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Zhang ZH, Barajas-Martinez H, Jiang H, Huang CX, Antzelevitch C, Xia H, Hu D. Gene and stem cell therapy for inherited cardiac arrhythmias. Pharmacol Ther 2024; 256:108596. [PMID: 38301770 DOI: 10.1016/j.pharmthera.2024.108596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 12/11/2023] [Accepted: 01/13/2024] [Indexed: 02/03/2024]
Abstract
Inherited cardiac arrhythmias are a group of genetic diseases predisposing to sudden cardiac arrest, mainly resulting from variants in genes encoding cardiac ion channels or proteins involved in their regulation. Currently available therapeutic options (pharmacotherapy, ablative therapy and device-based therapy) can not preclude the occurrence of arrhythmia events and/or provide complete protection. With growing understanding of the genetic background and molecular mechanisms of inherited cardiac arrhythmias, advancing insight of stem cell technology, and development of vectors and delivery strategies, gene therapy and stem cell therapy may be promising approaches for treatment of inherited cardiac arrhythmias. Recent years have witnessed impressive progress in the basic science aspects and there is a clear and urgent need to be translated into the clinical management of arrhythmic events. In this review, we present a succinct overview of gene and cell therapy strategies, and summarize the current status of gene and cell therapy. Finally, we discuss future directions for implementation of gene and cell therapy in the therapy of inherited cardiac arrhythmias.
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Affiliation(s)
- Zhong-He Zhang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, 430060, PR China; Cardiovascular Research Institute, Wuhan University, Wuhan, 430060, PR China; Hubei Key Laboratory of Cardiology, Wuhan, 430060, PR China
| | - Hector Barajas-Martinez
- Lankenau Institute for Medical Research, Lankenau Heart Institute, Wynnwood, PA, 19096, USA; Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, 19107, USA
| | - Hong Jiang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, 430060, PR China; Cardiovascular Research Institute, Wuhan University, Wuhan, 430060, PR China; Hubei Key Laboratory of Cardiology, Wuhan, 430060, PR China
| | - Cong-Xin Huang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, 430060, PR China; Cardiovascular Research Institute, Wuhan University, Wuhan, 430060, PR China; Hubei Key Laboratory of Cardiology, Wuhan, 430060, PR China
| | - Charles Antzelevitch
- Lankenau Institute for Medical Research, Lankenau Heart Institute, Wynnwood, PA, 19096, USA; Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, 19107, USA
| | - Hao Xia
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, 430060, PR China; Cardiovascular Research Institute, Wuhan University, Wuhan, 430060, PR China; Hubei Key Laboratory of Cardiology, Wuhan, 430060, PR China.
| | - Dan Hu
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, 430060, PR China; Cardiovascular Research Institute, Wuhan University, Wuhan, 430060, PR China; Hubei Key Laboratory of Cardiology, Wuhan, 430060, PR China.
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2
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Ibrahim AGE, Ciullo A, Yamaguchi S, Li C, Antes T, Jones X, Li L, Murali R, Maslennikov I, Sundararaman N, Soetkamp D, Cingolani E, Van Eyk J, Marbán E. A novel micropeptide, Slitharin, exerts cardioprotective effects in myocardial infarction. Proteomics Clin Appl 2024:e2300128. [PMID: 38444254 DOI: 10.1002/prca.202300128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Revised: 02/19/2024] [Accepted: 02/21/2024] [Indexed: 03/07/2024]
Abstract
PURPOSE Micropeptides are an emerging class of proteins that play critical roles in cell signaling. Here, we describe the discovery of a novel micropeptide, dubbed slitharin (Slt), in conditioned media from Cardiosphere-derived cells (CDCs), a therapeutic cardiac stromal cell type. EXPERIMENTAL DESIGN We performed mass spectrometry of peptide-enriched fractions from the conditioned media of CDCs and a therapeutically inert cell type (human dermal fibrobasts). We then evaluated the therapeutic capacity of the candidate peptide using an in vitro model of cardiomyocyte injury and a rat model of myocardial infarction. RESULTS We identified a novel 24-amino acid micropeptide (dubbed Slitharin [Slt]) with a non-canonical leucine start codon, arising from long intergenic non-coding (LINC) RNA 2099. Neonatal rat ventricular myocytes (NRVMs) exposed to Slt were protected from hypoxic injury in vitro compared to a vehicle or scrambled control. Transcriptomic analysis of cardiomyocytes exposed to Slt reveals cytoprotective capacity, putatively through regulation of stress-induced MAPK-ERK. Slt also exerted cardioprotective effects in rats with myocardial infarction as shown by reduced infarct size 48 h post-injury. Conclusions and clinical relavance: Thus, Slt is a non-coding RNA-derived micropeptide, identified in the extracellular space, with a potential cardioprotective function.
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Affiliation(s)
- Ahmed G E Ibrahim
- Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Alessandra Ciullo
- Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Shukuro Yamaguchi
- Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Chang Li
- Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Travis Antes
- Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Xaviar Jones
- Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Liang Li
- Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Ramachandran Murali
- Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | | | - Niveda Sundararaman
- Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Daniel Soetkamp
- Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Eugenio Cingolani
- Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Jennifer Van Eyk
- Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Eduardo Marbán
- Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA
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Iijima A, Švecová O, Hošek J, Kula R, Bébarová M. Sildenafil affects the human Kir2.1 and Kir2.2 channels at clinically relevant concentrations: Inhibition potentiated by low Ba 2. Front Pharmacol 2023; 14:1136272. [PMID: 36817146 PMCID: PMC9932908 DOI: 10.3389/fphar.2023.1136272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Accepted: 01/23/2023] [Indexed: 02/05/2023] Open
Abstract
Sildenafil (Viagra), the first approved and widely used oral drug for the treatment of erectile dysfunction, was occasionally associated with life-threatening ventricular arrhythmias in patients. Since inward rectifier potassium current (I K1) may considerably contribute to this arrhythmogenesis, we investigated the effect of sildenafil on the human Kir2.1 and Kir2.2, the prevailing subunits forming the ventricular I K1 channels. Experiments were performed by the whole-cell patch clamp technique at 37°C using Chinese hamster ovary cells transiently expressing the human Kir2.1 and Kir2.2 channels. Changes of both the inward and outward current components (at -110 and -50 mV, respectively) were tested to be able to consider the physiological relevance of the sildenafil effect (changes at -110 and -50 mV did not significantly differ, results at -50 mV are listed below). A significant Kir2.1 inhibition was observed at all applied sildenafil concentrations (16.1% ± 3.7%, 20.0% ± 2.6%, and 15.0% ± 3.0% at 0.1, 1, and 10 μM, respectively). The inhibitory effect of 0.1 μM sildenafil was potentiated by the presence of a low concentration of Ba2+ (0.1 μM) which induced only a slight Kir2.1 inhibition by 5.95% ± 0.75% alone (the combined effect was 35.5% ± 3.4%). The subtherapeutic and therapeutic sildenafil concentrations (0.1 and 1 μM) caused a dual effect on Kir2.2 channels whereas a significant Kir2.2 activation was observed at the supratherapeutic sildenafil concentration (10 μM: 34.1% ± 5.6%). All effects were fully reversible. This is the first study demonstrating that sildenafil at clinically relevant concentrations inhibits both the inward and outward current components of the main human ventricular I K1 subunit Kir2.1. This inhibitory effect was significantly potentiated by a low concentration of environmental contaminant Ba2+ in agreement with recently reported data on rat ventricular I K1 which additionally showed a significant repolarization delay. Considering the similar subunit composition of the human and rat ventricular I K1 channels, the observed effects might contribute to sildenafil-associated arrhythmogenesis in clinical practice.
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Affiliation(s)
- Akimasa Iijima
- Department of Physiology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Olga Švecová
- Department of Physiology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Jan Hošek
- Department of Molecular Pharmacy, Faculty of Pharmacy, Masaryk University, Brno, Czech Republic
| | - Roman Kula
- Department of Physiology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Markéta Bébarová
- Department of Physiology, Faculty of Medicine, Masaryk University, Brno, Czech Republic,*Correspondence: Markéta Bébarová,
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Sanchez L, Mesquita T, Zhang R, Liao K, Rogers R, Lin YN, Miguel-dos-Santos R, Akhmerov A, Li L, Nawaz A, Holm K, Marbán E, Cingolani E. MicroRNA-dependent suppression of biological pacemaker activity induced by TBX18. Cell Rep Med 2022; 3:100871. [PMID: 36543116 PMCID: PMC9798022 DOI: 10.1016/j.xcrm.2022.100871] [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: 03/01/2022] [Revised: 08/18/2022] [Accepted: 11/19/2022] [Indexed: 12/24/2022]
Abstract
Chemically modified mRNA (CMmRNA) with selectively altered nucleotides are used to deliver transgenes, but translation efficiency is variable. We have transfected CMmRNA encoding human T-box transcription factor 18 (CMmTBX18) into heart cells or the left ventricle of rats with atrioventricular block. TBX18 protein expression from CMmTBX18 is weak and transient, but Acriflavine, an Argonaute 2 inhibitor, boosts TBX18 levels. Small RNA sequencing identified two upregulated microRNAs (miRs) in CMmTBX18-transfected cells. Co-administration of miR-1-3p and miR-1b antagomiRs with CMmTBX18 prolongs TBX18 expression in vitro and in vivo and is sufficient to generate electrical stimuli capable of pacing the heart. Different suppressive miRs likewise limit the expression of VEGF-A CMmRNA. Cells therefore resist translation of CMmRNA therapeutic transgenes by upregulating suppressive miRs. Blockade of suppressive miRs enhances CMmRNA expression of genes driving biological pacing or angiogenesis. Such counterstrategies constitute an approach to boost the efficacy and efficiency of CMmRNA therapies.
