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Ustaoglu A, Woodland P. Sensory Phenotype of the Oesophageal Mucosa in Gastro-Oesophageal Reflux Disease. Int J Mol Sci 2023; 24:ijms24032502. [PMID: 36768825 PMCID: PMC9917190 DOI: 10.3390/ijms24032502] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 01/14/2023] [Accepted: 01/18/2023] [Indexed: 02/03/2023] Open
Abstract
Gastroesophageal reflux disease (GORD) affects up to 20% of Western populations, yet sensory mechanisms underlying heartburn pathogenesis remain incompletely understood. While central mechanisms of heartburn perception have been established in earlier studies, recent studies have highlighted an important role of neurochemical, inflammatory, and cellular changes occurring in the oesophageal mucosa itself. The localization and neurochemical characterisation of sensory afferent nerve endings differ among GORD phenotypes, and could explain symptom heterogeneity among patients who are exposed to similar levels of reflux. Acid-induced stimulation of nociceptors on pain-sensing nerve endings can regulate afferent signal transmission. This review considers the role of peripheral mechanisms of sensitization in the amplification of oesophageal sensitivity in patients with GORD.
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Ustaoglu A, Nguyen A, Spechler S, Sifrim D, Souza R, Woodland P. Mucosal pathogenesis in gastro-esophageal reflux disease. Neurogastroenterol Motil 2020; 32:e14022. [PMID: 33118247 DOI: 10.1111/nmo.14022] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 10/02/2020] [Accepted: 10/05/2020] [Indexed: 12/14/2022]
Abstract
BACKGROUND Despite gastro-esophageal reflux disease affecting up to 20% of Western populations, relatively little is known about the molecular mechanisms underlying its most troublesome symptom: heartburn. Recent findings have unveiled the role of components of the esophageal mucosa in the pathogenesis of GERD including sensory nociceptive nerves and inflammatory mediators. Erosive esophagitis was long believed to develop as a result of acid injury at the esophageal lumen, but novel concepts suggest the generation of reflux-induced esophageal injury as a result of cytokine-mediated inflammation. Moreover, the localization and characterization of mucosal afferent nerves vary between GERD phenotypes and could explain the heterogeneity of symptom perception between patients who experience similar levels of acid reflux. PURPOSE The purpose of this review is to consider the crosstalk of different factors of the esophageal mucosa in the pathogenesis of GERD, with a particular focus on mucosal innervation and molecular basis of acid-induced cytokine response. We discuss the current understanding of the mucosal response to acid injury, the nociceptive role of acid-sensitive receptors expressed in the esophageal mucosa, and the role of esophageal epithelial cells in initiating the onset of erosive esophagitis.
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Affiliation(s)
- Ahsen Ustaoglu
- Wingate Institute of Neurogastroenterology, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Anh Nguyen
- Department of Medicine, Center for Esophageal Diseases, Baylor University Medical Center and Center for Esophageal Research, Baylor Scott & White Research Institute, Dallas, TX, USA
| | - Stuart Spechler
- Department of Medicine, Center for Esophageal Diseases, Baylor University Medical Center and Center for Esophageal Research, Baylor Scott & White Research Institute, Dallas, TX, USA
| | - Daniel Sifrim
- Wingate Institute of Neurogastroenterology, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Rhonda Souza
- Department of Medicine, Center for Esophageal Diseases, Baylor University Medical Center and Center for Esophageal Research, Baylor Scott & White Research Institute, Dallas, TX, USA
| | - Philip Woodland
- Wingate Institute of Neurogastroenterology, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
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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.
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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;
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Lowes H, Somarathna T, Shepherd NA. Definition, Derivation, and Diagnosis of Barrett’s Esophagus: Pathological Perspectives. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 908:111-36. [DOI: 10.1007/978-3-319-41388-4_7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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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.
