Butyrate reduces adherent-invasive E. coli-evoked disruption of epithelial mitochondrial morphology and barrier function: involvement of free fatty acid receptor 3

Gut bacteria provide benefits to the host and have been implicated in inflammatory bowel disease (IBD), where adherent-invasive E. coli (AIEC) pathobionts (e.g., strain LF82) are associated with Crohn's disease. E. coli-LF82 causes fragmentation of the epithelial mitochondrial network, leading to increased epithelial permeability. We hypothesized that butyrate would limit the epithelial mitochondrial disruption caused by E. coli-LF82. Human colonic organoids and the T84 epithelial cell line infected with E. coli-LF82 (MOI = 100, 4 h) showed a significant increase in mitochondrial network fission that was reduced by butyrate (10 mM) co-treatment. Butyrate reduced the loss of mitochondrial membrane potential caused by E. coli-LF82 and increased expression of PGC-1α mRNA, the master regulator of mitochondrial biogenesis. Metabolomics revealed that butyrate significantly altered E. coli-LF82 central carbon metabolism leading to diminished glucose uptake and increased succinate secretion. Correlating with preservation of mitochondrial network form/function, butyrate reduced E. coli-LF82 transcytosis across T84-cell monolayers. The use of the G-protein inhibitor, pertussis toxin, implicated GPCR signaling as critical to the effect of butyrate, and the free fatty acid receptor three (FFAR3, GPR41) agonist, AR420626, reproduced butyrate's effect in terms of ameliorating the loss of barrier function and reducing the mitochondrial fragmentation observed in E. coli-LF82 infected T84-cells and organoids. These data indicate that butyrate helps maintain epithelial mitochondrial form/function when challenged by E. coli-LF82 and that this occurs, at least in part, via FFAR3. Thus, loss of butyrate-producing bacteria in IBD in the context of pathobionts would contribute to loss of epithelial mitochondrial and barrier functions that could evoke disease and/or exaggerate a low-grade inflammation.

Fecal Biomarkers of Neutrophil and Eosinophil Origin Reflect the Response to Biological Therapy and Corticosteroids in Patients With Inflammatory Bowel Disease

INTRODUCTION

Fecal calprotectin (FC) is a noninvasive tool for examining response to biologics in inflammatory bowel disease (IBD), but its performance in relation to other novel fecal markers of various cellular origins is unknown.

METHODS

We performed a prospective multicenter cohort study and included patients with active IBD who provided a fecal sample at initiation of biological therapy. Levels of FC, myeloperoxidase (MPO), human neutrophil lipocalin (HNL), and eosinophil-derived neurotoxin (EDN) were analyzed and related to clinical remission status at 3 months. Changes in levels of markers at 3 months were calculated, and the impact of concomitant use of corticosteroids at baseline was estimated.

RESULTS

In patients achieving clinical remission (n = 27), a decrease in levels of FC ( P = 0.005), MPO ( P < 0.001), HNL ( P < 0.001), and EDN ( P < 0.001) was observed, whereas no significant decrease was seen in patients not achieving remission (n = 39). There was a significant difference in the change in the level of MPO ( P = 0.01) and HNL ( P = 0.02) between patients achieving clinical remission and those who did not, but changes in FC and EDN could not differentiate between these groups. Patients with concomitant systemic corticosteroids at inclusion had lower levels of HNL ( P = 0.01) and EDN ( P < 0.001) at baseline, compared with patients without corticosteroids.

DISCUSSION

Fecal MPO, HNL, and EDN are all promising biomarkers for assessing the treatment outcome of biologics in patients with IBD. Fecal levels of EDN and HNL are significantly affected by corticosteroids indicating a greater sensitivity to the effects of corticosteroids compared with levels of FC and MPO.

Human skin-resident CD8+ T cells require RUNX2 and RUNX3 for induction of cytotoxicity and expression of the integrin CD49a

The integrin CD49a marks highly cytotoxic epidermal-tissue-resident memory (T_RM) cells, but their differentiation from circulating populations remains poorly defined. We demonstrate enrichment of RUNT family transcription-factor-binding motifs in human epidermal CD8⁺CD103⁺CD49a⁺ T_RM cells, paralleled by high RUNX2 and RUNX3 protein expression. Sequencing of paired skin and blood samples revealed clonal overlap between epidermal CD8⁺CD103⁺CD49a⁺ T_RM cells and circulating memory CD8⁺CD45RA^-CD62L⁺ T cells. In vitro stimulation of circulating CD8⁺CD45RA^-CD62L⁺ T cells with IL-15 and TGF-β induced CD49a expression and cytotoxic transcriptional profiles in a RUNX2- and RUNX3-dependent manner. We therefore identified a reservoir of circulating cells with cytotoxic T_RM potential. In melanoma patients, high RUNX2, but not RUNX3, transcription correlated with a cytotoxic CD8⁺CD103⁺CD49a⁺ T_RM cell signature and improved patient survival. Together, our results indicate that combined RUNX2 and RUNX3 activity promotes the differentiation of cytotoxic CD8⁺CD103⁺CD49a⁺ T_RM cells, providing immunosurveillance of infected and malignant cells.

A postbiotic fermented oat gruel may have a beneficial effect on the colonic mucosal barrier in patients with irritable bowel syndrome

Background

Impaired intestinal permeability and microbial dysbiosis are important pathophysiological mechanisms underlying irritable bowel syndrome (IBS). ReFerm^®, also called Profermin^®, is a postbiotic product of oat gruel fermented with Lactobacillus plantarum 299v. In this study, we investigated whether ReFerm^® has a beneficial effect on the intestinal epithelial barrier function in patients with IBS.

Materials and methods

Thirty patients with moderate to severe IBS-diarrhoea (IBS-D) or IBS-mixed (IBS-M) were treated with enema containing ReFerm^® or placebo. The patients underwent sigmoidoscopy with biopsies obtained from the distal colon at baseline and after 14 days of treatment with ReFerm^® or placebo twice daily. The biopsies were mounted in Ussing chambers, and paracellular and transcellular permeabilities were measured for 120 min. In addition, the effects of ReFerm^® or placebo on the epithelial barrier were investigated in vitro using Caco-2 cells.

Results

ReFerm^® reduced paracellular permeability (p < 0.05) and increased transepithelial resistance (TER) over time (p < 0.01), whereas the placebo had no significant effect in patients. In ReFerm^®-treated Caco-2 cells, paracellular and transcellular permeabilities were decreased compared to the control (p < 0.05) and placebo (p < 0.01). TER was increased in Caco-2 ReFerm^®-treated cells, and normalised TER was increased in ReFerm^®-treated Caco-2 cells compared to control (p < 0.05) and placebo-treated (p < 0.05) cells.

Conclusion

ReFerm^® significantly reduced paracellular permeability and improved TER in colonic biopsies collected from patients with IBS and in a Caco-2 cell model. Our results offer new insights into the potential benefits of ReFerm^® in IBS management. Further studies are needed to identify the molecular mechanisms underlying the barrier-protective properties of ReFerm^®.

Clinical trial registration

[https://clinicaltrials.gov/], identifier [NCT05475314].

Acute psychological stress increases paracellular permeability and modulates immune activity in rectal mucosa of healthy volunteers

BACKGROUND

Psychological stress and increased permeability are implicated as contributing factors in the initiation and worsening of gastrointestinal diseases. A link between stress and intestinal permeability has been shown in animal models as well as in human small intestine, but stress effects on the human colorectal mucosal barrier has not been reported.

OBJECTIVE

To investigate the potential effects of acute psychological stress on colorectal mucosal barrier function and to explore stress-induced molecular events in the rectal mucosa under healthy conditions.

METHODS

Endoscopic biopsies were taken from the rectosigmoid region of healthy volunteers, who had been subjected to dichotomous listening stress and after a control session, respectively. Paracellular and transcellular permeability were assessed in modified Ussing chambers. RNA expression (microarray technology confirmed by quantitative real-time polymerase chain reaction) and biological pathway analysis were used to investigate the local mucosal response to acute stress.

RESULTS

Dichotomous listening stress induced a subjective and objective stress response, and significantly increased paracellular but not transcellular permeability. We also identified a stress-induced reduction in RNA expression of genes related to immune cell activation and maturation (CR2, CD20, TCLA1, BANK1, CD22, FDCSP), signaling molecules of homing of immune cells to the gut (chemokines: CCL21, CXCL13, and CCL19, and receptors: CCR7, CXCR5), and innate immunity (DUOX2). Eight of the 10 top down-regulated genes are directly involved in B cell activation, signaling and migration. The systemic stress response correlated positively with paracellular permeability and negatively with DUOX2 expression.

CONCLUSION

Dichotomous listening stress increases paracellular permeability and modulates immune cell activity in the rectal mucosa. Further studies are warranted to identify the primary mechanisms of stress-mediated reduction of mucosal defensive activity and barrier dysfunction, and their potential implications for gastrointestinal disorders.

