bochum, Bad Oeynhausen, Germany
| | - Eva Pfeil
- Molecular-, Cellular-, and Pharmacobiology Section, Institute of Pharmaceutical Biology, University of Bonn, Bonn, Germany
| | - Michaela Matthey
- Institute of Physiology, Department of Systems Physiology, Medical Faculty, Ruhr University of Bochum, Bochum, Germany
| | - Sarah Rieck
- Institute of Physiology I, Life&Brain Center, Medical Faculty, University of Bonn, Bonn, Germany
| | - Judith Alenfelder
- Molecular-, Cellular-, and Pharmacobiology Section, Institute of Pharmaceutical Biology, University of Bonn, Bonn, Germany
| | - Gabriele M König
- Institute of Pharmaceutical Biology, University of Bonn, Bonn, Germany
| | - Alexander Pfeifer
- Institute of Pharmacology and Toxicology, University Hospital Bonn, University of Bonn, Bonn, Germany
| | - Evi Kostenis
- Molecular-, Cellular-, and Pharmacobiology Section, Institute of Pharmaceutical Biology, University of Bonn, Bonn, Germany
| | - Anna Klinke
- Clinic for General and Interventional Cardiology/Angiology, Herz- und Diabeteszentrum NRW, University Hospital of the Ruhr University of Bochum, Bad Oeynhausen, Germany
- Agnes Wittenborg Institute for Translational Cardiovascular Research, Herz- und Diabeteszentrum NRW, University Hospital of the Ruhr University of Bochum, Bad Oeynhausen, Germany
| | - Bernd K Fleischmann
- Institute of Physiology I, Life&Brain Center, Medical Faculty, University of Bonn, Bonn, Germany
| | - Daniela Wenzel
- Institute of Physiology, Department of Systems Physiology, Medical Faculty, Ruhr University of Bochum, Bochum, Germany.
- Institute of Physiology I, Life&Brain Center, Medical Faculty, University of Bonn, Bonn, Germany.
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3
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Li J, Zhang Y, Zhang D, Wang W, Xie H, Ruan J, Jin Y, Li T, Li X, Zhao B, Zhang X, Lin J, Shi H, Jia JM. Ca 2+ oscillation in vascular smooth muscle cells control myogenic spontaneous vasomotion and counteract post-ischemic no-reflow. Commun Biol 2024; 7:332. [PMID: 38491167 PMCID: PMC10942987 DOI: 10.1038/s42003-024-06010-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 03/04/2024] [Indexed: 03/18/2024] Open
Abstract
Ischemic stroke produces the highest adult disability. Despite successful recanalization, no-reflow, or the futile restoration of the cerebral perfusion after ischemia, is a major cause of brain lesion expansion. However, the vascular mechanism underlying this hypoperfusion is largely unknown, and no approach is available to actively promote optimal reperfusion to treat no-reflow. Here, by combining two-photon laser scanning microscopy (2PLSM) and a mouse middle cerebral arteriolar occlusion (MCAO) model, we find myogenic vasomotion deficits correlated with post-ischemic cerebral circulation interruptions and no-reflow. Transient occlusion-induced transient loss of mitochondrial membrane potential (ΔΨm) permanently impairs mitochondria-endoplasmic reticulum (ER) contacts and abolish Ca2+ oscillation in smooth muscle cells (SMCs), the driving force of myogenic spontaneous vasomotion. Furthermore, tethering mitochondria and ER by specific overexpression of ME-Linker in SMCs restores cytosolic Ca2+ homeostasis, remotivates myogenic spontaneous vasomotion, achieves optimal reperfusion, and ameliorates neurological injury. Collectively, the maintaining of arteriolar myogenic vasomotion and mitochondria-ER contacts in SMCs, are of critical importance in preventing post-ischemic no-reflow.
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Affiliation(s)
- Jinze Li
- Key Laboratory of Growth Regulation and Translational Research of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China.
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China.
- Laboratory of Neurovascular Biology, Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China.
| | - Yiyi Zhang
- Key Laboratory of Growth Regulation and Translational Research of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Laboratory of Neurovascular Biology, Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Dongdong Zhang
- Key Laboratory of Growth Regulation and Translational Research of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Laboratory of Neurovascular Biology, Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Wentao Wang
- Key Laboratory of Growth Regulation and Translational Research of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Laboratory of Neurovascular Biology, Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Huiqi Xie
- Key Laboratory of Growth Regulation and Translational Research of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Laboratory of Neurovascular Biology, Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Jiayu Ruan
- Key Laboratory of Growth Regulation and Translational Research of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Laboratory of Neurovascular Biology, Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Yuxiao Jin
- Key Laboratory of Growth Regulation and Translational Research of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Laboratory of Neurovascular Biology, Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Tingbo Li
- Key Laboratory of Growth Regulation and Translational Research of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Laboratory of Neurovascular Biology, Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Xuzhao Li
- Key Laboratory of Growth Regulation and Translational Research of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Laboratory of Neurovascular Biology, Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Bingrui Zhao
- Key Laboratory of Growth Regulation and Translational Research of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Laboratory of Neurovascular Biology, Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Xiaoxuan Zhang
- Key Laboratory of Growth Regulation and Translational Research of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
- Laboratory of Neurovascular Biology, Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China
| | - Jiayi Lin
- Key Laboratory of Growth Regulation and Translational Research of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
| | - Hongjun Shi
- Key Laboratory of Growth Regulation and Translational Research of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China
| | - Jie-Min Jia
- Key Laboratory of Growth Regulation and Translational Research of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China.
