The role of epithelial cells in immune regulation in the gut

Spirobenzofuran Mitigates Ochratoxin A-Mediated Intestinal Adverse Effects in Pigs through Regulation of Beta Defensin 1

Antimicrobial peptides (AMPs) function to extensively suppress various problematic factors and are considered a new alternative for improving livestock health and enhancing immunomodulation. In this study, we explored whether AMP regulation has positive influences on Ochratoxin A (OTA) exposure using a porcine intestinal epithelial cell line (IPEC-J2 cells). We constructed a beta-defensin 1 (DEFB1) expression vector and used it to transfection IPEC-J2 cells to construct AMP overexpression cell lines. The results showed that OTA induced cytotoxicity, decreased cell migration, and increased inflammatory markers mRNA in IPEC-J2 cells. In DEFB1 overexpressing cell lines, OTA-induced reduced cell migration and increased inflammatory markers mRNA were alleviated. Additionally, a natural product capable of inducing DEFB1 expression, which was selected through high-throughput screening, showed significant alleviation of cytotoxicity, cell migration, and inflammatory markers compared to OTA-treated IPEC-J2 cells. Our finding provides novel insights and clues for the porcine industry, which is affected by OTA exposure.

Identification and validation of hub genes expressed in ulcerative colitis with metabolic dysfunction-associated steatotic liver disease

Objective

Ulcerative colitis (UC) and metabolic dysfunction-associated steatotic liver disease (MASLD) are closely intertwined; however, the precise molecular mechanisms governing their coexistence remain unclear.

Methods

We obtained UC (GSE75214) and MASLD (GSE151158) datasets from the Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) were acquired by the 'edgeR' and 'limma' packages of R. We then performed functional enrichment analysis of common DEGs. Hub genes were selected using the cytoHubba plugin and validated using GSE87466 for UC and GSE33814 for MASLD. Immunohistochemistry was employed to validate the hub genes' expression in clinical samples. Immune infiltration and gene set enrichment analyses of the hub genes were performed. Finally, we estimated the Spearman's correlation coefficients for the clinical correlation of the core genes.

Results

Within a cohort of 26 differentially regulated genes in both UC and MASLD, pathways involving cytokine-mediated signaling, cell chemotaxis, and leukocyte migration were enriched. After further validation, CXCR4, THY1, CCL20, and CD2 were identified as the hub genes. Analysis of immune infiltration patterns highlighted an association between elevated pivotal gene expression and M1 macrophage activation. Immunohistochemical staining revealed widespread expression of pivotal genes in UC- and MASLD-affected tissues. Furthermore, significant correlations were observed between the increased expression of hub genes and biochemical markers, such as albumin and prothrombin time.

Conclusion

This bioinformatics analysis highlights CXCR4, THY1, CCL20, and CD2 as crucial genes involved in the co-occurrence of UC and MASLD, providing insights into the underlying mechanisms of these two conditions.

The potential of dietary nanoparticles to enhance allergenicity of milk proteins: an in vitro investigation

In recent years, the popularity of dietary nanoparticles (NPs) in the food industry as additives has raised concerns because of the lack of knowledge about potential adverse health outcomes ensuing from the interactions of NPs with components of the food matrix and gastrointestinal system. In this study, we used a transwell culture system that consisted of human colorectal adenocarcinoma (Caco-2) cells in the apical insert and Laboratory of Allergic Diseases 2 mast cells in the basal compartment to study the effect of NPs on milk allergen delivery across the epithelial layer, mast cell responses and signaling between epithelial and mast cells in allergenic inflammation. A library of dietary particles (silicon dioxide NPs, titanium dioxide NPs and silver NPs) that varied in particle size, surface chemistry and crystal structures with or without pre-exposure to milk was used in this investigation. Milk-interacted particles were found to acquire surface corona and increased the bioavailability of milk allergens (casein and β-lactoglobulin) across the intestinal epithelial layer. The signaling between epithelial cells and mast cells resulted in significant changes in the early phase and late-phase activation of the mast cells. This study suggested that antigen challenge in mast cells with the presence of dietary NPs may cause the transition of allergic responses from an immunoglobulin E (IgE)-dependent mechanism to a mixed mechanism (both IgE-dependent and IgE-independent mechanisms).

TLR/MyD88-Mediated Inflammation Induced in Porcine Intestinal Epithelial Cells by Ochratoxin A Affects Intestinal Barrier Function

The intestinal epithelium performs vital functions such as nutrient absorption and acting as an intestinal barrier to maintain the host's homeostasis. Mycotoxin, which affects the processing and storage of animal feedstuff, is a problematic pollutant in farming products. Ochratoxin A generated by Aspergillus and Penicillium fungi causes inflammation, intestinal dysfunction, decline in growth, and reduced intake in porcine and other livestock. Despite these ongoing problems, OTA-related studies in intestinal epithelium are lacking. This study aimed to demonstrate that OTA regulates TLR/MyD88 signaling in IPEC-J2 cells and induces barrier function impairment through tight junction reduction. We measured expression of TLR/MyD88 signaling-related mRNAs and proteins. The indicator of intestinal barrier integrity was confirmed through immunofluorescence and transepithelial electrical resistance. Additionally, we confirmed whether inflammatory cytokines and barrier function were affected by MyD88 inhibition. MyD88 inhibition alleviated inflammatory cytokine levels, tight junction reduction, and damage to barrier function due to OTA. These results indicate that OTA induces TLR/MyD88 signaling-related genes and impairs tight junctions and intestinal barrier function in IPEC-J2 cells. MyD88 regulation in OTA-treated IPEC-J2 cells mitigates the tight junction and intestinal barrier function impairments. Our findings provide a molecular understanding of OTA toxicity in porcine intestinal epithelial cells.

P2X7 receptor as the regulator of T-cell function in intestinal barrier disruption

The intestinal mucosa is a highly compartmentalized structure that forms a direct barrier between the host intestine and the environment, and its dysfunction could result in a serious disease. As T cells, which are important components of the mucosal immune system, interact with gut microbiota and maintain intestinal homeostasis, they may be involved in the process of intestinal barrier dysfunction. P2X7 receptor (P2X7R), a member of the P2X receptors family, mediates the effects of extracellular adenosine triphosphate and is expressed by most innate or adaptive immune cells, including T cells. Current evidence has demonstrated that P2X7R is involved in inflammation and mediates the survival and differentiation of T lymphocytes, indicating its potential role in the regulation of T cell function. In this review, we summarize the available research about the regulatory role and mechanism of P2X7R on the intestinal mucosa-derived T cells in the setting of intestinal barrier dysfunction.

Sphingosine 1-phosphate modulation and immune cell trafficking in inflammatory bowel disease

Immune cell trafficking is a critical element of the intestinal immune response, both in homeostasis and in pathological conditions associated with inflammatory bowel disease (IBD). This process involves adhesion molecules, chemoattractants and receptors expressed on immune cell surfaces, blood vessels and stromal intestinal tissue as well as signalling pathways, including those modulated by sphingosine 1-phosphate (S1P). The complex biological processes of leukocyte recruitment, activation, adhesion and migration have been targeted by various monoclonal antibodies (vedolizumab, etrolizumab, ontamalimab). Promising preclinical and clinical data with several oral S1P modulators suggest that inhibition of lymphocyte egress from the lymph nodes to the bloodstream might be a safe and efficacious alternative mechanism for reducing inflammation in immune-mediated disorders, including Crohn's disease and ulcerative colitis. Although various questions remain, including the potential positioning of S1P modulators in treatment algorithms and their long-term safety, this novel class of compounds holds great promise. This Review summarizes the critical mediators and mechanisms involved in immune cell trafficking in IBD and the available evidence for efficacy, safety and pharmacokinetics of S1P receptor modulators in IBD and other immune-mediated disorders. Further, it discusses potential future approaches to incorporate S1P modulators into the treatment of IBD.

