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Results for “Intestinal Barrier Function”

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PubMed2006

[Effect of ubiquitin-proteasome pathway on inflammatory reaction in intestine and its barrier function in rats with postburn sepsis].

OBJECTIVE: To study the effect of ubiquitin-proteasome pathway inhibition on intestinal nuclear factor-KappaB (NF-KappaB) activity and tumor necrosis factor-alpha (TNF-alpha) release as well as plasma diamine oxidase (DAO) activity in rats with postburn sepsis. METHODS: Rats were subjected to 30% total body surface area (TBSA) full-thickness scald injury, followed by intraperitoneal injection of lipopolysaccharide (LPS) to mimic postburn sepsis. Sixty Wistar rats were randomly divided into normal control group, sepsis group, sepsis with proteasome inhibitor N-Acetyl leucinyl leucinyl norleucinal (ALLN) treatment group and sepsis with NF-KappaB inhibitor pyrrolidine dithiocarbamate (PDTC) treatment group. NF-KappaB activity, TNF-alpha protein content, and plasma DAO activity were determined by electrophoretic mobility shift assay (EMSA), enzyme-linked immunosorbent assay (ELISA), and spectrophotometric method, respectively. RESULTS: The results showed that NF-KappaB activity was markedly activated and reached its peak 1 hour after scalding and injection of LPS in each group (all P<0.01), then reduced gradually. Both ALLN and PDTC could decrease intestinal NF-KappaB activity at 1 hour and 2 hours after injury. TNF-alpha release was reduced by ALLN at 1 hour after injury (P<0.01). Plasma DAO activity was significantly elevated after scalding and injection of LPS (P<0.01). Pretreatment with PDTC or ALLN could not lower the activity of DAO. CONCLUSION: The results suggest that early treatment with inhibitor of ubiquitin-proteasome pathway might decrease the intestinal inflammatory reaction, but exert no effect on intestinal barrier function in rats with postburn sepsis.

Amine Oxidase (Copper-Containing)↗

PubMed2004

Intestinal failure: pathophysiological elements and clinical diseases.

There are two main functions of gastrointestinal tract, digestion and absorption, and barrier function. The latter has an important defensive effect, which keeps the body away from the invading and damaging of bacteria and endotoxin. It maintains the systemic homeostasis. Intestinal dysfunction would happen when body suffers from diseases or harmful stimulations. The lesser dysfunction of GI tract manifests only disorder of digestion and absorption, whereas the more serious intestinal disorders would harm the intestinal protective mechanism, or intestinal barrier function, and bacterial/endotoxin translocation, of intestinal failure (IF) would ensue. This review discussed the theory of the intestinal failure, aiming at attracting recognition and valuable comments by clinicians.

Animals↗

PubMed1998

[Lack of effect of EGF on epithelial barrier function in experimental TNBS colitis].

This study tested the hypothesis that EGF has a protective effect on the intestinal barrier function in experimental TNBS-induced colitis. EGF was given intraperitoneally one hour before and 24 hours after induction of colitis. The rats were killed 48 hours after induction of colitis: The distal colon was resected and mounted into Ussing chambers. Flux measurements were performed for Na+ and mannitol, and epithelial and subepithelial resistances were determined. A semiquantitative histological score was used to grade acute and chronic inflammation. Compared to controls, TNBS caused a 3-fold increase in both fluxy, indicating enhanced paracellular permeability. There rates was a severe reduction of total and epithelial resistances indicating a dramatic defect of epithelial barrier function. EGF failed to improve the electrophysiologic and histologic parameters. Therefore, EFG has no protective effective in experimental TNBS colitis.

Animals↗

PubMed2005

Abrogation of IFN-gamma mediated epithelial barrier disruption by serine protease inhibition.

The intestinal barrier function is often impaired in a variety of diseases including chronic inflammatory bowel disease. Increased intestinal permeability during episodes of active disease correlates with destruction or rearrangement of the tight junction protein complex. IFN-gamma has been widely studied for its effect on barrier function and tight junction structures but its mode of action remains unclear. Since the claudin family of tight junction proteins is proposed to be involved in barrier maintenance we studied the effect of IFN-gamma on claudin expression in relation to epithelial barrier function. Cycloheximide and protease inhibitors were used to study mechanisms of IFN-gamma mediated barrier disruption. Intestinal epithelial cells were exposed to IFN-gamma and permeability was evaluated by horse radish peroxidase (HRP) and 4 kD FITC-dextran fluxes. Occludin and claudin-1, -2, -3, and -4 tight junction protein expression was determined by Western blotting. Occludin and claudin-2 protein expression was dramatically reduced after IFN-gamma exposure, which correlated with increased permeability for HRP and FITC-dextran. Interestingly, cleavage of claudin-2 was observed after incubation with IFN-gamma. Serine protease inhibitor AEBSF completely abrogated IFN-gamma mediated barrier disruption which was associated with preservation of claudin-2 expression. Moreover, IFN-gamma induced loss of barrier integrity was found to affect claudin-2 and occludin expression through different mechanisms. Since inhibition of serine protease activity abrogates IFN-gamma mediated barrier disruption this may be an important target for therapeutic intervention.

