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Results for “Intestinal Barrier Function”

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PubMed2003

Prolonged interferon-gamma exposure decreases ion transport, NKCC1, and Na+-K+-ATPase expression in human intestinal xenografts in vivo.

IFN-gamma is elevated in intestinal inflammation and alters barrier and transport functions in human colonic epithelial cell lines, but its effects on normal human small intestinal epithelium in vivo are poorly defined. We investigated effects of prolonged IFN-gamma exposure on ion transport and expression of transporters by using human fetal small intestinal xenografts. Xenograft-bearing mice were injected with IFN-gamma, and 24 h later xenografts were harvested and mounted in Ussing chambers. Baseline potential difference (PD) was not affected by IFN-gamma treatment. However, conductance was enhanced and agonist-stimulated ion transport was decreased. IFN-gamma also decreased expression of the Na+-K+-2Cl- cotransporter and the alpha-subunit of Na+-K+-ATPase compared with controls, whereas levels of the calcium-activated Cl- channel and CFTR were unaltered. Thus prolonged exposure to IFN-gamma leads to decreased ion secretion due, in part, to decreased ion transporter levels. These findings demonstrate the implications of elevated IFN-gamma levels in human small intestine and validate the human intestinal xenograft as a model to study chronic effects of physiologically relevant stimuli.

Animals↗

PubMed2004

Toll-like receptor 2 enhances ZO-1-associated intestinal epithelial barrier integrity via protein kinase C.

BACKGROUND & AIMS: Protein kinase C (PKC) has been implicated in regulation of intestinal epithelial integrity in response to lumenal bacteria. Intestinal epithelial cells (IECs) constitutively express Toll-like receptor (TLR)2, which contains multiple potential PKC binding sites. The aim of this study was to determine whether TLR2 may activate PKC in response to specific ligands, thus potentially modulating barrier function in IECs. METHODS: TLR2 agonist (synthetic bacterial lipopeptide Pam(3)CysSK4, peptidoglycan)-induced activation of PKC-related signaling cascades were assessed by immunoprecipitation, Western blotting, immunofluorescence, and kinase assays-combined with functional transfection studies in the human model IEC lines HT-29 and Caco-2. Transepithelial electrical resistance characterized intestinal epithelial barrier function. RESULTS: Stimulation with TLR2 ligands led to activation (phosphorylation, enzymatic activity, translocation) of specific PKC isoforms (PKCalpha and PKCdelta). Phosphorylation of PKC by TLR2 ligands was blocked specifically by transfection with a TLR2 deletion mutant. Ligand-induced activation of TLR2 greatly enhanced transepithelial resistance in IECs, which was prevented by pretreatment with PKC-selective antagonists. This effect correlated with apical tightening and sealing of tight junction (TJ)-associated ZO-1, which was mediated via PKC in response to TLR2 ligands, whereas morphologic changes of occludin, claudin-1, or actin cytoskeleton were not evident. Downstream the endogenous PKC substrate myristoylated alanine-rich C kinase substrate (MARCKS), but not transcriptional factor activator protein-1 (AP-1), was activated significantly on stimulation. CONCLUSIONS: The present study provides evidence that PKC is an essential component of the TLR2 signaling pathway with the physiologic consequence of directly enhancing intestinal epithelial integrity through translocation of ZO-1 on activation.

Caco-2 Cells↗

PubMed1996

Effect of recombinant human growth hormone on the intestinal structure of rats receiving bowel resection and parenteral nutrition.

