Correlation between cyclical epithelial barrier dysfunction and bacterial translocation in the relapses of intestinal inflammation

Astragalus membranaceus as a Drug Candidate for Inflammatory Bowel Disease: The Preclinical Evidence

Inflammatory bowel disease (IBD) is a group of chronic inflammatory disorders that include Crohn's disease (CD) and ulcerative colitis (UC). Today, IBD has no successful treatment. As a result, it is of paramount importance to develop novel therapeutic agents for IBD prevention and treatment. Astragalus membranaceus (AMS) is a traditional Chinese medicine found in the AMS root. Modern pharmacological studies indicate that AMS and its constituents exhibit multiple bioactivities, such as anti-inflammatory, anti-oxidant, immune regulatory, anticancer, hypolipidemic, hypoglycemic, hepatoprotective, expectorant, and diuretic effects. AMS and its active constituents, which have been reported to be effective in IBD treatment, are believed to be viable candidate drugs for IBD treatment. These underlying mechanisms are associated with anti-inflammation, anti-oxidation, immunomodulation, intestinal epithelial repair, gut microbiota homeostasis, and improved energy metabolism. In this review, we summarize the efficacy and underlying mechanisms involved in IBD treatment with AMS and its active constituents in preclinical studies.

Understanding the Connection between Gut Homeostasis and Psychological Stress

Long-term exposure to adverse life events that provoke acute or chronic psychological stress (hereinafter "stress") can negatively affect physical health and even increase susceptibility to psychological illnesses, such as anxiety and depression. As a part of the hypothalamic-pituitary-adrenal axis, corticotropin-releasing factor (CRF) released from the hypothalamus is primarily responsible for the stress response. Typically, CRF disrupts the gastrointestinal system and leads to gut microbiota dysbiosis, thereby increasing risk of functional gastrointestinal diseases, such as irritable bowel syndrome. Furthermore, CRF increases oxidative damage to the colon and triggers immune responses involving mast cells, neutrophils, and monocytes. CRF even affects the differentiation of intestinal stem cells (ISCs), causing enterochromaffin cells to secrete excessive amounts of 5-hydroxytryptamine (5-HT). Therefore, stress is often accompanied by damage to the intestinal epithelial barrier function, followed by increased intestinal permeability and bacterial translocation. There are multi-network interactions between the gut microbiota and stress, and gut microbiota may relieve the effects of stress on the body. Dietary intake of probiotics can provide energy for ISCs through glycolysis, thereby alleviating the disruption to homeostasis caused by stress, and it significantly bolsters the intestinal barrier, alleviates intestinal inflammation, and maintains endocrine homeostasis. Gut microbiota also directly affect the synthesis of hormones and neurotransmitters, such as CRF, 5-HT, dopamine, and norepinephrine. Moreover, the Mediterranean diet enhances the stress resistance to some extent by regulating the intestinal flora. This article reviews recent research on how stress damages the gut and microbiota, how the gut microbiota can improve gut health by modulating injury due to stress, and how the diet relieves stress injury by interfering with intestinal microflora. This review gives insight into the potential role of the gut and its microbiota in relieving the effects of stress via the gut-brain axis.

Dietary fat induced chylomicron-mediated LPS translocation in a bicameral Caco-2cell model

BACKGROUND

There is increasing evidence that dietary fat, especially saturated fat, promotes the translocation of lipopolysaccharide (LPS) via chylomicron production in the gut. Chylomicrons can subsequently transport LPS to other parts of the body, where they can induce low-grade chronic inflammation that is linked to various metabolic and gut-related diseases. To identify promising (food) compounds that can prevent or ameliorate LPS-related low-grade inflammation, we developed and optimized a bicameral in vitro model for dietary fat-induced LPS translocation that closely mimics the in vivo situation and facilitates high-throughput screening.

METHODS

Caco-2 cells were cultured in monolayers and differentiated to a small intestinal phenotype in 21 days. Thereafter, optimal conditions for fat-induced chylomicron production were determined by apical exposure of Caco-2 cells to a dilution range of in vitro digested palm oil and sunflower oil, optionally preceded by a 1-week apical FBS deprivation (cultured without apical fetal bovine serum). Chylomicron production was assessed by measuring basolateral levels of the chylomicron-related marker apolipoprotein B. Next, LPS was coincubated at various concentrations with the digested oils, and fat-induced LPS translocation to the basolateral side was assessed.

RESULTS

We found that dietary fat-induced LPS translocation in Caco-2 cells was optimal after apical exposure to digested oils at a 1:50 dilution in combination with 750 ng/mL LPS, preceded by 1 week of apical FBS deprivation. Coincubation with the chylomicron blocker Pluronic L81 confirmed that fat-induced LPS translocation is mediated via chylomicron production in this Caco-2 cell model.

CONCLUSION

We developed a robust Caco-2 cell model for dietary fat-induced LPS translocation that can be used for high-throughput screening of (food) compounds that can reduce LPS-related low-grade inflammation.

Enhancing Atorvastatin In Vivo Oral Bioavailability in the Presence of Inflammatory Bowel Disease and Irritable Bowel Syndrome Using Supercritical Fluid Technology Guided by wbPBPK Modeling in Rat and Human

Inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS) are common disorders that can change the body's physiology and drugs pharmacokinetics. Solid dispersion (SD) preparation using supercritical fluid technology (SFT) has many advantages. Our study aimed to explore the effect of IBS and IBD on atorvastatin (ATV) pharmacokinetics, enhance ATV oral bioavailability (BCS II drug) using SFT, and analyze drug-disease-formulation interaction using a whole-body physiologically based pharmacokinetic (wbPBPK) model in rat and human. A novel ATV formulation was prepared using SFT and characterized in vitro and in vivo in healthy, IBS, and IBD rats. The resulting ATV plasma levels were analyzed using a combination of conventional and wbPBPK approaches. The novel formulation increased ATV solubility by 20-fold and resulted in a zero-order release of up to 95%. Both IBS and IBD increased ATV exposure after oral and intravenous administration by more than 30%. The novel SFT formulation increased ATV bioavailability by 28, 14, and 18% in control, IBD, and IBD rat groups and resulted in more consistent exposure as compared to raw ATV solution. Higher improvements in ATV bioavailability of more than 2-fold upon receiving the novel SFT formulation were predicted by the human wbPBPK model as compared to receiving the conventional tablets. Finally, the established wbPBPK model could describe ATV ADME in the presence of IBS and IBD after oral administration of raw ATV and using the novel SFT formula and can help scale the optimized ATV dosing regimens in the presence of IBS and IBD from rats to humans.

Prebiotic effects of goji berry in protection against inflammatory bowel disease

The prevalence of inflammatory bowel disease (IBD) is increasing, which is concerning because IBD is a known risk factor for the development of colorectal cancer. Emerging evidence highlights environmental factors, particularly dietary factors and gut microbiota dysbiosis, as pivotal inducers of IBD onset. Goji berry, an ancient tonic food and a nutraceutical supplement, contains a range of phytochemicals such as polysaccharides, carotenoids, and polyphenols. Among these phytochemicals, L. barbarum polysaccharides (LBPs) are the most important functional constituents, which have protective effects against oxidative stress, inflammation, and neurodegeneration. Recently, the beneficial effects of goji berry and associated LBPs consumption were linked to prebiotic effects, which can prevent dysbiosis associated with IBD. This review assessed pertinent literature on the protective effects of goji berry against IBD focusing on the gut microbiota and their metabolites in mediating the observed beneficial effects.

Tradition to Pathogenesis: A Novel Hypothesis for Elucidating the Pathogenesis of Diseases Based on the Traditional Use of Medicinal Plants

Traditional medicines embody knowledge on medicinal plants that has been accumulated through cultural evolution over millennia. In the latter half of the 20th century, two approaches to medicinal plant research have been established: the "Bench to Bedside" and the "Bedside to Bench" approaches which serve primarily for the development of more efficient therapeutics. Here, we propose a third, novel approach: from "Tradition to Pathogenesis" which aims to understand the pathogenesis of diseases based on the cultural evolution of their respective empirical treatments. We analyse multiple examples of diseases where the acting mechanism of traditional treatments across multiple cultures points to the pathogenesis of the respective disease. E.g., many cultures traditionally treat rheumatism with anti-bacterial botanical drugs, which is at odds with our current understanding that rheumatism is an aseptic inflammation. Furthermore, gastric ailments have traditionally been treated with anti-infectious botanical drugs indicating local infections, as demonstrated by the discovery of Helicobacter pylori as a common cause of gastric ulcer. Understanding traditional treatments can thus help to elucidate the pathogenesis of the disease.

