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Avagimyan A, Kajaia N, Gabunia L, Trofimenko A, Sulashvili N, Sanikidze T, Gorgaslidze N, Challa A, Sheibani M. The place of beta-adrenergic receptor blockers in the treatment of arterial hypertension: from bench-to-bedside. Curr Probl Cardiol 2024:102734. [PMID: 38944226 DOI: 10.1016/j.cpcardiol.2024.102734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2024] [Accepted: 06/26/2024] [Indexed: 07/01/2024]
Abstract
Arterial hypertension is a multifaceted condition influenced by numerous pathophysiological factors. The key contributors to its pathogenesis encompass an unhealthy lifestyle, dysregulation of the sympathetic nervous system, alterations in the activity of adrenergic receptors, disruptions in sodium metabolism, structural and functional abnormalities in the vascular bed, as well as endothelial dysfunction, low-grade inflammation, oxidative stress etc. Despite extensive research into the mechanisms of arterial hypertension development over the centuries, its pathogenesis remains incompletely understood, and the selection of an effective treatment strategy continues to pose a significant challenge. Arterial hypertension is characterized by a diminished sensitivity of the β-adrenergic system, leading to the utilization of β-adrenergic blockers and other antihypertensive drugs in its treatment. This review delves into the mechanisms of action of beta-adrenergic receptor blockers in the treatment of hypertension and their respective effects.
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Affiliation(s)
- Ashot Avagimyan
- Yerevan State Medical University after M. Heratsi, Yerevan, Armenia.
| | - Nana Kajaia
- Tbilisi State Medical University, Tbilisi, Georgia
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2
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Van NTH, Kim WK, Nam JH. Challenges in the Therapeutic Targeting of KCa Channels: From Basic Physiology to Clinical Applications. Int J Mol Sci 2024; 25:2965. [PMID: 38474212 PMCID: PMC10932353 DOI: 10.3390/ijms25052965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 01/23/2024] [Accepted: 01/25/2024] [Indexed: 03/14/2024] Open
Abstract
Calcium-activated potassium (KCa) channels are ubiquitously expressed throughout the body and are able to regulate membrane potential and intracellular calcium concentrations, thereby playing key roles in cellular physiology and signal transmission. Consequently, it is unsurprising that KCa channels have been implicated in various diseases, making them potential targets for pharmaceutical interventions. Over the past two decades, numerous studies have been conducted to develop KCa channel-targeting drugs, including those for disorders of the central and peripheral nervous, cardiovascular, and urinary systems and for cancer. In this review, we synthesize recent findings regarding the structure and activating mechanisms of KCa channels. We also discuss the role of KCa channel modulators in therapeutic medicine. Finally, we identify the major reasons behind the delay in bringing these modulators to the pharmaceutical market and propose new strategies to promote their application.
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Affiliation(s)
- Nhung Thi Hong Van
- Department of Physiology, Dongguk University College of Medicine, Gyeongju 38066, Republic of Korea;
- Channelopathy Research Center (CRC), Dongguk University College of Medicine, Goyang 10326, Republic of Korea
| | - Woo Kyung Kim
- Channelopathy Research Center (CRC), Dongguk University College of Medicine, Goyang 10326, Republic of Korea
- Department of Internal Medicine, Graduate School of Medicine, Dongguk University, Goyang 10326, Republic of Korea
| | - Joo Hyun Nam
- Department of Physiology, Dongguk University College of Medicine, Gyeongju 38066, Republic of Korea;
- Channelopathy Research Center (CRC), Dongguk University College of Medicine, Goyang 10326, Republic of Korea
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3
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Klbik I. Is post-hypertonic lysis of human red blood cells caused by excessive cell volume regulation? Cryobiology 2024; 114:104795. [PMID: 37984597 DOI: 10.1016/j.cryobiol.2023.104795] [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: 05/10/2023] [Revised: 11/13/2023] [Accepted: 11/14/2023] [Indexed: 11/22/2023]
Abstract
Human red blood cells (RBC) exposed to hypertonic media are subject to post-hypertonic lysis - an injury that only develops during resuspension to an isotonic medium. The nature of post-hypertonic lysis was previously hypothesized to be osmotic when cation leaks were observed, and salt loading was suggested as a cause of the cell swelling upon resuspension in an isotonic medium. However, it was problematic to account for the salt loading since the plasma membrane of human RBCs was considered impermeable to cations. In this study, the hypertonicity-related behavior of human RBCs is revisited within the framework of modern cell physiology, considering current knowledge on membrane ion transport mechanisms - an account still missing. It is recognized here that the hypertonic behavior of human RBCs is consistent with the acute regulatory volume increase (RVI) response - a healthy physiological reaction initiated by cells to regulate their volume by salt accumulation. It is shown by reviewing the published studies that human RBCs can increase cation conductance considerably by activating cell volume-regulated ion transport pathways inactive under normal isotonic conditions and thus facilitate salt loading. A simplified physiological model accounting for transmembrane ion fluxes and membrane voltage predicts the isotonic cell swelling associated with increased cation conductance, eventually reaching hemolytic volume. The proposed involvement of cell volume regulation mechanisms shows the potential to explain the complex nature of the osmotic response of human RBCs and other cells. Cryobiological implications, including mechanisms of cryoprotection, are discussed.
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Affiliation(s)
- Ivan Klbik
- Institute of Physics SAS, Dúbravská cesta 9, 845 11, Bratislava, Slovak Republic; Department of Experimental Physics, FMFI UK, Mlynská dolina F1, 842 48, Bratislava, Slovak Republic.
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4
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Chatzinikolaou PN, Margaritelis NV, Paschalis V, Theodorou AA, Vrabas IS, Kyparos A, D'Alessandro A, Nikolaidis MG. Erythrocyte metabolism. Acta Physiol (Oxf) 2024; 240:e14081. [PMID: 38270467 DOI: 10.1111/apha.14081] [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: 07/03/2023] [Revised: 12/11/2023] [Accepted: 01/01/2024] [Indexed: 01/26/2024]
Abstract
Our aim is to present an updated overview of the erythrocyte metabolism highlighting its richness and complexity. We have manually collected and connected the available biochemical pathways and integrated them into a functional metabolic map. The focus of this map is on the main biochemical pathways consisting of glycolysis, the pentose phosphate pathway, redox metabolism, oxygen metabolism, purine/nucleoside metabolism, and membrane transport. Other recently emerging pathways are also curated, like the methionine salvage pathway, the glyoxalase system, carnitine metabolism, and the lands cycle, as well as remnants of the carboxylic acid metabolism. An additional goal of this review is to present the dynamics of erythrocyte metabolism, providing key numbers used to perform basic quantitative analyses. By synthesizing experimental and computational data, we conclude that glycolysis, pentose phosphate pathway, and redox metabolism are the foundations of erythrocyte metabolism. Additionally, the erythrocyte can sense oxygen levels and oxidative stress adjusting its mechanics, metabolism, and function. In conclusion, fine-tuning of erythrocyte metabolism controls one of the most important biological processes, that is, oxygen loading, transport, and delivery.
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Affiliation(s)
- Panagiotis N Chatzinikolaou
- Department of Physical Education and Sports Science at Serres, Aristotle University of Thessaloniki, Serres, Greece
| | - Nikos V Margaritelis
- Department of Physical Education and Sports Science at Serres, Aristotle University of Thessaloniki, Serres, Greece
| | - Vassilis Paschalis
- School of Physical Education and Sport Science, National and Kapodistrian University of Athens, Athens, Greece
| | - Anastasios A Theodorou
- Department of Life Sciences, School of Sciences, European University Cyprus, Nicosia, Cyprus
| | - Ioannis S Vrabas
- Department of Physical Education and Sports Science at Serres, Aristotle University of Thessaloniki, Serres, Greece
| | - Antonios Kyparos
- Department of Physical Education and Sports Science at Serres, Aristotle University of Thessaloniki, Serres, Greece
| | - Angelo D'Alessandro
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Michalis G Nikolaidis
- Department of Physical Education and Sports Science at Serres, Aristotle University of Thessaloniki, Serres, Greece
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5
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Petkova-Kirova P, Murciano N, Iacono G, Jansen J, Simionato G, Qiao M, Van der Zwaan C, Rotordam MG, John T, Hertz L, Hoogendijk AJ, Becker N, Wagner C, Von Lindern M, Egee S, Van den Akker E, Kaestner L. The Gárdos Channel and Piezo1 Revisited: Comparison between Reticulocytes and Mature Red Blood Cells. Int J Mol Sci 2024; 25:1416. [PMID: 38338693 PMCID: PMC10855361 DOI: 10.3390/ijms25031416] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Revised: 12/28/2023] [Accepted: 01/03/2024] [Indexed: 02/12/2024] Open
Abstract
The Gárdos channel (KCNN4) and Piezo1 are the best-known ion channels in the red blood cell (RBC) membrane. Nevertheless, the quantitative electrophysiological behavior of RBCs and its heterogeneity are still not completely understood. Here, we use state-of-the-art biochemical methods to probe for the abundance of the channels in RBCs. Furthermore, we utilize automated patch clamp, based on planar chips, to compare the activity of the two channels in reticulocytes and mature RBCs. In addition to this characterization, we performed membrane potential measurements to demonstrate the effect of channel activity and interplay on the RBC properties. Both the Gárdos channel and Piezo1, albeit their average copy number of activatable channels per cell is in the single-digit range, can be detected through transcriptome analysis of reticulocytes. Proteomics analysis of reticulocytes and mature RBCs could only detect Piezo1 but not the Gárdos channel. Furthermore, they can be reliably measured in the whole-cell configuration of the patch clamp method. While for the Gárdos channel, the activity in terms of ion currents is higher in reticulocytes compared to mature RBCs, for Piezo1, the tendency is the opposite. While the interplay between Piezo1 and Gárdos channel cannot be followed using the patch clamp measurements, it could be proved based on membrane potential measurements in populations of intact RBCs. We discuss the Gárdos channel and Piezo1 abundance, interdependencies and interactions in the context of their proposed physiological and pathophysiological functions, which are the passing of small constrictions, e.g., in the spleen, and their active participation in blood clot formation and thrombosis.
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Affiliation(s)
- Polina Petkova-Kirova
- Institute of Neurobiology, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria;
- Department of Biochemistry, Saarland University, 66123 Saarbrücken, Germany
| | - Nicoletta Murciano
- Nanion Technologies, 80339 Munich, Germany; (N.M.); (M.G.R.); (N.B.)
- Theoretical Medicine and Biosciences, Campus University Hospital, Saarland University, 66421 Homburg, Germany; (J.J.); (M.Q.); (L.H.)
| | - Giulia Iacono
- Department of Hematopoiesis, Sanquin Research, 1066 CX Amsterdam, The Netherlands; (G.I.); (C.V.d.Z.); (A.J.H.); (M.V.L.); (E.V.d.A.)
- Landsteiner Laboratory, Amsterdam UMC, University of Amsterdam, 1007 MB Amsterdam, The Netherlands
| | - Julia Jansen
- Theoretical Medicine and Biosciences, Campus University Hospital, Saarland University, 66421 Homburg, Germany; (J.J.); (M.Q.); (L.H.)
- Department of Experimental Physics, Saarland University, 66123 Saarbrücken, Germany (T.J.); (C.W.)
| | - Greta Simionato
- Department of Experimental Physics, Saarland University, 66123 Saarbrücken, Germany (T.J.); (C.W.)
- Department of Experimental Surgery, Campus University Hospital, Saarland University, 66421 Homburg, Germany
| | - Min Qiao
- Theoretical Medicine and Biosciences, Campus University Hospital, Saarland University, 66421 Homburg, Germany; (J.J.); (M.Q.); (L.H.)
- Department of Experimental Physics, Saarland University, 66123 Saarbrücken, Germany (T.J.); (C.W.)
| | - Carmen Van der Zwaan
- Department of Hematopoiesis, Sanquin Research, 1066 CX Amsterdam, The Netherlands; (G.I.); (C.V.d.Z.); (A.J.H.); (M.V.L.); (E.V.d.A.)
- Landsteiner Laboratory, Amsterdam UMC, University of Amsterdam, 1007 MB Amsterdam, The Netherlands
| | | | - Thomas John
- Department of Experimental Physics, Saarland University, 66123 Saarbrücken, Germany (T.J.); (C.W.)
| | - Laura Hertz
- Theoretical Medicine and Biosciences, Campus University Hospital, Saarland University, 66421 Homburg, Germany; (J.J.); (M.Q.); (L.H.)
