scholarly journals Phosphatidylinositol 3-Kinase-dependent Pathways Oppose Fas-induced Apoptosis and Limit Chloride Secretion in Human Intestinal Epithelial Cells

2001 ◽  
Vol 276 (50) ◽  
pp. 47563-47574 ◽  
Author(s):  
Maria T. Abreu ◽  
Elizabeth T. Arnold ◽  
Jimmy Y. C. Chow ◽  
Kim E. Barrett
Keyword(s):  
Epithelial Cells ◽  
Barrier Function ◽  
Intestinal Inflammation ◽  
Short Circuit ◽  
Chloride Secretion ◽  
Pi3 Kinase ◽  
Secretory Diarrhea ◽  
Cross Linking ◽  
Barrier Dysfunction ◽  
Kinase Inhibition

The epithelial lining of the intestine serves as a barrier to lumenal bacteria and can be compromised by pathologic Fas-mediated epithelial apoptosis. Phosphatidylinositol (PI)3-kinase signaling has been described to limit apoptosis in other systems. We hypothesized that PI3-kinase-dependent pathways regulate Fas-mediated apoptosis and barrier function in intestiynal epithelial cells (IEC). IEC lines (HT-29 and T84) were exposed to agonist anti-Fas antibody in the presence or absence of chemical inhibitors of PI3-kinase (LY294002 and wortmannin). Apoptosis, barrier function, changes in short circuit current (ΔIsc), and expression of adhesion molecules were assessed. Inhibition of PI3-kinase strongly sensitized IEC to Fas-mediated apoptosis. Expression of constitutively active Akt, a principal downstream effector of the PI3-kinase pathway, protected against Fas-mediated apoptosis to an extent that was comparable with expression of a genetic caspase inhibitor, p35. PI3-kinase inhibition sensitized to apoptosis by increasing and accelerating Fas-mediated caspase activation. Inhibition of PI3-kinase combined with cross-linking Fas was associated with increased permeability to molecules that were <400 Da but not those that were >3,000 Da. Inhibition of PI3-kinase resulted in chloride secretion that was augmented by cross-linking Fas. Confocal analyses revealed polymerization of actin and maintenance of epithelial cell adhesion molecule-mediated interactions in monolayers exposed to anti-Fas antibody in the context of PI3-kinase inhibition. PI3-kinase-dependent pathways, especially Akt, protect IEC against Fas-mediated apoptosis. Inhibition of PI3-kinase in the context of Fas signaling results in increased chloride secretion and barrier dysfunction. These findings suggest that agonists of PI3-kinase such as growth factors may have a dual effect on intestinal inflammation by protecting epithelial cells against immune-mediated apoptosis and limiting chloride secretory diarrhea.

scholarly journals Apical leptin induces chloride secretion by intestinal epithelial cells and in a rat model of acute chemotherapy-induced colitis

2010 ◽  
Vol 298 (5) ◽  
pp. G714-G721 ◽  
Author(s):  
Raschid M. Hoda ◽  
Michael Scharl ◽  
Stephen J. Keely ◽  
Declan F. McCole ◽  
Kim E. Barrett
Keyword(s):  
Epithelial Cells ◽  
Rat Model ◽  
Intestinal Inflammation ◽  
Intestinal Epithelial Cells ◽  
Short Circuit ◽  
Chloride Secretion ◽  
Secretory Diarrhea ◽  
Intestinal Epithelial ◽  
Sprague Dawley ◽  
Ussing Chambers

