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Perisic M, Woolcock K, Hering A, Mendel H, Muttenthaler M. Oxytocin and vasopressin signaling in health and disease. Trends Biochem Sci 2024; 49:361-377. [PMID: 38418338 DOI: 10.1016/j.tibs.2024.01.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Revised: 01/22/2024] [Accepted: 01/26/2024] [Indexed: 03/01/2024]
Abstract
Neurohypophysial peptides are ancient and evolutionarily highly conserved neuropeptides that regulate many crucial physiological functions in vertebrates and invertebrates. The human neurohypophysial oxytocin/vasopressin (OT/VP) signaling system with its four receptors has become an attractive drug target for a variety of diseases, including cancer, pain, cardiovascular indications, and neurological disorders. Despite its promise, drug development faces hurdles, including signaling complexity, selectivity and off-target concerns, translational interspecies differences, and inefficient drug delivery. In this review we dive into the complexity of the OT/VP signaling system in health and disease, provide an overview of relevant pharmacological probes, and discuss the latest trends in therapeutic lead discovery and drug development.
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Affiliation(s)
- Monika Perisic
- Institute of Biological Chemistry, Faculty of Chemistry, University of Vienna, 1090 Vienna, Austria; Vienna Doctoral School in Chemistry, University of Vienna, 1090 Vienna, Austria
| | - Katrina Woolcock
- Institute of Biological Chemistry, Faculty of Chemistry, University of Vienna, 1090 Vienna, Austria
| | - Anke Hering
- Institute for Molecular Bioscience, The University of Queensland, 4072 Brisbane, Australia
| | - Helen Mendel
- Institute for Molecular Bioscience, The University of Queensland, 4072 Brisbane, Australia
| | - Markus Muttenthaler
- Institute of Biological Chemistry, Faculty of Chemistry, University of Vienna, 1090 Vienna, Austria; Institute for Molecular Bioscience, The University of Queensland, 4072 Brisbane, Australia.
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2
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Clemente-Suárez VJ, Martín-Rodríguez A, Redondo-Flórez L, Villanueva-Tobaldo CV, Yáñez-Sepúlveda R, Tornero-Aguilera JF. Epithelial Transport in Disease: An Overview of Pathophysiology and Treatment. Cells 2023; 12:2455. [PMID: 37887299 PMCID: PMC10605148 DOI: 10.3390/cells12202455] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Revised: 10/11/2023] [Accepted: 10/13/2023] [Indexed: 10/28/2023] Open
Abstract
Epithelial transport is a multifaceted process crucial for maintaining normal physiological functions in the human body. This comprehensive review delves into the pathophysiological mechanisms underlying epithelial transport and its significance in disease pathogenesis. Beginning with an introduction to epithelial transport, it covers various forms, including ion, water, and nutrient transfer, followed by an exploration of the processes governing ion transport and hormonal regulation. The review then addresses genetic disorders, like cystic fibrosis and Bartter syndrome, that affect epithelial transport. Furthermore, it investigates the involvement of epithelial transport in the pathophysiology of conditions such as diarrhea, hypertension, and edema. Finally, the review analyzes the impact of renal disease on epithelial transport and highlights the potential for future research to uncover novel therapeutic interventions for conditions like cystic fibrosis, hypertension, and renal failure.
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Affiliation(s)
- Vicente Javier Clemente-Suárez
- Faculty of Sports Sciences, Universidad Europea de Madrid, Tajo Street, s/n, 28670 Madrid, Spain;
- Group de Investigación en Cultura, Educación y Sociedad, Universidad de la Costa, Barranquilla 080002, Colombia
| | | | - Laura Redondo-Flórez
- Department of Health Sciences, Faculty of Biomedical and Health Sciences, Universidad Europea de Madrid, C/Tajo s/n, Villaviciosa de Odón, 28670 Madrid, Spain; (L.R.-F.); (C.V.V.-T.)
| | - Carlota Valeria Villanueva-Tobaldo
- Department of Health Sciences, Faculty of Biomedical and Health Sciences, Universidad Europea de Madrid, C/Tajo s/n, Villaviciosa de Odón, 28670 Madrid, Spain; (L.R.-F.); (C.V.V.-T.)
| | - Rodrigo Yáñez-Sepúlveda
- Faculty of Education and Social Sciences, Universidad Andres Bello, Viña del Mar 2520000, Chile;
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3
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Ren Z, Zhang X, Fan H, Yu Y, Yao S, Wang Y, Dong Y, Deng H, Zuo Z, Deng Y, Wang Y, Xu Z, Deng J. Effects of different dietary protein levels on intestinal aquaporins in weaned piglets. J Anim Physiol Anim Nutr (Berl) 2023; 107:541-555. [PMID: 35586975 DOI: 10.1111/jpn.13732] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 03/01/2022] [Accepted: 04/10/2022] [Indexed: 01/20/2023]
Abstract
This study was conducted to investigate the relationship between changes in intestinal aquaporins (AQPs) in piglets fed diets with different protein levels and nutritional diarrhoea in piglets. Briefly, 96 weaned piglets were randomly divided into four groups fed diets with crude protein (CP) levels of 18%, 20%, 22% and 24%. The small intestines and colons of the weaned piglets were collected, and several experiments were conducted. In the small intestine, AQP4 protein expression was higher in weaned piglets fed the higher-CP diets (22% and 24% CP) than in those fed the 20% CP diet except at 72 h (p < 0.01). At 72 h, the AQP4 protein expression in the small intestine was lower in the 18% group than in the other three groups (p < 0.01). Under 20% CP feeding, AQP2, AQP4 and AQP9 protein expression in the colons of piglets peaked at certain time points. The AQP2 and AQP4 mRNA levels in the colon and the AQP4 and AQP4 mRNA levels in the distal colon were approximately consistent with the protein expression levels. However, the AQP9 mRNA content in the colon was highest in the 18% group, and the AQP2 mRNA content in the distal colon was significantly higher in the 24% group than in the 20% group. AQP2 and AQP4 were expressed mainly around columnar cells in the upper part of the smooth colonic intestinal villi, and AQP9 was expressed mainly on columnar cells and goblet cells in the colonic mucosa. In conclusion, 20% CP is beneficial to the normal expression of AQP4 in the small intestine, AQP2, AQP4 and AQP9 in the colon of weaned piglets, which in turn maintains the balance of intestinal water absorption and secretion in piglets.
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Affiliation(s)
- Zhihua Ren
- College of Veterinary Medicine, Sichuan Agricultural University, Ya'an, Sichuan, P.R. China.,Sichuan Province Key Laboratory of Animal Disease & Human Health, Chengdu, Sichuan, P.R. China.,Key Laboratory of Environmental Hazard and Human Health of Sichuan Province, Chengdu, Sichuan, P.R. China
| | - Xinyue Zhang
- College of Veterinary Medicine, Sichuan Agricultural University, Ya'an, Sichuan, P.R. China.,Sichuan Province Key Laboratory of Animal Disease & Human Health, Chengdu, Sichuan, P.R. China.,Key Laboratory of Environmental Hazard and Human Health of Sichuan Province, Chengdu, Sichuan, P.R. China
| | - Haoyue Fan
- College of Veterinary Medicine, Sichuan Agricultural University, Ya'an, Sichuan, P.R. China.,Sichuan Province Key Laboratory of Animal Disease & Human Health, Chengdu, Sichuan, P.R. China.,Key Laboratory of Environmental Hazard and Human Health of Sichuan Province, Chengdu, Sichuan, P.R. China
| | - Yueru Yu
- College of Veterinary Medicine, Sichuan Agricultural University, Ya'an, Sichuan, P.R. China.,Sichuan Province Key Laboratory of Animal Disease & Human Health, Chengdu, Sichuan, P.R. China.,Key Laboratory of Environmental Hazard and Human Health of Sichuan Province, Chengdu, Sichuan, P.R. China
| | - Shuhua Yao
- College of Veterinary Medicine, Sichuan Agricultural University, Ya'an, Sichuan, P.R. China.,Sichuan Province Key Laboratory of Animal Disease & Human Health, Chengdu, Sichuan, P.R. China.,Key Laboratory of Environmental Hazard and Human Health of Sichuan Province, Chengdu, Sichuan, P.R. China
| | - Yuqian Wang
- College of Veterinary Medicine, Sichuan Agricultural University, Ya'an, Sichuan, P.R. China.,Sichuan Province Key Laboratory of Animal Disease & Human Health, Chengdu, Sichuan, P.R. China.,Key Laboratory of Environmental Hazard and Human Health of Sichuan Province, Chengdu, Sichuan, P.R. China
| | - Yanqiang Dong
- College of Veterinary Medicine, Sichuan Agricultural University, Ya'an, Sichuan, P.R. China.,Sichuan Province Key Laboratory of Animal Disease & Human Health, Chengdu, Sichuan, P.R. China.,Key Laboratory of Environmental Hazard and Human Health of Sichuan Province, Chengdu, Sichuan, P.R. China
| | - Huidan Deng
- College of Veterinary Medicine, Sichuan Agricultural University, Ya'an, Sichuan, P.R. China.,Sichuan Province Key Laboratory of Animal Disease & Human Health, Chengdu, Sichuan, P.R. China.,Key Laboratory of Environmental Hazard and Human Health of Sichuan Province, Chengdu, Sichuan, P.R. China
| | - Zhicai Zuo
- College of Veterinary Medicine, Sichuan Agricultural University, Ya'an, Sichuan, P.R. China.,Sichuan Province Key Laboratory of Animal Disease & Human Health, Chengdu, Sichuan, P.R. China.,Key Laboratory of Environmental Hazard and Human Health of Sichuan Province, Chengdu, Sichuan, P.R. China
| | - Youtian Deng
- College of Veterinary Medicine, Sichuan Agricultural University, Ya'an, Sichuan, P.R. China.,Sichuan Province Key Laboratory of Animal Disease & Human Health, Chengdu, Sichuan, P.R. China.,Key Laboratory of Environmental Hazard and Human Health of Sichuan Province, Chengdu, Sichuan, P.R. China
| | - Ya Wang
- College of Veterinary Medicine, Sichuan Agricultural University, Ya'an, Sichuan, P.R. China.,Sichuan Province Key Laboratory of Animal Disease & Human Health, Chengdu, Sichuan, P.R. China.,Key Laboratory of Environmental Hazard and Human Health of Sichuan Province, Chengdu, Sichuan, P.R. China
| | - Zhiwen Xu
- College of Veterinary Medicine, Sichuan Agricultural University, Ya'an, Sichuan, P.R. China.,Sichuan Province Key Laboratory of Animal Disease & Human Health, Chengdu, Sichuan, P.R. China.,Key Laboratory of Environmental Hazard and Human Health of Sichuan Province, Chengdu, Sichuan, P.R. China
| | - Junliang Deng
- College of Veterinary Medicine, Sichuan Agricultural University, Ya'an, Sichuan, P.R. China.,Sichuan Province Key Laboratory of Animal Disease & Human Health, Chengdu, Sichuan, P.R. China.,Key Laboratory of Environmental Hazard and Human Health of Sichuan Province, Chengdu, Sichuan, P.R. China
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Ikarashi N, Nagoya C, Kon R, Kitaoka S, Kajiwara S, Saito M, Kawabata A, Ochiai W, Sugiyama K. Changes in the Expression of Aquaporin-3 in the Gastrointestinal Tract Affect Drug Absorption. Int J Mol Sci 2019; 20:ijms20071559. [PMID: 30925715 PMCID: PMC6479729 DOI: 10.3390/ijms20071559] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 03/25/2019] [Accepted: 03/26/2019] [Indexed: 02/07/2023] Open
Abstract
Aquaporin-3 (AQP3) plays an important role in water transport in the gastrointestinal (GI) tract. In this study, we conducted a Caco-2 cell permeability assay to examine how changes in the expression and function of AQP3 affect the rate at which a drug is absorbed via passive transport in the GI tract. When the function of AQP3 was inhibited by mercuric chloride or phloretin, there was no change in warfarin permeability. In contrast, when the expression of AQP3 protein was decreased by prostaglandin E₂ (PGE₂) treatment, warfarin permeability increased to approximately twice the control level, and membrane fluidity increased by 15%. In addition, warfarin permeability increased to an extent comparable to that after PGE₂ treatment when cell membrane fluidity was increased by 10% via boric acid/EDTA treatment. These findings suggest the possibility that the increased drug absorption under decreased AQP3 expression was attributable to increased membrane fluidity. The results of this study demonstrate that the rate of water transport has little effect on drug absorption. However, our findings also indicate that although AQP3 and other similar transmembrane proteins do not themselves transport drugs, changes in their expression levels can cause changes in cell membrane fluidity, thus affecting drug absorption rates.
