Cloning of the human claudin-2 5'-flanking region revealed a TATA-less promoter with conserved binding sites in mouse and human for caudal-related homeodomain proteins and hepatocyte nuclear factor-1alpha

A preliminary therapeutic study of the effects of molecular hydrogen on intestinal dysbiosis and small intestinal injury in high-fat diet-loaded senescence-accelerated mice

OBJECTIVES

Aging and excessive fat intake may additively induce dysbiosis of the gut microbiota and intestinal inflammatory damage. Here, we analyzed microbiota dysbiosis and intestinal injury in high-fat diet-loaded senescence-accelerated mice (SAMP8). Additionally, we examined whether treatment with molecular hydrogen could improve the intestinal environment.

METHODS

SAMP8 and SAMR1 (control) mice were first fed a normal diet (ND) or high-fat diet (HFD) for 10 wk (n = 10 each group). Subsequently, HFD was supplemented with a placebo jelly or hydrogen-rich jelly (HRJ) for 4 wk. After treatment, isolated small intestinal tissues were used for hematoxylin and eosin staining, immunofluorescence staining, and thiobarbituric acid reactive substances (TBARS) assay. Furthermore, we analyzed alterations in the microbiota composition in cecal feces using 16S rRNA gene analysis for microbiota profiling. Statistical analyses were performed using unpaired Student's t tests or one-way analysis of variance and Tukey's post hoc test for multiple comparisons.

RESULT

HFD feeding reduced the expression of caudal-related homeobox transcription factor 2 (CDX2) and 5-bromo-2'-deoxyuridine (BrdU) and enhanced malondialdehyde (MDA) levels in the small intestine of SAMP8. HRJ treatment improved the reduction in CDX2 and BrdU and enhanced MDA levels. We performed a sequence analysis of the gut microbiota at the genus level and identified 283 different bacterial genera from the 30 samples analyzed in the study. Among them, Parvibacter positively correlated with both HFD intake and aging, whereas 10 bacteria, including Anaerofustis, Anaerosporobacter, Butyricicoccus, and Ruminococcus were negatively correlated with both HFD and aging. HRJ treatment increased Lactinobactor and decreased Akkermansia, Gracilibacter, and Marvinbryantia abundance.

CONCLUSION

Our findings suggest that treatment with molecular hydrogen may affect microbiota profiling and suppress intestinal injury in HFD-loaded SAMP8.

ACV with/without IVM: a new talk on intestinal CDX2 and muscular CD34 and Cyclin D1 during Trichinella spiralis infection

The current study assessed the efficacy of Acyclovir (ACV) and Ivermectin (IVM) as monotherapies and combined treatments for intestinal and muscular stages of Trichinella spiralis infection. One-hundred Swiss albino mice received orally 250 ± 50 infectious larvae and were divided into infected-untreated (Group-1), IVM-treated (Group-2), ACV-treated (Group-3), combined IVM+ACV (Group-4), and healthy controls (Group-5). Each group was subdivided into subgroup-A-enteric phase (10 mice, sacrificed day-7 p.i.) and subgroup-B-muscular phase (10 mice, sacrificed day-35 p.i.). Survival rate and body weight were recorded. Parasite burden and intestinal histopathology were assessed. In addition, immunohistochemical expression of epithelial CDX2 in the intestinal phase and CyclinD1 as well as CD34 in the muscular phase were evaluated. Compared, IVM and ACV monotherapies showed insignificant differences in the amelioration of enteric histopathology, except for lymphocytic counts. In the muscle phase, monotherapies showed variable disruptions in the encapsulated larvae. Compared with monotherapies, the combined treatment performed relatively better improvement of intestinal inflammation and reduction in the enteric and muscular parasite burden. CDX2 and CyclinD1 positively correlated with intestinal inflammation and parasite burden, while CD34 showed a negative correlation. CDX2 positively correlated with CyclinD1. CD34 negatively correlated with CDX2 and CyclinD1. IVM +ACV significantly ameliorated CDX2, CyclinD1, and CD34 expressions compared with monotherapies. Conclusion. T. spiralis infection-associated inflammation induced CDX2 and CyclinD1 expressions, whereas CD34 was reduced. The molecular tumorigenic effect of the nematode remains questionable. Nevertheless, IVM +ACV appeared to be a promising anthelminthic anti-inflammatory combination that, in parallel, rectified CDX2, CyclinD1, and CD34 expressions.

Gut permeability among Astronauts during Space missions

The space environment poses substantial challenges to human physiology, including potential disruptions in gastrointestinal health. Gut permeability has only recently become widely acknowledged for its potential to cause adverse effects on a systemic level, rendering it a critical factor to investigate in the context of spaceflight. Here, we propose that astronauts experience the onset of leaky gut during space missions supported by transcriptomic and metagenomic analysis of human and murine samples. A genetic map contributing to intestinal permeability was constructed from a systematic review of current literature. This was referenced against our re-analysis of three independent transcriptomic datasets which revealed significant changes in gene expression patterns associated with the gut barrier. Specifically, in astronauts during flight, we observed a substantial reduction in the expression genes that are crucial for intestinal barrier function, goblet cell development, gut microbiota modulation, and immune responses. Among rodent spaceflight studies, differential expression of cytokines, chemokines, and genes which regulate mucin production and post-translational modifications suggest a similar dysfunction of intestinal permeability. Metagenomic analysis of feces from two murine studies revealed a notable reduction probiotic, short chain fatty acid-producing bacteria and an increase in the Gram-negative pathogens, including Citrobacter rodentium, Enterobacter cloacea, Klebsiella aerogenes, and Proteus hauseri which promote LPS circulation, a recipe for barrier disruption and systemic inflammatory activation. These findings emphasize the critical need to understand the underlying mechanisms and develop interventions to maintain gastrointestinal health in space.

Evaluation of gene expression related to immunity, apoptosis, and gut integrity that underlies Artemisia's therapeutic effects in necrotic enteritis-challenged broilers

The experiment was designed to validate the effect of Artemisia annua and its novel commercial product (Navy Cox) on the control of necrotic enteritis (NE). A total of one hundred forty broiler chicks were randomly distributed into seven equal groups: G1, control negative; G2, infected with Eimeria (day 15) and C. perfringens (day 19); G3, treated with Navy Cox before challenge; G4, treated with Artemisia before challenge; G5, infected and then treated with Navy Cox; G6, infected and then treated with Artemisia; and G7, infected and treated with amoxicillin. Chicken response and immune organ indicants were recorded during the observation period (4 weeks). Whole blood and serum samples were collected for immunological evaluation, and tissue samples were collected for bacterial counts and estimation of mRNA expression of genes encoding apoptosis, tight junctions, and immunity. Chickens in the infected group revealed a significant decrease in RBCS, HB, PCV% total protein, Lysozyme, and nitric oxide activity in addition to leukocytosis, heterophilia, monocytosis, increase in cortisol, interleukins, and malondialdehyde. Treated groups displayed lower lesions, colony-forming units, and no mortality. Concurrently, a complete blood profile, antioxidants, and immune markers showed significant improvements. The mRNA expression levels of CASP, CLDN-1, OCLN, TJPI, MUC2, and cell-mediated immune response genes (p < 0.0001) were significantly alleviated in the treated groups compared with the challenged counterpart. This is the first-ever report on the efficacy valuation of Navy Cox compared to standard antibiotic treatment of clostridial NE. Navy Cox proved remarkable capability to minimize C. perfringens colonization in broiler intestines, modulation of mucus production, gut health integrity, immune organs, and immune response when used as a prophylactic agent in this form or naturally as Artemisia.

Alleviative mechanism and effect of Bifidobacterium animalisA6 on dextran sodium sulfate-induced ulcerative colitis in mice

Probiotics have been increasingly investigated for their role in alleviating symptoms of ulcerative colitis (UC), but the specific mechanism involved remains unclear. We investigated the alleviating effect of Bifidobacterium animalis A6 (BAA6) in UC through a mouse dextran sulfate sodium (DSS) model. When treated with a high dose of BAA6 (1 × 1010 cfu/ml), it was found that colitis symptoms were significantly alleviated, and mucosal damages experienced obvious relief. Moreover, a high dose of BAA6 effectively upregulated free fatty acid receptors 2 and 3 (FFAR2 and FFAR3) expression and butyric acid metabolism specifically. Furthermore, the supplement of BAA6 significantly suppressed pro-inflammatory cytokines levels (interleukin-13) and the expression of pore-forming protein claudin-2. The upstream regulatory genes of claudin-2, such as STAT6, GATA4, Cdx2, were also significantly inhibited by BAA6. Collectively, this study concludes that BAA6 attenuated DSS-induced colitis by increasing the levels of intestinal butyric acid, activating the butyric acid-FFAR pathway, suppressing excessive proinflammatory response, and protecting the function of the colon epithelial barrier.