The purpose of this study was to investigate whether luminal leptin alters ion transport properties of the intestinal epithelium under acute inflammatory conditions. Monolayers of human intestinal T84 epithelial cells and a rat model of chemotherapy-induced enterocolitis were used. Cells were treated with leptin and mounted in Ussing chambers to measure basal and secretagogue-induced changes in transepithelial short-circuit current ( Isc). Furthermore, the role of MAPK and phosphatidylinositol 3-kinase (PI3K) signaling pathways in mediating responses to leptin was investigated. Acute colitis in Sprague-Dawley rats was induced by intraperitoneal injection of 40 mg/kg methotrexate. Leptin (100 ng/ml) induced a time-dependent increase in basal Isc in T84 intestinal epithelial cells ( P < 0.01). Moreover, pretreatment of T84 cells with leptin for up to 1 h significantly potentiated carbachol- and forskolin-induced increases in Isc. Pretreatment with an inhibitor of MAPK abolished the effect of leptin on basal, carbachol- and forskolin-induced chloride secretion ( P < 0.05). However, the PI3K inhibitor, wortmannin, only blunted the effect of leptin on forskolin-induced increases in Isc. Furthermore, leptin treatment evoked both ERK1/2 and Akt1 phosphorylation in T84 cells. In the rat model, luminal leptin induced significant increases in Isc across segments of proximal and, to a lesser extent, distal colon ( P < 0.05). We conclude that luminal leptin is likely an intestinal chloride secretagogue, particularly when present at elevated concentrations and/or in the setting of inflammation. Our findings may provide a mechanistic explanation, at least in part, for the clinical condition of secretory diarrhea both in hyperleptinemic obese patients and in patients with chemotherapy-induced intestinal inflammation.

scholarly journals BAFF Blockade Attenuates Inflammatory Responses and Intestinal Barrier Dysfunction in a Murine Endotoxemia Model

2020 ◽  
Vol 11 ◽  
Author(s):  
Runze Quan ◽  
Chaoyue Chen ◽  
Wei Yan ◽  
Ying Zhang ◽  
Xi Zhao ◽  
...  
Keyword(s):  
Barrier Function ◽  
Intestinal Inflammation ◽  
Inflammatory Responses ◽  
Survival Rates ◽  
Intestinal Barrier ◽  
Intestinal Barrier Function ◽  
Barrier Dysfunction ◽  
Protein Levels ◽  
Lps Challenge ◽  
Endotoxemia Model

B cell-activating factor (BAFF) production is increased in septic patients. However, the specific role of BAFF in sepsis remains unknown. This study was designed to investigate the expression and function of BAFF in an experimental endotoxemia model and to identify the potential mechanisms. We established an endotoxemia mouse (6–8 weeks, 20–22 g) model by administering 30 mg/kg lipopolysaccharide (LPS). BAFF levels in the circulating system and organ tissues were measured 4 and 8 h after LPS injection. Survival rates in the endotoxemia mice were monitored for 72 h after BAFF blockade. The effects of BAFF blockade on systemic and local inflammation, organ injuries, and intestinal barrier function were also evaluated 4 h after LPS treatment. BAFF production was systemically and locally elevated after LPS challenge. BAFF blockade improved the survival rate, systemic inflammation, and multi-organ injuries. Moreover, BAFF blockade attenuated both intestinal inflammation and impaired intestinal permeability. BAFF blockade upregulated ZO-1 and occludin protein levels via the NF-κB/MLCK/MLC signaling pathway. These results suggested that BAFF blockade protects against lethal endotoxemia at least partially by alleviating inflammation, multi-organ injuries, and improving intestinal barrier function and provides a novel focus for further research on sepsis and experimental evidence for clinical therapy.

Endothelin stimulates chloride secretion across canine tracheal epithelium

1991 ◽  
Vol 261 (2) ◽  
pp. L188-L194 ◽  
Author(s):  
P. I. Plews ◽  
Z. A. Abdel-Malek ◽  
C. A. Doupnik ◽  
G. D. Leikauf
Keyword(s):  
Epithelial Cells ◽  
Short Circuit ◽  
Second Messengers ◽  
Short Circuit Current ◽  
Chloride Secretion ◽  
Tracheal Epithelium ◽  
Membrane Phospholipids ◽  
Cl Secretion ◽  
Tracheal Epithelial Cells ◽  
Tracheal Epithelial

