A guide to histomorphological evaluation of intestinal inflammation in mouse models.

Histomorphology remains a powerful routine evaluating intestinal inflammation in animal models. Emphasizing the focus of a given animal study, histopathology can overstate differences between established models. We aimed to systematize histopathological evaluation of intestinal inflammation in mouse models facilitating inter-study comparisons. Samples of all parts of the intestinal tract from well-established mouse models of intestinal inflammation were evaluated from hematoxylin/eosin-stained sections and specific observations confirmed by subsequent immunohistochemistry. Three main categories sufficiently reflected the severity of histopathology independent of the localization and the overall extent of an inflammation: (i) quality and dimension of inflammatory cell infiltrates, (ii) epithelial changes and (iii) overall mucosal architecture. Scoring schemata were defined along specified criteria for each of the three categories. The direction of the initial hit proved crucial for the comparability of histological changes. Chemical noxes, infection with intestinal parasites or other models where the barrier was disturbed from outside, the luminal side, showed high levels of similarity and distinct differences to changes in the intestinal balance resulting from inside events like altered cytokine responses or disruption of the immune cell homeostasis. With a high degree of generalisation and maximum scores from 4-8 suitable scoring schemata accounted specific histopathological hallmarks. Truly integrating demands and experiences of gastroenterologists, mouse researchers, microbiologists and pathologists we provide an easy-to-use guideline evaluating histomorphology in mouse models of intestinal inflammation. Standard criteria and definitions facilitate classification and rating of new relevant models, allow comparison in animal studies and transfer of functional findings to comparable histopathologies in human disease.

Dendritic cells from human mesenteric lymph nodes in inflammatory and non-inflammatory bowel diseases: subsets and function of plasmacytoid dendritic cells.

Plasmacytoid dendritic cells (pDC) in mesenteric lymph nodes (MLN) may be important regulators of both inflammatory and non-inflammatory mucosal immune responses but human studies are rare. Here we compare pDC from human MLN and peripheral blood (PB) by phenotype and function. MLN from patients with or without inflammatory bowel disease (IBD) undergoing colon surgery and PB from patients with IBD and from controls were used to isolate mononuclear cells. The pDC were analysed by flow cytometry for the expression of CD40, CD80, CD83, CD86, CCR6, CCR7, CX3CR1, CD103 and HLA-DR. Purified pDC from MLN and PB were stimulated with staphylococcus enterotoxin B (SEB), CpG-A, interleukin-3 (IL-3), SEB + IL-3, CpG-A + IL-3 or left unstimulated, and cultured alone or with purified allogeneic CD4(+) CD45RA(+) HLA-DR- T cells. Subsequently, concentrations of IL-1ß, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-17, interferon-α (IFN-α), IFN-γ and tumour necrosis factor-α (TNF-α) in culture supernatants were determined by multiplex bead array. The PB pDC from IBD patients exhibited an activated and matured phenotype whereas MLN pDC and control PB pDC were less activated. CpG-A and CpG-A + IL-3-stimulated MLN pDC secreted less IL-6 and TNF-α compared with PB pDC from controls. Compared with co-cultures of naive CD4 T cells with PB pDC, co-cultures with MLN pDC contained more IL-2, IL-10 and IFN-γ when stimulated with SEB and SEB + IL-3, and less IFN-α when stimulated with CpG-A. MLN pDC differ phenotypically from PB pDC and their pattern of cytokine secretion and may contribute to specific outcomes of mucosal immune reactions.

Adipokines from local fat cells shape the macrophage compartment of the creeping fat in Crohn's disease.

