Intestinal Epithelial Barrier Integrity Research Articles

SIRT1 Stabilizes β-TrCP1 to Inhibit Snail1 Expression in Maintaining Intestinal Epithelial Integrity to Alleviate Colitis

Dysfunction of the intestinal epithelial barrier comprising the junctional complex of tight junctions and adherent junctions leads to increased intestinal permeability, which is a major cause of uncontrolled inflammation related to inflammatory bowel disease (IBD). The NAD+-dependent deacetylase SIRT1 is implicated in inflammation and the pathologic process of IBD. We aimed to elucidate the protective role and underlying mechanism of SIRT1 in cell-cell junction and intestinal epithelial integrity. The correlation of SIRT1 expression and human IBD was analyzed by GEO or immunohistochemical analyses. BK5.mSIRT1 transgenic mice and wild-type mice were given dextran sodium sulfate (DSS) and the manifestation of colitis-related phenotypes was analyzed. Intestinal permeability was measured by FITC-dextran and cytokines expression was analyzed by quantitative polymerase chain reaction. The expression of the cell junction-related proteins in DSS-treated or SIRT1-knockdown Caco2 or HCT116 cells was analyzed by Western blotting. The effects of nicotinamide mononucleotide in DSS-induced mice colitis were investigated. Correlations ofthe SIRT1-β-TrCP1-Snail1-Occludin/Claudin-1/E-cadherin pathway with human IBD samples were analyzed. Reduced SIRT1 expression is associated with human IBD specimens. SIRT1 transgenic mice exhibit much-reduced manifestations of DSS-induced colitis. The activation of SIRT1 by nicotinamide mononucleotide bolsters intestinal epithelial barrier function and ameliorates DSS-induced colitis in mice. Mechanistically, DSS downregulates SiRT1 expression, leading to destabilization of β-TrCP1 and upregulation of Snail1, accompanied by reduced expression of E-cadherin, Occludin, and Claudin-1, consequently resulting in increased epithelial permeability and inflammation. The deregulated SIRT1-β-TrCP1-Snail1-Occludin/Claudin-1/E-cadherin pathway correlates with human IBD. SIRT1 is pivotal in maintaining the intestinal epithelial barrier integrity via modulation of the β-TrCP1-Snail1-E-cadhein/Occludin/Claudin-1 pathway.

Modulating intestinal health: Impact of chitooligosaccharide molecular weight on suppressing RAGE expression and inflammatory response in methylglyoxal-induced advanced glycation end-products

The accumulation of methylglyoxal (MGO) produced in high-temperature processed foods and excessive production in the body contributes to intestinal barrier dysfunction. In this study, we investigated the effects of chitooligosaccharides (COSs) of different molecular weights (<1 kDa, 1–3 kDa, 3–5 kDa, 5–10 kDa, and >10 kDa) on MGO-induced intestinal barrier dysfunction. We investigated the effect of COSs on inhibiting intracellular MGO accumulation/MGO-derived AGEs production and regulating the receptor for AGE (RAGE)-mediated downstream protein expression, including proteins related to apoptosis and inflammation, intestinal barrier integrity, and paracellular permeability. Pretreatment with COSs ameliorated MGO-induced increased RAGE protein expression, activation of apoptotic cascade/inflammatory response, loss of intestinal epithelial barrier integrity, and increased paracellular permeability, ameliorating intestinal dysfunction through MGO scavenging. 1–3 kDa COSs most effectively ameliorated MGO-induced intestinal dysfunction. Our results suggest the potential of COSs in improving intestinal health by ameliorating intestinal barrier dysfunction by acting as an MGO scavenger and highlighting the need for the optimization of the molecular weight of COSs to optimize its protective effects.

