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Reglodi D, Illes A, Opper B, Schafer E, Tamas A, Horvath G. Presence and Effects of Pituitary Adenylate Cyclase Activating Polypeptide Under Physiological and Pathological Conditions in the Stomach. Front Endocrinol (Lausanne) 2018; 9:90. [PMID: 29615974 PMCID: PMC5868562 DOI: 10.3389/fendo.2018.00090] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Accepted: 02/26/2018] [Indexed: 12/29/2022] Open
Abstract
Pituitary adenylate cyclase activating polypeptide (PACAP) is a multifunctional neuropeptide with widespread occurrence throughout the body including the gastrointestinal system. In the small and large intestine, effects of PACAP on cell proliferation, secretion, motility, gut immunology and blood flow, as well as its importance in bowel inflammatory reactions and cancer development have been shown and reviewed earlier. However, no current review is available on the actions of PACAP in the stomach in spite of numerous data published on the gastric presence and actions of the peptide. Therefore, the aim of the present review is to summarize currently available data on the distribution and effects of PACAP in the stomach. We review data on the localization of PACAP and its receptors in the stomach wall of various mammalian and non-mammalian species, we then give an overview on PACAP's effects on secretion of gastric acid and various hormones. Effects on cell proliferation, differentiation, blood flow and gastric motility are also reviewed. Finally, we outline PACAP's involvement and changes in various human pathological conditions.
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Affiliation(s)
- Dora Reglodi
- Department of Anatomy, MTA-PTE PACAP Research Team, Centre for Neuroscience, University of Pecs Medical School, Pecs, Hungary
- *Correspondence: Dora Reglodi,
| | - Anita Illes
- Department of Anatomy, MTA-PTE PACAP Research Team, Centre for Neuroscience, University of Pecs Medical School, Pecs, Hungary
- 1st Department of Internal Medicine, University of Pecs Medical School, Pecs, Hungary
| | - Balazs Opper
- Department of Anatomy, MTA-PTE PACAP Research Team, Centre for Neuroscience, University of Pecs Medical School, Pecs, Hungary
| | - Eszter Schafer
- Department of Gastroenterology, Medical Centre, Hungarian Defence Forces, Budapest, Hungary
| | - Andrea Tamas
- Department of Anatomy, MTA-PTE PACAP Research Team, Centre for Neuroscience, University of Pecs Medical School, Pecs, Hungary
| | - Gabriella Horvath
- Department of Anatomy, MTA-PTE PACAP Research Team, Centre for Neuroscience, University of Pecs Medical School, Pecs, Hungary
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Zhao CM, Kodama Y, Flatberg A, Beisvag V, Kulseng B, Sandvik AK, Rehfeld JF, Chen D. Gene expression profiling of gastric mucosa in mice lacking CCK and gastrin receptors. ACTA ACUST UNITED AC 2014; 192-193:35-44. [PMID: 25160855 DOI: 10.1016/j.regpep.2014.08.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Revised: 08/07/2014] [Accepted: 08/12/2014] [Indexed: 01/04/2023]
Abstract
The stomach produces acid, which may play an important role in the regulation of bone homeostasis. The aim of this study was to reveal signaling pathways in the gastric mucosa that involve the acid secretion and possibly the bone metabolism in CCK1 and/or CCK2 receptor knockout (KO) mice. Gastric acid secretion was impaired and the ECL cell signaling pathway was inhibited in CCK2 receptor KO mice but not in CCK1 receptor KO mice. However, in CCK1+2 receptor double KO mice the acid secretion in response to pylorus ligation-induced vagal stimulation and the ECL cell pathway were partially normalized, which was associated with an up-regulated pituitary adenylate cyclase-activating polypeptide (PACAP) type 1 receptor (PAC1). The basal part of the gastric mucosa expressed parathyroid hormone-like hormone (PTHLH) in a subpopulation of likely ECL cells (and possibly other cells) and vitamin D3 1α hydroxylase probably in trefoil peptide2-immunoreactive cells. In conclusion, mice lacking CCK receptors exhibited a functional shift from the gastrin-CCK pathways to the neuronal pathway in control of the ECL cells and eventually the acid secretion. Taking the present data together with previous findings, we suggest a possible link between gastric PTHLH and vitamin D and bone metabolism.
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Affiliation(s)
- Chun-Mei Zhao
- Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, 7006 Trondheim, Norway.
| | - Yosuke Kodama
- Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, 7006 Trondheim, Norway
| | - Arnar Flatberg
- Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, 7006 Trondheim, Norway
| | - Vidar Beisvag
- Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, 7006 Trondheim, Norway
| | - Bård Kulseng
- Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, 7006 Trondheim, Norway
| | - Arne K Sandvik
- Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, 7006 Trondheim, Norway; Department of Gastrointestinal and Liver Diseases, St. Olav's University Hospital, 7006 Trondheim, Norway
| | - Jens F Rehfeld
- Department of Clinical Biochemistry, Rigshospitalet, University of Copenhagen, 2100 København Ø, Denmark
| | - Duan Chen
- Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, 7006 Trondheim, Norway
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3
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Aihara E, Hentz CL, Korman AM, Perry NPJ, Prasad V, Shull GE, Montrose MH. In vivo epithelial wound repair requires mobilization of endogenous intracellular and extracellular calcium. J Biol Chem 2013; 288:33585-33597. [PMID: 24121509 DOI: 10.1074/jbc.m113.488098] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
We report that a localized intracellular and extracellular Ca(2+) mobilization occurs at the site of microscopic epithelial damage in vivo and is required to mediate tissue repair. Intravital confocal/two-photon microscopy continuously imaged the surgically exposed stomach mucosa of anesthetized mice while photodamage of gastric epithelial surface cells created a microscopic lesion that healed within 15 min. Transgenic mice with an intracellular Ca(2+)-sensitive protein (yellow cameleon 3.0) report that intracellular Ca(2+) selectively increases in restituting gastric epithelial cells adjacent to the damaged cells. Pretreatment with U-73122, indomethacin, 2-aminoethoxydiphenylborane, or verapamil inhibits repair of the damage and also inhibits the intracellular Ca(2+) increase. Confocal imaging of Fura-Red dye in luminal superfusate shows a localized extracellular Ca(2+) increase at the gastric surface adjacent to the damage that temporally follows intracellular Ca(2+) mobilization. Indomethacin and verapamil also inhibit the luminal Ca(2+) increase. Intracellular Ca(2+) chelation (1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid/acetoxymethyl ester, BAPTA/AM) fully inhibits intracellular and luminal Ca(2+) increases, whereas luminal calcium chelation (N-(2-hydroxyetheyl)-ethylendiamin-N,N,N'-triacetic acid trisodium, HEDTA) blocks the increase of luminal Ca(2+) and unevenly inhibits late-phase intracellular Ca(2+) mobilization. Both modes of Ca(2+) chelation slow gastric repair. In plasma membrane Ca-ATPase 1(+/-) mice, but not plasma membrane Ca-ATPase 4(-/-) mice, there is slowed epithelial repair and a diminished gastric surface Ca(2+) increase. We conclude that endogenous Ca(2+), mobilized by signaling pathways and transmembrane Ca(2+) transport, causes increased Ca(2+) levels at the epithelial damage site that are essential to gastric epithelial cell restitution in vivo.
