1
|
Petersen OH, Gerasimenko JV, Gerasimenko OV, Gryshchenko O, Peng S. The roles of calcium and ATP in the physiology and pathology of the exocrine pancreas. Physiol Rev 2021; 101:1691-1744. [PMID: 33949875 DOI: 10.1152/physrev.00003.2021] [Citation(s) in RCA: 61] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
This review deals with the roles of calcium ions and ATP in the control of the normal functions of the different cell types in the exocrine pancreas as well as the roles of these molecules in the pathophysiology of acute pancreatitis. Repetitive rises in the local cytosolic calcium ion concentration in the apical part of the acinar cells not only activate exocytosis but also, via an increase in the intramitochondrial calcium ion concentration, stimulate the ATP formation that is needed to fuel the energy-requiring secretion process. However, intracellular calcium overload, resulting in a global sustained elevation of the cytosolic calcium ion concentration, has the opposite effect of decreasing mitochondrial ATP production, and this initiates processes that lead to necrosis. In the last few years it has become possible to image calcium signaling events simultaneously in acinar, stellate, and immune cells in intact lobules of the exocrine pancreas. This has disclosed processes by which these cells interact with each other, particularly in relation to the initiation and development of acute pancreatitis. By unraveling the molecular mechanisms underlying this disease, several promising therapeutic intervention sites have been identified. This provides hope that we may soon be able to effectively treat this often fatal disease.
Collapse
Affiliation(s)
- Ole H Petersen
- School of Biosciences, Cardiff University, Cardiff, United Kingdom
| | | | | | | | - Shuang Peng
- Department of Pathophysiology, Key Laboratory of State Administration of Traditional Chinese Medicine of the People's Republic of China, School of Medicine, Jinan University, Guangzhou, Guangdong, People's Republic of China
| |
Collapse
|
2
|
Schnipper J, Dhennin-Duthille I, Ahidouch A, Ouadid-Ahidouch H. Ion Channel Signature in Healthy Pancreas and Pancreatic Ductal Adenocarcinoma. Front Pharmacol 2020; 11:568993. [PMID: 33178018 PMCID: PMC7596276 DOI: 10.3389/fphar.2020.568993] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 09/16/2020] [Indexed: 12/11/2022] Open
Abstract
Pancreatic ductal adenocarcinoma (PDAC) is the fourth most common cause of cancer-related deaths in United States and Europe. It is predicted that PDAC will become the second leading cause of cancer-related deaths during the next decades. The development of PDAC is not well understood, however, studies have shown that dysregulated exocrine pancreatic fluid secretion can contribute to pathologies of exocrine pancreas, including PDAC. The major roles of healthy exocrine pancreatic tissue are secretion of enzymes and bicarbonate rich fluid, where ion channels participate to fine-tune these biological processes. It is well known that ion channels located in the plasma membrane regulate multiple cellular functions and are involved in the communication between extracellular events and intracellular signaling pathways and can function as signal transducers themselves. Hereby, they contribute to maintain resting membrane potential, electrical signaling in excitable cells, and ion homeostasis. Despite their contribution to basic cellular processes, ion channels are also involved in the malignant transformation from a normal to a malignant phenotype. Aberrant expression and activity of ion channels have an impact on essentially all hallmarks of cancer defined as; uncontrolled proliferation, evasion of apoptosis, sustained angiogenesis and promotion of invasion and migration. Research indicates that certain ion channels are involved in the aberrant tumor growth and metastatic processes of PDAC. The purpose of this review is to summarize the important expression, localization, and function of ion channels in normal exocrine pancreatic tissue and how they are involved in PDAC progression and development. As ion channels are suggested to be potential targets of treatment they are furthermore suggested to be biomarkers of different cancers. Therefore, we describe the importance of ion channels in PDAC as markers of diagnosis and clinical factors.
Collapse
Affiliation(s)
- Julie Schnipper
- Laboratory of Cellular and Molecular Physiology, UR-4667, University of Picardie Jules Verne, Amiens, France
| | - Isabelle Dhennin-Duthille
- Laboratory of Cellular and Molecular Physiology, UR-4667, University of Picardie Jules Verne, Amiens, France
| | - Ahmed Ahidouch
- Laboratory of Cellular and Molecular Physiology, UR-4667, University of Picardie Jules Verne, Amiens, France.,Department of Biology, Faculty of Sciences, Ibn Zohr University, Agadir, Morocco
| | - Halima Ouadid-Ahidouch
- Laboratory of Cellular and Molecular Physiology, UR-4667, University of Picardie Jules Verne, Amiens, France
| |
Collapse
|
3
|
Cuevas-Ocaña S, Laselva O, Avolio J, Nenna R. The era of CFTR modulators: improvements made and remaining challenges. Breathe (Sheff) 2020; 16:200016. [PMID: 33304402 PMCID: PMC7714553 DOI: 10.1183/20734735.0016-2020] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The entry into the clinic of CFTR modulators such as TRIKAFTA has significantly improved life for ∼90% CF patients carrying one or two F508del mutations but challenges remain for rare CFTR mutations and the management of lung infections @SaraOcana1 https://bit.ly/3aRafQF.
Collapse
Affiliation(s)
- Sara Cuevas-Ocaña
- Wolfson Centre for Stem Cells, Tissue Engineering and Modelling, School of Medicine, University of Nottingham Biodiscovery Institute, Nottingham, UK
| | - Onofrio Laselva
- Program in Molecular Medicine, The Hospital for Sick Children, Toronto, Canada
- Dept of Physiology, University of Toronto, Toronto, Canada
| | - Julie Avolio
- Program in Translational Medicine, SickKids Research Institute, The Hospital for Sick Children, Toronto, Canada
| | - Raffaella Nenna
- Dept of Paediatrics, “Sapienza” University of Rome, Rome, Italy
| |
Collapse
|
4
|
Lin L, Wan L, He H, Liu W. Drug vector representation: a tool for drug similarity analysis. Mol Genet Genomics 2020; 295:1055-1062. [PMID: 32222838 DOI: 10.1007/s00438-020-01665-x] [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: 12/14/2019] [Accepted: 03/11/2020] [Indexed: 10/24/2022]
Abstract
DrugMatrix is a valuable toxicogenomic dataset, which provides in vivo transcriptome data corresponding to hundreds of chemical drugs. However, the relationships between drugs and how those drugs affect the biological process are still unknown. The high dimensionality of the microarray data hinders its application. The aims of this study are to (1) represent the transcriptome data by lower-dimensional vectors, (2) compare drug similarity, (3) represent drug combinations by adding vectors and (4) infer drug mechanism of action (MoA) and genotoxicity features. We borrowed the latent semantic analysis (LSA) technique from natural language processing to represent treatments (drugs with multiple concentrations and time points) by dense vectors, each dimension of which is an orthogonal biological feature. The gProfiler enrichment tool was used for the 100-dimensional vector feature annotation. The similarity between treatments vectors was calculated by the cosine function. Adding vectors may represent drug combinations, treatment times or treatment doses that are not presented in the original data. Drug-drug interaction pairs had a higher similarity than random drug pairs in the hepatocyte data. The vector features helped to reveal the MoA. Differential feature expression was also implicated for genotoxic and non-genotoxic carcinogens. An easy-to-use Web tool was developed by Shiny Web application framework for the exploration of treatment similarities and drug combinations (https://bioinformatics.fafu.edu.cn/drugmatrix/). We represented treatments by vectors and provided a tool that is useful for hypothesis generation in toxicogenomic, such as drug similarity, drug repurposing, combination therapy and MoA.
Collapse
Affiliation(s)
- Liping Lin
- School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, People's Republic of China
| | - Luoyao Wan
- School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, People's Republic of China
| | - Huaqin He
- School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, People's Republic of China
| | - Wei Liu
- School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, People's Republic of China.
| |
Collapse
|
5
|
Shamsuddin AKM, Quinton PM. Concurrent absorption and secretion of airway surface liquids and bicarbonate secretion in human bronchioles. Am J Physiol Lung Cell Mol Physiol 2019; 316:L953-L960. [PMID: 30838869 PMCID: PMC6589593 DOI: 10.1152/ajplung.00545.2018] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 03/01/2019] [Accepted: 03/01/2019] [Indexed: 01/15/2023] Open
Abstract
Although small airways account for the largest fraction of the total conducting airway surfaces, the epithelial fluid and electrolyte transport in small, native airway epithelia has not been well characterized. Investigations have been limited, no doubt, by the complex tissue architecture as well as by its inaccessibility, small dimensions, and lack of applicable assays, especially in human tissues. To better understand how the critically thin layer of airway surface liquid (ASL) is maintained, we applied a "capillary"-Ussing chamber (area ≈1 mm2) to measure ion transport properties of bronchioles with diameters of ~2 mm isolated from resected specimens of excised human lungs. We found that the small human airway, constitutively and concurrently, secretes and absorbs fluid as observed in porcine small airways (50). We found that the human bronchiolar epithelium is also highly anion selective and constitutively secretes bicarbonate ( HCO 3 - ), which can be enhanced pharmacologically by cAMP as well as Ca2+-mediated agonists. Concurrent secretion and absorption of surface liquid along with HCO 3 - secretion help explain how the delicate volume of the fluid lining the human small airway is physiologically buffered and maintained in a steady state that avoids desiccating or flooding the small airway with ASL.
Collapse
Affiliation(s)
- A K M Shamsuddin
- Department of Pediatrics, University of California , San Diego, California
| | - Paul M Quinton
- Department of Pediatrics, University of California , San Diego, California
- Division of Biomedical Sciences, University of California , Riverside, California
| |
Collapse
|
6
|
Andharia N, Hayashi M, Matsuda H. Electrophysiological properties of anion exchangers in the luminal membrane of guinea pig pancreatic duct cells. Pflugers Arch 2018; 470:897-907. [PMID: 29399744 PMCID: PMC5945753 DOI: 10.1007/s00424-018-2116-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 01/10/2018] [Accepted: 01/23/2018] [Indexed: 12/12/2022]
Abstract
The pancreatic duct epithelium secretes the HCO3−-rich pancreatic juice. The HCO3− transport across the luminal membrane has been proposed to be mediated by SLC26A Cl−–HCO3− exchangers. To examine the electrophysiological properties of Cl−–HCO3− exchangers, we directly measured HCO3− conductance in the luminal membrane of the interlobular pancreatic duct cells from guinea pigs using an inside-out patch-clamp technique. Intracellular HCO3− increased the HCO3− conductance with a half-maximal effective concentration value of approximately 30 mM. The selectivity sequence based on permeability ratios was SCN− (1.4) > Cl− (1.2) = gluconate (1.1) = I− (1.1) = HCO3− (1.0) > methanesulfonate (0.6). The sequence of the relative conductance was HCO3− (1.0) > SCN− (0.7) = I− (0.7) > Cl− (0.5) = gluconate (0.4) > methanesulfonate (0.2). The current dependent on intracellular HCO3− was reduced by replacement of extracellular Cl− with gluconate or by H2DIDS, an inhibitor of Cl−–HCO3− exchangers. RT-PCR analysis revealed that the interlobular and main ducts expressed all SLC26A family members except Slc26a5 and Slc26a8. SLC26A1, SLC26A4, SLC26A6, and SLC26A10 were found to be localized to the luminal membrane of the guinea pig pancreatic duct by immunohistochemistry. These results demonstrate that these SLC26A Cl−–HCO3− exchangers may mediate the electrogenic HCO3− transport through the luminal membrane and may be involved in pancreatic secretion in guinea pig ducts.