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Affiliation(s)
- Lizbeth Sanchez
- Smidt Heart Institute, Cedars-Sinai Medical Center, 127 S San Vicente Blvd, Los Angeles, CA 90048, USA
| | - Thassio Mesquita
- Smidt Heart Institute, Cedars-Sinai Medical Center, 127 S San Vicente Blvd, Los Angeles, CA 90048, USA
| | - Rui Zhang
- Smidt Heart Institute, Cedars-Sinai Medical Center, 127 S San Vicente Blvd, Los Angeles, CA 90048, USA
| | - Ke Liao
- Smidt Heart Institute, Cedars-Sinai Medical Center, 127 S San Vicente Blvd, Los Angeles, CA 90048, USA
| | - Russell Rogers
- Smidt Heart Institute, Cedars-Sinai Medical Center, 127 S San Vicente Blvd, Los Angeles, CA 90048, USA
| | - Yen-Nien Lin
- Smidt Heart Institute, Cedars-Sinai Medical Center, 127 S San Vicente Blvd, Los Angeles, CA 90048, USA
| | - Rodrigo Miguel-dos-Santos
- Smidt Heart Institute, Cedars-Sinai Medical Center, 127 S San Vicente Blvd, Los Angeles, CA 90048, USA
| | - Akbarshakh Akhmerov
- Smidt Heart Institute, Cedars-Sinai Medical Center, 127 S San Vicente Blvd, Los Angeles, CA 90048, USA
| | - Liang Li
- Smidt Heart Institute, Cedars-Sinai Medical Center, 127 S San Vicente Blvd, Los Angeles, CA 90048, USA
| | - Asma Nawaz
- Smidt Heart Institute, Cedars-Sinai Medical Center, 127 S San Vicente Blvd, Los Angeles, CA 90048, USA
| | - Kevin Holm
- Smidt Heart Institute, Cedars-Sinai Medical Center, 127 S San Vicente Blvd, Los Angeles, CA 90048, USA
| | - Eduardo Marbán
- Smidt Heart Institute, Cedars-Sinai Medical Center, 127 S San Vicente Blvd, Los Angeles, CA 90048, USA
| | - Eugenio Cingolani
- Smidt Heart Institute, Cedars-Sinai Medical Center, 127 S San Vicente Blvd, Los Angeles, CA 90048, USA,Corresponding author
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Calcium Overload or Underload? The Effects of Doxorubicin on the Calcium Dynamics in Guinea Pig Hearts. Biomedicines 2022; 10:biomedicines10092197. [PMID: 36140298 PMCID: PMC9496179 DOI: 10.3390/biomedicines10092197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2022] [Revised: 08/29/2022] [Accepted: 08/31/2022] [Indexed: 11/17/2022] Open
Abstract
The severe doxorubicin (DOXO) side effect of cardiomyopathy limits it clinical application as an effective anticancer drug. Although Ca2+ overload was postulated as one of the mechanisms for this toxicity, its role was, however, disputable in terms of the contractile dysfunction. In this work, the dynamics of the intracellular Ca2+ signal were optically mapped in a Langendorff guinea pig heart. We found that DOXO treatment: (1) Delayed the activation of the Ca2+ signal. With the reference time set at the peak of the action potential (AP), the time lag between the peak of the Ca2+ signal and AP (Ca-AP-Lag) was significantly prolonged. (2) Slowed down the intracellular Ca2+ releasing and sequestering process. Both the maximum rising (MRV) and falling (MFV) velocity of the Ca2+ signal were decreased. (3) Shortened the duration of the Ca2+ signal in one cycle of Ca2+ oscillation. The duration of the Ca2+ signal at 50% amplitude (CaD50) was significantly shortened. These results suggested a reduced level of intracellular Ca2+ after DOXO treatment. Furthermore, we found that the effect of tachypacing was similar to that of DOXO, and, interestingly, DOXO exerted contradictory effects on the tachypaced hearts: it shortened the Ca-AP-Lag, accelerated the MRV and MFV, and prolonged the CaD50. We, therefore, concluded that DOXO had a different effect on intracellular Ca2+. It caused Ca2+ underload in hearts with sinus rhythm; this might relate to the contractile dysfunction in DOXO cardiomyopathy. It led to Ca2+ overload in the tachypaced hearts, which might contribute to the Ca2+-overload-related toxicity.
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Chou PC, Liu CM, Weng CH, Yang KC, Cheng ML, Lin YC, Yang RB, Shyu BC, Shyue SK, Liu JD, Chen SP, Hsiao M, Hu YF. Fibroblasts Drive Metabolic Reprogramming in Pacemaker Cardiomyocytes. Circ Res 2022; 131:6-20. [PMID: 35611699 DOI: 10.1161/circresaha.121.320301] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND The sinoatrial node (SAN) is characterized by the microenvironment of pacemaker cardiomyocytes (PCs) encased with fibroblasts. An altered microenvironment leads to rhythm failure. Operable cell or tissue models are either generally lacking or difficult to handle. The biological process behind the milieu of SANs to evoke pacemaker rhythm is unknown. We explored how fibroblasts interact with PCs and regulate metabolic reprogramming and rhythmic activity in the SAN. METHODS Tbx18 (T-box transcription factor 18)-induced PCs and fibroblasts were used for cocultures and engineered tissues, which were used as the in vitro models to explore how fibroblasts regulate the functional integrity of SANs. RNA-sequencing, metabolomics, and cellular and molecular techniques were applied to characterize the molecular signals underlying metabolic reprogramming and identify its critical regulators. These pathways were further validated in vivo in rodents and induced human pluripotent stem cell-derived cardiomyocytes. RESULTS We observed that rhythmicity in Tbx18-induced PCs was regulated by aerobic glycolysis. Fibroblasts critically activated metabolic reprogramming and aerobic glycolysis within PCs, and, therefore, regulated pacemaker activity in PCs. The metabolic reprogramming was attributed to the exclusive induction of Aldoc (aldolase c) within PCs after fibroblast-PC integration. Fibroblasts activated the integrin-dependent mitogen-activated protein kinase-E2F1 signal through cell-cell contact and turned on Aldoc expression in PCs. Interruption of fibroblast-PC interaction or Aldoc knockdown nullified electrical activity. Engineered Tbx18-PC tissue sheets were generated to recapitulate the microenvironment within SANs. Aldoc-driven rhythmic machinery could be replicated within tissue sheets. Similar machinery was faithfully validated in de novo PCs of adult mice and rats, and in human PCs derived from induced pluripotent stem cells. CONCLUSIONS Fibroblasts drive Aldoc-mediated metabolic reprogramming and rhythmic regulation in SANs. This work details the cellular machinery behind the complex milieu of vertebrate SANs and opens a new direction for future therapy.
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Affiliation(s)
- Pei-Chun Chou
- Division of Cardiology, Department of Medicine, Heart Rhythm Center, Taipei Veterans General Hospital, Taiwan. (P.-C.C., C.-M.L., C.-H.W., J.-D.L., Y.-F.H.).,Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan (P.-C.C., C.-H.W., K.-C.Y., Y.-C.L., R.-B.Y., B.-C.S., S.-K.S., J.-D.L., Y.-F.H.)
| | - Chih-Min Liu
- Division of Cardiology, Department of Medicine, Heart Rhythm Center, Taipei Veterans General Hospital, Taiwan. (P.-C.C., C.-M.L., C.-H.W., J.-D.L., Y.-F.H.).,Faculty of Medicine, School of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan (C.-M.L., Y.-F.H.)
| | - Ching-Hui Weng
- Division of Cardiology, Department of Medicine, Heart Rhythm Center, Taipei Veterans General Hospital, Taiwan. (P.-C.C., C.-M.L., C.-H.W., J.-D.L., Y.-F.H.).,Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan (P.-C.C., C.-H.W., K.-C.Y., Y.-C.L., R.-B.Y., B.-C.S., S.-K.S., J.-D.L., Y.-F.H.)
| | - Kai-Chien Yang
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan (P.-C.C., C.-H.W., K.-C.Y., Y.-C.L., R.-B.Y., B.-C.S., S.-K.S., J.-D.L., Y.-F.H.).,Department and Graduate Institute of Pharmacology, National Taiwan University College of Medicine, Taipei (K.-C.Y.)
| | - Mei-Ling Cheng
- Metabolomics Core Laboratory, Healthy Aging Research Center, Chang Gung University, Taoyuan City, Taiwan (M.-L.C.)
| | - Yuh-Charn Lin
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan (P.-C.C., C.-H.W., K.-C.Y., Y.-C.L., R.-B.Y., B.-C.S., S.-K.S., J.-D.L., Y.-F.H.).,Department of Physiology, School of Medicine, College of Medicine, Taipei Medical University, Taiwan (Y.-C.L.)
| | - Ruey-Bing Yang
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan (P.-C.C., C.-H.W., K.-C.Y., Y.-C.L., R.-B.Y., B.-C.S., S.-K.S., J.-D.L., Y.-F.H.)
| | - Bai-Chuang Shyu
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan (P.-C.C., C.-H.W., K.-C.Y., Y.-C.L., R.-B.Y., B.-C.S., S.-K.S., J.-D.L., Y.-F.H.)
| | - Song-Kun Shyue
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan (P.-C.C., C.-H.W., K.-C.Y., Y.-C.L., R.-B.Y., B.-C.S., S.-K.S., J.-D.L., Y.-F.H.)
| | - Jin-Dian Liu
- Division of Cardiology, Department of Medicine, Heart Rhythm Center, Taipei Veterans General Hospital, Taiwan. (P.-C.C., C.-M.L., C.-H.W., J.-D.L., Y.-F.H.).,Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan (P.-C.C., C.-H.W., K.-C.Y., Y.-C.L., R.-B.Y., B.-C.S., S.-K.S., J.-D.L., Y.-F.H.)
| | - Shih-Pin Chen
- Department of Neurology, Neurological Institute, Taipei Veterans General Hospital, Taiwan. (S.-P.C.)
| | - Michael Hsiao
- The Genomics Research Center, Academia Sinica, Taipei, Taiwan (M.H.)
| | - Yu-Feng Hu
- Division of Cardiology, Department of Medicine, Heart Rhythm Center, Taipei Veterans General Hospital, Taiwan. (P.-C.C., C.-M.L., C.-H.W., J.-D.L., Y.-F.H.).,Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan (P.-C.C., C.-H.W., K.-C.Y., Y.-C.L., R.-B.Y., B.-C.S., S.-K.S., J.-D.L., Y.-F.H.).,Faculty of Medicine, School of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan (C.-M.L., Y.-F.H.)
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Ciullo A, Li C, Li L, Ungerleider KC, Peck K, Marbán E, Ibrahim AG. Biodistribution of unmodified cardiosphere-derived cell extracellular vesicles using single RNA tracing. J Extracell Vesicles 2022; 11:e12178. [PMID: 35005847 PMCID: PMC8743874 DOI: 10.1002/jev2.12178] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Revised: 12/01/2021] [Accepted: 12/07/2021] [Indexed: 12/25/2022] Open
Abstract
Extracellular vesicles (EVs) are potent signalling mediators. Although interest in EV translation is ever-increasing, development efforts are hampered by the inability to reliably assess the uptake of EVs and their RNA cargo. Here, we establish a novel qPCR-based method for the detection of unmodified EVS using an RNA Tracer (DUST). In this proof-of-concept study we use a human-specific Y RNA-derived small RNA (YsRNA) we dub "NT4" that is enriched in cardiosphere-derived cell small EVs (CDC-sEVs). The assay is robust, sensitive, and reproducible. Intravenously administered CDC-sEVs accumulated primarily in the heart on a per mg basis. Cardiac injury enhanced EV uptake in the heart, liver, and brain. Inhibition of EV docking by heparin suppressed uptake variably, while inhibition of endocytosis attenuated uptake in all organs. In vitro, EVs were uptaken more efficiently by macrophages, endothelial cells, and cardiac fibroblasts compared to cardiomyocytes. These findings demonstrate the utility of DUST to assess uptake of EVs in vivo and in vitro.
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Affiliation(s)
- Alessandra Ciullo
- Smidt Heart InstituteCedars‐Sinai Medical CenterLos AngelesCaliforniaUSA
| | - Chang Li
- Smidt Heart InstituteCedars‐Sinai Medical CenterLos AngelesCaliforniaUSA
| | - Liang Li
- Smidt Heart InstituteCedars‐Sinai Medical CenterLos AngelesCaliforniaUSA
| | | | - Kiel Peck
- Smidt Heart InstituteCedars‐Sinai Medical CenterLos AngelesCaliforniaUSA
| | - Eduardo Marbán
- Smidt Heart InstituteCedars‐Sinai Medical CenterLos AngelesCaliforniaUSA
| | - Ahmed G.E. Ibrahim
- Smidt Heart InstituteCedars‐Sinai Medical CenterLos AngelesCaliforniaUSA
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8
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Naumova N, Iop L. Bioengineering the Cardiac Conduction System: Advances in Cellular, Gene, and Tissue Engineering for Heart Rhythm Regeneration. Front Bioeng Biotechnol 2021; 9:673477. [PMID: 34409019 PMCID: PMC8365186 DOI: 10.3389/fbioe.2021.673477] [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: 02/27/2021] [Accepted: 06/24/2021] [Indexed: 01/01/2023] Open
Abstract
Heart rhythm disturbances caused by different etiologies may affect pediatric and adult patients with life-threatening consequences. When pharmacological therapy is ineffective in treating the disturbances, the implantation of electronic devices to control and/or restore normal heart pacing is a unique clinical management option. Although these artificial devices are life-saving, they display many limitations; not least, they do not have any capability to adapt to somatic growth or respond to neuroautonomic physiological changes. A biological pacemaker could offer a new clinical solution for restoring heart rhythms in the conditions of disorder in the cardiac conduction system. Several experimental approaches, such as cell-based, gene-based approaches, and the combination of both, for the generation of biological pacemakers are currently established and widely studied. Pacemaker bioengineering is also emerging as a technology to regenerate nodal tissues. This review analyzes and summarizes the strategies applied so far for the development of biological pacemakers, and discusses current translational challenges toward the first-in-human clinical application.
