A230 A MISSENSE MUTATION IN GOBLET CELL PROTEIN FCGBP ALTERS THE GLYCOMIC PROFILE AND FUNCTION OF THE COLONIC MUCUS BARRIER

Background

MUC2 mucin, produced by colonic goblet cells, forms a mucus bilayer that provides a physical barrier between potential pathogens in the lumen and the underlying epithelial cells. Mucus is thus the first line of innate host defense in the gastrointestinal (GI) tract. Many GI diseases including inflammatory bowel disease and colon cancer affect the glycosylation of mucus. Goblet cells produce a variety of proteins that are associated with the mucus layer. Of these proteins, FCGBP is of significant interest due to its structural similarities to MUC2 mucin with unknown functions. In this study, we investigated how a missense mutation in FCGBP altered the glycosylation of goblet cell MUC2 and affected its barrier functions.

Purpose

Hypothesis: A missense mutation in FCGBP results an impaired mucus layer by the altering glycomic profiles of goblet cell mucins. Specific aims:

1) To determine mechanistically how FCGBP impeded the structural integrity of the mucus layer

2) To quantify MUC2 glycoprotein modifications in the altered mucus layer

Method

To investigate whether FCGBP impaired mucus barrier functions, two cell types were investigated: wildtype LS174T (WT) MUC2 mucus-producing goblet cells and LS174T cells with a missense mutation in FCGBP (FCGBP MS). To determine if FCGBP MS led to loss in barrier function in the mucus layer, the penetration of 0.2, 1, and 2 μm fluorescent beads (to mimic bacteria) through the mucus layer were quantified. To determine if the differences in penetrability were caused by differences in MUC2 glycosylation in the goblet cell lines, sensitive glycomic analyses were performed by high-performance liquid chromatography-mass spectrometry (HPLC-MS) and capillary electrophoresis with laser-induced fluorescence detection (CE-LIF). Both intact cells and isolated MUC2 mucin granules were analyzed. To determine if differences in the glycomic profiles was caused by differences in glycotransferases, RT-PCR was performed on over 30 human glycosyltransferases.

Result(s)

FCGBP MS cells exhibited significant loss in MUC2 mucus barrier function as quantified by fluorescent beads penetration through the mucus layer in a temporal manner. FCGBP MS cells exhibited an altered glycomic profile with a notable increase in sialylated glycans as quantified by HPLC-MS. The increase in sialylated glycans was associated with a significant increase in sialyl-transferase expression in FCGBP MS cells.

Conclusion(s)

These data demonstrate that a single missense mutation in FCGBP altered the penetrability of the mucus layer associated with an increase in sialylated proteins, a signature hallmark of numerous colonic diseases. FCGBP was critical in providing structural integrity of the mucus layer and maintenance of goblet cell glycosylation profiles.

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CIHR

Disclosure of Interest

None Declared

A187 DIETARY FIBERS ELICIT GUT IMMUNE AND EPITHELIAL BARRIER MODIFYING EFFECTS IN INFLAMMATORY BOWEL DISEASES BASED ON FOOD SOURCE AND FIBER CHEMICAL FEATURES

Background

Dietary fibers are not digested in the bowel; they are fermented by microbes, typically promoting gut health. However, IBD patients experience sensitivity to consumption of fibers. Our previous findings offered the first mechanistic evidence demonstrating that unfermented dietary β-fructans (inulin and oligofructose) can induce pro-inflammatory cytokines and altered epithelial barrier integrity in a subset of pediatric IBD colonic biopsies cultured ex vivo, and in the SYNERGY-1 (β-fructan) clinical study of adult remission UC patients. Fermentation of β-fructan by whole-microbiota intestinal washes from non-IBD or remission IBD patients (but not non-IBD microbes) reduced pro-inflammatory responses.

Purpose

Here we aimed to expand our findings to uncover the physiologically relevant gut immune and epithelial responses to over 50 unfermented and partially fermented dietary fibers (arabinoxylans, β-glucans, β-mannans, galatooligosaccharides, inulins, oligofructoses, pectins, raffinooligosaccharides, xyloglucans) sourced from commonly consumed fruits, grains, and vegetables to better understand which foods are safe for IBD patients, and in which disease state settings.

