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The ClC-2 Chloride Channel Activator, Lubiprostone, Improves Intestinal Barrier Function in Biopsies from Crohn’s Disease but Not Ulcerative Colitis Patients. Pharmaceutics 2023; 15:pharmaceutics15030811. [PMID: 36986672 PMCID: PMC10053841 DOI: 10.3390/pharmaceutics15030811] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2022] [Revised: 02/05/2023] [Accepted: 02/22/2023] [Indexed: 03/06/2023] Open
Abstract
The prostone analog, lubiprostone, is approved to manage constipation-predominant irritable bowel syndrome. Lubiprostone also protects intestinal mucosal barrier function in animal models of colitis. The aim of this study was to determine if lubiprostone improves barrier properties in isolated colonic biopsies from Crohn’s disease (CD) and ulcerative colitis (UC) patients. Sigmoid colon biopsies from healthy subjects, CD and UC patients in remission, and CD patients with active disease were mounted in Ussing chambers. Tissues were treated with lubiprostone or vehicle to determine the effects on transepithelial electrical resistance (TER), FITC-dextran 4kD (FD4) permeability, and electrogenic ion transport responses to forskolin and carbachol. Localization of the tight junction protein, occludin, was determined by immunofluorescence. Lubiprostone significantly increased ion transport across control, CD and UC remission biopsies but not active CD. Lubiprostone selectively improved TER in both CD remission and active disease biopsies but not in control or UC biopsies. The improved TER was associated with increased membrane localization of occludin. Lubiprostone selectively improved barrier properties of biopsies from CD patients vs. UC and independent of an ion transport response. These data indicate that lubiprostone has potential efficacy in improving mucosal integrity in Crohn’s disease.
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Boger KD, Sheridan AE, Ziegler AL, Blikslager AT. Mechanisms and modeling of wound repair in the intestinal epithelium. Tissue Barriers 2022; 11:2087454. [PMID: 35695206 PMCID: PMC10161961 DOI: 10.1080/21688370.2022.2087454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
The intestinal epithelial barrier is susceptible to injury from insults, such as ischemia or infectious disease. The epithelium's ability to repair wounded regions is critical to maintaining barrier integrity. Mechanisms of intestinal epithelial repair can be studied with models that recapitulate the in vivo environment. This review focuses on in vitro injury models and intestinal cell lines utilized in such systems. The formation of artificial wounds in a controlled environment allows for the exploration of reparative physiology in cell lines modeling diverse aspects of intestinal physiology. Specifically, the use of intestinal cell lines, IPEC-J2, Caco-2, T-84, HT-29, and IEC-6, to model intestinal epithelium is discussed. Understanding the unique systems available for creating intestinal injury and the differences in monolayers used for in vitro work is essential for designing studies that properly capture relevant physiology for the study of intestinal wound repair.
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Affiliation(s)
- Kasey D Boger
- Comparative Medicine Institute, Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA
| | - Ana E Sheridan
- Comparative Medicine Institute, Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA
| | - Amanda L Ziegler
- Comparative Medicine Institute, Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA
| | - Anthony T Blikslager
- Comparative Medicine Institute, Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA
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3
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Zhao Y, Deng Z, Ma Z, Zhang M, Wang H, Tuo B, Li T, Liu X. Expression alteration and dysfunction of ion channels/transporters in the parietal cells induces gastric diffused mucosal injury. Biomed Pharmacother 2022; 148:112660. [PMID: 35276516 DOI: 10.1016/j.biopha.2022.112660] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Revised: 01/16/2022] [Accepted: 01/18/2022] [Indexed: 11/26/2022] Open
Abstract
Gastric mucosal injuries include focal and diffused injuries, which do and do not change the cell differentiation pattern. Parietal cells loss is related to the occurrence of gastric mucosal diffused injury, with two phenotypes of spasmolytic polypeptide-expressing metaplasia and neuroendocrine cell hyperplasia, which is the basis of gastric cancer and gastric neuroendocrine tumor respectively. Multiple ion channels and transporters are located and expressed in the parietal cells, which is not only regulate the gastric acid-base homeostasis, but also regulate the growth and development of parietal cells. Therefore, alteration and dysregulation of ion channels and transporters in the parietal cells impairs the morphology and physiological functions of stomach, resulted in gastric diffused mucosal damage. In this review, multiple ion channels and transporters in parietal cells, including K+ channels, aquaporins, Cl- channels, Na+/H+ transporters, and Cl-/HCO3- transporters are described, and their roles in gastric diffused mucosal injury are discussed. We hope to drive researcher's attention to focus on the role of ion channels/transporters loss in the parietal cells induced gastric diffused mucosal injury.
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Affiliation(s)
- Yingying Zhao
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou Province, China
| | - Zilin Deng
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou Province, China
| | - Zhiyuan Ma
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou Province, China
| | - Minglin Zhang
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou Province, China
| | - Hu Wang
- Department of Thyroid and Breast Surgery, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou Province, China
| | - Biguang Tuo
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou Province, China
| | - Taolang Li
- Department of Thyroid and Breast Surgery, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou Province, China.
| | - Xuemei Liu
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou Province, China.
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Nighot M, Ganapathy AS, Saha K, Suchanec E, Castillo EF, Gregory A, Shapiro S, Ma T, Nighot P. Matrix Metalloproteinase MMP-12 Promotes Macrophage Transmigration Across Intestinal Epithelial Tight Junctions and Increases Severity of Experimental Colitis. J Crohns Colitis 2021; 15:1751-1765. [PMID: 33836047 PMCID: PMC8495490 DOI: 10.1093/ecco-jcc/jjab064] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
BACKGROUND AND AIMS Matrix metalloproteinases [MMPs] play an important role in extracellular matrix regulation during cell growth and wound healing. Increased expression of MMP-12 [human macrophage elastase] has been reported in inflammatory bowel disease [IBD] which is characterised by the loss of epithelial tight junction [TJ] barrier function and an excessive inflammatory response. The aim of this study was to investigate the role of MMP-12 in intestinal TJ barrier function and inflammation. METHODS Wild type [WT] and MMP-12-/- mice were subjected to experimental acute or chronic dextran sodium sulphate [DSS] colitis. The mouse colonic permeability was measured in vivo by recycling perfusion of the entire colon and ex vivo by Ussing chamber studies. RESULTS DSS administration increased colonic permeability through modulation of TJ proteins and also increased MMP-12 expression in the colonic mucosa of WT mice. The acute as well as chronic DSS-induced increase in colonic TJ permeability and the severity of DSS colitis was found to be markedly attenuated in MMP-12-/- mice. The resistance of MMP-12-/- mice to DSS colitis was characterised by reduced macrophage infiltration and transmigration, and reduced basement membrane laminin degradation. Further in vitro and in vivo studies show that macrophage transmigration across the epithelial layer is MMP-12 dependent and the epithelial TJ barrier is compromised during macrophage transmigration. Conclusions: Together, these data demonstrate that MMP-12 mediated degradation of basement membrane laminin, macrophage transmigration, and associated loss of intestinal TJ barrier are key pathogenic factors for intestinal inflammation.