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Affiliation(s)
| | - Laura Iop
- Department of Cardiac Thoracic Vascular Sciences and Public Health, University of Padua, Padua, Italy
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9
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Grijalva SI, Gu J, Li J, Fernandez N, Fan J, Sung JH, Lee SY, Herndon C, Buckley EM, Park S, Fenton FH, Cho HC. Engineered Cardiac Pacemaker Nodes Created by TBX18 Gene Transfer Overcome Source-Sink Mismatch. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2019; 6:1901099. [PMID: 31763140 PMCID: PMC6864514 DOI: 10.1002/advs.201901099] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Revised: 08/23/2019] [Indexed: 06/10/2023]
Abstract
Every heartbeat originates from a tiny tissue in the heart called the sinoatrial node (SAN). The SAN harbors only ≈10 000 cardiac pacemaker cells, initiating an electrical impulse that captures the entire heart, consisting of billions of cardiomyocytes for each cardiac contraction. How these rare cardiac pacemaker cells (the electrical source) can overcome the electrically hyperpolarizing and quiescent myocardium (the electrical sink) is incompletely understood. Due to the scarcity of native pacemaker cells, this concept of source-sink mismatch cannot be tested directly with live cardiac tissue constructs. By exploiting TBX18 induced pacemaker cells by somatic gene transfer, 3D cardiac pacemaker spheroids can be tissue-engineered. The TBX18 induced pacemakers (sphTBX18) pace autonomously and drive the contraction of neighboring myocardium in vitro. TBX18 spheroids demonstrate the need for reduced electrical coupling and physical separation from the neighboring ventricular myocytes, successfully recapitulating a key design principle of the native SAN. β-Adrenergic stimulation as well as electrical uncoupling significantly increase sphTBX18s' ability to pace-and-drive the neighboring myocardium. This model represents the first platform to test design principles of the SAN for mechanistic understanding and to better engineer biological pacemakers for therapeutic translation.
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Affiliation(s)
- Sandra I. Grijalva
- Department of Biomedical EngineeringGeorgia Institute of Technology and Emory UniversityAtlantaGA30332USA
| | - Jin‐mo Gu
- Department of PediatricsEmory UniversityAtlantaGA30322USA
| | - Jun Li
- Department of PediatricsEmory UniversityAtlantaGA30322USA
| | | | - Jinqi Fan
- Department of PediatricsEmory UniversityAtlantaGA30322USA
| | - Jung Hoon Sung
- Department of PediatricsEmory UniversityAtlantaGA30322USA
- Department of Internal MedicineCHA Bundang Medical CenterSeoul13557South Korea
| | - Seung Yup Lee
- Department of Biomedical EngineeringGeorgia Institute of Technology and Emory UniversityAtlantaGA30332USA
| | - Conner Herndon
- Department of PhysicsGeorgia Institute of TechnologyAtlantaGA30332USA
| | - Erin M. Buckley
- Department of Biomedical EngineeringGeorgia Institute of Technology and Emory UniversityAtlantaGA30332USA
| | - Sung‐Jin Park
- Department of Biomedical EngineeringGeorgia Institute of Technology and Emory UniversityAtlantaGA30332USA
| | - Flavio H. Fenton
- Department of PhysicsGeorgia Institute of TechnologyAtlantaGA30332USA
| | - Hee Cheol Cho
- Department of Biomedical EngineeringGeorgia Institute of Technology and Emory UniversityAtlantaGA30332USA
- Department of PediatricsEmory UniversityAtlantaGA30322USA
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10
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Park JS, Grijalva SI, Aziz MK, Chi T, Li S, Sayegh MN, Wang A, Cho HC, Wang H. Multi-parametric cell profiling with a CMOS quad-modality cellular interfacing array for label-free fully automated drug screening. LAB ON A CHIP 2018; 18:3037-3050. [PMID: 30168827 PMCID: PMC8513687 DOI: 10.1039/c8lc00156a] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Cells are complex systems with concurrent multi-physical responses, and cell physiological signals are often encoded with spatiotemporal dynamics and further coupled with multiple cellular activities. However, most existing electronic sensors are only single-modality and cannot capture multi-parametric cellular responses. In this paper, a 1024-pixel CMOS quad-modality cellular interfacing array that enables multi-parametric cell profiling for drug development is presented. The quad-modality CMOS array features cellular impedance characterization, optical detection, extracellular potential recording, and biphasic current stimulation. The fibroblast transparency and surface adhesion are jointly monitored by cellular impedance and optical sensing modalities for comprehensive cell growth evaluation. Simultaneous current stimulation and opto-mechanical monitoring based on cardiomyocytes are demonstrated without any stimulation/sensing dead-zone. Furthermore, drug dose-dependent multi-parametric feature extractions in cardiomyocytes from their extracellular potentials and opto-mechanical signals are presented. The CMOS array demonstrates great potential for fully automated drug screening and drug safety assessments, which may substantially reduce the drug screening time and cost in future new drug development.
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Affiliation(s)
- Jong Seok Park
- The School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30308, USA.
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11
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Bébarová M, Horáková Z, Kula R. Addictive drugs, arrhythmias, and cardiac inward rectifiers. Europace 2017; 19:346-355. [PMID: 27302393 DOI: 10.1093/europace/euw071] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Accepted: 02/20/2016] [Indexed: 12/30/2022] Open
Abstract
In many addictive drugs including alcohol and nicotine, proarrhythmic effects were reported. This review provides an overview of the current knowledge in this field (with a focus on the inward rectifier potassium currents) to promote the lacking data and appeal for their completion, thus, to improve understanding of the proarrhythmic potential of addictive drugs.
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12
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Cambier L, de Couto G, Ibrahim A, Echavez AK, Valle J, Liu W, Kreke M, Smith RR, Marbán L, Marbán E. Y RNA fragment in extracellular vesicles confers cardioprotection via modulation of IL-10 expression and secretion. EMBO Mol Med 2017; 9:337-352. [PMID: 28167565 PMCID: PMC5331234 DOI: 10.15252/emmm.201606924] [Citation(s) in RCA: 169] [Impact Index Per Article: 24.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Cardiosphere‐derived cells (CDCs) reduce myocardial infarct size via secreted extracellular vesicles (CDC‐EVs), including exosomes, which alter macrophage polarization. We questioned whether short non‐coding RNA species of unknown function within CDC‐EVs contribute to cardioprotection. The most abundant RNA species in CDC‐EVs is a Y RNA fragment (EV‐YF1); its relative abundance in CDC‐EVs correlates with CDC potency in vivo. Fluorescently labeled EV‐YF1 is actively transferred from CDCs to target macrophages via CDC‐EVs. Direct transfection of macrophages with EV‐YF1 induced transcription and secretion of IL‐10. When cocultured with rat cardiomyocytes, EV‐YF1‐primed macrophages were potently cytoprotective toward oxidatively stressed cardiomyocytes through induction of IL‐10. In vivo, intracoronary injection of EV‐YF1 following ischemia/reperfusion reduced infarct size. A fragment of Y RNA, highly enriched in CDC‐EVs, alters Il10 gene expression and enhances IL‐10 protein secretion. The demonstration that EV‐YF1 confers cardioprotection highlights the potential importance of diverse exosomal contents of unknown function, above and beyond the usual suspects (e.g., microRNAs and proteins).
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Affiliation(s)
- Linda Cambier
- Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Geoffrey de Couto
- Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | | | - Antonio K Echavez
- Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Jackelyn Valle
- Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | - Weixin Liu
- Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
| | | | | | | | - Eduardo Marbán
- Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA, USA
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13
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Koepple C, Scherer D, Seyler C, Scholz E, Thomas D, Katus HA, Zitron E. Dual Mechanism for Inhibition of Inwardly Rectifying Kir2.x Channels by Quinidine Involving Direct Pore Block and PIP 2-interference. J Pharmacol Exp Ther 2017; 361:209-218. [PMID: 28188270 DOI: 10.1124/jpet.116.238287] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Accepted: 02/08/2017] [Indexed: 11/22/2022] Open
Abstract
Class IA antiarrhythmic drug quinidine was one of the first clinically used compounds to terminate atrial fibrillation and acts as multichannel inhibitor with well-documented inhibitory effects on several cardiac potassium channels. In the mammalian heart, heteromeric assembly of Kir2.1-2.3 channels underlies IK1 current. Although a low-affinity block of quinidine on Kir2.1 has already been described, a comparative analysis of effects on other Kir2.x channels has not been performed to date. Therefore, we analyzed the effects of quinidine on wild-type and mutant Kir2.x channels in the Xenopus oocyte expression system. Quinidine exerted differential inhibitory effects on Kir2.x channels with the highest affinity toward Kir2.3 subunits. Onset of block was slow and solely reversible in Kir2.2 subunits. Quinidine inhibited Kir2.x currents in a voltage-independent manner. By means of comparative Ala-scanning mutagenesis, we further found that residues E224, F254, D259, and E299 are essential for quinidine block in Kir2.1 subunits. Analogously, quinidine mediated Kir2.3 inhibition by binding corresponding residues E216, D247, D251, and E291. In contrast, Kir2.2 current block merely involved corresponding residue D260. Using channel mutants with altered (phosphatidylinositol 4,5-bisphosphate PIP2) affinities, we were able to demonstrate that high PIP2 affinities (i.e., Kir2.3 I214L) correlate with low quinidine sensitivity. Inversely, mutant channels interacting only weakly with PIP2 (i.e., Kir2.1 K182Q, and L221I) are prone to a higher inhibitory effect. Thus, we conclude that inhibition of Kir2.x channels by quinidine is mediated by joint modes of action involving direct cytoplasmic pore block and an impaired channel stabilization via interference with PIP2.
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Affiliation(s)
- Christoph Koepple
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany (C.K., D.S., C.S., E.S., D.T., H.A.K., E.Z.); DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany (C.S., E.S., D.T., H.A.K., E.Z.); and Department for Hand-, Plastic- and Reconstructive Surgery, BG Unfallklinik Ludwigshafen, University of Heidelberg, Heidelberg, Germany (C.K.)
| | - Daniel Scherer
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany (C.K., D.S., C.S., E.S., D.T., H.A.K., E.Z.); DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany (C.S., E.S., D.T., H.A.K., E.Z.); and Department for Hand-, Plastic- and Reconstructive Surgery, BG Unfallklinik Ludwigshafen, University of Heidelberg, Heidelberg, Germany (C.K.)
| | - Claudia Seyler
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany (C.K., D.S., C.S., E.S., D.T., H.A.K., E.Z.); DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany (C.S., E.S., D.T., H.A.K., E.Z.); and Department for Hand-, Plastic- and Reconstructive Surgery, BG Unfallklinik Ludwigshafen, University of Heidelberg, Heidelberg, Germany (C.K.)
| | - Eberhard Scholz
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany (C.K., D.S., C.S., E.S., D.T., H.A.K., E.Z.); DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany (C.S., E.S., D.T., H.A.K., E.Z.); and Department for Hand-, Plastic- and Reconstructive Surgery, BG Unfallklinik Ludwigshafen, University of Heidelberg, Heidelberg, Germany (C.K.)
| | - Dierk Thomas
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany (C.K., D.S., C.S., E.S., D.T., H.A.K., E.Z.); DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany (C.S., E.S., D.T., H.A.K., E.Z.); and Department for Hand-, Plastic- and Reconstructive Surgery, BG Unfallklinik Ludwigshafen, University of Heidelberg, Heidelberg, Germany (C.K.)
| | - Hugo A Katus
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany (C.K., D.S., C.S., E.S., D.T., H.A.K., E.Z.); DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany (C.S., E.S., D.T., H.A.K., E.Z.); and Department for Hand-, Plastic- and Reconstructive Surgery, BG Unfallklinik Ludwigshafen, University of Heidelberg, Heidelberg, Germany (C.K.)
| | - Edgar Zitron
- Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany (C.K., D.S., C.S., E.S., D.T., H.A.K., E.Z.); DZHK (German Centre for Cardiovascular Research), partner site Heidelberg/Mannheim, University of Heidelberg, Heidelberg, Germany (C.S., E.S., D.T., H.A.K., E.Z.); and Department for Hand-, Plastic- and Reconstructive Surgery, BG Unfallklinik Ludwigshafen, University of Heidelberg, Heidelberg, Germany (C.K.)