Recombinant human growth hormone (rHGH) can improve nitrogen balance and promotecell proliferation. Little is known about the relationship between rHGH and gastrointestinal mucosal structure and function after bowel resection and parenteral nutrition (PN). The aim of this study was to determine the effect of rHGH on bowel mucosal structure and barrier function in rats receiving 50% small intestinal resection and PN. Thirty Wistar rats with central vein catheterization plus 50% small bowel resection were divided into three groups: chow (chow), standard (STD) and rHGH (rHGH). The chow group received chow food; the STD group was given standard PN; the rHGH group received standard PN plus rHGH (4.8 mg/kg/day, subcutaneously). The groups were maintained on their respective diets for 8 days and then killed. Body weight, small intestinal mucosal thickness, villus height and Goblet cells in the villus were measured. Body weight loss in the STD group was significantly greater than that in the chow and rHGH groups (P< 0.01). The mucosal thickness and villus height of rHGH group were significantly greater than the STD and chow groups (mucosal thickness: 806 +/- 5.5 vs. 533 +/- 6.0 and 593 +/- 6.0 microm; Villus height: 506 +/- 6.0 vs. 295 +/- 5.5 gm and 400 +/- 6.7 lam, respectively) (P< 0.05). The number of Goblet cells in the STD group was significantly greater than the rHGH and chow groups (9.06 +/- 1.07 vs. 5.35 +/- 1.48 and 6.10 +/- 1.51/per villus) (P < 0.01). rHGH can maintain body weight and promote bowel mucosal cell growth and might improve the barrier function of the bowel in rats after 50% small intestinal resection and PN.

Journal Article↗

PubMed1995

FK506 increases permeability in rat intestine by inhibiting mitochondrial function.

BACKGROUND & AIMS: Under normal physiological conditions, the intestine presents an adenosine triphosphate (ATP)-dependent barrier to luminal contents. Disruption of this barrier function can occur when cellular metabolism is compromised. This study examined the effects of FK506 on intestinal permeability and enterocyte metabolic function in Lewis rats. METHODS: Rats were administered FK506 at a dose of 0.1, 0.5, or 2 mg/kg on alternate days for 6 weeks. Intestinal permeability was assessed by measuring urinary recovery of 99mTc-diethylenetriamine pentacetate, and electrophysiological conductance measurements were performed in Ussing chambers. Metabolic function was assessed in isolated enterocytes by measuring total ATP and CO2 release from [14C]pyruvate and [14C]glucose. RESULTS: Rats treated with FK506 showed a dose-dependent reduction in weight gain as well as increased in vivo and in vitro intestinal permeability. There was no difference in plasma creatinine or urinary output. Changes in permeability correlated with reduced ATP levels and CO2 release because of diminished mitochondrial function. Lactate production, as a measure of glycolytic activity, was not altered by FK506. CONCLUSIONS: In a dose-dependent manner, FK506 treatment in rats reduces weight gain, increases intestinal permeability, and decreases the ability of the small intestine to use glucose as an energy source.

Adenosine Triphosphate↗

PubMed1989

Villus contraction aids repair of intestinal epithelium after injury.

A highly reproducible in vitro model of intestinal epithelial injury in guinea pig ileum was used to study the structural and functional events that accompany rapid epithelial repair. This model is characterized by denudation of the villus tip followed by rapid restitution of the epithelial barrier. Using standard electrophysiological and quantitative morphometric techniques, we found that immediately after injury the number of cells lost exceeded the number of empty cell positions on the denuded basement membrane by 100%. Concurrently, cytoplasmic processes of subepithelial myofibroblasts contained condensations of microfilaments that were not apparent in controls. Additionally, villus height was diminished immediately after injury, and progressively decreased during the restitution period. In tissues that were depleted of ATP using the uncoupler dinitrophenol and in tissues functionally denervated by tetrodotoxin, villus shortening after injury was significantly reduced. Denervation also retarded functionally and structurally defined reestablishment of epithelial barrier function. These data suggest that intestinal epithelial repair is aided by energy-dependent, neurally mediated villus contraction. We speculate that the subepithelial network of myofibroblasts is responsible for this process, which effectively minimizes the denuded surface area to be reepithelialized.

2,4-Dinitrophenol↗

PubMed1998

[The intestine as the central organ in the development of multiple organ failure after severe trauma--pathophysiology and therapeutic approaches].

