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Huang CK, Paylaga GJ, Bupphathong S, Lin KH. Spherical microwell arrays for studying single cells and microtissues in 3D confinement. Biofabrication 2020; 12:025016. [PMID: 31974317 DOI: 10.1088/1758-5090/ab6eda] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Microwell arrays have emerged as three-dimensional substrates for cell culture due to their simplicity of fabrication and promise for high-throughput applications such as 3D cell-based assays for drug screening. To date, most microwells have had cylindrical geometries. Motivated by our previous findings that cells display 3D physiological characteristics when grown in the spherical micropores of monodisperse foam scaffolds (Lee et al 2013 Integr. Biol. 5 1447-55 and Lin et al 2011 Soft Matter 7 10010-6), here we engineered novel microwells shaped as spherical caps with obtuse polar angles, yielding narrow apertures. When used as bare substrates, these microwells were suitable for culturing cell spheroids; the narrow apertures sterically hindered unattached cultured cells from rolling out of microwells under agitation. When only the walls of the microwell were conjugated with extracellular matrix proteins, cells remained confined in the microwells. Epithelial cells proliferated and burst out of the aperture, and cell polarity was oriented based on the distribution of extracellular matrix proteins in the microwells. Surprisingly, single fibroblast cells in spherical wells of various diameters (40-100 μm) underwent cell-cycle arrest, while cells in circular cylindrical microwells continued to proliferate. Spatial confinement was not sufficient to cause cell-cycle arrest; however, confinement in a constant negative-curvature microenvironment led to cell-cycle arrest. Overall, these investigations demonstrate that this spherical microwell substrate constitutes a novel basic research tool for elucidating how cells respond to dimensionality and microenvironment with radii of curvature at the cellular length scale.
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Garber JJ, Mallick EM, Scanlon KM, Turner JR, Donnenberg MS, Leong JM, Snapper SB. Attaching-and-Effacing Pathogens Exploit Junction Regulatory Activities of N-WASP and SNX9 to Disrupt the Intestinal Barrier. Cell Mol Gastroenterol Hepatol 2017; 5:273-288. [PMID: 29675452 PMCID: PMC5904039 DOI: 10.1016/j.jcmgh.2017.11.015] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Accepted: 11/28/2017] [Indexed: 02/05/2023]
Abstract
BACKGROUND & AIMS Neural Wiskott-Aldrich Syndrome protein (N-WASP) is a key regulator of the actin cytoskeleton in epithelial tissues and is poised to mediate cytoskeletal-dependent aspects of apical junction complex (AJC) homeostasis. Attaching-and-effacing (AE) pathogens disrupt this homeostasis through translocation of the effector molecule early secreted antigenic target-6 (ESX)-1 secretion-associated protein F (EspF). Although the mechanisms underlying AJC disruption by EspF are unknown, EspF contains putative binding sites for N-WASP and the endocytic regulator sorting nexin 9 (SNX9). We hypothesized that N-WASP regulates AJC integrity and AE pathogens use EspF to induce junction disassembly through an N-WASP- and SNX9-dependent pathway. METHODS We analyzed mice with intestine-specific N-WASP deletion and generated cell lines with N-WASP and SNX9 depletion for dynamic functional assays. We generated EPEC and Citrobacter rodentium strains complemented with EspF bearing point mutations abolishing N-WASP and SNX9 binding to investigate the requirement for these interactions. RESULTS Mice lacking N-WASP in the intestinal epithelium showed spontaneously increased permeability, abnormal AJC morphology, and mislocalization of occludin. N-WASP depletion in epithelial cell lines led to impaired assembly and disassembly of tight junctions in response to changes in extracellular calcium. Cells lacking N-WASP or SNX9 supported actin pedestals and type III secretion, but were resistant to EPEC-induced AJC disassembly and loss of transepithelial resistance. We found that during in vivo infection with AE pathogens, EspF must bind both N-WASP and SNX9 to disrupt AJCs and induce intestinal barrier dysfunction. CONCLUSIONS Overall, these studies show that N-WASP critically regulates AJC homeostasis, and the AE pathogen effector EspF specifically exploits both N-WASP and SNX9 to disrupt intestinal barrier integrity during infection.
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Key Words
- ADF, actin depolymerization factor
- AE, attaching-and-effacing
- AJ, adherens junction
- AJC, apical junction complex
- Arp, actin-related protein
- CR, Citrobacter rodentium
- Crb, Crumbs
- Cytoskeleton
- DBS100, David B. Schauer 100
- EHEC, enterohemorrhagic Escherichia coli
- EM, electron microscopy
- EPEC, enteropathogenic Escherichia coli
- EcoRI, E. coli RY13 I
- EspF
- EspF, early secreted antigenic target-6 (ESX)-1 secretion-associated protein F
- FITC, fluorescein isothiocyanate
- Junction Regulation
- KO, knockout
- N-WASP
- N-WASP, Neural Wiskott-Aldrich Syndrome protein
- NWKD, Neural Wiskott-Aldrich Syndrome protein knockdown
- PBS, phosphate-buffered saline
- PCR, polymerase chain reaction
- SNX9, sorting nexin 9
- SNX9KD, sorting nexin 9 knockdown
- TER, transepithelial electrical resistance
- TJ, tight junction
- Tir, translocated intimin receptor
- ZO-1, zonula occludens-1
- iNWKO, intestine Neural Wiskott-Aldrich Syndrome protein knockout
- shRNA, short hairpin RNA
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Affiliation(s)
- John J. Garber
- Gastrointestinal Unit, Massachusetts General Hospital, Boston, Massachusetts,Division of Gastroenterology/Nutrition and Center for Inflammatory Bowel Disease Treatment and Research, Boston Children's Hospital, Boston, Massachusetts,Department of Medicine, Harvard Medical School, Boston, Massachusetts
| | - Emily M. Mallick
- Department of Medicine Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, Massachusetts
| | - Karen M. Scanlon
- Department of Medicine and Department of Microbiology and Immunology, School of Medicine, University of Maryland, Baltimore, Maryland
| | - Jerrold R. Turner
- Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts,Department of Medicine, Harvard Medical School, Boston, Massachusetts
| | - Michael S. Donnenberg
- Department of Medicine and Department of Microbiology and Immunology, School of Medicine, University of Maryland, Baltimore, Maryland
| | - John M. Leong
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts
| | - Scott B. Snapper
- Division of Gastroenterology/Nutrition and Center for Inflammatory Bowel Disease Treatment and Research, Boston Children's Hospital, Boston, Massachusetts,Division of Gastroenterology and Hepatology, Brigham and Women's Hospital, Boston, Massachusetts,Department of Medicine, Harvard Medical School, Boston, Massachusetts,Correspondence Address correspondence to: Scott B. Snapper, MD, PhD, Division of Gastroenterology/Nutrition, Boston Children’s Hospital, Enders 676, 300 Longwood Avenue, Boston, Massachusetts 02115. fax: (617) 730-0498.
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Ourradi K, Blythe T, Jarrett C, Barratt SL, Welsh GI, Millar AB. VEGF isoforms have differential effects on permeability of human pulmonary microvascular endothelial cells. Respir Res 2017; 18:116. [PMID: 28578669 PMCID: PMC5457598 DOI: 10.1186/s12931-017-0602-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Accepted: 05/30/2017] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Alternative splicing of Vascular endothelial growth factor-A mRNA transcripts (commonly referred as VEGF) leads to the generation of functionally differing isoforms, the relative amounts of which have potentially significant physiological outcomes in conditions such as acute respiratory distress syndrome (ARDS). The effect of such isoforms on pulmonary vascular permeability is unknown. We hypothesised that VEGF165a and VEGF165b isoforms would have differing effects on pulmonary vascular permeability caused by differential activation of intercellular signal transduction pathways. METHOD To test this hypothesis we investigated the physiological effect of VEGF165a and VEGF165b on Human Pulmonary Microvascular Endothelial Cell (HPMEC) permeability using three different methods: trans-endothelial electrical resistance (TEER), Electric cell-substrate impedance sensing (ECIS) and FITC-BSA passage. In addition, potential downstream signalling pathways of the VEGF isoforms were investigated by Western blotting and the use of specific signalling inhibitors. RESULTS VEGF165a increased HPMEC permeability using all three methods (paracellular and transcellular) and led to associated VE-cadherin and actin stress fibre changes. In contrast, VEGF165b decreased paracellular permeability and did not induce changes in VE-cadherin cell distribution. Furthermore, VEGF165a and VEGF165b had differing effects on both the phosphorylation of VEGF receptors and downstream signalling proteins pMEK, p42/44MAPK, p38 MAPK, pAKT and peNOS. Interestingly specific inhibition of the pMEK, p38 MAPK, PI3 kinase and eNOS pathways blocked the effects of both VEGF165a and VEGF165b on paracellular permeability and the effect of VEGF165a on proliferation/migration, suggesting that this difference in cellular response is mediated by an as yet unidentified signalling pathway(s). CONCLUSION This study demonstrates that the novel isoform VEGF165a and VEGF165b induce differing effects on permeability in pulmonary microvascular endothelial cells.
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Affiliation(s)
- Khadija Ourradi
- Academic Respiratory Unit, School of Clinical Sciences, University of Bristol, Bristol, UK
| | - Thomas Blythe
- Academic Respiratory Unit, School of Clinical Sciences, University of Bristol, Bristol, UK
| | - Caroline Jarrett
- Academic Respiratory Unit, School of Clinical Sciences, University of Bristol, Bristol, UK
| | - Shaney L Barratt
- Academic Respiratory Unit, School of Clinical Sciences, University of Bristol, Bristol, UK
| | - Gavin I Welsh
- Bristol Renal, School of Clinical Sciences, University of Bristol, Bistol, UK
| | - Ann B Millar
- Academic Respiratory Unit, School of Clinical Sciences, University of Bristol, Bristol, UK.
