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Pugsley MK, Authier S, Hayes ES, Hamlin RL, Accardi MV, Curtis MJ. Recalibration of nonclinical safety pharmacology assessment to anticipate evolving regulatory expectations. J Pharmacol Toxicol Methods 2016; 81:1-8. [PMID: 27343819 DOI: 10.1016/j.vascn.2016.06.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Safety pharmacology (SP) has evolved in terms of architecture and content since the inception of the SP Society (SPS). SP was initially focused on the issue of drug-induced QT prolongation, but has now become a broad spectrum discipline with expanding expectations for evaluation of drug adverse effect liability in all organ systems, not merely the narrow consideration of torsades de pointes (TdP) liability testing. An important part of the evolution of SP has been the elaboration of architecture for interrogation of non-clinical models in terms of model development, model validation and model implementation. While SP has been defined by mandatory cardiovascular, central nervous system (CNS) and respiratory system studies ever since the core battery was elaborated, it also involves evaluation of drug effects on other physiological systems. The current state of SP evolution is the incorporation of emerging new technologies in a wide range of non-clinical drug safety testing models. This will refine the SP process, while potentially expanding the core battery. The continued refinement of automated technologies (e.g., automated patch clamp systems) is enhancing the scope for detection of adverse effect liability (i.e., for more than just IKr blockade), while introducing a potential for speed and accuracy in cardiovascular and CNS SP by providing rapid, high throughput ion channel screening methods for implementation in early drug development. A variety of CNS liability assays, which exploit isolated brain tissue, and in vitro electrophysiological techniques, have provided an additional level of complimentary preclinical safety screens aimed at establishing the seizurogenic potential and risk for memory dysfunction of new chemical entities (NCEs). As with previous editorials that preface the annual themed issue on SP methods published in the Journal of Pharmacological and Toxicological Methods (JPTM), we highlight here the content derived from the most recent (2015) SPS meeting held in Prague, Czech Republic. This issue of JPTM continues the tradition of providing a publication summary of articles primarily presented at the SPS meeting with direct bearing on the discipline of SP. Novel method development and refinement in all areas of the discipline are reflected in the content.
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Affiliation(s)
- Michael K Pugsley
- Department of Toxicology & PKDM, Purdue Pharma LP., 6 Cedar Brook Dr., Cranbury, NJ 08512, U.S.A..
| | - Simon Authier
- CiToxLAB Research Inc., 445 Armand Frappier, Laval, QC H7V 4B3, Canada
| | | | | | - Michael V Accardi
- CiToxLAB Research Inc., 445 Armand Frappier, Laval, QC H7V 4B3, Canada
| | - Michael J Curtis
- Cardiovascular Division, Rayne Institute, St Thomas' Hospital, London, SE17EH, UK
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Brinks D, Klein AJ, Cohen AE. Two-Photon Lifetime Imaging of Voltage Indicating Proteins as a Probe of Absolute Membrane Voltage. Biophys J 2016; 109:914-21. [PMID: 26331249 DOI: 10.1016/j.bpj.2015.07.038] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Revised: 06/15/2015] [Accepted: 07/28/2015] [Indexed: 01/03/2023] Open
Abstract
Genetically encoded voltage indicators (GEVIs) can report cellular electrophysiology with high resolution in space and time. Two-photon (2P) fluorescence has been explored as a means to image voltage in tissue. Here, we used the 2P electronic excited-state lifetime to probe absolute membrane voltage in a manner that is insensitive to the protein expression level, illumination intensity, or photon detection efficiency. First, we tested several GEVIs for 2P brightness, response speed, and voltage sensitivity. ASAP1 and a previously described citrine-Arch electrochromic Förster resonance energy transfer sensor (dubbed CAESR) showed the best characteristics. We then characterized the voltage-dependent lifetime of ASAP1, CAESR, and ArcLight under voltage-clamp conditions. ASAP1 and CAESR showed voltage-dependent lifetimes, whereas ArcLight did not. These results establish 2P fluorescence lifetime imaging as a viable means of measuring absolute membrane voltage. We discuss the prospects and improvements necessary for applications in tissue.