Blotting, Western↗

PubMed2001

Interleukin-2 receptor beta subunit-dependent and -independent regulation of intestinal epithelial tight junctions.

Interleukin (IL)-15 is able to regulate tight junction formation in intestinal epithelial cells. However, the mechanisms that regulate the intestinal barrier function in response to IL-15 and the involved subunits of the IL-15 ligand-receptor system are unknown. We determined the IL-2Rbeta subunit and IL-15-dependent regulation of tight junction-associated proteins in the human intestinal epithelial cell line T-84. The IL-2Rbeta subunit was expressed and induced signal transduction in caveolin enriched rafts in intestinal epithelial cells. IL-15-mediated tightening of intestinal epithelial monolayers correlated with the enhanced recruitment of tight junction proteins into Triton X-100-insoluble protein fractions. IL-15-mediated up-regulation of ZO-1 and ZO-2 expression was independent of the IL-2Rbeta subunit, whereas the phosphorylation of occludin and enhanced membrane association of claudin-1 and claudin-2 by IL-15 required the presence of the IL-2Rbeta subunit. Recruitment of claudins and hyperphosphorylated occludin into tight junctions resulted in a more marked induction of tight junction formation in intestinal epithelial cells than the up-regulation of ZO-1 and ZO-2 by itself. The regulation of the intestinal epithelial barrier function by IL-15 involves IL-2Rbeta-dependent and -independent signaling pathways leading to the recruitment of claudins, hyperphosphorylated occludin, ZO-1, and ZO-2 into the tight junctional protein complex.

Base Sequence↗

PubMed2004

Genetic aspects of intestinal permeability in inflammatory bowel disease.

There is a long-standing belief that disruption of the intestinal barrier function may lead to systemic and local intestinal disease. The role of increased intestinal permeability in Crohn's disease is reviewed here. What is not in doubt is that intestinal permeability in patients with Crohn's disease is increased proportional to disease activity; it can be used to predict clinical relapse of disease and prognosis; and a small proportion of first-degree relatives have increased intestinal permeability. This last finding has been subject to much speculation. In particular it has been suggested that it represents a genetically determined abnormality. If so it might play an important pathogenic process in the disease. However this permeability change in relatives does not conform to a classical inheritance pattern and in some studies it is found in the patients' spouses. This suggests an environmental cause for the changes. However proponents of an environmental factor have been singularly inactive in attempting to identify this agent(s). In view of recent research it seems likely that the increased intestinal permeability in relatives of Crohn's patients may be secondary to sub-clinical intestinal inflammation. This inflammation conforms to an inherited additive trait. The genetic basis for this inflammation is being studied.

Crohn Disease↗

PubMed1998

Role of intestinal permeability in monitoring mucosal barrier function. History, methodology, and significance of pathophysiology.

The intestinal barrier function is considered to play an important role in protecting the penetration of luminal antigens, associated with the development of secondary infection and sepsis and the initiation of the multiple organ dysfunction syndrome. The intestinal mucosal barrier against luminal macromolecules and microorganisms consists of both non-immunological and immunological defence mechanisms. The main constituents of the intestinal barrier are the endothelial and epithelial barriers. The epithelial barrier selectively restricts micromolecular permeation and almost completely restricts macromolecular permeation, while the endothelial barrier has a very limited restriction to micromolecules and only partly to macromolecules. Maintenance of the barrier depends on the integrity of cellular plasma membranes and tight junctions, as well as the elaboration of endothelial and epithelial secretory products. Focal denudation of the barrier results in permeation of potentially threatening luminal compounds including antigens, proteases, H+, bacteria and endotoxin, and also other factors chemotactic for inflammatory cells. By initiating inflammation and thus acting on subepithelial tissues, such factors can further influence endothelial and epithelial transport and barrier function. The repair of endothelial and epithelial injury is also complex, and both restitution and enhanced endothelial and epithelial cell proliferation are likely to be important. At present, however, mechanisms for intestinal epithelial and endothelial permeation, their alterations in disease and potential ways to prevent or repair injury, are still not fully elucidated.

