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

Tussilagone ameliorates high-fat diet-induced hepatic steatosis by enhancing energy metabolism and antioxidant activity

Non-alcoholic fatty liver disease (NAFLD) is a major health problem. However, no effective treatments are currently available. Thus, there is a critical need to develop novel drugs that can prevent and treat NAFLD with few side effects. In this study, Tussilagone (TUS), a natural sesquiterpene isolated from Tussilago farfara L, was explored in vitro and in vivo for its potential to treat NAFLD. Our results showed that in vitro TUS reduced oleic acid palmitate acid-induced triglyceride and cholesterol synthesis in HepG2cells, reduced intracellular lipid droplet accumulation, improved glucose metabolism disorders and increased energy metabolism and reduced oxidative stress levels. In vivo, TUS significantly reduced fat accumulation and improved liver injury in high-fat diet (HFD)-induced mice. TUS treatment significantly increased liver mitochondrial counts and antioxidant levels compared to the HFD group of mice. In addition, TUS was found to reduce the expression of genes involved in lipid synthesis sterol regulatory element binding protein-1 (SREBP1), fatty acid synthase (FASN), and stearoy-CoA desaturase 1 (SCD1) in vitro and in vivo. Our results suggest that TUS may be helpful in the treatment of NAFLD, suggesting that TUS is a promising compound for the treatment of NAFLD. Our findings provided novel insights into the application of TUS in regulating lipid metabolism.

Hydroxychloroquine ameliorates immune functionality and intestinal flora disorders of IgA nephropathy by inhibition of C1GALT1/Cosmc pathway

BACKGROUND

Hydroxychloroquine (HCQ) has emerged as a potential and secure antiproteinuric agent in IgA nephropathy (IgAN). This study endeavored to explore the impact of HCQ on the immune functionality and intestinal flora disorders in IgAN rats, as well as to elucidate the underlying mechanisms through in vivo and in vitro experiments.

METHODS

IgAN model was established in Sprague-Dawley rats through the administration of BSA, LPS, and CCl4, and the IgAN rats received a continuous 8-week treatment with HCQ. Moreover, the human glomerular mesangial cells (HMCs) were incubated with IgA1 to establish an in vitro cellular model of IgAN. At the end of experimental period, samples were collected for further analysis.

RESULTS

HCQ ameliorated the elevated levels of 24hUTP, SCr, BUN, the number of urinary RBC, and the activation of inflammation-related proteins within the TLR4/NF-κB signaling pathway. In the IgAN rat group, there was a pronounced escalation in IgA deposition, mesangial matrix hyperplasia, and glomerular inflammatory cell infiltration, while the administration of HCQ effectively mitigated these pathological changes. In addition, the reduced production of CD4+CD25+Foxp3+ Treg in the IgAN group was effectively reversed by HCQ. Furthermore, HCQ has the capacity to restore the compromised state of the intestinal mucosal barrier induced by IgAN and mitigate the circumstances of intestinal permeability and disruption in the intestinal flora.

CONCLUSION

HCQ diminishes IgA aberrant glycosylation levels, ameliorates renal and intestinal histopathological damage, and attenuates intestinal flora disorders and immune dysfunction in IgAN rats by means of activating the C1GALT1/Cosmc pathway.

Border Control: The Role of the Microbiome in Regulating Epithelial Barrier Function

The gut mucosal epithelium is one of the largest organs in the body and plays a critical role in regulating the crosstalk between the resident microbiome and the host. To this effect, the tight control of what is permitted through this barrier is of high importance. There should be restricted passage of harmful microorganisms and antigens while at the same time allowing the absorption of nutrients and water. An increased gut permeability, or "leaky gut", has been associated with a variety of diseases ranging from infections, metabolic diseases, and inflammatory and autoimmune diseases to neurological conditions. Several factors can affect gut permeability, including cytokines, dietary components, and the gut microbiome. Here, we discuss how the gut microbiome impacts the permeability of the gut epithelial barrier and how this can be harnessed for therapeutic purposes.

Characterization of Molecular Chaperone GroEL as a Potential Virulence Factor in Cronobacter sakazakii

The molecular chaperone GroEL of C. sakazakii, a highly conserved protein encoded by the gene grol, has the basic function of responding to heat shock, thus enhancing the bacterium's adaptation to dry and high-temperature environments, which poses a threat to food safety and human health. Our previous study demonstrated that GroEL was found in the bacterial membrane fraction and caused a strong immune response in C. sakazakii. In this study, we tried to elucidate the subcellular location and virulent effects of GroEL. In live C. sakazakii cells, GroEL existed in both the soluble and insoluble fractions. To study the secretory mechanism of GroEL protein, a non-reduced Western immunoblot was used to analyze the form of the protein, and the result showed that the exported GroEL protein was mainly in monomeric form. The exported GroEL could also be located on bacterial surface. To further research the virulent effect of C. sakazakii GroEL, an indirect immunofluorescence assay was used to detect the adhesion of recombinant GroEL protein to HCT-8 cells. The results indicated that the recombinant GroEL protein could adhere to HCT-8 cells in a short period of time. The recombinant GroEL protein could activate the NF-κB signaling pathway to release more pro-inflammatory cytokines (TNF-α, IL-6 and IL-8), downregulating the expression of tight-junction proteins (claudin-1, occluding, ZO-1 and ZO-2), which collectively resulted in dose-dependent virulent effects on host cells. Inhibition of the grol gene expression resulted in a significant decrease in bacterial adhesion to and invasion of HCT-8 cells. Moreover, the deficient GroEL also caused slow growth, decreased biofilm formation, defective motility and abnormal filamentation of the bacteria. In brief, C. sakazakii GroEL was an important virulence factor. This protein was not only crucial for the physiological activity of C. sakazakii but could also be secreted to enhance the bacterium's adhesion and invasion capabilities.

Holothurian Wall Hydrolysate Ameliorates Cyclophosphamide-Induced Immunocompromised Mice via Regulating Immune Response and Improving Gut Microbiota

Some biologically active compounds isolated from sea cucumbers stimulate the body's immune response by activating immune cells. Immune function is closely related to the integrity intestinal barrier and balanced gut microbiota. However, it is unknown whether the daily administration of holothurian wall hydrolysate (HWH) ameliorated intestinal dysbiosis and barrier injury induced by immunodeficiency. This study aimed to investigate the immunomodulatory effect and the underlying mechanism of HWH in cyclophosphamide (CTX)-induced immunocompromised mice. BALB/c mice received CTX (80 mg/kg, intraperitoneally) once a day for 3 days to induce immunodeficiency, and then they received the oral administration of HWH (80 or 240 mg/kg) or levamisole hydrochloride (LH, 40 mg/kg, positive control), respectively, once a day for 7 days. We utilized 16S rRNA sequencing for microbial composition alterations, histopathological analysis for splenic and colonic morphology, Western blotting for expressions of tight junction proteins (TJs), and quantitative real-time (qRT)-PCR for measurements of pro-inflammatory cytokines. HWH attenuated the immune organ damage induced by CTX, increased the secretions of interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α, and promoted the recovery of goblet cells and the production of TJs (claudin-1, occludin, and ZO-1) in the colon of the immunocompromised mice. Moreover, HWH promoted the growth of beneficial microorganisms such as Lactobacillus, Lachnospiraceae, Christensenellaceae, and Bifidobacterium, while it suppressed the populations of Ruminococcus, Staphylococcus, and Streptococcus. These results demonstrate that HWH elicits intestinal mucosal immunity, repairs the damage to intestinal mucosal integrity, and normalizes the imbalanced intestinal microbial profiles in immunocompromised mice. It may be helpful to identify the biological activities of HWH to support its potential use in new prebiotics, immunomodulatory agents, and medical additives for intestinal repair.