Dietary nanoparticles compromise epithelial integrity and enhance translocation and antigenicity of milk proteins: An in vitro investigation

Nanoparticles (NPs) are increasingly being used in the food sector, yet little is known about the potential health risks associated with oral exposure to dietary NPs. In this study, the most widely used NPs in food industry including food grade silicon dioxide (SiO₂), titanium dioxide (TiO₂) and silver (Ag), along with their non-food grade and bulk counterparts, are characterized for physicochemical properties and molecular, cellular, and intracellular effects on human intestinal epithelial cells (Caco-2 and HIEC-6). Silver NPs are the most cytotoxic and induce significant cellular changes in oxidative stress, Ca²⁺ flux and mitochondria function, leading to cellular junction disruption at the lowest exposure concentration. At higher testing concentrations, NPs but not microparticles of SiO₂ and TiO₂ cause sublethal cellular responses and remodel tight junctions without impairing epithelial integrity. To relate the cellular results to key events in GI disorder progression, NPs are exposed to an in vitro co-culture model for cow's milk allergy comprised of Caco-2 and allergy sera-primed mast cells (LUVA). All particle treatments increase the allergen delivery across intestinal epithelium and subsequent allergy responses. Overall, the study has identified a particle-dependent alteration in intestinal epithelium and highlighted potential safety concerns of dietary NPs.

Extracellular Vesicles Derived from Kefir Grain Lactobacillus Ameliorate Intestinal Inflammation via Regulation of Proinflammatory Pathway and Tight Junction Integrity

The aim of this study was to demonstrate the anti-inflammatory effect of Lactobacillus kefirgranum PRCC-1301-derived extracellular vesicles (PRCC-1301 EVs) on intestinal inflammation and intestinal barrier function. Human intestinal epithelial cells (IECs) Caco-2 were treated with PRCC-1301 EVs and then stimulated with dextran sulfate sodium (DSS). Real-time RT-PCR revealed that PRCC-1301 EVs inhibited the expression of pro-inflammatory cytokines in Caco-2 cells. PRCC-1301 EVs enhanced intestinal barrier function by maintaining intestinal cell integrity and the tight junction. Loss of Zo-1, claudin-1, and occludin in Caco-2 cells and the colitis tissues was recovered after PRCC-1301 EVs treatment, as evidenced by immunofluorescence analysis. Acute murine colitis was induced using 4% DSS and chronic colitis was generated in piroxicam-treated IL-10^-/- mice. PRCC-1301 EVs attenuated body weight loss, colon shortening, and histological damage in acute and chronic colitis models in mice. Immunohistochemistry revealed that phosphorylated NF-κB p65 and IκBα were reduced in the colon tissue sections treated with PRCC-1301 EVs. Our results suggest that PRCC-1301 EVs may have an anti-inflammatory effect on colitis by inhibiting the NF-κB pathway and improving intestinal barrier function.

Intestinal Epithelial Expression of MHCII Determines Severity of Chemical, T-Cell-Induced, and Infectious Colitis in Mice

BACKGROUND & AIMS

Intestinal epithelial cells (IECs) provide a barrier that separates the mucosal immune system from the luminal microbiota. IECs constitutively express low levels of major histocompatibility complex (MHC) class II proteins, which are upregulated upon exposure to interferon gamma. We investigated the effects of deleting MHCII proteins specifically in mice with infectious, dextran sodium sulfate (DSS)-, and T-cell-induced colitis.

METHODS

We disrupted the histocompatibility 2, class II antigen A, beta 1 gene (H2-Ab1) in IECs of C57BL/6 mice (I-Ab^ΔIEC) or Rag1^-/- mice (Rag1^-/-I-Ab^ΔIEC); we used I-Ab^WT mice as controls. Colitis was induced by administration of DSS, transfer of CD4⁺CD45RB^hi T cells, or infection with Citrobacter rodentium. Colon tissues were collected and analyzed by histology, immunofluorescence, xMAP, and reverse-transcription polymerase chain reaction and organoids were generated. Microbiota (total and immunoglobulin [Ig]A-coated) in intestinal samples were analyzed by16S amplicon profiling. IgA⁺CD138⁺ plasma cells from Peyer's patches and lamina propria were analyzed by flow cytometry and IgA repertoire was determined by next-generation sequencing.

RESULTS

Mice with IEC-specific loss of MHCII (I-Ab^ΔIEC mice) developed less severe DSS- or T-cell transfer-induced colitis than control mice. Intestinal tissues from I-Ab^ΔIEC mice had a lower proportion of IgA-coated bacteria compared with control mice, and a reduced luminal concentration of secretory IgA (SIgA) following infection with C rodentium. There was no significant difference in the mucosal IgA repertoire of I-Ab^ΔIEC vs control mice, but opsonization of cultured C rodentium by SIgA isolated from I-Ab^ΔIEC mice was 50% lower than that of SIgA from mAb^WT mice. Fifty percent of I-Ab^ΔIEC mice died after infection with C rodentium, compared with none of the control mice. We observed a transient but significant expansion of the pathogen in the feces of I-Ab^ΔIEC mice compared with I-Ab^WT mice.

CONCLUSIONS

In mice with DSS or T-cell-induced colitis, loss of MHCII from IECs reduces but does not eliminate mucosal inflammation. However, in mice with C rodentium-induced colitis, loss of MHCII reduces bacterial clearance by decreasing binding of IgA to commensal and pathogenic bacteria.

The impact of synthetic amorphous silica (E 551) on differentiated Caco-2 cells, a model for the human intestinal epithelium

For several decades, food-grade synthetic amorphous silica (SAS) have been used as a technological additive to reduce caking of food powders. Human exposure is thus inevitable and safety concerns are taken seriously. The toxicity of silica in general and SAS in particular has been studied extensively. Overall, there is little evidence that food-grade SAS pose any health risks to humans. However, from the available data it was often not clear which type of silica was used. Accordingly, the latest report of the European food safety authority requested additional toxicity data for well-characterised "real food-grade SAS". To close this gap, we screened a panel of ten well-defined, food-grade SAS for potential adverse effects on differentiated Caco-2 cells. Precipitated and fumed SAS with low, intermediate and high specific surface area were included to determine structure-activity relationships. In a physiological dose-range up to 50 μg/ml and 48 h of incubation, none of the materials induced adverse effects on differentiated Caco-2 cells. This held true for endpoints of acute cytotoxicity as well as epithelial specific measures of barrier integrity. These results showed that despite considerable differences in production routes and material characteristics, food-relevant SAS did not elicit acute toxicity responses in intestinal epithelial cells.

l-Arginine Ameliorates Lipopolysaccharide-Induced Intestinal Inflammation through Inhibiting the TLR4/NF-κB and MAPK Pathways and Stimulating β-Defensin Expression in Vivo and in Vitro

