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Amoakon JP, Mylavarapu G, Amin RS, Naren AP. Pulmonary Vascular Dysfunctions in Cystic Fibrosis. Physiology (Bethesda) 2024; 39:0. [PMID: 38501963 DOI: 10.1152/physiol.00024.2023] [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: 11/16/2023] [Revised: 01/26/2024] [Accepted: 03/14/2024] [Indexed: 03/20/2024] Open
Abstract
Cystic fibrosis (CF) is an inherited disorder caused by a deleterious mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Given that the CFTR protein is a chloride channel expressed on a variety of cells throughout the human body, mutations in this gene impact several organs, particularly the lungs. For this very reason, research regarding CF disease and CFTR function has historically focused on the lung airway epithelium. Nevertheless, it was discovered more than two decades ago that CFTR is also expressed and functional on endothelial cells. Despite the great strides that have been made in understanding the role of CFTR in the airway epithelium, the role of CFTR in the endothelium remains unclear. Considering that the airway epithelium and endothelium work in tandem to allow gas exchange, it becomes very crucial to understand how a defective CFTR protein can impact the pulmonary vasculature and overall lung function. Fortunately, more recent research has been dedicated to elucidating the role of CFTR in the endothelium. As a result, several vascular dysfunctions associated with CF disease have come to light. Here, we summarize the current knowledge on pulmonary vascular dysfunctions in CF and discuss applicable therapies.
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Affiliation(s)
- Jean-Pierre Amoakon
- Department of Systems Biology and Physiology, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States
- Division of Pulmonary Medicine and Critical Care, Cedars-Sinai Medical Center, Los Angeles, California, United States
| | - Goutham Mylavarapu
- Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States
| | - Raouf S Amin
- Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States
| | - Anjaparavanda P Naren
- Department of Systems Biology and Physiology, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States
- Division of Pulmonary Medicine and Critical Care, Cedars-Sinai Medical Center, Los Angeles, California, United States
- Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States
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2
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Stanforth KJ, Zakhour MI, Chater PI, Wilcox MD, Adamson B, Robson NA, Pearson JP. The MUC2 Gene Product: Polymerisation and Post-Secretory Organisation-Current Models. Polymers (Basel) 2024; 16:1663. [PMID: 38932019 PMCID: PMC11207715 DOI: 10.3390/polym16121663] [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: 05/22/2024] [Revised: 06/03/2024] [Accepted: 06/10/2024] [Indexed: 06/28/2024] Open
Abstract
MUC2 mucin, the primary gel-forming component of intestinal mucus, is well researched and a model of polymerisation and post-secretory organisation has been published previously. Recently, several significant developments have been made which either introduce new ideas or challenge previous theories. New ideas include an overhaul of the MUC2 C-terminal globular structure which is proposed to harbour several previously unobserved domains, and include a site for an extra intermolecular disulphide bridge dimer between the cysteine 4379 of adjacent MUC2 C-termini. MUC2 polymers are also now thought to be secreted attached to the epithelial surface of goblet cells in the small intestine and removed following secretion via a metalloprotease meprin β-mediated cleavage of the von Willebrand D2 domain of the N-terminus. It remains unclear whether MUC2 forms intermolecular dimers, trimers, or both, at the N-termini during polymerisation, with several articles supporting either trimer or dimer formation. The presence of a firm inner mucus layer in the small intestine is similarly unclear. Considering this recent research, this review proposes an update to the previous model of MUC2 polymerisation and secretion, considers conflicting theories and data, and highlights the importance of this research to the understanding of MUC2 mucus layers in health and disease.
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Affiliation(s)
- Kyle J. Stanforth
- Aelius Biotech, The Medical School, Framlington Place, Newcastle-upon-Tyne NE2 4HH, UK; (P.I.C.); (M.D.W.); (B.A.); (N.A.R.)
| | - Maria I. Zakhour
- Biosciences Institute, Newcastle University Biosciences Institute, Catherine Cookson Building, Framlington Place, Newcastle-upon-Tyne NE2 4HH, UK; (M.I.Z.); (J.P.P.)
| | - Peter I. Chater
- Aelius Biotech, The Medical School, Framlington Place, Newcastle-upon-Tyne NE2 4HH, UK; (P.I.C.); (M.D.W.); (B.A.); (N.A.R.)
| | - Matthew D. Wilcox
- Aelius Biotech, The Medical School, Framlington Place, Newcastle-upon-Tyne NE2 4HH, UK; (P.I.C.); (M.D.W.); (B.A.); (N.A.R.)
| | - Beth Adamson
- Aelius Biotech, The Medical School, Framlington Place, Newcastle-upon-Tyne NE2 4HH, UK; (P.I.C.); (M.D.W.); (B.A.); (N.A.R.)
| | - Niamh A. Robson
- Aelius Biotech, The Medical School, Framlington Place, Newcastle-upon-Tyne NE2 4HH, UK; (P.I.C.); (M.D.W.); (B.A.); (N.A.R.)
| | - Jeffrey P. Pearson
- Biosciences Institute, Newcastle University Biosciences Institute, Catherine Cookson Building, Framlington Place, Newcastle-upon-Tyne NE2 4HH, UK; (M.I.Z.); (J.P.P.)
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Becker HM, Seidler UE. Bicarbonate secretion and acid/base sensing by the intestine. Pflugers Arch 2024; 476:593-610. [PMID: 38374228 PMCID: PMC11006743 DOI: 10.1007/s00424-024-02914-3] [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: 11/16/2023] [Revised: 01/15/2024] [Accepted: 01/17/2024] [Indexed: 02/21/2024]
Abstract
The transport of bicarbonate across the enterocyte cell membrane regulates the intracellular as well as the luminal pH and is an essential part of directional fluid movement in the gut. Since the first description of "active" transport of HCO3- ions against a concentration gradient in the 1970s, the fundamental role of HCO3- transport for multiple intestinal functions has been recognized. The ion transport proteins have been identified and molecularly characterized, and knockout mouse models have given insight into their individual role in a variety of functions. This review describes the progress made in the last decade regarding novel techniques and new findings in the molecular regulation of intestinal HCO3- transport in the different segments of the gut. We discuss human diseases with defects in intestinal HCO3- secretion and potential treatment strategies to increase luminal alkalinity. In the last part of the review, the cellular and organismal mechanisms for acid/base sensing in the intestinal tract are highlighted.
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Affiliation(s)
- Holger M Becker
- Department of Gastroenterology, Hannover Medical School, 30625, Hannover, Germany
| | - Ursula E Seidler
- Department of Gastroenterology, Hannover Medical School, 30625, Hannover, Germany.
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Zajac M, Jakiela S, Dolowy K. Understanding Bidirectional Water Transport across Bronchial Epithelial Cell Monolayers: A Microfluidic Approach. MEMBRANES 2023; 13:901. [PMID: 38132905 PMCID: PMC10744786 DOI: 10.3390/membranes13120901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Revised: 11/24/2023] [Accepted: 12/02/2023] [Indexed: 12/23/2023]
Abstract
Deciphering the dynamics of water transport across bronchial epithelial cell monolayers is pivotal for unraveling respiratory physiology and pathology. In this study, we employ an advanced microfluidic system to explore bidirectional water transport across 16HBE14σ bronchial epithelial cells. Previous experiments unveiled electroneutral multiple ion transport, with chloride ions utilizing transcellular pathways and sodium ions navigating both paracellular and transcellular routes. Unexpectedly, under isoosmotic conditions, rapid bidirectional movement of Na+ and Cl- was observed, leading to the hypothesis of a substantial transport of isoosmotic solution (145 mM NaCl) across cell monolayers. To validate this conjecture, we introduce an innovative microfluidic device, offering a 500-fold sensitivity improvement in quantifying fluid flow. This system enables the direct measurement of minuscule fluid volumes traversing cell monolayers with unprecedented precision. Our results challenge conventional models, indicating a self-regulating mechanism governing water transport that involves the CFTR channel and anion exchangers. In healthy subjects, equilibrium is achieved at an apical potential of Δφap = -30 mV, while subjects with cystic fibrosis exhibit modulation by an anion exchanger, reaching equilibrium at [Cl] = 67 mM in the airway surface liquid. This nuanced electrochemical basis for bidirectional water transport in bronchial epithelia sheds light on physiological intricacies and introduces a novel perspective for understanding respiratory conditions.
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Affiliation(s)
- Miroslaw Zajac
- Department of Physics and Biophysics, Institute of Biology, Warsaw University of Life Sciences, 02-776 Warsaw, Poland;
| | | | - Krzysztof Dolowy
- Department of Physics and Biophysics, Institute of Biology, Warsaw University of Life Sciences, 02-776 Warsaw, Poland;
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Cong S, Zhang J, Pan F, Pan L, Zhang A, Ma J. Research progress on ion channels and their molecular regulatory mechanisms in the human sperm flagellum. FASEB J 2023; 37:e23052. [PMID: 37352114 DOI: 10.1096/fj.202300756r] [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: 04/17/2023] [Revised: 06/06/2023] [Accepted: 06/09/2023] [Indexed: 06/25/2023]
Abstract
The ion channels in sperm tail play an important role in triggering key physiological reactions, e.g., progressive motility, hyperactivation, required for successful fertilization. Among them, CatSper and KSper have been shown to be important ion channels for the transport of Ca2+ and K+ . Moreover, the voltage-gated proton channel Hv1, the sperm-specific sodium-hydrogen exchanger (sNHE), the epithelial sodium channel (ENaC), members of the temperature-sensitive TRP channel family, and the cystic fibrosis transmembrane regulator (CFTR) are also found in the flagellum. This review focuses on the latest advances in ion channels located at the flagellum, describes how they affect sperm physiological function, and summarizes some primary mutual regulation mechanism between ion channels, including PH, membrane potential, and cAMP. These ion channels may be promising targets for clinical application in infertility.
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Affiliation(s)
- Shengnan Cong
- Obstetrics and Gynecology Department, Tongren Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, P.R. China
- Women's Hospital of Nanjing Medical University (Nanjing Maternity and Child Health Care Hospital), Nanjing, P.R. China
| | - Jingjing Zhang
- Women's Hospital of Nanjing Medical University (Nanjing Maternity and Child Health Care Hospital), Nanjing, P.R. China
| | - Feng Pan
- Women's Hospital of Nanjing Medical University (Nanjing Maternity and Child Health Care Hospital), Nanjing, P.R. China
| | - Lianjun Pan
- Women's Hospital of Nanjing Medical University (Nanjing Maternity and Child Health Care Hospital), Nanjing, P.R. China
| | - Aixia Zhang
- Women's Hospital of Nanjing Medical University (Nanjing Maternity and Child Health Care Hospital), Nanjing, P.R. China
| | - Jiehua Ma
- Obstetrics and Gynecology Department, Tongren Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, P.R. China
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Rehman T, Karp PH, Thurman AL, Mather SE, Jain A, Cooney AL, Sinn PL, Pezzulo AA, Duffey ME, Welsh MJ. WNK Inhibition Increases Surface Liquid pH and Host Defense in Cystic Fibrosis Airway Epithelia. Am J Respir Cell Mol Biol 2022; 67:491-502. [PMID: 35849656 PMCID: PMC9564924 DOI: 10.1165/rcmb.2022-0172oc] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Accepted: 07/18/2022] [Indexed: 02/05/2023] Open
Abstract
In cystic fibrosis (CF), reduced HCO3- secretion acidifies the airway surface liquid (ASL), and the acidic pH disrupts host defenses. Thus, understanding the control of ASL pH (pHASL) in CF may help identify novel targets and facilitate therapeutic development. In diverse epithelia, the WNK (with-no-lysine [K]) kinases coordinate HCO3- and Cl- transport, but their functions in airway epithelia are poorly understood. Here, we tested the hypothesis that WNK kinases regulate CF pHASL. In primary cultures of differentiated human airway epithelia, inhibiting WNK kinases acutely increased both CF and non-CF pHASL. This response was HCO3- dependent and involved downstream SPAK/OSR1 (Ste20/SPS1-related proline-alanine-rich protein kinase/oxidative stress responsive 1 kinase). Importantly, WNK inhibition enhanced key host defenses otherwise impaired in CF. Human airway epithelia expressed two WNK isoforms in secretory cells and ionocytes, and knockdown of either WNK1 or WNK2 increased CF pHASL. WNK inhibition decreased Cl- secretion and the response to bumetanide, an NKCC1 (sodium-potassium-chloride cotransporter 1) inhibitor. Surprisingly, bumetanide alone or basolateral Cl- substitution also alkalinized CF pHASL. These data suggest that WNK kinases influence the balance between transepithelial Cl- versus HCO3- secretion. Moreover, reducing basolateral Cl- entry may increase HCO3- secretion and raise pHASL, thereby improving CF host defenses.
