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Majumder R. In silico thermal control of spiral wave dynamics in excitable cardiac tissue. BIOPHYSICAL REPORTS 2024; 4:100170. [PMID: 38960373 PMCID: PMC11304022 DOI: 10.1016/j.bpr.2024.100170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2024] [Revised: 06/26/2024] [Accepted: 06/28/2024] [Indexed: 07/05/2024]
Abstract
Self-organizing spiral waves of excitation occur in many complex excitable systems. In the heart, for example, they are associated with the occurrence of fatal cardiac arrhythmias such as tachycardia and fibrillation, which can lead to sudden cardiac death. The control of these waves is therefore necessary for the treatment of the disease. In this letter, I present an innovative approach to control cardiac arrhythmias using low (nonfreezing) temperatures. This approach differs from all previous established techniques in that it involves no drugs, no genetic modification, no injection of foreign bodies, no application of voltage shocks (high or low, single or pulsed), and no curative damage to the heart. It relies on regional cooling of cardiac tissue to create a transient inhomogeneity in the electrophysiological properties. This inhomogeneity can then be manipulated to control the dynamics of the reentrant waves. This approach is, to my knowledge, the most sustainable theoretical proposal for the treatment of cardiac arrhythmias in the clinic.
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2
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Crispino A, Loppini A, Uzelac I, Iravanian S, Bhatia NK, Burke M, Filippi S, Fenton FH, Gizzi A. A cross species thermoelectric and spatiotemporal analysis of alternans in live explanted hearts using dual voltage-calcium fluorescence optical mapping. Physiol Meas 2024; 45:065001. [PMID: 38772394 DOI: 10.1088/1361-6579/ad4e8f] [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: 11/20/2023] [Accepted: 05/21/2024] [Indexed: 05/23/2024]
Abstract
Objective.Temperature plays a crucial role in influencing the spatiotemporal dynamics of the heart. Electrical instabilities due to specific thermal conditions typically lead to early period-doubling bifurcations and beat-to-beat alternans. These pro-arrhythmic phenomena manifest in voltage and calcium traces, resulting in compromised contractile behaviors. In such intricate scenario, dual optical mapping technique was used to uncover unexplored multi-scale and nonlinear couplings, essential for early detection and understanding of cardiac arrhythmia.Approach.We propose a methodological analysis of synchronized voltage-calcium signals for detecting alternans, restitution curves, and spatiotemporal alternans patterns under different thermal conditions, based on integral features calculation. To validate our approach, we conducted a cross-species investigation involving rabbit and guinea pig epicardial ventricular surfaces and human endocardial tissue under pacing-down protocols.Main results.We show that the proposed integral feature, as the area under the curve, could be an easily applicable indicator that may enhance the predictability of the onset and progression of cardiac alternans. Insights into spatiotemporal correlation analysis of characteristic spatial lengths across different heart species were further provided.Significance.Exploring cross-species thermoelectric features contributes to understanding temperature-dependent proarrhythmic regimes and their implications on coupled spatiotemporal voltage-calcium dynamics. The findings provide preliminary insights and potential strategies for enhancing arrhythmia detection and treatment.
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Affiliation(s)
- Anna Crispino
- Department of Engineering, Università Campus Bio-Medico di Roma, Rome, Italy
| | - Alessandro Loppini
- Department of Medicine and Surgery, Università Campus Bio-Medico di Roma, Rome, Italy
| | - Ilija Uzelac
- Virginia Commonwealth University, Richmond, VA, United States of America
| | - Shahriar Iravanian
- Department of Cardiovascular Medicine, Emory University School of Medicine, Atlanta, GA, United States of America
| | - Neal K Bhatia
- Department of Cardiovascular Medicine, Emory University School of Medicine, Atlanta, GA, United States of America
| | - Michael Burke
- Department of Cardiovascular Medicine, Emory University School of Medicine, Atlanta, GA, United States of America
| | - Simonetta Filippi
- Department of Engineering, Università Campus Bio-Medico di Roma, Rome, Italy
| | - Flavio H Fenton
- School of Physics, Georgia Institute of Technology, Atlanta, GA, United States of America
| | - Alessio Gizzi
- Department of Engineering, Università Campus Bio-Medico di Roma, Rome, Italy
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3
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Averin AS, Storey KB, Nenov MN. The effects of nickel chloride on papillary muscle contractility under normothermic and hypothermic conditions: Comparison of active and hibernating ground squirrels (Urocitellus undulatus) with Wistar rats. J Therm Biol 2024; 119:103785. [PMID: 38320933 DOI: 10.1016/j.jtherbio.2024.103785] [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: 06/03/2023] [Revised: 01/08/2024] [Accepted: 01/16/2024] [Indexed: 02/08/2024]
Abstract
Extracellular Ca2+ plays a pivotal role in the regulation of cardiac contractility under normal and extreme conditions. Here, by using nickel chloride (NiCl2), a non-specific blocker of extracellular Ca2+ influx, we studied the input of extracellular Ca2+ on the regulation of papillary muscle (PM) contractility under normal and hypothermic conditions in ground squirrels (GS), and rats. By measuring isometric force of contraction, we studied how NiCl2 affects force-frequency relationship and the rest effect in PM of these species at 30 °C and 10 °C. We found that at 30 °C 1.5 mM NiCl2 significantly reduced force of contraction across entire frequency range in active GS and rats, whereas in hibernating GS force of contraction was reduced at low and high frequency range. Additionally, NiCl2 evoked spontaneous contractility in rats but not GS PM. The rest effect was significantly reduced by NiCl2 for active GS and rats but not hibernating GS. At 10 °C, NiCl2 fully reduced contractility in active GS and, to a lesser extent, in rats, whereas in hibernating GS it was significant only at 0.3 Hz. The rest effect was significantly reduced by NiCl2 in both active and hibernating GS, whereas it was unmasked in rats that had high contractility under hypothermic conditions in control. Our results show a significant contribution of extracellular Ca2+ to myocardial contractility in GS not only in active but also in hibernating states, especially under hypothermic conditions, whereas limitation of extracellular Ca2+ influx in rats under hypothermia can play protective role for myocardial contractility.
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Affiliation(s)
- Alexey S Averin
- Institute of Cell Biophysics, Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences", Pushchino, 142290, Russia
| | - Kenneth B Storey
- Department of Biology and Institute of Biochemistry, Carleton University, Ottawa, ON, K1S 5B6, Canada
| | - Miroslav N Nenov
- Department of Psychology and Neuroscience, Temple University, Weiss Hall, 1701 North 13th Street, Philadelphia, PA, 19122, USA.
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Filatova TS, Kuzmin VS, Guskova VO, Abramochkin DV. Sodium current preserves electrical excitability in the heart of hibernating ground squirrel (Citellus undulatus). Comp Biochem Physiol A Mol Integr Physiol 2023; 282:111452. [PMID: 37207928 DOI: 10.1016/j.cbpa.2023.111452] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Revised: 05/16/2023] [Accepted: 05/16/2023] [Indexed: 05/21/2023]
Abstract
Hibernating mammals are capable of maintaining normal cardiac function at low temperatures. Excitability of cardiac myocytes crucially depends on the fast sodium current (INa), which is decreased in hypothermia due to both depolarization of resting membrane potential and direct negative effect of low temperature. Therefore, INa in hibernating mammals should have specific features allowing to maintain excitability of myocardium at low temperatures. The current-voltage dependence of INa, its steady-state inactivation and activation and recovery from inactivation were studied in winter hibernating (WH) and summer active (SA) ground squirrels and in rats using whole-cell patch clamp at 10 °C and 20 °C. INa peak amplitude and the parameters of steady-state activation and inactivation curves did not differ between SA and WH ground squirrels at both temperatures. However, at both temperatures strong positive shift of activation and inactivation curves by 5-12 mV was observed in both WH and SA ground squirrels if compared to rats. This peculiarity of cardiac INa in ground squirrels helps to maintain excitability in conditions of depolarized resting membrane potential. The time course of INa recovery from inactivation at 10 °C was faster in WH than in SA ground squirrels, which could ensure normal activation of myocardium during hibernation.
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Affiliation(s)
- Tatiana S Filatova
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye Gory, 1, 12, Moscow 119234, Russia
| | - Vladislav S Kuzmin
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye Gory, 1, 12, Moscow 119234, Russia; Laboratory of Cardiac Electrophysiology, Chazov National Medical Research Center for Cardiology, Moscow, Russia
| | - Viktoria O Guskova
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye Gory, 1, 12, Moscow 119234, Russia
| | - Denis V Abramochkin
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye Gory, 1, 12, Moscow 119234, Russia.