- Department of Experimental Physics, Saarland University, 66123 Saarbrücken, Germany (T.J.); (C.W.)
| | - Arjan J. Hoogendijk
- Department of Hematopoiesis, Sanquin Research, 1066 CX Amsterdam, The Netherlands; (G.I.); (C.V.d.Z.); (A.J.H.); (M.V.L.); (E.V.d.A.)
- Landsteiner Laboratory, Amsterdam UMC, University of Amsterdam, 1007 MB Amsterdam, The Netherlands
| | - Nadine Becker
- Nanion Technologies, 80339 Munich, Germany; (N.M.); (M.G.R.); (N.B.)
| | - Christian Wagner
- Department of Experimental Physics, Saarland University, 66123 Saarbrücken, Germany (T.J.); (C.W.)
- Physics and Materials Science Research Unit, University of Luxembourg, L-1511 Luxembourg, Luxembourg
| | - Marieke Von Lindern
- Department of Hematopoiesis, Sanquin Research, 1066 CX Amsterdam, The Netherlands; (G.I.); (C.V.d.Z.); (A.J.H.); (M.V.L.); (E.V.d.A.)
- Landsteiner Laboratory, Amsterdam UMC, University of Amsterdam, 1007 MB Amsterdam, The Netherlands
| | - Stephane Egee
- Biological Station Roscoff, Sorbonne University, CNRS, UMR8227 LBI2M, F-29680 Roscoff, France;
- Laboratory of Excellence GR-Ex, F-75015 Paris, France
| | - Emile Van den Akker
- Department of Hematopoiesis, Sanquin Research, 1066 CX Amsterdam, The Netherlands; (G.I.); (C.V.d.Z.); (A.J.H.); (M.V.L.); (E.V.d.A.)
- Landsteiner Laboratory, Amsterdam UMC, University of Amsterdam, 1007 MB Amsterdam, The Netherlands
| | - Lars Kaestner
- Theoretical Medicine and Biosciences, Campus University Hospital, Saarland University, 66421 Homburg, Germany; (J.J.); (M.Q.); (L.H.)
- Department of Experimental Physics, Saarland University, 66123 Saarbrücken, Germany (T.J.); (C.W.)
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Kondratov KA, Artamonov AA, Mikhailovskii VY, Velmiskina AA, Mosenko SV, Grigoryev EA, Anisenkova AY, Nikitin YV, Apalko SV, Sushentseva NN, Ivanov AM, Scherbak SG. SARS-CoV-2 Impact on Red Blood Cell Morphology. Biomedicines 2023; 11:2902. [PMID: 38001903 PMCID: PMC10669871 DOI: 10.3390/biomedicines11112902] [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: 09/01/2023] [Revised: 10/22/2023] [Accepted: 10/24/2023] [Indexed: 11/26/2023] Open
Abstract
Severe COVID-19 alters the biochemical and morphological characteristics of blood cells in a wide variety of ways. To date, however, the vast majority of research has been devoted to the study of leukocytes, while erythrocyte morphological changes have received significantly less attention. The aim of this research was to identify erythrocyte morphology abnormalities that occur in COVID-19, compare the number of different poikilocyte types, and measure erythrocyte sizes to provide data on size dispersion. Red blood cells obtained from 6 control donors (800-2200 cells per donor) and 5 COVID-19 patients (800-1900 cells per patient) were examined using low-voltage scanning electron microscopy. We did not discover any forms of erythrocyte morphology abnormalities that would be specific to COVID-19. Among COVID-19 patients, we observed an increase in the number of acanthocytes (p = 0.01) and a decrease in the number of spherocytes (p = 0.03). In addition, our research demonstrates that COVID-19 causes an increase in the median (p = 0.004) and interquartile range (p = 0.009) when assessing erythrocyte size. The limitation of our study is a small number of participants.
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Affiliation(s)
- Kirill A. Kondratov
- City Hospital No. 40, St. Petersburg 197706, Russia
- S. M. Kirov Military Medical Academy, St. Petersburg 194044, Russia
- Saint-Petersburg State University, St. Petersburg 199034, Russia
| | | | | | - Anastasiya A. Velmiskina
- City Hospital No. 40, St. Petersburg 197706, Russia
- Saint-Petersburg State University, St. Petersburg 199034, Russia
| | - Sergey V. Mosenko
- City Hospital No. 40, St. Petersburg 197706, Russia
- Saint-Petersburg State University, St. Petersburg 199034, Russia
| | | | - Anna Yu. Anisenkova
- City Hospital No. 40, St. Petersburg 197706, Russia
- Saint-Petersburg State University, St. Petersburg 199034, Russia
| | - Yuri V. Nikitin
- S. M. Kirov Military Medical Academy, St. Petersburg 194044, Russia
| | - Svetlana V. Apalko
- City Hospital No. 40, St. Petersburg 197706, Russia
- Saint-Petersburg State University, St. Petersburg 199034, Russia
| | | | - Andrey M. Ivanov
- S. M. Kirov Military Medical Academy, St. Petersburg 194044, Russia
| | - Sergey G. Scherbak
- City Hospital No. 40, St. Petersburg 197706, Russia
- Saint-Petersburg State University, St. Petersburg 199034, Russia
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7
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Logue MJE, Farquhar RE, Eckhoff-Björngard Y, Cheung TT, Devor DC, McDonald FJ, Hamilton KL. The exocyst complex is required for the trafficking and delivery of KCa3.1 to the basolateral membrane of polarized epithelia. Am J Physiol Cell Physiol 2023; 324:C1249-C1262. [PMID: 37125772 PMCID: PMC10243536 DOI: 10.1152/ajpcell.00374.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 04/19/2023] [Accepted: 04/19/2023] [Indexed: 05/02/2023]
Abstract
Control of the movement of ions and water across epithelia is essential for homeostasis. Changing the number or activity of ion channels at the plasma membrane is a significant regulator of epithelial transport. In polarized epithelia, the intermediate-conductance calcium-activated potassium channel, KCa3.1 is delivered to the basolateral membrane where it generates and maintains the electrochemical gradients required for epithelial transport. The mechanisms that control the delivery of KCa3.1 to the basolateral membrane are still emerging. Herein, we investigated the role of the highly conserved tethering complex exocyst. In epithelia, exocyst is involved in the tethering of post-Golgi secretory vesicles with the basolateral membrane, which is required before membrane fusion. In our Fisher rat thyroid cell line that stably expresses KCa3.1, siRNA knockdown of either of the exocyst subunits Sec3, Sec6, or Sec8 significantly decreased KCa3.1-specific current. In addition, knockdown of exocyst complex subunits significantly reduced the basolateral membrane protein level of KCa3.1. Finally, co-immunoprecipitation experiments suggest associations between Sec6 and KCa3.1, but not between Sec8 and KCa3.1. Collectively, based on these data and our previous studies, we suggest that components of exocyst complex are crucially important in the tethering of KCa3.1 to the basolateral membrane. After which, Soluble N-ethylmaleimide-sensitive factor (SNF) Attachment Receptors (SNARE) proteins aid in the insertion of KCa3.1-containing vesicles into the basolateral membrane of polarized epithelia.NEW & NOTEWORTHY Our Ussing chamber and immunoblot experiments demonstrate that when subunits of the exocyst complex were transiently knocked down, this significantly reduced the basolateral population and functional expression of KCa3.1. These data suggest, combined with our protein association experiments, that the exocyst complex regulates the tethering of KCa3.1-containing vesicles to the basolateral membrane prior to the SNARE-dependent insertion of channels into the basolateral membrane of epithelial cells.
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Affiliation(s)
- Matthew J E Logue
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Rachel E Farquhar
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Yoakim Eckhoff-Björngard
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Tanya T Cheung
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Daniel C Devor
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Fiona J McDonald
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Kirk L Hamilton
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
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8
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Gibson JS, Rees DC. Emerging drug targets for sickle cell disease: shedding light on new knowledge and advances at the molecular level. Expert Opin Ther Targets 2023; 27:133-149. [PMID: 36803179 DOI: 10.1080/14728222.2023.2179484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Abstract
INTRODUCTION In sickle cell disease (SCD), a single amino acid substitution at β6 of the hemoglobin (Hb) chain replaces glutamate with valine, forming HbS instead of the normal adult HbA. Loss of a negative charge, and the conformational change in deoxygenated HbS molecules, enables formation of HbS polymers. These not only distort red cell morphology but also have other profound effects so that this simple etiology belies a complex pathogenesis with multiple complications. Although SCD represents a common severe inherited disorder with life-long consequences, approved treatments remain inadequate. Hydroxyurea is currently the most effective, with a handful of newer treatments, but there remains a real need for novel, efficacious therapies. AREAS COVERED This review summarizes important early events in pathogenesis to highlight key targets for novel treatments. EXPERT OPINION A thorough understanding of early events in pathogenesis closely associated with the presence of HbS is the logical starting point for identification of new targets rather than concentrating on more downstream effects. We discuss ways of reducing HbS levels, reducing the impact of HbS polymers, and of membrane events perturbing cell function, and suggest using the unique permeability of sickle cells to target drugs specifically into those more severely compromised.
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Affiliation(s)
- John S Gibson
- Department of Veterinary Medicine, University of Cambridge, Cambridge, UK
| | - David C Rees
- Department of Paediatric Haematology, King's College Hospital, London, UK
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9
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Lew VL. The circulatory dynamics of human red blood cell homeostasis: Oxy-deoxy and PIEZO1-triggered changes. Biophys J 2023; 122:484-495. [PMID: 36588342 PMCID: PMC9941722 DOI: 10.1016/j.bpj.2022.12.038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 11/14/2022] [Accepted: 12/30/2022] [Indexed: 01/02/2023] Open
Abstract
The vital function of red blood cells (RBCs) is to mediate the transport of oxygen from lungs to tissues and of CO2 from tissues to lungs. The gas exchanges occur during capillary transits within fractions of a second. Each oxygenation-deoxygenation and deoxygenation-reoxygenation transition on hemoglobin triggers sharp changes in RBC pH, leading to downstream changes in ion fluxes, membrane potential, and cell volume. The dynamics of these changes during the variable periods between capillary transits in vivo remains a mystery inaccessible to study by current methodologies, a knowledge gap on a fundamental physiological process that is the focus of the present study. The use of a computational model of human RBC homeostasis of tested accreditation enabled a detailed investigation of the expected RBC changes during intercapillary transits, with results advancing novel insights and predictions. The predicted rates of relative RBC volume change on oxygenation-deoxygenation (oxy-deoxy) and deoxygenation-reoxygenation transitions were about 1.5%/min and -0.9%/min, respectively, far too slow to allow the cells to reach steady states in the intervals between capillary transits. The amplitude of the oxy-deoxy-reoxygenation volume fluctuations varied in proportion with the duration of the intercapillary transit intervals. Upon capillary entry, oxy-deoxy-induced changes occur concurrently with deformation-induced PIEZO1 channel activation, both processes affecting cell pH, membrane potential, and cell volume during intertransit periods. The model showed that the effects were strictly additive as expected from processes operating independently on the cell's homeostatic fabric. Analysis of the mechanisms behind these predictions revealed, for the first time, the complex interactions between oxy-deoxy and ion transport processes that ensure the long-term homeostatic stability of RBCs for optimal gas transport in physiological conditions and how these may become altered in diseased states. Possible designs of microfluidic devices to test the model predictions are discussed.
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Affiliation(s)
- Virgilio L Lew
- Physiological Laboratory, Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Site, Cambridge, United Kingdom.
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10
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Nam YW, Downey M, Rahman MA, Cui M, Zhang M. Channelopathy of small- and intermediate-conductance Ca 2+-activated K + channels. Acta Pharmacol Sin 2023; 44:259-267. [PMID: 35715699 PMCID: PMC9889811 DOI: 10.1038/s41401-022-00935-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2022] [Accepted: 05/31/2022] [Indexed: 02/04/2023] Open
Abstract
Small- and intermediate-conductance Ca2+-activated K+ (KCa2.x/KCa3.1 also called SK/IK) channels are gated exclusively by intracellular Ca2+. The Ca2+ binding protein calmodulin confers sub-micromolar Ca2+ sensitivity to the channel-calmodulin complex. The calmodulin C-lobe is constitutively associated with the proximal C-terminus of the channel. Interactions between calmodulin N-lobe and the channel S4-S5 linker are Ca2+-dependent, which subsequently trigger conformational changes in the channel pore and open the gate. KCNN genes encode four subtypes, including KCNN1 for KCa2.1 (SK1), KCNN2 for KCa2.2 (SK2), KCNN3 for KCa2.3 (SK3), and KCNN4 for KCa3.1 (IK). The three KCa2.x channel subtypes are expressed in the central nervous system and the heart. The KCa3.1 subtype is expressed in the erythrocytes and the lymphocytes, among other peripheral tissues. The impact of dysfunctional KCa2.x/KCa3.1 channels on human health has not been well documented. Human loss-of-function KCa2.2 mutations have been linked with neurodevelopmental disorders. Human gain-of-function mutations that increase the apparent Ca2+ sensitivity of KCa2.3 and KCa3.1 channels have been associated with Zimmermann-Laband syndrome and hereditary xerocytosis, respectively. This review article discusses the physiological significance of KCa2.x/KCa3.1 channels, the pathophysiology of the diseases linked with KCa2.x/KCa3.1 mutations, the structure-function relationship of the mutant KCa2.x/KCa3.1 channels, and potential pharmacological therapeutics for the KCa2.x/KCa3.1 channelopathy.
