1
|
Li Q, Zhang H, Liu R, Wang L, Guo X, You H, Xue J, Luo D. A modified method for isolating sinoatrial node myocytes from adult mice. In Vitro Cell Dev Biol Anim 2024; 60:815-823. [PMID: 38898365 DOI: 10.1007/s11626-024-00920-4] [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: 12/04/2023] [Accepted: 04/19/2024] [Indexed: 06/21/2024]
Abstract
Sinoatrial node (SAN) is the pacemaker of the heart in charge of initiating spontaneous electronical activity and controlling heart rate. Myocytes from SAN can generate spontaneous rhythmic action potentials, which propagate through the myocardium, thereby triggering cardiac myocyte contraction. Acutely, the method for isolating sinoatrial node myocytes (SAMs) is critical in studying the protein expression and function of myocytes in SAN. Currently, the SAMs were isolated by transferring SAN tissue directly into the digestion solution, but it is difficult to judge the degree of digestion, and the system was unstable. Here, we present a modified protocol for the isolation of SAMs in mice, based on the collagenase II and protease perfusion of the heart using a Langendorff apparatus and subsequent dissociation of SAMs. The appearance and droplet flow rate of the heart could be significantly changed during enzymatic digestion via perfusion, which allowed us to easily judge the degree of digestion and avoid incomplete or excessive digestion. The SAMs with stable yield and viability achieved from our optimized approach would facilitate the follow-up experiments.
Collapse
Affiliation(s)
- Qiang Li
- Department of Pharmacology, School of Basic Medical Sciences, Beijing Key Laboratory of Metabolic Disturbance Related Cardiovascular Disease, Capital Medical University, Beijing, 100069, People's Republic of China
| | - Hanying Zhang
- Department of Pharmacology, School of Basic Medical Sciences, Beijing Key Laboratory of Metabolic Disturbance Related Cardiovascular Disease, Capital Medical University, Beijing, 100069, People's Republic of China
| | - Ronghua Liu
- Department of Pharmacology, School of Basic Medical Sciences, Beijing Key Laboratory of Metabolic Disturbance Related Cardiovascular Disease, Capital Medical University, Beijing, 100069, People's Republic of China
| | - Luqi Wang
- Department of Pharmacology, School of Basic Medical Sciences, Beijing Key Laboratory of Metabolic Disturbance Related Cardiovascular Disease, Capital Medical University, Beijing, 100069, People's Republic of China
| | - Xintong Guo
- Department of Pharmacology, School of Basic Medical Sciences, Beijing Key Laboratory of Metabolic Disturbance Related Cardiovascular Disease, Capital Medical University, Beijing, 100069, People's Republic of China
| | - Hongjie You
- Department of Pharmacology, School of Basic Medical Sciences, Beijing Key Laboratory of Metabolic Disturbance Related Cardiovascular Disease, Capital Medical University, Beijing, 100069, People's Republic of China
| | - Jingyi Xue
- Department of Pharmacology, School of Basic Medical Sciences, Beijing Key Laboratory of Metabolic Disturbance Related Cardiovascular Disease, Capital Medical University, Beijing, 100069, People's Republic of China.
| | - Dali Luo
- Department of Pharmacology, School of Basic Medical Sciences, Beijing Key Laboratory of Metabolic Disturbance Related Cardiovascular Disease, Capital Medical University, Beijing, 100069, People's Republic of China.
| |
Collapse
|
2
|
Hennis K, Piantoni C, Biel M, Fenske S, Wahl-Schott C. Pacemaker Channels and the Chronotropic Response in Health and Disease. Circ Res 2024; 134:1348-1378. [PMID: 38723033 PMCID: PMC11081487 DOI: 10.1161/circresaha.123.323250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 05/13/2024]
Abstract
Loss or dysregulation of the normally precise control of heart rate via the autonomic nervous system plays a critical role during the development and progression of cardiovascular disease-including ischemic heart disease, heart failure, and arrhythmias. While the clinical significance of regulating changes in heart rate, known as the chronotropic effect, is undeniable, the mechanisms controlling these changes remain not fully understood. Heart rate acceleration and deceleration are mediated by increasing or decreasing the spontaneous firing rate of pacemaker cells in the sinoatrial node. During the transition from rest to activity, sympathetic neurons stimulate these cells by activating β-adrenergic receptors and increasing intracellular cyclic adenosine monophosphate. The same signal transduction pathway is targeted by positive chronotropic drugs such as norepinephrine and dobutamine, which are used in the treatment of cardiogenic shock and severe heart failure. The cyclic adenosine monophosphate-sensitive hyperpolarization-activated current (If) in pacemaker cells is passed by hyperpolarization-activated cyclic nucleotide-gated cation channels and is critical for generating the autonomous heartbeat. In addition, this current has been suggested to play a central role in the chronotropic effect. Recent studies demonstrate that cyclic adenosine monophosphate-dependent regulation of HCN4 (hyperpolarization-activated cyclic nucleotide-gated cation channel isoform 4) acts to stabilize the heart rate, particularly during rapid rate transitions induced by the autonomic nervous system. The mechanism is based on creating a balance between firing and recently discovered nonfiring pacemaker cells in the sinoatrial node. In this way, hyperpolarization-activated cyclic nucleotide-gated cation channels may protect the heart from sinoatrial node dysfunction, secondary arrhythmia of the atria, and potentially fatal tachyarrhythmia of the ventricles. Here, we review the latest findings on sinoatrial node automaticity and discuss the physiological and pathophysiological role of HCN pacemaker channels in the chronotropic response and beyond.