Animals↗

PubMed2026

Opposite metabolic and gut responses to oral glutamine in male and female mice with diet-induced obesity.

Obesity is often associated with sex-dependent metabolic complications, to which altered intestinal barrier function and gut microbiota contribute. Glutamine supplementation has previously shown beneficial effects on gut barrier function and glycemic control. We thus aimed to characterize, in male and female mice, the effects of oral glutamine supplementation during high-fat-diet-induced obesity. Male and female C57BL/6 mice received a standard (SD) or high-fat diet (HFD; 60 % kcal from fat) for 14 weeks (W14). From W12 onward, mice received glutamine in drinking water (2 g/kg/day) or no supplementation. Body composition, glucose tolerance, insulin sensitivity, intestinal permeability, colonic inflammatory response, cecal microbiota and inflammatory/endocrine adipose response were assessed. In both male and female mice, glutamine supplementation failed to improve body weight and body composition. However, glutamine reduced glucose intolerance in HFD-fed males (AUC reduced by 14.57 %) that was associated with a partial restoration of plasma resistin and insulin and a trend toward limiting adipose inflammatory response. In males, glutamine did not affect gut microbiota composition and colonic response. Conversely, in HFD-fed females, glutamine supplementation led to gut microbiota changes (increase in Bacteroidota and Pseudomonadota phyla; increase in Muribaculaceae and Tannerellaceae families), increased colonic inflammatory markers (Il1b, Tlr4, Myd88, Irf3), increased inflammatory response in subcutaneous adipose tissue and increased HOMA-IR. Finally, HFD-fed mice exhibited sex-specific responses to glutamine supplementation with protective effects in males and harmful effects in females that need to be further deeply explored.

Animals↗

PubMed2003

Determining small bowel integrity following drug treatment.

Intestinal integrity is maintained by a delicate balance between mucosal defence and luminal aggressors that cause damage if exposed to the mucosa. The intestinal barrier function appears to be the gatekeeper for controlling this balance. It is becoming increasingly clear that if the intestinal barrier is disrupted the consequences are low grade intestinal inflammation which carry with it the risk of significant blood and protein loss both of which may cause clinical management problems. We review the strength and weaknesses of methods for assessing small bowel function that are useful for assessing drug-induced intestinal toxicity. There are a number of imaging methods for assessing intestinal integrity but these do not provide functional information. Intestinal permeability measurements have been optimized for specificity and there are now ways of measuring intestinal permeability regionally, but marker analyses continue to be cumbersome. Recent developments of faecal inflammatory markers make it a matter of routine to assess this in any routine chemical pathology laboratory. Bleeding, protein loss and other complications of inflammation can also be measured with good specificity, but again the methods are cumbersome. Using a combination of functional and imaging techniques it is now possible to characterize and define with precision, the small bowel side-effects of drugs, the best example being the small bowel side-effects of nonsteroidal anti-inflammatory drugs (NSAIDs).

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2000

The key role of Pseudomonas aeruginosa PA-I lectin on experimental gut-derived sepsis.

OBJECTIVE: To examine the effect of Pseudomonas aeruginosa on intestinal barrier function and its lethal potential when introduced into the intestinal tract of mice. SUMMARY BACKGROUND DATA: The mere presence of P. aeruginosa in the intestinal tract of critically ill patients is associated with a threefold increase in death compared with matched cohorts without this pathogen. Whether this effect is a cause or a consequence of the critically ill state has not been previously addressed. METHODS: Transepithelial electrical resistance, a measure of tight junction permeability, was evaluated in Caco-2 intestinal epithelial cells cells apically inoculated with live P. aeruginosa, exotoxin A, or purified PA-I lectin, an adhesin of P. aeruginosa. Lethality studies to P. aeruginosa were carried out in mice undergoing 30% surgical hepatectomy by injecting the bacteria or its various components directly into the cecum. RESULTS: Only cells exposed to P. aeruginosa or its PA-I lectin developed alterations in barrier function. P. aeruginosa or the combination of PA-I and exotoxin A was lethal to mice when injected into the cecum after partial hepatectomy. Alterations in epithelial barrier function and death in mice were prevented when Pseudomonas was pretreated with N-acetyl D-galactosamine (GalNAc), a binder of PA-I. CONCLUSIONS: P. aeruginosa may act as a pathogen in the gastrointestinal tract, resulting in altered epithelial barrier function and death in a susceptible host. The PA-I lectin of P. aeruginosa may play a key role in its pathogenicity to the intestinal epithelium by inducing a permeability defect to its cytotoxic exoproducts such as exotoxin A.