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Affiliation(s)
- Eitaro Aihara
- Department of Molecular and Cellular Physiology, University of Cincinnati, Cincinnati, Ohio 45267
| | - Courtney L Hentz
- Department of Molecular and Cellular Physiology, University of Cincinnati, Cincinnati, Ohio 45267
| | - Abraham M Korman
- Department of Molecular and Cellular Physiology, University of Cincinnati, Cincinnati, Ohio 45267
| | - Nicholas P J Perry
- Department of Molecular and Cellular Physiology, University of Cincinnati, Cincinnati, Ohio 45267
| | - Vikram Prasad
- Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati, Cincinnati, Ohio 45267
| | - Gary E Shull
- Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati, Cincinnati, Ohio 45267
| | - Marshall H Montrose
- Department of Molecular and Cellular Physiology, University of Cincinnati, Cincinnati, Ohio 45267.
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4
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Kopic S, Geibel JP. Gastric acid, calcium absorption, and their impact on bone health. Physiol Rev 2013; 93:189-268. [PMID: 23303909 DOI: 10.1152/physrev.00015.2012] [Citation(s) in RCA: 102] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Calcium balance is essential for a multitude of physiological processes, ranging from cell signaling to maintenance of bone health. Adequate intestinal absorption of calcium is a major factor for maintaining systemic calcium homeostasis. Recent observations indicate that a reduction of gastric acidity may impair effective calcium uptake through the intestine. This article reviews the physiology of gastric acid secretion, intestinal calcium absorption, and their respective neuroendocrine regulation and explores the physiological basis of a potential link between these individual systems.
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Affiliation(s)
- Sascha Kopic
- Department of Surgery and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut, USA
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Shafik AN, Khodeir MM, Gouda NA, Mahmoud ME. Improved antifibrotic effect of a combination of verapamil and silymarin in rat-induced liver fibrosis. Arab J Gastroenterol 2011; 12:143-9. [PMID: 22055593 DOI: 10.1016/j.ajg.2011.07.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2010] [Revised: 02/17/2011] [Accepted: 07/03/2011] [Indexed: 11/24/2022]
Abstract
BACKGROUND AND STUDY AIMS Liver fibrosis progresses to cirrhosis in several settings, for example, severe acute alcoholic hepatitis, and hepatitis C virus (HCV) reinfection after liver transplantation. Cirrhosis produces hepatocellular dysfunction, which is also a risk factor for hepatocellular carcinoma. We studied verapamil as a prophylactic, therapeutic antifibrotic drug alone and in combination with silymarin in experimental rat's liver-induced fibrosis. MATERIAL AND METHODS Liver fibrosis was induced by intra-peritoneal injection of rats with pig serum 0.5ml twice weekly for 6 weeks, which resulted in score three fibrosis. Prophylactic verapamil alone and silymarin alone and a combination of both were administered at the same time of induction of liver fibrosis and continued for the duration of induction. Therapeutic verapamil was started on the last day of fibrosis induction and continued for 4 weeks. The extent of liver fibrosis was evaluated using Ishak's fibrosis score. Serum alanine aminotransferase (ALT) was measured for follow-up. RESULTS Compared to fibrotic model rats, prophylactic verapamil, silymarin and combined verapamil plus silymarin significantly resulted in lower serum ALT levels. Prophylactic use of verapamil and silymarin each alone revealed score 2 fibrosis with positive α-SMA immunostaining; while prophylactic treatment with combined verapamil plus silymarin revealed no fibrosis supported by negative α-SMA immunostaining. Verapamil treated fibrotic rat's liver revealed significant regression in liver fibrosis scores with positive α-SMA immunostaining. CONCLUSIONS Verapamil alone has a more significant prophylactic than therapeutic antifibrotic effect against induced liver fibrosis; it was more significant than silymarin. The combination of verapamil and silymarin, showed the best protection through their synergistic antifibrotic effect.
