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Cartwright IM, Dowdell AS, Hanson C, Kostelecky RE, Welch N, Steiner CA, Colgan SP. Contact-dependent, polarized acidification response during neutrophil-epithelial interactions. J Leukoc Biol 2022; 112:1543-1553. [PMID: 35674095 PMCID: PMC9701153 DOI: 10.1002/jlb.3ma0422-742r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 04/29/2022] [Indexed: 01/04/2023] Open
Abstract
Neutrophil (PMN) infiltration during active inflammation imprints changes in the local tissue environment. Such responses are often accompanied by significant extracellular acidosis that result in predictable transcriptional responses. In this study, we explore the mechanisms involved in inflammatory acidification as a result of PMN-intestinal epithelial cell (IEC) interactions. Using recently developed tools, we revealed that PMN transepithelial migration (TEM)-associated inflammatory acidosis is dependent on the total number of PMNs present during TEM and is polarized toward the apical surface. Extending these studies, we demonstrate that physical separation of the PMNs and IECs prevented acidification, whereas inhibition of PMN TEM using neutralizing antibodies enhanced extracellular acidification. Utilizing pharmaceutical inhibitors, we demonstrate that the acidification response is independent of myeloperoxidase and dependent on reactive oxygen species generated during PMN TEM. In conclusion, inflammatory acidosis represents a polarized PMN-IEC-dependent response by an as yet to be fully determined mechanism.
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Affiliation(s)
- Ian M. Cartwright
- Mucosal Inflammation Program, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
- Rocky Mountain Regional Veterans Affairs Medical Center, Aurora, Colorado, USA
| | - Alexander S. Dowdell
- Mucosal Inflammation Program, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Camila Hanson
- Mucosal Inflammation Program, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
- Rocky Mountain Regional Veterans Affairs Medical Center, Aurora, Colorado, USA
| | - Rachael E. Kostelecky
- Mucosal Inflammation Program, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Nichole Welch
- Mucosal Inflammation Program, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Calen A. Steiner
- Mucosal Inflammation Program, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Sean P. Colgan
- Mucosal Inflammation Program, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
- Rocky Mountain Regional Veterans Affairs Medical Center, Aurora, Colorado, USA
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2
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Phytochemical and pharmacological studies on the genus Arcangelisia: A mini review. ARAB J CHEM 2021. [DOI: 10.1016/j.arabjc.2021.103346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Shan W, Hu Y, Ding J, Yang X, Lou J, Du Q, Liao Q, Luo L, Xu J, Xie R. Advances in Ca 2+ modulation of gastrointestinal anion secretion and its dysregulation in digestive disorders (Review). Exp Ther Med 2020; 20:8. [PMID: 32934673 PMCID: PMC7471861 DOI: 10.3892/etm.2020.9136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 05/22/2020] [Indexed: 11/29/2022] Open
Abstract
Intracellular calcium (Ca2+) is a critical cell signaling component in gastrointestinal (GI) physiology. Cytosolic calcium ([Ca2+]cyt), as a secondary messenger, controls GI epithelial fluid and ion transport, mucus and neuropeptide secretion, as well as synaptic transmission and motility. The key roles of Ca2+ signaling in other types of secretory cell (including those in the airways and salivary glands) are well known. However, its action in GI epithelial secretion and the underlying molecular mechanisms have remained to be fully elucidated. The present review focused on the role of [Ca2+]cyt in GI epithelial anion secretion. Ca2+ signaling regulates the activities of ion channels and transporters involved in GI epithelial ion and fluid transport, including Cl- channels, Ca2+-activated K+ channels, cystic fibrosis (CF) transmembrane conductance regulator and anion/HCO3- exchangers. Previous studies by the current researchers have focused on this field over several years, providing solid evidence that Ca2+ signaling has an important role in the regulation of GI epithelial anion secretion and uncovering underlying molecular mechanisms. The present review is largely based on previous studies by the current researchers and provides an overview of the currently known molecular mechanisms of GI epithelial anion secretion with an emphasis on Ca2+-mediated ion secretion and its dysregulation in GI disorders. In addition, previous studies by the current researchers demonstrated that different regulatory mechanisms are in place for GI epithelial HCO3- and Cl- secretion. An increased understanding of the roles of Ca2+ signaling and its targets in GI anion secretion may lead to the development of novel strategies to inhibit GI diseases, including the enhancement of fluid secretion in CF and protection of the GI mucosa in ulcer diseases.
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Affiliation(s)
- Weixi Shan
- Department of Gastroenterology, The Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou 563003, P.R. China
| | - Yanxia Hu
- Department of Gastroenterology, The Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou 563003, P.R. China
| | - Jianhong Ding
- Department of Gastroenterology, The Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou 563003, P.R. China
| | - Xiaoxu Yang
- Department of Gastroenterology, The Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou 563003, P.R. China
| | - Jun Lou
- Department of Gastroenterology, The Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou 563003, P.R. China
| | - Qian Du
- Department of Gastroenterology, The Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou 563003, P.R. China
| | - Qiushi Liao
- Department of Gastroenterology, The Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou 563003, P.R. China
| | - Lihong Luo
- Department of Oncology and Geriatrics, Traditional Chinese Medicine Hospital of Chishui City, Guizhou 564700, P.R. China
| | - Jingyu Xu
- Department of Gastroenterology, The Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou 563003, P.R. China
| | - Rui Xie
- Department of Gastroenterology, The Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou 563003, P.R. China
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Rehman S, Narayanan K, Nickerson AJ, Coon SD, Hoque KM, Sandle GI, Rajendran VM. Parallel intermediate conductance K + and Cl - channel activity mediates electroneutral K + exit across basolateral membranes in rat distal colon. Am J Physiol Gastrointest Liver Physiol 2020; 319:G142-G150. [PMID: 32567323 PMCID: PMC7500264 DOI: 10.1152/ajpgi.00011.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Transepithelial K+ absorption requires apical K+ uptake and basolateral K+ exit. In the colon, apical H+-K+-ATPase mediates cellular K+ uptake, and it has been suggested that electroneutral basolateral K+ exit reflects K+-Cl- cotransporter-1 (KCC1) operating in parallel with K+ and Cl- channels. The present study was designed to identify basolateral transporter(s) responsible for K+ exit in rat distal colon. Active K+ absorption was determined by measuring 86Rb+ (K+ surrogate) fluxes across colonic epithelia under voltage-clamp conditions. With zero Cl- in the mucosal solution, net K+ absorption was reduced by 38%, indicating that K+ absorption was partially Cl--dependent. Serosal addition of DIOA (KCC1 inhibitor) or Ba2+ (nonspecific K+ channel blocker) inhibited net K+ absorption by 21% or 61%, respectively, suggesting that both KCC1 and K+ channels contribute to basolateral K+ exit. Clotrimazole and TRAM34 (IK channel blockers) added serosally inhibited net K+ absorption, pointing to the involvement of IK channels in basolateral K+ exit. GaTx2 (CLC2 blocker) added serosally also inhibited net K+ absorption, suggesting that CLC2-mediated Cl- exit accompanies IK channel-mediated K+ exit across the basolateral membrane. Net K+ absorption was not inhibited by serosal addition of either IbTX (BK channel blocker), apamin (SK channel blocker), chromanol 293B (KV7 channel blocker), or CFTRinh172 (CFTR blocker). Immunofluorescence studies confirmed basolateral membrane colocalization of CLC2-like proteins and Na+-K+-ATPase α-subunits. We conclude that active K+ absorption in rat distal colon involves electroneutral basolateral K+ exit, which may reflect IK and CLC2 channels operating in parallel.NEW & NOTEWORTHY This study demonstrates that during active electroneutral K+ absorption in rat distal colon, K+ exit across the basolateral membrane mainly reflects intermediate conductance K+ channels operating in conjunction with chloride channel 2, with a smaller, but significant, contribution from K+-Cl- cotransporter-1 (KCC1) activity.
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Affiliation(s)
- Shabina Rehman
- 1Departments of Biochemistry West Virginia University School of Medicine, Morgantown, West Virginia
| | - Karthikeyan Narayanan
- 1Departments of Biochemistry West Virginia University School of Medicine, Morgantown, West Virginia
| | - Andrew J. Nickerson
- 1Departments of Biochemistry West Virginia University School of Medicine, Morgantown, West Virginia,2Departments of Physiology and Pharmacology, West Virginia University School of Medicine, Morgantown, West Virginia
| | - Steven D. Coon
- 3Department of Biological Sciences, Port Peck Community College, Poplar, Montana
| | - Kazi Mirajul Hoque
- 4Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Geoffrey I. Sandle
- 5Leeds Institute for Medical Research at St. James’s, St. James’s University Hospital. Leeds, United Kingdom
| | - Vazhaikkurichi M. Rajendran
- 1Departments of Biochemistry West Virginia University School of Medicine, Morgantown, West Virginia,6Departments of Medicine, West Virginia University School of Medicine, Morgantown, West Virginia
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Hynes D, Harvey BJ. Dexamethasone reduces airway epithelial Cl - secretion by rapid non-genomic inhibition of KCNQ1, KCNN4 and KATP K + channels. Steroids 2019; 151:108459. [PMID: 31330137 DOI: 10.1016/j.steroids.2019.108459] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Revised: 07/05/2019] [Accepted: 07/07/2019] [Indexed: 11/26/2022]
Abstract
Basolateral membrane K+ channels play a key role in basal and agonist stimulated Cl- transport across airway epithelial cells by generating a favourable electrical driving force for Cl- efflux. The K+ channel sub-types and molecular mechanisms of regulation by hormones and secretagoues are still poorly understood. Here we have identified the type of K+ channels involved in cAMP and Ca2+ stimulated Cl- secretion and uncovered a novel anti-secretory effect of dexamethasone mediated by inhibition of basolateral membrane K+ channels in a human airway cell model of 16HBE14o- cells commonly used for ion transport studies. Dexamethasone produced a rapid inhibition of transepithelial chloride ion secretion under steady state conditions and after stimulation with cAMP agonist (forskolin) or a Ca2+ mobilizing agonist (ATP). Our results show three different types of K+ channels are targeted by dexamethasone to reduce airway secretion, namely Ca2+-activated secretion via KCNN4 (KCa3.1) channels and cAMP-activated secretion via KCNQ1 (Kv7.1) and KATP (Kir6.1,6.2) channels. The down-regulation of KCNN4 and KCNQ1 channel activities by dexamethasone involves rapid non-genomic activation of PKCα and PKA signalling pathways, respectively. Dexamethasone signal transduction for PKC and PKA activation was demonstrated to occur through a rapid non-genomic pathway that did not implicate the classical nuclear receptors for glucocorticoids or mineralocorticoids but occurred via a novel signalling cascade involving sequentially a Gi-protein coupled receptor, PKC, adenylyl cyclase Type IV, cAMP, PKA and ERK1/2 activation. The rapid, non-genomic, effects of dexamethasone on airway epithelial ion transport and cell signalling introduces a new paradigm for glucocorticoid actions in lung epithelia which may serve to augment the anti-inflammatory activity of the steroid and enhance its therapeutic potential in treating airway hypersecretion in asthma and COPD.
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Affiliation(s)
- Darina Hynes
- Department of Molecular Medicine, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin 9, Ireland
| | - Brian J Harvey
- Department of Molecular Medicine, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin 9, Ireland; Centro di Estudios Cientificos CECs, Valdivia, Chile.
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6
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Rajendran VM, Sandle GI. Colonic Potassium Absorption and Secretion in Health and Disease. Compr Physiol 2018; 8:1513-1536. [PMID: 30215859 PMCID: PMC9769410 DOI: 10.1002/cphy.c170030] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The colon has large capacities for K+ absorption and K+ secretion, but its role in maintaining K+ homeostasis is often overlooked. For many years, passive diffusion and/or solvent drag were thought to be the primary mechanisms for K+ absorption in human and animal colon. However, it is now clear that apical H+ ,K+ -ATPase, in coordination with basolateral K+ -Cl- cotransport and/or K+ and Cl- channels operating in parallel, mediate electroneutral K+ absorption in animal colon. We now know that K+ absorption in rat colon reflects ouabain-sensitive and ouabain-insensitive apical H+ ,K+ -ATPase activities. Ouabain-insensitive and ouabain-sensitive H+ ,K+ -ATPases are localized in surface and crypt cells, respectively. Colonic H+ ,K+ -ATPase consists of α- (HKCα ) and β- (HKCβ ) subunits which, when coexpressed, exhibit ouabain-insensitive H+ ,K+ -ATPase activity in HEK293 cells, while HKCα coexpressed with the gastric β-subunit exhibits ouabain-sensitive H+ ,K+ -ATPase activity in Xenopus oocytes. Aldosterone enhances apical H+ ,K+ -ATPase activity, HKCα specific mRNA and protein expression, and K+ absorption. Active K+ secretion, on the other hand, is mediated by apical K+ channels operating in a coordinated way with the basolateral Na+ -K+ -2Cl- cotransporter. Both Ca2+ -activated intermediate conductance K+ (IK) and large conductance K+ (BK) channels are located in the apical membrane of colonic epithelia. IK channel-mediated K+ efflux provides the driving force for Cl- secretion, while BK channels mediate active (e.g., cAMP-activated) K+ secretion. BK channel expression and activity are increased in patients with end-stage renal disease and ulcerative colitis. This review summarizes the role of apical H+ ,K+ -ATPase in K+ absorption, and apical BK channel function in K+ secretion in health and disease. © 2018 American Physiological Society. Compr Physiol 8:1513-1536, 2018.
