Loss Of Barrier Function Research Articles

Enteropathogenic Escherichia coli outer membrane proteins induce changes in cadherin junctions of Caco-2 cells through activation of PKCα

Enteropathogenic Escherichia coli (EPEC) is a Gram-negative bacterial pathogen that adheres to human intestinal epithelial cells, resulting in watery, persistent diarrhoea. Despite the advances made in understanding EPEC–host cell interactions, the molecular mechanisms underlying watery diarrhoea have not been understood fully. Loss of transepithelial resistance and increased monolayer permeability by disruption of tight junctions has been implicated in this process. Apart from disruption of tight junctions, an important factor known to regulate monolayer permeability is E-cadherin and its interaction with β-catenin, both of which constitute the adherens junctions. Our previous studies using HEp-2 cells demonstrated the morphological and cytoskeletal changes caused by cell-free outer membrane preparations (OMPs) of EPEC. In this study, we have shown that EPEC and its OMP induce significant changes in the adherens junctions of Caco-2 monolayers. We also observed significant phosphorylation of protein kinase Cα (PKCα) in cells treated with either whole EPEC or its OMP. Immunoprecipitation of cell lysates with anti-E-cadherin and probing with phospho-PKCα monoclonal antibodies and anti-β-catenins revealed that in these cells, phosphorylated PKCα is associated with cadherins, leading to the dissociation of the cadherin/β-catenin complex. Immunofluorescence showed β-catenins dissociated from the membrane-bound cadherins and redistributed into the cytoplasm. Expression of dominant negative PKCα reversed these effects caused by either whole EPEC or its OMP and also reduced the associated increase in monolayer permeability. It is possible that this mechanism may complement the earlier known pathways for loss of barrier function involving myosin light chain kinase activation and also may play a role in causing host cell death by apoptosis.

Actin re-distribution in response to hydrogen peroxide in airway epithelial cells.

Reactive oxygen species (ROS) disrupt the barrier function of airway epithelial cells through a mechanism that appears to involve remodeling of the actin cytoskeleton. Similarly, keratinocyte growth factor (KGF) has been shown to protect against ROS-induced loss of barrier function through a mechanism that may also involve the actin cytoskeleton. To further determine the role of the actin cytoskeleton in ROS-induced barrier injury, we quantified the relative amount of total actin associated with the cytoskeleton following exposure to hydrogen peroxide (H(2)O(2)) and pretreatment with KGF. We also determined the role of the actin-myosin contractile mechanism in the process by quantifying the relative amount of myosin heavy chain (MHC) associated with the cytoskeleton. While the transepithelial resistance (TER) of a monolayer of airway epithelial cells (Calu-3) decreased after 2 h of continuous exposure to 0.5 mM H(2)O(2), actin and MHC, both dissociated from the cytoskeleton within 15 min of H(2)O(2) exposure. The TER of the monolayers remained depressed although both actin and myosin returned to the cytoskeleton by 4 h after the initiation of H(2)O(2) exposure. Filamentous actin (f-actin) staining suggested that the re-associating actin took the form of short fibers associated with cortical actin rather than long stress fibers. Furthermore, pretreatment with KGF prevented the loss of actin and MHC from the actin cytoskeleton but did not prevent the decrease in TER. These studies suggest that actin disassembly from the cytoskeleton is important in the loss of barrier function, but that it is not the overall amount of actin that is associated with the cytoskeleton that is important, rather it is the contribution this actin makes to the architectural cohesiveness of the cell that contributes to the barrier function.

A Deficit of Proteoglycans on the Bladder Uroepithelium in Interstitial Cystitis

Physical and immunohistochemical data confirm that the luminal surface of the bladder is richly endowed with proteoglycans. Their likely function is to make the bladder nonadherent and produce a water layer to exclude salts and urinary proteins from the surface. IC patients are shown to have a deficit of chondroitin sulphate from the luminal surface as determined by immunohistochemistry. These studies strongly support previous hypotheses suggesting an etiologic role for loss of barrier function in IC and a rationale for replacement therapy with chondroitin sulphate.

Hyperoxia mediates acute lung injury and increased lethality in murine Legionella pneumonia: the role of apoptosis.