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Affiliation(s)
- Amani N Shafik
- Department of Pharmacology, Faculty of Medicine, Cairo University, Cairo, Egypt
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Rogers GJ, Tolhurst G, Ramzan A, Habib AM, Parker HE, Gribble FM, Reimann F. Electrical activity-triggered glucagon-like peptide-1 secretion from primary murine L-cells. J Physiol 2011; 589:1081-93. [PMID: 21224236 PMCID: PMC3060588 DOI: 10.1113/jphysiol.2010.198069] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2010] [Accepted: 12/31/2010] [Indexed: 01/21/2023] Open
Abstract
Glucagon like peptide 1 (GLP-1) based therapies are now widely used for the treatment of type 2 diabetes. Developing our understanding of intestinal GLP-1 release may facilitate the development of new therapeutics aimed at targeting the GLP-1 producing L-cells. This study was undertaken to characterise the electrical activity of primary L-cells and the importance of voltage gated sodium and calcium channels for GLP-1 secretion. Primary murine L-cells were identified and purified using transgenic mice expressing a fluorescent protein driven by the proglucagon promoter. Fluorescent L-cells were identified within primary colonic cultures for patch clamp recordings. GLP-1 secretion was measured from primary colonic cultures. L-cells purified by flow cytometry were used to measure gene expression by microarray and quantitative RT-PCR. Electrical activity in L-cells was due to large voltage gated sodium currents, inhibition of which by tetrodotoxin reduced both basal and glutamine-stimulated GLP-1 secretion. Voltage gated calcium channels were predominantly of the L-type, Q-type and T-type, by expression analysis, consistent with the finding that GLP-1 release was blocked both by nifedipine and ω-conotoxin MVIIC. We observed large voltage-dependent potassium currents, but only a small chromanol sensitive current that might be attributable to KCNQ1. GLP-1 release from primary L-cells is linked to electrical activity and activation of L-type and Q-type calcium currents. The concept of an electrically excitable L-cell provides a basis for understanding how GLP-1 release may be modulated by nutrient, hormonal and pharmaceutical stimuli.
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Affiliation(s)
- G J Rogers
- Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Box 139, Hills Road, Cambridge CB2 0XY, UK
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PAC1 deficiency in a murine model induces gastric mucosa hypertrophy and higher basal gastric acid output. J Mol Neurosci 2010; 43:76-84. [PMID: 20821075 PMCID: PMC3018609 DOI: 10.1007/s12031-010-9440-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2010] [Accepted: 08/10/2010] [Indexed: 01/01/2023]
Abstract
Pituitary adenylate cyclase-activating polypeptide (PACAP) has been shown to increase the histamine release from gastric enterochromaffin-like (ECL) cells and promote gastric acid secretion in rats. In contrast, in mice, PACAP has been demonstrated to induce a decrease of gastric acid secretion, an effect presumably due to somatostatin release. To more clearly define the role of PACAP in the regulation of gastric acid output, a knockout mouse model for the PACAP-specific receptor PAC1 was applied in this study. Measurements of the basal and stimulated gastric acid secretion and morphological studies on the gastric mucosa were performed in both wild-type and PAC1-deficient mice. Compared with the wild-type mice, the PAC1-deficient mice showed a nearly threefold higher basal gastric acid output, increased gastric mucosa thickness and glands height, and proportional increases in parietal and total cell counts in the gastric mucosa. The PAC1-deficient mice also showed a trend of increased plasma gastrin levels and gastrin gene expression in the gastric mucosa. This study indicates that the expression of PAC1 is clearly important for maintaining the homeostasis of gastric acid secretion. Loss of PACAP receptor during development may lead to a compensatory mechanism regulating gastric acid secretion.
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Volume density, distribution, and ultrastructure of secretory and basolateral membranes and mitochondria predict parietal cell secretory (dys)function. J Biomed Biotechnol 2010; 2010:394198. [PMID: 20339514 PMCID: PMC2842899 DOI: 10.1155/2010/394198] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Revised: 11/03/2009] [Accepted: 12/07/2009] [Indexed: 11/24/2022] Open
Abstract
Acid secretion in gastric parietal cells requires highly coordinated membrane transport and vesicle trafficking. Histologically, consensus defines acid secretion as the ratio of the volume density (Vd) of canalicular and apical membranes (CAMs) to tubulovesicular (TV) membranes, a value which varies widely under normal conditions. Examination of numerous achlorhydric mice made it clear that this paradigm is discrepant when used to assess most mice with genetic mutations affecting acid secretion. Vd of organelles in parietal cells of 6 genetically engineered mouse strains was obtained to identify a stable histological phenotype of acid secretion. We confirmed that CAM to TV ratio fairly represented secretory activity in untreated and secretion-inhibited wild-type (WT) mice and in NHE2−/− mice as well, though the response was significantly attenuated in the latter. However, high CAM to TV ratios wrongly posed as active acid secretion in AE2−/−, GHKAα−/−, and NHE4−/− mice. Achlorhydric genotypes also had a significantly higher Vd of basolateral membrane than WT mice, and reduced Vd of mitochondria and canaliculi. The Vd of mitochondria, and ratio of the Vd of basolateral membranes/Vd of mitochondria were preferred predictors of the level of acid secretion. Alterations in acid secretion, then, cause significant changes not only in the Vd of secretory membranes but also in mitochondria and basolateral membranes.