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Affiliation(s)
- Daan Brinks
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts
| | - Aaron J Klein
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts
| | - Adam E Cohen
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts; Department of Physics, Harvard University, Cambridge, Massachusetts; Howard Hughes Medical Institute, Harvard University, Cambridge, Massachusetts.
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Abstract
The molecular mechanisms underlying cardiogenesis are of critical biomedical importance due to the high prevalence of cardiac birth defects. Over the past two decades, the zebrafish has served as a powerful model organism for investigating heart development, facilitated by its powerful combination of optical access to the embryonic heart and plentiful opportunities for genetic analysis. Work in zebrafish has identified numerous factors that are required for various aspects of heart formation, including the specification and differentiation of cardiac progenitor cells, the morphogenesis of the heart tube, cardiac chambers, and atrioventricular canal, and the establishment of proper cardiac function. However, our current roster of regulators of cardiogenesis is by no means complete. It is therefore valuable for ongoing studies to continue pursuit of additional genes and pathways that control the size, shape, and function of the zebrafish heart. An extensive arsenal of techniques is available to distinguish whether particular mutations, morpholinos, or small molecules disrupt specific processes during heart development. In this chapter, we provide a guide to the experimental strategies that are especially effective for the characterization of cardiac phenotypes in the zebrafish embryo.
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Affiliation(s)
- A R Houk
- University of California, San Diego, CA, United States
| | - D Yelon
- University of California, San Diego, CA, United States
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Abstract
The zebrafish model is the only available high-throughput vertebrate assessment system, and it is uniquely suited for studies of in vivo cell biology. A sequenced and annotated genome has revealed a large degree of evolutionary conservation in comparison to the human genome. Due to our shared evolutionary history, the anatomical and physiological features of fish are highly homologous to humans, which facilitates studies relevant to human health. In addition, zebrafish provide a very unique vertebrate data stream that allows researchers to anchor hypotheses at the biochemical, genetic, and cellular levels to observations at the structural, functional, and behavioral level in a high-throughput format. In this review, we will draw heavily from toxicological studies to highlight advances in zebrafish high-throughput systems. Breakthroughs in transgenic/reporter lines and methods for genetic manipulation, such as the CRISPR-Cas9 system, will be comprised of reports across diverse disciplines.
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Affiliation(s)
- Gloria R Garcia
- Oregon State University, Department of Environmental and Molecular Toxicology, Environmental Health Sciences Center, Corvallis, OR 97331, USA
| | - Pamela D Noyes
- Oregon State University, Department of Environmental and Molecular Toxicology, Environmental Health Sciences Center, Corvallis, OR 97331, USA
| | - Robert L Tanguay
- Oregon State University, Department of Environmental and Molecular Toxicology, Environmental Health Sciences Center, Corvallis, OR 97331, USA.
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Watanabe M, Rollins AM, Polo-Parada L, Ma P, Gu S, Jenkins MW. Probing the Electrophysiology of the Developing Heart. J Cardiovasc Dev Dis 2016; 3:jcdd3010010. [PMID: 29367561 PMCID: PMC5715694 DOI: 10.3390/jcdd3010010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Revised: 03/08/2016] [Accepted: 03/10/2016] [Indexed: 12/14/2022] Open
Abstract
Many diseases that result in dysfunction and dysmorphology of the heart originate in the embryo. However, the embryonic heart presents a challenging subject for study: especially challenging is its electrophysiology. Electrophysiological maturation of the embryonic heart without disturbing its physiological function requires the creation and deployment of novel technologies along with the use of classical techniques on a range of animal models. Each tool has its strengths and limitations and has contributed to making key discoveries to expand our understanding of cardiac development. Further progress in understanding the mechanisms that regulate the normal and abnormal development of the electrophysiology of the heart requires integration of this functional information with the more extensively elucidated structural and molecular changes.
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Affiliation(s)
- Michiko Watanabe
- Department of Pediatrics, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA.
- Rainbow Babies and Children's Hospital, Case Western Reserve University, Cleveland, OH 44106, USA.
| | - Andrew M Rollins
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA.
| | - Luis Polo-Parada
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO 65201, USA.
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO 65201, USA.
| | - Pei Ma
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA.
| | - Shi Gu
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA.
| | - Michael W Jenkins
- Department of Pediatrics, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA.