Legionella pneumophila is a major cause of life-threatening pneumonia, which is characterized by a high incidence of acute lung injury and resultant severe hypoxemia. Mechanical ventilation using high oxygen concentrations is often required in the treatment of patients with L. pneumophila pneumonia. Unfortunately, oxygen itself may propagate various forms of tissue damage, including acute lung injury. The effect of hyperoxia as a cofactor in the course of L. pneumophila pneumonia is poorly understood. In this study, we show that exposure to hyperoxic conditions during the evolution of pneumonia results in a marked increase in lethality in mice with Legionella pneumonia. The enhanced lethality was associated with an increase in lung permeability, but not changes in either lung bacterial burden or leukocyte accumulation. Interestingly, accelerated apoptosis as evidenced by assessment of histone-DNA fragments and caspase-3 activity were noted in the infected lungs of mice exposed to hyperoxia. TUNEL staining of infected lung sections demonstrated increased apoptosis in hyperoxic mice, predominantly in macrophages and alveolar epithelial cells. In vitro exposure of primary murine alveolar epithelial cells to Legionella in conjunction with hyperoxia accelerated apoptosis and loss of barrier function. Fas-deficient mice demonstrated partial resistance to the lethal effects of Legionella infection induced by hyperoxia, which was associated with attenuated apoptosis in the lung. These results demonstrate that hyperoxia serves as an important cofactor for the development of acute lung injury and lethality in L. pneumophila pneumonia. Exaggerated apoptosis, in part through Fas-mediated signaling, may accelerate hyperoxia-induced acute lung injury in Legionella pneumonia.

Lymphoedema: Pathophysiology and management in resource-poor settings - relevance for lymphatic filariasis control programmes

Low cost reduction of morbidity in lymphoedema is an essential goal in the management of lymphatic filariasis. This review emphasises the role of movement and elevation, and refers to the literature on the effects of these on the venous and lymphatic system. The patient with lymphoedema becomes increasingly immobile and the affected limb is often in a permanently dependent position causing venous hypertension and resultant overloading of the failing lymphatics. The evidence that breathing exercises are important for reducing venous hypertension and inducing lymphatic flow is discussed.The contribution of a damaged epidermis to lymphatic failure is emphasised. Loss of barrier function encourages penetration of bacteria and stimulates repair mechanisms that generate cytokines, which, in turn lead to inflammation. Management programmes that improve the health of the epidermis play a part in reducing lymphatic load.In taking morbidity management of lymphoedema into the general health services there are benefits in promoting skin hygiene and self-help regimes that can ameliorate many diseases along with lymphoedema.

Transforming growth factor-beta and epidermal growth factor synergistically stimulate epithelial to mesenchymal transition (EMT) through a MEK-dependent mechanism in primary cultured pig thyrocytes.

Enhancement of tumor cell growth and invasiveness by transforming growth factor-beta (TGF-beta) requires constitutive activation of the ras/MAPK pathway. Here we have investigated how MEK activation by epidermal growth factor (EGF) influences the response of fully differentiated and growth-arrested pig thyroid epithelial cells in primary culture to TGF-beta1. The epithelial tightness was maintained after single stimulation with EGF or TGF-beta1 (both 10 ng/ml) for 48 hours. In contrast, co-stimulation abolished the transepithelial resistance and increased the paracellular flux of [(3)H]inulin within 24 hours. Reduced levels of the tight junction proteins claudin-1 and occludin accompanied the loss of barrier function. N-cadherin, expressed only in few cells of untreated or single-stimulated cultures, was at the same time increased 30-fold and co-localised with E-cadherin at adherens junctions in all cells. After 48 hours of co-stimulation, both E- and N-cadherin were downregulated and the cells attained a fibroblast-like morphology and formed multilayers. TGF-beta1 only partially inhibited EGF-induced Erk phosphorylation. The MEK inhibitor U0126 prevented residual Erk phosphorylation and abrogated the synergistic responses to TGF-beta1 and EGF. The observations indicate that concomitant growth factor-induced MEK activation is necessary for TGF-beta1 to convert normal thyroid epithelial cells to a mesenchymal phenotype.