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Mancardi D, Ottolenghi S, Attanasio U, Tocchetti CG, Paroni R, Pagliaro P, Samaja M. Janus, or the Inevitable Battle Between Too Much and Too Little Oxygen. Antioxid Redox Signal 2022; 37:972-989. [PMID: 35412859 DOI: 10.1089/ars.2021.0232] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Significance: Oxygen levels are key regulators of virtually every living mammalian cell, under both physiological and pathological conditions. Starting from embryonic and fetal development, through the growth, onset, and progression of diseases, oxygen is a subtle, although pivotal, mediator of key processes such as differentiation, proliferation, autophagy, necrosis, and apoptosis. Hypoxia-driven modifications of cellular physiology are investigated in depth or for their clinical and translational relevance, especially in the ischemic scenario. Recent Advances: The mild or severe lack of oxygen is, undoubtedly, related to cell death, although abundant evidence points at oscillating oxygen levels, instead of permanent low pO2, as the most detrimental factor. Different cell types can consume oxygen at different rates and, most interestingly, some cells can shift from low to high consumption according to the metabolic demand. Hence, we can assume that, in the intracellular compartment, oxygen tension varies from low to high levels depending on both supply and consumption. Critical Issues: The positive balance between supply and consumption leads to a pro-oxidative environment, with some cell types facing hypoxia/hyperoxia cycles, whereas some others are under fairly constant oxygen tension. Future Directions: Within this frame, the alterations of oxygen levels (dysoxia) are critical in two paradigmatic organs, the heart and brain, under physiological and pathological conditions and the interactions of oxygen with other physiologically relevant gases, such as nitric oxide, can alternatively contribute to the worsening or protection of ischemic organs. Further, the effects of dysoxia are of pivotal importance for iron metabolism. Antioxid. Redox Signal. 37, 972-989.
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Affiliation(s)
- Daniele Mancardi
- Department of Clinical and Biological Sciences, University of Torino, Turin, Italy
| | - Sara Ottolenghi
- Department of Health Sciences, University of Milano, Milan, Italy
- School of Medicine and Surgery, University of Milano Bicocca, Milan, Italy
| | - Umberto Attanasio
- Cardio-Oncology Unit, Department of Translational Medical Sciences, Federico II University, Naples, Italy
| | - Carlo Gabriele Tocchetti
- Cardio-Oncology Unit, Department of Translational Medical Sciences, Federico II University, Naples, Italy
- Interdepartmental Center for Clinical and Translational Research (CIRCET), Federico II University, Naples, Italy
- Interdepartmental Hypertension Research Center (CIRIAPA), Federico II University, Naples, Italy
- Center for Basic and Clinical Immunology Research (CISI), Federico II University, Naples, Italy
| | - Rita Paroni
- Department of Health Sciences, University of Milano, Milan, Italy
| | - Pasquale Pagliaro
- Department of Clinical and Biological Sciences, University of Torino, Turin, Italy
| | - Michele Samaja
- Department of Health Sciences, University of Milano, Milan, Italy
- MAGI GROUP, San Felice del Benaco, Italy
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Lee HL, Chang PC, Wo HT, Liu HT, Wen MS, Chou CC. Beneficial Electrophysiological Effects of Rotigaptide Are Unable to Suppress Therapeutic Hypothermia-Provoked Ventricular Fibrillation in Failing Rabbit Hearts With Acute Ischemia-Reperfusion Injury. Front Physiol 2021; 12:726389. [PMID: 34588996 PMCID: PMC8473906 DOI: 10.3389/fphys.2021.726389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Accepted: 08/18/2021] [Indexed: 11/26/2022] Open
Abstract
Aims: Whether therapeutic hypothermia (TH) is proarrhythmic in preexisting failing hearts with acute ischemia–reperfusion (IR) injury is unknown. Additionally, the effectiveness of rotigaptide on improving conduction slowing in hearts with IR injury is ambiguous. We investigated the electrophysiological effects of TH and rotigaptide in failing rabbit hearts with acute IR injury and determined the underlying molecular mechanisms. Methods and Results: Heart failure was induced by right ventricular pacing (320 beats/min, 4 weeks). Rabbits with pacing-induced heart failure were randomly divided into TH (n = 14) and non-TH (n = 7) groups. The IR rabbit model was created by ligating the coronary artery for 60 min, followed by reperfusion for 15 min in vivo. Then, the hearts were excised quickly and Langendorff-perfused for simultaneous voltage and intracellular Ca2+ (Cai) optical mapping. Electrophysiological studies were conducted, and vulnerability to ventricular fibrillation (VF) was evaluated using pacing protocols. TH (33°C) was instituted after baseline studies, and electrophysiological studies were repeated. Rotigaptide (300 nM) was infused for 20 min, and electrophysiological studies were repeated under TH. Cardiac tissues were sampled for Western blotting. TH increased the dispersion and beat-to-beat variability of action potential duration (APD), aggravated conduction slowing, and prolonged Cai decay to facilitate spatially discordant alternans (SDA) and VF induction. Rotigaptide reduced the dispersion and beat-to-beat variability of APD and improved slowed conduction to defer the onset of arrhythmogenic SDA by dynamic pacing and elevate the pacing threshold of VF during TH. However, the effect of rotigaptide on TH-enhanced VF inducibility was statistically insignificant. TH attenuated IR-induced dysregulation of protein expression, but its functional role remained uncertain. Conclusion: Therapeutic hypothermia is proarrhythmic in failing hearts with acute IR injury. Rotigaptide improves TH-induced APD dispersion and beat-to-beat variability and conduction disturbance to defer the onset of arrhythmogenic SDA and elevate the VF threshold by dynamic pacing, but these beneficial electrophysiological effects are unable to suppress TH-enhanced VF inducibility significantly.
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Affiliation(s)
- Hui-Ling Lee
- Department of Anesthesia, Chang Gung Memorial Hospital, Taipei City, Taiwan
| | - Po-Cheng Chang
- Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Taoyuan City, Taiwan
| | - Hung-Ta Wo
- Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Taoyuan City, Taiwan
| | - Hao-Tien Liu
- Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Taoyuan City, Taiwan
| | - Ming-Shien Wen
- Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Taoyuan City, Taiwan.,Chang Gung University College of Medicine, Taoyuan City, Taiwan
| | - Chung-Chuan Chou
- Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Taoyuan City, Taiwan.,Chang Gung University College of Medicine, Taoyuan City, Taiwan
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Kharche SR, Lemoine S, Tamasi T, Hur L, So A, McIntyre CW. Therapeutic Hypothermia Reduces Peritoneal Dialysis Induced Myocardial Blood Flow Heterogeneity and Arrhythmia. Front Med (Lausanne) 2021; 8:700824. [PMID: 34395480 PMCID: PMC8362929 DOI: 10.3389/fmed.2021.700824] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Accepted: 06/30/2021] [Indexed: 11/13/2022] Open
Abstract
Background: Moderate therapeutic hypothermia (TH) is a well-recognized cardio-protective strategy. The instillation of fluid into the peritoneum provides an opportunity to deliver moderate hypothermia as primary prevention against cardiovascular events. We aimed to to investigate both cardiac perfusion consequences (overall blood flow and detailed assessment of perfusion heterogeneity) and subsequently simulate the associated arrhythmic risk for patients undergoing peritoneal dialysis (PD) induced TH. Methods: Patients underwent high resolution myocardial perfusion scanning using high resolution 256 slice CT scanning, at rest and with adenosine stress. The first visit using the patient's usual PD regimen, on the second visit the same regime was utilized but with cooled peritoneal dialysate at 32°C. Myocardial blood flow (MBF) was quantified from generated perfusion maps, reconstructed in 3D. MBF heterogeneity was assessed by fractal dimension (FD) measurement on the 3D left ventricular reconstruction. Arrhythmogenicity was quantified from a sophisticated computational simulation using a multi-scale human 3D ventricle wedge electrophysiological computational model. Results: We studied 7 PD patients, mean age of 60 ± 7 and mean vintage dialysis of 23.6 ± 17.6 months. There were no significant different in overall segmental MBF between normothermic condition (NT) and TH. MBF heterogeneity was significantly decreased (-14%, p = 0.03) at rest and after stress (-14%, p = 0.03) when cooling was applied. Computational simulation showed that TH allowed a normalization of action potential, QT duration and T wave. Conclusion: TH-PD results in moderate hypothermia leading to a reduction in perfusion heterogeneity and simulated risk of non-terminating malignant ventricular arrhythmias.
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Affiliation(s)
- Sanjay R. Kharche
- Kidney Clinical Research Unit, Lawson's Health Research Institute, Victoria Hospital, London, ON, Canada
- Department of Medical Biophysics, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, Canada
| | - Sandrine Lemoine
- Kidney Clinical Research Unit, Lawson's Health Research Institute, Victoria Hospital, London, ON, Canada
| | - Tanya Tamasi
- Kidney Clinical Research Unit, Lawson's Health Research Institute, Victoria Hospital, London, ON, Canada
| | - Lisa Hur
- Kidney Clinical Research Unit, Lawson's Health Research Institute, Victoria Hospital, London, ON, Canada
| | - Aaron So
- Department of Medical Biophysics, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, Canada
- Imaging Program, Lawson Health Research Institute, London, ON, Canada
| | - Christopher W. McIntyre
- Kidney Clinical Research Unit, Lawson's Health Research Institute, Victoria Hospital, London, ON, Canada
- Department of Medical Biophysics, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, Canada
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Majumder R, Mohamed Nazer AN, Panfilov AV, Bodenschatz E, Wang Y. Electrophysiological Characterization of Human Atria: The Understated Role of Temperature. Front Physiol 2021; 12:639149. [PMID: 34366877 PMCID: PMC8346027 DOI: 10.3389/fphys.2021.639149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Accepted: 04/01/2021] [Indexed: 11/13/2022] Open
Abstract
Ambient temperature has a profound influence on cellular electrophysiology through direct control over the gating mechanisms of different ion channels. In the heart, low temperature is known to favor prolongation of the action potential. However, not much is known about the influence of temperature on other important characterization parameters such as the resting membrane potential (RMP), excitability, morphology and characteristics of the action potential (AP), restitution properties, conduction velocity (CV) of signal propagation, etc. Here we present the first, detailed, systematic in silico study of the electrophysiological characterization of cardiomyocytes from different regions of the normal human atria, based on the effects of ambient temperature (5-50°C). We observe that RMP decreases with increasing temperature. At ~ 48°C, the cells lose their excitability. Our studies show that different parts of the atria react differently to the same changes in temperature. In tissue simulations a drop in temperature correlated positively with a decrease in CV, but the decrease was region-dependent, as expected. In this article we show how this heterogeneous response can provide an explanation for the development of a proarrhythmic substrate during mild hypothermia. We use the above concept to propose a treatment strategy for atrial fibrillation that involves severe hypothermia in specific regions of the heart for a duration of only ~ 200 ms.