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Affiliation(s)
- Young-Woo Nam
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, 92618, USA
| | - Myles Downey
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, 92618, USA
| | - Mohammad Asikur Rahman
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, 92618, USA
| | - Meng Cui
- Department of Pharmaceutical Sciences, Northeastern University School of Pharmacy, Boston, MA, 02115, USA
| | - Miao Zhang
- Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, 92618, USA.
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11
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Ca 2+-Sensitive Potassium Channels. MOLECULES (BASEL, SWITZERLAND) 2023; 28:molecules28020885. [PMID: 36677942 PMCID: PMC9861210 DOI: 10.3390/molecules28020885] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 01/07/2023] [Accepted: 01/10/2023] [Indexed: 01/18/2023]
Abstract
The Ca2+ ion is used ubiquitously as an intracellular signaling molecule due to its high external and low internal concentration. Many Ca2+-sensing ion channel proteins have evolved to receive and propagate Ca2+ signals. Among them are the Ca2+-activated potassium channels, a large family of potassium channels activated by rises in cytosolic calcium in response to Ca2+ influx via Ca2+-permeable channels that open during the action potential or Ca2+ release from the endoplasmic reticulum. The Ca2+ sensitivity of these channels allows internal Ca2+ to regulate the electrical activity of the cell membrane. Activating these potassium channels controls many physiological processes, from the firing properties of neurons to the control of transmitter release. This review will discuss what is understood about the Ca2+ sensitivity of the two best-studied groups of Ca2+-sensitive potassium channels: large-conductance Ca2+-activated K+ channels, KCa1.1, and small/intermediate-conductance Ca2+-activated K+ channels, KCa2.x/KCa3.1.
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12
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Jiao P, Li B, Zhang F, Tang C. Chitosan-based matrix solid-phase dispersion extraction assisted cell membrane magnetic bead ligand-affinity assay for screening active compounds from Fructus Cnidii. J Sep Sci 2022; 45:3725-3734. [PMID: 35906749 DOI: 10.1002/jssc.202200286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 07/20/2022] [Accepted: 07/25/2022] [Indexed: 11/09/2022]
Abstract
Cell membrane ligand-affinity assay is a useful tool for screening the active compounds from natural products. However, in traditional cell membrane ligand-affinity assays, natural products need to be refluxed, before being analyzed. This process consumes considerable time and energy and cannot be used for screening natural products that contain thermally unstable compounds. Therefore, an efficient analytical method is required. In this study, chitosan-based matrix solid-phase dispersion extraction was combined with cell membrane magnetic bead ligand-affinity assay to form a novel method for identifying the active compounds in Fructus Cnidii such as osthole and imperatorin. When compared with traditional cell membrane ligand-affinity assays, this assay requires less energy, extraction time (7 min), solvent volume (1.2 mL) and fewer natural products (40 mg). This indicates that the chitosan-based matrix solid-phase dispersion extraction assisted cell membrane magnetic beads ligand-affinity assay is an alternative analytical method for studying natural products. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Pan Jiao
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy, Tianjin Medical University, Tianjin, 300070, China
| | - Bing Li
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy, Tianjin Medical University, Tianjin, 300070, China
| | - Fan Zhang
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy, Tianjin Medical University, Tianjin, 300070, China
| | - Cheng Tang
- Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy, Tianjin Medical University, Tianjin, 300070, China
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13
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Weisbrod D. Small and Intermediate Calcium Activated Potassium Channels in the Heart: Role and Strategies in the Treatment of Cardiovascular Diseases. Front Physiol 2020; 11:590534. [PMID: 33329039 PMCID: PMC7719780 DOI: 10.3389/fphys.2020.590534] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Accepted: 10/02/2020] [Indexed: 12/11/2022] Open
Abstract
Calcium-activated potassium channels are a heterogeneous family of channels that, despite their different biophysical characteristics, structures, and pharmacological signatures, play a role of transducer between the ubiquitous intracellular calcium signaling and the electric variations of the membrane. Although this family of channels was extensively described in various excitable and non-excitable tissues, an increasing amount of evidences shows their functional role in the heart. This review aims to focus on the physiological role and the contribution of the small and intermediate calcium-activated potassium channels in cardiac pathologies.
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Föller M, Lang F. Ion Transport in Eryptosis, the Suicidal Death of Erythrocytes. Front Cell Dev Biol 2020; 8:597. [PMID: 32733893 PMCID: PMC7360839 DOI: 10.3389/fcell.2020.00597] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Accepted: 06/18/2020] [Indexed: 12/14/2022] Open
Abstract
Erythrocytes are among the most abundant cells in mammals and are perfectly adapted to their main functions, i.e., the transport of O2 to peripheral tissues and the contribution to CO2 transport to the lungs. In contrast to other cells, they are fully devoid of organelles. Similar to apoptosis of nucleated cells erythrocytes may enter suicidal death, eryptosis, which is characterized by the presentation of membrane phosphatidylserine on the cell surface and cell shrinkage, hallmarks that are also typical of apoptosis. Eryptosis may be triggered by an increase in the cytosolic Ca2+ concentration, which may be due to Ca2+ influx via non-selective cation channels of the TRPC family. Eryptosis is further induced by ceramide, which sensitizes erythrocytes to the eryptotic effect of Ca2+. Signaling regulating eryptosis further involves a variety of kinases including AMPK, PAK2, cGKI, JAK3, CK1α, CDK4, MSK1/2 and casein kinase. Eryptosis-dependent shrinkage is induced by K+ efflux through Ca2+-activated K+ channel KCa3.1, the Gardos channel. Eryptotic cells are phagocytosed and may adhere to endothelial cells. Eryptosis may help prevent hemolysis since defective erythrocytes usually undergo eryptosis followed by rapid clearance from circulating blood. Excessive eryptosis stimulated by various diseases and xenobiotics may result in anemia and/or impaired microcirculation. This review focuses on the significance and mechanisms of eryptosis as well as on the ion fluxes involved. Moreover, a short summary of further ion transport mechanisms of the erythrocyte membrane is provided.
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Affiliation(s)
- Michael Föller
- Department of Physiology, University of Hohenheim, Stuttgart, Germany
| | - Florian Lang
- Department of Physiology Institute of Physiology, University of Tübingen, Tübingen, Germany
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15
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Kaestner L, Bogdanova A, Egee S. Calcium Channels and Calcium-Regulated Channels in Human Red Blood Cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1131:625-648. [PMID: 31646528 DOI: 10.1007/978-3-030-12457-1_25] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Free Calcium (Ca2+) is an important and universal signalling entity in all cells, red blood cells included. Although mature mammalian red blood cells are believed to not contain organelles as Ca2+ stores such as the endoplasmic reticulum or mitochondria, a 20,000-fold gradient based on a intracellular Ca2+ concentration of approximately 60 nM vs. an extracellular concentration of 1.2 mM makes Ca2+-permeable channels a major signalling tool of red blood cells. However, the internal Ca2+ concentration is tightly controlled, regulated and maintained primarily by the Ca2+ pumps PMCA1 and PMCA4. Within the last two decades it became evident that an increased intracellular Ca2+ is associated with red blood cell clearance in the spleen and promotes red blood cell aggregability and clot formation. In contrast to this rather uncontrolled deadly Ca2+ signals only recently it became evident, that a temporal increase in intracellular Ca2+ can also have positive effects such as the modulation of the red blood cells O2 binding properties or even be vital for brief transient cellular volume adaptation when passing constrictions like small capillaries or slits in the spleen. Here we give an overview of Ca2+ channels and Ca2+-regulated channels in red blood cells, namely the Gárdos channel, the non-selective voltage dependent cation channel, Piezo1, the NMDA receptor, VDAC, TRPC channels, CaV2.1, a Ca2+-inhibited channel novel to red blood cells and i.a. relate these channels to the molecular unknown sickle cell disease conductance Psickle. Particular attention is given to correlation of functional measurements with molecular entities as well as the physiological and pathophysiological function of these channels. This view is in constant progress and in particular the understanding of the interaction of several ion channels in a physiological context just started. This includes on the one hand channelopathies, where a mutation of the ion channel is the direct cause of the disease, like Hereditary Xerocytosis and the Gárdos Channelopathy. On the other hand it applies to red blood cell related diseases where an altered channel activity is a secondary effect like in sickle cell disease or thalassemia. Also these secondary effects should receive medical and pharmacologic attention because they can be crucial when it comes to the life-threatening symptoms of the disease.
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Affiliation(s)
- Lars Kaestner
- Theoretical Medicine and Biosciences, Saarland University, Homburg, Germany. .,Experimental Physics, Saarland University, Saarbrücken, Germany.
| | - Anna Bogdanova
- Red Blood Cell Research Group, Institute of Veterinary Physiology, Vetsuisse Faculty and the Zürich Center for Integrative Human Physiology (ZIHP), University of Zürich, Zürich, Switzerland
| | - Stephane Egee
- CNRS, UMR8227 LBI2M, Sorbonne Université, Roscoff, France.,Laboratoire d'Excellence GR-Ex, Paris, France
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16
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Sikimic J, Hoffmeister T, Gresch A, Kaiser J, Barthlen W, Wolke C, Wieland I, Lendeckel U, Krippeit-Drews P, Düfer M, Drews G. Possible New Strategies for the Treatment of Congenital Hyperinsulinism. Front Endocrinol (Lausanne) 2020; 11:545638. [PMID: 33193079 PMCID: PMC7653201 DOI: 10.3389/fendo.2020.545638] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 10/02/2020] [Indexed: 01/21/2023] Open
Abstract
OBJECTIVE Congenital hyperinsulinism (CHI) is a rare disease characterized by persistent hypoglycemia as a result of inappropriate insulin secretion, which can lead to irreversible neurological defects in infants. Poor efficacy and strong adverse effects of the current medications impede successful treatment. The aim of the study was to investigate new approaches to silence β-cells and thus attenuate insulin secretion. RESEARCH DESIGN AND METHODS In the scope of our research, we tested substances more selective and more potent than the gold standard diazoxide that also interact with neuroendocrine ATP-sensitive K+ (KATP) channels. Additionally, KATP channel-independent targets as Ca2+-activated K+ channels of intermediate conductance (KCa3.1) and L-type Ca2+ channels were investigated. Experiments were performed using human islet cell clusters isolated from tissue of CHI patients (histologically classified as pathological) and islet cell clusters obtained from C57BL/6N (WT) or SUR1 knockout (SUR1-/-) mice. The cytosolic Ca2+ concentration ([Ca2+]c) was used as a parameter for the pathway regulated by electrical activity and was determined by fura-2 fluorescence. The mitochondrial membrane potential (ΔΨ) was determined by rhodamine 123 fluorescence and single channel currents were measured by the patch-clamp technique. RESULTS The selective KATP channel opener NN414 (5 µM) diminished [Ca2+]c in isolated human CHI islet cell clusters and WT mouse islet cell clusters stimulated with 10 mM glucose. In islet cell clusters lacking functional KATP channels (SUR1-/-) the drug was without effect. VU0071063 (30 µM), another KATP channel opener considered to be selective, lowered [Ca2+]c in human CHI islet cell clusters. The compound was also effective in islet cell clusters from SUR1-/- mice, showing that [Ca2+]c is influenced by additional effects besides KATP channels. Contrasting to NN414, the drug depolarized ΔΨ in murine islet cell clusters pointing to severe interference with mitochondrial metabolism. An opener of KCa3.1 channels, DCEBIO (100 µM), significantly decreased [Ca2+]c in SUR1-/- and human CHI islet cell clusters. To target L-type Ca2+ channels we tested two already approved drugs, dextromethorphan (DXM) and simvastatin. DXM (100 µM) efficiently diminished [Ca2+]c in stimulated human CHI islet cell clusters as well as in stimulated SUR1-/- islet cell clusters. Similar effects on [Ca2+]c were observed in experiments with simvastatin (7.2 µM). CONCLUSIONS NN414 seems to provide a good alternative to the currently used KATP channel opener diazoxide. Targeting KCa3.1 channels by channel openers or L-type Ca2+ channels by DXM or simvastatin might be valuable approaches for treatment of CHI caused by mutations of KATP channels not sensitive to KATP channel openers.