Collapse
Affiliation(s)
- N Andharia
- Department of Physiology, Kansai Medical University, 2-5-1 Shinmachi, Hirakata, 573-1010, Japan
| | - M Hayashi
- Department of Physiology, Kansai Medical University, 2-5-1 Shinmachi, Hirakata, 573-1010, Japan.
| | - H Matsuda
- Department of Physiology, Kansai Medical University, 2-5-1 Shinmachi, Hirakata, 573-1010, Japan
| |
Collapse
|
7
|
Saint-Criq V, Gray MA. Role of CFTR in epithelial physiology. Cell Mol Life Sci 2016; 74:93-115. [PMID: 27714410 PMCID: PMC5209439 DOI: 10.1007/s00018-016-2391-y] [Citation(s) in RCA: 252] [Impact Index Per Article: 31.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Accepted: 09/28/2016] [Indexed: 12/20/2022]
Abstract
Salt and fluid absorption and secretion are two processes that are fundamental to epithelial function and whole body fluid homeostasis, and as such are tightly regulated in epithelial tissues. The CFTR anion channel plays a major role in regulating both secretion and absorption in a diverse range of epithelial tissues, including the airways, the GI and reproductive tracts, sweat and salivary glands. It is not surprising then that defects in CFTR function are linked to disease, including life-threatening secretory diarrhoeas, such as cholera, as well as the inherited disease, cystic fibrosis (CF), one of the most common life-limiting genetic diseases in Caucasian populations. More recently, CFTR dysfunction has also been implicated in the pathogenesis of acute pancreatitis, chronic obstructive pulmonary disease (COPD), and the hyper-responsiveness in asthma, underscoring its fundamental role in whole body health and disease. CFTR regulates many mechanisms in epithelial physiology, such as maintaining epithelial surface hydration and regulating luminal pH. Indeed, recent studies have identified luminal pH as an important arbiter of epithelial barrier function and innate defence, particularly in the airways and GI tract. In this chapter, we will illustrate the different operational roles of CFTR in epithelial function by describing its characteristics in three different tissues: the airways, the pancreas, and the sweat gland.
Collapse
Affiliation(s)
- Vinciane Saint-Criq
- Epithelial Research Group, Institute for Cell and Molecular Biosciences, University Medical School, Newcastle University, Framlington Place, Newcastle upon Tyne, NE2 4HH UK
| | - Michael A. Gray
- Epithelial Research Group, Institute for Cell and Molecular Biosciences, University Medical School, Newcastle University, Framlington Place, Newcastle upon Tyne, NE2 4HH UK
| |
Collapse
|
8
|
Ito H, Wang J, Strandhoy JW, Rose JC. Importance of the Renal Nerves for Basal and Stimulated Renin mRNA Levels in Fetal and Adult Ovine Kidneys. ACTA ACUST UNITED AC 2016. [DOI: 10.1177/107155760100800604] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
| | | | - Jack W. Strandhoy
- Department of Physiology and Pharmacology, and Department of Obstetrics and Gynecology and Perinatal Research Laboratories, Wake Forest University School of Medicine, Winston-Salem, North Carolina
| | - James C. Rose
- Department of Physiology and Pharmacology, and Department of Obstetrics and Gynecology and Perinatal Research Laboratories, Wake Forest University School of Medicine, Winston-Salem, North Carolina; Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157
| |
Collapse
|
9
|
Harrison PT, Sanz DJ, Hollywood JA. Impact of gene editing on the study of cystic fibrosis. Hum Genet 2016; 135:983-92. [PMID: 27325484 DOI: 10.1007/s00439-016-1693-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2016] [Accepted: 05/31/2016] [Indexed: 12/30/2022]
Abstract
Cystic fibrosis (CF) is a chronic and progressive autosomal recessive disorder of secretory epithelial cells, which causes obstructions in the lung airways and pancreatic ducts of 70,000 people worldwide (for recent review see Cutting Nat Rev Genet 16(1):45-56, 2015). The finding that mutations in the CFTR gene cause CF (Kerem et al. Science 245(4922):1073-1080, 1989; Riordan et al. Science 245(4922):1066-1073, 1989; Rommens et al. Science 245(4922):1059-1065, 1989), was hailed as the very happy middle of a story whose end is a cure for a fatal disease (Koshland Science 245(4922):1029, 1989). However, despite two licensed drugs (Ramsey et al. N Engl J Med 365(18):1663-1672, 2011; Wainwright et al. N Engl J Med 373(3):220-231, 2015), and a formal demonstration that repeated administration of CFTR cDNA to patients is safe and effects a modest but significant stabilisation of disease (Alton et al. Lancet Respir Med 3(9):684-691, 2015), we are still a long way from a cure, with many patients taking over 100 tablets per day, and a mean age at death of 28 years. The aim of this review is to discuss the impact on the study of CF of gene-editing techniques as they have developed over the last 30 years, up to and including the possibility of editing as a therapeutic approach.
Collapse
Affiliation(s)
| | | | - Jennifer A Hollywood
- University College Cork, Cork, Ireland.,The University of Auckland, Auckland, New Zealand
| |
Collapse
|
10
|
Ferreira MJ, McKenna LB, Zhang J, Reichert M, Bakir B, Buza EL, Furth EE, Bogue CW, Rustgi AK, Kaestner KH. Spontaneous Pancreatitis Caused by Tissue-Specific Gene Ablation of Hhex in Mice. Cell Mol Gastroenterol Hepatol 2015; 1:550-569. [PMID: 26740970 PMCID: PMC4698881 DOI: 10.1016/j.jcmgh.2015.06.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
BACKGROUND & AIMS Perturbations in pancreatic ductal bicarbonate secretion cause chronic pancreatitis. The physiologic mechanism of ductal secretion is known, but its transcriptional control is not. We determine the role of the transcription factor hematopoietically expressed homeobox protein (Hhex) in ductal secretion and pancreatitis. METHODS We derived mice with pancreas-specific, Cremediated Hhex gene ablation to determine the requirement of Hhex in the pancreatic duct in early life and in adult stages. Histologic and immunostaining analyses were used to detect the presence of pathology. Pancreatic primary ductal cells were isolated to discover differentially expressed transcripts upon acute Hhex ablation on a cell autonomous level. RESULTS Hhex protein was detected throughout the embryonic and adult ductal trees. Ablation of Hhex in pancreatic progenitors resulted in postnatal ductal ectasia associated with acinar-to-ductal metaplasia, a progressive phenotype that ultimately resulted in chronic pancreatitis. Hhex ablation in adult mice, however, did not cause any detectable pathology. Ductal ectasia in young mice did not result from perturbation of expression of Hnf6, Hnf1β, or the primary cilia genes. RNA-seq analysis of Hhex-ablated pancreatic primary ductal cells showed mRNA levels of the G-protein coupled receptor natriuretic peptide receptor 3 (Npr3), implicated in paracrine signaling, up-regulated by 4.70-fold. CONCLUSIONS Although Hhex is dispensable for ductal cell function in the adult, ablation of Hhex in pancreatic progenitors results in pancreatitis. Our data highlight the critical role of Hhex in maintaining ductal homeostasis in early life and support ductal hypersecretion as a novel etiology of pediatric chronic pancreatitis.
Collapse
Affiliation(s)
- Mark J. Ferreira
- Department of Genetics and Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Lindsay B. McKenna
- Department of Genetics and Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Jia Zhang
- Department of Genetics and Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Maximilian Reichert
- Division of Gastroenterology, Department of Medicine, Abramson Cancer Center, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Basil Bakir
- Division of Gastroenterology, Department of Medicine, Abramson Cancer Center, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Elizabeth L. Buza
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Emma E. Furth
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Clifford W. Bogue
- Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut
| | - Anil K. Rustgi
- Division of Gastroenterology, Department of Medicine, Abramson Cancer Center, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Klaus H. Kaestner
- Department of Genetics and Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania,Correspondence Address correspondence to: Klaus H. Kaestner, PhD, Department of Genetics, Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania, 12–126 Translational Research Center, 3400 Civic Center Boulevard, Philadelphia, Pennsylvania 19104. fax: 215-573-5892.
| |
Collapse
|
11
|
Shamsuddin AKM, Quinton PM. Native small airways secrete bicarbonate. Am J Respir Cell Mol Biol 2014; 50:796-804. [PMID: 24224935 DOI: 10.1165/rcmb.2013-0418oc] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Since the discovery of Cl(-) impermeability in cystic fibrosis (CF) and the cloning of the responsible channel, CF pathology has been widely attributed to a defect in epithelial Cl(-) transport. However, loss of bicarbonate (HCO3(-)) transport also plays a major, possibly more critical role in CF pathogenesis. Even though HCO3(-) transport is severely affected in the native pancreas, liver, and intestines in CF, we know very little about HCO3(-) secretion in small airways, the principle site of morbidity in CF. We used a novel, mini-Ussing chamber system to investigate the properties of HCO3(-) transport in native porcine small airways (∼ 1 mm φ). We assayed HCO3(-) transport across small airway epithelia as reflected by the transepithelial voltage, conductance, and equivalent short-circuit current with bilateral 25-mM HCO3(-) plus 125-mM NaGlu Ringer's solution in the presence of luminal amiloride (10 μM). Under these conditions, because no major transportable anions other than HCO3(-) were present, we took the equivalent short-circuit current to be a direct measure of active HCO3(-) secretion. Applying selective agonists and inhibitors, we show constitutive HCO3(-) secretion in small airways, which can be stimulated significantly by β-adrenergic- (cAMP) and purinergic (Ca(2+)) -mediated agonists, independently. These results indicate that two separate components for HCO3(-) secretion, likely via CFTR- and calcium-activated chloride channel-dependent processes, are physiologically regulated for likely roles in mucus clearance and antimicrobial innate defenses of small airways.
Collapse
Affiliation(s)
- A K M Shamsuddin
- 1 Department of Pediatrics, University of California San Diego, La Jolla, California; and
| | | |
Collapse
|
12
|
Ruan YC, Chen H, Chan HC. Ion channels in the endometrium: regulation of endometrial receptivity and embryo implantation. Hum Reprod Update 2014; 20:517-29. [PMID: 24591147 DOI: 10.1093/humupd/dmu006] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND Although embryo implantation is a prerequisite for human reproduction, it remains a poorly understood process. The molecular mechanisms regulating endometrial receptivity and/or embryo implantation are still largely unclear. METHODS Pubmed and Medline literature databases were searched for articles in English published up to December 2013 with relevant keywords including 'endometrium', 'Na(+), Cl(-), K(+), or Ca(2+) channels', 'ion channels', 'endometrial receptivity', 'blastocyst implantation' and 'embryo implantation'. RESULTS At the time of writing, more than 14 types of ion channels, including the cystic fibrosis transmembrane conductance regulator, epithelial sodium channel and various Ca(2+) and K(+) channels, had been reported to be expressed in the endometrium or cells of endometrial origin. In vitro and/or in vivo studies conducted on different species, including rodents, pigs and humans, demonstrated the involvement of various ion channels in the process of embryo implantation by regulating: (i) uterine luminal fluid volume; (ii) decidualization; and (iii) the expression of the genes associated with implantation. Importantly, abnormal ion channel expression was found to be associated with implantation failure in IVF patients. CONCLUSIONS Ion channels in the endometrium are emerging as important players in regulating endometrial receptivity and embryo implantation. Abnormal expression or function of ion channels in the endometrium may lead to impaired endometrial receptivity and/or implantation failure. Further investigation into the roles of endometrial ion channels may provide a better understanding of the complex process of embryo implantation and thus reveal novel targets for diagnosis and treatment of implantation failure.