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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
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Magierowski M, Magierowska K, Kwiecien S, Brzozowski T. Gaseous mediators nitric oxide and hydrogen sulfide in the mechanism of gastrointestinal integrity, protection and ulcer healing. Molecules 2015; 20:9099-123. [PMID: 25996214 PMCID: PMC6272495 DOI: 10.3390/molecules20059099] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Revised: 04/29/2015] [Accepted: 05/13/2015] [Indexed: 12/16/2022] Open
Abstract
Nitric oxide (NO) and hydrogen sulfide (H2S) are known as biological messengers; they play an important role in human organism and contribute to many physiological and pathophysiological processes. NO is produced from l-arginine by constitutive NO synthase (NOS) and inducible NOS enzymatic pathways. This gaseous mediator inhibits platelet aggregation, leukocyte adhesion and contributes to the vessel homeostasis. NO is known as a vasodilatory molecule involved in control of the gastric blood flow (GBF) and the maintenance of gastric mucosal barrier integrity in either healthy gastric mucosa or that damaged by strong irritants. Biosynthesis of H2S in mammals depends upon two enzymes cystathionine-β-synthase and cystathionine γ-lyase. This gaseous mediator, similarly to NO and carbon monoxide, is involved in neuromodulation, vascular contractility and anti-inflammatory activities. For decades, H2S has been known to inhibit cytochrome c oxidase and reduce cell energy production. Nowadays it is generally considered to act through vascular smooth muscle ATP-dependent K+ channels, interacting with intracellular transcription factors and promote sulfhydration of protein cysteine moieties within the cell, but the mechanism of potential gastroprotective and ulcer healing properties of H2S has not been fully explained. The aim of this review is to compare current results of the studies concerning the role of H2S and NO in gastric mucosa protection and outline areas that may pose new opportunities for further development of novel therapeutic targets.
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Affiliation(s)
- Marcin Magierowski
- Department of Physiology, Jagiellonian University Medical College, Cracow 31-531, Poland.
| | - Katarzyna Magierowska
- Department of Physiology, Jagiellonian University Medical College, Cracow 31-531, Poland.
| | - Slawomir Kwiecien
- Department of Physiology, Jagiellonian University Medical College, Cracow 31-531, Poland.
| | - Tomasz Brzozowski
- Department of Physiology, Jagiellonian University Medical College, Cracow 31-531, Poland.
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McDonald SA, Graham TA, Lavery DL, Wright NA, Jansen M. The Barrett's Gland in Phenotype Space. Cell Mol Gastroenterol Hepatol 2015; 1:41-54. [PMID: 28247864 PMCID: PMC5301147 DOI: 10.1016/j.jcmgh.2014.10.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Accepted: 10/15/2014] [Indexed: 02/06/2023]
Abstract
Barrett's esophagus is characterized by the erosive replacement of esophageal squamous epithelium by a range of metaplastic glandular phenotypes. These glandular phenotypes likely change over time, and their distribution varies along the Barrett's segment. Although much recent work has addressed Barrett's esophagus from the genomic viewpoint-its genotype space-the fact that the phenotype of Barrett's esophagus is nonstatic points to conversion between phenotypes and suggests that Barrett's esophagus also exists in phenotype space. Here we explore this latter concept, investigating the scope of glandular phenotypes in Barrett's esophagus and how they exist in physical and temporal space as well as their evolution and their life history. We conclude that individual Barrett's glands are clonal units; because of this important fact, we propose that it is the Barrett's gland that is the unit of selection in phenotypic and indeed neoplastic progression. Transition between metaplastic phenotypes may be governed by neutral drift akin to niche turnover in normal and dysplastic niches. In consequence, the phenotype of Barrett's glands assumes considerable importance, and we make a strong plea for the integration of the Barrett's gland in both genotype and phenotype space in future work.