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Affiliation(s)
- Nobutomo Ikarashi
- Department of Biomolecular Pharmacology, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
| | - Chika Nagoya
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
| | - Risako Kon
- Department of Biomolecular Pharmacology, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
| | - Satoshi Kitaoka
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
| | - Sayuri Kajiwara
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
| | - Masayo Saito
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
| | - Akane Kawabata
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
| | - Wataru Ochiai
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
| | - Kiyoshi Sugiyama
- Department of Functional Molecular Kinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
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Downregulation of Aquaporin 3 Mediated the Laxative Effect in the Rat Colon by a Purified Resin Glycoside Fraction from Pharbitis Semen. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2019; 2019:9406342. [PMID: 30733814 PMCID: PMC6348868 DOI: 10.1155/2019/9406342] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Revised: 11/27/2018] [Accepted: 12/30/2018] [Indexed: 02/07/2023]
Abstract
Background Pharbitis Semen, the seeds of Pharbitis nil, is widely used as a traditional purgative medicine in China, Korea, and Japan. This study investigated the laxative effects of a purified resin glycoside fraction obtained in our previous study from Pharbitis Semen in vivo and in vitro. Materials and Methods After orally administering a purified resin glycoside fraction from Pharbitis Semen (RFP) to rats, the content of fecal water, AQP3, NF-κB, COX-2 expression, and the prostaglandin E2 (PGE2) concentrations in the colon were examined. Moreover, human intestinal epithelial cells (HT-29) were used to investigate the mechanism of RFP decreasing the AQP3 expression. Results Results obtained showed that treatment with RFP increased the feces excretion and fecal water content of rats in a dose-dependent manner. More interestingly, AQP3 expression was suppressed by RFP treatment both in the rat colons and in HT-29 cells, while the NF-κB pathway-mediated PGE2 production was activated. Interestingly, pretreating rats with BAY-11-7082 (NF-κB inhibitor) or indomethacin (COX-2 inhibitor) and RFP neither induced diarrhea nor decreased the AQP3 expression in the colon. Conclusions The purgative property of the purified resin glycoside fraction was attributed to NF-κB activation in the colon, which increased the COX-2-mediated secretion of PGE2. PGE2 decreased AQP3 expression which inhibits water absorbed from the intestine to the blood vessel side, resulting in the laxative effect of RFP.
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Zhai X, Lin D, Zhao Y, Yang X. Bacterial Cellulose Relieves Diphenoxylate-Induced Constipation in Rats. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2018; 66:4106-4117. [PMID: 29627986 DOI: 10.1021/acs.jafc.8b00385] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
This study was to probe the effects of bacterial cellulose (BC) on diphenoxylate-induced constipation in rats. Administration with BC at 500 mg/kg of body weight in diphenoxylate-induced constipation rats distinctly improved the carmine propulsion rate (83.5 ± 5.2%), shortened the defecating time of the first red feces (249.0 ± 23.3 min), and increased the weight of carmine red feces within 5 h (2.7 ± 1.3 g). The levels of aquaporins (AQP-2, AQP-3, and AQP-4) and inhibitory neurotransmitters (nitric oxide, nitric oxide synthetase, vasoactive intestinal peptide, and arginine vasopressin) in the BC-treated groups reduced by 31.9-40.0% ( p < 0.01) and 21.1-67.7% ( p < 0.01) compared to those in the constipation group, respectively. However, the secretion of excitability neurotransmitters (substance P and motilin) in the BC-treated groups was increased by 20.0-39.9% ( p < 0.01). The activities of ATPases in the colon of constipation rats were significantly weakened by BC administration ( p < 0.01). Histological morphology of the colon showed that BC supplementation could effectively increase the length of villus cells and the thickness of colonic mucosa and muscle ( p < 0.01). Moreover, BC supplementation could protect colonic smooth muscle cells against apoptosis. All of the findings suggest that BC supplementation effectively relieves constipation in rats and BC would be used as a great promising dietary fiber for alleviating constipation.
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Kon R, Tsubota Y, Minami M, Kato S, Matsunaga Y, Kimura H, Murakami Y, Fujikawa T, Sakurai R, Tomimoto R, Machida Y, Ikarashi N, Sugiyama K. CPT-11-Induced Delayed Diarrhea Develops via Reduced Aquaporin-3 Expression in the Colon. Int J Mol Sci 2018; 19:ijms19010170. [PMID: 29316651 PMCID: PMC5796119 DOI: 10.3390/ijms19010170] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Revised: 12/19/2017] [Accepted: 12/31/2017] [Indexed: 02/08/2023] Open
Abstract
While irinotecan (CPT-11) has a potent anti-cancer effect, it also causes serious diarrhea as an adverse reaction. In this study, we analyzed the pathogenic mechanism of CPT-11-induced delayed diarrhea by focusing on water channel aquaporin-3 (AQP3) in the colon. When rats received CPT-11, the expression level of AQP3 was reduced during severe diarrhea. It was found that the expression levels of inflammatory cytokines and the loss of crypt cells were increased in the colon when CPT-11 was administered. When celecoxib, an anti-inflammatory drug, was concomitantly administered, both the diarrhea and the reduced expression of AQP3 induced by CPT-11 were suppressed. The inflammation in the rat colon during diarrhea was caused via activated macrophage by CPT-11. These results showed that when CPT-11 is administered, the expression level of AQP3 in the colon is reduced, resulting in delayed diarrhea by preventing water transport from the intestinal tract. It was also suggested that the reduced expression of AQP3 might be due to the inflammation that occurs following the loss of colonic crypt cells and to the damage caused by the direct activation of macrophages by CPT-11. Therefore, it was considered that anti-inflammatory drugs that suppress the reduction of AQP3 expression could prevent CPT-11-induced delayed diarrhea.
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Affiliation(s)
- Risako Kon
- Global Research Center for Innovative Life Science, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
| | - Yuika Tsubota
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
| | - Moe Minami
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
| | - Saki Kato
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
| | - Yukari Matsunaga
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
| | - Hiroshi Kimura
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
| | - Yuta Murakami
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
| | - Tetsuya Fujikawa
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
| | - Ryoya Sakurai
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
| | - Rei Tomimoto
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
| | - Yoshiaki Machida
- Division of Applied Pharmaceutical Education and Research, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
| | - Nobutomo Ikarashi
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
| | - Kiyoshi Sugiyama
- Department of Functional Molecular Kinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
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Expression, Distribution and Role of Aquaporin Water Channels in Human and Animal Stomach and Intestines. Int J Mol Sci 2016; 17:ijms17091399. [PMID: 27589719 PMCID: PMC5037679 DOI: 10.3390/ijms17091399] [Citation(s) in RCA: 95] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Revised: 08/09/2016] [Accepted: 08/22/2016] [Indexed: 12/22/2022] Open
Abstract
Stomach and intestines are involved in the secretion of gastrointestinal fluids and the absorption of nutrients and fluids, which ensure normal gut functions. Aquaporin water channels (AQPs) represent a major transcellular route for water transport in the gastrointestinal tract. Until now, at least 11 AQPs (AQP1–11) have been found to be present in the stomach, small and large intestines. These AQPs are distributed in different cell types in the stomach and intestines, including gastric epithelial cells, gastric glands cells, absorptive epithelial cells (enterocytes), goblet cells and Paneth cells. AQP1 is abundantly distributed in the endothelial cells of the gastrointestinal tract. AQP3 and AQP4 are mainly distributed in the basolateral membrane of epithelial cells in the stomach and intestines. AQP7, AQP8, AQP10 and AQP11 are distributed in the apical of enterocytes in the small and large intestines. Although AQP-null mice displayed almost no phenotypes in gastrointestinal tracts, the alterations of the expression and localization of these AQPs have been shown to be associated with the pathology of gastrointestinal disorders, which suggests that AQPs play important roles serving as potential therapeutic targets. Therefore, this review provides an overview of the expression, localization and distribution of AQPs in the stomach, small and large intestine of human and animals. Furthermore, this review emphasizes the potential roles of AQPs in the physiology and pathophysiology of stomach and intestines.
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Pelagalli A, Squillacioti C, Mirabella N, Meli R. Aquaporins in Health and Disease: An Overview Focusing on the Gut of Different Species. Int J Mol Sci 2016; 17:ijms17081213. [PMID: 27472320 PMCID: PMC5000611 DOI: 10.3390/ijms17081213] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Revised: 07/14/2016] [Accepted: 07/14/2016] [Indexed: 12/11/2022] Open
Abstract
Aquaporins (AQPs) play a pivotal role in gut homeostasis since their distribution and function is modulated both in physiological and in pathophysiological conditions. The transport of water and solutes through gut epithelia is essential for osmoregulation and digestive and absorptive functions. This passage is regulated by different AQP isoforms and characterized by their peculiar distribution in the gastrointestinal tract. To date, AQP localization has been identified in the gut and associated organs of several mammalian species by different techniques (immunohistochemical, western blotting, and RT-PCR). The present review describes the modulation of AQP expression, distribution, and function in gut pathophysiology. At the same time, the comparative description of AQP in animal species sheds light on the full range of AQP functions and the screening of their activity as transport modulators, diagnostic biomarkers, and drug targets. Moreover, the phenotype of knockout mice for several AQPs and their compensatory role and the use of specific AQP inhibitors have been also reviewed. The reported data could be useful to design future research in both basic and clinical fields.