Mechanism of Ulcerative Colitis-Aggravated Liver Fibrosis: The Activation of Hepatic Stellate Cells and TLR4 Signaling Through Gut-Liver Axis

Background: The progression of liver disorders is frequently associated with inflammatory bowel disease through the gut-liver axis. However, no direct evidence showed the mechanisms of ulcerative colitis (UC) in the development of liver fibrosis per se. Thus, this study aimed to evaluate the effects of UC on liver fibrosis and its potential mechanism in the experimental model. Methods: Male C57BL/6 mice were allocated into five groups (n = 10 per group) to receive either drinking water (control), 2% dextran sulfate sodium (DSS), olive oil, carbon tetrachloride (CCl₄) or DSS + CCl₄ for 4 cycles. Blood was collected for biochemical analysis. Colons were excised for the evaluation of colon length and morphological score. Liver, colon, and mesenteric lymph nodes (MLNs) were collected for histopathological staining, expression analysis, and bacterial translocation assay to evaluate the inflammation, fibrosis, the activation of hepatic stellate cells (HSCs), and gut barrier function. Results: DSS caused severe colitis in mice treated or treated with CCl₄, as evident from the elevation of disease activity index (DAI), histological abnormalities, and increased pro-inflammatory cytokines (TNF-α, IFN-γ, and IL-17A). Histopathological staining revealed that DSS treatment aggravated the CCl₄-induced extracellular matrix deposition, liver fibrosis, and inflammation in mice. Additionally, biochemical and expression analysis indicated the DSS treatment caused the increase of hydroxyproline and pro-inflammatory cytokines, as well as the abnormal liver function indexes in CCl₄-induced mice. Gut barrier function was impaired in DSS- and DSS + CCl₄-treated mice, manifesting as the increase in bacterial translocation and lipopolysaccharide level, and the reduction in tight junction proteins (occluding, claudin-1 and ZO-1) expression. Further, the activations of HSCs and TLR4 signaling pathway were observed after DSS + CCl₄ treatment, presenting with the increase in expression of α-SMA, vimentin, TGF-β, collagen type I, collagen type II, TIMP-2, TLR4, TRAF6, and NF-κB p65, and a decrease in GFAP and MMP-2 expression. Conclusion: The present study verified that UC aggravated CCl₄-induced liver injury, inflammation, and fibrosis in mice through the gut-liver axis. Gut barrier dysfunction in UC leads to bacterial translocation and elevated lipopolysaccharide, which may promote the activation of TLR4 signaling and HSCs in the liver.

Clinical relevance of intestinal barrier dysfunction in common gastrointestinal diseases

The intestinal barrier is a complex and well-controlled physiological construct designed to separate luminal contents from the bowel wall. In this review, we focus on the intestinal barrier’s relationship with the host’s immune system interaction and the external environment, specifically the microbiome. The bowel allows the host to obtain nutrients vital to survival while protecting itself from harmful pathogens, luminal antigens, or other pro-inflammatory factors. Control over barrier function and the luminal milieu is maintained at the biochemical, cellular, and immunological level. However, disruption to this highly regulated environment can cause disease. Recent advances to the field have progressed the mechanistic understanding of compromised intestinal barrier function in the context of gastrointestinal pathology. There are numerous examples where bowel barrier dysfunction and the resulting interaction between the microbiome and the immune system has disease-triggering consequences. The purpose of this review is to summarize the clinical relevance of intestinal barrier dysfunction in common gastrointestinal and related diseases. This may help highlight the importance of restoring barrier function as a therapeutic mechanism of action in gastrointestinal pathology.

The Intestinal Barrier and Current Techniques for the Assessment of Gut Permeability

The intestinal barrier is essential in human health and constitutes the interface between the outside and the internal milieu of the body. A functional intestinal barrier allows absorption of nutrients and fluids but simultaneously prevents harmful substances like toxins and bacteria from crossing the intestinal epithelium and reaching the body. An altered intestinal permeability, a sign of a perturbed barrier function, has during the last decade been associated with several chronic conditions, including diseases originating in the gastrointestinal tract but also diseases such as Alzheimer and Parkinson disease. This has led to an intensified interest from researchers with diverse backgrounds to perform functional studies of the intestinal barrier in different conditions. Intestinal permeability is defined as the passage of a solute through a simple membrane and can be measured by recording the passage of permeability markers over the epithelium via the paracellular or the transcellular route. The methodological tools to investigate the gut barrier function are rapidly expanding and new methodological approaches are being developed. Here we outline and discuss, in vivo, in vitro and ex vivo techniques and how these methods can be utilized for thorough investigation of the intestinal barrier.

Dual role of Ca2+-activated Cl- channel transmembrane member 16A in lipopolysaccharide-induced intestinal epithelial barrier dysfunction in vitro

Dysfunction of intestinal epithelial Cl⁻ currents and channels have previously been reported in inflammatory intestinal diseases. However, the expression and function of the newly identified Ca²⁺-activated Cl⁻ channel transmembrane member 16A (TMEM16A) in the intestinal epithelium is unclear. In this study, we investigated the effects of TMEM16A on intestinal epithelial barrier function in vitro. Intestinal epithelial barrier dysfunction was modeled by lipopolysaccharide (LPS)-induced cell damage in intestinal epithelial IEC-6 cells and the effects of TMEM16A knockdown and overexpression on cell apoptosis and tight junctions were studied. Corresponding mRNA and protein expression levels were measured by quantitative real-time polymerase chain reaction, western blotting, and immunofluorescence analysis, respectively. TMEM16A expression was significantly increased by LPS, possibly via a process involving the transcription factor nuclear factor-κB and both Th1 and Th2 cytokines. Low- and high-dose LPS dysregulated tight junctions (high-myosin light-chain kinase expression) and cell apoptosis-dependent cell barrier dysfunction, respectively. TMEM16A aggravated cell barrier dysfunction in IEC-6 cells pretreated with low-dose LPS by activating ERK1/MLCK signaling pathways, but protected against cell barrier dysfunction by activating ERK/Bcl-2/Bax signaling pathways in IEC-6 cells pretreated with high-dose LPS. We concluded that TMEM16A played a dual role in LPS-induced epithelial dysfunction in vitro. The present results indicated the complex regulatory mechanisms and targeting of TMEM16A may provide potential treatment strategies for intestinal epithelial barrier damage, as well as forming the basis for future studies of the expression and function of TMEM16A in normal and inflammatory intestinal diseases in vivo.

Review: innovation through research in the North American pork industry

This article involved a broad search of applied sciences for milestone technologies we deem to be the most significant innovations applied by the North American pork industry, during the past 10 to 12 years. Several innovations shifted the trajectory of improvement or resolved significant production limitations. Each is being integrated into practice, with the exception being gene editing technology, which is undergoing the federal approval process. Advances in molecular genomics have been applied to gene editing for control of porcine reproductive and respiratory syndrome and to identify piglet genome contributions from each parent. Post-cervical artificial insemination technology is not novel, but this technology is now used extensively to accelerate the rate of genetic progress. A milestone was achieved with the discovery that dietary essential fatty acids, during lactation, were limiting reproduction. Their provision resulted in a dose-related response for pregnancy, pregnancy maintenance and litter size, especially in maturing sows and ultimately resolved seasonal infertility. The benefit of segregated early weaning (12 to 14 days of age) was realized for specific pathogen removal for genetic nucleus and multiplication. Application was premature for commercial practice, as piglet mortality and morbidity increased. Early weaning impairs intestinal barrier and mucosal innate immune development, which coincides with diminished resilience to pathogens and viability later in life. Two important milestones were achieved to improve precision nutrition for growing pigs. The first involved the updated publication of the National Research Council nutrient requirements for pigs, a collaboration between scientists from America and Canada. Precision nutrition advanced further when ingredient description, for metabolically available amino acids and net energy (by source plant), became a private sector nutrition product. The past decade also led to fortuitous discoveries of health-improving components in ingredients (xylanase, soybeans). Finally, two technologies converged to facilitate timely detection of multiple pathogens in a population: oral fluids sampling and polymerase chain reaction (PCR) for pathogen analysis. Most critical diseases in North America are now routinely monitored by oral fluid sampling and prepared for analysis using PCR methods.

Intestinal Hyperpermeability in Gulf War Veterans With Chronic Gastrointestinal Symptoms

BACKGROUND

Well over 700,000 United States military personnel participated in the Persian Gulf War in which they developed chronic health disorders of undetermined etiology. Up to 25% of Veterans had persistent and chronic gastrointestinal (GI) symptoms, which they suspected were related to their military service in the Gulf.

AIM

The overall aim of the current study was to evaluate intestinal permeability in previously deployed Gulf War Veterans who developed chronic GI symptoms during their tour in the Persian Gulf.

METHODS

To accomplish this, we evaluated intestinal permeability (IP) using the urinary lactulose/mannitol test. Measurements of intestinal permeability were then correlated with mean ratings of daily abdominal pain, frequency of bowel movements, and consistency of bowel movements on the Bristol Stool Scale in all Veterans.