OBJECTIVE: The creeping fat in Crohn's disease (CD) is infiltrated by macrophages; local adipokine levels are increased. This study aimed to link these observations to define a role for macrophages in the pathology of human CD. METHODS: Human peripheral blood CD14 cells were polarised in vitro into M1 and M2 macrophages. The effects on adipokine receptors, phenotypic surface markers, cytokines and chemokines were assessed after treatment with leptin and adiponectin. Immunohistochemistry visualised macrophage subtypes in samples of mesenteric fat tissue from patients with CD. The chemotactic potential of secreted macrophage products was determined by T cell migration and chemokine production in vitro. RESULTS: Although both adipokines altered the phenotype and function of M1 and M2 macrophages, M2 macrophages were more susceptible. M1 responded to leptin by increased cytokine production, but the stronger effect was seen in M2 macrophages with high expression of interleukin (IL)-10, IL-6 and tumour necrosis factor α. Adiponectin exerted similar effects and led to upregulated mannose receptor expression by M2 macrophages. Large macrophage numbers within the mesenteric fat tissue of patients with CD comprise a unique infiltration predominantly of M2 macrophages, leading to an IL-10-rich environment. While leptin increased the potency of both subtypes to attract CD3 T cells, adiponectin only affected M2 macrophages. CONCLUSION: The adipocyte-dependent microenvironment within the creeping fat of patients with CD modulates the local macrophage compartment to a preference for the M2 subtype. The findings in this study with human cells suggest a protective role for the mesenteric fat in CD in terms of an enveloping barrier with the potential to limit intestinal inflammation.

Prognostic relevance of gastric cancer staging by endoscopic ultrasound.

BACKGROUND: Recent trials and guidelines have established the use of neoadjuvant chemotherapy for resectable UICC stage II to IV gastric cancers. In this setting, preoperative staging is pivotal for correct patient selection. This cohort study was designed to assess the accuracy of endoscopic ultrasound (EUS) and the ability to select correctly patients for neoadjuvant chemotherapy on the basis of survival outcome. METHODS: Eighty-two consecutive Caucasian patients (46 male; median age 72 years) with gastric cancer underwent EUS staging and subsequent surgery without perioperative chemotherapy or radiotherapy. Patients were followed for a median of 800 days postoperatively. Pathology and EUS UICC and T stages were compared and evaluated as predictors of survival using Kaplan-Meier and Cox regression analysis. RESULTS: The overall accuracy of EUS for UICC classification compared with pathology was 62 %, and the accuracy for delineation of UICC I was 89 %. For the therapeutically relevant differentiation of early gastric cancer (UICC stage I), EUS (mean survival, 2,298 days, R2 = 0.23) and pathology (2,461 days, R2 = 0.24) predicted survival equally well. Similar results were obtained for T staging by EUS (mean survival, 2,065 days for uT1/2, R2 = 0.24) or pathology (2,185 days, R2 = 0.22). CONCLUSIONS: EUS identifies the low risk subgroup (uUICC stage I or uT1/2) with similar performance as pUICC stage I or stage pT1/2 in gastric cancer and very similar survival characteristics. EUS thus may be the noninvasive method of choice for preoperative selection of patients for immediate resection versus neoadjuvant chemotherapy.

(+)-Episesamin inhibits adipogenesis and exerts anti-inflammatory effects in 3T3-L1 (pre)adipocytes by sustained Wnt signaling, down-regulation of PPARγ and induction of iNOS.

Obesity and its associated health risks still demand for effective therapeutic strategies. Drugs and compositions derived from Oriental medicine such as green tea polyphenols attract growing attention. Previously, an extract from the Japanese spice bush Lindera obtusiloba (L. obtusiloba) traditionally used for treatment of inflammation and prevention of liver damage was shown to inhibit adipogenesis. Aiming for the active principle of this extract (+)-episesamin was identified, isolated and applied in adipogenic research using 3T3-L1 (pre)adipocytes, an established cell line for studying adipogenesis. With an IC50 of 10µM (+)-episesamin effectively reduced the growth of 3T3-L1 preadipocytes and decreased hormone-induced 3T3-L1 differentiation as shown by reduced accumulation of intracellular lipid droplets and diminished protein expression of GLUT-4 and vascular endothelial growth factor. Mechanistically, the presence of (+)-episesamin during hormone-induced differentiation provoked a reduced phosphorylation of ERK1/2 and ß-catenin along with a reduced protein expression of peroxisome proliferator-activated receptor γ and a strongly increased protein expression of iNOS. Treatment of mature adipocytes with (+)-episesamin resulted in a reduction of intracellular stored lipid droplets and induced the proapoptotic enzymes caspases-3/-7. Besides interfering with adipogenesis, (+)-episesamin showed anti-inflammatory activity by counteracting the lipopolysaccharide- and tumor necrosis factor α-induced secretion of interleukin 6 by 3T3-L1 preadipocytes. In conclusion, (+)-episesamin seems to be the active drug in the L. obtusiloba extract being responsible for the inhibition of adipogenesis and, thus, should be evaluated as a novel potential complementary treatment for obesity.