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Affiliation(s)
- Jelena Sikimic
- Department of Pharmacology, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Theresa Hoffmeister
- Department of Pharmacology, Institute of Pharmaceutical and Medicinal Chemistry, University of Münster, Münster, Germany
| | - Anne Gresch
- Department of Pharmacology, Institute of Pharmaceutical and Medicinal Chemistry, University of Münster, Münster, Germany
| | - Julia Kaiser
- Department of Pharmacology, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
| | - Winfried Barthlen
- Department of Pediatric Surgery, University Medicine Greifswald, Greifswald, Germany
| | - Carmen Wolke
- Institute of Medical Biochemistry and Molecular Biology, University Medicine Greifswald, Greifswald, Germany
| | - Ilse Wieland
- Institute of Human Genetics, University Hospital Magdeburg, Magdeburg, Germany
| | - Uwe Lendeckel
- Institute of Medical Biochemistry and Molecular Biology, University Medicine Greifswald, Greifswald, Germany
| | - Peter Krippeit-Drews
- Department of Pharmacology, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
- *Correspondence: Peter Krippeit-Drews,
| | - Martina Düfer
- Department of Pharmacology, Institute of Pharmaceutical and Medicinal Chemistry, University of Münster, Münster, Germany
| | - Gisela Drews
- Department of Pharmacology, Institute of Pharmacy, University of Tübingen, Tübingen, Germany
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17
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Brown BM, Shim H, Christophersen P, Wulff H. Pharmacology of Small- and Intermediate-Conductance Calcium-Activated Potassium Channels. Annu Rev Pharmacol Toxicol 2019; 60:219-240. [PMID: 31337271 DOI: 10.1146/annurev-pharmtox-010919-023420] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The three small-conductance calcium-activated potassium (KCa2) channels and the related intermediate-conductance KCa3.1 channel are voltage-independent K+ channels that mediate calcium-induced membrane hyperpolarization. When intracellular calcium increases in the channel vicinity, it calcifies the flexible N lobe of the channel-bound calmodulin, which then swings over to the S4-S5 linker and opens the channel. KCa2 and KCa3.1 channels are highly druggable and offer multiple binding sites for venom peptides and small-molecule blockers as well as for positive- and negative-gating modulators. In this review, we briefly summarize the physiological role of KCa channels and then discuss the pharmacophores and the mechanism of action of the most commonly used peptidic and small-molecule KCa2 and KCa3.1 modulators. Finally, we describe the progress that has been made in advancing KCa3.1 blockers and KCa2.2 negative- and positive-gating modulators toward the clinic for neurological and cardiovascular diseases and discuss the remaining challenges.
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Affiliation(s)
- Brandon M Brown
- Department of Pharmacology, University of California, Davis, California 95616, USA;
| | - Heesung Shim
- Department of Pharmacology, University of California, Davis, California 95616, USA;
| | | | - Heike Wulff
- Department of Pharmacology, University of California, Davis, California 95616, USA;
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18
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Evidence against a Role of Elevated Intracellular Ca 2+ during Plasmodium falciparum Preinvasion. Biophys J 2019; 114:1695-1706. [PMID: 29642038 DOI: 10.1016/j.bpj.2018.02.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Revised: 01/19/2018] [Accepted: 02/09/2018] [Indexed: 12/11/2022] Open
Abstract
Severe malaria is primarily caused by Plasmodium falciparum parasites during their asexual reproduction cycle within red blood cells. One of the least understood stages in this cycle is the brief preinvasion period during which merozoite-red cell contacts lead to apical alignment of the merozoite in readiness for penetration, a stage of major relevance in the control of invasion efficiency. Red blood cell deformations associated with this process were suggested to be active plasma membrane responses mediated by transients of elevated intracellular calcium. Few studies have addressed this hypothesis because of technical challenges, and the results remained inconclusive. Here, Fluo-4 was used as a fluorescent calcium indicator with optimized protocols to investigate the distribution of the dye in red blood cell populations used as P. falciparum invasion targets in egress-invasion assays. Preinvasion dynamics was observed simultaneously under bright-field and fluorescence microscopy by recording egress-invasion events. All the egress-invasion sequences showed red blood cell deformations of varied intensities during the preinvasion period and the echinocytic changes that follow during invasion. Intraerythrocytic calcium signals were absent throughout this interval in over half the records and totally absent during the preinvasion period, regardless of deformation strength. When present, calcium signals were of a punctate modality, initiated within merozoites already poised for invasion. These results argue against a role of elevated intracellular calcium during the preinvasion stage. We suggest an alternative mechanism of merozoite-induced preinvasion deformations based on passive red cell responses to transient agonist-receptor interactions associated with the formation of adhesive coat filaments.
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19
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Al Balushi H, Dufu K, Rees DC, Brewin JN, Hannemann A, Oksenberg D, Lu DC, Gibson JS. The effect of the antisickling compound GBT1118 on the permeability of red blood cells from patients with sickle cell anemia. Physiol Rep 2019; 7:e14027. [PMID: 30916477 PMCID: PMC6436144 DOI: 10.14814/phy2.14027] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Revised: 02/21/2019] [Accepted: 02/23/2019] [Indexed: 12/27/2022] Open
Abstract
Sickle cell anemia (SCA) is one of the commonest severe inherited disorders. Nevertheless, effective treatments remain inadequate and novel ones are avidly sought. A promising advance has been the design of novel compounds which react with hemoglobin S (HbS) to increase oxygen (O2 ) affinity and reduce sickling. One of these, voxelotor (GBT440), is currently in advanced clinical trials. A structural analogue, GBT1118, was investigated in the current work. As RBC dehydration is important in pathogenesis of SCA, the effect of GBT1118 on RBC cation permeability was also studied. Activities of Psickle , the Gardos channel and the KCl cotransporter (KCC) were all reduced. Gardos channel and KCC activities were also inhibited in RBCs treated with Ca2+ ionophore or the thiol reagent N-ethylmaleimide, indicative of direct effects on these two transport systems. Consistent with its action on RBC membrane transporters, GBT1118 significantly increased RBC hydration. RBC hemolysis was reduced in a nonelectrolyte lysis assay. Further to its direct effects on O2 affinity, GBT1118 was therefore found to reduce RBC shrinkage and fragility. Findings reveal important effects of GBT1118 on protecting sickle cells and suggest that this is approach may represent a useful therapy for amelioration of the clinical complications of SCA.
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Affiliation(s)
- Halima Al Balushi
- Department of Veterinary MedicineUniversity of CambridgeCambridgeUnited Kingdom
| | - Kobina Dufu
- Global Blood TherapeuticsSouth San FranciscoCalifornia
| | - David C. Rees
- Department of Paediatric HaematologyKing's College London School of MedicineKing's College Hospital NHS Foundation TrustLondonUnited Kingdom
| | - John N. Brewin
- Department of Paediatric HaematologyKing's College London School of MedicineKing's College Hospital NHS Foundation TrustLondonUnited Kingdom
| | - Anke Hannemann
- Department of Veterinary MedicineUniversity of CambridgeCambridgeUnited Kingdom
| | | | - David C.‐Y. Lu
- Department of Veterinary MedicineUniversity of CambridgeCambridgeUnited Kingdom
| | - John S. Gibson
- Department of Veterinary MedicineUniversity of CambridgeCambridgeUnited Kingdom
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20
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Lee CH, MacKinnon R. Activation mechanism of a human SK-calmodulin channel complex elucidated by cryo-EM structures. Science 2018; 360:508-513. [PMID: 29724949 DOI: 10.1126/science.aas9466] [Citation(s) in RCA: 123] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Accepted: 03/16/2018] [Indexed: 12/17/2022]
Abstract
Small-conductance Ca2+-activated K+ (SK) channels mediate neuron excitability and are associated with synaptic transmission and plasticity. They also regulate immune responses and the size of blood cells. Activation of SK channels requires calmodulin (CaM), but how CaM binds and opens SK channels has been unclear. Here we report cryo-electron microscopy (cryo-EM) structures of a human SK4-CaM channel complex in closed and activated states at 3.4- and 3.5-angstrom resolution, respectively. Four CaM molecules bind to one channel tetramer. Each lobe of CaM serves a distinct function: The C-lobe binds to the channel constitutively, whereas the N-lobe interacts with the S4-S5 linker in a Ca2+-dependent manner. The S4-S5 linker, which contains two distinct helices, undergoes conformational changes upon CaM binding to open the channel pore. These structures reveal the gating mechanism of SK channels and provide a basis for understanding SK channel pharmacology.
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Affiliation(s)
- Chia-Hsueh Lee
- Laboratory of Molecular Neurobiology and Biophysics, The Rockefeller University, Howard Hughes Medical Institute, 1230 York Avenue, New York, NY 10065, USA
| | - Roderick MacKinnon
- Laboratory of Molecular Neurobiology and Biophysics, The Rockefeller University, Howard Hughes Medical Institute, 1230 York Avenue, New York, NY 10065, USA.
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21
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Kaestner L, Wang X, Hertz L, Bernhardt I. Voltage-Activated Ion Channels in Non-excitable Cells-A Viewpoint Regarding Their Physiological Justification. Front Physiol 2018; 9:450. [PMID: 29755371 PMCID: PMC5934782 DOI: 10.3389/fphys.2018.00450] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Accepted: 04/10/2018] [Indexed: 01/27/2023] Open
Affiliation(s)
- Lars Kaestner
- Theoretical Medicine and Biosciences, Saarland University, Homburg, Germany.,Experimental Physics, Saarland University, Saarbrücken, Germany
| | - Xijia Wang
- Laboratory of Biophysics, Saarland University, Saarbrücken, Germany
| | - Laura Hertz
- Medical Faculty, Institute for Molecular Cell Biology, Saarland University, Homburg, Germany
| | - Ingolf Bernhardt
- Laboratory of Biophysics, Saarland University, Saarbrücken, Germany
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22
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Flatt JF, Bruce LJ. The Molecular Basis for Altered Cation Permeability in Hereditary Stomatocytic Human Red Blood Cells. Front Physiol 2018; 9:367. [PMID: 29713289 PMCID: PMC5911802 DOI: 10.3389/fphys.2018.00367] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Accepted: 03/27/2018] [Indexed: 11/20/2022] Open
Abstract
Normal human RBCs have a very low basal permeability (leak) to cations, which is continuously corrected by the Na,K-ATPase. The leak is temperature-dependent, and this temperature dependence has been evaluated in the presence of inhibitors to exclude the activity of the Na,K-ATPase and NaK2Cl transporter. The severity of the RBC cation leak is altered in various conditions, most notably the hereditary stomatocytosis group of conditions. Pedigrees within this group have been classified into distinct phenotypes according to various factors, including the severity and temperature-dependence of the cation leak. As recent breakthroughs have provided more information regarding the molecular basis of hereditary stomatocytosis, it has become clear that these phenotypes elegantly segregate with distinct genetic backgrounds. The cryohydrocytosis phenotype, including South-east Asian Ovalocytosis, results from mutations in SLC4A1, and the very rare condition, stomatin-deficient cryohydrocytosis, is caused by mutations in SLC2A1. Mutations in RHAG cause the very leaky condition over-hydrated stomatocytosis, and mutations in ABCB6 result in familial pseudohyperkalemia. All of the above are large multi-spanning membrane proteins and the mutations may either modify the structure of these proteins, resulting in formation of a cation pore, or otherwise disrupt the membrane to allow unregulated cation movement across the membrane. More recently mutations have been found in two RBC cation channels, PIEZO1 and KCNN4, which result in dehydrated stomatocytosis. These mutations alter the activation and deactivation kinetics of these channels, leading to increased opening and allowing greater cation fluxes than in wild type.