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Affiliation(s)
| | - Philip H. Karp
- Department of Internal Medicine and
- Howard Hughes Medical Institute, University of Iowa, Iowa City, Iowa; and
| | | | | | | | | | | | | | - Michael E. Duffey
- Department of Physiology and Biophysics, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York
| | - Michael J. Welsh
- Department of Internal Medicine and
- Department of Molecular Physiology and Biophysics, Roy J. and Lucille A. Carver College of Medicine, and
- Howard Hughes Medical Institute, University of Iowa, Iowa City, Iowa; and
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Colonic Fluid and Electrolyte Transport 2022: An Update. Cells 2022; 11:cells11101712. [PMID: 35626748 PMCID: PMC9139964 DOI: 10.3390/cells11101712] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Revised: 05/16/2022] [Accepted: 05/17/2022] [Indexed: 01/25/2023] Open
Abstract
Colonic epithelial cells are responsible for maintaining a delicate balance between luminal secretion and the absorption of fluids and ions. This review aims to discuss and update the model of colonic electrolyte secretion and absorption via the cystic fibrosis transmembrane regulator (CFTR), epithelial sodium channel (ENaC), Na-K-Cl cotransporters (NKCC1 and 2), Na-H exchangers (NHE1–4), colonic H,KATPase, and several other key components involved in multi-level transepithelial ion transport. Developments in our understanding of the activity, regulation, localization, and relationships of these ion transporters and their interactions have helped forge a more robust understanding of colonic ion movement that accounts for the colonic epithelium’s role in mucosal pH modulation, the setting of osmotic gradients pivotal for fluid retention and secretion, and cell death regulation. Deviations from homeostatic ion transport cause diarrhea, constipation, and epithelial cell death and contribute to cystic fibrosis, irritable bowel syndrome (IBS), ulcerative colitis, and cancer pathologies. Signal transduction pathways that regulate electrolyte movement and the regulatory relationships between various sensors and transporters (CFTR as a target of CaSR regulation and as a regulator of ENaC and DRA, for example) are imperative aspects of a dynamic and comprehensive model of colonic ion homeostasis.
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Boyne K, Corey DA, Zhao P, Lu B, Boron WF, Moss FJ, Kelley TJ. Carbonic anhydrase and soluble adenylate cyclase regulation of cystic fibrosis cellular phenotypes. Am J Physiol Lung Cell Mol Physiol 2022; 322:L333-L347. [PMID: 34986321 PMCID: PMC8858677 DOI: 10.1152/ajplung.00022.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Several aspects of the cell biology of cystic fibrosis (CF) epithelial cells are altered including impaired lipid regulation, disrupted intracellular transport, and impaired microtubule regulation. It is unclear how the loss of cystic fibrosis transmembrane conductance regulator (CFTR) function leads to these differences. It is hypothesized that the loss of CFTR function leads to altered regulation of carbonic anhydrase (CA) activity resulting in cellular phenotypic changes. In this study, it is demonstrated that CA2 protein expression is reduced in CF model cells, primary mouse nasal epithelial (MNE) cells, excised MNE tissue, and primary human nasal epithelial cells (P < 0.05). This corresponds to a decrease in CA2 RNA expression measured by qPCR as well as an overall reduction in CA activity in primary CF MNEs. The addition of CFTR-inhibitor-172 to WT MNE cells for ≥24 h mimics the significantly lower protein expression of CA2 in CF cells. Treatment of CF cells with l-phenylalanine (L-Phe), an activator of CA activity, restores endosomal transport through an effect on microtubule regulation in a manner dependent on soluble adenylate cyclase (sAC). This effect can be blocked with the CA2-selective inhibitor dorzolamide. These data suggest that the loss of CFTR function leads to the decreased expression of CA2 resulting in the downstream cell signaling alterations observed in CF.
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Affiliation(s)
- Kathleen Boyne
- Division of Pulmonary and Sleep Medicine, Department of Pediatrics, Ann and Robert H. Lurie Children's Hospital of Chicago, Northwestern University, Feinberg School of Medicine, Chicago, IL, United States
| | - Deborah A Corey
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, United States
| | - Pan Zhao
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, United States
| | - Binyu Lu
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, United States
| | - Walter F Boron
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, United States.,Department of Medicine and Department of Biochemistry, Case Western Reserve University, Cleveland, OH, United States
| | - Fraser J Moss
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, United States
| | - Thomas J Kelley
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, United States
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Whittamore JM, Hatch M. Oxalate Flux Across the Intestine: Contributions from Membrane Transporters. Compr Physiol 2021; 12:2835-2875. [PMID: 34964122 DOI: 10.1002/cphy.c210013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Epithelial oxalate transport is fundamental to the role occupied by the gastrointestinal (GI) tract in oxalate homeostasis. The absorption of dietary oxalate, together with its secretion into the intestine, and degradation by the gut microbiota, can all influence the excretion of this nonfunctional terminal metabolite in the urine. Knowledge of the transport mechanisms is relevant to understanding the pathophysiology of hyperoxaluria, a risk factor in kidney stone formation, for which the intestine also offers a potential means of treatment. The following discussion presents an expansive review of intestinal oxalate transport. We begin with an overview of the fate of oxalate, focusing on the sources, rates, and locations of absorption and secretion along the GI tract. We then consider the mechanisms and pathways of transport across the epithelial barrier, discussing the transcellular, and paracellular components. There is an emphasis on the membrane-bound anion transporters, in particular, those belonging to the large multifunctional Slc26 gene family, many of which are expressed throughout the GI tract, and we summarize what is currently known about their participation in oxalate transport. In the final section, we examine the physiological stimuli proposed to be involved in regulating some of these pathways, encompassing intestinal adaptations in response to chronic kidney disease, metabolic acid-base disorders, obesity, and following gastric bypass surgery. There is also an update on research into the probiotic, Oxalobacter formigenes, and the basis of its unique interaction with the gut epithelium. © 2021 American Physiological Society. Compr Physiol 11:1-41, 2021.
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Affiliation(s)
- Jonathan M Whittamore
- Department of Pathology, Immunology and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Marguerite Hatch
- Department of Pathology, Immunology and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, Florida, USA
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Angyal D, Bijvelds MJC, Bruno MJ, Peppelenbosch MP, de Jonge HR. Bicarbonate Transport in Cystic Fibrosis and Pancreatitis. Cells 2021; 11:cells11010054. [PMID: 35011616 PMCID: PMC8750324 DOI: 10.3390/cells11010054] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2021] [Revised: 12/20/2021] [Accepted: 12/21/2021] [Indexed: 12/12/2022] Open
Abstract
CFTR, the cystic fibrosis (CF) gene-encoded epithelial anion channel, has a prominent role in driving chloride, bicarbonate and fluid secretion in the ductal cells of the exocrine pancreas. Whereas severe mutations in CFTR cause fibrosis of the pancreas in utero, CFTR mutants with residual function, or CFTR variants with a normal chloride but defective bicarbonate permeability (CFTRBD), are associated with an enhanced risk of pancreatitis. Recent studies indicate that CFTR function is not only compromised in genetic but also in selected patients with an acquired form of pancreatitis induced by alcohol, bile salts or smoking. In this review, we summarize recent insights into the mechanism and regulation of CFTR-mediated and modulated bicarbonate secretion in the pancreatic duct, including the role of the osmotic stress/chloride sensor WNK1 and the scaffolding protein IRBIT, and current knowledge about the role of CFTR in genetic and acquired forms of pancreatitis. Furthermore, we discuss the perspectives for CFTR modulator therapy in the treatment of exocrine pancreatic insufficiency and pancreatitis and introduce pancreatic organoids as a promising model system to study CFTR function in the human pancreas, its role in the pathology of pancreatitis and its sensitivity to CFTR modulators on a personalized basis.
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11
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Bijvelds MJC, Roos FJM, Meijsen KF, Roest HP, Verstegen MMA, Janssens HM, van der Laan LJW, de Jonge HR. Rescue of chloride and bicarbonate transport by elexacaftor-ivacaftor-tezacaftor in organoid-derived CF intestinal and cholangiocyte monolayers. J Cyst Fibros 2021; 21:537-543. [PMID: 34922851 DOI: 10.1016/j.jcf.2021.12.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 11/04/2021] [Accepted: 12/07/2021] [Indexed: 12/14/2022]
Abstract
BACKGROUND In cystic fibrosis (CF), loss of CF transmembrane conductance regulator (CFTR)-dependent bicarbonate secretion precipitates the accumulation of viscous mucus in the lumen of respiratory and gastrointestinal epithelial tissues. We investigated whether the combination of elexacaftor (ELX), ivacaftor (IVA) and tezacaftor (TEZ), apart from its well-documented effect on chloride transport, also restores Phe508del-CFTR-mediated bicarbonate transport. METHODS Epithelial monolayers were cultured from intestinal and biliary (cholangiocyte) organoids of homozygous Phe508del-CFTR patients and controls. Transcriptome sequencing was performed, and bicarbonate and chloride transport were assessed in the presence or absence of ELX/IVA/TEZ, using the intestinal current measurement technique. RESULTS ELX/IVA/TEZ markedly enhanced bicarbonate and chloride transport across intestinal epithelium. In biliary epithelium, it failed to enhance CFTR-mediated bicarbonate transport but effectively rescued CFTR-mediated chloride transport, known to be requisite for bicarbonate secretion through the chloride-bicarbonate exchanger AE2 (SLC4A2), which was highly expressed by cholangiocytes. Biliary but not intestinal epithelial cells expressed an alternative anion channel, anoctamin-1/TMEM16A (ANO1), and secreted bicarbonate and chloride upon purinergic receptor stimulation. CONCLUSIONS ELX/IVA/TEZ has the potential to restore both chloride and bicarbonate secretion across CF intestinal and biliary epithelia and may counter luminal hyper-acidification in these tissues.
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Affiliation(s)
- Marcel J C Bijvelds
- Department of Gastroenterology and Hepatology, Erasmus MC, University Medical Center Rotterdam, PO Box 2040, 3000CA Rotterdam, the Netherlands.
| | - Floris J M Roos
- Department of Surgery, Erasmus MC Transplant Institute, Erasmus MC, University Medical Center Rotterdam, PO Box 2040, 3000CA Rotterdam, the Netherlands
| | - Kelly F Meijsen
- Department of Gastroenterology and Hepatology, Erasmus MC, University Medical Center Rotterdam, PO Box 2040, 3000CA Rotterdam, the Netherlands
| | - Henk P Roest
- Department of Surgery, Erasmus MC Transplant Institute, Erasmus MC, University Medical Center Rotterdam, PO Box 2040, 3000CA Rotterdam, the Netherlands
| | - Monique M A Verstegen
- Department of Surgery, Erasmus MC Transplant Institute, Erasmus MC, University Medical Center Rotterdam, PO Box 2040, 3000CA Rotterdam, the Netherlands
| | - Hettie M Janssens
- Department of Pediatrics, Division of Respiratory Medicine and Allergology, Erasmus MC-Sophia Children's Hospital, Erasmus MC, University Medical Center Rotterdam, PO Box 2040, 3000CA Rotterdam, the Netherlands
| | - Luc J W van der Laan
- Department of Surgery, Erasmus MC Transplant Institute, Erasmus MC, University Medical Center Rotterdam, PO Box 2040, 3000CA Rotterdam, the Netherlands
| | - Hugo R de Jonge
- Department of Gastroenterology and Hepatology, Erasmus MC, University Medical Center Rotterdam, PO Box 2040, 3000CA Rotterdam, the Netherlands
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12
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Ion Channels, Transporters, and Sensors Interact with the Acidic Tumor Microenvironment to Modify Cancer Progression. Rev Physiol Biochem Pharmacol 2021; 182:39-84. [PMID: 34291319 DOI: 10.1007/112_2021_63] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Solid tumors, including breast carcinomas, are heterogeneous but typically characterized by elevated cellular turnover and metabolism, diffusion limitations based on the complex tumor architecture, and abnormal intra- and extracellular ion compositions particularly as regards acid-base equivalents. Carcinogenesis-related alterations in expression and function of ion channels and transporters, cellular energy levels, and organellar H+ sequestration further modify the acid-base composition within tumors and influence cancer cell functions, including cell proliferation, migration, and survival. Cancer cells defend their cytosolic pH and HCO3- concentrations better than normal cells when challenged with the marked deviations in extracellular H+, HCO3-, and lactate concentrations typical of the tumor microenvironment. Ionic gradients determine the driving forces for ion transporters and channels and influence the membrane potential. Cancer and stromal cells also sense abnormal ion concentrations via intra- and extracellular receptors that modify cancer progression and prognosis. With emphasis on breast cancer, the current review first addresses the altered ion composition and the changes in expression and functional activity of ion channels and transporters in solid cancer tissue. It then discusses how ion channels, transporters, and cellular sensors under influence of the acidic tumor microenvironment shape cancer development and progression and affect the potential of cancer therapies.