- Rainbow Babies and Children's Hospital, Case Western Reserve University, Cleveland, OH 44106, USA.
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Genetically Encoded Voltage Indicators in Circulation Research. Int J Mol Sci 2015; 16:21626-42. [PMID: 26370981 PMCID: PMC4613271 DOI: 10.3390/ijms160921626] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Revised: 08/27/2015] [Accepted: 08/31/2015] [Indexed: 01/18/2023] Open
Abstract
Membrane potentials display the cellular status of non-excitable cells and mediate communication between excitable cells via action potentials. The use of genetically encoded biosensors employing fluorescent proteins allows a non-invasive biocompatible way to read out the membrane potential in cardiac myocytes and other cells of the circulation system. Although the approaches to design such biosensors date back to the time when the first fluorescent-protein based Förster Resonance Energy Transfer (FRET) sensors were constructed, it took 15 years before reliable sensors became readily available. Here, we review different developments of genetically encoded membrane potential sensors. Furthermore, it is shown how such sensors can be used in pharmacological screening applications as well as in circulation related basic biomedical research. Potentials and limitations will be discussed and perspectives of possible future developments will be provided.
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Knöpfel T, Gallero-Salas Y, Song C. Genetically encoded voltage indicators for large scale cortical imaging come of age. Curr Opin Chem Biol 2015; 27:75-83. [PMID: 26115448 DOI: 10.1016/j.cbpa.2015.06.006] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2015] [Revised: 05/22/2015] [Accepted: 06/05/2015] [Indexed: 11/19/2022]
Abstract
Electrical signals are fundamental to cellular sensing, communication and motility. In the nervous system, information is represented as receptor, synaptic and action potentials. Understanding how brain functions emerge from these electrical signals is one of the ultimate challenges in neuroscience and requires a methodology to monitor membrane voltage transients from large numbers of cells at high spatio-temporal resolution. Optical voltage imaging holds longstanding promises to achieve this, and has gained a fresh powerful momentum with the development of genetically encoded voltage indicators (GEVIs). With a focus on neuroimaging studies on intact mouse brains, we highlight recent advances in this field.
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Affiliation(s)
- Thomas Knöpfel
- Department of Medicine, Imperial College London, London W12 0NN, United Kingdom.
| | - Yasir Gallero-Salas
- Department of Medicine, Imperial College London, London W12 0NN, United Kingdom
| | - Chenchen Song
- Department of Medicine, Imperial College London, London W12 0NN, United Kingdom
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St-Pierre F, Chavarha M, Lin MZ. Designs and sensing mechanisms of genetically encoded fluorescent voltage indicators. Curr Opin Chem Biol 2015; 27:31-8. [PMID: 26079047 DOI: 10.1016/j.cbpa.2015.05.003] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 05/04/2015] [Indexed: 11/24/2022]
Abstract
Neurons tightly regulate the electrical potential difference across the plasma membrane with millivolt accuracy and millisecond resolution. Membrane voltage dynamics underlie the generation of an impulse, the transduction of impulses from one end of the neuron to the other, and the release of neurotransmitters. Imaging these voltage dynamics in multiple neurons simultaneously is therefore crucial for understanding how neurons function together within circuits in intact brains. Genetically encoded fluorescent voltage sensors have long been desired to report voltage in defined subsets of neurons with optical readout. In this review, we discuss the diverse strategies used to design and optimize protein-based voltage sensors, and highlight the chemical mechanisms by which different classes of reporters sense voltage. To guide neuroscientists in choosing an appropriate sensor for their applications, we also describe operating trade-offs of each class of voltage indicators.
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Affiliation(s)
- François St-Pierre
- Department of Pediatrics, Stanford University, Stanford, CA, USA; Department of Bioengineering, Stanford University, Stanford, CA, USA
| | - Mariya Chavarha
- Department of Pediatrics, Stanford University, Stanford, CA, USA; Department of Bioengineering, Stanford University, Stanford, CA, USA
| | - Michael Z Lin
- Department of Pediatrics, Stanford University, Stanford, CA, USA; Department of Bioengineering, Stanford University, Stanford, CA, USA.