Nutritional regulation of endogenous antimicrobial peptide (AMP) expression is considered a promising nonantibiotic approach to suppressing intestinal infection of pathogen. The current study investigated the effects of l-arginine on LPS-induced intestinal inflammation and barrier dysfunction in vivo and in vitro. The results revealed that l-arginine attenuated LPS-induced inflammatory response, inhibited the downregulation of tight junction proteins (TJP) (p < 0.05) by LPS, and maintained intestinal integrity. In porcine intestinal epithelial cells (IPEC-J2), l-arginine obviously suppressed (p < 0.05) the levels of IL-6 (220.63 ± 2.82), IL-8 (333.95 ± 3.75), IL-1β (693.08 ± 2.38), and TNF-α (258.04 ± 4.14) induced by LPS. Furthermore, l-arginine diminished the LPS-induced expression of Toll-like receptor 4 (TLR4) and inhibited activation of TLR4-mediated nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways. Importantly, we proposed a new mechanism that l-arginine had the ability to stimulate the expression of porcine epithelial β-defensins through activating the mammalian target of the rapamycin (mTOR) pathway, which exerts anti-inflammatory influence. Moreover, pBD-1 gene overexpression decreased (p < 0.05) the TNF-α level stimulated by LPS in IPEC-J2 cells (4.22 ± 1.64). The present study indicated that l-arginine enhanced disease resistance through inhibiting the TLR4/NF-κB and MAPK pathways and partially, possibly through increasing the intestinal β-defensin expression.

Cytokine response after stimulation of culture cells by zinc and probiotic strain

Intestinal porcine epithelial cells were used for an in vitro analysis of mRNA expression levels of inflammatory cytokines (IL-8, IL-18) and transcriptional factors (MyD88 and NF-κβ). Cells were exposed to inorganic and organic zinc sources (in two different concentrations-50 μmol/L and 100 μmol/L) alone or combined with Lactobacillus reuteri B6/1, which was also applied individually. The total exposure time was 4 h. Quantitative reverse transcriptase PCR was used to determine expression levels of the aforementioned parameters. In general, upregulation was observed; however, a decrease of some mRNA's abundance was also determined. Differences in expression were analysed statistically using ANOVA and Tukey analyses. High relative expression was shown for IL-8, IL-18 and MyD88 in groups treated with 100 μmol/L of inorganic sources of zinc (ZnSO₄) (p < 0.05), while groups treated with the organic form did not exhibit significant changes in expression. Also, 50 μmol/L of either zinc source did not significantly modify the transcriptional profile of the cytokines and transcription factors, showing that even inorganic sources, at lower concentrations, do not elicit a significant inflammatory reaction. In summary, supplementation of organic zinc source (Gly-Zn chelate) ensures that IL-8, IL-18, MyD88 and NF-κβ expression levels are not positively regulated. In contrast, inorganic sources of zinc (ZnSO₄) could induce an inflammatory reaction. However, this response could be dampened if L. reuteri B6/1 is administered, showing the helpful aspect of using probiotics to modulate an inflammatory response. Conclusively, the use Gly-Zn chelate appears as an optimal alternative for Zn administration that does not compromise normal intestinal homeostasis.

L-Arginine Inhibited Inflammatory Response and Oxidative Stress Induced by Lipopolysaccharide via Arginase-1 Signaling in IPEC-J2 Cells

This study aimed to explore the effect of L-arginine on lipopolysaccharide (LPS)-induced inflammatory response and oxidative stress in IPEC-2 cells. We found that the expression of toll-like receptor 4 (TLR4), myeloid differentiation primary response 88 (MyD88), cluster of differentiation 14 (CD14), nuclear factor-kappaBp65 (NF-κBp65), chemokine-8 (IL-8), tumor necrosis factor (TNF-α) and chemokine-6 (IL-6) mRNA were significantly increased by LPS. Exposure to LPS induced oxidative stress as reactive oxygen species (ROS) and malonaldehyde (MDA) production were increased while glutathione peroxidase (GSH-Px) were decreased in LPS-treated cells compared to those in the control. LPS administration also effectively induced cell growth inhibition through induction of G0/G1 cell cycle arrest. However, compared with the LPS group, cells co-treatment with L-arginine effectively increased cell viability and promoted the cell cycle into the S phase; L-arginine exhibited an anti-inflammatory effect in alleviating inflammation induced by LPS by reducing the abundance of TLR4, MyD88, CD14, NF-κBp65, and IL-8 transcripts. Cells treated with LPS+L-arginine significantly enhanced the content of GSH-Px, while they decreased the production of ROS and MDA compared with the LPS group. Furthermore, L-arginine increased the activity of arginase-1 (Arg-1), while Arg-1 inhibitor abolished the protection of arginine against LPS-induced inflammation and oxidative stress. Taken together, these results suggested that L-arginine exerted its anti-inflammatory and antioxidant effects to protect IPEC-J2 cells from inflammatory response and oxidative stress challenged by LPS at least partly via the Arg-1 signaling pathway.

Transcriptomic insights into the early host-pathogen interaction of cat intestine with Toxoplasma gondii

Background

Although sexual reproduction of the parasite Toxoplasma gondii exclusively occurs in the cat intestine, knowledge about the alteration of gene expression in the intestine of cats infected with T. gondii is still limited. Here, we investigated the temporal transcriptional changes that occur in the cat intestine during T. gondii infection.

Methods

Cats were infected with 100 T. gondii cysts and their intestines were collected at 6, 12, 18, 24, 72 and 96 hours post-infection (hpi). RNA sequencing (RNA-Seq) Illumina technology was used to gain insight into the spectrum of genes that are differentially expressed due to infection. Quantitative RT-PCR (qRT-PCR) was also used to validate the level of expression of a set of differentially expressed genes (DEGs) obtained by sequencing.

Results

Our transcriptome analysis revealed 2363 DEGs that were clustered into six unique patterns of gene expression across all the time points after infection. Our analysis revealed 56, 184, 404, 508, 400 and 811 DEGs in infected intestines compared to uninfected controls at 6, 12, 18, 24, 72 and 96 hpi, respectively. RNA-Seq results were confirmed by qRT-PCR. DEGs were mainly enriched in catalytic activity and metabolic process based on gene ontology enrichment analysis. Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that transcriptional changes in the intestine of infected cats evolve over the course of infection, and the largest difference in the enriched pathways was observed at 96 hpi. The anti-T. gondii defense response of the feline host was mediated by Major Histocompatibility Complex class I, proteasomes, heat-shock proteins and fatty acid binding proteins.

Conclusions

This study revealed novel host factors, which may be critical for the successful establishment of an intracellular niche during T. gondii infection in the definitive feline host.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-3179-8) contains supplementary material, which is available to authorized users.

Chemokines and Chemokine Receptors as Therapeutic Targets in Inflammatory Bowel Disease; Pitfalls and Promise

The principal targets for anti-chemokine therapy in inflammatory bowel disease (IBD) have been the receptors CCR9 and CXCR3 and their respective ligands CCL25 and CXCL10. More recently CCR6 and its ligand CCL20 have also received attention, the expression of the latter in enterocytes being manipulated through Smad7 signalling. These pathways, selected based on their fundamental role in regulating mucosal immunity, have led to the development of several therapeutic candidates that have been tested in early phase clinical trials with variable clinical efficacy. In this article, we appraise the status of chemokine-directed therapy in IBD, review recent developments, and nominate future areas for therapeutic focus.

Involvement of CRF2 signaling in enterocyte differentiation

AIM

To determine the role of corticotropin releasing factor receptor (CRF2) in epithelial permeability and enterocyte cell differentiation.