Paracellular permeability and tight junction regulation in gut health and disease

Epithelial tight junctions define the paracellular permeability of the intestinal barrier. Molecules can cross the tight junctions via two distinct size-selective and charge-selective paracellular pathways: the pore pathway and the leak pathway. These can be distinguished by their selectivities and differential regulation by immune cells. However, permeability increases measured in most studies are secondary to epithelial damage, which allows non-selective flux via the unrestricted pathway. Restoration of increased unrestricted pathway permeability requires mucosal healing. By contrast, tight junction barrier loss can be reversed by targeted interventions. Specific approaches are needed to restore pore pathway or leak pathway permeability increases. Recent studies have used preclinical disease models to demonstrate the potential of pore pathway or leak pathway barrier restoration in disease. In this Review, we focus on the two paracellular flux pathways that are dependent on the tight junction. We discuss the latest evidence that highlights tight junction components, structures and regulatory mechanisms, their impact on gut health and disease, and opportunities for therapeutic intervention.

Evaluation of Selenomethionine Entrapped in Nanoparticles for Oral Supplementation Using In Vitro, Ex Vivo and In Vivo Models

Selenium methionine (SeMet) is an essential micronutrient required for normal body function and is associated with additional health benefits. However, oral administration of SeMet can be challenging due to its purported narrow therapeutic index, low oral bioavailability, and high susceptibility to oxidation. To address these issues, SeMet was entrapped in zein-coated nanoparticles made from chitosan using an ionic gelation formulation. The high stability of both the SeMet and selenomethionine nanoparticles (SeMet-NPs) was established using cultured human intestinal and liver epithelial cells, rat liver homogenates, and rat intestinal homogenates and lumen washes. Minimal cytotoxicity to Caco-2 and HepG2 cells was observed for SeMet and SeMet-NPs. Antioxidant properties of SeMet were revealed using a Reactive Oxygen Species (ROS) assay, based on the observation of a concentration-dependent reduction in the build-up of peroxides, hydroxides and hydroxyl radicals in Caco-2 cells exposed to SeMet (6.25–100 μM). The basal apparent permeability coefficient (Papp) of SeMet across isolated rat jejunal mucosae mounted in Ussing chambers was low, but the Papp was increased when presented in NP. SeMet had minimal effects on the electrogenic ion secretion of rat jejunal and colonic mucosae in Ussing chambers. Intra-jejunal injections of SeMet-NPs to rats yielded increased plasma levels of SeMet after 3 h for the SeMet-NPs compared to free SeMet. Overall, there is potential to further develop SeMet-NPs for oral supplementation due to the increased intestinal permeability, versus free SeMet, and the low potential for toxicity.

The Absence of IL-12Rβ2 Expression on Recipient Nonhematopoietic Cells Diminishes Acute Graft-versus-Host Disease in the Gastrointestinal Tract

The gastrointestinal (GI) tract is a frequent target organ in acute graft-versus-host disease (aGVHD), which can determine the morbidity and nonrelapse mortality after allogeneic hematopoietic cell transplantation (allo-HCT). Donor T cells recognize allogeneic Ags presented by host APCs, proliferate, and differentiate into Th1 and Th17 cells that drive GVHD pathogenesis. IL-12 has been shown to play an important role in amplifying the allogeneic response in preclinical and clinical studies. This study demonstrates that IL-12Rβ2 expression on recipient nonhematopoietic cells is required for optimal development of aGVHD in murine models of allo-HCT. aGVHD attenuation by genetic depletion of IL-12R signaling is associated with reduced MHC class II expression by intestinal epithelial cells and maintenance of intestinal integrity. We verified IL-12Rβ2 expression on activated T cells and in the GI tract. This study, to our knowledge, reveals a novel function of IL-12Rβ2 in GVHD pathogenesis and suggests that selectively targeting IL-12Rβ2 on host nonhematopoietic cells may preserve the GI tract after allo-HCT.

Microbial and host factors contribute to bloodstream infection in a pediatric acute lymphocytic leukemia mouse model

Background

Hematological malignancies are the most common cancers in the pediatric population, and T-cell acute lymphocytic leukemia (T-ALL) is the most common hematological malignancy in children. Bloodstream infection (BSI) is a commonly occurring complication in leukemia due to underlying conditions and therapy-induced neutropenia. Several studies identified the gut microbiome as a major source of BSI due to bacterial translocation. This study aimed to investigate changes in the intestinal and fecal microbiome, and their roles in the pathophysiology of BSI in a pediatric T-ALL mouse model using high-throughput shotgun metagenomics sequencing, and metabolomics.

Results

Our results show that BSI in ALL is characterized by an increase of a mucin degrading bacterium (Akkermansia muciniphila) and a decrease of butyrate producer Clostridia spp., along with a decrease in short-chain fatty acid (SCFA) concentrations and differential expression of tight junction proteins in the small intestine. Functional analysis of the small intestinal microbiome indicated a reduced capability of SCFA synthesis, while SCFA supplementation ameliorated the development of BSI in ALL.

Conclusions

Our data indicates that changes in the microbiome, and the resulting changes in levels of SCFAs contribute significantly to the pathogenesis of bloodstream infection in ALL. Our study provides tailored preventive or therapeutic approaches to reduce BSI-associated mortality in ALL.

How Nanoparticles Open the Paracellular Route of Biological Barriers: Mechanisms, Applications, and Prospects

Biological barriers are essential physiological protective systems and obstacles to drug delivery. Nanoparticles (NPs) can access the paracellular route of biological barriers, either causing adverse health impacts on humans or producing therapeutic opportunities. This Review introduces the structural and functional influences of NPs on the key components that govern the paracellular route, mainly tight junctions, adherens junctions, and cytoskeletons. Furthermore, we evaluate their interaction mechanisms and address the influencing factors that determine the ability of NPs to open the paracellular route, which provides a better knowledge of how NPs can open the paracellular route in a safer and more controllable way. Finally, we summarize limitations in the research models and methodologies of the existing research in the field and provide future research direction. This Review demonstrates the in-depth causes for the reversible opening or destruction of the integrity of barriers generated by NPs; more importantly, it contributes insights into the design of NP-based medications to boost paracellular drug delivery efficiency.

Effect of crude polysaccharide from seaweed, Dictyopteris divaricata (CDDP) on gut microbiota restoration and anti-diabetic activity in streptozotocin (STZ)-induced T1DM mice

Type-1 Diabetes Mellitus (T1DM) is regarded as a multifunctional, immune-related disease which causes massive destruction of islet β-cells in pancreas resulting in hyperglycemic, hypoinsulinemia and hyperlipidimic conditions. The aim of the present study, was to investigate the hypothesis that streptozotocin (STZ)-induced T1DM in Balb/c mice when treated with crude polysaccharide from seaweed, Dictyopteris divaricata (CDDP) depicts improvement in diabetes-related symptoms. Treatment with CDDP resulted in decreased body weight loss, improved food consumption and water intake disbalances. The CDDP effectively improved fasting blood glucose, oral glucose tolerance (OGTT), serum insulin, insulin secretion, rejuvenation of β-cells mass, serum lipid profile and pro-inflammatory cytokines levels. Additionally, treatment with CDDP increased the population of beneficial bacteria such as Firmicutes, Bacteroidetes and Lactobacillus at phylum, family and genus levels by 16S rRNA sequencing. Furthermore, immunohistological examination confirmed that CDDP reduces the inflammation and restored the structural morphology of colon and upraised the levels of insulin receptor substrate-1 (IRS-1), Mucin-2 (MUC-2) and tight-junction proteins (TJs) whereby maintaining the gut structures and barrier permeability. Thus, the above presented data, highlights the safe and therapeutic effects of crude polysaccharide (CDDP) from D. divaricata in the treatment and restoration of T1DM disorders and can be used as a food supplement alternative to diabetes medicine.