HUC-MSCs therapy for Crohn’s disease: efficacy in TNBS-induced colitis in rats and pilot clinical study

The use of mesenchymal stem cells (MSCs) has recently emerged as a promising new therapeutic strategy for many diseases including perianal fistulizing Crohn's disease (CD). Whether hUC-MSCs can promote the healing of luminal ulcer in CD has not been studied so far. The model of TNBS-induced colitis in rats was used to confirm the efficacy of hUC-MSCs in the treatment of CD. Then, seventeen CD patients refractory to or unsuitable for currently available therapies were enrolled and received once submucosal local injection through colonoscopy combined with once intravenous drip on the next day. All patients received a 24-week follow-up. Clinical and laboratory assessments were monitored at baseline, week 4, 8, 12, and 24. Endoscopic evaluations were conducted at baseline and week 12. Mucosal specimens were obtained at the margin of lesions by endoscopy biopsies and used for RNA sequencing. Two hUC-MSCs co-culture systems were established invitro, one with the mucosa specimens and the other with M1 macrophages induced from THP1. The expressions of genes representing inflammation (TNFα, IL-6, and IL-1β) and intestinal barrier function (ZO1, CLAUDIN1, and CDH1) were tested by RT-PCR. hUC-MSCs treatment increased body weight and decreased disease activity index (DAI), colon macroscopic damage index (CMDI), and histopathological score (HPS) of rats with TNBS-induced colitis. The results of the clinical study also showed that this mode of hUC-MSCs application was associated with regression of intestinal ulceration. Eight patients (47%) got endoscopic responses (SES-CD improvement of ≥50% from baseline) and three patients (17.65%) got mucosal healing (SES-CD is zero), with a parallel improvement of clinical and laboratory parameters without serious adverse events. RNA sequencing showed hUC-MSCs therapy was associated with an upregulation of transcripts linked to intestinal epithelial barrier integrity and a downregulation of inflammatory signaling pathways in the intestinal mucosa, especially the TNF signaling pathway, IL-17 signaling pathway, and TLR signaling pathway. RNA expression of intestinal epithelial tight junction protein (ZO1, CLAUDIN1, and CDH1), and the RNA expression of major intestinal inflammatory factors in CD (IL-1β, IL-6, and TNFα, p<0.001 for all) were improved significantly. Moreover, hUC-MSCs could attenuate the polarization of M1 macrophage induced from THP1, thereby decreasing the mRNA expression of IL-1β, IL-6, and TNFα significantly (p<0.05 for all). TSG-6 expression was evaluated in hUC-MSCs culture supernatant after treatment with TNFα, IFNγ, and LPS for 48h. And hUC-MSCs could inhibit the phosphorylation of JAK/STAT1 in the intestinal mucosa of CD patients. hUC-MSCs transplantation alleviated TNBS-induced colitis in rats. In this pilot clinical study, preliminary data suggested that this approach to administering hUC-MSCs might have potential for clinical efficacy and manageable safety in treating refractory CD, potentially providing hope for better outcomes. No serious adverse events were observed. This work was funded by General Program of National Natural Science Foundation of China (Grant No. 82270639), the Scientific research project of Shanghai Municipal Health Committee (Grant No. 202240001), Specialty Feature Construction Project of Shanghai Pudong New Area Health Commission (Grant No. PWZzb2022-05), Shanghai East Hospital Youth Research and Cultivation Foundation program (Grant No. DFPY2022015), Peak Disciplines (Type IV) of Institutions of Higher Learning in Shanghai and Technology Development Project of Pudong Science, Technology and Economic Commission of Shanghai (Grant No. PKJ2021-Y08).

Allergenic Shrimp Tropomyosin Distinguishes from a Non-Allergenic Chicken Homolog by Pronounced Intestinal Barrier Disruption and Downstream Th2 Responses in Epithelial and Dendritic Cell (Co)Culture.

