1
|
Boudaka A, Tominaga M. Physiological and Pathological Significance of Esophageal TRP Channels: Special Focus on TRPV4 in Esophageal Epithelial Cells. Int J Mol Sci 2022; 23:ijms23094550. [PMID: 35562940 PMCID: PMC9099744 DOI: 10.3390/ijms23094550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 04/16/2022] [Accepted: 04/19/2022] [Indexed: 12/10/2022] Open
Abstract
Transient receptor potential vanilloid 4 (TRPV4) is a non-selective cation channel that is broadly expressed in different human tissues, including the digestive system, where it acts as a molecular sensor and a transducer that regulates a variety of functional activities. Despite the extensive research to determine the role of this channel in the physiology and pathophysiology of different organs, the unique morphological and functional features of TRPV4 in the esophagus remain largely unknown. Ten years ago, TRPV4 was shown to be highly expressed in esophageal epithelial cells where its activation induces Ca2+-dependent ATP release, which, in turn, mediates several functions, ranging from mechanosensation to wound healing. This review summarizes the research progress on TRPV4, and focuses on the functional expression of TRPV4 in esophageal epithelium and its possible role in different esophageal diseases that would support TRPV4 as a candidate target for future therapeutic approaches to treat patients with these conditions.
Collapse
Affiliation(s)
- Ammar Boudaka
- Department of Physiology, College of Medicine and Health Sciences, Sultan Qaboos University, Al-Khoud, P.O. Box 35, Muscat 123, Oman
- Division of Cell Signaling, National Institute for Physiological Sciences, Okazaki 444-8787, Aichi, Japan;
- Correspondence:
| | - Makoto Tominaga
- Division of Cell Signaling, National Institute for Physiological Sciences, Okazaki 444-8787, Aichi, Japan;
- Department of Physiological Sciences, SOKENDAI (The Graduate University for Advanced Studies), Okazaki 444-8787, Aichi, Japan
- Exploratory Research Center on Life and Living Systems, Thermal Biology Group, Okazaki 444-8787, Aichi, Japan
| |
Collapse
|
2
|
Becskeházi E, Korsós MM, Erőss B, Hegyi P, Venglovecz V. OEsophageal Ion Transport Mechanisms and Significance Under Pathological Conditions. Front Physiol 2020; 11:855. [PMID: 32765303 PMCID: PMC7379034 DOI: 10.3389/fphys.2020.00855] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Accepted: 06/25/2020] [Indexed: 12/20/2022] Open
Abstract
Ion transporters play an important role in several physiological functions, such as cell volume regulation, pH homeostasis and secretion. In the oesophagus, ion transport proteins are part of the epithelial resistance, a mechanism which protects the oesophagus against reflux-induced damage. A change in the function or expression of ion transporters has significance in the development or neoplastic progression of Barrett’s oesophagus (BO). In this review, we discuss the physiological and pathophysiological roles of ion transporters in the oesophagus, highlighting transport proteins which serve as therapeutic targets or prognostic markers in eosinophilic oesophagitis, BO and esophageal cancer. We believe that this review highlights important relationships which might contribute to a better understanding of the pathomechanisms of esophageal diseases.
Collapse
Affiliation(s)
- Eszter Becskeházi
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
| | | | - Bálint Erőss
- Institute for Translational Medicine, Szentágothai Research Centre, Medical School, University of Pécs, Pécs, Hungary
| | - Péter Hegyi
- Institute for Translational Medicine, Szentágothai Research Centre, Medical School, University of Pécs, Pécs, Hungary.,Division of Gastroenterology, First Department of Medicine, Medical School, University of Pécs, Pécs, Hungary.,First Department of Medicine, University of Szeged, Szeged, Hungary
| | - Viktória Venglovecz
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
| |
Collapse
|
3
|
Honda K, Kim SH, Kelly MC, Burns JC, Constance L, Li X, Zhou F, Hoa M, Kelley MW, Wangemann P, Morell RJ, Griffith AJ. Molecular architecture underlying fluid absorption by the developing inner ear. eLife 2017; 6. [PMID: 28994389 PMCID: PMC5634787 DOI: 10.7554/elife.26851] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 09/10/2017] [Indexed: 12/26/2022] Open
Abstract
Mutations of SLC26A4 are a common cause of hearing loss associated with enlargement of the endolymphatic sac (EES). Slc26a4 expression in the developing mouse endolymphatic sac is required for acquisition of normal inner ear structure and function. Here, we show that the mouse endolymphatic sac absorbs fluid in an SLC26A4-dependent fashion. Fluid absorption was sensitive to ouabain and gadolinium but insensitive to benzamil, bafilomycin and S3226. Single-cell RNA-seq analysis of pre- and postnatal endolymphatic sacs demonstrates two types of differentiated cells. Early ribosome-rich cells (RRCs) have a transcriptomic signature suggesting expression and secretion of extracellular proteins, while mature RRCs express genes implicated in innate immunity. The transcriptomic signature of mitochondria-rich cells (MRCs) indicates that they mediate vectorial ion transport. We propose a molecular mechanism for resorption of NaCl by MRCs during development, and conclude that disruption of this mechanism is the root cause of hearing loss associated with EES.