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Affiliation(s)
| | - Geoffrey I. Sandle
- Leeds Institute of Biomedical and Clinical Sciences, St James’s University Hospital, Leeds LS9 7TF, UK
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Hermidorff MM, de Assis LVM, Isoldi MC. Genomic and rapid effects of aldosterone: what we know and do not know thus far. Heart Fail Rev 2018; 22:65-89. [PMID: 27942913 DOI: 10.1007/s10741-016-9591-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Aldosterone is the most known mineralocorticoid hormone synthesized by the adrenal cortex. The genomic pathway displayed by aldosterone is attributed to the mineralocorticoid receptor (MR) signaling. Even though the rapid effects displayed by aldosterone are long known, our knowledge regarding the receptor responsible for such event is still poor. It is intense that the debate whether the MR or another receptor-the "unknown receptor"-is the receptor responsible for the rapid effects of aldosterone. Recently, G protein-coupled estrogen receptor-1 (GPER-1) was elegantly shown to mediate some aldosterone-induced rapid effects in several tissues, a fact that strongly places GPER-1 as the unknown receptor. It has also been suggested that angiotensin receptor type 1 (AT1) also participates in the aldosterone-induced rapid effects. Despite this open question, the relevance of the beneficial effects of aldosterone is clear in the kidneys, colon, and CNS as aldosterone controls the important water reabsorption process; on the other hand, detrimental effects displayed by aldosterone have been reported in the cardiovascular system and in the kidneys. In this line, the MR antagonists are well-known drugs that display beneficial effects in patients with heart failure and hypertension; it has been proposed that MR antagonists could also play an important role in vascular disease, obesity, obesity-related hypertension, and metabolic syndrome. Taken altogether, our goal here was to (1) bring a historical perspective of both genomic and rapid effects of aldosterone in several tissues, and the receptors and signaling pathways involved in such processes; and (2) critically address the controversial points within the literature as regarding which receptor participates in the rapid pathway display by aldosterone.
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Affiliation(s)
- Milla Marques Hermidorff
- Laboratory of Hypertension, Research Center in Biological Science, Institute of Exact and Biological Sciences, Federal University of Ouro Preto, Campus Morro do Cruzeiro, Ouro Preto, MG, 35400-000, Brazil
| | - Leonardo Vinícius Monteiro de Assis
- Laboratory of Comparative Physiology of Pigmentation, Department of Physiology, Institute of Biosciences, University of São Paulo, São Paulo, Brazil
| | - Mauro César Isoldi
- Laboratory of Hypertension, Research Center in Biological Science, Institute of Exact and Biological Sciences, Federal University of Ouro Preto, Campus Morro do Cruzeiro, Ouro Preto, MG, 35400-000, Brazil.
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Lundquist P, Artursson P. Oral absorption of peptides and nanoparticles across the human intestine: Opportunities, limitations and studies in human tissues. Adv Drug Deliv Rev 2016; 106:256-276. [PMID: 27496705 DOI: 10.1016/j.addr.2016.07.007] [Citation(s) in RCA: 310] [Impact Index Per Article: 38.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Revised: 07/02/2016] [Accepted: 07/08/2016] [Indexed: 12/23/2022]
Abstract
In this contribution, we review the molecular and physiological barriers to oral delivery of peptides and nanoparticles. We discuss the opportunities and predictivity of various in vitro systems with special emphasis on human intestine in Ussing chambers. First, the molecular constraints to peptide absorption are discussed. Then the physiological barriers to peptide delivery are examined. These include the gastric and intestinal environment, the mucus barrier, tight junctions between epithelial cells, the enterocytes of the intestinal epithelium, and the subepithelial tissue. Recent data from human proteome studies are used to provide information about the protein expression profiles of the different physiological barriers to peptide and nanoparticle absorption. Strategies that have been employed to increase peptide absorption across each of the barriers are discussed. Special consideration is given to attempts at utilizing endogenous transcytotic pathways. To reliably translate in vitro data on peptide or nanoparticle permeability to the in vivo situation in a human subject, the in vitro experimental system needs to realistically capture the central aspects of the mentioned barriers. Therefore, characteristics of common in vitro cell culture systems are discussed and compared to those of human intestinal tissues. Attempts to use the cell and tissue models for in vitro-in vivo extrapolation are reviewed.
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Affiliation(s)
- P Lundquist
- Department of Pharmacy, Uppsala University, Box 580, SE-752 37 Uppsala, Sweden.
| | - P Artursson
- Department of Pharmacy, Uppsala University, Box 580, SE-752 37 Uppsala, Sweden.
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Medani M, Collins D, Mohan HM, Walsh E, Winter DC, Baird AW. Prostaglandin D2 regulates human colonic ion transport via the DP1 receptor. Life Sci 2014; 122:87-91. [PMID: 25534438 DOI: 10.1016/j.lfs.2014.12.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 11/20/2014] [Accepted: 12/09/2014] [Indexed: 01/07/2023]
Abstract
AIMS Prostaglandin D2 is released by mast cells and is important in allergies. Its role in gastrointestinal function is not clearly defined. This study aimed to determine the effect of exogenous PGD2 on ion transport in ex vivo normal human colonic mucosa. MATERIALS AND METHODS Mucosal sheets were mounted in Ussing chambers and voltage clamped to zero electric potential. Ion transport was quantified as changes in short-circuit current. In separate experiments epithelial monolayers or colonic crypts, isolated by calcium chelation, were treated with PGD2 and cAMP levels determined by ELISA or calcium levels were determined by fluorimetry. KEY FINDINGS PGD2 caused a sustained, concentration-dependent rise in short-circuit current by increasing chloride secretion (EC50=376nM). This effect of PGD2 is mediated by the DP1 receptor, as the selective DP1 receptor antagonist BW A686C inhibited PGD2-induced but not PGE2-induced rise in short-circuit current. PGD2 also increased intracellular cAMP in isolated colonic crypts with no measurable influence on cytosolic calcium. PGD2 induces chloride secretion in isolated human colonic mucosa in a concentration-dependent manner with concomitant elevation of cytoplasmic cAMP in epithelial cells. SIGNIFICANCE The involvement of DP2 receptor subtypes has not previously been considered in regulation of ion transport in human intestine. Since inflammatory stimuli may induce production of eicosanoids, selective regulation of these pathways may be pivotal in determining therapeutic strategies and in understanding disease.
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Affiliation(s)
- M Medani
- Department of Surgery, St Vincent's University Hospital, Elm Park, Dublin 4, Ireland; UCD School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland; Conway Institute of Biomolecular & Biomedical Science, University College Dublin, Belfield, Dublin 4, Ireland; UCD School of Medicine and Medical Science, University College Dublin, Belfield, Dublin 4, Ireland
| | - D Collins
- Department of Surgery, St Vincent's University Hospital, Elm Park, Dublin 4, Ireland; UCD School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland; Conway Institute of Biomolecular & Biomedical Science, University College Dublin, Belfield, Dublin 4, Ireland; UCD School of Medicine and Medical Science, University College Dublin, Belfield, Dublin 4, Ireland
| | - H M Mohan
- Department of Surgery, St Vincent's University Hospital, Elm Park, Dublin 4, Ireland; UCD School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland; Conway Institute of Biomolecular & Biomedical Science, University College Dublin, Belfield, Dublin 4, Ireland; UCD School of Medicine and Medical Science, University College Dublin, Belfield, Dublin 4, Ireland
| | - E Walsh
- UCD School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland; Conway Institute of Biomolecular & Biomedical Science, University College Dublin, Belfield, Dublin 4, Ireland
| | - D C Winter
- Department of Surgery, St Vincent's University Hospital, Elm Park, Dublin 4, Ireland; UCD School of Medicine and Medical Science, University College Dublin, Belfield, Dublin 4, Ireland
| | - A W Baird
- UCD School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland; Conway Institute of Biomolecular & Biomedical Science, University College Dublin, Belfield, Dublin 4, Ireland.
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Würner L, Diener M. Receptors and mechanisms mediating the biphasic response evoked by bradykinin in rat colonic smooth muscle. Neurogastroenterol Motil 2013; 25:e581-90. [PMID: 23742018 DOI: 10.1111/nmo.12165] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Accepted: 05/13/2013] [Indexed: 02/08/2023]
Abstract
BACKGROUND In rat duodenum, bradykinin induces a relaxation followed by a contraction. Different types of ion channels and receptors as well as non-muscle cells have been suggested to be involved in this response. As it is unclear whether these changes are observed also in rat large intestine and the mechanisms which might underlie this response, the effect of bradykinin on rat colonic motility was tested. METHODS Isometric contractions were measured on full-thickness preparations or preparations, from which individual layers had been dissected. The expression of bradykinin receptors was analyzed by immunohistochemistry and RT-PCR. Isolated intestinal muscle cells were investigated with Ca(2+) -imaging techniques. KEY RESULTS Bradykinin caused a biphasic contractile response (initial relaxation followed by contraction) in rat colon, which was resistant against tetrodotoxin. The kinin-induced relaxation was inhibited by tetrapentylammonium chloride, a blocker of Ca(2+) -activated K(+) channels. Des-arg(9) -bradykinin did not induce any effect on the native colon, although after 5 h in vitro preincubation, a contractile response was evoked by this B1 receptor agonist. The consecutive ablation of adherent layers of the intestinal wall strongly reduced the response to bradykinin in comparison with a control stimulus, i.e., carbachol, suggesting a contribution of non-muscle cells in the mediation of this response. CONCLUSIONS & INFERENCES Bradykinin induced a biphasic change in contractility in the rat colon. In the native intestine, only the B2 receptor is involved in this effect. Neighboring cell obviously sensitize the smooth muscle to the stimulation of these receptors.
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Affiliation(s)
- L Würner
- Institute for Veterinary Physiology and Biochemistry, Justus-Liebig-University Giessen, Giessen, Germany
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11
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Jared SR, Rao JP. Effects of Evans Blue and Amiloride on Anti-Diuretic Hormone (ADH)-Induced Sodium Transport Across Frog (Rana hexadactyla) Skin. Zoolog Sci 2013; 30:402-7. [DOI: 10.2108/zsj.30.402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Bouyer PG, Tang X, Weber CR, Shen L, Turner JR, Matthews JB. Capsaicin induces NKCC1 internalization and inhibits chloride secretion in colonic epithelial cells independently of TRPV1. Am J Physiol Gastrointest Liver Physiol 2013; 304:G142-56. [PMID: 23139219 PMCID: PMC3543646 DOI: 10.1152/ajpgi.00483.2011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Colonic chloride secretion is regulated via the neurohormonal and immune systems. Exogenous chemicals (e.g., butyrate, propionate) can affect chloride secretion. Capsaicin, the pungent ingredient of the chili peppers, exerts various effects on gastrointestinal function. Capsaicin is known to activate the transient receptor potential vanilloid type 1 (TRPV1), expressed in the mesenteric nervous system. Recent studies have also demonstrated its presence in epithelial cells but its role remains uncertain. Because capsaicin has been reported to inhibit colonic chloride secretion, we tested whether this effect of capsaicin could occur by direct action on epithelial cells. In mouse colon and model T84 human colonic epithelial cells, we found that capsaicin inhibited forskolin-dependent short-circuit current (FSK-I(sc)). Using PCR and Western blot, we demonstrated the presence of TRPV1 in colonic epithelial cells. In T84 cells, TRPV1 localized at the basolateral membrane and in vesicular compartments. In permeabilized monolayers, capsaicin activated apical chloride conductance, had no effect on basolateral potassium conductance, but induced NKCC1 internalization demonstrated by immunocytochemistry and basolateral surface biotinylation. AMG-9810, a potent inhibitor of TRPV1, did not prevent the inhibition of the FSK-I(sc) by capsaicin. Neither resiniferatoxin nor N-oleoyldopamine, two selective agonists of TRPV1, blocked the FSK-I(sc). Conversely capsaicin, resiniferatoxin, and N-oleoyldopamine raised intracellular calcium ([Ca(2+)](i)) in T84 cells and AMG-9810 blocked the rise in [Ca(2+)](i) induced by capsaicin and resiniferatoxin suggesting the presence of a functional TRPV1 channel. We conclude that capsaicin inhibits chloride secretion in part by causing NKCC1 internalization, but by a mechanism that appears to be independent of TRPV1.