METHODS

For this purpose, we used rat Sprague Dawley and various colon carcinoma cell lines (SW620, HCT8R, HT-29 and Caco-2 cell lines). Expression of CRF2 protein was analyzed by fluorescent immunolabeling in normal rat colon and then by western blot in dissociated colonic epithelial cells and in the lysates of colon carcinoma cell lines or during the early differentiation of HT-29 cells (ten first days). To assess the impact of CRF2 signaling on colonic cell differentiation, HT-29 and Caco-2 cells were exposed to Urocortin 3 recombinant proteins (Ucn3, 100 nmol/L). In some experiments, cells were pre-exposed to the astressin 2b (A2b) a CRF2 antagonist in order to inhibit the action of Ucn3. Intestinal cell differentiation was first analyzed by functional assays: the trans-cellular permeability and the para-cellular permeability were determined by Dextran-FITC intake and measure of the transepithelial electrical resistance respectively. Morphological modifications associated to epithelial dysfunction were analyzed by confocal microscopy after fluorescent labeling of actin (phaloidin-TRITC) and intercellular adhesion proteins such as E-cadherin, p120ctn, occludin and ZO-1. The establishment of mature adherens junctions (AJ) was monitored by following the distribution of AJ proteins in lipid raft fractions, after separation of cell lysates on sucrose gradients. Finally, the mRNA and the protein expression levels of characteristic markers of intestinal epithelial cell (IEC) differentiation such as the transcriptional factor krüppel-like factor 4 (KLF4) or the dipeptidyl peptidase IV (DPPIV) were performed by RT-PCR and western blot respectively. The specific activities of DPPIV and alkaline phosphatase (AP) enzymes were determined by a colorimetric method.

RESULTS

CRF2 protein is preferentially expressed in undifferentiated epithelial cells from the crypts of colon and in human colon carcinoma cell lines. Furthermore, CRF2 expression is down regulated according to the kinetic of HT-29 cell differentiation. By performing functional assays, we found that Ucn3-induced CRF2 signaling alters both para- and trans-cellular permeability of differentiated HT-29 and Caco-2 cells. These effects are partly mediated by Ucn3-induced morphological changes associated with the disruption of mature AJ in HT-29 cells and tight junctions (TJ) in Caco-2 cells. Ucn3-mediated activation of CRF2 decreases mRNA and protein expression levels of KLF4 a transcription factor involved in IEC differentiation. This signaling is correlated to a down-regulation of key IEC markers such as DPPIV and AP, at both transcriptional and post-transcriptional levels.

CONCLUSION

Our findings suggest that CRF2 signaling could modulate IEC differentiation. These mechanisms could be relevant to the stress induced epithelial alterations found in inflammatory bowel diseases.

CCL20 Is Negatively Regulated by TGF-β1 in Intestinal Epithelial Cells and Reduced in Crohn's Disease Patients With a Successful Response to Mongersen, a Smad7 Antisense Oligonucleotide

BACKGROUND AND AIMS

The chemokine CCL20 is over-produced in epithelium of Crohn's disease [CD] patients and contributes to recruiting immune cells to inflamed gut. Tumour necrosis factor-α [TNF-α] is a powerful inducer of CCL20 in intestinal epithelial cells. In CD, high levels of Smad7 block the activity of transforming growth factor-β1 [TGF-β1], a negative regulator of TNF signalling. We investigated whether intestinal epithelial cell-derived CCL20 is negatively regulated by TGF-β1 and whether Smad7 knock-down reduces CCL20 in CD.

METHODS

CCL20 was evaluated in NCM460, a normal colonic epithelial cell line, stimulated with TGF-β1 and TNF-α, and in Smad7 over-expressing NCM460 cells. CCL20 and Smad7 expression were assessed in sections of CD intestinal specimens by immunochemistry, and in CD colonic explants treated with mongersen, a Smad7 antisense oligonucleotide. CCL20 was examined in serum samples taken from 95 of 166 active CD patients receiving mongersen or placebo for 2 weeks and participating in a phase II, multicentre, double-blind, placebo-controlled study.

RESULTS

CCL20 expression was increased by TNF-α, and this effect was inhibited by TGF-β1 in NCM460 cells, but not in Smad7 over-expressing NCM460 cells. In CD, epithelium CCL20 and Smad7 co-localised, and treatment of CD explants with mongersen reduced CCL20 production. During follow-up, in responders to mongersen, serum CCL20 levels significantly decreased, whereas patients without response/remission to mongersen and placebo patients did not have change in CCL20.

CONCLUSIONS

TGF-β1 reduces intestinal epithelial cell-derived CCL20 production, an effect abrogated by Smad7. CD patients responding to mongersen demonstrated a reduction in serum CCL20.

Immunohistochemical characterization of Toll-like receptor 2 in gut epithelial cells and macrophages of goldfish Carassius auratus fed with a high-cholesterol diet

Toll-like receptors (TLRs) are a group of pattern recognition molecules that play a crucial role in innate immunity. The structural conservation of the archaic TLR system suggests that the regulation of the immune response might be similar in fish and mammals. Several TLRs (TLR-1, -2, and -4) are expressed by activated macrophages, "foam cells" in human atherosclerotic lesions. To date, 20 different TLRs were identified in more than a dozen different fish species. In this study we found that feeding goldfish, Carrassius auratus, a high-cholesterol diet (HCD) resulted macrophage foam cell formation in the intestinal tissues. The expression of TLR2 has been found in foam cells and in the cytoplasm of enterocytes, however the staining was more intense at the apical surface of polarized intestinal epithelial cells and in the lamina propria. In the intestinal epithelial cells and in the lamina propria cells of the control fish the TLR2 was expressed at low levels. The intestinal epithelium is directly involved in the mucosal immune response through its expression of proinflammatory genes, release of inflammatory cytokines, and recruitment of inflammatory cells.

Interleukin-34 Induces Cc-chemokine Ligand 20 in Gut Epithelial Cells

BACKGROUND AND AIM

Production of chemokines by intestinal epithelial cells is a key step in the amplification of the destructive immune-inflammatory response in patients with inflammatory bowel diseases [IBD]. In this study, we examined whether intestinal epithelial cells express macrophage colony-stimulating factor receptor 1 [M-CSFR-1], the functional receptor of interleukin-34 [IL-34], a cytokine that is over-produced in IBD and supposed to sustain inflammatory pathways.

METHODS

M-CSFR-1 expression was evaluated in intestinal samples of IBD patients, controls, and colon epithelial cell lines by real-time polymerase chain reaction [PCR], immunohistochemistry, and western blotting. DLD-1 cells were stimulated with IL-34 in the presence or absence of MAP kinase inhibitors, chemokine induction was assessed by real-time PCR and enzyme-linked immunosorbent assay [ELISA], and mitogen-activated protein (MAP) kinase activation was monitored by western blotting. The effect of a neutralising IL-34 antibody on CC chemokine ligand (CCL) 20 synthesis was tested in ex vivo organ cultures of IBD mucosal explants.

RESULTS

Enhanced expression of M-CSFR-1 RNA transcripts was seen in inflamed mucosa of IBD patients as compared with controls. Immunohistochemical analysis confirmed up-regulation of M-CSFR-1 in IBD and showed that both epithelial and lamina propria mononuclear cells expressed this receptor. Stimulation of DLD-1 with IL-34 increased CCL20 production through an ERK1/2-dependent mechanism. Consistently, treatment of IBD explants with anti-IL-34 reduced CCL20 production.