Barriers to the Intestinal Absorption of Four Insulin-Loaded Arginine-Rich Nanoparticles in Human and Rat

Peptide drugs and biologics provide opportunities for treatments of many diseases. However, due to their poor stability and permeability in the gastrointestinal tract, the oral bioavailability of peptide drugs is negligible. Nanoparticle formulations have been proposed to circumvent these hurdles, but systemic exposure of orally administered peptide drugs has remained elusive. In this study, we investigated the absorption mechanisms of four insulin-loaded arginine-rich nanoparticles displaying differing composition and surface characteristics, developed within the pan-European consortium TRANS-INT. The transport mechanisms and major barriers to nanoparticle permeability were investigated in freshly isolated human jejunal tissue. Cytokine release profiles and standard toxicity markers indicated that the nanoparticles were nontoxic. Three out of four nanoparticles displayed pronounced binding to the mucus layer and did not reach the epithelium. One nanoparticle composed of a mucus inert shell and cell-penetrating octarginine (ENCP), showed significant uptake by the intestinal epithelium corresponding to 28 ± 9% of the administered nanoparticle dose, as determined by super-resolution microscopy. Only a small fraction of nanoparticles taken up by epithelia went on to be transcytosed via a dynamin-dependent process. In situ studies in intact rat jejunal loops confirmed the results from human tissue regarding mucus binding, epithelial uptake, and negligible insulin bioavailability. In conclusion, while none of the four arginine-rich nanoparticles supported systemic insulin delivery, ENCP displayed a consistently high uptake along the intestinal villi. It is proposed that ENCP should be further investigated for local delivery of therapeutics to the intestinal mucosa.

Characterisation of the Circulating Transcriptomic Landscape in Inflammatory Bowel Disease Provides Evidence for Dysregulation of Multiple Transcription Factors Including NFE2, SPI1, CEBPB, and IRF2

AIM

To assess the pathobiological and translational importance of whole-blood transcriptomic analysis in inflammatory bowel disease [IBD].

METHODS

We analysed whole-blood expression profiles from paired-end sequencing in a discovery cohort of 590 Europeans recruited across six countries in the IBD Character initiative (newly diagnosed patients with Crohn's disease [CD; n = 156], ulcerative colitis [UC; n = 167], and controls [n = 267]), exploring differential expression [DESeq2], co-expression networks [WGCNA], and transcription factor involvement [EPEE, ChEA, DoRothEA]. Findings were validated by analysis of an independent replication cohort [99 CD, 100 UC, 95 controls]. In the discovery cohort, we also defined baseline expression correlates of future treatment escalation using cross-validated elastic-net and random forest modelling, along with a pragmatic ratio detection procedure.

RESULTS

Disease-specific transcriptomes were defined in IBD [8697 transcripts], CD [7152], and UC [8521], with the most highly significant changes in single genes, including CD177 (log2-fold change [LFC] = 4.63, p = 4.05 × 10-118), MCEMP1 [LFC = 2.45, p = 7.37 × 10-109], and S100A12 [LFC = 2.31, p = 2.15 × 10-93]. Significantly over-represented pathways included IL-1 [p = 1.58 × 10-11], IL-4, and IL-13 [p = 8.96 × 10-9]. Highly concordant results were obtained using multiple regulatory activity inference tools applied to the discovery and replication cohorts. These analyses demonstrated central roles in IBD for the transcription factors NFE2, SPI1 [PU.1], CEBPB, and IRF2, all regulators of cytokine signalling, based on a consistent signal across cohorts and transcription factor ranking methods. A number of simple transcriptome-based models were associated with the need for treatment escalation, including the binary CLEC5A/CDH2 expression ratio in UC (hazard ratio = 23.4, 95% confidence interval [CI] 5.3-102.0).

CONCLUSIONS

Transcriptomic analysis has allowed for a detailed characterisation of IBD pathobiology, with important potential translational implications.

CD45RA+CD62L- ILCs in human tissues represent a quiescent local reservoir for the generation of differentiated ILCs

Innate lymphoid cells (ILCs) are highly plastic and predominantly mucosal tissue-resident cells that contribute to both homeostasis and inflammation depending on the microenvironment. The discovery of naïve-like ILCs suggests an ILC differentiation process that is akin to naïve T cell differentiation. Delineating the mechanisms that underlie ILC differentiation in tissues is crucial for understanding ILC biology in health and disease. Here, we showed that tonsillar ILCs expressing CD45RA lacked proliferative activity, indicative of cellular quiescence. CD62L distinguished two subsets of CD45RA⁺ ILCs. CD45RA⁺CD62L⁺ ILCs (CD62L⁺ ILCs) resembled circulating naïve ILCs because they lacked the transcriptional, metabolic, epigenetic, and cytokine production signatures of differentiated ILCs. CD45RA⁺CD62L^- ILCs (CD62L^- ILCs) were epigenetically similar to CD62L⁺ ILCs but showed a transcriptional, metabolic, and cytokine production signature that was more akin to differentiated ILCs. CD62L⁺ and CD62L^- ILCs contained uni- and multipotent precursors of ILC1s/NK cells and ILC3s. Differentiation of CD62L⁺ and CD62L^- ILCs led to metabolic reprogramming including up-regulation of genes associated with glycolysis, which was needed for their effector functions after differentiation. CD62L^- ILCs with preferential differentiation capacity toward IL-22-producing ILC3s accumulated in the inflamed mucosa of patients with inflammatory bowel disease. These data suggested distinct differentiation potential of CD62L⁺ and CD62L^- ILCs between tissue microenvironments and identified that manipulation of these cells is a possible approach to restore tissue-immune homeostasis.

Mucosal Gene Transcript Signatures in Treatment Naïve Inflammatory Bowel Disease: A Comparative Analysis of Disease to Symptomatic and Healthy Controls in the European IBD-Character Cohort

Background

Studies of the mucosal transcriptomic landscape have given new insight into the pathogenesis of inflammatory bowel disease (IBD). Recently, the predictive biomarker potential of gene expression signatures has been explored. To further investigate the mucosal gene expression in IBD, we recruited a cohort of treatment naïve patients and compared them to both symptomatic and healthy controls.

Methods

Altogether, 323 subjects were included: Crohn’s disease (N = 75), ulcerative colitis (N = 87) and IBD unclassified (N = 3). Additionally, there were two control groups: symptomatic controls (N = 131) and healthy controls (N = 27). Mucosal biopsies were collected during ileocolonoscopy and gene expression in inflamed and non-inflamed mucosa was explored. Gene expression profiling was performed using Agilent G3 Human Gene Expression 860K v3 One-Color microarray. We recorded information about treatment escalation to anti-TNF agents or surgery, and anti-TNF response, to explore predictive opportunities of the mucosal transcriptome.

Results

Gene expression profiles in symptomatic controls in whom IBD had been excluded resembled that of IBD patients and diverged from that of healthy controls. In non-inflamed Crohn’s disease and ulcerative colitis, gene set enrichment analysis revealed dysregulation of pathways involved in basic cellular biological processes. Mitochondria-associated pathways were dysregulated both in non-inflamed and inflamed Crohn’s disease and ulcerative colitis (>2.6 normalized enrichment scores <−1.8). Gene expression signatures of Crohn’s disease and ulcerative colitis did not predict time for treatment escalation (p = 0.175). No significant association was found between gene expression signatures and anti-TNF response.

Conclusion

Non-inflamed samples are probably superior to inflamed samples when exploring gene expression signatures in IBD and might reveal underlying mechanisms central for disease initiation. The gene expression signatures of the control groups were related to if they were symptomatic or not, which may have important implications for future study designs.

Altered interaction between enteric glial cells and mast cells in the colon of women with irritable bowel syndrome

BACKGROUND

Enteric glial cells (EGC) and mast cells (MC) are intimately associated with gastrointestinal physiological functions. We aimed to investigate EGC-MC interaction in irritable bowel syndrome (IBS), a gut-brain disorder linked to increased intestinal permeability, and MC.

METHODS

Parallel approaches were used to quantify EGC markers in colonic biopsies from healthy controls (HC) and patients with IBS. Data were correlated with MC, vasoactive intestinal polypeptide (VIP) and VIP receptors (VPAC1/VPAC2) expressions, and bacterial translocation through biopsies mounted in Ussing chambers. In addition, we investigated the effects of EGC mediators on colonic permeability and the pharmacological-induced responses of EGC and MC cell lines.

KEY RESULTS

Immunofluorescence of IBS colonic mucosa, as well as Western blotting and ELISA of IBS biopsy lysates, revealed increased glial fibrillary intermediate filament (GFAP) expression, indicating EGC activation. Mucosal GFAP correlated with increased MC and VPAC1⁺ MC numbers and decreased VIP⁺ MC, which seemed to control bacterial translocation in HC. In the contrary, EGC activation in IBS correlated with less MC and VPAC1⁺ MC numbers, and more VIP⁺ MC. In vitro, MC and EGC cell lines showed intracellular calcium responses to each other's mediators. Furthermore, EGC mediators prevented VIP-induced MC degranulation, while MC mediators induced a reactive EGC phenotype. In Ussing chambers, EGC mediators decreased paracellular passage through healthy colonic biopsies.

CONCLUSIONS & INFERENCES

Findings suggest the involvement of EGC and MC in the control of barrier function in the human colon and indicate a potential EGC-MC interaction that seems altered in IBS, with detrimental consequences to colonic permeability. Altogether, results suggest that imbalanced EGC-MC communication contributes to the pathophysiology of IBS.

Systemic Inflammation in Preclinical Ulcerative Colitis

BACKGROUND & AIMS

Preclinical ulcerative colitis is poorly defined. We aimed to characterize the preclinical systemic inflammation in ulcerative colitis, using a comprehensive set of proteins.