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Vaudry D, Falluel-Morel A, Bourgault S, Basille M, Burel D, Wurtz O, Fournier A, Chow BKC, Hashimoto H, Galas L, Vaudry H. Pituitary Adenylate Cyclase-Activating Polypeptide and Its Receptors: 20 Years after the Discovery. Pharmacol Rev 2009; 61:283-357. [DOI: 10.1124/pr.109.001370] [Citation(s) in RCA: 829] [Impact Index Per Article: 55.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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Ischemia mobilizes histamine but not pancreastatin from ECL cells of rat stomach: evidence for a cytosolic histamine compartment. Cell Tissue Res 2008; 333:405-15. [DOI: 10.1007/s00441-008-0648-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2008] [Accepted: 05/19/2008] [Indexed: 01/29/2023]
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Bernsand M, Håkanson R, Norlén P. Tachyphylaxis of the ECL-cell response to PACAP: receptor desensitization and/or depletion of secretory products. Br J Pharmacol 2007; 152:240-8. [PMID: 17660849 PMCID: PMC1978265 DOI: 10.1038/sj.bjp.0707385] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND AND PURPOSE Rat stomach ECL cells secrete histamine and pancreastatin in response to gastrin and pituitary adenylate cyclase-activating peptide-27 (PACAP). This study applies microdialysis to explore how ECL cells in situ respond to PACAP and gastrin. EXPERIMENTAL APPROACH Both peptides were administered by microinfusion into the gastric submucosa. The microdialysate was analysed for histamine and pancreastatin (ECL-cell markers) and for somatostatin (D-cell marker). KEY RESULTS Microinfusion of PACAP (0.01-0.3 nmol microl(-1)) raised microdialysate histamine and pancreastatin dose-dependently. The response was powerful but short-lived. The response to gastrin was sustained at all doses tested. It is unlikely that the transient nature of the histamine response to PACAP reflects inadequate histamine synthesis, since the pancreastatin response to PACAP was short-lived too, and both gastrin and PACAP activated ECL-cell histidine decarboxylase. Unlike gastrin, PACAP mobilized somatostatin. Co-infusion of somatostatin abolished the histamine-mobilizing effect of PACAP. However, pretreatment with the somatostatin receptor type-2 antagonist (PRL-2903) did not prolong the histamine response to PACAP, suggesting that mobilization of somatostatin does not explain the transient nature of the response. Repeated administration of 0.1 nmol microl(-1) of PACAP (1 h infusions, 1 h intervals) failed to induce a second histamine response. Pretreatment with a low dose of PACAP (0.03 nmol microl(-1)) abolished the response to a subsequent near-maximal PACAP challenge (0.3 nmol microl(-1)). CONCLUSION The transient nature of the histamine response to PACAP reflects desensitization of the PACAP receptor and/or exhaustion of a specific storage compartment that responds to PACAP but not to gastrin.
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Affiliation(s)
- M Bernsand
- Unit of Cellular and Molecular Pharmacology, Department of Experimental Medical Sciences, Lund University Lund, Sweden
| | - R Håkanson
- Unit of Cellular and Molecular Pharmacology, Department of Experimental Medical Sciences, Lund University Lund, Sweden
| | - P Norlén
- Unit of Cellular and Molecular Pharmacology, Department of Experimental Medical Sciences, Lund University Lund, Sweden
- Unit of Clinical and Experimental Pharmacology, Department of Laboratory Medicine, Lund University Hospital Lund, Sweden
- Author for correspondence:
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Friis-Hansen L, Schjerling CK, de la Cour CD, Håkanson R, Rehfeld JF. Characteristics of gastrin controlled ECL cell specific gene expression. ACTA ACUST UNITED AC 2007; 140:153-61. [PMID: 17239973 DOI: 10.1016/j.regpep.2006.12.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2006] [Revised: 11/23/2006] [Accepted: 12/01/2006] [Indexed: 11/28/2022]
Abstract
BACKGROUND The ECL cells are histamine-producing endocrine cells in the oxyntic mucosa that synthesize and secrete proteins and peptides. They are the primary target for gastrin and mediate the control of gastrin on acid secretion and oxyntic mucosal growth. Knowledge of the molecular biology of the ECL cell is therefore important for understanding gastric physiology. Accordingly, we wanted to identify genes that are characteristically expressed in the ECL cells and controlled by gastrin. METHODS Using Affymetrix GeneChips, RNA expression profiles were generated from ECL cells isolated by counterflow elutriation from hyper- or hypogastrinemic rats. Contamination from non-endocrine cells was eliminated by subtraction of the expression profiles of the fundic and antral mucosa. RESULTS The expression of 365 genes was ECL cell characteristic. Gastrin was found to control the expression of 120 which could be divided into two major groups depending on the known or anticipated biological function of the encoded protein: genes encoding proteins involved in the secretory process and genes encoding proteins needed to generate energy for secretion. Interestingly, gastrin stimulation also increased ECL cells expression of anti-apoptotic genes. CONCLUSION The ECL cell specific expression profile is reminiscent of that of neurons and other endocrine cells exhibiting high expression of genes encoding proteins involved in the synthesis, storage and secretion of neuropeptides or peptide hormones. Gastrin regulated the expression of one third of these genes and is thus involved in the control of secretion from the ECL cells.
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Affiliation(s)
- Lennart Friis-Hansen
- Department of Clinical Biochemistry, Rigshospitalet, University of Copenhagen, Denmark.
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Cui G, Waldum HL. Physiological and clinical significance of enterochromaffin-like cell activation in the regulation of gastric acid secretion. World J Gastroenterol 2007; 13:493-6. [PMID: 17278212 PMCID: PMC4065968 DOI: 10.3748/wjg.v13.i4.493] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Gastric acid plays an important role in digesting food (especially protein), iron absorption, and destroying swallowed micro-organisms. H+ is secreted by the oxyntic parietal cells and its secretion is regulated by endocrine, neurocrine and paracrine mechanisms. Gastrin released from the antral G cell is the principal physiological stimulus of gastric acid secretion. Activation of the enterochromaffin-like (ECL) cell is accepted as the main source of histamine participating in the regulation of acid secretion and is functionally and trophically controlled by gastrin, which is mediated by gastrin/CCK-2 receptors expressed on the ECL cell. However, long-term hypergastrinemia will induce ECL cell hyperplasia and probably carcinoids. Clinically, potent inhibitors of acid secretion have been prescribed widely to patients with acid-related disorders. Long-term potent acid inhibition evokes a marked increase in plasma gastrin levels, leading to enlargement of oxyntic mucosa with ECL cell hyperplasia. Accordingly, the induction of ECL cell hyperplasia and carcinoids remains a topic of considerable concern, especially in long-term use. In addition, the activation of ECL cells also induces another clinical concern, i.e., rebound acid hypersecretion after acid inhibition. Recent experimental and clinical findings indicate that the activation of ECL cells plays a critical role both physiologically and clinically in the regulation of gastric acid secretion.
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Affiliation(s)
- Guanglin Cui
- Laboratory of Gastroenterology, Institute of Clinical Medicine, Faculty of Medicine, University of Tromsø, Tromsø N-9037, Norway.