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Affiliation(s)
- Rupamanjari Majumder
- Laboratory for Fluid Physics, Pattern Formation and Biocomplexity, Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Göttingen, Göttingen, Germany
| | | | - Alexander V Panfilov
- World-Class Research Center "Digital Biodesign and Personalized Healthcare", Sechenov University, Moscow, Russia.,Department of Physics and Astronomy, Ghent University, Ghent, Belgium.,Laboratory of Computational Biology and Medicine, Ural Federal University, Yekaterinburg, Russia
| | - Eberhard Bodenschatz
- Laboratory for Fluid Physics, Pattern Formation and Biocomplexity, Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Göttingen, Göttingen, Germany.,Laboratory of Atomic and Solid-State Physics and Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY, United States
| | - Yong Wang
- Laboratory for Fluid Physics, Pattern Formation and Biocomplexity, Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Göttingen, Göttingen, Germany
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Herndon C, Astley HC, Owerkowicz T, Fenton FH. Defibrillate You Later, Alligator: Q10 Scaling and Refractoriness Keeps Alligators from Fibrillation. Integr Org Biol 2021; 3:obaa047. [PMID: 33977229 PMCID: PMC8101277 DOI: 10.1093/iob/obaa047] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Effective cardiac contraction during each heartbeat relies on the coordination of an electrical wave of excitation propagating across the heart. Dynamically induced heterogeneous wave propagation may fracture and initiate reentry-based cardiac arrhythmias, during which fast-rotating electrical waves lead to repeated self-excitation that compromises cardiac function and potentially results in sudden cardiac death. Species which function effectively over a large range of heart temperatures must balance the many interacting, temperature-sensitive biochemical processes to maintain normal wave propagation at all temperatures. To investigate how these species avoid dangerous states across temperatures, we optically mapped the electrical activity across the surfaces of alligator (Alligator mississippiensis) hearts at 23°C and 38°C over a range of physiological heart rates and compare them with that of rabbits (Oryctolagus cuniculus). We find that unlike rabbits, alligators show minimal changes in wave parameters (action potential duration and conduction velocity) which complement each other to retain similar electrophysiological wavelengths across temperatures and pacing frequencies. The cardiac electrophysiology of rabbits accommodates the high heart rates necessary to sustain an active and endothermic metabolism at the cost of increased risk of cardiac arrhythmia and critical vulnerability to temperature changes, whereas that of alligators allows for effective function over a range of heart temperatures without risk of cardiac electrical arrhythmias such as fibrillation, but is restricted to low heart rates. Synopsis La contracción cardíaca efectiva durante cada latido del corazón depende de la coordinación de una onda eléctrica de excitación que se propaga a través del corazón. Heterogéidades inducidas dinámicamente por ondas de propagación pueden resultar en fracturas de las ondas e iniciar arritmias cardíacas basadas en ondas de reingreso, durante las cuales ondas espirales eléctricas de rotación rápida producen una autoexcitación repetida que afecta la función cardíaca y pude resultar en muerte súbita cardíaca. Las especies que funcionan eficazmente en una amplia gama de temperaturas cardíacas deben equilibrar los varios procesos bioquímicos que interactúan, sensibles a la temperatura para mantener la propagación normal de ondas a todas las temperaturas. Para investigar cómo estas especies evitan los estados peligrosos a través de las temperaturas, mapeamos ópticamente la actividad eléctrica a través de las superficies de los corazones de caimanes (Alligator mississippiensis) a 23°C and 38°C sobre un rango de frecuencias fisiológicas del corazón y comparamos con el de los conejos (Oryctolagus cuniculus). Encontramos que a diferencia de los conejos, los caimanes muestran cambios mínimos en los parámetros de onda (duración potencial de acción y velocidad de conducción) que se complementan entre sí para retener longitudes de onda electrofisiológicas similares a través de los rangos de temperaturas y frecuencias de ritmo. La electrofisiología cardíaca de los conejos acomoda las altas frecuencias cardíacas necesarias para mantener un metabolismo activo y endotérmico a costa de un mayor riesgo de arritmia cardíaca y vulnerabilidad crítica a los cambios de temperatura, mientras que la de los caimanes permite un funcionamiento eficaz en una serie de temperaturas cardíacas sin riesgo de arritmias eléctricas cardíacas como la fibrilación, pero está restringida a bajas frecuencias cardíacas.
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Affiliation(s)
- Conner Herndon
- School of Physics, Georgia Institute of Technology, Atlanta, GA, USA
| | - Henry C Astley
- Department of Biology, Biomimicry Research & Innovation Center, University of Akron, Akron, OH, USA
| | - Tomasz Owerkowicz
- Department of Biology, California State University, San Bernardino, CA, USA
| | - Flavio H Fenton
- School of Physics, Georgia Institute of Technology, Atlanta, GA, USA
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10
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Simpson KE, Venkateshappa R, Pang ZK, Faizi S, Tibbits GF, Claydon TW. Utility of Zebrafish Models of Acquired and Inherited Long QT Syndrome. Front Physiol 2021; 11:624129. [PMID: 33519527 PMCID: PMC7844309 DOI: 10.3389/fphys.2020.624129] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 12/21/2020] [Indexed: 01/12/2023] Open
Abstract
Long-QT Syndrome (LQTS) is a cardiac electrical disorder, distinguished by irregular heart rates and sudden death. Accounting for ∼40% of cases, LQTS Type 2 (LQTS2), is caused by defects in the Kv11.1 (hERG) potassium channel that is critical for cardiac repolarization. Drug block of hERG channels or dysfunctional channel variants can result in acquired or inherited LQTS2, respectively, which are typified by delayed repolarization and predisposition to lethal arrhythmia. As such, there is significant interest in clear identification of drugs and channel variants that produce clinically meaningful perturbation of hERG channel function. While toxicological screening of hERG channels, and phenotypic assessment of inherited channel variants in heterologous systems is now commonplace, affordable, efficient, and insightful whole organ models for acquired and inherited LQTS2 are lacking. Recent work has shown that zebrafish provide a viable in vivo or whole organ model of cardiac electrophysiology. Characterization of cardiac ion currents and toxicological screening work in intact embryos, as well as adult whole hearts, has demonstrated the utility of the zebrafish model to contribute to the development of therapeutics that lack hERG-blocking off-target effects. Moreover, forward and reverse genetic approaches show zebrafish as a tractable model in which LQTS2 can be studied. With the development of new tools and technologies, zebrafish lines carrying precise channel variants associated with LQTS2 have recently begun to be generated and explored. In this review, we discuss the present knowledge and questions raised related to the use of zebrafish as models of acquired and inherited LQTS2. We focus discussion, in particular, on developments in precise gene-editing approaches in zebrafish to create whole heart inherited LQTS2 models and evidence that zebrafish hearts can be used to study arrhythmogenicity and to identify potential anti-arrhythmic compounds.
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Affiliation(s)
- Kyle E. Simpson
- Molecular Cardiac Physiology Group, Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada
| | - Ravichandra Venkateshappa
- Molecular Cardiac Physiology Group, Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada
| | - Zhao Kai Pang
- Molecular Cardiac Physiology Group, Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada
| | - Shoaib Faizi
- Molecular Cardiac Physiology Group, Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada
| | - Glen F. Tibbits
- Molecular Cardiac Physiology Group, Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada
- Department of Cardiovascular Science, British Columbia Children’s Hospital, Vancouver, BC, Canada
| | - Tom W. Claydon
- Molecular Cardiac Physiology Group, Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada
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11
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Shi YP, Pang Z, Venkateshappa R, Gunawan M, Kemp J, Truong E, Chang C, Lin E, Shafaattalab S, Faizi S, Rayani K, Tibbits GF, Claydon VE, Claydon TW. The hERG channel activator, RPR260243, enhances protective IKr current early in the refractory period reducing arrhythmogenicity in zebrafish hearts. Am J Physiol Heart Circ Physiol 2020; 319:H251-H261. [PMID: 32559136 DOI: 10.1152/ajpheart.00038.2020] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Human ether-à-go-go related gene (hERG) K+ channels are important in cardiac repolarization, and their dysfunction causes prolongation of the ventricular action potential, long QT syndrome, and arrhythmia. As such, approaches to augment hERG channel function, such as activator compounds, have been of significant interest due to their marked therapeutic potential. Activator compounds that hinder channel inactivation abbreviate action potential duration (APD) but carry risk of overcorrection leading to short QT syndrome. Enhanced risk by overcorrection of the APD may be tempered by activator-induced increased refractoriness; however, investigation of the cumulative effect of hERG activator compounds on the balance of these effects in whole organ systems is lacking. Here, we have investigated the antiarrhythmic capability of a hERG activator, RPR260243, which primarily augments channel function by slowing deactivation kinetics in ex vivo zebrafish whole hearts. We show that RPR260243 abbreviates the ventricular APD, reduces triangulation, and steepens the slope of the electrical restitution curve. In addition, RPR260243 increases the post-repolarization refractory period. We provide evidence that this latter effect arises from RPR260243-induced enhancement of hERG channel-protective currents flowing early in the refractory period. Finally, the cumulative effect of RPR260243 on arrhythmogenicity in whole organ zebrafish hearts is demonstrated by the restoration of normal rhythm in hearts presenting dofetilide-induced arrhythmia. These findings in a whole organ model demonstrate the antiarrhythmic benefit of hERG activator compounds that modify both APD and refractoriness. Furthermore, our results demonstrate that targeted slowing of hERG channel deactivation and enhancement of protective currents may provide an effective antiarrhythmic approach.NEW & NOTEWORTHY hERG channel dysfunction causes long QT syndrome and arrhythmia. Activator compounds have been of significant interest due to their therapeutic potential. We used the whole organ zebrafish heart model to demonstrate the antiarrhythmic benefit of the hERG activator, RPR260243. The activator abbreviated APD and increased refractoriness, the combined effect of which rescued induced ventricular arrhythmia. Our findings show that the targeted slowing of hERG channel deactivation and enhancement of protective currents caused by the RPR260243 activator may provide an effective antiarrhythmic approach.