Tropomyosins (TM) from vertebrates are generally non-allergenic, while invertebrate homologs are potent pan-allergens. This study aims to compare the risk of sensitization between chicken TM and shrimp TM through affecting the intestinal epithelial barrier integrity and type 2 mucosal immune activation. Epithelial activation and/or barrier effects upon exposure to 2-50 μg/mL chicken TM, shrimp TM or ovalbumin (OVA) as a control allergen, were studied using Caco-2, HT-29MTX, or HT-29 intestinal epithelial cells. Monocyte-derived dendritic cells (moDC), cocultured with HT-29 cells or moDC alone, were exposed to 50 μg/mL chicken TM or shrimp TM. Primed moDC were cocultured with naïve Th cells. Intestinal barrier integrity (TEER), gene expression, cytokine secretion and immune cell phenotypes were determined in these human in vitro models. Shrimp TM, but not chicken TM or OVA exposure, profoundly disrupted intestinal barrier integrity and increased alarmin genes expression in Caco-2 cells. Proinflammatory cytokine secretion in HT-29 cells was only enhanced upon shrimp TM or OVA, but not chicken TM, exposure. Shrimp TM enhanced the maturation of moDC and chemokine secretion in the presence or absence of HT-29 cells, while only in the absence of epithelial cells chicken TM activated moDC. Direct exposure of moDC to shrimp TM increased IL13 and TNFα secretion by Th cells cocultured with these primed moDC, while shrimp TM exposure via HT-29 cells cocultured with moDC sequentially increased IL13 expression and IL4 secretion in Th cells. Shrimp TM, but not chicken TM, disrupted the epithelial barrier while triggering type 2 mucosal immune activation, both of which are key events in allergic sensitization.

Targeting staphylococcal enterotoxin B binding to CD28 as a new strategy for dampening superantigen-mediated intestinal epithelial barrier dysfunctions.

Staphylococcus aureus is a gram-positive bacterium that may cause intestinal inflammation by secreting enterotoxins, which commonly cause food-poisoning and gastrointestinal injuries. Staphylococcal enterotoxin B (SEB) acts as a superantigen (SAg) by binding in a bivalent manner the T-cell receptor (TCR) and the costimulatory receptor CD28, thus stimulating T cells to produce large amounts of inflammatory cytokines, which may affect intestinal epithelial barrier integrity and functions. However, the role of T cell-mediated SEB inflammatory activity remains unknown. Here we show that inflammatory cytokines produced by T cells following SEB stimulation induce dysfunctions in Caco-2 intestinal epithelial cells by promoting actin cytoskeleton remodelling and epithelial cell-cell junction down-regulation. We also found that SEB-activated inflammatory T cells promote the up-regulation of epithelial-mesenchymal transition transcription factors (EMT-TFs) in a nuclear factor-κB (NF-κB)- and STAT3-dependent manner. Finally, by using a structure-based design approach, we identified a SEB mimetic peptide (pSEB116-132) that, by blocking the binding of SEB to CD28, dampens inflammatory-mediated dysregulation of intestinal epithelial barrier.

First person – Celia Segui-Perez

ABSTRACT First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping researchers promote themselves alongside their papers. Celia Segui-Perez is first author on ‘ MUC13 negatively regulates tight junction proteins and intestinal epithelial barrier integrity via protein kinase C’, published in JCS. Celia is a PhD student in the lab of Karin Strijbis at the Department of Biomolecular Health Sciences, Utrecht University, The Netherlands, investigating the role of mucins in health and disease.

MUC13 negatively regulates tight junction proteins and intestinal epithelial barrier integrity via protein kinase C.

Glycosylated mucin proteins contribute to the essential barrier function of the intestinal epithelium. The transmembrane mucin MUC13 is an abundant intestinal glycoprotein with important functions for mucosal maintenance that are not yet completely understood. We demonstrate that in human intestinal epithelial monolayers, MUC13 localized to both the apical surface and the tight junction (TJ) region on the lateral membrane. MUC13 deletion resulted in increased transepithelial resistance (TEER) and reduced translocation of small solutes. TEER buildup in ΔMUC13 cells could be prevented by addition of MLCK, ROCK or protein kinase C (PKC) inhibitors. The levels of TJ proteins including claudins and occludin were highly increased in membrane fractions of MUC13 knockout cells. Removal of the MUC13 cytoplasmic tail (CT) also altered TJ composition but did not affect TEER. The increased buildup of TJ complexes in ΔMUC13 and MUC13-ΔCT cells was dependent on PKC. The responsible PKC member might be PKCδ (or PRKCD) based on elevated protein levels in the absence of full-length MUC13. Our results demonstrate for the first time that a mucin protein can negatively regulate TJ function and stimulate intestinal barrier permeability.

