Role of TNF-alpha in ileum tight junction alteration in mouse model of restraint stress

Curcumin attenuates aflatoxin B1-induced ileum injury in ducks by inhibiting NLRP3 inflammasome and regulating TLR4/NF-κB signaling pathway

Aflatoxin B1 (AFB1) is a widespread toxic contamination in feed for animals. The primary active component of turmeric, curcumin (Cur), is an antioxidant and an anti-inflammatory. However, it is yet unknown how AFB1 affects the intestinal epithelial barrier and whether Cur acts as a protective mechanism when exposed to AFB1. Here, we explored the mechanism of AFB1-induced intestinal injury from intestinal epithelial barrier, inflammation, pyroptosis, and intestinal flora, and evaluated the protective role of Cur. We found that AFB1 caused weight loss and intestinal morphological damage that is mainly characterized by shortened intestinal villi, deepened crypts, and damaged intestinal epithelium. Exposure to AFB1 decreased the expression of Claudin-1, MUC2, ZO-1, and Occludin and increased the expression of pyroptosis-related factors (NLRP3, GSDMD, Caspase-1, IL-1β, and IL-18) and inflammation-related factors (TLR4, NF-κB, IκB, IFN-γ, and TNF-α). Furthermore, ileal gut microbiota was altered, and simultaneously, the Lactobacillus abundance was decreased. The gut microbiota interacts with a wide range of physiologic functions and disease development in the host through its metabolites, and disturbances in gut microbial metabolism can cause functional impairment of the ileum. Meanwhile, Cur can ameliorate histological ileum injuries and intestinal flora disturbance caused by AFB1. We found that Cur reversed the effects of AFB1 through modulating both NLRP3 inflammasome and the TLR4/NF-κB signaling pathway. In conclusion, AFB1 can induce inflammatory damage and pyroptosis in duck ileum, while Cur has obviously protective effects on all the above damages.

Chronic Stress Exposure Alters the Gut Barrier: Sex-Specific Effects on Microbiota and Jejunum Tight Junctions

Background

Major depressive disorder (MDD) is the leading cause of disability worldwide. Of individuals with MDD, 30% to 50% are unresponsive to common antidepressants, highlighting untapped causal biological mechanisms. Dysfunction in the microbiota-gut-brain axis has been implicated in MDD pathogenesis. Exposure to chronic stress disrupts blood-brain barrier integrity; still, little is known about intestinal barrier function in these conditions, particularly for the small intestine, where absorption of most foods and drugs takes place.

Methods

We investigated how chronic social or variable stress, two mouse models of depression, impact the jejunum intestinal barrier in males and females. Mice were subjected to stress paradigms followed by analysis of gene expression profiles of intestinal barrier-related targets, fecal microbial composition, and blood-based markers.

Results

Altered microbial populations and changes in gene expression of jejunum tight junctions were observed depending on the type and duration of stress, with sex-specific effects. We used machine learning to characterize in detail morphological tight junction properties, identifying a cluster of ruffled junctions in stressed animals. Junctional ruffling is associated with inflammation, so we evaluated whether lipopolysaccharide injection recapitulates stress-induced changes in the jejunum and observed profound sex differences. Finally, lipopolysaccharide-binding protein, a marker of gut barrier leakiness, was associated with stress vulnerability in mice, and translational value was confirmed on blood samples from women with MDD.

Conclusions

Our results provide evidence that chronic stress disrupts intestinal barrier homeostasis in conjunction with the manifestation of depressive-like behaviors in a sex-specific manner in mice and, possibly, in human depression.

Fenofibrate reduces glucose-induced barrier dysfunction in feline enteroids

Diabetes mellitus (DM) is a common chronic metabolic disease in humans and household cats that is characterized by persistent hyperglycemia. DM is associated with dysfunction of the intestinal barrier. This barrier is comprised of an epithelial monolayer that contains a network of tight junctions that adjoin cells and regulate paracellular movement of water and solutes. The mechanisms driving DM-associated barrier dysfunction are multifaceted, and the direct effects of hyperglycemia on the epithelium are poorly understood. Preliminary data suggest that fenofibrate, An FDA-approved peroxisome proliferator-activated receptor-alpha (PPARα) agonist drug attenuates intestinal barrier dysfunction in dogs with experimentally-induced DM. We investigated the effects of hyperglycemia-like conditions and fenofibrate treatment on epithelial barrier function using feline intestinal organoids. We hypothesized that glucose treatment directly increases barrier permeability and alters tight junction morphology, and that fenofibrate administration can ameliorate these deleterious effects. We show that hyperglycemia-like conditions directly increase intestinal epithelial permeability, which is mitigated by fenofibrate. Moreover, increased permeability is caused by disruption of tight junctions, as evident by increased junctional tortuosity. Finally, we found that increased junctional tortuosity and barrier permeability in hyperglycemic conditions were associated with increased protein kinase C-α (PKCα) activity, and that fenofibrate treatment restored PKCα activity to baseline levels. We conclude that hyperglycemia directly induces barrier dysfunction by disrupting tight junction structure, a process that is mitigated by fenofibrate. We further propose that counteracting modulation of PKCα activation by increased intracellular glucose levels and fenofibrate is a key candidate regulatory pathway of tight junction structure and epithelial permeability.

Role of Stress on Driving the Intestinal Paracellular Permeability

The gut epithelium is a polarized monolayer that exhibits apical and basolateral membrane surfaces. Monolayer cell components are joined side by side via protein complexes known as tight junction proteins (TJPs), expressed at the most apical extreme of the basolateral membrane. The gut epithelium is a physical barrier that determinates intestinal permeability, referred to as the measurement of the transit of molecules from the intestinal lumen to the bloodstream or, conversely, from the blood to the gut lumen. TJPs play a role in the control of intestinal permeability that can be disrupted by stress through signal pathways triggered by the ligation of receptors with stress hormones like glucocorticoids. Preclinical studies conducted under in vitro and/or in vivo conditions have addressed underlying mechanisms that account for the impact of stress on gut permeability. These mechanisms may provide insights for novel therapeutic interventions in diseases in which stress is a risk factor, like irritable bowel syndrome. The focus of this study was to review, in an integrative context, the neuroendocrine effects of stress, with special emphasis on TJPs along with intestinal permeability.

Association of Age-Related Macular Degeneration with a Blood Biomarker of Lipopolysaccharide, a Gut Bacterial Proinflammatory Toxin

Purpose

Chronic inflammation, immune dysregulation, and oxidative stress are major drivers of age-related macular degeneration (AMD) pathogenesis. Lipopolysaccharide (LPS) is a potent proinflammatory toxin originating from gut bacteria. We assessed the association of a blood biomarker of LPS exposure with incident AMD.

Methods

The Alienor Study is a prospective population-based study, including 963 residents of Bordeaux (France), aged 73 years or more at baseline. Esterified 3-hydroxy fatty acids (3-OH FAs) were measured from blood samples as a proxy of LPS burden. AMD was graded from color retinal photographs and spectral domain optical coherence tomography, performed every two years from 2006 to 2017. Cox proportional hazards models were used to estimate associations of between esterified 3-OH FAs, using 722 eyes at risk for incident early AMD and 981 eyes at risk for incident advanced AMD.

Results

Higher esterified 3-OH FAs were associated with incident early AMD after adjusting for age and gender (hazard ratio [HR] = 1.21 for 1 standard deviation [SD] increase; 95% confidence interval [CI], 1.01-1.45; P = 0.04) but not with incident advanced AMD (HR = 1.03 for 1 SD increase; 95% CI, 0.73-1.45; P = 0.86). These associations remained stable after multivariate adjustment and imputation for missing covariates (early AMD HR = 1.22 for 1 SD increase; 95% CI, 1.01-1.46; P = 0.04; advanced AMD HR = 0.98 for 1 SD increase; 95% CI, 0.69-1.38; P = 0.91).

Conclusions

This study evidenced an association between higher esterified 3-OH FAs and incident early AMD, suggesting that exposure to LPS may be involved in the early pathophysiological processes of AMD.

The PPARα Regulation of the Gut Physiology in Regard to Interaction with Microbiota, Intestinal Immunity, Metabolism, and Permeability

Peroxisome proliferator-activated receptor alpha (PPARα) is expressed throughout the mammalian gut: in epithelial cells, in the villi of enterocytes and in Paneth cells of intestinal crypts, as well as in some immune cells (e.g., lamina propria macrophages, dendritic cells) of the mucosa. This review examines the reciprocal interaction between PPARα activation and intestinal microbiota. We refer to the published data confirming that microbiota products can influence PPARα signaling and, on the other hand, PPARα activation is able to affect microbiota profile, viability, and diversity. PPARα impact on the broad spectrum of events connected to metabolism, signaling (e.g., NO production), immunological tolerance to dietary antigens, immunity and permeability of the gut are also discussed. We believe that the phenomena described here play a prominent role in gut homeostasis. Therefore, in conclusion we propose future directions for research, including the application of synthetic activators and natural endogenous ligands of PPARα (i.e., endocannabinoids) as therapeutics for intestinal pathologies and systemic diseases assumed to be related to gut dysbiosis.