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Affiliation(s)
- Yu Patrick Shi
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - ZhaoKai Pang
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - Ravichandra Venkateshappa
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - Marvin Gunawan
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - Jacob Kemp
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - Elson Truong
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - Cherlene Chang
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - Eric Lin
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - Sanam Shafaattalab
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - Shoaib Faizi
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - Kaveh Rayani
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - Glen F Tibbits
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - Victoria E Claydon
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
| | - Thomas W Claydon
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, British Columbia, Canada
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12
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Kuzmin VS, Abramov AA, Egorov YV, Rosenshtraukh LV. Hypothermia-Induced Postrepolarization Refractoriness Is the Reason of the Atrial Myocardium Tolerance to the Bioelectrical Activity Disorders in the Hibernating and Active Ground Squirrel Citellus undulatus. DOKLADY BIOLOGICAL SCIENCES : PROCEEDINGS OF THE ACADEMY OF SCIENCES OF THE USSR, BIOLOGICAL SCIENCES SECTIONS 2019; 486:63-68. [PMID: 31317446 DOI: 10.1134/s0012496619030050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 03/18/2019] [Accepted: 03/18/2019] [Indexed: 11/23/2022]
Abstract
The electrophysiological mechanism of the atrial myocardium resistance to the cold-induced arrhythmias was studied in the hibernating ground squirrel Citellus undulatus. The atrial action potentials (APs) and refractoriness were recorded with microelectrodes in isolated multicellular preparations of the atrial myocardium taken from the hibernating and summer active ground squirrels (HS and SAS, respectively) at 37, 27, and 17°С to estimate the AP and refractoriness durations. In both HS and SAS, hypothermia increased the duration of the AP and refractoriness period (APD and RD, respectively), and in both animal groups RD was longer than APD under hypothermia but not at 37°С. This last observation can be a result of the postrepolarization refractoriness (PRR), which seems to contribute substantially to the atrial myocardium tolerance of the hibernating animals to the hypothermia-induced arrhythmias because it prevents afterdepolarizations.
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Affiliation(s)
- V S Kuzmin
- Institute of Experimental Cardiology, Russian Research and Production Cardiological Complex, Ministry of Health, 121552, Moscow, Russia.
| | - A A Abramov
- Institute of Experimental Cardiology, Russian Research and Production Cardiological Complex, Ministry of Health, 121552, Moscow, Russia
| | - Yu V Egorov
- Institute of Experimental Cardiology, Russian Research and Production Cardiological Complex, Ministry of Health, 121552, Moscow, Russia
| | - L V Rosenshtraukh
- Institute of Experimental Cardiology, Russian Research and Production Cardiological Complex, Ministry of Health, 121552, Moscow, Russia
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13
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Horii Y, Shimaoka H, Horii K, Shiina T, Shimizu Y. Mild hypothermia causes a shift in the alternative splicing of cold-inducible RNA-binding protein transcripts in Syrian hamsters. Am J Physiol Regul Integr Comp Physiol 2019; 317:R240-R247. [PMID: 31188649 DOI: 10.1152/ajpregu.00012.2019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cold-shock proteins are thought to participate in the cold-tolerant nature of hibernating animals. We previously demonstrated that an alternative splicing may allow rapid induction of functional cold-inducible RNA-binding protein (CIRBP) in the hamster heart. The purpose of the present study was to determine the major cause of the alternative splicing in Syrian hamsters. RT-PCR analysis revealed that CIRBP mRNA is constitutively expressed in the heart, brain, lung, liver, and kidney of nonhibernating euthermic hamsters with several alternative splicing variants. In contrast, the short variant containing an open-reading frame for functional CIRBP was dominantly found in the hibernating animals. Keeping the animals in a cold and dark environment did not cause a shift in the alternative splicing. Induction of hypothermia by central administration of an adenosine A1-receptor agonist reproduced the shift in the splicing pattern. However, the agonist failed to shift the pattern when body temperature was kept at 37°C, suggesting that central adenosine A1 receptors are not directly linked to the shift of the alternative splicing. Rapid reduction of body temperature to 10°C by isoflurane anesthesia combined with cooling did not alter the splicing pattern, but maintenance of mild hypothermia (~28°C) for 2 h elicited the shift in the pattern. The results suggest that animals need to be maintained at mild hypothermia for an adequate duration to induce the shift in the alternative splicing. This is applicable to natural hibernation because hamsters entering hibernation show a gradual decrease in body temperature, being maintained at mild hypothermia for several hours.
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Affiliation(s)
- Yuuki Horii
- Laboratory of Physiology, Department of Basic Veterinary Science, The United Graduate School of Veterinary Sciences, Gifu University , Gifu , Japan
| | - Hiroki Shimaoka
- Laboratory of Physiology, Department of Basic Veterinary Science, The United Graduate School of Veterinary Sciences, Gifu University , Gifu , Japan
| | - Kazuhiro Horii
- Laboratory of Physiology, Department of Basic Veterinary Science, The United Graduate School of Veterinary Sciences, Gifu University , Gifu , Japan
| | - Takahiko Shiina
- Laboratory of Physiology, Department of Basic Veterinary Science, The United Graduate School of Veterinary Sciences, Gifu University , Gifu , Japan
| | - Yasutake Shimizu
- Laboratory of Physiology, Department of Basic Veterinary Science, The United Graduate School of Veterinary Sciences, Gifu University , Gifu , Japan.,Center for Highly Advanced Integration of Nano and Life Sciences (G-CHAIN), Gifu University , Gifu , Japan
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14
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Li WC, Gao H, Gao J, Wang ZJ. Antiarrhythmic effect of sevoflurane as an additive to HTK solution on reperfusion arrhythmias induced by hypothermia and ischaemia is associated with the phosphorylation of connexin 43 at serine 368. BMC Anesthesiol 2019; 19:5. [PMID: 30621602 PMCID: PMC6325883 DOI: 10.1186/s12871-018-0656-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Accepted: 11/29/2018] [Indexed: 12/22/2022] Open
Abstract
Background Reperfusion ventricular arrhythmia (RA) associated with hypothermic ischaemic storage is increasingly recognized as a substantial contributor to adverse consequences after heart transplantation. Ischemia- or hypothermia-induced gap junction (GJ) remodelling is closely linked to RA. Reducing GJ remodelling contributes to RA attenuation and is important in heart transplantation. However, sevoflurane has an antiarrhythmic effect associated with the connexin 43 (Cx43) protein that has not yet been fully established. Methods Hearts were divided into two groups according to a random number table: all hearts were arrested by an infusion of histidine-tryptophan-ketoglutarate (HTK) solution (4 °C) followed by (1) storage in HTK solution (4 °C) alone for 6 h (n = 8, Control group) or (2) storage in HTK solution supplemented with sevoflurane (2.5%) (4 °C) for 6 h (n = 8, Sevo-HTK group). First, the total Cx43 level and the phosphorylation of Cx43 at Ser368 (Cx43-pS368) were assessed by Western blotting, and the distribution of Cx43 was assessed by immunohistochemistry. Second, programmed electrical stimulation (PES) and monophasic action potential (MAP) recording were used to analyse the MAP duration (MAPD), conduction velocity (CV) and transmural repolarization dispersion (TDR). In addition, haematoxylin and eosin (HE) and terminal deoxynucleotidyl transferase-dUTP nick end labelling (TUNEL) staining were individually used to investigate the degree of myocardial pathological damage and cell apoptosis. Finally, bipolar electrograms were used to record the graft re-beating time and monitor RA during reperfusion for 15 to 30 min. Results Sevo-HTK solution relatively increased the total Cx43 (P < 0.01) and Cx43-pS368 (P < 0.01) levels and prevented Cx43 redistribution (P < 0.05) and CV slowing (P < 0.001) but did not change TDR (P > 0.05). Additionally, the Cx43-pS368/total Cx43 ratio (P>0.05) was similar in the two groups. However, with Sevo-HTK solution, the graft re-beating times were shortened, myocardial pathological damage was ameliorated, and the number of apoptotic cells was markedly decreased. Conclusion The reduction in hypothermia and ischaemia-induced reperfusion arrhythmias by the addition of sevoflurane to HTK solution may be related to the phosphorylation of Cx43 at serine 368.