Chicken LEAP2 Level Substantially Changes with Feed Intake and May Be Regulated by CDX4 in Small Intestine

Ghrelin O-acyltransferase (GOAT), ghrelin, and GHSR have been reported to play important roles that influence feed intake in mammals. LEAP2, an endogenous antagonist of GHSR, plays an important role in the regulation of feed intake. However, chicken ghrelin has also been reported to have an inhibitory effect on feed intake. The role of the GOAT-Ghrelin-GHSR-LEAP2 axis in chicken-feed intake remains unclear. Therefore, it is necessary to systematically evaluate the changes in the tissue expression levels of these genes under different energy states. In this study, broiler chicks in different energy states were subjected to starvation and feeding, and relevant gene expression levels were measured using quantitative real-time PCR. Different energy states significantly modulated the expression levels of LEAP2 and GHSR but did not significantly affect the expression levels of GOAT and ghrelin. A high expression level of LEAP2 was detected in the liver and the whole small intestine. Compared to the fed group, the fasted chicks showed significantly reduced LEAP2 expression levels in the liver and the small intestine; 2 h after being refed, the LEAP2 expression of the fasted chicks returned to the level of the fed group. Transcription factor prediction and results of a dual luciferase assay indicated that the transcription factor CDX4 binds to the LEAP2 promoter region and positively regulates its expression. High expression levels of GHSR were detected in the hypothalamus and pituitary. Moreover, we detected GHSR highly expressed in the jejunum-this finding has not been previously reported. Thus, GHSR may regulate intestinal motility, and this aspect needs further investigation. In conclusion, this study revealed the function of chicken LEAP2 as a potential feed-intake regulator and identified the potential mechanism governing its intestine-specific expression. Our study lays the foundations for future studies on avian feed-intake regulation.

Single-Cell Transcriptomic Analysis of the Mouse Pancreas: Characteristic Features of Pancreatic Ductal Cells in Chronic Pancreatitis

Chronic pancreatitis (CP) is a fibroinflammatory disorder of the pancreas. Our understanding of CP pathogenesis is partly limited by the incomplete characterization of pancreatic cell types. Here, we performed single-cell RNA sequencing on 3825 cells from the pancreas of one control mouse and mice with caerulein-induced CP. An analysis of the single-cell transcriptomes revealed 16 unique clusters and cell type-specific gene expression patterns in the mouse pancreas. Sub-clustering of the pancreatic mesenchymal cells from the control mouse revealed four clusters of cells with specific gene expression profiles (combinatorial expressions of Smoc2, Cxcl14, Tnfaip6, and Fn1). We observed that immune cells in the pancreas of the CP mice were abundant and diverse in cellular type. Compared to the control, 547 upregulated genes (including Mmp7, Ttr, Rgs5, Adh1, and Cldn2) and 257 downregulated genes were identified in ductal cells from the CP group. The elevated expression levels of MMP7 and TTR were further verified in the pancreatic ducts of CP patients. This study provides a preliminary description of the single-cell transcriptome profiles of mouse pancreata and accurately demonstrates the characteristics of pancreatic ductal cells in CP. The findings provide insight into novel disease-specific biomarkers and potential therapeutic targets of CP.

Vitamin D Receptor Influences Intestinal Barriers in Health and Disease

Vitamin D receptor (VDR) executes most of the biological functions of vitamin D. Beyond this, VDR is a transcriptional factor regulating the expression levels of many target genes, such as genes for tight junction proteins claudin-2, -5, -12, and -15. In this review, we discuss the progress of research on VDR that influences intestinal barriers in health and disease. We searched PubMed and Google Scholar using key words vitamin D, VDR, tight junctions, cancer, inflammation, and infection. We summarize the literature and progress reports on VDR regulation of tight junction distribution, cellular functions, and mechanisms (directly or indirectly). We review the impacts of VDR on barriers in various diseases, e.g., colon cancer, infection, inflammatory bowel disease, and chronic inflammatory lung diseases. We also discuss the limits of current studies and future directions. Deeper understanding of the mechanisms by which the VDR signaling regulates intestinal barrier functions allow us to develop efficient and effective therapeutic strategies based on levels of tight junction proteins and vitamin D/VDR statuses for human diseases.

Exosomal CagA from Helicobacter pylori aggravates intestinal epithelium barrier dysfunction in chronic colitis by facilitating Claudin-2 expression

BACKGROUND

The chronic infection with Helicobacter pylori (H. pylori), especially cytotoxin-associated gene A-positive (CagA⁺) strains, has been associated with various extragastric disorders. Evaluating the potential impacts of virulence factor CagA on intestine may provide a better understanding of H. pylori pathogenesis such as colitis. The intestinal mucosal barrier is essential for maintaining its integrity and functions. However, how persistent CagA⁺ H. pylori colonization influences barrier disruption and thereby affects chronic colitis is not fully understood.

RESULTS

Chronic colitis models of CagA⁺ H. pylori-colonized mice treated with 2% Dextran sulphate sodium (DSS) were established to assess the disease activity and pertinent expression of tight junction proteins closely related to mucosal integrity. The aggravating effect of CagA⁺ H. pylori infection on DSS-induced chronic colitis was confirmed in mouse models. In addition, augmented Claudin-2 expression was detected in CagA⁺ H. pylori infection conditions and selected for mechanistic analysis. Next, GES-1 human gastric epithelial cells were cultured with CagA⁺ H. pylori or a recombinant CagA protein, and exosomes isolated from conditioned media were then identified. We assessed the Claudin-2 levels after exposure to CagA⁺ exosomes, CagA^- exosomes, and IFN-γ incubation, revealing that CagA⁺ H. pylori compromised the colonic mucosal barrier and facilitated IFN-γ-induced intestinal epithelial destruction through CagA-containing exosome-mediated mechanisms. Specifically, CagA upregulated Claudin-2 expression at the transcriptional level via a CDX2-dependent mechanism to slow the restoration of wounded mucosa in colitis in vitro.

CONCLUSIONS

These data suggest that exosomes containing CagA facilitate CDX2-dependent Claudin-2 maintenance. The exosome-dependent mechanisms of CagA⁺ H. pylori infection are indispensable for damaging the mucosal barrier integrity in chronic colitis, which may provide a new idea for inflammatory bowel disease (IBD) treatment.

Integrative omics analysis reveals the protective role of vitamin C on perfluorooctanoic acid-induced hepatoxicity

Introduction

Perfluorooctanoic acid (PFOA) is a compound used as an industrial surfactant in chemical processes worldwide. Population and cross-sectional studies have demonstrated positive correlations between PFOA levels and human health problems.

Objectives

Many studies have focused on the hepatotoxicity and liver problems caused by PFOA, with little attention to remediation of these problems. As an antioxidant, vitamin C is frequently utilized as a supplement for hepatic detoxification.

Methods

In this study, we use a mouse model to study the possible role of vitamin C in reducing PFOA-induced liver damage. Based on comparative transcriptomic and metabolomic analysis, we elucidate the mechanisms underlying the protective effect of vitamin C.

Results

Our results show that vitamin C supplementation reduces signs of PFOA-induced liver damage including total cholesterol and triglyceride levels increase, liver damage markers aspartate, transaminase, and alanine aminotransferase elevation, and liver enlargement. Further, we show that the protective role of vitamin C is associated with signaling networks control, suppressing linoleic acid metabolism, reducing thiodiglycolic acid, and elevating glutathione in the liver.

Conclusion

The findings in this study demonstrate, for the first time, the utility of vitamin C for preventing PFOA-induced hepatotoxicity.

Modulations of genes related to gut integrity, apoptosis, and immunity underlie the beneficial effects of Bacillus amyloliquefaciens CECT 5940 in broilers fed diets with different protein levels in a necrotic enteritis challenge model

Background

The ban of in-feed antimicrobial additives has negatively affected the poultry industry by causing necrotic enteritis (NE) to emerge in the flocks. Alternatives such as Bacillus probiotics have shown to be effective on eliminating the negative effects of this disease. Two experiments were conducted to investigate the effect of Bacillus amyloliquefaciens CECT 5940 (BA) in broiler chickens under NE challenge and/or fed diets with different protein levels.