Collapse
Affiliation(s)
- Konstantin Hennis
- Institute of Cardiovascular Physiology and Pathophysiology, Biomedical Center Munich, Walter Brendel Centre of Experimental Medicine, Faculty of Medicine (K.H., C.P., C.W.-S.), Ludwig-Maximilians-Universität München, Germany
| | - Chiara Piantoni
- Institute of Cardiovascular Physiology and Pathophysiology, Biomedical Center Munich, Walter Brendel Centre of Experimental Medicine, Faculty of Medicine (K.H., C.P., C.W.-S.), Ludwig-Maximilians-Universität München, Germany
| | - Martin Biel
- Department of Pharmacy, Center for Drug Research (M.B., S.F.), Ludwig-Maximilians-Universität München, Germany
- German Centre for Cardiovascular Research (DZHK), Partner Site Munich Heart Alliance, Germany (M.B., S.F.)
| | - Stefanie Fenske
- Department of Pharmacy, Center for Drug Research (M.B., S.F.), Ludwig-Maximilians-Universität München, Germany
- German Centre for Cardiovascular Research (DZHK), Partner Site Munich Heart Alliance, Germany (M.B., S.F.)
| | - Christian Wahl-Schott
- Institute of Cardiovascular Physiology and Pathophysiology, Biomedical Center Munich, Walter Brendel Centre of Experimental Medicine, Faculty of Medicine (K.H., C.P., C.W.-S.), Ludwig-Maximilians-Universität München, Germany
| |
Collapse
|
3
|
Li T, Marashly Q, Kim JA, Li N, Chelu MG. Cardiac conduction diseases: understanding the molecular mechanisms to uncover targets for future treatments. Expert Opin Ther Targets 2024; 28:385-400. [PMID: 38700451 PMCID: PMC11395937 DOI: 10.1080/14728222.2024.2351501] [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: 11/18/2023] [Accepted: 05/01/2024] [Indexed: 05/05/2024]
Abstract
INTRODUCTION The cardiac conduction system (CCS) is crucial for maintaining adequate cardiac frequency at rest and modulation during exercise. Furthermore, the atrioventricular node and His-Purkinje system are essential for maintaining atrioventricular and interventricular synchrony and consequently maintaining an adequate cardiac output. AREAS COVERED In this review article, we examine the anatomy, physiology, and pathophysiology of the CCS. We then discuss in detail the most common genetic mutations and the molecular mechanisms of cardiac conduction disease (CCD) and provide our perspectives on future research and therapeutic opportunities in this field. EXPERT OPINION Significant advancement has been made in understanding the molecular mechanisms of CCD, including the recognition of the heterogeneous signaling at the subcellular levels of sinoatrial node, the involvement of inflammatory and autoimmune mechanisms, and the potential impact of epigenetic regulations on CCD. However, the current treatment of CCD manifested as bradycardia still relies primarily on cardiovascular implantable electronic devices (CIEDs). On the other hand, an If specific inhibitor was developed to treat inappropriate sinus tachycardia and sinus tachycardia in heart failure patients with reduced ejection fraction. More work is needed to translate current knowledge into pharmacologic or genetic interventions for the management of CCDs.