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Affiliation(s)
- Alessandra Pelagalli
- Department of Advanced Biomedical Sciences, University of Naples "Federico II", Via Pansini 5, 80131 Naples, Italy.
- Institute of Biostructures and Bioimages, National Research Council, Via De Amicis 95, 80131 Naples, Italy.
| | - Caterina Squillacioti
- Department of Veterinary Medicine and Animal Productions, University of Naples "Federico II", Via Veterinaria 1, 80137 Naples, Italy.
| | - Nicola Mirabella
- Department of Veterinary Medicine and Animal Productions, University of Naples "Federico II", Via Veterinaria 1, 80137 Naples, Italy.
| | - Rosaria Meli
- Department of Pharmacy, University of Naples "Federico II", Via D. Montesano 49, 80131 Naples, Italy.
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Ikarashi N, Kon R, Sugiyama K. Aquaporins in the Colon as a New Therapeutic Target in Diarrhea and Constipation. Int J Mol Sci 2016; 17:ijms17071172. [PMID: 27447626 PMCID: PMC4964543 DOI: 10.3390/ijms17071172] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 07/12/2016] [Accepted: 07/14/2016] [Indexed: 12/29/2022] Open
Abstract
Aquaporins (AQPs) play important roles in the water transport system in the human body. There are currently 13 types of AQP, AQP0 through AQP12, which are expressed in various organs. Many members of the AQP family are expressed in the intestinal tract. AQP3 is predominantly expressed in the colon, ultimately controlling the water transport. Recently, it was clarified that several laxatives exhibit a laxative effect by changing the AQP3 expression level in the colon. In addition, it was revealed that morphine causes severe constipation by increasing the AQP3 expression level in the colon. These findings have shown that AQP3 is one of the most important functional molecules in water transport in the colon. This review will focus on the physiological and pathological roles of AQP3 in the colon, and discuss clinical applications of colon AQP3.
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Affiliation(s)
- Nobutomo Ikarashi
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
| | - Risako Kon
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
| | - Kiyoshi Sugiyama
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
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Abstract
Desert rodents face a sizeable challenge in maintaining salt and water homeostasis due to their life in an arid environment. A number of their organ systems exhibit functional characteristics that limit water loss above that which occurs in non-desert species under similar conditions. These systems include renal, pulmonary, gastrointestinal, nasal, and skin epithelia. The desert rodent kidney preserves body water by producing a highly concentrated urine that reaches a maximum osmolality nearly three times that of the common laboratory rat. The precise mechanism by which urine is concentrated in any mammal is unknown. Insights into the process may be more apparent in species that produce highly concentrated urine. Aquaporin water channels play a fundamental role in water transport in several desert rodent organ systems. The role of aquaporins in facilitating highly effective water preservation in desert rodents is only beginning to be explored. The organ systems of desert rodents and their associated AQPs are described.
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Affiliation(s)
- Thomas L Pannabecker
- Department of Physiology, AHSC 4128, University of Arizona Health Sciences Center, 1501 N. Campbell Avenue, Tucson, Arizona 85724-5051
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12
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Kon R, Ikarashi N, Hayakawa A, Haga Y, Fueki A, Kusunoki Y, Tajima M, Ochiai W, Machida Y, Sugiyama K. Morphine-Induced Constipation Develops With Increased Aquaporin-3 Expression in the Colon via Increased Serotonin Secretion. Toxicol Sci 2015; 145:337-47. [PMID: 25766885 DOI: 10.1093/toxsci/kfv055] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Aquaporin-3 (AQP3) is a water channel that is predominantly expressed in the colon, where it plays a critical role in the regulation of fecal water content. This study investigated the role of AQP3 in the colon in morphine-induced constipation. AQP3 expression levels in the colon were analyzed after oral morphine administration to rats. The degree of constipation was analyzed after the combined administration of HgCl(2) (AQP3 inhibitor) or fluoxetine (5-HT reuptake transporter [SERT] inhibitor) and morphine. The mechanism by which morphine increased AQP3 expression was examined in HT-29 cells. AQP3 expression levels in rat colon were increased during morphine-induced constipation. The combination of HgCl(2) and morphine improved morphine-induced constipation. Treatment with morphine in HT-29 cells did not change AQP3 expression. However, 5-HT treatment significantly increased the AQP3 expression level and the nuclear translocation of peroxisome proliferator-activated receptor gamma (PPARγ) 1 h after treatment. Pretreatment with fluoxetine significantly suppressed these increases. Fluoxetine pretreatment suppressed the development of morphine-induced constipation and the associated increase in AQP3 expression in the colon. The results suggest that morphine increases the AQP3 expression level in the colon, which promotes water absorption from the luminal side to the vascular side and causes constipation. This study also showed that morphine-induced 5-HT secreted from the colon was taken into cells by SERT and activated PPARγ, which subsequently increased AQP3 expression levels.
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Affiliation(s)
- Risako Kon
- Department of Clinical Pharmacokinetics, Hoshi University, Tokyo, Japan; and Division of Applied Pharmaceutical Education and Research, Hoshi University, Tokyo, Japan
| | - Nobutomo Ikarashi
- Department of Clinical Pharmacokinetics, Hoshi University, Tokyo, Japan; and Division of Applied Pharmaceutical Education and Research, Hoshi University, Tokyo, Japan Department of Clinical Pharmacokinetics, Hoshi University, Tokyo, Japan; and Division of Applied Pharmaceutical Education and Research, Hoshi University, Tokyo, Japan
| | - Akio Hayakawa
- Department of Clinical Pharmacokinetics, Hoshi University, Tokyo, Japan; and Division of Applied Pharmaceutical Education and Research, Hoshi University, Tokyo, Japan
| | - Yusuke Haga
- Department of Clinical Pharmacokinetics, Hoshi University, Tokyo, Japan; and Division of Applied Pharmaceutical Education and Research, Hoshi University, Tokyo, Japan
| | - Aika Fueki
- Department of Clinical Pharmacokinetics, Hoshi University, Tokyo, Japan; and Division of Applied Pharmaceutical Education and Research, Hoshi University, Tokyo, Japan
| | - Yoshiki Kusunoki
- Department of Clinical Pharmacokinetics, Hoshi University, Tokyo, Japan; and Division of Applied Pharmaceutical Education and Research, Hoshi University, Tokyo, Japan
| | - Masataka Tajima
- Department of Clinical Pharmacokinetics, Hoshi University, Tokyo, Japan; and Division of Applied Pharmaceutical Education and Research, Hoshi University, Tokyo, Japan
| | - Wataru Ochiai
- Department of Clinical Pharmacokinetics, Hoshi University, Tokyo, Japan; and Division of Applied Pharmaceutical Education and Research, Hoshi University, Tokyo, Japan
| | - Yoshiaki Machida
- Department of Clinical Pharmacokinetics, Hoshi University, Tokyo, Japan; and Division of Applied Pharmaceutical Education and Research, Hoshi University, Tokyo, Japan
| | - Kiyoshi Sugiyama
- Department of Clinical Pharmacokinetics, Hoshi University, Tokyo, Japan; and Division of Applied Pharmaceutical Education and Research, Hoshi University, Tokyo, Japan
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Rhubarb tannins extract inhibits the expression of aquaporins 2 and 3 in magnesium sulphate-induced diarrhoea model. BIOMED RESEARCH INTERNATIONAL 2014; 2014:619465. [PMID: 25215286 PMCID: PMC4151595 DOI: 10.1155/2014/619465] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Revised: 07/14/2014] [Accepted: 07/21/2014] [Indexed: 01/29/2023]
Abstract
Tannins, a group of major active components of Chinese rhubarb and widely distributed in nature, have a significant antidiarrhoeal activity. Aquaporins (AQPs) 2 and 3 play important roles in regulating water transfer during diarrhoea. The present study aims to determine the effect of the total tannins extract of rhubarb on aquaporins (AQPs) 2 and 3 in diarrhoea mice and HT-29 cells both induced by magnesium sulphate (MgSO4). Our results showed that rhubarb tannins extract (RTE) significantly decreased the faecal water content in colon and evaluation index of defecation of diarrhoea mice. Interestingly, RTE could markedly reduce the mRNA and protein expression levels of AQPs 2 and 3 in apical and lateral mucosal epithelial cells in the colons of diarrhoea mice and HT-29 cells both induced by MgSO4 in a dose-dependent manner. Furthermore, RTE suppressed the production of cyclic monophosphate- (cAMP-) dependent protein kinase A catalytic subunits α (PKA C-α) and phosphorylated cAMP response element-binding protein (p-CREB, Ser133) in MgSO4-induced HT-29 cells. Our data showed for the first time that RTE inhibit AQPs 2 and 3 expression in vivo and in vitro via downregulating PKA/p-CREB signal pathway, which accounts for the antidiarrhoeal effect of RTE.
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Miró L, Pérez-Bosque A, Maijó M, Naftalin RJ, Moretó M. Vasopressin regulation of epithelial colonic proliferation and permeability is mediated by pericryptal platelet-derived growth factor A. Exp Physiol 2014; 99:1325-34. [PMID: 25085844 DOI: 10.1113/expphysiol.2014.080952] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Arginine vasopressin (AVP) has trophic effects on the rat distal colon, increasing the growth of pericryptal myofibroblasts and reducing the colonic crypt wall permeability. This study aimed to reproduce in vitro the effects of AVP observed in vivo using cultures of human CCD-18Co myofibroblasts and T84 colonic epithelial cells. Proliferation of myofibroblasts was quantified by bromodeoxyuridine incorporation; the expression of platelet-derived growth factor A (PDGFA), platelet-derived growth factor B, epidermal growth factor, transforming growth factor-β and vascular endothelial growth factor was measured by PCR and the expression of epithelial junction proteins by Western blot. Arginine vasopressin stimulated myofibroblast proliferation and the expression of PDGFA without affecting the expression of platelet-derived growth factor B, epidermal growth factor, transforming growth factor-β or vascular endothelial growth factor. These effects were prevented when AVP receptor inhibitors were present in the medium. Pre-incubation of CCD-18Co cells with anti-PDGF antibody or with an inhibitor of the PDGF receptor abolished the effects of AVP. When colonocytes were incubated with medium obtained from myofibroblasts incubated with AVP, both cell proliferation and the expression of epithelial junction proteins increased; however, direct incubation of colonocytes with AVP did not modify these variables. These results demonstrate that AVP stimulates myofibroblast proliferation and induces PDGFA secretion, implying that PDGFA mediates local myofibroblast proliferation by an autocrine feedback loop and regulates epithelial proliferation and permeability by a paracrine mechanism.