Methods

In both experiments, 480 day-old mix-sexed Ross-308 broilers were arranged in a 2 × 2 factorial arrangement of treatments. In experiment 1, the factors were NE challenge (yes or no) and probiotic (yes or no). In experiment 2, the factors were dietary crude protein levels (standard or reduced) and probiotic (yes or no) and were used under NE challenge condition. Oral administration of Eimeria oocysts (day 9) followed by inoculation with Clostridium perfringens (day 14 and 15) was used to induce NE challenge. On day 16, two birds from each treatment were gavaged with fluorescein isothiocyanate-dextran (FITC-d) and blood samples were collected for gut integrity evaluation, and jejunal samples were collected for gene expression assay.

Results

In experiment 1, BA supplementation decreased caspase-3 (CASP3) (P < 0.001) and caspase-8 (CASP8) (P < 0.05) and increased occludin (OCLD) (P < 0.05) expression regardless of the challenge. Additionally, BA supplementation downregulated interfron-γ (IFN-γ) expression (P < 0.01) and upregulated immunoglobulin-G (IgG) (P < 0.01) and immunoglobulin-M (IgM) (P < 0.05) only in challenged birds. In experiment 2, the expression of genes encoding mucin-2 (MUC2) (P < 0.001), tight junction protein-1 (TJP1) (P < 0.05) and OCLD (P < 0.05) were upregulated by the addition of BA in the diet, regardless of the crude protein level. Further, BA supplementation downregulated INF-γ (P < 0.01) and upregulated immunoglobulin-A (IgA) (P < 0.05), IgM (P < 0.05) and IgG (P < 0.01) regardless of the crude protein level.

Conclusion

These findings suggest that supplementation of BA in broiler diets can improve gut health by modulation of genes related to the mucosal barrier, tight junction, and immunity in broilers challenged by unfavourable conditions such as NE challenge.

Immunofluorescent Staining of Claudin-2 in Cultured Kidney Tubular Cells

Members of the claudin family of tight junction proteins regulate paracellular permeability and modulate cell signaling. During junction remodeling, these proteins are selectively inserted into or retrieved from the tight junctions, but the control and coordination of these processes remain incompletely understood. Visualization of claudins allows the assessment of changes in their localization and abundance. We use the described protocol to stain claudin-2, but it can also be adapted to stain any tight junction protein. We found that using methanol for fixing allows the best preservation of claudin-2 both at the membrane and in cytoplasmic vesicles. Staining is done using a claudin-2 specific primary and a fluorescently labelled secondary antibody, along with DAPI to label nuclei. The samples are then imaged using confocal microscopy, and a z-stack is obtained allowing visualization of both junctional and intracellular claudin-2. Total claudin-2 signal can be quantified after 3D reconstruction of the images using the Imaris software.

CDX2 expression and perioperative patient serum affects the adhesion properties of cultured colon cancer cells

Background

Colon cancer is one of the most commonly diagnosed types of cancer with surgical resection of the tumor being the primary choice of treatment. However, the surgical stress response induced during treatment may be related to a higher risk of recurrence. The aim of this study was to examine the effect of surgery on adhesion of cultured colon cancer cells with or without expression of the tumour suppressor CDX2.

Method

We enrolled 30 patients undergoing elective, curatively intended laparoscopic surgery for colon cancer in this study. Blood samples were drawn 1 day prior to surgery and 24 h after surgery. The samples of pre- and postoperative serum was applied to wild type colon cancer LS174T cells and CDX2 inducible LS174T cells and adhesion was measured with Real-Time Cell-Analysis iCELLigence using electrical impedance as a readout to monitor changes in the cellular adhesion.

Results

Adhesion abilities of wild type LS174T cells seeded in postoperative serum was significantly increased compared to cells seeded in preoperative serum. When seeding the CDX2 inducible LS174T cells without CDX2 expression in pre- and postoperative serum, no significant difference in adhesion was found. However, when inducing CDX2 expression in these cells, the adhesion abilities in pre- and postoperative serum resembled those of the LS174T wild type cell line.

Conclusions

We found that the adhesion of colon cancer cells was significantly increased in postoperative versus preoperative serum, and that CDX2 expression affected the adhesive ability of cancer cells. The results of this study may help to elucidate the pro-metastatic mechanisms in the perioperative phase and the role of CDX2 in colon cancer metastasis.

A male infant with Xq22.2q22.3 duplication containing PLP1 and MID2

Background

The Xq22.2 q23 is a complex genomic region which includes the genes MID2 and PLP1 associated with FG syndrome 5 and Pelizaeus–Merzbacher disease, respectively. There is limited information regarding the clinical outcomes observed in patients with deletions within this region.

Methods

We report on a male infant with intrauterine growth retardation (IUGR) who developed head titubation and spasticity during his postnatal hospital course.

Results

Chromosome microarray revealed a 6.7 Mb interstitial duplication of Xq22.2q22.3. Fluorescence in situ hybridization showed that the patient's mother also possessed the identical duplication in the Xq22.3q22.3 region. Among the 34 OMIM genes in this interval, the duplication of the PLP1 (OMIM# 300401) and MID2 (OMIM# 300204) appears to be the most significant contributors to the patient's clinical features. Mutations and duplications of PLP1 are associated with X‐linked recessive Pelizaeus–Merzbacher disease (PMD). A single case of a Xq22.3 duplication including the MID2 has been reported in boy with features of FG syndrome. However, our patient's clinical features are not consistent with the FG syndrome phenotype.

Conclusion

Our patient's clinical features appear to be influenced by the PLP1 duplication but the clinical effect of other dosage sensitive genes influencing brain development cannot be ruled out.

Claudin-2: Roles beyond Permeability Functions

Claudin-2 is expressed in the tight junctions of leaky epithelia, where it forms cation-selective and water permeable paracellular channels. Its abundance is under fine control by a complex signaling network that affects both its synthesis and turnover in response to various environmental inputs. Claudin-2 expression is dysregulated in many pathologies including cancer, inflammation, and fibrosis. Claudin-2 has a key role in energy-efficient ion and water transport in the proximal tubules of the kidneys and in the gut. Importantly, strong evidence now also supports a role for this protein as a modulator of vital cellular events relevant to diseases. Signaling pathways that are overactivated in diseases can alter claudin-2 expression, and a good correlation exists between disease stage and claudin-2 abundance. Further, loss- and gain-of-function studies showed that primary changes in claudin-2 expression impact vital cellular processes such as proliferation, migration, and cell fate determination. These effects appear to be mediated by alterations in key signaling pathways. The specific mechanisms linking claudin-2 to these changes remain poorly understood, but adapters binding to the intracellular portion of claudin-2 may play a key role. Thus, dysregulation of claudin-2 may contribute to the generation, maintenance, and/or progression of diseases through both permeability-dependent and -independent mechanisms. The aim of this review is to provide an overview of the properties, regulation, and functions of claudin-2, with a special emphasis on its signal-modulating effects and possible role in diseases.

The UDP-Glycosyltransferase (UGT) Superfamily: New Members, New Functions, and Novel Paradigms

UDP-glycosyltransferases (UGTs) catalyze the covalent addition of sugars to a broad range of lipophilic molecules. This biotransformation plays a critical role in elimination of a broad range of exogenous chemicals and by-products of endogenous metabolism, and also controls the levels and distribution of many endogenous signaling molecules. In mammals, the superfamily comprises four families: UGT1, UGT2, UGT3, and UGT8. UGT1 and UGT2 enzymes have important roles in pharmacology and toxicology including contributing to interindividual differences in drug disposition as well as to cancer risk. These UGTs are highly expressed in organs of detoxification (e.g., liver, kidney, intestine) and can be induced by pathways that sense demand for detoxification and for modulation of endobiotic signaling molecules. The functions of the UGT3 and UGT8 family enzymes have only been characterized relatively recently; these enzymes show different UDP-sugar preferences to that of UGT1 and UGT2 enzymes, and to date, their contributions to drug metabolism appear to be relatively minor. This review summarizes and provides critical analysis of the current state of research into all four families of UGT enzymes. Key areas discussed include the roles of UGTs in drug metabolism, cancer risk, and regulation of signaling, as well as the transcriptional and posttranscriptional control of UGT expression and function. The latter part of this review provides an in-depth analysis of the known and predicted functions of UGT3 and UGT8 enzymes, focused on their likely roles in modulation of levels of endogenous signaling pathways.

Lack of Vitamin D Receptor Leads to Hyperfunction of Claudin-2 in Intestinal Inflammatory Responses

BACKGROUND

Vitamin D3 and vitamin D receptor (VDR) are involved in the pathogenesis of inflammatory bowel disease (IBD) and bacterial infection. Claudin-2 is a junction protein that mediates paracellular water transport in epithelia. Elevation of Claudin-2 is associated with active IBD. However, VDR involved in epithelial junctions under inflammation and infection remains largely unknown. We investigated the mechanisms on how VDR and Claudin-2 are related in inflamed states.

