| 1. |
- Carlsson, Anders, 1980-
(författare)
-
Role of mast cells and probiotics in the regulation of intestinal barrier function
- 2013
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The intestinal mucosa is the largest contact area and one of the most important barriers to the outside environment. It is highly specialized in aiding us digest and absorb nutrients. It is daily exposed to several potentially dangerous substances and microorganisms, which if they were allowed to pass into the body, could give rise to diseases. Throughout the small intestine certain sites specialized in antigen sampling are found. These sites are named Peyer’s patches and are lymphoid follicles. The epithelium covering the Peyer’s patches is called follicle-associated epithelium and is specialized in antigen sampling and uptake. The special epithelium enables presentation of luminal antigen to immune cells in the underlying follicle.Persistent life stress and stressful life events affect the course of irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) through largely unknown mechanisms. Regulation of epithelial permeability to antigens is crucial for the balance between inflammation and immune-surveillance, and increased intestinal permeability has been shown in patients with ulcerative colitis and Crohns disease. Vasoactive intestinal polypeptide (VIP) and corticotropin-releasing factor have been implicated as important mediators of stress-induced abnormalities in intestinal mucosal functions in animal models. Both of these mediators have been reported to regulate bowel ion secretion in humans during stress and uptake of horseradish peroxidase in rodents. Probiotics have been shown to ameliorate the deleterious effects of stress on intestinal function, but mechanisms remain to be elucidated.The aim of this thesis was to elucidate whether mast cells play an important role in intestinal barrier function during stress and inflammation. Moreover, we wanted to determine whether probiotics can ameliorate the mucosal barrier integrity during stress and inflammation.To study the function of mast cells we conducted in vitro experiments on cell lines and ex vivo experiments in Ussing chambers on mouse, rat and human intestinal tissue. The Ussing chamber technique measures electrophysiological properties of the tissue and also gives the possibility to study transcellular and paracellular passage of markers and bacteria. Immunohistology and confocal microscopy have been used to identify mast cells and receptors of interest.Our results show that stress affects the follicle-associated epithelium barrier by mechanisms involving VIP and mast cells. These findings were corroborated by the localization of VIP receptors on mucosal mast cells. Furthermore, pretreatment with probiotics was effective in protecting the gut against stress-induced intestinal barrier dysfunction and mucosal inflammation. This protection appeared to involve a mast cell and peroxisome proliferatoractivated receptor-γ dependent mechanism.
|
|
| 2. |
- Ermund, Anna, et al.
(författare)
-
Mucus properties and goblet cell quantification in mouse, rat and human ileal Peyer's patches.
- 2013
-
Ingår i: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 8:12
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 3. |
- Keita, Åsa V., et al.
(författare)
-
Barrier dysfunction and bacterial uptake in the follicle-associated epithelium of ileal Crohns disease
- 2012
-
Ingår i: Annals of the New York Academy of Sciences. - : Wiley. - 0077-8923 .- 1749-6632. ; 1258:1, s. 125-134
-
Tidskriftsartikel (refereegranskat)abstract
- The ability to control uptake across the mucosa and protect from harmful substances in the gut lumen is defined as intestinal barrier function. The etiology of Crohns disease is unknown, but genetic, environmental, and immunological factors all contribute. The frontline between these factors lies in the intestinal barrier. The most important inflammation-driving environmental factor in Crohns disease is the microbiota, where Esherichia coli strains have been assigned a key role. The first observable signs of Crohns disease are small aphtoid ulcers over Peyers patches and lymphoid follicles. The overlaying follicle-associated epithelium (FAE) is specialized for luminal sampling and is an entry site for antigens and bacteria. We have demonstrated increased E. coli uptake across the FAE in Crohns disease, which may initiate inflammation. This short review will discuss barrier dysfunction and bacteria in the context of ileal Crohns disease, and how the FAE might be the site of initial inflammation.
|
|
| 4. |
- Keita, Åsa V, et al.