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13
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Manneck D, Manz G, Braun HS, Rosendahl J, Stumpff F. The TRPA1 Agonist Cinnamaldehyde Induces the Secretion of HCO 3- by the Porcine Colon. Int J Mol Sci 2021; 22:ijms22105198. [PMID: 34068986 PMCID: PMC8156935 DOI: 10.3390/ijms22105198] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 05/09/2021] [Accepted: 05/10/2021] [Indexed: 02/07/2023] Open
Abstract
A therapeutic potential of the TRPA1 channel agonist cinnamaldehyde for use in inflammatory bowel disease is emerging, but the mechanisms are unclear. Semi-quantitative qPCR of various parts of the porcine gastrointestinal tract showed that mRNA for TRPA1 was highest in the colonic mucosa. In Ussing chambers, 1 mmol·L-1 cinnamaldehyde induced increases in short circuit current (ΔIsc) and conductance (ΔGt) across the colon that were higher than those across the jejunum or after 1 mmol·L-1 thymol. Lidocaine, amiloride or bumetanide did not change the response. The application of 1 mmol·L-1 quinidine or the bilateral replacement of 120 Na+, 120 Cl- or 25 HCO3- reduced ΔGt, while the removal of Ca2+ enhanced ΔGt with ΔIsc numerically higher. ΔIsc decreased after 0.5 NPPB, 0.01 indometacin and the bilateral replacement of 120 Na+ or 25 HCO3-. The removal of 120 Cl- had no effect. Cinnamaldehyde also activates TRPV3, but comparative measurements involving patch clamp experiments on overexpressing cells demonstrated that much higher concentrations are required. We suggest that cinnamaldehyde stimulates the secretion of HCO3- via apical CFTR and basolateral Na+-HCO3- cotransport, preventing acidosis and damage to the epithelium and the colonic microbiome. Signaling may involve the opening of TRPA1, depolarization of the epithelium and a rise in PGE2 following a lower uptake of prostaglandins via OATP2A1.
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Affiliation(s)
- David Manneck
- Department of Veterinary Medicine, Institute of Veterinary Physiology, Freie Universität Berlin, Oertzenweg 19b, 14163 Berlin, Germany; (D.M.); (G.M.)
| | - Gisela Manz
- Department of Veterinary Medicine, Institute of Veterinary Physiology, Freie Universität Berlin, Oertzenweg 19b, 14163 Berlin, Germany; (D.M.); (G.M.)
| | - Hannah-Sophie Braun
- PerformaNat GmbH, Hohentwielsteig 6, 14163 Berlin, Germany; (H.-S.B.); (J.R.)
| | - Julia Rosendahl
- PerformaNat GmbH, Hohentwielsteig 6, 14163 Berlin, Germany; (H.-S.B.); (J.R.)
| | - Friederike Stumpff
- Department of Veterinary Medicine, Institute of Veterinary Physiology, Freie Universität Berlin, Oertzenweg 19b, 14163 Berlin, Germany; (D.M.); (G.M.)
- Correspondence: ; Tel.: +49-30-838-62595
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14
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Roos FJM, Bijvelds MJC, Verstegen MMA, Roest HP, Metselaar HJ, Polak WG, Jonge HRD, IJzermans JNM, van der Laan LJW. Impact of hypoxia and AMPK on CFTR-mediated bicarbonate secretion in human cholangiocyte organoids. Am J Physiol Gastrointest Liver Physiol 2021; 320:G741-G752. [PMID: 33655768 DOI: 10.1152/ajpgi.00389.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Cholangiocytes express cystic fibrosis transmembrane conductance regulator (CFTR), which is involved in bicarbonate secretion for the protection against bile toxicity. During liver transplantation, prolonged hypoxia of the graft is associated with cholangiocyte loss and biliary complications. Hypoxia is known to diminish CFTR activity in the intestine, but whether it affects CFTR activity in cholangiocytes remains unknown. Thus, the aim of this study is to investigate the effect of hypoxia on CFTR activity in intrahepatic cholangiocyte organoids (ICOs) and test drug interventions to restore bicarbonate secretion. Fifteen different human ICOs were cultured as monolayers and ion channel [CFTR and anoctamin-1 (ANO1)] activity was determined using an Ussing chamber assay with or without AMP kinase (AMPK) inhibitor under hypoxic and oxygenated conditions. Bile toxicity was tested by apical exposure of cells to fresh human bile. Overall gene expression analysis showed a high similarity between ICOs and primary cholangiocytes. Under oxygenated conditions, both CFTR and ANO1 channels were responsible for forskolin and uridine-5'-triphosphate (UTP) UTP-activated anion secretion. Forskolin stimulation in the absence of intracellular chloride showed ion transport, indicating that bicarbonate could be secreted by CFTR. During hypoxia, CFTR activity significantly decreased (P = 0.01). Switching from oxygen to hypoxia during CFTR measurements reduced CFTR activity (P = 0.03). Consequently, cell death increased when ICO monolayers were exposed to bile during hypoxia compared with oxygen (P = 0.04). Importantly, addition of AMPK inhibitor restored CFTR-mediated anion secretion during hypoxia. ICOs provide an excellent model to study cholangiocyte anion channels and drug-related interventions. Here, we demonstrate that hypoxia affects cholangiocyte ion secretion, leaving cholangiocytes vulnerable to bile toxicity. The mechanistic insights from this model maybe relevant for hypoxia-related biliary injury during liver transplantation.NEW & NOTEWORTHY The previously described liver-derived organoids resemble primary cholangiocytes and should be properly named intrahepatic cholangiocyte organoids (ICOs). ICOs have functional cholangiocyte ion channels (CFTR and ANO1). CFTR might be able to secrete bicarbonate directly into the bile duct lumen. Hypoxia inhibits CFTR and ANO1 functionality in ICOs, which can partially be restored by addition of an AMP kinase inhibitor. Hypoxia impairs cholangiocyte resistance against cytotoxic effects of bile, resulting in increased cell death.
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Affiliation(s)
- Floris J M Roos
- Department of Surgery, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Marcel J C Bijvelds
- Department of Gastroenterology and Hepatology, Erasmus Medical Center, Rotterdam, The Netherlands
| | | | - Henk P Roest
- Department of Surgery, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Herold J Metselaar
- Department of Gastroenterology and Hepatology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Wojciech G Polak
- Division of Hepato-Pancreato-Biliary and Transplant Surgery, Department of Surgery, Erasmus Medical Center, University Medical Center Rotterdam, Transplant Institute, Rotterdam, The Netherlands
| | - Hugo R de Jonge
- Department of Gastroenterology and Hepatology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Jan N M IJzermans
- Department of Surgery, Erasmus Medical Center, Rotterdam, The Netherlands
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15
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Role of pirfenidone in TGF-β pathways and other inflammatory pathways in acute respiratory syndrome coronavirus 2 (SARS-Cov-2) infection: a theoretical perspective. Pharmacol Rep 2021; 73:712-727. [PMID: 33880743 PMCID: PMC8057922 DOI: 10.1007/s43440-021-00255-x] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 03/14/2021] [Accepted: 03/23/2021] [Indexed: 12/13/2022]
Abstract
Background Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes pulmonary injury or multiple-organ injury by various pathological pathways. Transforming growth factor-beta (TGF-β) is a key factor that is released during SARS-CoV-2 infection. TGF-β, by internalization of the epithelial sodium channel (ENaC), suppresses the anti-oxidant system, downregulates the cystic fibrosis transmembrane conductance regulator (CFTR), and activates the plasminogen activator inhibitor 1 (PAI-1) and nuclear factor-kappa-light-chain-enhancer of activated B cells (NF-kB). These changes cause inflammation and lung injury along with coagulopathy. Moreover, reactive oxygen species play a significant role in lung injury, which levels up during SARS-CoV-2 infection. Drug Suggestion Pirfenidone is an anti-fibrotic drug with an anti-oxidant activity that can prevent lung injury during SARS-CoV-2 infection by blocking the maturation process of transforming growth factor-beta (TGF-β) and enhancing the protective role of peroxisome proliferator-activated receptors (PPARs). Pirfenidone is a safe drug for patients with hypertension or diabetes and its side effect tolerated well. Conclusion The drug as a theoretical perspective may be an effective and safe choice for suppressing the inflammatory response during COVID-19. The recommendation would be a combination of pirfenidone and N-acetylcysteine to achieve maximum benefit during SARS-CoV-2 treatment.
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16
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Dabaghi M, Saraei N, Xu G, Chandiramohan A, Yeung J, Nguyen JP, Vukmirovic M, Selvaganapathy PR, Hirota JA. PHAIR: a biosensor for pH measurement in air-liquid interface cell culture. Sci Rep 2021; 11:3477. [PMID: 33568708 PMCID: PMC7875988 DOI: 10.1038/s41598-021-83189-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 01/28/2021] [Indexed: 01/30/2023] Open
Abstract
In many biological systems, pH can be used as a parameter to understand and study cell dynamics. However, measuring pH in live cell culture is limited by the sensor ion specificity, proximity to the cell surface, and scalability. Commercially available pH sensors are difficult to integrate into a small-scale cell culture system due to their size and are not cost-effective for disposable use. We made PHAIR-a new pH sensor that uses a micro-wire format to measure pH in vitro human airway cell culture. Tungsten micro-wires were used as the working electrodes, and silver micro-wires with a silver/silver chloride coating were used as a pseudo reference electrode. pH sensitivity, in a wide and narrow range, and stability of these sensors were tested in common standard buffer solutions as well as in culture media of human airway epithelial cells grown at the air-liquid interface in a 24 well cell culture plate. When measuring the pH of cells grown under basal and challenge conditions using PHAIR, cell viability and cytokine responses were not affected. Our results confirm that micro-wire-based sensors have the capacity for miniaturization and detection of diverse ions while maintaining sensitivity. This suggests the broad application of PHAIR in various biological experimental settings.
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Affiliation(s)
- Mohammadhossein Dabaghi
- Firestone Institute for Respiratory Health-Division of Respirology, Department of Medicine, McMaster University, Hamilton, ON, L8N 4A6, Canada
| | - Neda Saraei
- Firestone Institute for Respiratory Health-Division of Respirology, Department of Medicine, McMaster University, Hamilton, ON, L8N 4A6, Canada
| | - Gang Xu
- Firestone Institute for Respiratory Health-Division of Respirology, Department of Medicine, McMaster University, Hamilton, ON, L8N 4A6, Canada
| | - Abiram Chandiramohan
- Firestone Institute for Respiratory Health-Division of Respirology, Department of Medicine, McMaster University, Hamilton, ON, L8N 4A6, Canada
| | - Jonas Yeung
- Department of Mechanical Engineering, McMaster University, Hamilton, ON, L8S 4L7, Canada
| | - Jenny P Nguyen
- Firestone Institute for Respiratory Health-Division of Respirology, Department of Medicine, McMaster University, Hamilton, ON, L8N 4A6, Canada
| | - Milica Vukmirovic
- Firestone Institute for Respiratory Health-Division of Respirology, Department of Medicine, McMaster University, Hamilton, ON, L8N 4A6, Canada
| | - Ponnambalam Ravi Selvaganapathy
- Department of Mechanical Engineering, McMaster University, Hamilton, ON, L8S 4L7, Canada
- School of Biomedical Engineering, McMaster University, Hamilton, ON, L8S 4K1, Canada
| | - Jeremy A Hirota
- Firestone Institute for Respiratory Health-Division of Respirology, Department of Medicine, McMaster University, Hamilton, ON, L8N 4A6, Canada.
- School of Biomedical Engineering, McMaster University, Hamilton, ON, L8S 4K1, Canada.
- Department of Pathology and Molecular Medicine, McMaster Immunology Research Centre, McMaster University, Hamilton, ON, L8S 4K1, Canada.
- Division of Respiratory Medicine, Department of Medicine, University of British Columbia, Vancouver, BC, V6H 3Z6, Canada.
- Department of Biology, University of Waterloo, Waterloo, ON, N2L 3G1, Canada.
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17
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Jaques R, Shakeel A, Hoyle C. Novel therapeutic approaches for the management of cystic fibrosis. Multidiscip Respir Med 2020; 15:690. [PMID: 33282281 PMCID: PMC7706361 DOI: 10.4081/mrm.2020.690] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 11/06/2020] [Indexed: 12/19/2022] Open
Abstract
Cystic fibrosis (CF) is a genetic condition characterised by the build-up of thick, sticky mucus that can damage many of the body's organs. It is a life-long disease that results in a shortened life expectancy, often due to the progression of advanced lung disease. Treatment has previously targeted the downstream symptoms such as diminished mucus clearance and recurrent infection. More recently, significant advances have been made in treating the cause of the disease by targeting the faulty gene responsible. Hope for the development of potential therapies lies with ongoing research into new pharmacological agents and gene therapy. This review gives an overview of CF, and summarises the current evidence regarding the disease management and upcoming strategies aimed at treating or potentially curing this condition.