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Xu D, Wu Y, Liao ZX, Wang H. Protective effect of verapamil on multiple hepatotoxic factors-induced liver fibrosis in rats. Pharmacol Res 2006; 55:280-6. [PMID: 17223571 DOI: 10.1016/j.phrs.2006.12.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2006] [Revised: 12/02/2006] [Accepted: 12/07/2006] [Indexed: 12/11/2022]
Abstract
The purpose of the present work was to investigate the effect of verapamil on liver fibrosis induced by multiple hepatotoxic factors in rats. Male Wistar rats were divided into a normal control group, a liver fibrosis model control group, and verapamil groups with different dosages. Multiple hepatotoxic factors including carbon tetrachloride (CCl(4)), ethanol and high cholesterol were used to make the animal model of liver fibrosis. The parameters of serum l-alanine aminotransferase (ALT), liver malondialdehyde and hydroxyproline contents were measured. Samples of the liver obtained by biopsy were subjected to histological and immunohistochemical studies for the expressions of alpha-smooth muscle actin (alpha-SMA) and transforming growth factor-beta(1) (TGF-beta(1)). Results showed that verapamil induced a dose-dependent decrease of serum ALT, liver malondialdehyde and hydroxyproline compared with liver fibrosis model control. Verapamil reduced hepatocyte degeneration and necrosis, and delayed the formation of liver fibrosis. The levels of expression of alpha-SMA and TGF-beta(1) in the hepatic tissue of three of the verapamil-treated groups were significantly less than those of the liver fibrosis model control group. The results showed that verapamil acts against the formation of liver fibrosis, the mechanism might be due to a protective effect for hepatocytes and through decreasing TGF-beta(1) to block the activation of hepatic stellate cells (HSCs) and collagen gene expression.
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Affiliation(s)
- Dan Xu
- Department of Pharmacology, Basic Medical School, Wuhan University, Wuhan 430071, Hubei Province, China
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15
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Oh DS, Lieu SN, Yamaguchi DJ, Tachiki K, Lambrecht N, Ohning GV, Sachs G, Germano PM, Pisegna JR. PACAP regulation of secretion and proliferation of pure populations of gastric ECL cells. J Mol Neurosci 2005; 26:85-97. [PMID: 15968088 PMCID: PMC6719686 DOI: 10.1385/jmn:26:1:085] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The gastric enterochromaffin-like (ECL) cell plays a major role in the regulation of gastric acid secretion. We have previously described that Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) is present on myenteric neurons in the rat and colocalizes with its high-affinity receptor, PAC1, expressed on the surface of gastric ECL cells. The study of ECL cell physiology has been hampered by the inability to isolate and purify ECL cells to homogeneity. Density gradient elutriation alone yields only 65-70% purity of ECL cells. In the present study, we used fluorescence-activated cell sorting (FACS) with a novel fluorescent ligand, Fluor-PACAP-38, for isolating pure ECL cells. FACS was used to isolate ECL cells based on their relatively small size, low density, and ability to bind the fluorescent ligand Fluor-PACAP-38. The sorted cells were unambiguously identified as ECL cells by immunohistochemical analysis using anti-PACAP type-I (PAC1), anti-histidine decarboxylase (HDC), and anti-somatostatin antibodies. Further confocal microscopy demonstrated that Fluor-PACAP-38, a ligand with a higher affinity for PAC1, bound to extracellular receptors of these FACS-purified cells. FACS yielded an average of 2 million ECL cells/4 rat stomachs, and >99% of the sorted cells were positive for PAC1 receptor and HDC expression. The absence of immunohistochemical staining for somatostatin indicated lack of contamination by gastric D cells, which are similar in size and shape to the ECL cells. Internalization of PACAP receptors and a rapid Ca2+ response in purified ECL cells were observed upon PACAP activation, suggesting that these cells are viable and biologically active. These ECL cells demonstrated a dose-dependent stimulation of proliferation in response to PACAP, with a maximum of 30% proliferation at a concentration of 10-7 M. Microarray studies were perfor med to confirm the expression of genes specific for ECL cells. These results demonstrate that rat gastric ECL cells can be isolated to homogeneity by using a combination of density gradient centrifugation, followed by cell sorting using Fluor-PACAP. These techniques now allow microarray studies to be performed in ECL cells to characterize their functional gene expression and will facilitate pharmacological, biochemical, and molecular studies on ECL cell function.
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Affiliation(s)
- David S. Oh
- Division of Gastroenterology and Hepatology, Los Angeles, CA 90073
- Department of Research and Development, Los Angeles, CA 90073
- VA Greater Los Angeles Healthcare System and CURE: VA/UCLA Digestive Disease Research Center, Department of Medicine, Los Angeles, CA 90073
| | - Sandy N. Lieu
- Department of Research and Development, Los Angeles, CA 90073
- VA Greater Los Angeles Healthcare System and CURE: VA/UCLA Digestive Disease Research Center, Department of Medicine, Los Angeles, CA 90073
| | | | - Ken Tachiki
- Department of Research and Development, Los Angeles, CA 90073
| | - Nils Lambrecht
- Pathology and Laboratory Medicine, Los Angeles, CA 90073
| | - Gordon V. Ohning
- Division of Gastroenterology and Hepatology, Los Angeles, CA 90073
- Department of Research and Development, Los Angeles, CA 90073
- VA Greater Los Angeles Healthcare System and CURE: VA/UCLA Digestive Disease Research Center, Department of Medicine, Los Angeles, CA 90073
| | - George Sachs
- Department of Research and Development, Los Angeles, CA 90073
- VA Greater Los Angeles Healthcare System and CURE: VA/UCLA Digestive Disease Research Center, Department of Medicine, Los Angeles, CA 90073
- Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90073
| | - Patrizia M. Germano
- Department of Research and Development, Los Angeles, CA 90073
- VA Greater Los Angeles Healthcare System and CURE: VA/UCLA Digestive Disease Research Center, Department of Medicine, Los Angeles, CA 90073
| | - Joseph R. Pisegna
- Division of Gastroenterology and Hepatology, Los Angeles, CA 90073
- Department of Research and Development, Los Angeles, CA 90073
- VA Greater Los Angeles Healthcare System and CURE: VA/UCLA Digestive Disease Research Center, Department of Medicine, Los Angeles, CA 90073
- Author to whom all correspondence and reprint requests should be addressed.