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China.
- Laboratory of Neurovascular Biology, Institute of Basic Medical Sciences, Westlake Institute for Advanced Study, Hangzhou, China.
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4
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Terrar DA. Timing mechanisms to control heart rhythm and initiate arrhythmias: roles for intracellular organelles, signalling pathways and subsarcolemmal Ca 2. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220170. [PMID: 37122228 PMCID: PMC10150226 DOI: 10.1098/rstb.2022.0170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023] Open
Abstract
Rhythms of electrical activity in all regions of the heart can be influenced by a variety of intracellular membrane bound organelles. This is true both for normal pacemaker activity and for abnormal rhythms including those caused by early and delayed afterdepolarizations under pathological conditions. The influence of the sarcoplasmic reticulum (SR) on cardiac electrical activity is widely recognized, but other intracellular organelles including lysosomes and mitochondria also contribute. Intracellular organelles can provide a timing mechanism (such as an SR clock driven by cyclic uptake and release of Ca2+, with an important influence of intraluminal Ca2+), and/or can act as a Ca2+ store involved in signalling mechanisms. Ca2+ plays many diverse roles including carrying electric current, driving electrogenic sodium-calcium exchange (NCX) particularly when Ca2+ is extruded across the surface membrane causing depolarization, and activation of enzymes which target organelles and surface membrane proteins. Heart function is also influenced by Ca2+ mobilizing agents (cADP-ribose, nicotinic acid adenine dinucleotide phosphate and inositol trisphosphate) acting on intracellular organelles. Lysosomal Ca2+ release exerts its effects via calcium/calmodulin-dependent protein kinase II to promote SR Ca2+ uptake, and contributes to arrhythmias resulting from excessive beta-adrenoceptor stimulation. A separate arrhythmogenic mechanism involves lysosomes, mitochondria and SR. Interacting intracellular organelles, therefore, have profound effects on heart rhythms and NCX plays a central role. This article is part of the theme issue 'The heartbeat: its molecular basis and physiological mechanisms'.
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Affiliation(s)
- Derek A Terrar
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
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5
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Bose SJ, Read MJ, Akerman E, Capel RA, Ayagama T, Russell A, Terrar DA, Zaccolo M, Burton RAB. Inhibition of adenylyl cyclase 1 by ST034307 inhibits IP 3-evoked changes in sino-atrial node beat rate. Front Pharmacol 2022; 13:951897. [PMID: 36105228 PMCID: PMC9465815 DOI: 10.3389/fphar.2022.951897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Accepted: 08/01/2022] [Indexed: 11/13/2022] Open
Abstract
Atrial arrhythmias, such as atrial fibrillation (AF), are a major mortality risk and a leading cause of stroke. The IP3 signalling pathway has been proposed as an atrial-specific target for AF therapy, and atrial IP3 signalling has been linked to the activation of calcium sensitive adenylyl cyclases AC1 and AC8. We investigated the involvement of AC1 in the response of intact mouse atrial tissue and isolated guinea pig atrial and sino-atrial node (SAN) cells to the α-adrenoceptor agonist phenylephrine (PE) using the selective AC1 inhibitor ST034307. The maximum rate change of spontaneously beating mouse right atrial tissue exposed to PE was reduced from 14.5% to 8.2% (p = 0.005) in the presence of 1 μM ST034307, whereas the increase in tension generated in paced left atrial tissue in the presence of PE was not inhibited by ST034307 (Control = 14.2%, ST034307 = 16.3%; p > 0.05). Experiments were performed using isolated guinea pig atrial and SAN cells loaded with Fluo-5F-AM to record changes in calcium transients (CaT) generated by 10 μM PE in the presence and absence of 1 μM ST034307. ST034307 significantly reduced the beating rate of SAN cells (0.34-fold decrease; p = 0.003) but did not inhibit changes in CaT amplitude in response to PE in atrial cells. The results presented here demonstrate pharmacologically the involvement of AC1 in the downstream response of atrial pacemaker activity to α-adrenoreceptor stimulation and IP3R calcium release.
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Affiliation(s)
- Samuel J. Bose
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Matthew J. Read
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Emily Akerman
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Rebecca A. Capel
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Thamali Ayagama
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Angela Russell
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
- Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Oxford, United Kingdom
| | - Derek A. Terrar
- Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Manuela Zaccolo
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
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MacDonald EA, Rose RA, Quinn TA. Neurohumoral Control of Sinoatrial Node Activity and Heart Rate: Insight From Experimental Models and Findings From Humans. Front Physiol 2020; 11:170. [PMID: 32194439 PMCID: PMC7063087 DOI: 10.3389/fphys.2020.00170] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Accepted: 02/13/2020] [Indexed: 12/22/2022] Open
Abstract
The sinoatrial node is perhaps one of the most important tissues in the entire body: it is the natural pacemaker of the heart, making it responsible for initiating each-and-every normal heartbeat. As such, its activity is heavily controlled, allowing heart rate to rapidly adapt to changes in physiological demand. Control of sinoatrial node activity, however, is complex, occurring through the autonomic nervous system and various circulating and locally released factors. In this review we discuss the coupled-clock pacemaker system and how its manipulation by neurohumoral signaling alters heart rate, considering the multitude of canonical and non-canonical agents that are known to modulate sinoatrial node activity. For each, we discuss the principal receptors involved and known intracellular signaling and protein targets, highlighting gaps in our knowledge and understanding from experimental models and human studies that represent areas for future research.