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Affiliation(s)
- Meghali Nighot
- Department of Medicine, College of Medicine, Penn State University, Hershey, PA, USA
| | | | - Kushal Saha
- Department of Medicine, College of Medicine, Penn State University, Hershey, PA, USA
| | - Eric Suchanec
- Department of Medicine, College of Medicine, Penn State University, Hershey, PA, USA
| | - Eliseo F Castillo
- University of New Mexico School of Medicine, Albuquerque, New Mexico, USA
| | - Alyssa Gregory
- Division of Pulmonary, Allergy, and Critical Care Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Steven Shapiro
- Division of Pulmonary, Allergy, and Critical Care Medicine, University of Pittsburgh, Pittsburgh, PA, USA
| | - Thomas Ma
- Department of Medicine, College of Medicine, Penn State University, Hershey, PA, USA
| | - Prashant Nighot
- Department of Medicine, College of Medicine, Penn State University, Hershey, PA, USA
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Huang W, Tan M, Wang Y, Liu L, Pan Y, Li J, Ouyang M, Long C, Qu X, Liu H, Liu C, Wang J, Deng L, Xiang Y, Qin X. Increased intracellular Cl - concentration improves airway epithelial migration by activating the RhoA/ROCK Pathway. Theranostics 2020; 10:8528-8540. [PMID: 32754261 PMCID: PMC7392015 DOI: 10.7150/thno.46002] [Citation(s) in RCA: 3] [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: 03/14/2020] [Accepted: 06/24/2020] [Indexed: 12/19/2022] Open
Abstract
In the airway, Cl- is the most abundant anion and is critically involved in transepithelial transport. The correlation of the abnormal expression and activation of chloride channels (CLCs), such as cystic fibrosis transmembrane conductance regulators (CFTRs), anoctamin-1, and CLC-2, with cell migration capability suggests a relationship between defective Cl- transport and epithelial wound repair. However, whether a correlation exists between intracellular Cl- and airway wound repair capability has not been explored thus far, and the underlying mechanisms involved in this relationship are not fully defined. Methods: In this work, the alteration of intracellular chloride concentration ([Cl-]i) was measured by using a chloride-sensitive fluorescent probe (N-[ethoxycarbonylmethyl]-6-methoxyquinolium bromide). Results: We found that clamping with high [Cl-]i and 1 h of treatment with the CLC inhibitor CFTR blocker CFTRinh-172 and chloride intracellular channel inhibitor IAA94 increased intracellular Cl- concentration ([Cl-]i) in airway epithelial cells. This effect improved epithelial cell migration. In addition, increased [Cl-]i in cells promoted F-actin reorganization, decreased cell stiffness, and improved RhoA activation and LIMK1/2 phosphorylation. Treatment with the ROCK inhibitor of Y-27632 and ROCK1 siRNA significantly attenuated the effects of increased [Cl-]i on LIMK1/2 activation and cell migration. In addition, intracellular Ca2+ concentration was unaffected by [Cl-]i clamping buffers and CFTRinh-172 and IAA94. Conclusion: Taken together, these results suggested that Cl- accumulation in airway epithelial cells could activate the RhoA/ROCK/LIMK cascade to induce F-actin reorganization, down-regulate cell stiffness, and improve epithelial migration.
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Affiliation(s)
- Wenjie Huang
- School of Basic Medicine, Central South University, Changsha, Hunan 410078, China
- Affiliated Liutie Central Hospital of Guangxi medical university, Liuzhou, Guangxi 545007, China
| | - Meiling Tan
- School of Basic Medicine, Central South University, Changsha, Hunan 410078, China
| | - Yue Wang
- Changzhou Key Laboratory of Respiratory Medical Engineering, Institute of Biomedical Engineering and Health Sciences, Changzhou, Jiangsu 213164, China
- School of Nursing, Changzhou University, Changzhou, Jiangsu 213164, China
| | - Lei Liu
- Changzhou Key Laboratory of Respiratory Medical Engineering, Institute of Biomedical Engineering and Health Sciences, Changzhou, Jiangsu 213164, China
| | - Yan Pan
- Changzhou Key Laboratory of Respiratory Medical Engineering, Institute of Biomedical Engineering and Health Sciences, Changzhou, Jiangsu 213164, China
| | - Jingjing Li
- Changzhou Key Laboratory of Respiratory Medical Engineering, Institute of Biomedical Engineering and Health Sciences, Changzhou, Jiangsu 213164, China
| | - Mingxing Ouyang
- Changzhou Key Laboratory of Respiratory Medical Engineering, Institute of Biomedical Engineering and Health Sciences, Changzhou, Jiangsu 213164, China
| | - Chunjiao Long
- School of Basic Medicine, Central South University, Changsha, Hunan 410078, China
| | - Xiangping Qu
- School of Basic Medicine, Central South University, Changsha, Hunan 410078, China
| | - Huijun Liu
- School of Basic Medicine, Central South University, Changsha, Hunan 410078, China
| | - Chi Liu
- School of Basic Medicine, Central South University, Changsha, Hunan 410078, China
| | - Jia Wang
- School of Basic Medicine, Central South University, Changsha, Hunan 410078, China
| | - Linhong Deng
- Changzhou Key Laboratory of Respiratory Medical Engineering, Institute of Biomedical Engineering and Health Sciences, Changzhou, Jiangsu 213164, China
| | - Yang Xiang
- School of Basic Medicine, Central South University, Changsha, Hunan 410078, China
| | - Xiaoqun Qin
- School of Basic Medicine, Central South University, Changsha, Hunan 410078, China
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Krüger L, Pridgen TA, Taylor ER, Garman KS, Blikslager AT. Lubiprostone protects esophageal mucosa from acid injury in porcine esophagus. Am J Physiol Gastrointest Liver Physiol 2020; 318:G613-G623. [PMID: 32068440 PMCID: PMC7191458 DOI: 10.1152/ajpgi.00086.2019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Esophageal injury from acid exposure related to gastroesophageal reflux disease is a common problem and a risk factor for development of Barrett's esophagus and esophageal adenocarcinoma. Our previous work highlights the benefits of using porcine esophagus to study human esophageal disease because of the similarities between porcine and human esophagus. In particular, esophageal submucosal glands (ESMGs) are present in human esophagus and proximal porcine esophagus but not in rodent esophagus. Although CFTR is expressed in the ducts of ESMGs, very little is known about CFTR and alternate anion channels, including ClC-2, in the setting of acid-related esophageal injury. After finding evidence of CFTR and ClC-2 in the basal layers of the squamous epithelium, and in the ducts of the ESMGs, we developed an ex vivo porcine model of esophageal acid injury. In this model, esophageal tissue was placed in Ussing chambers to determine the effect of pretreatment with the ClC-2 agonist lubiprostone on tissue damage related to acid exposure. Pretreatment with lubiprostone significantly reduced the level of acid injury and significantly augmented the recovery of the injured tissue (P < 0.05). Evaluation of the interepithelial tight junctions showed well-defined membrane localization of occludin in lubiprostone-treated injured tissues. Pretreatment of tissues with the Na+-K+-2Cl- cotransporter inhibitor bumetanide blocked lubiprostone-induced increases in short-circuit current and inhibited the reparative effect of lubiprostone. Furthermore, inhibition of ClC-2 with ZnCl2 blocked the effects of lubiprostone. We conclude that ClC-2 contributes to esophageal protection from acid exposure, potentially offering a new therapeutic target.NEW & NOTEWORTHY This research is the first to describe the presence of anion channels ClC-2 and CFTR localized to the basal epithelia of porcine esophageal mucosa and the esophageal submucosal glands. In the setting of ex vivo acid exposure, the ClC-2 agonist lubiprostone reduced acid-related injury and enhanced recovery of the epithelial barrier. This work may ultimately provide an alternate mechanism for treating gastroesophageal reflux disease.
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Affiliation(s)
- Leandi Krüger
- 1Center for Gastrointestinal Biology and Disease, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina
| | - Tiffany A. Pridgen
- 1Center for Gastrointestinal Biology and Disease, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina
| | - Ellie R. Taylor
- 1Center for Gastrointestinal Biology and Disease, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina
| | - Katherine S. Garman
- 2Division of Gastroenterology, Department of Medicine, Duke University, Durham, North Carolina
| | - Anthony T. Blikslager
- 1Center for Gastrointestinal Biology and Disease, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina
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7
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Rao MC. Physiology of Electrolyte Transport in the Gut: Implications for Disease. Compr Physiol 2019; 9:947-1023. [PMID: 31187895 DOI: 10.1002/cphy.c180011] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We now have an increased understanding of the genetics, cell biology, and physiology of electrolyte transport processes in the mammalian intestine, due to the availability of sophisticated methodologies ranging from genome wide association studies to CRISPR-CAS technology, stem cell-derived organoids, 3D microscopy, electron cryomicroscopy, single cell RNA sequencing, transgenic methodologies, and tools to manipulate cellular processes at a molecular level. This knowledge has simultaneously underscored the complexity of biological systems and the interdependence of multiple regulatory systems. In addition to the plethora of mammalian neurohumoral factors and their cross talk, advances in pyrosequencing and metagenomic analyses have highlighted the relevance of the microbiome to intestinal regulation. This article provides an overview of our current understanding of electrolyte transport processes in the small and large intestine, their regulation in health and how dysregulation at multiple levels can result in disease. Intestinal electrolyte transport is a balance of ion secretory and ion absorptive processes, all exquisitely dependent on the basolateral Na+ /K+ ATPase; when this balance goes awry, it can result in diarrhea or in constipation. The key transporters involved in secretion are the apical membrane Cl- channels and the basolateral Na+ -K+ -2Cl- cotransporter, NKCC1 and K+ channels. Absorption chiefly involves apical membrane Na+ /H+ exchangers and Cl- /HCO3 - exchangers in the small intestine and proximal colon and Na+ channels in the distal colon. Key examples of our current understanding of infectious, inflammatory, and genetic diarrheal diseases and of constipation are provided. © 2019 American Physiological Society. Compr Physiol 9:947-1023, 2019.