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Affiliation(s)
| | - Xu Tang
- 1Department of Surgery, The University of Chicago; and
| | | | - Le Shen
- 1Department of Surgery, The University of Chicago; and
| | - Jerrold R. Turner
- 2Department of Pathology, The University of Chicago, Chicago, Illinois
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Bzik VA, Medani M, Baird AW, Winter DC, Brayden DJ. Mechanisms of action of zinc on rat intestinal epithelial electrogenic ion secretion: insights into its antidiarrhoeal actions. ACTA ACUST UNITED AC 2012; 64:644-53. [PMID: 22471360 DOI: 10.1111/j.2042-7158.2011.01441.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
OBJECTIVES Zinc is a useful addition to oral rehydration therapy for acute diarrhoea. We have assessed the mechanism of its epithelial antisecretory action when intestinal epithelial tight junctions were pharmacologically opened. METHODS Rat isolated ileal and colonic mucosae were mounted in Ussing chambers and exposed to ZnSO(4) (Zn(2+) ) in the presence of secretagogues and inhibition of short circuit current (I(sc) ) was measured. KEY FINDINGS Pre-incubation with basolateral but not apical Zn(2+) reduced I(sc) stimulated by forskolin, carbachol and A23187. In the presence of the tight junction-opener, cytochalasin D, antisecretory effects of apically-applied Zn(2+) were enabled in colon and ileum. The apparent permeability coefficient (P(app) ) of Zn(2+) was increased 1.4- and 2.4-fold across rat ileum and colon, respectively, by cytochalasin D. Basolateral addition of Zn(2+) also reduced the I(sc) stimulated by nystatin in rat colon, confirming K channel inhibition. In comparison with other inhibitors, Zn(2+) was a relatively weak blocker of basolateral K(ATP) and K (Ca2+) channels. Exposure of ileum and colon to Zn(2+) for 60 min had minimal effects on epithelial histology. CONCLUSIONS Antisecretory effects of Zn(2+) on intestinal epithelia arose in part through nonselective blockade of basolateral K channels, which was enabled when tight junctions were open.
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Affiliation(s)
- Victoria A Bzik
- Conway Institute and School of Veterinary Medicine, University College Dublin, Belfield, Ireland
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Keating N, Quinlan LR. Small conductance potassium channels drive ATP-activated chloride secretion in the oviduct. Am J Physiol Cell Physiol 2011; 302:C100-9. [PMID: 21918183 DOI: 10.1152/ajpcell.00503.2010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The molecular mechanisms controlling fluid secretion within the oviduct have yet to be determined. As in other epithelia, both secretory and absorptive pathways are likely to work in tandem to drive appropriate ionic movement to support fluid movement across the oviduct epithelium. This study explored the role of potassium channels in basolateral extracellular ATP (ATP(e))-stimulated ion transport in bovine oviduct epithelium using the Ussing chamber short-circuit current (I(SC)) technique. Basal I(SC) in bovine oviduct epithelium comprises both chloride secretion and sodium absorption and was inhibited by treatment with basolateral K(+) channel inhibitors tetrapentlyammonium chloride (TPeA) or BaCl(2). Similarly, ATP-stimulated chloride secretion was significantly attenuated by pretreatment with BaCl(2,) tetraethylammonium (TEA), tolbutamide, and TPeA. Basolateral K(+) current, isolated using nystatin-perforation technique, was rapidly activated by ATP(e), and pretreatment of monolayers with thapsigargin or TPeA abolished this ATP-stimulated K(+) current. To further investigate the type of K(+) channel involved in the ATP response in the bovine oviduct, a number of specific Ca(2+)-activated K(+) channel inhibitors were tested on the ATP-induced ΔI(SC) in intact monolayers. Charbydotoxin, (high conductance and intermediate conductance inhibitor), or paxilline, (high conductance inhibitor) did not significantly alter the ATP(e) response. However, pretreatment with the small conductance inhibitor apamin resulted in a 60% reduction in the response to ATP(e). The presence of small conductance family member KCNN3 was confirmed by RT-PCR and immunohistochemistry. Measurements of intracellular calcium using Fura-2 spectrofluorescence imaging revealed the ability of ATP(e) to increase intracellular calcium in a phospholipase C-inositol 1,4,5-trisphosphate pathway-sensitive manner. In conclusion, these results provide strong evidence that purinergic activation of a calcium-dependent, apamin-sensitive potassium conductance is essential to promote chloride secretion and thus fluid formation in the oviduct.
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Affiliation(s)
- N Keating
- Department of Physiology, School of Medicine, National University of Ireland Galway, Galway, Ireland
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Alzamora R, O'Mahony F, Bustos V, Rapetti-Mauss R, Urbach V, Cid LP, Sepúlveda FV, Harvey BJ. Sexual dimorphism and oestrogen regulation of KCNE3 expression modulates the functional properties of KCNQ1 K⁺ channels. J Physiol 2011; 589:5091-107. [PMID: 21911611 DOI: 10.1113/jphysiol.2011.215772] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The KCNQ1 potassium channel associates with various KCNE ancillary subunits that drastically affect channel gating and pharmacology. Co-assembly with KCNE3 produces a current with nearly instantaneous activation, some time-dependent activation at very positive potentials, a linear current-voltage relationship and a 10-fold higher sensitivity to chromanol 293B. KCNQ1:KCNE3 channels are expressed in colonic crypts and mediate basolateral K(+) recycling required for Cl(-) secretion. We have previously reported the female-specific anti-secretory effects of oestrogen via KCNQ1:KCNE3 channel inhibition in colonic crypts. This study was designed to determine whether sex and oestrogen regulate the expression and function of KCNQ1 and KCNE3 in rat distal colon. Colonic crypts were isolated from Sprague-Dawley rats and used for whole-cell patch-clamp and to extract total RNA and protein. Sheets of epithelium were used for short-circuit current recordings. KCNE1 and KCNE3 mRNA and protein abundance were significantly higher in male than female crypts. No expression of KCNE2 was found and no difference was observed in KCNQ1 expression between male and female (at oestrus) colonic crypts. Male crypts showed a 2.2-fold higher level of association of KCNQ1 and KCNE3 compared to female cells. In female colonic crypts, KCNQ1 and KCNE3 protein expression fluctuated throughout the oestrous cycle and 17β-oestradiol (E2 10 nM) produced a rapid (<15 min) dissociation of KCNQ1 and KCNE3 in female crypts only. Whole-cell K(+) currents showed a linear current-voltage relationship in male crypts, while K(+) currents in colonic crypts isolated from females displayed voltage-dependent outward rectification. Currents in isolated male crypts and epithelial sheets were 10-fold more sensitive to specific KCNQ1 inhibitors, such as chromanol 293B and HMR-1556, than in female. The effect of E2 on K(+) currents mediated by KCNQ1 with or without different β-subunits was assayed from current-voltage relations elicited in CHO cells transfected with KCNQ1 and KCNE3 or KCNE1 cDNA. E2 (100 nM) reduced the currents mediated by the KCNQ1:KCNE3 potassium channel and had no effect on currents via KCNQ1:KCNE1 or KCNQ1 alone. Currents mediated by the complex formed by KCNQ1 and the mutant KCNE3-S82A β-subunit (mutation of the site for PKCδ-promoted phosphorylation and modulation of the activity of KCNE3) showed rapid run-down and insensitivity to E2. Together, these data suggest that oestrogen regulates the expression of the KCNE1 and KCNE3 and with it the gating and pharmacological properties of the K(+) conductance required for Cl(-) secretion. The decreased association of the KCNQ1:KCNE3 channel complex promoted by oestrogen exposure underlies the molecular mechanism for the sexual dimorphism and oestrous cycle dependence of the anti-secretory actions of oestrogen in the intestine.
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Affiliation(s)
- Rodrigo Alzamora
- Department of Molecular Medicine, Education and Research Centre, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin, Republic of Ireland
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Electrogenic transport, oxygen consumption, and sensitivity to acute hypoxia of human colonic epithelium. Int J Colorectal Dis 2011; 26:1205-10. [PMID: 21519802 DOI: 10.1007/s00384-011-1215-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 04/11/2011] [Indexed: 02/04/2023]
Abstract
INTRODUCTION It is recognized that epithelial ion transport depends on oxygen supply, but this dependence has not been characterized in the human colon in vitro despite its surgical and clinical implications. PURPOSES The aim of this study is to measure the oxygen consumption of colonic epithelium under conditions which preserve vectorial ion transport and to assess the sensitivity of the human colonic epithelium short-circuit current (I (sc)) to acute hypoxia induced in vitro. METHODS Isolated mucosa preparations from human sigmoid colon were placed in a modified Ussing chamber which allows simultaneous measurement of short-circuit current (I (sc)) and oxygen consumption (QO(2)). In separate experiments, the sensitivity to acute hypoxia induced in a conventional Ussing chamber was assessed. RESULTS Basal mean ± SEM values (n = 8) were I (sc) = 3.3 ± 0.5 μEq h(-1) cm(-2) and QO(2) = 8.09 ± 0.55 μmol h(-1) cm(-2). The contribution of the serosal side to the oxygen supply was higher than that of the mucosal side (p = 0.0023). Ouabain reduced I (sc) by 70% (P < 0.0001) and QO(2) by 26% (n = 8; P = 0.0009), suggesting that a large fraction of QO(2) is needed to support ouabain-sensitive electrogenic transport. Induction of hypoxia at both sides of the Ussing chamber caused a rapid decrease in I (sc) after 2 min. I (sc) was also significantly depressed when hypoxia was induced by 5 min in the serosal side (n = 6, P < 0.0001), but was unaffected by hypoxia induced in the mucosal side. CONCLUSION The present results allow a better understanding of the clinical consequences of acute hypoxia on intestinal ion transport.
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Zhu JX, Xue H, Ji T, Xing Y. Cellular localization of NKCC2 and its possible role in the Cl- absorption in the rat and human distal colonic epithelia. Transl Res 2011; 158:146-54. [PMID: 21867980 DOI: 10.1016/j.trsl.2011.04.003] [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] [Received: 12/21/2010] [Revised: 04/07/2011] [Accepted: 04/20/2011] [Indexed: 12/16/2022]
Abstract
Recently, we demonstrated the expression of NKCC2, an absorptive isoform of NKCC specifically expressed in the kidney, in the rat gastrointestinal tract including the distal colonic mucosa. This study aims to investigate its localization in colonic epithelia and possible role in the colonic ion transport. Reverse transcription polymerase chain reaction (RT-PCR), Western blotting, and immunohistochemistry were used to investigate the expression and localization of NKCC2. The role of NKCC2 on the colonic ion transport was examined by mean of short-circuit current (I(SC)) monitoring. The results indicated that NKCC2 was expressed in the apical region of the epithelia in rat distal colon and human sigmoid colon. NKCC1, which is a secretive NKCC isoform, was localized predominantly in the basolateral membrane, which has been well documented. Serosal (basolateral) administration of bumetanide, an inhibitor of both NKCC1 and NKCC2, inhibited serosal forskolin-induced I(SC) increase by 66% but enhanced the luminal (apical) forskolin-induced I(SC) response by 63%. Furthermore, the blocking of epithelial Na(+) channels by apical addition of amiloride (10 μmol/L), K(+) channels by tetraethylammoniumion (TEA) (5 mmol/L), or glibenclimide (0.1 mmol/L) did not affect apical forskolin-induced I(SC) increase, excluding the involvement of cations, Na(+) and K(+), in the I(SC) response. The luminal forskolin-induced I(SC) increase was enhanced markedly by the apical pretreatment with bumetanide or the reduction of apical Cl(-) concentration by 114% and 198%, respectively, which were inhibited by apical addition of glibenclimide (1 mmol/L) by more than 60%. This finding suggests the involvement of an anion. Furthermore, the removal of basolateral HCO(3)(-) reduced apical forskolin-induced I(SC) by more than 75% indicated that the apical forskolin-induced I(SC) increase in rat distal colon was mediated by Cl(-) absorption and HCO(3)(-) secretion. In conclusion, NKCC2 is expressed widely in the colonic epithelium in rat distal colon and human sigmoid colon, especially in the apical membrane. It involves the process of colonic Cl(-) absorption coupled with HCO(3)(-) secretion.
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Affiliation(s)
- Jin-Xia Zhu
- Department of Anatomy and Physiology, Basic Medical College, Xinxiang Medical University, Xinxiang, Henan, China.