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Martínez-Rendón J, Sánchez-Guzmán E, Rueda A, González J, Gulias-Cañizo R, Aquino-Jarquín G, Castro-Muñozledo F, García-Villegas R. TRPV4 Regulates Tight Junctions and Affects Differentiation in a Cell Culture Model of the Corneal Epithelium. J Cell Physiol 2016; 232:1794-1807. [PMID: 27869310 DOI: 10.1002/jcp.25698] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 11/17/2016] [Indexed: 11/09/2022]
Abstract
TRPV4 (transient receptor potential vanilloid 4) is a cation channel activated by hypotonicity, moderate heat, or shear stress. We describe the expression of TRPV4 during the differentiation of a corneal epithelial cell model, RCE1(5T5) cells. TRPV4 is a late differentiation feature that is concentrated in the apical membrane of the outmost cell layer of the stratified epithelia. Ca2+ imaging experiments showed that TRPV4 activation with GSK1016790A produced an influx of calcium that was blunted by the specific TRPV4 blocker RN-1734. We analyzed the involvement of TRPV4 in RCE1(5T5) epithelial differentiation by measuring the development of transepithelial electrical resistance (TER) as an indicator of the tight junction (TJ) assembly. We showed that TRPV4 activity was necessary to establish the TJ. In differentiated epithelia, activation of TRPV4 increases the TER and the accumulation of claudin-4 in cell-cell contacts. Epidermal Growth Factor (EGF) up-regulates the TER of corneal epithelial cultures, and we show here that TRPV4 activation mimicked this EGF effect. Conversely, TRPV4 inhibition or knock down by specific shRNA prevented the increase in TER. Moreover, TRPP2, an EGF-activated channel that forms heteromeric complexes with TRPV4, is also concentrated in the outmost cell layer of differentiated RCE1(5T5) sheets. This suggests that the EGF regulation of the TJ may involve a heterotetrameric TRPV4-TRPP2 channel. These results demonstrated TRPV4 activity was necessary for the correct establishment of TJ in corneal epithelia and as well as the regulation of both the barrier function of TJ and its ability to respond to EGF. J. Cell. Physiol. 232: 1794-1807, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Jacqueline Martínez-Rendón
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
| | - Erika Sánchez-Guzmán
- Departamento de Biología Celular, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
| | - Angélica Rueda
- Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
| | - James González
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
| | - Rosario Gulias-Cañizo
- Departamento de Biología Celular, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
| | - Guillermo Aquino-Jarquín
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
| | - Federico Castro-Muñozledo
- Departamento de Biología Celular, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
| | - Refugio García-Villegas
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
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Thakkar A, Aljameeli A, Thomas S, Shah GV. A-kinase anchoring protein 2 is required for calcitonin-mediated invasion of cancer cells. Endocr Relat Cancer 2016; 23:1-14. [PMID: 26432469 PMCID: PMC4734633 DOI: 10.1530/erc-15-0425] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 10/02/2015] [Indexed: 12/20/2022]
Abstract
Expression of neuropeptide calcitonin (CT) and its receptor (CTR) is frequently elevated in prostate cancers (PCs) and activation of CT-CTR axis in non-invasive PC cells induces an invasive phenotype. Specific, cell-permeable inhibitors of protein kinase A abolish CTR-stimulated invasion of PC cells. Since PKA is ubiquitously distributed in cells, the present study examined the mechanism(s) by which CTR-stimulated PKA activity is regulated in time and space. CT reduced cell adhesion but increased invasion of PC cells. Both these actions were abolished by st-Ht31 inhibitory peptide suggesting the involvement of an A-kinase anchoring protein (AKAP) in CT action. Next, we identified the AKAP associated with CT action by the subtraction of potential AKAP candidates using siRNAs. Knock-down of membrane-associated AKAP2, but not other AKAPs, abolished CT-stimulated invasion. Stable knock-down of AKAP2 in PC3-CTR cells remarkably decreased their cell proliferation, invasion, clonogenicity and ability to form orthotopic tumors and distant metastases in nude mice. Re-expression of AKAP2-wt restored these characteristics. Primary PC specimens displayed remarkable upregulation of CTR/AKAP2 expression as compared to benign prostates. Metastatic cancers displayed significantly higher CTR/AKAP2 expression than localized cancers. These results for the first time demonstrate that AKAP2 is expressed in human prostates, its expression is elevated in metastatic prostate cancer, and the knock-down of its expression remarkably decreased tumorigenicity and metastatic ability of prostate cancer cells. AKAP2 may serve as a critical component of CTR-mediated oncogenic actions.
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Affiliation(s)
- Arvind Thakkar
- PharmacologyCollege of Pharmacy, University of Louisiana, Monroe, Louisiana 71291, USA
| | - Ahmed Aljameeli
- PharmacologyCollege of Pharmacy, University of Louisiana, Monroe, Louisiana 71291, USA
| | - Shibu Thomas
- PharmacologyCollege of Pharmacy, University of Louisiana, Monroe, Louisiana 71291, USA
| | - Girish V Shah
- PharmacologyCollege of Pharmacy, University of Louisiana, Monroe, Louisiana 71291, USA
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Gerber J, Heinrich J, Brehm R. Blood-testis barrier and Sertoli cell function: lessons from SCCx43KO mice. Reproduction 2015; 151:R15-27. [PMID: 26556893 DOI: 10.1530/rep-15-0366] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 11/10/2015] [Indexed: 01/23/2023]
Abstract
The gap junction protein connexin43 (CX43) plays a vital role in mammalian spermatogenesis by allowing for direct cytoplasmic communication between neighbouring testicular cells. In addition, different publications suggest that CX43 in Sertoli cells (SC) might be important for blood-testis barrier (BTB) formation and BTB homeostasis. Thus, through the use of the Cre-LoxP recombination system, a transgenic mouse line was developed in which only SC are deficient of the gap junction protein, alpha 1 (Gja1) gene. Gja1 codes for the protein CX43. This transgenic mouse line has been commonly defined as the SC specific CX43 knockout (SCCx43KO) mouse line. Within the seminiferous tubule, SC aid in spermatogenesis by nurturing germ cells and help them to proliferate and mature. Owing to the absence of CX43 within the SC, homozygous KO mice are infertile, have reduced testis size, and mainly exhibit spermatogenesis arrest at the level of spermatogonia, seminiferous tubules containing only SC (SC-only syndrome) and intratubular SC-clusters. Although the SC specific KO of CX43 does not seem to have an adverse effect on BTB integrity, CX43 influences BTB composition as the expression pattern of different BTB proteins (like OCCLUDIN, β-CATENIN, N-CADHERIN, and CLAUDIN11) is altered in mutant males. The supposed roles of CX43 in dynamic BTB regulation, BTB assembly and/or disassembly and its possible interaction with other junctional proteins composing this unique barrier are discussed. Data collectively indicate that CX43 might represent an important regulator of dynamic BTB formation, composition and function.
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Affiliation(s)
- Jonathan Gerber
- Institute of AnatomyUniversity of Veterinary Medicine Hannover, Foundation, Bischofsholer Damm 15, 30173 Hannover, Germany
| | - Julia Heinrich
- Institute of AnatomyUniversity of Veterinary Medicine Hannover, Foundation, Bischofsholer Damm 15, 30173 Hannover, Germany
| | - Ralph Brehm
- Institute of AnatomyUniversity of Veterinary Medicine Hannover, Foundation, Bischofsholer Damm 15, 30173 Hannover, Germany
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Bauer HC, Krizbai IA, Bauer H, Traweger A. "You Shall Not Pass"-tight junctions of the blood brain barrier. Front Neurosci 2014; 8:392. [PMID: 25520612 PMCID: PMC4253952 DOI: 10.3389/fnins.2014.00392] [Citation(s) in RCA: 165] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Accepted: 11/14/2014] [Indexed: 12/31/2022] Open
Abstract
The structure and function of the barrier layers restricting the free diffusion of substances between the central nervous system (brain and spinal cord) and the systemic circulation is of great medical interest as various pathological conditions often lead to their impairment. Excessive leakage of blood-borne molecules into the parenchyma and the concomitant fluctuations in the microenvironment following a transient breakdown of the blood-brain barrier (BBB) during ischemic/hypoxic conditions or because of an autoimmune disease are detrimental to the physiological functioning of nervous tissue. On the other hand, the treatment of neurological disorders is often hampered as only minimal amounts of therapeutic agents are able to penetrate a fully functional BBB or blood cerebrospinal fluid barrier. An in-depth understanding of the molecular machinery governing the establishment and maintenance of these barriers is necessary to develop rational strategies allowing a controlled delivery of appropriate drugs to the CNS. At the basis of such tissue barriers are intimate cell-cell contacts (zonulae occludentes, tight junctions) which are present in all polarized epithelia and endothelia. By creating a paracellular diffusion constraint TJs enable the vectorial transport across cell monolayers. More recent findings indicate that functional barriers are already established during development, protecting the fetal brain. As an understanding of the biogenesis of TJs might reveal the underlying mechanisms of barrier formation during ontogenic development numerous in vitro systems have been developed to study the assembly and disassembly of TJs. In addition, monitoring the stage-specific expression of TJ-associated proteins during development has brought much insight into the “developmental tightening” of tissue barriers. Over the last two decades a detailed molecular map of transmembrane and cytoplasmic TJ-proteins has been identified. These proteins not only form a cell-cell adhesion structure, but integrate various signaling pathways, thereby directly or indirectly impacting upon processes such as cell-cell adhesion, cytoskeletal rearrangement, and transcriptional control. This review will provide a brief overview on the establishment of the BBB during embryonic development in mammals and a detailed description of the ultrastructure, biogenesis, and molecular composition of epithelial and endothelial TJs will be given.
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Affiliation(s)
- Hans-Christian Bauer
- Institute of Tendon and Bone Regeneration, Paracelsus Medical University - Spinal Cord Injury and Tissue Regeneration Center Salzburg Salzburg, Austria ; Department of Traumatology and Sports Injuries, Paracelsus Medical University Salzburg, Austria ; Austrian Cluster for Tissue Regeneration Vienna, Austria
| | - István A Krizbai
- Biological Research Centre, Institute of Biophysics, Hungarian Academy of Sciences Szeged, Hungary ; Institute of Life Sciences, Vasile Goldis Western University of Arad Arad, Romania
| | - Hannelore Bauer
- Department of Organismic Biology, University of Salzburg Salzburg, Austria
| | - Andreas Traweger
- Institute of Tendon and Bone Regeneration, Paracelsus Medical University - Spinal Cord Injury and Tissue Regeneration Center Salzburg Salzburg, Austria ; Austrian Cluster for Tissue Regeneration Vienna, Austria
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Yamamoto T, Takahashi H, Suzuki K, Hirano A, Kamei M, Goto T, Takahashi N, Kawada T. Theobromine enhances absorption of cacao polyphenol in rats. Biosci Biotechnol Biochem 2014; 78:2059-63. [PMID: 25079983 DOI: 10.1080/09168451.2014.942252] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Several concentrations of theobromine (TB) and (-)-epicatechin (EC) were coadministered to rats, and plasma EC and its metabolites were determined using ultra-high-performance liquid chromatography-tandem mass spectrometry. It has been demonstrated that TB increases the absorption of EC in a dose-dependent manner. Cocoa powder had a similar effect, and the mechanism involved is not thought to depend on tight junctions.