Apical, but not basolateral, endotoxin preincubation protects alveolar epithelial cells against hydrogen peroxide-induced loss of barrier function: the role of nitric oxide synthesis.

The influence of LPS preincubation on hydrogen peroxide (H(2)O(2))-induced loss of epithelial barrier function was investigated in rat alveolar epithelial type II cells (ATII). Both apical and basolateral H(2)O(2) administration caused a manyfold increase in transepithelial [(3)H]mannitol passage. Apical but not basolateral preincubation of ATII with LPS did not influence control barrier properties but fully abrogated the H(2)O(2)-induced leakage response. The effect of apical LPS was CD14 dependent and was accompanied by a strong up-regulation of NO synthase II mRNA and protein and NO release. Inhibition of NO by N(G)-monomethyl-L-arginine suppressed the LPS effect, whereas it was reproduced by exogenous application of gaseous NO or NO donor agents. Manipulation of the glutathione homeostasis (buthionine-(S,R)-sulfoximine) and the cGMP pathway (1H-(1,2,4)oxadiazolo[4,3-alpha]quinoxaline-1-one; zaprinast) did not interfere with the protective effect of LPS. Superoxide (O*(-)(2)) generation by ATII cells was reduced by exogenous NO and LPS preincubation. O*(-)(2) scavenging with exogenous superoxide dismutase, the intracellular superoxide dismutase analog Mn(III)tetrakis(4-benzoic acid) porphyrin, and the superoxide scavenger nitroblue tetrazolium and, in particular, hydroxyl radical scavenging with hydroxyl radical scavenger 1,3-dimethyl-thiourea inhibited the H(2)O(2)-induced epithelial leakage response. In conclusion, apical but not basolateral LPS preincubation of ATII cells provides strong protection against H(2)O(2)-induced transepithelial leakage, attributable to an up-regulation of epithelial NO synthesis. It is suggested that the LPS-induced NO formation is effective via interaction with reactive oxygen species, including superoxide and hydroxyl radicals. The polarized epithelial response to LPS may be part of the lung innate immune system, activated by inhaled endotoxin or under conditions of pneumonia.

The effects of keratinocyte growth factor in preclinical models of mucositis.

The epithelium of the oral cavity and small intestine of the gastrointestinal tract have a high rate of cell renewal and as such, are sensitive to cytotoxic therapies that kill rapidly dividing cells. Mucositis is a complication of cancer therapy where impairment of the regenerative capacity of the epithelium leads to atrophy, ulceration and a loss of barrier function. Keratinocyte growth factor (KGF) is an epithelial cell-specific growth and differentiation factor that is trophic for the mucosal epithelium of the gastrointestinal tract. In this study, KGF in normal animals caused epithelial thickening in the squamous epithelium of the oral cavity and increased crypt depth and villus height of the small intestine. It also appeared to regulate gene expression in these tissues including that of some antioxidant enzymes and intestinal trefoil protein. KGF has been shown to be efficacious in several preclinical models of mucositis where KGF pretreatment reduced weight loss typically seen during and after the course of therapy and significantly improved survival. At a tissue level KGF reduced atrophy, accelerated regrowth, and decreased ulcer formation of the oral epithelium after irradiation, and improved crypt survival and prevented villus atrophy in the small intestine of irradiated or chemotherapy-treated mice. Preliminary studies suggest that its efficacy may be partly a consequence of the growth and differentiation effect, and also partly due to regulation of the expression of genes that play a role in mucosal protection. These data suggest that KGF may be useful for the prevention or treatment of mucositis in patients treated with regimens of cancer therapy that have gastrointestinal toxicity.