Chronic stress and corticosterone exacerbate alcohol-induced tissue injury in the gut-liver-brain axis

Alcohol use disorders are associated with altered stress responses, but the impact of stress or stress hormones on alcohol-associated tissue injury remain unknown. We evaluated the effects of chronic restraint stress on alcohol-induced gut barrier dysfunction and liver damage in mice. To determine whether corticosterone is the stress hormone associated with the stress-induced effects, we evaluated the effect of chronic corticosterone treatment on alcoholic tissue injury at the Gut-Liver-Brain (GLB) axis. Chronic restraint stress synergized alcohol-induced epithelial tight junction disruption and mucosal barrier dysfunction in the mouse intestine. These effects of stress on the gut were reproduced by corticosterone treatment. Corticosterone synergized alcohol-induced expression of inflammatory cytokines and chemokines in the colonic mucosa, and it potentiated the alcohol-induced endotoxemia and systemic inflammation. Corticosterone also potentiated alcohol-induced liver damage and neuroinflammation. Metagenomic analyses of 16S RNA from fecal samples indicated that corticosterone modulates alcohol-induced changes in the diversity and abundance of gut microbiota. In Caco-2 cell monolayers, corticosterone dose-dependently potentiated ethanol and acetaldehyde-induced tight junction disruption and barrier dysfunction. These data indicate that chronic stress and corticosterone exacerbate alcohol-induced mucosal barrier dysfunction, endotoxemia, and systemic alcohol responses. Corticosterone-mediated promotion of alcohol-induced intestinal epithelial barrier dysfunction and modulation of gut microbiota may play a crucial role in the mechanism of stress-induced promotion of alcohol-associated tissue injury at the GLB axis.

Protective effects of Colomast®, A New Formulation of Adelmidrol and Sodium Hyaluronate, in A Mouse Model of Acute Restraint Stress

Stress is generally defined as a homeostatic disruption from actual or implied threats and alters the homeostatic balance of different body organs, such as gastrointestinal function and the hypothalamic-pituitary-adrenal axis (HPA), inducing the release of glucocorticoid hormones. Stress is also known to be a risk factor for the development of depression and anxiety. However, until today there are no suitable therapies for treating of stress. The aim of this study was to explore the protective effect of Colomast®, a new preparation containing Adelmidrol, an enhancer of physiological of palmitoylethanolamide (PEA), and sodium hyaluronate in an animal model of immobilization stress. Acute restraint stress (ARS) was induced in mice by fixation for 2 h of the four extremities with an adhesive tape and Colomast® (20 mg/kg) was administered by oral gavage 30 min before the immobilization. Colomast® pre-treatment was able to decrease histopathological changes in the gastrointestinal tract, cytokines expression, neutrophil infiltration, mast cell activation, oxidative stress, as well as modulate nuclear factor NF-kB and apoptosis pathways after ARS induction. Moreover, Colomast® was able to restore tight junction in both ileum and hippocampus and cortex. Additionally, we demonstrated that Colomast® ameliorated depression and anxiety-related behaviours, and modulate inflammatory and apoptosis pathways also in brain after ARS induction. In conclusion, our results suggest Colomast® to be a potential approach to ARS.

Comparing the gastrointestinal barrier function between growth-retarded and normal yaks on the Qinghai-Tibetan Plateau

Background

Yak (Bos grunniens) is an ancient bovine species on the Qinghai-Tibetan Plateau. Due to extremely harsh condition in the plateau, the growth retardation of yaks commonly exist, which can reduce the incomes of herdsman. The gastrointestinal barrier function plays a vital role in the absorption of nutrients and healthy growth. Functional deficiencies of the gastrointestinal barrier may be one of the contributors for yaks with growth retardation.

Methods

To this end, we compared the growth performance and gastrointestinal barrier function of growth-retarded (GRY) and normal yaks (GNY) based on average daily gain (ADG), serum parameters, tissue slice, real-time PCR, and western blotting, with eight yaks in each group.

Results

GRY exhibited lower (P < 0.05) average daily gain as compared to GNY. The diamine oxidase, D-lactic acid, and lipopolysaccharide concentrations in the serum of GRY were significantly higher (P < 0.05) than those of GNY. Compared to GNY, the papillae height in the rumen of GRY exhibited lower (P = 0.004). In jejunum, with the exception of higher villus height, width, and surface area in GNY, numerical difference (P = 0.61) was detected between two groups for crypt depth. Both in rumen and jejunum, the mRNA expression of interleukin-1beta in GRY was markedly higher (P < 0.05) than that in GNY, but an opposite trend was found in interleukin-10 expression. Moreover, GRY showed a higher (P < 0.05) tumor necrosis factor-alpha mRNA expression in the rumen. The claudin-1 (CLDN1), occludin (OCLN), and zonula occludens-1 (ZO1) expressions of GRY in rumen and jejunum were significantly down-regulated (P < 0.05) as compared to GNY. The correlation analysis identified that in rumen and jejunum, there was a positive correlation between interleukin-10 and CLDN1, OCLN, and ZO1 mRNA expressions, but the tumor necrosis factor-alpha was negatively correlated with CLDN1, OCLN, and ZO1. In the rumen, the ADG was positively correlated with papillae surface area, and a same relationship between ADG and CLDN1, OCLN, and ZO1 expressions was found.

Conclusion

The results indicated that the ruminal and jejunal barrier functions of GRY are disrupted as compared to GNY. In addition, our study provides a potential solution for promoting the growth of GRY by enhancing the gastrointestinal barrier function.

Impact of chronic exercise on counteracting chronic stress-induced functional and morphological pancreatic changes in male albino rats

Chronic stress has been linked to many diseases resulted from dysfunction of both the nervous system and peripheral organ systems. Yet, the effects of chronic stress on the pancreas have received relatively little attention. This work aims to investigate the influence of chronic stress exposure on both the endocrine and exocrine pancreatic function and morphology and its possible mechanism of action, and also to evaluate the impact of chronic exercise with moderate intensity on ameliorating the stress-induced pancreatic changes. Forty adult male albino rats were used and divided into four groups: control group, exercised group (3 weeks of swimming exercise), stressed group (3 weeks of immobilization stress), and stressed group practicing exercise (3 weeks of exercise, concomitant with 21 daily sessions of stress). On the final day of the experiment, all rats were sacrificed. Biochemical, immunohistochemical, and histological studies were conducted. The results showed that chronic immobilization stress produced hyperglycemia, hyperinsulinemia, and increased homeostatic model assessment of insulin resistance index (HOMA-IR) with increasing exocrine pancreatic injury markers by increasing oxidative and inflammatory status of the pancreatic tissue. Histological study showed the injurious effect of stress on the morphology of pancreatic tissue. Physical exercise protected the pancreas from the negative effects of stress through its anti-inflammatory and anti-oxidative effects, evidenced by increasing pancreatic interleukin 10 and total antioxidant capacity and decreasing pancreatic tumor necrosis factor-alpha, and malondialdehyde with ameliorating most of the histological changes induced by stress exposure. Physical exercise effectively counteracts chronic stress-induced pancreatic changes through different mechanisms.

Role of dietary lipids in food allergy

The prevalence of food allergy is raising in industrialized countries, but the mechanisms behind this increased incidence are not fully understood. Environmental factors are believed to play a role in allergic diseases, including lifestyle influences, such as diet. There is a close relationship between allergens and lipids, with many allergenic proteins having the ability to bind lipids. Dietary lipids exert pro-inflammatory or anti-inflammatory functions on cells of the innate immunity and influence antigen presentation to cells of the adaptive immunity. In addition to modifying the immunostimulating properties of proteins, lipids also alter their digestibility and intestinal absorption, changing allergen bioavailability. This study provides an overview of the role of dietary lipids in food allergy, taking into account epidemiological information, as well as results of mechanistic investigations using in vivo, ex vivo and in vitro models. The emerging link among high-fat diets, obesity, and allergy is also discussed.