Collapse
Affiliation(s)
- Ye Chun Ruan
- Sichuan University - The Chinese University of Hong Kong Joint Laboratory for Reproductive Medicine, Key Laboratory of Obstetric, Gynecologic and Pediatric Diseases and Birth Defects of Ministry of Education, West China Second University Hospital, Sichuan University, Chengdu 610041, People's Republic of China Epithelial Cell Biology Research Center, School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong
| | - Hui Chen
- Sichuan University - The Chinese University of Hong Kong Joint Laboratory for Reproductive Medicine, Key Laboratory of Obstetric, Gynecologic and Pediatric Diseases and Birth Defects of Ministry of Education, West China Second University Hospital, Sichuan University, Chengdu 610041, People's Republic of China Epithelial Cell Biology Research Center, School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong
| | - Hsiao Chang Chan
- Sichuan University - The Chinese University of Hong Kong Joint Laboratory for Reproductive Medicine, Key Laboratory of Obstetric, Gynecologic and Pediatric Diseases and Birth Defects of Ministry of Education, West China Second University Hospital, Sichuan University, Chengdu 610041, People's Republic of China Epithelial Cell Biology Research Center, School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong
| |
Collapse
|
13
|
Linley J, Loganathan A, Kopanati S, Sandle GI, Hunter M. Evidence that two distinct crypt cell types secrete chloride and potassium in human colon. Gut 2014; 63:472-9. [PMID: 23740188 DOI: 10.1136/gutjnl-2013-304695] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/08/2022]
Abstract
BACKGROUND Human colon may secrete substantial amounts of water secondary to chloride (Cl(-)) and/or potassium (K(+)) secretion in a variety of diarrhoeal diseases. Ion secretion occurs via Cl(-) and K(+) channels, which are generally assumed to be co-located in the colonocyte apical membrane, although their exact cellular sites remain unclear. OBJECTIVE To investigate the location of apical Cl(-) (CFTR) and apical K(+) (large conductance; BK) channels within human colonic epithelium. DESIGN Whole-cell patch clamp recordings were obtained from intact human colonic crypts. Specific blockers of K(+) channels and CFTR identified different types of K(+) channel and CFTR under resting conditions and after stimulating intracellular cAMP with forskolin. The BK channel β3-subunit was localised by immunostaining. RESULTS Two types of crypt cells were identified. One (73% of cells) had whole-cell currents dominated by intermediate conductance (IK) K(+) channels under resting conditions, which developed large CFTR-mediated currents in response to increasing intracellular cAMP. The other (27% of cells) had resting currents dominated by BK channels inhibited by the BK channel blocker penitrem A, but insensitive to both forskolin and the IK channel blocker clotrimazole. Immunostaining showed co-localisation of the BK channel β3-subunit and the goblet cell marker, MUC2. CONCLUSIONS In human colon, Cl(-) secretion originates from the dominant population of colonocytes expressing apical CFTR, whereas K(+) secretion is derived from a smaller population of goblet cells expressing apical BK channels. These findings provide new insights into the pathophysiology of secretory diarrhoea and should be taken into account during the development of anti-diarrhoeal drugs.
Collapse
Affiliation(s)
- John Linley
- Institute of Systems and Membrane Biology, University of Leeds, , Leeds, West Yorkshire, UK
| | | | | | | | | |
Collapse
|
14
|
Lazrak A, Fu L, Bali V, Bartoszewski R, Rab A, Havasi V, Keiles S, Kappes J, Kumar R, Lefkowitz E, Sorscher EJ, Matalon S, Collawn JF, Bebok Z. The silent codon change I507-ATC->ATT contributes to the severity of the ΔF508 CFTR channel dysfunction. FASEB J 2013; 27:4630-45. [PMID: 23907436 PMCID: PMC4046180 DOI: 10.1096/fj.13-227330] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Accepted: 07/15/2013] [Indexed: 01/08/2023]
Abstract
The most common disease-causing mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene is the out-of-frame deletion of 3 nucleotides (CTT). This mutation leads to the loss of phenylalanine-508 (ΔF508) and a silent codon change (SCC) for isoleucine-507 (I507-ATC→ATT). ΔF508 CFTR is misfolded and degraded by endoplasmic reticulum-associated degradation (ERAD). We have demonstrated that the I507-ATC→ATT SCC alters ΔF508 CFTR mRNA structure and translation dynamics. By comparing the biochemical and functional properties of the I507-ATT and I507-ATC ΔF508 CFTR, we establish that the I507-ATC→ATT SCC contributes to the cotranslational misfolding, ERAD, and to the functional defects associated with ΔF508 CFTR. We demonstrate that the I507-ATC ΔF508 CFTR is less susceptible to the ER quality-control machinery during translation than the I507-ATT, although 27°C correction is necessary for sufficient cell-surface expression. Whole-cell patch-clamp recordings indicate sustained, thermally stable cAMP-activated Cl(-) transport through I507-ATC and unstable function of the I507-ATT ΔF508 CFTR. Single-channel recordings reveal improved gating properties of the I507-ATC compared to I507-ATT ΔF508 CFTR (NPo=0.45±0.037 vs. NPo=0.09±0.002; P<0.001). Our results signify the role of the I507-ATC→ATT SCC in the ΔF508 CFTR defects and support the importance of synonymous codon choices in determining the function of gene products.
Collapse
Affiliation(s)
- Ahmed Lazrak
- 2Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham, 1918 University Blvd., MCLM 350A, Birmingham, AL 35294, USA.
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
15
|
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) protein is highly expressed in the pancreatic duct epithelia and permits anions and water to enter the ductal lumen. This results in an increased volume of alkaline fluid allowing the highly concentrated proteins secreted by the acinar cells to remain in a soluble state. This work will expound on the pathophysiology and pathology caused by the malfunctioning CFTR protein with special reference to ion transport and acid-base abnormalities both in humans and animal models. We will also discuss the relationship between cystic fibrosis (CF) and pancreatitis, and outline present and potential therapeutic approaches in CF treatment relevant to the pancreas.
Collapse
Affiliation(s)
- Michael Wilschanski
- Pediatric Gastroenterology, Hadassah University Hospital, Jerusalem 91240, Israel
| | | |
Collapse
|
16
|
Uc A, Giriyappa R, Meyerholz DK, Griffin M, Ostedgaard LS, Tang XX, Abu-El-Haija M, Stoltz DA, Ludwig P, Pezzulo A, Abu-El-Haija M, Taft P, Welsh MJ. Pancreatic and biliary secretion are both altered in cystic fibrosis pigs. Am J Physiol Gastrointest Liver Physiol 2012; 303:G961-8. [PMID: 22936270 PMCID: PMC3469695 DOI: 10.1152/ajpgi.00030.2012] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The pancreas, liver, and gallbladder are commonly involved in cystic fibrosis (CF), and acidic, dehydrated, and protein-rich secretions are characteristic findings. Pancreatic function studies in humans have been done by sampling the jejunal fluid. However, it has been difficult to separately study the function of pancreatic and biliary systems in humans with CF, because jejunal fluid contains a mixture of bile and pancreatic fluids. In contrast, pancreatic and biliary ducts open separately into the porcine intestine; therefore, biliary and pancreatic fluid can be individually analyzed in CF pigs. We studied newborn wild-type (WT) and CF pigs and found that CFTR was localized to the pancreatic ducts. We collected bile and pancreatic fluid and analyzed pancreatic enzymes with activity assays and immunoblot. Pancreatic enzyme expression was significantly decreased in CF compared with WT pigs. The volume and pH of pancreatic fluid were significantly lower and protein concentration was >5-fold higher in CF pigs. Secretin stimulation increased pancreatic fluid volume and pH in WT, but not CF, pigs. Baseline bile volume did not differ between WT and CF pigs, but volume did not increase in response to secretin in CF pigs. Bile pH was lower and protein concentration was twofold higher in CF pigs. These results indicate that pancreatic and biliary secretions are altered in CF pigs. Abnormal pancreatic and biliary secretion in CF may have important implications in disease pathogenesis.
Collapse
Affiliation(s)
- Aliye Uc
- Department of Pediatrics, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242, USA.
| | - Radhamma Giriyappa
- 1Department of Pediatrics, University of Iowa Carver College of Medicine, Iowa City, Iowa;
| | - David K. Meyerholz
- 2Department of Pathology, University of Iowa Carver College of Medicine, Iowa City, Iowa;
| | - Michelle Griffin
- 1Department of Pediatrics, University of Iowa Carver College of Medicine, Iowa City, Iowa;
| | - Lynda S. Ostedgaard
- 3Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa; and
| | - Xiao Xiao Tang
- 3Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa; and
| | - Marwa Abu-El-Haija
- 1Department of Pediatrics, University of Iowa Carver College of Medicine, Iowa City, Iowa;
| | - David A. Stoltz
- 3Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa; and
| | - Paula Ludwig
- 3Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa; and
| | - Alejandro Pezzulo
- 3Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa; and
| | - Maisam Abu-El-Haija
- 1Department of Pediatrics, University of Iowa Carver College of Medicine, Iowa City, Iowa;
| | - Peter Taft
- 3Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa; and
| | - Michael J. Welsh
- 3Department of Internal Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa; and ,4Howard Hughes Medical Institute, University of Iowa Carver College of Medicine, Iowa City, Iowa
| |
Collapse
|
17
|
Lee MG, Ohana E, Park HW, Yang D, Muallem S. Molecular mechanism of pancreatic and salivary gland fluid and HCO3 secretion. Physiol Rev 2012; 92:39-74. [PMID: 22298651 DOI: 10.1152/physrev.00011.2011] [Citation(s) in RCA: 275] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Fluid and HCO(3)(-) secretion is a vital function of all epithelia and is required for the survival of the tissue. Aberrant fluid and HCO(3)(-) secretion is associated with many epithelial diseases, such as cystic fibrosis, pancreatitis, Sjögren's syndrome, and other epithelial inflammatory and autoimmune diseases. Significant progress has been made over the last 20 years in our understanding of epithelial fluid and HCO(3)(-) secretion, in particular by secretory glands. Fluid and HCO(3)(-) secretion by secretory glands is a two-step process. Acinar cells secrete isotonic fluid in which the major salt is NaCl. Subsequently, the duct modifies the volume and electrolyte composition of the fluid to absorb the Cl(-) and secrete HCO(3)(-). The relative volume secreted by acinar and duct cells and modification of electrolyte composition of the secreted fluids varies among secretory glands to meet their physiological functions. In the pancreas, acinar cells secrete a small amount of NaCl-rich fluid, while the duct absorbs the Cl(-) and secretes HCO(3)(-) and the bulk of the fluid in the pancreatic juice. Fluid secretion appears to be driven by active HCO(3)(-) secretion. In the salivary glands, acinar cells secrete the bulk of the fluid in the saliva that is driven by active Cl(-) secretion and contains high concentrations of Na(+) and Cl(-). The salivary glands duct absorbs both the Na(+) and Cl(-) and secretes K(+) and HCO(3)(-). In this review, we focus on the molecular mechanism of fluid and HCO(3)(-) secretion by the pancreas and salivary glands, to highlight the similarities of the fundamental mechanisms of acinar and duct cell functions, and to point out the differences to meet gland-specific secretions.
Collapse
Affiliation(s)
- Min Goo Lee
- Department of Pharmacology, Yonsei University College of Medicine, Seoul, Korea
| | | | | | | | | |
Collapse
|
18
|
Gill M, Bartolo RC, Demmers K, Harfoot N, Fan S, Butt G. The distribution and expression of CFTR restricts electrogenic anion secretion to the ileum of the brushtail possum, Trichosurus vulpecula. ACTA ACUST UNITED AC 2011; 214:1943-54. [PMID: 21562182 DOI: 10.1242/jeb.053371] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In eutherian mammals, fluid secretion is essential for intestinal function. This is driven by electrogenic Cl(-) secretion, which involves a NaK2Cl cotransporter (NKCC1) in the enterocyte basolateral membrane and the cystic fibrosis transmembrane conductance regulator (CFTR) in the apical membrane. However, in the possum ileum, NKCC1 expression is low and secretagogues stimulate electrogenic HCO(3)(-) secretion driven by a basolateral NaHCO(3) cotransporter (pNBCe1). Here we investigated whether electrogenic anion secretion occurs in possum duodenum and jejunum and determined the role of CFTR in possum intestinal anion secretion. Prostaglandin E(2) (PGE(2)) and forskolin stimulated a large increase in ileal short-circuit current (I(sc)), consistent with electrogenic HCO(3)(-) secretion, but had little effect on the duodenal and jejunal I(sc). Furthermore, 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) and N-(2-naphthalenyl)-[(3,5-dibromo-2,4-dihydroxyphenyl)methylene]glycine hydrazide (GlyH101) inhibited cloned possum CFTR in cultured cells and the PGE(2)-stimulated ileal I(sc), implicating CFTR in ileal HCO(3)(-) secretion. Consistent with this, CFTR is expressed in the apical membrane of ileal crypt and lower villous cells, which also express pNBCe1 in the basolateral membrane. In contrast, duodenal and jejunal CFTR expression is low relative to the ileum. Jejunal pNBCe1 expression is also low, whereas duodenal and ileal pNBCe1 expression are comparable. All regions have low NKCC1 expression. These results indicate that cAMP-dependent electrogenic Cl(-) secretion does not occur in the possum small intestine because of the absence of CFTR and NKCC1. Furthermore, CFTR functions as the apical anion conductance associated with HCO(3)(-) secretion and its distribution limits electrogenic HCO(3)(-) secretion to the ileum.