METHODS

We obtained plasma samples biobanked from individuals who developed ulcerative colitis later in life (n = 72) and matched healthy controls (n = 140) within a population-based screening cohort. We measured 92 proteins related to inflammation using a proximity extension assay. The biologic relevance of these findings was validated in an inception cohort of patients with ulcerative colitis (n = 101) and healthy controls (n = 50). To examine the influence of genetic and environmental factors on these markers, a cohort of healthy twin siblings of patients with ulcerative colitis (n = 41) and matched healthy controls (n = 37) were explored.

RESULTS

Six proteins (MMP10, CXCL9, CCL11, SLAMF1, CXCL11 and MCP-1) were up-regulated (P < .05) in preclinical ulcerative colitis compared with controls based on both univariate and multivariable models. Ingenuity Pathway Analyses identified several potential key regulators, including interleukin-1β, tumor necrosis factor, interferon-gamma, oncostatin M, nuclear factor-κB, interleukin-6, and interleukin-4. For validation, we built a multivariable model to predict disease in the inception cohort. The model discriminated treatment-naïve patients with ulcerative colitis from controls with leave-one-out cross-validation (area under the curve = 0.92). Consistently, MMP10, CXCL9, CXCL11, and MCP-1, but not CCL11 and SLAMF1, were significantly up-regulated among the healthy twin siblings, even though their relative abundances seemed higher in incident ulcerative colitis.

CONCLUSIONS

A set of inflammatory proteins are up-regulated several years before a diagnosis of ulcerative colitis. These proteins were highly predictive of an ulcerative colitis diagnosis, and some seemed to be up-regulated already at exposure to genetic and environmental risk factors.

A biliary immune landscape map of primary sclerosing cholangitis reveals a dominant network of neutrophils and tissue-resident T cells

The human biliary system, a mucosal barrier tissue connecting the liver and intestine, is an organ often affected by serious inflammatory and malignant diseases. Although these diseases are linked to immunological processes, the biliary system represents an unexplored immunological niche. By combining endoscopy-guided sampling of the biliary tree with a high-dimensional analysis approach, comprehensive mapping of the human biliary immunological landscape in patients with primary sclerosing cholangitis (PSC), a severe biliary inflammatory disease, was conducted. Major differences in immune cell composition in bile ducts compared to blood were revealed. Furthermore, biliary inflammation in patients with PSC was characterized by high presence of neutrophils and T cells as compared to control individuals without PSC. The biliary T cells displayed a CD103⁺CD69⁺ effector memory phenotype, a combined gut and liver homing profile, and produced interleukin-17 (IL-17) and IL-22. Biliary neutrophil infiltration in PSC associated with CXCL8, possibly produced by resident T cells, and CXCL16 was linked to the enrichment of T cells. This study uncovers the immunological niche of human bile ducts, defines a local immune network between neutrophils and biliary-resident T cells in PSC, and provides a resource for future studies of the immune responses in biliary disorders.

Elevated F-EDN correlates with mucosal eosinophil degranulation in patients with IBS-A possible association with microbiota?

Eosinophils have been linked to functional dyspepsia; however, less is known about their role in irritable bowel syndrome (IBS). This study tested the hypothesis of alterations in levels of fecal eosinophil-derived neurotoxin (F-EDN) and eosinophil density and degranulation within the colonic mucosa of IBS patients compared with healthy controls (HC). Colonic biopsies were collected from 37 IBS patients and 20 HC and analyzed for eosinophil numbers and local degranulation of eosinophil cationic protein (ECP) by histologic procedures. Fecal samples were collected for F-EDN and microbiota analysis. Differentiated 15HL-60 cells were used in vitro to investigate the direct effect of live bacteria on eosinophil activation measured by a colorimetric assay with o-phenylenediamine (OPD) substrate. We observed a higher number of eosinophils and increased extracellular ECP in the mucosa of IBS patients compared with HC. Moreover, F-EDN levels in IBS samples were elevated compared with HC and positively correlated to extracellular ECP. Metagenomic analysis showed significant correlations between bacterial composition and eosinophil measurements in both HC and IBS patients. In vitro experiments revealed an increased degranulation of 15HL-60 after stimulation with Salmonella typhimurium, Salmonella enterica, and Yersinia enterocolitica. To conclude, we could demonstrate alterations related to eosinophils in IBS, and, for the first time, a positive correlation between F-EDN levels and degranulated eosinophils in the colonic mucosa of IBS patients. Together our results suggest that eosinophils play a role in the pathophysiology of IBS and the mechanisms might be linked to an altered microbiota.

Effects of analgesic and surgical modality on immune response in colorectal cancer surgery

BACKGROUND AND OBJECTIVE

Different surgical methods, anesthesia, and analgesia are known to modify the surgical stress response, especially in patients with malignancy. We compared the impact of patient-controlled intravenous (PCA) versus epidural analgesia (EDA) on tumor-related mucosal immune response in patients undergoing open or laparoscopic surgery for colorectal cancer.

METHODS

In a University Hospital subgroup (n = 43) of a larger cohort (n = 235) of patients undergoing open or laparoscopic surgery for colorectal carcinoma randomized to PCA or EDA, colorectal tissues were stained for interleukin-10 (IL-10), tumor necrosis factor (TNF), and mast cell tryptase and then examined by immunofluorescence microscopy.

RESULTS

More IL-10⁺-cells were found in patients undergoing open compared to laparoscopic surgery in the PCA (P < 0.05) and EDA group (P < 0.0005), respectively, and numbers of TNF⁺-cells were higher in the open surgery group who received PCA (P < 0.05). No differences in IL-10 or TNF expressions were detected between EDA/PCA within the open or laparoscopic surgery groups, respectively. Fewer mast cells were observed in patients undergoing laparoscopic compared to open surgery combined with PCA (P < 0.05). Within the open surgery group, EDA resulted in fewer mucosal mast cells compared to the PCA group (P < 0.05).

CONCLUSIONS

The surgical method, rather than type of analgesia, may have higher impact on peri-operative inflammation. Laparoscopic surgery when combined with EDA for colorectal cancer caused a decrease in the TNF and IL-10 expression and mast cells. EDA seems to have an anti-inflammatory effect on cancer-related inflammation during open surgery.

Colonic paracellular permeability and circulating zonulin-related proteins

OBJECTIVE

Irritable bowel syndrome (IBS) is a gut-brain disorder associated with increased gut permeability. Zonulin has been suggested to regulate the gut barrier and claimed to be pre-haptoglobin 2 (pre-HP2) and circulating zonulin is often used as a proxy for gastrointestinal permeability. This study investigated the correlation between colonic paracellular permeability and levels of circulating zonulin and pre-HP2.

MATERIALS AND METHODS

Colonic biopsies from 32 patients with IBS and 15 healthy controls (HC) were used to measure permeability in Ussing chambers and levels of zonulin (Cusabio ELISA). Zonulin was also measured in blood samples from 40 HC, 78 patients with IBS and 20 patients with celiac disease (CeD), before and after a gluten-free diet. In addition, we verified HP genotype and circulating pre-HP2 using a monoclonal pre-HP2 antibody (Bio-Rad) by ELISA.

RESULTS

Increased colonic paracellular permeability correlated positively with zonulin levels in IBS biopsies, but negatively with plasma zonulin. We found no agreement between circulating zonulin and pre-HP2. Genotyping revealed non-specificity of the zonulin kit, as all pre-HP2 non-producers presented detectable levels. Patients with CeD displayed higher pre-HP2 and zonulin levels compared to HC. A gluten-free diet in patients with CeD led to lower serum zonulin and pre-HP2 concentrations.

CONCLUSIONS

Our study suggests that neither circulating zonulin nor pre-HP2 mirror colonic permeability. Our data corroborate previous reports showing the inability of the Cusabio zonulin kit to target zonulin and highlights that the results of studies using this kit must be re-examined with caution.

Prognostic significance of interleukin-17A-producing colorectal tumour antigen-specific T cells

BACKGROUND

The T cell cytokine profile is a key prognostic indicator of post-surgical outcome for colorectal cancer (CRC). Whilst TH1 (IFN-γ+) cell-mediated responses generated in CRC are well documented and are associated with improved survival, antigen-specific TH17 (IL-17A+) responses have not been similarly measured.

METHODS

We sought to determine the cytokine profile of circulating tumour antigen-(5T4/CEA) specific T cells of 34 CRC patients to address whether antigen-specific IL-17A responses were detectable and whether these were distinct to IFN-γ responses.

RESULTS

As with IFN-γ-producing T cells, anti-5T4/CEA TH17 responses were detectable predominantly in early stage (TNM I/II) CRC patients. Moreover, whilst IL-17A was always produced in association with IFN-γ, this release was mainly from two distinct T cell populations rather than by 'dual producing' T cells. Patients mounting both tumour-specific TH1+/TH17+ responses exhibited prolonged relapse-free survival.

CONCLUSIONS

Tumour antigen-specific TH17 responses play a beneficial role in preventing post-operative colorectal tumour recurrence.