Effects of pyrroloquinoline quinone supplementation on growth performance and small intestine characteristics in weaned pigs

This study was conducted to explore the effect of graded levels of pyrroloquinoline quinone disodium (PQQ·Na2) on the performance and intestinal development of weaned pigs. A total of 216 pigs weaned at 28 d were assigned in a randomized complete block design to 6 diets containing 0, 1.5, 3.0, 4.5, 6.0, or 7.5 mg/kg PQQ·Na2 for 28 d. Performance, diarrhea incidence, intestinal morphology, redox status, cytokines, and the expression of tight junction proteins were determined. Pigs had increased ADG (linear, P < 0.01), G:F (quadratic, P < 0.01), and lower diarrhea incidence (P < 0.01) with the increase of PQQ·Na2 supplementation. Villus height increased (quadratic, P < 0.01) in all segments of the small intestine, and crypt depth in the duodenum and jejunum was decreased (linear, P < 0.05) in pigs with the increase of PQQ·Na2 supplementation. Pigs fed PQQ·Na2-supplemented diets had higher (P < 0.05) activities of antioxidant enzymes including total superoxide dismutase in duodenum, jejunum, and ileum; glutathione peroxidase (GSH-Px) in jejunum and ileum; catalase (CAT) in duodenum and ileum; and lower (P < 0.05) malondialdehyde concentrations in the intestinal mucosa of all segments. In the intestinal mucosa, cytokines including interleukin (IL)-1β, IL-2, and interferon-γ were significantly decreased (P < 0.05) in pigs fed PQQ·Na2-supplemented diets. The protein expression of zonula occluden protein-1 (ZO-1) and occludin in the jejunum was significantly increased (P < 0.05) in pigs fed diets containing PQQ·Na2. In conclusion, these results have indicated that dietary PQQ·Na2 supplementation improves growth performance and gut health in weaned pigs. Moreover, pigs fed diet with as low as 1.5-mg/kg PQQ·Na2 have better performance compared with pigs fed no PQQ·Na2-supplemented diet; pigs fed diet with 4.5-mg/kg PQQ·Na2 have highest G:F among treatments during the whole period.

Ginseng oligopeptides protect against irradiation-induced immune dysfunction and intestinal injury

Intestinal injury and immune dysfunction are commonly encountered after irradiation therapy. While the curative abilities of ginseng root have been reported in prior studies, there is little known regarding its role in immunoregulation of intestinal repairability in cancer patients treated with irradiation. Our current study aims to closely examine the protective effects of ginseng-derived small molecule oligopeptides (Panax ginseng C. A. Mey.) (GOP) against irradiation-induced immune dysfunction and subsequent intestinal injury, using in vitro and in vivo models. Expectedly, irradiation treatment resulted in increased intestinal permeability along with mucosal injury in both Caco-2 cells and mice, probably due to disruption of the intestinal epithelial barrier, leading to high plasma lipopolysaccharide (LPS) and pro-inflammatory cytokines levels. However, when the cells were treated with GOP, this led to diminished concentration of plasma LPS and cytokines (IL-1 and TNF-α), suggesting its dampening effect on inflammatory and oxidative stress, and potential role in restoring normal baseline intestinal permeability. Moreover, the Caco-2 cells treated with GOP showed high trans-epithelial electrical resistance (TEER) and low FITC-dextran paracellular permeability when compared to the control group. This could be explained by the higher levels of tight junction proteins (ZO-1 and Occludin) expression along with reduced expression of the apoptosis-related proteins (Bax and Caspase-3) noticed in the GOP-treated cells, highlighting its role in preserving intestinal permeability, through prevention of their degradation while maintaining normal levels of expression. Further confirmatory in vivo data showed that GOP-treated mice exhibited high concentrations of lymphocytes (CD3+, CD4+, CD8+) in the intestine, to rescue the irradiation-induced damage and restore baseline intestinal integrity. Therefore, we propose that GOP can be used as an adjuvant therapy to attenuate irradiation-induced immune dysfunction and intestinal injury in cancer patients.

High-Glucose or -Fructose Diet Cause Changes of the Gut Microbiota and Metabolic Disorders in Mice without Body Weight Change

High fat diet-induced changes in gut microbiota have been linked to intestinal permeability and metabolic endotoxemia, which is related to metabolic disorders. However, the influence of a high-glucose (HGD) or high-fructose (HFrD) diet on gut microbiota is largely unknown. We performed changes of gut microbiota in HGD- or HFrD-fed C57BL/6J mice by 16S rRNA analysis. Gut microbiota-derived endotoxin-induced metabolic disorders were evaluated by glucose and insulin tolerance test, gut permeability, Western blot and histological analysis. We found that the HGD and HFrD groups had comparatively higher blood glucose and endotoxin levels, fat mass, dyslipidemia, and glucose intolerance without changes in bodyweight. The HGD- and HFrD-fed mice lost gut microbial diversity, characterized by a lower proportion of Bacteroidetes and a markedly increased proportion of Proteobacteria. Moreover, the HGD and HFrD groups had increased gut permeability due to alterations to the tight junction proteins caused by gut inflammation. Hepatic inflammation and lipid accumulation were also markedly increased in the HGD and HFrD groups. High levels of glucose or fructose in the diet regulate the gut microbiota and increase intestinal permeability, which precedes the development of metabolic endotoxemia, inflammation, and lipid accumulation, ultimately leading to hepatic steatosis and normal-weight obesity.

Butyrate ameliorated-NLRC3 protects the intestinal barrier in a GPR43-dependent manner

BACKGROUND

Intestinal barrier dysfunctions are related to dysbacteriosis and chronic gut inflammation in type 2 diabetes. Although there is emerging evidence that the chronic gut inflammatory response is stimulated by nucleotide-binding oligomerization domain-like receptors (NLRs), the relationship and precise mechanism between NLRC3 and the colonic epithelial barrier remains largely elusive.

METHODS

We investigated the function and mechanism of NLRC3 in the colonic tissues of diabetic mice and colonic epithelial cell lines. The regulatory mechanism between NLRC3, butyrate and tight junctions was elucidated via a transepithelial electrical resistance measurement, transmission electron microscopy, RNA interference and western blotting.

RESULTS

In this study, we found that NLRC3 expression was decreased in the colonic tissues of diabetic mice. NLRC3 over-expression ameliorated colonic epithelial barrier integrity and up-regulated tight junction proteins in colonic epithelial cells. Knockdown of TRAF6 diminished NLRC3-induced ZO-1/occludin expression. In addition, we demonstrated that butyrate could stimulate NLRC3 expression in both diabetic mice and colonic epithelial cells. GPR43 on colonic epithelial cells is involved in the activation of NLRC3 induced by butyrate.

CONCLUSION

Our findings demonstrated that NLCR3 could ameliorate colonic epithelial barrier integrity in diabetes mellitus in a TRAF6-dependent manner, and NLCR3 was stimulated by butyrate via binding GPR43 on colonic epithelial cells.

Acute intraperitoneal lipopolysaccharide influences the immune system in the absence of gut dysbiosis

There is bidirectional communication between the immune system and the gut microbiome, however the precise mechanisms regulating this crosstalk are not well understood. Microbial-associated molecular patterns (MAMPs) within the gut, including lipopolysaccharide (LPS) that produces a quick and robust activation of the immune system, may be one way by which these interactions occur. Endogenous levels of LPS in the gut are low enough that they do not usually cause disease, although, in times of increased LPS loads, they may be capable of increasing vulnerability of the gut to pathogenic bacteria. Furthermore, chronic, low-grade inflammation can have lasting effects on the gut, but the effects of acute inflammation on gut communities have not been thoroughly assessed. In this study, we first investigated whether a single modest dose of LPS administered to adult male and female Siberian hamsters (Phodopus sungorus) activated the immune system by measuring levels of circulating cortisol and the proinflammatory cytokine TNF-α in the liver compared with saline-treated animals. We then investigated whether this same acute dose of LPS altered the microbiome 48 h after treatment. We found that, although LPS increased cortisol and liver cytokine levels, and produced changes in food intake and body mass in both sexes, immunological changes were independent of gut dysbiosis 48 h after LPS injection. These data suggest that an acute immune activation may not be capable of altering the gut microbiome in healthy individuals. It is likely, however, that this type of immune challenge may have other physiological impacts on the gut's vulnerability, and future studies will investigate these relationships further.

