scholarly journals Modulation of distal colonic epithelial barrier function by dietary fibre in normal rats

Gut ◽  
1999 ◽  
Vol 44 (3) ◽  
pp. 394-399 ◽  
Author(s):  
J M Mariadason ◽  
A Catto-Smith ◽  
P R Gibson
Keyword(s):  
Wheat Bran ◽  
Barrier Function ◽  
Dietary Fibre ◽  
Short Chain Fatty Acid ◽  
Distal Colon ◽  
Paracellular Permeability ◽  
Mechanisms Of Action ◽  
Epithelial Injury ◽  
Epithelial Barrier Function ◽  
Ussing Chambers

BACKGROUNDDietary fibre influences the turnover and differentiation of the colonic epithelium, but its effects on barrier function are unknown.AIMSTo determine whether altering the type and amount of fibre in the diet affects paracellular permeability of intestinal epithelium, and to identify the mechanisms of action.METHODSRats were fed isoenergetic low fibre diets with or without supplements of wheat bran (10%) or methylcellulose (10%), for four weeks. Paracellular permeability was determined by measurement of conductance and 51Cr-EDTA flux across tissue mounted in Ussing chambers. Faecal short chain fatty acid (SCFA) concentrations were assessed by gas chromatography, epithelial kinetics stathmokinetically, and mucosal brush border hydrolase activities spectrophotometrically.RESULTSBody weight was similar across the dietary groups. Conductance and 51Cr-EDTA flux were approximately 25% higher in animals fed no fibre, compared with those fed wheat bran or methylcellulose in the distal colon, but not in the caecum or jejunum. Histologically, there was no evidence of epithelial injury or erosion associated with any diet. The fibres exerted different spectra of effects on luminal SCFA concentrations and pH, and on mucosal indexes, but both bulked the faeces, were trophic to the epithelium, and stimulated expression of a marker of epithelial differentiation.CONCLUSIONSBoth a fermentable and a non-fermentable fibre reduce paracellular permeability specifically in the distal colon, possibly by promoting epithelial cell differentiation. The mechanisms by which the two fibres exert their effects are likely to be different.

scholarly journals JAM-A associates with ZO-2, afadin, and PDZ-GEF1 to activate Rap2c and regulate epithelial barrier function

2013 ◽  
Vol 24 (18) ◽  
pp. 2849-2860 ◽  
Author(s):  
Ana C. Monteiro ◽  
Ronen Sumagin ◽  
Carl R. Rankin ◽  
Giovanna Leoni ◽  
Michael J. Mina ◽  
...  
Keyword(s):  
Barrier Function ◽  
Intestinal Barrier ◽  
Paracellular Permeability ◽  
Small Gtpase ◽  
Intestinal Barrier Function ◽  
Epithelial Permeability ◽  
Functional Link ◽  
Epithelial Barrier Function ◽  
And Control ◽  
Interfering Rna

Intestinal barrier function is regulated by epithelial tight junctions (TJs), structures that control paracellular permeability. Junctional adhesion molecule-A (JAM-A) is a TJ-associated protein that regulates barrier; however, mechanisms linking JAM-A to epithelial permeability are poorly understood. Here we report that JAM-A associates directly with ZO-2 and indirectly with afadin, and this complex, along with PDZ-GEF1, activates the small GTPase Rap2c. Supporting a functional link, small interfering RNA–mediated down-regulation of the foregoing regulatory proteins results in enhanced permeability similar to that observed after JAM-A loss. JAM-A–deficient mice and cultured epithelial cells demonstrate enhanced paracellular permeability to large molecules, revealing a potential role of JAM-A in controlling perijunctional actin cytoskeleton in addition to its previously reported role in regulating claudin proteins and small-molecule permeability. Further experiments suggest that JAM-A does not regulate actin turnover but modulates activity of RhoA and phosphorylation of nonmuscle myosin, both implicated in actomyosin contraction. These results suggest that JAM-A regulates epithelial permeability via association with ZO-2, afadin, and PDZ-GEF1 to activate Rap2c and control contraction of the apical cytoskeleton.