Functional and morphological consequences of removing astrocytes from the in vivo blood–brain barrier

Our purpose was to attempt to determine the role of astrocytes in the maintenance and repair of the blood–brain barrier in adult F344 rats. Systemic administration of the glyceraldehyde‐3‐phosphate dehydrogenase inhibitor S‐alpha‐chlorohydrin produces selective destruction of astrocytes within specific brain stem nuclei (Cavanagh et al. Neuropath. Appl. Neurobiol. 19, 1993). At appropriate dose levels (140–160 mg/kg i.p.) other brain areas are undamaged, which allows the full time course of the response of sensitive areas to be studied in rats showing relatively little functional impairment. All experiments were carried out in accordance with UK Home Office requirements. Lesion development was followed by in vivo Magnetic Resonance Imaging, by post mortem immunohistochemistry and confocal microscopy, or electron microscopy. Barrier function was studied by the permeation of fluorescent conjugated dextrans of 3–500 KDa molecular weight given intravenously 1 h before perfusion with fixative, and visualised by confocal microscopy (Guérin et al. Neurosci. 103, 2001).Astrocytic death was seen throughout areas such as the inferior colliculi and vestibular nuclei over 6–24 h and was followed by secondary neuronal death and a microglial reaction from 48 h. After a delay of about 12 h following the loss of astrocytes, endothelial cells become permeable to dextran for up to 4 d and then recovered. This recovery was seen in the absence of direct contact with astrocytes, as determined by immunohistochemistry and electron microscopy.Since chlorohydrin does not increase endothelial monolayer permeability in vitro (Romero et al. Neurotoxicol. 18, 1997), we hypothesise that this transient loss of barrier function in vivo represents a partial dedifferentiation in response to loss of astrocytic contact. The subsequent restoration of endothelial barrier function in areas devoid of astrocytes represents the first in vivo demonstration that direct astrocytic contact is not needed for establishment of the blood–brain barrier.

Syndrome aigu d'irradiation : les atteintes du système gastro-intestinal

Acute syndrome of radiation: injuries to the gastrointestinal tract. Exposure to ionising radiation at medium to high doses results in the manifestation of mixed pathologies. Following the analysis of several radiation accidents it is clear that intestinal injury influences patient survival. However the appearance of the classically defined gastrointestinal syndrome is not always evident. Nevertheless injury to the gastrointestinal tract, in particular loss of barrier function, seems to play an important role in the development of Multiple Organ Failure such as reported in the recent accident at Tokai Mura. lonising radiation overexposure results in changes in intestinal motility and nutrient, fluid and electrolyte absorption and secretion all which may contribute to the genesis of diarrhoea. In addition to modified cellular transport properties for nutrients or electrolytes, important loss of epithelial cells is also a major contributing factor. Intestinal functions are controlled by many factors such as neurotransmitters, locally released mediators from endocrine cells or immunocompetent cells in addition to luminal agents. To date, treatment of radiation-induced gastrointestinal injury is mainly symptomatic. However treatments such as growth factors, anti-inflammatory cytokines as well as cellular transplantation remain to he validated in the radiation accident situation.

Intestinal and Hemodynamic Impairment Following Mesenteric Ischemia/Reperfusion

Background. Clinical intestinal ischemia/reperfusion (I/R) injury results in local and systemic dysfunction. A rat model of transient mesenteric occlusion has been used to study this phenomenon. However, a systematic analysis of the rat model with respect to intestinal permeability and hemodynamics has not been carried out.Materials and methods. In anesthetized rats, the superior mesenteric artery was occluded for 60 min, followed by reperfusion for 4 h. Intestinal impairment was evaluated via histological examination and by measuring ex vivo apparent permeability coefficients (Papp) of mannitol (0.18 kDa), inulin (5 kDa), and dextran (70 kDa). Hemodynamic effects of intestinal I/R were determined by monitoring mean arterial pressure (MAP) and heart rate (HR) via a catheter placed in the femoral artery.Results. The animal model was associated with increased ex vivo Papp for mannitol and inulin. Although I/R injury was accompanied by significant histological disruption, there was no observable alteration in dextran permeability, suggesting that the loss in normal barrier function was limited to low-molecular-weight compounds. Hemodynamic measurements indicated that reperfusion induced a precipitous and sustained fall in MAP. HR values fell sharply following reperfusion but gradually increased and eventually “overshot” to values greater than baseline.Conclusions. Our findings demonstrate the selective loss of barrier function of the small bowel following intestinal I/R. Furthermore, these results also illustrate the importance of selecting appropriate permeability markers for the evaluation of intestinal damage. In light of the significant hemodynamic disruption accompanying the animal model, our investigation also points toward the need for developing therapeutic strategies that mitigate the local and systemic effects of intestinal I/R injury.