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Affiliation(s)
- Takayuki Yamamoto
- a Laboratory of Molecular Functions of Food, Division of Food Science and Biotechnology , Graduate School of Agriculture, Kyoto University , Uji , Japan
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Abstract
Hepatocytes, like other epithelia, are situated at the interface between the organism's exterior and the underlying internal milieu and organize the vectorial exchange of macromolecules between these two spaces. To mediate this function, epithelial cells, including hepatocytes, are polarized with distinct luminal domains that are separated by tight junctions from lateral domains engaged in cell-cell adhesion and from basal domains that interact with the underlying extracellular matrix. Despite these universal principles, hepatocytes distinguish themselves from other nonstriated epithelia by their multipolar organization. Each hepatocyte participates in multiple, narrow lumina, the bile canaliculi, and has multiple basal surfaces that face the endothelial lining. Hepatocytes also differ in the mechanism of luminal protein trafficking from other epithelia studied. They lack polarized protein secretion to the luminal domain and target single-spanning and glycosylphosphatidylinositol-anchored bile canalicular membrane proteins via transcytosis from the basolateral domain. We compare this unique hepatic polarity phenotype with that of the more common columnar epithelial organization and review our current knowledge of the signaling mechanisms and the organization of polarized protein trafficking that govern the establishment and maintenance of hepatic polarity. The serine/threonine kinase LKB1, which is activated by the bile acid taurocholate and, in turn, activates adenosine monophosphate kinase-related kinases including AMPK1/2 and Par1 paralogues has emerged as a key determinant of hepatic polarity. We propose that the absence of a hepatocyte basal lamina and differences in cell-cell adhesion signaling that determine the positioning of tight junctions are two crucial determinants for the distinct hepatic and columnar polarity phenotypes.
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Affiliation(s)
- Aleksandr Treyer
- Albert Einstein College of Medicine, Department of Developmental and Molecular Biology, Bronx, New York, USA
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Liu C, Wu J, Zou MH. Activation of AMP-activated protein kinase alleviates high-glucose-induced dysfunction of brain microvascular endothelial cell tight-junction dynamics. Free Radic Biol Med 2012; 53:1213-21. [PMID: 22796592 PMCID: PMC3437014 DOI: 10.1016/j.freeradbiomed.2012.07.003] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2012] [Revised: 05/10/2012] [Accepted: 07/03/2012] [Indexed: 11/28/2022]
Abstract
The blood-brain barrier, formed by specialized brain endothelial cells that are interconnected by tight junctions, strictly regulates paracellular permeability to maintain an optimal extracellular environment for brain homeostasis. Diabetes is known to compromise the blood-brain barrier, although the underlying mechanism remains unknown. The aim of this study was to elucidate the molecular mechanisms underlying disruption of the blood-brain barrier in diabetes and to determine whether activation of AMP-activated protein kinase prevents diabetes-induced blood-brain barrier dysfunction. Exposure of human brain microvascular endothelial cells to high glucose (25 mmol/L D-glucose), but not to high osmotic conditions (20 mmol/L L-glucose plus 5 mmol/L D-glucose), for 2h to 1 week significantly increased the permeability of the blood-brain barrier in parallel with lowered expression levels of zonula occludens-1, occludin, and claudin-5, three proteins that are essential to maintaining endothelial cell tight junctions. In addition, high glucose significantly increased the generation of superoxide anions. Adenoviral overexpression of superoxide dismutase or catalase significantly attenuated the high-glucose-induced reduction of endothelial cell tight-junction proteins. Furthermore, administration of apocynin reversed the effects of high glucose on endothelial cell tight-junction proteins. Finally, activation of AMP-activated protein kinase with 5-amino-4-imidazole carboxamide riboside or adenoviral overexpression of constitutively active AMP-activated protein kinase mutants abolished both the induction of NAD(P)H oxidase-derived superoxide anions and the tight-junction protein degradation induced by high glucose. We conclude that high glucose increases blood-brain barrier dysfunction in diabetes through induction of superoxide anions and that the activation of AMP-activated protein kinase protects the integrity of the blood-brain barrier by suppressing the induction of NAD(P)H oxidase-derived superoxide anions.
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Affiliation(s)
- Chao Liu
- Hubei Province Key Laboratory on Cardiovascular, Cerebrovascular, and Metabolic Disorders, Xianning University, Xianning, Hubei 437100, China
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Abstract
The formation of axon/dendrite polarity is critical for the neuron to perform its signaling function in the brain. Recent advance in our understanding of cellular and molecular mechanisms underlying the development and maintenance of neuronal polarity has been greatly facilitated by the use of the culture system of dissociated hippocampal neurons. Among many polarization-related proteins, we here focus on the mammalian LKB1, the counterpart of the C. elegans Par-4, which is an upstream regulator among six Par (partitioning-defective) genes that act as master regulators of cell polarity in different cell types across evolutionary distant species. Recent studies have identified LKB1 and its downstream targets SAD/MARK kinases (mammalian homologs of Par-1) as key regulators of neuronal polarization and axon development in cultured neurons and in developing cortical neurons in vivo. We will review the properties of and interactions among proteins in this LKB1-SAD/MARK pathway, drawing upon information obtained from both neuronal and non-neuronal systems. Due to central role of the protein kinase A-dependent phosphorylation of LKB1 in the activation of this pathway, we will review recent findings on how cAMP and cGMP signaling may serve as antagonistic second messengers for axon/dendrite development, and how these cyclic nucleotides may mediate the action of extracellular polarizing factors by modulating the activity of the LKB1-SAD/MARK pathway.
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Affiliation(s)
- Maya Shelly
- Department of Neurobiology and Behavior, State University of New York, Stony Brook, NY 11794-5230, USA.
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Klein RR, Bourdon DM, Costales CL, Wagner CD, White WL, Williams JD, Hicks SN, Sondek J, Thakker DR. Direct activation of human phospholipase C by its well known inhibitor u73122. J Biol Chem 2011; 286:12407-16. [PMID: 21266572 DOI: 10.1074/jbc.m110.191783] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phospholipase C (PLC) enzymes are an important family of regulatory proteins involved in numerous cellular functions, primarily through hydrolysis of the polar head group from inositol-containing membrane phospholipids. U73122 (1-(6-((17β-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione), one of only a few small molecules reported to inhibit the activity of these enzymes, has been broadly applied as a pharmacological tool to implicate PLCs in diverse experimental phenotypes. The purpose of this study was to develop a better understanding of molecular interactions between U73122 and PLCs. Hence, the effects of U73122 on human PLCβ3 (hPLCβ3) were evaluated in a cell-free micellar system. Surprisingly, U73122 increased the activity of hPLCβ3 in a concentration- and time-dependent manner; up to an 8-fold increase in enzyme activity was observed with an EC50=13.6±5 μm. Activation of hPLCβ3 by U73122 required covalent modification of cysteines as evidenced by the observation that enzyme activation was attenuated by thiol-containing nucleophiles, l-cysteine and glutathione. Mass spectrometric analysis confirmed covalent reaction with U73122 at eight cysteines, although maximum activation was achieved without complete alkylation; the modified residues were identified by LC/MS/MS peptide sequencing. Interestingly, U73122 (10 μm) also activated hPLCγ1 (>10-fold) and hPLCβ2 (∼2-fold); PLCδ1 was neither activated nor inhibited. Therefore, in contrast to its reported inhibitory potential, U73122 failed to inhibit several purified PLCs. Most of these PLCs were directly activated by U73122, and a simple mechanism for the activation is proposed. These results strongly suggest a need to re-evaluate the use of U73122 as a general inhibitor of PLC isozymes.
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Affiliation(s)
- Ryan R Klein
- Division of Molecular Pharmaceutics, UNC Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, NC 27599-7360, USA
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13
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Terry S, Nie M, Matter K, Balda MS. Rho signaling and tight junction functions. Physiology (Bethesda) 2010; 25:16-26. [PMID: 20134025 DOI: 10.1152/physiol.00034.2009] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Tight junctions are heteromeric protein complexes that act as signaling centers by mediating the bidirectional transmission of information between the environment and the cell interior to control paracellular permeability and differentiation. Insight into tight junction-associated signaling mechanisms is of fundamental importance for our understanding of the physiology of epithelia and endothelia in health and disease.
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Affiliation(s)
- Steve Terry
- Department of Cell Biology, UCL Institute of Ophthalmology, University College London, London, United Kingdom
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14
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Epithelial cell–cell junctions and plasma membrane domains. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:820-31. [DOI: 10.1016/j.bbamem.2008.07.015] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2008] [Revised: 07/10/2008] [Accepted: 07/21/2008] [Indexed: 12/16/2022]
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15
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Sabath E, Negoro H, Beaudry S, Paniagua M, Angelow S, Shah J, Grammatikakis N, Yu ASL, Denker BM. Galpha12 regulates protein interactions within the MDCK cell tight junction and inhibits tight-junction assembly. J Cell Sci 2008; 121:814-24. [PMID: 18285450 DOI: 10.1242/jcs.014878] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The polarized functions of epithelia require an intact tight junction (TJ) to restrict paracellular movement and to separate membrane proteins into specific domains. TJs contain scaffolding, integral membrane and signaling proteins, but the mechanisms that regulate TJs and their assembly are not well defined. Galpha12 (GNA12) binds the TJ protein ZO-1 (TJP1), and Galpha12 activates Src to increase paracellular permeability via unknown mechanisms. Herein, we identify Src as a component of the TJ and find that recruitment of Hsp90 to activated Galpha12 is necessary for signaling. TJ integrity is disrupted by Galpha12-stimulated Src phosphorylation of ZO-1 and ZO-2 (TJP2); this phosphorylation leads to dissociation of occludin and claudin 1 from the ZO-1 protein complex. Inhibiting Hsp90 with geldanamycin blocks Galpha12-stimulated Src activation and phosphorylation, but does not affect protein levels or the Galpha12-ZO-1 interaction. Using the calcium-switch model of TJ assembly and GST-TPR (GST-fused TPR domain of PP5) pull-downs of activated Galpha12, we demonstrate that switching to normal calcium medium activates endogenous Galpha12 during TJ assembly. Thrombin increases permeability and delays TJ assembly by activating Galpha12, but not Galpha13, signaling pathways. These findings reveal an important role for Galpha12, Src and Hsp90 in regulating the TJ in established epithelia and during TJ assembly.
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Affiliation(s)
- Ernesto Sabath
- Renal Division, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
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16
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Jacquillet G, Barbier O, Rubera I, Tauc M, Borderie A, Namorado MC, Martin D, Sierra G, Reyes JL, Poujeol P, Cougnon M. Cadmium causes delayed effects on renal function in the offspring of cadmium-contaminated pregnant female rats. Am J Physiol Renal Physiol 2007; 293:F1450-60. [PMID: 17686954 DOI: 10.1152/ajprenal.00223.2007] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In the adult rat, chronic cadmium intoxication induces nephropathy with Fanconi-like features. This result raises the question of whether intoxication of pregnant rats has any deleterious effects on renal function in their offspring. To test this hypothesis, we measured the renal function of 2- to 60-day-old postnatal offspring from female rats administered cadmium chloride by the oral route (0.5 mg·kg−1·day−1) throughout their entire gestation. Investigations of rat offspring from contaminated pregnant rats showed the presence of cadmium in the kidney at gestational day 20. After birth, the cadmium kidney concentration increased from postnatal day 2 to day 60 (PND2 to PND60), presumably because of 1) milk contamination and 2) neonatal liver cadmium content release. Although the renal parameters (glomerular filtration, U/P inulin, and urinary excretion rate) were not significantly affected until PND45, renal failure appeared at PND60, as demonstrated by a dramatic decrease of the glomerular filtration rate associated with increased excretion of the main ions. In parallel, an immunofluorescence study of tight-junction protein expression of PND60 offspring from contaminated rats showed a disorganization of the tight-junction proteins claudin-2 and claudin-5, specifically expressed in the proximal tubule and glomerulus, respectively. In contrast, expression of a distal claudin protein, claudin-3, was not affected. In conclusion, in utero exposure of cadmium leads to toxic renal effects in adult offspring. These results suggest that contamination of pregnant rats is a serious and critical hazard for renal function of their offspring.