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Affiliation(s)
- Lluïsa Miró
- Departament de Fisiologia, Facultat de Farmàcia, Universitat de Barcelona (UB), Barcelona, Spain
| | - Anna Pérez-Bosque
- Departament de Fisiologia, Facultat de Farmàcia, Universitat de Barcelona (UB), Barcelona, Spain
| | - Mònica Maijó
- Departament de Fisiologia, Facultat de Farmàcia, Universitat de Barcelona (UB), Barcelona, Spain
| | | | - Miquel Moretó
- Departament de Fisiologia, Facultat de Farmàcia, Universitat de Barcelona (UB), Barcelona, Spain
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15
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Zheng YF, Liu CF, Lai WF, Xiang Q, Li ZF, Wang H, Lin N. The laxative effect of emodin is attributable to increased aquaporin 3 expression in the colon of mice and HT-29 cells. Fitoterapia 2014; 96:25-32. [DOI: 10.1016/j.fitote.2014.04.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Revised: 03/28/2014] [Accepted: 04/01/2014] [Indexed: 12/01/2022]
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16
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Kon R, Ikarashi N, Nagoya C, Takayama T, Kusunoki Y, Ishii M, Ueda H, Ochiai W, Machida Y, Sugita K, Sugiyama K. Rheinanthrone, a metabolite of sennoside A, triggers macrophage activation to decrease aquaporin-3 expression in the colon, causing the laxative effect of rhubarb extract. JOURNAL OF ETHNOPHARMACOLOGY 2014; 152:190-200. [PMID: 24412547 DOI: 10.1016/j.jep.2013.12.055] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Revised: 12/26/2013] [Accepted: 12/31/2013] [Indexed: 06/03/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Aquaporin-3 (AQP3) is expressed in mucosal epithelial cells in the colon and is important for regulating fecal water content. We examined the role of AQP3 in the laxative effect of rhubarb extract. METHODS After orally administering rhubarb extract or its major component (sennoside A) to rats, the fecal water content, AQP3 expression and prostaglandin E2 (PGE2) concentrations in the colon were examined. The mechanism by which sennoside A decreases the expression of AQP3 was examined using the human colon cancer HT-29 cells and macrophage-derived Raw264.7 cells. RESULTS During diarrhea by rhubarb extract administration, the PGE2 levels in the colon increased while the AQP3 expression significantly decreased. Similar changes were also observed when sennoside A was administered. When sennoside A or its metabolites, rheinanthrone and rhein were added to Raw264.7 cells, a significant increase in the PGE2 concentration was observed only in cells treated with rheinanthrone. Fifteen minutes after adding PGE2 to the HT-29 cells, the AQP3 expression decreased to approximately 40% of the control. When pretreated with indomethacin, sennoside A neither decreased the AQP3 expression nor induced diarrhea. CONCLUSIONS Sennoside A may decrease AQP3 expression in the colon to inhibit water transport from the luminal to the vascular side, leading to a laxative effect. The decreases in the levels of AQP3 are caused by rheinanthrone, which is a metabolite of sennoside A, this metabolite activates the macrophages in the colon and increases the secretion of PGE2; PGE2 acts as a paracrine factor and decreases AQP3 expression in colon mucosal epithelial cells.
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Affiliation(s)
- Risako Kon
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan
| | - Nobutomo Ikarashi
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan
| | - Chika Nagoya
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan
| | | | - Yoshiki Kusunoki
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan
| | - Makoto Ishii
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan
| | - Harumi Ueda
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan
| | - Wataru Ochiai
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan
| | - Yoshiaki Machida
- Division of Applied Pharmaceutical Education and Research, Hoshi University, Japan
| | | | - Kiyoshi Sugiyama
- Department of Clinical Pharmacokinetics, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
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17
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Zhao G, Li J, Wang J, Shen X, Sun J. Aquaporin 3 and 8 are down-regulated in TNBS-induced rat colitis. Biochem Biophys Res Commun 2013; 443:161-6. [PMID: 24286754 DOI: 10.1016/j.bbrc.2013.11.067] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Accepted: 11/16/2013] [Indexed: 12/15/2022]
Abstract
Aquaporins (AQPs) plays an important role in transcellular water movement, but the AQPs expression profile has not been demonstrated in 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis which closely mimics human Crohn's disease (CD) histopathologically. To solve the problem, 30 female Sprague-Dawley (SD) rats were randomly divided into a model group (n=18), an ethanol control group (n=6) and a normal control group (n=6). On day 1, the rats in the model group received TNBS+50% ethanol via the rectum, while the ethanol control rats received an equal volume of 50% ethanol and the normal control rats did not receive any treatment. All rats were sacrificed on day 7, and ileum, proximal colon and distal colon specimens were obtained to examine the alteration in AQP3 and AQP8 using real-time polymerase chain reaction, Western blot analysis and immunohistochemistry. As a result, exposure to TNBS+ethanol resulted in a marked decrease in both the mRNA and protein expression of AQP3 and AQP8, with the exception of AQP8 protein which was negative in the distal colon in all three groups. These reductions in AQP3 and AQP8 were accompanied by an increase in intestinal inflammation and injury. The results obtained here implied that both AQP3 and AQP8 may be involved in the pathogenesis of inflammatory bowel disease.
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Affiliation(s)
- Guangxi Zhao
- Department of Gastroenterology, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Jing Li
- Department of Gastroenterology, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Jiyao Wang
- Department of Gastroenterology, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Xizhong Shen
- Department of Gastroenterology, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Jianyong Sun
- Department of Gastroenterology, Zhongshan Hospital, Fudan University, Shanghai, China.
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18
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Ikarashi N, Kon R, Iizasa T, Suzuki N, Hiruma R, Suenaga K, Toda T, Ishii M, Hoshino M, Ochiai W, Sugiyama K. Inhibition of aquaporin-3 water channel in the colon induces diarrhea. Biol Pharm Bull 2012; 35:957-62. [PMID: 22687538 DOI: 10.1248/bpb.35.957] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Aquaporin (AQP) 3, which is predominantly expressed in the colon, is considered to play an important role in regulating the fecal water content in the colon. In this study, the role of AQP3 in the colon was examined using HgCl(2) and CuSO(4), which are known to inhibit AQP3 function. The fecal water content was measured up to 1 h after the rectal administration of HgCl(2) or CuSO(4) to rats. The results showed that the fecal water content in the HgCl(2) administration group increased significantly to approximately 4 times that in the control group, and severe diarrhea was observed. However, no changes were observed in the mRNA expression level of the osmoregulatory genes (sodium myo-inositol transporter and taurine transporter) and the level and distribution of AQP3 protein expression, as determined 1 h after the administration of HgCl(2). Comparable results were observed in the CuSO(4) administration group. The results of this study indicated that the inhibition of AQP3 function in the colon caused diarrhea. Therefore, it has been revealed that the fecal water content in the colon is controlled by the transport of water from the luminal side to the vascular side, which is mediated by AQP3. Our findings suggest that a drug that modulates the function or expression of AQP3 in the colon may represent a new target for the development of laxatives.
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Affiliation(s)
- Nobutomo Ikarashi
- Department of Clinical Pharmacokinetics, Hoshi University, Shinagawa-ku, Tokyo, Japan
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19
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Ikarashi N, Ushiki T, Mochizuki T, Toda T, Kudo T, Baba K, Ishii M, Ito K, Ochiai W, Sugiyama K. Effects of magnesium sulphate administration on aquaporin 3 in rat gastrointestinal tract. Biol Pharm Bull 2011; 34:238-42. [PMID: 21415534 DOI: 10.1248/bpb.34.238] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Aquaporin (AQP) 3 plays an important role in regulating faecal water content in the colon. We investigated the role of AQP3 in the colon in the laxative effect of magnesium sulphate (MgSO(4)), a widely used osmotic laxative. Rats were administered MgSO(4), after which faecal water content, the colon mRNA expression levels of sodium myo-inositol transporter (SMIT) and taurine transporter (TauT), the colon protein expression levels of AQP3 were examined. Faecal water content increased over time after MgSO(4) administration, and severe diarrhoea was observed between 4 and 8 h after administration. The mRNA expression levels of SMIT and TauT, which are indicators of variations in osmotic pressure, were highest at 2 h after the administration of MgSO(4) and were still elevated at 8 h after administration when compared to immediately after the administration. The immunostaining analysis showed that AQP3 is a dominant AQP in the rat colon. The protein expression levels of AQP3 in the colon increased over time following the administration of MgSO(4) and at 8 h after administration were approximately 8 times higher than baseline levels. Previously, osmotic laxatives were believed to induce diarrhoea by elevating the osmotic pressure in the intestinal tract. The results of the present study suggest that the laxative effect of MgSO(4) is not simply caused by a change in the osmotic pressure in the intestinal tract, but could be a response to increased expression of AQP3.
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Affiliation(s)
- Nobutomo Ikarashi
- Department of Clinical Pharmacokinetics, School of Pharmacy and Pharmaceutical Sciences, Hoshi University, 2–4–41 Ebara, Shinagawa-ku, Tokyo 142–8501, Japan
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20
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Ikarashi N, Baba K, Ushiki T, Kon R, Mimura A, Toda T, Ishii M, Ochiai W, Sugiyama K. The laxative effect of bisacodyl is attributable to decreased aquaporin-3 expression in the colon induced by increased PGE2 secretion from macrophages. Am J Physiol Gastrointest Liver Physiol 2011; 301:G887-95. [PMID: 21868635 DOI: 10.1152/ajpgi.00286.2011] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The purpose of this study was to investigate the role of aquaporin3 (AQP3) in the colon in the laxative effect of bisacodyl. After oral administration of bisacodyl to rats, AQP3, macrophages, cyclooxygenase 2 (COX2), and prostaglandin E(2) (PGE(2)) were examined in the colon. The mechanism by which bisacodyl decreases the expression of AQP3 was examined using HT-29 and Raw264.7 cells. When diarrhea occurred, a significant increase in the expression of PGE(2) and a decrease in AQP3 expression were observed. Immunostaining showed COX2 expression only in macrophages. The PGE(2) concentration increased significantly 30 min after the addition of bisacodyl to Raw264.7 cells. Thirty minutes after PGE(2) addition to HT-29 cells, the AQP3 expression level decreased to 40% of the control. When pretreated with indomethacin, bisacodyl did not induce an increase in the colon PGE(2) level, a decrease in the AQP3 expression level, or diarrhea. The results suggest that bisacodyl may decrease the expression of AQP3 in the colon, which inhibits water transfer from the luminal to the vascular side and leads to a laxative effect. This study also showed that direct activation of colon macrophages by bisacodyl increases the secretion of PGE(2), which acts as a paracrine factor and decreases AQP3 expression in colon mucosal epithelial cells.