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Affiliation(s)
- Mrinalini C Rao
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois, USA
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8
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Jin Y, Ibrahim D, Magness ST, Blikslager AT. Knockout of ClC-2 reveals critical functions of adherens junctions in colonic homeostasis and tumorigenicity. Am J Physiol Gastrointest Liver Physiol 2018; 315:G966-G979. [PMID: 30285466 PMCID: PMC6336945 DOI: 10.1152/ajpgi.00087.2018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Adherens junctions (AJs), together with tight junctions (TJs), form an apical junctional complex that regulates intestinal epithelial cell-to-cell adherence and barrier homeostasis. Within the AJ, membrane-bound E-cadherin binds β-catenin, which functions as an essential intracellular signaling molecule. We have previously identified a novel protein in the region of the apical junction complex, chloride channel protein-2 (ClC-2), that we have used to study TJ regulation. In this study, we investigated the possible effects of ClC-2 on the regulation of AJs in intestinal mucosal epithelial homeostasis and tumorigenicity. Mucosal homeostasis and junctional proteins were examined in wild-type (WT) and ClC-2 knockout (KO) mice as well as associated colonoids. Tumorigenicity and AJ-associated signaling were evaluated in a murine colitis-associated tumor model and in a colorectal cancer cell line (HT-29). Colonic tissues from ClC-2 KO mice had altered ultrastructural morphology of intercellular junctions with reduced colonocyte differentiation, whereas jejunal tissues had minimal changes. Colonic crypts from ClC-2 KO mice had significantly higher numbers of less-differentiated forms of colonoids compared with WT. Furthermore, the absence of ClC-2 resulted in redistribution of AJ proteins and increased β-catenin activity. Downregulation of ClC-2 in colorectal cells resulted in significant increases in proliferation associated with disruption of AJs. Colitis-associated tumors in ClC-2 KO mice were significantly increased, associated with β-catenin transcription factor activation. The absence of ClC-2 results in less differentiated colonic crypts and increased tumorigenicity associated with colitis via dysregulation of AJ proteins and activation of β-catenin-associated signaling. NEW & NOTEWORTHY Disruption of adherens junctions in the absence of chloride channel protein-2 revealed critical functions of these junctional structures, including maintenance of colonic homeostasis and differentiation as well as driving tumorigenicity by regulating β-catenin signaling.
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Affiliation(s)
- Younggeon Jin
- 1Department of Clinical Sciences, Center for Gastrointestinal Biology and Disease, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina
| | - Dina Ibrahim
- 1Department of Clinical Sciences, Center for Gastrointestinal Biology and Disease, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina
| | - Scott T. Magness
- 1Department of Clinical Sciences, Center for Gastrointestinal Biology and Disease, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina,2Joint Department of Biomedical Engineering, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina
| | - Anthony T. Blikslager
- 1Department of Clinical Sciences, Center for Gastrointestinal Biology and Disease, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina
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Cuppoletti J, Tewari KP, Chakrabarti J, Malinowska DH. Identification of the fatty acid activation site on human ClC-2. Am J Physiol Cell Physiol 2017; 312:C707-C723. [PMID: 28424169 DOI: 10.1152/ajpcell.00267.2016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2016] [Revised: 04/11/2017] [Accepted: 04/11/2017] [Indexed: 01/26/2023]
Abstract
Fatty acids (including lubiprostone and cobiprostone) are human ClC-2 (hClC-2) Cl- channel activators. Molecular and cellular mechanisms underlying this activation were examined. Role of a four-amino acid PKA activation site, RGET691, of hClC-2 was investigated using wild-type (WT) and mutant (AGET, RGEA, and AGAA) hClC-2 expressed in 293EBNA cells as well as involvement of PKA, intracellular cAMP concentration ([cAMP]i), EP2, or EP4 receptor agonist activity. All fatty acids [lubiprostone, cobiprostone, eicosatetraynoic acid (ETYA), oleic acid, and elaidic acid] caused significant rightward shifts in concentration-dependent Cl- current activation (increasing EC50s) with mutant compared with WT hClC-2 channels, without changing time and voltage dependence, current-voltage rectification, or methadone inhibition of the channel. As with lubiprostone, cobiprostone activation of hClC-2 occurred with PKA inhibitor (myristoylated protein kinase inhibitor) present or when using double PKA activation site (RRAA655/RGEA691) mutant. Cobiprostone did not activate human CFTR. Fatty acids did not increase [cAMP]i in hClC-2/293EBNA or T84 cells. Using T84 CFTR knockdown cells, cobiprostone increased hClC-2 Cl- currents without increasing [cAMP]i, while PGE2 and forskolin-IBMX increased both. Fatty acids were not agonists of EP2 or EP4 receptors. L-161,982, a supposed EP4-selective inhibitor, had no effect on lubiprostone-activated hClC-2 Cl- currents but significantly decreased T84 cell barrier function measured by transepithelial resistance and fluorescent dextran transepithelial movement. The present findings show that RGET691 of hClC-2 (possible binding site) plays an important functional role in fatty acid activation of hClC-2. PKA, [cAMP]i, and EP2 or EP4 receptors are not involved. These studies provide the molecular basis for fatty acid regulation of hClC-2.
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Affiliation(s)
- John Cuppoletti
- Department of Molecular and Cellular Physiology, University of Cincinnati, Cincinnati, Ohio
| | - Kirti P Tewari
- Department of Molecular and Cellular Physiology, University of Cincinnati, Cincinnati, Ohio
| | - Jayati Chakrabarti
- Department of Molecular and Cellular Physiology, University of Cincinnati, Cincinnati, Ohio
| | - Danuta H Malinowska
- Department of Molecular and Cellular Physiology, University of Cincinnati, Cincinnati, Ohio
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10
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Nighot PK, Leung L, Ma TY. Chloride channel ClC- 2 enhances intestinal epithelial tight junction barrier function via regulation of caveolin-1 and caveolar trafficking of occludin. Exp Cell Res 2017; 352:113-122. [PMID: 28161538 DOI: 10.1016/j.yexcr.2017.01.024] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Revised: 01/09/2017] [Accepted: 01/31/2017] [Indexed: 12/16/2022]
Abstract
Previous studies have demonstrated that the chloride channel ClC-2 plays a critical role in intestinal epithelial tight junction (TJ) barrier function via intracellular trafficking of TJ protein occludin. To study the mechanism of ClC-2-mediated TJ barrier function and intracellular trafficking of occludin, we established ClC-2 over-expressing Caco-2 cell line (Caco-2CLCN2) by full length ClC-2 ORF transfection. ClC-2 over-expression (Caco-2CLCN2) significantly enhanced TJ barrier (increased TER by ≥2 times and reduced inulin flux by 50%) compared to control Caco-2pEZ cells. ClC-2 over-expression (Caco-2CLCN2) increased occludin protein level compared to control Caco-2pEZ cells. Surface biotinylation assay revealed reduced steady state endocytosis of occludin in Caco-2CLCN2 cells. Furthermore, ClC-2 over-expression led to reduction in caveolin-1 protein level and diminishment of caveolae assembly. Caveolae disruption increased TJ permeability in control but not ClC-2 over-expressing Caco-2CLCN2 cells. Selective ClC-2 channel blocker GaTx2 caused an increase in caveolin-1 protein level and reduced occludin level. Delivery of cell permeable caveolin-1 scaffolding domain reduced the occludin protein level. Over all, these results suggest that ClC- 2 enhances TJ barrier function in intestinal epithelial cells via regulation of caveolin-1 and caveolae-mediated trafficking of occludin.