Oral tolerance induction in humans.

Oral tolerance designates the status of systemic hyporesponsiveness against an antigen that makes contact with the immune system via the mucosa of the gastrointestinal tract. In various animal models of autoimmune disease the feeding of the particular autoantigen has been shown to tolerize the animal, thereby ameliorating the course of disease. In contrast, effectivity has not been found in human trials to induce oral tolerance in patients suffering from autoimmune disease. However, the underlying mechanisms of tolerance in rodents, in particular the induction of anti-inflammatory cytokines, seem to be functional in humans as well. Studies using the human neoantigen keyhole limpet hemocyanin (KLH) offer experimental access to examine cellular and molecular basics of oral tolerance in humans required to raise the efficiency of oral tolerance induction in clinical trials.

HIV infection and the intestinal mucosal barrier.

HIV infection induces a barrier defect of the intestinal mucosa, which is closely linked to immune activation and CD4 T cell depletion. The HIV-induced barrier defect is initiated in early acute and maintained through chronic infection. In acute infection, increased epithelial permeability is associated with increased epithelial apoptosis possibly caused by perforin-expressing cytotoxic T cells. In chronic infection, mucosal production of inflammatory cytokines is associated with increased epithelial permeability, epithelial apoptosis, and alterations of epithelial tight junctions. In addition to HIV-induced immune-mediated effects, viral proteins have the potential to directly affect epithelial barrier function. After prolonged viral suppression by antiretroviral therapy, there is, at least partial, restoration of the HIV-associated intestinal mucosal barrier defect despite persisting alterations of the mucosal immune system.

Effects of quercetin studied in colonic HT-29/B6 cells and rat intestine in vitro.

The aim of this study was to analyze the influence of quercetin on intestinal barrier function using the human colonic epithelial cell line HT-29/B6 and rat small and large intestine in vitro. Rat native ileum and late distal colon were incubated in Ussing chambers, and the total resistance (R(T) ) was measured, and expression of tight junction proteins was characterized in immunoblots. By simulating inflammatory conditions with TNF-α, we examined the barrier-preventive effects of quercetin. Incubation with TNF-α led to a decrease of R(T) in HT-29/B6 cell monolayers, which could be partially inhibited by quercetin. In accordance with cell culture experiments, quercetin increased mucosal resistance of rat ileum and late distal colon. Thus, barrier disturbance in late distal colon specimens induced by TNF-α and IFN-γ could be partially prevented by coincubation with quercetin. These findings demonstrate that quercetin enhances barrier function in rat small and large intestine and possesses protective effects on cytokine-induced barrier damage.

Ion transport and barrier function are disturbed in microscopic colitis.

In this paper, we identify mechanisms of watery diarrhea in microscopic colitis (MC). Biopsies from the sigmoid colon of patients with collagenous colitis and treated lymphocytic colitis were analyzed in miniaturized Ussing chambers for electrogenic sodium transport and barrier function with one-path impedance spectroscopy. Cytometric bead arrays (CBA) served to analyze cytokine profiles. In active MC, electrogenic sodium transport was diminished and epithelial resistance decreased. CBA revealed a Th1 cytokine profile featuring increased IFN-γ, TNF-α, and IL-1ß levels. After four weeks of steroid treatment with budesonide, electrogenic sodium transport recovered while epithelial barrier defects remained. Diarrhea in MC results at least in part from a combination of impaired electrogenic sodium transport and barrier defects. From a therapeutic perspective it can be postulated that the functional importance of loss of ions may be higher than that caused by barrier impairment.