Collapse
Affiliation(s)
- Mike Gill
- Department of Physiology, School of Medical Sciences, University of Otago, Dunedin, New Zealand
| | | | | | | | | | | |
Collapse
|
19
|
Zhang K, Yin L, Zhang M, Parker MD, Binder HJ, Salzman P, Zhang L, Okunieff P, Vidyasagar S. Radiation decreases murine small intestinal HCO3−secretion. Int J Radiat Biol 2011; 87:878-88. [DOI: 10.3109/09553002.2011.583314] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
|
20
|
Abstract
The pancreas has both endocrine and exocrine functions. As an endocrine organ, stimulation of the pancreatic β-cells results in insulin secretion to control systemic glucose levels. The exocrine function of the pancreas and the need for alkaline pancreatic secretion (pH 8.0-8.5) have been appreciated for more than 40 years. Yet, our knowledge of the cellular mechanisms (signaling, transporters and channels) which accomplish these critical functions has evolved greatly. In the mid-1990s, basolateral Na-bicarbonate (HCO(3)(-)) uptake by NBCe1 (Slc4a4) was shown to be critical for the generation of approximately 75% of stimulated HCO(3)(-) secretion. In the last 10 years, several new HCO(3)(-) transporters in the Slc26 family and their interaction with the cystic fibrosis transmembrane conductance regulator-chloride channel have elucidated the HCO(3)(-) exit step at the ductal lumen. Most recently, both IRBIT (inositol 1,4,5-trisphosphate receptor-binding protein) and WNK [with no lysine (K)] kinase have been implicated as additional HCO(3)(-) secretory controllers. and IAP.
Collapse
Affiliation(s)
- Aleksandra Sinđić
- Department of Physiology, School of Medicine, University of Zagreb, Zagreb, Croatia
| | | | - Michael F. Romero
- Department of Physiology and Biomedical Engineering, Rochester, Minn., USA,Mayo Clinic O'Brien Urology Research Center, Mayo Clinic College of Medicine, Rochester, Minn., USA,*Michael F. Romero, PhD, Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, 200 First St SW, Rochester, MN 55905 (USA), Tel. +1 507 284 8127, E-Mail
| |
Collapse
|
21
|
Hug MJ, Clarke LL, Gray MA. How to measure CFTR-dependent bicarbonate transport: from single channels to the intact epithelium. Methods Mol Biol 2011; 741:489-509. [PMID: 21594803 DOI: 10.1007/978-1-61779-117-8_30] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Bicarbonate serves many functions in our body. It is the predominant buffer maintaining a physiological pH in the blood and within our cells. It is also essential for proper digestion of nutrients and solubilization of complex protein mixtures, such as digestive enzymes and mucins, in epithelial secretions. Transepithelial HCO3- transport also drives net fluid secretion in many epithelial tissues including those in the gastrointestinal and reproductive tracts as well as the airways. Indeed, defective bicarbonate secretion is a hallmark of the pathophysiology in the pancreas of most patients suffering from cystic fibrosis. Some, but not all, disease-causing mutations in the CF gene lead to impaired bicarbonate transport when expressed in heterologous systems. Recently developed pharmacological modulators of mutant CFTR have demonstrated an ability to activate chloride transport but little is known about whether they also increase the secretion of bicarbonate. It is therefore essential to assay bicarbonate transport when studying the effect of small molecules on CFTR function. However, due to the chaotropic nature of the ion, the measurement of the absolute bicarbonate concentration and its permeability through CFTR is far from trivial. In this chapter we will review some of the techniques available to measure bicarbonate transport through single ion channels, individual cells, and intact epithelial layers.
Collapse
Affiliation(s)
- Martin J Hug
- Pharmacy, University Medical Center Freiburg, Freiburg, Germany.
| | | | | |
Collapse
|
22
|
Quinton PM. Role of epithelial HCO3⁻ transport in mucin secretion: lessons from cystic fibrosis. Am J Physiol Cell Physiol 2010; 299:C1222-33. [PMID: 20926781 DOI: 10.1152/ajpcell.00362.2010] [Citation(s) in RCA: 148] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The invitation to present the 2010 Hans Ussing lecture for the Epithelial Transport Group of the American Physiological Society offered me a unique, special, and very surprising opportunity to join in saluting a man whom I met only once, but whose work was the basis, not only for my career, but also for finding the molecular defect in the inherited disease cystic fibrosis (CF). In this context, I will venture to make the tribute with a new explanation of why a mutation in a single gene that codes for an anion channel can cause devastation of multiple epithelial systems with pathogenic mucus. In so doing, I hope to raise awareness of a new role for that peculiar anion around which so much physiology revolves, HCO(3)(-). I begin by introducing CF pathology as I question the name of the disease as well as the prevalent view of the basis of its pathology by considering: 1) mucus, 2) salt, and 3) HCO(3)(-). I then present recent data showing that HCO(3)(-) is required for normal mucus discharge, and I will close with conjecture as to how HCO(3)(-) may support mucus discharge and why the failure to transport this electrolyte is pathogenic in CF.
Collapse
Affiliation(s)
- Paul M Quinton
- Department of Pediatrics, Rady Children’s Hospital, University of California San Diego School of Medicine, La Jolla, California 92093-0830, USA.
| |
Collapse
|
23
|
Kim D, Steward MC. The role of CFTR in bicarbonate secretion by pancreatic duct and airway epithelia. THE JOURNAL OF MEDICAL INVESTIGATION 2010; 56 Suppl:336-42. [PMID: 20224219 DOI: 10.2152/jmi.56.336] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
The secretory epithelia of the pancreatic duct and airway share the ability to generate HCO(3)(-)-rich fluids. They both express CFTR (cystic fibrosis transmembrane conductance regulator) at the apical membrane and both are adversely affected by cystic fibrosis. CFTR is predominantly a Cl(-) channel, and it is widely believed that HCO(3)(-) secretion in the pancreatic duct is mediated mainly by a Cl(-)/HCO(3)(-) exchanger at the apical membrane. Studies on airway epithelia, however, have suggested that CFTR, despite its low permeability to HCO(3)(-), may nonetheless be directly responsible for HCO(3)(-) secretion across the apical membrane. This article reviews recent work that has re-examined both of these hypotheses.
Collapse
Affiliation(s)
- Dusik Kim
- Faculty of Life Sciences, University of Manchester, Manchester, UK
| | | |
Collapse
|
24
|
Hoque KM, Woodward OM, van Rossum DB, Zachos NC, Chen L, Leung GPH, Guggino WB, Guggino SE, Tse CM. Epac1 mediates protein kinase A-independent mechanism of forskolin-activated intestinal chloride secretion. ACTA ACUST UNITED AC 2010; 135:43-58. [PMID: 20038525 PMCID: PMC2806414 DOI: 10.1085/jgp.200910339] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Intestinal Cl− secretion is stimulated by cyclic AMP (cAMP) and intracellular calcium ([Ca2+]i). Recent studies show that protein kinase A (PKA) and the exchange protein directly activated by cAMP (Epac) are downstream targets of cAMP. Therefore, we tested whether both PKA and Epac are involved in forskolin (FSK)/cAMP-stimulated Cl− secretion. Human intestinal T84 cells and mouse small intestine were used for short circuit current (Isc) measurement in response to agonist-stimulated Cl− secretion. FSK-stimulated Cl− secretion was completely inhibited by the additive effects of the PKA inhibitor, H89 (1 µM), and the [Ca2+]i chelator, 1,2-bis-(o-aminophenoxy)-ethane-N,N,N’,N’-tetraacetic acid, tetraacetoxymethyl ester (BAPTA-AM; 25 µM). Both FSK and the Epac activator 8-pCPT-2’-O-Me-cAMP (50 µM) elevated [Ca2+]i, activated Ras-related protein 2, and induced Cl− secretion in intact or basolateral membrane–permeabilized T84 cells and mouse ileal sheets. The effects of 8-pCPT-2’-O-Me-cAMP were completely abolished by BAPTA-AM, but not by H89. In contrast, T84 cells with silenced Epac1 had a reduced Isc response to FSK, and this response was completely inhibited by H89, but not by the phospholipase C inhibitor U73122 or BAPTA-AM. The stimulatory effect of 8-pCPT-2’-O-Me-cAMP on Cl− secretion was not abolished by cystic fibrosis transmembrane conductance (CFTR) inhibitor 172 or glibenclamide, suggesting that CFTR channels are not involved. This was confirmed by lack of effect of 8-pCPT-2’-O-Me-cAMP on whole cell patch clamp recordings of CFTR currents in Chinese hamster ovary cells transiently expressing the human CFTR channel. Furthermore, biophysical characterization of the Epac1-dependent Cl− conductance of T84 cells mounted in Ussing chambers suggested that this conductance was hyperpolarization activated, inwardly rectifying, and displayed a Cl−>Br−>I− permeability sequence. These results led us to conclude that the Epac-Rap-PLC-[Ca2+]i signaling pathway is involved in cAMP-stimulated Cl− secretion, which is carried by a novel, previously undescribed Cl− channel.
Collapse
Affiliation(s)
- Kazi Mirajul Hoque
- Department of Medicine, GI Division, Johns Hopkins University, Baltimore, MD 21205, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
25
|
Connors N, Valego NK, Carey LC, Figueroa JP, Rose JC. Fetal and postnatal renin secretion in female sheep exposed to prenatal betamethasone. Reprod Sci 2010; 17:239-46. [PMID: 20065298 DOI: 10.1177/1933719109351752] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Prenatal glucocorticoids have long-term effects on the kidney and blood pressure that may be mediated by the renin-angiotensin system (RAS). We studied the effects of antenatal betamethasone administration on renin in fetal and adult female sheep. Pregnant sheep received 2 doses of betamethasone or vehicle, at 80 and 81 days of gestation (dGA). Fetuses were delivered within 24 hours following treatment, at 135 dGA, or allowed to continue to term. Plasma and kidney samples were collected from fetal and 1-year-old sheep. Plasma and renal renin and renin messenger RNA (mRNA) were measured. Significant decreases in plasma and renal renin and renin mRNA were apparent in female betamethasone fetuses at 80 dGA (P < .05). At 135 dGA, renal renin concentrations were significantly increased in betamethasone fetuses. At 1 year, renin levels were similar in the 2 groups. These findings suggest that prenatal betamethasone has an immediate effect on expression and secretion of renin. The downregulation of renin at 80 dGA may affect nephron development.