RESULTS

A total of 73 veterans had documented chronic GI symptoms (diarrhea, abdominal pain) and were included in the study. A total of 29/73 (39%) of veterans has increased IP and had a higher average daily stool frequency (P<0.05); increased liquid stools as indicated by a higher Bristol Stool Scale (P<0.01); and a higher mean M-VAS abdominal pain rating (P<0.01). Pearson correlation coefficients revealed that there was a positive correlation between increased IP and stool frequency, Bristol Stool Scale, and M-VAS abdominal pain rating.

CONCLUSIONS

Our study demonstrates that deployed Gulf War Veterans with persistent GI symptoms commonly have increased intestinal permeability that potentiates the severity of abdominal pain, diarrhea, and stool consistency. These new findings in our study are important as they may lead to novel diagnostic biomarkers for returning Gulf War Veterans who suffer from chronic functional gastrointestinal disorders. These advances are also important for an increasing number of veterans who are now serving in the Persian Gulf and are at a high risk of developing these chronic pain disorders.

Spontaneous colitis in IL-10-deficient mice was ameliorated via inhibiting glutaminase1

Immunity imbalance and barrier damage in the intestinal mucosa are the main pathogenic factors of Crohn's disease (CD). Bis‐2‐(5‐phenylacetamido‐1,2,4‐thiadiazol‐2‐yl) ethyl sulfide (BPTES) is a glutaminase 1 (Gls1) inhibitor with the dual functions of increasing glutamine levels and immune regulation. In this study, we focused on the role of BPTES in CD‐like enteritis and the possible mechanisms. We found that Gls1 expression was significantly increased in CD intestinal tissue compared with control tissue. Bis‐2‐(5‐phenylacetamido‐1,2,4‐thiadiazol‐2‐yl) ethyl sulfide treatment significantly ameliorated chronic colitis in the IL‐10^−/−, as manifested by decreased disease activity index, body weight change, histological inflammatory degree and inflammatory cytokine expression. Bis‐2‐(5‐phenylacetamido‐1,2,4‐thiadiazol‐2‐yl) ethyl sulfide treatment exerted protective effects on CD that were associated with the maintenance of intestinal barrier integrity and the Th/Treg balance. Bis‐2‐(5‐phenylacetamido‐1,2,4‐thiadiazol‐2‐yl) ethyl sulfide treatment may act in part through TCR‐mediated mammalian target of rapamycin complex 1 (mTORC1) signalling activation. In conclusion, inhibition of Gls1 expression attenuated chronic colitis by maintaining intestinal barrier integrity and the Th/Treg balance, thereby ameliorating CD‐like colitis.

Coeliac disease: beyond genetic susceptibility and gluten. A narrative review

Coeliac disease (CD) is an immune-mediated disorder triggered by the ingestion of gluten in genetically susceptible individuals. However, only a small proportion of subjects harbouring CD-related genetic risk develop the disease. Among the environmental factors that may influence CD risk, pre- and perinatal factors, delivery methods, parental lifestyle, infant feeding practices, seasonality, dietary factors, drug use, childhood infections and variability in gut microbiota are those most widely studied regarding the risk to develop CD. Although for many of these external factors the exact mechanism of action is unknown, most of them are thought to act by disrupting the intestinal barrier, facilitating contact between potential antigens and the immune system effector cells. Management of CD is relatively easy in patients with a definite diagnosis and requires a strict, lifelong, gluten-free diet. Better knowledge of environmental exposures apart from gluten can facilitate understanding of the pathogenesis of the disorder and the wide heterogeneity of its clinical spectrum. The purpose of this review is to discuss current knowledge on environmental CD risk factors, as well as possible interaction between them, on the grounds of the reliable scientific evidence available. Key messages The risk of developing CD is influenced not only by gluten ingestion but also by a number of environmental factors including childhood infections and variability in gut microbiota, pre- and perinatal factors, infant feeding practices, delivery methods, parental lifestyle, seasonality, dietary factors and drug use, acting mainly by disrupting intestinal permeability. Better knowledge of exposure to these factors can facilitate their identification, and subsequent elimination, in the individual patient.

Astragaloside II promotes intestinal epithelial repair by enhancing L-arginine uptake and activating the mTOR pathway

Astragaloside II (AS II) extracted from Astragalus membranaceus has been reported to promote tissue wound repair. However, the effect of AS II on inflammatory bowel disease is unknown. We investigated the effects and mechanism of AS II on intestinal wound healing in both in vitro and in vivo models. Human intestinal Caco-2 cells were treated with multiple concentrations of AS II to assess cell proliferation, scratch wound closure, L-arginine uptake, cationic amino acid transporter activity, and activation of the mTOR signaling pathway. These effects were also measured in a mouse model of colitis. AS II promoted wound closure and increased cell proliferation, L-arginine uptake, CAT1 and CAT2 protein levels, total protein synthesis, and phosphorylation of mTOR, S6K, and 4E-BP1 in Caco-2 cells. These effects were suppressed by lysine or rapamycin treatment, suggesting that the enhanced arginine uptake mediates AS II-induced wound healing. Similar results were also observed in vivo. Our findings indicate that AS II can contribute to epithelial barrier repair following intestinal injury, and may offer a therapeutic avenue in treating irritable bowel disease.

Measurement of gut permeability using fluorescent tracer agent technology

The healthy gut restricts macromolecular and bacterial movement across tight junctions, while increased intestinal permeability accompanies many intestinal disorders. Dual sugar absorption tests, which measure intestinal permeability in humans, present challenges. Therefore, we asked if enterally administered fluorescent tracers could ascertain mucosal integrity, because transcutaneous measurement of differentially absorbed molecules could enable specimen-free evaluation of permeability. We induced small bowel injury in rats using high- (15 mg/kg), intermediate- (10 mg/kg), and low- (5 mg/kg) dose indomethacin. Then, we compared urinary ratios of enterally administered fluorescent tracers MB-402 and MB-301 to urinary ratios of sugar tracers lactulose and rhamnose. We also tested the ability of transcutaneous sensors to measure the ratios of absorbed fluorophores. Urinary fluorophore and sugar ratios reflect gut injury in an indomethacin dose dependent manner. The fluorophores generated smooth curvilinear ratio trajectories with wide dynamic ranges. The more chaotic sugar ratios had narrower dynamic ranges. Fluorophore ratios measured through the skin distinguished indomethacin-challenged from same day control rats. Enterally administered fluorophores can identify intestinal injury in a rat model. Fluorophore ratios are measureable through the skin, obviating drawbacks of dual sugar absorption tests. Pending validation, this technology should be considered for human use.

The glucocorticoid budesonide has protective and deleterious effects in experimental colitis in mice

Glucocorticoids are widely used for the management of inflammatory bowel disease, albeit with known limitations for long-term use and relevant adverse effects. In turn, they have harmful effects in experimental colitis. We aimed to explore the mechanism and possible implications of this phenomenon. Regular and microbiota depleted C57BL/6 mice were exposed to dextran sulfate sodium (DSS) to induce colitis and treated with budesonide. Colonic inflammation and animal status were compared. In vitro epithelial models of wound healing were used to confirm the effects of glucocorticoids. Budesonide was also tested in lymphocyte transfer colitis. Budesonide (1-60μg/day) exerted substantial colonic antiinflammatory effects in DSS colitis. At the same time, it aggravated body weight loss, increased rectal bleeding, and induced general deterioration of animal status, bacterial translocation and endotoxemia. As a result, there was an associated increase in parameters of sepsis, such as plasma NOx, IL-1β, IL-6, lung myeloperoxidase and iNOS, as well as significant hypothermia. Budesonide also enhanced DSS induced colonic damage in microbiota depleted mice. These effects were correlated with antiproliferative effects at the epithelial level, which are expected to impair wound healing. In contrast, budesonide had significant but greatly diminished deleterious effects in noncolitic mice or in mice with lymphocyte transfer colitis. We conclude that budesonide weakens mucosal barrier function by interfering with epithelial dynamics and dampening the immune response in the context of significant mucosal injury, causing sepsis. This may be a contributing factor, at least in part, limiting clinical usefulness of corticoids in inflammatory bowel disease.

Sacral nerve stimulation enhances early intestinal mucosal repair following mucosal injury in a pig model

KEY POINTS

Reducing intestinal epithelial barrier (IEB) dysfunctions is recognized as being of major therapeutic interest for various intestinal disorders. Sacral nerve stimulation (SNS) is known to reduce IEB permeability. Here, we report in a pig model that SNS enhances morphological and functional recovery of IEB following mucosal injury induced via 2,4,6-trinitrobenzenesulfonic acid. These effects are associated with an increased expression of tight junction proteins such as ZO-1 and FAK. These results establish that SNS enhances intestinal barrier repair in acute mucosal injury. They further set the scientific basis for future use of SNS as a complementary or alternative therapeutic option for the treatment of gut disorders with IEB dysfunctions such as inflammatory bowel diseases or irritable bowel syndrome.