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Affiliation(s)
- Wei Chao Li
- Department of Anesthesiology, The Affiliated Hospital of Guizhou Medical University, Guiyang, Guizhou, China
| | - Hong Gao
- Department of Anesthesiology, The Affiliated Hospital of Guizhou Medical University, Guiyang, Guizhou, China.
| | - Ju Gao
- Department of Anaesthesiology, North Jiangsu People's Hospital, Yangzhou University, Yangzhou, China
| | - Zi Jun Wang
- Department of Anesthesiology, The Affiliated Hospital of Guizhou Medical University, Guiyang, Guizhou, China
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15
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Shimaoka H, Kawaguchi T, Morikawa K, Sano Y, Naitou K, Nakamori H, Shiina T, Shimizu Y. Induction of hibernation-like hypothermia by central activation of the A1 adenosine receptor in a non-hibernator, the rat. J Physiol Sci 2018; 68:425-430. [PMID: 28508339 PMCID: PMC10717028 DOI: 10.1007/s12576-017-0543-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2017] [Accepted: 05/10/2017] [Indexed: 11/30/2022]
Abstract
Central adenosine A1-receptor (A1AR)-mediated signals play a role in the induction of hibernation. We determined whether activation of the central A1AR enables rats to maintain normal sinus rhythm even after their body temperature has decreased to less than 20 °C. Intracerebroventricular injection of an adenosine A1 agonist, N6-cyclohexyladenosine (CHA), followed by cooling decreased the body temperature of rats to less than 20 °C. Normal sinus rhythm was fundamentally maintained during the extreme hypothermia. In contrast, forced induction of hypothermia by cooling anesthetized rats caused cardiac arrest. Additional administration of pentobarbital to rats in which hypothermia was induced by CHA also caused cardiac arrest, suggesting that the operation of some beneficial mechanisms that are not activated under anesthesia may be essential to keep heart beat under the hypothermia. These results suggest that central A1AR-mediated signals in the absence of anesthetics would provide an appropriate condition for maintaining normal sinus rhythm during extreme hypothermia.
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Affiliation(s)
- Hiroki Shimaoka
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Takayuki Kawaguchi
- Laboratory of Veterinary Physiology, Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Kahori Morikawa
- Laboratory of Veterinary Physiology, Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Yuuki Sano
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Kiyotada Naitou
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Hiroyuki Nakamori
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Takahiko Shiina
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
- Laboratory of Veterinary Physiology, Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan
| | - Yasutake Shimizu
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan.
- Laboratory of Veterinary Physiology, Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan.
- Center for Highly Advanced Integration of Nano and Life Sciences (G-CHAIN), Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan.
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16
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Wiersma M, Beuren TMA, de Vrij EL, Reitsema VA, Bruintjes JJ, Bouma HR, Brundel BJJM, Henning RH. Torpor-arousal cycles in Syrian hamster heart are associated with transient activation of the protein quality control system. Comp Biochem Physiol B Biochem Mol Biol 2018; 223:23-28. [PMID: 29894736 DOI: 10.1016/j.cbpb.2018.06.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Revised: 05/28/2018] [Accepted: 06/04/2018] [Indexed: 12/14/2022]
Abstract
Hibernation consists of torpor, with marked suppression of metabolism and physiological functions, alternated with arousal periods featuring their full restoration. The heart is particularly challenged, exemplified by its rate reduction from 400 to 5-10 beats per minute during torpor in Syrian hamsters. In addition, during arousals, the heart needs to accommodate the very rapid return to normal function, which lead to our hypothesis that cardiac function during hibernation is supported by maintenance of protein homeostasis through adaptations in the protein quality control (PQC) system. Hereto, we examined autophagy, the endoplasmic reticulum (ER) unfolded protein (UPRER) response and the heat shock response (HSR) in Syrian hamster hearts during torpor and arousal. Transition from torpor to arousal (1.5 h) was associated with stimulation of the PQC system during early arousal, demonstrated by induction of autophagosomes, as shown by an increase in LC3B-II protein abundance, likely related to the activation of the UPRER during late torpor in response to proteotoxic stress. The HSR was not activated during torpor or arousal. Our results demonstrate activation of the cardiac PQC system - particularly autophagosomal degradation - in early arousal in response to cardiac stress, to clear excess aberrant or damaged proteins, being gradually formed during the torpor bout and/or the rapid increase in heart rate during the transition from torpor to arousal. This mechanism may enable the large gain in cardiac function during the transition from torpor to arousal, which may hold promise to further understand 'hibernation' of cardiomyocytes in human heart disease.
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Affiliation(s)
- Marit Wiersma
- Department of Physiology, Amsterdam Cardiovascular Sciences, VU University Medical Center, Amsterdam, The Netherlands; Department of Clinical Pharmacy and Pharmacology, University of Groningen, University Medical Center Groningen, The Netherlands.
| | - Thais M A Beuren
- Department of Physiology, Amsterdam Cardiovascular Sciences, VU University Medical Center, Amsterdam, The Netherlands; Department of Clinical Pharmacy and Pharmacology, University of Groningen, University Medical Center Groningen, The Netherlands
| | - Edwin L de Vrij
- Department of Clinical Pharmacy and Pharmacology, University of Groningen, University Medical Center Groningen, The Netherlands; Department of Surgery, Martini Hospital, Groningen, The Netherlands
| | - Vera A Reitsema
- Department of Clinical Pharmacy and Pharmacology, University of Groningen, University Medical Center Groningen, The Netherlands
| | - Jantje J Bruintjes
- Department of Clinical Pharmacy and Pharmacology, University of Groningen, University Medical Center Groningen, The Netherlands
| | - Hjalmar R Bouma
- Department of Clinical Pharmacy and Pharmacology, University of Groningen, University Medical Center Groningen, The Netherlands; Department of Internal Medicine, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Bianca J J M Brundel
- Department of Physiology, Amsterdam Cardiovascular Sciences, VU University Medical Center, Amsterdam, The Netherlands; Department of Clinical Pharmacy and Pharmacology, University of Groningen, University Medical Center Groningen, The Netherlands
| | - Robert H Henning
- Department of Clinical Pharmacy and Pharmacology, University of Groningen, University Medical Center Groningen, The Netherlands
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17
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Manninger M, Alogna A, Zweiker D, Zirngast B, Reiter S, Herbst V, Maechler H, Pieske BM, Heinzel FR, Brussee H, Post H, Scherr D. Mild hypothermia (33°C) increases the inducibility of atrial fibrillation: An
in vivo
large animal model study. Pacing Clin Electrophysiol 2018; 41:720-726. [DOI: 10.1111/pace.13351] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Revised: 03/05/2018] [Accepted: 03/30/2018] [Indexed: 11/28/2022]
Affiliation(s)
| | - Alessio Alogna
- Department of Internal Medicine and Cardiology, Campus Virchow KlinikumCharité University Medicine Berlin Berlin Germany
- Berlin Institute of Health (BIH) Berlin Germany
| | - David Zweiker
- Department of CardiologyMedical University of Graz Graz Austria
| | - Birgit Zirngast
- Department of Cardiothoracic SurgeryMedical University of Graz Graz Austria
| | - Stefan Reiter
- Department of CardiologyMedical University of Graz Graz Austria
| | - Viktoria Herbst
- Department of CardiologyMedical University of Graz Graz Austria
| | - Heinrich Maechler
- Department of Cardiothoracic SurgeryMedical University of Graz Graz Austria
| | - Burkert M. Pieske
- Department of Internal Medicine and Cardiology, Campus Virchow KlinikumCharité University Medicine Berlin Berlin Germany
| | - Frank R. Heinzel
- Department of Internal Medicine and Cardiology, Campus Virchow KlinikumCharité University Medicine Berlin Berlin Germany
| | - Helmut Brussee
- Department of CardiologyMedical University of Graz Graz Austria
| | - Heiner Post
- Department of Internal Medicine and Cardiology, Campus Virchow KlinikumCharité University Medicine Berlin Berlin Germany
| | - Daniel Scherr
- Department of CardiologyMedical University of Graz Graz Austria
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18
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Stancic A, Jankovic A, Korac A, Cirovic D, Otasevic V, Storey KB, Korac B. A lesson from the oxidative metabolism of hibernator heart: Possible strategy for cardioprotection. Comp Biochem Physiol B Biochem Mol Biol 2018; 219-220:1-9. [PMID: 29501789 DOI: 10.1016/j.cbpb.2018.02.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Revised: 02/13/2018] [Accepted: 02/22/2018] [Indexed: 01/20/2023]
Abstract
In the present study we hypothesized that myocardial adaptive phenotype in mammalian hibernation involves rearrangement of mitochondria bioenergetic pathways providing protective pattern in states of reduced metabolism and low temperature. European ground squirrels (Spermophilus citellus) were exposed to low temperature (4 ± 1 °C) and then divided into two groups: (1) animals that fell into torpor (hibernating group) and (2) animals that stayed active and euthermic for 1, 3, 7, 12, or 21 days (cold-exposed group). Protein levels of selected components of the electron transport chain and ATP synthase in the heart increased after prolonged cold acclimation (mainly from day 7-21 of cold exposure) and during hibernation. Peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) was also upregulated under both cold exposure and hibernating conditions. The phosphorylation state (Thr172) of 5'-AMP-activated protein kinase α increased early in cold exposure (at day 1 and 3) along with increased protein levels of phosphofructokinase and pyruvate dehydrogenase, whereas hypoxia inducible factor 1α protein levels showed no changes in response to cold exposure or hibernation. Hibernation also resulted in protein upregulation of three antioxidant defense enzymes (manganese and copper/zinc superoxide dismutases and glutathione peroxidase) and thioredoxin in the heart. Cold-exposed and hibernation-related phenotypes of the heart are characterized by improved molecular basis for mitochondrial energy-producing and antioxidant capacities that are achieved in a controlled manner. The recapitulation of such adaptive mechanisms found in hibernators could have broad application for myocardial protection from ishemia/reperfusion to improve hypothermic survival and cold preservation of hearts from non-hibernating species, including humans.