METHODS

Using cultured VDR-/- enteroids, human intestinal epithelial cells, VDR-/- mice with Salmonella- or DSS-colitis, and human IBD samples, we investigated the mechanisms how VDR and Claudin-2 are related in inflamed states.

RESULTS

After Salmonella infection had taken place, we observed significantly enhanced Claudin-2 and an increased bacterial invasion and translocation. A lack of VDR regulation led to a robust increase of Claudin-2 at the mRNA and protein levels post-infection. In DSS-treated VDR-/- mice, Claudin-2 was significantly increased. Location and quantification of Claudin-2 protein in the mouse colons treated with DSS also confirmed these results. Inflammatory cytokines were significantly higher in the serum and mRNA levels in intestine, which are known to increase Claudin-2. Furthermore, in inflamed intestine of ulcerative colitis patients, VDR expression was low and Claudin-2 was enhanced. Mechanistically, we identified the enhanced Claudin-2 promoter activity through the binding sites of NF-κB and STAT in inflamed VDR-/- cells.

CONCLUSIONS

Our studies have identified a new role for intestinal epithelial VDR in regulating barrier functions in the context of infection and inflammation.

Intestinal regulation of suppression of tumorigenicity 14 (ST14) and serine peptidase inhibitor, Kunitz type -1 (SPINT1) by transcription factor CDX2

The type II membrane-anchored serine protease, matriptase, encoded by suppression of tumorgenicity-14 (ST14) regulates the integrity of the intestinal epithelial barrier in concert with its inhibitor, HAI-1 encoded by serine peptidase inhibitor, Kunitz type -1 (SPINT1). The balance of the protease/inhibitor gene expression ratio is vital in preventing the oncogenic potential of matriptase. The intestinal cell lineage is regulated by a transcriptional regulatory network where the tumor suppressor, Caudal homeobox 2 (CDX2) is considered to be an intestinal master transcription factor. In this study, we show that CDX2 has a dual function in regulating both ST14 and SPINT1, gene expression in intestinal cells. We find that CDX2 is not required for the basal ST14 and SPINT1 gene expression; however changes in CDX2 expression affects the ST14/SPINT1 mRNA ratio. Exploring CDX2 ChIP-seq data from intestinal cell lines, we identified genomic CDX2-enriched enhancer elements for both ST14 and SPINT1, which regulate their corresponding gene promoter activity. We show that CDX2 displays both repressive and enhancing regulatory abilities in a cell specific manner. Together, these data reveal new insight into transcriptional mechanisms controlling the intestinal matriptase/inhibitor balance.

6-Formylindolo(3,2-b)carbazole induced aryl hydrocarbon receptor activation prevents intestinal barrier dysfunction through regulation of claudin-2 expression

6-Formylindolo(3,2-b)carbazole (FICZ), a high-affinity aryl hydrocarbon receptor (AhR) ligand, plays a protective role in inflammatory bowel disease (IBD) through activation of AhR. Interleukin-6 (IL-6) induced intestinal epithelial barrier dysfunction is involved in the pathological process of IBD. In this study, we investigated the protective effects of FICZ on IL-6 induced intestinal epithelial barrier injury. Our data show that AhR activation by FICZ ameliorated colonic inflammation, decreased IL-6 and claudin-2 expression, and maintained intestinal barrier function in a mouse model of dextran sulphate sodium (DSS)-induced colitis. In Caco-2 and T84 intestinal epithelial cells, FICZ also prevented the increase of intestinal epithelial permeability and claudin-2 expression induced by IL-6. Depletion of AhR expression by small interfering (si)RNA reversed FICZ induced decrease of claudin-2. Furthermore, IL-6 induced upregulation of claudin-2 was required for increased caudal-related homeobox 2 (CDX-2) and hepatocyte-nuclear factor (HNF)-1α. However, FICZ repressed the increase of CDX-2 and HNF-1α expression induced by IL-6. These results reveal the protective effects of FICZ on IL-6 induced disruption of intestinal epithelial barrier function through suppressing the expression of claudin-2. In addition, CDX-2 and HNF-1α are involved in the regulation of claudin-2 after IL-6 and FICZ treatment. Therefore compounds related to AhR ligands may be potential pharmaceutical agents to treat IBD.

Purple Potato Extract Promotes Intestinal Epithelial Differentiation and Barrier Function by Activating AMP-Activated Protein Kinase

SCOPE

Perturbation of gut epithelial barrier function induces inflammation and other health problems that originate from the gut. Purple potato contains a high content of beneficial polyphenolic compounds. The objective of this study is to evaluate the effect of purple potato extract (PPE) on intestinal differentiation and barrier function, and explore its underlying mechanism using Caco-2 cells and ex vivo cultured gut tissues.

METHODS AND RESULTS

PPE increases transepithelial electrical resistance and decreases FITC-dextran paracellular flux in Caco-2 cells, which are associated with strengthened intestinal epithelial differentiation in both Caco-2 cells and ex vivo guts. Furthermore, PPE treatment enhances AMP-activated protein kinase (AMPK) activity, concomitant with the increased expression of CDX2, a key transcriptional factor regulating intestinal epithelial differentiation. Knocking out AMPK using CRISPR/Cas9 system abolishes the positive effects of PPE on intestinal epithelial differentiation and barrier function, in junction with the reduced expression of CDX2.

CONCLUSION

PPE improves gut epithelial differentiation and barrier function via activating AMPK, indicating that PPE, as well as associated purple potato consumption, could be used as a supportive dietary therapeutic strategy for improving gut epithelial health.

CDX2 increases SLC7A7 expression and proliferation of pig intestinal epithelial cells

Nutrient absorption mediated by nutrient transporters expressed in the intestinal epithelium supplies substrates to support intestinal processes, including epithelial cell proliferation. We evaluated the role of Caudal type homeobox 2 (CDX2), an intestine-specific transcription factor, in the proliferation of pig intestinal epithelial cells (IPEC-1) and searched for novel intestinal nutrient transporter genes activated by CDX2. Our cloned pig CDX2 cDNA contains a “homeobox” DNA binding motif, suggesting it is a transcriptional activator. CDX2 overexpression in IPEC-1 cells increased cell proliferation, the percentage of cells in S/G2 phase, and the abundance of transcripts of the cell cycle-related genes Cyclin A2; Cyclin B; Cyclin D2; proliferating cell nuclear antigen; and cell cycle cyclin-dependent kinases 1, 2 and 4, as well as the predicted CDX2 target genes SLC1A1, SLC5A1 and SLC7A7. In addition, luciferase reporter and chromatin immunoprecipitation assays revealed that CDX2 binds directly to the SLC7A7 promoter. This is the first report of CDX2 function in pig intestinal epithelial cells and identifies SLC7A7 as a novel CDX2 target gene. Our findings show that nutrient transporters are activated during CDX2-induced proliferation of normal intestinal epithelial cells.

T cell protein tyrosine phosphatase prevents STAT1 induction of claudin-2 expression in intestinal epithelial cells

T cell protein tyrosine phosphatase (TCPTP) dephosphorylates a number of substrates, including JAK-STAT (signal transducer and activator of transcription) signaling proteins, which are activated by interferon (IFN)-γ, a major proinflammatory cytokine involved in conditions such as inflammatory bowel disease. A critical function of the intestinal epithelium is formation of a selective barrier to luminal contents. The structural units of the epithelium that regulate barrier function are the tight junctions (TJs), and the protein composition of the TJ determines the tightness of the barrier. Claudin-2 is a TJ protein that increases permeability to cations and reduces transepithelial electrical resistance (TER). We previously showed that transient knockdown (KD) of TCPTP permits increased expression of claudin-2 by IFN-γ. Here, we demonstrate that the decreased TER in TCPTP-deficient epithelial cells is alleviated by STAT1 KD. Moreover, increased claudin-2 in TCPTP-deficient cells requires enhanced STAT1 activation and STAT1 binding to the CLDN2 promoter. We also show that mutation of this STAT-binding site prevents elevated CLDN2 promoter activity in TCPTP-deficient epithelial cells. In summary, we demonstrate that TCPTP protects the intestinal epithelial barrier by restricting STAT-induced claudin-2 expression. This is a potential mechanism by which loss-of-function mutations in the gene encoding TCPTP may contribute to barrier defects in chronic intestinal inflammatory disease.