Fatigue in irritable bowel syndrome is associated with plasma levels of TNF-α and mesocorticolimbic connectivity

Irritable bowel syndrome (IBS) is a symptom-based disorder of gut-brain interactions generating abdominal pain. It is also associated with a vulnerability to develop extraintestinal symptoms, with fatigue often reported as one of the most disturbing. Fatigue is related to brain function and inflammation in several disorders, however, the mechanisms of such relations in IBS remain elusive. This study aimed to elucidate fatigue and its association with a resting state network of mesocorticolimbic regions of known importance in fatigue, and to explore the possible role of circulating TNF-α levels in IBS and healthy controls (HC). Resting state functional magnetic resonance imaging (fMRI) was conducted in 88 IBS patients and 47 HC of similar age and gender to investigate functional connectivity between mesocorticolimbic regions. Further, fatigue impact on daily life and plasma levels of the proinflammatory cytokine tumor necrosis factor-α (TNF-α), of known relevance to immune activation in IBS, were also measured. The selected mesocorticolimbic regions indeed formed a functionally connected network in all participants. The nucleus accumbens (NAc), in particular, exhibited functional connectivity to all other regions of interest. In IBS, fatigue impact on daily life was negatively correlated with the connectivity between NAc and dorsolateral prefrontal cortex bilaterally (left p = 0.019; right p = 0.038, corrected for multiple comparisons), while in HC, fatigue impact on daily life was positively correlated to the connectivity between the right NAc and anterior middle insula in both hemispheres (left p = 0.009; right p = 0.011). We found significantly higher levels of TNF-α in IBS patients compared to HC (p = 0.001) as well as a positive correlation between TNF-α and fatigue impact on daily life in IBS patients (rho = 0.25, p = 0.02) but not in HC (rho = -0.13, p = 0.37). There was no association between functional connectivity in the mesocorticolimbic network and plasma levels of TNF-α in either group In summary, this novel multimodal study provides the first evidence that the vulnerability to fatigue in IBS is associated with connectivity within a mesocorticolimbic network as well as immune activation. These findings warrant further investigation, both peripherally and potentially with measurements of central immune activation as well.

Antagonism of Adherent Invasive E. coli LF82 With Human α-defensin 5 in the Follicle-associated Epithelium of Patients With Ileal Crohn's Disease

BACKGROUND

The first visible signs of Crohn's disease (CD) are microscopic erosions over the follicle-associated epithelium (FAE). The aim of the study was to investigate the effects of human α-defensin 5 (HD5) on adherent-invasive Escherichia coli LF82 translocation and HD5 secretion after LF82 exposure in an in vitro model of human FAE and in human FAE ex vivo.

METHODS

An in vitro FAE-model was set up by the coculture of Raji B cells and Caco-2-cl1 cells. Ileal FAE from patients with CD and controls were mounted in Ussing chambers. The effect of HD5 on LF82 translocation was studied by LF82 exposure to the cells or tissues with or without incubation with HD5. The HD5 secretion was measured in human FAE exposed to LF82 or Salmonella typhimurium. The HD5 levels were evaluated by immunofluorescence, immunoblotting, and ELISA.

RESULTS

There was an increased LF82 translocation across the FAE-model compared with Caco-2-cl1 (P < 0.05). Incubation of cell/tissues with HD5 before LF82 exposure reduced bacterial passage in both models. Human FAE showed increased LF82 translocation in CD compared with controls and attenuated passage after incubation with sublethal HD5 in both CD and controls (P < 0.05). LF82 exposure resulted in a lower HD5 secretion in CD FAE compared with controls (P < 0.05), whereas Salmonella exposure caused equal secretion on CD and controls. There were significantly lower HD5 levels in CD tissues compared with controls.

CONCLUSIONS

Sublethal HD5 reduces the ability of LF82 to translocate through FAE. The HD5 is secreted less in CD in response to LF82, despite a normal response to Salmonella. This further implicates the integrated role of antimicrobial factors and barrier function in CD pathogenesis.

Crohn's Disease Pathobiont Adherent-Invasive E coli Disrupts Epithelial Mitochondrial Networks With Implications for Gut Permeability

BACKGROUND & AIMS

Adherent-invasive Escherichia coli are implicated in inflammatory bowel disease, and mitochondrial dysfunction has been observed in biopsy specimens from patients with inflammatory bowel disease. As a novel aspect of adherent-invasive E coli-epithelial interaction, we hypothesized that E coli (strain LF82) would elicit substantial disruption of epithelial mitochondrial form and function.

METHODS

Monolayers of human colon-derived epithelial cell lines were exposed to E coli-LF82 or commensal E coli and RNA sequence analysis, mitochondrial function (adenosine triphosphate synthesis) and dynamics (mitochondrial network imaging, immunoblotting for fission and fusion proteins), and epithelial permeability (transepithelial resistance, flux of fluorescein isothiocyanate-dextran and bacteria) were assessed.

RESULTS

E coli-LF82 significantly affected epithelial expression of ∼8600 genes, many relating to mitochondrial function. E coli-LF82-infected epithelia showed swollen mitochondria, reduced mitochondrial membrane potential and adenosine triphosphate, and fragmentation of the mitochondrial network: events not observed with dead E coli-LF82, medium from bacterial cultures, or control E coli. Treatment with Mitochondrial Division Inhibitor 1 (Mdivi1, inhibits dynamin-related peptide 1, guanosine triphosphatase principally responsible for mitochondrial fission) or P110 (prevents dynamin-related peptide 1 binding to mitochondrial fission 1 protein) partially reduced E coli-LF82-induced mitochondrial fragmentation in the short term. E coli-LF82-infected epithelia showed loss of the long isoform of optic atrophy factor 1, which mediates mitochondrial fusion. Mitochondrial Division Inhibitor 1 reduced the magnitude of E coli-LF82-induced increased transepithelial flux of fluorescein isothiocyanate dextran. By 8 hours after infection, increased cytosolic cytochrome C and DNA fragmentation were apparent without evidence of caspase-3 or apoptosis inducing factor activation.

CONCLUSIONS

Epithelial mitochondrial fragmentation caused by E coli-LF82 could be targeted to maintain cellular homeostasis and mitigate infection-induced loss of epithelial barrier function. Data have been deposited in NCBI's Gene Expression Omnibus and are accessible through GEO series accession numbers GSE154121 and GSE154122 (https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE154121).

Complement opsonization of HIV affects primary infection of human colorectal mucosa and subsequent activation of T cells

HIV transmission via genital and colorectal mucosa are the most common routes of dissemination. Here, we explored the effects of free and complement-opsonized HIV on colorectal tissue. Initially, there was higher antiviral responses in the free HIV compared to complement-opsonized virus. The mucosal transcriptional response at 24 hr revealed the involvement of activated T cells, which was mirrored in cellular responses observed at 96 hr in isolated mucosal T cells. Further, HIV exposure led to skewing of T cell phenotypes predominantly to inflammatory CD4+ T cells, that is Th17 and Th1Th17 subsets. Of note, HIV exposure created an environment that altered the CD8+ T cell phenotype, for example expression of regulatory factors, especially when the virions were opsonized with complement factors. Our findings suggest that HIV-opsonization alters the activation and signaling pathways in the colorectal mucosa, which promotes viral establishment by creating an environment that stimulates mucosal T cell activation and inflammatory Th cells.

Increased Colonic Epithelial Permeability and Mucosal Eosinophilia in Ulcerative Colitis in Remission Compared With Irritable Bowel Syndrome and Health

BACKGROUND

Barrier dysfunction is recognized as a pathogenic factor in ulcerative colitis (UC) and irritable bowel syndrome (IBS), but it is unclear to what extent the factors related to barrier dysfunction are disease-specific. The aim of this study was to compare these aspects in UC patients in remission, IBS patients, and healthy controls (HCs).

METHODS

Colonic biopsies were collected from 13 patients with UC in remission, 15 patients with IBS-mixed, and 15 HCs. Ulcerative colitis patients had recently been treated for relapse, and biopsies were taken from earlier inflamed areas. Biopsies were mounted in Ussing chambers for measurements of intestinal paracellular permeability to 51chromium (Cr)-ethylenediaminetetraacetic acid (EDTA). In addition, biopsies were analyzed for mast cells and eosinophils by histological procedures, and plasma tumor necrosis factor (TNF)-α was assessed by ELISA.

RESULTS

Ussing chamber experiments revealed an increased 51Cr-EDTA permeability in UC and IBS (P < 0.05). The 51Cr-EDTA permeability was higher in UC compared with IBS (P < 0.005). There were increased numbers of mucosal mast cells and eosinophils in UC and IBS and more eosinophils in UC compared with IBS (P < 0.05). Also, increased extracellular granule content was found in UC compared with HCs (P < 0.05). The 51Cr-EDTA permeability correlated significantly with eosinophils in all groups. Plasma TNF-α concentration was higher in UC compared with IBS and HCs (P < 0.0005).

CONCLUSIONS

Results indicate a more permeable intestinal epithelium in inactive UC and IBS compared with HCs. Ulcerative colitis patients, even during remission, demonstrate a leakier barrier compared with IBS. Both eosinophil numbers and activation state might be involved in the increased barrier function seen in UC patients in remission.

Image-Based Cell Profiling Enables Quantitative Tissue Microscopy in Gastroenterology

Immunofluorescence microscopy is an essential tool for tissue-based research, yet data reporting is almost always qualitative. Quantification of images, at the per-cell level, enables "flow cytometry-type" analyses with intact locational data but achieving this is complex. Gastrointestinal tissue, for example, is highly diverse: from mixed-cell epithelial layers through to discrete lymphoid patches. Moreover, different species (e.g., rat, mouse, and humans) and tissue preparations (paraffin/frozen) are all commonly studied. Here, using field-relevant examples, we develop open, user-friendly methodology that can encompass these variables to provide quantitative tissue microscopy for the field. Antibody-independent cell labeling approaches, compatible across preparation types and species, were optimized. Per-cell data were extracted from routine confocal micrographs, with semantic machine learning employed to tackle densely packed lymphoid tissues. Data analysis was achieved by flow cytometry-type analyses alongside visualization and statistical definition of cell locations, interactions and established microenvironments. First, quantification of Escherichia coli passage into human small bowel tissue, following Ussing chamber incubations exemplified objective quantification of rare events in the context of lumen-tissue crosstalk. Second, in rat jejenum, precise histological context revealed distinct populations of intraepithelial lymphocytes between and directly below enterocytes enabling quantification in context of total epithelial cell numbers. Finally, mouse mononuclear phagocyte-T cell interactions, cell expression and significant spatial cell congregations were mapped to shed light on cell-cell communication in lymphoid Peyer's patch. Accessible, quantitative tissue microscopy provides a new window-of-insight to diverse questions in gastroenterology. It can also help combat some of the data reproducibility crisis associated with antibody technologies and over-reliance on qualitative microscopy. © 2020 The Authors. Cytometry Part A published by Wiley Periodicals LLC. on behalf of International Society for Advancement of Cytometry.