Collapse
Affiliation(s)
- Keiji Honda
- Molecular Biology and Genetics Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, United States
| | - Sung Huhn Kim
- Anatomy and Physiology Department, Kansas State University, Manhattan, United States
| | - Michael C Kelly
- Developmental Neuroscience Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, United States
| | - Joseph C Burns
- Developmental Neuroscience Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, United States
| | - Laura Constance
- Anatomy and Physiology Department, Kansas State University, Manhattan, United States
| | - Xiangming Li
- Anatomy and Physiology Department, Kansas State University, Manhattan, United States
| | - Fei Zhou
- Anatomy and Physiology Department, Kansas State University, Manhattan, United States
| | - Michael Hoa
- Auditory Development and Restoration Program, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, United States
| | - Matthew W Kelley
- Developmental Neuroscience Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, United States
| | - Philine Wangemann
- Anatomy and Physiology Department, Kansas State University, Manhattan, United States
| | - Robert J Morell
- Genomics and Computational Biology Core, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, United States
| | - Andrew J Griffith
- Molecular Biology and Genetics Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, United States
| |
Collapse
|
4
|
Laczkó D, Rosztóczy A, Birkás K, Katona M, Rakonczay Z, Tiszlavicz L, Róka R, Wittmann T, Hegyi P, Venglovecz V. Role of ion transporters in the bile acid-induced esophageal injury. Am J Physiol Gastrointest Liver Physiol 2016; 311:G16-31. [PMID: 27198194 DOI: 10.1152/ajpgi.00159.2015] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Accepted: 04/20/2016] [Indexed: 01/31/2023]
Abstract
Barrett's esophagus (BE) is considered to be the most severe complication of gastro-esophageal reflux disease (GERD), in which the prolonged, repetitive episodes of combined acidic and biliary reflux result in the replacement of the squamous esophageal lining by columnar epithelium. Therefore, the acid-extruding mechanisms of esophageal epithelial cells (EECs) may play an important role in the defense. Our aim was to identify the presence of acid/base transporters on EECs and to investigate the effect of bile acids on their expressions and functions. Human EEC lines (CP-A and CP-D) were acutely exposed to bile acid cocktail (BAC) and the changes in intracellular pH (pHi) and Ca(2+) concentration ([Ca(2+)]i) were measured by microfluorometry. mRNA and protein expression of ion transporters was investigated by RT-PCR, Western blot, and immunohistochemistry. We have identified the presence of a Na(+)/H(+) exchanger (NHE), Na(+)/HCO3 (-) cotransporter (NBC), and a Cl(-)-dependent HCO3 (-) secretory mechanism in CP-A and CP-D cells. Acute administration of BAC stimulated HCO3 (-) secretion in both cell lines and the NHE activity in CP-D cells by an inositol triphosphate-dependent calcium release. Chronic administration of BAC to EECs increased the expression of ion transporters compared with nontreated cells. A similar expression pattern was observed in biopsy samples from BE compared with normal epithelium. We have shown that acute administration of bile acids differently alters ion transport mechanisms of EECs, whereas chronic exposure to bile acids increases the expression of acid/base transporters. We speculate that these adaptive processes of EECs represent an important mucosal defense against the bile acid-induced epithelial injury.