(författare)
-
Stress-induced barrier disruption of the follicle-associated epithelium involves corticotropin-releasing hormone, vasoactive intestinal peptide and mast cells
- 2010
-
Ingår i: Neurogastroenterology and Motility. - : Wiley. - 1350-1925 .- 1365-2982. ; 22:7, s. 770-e222
-
Tidskriftsartikel (refereegranskat)abstract
- Background The follicle-associated epithelium (FAE) is specialized in uptake and sampling of luminal antigens and bacteria. We previously showed that stress increased FAE permeability in rats. An increased uptake may alter antigen exposure in Peyers patches leading to intestinal disease. The aim of this study was to elucidate mechanisms involved in the acute stress-induced increase in FAE permeability. Methods Rats were pretreated i.p. with corticotropin-releasing hormone receptor (CRH-R) antagonist, neurokinin receptor 1 (NK-1R) antagonist, atropine, the mast cell stabilizer doxantrazole (DOX), or NaCl, and submitted to 1-h acute water avoidance stress. FAE tissues were mounted in Ussing chambers for measurements of permeability to 51Cr-EDTA, horseradish peroxidase (HRP) and chemically killed Escherichia coli K-12. Further, FAE segments were exposed in vitro in chambers to CRH, substance P (SP), carbachol, and DOX. Neurotransmitter- and receptor distribution was studied by immunohistochemistry. Key Results Stress-induced increases in uptake across FAE of HRP and E. coli were reduced by DOX, CRH-R antagonist and atropine, whereas the NK-1R antagonist decreased 51Cr-EDTA permeability. Exposure to CRH and carbachol increased HRP and E. coli passage, whereas SP increased bacterial and 51Cr-EDTA permeability. DOX counteracted all of these effects. Immunohistochemistry revealed CRH, acetylcholine, SP, and their receptors on mast cells within the Peyers patches, subepithelial dome, and adjacent villi. Conclusions & Inferences Corticotropin-releasing hormone and acetylcholine signaling affect mainly transcellular permeability while SP seems more selective toward the paracellular pathways. Our findings may be of importance for the understanding of the pathogenesis of stress-related intestinal disorders.
|
|
| 5. |
- Keita, Åsa V., et al.
(författare)
-
The intestinal barrier and its regulation by neuroimmune factors
- 2010
-
Ingår i: Neurogastroenterology and Motility. - : Blackwell Publishing Ltd. - 1350-1925 .- 1365-2982. ; 22:7, s. 718-733
-
Forskningsöversikt (refereegranskat)abstract
- Background The ability to control uptake across the mucosa and protect from damage of harmful substances from the lumen is defined as intestinal barrier function. A disturbed barrier dysfunction has been described in many human diseases and animal models, for example, inflammatory bowel disease, irritable bowel syndrome, and intestinal hypersensitivity. In most diseases and models, alterations are seen both of the paracellular pathway, via the tight junctions, and of the transcellular routes, via different types of endocytosis. Recent studies of pathogenic mechanisms have demonstrated the important role of neuroimmune interaction with the epithelial cells in the regulation of barrier function. Neural impulses from extrinsic vagal and/or sympathetic efferent fibers or intrinsic enteric nerves influence mucosal barrier function via direct effects on epithelial cells or via interaction with immune cells. For example, by nerve-mediated activation by corticotropin-releasing hormone or cholinergic pathways, mucosal mast cells release a range of mediators with effects on transcellular, and/or paracellular permeability (for example, tryptase, TNF-alpha, nerve growth factor, and interleukins). Purpose In this review, we discuss current physiological and pathophysiological aspects of the intestinal barrier and, in particular, its regulation by neuroimmune factors.
|
|
| 6. |
- Keita, Åsa, et al.