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Affiliation(s)
- Prashant K Nighot
- Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA.
| | - Lana Leung
- Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA
| | - Thomas Y Ma
- Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA
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11
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Jin Y, Blikslager AT. Myosin light chain kinase mediates intestinal barrier dysfunction via occludin endocytosis during anoxia/reoxygenation injury. Am J Physiol Cell Physiol 2016; 311:C996-C1004. [PMID: 27760753 DOI: 10.1152/ajpcell.00113.2016] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 10/13/2016] [Indexed: 01/13/2023]
Abstract
Intestinal anoxia/reoxygenation (A/R) injury induces loss of barrier function followed by epithelial repair. Myosin light chain kinase (MLCK) has been shown to alter barrier function via regulation of interepithelial tight junctions, but has not been studied in intestinal A/R injury. We hypothesized that A/R injury would disrupt tight junction barrier function via MLCK activation and myosin light chain (MLC) phosphorylation. Caco-2BBe1 monolayers were subjected to anoxia for 2 h followed by reoxygenation in 21% O2, after which barrier function was determined by measuring transepithelial electrical resistance (TER) and FITC-dextran flux. Tight junction proteins and MLCK signaling were assessed by Western blotting, real-time PCR, or immunofluorescence microscopy. The role of MLCK was further investigated with select inhibitors (ML-7 and peptide 18) by using in vitro and ex vivo models. Following A/R injury, there was a significant increase in paracellular permeability compared with control cells, as determined by TER and dextran fluxes (P < 0.05). The tight junction protein occludin was internalized during A/R injury and relocalized to the region of the tight junction after 4 h of recovery. MLC phosphorylation was significantly increased by A/R injury (P < 0.05), and treatment with the MLCK inhibitor peptide 18 attenuated the increased epithelial monolayer permeability and occludin endocytosis caused by A/R injury. Application of MLCK inhibitors to ischemia-injured porcine ileal mucosa induced significant increases in TER and reduced mucosal-to-serosal fluxes of 3H-labeled mannitol. These data suggest that MLCK-induced occludin endocytosis mediates intestinal epithelial barrier dysfunction during A/R injury. Our results also indicate that MLCK-dependent occludin regulation may be a target for the therapeutic treatment of ischemia/reperfusion injury.
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Affiliation(s)
- Younggeon Jin
- Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina
| | - Anthony T Blikslager
- Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina
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12
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Pharmaceutical Activation or Genetic Absence of ClC-2 Alters Tight Junctions During Experimental Colitis. Inflamm Bowel Dis 2015; 21:2747-57. [PMID: 26332307 DOI: 10.1097/mib.0000000000000550] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
BACKGROUND We have previously reported that the ClC-2 chloride channel has an important role in regulation of tight junction barrier function during experimental colitis, and the pharmaceutical ClC-2 activator lubiprostone initiates intestinal barrier repair in ischemic-injured intestine. Thus, we hypothesized that pharmaceutical ClC-2 activation would have a protective and therapeutic effect in murine models of colitis, which would be absent in ClC-2 mice. METHODS We administered lubiprostone to wild-type or ClC-2 mice with dextran sulfate sodium (DSS) or 2, 4, 5-trinitrobenzene sulfonic acid-induced colitis. We determined the severity of colitis and assessed intestinal permeability. Selected tight junction proteins were analyzed by Western blotting and immunofluorescence/confocal microscopy, whereas proliferative and differentiated cells were examined with special staining and immunohistochemistry. RESULTS Oral preventive or therapeutic administration of lubiprostone significantly reduced the severity of colitis and reduced intestinal permeability in both DSS and trinitrobenzene sulfonic acid-induced colitis. Preventive treatment with lubiprostone induced significant recovery of the expression and distribution of selected sealing tight junction proteins in mice with DSS-induced colitis. In addition, lubiprostone reduced crypt proliferation and increased the number of differentiated epithelial cells. Alternatively, when lubiprostone was administered to ClC-2 mice, the protective effect against DSS colitis was limited. CONCLUSIONS This study suggests a central role for ClC-2 in restoration of barrier function and tight junction architecture in experimental murine colitis, which can be therapeutically targeted with lubiprostone.
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Jin Y, Blikslager AT. ClC-2 regulation of intestinal barrier function: Translation of basic science to therapeutic target. Tissue Barriers 2015; 3:e1105906. [PMID: 26716076 DOI: 10.1080/21688370.2015.1105906] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 09/28/2015] [Accepted: 10/01/2015] [Indexed: 02/06/2023] Open
Abstract
The ClC-2 chloride channel is a member of the voltage-gated chloride channel family. ClC-2 is involved in various physiological processes, including fluid transport and secretion, regulation of cell volume and pH, maintaining the membrane potential of the cell, cell-to-cell communication, and tissue homeostasis. Recently, our laboratory has accumulated evidence indicating a critical role of ClC-2 in the regulation of intestinal barrier function by altering inter-epithelial tight junction composition. This review will detail the role of ClC-2 in intestinal barrier function during intestinal disorders, including experimental ischemia/reperfusion injury and dextran sodium sulfate (DSS)-induced inflammatory bowel disease. Details of pharmacological manipulation of ClC-2 via prostone agonists will also be provided in an effort to show the potential therapeutic relevance of ClC-2 regulation, particularly during intestinal barrier disruption.
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Affiliation(s)
- Younggeon Jin
- Department of Clinical Sciences; College of Veterinary Medicine, North Carolina State University ; Raleigh, NC, USA
| | - Anthony T Blikslager
- Department of Clinical Sciences; College of Veterinary Medicine, North Carolina State University ; Raleigh, NC, USA
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14
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Nighot MP, Nighot PK, Ma TY, Malinowska DH, Shull GE, Cuppoletti J, Blikslager AT. Genetic Ablation of the ClC-2 Cl- Channel Disrupts Mouse Gastric Parietal Cell Acid Secretion. PLoS One 2015; 10:e0138174. [PMID: 26378782 PMCID: PMC4574764 DOI: 10.1371/journal.pone.0138174] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2015] [Accepted: 08/27/2015] [Indexed: 11/30/2022] Open
Abstract
The present studies were designed to examine the effects of ClC-2 ablation on cellular morphology, parietal cell abundance, H/K ATPase expression, parietal cell ultrastructure and acid secretion using WT and ClC-2-/- mouse stomachs. Cellular histology, morphology and proteins were examined using imaging techniques, electron microscopy and western blot. The effect of histamine on the pH of gastric contents was measured. Acid secretion was also measured using methods and secretagogues previously established to give maximal acid secretion and morphological change. Compared to WT, ClC-2-/- gastric mucosal histological organization appeared disrupted, including dilation of gastric glands, shortening of the gastric gland region and disorganization of all cell layers. Parietal cell numbers and H/K ATPase expression were significantly reduced by 34% (P<0.05) and 53% (P<0.001) respectively and cytoplasmic tubulovesicles appeared markedly reduced on electron microscopic evaluation without evidence of canalicular expansion. In WT parietal cells, ClC-2 was apparent in a similar cellular location as the H/K ATPase by immunofluorescence and appeared associated with tubulovesicles by immunogold electron microscopy. Histamine-stimulated [H+] of the gastric contents was significantly (P<0.025) lower by 9.4 fold (89%) in the ClC-2-/- mouse compared to WT. Histamine/carbachol stimulated gastric acid secretion was significantly reduced (range 84–95%, P<0.005) in ClC-2-/- compared to WT, while pepsinogen secretion was unaffected. Genetic ablation of ClC-2 resulted in reduced gastric gland region, reduced parietal cell number, reduced H/K ATPase, reduced tubulovesicles and reduced stimulated acid secretion.
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Affiliation(s)
- Meghali P. Nighot
- North Carolina State University, College of Veterinary Medicine, Raleigh, North Carolina, United States of America
| | - Prashant K. Nighot
- North Carolina State University, College of Veterinary Medicine, Raleigh, North Carolina, United States of America
| | - Thomas Y. Ma
- University of New Mexico School of Medicine, Albuquerque, New Mexico, United States of America
| | - Danuta H. Malinowska
- University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Gary E. Shull
- University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - John Cuppoletti
- University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Anthony T. Blikslager
- North Carolina State University, College of Veterinary Medicine, Raleigh, North Carolina, United States of America
- * E-mail:
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Li Z, Liu YH, Liu XB, Xue YX, Wang P, Liu LB. Low-dose endothelial monocyte-activating polypeptide-II increases permeability of blood–tumor barrier via a PKC-ζ/PP2A-dependent signaling mechanism. Exp Cell Res 2015; 331:257-66. [DOI: 10.1016/j.yexcr.2014.12.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Revised: 12/27/2014] [Accepted: 12/31/2014] [Indexed: 12/23/2022]
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Cuppoletti J, Chakrabarti J, Tewari KP, Malinowska DH. Differentiation between human ClC-2 and CFTR Cl− channels with pharmacological agents. Am J Physiol Cell Physiol 2014; 307:C479-92. [DOI: 10.1152/ajpcell.00077.2014] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It has been difficult to separate/identify the roles of ClC-2 and CFTR in Cl− transport studies. Using pharmacological agents, we aimed to differentiate functionally between ClC-2 and CFTR Cl− channel currents. Effects of CFTR inhibitor 172 (CFTRinh172), N-(4-methylphenylsulfonyl)- N′-(4-trifluoromethylphenyl)urea (DASU-02), and methadone were examined by whole cell patch clamp on Cl− currents in recombinant human ClC-2/human embryonic kidney 293 (ClC-2/HEK293) cells stably transformed with Epstein-Barr nuclear antigen 1 (hClC-2/293EBNA) and human CFTR/HEK293 (hCFTR/HEK293) cells and by short-circuit current ( Isc) measurements in T84 cells. Lubiprostone and forskolin-IBMX were used as activators. CFTRinh172 inhibited forskolin-IBMX-stimulated recombinant human CFTR (hCFTR) and lubiprostone-stimulated recombinant human ClC-2 (hClC-2) Cl− currents in a concentration-dependent manner equipotently. DASU-02 inhibited forskolin-IBMX-stimulated Cl− currents in hCFTR/HEK293 cells, but not lubiprostone-stimulated Cl− currents in hClC-2/293EBNA cells. In T84 cells with basolateral nystatin or 1-ethyl-2-benzimidazolinone (1-EBIO), lubiprostone-stimulated and forskolin-IBMX-cyclosporin A (FICA)-stimulated Isc components were observed. CFTRinh172 inhibited major portions of both components. DASU-02 had no effect on lubiprostone-stimulated Isc but partially inhibited FICA-stimulated Isc. T84 cells in which ClC-2 or CFTR was knocked down using siRNAs were constructed. T84 ClC-2 knockdown cells did not respond to lubiprostone but did respond to forskolin-IBMX in a methadone-insensitive, DASU-02-sensitive manner, indicating CFTR function. T84 CFTR knockdown cells responded separately to lubiprostone and forskolin-IBMX in a methadone-sensitive and DASU-02-insensitive manner, indicating ClC-2 function. Low lubiprostone concentrations activated ClC-2, but not CFTR, and both channels were activated by forskolin-IBMX but have different inhibitor sensitivities. Methadone, but not DASU-02, inhibited ClC-2. DASU-02, but not methadone, inhibited CFTR. In T84 cells, both ClC-2 and CFTR are present and likely play roles in Cl− secretion.