Collapse
Affiliation(s)
- Ngina Connors
- Department of Obstetrics and Gynecology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA
| | | | | | | | | |
Collapse
|
26
|
Martens CJ, Ballard ST. Effects of secretagogues on net and unidirectional liquid fluxes across porcine bronchial airways. Am J Physiol Lung Cell Mol Physiol 2009; 298:L270-6. [PMID: 19915159 DOI: 10.1152/ajplung.00253.2009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Rates of liquid secretion and absorption across the bronchopulmonary airways are important for regulating airway surface liquid volume and maintaining mucociliary transport. The current study demonstrates the feasibility of measuring not just net liquid movements but unidirectional liquid movements across isolated intact bronchi from swine. Airways were liquid filled to assess both net liquid movements, and, in the presence of NPPB to selectively inhibit secretion, unidirectional absorption. Unidirectional liquid secretion rates were determined by subtraction. For comparison, net liquid movements were assessed in air-filled airways in parallel. In the absence of secretagogues, unidirectional absorption was observed (4.63 +/- 0.53 microl.cm(-2).h(-1)) with little unidirectional secretion (1.42 +/- 0.36 microl.cm(-2).h(-1)). ACh, substance P (SP), and vasoactive intestinal peptide (VIP) all induced unidirectional secretion (10.64 +/- 1.52 microl.cm(-2).h(-1), 14.16 +/- 1.39 microl.cm(-2).h(-1), and 4.25 +/- 0.25 microl.cm(-2).h(-1), respectively) without affecting unidirectional absorption. Net liquid secretion in air-filled airways was close to that in liquid-filled airways except with VIP. VIP induced net secretion in air-filled airways (4.44 +/- 1.26 microl.cm(-2).h(-1)), but negligible net change in liquid movement occurred in liquid-filled airways. This effect was likely to have been caused by the higher solid content of the VIP-induced mucous liquid (3.98 +/- 0.26%) compared with the ACh- and SP-induced liquid (2.06 +/- 0.07% and 2.15 +/- 0.07%, respectively). We conclude that this technique allows important quantitative distinctions to be made between liquid secretion and absorption in intact bronchial airways.
Collapse
Affiliation(s)
- Chelsea J Martens
- Department of Physiology, College of Medicine, University of South Alabama, Mobile, Alabama, USA
| | | |
Collapse
|
27
|
CFTR expression but not Cl- transport is involved in the stimulatory effect of bile acids on apical Cl-/HCO3- exchange activity in human pancreatic duct cells. Pancreas 2009; 38:921-9. [PMID: 19752774 DOI: 10.1097/mpa.0b013e3181b65d34] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
OBJECTIVES Low doses of chenodeoxycholate (CDC) stimulate apical anion exchange and HCO3(-) secretion in guinea pig pancreatic duct cells (Gut. 2008;57:1102-1112). We examined the effects of CDC on intracellular pH (pHi), intracellular Ca(2+) concentration ([Ca(2+)]i), and apical Cl(-)/HCO3(-) exchange activity in human pancreatic duct cells and determined whether any effects were dependent on cystic fibrosis transmembrane conductance regulator (CFTR) expression and Cl(-) channel activity. METHODS Polarized CFPAC-1 cells (expressing F508del CFTR) were transduced with Sendai virus constructs containing complementary DNAs for either wild-type CFTR or beta-galactosidase. Microfluorimetry was used to record pHi and [Ca(2+)]i and apical Cl(-)/HCO3(-) exchange activity. Patch clamp experiments were performed on isolated guinea pig duct cells. RESULTS Chenodeoxycholate induced a dose-dependent intracellular acidification and a marked increase in [Ca(2+)]i in CFPAC-1 cells. CFTR expression slightly reduced the rate of acidification but did not affect the [Ca(2+)]i changes. Luminal administration of 0.1 mmol/L of CDC significantly elevated apical Cl(-)/HCO3(-) exchange activity but only in cells that expressed CFTR. However, CDC did not activate CFTR Cl(-) conductance. CONCLUSIONS Bile salts modulate pHi, [Ca(2+)]i, and apical anion exchange activity in human pancreatic duct cells. The stimulatory effect of CDC on anion exchangers requires CFTR expression but not CFTR channel activity.
Collapse
|
28
|
Tuo B, Wen G, Seidler U. Differential activation of the HCO(3)(-) conductance through the cystic fibrosis transmembrane conductance regulator anion channel by genistein and forskolin in murine duodenum. Br J Pharmacol 2009; 158:1313-21. [PMID: 19788494 DOI: 10.1111/j.1476-5381.2009.00398.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND AND PURPOSE Many cystic fibrosis (CF)-associated mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) anion channels affect CFTR-activated HCO(3)(-) transport more than Cl(-) transport. Targeting the CFTR HCO(3)(-) conductance, if possible, may therefore be of major therapeutic benefit. In the present study, we examined the effects of genistein and forskolin on duodenal mucosal HCO(3)(-) and Cl(-) secretion. EXPERIMENTAL APPROACH Murine duodenal mucosal HCO(3)(-) and Cl(-) secretions were examined in vitro in Ussing chambers by the pH stat and short circuit current (I(sc)) techniques. KEY RESULTS Genistein markedly stimulated duodenal HCO(3)(-) secretion and I(sc) in a dose-dependent manner in CFTR wild-type mice, but not in CFTR null mice. CFTR(inh)-172, a highly specific CFTR inhibitor, inhibited genistein-stimulated duodenal HCO(3)(-) secretion and I(sc) in wild-type mice. Genistein induced 59% net HCO(3)(-) increase and 123% net I(sc) increase over basal value, whereas forskolin, an activator of adenylate cyclase, induced 94% net HCO(3)(-) increase and 507% net I(sc) increase, indicating that, compared with forskolin, genistein induced a relatively high HCO(3)(-)/I(sc) ratio. Further data showed that CFTR HCO(3)(-)/Cl(-) conductance ratio was 1.05 after genistein stimulation, whereas after forskolin stimulation, the CFTR HCO(3)(-)/Cl(-) conductance ratio was 0.27. CONCLUSIONS AND IMPLICATIONS Genistein stimulates duodenal HCO(3)(-) and Cl(-) secretion through CFTR, and has a relatively high selectivity for the CFTR HCO(3)(-) conductance, compared with forskolin. This may indicate the feasibility of selective targeting of the HCO(3)(-) conductance of the CFTR channels.
Collapse
Affiliation(s)
- Biguang Tuo
- Department of Gastroenterology, Affiliated Hospital, Zunyi Medical College, Zunyi, China.
| | | | | |
Collapse
|
29
|
Ducts isolated from the pancreas of CFTR-null mice secrete fluid. Pflugers Arch 2009; 459:203-14. [PMID: 19655163 DOI: 10.1007/s00424-009-0704-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2009] [Accepted: 07/21/2009] [Indexed: 01/01/2023]
Abstract
The pancreatic pathology in cystic fibrosis (CF) is normally attributed to the failure of ductal fluid secretion resulting from the lack of functional CF transmembrane conductance regulator (CFTR). However, murine models of CF show little or no pancreatic pathology. To resolve this dichotomy we analysed the transport mechanisms involved in fluid and electrolyte secretion by pancreatic ducts isolated from CFTR-null mice. Experiments were performed on cultured interlobular duct segments isolated from the pancreas of the Cftr(tm1Cam) strain of CFTR-null mouse. Fluid secretion to the closed luminal space was measured by video microscopy. The secretory response of ducts isolated from CF mice to cAMP-elevating agonists forskolin and secretin was significantly reduced compared with wild type but not abolished. The Cl(-)- and HCO(3) (-) -dependent components of the ductal secretion were affected equally by the absence of CFTR. The secretory response to carbachol stimulation was unaltered in CF ducts. Loading the ductal cells with the Ca2+ chelator BAPTA completely abolished carbachol-evoked secretion, but did not affect forskolin-evoked secretion in CF or wild-type ducts. We conclude that pancreatic duct cells from CF mice can secrete a significant amount of water and electrolytes by a cAMP-stimulated mechanism that is independent of CFTR and cannot be ascribed to the activation of calcium-activated chloride channels.
Collapse
|
30
|
Kantorowicz L, Valego NK, Tang L, Figueroa JP, Chappell MC, Carey LC, Rose JC. Plasma and renal renin concentrations in adult sheep after prenatal betamethasone exposure. Reprod Sci 2009; 15:831-8. [PMID: 19017818 DOI: 10.1177/1933719108318599] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
This study examined whether renin expression and secretion and plasma angiotensin II (Ang II) levels were altered in adult sheep exposed to antenatal betamethasone. Pregnant sheep received injections of 0.17 mg/kg betamethasone or vehicle, at 80 and 81 days of gestation, and offspring were studied at 6 and 18 months of age. At 6 months, plasma prorenin concentrations were significantly lower in betamethasone animals (4.63 +/- 0.64 vs 7.09 +/- 0.83 ng angiotensin I/mL/h, P < .01). The percentage of plasma active renin was significantly higher in the betamethasone group (31.93 +/- 4.09% vs 18.57 +/- 2.79%, P < .01). Plasma and renocortical renin levels were similar in both groups at 18 months, but plasma renin activity was lower than at 6 months. Ang II levels were suppressed by betamethasone. The data indicate that prenatal exposure to betamethasone alters processing and secretion of renin in offspring at 6 months, but that this difference is not apparent at 18 months.
Collapse
Affiliation(s)
- Lucia Kantorowicz
- Department of Obstetrics and Gynecology, Center of Research for Obstetrics and Gynecology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA
| | | | | | | | | | | | | |
Collapse
|
31
|
Pancreatic duct secretion: experimental methods, ion transport mechanisms and regulation. J Physiol Biochem 2008; 64:243-57. [DOI: 10.1007/bf03178846] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
|
32
|
Rakonczay Z, Hegyi P, Hasegawa M, Inoue M, You J, Iida A, Ignáth I, Alton EWFW, Griesenbach U, Ovári G, Vág J, Da Paula AC, Crawford RM, Varga G, Amaral MD, Mehta A, Lonovics J, Argent BE, Gray MA. CFTR gene transfer to human cystic fibrosis pancreatic duct cells using a Sendai virus vector. J Cell Physiol 2007; 214:442-55. [PMID: 17654517 DOI: 10.1002/jcp.21220] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Cystic fibrosis (CF) is a fatal inherited disease caused by the absence or dysfunction of the CF transmembrane conductance regulator (CFTR) Cl- channel. About 70% of CF patients are exocrine pancreatic insufficient due to failure of the pancreatic ducts to secrete a HCO3- -rich fluid. Our aim in this study was to investigate the potential of a recombinant Sendai virus (SeV) vector to introduce normal CFTR into human CF pancreatic duct (CFPAC-1) cells, and to assess the effect of CFTR gene transfer on the key transporters involved in HCO3- transport. Using polarized cultures of homozygous F508del CFPAC-1 cells as a model for the human CF pancreatic ductal epithelium we showed that SeV was an efficient gene transfer agent when applied to the apical membrane. The presence of functional CFTR was confirmed using iodide efflux assay. CFTR expression had no effect on cell growth, monolayer integrity, and mRNA levels for key transporters in the duct cell (pNBC, AE2, NHE2, NHE3, DRA, and PAT-1), but did upregulate the activity of apical Cl-/HCO3- and Na+/H+ exchangers (NHEs). In CFTR-corrected cells, apical Cl-/HCO3- exchange activity was further enhanced by cAMP, a key feature exhibited by normal pancreatic duct cells. The cAMP stimulated Cl-/HCO3- exchange was inhibited by dihydro-4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (H2-DIDS), but not by a specific CFTR inhibitor, CFTR(inh)-172. Our data show that SeV vector is a potential CFTR gene transfer agent for human pancreatic duct cells and that expression of CFTR in CF cells is associated with a restoration of Cl- and HCO3- transport at the apical membrane.