Relationship between bile salts, bacterial translocation, and duodenal mucosal integrity in functional dyspepsia

BACKGROUND

Functional dyspepsia (FD) is a complex disorder, in which multiple mechanisms underlie symptom generation, including impaired duodenal barrier function. Moreover, an altered duodenal bile salt pool was recently discovered in patients with FD. We aimed to evaluate the relationship between bile salts, bacterial translocation, and duodenal mucosal permeability in FD.

METHODS

Duodenal biopsies from patients with FD and healthy volunteers (HV) were mounted in Ussing chambers to measure mucosal resistance and bacterial passage in the absence and presence of fluorescein-conjugated Escherichia coli and glyco-ursodeoxycholic acid (GUDCA) exposure. In parallel, duodenal fluid aspirates were collected from patients and bile salts were analyzed.

KEY RESULTS

The transepithelial electrical resistance of duodenal biopsies from patients was lower compared with HV (21.4 ± 1.3 Ω.cm² vs. 24.4 ± 1.2 Ω.cm² ; P = .02; N = 21). The ratio of glyco-cholic and glyco-chenodeoxycholic acid (GCDCA) to tauro- and GUDCA correlated positively with transepithelial electrical resistance in patients. Glyco-ursodeoxycholic acid slightly altered the mucosal resistance, resulting in similar values between patient and healthy biopsies (22.1 ± 1.0 Ω.cm² vs. 23.0 ± 1.0 Ω.cm² ; P = .5). Bacterial passage after 120 minutes was lower for patient than for healthy biopsies (0.0 [0.0-681.8] vs. 1684.0 [0.0-4773.0] E coli units; P = .02). Glyco-ursodeoxycholic acid increased bacterial passage in patient biopsies (102.1 [0.0-733.0] vs. 638.9 [280.6-2124.0] E coli units; P = .009). No correlation was found between mucosal resistance and bacterial passage.

CONCLUSIONS & INFERENCES

Patients with FD displayed decreased duodenal mucosal resistance associated with bile salts, however, not associated with bacterial passage in vitro. In addition, the hydrophilic bile salt glyco-ursodeoxycholic acid abolished differences in mucosal resistance and bacterial passage between patient and control group.

Potential neuro-immune therapeutic targets in irritable bowel syndrome

Irritable bowel syndrome (IBS) is a functional gastrointestinal (GI) disorder characterized by recurring abdominal pain and disturbed bowel habits. The aetiology of IBS is unknown but there is evidence that genetic, environmental and immunological factors together contribute to the development of the disease. Current treatment of IBS includes lifestyle and dietary interventions, laxatives or antimotility drugs, probiotics, antispasmodics and antidepressant medication. The gut-brain axis comprises the central nervous system, the hypothalamic pituitary axis, the autonomic nervous system and the enteric nervous system. Within the intestinal mucosa there are close connections between immune cells and nerve fibres of the enteric nervous system, and signalling between, for example, mast cells and nerves has shown to be of great importance during GI disorders such as IBS. Communication between the gut and the brain is most importantly routed via the vagus nerve, where signals are transmitted by neuropeptides. It is evident that IBS is a disease of a gut-brain axis dysregulation, involving altered signalling between immune cells and neurotransmitters. In this review, we analyse the most novel and distinct neuro-immune interactions within the IBS mucosa in association with already existing and potential therapeutic targets.

Enhanced E. coli LF82 Translocation through the Follicle-associated Epithelium in Crohn's Disease is Dependent on Long Polar Fimbriae and CEACAM6 expression, and Increases Paracellular Permeability

BACKGROUND AND AIMS

Patients with Crohn's disease [CD] harbour an increased number of adherent-invasive E. coli [AIEC]. The strain LF82, identified in the ileal mucosa of CD patients, has been extensively studied for pathogenic mechanisms. However, understanding of the interaction of LF82 with the intestinal mucosa of CD patients is lacking.

METHODS

Here, we investigated the importance of long polar fimbriae [LPF] type 1 pili and the carcinoembryonic antigen-related cell-adhesion molecule 6 [CEACAM6] for translocation of LF82 in an in vitro model of follicle-associated epithelium [FAE], and in the FAE and villus epithelium [VE] of patients with CD and controls, using Ussing chambers.

RESULTS

Significantly greater LF82 passage occurred in the FAE model compared with in the VE Caco-2cl1 mono-culture. Moreover, bacterial translocation was inhibited by either LPF disruption or pre-incubation with anti-CEACAM6 antibody. Tissue mounted in Ussing chambers showed significantly higher LF82 passage in FAE from patients with CD compared with control FAE, that was diminished in LF82 lacking LPF and by blocking host CEACAM6. Interestingly, addition of LF82 to the CD FAE tissues significantly increased paracellular permeability [of 51Chromium-EDTA] compared with baseline, and the increase was inhibited by anti-CEACAM6. Immunofluorescence and immunoblots showed higher expression of CEACAM6 in FAE of patients with CD compared with in FAE from controls.

CONCLUSIONS

These data suggest that the FAE of CD patients is a site of vulnerability for invasion by LF82 via a mechanism that requires both bacterial LPF and host CEACAM6. Further, LF82 has the ability to increase paracellular passage through the FAE of patients with CD. These data can help define novel therapeutic targets in CD for the prevention of clinical recurrence.

Possible Involvement of Intracellular Calcium-Independent Phospholipase A2 in the Release of Secretory Phospholipases from Mast Cells-Increased Expression in Ileal Mast Cells of Crohn's Disease

Increased activity of secretory phospholipases A₂ (sPLA₂) type-II was previously observed in ileum of Crohn’s disease (CD). Our aims were to explore the involvement of calcium-independent (i)PLA₂β in the release of sPLA₂s from the human mast cell (MC) line (HMC-1) and investigate expressions of cytosolic (c)PLA₂α, iPLA₂β, sPLA₂-IIA and sPLA₂-V in MCs of CD ileum. The release of sPLA₂ was investigated in HMC-1 by immunocytochemistry and ELISA. The expression intensities of PLA₂s in mucosal MCs, and the proportion of PLA₂-positive MCs, were investigated in normal ileum and in ileum from patients with CD by immunohistochemistry. The calcium ionophore-stimulated release of sPLA₂-IIA and sPLA₂-V from HMC-1 was reduced by the iPLA₂-inhibitor bromoenol lactone. All four PLA₂s were detectable in mucosal MCs, both in normal ileum and in CD, but the proportion of iPLA₂β-containing mucosal MCs and the expression intensity of sPLA₂-IIA was increased in CD. Results indicate that iPLA₂β is involved in the secretion of sPLA₂s from HMC-1, and suggest that iPLA₂β-mediated release of sPLA₂ from intestinal MCs may contribute to CD pathophysiology. Ex vivo studies on isolated mucosal mast cells are however needed to clarify the precise role of MC PLA₂s in the inflammatory processes of CD.

The Ussing chamber system for measuring intestinal permeability in health and disease

BACKGROUND

The relationship between intestinal epithelial integrity and the development of intestinal disease is of increasing interest. A reduction in mucosal integrity has been associated with ulcerative colitis, Crohn's disease and potentially could have links with colorectal cancer development. The Ussing chamber system can be utilised as a valuable tool for measuring gut integrity. Here we describe step-by-step methodology required to measure intestinal permeability of both mouse and human colonic tissue samples ex vivo, using the latest equipment and software. This system can be modified to accommodate other tissues.

METHODS

An Ussing chamber was constructed and adapted to support both mouse and human tissue to measure intestinal permeability, using paracellular flux and electrical measurements. Two mouse models of intestinal inflammation (dextran sodium sulphate treatment and T regulatory cell depletion using C57BL/6-FoxP3DTR mice) were used to validate the system along with human colonic biopsy samples.

RESULTS

Distinct regional differences in permeability were consistently identified within mouse and healthy human colon. In particular, mice showed increased permeability in the mid colonic region. In humans the left colon is more permeable than the right. Furthermore, inflammatory conditions induced chemically or due to autoimmunity reduced intestinal integrity, validating the use of the system.

CONCLUSIONS

The Ussing chamber has been used for many years to measure barrier function. However, a clear and informative methods paper describing the setup of modern equipment and step-by-step procedure to measure mouse and human intestinal permeability isn't available. The Ussing chamber system methodology we describe provides such detail to guide investigation of gut integrity.

Upregulation of intestinal mucosal mast cells expressing VPAC1 in close proximity to vasoactive intestinal polypeptide in inflammatory bowel disease and murine colitis

BACKGROUND

Mast cells (MCs) and vasoactive intestinal polypeptide (VIP) have been proposed as regulators of the intestinal barrier and inflammation. Our aim was to map the distribution in inflammatory bowel disease (IBD) and murine colitis.