Fibromodulin Ablation Exacerbates the Severity of Acute Colitis

Introduction

Epidemiological studies have associated pigment production with protection against certain human diseases. In contrast to African Americans, European descendants are more likely to suffer from angiogenesis-dependent and inflammatory diseases, such as wet age-related macular degeneration (ARMD) and ulcerative colitis (UC), respectively.

Methods

In a mouse model of dextran sulfate sodium (DSS)-induced acute colitis, the effect of fibromodulin (FMOD) depletion was examined on colitis severity.

Results

In this study, albino mice that produce high levels of FMOD developed less severe acute colitis compared with mice lacking in FMOD as assessed by clinical symptoms and histopathological changes. FMOD depletion affected the expression of tight junction proteins, contributing to the destruction of the epithelial barrier. Furthermore, this study revealed a stronger inflammatory response after DSS treatment in the absence of FMOD, where FMOD depletion led to an increase in activated T cells, plasmacytoid dendritic cells (pDCs), and type I interferon (IFN) production.

Discussion

These findings point to FMOD as a potential biomarker of disease severity in UC among light-skinned individuals of European descent.

GOS Ameliorates Nonalcoholic Fatty Liver Disease Induced by High Fat and High Sugar Diet through Lipid Metabolism and Intestinal Microbes

The treatment of nonalcoholic fatty liver disease (NAFLD) remains very challenging. This study investigated the therapeutic effect of galactose oligosaccharide (GOS), an important prebiotic, on NAFLD through in vivo and in vitro experiments and preliminarily explored the mechanism by which GOS improves liver lipid metabolism and inflammation through liver and intestinal microbiological analysis. The results of mouse liver lipidomics showed that GOS could promote body thermogenesis in mice with high-fat and high-sugar diet (HFHSD)-induced NAFLD, regulate lipolysis in liver fat cells, and accelerate glycine and cholesterol metabolism. GOS dose-dependently reduced the contents of total cholesterol (TC) and triglyceride (TG) in cells and reduced the accumulation of lipid droplets in cells. GOS also reduced the Firmicutes/Bacteroidetes ratio and altered the composition of the intestinal microbiota in mice fed a HFHSD. GOS can improve liver lipid metabolism and intestinal structure of NAFLD. These results provide a theoretical and experimental basis supporting the use of GOS as a health food with anti-NAFLD functions.

Decreased Plasma Level of Cytokeratin 20 (KRT20) Is Indicative of the Emergence and Severity of Acute GvHD Irrespective to the Type of Organ Involvement

Accurate risk prediction of acute graft versus host disease (aGvHD) is currently an unmet clinical need. This study sought to analyze whether three plasma proteins expressed in a largely skin- and gut-restricted manner would be affected by the development of acute cutaneous and gastrointestinal aGvHD. The diagnostic sensitivity, specificity, and prognostic value of plasma cytokeratin-15 (KRT15) cytokeratin-20 (KRT20), and occludin (OCLN) were evaluated in a discovery and a validation cohort using ELISA in comparison with elafin (PI3) and regenerating family member 3 alpha (REG3A), two established markers of skin- and gut aGvHD. The discovery cohort (n = 39) revealed that at the time of diagnosis, plasma KRT20 showed a progressive decrease from unaffected individuals to patients with single-, and patients with multi-organ aGvHD. KRT20 was affected by cutaneous (p = 0.0263) and gastrointestinal aGvHD (p = 0.0242) independently and in an additive manner. Sensitivity and specificity of KRT20 for aGvHD involving both target organs (AUC = 0.852) were comparable to that of PI3 for skin-aGvHD (AUC = 0.708) or that of REG3A for gut-aGvHD (AUC = 0.855). Patient follow-up in the validation cohort (n = 67) corroborated these observations (p < 0.001), and linked low KRT20 to grade 2+ disease (p < 0.001), but failed to confirm low KRT20 as an independent risk factor. These data established a link between low plasma KRT20 levels and moderate to severe aGvHD involving multiple target organs.

Early remodeling of the colonic mucosa after allogeneic hematopoietic stem cells transplantation: An open-label controlled pilot study on 19 patients

Background

Graft‐versus‐host disease (GVHD), particularly acute digestive GVHD (aDGVHD), is a severe complication of allogeneic hematopoietic stem cell transplantation (allo‐HSCT). It is necessary to identify predictive factors of GVHD to adapt prophylactic treatment.

Objective

In this context, our pilot study aimed (i) to determine whether an early remodeling of the colonic mucosa occurred after allo‐HSCT and (ii) to identify potential predictive mucosal markers of aDGVHD after allo‐HSCT.

Methods

Between day 21 and day 28 after the allo‐HSCT, 19 allo‐HSCT patients were included and had a rectosigmoidoscopy with probe‐based confocal laser endomicroscopy (pCLE) recording and biopsies. Sixteen patients were included in the control group. Morphological (pCLE), functional (intestinal permeability), and inflammatory parameters (cytokine multiplex immunoassay) were assessed.

Results

Among allo‐HSCT patients, 11 patients developed GVHD, and 6 of them developed aDGVHD. Morphological and functional changes of the colonic mucosa occurred after allo‐HSCT. Indeed, the perimeter of colonic crypts was significantly increased in allo‐HSCT patients compared to controls as well as crypt lumen fluorescein leakage (53% vs. 9%), whereas crypts sphericity, roundness, Feret diameter, and mean vessel area were significantly decreased in allo‐HSCT patients compared to the control group. In addition, interleukin‐6 (IL‐6), IL‐33, and IL‐15 levels in the supernatants of 24 h explant cultures of colonic biopsies were significantly increased in allo‐HSCT patients compared to controls. Finally, there was no difference in pCLE parameters, intestinal permeability, and inflammatory cytokines between patients who developed aDGVHD and those who did not.

Conclusion

This pilot study identified early colonic mucosa remodeling after allo‐HSCT conditioning therapy, that is morphological and functional mucosal alterations as well as mucosal inflammation. As to whether these changes are first steps in GVHD initiation and could be considered as predictive biomarkers of aDGVHD need to be determined in a larger cohort of patients.

Advances in Intestinal Barrier Preservation and Restoration in the Allogeneic Hematopoietic Cell Transplantation Setting

The intestinal barrier consists of an epithelial lining covered with specialized mucus inhabited by intestinal microbiota. An intact gut barrier ensures a resistance to bacteria and toxins translocation. On the other hand, gut permeability allows the absorption of essential nutrients, fluids and ions. This balance is achieved only by the complex structure and functional characteristics of the intestinal barrier. Allogenic hematopoietic cell transplantation remains the only curative treatment for many hematological diseases, but its application is limited because of possible transplant-related mortality mainly due to graft-versus-host disease and infectious complications. The intestinal barrier has been extensively studied in recent years as the primary site of graft-versus-host disease initiation and propagation. In the present review, we focused on the physiological structure and function of the gut barrier and the evidence of how the disruption of the gut barrier and increased intestinal permeability affects transplant recipients. Finally, therapeutic strategies aiming at intestinal barrier protection with a special focus on microbiome preservation and restoration in the allogenic hematopoietic cell transplantation setting are discussed.