Collapse
Affiliation(s)
- Dorottya Laczkó
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary; First Department of Medicine, University of Szeged, Szeged, Hungary
| | - András Rosztóczy
- First Department of Medicine, University of Szeged, Szeged, Hungary
| | - Klaudia Birkás
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
| | - Máté Katona
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
| | - Zoltán Rakonczay
- First Department of Medicine, University of Szeged, Szeged, Hungary; Department of Pathophysiology, University of Szeged, Szeged, Hungary
| | | | - Richárd Róka
- First Department of Medicine, University of Szeged, Szeged, Hungary
| | - Tibor Wittmann
- First Department of Medicine, University of Szeged, Szeged, Hungary
| | - Péter Hegyi
- First Department of Medicine, University of Szeged, Szeged, Hungary; MTA-SZTE Translational Gastroenterology Research Group, University of Szeged, Szeged, Hungary; and Institute for Translational Medicine and First Department of Medicine, University of Pécs, Pécs, Hungary
| | - Viktória Venglovecz
- Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary;
| |
Collapse
|
5
|
Suzuki N, Mihara H, Nishizono H, Tominaga M, Sugiyama T. Protease-Activated Receptor-2 Up-Regulates Transient Receptor Potential Vanilloid 4 Function in Mouse Esophageal Keratinocyte. Dig Dis Sci 2015; 60:3570-8. [PMID: 26233549 DOI: 10.1007/s10620-015-3822-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 07/20/2015] [Indexed: 12/16/2022]
Abstract
BACKGROUND The reflux of pancreatic-duodenal fluids is implicated in the pathophysiology of proton-pump inhibitor-resistant gastroesophageal reflux disease (GERD). Protease-activated receptor-2 (PAR-2) is activated by proteases, the pancreatic enzyme, trypsin, and the activated PAR-2 enhances transient receptor potential vanilloid 4 (TRPV4) function in neurons. TRPV4 stimulates ATP exocytosis in conjunction with the vesicular nucleotide transporter, which mediates mechano-transduction and vagal stimulation. The aim of the present study was to verify whether the activated PAR-2 up-regulates TRPV4 function in mouse esophageal keratinocytes, which may link to the pathophysiology in PPI-resistant GERD. METHODS TRPV4 and PAR-2 expressions were detected by RT-PCR, immunostaining, and western blotting in mouse esophageal keratinocytes. The functional response of TRPV4 to esophageal keratinocytes was analyzed using a Ca(2+) imaging system. Cellular ATP release was examined by luciferase-luciferin reaction. TRPV4 phosphorylation was studied by immunoprecipitation and western blotting. RESULTS PAR-2 and TRPV4 mRNAs and proteins were expressed in esophageal keratinocytes. Pre-treatment with trypsin significantly increased the responses to TRPV4 activator in esophageal keratinocytes, probably via the phosphorylation of serine residue of TRPV4 by protein kinase C and resulted in cellular ATP release from the cells. CONCLUSIONS Activated PAR-2 with trypsin exposure up-regulated TRPV4 function and increased ATP release in mouse esophageal keratinocytes. This mechanism might be related to the pathophysiology of GERD, especially non-erosive GERD.
Collapse
Affiliation(s)
- Nobuhiro Suzuki
- Department of Gastroenterology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama, Toyama, 930-0194, Japan.
| | - Hiroshi Mihara
- Department of Gastroenterology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama, Toyama, 930-0194, Japan.
| | - Hirofumi Nishizono
- Division of Animal Experimental Laboratory, Life Science Research Center, University of Toyama, 2630 Sugitani, Toyama, Toyama, 930-0194, Japan.
| | - Makoto Tominaga
- Division of Cell Signaling, Okazaki Institute for Integrative Bioscience (National Institute for Physiological Sciences), National Institutes of Natural Sciences, Nishigonaka 38, Myodaiji, Okazaki, Aichi, 444-8585, Japan.
| | - Toshiro Sugiyama
- Department of Gastroenterology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama, Toyama, 930-0194, Japan.
| |
Collapse
|
6
|
Li XM, Wang H, Zhu LL, Zhao RZ, Ji HL. Genes Regulating Epithelial Polarity Are Critical Suppressors of Esophageal Oncogenesis. J Cancer 2015; 6:694-700. [PMID: 26185530 PMCID: PMC4504104 DOI: 10.7150/jca.11709] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 05/05/2015] [Indexed: 02/06/2023] Open
Abstract
Esophageal cancer is an aggressive disease featured by early lymphatic and hematogenous dissemination, and is the sixth leading cause of cancer-related deaths worldwide. The proper formation of apicobasal polarity is essential for normal epithelium physiology and tissue homeostasis, while loss of polarity is a hallmark of cancer development including esophageal oncogenesis. In this review, we summarized the stages of esophageal cancer development associated with the loss or deregulation of epithelial cell apicobasal polarity. Loss of epithelial apicobasal polarity exerts an indispensable role in the initiation of esophageal oncogenesis, tumor progression, and the advancement of tumors from benign to malignant. In particular, we reviewed the involvement of several critical genes, including Lkb1, claudin-4, claudin-7, Par3, Lgl1, E-cadherin, and the Scnn1 gene family. Understanding the role of apicobasal regulators may lead to new paradigms for treatment of esophageal tumors, including improvement of prognostication, early diagnosis, and individually tailored therapeutic interventions in esophageal oncology.