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Affiliation(s)
- Nobutomo Ikarashi
- Department of Clinical Pharmacokinetics, Hoshi University, Tokyo, Japan
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21
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Moeller HB, Olesen ETB, Fenton RA. Regulation of the water channel aquaporin-2 by posttranslational modification. Am J Physiol Renal Physiol 2011; 300:F1062-73. [DOI: 10.1152/ajprenal.00721.2010] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The cellular functions of many eukaryotic membrane proteins, including the vasopressin-regulated water channel aquaporin-2 (AQP2), are regulated by posttranslational modifications. In this article, we discuss the experimental discoveries that have advanced our understanding of how posttranslational modifications affect AQP2 function, especially as they relate to the role of AQP2 in the kidney. We review the most recent data demonstrating that glycosylation and, in particular, phosphorylation and ubiquitination are mechanisms that regulate AQP2 activity, subcellular sorting and distribution, degradation, and protein interactions. From a clinical perspective, posttranslational modification resulting in protein misrouting or degradation may explain certain forms of nephrogenic diabetes insipidus. In addition to providing major insight into the function and dynamics of renal AQP2 regulation, the analysis of AQP2 posttranslational modification may provide general clues as to the role of posttranslational modification for regulation of other membrane proteins.
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Affiliation(s)
- Hanne B. Moeller
- The Water and Salt Research Center, Department of Anatomy, Aarhus University, Aarhus, Denmark
| | - Emma T. B. Olesen
- The Water and Salt Research Center, Department of Anatomy, Aarhus University, Aarhus, Denmark
| | - Robert A. Fenton
- The Water and Salt Research Center, Department of Anatomy, Aarhus University, Aarhus, Denmark
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22
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Ferrier L, Serradeil-Le Gal C, Schulte AM, Vasina V, Gaultier E, Schroedel S, Ursino MG, Chaumaz G, Pascal M, De Ponti F, Bueno L. Proinflammatory role of vasopressin through V1b receptors in hapten-induced experimental colitis in rodents: implication in IBD. Am J Physiol Gastrointest Liver Physiol 2010; 299:G1298-307. [PMID: 20864658 DOI: 10.1152/ajpgi.00022.2010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Vasopressin and its receptors modulate several gut functions, but their role in intestinal inflammation is unknown. Our aims were to determine 1) the localization of V1b receptors in human and rodent colon, 2) the role of vasopressin and V1b receptors in experimental colitis using two approaches: V1b⁻(/)⁻ mice and a selective V1b receptor antagonist, SSR149415, and 3) the mechanisms involved. V1b receptors were localized in normal and inflamed colon from humans and rats. Experimental colitis was induced in rats and mice and some groups were treated before or after colitis induction with oral SSR149415 (3-30 mg/kg). Other groups of mice were submitted to dehydration to increase vasopressin plasma levels, prior to colitis induction. Body weight, damage scores, MPO, and TNF-α tissue levels were determined. Finally, colonic segments of wild-type (WT) and V1b⁻(/)⁻ mice were mounted in Ussing chambers and paracellular permeability in response to vasopressin was studied. V1b receptors were expressed in enterocytes and ganglia cells of the enteric nervous system of human and rat intestine. Expression levels were independent from inflammatory status. Colitis was less severe in rodents treated by either preventive or curative SSR149415 and in V1b⁻(/)⁻ mice. 2,4,6-Trinitrobenzene sulfonic acid induced a strong mortality in dehydrated animals that was reversed by preventive SSR149415 or mast cell stabilizer. Vasopressin significantly increased paracellular permeability in WT, but not in V1b⁻(/)⁻ mice. Preincubation of colon tissues with SSR149415 abolished the vasopressin effect. Similarly, vasopressin had no effect in colonic preparations from WT mice pretreated with mast cell stabilizers. Vasopressin, through V1b receptor interaction, has proinflammatory properties linked to mast cell activation and downstream alterations of the colonic epithelial barrier. These findings underline the potential interest of V1b receptor blockers in gut inflammatory diseases.
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Affiliation(s)
- Laurent Ferrier
- INRA, UMR Neuro-Gastroentérologie et Nutrition, Toulouse, France
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23
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Ikarashi N, Mochiduki T, Takasaki A, Ushiki T, Baba K, Ishii M, Kudo T, Ito K, Toda T, Ochiai W, Sugiyama K. A mechanism by which the osmotic laxative magnesium sulphate increases the intestinal aquaporin 3 expression in HT-29 cells. Life Sci 2010; 88:194-200. [PMID: 21094173 DOI: 10.1016/j.lfs.2010.11.013] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2010] [Revised: 10/28/2010] [Accepted: 11/09/2010] [Indexed: 01/21/2023]
Abstract
AIMS We have suggested that an osmotic laxative, magnesium sulphate (MgSO(4)), may act as a cathartic in a very rational manner by increasing the aquaporin 3 (AQP3) expression level and by changing osmotic pressure in the colon. In this study, we examined the mechanism by which MgSO(4) increases the intestinal AQP3 expression level by using the human colon cancer HT-29 cell line. MAIN METHODS After the addition of MgSO(4) to HT-29 cells, the expression levels of AQP3 mRNA and protein were measured using real-time RT-PCR and western blotting, respectively. The intracellular Mg(2+) concentration, adenylate cyclase (AC) activity and protein kinase A (PKA) activity were also determined. The phosphorylated cAMP response element-binding protein (CREB) expression levels were determined by western blotting. KEY FINDINGS The AQP3 mRNA expression level started to increase significantly at 1 h after MgSO(4) addition and peaked at 9 h, at a level 3 times as high as the control levels. The AQP3 protein expression level started to increase 6 h after the addition and reached a level almost twice as high as the control levels by hour 12. In the HT-29 cells treated with MgSO(4), there was a 1.4-fold increase in the intracellular Mg(2+) concentration, a 1.5-fold increase in AC activity, a 1.6-fold increase in PKA activity, and a significant increase in phosphorylation of the CREB. SIGNIFICANCE These results suggest that the AC activation caused by an increase in the intracellular Mg(2+) concentration may trigger CREB phosphorylation through PKA activation and promote AQP3 gene transcription.
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Francis RCE, Höhne C, Klein A, Kaisers UX, Pickerodt PA, Boemke W. Endothelin receptor subtype A blockade does not affect the haemodynamic recovery from haemorrhage during xenon/remifentanil or isoflurane/remifentanil anaesthesia in dogs. Vet Anaesth Analg 2010; 37:258-68. [PMID: 20230551 DOI: 10.1111/j.1467-2995.2010.00530.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
OBJECTIVE To test the compensatory role of endothelin-1 when acute blood loss is superimposed on anaesthesia, by characterizing the effect of systemic endothelin receptor subtype A (ET(A)) blockade on the haemodynamic and hormonal responses to haemorrhage in dogs anaesthetized with xenon/remifentanil (X/R) or isoflurane/remifentanil (I/R). STUDY DESIGN Prospective experimental randomized controlled study. ANIMALS Six female Beagle dogs, 13.4 +/- 1.3 kg. METHODS Animals were anaesthetized with remifentanil 0.5 microg kg(-1) minute(-1) plus either 0.8% isoflurane (I/R) or 63% xenon (X/R), with and without (Control) the systemic intravenous endothelin receptor subtype A antagonist atrasentan (four groups, n = 6 each). After 60 minutes of baseline anaesthesia, the dogs were bled (20 mL kg(-1)) over 5 minutes and hypovolemia was maintained for 1 hour. Continuous haemodynamic monitoring was performed via femoral and pulmonary artery catheters; vasoactive hormones were measured before and after haemorrhage. RESULTS In Controls, systemic vascular resistance (SVR), vasopressin and catecholamine plasma concentrations were higher with X/R than with I/R anaesthesia at pre-haemorrhage baseline. The peak increase after haemorrhage was higher during X/R than during I/R anaesthesia (SVR 7420 +/- 867 versus 5423 +/- 547 dyne seconds cm(-5); vasopressin 104 +/- 23 versus 44 +/- 6 pg mL(-1); epinephrine 2956 +/- 310 versus 177 +/- 99 pg mL(-1); norepinephrine 862 +/- 117 versus 195 +/- 33 pg mL(-1), p < 0.05). Haemorrhage reduced central venous pressure from 3 +/- 1 to 1 +/- 1 cm H(2)O (I/R, ns) and from 8 +/- 1 to 5 +/- 1 cm H(2)O (X/R, p < 0.05), but did not reduce mean arterial pressure, nor cardiac output. Atrasentan did not alter the haemodynamic and hormonal response to haemorrhage during either anaesthetic protocol. CONCLUSIONS AND CLINICAL RELEVANCE Selective ET(A) receptor blockade with atrasentan did not impair the haemodynamic and hormonal compensation of acute haemorrhage during X/R or I/R anaesthesia in dogs.
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Affiliation(s)
- Roland C E Francis
- Department of Anesthesiology and Intensive Care Medicine, Charité-Universitätsmedizin Berlin, Campus Virchow-Klinikum, Berlin, Germany.
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Hasler U. Controlled aquaporin-2 expression in the hypertonic environment. Am J Physiol Cell Physiol 2009; 296:C641-53. [PMID: 19211910 DOI: 10.1152/ajpcell.00655.2008] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The corticomedullary osmolality gradient is the driving force for water reabsorption occurring in the kidney. In the collecting duct, this gradient allows luminal water to move across aquaporin (AQP) water channels, thereby increasing urine concentration. However, this same gradient exposes renal cells to great osmotic challenges. These cells must constantly adapt to fluctuations of environmental osmolality that challenge cell volume and incite functional change. This implies profound alterations of cell phenotype regarding water permeability. AQP2 is an essential component of the urine concentration mechanism whose controlled expression dictates apical water permeability of collecting duct principal cells. This review focuses on changes of AQP2 abundance and trafficking in hypertonicity-challenged cells. Intracellular mechanisms governing these events are discussed and the biological relevance of altered AQP2 expression by hypertonicity is outlined.
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Affiliation(s)
- Udo Hasler
- Service de Néphrologie, Fondation pour Recherches Médicales, 64 Ave. de la Roseraie, CH-1211, Geneva 4, Switzerland.
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26
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Guttman JA, Finlay BB. Subcellular alterations that lead to diarrhea during bacterial pathogenesis. Trends Microbiol 2008; 16:535-42. [PMID: 18819802 DOI: 10.1016/j.tim.2008.08.004] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2008] [Revised: 08/20/2008] [Accepted: 08/27/2008] [Indexed: 12/23/2022]
Abstract
Pathogenic microorganisms routinely exploit host cellular functions for their benefit. These alterations often enhance the survival and/or dissemination of the pathogen. However, these effects on the host can be quite debilitating. Consequently, an in-depth understanding of the molecular mechanisms employed by pathogens to manipulate their hosts is crucial. One of the common host phenotypes elicited by enteric pathogens is the generation of diarrhea. Here, we overview the current advances in understanding strategies used by bacterial pathogens to cause diarrheal diseases and discuss how the coordination of various subcellular events can influence disease progression.
