Multifunctional role of dextran sulfate sodium for in vivo modeling of intestinal diseases

Fmo5 plays a sex-specific role in goblet cell maturation and mucus barrier formation

The intestine plays a key role in metabolism, nutrient and water absorption, and provides both physical and immunological defense against dietary and luminal antigens. The protective mucus lining in the intestine is a critical component of intestinal barrier function that when compromised, can lead to dysfunctional intestinal barriers that are a defining characteristic of inflammatory bowel disease (IBD), among other intestinal diseases. Here, we define a new role for the flavin-containing monooxygenase family of enzymes in maintaining a healthy intestinal epithelium. In nematodes, we find that Cefmo-2 is necessary and sufficient for proper intestinal barrier function, intestinal actin expression, and is induced by intestinal damage. In mice, we utilize an intestine-specific, inducible knockout model of the prevalent gut Fmo (Fmo5) and find striking phenotypes within two weeks of knockout. These phenotypes include sex-dependent changes in colon epithelial histology, goblet cell localization and maturation factors, and mucus barrier formation. Each of these changes are significantly more severe in female mice, plausibly mirroring differences observed in some types of IBD in humans. Looking further at these phenotypes, we find increased protein folding stress in Fmo5 knockout animals and successfully rescue the severe female phenotype with addition of a chemical ER chaperone. Together, our results identify a new role for Fmo5 in the mammalian intestine and support a key role for Fmo5 in maintenance of ER/protein homeostasis and proper mucus barrier formation.

Detection of Intestinal Inflammation by Vascular Adhesion Protein-1-Targeted [68Ga]Ga-DOTA-Siglec-9 Positron Emission Tomography in Murine Models of Inflammatory Bowel Disease

PURPOSE

Inflammatory bowel disease (IBD) can be imaged with positron emission tomography (PET), but existing PET radiopharmaceuticals have limited diagnostic accuracy. Vascular adhesion protein-1 (VAP-1) is an endothelial cell surface molecule that controls leukocyte extravasation into sites of inflammation. However, the role of inflammation-induced VAP-1 expression in IBD is still unclear. Therefore, this study investigated the utility of VAP-1-targeted [68Ga]Ga-DOTA-Siglec-9 positron emission tomography/computed tomography (PET/CT) for assessing inflammation in two mouse models of IBD.

PROCEDURES

Studies were performed using K8-/- mice that develop a chronic colitis-phenotype and C57Bl/6NCrl mice with acute intestinal inflammation chemically-induced using 2.5% dextran sodium sulfate (DSS) in drinking water. In both diseased and control mice, uptake of the VAP-1-targeting peptide [68Ga]Ga-DOTA-Siglec-9 was assessed in intestinal regions of interest using in vivo PET/CT, after which ex vivo gamma counting, digital autoradiography, and histopathological analyses were performed. Immunofluorescence staining was performed to determine VAP-1-expression in the intestine, including in samples from patients with ulcerative colitis.

RESULTS

Intestinal inflammation could be visualized by [68Ga]Ga-DOTA-Siglec-9 PET/CT in two murine models of IBD. In both models, the in vivo PET/CT and ex vivo studies of [68Ga]Ga-DOTA-Siglec-9 uptake were significantly higher than in control mice. The in vivo uptake was increased on average 1.4-fold in the DSS model and 2.0-fold in the K8-/- model. Immunofluorescence staining revealed strong expression of VAP-1 in the inflamed intestines of both mice and patients.

CONCLUSIONS

This study suggests that the VAP-1-targeting [68Ga]Ga-DOTA-Siglec-9 PET tracer is a promising tool for non-invasive imaging of intestinal inflammation. Future studies in patients with IBD and evaluation of the potential value of [68Ga]Ga-DOTA-Siglec-9 in diagnosis and monitoring of the disease are warranted.

Protective effect of traditional Korean fermented soybean foods (doenjang) on a dextran sulfate sodium-induced colitis mouse model

Objective: The cause of ulcerative colitis (UC) is unknown, and the use of anti-inflammatory and immunosuppressive drugs with certain side effects is currently replacing treatment. Therefore, it is important to find new healthy foods or ingredients that exhibit potential protective and anti-inflammatory effects on UC. This study investigated the potential protective effect of doenjang on dextran sulfate sodium (DSS)-induced colitis in a mouse model. Materials and methods: Four doenjang samples (TCD21-51-1, TCD21-55-1, TMD21-16-1, and TFD21-1-1) were used. To examine the effects of the four doenjang samples on UC caused by DSS in a mouse model, the clinical symptoms of UC, such as body weight, disease activity index (DAI), and colon macroscopic damage index (CMDI) were analyzed. Moreover, immune-related blood cell counts, serum levels and protein expression of tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6), and nitric oxide (NO) production were measured in DSS-induced UC in mice for analysis. Results: The four doenjang samples increased the colon length shortened by DSS, reduced DAI (diarrhea and hemoccult), CMDI (ulceration, inflammation, and hemorrhage) and the content of immune-related cells in the blood. Moreover, the levels of TNF-α, IL-6, and NO increased by DSS were decreased by doenjang, and tissue damage was significantly reduced. Conclusions: These findings confirmed that doenjang exerts protective effects against UC, suggesting its possible use in developing therapeutic strategies or functional products.

Identification of highly selective type II kinase inhibitors with chiral peptidomimetic tails

Identification of highly selective type II kinase inhibitors is described. Two different chiral peptidomimetic scaffolds were introduced on the tail region of non-selective type II kinase inhibitor GNF-7 to enhance the selectivity. Kinome-wide selectivity profiling analysis showed that type II kinase inhibitor 7a potently inhibited Lck kinase with great selectivity (IC₅₀ of 23.0 nM). It was found that 7a and its derivatives possessed high selectivity for Lck over even structurally conserved all Src family kinases. We also observed that 7a inhibited Lck activation in Jurkat T cells. Moreover, 7a was found to alleviate clinical symptoms in DSS-induced colitis mice. This study provides a novel insight into the design of selective type II kinase inhibitors by adopting chiral peptidomimetic moieties on the tail region.