Intestinal epithelial claudins: expression and regulation in homeostasis and inflammation

The intestinal epithelium forms a highly dynamic and selective barrier that controls absorption of fluid and solutes while restricting pathogen access to underlying tissues. Barrier properties are achieved by intercellular junctions that include an apical tight junction (TJ) and subjacent adherens junctions and desmosomes. The TJ tetraspan claudin proteins form pores between epithelial cells to control paracellular fluid and ion movement. In addition to regulation of barrier function, claudin family members control epithelial homeostasis and are expressed in a spatiotemporal manner in the intestinal crypt-luminal axis. This delicate balance of physiologic differential claudin protein expression is altered during mucosal inflammation. Inflammatory mediators influence transcriptional regulation, as well as endocytic trafficking, targeting, and retention of claudins in the TJ. Increased expression of intestinal epithelial claudin-1, -2, and -18 with downregulation of claudin-3, -4, -5, -7, -8, and -12 has been observed in intestinal inflammatory disorders. Such changes in claudin proteins modify the epithelial barrier function in addition to influencing epithelial and mucosal homeostasis. An improved understanding of the regulatory mechanisms that control epithelial claudin proteins will provide strategies to strengthen the epithelial barrier function and restore mucosal homeostasis in inflammatory disorders.

Association Analysis of PRSS1-PRSS2 and CLDN2-MORC4 Variants in Nonalcoholic Chronic Pancreatitis Using Tropical Calcific Pancreatitis as Model

OBJECTIVE

Association of PRSS1-PRSS2 (rs10273639) and CLDN2-MORC4 (rs12688220 and rs7057398) variants with alcohol-related chronic pancreatitis (CP) is established but with nonalcoholic CP is unclear. We addressed this inconsistency using tropical calcific pancreatitis (TCP) as model.

METHODS

We sequenced 5'-UTR of PRSS1 and genotyped CLDN2-MORC4 variants in 555 patients with TCP and 801 controls and performed association analysis. Gene-gene interaction between PRSS1 and CLDN2-MORC4 variants and with p.Asn34Ser SPINK1 and p.Leu26Val CTSB was also evaluated.

RESULTS

We observed significant association of rs10273639/rs4726576 in PRSS1-PRSS2 (odds ratio [OR] = 0.72; P = 3.50 × 10) and CLDN2-MORC4 variants, rs12688220 (OR = 1.54; P = 1.22 × 10) and rs7057398 (OR = 1.50; P = 1.22 × 10) with TCP. Patients carrying p.Asn34Ser SPINK1 were significantly younger than those with rs4726576 risk genotype (30.0 vs 38.0 years; P = 0.015) and those carrying both were even younger (22.0 years; P = 0.001). Presence of risk allele at rs12688220 in patients carrying p.Asn34Ser SPINK1 delayed the age of onset (32.0 vs 24.0 years; P = 0.013).

CONCLUSIONS

Our study establishes strong association of PRSS1-PRSS2 and CLDN2-MORC4 variants with TCP and thus with nonalcoholic CP. These variants independently interact with p.Asn34Ser SPINK1 and influence the age of onset in TCP. However, latter results need to be replicated in other cohorts.

HNF4α regulates claudin-7 protein expression during intestinal epithelial differentiation

The intestinal epithelium is a dynamic barrier that maintains the distinct environments of intestinal tissue and lumen. Epithelial barrier function is defined principally by tight junctions, which, in turn, depend on the regulated expression of claudin family proteins. Claudins are expressed differentially during intestinal epithelial cell (IEC) differentiation. However, regulatory mechanisms governing claudin expression during epithelial differentiation are incompletely understood. We investigated the molecular mechanisms regulating claudin-7 during IEC differentiation. Claudin-7 expression is increased as epithelial cells differentiate along the intestinal crypt-luminal axis. By using model IECs we observed increased claudin-7 mRNA and nascent heteronuclear RNA levels during differentiation. A screen for potential regulators of the CLDN7 gene during IEC differentiation was performed using a transcription factor/DNA binding array, CLDN7 luciferase reporters, and in silico promoter analysis. We identified hepatocyte nuclear factor 4α as a regulatory factor that bound endogenous CLDN7 promoter in differentiating IECs and stimulated CLDN7 promoter activity. These findings support a role of hepatocyte nuclear factor 4α in controlling claudin-7 expression during IEC differentiation.

Common Variants in CLDN2 and MORC4 Genes Confer Disease Susceptibility in Patients with Chronic Pancreatitis

A recent genome-wide association study (GWAS) identified association with variants in X-linked CLDN2 and MORC4, and PRSS1-PRSS2 loci with chronic pancreatitis (CP) in North American patients of European ancestry. We selected 9 variants from the reported GWAS and replicated the association with CP in Indian patients by genotyping 1807 unrelated Indians of Indo-European ethnicity, including 519 patients with CP and 1288 controls. The etiology of CP was idiopathic in 83.62% and alcoholic in 16.38% of 519 patients. Our study confirmed a significant association of 2 variants in CLDN2 gene (rs4409525-OR 1.71, P = 1.38 x 10-09; rs12008279-OR 1.56, P = 1.53 x 10-04) and 2 variants in MORC4 gene (rs12688220-OR 1.72, P = 9.20 x 10-09; rs6622126-OR 1.75, P = 4.04x10-05) in Indian patients with CP. We also found significant association at PRSS1-PRSS2 locus (OR 0.60; P = 9.92 x 10-06) and SAMD12-TNFRSF11B (OR 0.49, 95% CI [0.31-0.78], P = 0.0027). A variant in the gene MORC4 (rs12688220) showed significant interaction with alcohol (OR for homozygous and heterozygous risk allele -14.62 and 1.51 respectively, P = 0.0068) suggesting gene-environment interaction. A combined analysis of the genes CLDN2 and MORC4 based on an effective risk allele score revealed a higher percentage of individuals homozygous for the risk allele in CP cases with 5.09 fold enhanced risk in individuals with 7 or more effective risk alleles compared with individuals with 3 or less risk alleles (P = 1.88 x 10-14). Genetic variants in CLDN2 and MORC4 genes were associated with CP in Indian patients.

Hyperosmolarity-Induced Down-Regulation of Claudin-2 Mediated by Decrease in PKCβ-Dependent GATA-2 in MDCK Cells

Hyperosmolarity decreases claudin-2 expression in renal tubular epithelial cells, but the molecular mechanism remains undefined. Here, we found that the hyperosmolarity-induced decrease in claudin-2 expression is inhibited by Go6983, a non-selective protein kinase C (PKC) inhibitor, and PKCβ specific inhibitor in Madin-Darby canine kidney II cells. Hyperosmolarity increased intracellular free Ca(2+) concentration and phosphorylated PKCβ level, which were inhibited by RN-1734, an antagonist of transient receptor potential vanilloid 4 channel. Phorbol 12-myristate 13-acetate, a PKC activator, decreased claudin-2 expression. These results indicate hyperosmolarity decreases claudin-2 expression mediated by the activation of RN-1734-sensitive channel and PKCβ. Hyperosmolarity decreased promoter activity of claudin-2, which was inhibited by Go6983 and PKCβ inhibitor similar to those in real-time PCR and Western blotting. The effect of hyperosmolarity on promoter activity was not observed in the construct of -469/-6, a deletion mutant. Claudin-2 has hyperosmolarity-sensitive region in its promoter, which includes GATA binding site. Hyperosmolarity decreased the nuclear level of GATA-2, which was inhibited by Go6983 and PKCβ inhibitor. Mutation of GATA binding site decreased the basal promoter activity and inhibited the effect of hyperosmolarity. In contrast, the hyperosmolarity-induced decrease in reporter activity and claudin-2 expression were rescued by over-expression of wild type GATA-2. Chromatin immunoprecipitation assay showed that GATA-2 bound to promoter region of claudin-2. These results suggest that hyperosmolarity decreases the expression level of claudin-2 via a decrease in PKCβ-dependent GATA-2 transcriptional activity in renal tubular epithelial cells.

Tight junction CLDN2 gene is a direct target of the vitamin D receptor

The breakdown of the intestinal barrier is a common manifestation of many diseases. Recent evidence suggests that vitamin D and its receptor VDR may regulate intestinal barrier function. Claudin-2 is a tight junction protein that mediates paracellular water transport in intestinal epithelia, rendering them “leaky”. Using whole body VDR^-/- mice, intestinal epithelial VDR conditional knockout (VDR^ΔIEC) mice, and cultured human intestinal epithelial cells, we demonstrate here that the CLDN2 gene is a direct target of the transcription factor VDR. The Caudal-Related Homeobox (Cdx) protein family is a group of the transcription factor proteins which bind to DNA to regulate the expression of genes. Our data showed that VDR-enhances Claudin-2 promoter activity in a Cdx1 binding site-dependent manner. We further identify a functional vitamin D response element (VDRE) 5΄-AGATAACAAAGGTCA-3΄ in the Cdx1 site of the Claudin-2 promoter. It is a VDRE required for the regulation of Claudin-2 by vitamin D. Absence of VDR decreased Claudin-2 expression by abolishing VDR/promoter binding. In vivo, VDR deletion in intestinal epithelial cells led to significant decreased Claudin-2 in VDR^-/- and VDR^ΔIEC mice. The current study reveals an important and novel mechanism for VDR by regulation of epithelial barriers.