Adenosine in Intestinal Epithelial Barrier Function.

At the intestinal front, several lines of defense are in place to resist infection and injury, the mucus layer, gut microbiome and strong epithelial junctions, to name a few. Their collaboration creates a resilient barrier. In intestinal disorders, such as inflammatory bowel disease (IBD), barrier function is compromised, which results in rampant inflammation and tissue injury. In response to the destruction, the intestinal epithelium releases adenosine, a small but powerful nucleoside that functions as an alarm signal. Amidst the chaos of inflammation, adenosine aims to restore order. Within the scope of its effects is the ability to regulate intestinal epithelial barrier integrity. This review aims to define the contributions of adenosine to mucus production, microbiome-dependent barrier protection, tight junction dynamics, chloride secretion and acid-base balance to reinforce its importance in the intestinal epithelial barrier.

P059 GSDMB triggers intestinal inflammation via regulating BHLHA15-mediated hyperactive unfolded protein response

Abstract Background Impaired intestinal epithelial barrier has been considered to be associated with an increasing variety of gastrointestinal diseases, especially inflammatory bowel disease (IBD) encompassing Crohn’s disease (CD) and ulcerative colitis (UC). Herein, we investigated the role of Gasdermin B (GSDMB) in modulating intestinal epithelial barrier integrity and proposed a promising therapeutic strategy. Methods We generated GSDMB (GSDMBfl/fl;Villin-Cre) intestinal epithelial-specific knock in mice to observe the functions of GSDMB in intestinal epithelial barrier. RNA-seq analysis and human and murine intestine-derived organoids were used to determine the mechanism of function of GSDMB. Results To interrogate the intestinal functions of GSDMB in vivo, we generated GSDMB conditional knock in mice (heterozygote: GSDMBfl/-;Villin-Cre; homozygote: GSDMBfl/fl;Villin-Cre) by crossing a mouse line containing the floxed alleles of human GSDMB and a transcriptional stop codon at the transcriptional initiation site (GSDMBfl/fl) with the mouse line expressing Cre-recombinase under control of the Villin promoter (Villin-Cre). GSDMBfl/fl;Villin-Cre mice developed spontaneous enterocolitis and exhibited aberrant intestinal barrier integrity (as shown in the figure). GSDMB prominently provoked cell death of absorptive enterocytes and affected the function of goblet cells and Paneth cells in this setting. Mechanistically, epithelial GSDMB modulated hyperactive unfolded protein response of IECs by up-regulating BHLHA15 to mediate intestinal barrier injury instead of by the invasion of pathogenic microorganisms. Conclusion We have uncovered an important and a previously unrecognized role of GSDMB in intestinal inflammation, which represents a potential therapeutic target for IBD.

Bile Acid Metabolic Profiles and Their Correlation with Intestinal Epithelial Cell Proliferation and Barrier Integrity in Suckling Piglets.

Bile acids (BAs) are crucial for maintaining intestinal epithelial homeostasis. However, the metabolic changes in BAs and the communication between intestinal epithelial cells (IECs) in infants after birth remain unclear. This study aims to elucidate the BA profiles of newborn piglets (NPs) and suckling piglets (SPs), and to investigate their regulatory effects on IEC proliferation and barrier integrity, as well as the potential underlying mechanisms. In this study, compared with NPs, there were significant increases in serum triglycerides, total cholesterol, glucose, and albumin levels for SPs. The total serum BA content in SPs exhibited an obvious increase. Moreover, the expression of BA synthase cytochrome P450 27A1 (CYP27A1) was increased, and the ileal BA receptor Takeda G-coupled protein receptor 5 (TGR5) and proliferation marker Ki-67 were upregulated and showed a strong positive correlation through a Spearman correlation analysis, whereas the expression of farnesoid X receptor (FXR) and occludin was markedly downregulated in SPs and also revealed a strong positive correlation. These findings indicate that the increased synthesis and metabolism of BAs may upregulate TGR5 and downregulate FXR to promote IEC proliferation and influence barrier function; this offers a fresh perspective and evidence for the role of BAs and BA receptors in regulating intestinal development in neonatal pigs.