Collapse
Affiliation(s)
- Xiu-Min Li
- 1. Center for Cancer Research, Xinxiang Medical University, Xinxiang Henan, 453003, China
| | - Hui Wang
- 2. Ontario Cancer Institute, Campbell Family Institute for Breast Cancer Research, University of Toronto, Toronto, Ontario, M5G 2M9, Canada
| | - Li-Li Zhu
- 1. Center for Cancer Research, Xinxiang Medical University, Xinxiang Henan, 453003, China
| | - Run-Zhen Zhao
- 3. Department of Cellular and Molecular Biology, University of Texas Health Science Center at Tyler, Tyler, Texas, 75708, USA
| | - Hong-Long Ji
- 3. Department of Cellular and Molecular Biology, University of Texas Health Science Center at Tyler, Tyler, Texas, 75708, USA ; 4. Texas Lung Injury Institute, University of Texas Health Science Center at Tyler, Tyler, Texas, 75708, USA
| |
Collapse
|
7
|
Effect of amiloride on experimental acid-induced heartburn in non-erosive reflux disease. Dig Dis Sci 2013; 58:1955-9. [PMID: 23649374 DOI: 10.1007/s10620-013-2586-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Accepted: 01/24/2013] [Indexed: 01/06/2023]
Abstract
BACKGROUND Acid-sensing ion channels (ASICs) are esophageal nociceptors that are candidates to mediate heartburn in non-erosive reflux disease (NERD). Amiloride, a diuretic, is known to inhibit ASICs. For this reason, we sought a role for ASICs in mediating heartburn by determining whether amiloride could block heartburn in NERD induced by esophageal acid perfusion. METHODS In a randomized double-blind crossover study, we perfused the esophagus with amiloride or (saline) placebo prior to eliciting acid-induced heartburn in patients with a history of proton pump inhibitor-responsive NERD. Those with NERD and positive modified Bernstein test were randomized to perfusion with amiloride, 1 mmol/l, or placebo for 5 min, followed by repeat acid-perfusion. Heartburn severity and time to onset was measured and the process repeated following crossover to the alternative agent. RESULTS 14 subjects completed the study. Amiloride did not reduce the frequency (100 vs. 100 %) or severity of acid-induced heartburn (Mean 2.50 ± SEM 0.33 vs. 2.64 ± 0.45), respectively. There was a trend towards longer time to onset of heartburn for amiloride versus placebo (Mean 2.93 ± SEM 0.3 vs. 2.36 ± 0.29 min, respectively), though these differences did not reach statistical significance (p > 0.05). CONCLUSIONS Amiloride had no significant effect on acid-induced heartburn frequency or severity in NERD, although there was a trend towards prolonged time to onset of symptoms.
Collapse
|
8
|
Abstract
The epithelial Na(+) channel (ENaC) and acid-sensitive ion channel (ASIC) branches of the ENaC/degenerin superfamily of cation channels have drawn increasing attention as potential therapeutic targets in a variety of diseases and conditions. Originally thought to be solely expressed in fluid absorptive epithelia and in neurons, it has become apparent that members of this family exhibit nearly ubiquitous expression. Therapeutic opportunities range from hypertension, due to the role of ENaC in maintaining whole body salt and water homeostasis, to anxiety disorders and pain associated with ASIC activity. As a physiologist intrigued by the fundamental mechanics of salt and water transport, it was natural that Dale Benos, to whom this series of reviews is dedicated, should have been at the forefront of research into the amiloride-sensitive sodium channel. The cloning of ENaC and subsequently the ASIC channels has revealed a far wider role for this channel family than was previously imagined. In this review, we will discuss the known and potential roles of ENaC and ASIC subunits in the wide variety of pathologies in which these channels have been implicated. Some of these, such as the role of ENaC in Liddle's syndrome are well established, others less so; however, all are related in that the fundamental defect is due to inappropriate channel activity.