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Affiliation(s)
- John Cuppoletti
- Department of Molecular and Cellular Physiology, University of Cincinnati College of Medicine, Cincinnati, Ohio
| | - Jayati Chakrabarti
- Department of Molecular and Cellular Physiology, University of Cincinnati College of Medicine, Cincinnati, Ohio
| | - Kirti P. Tewari
- Department of Molecular and Cellular Physiology, University of Cincinnati College of Medicine, Cincinnati, Ohio
| | - Danuta H. Malinowska
- Department of Molecular and Cellular Physiology, University of Cincinnati College of Medicine, Cincinnati, Ohio
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Hayes KS, Hager R, Grencis RK. Sex-dependent genetic effects on immune responses to a parasitic nematode. BMC Genomics 2014; 15:193. [PMID: 24628794 PMCID: PMC4022179 DOI: 10.1186/1471-2164-15-193] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Accepted: 03/06/2014] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND Many disease aetiologies have sex specific effects, which have important implications for disease management. It is now becoming increasingly evident that such effects are the result of the differential expression of autosomal genes rather than sex-specific genes. Such sex-specific variation in the response to Trichuris muris, a murine parasitic nematode infection and model for the human parasitic nematode T. trichiura, has been well documented, however, the underlying genetic causes of these differences have been largely neglected. We used the BXD mouse set of recombinant inbred strains to identify sex-specific loci that contribute to immune phenotypes in T. muris infection. RESULTS Response phenotypes to T. muris infection were found to be highly variable between different lines of BXD mice. A significant QTL on chromosome 5 (TM5) associated with IFN-γ production was found in male mice but not in female mice. This QTL was in the same location as a suggestive QTL for TNF-α and IL-6 production in male mice suggesting a common control of these pro-inflammatory cytokines. A second QTL was identified on chromosome 4 (TM4) affecting worm burden in both male and female cohorts. We have identified several genes as potential candidates for modifying responses to T. muris infection. CONCLUSIONS We have used the largest mammalian genetic model system, the BXD mouse population, to identify candidate genes with sex-specific effects in immune responses to T. muris infection. Some of these genes may be differentially expressed in male and female mice leading to the difference in immune response between the sexes reported in previous studies. Our study further highlights the importance of considering sex as an important factor in investigations of immune response at the genome-wide level, in particular the bias that can be introduced when generalizing results obtained from only one sex or a mixed sex population. Rather, analyses of interaction effects between sex and genotype should be part of future studies.
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Affiliation(s)
| | - Reinmar Hager
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK.
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Bi MM, Hong S, Zhou HY, Wang HW, Wang LN, Zheng YJ. Chloride channelopathies of ClC-2. Int J Mol Sci 2013; 15:218-49. [PMID: 24378849 PMCID: PMC3907807 DOI: 10.3390/ijms15010218] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Revised: 11/14/2013] [Accepted: 12/16/2013] [Indexed: 12/15/2022] Open
Abstract
Chloride channels (ClCs) have gained worldwide interest because of their molecular diversity, widespread distribution in mammalian tissues and organs, and their link to various human diseases. Nine different ClCs have been molecularly identified and functionally characterized in mammals. ClC-2 is one of nine mammalian members of the ClC family. It possesses unique biophysical characteristics, pharmacological properties, and molecular features that distinguish it from other ClC family members. ClC-2 has wide organ/tissue distribution and is ubiquitously expressed. Published studies consistently point to a high degree of conservation of ClC-2 function and regulation across various species from nematodes to humans over vast evolutionary time spans. ClC-2 has been intensively and extensively studied over the past two decades, leading to the accumulation of a plethora of information to advance our understanding of its pathophysiological functions; however, many controversies still exist. It is necessary to analyze the research findings, and integrate different views to have a better understanding of ClC-2. This review focuses on ClC-2 only, providing an analytical overview of the available literature. Nearly every aspect of ClC-2 is discussed in the review: molecular features, biophysical characteristics, pharmacological properties, cellular function, regulation of expression and function, and channelopathies.
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Affiliation(s)
- Miao Miao Bi
- Department of Ophthalmology, the Second Hospital of Jilin University, Jilin University, Changchun 130041, Jilin, China.
| | - Sen Hong
- Department of Ophthalmology, the Second Hospital of Jilin University, Jilin University, Changchun 130041, Jilin, China.
| | - Hong Yan Zhou
- Department of Ophthalmology, the Second Hospital of Jilin University, Jilin University, Changchun 130041, Jilin, China.
| | - Hong Wei Wang
- Department of Ophthalmology, the Second Hospital of Jilin University, Jilin University, Changchun 130041, Jilin, China.
| | - Li Na Wang
- Department of Ophthalmology, the Second Hospital of Jilin University, Jilin University, Changchun 130041, Jilin, China.
| | - Ya Juan Zheng
- Department of Ophthalmology, the Second Hospital of Jilin University, Jilin University, Changchun 130041, Jilin, China.
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Abstract
BACKGROUND Previously, it was shown that the chloride channel ClC-2 modulates intestinal tight junction (TJ) barrier function. The aim of the present study was to investigate the role of ClC-2 in epithelial barrier function and recovery in the event of epithelial injury. METHODS The role of ClC-2 was investigated in TJ barrier function in dextran sodium sulfate (DSS)-induced colitis in ClC-2 knockout mice and ClC-2 knockdown intestinal Caco-2 cells. Barrier function was measured electrophysiologically and by transepithelial mannitol fluxes. Selected TJ and associated proteins were Western blotted, cytokines were measured using quantitative PCR, and human colonic biopsies were examined with immunohistochemistry. RESULTS ClC-2 mice had a higher disease activity index, higher histological scores, and increased paracellular permeability compared with wild-type mice when treated with DSS. DSS-treated ClC-2 mice had increased claudin-2 expression, greater loss of occludin in the membrane, increased association of occludin with caveolin-1, and significantly increased tumor necrosis factor-α and interleukin-1β messenger RNA. ClC-2 knockdown in human intestinal Caco-2 cells resulted in a greater loss of epithelial resistance in the event of epithelial injury. The restoration of colonic barrier function after DSS colitis was delayed in ClC-2 mice. In human colonic biopsies, the protein and messenger RNA expression of ClC-2 was found to be reduced in patients with ulcerative colitis. CONCLUSIONS ClC-2 plays a critical role in experimental colitis in that its absence increases disease activity, reduces barrier function and recovery, and perturbs TJs. Furthermore, ClC-2 expression is markedly reduced in the colon of human patients with ulcerative colitis.