Multiple organ failure is with an incidence of 10-25% and a mortality of 50-70% the most severe complication after severe trauma. Intestinal ischemia and a corresponding impaired gut barrier function is thought to have a high impact on the development of multiple organ failure after severe trauma. Under normal conditions the intestinal wall is a sufficient barrier against bacteria and their products. Gut ischemia is followed by mucosal lesions, the intestinal permeability is increased. Translocating bacteria and bacterial products (endotoxin, peptidoglykan) can lead to a local and/or systemic immun-inflammatory response, which is made responsible for the development of multiple organ failure. Tonometry as a possibility of monitoring intestinal ischemia as well as a tool to estimate the prognosis of multiple trauma patients is still discussed controversially. Dopexamin, which directly influences intestinal ischemia (goal directed therapy) might be a successful treatment option, however until now no clinical study about beneficial effects of dopexamine in severely injured patients is available. Selective gut decontamination showed no clinical benefits in multiple trauma patients. Early enteral nutrition especially with immunomodulating ingredients ("immunonutrition") decreases posttraumatic complications as well as the incidence of MOF. However a reduction of mortality could not be described in severely injured patients so far.

Bacterial Translocation↗

PubMed2006

Interactions of intestinal epithelial cells with bacteria and immune cells: methods to characterize microflora and functional consequences.

Epithelial cells at all mucosal surfaces are potentially apposed to bacteria, particularly in the intestine. It is established that intestinal epithelial cells (IECs) represent an important barrier between lamina propria cells and the potentially harmful lumenal contents. In addition, IECs are important immunoeffector cells with the capacity to release cytokines, chemokines, and other molecules involved in antigen presentation and immune defense. The interaction of IECs with intestinal bacteria can result in a decrease in barrier function and the development of inflammation, which is known to be an important factor in the development of intestinal pathology. The potential role of such crosstalk between bacteria and other intestinal cell types in normal physiology and/or pathophysiology is therefore a topic of intense investigation. In this chapter, we provide protocols for the identification of bacteria that are associated with the epithelium and mucosa in addition to functional assays examining the interactions of neutrophils with epithelial cells and epithelial cell-mediated killing of bacteria.

Animals↗

PubMed2004

Intestinal bacterial overgrowth induces the production of biologically active intestinal lymph.

OBJECTIVE: We have previously documented that gut-derived lymph from rats subjected to trauma plus hemorrhagic shock (T/HS) is injurious to vascular endothelial cells and activates neutrophils (PMNs), two key events in postshock organ injury. Because T/HS leads to gut injury, intestinal bacterial overgrowth, and the loss of gut barrier function, the relative role of gut injury as opposed to intestinal bacterial overgrowth per se in the pathogenesis of biologically active intestinal lymph is unclear. We therefore studied whether mesenteric lymph can injure endothelial cells and/or active PMNs in an intestinal bacterial overgrowth model where there is no gut injury (monoassociation). METHODS: Bacterial overgrowth was established in male rats by treating the animals with 4 days of oral antibiotics followed by administration of a nonpathogenic, streptomycin-resistant strain of Escherichia coli C25. Mesenteric lymph was then collected from rats with normal flora and from E. coli C25 monoassociated rats. Its effects were tested on human umbilical vein endothelial cells (HUVECs) and human PMNs. As an additional control, lymph was collected from antibiotic-decontaminated rats that received antibiotics but were not colonized with E. coli C25. RESULTS: As compared with medium, normal flora intestinal lymph, antibiotic-decontaminated lymph, or portal plasma from the monoassociated rats, mesenteric lymph from the monoassociated rats killed HUVECs and increased the permeability of a HUVEC monolayer. In contrast to the effects on HUVECs, lymph from the monoassociated rats did not increase PMN CD11b expression or prime PMNs for an augmented respiratory burst, as compared with lymph from the rats with normal flora or from antibiotic-decontaminated rats. The effects of lymph from the monoassociated rats was not caused by bacteria, because these lymph samples were sterile. CONCLUSION: These results indicate that disruption of the normal intestinal microflora resulting in bacterial overgrowth with enteric bacilli may participate in the production of mesenteric lymph that is injurious to endothelial cells in shock, but this mechanism does not appear to be significantly involved in the activation of PMNs.