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Affiliation(s)
- G Jacquillet
- Unité Mixte de Recherche-Centre National de la Recherche Scientifique 6548, Université de Nice-Sophia Antipolis, Nice, France
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17
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Wu J, Yang Y, Zhang J, Ji P, Du W, Jiang P, Xie D, Huang H, Wu M, Zhang G, Wu J, Shi Y. Domain-swapped dimerization of the second PDZ domain of ZO2 may provide a structural basis for the polymerization of claudins. J Biol Chem 2007; 282:35988-99. [PMID: 17897942 DOI: 10.1074/jbc.m703826200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Zonula occludens proteins (ZOs), including ZO1/2/3, are tight junction-associated proteins. Each of them contains three PDZ domains. It has been demonstrated that ZO1 can form either homodimers or heterodimers with ZO2 or ZO3 through the second PDZ domain. However, the underlying structural basis is not well understood. In this study, the solution structure of the second PDZ domain of ZO2 (ZO2-PDZ2) was determined using NMR spectroscopy. The results revealed a novel dimerization mode for PDZ domains via three-dimensional domain swapping, which can be generalized to homodimers of ZO1-PDZ2 or ZO3-PDZ2 and heterodimers of ZO1-PDZ2/ZO2-PDZ2 or ZO1-PDZ2/ZO3-PDZ2 due to high conservation between PDZ2 domains in ZO proteins. Furthermore, GST pulldown experiments and immunoprecipitation studies demonstrated that interactions between ZO1-PDZ2 and ZO2-PDZ2 and their self-associations indeed exist both in vitro and in vivo. Chemical cross-linking and dynamic laser light scattering experiments revealed that both ZO1-PDZ2 and ZO2-PDZ2 can form oligomers in solution. This PDZ domain-mediated oligomerization of ZOs may provide a structural basis for the polymerization of claudins, namely the formation of tight junctions.
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Affiliation(s)
- Jiawen Wu
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
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18
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Cereijido M, Contreras RG, Shoshani L, Flores-Benitez D, Larre I. Tight junction and polarity interaction in the transporting epithelial phenotype. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1778:770-93. [PMID: 18028872 DOI: 10.1016/j.bbamem.2007.09.001] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2007] [Revised: 08/28/2007] [Accepted: 09/03/2007] [Indexed: 12/21/2022]
Abstract
Development of tight junctions and cell polarity in epithelial cells requires a complex cellular machinery to execute an internal program in response to ambient cues. Tight junctions, a product of this machinery, can act as gates of the paracellular pathway, fences that keep the identity of plasma membrane domains, bridges that communicate neighboring cells. The polarization internal program and machinery are conserved in yeast, worms, flies and mammals, and in cell types as different as epithelia, neurons and lymphocytes. Polarization and tight junctions are dynamic features that change during development, in response to physiological and pharmacological challenges and in pathological situations like infection.
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Affiliation(s)
- Marcelino Cereijido
- Department of Physiology, Biophysics and Neurosciences, CINVESTAV, AP 14-740, México D.F. 07000, México.
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19
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Moyes SM, Smyth SH, Shipman A, Long S, Morris JF, Carr KE. Parameters influencing intestinal epithelial permeability and microparticle uptake in vitro. Int J Pharm 2007; 337:133-41. [PMID: 17306478 DOI: 10.1016/j.ijpharm.2006.12.036] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2006] [Revised: 12/21/2006] [Accepted: 12/23/2006] [Indexed: 10/23/2022]
Abstract
The hypothesis that, in vivo in situ, villous uptake of 2 microm latex microparticles involves changes at enterocyte tight junctions (TJs) was tested using Caco-2 cells on porous membranes. Epithelial permeability was measured by transepithelial resistance (TER) and particle numbers in surface, intraepithelial and sub-epithelial compartments by microscopy. Apical particle or medium addition initially closed TJs, but this was subsequently reversed in particle-treated groups. Peristaltic onward movement of a bolus was simulated by removing apical particles after an exposure period and leaving the remaining particles to interact with the epithelium: this produced marked TJ loosening during the interaction period. For particle exposure groups, the early similarity with particle numbers in vivo taken up in young adult rats became less marked with time, although bolus removal counteracted this tendency. The TJ response to vasoactive intestinal polypeptide (VIP) was time-dependent. Adsorbed and intraepithelial particle numbers increased with particle exposure time; epithelial-associated microparticle aggregation varied with treatment and submembranous particles were seen in all groups. Correlation between TER changes and particle numbers suggests TJ loosening may be important in microparticle uptake. This Caco-2 model gives epithelial particle numbers that approximate well to published figures for microparticle uptake in vivo and allows effective microenvironmental manipulation.
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Affiliation(s)
- S M Moyes
- Department of Physiology, Anatomy and Genetics, Le Gros Clark Building, University of Oxford, South Parks Road, Oxford OX1 3QX, United Kingdom.
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20
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Alexandre MD, Jeansonne BG, Renegar RH, Tatum R, Chen YH. The first extracellular domain of claudin-7 affects paracellular Cl- permeability. Biochem Biophys Res Commun 2007; 357:87-91. [PMID: 17400193 DOI: 10.1016/j.bbrc.2007.03.078] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2007] [Accepted: 03/14/2007] [Indexed: 12/22/2022]
Abstract
Tight junctions (TJ) constitute paracellular diffusion channels regulating the passage of ions and solutes across epithelia. We recently demonstrated that overexpression of the TJ membrane protein claudin-7 in LLC-PK1 cells decreases paracellular permeability to Cl(-) and increases paracellular permeability to Na(+). To investigate the effect of charged amino acid residues in extracellular domains (ED) of claudin-7 on paracellular charge selectivity, we created claudin-7 mutants by replacing negatively charged amino acids on ED with positively charged amino acids. Immunofluorescence light microscopy showed that these mutant proteins were correctly targeted to the cell junction. Ultrastructure examination of TJ morphology did not reveal any difference between cells expressing wildtype (WT) and mutant claudin-7. However, electrophysiological studies showed increased Cl(-) permeability in cells expressing first extracellular domain (ED1) mutants, but not second extracellular domain (ED2) mutants, compared to that of WT claudin-7. Our results demonstrate that negatively charged amino acids in ED1 of claudin-7 are involved in modulating paracellular Cl(-) permeability.
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Affiliation(s)
- Michele D Alexandre
- Department of Anatomy and Cell Biology, East Carolina University, Brody School of Medicine, Greenville, NC 27834, USA
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21
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Siddharthan V, V. Kim Y, Liu S, Kim KS. Human astrocytes/astrocyte-conditioned medium and shear stress enhance the barrier properties of human brain microvascular endothelial cells. Brain Res 2007; 1147:39-50. [PMID: 17368578 PMCID: PMC2691862 DOI: 10.1016/j.brainres.2007.02.029] [Citation(s) in RCA: 145] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2005] [Revised: 01/12/2007] [Accepted: 02/02/2007] [Indexed: 11/20/2022]
Abstract
The blood-brain barrier (BBB) is a structural and functional barrier that regulates the passage of molecules into and out of the brain to maintain the neural microenvironment. We have previously developed the in vitro BBB model with human brain microvascular endothelial cells (HBMEC). However, in vivo HBMEC are shown to interact with astrocytes and also exposed to shear stress through blood flow. In an attempt to develop the BBB model to mimic the in vivo condition we constructed the flow-based in vitro BBB model using HBMEC and human fetal astrocytes (HFA). We also examined the effect of astrocyte-conditioned medium (ACM) in lieu of HFA to study the role of secreted factor(s) on the BBB properties. The tightness of HBMEC monolayer was assessed by the permeability of dextran and propidium iodide as well as by measuring the transendothelial electrical resistance (TEER). We showed that the HBMEC permeability was reduced and TEER was increased by non-contact, co-cultivation with HFA and ACM. The exposure of HBMEC to shear stress also exhibited decreased permeability. Moreover, HFA/ACM and shear flow exhibited additive effect of decreasing the permeability of HBMEC monolayer. In addition, we showed that the HBMEC expression of ZO-1 (tight junction protein) was increased by co-cultivation with ACM and in response to shear stress. These findings suggest that the non-contact co-cultivation with HFA helps maintain the barrier properties of HBMEC by secreting factor(s) into the medium. Our in vitro flow model system with the cells of human origin should be useful for studying the interactions between endothelial cells, glial cells, and secreted factor(s) as well as the role of shear stress in the barrier property of HBMEC.
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Affiliation(s)
- Venkatraman Siddharthan
- Division of Pediatric Infectious Diseases, Johns Hopkins University, School of Medicine, Baltimore, MD 21287
| | - Yuri V. Kim
- Division of Pediatric Infectious Diseases, Johns Hopkins University, School of Medicine, Baltimore, MD 21287
| | - Suyi Liu
- World Precision Instruments Inc., 175 Sarasota Center Blvd, Sarasota FL 34240 U.S.A
| | - Kwang Sik Kim
- Correspondence: Prof. Kwang Sik Kim, Division of Pediatric Infectious Diseases, Johns Hopkins University, School of Medicine, 600 North Wolfe Street, Park 256, Baltimore, MD 21287. , Phone: 410-614-3917, Fax: 410-614-1491
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22
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Jacquillet G, Barbier O, Cougnon M, Tauc M, Namorado MC, Martin D, Reyes JL, Poujeol P. Zinc protects renal function during cadmium intoxication in the rat. Am J Physiol Renal Physiol 2005; 290:F127-37. [PMID: 15942048 DOI: 10.1152/ajprenal.00366.2004] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
This study investigates the effect in the rat of chronic CdCl2 intoxication (500 microg Cd2+/kg, daily i.p. injection for 5 days) on renal function and the changes in tight junction proteins claudin-2, claudin-3, and claudin-5 present in rat kidney. We also studied the effect of coadministration of ZnCl2 (500 microg Zn2+/kg) during chronic CdCl2 intoxication. Our results indicate that 1) most of the filtered Cd2+ is reabsorbed within the kidney; 2) chronic Cd2+ intoxication can induce a change in renal handling of ions without altering glomerular filtration rate; 3) a delayed nephropathy, showing Fanconi-like features, appears more than 5 days after the end of CdCl2 exposure; 4) epithelial integrity is altered by chronic Cd2+ intoxication affecting the expression and localization of claudin tight junction proteins; and 5) cotreatment with Zn2+ protects against the renal toxic effects of Cd2+, preventing altered claudin expression and inhibiting apoptosis. In conclusion, these results show that Cd2+ toxicity and cellular toxic mechanisms are complex, probably affecting both membrane transporters and tight junction proteins. Finally, Zn2+ supplementation may provide a basis for future treatments.