Quercetin Decreases Claudin-2 Expression Mediated by Up-Regulation of microRNA miR-16 in Lung Adenocarcinoma A549 Cells

Claudin-2 is highly expressed in human lung adenocarcinoma tissues and cells. Knockdown of claudin-2 decreases cell proliferation and migration. Claudin-2 may be a novel target for lung adenocarcinoma. However, there are no physiologically active substances of foods which decrease claudin-2 expression. We here found that quercetin, a flavonoid present in fruits and vegetables, time- and concentration-dependently decreases claudin-2 expression in lung adenocarcinoma A549 cells. In the present study, we examined what regulatory mechanism is involved in the decrease in claudin-2 expression by quercetin. Claudin-2 expression was decreased by LY-294002, a phosphatidylinositol 3-kinase (PI3-K) inhibitor, and U0126, a MEK inhibitor. These drugs inhibited the phosphorylation of Akt and ERK1/2, which are downstream targets of PI3-K and MEK, respectively. In contrast, quercetin did not inhibit the phosphorylation. Both LY-294002 and U0126 inhibited promoter activity of claudin-2, but quercetin did not. The stability of claudin-2 mRNA was decreased by quercetin. Quercetin increased the expression of microRNA miR-16. An inhibitor of miR-16 rescued quercetin-induced decrease in the claudin-2 expression. These results suggest that quercetin decreases claudin-2 expression mediated by up-regulation of miR-16 expression and instability of claudin-2 mRNA in lung adenocarcinoma cells.

Overexpression of caudal-related homeobox transcription factor 2 inhibits the growth of transplanted colorectal tumors in nude mice

Caudal-related homeobox transcription factor 2 (CDX2) is a transcription factor, which is specifically expressed in the adult intestine. It is essential for the development and homeostasis of the intestinal epithelium and its functions as a tumor suppressor have been demonstrated in the adult colon. The present study aimed to examine the inhibitory effects of the overexpression of CDX2 on subcutaneously-transplanted tumors, derived from LoVo colon cancer cells, in nude mice, and to provide experimental evidence for the biotherapy of colon cancer. A pEGFP-C1-CDX2 eukaryotic expression vector was transfected into the LoVo cells via lipofection, and LoVo cells stably-expressing CDX2 (pEGFP-C1-CDX2 cells) were obtained using G418 selection. A nude mouse subcutaneously-transplanted tumor model was established by inoculating the nude mice with the pEGFP-C1-CDX2 cells, and the effects of overexpression of CDX2 on transplanted tumor growth in the LoVo cells were observed. Western blotting results demonstrated that the protein expression of CDX2 in the LoVo cells was higher in the pEGFP-C1-CDX2 cell group, compared with that in the pEGFP-C1 cell group and the untreated cell group. At 20 days post-inoculation with either pEGFP-C1-CDX2 or pEGFP-C1, the transplanted tumor masses were significantly lower in the pEGFP-C1-CDX2 group, compared with those in the pEGFP-C1 and untreated groups. Immunohistochemistry revealed that the expression levels of CDX2 and matrix metalloproteinase-2 (MMP-2) were detected in each group, and the protein expression of CDX2 was increased in the tumor tissues from the nude mice in the pEGFP-C1-CDX2 group. However the expression of MMP-2 was downregulated in the tumor tissues of the nude mice in the pEGFP-C1-CDX2 group. Taken together, these data suggested that pEGFP-C1-CDX2 cells exhibited suppressed tumor growth in vivo. Overexpression of CDX2 was observed in transplanted tumors in the pEGFP-C1-CDX2 group, and the gene expression of MMP-2 was reduced. These results indicate that CDX2 inhibited the growth of colorectal tumor cells, possibly by downregulating the gene expression.

Tumor necrosis factor-α induces a biphasic change in claudin-2 expression in tubular epithelial cells: role in barrier functions

The inflammatory cytokine tumor necrosis factor-α (TNF-α) is a pathogenic factor in acute and chronic kidney disease. TNF-α is known to alter expression of epithelial tight junction (TJ) proteins; however, the underlying mechanisms and the impact of this effect on epithelial functions remain poorly defined. Here we describe a novel biphasic effect of TNF-α on TJ protein expression. In LLC-PK1 tubular cells, short-term (1-6 h) TNF-α treatment selectively elevated the expression of the channel-forming TJ protein claudin-2. In contrast, prolonged (>8 h) TNF-α treatment caused a marked downregulation in claudin-2 and an increase in claudin-1, -4, and -7. The early increase and the late decrease in claudin-2 expression involved distinct mechanisms. TNF-α slowed claudin-2 degradation through ERK, causing the early increase. This increase was also mediated by the EGF receptor and RhoA and Rho kinase. In contrast, prolonged TNF-α treatment reduced claudin-2 mRNA levels and promoter activity independent from these signaling pathways. Electric Cell-substrate Impedance Sensing measurements revealed that TNF-α also exerted a biphasic effect on transepithelial resistance (TER) with an initial decrease and a late increase. Thus there was a good temporal correlation between TNF-α-induced claudin-2 protein and TER changes. Indeed, silencing experiments showed that the late TER increase was at least in part caused by reduced claudin-2 expression. Surprisingly, however, claudin-2 silencing did not prevent the early TER drop. Taken together, the TNF-α-induced changes in claudin-2 levels might contribute to TER changes and could also play a role in newly described functions of claudin-2 such as proliferation regulation.

Intestinal alkaline phosphatase inhibits the translocation of bacteria of gut-origin in mice with peritonitis: mechanism of action

Exogenous intestinal alkaline phosphatase (IAP), an enzyme produced endogenously at the brush edge of the intestinal mucosa, may mitigate the increase in aberrant intestinal permeability increased during sepsis. The aim of this study was to test the efficacy of the inhibitory effect of IAP on acute intestinal inflammation and to study the molecular mechanisms underlying IAP in ameliorating intestinal permeability. We used an in vivo imaging method to evaluate disease status and the curative effect of IAP. Two Escherichia coli (E.coli) B21 strains, carrying EGFP labeled enhanced green fluorescent protein (EGFP) and RFP labeled red fluorescent protein (RFP), were constructed as tracer bacteria and were administered orally to C57/B6N mice to generate an injection peritonitis (IP) model. The IP model was established by injecting inflammatory lavage fluid. C57/B6N mice bearing the tracer bacteria were subsequently treated with (IP+IAP group), or without IAP (IP group). IAP was administered to the mice via tail vein injections. The amount of tracer bacteria in the blood, liver, and lungs at 24 h post-injection was analyzed via flow cytometry (FCM), in vivo imaging, and Western blotting. Intestinal barrier function was measured using a flux assay with the macro-molecule fluorescein isothiocyanate dextran, molecular weight 40kD, (FD40). To elucidate the molecular mechanism underlying the effects of IAP, we examined the levels of ERK phosphorylation, and the expression levels of proteins in the ERK-SP1-VEGF and ERK-Cdx-2-Claudin-2 pathways. We observed that IAP inhibited the expression of Claudin-2, a type of cation channel-forming protein, and VEGF, a cytokine that may increase intestinal permeability by reducing the levels of dephosphorylated ERK. In conclusion, exogenous IAP shows a therapeutic effect in an injection peritonitis model. This including inhibition of bacterial translocation. Moreover, we have established an imaging methodology for live-animals can effectively evaluate intestinal permeability and aberrant bacterial translocation in IP models.