Homeostasis effects of fermented Maillard reaction products by Lactobacillus gasseri 4M13 in dextran sulfate sodium-induced colitis mice

BACKGROUND

The incidence of inflammatory bowel disease (IBD) continues to increase worldwide. Multiple factors, including diet, loss of the intestinal barrier function, and imbalance of the immune system can cause IBD. A balanced diet is important for maintaining a healthy bowel and preventing IBD from occurring. The effects of probiotic Lactobacillus gasseri-fermented Maillard reaction products (MRPs) prepared by reacting whey protein with galactose on anti-inflammation and intestinal homeostasis were investigated in this study, which compared MPRs and probiotics separately.

RESULTS

In an animal colitis model induced by 2% dextran sulfate sodium (DSS), FWG administration alleviated colon length loss and maintained intestinal immune system homeostasis as reflected by down-regulated interleukin (IL)-6, IL-10, tumor necrosis factor (TNF)-α output, and metallopeptidase-9, and epithelial barrier balance as reflected by up-regulated occludin, E-cadherin, and zonula occludens-1 production in the colon. Furthermore, the expression of splenic cytokines such as IL-6, TNF-α, and IL-10 was up-regulated in the FWG-treated mice in a comparable amount to the control group to ensure the balance of immune responses.

CONCLUSION

This study showed that the use of FWG protects the intestines from colitis caused by DSS and maintains immune balance. FWG increased antioxidant enzyme activity, increased intestinal permeability, and regulated the balance of pro- and anti-inflammatory cytokines in the intestines and spleen. Continued intake of FWG can alleviate IBD symptoms through the preservation of mucosal immune responses, epithelial junction and homeostasis through the regulated splenic cytokines. © 2021 Society of Chemical Industry.

Protective effect of exopolysaccharide fraction from Bacillus subtilis against dextran sulfate sodium-induced colitis through maintenance of intestinal barrier and suppression of inflammatory responses

We previously reported that an exopolysaccharide-enriched fraction from Bacillus subtilis J92 (B-EPS) could improve immune functions by regulating the immunological parameters of IFN-γ-primed macrophages, CD3/CD28-stimulated splenocytes, and in cyclophosphamide-induced immunosuppressed mice. In the present study, we investigated whether B-EPS contributes to the maintenance of intestinal barrier integrity in a dextran sodium sulfate (DSS)-induced colitis mouse model that mimics human inflammatory bowel disease (IBD). B-EPS treatment improved histological characteristics and common features including a high disease activity index (DAI), an increased spleen weight, and colon shortening in DSS-induced colitis. B-EPS also effectively restored intestinal barrier function by modulating tight junction-related proteins (claudin-1, claudin-2, and occludin) and epithelial-mesenchymal transition (EMT) marker proteins (E-cadherin, N-cadherin, and vimentin). Moreover, B-EPS downregulated immune cell infiltration and inflammatory responses including the production of inflammatory cytokines, such as IL-6 and IL-1β, and activation of nuclear factor-kappa B (NF-κB) and signal transducer and activator of transcription 3 (STAT3). Taken together, these results suggest that B-EPS could serve as a functional food ingredient for improving intestinal barrier function and alleviating colonic inflammation in IBD.

Rumex japonicus Houtt. alleviates dextran sulfate sodium-induced colitis by protecting tight junctions in mice

Background

Rumex japonicus Houtt. (RJ) is widely distributed in Korea, Japan, and China. The root of RJ has traditionally been used to treat constipation, jaundice, hematemesis, dysfunctional uterine bleeding, and gastrointestinal diseases. According to recent studies, plants of the genus Rumex have beneficial functionalities such as anti-microbial, antioxidative, and anti-inflammatory effects. Inflammatory bowel disease, including Crohn's disease and ulcerative colitis, is a chronic inflammatory disease characterized by an abnormal immune response and epithelial barrier dysfunction. This study evaluates the protective effect of RJ against dextran sulfate sodium (DSS)-induced colitis.

Methods

Male 8-week-old C57BL/6 N mice were treated with methanolic extract of RJ for 14 days, and DSS-induced groups were administered 2.5% DSS for last 7 days. After sacrifice, the length and weight of the colon were measured, and colon sections were subjected to H&E staining, immunohistochemistry and Western blotting to investigate the changes of inflammatory cytokines, tight junction and apoptosis-related factors.

Results

The colon of DSS-treated mouse was significantly shorter and heavier than the normal mouse. Moreover, DSS exposure induced an increase of tumor necrosis factor-α, interleukin (IL)-1β, IL-6, occludin, zonula occludens-1, p21, p53 and Bcl-2, and decreased the expressions of IL-10, claudin-2 and cleaved caspase-3 in the colon tissue. These DSS-induced changes were inhibited by RJ treatment.

Conclusion

Our results indicate that RJ effectively suppresses DSS-induced colitis by protecting tight junction connections in the colonic tissue. We therefore infer that RJ has the potential as a medicine or ingredient for treating colitis.

Remission Effects of Dietary Soybean Isoflavones on DSS-Induced Murine Colitis and an LPS-Activated Macrophage Cell Line

Inflammatory bowel diseases (IBDs), including ulcerative colitis and Crohn's disease, are chronic disorders of the gastrointestinal tract, although the exact causes of IBD remain unknown. Present treatments for IBDs have poor tolerability and insufficient therapeutic efficacy, thus, alternative therapeutic approaches are required. Soybean-derived isoflavones have multiple bioactivities such as anti-inflammation. However, the low water solubility of soybean isoflavones limits their bioavailability and practical use. Therefore, in order to study the preventive effects of water-soluble soybean isoflavones on colonic inflammatory status, we examined soybean-derived isoflavone glycosides (SIFs) in a dextran sodium sulfate (DSS)-induced murine colitis model and in lipopolysaccharide (LPS)-activated RAW264.7 macrophages. Oral administration of SIF (0.5 w/v%) attenuated DSS-induced colitis in terms of body weight decrease, colon shortening, epithelial apoptosis, histological score, mRNA levels of inflammatory cytokines, and immune cell infiltration in colon tissues. In the in vitro assessment, we observed the inhibitory effects of SIF on the production of nitric oxide and prostaglandin E2, via suppression of inducible nitric oxide synthase and cyclooxygenase-2 expression in RAW264.7 macrophages in response to LPS. Furthermore, we confirmed that the expression of inflammatory cytokines and chemokines were decreased by pre-treatment with SIF in LPS-activated RAW264.7 macrophages. Moreover, we demonstrated that SIF suppressed inflammatory mediators involved in nuclear factor-κB signaling pathway via inhibitory κB kinase phosphorylation and degradation of inhibitory κB. Our results suggested that SIF may be beneficial for the remission of colonic inflammatory status including IBDs.