Collapse
Affiliation(s)
- Tingting Li
- Department of Medicine (Section of Cardiovascular Research), Baylor College of Medicine, Houston, TX, USA
- Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX, USA
| | - Qussay Marashly
- Department of Cardiology, Montefiore Medical Center, New York, NY, USA
| | - Jitae A Kim
- Division of CardiovasculMedicine, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, USA
| | - Na Li
- Department of Medicine (Section of Cardiovascular Research), Baylor College of Medicine, Houston, TX, USA
- Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX, USA
| | - Mihail G Chelu
- Cardiovascular Research Institute, Baylor College of Medicine, Houston, TX, USA
- Department of Medicine (Division of Cardiology), Baylor College of Medicine, Houston, TX, USA
- Division of Cardiology, Baylor St. Luke's Medical Center, Houston, TX, USA
- Division of Cardiology, Texas Heart Institute, Houston, TX, USA
| |
Collapse
|
4
|
Wang F, Yin L, Zhang W, Tang Y, Wang X, Huang C. The method of sinus node-like pacemaker cells from human induced pluripotent stem cells by BMP and Wnt signaling. Cell Biol Toxicol 2023; 39:2725-2741. [PMID: 36856942 DOI: 10.1007/s10565-023-09797-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Accepted: 02/15/2023] [Indexed: 03/02/2023]
Abstract
The embryonic development of sinus nodes (SAN) is co-regulated by multiple signaling pathways. Among these, the bone morphogenetic protein (BMP) and Wnt signaling pathways are involved in the development of SAN. In this study, the effects of BMP and Wnt signaling on the differentiation of SAN-like pacemaker cells (SANLPCs) were investigated. Human induced pluripotent stem cells (hiPSCs) were divided into four groups: control, BMP4, CHIR-3, and BMP4 + CHIR (CHIR: a Wnt signaling activator). The samples were tested at day (D) 15 of differentiation. The final protocol for the activation of BMP signaling at D0-D3 and reactivation of Wnt signaling at D5-D7 in the differentiation of hiPSCs were determined. The results showed that the mRNA levels of pacemaker markers (TBX18, SHOX2, TBX3, HCN4, and HCN1) were higher in the BMP4 + CHIR group than in the control group, and working myocardial genes were downregulated. The immunofluorescence assay revealed that the expression of SHOX2 and HCN4 increased in the BMP4 + CHIR group compared to that in the other groups. In addition, the results of patch clamps revealed that a funny current of higher density and typical SAN action potentials were recorded, except in the control group, in which the L-type calcium current was higher in the BMP4 + CHIR group than in the other groups. Finally, the proportion of SANLPCs (cTnT+ NKX2.5-) was further enhanced by the combination of BMP4 and CHIR treatment. In summary, the combination of BMP and Wnt signaling promotes the differentiation of SANLPCs from hiPSCs.
Collapse
Affiliation(s)
- Fengyuan Wang
- Department of Cardiology, Renmin Hospital of Wuhan University, Cardiovascular Research Institute, Wuhan University, Hubei Key Laboratory of Cardiology, 238 Jiefang Road, Wuchang, Wuhan, Hubei, 430060, People's Republic of China
| | - Lin Yin
- Department of Cardiology, Renmin Hospital of Wuhan University, Cardiovascular Research Institute, Wuhan University, Hubei Key Laboratory of Cardiology, 238 Jiefang Road, Wuchang, Wuhan, Hubei, 430060, People's Republic of China
| | - Wei Zhang
- Department of Cardiology, Renmin Hospital of Wuhan University, Cardiovascular Research Institute, Wuhan University, Hubei Key Laboratory of Cardiology, 238 Jiefang Road, Wuchang, Wuhan, Hubei, 430060, People's Republic of China
| | - Yanhong Tang
- Department of Cardiology, Renmin Hospital of Wuhan University, Cardiovascular Research Institute, Wuhan University, Hubei Key Laboratory of Cardiology, 238 Jiefang Road, Wuchang, Wuhan, Hubei, 430060, People's Republic of China
| | - Xi Wang
- Department of Cardiology, Renmin Hospital of Wuhan University, Cardiovascular Research Institute, Wuhan University, Hubei Key Laboratory of Cardiology, 238 Jiefang Road, Wuchang, Wuhan, Hubei, 430060, People's Republic of China
| | - Congxin Huang
- Department of Cardiology, Renmin Hospital of Wuhan University, Cardiovascular Research Institute, Wuhan University, Hubei Key Laboratory of Cardiology, 238 Jiefang Road, Wuchang, Wuhan, Hubei, 430060, People's Republic of China.