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14
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Berenfeld O. The Major Role of IK1 in Mechanisms of Rotor Drift in the Atria: A Computational Study. CLINICAL MEDICINE INSIGHTS-CARDIOLOGY 2016; 10:71-79. [PMID: 28096699 PMCID: PMC5175588 DOI: 10.4137/cmc.s39773] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 11/17/2016] [Accepted: 11/20/2016] [Indexed: 12/19/2022]
Abstract
Maintenance of paroxysmal atrial fibrillation (AF) by fast rotors in the left atrium (LA) or at the pulmonary veins (PVs) is not fully understood. This review describes the role of the heterogeneous distribution of transmembrane currents in the PVs and LA junction (PV-LAJ) in the localization of rotors in the PVs. Experimentally observed heterogeneities in IK1, IKs, IKr, Ito, and ICaL in the PV-LAJ were incorporated into models of human atrial kinetics to simulate various conditions and investigate rotor drifting mechanisms. Spatial gradients in the currents resulted in shorter action potential duration, less negative minimum diastolic potential, slower upstroke and conduction velocity for rotors in the PV region than in the LA. Rotors under such conditions drifted toward the PV and stabilized at the less excitable region. Our simulations suggest that IK1 heterogeneity is dominant in determining the drift direction through its impact on the excitability gradient. These results provide a novel framework for understanding the complex dynamics of rotors in AF.
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Affiliation(s)
- Omer Berenfeld
- Center for Arrhythmia Research, Internal Medicine and Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
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15
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Varghese A. Reciprocal Modulation of I K1-I Na Extends Excitability in Cardiac Ventricular Cells. Front Physiol 2016; 7:542. [PMID: 27895596 PMCID: PMC5108932 DOI: 10.3389/fphys.2016.00542] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Accepted: 10/28/2016] [Indexed: 12/26/2022] Open
Abstract
The inwardly rectifying potassium current (IK1) and the fast inward sodium current (INa) are reciprocally modulated in mammalian ventricular myocytes. An increase in the expression of channels responsible for one of these two currents results in a corresponding increase in expression of the other. These currents are critical in the propagation of action potentials (AP) during the normal functioning of the heart. This study identifies a physiological role for IK1–INa reciprocal modulation in ventricular fiber activation thresholds and conduction. Simulations of action potentials in single cells and propagating APs in cardiac fibers were carried out using an existing model of electrical activity in cardiac ventricular myocytes. The conductances, GK1, of the inwardly rectifying potassium current, and GNa, of the fast inward sodium current were modified independently and in tandem to simulate reciprocal modulation. In single cells, independent modulation of GK1 alone resulted in changes in activation thresholds that were qualitatively similar to those for reciprocal GK1–GNa modulation and unlike those due to independent modulation of GNa alone, indicating that GK1 determines the cellular activation threshold. On the other hand, the variations in conduction velocity in cardiac cell fibers were similar for independent GNa modulation and for tandem changes in GK1–GNa, suggesting that GNa is primarily responsible for setting tissue AP conduction velocity. Conduction velocity dependence on GK1–GNa is significantly affected by the intercellular gap junction conductance. While the effects on the passive fiber space constant due to changes in both GK1 and the intercellular gap junction conductance, Ggj, were in line with linear cable theory predictions, both conductances had surprisingly large effects on fiber activation thresholds. Independent modulation of GK1 rendered cardiac fibers inexcitable at higher levels of GK1 whereas tandem GK1–GNa changes allowed fibers to remain excitable at high GK1 values. Reciprocal modulation of the inwardly rectifying potassium current and the fast inward sodium current may have a functional role in allowing cardiac tissue to remain excitable when IK1 is upregulated.
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Affiliation(s)
- Anthony Varghese
- Department of Computer Science, University of Wisconsin-River Falls River Falls, WI, USA
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16
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Kushiyama Y, Honjo H, Niwa R, Takanari H, Yamazaki M, Takemoto Y, Sakuma I, Kodama I, Kamiya K. Partial IK1 blockade destabilizes spiral wave rotation center without inducing wave breakup and facilitates termination of reentrant arrhythmias in ventricles. Am J Physiol Heart Circ Physiol 2016; 311:H750-8. [PMID: 27422985 DOI: 10.1152/ajpheart.00228.2016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 07/13/2016] [Indexed: 11/22/2022]
Abstract
It has been reported that blockade of the inward rectifier K(+) current (IK1) facilitates termination of ventricular fibrillation. We hypothesized that partial IK1 blockade destabilizes spiral wave (SW) re-entry, leading to its termination. Optical action potential (AP) signals were recorded from left ventricles of Langendorff-perfused rabbit hearts with endocardial cryoablation. The dynamics of SW re-entry were analyzed during ventricular tachycardia (VT), induced by cross-field stimulation. Intercellular electrical coupling in the myocardial tissue was evaluated by the space constant. In separate experiments, AP recordings were made using the microelectrode technique from right ventricular papillary muscles of rabbit hearts. Ba(2+) (10-50 μM) caused a dose-dependent prolongation of VT cycle length and facilitated termination of VT in perfused hearts. Baseline VT was maintained by a stable rotor, where an SW rotated around an I-shaped functional block line (FBL). Ba(2+) at 10 μM prolonged I-shaped FBL and phase-singularity trajectory, whereas Ba(2+) at 50 μM transformed the SW rotation dynamics from a stable linear pattern to unstable circular/cycloidal meandering. The SW destabilization was not accompanied by SW breakup. Under constant pacing, Ba(2+) caused a dose-dependent prolongation of APs, and Ba(2+) at 50 μM decreased conduction velocity. In papillary muscles, Ba(2+) at 50 μM depolarized the resting membrane potential. The space constant was increased by 50 μM Ba(2+) Partial IK1 blockade destabilizes SW rotation dynamics through a combination of prolongation of the wave length, reduction of excitability, and enhancement of electrotonic interactions, which facilitates termination of ventricular tachyarrhythmias.
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Affiliation(s)
- Yasunori Kushiyama
- Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan; and
| | - Haruo Honjo
- Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan; and
| | - Ryoko Niwa
- Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan; and
| | - Hiroki Takanari
- Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan; and
| | - Masatoshi Yamazaki
- Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan; and
| | - Yoshio Takemoto
- Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan; and
| | - Ichiro Sakuma
- Graduate School of Engineering, The University of Tokyo, Tokyo, Japan
| | - Itsuo Kodama
- Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan; and
| | - Kaichiro Kamiya
- Department of Cardiovascular Research, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan; and
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17
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BÉBAROVÁ M, MATEJOVIČ P, ŠIMURDOVÁ M, ŠIMURDA J. Acetaldehyde at Clinically Relevant Concentrations Inhibits Inward Rectifier Potassium Current IK1 in Rat Ventricular Myocytes. Physiol Res 2015; 64:939-43. [DOI: 10.33549/physiolres.932985] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Considering the effects of alcohol on cardiac electrical behavior as well as the important role of the inward rectifier potassium current IK1 in arrhythmogenesis, this study was aimed at the effect of acetaldehyde, the primary metabolite of ethanol, on IK1 in rat ventricular myocytes. Acetaldehyde induced a reversible inhibition of IK1 with IC50 = 53.7±7.7 µM at –110 mV; a significant inhibition was documented even at clinically-relevant concentrations (at 3 µM by 13.1±3.0 %). The inhibition was voltage-independent at physiological voltages above –90 mV. The IK1 changes under acetaldehyde may contribute to alcohol-induced alterations of cardiac electrophysiology, especially in individuals with a genetic defect of aldehyde dehydrogenase where the acetaldehyde level may be elevated.
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Affiliation(s)
- M. BÉBAROVÁ
- Department of Physiology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
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18
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de Couto G, Liu W, Tseliou E, Sun B, Makkar N, Kanazawa H, Arditi M, Marbán E. Macrophages mediate cardioprotective cellular postconditioning in acute myocardial infarction. J Clin Invest 2015. [PMID: 26214527 DOI: 10.1172/jci81321] [Citation(s) in RCA: 177] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Ischemic injury in the heart induces an inflammatory cascade that both repairs damage and exacerbates scar tissue formation. Cardiosphere-derived cells (CDCs) are a stem-like population that is derived ex vivo from cardiac biopsies; they confer both cardioprotection and regeneration in acute myocardial infarction (MI). While the regenerative effects of CDCs in chronic settings have been studied extensively, little is known about how CDCs confer the cardioprotective process known as cellular postconditioning. Here, we used an in vivo rat model of ischemia/reperfusion (IR) injury-induced MI and in vitro coculture assays to investigate how CDCs protect stressed cardiomyocytes. Compared with control animals, animals that received CDCs 20 minutes after IR had reduced infarct size when measured at 48 hours. CDCs modified the myocardial leukocyte population after ischemic injury. Specifically, introduction of CDCs reduced the number of CD68+ macrophages, and these CDCs secreted factors that polarized macrophages toward a distinctive cardioprotective phenotype that was not M1 or M2. Systemic depletion of macrophages with clodronate abolished CDC-mediated cardioprotection. Using both in vitro coculture assays and a rat model of adoptive transfer after IR, we determined that CDC-conditioned macrophages attenuated cardiomyocyte apoptosis and reduced infarct size, thereby recapitulating the beneficial effects of CDC therapy. Together, our data indicate that CDCs limit acute injury by polarizing an effector macrophage population within the heart.
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19
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Cingolani E, Ionta V, Cheng K, Giacomello A, Cho HC, Marbán E. Engineered electrical conduction tract restores conduction in complete heart block: from in vitro to in vivo proof of concept. J Am Coll Cardiol 2015; 64:2575-2585. [PMID: 25524335 DOI: 10.1016/j.jacc.2014.09.056] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Revised: 08/27/2014] [Accepted: 09/16/2014] [Indexed: 12/31/2022]
Abstract
BACKGROUND Cardiac electrical conduction delays and blocks cause rhythm disturbances such as complete heart block, which can be fatal. Standard of care relies on electronic devices to artificially restore synchrony. We sought to create a new modality for treating these disorders by engineering electrical conduction tracts designed to propagate electrical impulses. OBJECTIVES This study sought to create a new approach for treating cardiac conduction disorders by using engineered electrical conduction tracts (EECTs). METHODS Paramagnetic beads were conjugated with an antibody to gamma-sarcoglycan, a cardiomyocyte cell surface antigen, and mixed with freshly isolated neonatal rat ventricular cardiomyocytes. A magnetic field was used to pattern a linear EECT. RESULTS In an in vitro model of conduction block, the EECT was patterned so that it connected 2 independently beating neonatal rat ventricular cardiomyocyte monolayers; it achieved coordinated electrical activity, with action potentials propagating from 1 region to the other via EECT. Spiking the EECT with heart-derived stromal cells yielded stable structures with highly reproducible conduction velocities. Transplantation of EECTs in vivo restored atrioventricular conduction in a rat model of complete heart block. CONCLUSIONS An EECT can re-establish electrical conduction in the heart. This novel approach could, in principle, be used not only to treat cardiac arrhythmias but also to repair other organs.
