New ways of thinking about (and teaching about) intestinal epithelial function

2008 ◽  
Vol 32 (1) ◽  
pp. 25-34 ◽  
Author(s):  
Kim E. Barrett
Keyword(s):  
Ion Transport ◽  
Tight Junctions ◽  
Hydrogen Exchange ◽  
De Novo ◽  
Intestinal Barrier ◽  
Barrier Properties ◽  
Chloride Secretion ◽  
Sodium Absorption ◽  
Intestinal Epithelial ◽  
The Impact

This article summarizes a presentation made at the Teaching Refresher Course of the American Physiological Society, which was held at the Experimental Biology meeting in 2007. The intestinal epithelium has important ion transport and barrier functions that contribute pivotally to normal physiological functioning of the intestine and other body systems. These functions are also frequently the target of dysfunction that, in turn, results in specific digestive disease states, such as diarrheal illnesses. Three emerging concepts are discussed with respect to ion transport: the complex interplay of intracellular signals that both activate and inhibit chloride secretion; the role of multiprotein complexes in the regulation of ion transport, taking sodium/hydrogen exchange as an example; and acute and chronic regulation of colonic sodium absorption, involving both sodium channel internalization and de novo synthesis of new channels. Similarly, recently obtained information about the molecular components of epithelial tight junctions and the ways in which tight junctions are regulated both in health and disease are discussed to exemplify ways to teach about intestinal barrier properties. Finally, both genetically determined intestinal diseases and those arising as a result of infections and/or inflammation are described, and these can be used as the means to enhance the basic and clinical relevance of teaching about intestinal epithelial physiology as well as the impact that the understanding of such physiology has had on associated therapeutics. The article also indicates, where relevant, how different approaches may be used effectively to teach related concepts to graduate versus medical/professional student audiences.

Intestinal ion transport in rats with spontaneous arterial hypertension

1988 ◽  
Vol 75 (2) ◽  
pp. 127-133 ◽  
Author(s):  
Ralf Lübcke ◽  
Gilbert O. Barbezat
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Membrane Resistance ◽  
Chloride Secretion ◽  
Sodium Absorption ◽  
Spontaneously Hypertensive ◽  
Wistar Kyoto ◽  
Intestinal Ion Transport

1. Ion balance, intestinal ion transport in vivo with luminal Ringer, and direct voltage clamping in vivo with luminal Ringer and sodium-free choline-Ringer were studied in young (40 days old) and adult (120 days old) spontaneously hypertensive rats (SHR) and age-matched normotensive controls (Wistar–Kyoto rats, WKY). 2. Faecal sodium output was significantly higher in SHR compared with WKY in both young (+ 67%) and adult (+ 43%) rats. 3. Small-intestinal sodium absorption was equal in young SHR and WKY, but significantly greater net sodium absorption was found in the ileum of adult SHR. In contrast, net sodium absorption was reduced from the colon of both young and adult SHR. 4. In adult SHR, the colonic transepithelial short-circuit current (Isc) and the transepithelial potential difference (PD) were significantly higher, whereas the transepithelial membrane resistance (Rm) was significantly lower than in WKY. There was an identical drop in Isc in both strains when luminal sodium was replaced by choline. These data cannot be explained by increased electrogenic cation (sodium) absorption in the SHR, but would favour chloride secretion. 5. It is suggested that in SHR membrane electrolyte transport abnormalities may also be present in the epithelial cells of the small and large intestine, as have been demonstrated already in blood cells by several investigators. The SHR may become an interesting experimental animal model for the study of generalized ion transport disorders.

scholarly journals Impaired Gut Epithelial Tight Junction Expression in Hemodialysis Patients Complicated with Intradialytic Hypotension

2018 ◽  
Vol 2018 ◽  
pp. 1-6
Author(s):  
Tsai-Kun Wu ◽  
Paik-Seong Lim ◽  
Jong-Shiaw Jin ◽  
Ming-Ying Wu ◽  
Chang-Hsu Chen
Keyword(s):  
Tight Junction ◽  
Intestinal Barrier ◽  
Intradialytic Hypotension ◽  
Intestinal Epithelial ◽  
Advanced Chronic Kidney Disease ◽  
Epithelial Tight Junction ◽  
Group 3 ◽  
Group 2 ◽  
The Impact ◽  
Group 1