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Akemann W, Song C, Mutoh H, Knöpfel T. Route to genetically targeted optical electrophysiology: development and applications of voltage-sensitive fluorescent proteins. NEUROPHOTONICS 2015; 2:021008. [PMID: 26082930 PMCID: PMC4465821 DOI: 10.1117/1.nph.2.2.021008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Accepted: 12/11/2014] [Indexed: 06/04/2023]
Abstract
The invention of membrane voltage protein indicators widens the reach of optical voltage imaging in cell physiology, most notably neurophysiology, by enabling membrane voltage recordings from genetically defined cell types in chronic and life-long preparations. While the last years have seen a dramatic improvement in the technical performance of these indicators, concomitant innovations in optogenetics, optical axon tracing, and high-speed digital microscopy are beginning to fulfill the age-old vision of an all-optical analysis of neuronal circuits, reaching beyond the limits of traditional electrode-based recordings. We will present our personal account of the development of protein voltage indicators from the pioneering days to the present state, including their applications in neurophysiology that has inspired our own work for more than a decade.
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Affiliation(s)
- Walther Akemann
- Imperial College London, Department of Medicine, London W12 ONN, United Kingdom
- Institute of Biology, CNRS UMR 8197, École Normale Supérieure, 46 rue d’Ulm, 75005 Paris, France
| | - Chenchen Song
- Imperial College London, Department of Medicine, London W12 ONN, United Kingdom
| | - Hiroki Mutoh
- Hamamatsu University School of Medicine, Department of Neurophysiology, Shizuoka 431-3192, Japan
| | - Thomas Knöpfel
- Imperial College London, Department of Medicine, London W12 ONN, United Kingdom
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60
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Lin E, Craig C, Lamothe M, Sarunic MV, Beg MF, Tibbits GF. Construction and use of a zebrafish heart voltage and calcium optical mapping system, with integrated electrocardiogram and programmable electrical stimulation. Am J Physiol Regul Integr Comp Physiol 2015; 308:R755-68. [PMID: 25740339 DOI: 10.1152/ajpregu.00001.2015] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Accepted: 02/26/2015] [Indexed: 12/31/2022]
Abstract
Zebrafish are increasingly being used as a model of vertebrate cardiology due to mammalian-like cardiac properties in many respects. The size and fecundity of zebrafish make them suitable for large-scale genetic and pharmacological screening. In larger mammalian hearts, optical mapping is often used to investigate the interplay between voltage and calcium dynamics and to investigate their respective roles in arrhythmogenesis. This report outlines the construction of an optical mapping system for use with zebrafish hearts, using the voltage-sensitive dye RH 237 and the calcium indicator dye Rhod-2 using two industrial-level CCD cameras. With the use of economical cameras and a common 532-nm diode laser for excitation, the rate dependence of voltage and calcium dynamics within the atrial and ventricular compartments can be simultaneously determined. At 140 beats/min, the atrial action potential duration was 36 ms and the transient duration was 53 ms. With the use of a programmable electrical stimulator, a shallow rate dependence of 3 and 4 ms per 100 beats/min was observed, respectively. In the ventricle the action potential duration was 109 ms and the transient duration was 124 ms, with a steeper rate dependence of 12 and 16 ms per 100 beats/min. Synchronous electrocardiograms and optical mapping recordings were recorded, in which the P-wave aligns with the atrial voltage peak and R-wave aligns with the ventricular peak. A simple optical pathway and imaging chamber are detailed along with schematics for the in-house construction of the electrocardiogram amplifier and electrical stimulator. Laboratory procedures necessary for zebrafish heart isolation, cannulation, and loading are also presented.
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Affiliation(s)
- Eric Lin
- Molecular Cardiac Physiology Group, Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada
| | - Calvin Craig
- Molecular Cardiac Physiology Group, Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada
| | - Marcel Lamothe
- Molecular Cardiac Physiology Group, Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada
| | - Marinko V Sarunic
- Biomedical Optics Research Group, School of Engineering Science, Simon Fraser University, Burnaby
| | - Mirza Faisal Beg
- Medical Image Analysis Lab, School of Engineering Science, Simon Fraser University, Burnaby, Canada; and
| | - Glen F Tibbits
- Molecular Cardiac Physiology Group, Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada; Cardiovascular Sciences, Child and Family Research Institute, Vancouver, Canada
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