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Affiliation(s)
- Joanna F Flatt
- Bristol Institute for Transfusion Sciences, NHS Blood and Transplant, Bristol, United Kingdom
| | - Lesley J Bruce
- Bristol Institute for Transfusion Sciences, NHS Blood and Transplant, Bristol, United Kingdom
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23
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Red blood cells, compasses and snap shots. Blood Cells Mol Dis 2018; 71:67-70. [PMID: 29599084 DOI: 10.1016/j.bcmd.2018.03.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Accepted: 03/20/2018] [Indexed: 12/11/2022]
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24
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Lew VL, Tiffert T. On the Mechanism of Human Red Blood Cell Longevity: Roles of Calcium, the Sodium Pump, PIEZO1, and Gardos Channels. Front Physiol 2017; 8:977. [PMID: 29311949 PMCID: PMC5732905 DOI: 10.3389/fphys.2017.00977] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2017] [Accepted: 11/15/2017] [Indexed: 11/13/2022] Open
Abstract
In a healthy adult, the transport of O2 and CO2 between lungs and tissues is performed by about 2 · 1013 red blood cells, of which around 1.7 · 1011 are renewed every day, a turnover resulting from an average circulatory lifespan of about 120 days. Cellular lifespan is the result of an evolutionary balance between the energy costs of maintaining cells in a fit functional state versus cell renewal. In this Review we examine how the set of passive and active membrane transporters of the mature red blood cells interact to maximize their circulatory longevity thus minimizing costs on expensive cell turnover. Red blood cell deformability is critical for optimal rheology and gas exchange functionality during capillary flow, best fulfilled when the volume of each human red blood cell is kept at a fraction of about 0.55-0.60 of the maximal spherical volume allowed by its membrane area, the optimal-volume-ratio range. The extent to which red blood cell volumes can be preserved within or near these narrow optimal-volume-ratio margins determines the potential for circulatory longevity. We show that the low cation permeability of red blood cells allows volume stability to be achieved with extraordinary cost-efficiency, favouring cell longevity over cell turnover. We suggest a mechanism by which the interplay of a declining sodium pump and two passive membrane transporters, the mechanosensitive PIEZO1 channel, a candidate mediator of Psickle in sickle cells, and the Ca2+-sensitive, K+-selective Gardos channel, can implement red blood cell volume stability around the optimal-volume-ratio range, as required for extended circulatory longevity.
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Affiliation(s)
- Virgilio L Lew
- Physiological Laboratory, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Teresa Tiffert
- Physiological Laboratory, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
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25
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Danielczok JG, Terriac E, Hertz L, Petkova-Kirova P, Lautenschläger F, Laschke MW, Kaestner L. Red Blood Cell Passage of Small Capillaries Is Associated with Transient Ca 2+-mediated Adaptations. Front Physiol 2017; 8:979. [PMID: 29259557 PMCID: PMC5723316 DOI: 10.3389/fphys.2017.00979] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 11/16/2017] [Indexed: 12/15/2022] Open
Abstract
When red blood cells (RBCs) pass constrictions or small capillaries they need to pass apertures falling well below their own cross section size. We used different means of mechanical stimulations (hypoosmotic swelling, local mechanical stimulation, passing through microfluidic constrictions) to observe cellular responses of human RBCs in terms of intracellular Ca2+-signaling by confocal microscopy of Fluo-4 loaded RBCs. We were able to confirm our in vitro results in a mouse dorsal skinfold chamber model showing a transiently increased intracellular Ca2+ when RBCs were passing through small capillaries in vivo. Furthermore, we performed the above-mentioned in vitro experiments as well as measurements of RBCs filterability under various pharmacological manipulations (GsMTx-4, TRAM-34) to explore the molecular mechanism of the Ca2+-signaling. Based on these experiments we conclude that mechanical stimulation of RBCs activates mechano-sensitive channels most likely Piezo1. This channel activity allows Ca2+ to enter the cell, leading to a transient activation of the Gardos-channel associated with K+, Cl-, and water loss, i.e., with a transient volume adaptation facilitating the passage of the RBCs through the constriction.
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Affiliation(s)
- Jens G Danielczok
- Institute for Molecular Cell Biology, Saarland University, Homburg, Germany
| | - Emmanuel Terriac
- Experimental Physics, Saarland University, Saarbrücken, Germany.,Leibniz Institute for New Materials, Saarbrücken, Germany
| | - Laura Hertz
- Institute for Molecular Cell Biology, Saarland University, Homburg, Germany
| | | | - Franziska Lautenschläger
- Experimental Physics, Saarland University, Saarbrücken, Germany.,Leibniz Institute for New Materials, Saarbrücken, Germany
| | - Matthias W Laschke
- Institute for Clinical and Experimental Surgery, Saarland University, Homburg, Germany
| | - Lars Kaestner
- Experimental Physics, Saarland University, Saarbrücken, Germany.,Theoretical Medicine and Biosciences, Saarland University, Homburg, Germany
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26
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Al Balushi HWM, Wali Y, Al Awadi M, Al-Subhi T, Rees DC, Brewin JN, Hannemann A, Gibson JS. The super sickling haemoglobin HbS-Oman: a study of red cell sickling, K + permeability and associations with disease severity in patients heterozygous for HbA and HbS-Oman (HbA/S-Oman genotype). Br J Haematol 2017; 179:256-265. [PMID: 28699687 DOI: 10.1111/bjh.14851] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 06/04/2017] [Indexed: 11/30/2022]
Abstract
Studying different sickle cell genotypes may throw light on the pathogenesis of sickle cell disease (SCD). Here, the clinical profile, red cell sickling and K+ permeability in 29 SCD patients (15 patients with severe disease and 14 with a milder form) of HbA/S-Oman genotype were analysed. The super sickling nature of this Hb variant was confirmed. The red cell membrane permeability to K+ was markedly abnormal with elevated activities of Psickle , Gardos channel and KCl cotransporter (KCC). Results were consistent with Ca2+ entry and Mg2+ loss via Psickle stimulating Gardos channel and KCC activities. The abnormal red cell behaviour was similar to that in the commonest genotype of SCD, HbSS, in which the level of mutated Hb is considerably higher. Although activities of all three K+ transporters also correlated with the level of HbS-Oman, there was no association between transport phenotype and disease severity. The super sickling behaviour of HbS-Oman may obviate the need for solute loss and red cell dehydration to encourage Hb polymerisation, required in other SCD genotypes. Disease severity was reduced by concurrent α thalassaemia, as observed in other SCD genotypes, and represents an obvious genetic marker for prognostic tests of severity in young SCD patients of the HbA/S-Oman genotype.
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Affiliation(s)
| | - Yasser Wali
- Department of Child Health, Sultan Qaboos University, Muscat, Oman
| | - Maha Al Awadi
- Department of Genetics, Sultan Qaboos University, Muscat, Oman
| | | | - David C Rees
- Department of Paediatric Haematology, King's College Hospital, King's College London School of Medicine, London, UK
| | - John N Brewin
- Department of Paediatric Haematology, King's College Hospital, King's College London School of Medicine, London, UK
| | - Anke Hannemann
- Department of Veterinary Medicine, University of Cambridge, Cambridge, UK
| | - John S Gibson
- Department of Veterinary Medicine, University of Cambridge, Cambridge, UK
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27
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Fermo E, Bogdanova A, Petkova-Kirova P, Zaninoni A, Marcello AP, Makhro A, Hänggi P, Hertz L, Danielczok J, Vercellati C, Mirra N, Zanella A, Cortelezzi A, Barcellini W, Kaestner L, Bianchi P. 'Gardos Channelopathy': a variant of hereditary Stomatocytosis with complex molecular regulation. Sci Rep 2017; 7:1744. [PMID: 28496185 PMCID: PMC5431847 DOI: 10.1038/s41598-017-01591-w] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 03/31/2017] [Indexed: 11/17/2022] Open
Abstract
The Gardos channel is a Ca2+ sensitive, K+ selective channel present in several tissues including RBCs, where it is involved in cell volume regulation. Recently, mutations at two different aminoacid residues in KCNN4 have been reported in patients with hereditary xerocytosis. We identified by whole exome sequencing a new family with two members affected by chronic hemolytic anemia carrying mutation R352H in the KCNN4 gene. No additional mutations in genes encoding for RBCs cytoskeletal, membrane or channel proteins were detected. We performed functional studies on patients’ RBCs to evaluate the effects of R352H mutation on the cellular properties and eventually on the clinical phenotype. Gardos channel hyperactivation was demonstrated in circulating erythrocytes and erythroblasts differentiated ex-vivo from peripheral CD34+ cells. Pathological alterations in the function of multiple ion transport systems were observed, suggesting the presence of compensatory effects ultimately preventing cellular dehydration in patient’s RBCs; moreover, flow cytometry and confocal fluorescence live-cell imaging showed Ca2+ overload in the RBCs of both patients and hypersensitivity of Ca2+ uptake by RBCs to swelling. Altogether these findings suggest that the ‘Gardos channelopathy’ is a complex pathology, to some extent different from the common hereditary xerocytosis.
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Affiliation(s)
- Elisa Fermo
- UOC Oncoematologia, UOS. Fisiopatologia delle Anemie Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milano, Italy
| | - Anna Bogdanova
- Vetsuisse Faculty and the Zurich Center for Integrative Human Physiology (ZIHP), Institute of Veterinary Physiology, University of Zurich, Zurich, Switzerland
| | - Polina Petkova-Kirova
- Research Center for Molecular Imaging and Screening, Medical School, Institute for Molecular Cell Biology, Saarland University, Homburg/Saar, Germany
| | - Anna Zaninoni
- UOC Oncoematologia, UOS. Fisiopatologia delle Anemie Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milano, Italy
| | - Anna Paola Marcello
- UOC Oncoematologia, UOS. Fisiopatologia delle Anemie Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milano, Italy
| | - Asya Makhro
- Vetsuisse Faculty and the Zurich Center for Integrative Human Physiology (ZIHP), Institute of Veterinary Physiology, University of Zurich, Zurich, Switzerland
| | - Pascal Hänggi
- Vetsuisse Faculty and the Zurich Center for Integrative Human Physiology (ZIHP), Institute of Veterinary Physiology, University of Zurich, Zurich, Switzerland
| | - Laura Hertz
- Research Center for Molecular Imaging and Screening, Medical School, Institute for Molecular Cell Biology, Saarland University, Homburg/Saar, Germany
| | - Jens Danielczok
- Research Center for Molecular Imaging and Screening, Medical School, Institute for Molecular Cell Biology, Saarland University, Homburg/Saar, Germany
| | - Cristina Vercellati
- UOC Oncoematologia, UOS. Fisiopatologia delle Anemie Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milano, Italy
| | - Nadia Mirra
- UOC Pronto soccorso, Pediatria ambulatoriale e DH/MAC. Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milano, Italy
| | - Alberto Zanella
- UOC Oncoematologia, UOS. Fisiopatologia delle Anemie Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milano, Italy
| | - Agostino Cortelezzi
- UOC Oncoematologia, UOS. Fisiopatologia delle Anemie Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milano, Italy.,Universita' degli Studi di Milano, Milano, Italy
| | - Wilma Barcellini
- UOC Oncoematologia, UOS. Fisiopatologia delle Anemie Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milano, Italy
| | - Lars Kaestner
- Experimental Physics, Saarland University, Saarbruecken, Germany.,Theoretical Medicine and Biosciences, Saarland University, Homburg/Saar, Germany
| | - Paola Bianchi
- UOC Oncoematologia, UOS. Fisiopatologia delle Anemie Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milano, Italy.
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28
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Kaczmarek LK, Aldrich RW, Chandy KG, Grissmer S, Wei AD, Wulff H. International Union of Basic and Clinical Pharmacology. C. Nomenclature and Properties of Calcium-Activated and Sodium-Activated Potassium Channels. Pharmacol Rev 2017; 69:1-11. [PMID: 28267675 PMCID: PMC11060434 DOI: 10.1124/pr.116.012864] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2024] Open
Abstract
A subset of potassium channels is regulated primarily by changes in the cytoplasmic concentration of ions, including calcium, sodium, chloride, and protons. The eight members of this subfamily were originally all designated as calcium-activated channels. More recent studies have clarified the gating mechanisms for these channels and have documented that not all members are sensitive to calcium. This article describes the molecular relationships between these channels and provides an introduction to their functional properties. It also introduces a new nomenclature that differentiates between calcium- and sodium-activated potassium channels.
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Affiliation(s)
- Leonard K Kaczmarek
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - Richard W Aldrich
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - K George Chandy
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - Stephan Grissmer
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - Aguan D Wei
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
| | - Heike Wulff
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut (L.K.K.); Center for Learning and Memory and Department of Neuroscience, University of Texas at Austin, Austin, Texas (R.W.A.); Laboratory of Molecular Physiology in the Infection and Immunity Theme, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore (K.G.C.); Institute of Applied Physiology, Ulm University, Ulm, Germany (S.G.); Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington (A.D.W.); and Department of Pharmacology, School of Medicine, University of California, Davis, California (H.W.)