ABSTRACT

Intestinal epithelial barrier (IEB) dysfunctions, such as increased permeability or altered healing, are central to intestinal disorders. Sacral nerve stimulation (SNS) is known to reduce IEB permeability, but its ability to modulate IEB repair remains unknown. This study aimed to characterize the impact of SNS on mucosal repair following 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced lesions. Six pigs were stimulated by SNS 3 h prior to and 3 h after TNBS enema, while sham animals (n = 8) were not stimulated. The impact of SNS on mucosal changes was evaluated by combining in vivo imaging, histological and functional methods. Biochemical and transcriptomic approaches were used to analyse the IEB and mucosal inflammatory response. We observed that SNS enhanced the recovery from TNBS-induced increase in transcellular permeability. At 24 h, TNBS-induced alterations of mucosal morphology were significantly less in SNS compared with sham animals. SNS reduced TNBS-induced changes in ZO-1 expression and its epithelial pericellular distribution, and also increased pFAK/FAK expression compared with sham. Interestingly, SNS increased the mucosal density of neutrophils, which was correlated with an increase in trypsin and TGF-β1 levels compared with sham. Finally, SNS prevented the TNBS-induced increases in IL-1β and IL-4 over time that were observed with sham treatment. In conclusion, our results show that SNS enhances mucosal repair following injury. This study highlights novel mechanisms of action of SNS and identifies SNS as a new therapy for diseases with IEB repair disorders.

Preventative Effects of Sodium Alginate on Indomethacin-induced Small-intestinal Injury in Mice

Recent advances in diagnostic technologies have revealed that nonsteroidal anti-inflammatory drugs (NSAIDs) can cause serious mucosal injury in the upper and lower gastrointestinal tract (including the small intestine). A drug to treat NSAID-induced small-intestinal injury (SII) is lacking. Sodium alginate is a soluble dietary fiber extracted from brown seaweed and its solution has been used as a hemostatic agent to treat gastrointestinal bleeding due to gastric ulcers. Whether sodium alginate has therapeutic effects on NSAID-induced SII and its mechanism of action are not known. Here, we investigated if administration of two forms (high-molecular-weight (HMW) and low-molecular-weight (LMW)) of sodium alginate could ameliorate indomethacin-induced SII. Pretreatment with HMW sodium alginate or LMW sodium alginate before indomethacin administration improved ulceration and the resultant intestinal shortening was associated with reduced histological severity of mucosal injury and ameliorated mRNA expression of inflammation-related molecules in the small intestine. We found that mRNAs of secretory Muc2 and membrane-associated Muc1, Muc3 and Muc4 were expressed in the small intestine. mRNA expression of Muc1-4 was increased in indomethacin-induced SII, and these increases were prevented by sodium alginate. Thus, administration of sodium alginate could be a therapeutic approach to prevent indomethacin-induced SII.

Increased serum levels of lipopolysaccharide and antiflagellin antibodies in patients with diarrhea-predominant irritable bowel syndrome

BACKGROUND

Innate immune responses to conserved microbial products such as lipopolysaccharide (LPS) and flagellin are likely important in microbial-host interactions and intestinal homeostasis. We hypothesized that bacterial translocation and activation of mucosal immunity against common microbial antigens might be involved in the development of irritable bowel syndrome (IBS). We therefore compared serum levels of LPS, soluble CD14 (sCD14), and flagellin antibodies between patients with different subtypes of IBS and healthy controls.

METHODS

We analyzed serum obtained from 88 patients (74 females) aged 19(43)-73 years and 106 healthy volunteers (77 females) aged 19(38)-62 years. Diarrhea-predominant IBS (D-IBS) was present in 32 patients (36%), 23 patients (26%) had constipation-predominant IBS (C-IBS), and 33 patients (38%) had A-IBS. We used ELISA for sCD14 and antiflagellin immunoglobulin G and limulus amebocyte assay for LPS. Abdominal symptoms and psychiatric comorbidities were assessed using validated questionnaires.

KEY RESULTS

We found a significantly higher serum level of LPS in patients with D-IBS compared to controls (p = 0.0155). The level of antibodies to flagellin was higher in patients with IBS than in controls (mainly driven by higher levels in D-IBS, p = 0.0018). The levels of sCD14 were lower in D-IBS patients compared to controls (p = 0.0498). We found a weak, but significant correlation between the levels of antiflagellin antibodies and anxiety among IBS patients (ρ = 0.38; p = 0.0045).

CONCLUSIONS & INFERENCES

Our results support the concept that immune reactivity to luminal antigens may have a role in the development of D-IBS. The serum level of antiflagellin antibodies was found to correlate with patients' self-reported anxiety score.

Transplantation of bone marrow-derived mesenchymal stem cells facilitates epithelial repair and relieves the impairment of gastrointestinal function in a rat model of enteritis

BACKGROUND

To examine whether the bone marrow-derived MSCs (BM-MSCs) could facilitate epithelial repair and thereby reduce impairment of gastrointestinal structure and function in chronic murine enteritis induced by indomethacin (IDM).

METHODS

MSCs were isolated from young Sprague-Dawley rats. After in vitro expansion and characterization, BM-MSCs were labelled with the fluorescent dye PKH26 and transfused, via the tail veins, into rats with enteritis induced by IDM. The controls were infused with sterile saline. The homing and differentiation of the transplanted BM-MSCs were tracked by means of fluorescent staining. The clinical symptoms of the IDM-treated rats were assessed, and the macroscopic and microscopic histological evaluations of the intestines were performed.

RESULTS

Compared to controls that received saline infusion, BM-MSCs treated rats showed lower scores of weight loss, stool consistency, and stool blood. The PKH26-labelled cells resided at the injured intestine, where they co-localize with the proliferating cell nuclear antigen (PCNA), Lgr-5, and Msi-1. The BM-MSCs treated rats showed significantly higher intestinal villi with larger areas relative to the saline-treated rats.

CONCLUSION

The transplanted BM-MSCs are able to recognize the injured intestine, where they proliferate and transdifferentiate into intestinal stem cells which repair the injured intestinal tissues. Therefore, BM-MSCs are able to relieve the impairment of gastrointestinal function in IMD-treated rats.

Cigarette smoking is associated with intestinal barrier dysfunction in the small intestine but not in the large intestine of mice

AIMS

To observe the effect of cigarette smoke (CS) on the small bowel and colon in mice and to attempt to explain the potential mechanisms that account for these effects.

METHODS

Male BALB/c mice age 6-8 weeks were randomly divided into a CS group and a control group (n=10 per group). CS mice were exposed to CS (five cigarettes each time, four times a day for 5 days a week using Hamburg II smoking machine and CS was diluted with air at a ratio of 1:6) for 10 weeks, and control mice were exposed to room air. After 10 weeks, mice were sacrificed for analysis (colon and small bowel).

RESULTS

CS exposure impaired the intestinal barrier of the small bowel, based on evidence that CS mice exhibited increased intestinal permeability, bacterial translocation, intestinal villi atrophy, damaged tight junctions and abnormal tight junction proteins. These changes were partly mediated through the activated NF-κB (p65) signalling pathway. However, no obvious changes associated with the intestinal barrier were identified in the small bowel of control mice or the colons of control or CS mice.

CONCLUSIONS

CS is associated with intestinal barrier dysfunction in the small intestine but not in the large intestine of mice.

Human gut dendritic cells drive aberrant gut-specific t-cell responses in ulcerative colitis, characterized by increased IL-4 production and loss of IL-22 and IFNγ

: The pathogenesis of inflammatory bowel disease is incompletely understood but results from a dysregulated intestinal immune response to the luminal microbiota. CD4 T cells mediate tissue injury in the inflammatory bowel disease-associated immune response. Dendritic cells (DC) generate primary T-cell responses and mediate intestinal immune tolerance to prevent overt inflammation in response to the gut microbiota. However, most information regarding function of intestinal DC has come from mouse models, and information in humans is scarce. We show here that intestinal DC subsets are skewed in ulcerative colitis (UC) in humans, with a loss of CD103 lymph-node homing DC; this intestinal DC subset preferentially generates regulatory T cells in mice. We show infiltrates of DC negative for myeloid marker CD11c, with enhanced expression of Toll-like receptors for bacterial recognition. After mixed leukocyte reaction, DC from the inflamed UC colon had an enhanced ability to generate gut-specific CD4 T cells with enhanced production of interleukin-4 but a loss of interferon γ and interleukin-22 production. Conditioning intestinal DC with probiotic strain Lactobacillus casei Shirota in UC partially restored their normal function indicated by reduced Toll-like receptor 2/4 expression and restoration of their ability to imprint homing molecules on T cells and to generate interleukin-22 production by stimulated T cells. This study suggests that T-cell dysfunction in UC is driven by DC. T-cell responses can be manipulated indirectly through effects of bacterial conditioning on gut DC with implications for immunomodulatory effects of the commensal microbiota in vivo. Manipulation of DC to allow generation of DC-specific therapy may be beneficial in inflammatory bowel disease.