The chemopreventive agent ursodeoxycholic acid inhibits proliferation of colon carcinoma cells by suppressing c-Myc expression.

Ursodeoxycholic acid (UDCA) can prevent chemical and colitis-associated colon carcinogenesis by unknown mechanism(s). One of the processes underlying the chemopreventive action could be the inhibition of proliferation by UDCA. To clarify the antiproliferative mechanism of UDCA, we used p53 wt colon carcinoma cell lines HCT8 and HCT116. UDCA-induced inhibition of proliferation was reversible and was associated with a decrease of the S-phase and an increase of G1 phase population, but not with apoptosis or senescence. The treatment suppressed the expression of c-Myc protein and, as a consequence, of several cell cycle regulatory molecules, including CDK4 and CDK6. Using the HCT8 cell line as a model, we show that UDCA suppresses c-Myc at the protein level. The suppression of c-Myc alone or a simultaneous suppression of CDK4 and of CDK6 kinase is sufficient to inhibit cell proliferation. In sum, we identified c-Myc as a primary UDCA target in colon carcinoma cells. The degradation of c-Myc protein decreases the expression of the cell cycle regulators CDK4 and CDK6, which reversibly slows down the cell cycle. The suppression of these proproliferatory molecules is the likely initial mechanism of antiproliferatory action of UDCA on colon cancer cells.

Ulcerative colitis: immune function, tissue fibrosis and current therapeutic considerations.

BACKGROUND: Ulcerative colitis (UC) is a complex disease in which the interaction of genetic, environmental and microbial factors drives chronic intestinal inflammation that finally leads to extensive tissue fibrosis. DISCUSSION: The present review discusses the current knowledge on genetic susceptibility, especially of the IL-12/IL-23 pathway, the pathophysiologic role of the involved cytokines (e.g. IL-13, IL-23, TGFß1) and immune cells (e.g. T cells, epithelial cells, fibroblasts) in UC followed by an overview on actual therapeutic considerations. These future therapies will target selectively the involved cell types by blocking their activation and its downstream signalling, by inhibiting their migration to the inflamed site and by anti-cytokine strategies. This may avoid-when initiated in time-the perpetuation of the inflammatory mechanisms thus preventing fibrosis. With respect to animal models that have guided the most productive efforts for understanding human inflammatory bowel disease, these will be shortly discussed in the respective context.

The JAK2 variant rs10758669 in Crohn's disease: altering the intestinal barrier as one mechanism of action.

PURPOSE: The aetiology of intestinal barrier dysfunction in Crohn's disease (CD) is poorly understood. Associations in relatives of CD families suggest a genetic basis, but the relevant variants are still unknown. We hypothesized that variants in genes occurring in pathways such as autophagy and IL23 signalling might contribute to CD by altering intestinal permeability. METHODS: We analysed five variants (rs10758669 within JAK2, rs744166 within STAT3, rs4958847, rs11747270 and rs13361189 within IRGM) in adult German inflammatory bowel disease patients (CD, n = 464; ulcerative colitis (UC), n = 292) and matched healthy controls (n = 508). These data were correlated with gastrointestinal permeability as assessed by lactulose/mannitol ratio in CD patients (n = 141) in remission. RESULTS: Our data confirm the association between JAK2 rs10758669 (p = 0.026, OR = 1.25, 95% CI = 1.04-1.50) and STAT3 rs744166 (p = 0.04, OR = 0.83, 95% CI = 0.688-0.998) with CD, but not UC. With respect to all the analysed IRGM variants, no association was found to either CD or UC. Among CD patients, an increased intestinal permeability was detected in 65 out of 141 patients (46.1%). Most importantly, patients carrying the C risk allele within JAK2 rs10758669 displayed an increased permeability more often compared with patients without the C allele (p = 0.004). No association with intestinal permeability was found for STAT3 rs744166 and all IRGM variants. CONCLUSIONS: JAK2 rs10758669 and STAT3 rs744166 increase susceptibility for CD. We show that the A>C substitution in rs10758669 of the JAK2 gene is associated with increased intestinal permeability. Altering intestinal barrier function might thus be one mechanism how JAK2 contributes to CD pathogenesis.