| |
Collapse
|
5
|
Mishra P, Narayanan R. The enigmatic HCN channels: A cellular neurophysiology perspective. Proteins 2023. [PMID: 37982354 DOI: 10.1002/prot.26643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Revised: 10/24/2023] [Accepted: 11/09/2023] [Indexed: 11/21/2023]
Abstract
What physiological role does a slow hyperpolarization-activated ion channel with mixed cation selectivity play in the fast world of neuronal action potentials that are driven by depolarization? That puzzling question has piqued the curiosity of physiology enthusiasts about the hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, which are widely expressed across the body and especially in neurons. In this review, we emphasize the need to assess HCN channels from the perspective of how they respond to time-varying signals, while also accounting for their interactions with other co-expressing channels and receptors. First, we illustrate how the unique structural and functional characteristics of HCN channels allow them to mediate a slow negative feedback loop in the neurons that they express in. We present the several physiological implications of this negative feedback loop to neuronal response characteristics including neuronal gain, voltage sag and rebound, temporal summation, membrane potential resonance, inductive phase lead, spike triggered average, and coincidence detection. Next, we argue that the overall impact of HCN channels on neuronal physiology critically relies on their interactions with other co-expressing channels and receptors. Interactions with other channels allow HCN channels to mediate intrinsic oscillations, earning them the "pacemaker channel" moniker, and to regulate spike frequency adaptation, plateau potentials, neurotransmitter release from presynaptic terminals, and spike initiation at the axonal initial segment. We also explore the impact of spatially non-homogeneous subcellular distributions of HCN channels in different neuronal subtypes and their interactions with other channels and receptors. Finally, we discuss how plasticity in HCN channels is widely prevalent and can mediate different encoding, homeostatic, and neuroprotective functions in a neuron. In summary, we argue that HCN channels form an important class of channels that mediate a diversity of neuronal functions owing to their unique gating kinetics that made them a puzzle in the first place.
Collapse
Affiliation(s)
- Poonam Mishra
- Department of Neuroscience, Yale School of Medicine, Yale University, New Haven, Connecticut, USA
| | - Rishikesh Narayanan
- Cellular Neurophysiology Laboratory, Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| |
Collapse
|
6
|
Shemarova I. The Dysfunction of Ca 2+ Channels in Hereditary and Chronic Human Heart Diseases and Experimental Animal Models. Int J Mol Sci 2023; 24:15682. [PMID: 37958665 PMCID: PMC10650855 DOI: 10.3390/ijms242115682] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 10/20/2023] [Accepted: 10/23/2023] [Indexed: 11/15/2023] Open
Abstract
Chronic heart diseases, such as coronary heart disease, heart failure, secondary arterial hypertension, and dilated and hypertrophic cardiomyopathies, are widespread and have a fairly high incidence of mortality and disability. Most of these diseases are characterized by cardiac arrhythmias, conduction, and contractility disorders. Additionally, interruption of the electrical activity of the heart, the appearance of extensive ectopic foci, and heart failure are all symptoms of a number of severe hereditary diseases. The molecular mechanisms leading to the development of heart diseases are associated with impaired permeability and excitability of cell membranes and are mainly caused by the dysfunction of cardiac Ca2+ channels. Over the past 50 years, more than 100 varieties of ion channels have been found in the cardiovascular cells. The relationship between the activity of these channels and cardiac pathology, as well as the general cellular biological function, has been intensively studied on several cell types and experimental animal models in vivo and in situ. In this review, I discuss the origin of genetic Ca2+ channelopathies of L- and T-type voltage-gated calcium channels in humans and the role of the non-genetic dysfunctions of Ca2+ channels of various types: L-, R-, and T-type voltage-gated calcium channels, RyR2, including Ca2+ permeable nonselective cation hyperpolarization-activated cyclic nucleotide-gated (HCN), and transient receptor potential (TRP) channels, in the development of cardiac pathology in humans, as well as various aspects of promising experimental studies of the dysfunctions of these channels performed on animal models or in vitro.
Collapse
Affiliation(s)
- Irina Shemarova
- I.M. Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, 194223 Saint-Petersburg, Russia
| |
Collapse
|
7
|
Manoj P, Kim JA, Kim S, Li T, Sewani M, Chelu MG, Li N. Sinus node dysfunction: current understanding and future directions. Am J Physiol Heart Circ Physiol 2023; 324:H259-H278. [PMID: 36563014 PMCID: PMC9886352 DOI: 10.1152/ajpheart.00618.2022] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 12/20/2022] [Accepted: 12/21/2022] [Indexed: 12/24/2022]
Abstract
The sinoatrial node (SAN) is the primary pacemaker of the heart. Normal SAN function is crucial in maintaining proper cardiac rhythm and contraction. Sinus node dysfunction (SND) is due to abnormalities within the SAN, which can affect the heartbeat frequency, regularity, and the propagation of electrical pulses through the cardiac conduction system. As a result, SND often increases the risk of cardiac arrhythmias. SND is most commonly seen as a disease of the elderly given the role of degenerative fibrosis as well as other age-dependent changes in its pathogenesis. Despite the prevalence of SND, current treatment is limited to pacemaker implantation, which is associated with substantial medical costs and complications. Emerging evidence has identified various genetic abnormalities that can cause SND, shedding light on the molecular underpinnings of SND. Identification of these molecular mechanisms and pathways implicated in the pathogenesis of SND is hoped to identify novel therapeutic targets for the development of more effective therapies for this disease. In this review article, we examine the anatomy of the SAN and the pathophysiology and epidemiology of SND. We then discuss in detail the most common genetic mutations correlated with SND and provide our perspectives on future research and therapeutic opportunities in this field.