The Prolyl Hydroxylase Inhibitor Dimethyl Oxalyl Glycine Decreases Early Gastrointestinal GVHD in Experimental Allogeneic Hematopoietic Cell Transplantation

BACKGROUND

Prolyl hydroxylase inhibitors (PHI) promote stabilization of hypoxia-inducible factor-1 alpha and affect signaling cascades of inflammation and cell death. Their beneficial use in experimental models of ulcerative colitis and lung allograft rejection led us to test the effect of the PHI dimethyl oxalyl glycine (DMOG) in the pathophysiology of graft versus host disease (GVHD).

METHODS

Acute GVHD was induced in lethally irradiated BALB/c mice. DMOG was administered intraperitoneally on alternate days for the first 2-weeks posttransplant, and then twice a week till day +50, while controls received vehicle only. Animals were monitored for clinical GVHD and analyzed at day +7 and at day +50.

RESULTS

DMOG treatment of allogeneic recipients improved survival by day +50, which was associated with decreased early gut injury and serum tumor necrosis factor-α compared with allogeneic controls. DMOG treatment of allogeneic recipients resulted in increased hypoxia-inducible factor-1 alpha expression and reduced apoptosis in the terminal ileum via Fas-associated protein with death domain protein repression along with decreased T-cell infiltration. Reduced pathology in colon after DMOG treatment associates with intestinal epithelium integrity and reduced damage caused by diminished recruitment of neutrophils.

CONCLUSIONS

Taken together, we show protective effects of DMOG on early gut GVHD and improved survival in a model of allogeneic hematopoietic cell transplantation, providing the rationale for further evaluation of PHIs, in the prevention and treatment of acute GVHD.

Lactobacillus plantarum BSGP201683 Improves the Intestinal Barrier of Giant Panda Microbiota-Associated Mouse Infected by Enterotoxigenic Escherichia coli K88

Giant pandas often suffered from gastrointestinal disease, especially the captive sub-adult one. Our study aims to investigate whether L. plantarum G83, a good panda-derived probiotic, can improve the intestinal barrier against the enterotoxigenic Escherichia coli K88 (E. coli K88) infection in giant panda microbiota-associated mice (GPAM). We treated SPF mice with antibiotics cocktail and transplanted the giant panda intestinal microbiota to set up a GPAM. Our results demonstrated that the microbiota of GPAM changed over time and was relatively stable in the short-term experiment (2-4 weeks). Whereafter, the GPAM pretreated with L. plantarum G83 for 15 days and infected with enterotoxigenic E. coli K88. The result indicated that the number of Bifidobacteria spp. increased in GPAM-G and GPAM-GE groups; the Lactobacillus spp. only increased in the GPAM-G group. Although the abundance of Enterobacteriaceae spp. only decreased in the GPAM-G group, the copy number of Escherichia coli in the GPAM-E group was significantly lower than that in the other groups. Meanwhile, the L. plantarum G83-induced alteration of microbiota could increase the mRNA expression of Claudin-1, Zo-1, and Occludin-1 in the GPAM-G group in the ileum; only Occludin-1 was increased in the GPAM-GE group. The sIgA in the ileum showed a positive response, also the result of body weight and histology in both the GPAM-G and GPAM-GE group. These results indicated that the L. plantarum G83 could improve the intestinal barrier to defense the enterotoxigenic E. coli K88 invasion.

The DNA Sensor AIM2 Protects against Streptozotocin-Induced Type 1 Diabetes by Regulating Intestinal Homeostasis via the IL-18 Pathway

Pattern recognition receptors (PRRs), such as Nod2, Nlrp3, Tlr2, Trl4, and Tlr9, are directly involved in type 1 diabetes (T1D) susceptibility. However, the role of the cytosolic DNA sensor, AIM2, in T1D pathogenesis is still unknown. Here, we demonstrate that C57BL/6 mice lacking AIM2 (AIM2^−/−) are prone to streptozotocin (STZ)-induced T1D, compared to WT C57BL/6 mice. The AIM2^−/− mice phenotype is associated with a greater proinflammatory response in pancreatic tissues, alterations in gut microbiota and bacterial translocation to pancreatic lymph nodes (PLNs). These alterations are related to an increased intestinal permeability mediated by tight-junction disruption. Notably, AIM2^−/− mice treated with broad-spectrum antibiotics (ABX) are protected from STZ-induced T1D and display a lower pancreatic proinflammatory response. Mechanistically, the AIM2 inflammasome is activated in vivo, leading to an IL-18 release in the ileum at 15 days after an STZ injection. IL-18 favors RegIIIγ production, thus mitigating gut microbiota alterations and reinforcing the intestinal barrier function. Together, our findings show a regulatory role of AIM2, mediated by IL-18, in shaping gut microbiota and reducing bacterial translocation and proinflammatory response against insulin-producing β cells, which ultimately results in protection against T1D onset in an STZ-induced diabetes model.

A three-dimensional immunocompetent intestine-on-chip model as in vitro platform for functional and microbial interaction studies

Alterations of the microbial composition in the gut and the concomitant dysregulation of the mucosal immune response are associated with the pathogenesis of opportunistic infections, chronic inflammation, and inflammatory bowel disease. To create a platform for the investigation of the underlying mechanisms, we established a three-dimensional microphysiological model of the human intestine. This model resembles organotypic microanatomical structures and includes tissue resident innate immune cells exhibiting features of mucosal macrophages and dendritic cells. The model displays the physiological immune tolerance of the intestinal lumen to microbial-associated molecular patterns and can, therefore, be colonised with living microorganisms. Functional studies on microbial interaction between probiotic Lactobacillus rhamnosus and the opportunistic pathogen Candida albicans show that pre-colonization of the intestinal lumen of the model by L. rhamnosus reduces C. albicans-induced tissue damage, lowers its translocation, and limits fungal burden. We demonstrate that microbial interactions can be efficiently investigated using the in vitro model creating a more physiological and immunocompetent microenvironment. The intestinal model allows a detailed characterisation of the immune response, microbial pathogenicity mechanisms, and quantification of cellular dysfunction attributed to alterations in the microbial composition.

Ileostomy for steroid-resistant acute graft-versus-host disease of the gastrointestinal tract

Steroid-resistant acute graft-versus-host disease (GVHD) of the gastrointestinal tract associates with important morbidity and mortality. While high-dose steroids are the established first-line therapy in GVHD, no second-line therapy is generally accepted. In this analysis of 65 consecutive patients with severe, steroid-resistant, intestinal GVHD (92% stage 4), additional ileostomy surgery significantly reduced overall mortality (hazard ratio 0.54; 95% confidence interval, 0.36-0.81; p = 0.003) compared to conventional GVHD therapy. Median overall survival was 16 months in the ileostomy cohort compared to 4 months in the conventional therapy cohort. In the ileostomy cohort, both infectious- and GVHD-associated mortality were reduced (40% versus 77%). Significantly declined fecal volumes (p = 0.001) after surgery provide evidence of intestinal adaptation following ileostomy. Correlative studies indicated ileostomy-induced immune-modulation with a > 50% decrease of activated T cells (p = 0.04) and an increase in regulatory T cells. The observed alterations of the patients' gut microbiota may also contribute to ileostomy's therapeutic effect. These data show that ileostomy induced significant clinical responses in patients with steroid-resistant GVHD along with a reduction of pro-inflammatory immune cells and changes of the intestinal microbiota. Ileostomy is a treatment option for steroid-resistant acute GVHD of the gastrointestinal tract that needs further validation in a prospective clinical trial.