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29
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Sevelsted Møller L, Fialla AD, Schierwagen R, Biagini M, Liedtke C, Laleman W, Klein S, Reul W, Koch Hansen L, Rabjerg M, Singh V, Surra J, Osada J, Reinehr R, de Muckadell OBS, Köhler R, Trebicka J. The calcium-activated potassium channel KCa3.1 is an important modulator of hepatic injury. Sci Rep 2016; 6:28770. [PMID: 27354175 PMCID: PMC4926059 DOI: 10.1038/srep28770] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 06/10/2016] [Indexed: 12/12/2022] Open
Abstract
The calcium-activated potassium channel KCa3.1 controls different cellular processes such as proliferation and volume homeostasis. We investigated the role of KCa3.1 in experimental and human liver fibrosis. KCa3.1 gene expression was investigated in healthy and injured human and rodent liver. Effect of genetic depletion and pharmacological inhibition of KCa3.1 was evaluated in mice during carbon tetrachloride induced hepatic fibrogenesis. Transcription, protein expression and localisation of KCa3.1 was analysed by reverse transcription polymerase chain reaction, Western blot and immunohistochemistry. Hemodynamic effects of KCa3.1 inhibition were investigated in bile duct-ligated and carbon tetrachloride intoxicated rats. In vitro experiments were performed in rat hepatic stellate cells and hepatocytes. KCa3.1 expression was increased in rodent and human liver fibrosis and was predominantly observed in the hepatocytes. Inhibition of KCa3.1 aggravated liver fibrosis during carbon tetrachloride challenge but did not change hemodynamic parameters in portal hypertensive rats. In vitro, KCa3.1 inhibition leads to increased hepatocyte apoptosis and DNA damage, whereas proliferation of hepatic stellate cells was stimulated by KCa3.1 inhibition. Our data identifies KCa3.1 channels as important modulators in hepatocellular homeostasis. In contrast to previous studies in vitro and other tissues this channel appears to be anti-fibrotic and protective during liver injury.
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Affiliation(s)
- Linda Sevelsted Møller
- Department of Medical Gastroenterology and Hepatology, Odense University Hospital, Odense, Denmark.,Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark
| | - Annette Dam Fialla
- Department of Medical Gastroenterology and Hepatology, Odense University Hospital, Odense, Denmark
| | | | - Matteo Biagini
- Department of Pathology, Odense University Hospital, Odense, Denmark
| | - Christian Liedtke
- Department of Internal Medicine III, University Hospital RWTH Aachen, Aachen, Germany
| | - Wim Laleman
- Department of Liver and Biliopancreatic disorders, University of Leuven, Leuven, Belgium
| | - Sabine Klein
- Department of Internal Medicine I, University of Bonn, Bonn, Germany
| | - Winfried Reul
- Department of Internal Medicine I, University of Bonn, Bonn, Germany
| | - Lars Koch Hansen
- Department of Medical Gastroenterology and Hepatology, Vejle Hospital, Vejle, Denmark
| | - Maj Rabjerg
- Department of Pathology, Odense University Hospital, Odense, Denmark
| | - Vikrant Singh
- Department of Pharmacology, University of California, Davis, California, USA
| | - Joaquin Surra
- Departament de Producción Animal, Escuela Politécnica Superior, Huesca, Spain
| | - Jesus Osada
- Departamento Bioquímica y Biología Molecular y Celular, Facultad de Veterinaria, Instituto de Investigación Sanitaria de Aragón (IIS), Universidad de Zaragoza-CIBEROBN, Zaragoza, Spain
| | - Roland Reinehr
- Elbe-Elster Klinikum, Krankenhaus Herzberg, Herzberg, Germany
| | | | - Ralf Köhler
- Aragon Institute of Health Science I CS, Zaragoza, Spain
| | - Jonel Trebicka
- Department of Medical Gastroenterology and Hepatology, Odense University Hospital, Odense, Denmark.,Department of Internal Medicine I, University of Bonn, Bonn, Germany
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30
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Bae H, Lee D, Kim YW, Choi J, Lee HJ, Kim SW, Kim T, Noh YH, Ko JH, Bang H, Lim I. Effects of hydrogen peroxide on voltage-dependent K(+) currents in human cardiac fibroblasts through protein kinase pathways. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2016; 20:315-24. [PMID: 27162486 PMCID: PMC4860374 DOI: 10.4196/kjpp.2016.20.3.315] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Revised: 04/01/2016] [Accepted: 04/04/2016] [Indexed: 01/29/2023]
Abstract
Human cardiac fibroblasts (HCFs) have various voltage-dependent K(+) channels (VDKCs) that can induce apoptosis. Hydrogen peroxide (H2O2) modulates VDKCs and induces oxidative stress, which is the main contributor to cardiac injury and cardiac remodeling. We investigated whether H2O2 could modulate VDKCs in HCFs and induce cell injury through this process. In whole-cell mode patch-clamp recordings, application of H2O2 stimulated Ca(2+)-activated K(+) (KCa) currents but not delayed rectifier K(+) or transient outward K(+) currents, all of which are VDKCs. H2O2-stimulated KCa currents were blocked by iberiotoxin (IbTX, a large conductance KCa blocker). The H2O2-stimulating effect on large-conductance KCa (BKCa) currents was also blocked by KT5823 (a protein kinase G inhibitor) and 1 H-[1, 2, 4] oxadiazolo-[4, 3-a] quinoxalin-1-one (ODQ, a soluble guanylate cyclase inhibitor). In addition, 8-bromo-cyclic guanosine 3', 5'-monophosphate (8-Br-cGMP) stimulated BKCa currents. In contrast, KT5720 and H-89 (protein kinase A inhibitors) did not block the H2O2-stimulating effect on BKCa currents. Using RT-PCR and western blot analysis, three subtypes of KCa channels were detected in HCFs: BKCa channels, small-conductance KCa (SKCa) channels, and intermediate-conductance KCa (IKCa) channels. In the annexin V/propidium iodide assay, apoptotic changes in HCFs increased in response to H2O2, but IbTX decreased H2O2-induced apoptosis. These data suggest that among the VDKCs of HCFs, H2O2 only enhances BKCa currents through the protein kinase G pathway but not the protein kinase A pathway, and is involved in cell injury through BKCa channels.
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Affiliation(s)
- Hyemi Bae
- Department of Physiology, College of Medicine, Chung-Ang University, Seoul 06974, Korea
| | - Donghee Lee
- Department of Physiology, College of Medicine, Chung-Ang University, Seoul 06974, Korea
| | - Young-Won Kim
- Department of Physiology, College of Medicine, Chung-Ang University, Seoul 06974, Korea
| | - Jeongyoon Choi
- Department of Physiology, College of Medicine, Chung-Ang University, Seoul 06974, Korea
| | - Hong Jun Lee
- Biomedical Research Institute, College of Medicine, Chung-Ang University, Seoul 06974, Korea
| | - Sang-Wook Kim
- Department of Internal Medicine, College of Medicine, Chung-Ang University, Seoul 06974, Korea
| | - Taeho Kim
- Department of Internal Medicine, College of Medicine, Chung-Ang University, Seoul 06974, Korea
| | - Yun-Hee Noh
- Department of Biochemistry, School of Medicine, Konkuk University, Seoul 05029, Korea
| | - Jae-Hong Ko
- Department of Physiology, College of Medicine, Chung-Ang University, Seoul 06974, Korea
| | - Hyoweon Bang
- Department of Physiology, College of Medicine, Chung-Ang University, Seoul 06974, Korea
| | - Inja Lim
- Department of Physiology, College of Medicine, Chung-Ang University, Seoul 06974, Korea
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31
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Kaestner L. Channelizing the red blood cell: molecular biology competes with patch-clamp. Front Mol Biosci 2015; 2:46. [PMID: 26322315 PMCID: PMC4531249 DOI: 10.3389/fmolb.2015.00046] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Accepted: 07/24/2015] [Indexed: 11/13/2022] Open
Affiliation(s)
- Lars Kaestner
- Research Center for Molecular Imaging and Screening, Medical School, Saarland University Homburg, Germany
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32
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Muravyov A, Tikhomirova I. Red blood cell microrheological changes and drug transport efficiency. ACTA ACUST UNITED AC 2015. [DOI: 10.3233/jcb-15005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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33
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Neurodegeneration in the elderly – When the blood type matters: An overview of the McLeod syndrome with focus on hematological features. Transfus Apher Sci 2015; 52:277-84. [DOI: 10.1016/j.transci.2015.04.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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34
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Molecular dynamics simulations of scorpion toxin recognition by the Ca(2+)-activated potassium channel KCa3.1. Biophys J 2014; 105:1829-37. [PMID: 24138859 DOI: 10.1016/j.bpj.2013.08.046] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Revised: 08/26/2013] [Accepted: 08/30/2013] [Indexed: 02/06/2023] Open
Abstract
The Ca(2+)-activated channel of intermediate-conductance (KCa3.1) is a target for antisickling and immunosuppressant agents. Many small peptides isolated from animal venoms inhibit KCa3.1 with nanomolar affinities and are promising drug scaffolds. Although the inhibitory effect of peptide toxins on KCa3.1 has been examined extensively, the structural basis of toxin-channel recognition has not been understood in detail. Here, the binding modes of two selected scorpion toxins, charybdotoxin (ChTx) and OSK1, to human KCa3.1 are examined in atomic detail using molecular dynamics (MD) simulations. Employing a homology model of KCa3.1, we first determine conduction properties of the channel using Brownian dynamics and ascertain that the simulated results are in accord with experiment. The model structures of ChTx-KCa3.1 and OSK1-KCa3.1 complexes are then constructed using MD simulations biased with distance restraints. The ChTx-KCa3.1 complex predicted from biased MD is consistent with the crystal structure of ChTx bound to a voltage-gated K(+) channel. The dissociation constants (Kd) for the binding of both ChTx and OSK1 to KCa3.1 determined experimentally are reproduced within fivefold using potential of mean force calculations. Making use of the knowledge we gained by studying the ChTx-KCa3.1 complex, we attempt to enhance the binding affinity of the toxin by carrying out a theoretical mutagenesis. A mutant toxin, in which the positions of two amino acid residues are interchanged, exhibits a 35-fold lower Kd value for KCa3.1 than that of the wild-type. This study provides insight into the key molecular determinants for the high-affinity binding of peptide toxins to KCa3.1, and demonstrates the power of computational methods in the design of novel toxins.
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35
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Tiffert T, Lew VL. Dynamic morphology and cytoskeletal protein changes during spontaneous inside-out vesiculation of red blood cell membranes. Pflugers Arch 2014; 466:2279-88. [PMID: 24615169 PMCID: PMC4233320 DOI: 10.1007/s00424-014-1483-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2013] [Revised: 02/06/2014] [Accepted: 02/13/2014] [Indexed: 11/25/2022]
Abstract
Vesicle preparations from cell plasma membranes, red blood cells in particular, are extensively used in transport and enzymic studies and in the fields of drug delivery and drug-transport interactions. Here we investigated the role of spectrin–actin, the main components of the red cell cortical cytoskeleton, in a particular mechanism of vesicle generation found to be relevant to the egress process of Plasmodium falciparum merozoites from infected red blood cells. Plasma membranes from red blood cells lysed in ice-cold media of low ionic strength and free of divalent cations spontaneously and rapidly vesiculate upon incubation at 37 °C rendering high yields of inside-out vesicles. We tested the working hypothesis that the dynamic shape transformations resulted from changes in spectrin–actin configuration within a disintegrating cytoskeletal mesh. We showed that cytoskeletal-free membranes behave like a two-dimensional fluid lacking shape control, that spectrin–actin remain attached to vesiculating membranes for as long as spontaneous movement persists, that most of the spectrin–actin detachment occurs terminally at the time of vesicle sealing and that naked membrane patches increasingly appear during vesiculation. These results support the proposed role of spectrin–actin in spontaneous vesiculation. The implications of these results to membrane dynamics and to the mechanism of merozoite egress are discussed.