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Affiliation(s)
- Ryan Jaques
- Centre for Atherothrombosis and Metabolic Disease, Hull York Medical School, University of Hull, UK
| | - Arslan Shakeel
- Centre for Atherothrombosis and Metabolic Disease, Hull York Medical School, University of Hull, UK
| | - Cameron Hoyle
- Centre for Atherothrombosis and Metabolic Disease, Hull York Medical School, University of Hull, UK
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18
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Adewale AT, Falk Libby E, Fu L, Lenzie A, Boitet ER, Birket SE, Petty CF, Johns JD, Mazur M, Tearney GJ, Copeland D, Durham C, Rowe SM. Novel Therapy of Bicarbonate, Glutathione, and Ascorbic Acid Improves Cystic Fibrosis Mucus Transport. Am J Respir Cell Mol Biol 2020; 63:362-373. [PMID: 32374624 DOI: 10.1165/rcmb.2019-0287oc] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Defective airway mucus clearance is a defining characteristic of cystic fibrosis lung disease, and improvements to current mucolytic strategies are needed. Novel approaches targeting a range of contributing mechanisms are in various stages of preclinical and clinical development. ARINA-1 is a new nebulized product comprised of ascorbic acid, glutathione, and bicarbonate. Using microoptical coherence tomography, we tested the effect of ARINA-1 on central features of mucociliary clearance in F508del/F508del primary human bronchial epithelial cells to assess its potential as a mucoactive therapy in cystic fibrosis. We found that ARINA-1 significantly augmented mucociliary transport rates, both alone and with CFTR (cystic fibrosis transmembrane conductance regulator) modulator therapy, whereas airway hydration and ciliary beating were largely unchanged compared with PBS vehicle control. Analysis of mucus reflectivity and particle-tracking microrheology indicated that ARINA-1 restores mucus clearance by principally reducing mucus layer viscosity. The combination of bicarbonate and glutathione elicited increases in mucociliary transport rate comparable to those seen with ARINA-1, indicating the importance of this interaction to the impact of ARINA-1 on mucus transport; this effect was not recapitulated with bicarbonate alone or bicarbonate combined with ascorbic acid. Assessment of CFTR chloride transport revealed an increase in CFTR-mediated chloride secretion in response to ARINA-1 in CFBE41o- cells expressing wild-type CFTR, driven by CFTR activity stimulation by ascorbate. This response was absent in CFBE41o- F508del cells treated with VX-809 and primary human bronchial epithelial cells, implicating CFTR-independent mechanisms for the effect of ARINA-1 on cystic fibrosis mucus. Together, these studies indicate that ARINA-1 is a novel potential therapy for the treatment of impaired mucus clearance in cystic fibrosis.
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Affiliation(s)
| | | | - Lianwu Fu
- Department of Cellular, Developmental, and Integrative Biology.,Department of Pediatrics, and
| | | | | | - Susan E Birket
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | | | | | | | - Guillermo J Tearney
- Wellman Center for Photomedicine and.,Department of Pathology, Massachusetts General Hospital, Boston, Massachusetts.,Harvard Medical School, Boston, Massachusetts.,Harvard-MIT Division of Health Sciences and Technology, Cambridge, Massachusetts; and
| | | | | | - Steven M Rowe
- Cystic Fibrosis Research Center.,Department of Cellular, Developmental, and Integrative Biology.,Department of Pediatrics, and.,Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
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19
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The first report on immunoglobulins A, E, G and M levels in cystic fibrosis patients in Saudi Arabia. Saudi J Biol Sci 2020; 27:2617-2621. [PMID: 32994719 PMCID: PMC7499114 DOI: 10.1016/j.sjbs.2020.05.041] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Revised: 05/22/2020] [Accepted: 05/23/2020] [Indexed: 12/22/2022] Open
Abstract
Background Previous reports have shown that pulmonary and systemic hypergamma-globulinemia in CF patients is a reflection of chronic pulmonary infection. Infection with Pseudomonas aeruginosa is known to have major prognostic significance in patients CF. This study aims to identify the incidence of immunoglobulins (especially: IgG, and IgE) in a cohort of CF patients. Methods A total of 297 patients recruited all over the country’s region for this study were a as part of the CF registry data from 1st January 1984 to 1st June 2016. All patients had their immunoglobulin levels measured by enzyme link immunosorbent assay (ELISA) in 3 stages, at presentation and two follow-ups. Results Of the 297 patients recruited, 139 (46.8%) were males while 158 (53.2%) were females. IgA and IgM levels were found not to have risen above the previously reported levels in healthy individuals in all stages. On the contrary, IgE level increased from 209.51 ± 32.30 KU/L to 303.58 ± 37.11 KU/L from baseline to stage 3 while IgG level rose from 12.26 ± 0.43 mg/mL to 17.17 ± 1.68 mg/mL for baseline and stage 3 respectively all above previously reported levels in healthy individuals. Conclusion This study establishes a potential for the use of IgE and IgG in disease diagnosis as well as the prognostic implications. However, further study is needed to identify the role of infection or medications in relation to the rise of both IgE and IgG with advancement of age and progression of disease severity which may inherently confound the observed results.
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20
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Wang Y, Zhao J, Cai Y, Ballard HJ. Cystic fibrosis transmembrane conductance regulator-dependent bicarbonate entry controls rat cardiomyocyte ATP release via pannexin1 through mitochondrial signalling and caspase activation. Acta Physiol (Oxf) 2020; 230:e13495. [PMID: 32386453 DOI: 10.1111/apha.13495] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Revised: 04/27/2020] [Accepted: 05/01/2020] [Indexed: 12/20/2022]
Abstract
AIM Cystic fibrosis transmembrane conductance regulator (CFTR) is expressed in the heart, but its function there is unclear. CFTR regulates an ATP release pore in many tissues, but the identity and regulatory mechanism of the pore are unknown. We investigated the role of CFTR in ATP release from primary cardiomyocytes and ventricular wall in vivo. METHODS Proteins involved in the signalling pathway for ATP release during simulated ischaemia (lactic acid treatment) were investigated using inhibitors and siRNA; colocalization was identified by coimmunofluorescence and proximity ligation assays; changes in near-membrane pH and calcium were identified with total internal reflection microscopy; in vivo ATP release was investigated using interstitial microdialysis of rat heart. RESULTS Lactic acid-induced CFTR-dependent ATP release from cultured cardiomyocytes and left ventricle in vivo. Lactic acid entry elevated near-membrane calcium, which involved Na/H- and Na/Ca-exchangers colocalized with CFTR. Calcium entry-induced CFTR activation, which involved cAMP, protein kinase A, FAK, Pyk2 and Src. Removal of extracellular bicarbonate abolished cardiomyocyte ATP release induced by lactic acid or CFTR activators. Bicarbonate stimulated cytochrome c expression, cytochrome c release and ATP release from isolated cardiomyocyte mitochondria. Pannexin 1 (Panx1) colocalized with CFTR. Lactic acid increased cardiomyocyte caspase activity: caspase inhibitors or Panx1 siRNA abolished cardiomyocyte ATP release, while pannexin inhibition abolished cardiac ATP release in vivo. CONCLUSION During simulated ischaemia, CFTR-dependent bicarbonate entry stimulated ATP and cytochrome c release from mitochondria; in the cytoplasm, cytochrome c-activated caspase 3, which in turn activated Panx1, and ATP was released through the opened Panx1 channel.
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Affiliation(s)
- Yongshun Wang
- School of Biomedical Sciences The University of Hong Kong Pokfulam Hong Kong
| | - Junjun Zhao
- School of Biomedical Sciences The University of Hong Kong Pokfulam Hong Kong
| | - Yin Cai
- Department of Anaesthesiology The University of Hong Kong Pokfulam Hong Kong
| | - Heather J. Ballard
- School of Biomedical Sciences The University of Hong Kong Pokfulam Hong Kong
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21
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Shin DH, Kim M, Kim Y, Jun I, Jung J, Nam JH, Cheng MH, Lee MG. Bicarbonate permeation through anion channels: its role in health and disease. Pflugers Arch 2020; 472:1003-1018. [PMID: 32621085 DOI: 10.1007/s00424-020-02425-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 06/19/2020] [Accepted: 06/26/2020] [Indexed: 12/31/2022]
Abstract
Many anion channels, frequently referred as Cl- channels, are permeable to different anions in addition to Cl-. As the second-most abundant anion in the human body, HCO3- permeation via anion channels has many important physiological roles. In addition to its classical role as an intracellular pH regulator, HCO3- also controls the activity and stability of dissolved proteins in bodily fluids such as saliva, pancreatic juice, intestinal fluid, and airway surface liquid. Moreover, HCO3- permeation through these channels affects membrane potentials that are the driving forces for transmembrane transport of solutes and water in epithelia and affect neuronal excitability in nervous tissue. Consequently, aberrant HCO3- transport via anion channels causes a number of human diseases in respiratory, gastrointestinal, genitourinary, and neuronal systems. Notably, recent studies have shown that the HCO3- permeabilities of several anion channels are not fixed and can be altered by cellular stimuli, findings which may have both physiological and pathophysiological significance. In this review, we summarize recent progress in understanding the molecular mechanisms and the physiological roles of HCO3- permeation through anion channels. We hope that the present discussions can stimulate further research into this very important topic, which will provide the basis for human disorders associated with aberrant HCO3- transport.
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Affiliation(s)
- Dong Hoon Shin
- Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, 03722, South Korea
| | - Minjae Kim
- Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, 03722, South Korea
| | - Yonjung Kim
- Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, 03722, South Korea
| | - Ikhyun Jun
- Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, 03722, South Korea
- The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, 03722, South Korea
| | - Jinsei Jung
- Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, 03722, South Korea
- Department of Otorhinolaryngology, Yonsei University College of Medicine, Seoul, 03722, South Korea
| | - Joo Hyun Nam
- Department of Physiology, Dongguk University College of Medicine, 123 Dongdae-ro, Kyungju, 780-714, Republic of Korea
| | - Mary Hongying Cheng
- Department of Computational & Systems Biology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Min Goo Lee
- Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, 03722, South Korea.
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22
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Correctors modify the bicarbonate permeability of F508del-CFTR. Sci Rep 2020; 10:8440. [PMID: 32439937 PMCID: PMC7242338 DOI: 10.1038/s41598-020-65287-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Accepted: 04/29/2020] [Indexed: 01/17/2023] Open
Abstract
One of the most common mutations in Cystic Fibrosis (CF) patients is the deletion of the amino acid phenylalanine at position 508. This mutation causes both the protein trafficking defect and an early degradation. Over time, small molecules, called correctors, capable of increasing the amount of mutated channel in the plasma membrane and causing an increase in its transport activity have been developed. This study shows that incubating in vitro cells permanently transfected with the mutated channel with the correctors VX809, VX661 and Corr4a, and the combination of VX809 and Corr4a, a recovery of anion transport activity is observed. Interestingly, the permeability of bicarbonate increases in the cells containing corrected p.F508del CFTR channels is greater than the increase of the halide permeability. These different increases of the permeability of bicarbonate and halides are consistent with the concept that the structural conformation of the pore of the corrector-rescued p.F508del channels would be different than the normal wild type CFTR protein.
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23
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Stillhart C, Vučićević K, Augustijns P, Basit AW, Batchelor H, Flanagan TR, Gesquiere I, Greupink R, Keszthelyi D, Koskinen M, Madla CM, Matthys C, Miljuš G, Mooij MG, Parrott N, Ungell AL, de Wildt SN, Orlu M, Klein S, Müllertz A. Impact of gastrointestinal physiology on drug absorption in special populations––An UNGAP review. Eur J Pharm Sci 2020; 147:105280. [DOI: 10.1016/j.ejps.2020.105280] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2019] [Revised: 02/10/2020] [Accepted: 02/24/2020] [Indexed: 02/07/2023]
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Measurement of Multi Ion Transport through Human Bronchial Epithelial Cell Line Provides an Insight into the Mechanism of Defective Water Transport in Cystic Fibrosis. MEMBRANES 2020; 10:membranes10030043. [PMID: 32178452 PMCID: PMC7142439 DOI: 10.3390/membranes10030043] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 03/02/2020] [Accepted: 03/09/2020] [Indexed: 12/28/2022]
Abstract
We measured concentration changes of sodium, potassium, chloride ions, pH and the transepithelial potential difference by means of ion-selective electrodes, which were placed on both sides of a human bronchial epithelial 16HBE14σ cell line grown on a porous support in the presence of ion channel blockers. We found that, in the isosmotic transepithelial concentration gradient of either sodium or chloride ions, there is an electroneutral transport of the isosmotic solution of sodium chloride in both directions across the cell monolayer. The transepithelial potential difference is below 3 mV. Potassium and pH change plays a minor role in ion transport. Based on our measurements, we hypothesize that in a healthy bronchial epithelium, there is a dynamic balance between water absorption and secretion. Water absorption is caused by the action of two exchangers, Na/H and Cl/HCO3, secreting weakly dissociated carbonic acid in exchange for well dissociated NaCl and water. The water secretion phase is triggered by an apical low volume-dependent factor opening the Cystic Fibrosis Transmembrane Regulator CFTR channel and secreting anions that are accompanied by paracellular sodium and water transport.