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Affiliation(s)
- Ana Stancic
- University of Belgrade, Institute for Biological Research "Sinisa Stankovic", Belgrade, Serbia
| | - Aleksandra Jankovic
- University of Belgrade, Institute for Biological Research "Sinisa Stankovic", Belgrade, Serbia
| | - Aleksandra Korac
- University of Belgrade, Faculty of Biology, Centre for Electron Microscopy, Belgrade, Serbia
| | - Dusko Cirovic
- University of Belgrade, Faculty of Biology, Belgrade, Serbia
| | - Vesna Otasevic
- University of Belgrade, Institute for Biological Research "Sinisa Stankovic", Belgrade, Serbia
| | - Kenneth B Storey
- Carleton University, Department of Biology, Ottawa, Ontario, Canada
| | - Bato Korac
- University of Belgrade, Institute for Biological Research "Sinisa Stankovic", Belgrade, Serbia.
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19
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Horii Y, Shiina T, Shimizu Y. The Mechanism Enabling Hibernation in Mammals. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1081:45-60. [PMID: 30288703 DOI: 10.1007/978-981-13-1244-1_3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Some rodents including squirrels and hamsters undergo hibernation. During hibernation, body temperature drops to only a few degrees above ambient temperature. The suppression of whole-body energy expenditure is associated with regulated, but not passive, reduction of cellular metabolism. The heart retains the ability to beat constantly, although body temperature drops to less than 10 °C during hibernation. Cardiac myocytes of hibernating mammals are characterized by reduced Ca2+ entry into the cell membrane and a concomitant enhancement of Ca2+ release from and reuptake by the sarcoplasmic reticulum. These adaptive changes would help in preventing excessive Ca2+ entry and its overload and in maintaining the resting levels of intracellular Ca2+. Adaptive changes in gene expression in the heart prior to hibernation may be indispensable for acquiring cold resistance. In addition, protective effects of cold-shock proteins are thought to have an important role. We recently reported the unique expression pattern of cold-inducible RNA-binding protein (CIRP) in the hearts of hibernating hamsters. The CIRP mRNA is constitutively expressed in the heart of a nonhibernating euthermic hamster with several different forms probably due to alternative splicing. The short product contained the complete open reading frame for full-length CIRP, while the long product had inserted sequences containing a stop codon, suggesting production of a C-terminal deletion isoform of CIRP. In contrast to nonhibernating hamsters, only the short product was found in hibernating animals. Thus, these results indicate that CIRP expression in the hamster heart is regulated at the level of alternative splicing, which would permit a rapid increment of functional CIRP when entering hibernation. We will summarize the current understanding of the cold-resistant property of the heart in hibernating animals.
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Affiliation(s)
- Yuuki Horii
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan
| | - Takahiko Shiina
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan
| | - Yasutake Shimizu
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan.
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20
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Gap junction modifier rotigaptide decreases the susceptibility to ventricular arrhythmia by enhancing conduction velocity and suppressing discordant alternans during therapeutic hypothermia in isolated rabbit hearts. Heart Rhythm 2016; 13:251-61. [DOI: 10.1016/j.hrthm.2015.07.023] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Indexed: 11/23/2022]
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21
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Thermoregulation and energetics in hibernating black bears: metabolic rate and the mystery of multi-day body temperature cycles. J Comp Physiol B 2015; 185:447-61. [DOI: 10.1007/s00360-015-0891-y] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Revised: 01/12/2015] [Accepted: 01/17/2015] [Indexed: 11/30/2022]
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22
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Yan L, Kudej RK, Vatner DE, Vatner SF. Myocardial ischemic protection in natural mammalian hibernation. Basic Res Cardiol 2015; 110:9. [PMID: 25613166 DOI: 10.1007/s00395-015-0462-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Revised: 12/08/2014] [Accepted: 01/07/2015] [Indexed: 12/31/2022]
Abstract
Hibernating myocardium is an important clinical syndrome protecting the heart with chronic myocardial ischemia, named for its assumed resemblance to hibernating mammals in winter. However, the effects of myocardial ischemic protection have never been studied in true mammalian hibernation, which is a unique strategy for surviving extreme winter environmental stress. The goal of this investigation was to test the hypothesis that ischemic stress may also be protected in woodchucks as they hibernate in winter. Myocardial infarction was induced by coronary occlusion followed by reperfusion in naturally hibernating woodchucks in winter with and without hibernation and in summer, when not hibernating. The ischemic area at risk was similar among groups. Myocardial infarction was significantly less in woodchucks in winter, whether hibernating or not, compared with summer, and was similar to that resulting after ischemic preconditioning. Whereas several genes were up or downregulated in both hibernating woodchuck and with ischemic preconditioning, one mechanism was unique to hibernation, i.e., activation of cAMP-response element binding protein (CREB). When CREB was upregulated in summer, it induced protection similar to that observed in the woodchuck heart in winter. The cardioprotection in hibernation was also mediated by endothelial nitric oxide synthase, rather than inducible nitric oxide synthase. Thus, the hibernating woodchuck heart is a novel model to study cardioprotection for two major reasons: (1) powerful cardioprotection occurs naturally in winter months in the absence of any preconditioning stimuli, and (2) it resembles ischemic preconditioning, but with novel mechanisms, making this model potentially useful for clinical translation.
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Affiliation(s)
- Lin Yan
- Department of Cell Biology and Molecular Medicine, Cardiovascular Research Institute, Rutgers-New Jersey Medical School, 185 South Orange Ave, MSB G-609, Newark, NJ, 07103, USA
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Li H, Liu T, Chen W, Jain MR, Vatner DE, Vatner SF, Kudej RK, Yan L. Proteomic mechanisms of cardioprotection during mammalian hibernation in woodchucks, Marmota monax. J Proteome Res 2013; 12:4221-9. [PMID: 23855383 DOI: 10.1021/pr400580f] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Mammalian hibernation is a unique strategy for winter survival in response to limited food supply and harsh climate, which includes resistance to cardiac arrhythmias. We previously found that hibernating woodchucks (Marmota monax) exhibit natural resistance to Ca2+ overload-related cardiac dysfunction and nitric oxide (NO)-dependent vasodilation, which maintains myocardial blood flow during hibernation. Since the cellular/molecular mechanisms mediating the protection are less clear, the goal of this study was to investigate changes in the heart proteome and reveal related signaling networks that are involved in establishing cardioprotection in woodchucks during hibernation. This was accomplished using isobaric tags for a relative and absolute quantification (iTRAQ) approach. The most significant changes observed in winter hibernation compared to summer non-hibernation animals were upregulation of the antioxidant catalase and inhibition of endoplasmic reticulum (ER) stress response by downregulation of GRP78, mechanisms which could be responsible for the adaptation and protection in hibernating animals. Furthermore, protein networks pertaining to NO signaling, acute phase response, CREB and NFAT transcriptional regulations, protein kinase A and α-adrenergic signaling were also dramatically upregulated during hibernation. These adaptive mechanisms in hibernators may provide new directions to protect myocardium of non-hibernating animals, especially humans, from cardiac dysfunction induced by hypothermic stress and myocardial ischemia.
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Affiliation(s)
- Hong Li
- Center for Advanced Proteomics Research and Department of Biochemistry and Molecular Biology, Rutgers University-New Jersey Medical School Cancer Center, Newark, New Jersey 07103, United States.