Background. There is accumulating evidence pointing to uremia-induced impairment of the intestinal epithelial barrier structure in advanced chronic kidney disease (CKD) and hemodialysis (HD) patients. In this study, the impact of intradialytic hypotension on intestinal barrier integrity is being explored. Methods. Immunohistochemical staining was used to detect the expression of 4 types of tight junction (TJ) proteins such as occludin, zonula occludens-1 (ZO-1), claudin-1, and claudin-4, in colonic samples of a group of patients receiving segmental colectomy. Five patients with nondialysis CKD (group 2), 5 HD patients with intradialytic hypotension (group 3), and 5 non-CKD subjects (group 1) were examined. Results. Both patients’ groups 2 and 3 demonstrated significantly reduced expression of occludin as compared to group 1 (p<0.05 and p<0.01, resp.). Except for claudin-4, expression of all markers of TJ proteins was significantly reduced in patients’ group 3 as compared to control (p<0.01). In addition, decreased expressions of claudin-1 and ZO-1 were also more pronounced in group 3 when compared to group 2. Conclusions. This study extends the earlier finding by demonstrating that dialysis-related hypotension caused even marked depletion of the key protein constituents of the epithelial TJ.

Role of Epithelial Cells in Initiation and Propagation of Intestinal Inflammation. Eliminating the static: tight junction dynamics exposed

2006 ◽  
Vol 290 (4) ◽  
pp. G577-G582 ◽  
Author(s):  
Le Shen ◽  
Jerrold R. Turner
Keyword(s):  
Epithelial Cells ◽  
Tight Junction ◽  
Tight Junctions ◽  
Plasma Membranes ◽  
Intestinal Inflammation ◽  
Intestinal Barrier ◽  
Barrier Properties ◽  
Structural Modifications ◽  
Mucosal Surfaces

Like all mucosal surfaces, the intestine forms a barrier that separates the external environment, i.e., the gut lumen, from the protected internal milieu. The intestinal barrier is formed by the epithelial cells that line the luminal surface. Plasma membranes of these cells prevent free passage of hydrophilic molecules across this barrier but do not seal the space between cells. This function is provided by the tight junction. Each cell is encircled at the apicolateral boundary by the tight junction, which seals the paracellular space. The tight junction does not form a completely impermeant seal, however, because that would prevent paracellular absorption of essential nutrients and ions; intestinal tight junctions are “leaky” and allow solutes to be transported paracellularly according to size and charge. Abundant data are available to demonstrate that barrier properties of tight junctions can be modulated in response to physiological, pharmacological, and pathophysiological stimuli, but the structural modifications responsible for these responses are poorly defined. Recent advances in understanding the role of tight junction dynamics in response to such stimuli are the focus of this review.

scholarly journals Caprate Modulates Intestinal Barrier Function in Porcine Peyer’s Patch Follicle-Associated Epithelium

2019 ◽  
Vol 20 (6) ◽  
pp. 1418 ◽  
Author(s):  
Judith Radloff ◽  
Valeria Cornelius ◽  
Alexander G. Markov ◽  
Salah Amasheh
Keyword(s):  
Barrier Function ◽  
Ex Vivo ◽  
Intestinal Barrier ◽  
Barrier Properties ◽  
Food Allergies ◽  
Intestinal Barrier Function ◽  
Intestinal Epithelial ◽  
Food Component ◽  
Follicle Associated Epithelium