Mucosal healing progression after acute colitis in mice

BACKGROUND

Mucosal healing has become a therapeutic goal to achieve stable remission in patients with inflammatory bowel diseases. To achieve this objective, overlapping actions of complex cellular processes, such as migration, proliferation, and differentiation, are required. These events are longitudinally and tightly controlled by numerous factors including a wide range of distinct regulatory proteins. However, the sequence of events associated with colon mucosal repair after colitis and the evolution of the luminal content characteristics during this process have been little studied.

AIM

To document the evolution of colon mucosal characteristics during mucosal healing using a mouse model with chemically-induced colitis.

METHODS

C57BL/6 male mice were given 3.5% dextran sodium sulfate (DSS) in drinking water for 5 d. They were euthanized 2 (day 7), 5 (day 10), 8 (day 13), and 23 (day 28) d after DSS removal. The colonic luminal environment and epithelial repair processes during the inflammatory flare and colitis resolution were analyzed with reference to a non-DSS treated control group, euthanized at day 0. Epithelial repair events were assessed histo-morphologically in combination with functional permeability tests, expression of key inflammatory and repairing factors, and evaluation of colon mucosa-adherent microbiota composition by 16S rRNA sequencing.

RESULTS

The maximal intensity of colitis was concomitant with maximal alterations of intestinal barrier function and histological damage associated with goblet cell depletion in colon mucosa. It was recorded 2 d after termination of the DSS-treatment, followed by a progressive return to values similar to those of control mice. Although signs of colitis were severe (inflammatory cell infiltrate, crypt disarray, increased permeability) and associated with colonic luminal alterations (hyperosmolarity, dysbiosis, decrease in short-chain fatty acid content), epithelial healing processes were launched early during the inflammatory flare with increased gene expression of certain key epithelial repair modulators, including transforming growth factor-β, interleukin (Il)-15, Il-22, Il-33, and serum amyloid A. Whereas signs of inflammation progressively diminished, luminal colonic environment alterations and microscopic abnormalities of colon mucosa persisted long after colitis induction.

CONCLUSION

This study shows that colon repair can be initiated in the context of inflamed mucosa associated with alterations of the luminal environment and highlights the longitudinal involvement of key modulators.

Elevated apoptosis impairs epithelial cell turnover and shortens villi in TNF-driven intestinal inflammation

The intestinal epithelial monolayer, at the boundary between microbes and the host immune system, plays an important role in the development of inflammatory bowel disease (IBD), particularly as a target and producer of pro-inflammatory TNF. Chronic overexpression of TNF leads to IBD-like pathology over time, but the mechanisms driving early pathogenesis events are not clear. We studied the epithelial response to inflammation by combining mathematical models with in vivo experimental models resembling acute and chronic TNF-mediated injury. We found significant villus atrophy with increased epithelial cell death along the crypt-villus axis, most dramatically at the villus tips, in both acute and chronic inflammation. In the acute model, we observed overexpression of TNF receptor I in the villus tip rapidly after TNF injection and concurrent with elevated levels of intracellular TNF and rapid shedding at the tip. In the chronic model, sustained villus atrophy was accompanied by a reduction in absolute epithelial cell turnover. Mathematical modelling demonstrated that increased cell apoptosis on the villus body explains the reduction in epithelial cell turnover along the crypt-villus axis observed in chronic inflammation. Cell destruction in the villus was not accompanied by changes in proliferative cell number or division rate within the crypt. Epithelial morphology and immunological changes in the chronic setting suggest a repair response to cell damage although the villus length is not recovered. A better understanding of how this state is further destabilised and results in clinical pathology resembling IBD will help identify suitable pathways for therapeutic intervention.

Active Vaccination With EMMPRIN-Derived Multiple Antigenic Peptide (161-MAP) Reduces Angiogenesis in a Dextran Sodium Sulfate (DSS)-Induced Colitis Model

Ulcerative colitis (UC) is an autoimmune disease that affects the colon and shares many clinical and histological features with the dextran sulfate sodium (DSS)-induced colitis model in mice. Angiogenesis is a critical component in many autoimmune diseases, as well as in the DSS-induced colitis model, and is it partially mediated by EMMPRIN, a multifunctional protein that can induce the expression of both the potent pro-angiogenic vascular endothelial growth factor (VEGF) and matrix metalloproteinases (MMPs). We asked whether targeting EMMPRIN by active vaccination, using a novel, specific epitope in the protein, synthesized as a multiple antigenic peptide (MAP), could trigger beneficial effects in the DSS-induced colitic C57BL/6J mice. Mice were vaccinated with four boost injections (50 μg each) of either 161-MAP coding for the EMMPRIN epitope or the scrambled control peptide (Scr-MAP) emulsified in Freund's adjuvant. We show that male mice that were vaccinated with 161-MAP lost less weight, demonstrated improved disease activity indices (DAI), had reduced colitis histological score, and their colons were longer in comparison to mice vaccinated with the Scr-MAP. The 161-MAP vaccination also reduced serum and colon levels of EMMPRIN, colon concentrations of VEGF, MMP-9, and TGFβ, and vessel density assessed by CD31 staining. A similar effect was observed in female mice vaccinated with 161-MAP, including weight loss, colitis histological score, colon length, colon levels of EMMPRIN and colon concentrations of VEGF. However, for female mice, the changes in DAI values, EMMPRIN serum levels, and MMP-9 and TGFβ colon concentrations did not reach significance. We conclude that our strategy of alleviating autoimmunity in this model through targeting angiogenesis by actively vaccinating against EMMPRIN was successful and efficient in reducing angiogenesis.