Capsule endoscopy: comparison of two different reading modes.

PURPOSE: Capsule endoscopy (CE) is a very useful tool for the evaluation of the small intestine, but it is time consuming. The aim of this study was to compare evaluation times and detection rates in two different reading modes (single view at a speed of 10 frames per second (fps) and four images simultaneously, i.e., quadview mode at a speed of 20 fps) to find the optimum setting mode for evaluation of CE videos. METHODS: CE videos of 70 patients performed for different indications (obscure bleeding, n = 50; suspected Crohn's disease, n = 10; and suspected or complicated celiac disease, n = 10) were reviewed by investigators A and B in the two different reading modes. RESULTS: The mean evaluation time using single view at 10 fps was 22 min (SD ± 9.1 min) and 11.9 min (SD ± 4.8 min) using quadview mode at 20 fps. The detection rates of angiodysplasias, erosions, small ulcers, and small polyps were only discreetly lower using the quadview mode at 20 fps. In Crohn's disease and celiac disease, the essential aspects of inflamed or atrophic mucosa segments were equally detected in both reading modes. In one case of complicated celiac disease with severe erosive jejunitis, a lymphoma-suspect lesion was overlooked in the quadview mode at 20 fps. CONCLUSIONS: It is often possible to read CE videos in quadview mode at a higher speed with even so a high diagnostic yield in a shortened evaluation time.

(+)-Episesamin exerts anti-neoplastic effects in human hepatocellular carcinoma cell lines via suppression of nuclear factor-kappa B and inhibition of MMP-9.

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide. Treatment options, especially in advanced tumor stages, are still limited. Inhibition of signaling cascades involved in the pathogenesis of HCC - such as NF-ĸB - offer a promising therapeutic approach. Aim of this study was to examine anti-neoplastic effects of (+)-episesamin which has been isolated from an anti-fibrotic extract of Lindera obtusiloba on human HCC cells with particular interest in activation of NF-κB. The human HCC cell lines HepG2, Huh-7 and SK-Hep1 were treated with (+)-episesamin. Beside measurement of proliferation, invasion and apoptosis, effects of (+)-episesamin on NF-κB-activity, VEGF secretion and enzymatic MMP-9 activity were determined. Anti-inflammatory effects were assessed by IL-6 ELISA using HCC cells and RAW264.7 macrophages. 10 µM (+)-episesamin reduced the proliferation of HCC cells by ~50%, suppressed invasion and induced apoptosis. DNA-binding ELISA experiments revealed that (+)-episesamin treated HCC cells showed a suppressed basal and TNFα-induced activation of NF-κB and a subsequent suppression of TNFα- and LPS-induced IL-6 production. Further, (+)-episesamin exhibited inhibitory effects on the enzymatic activity of recombinant MMP-9 and the secretion of MMP-9 and VEGF by HCC cells into their supernatants. Our findings show that anti-neoplastic effects of (+)-episesamin are mediated via suppressed activation of NF-κB which entails a decreased release of pro-inflammatory IL-6. In addition, (+)-episesamin inhibits MMP-9, which is strongly expressed in invasive HCC, and the production of proangiogenic VEGF. We conclude that (+)-episesamin has the potential to be further explored as a complementary treatment for HCC.

Cell polarity-determining proteins Par-3 and PP-1 are involved in epithelial tight junction defects in coeliac disease.