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Abstract
The lack of small-molecule inhibitors for anion-selective transporters and channels has impeded our understanding of the complex mechanisms that underlie ion passage. The ubiquitous CLC "Chloride Channel" family represents a unique target for biophysical and biochemical studies because its distinctive protein fold supports both passive chloride channels and secondary-active chloride-proton transporters. Here, we describe the synthesis and characterization of a specific small-molecule inhibitor directed against a CLC antiporter (ClC-ec1). This compound, 4,4'-octanamidostilbene-2,2'-disulfonate (OADS), inhibits ClC-ec1 with low micromolar affinity and has no specific effect on a CLC channel (ClC-1). Inhibition of ClC-ec1 occurs by binding to two distinct intracellular sites. The location of these sites and the lipid dependence of inhibition suggest potential mechanisms of action. This compound will empower research to elucidate differences between antiporter and channel mechanisms and to develop treatments for CLC-mediated disorders.
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Evidence for the Involvement of RhoA Signaling in the Ethanol-Induced Increase in Intestinal Epithelial Barrier Permeability. Int J Mol Sci 2013; 14:3946-60. [PMID: 23429187 PMCID: PMC3588079 DOI: 10.3390/ijms14023946] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Revised: 01/19/2013] [Accepted: 01/24/2013] [Indexed: 01/04/2023] Open
Abstract
In this work, we investigated the potential role of the small G protein RhoA in ethanol-induced tight junction (TJ) protein disassembly and increased intestinal epithelial barrier (IEB) permeability. Our study used Caco-2 cells as an in vitro IEB model and RhoA short hairpin RNA (shRNA) interference to establish whether RhoA plays a role in ethanol-induced TJ opening. RhoA shRNA interference partially inhibited epithelial leakage and restored normal transepithelial electrical resistance (TEER) values in the IEB. Moreover, RhoA shRNA interference prevented a shift in occludin distribution from insoluble to soluble fractions. Additionally, RhoA shRNA interference inhibited the ethanol-induced expression of zonula occludens-1 (ZO-1). Finally, RhoA shRNA interference inhibited an ethanol-induced increase in RhoA activity. The contributions of RhoA to an ethanol-induced increase in IEB permeability are associated with TJ disassembly.
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Camilleri M, Lasch K, Zhou W. Irritable bowel syndrome: methods, mechanisms, and pathophysiology. The confluence of increased permeability, inflammation, and pain in irritable bowel syndrome. Am J Physiol Gastrointest Liver Physiol 2012; 303:G775-85. [PMID: 22837345 DOI: 10.1152/ajpgi.00155.2012] [Citation(s) in RCA: 260] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Irritable bowel syndrome (IBS) is one of the most common gastrointestinal ailments among those seeking health care for gastrointestinal disorders. Despite its prevalence, IBS pathophysiology is still not completely understood. Continued elucidation of IBS etiological mechanisms will lead to a greater appreciation of possible therapeutic targets. In the past decade, there has been increasing focus on the possible connection between increased intestinal mucosal permeability, inflammation, and visceral hypersensitivity. Increased permeability in subsets of IBS patients has been observed and the possible mechanisms underlying this defect are just beginning to be understood. The objectives of this review are to summarize the role of the healthy intestinal epithelium as a barrier between the lumen and the rest of the body with a focus on tight junctions; to examine the lines of evidence that suggest that different triggers lead to increased intestinal mucosal permeability and disruption of tight junctions in IBS patients; and to explore how this increased permeability may elicit immune responses that affect afferent nerves, resulting in the pain associated with IBS.
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Affiliation(s)
- Michael Camilleri
- Clinical Enteric Neuroscience Translational and Epidemiological Research, College of Medicine, Mayo Clinic, Charlton 8-110, 200 First St. S.W., Rochester, MN 55905, USA.
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Nighot M, Moeser A, Ueno R, Blikslager A. Gastro protective properties of the novel prostone SPI-8811 against acid-injured porcine mucosa. World J Gastroenterol 2012; 18:4684-92. [PMID: 23002337 PMCID: PMC3442206 DOI: 10.3748/wjg.v18.i34.4684] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2011] [Revised: 07/23/2012] [Accepted: 08/14/2012] [Indexed: 02/06/2023] Open
Abstract
AIM: To evaluate the protective properties of novel prostone ClC-2 agonist SPI-8811 in porcine model of gastric acid injury.
METHODS: Porcine gastric mucosa was mounted in Ussing chambers and injured by bathing mucosal tissues in an HCl Ringer’s solution (pH = 1.5) with or without SP1-8811 (1 μmol/L), cystic fibrosis transmembrane conductance regulator (CFTR) inhibitor (inhibitor 172, 10 μmol/L, apical) and ClC-2 inhibitor ZnCl2, 300 μmol/L, apical), on the apical surface of tissues. Transepithelial resistance and mucosal-to-serosal 3H-mannitol fluxes were measured over a 90-min period. Tissues were analyzed by morph metric techniques, Immunofluorescence and by western blots.
RESULTS: Compared with control tissues, acid exposure decreased transepithelial electrical resistance (TER) and increased 3H-mannitol flux. Pretreatment of gastric mucosa with SPI-8811 was protective against acid-induced decreases in TER (TER, 50 Ω.cm2vs 100 Ω.cm2) and abolished increases in flux (3H-mannitol flux, 0.10 μmol/L.cm2vs 0.04 μmol/L.cm2). Evidence of histological damage in the presence of acid was markedly attenuated by SPI-0811. Immunofluorescence and western analysis for occludin revealed enhanced localization to the region of the tight junction (TJ) after treatment with SPI-8811. Pretreatment with the ClC-2 inhibitor ZnCl2, but not the selective CFTR inhibitor 172, attenuated SPI-8811-mediated mucosal protection, suggesting a role for ClC-2. Prostone may serve both protective and reparative roles in injured tissues.
CONCLUSION: ClC-2 agonist SPI-8811 stimulated enhancement of mucosal barrier function by protecting TJ protein occludin in porcine gastric mucosa and thus protected the gastric acid injury in porcine stomach.
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Contrasting effects of linaclotide and lubiprostone on restitution of epithelial cell barrier properties and cellular homeostasis after exposure to cell stressors. BMC Pharmacol 2012; 12:3. [PMID: 22553939 PMCID: PMC3403872 DOI: 10.1186/1471-2210-12-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Accepted: 05/03/2012] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND Linaclotide has been proposed as a treatment for the same gastrointestinal indications for which lubiprostone has been approved, chronic idiopathic constipation and irritable bowel syndrome with constipation. Stressors damage the epithelial cell barrier and cellular homeostasis leading to loss of these functions. Effects of active linaclotide on repair of barrier and cell function in pig jejunum after ischemia and in T84 cells after treatment with proinflammatory cytokines, interferon-γ and tumor necrosis factor-α were examined. Comparison with effects of lubiprostone, known to promote repair of barrier function was carried out. RESULTS In ischemia-damaged pig jejunum, using measurements of transepithelial resistance, (3)H-mannitol fluxes, short-circuit current (Cl(-) secretion) and occludin localization, active linaclotide failed to effectively promote repair of the epithelial barrier or recovery of short-circuit current, whereas lubiprostone promoted barrier repair and increased short-circuit current. In control pig jejunum, 1 μM linaclotide and 1 μM lubiprostone both caused similar increases in short-circuit current (Cl(-) secretion). In T84 cells, using measurements of transepithelial resistance, fluxes of fluorescent macromolecules, occludin and mitochondrial membrane potential, active linaclotide was virtually ineffective against damage caused by interferon-γ and tumor necrosis factor-α, while lubiprostone protected or promoted repair of epithelial barrier and cell function. Barrier protection/repair by lubiprostone was inhibited by methadone, a ClC-2 inhibitor. Linaclotide, but not lubiprostone increased [cGMP]i as expected and [Ca(2+)]i and linaclotide depolarized while lubiprostone hyperpolarized the T84 plasma membrane potential suggesting that lubiprostone may lead to greater cellular stability compared to linaclotide. In T84 cells, as found with linaclotide but not with lubiprostone, transepithelial resistance was slightly but significantly decreased by guanylin, STa and 8-bromo cGMP and fluorescent dextran fluxes were increased by guanylin. However the physiological implications of these small but statistically significant changes remain unclear. CONCLUSIONS Considering the physiological importance of epithelial barrier function and cell integrity and the known impact of stressors, the finding that lubiprostone, but not active linaclotide, exhibits the additional distinct property of effective protection or repair of the epithelial barrier and cell function after stress suggests potential clinical importance for patients with impaired or compromised barrier function such as might occur in IBS.
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Maduke MC, Reimer RJ. Biochemistry to the rescue: a ClC-2 auxiliary subunit provides a tangible link to leukodystrophy. Neuron 2012; 73:855-7. [PMID: 22405196 DOI: 10.1016/j.neuron.2012.02.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
ClC-2 is a broadly distributed chloride channel with an enigmatic neurophysiological function. In this issue of Neuron, Jeworutzki et al. (2012) use a biochemical approach to identify GlialCAM, a protein with a defined link to leukodystrophy, as a ClC-2 auxiliary subunit.