Collapse
Affiliation(s)
- Zoltán Rakonczay
- Institute for Cell and Molecular Biosciences, University of Newcastle, Newcastle upon Tyne, United Kingdom
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
33
|
Chambers LA, Rollins BM, Tarran R. Liquid movement across the surface epithelium of large airways. Respir Physiol Neurobiol 2007; 159:256-70. [PMID: 17692578 PMCID: PMC2696130 DOI: 10.1016/j.resp.2007.06.005] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2007] [Revised: 06/08/2007] [Accepted: 06/08/2007] [Indexed: 01/25/2023]
Abstract
The cystic fibrosis transmembrane conductance regulator CFTR gene is found on chromosome 7 [Kerem, B., Rommens, J.M., Buchanan, J.A., Markiewicz, D., Cox, T.K., Chakravarti, A., Buchwald, M., Tsui, L.C., 1989. Identification of the cystic fibrosis gene: genetic analysis. Science 245, 1073-1080; Riordan, J.R., Rommens, J.M., Kerem, B., Alon, N., Rozmahel, R., Grzelczak, Z., Zielenski, J., Lok, S., Plavsic, N., Chou, J.L., et al., 1989. Identification of the cystic fibrosis gene: cloning and characterization of complementary DNA. Science 245, 1066-1073] and encodes for a 1480 amino acid protein which is present in the plasma membrane of epithelial cells [Anderson, M.P., Sheppard, D.N., Berger, H.A., Welsh, M.J., 1992. Chloride channels in the apical membrane of normal and cystic fibrosis airway and intestinal epithelia. Am. J. Physiol. 263, L1-L14]. This protein appears to have many functions, but a unifying theme is that it acts as a protein kinase C- and cyclic AMP-regulated Cl(-) channel [Winpenny, J.P., McAlroy, H.L., Gray, M.A., Argent, B.E., 1995. Protein kinase C regulates the magnitude and stability of CFTR currents in pancreatic duct cells. Am. J. Physiol. 268, C823-C828; Jia, Y., Mathews, C.J., Hanrahan, J.W., 1997. Phosphorylation by protein kinase C is required for acute activation of cystic fibrosis transmembrane conductance regulator by protein kinase A. J. Biol. Chem. 272, 4978-4984]. In the superficial epithelium of the conducting airways, CFTR is involved in Cl(-) secretion [Boucher, R.C., 2003. Regulation of airway surface liquid volume by human airway epithelia. Pflugers Arch. 445, 495-498] and also acts as a regulator of the epithelial Na(+) channel (ENaC) and hence Na(+) absorption [Boucher, R.C., Stutts, M.J., Knowles, M.R., Cantley, L., Gatzy, J.T., 1986. Na(+) transport in cystic fibrosis respiratory epithelia. Abnormal basal rate and response to adenylate cyclase activation. J. Clin. Invest. 78, 1245-1252; Stutts, M.J., Canessa, C.M., Olsen, J.C., Hamrick, M., Cohn, J.A., Rossier, B.C., Boucher, R.C., 1995. CFTR as a cAMP-dependent regulator of sodium channels. Science 269, 847-850]. In this chapter, we will discuss the regulation of these two ion channels, and how they can influence liquid movement across the superficial airway epithelium.
Collapse
Affiliation(s)
- Lucy A Chambers
- Cystic Fibrosis/Pulmonary Research & Treatment Center, University of North Carolina, Chapel Hill, NC 27599-7248, USA
| | | | | |
Collapse
|
34
|
Tokuda S, Shimamoto C, Yoshida H, Murao H, Kishima GI, Ito S, Kubota T, Hanafusa T, Sugimoto T, Niisato N, Marunaka Y, Nakahari T. % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX! % MathType!MTEF!2!1!+- % feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX % garmWu51MyVXgatuuDJXwAK1uy0HwmaeHbfv3ySLgzG0uy0Hgip5wz % aebbnrfifHhDYfgasaacH8qrps0lbbf9q8WrFfeuY-Hhbbf9v8qqaq % Fr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qq % Q8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeWaeaaakeaaca % qGibGaae4qaiaab+eadaqhaaWcbaGaae4maaqaaiaab2caaaaaaa!3B86! $$ {\text{HCO}}^{{\text{ - }}}_{{\text{3}}}$$ -dependent pHi recovery and overacidification induced by % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX! % MathType!MTEF!2!1!+- % feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX % garmWu51MyVXgatuuDJXwAK1uy0HwmaeHbfv3ySLgzG0uy0Hgip5wz % aebbnrfifHhDYfgasaacH8qrps0lbbf9q8WrFfeuY-Hhbbf9v8qqaq % Fr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qq % Q8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeWaeaaakeaaca % qGobGaaeisamaaDaaaleaacaaI0aaabaGaey4kaScaaaaa!3AF9! $$ {\text{NH}}^{ + }_{4}$$ pulse in rat lung alveolar type II cells: % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX! % MathType!MTEF!2!1!+- % feaaeaart1ev0aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX % garmWu51MyVXgatuuDJXwAK1uy0HwmaeHbfv3ySLgzG0uy0Hgip5wz % aebbnrfifHhDYfgasaacH8qrps0lbbf9q8WrFfeuY-Hhbbf9v8qqaq % Fr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qq % Q8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeWaeaaakeaaca % qGibGaae4qaiaab+eadaqhaaWcbaGaaG4maaqaaiabgkHiTaaaaaa!3BCA! $$ {\text{HCO}}^{ - }_{3} $$ -dependent NH3 excretion from lungs? Pflugers Arch 2007; 455:223-39. [PMID: 17562070 DOI: 10.1007/s00424-007-0281-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2007] [Revised: 04/13/2007] [Accepted: 04/19/2007] [Indexed: 11/24/2022]
Abstract
Intracellular pH (pHi) after the NH+4 pulse addition and its removal were measured in isolated alveolar type II cells (ATII cells) using BCECF fluorescence. In the absence of HCO(-3), the NH+4 pulse addition increased pHi (alkali jump) and its removal decreased pH(i) (acid jump) to the control level (no overacidification). This pHi change was induced by reaction 1 (NH3 + H+ <--> NH+4). However, in the presence of HCO(-3), the NH+4 pulse removal decreased pHi (acid jump) with overacidification. The extent of overacidification was decreased by acetazolamide (a carbonic anhydrase inhibitor), bumetanide (an inhibitor of Na+/K+/2Cl(-) cotransporter [NKCC]), and NPPB (an inhibitor of Cl(-) channel). The NH+4 pulse addition led to the accumulation of NH+4 in ATII cells via reaction 1 and NKCC, and the NH+4 pulse removal induced reaction 2 (NH+4 + HCO(-3) --> NH3 + H+ HCO(-3)) in addition to the reversal of reaction 1. Thus, NH+4 that entered via NKCC reacts with HCO(-3) (reaction 2) to produce H+, which induces overacidification in the acid jump. After the overacidification, the pH(i) recovery consisted of a rapid recovery (first phase) followed by a slow recovery (second phase). The first phase was inhibited by NPPB, glybenclamide, amiloride, and an Na+-free solution, and the second phase was inhibited by DIDS, MIA, and an Na+-free solution. Both phases were accelerated by a high extracellular HCO(-3) concentration. These observations indicate that the first phase was induced by HCO(-3) entry via Cl(-) channels coupled with Na+ channels activities, and that the second phase was induced by H+ extrusion via Na+/H+ exchanger and by HCO(-3) entry via HCO(-3) cotransporter. Thus, in ATII cells, HCO(-3) entry via Cl(-) channels is essential for recovering pHi after overacidification during the acid jump and for removing NH+4 that entered via NKCC from ATII cells, suggesting HCO(-3)-dependent NH3 excretion from lungs.
Collapse
Affiliation(s)
- Sachiko Tokuda
- Central Research Laboratory Nakahari Project, Osaka Medical College, 2-7 Daigakucho, Takatsuki 569-8686, Japan
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
35
|
Abstract
Lessons from the sweat gland on cystic fibrosis (CF) began long before modern medicine became a science. In European folklore, the curse that “a child that taste salty when kissed will soon die” (Alonso y de los Ruyzes de Fonteca J. Diez Previlegios para Mugeres Prenadas. Henares, Spain, 1606) has been taken by many as a direct reference to cystic fibrosis [Busch R. Acta Univ Carol Med (Praha) 36: 13–15, 1990]. The high salt concentration in sweat from patients with CF is now accepted as almost pathognomonic with this fatal genetic disease, but the earliest descriptions of cystic fibrosis as a disease entity did not mention sweat or sweat glands (Andersen DH. Am J Dis Child 56: 344–399, 1938; Andersen DH, Hodges RG. Am J Dis Child 72: 62–80, 1946). Nonetheless, defective sweating soon became an inseparable, and major, component of the constellation of symptoms that diagnose “cystic fibrosis” (Davis PB. Am J Respir Crit Care Med 173: 475–482, 2006). The sweat gland has played a foremost role in diagnosing, defining pathophysiology, debunking misconceptions, and increasing our understanding of the effects of the disease on organs, tissues, cells, and molecules. The sweat gland has taught us much.
Collapse
Affiliation(s)
- Paul M Quinton
- Biomedical Sciences, University of California, Riverside, USA.
| |
Collapse
|
36
|
Chen K, Carey LC, Valego NK, Liu J, Rose JC. Combined thyroidectomy and renal denervation suppress renin expression and secretion in fetal sheep. ACTA ACUST UNITED AC 2006; 13:604-9. [PMID: 17056283 DOI: 10.1016/j.jsgi.2006.07.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2006] [Indexed: 10/24/2022]
Abstract
BACKGROUND AND OBJECTIVES Activity of the fetal renin-angiotensin system (RAS) is developmentally regulated, increasing in late gestation toward term. Thyroid hormone and the renal nerves are both important modulators of renal RAS maturation; however, ablation of either influence alone does not totally block the aforementioned developmental late gestation increase in RAS in fetal sheep. In the current study, we used the technique of thyroidectomy combined with bilateral renal denervation (TX+D), which removes thyroid hormone from the circulation and abolishes effects of renal nerve activity, to determine if simultaneous removal of their effects on the kidney would markedly alter renin expression and secretion in late gestation. METHODS TX+D was performed at 120 days of gestation age (dGA). Control fetuses were sham-operated. Immediately before necropsy (approximately 138 dGA), fetuses were infused with isoproterenol to examine plasma active and prorenin changes in response to beta-adrenergic stimulation. RESULTS TX+D decreased plasma thyroid hormone concentrations, renal renin mRNA, renal active and prorenin levels, and plasma active and prorenin concentrations. Isoproterenol-induced increases in plasma active renin were also reduced in TX+D fetuses. TX+D did not alter renal angiotensin (Ang) II subtype receptor (AT2) expression close to term. CONCLUSION These findings suggest that TX+D synergize in the suppression of fetal renin expression.
Collapse
Affiliation(s)
- Kai Chen
- Department of Obstetrics/Gynecology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157-1066, USA
| | | | | | | | | |
Collapse
|
37
|
Palmer ML, Lee SY, Carlson D, Fahrenkrug S, O'Grady SM. Stable knockdown of CFTR establishes a role for the channel in P2Y receptor-stimulated anion secretion. J Cell Physiol 2006; 206:759-70. [PMID: 16245306 DOI: 10.1002/jcp.20519] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
P2Y receptor regulation of anion secretion was investigated in porcine endometrial gland (PEG) epithelial cells. P2Y2, P2Y4, and P2Y6 receptors were detected in monolayers of PEG cells and immunocytochemistry indicated that P2Y4 receptors were located in the apical membrane. Apical membrane current measurements showed that Ca2+-dependent and PKC-dependent Cl- channels were activated following treatment with uridine triphosphate (UTP) (5 microM). Current-voltage relationships comparing calcium-dependent and PKC-dependent UTP responses under biionic conditions showed significant differences in selectivity between Cl-)and I- for the PKC-dependent conductance (P(I)/P(Cl) = 0.76), but not for Ca2+-dependent conductance (PI/P(Cl) = 1.02). The I-/Cl- permeability ratio for the PKC-dependent conductance was identical to that measured for 8-cpt cAMP. Furthermore, PKC stimulation using phorbol 12-myristate 13-acetate (PMA) activated an apical membrane Cl- conductance that was blocked by the CFTR selective inhibitor, CFTRinh-172. CFTR silencing, accomplished by stable expression of small hairpin RNAs (shRNA), blocked the PKC-activated conductance associated with UTP stimulation and provided definitive evidence of a role for CFTR in anion secretion. CFTR activation increased the initial magnitude of Cl- secretion, and provided a more sustained secretory response compared to conditions where only Ca2+-activated Cl- channels were activated by UTP. Measurements of [cAMP]i following UTP and PMA stimulation were not significantly different than untreated controls. Thus, these results demonstrate that UTP and PMA activation of CFTR occurs independently of increases in intracellular cAMP and extend the findings of earlier studies of CFTR regulation by PKC in Xenopus oocytes to a mammalian anion secreting epithelium.