Hypersampsonone H attenuates ulcerative colitis via inhibition of PDE4 and regulation of cAMP/PKA/CREB signaling pathway

Background and objectivesUlcerative colitis (UC) is a recurrent intestinal inflammatory disease which poses a serious threat to the life of patients. However, there are no specific drugs for UC yet. Hypericum sampsonii Hance (HS) is a Chinese herbal medicine traditionally used to treat enteritis and dysentery. Our previous studies have demonstrated that HS holds potential anti-UC effects, and a novel compound named Hypersampsonone H (HS-1) isolated from HS possesses significant anti-inflammatory activity. However, the beneficial effects of HS-1 on UC remain unclear. This study aimed to investigate the therapeutic effects of HS-1 on UC and its potential mechanisms, both in vitro and in vivo. MethodsThe in vitro model was employed using LPS-induced RAW264.7 cells to investigate the anti-inflammatory effects of HS-1 and its possible mechanisms. Furthermore, the therapeutic efficacy and potential mechanisms of HS-1 against dextran sulfate sodium (DSS)-induced acute colitis were assessed through histopathological examination, biochemical analysis, and molecular docking. ResultsIn vitro, HS-1 significantly reduced LPS-induced inflammatory responses, as indicated by inhibiting NO production, down-regulating the overexpression of COX-2 and iNOS, as well as regulating the imbalanced levels of IL-6, TNF-α, and IL-10. Moreover, HS-1 also inhibited the expression of PDE4, elevated the intracellular cAMP level, and promoted the phosphorylation of CREB, thereby activating the PKA/CREB pathway in RAW264.7 cells. In vivo, HS-1 demonstrated therapeutic capacity against DSS-induced colitis by alleviating the symptoms of colitis mice, regulating the abnormal expression of inflammatory mediators, protecting the integrity of intestinal epithelial barrier, and reducing tissue fibrosis. Consistently, HS-1 was found to decrease the expression of PDE4 isoforms, subsequently activating the cAMP/PKA/CREB signaling pathway. Furthermore, the molecular docking results indicated that HS-1 exhibited a high affinity for PDE4, particularly PDE4D. Further mechanistic validation in vitro demonstrated that HS-1 possessed a synergistic effect on forskolin and an antagonistic effect on H-89 dihydrochloride, thereby exerting anti-inflammatory effects through the cAMP/PKA/CREB signaling pathway. ConclusionWe disclose that HS-1 serves as a promising candidate drug for the treatment of UC by virtue of its ability to reduce DSS-induced colitis via the inhibition of PDE4 and the activation of cAMP/PKA/CREB signaling pathway.

A novel Trichinella spiralis serine proteinase disrupted gut epithelial barrier and mediated larval invasion through binding to RACK1 and activating MAPK/ERK1/2 pathway.