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Affiliation(s)
- Merritt C Maduke
- Department of Molecular and Cellular Physiology, Stanford University, 279 Campus Drive West, Stanford, CA 94305, USA.
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26
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Marshall JF, Blikslager AT. The effect of nonsteroidal anti-inflammatory drugs on the equine intestine. Equine Vet J 2012:140-4. [PMID: 21790769 DOI: 10.1111/j.2042-3306.2011.00398.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used in the management of pain and endotoxaemia associated with colic in the horse. While NSAIDs effectively treat the symptoms of colic, there is evidence to suggest that their administration is associated with adverse gastrointestinal effects including right dorsal colitis and inhibition of mucosal barrier healing. Several studies have examined the pathophysiology of NSAID associated effects on the large and small intestine in an effort to avoid these complications and identify effective alternative medications. Differences in the response of the large and small intestines to injury and NSAID treatment have been identified. Flunixin meglumine has been shown in the small intestine to inhibit barrier function recovery and increase permeability to lipopolysaccharide (LPS). A range of NSAIDs has been examined in the small intestine and experimental evidence suggests that those NSAIDs with cyclooxygenase independent anti-inflammatory effects or a COX-2 selective mode of action may offer significant advantages over traditional NSAIDs.
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Affiliation(s)
- J F Marshall
- Weipers Centre Equine Hospital, School of Veterinary Medicine, University of Glasgow, UK.
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27
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Nighot PK, Blikslager AT. Chloride channel ClC-2 modulates tight junction barrier function via intracellular trafficking of occludin. Am J Physiol Cell Physiol 2012; 302:C178-87. [DOI: 10.1152/ajpcell.00072.2011] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Previously, we have demonstrated that the chloride channel ClC-2 modulates intestinal mucosal barrier function. In the present study, we investigated the role of ClC-2 in epithelial barrier development and maintenance in Caco-2 cells. During early monolayer formation, silencing of ClC-2 with small interfering (si)RNA led to a significant delay in the development of transepithelial resistance (TER) and disruption of occludin localization. Proteomic analysis employing liquid chromatography-mass spectrometry /mass spectrometry revealed association of ClC-2 with key proteins involved in intracellular trafficking, including caveolin-1 and Rab5. In ClC-2 siRNA-treated cells, occludin colocalization with caveolin-1 was diffuse and in the subapical region. Subapically distributed occludin in ClC-2 siRNA-treated cells showed marked colocalization with Rab5. To study the link between ClC-2 and trafficking of occludin in confluent epithelial monolayers, a Caco-2 cell clone expressing ClC-2 short hairpin (sh)RNA was established. Disruption of caveolae with methyl-β-cyclodextrin (MβCD) caused a marked drop in TER and profound redistribution of caveolin-1-occludin coimmunofluorescence in ClC-2 shRNA cells. In ClC-2 shRNA cells, focal aggregations of Rab5-occludin coimmunofluorescence were present within the cytoplasm. Wortmannin caused an acute fall in TER in ClC-2 shRNA cells and subapical, diffuse redistribution of Rab5-occludin coimmunofluorescence in ClC-2 shRNA cells. An endocytosis and recycling assay for occludin revealed higher basal rate of endocytosis of occludin in ClC-2 shRNA cells. Wortmannin significantly reduced the rate of recycling of occludin in ClC-2 shRNA cells. These data clearly indicate that ClC-2 plays an important role in the modulation of tight junctions by influencing caveolar trafficking of the tight junction protein occludin.
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Affiliation(s)
- Prashant K. Nighot
- Department of Clinical Sciences, North Carolina State University, Raleigh, North Carolina
| | - Anthony T. Blikslager
- Department of Clinical Sciences, North Carolina State University, Raleigh, North Carolina
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Chen ZY, Wang YG, Yang P, Huang WG, Zhou YS, Feng XS. Relationship between CLC-2 and intestinal mucosal barrier in rats with obstructive jaundice. Shijie Huaren Xiaohua Zazhi 2011; 19:2829-2834. [DOI: 10.11569/wcjd.v19.i27.2829] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate the relationship between chloride channel-2 (CLC-2) and intestinal mucosal barrier in rats with obstructive jaundice (OJ).
METHODS: Rats were randomly divided into five groups: sham operation group, OJ group, lubiprostone (Lu) group, glucagon-like peptide-2 (GLP-2) group, and Lu + GLP group. Except for the sham operation group, OJ was induced by bile duct ligation in rats of other groups. The Lu group was subcutaneously injected with LU, and the GLP-2 group was injected with GLP-2. The Lu + GLP group was injected with both Lu and GLP-2. The animals were sacrificed 7 days after treatment. The ratio of lactulose to mannitol (L/M) and plasma endotoxin levels were measured. Western blot was used to examine the changes in the expression tight junction proteins zonula occludens-1 (ZO-1) and CLC-2 in epithelial cells in the terminal ileum.
RESULTS: The ratio of L/M was significantly higher in all the experiment groups than in the sham operation group (all P = 0.00), but was significantly lower in the Lu group, GLP-2 group and Lu + GLP group than in the OJ group (0.545 ± 0.03, 0.512 ± 0.03, 0.482 ± 0.05 vs 0.656 ± 0.04, all P = 0.00). Plasma endotoxin levels increased in all the experiment groups, highest in the OJ group and decreasing somewhat in the Lu group, GLP-2 group and Lu + GLP group. The relative expression of ZO-1 in the Lu group (0.209 ± 0.03) was higher than that in the OJ group (0.178 ± 0.03) but lower than that in the sham operation group (P = 0.02). The relative expression of ZO-1 in the Lu + GLP group was comparable to that in the sham operation group. The relative expression of CLC-2 descended more obviously in the OJ, GLP-2 and Lu + GLP groups than in the sham operation group (0.195 ± 0.04, 0.217 ± 0.05, 0.222 ± 0.03 vs 0.267 ± 0.04, all P = 0.00).
CONCLUSION: CLC-2 and tight junction protein participate in the maintenance of intestinal mucosal barrier. Acute biliary obstruction-induced destruction of intestinal mucosa barrier is associated with CLC-2 in enterocytes. CLC-2 activation could activate tight junction protein and repair impaired intestinal mucosa barrier.
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Evidence for involvement of ROCK signaling in bradykinin-induced increase in murine blood–tumor barrier permeability. J Neurooncol 2011; 106:291-301. [DOI: 10.1007/s11060-011-0685-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2010] [Accepted: 08/03/2011] [Indexed: 01/23/2023]
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Abstract
Na(+) and Cl(-) movement across the intestinal epithelium occurs by several interconnected mechanisms: (a) nutrient-coupled Na(+) absorption, (b) electroneutral NaCl absorption, (c) electrogenic Cl(-) secretion by CFTR, and (d) electrogenic Na(+) absorption by ENaC. All these transport modes require a favorable electrochemical gradient maintained by the basolateral Na(+)/K(+)-ATPase, a Cl(-) channel, and K(+) channels. Electroneutral NaCl absorption is observed from the small intestine to the distal colon. This transport is mediated by apical Na(+)/H(+) (NHE2/3) and Cl(-)/HCO(3)(-) (Slc26a3/a6 and others) exchangers that provide the major route of NaCl absorption. Electroneutral NaCl absorption and Cl(-) secretion by CFTR are oppositely regulated by the autonomic nerve system, the immune system, and the endocrine system via PKAα, PKCα, cGKII, and/or SGK1. This integrated regulation requires the formation of macromolecular complexes, which are mediated by the NHERF family of scaffold proteins and involve internalization of NHE3. Through use of knockout mice and human mutations, a more detailed understanding of the integrated as well as subtle regulation of electroneutral NaCl absorption by the mammalian intestine has emerged.
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Affiliation(s)
- Akira Kato
- Biological Sciences, Tokyo Institute of Technology, Yokohama, Japan.