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25
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Day BJ, Bratcher PE, Chandler JD, Kilgore MB, Min E, LiPuma JJ, Hondal RJ, Nichols DP. The thiocyanate analog selenocyanate is a more potent antimicrobial pro-drug that also is selectively detoxified by the host. Free Radic Biol Med 2020; 146:324-332. [PMID: 31740228 PMCID: PMC6951815 DOI: 10.1016/j.freeradbiomed.2019.11.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2019] [Revised: 11/04/2019] [Accepted: 11/13/2019] [Indexed: 11/17/2022]
Abstract
A hallmark of cystic fibrosis (CF) lung pathology is an increased susceptibility to pulmonary infections. Thiocyanate (-SCN) is an endogenous component of the innate immunity's peroxidase system that converts -SCN to the antimicrobial agent hypothiocyanite (HOSCN). We have previously shown that the host thioredoxin reductase (TrxR), but not the pathogen's TrxR, can selectively detoxify HOSCN thereby decreasing inflammation and oxidative stress. We tested whether the -SCN analog selenocyanate (-SeCN) shares these properties against several clinical CF bacterial isolates. We examined oxidant production from a lactoperoxidase (LPO) system using -SeCN as a potential substrate. The LPO system generated an oxidant similar in nature to HOSCN and consistent with being HOSeCN. The rate of oxidant generation using -SeCN was significantly less than seen for -SCN. An LPO system was used to generate HOSCN or HOSeCN and compared for antimicrobial activity during in situ exposure of clinical CF isolates of P. aeruginosa (PA), B. cepacia complex (BCC), and methicillin-resistant S. aureus (MRSA) obtained from CF sputum samples. Bacterial viability was assessed by colony forming units. Selective detoxification of HOSeCN was determined by comparing its metabolism by mammalian thioredoxin reductase (TrxR) to bacterial TrxR following the consumption of NADPH. We also assessed potential toxicity of equivalent HOSeCN generation, which demonstrated in situ antimicrobial activity, in human bronchial epithelial cells with a cell viability assay. The -SeCN/HOSeCN system was much more potent than -SCN/HOSCN system at killing PA, BCC and MRSA isolates. The -SeCN/HOSeCN system was more effective at killing -SCN/HOSCN resistant isolates. Mammalian TrxR selectively detoxified HOSeCN whereas the bacterial TrxR enzyme showed little activity. Human bronchial epithelial cells exposed to equivalent flux of HOSeCN that killed several CF pathogens showed no decrease in viability. -SeCN may be an effective therapeutic for the treatment of CF lung pathogens that are difficult to treat with current antibiotics.
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Affiliation(s)
- Brian J Day
- Department of Medicine, National Jewish Health, Denver, CO, 80206, USA; Department of Medicine University of Colorado, Aurora, CO, 80045, USA; Department of Pharmaceutical Sciences, University of Colorado, Aurora, CO, 80045, USA.
| | - Preston E Bratcher
- Department of Pediatrics, National Jewish Health, Denver, CO, 80206, USA
| | - Joshua D Chandler
- Department of Pediatrics, Emory University, Atlanta, GA, 30322, USA; Center for CF and Airways Disease Research, Children's Healthcare of Atlanta, Atlanta, GA, 30322, USA
| | - Matthew B Kilgore
- Department of Pediatrics, Emory University, Atlanta, GA, 30322, USA; Center for CF and Airways Disease Research, Children's Healthcare of Atlanta, Atlanta, GA, 30322, USA
| | - Elysia Min
- Department of Medicine, National Jewish Health, Denver, CO, 80206, USA
| | - John J LiPuma
- Department of Pediatrics, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Robert J Hondal
- Department of Biochemistry, University of Vermont, Burlington, VT, 05405, USA
| | - David P Nichols
- Department of Pediatrics, University of Washington, Seattle, WA, 98105, USA
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26
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Kim Y, Jun I, Shin DH, Yoon JG, Piao H, Jung J, Park HW, Cheng MH, Bahar I, Whitcomb DC, Lee MG. Regulation of CFTR Bicarbonate Channel Activity by WNK1: Implications for Pancreatitis and CFTR-Related Disorders. Cell Mol Gastroenterol Hepatol 2019; 9:79-103. [PMID: 31561038 PMCID: PMC6889609 DOI: 10.1016/j.jcmgh.2019.09.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 09/16/2019] [Accepted: 09/17/2019] [Indexed: 12/28/2022]
Abstract
BACKGRAOUD & AIMS Aberrant epithelial bicarbonate (HCO3-) secretion caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene is associated with several diseases including cystic fibrosis and pancreatitis. Dynamically regulated ion channel activity and anion selectivity of CFTR by kinases sensitive to intracellular chloride concentration ([Cl-]i) play an important role in epithelial HCO3- secretion. However, the molecular mechanisms of how [Cl-]i-dependent mechanisms regulate CFTR are unknown. METHODS We examined the mechanisms of the CFTR HCO3- channel regulation by [Cl-]i-sensitive kinases using an integrated electrophysiological, molecular, and computational approach including whole-cell, outside-out, and inside-out patch clamp recordings and molecular dissection of WNK1 and CFTR proteins. In addition, we analyzed the effects of pancreatitis-causing CFTR mutations on the WNK1-mediated regulation of CFTR. RESULTS Among the WNK1, SPAK, and OSR1 kinases that constitute a [Cl-]i-sensitive kinase cascade, the expression of WNK1 alone was sufficient to increase the CFTR bicarbonate permeability (PHCO3/PCl) and conductance (GHCO3) in patch clamp recordings. Molecular dissection of the WNK1 domains revealed that the WNK1 kinase domain is responsible for CFTR PHCO3/PCl regulation by direct association with CFTR, while the surrounding N-terminal regions mediate the [Cl-]i-sensitivity of WNK1. Furthermore, the pancreatitis-causing R74Q and R75Q mutations in the elbow helix 1 of CFTR hampered WNK1-CFTR physical associations and reduced WNK1-mediated CFTR PHCO3/PCl regulation. CONCLUSION The CFTR HCO3- channel activity is regulated by [Cl-]i and a WNK1-dependent mechanism. Our results provide new insights into the regulation of the ion selectivity of CFTR and the pathogenesis of CFTR-related disorders.
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Affiliation(s)
- Yonjung Kim
- Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, Korea
| | - Ikhyun Jun
- Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, Korea,Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea
| | - Dong Hoon Shin
- Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, Korea
| | - Jihoon G. Yoon
- Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, Korea
| | - He Piao
- Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, Korea
| | - Jinsei Jung
- Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, Korea,Department of Otorhinolaryngology, Yonsei University College of Medicine, Seoul, Korea
| | - Hyun Woo Park
- Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul, Korea
| | - Mary Hongying Cheng
- Department of Computational & Systems Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Ivet Bahar
- Department of Computational & Systems Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - David C. Whitcomb
- Division of Gastroenterology, Hepatology and Nutrition, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Min Goo Lee
- Department of Pharmacology, Brain Korea 21 PLUS Project for Medical Sciences, Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, Korea,Correspondence Address correspondence to: Min Goo Lee, Department of Pharmacology, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seoul 03722, Korea. fax: +82 2 313 1894.
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Marinko J, Huang H, Penn WD, Capra JA, Schlebach JP, Sanders CR. Folding and Misfolding of Human Membrane Proteins in Health and Disease: From Single Molecules to Cellular Proteostasis. Chem Rev 2019; 119:5537-5606. [PMID: 30608666 PMCID: PMC6506414 DOI: 10.1021/acs.chemrev.8b00532] [Citation(s) in RCA: 153] [Impact Index Per Article: 30.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2018] [Indexed: 12/13/2022]
Abstract
Advances over the past 25 years have revealed much about how the structural properties of membranes and associated proteins are linked to the thermodynamics and kinetics of membrane protein (MP) folding. At the same time biochemical progress has outlined how cellular proteostasis networks mediate MP folding and manage misfolding in the cell. When combined with results from genomic sequencing, these studies have established paradigms for how MP folding and misfolding are linked to the molecular etiologies of a variety of diseases. This emerging framework has paved the way for the development of a new class of small molecule "pharmacological chaperones" that bind to and stabilize misfolded MP variants, some of which are now in clinical use. In this review, we comprehensively outline current perspectives on the folding and misfolding of integral MPs as well as the mechanisms of cellular MP quality control. Based on these perspectives, we highlight new opportunities for innovations that bridge our molecular understanding of the energetics of MP folding with the nuanced complexity of biological systems. Given the many linkages between MP misfolding and human disease, we also examine some of the exciting opportunities to leverage these advances to address emerging challenges in the development of therapeutics and precision medicine.
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Affiliation(s)
- Justin
T. Marinko
- Department
of Biochemistry, Vanderbilt University, Nashville, Tennessee 37240, United States
- Center
for Structural Biology, Vanderbilt University, Nashville, Tennessee 37240, United States
| | - Hui Huang
- Department
of Biochemistry, Vanderbilt University, Nashville, Tennessee 37240, United States
- Center
for Structural Biology, Vanderbilt University, Nashville, Tennessee 37240, United States
| | - Wesley D. Penn
- Department
of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - John A. Capra
- Center
for Structural Biology, Vanderbilt University, Nashville, Tennessee 37240, United States
- Department
of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37245, United States
| | - Jonathan P. Schlebach
- Department
of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Charles R. Sanders
- Department
of Biochemistry, Vanderbilt University, Nashville, Tennessee 37240, United States
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Enns CB, Harding JCS, Loewen ME. Decreased electrogenic anionic secretory response in the porcine colon following in vivo challenge with Brachyspira spp. supports an altered mucin environment. Am J Physiol Gastrointest Liver Physiol 2019; 316:G495-G508. [PMID: 30629469 DOI: 10.1152/ajpgi.00348.2018] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Brachyspira spp. cause diarrheal disease in multiple animal species by colonization of the colon, resulting in colitis, mucus induction, and disrupted ion transport. Unique to spirochete pathogenesis is the immense production of mucus, resulting in a niche mucin environment likely favoring spirochete colonization. Mucin rheological properties are heavily influenced by anionic secretion, and loss of secretory function has been implicated in diseases such as cystic fibrosis. Here, the effects on the agonist-induced electrogenic anionic secretory response by infectious colonic spirochete bacteria Brachyspira hyodysenteriae and Brachyspira hampsonii were assessed in the proximal, apex, and distal sections of colon in Ussing chambers. Activation of secretion via isoproterenol, carbachol, and forskolin/3-isobutyl-1-methylxanthine demonstrated a significantly decreased change in short-circuit current ( Isc) in Brachyspira-infected pigs in all sections. Tissue resistances did not account for this difference, rather, it was attributed to a decrease in anionic secretion as indicated by a decrease in bumetanide inhibitable Isc. Quantitative RT-PCR and Western blot analyses determined that the major anionic channels of the epithelium were downregulated in diarrheic pigs paired with altered mucin gene expression. The investigated cytokines were not responsible for the downregulation of anion channel gene transcripts. Although IL-1α was upregulated in all segments, it did not alter cystic fibrosis transmembrane conductance regulator (CFTR) mRNA expression in Caco-2 monolayers. However, a whole cell Brachyspira hampsonii lysate significantly reduced CFTR mRNA expression in Caco-2 monolayers. Together, these findings indicate that these two Brachyspira spp. may directly cause a decreased anionic secretory response in the porcine colon, supporting an altered mucin environment likely favoring spirochete colonization. NEW & NOTEWORTHY This research demonstrates for the first time that the niche mucin environment produced by two infectious spirochete spp. is supported by a decrease in the electrogenic anionic secretory response throughout the porcine colon. Our findings suggest that the host's cytokine response is not likely responsible for the decrease in anionic secretory function. Rather, it appears that Brachyspira spp. directly impede ion channel transcription and translation, potentially altering colonic mucin rheological properties, which may favor spirochete colonization.
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Affiliation(s)
- Cole B Enns
- Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan , Saskatoon , Canada
| | - John C S Harding
- Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan , Saskatoon , Canada
| | - Matthew E Loewen
- Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan , Saskatoon , Canada
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29
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Villella VR, Tosco A, Esposito S, Bona G, Raia V, Maiuri L. Mutation-specific therapies and drug repositioning in cystic fibrosis. Minerva Pediatr 2019; 71:287-296. [DOI: 10.23736/s0026-4946.19.05506-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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Kunzelmann K, Ousingsawat J, Cabrita I, Doušová T, Bähr A, Janda M, Schreiber R, Benedetto R. TMEM16A in Cystic Fibrosis: Activating or Inhibiting? Front Pharmacol 2019; 10:3. [PMID: 30761000 PMCID: PMC6362895 DOI: 10.3389/fphar.2019.00003] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Accepted: 01/04/2019] [Indexed: 12/26/2022] Open
Abstract
The inflammatory airway disease cystic fibrosis (CF) is characterized by airway obstruction due to mucus hypersecretion, airway plugging, and bronchoconstriction. The cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel is dysfunctional in CF, leading to defects in epithelial transport. Although CF pathogenesis is still disputed, activation of alternative Cl- channels is assumed to improve lung function in CF. Two suitable non-CFTR Cl- channels are present in the airway epithelium, the Ca2+ activated channel TMEM16A and SLC26A9. Activation of these channels is thought to be feasible to improve hydration of the airway mucus and to increase mucociliary clearance. Interestingly, both channels are upregulated during inflammatory lung disease. They are assumed to support fluid secretion, necessary to hydrate excess mucus and to maintain mucus clearance. During inflammation, however, TMEM16A is upregulated particularly in mucus producing cells, with only little expression in ciliated cells. Recently it was shown that knockout of TMEM16A in ciliated cells strongly compromises Cl- conductance and attenuated mucus secretion, but does not lead to a CF-like lung disease and airway plugging. Along this line, activation of TMEM16A by denufosol, a stable purinergic ligand, failed to demonstrate any benefit to CF patients in earlier studies. It rather induced adverse effects such as cough. A number of studies suggest that TMEM16A is essential for mucus secretion and possibly also for mucus production. Evidence is now provided for a crucial role of TMEM16A in fusion of mucus-filled granules with the apical plasma membrane and cellular exocytosis. This is probably due to local Ca2+ signals facilitated by TMEM16A. Taken together, TMEM16A supports fluid secretion by ciliated airway epithelial cells, but also maintains excessive mucus secretion during inflammatory airway disease. Because TMEM16A also supports airway smooth muscle contraction, inhibition rather than activation of TMEM16A might be the appropriate treatment for CF lung disease, asthma and COPD. As a number of FDA-approved and well-tolerated drugs have been shown to inhibit TMEM16A, evaluation in clinical trials appears timely.