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Egorov YV, Glukhov AV, Efimov IR, Rosenshtraukh LV. Hypothermia-induced spatially discordant action potential duration alternans and arrhythmogenesis in nonhibernating versus hibernating mammals. Am J Physiol Heart Circ Physiol 2012; 303:H1035-46. [PMID: 22886418 DOI: 10.1152/ajpheart.00786.2011] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The heart of hibernating species is resistant to lethal ventricular fibrillation (VF) induced by hypothermia. Spatially discordant (SDA) cardiac alternans is a promising predictor of VF, yet its role in the mechanism of hypothermic arrhythmogenesis in both nonhibernating and hibernating mammals remains unclear. We optically mapped the posterior epicardial surface of Langendorff-perfused hearts of winter hibernating (WH, n = 13), interbout arousal (IBA; n = 4), and summer active (SA, n = 6) ground squirrels (GSs; Spermophilus undulatus) and rabbits (n = 10). Action potential duration (APD) and conduction velocity (CV) dynamic restitution and alternans were determined at 37 to 17°C. In all animals, hypothermia induced heterogeneous APD prolongation, enhanced APD dispersion, and slowed CV. In all groups, hypothermia promoted the formation of APD alternans, which was predominantly spatially concordant in GSs and SDA in rabbits (SD of APD dispersion: 4.2 ± 0.4% vs. 2.0 ± 0.3% at 37°C and 7.5 ± 1.1% vs. 3.4 ± 0.5% at 17°C, P < 0.001 for rabbits vs. the WH group, respectively). In rabbits, hypothermia significantly increased the magnitude of SDA, which enhanced the ventricular repolarization gradient, caused conduction delays (CV: 3.2 vs. 8.2 cm/s at 17°C in rabbits vs. the WH group), conduction block, and the onset of VF (0% at 37°C vs. 60% at 17°C, P < 0.01). In contrast, no arrhythmia was observed in GS hearts at any temperature. The amplitude of CV alternans was greater in rabbits (5.2 ± 0.4% versus 4.5 ± 0.3% at 37°C and 35.3 ± 4.2% vs. 14.9 ± 1.5% at 17°C in rabbits vs. the WH group, P < 0.001 at 17°C) and correlated with the amplitude of SDA. In conclusion, the mechanism underlying SDA formation during hypothermia is likely associated with CV alternans conditioned by an enhanced dispersion of repolarization. The factors of hibernating species resistance to SDA and VF seem to be the safe and dynamically stable conduction and the low dispersion of repolarization.
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Affiliation(s)
- Yuriy V Egorov
- Laboratory of Heart Electrophysiology, Cardiology Research Center, Moscow 121552, Russia
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Carey HV, Martin SL, Horwitz BA, Yan L, Bailey SM, Podrabsky J, Storz JF, Ortiz RM, Wong RP, Lathrop DA. Elucidating nature's solutions to heart, lung, and blood diseases and sleep disorders. Circ Res 2012; 110:915-21. [PMID: 22461362 DOI: 10.1161/circresaha.111.255398] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Evolution has provided a number of animal species with extraordinary phenotypes. Several of these phenotypes allow species to survive and thrive in environmental conditions that mimic disease states in humans. The study of evolved mechanisms responsible for these phenotypes may provide insights into the basis of human disease and guide the design of new therapeutic approaches. Examples include species that tolerate acute or chronic hypoxemia like deep-diving mammals and high-altitude inhabitants, as well as those that hibernate and interrupt their development when exposed to adverse environments. The evolved traits exhibited by these animal species involve modifications of common biological pathways that affect metabolic regulation, organ function, antioxidant defenses, and oxygen transport. In 2006, the National Heart, Lung, and Blood Institute released a funding opportunity announcement to support studies that were designed to elucidate the natural molecular and cellular mechanisms of adaptation in species that tolerate extreme environmental conditions. The rationale for this funding opportunity is detailed in this article, and the specific evolved mechanisms examined in the supported research are described. Also highlighted are past medical advances achieved through the study of animal species that have evolved extraordinary phenotypes as well as the expectations for new understanding of nature's solutions to heart, lung, blood, and sleep disorders through future research in this area.
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Affiliation(s)
- Hannah V Carey
- Department of Comparative Biosciences, University of Wisconsin-Madison, 2015 Linden Drive, Madison, WI 53706, USA.
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Postrepolarization refractoriness in acute ischemia and after antiarrhythmic drug administration: Action potential duration is not always an index of the refractory period. Heart Rhythm 2012; 9:977-82. [DOI: 10.1016/j.hrthm.2012.01.021] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2011] [Indexed: 11/17/2022]
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Glukhov AV, Fedorov VV, Kalish PW, Ravikumar VK, Lou Q, Janks D, Schuessler RB, Moazami N, Efimov IR. Conduction remodeling in human end-stage nonischemic left ventricular cardiomyopathy. Circulation 2012; 125:1835-47. [PMID: 22412072 DOI: 10.1161/circulationaha.111.047274] [Citation(s) in RCA: 122] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Several arrhythmogenic mechanisms have been inferred from animal heart failure models. However, the translation of these hypotheses is difficult because of the lack of functional human data. We aimed to investigate the electrophysiological substrate for arrhythmia in human end-stage nonischemic cardiomyopathy. METHODS AND RESULTS We optically mapped the coronary-perfused left ventricular wedge preparations from human hearts with end-stage nonischemic cardiomyopathy (heart failure, n=10) and nonfailing hearts (NF, n=10). Molecular remodeling was studied with immunostaining, Western blotting, and histological analyses. Heart failure produced heterogeneous prolongation of action potential duration resulting in the decrease of transmural action potential duration dispersion (64 ± 12 ms versus 129 ± 15 ms in NF, P<0.005). In the failing hearts, transmural activation was significantly slowed from the endocardium (39 ± 3 cm/s versus 49 ± 2 cm/s in NF, P=0.008) to the epicardium (28 ± 3 cm/s versus 40 ± 2 cm/s in NF, P=0.008). Conduction slowing was likely due to connexin 43 (Cx43) downregulation, decreased colocalization of Cx43 with N-cadherin (40 ± 2% versus 52 ± 5% in NF, P=0.02), and an altered distribution of phosphorylated Cx43 isoforms by the upregulation of the dephosphorylated Cx43 in both the subendocardium and subepicardium layers. Failing hearts further demonstrated spatially discordant conduction velocity alternans which resulted in nonuniform propagation discontinuities and wave breaks conditioned by strands of increased interstitial fibrosis (fibrous tissue content in heart failure 16.4 ± 7.7 versus 9.9 ± 1.4% in NF, P=0.02). CONCLUSIONS Conduction disorder resulting from the anisotropic downregulation of Cx43 expression, the reduction of Cx43 phosphorylation, and increased fibrosis is likely to be a critical component of arrhythmogenic substrate in patients with nonischemic cardiomyopathy.
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Affiliation(s)
- Alexey V Glukhov
- Department of Biomedical Engineering, Washington University in St. Louis, MO 63130, USA
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Grabek KR, Karimpour-Fard A, Epperson LE, Hindle A, Hunter LE, Martin SL. Multistate proteomics analysis reveals novel strategies used by a hibernator to precondition the heart and conserve ATP for winter heterothermy. Physiol Genomics 2011; 43:1263-75. [PMID: 21914784 PMCID: PMC3217319 DOI: 10.1152/physiolgenomics.00125.2011] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Accepted: 09/02/2011] [Indexed: 11/22/2022] Open
Abstract
The hibernator's heart functions continuously and avoids damage across the wide temperature range of winter heterothermy. To define the molecular basis of this phenotype, we quantified proteomic changes in the 13-lined ground squirrel heart among eight distinct physiological states encompassing the hibernator's year. Unsupervised clustering revealed a prominent seasonal separation between the summer homeotherms and winter heterotherms, whereas within-season state separation was limited. Further, animals torpid in the fall were intermediate to summer and winter, consistent with the transitional nature of this phase. A seasonal analysis revealed that the relative abundances of protein spots were mainly winter-increased. The winter-elevated proteins were involved in fatty acid catabolism and protein folding, whereas the winter-depleted proteins included those that degrade branched-chain amino acids. To identify further state-dependent changes, protein spots were re-evaluated with respect to specific physiological state, confirming the predominance of seasonal differences. Additionally, chaperone and heat shock proteins increased in winter, including HSPA4, HSPB6, and HSP90AB1, which have known roles in protecting against ischemia-reperfusion injury and apoptosis. The most significant and greatest fold change observed was a disappearance of phospho-cofilin 2 at low body temperature, likely a strategy to preserve ATP. The robust summer-to-winter seasonal proteomic shift implies that a winter-protected state is orchestrated before prolonged torpor ensues. Additionally, the general preservation of the proteome during winter hibernation and an increase of stress response proteins, together with dephosphorylation of cofilin 2, highlight the importance of ATP-conserving mechanisms for winter cardioprotection.