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Affiliation(s)
- Eilidh A. MacDonald
- Department of Physiology and Biophysics, Dalhousie University, Halifax, NS, Canada
| | - Robert A. Rose
- Cumming School of Medicine, Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, AB, Canada
| | - T. Alexander Quinn
- Department of Physiology and Biophysics, Dalhousie University, Halifax, NS, Canada
- School of Biomedical Engineering, Dalhousie University, Halifax, NS, Canada
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7
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Abstract
The aim of this chapter is to discuss evidence concerning the many roles of calcium ions, Ca2+, in cell signaling pathways that control heart function. Before considering details of these signaling pathways, the control of contraction in ventricular muscle by Ca2+ transients accompanying cardiac action potentials is first summarized, together with a discussion of how myocytes from the atrial and pacemaker regions of the heart diverge from this basic scheme. Cell signaling pathways regulate the size and timing of the Ca2+ transients in the different heart regions to influence function. The simplest Ca2+ signaling elements involve enzymes that are regulated by cytosolic Ca2+. Particularly important examples to be discussed are those that are stimulated by Ca2+, including Ca2+-calmodulin-dependent kinase (CaMKII), Ca2+ stimulated adenylyl cyclases, Ca2+ stimulated phosphatase and NO synthases. Another major aspect of Ca2+ signaling in the heart concerns actions of the Ca2+ mobilizing agents, inositol trisphosphate (IP3), cADP-ribose (cADPR) and nicotinic acid adenine dinucleotide phosphate, (NAADP). Evidence concerning roles of these Ca2+ mobilizing agents in different regions of the heart is discussed in detail. The focus of the review will be on short term regulation of Ca2+ transients and contractile function, although it is recognized that Ca2+ regulation of gene expression has important long term functional consequences which will also be briefly discussed.
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Angiotensin II Induces Automatic Activity of the Isolated Guinea Pig Pulmonary Vein Myocardium through Activation of the IP₃ Receptor and the Na⁺-Ca 2+ Exchanger. Int J Mol Sci 2019; 20:ijms20071768. [PMID: 30974804 PMCID: PMC6479489 DOI: 10.3390/ijms20071768] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 04/01/2019] [Accepted: 04/05/2019] [Indexed: 11/16/2022] Open
Abstract
The automaticity of the pulmonary vein myocardium is known to be the major cause of atrial fibrillation. We examined the involvement of angiotensin II in the automatic activity of isolated guinea pig pulmonary vein preparations. In tissue preparations, application of angiotensin II induced an automatic contractile activity; this effect was mimicked by angiotensin I and blocked by losartan, but not by PD123,319 or carvedilol. In cardiomyocytes, application of angiotensin II induced an increase in the frequency of spontaneous Ca2+ sparks and the generation of Ca2+ transients; these effects were inhibited by losartan or xestospongin C. In tissue preparations, angiotensin II caused membrane potential oscillations, which lead to repetitive generation of action potentials. Angiotensin II increased the diastolic depolarization slope of the spontaneous or evoked action potentials. These effects of angiotensin II were inhibited by SEA0400. In tissue preparations showing spontaneous firing of action potentials, losartan, xestospongin C or SEA0400 decreased the slope of the diastolic depolarization and inhibited the firing of action potentials. In conclusion, in the guinea pig pulmonary vein myocardium, angiotensin II induces the generation of automatic activity through activation of the IP3 receptor and the Na+-Ca2+ exchanger.
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Interaction among hERG channel blockers is a potential mechanism of death in caffeine overdose. Eur J Pharmacol 2017; 800:23-33. [PMID: 28216052 DOI: 10.1016/j.ejphar.2017.02.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2016] [Revised: 02/09/2017] [Accepted: 02/10/2017] [Indexed: 11/22/2022]
Abstract
Caffeine overdose death is due to cardiac arrest, but its mechanism has not been explored in detail. In this study, our data showed that caffeine significantly prolonged the heart rate-corrected QT interval (QTc) of rabbits in vivo (P<0.05; n=7). Caffeine was also found to be a hERG channel blocker with an IC50 of 5.04mM (n=5). Although these two findings likely link caffeine overdose death with hERG channel blockade, the amount of caffeine consumption needed to reach the IC50 is very high. Further study demonstrated that addition another hERG blocker could lower the consumption of caffeine significantly, no matter whether two hERG blockers share the same binding sites. Our data does not rule out other possibility, however, it suggests that there is a potential causal relationship between caffeine overdose death with hERG channel and the interaction among these hERG blockers.