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Affiliation(s)
- Karl Kunzelmann
- Institut für Physiologie, Universität Regensburg, Regensburg, Germany
| | | | - Inês Cabrita
- Institut für Physiologie, Universität Regensburg, Regensburg, Germany
| | - Tereza Doušová
- Department of Pediatrics, Second Faculty of Medicine, University Hospital Motol, Charles University in Prague, Prague, Czechia
| | - Andrea Bähr
- Institute of Molecular Animal Breeding and Biotechnology, Ludwig-Maximilians-Universität München, Munich, Germany
- Innere Medizin I, Klinikum Rechts der Isar der TU München, München, Germany
| | - Melanie Janda
- Institute of Molecular Animal Breeding and Biotechnology, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Rainer Schreiber
- Institut für Physiologie, Universität Regensburg, Regensburg, Germany
| | - Roberta Benedetto
- Institut für Physiologie, Universität Regensburg, Regensburg, Germany
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31
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Hatton GB, Madla CM, Rabbie SC, Basit AW. Gut reaction: impact of systemic diseases on gastrointestinal physiology and drug absorption. Drug Discov Today 2018; 24:417-427. [PMID: 30453059 DOI: 10.1016/j.drudis.2018.11.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Revised: 10/25/2018] [Accepted: 11/13/2018] [Indexed: 12/17/2022]
Abstract
It was in 400 BC that Hippocrates reportedly stated that "death sits in the colon". The growth in our knowledge of the intestinal microbiome, the gut-brain axis and their function and imbalance has distinctly uncovered the complex relationship between the gut to disease predisposition and development, heralding the problem and the solution to disease pathology. Human studies of new drug molecules are typically performed in healthy volunteers and their specific disease indication. Approved drugs, however, are used by patients with diverse disease backgrounds. Here, we review the current literature of the gastrointestinal tract reacting to systemic disease pathology that elicits physiological and functional changes that consequently affect oral drug product performance.
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Affiliation(s)
- Grace B Hatton
- UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London, WC1N 1AX, UK
| | - Christine M Madla
- UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London, WC1N 1AX, UK
| | - Sarit C Rabbie
- UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London, WC1N 1AX, UK
| | - Abdul W Basit
- UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London, WC1N 1AX, UK.
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32
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Mucus-penetrating phage-displayed peptides for improved transport across a mucus-like model. Int J Pharm 2018; 553:57-64. [PMID: 30268850 DOI: 10.1016/j.ijpharm.2018.09.055] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 09/21/2018] [Accepted: 09/21/2018] [Indexed: 01/19/2023]
Abstract
The objective of this work is to use phage display libraries as a screening tool to identify peptides that facilitate transport across the mucus barrier. Mucus is a complex selective barrier to particles and molecules, limiting penetration to the epithelial surface of mucosal tissues. In mucus-associated diseases such as cystic fibrosis (CF), mucus has increased viscoelasticity and a higher concentration of covalent and non-covalent physical entanglements compared to healthy tissues, which greatly hinders permeability and transport of drugs and particles across the mucosae for therapeutic delivery. Treatment of CF lung diseases and associated infections must overcome this abnormal mucosal barrier. Critical bottlenecks hindering effective drug penetration remain and while recent studies have shown hydrophilic, net-neutral charge polymers can improve the transport of nanoparticles and minimize interactions with mucus, there is a dearth of alternative carriers available. We hypothesized that the screening of a phage peptide library against a CF mucus model would lead to the identification of phage-displayed peptide sequences able to improve transport in mucus. These combinatorial libraries possess a large diversity of peptide-based formulations (108-109) to achieve unprecedented screening for potential mucus-penetrating peptides. Here, phage clones displaying discovered peptides were shown to have up to 2.6-fold enhanced diffusivity in the CF mucus model. In addition, we demonstrate reduced binding affinities to mucin compared to wild-type control. These findings suggest that phage display libraries can be used as a strategy to improve transmucosal delivery.
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Tosco A, Villella VR, Castaldo A, Kroemer G, Maiuri L, Raia V. Repurposing therapies for the personalised treatment of cystic fibrosis. Expert Opin Orphan Drugs 2018. [DOI: 10.1080/21678707.2018.1483231] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Antonella Tosco
- Regional Cystic Fibrosis Center, Pediatric Unit, Department of Translational Medical Sciences, Federico II University, Naples, Italy
| | - Valeria R. Villella
- European Institute for Research in Cystic Fibrosis, Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Milan, Italy
| | - Alice Castaldo
- Regional Cystic Fibrosis Center, Pediatric Unit, Department of Translational Medical Sciences, Federico II University, Naples, Italy
| | - Guido Kroemer
- Equipe11 labellisée Ligue Nationale Contrele Cancer, Centre de Recherche des Cordeliers, Paris, France
- INSERM U1138, Centre de Recherche des Cordeliers, Paris, France
- Université Paris Descartes, Paris, Sorbonne Paris Cité, France
- Metabolomics and Cell Biology Platforms, Institut Gustave Roussy, Villejuif, France
- Pôle de Biologie, HôpitalEuropéen Georges Pompidou, AP-HP, Paris, France
| | - Luigi Maiuri
- European Institute for Research in Cystic Fibrosis, Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Milan, Italy
- Department of Health Sciences, University of Eastern Piedmont, Novara, Italy
| | - Valeria Raia
- Regional Cystic Fibrosis Center, Pediatric Unit, Department of Translational Medical Sciences, Federico II University, Naples, Italy
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Ritagliati C, Baro Graf C, Stival C, Krapf D. Regulation mechanisms and implications of sperm membrane hyperpolarization. Mech Dev 2018; 154:33-43. [PMID: 29694849 DOI: 10.1016/j.mod.2018.04.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 04/16/2018] [Accepted: 04/18/2018] [Indexed: 12/21/2022]
Abstract
Mammalian sperm are unable to fertilize the egg immediately after ejaculation. In order to gain fertilization competence, they need to undergo a series of biochemical and physiological modifications inside the female reproductive tract, known as capacitation. Capacitation correlates with two essential events for fertilization: hyperactivation, an asymmetric and vigorous flagellar motility, and the ability to undergo the acrosome reaction. At a molecular level, capacitation is associated to: phosphorylation cascades, modification of membrane lipids, alkalinization of the intracellular pH, increase in the intracellular Ca2+ concentration and hyperpolarization of the sperm plasma membrane potential. Hyperpolarization is a crucial event in capacitation since it primes the sperm to undergo the exocytosis of the acrosome content, essential to achieve fertilization of the oocyte.
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Affiliation(s)
- Carla Ritagliati
- Laboratory of Cell Signal Transduction Networks, Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET-UNR), Rosario 2000, Argentina.
| | - Carolina Baro Graf
- Laboratory of Cell Signal Transduction Networks, Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET-UNR), Rosario 2000, Argentina
| | - Cintia Stival
- Laboratory of Cell Signal Transduction Networks, Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET-UNR), Rosario 2000, Argentina
| | - Dario Krapf
- Laboratory of Cell Signal Transduction Networks, Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET-UNR), Rosario 2000, Argentina; Laboratorio de Especialidades Reproductivas, Facultad de Ciencias Bioquimicas y Farmacéuticas, UNR, Rosario 2000, Argentina.
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Yin J, Tse CM, Avula LR, Singh V, Foulke-Abel J, de Jonge HR, Donowitz M. Molecular Basis and Differentiation-Associated Alterations of Anion Secretion in Human Duodenal Enteroid Monolayers. Cell Mol Gastroenterol Hepatol 2018; 5:591-609. [PMID: 29930980 PMCID: PMC6009799 DOI: 10.1016/j.jcmgh.2018.02.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 02/05/2018] [Indexed: 12/12/2022]
Abstract
BACKGROUND & AIMS Human enteroids present a novel tool to study human intestinal ion transport physiology and pathophysiology. The present study describes the contributions of Cl- and HCO3- secretion to total cyclic adenosine monophosphate (cAMP)-stimulated electrogenic anion secretion in human duodenal enteroid monolayers and the relevant changes after differentiation. METHODS Human duodenal enteroids derived from 4 donors were grown as monolayers and differentiated by a protocol that includes the removal of Wnt3A, R-spondin1, and SB202190 for 5 days. The messenger RNA level and protein expression of selected ion transporters and carbonic anhydrase isoforms were determined by quantitative real-time polymerase chain reaction and immunoblotting, respectively. Undifferentiated and differentiated enteroid monolayers were mounted in the Ussing chamber/voltage-current clamp apparatus, using solutions that contained as well as lacked Cl- and HCO3-/CO2, to determine the magnitude of forskolin-induced short-circuit current change and its sensitivity to specific inhibitors that target selected ion transporters and carbonic anhydrase(s). RESULTS Differentiation resulted in a significant reduction in the messenger RNA level and protein expression of cystic fibrosis transmembrane conductance regulator, (CFTR) Na+/K+/2Cl- co-transporter 1 (NKCC1), and potassium channel, voltage gated, subfamily E, regulatory subunit 3 (KCNE3); and, conversely, increase of down-regulated-in-adenoma (DRA), electrogenic Na+/HCO3- co-transporter 1 (NBCe1), carbonic anhydrase 2 (CA2), and carbonic anhydrase 4 (CA4). Both undifferentiated and differentiated enteroids showed active cAMP-stimulated anion secretion that included both Cl- and HCO3- secretion as the magnitude of total active anion secretion was reduced after the removal of extracellular Cl- or HCO3-/CO2. The magnitude of total anion secretion in differentiated enteroids was approximately 33% of that in undifferentiated enteroids, primarily owing to the reduction in Cl- secretion with no significant change in HCO3- secretion. Anion secretion was consistently lower but detectable in differentiated enteroids compared with undifferentiated enteroids in the absence of extracellular Cl- or HCO3-/CO2. Inhibiting CFTR, NKCC1, carbonic anhydrase(s), cAMP-activated K+ channel(s), and Na+/K+-adenosine triphosphatase reduced cAMP-stimulated anion secretion in both undifferentiated and differentiated enteroids. CONCLUSIONS Human enteroids recapitulate anion secretion physiology of small intestinal epithelium. Enteroid differentiation is associated with significant alterations in the expression of several ion transporters and carbonic anhydrase isoforms, leading to a reduced but preserved anion secretory phenotype owing to markedly reduced Cl- secretion but no significant change in HCO3- secretion.
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Key Words
- AE2, anion exchanger 2
- Bicarbonate Secretion
- CA, carbonic anhydrase
- CFTR, cystic fibrosis transmembrane conductance regulator
- Chloride Secretion
- DRA
- DRA, down-regulated-in-adenoma
- Ion Transport
- Isc, short-circuit current
- KRB, Krebs–Ringer bicarbonate
- NBC, Na+/HCO3- co-transporter
- NBCe1, electrogenic Na+/HCO3- co-transporter 1
- NHE, Na+/H+ exchanger
- NKCC1, Na+/K+/2Cl- co-transporter 1
- SDS, sodium dodecyl sulfate
- SITS, 4-Acetamido-4′-isothiocyanato-2,2′-stilbenedisulfonic acid disodium salt hydrate
- TER, transepithelial electrical resistance
- cAMP, cyclic adenosine monophosphate
- mRNA, messenger ribonucleic acid
- qRT-PCR, quantitative real-time polymerase chain reaction
- ΔIsc, change in short-circuit current
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Affiliation(s)
- Jianyi Yin
- Department of Medicine, Division of Gastroenterology and Hepatology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Chung-Ming Tse
- Department of Medicine, Division of Gastroenterology and Hepatology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Leela Rani Avula
- Department of Medicine, Division of Gastroenterology and Hepatology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Varsha Singh
- Department of Medicine, Division of Gastroenterology and Hepatology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Jennifer Foulke-Abel
- Department of Medicine, Division of Gastroenterology and Hepatology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Hugo R. de Jonge
- Department of Gastroenterology and Hepatology, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Mark Donowitz
- Department of Medicine, Division of Gastroenterology and Hepatology, Johns Hopkins University School of Medicine, Baltimore, Maryland,Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland,Correspondence Address correspondence to: Mark Donowitz, MD, Johns Hopkins University School of Medicine, 720 Rutland Avenue, 925 Ross Research Building, Baltimore, Maryland 21205. fax: (410) 955-9677.