Membrane activity of the peptide antibiotic clavanin and the importance of its glycine residues.

The peptide antibiotic clavanin A (VFQFLGKIIHHVGNFVHGFSHVF-NH(2)) is rich in histidine and glycine residues. In this study the antimicrobial activity and membrane activity of wild-type clavanin A and seven Gly --> Ala mutants thereof were investigated. Clavanin A effectively killed the test microorganism Micrococcus flavus and permeabilized its cytoplasmic membrane in the micromolar concentration range, suggesting that the membrane is the target for this molecule. Consistent with this suggestion, it was observed that clavanin A efficiently inserted into different phospholipid monolayers mainly via hydrophobic interactions. Bilayer permeabilization was observed for both low and high molecular mass fluorophores enclosed in unilamellar vesicles and occurred at the same concentration as the antimicrobial activity. It is therefore suggested that the loss of barrier function does not involve specific receptors in the target membrane. Circular dichroism spectroscopy indicated that under membrane mimicking conditions a random coil --> helical transition was induced for all clavanin derivatives tested. Observed differences in peptide-membrane interaction and biological activity between the various clavanin derivatives demonstrated the functional importance of Gly at the positions 6 and 13. These two glycines may act as flexible hinges that facilitate the hydrophobic N-terminal end of clavanin to deeply insert into the bilayer. On the contrary, no such role is evident for Gly 18, as its substitution by Ala actually stimulated membrane interaction and biological activity. This study suggests that the combined hydrophobicity, overall state of charge, and conformational flexibility of the peptide determine the (membrane) activity of clavanin A and its Gly --> Ala mutants.

Hypoxia-inducible factor 1-dependent induction of intestinal trefoil factor protects barrier function during hypoxia.

Mucosal organs such as the intestine are supported by a rich and complex underlying vasculature. For this reason, the intestine, and particularly barrier-protective epithelial cells, are susceptible to damage related to diminished blood flow and concomitant tissue hypoxia. We sought to identify compensatory mechanisms that protect epithelial barrier during episodes of intestinal hypoxia. Initial studies examining T84 colonic epithelial cells revealed that barrier function is uniquely resistant to changes elicited by hypoxia. A search for intestinal-specific, barrier-protective factors revealed that the human intestinal trefoil factor (ITF) gene promoter bears a previously unappreciated binding site for hypoxia-inducible factor (HIF)-1. Hypoxia resulted in parallel induction of ITF mRNA and protein. Electrophoretic mobility shift assay analysis using ITF-specific, HIF-1 consensus motifs resulted in a hypoxia-inducible DNA binding activity, and loading cells with antisense oligonucleotides directed against the alpha chain of HIF-1 resulted in a loss of ITF hypoxia inducibility. Moreover, addition of anti-ITF antibody resulted in a loss of barrier function in epithelial cells exposed to hypoxia, and the addition of recombinant human ITF to vascular endothelial cells partially protected endothelial cells from hypoxia-elicited barrier disruption. Extensions of these studies in vivo revealed prominent hypoxia-elicited increases in intestinal permeability in ITF null mice. HIF-1-dependent induction of ITF may provide an adaptive link for maintenance of barrier function during hypoxia.

Development of noninvasive and quantitative methodologies for the assessment of chronic ulcers and scars in humans.