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16
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Björkqvist M, Bernsand M, Eliasson L, Håkanson R, Lindström E. Somatostatin, misoprostol and galanin inhibit gastrin- and PACAP-stimulated secretion of histamine and pancreastatin from ECL cells by blocking specific Ca2+ channels. ACTA ACUST UNITED AC 2005; 130:81-90. [PMID: 15935492 DOI: 10.1016/j.regpep.2005.04.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2004] [Revised: 03/21/2005] [Accepted: 04/11/2005] [Indexed: 10/25/2022]
Abstract
The oxyntic mucosa is rich in ECL cells. They secrete histamine and chromogranin A-derived peptides, such as pancreastatin, in response to gastrin and pituitary adenylate cyclase-activating peptide (PACAP). Secretion is initiated by Ca2+ entry. While gastrin stimulates secretion by opening L-type and N-type Ca2+ channels, PACAP stimulates secretion by activating L-type and receptor-operated Ca2+ channels. Somatostatin, galanin and prostaglandin E2 (PGE2) inhibit gastrin- and PACAP-stimulated secretion from the ECL cells. In the present study, somatostatin and the PGE2 congener misoprostol inhibited gastrin- and PACAP-stimulated secretion 100%, while galanin inhibited at most 60-65%. Bay K 8644, a specific activator of L-type Ca2+ channels, stimulated ECL-cell secretion, an effect that was inhibited equally effectively by somatostatin, misoprostol and galanin (75-80% inhibition). Pretreatment with pertussis toxin, that inactivates inhibitory G-proteins, prevented all three agents from inhibiting stimulated secretion (regardless of the stimulus). Pretreatment with nifedipine (10 microM), an L-type Ca2+ channel blocker, reduced PACAP-evoked pancreastatin secretion by 50-60%, gastrin-evoked secretion by approximately 80% and abolished the response to Bay K 8644. The nifedipine-resistant response to PACAP was abolished by somatostatin and misoprostol but not by galanin. Gastrin and PACAP raised the intracellular Ca2+ concentration in a biphasic manner, believed to reflect mobilization of internal Ca2+ followed by Ca2+ entry. Somatostatin and misoprostol blocked Ca2+ entry (and histamine and pancreastatin secretion) but not mobilization of internal Ca2+. The present observations on isolated ECL cells suggest that Ca2+ entry rather than mobilization of internal Ca2+ triggers exocytosis, that gastrin and PACAP activate different (but over-lapping) Ca2+ channels, that somatostatin, misoprostol and galanin interact with inhibitory G-proteins to block Ca2+ entry via L-type Ca2+ channels, and that somatostatin and misoprostol (but not galanin) in addition block N-type and/or receptor-operated Ca2+ channels.
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MESH Headings
- 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester/pharmacology
- Animals
- Anti-Ulcer Agents/pharmacology
- Calcium/metabolism
- Calcium Channels/metabolism
- Cells, Cultured
- Chromogranin A
- Dose-Response Relationship, Drug
- Enterochromaffin-like Cells/metabolism
- Exocytosis
- Galanin/metabolism
- Galanin/pharmacology
- Gastrins/metabolism
- Histamine/metabolism
- Hormones/pharmacology
- Male
- Microscopy, Video
- Misoprostol/metabolism
- Misoprostol/pharmacology
- Models, Biological
- Nifedipine/pharmacology
- Pancreatic Hormones/metabolism
- Peptides, Cyclic/pharmacology
- Rats
- Rats, Sprague-Dawley
- Somatostatin/metabolism
- Somatostatin/pharmacology
- Time Factors
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Affiliation(s)
- Maria Björkqvist
- Institute of Physiological Sciences, Department of Pharmacology, University of Lund, Sölvegatan 19, BMC F13, S-227 34 Lund, Sweden.
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17
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Bhattacharya A, Lakhman SS, Singh S. Modulation of L-type calcium channels in Drosophila via a pituitary adenylyl cyclase-activating polypeptide (PACAP)-mediated pathway. J Biol Chem 2004; 279:37291-7. [PMID: 15201281 DOI: 10.1074/jbc.m403819200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Modulation of calcium channels plays an important role in many cellular processes. Previous studies have shown that the L-type Ca(2+) channels in Drosophila larval muscles are modulated via a cAMP-protein kinase A (PKA)-mediated pathway. This raises questions on the identity of the steps prior to cAMP, particularly the endogenous signal that may initiate this modulatory cascade. We now present data suggesting the possible role of a neuropeptide, pituitary adenylyl cyclase-activating polypeptide (PACAP), in this modulation. Mutations in the amnesiac (amn) gene, which encodes a polypeptide homologous to human PACAP-38, reduced the L-type current in larval muscles. Conditional expression of a wild-type copy of the amn gene rescued the current from this reduction. Bath application of human PACAP-38 also rescued the current. PACAP-38 did not rescue the mutant current in the presence of PACAP-6-38, an antagonist at type-I PACAP receptor. 2',5'-dideoxyadenosine, an inhibitor of adenylyl cyclase, prevented PACAP-38 from rescuing the amn current. In addition, 2',5'-dideoxyadenosine reduced the wild-type current to the level seen in amn, whereas it failed to further reduce the current observed in amn muscles. H-89, an inhibitor of PKA, suppressed the effect of PACAP-38 on the current. The above data suggest that PACAP, the type-I PACAP receptors, and adenylyl cyclase play a role in the modulation of L-type Ca(2+) channels via cAMP-PKA pathway. The data also provide support for functional homology between human PACAP-38 and the amn gene product in Drosophila.