Method

Colonic biopsies cultured ex vivo, peripheral blood mononuclear cells (PBMCs), colonic organoids, and cell lines were incubated with individual dietary fibers or mixture of fibers extracted from commonly consumed fruits, grains, and vegetables. Epithelial barrier integrity (TEER, microscopy, FITC-dextran) and immune responses (cytokine secretion [ELISA/MSD] and expression [qPCR]) were assessed. Structural features of the different fibers (e.g., degree of polymerization, phenolic/phytic content, branching, sugar content) were measured by HPLC and gas chromatography and correlated to host cell responses.

Result(s)

Most significantly unfermented inulin, oligofructose, and arabinoxylan induced pro-inflammatory responses, particularly in myeloid cells. Pectin and galatooligosaccharides were either non-inflammatory or anti-inflammatory depending on the food source. The epithelial barrier response to select dietary fibers correlated more significantly with the chemical properties of the fibers; longer fibers (greater degree of polymerization; e.g., inulin) displayed improved barrier integrity while shorter dietary fibers with higher phenolic content displayed reduced barrier integrity. Fiber structural properties varied significantly between different fiber subtypes along with the same fiber subtype sourced from different foods.

Conclusion(s)

Our findings suggest that intolerance and avoidance of fibers in select IBD patients occurs in patients whose gut microbiota do not support fermentation of fibers resulting in increased presence of unfermented dietary fibers in the gut. Here we show which specific dietary fibers from specific food items can elicit gut barrier damage and inflammation in the gut dependent on fiber structural features, suggesting mechanisms underlying IBD patient avoidance of specific high-fiber foods.

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Other

Please indicate your source of funding;

Weston Family Foundation, MMSF, NSERC, CRC

Disclosure of Interest

None Declared

A43 HIGH MUC2 MUCIN BIOSYNTHESIS BY GOBLET CELLS UNDER METABOLIC STRESS PRODUCE ELEVATED LEVELS OF PRO-INFLAMMATORY CYTOKINES

Background

The colonic mucus bilayer is an integral innate host defense mechanism that houses the commensal gut microbiota whilst protecting the underlying mucosa against harmful pathogens. This essential barrier is generated via a highly ER stressful mechanism by goblet cells that produce MUC2 mucin. Goblet cells also produce a variety of proteins and peptides as well as pro-inflammatory cytokines that interact with and activate other arms of the innate immune system. In ulcerative and infectious colitis, goblet cells hyper secrete mucus and become depleted of their mucin stores. However, it is not known if other proteins or pro-inflammatory responses are altered in mucin-depleted goblet cells. Here, we elucidated the molecular mechanisms that regulate pro-inflammatory responses in WT and CRISPR/Cas9 MUC2 KO human goblet cells.

Aims

Hypothesis: MUC2 biosynthesis and production augment pro-inflammatory responses in goblet cells. The specific aims are:

1. To determine the pro-inflammatory responses in WT and MUC2KO goblet cells

2. To determine if the MAPK signaling pathway is altered in WT and MUC2KO goblet cells

Methods

mRNA and protein expression of various pro-inflammatory chemokines/cytokines in WT and CRISPR/Cas9 MUC2KO LS174T goblet cells were analyzed by RT-qPCR and 15-plex Luminex array. IL-22 was used to alleviate ER stress, as quantified by the expression of stress proteins by Western blotting. To determine differences in pro-inflammatory cytokine release, cells were stimulated with phorbol myristate acetate (PMA, positive control), live Entamoeba histolytica (Eh), and lysed soluble amebic proteins (SAP). MAPK signaling was enumerated by specific pharmacological inhibitors and analyzed by Western blotting.

Results

Basally and in response to live Eh, WT goblet cells expressed high levels of the metabolic stress proteins, ATF4, GRP78, and CHOP as compared to MUC2KO cells. In response to PMA, live Eh, and SAP, WT cells expressed high levels of mRNA transcripts and secreted significant amounts of the pro-inflammatory chemokines, monocyte chemoattractant protein-1 (MCP-1), interleukin-8 (IL-8), and interleukin-13 (IL-13) as compared to MUC2KO cells. Reducing ER stress with IL-22 significantly augmented IL-8 protein release in both WT and MUC2KO cells. Signaling via the ERK MAPK pathway was elevated in WT whereas in MUC2KO goblet the response was delayed.