Tissue invasion and metastasis: Molecular, biological and clinical perspectives

Cancer is a key health issue across the world, causing substantial patient morbidity and mortality. Patient prognosis is tightly linked with metastatic dissemination of the disease to distant sites, with metastatic diseases accounting for a vast percentage of cancer patient mortality. While advances in this area have been made, the process of cancer metastasis and the factors governing cancer spread and establishment at secondary locations is still poorly understood. The current article summarizes recent progress in this area of research, both in the understanding of the underlying biological processes and in the therapeutic strategies for the management of metastasis. This review lists the disruption of E-cadherin and tight junctions, key signaling pathways, including urokinase type plasminogen activator (uPA), phosphatidylinositol 3-kinase/v-akt murine thymoma viral oncogene (PI3K/AKT), focal adhesion kinase (FAK), β-catenin/zinc finger E-box binding homeobox 1 (ZEB-1) and transforming growth factor beta (TGF-β), together with inactivation of activator protein-1 (AP-1) and suppression of matrix metalloproteinase-9 (MMP-9) activity as key targets and the use of phytochemicals, or natural products, such as those from Agaricus blazei, Albatrellus confluens, Cordyceps militaris, Ganoderma lucidum, Poria cocos and Silybum marianum, together with diet derived fatty acids gamma linolenic acid (GLA) and eicosapentanoic acid (EPA) and inhibitory compounds as useful approaches to target tissue invasion and metastasis as well as other hallmark areas of cancer. Together, these strategies could represent new, inexpensive, low toxicity strategies to aid in the management of cancer metastasis as well as having holistic effects against other cancer hallmarks.

Claudin-2 as a mediator of leaky gut barrier during intestinal inflammation

The epithelial tight junction determines the paracellular water and ion movement in the intestine and also prevents uptake of larger molecules, including antigens, in an uncontrolled manner. Claudin-2, one of the 27 mammalian claudins regulating that barrier function, forms a paracellular channel for small cations and water. It is typically expressed in leaky epithelia like proximal nephron and small intestine and provides a major pathway for the paracellular transport of sodium, potassium, and fluid. In intestinal inflammation (Crohn's disease, ulcerative colitis), immune-mediated diseases (celiac disease), and infections (HIV enteropathy), claudin-2 is upregulated in small and large intestine and contributes to diarrhea via a leak flux mechanism. In parallel to that upregulation, other epithelial and tight junctional features are altered and the luminal uptake of antigenic macromolecules is enhanced, for which claudin-2 may be partially responsible through induction of tight junction strand discontinuities.

Extending the functions of the homeotic transcription factor Cdx2 in the digestive system through nontranscriptional activities

The homeoprotein encoded by the intestinal-specific Cdx2 gene is a major regulator of gut development and homeostasis, also involved in colon cancer as well as in intestinal-type metaplasias when it is abnormally expressed outside the gut. At the molecular level, structure/function studies have demonstrated that the Cdx2 protein is a transcription factor containing a conserved homeotic DNA-binding domain made of three alpha helixes arranged in a helix-turn-helix motif, preceded by a transcriptional domain and followed by a regulatory domain. The protein interacts with several thousand sites on the chromatin and widely regulates intestinal functions in stem/progenitor cells as well as in mature differentiated cells. Yet, this transcription factor also acts trough original nontranscriptional mechanisms. Indeed, the identification of novel protein partners of Cdx2 and also of a splicing variant revealed unexpected functions in the control of signaling pathways like the Wnt and NF-κB pathways, in double-strand break DNA repair and in premessenger RNA splicing. These novel functions of Cdx2 must be considered to fully understand the complexity of the role of Cdx2 in the healthy intestine and in diseases.

Transcriptional regulation of human UDP-glucuronosyltransferase genes

Glucuronidation is an important metabolic pathway for many small endogenous and exogenous lipophilic compounds, including bilirubin, steroid hormones, bile acids, carcinogens and therapeutic drugs. Glucuronidation is primarily catalyzed by the UDP-glucuronosyltransferase (UGT) 1A and two subfamilies, including nine functional UGT1A enzymes (1A1, 1A3-1A10) and 10 functional UGT2 enzymes (2A1, 2A2, 2A3, 2B4, 2B7, 2B10, 2B11, 2B15, 2B17 and 2B28). Most UGTs are expressed in the liver and this expression relates to the major role of hepatic glucuronidation in systemic clearance of toxic lipophilic compounds. Hepatic glucuronidation activity protects the body from chemical insults and governs the therapeutic efficacy of drugs that are inactivated by UGTs. UGT mRNAs have also been detected in over 20 extrahepatic tissues with a unique complement of UGT mRNAs seen in almost every tissue. This extrahepatic glucuronidation activity helps to maintain homeostasis and hence regulates biological activity of endogenous molecules that are primarily inactivated by UGTs. Deciphering the molecular mechanisms underlying tissue-specific UGT expression has been the subject of a large number of studies over the last two decades. These studies have shown that the constitutive and inducible expression of UGTs is primarily regulated by tissue-specific and ligand-activated transcription factors (TFs) via their binding to cis-regulatory elements (CREs) in UGT promoters and enhancers. This review first briefly summarizes published UGT gene transcriptional studies and the experimental models and tools utilized in these studies, and then describes in detail the TFs and their respective CREs that have been identified in the promoters and/or enhancers of individual UGT genes.

Cloning and characterization of the human trefoil factor 3 gene promoter

Human trefoil factor 3 (hTFF3) is a small-molecule peptide with potential medicinal value. Its main pharmacological function is to alleviate gastrointestinal mucosal injuries caused by various factors and promote the repair of damaged mucosa. However, how its transcription is regulated is not yet known. The aim of this study was to clone the hTFF3 gene promoter region, identify the core promoter and any transcription factors that bind to the promoter, and begin to clarify the regulation of its expression. The 5′ flanking sequence of the hTFF3 gene was cloned from human whole blood genomic DNA by PCR. Truncated promoter fragments with different were cloned and inserted into the pGL3-Basic vector to determine the position of the core hTFF3 promoter. Transcription element maintaining basic transcriptional activity was assessed by mutation techniques. Protein-DNA interactions were analyzed by chromatin immunoprecipitation (ChIP). RNA interference and gene over-expression were performed to assay the effect of transcription factor on the hTFF3 expression. The results showed that approximately 1,826 bp of the fragment upstream of hTFF3 was successfully amplified, and its core promoter region was determined to be from −300 bp to −280 bp through analysis of truncated mutants. Mutation analysis confirmed that the sequence required to maintain basic transcriptional activity was accurately positioned from −300 bp to −296 bp. Bioinformatic analysis indicated that this area contained a Sp1 binding site. Sp1 binding to the hTFF3 promoter was confirmed by ChIP experiments. Sp1 over-expression and interference experiments showed that Sp1 enhanced the transcriptional activity of the hTFF3 promoter and increased hTFF3 expression. This study demonstrated that Sp1 plays an important role in maintaining the transcription of hTFF3.

H. pylori-encoded CagA disrupts tight junctions and induces invasiveness of AGS gastric carcinoma cells via Cdx2-dependent targeting of Claudin-2

Helicobacter pylori encoded CagA is presently the only known virulence factor that is injected into gastric epithelial cells where it destroys apical junctional complexes and induces dedifferentiation of gastric epithelial cells, leading to H. pylori-related gastric carcinogensis. However, little is known about the molecular mechanisms by which CagA mediates these changes. Caudal-related homeobox 2 (Cdx2) is an intestine-specific transcription factor highly expressed in multistage tissues of dysplasia and cancer. One specific target of Cdx2, Claudin-2, is involved in the regulation of tight junction (TJ) permeability. In this study, our findings showed that the activity of Cdx2 binding to Cdx binding sites of CdxA (GTTTATG) and CdxB (TTTTAGG) of probes corresponding to claudin-2 flanking region increased in AGS cells, infected with CagA positive wild-type strain of H. pylori, compared to CagA negative isogenic mutant-type strain. Moreover, Cdx2 upregulated claudin-2 expression at transcriptional level and translational level. In the meantime, we found that TJs of AGS cells, infected with CagA positive wild-type strain of H. pylori, compared to CagA negative isogenic mutant-type strain, were more severely destroyed, leading to wider cell gap, interference of contact, scattering and highly elevated migration of cells. Herein, this study is firstly demonstrated that H. pylori-encoded CagA disrupts TJs and induces invasiveness of AGS gastric carcinoma cells via Cdx2-dependent targeting of Claudin-2. This provides a new mechanism whereby CagA induced dedifferentiation of AGS cells, leading to malignant behavior of biology.

Comprehensive screening for PRSS1, SPINK1, CFTR, CTRC and CLDN2 gene mutations in Chinese paediatric patients with idiopathic chronic pancreatitis: a cohort study

OBJECTIVE

Genetic alterations may contribute to chronic pancreatitis (CP) in Chinese young patients. This study was designed to investigate mutations of cationic trypsinogen (PRSS1), pancreatic secretory trypsin inhibitor or serine protease inhibitor Kazal type 1 (SPINK1), cystic fibrosis transmembrane conductance regulator (CFTR), chymotrypsin C (CTRC) and CLDN2 genes and the copy number variations (CNVs) of PRSS1 and asses associations with the development of idiopathic CP (ICP) in Chinese children.