BACKGROUND: Epithelial barrier defects are well known in coeliac disease, but the mechanisms are only poorly defined. It is unclear, whether barrier disturbance reflects upregulated epithelial transcytosis or paracellular leakage. OBJECTIVE: To characterise the molecular structure and function of the epithelial tight junction (TJ) and mechanisms of its dysregulation. METHODS: Molecular analysis of proteins involved in TJ assembly and their regulation was performed by western blotting and confocal microscopy correlated to electrophysiology. RESULTS: A complex alteration of the composition of epithelial TJ proteins (with more pore-forming claudins like claudin-2 and a reduction in tightening claudins like claudin-3, -5 and -7) was found for protein expression and subcellular localisation, responsible for an increase in paracellular biotin-NHS uptake. In contrast, epithelial apoptosis was only moderately elevated (accounting for a minor portion of barrier defects) and epithelial gross lesions--for example, at cell extrusion zones, were absent. This TJ alteration was linked to an altered localisation/expression of proteins regulating TJ assembly, the polarity complex protein Par-3 and the serine-/threonine phosphatase PP-1. CONCLUSIONS: Changes in cell polarity proteins Par-3 and PP-1 are associated with altered expression and assembly of TJ proteins claudin-2, -3, -5 and -7 and ZO-1, causing paracellular leakage in active coeliac disease.

Connecting liver and gut: murine liver sinusoidal endothelium induces gut tropism of CD4+ T cells via retinoic acid.

UNLABELLED: Gut-activated T cells migrating into the liver can cause extraintestinal manifestations of inflammatory bowel disease. T cells acquire a gut-homing phenotype dependent on retinoic acid (RA) provided by intestinal dendritic cells (DC). We investigated whether liver antigen-presenting cells can induce gut tropism supporting an enterohepatic lymphocyte circulation. Priming of CD4(+) T cells by liver sinusoidal endothelial cells (LSEC) supported migration into gut and gut-associated lymphoid tissue. As observed for T cells primed by intestinal DCs, this gut tropism depended on α(4) ß(7) integrin and CC chemokine receptor 9 (CCR9) expression by LSEC-primed CD4(+) T cells. The induction of gut-homing molecules was mediated by RA, a derivate of vitamin A that is stored in large amounts within the liver. LSECs expressed functional retinal dehydrogenases and could convert vitamin A to RA. Conversely, the lack of signaling via the RA receptor prevented the expression of α(4) ß(7) integrin and CCR9 on LSEC-primed CD4(+) T cells, consequently reducing their in vivo migration to the intestine. Other liver antigen-presenting cells failed to support high expression of α(4) ß(7) integrin on CD4(+) T cells, thus, the potential to induce gut homing is restricted to LSECs. CONCLUSION: The capacity to promote gut tropism via vitamin A use is not unique for intestinal DCs but is also a feature of LSECs. Our data support the assumption that CD4(+) T cells can migrate from the liver to the gut as one branch of a postulated enterohepatic lymphocyte circulation.

Oral and fecal Campylobacter concisus strains perturb barrier function by apoptosis induction in HT-29/B6 intestinal epithelial cells.

Campylobacter concisus infections of the gastrointestinal tract can be accompanied by diarrhea and inflammation, whereas colonization of the human oral cavity might have a commensal nature. We focus on the pathophysiology of C. concisus and the effects of different clinical oral and fecal C. concisus strains on human HT-29/B6 colon cells. Six oral and eight fecal strains of C. concisus were isolated. Mucus-producing HT-29/B6 epithelial monolayers were infected with the C. concisus strains. Transepithelial electrical resistance (R(t)) and tracer fluxes of different molecule size were measured in Ussing chambers. Tight junction (TJ) protein expression was determined by Western blotting, and subcellular TJ distribution was analyzed by confocal laser-scanning microscopy. Apoptosis induction was examined by TUNEL-staining and Western blot of caspase-3 activation. All strains invaded confluent HT-29/B6 cells and impaired epithelial barrier function, characterized by a time- and dose-dependent decrease in R(t) either after infection from the apical side but even more from the basolateral compartment. TJ protein expression changes were sparse, only in apoptotic areas of infected monolayers TJ proteins were redistributed. Solely the barrier-forming TJ protein claudin-5 showed a reduced expression level to 66±8% (P<0.05), by expression regulation from the gene. Concomitantly, Lactate dehydrogenase release was elevated to 3.1±0.3% versus 0.7±0.1% in control (P<0.001), suggesting cytotoxic effects. Furthermore, oral and fecal C. concisus strains elevated apoptotic events to 5-fold. C. concisus-infected monolayers revealed an increased permeability for 332 Da fluorescein (1.74±0.13 vs. 0.56±0.17 10(-6) cm/s in control, P<0.05) but showed no difference in permeability for 4 kDa FITC-dextran (FD-4). The same was true in camptothecin-exposed monolayers, where camptothecin was used for apoptosis induction.In conclusion, epithelial barrier dysfunction by oral and fecal C. concisus strains could mainly be assigned to apoptotic leaks together with moderate TJ changes, demonstrating a leak-flux mechanism that parallels the clinical manifestation of diarrhea.