Collapse
Affiliation(s)
- Pavan Manoj
- School of Public Health, Texas A&M University, College Station, Texas
| | - Jitae A Kim
- Department of Medicine, Baylor College of Medicine, Houston, Texas
| | - Stephanie Kim
- Department of BioSciences, Rice University, Houston, Texas
| | - Tingting Li
- Section of Cardiovascular Research, Department of Medicine, Baylor College of Medicine, Houston, Texas
| | - Maham Sewani
- Department of BioSciences, Rice University, Houston, Texas
| | - Mihail G Chelu
- Division of Cardiology, Department of Medicine, Baylor College of Medicine, Houston, Texas
| | - Na Li
- Section of Cardiovascular Research, Department of Medicine, Baylor College of Medicine, Houston, Texas
| |
Collapse
|
8
|
Guarina L, Moghbel AN, Pourhosseinzadeh MS, Cudmore RH, Sato D, Clancy CE, Santana LF. Biological noise is a key determinant of the reproducibility and adaptability of cardiac pacemaking and EC coupling. J Gen Physiol 2022; 154:e202012613. [PMID: 35482009 PMCID: PMC9059386 DOI: 10.1085/jgp.202012613] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 03/16/2022] [Accepted: 04/07/2022] [Indexed: 12/23/2022] Open
Abstract
Each heartbeat begins with the generation of an action potential in pacemaking cells in the sinoatrial node. This signal triggers contraction of cardiac muscle through a process termed excitation-contraction (EC) coupling. EC coupling is initiated in dyadic structures of cardiac myocytes, where ryanodine receptors in the junctional sarcoplasmic reticulum come into close apposition with clusters of CaV1.2 channels in invaginations of the sarcolemma. Cooperative activation of CaV1.2 channels within these clusters causes a local increase in intracellular Ca2+ that activates the juxtaposed ryanodine receptors. A salient feature of healthy cardiac function is the reliable and precise beat-to-beat pacemaking and amplitude of Ca2+ transients during EC coupling. In this review, we discuss recent discoveries suggesting that the exquisite reproducibility of this system emerges, paradoxically, from high variability at subcellular, cellular, and network levels. This variability is attributable to stochastic fluctuations in ion channel trafficking, clustering, and gating, as well as dyadic structure, which increase intracellular Ca2+ variance during EC coupling. Although the effects of these large, local fluctuations in function and organization are sometimes negligible at the macroscopic level owing to spatial-temporal summation within and across cells in the tissue, recent work suggests that the "noisiness" of these intracellular Ca2+ events may either enhance or counterintuitively reduce variability in a context-dependent manner. Indeed, these noisy events may represent distinct regulatory features in the tuning of cardiac contractility. Collectively, these observations support the importance of incorporating experimentally determined values of Ca2+ variance in all EC coupling models. The high reproducibility of cardiac contraction is a paradoxical outcome of high Ca2+ signaling variability at subcellular, cellular, and network levels caused by stochastic fluctuations in multiple processes in time and space. This underlying stochasticity, which counterintuitively manifests as reliable, consistent Ca2+ transients during EC coupling, also allows for rapid changes in cardiac rhythmicity and contractility in health and disease.
Collapse
Affiliation(s)
- Laura Guarina
- Department of Physiology and Membrane Biology, University of California Davis School of Medicine, Davis, CA
| | - Ariana Neelufar Moghbel
- Department of Physiology and Membrane Biology, University of California Davis School of Medicine, Davis, CA
| | | | - Robert H. Cudmore
- Department of Physiology and Membrane Biology, University of California Davis School of Medicine, Davis, CA
| | - Daisuke Sato
- Department of Pharmacology, University of California Davis School of Medicine, Davis, CA
| | - Colleen E. Clancy
- Department of Physiology and Membrane Biology, University of California Davis School of Medicine, Davis, CA
| | - Luis Fernando Santana
- Department of Physiology and Membrane Biology, University of California Davis School of Medicine, Davis, CA
| |
Collapse
|
9
|
Paradigm shift: new concepts for HCN4 function in cardiac pacemaking. Pflugers Arch 2022; 474:649-663. [PMID: 35556164 PMCID: PMC9192375 DOI: 10.1007/s00424-022-02698-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Accepted: 04/29/2022] [Indexed: 11/05/2022]
Abstract
Hyperpolarization-activated cyclic nucleotide–gated (HCN) channels are the molecular correlate of the If current and are critically involved in controlling neuronal excitability and the autonomous rhythm of the heart. The HCN4 isoform is the main HCN channel subtype expressed in the sinoatrial node (SAN), a tissue composed of specialized pacemaker cells responsible for generating the intrinsic heartbeat. More than 40 years ago, the If current was first discovered in rabbit SAN tissue. Along with this discovery, a theory was proposed that cyclic adenosine monophosphate–dependent modulation of If mediates heart rate regulation by the autonomic nervous system—a process called chronotropic effect. However, up to the present day, this classical theory could not be reliably validated. Recently, new concepts emerged confirming that HCN4 channels indeed play an important role in heart rate regulation. However, the cellular mechanism by which HCN4 controls heart rate turned out to be completely different than originally postulated. Here, we review the latest findings regarding the physiological role of HCN4 in the SAN. We describe a newly discovered mechanism underlying heart rate regulation by HCN4 at the tissue and single cell levels, and we discuss these observations in the context of results from previously studied HCN4 mouse models.