Collapse
Affiliation(s)
- Yawar J Qadri
- Department of Physiology and Biophysics, University of Alabama at Birmingham, AL 35294, USA
| | | | | |
Collapse
|
9
|
Shikano M, Ueda T, Kamiya T, Ishida Y, Yamada T, Mizushima T, Shimura T, Mizoshita T, Tanida S, Kataoka H, Shimada S, Ugawa S, Joh T. Acid inhibits TRPV4-mediated Ca²⁺ influx in mouse esophageal epithelial cells. Neurogastroenterol Motil 2011; 23:1020-8, e497. [PMID: 21883699 DOI: 10.1111/j.1365-2982.2011.01767.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
BACKGROUND The transient receptor potential vanilloid 4 (TRPV4), a thermo-sensitive stretch-activated cation channel, is expressed in the skin stratified squamous epithelium, contributing to the acquisition of barrier function. Similarly, functional TRPV4 may be located in the stratified squamous epithelial lining of the esophagus, being involved in the pathogenesis of gastroesophageal reflux disease (GERD). Here we investigated the expression of TRPV4 in the mouse esophageal epithelium. METHODS TRPV4 expression at the mRNA and protein levels was examined by reverse transcription-polymerase chain reaction (RT-PCR), in situ hybridization, and immunohistochemistry. A calcium imaging technique and ATP assay were used to evaluate the functionality of TRPV4 in freshly isolated esophageal epithelial cells. KEY RESULTS Transcripts and proteins encoding TRPV4 were colocalized in the basal and intermediate layers of the esophageal epithelium. Both 4α-phorbol 12,13- didecanoate (4α-PDD), a selective agonist for TRPV4, and hypo-osmolar solution (160 mOsm) elevated the intracellular calcium concentration ([Ca(2+) ](i) ) in a subset of the isolated cells (70%). These [Ca(2+) ](i) increases were potently inhibited by ruthenium red (RuR), a TRPV4 channel antagonist, and were suppressed by extracellular protons (pH 5.0). Finally, application of 4α-PDD evoked ATP release in primary esophageal epithelial cells. CONCLUSIONS & INFERENCES Acid-sensitive TRPV4 channels were mainly expressed in the esophageal epithelial cells of the basal and intermediate layers. Direct exposure of TRPV4-expressing cells to gastric acid, as would occur in cases of GERD, could influence their cellular functions, possibly aggravating the disease state.
Collapse
Affiliation(s)
- M Shikano
- Department of Gastroenterology and Metabolism, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Wiemuth D, Gründer S. The Pharmacological Profile of Brain Liver Intestine Na+ Channel: Inhibition by Diarylamidines and Activation by Fenamates. Mol Pharmacol 2011; 80:911-9. [DOI: 10.1124/mol.111.073726] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
|
11
|
Orlando RC. The integrity of the esophageal mucosa. Balance between offensive and defensive mechanisms. Best Pract Res Clin Gastroenterol 2010; 24:873-82. [PMID: 21126700 PMCID: PMC2995989 DOI: 10.1016/j.bpg.2010.08.008] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2010] [Revised: 08/17/2010] [Accepted: 08/23/2010] [Indexed: 01/31/2023]
Abstract
Heartburn is the most common and characteristic symptom of gastroesophageal reflux disease. It ultimately results from contact of refluxed gastric acid with nociceptors within the esophageal mucosa and transmission of this peripheral signal to the central nervous system for cognition. Healthy esophageal epithelium provides an effective barrier between refluxed gastric acid and esophageal nociceptors; but this barrier is vulnerable to attack and damage, particularly by acidic gastric contents. How gastric acid is countered by defensive elements within the esophageal mucosa is a major focus of this discussion. When the defense is successful, the subject is asymptomatic and when unsuccessful, the subject experiences heartburn. Those with heartburn commonly fall into one of three endoscopic types: nonerosive reflux disease, erosive esophagitis and Barrett's esophagus. Although what determines endoscopic type remains unknown; it is proposed herein that inflammation plays a key, modulating role.
Collapse
Affiliation(s)
- Roy C. Orlando
- Mary Kay & Eugene Bozymski and Linda & William Heizer Distinguished Professor of Gastroenterology; and Adjunct Professor of Cell and Molecular Physiology, University of North Carolina at Chapel Hill, Division of Gastroenterology & Hepatology, 103 Mason Farm Road, Molecular Biomedical Research Building, CB#7032, Chapel Hill, N.C.,27599, USA, Tel: 919-843-4583, Fax # 919-843-6899
| |
Collapse
|
12
|
Transport of cations and anions across forestomach epithelia: conclusions from in vitro studies. Animal 2010; 4:1037-56. [DOI: 10.1017/s1751731110000261] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
|
13
|
Yamamura H, Ugawa S, Ueda T, Nagao M, Joh T, Shimada S. Epithelial Na+ channel delta subunit is an acid sensor in the human oesophagus. Eur J Pharmacol 2008; 600:32-6. [PMID: 18951889 DOI: 10.1016/j.ejphar.2008.10.022] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2008] [Accepted: 10/09/2008] [Indexed: 01/11/2023]
Abstract
Gastro-oesophageal reflux disease is caused by the reflux of gastric contents into the oesophagus, and thus the oesophageal lumen is damaged by gastric acid. The acid sensor involved in oesophageal epithelial defense is still unclear. Recently, we described that the epithelial Na(+) channel delta subunit (ENaCdelta) is a candidate molecule for a pH sensor in the human brain. Here, using reverse transcription-polymerase chain reaction and in situ hybridization methods, we showed that the proton-sensitive ENaCdelta was strongly expressed in the epithelial layer of the human oesophagus, representative peripheral tissue that can be exposed to an acidic environment. Other ENaC subunits (alpha, beta, and gamma) were also localized there. Based on the expression pattern, human oesophageal ENaC complex was mimicked in the Xenopus oocyte expression system and the response to acidic pH was recorded using a two-electrode voltage-clamp technique. The human oesophageal-mimicking ENaCdeltabetagammaalpha complex generated an amiloride-sensitive inward current at the holding potential of -60 mV. The ENaCdeltabetagammaalpha current was significantly activated by acidic pH (pH 4.0), approximately equal to the luminal value when gastric acid refluxes into the oesophagus. In conclusion, ENaCdelta is a candidate molecule for pH sensing in the gastrointestinal system in humans, providing a novel therapeutic target for gastro-oesophageal reflux disease.