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Abstract
Amelogenesis (tooth enamel formation) is a biomineralization process consisting primarily of two stages (secretory stage and maturation stage) with unique features. During the secretory stage, the inner epithelium of the enamel organ (i.e., the ameloblast cells) synthesizes and secretes enamel matrix proteins (EMPs) into the enamel space. The protein-rich enamel matrix forms a highly organized architecture in a pH-neutral microenvironment. As amelogenesis transitions to maturation stage, EMPs are degraded and internalized by ameloblasts through endosomal-lysosomal pathways. Enamel crystallite formation is initiated early in the secretory stage, however, during maturation stage the more rapid deposition of calcium and phosphate into the enamel space results in a rapid expansion of crystallite length and mineral volume. During maturation-stage amelogenesis, the pH value of enamel varies considerably from slightly above neutral to acidic. Extracellular acid-base balance during enamel maturation is tightly controlled by ameloblast-mediated regulatory networks, which include significant synthesis and movement of bicarbonate ions from both the enamel papillary layer cells and ameloblasts. In this review we summarize the carbonic anhydrases and the carbonate transporters/exchangers involved in pH regulation in maturation-stage amelogenesis. Proteins that have been shown to be instrumental in this process include CA2, CA6, CFTR, AE2, NBCe1, SLC26A1/SAT1, SLC26A3/DRA, SLC26A4/PDS, SLC26A6/PAT1, and SLC26A7/SUT2. In addition, we discuss the association of miRNA regulation with bicarbonate transport in tooth enamel formation.
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Affiliation(s)
- Kaifeng Yin
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, 2250 Alcazar Street, CSA103, Los Angeles, CA, 90033, USA
- Department of Orthodontics, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA, USA
| | - Michael L Paine
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, 2250 Alcazar Street, CSA103, Los Angeles, CA, 90033, USA.
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Leal J, Smyth HDC, Ghosh D. Physicochemical properties of mucus and their impact on transmucosal drug delivery. Int J Pharm 2017; 532:555-572. [PMID: 28917986 PMCID: PMC5744044 DOI: 10.1016/j.ijpharm.2017.09.018] [Citation(s) in RCA: 262] [Impact Index Per Article: 37.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2017] [Revised: 09/06/2017] [Accepted: 09/07/2017] [Indexed: 02/06/2023]
Abstract
Mucus is a selective barrier to particles and molecules, preventing penetration to the epithelial surface of mucosal tissues. Significant advances in transmucosal drug delivery have recently been made and have emphasized that an understanding of the basic structure, viscoelastic properties, and interactions of mucus is of great value in the design of efficient drug delivery systems. Mucins, the primary non-aqueous component of mucus, are polymers carrying a complex and heterogeneous structure with domains that undergo a variety of molecular interactions, such as hydrophilic/hydrophobic, hydrogen bonds and electrostatic interactions. These properties are directly relevant to the numerous mucin-associated diseases, as well as delivering drugs across the mucus barrier. Therefore, in this review we discuss regional differences in mucus composition, mucus physicochemical properties, such as pore size, viscoelasticity, pH, and ionic strength. These factors are also discussed with respect to changes in mucus properties as a function of disease state. Collectively, the review seeks to provide a state of the art roadmap for researchers who must contend with this critical barrier to drug delivery.
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Affiliation(s)
- Jasmim Leal
- Division of Molecular Pharmaceutics and Drug Delivery, College of Pharmacy, The University of Texas at Austin, 2409 University Ave., Austin, TX 78712, USA
| | - Hugh D C Smyth
- Division of Molecular Pharmaceutics and Drug Delivery, College of Pharmacy, The University of Texas at Austin, 2409 University Ave., Austin, TX 78712, USA
| | - Debadyuti Ghosh
- Division of Molecular Pharmaceutics and Drug Delivery, College of Pharmacy, The University of Texas at Austin, 2409 University Ave., Austin, TX 78712, USA.
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Puga Molina LC, Pinto NA, Torres Rodríguez P, Romarowski A, Vicens Sanchez A, Visconti PE, Darszon A, Treviño CL, Buffone MG. Essential Role of CFTR in PKA-Dependent Phosphorylation, Alkalinization, and Hyperpolarization During Human Sperm Capacitation. J Cell Physiol 2016; 232:1404-1414. [PMID: 27714810 DOI: 10.1002/jcp.25634] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Accepted: 10/05/2016] [Indexed: 12/17/2022]
Abstract
Mammalian sperm require to spend a limited period of time in the female reproductive tract to become competent to fertilize in a process called capacitation. It is well established that HCO3- is essential for capacitation because it activates the atypical soluble adenylate cyclase ADCY10 leading to cAMP production, and promotes alkalinization of cytoplasm, and membrane hyperpolarization. However, how HCO3- is transported into the sperm is not well understood. There is evidence that CFTR activity is involved in the human sperm capacitation but how this channel is integrated in the complex signaling cascades associated with this process remains largely unknown. In the present work, we have analyzed the extent to which CFTR regulates different events in human sperm capacitation. We observed that inhibition of CFTR affects HCO3- -entrance dependent events resulting in lower PKA activity. CFTR inhibition also affected cAMP/PKA-downstream events such as the increase in tyrosine phosphorylation, hyperactivated motility, and acrosome reaction. In addition, we demonstrated for the first time, that CFTR and PKA activity are essential for the regulation of intracellular pH, and membrane potential in human sperm. Addition of permeable cAMP partially recovered all the PKA-dependent events altered in the presence of inh-172 which is consistent with a role of CFTR upstream of PKA activation. J. Cell. Physiol. 232: 1404-1414, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Lis C Puga Molina
- Instituto de Biología y Medicina Experimental (IBYME), Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET), Buenos Aires, Argentina
| | - Nicolás A Pinto
- Instituto de Biología y Medicina Experimental (IBYME), Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET), Buenos Aires, Argentina
| | - Paulina Torres Rodríguez
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Morelos, México
| | - Ana Romarowski
- Instituto de Biología y Medicina Experimental (IBYME), Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET), Buenos Aires, Argentina
| | - Alberto Vicens Sanchez
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Morelos, México
| | - Pablo E Visconti
- Department of Veterinary and Animal Science, Paige Labs, University of Massachusetts, Amherst, Massachusetts
| | - Alberto Darszon
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Morelos, México
| | - Claudia L Treviño
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Morelos, México
| | - Mariano G Buffone
- Instituto de Biología y Medicina Experimental (IBYME), Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET), Buenos Aires, Argentina
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Schmidt BZ, Haaf JB, Leal T, Noel S. Cystic fibrosis transmembrane conductance regulator modulators in cystic fibrosis: current perspectives. Clin Pharmacol 2016; 8:127-140. [PMID: 27703398 PMCID: PMC5036583 DOI: 10.2147/cpaa.s100759] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Mutations of the CFTR gene cause cystic fibrosis (CF), the most common recessive monogenic disease worldwide. These mutations alter the synthesis, processing, function, or half-life of CFTR, the main chloride channel expressed in the apical membrane of epithelial cells in the airway, intestine, pancreas, and reproductive tract. Lung disease is the most critical manifestation of CF. It is characterized by airway obstruction, infection, and inflammation that lead to fatal tissue destruction. In spite of great advances in early and multidisciplinary medical care, and in our understanding of the pathophysiology, CF is still considerably reducing the life expectancy of patients. This review highlights the current development in pharmacological modulators of CFTR, which aim at rescuing the expression and/or function of mutated CFTR. While only Kalydeco® and Orkambi® are currently available to patients, many other families of CFTR modulators are undergoing preclinical and clinical investigations. Drug repositioning and personalized medicine are particularly detailed in this review as they represent the most promising strategies for restoring CFTR function in CF.
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Affiliation(s)
- Béla Z Schmidt
- Stem Cell Biology and Embryology, Department of Development and Regeneration, Katholieke Universiteit Leuven, Leuven
| | - Jérémy B Haaf
- Louvain Center for Toxicology and Applied Pharmacology, Université Catholique de Louvain, Brussels, Belgium
| | - Teresinha Leal
- Louvain Center for Toxicology and Applied Pharmacology, Université Catholique de Louvain, Brussels, Belgium
| | - Sabrina Noel
- Louvain Center for Toxicology and Applied Pharmacology, Université Catholique de Louvain, Brussels, Belgium
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40
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Zwick M, Esposito C, Hellstern M, Seelig A. How Phosphorylation and ATPase Activity Regulate Anion Flux though the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR). J Biol Chem 2016; 291:14483-98. [PMID: 27226582 DOI: 10.1074/jbc.m116.721415] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Indexed: 01/25/2023] Open
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR, ABCC7), mutations of which cause cystic fibrosis, belongs to the ATP-binding cassette (ABC) transporter family and works as a channel for small anions, such as chloride and bicarbonate. Anion channel activity is known to depend on phosphorylation by cAMP-dependent protein kinase A (PKA) and CFTR-ATPase activity. Whereas anion channel activity has been extensively investigated, phosphorylation and CFTR-ATPase activity are still poorly understood. Here, we show that the two processes can be measured in a label-free and non-invasive manner in real time in live cells, stably transfected with CFTR. This study reveals three key findings. (i) The major contribution (≥90%) to the total CFTR-related ATP hydrolysis rate is due to phosphorylation by PKA and the minor contribution (≤10%) to CFTR-ATPase activity. (ii) The mutant CFTR-E1371S that is still conductive, but defective in ATP hydrolysis, is not phosphorylated, suggesting that phosphorylation requires a functional nucleotide binding domain and occurs in the post-hydrolysis transition state. (iii) CFTR-ATPase activity is inversely related to CFTR anion flux. The present data are consistent with a model in which CFTR is in a closed conformation with two ATPs bound. The open conformation is induced by ATP hydrolysis and corresponds to the post-hydrolysis transition state that is stabilized by phosphorylation and binding of chloride channel potentiators.
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Affiliation(s)
- Matthias Zwick
- From the Biophysical Chemistry, Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland
| | - Cinzia Esposito
- From the Biophysical Chemistry, Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland
| | - Manuel Hellstern
- From the Biophysical Chemistry, Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland
| | - Anna Seelig
- From the Biophysical Chemistry, Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland
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41
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Linsdell P. Anion conductance selectivity mechanism of the CFTR chloride channel. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:740-7. [DOI: 10.1016/j.bbamem.2016.01.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Revised: 01/11/2016] [Accepted: 01/13/2016] [Indexed: 02/08/2023]
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Spielberg DR, Clancy JP. Cystic Fibrosis and Its Management Through Established and Emerging Therapies. Annu Rev Genomics Hum Genet 2016; 17:155-75. [PMID: 26905785 DOI: 10.1146/annurev-genom-090314-050024] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Cystic fibrosis (CF) is the most common life-shortening autosomal recessive disorder in the Caucasian population and occurs in many other ethnicities worldwide. The daily treatment burden is substantial for CF patients even when they are well, with numerous pharmacologic and physical therapies targeting lung disease requiring the greatest time commitment. CF treatments continue to advance with greater understanding of factors influencing long-term morbidity and mortality. In recent years, in-depth understanding of genetic and protein structure-function relationships has led to the introduction of targeted therapies for patients with specific CF genotypes. With these advances, CF has become a model of personalized or precision medicine. The near future will see greater access to targeted therapies for most patients carrying common mutations, which will mandate individualized bench-to-bedside methodologies for those with rare genotypes.
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Affiliation(s)
- David R Spielberg
- Department of Pediatrics, Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center and University of Cincinnati, Cincinnati, Ohio 45229; ,
| | - John P Clancy
- Department of Pediatrics, Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center and University of Cincinnati, Cincinnati, Ohio 45229; ,
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43
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Characterization and small-molecule stabilization of the multisite tandem binding between 14-3-3 and the R domain of CFTR. Proc Natl Acad Sci U S A 2016; 113:E1152-61. [PMID: 26888287 DOI: 10.1073/pnas.1516631113] [Citation(s) in RCA: 107] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Cystic fibrosis is a fatal genetic disease, most frequently caused by the retention of the CFTR (cystic fibrosis transmembrane conductance regulator) mutant protein in the endoplasmic reticulum (ER). The binding of the 14-3-3 protein to the CFTR regulatory (R) domain has been found to enhance CFTR trafficking to the plasma membrane. To define the mechanism of action of this protein-protein interaction, we have examined the interaction in vitro. The disordered multiphosphorylated R domain contains nine different 14-3-3 binding motifs. Furthermore, the 14-3-3 protein forms a dimer containing two amphipathic grooves that can potentially bind these phosphorylated motifs. This results in a number of possible binding mechanisms between these two proteins. Using multiple biochemical assays and crystal structures, we show that the interaction between them is governed by two binding sites: The key binding site of CFTR (pS768) occupies one groove of the 14-3-3 dimer, and a weaker, secondary binding site occupies the other binding groove. We show that fusicoccin-A, a natural-product tool compound used in studies of 14-3-3 biology, can stabilize the interaction between 14-3-3 and CFTR by selectively interacting with a secondary binding motif of CFTR (pS753). The stabilization of this interaction stimulates the trafficking of mutant CFTR to the plasma membrane. This definition of the druggability of the 14-3-3-CFTR interface might offer an approach for cystic fibrosis therapeutics.