Extracellular vesicles regulate immune responses and cellular function in intestinal inflammation and repair

Tightly controlled communication among the various resident and recruited cells in the intestinal tissue is critical for maintaining tissue homeostasis, re-establishment of the barrier function and healing responses following injury. Emerging evidence convincingly implicates extracellular vesicles (EVs) in facilitating this important cell-to-cell crosstalk by transporting bioactive effectors and genetic information in healthy tissue and disease. While many aspects of EV biology, including release mechanisms, cargo packaging, and uptake by target cells are still not completely understood, EVs contribution to cellular signaling and function is apparent. Moreover, EV research has already sparked a clinical interest, as a potential diagnostic, prognostic and therapeutic tool. The current review will discuss the function of EVs originating from innate immune cells, namely, neutrophils, monocytes and macrophages, as well as intestinal epithelial cells in healthy tissue and inflammatory disorders of the intestinal tract. Our discussion will specifically emphasize the contribution of EVs to the regulation of vascular and epithelial barrier function in inflamed intestines, wound healing, as well as trafficking and activity of resident and recruited immune cells.

TDB protects vascular endothelial cells against oxygen-glucose deprivation/reperfusion-induced injury by targeting miR-34a to increase Bcl-2 expression

Prolonged ischemia can result in apoptotic death of vascular endothelial cells and lead to ischemic vascular diseases including vascular dementia, arteriosclerosis and brain oedema. Finding protective strategies to prevent this is therefore an urgent mission. Recent studies have shown that dysregulation of microRNAs (miRNAs) can lead to imbalance of Bcl-2 family proteins and mitochondrial dysfunction, leading to further damage of vascular cells under ischemic conditions. However, whether miRNAs can be used as a drug target for treating vascular diseases is not fully understood. In this study, we observed that the natural product 2,4,5-trihydroxybenzaldehyde (TDB) could effectively inhibit vascular cell apoptosis following oxygen-glucose deprivation/reperfusion (OGD/R) by maintaining mitochondrial membrane potential (MMP) and suppressing activation of the mitochondria-dependent caspase-9/3 apoptosis pathway. Furthermore, we identified miR-34a, a crucial negative regulator of Bcl-2, as a target for the protective effect of TDB on vascular cells. TDB-induced suppression of miR-34a resulted in a significant upregulation of Bcl-2 protein, MMP maintenance, and the survival of vascular cells following OGD/R. Our findings suggest that targeting miR-34a with the natural product TDB may provide a novel strategy for the treatment of ischemic vascular injuries, and demonstrate the therapeutic potential in targeting miRNAs using appropriate small molecules.

Suppression of TNF-α and free radicals reduces systematic inflammatory and metabolic disorders: Radioprotective effects of ginseng oligopeptides on intestinal barrier function and antioxidant defense

Irradiation therapy is markedly associated with intestinal injure and oxidant stress. This study aimed to investigate the effects of ginseng (Panax ginseng C.A. Mey.) oligopeptides (GOP) on irradiation-induced intestinal injury and antioxidant defense in mice. BALB/c mice (8 weeks old) were randomly divided into six groups: vehicle control, irradiation control (IR), IR+whey protein [0.30 g/kg body weight (BW)], IR+GOP 0.15 g/kg BW, IR+GOP 0.30 g/kg BW and IR+GOP 0.60 g/kg BW. Postirradiation 30-day survival trial, white blood cells count and bone marrow hematopoietic system damage were performed to identify the injury degree induced by irradiation. Then, histopathology analysis was observed and intestinal permeability in vivo was quantified with fluorescein isothiocyanate-dextran. The enzyme-linked immunosorbent assay was used to determine antioxidant ability, plasma inflammatory cytokines, diamine oxidase (DAO) and endotoxin (LPS) levels. The immunohistochemistry assay was used to analyze the expression levels of tight junction proteins. We found that GOP-treated mice exhibited lower concentrations of plasma LPS and DAO and decreased instructors of inflammatory and oxidative stress which were linked to the lower intestinal permeability and higher tight junction proteins expression. The blockage of GOP was linked with the reduction of TNF-α and free radicals. The 15-day pretreatment of GOP could exhibit radioprotective effects, and another 15-day posttreatment benefited the quick repair of irradiation-induced injury. We confirm that GOP would exhibit effective therapeutic value on attenuating irradiation-induced hematopoietic, gastrointestinal and oxidative injury in cancer patients.

Plasmadiafiltration ameliorating gut mucosal barrier dysfunction and improving survival in porcine sepsis models

BACKGROUND

The object of this study is to explore whether the plasmadiafiltration (PDF) is more effective in improving the intestinal mucosal barrier function by removing more key large molecular inflammatory mediators and then prolonging the survival time.

METHODS

Totally, 24 porcine sepsis models induced by cecal ligation and puncture (CLP) operation were randomly divided into three groups: PDF group, high-volume hemofiltration (HVHF) group, and control group, and received 8 h treatment, respectively. The expression of ZO-1 and occludin in intestinal mucosal epithelial cells were detected by immunohistochemistry, and apoptotic protein caspase-3-positive lymphocytes were signed in mesenteric lymph nodes by TUNEL staining. The hemodynamic parameters were measured by invasive cavity detection. The tumor necrosis factor alpha (TNFα) and high-mobility group protein 1 (HMGB1) were tested by ELISA method. And then, the survival curves with all-cause death were compared with three groups.

RESULTS

PDF led to a superior reversal of sepsis-related hemodynamic impairment and serum biochemistry abnormalities and resulted in longer survival time compared with HVHF and control (p < 0.01). Definitive protection from excessive TNF-α and HMGB1 response were only achieved by PDF. A more regular distribution pattern of ZO-1 and occludin along the epithelium was found in PDF animals (p < 0.01). The presence of apoptotic lymphocytes was significantly reduced in the PDF animals (p < 0.01).

CONCLUSIONS

PDF can effectively eliminate more pivotal inflammatory mediators of TNFα and HMGB1 and reduce the inflammation damage of the intestinal mucosal barrier and apoptosis of lymphocyte then improve the circulation function and prolong the survival time.

Lactobacillus gasseri SBT2055 inhibits adipose tissue inflammation and intestinal permeability in mice fed a high-fat diet

The probiotic Lactobacillus gasseri SBT2055 (LG2055) has anti-obesity effects. Obesity is closely correlated with inflammation in adipose tissue, and maintaining adipose tissue in a less-inflamed state requires intestinal integrity or a barrier function to protect the intestine from the disruption that can be caused by a high-fat diet (HFD). Here, we examined the anti-inflammatory and intestinal barrier-protecting effects of LG2055 in C57BL/6 mice fed a normal-fat diet (NFD), HFD, or the HFD containing LG2055 (HFD-LG) for 21 weeks. HFD-LG intake significantly prevented HFD-induced increases in body weight, visceral fat mass, and the ratio of inflammatory-type macrophages to anti-inflammatory ones in adipose tissue. Mice fed the HFD showed higher intestinal permeability to a fluorescent dextran administered by oral administration and an elevated concentration of antibodies specific to lipopolysaccharides (LPS) in the blood compared with those fed the NFD, suggesting an increased penetration of the gut contents into the systemic circulation. These elevations of intestinal permeability and anti-LPS antibody levels were significantly suppressed in mice fed the HFD-LG. Moreover, treatment with LG2055 cells suppressed an increase in the cytokine-induced permeability of Caco-2 cell monolayers. These results suggest that LG2055 improves the intestinal integrity, reducing the entry of inflammatory substances like LPS from the intestine, which may lead to decreased inflammation in adipose tissue.

Blood glucose regulation mechanism in depressive disorder animal model during hyperglycemic states

Depression is more common among diabetes people than in the general population. In the present study, blood glucose change in depression animal model was characterized by various types of hyperglycemia models such as d-glucose-fed-, immobilization stress-, and drug-induced hyperglycemia models. First, the ICR mice were enforced into chronic restraint stress for 2h daily for 2 weeks to produce depression animal model. The animals were fed with d-glucose (2g/kg), forced into restraint stress for 30min, or administered with clonidine (5μg/5μl) supraspinally or spinally to produce hyperglycemia. The blood glucose level in depression group was down-regulated compared to that observed in the normal group in d-glucose-fed-, restraint stress-, and clonidine-induced hyperglycemia models. The up-regulated corticosterone level induced by d-glucose feeding or restraint stress was reduced in the depression group while the up-regulation of plasma corticosterone level is further elevated after i.t. or i.c.v. clonidine administration in the depression group. The up-regulated insulin level induced by d-glucose feeding or restraint stress was reduced in the depression group. On the other hand, blood corticosterone level in depression group was up-regulated compared to the normal group after i.t. or i.c.v. clonidine administration. Whereas the insulin level in depression group was not altered when mice were administered clonidine i.t. or i.c.v. Our results suggest that the blood glucose level in depression group is down-regulated compared to the normal group during d-glucose-fed-, immobilization stress-, and clonidine-induced hyperglycemia in mice. The down-regulation of the blood glucose level might be one of the important pathophysiologic changes in depression.