scholarly journals Short-term adaptation of the ruminal epithelium involves abrupt changes in sodium and short-chain fatty acid transport

2014 ◽  
Vol 307 (7) ◽  
pp. R802-R816 ◽  
Author(s):  
Brittney L. Schurmann ◽  
Matthew E. Walpole ◽  
Pawel Górka ◽  
John C. H. Ching ◽  
Matthew E. Loewen ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Barrier Function ◽  
Short Chain Fatty Acid ◽  
Control Diet ◽  
Chain Fatty Acid ◽  
Short Chain ◽  
Fatty Acid Transport ◽  
Epithelial Surface ◽  
Ussing Chambers ◽  
Ruminal Epithelium

The objectives of this study were to determine the effect of an increase in diet fermentability on 1) the rate and extent to which short-chain fatty acid (SCFA) absorption pathways adapt relative to changes in Na+transport, 2) the epithelial surface area (SA), and 3) the barrier function of the bovine ruminal epithelium. Twenty-five Holstein steer calves were assigned to either the control diet (CON; 91.5% hay and 8.5% supplement) or a moderately fermentable diet (50% hay; 41.5% barley grain (G), and 8.5% supplement) fed for 3 (G3), 7 (G7), 14 (G14), or 21 days (G21). All calves were fed at 2.25% body weight at 0800. Calves were killed (at 1000), and ruminal tissue was collected to determine the rate and pathway of SCFA transport, Na+transport and barrier function in Ussing chambers. Tissue was also collected for SA measurement and gene expression. Mean reticular pH decreased from 6.90 for CON to 6.59 for G7 and then increased (quadratic P < 0.001). While effective SA of the ruminal epithelium was not affected ( P > 0.10) by dietary treatment, the net Na+flux increased by 125% within 7 days (quadratic P = 0.016). Total acetate and butyrate flux increased from CON to G21, where passive diffusion was the primary SCFA absorption pathway affected. Increased mannitol flux, tissue conductance, and tendencies for increased expression of IL-1β and TLR2 indicated reduced rumen epithelium barrier function. This study indicates that an increase in diet fermentability acutely increases Na+and SCFA absorption in the absence of increased SA, but reduces barrier function.

TGF-β effects on epithelial ion transport and barrier: reduced Cl− secretion blocked by a p38 MAPK inhibitor

2002 ◽  
Vol 283 (6) ◽  
pp. C1667-C1674 ◽  
Author(s):  
Kathryn Howe ◽  
Jack Gauldie ◽  
Derek M. McKay
Keyword(s):  
Ion Transport ◽  
P38 Mapk ◽  
Barrier Function ◽  
Short Circuit ◽  
Specific Inhibitor ◽  
Short Circuit Current ◽  
Epithelial Barrier Function ◽  
Ussing Chambers ◽  
Epithelial Ion Transport ◽  
P38 Mapk Inhibitor

Growth factors affect a variety of epithelial functions. We examined the ability of TGF-β to modulate epithelial ion transport and permeability. Filter-grown monolayers of human colonic epithelia, T84 and HT-29 cells, were treated with TGF-β (0.1–100 ng/ml, 15 min–72 h) or infected with an adenoviral vector encoding TGF-β (Ad-TGFβ) for 144 h. Ion transport (i.e., short-circuit current, I sc) and transepithelial resistance (TER) were assessed in Ussing chambers. Neither recombinant TGF-β nor Ad-TGFβ infection affected baseline I sc; however, exposure to ≥1 ng/ml TGF-β led to a significant (30–50%) reduction in the I sc responses to forskolin, vasoactive intestinal peptide, and cholera toxin (agents that evoke Cl− secretion via cAMP mobilization) and to the cell-permeant dibutyryl cAMP. Pharmacological analysis of signaling pathways revealed that the inhibition of cAMP-driven epithelial Cl− secretion by TGF-β was blocked by pretreatment with SB-203580, a specific inhibitor of p38 MAPK, but not by inhibitors of JNK, ERK1/2 MAPK, or phosphatidylinositol 3′-kinase. TGF-β enhanced the barrier function of the treated monolayers by up to threefold as assessed by TER; however, this event was temporally displaced from the altered I sc response, being statistically significant only at 72 h posttreatment. Thus, in addition to TGF-β promotion of epithelial barrier function, we show that this growth factor also reduces responsiveness to cAMP-dependent secretagogues in a chronic manner and speculate that this serves as a braking mechanism to limit secretory enteropathies.