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Affiliation(s)
- G Jacquillet
- UMR-CNRS 6548, Bâtiment Sciences Naturelles, Université de Nice-Sophia Antipolis, Parc Valrose, 06108 Nice Cedex 2, France
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23
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Salamat-Miller N, Johnston TP. Current strategies used to enhance the paracellular transport of therapeutic polypeptides across the intestinal epithelium. Int J Pharm 2005; 294:201-16. [PMID: 15814245 DOI: 10.1016/j.ijpharm.2005.01.022] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2004] [Revised: 01/12/2005] [Accepted: 01/27/2005] [Indexed: 11/26/2022]
Abstract
The intent of this paper is to update the reader on various strategies which have been utilized to increase the paracellular permeability of protein and polypeptide drugs across the intestinal epithelium. Structural features of protein and polypeptide drugs, together with the natural anatomical and physiological features of the gastrointestinal (GI) tract, have made oral delivery of this class of compounds extremely challenging. Interest in the paracellular route for the transport of therapeutic proteins and polypeptides following oral administration has recently intensified and continues to be explored. The assumption that molecules with a large molecular weight are not able to diffuse through the tight junctions of the intestinal membrane has been challenged by current research, along with an increased understanding of tight junction physiology.
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Affiliation(s)
- Nazila Salamat-Miller
- Division of Pharmaceutical Sciences, Room 211A, School of Pharmacy, University of Missouri-Kansas City, Kansas City, MO 64110-2499, USA
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24
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Wegener J, Abrams D, Willenbrink W, Galla HJ, Janshoff A. Automated multi-well device to measure transepithelial electrical resistances under physiological conditions. Biotechniques 2005; 37:590, 592-4, 596-7. [PMID: 15517971 DOI: 10.2144/04374st03] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Measurement of transendothelial or transepithelial electrical resistances (TERs) is a straightforward in situ experimental approach to monitor the expression or modulation of barrier-forming cell-to-cell contacts (tight junctions) in cultured cells grown on porous filters. Although widely accepted, there is currently no device available to automatically measure the time course of TERs under ordinary cell culture conditions (37 degrees C, 5% or 10% CO2). This paper describes a development from our laboratory that is capable of following in parallel the TERs of several filter-grown cell layers with time and in an entirely computer-controlled fashion. The cell cultures can be followed even in long-term experiments without any manual assistance or opening of the incubator Besides reading TER values, this approach also returns the electrical capacitance of the cell layers, which is indicative of the expression of microvilli and other membrane extrusions. The device is based on reading the frequencydependent impedance of the cell layer, followed by equivalent circuit modeling to extract the cell-related parameters. It is compatible with several multi-well formats (up to 96 wells) and controlled by custom-designed software that reads, analyzes, and presents the data.
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Affiliation(s)
- Joachim Wegener
- Institüt für Biochemie, Westfälische Wilhelms-Universität Münster, Münster, Germany.
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25
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Kim KJ, Borok Z, Ehrhardt C, Willis BC, Lehr CM, Crandall ED. Estimation of paracellular conductance of primary rat alveolar epithelial cell monolayers. J Appl Physiol (1985) 2005; 98:138-43. [PMID: 15273240 DOI: 10.1152/japplphysiol.00478.2004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Freshly isolated rat type II pneumocytes, when grown on permeable tissue culture-treated polycarbonate filters, form confluent alveolar epithelial cell monolayers (RAECM). Cells in RAECM undergo transdifferentiation, exhibiting over time morphological and phenotypic characteristics of type I pneumocytes in vivo. We recently reported that transforming growth factor-β1 (TGF-β1) decreases overall monolayer resistance ( Rte) and stimulates short-circuit current in a dose-dependent manner. In this study, we investigated the effects of TGF-β1 (50 pM) or 10% newborn bovine serum (NBS) on modulation of paracellular passive ion conductance and its contribution to total passive ion conductance across RAECM. On days 5–7 in culture, tight-junctional resistance ( Rtj, kΩcm2) of RAECM, cultured in minimally defined serum-free medium (MDSF) with or without TGF-β1 or NBS, was estimated from the relationship between observed transmonolayer voltage and resistance after addition of gramicidin D to apical potassium isethionate Ringer solution under open-circuit conditions. NaCl Ringer solution bathed the basolateral side throughout the experimental period. Results showed that transmonolayer conductance (1/ Rte) and tight-junctional conductance (1/ Rtj) are 0.59 and 0.14 mS/cm2 for control monolayers in MDSF, 1.59 and 0.38 mS/cm2 for monolayers exposed to TGF-β1, and 0.38 and 0.18 mS/cm2 for monolayers grown in the presence of NBS. The contributions to total transepithelial ion conductance by the paracellular pathway are estimated to be 23, 23, and 47% for control, TGF-β1-exposed, and newborn bovine serum (NBS)-treated RAECM, respectively.
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Affiliation(s)
- Kwang-Jin Kim
- Dept. of Medicine, University of Southern California, Keck School of Medicine, Rm. HMR-914, 2011 Zonal Avenue, Los Angeles, CA 90033, USA.
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26
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Contreras RG, Flores-Maldonado C, Lázaro A, Shoshani L, Flores-Benitez D, Larré I, Cereijido M. Ouabain Binding to Na+,K+-ATPase Relaxes Cell Attachment and Sends a SpecificSignal (NACos) to the Nucleus. J Membr Biol 2004; 198:147-58. [PMID: 15216416 DOI: 10.1007/s00232-004-0670-2] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2003] [Revised: 03/01/2004] [Indexed: 10/26/2022]
Abstract
Abstract. In previous work we described a "P-->A mechanism" that transduces occupancy of the pump ( P) by ouabain into changes in phosphorylation, stimulation of mitogen-activated protein kinase (MAPK), and endocytosis of cell-cell- and cell-substrate-attaching molecules ( A), thereby causing a release of the cell from the monolayer. In the present work we try to understand the mechanism of this effect; whether, in order to trigger the P-->A mechanism, ouabain should block the pumping activity of Na(+),K(+)-ATPase as pump, or whether it would suffice that the drug occupies this enzyme as a receptor. We assay a series of drugs known to act on the pump, such as ouabain, digoxin, digitoxin, palytoxin, oligomycin, strophanthidin, neothyoside-A, proscillaridin-A, etc. We gauge their ability to block the pump by measuring the K(+) content in the cells, and their ability to detach the cells from the monolayer by determining the amount of protein remaining in the culturing well. None of the drugs tested was able to cause detachment without stopping the pump. Ouabain also enhances phosphorylation, yet pump inhibition and signal transduction do not seem to be intimately associated in a causal chain, but to occur simultaneously. To investigate the response of the site of cell attachment, we analyze the position of beta-catenin by fluorescence confocal microscopy, and find that this adherent junction-associated molecule is sent to the nucleus, where it is known to act as a transcriptional cofactor.
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Affiliation(s)
- R G Contreras
- Department of Physiology, Biophysics and Neurosciences, Av., Center for Research & Advanced Studies, Instituto Politécnico Nacional 2508, 07300, México, D.F., Mexico.
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27
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Alvarado JA, Betanzos A, Franse-Carman L, Chen J, González-Mariscal L. Endothelia of Schlemm's canal and trabecular meshwork: distinct molecular, functional, and anatomic features. Am J Physiol Cell Physiol 2004; 286:C621-34. [PMID: 14613887 DOI: 10.1152/ajpcell.00108.2003] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The purpose of this study was to compare human endothelial cells from Schlemm's canal (SCEs) and the trabecular meshwork (TMEs) in terms of ZO-1 isoform expression, hydraulic conductivity (HC) properties, and “giant” vacuole (GV) formation. The principal study methods were Western blot, RT-PCR, immunofluorescence, and perfusion chambers. Blot signals for α+-and α--isoforms were similar in SCEs but less intense for the α+-relative to the α--signal in TMEs. With the anti-α+antibody used at 1/50 dilution, binding occurred at cell borders of both cell types, but only to SCEs when used at a ≥1/200 dilution in vitro and in vivo. SCEs were more resistive than TMEs (HC = 0.66 vs. 1.32 μl·min-1·mmHg-1·cm-2; P < 0.001) when perfused from apex to base. When perfused in the other direction, SCEs were again more resistive (5.23 vs. 9.04 μl·min-1·mmHg-1·cm-2; P < 0.01). GV formation occurred only in SCEs as a function of flow direction, perfusion pressure, and time. We conclude that SCEs and TMEs have distinctive phenotypic properties involving their content of ZO-1 isoforms, barrier function, and GV formation.
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Affiliation(s)
- Jorge A Alvarado
- Department of Ophthalmology, University of California, San Francisco, California 94143-0730, USA.
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Orosz DE, Woost PG, Kolb RJ, Finesilver MB, Jin W, Frisa PS, Choo CK, Yau CF, Chan KW, Resnick MI, Douglas JG, Edwards JC, Jacobberger JW, Hopfer U. GROWTH, IMMORTALIZATION, AND DIFFERENTIATION POTENTIAL OF NORMAL ADULT HUMAN PROXIMAL TUBULE CELLS. ACTA ACUST UNITED AC 2004; 40:22-34. [PMID: 14748622 DOI: 10.1290/1543-706x(2004)40<22:giadpo>2.0.co;2] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Human proximal tubule epithelial cell lines are potentially useful models to elucidate the complex cellular and molecular details of water and electrolyte homeostasis in the kidney. Samples of normal adult human kidney tissue were obtained from surgical specimens, and S1 segments of proximal convoluted tubules were microdissected, placed on collagen-coated culture plate inserts, and cocultured with lethally irradiated 3T3 fibroblasts. Primary cultures of proximal tubule epithelial cells were infected with a replication-defective retroviral construct encoding either wild-type or temperature-sensitive simian virus 40 large T-antigen. Cells forming electrically resistive monolayers were selected and expanded in culture. Three cell lines (HPCT-03-ts, HPCT-05-wt, and HPCT-06-wt) were characterized for proximal tubule phenotype by electron microscopy, electrophysiology, immunofluorescence, Southern hybridization, and reverse transcriptase-polymerase chain reaction. Each of the three formed polarized, resistive epithelial monolayers with apical microvilli, tight junctional complexes, numerous mitochondria, well-developed Golgi complexes, extensive endoplasmic reticulum, convolutions of the basolateral plasma membrane, and a primary cilium. Each exhibited succinate, phosphate, and Na,K- adenosine triphosphatase (ATPase) transport activity, as well as acidic dipeptide- and adenosine triphosphate-regulated mechanisms of ion transport. Transcripts for Na(+)-bicarbonate cotransporter, Na(+)-H(+) exchanger isoform 3, Na,K-ATPase, parathyroid hormone receptor, epidermal growth factor receptor, and vasopressin V2 receptor were identified. Furthermore, immunoreactive sodium phosphate cotransporter type II, vasopressin receptor V1a, and CLIC-1 (NCC27) were also identified. These well-differentiated, transport-competent cell lines demonstrated the growth, immortalization, and differentiation potential of normal, adult, human proximal tubule cells and consequently have wide applicability in cell biology and renal physiology.