DESIGN

Retrospective.

SETTING

A single center.

PARTICIPANTS

75 ICP Chinese children (40 boys and 35 girls).

PRIMARY AND SECONDARY OUTCOME MEASURES

Mutations of PRSS1, SPINK1, CFTR, CTRC and CLDN2 genes and CNVs.

RESULTS

7 patients had heterozygous mutations in PRSS1, that is, N29I (n=1), R122H or R122C (n=6). The CNVs of PRSS1 in five patients had abnormal copies (1 copy (n=4), five copies (n=1)). 43 patients had IVS3+2T>C (rs148954387) (10 homozygous and 33 heterozygous) in SPINK1. None of the PRSS1 mutation patients carried a SPINK1 mutation. Frequency of PRSS1 and SPINK1 mutations was 9.3% and 57.3%, respectively, with an overall frequency of 66.6% (50/75). In addition, one patient had a novel deletion of CFTR (GCTTCCTA from c.500 to c.508 leading to the shortened polypeptide molecule via a stop codon). Another patient had a novel missense in CLDN2 exon 2 (c.592A>C mutation). Clinically, patients with SPINK1 mutations had a higher rate of pancreatic duct stones, pancreatic pseudocyst and pancreatic calcification than those without SPINK1 mutations (p<0.05).

CONCLUSIONS

SPINK1 mutations were more commonly associated with Chinese children with ICP. SPINK1 IVS3+2T>C mutation may play an important role in the pathogenesis of Chinese paediatric ICP. However, further study is needed to confirm and to investigate the role of these genes in the development of Chinese ICP.

Analysis of single nucleotide polymorphisms in the region of CLDN2-MORC4 in relation to inflammatory bowel disease

AIM: To investigate a possible genetic influence of claudin (CLDN)1, CLDN2 and CLDN4 in the etiology of inflammatory bowel disease.

METHODS: Allelic association between genetic regions of CLDN1, CLDN2 or CLDN4 and patients with inflammatory bowel disease, Crohn’s disease (CD) or ulcerative colitis were investigated using both a case-control study approach (one case randomly selected from each of 191 Swedish inflammatory bowel disease families and 333 controls) and a family-based study (463 non-Swedish European inflammatory bowel disease -families). A nonsynonymous coding single nucleotide polymorphism in MORC4, located on the same linkage block as CLDN2, was investigated for association, as were two novel CLDN2 single nucleotide polymorphism markers, identified by resequencing.

RESULTS: A single nucleotide polymorphism marker (rs12014762) located in the genetic region of CLDN2 was significantly associated to CD (case-control allelic OR = 1.98, 95%CI: 1.17-3.35, P = 0.007). MORC4 was present on the same linkage block as this CD marker. Using the case-control approach, a significant association (case control allelic OR = 1.61, 95%CI: 1.08-2.41, P = 0.018) was found between CD and a nonsynonymous coding single nucleotide polymorphism (rs6622126) in MORC4. The association between the CLDN2 marker and CD was not replicated in the family-based study. Ulcerative colitis was not associated to any of the single nucleotide polymorphism markers.

CONCLUSION: These findings suggest that a variant of the CLDN2-MORC4 region predisposes to CD in a Swedish population.

Effect of Saccharomyces boulardii and Bacillus subtilis B10 on intestinal ultrastructure modulation and mucosal immunity development mechanism in broiler chickens

The recent ban on the use of antibiotics as a feed additive has led to the search for alternative sources of antibiotics in the feed industry. Presently, probiotics are considered as a potential substitute for antibiotic as a live biotherapeutic agent to improve animal health and performance. Accordingly, study was focused on evaluating the effect of Saccharomyces boulardii (Sb) and Bacillus subtilis B10 (Bs) on ultrastructure modulation and mucosal immunity development in broiler chickens. A total of three hundred 1-d-old Sanhuang broilers (a Chinese cross breed) were randomized into 3 groups, each group with 5 replications (n = 20). The control group (Ctr) was fed a basal diet containing an antibiotic (virginiamycin, 20 mg/kg). Meanwhile, broilers in experimental groups received Sb and Bs (1 × 10(8) cfu/kg of feed) in addition to the basal diet for 72 d. The results of the experimental groups revealed a significant improvement in live BW and relative weight of bursa of Fabricius and thymus. Also, intestinal villus height, width, and number of goblet cells increased in the Sb and Bs groups. Meanwhile, modulation in the intestinal ultrastructure and increased mRNA expression levels of occluding, cloudin2, and cloudin3 (P < 0.05) were observed in the Sb and Bs groups. Moreover, IgA-positive cells significantly increased in the jejunum of Sb- and Bs-supplemented groups (P < 0.05). Intestinal cytokines interleukin-6, tumor necrosis factor-α, interleukin-10, transforming growth factor-β, and secretory IgA concentrations were (P < 0.05) improved in the probiotic groups; however, Sb induced inflammatory and antiinflammatory cytokines (P < 0.05) in comparison with the Ctr group. The present findings conclusively revealed that Sb and Bs increased IgA-positive cells in the lumen of the intestinal villus and revealed that Sb and Bs could modulate intestinal ultrastructure through increasing occluding, cloudin2, and cloudin3 mRNA expression levels in broiler intestine.

Build them up and break them down: Tight junctions of cell lines expressing typical hepatocyte polarity with a varied repertoire of claudins

Tight junctions (TJs) of cells expressing simple epithelial polarity have been extensively studied, but less is known about TJs of cells expressing complex polarity. In this paper we analyzed, TJs of four different lines, that form bile canaliculi (BC) and express typical hepatocyte polarity; WIF-B9, 11–3, Can 3–1, Can 10. Striking differences were observed in claudin expression. None of the cell lines produced claudin-1. WIF-B9 and 11–3 expressed only claudin-2 while Can 3–1 and Can 10 expressed claudin-2,-3,-4,-5. TJs of these two classes of lines differed in their ultra-stucture, paracellular permeability, and robustness. Lines expressing a large claudin repertoire, especially Can 10, had complex and efficient TJs, that were maintained when cells were depleted in calcium. Inversely, TJs of WIF-B9 and 11–3 were leaky, permissive and dismantled by calcium depletion. Interestingly, we found that during the polarization process, TJ proteins expressed by all lines were sequentially settled in a specific order: first occludin, ZO-1 and cingulin, then JAM-A and ZO-2, finally claudin-2. Claudins expressed only in Can lines were also sequentially settled: claudin-3 was the first settled. Inhibition of claudin-3 expression delayed BC formation in Can10 and induced the expression of simple epithelial polarity. These results highlight the role of claudins in the settlement and the efficiency of TJs in lines expressing typical hepatocyte polarity. Can 10 seems to be the most promising of these lines because of its claudin repertoire near that of hepatocytes and its capacity to form extended tubular BC sealed by efficient TJs.

Genetic risk factors for pancreatic disorders

A combination of genetic, environmental, and metabolic factors contribute to the development and recurrence of acute and chronic pancreatitis; information on all of these is required to manage patients effectively. For example, variants that affect regulation of the protease, serine (PRSS)1-PRSS2, and claudin (CLDN)2 loci, rather than their coding sequences, interact with other genetic and environmental factors to affect disease development. New strategies are needed to use these data and determine their contribution to pathogenesis, because these variants differ from previously studied, rare variants in exons (coding regions) of genes such as PRSS1, SPINK1, cystic fibrosis transmembrane conductance regulator (CFTR), chymotrypsin (CTR)C, and calcium-sensing receptor (CASR). Learning how various genetic factors affect pancreatic cells and systems could lead to etiology-based therapies rather than treatment of symptoms.

Claudins in intestines: Distribution and functional significance in health and diseases

Intestines are organs that not only digest food and absorb nutrients, but also provide a defense barrier against pathogens and noxious agents ingested. Tight junctions (TJs) are the most apical component of the junctional complex, providing one form of cell-cell adhesion in enterocytes and playing a critical role in regulating paracellular barrier permeability. Alteration of TJs leads to a number of pathophysiological diseases causing malabsorption of nutrition and intestinal structure disruption, which may even contribute to systemic organ failure. Claudins are the major structural and functional components of TJs with at least 24 members in mammals. Claudins have distinct charge-selectivity, either by tightening the paracellular pathway or functioning as paracellular channels, regulating ions and small molecules passing through the paracellular pathway. In this review, we have discussed the functions of claudin family members, their distribution and localization in the intestinal tract of mammals, their alterations in intestine-related diseases and chemicals/agents that regulate the expression and localization of claudins as well as the intestinal permeability, which provide a therapeutic view for treating intestinal diseases.