Impaired peripheral Th1 CD4+ T cell response to Escherichia coli proteins in patients with Crohn's disease and ankylosing spondylitis.

BACKGROUND: To clarify the impact of T cell responses towards enteric antigens for chronic intestinal inflammation, we determined T helper 1 reactivity towards conserved Escherichia coli proteins in patients with Crohn's disease (CD) and healthy individuals and patients with ankylosing spondylitis (AS), who also often show microscopic inflammatory lesions within the gut or even develop overt inflammatory bowel disease. METHODS: We determined the frequency of IFNγ+CD40L+ cells/CD4+ T cells after stimulation of whole blood with pools of E. coli proteins. RESULTS: The E. coli-specific Th1 response was significantly reduced in CD patients and to a lower extent also in AS patients. CONCLUSIONS: E. coli is a target for polyclonal Th1 responses in healthy individuals. The impairment of these responses in CD and AS patients might be due to recruitment of enterobacteria-specific Th1 cells to the gut or might reflect inadequate priming of adaptive immune response.

Innate and adaptive immunity in inflammatory bowel disease.

Inflammatory bowel diseases are the consequence of a dysregulated mucosal immune system. The mucosal immune system consists of two arms, innate and adaptive immunity, that have been studied separately for a long time. Functional studies from in vivo models of intestinal inflammation as well as results from genome-wide association studies strongly suggest a cross-regulation of both arms. The present review will illustrate this interaction by selecting examples from innate immunity and adaptive immunity, and their direct impact on each other. Broadening our view by focusing on the cross-regulated areas of the mucosal immune system will not only facilitate our understanding of disease, but furthermore will allow identification of future therapeutic targets.

Aerolysin from Aeromonas hydrophila perturbs tight junction integrity and cell lesion repair in intestinal epithelial HT-29/B6 cells.

BACKGROUND: Aeromonads cause a variety of infections, including gastroenteritis, sepsis, and wound necrosis. Pathogenesis of Aeromonas hydrophila and its hemolysin has been characterized, but the mechanism of the epithelial barrier dysfunction is currently poorly understood. METHODS: Human colon epithelial monolayers HT-29/B6 were apically inoculated with clinical isolates of A. hydrophila or with the secreted pore-forming toxin aerolysin. Epithelial resistance and permeability for several markers were determined in Ussing chambers, using 2-path impedance spectroscopy. The subcellular distribution of tight junction (TJ) and cytoskeleton proteins was analyzed by Western blotting and confocal laser-scanning microscopy. RESULTS: A. hydrophila infection induces chloride secretion with a small decrease in transcellular resistance. However, the major effect of A. hydrophila, mediated by its toxin aerolysin, was a sustained reduction of paracellular resistance by retracting sealing TJ proteins from the TJ strands. Aerolysin-treated monolayers showed increased paracellular permeability to FITC-dextran-4000 (0.104 ± 0.014 vs 0.047 ± 0.001 10(-6) cm/s in control; P < .05). Moreover, restitution of epithelial lesions was impaired. The effects were myosin light chain kinase (MLCK) dependent and mediated by intracellular Ca(2+) signaling. CONCLUSIONS: During Aeromonas infection, pore formation by aerolysin impairs epithelial integrity by promoting TJ protein redistribution and consequently affecting wound closure. Thus, Aeromonas-induced diarrhea is mediated by 2 mechanisms, transcellular secretion and paracellular leak flux.