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Affiliation(s)
- David E Orosz
- Department of Physiology, Case Western Reserve University, Cleveland, Ohio 44106-4970, USA
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Ward PD, Ouyang H, Thakker DR. Role of phospholipase C-beta in the modulation of epithelial tight junction permeability. J Pharmacol Exp Ther 2003; 304:689-98. [PMID: 12538823 DOI: 10.1124/jpet.102.043638] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The results presented in this study establish an association between phospholipase C-beta (PLC-beta) and tight junction permeability across Madin-Darby canine kidney (MDCK) cell monolayers, an in vitro model for epithelial tissue. These results further show that PLC-beta modulates tight junction permeability by affecting actin filament organization. Hexadecylphosphocholine (HPC) inhibited PLC-beta and increased tight junction permeability in MDCK cells. Interestingly, the analogs of HPC, a series of alkylphosphocholines containing various lengths of linear alkyl chains, inhibited PLC-beta and increased tight junction permeability with a wide range of potency. The potency of alkylphosphocholines as enhancers of tight junction permeability significantly correlated (p < 0.05) with their potency as PLC-beta inhibitors. U73122, a steroid derivative that is structurally unrelated to alkylphosphocholines, inhibited PLC-beta and increased tight junction permeability with potencies that fit into the correlation observed for the alkylphosphocholine series. U73122 and HPC induced disorganization of actin filaments in MDCK cell monolayers. The potencies to cause disorganization of actin filaments were consistent with the potencies of these agents as inhibitors of PLC-beta and enhancers of tight junction permeability. Furthermore, ATP, an activator of PLC-beta, attenuated U73122-induced increase in tight junction permeability as well as disorganization of actin filaments. These results provide strong evidence that PLC-beta inhibition leads to increased tight junction permeability across MDCK cell monolayers through disorganization of actin filaments.
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Affiliation(s)
- Peter D Ward
- Department of Pharmacology, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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30
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Suchy SF, Nussbaum RL. The deficiency of PIP2 5-phosphatase in Lowe syndrome affects actin polymerization. Am J Hum Genet 2002; 71:1420-7. [PMID: 12428211 PMCID: PMC378584 DOI: 10.1086/344517] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2002] [Accepted: 08/28/2002] [Indexed: 11/03/2022] Open
Abstract
Lowe syndrome is a rare X-linked disorder characterized by bilateral congenital cataracts, renal Fanconi syndrome, and mental retardation. Lowe syndrome results from mutations in the OCRL1 gene, which encodes a phosphatidylinositol 4,5 bisphosphate 5-phosphatase located in the trans-Golgi network. As a first step in identifying the link between ocrl1 deficiency and the clinical disorder, we have identified a reproducible cellular abnormality of the actin cytoskeleton in fibroblasts from patients with Lowe syndrome. The cellular abnormality is characterized by a decrease in long actin stress fibers, enhanced sensitivity to actin depolymerizing agents, and an increase in punctate F-actin staining in a distinctly anomalous distribution in the center of the cell. We also demonstrate an abnormal distribution of two actin-binding proteins, gelsolin and alpha-actinin, proteins regulated by both PIP(2) and Ca(+2) that would be expected to be altered in Lowe cells. Actin polymerization plays a key role in the formation, maintenance, and proper function of tight junctions and adherens junctions, which have been demonstrated to be critical in renal proximal tubule function, and in the differentiation of the lens. These findings point to a general mechanism to explain how this PIP(2) 5-phosphatase deficiency might produce the Lowe syndrome phenotype.
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Affiliation(s)
- Sharon F Suchy
- National Human Genome Research Institute, Bethesda, MD 20892, USA.
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31
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Reyes JL, Lamas M, Martin D, del Carmen Namorado M, Islas S, Luna J, Tauc M, González-Mariscal L. The renal segmental distribution of claudins changes with development. Kidney Int 2002; 62:476-87. [PMID: 12110008 DOI: 10.1046/j.1523-1755.2002.00479.x] [Citation(s) in RCA: 137] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND Permeability properties of mammalian nephron are tuned during postnatal maturation. The transepithelial electrical resistance (TER) and complexity of tight junctions (TJs) vary along the different tubular segments, suggesting that the molecules constituting this structure change. We studied the differential expression of occludin and several claudins in isolated renal tubules from newborn and adult rabbits. METHODS Isolated renal tubules from newborn and adult rabbits were processed for occludin, claudin-1 and claudin-2 immunofluorescence, and Western blot detection of claudin-1 and -2. Claudin-5 was detected in whole kidney frozen sections. RT-PCR from isolated tubules was performed for claudins-1 to -8. RESULTS Immunofluorescence revealed that occludin, claudin-1 and -2 were present at the cell boundaries at the neonatal stage of development. Claudin-1 was detected in the tighter segments of the nephron (distal and collecting duct), while claudin-2 was found in the leaky portions (proximal). Claudin 5 was found in the kidney vasculature. PCR amplification revealed the presence of claudins-1 to -4 in tubules of newborns. In adults, claudins-1, -2 and -4 were present in proximal, Henle's loop and collecting segments; claudin-3 was in proximal and collecting tubules, while claudins-5 and -6 were absent from all tubular portions. Claudin-7 was restricted to proximal tubules, while claudin-8 was present in proximal and Henle's segments. CONCLUSIONS The pattern of occludin distribution is present from the neonatal age. Claudins-7 and -8 are up-regulated after birth. Each tubular segment expresses a peculiar set of claudins that might be responsible for the permeability properties of their TJs.
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Affiliation(s)
- Jose Luis Reyes
- Center for Research and Advanced Studies (CINVESTAV), Department of Physiology, Biophysics and Neurosciences, México City, Mexico
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32
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Gopalakrishnan S, Dunn KW, Marrs JA. Rac1, but not RhoA, signaling protects epithelial adherens junction assembly during ATP depletion. Am J Physiol Cell Physiol 2002; 283:C261-72. [PMID: 12055095 DOI: 10.1152/ajpcell.00604.2001] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Rho family GTPase signaling regulates actin cytoskeleton and junctional complex assembly. Our previous work showed that RhoA signaling protects tight junctions from damage during ATP depletion. Here, we examined whether RhoA GTPase signaling protects adherens junction assembly during ATP depletion. Despite specific RhoA signaling- and ATP depletion-induced effects on adherens junction assembly, RhoA signaling did not alter adherens junction disassembly rates during ATP depletion. This shows that RhoA signaling specifically protects tight junctions from damage during ATP depletion. Rac1 GTPase signaling also regulates adherens junction assembly and therefore may regulate adherens junction assembly during ATP depletion. Indeed, we found that Rac1 signaling protects adherens junctions from damage during ATP depletion. Adherens junctions are regulated by various GTPases, including RhoA and Rac1, but adherens junctions are specifically protected by Rac1 signaling.
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Affiliation(s)
- Shobha Gopalakrishnan
- Department of Medicine, Indiana University Medical Center, Indianapolis, Indiana 46202-5116, USA
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33
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Islas S, Vega J, Ponce L, González-Mariscal L. Nuclear localization of the tight junction protein ZO-2 in epithelial cells. Exp Cell Res 2002; 274:138-48. [PMID: 11855865 DOI: 10.1006/excr.2001.5457] [Citation(s) in RCA: 143] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The tight junction constitutes the major barrier to solute and water flow through the paracellular space of epithelia and endothelia. It is formed by transmembrane proteins and submembranous molecules such as the MAGUKs ZOs. We have previously found that several MAGUKs, including those of the tight (ZO-1, ZO-2, and ZO-3) and septate junction (tamou and Dlg), contain one or two nuclear sorting signals located at their first PDZ and GK domains. Now we show that these proteins also contain a nuclear export signal and focus our study on the nuclear membrane shuttling of ZO-2. In sparse cultures this molecule concentrates at the nucleus in clusters, where it partially colocalizes with splicing factor SC35. Nuclear staining diminishes as the monolayer acquires confluence through a process sensitive to the nuclear export inhibitor leptomycin B. Nuclear localization can be induced by impairing cell-cell contacts, by mechanical injury. ZO-2 that shuttles from the cell periphery into the nucleus is not newly synthesized but originates from a preexistent pool. The movement of this protein is mediated by the actin cytoskeleton.
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Affiliation(s)
- Socorro Islas
- Department of Physiology, Biophysics and Neuroscience, Center for Research and Advanced Studies (CINVESTAV), D.F, 07000, México
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34
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Mesiwala AH, Farrell L, Wenzel HJ, Silbergeld DL, Crum LA, Winn HR, Mourad PD. High-intensity focused ultrasound selectively disrupts the blood-brain barrier in vivo. ULTRASOUND IN MEDICINE & BIOLOGY 2002; 28:389-400. [PMID: 11978420 DOI: 10.1016/s0301-5629(01)00521-x] [Citation(s) in RCA: 186] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
High-intensity focused ultrasound (HIFU) has been shown to generate lesions that destroy brain tissue while disrupting the blood-brain barrier (BBB) in the periphery of the lesion. BBB opening, however, has not been shown without damage, and the mechanisms by which HIFU induces BBB disruption remain unknown. We show that HIFU is capable of reversible, nondestructive, BBB disruption in a targeted region-of-interest (ROI) (29 of 55 applications; 26 of 55 applications showed no effect); this opening reverses after 72 h. Light microscopy demonstrates that HIFU either entirely preserves brain architecture while opening the BBB (18 of 29 applications), or generates tissue damage in a small volume within the region of BBB opening (11 of 29 applications). Electron microscopy supports these observations and suggests that HIFU disrupts the BBB by opening capillary endothelial cell tight junctions, an isolated ultrastructural effect that is different from the mechanisms through which other (untargeted) modalities, such as hyperosmotic solutions, hyperthermia and percussive injury disrupt the BBB.
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Affiliation(s)
- Ali H Mesiwala
- Department of Neurological Surgery, University of Washington, Seattle, WA 98105, USA
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35
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Caplan MS, Jilling T. The role of polyunsaturated fatty acid supplementation in intestinal inflammation and neonatal necrotizing enterocolitis. Lipids 2001; 36:1053-7. [PMID: 11724457 DOI: 10.1007/s11745-001-0816-3] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Dietary polyunsaturated fatty acid (PUFA) supplementation has been shown to reduce the incidence of necrotizing enterocolitis (NEC) in a recent randomized, controlled trial. These compounds are known to modulate the inflammatory cascade and to influence intestinal health in a variety of ways. Although the pathophysiology of NEC is not well understood, recent evidence suggests that platelet-activating factor (PAF) is a key endogenous mediator of intestinal necrosis in animals. Using a neonatal rat model of NEC that includes the key risk factors of asphyxia and formula feeding, we investigated the role of dietary PUFA supplementation on the incidence and pathophysiology of NEC. Our findings suggest that PUFA reduce the incidence of NEC by modulating PAF metabolism and endotoxin translocation.