The anti-inflammatory effects of a high-frequency oligodeoxynucleotide from the genomic DNA of Lactobacillus casei

Genomic DNA has been identified as an anti-inflammatory component of Lactobacillus species, the effects of which are mediated through toll-like receptor (TLR) 9. In this study, we identified 14 novel anti-inflammatory oligodeoxynucleotide (ODN) from the genomic DNA of Lactobacillus casei by measuring their effects on the secretion of interleukin (IL)-8 (CXCL8) in the human epithelial colorectal adenocarcinoma cell line Caco-2 cells. The ODN TTTTGCCG strongly decreased IL-8 secretion. In the genomic DNA of Lactobacillus species, the frequency of TTTTGCCG was highest in the genomic DNA of L. casei and similar among strains of L. casei. Decreases in inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 expressions in macrophage-like differentiated THP-1 cells confirmed the anti-inflammatory effect of TTTTGCCG. Furthermore, oral administration of TTTTGCCG ameliorated dextran sodium sulfate (DSS)-induced murine colitis and DSS-induced increased expression of inflammatory factor mRNAs, such as macrophage inflammatory protein (MIP)-2 (CXCL2), iNOS, and COX-2. The anti-inflammatory effect of TTTTGCCG was mainly regulated by an increase in heat shock protein (Hsp) 70 expression in the epithelium. TLR9 and Hsp90 may primarily mediate the anti-inflammatory effect of TTTTGCCG on Hsp70 signaling.

Sodium alginate ameliorates indomethacin-induced gastrointestinal mucosal injury via inhibiting translocation in rats

AIM: To investigate the effects of sodium alginate (AL-Na) on indomethacin-induced small intestinal lesions in rats.

METHODS: Gastric injury was assessed by measuring ulcerated legions 4 h after indomethacin (25 mg/kg) administration. Small intestinal injury was assessed by measuring ulcerated legions 24 h after indomethacin (10 mg/kg) administration. AL-Na and rebamipide were orally administered. Myeloperoxidase activity in the stomach and intestine were measured. Microvascular permeability, superoxide dismutase content, glutathione peroxidase activity, catalase activity, red blood cell count, white blood cell count, mucin content and enterobacterial count in the small intestine were measured.

RESULTS: AL-Na significantly reduced indomethacin-induced ulcer size and myeloperoxidase activity in the stomach and small intestine. AL-Na prevented increases in microvascular permeability, superoxide dismutase content, glutathione peroxidase activity and catalase activity in small intestinal injury induced by indomethacin. AL-Na also prevented decreases in red blood cells and white blood cells in small intestinal injury induced by indomethacin. Moreover, AL-Na suppressed mucin depletion by indomethacin and inhibited infiltration of enterobacteria into the small intestine.

CONCLUSION: These results indicate that AL-Na ameliorates non-steroidal anti-inflammatory drug-induced small intestinal enteritis via bacterial translocation.

Pathogenesis implication for necrotizing enterocolitis prevention in preterm very-low-birth-weight infants

Recent reports show that the incidence of and deaths caused by necrotizing enterocolitis (NEC) in preterm very-low-birth-weight (PVLBW) infants are on the rise. Unfortunately, NEC often rapidly progresses from early signs of intestinal inflammation to extensive necrosis within a matter of hours, making treatment and secondary prevention extremely difficult to achieve. Primary prevention should thus be the priority. Recent studies provide information that enhances our understanding of the pathophysiology and provides more practical options for the prevention of NEC. The most accepted hypothesis at present is that enteral feeding (providing substrate) in the presence of abnormal intestinal colonization by pathogens provokes an inappropriately heightened inflammatory response in immature intestinal epithelial cells of PVLBW infants. Seventy-four relevant articles were reviewed. Our focus was on the present understanding of the pathophysiology of NEC in the context of developing optimal strategies to prevent NEC in PVLBW infants. Strategies such as antenatal glucocorticoids, postnatal breast milk feeding, and cautious approach to enteral feeding failed to eliminate NEC in PVLBW infants because these strategies did not address the complexity of the pathogenesis. Probiotics seem to be the most significant advance in NEC prevention at present because of the significant range of beneficial effects at various levels of gut function and defense mechanism and the present evidence based on 19 randomized controlled trials.

Luminal cysteine-proteases degrade colonic tight junction structure and are responsible for abdominal pain in constipation-predominant IBS

OBJECTIVES

Luminal serine-proteases lead to increased colonic paracellular permeability and visceral hypersensitivity in patients with diarrhea-predominant irritable bowel syndrome (IBS-D). Other proteases, namely cysteine-proteases (CPs), increase airway permeability by digesting epithelial tight junction proteins. In this study, we focused on constipation-predominant IBS (IBS-C) and we aimed to (i) evaluate CP levels in two cohorts of IBS patients, (ii) test if IBS-C fecal supernatant (FSN) affects permeability, and visceral sensitivity after repeated administrations in mice, and (iii) evaluate occludin expression in IBS-C colonic biopsies.

METHODS

Fecal CP activity was determined using selective substrate and inhibitor (E64). The effect of papain, as positive control, and IBS-C FSN administrations were evaluated on colonic paracellular permeability and mucosal occludin levels in mice and T84 monolayers. Occludin protein levels were evaluated in IBS-C colonic biopsies. Sensitivity to colorectal distension (CRD) was measured after repeated administrations of IBS-C FSN.

RESULTS

We found in a subset of IBS-C patients an enhanced fecal CP activity, in comparison with healthy controls and IBS-D patients. CP activity levels positively correlated with disease severity and abdominal pain scoring. This association was confirmed by receiver operating characteristic curve analysis. In mice, repeated application of IBS-C FSN into colon triggered increased permeability, linked to the enzymatic degradation of occludin, and was associated with enhanced visceral sensitivity to CRD. Finally, occludin levels were found decreased in colonic biopsies from IBS-C patients, and IBS-C FSNs were able to degrade recombinant human occludin in vitro. All these effects were abolished by preincubation of IBS-C FSN with a CP inhibitor, E64.

CONCLUSIONS

These data suggest that luminal CPs may represent a new factor contributing to the genesis of symptoms in IBS.

Prevention of necrotizing enterocolitis in preterm very low birth weight infants: is it feasible?

Necrotizing enterocolitis (NEC) is still one of the most catastrophic intestinal emergencies in preterm very low-birth weight infants. Primary prevention of NEC should be the priority, since NEC frequently progresses from nonspecific signs, to extensive necrosis within a matter of hours with medical or surgical treatment, making successful treatment and secondary prevention difficult to achieve. Currently available strategies for primary prevention of NEC include antenatal glucocorticosteroids, breast milk feeding, cautious feeding strategy, fluid restriction and probiotics. Nonetheless, based on current research evidence, mixed flora probiotics, and/or breast milk feeding, would appear to be the most effective feasible methods in the prevention of NEC at present.

miR-200b inhibits TGF-β1-induced epithelial-mesenchymal transition and promotes growth of intestinal epithelial cells

Inflammatory bowel disease (IBD), which consists of Crohn's disease (CD) and ulcerative colitis (UC), is a chronic, inflammatory disorder of the gastro-intestinal tract with unknown etiology. Current evidence suggests that intestinal epithelial cells (IECs) is prominently linked to the pathogenesis of IBD. Therefore, maintaining the intact of epithelium has potential roles in improving pathophysiology and clinical outcomes of IBD. MicroRNAs (miRNAs) act as post-transcriptional gene regulators and regulate many biological processes, including embryonal development, cell differentiation, apoptosis and proliferation. In this study, we found that miR-200b decreased significantly in inflamed mucosa of IBD, especially for UC, when compared with their adjacent normal tissue. Simultaneously, we also found that the genes of E-cadherin and cyclin D1 were reduced significantly and correlated positively to the miR-200b. In addition, the upregulation of transforming growth factor-beta 1 (TGF-β1) was inversely correlated to the miR-200b in IBD. To investigate the possible roles of miR-200b in IECs maintaining, we used TGF-β1 to induce epithelial-mesenchymal transition (EMT) in IEC-6 initially. After sustained over-expressing miR-200b in IEC-6, the EMT was inhibited significantly that was characterized by downregulation of vimentin and upregulation of E-cadherin. Furthermore, we found that miR-200b enhanced E-cadherin expression through targeting of ZEB1, which encode transcriptional repressors of E-cadherin. SMAD2 was found to act as a target of miR-200b with direct evidence that miR-200b binding to the 3′ UTR of SAMD2 and the ability of miR-200b to repress SMAD2 protein expression. With SMAD2 depletion, the expression of vimentin decreased correspondingly, which suggested miR-200b might reduce vimentin through regulating the SMAD2. With endogenous over-expression of miR-200b, the proliferation of IEC-6 cells increased significantly by increasing S-phase entry and promoting expression of the protein cyclin D1. Summarily, our study suggested a potential role for mir-200b in maintaining intact of intestinal epithelium through inhibiting EMT and promoting proliferation of IECs.