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Affiliation(s)
- Julian A Guttman
- Simon Fraser University, Department of Biological Sciences, Shrum Science Centre, Room B8276, Burnaby, BC V5A 1S6, Canada.
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Mochida H, Nakakura T, Suzuki M, Hayashi H, Kikuyama S, Tanaka S. Immunolocalization of a mammalian aquaporin 3 homolog in water-transporting epithelial cells in several organs of the clawed toad Xenopus laevis. Cell Tissue Res 2008; 333:297-309. [PMID: 18548281 DOI: 10.1007/s00441-008-0628-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2008] [Accepted: 04/28/2008] [Indexed: 12/13/2022]
Abstract
Nucleotide sequences of cDNA were used to construct antibodies against an aquaporin (AQP) expressed in the clawed toad, Xenopus laevis, viz., Xenopus AQP3, a homolog of mammalian AQP3. Xenopus AQP3 was immunolocalized in the basolateral membrane of the principal cells of the ventral skin, the urinary bladder, the collecting duct and late distal tubule of the kidney, the absorptive epithelial cells of the large intestine, and the ciliated epithelial cells of the oviducts. Therefore, we designated this AQP as basolateral Xenopus AQP3 (AQP-x3BL). The intensity of labeling for AQP-x3BL differed between the ventral and dorsal skin, with the basolateral membrane of the principal cells in the ventral skin showing intense labeling, whereas that in the dorsal skin was lightly labeled. AQP-x3BL was also immunolocalized in the basolateral membrane of secretory cells in the small granular and mucous glands of the skin. As AQP-x5, a homolog of mammalian AQP5, is localized in the apical membrane of these same cells, this provides a pathway for fluid secretion by the glands. Although Hyla AQP-h2 is translocated from the cytoplasm to the apical membrane of the Hyla urinary bladder in response to arginine vasotocin (AVT), AQP-h2 immunoreactivity in Xenopus bladder remains in the cytoplasm and barely moves to the apical membrane, regardless of AVT stimulation. AQP-x3 is localized in the basolateral membrane, even though the AVT-stimulated AQP-h2 does not translocate to the apical membrane. These findings provide new insights into AQP function in aquatic anurans.
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Affiliation(s)
- Hiroshi Mochida
- Department of Environmental Science, Shizuoka University, Ohya 836, Suruga-ku, Shizuoka, Japan
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Urra J, Sandoval M, Cornejo I, Barros LF, Sepúlveda FV, Cid LP. A genetically encoded ratiometric sensor to measure extracellular pH in microdomains bounded by basolateral membranes of epithelial cells. Pflugers Arch 2008; 457:233-42. [PMID: 18427834 DOI: 10.1007/s00424-008-0497-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2008] [Revised: 03/03/2008] [Accepted: 03/17/2008] [Indexed: 02/05/2023]
Abstract
Extracellular pH, especially in relatively inaccessible microdomains between cells, affects transport membrane protein activity and might have an intercellular signaling role. We have developed a genetically encoded extracellular pH sensor capable of detecting pH changes in basolateral spaces of epithelial cells. It consists of a chimerical membrane protein displaying concatenated enhanced variants of cyan fluorescence protein (ECFP) and yellow fluorescence protein (EYFP) at the external aspect of the cell surface. The construct, termed pHCECSensor01, was targeted to basolateral membranes of Madin-Darby canine kidney (MDCK) cells by means of a sequence derived from the aquaporin AQP4. The fusion of pH-sensitive EYFP with pH-insensitive ECFP allows ratiometric pH measurements. The titration curve of pHCECSensor01 in vivo had a pK (a) value of 6.5 +/- 0.04. Only minor effects of extracellular chloride on pHCECSensor01 were observed around the physiological concentrations of this anion. In MDCK cells, the sensor was able to detect changes in pH secondary to H(+) efflux into the basolateral spaces elicited by an ammonium prepulse or lactate load. This genetically encoded sensor has the potential to serve as a noninvasive tool for monitoring changes in extracellular pH microdomains in epithelial and other tissues in vivo.
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Affiliation(s)
- Javier Urra
- Centro de Estudios Científicos, Av. Arturo Prat 514, Valdivia, Chile
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29
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Floyd RV, Mason SL, Proudman CJ, German AJ, Marples D, Mobasheri A. Expression and nephron segment-specific distribution of major renal aquaporins (AQP1-4) in Equus caballus, the domestic horse. Am J Physiol Regul Integr Comp Physiol 2007; 293:R492-503. [PMID: 17442782 DOI: 10.1152/ajpregu.00689.2005] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Aquaporins (AQPs) play fundamental roles in water and osmolyte homeostasis by facilitating water and small solute movement across plasma membranes of epithelial, endothelial, and other tissues. AQP proteins are abundantly expressed in the mammalian kidney, where they have been shown to play essential roles in fluid balance and urine concentration. Thus far, the majority of studies on renal AQPs have been carried out in laboratory rodents and sheep; no data have been published on the expression of AQPs in kidneys of equines or other large mammals. The aim of this comparative study was to determine the expression and nephron segment localization of AQP1-4 in Equus caballus by immunoblotting and immunohistochemistry with custom-designed rabbit polyclonal antisera. AQP1 was found in apical and basolateral membranes of the proximal convoluted tubules and thin descending limbs of the loop of Henle. AQP2 expression was specifically detected in apical membranes of cortical, medullary, and papillary collecting ducts. AQP3 was expressed in basolateral membranes of cortical, medullary, and papillary collecting ducts. Immunohistochemistry also confirmed AQP4 expression in basolateral membranes of cells lining the distal convoluted and connecting tubules. Western blots revealed high expression of AQP1-4 in the equine kidney. These observations confirm that AQPs are expressed in the equine kidney and are found in similar nephron locations to mouse, rat, and human kidney. Equine renal AQP proteins are likely to be involved in acute and chronic regulation of body fluid composition and may be implicated in water balance disorders brought about by colic and endotoxemia.
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Affiliation(s)
- R V Floyd
- Department of Physiology, Faculty of Veterinary Science, University of Liverpool, Liverpool, UK
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Abstract
The specific role of vasopressin in colonic crypt function and its possible synergistic action with aldosterone were studied. Sprague-Dawley rats fed a high-Na+ (HS; 150 mM NaCl) or a low-Na+ (LS; 150 microM NaCl) diet were deprived of water or infused with vasopressin, and some animals were treated with specific vasopressin receptor subtype V1 and V2 antagonists. The expression of the epithelial Na+ channel (ENaC), alpha-smooth muscle actin (alpha-SMA) and aquaporin-2 (AQP-2) were determined by immunolocalization in distal colonic mucosa. The pericryptal Na+ concentration was determined by confocal microscopy, using a low-affinity Na+-sensitive fluorescent dye (sodium red) and crypt permeability was measured by the rate of escape of fluorescein isothiocyanate-labelled dextran (10 kDa) from the crypt lumen into the pericryptal space in isolated rat distal colonic mucosa. A high plasma concentration of vasopressin raised alpha-SMA expression in the pericryptal sheath (P < 0.05), increased the pericryptal Na+ accumulation in this space (P < 0.01) and caused a reduction of crypt wall permeability (P < 0.01). All these effects were reversed by selective blockade of V1 and V2 receptors. No synergistic effects with aldosterone were observed. Dehydration and vasopressin infusion increased AQP-2 expression in distal colonic mucosa (P < 0.05). This action of vasopressin was prevented by tolvaptan, a specific V2 receptor antagonist (P < 0.05). It is concluded that vasopressin has trophic effects in the rat distal colon, increasing pericryptal myofibroblast growth which affects crypt absorption, and these effects are independent of the presence of aldosterone.
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Affiliation(s)
- Esther Cristià
- Departament de Fisiologia, Facultat de Farmàcia, Universitat de Barcelona, Barcelona, Spain
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Guttman JA, Samji FN, Li Y, Deng W, Lin A, Finlay BB. Aquaporins contribute to diarrhoea caused by attaching and effacing bacterial pathogens. Cell Microbiol 2006; 9:131-41. [PMID: 16889624 DOI: 10.1111/j.1462-5822.2006.00773.x] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Attaching and effacing (A/E) pathogens such as enterohemorrhagic Escherichia coli (EHEC) and enteropathogenic E. coli (EPEC) cause serious global health problems. These bacteria colonize the gastrointestinal system, attach to intestinal epithelial cells, efface (collapse) infected cell microvilli and cause overt diarrhoea that may ultimately result in death of the host. Although pathogenically induced diarrhoea is a significant global health issue, the molecular mechanisms that underlie this disease remain largely unknown. A natural murine infection model, employing the A/E pathogen Citrobacter rodentium, has been helpful in studying the diseases in vivo. C. rodentium colonize the colon at high levels, attach to colonocytes, efface microvilli and cause hyperplasia and inflammation in infected mice. As the disease progresses, the mice develop a diarrhoea-like phenotype. Aquaporin (AQP) water channels have been proposed to play a role in the normal dehydration of faecal contents. Here we examine whether C. rodentium infection may alter AQP localization in colonocytes. We demonstrate that during infection, AQP2 and AQP3 are mislocalized from their normal location along cell membranes to the cell cytoplasm. The change in localization of these proteins correlates with the diarrhoea-like phenotype present in infected mice. Mice that recover from the infection at 28-35 days post inoculum regain their normal membrane AQP localization. The altered localization of AQPs is partially dependent on the bacterial type III effector proteins EspF and EspG. We conclude that altered AQP localization may be a contributing factor to diarrhoea during bacterial infection.