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Beasley V, Dowse H. Suppression of Tryptophan 2,3-Dioxygenase Produces a Slow Heartbeat Phenotype in Drosophila melanogaster. ACTA ACUST UNITED AC 2017; 325:651-664. [PMID: 28127944 DOI: 10.1002/jez.2057] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 11/23/2016] [Accepted: 12/01/2016] [Indexed: 12/27/2022]
Abstract
The primary pathway utilizing tryptophan leads initially to kynurenine before branching. Products include nicotinamide adenine dinucleotide and important pigments in the eye. Products in this pathway have been linked to a number of pathologies. The gene encoding the first step in this pathway, tryptophan 2,3-dioxegenase, is encoded by the gene vermilion, initially discovered in Drosophila. In the fly, v is an important eye color marker, but is found to have multiple pleiotropic effects. We have uncovered significant effects of this mutation on the fly heart. The heart beats more slowly and more rhythmically in both males and females and in strains which we have outcrossed. In addition, the fly heart normally beats irregularly with multiple brief stoppages, and the time structure of these stoppages, as investigated by looking at interbeat intervals, is changed in flies bearing this mutation. Fewer flies bearing the v1 mutation show long hiatuses in beat compared to wild type, however, in some strains of the mutant animals that do, the number of stoppages in much greater and the mean duration is longer.
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Affiliation(s)
- Vernon Beasley
- School of Biology and Ecology, University of Maine, Orono, Maine
| | - Harold Dowse
- School of Biology and Ecology, University of Maine, Orono, Maine.,Department of Mathematics and Statistics, University of Maine, Orono, Maine
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11
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Groschner K, Shrestha N, Fameli N. Cardiovascular and Hemostatic Disorders: SOCE in Cardiovascular Cells: Emerging Targets for Therapeutic Intervention. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 993:473-503. [PMID: 28900929 DOI: 10.1007/978-3-319-57732-6_24] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The discovery of the store-operated Ca2+ entry (SOCE) phenomenon is tightly associated with its recognition as a pathway of high (patho)physiological significance in the cardiovascular system. Early on, SOCE has been investigated primarily in non-excitable cell types, and the vascular endothelium received particular attention, while a role of SOCE in excitable cells, specifically cardiac myocytes and pacemakers, was initially ignored and remains largely enigmatic even to date. With the recent gain in knowledge on the molecular components of SOCE as well as their cellular organization within nanodomains, potential tissue/cell type-dependent heterogeneity of the SOCE machinery along with high specificity of linkage to downstream signaling pathways emerged for cardiovascular cells. The basis of precise decoding of cellular Ca2+ signals was recently uncovered to involve correct spatiotemporal organization of signaling components, and even minor disturbances in these assemblies trigger cardiovascular pathologies. With this chapter, we wish to provide an overview on current concepts of cellular organization of SOCE signaling complexes in cardiovascular cells with particular focus on the spatiotemporal aspects of coupling to downstream signaling and the potential disturbance of these mechanisms by pathogenic factors. The significance of these mechanistic concepts for the development of novel therapeutic strategies will be discussed.
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Affiliation(s)
- Klaus Groschner
- Institute of Biophysics, Medical University of Graz, Neue Stiftingtalstrasse 6/4, 8010, Graz, Austria.
| | - Niroj Shrestha
- Institute of Biophysics, Medical University of Graz, Neue Stiftingtalstrasse 6/4, 8010, Graz, Austria
| | - Nicola Fameli
- Institute of Biophysics, Medical University of Graz, Neue Stiftingtalstrasse 6/4, 8010, Graz, Austria
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, BC, Canada
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12
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Berridge MJ. The Inositol Trisphosphate/Calcium Signaling Pathway in Health and Disease. Physiol Rev 2016; 96:1261-96. [DOI: 10.1152/physrev.00006.2016] [Citation(s) in RCA: 377] [Impact Index Per Article: 47.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Many cellular functions are regulated by calcium (Ca2+) signals that are generated by different signaling pathways. One of these is the inositol 1,4,5-trisphosphate/calcium (InsP3/Ca2+) signaling pathway that operates through either primary or modulatory mechanisms. In its primary role, it generates the Ca2+ that acts directly to control processes such as metabolism, secretion, fertilization, proliferation, and smooth muscle contraction. Its modulatory role occurs in excitable cells where it modulates the primary Ca2+ signal generated by the entry of Ca2+ through voltage-operated channels that releases Ca2+ from ryanodine receptors (RYRs) on the internal stores. In carrying out this modulatory role, the InsP3/Ca2+ signaling pathway induces subtle changes in the generation and function of the voltage-dependent primary Ca2+ signal. Changes in the nature of both the primary and modulatory roles of InsP3/Ca2+ signaling are a contributory factor responsible for the onset of a large number human diseases.