Effects of a Lactulose-Rich Diet on Fecal Microbiome and Metabolome in Pregnant Mice

Lactulose, a safe and beneficial molecule, can be used in food as a prebiotic and as an osmotic laxative during pregnancy. This work evaluated the effects of dietary lactulose on the gut microenvironment of pregnant mice using the fecal microbiota and metabolomic profiling. After 2 weeks of feeding, the Bifidobacterium and Bacteroides abundances in the mouse feces were significantly increased in the LAC-high (the diet supplemented with 15% lactulose) group. A total of 15 metabolites, including 1-monoolein, glucose-6-phosphate, and short-chain fatty acids, were increased significantly in the LAC-high group. The serum glucose and total cholesterol concentrations were significantly decreased, while the progesterone level was significantly increased in the lactulose-fed mice. In the LAC-high group, the colonic pH and intestinal permeability were decreased, while the immunoglobulins in the colonic epithelial cells and the small intestinal absorption capacity were significantly increased. These findings indicated that lactulose supplementation benefitted pregnancy performance in mice.

Effect of Intestinal Flora Clearance on Liver Proteomics in Mice

Background:

Intestinal flora dynamically affects the host&#039;s systemic immune system. Liver is one of the organs that may be affected by intestinal microbiota. </P><P> Materials and Methods: In this study, we aimed to identify proteome level differences between liver tissue from mice cleared intestinal flora and control using tandem mass spectrometry (LC-MS/MS) and label free quantification. Additionally, protein-protein interactions were mapped by STRING, and also, the enrichment of inflammation-related signaling pathways and biological processes was identified using GO and IPA network system. RT-PCR and Western blot were used for validation of the proteomics findings.

Results:

Our study demonstrated that mice with cleared intestinal flora exhibited decreased sensitivity to Concanavalin A induced acute hepatitis. 324 Proteins in liver were differently expressed after intestinal flora clearance for one week while 210 proteins were differently expressed after intestinal flora clearance for two weeks. Furthermore, five of the identified proteins were validated by western blotting and further investigated by semi-quantitative RT-PCR.

Conclusion:

Our results showed that intestinal flora clearance in mice could reduce sensitivity to Concanavalin A induced liver injury and influence the expression of proteins in liver, which provides a clue for studying the relationship between gut bacteria and Concanavalin A induced hepatitis.

Graft-versus-host disease propagation depends on increased intestinal epithelial tight junction permeability

Graft-versus-host disease (GVHD) is a complication of hematopoietic stem cell transplantation (HSCT) that affects multiple organs. GVHD-associated intestinal damage can be separated into two distinct phases, initiation and propagation, which correspond to conditioning-induced damage and effector T cell activation and infiltration, respectively. Substantial evidence indicates that intestinal damage induced by pretransplant conditioning is a key driver of GVHD initiation. Here, we aimed to determine the impact of dysregulated intestinal permeability on the subsequent GVHD propagation phase. The initiation phase of GVHD was unchanged in mice lacking long MLCK (MLCK210), an established regulator of epithelial tight junction permeability. However, MLCK210-deficient mice were protected from sustained barrier loss and exhibited limited GVHD propagation, as indicated by reduced histopathology, fewer CD8+ effector T cells in the gut, and improved overall survival. Consistent with these findings, intestinal epithelial MLCK210 expression and enzymatic activity were similarly increased in human and mouse GVHD biopsies. Intestinal epithelial barrier loss mediated by MLCK210 is therefore a key driver of the GVHD propagation. These data suggest that inhibition of MLCK210-dependent barrier regulation may be an effective approach to limiting GVHD progression.

The protective effect of protopanaxatriol-type saponin on intestinal health in antibiotic-treated mice

This experiment is the first to explore the regulation of PPT on intestinal microbiota and integrity of the intestinal barrier.

IL-17C Mitigates Murine Acute Graft-vs.-Host Disease by Promoting Intestinal Barrier Functions and Treg Differentiation

Acute graft-vs.-host disease (aGVHD) is one of the major complications and results in high mortality after allogeneic hematopoietic stem cell transplantation (allo-HSCT). IL-17C is involved in many inflammatory immune disorders. However, the role of IL-17C in aGVHD remains unknown. Here we demonstrated that IL-17C deficiency in the graft significantly promoted alloreactive T cell responses and induced aggravated aGVHD compared with wildtype donors in a fully MHC-mismatched allo-HSCT model. In contrast, IL-17C overexpression ameliorated aGVHD. IL-17C deficiency increased intestinal epithelial permeability and elevated inflammatory cytokine production, leading to an enhanced aGVHD progression. Tregs was reduced in recipients of IL-17C^−/− graft, whilst restored after IL-17C overexpression. Decreased Treg differentiation was abrogated after neutralizing IFN-γ, but not IL-6. Moreover, depletion of Tregs diminished the protective effect of IL-17C. Of note, patients with low IL-17C expression displayed higher aGVHD incidence together with poor overall survival, thereby IL-17C could be an independent risk factor for aGVHD development. Our results are the first demonstrating the protective role of IL-17C in aGVHD by promoting intestinal barrier functions and Treg differentiation in a MHC fully mismatched murine aGVHD model. IL-17C may serve as a novel biomarker and potential therapeutic target for aGVHD.

Postnatal maturation of the intestinal epithelial barrier in prairie voles

Intestinal epithelium develops during gestation and continues to mature post-natally into a selective barrier that will protect the individual while still allowing passage of nutrients. Until fully mature, the risk of translocation of microorganisms, toxins or antigens into the sub-epithelial tissue is high and could result in pathologies with life-altering consequences, or even premature death. Because of their monogamous mating system, prairie voles are an emerging model for studying the role of the intestinal microbiota in modulating social behavior via the microbiota-gut-brain-behavior axis. However, knowledge about the voles' intestinal barrier maturation is lacking. Understanding the maturation of the intestine epithelial barrier can complement the extensive behavioral literature for future studies involving the vole gut-brain axis. In this study, we characterized intestinal barrier function by demonstrating that two-week-old prairie voles have high paracellular absorption of FITC-dextran molecules prior to markedly decreased permeability at three weeks of age. In light of the fundamental role of tight junctions in maintaining epithelial integrity regulating intestinal permeability, we examined tight junction gene expression profiles. Transmission electron microscopy was used to visualize tight junction structure. Our results provide a timeline for intestinal barrier maturation and point to tight junction proteins involved in this process in prairie voles.

A Polysaccharide Isolated from Dictyophora indusiata Promotes Recovery from Antibiotic-Driven Intestinal Dysbiosis and Improves Gut Epithelial Barrier Function in a Mouse Model

Despite the tremendous biological activity of polysaccharides from the mushroom Dictyophora indusiata, its role in the restoration of gut microbiota has not yet been explored. The present study aimed to investigate whether D. indusiata polysaccharide (DIP) could modulate the recovery of gut microbiota composition and intestinal barrier function after broad-spectrum antibiotic-driven dysbiosis. Alteration and restoration in the microbial communities were elucidated by the Illumina MiSeq platform. Colon histology, expression of tight-junction associated proteins, and serum/tissue endotoxin and cytokine levels were evaluated. Two-week daily oral administration of clindamycin and metronidazole resulted in reduced bacterial diversity and richness, and perturbed the microbial flora at various taxonomic levels (altered Firmicutes/Bacteroidetes ratio and increased relative abundance of harmful flora (Proteobacteria, Enterococcus, and Bacteroides)), whereas DIP administration reversed the dysbiosis and increased beneficial flora, including Lactobacillaceae (lactic acid-producing bacteria), and Ruminococaceae (butyrate-producing bacteria). In addition, it resulted in the reduction of endotoxemia (through lipopolysaccharides (LPSs)) and pro-inflammatory cytokine (tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), and interleukin 1β (IL-1β)) levels, with the increased expression of tight-junction associated proteins (claudin-1, occludin, and zonula occludens-1). These findings not only suggested a comprehensive understanding of the protective effects of a DIP in the restoration of gut microbiota but also highlighted its role in the enhancement of gut barrier integrity, reduction of inflammation and lowering of endotoxin levels in mice.