Gut epithelium is the first natural barrier against Trichinella spiralis larval invasion, but the mechanism by which larval penetration of gut epithelium is not completely elucidated. Previous studies showed that proteases secreted by T. spiralis intestinal infective larvae (IIL) degraded tight junctions (TJs) proteins of gut epithelium and mediated larval invasion. A new T. spiralis serine proteinase (TsSPc) was identified in the IIL surface proteins and ES proteins, rTsSPc bound to the intestinal epithelial cell (IECs) and promoted larval invasion of IECs. The aim of this study was to characterize the interacted proteins of TsSPc and IECs, and to investigate the molecular mechanisms of TsSPc mediating larval invasion of gut mucosa. IIFT results showed natural TsSPc was detected in infected murine intestine at 6, 12 hours post infection (hpi) and 3 dpi. The results of GST pull-down, mass spectrometry (MS) and Co-IP indicated that rTsSPc bound and interacted specifically with receptor for activated protein C kinase 1 (RACK1) in Caco-2 cells. rTsSPc did not directly hydrolyze the TJs proteins. qPCR and Western blot showed that rTsSPc up-regulated RACK1 expression, activated MAPK/ERK1/2 pathway, reduced the expression levels of gut TJs (occludin and claudin-1) and adherent protein E-cad, increased the paracellular permeability and damaged the integrity of intestinal epithelial barrier. Moreover, the RACK1 inhibitor HO and ERK1/2 pathway inhibitor PD98059 abolished the rTsSPc activating ERK1/2 pathway, they also inhibited and abrogated the rTsSPc down-regulating expression of occludin, claudin-1 and E-cad in Caco-2 monolayer and infected murine intestine, impeded larval invasion and improved intestinal epithelial integrity and barrier function, reduced intestinal worm burdens and alleviated intestinal inflammation. rTsSPc bound to RACK1 receptor in gut epithelium, activated MAPK/ERK1/2 pathway, decreased the expression of gut epithelial TJs proteins and disrupted the epithelial integrity, consequently mediated T. spiralis larval invasion of gut epithelium. The results are valuable to understand T. spiralis invasion mechanism, and TsSPc might be regarded as a vaccine target against T. spiralis invasion and infection.

Overview of the compromised mucosal integrity in celiac disease.

Intestinal epithelium is a dynamic cellular layer that lines the small-bowel and makes a relatively impenetrable barrier to macromolecules. Intestinal epithelial cell polarity is crucial in coordinating signalling pathways within cells and mainly regulated by three conserved polarity protein complexes, the Crumbs (Crb) complex, partitioning defective (PAR) complex, and Scribble (Scrib) complex. Polarity proteins regulate the proper establishment of the intercellular junctional complexes including tight junctions (TJs), adherence junctions (AJs), and desmosomes which hold epithelial cells together and play a major role in maintaining intestinal barrier integrity. Impaired intestinal epithelial cell polarity and barrier integrity result in irreversible immune responses, the host- microbial imbalance and intestinal inflammatory disorders. Disassembling the epithelial tight junction and augmented paracellular permeability is a conspicuous hallmark of celiac disease (CD) pathogenesis. There are several dietary components that can improve intestinal integrity and function. The aim of this review article is to summarize current information about the association of polarity proteins and AJC damages with pathogenesis of CD.

Retracted: Curcumin Improved Intestinal Epithelial Barrier Integrity by Up-Regulating ZO-1/Occludin/Claudin-1 in Septic Rats.

[This retracts the article DOI: 10.1155/2022/2884522.].

Akkermansia muciniphila protects the intestine from irradiation-induced injury by secretion of propionic acid

ABSTRACT Intestinal dysbiosis frequently occurs in abdominal radiotherapy and contributes to irradiation (IR)-induced intestinal damage and inflammation. Akkermansia muciniphila (A. muciniphila) is a recently characterized probiotic, which is critical for maintaining the dynamics of the intestinal mucus layer and preserving intestinal microbiota homeostasis. However, the role of A. muciniphila in the alleviation of radiation enteritis remains unknown. In this study, we reported that the abundance of A. muciniphila was markedly reduced in the intestines of mice exposed to abdominal IR and in the feces of patients who received abdominal radiotherapy. Abundance of A. muciniphila in feces of radiotherapy patients was negatively correlated with the duration of diarrhea in patients. Administration of A. muciniphila substantially mitigated IR-induced intestinal damage and prevented mouse death. Analyzing the metabolic products of A. muciniphila revealed that propionic acid, a short-chain fatty acid secreted by the microbe, mediated the radioprotective effect. We further demonstrated that propionic acid bound to G-protein coupled receptor 43 (GRP43) on the surface of intestinal epithelia and increased histone acetylation and hence enhanced the expression of tight junction proteins occludin and ZO-1 and elevated the level of mucins, leading to enhanced integrity of intestinal epithelial barrier and reduced radiation-induced intestinal damage. Metformin, a first-line agent for the treatment of type II diabetes, promoted intestinal epithelial barrier integrity and reduced radiation intestinal damage through increasing the abundance of A. muciniphila. Together, our results demonstrated that A. muciniphila plays a critical role in the reduction of abdominal IR-induced intestinal damage. Application of probiotics or their regulators, such as metformin, could be an effective treatment for the protection of radiation exposure-damaged intestine.