Background: Many food components influence intestinal epithelial barrier properties and might therefore also affect susceptibility to the development of food allergies. Such allergies are triggered by increased antibody production initiated in Peyer’s patches (PP). Usually, the presentation of antigens in the lumen of the gut to the immune cells of the PP is strongly regulated by the follicle-associated epithelium (FAE) that covers the PP. As the food component caprate has been shown to impede barrier properties in villous epithelium, we hypothesized that caprate also affects the barrier function of the PP FAE, thereby possibly contributing a risk factor for the development of food allergies. Methods: In this study, we have focused on the effects of caprate on the barrier function of PP, employing in vitro and ex vivo experimental setups to investigate functional and molecular barrier properties. Incubation with caprate induced an increase of transepithelial resistance, and a marked increase of permeability for the paracellular marker fluorescein in porcine PP to 180% of control values. These effects are in accordance with changes in the expression levels of the barrier-forming tight junction proteins tricellulin and claudin-5. Conclusions: This barrier-affecting mechanism could be involved in the initial steps of a food allergy, since it might trigger unregulated contact of the gut lumen with antigens.

Desmoglein 2-mediated adhesion is required for intestinal epithelial barrier integrity

2010 ◽  
Vol 298 (5) ◽  
pp. G774-G783 ◽  
Author(s):  
Nicolas Schlegel ◽  
Michael Meir ◽  
Wolfgang-Moritz Heupel ◽  
Bastian Holthöfer ◽  
Rudolf E. Leube ◽  
...  
Keyword(s):  
Tight Junction ◽  
Intestinal Barrier ◽  
Intercellular Junctions ◽  
Barrier Properties ◽  
Epithelial Barrier ◽  
Intestinal Epithelial ◽  
Intestinal Epithelial Barrier ◽  
Barrier Functions ◽  
Epithelial Monolayers

The integrity of intercellular junctions that form the “terminal bar” in intestinal epithelium is crucial for sealing the intestinal barrier. Whereas specific roles of tight and adherens junctions are well known, the contribution of desmosomal adhesion for maintaining the intestinal epithelial barrier has not been specifically addressed. For the present study, we generated a desmoglein 2 antibody directed against the extracellular domain (Dsg2 ED) to test whether impaired Dsg2-mediated adhesion affects intestinal epithelial barrier functions in vitro. This antibody was able to specifically block Dsg2 interaction in cell-free atomic-force microscopy experiments. For in vitro studies of the intestinal barrier we used Caco2 cells following differentiation into tight enterocyte-like epithelial monolayers. Application of Dsg2 ED to Caco2 monolayers resulted in increased cell dissociation compared with controls in a dispase-based enterocyte dissociation assay. Under similar conditions, Dsg2 antibody significantly decreased transepithelial electrical resistance and increased FITC-dextran flux, indicating that Dsg2 interaction is critically involved in the maintenance of epithelial intestinal barrier functions. As revealed by immunostaining, this was due to Dsg2 ED antibody-induced rupture of tight junctions because tight junction proteins claudins 1, 4, and 5, occludin, and tight junction-associated protein zonula occludens-1 were partially removed from cell borders by Dsg2 ED treatment. Similar results were obtained by application of a commercial monoclonal antibody directed against the ED of Dsg2. Antibody-induced effects were blocked by absorption experiments using Dsg2-Fc-coated beads. Our data indicate that Dsg2-mediated adhesion affects tight junction integrity and is required to maintain intestinal epithelial barrier properties.

scholarly journals Organoids and Their Use in Modeling Gut Epithelial Cell Lineage Differentiation and Barrier Properties During Intestinal Diseases

2021 ◽  
Vol 9 ◽  
Author(s):  
Dianne Pupo Gómez ◽  
Francois Boudreau
Keyword(s):  
Intestinal Epithelium ◽  
Cell Lineage ◽  
Intestinal Barrier ◽  
Barrier Properties ◽  
Cell Types ◽  
Food Allergies ◽  
Complex Nature ◽  
Intestinal Epithelial ◽  
Normal Epithelium

Maintenance of intestinal epithelium homeostasis is a complex process because of the multicellular and molecular composition of the gastrointestinal wall and the involvement of surrounding interactive signals. The complex nature of this intestinal barrier system poses challenges in the detailed mechanistic understanding of intestinal morphogenesis and the onset of several gut pathologies, including intestinal inflammatory disorders, food allergies, and cancer. For several years, the gut scientific community has explored different alternatives in research involving animals and in vitro models consisting of cultured monolayers derived from the immortalized or cancerous origin cell lines. The recent ability to recapitulate intestinal epithelial dynamics from mini-gut cultures has proven to be a promising step in the field of scientific research and biomedicine. The organoids can be grown as two- or three-dimensional structures, and are derived from adult or pluripotent stem cells that ultimately establish an intestinal epithelium that is composed of all differentiated cell types present in the normal epithelium. In this review, we summarize the different origins and recent use of organoids in modeling intestinal epithelial differentiation and barrier properties.