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Affiliation(s)
- Stuart A.C. McDonald
- Centre for Tumour Biology, Barts Cancer Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Trevor A. Graham
- Centre for Tumour Biology, Barts Cancer Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Danielle L. Lavery
- Centre for Tumour Biology, Barts Cancer Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Nicholas A. Wright
- Centre for Tumour Biology, Barts Cancer Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Marnix Jansen
- Centre for Tumour Biology, Barts Cancer Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
- Department of Pathology, Academic Medical Center, Amsterdam, the Netherlands
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Woodland P, Lee C, Duraisamy Y, Farré R, Dettmar P, Sifrim D, Sifrim D. Assessment and protection of esophageal mucosal integrity in patients with heartburn without esophagitis. Am J Gastroenterol 2013; 108:535-43. [PMID: 23358463 DOI: 10.1038/ajg.2012.469] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
OBJECTIVES Intact esophageal mucosal integrity is essential to prevent symptoms during gastroesophageal reflux events. Approximately 70% of patients with heartburn have macroscopically normal esophageal mucosa. In patients with heartburn, persistent functional impairment of esophageal mucosal barrier integrity may underlie remaining symptoms. Topical protection of a functionally vulnerable mucosa may be an attractive therapeutic strategy. We aimed to evaluate esophageal mucosal functional integrity in patients with heartburn without esophagitis, and test the feasibility of an alginate-based topical mucosal protection. METHODS Three distal esophageal biopsies were obtained from 22 patients with heartburn symptoms, and 22 control subjects. In mini-Ussing chambers, the change in transepithelial electrical resistance (TER) of biopsies when exposed to neutral, weakly acidic, and acidic solutions was measured. The experiment was repeated in a further 10 patients after pretreatment of biopsies with sodium alginate, viscous control, or liquid control "protectant" solutions. RESULTS Biopsy exposure to neutral solution caused no change in TER. Exposure to weakly acidic and acidic solutions caused a greater reduction in TER in patients than in controls (weakly acid -7.2% (95% confidence interval (CI) -9.9 to -4.5) vs. 3.2% (-2.2 to 8.6), P<0.05; acidic -22.8% (-31.4 to 14.1) vs. -9.4% (-17.2 to -1.6), P<0.01). Topical pretreatment with alginate but not with control solutions prevented the acid-induced decrease in TER (-1% (-5.9 to 3.9) vs. -13.5 (-24.1 to -3.0) vs. -13.2 (-21.7 to -4.8), P<0.05). CONCLUSIONS Esophageal mucosa in patients with heartburn without esophagitis shows distinct vulnerability to acid and weakly acidic exposures. Experiments in vitro suggest that such vulnerable mucosa may be protected by application of an alginate-containing topical solution.
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Affiliation(s)
- Philip Woodland
- Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
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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.
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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
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10
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Tobey NA, Djukic Z, Brighton LE, Gambling TM, Carson JL, Orlando RC. Lateral cell membranes and shunt resistance in rabbit esophageal epithelium. Dig Dis Sci 2010; 55:1856-65. [PMID: 20503073 DOI: 10.1007/s10620-010-1215-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2009] [Accepted: 12/10/2009] [Indexed: 12/09/2022]
Abstract
BACKGROUND AND AIMS The structures that contribute to shunt resistance (Rs) in esophageal epithelium are incompletely understood, with 35-40% of Rs known to be calcium-dependent, reflecting the role of e-cadherin. Two calcium-independent candidates for the remaining approximately 60% of Rs have been identified: the glycoprotein matrix (GPM) within stratum corneum of esophageal epithelium, and the lateral cell membranes (LCMs) from neighboring cells. METHODS To determine the contribution of GPM and LCMs to Rs, rabbit esophageal epithelium was mounted in Ussing chambers so that transepithelial resistance (R(T)), a marker of Rs, could be monitored during luminal exposure to either glycosidases for disruption of the GPM or to hypertonic urea for separation of the LCMs. RESULTS Glycosidases had no effect on R(T). In contrast, hypertonic urea reduced R(T), increased fluorescein flux and widened the intercellular spaces. That urea reduced R(T), and so Rs, by widening the intercellular spaces, and not by altering the e-cadherin-dependent apical junctional complex, was supported by the ability of: (a) calcium-free solution to reduce R(T) beyond that produced by urea, (b) hypertonic urea to reduce R(T) beyond that produced by calcium free solution, (c) hypertonic sucrose to collapse the intercellular spaces and raise R(T), and (d) empigen, a zwitterionic detergent, to non-osmotically widen the intercellular spaces and reduce R(T). CONCLUSION These data indicate that the LCMs from neighboring cells are a major contributor to shunt resistance in esophageal epithelium. As resistor, they are distinguishable from the apical junctional complex by their sensitivity to (luminal) hypertonicity and insensitivity to removal of calcium.
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Affiliation(s)
- Nelia A Tobey
- Department of Medicine, University of North Carolina, Chapel Hill, NC 27599-7310, USA.