Subacute stress and chronic stress interact to decrease intestinal barrier function in rats

Psychological stress increases intestinal permeability, potentially leading to low-grade inflammation and symptoms in functional gastrointestinal disorders. We assessed the effect of subacute, chronic and combined stress on intestinal barrier function and mast cell density. Male Wistar rats were allocated to four experimental groups (n = 8/group): 1/sham; 2/subacute stress (isolation and limited movement for 24 h); 3/chronic crowding stress for 14 days and 4/combined subacute and chronic stress. Jejunum and colon were collected to measure: transepithelial electrical resistance (TEER; a measure of epithelial barrier function); gene expression of tight junction molecules; mast cell density. Plasma corticosterone concentration was increased in all three stress conditions versus sham, with highest concentrations in the combined stress condition. TEER in the jejunum was decreased in all stress conditions, but was significantly lower in the combined stress condition than in the other groups. TEER in the jejunum correlated negatively with corticosterone concentration. Increased expression of claudin 1, 5 and 8, occludin and zonula occludens 1 mRNAs was detected after subacute stress in the jejunum. In contrast, colonic TEER was decreased only after combined stress, and the expression of tight junction molecules was unaltered. Increased mast cell density was observed in the chronic and combined stress condition in the colon only. In conclusion, our data show that chronic stress sensitizes the gastrointestinal tract to the effects of subacute stress on intestinal barrier function; different underlying cellular and molecular alterations are indicated in the small intestine versus the colon.

Alleviation of high fat diet-induced obesity by oligofructose in gnotobiotic mice is independent of presence of Bifidobacterium longum

Scope

Diet‐induced obesity is associated with changes in the gut microbiota and low‐grade inflammation. Oligofructose was reported to ameliorate high fat diet‐induced metabolic disorders in mice by restoring the number of intestinal bifidobacteria. However, this has not been experimentally demonstrated.

Methods and results

We fed conventional mice, germfree mice, mice associated with a simplified human gut microbiota composed of eight bacterial species including Bifidobacterium longum (SIHUMI), and mice associated with SIHUMI without B. longum a low fat diet (LFD), a high fat diet (HFD), or a HFD containing 10% oligofructose (HFD + OFS) for five weeks. We assessed body composition, bacterial cell numbers and metabolites, markers of inflammation, and gut permeability. Conventional mice fed HFD or HFD + OFS did not differ in body weight gain and glucose tolerance. The gnotobiotic mouse groups fed LFD or HFD + OFS gained less body weight and body fat, and displayed an improved glucose tolerance compared with mice fed HFD. These differences were not affected by the presence of B. longum. Mice fed HFD showed no signs of inflammation or increased intestinal permeability.

Conclusion

The ability of oligofructose to reduce obesity and to improve glucose tolerance in gnotobiotic mice fed HFD was independent of the presence of B. longum.

Increased oxidative stress and disrupted small intestinal tight junctions in cigarette smoke-exposed rats

Chronic obstructive pulmonary disease (COPD) is a major public health problem, and cigarette smoke (CS) is the primary risk factor. The pathology is often observed in the lung, but COPD is also associated with intestinal barrier disruption, although the underlying mechanisms are poorly understood. To address this, a CS‑exposed rat model was evaluated in the present study by analyzing small intestinal gene expression using reverse transcription‑quantitative polymerase chain reaction. CS exposure caused upregulation of the nicotinamide adenine dinucleotide phosphate‑oxidase subunits nox2 and p22phox in the small intestine, while the antioxidative enzyme superoxide dismutase was downregulated. CS exposure also increased bax expression and decreased bcl‑2 expression. This was associated with an elevation of hypoxia‑inducible factor (HIF)‑1α. Claudin‑1 was decreased and claudin‑2 increased, indicating a loosening of small intestinal tight junctions (TJs). These data suggest that during the development of COPD, HIF‑1α expression is altered in the small intestine, which may be associated with the increased oxidative stress and apoptosis, eventually resulting in disruption of the intestinal TJs.

Acute pancreatitis: The stress factor

Acute pancreatitis is an inflammatory disorder of the pancreas that may cause life-threatening complications. Etiologies of pancreatitis vary, with gallstones accounting for the majority of all cases, followed by alcohol. Other causes of pancreatitis include trauma, ischemia, mechanical obstruction, infections, autoimmune, hereditary, and drugs. The main events occurring in the pancreatic acinar cell that initiate and propagate acute pancreatitis include inhibition of secretion, intracellular activation of proteases, and generation of inflammatory mediators. Small cytokines known as chemokines are released from damaged pancreatic cells and attract inflammatory cells, whose systemic action ultimately determined the severity of the disease. Indeed, severe forms of pancreatitis may result in systemic inflammatory response syndrome and multiorgan dysfunction syndrome, characterized by a progressive physiologic failure of several interdependent organ systems. Stress occurs when homeostasis is threatened, and stressors can include physical or mental forces, or combinations of both. Depending on the timing and duration, stress can result in beneficial or harmful consequences. While it is well established that a previous acute-short-term stress decreases the severity of experimentally-induced pancreatitis, the worsening effects of chronic stress on the exocrine pancreas have received relatively little attention. This review will focus on the influence of both prior acute-short-term and chronic stress in acute pancreatitis.

The probiotic Lactobacillus coryniformis CECT5711 reduces the vascular pro-oxidant and pro-inflammatory status in obese mice

Obesity is associated with intestine dysbiosis and is characterized by a low-grade inflammatory status, which affects vascular function. In the present study, we evaluated the effects of a probiotic with immunomodulatory properties, Lactobacillus coryniformis CECT5711, in obese mice fed on an HFD (high-fat diet). The probiotic treatment was given for 12 weeks, and it did not affect the weight evolution, although it reduced basal glycaemia and insulin resistance. L. coryniformis administration to HFD-induced obese mice induced marked changes in microbiota composition and reduced the metabolic endotoxaemia as it decreased the LPS (lipopolysaccharide) plasma level, which was associated with a significant improvement in gut barrier disruption. Furthermore, it lowered TNFα (tumour necrosis factor α) expression in liver, improving the inflammatory status, and thus the glucose metabolism. Additionally, the probiotic reversed the endothelial dysfunction observed in obese mice when endothelium- and NO (nitric oxide)-dependent vasodilatation induced by acetylcholine in aortic rings was studied. It also restored the increased vessel superoxide levels observed in obese mice, by reducing NADPH oxidase activity and increasing antioxidant enzymes. Moreover, chronic probiotic administration for 2 weeks also improved endothelial dysfunction and vascular oxidative stress induced by in vivo administration of LPS in control mice fed on a standard chow diet. The results of the present study demonstrate an endothelial-protective effect of L. coryniformis CECT5711 in obese mice by increasing NO bioavailability, suggesting the therapeutic potential of this gut microbiota manipulation to prevent vasculopathy in obesity.

Disrupted tight junctions in the small intestine of cystic fibrosis mice

The tight junction (TJ) is the major determinant of paracellular permeability, which in the gut protects the body from entry of harmful substances such as microbial components. In cystic fibrosis (CF), there is increased permeability of the small intestine both in humans and in CF mice. To gain insight into the mechanisms of increased intestinal permeability in CF, I analyze the composition of the TJ in a cystic fibrosis transmembrane conductance regulator (Cftr) knockout mouse model. Significant changes in TJ gene expression in the CF intestine were found for Cldn1, Cldn7, Cldn8 and Pmp22, which were expressed at lower levels and Cldn2 that was expressed at a higher level. Protein levels of claudin-2 were increased in the CF intestine as compared to wild-type, while other TJ proteins were not significantly different. In the villus epithelium of the CF intestine, all TJ components analyzed were mislocalized to the basal cytoplasm and showed varying degrees of loss from the TJ and apico-lateral surfaces. The pore-forming claudin-2 in the CF intestine showed more intense staining but was correctly localized to the TJ, principally in the crypts that are enlarged in CF. The cytokine TNFα, known to affect TJ, was elevated to 160% of wild-type in the CF intestine. In summary, there is a dramatic redistribution of claudin proteins from the TJ/lateral membrane to the basal cytoplasm of the villus epithelium in the CF intestine. These changes in TJ protein localization in CF are likely to be involved in the increased permeability of the CF small intestine to macromolecules and TNFα may be a causative factor.