scholarly journals Dual Action of the PN159/KLAL/MAP Peptide: Increase of Drug Penetration across Caco-2 Intestinal Barrier Model by Modulation of Tight Junctions and Plasma Membrane Permeability

Pharmaceutics ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 73 ◽  
Author(s):  
Alexandra Bocsik ◽  
Ilona Gróf ◽  
Lóránd Kiss ◽  
Ferenc Ötvös ◽  
Ottó Zsíros ◽  
...  
Keyword(s):  
Tight Junction ◽  
Tight Junctions ◽  
Efflux Pump ◽  
Intestinal Barrier ◽  
Cell Penetrating Peptides ◽  
Intestinal Epithelial ◽  
Plasma Membrane Permeability ◽  
Cell Penetrating ◽  
Dual Action ◽  
Epithelial Barriers

The absorption of drugs is limited by the epithelial barriers of the gastrointestinal tract. One of the strategies to improve drug delivery is the modulation of barrier function by the targeted opening of epithelial tight junctions. In our previous study the 18-mer amphiphilic PN159 peptide was found to be an effective tight junction modulator on intestinal epithelial and blood–brain barrier models. PN159, also known as KLAL or MAP, was described to interact with biological membranes as a cell-penetrating peptide. In the present work we demonstrated that the PN159 peptide as a penetration enhancer has a dual action on intestinal epithelial cells. The peptide safely and reversibly enhanced the permeability of Caco-2 monolayers by opening the intercellular junctions. The penetration of dextran molecules with different size and four efflux pump substrate drugs was increased several folds. We identified claudin-4 and -7 junctional proteins by docking studies as potential binding partners and targets of PN159 in the opening of the paracellular pathway. In addition to the tight junction modulator action, the peptide showed cell membrane permeabilizing and antimicrobial effects. This dual action is not general for cell-penetrating peptides (CPPs), since the other three CPPs tested did not show barrier opening effects.

Effects of ion transport inhibitors on MCh-mediated secretion from porcine airway submucosal glands

2002 ◽  
Vol 93 (3) ◽  
pp. 873-881 ◽  
Author(s):  
Jonathan E. Phillips ◽  
John A. Hey ◽  
Michel R. Corboz
Keyword(s):  
Ion Transport ◽  
Channel Blocker ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Chloride Secretion ◽  
Gland Secretion ◽  
Sodium Absorption ◽  
Airway Function ◽  
Submucosal Glands ◽  
Chloride Channel Blocker

Submucosal glands secrete macromolecules and liquid that are essential for normal airway function. To determine the mechanisms responsible for airway gland secretion and the interaction between gland secretion and epithelial ion transport, studies were performed in porcine tracheal epithelia by using the hillocks and Ussing techniques. No significant baseline gland fluid flux ( J G) was measured by the hillocks technique after 3 min, and the epithelia had an average potential difference of 7.5 ± 0.5 mV (lumen negative) with a short-circuit current of 73 ± 4 μA/cm2, as measured by the Ussing technique. The secretagogue methacholine induced concentration-dependent increases in J G after 3 min from 0.003 μl · min−1 · cm−2 at 0.1 μM to 0.41 ± 0.04 μl · min−1 · cm−2 at 1,000 μM, with a 0.9 ± 0.1 mV hyperpolarization of the epithelium at 1,000 μM. When the epithelium was pretreated for 3 min with the sodium channel blocker amiloride, the methacholine (1,000 μM)-induced J G increased to 0.67 ± 0.09 μl · min−1 · cm−2, and the hyperpolarization increased to 2.2 ± 0.5 mV over the amiloride-pretreated level. When pretreated for 3 min with the chloride channel blocker diphenylamine-2-carboxylic acid, the methacholine (1,000 μM)-induced J G was inhibited to 0.20 ± 0.06 μl · min−1 · cm−2, and the methacholine-induced hyperpolarization was abolished. These data indicate that, in porcine airways, methacholine-induced J G may be increased by inhibition of sodium absorption and decreased by inhibition of chloride secretion.