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Collins D, Kopic S, Geibel JP, Hogan AM, Medani M, Baird AW, Winter DC. The flavonone naringenin inhibits chloride secretion in isolated colonic epithelia. Eur J Pharmacol 2011; 668:271-7. [PMID: 21762688 DOI: 10.1016/j.ejphar.2011.06.052] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2010] [Revised: 06/19/2011] [Accepted: 06/27/2011] [Indexed: 02/06/2023]
Abstract
Studies investigating the activating and inhibitory actions of bioflavonoids on colonic function have yielded conflicting results. At low concentrations, flavonoids may stimulate chloride secretion while at higher concentrations they may have antisecretory actions in the colon. Naringenin (4',5,7-trihydroxyflavanone), found predominantly in citrus fruits, confers a protective effect against colorectal cancer and is purported to modulate secretory function in colonic cell lines. The aim of this study was to investigate the effects of naringenin on ion transport in rat and human colonic mucosae. Naringenin inhibited basal and stimulated chloride secretion in rat and human colonic mucosae mounted in Ussing chambers (IC(50) 330 μMol/L and 360 μMol/L respectively) and did not alter intracellular cAMP generation. Naringenin inhibited chloride secretion in MQAE (N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide) loaded crypts stimulated with forskolin. In BCECF (2',7'-bis-(2-carboxyethyl)-5-(and 6)-carboxyfluorescein acetoxymethyl ester) loaded crypts, naringenin caused an intracellular acidification (ΔpH/min=0.05 ± 0.004) which was sensitive to the Na-K-Cl co-transporter (NKCC) inhibitor bumetanide. In addition, the antisecretory effect of naringenin was not inhibited by blockade of barium sensitive basolateral K(+) transporters or by inhibition of Na+/H(+) exchange by amiloride. We propose that the antisecretory action of naringenin is due to inhibition of basolateral NKCC1 in rat and human colon.
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Affiliation(s)
- Danielle Collins
- College of Life Sciences & Conway Institute, National University of Ireland, Dublin, Ireland
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Wu D, Zhou J, Wang X, Cui B, An R, Shi H, Yuan J, Hu Z. Traditional Chinese formula, lubricating gut pill, stimulates cAMP-dependent CI(−) secretion across rat distal colonic mucosa. JOURNAL OF ETHNOPHARMACOLOGY 2011; 134:406-413. [PMID: 21195154 DOI: 10.1016/j.jep.2010.12.031] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2010] [Revised: 12/13/2010] [Accepted: 12/27/2010] [Indexed: 05/30/2023]
Abstract
AIM OF THE STUDY Lubricating gut pill (LGP), a traditional Chinese formula, had been conformed to improve the loperamide-induced rat constipation by stimulation of Cl(-) secretion, but its mechanism has not been fully explored. Thus, the purpose of this study was to identify the action sites of LGP-stimulated Cl(-) secretion across rat distal colonic mucosa. MATERIALS AND METHODS Rat distal colonic mucosa was mounted in Ussing chambers and short circuit current (I(SC)), apical Cl(-) current and basolateral K(+) current were recorded. Intracellular cyclic adenosine monophosphate (cAMP) content and protein kinase A (PKA) activity were determined with ELISA kit and the non-radioactive PepTag test, respectively. RESULTS LGP at 800μg/ml elicited a sustained increase in Cl(-) secretory response, which was inhibited by CFTR(inh)172, a cystic fibrosis transmembrane conductance regulator (CFTR) inhibitor. Permeabilizing apical membrane with nystatin revealed that LGP-stimulated basolateral K(+) current was significantly inhibited by KCNQ1 K(+) channel inhibitor chromanol 293B. LGP-stimulated I(SC) was markedly reduced by pretreatment with cis-N-[2-phenylcyclopentyl]-azacyclotridec-1-en-2amine (MDL-12,330A) and N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide (H-89), but not with inhibitors of Ca(2+)-dependent signaling pathway. Treatment of tissue with LGP resulted in an increase in intracellular cAMP level and the activation in protein kinase A. The E-prostanoid(4) (EP)(4) receptor antagonist L-161,982 completely eliminated LGP-induced response. CONCLUSIONS The results showed that LGP enhances Cl(-) and fluid secretion via prostanoid receptor signaling and also cAMP and protein kinase A pathway, subsequently triggering the activation of apical Cl(-) channels mostly CFTR and basolateral cAMP-dependent K(+) channel.
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Affiliation(s)
- Dazheng Wu
- Institute of Chinese Materia Medica, Shanghai University of TCM, Shanghai 201203, China
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20
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Wu D, Wang X, Zhou J, Yuan J, Cui B, An R, Hu Z. Traditional Chinese formula, lubricating gut pill, improves loperamide-induced rat constipation involved in enhance of Cl- secretion across distal colonic epithelium. JOURNAL OF ETHNOPHARMACOLOGY 2010; 130:347-353. [PMID: 20488235 DOI: 10.1016/j.jep.2010.05.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2010] [Revised: 04/28/2010] [Accepted: 05/08/2010] [Indexed: 05/29/2023]
Abstract
AIM OF THE STUDY Lubricating gut pill (LGP), a traditional Chinese formula, was widely used for the treatment of chronic constipation, especially in the elderly, in China. However, it is unclear whether LGP-induced laxative and/or lubricating effect is involved in water and electrolytes transport in distal colonic epithelium. MATERIALS AND METHODS The present study was designed to evaluate the effect of LGP on Cl(-) secretion across rat distal colonic epithelium mounted in Ussing chambers, and on a rat constipation model induced by loperamide, respectively. RESULTS Application of LGP in the apical side elicited a sustained increase in short circuit current (I(SC)) response in a concentration-dependent manner. Evidence that LGP-stimulated I(SC) was due to Cl(-) secretion is based on inhibition of current by (a) a Na(+)-K(+)-2Cl(-) cotransporter inhibitor bumetanide, (b) removal of Cl(-) ions in bath solution, and (c) the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel blocker DPC, suggesting that a apical cAMP-dependent Cl(-) channel was activated. LGP-stimulated I(SC) was also strongly inhibited by pretreatment with clotrimazole, indicating that the basolateral K(+) channel was also involved in maintaining this cAMP-dependent Cl(-) secretion. Pretreatment of tissues with indomethacin, but not atropine, tetrodotoxin or hexamethonium, inhibited LGP-induced response. In a rat constipation model, oral administration with LGP was significantly restored number of fecal pellets, water content and mucus secretion compared with loperamide-treated group alone. CONCLUSIONS LGP enhances Cl(-) secretion that is mostly mediated through the release of cyclooxygenase metabolites, by which provided an osmotic force for the subsequent laxative action observed in the rat constipation model.
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Affiliation(s)
- Dazheng Wu
- Institute of Chinese Materia Medica, Shanghai University of TCM, Shanghai, China
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21
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Collins D, Hogan AM, Skelly MM, Baird AW, Winter DC. Cyclic AMP-mediated chloride secretion is induced by prostaglandin F2alpha in human isolated colon. Br J Pharmacol 2010; 158:1771-6. [PMID: 19889058 DOI: 10.1111/j.1476-5381.2009.00464.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND AND PURPOSE Prostaglandin F(2alpha) (PGF(2alpha)) is implicated in the pathogenesis of inflammatory bowel disease and colorectal cancer. This study investigates the effects of PGF(2alpha) on electrophysiological parameters in isolated human colonic mucosa. EXPERIMENTAL APPROACH Ion transport was measured as changes in short-circuit current across human colonic epithelia mounted in Ussing chambers. Colonic crypts were isolated by calcium chelation and cyclic adenosine monophosphate (cAMP) was measured by ELISA. KEY RESULTS PGF(2alpha) stimulated chloride secretion in a concentration-dependent manner with an EC(50) of 130 nM. The PGF(2alpha) induced increase in chloride secretion was inhibited by AL8810 (10 microM), a specific PGF(2alpha) receptor antagonist. In addition, PGF(2alpha) (1 microM) significantly increased levels of cAMP in isolated colonic crypts. CONCLUSIONS AND IMPLICATIONS PGF(2alpha) stimulated chloride secretion in samples of human colon in vitro through a previously unrecognizd cAMP-mediated mechanism. These findings have implications for inflammatory states.
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Affiliation(s)
- D Collins
- College of Life Sciences & Conway Institute of Biomolecular & Biomedical Science, University College Dublin, Belfield.
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O'Mahony F, Alzamora R, Chung HL, Thomas W, Harvey BJ. Genomic priming of the antisecretory response to estrogen in rat distal colon throughout the estrous cycle. Mol Endocrinol 2009; 23:1885-99. [PMID: 19846538 DOI: 10.1210/me.2008-0248] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The secretion of Cl(-) across distal colonic crypt cells provides the driving force for the movement of fluid into the luminal space. 17beta-Estradiol (E2) produces a rapid and sustained reduction in secretion in females, which is dependent on the novel protein kinase C delta (PKC delta) isozyme and PKA isoform I targeting of KCNQ1 channels. This sexual dimorphism in the E2 response is associated with a higher expression level of PKC delta in female compared with the male tissue. The present study revealed the antisecretory response is regulated throughout the female reproductive (estrous) cycle and is primed by genomic regulation of the kinases. E2 (1-10 nm) decreased cAMP-dependent secretion in colonic epithelia during the estrus, metestrus, and diestrus stages. A weak inhibition of secretion was demonstrated in the proestrus stage. The expression levels of PKC delta and PKA fluctuated throughout the estrous cycle and correlated with the potency of the antisecretory effect of E2. The expression of PKC delta and PKA were up-regulated by estrogen at a transcriptional level via a PKC delta-MAPK-cAMP response element-binding protein-regulated pathway indicating a genomic priming of the antisecretory response. PK Cdelta was activated by the membrane-impermeant E2-BSA, and this response was inhibited by the estrogen receptor antagonist ICI 182,780. The 66-kDa estrogen receptor-alpha isoform was present at the plasma membrane of female colonic crypt cells with a lower abundance found in male colonic crypts. The study demonstrates estrogen regulation of intestinal secretion both at a rapid and transcriptional level, demonstrating an interdependent relationship between both nongenomic and genomic hormone responses.
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Affiliation(s)
- Fiona O'Mahony
- Department of Molecular Medicine, Royal College of Surgeons in Ireland, Education and Research Centre Smurfit Building, Beaumont Hospital, P.O. Box 9063, Dublin 9, Ireland.
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O'Mahony F, Thomas W, Harvey BJ. Novel female sex-dependent actions of oestrogen in the intestine. J Physiol 2009; 587:5039-44. [PMID: 19723780 DOI: 10.1113/jphysiol.2009.177972] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The intestine is an oestrogen responsive organ and circulatory oestrogens suppress Cl(-) secretion across the epithelium of the colon to promote fluid retention at the luteal stage of the menstrual cycle. Ion transporters in the colon which are involved in Cl(-) secretion show differential expression between males and females as do the signalling protein kinase intermediates involved in acutely regulating these transporters. Work from our laboratory has identified the KCNQ1/KCNE3 channel as one of the principal targets for oestrogen-induced signalling cascades in the distal colon. Through inhibition of the KCNQ1 channel, basolateral K(+) recycling is decreased so reducing the favourable electrochemical gradient for Cl(-) extrusion at the apical membrane. The actions of oestrogen on non-reproductive tissues such as the colon, kidney, lung and sweat gland will affect whole body electrolyte and fluid homeostasis and also have consequences for reproductive potential.
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Affiliation(s)
- Fiona O'Mahony
- Royal College of Surgeons in Ireland, Department of Molecular Medicine, Dublin 17, Ireland.
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Harvey BJ, Alzamora R, Stubbs AK, Irnaten M, McEneaney V, Thomas W. Rapid responses to aldosterone in the kidney and colon. J Steroid Biochem Mol Biol 2008; 108:310-7. [PMID: 17951051 DOI: 10.1016/j.jsbmb.2007.09.005] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Aldosterone is a crucial modulator of ion transport across high resistance epithelia and regulates whole body electrolyte balance through its effects on the kidney and colon. The net consequence of aldosterone release is to promote salt conservation. The genomic mechanism of aldosterone action is relatively well characterized and the role of the classical mineralocorticoid receptor as a ligand-dependent transcription factor is well established. The rapid effects of aldosterone on target tissues are less well understood and there is still controversy over the identity of the aldosterone non-genomic receptor. Greater understanding of the physiological consequences of aldosterone's rapid responses in the kidney and colon has been achieved through the identification of definite and putative membrane targets and their signaling regulators.
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Affiliation(s)
- Brian J Harvey
- Department of Molecular Medicine, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin 9, Ireland.