Yogurt starter cultures of Streptococcus thermophilus and Lactobacillus bulgaricus ameliorate symptoms and modulate the immune response in a mouse model of dextran sulfate sodium-induced colitis

We investigated the yogurt starter cultures of Lactobacillus bulgaricus 151 and Streptococcus thermophilus MK-10 for their effect on the severity of experimental colitis, lymphocyte profile, and regulatory T-cell response. Colitis was induced in BALB/c mice via the administration of 3.5% dextran sulfate sodium salt (DSS) in drinking water for 6 d. Next, the mice were gavaged intragastrically with an active yogurt cultures (YC) mixture (∼5 × 10⁹ cfu/mouse per day) or saline (vehicle) for 8 d. Mice receiving DSS or saline alone served as positive and negative controls, respectively. The length of the colon, disease activity index, histological scores, myeloperoxidase activity, epithelium-associated microbes, short-chain fatty acid profile, total IgA antibody-forming cells, CD3⁺CD8⁺, CD3⁺CD4⁺, CD3⁺CD4⁺CD25⁺, CD3⁺CD4⁺CD25⁺Foxp3⁺ T-cell subsets, and cytokine profiles (IL-2, IL-4, IL-6, IL-10, IL-17A, IFN-γ, and tumor necrosis factor) were examined after termination of the mice. Feeding mice with YC mixture reduced disease symptoms and modified intestinal microbiota and host inflammatory responsiveness to DSS. We observed limited weight loss and a decreased disease activity index score, lowered myeloperoxidase activity, and somewhat reduced damage of the intestine. The YC mixture upregulated the colon length, increased the amount and diversity of mucosa-associated microbes (enterobacteria, enterococci, and yeast), and decreased the concentration of putrefactive short-chain fatty acids in the cecal contents. It downregulated the input of cytotoxic CD3⁺CD8⁺ T cells and CD3⁺CD4⁺CD25⁺FoxP3⁺ regulatory T cells in Peyer's patches and enhanced CD3⁺CD4⁺CD25⁺ T cells in spleens and CD3⁺CD4⁺CD25⁺FoxP3⁺ cells in peripheral blood mononuclear cells. Simultaneously, IgA antibody-forming cells were downregulated in mesenteric lymph nodes (MLN) and enhanced in spleens (SPL). The cultures mostly enhanced the production of cytokines tested in MLN and SPL, except for IL-6, which was downregulated in MLN. Interleukin-2 and IL-4 were the most upregulated in MLN, whereas IL-10, IL-4, IL-2, IFN-γ, and tumor necrosis factor were most upregulated in SPL. In serum, the YC mixture downregulated IFN-γ and clearly increased IL-2. Based on these results, we recognize the high anti-inflammatory and immunomodulatory potential of the L. bulgaricus 151 and S. thermophilus MK-10 set. The strains possess the ability to modulate the intestinal mucosal and systemic immune system toward both IgA production and induction of regulatory T cells, shifting Th1/Th2 balance.

Chitin protects the gut epithelial barrier in a protochordate model of DSS-induced colitis

The gastrointestinal tract of Ciona intestinalis, a solitary tunicate that siphon-filters water, shares similarities with its mammalian counterpart. The Ciona gut exhibits other features that are unique to protochordates, including certain immune molecules, and other characteristics, e.g. chitin-rich mucus, which appears to be more widespread than considered previously. Exposure of Ciona to dextran sulphate sodium (DSS) induces a colitis-like phenotype similar to that seen in other systems, and is characterized by alteration of epithelial morphology and infiltration of blood cells into lamina propria-like regions. DSS treatment also influences the production and localization of a secreted immune molecule shown previously to co-localize to chitin-rich mucus in the gut. Resistance to DSS is enhanced by exposure to exogenous chitin microparticles, suggesting that endogenous chitin is critical to barrier integrity. Protochordates, such as Ciona, retain basic characteristics found in other more advanced chordates and can inform us of uniquely conserved signals shaping host-microbiota interactions in the absence of adaptive immunity. These simpler model systems may also reveal factors and processes that modulate recovery from colitis, the role gut microbiota play in the onset of the disease, and the rules that help govern the reestablishment and maintenance of gut homeostasis.

In Vivo Models of Inflammatory Bowel Disease and Colitis-Associated Cancer

A single layer of epithelial cells separates luminal antigens from the host immune system throughout the gastrointestinal tract. A breakdown in the integrity of the epithelial barrier can lead to chronic inflammation, which is associated with numerous complications including cancer. Here we describe three experimental protocols to chemically induce acute and chronic inflammatory bowel disease (IBD) symptoms and colitis-associated colorectal cancer (CRC) progression. These in vivo mouse models are based on the induction of damage to the colonic epithelium, resulting in an inflammatory and wound healing response. In addition, we outline colonoscopy procedures to monitor the onset of disease in individual live mice.

The zinc sensing receptor, ZnR/GPR39, triggers metabotropic calcium signalling in colonocytes and regulates occludin recovery in experimental colitis

Impaired epithelial barrier function is a hallmark of inflammatory bowel diseases, such as colitis, contributing to diarrhoea and perpetuating inflammation. We show that the zinc sensing receptor, ZnR/GPR39, triggers intracellular Ca(2+) signalling in colonocytes thereby inducing occludin expression. Moreover, ZnR/GPR39 is essential for epithelial barrier recovery in the dextran sodium sulfate (DSS) ulcerative colitis model. Loss of ZnR/GPR39 results in increased susceptibility to DSS-induced inflammation, owing to low expression of the tight junction protein occludin and impaired epithelial barrier. Recovery of wild-type (WT) mice from the DSS insult was faster than that of ZnR/GPR39 knockout (KO) mice. Enhanced recovery of the epithelial layer and increased crypt regeneration were observed in WT mice compared with ZnR/GPR39 KO, suggesting that ZnR/GPR39 is promoting epithelial barrier integrity following DSS insult. Indeed, cell proliferation and apical expression of occludin, following the DSS-induced epithelial erosion, were increased in WT tissue but not in ZnR/GPR39 KO tissue. Importantly, survival following DSS treatment was higher in WT mice compared with ZnR/GPR39 KO mice. Our results support a direct role for ZnR/GPR39 in promoting epithelial renewal and barrier function following DSS treatment, thereby affecting the severity of the disease. We suggest ZnR/GPR39 as a novel therapeutic target that can improve epithelial barrier function in colitis.This article is part of the themed issue 'Evolution brings Ca(2+) and ATP together to control life and death'.