Animals↗

PubMed2006

Identification of multi-drug resistant Pseudomonas aeruginosa clinical isolates that are highly disruptive to the intestinal epithelial barrier.

BACKGROUND: Multi-drug resistant Pseudomonas aeruginosa nosocomial infections are increasingly recognized worldwide. In this study, we focused on the virulence of multi-drug resistant clinical strains P. aeruginosa against the intestinal epithelial barrier, since P. aeruginosa can cause lethal sepsis from within the intestinal tract of critically ill and immuno-compromised patients via mechanisms involving disruption of epithelial barrier function. METHODS: We screened consecutively isolated multi-drug resistant P. aeruginosa clinical strains for their ability to disrupt the integrity of human cultured intestinal epithelial cells (Caco-2) and correlated these finding to related virulence phenotypes such as adhesiveness, motility, biofilm formation, and cytotoxicity. RESULTS: Results demonstrated that the majority of the multi-drug resistant P. aeruginosa clinical strains were attenuated in their ability to disrupt the barrier function of cultured intestinal epithelial cells. Three distinct genotypes were found that displayed an extreme epithelial barrier-disrupting phenotype. These strains were characterized and found to harbor the exoU gene and to display high swimming motility and adhesiveness. CONCLUSION: These data suggest that detailed phenotypic analysis of the behavior of multi-drug resistant P. aeruginosa against the intestinal epithelium has the potential to identify strains most likely to place patients at risk for lethal gut-derived sepsis. Surveillance of colonizing strains of P. aeruginosa in critically ill patients beyond antibiotic sensitivity is warranted.

Bacterial Adhesion↗

PubMed2001

Extraperitoneal approach reduces intestinal and renal dysfunction in elective abdominal aortic aneurysm repair.

BACKGROUND: Intestinal mucosal barrier dysfunction observed in patients undergoing transperitoneal abdominal aortic aneurysm (AAA) repair may contribute to the development of the systemic inflammatory response syndrome and dysfunction of various organs. The aim of this study is to investigate whether an extraperitoneal approach reduces intestinal mucosal barrier and renal dysfunction in elective infrarenal AAA repair. METHODS: Twenty patients admitted for elective infrarenal AAA repair were randomized into either the transperitoneal approach (n=10) or the extraperitoneal approach (n=10). Intestinal permeability was measured preoperatively, and at day 1 and day 3 after surgery using the lactulose/mannitol test by calculating the differential urinary excretion ratio of the two sugars after oral administration. Renal dysfunction was assessed by measuring the urinary albumin/creatinine ratio (ACR) at the same time points. RESULTS: Intestinal permeability was significantly increased in the transperitoneal group at day 1 [0.124+/-0.035 (mean+/-s.e.m.)] compared to the preoperative level (0.020+/-0.003), (p=0.001) and to the extraperitoneal group at day 1 (0.025+/-0.008), (p<0.05) which showed no change in comparison with the preoperative level (0.020+/-0.003). The ACR was also significantly increased in the transperitoneal group at day 1 (16.69+/-5.12) compared to the preoperative level (5.71+/-2.89), (p<0.05) and to the extraperitoneal group at day 1 (4.33+/-1.49), (p<0.05) which showed no significant change at any of the times examined. No correlation was observed between the lactulose/mannitol ratio and the albumin/creatinine ratio, or between age, operating time, aortic clamping time, amount of blood lost or blood transfused. CONCLUSIONS: These results support the suggestion that minimising intestinal manipulation using an extraperitoneal approach in AAA repair preserves intestinal mucosal barrier and renal glomerular functions.

Aged↗

PubMed2005

Regulation of intestinal epithelial function: a link between opportunities for macromolecular drug delivery and inflammatory bowel disease.