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Affiliation(s)
- Anindya Bhattacharya
- Department of Pharmacology and Toxicology, State University of New York at Buffalo, Buffalo, New York 14214-3000, USA
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18
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Kamaishi H, Endoh T, Suzuki T. Multiple signal pathways coupling VIP and PACAP receptors to calcium channels in hamster submandibular ganglion neurons. Auton Neurosci 2004; 111:15-26. [PMID: 15109935 DOI: 10.1016/j.autneu.2004.01.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2003] [Revised: 01/07/2004] [Accepted: 01/08/2004] [Indexed: 11/29/2022]
Abstract
The Vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are two novel neuropeptides which produce particular biological effects caused by interaction with G-protein-coupled receptors. We have shown in a previous study where VIP and PACAP 38 inhibit voltage-dependent calcium channel (VDCC) currents (ICa) via G-proteins in hamster submandibular ganglion (SMG) neurons. In this study, we attempt to further characterize the signal transduction pathways of VIP-and PACAP 38-induced modulation of ICa. Application of 1 microM VIP and PACAP 38 inhibited ICa by 33.0 +/- 3.1% and 36.8 +/- 2.6%, respectively (mean +/- S.E.M., n = 8). Application of strong voltage prepulse attenuated PACAP 38-induced inhibition of ICa. Pretreatment of cAMP dependent protein kinase (PKA) activator attenuated VIP-induced inhibition, but not the PACAP 38-induced inhibition. Intracellular dialysis of the PKA inhibitor attenuated the VIP-induced inhibition, but not the PACAP 38-induced inhibition. Pretreatment of protein kinase C (PKC) activator and inhibitor attenuated VIP-induced inhibition, but not the PACAP 38-induced inhibition. Pretreatment of cholera toxin (CTX) attenuated PACAP 38-induced inhibition of ICa. These findings indicate that there are multiple signaling pathways in VIP and PACAP 38-induced inhibitions of ICa: one pathway would be the VPAC1/VPAC2 receptors-induced inhibition involving both the PKA and PKC, and another one concerns the PAC1 receptor-induced inhibition via Gs-protein betagamma subunits. The VIP-and PACAP 38-induced facilitation of ICa can be observed in the SMG neurons in addition to inhibiting of ICa.
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Affiliation(s)
- Hideaki Kamaishi
- Department of Physiology, Tokyo Dental College, 1-2-2, Masago, Mihama, Chiba 261-8502, Japan
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19
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Bernsand M, Ericsson P, Björkqvist M, Zhao CM, Håkanson R, Norlén P. Submucosal microinfusion of endothelin and adrenaline mobilizes ECL-cell histamine in rat stomach, and causes mucosal damage: a microdialysis study. Br J Pharmacol 2003; 140:707-17. [PMID: 14504142 PMCID: PMC1574064 DOI: 10.1038/sj.bjp.0705473] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Rat stomach ECL cells release histamine in response to gastrin. Submucosal microinfusion of endothelin or adrenaline, known to cause vasoconstriction and gastric lesions, mobilized striking amounts of histamine. While the histamine response to gastrin is sustainable for hours, that to endothelin and adrenaline was characteristically short-lasting (1-2 h). The aims of this study were to identify the cellular source of histamine mobilized by endothelin and adrenaline, and examine the differences between the histamine-mobilizing effects of gastrin, and of endothelin and adrenaline. Endothelin, adrenaline or gastrin were administered by submucosal microinfusion. Gastric histamine mobilization was monitored by microdialysis. Local pretreatment with the H1-receptor antagonist mepyramine and the H2-receptor antagonist ranitidine did not prevent endothelin- or adrenaline-induced mucosal damage. Submucosal microinfusion of histamine did not cause damage. Acid blockade by ranitidine or omeprazole prevented the damage, suggesting that acid back diffusion contributes. Gastrin raised histidine decarboxylase (HDC) activity close to the probe, without affecting the histamine concentration. Endothelin and adrenaline lowered histamine by 50-70%, without activating HDC. Histamine mobilization declined upon repeated administration. Endothelin reduced the number of histamine-immunoreactive ECL cells locally, and reduced the number of secretory vesicles. Thus, unlike gastrin, endothelin (and adrenaline) is capable of exhausting ECL-cell histamine. Microinfusion of alpha-fluoromethylhistidine (known to deplete ECL cells but not mast cells of histamine) reduced the histamine-mobilizing effect of endothelin by 80%, while 1-week pretreatment with omeprazole enhanced it, supporting the involvement of ECL cells. Somatostatin or the prostanoid misoprostol inhibited gastrin-, but not endothelin-stimulated histamine release, suggesting that endothelin and gastrin mobilize histamine via different mechanisms. While gastrin effectively mobilized histamine from ECL cells in primary culture, endothelin had no effect, and adrenaline, a modest effect. Hence, the striking effects of endothelin and adrenaline on ECL cells in situ are probably indirect, possibly a consequence of ischemia.
