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Lerman BB, Markowitz SM, Cheung JW, Thomas G, Ip JE. Ventricular Tachycardia Due to Triggered Activity: Role of Early and Delayed Afterdepolarizations. JACC Clin Electrophysiol 2024; 10:379-401. [PMID: 38127010 DOI: 10.1016/j.jacep.2023.10.033] [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: 06/22/2023] [Revised: 10/24/2023] [Accepted: 10/28/2023] [Indexed: 12/23/2023]
Abstract
Most forms of sustained ventricular tachycardia (VT) are caused by re-entry, resulting from altered myocardial conduction and refractoriness secondary to underlying structural heart disease. In contrast, VT caused by triggered activity (TA) is unrelated to an abnormal structural substrate and is often caused by molecular defects affecting ion channel function or regulation of intracellular calcium cycling. This review summarizes the cellular and molecular bases underlying TA and exemplifies their clinical relevance with selective representative scenarios. The underlying basis of TA caused by delayed afterdepolarizations is related to sarcoplasmic reticulum calcium overload, calcium waves, and diastolic sarcoplasmic reticulum calcium leak. Clinical examples of TA caused by delayed afterdepolarizations include sustained right and left ventricular outflow tract tachycardia and catecholaminergic polymorphic VT. The other form of afterpotentials, early afterdepolarizations, are systolic events and inscribe early afterdepolarizations during phase 2 or phase 3 of the action potential. The fundamental defect is a decrease in repolarization reserve with associated increases in late plateau inward currents. Malignant ventricular arrhythmias in the long QT syndromes are initiated by early afterdepolarization-mediated TA. An understanding of the molecular and cellular bases of these arrhythmias has resulted in generally effective pharmacologic-based therapies, but these are nonspecific agents that have off-target effects. Therapeutic efficacy may need to be augmented with an implantable defibrillator. Next-generation therapies will include novel agents that rescue arrhythmogenic abnormalities in cellular signaling pathways and gene therapy approaches that transfer or edit pathogenic gene variants or silence mutant messenger ribonucleic acid.
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Affiliation(s)
- Bruce B Lerman
- Department of Medicine, Division of Cardiology and the Greenberg Institute for Cardiac Electrophysiology, Department of Medicine, Cornell University Medical Center, New York, New York, USA.
| | - Steven M Markowitz
- Department of Medicine, Division of Cardiology and the Greenberg Institute for Cardiac Electrophysiology, Department of Medicine, Cornell University Medical Center, New York, New York, USA
| | - Jim W Cheung
- Department of Medicine, Division of Cardiology and the Greenberg Institute for Cardiac Electrophysiology, Department of Medicine, Cornell University Medical Center, New York, New York, USA
| | - George Thomas
- Department of Medicine, Division of Cardiology and the Greenberg Institute for Cardiac Electrophysiology, Department of Medicine, Cornell University Medical Center, New York, New York, USA
| | - James E Ip
- Department of Medicine, Division of Cardiology and the Greenberg Institute for Cardiac Electrophysiology, Department of Medicine, Cornell University Medical Center, New York, New York, USA
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Veron G, Maltsev VA, Stern MD, Maltsev AV. Elementary intracellular Ca signals approximated as a transition of release channel system from a metastable state. JOURNAL OF APPLIED PHYSICS 2023; 134:124701. [PMID: 37744735 PMCID: PMC10517864 DOI: 10.1063/5.0151255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Accepted: 09/04/2023] [Indexed: 09/26/2023]
Abstract
Cardiac muscle contraction is initiated by an elementary Ca signal (called Ca spark) which is achieved by collective action of Ca release channels in a cluster. The mechanism of this synchronization remains uncertain. We approached Ca spark activation as an emergent phenomenon of an interactive system of release channels. We constructed a weakly lumped Markov chain that applies an Ising model formalism to such release channel clusters and probable open channel configurations and demonstrated that spark activation is described as a system transition from a metastable to an absorbing state, analogous to the pressure required to overcome surface tension in bubble formation. This yielded quantitative estimates of the spark generation probability as a function of various system parameters. We performed numerical simulations to find spark probabilities as a function of sarcoplasmic reticulum Ca concentration, obtaining similar values for spark activation threshold as our analytic model, as well as those reported in experimental studies. Our parametric sensitivity analyses also showed that the spark activation threshold decreased as Ca sensitivity of RyR activation and RyR cluster size increased.