Conclusions

This study demonstrates that high MUC2 mucin biosynthesis regulates the expression and secretion of the pro-inflammatory cytokines MCP-1, IL-8, and IL-13. Mechanistically, MUC2 induced metabolic stress regulated MAPK activity for high output pro-inflammatory responses as compared to MUC2KO goblet cells.

Funding Agencies

CIHR

A198 COLONIC MUC2 MUCIN IS STABILIZED BY FCGBP TO RESIST SALMONELLA TYPHIMURIUM INVASION IN GOBLET CELLS

Background

The colonic mucus bilayer is the first line of innate defense against pathogen invasion in the gut by forming a physical barrier between the lumen and the underlying single layer of mucosal epithelial cells. While MUC2 mucin is the primary component of the mucus layer, it also contains several mucus associated proteins of which FCGBP is of significant interest due to its structural similarities to MUC2 with unknown functions. Here we elucidated the functions of FCGBP in MUC2 mucin in response to S. typhimurium ( St) adherence and invasion in human colonic goblet cells.

Aims

Hypothesis: FCGBP is coordinately produced with MUC2 mucin and plays an important role in innate host defense. The specific aims are:

1. To determine if FCGBP alters the structural integrity of the mucus layer

2. To determine the role of FCGBP in St adherence and invasion of goblet cells

Methods

To investigate whether FCGBP impaired mucus barrier functions, wildtype LS174T (WT) MUC2 mucus-producing goblet cells and LS174T cells with a missense mutation in FCGBP (FCGBP MS) were used. To determine if FCGBP MS led to loss in barrier function, St adherence and invasion, and 0.2, 1, and 2 μM fluorescent bead penetration through the mucus monolayers were quantified. MUC2 and FCGBP mRNA and protein expression induced by St were analysed by RT-PCR and Western blotting. St-induced pro-inflammatory cytokines responses were analyzed by RT-PCR and human focus 15-plex cytokine and chemokine array. Cell killing was enumerated by LDH assay.

Results

FCGBP MS cells exhibited significant loss in MUC2 mucus barrier function as quantified by fluorescent beads penetration closer towards the epithelial cell surface temporally as compared to WT cells independent of bead size. Adherence of St was significantly increased in FCGBP MS cells and induced robust MUC2 mRNA and protein expressions in a time-dependent manner. Similarly, St elicited robust expression of pro-inflammatory cytokine mRNA and protein release in FCGBP MS as compared to WT cells. FCGBP MS were readily invaded by St that resulted in increased cell death as compared to WT cells.

Conclusions

Loss of function by FCGBP MS, but not in WT cells, showed increased penetration of fluorescent beads through the mucus layer that resulted in increased St adherence, invasion, and cell death. In WT cells, FCGBP and MUC2 were coordinately upregulated in response to St. The concurrent increase in pro-inflammatory cytokine expression in FCGBP MS cells in response to St suggests that bacteria directly interacted with the cell surface indicative of an impaired mucus layer. The overall trend for increased bacterial invasion, pro-inflammatory response and cell death in FCGBP MS demonstrates that FCGBP was critical in providing structural integrity and protective functions of the mucus layer.

Funding Agencies

CIHR

A24 FCGBP MAINTAINS MUC2 MUCUS STRUCTURAL INTEGRITY BY STABILIZING THE MUCUS LAYER IN RESPONSE TO THE COLONIC PATHOGEN, ENTAMOEBA HISTOLYTICA

Background

MUC2 mucin is the major component of the colonic mucus bilayer that serves as the first line of innate host defense against pathogens while supporting a healthy microbiota and regulating epithelial barrier function. Proteomic studies of colonic mucus have identified various mucus-associated proteins. One of the most abundant is FCGBP, similar to MUC2 mucin, but its interaction with MUC2 or function is not known. Here, we elucidated FCGBP functional role in stabilizing MUC2 mucus and in innate host defence against Entamoeba histolytica (Eh).