Disruption of ZO-1/claudin-4 interaction in relation to inflammatory responses in methotrexate-induced intestinal mucositis

PURPOSE

Methotrexate (MTX)-induced intestinal mucositis limits the use of the drug. We previously reported that MTX-dependent production of reactive oxygen species is an initiating signal leading to neutrophil migration and intestinal barrier dysfunction. Moreover, alterations of zonula occludens (ZO)-1, an integral component of tight junctions (TJs), contribute to its dysfunction. This study aimed to clarify the identity of inflammatory mediators in the intestine of MTX-treated rats and to evaluate MTX-stimulated alterations in the expression of TJ proteins other than ZO-1 (e.g., occludin and claudins).

METHODS

Male Wistar rats were administrated MTX (15 mg kg(-1)) orally once daily for 4 days. Tumor necrosis factor (TNF)-α, interleukin (IL)-1β, macrophage inflammatory protein (MIP)-2, cytokine-induced neutrophil chemoattractant-2, Toll-like receptor 4 (TLR4), and occludin were determined by real-time RT-PCR. Expression, distribution, and interactions of TJ proteins were evaluated by Western blotting, immunohistochemistry, and immunoprecipitation.

RESULTS

MTX increased the mRNA levels of TNF-α, IL-1β, MIP-2, and TLR4 in the small intestine, as well as the protein expression of claudin-2. Increased claudin-2 and decreased claudin-4 immunostaining were also observed. Occludin mRNA levels were significantly diminished by MTX administration, whereas occludin protein levels and the interaction between ZO-1 and occludin were unaltered; however, the interaction between ZO-1 and claudin-4 was significantly compromised.

CONCLUSIONS

These results indicate that elevated levels of inflammatory cytokines and chemokines in the small intestine of MTX-treated rats may contribute to the inhibition of ZO-1/claudin-4 binding, and that inhibition of ZO-1/claudin-4 binding may in turn lead to a reduction in claudin-4 expression.

Stress-Derived Corticotropin Releasing Factor Breaches Epithelial Endotoxin Tolerance

BACKGROUND AND AIMS

Loss of the endotoxin tolerance of intestinal epithelium contributes to a number of intestinal diseases. The etiology is not clear. Psychological stress is proposed to compromise the intestinal barrier function. The present study aims to elucidate the role of the stress-derived corticotropin releasing factor (CRF) in breaching the established intestinal epithelial endotoxin tolerance.

METHODS

Epithelial cells of HT-29, T84 and MDCK were exposed to lipopolysaccharide to induce the endotoxin tolerance; the cells were then stimulated with CRF. The epithelial barrier function was determined using as indicators of the endotoxin tolerant status. A water-avoid stress mouse model was employed to test the role of CRF in breaching the established endotoxin tolerance in the intestine.

RESULTS

The established endotoxin tolerance in the epithelial cell monolayers was broken down by a sequent exposure to CRF and LPS manifesting a marked drop of the transepithelial resistance (TER) and an increase in the permeability to a macromolecular tracer, horseradish peroxidase (HRP). The exposure to CRF also increased the expression of Cldn2 in the epithelial cells, which could be mimicked by over expression of TLR4 in epithelial cells. Over expression of Cldn2 resulted in low TER in epithelial monolayers and high permeability to HRP. After treating mice with the 10-day chronic stress, the intestinal epithelial barrier function was markedly compromised, which could be prevented by blocking either CRF, or TLR4, or Cldn2.

CONCLUSIONS

Psychological stress-derived CRF can breach the established endotoxin tolerance in the intestinal mucosa.

Interleukin-1β (IL-1β) increases pain behavior and the blood glucose level: possible involvement of glucocorticoid system

The possible involvement of glucocorticoid system in interleukin-1β (IL-1β)-induced nociception and the blood glucose level was studied in ICR mice. In the first experiment, mice were treated intrathecally (i.t.) with IL-1β (100 pg). Corticotrophin releasing hormone (CRH) mRNA (hypothalamus) and c-Fos mRNA (pituitary gland, spinal cord, and the adrenal gland) levels were measured at 30, 60 and 120 min after IL-1β administration. We found that i.t. injection with IL-1β increased CRH mRNA level in the hypothalamus. The IL-1β administered i.t. elevated c-Fos mRNA levels in the spinal cord, pituitary and adrenal glands. Furthermore, i.t. administration of IL-1β significantly increased the plasma corticosterone level up to 60 min. In addition, the adrenalectomy caused the reductions of the blood glucose level and pain behavior induced by IL-1β injected i.t. in normal and D-glucose-fed groups. Furthermore, intraperitoneal (i.p.) pretreatment with RU486 (100mg/kg) attenuated the blood glucose level and pain behavior induced by IL-1β administered i.t. in normal and D-glucose-fed groups. Our results suggest that IL-1β administered i.t. increases the blood glucose level and pain behavior via an activation of the glucocorticoid system.

A high-grain diet causes massive disruption of ruminal epithelial tight junctions in goats

Alterations in rumen epithelial tight junctions (TJs) at the tissue and molecular levels during high-grain (HG) diet feeding are unknown. Here, 10 male goats were randomly assigned to either a hay diet (0% grain; n = 5) or HG diet group (65% grain; n = 5) to characterize the changes in ruminal epithelial structure and TJ protein expression and localization using scanning and transmission electron microscopy, quantitative real-time PCR, Western blot analysis, and immunofluorescence. After 7 wk of feeding, ruminal free LPS in HG group increased significantly (P < 0.001) compared with the hay group, and free LPS in the peripheral blood was detectable with concentrations of 0.8 ± 0.20 EU/ml, while not detectable in the control, suggesting a leakage of LPS into the blood in the HG group. Correspondingly, the HG-fed goats showed profound alterations in ruminal epithelial structure and TJ proteins, depicted by marked epithelial cellular damage and intercellular junction erosion, down-regulation of TJ proteins claudin-4, occludin, and zonula occludens-1 mRNA and protein expression, as well as redistribution of claudin-1, claudin-4, and occludin. Furthermore, these changes in TJ proteins in the HG group were coupled with the upregulation of mRNA levels for the cytokines TNF-α and IFN-γ in the ruminal epithelia. These results demonstrated for the first time that the HG diet feeding caused disruption of ruminal epithelial TJs that was associated with a local inflammatory response in the rumen epithelium. These findings may provide new insights into understanding the role of TJ proteins in the ruminal epithelial immune homeostasis of ruminants.

Synergistic protection of combined probiotic conditioned media against neonatal necrotizing enterocolitis-like intestinal injury

Balance among the complex interactions of the gut microbial community is important for intestinal health. Probiotic bacteria can improve bacterial balance and have been used to treat gastrointestinal diseases. Neonatal necrotizing enterocolitis (NEC) is a life-threatening inflammatory bowel disorder primarily affecting premature infants. NEC is associated with extensive inflammatory NF-κB signaling activation as well as intestinal barrier disruption. Clinical studies have shown that probiotic administration may protect against NEC, however there are safety concerns associated with the ingestion of large bacterial loads in preterm infants. Bacteria-free conditioned media (CM) from certain probiotic organisms have been shown to retain bioactivity including anti-inflammatory and cytoprotective properties without the risks of live organisms. We hypothesized that the CM from Lactobacillus acidophilus (La), Bifidobacterium infantis (Bi), and Lactobacillus plantarum (Lp), used separately or together would protect against NEC. A rodent model with intestinal injury similar to NEC was used to study the effect of CM from Lp, La/Bi, and La/Bi/Lp on the pathophysiology of NEC. All the CM suppressed NF-κB activation via preserved IκBα expression and this protected IκBα was associated with decreased liver activity of the proteasome, which is the degrading machinery for IκBα. These CM effects also caused decreases in intestinal production of the pro-inflammatory cytokine TNF-α, a downstream target of the NF-κB pathway. Combined La/Bi and La/Bi/Lp CM in addition protected intestinal barrier function by maintaining tight junction protein ZO-1 levels and localization at the tight junction. Double combined La/Bi CM significantly reduced intestinal injury incidence from 43% to 28% and triple combined La/Bi/Lp CM further reduced intestinal injury incidence to 20%. Thus, this study demonstrates different protective mechanisms and synergistic bioactivity of the CM from different organisms in ameliorating NEC-like intestinal injury in an animal model.

Recent advances in small bowel diseases: Part I

As is the case in all parts of gastroenterology and hepatology, there have been many advances in our knowledge and understanding of small intestinal diseases. Over 1000 publications were reviewed for 2008 and 2009, and the important advances in basic science as well as clinical applications were considered. In Part I of this Editorial Review, seven topics are considered: intestinal development; proliferation and repair; intestinal permeability; microbiotica, infectious diarrhea and probiotics; diarrhea; salt and water absorption; necrotizing enterocolitis; and immunology/allergy. These topics were chosen because of their importance to the practicing physician.