The intestinal epithelium performs a multitude of tasks related to digestion and homeostasis. As a consequence of ingestion, this tissue must also participate in activities associated with protecting the body from potential pathogenic agents and toxic materials. To efficiently perform tasks associated with digestion and these protective functions, the intestinal epithelium has established several anatomical, biochemical and physiological barriers to impede unregulated uptake of materials. In order to perform functions of digestion and homeostasis, the intestinal epithelium uses mechanisms that allow dynamic modulation of regulated uptake pathways that can respond rapidly to changes in diet, health and challenges from pathogenic agents and macromolecules. This review focuses on specific, recent advances made in understanding cellular pathways and mechanisms that regulate dynamic processes of these barriers and examines the feasibility of drug delivery strategies focusing on macromolecular therapeutics potentially useful in the treatment of inflammatory bowel disease (IBD).

Animals↗

PubMed1994

Intestinal carbohydrate absorption and permeability at high altitude (5,730 m).

To investigate the effects of high altitude on intestinal function, the absorption and permeation of nonmetabolizable carbohydrates were measured in 14 volunteers (median age 21 yr, range 19-37 yr) at sea level in Oxford, UK; at 1,050 m in Nepal; at 5,570 m after 5 days at > 5,500 m; and at 5,730 m after 11 days at > 5,500 m. Body weight decreased 5.7 +/- 1.19 kg from sea level to 5,570 m (P < 0.001 by paired t test) despite 72-h dietary records showing no change in energy intake. Absorption of carbohydrates by mediated transport was measured by urinary xylose and 3-O-methyl-D-glucose excretion. Xylose excretion (%oral dose) decreased from 31.4 +/- 4.5% to 20.7 +/- 4.5% (P < 0.001) and 3-O-methyl-D-glucose excretion decreased from 39.7 +/- 6.1 to 33.7 +/- 7.0% (P = 0.003) from sea level to 5,730 m. Monosaccharide permeation measured by L-rhamnose excretion decreased from 11.3 +/- 2.5 to 6.2 +/- 2.0% (P = 0.001). Intestinal permeability, a measure of barrier function (ratio of lactulose to L-rhamnose), increased from 0.036 +/- 0.014 at sea level to 0.084 +/- 0.042 at 1,050 m (P = 0.006), possibly due to infective enteropathy after arrival in Nepal, but reverted to normal (0.045 +/- 0.013; P = 0.062) at 5,730 m. Absorption of all carbohydrates returned to normal after return to the UK. This study showed that a decrease in mediated (D-xylose or 3-O-methyl-D-glucose) and diffusional (L-rhamnose) monosaccharide absorption occurs at high altitude but that intestinal permeability at 5,730 m is unchanged.

3-O-Methylglucose↗

PubMed1979

[Role of epithelial basement membrane of the small intestine in providing immunologic homeostasis].

A morphometric method was used experimentally to prove the immune barrier function of the epithelial basal membrane of the small intestine mucous membrane. The epithelial basal membrane located on the border of the epithelium and connective tissue provides biochemical and immunological protection of the layer proper against penetrotion into it of antigens from the epithelium, being a barrier of immunological homeostasis. The damage of the epithelial membrane is accompanied by coming of the intestinal lumen antigens into the layer proper causing there a disturbance of immunological homeostasis. In response to this lymphoid cells migrate from the stroma to the epithelium towards the antigens, and lymphocytic reaction in the layer proper increases.

Animals↗

PubMed1996

Intestinal paracellular permeability during malnutrition in guinea pigs: effect of high dietary zinc.