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Wu DZ, Yuan JY, Shi HL, Hu ZB. Palmatine, a protoberberine alkaloid, inhibits both Ca(2+)- and cAMP-activated Cl(-) secretion in isolated rat distal colon. Br J Pharmacol 2008; 153:1203-13. [PMID: 18204477 DOI: 10.1038/sj.bjp.0707684] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND AND PURPOSE The protoberberine alkaloid berberine has been reported to inhibit colonic Cl(-) secretion. However, it is not known if other protoberberine alkaloids share these effects. We have therefore selected another protoberberine alkaloid, palmatine, to assess its effects on active ion transport across rat colonic epithelium. EXPERIMENTAL APPROACH Rat colonic mucosa was mounted in Ussing chambers and short circuit current (I (SC)), apical Cl(-) current and basolateral K(+) current were recorded. Intracellular cAMP content was determined by an enzyme immunoassay. Intracellular Ca(2+) concentration was measured with Fura-2 AM. KEY RESULTS Palmatine inhibited carbachol-induced Ca(2+)-activated Cl(-) secretion and the carbachol-induced increase of intracellular Ca(2+) concentration. Palmatine also inhibited cAMP-activated Cl(-) secretion induced by prostaglandin E(2) (PGE(2)) or forskolin. Palmatine prevented the elevation of intracellular cAMP by forskolin. Determination of apical Cl(-) currents showed that palmatine suppressed the forskolin-stimulated, apical cAMP-activated Cl(-) current but not the carbachol-stimulated apical Ca(2+)-activated Cl(-) current. Following permeabilization of apical membranes with nystatin, we found that palmatine inhibited a carbachol-stimulated basolateral K(+) current that was sensitive to charybdotoxin and resistant to chromanol 293B. However, the forskolin-stimulated basolateral K(+) current inhibited by palmatine was specifically blocked by chromanol 293B and not by charybdotoxin. CONCLUSIONS AND IMPLICATIONS Palmatine attenuated Ca(2+)-activated Cl(-) secretion through inhibiting basolateral charybdotoxin-sensitive, SK4 K(+) channels, whereas it inhibited cAMP-activated Cl(-) secretion by inhibiting apical CFTR Cl(-) channels and basolateral chromanol 293B-sensitive, KvLQT1 K(+) channels.
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Affiliation(s)
- D Z Wu
- Laboratory of Pharmacology, Institute of Chinese Materia Medica, Shanghai University of TCM, Shanghai, PR China
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Wu D, Hu Z. Rutaecarpine induces chloride secretion across rat isolated distal colon. J Pharmacol Exp Ther 2008; 325:256-66. [PMID: 18187619 DOI: 10.1124/jpet.107.131961] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The present study evaluated the effect of rutaecarpine (Rut) on Cl(-) secretion across rat distal colonic mucosa. Basolateral application of Rut elicited an increase in short-circuit current (I(SC)) response in a concentration-dependent manner. Evidence that Rut-stimulated I(SC) was due to Cl(-) secretion is based on 1) inhibition of current by bumetanide; 2) Cl(-) channel blockers diphenylamine-2-carboxylate, 5-nitro-2-(3-phenylpropylamino)-benzoic acid, and glibenclamide; and 3) removal of Cl(-) ions in bath solution. Determination of neurogenic blockers on Rut-induced I(SC) indicated that pretreatment of tissues with tetrodotoxin or indomethacin, but not atropine or hexamethonium, inhibited Rut-induced response. Treatment with Rut led to release and synthesis of prostaglandin E(2) in rat colonic mucosa. Rut-stimulated I(SC) was markedly reduced by pretreatment with MDL-12,330A [cis-N-[2-phenylcyclopentyl]-azacyclotridec-1-en-2-amine] and N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide (H-89), but not with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester, bisindolylmaleimide, and thapsigargin. Elimination of the extracellular Ca(2+) also did not alter Rut response. Rut treatment resulted in the increase in intracellular cAMP levels and the activation of protein kinase A. Depolarizing the basolateral membrane with high K(+) showed that Rut-stimulated apical Cl(-) current was largely prevented by cystic fibrosis transmembrane conductance regulator (CFTR) inhibitors. Permeabilizing apical membrane with nystatin revealed that Rut-stimulated basolateral K(+) current was specifically inhibited by Ba(2+) ions and chromanol 293B. The evidence derived from present study suggests that Rut-stimulated Cl(-) secretion is mediated by generation of endogenous prostaglandin E(2) and that it also involves the stimulation of cAMP and protein kinase A pathways, which subsequently lead to the activation of apical Cl(-) channels, mostly the CFTR and basolateral cAMP-dependent K(+) channels.
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Affiliation(s)
- DaZheng Wu
- Institute of Chinese Materia Medica, Shanghai University of Traditional Chinese Medicine, 1200 Cailun Rd., Zhangjiang Hi-tech Park, Shanghai 201203, People's Republic of China.
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Osbak PS, Bindslev N, Poulsen SS, Kaltoft N, Tilotta MC, Hansen MB. Colonic epithelial ion transport is not affected in patients with diverticulosis. BMC Gastroenterol 2007; 7:37. [PMID: 17888183 PMCID: PMC2064914 DOI: 10.1186/1471-230x-7-37] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2007] [Accepted: 09/23/2007] [Indexed: 11/10/2022] Open
Abstract
Background Colonic diverticular disease is a bothersome condition with an unresolved pathogenesis. It is unknown whether a neuroepithelial dysfunction is present. The aim of the study was two-fold; (1) to investigate colonic epithelial ion transport in patients with diverticulosis and (2) to adapt a miniaturized Modified Ussing Air-Suction (MUAS) chamber for colonic endoscopic biopsies. Methods Biopsies were obtained from the sigmoid part of the colon. 86 patients were included. All patients were referred for colonoscopy on suspicion of neoplasia and they were without pathological findings at colonoscopy (controls) except for diverticulosis in 22 (D-patients). Biopsies were mounted in MUAS chambers with an exposed area of 5 mm2. Electrical responses to various stimulators and inhibitors of ion transport were investigated together with histological examination. The MUAS chamber was easy to use and reproducible data were obtained. Results Median basal short circuit current (SCC) was 43.8 μA·cm-2 (0.8 – 199) for controls and 59.3 μA·cm-2 (3.0 – 177.2) for D-patients. Slope conductance was 77.0 mS·cm-2 (18.6 – 204.0) equal to 13 Ω·cm2 for controls and 96.6 mS·cm-2 (8.4 – 191.4) equal to 10.3 Ω·cm2 for D-patients. Stimulation with serotonin, theophylline, forskolin and carbachol induced increases in SCC in a range of 4.9 – 18.6 μA·cm-2, while inhibition with indomethacin, bumetanide, ouabain and amiloride decreased SCC in a range of 6.5 – 27.4 μA·cm-2, and all with no significant differences between controls and D-patients. Histological examinations showed intact epithelium and lamina propria before and after mounting for both types of patients. Conclusion We conclude that epithelial ion transport is not significantly altered in patients with diverticulosis and that the MUAS chamber can be adapted for studies of human colonic endoscopic biopsies.
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Affiliation(s)
- Philip S Osbak
- Department of Gastrointestinal Surgery K, Bispebjerg University Hospital of Copenhagen, Denmark
| | - Niels Bindslev
- Department of Medical Physiology, Panum Institute, University of Copenhagen, Denmark
| | - Steen S Poulsen
- Department of Anatomy B, Panum Institute, University of Copenhagen, Denmark
| | - Nicolai Kaltoft
- Department of Gastrointestinal Surgery K, Bispebjerg University Hospital of Copenhagen, Denmark
| | - Maria C Tilotta
- Department of Gastrointestinal Surgery K, Bispebjerg University Hospital of Copenhagen, Denmark
| | - Mark B Hansen
- Department of Gastrointestinal Surgery K, Bispebjerg University Hospital of Copenhagen, Denmark
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Xue H, Tian YM, Yan M, Yang N, Chen X, Xing Y, Zhu JX. Appearance of segmental discrepancy of anion transport in rat distal colon. Biol Pharm Bull 2007; 30:1407-11. [PMID: 17666794 DOI: 10.1248/bpb.30.1407] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The present study investigated the segmental discrepancy of the rat distal colonic anion transport induced by luminal forskolin and the possible underlying mechanisms using short-circuit current recording technique and comparative quantity real-time PCR analysis. Forskolin-induced I(SC) in the segment next to lymph node (DC(1)) and the segment 4 cm away from lymph node (DC(4)) were 4.09+/-0.66 muA/cm(2) and 18.84+/-3.18 muA/cm(2) (n=13), respectively, which were blocked by luminal Cl(-) channel blocker, glybenclamide (1 mM) (n=5, p<0.01), as well as removal of extracellular Cl(-) and HCO(3)(-) in both DC(1) and DC(4) (n=5, p<0.001). Furthermore luminal pretreatment with K(+) blockers, TEA (5 mM) and glybenclamide (100 muM) didn't affect forskolin and bumetanide-enhanced I(SC). Reducing serosal Cl(-) concentration increased forskolin-induced I(SC) by 90% in DC(1) but decreased forskolin-induced I(SC) in DC(4) by 50%. Furthermore, pretreatment with serosal bumetanide, an inhibitor of Na(+)-K(+)-2Cl(-) cotransporter, enhanced forskolin-induced I(SC) by 87% in DC(1), from 4.09+/-0.66 muA/cm(2) to 7.65+/-0.53 muA/cm(2) (n=6, p<0.01), but inhibited forskolin-induced I(SC) by 50% in DC(4), from 29.19+/-4.51 muA/cm(2) to 15.06+/-4.10 muA/cm(2) (n=6, p<0.05). Pretreatment with luminal amiloride (10 muM), an inhibitor of ENaC, and serosal 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS) (200 muM), an inhibitor of NBC, significantly inhibited the forskolin-induced I(SC) in DC(1) (n=6, p<0.05), but not in DC(4). Real-time PCR analysis did not show the significant differences between the two segments in the expression amounts of CFTR and NKCC mRNAs, however the expression of NBC mRNA in DC(4) was significantly higher than that in DC(1). In conclusion, the rat distal colon manifests a segmental discrepancy in anion transport stimulated by luminal forskolin. HCO(3)(-) might be predominantly involved in the forskolin-induced anion secretion in DC(1), but Cl(-) might be the main component of the anion secretion in DC(4).
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Affiliation(s)
- Hong Xue
- Department of Physiology, Basic Medical College, Capital Medical University, Beijing 100069, China
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O'Mahony F, Alzamora R, Betts V, LaPaix F, Carter D, Irnaten M, Harvey BJ. Female gender-specific inhibition of KCNQ1 channels and chloride secretion by 17beta-estradiol in rat distal colonic crypts. J Biol Chem 2007; 282:24563-73. [PMID: 17556370 DOI: 10.1074/jbc.m611682200] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The estrogen sex steroid 17beta-estradiol rapidly inhibits secretagogue-stimulated cAMP-dependent Cl(-) secretion in the female rat distal colonic crypt by the inhibition of basolateral K(+) channels. In Ussing chamber studies, both the anti-secretory response and inhibition of basolateral K(+) current was shown to be attenuated by pretreatment with rottlerin, a PKCdelta-specific inhibitor. In whole cell patch-clamp analysis, 17beta-estradiol inhibited a chromanol 293B-sensitive KCNQ1 channel current in isolated female rat distal colonic crypts. Estrogen had no effect on KCNQ1 channel currents in colonic crypts isolated from male rats. Female distal colonic crypts expressed a significantly higher amount of PKCdelta in comparison to male tissue. PKCdelta and PKA were activated at 5 min in response to 17beta-estradiol in female distal colonic crypts only. Both PKCdelta- and PKA-associated with the KCNQ1 channel in response to 17beta-estradiol in female distal colonic crypts, and no associations were observed in crypts from males. PKA activation, association with KCNQ1, and phosphorylation of the channel were regulated by PKCdelta as the responses were blocked by pretreatment with rottlerin. Taken together, our experiments have identified the molecular targets underlying the anti-secretory response to estrogen involving the inhibition of KCNQ1 channel activity via PKCdelta- and PKA-dependent signaling pathways. This is a novel gender-specific mechanism of regulation of an ion channel by estrogen. The anti-secretory response described in this study provides molecular insights whereby estrogen causes fluid retention effects in the female during periods of high circulating plasma estrogen levels.
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Affiliation(s)
- Fiona O'Mahony
- Department of Molecular Medicine, Beaumont Hospital, Royal College of Surgeons in Ireland, Dublin 9, Ireland.