Protective effect of Rumenic acid rich cow's milk against colitis is associated with the activation of Nrf2 pathway in a murine model

Dietary supplementation with pure cis9, trans11 isomer of Conjugated Linoleic Acid -known as Rumenic Acid (RA)- improves cytoprotective defenses downstream through the activation of nuclear factor-E2-related factor-2(Nrf2). This capability, when Rumenic Acid is consumed in the form of foods, is still unknown. The ability of standard (St) or cow milk naturally-enriched in RA (En) to activate Nrf2 pathway and its impact on dextran sodium sulfate (DSS)-induced colitis was comparatively evaluated. Activity of Nrf2 pathway was investigated in colonic tissue of BALB/c mice, receiving 4-week supplement with skimmed milk (SK), St or St reinforced with pure RA (RSt) providing increasing RA dose (0, 124 or 404mg RA/kg^-1 b.w, respectively). Next, the anti-oxidant/ anti-inflammatory effect produced by St or En treatment (383mg RA/kg^-1 b.w.) was explored. Finally, macroscopic and histomorphologic features of colitis were evaluated in animals challenged with 5% (w/v) DSS, at the end of St or En treatment. Significant activation of Nrf2 pathway is associated with RSt and En intake (P<0.05), but not with SK or En treatment. En pre-treatment offers better protection, in comparison with St, against pro-oxidant, pro-inflammatory signs (P<0.01) and macroscopic signs triggered by DSS. It can be concluded that Nrf2 activation by higher RA amount contained in En is, at least in part, responsible for the improved protection associated with En intake against DSS-induced colitis.

Activation of Epithelial Signal Transducer and Activator of Transcription 1 by Interleukin 28 Controls Mucosal Healing in Mice With Colitis and Is Increased in Mucosa of Patients With Inflammatory Bowel Disease

BACKGROUND & AIMS

We investigated the roles of interleukin 28A (also called IL28A or interferon λ2) in intestinal epithelial cell (IEC) activation, studying its effects in mouse models of inflammatory bowel diseases (IBD) and intestinal mucosal healing.

METHODS

Colitis was induced in C57BL/6JCrl mice (controls), mice with IEC-specific disruption of Stat1 (Stat1IEC-KO), mice with disruption of the interferon λ receptor 1 gene (Il28ra-/-), and mice with disruption of the interferon regulatory factor 3 gene (Irf3-/-), with or without disruption of Irf7 (Irf7-/-). We used high-resolution mini-endoscopy and in vivo imaging methods to assess colitis progression. We used 3-dimensional small intestine and colon organoids, along with RNA-Seq and gene ontology methods, to characterize the effects of IL28 on primary IECs. We studied the effects of IL28 on the human intestinal cancer cell line Caco-2 in a wound-healing assay, and in mice colon wounds. Colonic biopsies and resected tissue from patients with IBD (n = 62) and patients without colon inflammation (controls, n = 23) were analyzed by quantitative polymerase chain rection to measure expression of IL28A, IL28RA, and other related cytokines; biopsy samples were also analyzed by immunofluorescence to identify sources of IL28 production. IECs were isolated from patient tissues and incubated with IL28; signal transducer and activator of transcription 1 (STAT1) phosphorylation was measured by immunoblots and confocal imaging.

RESULTS

Lamina propria cells in colon tissues of patients with IBD, and mice with colitis, had increased expression of IL28 compared with controls; levels of IL28R were increased in the colonic epithelium of patients with IBD and mice with colitis. Administration of IL28 induced phosphorylation of STAT1 in primary human and mouse IECs, increasing with dose. Il28ra-/-, Irf3-/-, Irf3-/-Irf7-/-, as well as Stat1IEC-KO mice, developed more severe colitis after administration of dextran sulfate sodium than control mice, with reduced epithelial restitution. Il28ra-/- and Stat1IEC-KO mice also developed more severe colitis in response to oxazolone than control mice. We found IL28 to induce phosphorylation (activation) of STAT1 in epithelial cells, leading to their proliferation in organoid culture. Administration of IL28 to mice with induced colonic wounds promoted mucosal healing.

CONCLUSIONS

IL28 controls proliferation of IECs in mice with colitis and accelerates mucosal healing by activating STAT1. IL28 might be developed as a therapeutic agent for patients with IBD.

Loss of T-cell protein tyrosine phosphatase in the intestinal epithelium promotes local inflammation by increasing colonic stem cell proliferation

T-cell protein tyrosine phosphatase (TC-PTP) has a critical role in the development of the immune system and has been identified as a negative regulator of inflammation. Single-nucleotide polymorphisms in the TC-PTP locus have been associated with increased susceptibility to inflammatory bowel diseases (IBDs) in patients. To further understand how TC-PTP is related to IBDs, we investigated the role of TC-PTP in maintaining the intestinal epithelial barrier using an in vivo genetic approach. Intestinal epithelial cell (IEC)-specific deletion of TC-PTP was achieved in a mouse model at steady state and in the context of dextran sulphate sodium (DSS)-induced colitis. Knockout (KO) of TC-PTP in IECs did not result in an altered intestinal barrier. However, upon DSS treatment, IEC-specific TC-PTP KO mice displayed a more severe colitis phenotype with a corresponding increase in the immune response and inflammatory cytokine profile. The absence of TC-PTP caused an altered turnover of IECs, which is further explained by the role of the tyrosine phosphatase in colonic stem cell (CoSC) proliferation. Our results suggest a novel role for TC-PTP in regulating the homeostasis of CoSC proliferation. This supports the protective function of TC-PTP against IBDs, independently of its previously demonstrated role in intestinal immunity.