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Affiliation(s)
- Katharine R Grabek
- Human Medical Genetics Program, Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, Colorado 80045, USA
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Hsieh YC, Yeh HI, Lin SF, Hsu YW, Huang JL, Lin TC, Ting CT, Wu TJ. Short-Duration Therapeutic Hypothermia Causes Prompt Connexin43 Gap Junction Remodeling in Isolated Rabbit Hearts. Circ J 2011; 75:1706-16. [DOI: 10.1253/circj.cj-10-1001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Yu-Cheng Hsieh
- Cardiovascular Center, Taichung Veterans General Hospital and Department of Internal Medicine, Faculty of Medicine, Institute of Clinical Medicine, Cardiovascular Research Center, National Yang-Ming University School of Medicine
| | - Hung-I Yeh
- Departments of Medical Research and Internal Medicine, Mackay Memorial Hospital, Mackay Medical College
| | - Shien-Fong Lin
- Krannert Institute of Cardiology and the Division of Cardiology, Department of Medicine, Indiana University School of Medicine
| | - Ya-Wen Hsu
- Cardiovascular Center, Taichung Veterans General Hospital and Department of Internal Medicine, Faculty of Medicine, Institute of Clinical Medicine, Cardiovascular Research Center, National Yang-Ming University School of Medicine
| | - Jin-Long Huang
- Cardiovascular Center, Taichung Veterans General Hospital and Department of Internal Medicine, Faculty of Medicine, Institute of Clinical Medicine, Cardiovascular Research Center, National Yang-Ming University School of Medicine
- School of Medicine, Chung-Shan Medical University
| | - Tung-Chao Lin
- Cardiovascular Center, Taichung Veterans General Hospital and Department of Internal Medicine, Faculty of Medicine, Institute of Clinical Medicine, Cardiovascular Research Center, National Yang-Ming University School of Medicine
| | - Chih-Tai Ting
- Cardiovascular Center, Taichung Veterans General Hospital and Department of Internal Medicine, Faculty of Medicine, Institute of Clinical Medicine, Cardiovascular Research Center, National Yang-Ming University School of Medicine
| | - Tsu-Juey Wu
- Cardiovascular Center, Taichung Veterans General Hospital and Department of Internal Medicine, Faculty of Medicine, Institute of Clinical Medicine, Cardiovascular Research Center, National Yang-Ming University School of Medicine
- School of Medicine, Chung-Shan Medical University
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Piktel JS, Jeyaraj D, Said TH, Rosenbaum DS, Wilson LD. Enhanced dispersion of repolarization explains increased arrhythmogenesis in severe versus therapeutic hypothermia. Circ Arrhythm Electrophysiol 2010; 4:79-86. [PMID: 21163888 DOI: 10.1161/circep.110.958355] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
BACKGROUND Hypothermia is proarrhythmic, and, as the use of therapeutic hypothermia (TH) increases, it is critically important to understand the electrophysiological effects of hypothermia on cardiac myocytes and arrhythmia substrates. We tested the hypothesis that hypothermia-enhanced transmural dispersion of repolarization (DOR) is a mechanism of arrhythmogenesis in hypothermia. In addition, we investigated whether the degree of hypothermia, the rate of temperature change, and cooling versus rewarming would alter hypothermia-induced arrhythmia substrates. METHODS AND RESULTS Optical action potentials were recorded from cells spanning the transmural wall of canine left ventricular wedge preparations at baseline (36°C), during cooling and during rewarming. Electrophysiological parameters were examined while varying the depth of hypothermia. On cooling to 26°C, DOR increased from 26±4 ms to 93±18 ms (P=0.021); conduction velocity decreased from 35±5 cm/s to 22±5 cm/s (P=0.010). On rewarming to 36°C, DOR remained prolonged, whereas conduction velocity returned to baseline. Conduction block and reentry was observed in all severe hypothermia preparations. Ventricular fibrillation/ventricular tachycardia was seen more during rewarming (4/5) versus cooling (2/6). In TH (n=7), cooling to 32°C mildly increased DOR (31±6 to 50±9, P=0.012), with return to baseline on rewarming and was associated with decreased arrhythmia susceptibility. Increased rate of cooling did not further enhance DOR or arrhythmogenesis. CONCLUSIONS Hypothermia amplifies DOR and is a mechanism for arrhythmogenesis. DOR is directly dependent on the depth of cooling and rewarming. This provides insight into the clinical observation of a low incidence of arrhythmias in TH and has implications for protocols for the clinical application of TH.
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Affiliation(s)
- Joseph S Piktel
- The Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University, Cleveland, OH, USA.
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Hampton M, Nelson BT, Andrews MT. Circulation and metabolic rates in a natural hibernator: an integrative physiological model. Am J Physiol Regul Integr Comp Physiol 2010; 299:R1478-88. [PMID: 20844258 PMCID: PMC3008751 DOI: 10.1152/ajpregu.00273.2010] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2010] [Accepted: 09/13/2010] [Indexed: 11/22/2022]
Abstract
Small hibernating mammals show regular oscillations in their heart rate and body temperature throughout the winter. Long periods of torpor are abruptly interrupted by arousals with heart rates that rapidly increase from 5 beats/min to over 400 beats/min and body temperatures that increase by ∼30°C only to drop back into the hypothermic torpid state within hours. Surgically implanted transmitters were used to obtain high-resolution electrocardiogram and body temperature data from hibernating thirteen-lined ground squirrels (Spermophilus tridecemlineatus). These data were used to construct a model of the circulatory system to gain greater understanding of these rapid and extreme changes in physiology. Our model provides estimates of metabolic rates during the torpor-arousal cycles in different model compartments that would be difficult to measure directly. In the compartment that models the more metabolically active tissues and organs (heart, brain, liver, and brown adipose tissue) the peak metabolic rate occurs at a core body temperature of 19°C approximately midway through an arousal. The peak metabolic rate of the active tissues is nine times the normothermic rate after the arousal is complete. For the overall metabolic rate in all tissues, the peak-to-resting ratio is five. This value is high for a rodent, which provides evidence for the hypothesis that the arousal from torpor is limited by the capabilities of the cardiovascular system.
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Affiliation(s)
- Marshall Hampton
- Department of Mathematics and Statistics, University of Minnesota Duluth, Duluth, Minnesota, USA.
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Glukhov AV, Fedorov VV, Lou Q, Ravikumar VK, Kalish PW, Schuessler RB, Moazami N, Efimov IR. Transmural dispersion of repolarization in failing and nonfailing human ventricle. Circ Res 2010; 106:981-91. [PMID: 20093630 DOI: 10.1161/circresaha.109.204891] [Citation(s) in RCA: 223] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
RATIONALE Transmural dispersion of repolarization has been shown to play a role in the genesis of ventricular tachycardia and fibrillation in different animal models of heart failure (HF). Heterogeneous changes of repolarization within the midmyocardial population of ventricular cells have been considered an important contributor to the HF phenotype. However, there is limited electrophysiological data from the human heart. OBJECTIVE To study electrophysiological remodeling of transmural repolarization in the failing and nonfailing human hearts. METHODS AND RESULTS We optically mapped the action potential duration (APD) in the coronary-perfused scar-free posterior-lateral left ventricular free wall wedge preparations from failing (n=5) and nonfailing (n=5) human hearts. During slow pacing (S1S1=2000 ms), in the nonfailing hearts we observed significant transmural APD gradient: subepicardial, midmyocardial, and subendocardial APD80 were 383+/-21, 455+/-20, and 494+/-22 ms, respectively. In 60% of nonfailing hearts (3 of 5), we found midmyocardial islands of cells that presented a distinctly long APD (537+/-40 ms) and a steep local APD gradient (27+/-7 ms/mm) compared with the neighboring myocardium. HF resulted in prolongation of APD80: 477+/-22 ms, 495+/-29 ms, and 506+/-35 ms for the subepi-, mid-, and subendocardium, respectively, while reducing transmural APD80 difference from 111+/-13 to 29+/-6 ms (P<0.005) and presence of any prominent local APD gradient. In HF, immunostaining revealed a significant reduction of connexin43 expression on the subepicardium. CONCLUSIONS We present for the first time direct experimental evidence of a transmural APD gradient in the human heart. HF results in the heterogeneous prolongation of APD, which significantly reduces the transmural and local APD gradients.
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Affiliation(s)
- Alexey V Glukhov
- Department of Biomedical Engineering, Washington University, St Louis, MO 63130, USA
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Hsieh YC, Lin SF, Lin TC, Ting CT, Wu TJ. Therapeutic hypothermia (30 degrees C) enhances arrhythmogenic substrates, including spatially discordant alternans, and facilitates pacing-induced ventricular fibrillation in isolated rabbit hearts. Circ J 2009; 73:2214-22. [PMID: 19789414 DOI: 10.1253/circj.cj-09-0432] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
BACKGROUND Therapeutic hypothermia (TH, 30 degrees C) protects the brain from hypoxic injury. However, TH may potentiate the occurrence of lethal ventricular fibrillation (VF), although the mechanism remains unclear. The present study explored the hypothesis that TH enhances wavebreaks during VF and S(1) pacing, facilitates pacing-induced spatially discordant alternans (SDA), and increases the vulnerability of pacing-induced VF. METHODS AND RESULTS Using an optical mapping system, epicardial activations of VF were studied in 7 Langendorff-perfused isolated rabbit hearts at baseline (37 degrees C), TH (30 degrees C), and rewarming (37 degrees C). Action potential duration (APD)/conduction velocity (CV) restitution and APD alternans (n=6 hearts) were determined by S(1) pacing at these 3 stages. During TH, there was a higher percentage of VF duration containing epicardial repetitive activities (spatiotemporal periodicity) (P<0.001). However, TH increased phase singularity number (wavebreaks) during VF (P<0.05) and S(1) pacing (P<0.05). TH resulted in earlier onset of APD alternans (P<0.001), which was predominantly SDA (P<0.05), and increased pacing-induced VF episodes (P<0.05). TH also decreased CV, shortened wavelength, and enhanced APD dispersion and the spatial heterogeneity of CV restitution. CONCLUSIONS TH (30 degrees C) increased the vulnerability of pacing-induced VF by (1)facilitating wavebreaks during VF and S(1) pacing, and (2)enhancing proarrhythmic electrophysiological parameters, including promoting earlier onset of APD alternans (predominantly SDA) during S(1) pacing.
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Affiliation(s)
- Yu-Cheng Hsieh
- Cardiovascular Center, Taichung Veterans General Hospital, Taichung and Department of Internal Medicine, Institute of Clinical Medicine, National Yang-Ming University School of Medicine, Taipei, Taiwan
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Does the postrepolarization refractoriness play a role in amiodarone's antiarrhythmic efficacy? Heart Rhythm 2008; 5:1743-4. [PMID: 19084814 DOI: 10.1016/j.hrthm.2008.09.032] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2008] [Indexed: 11/20/2022]
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