Collapse
|
10
|
Al Kury LT, Chacar S, Alefishat E, Khraibi AA, Nader M. Structural and Electrical Remodeling of the Sinoatrial Node in Diabetes: New Dimensions and Perspectives. Front Endocrinol (Lausanne) 2022; 13:946313. [PMID: 35872997 PMCID: PMC9302195 DOI: 10.3389/fendo.2022.946313] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 06/14/2022] [Indexed: 11/14/2022] Open
Abstract
The sinoatrial node (SAN) is composed of highly specialized cells that mandate the spontaneous beating of the heart through self-generation of an action potential (AP). Despite this automaticity, the SAN is under the modulation of the autonomic nervous system (ANS). In diabetes mellitus (DM), heart rate variability (HRV) manifests as a hallmark of diabetic cardiomyopathy. This is paralleled by an impaired regulation of the ANS, and by a pathological remodeling of the pacemaker structure and function. The direct effect of diabetes on the molecular signatures underscoring this pathology remains ill-defined. The recent focus on the electrical currents of the SAN in diabetes revealed a repressed firing rate of the AP and an elongation of its tracing, along with conduction abnormalities and contractile failure. These changes are blamed on the decreased expression of ion transporters and cell-cell communication ports at the SAN (i.e., HCN4, calcium and potassium channels, connexins 40, 45, and 46) which further promotes arrhythmias. Molecular analysis crystallized the RGS4 (regulator of potassium currents), mitochondrial thioredoxin-2 (reactive oxygen species; ROS scavenger), and the calcium-dependent calmodulin kinase II (CaMKII) as metabolic culprits of relaying the pathological remodeling of the SAN cells (SANCs) structure and function. A special attention is given to the oxidation of CaMKII and the generation of ROS that induce cell damage and apoptosis of diabetic SANCs. Consequently, the diabetic SAN contains a reduced number of cells with significant infiltration of fibrotic tissues that further delay the conduction of the AP between the SANCs. Failure of a genuine generation of AP and conduction of their derivative waves to the neighboring atrial myocardium may also occur as a result of the anti-diabetic regiment (both acute and/or chronic treatments). All together, these changes pose a challenge in the field of cardiology and call for further investigations to understand the etiology of the structural/functional remodeling of the SANCs in diabetes. Such an understanding may lead to more adequate therapies that can optimize glycemic control and improve health-related outcomes in patients with diabetes.