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Affiliation(s)
| | - Vittoria Ionta
- Cedars-Sinai Heart Institute, Los Angeles, California; University of Rome "La Sapienza," Rome, Italy
| | - Ke Cheng
- Cedars-Sinai Heart Institute, Los Angeles, California
| | | | - Hee Cheol Cho
- Cedars-Sinai Heart Institute, Los Angeles, California.
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20
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Calvo CJ, Deo M, Zlochiver S, Millet J, Berenfeld O. Attraction of rotors to the pulmonary veins in paroxysmal atrial fibrillation: a modeling study. Biophys J 2014; 106:1811-21. [PMID: 24739180 DOI: 10.1016/j.bpj.2014.02.030] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 02/10/2014] [Accepted: 02/25/2014] [Indexed: 12/19/2022] Open
Abstract
Maintenance of paroxysmal atrial fibrillation (AF) by fast rotors in the left atrium (LA) or at the pulmonary veins (PVs) is not fully understood. To gain insight into this dynamic and complex process, we studied the role of the heterogeneous distribution of transmembrane currents in the PVs and LA junction (PV-LAJ) in the localization of rotors in the PVs. We also investigated whether simple pacing protocols could be used to predict rotor drift in the PV-LAJ. Experimentally observed heterogeneities in IK1, IKs, IKr, Ito, and ICaL in the PV-LAJ were incorporated into two- and pseudo three-dimensional models of Courtemanche-Ramirez-Nattel-Kneller human atrial kinetics to simulate various conditions and investigate rotor drifting mechanisms. Spatial gradients in the currents resulted in shorter action potential duration, minimum diastolic potential that was less negative, and slower upstroke and conduction velocity for rotors in the PV region than in the LA. Rotors under such conditions drifted toward the PV and stabilized at the shortest action potential duration and less-excitable region, consistent with drift direction under intercellular coupling heterogeneities and regardless of the geometrical constraint in the PVs. Simulations with various IK1 gradient conditions and current-voltage relationships substantiated its major role in the rotor drift. In our 1:1 pacing protocol, we found that among various action potential properties, only the minimum diastolic potential gradient was a rate-independent predictor of rotor drift direction. Consistent with experimental and clinical AF studies, simulations in an electrophysiologically heterogeneous model of the PV-LAJ showed rotor attraction toward the PV. Our simulations suggest that IK1 heterogeneity is dominant compared to other currents in determining the drift direction through its impact on the excitability gradient. These results provide a believed novel framework for understanding the complex dynamics of rotors in AF.
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Affiliation(s)
- Conrado J Calvo
- Center for Arrhythmia Research, Department of Internal Medicine, and Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan; BioITACA Grupo de Bioingeniería, Instituto de Aplicaciones Avanzadas, Valencia, Spain; Departamento Ingeniería Electrónica, Universitat Politècnica de Valencia, Valencia, Spain
| | - Makarand Deo
- Center for Arrhythmia Research, Department of Internal Medicine, and Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan; Department of Engineering, Norfolk State University, Norfolk, Virginia
| | - Sharon Zlochiver
- Center for Arrhythmia Research, Department of Internal Medicine, and Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan; Department of Biomedical Engineering, Tel Aviv University, Ramat Aviv, Israel
| | - José Millet
- BioITACA Grupo de Bioingeniería, Instituto de Aplicaciones Avanzadas, Valencia, Spain; Departamento Ingeniería Electrónica, Universitat Politècnica de Valencia, Valencia, Spain
| | - Omer Berenfeld
- Center for Arrhythmia Research, Department of Internal Medicine, and Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan; Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan.
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21
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Ibrahim AGE, Cheng K, Marbán E. Exosomes as critical agents of cardiac regeneration triggered by cell therapy. Stem Cell Reports 2014; 2:606-19. [PMID: 24936449 PMCID: PMC4050492 DOI: 10.1016/j.stemcr.2014.04.006] [Citation(s) in RCA: 628] [Impact Index Per Article: 62.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2014] [Revised: 04/08/2014] [Accepted: 04/09/2014] [Indexed: 12/17/2022] Open
Abstract
The CADUCEUS trial of cardiosphere-derived cells (CDCs) has shown that it may be possible to regenerate injured heart muscle previously thought to be permanently scarred. The mechanisms of benefit are known to be indirect, but the mediators have yet to be identified. Here we pinpoint exosomes secreted by human CDCs as critical agents of regeneration and cardioprotection. CDC exosomes inhibit apoptosis and promote proliferation of cardiomyocytes, while enhancing angiogenesis. Injection of exosomes into injured mouse hearts recapitulates the regenerative and functional effects produced by CDC transplantation, whereas inhibition of exosome production by CDCs blocks those benefits. CDC exosomes contain a distinctive complement of microRNAs, with particular enrichment of miR-146a. Selective administration of a miR-146a mimic reproduces some (but not all) of the benefits of CDC exosomes. The findings identify exosomes as key mediators of CDC-induced regeneration, while highlighting the potential utility of exosomes as cell-free therapeutic candidates. Cardiosphere-derived cells (CDCs) regenerate the heart by unclear indirect mechanisms Exosomes from CDCs promote angiogenesis, cardiomyocyte survival and proliferation CDC exosomes are necessary and sufficient to explain the therapeutic effects of CDCs MicroRNAs transferred by CDC exosomes at least partially mediate the benefits of CDCs
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Affiliation(s)
| | - Ke Cheng
- Heart Institute, Cedars Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Eduardo Marbán
- Heart Institute, Cedars Sinai Medical Center, Los Angeles, CA 90048, USA
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Aiba T, Farinelli F, Kostecki G, Hesketh GG, Edwards D, Biswas S, Tung L, Tomaselli GF. A mutation causing Brugada syndrome identifies a mechanism for altered autonomic and oxidant regulation of cardiac sodium currents. ACTA ACUST UNITED AC 2014; 7:249-56. [PMID: 24795344 DOI: 10.1161/circgenetics.113.000480] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND The mechanisms of the electrocardiographic changes and arrhythmias in Brugada syndrome (BrS) remain controversial. Mutations in the sodium channel gene, SCN5A, and regulatory proteins that reduce or eliminate sodium current (INa) have been linked to BrS. We studied the properties of a BrS-associated SCN5A mutation in a protein kinase A (PKA) consensus phosphorylation site, R526H. METHODS AND RESULTS In vitro PKA phosphorylation was detected in the I-II linker peptide of wild-type (WT) channels but not R526H or S528A (phosphorylation site) mutants. Cell surface expression of R526H and S528A channels was reduced compared with WT. Whole-cell INa through all channel variants revealed no significant differences in the steady-state activation, inactivation, and recovery from inactivation. Peak current densities of the mutants were significantly reduced compared with WT. Infection of 2D cultures of neonatal rat ventricular myocytes with WT and mutant channels increased conduction velocity compared with noninfected cells. PKA stimulation significantly increased peak INa and conduction velocity of WT but not mutant channels. Oxidant stress inhibits cardiac INa; WT and mutant INa decreases with the intracellular application of reduced nicotinamide adenine dinucleotide (NADH), an effect that is reversed by PKA stimulation in WT but not in R526H or S528A channels. CONCLUSIONS We identified a family with BrS and an SCN5A mutation in a PKA consensus phosphorylation site. The BrS mutation R526H is associated with a reduction in the basal level of INa and a failure of PKA stimulation to augment the current that may contribute to the predisposition to arrhythmias in patients with BrS, independent of the precipitants.
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Affiliation(s)
- Takeshi Aiba
- From the Division of Cardiology, Department of Internal Medicine, Johns Hopkins University School of Medicine, Baltimore, MD (T.A., F.F., D.E., S.B., G.F.T.); and Department of Biomedical Engineering (G.K., L.T.) and Department of Biological Chemistry (G.G.H.), Johns Hopkins University, Baltimore, MD
| | - Federica Farinelli
- From the Division of Cardiology, Department of Internal Medicine, Johns Hopkins University School of Medicine, Baltimore, MD (T.A., F.F., D.E., S.B., G.F.T.); and Department of Biomedical Engineering (G.K., L.T.) and Department of Biological Chemistry (G.G.H.), Johns Hopkins University, Baltimore, MD
| | - Geran Kostecki
- From the Division of Cardiology, Department of Internal Medicine, Johns Hopkins University School of Medicine, Baltimore, MD (T.A., F.F., D.E., S.B., G.F.T.); and Department of Biomedical Engineering (G.K., L.T.) and Department of Biological Chemistry (G.G.H.), Johns Hopkins University, Baltimore, MD
| | - Geoffrey G Hesketh
- From the Division of Cardiology, Department of Internal Medicine, Johns Hopkins University School of Medicine, Baltimore, MD (T.A., F.F., D.E., S.B., G.F.T.); and Department of Biomedical Engineering (G.K., L.T.) and Department of Biological Chemistry (G.G.H.), Johns Hopkins University, Baltimore, MD
| | - David Edwards
- From the Division of Cardiology, Department of Internal Medicine, Johns Hopkins University School of Medicine, Baltimore, MD (T.A., F.F., D.E., S.B., G.F.T.); and Department of Biomedical Engineering (G.K., L.T.) and Department of Biological Chemistry (G.G.H.), Johns Hopkins University, Baltimore, MD
| | - Subrata Biswas
- From the Division of Cardiology, Department of Internal Medicine, Johns Hopkins University School of Medicine, Baltimore, MD (T.A., F.F., D.E., S.B., G.F.T.); and Department of Biomedical Engineering (G.K., L.T.) and Department of Biological Chemistry (G.G.H.), Johns Hopkins University, Baltimore, MD
| | - Leslie Tung
- From the Division of Cardiology, Department of Internal Medicine, Johns Hopkins University School of Medicine, Baltimore, MD (T.A., F.F., D.E., S.B., G.F.T.); and Department of Biomedical Engineering (G.K., L.T.) and Department of Biological Chemistry (G.G.H.), Johns Hopkins University, Baltimore, MD
| | - Gordon F Tomaselli
- From the Division of Cardiology, Department of Internal Medicine, Johns Hopkins University School of Medicine, Baltimore, MD (T.A., F.F., D.E., S.B., G.F.T.); and Department of Biomedical Engineering (G.K., L.T.) and Department of Biological Chemistry (G.G.H.), Johns Hopkins University, Baltimore, MD.
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Mustroph J, Maier LS, Wagner S. CaMKII regulation of cardiac K channels. Front Pharmacol 2014; 5:20. [PMID: 24600393 PMCID: PMC3930912 DOI: 10.3389/fphar.2014.00020] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Accepted: 01/31/2014] [Indexed: 11/23/2022] Open
Abstract
Cardiac K channels are critical determinants of cardiac excitability. In hypertrophied and failing myocardium, alterations in the expression and activity of voltage-gated K channels are frequently observed and contribute to the increased propensity for life-threatening arrhythmias. Thus, understanding the mechanisms of disturbed K channel regulation in heart failure (HF) is of critical importance. Amongst others, Ca/calmodulin-dependent protein kinase II (CaMKII) has been identified as an important regulator of K channel activity. In human HF but also various animal models, increased CaMKII expression and activity has been linked to deteriorated contractile function and arrhythmias. This review will discuss the current knowledge about CaMKII regulation of several K channels, its influence on action potential properties, dispersion of repolarization, and arrhythmias with special focus on HF.