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44
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Laube M, Bossmann M, Thome UH. Glucocorticoids Distinctively Modulate the CFTR Channel with Possible Implications in Lung Development and Transition into Extrauterine Life. PLoS One 2015; 10:e0124833. [PMID: 25910246 PMCID: PMC4409322 DOI: 10.1371/journal.pone.0124833] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Accepted: 03/20/2015] [Indexed: 11/18/2022] Open
Abstract
During fetal development, the lung is filled with fluid that is secreted by an active Cl- transport promoting lung growth. The basolateral Na+,K+,2Cl- cotransporter (NKCC1) participates in Cl- secretion. The apical Cl- channels responsible for secretion are unknown but studies suggest an involvement of the cystic fibrosis transmembrane conductance regulator (CFTR). CFTR is developmentally regulated with a high expression in early fetal development and a decline in late gestation. Perinatal lung transition is triggered by hormones that stimulate alveolar Na+ channels resulting in fluid absorption. Little is known on how hormones affect pulmonary Cl- channels. Since the rise of fetal cortisol levels correlates with the decrease in fetal CFTR expression, a causal relation may be assumed. The aim of this study was to analyze the influence of glucocorticoids on pulmonary Cl- channels. Alveolar cells from fetal and adult rats, A549 cells, bronchial Calu-3 and 16HBE14o- cells, and primary rat airway cells were studied with real-time quantitative PCR and Ussing chambers. In fetal and adult alveolar cells, glucocorticoids strongly reduced Cftr expression and channel activity, which was prevented by mifepristone. In bronchial and primary airway cells CFTR mRNA expression was also reduced, whereas channel activity was increased which was prevented by LY-294002 in Calu-3 cells. Therefore, glucocorticoids strongly reduce CFTR expression while their effect on CFTR activity depends on the physiological function of the cells. Another apical Cl- channel, anoctamin 1 showed a glucocorticoid-induced reduction of mRNA expression in alveolar cells and an increase in bronchial cells. Furthermore, voltage-gated chloride channel 5 and anoctamine 6 mRNA expression were increased in alveolar cells. NKCC1 expression was reduced by glucocorticoids in alveolar and bronchial cells alike. The results demonstrate that glucocorticoids differentially modulate pulmonary Cl- channels and are likely causing the decline of CFTR during late gestation in preparation for perinatal lung transition.
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Affiliation(s)
- Mandy Laube
- Center for Pediatric Research Leipzig, Hospital for Children & Adolescents, Division of Neonatology, University of Leipzig, Leipzig, Germany
- * E-mail:
| | - Miriam Bossmann
- Center for Pediatric Research Leipzig, Hospital for Children & Adolescents, Division of Neonatology, University of Leipzig, Leipzig, Germany
| | - Ulrich H. Thome
- Center for Pediatric Research Leipzig, Hospital for Children & Adolescents, Division of Neonatology, University of Leipzig, Leipzig, Germany
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45
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Pierucci-Alves F, Akoyev V, Schultz BD. Bicarbonate exchangers SLC26A3 and SLC26A6 are localized at the apical membrane of porcine vas deferens epithelium. Physiol Rep 2015; 3:3/4/e12380. [PMID: 25907791 PMCID: PMC4425982 DOI: 10.14814/phy2.12380] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The goal of this study was to test for expression of HCO3 (-) exchangers SLC26A3 and SLC26A6 in primary cultures of porcine vas deferens epithelial cells (1°PVD) and native porcine vas deferens. Quantitative RT-PCR revealed that mRNA coding for SLC26A6 was six times more abundant than mRNA coding for SLC26A3 in 1°PVD cells. Western blot analyses combined with surface biotinylation of 1°PVD demonstrated SLC26A3 and SLC26A6 immunoreactivities in whole-cell lysates and apical surfaces of monolayers. Laser scanning confocal microscopy (LSCM) of the 1°PVD cell monolayers demonstrated that SLC26A3 immunoreactivity was primarily in the apical region but present throughout the basal-apical cellular axis, whereas SLC26A6 immunoreactivity was present in the apical region and sometimes accumulated in the nuclear region. LSCM also demonstrated SLC26A3 and SLC26A6 immunoreactivities present along the entire apical lining of the native porcine vas deferens epithelium and in basal cells. The patterns and apparent abundance of SLC26A3 and SLC26A6 immunoreactivities in the proximal vas deferens were not different from the corresponding immunoreactivities in the distal region. There is no evidence of preferential expression of SLC26A3 or SLC26A6 in any portion of the vas deferens, as has been proposed for epithelia that secrete HCO3 (-) in other duct systems. Thus, vas deferens epithelia express transporters throughout the duct that can contribute to rapid alkalinization of the luminal contents as it has been demonstrated in vivo.
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Affiliation(s)
| | - Vladimir Akoyev
- Department of Anatomy & Physiology, Kansas State University, Manhattan, Kansas, USA
| | - Bruce D Schultz
- Department of Anatomy & Physiology, Kansas State University, Manhattan, Kansas, USA
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46
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Yan Z, Stewart ZA, Sinn PL, Olsen JC, Hu J, McCray PB, Engelhardt JF. Ferret and pig models of cystic fibrosis: prospects and promise for gene therapy. HUM GENE THER CL DEV 2015; 26:38-49. [PMID: 25675143 PMCID: PMC4367511 DOI: 10.1089/humc.2014.154] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Accepted: 12/26/2014] [Indexed: 12/13/2022] Open
Abstract
Large animal models of genetic diseases are rapidly becoming integral to biomedical research as technologies to manipulate the mammalian genome improve. The creation of cystic fibrosis (CF) ferrets and pigs is an example of such progress in animal modeling, with the disease phenotypes in the ferret and pig models more reflective of human CF disease than mouse models. The ferret and pig CF models also provide unique opportunities to develop and assess the effectiveness of gene and cell therapies to treat affected organs. In this review, we examine the organ disease phenotypes in these new CF models and the opportunities to test gene therapies at various stages of disease progression in affected organs. We then discuss the progress in developing recombinant replication-defective adenoviral, adeno-associated viral, and lentiviral vectors to target genes to the lung and pancreas in ferrets and pigs, the two most affected organs in CF. Through this review, we hope to convey the potential of these new animal models for developing CF gene and cell therapies.
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Affiliation(s)
- Ziying Yan
- Department of Anatomy and Cell Biology, University of Iowa School of Medicine, Iowa City, IA 52242
- Center for Gene Therapy of Cystic Fibrosis, University of Iowa School of Medicine, Iowa City, IA 52242
| | - Zoe A. Stewart
- Department of Surgery, University of Iowa School of Medicine, Iowa City, IA 52242
| | - Patrick L. Sinn
- Center for Gene Therapy of Cystic Fibrosis, University of Iowa School of Medicine, Iowa City, IA 52242
- Department of Pediatrics, University of Iowa School of Medicine, Iowa City, IA 52242
| | - John C. Olsen
- Cystic Fibrosis/Pulmonary Research and Treatment Center, Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Jim Hu
- Department of Laboratory Medicine and Pathobiology, Hospital for Sick Children and University of Toronto, Toronto, ON M5G 0A4, Canada
| | - Paul B. McCray
- Center for Gene Therapy of Cystic Fibrosis, University of Iowa School of Medicine, Iowa City, IA 52242
- Department of Pediatrics, University of Iowa School of Medicine, Iowa City, IA 52242
| | - John F. Engelhardt
- Department of Anatomy and Cell Biology, University of Iowa School of Medicine, Iowa City, IA 52242
- Center for Gene Therapy of Cystic Fibrosis, University of Iowa School of Medicine, Iowa City, IA 52242
- Department of Internal Medicine, University of Iowa School of Medicine, Iowa City, IA 52242
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47
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Bodewes FAJA, Verkade HJ, Taminiau JAJM, Borowitz D, Wilschanski M. Cystic fibrosis and the role of gastrointestinal outcome measures in the new era of therapeutic CFTR modulation. J Cyst Fibros 2015; 14:169-77. [PMID: 25677689 DOI: 10.1016/j.jcf.2015.01.006] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Revised: 01/20/2015] [Accepted: 01/20/2015] [Indexed: 01/01/2023]
Abstract
With the development of new drugs that directly affect CFTR protein function, clinical trials are being designed or initiated for a growing number of patients with cystic fibrosis. The currently available and accepted clinical endpoints, FEV1 and BMI, have limitations. The aim of this report is to draw attention to the need and the ample possibilities for the development and validation of relevant gastrointestinal clinical endpoints for scientific evaluation of CFTR modulation treatment, particularly in young children and infants. The gastrointestinal tract offers very good opportunities to measure CFTR protein function and systematically evaluate CF related clinical outcomes based on the principal clinical gastrointestinal manifestations of CF: intestinal pH, intestinal transit time, intestinal bile salt malabsorption, intestinal inflammation, exocrine pancreatic function and intestinal fat malabsorption. We present a descriptive analysis of a variety of gastrointestinal outcome measures for clinical relevance, reliability, validity, responsiveness to interventions, feasibility in particular in young children and the availability of reference values.
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Affiliation(s)
- Frank A J A Bodewes
- Pediatric Gastroenterology and Hepatology, University of Groningen, University Medical Center, Groningen, The Netherlands.
| | - Henkjan J Verkade
- Pediatric Gastroenterology and Hepatology, University of Groningen, University Medical Center, Groningen, The Netherlands
| | | | - Drucy Borowitz
- Department of Pediatrics, State University of New York at Buffalo School of Medicine and Biomedical Sciences, Women and Children's Hospital of Buffalo, Buffalo, NY, United States
| | - Michael Wilschanski
- Pediatric Gastroenterology, Hadassah Hebrew University Medical Center, Jerusalem, Israel
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48
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Yan Z, Stewart ZA, Sinn PL, Olsen JC, Hu J, McCray, Jr. PB, Engelhardt JF. Ferret and Pig Models of Cystic Fibrosis: Prospects and Promise for Gene Therapy. HUM GENE THER CL DEV 2014. [DOI: 10.1089/hum.2014.154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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49
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El Hiani Y, Linsdell P. Conformational changes opening and closing the CFTR chloride channel: insights from cysteine scanning mutagenesis. Biochem Cell Biol 2014; 92:481-8. [PMID: 25367045 DOI: 10.1139/bcb-2014-0038] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Cystic fibrosis, the most common lethal genetic disease affecting young people in North America, is caused by failure of the chloride ion channel known as CFTR (cystic fibrosis transmembrane conductance regulator). CFTR belongs to the large family of ATP-binding cassette (ABC) membrane transporters. In CFTR, ATP-driven events at the nucleotide-binding domains (NBDs) open and close a gate that controls chloride permeation. However, the conformational changes concomitant with opening and closing of the CFTR gate are unknown. Diverse techniques including substituted cysteine accessibility method, disulfide cross-linking, and patch-clamp recording have been used to explore CFTR channel structure. Here, we consider the architecture of both the open and the closed CFTR channel. We review how CFTR channel structure changes between the closed and the open channel conformations and portray the relative function of both cytoplasmic and vestigial gates during the gating cycle. Understanding how the CFTR channel gates chloride permeation is central for understanding how CFTR defects lead to CF. Such knowledge opens the door for novel ways to maximize CFTR channel activity in a CF setting.
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Affiliation(s)
- Yassine El Hiani
- Department of Physiology & Biophysics, Dalhousie University, Halifax, NS B3H 4R2, Canada
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50
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Wang Y, Wrennall JA, Cai Z, Li H, Sheppard DN. Understanding how cystic fibrosis mutations disrupt CFTR function: from single molecules to animal models. Int J Biochem Cell Biol 2014; 52:47-57. [PMID: 24727426 DOI: 10.1016/j.biocel.2014.04.001] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Revised: 04/01/2014] [Accepted: 04/02/2014] [Indexed: 12/21/2022]
Abstract
Defective epithelial ion transport is the hallmark of the life-limiting genetic disease cystic fibrosis (CF). This abnormality is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR), the ATP-binding cassette transporter that functions as a ligand-gated anion channel. Since the identification of the CFTR gene, almost 2000 disease-causing mutations associated with a spectrum of clinical phenotypes have been reported, but the majority remain poorly characterised. Studies of a small number of mutations including the most common, F508del-CFTR, have identified six general mechanisms of CFTR dysfunction. Here, we review selectively progress to understand how CF mutations disrupt CFTR processing, stability and function. We explore CFTR structure and function to explain the molecular mechanisms of CFTR dysfunction and highlight new knowledge of disease pathophysiology emerging from large animal models of CF. Understanding CFTR dysfunction is crucial to the development of transformational therapies for CF patients.
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Affiliation(s)
- Yiting Wang
- School of Physiology and Pharmacology, University of Bristol, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK
| | - Joe A Wrennall
- School of Physiology and Pharmacology, University of Bristol, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK
| | - Zhiwei Cai
- School of Physiology and Pharmacology, University of Bristol, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK
| | - Hongyu Li
- School of Physiology and Pharmacology, University of Bristol, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK
| | - David N Sheppard
- School of Physiology and Pharmacology, University of Bristol, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK.
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