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Affiliation(s)
- M S Caplan
- Department of Pediatrics, Evanston Northwestern Healthcare, Northwestern University Medical School, Evanston, Illinois 60201, USA.
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36
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Saha C, Nigam SK, Denker BM. Expanding role of G proteins in tight junction regulation: Galpha(s) stimulates TJ assembly. Biochem Biophys Res Commun 2001; 285:250-6. [PMID: 11444833 DOI: 10.1006/bbrc.2001.5154] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Multiple signaling mechanisms regulate epithelial cell tight junction (TJ) assembly and maintenance. Several G proteins are likely to regulate these processes, but only G(i/o) have been specifically tested. Treatment of MDCK cells with cholera toxin, a Galpha(s) activator, accelerated TJ development in the calcium switch as measured by the time to half-maximal [T(50) (H)] transepithelial resistance (TER). Galpha(s) was predominantly localized in the lateral membrane, but a fraction colocalizes with ZO-1 in the TJ. MDCK cell lines expressing epitope-tagged Galpha(s) and constitutively active (R201Calpha(s)) showed a similar localization. TJ assembly was significantly faster in R201Calpha(s)-MDCK cell lines (T(50) (H) of 1.7 versus 3.3 h for controls) without detectable differences in cAMP levels. Confocal studies showed R201Calpha(s)-MDCK cells more rapidly localized ZO-1 and occludin into the developing TJ without affecting E-cadherin or Na(+)/K(+) ATPase localization. Endogenous Galpha(s) and R201Calpha(s) were immunoprecipitated with ZO-1 at baseline and during TJ assembly. The data supports a model of multiple Galpha subunits interacting with TJ proteins to regulate the assembly and maintenance of the TJ.
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Affiliation(s)
- C Saha
- Renal Division, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA
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37
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Bhattacharjee AK, Nagashima T, Kondoh T, Tamaki N. The effects of the Na(+)/Ca(++) exchange blocker on osmotic blood-brain barrier disruption. Brain Res 2001; 900:157-62. [PMID: 11334793 DOI: 10.1016/s0006-8993(01)02253-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Osmotic disruption of the blood-brain barrier (BBB) by mannitol is currently being used to enhance drug delivery in human brains. Despite clinical and experimental interest, to date the time course in the early phase of disruption has not been accurately identified. The mechanism in barrier closure also remains elusive. We first studied the rapid change in cerebrovascular permeability after BBB disruption in rats, and then demonstrated that the Na(+)/Ca(++) exchange blocker (KB-R7943) prolongs osmotic disruption. Osmotic BBB disruption was attained by using intra-arterial infusion of hypertonic mannitol in Sprague-Dawley (SD) rats. To measure the changes in cerebrovascular permeability, perfusate containing [14C]-sucrose was infused intra-arterially at different time points following osmotic stress. Cerebrovascular permeability was then measured with the in situ brain perfusion technique. This is the first in vivo study demonstrating that osmotic disruption is prolonged by the Na(+)/Ca(++) exchange blocker, which did not affect the peak level of BBB disruption. The exact time course of cerebrovascular reversibility was studied and the earliest BBB disruption was seen to occur 5 min after osmotic stress. Histopathological examination after osmotic disruption with the Na(+)/Ca(++) exchange blocker showed no neuronal damage in rat brains. Our findings represent important experimental information regarding pharmacological manipulation of BBB disruption. The possibility of prolonging the transient opening of the BBB has major clinical implications.
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Affiliation(s)
- A K Bhattacharjee
- Department of Neurosurgery, Kobe University School of Medicine, 7-5-1 Kusunoki Cho, Chuo-Ku, 650-0017, Kobe, Japan
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Kushida A, Yamato M, Kikuchi A, Okano T. Two-dimensional manipulation of differentiated Madin-Darby canine kidney (MDCK) cell sheets: the noninvasive harvest from temperature-responsive culture dishes and transfer to other surfaces. JOURNAL OF BIOMEDICAL MATERIALS RESEARCH 2001; 54:37-46. [PMID: 11077401 DOI: 10.1002/1097-4636(200101)54:1<37::aid-jbm5>3.0.co;2-7] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A renal epithelial cell line, Madin-Darby canine kidney (MDCK) cells, adheres, spreads, and proliferates to confluency on our developed temperature-responsive culture dishes grafted with a poly(N-isopropylacrylamide) (PIPAAm) at 37 degrees C. In addition to other cell types, including hepatocytes and endothelial cells, MDCK cell sheets noninvasively were harvested from PIPAAm-grafted dishes merely by reducing the temperature. However, during the early stage of culture (up to 3 weeks), confluent MDCK cell detachment is greatly repressed. In the present study, we succeeded in the rapid harvest of confluent MDCK cell sheets and intact transfer to other culture dishes by utilizing hydrophilically modified poly(vinylidene difluoride) (PVDF) membranes as supporting materials. Immunocytochemistry with anti-beta-catenin antibody revealed that the functional cell-cell junctions were well organized in the transferred MDCK cell sheets. The viability assay showed that the transferred cells were not damaged during the two-dimensional cell-sheet manipulation. By transmission electron microscopy it was confirmed that the harvested MDCK cells retained differentiated phenotypes and had many microvilli and tight junctions at the apical and lateral plasma membranes, respectively. This two-dimensional cell-sheet manipulation technique promises to be useful in tissue engineering as well as in the investigation of epithelial cell sheets.
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Affiliation(s)
- A Kushida
- Institute of Biomedical Engineering, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku, Tokyo 162-8666, Japan
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39
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Kushida A, Yamato M, Konno C, Kikuchi A, Sakurai Y, Okano T. Temperature-responsive culture dishes allow nonenzymatic harvest of differentiated Madin-Darby canine kidney (MDCK) cell sheets. JOURNAL OF BIOMEDICAL MATERIALS RESEARCH 2000; 51:216-23. [PMID: 10825221 DOI: 10.1002/(sici)1097-4636(200008)51:2<216::aid-jbm10>3.0.co;2-k] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We have developed a temperature-responsive culture dish grafted with a poly(N-isopropylacrylamide) (PIPAAm). Various types of cells adhere, spread, and proliferate on the grafted dishes in the presence of serum at 37 degrees C. By reducing only temperature, these cells can be harvested noninvasively from the dishes according to rapid hydration of the grafted polymer. Because the harvest does not need enzymatic digestion, differentiated cell phenotypes are retained. In the present study, a renal epithelial cell line, Madin-Darby canine kidney (MDCK) cell, was cultured on the dishes, and cell behavior was examined. MDCK cells showed differentiated phenotypes such as dome formation during long-term culture, similar to on ungrafted dishes. After 1-week culture at 37 degrees C, trypsin digestion disrupted cell-cell junctions but failed to liberate cells from both ungrafted and grafted dishes. However, short-term incubation at 20 degrees C released confluent MDCK cells as a single contiguous cell sheet only from the polymer-grafted dishes because of selective disruption of the cell-surface binding. Immunocytochemistry with anti-beta-catenin antibody revealed that functional cell-cell junctions were organized even in the recovered cell sheets. Intriguingly, incubation time at 20 degrees C required for cell sheet detachment gradually shortened during long-term culture before reducing temperature. The acceleration of cell detachment was correlated to the decrease of a single cell area by means of cell contractile force. These findings suggest that cell sheet detachment from PIPAAm-grafted dishes should be accomplished by both PIPAAm hydration and cellular metabolic activity such as cell contraction.
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Affiliation(s)
- A Kushida
- Institute of Biomedical Engineering, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku, Tokyo 162-8666, Japan
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40
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González-Mariscal L, Betanzos A, Avila-Flores A. MAGUK proteins: structure and role in the tight junction. Semin Cell Dev Biol 2000; 11:315-24. [PMID: 10966866 DOI: 10.1006/scdb.2000.0178] [Citation(s) in RCA: 338] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
ZO-1, ZO-2 and ZO-3 are tight junction (TJ)-associated proteins that belong to the MAGUK family. In addition to the presence of the characteristic MAGUK modules (PDZ, SH3 and GK), ZOs have a distinctive carboxyl terminal with splicing domains, acidic- and proline-rich regions. The modular organization of these proteins allows them to function as scaffolds, which associate to transmembrane TJ proteins, the cytoskeleton and signal transduction molecules. ZOs shuttle between the TJ and the nucleus, where they may regulate gene expression.
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Affiliation(s)
- L González-Mariscal
- Department of Physiology, Biophysics and Neurosciences, Center of Research and Advanced Studies (CINVESTAV), Ap. Postal 14-740, Mexico DF, 07000, Mexico.
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41
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Snigirevskaya ES. Structural correlates of the transepithelial water transport. INTERNATIONAL REVIEW OF CYTOLOGY 2000; 198:203-75. [PMID: 10804464 DOI: 10.1016/s0074-7696(00)98006-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
Transepithelial permeability is one of the fundamental problems in cell biology. Epithelial cell layers protect the organism from its environment and form a selective barrier to the exchange of molecules between the lumen of an organ and an underlying tissue. This chapter discusses some problems and analyzes the participation of intercellular junctions in the paracellular transport of water, migration of intramembrane particles in the apical membrane during its permeability changes for isotonic fluid in cells of leaky epithelia, insertion of water channels into the apical membrane and their cytoplasmic sources in cells of tight epithelia under ADH (antidiuretic hormone)-induced water flows, the osmoregulating function of giant vacuoles in the transcellular fluxes of hypotonic fluid across tight epithelia, and the role of actin filaments and microtubules in the transcellular transport of water across epithelia.
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Affiliation(s)
- E S Snigirevskaya
- Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia
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42
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Contreras RG, Shoshani L, Flores-Maldonado C, Lázaro A, Cereijido M. Relationship between Na(+),K(+)-ATPase and cell attachment. J Cell Sci 1999; 112 ( Pt 23):4223-32. [PMID: 10564641 DOI: 10.1242/jcs.112.23.4223] [Citation(s) in RCA: 122] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
A prolonged ouabain blockade of the Na(+),K(+)-ATPase detaches cells from each other and from the substrate. This suggests the existence of a link between pump (P) and attachment (A). In the present work, we report that MDCK-W cells treated with ouabain increase tyrosine phosphorylation and content of active MAP kinase, redistribute molecules involved in cell attachment (occludin, ZO-1, desmoplakin, cytokeratin, alpha-actinin, vinculin and actin), and detach. Genistein and UO126, inhibitors of protein tyrosine kinase and of MAP kinase kinase, respectively, block this detachment. The content of P190(Rho-GAP), a GTPase activating protein of the Rho small G-protein subfamily, is increased by ouabain, suggesting that both the Rho/Rac and MAPK pathways are involved. Another clone of MDCK cells whose Na(+),K(+)-ATPase has a negligible affinity for the drug, show none of the effects described for MDCK-W and remain attached. Ma104 cells, a line that has a high affinity for ouabain and stops pumping, fail to modify phosphorylation, as well as the pattern of distribution of attaching molecules, and remain in the monolayer. Taken together, these results suggest that there is a mechanism (P-->A) that transduces a blockade of the pump in a detachment of the cell from neighbors and substrate, in which Ma104 cells are faulty.