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Affiliation(s)
- Julian Mustroph
- Department of Cardiology, University Medical Center Göttingen Göttingen, Germany
| | - Lars S Maier
- Department of Cardiology, University Medical Center Göttingen Göttingen, Germany
| | - Stefan Wagner
- Department of Cardiology, University Medical Center Göttingen Göttingen, Germany
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24
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Sivagangabalan G, Nazzari H, Bignolais O, Maguy A, Naud P, Farid T, Massé S, Gaborit N, Varro A, Nair K, Backx P, Vigmond E, Nattel S, Demolombe S, Nanthakumar K. Regional ion channel gene expression heterogeneity and ventricular fibrillation dynamics in human hearts. PLoS One 2014; 9:e82179. [PMID: 24427266 PMCID: PMC3888386 DOI: 10.1371/journal.pone.0082179] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Accepted: 10/22/2013] [Indexed: 01/25/2023] Open
Abstract
RATIONALE Structural differences between ventricular regions may not be the sole determinant of local ventricular fibrillation (VF) dynamics and molecular remodeling may play a role. OBJECTIVES To define regional ion channel expression in myopathic hearts compared to normal hearts, and correlate expression to regional VF dynamics. METHODS AND RESULTS High throughput real-time RT-PCR was used to quantify the expression patterns of 84 ion-channel, calcium cycling, connexin and related gene transcripts from sites in the LV, septum, and RV in 8 patients undergoing transplantation. An additional eight non-diseased donor human hearts served as controls. To relate local ion channel expression change to VF dynamics localized VF mapping was performed on the explanted myopathic hearts right adjacent to sampled regions. Compared to non-diseased ventricles, significant differences (p<0.05) were identified in the expression of 23 genes in the myopathic LV and 32 genes in the myopathic RV. Within the myopathic hearts significant regional (LV vs septum vs RV) expression differences were observed for 13 subunits: Nav1.1, Cx43, Ca3.1, Cavα2δ2, Cavβ2, HCN2, Na/K ATPase-1, CASQ1, CASQ2, RYR2, Kir2.3, Kir3.4, SUR2 (p<0.05). In a subset of genes we demonstrated differences in protein expression between control and myopathic hearts, which were concordant with the mRNA expression profiles for these genes. Variability in the expression of Cx43, hERG, Na(+)/K(+) ATPase ß1 and Kir2.1 correlated to variability in local VF dynamics (p<0.001). To better understand the contribution of multiple ion channel changes on VF frequency, simulations of a human myocyte model were conducted. These simulations demonstrated the complex nature by which VF dynamics are regulated when multi-channel changes are occurring simultaneously, compared to known linear relationships. CONCLUSIONS Ion channel expression profile in myopathic human hearts is significantly altered compared to normal hearts. Multi-channel ion changes influence VF dynamic in a complex manner not predicted by known single channel linear relationships.
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Affiliation(s)
| | | | - Olivier Bignolais
- INSERM, UMR915, l'institut du thorax, Nantes, France
- CNRS, ERL3147, Nantes, France
- Université de Nantes, Nantes, France
| | - Ange Maguy
- IHU LIRYC, Electrophysiology and Heart Modeling Institute, Pessac, France
- Lab IMB, University Bordeaux 1, Talence, France
| | - Patrice Naud
- IHU LIRYC, Electrophysiology and Heart Modeling Institute, Pessac, France
- Lab IMB, University Bordeaux 1, Talence, France
| | | | | | - Nathalie Gaborit
- INSERM, UMR915, l'institut du thorax, Nantes, France
- CNRS, ERL3147, Nantes, France
- Université de Nantes, Nantes, France
| | - Andras Varro
- University of Szeged and Division of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary
| | | | | | - Edward Vigmond
- IHU LIRYC, Electrophysiology and Heart Modeling Institute, Pessac, France
- Lab IMB, University Bordeaux 1, Talence, France
| | - Stanley Nattel
- Montreal Heart Institute (MHI) and Université de Montréal Faculty of Medicine, Montreal, Canada
| | - Sophie Demolombe
- INSERM, UMR915, l'institut du thorax, Nantes, France
- CNRS, ERL3147, Nantes, France
- Université de Nantes, Nantes, France
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Joshi-Mukherjee R, Dick IE, Liu T, O'Rourke B, Yue DT, Tung L. Structural and functional plasticity in long-term cultures of adult ventricular myocytes. J Mol Cell Cardiol 2013; 65:76-87. [PMID: 24076394 DOI: 10.1016/j.yjmcc.2013.09.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Revised: 08/20/2013] [Accepted: 09/16/2013] [Indexed: 11/25/2022]
Abstract
Cultured heart cells have long been valuable for characterizing biological mechanism and disease pathogenesis. However, these preparations have limitations, relating to immaturity in key properties like excitation-contraction coupling and β-adrenergic stimulation. Progressive attenuation of the latter is intimately related to pathogenesis and therapy in heart failure. Highly valuable would be a long-term culture system that emulates the structural and functional changes that accompany disease and development, while concurrently permitting ready access to underlying molecular events. Accordingly, we here produce functional monolayers of adult guinea-pig ventricular myocytes (aGPVMs) that can be maintained in long-term culture for several weeks. At baseline, these monolayers exhibit considerable myofibrillar organization and a significant contribution of sarcoplasmic reticular (SR) Ca(2+) release to global Ca(2+) transients. In terms of electrical signaling, these monolayers support propagated electrical activity and manifest monophasic restitution of action-potential duration and conduction velocity. Intriguingly, β-adrenergic stimulation increases chronotropy but not inotropy, indicating selective maintenance of β-adrenergic signaling. It is interesting that this overall phenotypic profile is not fixed, but can be readily enhanced by chronic electrical stimulation of cultures. This simple environmental cue significantly enhances myofibrillar organization as well as β-adrenergic sensitivity. In particular, the chronotropic response increases, and an inotropic effect now emerges, mimicking a reversal of the progression seen in heart failure. Thus, these aGPVM monolayer cultures offer a valuable platform for clarifying long elusive features of β-adrenergic signaling and its plasticity.
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Affiliation(s)
- Rosy Joshi-Mukherjee
- Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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Abstract
The objective of this article is to present a broad review of the role of cardiac electric rotors and their accompanying spiral waves in the mechanism of cardiac fibrillation. At the outset, we present a brief historical overview regarding reentry and then discuss the basic concepts and terminologies pertaining to rotors and their initiation. Thereafter, the intrinsic properties of rotors and spiral waves, including phase singularities, wavefront curvature, and dominant frequency maps, are discussed. The implications of rotor dynamics for the spatiotemporal organization of fibrillation, independent of the species being studied, are described next. The knowledge gained regarding the role of cardiac structure in the initiation or maintenance of rotors and the ionic bases of spiral waves in the past 2 decades, as well as the significance for drug therapy, is reviewed subsequently. We conclude by examining recent evidence suggesting that rotors are critical in sustaining both atrial and ventricular fibrillation in the human heart and its implications for treatment with radiofrequency ablation.
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Affiliation(s)
- Sandeep V Pandit
- Center for Arrhythmia Research, University of Michigan, NCRC, 2800 Plymouth Rd, Ann Arbor, MI 48109, USA
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27
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Quintanilla JG, Moreno J, Archondo T, Chin A, Pérez-Castellano N, Usandizaga E, García-Torrent MJ, Molina-Morúa R, González P, Rodríguez-Bobada C, Macaya C, Pérez-Villacastín J. KATP channel opening accelerates and stabilizes rotors in a swine heart model of ventricular fibrillation. Cardiovasc Res 2013; 99:576-85. [PMID: 23612586 DOI: 10.1093/cvr/cvt093] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
AIMS The mechanisms underlying ventricular fibrillation (VF) are still disputed. Recent studies have highlighted the role of KATP-channels. We hypothesized that, under certain conditions, VF can be driven by stable and epicardially detectable rotors in large hearts. To test our hypothesis, we used a swine model of accelerated VF by opening KATP-channels with cromakalim. METHODS AND RESULTS Optical mapping, spectral analysis, and phase singularity tracking were performed in eight perfused swine hearts during VF. Pseudo-bipolar electrograms were computed. KATP-channel opening almost doubled the maximum dominant frequency (14.3 ± 2.2 vs. 26.5 ± 2.8 Hz, P < 0.001) and increased the maximum regularity index (0.82 ± 0.05 vs. 0.94 ± 0.04, P < 0.001), the density of rotors (2.0 ± 1.4 vs. 16.0 ± 7.0 rotors/cm²×s, P < 0.001), and their maximum lifespans (medians: 368 vs. ≥3410 ms, P < 0.001). Persistent rotors (≥1 movie = 3410 ms) were found in all hearts after cromakalim (mostly coinciding with the fastest and highest organized areas), but they were not epicardially visible at baseline VF. A 'beat phenomenon' ruled by inter-domain frequency gradients was observed in all hearts after cromakalim. Acceleration of VF did not reveal any significant regional preponderance. Complex fractionated electrograms were not found in areas near persistent rotors. CONCLUSION Upon KATP-channel opening, VF consisted of rapid and highly organized domains mainly due to stationary rotors, surrounded by poorly organized areas. A 'beat phenomenon' due to the quasi-periodic onset of drifting rotors was observed. These findings demonstrate the feasibility of a VF driven by stable rotors in hearts whose size is similar to the human heart. Our model also showed that complex fractionation does not seem to localize stationary rotors.
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Affiliation(s)
- Jorge G Quintanilla
- Optical Mapping Laboratory, Arrhythmia Unit, Cardiovascular Institute, Instituto de Investigación Sanitaria del Hospital Clínico San Carlos (IdISSC), CP 28040, Madrid, Spain.
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28
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Chang MG, de Lange E, Calmettes G, Garfinkel A, Qu Z, Weiss JN. Pro- and antiarrhythmic effects of ATP-sensitive potassium current activation on reentry during early afterdepolarization-mediated arrhythmias. Heart Rhythm 2013; 10:575-82. [PMID: 23246594 PMCID: PMC4285341 DOI: 10.1016/j.hrthm.2012.12.017] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2012] [Indexed: 11/26/2022]
Abstract
BACKGROUND Under conditions promoting early afterdepolarizations (EADs), ventricular tissue can become bi-excitable, that is, capable of wave propagation mediated by either the Na current (INa) or the L-type calcium current (ICa,L), raising the possibility that ICa,L-mediated reentry may contribute to polymorphic ventricular tachycardia (PVT) and torsades de pointes. ATP-sensitive K current (IKATP) activation suppresses EADs, but the effects on ICa,L-mediated reentry are unknown. OBJECTIVE To investigate the effects of IKATP activation on ICa,L-mediated reentry. METHODS We performed optical voltage mapping in cultured neonatal rat ventricular myocyte monolayers exposed to BayK8644 and isoproterenol. The effects of pharmacologically activating IKATP with pinacidil were analyzed. RESULTS In 13 monolayers with anatomic ICa,L-mediated reentry around a central obstacle, pinacidil (50 μM) converted ICa,L-mediated reentry to INa-mediated reentry. In 33 monolayers with functional ICa,L-mediated reentry (spiral waves), pinacidil terminated reentry in 17, converted reentry into more complex INa-mediated reentry resembling fibrillation in 12, and had no effect in 4. In simulated 2-dimensional bi-excitable tissue in which ICa,L- and INa-mediated wave fronts coexisted, slow IKATP activation (over minutes) reliably terminated rotors but rapid IKATP activation (over seconds) often converted ICa,L-mediated reentry to INa-mediated reentry resembling fibrillation. CONCLUSIONS IKATP activation can have proarrhythmic effects on EAD-mediated arrhythmias if ICa,L-mediated reentry is present.