The endothelins (ET) are a group of isopeptides produced by a number of cells, including canine tracheal epithelial cells. Because these compounds are endogenous peptides that may activate eicosanoid metabolism, we investigated the effects of ET on Cl secretion in canine tracheal epithelium. Endothelin 1 (ET-1) was found to produce a dose-dependent change in short-circuit current (Isc) that increased slowly and reached a maximal value within 10-15 min. When isopeptides of ET were compared, 300 nM ET-1 and ET-2 produced comparable maximal increases in Isc, whereas ET-3 produced smaller changes in Isc (half-maximal concentrations of 2.2, 7.2, and 10.4 nM, respectively). Ionic substitution of Cl with nontransported anions, iodide and gluconate, reduced ET-1-induced changes in Isc. Furthermore, the response was inhibited by the NaCl cotransport inhibitor, furosemide. In paired tissues, ET-1 significantly increased mucosal net 36Cl flux without significant effect on 22Na flux. The increase in Isc induced by ET was diminished by pretreatment with indomethacin. The second messengers mediating the increase in Isc were investigated in cultured canine tracheal epithelial cells. ET-1 stimulated the release of [3H]arachidonate from membrane phospholipids, increased intracellular Ca2+ (occasionally producing oscillations), and increased adenosine 3',5'-cyclic monophosphate accumulation. The latter was diminished by indomethacin. Thus ET is a potent agonist of Cl secretion (with the isopeptides having the following potency: ET-1 greater than or equal to ET-2 greater than ET-3) and acts, in part, through a cyclooxygenase-dependent mechanism.

scholarly journals Anthocyanins and intestinal barrier function: a review

2019 ◽  
Vol 5 ◽  
pp. 18-30 ◽  
Author(s):  
Jonathan C. Valdez ◽  
Bradley W. Bolling
Keyword(s):  
Barrier Function ◽  
Intestinal Inflammation ◽  
Intestinal Barrier ◽  
Intestinal Barrier Function ◽  
Barrier Dysfunction ◽  
Intestinal Barrier Dysfunction ◽  
Bowel Diseases ◽  
Inflammatory Bowel ◽  
Berry Anthocyanins ◽  
Chronic Intestinal Inflammation

Chronic intestinal inflammation, occurring in inflammatory bowel diseases (IBD), is associated with compromised intestinal barrier function. Inflammatory cytokines disrupt tight junctions and increase paracellular permeability of luminal antigens. Thus, chronic intestinal barrier dysfunction hinders the resolution of inflammation. Dietary approaches may help mitigate intestinal barrier dysfunction and chronic inflammation. A growing body of work in rodent models of colitis has demonstrated that berry consumption inhibits chronic intestinal inflammation. Berries are a rich dietary source of polyphenolic compounds, particularly anthocyanins. However, berry anthocyanins have limited bioavailability and are extensively metabolized by the gut microbiota and host tissue. This review summarizes the literature regarding the beneficial functions of anthocyanin-rich berries in treating and preventing IBD. Here, we will establish the role of barrier function in the pathogenesis of IBD and how dietary anthocyanins and their known microbial catabolites modulate intestinal barrier function.

Human colonic subepithelial myofibroblasts modulate transepithelial resistance and secretory response

1999 ◽  
Vol 277 (2) ◽  
pp. C271-C279 ◽  
Author(s):  
J. Beltinger ◽  
B. C. McKaig ◽  
S. Makh ◽  
W. A. Stack ◽  
C. J. Hawkey ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Barrier Function ◽  
Transforming Growth Factor ◽  
Short Circuit ◽  
Primary Cultures ◽  
Short Circuit Current ◽  
Transforming Growth Factor Β ◽  
Secretory Response ◽  
Transepithelial Resistance ◽  
T84 Cells

The epithelium of the gastrointestinal tract transports ions and water but excludes luminal microorganisms and toxic molecules. The factors regulating these important functions are not fully understood. Intestinal myofibroblasts lie subjacent to the basement membrane, at the basal surface of epithelial cells. We recently showed that primary cultures of adult human colonic subepithelial myofibroblasts express cyclooxygenase (COX)-1 and COX-2 enzymes and release bioactive transforming growth factor-β (TGF-β). In this study we have investigated the role of normal human colonic subepithelial myofibroblasts in the regulation of transepithelial resistance and secretory response in HCA-7 and T84 colonic epithelial cell lines. Cocultures of epithelial cells-myofibroblasts and medium conditioned by myofibroblasts enhanced transepithelial resistance and delayed mannitol flux. A panspecific antibody to TGF-β (but not piroxicam) antagonized this effect. In HCA-7 cells, myofibroblasts downregulated secretagogue-induced change in short-circuit current, and this effect was reversed by pretreatment of myofibroblasts with piroxicam. In contrast to HCA-7 cells, myofibroblasts upregulated the agonist-induced secretory response in T84 cells. This study shows that intestinal subepithelial myofibroblasts enhance barrier function and modulate electrogenic chloride secretion in epithelial cells. The enhancement of barrier function was mediated by TGF-β. In contrast, the modulation of agonist-induced change in short-circuit current was mediated by cyclooxygenase products. These findings suggest that colonic myofibroblasts regulate important functions of epithelial cells via distinct secretory products.