Keratins Are Altered in Intestinal Disease-Related Stress Responses

Keratin (K) intermediate filaments can be divided into type I/type II proteins, which form obligate heteropolymers. Epithelial cells express type I-type II keratin pairs, and K7, K8 (type II) and K18, K19 and K20 (type I) are the primary keratins found in the single-layered intestinal epithelium. Keratins are upregulated during stress in liver, pancreas, lung, kidney and skin, however, little is known about their dynamics in the intestinal stress response. Here, keratin mRNA, protein and phosphorylation levels were studied in response to murine colonic stresses modeling human conditions, and in colorectal cancer HT29 cells. Dextran sulphate sodium (DSS)-colitis was used as a model for intestinal inflammatory stress, which elicited a strong upregulation and widened crypt distribution of K7 and K20. K8 levels were slightly downregulated in acute DSS, while stress-responsive K8 serine-74 phosphorylation (K8 pS74) was increased. By eliminating colonic microflora using antibiotics, K8 pS74 in proliferating cells was significantly increased, together with an upregulation of K8 and K19. In the aging mouse colon, most colonic keratins were upregulated. In vitro, K8, K19 and K8 pS74 levels were increased in response to lipopolysaccharide (LPS)-induced inflammation in HT29 cells. In conclusion, intestinal keratins are differentially and dynamically upregulated and post-translationally modified during stress and recovery.

Molecular mechanisms of regulation of Toll-like receptor signaling

TLRs play a critical role in the detection of microbes and endogenous "alarmins" to initiate host defense, yet they can also contribute to the development and progression of inflammatory and autoimmune diseases. To avoid pathogenic inflammation, TLR signaling is subject to multilayer regulatory control mechanisms, including cooperation with coreceptors, post-translational modifications, cleavage, cellular trafficking, and interactions with negative regulators. Nucleic acid-sensing TLRs are particularly interesting in this regard, as they can both recognize host-derived structures and require internalization of their ligand as a result of intracellular sequestration of the nucleic acid-sensing TLRs. This review summarizes the regulatory mechanisms of TLRs, including regulation of their access to ligands, receptor folding, intracellular trafficking, and post-translational modifications, as well as how altered control mechanism could contribute to inflammatory and autoimmune disorders.

Angelica acutiloba Kitagawa Extract Attenuates DSS-Induced Murine Colitis

We examined the protective effects of Angelica acutiloba Kitagawa (AAK) extract on a murine model of acute experimental colitis. Colitis was induced by 4% dextran sulfate sodium (DSS) in the drinking water of male C57BL/6 mice, for 7 consecutive days. Oral administration of AAK extract (500 mg/kg/day) significantly alleviated DSS-induced symptoms such as anorexia, weight loss, events of diarrhea or bloody stools, and colon shortening. Histological damage was also ameliorated, as evidenced by the architectural preservation and suppression of inflammatory cell infiltration in colonic samples. Treatment improved the colonic mRNA expression of different inflammatory markers: cytokines, inducible enzymes, matrix metalloproteinases, and tight junction-related proteins. In the isolated serum, IgE levels were downregulated. Collectively, these findings indicate the therapeutic potentials of AAK as an effective complementary or alternative modality for the treatment of ulcerative colitis.

Galectin-3 suppresses mucosal inflammation and reduces disease severity in experimental colitis

Galectin-3, a member of the β-galactoside-binding lectin family, expresses in many different immune cells and modulates broad biological functions including cell adhesion, cell activation, cell growth, apoptosis, and inflammation. However, the role of galectin-3 in mucosal immunity or inflammatory bowel diseases is still not clear. We demonstrate here that galectin-3 knockout mice have more severe disease activity in the dextran sulfate sodium (DSS)-induced colitis model, indicating that galectin-3 may protect from inflammation in DSS-induced colitis. Furthermore, treating with galectin-3 reduced body weight loss, shortened colonic length, and ameliorated mucosal inflammation in mice having DSS-induced colitis. However, the protective effects of galectin-3 were eliminated by the administration of anti-CD25 mAb. In addition, primary T cells treated with galectin-3 ex vivo induced the expression of FOXP3, ICOS, and PD-1 with a Treg cell phenotype having a suppression function. Moreover, adoptive transfer of galectin-3-treated T cells reduced bowel inflammation and colitis in the T cell transfer colitis model. In conclusion, our results indicate that galectin-3 inhibited colonic mucosa inflammation and reduced disease severity by inducing regulatory T cells, suggesting that it is a potential therapeutic approach in inflammatory bowel disease.

KEY MESSAGES

Galectin-3 offers protection from inflammation in experimental colitis. Galectin-3 knockout mice have more severe disease activity in DSS-induced colitis. Adoptive transfer of galectin-3-treated T cells reduced bowel inflammation. Galectin-3 inhibited colonic mucosa inflammation by inducing regulatory T cells. Galectin-3 is a potential therapeutic approach in inflammatory bowel disease.

MicroRNA-146a constrains multiple parameters of intestinal immunity and increases susceptibility to DSS colitis

Host-microbial interactions within the mammalian intestines must be properly regulated in order to promote host health and limit disease. Because the microbiota provide constant immunological signals to intestinal tissues, a variety of regulatory mechanisms have evolved to ensure proper immune responses to maintain homeostasis. However, many of the genes that comprise these regulatory pathways, including immune-modulating microRNAs (miRNAs), have not yet been identified or studied in the context of intestinal homeostasis. Here, we investigated the role of microRNA-146a (miR-146a) in regulating intestinal immunity and barrier function and found that this miRNA is expressed in a variety of gut tissues in adult mice. By comparing intestinal gene expression in WT and miR-146a-/- mice, we demonstrate that miR-146a represses a subset of gut barrier and inflammatory genes all within a network of immune-related signaling pathways. We also found that miR-146a restricts the expansion of intestinal T cell populations, including Th17, Tregs, and Tfh cells. GC B cells, Tfh ICOS expression, and the production of luminal IgA were also reduced by miR-146a in the gut. Consistent with an enhanced intestinal barrier, we found that miR-146a-/- mice are resistant to DSS-induced colitis, a model of Ulcerative Colitis (UC), and this correlated with elevated colonic miR-146a expression in human UC patients. Taken together, our data describe a role for miR-146a in constraining intestinal barrier function, a process that alters gut homeostasis and enhances at least some forms of intestinal disease in mice.