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Affiliation(s)
- Marvin G. Chang
- Department of Medicine (Cardiology), David Geffen School of Medicine at University of California, Los Angeles, California
| | - Enno de Lange
- Department of Medicine (Cardiology), David Geffen School of Medicine at University of California, Los Angeles, California
| | - Guillaume Calmettes
- Department of Medicine (Cardiology), David Geffen School of Medicine at University of California, Los Angeles, California
| | - Alan Garfinkel
- Department of Medicine (Cardiology), David Geffen School of Medicine at University of California, Los Angeles, California
- Department of Integrative Biology and Physiology, David Geffen School of Medicine at University of California, Los Angeles, California
| | - Zhilin Qu
- Department of Medicine (Cardiology), David Geffen School of Medicine at University of California, Los Angeles, California
| | - James N. Weiss
- Department of Medicine (Cardiology), David Geffen School of Medicine at University of California, Los Angeles, California
- Department of Physiology, David Geffen School of Medicine at University of California, Los Angeles, California
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Campbell K, Calvo CJ, Mironov S, Herron T, Berenfeld O, Jalife J. Spatial gradients in action potential duration created by regional magnetofection of hERG are a substrate for wavebreak and turbulent propagation in cardiomyocyte monolayers. J Physiol 2012; 590:6363-79. [PMID: 23090949 DOI: 10.1113/jphysiol.2012.238758] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Spatial dispersion of action potential duration (APD) is a substrate for the maintenance of cardiac fibrillation, but the mechanisms are poorly understood. We investigated the role played by spatial APD dispersion in fibrillatory dynamics. We used an in vitro model in which spatial gradients in the expression of ether-à-go-go-related (hERG) protein, and thus rapid delayed rectifying K(+) current (I(Kr)) density, served to generate APD dispersion, high-frequency rotor formation, wavebreak and fibrillatory conduction. A unique adenovirus-mediated magnetofection technique generated well-controlled gradients in hERG and green fluorescent protein (GFP) expression in neonatal rat ventricular myocyte monolayers. Computer simulations using a realistic neonatal rat ventricular myocyte monolayer model provided crucial insight into the underlying mechanisms. Regional hERG overexpression shortened APD and increased rotor incidence in the hERG overexpressing region. An APD profile at 75 percent repolarization with a 16.6 ± 0.72 ms gradient followed the spatial profile of hERG-GFP expression; conduction velocity was not altered. Rotors in the infected region whose maximal dominant frequency was 12.9 Hz resulted in wavebreak at the interface (border zone) between infected and non-infected regions; dominant frequency distribution was uniform when the maximal dominant frequency was <12.9 Hz or the rotors resided in the uninfected region. Regularity at the border zone was lowest when rotors resided in the infected region. In simulations, a fivefold regional increase in I(Kr) abbreviated the APD and hyperpolarized the resting potential. However, the steep APD gradient at the border zone proved to be the primary mechanism of wavebreak and fibrillatory conduction. This study provides insight at the molecular level into the mechanisms by which spatial APD dispersion contributes to wavebreak, rotor stabilization and fibrillatory conduction.
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Affiliation(s)
- Katherine Campbell
- Center for Arrhythmia Research, Department of InternalMedicine, University of Michigan, Ann Arbor, MI 48108, USA
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Bingen BO, Askar SFA, Schalij MJ, Kazbanov IV, Ypey DL, Panfilov AV, Pijnappels DA. Prolongation of minimal action potential duration in sustained fibrillation decreases complexity by transient destabilization. Cardiovasc Res 2012; 97:161-70. [PMID: 22977009 DOI: 10.1093/cvr/cvs288] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
AIMS Sustained ventricular fibrillation (VF) is maintained by multiple stable rotors. Destabilization of sustained VF could be beneficial by affecting VF complexity (defined by the number of rotors). However, underlying mechanisms affecting VF stability are poorly understood. Therefore, the aim of this study was to correlate changes in arrhythmia complexity with changes in specific electrophysiological parameters, allowing a search for novel factors and underlying mechanisms affecting stability of sustained VF. METHODS AND RESULTS Neonatal rat ventricular cardiomyocyte monolayers and Langendorff-perfused adult rat hearts were exposed to increasing dosages of the gap junctional uncoupler 2-aminoethoxydiphenyl borate (2-APB) to induce arrhythmias. Ion channel blockers/openers were added to study effects on VF stability. Electrophysiological parameters were assessed by optical mapping and patch-clamp techniques. Arrhythmia complexity in cardiomyocyte cultures increased with increasing dosages of 2-APB (n > 38), leading to sustained VF: 0.0 ± 0.1 phase singularities/cm(2) in controls vs. 0.0 ± 0.1, 1.0 ± 0.9, 3.3 ± 3.2, 11.0 ± 10.1, and 54.3 ± 21.7 in 5, 10, 15, 20, and 25 µmol/L 2-APB, respectively. Arrhythmia complexity inversely correlated with wavelength. Lengthening of wavelength during fibrillation could only be induced by agents (BaCl(2)/BayK8644) increasing the action potential duration (APD) at maximal activation frequencies (minimal APD); 123 ± 32%/117 ± 24% of control. Minimal APD prolongation led to transient VF destabilization, shown by critical wavefront collision leading to rotor termination, followed by significant decreases in VF complexity and activation frequency (52%/37%). These key findings were reproduced ex vivo in rat hearts (n = 6 per group). CONCLUSION These results show that stability of sustained fibrillation is regulated by minimal APD. Minimal APD prolongation leads to transient destabilization of fibrillation, ultimately decreasing VF complexity, thereby providing novel insights into anti-fibrillatory mechanisms.
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Affiliation(s)
- Brian O Bingen
- Laboratory of Experimental Cardiology, Department of Cardiology, Leiden University Medical Center, P.O. Box 9600, Leiden 2300 RC, The Netherlands
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Blazeski A, Zhu R, Hunter DW, Weinberg SH, Boheler KR, Zambidis ET, Tung L. Electrophysiological and contractile function of cardiomyocytes derived from human embryonic stem cells. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2012; 110:178-95. [PMID: 22958937 DOI: 10.1016/j.pbiomolbio.2012.07.012] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Accepted: 07/30/2012] [Indexed: 12/23/2022]
Abstract
Human embryonic stem cells have emerged as the prototypical source from which cardiomyocytes can be derived for use in drug discovery and cell therapy. However, such applications require that these cardiomyocytes (hESC-CMs) faithfully recapitulate the physiology of adult cells, especially in relation to their electrophysiological and contractile function. We review what is known about the electrophysiology of hESC-CMs in terms of beating rate, action potential characteristics, ionic currents, and cellular coupling as well as their contractility in terms of calcium cycling and contraction. We also discuss the heterogeneity in cellular phenotypes that arises from variability in cardiac differentiation, maturation, and culture conditions, and summarize present strategies that have been implemented to reduce this heterogeneity. Finally, we present original electrophysiological data from optical maps of hESC-CM clusters.
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Affiliation(s)
- Adriana Blazeski
- Department of Biomedical Engineering, The Johns Hopkins University, 720 Rutland Ave., Baltimore, MD 21205, USA
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Cingolani E, Yee K, Shehata M, Chugh SS, Marbán E, Cho HC. Biological pacemaker created by percutaneous gene delivery via venous catheters in a porcine model of complete heart block. Heart Rhythm 2012; 9:1310-8. [PMID: 22521937 DOI: 10.1016/j.hrthm.2012.04.020] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Indexed: 01/07/2023]
Abstract
BACKGROUND Pacemaker-dependent patients with device infection require temporary pacing while the infection is treated. External transthoracic pacing is painful and variably effective, while temporary pacing leads are susceptible to superinfection. OBJECTIVE To create a biological pacemaker delivered via venous catheters in a porcine model of complete heart block, providing a temporary alternative/adjunct to external pacing devices without additional indwelling hardware. METHODS Complete atrioventricular (AV) nodal block was induced in pigs by radiofrequency ablation after the implantation of a single-chamber electronic pacemaker to maintain a ventricular backup rate of 50 beats/min. An adenoviral vector cocktail (K(AAA) + H2), expressing dominant-negative inward rectifier potassium channel (Kir2.1AAA) and hyperpolarization-activated cation channel (HCN2) genes, was injected into the AV junctional region via a NOGA Myostar catheter advanced through the femoral vein. RESULTS Animals injected with K(AAA) + H2 maintained a physiologically relevant ventricular rate of 93.5 ± 7 beats/min (n = 4) compared with control animals (average rate, 59.4 ± 4 beats/min; n = 6 at day 7 postinjection; P <.05). Backup electronic pacemaker utilization decreased by almost 4-fold in the K(AAA) + H2 group compared with the control (P <.05), an effect maintained for the entire 14-day window. In contrast to the efficacy of gene delivery into the AV junctional region, open-chest, direct injection of K(AAA) + H2 (or its individual vectors) into the ventricular myocardium failed to elicit significant pacemaker activity. CONCLUSIONS The right-sided delivery of K(AAA) + H2 to the AV junctional region provided physiologically relevant biological pacing over a 14-day period. Our approach may provide temporary, bridge-to-device pacing for the effective clearance of infection prior to the reimplantation of a definitive electronic pacemaker.
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Adeniran I, El Harchi A, Hancox JC, Zhang H. Proarrhythmia in KCNJ2-linked short QT syndrome: insights from modelling. Cardiovasc Res 2012; 94:66-76. [DOI: 10.1093/cvr/cvs082] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Shock-induced focal arrhythmias: not driven by calcium? Heart Rhythm 2011; 9:105-6. [PMID: 22079556 DOI: 10.1016/j.hrthm.2011.11.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Indexed: 11/23/2022]
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Kapoor N, Galang G, Marbán E, Cho HC. Transcriptional suppression of connexin43 by TBX18 undermines cell-cell electrical coupling in postnatal cardiomyocytes. J Biol Chem 2011; 286:14073-9. [PMID: 21205823 DOI: 10.1074/jbc.m110.185298] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
T-box transcription factors figure prominently in embryonic cardiac cell lineage specifications. Mesenchymal precursor cells expressing Tbx18 give rise to the heart's pacemaker, the sinoatrial node (SAN). We sought to identify targets of TBX18 transcriptional regulation in the heart by forced adenoviral overexpression in postnatal cardiomyocytes. Neonatal rat cardiomyocytes (NRCMs) transduced with GFP showed sarcolemmal, punctate Cx43 expression. In contrast, TBX18-transduced NRCMs exhibited sparse Cx43 expression. Both the transcript and protein levels of Cx43 were greatly down-regulated within 2 days of TBX18 transduction. Direct injection of TBX18 in the guinea pig heart in vivo inhibited Cx43 expression. The repressor activity of TBX18 on Cx43 was highly specific; protein levels of Cx45 and Cx40, which comprise the main gap junctions in the SAN and conduction system, were unchanged by TBX18. A reporter-based promoter assay demonstrated that TBX18 directly represses the Cx43 promoter. Phenotypically, TBX18-NRCMs exhibited slowed intercellular calcein dye transfer kinetics (421 ± 54 versus control 127 ± 43 ms). Intracellular Ca(2+) oscillations in control NRCM monolayers were highly synchronized. In contrast, TBX18 overexpression led to asynchronous Ca(2+) oscillations, demonstrating reduced cell-cell coupling. Decreased coupling led to slow electrical propagation; conduction velocity in TBX18 NRCMs slowed by more than 50% relative to control (2.9 ± 0.5 versus 14.3 ± 0.9 cm/s). Taken together, TBX18 specifically and directly represses Cx43 transcript and protein levels. Cx43 suppression leads to significant electrical uncoupling, but the preservation of other gap junction proteins supports slow action potential propagation, recapitulating a key phenotypic hallmark of the SAN.