Matriptase protects against experimental colitis and promotes intestinal barrier recovery

BACKGROUND

Matriptase is a membrane-anchored serine protease encoded by suppression of tumorigenicity-14 (ST14) that is required for epithelial barrier homeostasis. However, its functional role in inflammatory bowel disease (IBD) is unexplored.

METHODS

Matriptase expression in control, Crohn's disease, and ulcerative colitis tissue specimens was studied by quantitative polymerase chain reaction (qPCR) and immunostaining. Matriptase function was investigated by subjecting St14 hypomorphic and control littermates to dextran sodium sulfate (DSS)-induced colitis and by siRNA silencing in cultured monolayers. Mice were analyzed for clinical, histological, molecular, and cellular effects.

RESULTS

Matriptase protein and ST14 mRNA levels are significantly downregulated in inflamed colonic tissues from Crohn's disease and ulcerative colitis patients. Matriptase-deficient St14 hypomorphic mice administered DSS for 7 days followed by water without DSS for 3 days develop a severe colitis, with only 30% of the St14 hypomorphic mice surviving to day 14, compared with 100% of control littermates. Persistent colitis in surviving St14 hypomorphic mice was associated with sustained cytokine production, an inability to recover barrier integrity, and enhanced claudin-2 expression. Cytokines implicated in barrier disruption during IBD suppress matriptase expression in T84 epithelial monolayers and restoration of matriptase improves barrier integrity in the cytokine-perturbed monolayers.

CONCLUSIONS

These data demonstrate a critical role for matriptase in restoring barrier function to injured intestinal mucosa during colitis, which is suppressed by excessive activation of the immune system. Strategies to enhance matriptase-mediated barrier recovery could be important for intervening in the cycle of inflammation associated with IBD.

Chronic gastrointestinal consequences of acute infectious diarrhea: evolving concepts in epidemiology and pathogenesis

Acute infectious diarrhea is a frequent occurrence both in the developing world, where it results in considerable mortality, and in developed countries, where it accounts for a significant number of health visits, hospitalizations, and medical and non-medical losses. Recent evidence in basic, clinical, and epidemiological science domains has emerged that suggest that the burden caused by these infections is not limited to the acute illness, but may result in triggering or contributing to the pathogenesis of a number of chronic health problems. This review considers the breadth of this information for the purpose of consolidating what is currently known, identifying gaps in knowledge, and describing future directions and policy implications related to the chronic consequences of acute infectious diarrhea. A unifying hypothesis of this review is that infections may trigger a number of long-lasting changes in gut physiology and immunity that can increase the risk to a variety of chronic gastrointestinal diseases, particularly in genetically susceptible individuals.

Decreased leukocyte recruitment by inorganic nitrate and nitrite in microvascular inflammation and NSAID-induced intestinal injury

Nitric oxide (NO) generated by vascular NO synthases can exert anti-inflammatory effects, partly through its ability to decrease leukocyte recruitment. Inorganic nitrate and nitrite, from endogenous or dietary sources, have emerged as alternative substrates for NO formation in mammals. Bioactivation of nitrate is believed to require initial reduction to nitrite by oral commensal bacteria. Here we investigated the effects of inorganic nitrate and nitrite on leukocyte recruitment in microvascular inflammation and in NSAID-induced small-intestinal injury. We show that leukocyte emigration in response to the proinflammatory chemokine MIP-2 is reduced by 70% after 7 days of dietary nitrate supplementation as well as by acute intravenous nitrite administration. Nitrite also reduced leukocyte adhesion to a similar extent and this effect was inhibited by the soluble guanylyl cyclase inhibitor ODQ, whereas the effect on emigrated leukocytes was not altered by this treatment. Further studies in TNF-α-stimulated endothelial cells revealed that nitrite dose-dependently reduced the expression of ICAM-1. In rats and mice subjected to a challenge with diclofenac, dietary nitrate prevented the increase in myeloperoxidase and P-selectin levels in small-intestinal tissue. Antiseptic mouthwash, which eliminates oral nitrate reduction, markedly blunted the protective effect of dietary nitrate on P-selectin levels. Despite attenuation of the acute immune response, the overall ability to clear an infection with Staphylococcus aureus was not suppressed by dietary nitrate as revealed by noninvasive IVIS imaging. We conclude that dietary nitrate markedly reduces leukocyte recruitment to inflammation in a process involving attenuation of P-selectin and ICAM-1 upregulation. Bioactivation of dietary nitrate requires intermediate formation of nitrite by oral nitrate-reducing bacteria and then probably further reduction to NO and other bioactive nitrogen oxides in the tissues.

Stress-induced visceral analgesia assessed non-invasively in rats is enhanced by prebiotic diet

AIM

To investigate the influence of repeated water avoidance stress (rWAS) on the visceromotor response (VMR) to colorectal distension (CRD) and the modulation of the response by a prebiotic diet in rats using a novel surgery-free method of solid-state manometry.

METHODS

Male Wistar rats fed a standard diet with or without 4% enzyme-treated rice fiber (ERF) for 5 wk were subjected to rWAS (1 h daily x 10 d) or no stress. The VMR to graded phasic CRD was assessed by intraluminal colonic pressure recording on days 0 (baseline), 1 and 10 (45 min) and 11 (24 h) after rWAS and expressed as percentage change from baseline. Cecal content of short chain fatty acids and distal colonic histology were assessed on day 11.

RESULTS

WAS on day 1 reduced the VMR to CRD at 40 and 60 mmHg similarly by 28.9% ± 6.6% in both diet groups. On day 10, rWAS-induced reduction of VMR occurred only at 40 mmHg in the standard diet group (36.2% ± 17.8%) while in the ERF group VMR was lowered at 20, 40 and 60 mmHg by 64.9% ± 20.9%, 49.3% ± 11.6% and 38.9% ± 7.3% respectively. The visceral analgesia was still observed on day 11 in ERF- but not in standard diet-fed rats. By contrast the non-stressed groups (standard or ERF diet) exhibited no changes in VMR to CRD. In standard diet-fed rats, rWAS induced mild colonic histological changes that were absent in ERF-fed rats exposed to stress compared to non-stressed rats. The reduction of cecal content of isobutyrate and total butyrate, but not butyrate alone, was correlated with lower visceral pain response. Additionally, ERF diet increased rWAS-induced defecation by 26% and 75% during the first 0-15 min and last 15-60 min, respectively, compared to standard diet, and reduced rats' body weight gain by 1.3 fold independently of their stress status.

CONCLUSION

These data provide the first evidence of psychological stress-related visceral analgesia in rats that was enhanced by chronic intake of ERF prebiotic.

Ileal inducible nitric oxide synthase mRNA expression in response to stress is modified in Sprague-Dawley rats exposed to a previous intestinal inflammation

The ability of stress to initiate or reactivate an inflammatory process seems to depend on an individual's susceptibility to stressful stimuli. The aim of this study was to establish whether previous inflammation alters the response to stress in Sprague-Dawley rats, a strain not especially susceptible to stressful stimuli. Stress exposure was performed in rats treated with indomethacin, to induce cyclic intestinal inflammation, during the inactive phase of inflammation. Both control and indomethacin-treated rats submitted to stress showed a decrease in body weight gain and blood leukocyte levels, as well as an increase in fecal pellet output. The increase in intestinal mucosal mast cell count induced by stress was similar in both groups of animals. Moreover, no differences were observed between control and indomethacin-treated rats in the degree of bacterial translocation and myeloperoxidase levels after stress exposure. Despite these similarities, differences between groups were observed in inducible nitric oxide synthase (iNOS) mRNA expression. Although ileal iNOS mRNA expression was inhibited in healthy rats submitted to stress, stress failed to modify this parameter in indomethacin-treated rats. As iNOS is another inflammatory marker, our results may allow the possibility that a previous intestinal inflammation could change the intestinal susceptibility to stress. Whether these differences in ileal iNOS expression can be indicative of a possible change in the predisposition to develop an intestinal inflammatory reaction in response to stress in Sprague-Dawley rats remains to be elucidated.