Fluorescence contrast-enhanced proliferative lesion imaging by enema administration of indocyanine green in a rat model of colon carcinogenesis

The fluorescent contrast agent indocyanine green (ICG) is approved by the Food and Drug Administration for clinical applications. We previously reported that cultured human colon tumor cells preferentially take up ICG by endocytic activity in association with disruption of their tight junctions. The present study explored ICG availability in fluorescence imaging of the colon to identify proliferative lesions during colonoscopy. The cellular uptake of ICG in cultured rat colon tumor cells was examined using live-cell imaging. Colon lesions in rats administered an ICG-containing enema were further assessed in rats with azoxymethane-induced colon carcinogenesis, using in vivo endoscopy, ex vivo microscopy, and immunofluorescence microscopy. The uptake of ICG by the cultured cells was temperature-dependent. The intracellular retention of the dye in the membrane trafficking system suggested endocytosis as the uptake mechanism. ICG administered via enema accumulated in colon proliferative lesions ranging from tiny aberrant crypt foci to adenomas and localized in proliferating cells. Fluorescence endoscopy detected these ICG-positive colonic proliferative lesions in vivo. The immunoreactivity of the tight-junction molecule occludin was altered in the proliferative lesions, suggesting the disruption of the integrity of tight junctions. These results suggest that fluorescence contrast-enhanced imaging following the administration of an ICG-containing enema can enhance the detection of mucosal proliferative lesions of the colon during colonoscopy. The tissue preference of ICG in the rat model evaluated in this study can be attributed to the disruption of tight junctions, which in turn promotes endocytosis by proliferative cells and the cellular uptake of ICG.

Chronic high-dosage fish oil exacerbates gut-liver axis injury in alcoholic steatohepatitis in mice: the roles of endotoxin and IL-4 in Kupffer cell polarization imbalance

In the present study, intestinal tight junctions (TJs) and Kupffer cell polarization were investigated in an alcoholic steatohepatitis (ASH) mouse model to uncover the potential side effects of overexposure to fish oil or omega-3 fatty acids. The mice were fed ad libitum with a liquid diet containing ethanol and fish oil. In the meantime, ethanol was given every 5-7 days by gavage to simulate binge drinking. After the 7^th binge, steatosis, necrosis, inflammatory infiltration, and bridging fibrosis were observed in the liver by histological staining. After the 13^th binge, the inducers, markers and other downstream genes/proteins of the Kupffer cell M1/M2 phenotype in the liver, serum, and small intestine were analysed. The results suggested that a chronic high dosage of fish oil alone reduced the mRNA levels of most genes tested and showed a tendency to damage the intestinal zonula occludens-1 localization and reduce the number of M2 Kupffer cells. Meanwhile, the combination of fish oil and ethanol damaged the intestinal TJs, resulting in an increased endotoxin level in the liver. Gut-derived endotoxin polarized Kupffer cells to the M1 phenotype, whereas the number of cells with the M2 phenotype (markers: CD163 and CD206) was decreased. Interleukin-4 (IL-4), an M2 Kupffer cell inducer, was also decreased. Moreover, in vitro experiments showed that IL-4 reversed eicosapentaenoic acid-induced CD163 and CD206 mRNA suppression in RAW 264.7 cells. Overall, our results showed that a chronic high dosage of fish oil exacerbated gut-liver axis injury in alcoholic liver disease in mice, and endotoxin/IL-4-induced Kupffer cell polarization imbalance might play an important role in that process.

Lactobacillus delivery of bioactive interleukin-22

BACKGROUND

Interleukin-22 (IL-22) plays a prominent role in epithelial regeneration and dampening of chronic inflammatory responses by protecting intestinal stem cells from immune-mediated tissue damage. IL-22 has a considerable therapeutic potential in graft-versus-host disease (GVHD), which is a frequent and challenging complication following allogeneic stem cell transplantation. The aim of our study was to engineer Lactobacillus for delivery of IL-22 directly to the intestinal mucosa as a new therapeutic strategy for GVHD.

RESULTS

The secretion and surface anchoring of mouse IL-22 by Lactobacillus paracasei BL23 was demonstrated by Western blot and flow cytometry. Both secreted and anchored mouse IL-22 produced by Lactobacillus was biologically active, as determined by its ability to induce IL-10 secretion in the Colo 205 human colon cancer cell line.

CONCLUSIONS

We have demonstrated the secretion and surface anchoring of bioactive IL-22 by Lactobacillus. Our results suggest that IL-22 expressing lactobacilli may potentially be a useful mucosal therapeutic agent for the treatment of GVHD, provided that chromosomal integration of the IL-22 expression cassettes can be achieved.

Disruption of the epithelial barrier during intestinal inflammation: Quest for new molecules and mechanisms

The intestinal epithelium forms a key protective barrier that separates internal organs from the harmful environment of the gut lumen. Increased permeability of the gut barrier is a common manifestation of different inflammatory disorders contributing to the severity of disease. Barrier permeability is controlled by epithelial adherens junctions and tight junctions. Junctional assembly and integrity depend on fundamental homeostatic processes such as cell differentiation, rearrangements of the cytoskeleton, and vesicle trafficking. Alterations of intestinal epithelial homeostasis during mucosal inflammation may impair structure and remodeling of apical junctions, resulting in increased permeability of the gut barrier. In this review, we summarize recent advances in our understanding of how altered epithelial homeostasis affects the structure and function of adherens junctions and tight junctions in the inflamed gut. Specifically, we focus on the transcription reprogramming of the cell, alterations in the actin cytoskeleton, and junctional endocytosis and exocytosis. We pay special attention to knockout mouse model studies and discuss the relevance of these mechanisms to human gastrointestinal disorders.