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Affiliation(s)
- Nidhi Kapoor
- Cedars-Sinai Heart Institute, Los Angeles, California 90048, USA
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Mahida S, Lubitz SA, Rienstra M, Milan DJ, Ellinor PT. Monogenic atrial fibrillation as pathophysiological paradigms. Cardiovasc Res 2010; 89:692-700. [PMID: 21123219 DOI: 10.1093/cvr/cvq381] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Atrial fibrillation (AF) is the most common cardiac rhythm abnormality and represents a major burden, both to patients and to health-care systems. In recent years, increasing evidence from population-based studies has demonstrated that AF is a heritable condition. Although familial forms of AF have been recognized for many years, they represent a rare subtype of the arrhythmia. However, despite their limited prevalence, the identification of mutations in monogenic AF kindreds has provided valuable insights into the molecular pathways underlying the arrhythmia and a framework for investigating AF encountered in the general population. In contrast to these rare families, the typical forms of AF occurring in the community are likely to be multigenic and have significant environmental influences. Recently, genome-wide association studies have uncovered common sequence variants that confer increased susceptibility to the arrhythmia. In the future, the elucidation of the genetic substrate underlying both familial and more typical forms of AF will hopefully lead to the development of novel diagnostic tools as well as more targeted rhythm control strategies. In this article, we will focus on monogenic forms of AF and also provide an overview of case-control association studies for AF.
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Affiliation(s)
- Saagar Mahida
- Cardiovascular Research Center, Massachusetts General Hospital, Charlestown, MA, USA
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Voigt N, Trausch A, Knaut M, Matschke K, Varró A, Van Wagoner DR, Nattel S, Ravens U, Dobrev D. Left-to-right atrial inward rectifier potassium current gradients in patients with paroxysmal versus chronic atrial fibrillation. Circ Arrhythm Electrophysiol 2010; 3:472-80. [PMID: 20657029 DOI: 10.1161/circep.110.954636] [Citation(s) in RCA: 160] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND Recent evidence suggests that atrial fibrillation (AF) is maintained by high-frequency reentrant sources with a left-to-right-dominant frequency gradient, particularly in patients with paroxysmal AF (pAF). Unequal left-to-right distribution of inward rectifier K(+) currents has been suggested to underlie this dominant frequency gradient, but this hypothesis has never been tested in humans. METHODS AND RESULTS Currents were measured with whole-cell voltage-clamp in cardiomyocytes from right atrial (RA) and left (LA) atrial appendages of patients in sinus rhythm (SR) and patients with AF undergoing cardiac surgery. Western blot was used to quantify protein expression of I(K1) (Kir2.1 and Kir2.3) and I(K,ACh) (Kir3.1 and Kir3.4) subunits. Basal current was ≈2-fold larger in chronic AF (cAF) versus SR patients, without RA-LA differences. In pAF, basal current was ≈2-fold larger in LA versus RA, indicating a left-to-right atrial gradient. In both atria, Kir2.1 expression was ≈2-fold greater in cAF but comparable in pAF versus SR. Kir2.3 levels were unchanged in cAF and RA-pAF but showed a 51% decrease in LA-pAF. In SR, carbachol-activated (2 μmol/L) I(K,ACh) was 70% larger in RA versus LA. This right-to-left atrial gradient was decreased in pAF and cAF caused by reduced I(K,ACh) in RA only. Similarly, in SR, Kir3.1 and Kir3.4 proteins were greater in RA versus LA and decreased in RA of pAF and cAF. Kir3.1 and Kir3.4 expression was unchanged in LA of pAF and cAF. CONCLUSION Our results support the hypothesis that a left-to-right gradient in inward rectifier background current contributes to high-frequency sources in LA that maintain pAF. These findings have potentially important implications for development of atrial-selective therapeutic approaches.
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Affiliation(s)
- Niels Voigt
- Department of Pharmacology and Toxicology, Dresden University of Technology, Dresden, Germany
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Abstract
Cardiac rhythm disorders reflect failures of impulse generation and/or conduction. With the exception of ablation methods that yield selective endocardial destruction, present therapies are nonspecific and/or palliative. Progress in understanding the underlying biology opens up prospects for new alternatives. This article reviews the present state of the art in gene- and cell-based therapies to correct cardiac rhythm disturbances. We begin with the rationale for such approaches, briefly discuss efforts to address aspects of tachyarrhythmia, and review advances in creating a biological pacemaker to cure bradyarrhythmia. Insights gained bring the field closer to a paradigm shift away from devices and drugs, and toward biologics, in the treatment of rhythm disorders.
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Affiliation(s)
- Hee Cheol Cho
- Cedars-Sinai Heart Institute, 8700 Beverly Blvd., Los Angeles, CA 90048, USA.
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Grunnet M. Repolarization of the cardiac action potential. Does an increase in repolarization capacity constitute a new anti-arrhythmic principle? Acta Physiol (Oxf) 2010; 198 Suppl 676:1-48. [PMID: 20132149 DOI: 10.1111/j.1748-1716.2009.02072.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The cardiac action potential can be divided into five distinct phases designated phases 0-4. The exact shape of the action potential comes about primarily as an orchestrated function of ion channels. The present review will give an overview of ion channels involved in generating the cardiac action potential with special emphasis on potassium channels involved in phase 3 repolarization. In humans, these channels are primarily K(v)11.1 (hERG1), K(v)7.1 (KCNQ1) and K(ir)2.1 (KCNJ2) being the responsible alpha-subunits for conducting I(Kr), I(Ks) and I(K1). An account will be given about molecular components, biophysical properties, regulation, interaction with other proteins and involvement in diseases. Both loss and gain of function of these currents are associated with different arrhythmogenic diseases. The second part of this review will therefore elucidate arrhythmias and subsequently focus on newly developed chemical entities having the ability to increase the activity of I(Kr), I(Ks) and I(K1). An evaluation will be given addressing the possibility that this novel class of compounds have the ability to constitute a new anti-arrhythmic principle. Experimental evidence from in vitro, ex vivo and in vivo settings will be included. Furthermore, conceptual differences between the short QT syndrome and I(Kr) activation will be accounted for.
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Affiliation(s)
- M Grunnet
- NeuroSearch A/S, Ballerup, and Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Denmark.
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Anumonwo JMB, Lopatin AN. Cardiac strong inward rectifier potassium channels. J Mol Cell Cardiol 2009; 48:45-54. [PMID: 19703462 DOI: 10.1016/j.yjmcc.2009.08.013] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2009] [Revised: 08/13/2009] [Accepted: 08/18/2009] [Indexed: 10/20/2022]
Abstract
Cardiac I(K1) and I(KACh) are the major potassium currents displaying classical strong inward rectification, a unique property that is critical for their roles in cardiac excitability. In the last 15 years, research on I(K1) and I(KACh) has been propelled by the cloning of the underlying inwardly rectifying potassium (Kir) channels, the discovery of the molecular mechanism of strong rectification and the linking of a number of disorders of cardiac excitability to defects in genes encoding Kir channels. Disease-causing mutations in Kir genes have been shown experimentally to affect one or more of the following channel properties: structure, assembly, trafficking, and regulation, with the ultimate effect of a gain- or a loss-of-function of the channel. It is now established that I(K1) and I(KACh) channels are heterotetramers of Kir2 and Kir3 subunits, respectively. Each homomeric Kir channel has distinct biophysical and regulatory properties, and individual Kir subunits often display different patterns of regional, cellular, and membrane distribution. These differences are thought to underlie important variations in the physiological properties of I(K1) and I(KACh). It has become increasingly clear that the contribution of I(K1) and I(KACh) channels to cardiac electrical activity goes beyond their long recognized role in the stabilization of resting membrane potential and shaping the late phase of action potential repolarization in individual myocytes but extends to being critical elements determining the overall electrical stability of the heart.
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Affiliation(s)
- Justus M B Anumonwo
- Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109-5622, USA
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Pedrotty DM, Klinger RY, Kirkton RD, Bursac N. Cardiac fibroblast paracrine factors alter impulse conduction and ion channel expression of neonatal rat cardiomyocytes. Cardiovasc Res 2009; 83:688-97. [PMID: 19477968 DOI: 10.1093/cvr/cvp164] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
AIMS The pathological proliferation of cardiac fibroblasts (CFs) in response to heart injury results in fibrosis, which correlates with arrhythmia generation and heart failure. Here we systematically examined the effect of fibroblast-derived paracrine factors on electrical propagation in cardiomyocytes. METHODS AND RESULTS Neonatal rat cardiac monolayers were exposed for 24 h to media conditioned by CFs. Optical mapping, sharp microelectrode recordings, quantitative RT-PCR, and immunostaining were used to assess the changes in the propagation and shape of the action potential and underlying changes in gene and protein expression. The fibroblast paracrine factors produced a 52% reduction in cardiac conduction velocity, a 217% prolongation of action potential duration, a 64% decrease of maximum capture rate, a 21% increase in membrane resting potential, and an 80% decrease of action potential upstroke velocity. These effects were dose dependent and partially reversible with removal of the conditioned media. No fibroblast proliferation, cardiomyocyte apoptosis, or decreased connexin-43 expression, phosphorylation, and function were found in conditioned cardiac cultures. In contrast, the expression of the fast sodium, inward rectifying potassium, and transient outward potassium channels were, respectively, reduced 3.8-, 6.6-fold, and to undetectable levels. The expression of beta-myosin heavy chain increased 17.4-fold. No electrophysiological changes were observed from media conditioned by CFs in the presence of cardiomyocytes. CONCLUSION Paracrine factors from neonatal CFs alone produced significant electrophysiological changes in neonatal rat cardiomyocytes resembling those found in several cardiac pathologies.
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Affiliation(s)
- Dawn M Pedrotty
- Biomedical Engineering Department, Duke University, Hudson Hall 136, Durham, NC 27708, USA
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Remme CA, Scicluna BP, Verkerk AO, Amin AS, van Brunschot S, Beekman L, Deneer VHM, Chevalier C, Oyama F, Miyazaki H, Nukina N, Wilders R, Escande D, Houlgatte R, Wilde AAM, Tan HL, Veldkamp MW, de Bakker JMT, Bezzina CR. Genetically determined differences in sodium current characteristics modulate conduction disease severity in mice with cardiac sodium channelopathy. Circ Res 2009; 104:1283-92. [PMID: 19407241 DOI: 10.1161/circresaha.109.194423] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Conduction slowing of the electric impulse that drives the heartbeat may evoke lethal cardiac arrhythmias. Mutations in SCN5A, which encodes the pore-forming cardiac sodium channel alpha subunit, are associated with familial arrhythmia syndromes based on conduction slowing. However, disease severity among mutation carriers is highly variable. We hypothesized that genetic modifiers underlie the variability in conduction slowing and disease severity. With the aim of identifying such modifiers, we studied the Scn5a(1798insD/+) mutation in 2 distinct mouse strains, FVB/N and 129P2. In 129P2 mice, the mutation resulted in more severe conduction slowing particularly in the right ventricle (RV) compared to FVB/N. Pan-genomic mRNA expression profiling in the 2 mouse strains uncovered a drastic reduction in mRNA encoding the sodium channel auxiliary subunit beta4 (Scn4b) in 129P2 mice compared to FVB/N. This corresponded to low to undetectable beta4 protein levels in 129P2 ventricular tissue, whereas abundant beta4 protein was detected in FVB/N. Sodium current measurements in isolated myocytes from the 2 mouse strains indicated that sodium channel activation in myocytes from 129P2 mice occurred at more positive potentials compared to FVB/N. Using computer simulations, this difference in activation kinetics was predicted to explain the observed differences in conduction disease severity between the 2 strains. In conclusion, genetically determined differences in sodium current characteristics on the myocyte level modulate disease severity in cardiac sodium channelopathies. In particular, the sodium channel subunit beta4 (SCN4B) may constitute a potential genetic modifier of conduction and cardiac sodium channel disease.
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Affiliation(s)
- Carol Ann Remme
- Heart Failure Research Center, Department of Experimental Cardiology, Academic Medical Center, University of Amsterdam, Room K2-110, PO Box 22700, 1100 DE Amsterdam, The Netherlands.
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