METHODS

MCs, VIP, and VIP-receptors (VPACs) were quantified by immunofluorescence and enzyme-immunoassay (EIA) in ileal tissues (villus epithelium (VE) and adjacent VE, ie, VE next to the follicle-associated epithelium, (FAE)) from Crohn's disease (CD; n = 16) and non-IBD patients, and in colonic specimens of ulcerative colitis (UC; n = 12) and healthy controls (HCs). In addition, VIP levels were measured in plasma from HCs, non-IBD, and IBD in remission (CD n = 30; UC n = 30). Colon, ileum, and plasma from mice with dextran sulfate sodium (DSS)-induced colitis and control mice were analyzed likewise.

KEY RESULTS

FAE-adjacent VE in ileum of CD possessed more MCs (P < 0.05) and MCs expressing VPAC1 (P < 0.05), but not VPAC2, compared to controls. Both adjacent and regular VE of CD had more MCs co-localizing/in close proximity to VIP (P < 0.05). In UC colon, more MCs (P < 0.0005), MCs close to VIP (P < 0.0005), and MCs expressing VPAC1 (P < 0.05) were found compared to controls. VIP levels were elevated in plasma from CD and UC compared to controls (P < 0.0005). Colon of DSS mice showed more MCs and MCs close to VIP (P < 0.05) compared to control mice. In vitro experiments revealed MCs expressing VPACs and internalized VIP after 120 minutes of VIP-stimulation.

CONCLUSIONS AND INFERENCES

Communication between MCs and VIP is upregulated during IBD and mice colitis. In CD patients, the epithelium next to FAE seems to be more involved than the surrounding VE, suggesting increased MC-VIP-interactions in this intestinal region.

Gut Barrier Dysfunction-A Primary Defect in Twins with Crohn's Disease Predominantly Caused by Genetic Predisposition

BACKGROUND AND AIMS

The aetiology of Crohn's disease is poorly understood. By investigating twin pairs discordant for Crohn's disease, we aimed to assess whether the dysregulated barrier represents a cause or a consequence of inflammation and to evaluate the impact of genetic predisposition on barrier function.

METHODS

Ileal biopsies from 15 twin pairs discordant for Crohn's disease [monozygotic n = 9, dizygotic n = 6] and 10 external controls were mounted in Ussing chambers to assess paracellular permeability to 51Chromium [Cr]-EDTA and trancellular passage to non-pathogenic E. coli K-12. Experiments were performed with and without provocation with acetylsalicylic acid. Immunofluorescence and ELISA were used to quantify the expression level of tight junction proteins.

RESULTS

Healthy co-twins and affected twins displayed increased 51Cr-EDTA permeability at 120 min, both with acetylsalicylic acid [p < 0.001] and without [p < 0.001] when compared with controls. A significant increase in 51Cr-EDTA flux was already seen at 20 min in healthy monozygotic co-twins compared with controls [p≤0.05] when stratified by zygosity, but not in healthy dizygotic co-twins. No difference in E. coli passage was observed between groups. Immunofluorescence of the tight junction proteins claudin-5 and tricellulin showed lower levels in healthy co-twins [p < 0.05] and affected twins [p < 0.05] compared with external controls, while ELISA only showed lower tricellulin in Crohn's disease twins [p < 0.05].

CONCLUSION

Our results suggest that barrier dysfunction is a primary defect in Crohn's disease, since changes were predominantly seen in healthy monozygotic co-twins. Passage of E. coli seems to be a consequence of inflammation, rather than representing a primary defect.

Differential effects of dietary fibres on colonic barrier function in elderly individuals with gastrointestinal symptoms

Gastrointestinal problems are common in elderly and often associated with psychological distress and increased levels of corticotrophin-releasing hormone, a hormone known to cause mast cell (MC) degranulation and perturbed intestinal barrier function. We investigated if dietary fibres (non-digestible polysaccharides [NPS]) could attenuate MC-induced colonic hyperpermeability in elderly with gastrointestinal (GI) symptoms. Colonic biopsies from elderly with diarrhoea and/or constipation (n = 18) and healthy controls (n = 19) were mounted in Ussing chambers and pre-stimulated with a yeast-derived beta (β)-glucan (0.5 mg/ml) or wheat-derived arabinoxylan (0.1 mg/ml) before the addition of the MC-degranulator Compound (C) 48/80 (10 ng/ml). Permeability markers were compared pre and post exposure to C48/80 in both groups and revealed higher baseline permeability in elderly with GI symptoms. β-glucan significantly attenuated C48/80-induced hyperpermeability in elderly with GI symptoms but not in healthy controls. Arabinoxylan reduced MC-induced paracellular and transcellular hyperpermeability across the colonic mucosa of healthy controls, but did only attenuate transcellular permeability in elderly with GI symptoms. Our novel findings indicate that NPS affect the intestinal barrier differently depending on the presence of GI symptoms and could be important in the treatment of moderate constipation and/or diarrhoea in elderly.

Infliximab restores colonic barrier to adherent-invasive E. coli in Crohn's disease via effects on epithelial lipid rafts

OBJECTIVE

Infliximab is important in the therapeutic arsenal of Crohn's disease (CD). However, its effect on mucosal barrier function is not fully understood. Adherent-invasive Escherichia coli (AIEC) are important in CD pathophysiology, but the transmucosal uptake routes are partly unknown. We investigated effects of infliximab on uptake of colon-specific AIEC HM427 across CD colonic mucosa.

MATERIALS AND METHODS

Endoscopic biopsies from non-inflamed colon of seven patients with CD, before and after two infliximab infusions, and eight non-inflammation controls, were mounted in Ussing chambers. Paracellular permeability (⁵¹Cr-EDTA) and transmucosal passage of GFP-expressing HM427 were studied. Mechanisms of HM427 transepithelial transport were investigated in Caco-2 monolayers treated with TNF, in the presence of infliximab and/or endocytosis inhibitors.

RESULTS

Before infliximab treatment, colonic passage of HM427 [CD: 2475 CFU (450-3000); controls 1163(225-1950)] and ⁵¹Cr-EDTA permeability were increased in CD (p < .05), but were restored to control levels by infliximab (CD: 150 (18.8-1069)). In TNF-exposed Caco-2 monolayers HM427 transport and lipid rafts/HM427 co-localization was decreased by infliximab. The lipid raft inhibitor methyl-β-cyclodextrin decreased HM427 transport.

CONCLUSION

Infliximab restored the colonic barrier to AIEC in CD; an effect partially mediated by blocking lipid rafts in epithelial cells. This ability likely contributes to infliximab's clinical efficacy in colonic CD.

Are self-reported gastrointestinal symptoms among older adults associated with increased intestinal permeability and psychological distress?

Background

Despite the substantial number of older adults suffering from gastrointestinal (GI) symptoms little is known regarding the character of these complaints and whether they are associated with an altered intestinal barrier function and psychological distress. Our aim was to explore the relationship between self-reported gut health, intestinal permeability and psychological distress among older adults.

Methods

Three study populations were included: 1) older adults with GI symptoms (n = 24), 2) a group of older adults representing the general elderly population in Sweden (n = 22) and 3) senior orienteering athletes as a potential model of healthy ageing (n = 27). Questionnaire data on gut-health, psychological distress and level of physical activity were collected. Intestinal permeability was measured by quantifying zonulin in plasma. The level of systemic and local inflammation was monitored by measuring C-reactive protein (CRP), hydrogen peroxide in plasma and calprotectin in stool samples. The relationship between biomarkers and questionnaire data in the different study populations was illustrated using a Principal Component Analysis (PCA).

Results

Older adults with GI symptoms displayed significantly higher levels of both zonulin and psychological distress than both general older adults and senior orienteering athletes. The PCA analysis revealed a separation between senior orienteering athletes and older adults with GI symptoms and showed an association between GI symptoms, psychological distress and zonulin.

Conclusions

Older adults with GI symptoms express increased plasma levels of zonulin, which might reflect an augmented intestinal permeability. In addition, this group suffer from higher psychological distress compared to general older adults and senior orienteering athletes. This relationship was further confirmed by a PCA plot, which illustrated an association between GI symptoms, psychological distress and intestinal permeability.

A Novel Topical PPARγ Agonist Induces PPARγ Activity in Ulcerative Colitis Mucosa and Prevents and Reverses Inflammation in Induced Colitis Models

BACKGROUND

Peroxisome proliferator-activated receptor-gamma (PPARγ) exerts anti-inflammatory effects and is therefore a potential target in ulcerative colitis (UC). A novel PPARγ agonist (AS002) developed for local action was evaluated ex vivo in biopsies from UC patients and in vivo in mice with low-grade dextran sodium sulfate (DSS)- and trinitrobenzene sulfonic acid (TNBS)-induced colitis.

METHODS

Colonic biopsies from UC patients (n = 18) and healthy controls (n = 6) were incubated with AS002 or rosiglitazone (positive control) to measure mRNA expression of the PPARγ-responsive gene ADIPOPHILIN and protein levels of UC-related cytokines (enzyme-linked immunosorbent assay). AS002 absorption was determined in the colonic mucosa of UC patients. DSS-colitis mice received PPARγ agonists or vehicle daily by intrarectal administration starting 2 days before induction of colitis (preventive) or from days 3 to 8 (curative). Myeloperoxidase (MPO) and cytokine levels in colonic mucosa were determined. In addition, AS002 effects were studied in TNBS colitis.