Adhesins, Bacterial↗

PubMed1994

Effect of critical illness on microbial translocation and gastrointestinal mucosa permeability.

It has been hypothesized that the barrier function of the gastrointestinal tract is deranged in patients with trauma, sepsis, or other critical illnesses. Derangements in intestinal barrier function might lead to bloodstream invasion by gut-derived microbes and/or activation of inflammatory cells in the submucosa of the intestine or within the liver. Activated immune cells are capable of releasing a number of inflammatory mediators, including eicosanoids and cytokines, which have been implicated in the pathogenesis of the multiple organ dysfunction syndrome (MODS). Thus, gut-barrier dysfunction might be primary factor leading to MODS in patients with critical illness. Two distinct forms of gut-barrier dysfunction have been described. The first, called translocation, appears to a transcellular process, whereby particulate antigens, including viable microbes, are transported across enterocytes into the submucosal compartment. The second is an increase in the paracellular permeability of the intestinal epithelium, which permits increased transmucosal absorption of water-soluble macromolecules. Pathological increases in both translocation and permeability occur in a number of animal models of critical illness. Moreover, a number of studies have documented that intestinal permeability is increased in humans with trauma, sepsis, burns, or other serious, acute medical problems. Nevertheless, convincing data to establish a causal link between gut-barrier dysfunction and organ failure in humans are lacking, and the importance of translocation and/or mucosal hyperpermeability on the development of MODS in patients remains to be elucidated.

Bacterial Physiological Phenomena↗

PubMed2000

[Bacterial translocation from the gastrointestinal tract: catalyst of multiple organ dysfunction syndrome].

The abnormal colonization of gastrointestinal tract (GIT), the loss of the intestinal barrier function, the bacterial translocation (BT) are signs of intestinal insufficiency which are supposed to be involved in the pathogenesis of MODS. This worsens the condition or leads to lethal outcome in patients after major abdominal surgery in ICU. The goal of this investigation was to consider the scientific and clinical evidence for the BT role in the pathogenesis of MODS and to present evidence about the advantages and the efficiency of antibiotic combination Amikacin plus Clindamycin as a new therapeutic strategy for the improvement of the outcome in patients with MODS and sepsis. To that purpose patients with diffuse peritonitis of different origin were analyzed. After surgery some patients were left with laparostomy. This gave the possibility for revisions and lavages of the abdominal cavity and for taking material for microbiological analyses. The patients were grouped into two subgroups according to antibiotic treatment: 1st group--combination of usually used antibiotics; 2nd group--Amikacin plus Clindamycin. The second group patients showed good tolerance to this antibiotic combination and good therapeutic effect.

Anti-Bacterial Agents↗

PubMed2006

Protective effects of hyperoxygenated solution preconditioning on intestinal ischemia-reperfusion injury in rabbits.

BACKGROUND: The aim of this study was to investigate the protective effects of hyperoxygenated solution (HOS) preconditioning on intestinal ischemia-reperfusion (IR) injury in rabbits. MATERIALS AND METHODS: Thirty-two rabbits were randomly divided into four groups as follows: (1) control group in which sham operation was performed (Sham group); (2) sham operation and HOS treatment group (sham+H group); (3) ischemia-reperfusion group (IR group); (4) ischemia-reperfusion and HOS treatment group (H group). Intestinal IR model was produced by clamping superior mesenteric artery with an atraumatic vascular clamp for 1 h, followed by reperfusion for 2 h. Animals in H group received intravenous HOS infusion (20 mL/kg) every day for 5 days before ischemia-reperfusion; animals in the sham+H group received the same amount of HOS before sham operation, and animals in IR group received the same amount of normal saline in the same way. At the end of reperfusion, histopathological changes of intestine were observed, and malondialdehyde (MDA) levels, superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activities in intestinal tissues were also detected. Intestinal barrier function was assessed by blood d-lactate levels and bacterial translocation (BT). RESULTS: The H group showed significantly lower MDA levels and higher activities of SOD, CAT, and GSH-Px in the intestinal tissue compared with the IR group. Furthermore, the mean d-lactate levels and incidence of BT in the H group were significantly lower than those in the IR group. Histopathological analysis also indicated that there were significant histological improvements in the H group compared with the IR group. CONCLUSIONS: HOS preconditioning at an appropriate dose ameliorates the deleterious changes in intestinal mucosal injury and barrier function associated with IR by effectively preventing a decrease in the intestinal antioxidant defense system, which is another simple and effective measure to protect intestine from IR injury.