scholarly journals PG-mediated closure of paracellular pathway and not restitution is the primary determinant of barrier recovery in acutely injured porcine ileum

2003 ◽  
Vol 285 (5) ◽  
pp. G967-G979 ◽  
Author(s):  
Jody L. Gookin ◽  
Joseph A. Galanko ◽  
Anthony T. Blikslager ◽  
Robert A. Argenzio
Keyword(s):  
Epithelial Cells ◽  
Barrier Function ◽  
Intestinal Barrier ◽  
Acute Injury ◽  
Intestinal Barrier Function ◽  
Ileal Mucosa ◽  
Epithelial Barrier Function ◽  
Ussing Chambers ◽  
Relative Contribution ◽  
Primary Determinant

Small bowel epithelium is at the frontline of intestinal barrier function. Restitution is considered to be the major determinant of epithelial repair, because function recovers in parallel with restitution after acute injury. As such, studies of intact mucosa have largely been replaced by migration assays of cultured epithelia. These latter studies fail to account for the simultaneous roles played by villous contraction and paracellular permeability in recovery of barrier function. NSAIDs result in increased intestinal permeability and disease exacerbation in patients with inflammatory bowel disease (IBD). Thus we examined the reparative attributes of endogenous PGs after injury of ileal mucosa by deoxycholate (6 mM) in Ussing chambers. Recovery of transepithelial electrical resistance (TER) from 20-40 Ω·cm2 was abolished by indomethacin (Indo), whereas restitution of 40-100% of the villous surface was unaffected despite concurrent arrest of villous contraction. In the presence of PG, resident crypt and migrating epithelial cells were tightly apposed. In tissues treated with Indo, crypt epithelial cells had dilated intercellular spaces that were accentuated in the migrating epithelium. TER was fully rescued from the effects of Indo by osmotic-driven collapse of the paracellular space, and PG-mediated recovery was significantly impaired by blockade of Cl- secretion. These studies are the first to clearly distinguish the relative contribution of paracellular resistance vs. restitution to acute recovery of epithelial barrier function. Restitution was ineffective in the absence of PG-mediated paracellular space closure. Failure of PG-mediated repair mechanisms may underlie barrier failure resulting from NSAID use in patients with underlying enteropathy.

scholarly journals Increasing butyrate concentration in the distal colon by accelerating intestinal transit

Gut ◽  
1997 ◽  
Vol 41 (2) ◽  
pp. 245-251 ◽  
Author(s):  
S J Lewis ◽  
K W Heaton
Keyword(s):  
Wheat Bran ◽  
Continuous Monitoring ◽  
Short Chain Fatty Acid ◽  
Colonic Cancer ◽  
Distal Colon ◽  
Colonic Transit ◽  
Glucuronidase Activity ◽  
Stool Form ◽  
Dietary Fibre Intake