Collapse
Affiliation(s)
- Hisao Yamamura
- Department of Molecular Morphology, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan.
| | | | | | | | | | | |
Collapse
|
14
|
Intracellular Na+ modulates large conductance Ca2+-activated K+ currents in human umbilical vein endothelial cells. Pflugers Arch 2008; 457:67-75. [DOI: 10.1007/s00424-008-0490-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2007] [Accepted: 03/02/2008] [Indexed: 10/22/2022]
|
15
|
Tobey NA, Argote CM, Vanegas XC, Barlow W, Orlando RC. Electrical parameters and ion species for active transport in human esophageal stratified squamous epithelium and Barrett's specialized columnar epithelium. Am J Physiol Gastrointest Liver Physiol 2007; 293:G264-70. [PMID: 17431220 DOI: 10.1152/ajpgi.00047.2007] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The human esophagus is lined by stratified squamous epithelium (ESSE), and in some subjects with reflux disease the distal esophagus becomes lined by Barrett's specialized columnar epithelium (BSCE). ESSE and BSCE differ both histologically and functionally, the latter evident by differences in their in vivo transmural electrical potential difference (PD), ESSE averaging -15 mV and BSCE being greater than -25 mV. In this report we examine the basis for this difference in PD. This is done by mounting endoscopic biopsies of ESSE from 25 subjects without esophageal disease and BSCE from 19 with Barrett's esophagus in mini-Ussing chambers for electrical recordings basally and after bathing solution ion replacement. The results show that the PD of human ESSE reflects a low level of active ion transport (5.1 +/- 0.8 muA/cm(2)) combined with a high level of tissue (electrical) resistance (344 +/- 34 Omega.cm(2)) and that of BSCE reflects a high level of active transport (43.6 +/- 11.6 muA/cm(2)) combined with a low level of resistance (69 +/- 8 Omega.cm(2)). Furthermore, active transport in ESSE was principally due to sodium absorption whereas in BSCE it was equally divided between sodium absorption and anion (chloride/bicarbonate) secretion, the latter through an apical membrane, 4-acetamido4'-isothiocyano-2,2'-stilbenedisulfonic acid-sensitive anion channel. As an anion-secreting tissue with bicarbonate secretory capacity more than fivefold greater than ESSE, BSCE is better suited than ESSE for defense of the esophagus against reflux disease.
Collapse
Affiliation(s)
- N A Tobey
- Tulane University Health Sciences Center, 1430 Tulane Avenue, New Orleans, LA 70112, USA.