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Schicho R, Krueger D, Zeller F, Von Weyhern CWH, Frieling T, Kimura H, Ishii I, De Giorgio R, Campi B, Schemann M. Hydrogen sulfide is a novel prosecretory neuromodulator in the Guinea-pig and human colon. Gastroenterology 2006; 131:1542-52. [PMID: 17101327 DOI: 10.1053/j.gastro.2006.08.035] [Citation(s) in RCA: 166] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2005] [Accepted: 08/03/2006] [Indexed: 12/27/2022]
Abstract
BACKGROUND & AIMS Hydrogen sulfide (H(2)S) has been suggested as a novel gasomediator. We explored its unknown neuromodulatory role in human and guinea-pig colon. METHODS We used immunohistochemistry to detect H(2)S-producing enzymes cystathionine gamma-lyase (CSE) and cystathionine beta-synthase (CBS) in enteric neurons, Ussing chambers to measure mucosal ion secretion, and neuroimaging with voltage- and Ca(++)-sensitive dyes to record H(2)S effects on guinea-pig and human enteric neurons. RESULTS More than 90% of guinea-pig and human submucous and myenteric neurons were colabeled for CSE and CBS. Myenteric interstitial cells of Cajal were CSE-immunoreactive. The exogenous H(2)S donor NaHS (0.2-2.5 mmol/L) concentration-dependently increased chloride secretion in human and guinea-pig submucosa/mucosa preparations, but not in the colonic epithelial cell line T84. The secretory response was reduced significantly by tetrodotoxin (0.5 micromol/L), capsaicin desensitization (10 micromol/L), and the transient receptor potentials vanilloid receptor 1 antagonist capsazepine (10 micromol/L). The endogenous H(2)S donor L-cysteine also induced secretion that was diminished significantly by capsaicin desensitization, the CBS inhibitor amino-oxyacetic acid, and the CSE inhibitor propargylglycine. NaHS increased spike discharge in 23% of guinea-pig and 36% of human submucous neurons, but had no effect on Ca(++) mobilization in cultured guinea-pig enteric neurons. This excitatory response was reduced significantly by capsaicin desensitization and capsazepine, but not by glibenclamide (10 micromol/L). CONCLUSIONS The presence of H(2)S-producing enzymes in human and guinea-pig enteric neurons, the excitatory action on enteric neurons, and the prosecretory effects of NaHS suggest H(2)S as a novel gut-signaling molecule. Its action mainly involves transient receptor potentials vanilloid receptor 1 receptors on extrinsic afferent terminals, which in turn activate enteric neurons.
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Affiliation(s)
- Rudolf Schicho
- Department of Human Biology, Technical University Munich, Munich, Germany
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Horikawa N, Suzuki T, Uchiumi T, Minamimura T, Tsukada K, Takeguchi N, Sakai H. Cyclic AMP-dependent Cl- secretion induced by thromboxane A2 in isolated human colon. J Physiol 2005; 562:885-97. [PMID: 15611029 PMCID: PMC1665535 DOI: 10.1113/jphysiol.2004.077776] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 10/20/2004] [Accepted: 12/07/2004] [Indexed: 11/08/2022] Open
Abstract
Increased release of thromboxane A(2) (TXA(2)) has been shown to be involved in inflammatory bowel diseases. In the present study, we have investigated the effect of a stable TXA(2) analogue (STA(2)) on the electrical parameters in isolated human colonic mucosa. In the human mucosa set between Ussing chambers, STA(2) stimulated Cl- secretion in a concentration-dependent manner with an EC(50) of 0.06 microm. The STA(2)-induced Cl- secretion was significantly inhibited by ONO-3708 (10 microm), a specific TXA(2) receptor antagonist. The effect of STA(2) (0.3 microm) was independent of the colonic segment from which the tissue was obtained, from caecum to rectum. Chromanol 293B, an inhibitor of the cAMP-dependent KvLQT1 channel, attenuated the STA(2)-induced Cl- secretion in the human colonic mucosa (IC(50) value 1.18 microm). We found that KvLQT1 mRNA and protein were expressed in all the tested segments of the human colon. The STA(2)-induced Cl- secretion was significantly inhibited by 8-bromo-2'-monobutyryladenosine-3',5'-cyclic monophosphorothioate (50 microm), a membrane-permeant cAMP antagonist. STA(2) (0.3 microm) significantly increased the intracellular cAMP levels and the short-circuit current via TXA(2) receptor in a human colonic cell line. These results suggest that the TXA(2)-induced Cl- secretion in the colon is mediated via the cAMP pathway in addition to the Ca(2+)-calmodulin pathway which was previously reported.
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Affiliation(s)
- Naoki Horikawa
- Department of Surgery II, Faculty of Medicine, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama 930-0194, Japan
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Lam RS, Shaw AR, Duszyk M. Membrane cholesterol content modulates activation of BK channels in colonic epithelia. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2005; 1667:241-8. [PMID: 15581861 DOI: 10.1016/j.bbamem.2004.11.004] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2004] [Revised: 11/03/2004] [Accepted: 11/09/2004] [Indexed: 10/26/2022]
Abstract
Changes in the level of membrane cholesterol regulate a variety of signaling processes including those mediated by acylated signaling molecules that localize to lipid rafts. Recently several types of ion channels have been shown to have cholesterol-dependent activity and to localize to lipid rafts. In this study, we have investigated the role of cholesterol in the regulation of ion transport in colonic epithelial cells. We observed that methyl-beta-cyclodextrin (MbetaCD), a cholesterol-sequestering molecule, activated transepithelial short circuit current (Isc), but only from the basolateral side. Similar results were obtained with a cholesterol-binding agent, filipin, and with the sphingomyelin-degrading enzyme, sphingomyelinase. Experiments with DeltaF508CFTR mutant mice indicated that raft disruption affected CFTR-mediated anion secretion, while pharmacological studies showed that this effect was due to activation of basolateral large conductance Ca2+-activated K+ (BK) channels. Sucrose density gradient centrifugation studies demonstrated that BK channels were normally present in the high-density fraction containing the detergent-insoluble cytoskeleton, and that following treatment with MbetaCD, BK channels redistributed into detergent-soluble fractions. Our evidence therefore implicates novel high-density cholesterol-enriched plasma membrane microdomains in the modulation of BK channel activation and anion secretion in colonic epithelia.
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Affiliation(s)
- Rebecca S Lam
- Department of Physiology, University of Alberta, 7-46 Medical Sciences Bldg., Edmonton, Alberta, Canada T6G 2H7
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Boese SH, Aziz O, Simmons NL, Gray MA. Kinetics and regulation of a Ca2+-activated Cl- conductance in mouse renal inner medullary collecting duct cells. Am J Physiol Renal Physiol 2003; 286:F682-92. [PMID: 14678946 DOI: 10.1152/ajprenal.00123.2003] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Using the whole cell patch-clamp technique, a Ca2+-activated Cl- conductance (CaCC) was transiently activated by extracellular ATP (100 microM) in primary cultures of mouse inner medullary collecting duct (IMCD) cells and in the mouse IMCD-K2 cell line. ATP also transiently increased intracellular Ca2+ concentration ([Ca2+]i) from 100 nM to peak values of approximately 750 nM in mIMCD-K2 cells, with a time course similar to the ATP-induced activation and decay of the CaCC. Removal of extracellular Ca2+ had no major effect on the peak Cl- conductance or the increase in [Ca2+]i induced by ATP, suggesting that Ca2+ released from intracellular stores directly activates the CaCC. In mIMCD-K2 cells, a rectifying time- and voltage-dependent current was observed when [Ca2+]i was fixed via the patch pipette to between 100 and 500 nM. Maximal activation occurred at approximately 1 microM [Ca2+]i, with currents losing any kinetics and displaying a linear current-voltage relationship. From Ca2+-dose-response curves, an EC50 value of approximately 650 nM at -80 mV was obtained, suggesting that under physiological conditions the CaCC would be near fully activated by mucosal nucleotides. Noise analysis of whole cell currents in mIMCD-K2 cells suggests a single-channel conductance of 6-8 pS and a density of approximately 5,000 channels/cell. In conclusion, the CaCC in mouse IMCD cells is a low-conductance, nucleotide-sensitive Cl- channel, whose activity is tightly coupled to changes in [Ca2+]i over the normal physiological range.
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Affiliation(s)
- S H Boese
- School of Cell and Molecular Bioscience, Univ. Medical School, Newcastle Upon Tyne, NE2 4HH, UK
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Lam RS, App EM, Nahirney D, Szkotak AJ, Vieira-Coelho MA, King M, Duszyk M. Regulation of Cl- secretion by alpha2-adrenergic receptors in mouse colonic epithelium. J Physiol 2003; 548:475-84. [PMID: 12598592 PMCID: PMC2342847 DOI: 10.1113/jphysiol.2002.036806] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Previous studies have shown that alpha2 adrenoceptor (alpha2AR) agonists inhibit electrolyte secretion in colonic epithelia, but little is known about the molecular mechanisms involved in this process. In this study we examined the effect of alpha2AR activation on transepithelial anion secretion across isolated murine colonic epithelium. We found that alpha2AR agonists, UK 14,304, clonidine and medetomidine were potent inhibitors of anion secretion, especially in the proximal colon. Short circuit current measurements (Isc) in colonic epithelia from normal and cystic fibrosis (CF) mice showed that alpha2AR agonists inhibited basal cystic fibrosis transmembrane conductance regulator (CFTR)-mediated Cl- secretion but had no effect on CFTR activation by cAMP-dependent phosphorylation. Apical administration of an ionophore, nystatin (90 microg ml-1), was used to investigate the effect of UK 14,304 on basolateral K+ transport. The Na+-K+-ATPase current, measured as ouabain-sensitive current in the absence of ion gradients, was unaltered by pretreatment of the tissue with UK 14,304 (1 microM). In the presence of a basolaterally directed K+ gradient, UK 14,304 significantly reduced nystatin-activated Isc indicating that activation of alpha2ARs inhibits basolateral K+ channels. Studies with selective K+ channel inhibitors and openers showed that alpha2AR agonists inhibited KATP channels that were tonically active in mouse colonic epithelia. RT-PCR and pharmacological studies suggested that these channels could be similar to vascular smooth muscle KATP channels comprising Kir6.1/SUR2B or Kir6.2/SUR2B subunits. Inhibition of anion secretion by alpha2AR agonists required activation of pertussis toxin-sensitive Gi/o proteins, but did not involve classical second messengers, such as cAMP or Ca2+. In summary, alpha2ARs inhibit anion secretion in colonic epithelia by acting on basolateral KATP channels, through a process that does not involve classical second messengers.
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Affiliation(s)
- Rebecca S Lam
- Department of Physiology, University of Alberta, Edmonton, Canada T6G 2H7
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Doolan CM, Harvey BJ. A Galphas protein-coupled membrane receptor, distinct from the classical oestrogen receptor, transduces rapid effects of oestradiol on [Ca2+]i in female rat distal colon. Mol Cell Endocrinol 2003; 199:87-103. [PMID: 12581882 DOI: 10.1016/s0303-7207(02)00303-9] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We examined the hypothesis whether rapid non-genomic effects of oestradiol (E2) on [Ca(2+)](i) are mediated via a membrane-located oestrogen receptor (ER) and further elucidated the signalling pathways involved in rapid non-genomic effects of E2 on [Ca(2+)](i) in distal colonic crypts. Basal [Ca(2+)](i) was significantly increased, within minutes, in response to physiological concentrations of E2. Oestradiol linked to bovine serum albumin (E2-BSA), which renders the E2 membrane impermeable, rapidly increased [Ca(2+)](i) suggesting mediation by a membrane surface receptor. A classical ER is not involved however, as no inhibition of either the E2 or E2-BSA [Ca(2+)](i) response was seen in the presence of the classical ER antagonist ICI 182,780. Treatment with the Galphas inhibitor cholera toxin abolished both E2 and E2-BSA induced Ca(2+) increases. In contrast, treatment with pertussis toxin, an inhibitor of Galphai and Galphao, had no inhibitory effect. Following subsequent additions of E2 and E2-BSA, no further increases in [Ca(2+)](i) were observed, indicating receptor desensitisation. The E2-induced increase in [Ca(2+)](i) was completely abolished by the PKCdelta-specific inhibitor rottlerin, whereas Go6976, an inhibitor of Ca(2+)-sensitive PKC isoforms, was without inhibitory effect. The phospholipase A2 antagonist, quinacrine, and the COX1 inhibitor, indomethacin, abolished the E2-induced increase in [Ca(2+)](i). MAP kinase activation is not involved in rapid stimulatory effects of E2 on [Ca(2+)](i) as the specific inhibitor PD98059 did not inhibit the E2 response. These results demonstrate that rapid E2-induced stimulation of [Ca(2+)](i), in femal rat distal colonic crypts, occurs via a CTx-sensitive Galphas-coupled membrane receptor distinct from the classical ER. PKCdelta and fatty acids are involved in the E2 signalling pathway. In contrast, PKCalpha and MAP kinase are not required.
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Affiliation(s)
- Christina M Doolan
- Department of Physiology, Biosciences Institute, University College Cork, Ireland.
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Mayol JM, Alarma-Estrany P, O'Brien TC, Song JC, Prasad M, Adame-Navarrete Y, Fernández-Represa JA, Mun EC, Matthews JB. Electrogenic ion transport in mammalian colon involves an ammonia-sensitive apical membrane K+ conductance. Dig Dis Sci 2003; 48:116-25. [PMID: 12645799 DOI: 10.1023/a:1021746717702] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
It is remarkable that high ammonia concentrations can be present within the colonic lumen without compromising normal epithelial function. We investigated the impact of luminal ammonia on Cl- secretion in native tissue. Stripped human colonic mucosa and unstripped rat distal colon were used. Paired samples were mounted in modified Ussing chambers for electrophysiological studies. In rat distal colon, apical ammonia dose-dependently blocked forskolin-activated short-circuit current with an IC50 to approximately 5 mM. Basolateral NH4Cl was less effective. Luminal methylamine (50 mM), chromanol 293B (10-50 microM), and Ba2+ (5 mM) blocked cAMP-activated short-circuit current but apical clotrimazole (100 microM) was without effect. In stripped human colonic mucosa, luminal but not basolateral NH4Cl (10 mM) and luminal Ba2+ (5 mM) suppressed forskolin-activated short-circuit current. Ammonia may be an endogenous regulator of colonic water and salt secretion. Apical K+ channels may be involved in the regulation of cAMP-stimulated Cl- secretion in mammalian colon.