scholarly journals AMPK Activation Promotes Tight Junction Assembly in Intestinal Epithelial Caco-2 Cells

2019 ◽  
Vol 20 (20) ◽  
pp. 5171 ◽  
Author(s):  
Séverine Olivier ◽  
Jocelyne Leclerc ◽  
Adrien Grenier ◽  
Marc Foretz ◽  
Jérôme Tamburini ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Tight Junction ◽  
Tight Junctions ◽  
Paracellular Permeability ◽  
Cell Junctions ◽  
Epithelial Barrier ◽  
Intestinal Epithelial ◽  
Ampk Activation ◽  
Energy Status ◽  
The Impact

The AMP-activated protein kinase (AMPK) is principally known as a major regulator of cellular energy status, but it has been recently shown to play a key structural role in cell-cell junctions. The aim of this study was to evaluate the impact of AMPK activation on the reassembly of tight junctions in intestinal epithelial Caco-2 cells. We generated Caco-2 cells invalidated for AMPK α1/α2 (AMPK dKO) by CRISPR/Cas9 technology and evaluated the effect of the direct AMPK activator 991 on the reassembly of tight junctions following a calcium switch assay. We analyzed the integrity of the epithelial barrier by measuring the trans-epithelial electrical resistance (TEER), the paracellular permeability, and quantification of zonula occludens 1 (ZO-1) deposit at plasma membrane by immunofluorescence. Here, we demonstrated that AMPK deletion induced a delay in tight junction reassembly and relocalization at the plasma membrane during calcium switch, leading to impairments in the establishment of TEER and paracellular permeability. We also showed that 991-induced AMPK activation accelerated the reassembly and reorganization of tight junctions, improved the development of TEER and paracellular permeability after calcium switch. Thus, our results show that AMPK activation ensures a better recovery of epithelial barrier function following injury.

Zonulin and Its Regulation of Intestinal Barrier Function: The Biological Door to Inflammation, Autoimmunity, and Cancer

2011 ◽  
Vol 91 (1) ◽  
pp. 151-175 ◽  
Author(s):  
Alessio Fasano
Keyword(s):  
Gastrointestinal Tract ◽  
Tight Junctions ◽  
Barrier Function ◽  
Intestinal Barrier ◽  
Intestinal Barrier Function ◽  
Intestinal Epithelial ◽  
New Paradigm ◽  
Intestinal Epithelial Barrier ◽  
Neoplastic Disorders

The primary functions of the gastrointestinal tract have traditionally been perceived to be limited to the digestion and absorption of nutrients and to electrolytes and water homeostasis. A more attentive analysis of the anatomic and functional arrangement of the gastrointestinal tract, however, suggests that another extremely important function of this organ is its ability to regulate the trafficking of macromolecules between the environment and the host through a barrier mechanism. Together with the gut-associated lymphoid tissue and the neuroendocrine network, the intestinal epithelial barrier, with its intercellular tight junctions, controls the equilibrium between tolerance and immunity to non-self antigens. Zonulin is the only physiological modulator of intercellular tight junctions described so far that is involved in trafficking of macromolecules and, therefore, in tolerance/immune response balance. When the finely tuned zonulin pathway is deregulated in genetically susceptible individuals, both intestinal and extraintestinal autoimmune, inflammatory, and neoplastic disorders can occur. This new paradigm subverts traditional theories underlying the development of these diseases and suggests that these processes can be arrested if the interplay between genes and environmental triggers is prevented by reestablishing the zonulin-dependent intestinal barrier function. This review is timely given the increased interest in the role of a “leaky gut” in the pathogenesis of several pathological conditions targeting both the intestine and extraintestinal organs.

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