Collapse
Affiliation(s)
- Lina T. Al Kury
- Department of Health Sciences, College of Natural and Health Sciences, Zayed University, Abu Dhabi, United Arab Emirates
- *Correspondence: Lina T. Al Kury, ; Moni Nader,
| | - Stephanie Chacar
- Department of Physiology and Immunology, College of Medicine and Health Sciences, Khalifa University of Science and Technology, Abu Dhabi, United Arab Emirates
| | - Eman Alefishat
- Department of Pharmacology, College of Medicine and Health Sciences, Khalifa University of Science and Technology, Abu Dhabi, United Arab Emirates
- Department of Biopharmaceutics and Clinical Pharmacy, School of Pharmacy, The University of Jordan, Amman, Jordan
- Center for Biotechnology, Khalifa University of Science and Technology, Abu Dhabi, United Arab Emirates
| | - Ali A. Khraibi
- Department of Physiology and Immunology, College of Medicine and Health Sciences, Khalifa University of Science and Technology, Abu Dhabi, United Arab Emirates
- Center for Biotechnology, Khalifa University of Science and Technology, Abu Dhabi, United Arab Emirates
| | - Moni Nader
- Department of Physiology and Immunology, College of Medicine and Health Sciences, Khalifa University of Science and Technology, Abu Dhabi, United Arab Emirates
- Center for Biotechnology, Khalifa University of Science and Technology, Abu Dhabi, United Arab Emirates
- *Correspondence: Lina T. Al Kury, ; Moni Nader,
| |
Collapse
|
11
|
Dixon RE, Navedo MF, Binder MD, Santana LF. Mechanisms and Physiological Implications of Cooperative Gating of Ion Channels Clusters. Physiol Rev 2021; 102:1159-1210. [PMID: 34927454 DOI: 10.1152/physrev.00022.2021] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Ion channels play a central role in the regulation of nearly every cellular process. Dating back to the classic 1952 Hodgkin-Huxley model of the generation of the action potential, ion channels have always been thought of as independent agents. A myriad of recent experimental findings exploiting advances in electrophysiology, structural biology, and imaging techniques, however, have posed a serious challenge to this long-held axiom as several classes of ion channels appear to open and close in a coordinated, cooperative manner. Ion channel cooperativity ranges from variable-sized oligomeric cooperative gating in voltage-gated, dihydropyridine-sensitive Cav1.2 and Cav1.3 channels to obligatory dimeric assembly and gating of voltage-gated Nav1.5 channels. Potassium channels, transient receptor potential channels, hyperpolarization cyclic nucleotide-activated channels, ryanodine receptors (RyRs), and inositol trisphosphate receptors (IP3Rs) have also been shown to gate cooperatively. The implications of cooperative gating of these ion channels range from fine tuning excitation-contraction coupling in muscle cells to regulating cardiac function and vascular tone, to modulation of action potential and conduction velocity in neurons and cardiac cells, and to control of pace-making activity in the heart. In this review, we discuss the mechanisms leading to cooperative gating of ion channels, their physiological consequences and how alterations in cooperative gating of ion channels may induce a range of clinically significant pathologies.
Collapse
Affiliation(s)
- Rose Ellen Dixon
- Department of Physiology and Membrane Biology, University of California, Davis, CA, United States
| | - Manuel F Navedo
- Department of Pharmacology, University of California, Davis, CA, United States
| | - Marc D Binder
- Department of Physiology and Biophysics, University of Washington, Seattle, WA, United States
| | - L Fernando Santana
- Department of Physiology and Membrane Biology, University of California, Davis, CA, United States
| |
Collapse
|
12
|
Gruscheski L, Brand T. The Role of POPDC Proteins in Cardiac Pacemaking and Conduction. J Cardiovasc Dev Dis 2021; 8:160. [PMID: 34940515 PMCID: PMC8706714 DOI: 10.3390/jcdd8120160] [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: 10/27/2021] [Revised: 11/17/2021] [Accepted: 11/20/2021] [Indexed: 11/17/2022] Open
Abstract
The Popeye domain-containing (POPDC) gene family, consisting of Popdc1 (also known as Bves), Popdc2, and Popdc3, encodes transmembrane proteins abundantly expressed in striated muscle. POPDC proteins have recently been identified as cAMP effector proteins and have been proposed to be part of the protein network involved in cAMP signaling. However, their exact biochemical activity is presently poorly understood. Loss-of-function mutations in animal models causes abnormalities in skeletal muscle regeneration, conduction, and heart rate adaptation after stress. Likewise, patients carrying missense or nonsense mutations in POPDC genes have been associated with cardiac arrhythmias and limb-girdle muscular dystrophy. In this review, we introduce the POPDC protein family, and describe their structure function, and role in cAMP signaling. Furthermore, the pathological phenotypes observed in zebrafish and mouse models and the clinical and molecular pathologies in patients carrying POPDC mutations are described.
Collapse
Affiliation(s)
| | - Thomas Brand
- National Heart and Lung Institute, Imperial College London, London W12 0NN, UK;
| |
Collapse
|
13
|
f/HCN channels: From a tiny current controlling cardiac pacemaking to a pleiotropic current all over the body. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2021; 166:1-2. [PMID: 34648827 DOI: 10.1016/j.pbiomolbio.2021.10.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
14
|
DiFrancesco ML, Mesirca P, Bidaud I, Isbrandt D, Mangoni ME. The funny current in genetically modified mice. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2021; 166:39-50. [PMID: 34129872 DOI: 10.1016/j.pbiomolbio.2021.06.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 05/18/2021] [Accepted: 06/07/2021] [Indexed: 12/27/2022]
Abstract
Since its first description in 1979, the hyperpolarization-activated funny current (If) has been the object of intensive research aimed at understanding its role in cardiac pacemaker activity and its modulation by the sympathetic and parasympathetic branches of the autonomic nervous system. If was described in isolated tissue strips of the rabbit sinoatrial node using the double-electrode voltage-clamp technique. Since then, the rabbit has been the principal animal model for studying pacemaker activity and If for more than 20 years. In 2001, the first study describing the electrophysiological properties of mouse sinoatrial pacemaker myocytes and those of If was published. It was soon followed by the description of murine myocytes of the atrioventricular node and the Purkinje fibres. The sinoatrial node of genetically modified mice has become a very popular model for studying the mechanisms of cardiac pacemaker activity. This field of research benefits from the impressive advancement of in-vivo exploration techniques of physiological parameters, imaging, genetics, and large-scale genomic approaches. The present review discusses the influence of mouse genetic on the most recent knowledge of the funny current's role in the physiology and pathophysiology of cardiac pacemaker activity. Genetically modified mice have provided important insights into the role of If in determining intrinsic automaticity in vivo and in myocytes of the conduction system. In addition, gene targeting of f-(HCN) channel isoforms have contributed to elucidating the current's role in the regulation of heart rate by the parasympathetic nervous system. This review is dedicated to Dario DiFrancesco on his retirement.