Effects of β-(1,3-1,6)-D-glucan on irritable bowel syndrome-related colonic hypersensitivity

Irritable bowel syndrome (IBS) is a gastrointestinal disorder characterized by chronic abdominal pain associated with altered bowel habits. Since the prevalence of IBS is very high and thus, involves elevated health-care costs, treatment of this condition by methods other than prescribed medicines could be beneficial. β-(1,3)-D-glucan with β-(1,6) branches (β-glucan) has been used as a nutritional supplement for many years. In this study, we examined the effect of β-glucan on fecal pellet output and visceral pain response in animal models of IBS. Oral administration of β-glucan suppressed the restraint stress- or drug-induced fecal pellet output. β-Glucan also suppressed the visceral pain response to colorectal distension. These results suggest that β-glucan could be beneficial for the treatment and prevention of IBS.

CXCR4 antagonist AMD3100 modulates claudin expression and intestinal barrier function in experimental colitis

Ulcerative colitis is a gastrointestinal disorder characterized by local inflammation and impaired epithelial barrier. Previous studies demonstrated that CXC chemokine receptor 4 (CXCR4) antagonists could reduce colonic inflammation and mucosal damage in dextran sulfate sodium (DSS)-induced colitis. Whether CXCR4 antagonist has action on intestinal barrier and the possible mechanism, is largely undefined. In the present study, the experimental colitis was induced by administration of 5% DSS for 7 days, and CXCR4 antagonist AMD3100 was administered intraperitoneally once daily during the study period. For in vitro study, HT-29/B6 colonic cells were treated with cytokines or AMD3100 for 24 h until assay. DSS-induced colitis was characterized by morphologic changes in mice. In AMD3100-treated mice, epithelial destruction, inflammatory infiltration, and submucosal edema were markedly reduced, and the disease activity index was also significantly decreased. Increased intestinal permeability in DSS-induced colitis was also significantly reduced by AMD3100. The expressions of colonic claudin-1, claudin-3, claudin-5, claudin-7 and claudin-8 were markedly decreased after DSS administration, whereas colonic claudin-2 expression was significantly decreased. Treatment with AMD3100 prevented all these changes. However, AMD3100 had no influence on claudin-3, claudin-5, claudin-7 and claudin-8 expression in HT-29/B6 cells. Cytokines as TNF-α, IL-6, and IFN-γ increased apoptosis and monolayer permeability, inhibited the wound-healing and the claudin-3, claudin-7 and claudin-8 expression in HT-29/B6 cells. We suggest that AMD3100 acted on colonic claudin expression and intestinal barrier function, at least partly, in a cytokine-dependent pathway.

Increased intestinal permeability and tight junction disruption by altered expression and localization of occludin in a murine graft versus host disease model

Background

Hematopoietic stem cell transplantation is increasingly performed for hematologic diseases. As a major side effect, acute graft versus host disease (GvHD) with serious gastrointestinal symptoms including diarrhea, gastrointestinal bleeding and high mortality can be observed. Because surveillance and biopsies of human gastrointestinal GvHD are difficult to perform, rare information of the alterations of the gastrointestinal barrier exists resulting in a need for systematic animal models.

Methods

To investigate the effects of GvHD on the intestinal barrier of the small intestine we utilized an established acute semi allogenic GvHD in C57BL/6 and B6D2F1 mice.

Results

By assessing the differential uptake of lactulose and mannitol in the jejunum, we observed an increased paracellular permeability as a likely mechanism for disturbed intestinal barrier function. Electron microscopy, immunohistochemistry and PCR analysis indicated profound changes of the tight-junction complex, characterized by downregulation of the tight junction protein occludin without any changes in ZO-1. Furthermore TNF-α expression was significantly upregulated.

Conclusions

This analysis in a murine model of GvHD of the small intestine demonstrates serious impairment of intestinal barrier function in the jejunum, with an increased permeability and morphological changes through downregulation and localization shift of the tight junction protein occludin.

Protein kinase Cζ phosphorylates occludin and promotes assembly of epithelial tight junctions

Protein kinases play an important role in the regulation of epithelial tight junctions. In the present study, we investigated the role of PKCζ (protein kinase Cζ) in tight junction regulation in Caco-2 and MDCK (Madin-Darby canine kidney) cell monolayers. Inhibition of PKCζ by a specific PKCζ pseudosubstrate peptide results in redistribution of occludin and ZO-1 (zona occludens 1) from the intercellular junctions and disruption of barrier function without affecting cell viability. Reduced expression of PKCζ by antisense oligonucleotide or shRNA (short hairpin RNA) also results in compromised tight junction integrity. Inhibition or knockdown of PKCζ delays calcium-induced assembly of tight junctions. Tight junction disruption by PKCζ pseudosubstrate is associated with the dephosphorylation of occludin and ZO-1 on serine and threonine residues. PKCζ directly binds to the C-terminal domain of occludin and phosphorylates it on threonine residues. Thr403, Thr404, Thr424 and Thr438 in the occludin C-terminal domain are the predominant sites of PKCζ-dependent phosphorylation. A T424A or T438A mutation in full-length occludin delays its assembly into the tight junctions. Inhibition of PKCζ also induces redistribution of occludin and ZO-1 from the tight junctions and dissociates these proteins from the detergent-insoluble fractions in mouse ileum. The present study demonstrates that PKCζ phosphorylates occludin on specific threonine residues and promotes assembly of epithelial tight junctions.

Spray-dried porcine plasma influences intestinal barrier function, inflammation, and diarrhea in weaned pigs

The objective of this study was to evaluate the effects of dietary inclusion levels of spray-dried porcine plasma (SDPP) on postweaning (PW) intestinal barrier function, mucosal inflammation, and clinical indices of gut health in pigs. Ex vivo Ussing chamber studies were conducted to measure Ileal and colonic barrier function in terms of transepithelial electrical resistance and paracellular flux of (3)H-mannitol and (14)C-inulin. Intestinal inflammation was assessed by histological analysis and mucosal levels of proinflammatory cytokines. Dietary inclusion of 2.5 and 5% SDPP reduced colonic paracellular permeability of (14)C-inulin compared with controls (0% SDPP) on d 7 PW. Both 2.5 and 5% dietary SDPP reduced ileal (3)H-mannitol and (14)C-inulin permeability on d 14 PW. The 5% SDPP diet reduced colonic short-circuit current, an index of net electrogenic ion transport, and fecal scores when measured on d 7 and 14 PW compared with the control and 2.5% SDPP groups (P < 0.05). Histological analysis revealed fewer lamina propria cells in ileum and colon from pigs fed diets containing 2.5 and 5% SDPP on d 7 and 14 PW. Levels of the proinflammatory cytokine TNFα were reduced in the colon but not ileum from pigs fed the 5% SDPP on d 7 and 14 PW compared with controls (P < 0.05). IFNγ levels were lower than in controls in both of the SDPP-fed groups in the ileum and colon on d 7 but not on d 14 PW. Overall, this study demonstrated that dietary inclusion of SDPP had beneficial effects on intestinal barrier function, inflammation, and diarrhea in weaned pigs.

Effect of moderate exercise on IgA levels and lymphocyte count in mouse intestine

The aim of the present study was to determine the effect of moderate exercise on the production and secretion of IgA in mouse duodenum, on lymphocyte levels in the lamina propria, and on gene expression encoding for cytokines that regulate the synthesis of α-chain of IgA and the expression of pIgR in the lamina propria. Two groups of young Balb/c mice were fed ad libitum, one sedentary and the other with an exercise program (swimming) for 16 weeks. IgA levels in the duodenum were quantified by ELISA; the number of IgA containing cells as well as B cells, CD4(+) and CD8(+) T cells in the duodenal mucosa was determined by immunohistochemistry; gene expression was analyzed by real-time PCR, and the expression of proteins by Western blotting. Because of physical training, in the duodenum there was a decrease in the number of IgA producing cells, but an increase in the levels of IgA. Additionally, exercise increased the expression of the genes encoding for IL-4, IL-6, IL-10, TNF-α and TGF β, cytokines that regulate the synthesis of IgA and pIgR, the inflammatory response, and the immune response in the intestine. Thus, the increased IgA found in the duodenal lumen is probably due to the increased production of IgA in the LP and the increased transport of the pIgA-pIgR complex across epithelial cells. Possibly the increased S-IgA levels in the bile also contribute to the change in IgA levels.