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Affiliation(s)
- Michael J. Berridge
- Laboratory of Molecular Signalling, The Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT, United Kingdom
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Biphasic regulation of InsP3 receptor gating by dual Ca2+ release channel BH3-like domains mediates Bcl-xL control of cell viability. Proc Natl Acad Sci U S A 2016; 113:E1953-62. [PMID: 26976600 DOI: 10.1073/pnas.1517935113] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Antiapoptotic Bcl-2 family members interact with inositol trisphosphate receptor (InsP3R) Ca(2+)release channels in the endoplasmic reticulum to modulate Ca(2+)signals that affect cell viability. However, the molecular details and consequences of their interactions are unclear. Here, we found that Bcl-xL activates single InsP3R channels with a biphasic concentration dependence. The Bcl-xLBcl-2 homology 3 (BH3) domain-binding pocket mediates both high-affinity channel activation and low-affinity inhibition. Bcl-xL activates channel gating by binding to two BH3 domain-like helices in the channel carboxyl terminus, whereas inhibition requires binding to one of them and to a previously identified Bcl-2 interaction site in the channel-coupling domain. Disruption of these interactions diminishes cell viability and sensitizes cells to apoptotic stimuli. Our results identify BH3-like domains in an ion channel and they provide a unifying model of the effects of antiapoptotic Bcl-2 proteins on the InsP3R that play critical roles in Ca(2+) signaling and cell viability.
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Kapoor N, Tran A, Kang J, Zhang R, Philipson KD, Goldhaber JI. Regulation of calcium clock-mediated pacemaking by inositol-1,4,5-trisphosphate receptors in mouse sinoatrial nodal cells. J Physiol 2015; 593:2649-63. [PMID: 25903031 DOI: 10.1113/jp270082] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 04/15/2015] [Indexed: 01/30/2023] Open
Abstract
KEY POINTS Inositol-1,4,5-trisphosphate receptors (IP3 Rs) modulate pacemaking in embryonic heart, but their role in adult sinoatrial node (SAN) pacemaking is uncertain. We found that stimulation of IP3 Rs accelerates spontaneous pacing rate in isolated mouse SAN cells, whereas inhibition of IP3 Rs slows pacing. In atrial-specific sodium-calcium exchanger (NCX) knockout (KO) SAN cells, where the Ca(2+) clock is uncoupled from the membrane clock, IP3 R agonists and antagonists modulate the rate of spontaneous Ca(2+) waves, suggesting that IP3 R-mediated Ca(2+) release modulates the Ca(2+) clock. IP3 R modulation also regulates Ca(2+) spark parameters, a reflection of ryanodine receptor open probability, consistent with the effect of IP3 signalling on Ca(2+) clock frequency. Modulation of Ca(2+) clock frequency by IP3 signalling in NCX KO SAN cells demonstrates that the effect is independent of NCX. These findings support development of IP3 signalling modulators for regulation of heart rate, particularly in heart failure where IP3 Rs are upregulated. ABSTRACT Cardiac pacemaking initiated by the sinus node is attributable to the interplay of several membrane currents. These include the depolarizing 'funny current' (If ) and the sodium-calcium exchanger current (INCX ). The latter is activated by ryanodine receptor (RyR)-mediated calcium (Ca(2+) ) release from the sarcoplasmic reticulum (SR). Another SR Ca(2+) release channel, the inositol-1,4,5-triphosphate receptor (IP3 R), has been implicated in the generation of spontaneous Ca(2+) release in atrial and ventricular cardiomyocytes. Whether IP3 R-mediated Ca(2+) release also influences SAN automaticity is controversial, in part due to the confounding influence of periodic Ca(2+) flux through the sarcolemma accompanying each beat. We took advantage of atrial-specific sodium-calcium exchanger (NCX) knockout (KO) SAN cells to study the influence of IP3 signalling on cardiac pacemaking in a system where periodic intracellular Ca(2+) cycling persists despite the absence of depolarization or Ca(2+) flux across the sarcolemma. We recorded confocal line scans of spontaneous Ca(2+) release in WT and NCX KO SAN cells in the presence or absence of an IP3 R blocker (2-aminoethoxydiphenyl borate, 2-APB), or during block of IP3 production by the phospholipase C inhibitor U73122. 2-APB and U73122 decreased the frequency of spontaneous Ca(2+) transients and waves in WT and NCX KO cells, respectively. Alternatively, increased IP3 production induced by phenylephrine increased Ca(2+) transient and wave frequency. We conclude that IP3 R-mediated SR Ca(2+) flux is crucial for initiating and modulating the RyR-mediated Ca(2+) cycling that regulates SAN pacemaking. Our results in NCX KO SAN cells also demonstrate that RyRs, but not NCX, are required for IP3 to modulate Ca(2+) clock frequency.