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Warner L, Gomez SI, Bolterman R, Haas JA, Bentley MD, Lerman LO, Romero JC. Regional decreases in renal oxygenation during graded acute renal arterial stenosis: a case for renal ischemia. Am J Physiol Regul Integr Comp Physiol 2008; 296:R67-71. [PMID: 18971350 DOI: 10.1152/ajpregu.90677.2008] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ischemic nephropathy describes progressive renal failure, defined by significantly reduced glomerular filtration rate, and may be due to renal artery stenosis (RAS), a narrowing of the renal artery. It is unclear whether ischemia is present during RAS since a decrease in renal blood flow (RBF), O(2) delivery, and O(2) consumption occurs. The present study tests the hypothesis that despite proportional changes in whole kidney O(2) delivery and consumption, acute progressive RAS leads to decreases in regional renal tissue O(2). Unilateral acute RAS was induced in eight pigs with an extravascular cuff. RBF was measured with an ultrasound flow probe. Cortical and medullary tissue oxygen (P(t(O(2)))) of the stenotic kidney was measured continuously with sensors during baseline, three sequentially graded decreases in RBF, and recovery. O(2) consumption decreased proportionally to O(2) delivery during the graded stenosis (19 +/- 10.8, 48.2 +/- 9.1, 58.9 +/- 4.7 vs. 15.1 +/- 5, 35.4 +/- 3.5, 57 +/- 2.3%, respectively) while arterial venous O(2) differences were unchanged. Acute RAS produced a sharp reduction in O(2) efficiency for sodium reabsorption (P < 0.01). Cortical (P(t(O(2)))) decreases are exceeded by medullary decreases during stenosis (34.8 +/- 1.3%). Decreases in tissue oxygenation, more pronounced in the medulla than the cortex, occur despite proportional reductions in O(2) delivery and consumption. This demonstrates for the first time that hypoxia is present in the early stages of RAS and suggests a role for hypoxia in the pathophysiology of this disease. Furthermore, the notion that arteriovenous shunting and increased stoichiometric energy requirements are potential contributors toward ensuing hypoxia with graded and progressive acute RAS cannot be excluded.
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Affiliation(s)
- Lizette Warner
- Department of Physiology and Biomedical Engineering , Mayo Clinic, ST 7, 200 First St. SW, Rochester, MN 55905, USA
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Evans RG, Gardiner BS, Smith DW, O'Connor PM. Intrarenal oxygenation: unique challenges and the biophysical basis of homeostasis. Am J Physiol Renal Physiol 2008; 295:F1259-70. [PMID: 18550645 DOI: 10.1152/ajprenal.90230.2008] [Citation(s) in RCA: 196] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The kidney is faced with unique challenges for oxygen regulation, both because its function requires that perfusion greatly exceeds that required to meet metabolic demand and because vascular control in the kidney is dominated by mechanisms that regulate glomerular filtration and tubular reabsorption. Because tubular sodium reabsorption accounts for most oxygen consumption (Vo2) in the kidney, renal Vo2 varies with glomerular filtration rate. This provides an intrinsic mechanism to match changes in oxygen delivery due to changes in renal blood flow (RBF) with changes in oxygen demand. Renal Vo2 is low relative to supply of oxygen, but diffusional arterial-to-venous (AV) oxygen shunting provides a mechanism by which oxygen superfluous to metabolic demand can bypass the renal microcirculation. This mechanism prevents development of tissue hyperoxia and subsequent tissue oxidation that would otherwise result from the mismatch between renal Vo2 and RBF. Recent evidence suggests that RBF-dependent changes in AV oxygen shunting may also help maintain stable tissue oxygen tension when RBF changes within the physiological range. However, AV oxygen shunting also renders the kidney susceptible to hypoxia. Given that tissue hypoxia is a hallmark of both acute renal injury and chronic renal disease, understanding the causes of tissue hypoxia is of great clinical importance. The simplistic paradigm of oxygenation depending only on the balance between local perfusion and Vo2 is inadequate to achieve this goal. To fully understand the control of renal oxygenation, we must consider a triad of factors that regulate intrarenal oxygenation: local perfusion, local Vo2, and AV oxygen shunting.