RESULTS

AS002 displayed an absorption pattern of a lipophilic drug totally metabolized in the mucosa. AS002 and rosiglitazone increased ADIPOPHILIN mRNA expression (3-fold) and decreased TNF-α, IL-1β, and IL-13 levels in human UC biopsies. In DSS, in both preventive and curative treatment and in TNBS colitis, AS002 protected against macroscopic and histological damage and lowered MPO and TNF-α, IL-1β, and IL-13 levels.

CONCLUSIONS

AS002 triggers anti-inflammatory PPARγ activity in the human colonic mucosa of UC patients and prevents and reverses colitis in mice. Our data suggest that AS002 has potential for topical maintenance treatment of UC, which warrants further studies in vivo in patients.

ER-stress mobilization of death-associated protein kinase-1-dependent xenophagy counteracts mitochondria stress-induced epithelial barrier dysfunction

The gut microbiome contributes to inflammatory bowel disease (IBD), in which bacteria can be present within the epithelium. Epithelial barrier function is decreased in IBD, and dysfunctional epithelial mitochondria and endoplasmic reticulum (ER) stress have been individually associated with IBD. We therefore hypothesized that the combination of ER and mitochondrial stresses significantly disrupt epithelial barrier function. Here, we treated human colonic biopsies, epithelial colonoids, and epithelial cells with an uncoupler of oxidative phosphorylation, dinitrophenol (DNP), with or without the ER stressor tunicamycin and assessed epithelial barrier function by monitoring internalization and translocation of commensal bacteria. We also examined barrier function and colitis in mice exposed to dextran sodium sulfate (DSS) or DNP and co-treated with DAPK6, an inhibitor of death-associated protein kinase 1 (DAPK1). Contrary to our hypothesis, induction of ER stress (i.e. the unfolded protein response) protected against decreased barrier function caused by the disruption of mitochondrial function. ER stress did not prevent DNP-driven uptake of bacteria; rather, specific mobilization of the ATF6 arm of ER stress and recruitment of DAPK1 resulted in enhanced autophagic killing (xenophagy) of bacteria. Of note, epithelia with a Crohn's disease-susceptibility mutation in the autophagy gene ATG16L1 exhibited less xenophagy. Systemic delivery of the DAPK1 inhibitor DAPK6 increased bacterial translocation in DSS- or DNP-treated mice. We conclude that promoting ER stress-ATF6-DAPK1 signaling in transporting enterocytes counters the transcellular passage of bacteria evoked by dysfunctional mitochondria, thereby reducing the potential for metabolic stress to reactivate or perpetuate inflammation.

The stimulation of GLP-1 secretion and delivery of GLP-1 agonists via nanostructured lipid carriers

Nanoparticulate based drug delivery systems have been extensively studied to efficiently encapsulate and deliver peptides orally. However, most of the existing data mainly focus on the nanoparticles as a drug carrier, but the ability of nanoparticles having a biological effect has not been exploited. Herein, we hypothesize that nanostructured lipid carriers (NLCs) could activate the endogenous glucagon-like peptide-1 (GLP-1) secretion and also act as oral delivery systems for GLP-1 analogs (exenatide and liraglutide). NLCs effectively encapsulated the peptides, the majority of which were only released under the intestinal conditions. NLCs, with and without peptide encapsulation, showed effective induction of GLP-1 secretion in vitro from the enteroendocrinal L-cells (GLUTag). NLCs also showed a 2.9-fold increase in the permeability of exenatide across the intestinal cell monolayer. The intestinal administration of the exenatide and liraglutide loaded NLCs did not demonstrate any glucose lowering effect on normal mice. Further, ex vivo studies depicted that the NLCs mainly adhered to the mucus layer. In conclusion, this study demonstrates that NLCs need further optimization to overcome the mucosal barrier in the intestine; nonetheless, this study also presents a promising strategy to use a dual-action drug delivery nanosystem which synergizes its own biological effect and that of the encapsulated drug molecule.

A β-Glucan-Based Dietary Fiber Reduces Mast Cell-Induced Hyperpermeability in Ileum From Patients With Crohn's Disease and Control Subjects

BACKGROUND

Administration of β-glucan has shown immune-enhancing effects. Our aim was to investigate whether β-glucan could attenuate mast cell (MC)-induced hyperpermeability in follicle-associated epithelium (FAE) and villus epithelium (VE) of patients with Crohn's disease (CD) and in noninflammatory bowel disease (IBD)-controls. Further, we studied mechanisms of β-glucan uptake and effects on MCs in vitro.

METHODS

Segments of FAE and VE from 8 CD patients and 9 controls were mounted in Ussing chambers. Effects of the MC-degranulator compound 48/80 (C48/80) and yeast-derived β-1,3/1,6 glucan on hyperpermeability were investigated. Translocation of β-glucan and colocalization with immune cells were studied by immunofluorescence. Caco-2-cl1- and FAE-cultures were used to investigate β-glucan-uptake using endocytosis inhibitors and HMC-1.1 to study effects on MCs.

RESULTS

β-glucan significantly attenuated MC-induced paracellular hyperpermeability in CD and controls. Transcellular hyperpermeability was only significantly attenuated in VE. Baseline paracellular permeability was higher in FAE than VE in both groups, P<0.05, and exhibited a more pronounced effect by C48/80 and β-glucan P<0.05. No difference was observed between CD and controls. In vitro studies showed increased passage, P<0.05, of β-glucan through FAE-culture compared to Caco-2-cl1. Passage was mildly attenuated by the inhibitor methyl-β-cyclodextrin. HMC-1.1 experiments showed a trend to decreasing MC-degranulation and levels of TNF-α but not IL-6 by β-glucan. Immunofluorescence revealed more β-glucan-uptake and higher percentage of macrophages and dendritic cells close to β-glucan in VE of CD compared to controls.

CONCLUSIONS

We demonstrated beneficial effects of β-glucan on intestinal barrier function and increased β-glucan-passage through FAE model. Our results provide important and novel knowledge on possible applications of β-glucan in health disorders and diseases characterized by intestinal barrier dysfunction.

Vasoactive Intestinal Polypeptide and Mast Cells Regulate Increased Passage of Colonic Bacteria in Patients With Irritable Bowel Syndrome

BACKGROUND & AIMS

Irritable bowel syndrome (IBS) is associated with intestinal dysbiosis and symptoms of IBS develop following gastroenteritis. We aimed to study the passage of live bacteria through the colonic epithelium, and determine the role of mast cells (MCs) and vasoactive intestinal polypeptide (VIP) in barrier regulation in IBS and healthy individuals.

METHODS

Colon biopsies from 32 women with IBS and 15 age-matched healthy women (controls) were mounted in Ussing chambers; we measured numbers of fluorescently labeled Escherichia coli HS and Salmonella typhimurium that passed through from the mucosal side to the serosal side of the tissue. Some biopsies were exposed to agents that block the VIP receptors (VPAC1 and VPAC2) or MCs. Levels of VIP and tryptase were measured in plasma and biopsy lysates. Number of MCs and MCs that express VIP or VIP receptors were quantified by immunofluorescence. Biopsies from an additional 5 patients with IBS and 4 controls were mounted in chambers and Salmonella were added; we studied passage routes through the epithelium by transmission electron microscopy and expression of tight junctions by confocal microscopy.

RESULTS

In colon biopsies from patients with IBS, larger numbers of E coli HS and S typhimurium passed through the epithelium than in biopsies from controls (P < .0005). In transmission electron microscopy analyses, bacteria were found to cross the epithelium via only the transcellular route. Bacterial passage was reduced in biopsies from patients with IBS and controls after addition of antibodies against VPACs or ketotifen, which inhibits MCs. Plasma samples from patients with IBS had higher levels of VIP than plasma samples from controls. Biopsies from patients with IBS had higher levels of tryptase, larger numbers of MCs, and a higher percentage of MCs that express VPAC1 than biopsies from controls. In biopsies from patients with IBS, addition of Salmonella significantly reduced levels of occludin; subsequent addition of ketotifen significantly reversed this effect.

CONCLUSIONS

We found that colonic epithelium tissues from patients with IBS have increased translocation of commensal and pathogenic live bacteria compared with controls. The mechanisms of increased translocation include MCs and VIP.

Targeting mitochondria-derived reactive oxygen species to reduce epithelial barrier dysfunction and colitis

Epithelial permeability is often increased in inflammatory bowel diseases. We hypothesized that perturbed mitochondrial function would cause barrier dysfunction and hence epithelial mitochondria could be targeted to treat intestinal inflammation. Mitochondrial dysfunction was induced in human colon-derived epithelial cell lines or colonic biopsy specimens using dinitrophenol, and barrier function was assessed by transepithelial flux of Escherichia coli with or without mitochondria-targeted antioxidant (MTA) cotreatment. The impact of mitochondria-targeted antioxidants on gut permeability and dextran sodium sulfate (DSS)-induced colitis in mice was tested. Mitochondrial superoxide evoked by dinitrophenol elicited significant internalization and translocation of E. coli across epithelia and control colonic biopsy specimens, which was more striking in Crohn's disease biopsy specimens; the mitochondria-targeted antioxidant, MitoTEMPO, inhibited these barrier defects. Increased gut permeability and reduced epithelial mitochondrial voltage-dependent anion channel expression were observed 3 days after DSS. These changes and the severity of DSS-colitis were reduced by MitoTEMPO treatment. In vitro DSS-stimulated IL-8 production by epithelia was reduced by MitoTEMPO. Metabolic stress evokes significant penetration of commensal bacteria across the epithelium, which is mediated by mitochondria-derived superoxide acting as a signaling, not a cytotoxic, molecule. MitoTEMPO inhibited this barrier dysfunction and suppressed colitis in DSS-colitis, likely via enhancing barrier function and inhibiting proinflammatory cytokine production. These novel findings support consideration of MTAs in the maintenance of epithelial barrier function and the management of inflammatory bowel diseases.