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Affiliation(s)
- Julio M Mayol
- Servicio de Cirugía I, Hospital Clínico San Carlos, Universidad Complutense de Madrid, Madrid, Spain
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Harvey BJ, Alzamora R, Healy V, Renard C, Doolan CM. Rapid responses to steroid hormones: from frog skin to human colon. A homage to Hans Ussing. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1566:116-28. [PMID: 12421543 DOI: 10.1016/s0005-2736(02)00589-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Fifty years ago, Hans Ussing described the mechanism by which ions are actively transported across frog skin. Since then, an enormous amount of effort has been invested in determining the cellular and molecular specifics of the transport mechanisms and their regulatory pathways. Ion transport in high-resistance epithelia is regulated by a variety of hormonal and non-hormonal factors. In vertebrates, steroid hormones such as mineralocorticoids, glucocorticoids and estrogens are major regulators of ion and water transport and hence are central to the control of extracellular fluid volume and blood pressure. Steroid hormones act through nuclear receptors to control the transcriptional activity of specific target genes, such as ion channels, ion transporters and ion pumps. These effects are observed after a latency of several hours and can last for days leading to cellular differentiation that allows a higher transport activity. This pathway is the so-called genomic phase. However, in the past 10 years, it has become apparent that steroid hormones can regulate electrolyte and water transport in tight epithelia independently of the transcription of these ion channels and transporters by regulating ion transporter activity in a non-genomic fashion via modulation of various signal transduction pathways. The molecular mechanisms underlying the steroid hormone-induced activation of signal transduction pathways such as protein kinase C (PKC), protein kinase A (PKA), intracellular calcium, intracellular pH and mitogen-activated protein kinases (MAPKs) and how non-genomic activation of these pathways influences epithelial ion transport will be discussed in this review.
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Affiliation(s)
- Brian J Harvey
- Molecular Medicine, Royal College of Surgeons in Ireland, 123 St. Stephens Green, Dublin 2, Ireland.
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Hamilton KL, Butt AG, Cheng S, Carter DJ. Methoxsalen stimulates electrogenic Cl- secretion in the mouse jejunum. Exp Physiol 2002; 87:437-45. [PMID: 12392107 DOI: 10.1111/j.1469-445x.2002.tb00056.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
We used the short-circuit current (I(sc)) and patch-clamp techniques to investigate the effects of methoxsalen (MTX) on the electrogenic Cl- secretion of the mouse jejunum. MTX stimulated a sustained increase in Isc that was dose dependent. Bumetanide inhibited MTX-stimulated Isc in a dose-dependent manner consistent with activation of Cl- secretion. MTX failed to stimulate I(sc) following maximal activation of the cAMP pathway by forskolin, but did increase Isc after a submaximal dose of forskolin. Glibenclamide, a blocker of the cystic fibrosis transmembrane conductance regulator (CFTR), reduced the MTX-stimulated increase of Isc by 59 +/- 6%. The cAMP-dependent K+ channel blocker 293B did not alter the MTX-activated I(sc); however, clotrimazole, an intermediate Ca2(+)-activated K+ channel (IK(Ca)) blocker, reduced the MTX-stimulated I(sc). MTX did not alter Na(+)-glucose cotransport across the mouse jejunum. In cell-attached membrane patches, MTX increased the open probability of the basolateral IK(Ca) channel of isolated crypts. These data suggest that the CFTR and IK(Ca) channels participate in the MTX-activated, sustained Cl- secretory response of the mouse jejunum.
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Affiliation(s)
- Kirk L Hamilton
- Department of Physiology, School of Medical Sciences, University of Otago, Dunedin, New Zealand.
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Harvey BJ, Doolan CM, Condliffe SB, Renard C, Alzamora R, Urbach V. Non-genomic convergent and divergent signalling of rapid responses to aldosterone and estradiol in mammalian colon. Steroids 2002; 67:483-91. [PMID: 11960625 DOI: 10.1016/s0039-128x(01)00169-6] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Studies from our laboratory have demonstrated rapid ( < 1 min) non-genomic activation of Na(+)-H(+) exchange, K(+) recycling, PKC activity and a PKC-dependent Ca(2+) entry through L-type Ca(2+) channels specifically by mineralocorticoids in distal colon. Aldosterone directly stimulates the activity of the PKC alpha isoform (but not PKC delta, PKC epsilon and PKC zeta) in a cell-free assay system containing only purified commercially available enzyme, appropriate substrate peptide, co-factors and lipid vesicles. The primary ion transport target of the non-genomic signal transduction cascade elicited by aldosterone in epithelia is the Na(+)-H(+) exchanger. In isolated colonic crypts, aldosterone produced a PKC alpha sensitive intracellular alkalinisation within 1 min of hormone addition. Intracellular alkalinisation upregulates an ATP-dependent K(+) channel, which is involved in K(+) recycling to maintain the electrical driving force for Na(+) absorption, while inhibiting a Ca(2+) -dependent K(+) channel, which generates the charge balance for Cl(-) secretion. The non-genomic response to aldosterone in distal colon appears to enhance the capacity for absorption while down-regulating the potential for secretion. We have also demonstrated rapid (< 1 min) non-genomic activation of Na(+)-H(+) exchange, K(+) recycling, PKC alpha activity, and a PKC delta- and PKA-dependent Ca(2+) entry through di-hydropyridine-blockable Ca(2+) channels specifically by 17beta-estradiol in distal colon. These rapid effects are female gender specific and are insensitive to inhibitors of the classical estrogen receptor (ER). 17 beta-Estradiol directly stimulated the activity of both PKC delta and PKC alpha (but not PKC epsilon or PKC zeta) in a cell-free assay system. E2 rapidly inhibited basolateral K(Ca) channel activity which would be expected to result in an acute inhibition of Cl(-) secretion. Physiological concentrations of E2 (0.1-10 nM) reduced both basal and secretagogue-induced Cl(-) secretion. This anti-secretory effect of E2 is sensitive to PKC inhibition, intracellular Ca(2+) chelation, and is female gender specific and insensitive to inhibitors of the classical ER. These observations link rapid non-genomic activation of second messengers with a rapid gender-specific physiological effect in the whole tissue. Aldosterone and E2 differ in their protein kinase signal transduction and both hormones stimulate specific PKC isoforms indicating both common and divergent signalling systems for salt-retaining steroid hormones. The physiological function of non-genomic effects of aldosterone and estradiol is to shift the balance from net secretion to net absorption in a pluripotential epithelium.
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Affiliation(s)
- Brian J Harvey
- Wellcome Trust Cellular Physiology Research Unit, Department of Physiology, University College Cork, Cork, Ireland.
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Sievert MK, Pilli G, Liu Y, Sutkowski EM, Seamon KB, Ruoho AE. Photoaffinity labeling of adenylyl cyclase. Methods Enzymol 2002; 345:188-97. [PMID: 11665604 DOI: 10.1016/s0076-6879(02)45016-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Affiliation(s)
- Michael K Sievert
- Department of Pharmacology, University of Wisconsin Medical School, Madison, Wisconsin 53706, USA
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Cermak R, Kuhn G, Wolffram S. The flavonol quercetin activates basolateral K(+) channels in rat distal colon epithelium. Br J Pharmacol 2002; 135:1183-90. [PMID: 11877325 PMCID: PMC1573228 DOI: 10.1038/sj.bjp.0704564] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. The flavonol quercetin has been shown to activate a Cl(-) secretion in rat colon. Unlike the secretory activity of the related isoflavone genistein, quercetin's secretory activity does not depend on cyclic AMP; instead, it depends on Ca(2+). We investigated the possible involvement of Ca(2+) dependent basolateral K(+) channels using apically permeabilized rat distal colon epithelium mounted in Ussing chambers. 2. In intact epithelium, quercetin induced an increase in short-circuit current (I(sc)), which was diminished by the Cl(-) channel blockers NPPB and DPC, but not by glibenclamide, DIDS or anthracene-9-carboxylic acid. The effect of the flavonol was also inhibited by several serosally applied K(+) channel blockers (Ba(2+), quinine, clotrimazole, tetrapentylammonium, 293B), whereas other K(+) channel blockers failed to influence the quercetin-induced increase in I(sc) (tetraethylammonium, charybdotoxin). 3. The apical membrane was permeabilized by mucosal addition of nystatin and a serosally directed K(+) gradient was applied. The successful permeabilization was confirmed by experiments demonstrating the failure of bumetanide to inhibit the carbachol-induced current. 4. In apically permeabilized epithelium, quercetin induced a K(+) current (I(K)), which was neither influenced by ouabain nor by bumetanide. Whereas DPC, NPPB, charybdotoxin and 293B failed to inhibit this I(K), quinine, Ba(2+), clotrimazole and tetrapentylammonium were effective blockers of this current. 5. We conclude from these results that at least part of the quercetin-induced Cl(-) secretion can be explained by an activation of basolateral K(+) channels.
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Affiliation(s)
- Rainer Cermak
- Institut für Veterinär-Physiologie, Universität Zürich, Winterthurerstrasse 260, 8057 Zürich, Switzerland.
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Turnheim K, Plass H, Wyskovsky W. Basolateral potassium channels of rabbit colon epithelium: role in sodium absorption and chloride secretion. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1560:51-66. [PMID: 11958775 DOI: 10.1016/s0005-2736(01)00456-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In order to assess the role of different classes of K(+) channels in recirculation of K(+) across the basolateral membrane of rabbit distal colon epithelium, the effects of various K(+) channel inhibitors were tested on the activity of single K(+) channels from the basolateral membrane, on macroscopic basolateral K(+) conductance, and on the rate of Na(+) absorption and Cl(-) secretion. In single-channel measurements using the lipid bilayer reconstitution system, high-conductance (236 pS), Ca(2+)-activated K(+) (BK(Ca)) channels were most frequently detected; the second most abundant channel was a low-conductance K(+) channel (31 pS) that exhibited channel rundown. In addition to Ba(2+) and charybdotoxin (ChTX), the BK(Ca) channels were inhibited by quinidine, verapamil and tetraethylammonium (TEA), the latter only when present on the side of the channel from which K(+) flow originates. Macroscopic basolateral K(+) conductance, determined in amphotericin-permeabilised epithelia, was also markedly reduced by quinidine and verapamil, TEA inhibited only from the lumen side, and serosal ChTX was without effect. The chromanol 293B and the sulphonylurea tolbutamide did not affect BK(Ca) channels and had no or only a small inhibitory effect on macroscopic basolateral K(+) conductance. Transepithelial Na(+) absorption was partly inhibited by Ba(2+), quinidine and verapamil, suggesting that BK(Ca) channels are involved in basolateral recirculation of K(+) during Na(+) absorption in rabbit colon. The BK(Ca) channel inhibitors TEA and ChTX did not reduce Na(+) absorption, probably because TEA does not enter intact cells and ChTX is 'knocked off' its extracellular binding site by K(+) outflow from the cell interior. Transepithelial Cl(-) secretion was inhibited completely by Ba(2+) and 293B, partly by quinidine but not by the other K(+) channel blockers, indicating that the small (<3 pS) K(V)LQT1 channels are responsible for basolateral K(+) exit during Cl(-) secretion. Hence different types of K(+) channels mediate basolateral K(+) exit during transepithelial Na(+) and Cl(-) transport.
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Affiliation(s)
- Klaus Turnheim
- Institut für Pharmakologie, Universität Wien, Währinger Strasse 13a, A-1090, Vienna, Austria.