BACKGROUND: Zinc has been shown to have beneficial effects in vitro on epithelial barrier function, and in vivo to reduce intestinal permeability in malnourished children with diarrhoea. AIMS: To determine whether malnutrition alters intestinal paracellular permeability, and whether zinc prevents such alterations. METHODS: Guinea pigs were fed a normal protein diet (NP group), a low protein diet (LP group), or a low protein diet enriched with 1800 ppm zinc (LPZn group) for three weeks. Intestinal permeability was measured on jejunal segments mounted in Ussing chambers by measuring ionic conductance and mucosal to serosal fluxes of 14C-mannitol, 22Na, and horseradish peroxidase. Tight junction morphology was assessed on cryofracture replicas. RESULTS: Mannitol and Na fluxes and ionic conductance increased in the LP group compared with the NP group but remained normal in the LPZn group. Accordingly, jejunal epithelia from the LP group, but not from the LPZn group, showed a small decrease in number of tight junctional strands compared with epithelia from the NP group. Neither malnutrition nor zinc treatment modified horseradish peroxidase fluxes. CONCLUSIONS: Malnutrition is associated with increased intestinal paracellular permeability to small molecules, and pharmacological doses of zinc prevent such functional abnormality.

Animals↗

PubMed2003

Epithelial transport and gut barrier function in colitis.

PURPOSE OF REVIEW: Colitis is an inflammatory bowel disease that is confined to the colon and is characterized by a watery diarrhea that can also be accompanied by blood in the stool. The inflammation associated with colitis is generally confined to the mucosal and submucosal layers, although Crohn's colitis may be transmural. The principal functions of the colonic mucosa are to act as a barrier to the luminal contents of the intestinal tract and to facilitate the bidirectional transport of water and electrolytes. It is well established that barrier and transport defects occur in colitis and may be involved in pathogenesis. Consequently, this review discusses recent evidence of potential mechanisms that may be involved in the perturbation of mucosal transport and barrier functions in colitis and therapeutic advances to counteract these defects. RECENT FINDINGS: Mechanisms responsible for transport dysfunction and barrier defects in colitis are discussed, including decreased activity of transport proteins such as CFTR, bacterial interactions with the epithelium, including understanding of the regulation and function of NOD-2, and altered expression of components of the intestinal barrier, such as mucins and multidrug resistance proteins. SUMMARY: Recent advances in our understanding of how changes in barrier and transport function occur in colitis may illuminate the pathophysiology of this condition. The work discussed may also identify novel targets that are functionally altered in colitis, which potentially can be modulated therapeutically either with existing medications or with newer agents that are in development.

Journal Article↗

PubMed2004

Comparative analysis of EspF from enteropathogenic and enterohemorrhagic Escherichia coli in alteration of epithelial barrier function.

Enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic E. coli (EHEC) are related intestinal pathogens that harbor highly similar pathogenicity islands known as the locus of enterocyte effacement (LEE). Despite their genetic similarity, these two pathogens disrupt epithelial tight junction barrier function with distinct kinetics. EHEC-induced reduction in transepithelial electrical resistance (TER), a measure of barrier function disruption, is significantly slower and more modest in comparison to that induced by EPEC. The variation in bacterial adherence only partially accounted for these differences. The LEE-encoded effector protein EspF has been shown to be critical for EPEC-induced alterations in TER. EspF from both EPEC and EHEC is expressed and secreted upon growth in tissue culture medium. The mutation of EHEC cesF suggested that the optimal expression and secretion of EHEC EspF required its chaperone CesF, as has been shown for EPEC. In contrast to EPEC espF and cesF, mutation of the corresponding EHEC homologs did not dramatically alter the decrease in TER. These differences could possibly be explained by the presence of additional espF-like sequences (designated U- and M-espF, where the letter designations refer to the specific cryptic prophage sequences on the EHEC chromosome closest to the respective genes) in EHEC. Reverse transcription-PCR analyses revealed coordinate regulation of EHEC U-espF and the LEE-encoded espF, with enhanced expression in bacteria grown in Dulbecco-Vogt modified Eagle's medium compared to bacteria grown in Luria broth. Both EHEC espF and U-espF complemented an EPEC espF deletion strain for barrier function alteration. The overexpression of U-espF, but not espF, in wild-type EHEC potentiated the TER response. These studies reveal further similarities and differences in the pathogenesis of EPEC and EHEC.