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Affiliation(s)
- Teresa Tiffert
- Physiological Laboratory, Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge, CB2 3EG, UK,
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36
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Inhibitors of second messenger pathways and Ca(2+)-induced exposure of phosphatidylserine in red blood cells of patients with sickle cell disease. Pflugers Arch 2013; 466:1477-85. [PMID: 24158429 PMCID: PMC4062833 DOI: 10.1007/s00424-013-1343-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 08/25/2013] [Accepted: 08/25/2013] [Indexed: 01/09/2023]
Abstract
The present work investigates the contribution of various second messenger systems to Ca2+-induced phosphatidylserine (PS) exposure in red blood cells (RBCs) from sickle cell disease (SCD) patients. The Ca2+ dependence of PS exposure was confirmed using the Ca2+ ionophore bromo-A23187 to clamp intracellular Ca2+ over 4 orders of magnitude in high or low potassium-containing (HK or LK) saline. The percentage of RBCs showing PS exposure was significantly increased in LK over HK saline. This effect was reduced by the Gardos channel inhibitors, clotrimazole and charybdotoxin. Nevertheless, although Ca2+ loading in the presence of an outwardly directed electrochemical gradient for K+ stimulated PS exposure, substantial exposure still occurred in HK saline. Under the conditions used inhibitors of other second messenger systems (ABT491, quinacrine, acetylsalicylic acid, 3,4-dichloroisocoumarin, GW4869 and zVAD-fmk) did not inhibit the relationship between [Ca2+] and PS exposure. Inhibitors of phospholipase A2, cyclooxygenase, platelet-activating factor, sphingomyelinase and caspases, therefore, were without effect on Ca2+-induced PS exposure in RBCs, incubated in either HK or LK saline.
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Bogdanova A, Makhro A, Wang J, Lipp P, Kaestner L. Calcium in red blood cells-a perilous balance. Int J Mol Sci 2013; 14:9848-72. [PMID: 23698771 PMCID: PMC3676817 DOI: 10.3390/ijms14059848] [Citation(s) in RCA: 155] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Revised: 03/18/2013] [Accepted: 03/19/2013] [Indexed: 12/19/2022] Open
Abstract
Ca2+ is a universal signalling molecule involved in regulating cell cycle and fate, metabolism and structural integrity, motility and volume. Like other cells, red blood cells (RBCs) rely on Ca2+ dependent signalling during differentiation from precursor cells. Intracellular Ca2+ levels in the circulating human RBCs take part not only in controlling biophysical properties such as membrane composition, volume and rheological properties, but also physiological parameters such as metabolic activity, redox state and cell clearance. Extremely low basal permeability of the human RBC membrane to Ca2+ and a powerful Ca2+ pump maintains intracellular free Ca2+ levels between 30 and 60 nM, whereas blood plasma Ca2+ is approximately 1.8 mM. Thus, activation of Ca2+ uptake has an impressive impact on multiple processes in the cells rendering Ca2+ a master regulator in RBCs. Malfunction of Ca2+ transporters in human RBCs leads to excessive accumulation of Ca2+ within the cells. This is associated with a number of pathological states including sickle cell disease, thalassemia, phosphofructokinase deficiency and other forms of hereditary anaemia. Continuous progress in unravelling the molecular nature of Ca2+ transport pathways allows harnessing Ca2+ uptake, avoiding premature RBC clearance and thrombotic complications. This review summarizes our current knowledge of Ca2+ signalling in RBCs emphasizing the importance of this inorganic cation in RBC function and survival.
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Affiliation(s)
- Anna Bogdanova
- Institute of Veterinary Physiology, Vetsuisse Faculty and the Zürich, Center for Integrative Human Physiology, University of Zürich, Zürich 8057, Switzerland; E-Mails: (A.B.); (A.M.)
| | - Asya Makhro
- Institute of Veterinary Physiology, Vetsuisse Faculty and the Zürich, Center for Integrative Human Physiology, University of Zürich, Zürich 8057, Switzerland; E-Mails: (A.B.); (A.M.)
| | - Jue Wang
- Institute for Molecular Cell Biology and Research Centre for Molecular Imaging and Screening, Saarland University, Homburg/Saar 66421, Germany; E-Mails: (J.W.); (P.L.)
| | - Peter Lipp
- Institute for Molecular Cell Biology and Research Centre for Molecular Imaging and Screening, Saarland University, Homburg/Saar 66421, Germany; E-Mails: (J.W.); (P.L.)
| | - Lars Kaestner
- Institute for Molecular Cell Biology and Research Centre for Molecular Imaging and Screening, Saarland University, Homburg/Saar 66421, Germany; E-Mails: (J.W.); (P.L.)
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Kucherenko YV, Wagner-Britz L, Bernhardt I, Lang F. Effect of chloride channel inhibitors on cytosolic Ca2+ levels and Ca2+-activated K+ (Gardos) channel activity in human red blood cells. J Membr Biol 2013; 246:315-26. [PMID: 23430221 DOI: 10.1007/s00232-013-9532-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Accepted: 01/30/2013] [Indexed: 10/27/2022]
Abstract
DIDS, NPPB, tannic acid (TA) and AO1 are widely used inhibitors of Cl(-) channels. Some Cl(-) channel inhibitors (NPPB, DIDS, niflumic acid) were shown to affect phosphatidylserine (PS) scrambling and, thus, the life span of human red blood cells (hRBCs). Since a number of publications suggest Ca(2+) dependence of PS scrambling, we explored whether inhibitors of Cl(-) channels (DIDS, NPPB) or of Ca(2+)-activated Cl(-) channels (DIDS, NPPB, TA, AO1) modified intracellular free Ca(2+) concentration ([Ca(2+)]i) and activity of Ca(2+)-activated K(+) (Gardos) channel in hRBCs. According to Fluo-3 fluorescence in flow cytometry, a short treatment (15 min, +37 °C) with Cl(-) channels inhibitors decreased [Ca(2+)]i in the following order: TA > AO1 > DIDS > NPPB. According to forward scatter, the decrease of [Ca(2+)]i was accompanied by a slight but significant increase in cell volume following DIDS, NPPB and AO1 treatments. TA treatment resulted in cell shrinkage. According to whole-cell patch-clamp experiments, TA activated and NPPB and AO1 inhibited Gardos channels. The Cl(-) channel blockers further modified the alterations of [Ca(2+)]i following ATP depletion (glucose deprivation, iodoacetic acid, 6-inosine), oxidative stress (1 mM t-BHP) and treatment with Ca(2+) ionophore ionomycin (1 μM). The ability of the Cl(-) channel inhibitors to modulate PS scrambling did not correlate with their influence on [Ca(2+)]i as TA and AO1 had a particularly strong decreasing effect on [Ca(2+)]i but at the same time enhanced PS exposure. In conclusion, Cl(-) channel inhibitors affect Gardos channels, influence Ca(2+) homeostasis and induce PS exposure of hRBCs by Ca(2+)-independent mechanisms.
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Affiliation(s)
- Yuliya V Kucherenko
- Institute for Problems of Cryobiology and Cryomedicine, National Academy of Sciences of Ukraine, Kharkov, Ukraine
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Kirby BS, Bruhl A, Sullivan MN, Francis M, Dinenno FA, Earley S. Robust internal elastic lamina fenestration in skeletal muscle arteries. PLoS One 2013; 8:e54849. [PMID: 23359815 PMCID: PMC3554626 DOI: 10.1371/journal.pone.0054849] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2012] [Accepted: 12/17/2012] [Indexed: 11/18/2022] Open
Abstract
Holes within the internal elastic lamina (IEL) of blood vessels are sites of fenestration allowing for passage of diffusible vasoactive substances and interface of endothelial cell membrane projections with underlying vascular smooth muscle. Endothelial projections are sites of dynamic Ca2+ events leading to endothelium dependent hyperpolarization (EDH)-mediated relaxations and the activity of these events increase as vessel diameter decreases. We tested the hypothesis that IEL fenestration is greater in distal vs. proximal arteries in skeletal muscle, and is unlike other vascular beds (mesentery). We also determined ion channel protein composition within the endothelium of intramuscular and non-intramuscular skeletal muscle arteries. Popliteal arteries, subsequent gastrocnemius feed arteries, and first and second order intramuscular arterioles from rat hindlimb were isolated, cut longitudinally, fixed, and imaged using confocal microscopy. Quantitative analysis revealed a significantly larger total fenestration area in second and first order arterioles vs. feed and popliteal arteries (58% and 16% vs. 5% and 3%; N = 10 images/artery), due to a noticeably greater average size of holes (9.5 and 3.9 µm2 vs 1.5 and 1.9 µm2). Next, we investigated via immunolabeling procedures whether proteins involved in EDH often embedded in endothelial cell projections were disparate between arterial segments. Specific proteins involved in EDH, such as inositol trisphosphate receptors, small and intermediate conductance Ca2+-activated K+ channels, and the canonical (C) transient receptor potential (TRP) channel TRPC3 were present in both popliteal and first order intramuscular arterioles. However due to larger IEL fenestration in first order arterioles, a larger spanning area of EDH proteins is observed proximal to the smooth muscle cell plasma membrane. These observations highlight the robust area of fenestration within intramuscular arterioles and indicate that the anatomical architecture and endothelial cell hyperpolarizing apparatus for distinct vasodilatory signaling is potentially present.
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Affiliation(s)
- Brett S. Kirby
- Department of Biomedical Sciences, Vascular Physiology Research Group, Colorado State University, Fort Collins, Colorado, United States of America
| | - Allison Bruhl
- Department of Biomedical Sciences, Vascular Physiology Research Group, Colorado State University, Fort Collins, Colorado, United States of America
| | - Michelle N. Sullivan
- Department of Biomedical Sciences, Vascular Physiology Research Group, Colorado State University, Fort Collins, Colorado, United States of America
| | - Michael Francis
- Department of Physiology, University of South Alabama College of Medicine, Mobile, Alabama, United States of America
| | - Frank A. Dinenno
- Department of Biomedical Sciences, Vascular Physiology Research Group, Colorado State University, Fort Collins, Colorado, United States of America
- Department of Health and Exercise Science, Human Cardiovascular Physiology Laboratory, Colorado State University, Fort Collins, Colorado, United States of America
| | - Scott Earley
- Department of Biomedical Sciences, Vascular Physiology Research Group, Colorado State University, Fort Collins, Colorado, United States of America
- * E-mail:
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Balut CM, Hamilton KL, Devor DC. Trafficking of intermediate (KCa3.1) and small (KCa2.x) conductance, Ca(2+)-activated K(+) channels: a novel target for medicinal chemistry efforts? ChemMedChem 2012; 7:1741-55. [PMID: 22887933 DOI: 10.1002/cmdc.201200226] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Revised: 07/09/2012] [Indexed: 12/22/2022]
Abstract
Ca(2+)-activated K(+) (KCa) channels play a pivotal role in the physiology of a wide variety of tissues and disease states, including vascular endothelia, secretory epithelia, certain cancers, red blood cells (RBC), neurons, and immune cells. Such widespread involvement has generated an intense interest in elucidating the function and regulation of these channels, with the goal of developing pharmacological strategies aimed at selective modulation of KCa channels in various disease states. Herein we give an overview of the molecular and functional properties of these channels and their therapeutic importance. We discuss the achievements made in designing pharmacological tools that control the function of KCa channels by modulating their gating properties. Moreover, this review discusses the recent advances in our understanding of KCa channel assembly and anterograde trafficking toward the plasma membrane, the micro-domains in which these channels are expressed within the cell, and finally the retrograde trafficking routes these channels take following endocytosis. As the regulation of intracellular trafficking by agonists as well as the protein-protein interactions that modify these events continue to be explored, we anticipate this will open new therapeutic avenues for the targeting of these channels based on the pharmacological modulation of KCa channel density at the plasma membrane.
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Affiliation(s)
- Corina M Balut
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA
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Ma YL, Rees DC, Gibson JS, Ellory JC. The conductance of red blood cells from sickle cell patients: ion selectivity and inhibitors. J Physiol 2012; 590:2095-105. [PMID: 22411011 DOI: 10.1113/jphysiol.2012.229609] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The abnormally high cation permeability in red blood cells (RBCs) from patients with sickle cell disease (SCD) occupies a central role in pathogenesis. Sickle RBC properties are notably heterogeneous, however, thus limiting conventional flux techniques that necessarily average out the behaviour of millions of cells. Here we use the whole-cell patch configuration to characterise the permeability of single RBCs from patients with SCD in more detail. A non-specific cation conductance was reversibly induced upon deoxygenation and was permeable to both univalent (Na+, K+, Rb+) and also divalent (Ca2+, Mg2+) cations. It was sensitive to the tarantula spider toxin GsMTx-4. Mn2+ caused partial, reversible inhibition. The aromatic aldehyde o-vanillin also irreversibly inhibited the deoxygenation-induced conductance, partially at 1mM and almost completely at 5mM. Nifedipine, amiloride and ethylisopropylamiloride were ineffective. In oxygenated RBCs, the current was pH sensitive showing a marked increase as pH fell from 7.4 to 6, with no change apparent when pH was raised from 7.4 to 8. The effects of acidification and deoxygenation together were not additive. Many features of this deoxygenation-induced conductance (non-specificity for cations, permeability toCa2+ andMg2+, pH sensitivity, reversibility, partial inhibition by DIDS and Mn2+) are shared with the flux pathway sometimes referred to as Psickle. Sensitivity to GsMTx-4 indicates its possible identity as a stretch-activated channel. Sensitivity to o-vanillin implies that activation requires HbS polymerisation but since the conductance was observed in whole-cell patches, results suggest that bulk intracellular Hb is not involved; rather a membrane-bound subfraction is responsible for channel activation. The ability to record P(sickle)-like activity in single RBCs will facilitate further studies and eventual molecular identification of the pathway involved.