Orally Administered Enoxaparin Ameliorates Acute Colitis by Reducing Macrophage-Associated Inflammatory Responses

Inflammatory bowel diseases, such as ulcerative colitis, cause significant morbidity and decreased quality of life. The currently available treatments are not effective in all patients, can be expensive and have potential to cause severe side effects. This prompts the need for new treatment modalities. Enoxaparin, a widely used antithrombotic agent, is reported to possess anti-inflammatory properties and therefore we evaluated its therapeutic potential in a mouse model of colitis. Acute colitis was induced in male C57BL/6 mice by administration of dextran sulfate sodium (DSS). Mice were treated once daily with enoxaparin via oral or intraperitoneal administration and monitored for colitis activities. On termination (day 8), colons were collected for macroscopic evaluation and cytokine measurement, and processed for histology and immunohistochemistry. Oral but not intraperitoneal administration of enoxaparin significantly ameliorated DSS-induced colitis. Oral enoxaparin-treated mice retained their body weight and displayed less diarrhea and fecal blood loss compared to the untreated colitis group. Colon weight in enoxaparin-treated mice was significantly lower, indicating reduced inflammation and edema. Histological examination of untreated colitis mice showed a massive loss of crypt architecture and goblet cells, infiltration of immune cells and the presence of edema, while all aspects of this pathology were alleviated by oral enoxaparin. Reduced number of macrophages in the colon of oral enoxaparin-treated mice was accompanied by decreased levels of pro-inflammatory cytokines. Oral enoxaparin significantly reduces the inflammatory pathology associated with DSS-induced colitis in mice and could therefore represent a novel therapeutic option for the management of ulcerative colitis.

Colon carcinogenesis in wild type and immune compromised mice after treatment with azoxymethane, and azoxymethane with dextran sodium sulfate

The association between inflammation and the risk of colorectal cancer (CRC) is well documented in animal models and in humans, but the mechanistic role of inflammation in CRC is less well understood. To address this question, the induction of colon tumors was evaluated in (i) wild type (WT) and athymic BALB/c mice treated with the colon carcinogen azoxymethane (AOM) as a single agent, and (ii) in an inflammation model of colon cancer employing AOM and dextran sodium sulfate (DSS) in WT, athymic, TCRβ(-/-) , TCRδ(-/-) and TCRβ(-/-) TCRδ(-/-) C57Bl/6 mice. The athymic BALB/c mice treated with only AOM developed 90% fewer tumors than the WT mice. The difference in response was not due to metabolic activation of AOM or repair of DNA adducts. In the inflammation model using a standard sequential exposure to AOM followed by DSS treatment, the tumor incidence in WT mice was 58% with 7 adenomas and 6 adenocarcinomas. In contrast, the TCRβ(-/-) , TCRδ(-/-) and TCRβ(-/-) TCRδ(-/-) C57Bl/6 mice showed adenoma incidences of 10, 33, and 11%, respectively, and none of the immune compromised mice developed adenocarcinomas. When the DSS exposure was increased and the AOM lowered, no difference was observed between WT and TCRβ(-/-) mice due to an increase in the incidence in the TCR null mice without concomitant increase in the WT mice. No tumors were observed in mice treated with AOM or DSS alone. © 2015 Wiley Periodicals, Inc.

Local immune compartments are related to the severity of dextran sodium sulphate induced colitis

Dextran sodium sulphate (DSS) induced colitis is commonly used to simulate human ulcerative colitis (UC). However, the mucosal immune responses related to the severity of disease have not been comprehensively documented. We used different concentration of DSS, induced various severities of colitis, and simultaneously examined the frequency of immune cells, antibodies and cytokine production. We found that T regulatory cells (Tregs), B cells, and IgA secretion increased on the recovery phase of mild colitis, accompanied by CD11b(+) cells, interleukin (IL)-6 and tumor necrosis factor (TNF)-α accumulated mildly. While during severe and irreversible colitis, the CD11b(+) cells, IL-6, and TNF-α infiltrated severely with Tregs, B cells, and IgA increased inconspicuously. These results demonstrate that Tregs, B cells, and IgA may play a significant role in maintaining the homeostasis of gut, by suppressing CD11b(+) cells and the pro-inflammatory cytokines.

The Sasa quelpaertensis Leaf Extract Inhibits the Dextran Sulfate Sodium-induced Mouse Colitis Through Modulation of Antioxidant Enzyme Expression

Background:

Oxidative stress plays an important role in the pathogenesis of inflammatory bowel disease. The objective of this study is to investigate the protective effect of Sasa quelpaertensis leaf extract (SQE) against oxidative stress in mice with dextran sulfate sodium (DSS)-induced colitis.

Methods:

Mice were treated with SQE (100 mg/kg or 300 mg/kg body weight) by gavage in advance two weeks before inflammation was induced. Then, the mice were administered with 2.5% DSS in drinking water for 7 days and normal drinking water for 7 days between two DSS treatment. Disease activity index values, gut motility, and severity of the resulting oxidative DNA damage were analyzed. The antioxidant effect of SQE was evaluated by measuring malondialdehyde (MDA) and superoxide dismutase (SOD) activity in plasma samples. Catalase activity and expressions levels of glutathione peroxidase 1 (Gpx1), SOD1, and SOD2 were also detected in colon tissues.

Results:

Administration of SQE significantly reduced the severity of DSS-induced colitis compared to the control (Ctrl) group. Levels of 8-oxo-dG, an oxidative DNA damage marker, were significantly lower in the SQE group compared to the untreated DSS Ctrl group. In the SQE (300 mg/kg) group, MDA levels were significantly lower, while SOD and catalase activity levels in the plasma samples were significantly higher compared with the DSS Ctrl group. The expression levels of the antioxidant enzymes, SOD2 and Gpx1, were significantly higher, while the levels of SOD 1 expression were lower, in the colon tissues of the DSS Ctrl group compared with those of the Ctrl group. In contrast, administration of SQE significantly down-regulated SOD2 and Gpx1 expressions and up-regulated SOD1 expression.

Conclusions:

These results indicate that SQE efficiently suppresses oxidative stress in DSS-induced colitis in mice, and its action is associated with the regulation of antioxidant enzymes.