Chronic ulcers are a significant and common cause of morbidity and mortality worldwide. They disrupt the epidermis and dermis, resulting in a loss of barrier function. Keloids and hypertrophic scars (benign cutaneous tumors) represent an abnormal healing response. These fibroproliferative disorders are characterized by an overabundance of collagen and accumulation of extracellular matrix due to an imbalance between synthesis and degradation, culminating in excessive scarring. The objectives of this study were to evaluate and compare noninvasive biophysical methods for the measurement of outstanding quantitative parameters of scars and chronic ulcers, and to establish correlations between the parameters measured and the results of conventional subjective clinical evaluations. The development of new technologies, based on ultrasonography and laser Doppler, makes possible new dermatological evaluation methods. Fifteen patients (6 females and 9 males) with 15 chronic ulcers (4 diabetic ulcers, 10 venous ulcers and 1 pressure ulcer) and 30 patients (19 females and 11 males) with 30 scars (25 hypertrophic and 5 keloids) were included in this study. Clinical evaluation was performed by a dermatologist, an aesthetic surgeon and an endocrinologist. Biophysical measurements were used to assess local blood flow by laser Doppler flowmetry (Moor DRT4), thickness and echogenicity by high frequency ultrasonography (20 MHz, Dermascan C) and ulcer linear dimensions by image analysis. Our results show that blood flow within the ulcers and scars was higher than within normal skin. Also, skin thickness of chronic ulcers was decreased when compared to normal skin; the thickness of hypertrophic scars, but not of keloids, was increased in comparison to normal skin, and presented the possibility of measuring wound and scar surfaces with precision. In summary, this pilot study established the feasibility of measuring various biophysical parameters and adapted their potential utility to research on wounds.

Correlation of tight junction morphology with the expression of tight junction proteins in blood-brain barrier endothelial cells

Endothelial cells of the blood-brain barrier form complex tight junctions, which are more frequently associated with the protoplasmic (P-face) than with the exocytoplasmic (E-face) membrane leaflet. The association of tight junctional particles with either membrane leaflet is a result of the expression of various claudins, which are transmembrane constituents of tight junction strands. Mammalian brain endothelial tight junctions exhibit an almost balanced distribution of particles and lose this morphology and barrier function in vitro. Since it was shown that the brain endothelial tight junctions of submammalian species form P-face-associated tight junctions of the epithelial type, the question of which molecular composition underlies the morphological differences and how do these brain endothelial cells behave in vitro arose. Therefore, rat and chicken brain endothelial cells were investigated for the expression of junctional proteins in vivo and in vitro and for the morphology of the tight junctions. In order to visualize morphological differences, the complexity and the P-face association of tight junctions were quantified. Rat and chicken brain endothelial cells form tight junctions which are positive for claudin-1, claudin-5, occludin and ZO-1. In agreement with the higher P-face association of tight junctions in vivo, chicken brain endothelia exhibited a slightly stronger labeling for claudin-1 at membrane contacts. Brain endothelial cells of both species showed a significant alteration of tight junctions in vitro, indicating a loss of barrier function. Rat endothelial cells showed a characteristic switch of tight junction particles from the P-face to the E-face, accompanied by the loss of claudin-1 in immunofluorescence labeling. In contrast, chicken brain endothelial cells did not show such a switch of particles, although they also lost claudin-1 in culture. These results demonstrate that the maintenance of rat and chicken endothelial barrier function depends on the brain microenvironment. Interestingly, the alteration of tight junctions is different in rat and chicken. This implies that the rat and chicken brain endothelial tight junctions are regulated differently.

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Oxidant-induced intestinal barrier disruption and its prevention by growth factors in a human colonic cell line: role of the microtubule cytoskeleton

Reactive oxygen metabolites (ROM) are increased in the inflamed mucosa of inflammatory bowel disease (IBD) and may contribute to loss of intestinal barrier function in this disorder. Growth factors (GF) are protective. But the mechanisms of disruption and protection remain elusive. In the present investigation, we hypothesized that the microtubules (a critical cytoskeletal element) play a key role in the molecular mechanism of intestinal barrier dysfunction induced by ROM and in GF-mediated protection. Utilizing monolayers of a human colonic cell line (Caco-2), we evaluated the effects of ROM (H 2O 2 or HOCl), in the presence or absence of GF (epidermal growth factor [EGF]; transforming growth factor-α [TGF-α]), on intestinal barrier function, tubulin (microtubule structural protein), and microtubule stability. Monolayers were also processed for two highly sensitive western immunoblots: fractionated polymerized tubulin (S2; an index of stability); monomeric tubulin (S1; an index of disruption) to detect the oxidation and disassembly/assembly of tubulin. ROM exposure led to a significant increase in the oxidation of tubulin, decrease in the stable S2 polymerized tubulin, and increase in the unstable S1 monomeric tubulin. In concert, each ROM in a dose dependent manner damaged the microtubule cytoskeleton and disrupted barrier function. GF pretreatment not only increased the S2 stable tubulin and decreased tubulin oxidation but also, concomitantly, prevented the disruption of microtubules and loss of barrier function in monolayers exposed to ROM. Antibody against the GF-receptor and inhibitors of GF-receptor tyrosine kinase abolished GF protection, indicating the involvement of epidermal growth factor receptor (EGFR) signaling pathway. As predicted, colchicine, an inhibitor of microtubule assembly, caused barrier dysfunction and prevented GF protection whereas taxol, a microtubule-stabilizing agent, mimicked the protective effects of GF. Thus, organization and stability of the microtubule cytoskeleton appears to be critical to both oxidant-induced mucosal barrier dysfunction and protection of intestinal barrier mediated by GF. Therefore, microtubules may be useful targets for development of drugs for the treatment of IBD.