Loss of polarity protein Par3 in the intestinal epithelium promotes colitis-associated colorectal cancer progression by damaging tight junction assembly.

Partitioning defective 3 (Par3) is a polarity protein critical in establishing epithelial cell polarity and tight junctions (TJs). Impaired intestinal epithelial barrier integrity is closely associated with colitis-associated colorectal cancer (CRC) progression. According to the GEO and TCGA database analyses, we first observed that the expression of Par3 was reduced in CRC patients. To understand how Par3 is related to CRC, we investigated the role of Par3 in the development of CRC using an in vivo genetic approach. Our results show that the intestinal epithelium-specific PAR3 deletion mice demonstrated a more severe CRC phenotype in the context of azoxymethane/dextran sodium sulfate (AOM/DSS) treatment, with a corresponding increase in tumor number and inflammatory cytokines profile. Mechanistically, loss of Par3 disrupts the TJs of the intestinal epithelium and increases mucosal barrier permeability. The interaction of Par3 with ZO-1 prevents intramolecular interactions within ZO-1 protein and facilitates the binding of occludin to ZO-1, hence preserving TJs integrity. Our results suggest that Par3 deficiency permits pathogenic bacteria and their endotoxins to penetrate the intestinal submucosa and activate TLR4/MyD88/NF-κB signaling, promoting inflammation-driven CRC development and that Par3 may be a novel potential molecular marker for the diagnosis of early-stage CRC.

Protocadherin 20 maintains intestinal barrier function to protect against Crohn’s disease by targeting ATF6

BackgroundIntestinal barrier dysfunction plays a central role in the pathological onset of Crohn’s disease. We identify the cadherin superfamily member protocadherin 20 (PCDH20) as a crucial factor in Crohn’s disease. Here we describe the function of PCDH20 and its mechanisms in gut homeostasis, barrier integrity, and Crohn’s disease development.ResultsPCDH20 mRNA and protein expression is significantly downregulated in the colonic epithelium of Crohn’s disease patients and mice with induced colitis compared with controls. In mice, intestinal-specific Pcdh20 knockout causes defects in enterocyte proliferation and differentiation, while causing morphological abnormalities. Specifically, the deletion disrupts barrier integrity by unzipping adherens junctions via β-catenin regulation and p120-catenin phosphorylation, thus aggravating colitis in DSS- and TNBS-induced colitis mouse models. Furthermore, we identify activating transcription factor 6 (ATF6), a key chaperone of endoplasmic reticulum stress, as a functional downstream effector of PCDH20. By administering a selective ATF6 activator, the impairment of intestinal barrier integrity and dysregulation of CHOP/β-catenin/p-p120-catenin pathway was reversed in Pcdh20-ablated mice with colitis and PCDH20-deficient colonic cell lines.ConclusionsPCDH20 is an essential factor in maintaining intestinal epithelial homeostasis and barrier integrity. Specifically, PCDH20 helps to protect against colitis by tightening adherens junctions through the ATF6/CHOP/β-catenin/p-p120-catenin axis.

Anti-Inflammatory Effect and Signaling Mechanism of Glycine max Hydrolyzed with Enzymes from Bacillus velezensis KMU01 in a Dextran-Sulfate-Sodium-Induced Colitis Mouse Model.