Collapse
Affiliation(s)
- Melissa L Palmer
- Department of Physiology, University of Minnesota, St. Paul, Minnesota 55108, USA
| | | | | | | | | |
Collapse
|
38
|
Abstract
UNLABELLED Intrauterine growth retardation is associated with oligonephropathy and the risk of hypertension and renal disease in adulthood. Animal study data show that nephron density is directly related to protein nutrition status during nephrogenesis. Among infants born at low gestation, postnatal growth retardation and major deficits in energy and protein intake have been reported. CONCLUSION Since nephrogenesis occurs mainly in late gestation, increasing protein intake during nephrogenesis could minimize the risk of long-term morbidities associated with oligonephropathy.
Collapse
Affiliation(s)
- Melinda Y Yeung
- Department of Pharmacy, The Children's Hospital at Westmead, New South Wales, Australia.
| |
Collapse
|
39
|
Simpson JE, Gawenis LR, Walker NM, Boyle KT, Clarke LL. Chloride conductance of CFTR facilitates basal Cl-/HCO3- exchange in the villous epithelium of intact murine duodenum. Am J Physiol Gastrointest Liver Physiol 2005; 288:G1241-51. [PMID: 15650130 DOI: 10.1152/ajpgi.00493.2004] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Villi of the proximal duodenum are situated for direct exposure to gastric acid chyme. However, little is known about active bicarbonate secretion across villi that maintains the protective alkaline mucus barrier, a process that may be compromised in cystic fibrosis (CF), i.e., in the absence of a functional CF transmembrane conductance regulator (CFTR) anion channel. We investigated Cl(-)/HCO(3)(-) exchange activity across the apical membrane of epithelial cells located at the midregion of villi in intact duodenal mucosa from wild-type (WT) and CF mice using the pH-sensitive dye BCECF. Under basal conditions, the Cl(-)/HCO(3)(-) exchange rate was reduced by approximately 35% in CF compared with WT villous epithelium. Cl(-)/HCO(3)(-) exchange in WT and CF villi responded similarly to inhibitors of anion exchange, and membrane depolarization enhanced rates of Cl(-)(out)/HCO(3)(-)(in) exchange in both epithelia. In anion substitution studies, anion(in)/HCO(3)(-)(out) exchange rates were greater in WT epithelium using Cl(-) or NO(3)(-), but decreased to the level of the CF epithelium using the CFTR-impermeant anion, SO(4)(2-). Similarly, treatment of WT epithelium with the CFTR-selective blocker glybenclamide decreased the Cl(-)/HCO(3)(-) exchange rate to the level of CF epithelium. The mRNA expression of Slc26a3 (downregulated in adenoma) and Slc26a6 (putative anion exchanger-1) was similar between WT and CF duodena. From these studies of murine duodenum, we conclude 1) characteristics of Cl(-)/HCO(3)(-) exchange in the villous epithelium are most consistent with Slc26a6 activity, and 2) Cl(-) channel activity of CFTR facilitates apical membrane Cl(-)(in)/HCO(3)(-)(out) exchange by providing a Cl(-) "leak" under basal conditions.
Collapse
Affiliation(s)
- Janet E Simpson
- Departments of Biomedical Sciences , Univ. of Missouri-Columbia, Columbia, MO 65211, USA
| | | | | | | | | |
Collapse
|
40
|
Abstract
In many species the pancreatic duct epithelium secretes HCO3- ions at a concentration of around 140 mM by a mechanism that is only partially understood. We know that HCO3- uptake at the basolateral membrane is achieved by Na+-HCO3- cotransport and also by a H+-ATPase and Na+/H+ exchanger operating together with carbonic anhydrase. At the apical membrane, the secretion of moderate concentrations of HCO3- can be explained by the parallel activity of a Cl-/HCO3- exchanger and a Cl- conductance, either the cystic fibrosis transmembrane conductance regulator (CFTR) or a Ca2+-activated Cl- channel (CaCC). However, the sustained secretion of HCO3- into a HCO- -rich luminal fluid cannot be explained by conventional Cl-/HCO3- exchange. HCO3- efflux across the apical membrane is an electrogenic process that is facilitated by the depletion of intracellular Cl-, but it remains to be seen whether it is mediated predominantly by CFTR or by an electrogenic SLC26 anion exchanger.
Collapse
Affiliation(s)
- Martin C Steward
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom.
| | | | | |
Collapse
|
41
|
Abstract
The assembly of the cystic fibrosis transmembrane regulator (CFTR) chloride channel is of interest from the broad perspective of understanding how ion channels and ABC transporters are formed as well as dealing with the mis-assembly of CFTR in cystic fibrosis. CFTR is functionally distinct from other ABC transporters because it permits bidirectional permeation of anions rather than vectorial transport of solutes. This adaptation of the ABC transporter structure can be rationalized by considering CFTR as a hydrolyzable-ligand-gated channel with cytoplasmic ATP as ligand. Channel gating is initiated by ligand binding when the protein is also phosphorylated by protein kinase A and made reversible by ligand hydrolysis. The two nucleotide-binding sites play different roles in channel activation. CFTR self-associates, possibly as a function of its activation, but most evidence, including the low-resolution three-dimensional structure, indicates that the channel is monomeric. Domain assembly and interaction within the monomer is critical in maturation, stability, and function of the protein. Disease-associated mutations, including the most common, DeltaF508, interfere with domain folding and association, which occur both co- and post-translationally. Intermolecular interactions of mature CFTR have been detected primarily with the N- and C-terminal tails, and these interactions have some impact not only on channel function but also on localization and processing within the cell. The biosynthetic processing of the nascent polypeptide leading to channel assembly involves transient interactions with numerous chaperones and enzymes on both sides of the endoplasmic reticulum membrane.
Collapse
Affiliation(s)
- John R Riordan
- Mayo Clinic College of Medicine, Scottsdale, Arizona, 85259, USA.
| |
Collapse
|
42
|
Wang X, Lytle C, Quinton PM. Predominant constitutive CFTR conductance in small airways. Respir Res 2005; 6:7. [PMID: 15655076 PMCID: PMC548141 DOI: 10.1186/1465-9921-6-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2004] [Accepted: 01/17/2005] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The pathological hallmarks of chronic obstructive pulmonary disease (COPD) are inflammation of the small airways (bronchiolitis) and destruction of lung parenchyma (emphysema). These forms of disease arise from chronic prolonged infections, which are usually never present in the normal lung. Despite the fact that primary hygiene and defense of the airways presumably requires a well controlled fluid environment on the surface of the bronchiolar airway, very little is known of the fluid and electrolyte transport properties of airways of less than a few mm diameter. METHODS We introduce a novel approach to examine some of these properties in a preparation of minimally traumatized porcine bronchioles of about 1 mm diameter by microperfusing the intact bronchiole. RESULTS In bilateral isotonic NaCl Ringer solutions, the spontaneous transepithelial potential (TEP; lumen to bath) of the bronchiole was small (mean +/- sem: -3 +/- 1 mV; n = 25), but when gluconate replaced luminal Cl-, the bionic Cl- diffusion potentials (-58 +/- 3 mV; n = 25) were as large as -90 mV. TEP diffusion potentials from 2:1 NaCl dilution showed that epithelial Cl- permeability was at least 5 times greater than Na+ permeability. The anion selectivity sequence was similar to that of CFTR. The bionic TEP became more electronegative with stimulation by luminal forskolin (5 microM)+IBMX (100 microM), ATP (100 microM), or adenosine (100 microM), but not by ionomycin. The TEP was partially inhibited by NPPB (100 microM), GlyH-101* (5-50 microM), and CFTRInh-172* (5 microM). RT-PCR gave identifying products for CFTR, alpha-, beta-, and gamma-ENaC and NKCC1. Antibodies to CFTR localized specifically to the epithelial cells lining the lumen of the small airways. CONCLUSION These results indicate that the small airway of the pig is characterized by a constitutively active Cl- conductance that is most likely due to CFTR.
Collapse
Affiliation(s)
- Xiaofei Wang
- Dept. Pediatrics, Medical School, University of California, San Diego, San Diego, CA USA
| | - Christian Lytle
- Dept. Biomedical Sciences, University of California, Riverside, CA USA
| | - Paul M Quinton
- Dept. Pediatrics, Medical School, University of California, San Diego, San Diego, CA USA
- Dept. Biomedical Sciences, University of California, Riverside, CA USA
| |
Collapse
|
43
|
Jensen BL, Stubbe J, Madsen K, Nielsen FT, Skøtt O. The renin-angiotensin system in kidney development: role of COX-2 and adrenal steroids. ACTA ACUST UNITED AC 2004; 181:549-59. [PMID: 15283770 DOI: 10.1111/j.1365-201x.2004.01330.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Recent data from studies in rodents with targeted gene disruption and pharmacological antagonists have shown that the renin-angiotensin-aldosterone system (RAAS) and cyclooxygenase type-2 (COX-2) are necessary for late stages of kidney development. The present review summarizes data on the developmental changes of RAAS and COX-2 and the pathways by which they are activated; their possible interplay and the mechanisms by which they affect kidney development. Intrarenal and circulating renin and angiotensin II (ANG II) are stimulated at birth in most mammals. In rats, renin and ANG II stay significantly elevated in the suckling period while aldosterone stabilizes at an adult level. COX-2 is stimulated in thick ascending limb of Henle's loop in the suckling period at a time when urine concentrating ability is not developed. Data suggest that this induction is mediated by combined low plasma glucocorticoid concentration and by a low NaCl intake. Studies with selective inhibitors of COX-2 and COX-2 null mice show that COX-2 activity stimulates renin secretion from JG-cells during postnatal kidney development and that lack of COX-2 activity leads to pathological change in cortical architecture and eventually to renal failure. In the postnatal period, ANG II initiates and maintains pelvic and ureteric contractions necessary for urine flow. Lack of ANG II in the neonatal period is thought to cause injury by a chronic increase of renal pelvic pressure. Aldosterone is crucial for survival and growth in the neonatal period through its effects on sodium reabsorption and the intrarenal sensitivity to aldosterone is increased in the postnatal period. Final maturation of the kidney occurs through an intimate interplay between a low dietary sodium intake and a non-responsive HPA-axis which stimulates cortical COX-2 activity. COX-2 supports increased activity of the RAAS and may contribute to a low concentrating ability.
Collapse
Affiliation(s)
- B L Jensen
- Department of Physiology and Pharmacology, Institute of Medical Biology, University of Southern Denmark, Denmark
| | | | | | | | | |
Collapse
|
44
|
Dif F, Marty C, Baudoin C, de Vernejoul MC, Levi G. Severe osteopenia in CFTR-null mice. Bone 2004; 35:595-603. [PMID: 15336594 DOI: 10.1016/j.bone.2004.05.021] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2004] [Revised: 05/11/2004] [Accepted: 05/12/2004] [Indexed: 10/26/2022]
Abstract
Osteoporosis is a common complication in cystic fibrosis (CF) patients. In this study, we performed a histomorphometric analysis of the bones of a mouse genetic model of human CF in which both copies of the cystic fibrosis transmembrane conductance regulator (CFTR) gene are inactivated. We find that, even in the absence of obvious nutritional and therapeutic differences, the CFTR mutation is associated with severe osteopenia. Bone mineral density (BMD) of total body and of individual bones is significantly diminished. CFTR mutants display a striking significant (50%) reduction of cortical bone width and thinner trabeculae. Analysis of dynamic parameters indicates a significant reduction of bone formation and a concomitant strong increase in bone resorption. Active osteoclasts where found mostly associated with cortical bone. Our data support the concept that CF-associated osteoporosis is part of the syndromic symptoms associated with the CFTR mutation.