Neonatal maternal separation in male rats increases intestinal permeability and affects behavior after chronic social stress

Prolonged maternal separation in rats has several effects on health and behavior. Here we investigated how maternal separation might interact with social stress in adulthood on behavior and gastrointenstinal permeability. The effects of either daily 180 min long term pup-dam separation (LMS) during the stress hyporesponsive period or daily 10 min brief maternal separation (BMS) on behavior, corticosterone and intestinal permeability were investigated, compared to a non-handling (NH) condition in male offspring. The animals from each separation condition were then randomly assigned to adult stress and control conditions, where the stress condition was exposure to 14 days of social instability (CSI). Sucrose preference, elevated plus maze behavior and corticosterone were measured. Colitis was experimentally induced by dextran sulfate sodium for 7 days, followed by measurement of intestinal permeability using the (51)CrEDTA method. Granulocyte marker protein was measured in feces and colons were examined histologically for inflammation. Prior to the social stress, the LMS offspring showed elevated corticosterone levels, lower elevated plus maze activity and less fluid consumption. After social stress, corticosterone levels were suppressed in LMS animals and again they showed less fluid consumption. LMS animals had significantly higher intestinal permeability, but only when also exposed to the social stress in adulthood. The current results support a two-hit model, whereby early life events interact with adult life events in altering animals' vulnerability.

The immune system in irritable bowel syndrome

The potential relevance of systemic and gastrointestinal immune activation in the pathophysiology and symptom generation in the irritable bowel syndrome (IBS) is supported by a number of observations. Infectious gastroenteritis is the strongest risk factor for the development of IBS and increased rates of IBS-like symptoms have been detected in patients with inflammatory bowel disease in remission or in celiac disease patients on a gluten free diet. The number of T cells and mast cells in the small and large intestine of patients with IBS is increased in a large proportion of patients with IBS over healthy controls. Mediators released by immune cells and likely from other non-immune competent cells impact on the function of enteric and sensory afferent nerves as well as on epithelial tight junctions controlling mucosal barrier of recipient animals, isolated human gut tissues or cell culture systems. Antibodies against microbiota antigens (bacterial flagellin), and increased levels of cytokines have been detected systemically in the peripheral blood advocating the existence of abnormal host-microbial interactions and systemic immune responses. Nonetheless, there is wide overlap of data obtained in healthy controls; in addition, the subsets of patients showing immune activation have yet to be clearly identified. Gender, age, geographic differences, genetic predisposition, diet and differences in the intestinal microbiota likely play a role and further research has to be done to clarify their relevance as potential mechanisms in the described immune system dysregulation. Immune activation has stimulated interest for the potential identification of biomarkers useful for clinical and research purposes and the development of novel therapeutic approaches.

Function of the intestinal epithelium and its dysregulation in inflammatory bowel disease

The intestinal epithelium not only acts as a physical barrier to commensal bacteria and foreign antigens but is also actively involved in antigen processing and immune cell regulation. The inflammatory bowel diseases (IBDs) are characterized by inflammation at this mucosal surface with well-recognized defects in barrier and secretory function. In addition to this, defects in intraepithelial lymphocytes, chemokine receptors, and pattern recognition receptors promote an abnormal immune response, with increased differentiation of proinflammatory cells and a dysregulated relationship with professional antigen-presenting cells. This review focuses on recent developments in the structure of the epithelium, including a detailed account of the apical junctional complex in addition to the role of the enterocyte in antigen recognition, uptake, processing, and presentation. Recently described cytokines such as interleukin-22 and interleukin-31 are highlighted as is the dysregulation of chemokines and secretory IgA in IBD. Finally, the effect of the intestinal epithelial cell on T effector cell proliferation and differentiation are examined in the context of IBD with particular focus on T regulatory cells and the two-way interaction between the intestinal epithelial cell and certain immune cell populations.

Campylobacter jejuni induces transcytosis of commensal bacteria across the intestinal epithelium through M-like cells

BACKGROUND

Recent epidemiological analyses have implicated acute Campylobacter enteritis as a factor that may incite or exacerbate inflammatory bowel disease (IBD) in susceptible individuals. We have demonstrated previously that C. jejuni disrupts the intestinal barrier function by rapidly inducing epithelial translocation of non-invasive commensal bacteria via a transcellular lipid raft-mediated mechanism ('transcytosis'). To further characterize this mechanism, the aim of this current study was to elucidate whether C. jejuni utilizes M cells to facilitate transcytosis of commensal intestinal bacteria.

RESULTS

C. jejuni induced translocation of non-invasive E. coli across confluent Caco-2 epithelial monolayers in the absence of disrupted transepithelial electrical resistance or increased permeability to a 3 kDa dextran probe. C. jejuni-infected monolayers displayed increased numbers of cells expressing the M cell-specific marker, galectin-9, reduced numbers of enterocytes that stained with the absorptive enterocyte marker, Ulex europaeus agglutinin-1, and reduced activities of enzymes typically associated with absorptive enterocytes (namely alkaline phosphatase, lactase, and sucrase). Furthermore, in Campylobacter-infected monolayers, E. coli were observed to be internalized specifically within epithelial cells displaying M-like cell characteristics.

CONCLUSION

These data indicate that C. jejuni may utilize M cells to promote transcytosis of non-invasive bacteria across the intact intestinal epithelial barrier. This mechanism may contribute to the inflammatory immune responses against commensal intestinal bacteria commonly observed in IBD patients.

Campylobacter jejuni induces transcytosis of commensal bacteria across the intestinal epithelium through M-like cells

BACKGROUND

Recent epidemiological analyses have implicated acute Campylobacter enteritis as a factor that may incite or exacerbate inflammatory bowel disease (IBD) in susceptible individuals. We have demonstrated previously that C. jejuni disrupts the intestinal barrier function by rapidly inducing epithelial translocation of non-invasive commensal bacteria via a transcellular lipid raft-mediated mechanism ('transcytosis'). To further characterize this mechanism, the aim of this current study was to elucidate whether C. jejuni utilizes M cells to facilitate transcytosis of commensal intestinal bacteria.

RESULTS

C. jejuni induced translocation of non-invasive E. coli across confluent Caco-2 epithelial monolayers in the absence of disrupted transepithelial electrical resistance or increased permeability to a 3 kDa dextran probe. C. jejuni-infected monolayers displayed increased numbers of cells expressing the M cell-specific marker, galectin-9, reduced numbers of enterocytes that stained with the absorptive enterocyte marker, Ulex europaeus agglutinin-1, and reduced activities of enzymes typically associated with absorptive enterocytes (namely alkaline phosphatase, lactase, and sucrase). Furthermore, in Campylobacter-infected monolayers, E. coli were observed to be internalized specifically within epithelial cells displaying M-like cell characteristics.

CONCLUSION

These data indicate that C. jejuni may utilize M cells to promote transcytosis of non-invasive bacteria across the intact intestinal epithelial barrier. This mechanism may contribute to the inflammatory immune responses against commensal intestinal bacteria commonly observed in IBD patients.

Understanding measurements of intestinal permeability in healthy humans with urine lactulose and mannitol excretion

Our aim was to understand the information from differential two-sugar excretion (2-SE) in measuring intestinal permeability. In a crossover study in 12 healthy volunteers, we compared urinary excretion ratios of lactulose (L) to mannitol [(M) LMR] after ingestion in liquid formulation (LF) or in delayed-release, methacrylate-coated capsules (CAP). Both formulations were radiolabelled. Urine was collected every 2 h from 0 to 8 h, and from 8 to 24 h. Two hours after LF, gastric residual was 15.9 +/- 6.2% (SEM), and the percentage in colon was 49.6 +/- 7.8%; in 11/12 participants, liquid had entered colon within 2 h. Average CAP arrival time in colon was 5.16 +/- 0.46 h (mode 6 h). After LF, mannitol was extensively absorbed in the first 8 h; lactulose absorption was low throughout the 24 h. After the LF, the LMR (geometric mean, 95% CI per h) in the 0-2 h urine was [0.08 (0.05, 0.11)], which was lower than in 8-24 h urine [0.32 (0.16, 0.46); P < 0.05]. Urine LMRs at 8-24 h were similar after LF or CAP. We concluded that, after LF, sugar excretion in 0-2 h urine may reflect both SI and colon permeability. Colonic permeability is reflected by urine sugar excretion between 6 and 24 h. CAP delivery reduces mannitol excreted at 0-6 h, compared with LF. The 0-5 or 6 h 2-SE urine likely reflects both SI and colon permeability; the higher LMR in the 8-24 h urine relative to 0-2 h urine should be interpreted with caution and does not mean that colon is more permeable than SI.

A role for Campylobacter jejuni-induced enteritis in inflammatory bowel disease?