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Affiliation(s)
- M Bernsand
- Department of Pharmacology, Institute of Physiological Sciences, University of Lund, BMC F13, Lund S-221 84, Sweden
| | - P Ericsson
- Department of Pharmacology, Institute of Physiological Sciences, University of Lund, BMC F13, Lund S-221 84, Sweden
| | - M Björkqvist
- Department of Pharmacology, Institute of Physiological Sciences, University of Lund, BMC F13, Lund S-221 84, Sweden
| | - C -M Zhao
- Department of Medical Technology, Faculty of Technology, Sør-Trøndelag University College, Trondheim 7006, Norway
| | - R Håkanson
- Department of Pharmacology, Institute of Physiological Sciences, University of Lund, BMC F13, Lund S-221 84, Sweden
- Author for correspondence:
| | - P Norlén
- Department of Clinical Pharmacology, Lund University Hospital, Lund S-221 85, Sweden
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20
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Ericsson P, Norlén P, Bernsand M, Alm P, Höglund P, Håkanson R. ECL cell histamine mobilization studied by gastric submucosal microdialysis in awake rats: methodological considerations. PHARMACOLOGY & TOXICOLOGY 2003; 93:57-65. [PMID: 12899666 DOI: 10.1034/j.1600-0773.2003.930201.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The ECL cells are endocrine/paracrine cells in the acid-producing part of the stomach. They secrete histamine in response to circulating gastrin. Gastric submucosal microdialysis has been used to study ECL-cell histamine mobilization in awake rats. In the present study we assess the usefulness and limitations of the technique. Microdialysis probes were implanted in the gastric submucosa. Histological analysis of the stomach wall around the probe revealed a moderate, local inflammatory reaction 1-2 days after implantation; the inflammation persisted for at least 10 days. Experiments were conducted 3 days after the implantation. The "true" submucosal histamine concentration was determined by perfusing at different rates (the zero flow method) or with different concentrations of histamine at a constant rate (the no-net-flux method): in fasted rats it was calculated to be 87+/-5 (means+/-S.E.M.) nmol/l and 76+/-9 nmol/l, respectively. The corresponding histamine concentrations in fed rats were 93+/-5 and 102+/-8 nmol/l, respectively. With a perfusion rate of 74 microl/hr the recovery of submucosal histamine was 49%, at 34 microl/hr the recovery increased to 83%. At a perfusion rate below 20 microl/hr the microdialysate histamine concentration was close to the actual concentration in the submucosa. The ECL-cell histamine mobilization was independent of the concentrations of Ca2+ in the perfusion medium (0-3.4 mmol/l Ca2+). In one experiment, histamine mobilization in response to gastrin (10 nmol/kg/hr subcutaneously) was monitored in rats pretreated with prednisolone (60 mg/kg) or indomethacin (15 mg/kg). The two antiinflammatory agents failed to affect the concentration of histamine in the microdialysate either before or during the gastrin challenge, which was in accord with the observation that the inflammatory reaction was modest and that inflammatory cells were relatively few around the probe and in the wall of the probe. In another experiment, rats were given aminoguanidine (10 mg/kg) or metoprine (10 mg/kg) 4 hr before the start of gastrin infusion (5 nmol/kg/hr intravenously). Metoprine (inhibitor of histamine N-methyl transferase) did not affect the microdialysate histamine concentration, while aminoguanidine (inhibitor of diamine oxidase) raised both basal and gastrin-stimulated histamine concentrations. We conclude that microdialysis can be used to monitor changes in the concentration of histamine in the submucosa of the stomach, and that the inflammatory reaction to the probe is moderate and does not affect the submucosal histamine mobilization.
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Affiliation(s)
- Peter Ericsson
- Department of Pharmacology, Institute of Physiological Sciences, University of Lund, Lund, Sweden
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21
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Abstract
Enterochromaffin-like (ECL) cells are neuroendocrine cells in the gastric mucosa that control acid secretion by releasing histamine as a paracrine stimulant. The antral hormone gastrin and the neural messenger pituitary adenylyl cyclase-activating peptide (PACAP) potently stimulate histamine synthesis, storage, and secretion by ECL cells. Histamine is stored in secretory vesicles via V-type ATPases and vesicular monoamine transporters of subtype 2 (VMAT-2). Plasmalemmal calcium entry occurs via L-type calcium channels upon stimulation with secretagogues. K(+) and Cl(-) channels maintain the membrane potential. Calcium-triggered exocytosis of histamine is mediated by interacting SNARE proteins, especially by synaptobrevin and SNAP-25. Dynamins and amphiphysins appear to play a key role in endocytosis. ECL cells are under transcriptional control of various hormones. Gastrin stimulates transcriptional activity of the histidine decarboxylase (HDC), VMAT-2, and chromogranin A promoter by activation of Sp1 elements and CREB. During chronic Helicobacter pylori infection, pro-inflammatory cytokines are released that can also affect ECL cells, thus impairing their secretory function and viability, which can predispose to hypochlorhydria and gastric carcinogenesis.
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Affiliation(s)
- Christian Prinz
- II. Medizinische Klinik, Technische Universität München, D-81675 München, Germany.
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22
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Abstract
Overlapping neural, hormonal, and paracrine pathways finely regulate gastric acid secretion. In rats and guinea pigs, most of the intrinsic neural innervation to the gastric mucosa originates in the myenteric plexus. In contrast, human stomachs have a clearly defined submucosal plexus that contains a variety of transmitters including nitric oxide, vasoactive intestinal peptide (VIP), gastrin-releasing peptide (GRP), substance P, and calcitonin gene-related peptide (CGRP). Although GRP is known to participate in meal-stimulated acid secretion by releasing gastrin in a variety of laboratory animals, recent studies were unable to demonstrate a role for endogenous GRP in meal-stimulated gastrin secretion in humans. Pituitary adenylate cyclase-activating polypeptide (PACAP), a member of the secretin-glucagon-VIP family, has been localized to gastric mucosal neurons and may participate in vagally mediated acid secretion. Two novel peptides, ghrelin and leptin, have been localized to the stomach. Peripheral administration of ghrelin stimulates and of leptin inhibits acid secretion. The binding of secretagogues to parietal cells generates changes in second messengers that regulate the translocation and activation of the proton pump, HK-ATPase. In resting cells, HK-ATPase is contained within cytoplasmic tubulovesicles in an inactive form. At stimulation, the tubulovesicles fuse with the apical canaliculi and the HK-ATPase is incorporated into the apical membrane where it actively pumps H ions in exchange for K. Acute infection with Helicobacter pylori results in hypochlorhydria, whereas chronic infection can cause either hypo- or hyperchlorhydria, depending on the distribution of the infection and the degree of corpus gastritis. Recent studies suggest that inflammatory cytokines, produced in response to the organism, can play a role in the perturbations in acid and gastrin secretion induced by H. pylori.
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Affiliation(s)
- Mitchell L Schubert
- Department of Medicine, Division of Gastroenterology, Medical College of Virginia and McGuire VAMC Richmond, Virginia 23249, USA.
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