CONCLUSIONS

These data show that intestinal epithelial cells are a target of IL-34 and suggest that this cytokine contributes to mediating the cross-talk between epithelial cells and immune cells in IBD.

Intestinal barrier function and the brain-gut axis

The luminal-mucosal interface of the intestinal tract is the first relevant location where microorganism-derived antigens and all other potentially immunogenic particles face the scrutiny of the powerful mammalian immune system. Upon regular functioning conditions, the intestinal barrier is able to effectively prevent most environmental and external antigens to interact openly with the numerous and versatile elements that compose the mucosal-associated immune system. This evolutionary super system is capable of processing an astonishing amount of antigens and non-immunogenic particles, approximately 100 tons in one individual lifetime, only considering food-derived components. Most important, to develop oral tolerance and proper active immune responses needed to prevent disease and inflammation, this giant immunogenic load has to be managed in a way that physiological inflammatory balance is constantly preserved. Adequate functioning of the intestinal barrier involves local and distant regulatory networks integrating the so-called brain-gut axis. Along this complex axis both brain and gut structures participate in the processing and execution of response signals to external and internal changes coming from the digestive tract, using multidirectional pathways to communicate. Dysfunction of brain-gut axis facilitates malfunctioning of the intestinal barrier, and vice versa, increasing the risk of uncontrolled immunological reactions that may trigger mucosal and brain low-grade inflammation, a putative first step to the initiation of more permanent gut disorders. In this chapter, we describe the structure, function and interactions of intestinal barrier, microbiota and brain-gut axis in both healthy and pathological conditions.

The gut barrier: new acquisitions and therapeutic approaches

The intestinal barrier serves 2 critical functions for the survival of the individual: first, it allows nutrient absorption and second, it defends the body from dangerous macromolecule penetration. It is a complex multilayer system, consisting of an external "anatomic" barrier and an inner "functional" immunological barrier. The interaction of these 2 barriers enables equilibrated permeability to be maintained. Many factors can alter this balance: gut microflora modifications, mucus layer alterations, and epithelial damage can increase intestinal permeability, allowing the translocation of luminal content to the inner layer of intestinal wall. Several techniques are now available that enable us to study gut permeability: "in vitro" models (Caco-2 and HT29-MTX cells) and "in vivo" not invasive tests (sugar tests and radioisotope scanning tests) are used to estimate permeability and to suggest molecular pathophysiological mechanisms of intestinal permeability in health and diseases. Many medicinal products used in the treatment of gastrointestinal diseases have also found to play an active role in modulate intestinal permeability: corticosteroids, 5-aminosalicylic acid, anti-tumor necrosis factor, probiotics, and mucosal protectors, like gelatin tannate. This review will particularly address the role of the gut barrier in maintaining intestinal permeability (microbiota, mucus, and epithelial cells), the techniques used for estimating intestinal permeability and the therapeutic approaches able to modify it.

Cloning and functional characterization of rat stimulator of interferon genes (STING) regulated by miR-24

Stimulator of interferon (IFN) genes (STING), also known as MPYS/MITA/ERIS/TMEM173, is a recently discovered adaptor protein that functions downstream of RIG-I and upstream of TBK1 and plays an important role in type I interferon (IFN) production. Mammalian STINGs have been isolated from human, mouse, pig, cattle and chimpanzee. In this study, the rat STING cDNA was cloned by degenerate PCR and rapid amplification of 3'-cDNA ends (3'-RACE) strategies. The full-length cDNA of rat STING consists of 1615 bp with a 1140-bp open reading frame (ORF). The predicted protein is composed of 379 amino acids and contains 2 putative transmembrane domains. The amino acid similarities between the STING from rat and other mammals range from 68% to 82%. Real-time quantitative PCR analysis indicated that rat STING mRNA was most abundant in the spleen, pancreas and lymph node. Overexpression of rat STING led to upregulation of IFN-β mRNA expression in IEC-6 cells. Rat STING mRNA was up-regulated when IEC-6 cells were transfected with poly (I:C). In addition, a miR-24 binding site in the 3'UTR of rat STING was identified. We also found that endogenous STING could be regulated post-transcriptionally by miR-24 in IEC-6 cells. These results are of importance to reveal the biological function of STING in rat animal model.

Comparative tight junction protein expressions in colonic Crohn's disease, ulcerative colitis, and tuberculosis: a new perspective

We intended to see the pattern of TJ protein expression along with ultrastructural changes in colonic biopsies from patients with Crohn's disease (CD), ulcerative colitis (UC), and tuberculosis (cTB). Colonic biopsies from 11 patients with active CD and ten patients each with active UC and untreated cTB were taken along with biopsies from six patients with irritable bowel syndrome as controls. These were evaluated for expression pattern of key TJ proteins which included claudin-2 as TJ pore-forming protein, claudin-4 as pore-sealing protein, ZO-1 as scaffold protein, and occludin as TJ protein related to cell migration and polarity. Claudin-2 expression was upregulated along the whole length of intercellular junction (ICJ) in biopsies from patients with active CD and UC in comparison to the biopsies from cTB patients and controls, where its expression was limited to the uppermost part of ICJ. There was reduced expression of ZO-1 in UC, CD, and cTB. On transmission electron microscopic examination, the pentalaminar structure of TJs was destroyed in patients with CD and UC but no significant change was seen in those with cTB and in controls. The expression of claudin-2 was distinctly different in active CD and UC in comparison to its expression pattern in patients with cTB and in controls. The redistribution of claudin-2 expression was in accordance with the TJ ultrastructural changes in patients with UC, CD, and cTB. Altered claudin-2 expression, along with destroyed TJs, may result in loss of selective permeability in patients with UC and CD.

Lactobacillus acidophilus induces cytokine and chemokine production via NF-κB and p38 mitogen-activated protein kinase signaling pathways in intestinal epithelial cells

Intestinal epithelial cells can respond to certain bacteria by producing an array of cytokines and chemokines which are associated with host immune responses. Lactobacillus acidophilus NCFM is a characterized probiotic, originally isolated from human feces. This study aimed to test the ability of L. acidophilus NCFM to stimulate cytokine and chemokine production in intestinal epithelial cells and to elucidate the mechanisms involved in their upregulation. In experiments using intestinal epithelial cell lines and mouse models, we observed that L. acidophilus NCFM could rapidly but transiently upregulate a number of effector genes encoding cytokines and chemokines such as interleukin 1α (IL-1α), IL-1β, CCL2, and CCL20 and that cytokines showed lower expression levels with L. acidophilus NCFM treatment than chemokines. Moreover, L. acidophilus NCFM could activate a pathogen-associated molecular pattern receptor, Toll-like receptor 2 (TLR2), in intestinal epithelial cell lines. The phosphorylation of NF-κB p65 and p38 mitogen-activated protein kinase (MAPK) in intestinal epithelial cell lines was also enhanced by L. acidophilus NCFM. Furthermore, inhibitors of NF-κB (pyrrolidine dithiocarbamate [PDTC]) and p38 MAPK (SB203580) significantly reduced cytokine and chemokine production in the intestinal epithelial cell lines stimulated by L. acidophilus NCFM, suggesting that both NF-κB and p38 MAPK signaling pathways were important for the production of cytokines and chemokines induced by L. acidophilus NCFM.