The inflammatory bowel diseases (IBD), Crohn's disease and ulcerative colitis, are T cell-mediated diseases that are characterized by chronic, relapsing inflammation of the intestinal tract. The pathogenesis of IBD involves the complex interaction between the intestinal microflora, host genetic and immune factors, and environmental stimuli. Epidemiological analyses have implicated acute bacterial enteritis as one of the factors that may incite or exacerbate IBD in susceptible individuals. In this review, we examine how interactions between the common enteric pathogen Campylobacter jejuni (C. jejuni), the host intestinal epithelium, and resident intestinal microflora may contribute to the pathogenesis of IBD. Recent experimental evidence indicates that C. jejuni may permit the translocation of normal, noninvasive microflora via novel processes that implicate epithelial lipid rafts. This breach in intestinal barrier function may, in turn, prime the intestine for chronic inflammatory responses in susceptible individuals. Insights into the interactions between enteric pathogens, the host epithelia, and intestinal microflora will improve our understanding of disease processes that may initiate and/or exacerbate intestinal inflammation in patients with IBD and provide impetus for the development of new therapeutic approaches for the treatment of IBD.

Intestinal membrane permeability and hypersensitivity in the irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder in which the underlying pathophysiology is poorly understood; however, increased intestinal permeability in diarrhea-predominant IBS patients has been reported. Here we demonstrate that diarrhea-predominant IBS (D-IBS) patients display increased intestinal permeability. We have also found that increased intestinal membrane permeability is associated with visceral and thermal hypersensitivity in this subset of D-IBS patients. We evaluated 54 D-IBS patients and 22 controls for intestinal membrane permeability using the lactulose/mannitol method. All subjects ingested 5g of lactulose and 2g of mannitol in 100ml of water after which their urine was collected. We also evaluated the mean mechanical visual analogue scale (M-VAS) pain rating to nociceptive thermal and visceral stimulation in all subjects. All study participants also completed the FBDSI scale. Approximately 39% of diarrhea-predominant IBS patients had increased intestinal membrane permeability as measured by the lactulose/mannitol ratio. These IBS patients also demonstrated higher M-VAS pain intensity reading scale. Interestingly, the IBS patients with hypersensitivity and increased intestinal permeability had a higher FBDSI score (100.8 + or - 5.4) than IBS patients with normal membrane permeability and sensitivity (51.6 + or - 12.7) and controls (6.1 + or - 5.6) (p<0.001). A subset of D-IBS patients had increased intestinal membrane permeability that was associated with an increased FBDSI score and increased hypersensitivity to visceral and thermal nociceptive pain stimuli. Thus, increased intestinal membrane permeability in D-IBS patients may lead to more severe IBS symptoms and hypersensitivity to somatic and visceral stimuli.

Innate and adaptive immunity cooperate flexibly to maintain host-microbiota mutualism

Commensal bacteria in the lower intestine of mammals are 10 times as numerous as the body's cells. We investigated the relative importance of different immune mechanisms in limiting the spread of the intestinal microbiota. Here, we reveal a flexible continuum between innate and adaptive immune function in containing commensal microbes. Mice deficient in critical innate immune functions such as Toll-like receptor signaling or oxidative burst production spontaneously produce high-titer serum antibodies against their commensal microbiota. These antibody responses are functionally essential to maintain host-commensal mutualism in vivo in the face of innate immune deficiency. Spontaneous hyper-activation of adaptive immunity against the intestinal microbiota, secondary to innate immune deficiency, may clarify the underlying mechanisms of inflammatory diseases where immune dysfunction is implicated.

Host responses to intestinal microbial antigens in gluten-sensitive mice

BACKGROUND AND AIMS

Excessive uptake of commensal bacterial antigens through a permeable intestinal barrier may influence host responses to specific antigen in a genetically predisposed host. The aim of this study was to investigate whether intestinal barrier dysfunction induced by indomethacin treatment affects the host response to intestinal microbiota in gluten-sensitized HLA-DQ8/HCD4 mice.

METHODOLOGY/PRINCIPAL FINDINGS

HLA-DQ8/HCD4 mice were sensitized with gluten, and gavaged with indomethacin plus gluten. Intestinal permeability was assessed by Ussing chamber; epithelial cell (EC) ultra-structure by electron microscopy; RNA expression of genes coding for junctional proteins by Q-real-time PCR; immune response by in-vitro antigen-specific T-cell proliferation and cytokine analysis by cytometric bead array; intestinal microbiota by fluorescence in situ hybridization and analysis of systemic antibodies against intestinal microbiota by surface staining of live bacteria with serum followed by FACS analysis. Indomethacin led to a more pronounced increase in intestinal permeability in gluten-sensitized mice. These changes were accompanied by severe EC damage, decreased E-cadherin RNA level, elevated IFN-gamma in splenocyte culture supernatant, and production of significant IgM antibody against intestinal microbiota.

CONCLUSION

Indomethacin potentiates barrier dysfunction and EC injury induced by gluten, affects systemic IFN-gamma production and the host response to intestinal microbiota antigens in HLA-DQ8/HCD4 mice. The results suggest that environmental factors that alter the intestinal barrier may predispose individuals to an increased susceptibility to gluten through a bystander immune activation to intestinal microbiota.

Host species-specific translocation of Escherichia coli

The purpose of this paper is to investigate the rate of translocation of Escherichia coli strains in different experimental/animal models. Four proficient translocating E. coli strains isolated from mesenteric lymph nodes (MLNs) and/or the blood of rats (strains KIC-1 and KIC-2), from a fatal case of pancreatitis (HMLN-1) and from pigs (PC-1 isolated in this study) were tested for their ability to translocate across two host species and the Caco-2 cell line as a model of the human gut epithelium. HMLN-1 was found in the MLNs of all 15 pigs tested. This strain, however, did not translocate in any rats and only colonised the caecum of four rats in small numbers. HMLN-1 and PC-1 were the dominant translocating strains in Caco-2 cells compared to KIC-1 and KIC-2, which were found to translocate at a lower rate in pigs and in Caco-2 cells. The rate of translocation of PC-1 in rats was also very low compared to KIC-1 and KIC-2. We suggest that, in studies aiming to investigate the mechanism of translocation of E. coli strains isolated from humans, rats may not be an appropriate animal model and that the Caco-2 cells or pigs are more suitable in vitro and in vivo models, respectively.

Acute stress increases colonic paracellular permeability in mice through a mast cell-independent mechanism: involvement of pancreatic trypsin

AIMS

Increased colonic paracellular permeability (CPP) is a key feature of gastro-intestinal disorders as irritable bowel syndrome and inflammatory bowel diseases. Stress stimulates exocrine pancreatic secretion through cholinergic pathways, and trypsin is known to increase CPP. Consequently we have investigated in this work whether trypsin released into the gut lumen following an acute stress may participate to the short-term increase in CPP.

MAIN METHODS

Mice were treated with atropine or a non-selective CRF (corticotropin-releasing factor) receptor antagonist (alpha-helical CRF (9-41)), before being submitted to a 2-h stress session. Then, CPP and protease activity in colonic contents (total proteolytic, trypsin activity, and mouse mast cell protease (MMCP)-1 levels) were determined. The effects of colonic contents from sham-stressed or stressed animals on CPP were evaluated in mice colonic tissues mounted in Ussing chambers, in presence or not of soybean trypsin inhibitor (SBTI) or FSLLRY, a protease-activated receptor-2 (PAR2) antagonist.

KEY FINDINGS

Acute stress significantly increased CPP, proteolytic and trypsin activities, and MMCP-1 levels. Atropine inhibited stress-induced impairment of CPP and strongly diminished total proteolytic and trypsin activities in stressed animals, but not MMCP-1 levels. Colonic contents from stressed animals increased CPP in mice tissues, this effect being inhibited by SBTI and PAR2 antagonist.

SIGNIFICANCE

Acute stress activates cholinergic pathways, to trigger exocrine pancreatic secretion. Trypsin, released in these conditions, may be responsible for colonic barrier alterations through the activation of PAR2.

Bacterial-mucosal interactions in inflammatory bowel disease: an alliance gone bad

The complex interaction of genetic, microbial, and environmental factors may result in continuous activation of the mucosal immune system leading to inflammatory bowel disease (IBD). Most present treatments for IBD involve altering or suppressing the aberrant immune response; however, the role of the intestinal microbiota in the pathophysiology of IBD is becoming more evident. The epithelial layer is essential for the proper functioning of the gastrointestinal tract, and its increased permeability to the luminal antigens may lead to the inflammatory processes and mucosal damage observed in IBD. Factors affecting the efficacy of the epithelial barrier include presence of pathogenic bacteria (e.g., Helicobacter spp.), presence of probiotic bacteria, availability of selected nutrients, and others. Defective function of the mucosal barrier might facilitate the contact of bacterial antigens and adjuvants with innate and adaptive immune cells to generate prolonged inflammatory responses. This review will briefly describe the complex structure of the epithelial barrier in the context of bacterial-mucosal interactions observed in human IBD and mouse models of colitis.