Bacterial Adhesion↗

PubMed2003

Alteration of intestinal intraepithelial lymphocytes and increased bacterial translocation in a murine model of cirrhosis.

Alterations in immunological defense in the gut may lead to the bacterial infection that is frequently associated with cirrhosis of the liver. The aim of this study was to investigate the changes in distribution and function of intestinal intraepithelial lymphocytes (IELs) in relation to intestinal barrier dysfunction in experimental cirrhosis. Cirrhosis was induced in mice by treatment with carbon tetrachloride (CCl4) intraperitoneally with 5% alcohol in drinking water for 12 weeks. Bacterial translocation was assessed in mesenteric lymph nodes (MLNs) by the transport of fluorescence-labeled latex beads and by bacteriological cultures. The lymphocyte subpopulation was compared in three groups (cirrhosis, alcohol alone and controls). IFN-gamma production from isolated IELs was determined by ELISA after stimulation with anti-CD3 or IL-12/IL-18. The total number of IELs significantly increased in the cirrhosis and alcohol groups. There was a preferential increase in TCRgammadelta+CD8+ population in the alcohol group, but no change in cirrhosis. Bacterial translocation was negative in the control group, and a small number was noted in the alcohol group, whereas it was significantly noted in the cirrhosis group. Although the number of IEL was significantly increased in the cirrhosis group, their proliferative response was decreased, and IFN-gamma production from each IEL was markedly diminished in either stimulation by anti-CD3 or IL-12/IL-18. These changes were more remarkable in the cirrhosis group than in the alcohol group. In conclusion, bacterial translocation due to intestinal barrier dysfunction in cirrhosis may be closely correlated with the alteration of the immune function in IELs.

Animals↗

PubMed2006

5-lipoxygenase modulates the alteration of paracellular barrier function in mice ileum during experimental colitis.

Small intestine permeability is frequently altered in inflammatory bowel disease and may be caused by the translocation of intestinal toxins through leaky small intestine tight junctions (TJs) and adherence. Recently, it has been shown that 5-lipoxygenase (5-LO) plays an important role in the development of various inflammatory conditions like inflammatory bowel disease. In the present study, by comparing the responses in wild-type mice (5-LOWT) with those of mice lacking the 5-lipoxygenase (5-LOKO), we investigated the role played by this enzyme in the permeability and structure of small intestine TJs in an animal model of experimental colitis. To address this question, we used an experimental model of colitis, induced by dinitrobenzene sulfonic acid (DNBS). Four days after colitis induction by DNBS, the ileal TJs were studied by means of transmission electron microscopy using lanthanum nitrate and immunohistochemistry of occludin and ZO-1. When compared with DNBS-treated 5-LOWT mice, DNBS-treated 5-LOKO mice experienced a reduced rate of the extent and severity of the histological signs of colon injury. After administration of DNBS, 5-LOWT mice showed a significant increase of ileal permeability (88.3% +/- 1.2%) compared with sham (5.6% +/- 0.5%). In colitis, the percentage of "leaky" junctions in terminal ilea correlated positively with the macroscopic colon damage score. Distal colitis in 5-LOWT mice induces an increase of TJ permeability throughout the entire small intestine, and the extent of alterations correlates with colonic damage. On the contrary, a significant reduction of (1) the degree of colon injury, (2) the alteration of ZO-1 and occludin localization (immunohistochemistry), and (3) ileal permeability (8.1% +/- 0.7%) caused by DNBS in the colon was observed in 5-LOKO mice. Similarly, the treatment of 5-LOWT with zileuton (50 mg/kg per oral gavage twice a day), a 5-LO inhibitor, resulted in a significant reduction of all the previously described parameters. Taken together, our results clearly demonstrate that 5-LO modulates small intestinal permeability in experimental colitis through the regulation of TJ protein.

Animals↗