Animals↗

PubMed2002

Cloning of the human claudin-2 5'-flanking region revealed a TATA-less promoter with conserved binding sites in mouse and human for caudal-related homeodomain proteins and hepatocyte nuclear factor-1alpha.

Claudin-2 is a structural component of tight junctions in the kidneys, liver, and intestine, but the mechanisms regulating its expression have not been defined. The 5'-flanking region of the claudin-2 gene contains binding sites for intestine-specific Cdx homeodomain proteins and hepatocyte nuclear factor (HNF)-1, which are conserved in human and mouse. Both Cdx1 and Cdx2 activated the claudin-2 promoter in the human intestinal epithelial cell line Caco-2. HNF-1alpha augmented the Cdx2-induced but not Cdx1-induced transcriptional activation of the human claudin-2 promoter. In mice, HNF-1alpha was required for claudin-2 expression in the villus epithelium of the ileum and within the liver but not in the kidneys, indicating an organ-specific function of HNF-1alpha in the regulation of claudin-2 gene expression. Tight junction structural components, which determine epithelial polarization and intestinal barrier function, can be regulated by homeodomain proteins that control the differentiation of the intestinal epithelium.

3T3 Cells↗

PubMed2006

IL-22 is increased in active Crohn's disease and promotes proinflammatory gene expression and intestinal epithelial cell migration.

IL-22 is produced by activated T cells and signals through a receptor complex consisting of IL-22R1 and IL-10R2. The aim of this study was to analyze IL-22 receptor expression, signal transduction, and specific biological functions of this cytokine system in intestinal epithelial cells (IEC). Expression studies were performed by RT-PCR. Signal transduction was analyzed by Western blot experiments, cell proliferation by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay and Fas-induced apoptosis by flow cytometry. IEC migration was studied in wounding assays. The IEC lines Caco-2, DLD-1, SW480, HCT116, and HT-29 express both IL-22 receptor subunits IL-22R1 and IL-10R2. Stimulation with TNF-alpha, IL-1beta, and LPS significantly upregulated IL-22R1 without affecting IL-10R2 mRNA expression. IL-22 binding to its receptor complex activates STAT1/3, Akt, ERK1/2, and SAPK/JNK MAP kinases. IL-22 significantly increased cell proliferation (P = 0.002) and phosphatidylinsitol 3-kinase-dependent IEC cell migration (P < 0.00001) as well as mRNA expression of TNF-alpha, IL-8, and human beta-defensin-2. IL-22 had no effect on Fas-induced apoptosis. IL-22 mRNA expression was increased in inflamed colonic lesions of patients with Crohn's disease and correlated highly with the IL-8 expression in these lesions (r = 0.840). Moreover, IL-22 expression was increased in murine dextran sulfate sodium-induced colitis. IEC express functional receptors for IL-22, which increases the expression of proinflammatory cytokines and promotes the innate immune response by increased defensin expression. Moreover, our data indicate intestinal barrier functions for this cytokine-promoting IEC migration, which suggests an important function in intestinal inflammation and wound healing. IL-22 is increased in active Crohn's disease and promotes proinflammatory gene expression and IEC migration.

Cell Movement↗

PubMed2005

A murine model of ulcerative colitis: induced with sinusitis-derived superantigen and food allergen.