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Affiliation(s)
- Nidhi Kapoor
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Andrew Tran
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Jeanney Kang
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Rui Zhang
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Kenneth D Philipson
- Department of Physiology, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California, USA
| | - Joshua I Goldhaber
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
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15
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Ju YK, Lee BH, Trajanovska S, Hao G, Allen DG, Lei M, Cannell MB. The involvement of TRPC3 channels in sinoatrial arrhythmias. Front Physiol 2015; 6:86. [PMID: 25859221 PMCID: PMC4373262 DOI: 10.3389/fphys.2015.00086] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Accepted: 03/04/2015] [Indexed: 01/08/2023] Open
Abstract
Atrial fibrillation (AF) is a significant contributor to cardiovascular morbidity and mortality. The currently available treatments are limited and AF continues to be a major clinical challenge. Clinical studies have shown that AF is frequently associated with dysfunction in the sino-atrial node (SAN). The association between AF and SAN dysfunction is probably related to the communication between the SAN and the surrounding atrial cells that form the SAN-atrial pacemaker complex and/or pathological processes that affect both the SAN and atrial simultaneously. Recent evidence suggests that Ca2+ entry through TRPC3 (Transient Receptor Potential Canonical-3) channels may underlie several pathophysiological conditions -including cardiac arrhythmias. However, it is still not known if atrial and sinoatrial node cells are also involved. In this article we will first briefly review TRPC3 and IP3R signaling that relate to store/receptor-operated Ca2+ entry (SOCE/ROCE) mechanisms and cardiac arrhythmias. We will then present some of our recent research progress in this field. Our experiments results suggest that pacing-induced AF in angiotensin II (Ang II) treated mice are significantly reduced in mice lacking the TRPC3 gene (TRPC3−/− mice) compared to wild type controls. We also show that pacemaker cells express TRPC3 and several other molecular components related to SOCE/ROCE signaling, including STIM1 and IP3R. Activation of G-protein coupled receptors (GPCRs) signaling that is able to modulate SOCE/ROCE and Ang II induced Ca2+ homeostasis changes in sinoatrial complex being linked to TRPC3. The results provide new evidence that TRPC3 may play a role in sinoatrial and atrial arrhythmias that are caused by GPCRs activation.
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Affiliation(s)
- Yue-Kun Ju
- Department of Physiology, School of Medical Sciences, Bosch Institute, University of Sydney Sydney, NSW, Australia
| | - Bon Hyang Lee
- Department of Physiology, School of Medical Sciences, Bosch Institute, University of Sydney Sydney, NSW, Australia
| | - Sofie Trajanovska
- Department of Physiology, School of Medical Sciences, Bosch Institute, University of Sydney Sydney, NSW, Australia
| | - Gouliang Hao
- Department of Pharmacology, University of Oxford Oxford, UK
| | - David G Allen
- Department of Physiology, School of Medical Sciences, Bosch Institute, University of Sydney Sydney, NSW, Australia
| | - Ming Lei
- Department of Pharmacology, University of Oxford Oxford, UK
| | - Mark B Cannell
- Department of Physiology and Pharmacology, University of Bristol Bristol, UK
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16
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Yaniv Y, Lakatta EG, Maltsev VA. From two competing oscillators to one coupled-clock pacemaker cell system. Front Physiol 2015; 6:28. [PMID: 25741284 PMCID: PMC4327306 DOI: 10.3389/fphys.2015.00028] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2014] [Accepted: 01/17/2015] [Indexed: 01/01/2023] Open
Abstract
At the beginning of this century, debates regarding “what are the main control mechanisms that ignite the action potential (AP) in heart pacemaker cells” dominated the electrophysiology field. The original theory which prevailed for over 50 years had advocated that the ensemble of surface membrane ion channels (i.e., “M-clock”) is sufficient to ignite rhythmic APs. However, more recent experimental evidence in a variety of mammals has shown that the sarcoplasmic reticulum (SR) acts as a “Ca2+-clock” rhythmically discharges diastolic local Ca2+ releases (LCRs) beneath the cell surface membrane. LCRs activate an inward current (likely that of the Na+/Ca2+ exchanger) that prompts the surface membrane “M-clock” to ignite an AP. Theoretical and experimental evidence has mounted to indicate that this clock “crosstalk” operates on a beat-to-beat basis and determines both the AP firing rate and rhythm. Our review is focused on the evolution of experimental definition and numerical modeling of the coupled-clock concept, on how mechanisms intrinsic to pacemaker cell determine both the heart rate and rhythm, and on future directions to develop further the coupled-clock pacemaker cell concept.