The gut microbiome as therapeutic target

Obesity, type-2 diabetes and low-grade inflammation are becoming worldwide epidemics. In this regard, the literature provides a novel concept that we call "MicrObesity" (Microbes and Obesity), which is devoted to deciphering the specific role of dysbiosis and its impact on host metabolism and energy storage. In the present review, we discuss novel findings that may partly explain how the microbial community participates in the development of the fat mass development, insulin resistance and low-grade inflammation that characterise obesity. In recent years, numerous mechanisms have been proposed and several proteins identified. Amongst the key players involved in the control of fat mass development, Fasting induced adipose factor, AMP-activated protein kinase, G-protein coupled receptor 41 and G-protein coupled receptor 43 have been linked to gut microbiota. In addition, the discovery that low-grade inflammation might be directly linked to the gut microbiota through metabolic endotoxaemia (elevated plasma lipopolysaccharide levels) has led to the identification of novel mechanisms involved in the control of the gut barrier. Amongst these, the impacts of glucagon-like peptide-2, the endocannabinoid system and specific bacteria (e.g., Bifidobacterium spp.) have been investigated. Moreover, the advent of probiotic and prebiotic treatments appears to be a promising "pharmaco-nutritional" approach to reversing the host metabolic alterations linked to the dysbiosis observed in obesity. Although novel powerful molecular system biology approaches have offered great insight into this "small world within", more studies are needed to unravel how specific changes in the gut microbial community might affect or counteract the development of obesity and related disorders.

Effect of lactobacilli on paracellular permeability in the gut

Paracellular permeability is determined by the complex structures of junctions that are located between the epithelial cells. Already in 1996, it was shown that the human probiotic strain Lactobacillus plantarum 299v and the rat-originating strain Lactobacillus reuteri R2LC could reduce this permeability in a methotrexate-induced colitis model in the rat. Subsequently, many animal models and cell culture systems have shown indications that lactobacilli are able to counteract increased paracellular permeability evoked by cytokines, chemicals, infections, or stress. There have been few human studies focusing on the effect of lactobacilli on intestinal paracellular permeability but recently it has been shown that they could influence the tight junctions. More precisely, short-term administration of L. plantarum WCSF1 to healthy volunteers increased the relocation of occludin and ZO-1 into the tight junction area between duodenal epithelial cells.

Chronic stress sensitizes rats to pancreatitis induced by cerulein: Role of TNF-α

AIM: To investigate chronic stress as a susceptibility factor for developing pancreatitis, as well as tumor necrosis factor-α (TNF-α) as a putative sensitizer.

METHODS: Rat pancreatic acini were used to analyze the influence of TNF-α on submaximal (50 pmol/L) cholecystokinin (CCK) stimulation. Chronic restraint (4 h every day for 21 d) was used to evaluate the effects of submaximal (0.2 μg/kg per hour) cerulein stimulation on chronically stressed rats.

RESULTS: In vitro exposure of pancreatic acini to TNF-α disorganized the actin cytoskeleton. This was further increased by TNF-α/CCK treatment, which additionally reduced amylase secretion, and increased trypsin and nuclear factor-κB activities in a protein-kinase-C δ and ε-dependent manner. TNF-α/CCK also enhanced caspases’ activity and lactate dehydrogenase release, induced ATP loss, and augmented the ADP/ATP ratio. In vivo, rats under chronic restraint exhibited elevated serum and pancreatic TNF-α levels. Serum, pancreatic, and lung inflammatory parameters, as well as caspases’activity in pancreatic and lung tissue, were substantially enhanced in stressed/cerulein-treated rats, which also experienced tissues’ ATP loss and greater ADP/ATP ratios. Histological examination revealed that stressed/cerulein-treated animals developed abundant pancreatic and lung edema, hemorrhage and leukocyte infiltrate, and pancreatic necrosis. Pancreatitis severity was greatly decreased by treating animals with an anti-TNF-α-antibody, which diminished all inflammatory parameters, histopathological scores, and apoptotic/necrotic markers in stressed/cerulein-treated rats.

CONCLUSION: In rats, chronic stress increases susceptibility for developing pancreatitis, which involves TNF-α sensitization of pancreatic acinar cells to undergo injury by physiological cerulein stimulation.

Traumatic brain injury and intestinal dysfunction: uncovering the neuro-enteric axis

Traumatic brain injury (TBI) can lead to several physiologic complications including gastrointestinal dysfunction. Specifically, TBI can induce an increase in intestinal permeability, which may lead to bacterial translocation, sepsis, and eventually multi-system organ failure. However, the exact mechanism of increased intestinal permeability following TBI is unknown. We hypothesized that expression of tight junction protein ZO-1 and occludin, responsible for intestinal architectural and functional integrity, will decrease following TBI and increase intestinal permeability. BALB/c mice underwent a weight drop TBI model following anesthesia. Brain injury was confirmed by a neurologic assessment and gross brain pathology. Six hours following injury, FITC-dextran (25 mg 4.4 kDa FITC-dextran) was injected into the intact lumen of the isolated ileum. Intestinal permeability was measured in plasma 30 min following injection, by using spectrophotometry to determine plasma FITC-dextran concentrations. Whole ileum extracts were used to measure expression of tight junction proteins ZO-1 and occludin by Western blot. TBI caused a significant increase in intestinal permeability (110.0 microg/mL +/-22.2) compared to sham animals (29.4 microg/mL +/- 9.7) 6 h after injury (p = 0.016). Expression of ZO-1 was decreased by 49% relative to sham animals (p < 0.02), whereas expression of occludin was decreased by 73% relative to sham animals (p < 0.001). An increase in intestinal permeability corresponds with decreased expression of tight junction proteins ZO-1 and occludin following TBI. Expression of intestinal tight junction proteins may be an important factor in gastrointestinal dysfunction following brain injury.

Traumatic brain injury and intestinal dysfunction: uncovering the neuro-enteric axis

Traumatic brain injury (TBI) can lead to several physiologic complications including gastrointestinal dysfunction. Specifically, TBI can induce an increase in intestinal permeability, which may lead to bacterial translocation, sepsis, and eventually multi-system organ failure. However, the exact mechanism of increased intestinal permeability following TBI is unknown. We hypothesized that expression of tight junction protein ZO-1 and occludin, responsible for intestinal architectural and functional integrity, will decrease following TBI and increase intestinal permeability. BALB/c mice underwent a weight drop TBI model following anesthesia. Brain injury was confirmed by a neurologic assessment and gross brain pathology. Six hours following injury, FITC-dextran (25 mg 4.4 kDa FITC-dextran) was injected into the intact lumen of the isolated ileum. Intestinal permeability was measured in plasma 30 min following injection, by using spectrophotometry to determine plasma FITC-dextran concentrations. Whole ileum extracts were used to measure expression of tight junction proteins ZO-1 and occludin by Western blot. TBI caused a significant increase in intestinal permeability (110.0 microg/mL +/-22.2) compared to sham animals (29.4 microg/mL +/- 9.7) 6 h after injury (p = 0.016). Expression of ZO-1 was decreased by 49% relative to sham animals (p < 0.02), whereas expression of occludin was decreased by 73% relative to sham animals (p < 0.001). An increase in intestinal permeability corresponds with decreased expression of tight junction proteins ZO-1 and occludin following TBI. Expression of intestinal tight junction proteins may be an important factor in gastrointestinal dysfunction following brain injury.

Early weaning stress impairs development of mucosal barrier function in the porcine intestine

Early life stress is a predisposing factor for the development of chronic intestinal disorders in adult life. Here, we show that stress associated with early weaning in pigs leads to impaired mucosal barrier function. Early weaning (15- to 21-day weaning age) resulted in sustained impairment in intestinal barrier function, as indicated by reductions in jejunal transepithelial electrical resistance and elevations in mucosal-to-serosal flux of paracellular probes [(3)H]mannitol and [(14)C]inulin measured at 5 and 9 wk of age, compared with that shown in late-weaned pigs (23- to 28-day weaning age). Elevated baseline short-circuit current was observed in jejunum from early-weaned pigs and was shown to be mediated via enhanced Cl(-) secretion. Jejunal barrier dysfunction in early-weaned pigs coincided with increased lamina propria immune cell density particularly mucosal mast cells. The mast cell stabilizer drug sodium cromoglycolate ameliorated barrier dysfunction and hypersecretion in early-weaned pigs, demonstrating an important role of mast cells. Furthermore, activation of mast cells ex vivo with c48/80 and corticotrophin-releasing factor (CRF) in pig jejunum mounted in Ussing chambers induced barrier dysfunction and elevations in short-circuit current that were inhibited with mast cell protease inhibitors. Experiments in which selective CRF receptor antagonists were administered to early-weaned pigs revealed that CRF receptor 1 (CRFr1) activation mediates barrier dysfunction and hypersecretion, whereas CRFr2 activation may be responsible for novel protective properties in the porcine intestine in response to early life stress.