Background—Populations at low risk of colonic cancer consume large amounts of fibre and starch and pass acid, bulky stools. One short chain fatty acid (SCFA), butyrate, is the colon’s main energy source and inhibits malignant transformation in vitro.Aim—To test the hypothesis that altering colonic transit rate alters colonic pH and the SCFA content of the stools.Patients—Thirteen healthy adults recruited by advertisement.Methods—Volunteers consumed, in turn, wheat bran, senna and loperamide, each for nine days with a two week washout period between study periods, dietary intake being unchanged. Before, and in the last four days of each intervention, whole gut transit time (WGTT), defaecation frequency, stool form, stool β-glucuronidase activity, stool pH, stool SCFA concentrations and intracolonic pH (using a radiotelemetry capsule for continuous monitoring) were assessed.Results—WGTT decreased, stool output and frequency increased with wheat bran and senna, vice versa with loperamide. The pH was similar in the distal colon and stool. Distal colonic pH fell with wheat bran and senna and tended to increase with loperamide. Faecal SCFA concentrations, including butyrate, increased with senna and fell with loperamide. With wheat bran the changes were non-significant, possibly because of the short duration of the study. Baseline WGTT correlated with faecal SCFA concentration (r=−0.511, p=0.001), with faecal butyrate (r=−0.577, p<0.001) and with distal colonic pH (r=0.359, p=0.029).Conclusion—Bowel transit rate is a determinant of stool SCFA concentration including butyrate and distal colonic pH. This may explain the inter-relations between colonic cancer, dietary fibre intake, stool output, and stool pH.

scholarly journals Vibrio parahaemolyticus Disruption of Epithelial Cell Tight Junctions Occurs Independently of Toxin Production

2005 ◽  
Vol 73 (3) ◽  
pp. 1275-1283 ◽  
Author(s):  
Tarah Lynch ◽  
Scott Livingstone ◽  
Enrico Buenaventura ◽  
Erika Lutter ◽  
Jason Fedwick ◽  
...  
Keyword(s):  
Tight Junctions ◽  
Barrier Function ◽  
Vibrio Parahaemolyticus ◽  
Toxin Production ◽  
Paracellular Permeability ◽  
Clinical Isolates ◽  
Clinical Samples ◽  
Epithelial Barrier Function ◽  
Lactate Dehydrogenase Release ◽  
Associated Proteins

ABSTRACT Vibrio parahaemolyticus is a leading cause of seafood-borne gastroenteritis worldwide. Virulence is commonly associated with the production of two toxins, thermostable direct hemolysin (TDH) and TDH-related hemolysin (TRH). Although the majority of clinical isolates produce TDH and/or TRH, clinical samples lacking toxin genes have been identified. In the present study, we investigated the effects of V. parahaemolyticus on transepithelial resistance (TER) and paracellular permeability in Caco-2 cultured epithelial cells. We found that V. parahaemolyticus profoundly disrupts epithelial barrier function in Caco-2 cells and that this disruption occurs independently of toxin production. Clinical isolates with different toxin genotypes all led to a significant decrease in TER, which was accompanied by an increased flux of fluorescent dextran across the Caco-2 monolayer, and profound disruption of actin and the tight junction-associated proteins zonula occludin protein 1 and occludin. Purified TDH, even at concentrations eightfold higher than those produced by the bacteria, had no effect on either TER or paracellular permeability. We used lactate dehydrogenase release as a measure of cytotoxicity and found that this parameter did not correlate with the ability to disrupt tight junctions. As the effect on barrier function occurs independently of toxin production, we used PCR to determine the toxin genotypes of V. parahaemolyticus isolates obtained from both clinical and environmental sources, and we found that 5.6% of the clinical isolates were toxin negative. These data strongly indicate that the effect on tight junctions is not due to TDH and suggest that there are other virulence factors.

Physiological concentrations of bile salts inhibit recovery of ischemic-injured porcine ileum

2004 ◽  
Vol 287 (2) ◽  
pp. G399-G407 ◽  
Author(s):  
Nigel B. Campbell ◽  
Craig G. Ruaux ◽  
Donnie E. Shifflett ◽  
Jöerg M. Steiner ◽  
David A. Williams ◽  
...  
Keyword(s):  
Barrier Function ◽  
Bile Salts ◽  
Deoxycholic Acid ◽  
Paracellular Permeability ◽  
Mucosal Barrier ◽  
Histological Evaluation ◽  
Ileal Mucosa ◽  
Ussing Chambers ◽  
Mucosal Barrier Function ◽  
Mannitol Flux