Collapse
Affiliation(s)
- Fariel Dif
- UMR5166 CNRS-MNHN, Evolution des Régulations Endocriniennes, 75231 Paris Cedex 5, France
| | | | | | | | | |
Collapse
|
45
|
Fernández-Salazar MP, Pascua P, Calvo JJ, López MA, Case RM, Steward MC, San Román JI. Basolateral anion transport mechanisms underlying fluid secretion by mouse, rat and guinea-pig pancreatic ducts. J Physiol 2004; 556:415-28. [PMID: 14978209 PMCID: PMC1664956 DOI: 10.1113/jphysiol.2004.061762] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Fluid secretion by interlobular pancreatic ducts was determined by using video microscopy to measure the rate of swelling of isolated duct segments that had sealed following overnight culture. The aim was to compare the HCO(3)(-) requirement for secretin-evoked secretion in mouse, rat and guinea-pig pancreas. In mouse and rat ducts, fluid secretion could be evoked by 10 nm secretin and 5 microm forskolin in the absence of extracellular HCO(3)(-). In guinea-pig ducts, however, fluid secretion was totally dependent on HCO(3)(-). Forskolin-stimulated fluid secretion by mouse and rat ducts in the absence of HCO(3)(-) was dependent on extracellular Cl(-) and was completely inhibited by bumetanide (30 microm). It was therefore probably mediated by a basolateral Na(+)-K(+)-2Cl(-) cotransporter. In the presence of HCO(3)(-), forskolin-stimulated fluid secretion was reduced approximately 40% by bumetanide, approximately 50% by inhibitors of basolateral HCO(3)(-) uptake (3 microm EIPA and 500 microm H(2)DIDS), and was totally abolished by simultaneous application of all three inhibitors. We conclude that the driving force for secretin-evoked fluid secretion by mouse and rat ducts is provided by parallel basolateral mechanisms: Na(+)-H(+) exchange and Na(+)-HCO(3)(-) cotransport mediating HCO(3)(-) uptake, and Na(+)-K(+)-2Cl(-) cotransport mediating Cl(-) uptake. The absence or inactivity of the Cl(-) uptake pathway in the guinea-pig pancreatic ducts may help to account for the much higher concentrations of HCO(3)(-) secreted in this species.
Collapse
Affiliation(s)
- M Paz Fernández-Salazar
- Departamento de Fisiología y Farmacología, Universidad de Salamanca, Edificio Departamental, Campus Miguel de Unamuno, 37007 Salamanca, Spain
| | | | | | | | | | | | | |
Collapse
|
46
|
Jin NG, Kim JK, Yang DK, Cho SJ, Kim JM, Koh EJ, Jung HC, So I, Kim KW. Fundamental role of ClC-3 in volume-sensitive Cl- channel function and cell volume regulation in AGS cells. Am J Physiol Gastrointest Liver Physiol 2003; 285:G938-48. [PMID: 12842831 DOI: 10.1152/ajpgi.00470.2002] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Volume regulation is essential for cell function, but it is unknown which channels are involved in a regulatory volume decrease (RVD) in human gastric epithelial cells. Exposure to a hypotonic solution caused the increase in AGS cell volume, followed by the activation of a current. The reversal potential of the swelling-induced current suggested that Cl- was the primary charge carrier. The selectivity sequence for different anions was I- > Br- > Cl- > F- > gluconate. This current was inhibited by flufenamate, DIDS, tamoxifen, and 5-nitro-2-(3-phenylpropylamino)benzoate. Intracellular dialysis of three different anti-ClC-3 antibodies abolished or attenuated the Cl- current and disrupted RVD, whereas the current and RVD was unaltered by anti-ClC-2 antibody. Immunoblot studies demonstrated the presence of ClC-3 protein in Hela and AGS cells. RT-PCR analysis detected expression of ClC-3, MDR-1, and pICln mRNA in AGS cells. These results suggest a fundamental role of endogenous ClC-3 in the swelling-activated Cl- channels function and cell volume regulation in human gastric epithelial cells.
Collapse
Affiliation(s)
- Nan Ge Jin
- Dept. of Physiology and Biophysics, Seoul National Univ. College of Medicine, 28 Yongon-Dong, Chongro-Gu, Seoul, Korea 110-799
| | | | | | | | | | | | | | | | | |
Collapse
|
47
|
Spiegel S, Phillipper M, Rossmann H, Riederer B, Gregor M, Seidler U. Independence of apical Cl-/HCO3- exchange and anion conductance in duodenal HCO3- secretion. Am J Physiol Gastrointest Liver Physiol 2003; 285:G887-97. [PMID: 12842823 DOI: 10.1152/ajpgi.00083.2003] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Reduced gastrointestinal HCO3- secretion contributes to malabsorption and obstructive syndromes in cystic fibrosis. The apical HCO3- transport pathways in these organs have not been defined. We therefore assessed the involvement of apical Cl-/HCO3- exchangers and anion conductances in basal and cAMP-stimulated duodenal HCO3- secretion. Muscle-stripped rat and rabbit proximal duodena were mounted in Ussing chambers, and electrical parameters, HCO3- secretion rates, and 36Cl-, 22Na+, and 3H+ mannitol fluxes were assessed. mRNA expression levels were measured by a quantitative PCR technique. Removal of Cl- from or addition of 1 mM DIDS to the luminal perfusate markedly decreased basal HCO3- secretion but did not influence the HCO3- secretory response to 8-bromo-cAMP, which was inhibited by luminal 5-nitro-2-(3-phenylpropylamino)-benzoate. Bidirectional 22Na+ and 36Cl- flux measurements demonstrated an inhibition rather than a stimulation of apical anion exchange during cAMP-stimulated HCO3- secretion. The ratio of Cl- to HCO3- in the anion secretory response was compatible with both Cl- and HCO3- being secreted via the CFTR anion channel. CFTR expression was very high in the duodenal mucosa of both species. We conclude that in rat and rabbit duodena, an apical Cl-/HCO3- exchanger mediates a significant part of basal HCO3- secretion but is not involved in the HCO3- secretory response to cAMP analogs. The inhibitor profile, the strong predominance of Cl- over HCO3- in the anion secretory response, and the high duodenal CFTR expression levels suggest that a major portion of cAMP-stimulated duodenal HCO3- secretion is directly mediated by CFTR.
Collapse
Affiliation(s)
- S Spiegel
- Zentrum Innere Medizin, Abteilung IV, der Medizinischen Hochschule Hannover, Carl-Neuberg Str. 1, 30625 Hannover, Germany
| | | | | | | | | | | |
Collapse
|
48
|
Vanthanouvong V, Högman M, Roomans GM. In vitro and in situ experimental model for X-ray microanalysis of intestinal epithelium. Microsc Res Tech 2003; 62:211-7. [PMID: 14506686 DOI: 10.1002/jemt.10359] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Intestinal chloride (Cl) transport is disturbed in a number of diseases. X-ray microanalysis can be used to study the distribution of Cl and other ions in intestinal epithelial cells. In this study it was attempted to establish an experimental system that retains the in vivo elemental composition of intestinal epithelial cells. An in vitro system was set up in which a segment of rat intestine was mounted in a bath and perfused with different fluids. The chloride in the bath or in the perfusion fluid could be exchanged for gluconate or bromide to determine the direction of chloride fluxes. An in situ system was set up in which the animal was anesthetized and a segment of the intestine was perfused with different solutions. In the in vitro experiments the concentration of Na and Cl in the epithelial cells increased and that of K decreased. These changes occurred within the first 30 minutes of incubation. Uptake of chloride occurred mainly from the bath, as seen in experiments where bromide was used as a chloride analog. The concentration gradient between bath and tissue determined the extent of chloride uptake. Addition of glucose to the perfusion fluid and bath did not improve the results. In the in situ system, preservation of the intracellular ion composition was better. Acceptable results were obtained with perfusion with Krebs-Ringer's buffer without glucose for 30 minutes. In this case, the elemental content of the cell did not change appreciably during incubation. If glucose was added, the Na concentration increased in comparison to the control, both in crypt and villus cells. It is concluded that the intestinal epithelium is a sensitive system, very prone to disturbance of its homeostasis. However, the in situ system can be used in studies of agonist-induced ion transport.
Collapse
|
49
|
Abstract
BACKGROUND & AIMS 5-hydroxytryptamine (5-HT) is an important neurotransmitter and intercellular messenger that modulates many gastrointestinal functions. Because little is known about the role of 5-HT in the regulation of duodenal bicarbonate secretion, we examined the role of 5-HT on duodenal bicarbonate secretion and define neural pathways involved in the actions of 5-HT. METHODS Duodenal mucosa from National Institutes of Health Swiss mice was stripped of seromuscular layers and mounted in Ussing chambers. The effect of 5-HT on duodenal bicarbonate secretion was determined by the pH stat technique. Acetylcholine (ACh) release from duodenal mucosa was assessed by preincubating the tissue with [(3)H] choline and measuring 5-HT-evoked release of tritium. RESULTS 5-HT added to the serosal bath markedly stimulated duodenal bicarbonate secretion and short circuit current (Isc) in a dose-dependent manner (10(-7) mol/L to 10(-3) mol/L; P < 0.0001), whereas mucosally added 5-HT was without effect. 5-HT-stimulated bicarbonate secretion was independent of luminal Cl(-). Pretreatment with tetrodotoxin (TTX) (10(-6) mol/L) or atropine (10(-5) mol/L) markedly reduced 5-HT-stimulated duodenal bicarbonate secretion (by 60% and 65%, respectively; P < 0.001) and Isc (by 45% and 27%, respectively; P < 0.001 and P < 0.05). Pretreatment with N(omega)-nitro-l-arginine methyl ester (l-NAME) (10(-3) mol/L), propranolol (10(-5) mol/L), or phentolamine (10(-5) mol/L) did not significantly alter 5-HT-stimulated duodenal mucosal bicarbonate secretion or Isc. 5-HT concentration-dependently evoked ACh release from duodenal mucosal preparations (P < 0.0001). TTX markedly inhibited 5-HT-evoked ACh release (P < 0.001). CONCLUSIONS 5-HT is a potent activator of duodenal mucosal bicarbonate secretion in mice. Duodenal bicarbonate secretion induced by 5-HT in vitro occurs principally via a cholinergic neural pathway.
Collapse
Affiliation(s)
- Bi-Guang Tuo
- Department of Medicine, University of California, San Diego School of Medicine, San Diego, California 92103, USA
| | | |
Collapse
|
50
|
Walker NM, Flagella M, Gawenis LR, Shull GE, Clarke LL. An alternate pathway of cAMP-stimulated Cl secretion across the NKCC1-null murine duodenum. Gastroenterology 2002; 123:531-41. [PMID: 12145806 DOI: 10.1053/gast.2002.34757] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
BACKGROUND & AIMS Adenosine 3',5'-cyclic monophosphate (cAMP)-stimulated anion secretion across the duodenal epithelium requires the cystic fibrosis transmembrane conductance regulator (CFTR) in the apical membrane and anion uptake proteins in the basolateral membrane. NKCC1, the epithelial Na(+)/K(+)/2Cl(-) cotransporter, is the major protein responsible for Cl(-) uptake. In this study, we evaluate the role of NKCC1 in determining the relative rates of transepithelial Cl(-) and HCO(3)(-) secretion during cAMP stimulation of the duodenum. METHODS Bicarbonate and chloride secretion across duodenal mucosa was measured in Ussing chambers by pH stat and (36)Cl flux methods using mice with either gene-targeted deletion of NKCC1 (NKCC1-/-) or bumetanide blockade of NKCC1. RESULTS Total anion secretion stimulated by forskolin treatment of NKCC1-null duodenum resulted from approximately equivalent rates of electrogenic chloride, electrogenic bicarbonate, and electroneutral bicarbonate secretion. Evaluation of the alternate chloride secretory pathway indicated chloride uptake by a basolateral membrane anion exchange process with characteristics consistent with the anion exchanger isoform AE2. CONCLUSIONS Chloride uptake by basolateral anion exchanger activity (AE2) supports intracellular cAMP-stimulated chloride secretion in the NKCC1-null duodenum. A model for the alternate chloride secretion pathway is proposed whereby chloride uptake via AE2 is coupled to basolateral NaHCO(3) cotransport to support CFTR-mediated chloride and bicarbonate secretion.
Collapse
Affiliation(s)
- Nancy M Walker
- Dalton Cardiovascular Research Center and the Department of Biomedical Sciences, University of Missouri-Columbia, Columbia, Missouri 65211, USA
| | | | | | | | | |
Collapse
|