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Affiliation(s)
- Roger G Evans
- Department of Physiology, Monash University, Melbourne, Victoria, Australia.
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Tobey NA, Gambling TM, Vanegas XC, Carson JL, Orlando RC. Physicochemical basis for dilated intercellular spaces in non-erosive acid-damaged rabbit esophageal epithelium. Dis Esophagus 2008; 21:757-64. [PMID: 18522636 DOI: 10.1111/j.1442-2050.2008.00841.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Dilated intercellular spaces (DIS) within esophageal epithelium (EE) is a histopathologic feature of non-erosive reflux disease and early lesion in acid-damaged rabbit EE associated with increased paracellular permeability. Its cause remains unknown, but the lesion's morphology suggests a significant fluid shift into the intercellular spaces (ICS). Since water follows osmotic forces and consequently ion movements, we explored the role of active (ion) transport and ion gradients in its pathogenesis. This was done by quantifying the effect of inhibited active transport and altered ion gradients on electrical resistance (R(T)) and ICS diameter in acid-exposed Ussing-chambered rabbit EE. Compared with normal Ringer, pH 7.5, 30 minutes of luminal HCl (100 mmol/L), pH 1.1, increased permeability (R(T): +5 +/- 4% vs-52 +/- 4%) and ICS diameter (0.25 +/- 0.01 microm vs 0.42 +/- 0.02 microm), but had no effect on cell morphology or diameter. Ouabain pretreatment significantly reduced active transport but had no effect on the acid-induced changes. However, negating the chloride gradient created by luminal HCl either by adding choline chloride, 100 mmol/L, serosally or by replacing luminal HCl, pH 1.1, with luminal H(2)SO(4), pH 1.1, prevented the development of DIS while maintaining the increase in permeability. DIS was also prevented in the presence of a 100 mmol/L (choline) chloride gradient by luminal exposure at neutral pH. DIS in HCl-damaged EE is caused by an H(+)-induced increase in epithelial permeability; this enables Cl(-) to diffuse along its gradient into the ICS, creating an osmotic force for water movement into and (hydrostatic) dilation of the ICS.
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Affiliation(s)
- N A Tobey
- Department of Medicine, University of North Carolina at Chapel Hill, North Carolina 27599, USA.
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Mik EG, Johannes T, Ince C. Monitoring of renal venous PO2 and kidney oxygen consumption in rats by a near-infrared phosphorescence lifetime technique. Am J Physiol Renal Physiol 2008; 294:F676-81. [PMID: 18184739 DOI: 10.1152/ajprenal.00569.2007] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Renal oxygen consumption (Vo(2,ren)) is an important parameter that has been shown to be influenced by various pathophysiological circumstances. Vo(2,ren) has to be repeatedly measured during an experiment to gain insight in the dynamics of (dys)regulation of oxygen metabolism. In small animals, the classical approach of blood gas analysis of arterial and venous blood samples is only limitedly applicable due to fragile vessels and a low circulating blood volume. We present a phosphorescence lifetime technique that allows near-continuous measurement of renal venous Po(2) (vPo(2)) and Vo(2,ren) in rats. The technique does not rely on penetration of the blood vessel, but uses a small reflection probe. This probe is placed in close proximity to the renal vein for detection of the oxygen-dependent phosphorescence of the injected water-soluble near-infrared phosphor Oxyphor G2. The technique was calibrated in vitro and the calibration constants were validated in vivo in anesthetized and mechanically ventilated male Wistar rats. The hemoglobin saturation curve and its pH dependency were determined for calculation of renal venous oxygen content. The phosphorescence technique was in good agreement with blood gas analysis of renal venous blood samples, for both Po(2) and hemoglobin saturation. To demonstrate its feasibility in practice, the technique was used in four rats during endotoxin infusion (10 mg x kg(-1) x h(-1) during 1 h). Renal vPo(2) reduced by 40% upon reduction in oxygen delivery to 30% of baseline, but Vo(2) remained unchanged. This study documents the feasibility of near-continuous, nondestructive measurement of renal vPo(2) and Vo(2) by oxygen-dependent quenching of phosphorescence.
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Affiliation(s)
- Egbert G Mik
- Department of Physiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
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