BACKGROUND: The etiology of ulcerative colitis (UC) is to be understood. The basic pathological feature of UC is intestinal chronic inflammation. Superantigen, such as Staphylococcus enterotoxin B (SEB), is reported to compromise intestinal barrier function by increasing epithelial permeability and initiate inflammation in the intestinal mucosa. Inasmuch as anatomic position of the sinus, chronic sinusitis-derived SEB may follow the secretion and to be swallowed down to the gastrointestinal tract and induce lesions to the intestinal mucosa. METHODS: Sinus wash fluid (SWF, containing SEB) was collected from a group of patients with both chronic sinusitis (CS) and UC. A group of mice were sensitized to ovalbumin (OVA) in the presence of SWF. The sensitized mice were challenged with the specific antigen OVA. The inflammatory status of the colonic tissue was determined with histology, serology and electron microscopy. Using horseradish peroxidase (HRP) as a tracer, another group of mice was stimulated with SWF for 2 hours. The HRP activity was detected in the colonic tissue with enzymatic approaches and electron microscopy. RESULTS: Epithelial hyperpermeability in colonic epithelium was induced by stimulating with SWF. The HRP activity in the colonic mucosa was almost 11 times more in the SWF treated group (3.2 +/- 0.6 microg/g tissue) than the control group (0.3 +/- 0.1 microg/g tissue). Mice were sensitized using a mixture of SWF and OVA (serum OVA-specific IgE was detected with a highest titer as 1:64). Challenge with OVA induced extensive inflammation in the colonic mucosa by showing (1) marked degranulation in mast cells (MC, 46.3 +/- 4.5%) and eosinophils (Eo, 55.7 +/- 4.2%); (2) inflammatory cell infiltration (MC = 145.2 +/- 11.4; Eo = 215.8 +/- 12.5; mononuclear cell = 258.4 +/- 15.3/mm2 tissue); (3) increased MPO activity (12.9 +/- 3.2 U/g tissue) and inflammatory scores (1.8 +/- 0.3); (4) mucosal surface ulcers; (5) edema in the lamina propria; (6) bacterial translocation and abscess formation in the subepithelial region. CONCLUSION: Introducing Sinusitis-derived SEB-containing SWF to the gastrointestinal tract compromised colonic mucosal barrier function increasing epithelial permeability to luminal macromolecular protein in mice. The SWF facilitated colonic mucosal sensitization to luminal antigen. Multiple challenging the sensitized colonic mucosa with specific antigen OVA induced inflammation, induced a condition similar to human ulcerative colitis.

Adult↗

PubMed2000

Phagocytic and intestinal endothelial and epithelial barrier function during the early stage of small intestinal ischemia and reperfusion injury.

The effects of intestinal ischemia and reperfusion (I/R) on small intestinal mucosal endothelial and epithelial barrier integrity and phagocytic function were assessed in rats subjected to 20- or 40-min mesenteric ischemia and a 3-h reperfusion. The results showed that human serum albumin (125I-HSA) flux through the endothelial layer to the interstitial space increased as did 125I-HSA clearance from blood to the gut lumen and 131I-HSA flux from the gut lumen to the interstitial space in rats with I/R. E. coli adhering to microvilli, invading and passing into the microvessels, were noted on the small intestinal mucosa in animals subjected to 40-min ischemia and a 3-h reperfusion. Phagocytic function increased, especially in the small intestinal wall, lungs, liver, and spleen in the groups with I/R, correlating with the length of ischemia. The results imply that both endothelial and epithelial barrier integrity is impaired in the early phase after I/R and that the epithelial barrier more effectively restricts macromolecular leakage compared with the endothelial barrier. I/R impairs the intestinal barrier not only by causing tissue hypoxia but also by activating the phagocytic system and aggravating barrier damage, which finally may result in bacterial translocation and remote organ dysfunction.

Animals↗

PubMed1998

Effects of bryostatin 1, a novel anticancer agent, on intestinal transport and barrier function: role of protein kinase C.

BACKGROUND: Bryostatin 1 is a novel chemotherapeutic agent that activates specific members of the protein kinase C (PKC) family in a complex pattern overlapping with, but distinct from, that of tumor-promoting phorbol esters. Phorbol esters profoundly altered epithelial phenotype, abolishing both barrier function and Cl secretion (the latter due to loss of a key transport site, the Na-K-Cl cotransporter). The effects of bryostatin 1 on these parameters are unknown. METHODS: Cl secretion and barrier function of T84 human intestinal epithelia were assessed as cyclic adenosine monophosphate-stimulated short-circuit current and transepithelial resistance, respectively. Na-K-Cl cotransporter function and mRNA expression were assayed by 86Rb uptake and Northern analysis. RESULTS: Bryostatin 1 reduced Cl secretion, Na-K-Cl cotransport, and cotransporter mRNA expression. Unlike phorbol esters, these effects were largely transient. In contrast to phorbol esters, bryostatin 1 did not decrease barrier function. CONCLUSIONS: Bryostatin 1 transiently inhibits Na-K-Cl cotransport and Cl secretion, possibly through a PKC isoform also targeted by phorbol esters. Unlike phorbol esters, bryostatin 1 does not impair barrier function. The data imply that bryostatin 1 and phorbol esters differentially affect a PKC isoform involved in junctional regulation, and that epithelial transport and barrier function may be regulated by distinct PKC isoforms.

Antineoplastic Agents↗