The purpose of this study was to investigate the effect that Glycine max hydrolyzed with enzymes from Bacillus velezensis KMU01 has on dextran-sulfate-sodium (DSS)-induced colitis in mice. Hydrolysis improves functional health through the bioconversion of raw materials and increase in intestinal absorption rate and antioxidants. Therefore, G. max was hydrolyzed in this study using a food-derived microorganism, and its anti-inflammatory effect was observed. Enzymatically hydrolyzed G. max (EHG) was orally administered once daily for four weeks before DSS treatment. Colitis was induced in mice through the consumption of 5% (w/v) DSS in drinking water for eight days. The results showed that EHG treatment significantly alleviated DSS-induced body weight loss and decreased the disease activity index and colon length. In addition, EHG markedly reduced tumor necrosis factor-α, interleukin (IL)-1β, and IL-6 production, and increased that of IL-10. EHG improved DSS-induced histological changes and intestinal epithelial barrier integrity in mice. Moreover, we found that the abundance of 15 microorganisms changed significantly; that of Proteobacteria and Escherichia coli, which are upregulated in patients with Crohn's disease and ulcerative colitis, decreased after EHG treatment. These results suggest that EHG has a protective effect against DSS-induced colitis and is a potential candidate for colitis treatment.

Pathological Remodeling of the Gut Barrier as a Prodromal Event of High-Fat Diet-Induced Obesity

Intestinal barrier alterations represent a primum movens in obesity and related intestinal dysfunctions. However, whether gut barrier remodeling represents prodromal events in obesity before weight gain, metabolic alterations, and systemic inflammation remains unclear. Herein, we examined morphologic changes in the gut barrier in a mouse model of high-fat diet (HFD) since the earliest phases of diet assumption. C57BL/6J mice were fed with standard diet (SD) or HFD for 1, 2, 4, or 8 weeks. Remodeling of intestinal epithelial barrier, inflammatory infiltrate, and collagen deposition in the colonic wall was assessed by histochemistry and immunofluorescence analysis. Obese mice displayed increased body and epididymal fat weight along with increased plasma resistin, IL-1β, and IL-6 levels after 8 weeks of HFD. Starting from 1 week of HFD, mice displayed (1) a decreased claudin-1 expression in lining epithelial cells, (2) an altered mucus in goblet cells, (3) an increase in proliferating epithelial cells in colonic crypts, (4) eosinophil infiltration along with an increase in vascular P-selectin, and (5) deposition of collagen fibers. HFD intake is associated with morphologic changes in the large bowel at mucosal and submucosal levels. In particular, the main changes include alterations in the mucous layer and intestinal epithelial barrier integrity and activation of mucosal defense-enhanced fibrotic deposition. These changes represent early events occurring before the development of obesity condition that could contribute to compromising the intestinal mucosal barrier and functions, opening the way for systemic dissemination.

Dietary Supplementation with the Probiotic SF68 Reinforces Intestinal Epithelial Barrier in Obese Mice by Improving Butyrate Bioavailability.

Modifications in intestinal microbiota and its metabolites, the short-chain fatty acids (SCFA) are main factors altering intestinal epithelial barrier integrity and eliciting the onset of a meta-inflammation observed in obesity. The present study is aimed at evaluating the efficacy of Enterococcus faecium (SF68) administration in counteracting the impairment of gut barrier and enteric inflammation in a model of diet-induced obesity, characterizing the molecular mechanisms underlying such beneficial effects. Male C57BL/6J mice, fed with standard diet (SD) or high-fat diet (HFD), are treated with SF68 (108 CFUday-1 ). After 8weeks, plasma interleukin (IL)-1β and lipopolysaccharide binding protein (LBP) are measured, analysis of fecal microbiota composition and butyrate content as well as intestinal malondialdehyde, myeloperoxidase, mucins, tight junction protein, and butyrate transporter expression are investigated. After 8weeks, SF68 administration counteracts the body weight gain in HFD mice, reducing plasma IL-1β and LBP. In parallel, SF68 treatment acts against the intestinal inflammation in HFD-fed animals and improves the intestinal barrier integrity and functionality in obese mice via the increase in tight junction protein and intestinal butyrate transporter (sodium-coupled monocarboxylate transporter 1 ) expression. Supplementation with SF68 reduces intestinal inflammation and reinforces the enteric epithelial barrier in obese mice, improving the transport and utilization of butyrate.