Dietary supplementation with soluble plantain non-starch polysaccharides inhibits intestinal invasion of Salmonella Typhimurium in the chicken

Soluble fibres (non-starch polysaccharides, NSP) from edible plants but particularly plantain banana (Musa spp.), have been shown in vitro and ex vivo to prevent various enteric pathogens from adhering to, or translocating across, the human intestinal epithelium, a property that we have termed contrabiotic. Here we report that dietary plantain fibre prevents invasion of the chicken intestinal mucosa by Salmonella. In vivo experiments were performed with chicks fed from hatch on a pellet diet containing soluble plantain NSP (0 to 200 mg/d) and orally infected with S.Typhimurium 4/74 at 8 d of age. Birds were sacrificed 3, 6 and 10 d post-infection. Bacteria were enumerated from liver, spleen and caecal contents. In vitro studies were performed using chicken caecal crypts and porcine intestinal epithelial cells infected with Salmonella enterica serovars following pre-treatment separately with soluble plantain NSP and acidic or neutral polysaccharide fractions of plantain NSP, each compared with saline vehicle. Bacterial adherence and invasion were assessed by gentamicin protection assay. In vivo dietary supplementation with plantain NSP 50 mg/d reduced invasion by S.Typhimurium, as reflected by viable bacterial counts from splenic tissue, by 98.9% (95% CI, 98.1-99.7; P<0.0001). In vitro studies confirmed that plantain NSP (5-10 mg/ml) inhibited adhesion of S.Typhimurium 4/74 to a porcine epithelial cell-line (73% mean inhibition (95% CI, 64-81); P<0.001) and to primary chick caecal crypts (82% mean inhibition (95% CI, 75-90); P<0.001). Adherence inhibition was shown to be mediated via an effect on the epithelial cells and Ussing chamber experiments with ex-vivo human ileal mucosa showed that this effect was associated with increased short circuit current but no change in electrical resistance. The inhibitory activity of plantain NSP lay mainly within the acidic/pectic (homogalacturonan-rich) component. Supplementation of chick feed with plantain NSP was well tolerated and shows promise as a simple approach for reducing invasive salmonellosis.

Impaired duodenal mucosal integrity and low-grade inflammation in functional dyspepsia

OBJECTIVE

Functional dyspepsia (FD) is an extremely common functional gastrointestinal disorder, the pathophysiology of which is poorly understood. We hypothesised that impaired intestinal barrier function is involved in the onset and persistence of this disorder by inducing low-grade inflammation. Therefore, our aim was to evaluate duodenal mucosal integrity and low-grade inflammation in patients with FD.

DESIGN

Duodenal biopsy specimens were obtained from 15 patients with FD fulfilling the Rome III criteria and 15 age- and gender-matched healthy volunteers. Transepithelial electrical resistance (TEER) and paracellular permeability were measured in Ussing chambers. Expression of cell-to-cell adhesion proteins was evaluated by real-time PCR, western blot and/or immunofluorescence. Numbers of mast cells, eosinophils and intraepithelial lymphocytes were assessed by immunohistochemistry.

RESULTS

Patients with FD displayed lower TEER and increased paracellular passage compared with healthy controls, which is indicative of impaired mucosal integrity. In addition, abnormal expression of cell-to-cell adhesion proteins at the level of tight junctions, adherens junctions and desmosomes was shown. Furthermore, patients were characterised by the presence of low-grade inflammation, as demonstrated by increased infiltration of mucosal mast cells and eosinophils. A significant association between the expression level of several cell-to-cell adhesion proteins, the extent of increased permeability and the severity of low-grade inflammation was found.

CONCLUSIONS

These findings challenge the classical paradigm that patients with FD show no structural changes in the gastrointestinal tract. We suggest that impaired intestinal barrier function is a pathophysiological mechanism in FD. Thus, restoration of intestinal barrier integrity may be a potential therapeutic target for treating patients with FD.

Mucus properties and goblet cell quantification in mouse, rat and human ileal Peyer's patches

Peyer's patches (PPs) are collections of lymphoid follicles in the small intestine, responsible for scanning the intestinal content for foreign antigens such as soluble molecules, particulate matter as well as intact bacteria and viruses. The immune cells of the patch are separated from the intestinal lumen by a single layer of epithelial cells, the follicle-associated epithelium (FAE). This epithelium covers the dome of the follicle and contains enterocyte-like cells and M cells, which are particularly specialized in taking up antigens from the gut. However, the presence and number of goblet cells as well as the presence of mucus on top of the FAE is controversial. When mouse ileal PPs were mounted in a horizontal Ussing-type chamber, we could observe a continuous mucus layer at mounting and new, easily removable mucus was released from the villi on the patch upon stimulation. Confocal imaging using fluorescent beads revealed a penetrable mucus layer covering the domes. Furthermore, immunostaining of FAE from mice, rats and humans with a specific antibody against the main component of intestinal mucus, the MUC2 mucin, clearly identify mucin-containing goblet cells. Transmission electron micrographs further support the identification of mucus releasing goblet cells on the domes of PPs in these species.

Soluble plantain fibre blocks adhesion and M-cell translocation of intestinal pathogens

Dietary fibres may have prebiotic effects mediated by promotion of beneficial bacteria. This study explores the possibility that soluble plant fibre may also improve health by inhibiting epithelial adhesion and translocation by pathogenic bacteria. We have focussed on soluble non-starch polysaccharide (NSP) from plantain bananas (Musa spp.) which previous studies showed to be particularly effective at blocking Escherichia coli epithelial adherence. In vitro and ex vivo studies assessed the ability of plantain NSP to inhibit epithelial cell adhesion and invasion of various bacterial pathogens, and to inhibit their translocation through microfold (M)-cells and human Peyer′s patches mounted in Ussing chambers. Plantain NSP showed dose-related inhibition of epithelial adhesion and M-cell translocation by a range of pathogens. At 5 mg/ml, a concentration readily achievable in the gut lumen, plantain NSP inhibited adhesion to Caco2 cells by Salmonella Typhimurium (85.0±8.2%, P<.01), Shigella sonnei (46.6±29.3%, P<.01), enterotoxigenic E.coli (56.1±23.7%, P<.05) and Clostridium difficile (67.6±12.3%, P<.001), but did not inhibit adhesion by enteropathogenic E.coli. Plantain NSP also inhibited invasion of Caco2 cells by S. Typhimurium (80.2 ± 9.7%) and Sh. sonnei (46.7±13.4%); P<.01. Plantain NSP, 5 mg/ml, also inhibited translocation of S. Typhimurium and Sh. sonnei across M-cells by 73.3±5.2% and 46.4±7.7% respectively (P<.05). Similarly, S. Typhimurium translocation across Peyer′s patches was reduced 65.9±8.1% by plantain NSP (P<.01). Soluble plantain fibre can block epithelial adhesion and M-cell translocation of intestinal pathogens. This represents an important novel mechanism by which soluble dietary fibres can promote intestinal health and prevent infective diarrhoea.

Translocation of Crohn's disease Escherichia coli across M-cells: contrasting effects of soluble plant fibres and emulsifiers

BACKGROUND

Crohn's disease is common in developed nations where the typical diet is low in fibre and high in processed food. Primary lesions overlie Peyer's patches and colonic lymphoid follicles where bacterial invasion through M-cells occurs. We have assessed the effect of soluble non-starch polysaccharide (NSP) and food emulsifiers on translocation of Escherichia coli across M-cells.

METHODS

To assess effects of soluble plant fibres and food emulsifiers on translocation of mucosa-associated E coli isolates from Crohn's disease patients and from non-Crohn's controls, we used M-cell monolayers, generated by co-culture of Caco2-cl1 and Raji B cells, and human Peyer's patches mounted in Ussing chambers.

RESULTS

E coli translocation increased across M-cells compared to parent Caco2-cl1 monocultures; 15.8-fold (IQR 6.2-32.0) for Crohn's disease E coli (N=8) and 6.7-fold (IQR 3.7-21.0) for control isolates (N=5). Electron microscopy confirmed E coli within M-cells. Plantain and broccoli NSP markedly reduced E coli translocation across M-cells at 5 mg/ml (range 45.3-82.6% inhibition, p<0.01); apple and leek NSP had no significant effect. Polysorbate-80, 0.01% vol/vol, increased E coli translocation through Caco2-cl1 monolayers 59-fold (p<0.05) and, at higher concentrations, increased translocation across M-cells. Similarly, E coli translocation across human Peyer's patches was reduced 45±7% by soluble plantain NSP (5 mg/ml) and increased 2-fold by polysorbate-80 (0.1% vol/vol).

CONCLUSIONS

Translocation of E coli across M-cells is reduced by soluble plant fibres, particularly plantain and broccoli, but increased by the emulsifier Polysorbate-80. These effects occur at relevant concentrations and may contribute to the impact of dietary factors on Crohn's disease pathogenesis.