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Affiliation(s)
- Guillermo Veron
- Cellular Biophysics Section, Laboratory of Cardiovascular Science, National Institute on Aging, NIH, Baltimore, Maryland 21224, USA
| | - Victor A. Maltsev
- Cellular Biophysics Section, Laboratory of Cardiovascular Science, National Institute on Aging, NIH, Baltimore, Maryland 21224, USA
| | - Michael D. Stern
- Cellular Biophysics Section, Laboratory of Cardiovascular Science, National Institute on Aging, NIH, Baltimore, Maryland 21224, USA
| | - Anna V. Maltsev
- School of Mathematical Sciences, Queen Mary University of London, London E14NS, United Kingdom
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Yildiz B, Schiedt L, Mulaw M, Bockmann J, Jesse S, Lutz AK, Boeckers TM. Shank3 related muscular hypotonia is accompanied by increased intracellular calcium concentrations and ion channel dysregulation in striated muscle tissue. Front Cell Dev Biol 2023; 11:1243299. [PMID: 37745298 PMCID: PMC10511643 DOI: 10.3389/fcell.2023.1243299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Accepted: 08/17/2023] [Indexed: 09/26/2023] Open
Abstract
Phelan-McDermid syndrome (PMS) is a syndromic form of Autism Spectrum Disorders (ASD) classified as a rare genetic neurodevelopmental disorder featuring global developmental delay, absent or delayed speech, ASD-like behaviour and neonatal skeletal muscle hypotonia. PMS is caused by a heterozygous deletion of the distal end of chromosome 22q13.3 or SHANK3 mutations. We analyzed striated muscles of newborn Shank3Δ11(-/-) animals and found a significant enlargement of the sarcoplasmic reticulum as previously seen in adult Shank3Δ11(-/-) mice, indicative of a Shank3-dependent and not compensatory mechanism for this structural alteration. We analyzed transcriptional differences by RNA-sequencing of muscle tissue of neonatal Shank3Δ11(-/-) mice and compared those to Shank3(+/+) controls. We found significant differences in gene expression of ion channels crucial for muscle contraction and for molecules involved in calcium ion regulation. In addition, calcium storage- [i.e., Calsequestrin (CSQ)], calcium secretion- and calcium-related signaling-proteins were found to be affected. By immunostainings and Western blot analyses we could confirm these findings both in Shank3Δ11(-/-) mice and PMS patient muscle tissue. Moreover, alterations could be induced in vitro by the selective downregulation of Shank3 in C2C12 myotubes. Our results emphasize that SHANK3 levels directly or indirectly regulate calcium homeostasis in a cell autonomous manner that might contribute to muscular hypotonia especially seen in the newborn.
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Affiliation(s)
- Berra Yildiz
- Institute for Anatomy and Cell Biology, Ulm University, Ulm, Germany
- International Graduate School in Molecular Medicine, IGradU, Ulm, Germany
| | - Lisa Schiedt
- Institute for Anatomy and Cell Biology, Ulm University, Ulm, Germany
- International Graduate School in Molecular Medicine, IGradU, Ulm, Germany
| | - Medhanie Mulaw
- Unit for Single-cell Genomics, Medical Faculty, Ulm University, Ulm, Germany
| | - Jürgen Bockmann
- Institute for Anatomy and Cell Biology, Ulm University, Ulm, Germany
| | - Sarah Jesse
- Neurologie, Universitätsklinikum Ulm, Ulm, Germany
| | - Anne-Kathrin Lutz
- Institute for Anatomy and Cell Biology, Ulm University, Ulm, Germany
| | - Tobias M. Boeckers
- Institute for Anatomy and Cell Biology, Ulm University, Ulm, Germany
- Deutsches Zentrum für Neurodegenerative Erkrankungen, Ulm Site, Ulm, Germany
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Yang Y, Zhao Y, Wang Q, Liu M, Chang H, Li L, Meng X, Deng Y, Ling C, Wang K, Song G, Sui X. Effects of Nano-titanium Dioxide on Calcium Homeostasis in Vivo and in Vitro: a Systematic Review and Meta-analysis. Toxicol Mech Methods 2022; 33:249-259. [PMID: 36097686 DOI: 10.1080/15376516.2022.2124137] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/09/2022]
Abstract
With the extensive application of titanium dioxide nanoparticles (TiO2 NPs), their impacts on calcium homeostasis have aroused extensive attention from scholars. However, there are still some controversies in relevant reports. Therefore, a systematic review was performed followed by a meta-analysis to explore whether TiO2 NPs could induce the imbalance in calcium homeostasis in vivo and in vitro through Revman5.4 and Stata15.0 in this research. 14 studies were included through detailed database retrieval and literature screening. Results indicated that the calcium levels were significantly increased and the activity of Ca2+-ATPase was significantly decreased by TiO2 NPs in vivo and in vitro. Subgroup analysis of the studies in vivo showed that TiO2 NPs exposure caused a significant increase in calcium levels in rats, exposure to large-sized TiO2 NPs (> 10 nm) and long-term (> 30 d) exposure could significantly increase calcium levels, and the activity of Ca2+-ATPase showed a concentration-dependent downward trend. Subgroup analysis of the studies in vitro revealed that intracellular calcium levels increased significantly in animal cells, exposure to small-sized TiO2 NPs (≤ 10 nm) and high concentration (> 10 μg/mL) exposure could induce a significant increase in Ca2+ concentration, and the activity of Ca2+-ATPase also showed a concentration-dependent downward trend. This research showed that the physicochemical properties of TiO2 NPs and the experimental scheme could affect calcium homeostasis.