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Affiliation(s)
- Julian A Guttman
- The University of British Columbia, Michael Smith Laboratories, 301-2185 East Mall, Vancouver, BC, Canada V6T 1Z4
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Yang B, Zhao D, Qian L, Verkman AS. Mouse model of inducible nephrogenic diabetes insipidus produced by floxed aquaporin-2 gene deletion. Am J Physiol Renal Physiol 2006; 291:F465-72. [PMID: 16434568 DOI: 10.1152/ajprenal.00494.2005] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Transgenic mouse models of defective urinary concentrating ability produced by deletion of various membrane transport or receptor proteins, including aquaporin-2 (AQP2), are associated with neonatal mortality from polyuria. Here, we report an inducible mouse model of AQP2 gene deletion with severe polyuria in adult mice. LoxP sequences were inserted into introns 1 and 2 in the mouse AQP2 gene by homologous recombination in embryonic stem cells. Mating of germ-line AQP2-loxP mice with tamoxifen-inducible Cre-expressing mice produced offspring with inducible homozygous Cre-AQP2-loxP, which had a normal phenotype. Tamoxifen injections over 10 days resulted in AQP2 gene excision, with undetectable full-length AQP2 transcript in kidney and a >95% reduction in immunoreactive AQP2 protein. Urine osmolality decreased from approximately 2,000 to <500 mosmol/kgH(2)O after 4-5 days, with urine output increasing from 2 to 25 ml/day. Urine osmolality did not increase after water deprivation. Interestingly, AQP3 protein expression in the collecting duct was increased by about fivefold after AQP2 gene excision. Mild renal damage was seen after 6 wk of polyuria, with collecting duct dilatation, yet normal creatinine clearance and serum chemistries. These results establish the first adult model of nephrogenic diabetes insipidus (NDI) caused by AQP2 deficiency, with daily urine output comparable to body weight, although remarkable preservation of renal function compared with non-inducible NDI models.
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Affiliation(s)
- Baoxue Yang
- Department of Medicine, Cardiovascular Research Institute, University of California, San Francisco, California 94143-0521, USA.
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Laforenza U, Cova E, Gastaldi G, Tritto S, Grazioli M, LaRusso NF, Splinter PL, D'Adamo P, Tosco M, Ventura U. Aquaporin-8 is involved in water transport in isolated superficial colonocytes from rat proximal colon. J Nutr 2005; 135:2329-36. [PMID: 16177191 DOI: 10.1093/jn/135.10.2329] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Water is an essential nutrient because it must be introduced from exogenous sources to satisfy metabolic demand. Under physiologic conditions, the colon can absorb and secrete considerable amounts of water even against osmotic gradients, thus helping to maintain the body fluid balance. Here we describe studies on both aquaporin (AQP) expression and function using cells isolated from the superficial and lower crypt regions of the rat proximal colon. The expression of AQP-3, -4, and -8 in isolated colonocytes was determined by semiquantitative RT-PCR and by immunoblotting. The localization of AQP-8 in the colon was evaluated by immunohistochemistry. A stopped-flow light scattering method was used to examine osmotic water movement in isolated colonocytes. Moreover, the contribution of AQP-8 to overall water movement through isolated colonocytes was studied using RNA interference technology. Colonocytes from the proximal colon express AQP-3, -4, and -8 with increasing concentrations from the lower crypt cells toward those on the surface. Osmotic water permeability was higher in surface than in crypt colonocytes (P < 0.05); it was significantly inhibited by the water channel blocker dimethyl sulfoxide, and reversed by beta-mercaptoethanol (P < 0.05). Immunohistochemistry revealed a strong AQP-8 labeling in the apical membrane of the superficial colonocytes. Inhibition of aquaporin-8 expression by small interfering RNA significantly decreased osmotic water permeability (approximately 38%; P < 0.05). Current results indicate that aquaporin-8 may play a major role in water movement through the colon by acting on the apical side of the superficial cells.
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Affiliation(s)
- Umberto Laforenza
- Dipartimento di Medicina Sperimentale, Sezione di Fisiologia Umana, Università di Pavia, Italy.
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Peña-Münzenmayer G, Catalán M, Cornejo I, Figueroa CD, Melvin JE, Niemeyer MI, Cid LP, Sepúlveda FV. Basolateral localization of native ClC-2 chloride channels in absorptive intestinal epithelial cells and basolateral sorting encoded by a CBS-2 domain di-leucine motif. J Cell Sci 2005; 118:4243-52. [PMID: 16155254 DOI: 10.1242/jcs.02525] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Cl– channel ClC-2 is expressed in transporting epithelia and has been proposed as an alternative route for Cl– efflux that might compensate for the malfunction of CFTR in cystic fibrosis. There is controversy concerning the cellular and membrane location of ClC-2, particularly in intestinal tissue. The aim of this paper is to resolve this controversy by immunolocalization studies using tissues from ClC-2 knockout animals as control, ascertaining the sorting of ClC-2 in model epithelial cells and exploring the possible molecular signals involved in ClC-2 targeting. ClC-2 was exclusively localized at the basolateral membranes of surface colonic cells or villus duodenal enterocytes. ClC-2 was sorted to the basolateral membranes in MDCK, Caco-2 and LLC-PK1-μ1B, but not in LLC-PK1-μ1A cells. Mutating a di-leucine motif (L812L813) to a di-alanine changed the basolateral targeting of ClC-2 to an apical location. The basolateral membrane localization of ClC-2 in absorptive cells of the duodenum and the colon is compatible with an absorptive function for this Cl– channel. Basolateral targeting information is contained in a di-leucine motif (L812L813) within CBS-2 domain at the C-terminus of ClC-2. It is speculated that ClC-2 also contains an apical sorting signal masked by L812L813. The proposal that CBS domains in ClC channels might behave as regulatory sites sensing intracellular signals opens an opportunity for pharmacological modulation of ClC-2 targeting.
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Codina J, Li J, DuBose TD. CD63 interacts with the carboxy terminus of the colonic H+-K+-ATPase to decrease [corrected] plasma membrane localization and 86Rb+ uptake. Am J Physiol Cell Physiol 2005; 288:C1279-86. [PMID: 15647390 PMCID: PMC1868892 DOI: 10.1152/ajpcell.00463.2004] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The carboxy terminus (CT) of the colonic H(+)-K(+)-ATPase is required for stable assembly with the beta-subunit, translocation to the plasma membrane, and efficient function of the transporter. To identify protein-protein interactions involved in the localization and function of HKalpha(2), we selected 84 amino acids in the CT of the alpha-subunit of mouse colonic H(+)-K(+)-ATPase (CT-HKalpha(2)) as the bait in a yeast two-hybrid screen of a mouse kidney cDNA library. The longest identified clone was CD63. To characterize the interaction of CT-HKalpha(2) with CD63, recombinant CT-HKalpha(2) and CD63 were synthesized in vitro and incubated, and complexes were immunoprecipitated. CT-HKalpha(2) protein (but not CT-HKalpha(1)) coprecipitated with CD63, confirming stable assembly of HKalpha(2) with CD63. In HEK-293 transfected with HKalpha(2) plus beta(1)-Na(+)-K(+)-ATPase, suppression of CD63 by RNA interference increased cell surface expression of HKalpha(2)/NKbeta(1) and (86)Rb(+) uptake. These studies demonstrate that CD63 participates in the regulation of the abundance of the HKalpha(2)-NKbeta(1) complex in the cell membrane.
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Affiliation(s)
| | | | - Thomas D. DuBose
- Corresponding author: Thomas D. DuBose, Jr., M.D., Department of Internal Medicine, Wake Forest University School of Medicine, Medical Center Blvd., Winston-Salem, NC 27157, Tel. (336)-716-2715, Fax. (336)-716-2273, e-mail:
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Li J, Codina J, Petroske E, Werle MJ, Willingham MC, DuBose TD. The effect of beta-subunit assembly on function and localization of the colonic H+,K+-ATPase alpha-subunit. Kidney Int 2004; 66:1068-75. [PMID: 15327400 DOI: 10.1111/j.1523-1755.2004.00856.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Previous experiments from our laboratory have demonstrated that HKalpha(2) coimmunoprecipitated with beta(1)-Na(+),K(+)-ATPase. Although HKalpha(2) is expressed abundantly in the apical membrane of distal colon, the demonstration that beta(1) localizes to this same membrane in distal colon has not been demonstrated previously. METHODS Immunolocalization was performed in distal colon using a polyclonal antibody against HKalpha(2) and a monoclonal antibody against beta(1). RESULTS The results demonstrate that HKalpha(2) localizes to the apical membrane. Two pools of beta(1)-Na(+),K(+)-ATPase were detected. The first localized to the apical membrane. The second pool was detected in the basolateral membrane when distal colon sections were deglycosylated with glycosidase F. Therefore, our results demonstrate that beta(1) localizes to the apical membrane with HKalpha(2), and supports the view that beta(1) is the physiologic beta-subunit for HKalpha(2). We tested, therefore, the efficiency of the two beta-subunits expressed in distal colon (beta(1) and beta(3)) to support the activity of HKalpha(2). Human embryonic kidney HEK-293 cells were transiently cotransfected with HKalpha(2) plus beta(1) or HKalpha(2) plus beta(3). Subsequently, (86)Rb(+)-uptake and plasma membrane localization were evaluated. The results demonstrate that both HKalpha(2)/beta(1) and HKalpha(2)/beta(3) support (86)Rb(+)-uptake. However, (86)Rb(+)-uptake measured in the cells cotransfected with HKalpha(2) plus beta(1) exceeded that measured in cells expressing HKalpha(2)/beta(3). Fluorescence microscopy using enhanced green fluorescent protein cloned at the amino-terminus of HKalpha(2) demonstrated protein migration to the plasma membrane in cells cotransfected with EGFP-HKalpha(2) plus beta(1). In contrast, in cells cotransfected with EGFP-HKalpha(2) plus beta(3), the vast majority of the protein remained confined to intracellular compartments. The significantly higher (86)Rb(+)-uptake corresponded to additional localization of HKalpha(2) to the plasma membrane when coexpressed with beta(1) compared to beta(3). CONCLUSION Taken together, these and previous results from our laboratory indicate that beta(1)-Na(+),K(+)-ATPase is likely to represent the most physiologic and efficient subunit for HKalpha(2) assembly in distal colon.
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Affiliation(s)
- Jian Li
- Department of Internal Medicine, Wake Forest University Medical School, Winston-Salem, North Carolina 27157, USA
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Hardin JA, Wallace LE, Wong JFK, O'Loughlin EV, Urbanski SJ, Gall DG, MacNaughton WK, Beck PL. Aquaporin expression is downregulated in a murine model of colitis and in patients with ulcerative colitis, Crohn's disease and infectious colitis. Cell Tissue Res 2004; 318:313-23. [PMID: 15338270 DOI: 10.1007/s00441-004-0932-4] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2003] [Accepted: 05/26/2004] [Indexed: 12/13/2022]
Abstract
Colitis is associated with alterations in electrolyte and water transport. These changes give rise to some of the symptoms experienced by patients with colitis. Alterations in fluid flux may also contribute to increased susceptibility to mucosal injury. Recently, endogenous water channel proteins (aquaporins; AQPs), have been identified in colonic tissue. The expression of AQP4, AQP7 and AQP8 was examined, via reverse transcription/polymerase chain reaction, Western blotting and immunohistochemistry, in a murine model of colitis and in patients with inflammatory bowel disease or infectious colitis. Colitis was induced in C57BL/6 mice by the addition of 2.5% dextran sodium sulphate (DSS) to their drinking water. AQP expression in these mice was assessed following 12 h to 7 days of DSS exposure and during the recovery phase from 1 to 15 days following cessation of DSS exposure. Colonic water transport was measured after 1 and 3 days of DSS and following 7 days of recovery. The expression of AQP4 and AQP8 mRNA was significantly decreased after 12-24 h of DSS exposure and remained depressed throughout the treatment period. Expression of AQP7 was more variable. Protein expression followed a similar pattern to that observed for AQP mRNA. Significant alteration in colonic fluid secretion was correlated with reduced expression of AQP isoforms. Significantly, patients with active ulcerative colonic, Crohn's colitis or infectious colitis had similar dramatic reductions in AQP expression that appeared to be correlated with disease activity. Thus, colonic injury in both mouse and man is associated with a downregulation in AQP expression.