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Affiliation(s)
- Y-L Ma
- Department of Physiology, Anatomy & Genetics, Oxford, UK
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Lauf PK. Eryptotic red blood cell adhesion to vascular endothelium: CXCL16/SR-PSOX, a pathological amplifier. Focus on “Dynamic adhesion of eryptotic erythrocytes to endothelial cells via CXCL16/SR-PSOX”. Am J Physiol Cell Physiol 2012; 302:C642-3. [DOI: 10.1152/ajpcell.00453.2011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Peter K. Lauf
- Cell Biophysics Group, Department of Pathology, and Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio
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Muravyov A, Tikhomirova I. Role Ca(2+) in mechanisms of the red blood cells microrheological changes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 740:1017-38. [PMID: 22453982 DOI: 10.1007/978-94-007-2888-2_47] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
To assess the physiological role of intracellular Ca(2+) in the changes of microrheological red blood cell (RBC) properties (RBC deformability and aggregation), we employed several types of chemicals that can increase and decrease of the intracellular Ca(2+) concentration. The rise of Ca(2+) influx, stimulated by mechanical loading, A23187, thrombin, prostaglandin F(2α) was accompanied by a moderate red cell deformability lowering and an increase of their aggregation. In contrast, Ca(2+) entry blocking into the red cells by verapamil led to a significant RBC aggregation decrease and deformability rise. Similar microrheological changes were observed in the red blood cells treated with phosphodiesterase inhibitors IBMX, vinpocetine, rolipram, pentoxifylline. When forskolin (10 μM), an AC stimulator was added to RBC suspension, the RBC deformability was increased (p <0.05). Somewhat more significant deformability rise appeared after RBC incubation with dB-AMP. Red cell aggregation was significantly decreased under these conditions (p<0.01). On the whole the total data clearly show that the red cell aggregation and deformation changes were connected with an activation of both intracellular signaling pathways: Ca(2+) regulatory mechanism and Gs-protein/adenylyl-cyclase-cAMP system. And the final red cell microrheological regulatory effect is connected with the crosstalk between these systems.
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Affiliation(s)
- Alexei Muravyov
- Department of Medicine and Biology, State Pedagogical University, Yaroslavl, Russia.
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Nguyen DB, Wagner-Britz L, Maia S, Steffen P, Wagner C, Kaestner L, Bernhardt I. Regulation of phosphatidylserine exposure in red blood cells. Cell Physiol Biochem 2011; 28:847-56. [PMID: 22178937 DOI: 10.1159/000335798] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/28/2011] [Indexed: 02/04/2023] Open
Abstract
The exposure of phosphatidylserine (PS) on the outer membrane leaflet of red blood cells (RBCs) serves as a signal for eryptosis, a mechanism for the RBC clearance from blood circulation. The process of PS exposure was investigated as function of the intracellular Ca(2+) content and the activation of PKCα in human and sheep RBCs. Cells were treated with lysophosphatidic acid (LPA), 4-bromo-A23187, or phorbol-12 myristate-13 acetate (PMA) and analysed by flow cytometry, single cell fluorescence video imaging, or confocal microscopy. For human RBCs, no clear correlation existed between the number of cells with an elevated Ca(2+) content and PS exposure. Results are explained by three different mechanisms responsible for the PS exposure in human RBCs: (i) Ca(2+)-stimulated scramblase activation (and flippase inhibition) by LPA, 4-bromo-A23187, and PMA; (ii) PKC activation by LPA and PMA; and (iii) enhanced lipid flop caused by LPA. In sheep RBCs, only the latter mechanism occurs suggesting absence of scramblase activity.
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Affiliation(s)
- Duc Bach Nguyen
- Faculty of Natural and Technical Sciences III, Saarland University, Saarbruecken, Germany
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45
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Liebau S, Tischendorf M, Ansorge D, Linta L, Stockmann M, Weidgang C, Iacovino M, Boeckers T, von Wichert G, Kyba M, Kleger A. An inducible expression system of the calcium-activated potassium channel 4 to study the differential impact on embryonic stem cells. Stem Cells Int 2011; 2011:456815. [PMID: 21941566 PMCID: PMC3173888 DOI: 10.4061/2011/456815] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Accepted: 06/14/2011] [Indexed: 11/20/2022] Open
Abstract
Rationale. The family of calcium-activated potassium channels consists of four members with varying biological functions and conductances. Besides membrane potential modulation, SK channels have been found to be involved in cardiac pacemaker cell development from ES cells and morphological shaping of neural stem cells. Objective. Distinct SK channel subtype expression in ES cells might elucidate their precise impact during cardiac development. We chose SK channel subtype 4 as a potential candidate influencing embryonic stem cell differentiation. Methods. We generated a doxycycline inducible mouse ES cell line via targeted homologous recombination of a cassette expressing a bicistronic construct encoding SK4 and a fluorophore from the murine HPRT locus. Conclusion. We characterized the mouse ES cell line iSK4-AcGFP. The cassette is readily expressed under the control of doxycycline, and the overexpression of SK4 led to an increase in cardiac and pacemaker cell differentiation thereby serving as a unique tool to characterize the cell biological variances due to specific SK channel overexpression.
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Affiliation(s)
- Stefan Liebau
- Institute for Anatomy and Cell Biology, Ulm University, 89081 Ulm, Germany
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Hirschler-Laszkiewicz I, Zhang W, Keefer K, Conrad K, Tong Q, Chen SJ, Bronson S, Cheung JY, Miller BA. Trpc2 depletion protects red blood cells from oxidative stress-induced hemolysis. Exp Hematol 2011; 40:71-83. [PMID: 21924222 DOI: 10.1016/j.exphem.2011.09.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Revised: 08/22/2011] [Accepted: 09/09/2011] [Indexed: 11/29/2022]
Abstract
Transient receptor potential (TRP) channels Trpc2 and Trpc3 are expressed on normal murine erythroid precursors, and erythropoietin stimulates an increase in intracellular calcium ([Ca(2+)](i)) through TRPC2 and TRPC3. Because modulation of [Ca(2+)](i) is an important signaling pathway in erythroid proliferation and differentiation, Trpc2, Trpc3, and Trpc2/Trpc3 double knockout mice were utilized to explore the roles of these channels in erythropoiesis. Trpc2, Trpc3, and Trpc2/Trpc3 double knockout mice were not anemic, and had similar red blood cell counts, hemoglobins, and reticulocyte counts as wild-type littermate controls. Although the erythropoietin-induced increase in [Ca(2+)](i) was reduced, these knockout mice showed no defects in red cell production. The major phenotypic difference at steady state was that the mean corpuscular volume, mean corpuscular hemoglobin, and hematocrit of red cells were significantly greater in Trpc2 and Trpc2/Trpc3 double knockout mice, and mean corpuscular hemoglobin concentration was significantly reduced. All hematological parameters in Trpc3 knockout mice were similar to controls. When exposed to phenylhydrazine, unlike the Trpc3 knockouts, Trpc2 and Trpc2/Trpc3 double knockout mice showed significant resistance to hemolysis. This was associated with a significant reduction in hydrogen peroxide-induced calcium influx in erythroblasts. Although erythropoietin-induced calcium influx through TRPC2 or TRPC3 is not critical for erythroid production, these data demonstrate that TRPC2 plays an important role in oxidative stress-induced hemolysis, which may be related to reduced calcium entry in red cells in the presence of Trpc2 depletion.
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Gatidis S, Meier A, Jilani K, Lang E, Zelenak C, Qadri SM, Lang F. Phlorhizin protects against erythrocyte cell membrane scrambling. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2011; 59:8524-8530. [PMID: 21707031 DOI: 10.1021/jf201938d] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Phlorhizin interferes with glucose transport. Glucose depletion triggers suicidal erythrocyte death or eryptosis, characterized by cell shrinkage and cell membrane scrambling. Eryptosis is further triggered by oxidative stress. The present study explored whether phlorhizin influences eryptosis following glucose depletion or oxidative stress. Cell membrane scrambling was estimated from annexin binding, cell volume from forward scatter (FSC), and cytosolic Ca(2+) concentration from Fluo-3 fluorescence. Phlorhizin (10-100 μM) added alone did not modify scrambling, FSC, or Fluo-3 fluorescence. Glucose depletion (48 h) significantly increased Fluo-3 fluorescence, decreased FSC, and increased annexin binding, effects in part significantly blunted by phlorhizin (annexin binding ≥ 10 μM, FSC ≥ 50 μM). Oxidative stress (30 min 0.3 mM tert-butylhydroperoxide) again significantly increased Fluo-3 fluorescence and triggered annexin binding, effects again in part significantly blunted by phlorhizin (Fluo-3 fluorescence ≥ 50 μM, annexin-binding ≥ 10 μM). Phlorhizin did not blunt the cell shrinkage induced by oxidative stress. The present observations disclose a novel effect of phlorhizin, that is, an influence on suicidal erythrocyte death following energy depletion and oxidative stress.
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Affiliation(s)
- Sergios Gatidis
- Department of Physiology, University of Tübingen, Tuebingen, Germany
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Leptihn S, Thompson JR, Ellory JC, Tucker SJ, Wallace MI. In vitro reconstitution of eukaryotic ion channels using droplet interface bilayers. J Am Chem Soc 2011; 133:9370-5. [PMID: 21591742 DOI: 10.1021/ja200128n] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The ability to routinely study eukaryotic ion channels in a synthetic lipid environment would have a major impact on our understanding of how different lipids influence ion channel function. Here, we describe a straightforward, detergent-free method for the in vitro reconstitution of eukaryotic ion channels and ionotropic receptors into droplet interface bilayers and measure their electrical activity at both the macroscopic and single-channel level. We explore the general applicability of this method by reconstitution of channels from a wide range of sources including recombinant cell lines and native tissues, as well as preparations that are difficult to study by conventional methods including erythrocytes and mitochondria.
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Affiliation(s)
- Sebastian Leptihn
- Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
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49
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Steffen P, Jung A, Nguyen DB, Müller T, Bernhardt I, Kaestner L, Wagner C. Stimulation of human red blood cells leads to Ca2+-mediated intercellular adhesion. Cell Calcium 2011; 50:54-61. [PMID: 21616535 DOI: 10.1016/j.ceca.2011.05.002] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2011] [Revised: 04/30/2011] [Accepted: 05/03/2011] [Indexed: 10/24/2022]
Abstract
Red blood cells (RBCs) are a major component of blood clots, which form physiologically as a response to injury or pathologically in thrombosis. The active participation of RBCs in thrombus solidification has been previously proposed but not yet experimentally proven. Holographic optical tweezers and single-cell force spectroscopy were used to study potential cell-cell adhesion between RBCs. Irreversible intercellular adhesion of RBCs could be induced by stimulation with lysophosphatidic acid (LPA), a compound known to be released by activated platelets. We identified Ca(2+) as an essential player in the signaling cascade by directly inducing Ca(2+) influx using A23187. Elevation of the internal Ca(2+) concentration leads to an intercellular adhesion of RBCs similar to that induced by LPA stimulation. Using single-cell force spectroscopy, the adhesion of the RBCs was identified to be approximately 100 pN, a value large enough to be of significance inside a blood clot or in pathological situations like the vasco-occlusive crisis in sickle cell disease patients.
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Affiliation(s)
- Patrick Steffen
- Experimental Physics Department, Saarland University, 66123 Saarbruecken, Germany
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50
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Thomas SL, Bouyer G, Cueff A, Egée S, Glogowska E, Ollivaux C. Ion channels in human red blood cell membrane: Actors or relics? Blood Cells Mol Dis 2011; 46:261-5. [DOI: 10.1016/j.bcmd.2011.02.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2011] [Accepted: 02/15/2011] [Indexed: 10/18/2022]
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