Molecular cloning and functional characterization of Tibetan Porcine STING

Tibetan pig is well known for its strong disease resistance. However, little is known about the molecular basis of its strong resistance to disease. Stimulator of interferon (IFN) genes (STING), also known as MPYS/MITA/ERIS/TMEM173, is an adaptor that functions downstream of RIG-I and MAVS and upstream of TBK1 and plays a critical role in type I IFN induction. Here we report the first cloning and characterization of STING gene from Tibetan pig. The entire open reading frame (ORF) of the Tibetan porcine STING is 1137 bp, with a higher degree of sequence similarity with Landrace pig (98%) and cattle (88%) than with chimpanzee (84%), human (83%) or mouse (77%). The predicted protein is composed of 378 amino acids and has 4 putative transmembrane domains. Real-time quantitative PCR analysis indicated that Tibetan pig STING mRNA was most abundant in the lung and heart. Overexpression of Tibetan porcine STING led to upregulation of IFN-β and IFN-stimulated gene 15 (ISG15) in porcine jejunal epithelial cell line IPEC-J2 cells. This is the first study investigating the biological role of STING in intestinal epithelial cells, which lays a foundation for the further study of STING in intestinal innate immunity.

Hymenolepis diminuta: analysis of the expression of Toll-like receptor genes (TLR2 and TLR4) in the small and large intestines of rats

Toll receptors play a critical role in the rapid activation of innate immune responses to a variety of pathogens. In mammals, Toll-like receptors (TLR) have been found in both immune related cells and other cells. At present little is known about the participation of TLR in host defense mechanisms during parasitic infections. The aim of this study was to determine the expression of TLR2 and TLR4 genes in rat intestines during experimental hymenolepidosis. There is difference in expression of TLR2 and TLR4 genes in the colon and jejunum in uninfected rats: in the colon, mRNA of the examined TLR is present in much higher amounts than the jejunum, while the protein of the TLR also had a segmented specific distribution. In the jejunum isolated rats infected with Hymeolepis diminuta 6 and 8 days post infection (dpi), mRNA for TLR4 and TLR2 were significantly more strongly expressed in comparison with the uninfected controls. In the colon, a statistically significantly increased expression of TLR4 gene was observed only at 6 dpi, and at 8 dpi for the TLR2 gene. Moreover, we observed that during inflammation, the immunopositive cell number and the intensity of immunohistochemical staining (indicating the presence of TLR within intestinal epithelial cells), increased together with the duration of the infection period.

The signaling networks of the herpesvirus entry mediator (TNFRSF14) in immune regulation

The tumor necrosis factor (TNF) receptor superfamily member herpesvirus entry mediator (HVEM) (TNFRSF14) regulates T-cell immune responses by activating both inflammatory and inhibitory signaling pathways. HVEM acts as both a receptor for the canonical TNF-related ligands, LIGHT [lymphotoxin-like, exhibits inducible expression, and competes with herpes simplex virus glycoprotein D for HVEM, a receptor expressed on T lymphocytes] and lymphotoxin-α, and as a ligand for the immunoglobulin superfamily proteins BTLA (B and T lymphocyte attenuator) and CD160, a feature distinguishing HVEM from other immune regulatory molecules. The ability of HVEM to interact with multiple ligands in distinct configurations creates a functionally diverse set of intrinsic and bidirectional signaling pathways that control both inflammatory and inhibitory responses. The HVEM system is integrated into the larger LTβR and TNFR network through extensive shared ligand and receptor usage. Experimental mouse models and human diseases indicate that dysregulation of HVEM network may contribute to autoimmune pathogenesis, making it an attractive target for drug intervention.

Effects of Ganoderma lucidum polysaccharides on IEC-6 cell proliferation, migration and morphology of differentiation benefiting intestinal epithelium healing in vitro

OBJECTIVES

Restoration of epithelial continuity in the intestinal surface after extensive destruction is important since intestinal epithelial cells stand as a boundary between the body's internal and external environment. Polysaccharides from Ganoderma lucidum (Gl-PS) may benefit intestinal epithelial wound healing in different aspects, which awaits clarification. To identify potential effects, a non-transformed small-intestinal epithelial cell line, IEC-6 cells, was used.

METHODS

Effects on epithelial cell proliferation, migration, morphology of differentiation and transforming growth factor beta (TGF-β) protein expression, as well as the cellular ornithine decarboxylase (ODC) mRNA and c-Myc mRNA expression, were assessed, respectively, by MTT assay, wound model in vitro, observation under a microscope after hematoxylin and eosin staining, enzyme-linked immunosorbent assay and reverse transcription-polymerase chain reaction assays.

KEY FINDINGS

It was shown that Gl-PS stimulated IEC-6 cell proliferation and migration significantly in a dose-dependent manner; 10 µg/ml Gl-PS improved the morphology of differentiation in IEC-6 cells. Inefficacy in expression of TGF-β in IEC-6 cells indicated a possible TGF-β independent action of Gl-PS. However, Gl-PS increased ODC mRNA and c-Myc mRNA expression in a dose-dependent manner, indicating, at least partially possible involvement of ODC and c-Myc gene expression in improvement of intestinal wound healing.

CONCLUSIONS

These results suggest the potential usefulness of Gl-PS to cure intestinal disorders characterized by injury and ineffective repair of the intestinal mucosa.

Regulation of inflammation, autoimmunity, and infection immunity by HVEM-BTLA signaling

The HVEM, or TNFRSF14, is a membrane-bound receptor known to activate the NF-κB pathway, leading to the induction of proinflammatory and cell survival-promoting genes. HVEM binds several ligands that are capable of mediating costimulatory pathways, predominantly through its interaction with LIGHT (TNFSF14). However, it can also mediate coinhibitory effects, predominantly by interacting with IGSF members, BTLA or CD160. Therefore, it can function like a "molecular switch" for various activating or inhibitory functions. Furthermore, recent studies suggest the existence of bidirectional signaling with HVEM acting as a ligand for signaling through BTLA, which may act as a ligand in other contexts. Bidirectional signaling, together with new information indicating signaling in cis by cells that coexpress HVEM and its ligands, makes signaling within a HVEM-mediated network complicated, although potentially rich in biology. Accumulating in vivo evidence has shown that HVEM-mediated, coinhibitory signaling may be dominant over HVEM-mediated costimulatory signaling. In several disease models the absence of HVEM-BTLA signaling predominantly resulted in severe mucosal inflammation in the gut and lung, autoimmune-like disease, and impaired immunity during bacterial infection. Here, we will summarize the current view about how HVEM-BTLA signaling is involved in the regulation of mucosal inflammation, autoimmunity, and infection immunity.

Intestinal epithelial cells in inflammatory bowel diseases

The pathogenesis of inflammatory bowel diseases (IBDs) seems to involve a primary defect in one or more of the elements responsible for the maintenance of intestinal homeostasis and oral tolerance. The most important element is represented by the intestinal barrier, a complex system formed mostly by intestinal epithelial cells (IECs). IECs have an active role in producing mucus and regulating its composition; they provide a physical barrier capable of controlling antigen traffic through the intestinal mucosa. At the same time, they are able to play the role of non-professional antigen presenting cells, by processing and presenting antigens directly to the cells of the intestinal immune system. On the other hand, immune cells regulate epithelial growth and differentiation, producing a continuous bi-directional cross-talk within the barrier. Several alterations of the barrier function have been identified in IBD, starting from mucus features up to its components, from epithelial junctions up to the Toll-like receptors, and altered immune responses. It remains to be understood whether these defects are primary causes of epithelial damage or secondary effects. We review the possible role of the epithelial barrier and particularly describe the role of IECs in the pathogenesis of IBD.