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Affiliation(s)
- Yael Yaniv
- Biomedical Engineering Faculty, Technion-IIT Haifa, Israel
| | - Edward G Lakatta
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, National Institutes of Health Baltimore, MD, USA
| | - Victor A Maltsev
- Laboratory of Cardiovascular Science, Biomedical Research Center, Intramural Research Program, National Institute on Aging, National Institutes of Health Baltimore, MD, USA
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17
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Ben-Ari M, Schick R, Barad L, Novak A, Ben-Ari E, Lorber A, Itskovitz-Eldor J, Rosen MR, Weissman A, Binah O. From beat rate variability in induced pluripotent stem cell-derived pacemaker cells to heart rate variability in human subjects. Heart Rhythm 2014; 11:1808-1818. [PMID: 25052725 PMCID: PMC4283811 DOI: 10.1016/j.hrthm.2014.05.037] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Indexed: 01/27/2023]
Abstract
BACKGROUND We previously reported that induced pluripotent stem cell-derived cardiomyocytes manifest beat rate variability (BRV) resembling heart rate variability (HRV) in the human sinoatrial node. We now hypothesized the BRV-HRV continuum originates in pacemaker cells. OBJECTIVE To investigate whether cellular BRV is a source of HRV dynamics, we hypothesized 3 levels of interaction among different cardiomyocyte entities: (1) single pacemaker cells, (2) networks of electrically coupled pacemaker cells, and (3) the in situ sinoatrial node. METHODS We measured BRV/HRV properties in single pacemaker cells, induced pluripotent stem cell-derived contracting embryoid bodies (EBs), and electrocardiograms from the same individual. RESULTS Pronounced BRV/HRV was present at all 3 levels. The coefficient of variance of interbeat intervals and Poincaré plot indices SD1 and SD2 for single cells were 20 times greater than those for EBs (P < .05) and the in situ heart (the latter two were similar; P > .05). We also compared BRV magnitude among single cells, small EBs (~5-10 cells), and larger EBs (>10 cells): BRV indices progressively increased with the decrease in the cell number (P < .05). Disrupting intracellular Ca(2+) handling markedly augmented BRV magnitude, revealing a unique bimodal firing pattern, suggesting that intracellular mechanisms contribute to BRV/HRV and the fractal behavior of heart rhythm. CONCLUSION The decreased BRV magnitude in transitioning from the single cell to the EB suggests that the HRV of in situ hearts originates from the summation and integration of multiple cell-based oscillators. Hence, complex interactions among multiple pacemaker cells and intracellular Ca(2+) handling determine HRV in humans and cardiomyocyte networks.
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Affiliation(s)
- Meital Ben-Ari
- The Sohnis Family Stem Cells Center, Technion, Haifa, Israel
- The Rappaport Institute, Technion, Haifa, Israel
- Ruth & Bruce Rappaport Faculty of Medicine, Technion, Haifa, Israel
| | - Revital Schick
- The Sohnis Family Stem Cells Center, Technion, Haifa, Israel
- The Rappaport Institute, Technion, Haifa, Israel
- Ruth & Bruce Rappaport Faculty of Medicine, Technion, Haifa, Israel
| | - Lili Barad
- The Sohnis Family Stem Cells Center, Technion, Haifa, Israel
- The Rappaport Institute, Technion, Haifa, Israel
- Ruth & Bruce Rappaport Faculty of Medicine, Technion, Haifa, Israel
| | - Atara Novak
- The Sohnis Family Stem Cells Center, Technion, Haifa, Israel
- The Rappaport Institute, Technion, Haifa, Israel
- Ruth & Bruce Rappaport Faculty of Medicine, Technion, Haifa, Israel
| | - Erez Ben-Ari
- Department of Electrical Engineering, Technion, Haifa, Israel
| | - Avraham Lorber
- Ruth & Bruce Rappaport Faculty of Medicine, Technion, Haifa, Israel
- Department of Pediatric Cardiology, Rambam Medical Center
| | - Joseph Itskovitz-Eldor
- The Sohnis Family Stem Cells Center, Technion, Haifa, Israel
- Ruth & Bruce Rappaport Faculty of Medicine, Technion, Haifa, Israel
- Department of Obstetrics and Gynecology, Rambam Medical Center, Haifa, Israel
| | - Michael R Rosen
- Department of Pharmacology, College of Physicians and Surgeons of Columbia University, New York, USA
| | - Amir Weissman
- Ruth & Bruce Rappaport Faculty of Medicine, Technion, Haifa, Israel
- Department of Obstetrics and Gynecology, Rambam Medical Center, Haifa, Israel
| | - Ofer Binah
- The Sohnis Family Stem Cells Center, Technion, Haifa, Israel
- The Rappaport Institute, Technion, Haifa, Israel
- Ruth & Bruce Rappaport Faculty of Medicine, Technion, Haifa, Israel
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18
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Beiert T, Bruegmann T, Sasse P. Optogenetic activation of Gq signalling modulates pacemaker activity of cardiomyocytes. Cardiovasc Res 2014; 102:507-16. [PMID: 24576953 DOI: 10.1093/cvr/cvu046] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
AIMS Investigation of Gq signalling with pharmacological agonists of Gq-coupled receptors lacks spatio-temporal precision. The aim of this study was to establish melanopsin, a light-sensitive Gq-coupled receptor, as a new tool for the investigation of spatial and temporal effects of Gq stimulation on pacemaking in cardiomyocytes at an early developmental stage. METHODS AND RESULTS A vector for ubiquitous expression of melanopsin was tested in HEK293FT cells, which showed light-induced production of inositol-1,4,5-trisphosphate and elevation of intracellular Ca(2+) concentration. Mouse embryonic stem cells were stably transfected with this plasmid and differentiated into spontaneously beating embryoid bodies (EBs). Cardiomyocytes within EBs showed melanopsin expression and illumination (60 s, 308.5 nW/mm(2), 470 nm) of EBs increased beating rate within 10.2 ± 1.7 s to 317.1 ± 16.3% of baseline frequency. Illumination as short as 5 s was sufficient for generating the maximal frequency response. After termination of illumination, baseline frequency was reached with a decay constant of 27.1 ± 2.5 s. The light-induced acceleration of beating frequency showed a sigmoid dependence on light intensity with a half maximal effective light intensity of 41.7 nW/mm(2). Interestingly, EBs showed a high rate of irregular contractions after termination of high-intensity illumination. Local Gq activation by illumination of a small region in a functional syncytium of cardiomyocytes led to pacemaker activity within the illuminated area. CONCLUSIONS Light-induced Gq activation in melanopsin-expressing cardiomyocytes increases beating rate and generates local pacemaker activity. We propose that melanopsin is a powerful optogenetic tool for the investigation of spatial and temporal aspects of Gq signalling in cardiovascular research.