Collapse
Affiliation(s)
- Mattia L DiFrancesco
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Genoa, Italy; IRCCS Ospedale Policlinico San Martino, Genoa, Italy; Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France; LabEx Ion Channels Science and Therapeutics (ICST), France.
| | - Pietro Mesirca
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France; LabEx Ion Channels Science and Therapeutics (ICST), France
| | - Isabelle Bidaud
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France; LabEx Ion Channels Science and Therapeutics (ICST), France
| | - Dirk Isbrandt
- Deutsches Zentrum für Neurodegenerative Erktankungen (DZNE), Bonn, Germany; University of Cologne, Institute for Molecular and Behavioral Neuroscience, Cologne, Germany
| | - Matteo E Mangoni
- Institut de Génomique Fonctionnelle, Université de Montpellier, CNRS, INSERM, Montpellier, France; LabEx Ion Channels Science and Therapeutics (ICST), France.
| |
Collapse
|
15
|
Hennis K, Rötzer RD, Piantoni C, Biel M, Wahl-Schott C, Fenske S. Speeding Up the Heart? Traditional and New Perspectives on HCN4 Function. Front Physiol 2021; 12:669029. [PMID: 34122140 PMCID: PMC8191466 DOI: 10.3389/fphys.2021.669029] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Accepted: 04/19/2021] [Indexed: 01/20/2023] Open
Abstract
The sinoatrial node (SAN) is the primary pacemaker of the heart and is responsible for generating the intrinsic heartbeat. Within the SAN, spontaneously active pacemaker cells initiate the electrical activity that causes the contraction of all cardiomyocytes. The firing rate of pacemaker cells depends on the slow diastolic depolarization (SDD) and determines the intrinsic heart rate (HR). To adapt cardiac output to varying physical demands, HR is regulated by the autonomic nervous system (ANS). The sympathetic and parasympathetic branches of the ANS innervate the SAN and regulate the firing rate of pacemaker cells by accelerating or decelerating SDD-a process well-known as the chronotropic effect. Although this process is of fundamental physiological relevance, it is still incompletely understood how it is mediated at the subcellular level. Over the past 20 years, most of the work to resolve the underlying cellular mechanisms has made use of genetically engineered mouse models. In this review, we focus on the findings from these mouse studies regarding the cellular mechanisms involved in the generation and regulation of the heartbeat, with particular focus on the highly debated role of the hyperpolarization-activated cyclic nucleotide-gated cation channel HCN4 in mediating the chronotropic effect. By focusing on experimental data obtained in mice and humans, but not in other species, we outline how findings obtained in mice relate to human physiology and pathophysiology and provide specific information on how dysfunction or loss of HCN4 channels leads to human SAN disease.
Collapse
Affiliation(s)
- Konstantin Hennis
- Center for Drug Research, Department of Pharmacy, Ludwig-Maximilians-Universität München, Munich, Germany
| | - René D. Rötzer
- Center for Drug Research, Department of Pharmacy, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Chiara Piantoni
- Institute for Neurophysiology, Hannover Medical School, Hanover, Germany
| | - Martin Biel
- Center for Drug Research, Department of Pharmacy, Ludwig-Maximilians-Universität München, Munich, Germany
- German Center for Cardiovascular Research (DZHK), Partner Site Munich Heart Alliance, Munich, Germany
| | - Christian Wahl-Schott
- Institute for Neurophysiology, Hannover Medical School, Hanover, Germany
- German Center for Cardiovascular Research (DZHK), Partner Site Munich Heart Alliance, Munich, Germany
| | - Stefanie Fenske
- Center for Drug Research, Department of Pharmacy, Ludwig-Maximilians-Universität München, Munich, Germany
- German Center for Cardiovascular Research (DZHK), Partner Site Munich Heart Alliance, Munich, Germany
| |
Collapse
|