Lactobacillus acidophilus induces a slow but more sustained chemokine and cytokine response in naïve foetal enterocytes compared to commensal Escherichia coli

BACKGROUND

The first exposure to microorganisms at mucosal surfaces is critical for immune maturation and gut health. Facultative anaerobic bacteria are the first to colonise the infant gut, and the impact of these bacteria on intestinal epithelial cells (IEC) may be determinant for how the immune system subsequently tolerates gut bacteria.

RESULTS

To mirror the influence of the very first bacterial stimuli on infant IEC, we isolated IEC from mouse foetuses at gestational day 19 and from germfree neonates. IEC were stimulated with gut-derived bacteria, Gram-negative Escherichia coli Nissle and Gram-positive Lactobacillus acidophilus NCFM, and expression of genes important for immune regulation was measured together with cytokine production. E. coli Nissle and L. acidophilus NCFM strongly induced chemokines and cytokines, but with different kinetics, and only E. coli Nissle induced down-regulation of Toll-like receptor 4 and up-regulation of Toll-like receptor 2. The sensitivity to stimulation was similar before and after birth in germ-free IEC, although Toll-like receptor 2 expression was higher before birth than immediately after.

CONCLUSIONS

In conclusion, IEC isolated before gut colonisation occurs at birth, are highly responsive to stimulation with gut commensals, with L. acidophilus NCFM inducing a slower, but more sustained response than E. coli Nissle. E. coli may induce intestinal tolerance through very rapid up-regulation of chemokine and cytokine genes and down-regulation of Toll-like receptor 4, while regulating also responsiveness to Gram-positive bacteria.

Early response of mucosal epithelial cells during Toxoplasma gondii infection

The innate immune response of mucosal epithelial cells during pathogen invasion plays a central role in immune regulation in the gut. Toxoplasma gondii is a protozoan intracellular parasite that is usually transmitted through oral infection. Although much of the information on immunity to T. gondii has come from i.p. infection models, more recent studies have revealed the importance of studying immunity following infection through the natural peroral route. Oral infection studies have identified many of the key players in the intestinal response; however, they have relied on responses detected days to weeks following infection. Much less is known about how the gut epithelial layer senses and reacts during initial contact with the pathogen. Given the importance of epithelial cells during pathogen invasion, this study uses an in vitro approach to isolate the key players and examine the early response of intestinal epithelial cells during infection by T. gondii. We show that human intestinal epithelial cells infected with T. gondii elicit rapid MAPK phosphorylation, NF-kappaB nuclear translocation, and secretion of IL-8. Both ERK1/2 activation and IL-8 secretion responses were shown to be MyD88 dependent and TLR2 was identified to be involved in the recognition of the parasite regardless of the parasite genotype. Furthermore, we were able to identify additional T. gondii-regulated genes in the infected cells using a pathway-focused array. Together, our findings suggest that intestinal epithelial cells were able to recognize T. gondii during infection, and the outcome is important for modulating intestinal immune responses.

T cells, dendritic cells and epithelial cells in intestinal homeostasis

The mucosal immune system of the intestinal tract is continuously exposed to both potential pathogens and beneficial commensal microorganism. A variety of mechanisms contribute to the ability of the gut to either react or remain tolerant to antigen present in the intestinal lumen. Antigens of the gut commensals are not simply ignored, but rather trigger an active immunosuppressive process, which prevents the outcome of immunopathology. The aim of this review is to provide an update on the mechanism of intestinal homeostasis, with particular focus on the complex crosstalk between T cells, dendritic cells and intestinal epithelial cells.

Regulating the mucosal immune system: the contrasting roles of LIGHT, HVEM, and their various partners

LIGHT and herpes virus entry mediator (HVEM) comprise a ligand-receptor pair in the tumor necrosis factor superfamily. These molecules play an important role in regulating immunity, particularly in the intestinal mucosa. LIGHT also binds the lymphotoxin beta receptor, and HVEM can act as a ligand for immunoglobulin family molecules, including B- and T-lymphocyte attenuator, which suppresses immune responses. Complexity in this pivotal system arises from several factors, including the non-monogamous pairing of ligands and receptors, and reverse signaling or the ability of some ligands to serve as receptors. As a result, recognition events in this fascinating network of interacting molecules can have pro- or anti-inflammatory consequences. Despite complexity, experiments we and others are carrying out are establishing rules for understanding when and in what cell types these molecules contribute to intestinal inflammation.

Differential proteomic analysis of HT29 Cl.16E and intestinal epithelial cells by LC ESI/QTOF mass spectrometry

Intestinal epithelial cells (IECs) play a key role in Crohn's disease, a chronic inflammatory bowel disease which requires invasive examinations to be diagnosed. The comparison of the cellular protein expression profiles of Crohn's disease patients and healthy subjects is fundamental for the identification of proteins clinically relevant as new biomarkers or as drug targets. For this purpose a differential label-free nano-LC ESI/QTOF mass spectrometry (MS) approach combined with targeted MS/MS analysis has been developed and applied to isolated IECs. We report here a study of the protein variations in IECs from healthy subjects (H) and Crohn's disease patients (CD). The method was previously validated using HT29 Cl.16E cell line, normal or treated with interferon-gamma as a model of inflammation. Subcellular fractions proteins were extracted from HT29 and IECs and for each fraction monodimensional gel-electrophoresis was performed and the proteins subjected to tryptic digestion. The resulting peptides were analysed by LC ESI/QTOF MS and the obtained chromatographic runs were aligned with msInspect software. The peptides differently expressed were statistically evaluated using the Proteios Software Environment (ProSE) and identified by LC ESI/QTOF MS/MS analysis and database search. The preliminary results obtained allowed the identification of many proteins involved in the inflammation processes.

Expression of a splice variant of CXCR3 in Crohn's disease patients; indication for a lymphocyte--epithelial cell interaction

BACKGROUND AND AIM

T-lymphocyte migration is implicated in the pathogenesis of Crohn's disease (CD) and ulcerative colitis (UC). CXC chemokines MIG, IP-10, and I-TAC act by binding to CXCR3 receptor on T-lymphocytes. We investigated the role of these chemokines and their receptor in patients with UC, CD, and normal controls (NC).

METHODS

Chemokine expression and serum levels were examined in colonic biopsies from patients and NC using reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay. HT-29 and Caco2 colonic epithelial cells were studied following in vitro stimulation with proinflammatory (Th1) and Th2-derived cytokines. CXCR3 receptor expression was assessed in CD3+ peripheral blood lymphocytes (PBL) from patients and NC and in stimulated Jurkat leukaemia cells, using RT-PCR and flow cytometry.

RESULTS

Full size CXCR3 mRNA (FS) expression was found in CD3+ PBL from controls and UC, but not from CD patients. In contrast, CD3+ PBL from CD patients showed a marked mRNA expression of the spliced variant CXCR3 (TV). This finding explains the high expression of CXCR3 on CD3+ PBL from CD patients in flow cytometry. Increased chemokine expression and production was found in colonic biopsies and serum from CD compared to UC patients and controls. Stimulation of epithelial cells with proinflammatory cytokines significantly induced chemokine production. The addition of Th2 cytokines had an inhibitory effect. Stimulation of Jurkat cells with cytokines and supernatant conditioned media from epithelial cells induced CXCR3TV expression.