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Affiliation(s)
- R G Contreras
- Center for Research and Advanced Studies of México (CINVESTAV), Av. Instituto Politecnico Nacional 2508, Codigo Postal, 07660 Mexico
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43
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Ferruzza S, Sambuy Y, Rotilio G, Ciriolo MR, Scarino ML. The effect of copper on tight junctional permeability in a human intestinal cell line (Caco-2). ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1999; 448:215-22. [PMID: 10079829 DOI: 10.1007/978-1-4615-4859-1_19] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Affiliation(s)
- S Ferruzza
- Istituto Nazionale della Nutrizione, Roma, Italy
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44
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Yeaman C, Grindstaff KK, Nelson WJ. New perspectives on mechanisms involved in generating epithelial cell polarity. Physiol Rev 1999; 79:73-98. [PMID: 9922368 DOI: 10.1152/physrev.1999.79.1.73] [Citation(s) in RCA: 404] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Polarized epithelial cells form barriers that separate biological compartments and regulate homeostasis by controlling ion and solute transport between those compartments. Receptors, ion transporters and channels, signal transduction proteins, and cytoskeletal proteins are organized into functionally and structurally distinct domains of the cell surface, termed apical and basolateral, that face these different compartments. This review is about mechanisms involved in the establishment and maintenance of cell polarity. Previous reports and reviews have adopted a Golgi-centric view of how epithelial cell polarity is established, in which the sorting of apical and basolateral membrane proteins in the Golgi complex is a specialized process in polarized cells, and the generation of cell surface polarity is a direct consequence of this process. Here, we argue that events at the cell surface are fundamental to the generation of cell polarity. We propose that the establishment of structural asymmetry in the plasma membrane is the first, critical event, and subsequently, this asymmetry is reinforced and maintained by delivery of proteins that were constitutively sorted in the Golgi. We propose a hierarchy of stages for establishing cell polarity.
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Affiliation(s)
- C Yeaman
- Department of Molecular and Cellular Physiology, Beckman Center for Molecular and Genetic Medicine, Stanford University School of Medicine, Stanford, California, USA
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45
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Perez-Moreno M, Avila A, Islas S, Sanchez S, González-Mariscal L. Vinculin but not alpha-actinin is a target of PKC phosphorylation during junctional assembly induced by calcium. J Cell Sci 1998; 111 ( Pt 23):3563-71. [PMID: 9811570 DOI: 10.1242/jcs.111.23.3563] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The establishment of the junctional complex in epithelial cells requires the presence of extracellular calcium, and is controlled by a network of reactions involving G-proteins, phospholipase C and protein kinase C. Since potential candidates for phosphorylation are the tight junction associated proteins ZO1, ZO2 and ZO3, in a previous work we specifically explored these molecules but found no alteration in their phosphorylation pattern. To continue the search for the target of protein kinase C, in the present work we have studied the subcellular distribution and phosphorylation of vinculin and alpha-actinin, two actin binding proteins of the adherent junctions. We found that during the junctional sealing induced by Ca2+, both proteins move towards the cell periphery and, while there is a significant increase in the phosphorylation of vinculin, alpha-actinin remains unchanged. The increased phosphorylation of vinculin is due to changes in phosphoserine and phosphothreonine content and seems to be regulated by protein kinase C, since: (1) DiC8 (a kinase C stimulator) added to monolayers cultured without calcium significantly increases the vinculin phosphorylation level; (2) H7 and calphostin C (both protein kinase C inhibitors) completely abolish this increase during a calcium switch; (3) inhibition of phosphorylation during a calcium switch blocks the subcellular redistribution of vinculin and alpha-actinin. These results therefore suggest that vinculin phosphorylation by protein kinase C is a crucial step in the correct assembly of the epithelial junctional complex.
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Affiliation(s)
- M Perez-Moreno
- Center for Research and Advanced Studies (CINVESTAV), Department of Physiology, Biophysics and Neurosciences, Ap. Postal 14-740, Mexico D.F. 07000, Mexico
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46
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Inhibition of ammonia excretion and production in rainbow trout during severe alkaline exposure. Comp Biochem Physiol B Biochem Mol Biol 1998. [DOI: 10.1016/s0305-0491(98)10063-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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47
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Saha C, Nigam SK, Denker BM. Involvement of Galphai2 in the maintenance and biogenesis of epithelial cell tight junctions. J Biol Chem 1998; 273:21629-33. [PMID: 9705295 DOI: 10.1074/jbc.273.34.21629] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Polarized epithelial cells have highly developed tight junctions (TJ) to maintain an impermeant barrier and segregate plasma membrane functions, but the mechanisms that promote TJ formation and maintain its integrity are only partially defined. Treatment of confluent monolayers of Madin-Darby canine kidney (MDCK) cells with AlF4- (activator of heterotrimeric G protein alpha subunits) results in a 3-4-fold increase in transepithelial resistances (TER), a reliable indicator of TJ integrity. MOCK cells transfected with activated Galpha0 (Q205L) have acclerated TJ formation (Denker, B. M., Saha, C. , Khawaja, S., and Nigam, S. J. (1996) J. Biol. Chem. 271, 25750-25753). Galphai2 has been localized within the tight junction, and a role for Galphai2 in the formation and/or maintenance of the tight junction was studied by transfection of MDCK cells with vector without insert (PC), wild type Galphai2, or a GTPase-deficient mutant (constitutively activated), Q205Lalphai2. Tryptic conformational analysis confirmed expression of a constitutively active Galphai2 in Q205Lalphai2-MDCK cells, and confocal microscopy showed a similar pattern of Galphai2 localization in the three cell lines. Q205Lalphai2-MDCK cells had significantly higher base-line TER values than wild type Galphai2- or PC-MDCK cells (1187 +/- 150 versus 576 +/- 89 (Galphai2); 377 +/- 52 Omega.cm2 (PC)), and both Galphai2- and Q205Lalphai2-transfected cell lines more rapidly develop TER in the Ca2+ switch, a model widely used to study the mechanisms of junctional assembly. Treatment of cells with AlF4- during the Ca2+ switch had little effect on the kinetics of TER development in Galphai2- or Q205Lalphai2-MDCK cells, but PC cells reached half-maximal TER significantly sooner in the presence of AlF4- (similar times to Galphai2-transfected cells). Base-line TER values obtained after the switch were significantly higher for all three cell lines in the presence of AlF4-. These findings indicate that Galphai2 is important for both the maintenance and development of the TJ, although additional Galpha subunits are likely to play a role.
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Affiliation(s)
- C Saha
- Renal Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA
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48
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Jou TS, Schneeberger EE, Nelson WJ. Structural and functional regulation of tight junctions by RhoA and Rac1 small GTPases. J Cell Biol 1998; 142:101-15. [PMID: 9660866 PMCID: PMC2133025 DOI: 10.1083/jcb.142.1.101] [Citation(s) in RCA: 292] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Tight junctions (TJ) govern ion and solute diffusion through the paracellular space (gate function), and restrict mixing of membrane proteins and lipids between membrane domains (fence function) of polarized epithelial cells. We examined roles of the RhoA and Rac1 GTPases in regulating TJ structure and function in MDCK cells using the tetracycline repressible transactivator to regulate RhoAV14, RhoAN19, Rac1V12, and Rac1N17 expression. Both constitutively active and dominant negative RhoA or Rac1 perturbed TJ gate function (transepithelial electrical resistance, tracer diffusion) in a dose-dependent and reversible manner. Freeze-fracture EM and immunofluoresence microscopy revealed abnormal TJ strand morphology and protein (occludin, ZO-1) localization in RhoAV14 and Rac1V12 cells. However, TJ strand morphology and protein localization appeared normal in RhoAN19 and Rac1N17 cells. All mutant GTPases disrupted the fence function of the TJ (interdomain diffusion of a fluorescent lipid), but targeting and organization of a membrane protein in the apical membrane were unaffected. Expression levels and protein complexes of occludin and ZO-1 appeared normal in all mutant cells, although ZO-1 was more readily solubilized from RhoAV14-expressing cells with Triton X-100. These results show that RhoA and Rac1 regulate gate and fence functions of the TJ, and play a role in the spatial organization of TJ proteins at the apex of the lateral membrane.
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Affiliation(s)
- T S Jou
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305-5345, USA
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49
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Newton GR, Weise DW, Bowen JA, Woldesenbet S, Burghardt RC. Regulation of protein and prostaglandin secretion in polarized primary cultures of caprine uterine epithelial cells. In Vitro Cell Dev Biol Anim 1998; 34:578-84. [PMID: 9719418 DOI: 10.1007/s11626-998-0118-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Caprine uterine epithelial (UE) cells were cultured on Matrigel-coated filters. Transmission electron microscopy revealed polarized UE cells characterized by basally located nuclei, apical microvilli, convoluted lateral membranes, and junctional complexes. Domain-specific secretion of prostaglandins and radiolabeled proteins provide further evidence of functional epithelial cell polarity. Two experiments were conducted to evaluate factors controlling prostaglandin E2 (PGE) and prostaglandin F2alpha (PGF) secretion. In experiment one, steroid-treated (estradiol, progesterone, or estradiol + progesterone) polarized UE cells were treated with interferon tau (IFNtau) and/or oxytocin (OT). Steroid treatment did not influence PGE or PGF secretion. However, analysis of variance revealed an IFNtau by OT interaction (P < .01) for both PGE and PGF This interaction was caused by a reduction in PGE and PGF secretion by cultures receiving only IFNtau and the inability of IFNtau to block OT-induced release of PGE or PGF. In experiment 2, polarized UE cells were cultured in progesterone, with or without IFNtau, and sequentially challenged with estradiol and OT. Oxytocin stimulated the release of both PGE and PGF by polarized cUE cells (P < .01) and resulted in an increased accumulation of PGE (OT*domain; P < .01) in the basal compartment. Interferon tau did not influence PGE (P < .1) secretion. However, further analysis revealed that IFNtau reduced PGF secretion and was unable to block OT-induced PGF secretion (IFNtau*OT; P < .05) by polarized UE cells. Therefore, caprine UE cells form polarized monolayers and retain responsiveness to IFNtau and OT in vitro.
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Affiliation(s)
- G R Newton
- Cooperative Agricultural Research Center, Prairie View A&M University, Texas 77446-4079, USA
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50
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Aroeti B, Okhrimenko H, Reich V, Orzech E. Polarized trafficking of plasma membrane proteins: emerging roles for coats, SNAREs, GTPases and their link to the cytoskeleton. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1376:57-90. [PMID: 9666078 DOI: 10.1016/s0304-4157(98)00005-7] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- B Aroeti
- Department of Cell and Animal Biology, Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem 91904, Israel.
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