Aims

Hypothesis: MUC2 mucin and FCGBP are coordinately produced and play an important role in innate host defense. The specific aims are:

1. To determine if FCGBP alters the structural integrity of the mucus layer

2. To determine the role of FCGBP in Eh infection

Methods

FCGBP mRNA and protein expression induced by Eh, in WT and FCGBP CRISPR/Cas9 LS174T goblet cells were analysed by RT-PCR and Western blotting. To compare integrity of the mucus layer, fluorescent Eh and 1μM fluorescent beads were inoculated on WT and KO monolayers and adherent Eh and bead penetrability analyzed. To quantify MUC2 and FCGBP degradation by Eh, purified MUC2 and recombinant FCGBP were incubated with Eh proteases (SPs) and Western blotted using highly specific antibodies against various regions of the proteins.

Results

In response to live Eh, FCGBP and MUC2 mRNA and protein expressions were significantly increased in a time-dependent manner. Surprisingly, FCGBP KO cells elicited robust expression of pro-inflammatory cytokine mRNA and protein as compared to WT cells. More fluorescent Eh were attached to the mucus layer of FCGBP KO cells as compared to WT or MUC2 KO cells. Fluorescent beads penetrated further towards the epithelial cell surface in KO as compared to WT cells. Interestingly, while both MUC2 and FCGBP from purified polymeric mucins were degraded by Eh SPs, FCGBP cleavage occurred at a faster rate than MUC2. Degradation of FCGBP and MUC2 was mediated by EhCP-A5 cysteine proteinase using purified MUC2 and recombinant FCGBP.

Conclusions

In WT goblet cells, FCGBP and MUC2 were upregulated temporally in response to Eh. The increase in pro-inflammatory cytokine expression in FCGBP KO cells in response to Eh suggests that Eh directly interacted with the cell surface suggesting an impaired protective mucus layer. In support of this, fluorescent beads penetrated the mucus layer close to the cell surface and more Eh were attached to FCGBP KO mucus demonstrating that FCGBP was critical in providing structural integrity of the mucus layer. In response to Eh, FCGBP degradation was a prerequisite for MUC2 cleavage, providing direct evidence that FCGBP and MUC2 interactions conferred biophysical properties of the protective functions of the mucus gel.

Funding Agencies

CIHR

A31 COMPLEX ROLE OF DIETARY FIBERS IN IBD: MICROBES MEDIATE FIBER-INDUCED INFLAMMATION

Background

Dietary fibers pass through the bowel undigested and are fermented within the intestine by microbes, typically promoting gut health. However, many IBD patients describe experiencing sensitivity to fibers. β-glucan, found on the surface of fungal cells during fungal infection, has been shown to bind to fiber receptors, such as Dectin-1, on host immune cells, resulting in a pro-inflammatory response. These fungal fibres share properties with dietary fibers.

Aims

As an altered gut microbial composition has been associated with IBD, we hypothesized that the loss of fiber-fermenting microbes populating the gut in IBD could lead to dietary fibers not being efficiently broken down into their beneficial biproducts (e.g. short chain fatty acids; SCFA), resulting in binding of intact fibers to pro-inflammatory host cell receptors.

Methods

Immune and epithelial cell lines and colonic biopsies cultured ex vivo were incubated with oligofructose or inulin (5g/L), or pre-fermented fibers (24hr anaerobic fermentation). Immune responses were measured by cytokine secretion (ELISA), and expression (qPCR). Barrier integrity was measured by transepithelial resistance (TEER). Food frequency questionnaire (FFQ) data of patient fiber consumption were correlated with gut microbes (shotgun sequencing) and immune responses to fiber in patient biopsies.

Results

Unfermented oligofructose induced IL-1β secretion in leukocytes (macrophage, T cell, neutrophil) and in colon biopsies from pediatric Crohn disease (CD; n=38) and ulcerative colitis (UC; n=20) patients cultured ex vivo, but not in non-IBD patients (n=21). IL-1β secretion was greater in patients with more severe disease. Pre-fermentation of oligofructose by whole-microbe intestinal washes from non-IBD patients or remission patients reduced secretion of IL-1β, while whole microbe intestinal washes from severe IBD patients were unable to ferment oligofructose or reduce cytokine secretion. Fiber effects on IL-1β secretion in biopsies positively correlated with effects on barrier integrity in T84 cells. Fiber-associated immune responses in patient biopsies cultured ex vivo (ELISA) correlated with fiber avoidance (FFQ) and gut microbiome (sequencing) in matching patient samples.