We have previously shown rapid in vitro recovery of barrier function in porcine ischemic-injured ileal mucosa, attributable principally to reductions in paracellular permeability. However, these experiments did not take into account the effects of luminal contents, such as bile salts. Therefore, the objective of this study was to evaluate the role of physiological concentrations of deoxycholic acid in recovery of mucosal barrier function. Porcine ileum was subjected to 45 min of ischemia, after which mucosa was mounted in Ussing chambers and exposed to varying concentrations of deoxycholic acid. The ischemic episode resulted in significant reductions in transepithelial electrical resistance (TER), which recovered to control levels of TER within 120 min, associated with significant reductions in mucosal-to-serosal 3H-labeled mannitol flux. However, treatment of ischemic-injured tissues with 10−5 M deoxycholic acid significantly inhibited recovery of TER with significant increases in mucosal-to-serosal 3H-labeled mannitol flux, whereas 10−6 M deoxycholic acid had no effect. Histological evaluation at 120 min revealed complete restitution regardless of treatment, indicating that the breakdown in barrier function was due to changes in paracellular permeability. Similar effects were noted with the application of 10−5 M taurodeoxycholic acid, and the effects of deoxycholic acid were reversed with application of the Ca2+-mobilizing agent thapsigargin. Deoxycholic acid at physiological concentrations significantly impairs recovery of epithelial barrier function by an effect on paracellular pathways, and these effects appear to be Ca2+ dependent.

scholarly journals Probiotic mixture VSL#3 reduces colonic inflammation and improves intestinal barrier function in Muc2 mucin-deficient mice

2017 ◽  
Vol 312 (1) ◽  
pp. G34-G45 ◽  
Author(s):  
Manish Kumar ◽  
Vanessa Kissoon-Singh ◽  
Aralia Leon Coria ◽  
France Moreau ◽  
Kris Chadee
Keyword(s):  
Fatty Acid ◽  
Growth Factor ◽  
Barrier Function ◽  
Proinflammatory Cytokine ◽  
Short Chain Fatty Acid ◽  
Chain Fatty Acid ◽  
Host Cells ◽  
Short Chain ◽  
Epithelial Barrier ◽  
Epithelial Barrier Function

MUC2 mucin is the major glycoprotein in colonic mucus that separates intestinal microbiota from underlying host cells and serves as a food source for some eubacteria. MUC2 deficiency results in impaired epithelial barrier function, imbalance in gut microbiota, and spontaneous colitis. Probiotics have been shown to have a protective effect against colitis. In this study we used Muc2 mucin-deficient ( Muc2−/−) and Muc2+/+ littermates to test whether the probiotic mixture VSL#3 requires an intact mucin barrier to exert its beneficial effect. VSL#3 alone reduced basal colonic proinflammatory cytokine levels and improved epithelial barrier function in Muc2−/− animals. Similarly, in dextran sulfate sodium-induced colitis, VSL#3 dampened the proinflammatory chemokines KC, monocyte chemoattractant protein-1, and macrophage inflammatory protein-2 and upregulated the tissue regeneration growth factors transforming growth factor-β, fibroblast growth factor-1, and vascular endothelial growth factor-A, which accelerated resolution of colitis symptoms in Muc2−/− animals. Importantly, improved colonic health in VSL#3-treated animals was associated with attenuated reactive oxygen species production by peritoneal macrophages, restoration of antimicrobial peptide gene expression in the small intestine, and increased abundance of bacterial commensals in the gut. The beneficial effects of VSL#3 in Muc2−/− animals were mediated by acetate, an important short-chain fatty acid produced by gut bacteria. These studies provide evidence for the first time that VSL#3 can enhance epithelial barrier function by dampening the proinflammatory cytokine and chemokine response, accelerating restitution, and altering commensal microbiota in the absence of a functional mucus barrier. NEW & NOTEWORTHY It is unclear whether probiotics require an intact mucin barrier to first colonize and/or exert their protective functions. In this study we used mucin-deficient (Muc2 −/−) mice to interrogate if the multispecies probiotic mixture VSL#3 could enhance epithelial barrier function. In the absence of a mucus bilayer, VSL#3 dampened proinflammatory and chemokine production, accelerated restitution, and markedly improved gut permeability mediated by the short-chain fatty acid acetate in the colon.

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