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Affiliation(s)
- Yaqian Yang
- Department of Preventive Medicine/the Key Laboratories for Xinjiang Endemic and Ethnic Diseases, School of Medicine, Shihezi University, Shihezi, Xinjiang, 832002, China
| | - Yiman Zhao
- Department of Preventive Medicine/the Key Laboratories for Xinjiang Endemic and Ethnic Diseases, School of Medicine, Shihezi University, Shihezi, Xinjiang, 832002, China
| | - Qianqian Wang
- Department of Preventive Medicine/the Key Laboratories for Xinjiang Endemic and Ethnic Diseases, School of Medicine, Shihezi University, Shihezi, Xinjiang, 832002, China
| | - Mi Liu
- Department of Preventive Medicine/the Key Laboratories for Xinjiang Endemic and Ethnic Diseases, School of Medicine, Shihezi University, Shihezi, Xinjiang, 832002, China
| | - Hongmei Chang
- Department of Preventive Medicine/the Key Laboratories for Xinjiang Endemic and Ethnic Diseases, School of Medicine, Shihezi University, Shihezi, Xinjiang, 832002, China
| | - Li Li
- Department of Preventive Medicine/the Key Laboratories for Xinjiang Endemic and Ethnic Diseases, School of Medicine, Shihezi University, Shihezi, Xinjiang, 832002, China
| | - Xiaojia Meng
- Department of Preventive Medicine/the Key Laboratories for Xinjiang Endemic and Ethnic Diseases, School of Medicine, Shihezi University, Shihezi, Xinjiang, 832002, China
| | - Yaxin Deng
- Department of Preventive Medicine/the Key Laboratories for Xinjiang Endemic and Ethnic Diseases, School of Medicine, Shihezi University, Shihezi, Xinjiang, 832002, China
| | - Chunmei Ling
- The Third People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi, Xinjiang, 830091, China
| | - Kui Wang
- Department of Preventive Medicine/the Key Laboratories for Xinjiang Endemic and Ethnic Diseases, School of Medicine, Shihezi University, Shihezi, Xinjiang, 832002, China
| | - Guanling Song
- Department of Preventive Medicine/the Key Laboratories for Xinjiang Endemic and Ethnic Diseases, School of Medicine, Shihezi University, Shihezi, Xinjiang, 832002, China
| | - Xin Sui
- Department of Preventive Medicine/the Key Laboratories for Xinjiang Endemic and Ethnic Diseases, School of Medicine, Shihezi University, Shihezi, Xinjiang, 832002, China
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Bare DJ, Yue L, Ai X. A special issue on calcium dynamics of the heart: remodeling of ion channels and regulatory pathways. Pflugers Arch 2021; 473:313-316. [PMID: 33666746 PMCID: PMC7940331 DOI: 10.1007/s00424-021-02532-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 01/27/2021] [Accepted: 02/01/2021] [Indexed: 11/24/2022]
Affiliation(s)
- Dan J Bare
- Department of Physiology and Biophysics, Rush University Medical Center, Chicago, IL, 60612, USA
| | - Lixia Yue
- Department of Cell Biology, Calhoun Cardiology Center, University of Connecticut Health Center, Farmington, CT, 06030, USA.
| | - Xun Ai
- Department of Physiology and Biophysics, Rush University Medical Center, Chicago, IL, 60612, USA.
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