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Saccharomyces cerevisiae modulates immune gene expressions and inhibits ETEC-mediated ERK1/2 and p38 signaling pathways in intestinal epithelial cells. PLoS One 2011; 6:e18573. [PMID: 21483702 PMCID: PMC3070739 DOI: 10.1371/journal.pone.0018573] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Accepted: 03/05/2011] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Enterotoxigenic Escherichia coli (ETEC) infections result in large economic losses in the swine industry worldwide. ETEC infections cause pro-inflammatory responses in intestinal epithelial cells and subsequent diarrhea in pigs, leading to reduced growth rate and mortality. Administration of probiotics as feed additives displayed health benefits against intestinal infections. Saccharomyces cerevisiae (Sc) is non-commensal and non-pathogenic yeast used as probiotic in gastrointestinal diseases. However, the immuno-modulatory effects of Sc in differentiated porcine intestinal epithelial cells exposed to ETEC were not investigated. METHODOLOGY/PRINCIPAL FINDINGS We reported that the yeast Sc (strain CNCM I-3856) modulates transcript and protein expressions involved in inflammation, recruitment and activation of immune cells in differentiated porcine intestinal epithelial IPEC-1 cells. We demonstrated that viable Sc inhibits the ETEC-induced expression of pro-inflammatory transcripts (IL-6, IL-8, CCL20, CXCL2, CXCL10) and proteins (IL-6, IL-8). This inhibition was associated to a decrease of ERK1/2 and p38 MAPK phosphorylation, an agglutination of ETEC by Sc and an increase of the anti-inflammatory PPAR-γ nuclear receptor mRNA level. In addition, Sc up-regulates the mRNA levels of both IL-12p35 and CCL25. However, measurement of transepithelial electrical resistance displayed that Sc failed to maintain the barrier integrity in monolayer exposed to ETEC suggesting that Sc does not inhibit ETEC enterotoxin activity. CONCLUSIONS Sc (strain CNCM I-3856) displays multiple immuno-modulatory effects at the molecular level in IPEC-1 cells suggesting that Sc may influence intestinal inflammatory reaction.
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Serafini P, da Rocha AM, Smith GD, da Motta ELA, Baracat EC. Laboratory methods in the study of endometrial Claudin-4. Methods Mol Biol 2011; 762:281-290. [PMID: 21717364 DOI: 10.1007/978-1-61779-185-7_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Immunohistochemistry is a suitable method for the detection of proteins from the Claudin family and several antibodies are commercially available for the detection of Claudin congeners. Immunodetection of Caludin-4 in the paraffin-embedded specimens might be a useful tool for studying the role of these proteins in the cyclic transformation of the endometrium and its role in the endometrial receptivity; furthermore, other components of the junctional zone involved in the transformational process of the endometrium can be detected by means of immunohistochemistry/immunofluorescence with several polyclonal or monoclonal antibodies. The aim of this chapter is to comprehensively overview the materials and methods to perform the endometrial biopsy and to detect Claudin-4 in paraffin-embedded samples of endometrium. Additionally, the interpretation of the results is addressed.
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Affiliation(s)
- Paulo Serafini
- Huntington Center for Reproductive Medicine of Brazil, Sao Paulo, Brazil
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Nighot PK, Blikslager AT. ClC-2 regulates mucosal barrier function associated with structural changes to the villus and epithelial tight junction. Am J Physiol Gastrointest Liver Physiol 2010; 299:G449-56. [PMID: 20489043 DOI: 10.1152/ajpgi.00520.2009] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We have previously shown an important role of the chloride channel ClC-2 in orchestrating repair of tight junctions in ischemia-injured mucosa. In this study, we examined the role of ClC-2 in regulating barrier function of normal murine intestinal mucosa. Ex vivo, ClC-2-/- ileal mucosa mounted in Ussing chambers had significantly higher transepithelial electrical resistance (TER) and reduced [(3)H]mannitol mucosal-to-serosal flux compared with wild-type (WT) mouse mucosa. We also noted that ileum from ClC-2-/- mice had a significantly reduced in vivo [(3)H]mannitol blood-to-lumen clearance compared with WT animals. By scanning electron microscopy, flat leaflike villi were found to have tapering, rounded apical tips in ClC-2-/- mucosa. By transmission electron microscopy, the apical intercellular tight junctions in ClC-2-/- intestine revealed lateral membranes that were less well defined but closely aligned compared with electron-dense and closely apposed tight junctions in WT mucosa. The width of apical tight junctions was significantly reduced in ClC-2-/- intestine. Such an alteration in tight junction ultrastructure was also noted in the testicular tissue from ClC-2-/- mice. The ClC-2-/- intestinal mucosa had reduced expression of phospho-myosin light chain (MLC), and inhibition of myosin light chain kinase (MLCK) in WT mucosa partially increased TER toward the TER in ClC-2-/- intestine. Contrary to our prior work on the reparative role of ClC-2 in injured mucosa, this study indicates that ClC-2 reduces barrier function in normal mucosa. The mechanisms underlying these differing roles are not entirely clear, although ultrastructural morphology of tight junctions and MLCK appear to be important to the function of ClC-2 in normal mucosa.
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Affiliation(s)
- Prashant K Nighot
- Dept. of Clinical Sciences, North Carolina State Univ., Raleigh, 27606, USA
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RhoA-Mediated Potential Regulation of Blood–Tumor Barrier Permeability by Bradykinin. J Mol Neurosci 2010; 42:67-73. [DOI: 10.1007/s12031-010-9345-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2009] [Accepted: 02/22/2010] [Indexed: 12/28/2022]
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Nighot PK, Moeser A, Ali RA, Blikslager AT, Koci MD. Astrovirus infection induces sodium malabsorption and redistributes sodium hydrogen exchanger expression. Virology 2010; 401:146-54. [PMID: 20219227 DOI: 10.1016/j.virol.2010.02.004] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2009] [Revised: 11/03/2009] [Accepted: 02/03/2010] [Indexed: 01/04/2023]
Abstract
Astroviruses are known to be a leading cause of diarrhea in infants and the immunocompromised; however, our understanding of this endemic pathogen is limited. Histological analyses of astrovirus pathogenesis demonstrate clinical disease is not associated with changes to intestinal architecture, inflammation, or cell death. Recent studies in vitro have suggested that astroviruses induce actin rearrangement leading to loss of barrier function. The current study used the type-2 turkey astrovirus (TAstV-2) and turkey poult model of astrovirus disease to examine how astrovirus infection affects the ultrastructure and electrophysiology of the intestinal epithelium. These data demonstrate that infection results in changes to the epithelial ultrastructure, rearrangement of F-actin, decreased absorption of sodium, as well as redistribution of the sodium/hydrogen exchanger 3 (NHE3) from the membrane to the cytoplasm. Collectively, these data suggest astrovirus infection induces sodium malabsorption, possibly through redistribution of specific sodium transporters, which results in the development of an osmotic diarrhea.
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Affiliation(s)
- Prashant K Nighot
- Department of Clinical Sciences, North Carolina State University, Raleigh, NC, USA
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Abstract
PURPOSE OF REVIEW The 2009 review on small intestinal ion transport, in this series, focused on recent advances in duodenal bicarbonate secretion, the importance of scaffolding proteins and the pathophysiology of inflammation-associated diarrhea. The current review focuses on advances in ion-coupled solute transport, the dynamic role of the paracellular pathway in transepithelial-fluid transport and of elucidating the cellular basis of diarrheas associated with enteric infections. RECENT FINDINGS In understanding the cellular pathophysiology underlying diarrheal diseases, there is increased focus on the role of altering Na absorptive mechanisms as well as the role of the paracellular pathway. This is not to minimize the role of Cl-secretory pathways, especially cystic fibrosis transmembrane conductance regulator (CFTR), which continues to have pleiotropic roles in modulating other transporters. The Na-glucose cotransporter (SGLT) was the first transporter ever to be cloned. Twenty-one years later, with another first, the crystal structure of the related Na-galactose transporter has been described and opens new avenues to understand structure-function relationships and intelligent drug design for transporters. SUMMARY Progress continues to be made on integrating information obtained from reductionist models into more complex in-vivo animal models and where possible in human studies. Recognition of the coordinated regulation of cellular Na absorptive and Cl-secretory pathways together with the paracellular route in health and disease will help develop a more holistic picture of the multifaceted nature of small intestinal ion transport.
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Johnson AM, Kaushik RS, Hardwidge PR. Disruption of transepithelial resistance by enterotoxigenic Escherichia coli. Vet Microbiol 2009; 141:115-9. [PMID: 19733985 DOI: 10.1016/j.vetmic.2009.08.020] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2009] [Revised: 08/05/2009] [Accepted: 08/07/2009] [Indexed: 01/30/2023]
Abstract
Transepithelial resistance and tight junction protein localization in porcine intestinal epithelial cells were evaluated as a function of infection with porcine enterotoxigenic Escherichia coli isolates differing in adhesin and enterotoxin profiles. Robust heat-labile enterotoxin-independent reduction of host transepithelial resistance was observed in the absence of tight junction protein mislocalization.
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Affiliation(s)
- Amber M Johnson
- Department of Veterinary Science, South Dakota State University, Brookings, SD 57007, USA
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