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Kunzelmann K, Mall M. Electrolyte transport in the mammalian colon: mechanisms and implications for disease. Physiol Rev 2002; 82:245-89. [PMID: 11773614 DOI: 10.1152/physrev.00026.2001] [Citation(s) in RCA: 449] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The colonic epithelium has both absorptive and secretory functions. The transport is characterized by a net absorption of NaCl, short-chain fatty acids (SCFA), and water, allowing extrusion of a feces with very little water and salt content. In addition, the epithelium does secret mucus, bicarbonate, and KCl. Polarized distribution of transport proteins in both luminal and basolateral membranes enables efficient salt transport in both directions, probably even within an individual cell. Meanwhile, most of the participating transport proteins have been identified, and their function has been studied in detail. Absorption of NaCl is a rather steady process that is controlled by steroid hormones regulating the expression of epithelial Na(+) channels (ENaC), the Na(+)-K(+)-ATPase, and additional modulating factors such as the serum- and glucocorticoid-regulated kinase SGK. Acute regulation of absorption may occur by a Na(+) feedback mechanism and the cystic fibrosis transmembrane conductance regulator (CFTR). Cl(-) secretion in the adult colon relies on luminal CFTR, which is a cAMP-regulated Cl(-) channel and a regulator of other transport proteins. As a consequence, mutations in CFTR result in both impaired Cl(-) secretion and enhanced Na(+) absorption in the colon of cystic fibrosis (CF) patients. Ca(2+)- and cAMP-activated basolateral K(+) channels support both secretion and absorption of electrolytes and work in concert with additional regulatory proteins, which determine their functional and pharmacological profile. Knowledge of the mechanisms of electrolyte transport in the colon enables the development of new strategies for the treatment of CF and secretory diarrhea. It will also lead to a better understanding of the pathophysiological events during inflammatory bowel disease and development of colonic carcinoma.
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Affiliation(s)
- Karl Kunzelmann
- Department of Physiology and Pharmacology, University of Queensland, St. Lucia, Queensland, Brisbane, Australia.
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Harvey BJ, Condliffe S, Doolan CM. Sex and salt hormones: rapid effects in epithelia. NEWS IN PHYSIOLOGICAL SCIENCES : AN INTERNATIONAL JOURNAL OF PHYSIOLOGY PRODUCED JOINTLY BY THE INTERNATIONAL UNION OF PHYSIOLOGICAL SCIENCES AND THE AMERICAN PHYSIOLOGICAL SOCIETY 2001; 16:174-7. [PMID: 11479368 DOI: 10.1152/physiologyonline.2001.16.4.174] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Recent evidence points to protein kinase C isoforms as highly specific receptors for aldosterone and estradiol in epithelia. The end targets of the kinase activation are Na(+)/H(+) exchange and K(+) and Ca(2+) channels. The physiological role of the nongenomic response is to increase electrolyte absorption and inhibit secretion in pluripotential epithelia.
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Affiliation(s)
- B J Harvey
- Wellcome Trust Cellular Physiology Research Unit, Department of Physiology, University College Cork, Ireland
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45
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Anderson M, Burleigh D. Imidazolines inhibit secretory responses of rat colonic mucosa to calcium-dependent but not cyclic AMP-dependent secretagogues. J Pharm Pharmacol 2001; 53:213-7. [PMID: 11273018 DOI: 10.1211/0022357011775226] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
The purpose of this study was to investigate whether imidazolines have an anti-secretory action on intestinal epithelial cells. Muscle-stripped preparations of rat colon and monolayers of T84 human colonic epithelial cells were set up in Ussing chambers for measurement of short-circuit current. In rat colon acetylcholine, histamine, vasoactive intestinal polypeptide and forskolin elicited secretory responses which were recorded as increases in short-circuit current. Secretory responses to acetylcholine were inhibited in a concentration-dependent manner by the imidazolines phentolamine, idazoxan and clonidine. The effect of clonidine was not reversed by pre-incubation of mucosal preparations with yohimbine. Secretory responses to vasoactive intestinal polypeptide were unaffected by the three imidazolines. Phentolamine reduced responses of colonic mucosa to histamine but had no effect on responses to forskolin. Responses to vasoactive intestinal polypeptide and forskolin were significantly reduced in the presence of barium. In T84 cell monolayers phentolamine significantly reduced responses to acetylcholine. Three imidazolines, two with alpha-adrenoceptor-antagonist properties and one with alpha-agonist properties, have anti-secretory effects in rat colonic mucosal preparations. The anti-secretory action appears to discriminate between calcium-dependent and cyclic AMP-dependent secretagogues, inhibiting the former but not the latter.
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Affiliation(s)
- M Anderson
- Division of Biomedical Sciences, Queen Mary and Westfield College, University of London, UK
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46
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Condliffe SB, Doolan CM, Harvey BJ. 17beta-oestradiol acutely regulates Cl- secretion in rat distal colonic epithelium. J Physiol 2001; 530:47-54. [PMID: 11136857 PMCID: PMC2278391 DOI: 10.1111/j.1469-7793.2001.0047m.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
In this study we used the short circuit current (ISC) technique to measure the non-genomic effects of the female sex steroid 17beta-oestradiol (E2) on electrogenic transepithelial ion transport in rat distal colonic epithelium. Basal ISC was largely composed of a transepithelial Cl- secretory component with minimal electrogenic Na+ movement. E2 (1-100 nM) caused a significant decrease in basal ISC after 15 min. In addition, pre-treating colonic epithelial tissues with E2 (0.1-100 nM) for 10 min significantly reduced forskolin (20 microM)-induced Cl- secretion. E2 also down-regulated Cl- secretion which was pre-stimulated by forskolin. Cl- secretory responses to the Ca2+-dependent secretagogue carbachol (10 microM) were also significantly reduced in the presence of E2 (10- 100 nM). However, E2 had no effect on amiloride-sensitive Na+ absorption. The rapid anti-secretory effect of E2 was abolished in the presence of the intracellular Ca2+ chelator BAPTA (50 microM) or the protein kinase C (PKC) inhibitor chelerythrine chloride (1 microM). However, in the presence of the nuclear oestrogen receptor antagonist tamoxifen (10 microM), E2 still produced an inhibition of Cl- secretion. Testosterone, progesterone and 17alpha-oestradiol had no significant effect on colonic Cl- secretion. Also, E2 (100 nM) did not alter Cl- secretion in colonic epithelia isolated from male rats. We conclude that E2 inhibits colonic Cl- secretion via a non-genomic pathway that involves intracellular Ca2+ and PKC. It is possible that this gender-specific mechanism contributes to the salt and water retention associated with high E2 states.
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Affiliation(s)
- S B Condliffe
- Wellcome Trust Cellular Physiology Research Unit, Physiology Department, University College Cork, Ireland.
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47
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McNamara B, Winter DC, Cuffe J, Taylor C, O'Sullivan GC, Harvey BJ. Rapid activation of basolateral potassium transport in human colon by oestradiol. Br J Pharmacol 2000; 131:1373-8. [PMID: 11090109 PMCID: PMC1572471 DOI: 10.1038/sj.bjp.0703714] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2000] [Accepted: 09/18/2000] [Indexed: 11/09/2022] Open
Abstract
1. We investigated the effect of oestradiol on basolateral potassium channels in human colonic epithelium. 2. Ion transport was quantified using short circuit current (I:(sc)) measurements of samples mounted in Ussing chambers. Serosal K transport was studied using nystatin permeabilization of the apical membrane. Intracellular pH changes were quantified using spectroflouresence techniques. 3. Experiments were performed with either 10 nM or 1 microM Ca(2+) in the apical bathing solution. With 10 nM Ca(2+) in the apical bathing solution addition of oestradiol (1 nM) to the basolateral bath produced a rapid increase in current (delta I(K)=11.2+/-1.2 microA.cm(-2), n=6). This response was prevented by treatment of the serosal membrane with tolbutamide (1 microM). With 1 microM Ca(2+) in the apical bathing solution addition of oestradiol produced a rapid fall in current (delta I(K)=-12.8+/-1.4 microA.cm(-2)), this response was prevented by treatment of the basolateral membrane with tetra-pentyl-ammonium (TPeA). These responses were rapid and occurred independently of protein synthesis. 4. Inhibition of basolateral Na(+)/H(+) exchange with either amiloride or a low sodium bathing solution prevented this response. These responses were prevented by inhibition of protein kinase C (PKC) with bis-indolyl-maleimide. 5. Oestradiol (1 nM) produced a rapid intracellular alkanization (mean increase=0.11 pH units; n=6; P<0.01). 6. These results suggest that oestradiol rapidly modulates serosal K transport in human colon. These effects depend upon intact Na(+)/H(+) exchange and protein kinase C. We propose a non-classical, possibly membrane linked, mechanism for oestradiol action in human colonic epithelium.
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Affiliation(s)
- B McNamara
- Department of Clinical Neurophysiology, Box 124, Addenbrookes Hospital, Cambridge, CB2 2QQ
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Arn M, Butt G, Lubcke R, Ross I, Grigor M, Warhurst G, Barbezat G. Somatostatin and octreotide stimulate short-circuit current in human colonic epithelium. Dig Dis Sci 2000; 45:2100-7. [PMID: 11215722 DOI: 10.1023/a:1026479505738] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/09/2022]
Abstract
In vitro somatostatin is a potent inhibitor of intestinal ion secretion in animal models and cultured human cell lines, providing a rationale for its use in secretory diarrheas. However, the effects of somatostatin on ion transport in native human colonic epithelium have not been reported. In this study the effects of somatostatin and octreotide on the basal short-circuit current and the cAMP- and Ca2+-stimulated short-circuit current were studied in isolated human colonic mucosa mounted in Ussing chambers. Under basal conditions somatostatin and octreotide (1 micromol/liter) stimulated a small, bumetanide-sensitive increase in short-circuit current. Following stimulation of secretion with prostaglandin E2, somatostatin and octreotide further increased the short-circuit current in a dose dependent fashion (ED50 approximately 10 nmol/liter for both). This stimulation of short-circuit current was not affected by pretreatment of the tissue with basolateral tetrodotoxin (1 micromol/liter) or mucosal amiloride (10 micromol/liter). In contrast, somatostatin and octreotide had no effect when secretion was stimulated with 8-bromo-cAMP, and pretreatment of the tissue with somatostatin and octreotide (0.1 micromol/liter) did not alter the secretory response to carbachol. The absence of any inhibitory effect of somatostatin and octreotide on electrogenic secretion in the human colon may explain the variable results obtained when somatostatin or octreotide are used for the treatment of secretory diarrheas.
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Affiliation(s)
- M Arn
- Department of Medicine, Dunedin School of Medicine, University of Otago, New Zealand
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49
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Schultheiss G, Frings M, Hollingshaus G, Diener M. Multiple action sites of flufenamate on ion transport across the rat distal colon. Br J Pharmacol 2000; 130:875-85. [PMID: 10864895 PMCID: PMC1572125 DOI: 10.1038/sj.bjp.0703363] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The antisecretory effects of flufenamate in the rat distal colon were investigated with the Ussing-chamber and the patch-clamp method as well as by measurements of the intracellular Ca(2+) concentration using fura-2-loaded isolated crypts. Flufenamate (5.10(-4) mol l(-1)) suppressed the short-circuit current (Isc) induced by carbachol (5.10(-5) mol l(-1)), forskolin (5.10(-6) mol l(-1)) and the Isc induced by the membrane-permeable analogue of cyclic AMP, CPT - cyclic AMP (10(-4) mol l(-1)). Indomethacin (10(-6) - 10(-4) mol l(-1)) did not mimic the effect of flufenamate, indicating that the antisecretory effect of flufenamate is not related to the inhibition of the cyclo-oxygenase. When the basolateral membrane was depolarized by a high K(+) concentration and a Cl(-) current was induced by a mucosally directed Cl(-) gradient, the forskolin-stimulated Cl(-) current was blocked by flufenamate, indicating an inhibition of the cyclic AMP-stimulated apical Cl(-) conductance. When the apical membrane was permeabilized by the ionophore, nystatin, flufenamate decreased the basolateral K(+) conductance and inhibited the Na(+) - K(+)-ATPase. Patch-clamp experiments revealed a variable effect of flufenamate on membrane currents. In seven out of 11 crypt cells the drug induced an increase of the K(+) current, whereas in the remaining four cells an inhibition was observed. Experiments with fura-2-loaded isolated crypts indicated that flufenamate increased the basal as well as the carbachol-stimulated intracellular Ca(2+) concentration. These results demonstrate that flufenamate possesses multiple action sites in the rat colon: The apical Cl(-) conductance, basolateral K(+) conductances and the Na(+) - K(+)-ATPase.
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Affiliation(s)
- G Schultheiss
- Institut für Veterinär-Physiologie, Justus-Liebig-Universität Gießen, Frankfurter Str.100, D-35392 Gieben, Germany
| | - M Frings
- Institut für Veterinär-Physiologie, Justus-Liebig-Universität Gießen, Frankfurter Str.100, D-35392 Gieben, Germany
| | - G Hollingshaus
- Institut für Veterinär-Physiologie, Justus-Liebig-Universität Gießen, Frankfurter Str.100, D-35392 Gieben, Germany
| | - M Diener
- Institut für Veterinär-Physiologie, Justus-Liebig-Universität Gießen, Frankfurter Str.100, D-35392 Gieben, Germany
- Author for correspondence:
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50
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McNamara B, Winter DC, Harvey BJ, O'Sullivan GC. A significant advance in the understanding of intestinal anion secretion. Gastroenterology 2000; 118:1282-3. [PMID: 10866523 DOI: 10.1016/s0016-5085(00)70397-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Affiliation(s)
- B McNamara
- Department of Clinical Neurophysiology, Addenbrookes Hospital, Cambridge, England
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