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Affiliation(s)
- Thomas Beiert
- Institute of Physiology I, Life & Brain Center, University of Bonn, Sigmund-Freud-Strasse 25, Bonn 53105, Germany
| | - Tobias Bruegmann
- Institute of Physiology I, Life & Brain Center, University of Bonn, Sigmund-Freud-Strasse 25, Bonn 53105, Germany
| | - Philipp Sasse
- Institute of Physiology I, Life & Brain Center, University of Bonn, Sigmund-Freud-Strasse 25, Bonn 53105, Germany
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19
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Yu J, Deliu E, Zhang XQ, Hoffman NE, Carter RL, Grisanti LA, Brailoiu GC, Madesh M, Cheung JY, Force T, Abood ME, Koch WJ, Tilley DG, Brailoiu E. Differential activation of cultured neonatal cardiomyocytes by plasmalemmal versus intracellular G protein-coupled receptor 55. J Biol Chem 2013; 288:22481-92. [PMID: 23814062 DOI: 10.1074/jbc.m113.456178] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The L-α-lysophosphatidylinositol (LPI)-sensitive receptor GPR55 is coupled to Ca(2+) signaling. Low levels of GPR55 expression in the heart have been reported. Similar to other G protein-coupled receptors involved in cardiac function, GPR55 may be expressed both at the sarcolemma and intracellularly. Thus, to explore the role of GPR55 in cardiomyocytes, we used calcium and voltage imaging and extracellular administration or intracellular microinjection of GPR55 ligands. We provide the first evidence that, in cultured neonatal ventricular myocytes, LPI triggers distinct signaling pathways via GPR55, depending on receptor localization. GPR55 activation at the sarcolemma elicits, on one hand, Ca(2+) entry via L-type Ca(2+) channels and, on the other, inositol 1,4,5-trisphosphate-dependent Ca(2+) release. The latter signal is further amplified by Ca(2+)-induced Ca(2+) release via ryanodine receptors. Conversely, activation of GPR55 at the membrane of intracellular organelles promotes Ca(2+) release from acidic-like Ca(2+) stores via the endolysosomal NAADP-sensitive two-pore channels. This response is similarly enhanced by Ca(2+)-induced Ca(2+) release via ryanodine receptors. Extracellularly applied LPI produces Ca(2+)-independent membrane depolarization, whereas the Ca(2+) signal induced by intracellular microinjection of LPI converges to hyperpolarization of the sarcolemma. Collectively, our findings point to GPR55 as a novel G protein-coupled receptor regulating cardiac function at two cellular sites. This work may serve as a platform for future studies exploring the potential of GPR55 as a therapeutic target in cardiac disorders.
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Affiliation(s)
- Justine Yu
- Center for Translational Medicine, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA
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Decrock E, De Bock M, Wang N, Gadicherla AK, Bol M, Delvaeye T, Vandenabeele P, Vinken M, Bultynck G, Krysko DV, Leybaert L. IP3, a small molecule with a powerful message. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:1772-86. [PMID: 23291251 DOI: 10.1016/j.bbamcr.2012.12.016] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Revised: 12/18/2012] [Accepted: 12/19/2012] [Indexed: 12/22/2022]
Abstract
Research conducted over the past two decades has provided convincing evidence that cell death, and more specifically apoptosis, can exceed single cell boundaries and can be strongly influenced by intercellular communication networks. We recently reported that gap junctions (i.e. channels directly connecting the cytoplasm of neighboring cells) composed of connexin43 or connexin26 provide a direct pathway to promote and expand cell death, and that inositol 1,4,5-trisphosphate (IP3) diffusion via these channels is crucial to provoke apoptosis in adjacent healthy cells. However, IP3 itself is not sufficient to induce cell death and additional factors appear to be necessary to create conditions in which IP3 will exert proapoptotic effects. Although IP3-evoked Ca(2+) signaling is known to be required for normal cell survival, it is also actively involved in apoptosis induction and progression. As such, it is evident that an accurate fine-tuning of this signaling mechanism is crucial for normal cell physiology, while a malfunction can lead to cell death. Here, we review the role of IP3 as an intracellular and intercellular cell death messenger, focusing on the endoplasmic reticulum-mitochondrial synapse, followed by a discussion of plausible elements that can convert IP3 from a physiological molecule to a killer substance. Finally, we highlight several pathological conditions in which anomalous intercellular IP3/Ca(2+) signaling might play a role. This article is part of a Special Issue entitled:12th European Symposium on Calcium.
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Affiliation(s)
- Elke Decrock
- Department of Basic Medical Sciences, Ghent University, Ghent, Belgium
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