| | | | | | | | | |
Collapse
|
16
|
Ortiz RM, Graciano ML, Seth D, Awayda MS, Navar LG. Aldosterone receptor antagonism exacerbates intrarenal angiotensin II augmentation in ANG II-dependent hypertension. Am J Physiol Renal Physiol 2007; 293:F139-47. [PMID: 17376762 DOI: 10.1152/ajprenal.00504.2006] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Effects of aldosterone receptor (AR) blockade with eplerenone (epl) on renal Na(+) excretion, arterial blood pressure, intra-adrenal and renal ANG II, and plasma aldosterone levels during ANG II-dependent hypertension were evaluated. Rats from one cohort (n = 10/group) 1) control, 2) control + epl (25 mg/day), 3) ANG II (60 ng/min), and 4) ANG II + epl were maintained in metabolic cages for 28 days for daily urine collections. Systolic blood pressure (SBP) was measured weekly by tail-cuff. In a second cohort (n = 12/group), daily SBP was measured by telemetry (n = 6 rats/group) 1) control, 2) ANG II, and 3) ANG II + epl. A diet containing epl (0.1%) was provided after 1 wk of ANG II infusion. Direct monitoring of BP by telemetry showed that epl delayed the onset of the increase in SBP by 2 days and slightly reduced SBP (186 +/- 6 vs. 177 +/- 8 mmHg). Epl transiently increased Na(+) excretion within 24 h of treatment in both normo- and hypertensive rats; however, balance was reestablished within 5 days suggesting that alternative mechanisms for conserving Na(+) are activated. Cortical alpha-epithelial Na(+) channel content (alpha-ENaC) was not altered after 21 days of epl treatment. Epl exacerbated the ANG II-mediated increases in intrarenal ANG II (226 +/- 16 vs. 365 +/- 38 fmol/g) and further increased intra-adrenal ANG II (3.9 +/- 0.3 vs. 8.2 +/- 0.9 fmol/mg) and aldosterone (255 +/- 55 vs. 710 +/- 87 pmol/mg) content. Exacerbation of intrarenal ANG II levels likely contributes to the maintenance of alpha-ENaC protein content and thus Na(+) reabsorption, which helps explain the ineffectiveness of AR blockade in reducing SBP in ANG II-infused models of hypertension.
Collapse
Affiliation(s)
- Rudy M Ortiz
- Department of Renal Physiology, Tulane University Health Science Center, New Orleans, Louisiana, USA.
| | | | | | | | | |
Collapse
|
17
|
Tobey NA, Argote CM, Awayda MS, Vanegas XC, Orlando RC. Effect of luminal acidity on the apical cation channel in rabbit esophageal epithelium. Am J Physiol Gastrointest Liver Physiol 2007; 292:G796-805. [PMID: 16614374 DOI: 10.1152/ajpgi.00385.2005] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Esophageal epithelial cells contain an apical cation channel that actively absorbs sodium ions (Na(+)). Since these channels are exposed in vivo to acid reflux, we sought the impact of high acidity on Na(+) channel function in Ussing-chambered rabbit epithelium. Serosal nystatin abolished short-circuit current (I(sc)) and luminal pH titrated from pH 7.0 to pH > or = 2.0 had no effect on I(sc). Circuit analysis at pH 2.0 showed small, but significant, increases in apical and shunt resistances. At pH < 2.0, I(sc) increased whereas resistance (R(T)) decreased along with an increase in fluorescein flux. The change in I(sc), but not R(T), was reversible at pH 7.4. Reducing pH from 7.0 to 1.1 with H(2)SO(4) gave a similar pattern but higher I(sc) values, suggesting shunt permselectivity. A 10:1 Na(+) gradient after nystatin increased I(sc) by approximately 4 muAmps/cm(2) and this declined at pH < or = 3.5 until it reached approximately 0.0 at pH 2.0. Impedance analysis on acid-exposed (non-nystatin treated) tissues showed compensatory changes in apical (increase) and basolateral (decrease) resistance at modest luminal acidity that were poorly reversible at pH 2.0 and associated with declines in capacitance, a reflection of lower apical membrane area. In esophageal epithelium apical cation channels transport Na(+) at gradients as low as 10:1 but do not transport H(+) at gradients of 100,000:1 (luminal pH 2.0). Luminal acid also inhibits Na(+) transport via the channels and abolishes it at pH 2.0. These effects on the channel may serve as a protective function for esophageal epithelium exposed to acid reflux.
Collapse
Affiliation(s)
- N A Tobey
- Department of Medicine, Tulane University Health Sciences Center and the Veterans Administration Hospital, New Orleans, Louisiana 70112, USA.
| | | | | | | | | |
Collapse
|
18
|
Fujiwara Y, Higuchi K, Tominaga K, Watanabe T, Oshitani N, Arakawa T. Functional oesophageal epithelial defense against acid. Inflammopharmacology 2005; 13:1-13. [PMID: 16259724 DOI: 10.1163/156856005774423953] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Functional oesophageal epithelial defense, including cell proliferation, restitution, buffers and ion transporters, plays a significant role in maintaining mucosal integrity and enabling rapid repair after injury. Growth factors such as epidermal growth factor (EGF), transforming growth factor-alpha (TGF-alpha), hepatocyte growth factor (HGF) and keratinocyte growth factor (KGF) are associated with oesophageal epithelial proliferation or restitution. Na+/H+ exchanger-1, an ion transporter, regulates intracellular pH and cell volume, and may have roles in cell proliferation, migration and survival. Cytokine, adhesion molecules, cyclooxygenase-2 and free radicals are associated with oesophageal inflammation and breach of the functional epithelial defense. Although the oesophagus does not have strong functional epithelial defense against acid, this defensive mechanisms may be involved in the pathogenesis of non-erosive gastro-oesophageal reflux disease. Medical therapy may be developed in future to enhance functional oesophageal epithelial defense.