scholarly journals Role of JAM-A tyrosine phosphorylation in epithelial barrier dysfunction during intestinal inflammation

2019 ◽  
Vol 30 (5) ◽  
pp. 566-578 ◽  
Author(s):  
Shuling Fan ◽  
Caroline M. Weight ◽  
Anny-Claude Luissint ◽  
Roland S. Hilgarth ◽  
Jennifer C. Brazil ◽  
...  
Keyword(s):  
Tyrosine Phosphorylation ◽  
Barrier Function ◽  
Intestinal Inflammation ◽  
Kinase Inhibitor ◽  
Src Kinase ◽  
Small Gtpase ◽  
Epithelial Barrier ◽  
Barrier Dysfunction ◽  
Junction Protein

Junctional adhesion molecule-A (JAM-A), an epithelial tight junction protein, plays an important role in regulating intestinal permeability through association with a scaffold signaling complex containing ZO-2, Afadin, and the small GTPase Rap2. Under inflammatory conditions, we report that the cytoplasmic tail of JAM-A is tyrosine phosphorylated (p-Y280) in association with loss of barrier function. While barely detectable Y280 phosphorylation was observed in confluent monolayers of human intestinal epithelial cells under basal conditions, exposure to cytokines TNFα, IFNγ, IL-22, or IL-17A, resulted in compromised barrier function in parallel with increased p-Y280. Phosphorylation was Src kinase dependent, and we identified Yes-1 and PTPN13 as a major kinase and phosphatase for p-JAM-A Y280, respectively. Moreover, cytokines IL-22 or IL-17A induced increased activity of Yes-1. Furthermore, the Src kinase inhibitor PP2 rescued cytokine-induced epithelial barrier defects and inhibited phosphorylation of JAM-A Y280 in vitro. Phosphorylation of JAM-A Y280 and increased permeability correlated with reduced JAM-A association with active Rap2. Finally, we observed increased phosphorylation of Y280 in colonic epithelium of individuals with ulcerative colitis and in mice with experimentally induced colitis. These findings support a novel mechanism by which tyrosine phosphorylation of JAM-A Y280 regulates epithelial barrier function during inflammation.

Evidence that prostaglandin E2 stimulates chloride secretion in cultured A6 renal epithelial cells

1986 ◽  
Vol 250 (3) ◽  
pp. F511-F515 ◽  
Author(s):  
R. Keeler ◽  
N. L. Wong
Keyword(s):  
Epithelial Cells ◽  
Prostaglandin E2 ◽  
Short Circuit ◽  
Basal Medium ◽  
Short Circuit Current ◽  
Chloride Secretion ◽  
Apical Surface ◽  
Renal Epithelial Cells ◽  
Apical Side ◽  
Net Flux

The effects of prostaglandin E2 (PGE2) on the transport of sodium and chloride were studied in cultured A6 renal epithelial cells. PGE2 on the basolateral but not the apical surface increased transmonolayer short-circuit current (Isc) and conductance. These changes could not be inhibited with amiloride or furosemide in the apical medium. Flux measurements showed that although Isc and net flux of sodium were equal in unstimulated cells, after addition of PGE2 the current increased with no corresponding changes in bidirectional or net flux of sodium. Immersing the cells in sodium-free or chloride-free media inhibited the effects of PGE2. Measurements of the simultaneous fluxes of sodium and chloride showed that after PGE2 was added there was a net flux of chloride from the basal to the apical side (secretion) that was equal to the change in Isc. The effects of PGE2 were inhibited by furosemide in the basal medium. We conclude that PGE2 stimulates a process of chloride secretion in A6 cells.

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