CONCLUSIONS

These data demonstrate that PBL from CD patients express a spliced variant of the CXCR3 receptor and suggest a role for the colonic epithelial cells in T-lymphocyte migration in intestinal inflammation.

Maladaptive intestinal epithelial responses to life stress may predispose healthy women to gut mucosal inflammation

BACKGROUND & AIMS

Irritable bowel syndrome (IBS), a highly prevalent disorder among women, has been associated with life stress, but the peripheral mechanisms involved remain largely unexplored.

METHODS

A 20-cm jejunal segment perfusion was performed in 2 groups of young healthy women, equilibrated by menstrual phase, experiencing either low (LS; n = 13) or moderate background stress (MS; n = 11). Intestinal effluents were collected every 15 minutes, for 30 minutes under basal conditions, and for 1 hour after cold pain stress. Cardiovascular and psychological response, changes in circulating stress and gonadal hormones, and epithelial function (net water flux, albumin output and luminal release of tryptase and alpha-defensins) to cold stress were determined.

RESULTS

Cold pain induced a psychological response stronger in the MS than in the LS group, but similar increases in heart rate, blood pressure, adrenocorticotrophic hormone, and cortisol, whereas estradiol and progesterone remained unaltered. Notably, the jejunal epithelium of MS females showed a chloride-related decrease in peak secretory response (Delta[15-0 minutes]: LS, 97.5 [68.4-135.0]; MS, 48.8 [36.6-65.0] microL/min/cm; P < .001) combined with a marked enhancement of albumin permeability (LS(AUC), 6.35 [0.9-9.6]; MS(AUC), 13.97 [8.3-23.1] mg/60 min; P = .008) after cold stress. Epithelial response in both groups was associated with similar increases in luminal tryptase and alpha-defensins release.

CONCLUSIONS

Increased exposure to life events determines a defective jejunal epithelial response to incoming stimuli. This abnormal response may represent an initial step in the development of prolonged mucosal dysfunction, a finding that could be linked to enhanced susceptibility for IBS.

A crucial role for HVEM and BTLA in preventing intestinal inflammation

The interaction between the tumor necrosis factor (TNF) family member LIGHT and the TNF family receptor herpes virus entry mediator (HVEM) co-stimulates T cells and promotes inflammation. However, HVEM also triggers inhibitory signals by acting as a ligand that binds to B and T lymphocyte attenuator (BTLA), an immunoglobulin super family member. The contribution of HVEM interacting with these two binding partners in inflammatory processes remains unknown. In this study, we investigated the role of HVEM in the development of colitis induced by the transfer of CD4(+)CD45RB(high) T cells into recombination activating gene (Rag)(-/-) mice. Although the absence of HVEM on the donor T cells led to a slight decrease in pathogenesis, surprisingly, the absence of HVEM in the Rag(-/-) recipients led to the opposite effect, a dramatic acceleration of intestinal inflammation. Furthermore, the critical role of HVEM in preventing colitis acceleration mainly involved HVEM expression by radioresistant cells in the Rag(-/-) recipients interacting with BTLA. Our experiments emphasize the antiinflammatory role of HVEM and the importance of HVEM expression by innate immune cells in preventing runaway inflammation in the intestine.

Mapping specific adhesive interactions on living human intestinal epithelial cells with atomic force microscopy

Specific molecular-receptor interactions with gut epithelium cells are important in understanding bioactivity of food components and drugs, binding of commensal microflora, attachment and initiation of defense mechanisms against pathogenic bacteria and for development of targeted delivery systems to the gut. However, methods for probing such interactions are lacking. Methodology has been developed and validated to measure specific molecular-receptor interactions on living human colorectal cancer cells as in vitro models for the gut epithelium. Atomic force microscopy (AFM) was used to measure ligand-receptor interactions and to map receptor locations on cell surfaces. Measurements were made using silica beads attached to the AFM tip-cantilever assembly, which were functionalized by coupling of ligands to the bead surface. Wheat germ agglutinin (WGA) binds to the glycosylated extracellular domain III of the epidermal growth factor receptor. Methodology was tested by measuring binding of WGA to the surface of confluent monolayers of living Caco-2 human intestinal epithelial cells. The measured modal detachment force of 125 pN is typical of values expected for single molecule interactions. Adhesive events were used to map the location of binding sites on the cell surface revealing heterogeneity in their distribution within and between cells within the monolayer.

Understanding the susceptibility of the premature infant to necrotizing enterocolitis (NEC)

Necrotizing enterocolitis (NEC) is the most common life-threatening gastrointestinal emergency encountered in the neonatal intensive care unit. Despite advances in neonatal care, NEC remains a leading cause of morbidity and mortality among premature infants. Epidemiologic studies have identified multiple factors that increase an infant's risk for the development of NEC, although premature birth, bacterial colonization, and enteral feeding are thought to play central roles in disease pathogenesis. Appreciating factors that underlie the susceptibility of prematurely born infants to NEC is important for the development of new strategies aimed at the prevention and treatment of disease. In this review, we discuss defense mechanisms in the intestine and discuss how these systems may be insufficient in the prematurely born infant and thereby further contribute to initiation of NEC. In addition, based on a review of the literature, we suggest that, although numerous bacterial and viral pathogens have been associated with NEC, no individual organism is known to be responsible for disease. Finally, we comment on the possible role for probiotics in promoting maturation of intestinal defense mechanisms thereby attenuating or preventing the sequence of events that lead to NEC.

Molecular and cellular basis of microflora-host interactions

Mucosal surfaces represent the main sites in which environmental microorganisms and antigens interact with the host. In particular the intestinal mucosal surfaces are in continuous contact with a heterogeneous population of microorganisms of the endogenous flora and are exposed to food and microbes. As a result, the immune system of the host has to discriminate between pathogenic and commensal microorganisms. This article reviews the types of sentinel cells that continuously sense the environment and coordinate immune defenses as well as the mechanisms of the innate and adaptive immune systems that are activated by bacterial and viral molecular patterns leading to inflammatory, allergic, or regulatory immune response with special emphasis on probiotic bacteria.

Effects of Copper Source and Level on Intestinal Physiology and Growth of Broiler Chickens

Dietary copper sulfate (CuSO4) and tribasic copper chloride (TBCC) were examined for their effects on intestinal physiology and growth of broiler chickens. In 2 experiments (Experiments 1 and 2), day-old broiler chicks were fed 1 of 4 diets: a basal diet with no supplemental copper (Cu; negative control), a basal diet + 188 mg of Cu/kg of diet from TBCC or CuSO4, or a basal diet + subtherapeutic antibiotics (bacitracin and roxarsone; positive control). In Experiment 1 (recycled litter), CuSO4 and TBCC increased carcass weight (d 45 posthatch) compared with the negative control (P < 0.05 for each). In Experiment 2 (fresh litter), negative control and TBCC increased carcass weight (d 42 posthatch) compared with the positive control (P < 0.05 for each). At d 30 to 31 posthatch, intestinal histology was measured. In Experiment 1 (recycled litter), dietary TBCC, CuSO4, and positive control decreased the number of lamina propia lymphocytes or intraepithelial lymphocytes (IEL), or both, compared with the negative control (P < 0.05). However, in Experiment 2 (fresh litter), TBCC and positive control increased the number of duodenum IEL compared with the negative control (P < 0.05), and negative control and TBCC increased the number of ileum IEL. These data demonstrate that broiler performance and intestinal physiology can be influenced by dietary Cu source and level as well as microbial environment (fresh vs. recycled litter).