(författare)
-
Vasoactive intestinal polypeptide regulates barrier function via mast cells in human intestinal follicle-associated epithelium and during stress in rats
- 2013
-
Ingår i: Neurogastroenterology and Motility. - : Wiley-Blackwell. - 1350-1925 .- 1365-2982. ; 25:6, s. e406-e417
-
Tidskriftsartikel (refereegranskat)abstract
- Background Vasoactive intestinal polypeptide (VIP) has been implicated as a regulator of intestinal barrier function and inflammation. Our aim was to elucidate the role of VIP in follicle-associated epithelium (FAE) and villus epithelium (VE) permeability following stress in rats and on human intestinal barrier function. Methods Rats were injected intraperitoneally (i.p.) with VIP receptor-antagonists (anti-VPACs), a mast cell stabilizer, doxantrazole (DOX), or NaCl, and submitted to acute water avoidance stress. Ileal segments were mounted in Ussing chambers to assess 51chromium-edta (51Cr-edta) and Escherichia (E.) coli (strain K-12) permeability. Rat ileal and human ileal and colonic segments were exposed to VIP +/- anti-VPACs or DOX. An in vitro co-culture model of human FAE was used to study epithelial-VIP effects. VIP/VPACs distribution was assessed by microscopy. Key Results Stress increased 51Cr-edta and E.coli permeability in VE and FAE. The increases were abolished by i.p. injection of DOX or anti-VPACs. Ileal VIP-exposure ex vivo increased bacterial passage and this was reduced by DOX. In human FAE ex vivo, VIP treatment doubled bacterial uptake, which was normalized by DOX or anti-VPACs. No barrier effects were observed in human colonic tissue. VPACs were found in rat and human ileal follicles, with partial mast cell co-localization. The co-culture model confirmed VIPmast cellepithelial interactions in the regulation of barrier function. Conclusions andamp; Inferences Stress affects the FAE barrier by mechanisms involving VIP and VPACs on mucosal mast cells. We suggest a regulatory role for VIP in the control of ileal permeability that may be relevant to bacterialepithelial interactions in stress-related intestinal disorders.
|
|
| 7. |
- Parsons, Bryony N., et al.
(författare)
-
Dietary Supplementation with Soluble Plantain Non-Starch Polysaccharides Inhibits Intestinal Invasion of Salmonella Typhimurium in the Chicken
- 2014
-
Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 9:2, s. 87658-
-
Tidskriftsartikel (refereegranskat)abstract
- 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; Pless than0.0001). 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); Pless than0.001) and to primary chick caecal crypts (82% mean inhibition (95% CI, 75-90); Pless than0.001). 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.
|
|
| 8. |
- Roberts, Carol L., et al.
(författare)
-
Soluble plantain fibre blocks adhesion and M-cell translocation of intestinal pathogens
- 2013
-
Ingår i: Journal of Nutritional Biochemistry. - : Elsevier. - 0955-2863 .- 1873-4847. ; 24:1, s. 97-103
-
Tidskriftsartikel (refereegranskat)abstract
- 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 Peyers 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%, Pandlt;.01), Shigella sonnei (46.6 +/- 29.3%. Pandlt;.01), enterotoxigenic E.coli (56.1 +/- 23.7%, Pandlt;.05) and Clostridium difficile (67.6 +/- 12.3%, Pandlt;.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%); Pandlt;.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 (Pandlt;.05). Similarly, S. Typhimurium translocation across Peyers patches was reduced 65.9 +/- 8.1% by plantain NSP (Pandlt;.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. Crown Copyright
|
|
| 9. |
- Roberts, Carol L, et al.
(författare)
-
Translocation of Crohns disease Escherichia coli across M-cells: contrasting effects of soluble plant fibres and emulsifiers
- 2010
-
Ingår i: GUT. - : BMJ Publishing Group. - 0017-5749. ; 59:10, s. 1331-1339
-
Tidskriftsartikel (refereegranskat)abstract
- Background Crohns disease is common in developed nations where the typical diet is low in fibre and high in processed food. Primary lesions overlie Peyers 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 Crohns disease patients and from non-Crohns controls, we used M-cell monolayers, generated by co-culture of Caco2-cl1 and Raji B cells, and human Peyers 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 Crohns disease E coli (N=8) and 6.7-fold (IQR 3.7-21.0) for control isolates (N=5). Electronmicroscopy 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, pandlt;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 (pandlt;0.05) and, at higher concentrations, increased translocation across M-cells. Similarly, E coli translocation across human Peyers 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 Crohns disease pathogenesis.
|
|
| 10. |
- Vanheel, Hanne, et al.
(författare)
-
Impaired duodenal mucosal integrity and low-grade inflammation in functional dyspepsia
- 2014
-
Ingår i: Gut. - : BMJ Publishing Group. - 0017-5749 .- 1468-3288. ; 63:2, s. 262-271
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