Advances in small-bowel transplantation

Today small-bowel transplantation is an accepted alternative to total parenteral nutrition (TPN) for treatment of chronic intestinal failure. It has become a life-saving procedure for those patients who cannot be maintained on TPN. Although the first clinical successes were achieved after the introduction of cyclosporine in the 1980s and tacrolimus in the 1990s, many aspects of this process are still incompletely understood, with immunological manifestations remaining particularly complex. The problems after small-bowel transplantation remain the requirement of potent immunosuppression to prevent rejection, as well as infectious problems secondary to the resulting immunoincompetence and loss of barrier function in cases of rejection. However, significant progress has occurred in the last 3 years. In this article we review the background of small-bowel transplantation procedures, present recent results, and discuss future directions in immunosuppression.

Advances in small-bowel transplantation

Today small-bowel transplantation is an accepted alternative to total parenteral nutrition (TPN) for treatment of chronic intestinal failure. It has become a life-saving procedure for those patients who cannot be maintained on TPN. Although the first clinical successes were achieved after the introduction of cyclosporine in the 1980s and tacrolimus in the 1990s, many aspects of this process are still incompletely understood, with immunological manifestations remaining particularly complex. The problems after small-bowel transplantation remain the requirement of potent immunosuppression to prevent rejection, as well as infectious problems secondary to the resulting immunoincompetence and loss of barrier function in cases of rejection. However, significant progress has occurred in the last 3 years. In this article we review the background of small-bowel transplantation procedures, present recent results, and discuss future directions in immunosuppression.

IL-6 Rescues Enterocytes from Hemorrhage Induced Apoptosisin Vivoandin Vitroby abcl-2Mediated Mechanism

Following a hemorrhagic event, damage to the highly metabolic intestinal tissue induces loss of barrier function leading to bacterial escape and LPS contamination of the host. Orally administered IL-6 restores intestinal barrier function following hemorrhage in both rat and mouse models. IL-6 prevents apoptosis in a variety of lymphoid cells and lines, through the activation of the proto-oncogenebcl-2.This communication elucidates the role of the IL-6–bcl-2interaction in intestinal apoptosis following hemorrhagic shock. Terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling (TUNEL) and p53 immunohistochemical staining were used to examine intestines from mice hemorrhaged and fed saline or IL-6 and enterocytes (IEC-6) exposed to hypoxia and LPS alone or LPS and IL-6in vitro. In situhybridization forbcl-2expression was performed on intestines or enterocytes. Intestinal sections from mice hemorrhaged and fed IL-6 showed reduction in apoptosis and increases inbcl-2gene expression relative to sections taken from mice hemorrhaged and fed saline. IEC-6 cells exposed to hypoxia and LPS had high numbers of TUNEL staining cells. Subsequent exposure to IL-6 after hypoxia and LPS reduced apoptotic cell numbers and increasedbcl-2gene expression. The data show that exposure of intestinal epithelial cells to IL-6 either by oral administration in hemorrhaged mice or by coculture following hypoxia and LPS treatment results in increasedbcl-2gene expression and reduced damage from apoptosis.