Diet-driven microbiota dysbiosis is associated with vagal remodeling and obesity

Obesity is one of the major health issues in the United States. Consumption of diets rich in energy, notably from fats and sugars (high-fat/high-sugar diet: HF/HSD) is linked to the development of obesity and a popular dietary approach for weight loss is to reduce fat intake. Obesity research traditionally uses low and high fat diets and there has been limited investigation of the potential detrimental effects of a low-fat/high-sugar diet (LF/HSD) on body fat accumulation and health. Therefore, in the present study, we investigated the effects of HF/HSD and LF/HSD on microbiota composition, gut inflammation, gut-brain vagal communication and body fat accumulation. Specifically, we tested the hypothesis that LF/HSD changes the gut microbiota, induces gut inflammation and alters vagal gut-brain communication, associated with increased body fat accumulation. Sprague-Dawley rats were fed an HF/HSD, LF/HSD or control low-fat/low-sugar diet (LF/LSD) for 4weeks. Body weight, caloric intake, and body composition were monitored daily and fecal samples were collected at baseline, 1, 6 and 27days after the dietary switch. After four weeks, blood and tissues (gut, brain, liver and nodose ganglia) were sampled. Both HF/HSD and LF/HSD-fed rats displayed significant increases in body weight and body fat compared to LF/LSD-fed rats. 16S rRNA sequencing showed that both HF/HSD and LF/HSD-fed animals exhibited gut microbiota dysbiosis characterized by an overall decrease in bacterial diversity and an increase in Firmicutes/Bacteriodetes ratio. Dysbiosis was typified by a bloom in Clostridia and Bacilli and a marked decrease in Lactobacillus spp. LF/HSD-fed animals showed a specific increase in Sutterella and Bilophila, both Proteobacteria, abundances of which have been associated with liver damage. Expression of pro-inflammatory cytokines, such as IL-6, IL-1β and TNFα, was upregulated in the cecum while levels of tight junction protein occludin were downregulated in both HF/HSD and LF/HSD fed rats. HF/HSD and LF/HSD-fed rats also exhibited an increase in cecum and serum levels of lipopolysaccharide (LPS), a pro-inflammatory bacterial product. Immunofluorescence revealed the withdrawal of vagal afferents from the gut and at their site of termination the nucleus of the solitary tract (NTS) in both the HF/HSD and LF/HSD rats. Moreover, there was significant microglia activation in the nodose ganglia, which contain the vagal afferent neuron cell bodies, of HF/HSD and LF/HSD rats. Taken together, these data indicate that, similar to HF/HSD, consumption of an LF/HSD induces dysbiosis of gut microbiota, increases gut inflammation and alters vagal gut-brain communication. These changes are associated with an increase in body fat accumulation.

Treatment with alpha-galactosylceramide protects mice from early onset of nonalcoholic steatohepatitis: Role of intestinal barrier function

SCOPE

The role of invariant natural killer T cells in the development of nonalcoholic steatohepatitis (NASH) has not yet been fully understood. Here, the effect of the invariant natural killer T-cell activator alpha-galactosylceramide (αGalCer) on the development of nonalcoholic fatty liver disease and intestinal barrier function was assessed in a mouse model of early Western-style diet (WSD) induced NASH.

METHODS AND RESULTS

Female C57BL/6J mice were either fed a liquid control diet or a liquid fructose-enriched WSD for 6 wk while being treated three times weekly with αGalCer (2 μg intraperitoneal) or vehicle. Indices of liver damage, glucose metabolism, and intestinal permeability were measured. Treatment with αGalCer markedly suppressed hepatic fat accumulation and inflammation while not affecting fasting glucose. The protective effects of αGalCer were associated with a protection against the increased translocation of bacterial endotoxins and the decreased protein levels of tight junction proteins occludin and zonula occludens 1 found in vehicle-treated mice while being fed a WSD.

CONCLUSION

Taken together, our data suggest that the protective effects of αGalCer against the development of a diet-induced NASH in mice are associated with a protection against the increased translocation of intestinal bacterial endotoxins associated with the development of NASH.

Better Management of Alcohol Liver Disease Using a 'Microstructured Synbox' System Comprising L. plantarum and EGCG

Synergistic combination of probiotics with carbohydrate based prebiotics is widely employed for the treatment of various gut related disorders. However, such carbohydrate based prebiotics encourage the growth of pathogens and probiotics, equally. Aim of the study was (i) to explore the possibility of using epigallocatechin gallate (EGCG) a phenolic compound, as a prebiotic for L.plantarum; (ii) to develop and evaluate a microstructured synbox (microencapsulating both probiotic and EGCG together) in rat model of alcohol liver disease (ALD); and, (iii) to confirm whether the combination can address issues of EGCG bioavailability and probiotic survivability in adverse gut conditions. Growth enhancing effect of EGCG on L. plantarum (12.8±0.5 log 10 units) was significantly (p≤0.05) better than inulin (11.4±0.38 log 10 units), a natural storage carbohydrate. The formulated synbox significantly modulated the levels of alcohol, endotoxin, hepatic enzymes and restored the hepatoarchitecture in comparison to simultaneous administration of free agents. Additionally, using a battery of techniques, levels of various cellular and molecular markers viz. NF-kB/p50, TNF-α, IL12/p40, and signalling molecules TLR4, CD14, MD2, MyD88 and COX-2 were observed to be suppressed. Developed microbead synbox, as a single delivery system for both the agents showed synergism and hence, holds promise as a therapeutic option for ALD management.

The intestinal epithelial barrier: a therapeutic target?

A fundamental function of the intestinal epithelium is to act as a barrier that limits interactions between luminal contents such as the intestinal microbiota, the underlying immune system and the remainder of the body, while supporting vectorial transport of nutrients, water and waste products. Epithelial barrier function requires a contiguous layer of cells as well as the junctions that seal the paracellular space between epithelial cells. Compromised intestinal barrier function has been associated with a number of disease states, both intestinal and systemic. Unfortunately, most current clinical data are correlative, making it difficult to separate cause from effect in interpreting the importance of barrier loss. Some data from experimental animal models suggest that compromised epithelial integrity might have a pathogenic role in specific gastrointestinal diseases, but no FDA-approved agents that target the epithelial barrier are presently available. To develop such therapies, a deeper understanding of both disease pathogenesis and mechanisms of barrier regulation must be reached. Here, we review and discuss mechanisms of intestinal barrier loss and the role of intestinal epithelial barrier function in pathogenesis of both intestinal and systemic diseases. We conclude with a discussion of potential strategies to restore the epithelial barrier.

Structural and Functional Changes in the Tight Junctions of Asymptomatic and Serology-negative First-degree Relatives of Patients With Celiac Disease

BACKGROUND

Ten to 15% of first-degree relatives (FDRs) of celiac disease (CeD) patients develop CeD. Although intestinal barrier functions (intestinal permeability) are abnormal in the subset of serology-negative FDRs, what leads to the abnormal barrier function is not known.

GOALS

To study the ultrastructure and functions of tight junctions in serology-negative FDRs of CeD patients.

STUDY

The intestinal permeability was measured in 97 asymptomatic and anti-tissue transglutaminase antibody (anti-tTG Ab)-negative FDRs (using the lactulose mannitol ratio) and in 75 controls. The ultrastructure of tight junctions using transmission electron microscopy, and the expression of key tight junction proteins (claudin-2, claudin-3, occludin, JAM-A, and ZO-1) and zonulin using real-time PCR and immunohistochemistry were assessed in anti-tTG Ab-negative, HLA-DQ2/-DQ8-positive FDRs having normal villi and in disease controls. In addition, the serum zonulin level was measured in 172 anti-tTG Ab-negative FDRs and 198 controls.

RESULTS

The intestinal permeability was significantly increased in FDRs than in controls. Ultrastructural abnormalities such as dilatation of the tight junction (P=0.004) and loss of the pentalaminar structure (P=0.001) were more common in FDRs than in disease controls. There was significant underexpression of tight junction proteins ZO-1 (P=0.040) and occludin (P=0.041) in FDRs. There was no significant difference in the serum zonulin level between FDRs and controls (P=0.154).

CONCLUSIONS

Even asymptomatic, anti-tTG-Ab-negative FDRs with a normal villous histology have both ultrastructural and functional abnormalities in tight junctions. These findings are indirect evidence of the presence of tight junction abnormalities before the onset of the disease and may have therapeutic implications.