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Affiliation(s)
- J A Hardin
- The Gastrointestinal Research Unit, University of Calgary, Calgary, AB, Canada
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Li J, Codina J, Petroske E, Werle MJ, DuBose TD. The carboxy terminus of the colonic H+,K+-ATPase α-subunit is required for stable β subunit assembly and function. Kidney Int 2004; 65:1301-10. [PMID: 15086469 DOI: 10.1111/j.1523-1755.2004.00507.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
BACKGROUND The present experiments were designed to study the importance of the carboxy-terminus of colonic H(+), K(+)-ATPase alpha-subunit (HKalpha(2)), for both function as well as integrity of assembly with beta1-Na(+), K(+)-ATPase. METHODS For this purpose, a mutation of 84 amino acids in the carboxy-terminus was created (DeltaHKalpha(2)) and HEK-293 cells were used as expression systems for functional studies using (86)Rb(+)-uptake, coimmunoprecipitation using specific antibodies and fluorescence microscopy using green fluorescent protein. RESULTS The results demonstrate that comparable levels of expression of HKalpha(2) and DeltaHKalpha(2) mRNA were observed when cells were cotransfected with beta1 subunit. However, the abundance of expression of full length HKalpha(2) protein exceeded that of the truncated protein DeltaHKalpha(2). Ouabain-sensitive (86)Rb(+)-uptake was present only in cells cotransfected with HKalpha(2)/beta(1), indicating that the mutation was incapable of sustaining functionality. Coimmunoprecipitation experiments demonstrated that HKalpha(2) protein was immunoprecipitated more abundantly than DeltaHKalpha(2) when coexpressed with beta1. The use of sucrose gradients and green fluorescence protein immunofluorescence demonstrated that while the DeltaHKalpha(2)/beta(1) complex was confined to the endoplasmic reticulum, the HKalpha(2)/beta(1) complex translocated to the plasma membrane. CONCLUSION Taken together, our results are consistent with the view that the carboxy-terminus of HKalpha(2) facilitates the proper folding of the HKalpha(2)/beta(1) complex allowing translocation of the heterodimer to the plasma membrane where potassium uptake occurs. Otherwise, the alpha/beta complex is destined for degradation.
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Affiliation(s)
- Jian Li
- Department of Internal Medicine, Section on Nephrology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA
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Tsujikawa T, Itoh A, Fukunaga T, Satoh J, Yasuoka T, Fujiyama Y. Alteration of aquaporin mRNA expression after small bowel resection in the rat residual ileum and colon. J Gastroenterol Hepatol 2003; 18:803-8. [PMID: 12795752 DOI: 10.1046/j.1440-1746.2003.03033.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/09/2022]
Abstract
BACKGROUND Diarrhea occurring after small bowel resection gradually improves due to intestinal adaptation. It is known that several water channels, termed aquaporins (AQP), are expressed in the gastrointestinal tract and facilitate water transport. However, the changes of AQP after bowel resection remain unclear. In the present paper, the alterations in AQP mRNA expression were investigated after a massive small bowel resection in the rat residual ileum and colon. METHODS The 6-week-old male Sprague-Dawley rats (n = 15) underwent an 80% distal small bowel resection. The residual ileum and colon were dissected on postoperative day 1, 3, 5 or 7 (n= 3 on each day). Total RNA was purified from each mucosa, and the expressions of AQP and sodium-dependent glucose transporter (SGLT1) mRNA were analyzed by northern blot. The plasma vasoactive intestinal polypeptide (VIP) concentrations on the preoperative day and postoperative day 1 were assayed. RESULTS In the residual small intestine, the expression of AQP-1 and AQP-3 mRNA increased significantly on postoperative day 1. The AQP-7 mRNA increased on postoperative day 3, but the AQP-4 mRNA did not change after the bowel resection. The SGLT1 mRNA gradually decreased after the bowel resection. In the colon, the expression of AQP-3 increased on postoperative day 1 and 7, but AQP-4 mRNA did not change after surgery. The AQP-8 mRNA levels increased slightly on postoperative day 7. Plasma VIP concentration did not change between preoperative day and postoperative day 1. CONCLUSIONS These results indicate that several AQP, except for AQP-4, were up-regulated after a massive small bowel resection, and that AQP might play important roles during adaptation.
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Affiliation(s)
- Tomoyuki Tsujikawa
- Division of Gastroenterology, Shiga University of Medical Science, Seta, Shiga, Japan
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Itoh A, Tsujikawa T, Fujiyama Y, Bamba T. Enhancement of aquaporin-3 by vasoactive intestinal polypeptide in a human colonic epithelial cell line. J Gastroenterol Hepatol 2003; 18:203-10. [PMID: 12542607 DOI: 10.1046/j.1440-1746.2003.02949.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND Vasoactive intestinal polypeptide (VIP) plays an important role in water transport in the intestine. Several specialized channels termed aquaporins (AQP) facilitate water transport in the gastrointestinal tract. Aquaporin-3 localizes to epithelial cells in the human small intestine and colon. However, the regulatory mechanisms underlying the functions of AQP3 remain unclear. To characterize the regulation of AQP3 expression by VIP, we studied messenger (m)RNA expression, protein expression and DNA binding activity in a human colonic epithelial cell line, HT-29. METHOD Human colonic epithelial cells, HT-29, were incubated with VIP (10-12-10-7 M). The cells were treated with protein kinase-A (PK-A) inhibitors (H-89, H-9) or chloride channel-blockers (diphenylamine-2-carboxylate (DPC), 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPD)). The expression of AQP3 mRNA and protein was determined by Northern blot and Western blot, respectively. The DNA-binding activities of cyclic adenosine monophosphate (cAMP) response elements/activating transcription factor (CRE/ATF)) in the nuclear extract were determined by electrophoretic mobility shift assay. RESULTS Aquaporin-3 mRNA was up-regulated at a concentration of 10-10 M VIP. The expression of AQP3 protein was enhanced at 3 h after addition of VIP. The PK-A inhibitors (H-89, H-9) inhibited the expression of AQP3 mRNA enhanced by VIP and cAMP. The gel shift assay of CRE/ATF in HT-29 cells revealed a single band. CONCLUSION These results indicate that VIP upregulated the expression of AQP3 mRNA and protein, and that a cAMP-dependent pathway mediated this effect in a human colonic epithelial cell line, HT-29.
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Affiliation(s)
- Akihiko Itoh
- Division of Gastroenterology, Shiga University of Medical Science, Shiga, Japan
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Gallardo P, Olea N, Sepúlveda FV. Distribution of aquaporins in the colon of Octodon degus, a South American desert rodent. Am J Physiol Regul Integr Comp Physiol 2002; 283:R779-88. [PMID: 12185013 DOI: 10.1152/ajpregu.00218.2002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Octodon degus is a desert rodent of northern Chile, adapted to survive with a limited supply of water. This rodent has a high degree of fecal dehydration, related to colon water absorption. With the hypothesis that aquaporins (AQPs) might be present in the colon epithelium of O. degus and involved in fluid absorption, we studied colon water absorption in vivo and the distribution of AQPs and Na(+) transporters by immunocytochemistry. AQP-1 was found in apical and basolateral membranes of surface-absorptive and crypt epithelial cells. AQP-8 was found in the cytoplasm of enterocytes of surface colon. AQP-3 immunolabeling, on the other hand, was absent from the epithelium but present in a subepithelial fibroblast layer, pericryptal cells, and muscularis mucosae. The hydration state did not modify the amount of immunostaining for any of the AQPs. Colon water absorption was markedly decreased by the mercurial agent p-chloromercuribenzenesulfonic acid and was not affected by water deprivation. The NHE3 isoform of Na(+)/H(+) exchanger and alpha-1 subunit of the Na(+)-K(+)-ATPase were found in apical and basolateral membranes of surface-absorptive cells, respectively. These results suggest that colon water absorption is mostly transcellular and mediated by water channels like AQP-1. Apical Na(+)/H(+) exchanger and basolateral Na(+)-K(+)-ATPase in surface cells could be part of the Na(+) absorption pathway. It is hypothesized that this transport is necessary to provide an osmotic gradient for water absorption. The roles of AQP-8 and AQP-3 in water absorption remain to be established.
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Affiliation(s)
- Pedro Gallardo
- Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Casilla 70058, Santiago, Chile.
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Lambert DW, Wood IS, Ellis A, Shirazi-Beechey SP. Molecular changes in the expression of human colonic nutrient transporters during the transition from normality to malignancy. Br J Cancer 2002; 86:1262-9. [PMID: 11953883 PMCID: PMC2375337 DOI: 10.1038/sj.bjc.6600264] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2002] [Accepted: 02/27/2002] [Indexed: 11/29/2022] Open
Abstract
Healthy colonocytes derive 60-70% of their energy supply from short-chain fatty acids, particularly butyrate. Butyrate has profound effects on differentiation, proliferation and apoptosis of colonic epithelial cells by regulating expression of various genes associated with these processes. We have previously shown that butyrate is transported across the luminal membrane of the colonic epithelium via a monocarboxylate transporter, MCT1. In this paper, using immunohistochemistry and in situ hybridisation histochemistry, we have determined the profile of MCT1 protein and mRNA expression along the crypt to surface axis of healthy human colonic tissue. There is a gradient of MCT1 protein expression in the apical membrane of the cells along the crypt-surface axis rising to a peak in the surface epithelial cells. MCT1 mRNA is expressed along the crypt-surface axis and is most abundant in cells lining the crypt. Analysis of healthy colonic tissues and carcinomas using immunohistochemistry and Western blotting revealed a significant decline in the expression of MCT1 protein during transition from normality to malignancy. This was reflected in a corresponding reduction in MCT1 mRNA expression, as measured by Northern analysis. Carcinoma samples displaying reduced levels of MCT1 were found to express the high affinity glucose transporter, GLUT1, suggesting that there is a switch from butyrate to glucose as an energy source in colonic epithelia during transition to malignancy. The expression levels of MCT1 in association with GLUT1 could potentially be used as determinants of the malignant state of colonic tissue.
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Affiliation(s)
- D W Lambert
- Department of Veterinary Preclinical Sciences, University of Liverpool, Liverpool L69 7ZJ, UK
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