Collapse
Affiliation(s)
- Yasuhiro Fujiwara
- Department of Gastroenterology, Osaka City University Graduate School of Medicine, 1-4-3 Asahimachi, Abenoku, Osaka 545-8585, Japan.
| | | | | | | | | | | |
Collapse
|
19
|
Shao W, Orlando RC, Awayda MS. Bisphosphonates stimulate an endogenous nonselective cation channel in Xenopus oocytes: potential mechanism of action. Am J Physiol Cell Physiol 2005; 289:C248-56. [PMID: 15788487 DOI: 10.1152/ajpcell.00393.2004] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The mechanisms of action of bisphosphonates (BPs) have been poorly determined. Besides their actions on osteoclasts, these agents exhibit gastrointestinal complications. They have also recently been described as affecting various preparations that express an epithelial Na+ channel (ENaC). To understand the effects of BP on ion channels and the ENaC in particular, we used the Xenopus oocyte expression system. Alendronate, and similarly risedronate, two aminobisphosphonates, caused a large stimulation of an endogenous nonselective cation conductance (NSCC). This stimulation averaged 63 ± 12 μS ( n = 18) 60 min after the addition of 2 mM alendronate. The effects on the endogenous NSCC were blocked by extracellular acidification to pH 6.4. On the other hand, alendronate caused a small inhibition of ENaC conductance at pH 7.4 and 6.4, but the effects at pH 6.4 were more readily observed in the absence of changes of the endogenous conductance. The effects on membrane capacitance were also markedly different, with a clear decrease at pH 6.4 and no consistent changes at pH 7.4. The effects on the endogenous channel were further augmented by genistein and were inhibited by a tyrosine phosphatase inhibitor, indicating the involvement of the tyrosine kinase pathway. Stimulation of NSCC with BP is expected to cause membrane depolarization and may explain, in part, its mechanisms of action in inhibiting osteoclasts.
Collapse
Affiliation(s)
- Weijian Shao
- Department of Physiology, Tulane University Health Sciences Center, 1430 Tulane Ave., New Orleans, LA 70112, USA
| | | | | |
Collapse
|
20
|
Shlyonsky V, Goolaerts A, Van Beneden R, Sariban-Sohraby S. Differentiation of epithelial Na+ channel function. An in vitro model. J Biol Chem 2005; 280:24181-7. [PMID: 15817472 DOI: 10.1074/jbc.m413823200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Confluent monolayers of epithelial cells grown on nonporous support form fluid-filled hemicysts called domes, which reflect active ion transport across the epithelium. Clara-like H441 lung adenocarcinoma cells grown on glass supports and exposed to 50 nM dexamethasone developed domes in a time-dependent fashion. Uplifting of small groups of cells occurred within 6-12 h, well formed domes appeared between 24 and 48 h, and after 7 days, individual domes started to merge. Cells inside of domes compared with those outside domes, or with monolayers not exposed to dexamethasone, differed by higher surfactant production, an increased cytokeratin expression, and the localization of claudin-4 proteins to the plasma membrane. In patch clamp studies, amiloride-blockable sodium currents were detected exclusively in cells inside domes, whereas in cells outside of domes, sodium crossed the membrane through La3+-sensitive nonspecific cation channels. Cells grown on permeable support without dexamethasone expressed amiloride-sensitive currents only after tight electrical coupling was achieved (transepithelial electrical resistance (R(t)) > 1 kilohm). In real-time quantitative PCR experiments, the addition of dexamethasone increased the content of claudin-4, occludin, and Na+ channel gamma-subunit (gamma-ENaC) mRNAs by 1.34-, 1.32-, and 1.80-fold, respectively, after 1 h and was followed by an increase at 6 h in the content of mRNA of alpha- and beta-ENaC and of alpha1- and beta1-Na,K-ATPase. In the absence of dexamethasone, neither change in gene expression nor cell uplifting was observed. Our data suggest that during epithelial differentiation, coordinated expression of tight junction proteins precedes the development of vectorial transport of sodium, which in turn leads to the fluid accumulation in basolateral spaces that is responsible for dome formation.
Collapse
Affiliation(s)
- Vadim Shlyonsky
- Laboratoire de Physiologie et Physiopathologie, Université Libre de Bruxelles, 1070 Bruxelles, Belgium
| | | | | | | |
Collapse
|