Melatonin prevents secondary intra-abdominal hypertension in rats possibly through inhibition of the p38 MAPK pathway

Exogenous administration of melatonin has been demonstrated to down-regulate inflammatory responses and attenuate organ damage in various models. However, the salutary effect of melatonin against secondary intra-abdominal hypertension (IAH) remains unclear. This study sought to test the influence of melatonin on secondary IAH in a pathophysiological rat model and the underlying mechanisms involved. Before resuscitation, male rats underwent a combination of induced portal hypertension, applying an abdominal restraint device, and hemorrhaging to mean arterial pressure (MAP) of 40mmHg for 2h. After blood reinfusion, the rats were treated with lactated Ringer solution (LR) (30mL/h), melatonin (50mg/kg) +LR, and SB-203580 (10μmol/kg)+LR. LR was continuously infused for 6h. MAP, the inferior vena cava pressure and urine output were monitored. Histopathological examination, immunofluorescence of tight junction proteins, and transmission electron microscopy were administered. Intestinal permeability, myeloperoxidase activity, malondialdehyde, glutathione peroxidase, and levels of TNF-a, IL-2, and IL-6, were assessed. The expression of extracellular signal-regulated kinase, p38, c-Jun NH2-terminal kinase, translocation of nuclear factor kappa B subunit, signal transducers and activators of transcription and tight junction proteins were detected by Western blot. We found that melatonin inhibited the inflammatory responses, decreased expression of p38 MAPK, attenuated intestinal injury, and prevented secondary IAH. Moreover, administration of SB203580 abolished the increase in p38 MAPK and also attenuated intestinal injury. These data indicate that melatonin exerts a protective effect in intestine in secondary IAH primarily by attenuating the inflammatory responses which are in part attributable to p38 MAPK inhibition.

Tight Junction Ultrastructure Alterations in a Mouse Model of Enteral Nutrient Deprivation

BACKGROUND

Total parenteral nutrition (TPN), a necessary treatment for patients who cannot receive enteral nutrition, is associated with infectious complications due in part to a loss of intestinal epithelial barrier function (EBF). Using a mouse model of TPN, with enteral nutrient deprivation, we previously demonstrated an increase in mucosal interferon-γ and tumor necrosis factor-α; these cytokine changes are a major mediator driving a reduction in epithelial tight junction (TJ) protein expression. However, the exact ultrastructural changes to the intestinal epithelial barrier have not been previously described.

AIM

We hypothesized that TPN dependence results in ultrastructural changes in the intestinal epithelial TJ meshwork.

METHODS

C57BL/6 mice underwent internal jugular venous cannulation and were given enteral nutrition or TPN with enteral nutrient deprivation for 7 days. Freeze-fracture electron microscopy was performed on ileal tissue to characterize changes in TJ ultrastructure. EBF was measured using transepithelial resistance and tracer permeability, while TJ expression was measured via Western immunoblotting and immunofluorescence staining.

RESULTS

While strand density, linearity, and appearance were unchanged, TPN dependence led to a mean reduction in one horizontal strand out of the TJ compact meshwork to a more basal region, resulting in a reduction in meshwork depth. These findings were correlated with the loss of TJ localization of claudin-4 and tricellulin, reduced expression of claudin-5 and claudin-8, and reduced ex vivo EBF.

CONCLUSION

Tight junction ultrastructural changes may contribute to reduced EBF in the setting of TPN dependence.

Gut microbiome-derived metabolites modulate intestinal epithelial cell damage and mitigate graft-versus-host disease

The effect of alterations in intestinal microbiota on microbial metabolites and on disease processes such as graft-versus-host disease (GVHD) is not known. Here we carried out an unbiased analysis to identify previously unidentified alterations in gastrointestinal microbiota-derived short-chain fatty acids (SCFAs) after allogeneic bone marrow transplant (allo-BMT). Alterations in the amount of only one SCFA, butyrate, were observed only in the intestinal tissue. The reduced butyrate in CD326(+) intestinal epithelial cells (IECs) after allo-BMT resulted in decreased histone acetylation, which was restored after local administration of exogenous butyrate. Butyrate restoration improved IEC junctional integrity, decreased apoptosis and mitigated GVHD. Furthermore, alteration of the indigenous microbiota with 17 rationally selected strains of high butyrate-producing Clostridia also decreased GVHD. These data demonstrate a heretofore unrecognized role of microbial metabolites and suggest that local and specific alteration of microbial metabolites has direct salutary effects on GVHD target tissues and can mitigate disease severity.

Intestinal barrier loss as a critical pathogenic link between inflammatory bowel disease and graft-versus-host disease

Compromised intestinal barrier function is a prominent feature of inflammatory bowel disease (IBD). However, links between intestinal barrier loss and disease extend much further, including documented associations with celiac disease, type I diabetes, rheumatoid arthritis, and multiple sclerosis. Intestinal barrier loss has also been proposed to have a critical role in the pathogenesis of graft-versus-host disease (GVHD), a serious, potentially fatal consequence of hematopoietic stem cell transplantation. Experimental evidence has begun to support this view, as barrier loss and its role in initiating and establishing a pathogenic inflammatory cycle in GVHD is emerging. Here we discuss similarities between IBD and GVHD, mechanisms of intestinal barrier loss in these diseases, and the crosstalk between barrier loss and the immune system, with a special focus on natural killer (NK) cells. Unanswered questions and future research directions on the topic are discussed along with implications for treatment.

The Role of Intestinal Microbiota in Acute Graft-versus-Host Disease

The mammalian intestinal microbiota is a complex ecosystem that plays an important role in host immune responses. Recent studies have demonstrated that alterations in intestinal microbiota composition are linked to multiple inflammatory diseases in humans, including acute graft-versus-host disease (aGVHD). aGVHD is one of the major obstacles in allogeneic hematopoietic stem cell transplantation (allo-HSCT), characterized by tissue damage in the gastrointestinal (GI) tract, liver, lung, and skin. Here, we review the current understanding of the role of intestinal microbiota in the control of immune responses during aGVHD. Additionally, the possibility of using probiotic strains for potential treatment or prevention of aGVHD will be discussed.

Azithromycin attenuates cigarette smoke extract-induced oxidative stress injury in human alveolar epithelial cells

Cigarette smoking has been verified to be one of the most important etiological factors causing the development of bronchogenic carcinoma and chronic obstructive pulmonary disease. Azithromycin (AZM) has been demonstrated to have antioxidant capacity. In the present study, whether AZM is able to attenuate cigarette smoke extract (CSE)-induced A549 cell oxidative stress injury was investigated. Cells were incubated with CSE in the presence or absence of AZM. Cell viability was measured using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The expression of vascular endothelial growth factor (VEGF) was analyzed using western blotting and ELISA. The expression of epithelial cell structural proteins, zona occludens (ZO)-1 and occludin was determined using western blotting and immunofluorescence staining. Reactive oxygen species (ROS) production was examined by flow cytometry and fluorescence staining. The results demonstrated that the exposure of A549 cells to CSE decreased cell viability in a dose- and time-dependent manner. AZM significantly attenuated the CSE-induced decreases in the expression of VEGF and epithelial cell structural proteins, including ZO-1 and occludin. CSE also stimulated ROS production in the A549 cell, while AZM significantly reversed the effects of CSE. In addition, the inhibition of ROS by N-acetyl-L-cysteine had similar effects as AZM on the expression of VEGF and epithelial cell structural proteins and also enhanced cell proliferation. In conclusion, AZM attenuated CSE-induced oxidative stress injury in A549 cells and may be a promising therapeutic agent for smoking-associated pulmonary diseases.