Conclusions

Our findings demonstrate that intolerance and avoidance of prebiotic fibers in select IBD patients is associated with the inability to ferment these fibers, leading to pro-inflammatory immune responses and intestinal barrier disruption. This highlights select disease state scenarios, in which administration of fermentable fibers should be avoided and tailored dietary interventions should be considered in IBD patients.

Funding Agencies

CIHRWeston Foundation

An exploratory study of the association of adrenergic and serotonergic genotype and gastrointestinal motor functions

Adrenergic and serotonergic mechanisms alter human gut motor functions. Genotype variation influences phenotype. Our aim was to test the hypothesis that variation in genes that control these functions is associated with gastrointestinal (GI) motor functions in humans with functional GI disorders (FGID). A database of 251 people was assembled by combining genotype data with measurements of gut transit and gastric volumes. Genetic variations evaluated were: alpha(2A) adrenergic (C-1291G), alpha(2C) (Del 332-325), 5-HT transporter (SLC6A4) and GNbeta3 (C825T). We sought associations between motor function or disease groups and genotypes, adjusting for age, gender and body mass index. Among 251 participants, 82 were healthy, 20 with irritable bowel syndrome (IBS) with mixed bowel habit, 49 with constipation-predominant IBS, 67 with diarrhoea-predominant IBS and 33 with functional dyspepsia. For all candidate genes, there was no significant association between motor function and wildtype vs non-wildtype gene status. There were significant interactions between genotype and motility phenotype, specifically GNbeta3 and alpha(2A) and gastric emptying at 4 h. Borderline associations were noted for SCL6A4 and alpha(2A) and postprandial gastric volume, and for alpha(2C) and gastric emptying at 2 h. We conclude that genotype variation may affect gastric motor functions in different FGID phenotypes. However, these candidate genes account for only a limited amount of the variance in gastric function of patients with FGID.

Intestinal permeability and irritable bowel syndrome

Based on a systematic PubMed search, this short review addresses why intestinal permeability may be important in the pathobiology of irritable bowel syndrome (IBS), the evidence of abnormal permeability in patients with IBS, and the pros and cons of the different probe molecules available to assess intestinal permeability. While a subgroup of patients with IBS appears to have evidence of increased intestinal permeability, improvements in the methods and validation are key to further research in this field in order to better understand intestinal barrier functions in IBS.

Educating for collaboration in community care

Successful collaborative community care depends upon all agencies respecting and valuing each other. The key — according to Sheila Roy (former Director of Nursing Management and Research, North West Thames Regional Health Authority), a speaker at the recent conference held at CAIPE (Centre for the Advancement of Interprofessional Education in Primary Health Care) — is education and training throughout organizations at every level.

Improving the technique of nuclear cystography: the manometric approach

A simple technique of manometric scintigraphic retrograde cystography was applied prospectively to 125 patients (85 per cent children) with 142 studies. 99mTechnetium sulfur colloid (0.5 to 1 mCi.) was instilled in the bladder followed by increments of normal saline under manometric control. The sensitivity of the test was increased when the filling phase was concluded at 25 cm. water pressure rather than when the patient complained of fullness (usually at 15 cm.). The studies had a voiding phase that was essential for patients in whom pressures greater than 15 cm. could not be achieved. Reflux was not detected on the voiding phase alone in 5 patients and the voiding phase could not be performed in 5 of 34 positive studies. It was not possible to predict volumes of fluid instilled to achieve satisfactory pressures. Monitoring during the entire study was necessary to diagnose reflux, which may occur at low or high pressure, or while voiding only.

Childhood systemic lupus erythematosus. Association with pancreatitis, subcutaneous fat necrosis, and calcinosis cutis

Pancreatitis developed in a 12-year-old girl with a one-year history of systemic lupus erythematosus. The pancreatitis was first manifested by panniculitis of the lower extremities. Calcinosis cutis subsequently developed, both in areas of panniculitis and in areas free of panniculitis. The patient's medications at the time of onset of pancreatitis included prednisone, hydrochlorothiazide, and azathioprine, all of which have been reported to be causes of pancreatitis. We wish to alert physicians that pancreatitis associated with cutaneous panniculitis and calcinosis cutis may develop in children with systemic lupus erythematosus.