Fucoidan Extracts Ameliorate Acute Colitis

Inflammatory bowel diseases (IBD), such as ulcerative colitis and Crohn's disease, are an important cause of morbidity and impact significantly on quality of life. Overall, current treatments do not sustain a long-term clinical remission and are associated with adverse effects, which highlight the need for new treatment options. Fucoidans are complex sulphated, fucose-rich polysaccharides, found in edible brown algae and are described as having multiple bioactivities including potent anti-inflammatory effects. Therefore, the therapeutic potential of two different fucoidan preparations, fucoidan-polyphenol complex (Maritech Synergy) and depyrogenated fucoidan (DPF) was evaluated in the dextran sulphate sodium (DSS) mouse model of acute colitis. Mice were treated once daily over 7 days with fucoidans via oral (Synergy or DPF) or intraperitoneal administration (DPF). Signs and severity of colitis were monitored daily before colons and spleens were collected for macroscopic evaluation, cytokine measurements and histology. Orally administered Synergy and DPF, but not intraperitoneal DPF treatment, significantly ameliorated symptoms of colitis based on retention of body weight, as well as reduced diarrhoea and faecal blood loss, compared to the untreated colitis group. Colon and spleen weight in mice treated with oral fucoidan was also significantly lower, indicating reduced inflammation and oedema. Histological examination of untreated colitis mice confirmed a massive loss of crypt architecture and goblet cells, infiltration of immune cells and oedema, while all aspects of this pathology were alleviated by oral fucoidan. Importantly, in this model, the macroscopic changes induced by oral fucoidan correlated significantly with substantially decreased production of at least 15 pro-inflammatory cytokines by the colon tissue. Overall, oral fucoidan preparations significantly reduce the inflammatory pathology associated with DSS-induced colitis and could therefore represent a novel nutraceutical option for the management of IBD.

Dose titration of FITC-D for optimal measurement of enteric inflammation in broiler chicks

Traditionally, antibiotic growth promoters (AGP) have been used in foodstock animals to reduce enteric inflammation and maintain intestinal homeostasis, thus improving growth and performance. Due to increasing restrictions regarding the use of AGP however, precise and high throughput enteric inflammation models and markers to search for effective alternatives are urgently needed. In this paper, oral administration of fluorescein isothiocyanate dextran (FITC-d, 3-5 kDa) and its passage into blood was used as a marker for tight junction permeability. In experiement 1, broilers were assigned to a control group, a group which received 24 h feed restriction (FR), or a group which received dextran sodium sulfate (DSS) (0.75% in water for 5 d), and each group then underwent an oral gavage of FITC-d 2.5 h before sample collection on d10. FITC-d in serum and intestinal samples (duodenum and ceca) were found to be higher (P<0.05) after FR than in the DSS and control groups. In experiment 2, FR was evaluated for its effect on mucosal leakage and an oral dose of FITC-d of 0.5, 1.1, or 2.2 mg/chick was used to measure the gastrointestinal tract (GIT) permeability at 6 d of age. The amount of FITC-d remaining in the duodenal tissue of the control birds increased with dose, only the 1.1 mg FITC-d/chick dose resulted in differences (P<0.05) between the control and FR groups. No differences were noted between the control and FR groups, regardless of FITC-d dosage in cecal recovery of FITC-d. Additionally, FR increased FITC-d serum levels when compared to the control group and in a dose-dependent manner. Experiment 3 compared serum levels after administration of 0.55 and 1.1 mg/chick doses of FITC-d in birds treated with FR, rye-based diet (RBD), and DSS. Intestinal sections were collected for FITC-d recovery in the 1.1 mg dosage group. All inflammation treatments significantly increased serum FITC-d levels at both doses. Only FR resulted in increased (P<0.05) FITC-d recovery from duodenum, ileum, and ceca. In conclusion, FR, DSS, and RBD affected GIT tight junction integrity, suggesting their value for enteric inflammation models, and FITC-d may be a good indicator of permeability.

T-cells enhance stem cell mutagenesis in the mouse colon

A role of inflammation in the etiology of cancer is attributed to the production of reactive oxygen/nitrogen species that can damage DNA. To test this hypothesis, we determined the mutation frequency (MF) in colonic stem cells in C57Bl/6 mice exposed to azoxymethane (AOM), dextran sulfate sodium (DSS) and a combination of AOM and DSS (AOM+DSS). AOM+DSS efficiently and rapidly produces colon tumors in B6 mice. AOM produces promutagenic O(6)-methylguanine lesions in DNA but does not induce colon tumors in C57Bl/6 mice as a single agent. DSS produces inflammation in the colon but does not produce tumors except upon multiple cycles of treatment in some DNA repair deficient mouse models. In addition, using TCRβ null mice we tested whether α/β T cells have any effect on the colonic stem cell MF in mice treated with AOM, DSS and AOM+DSS. The TCRβ(-/-) mice are devoid of the critical receptor required for normal cytolytic and regulatory α/β T-cell functions. The MF in the untreated and DSS treated WT and TCRβ(-/-) mice was the same (<10(-5)) indicating that DSS and subsequent inflammation does not generate stem cell mutations in mice that are WT for DNA repair. AOM yielded mutant crypts in WT and TCRβ(-/-) mice with MF's of ∼4×10(-4) and 2×10(-4), respectively, which represents a statistically significant decrease in the MF in the immune compromised mice. The combined treatment of AOM+DSS afforded fully mutated crypts in both strains with a statistically significant lower MF in the TCRβ(-/-) mice. In addition, the MF in both strains of mice after the combination of AOM+DSS is lower than observed with AOM alone indicating that DSS inflammation destroyed pre-existing AOM mutated crypts. Using the MF in WT mice, the efficiency for the conversion of promutagenic O(6)-methylguanine lesions into a stem cell mutations was calculated to be ∼0.4%.

Non-invasive assessment of the efficacy of new therapeutics for intestinal pathologies using serial endoscopic imaging of live mice

Animal models of inflammatory bowel disease (IBD) and colorectal cancer (CRC) have provided significant insight into the cell intrinsic and extrinsic mechanisms that contribute to the onset and progression of intestinal diseases. The identification of new molecules that promote these pathologies has led to a flurry of activity focused on the development of potential new therapies to inhibit their function. As a result, various pre-clinical mouse models with an intact immune system and stromal microenvironment are now heavily used. Here we describe three experimental protocols to test the efficacy of new therapeutics in pre-clinical models of (1) acute mucosal damage, (2) chronic colitis and/or colitis-associated colon cancer, and (3) sporadic colorectal cancer. We also outline procedures for serial endoscopic examination that can be used to document the therapeutic response of an individual tumor and to monitor the health of individual mice. These protocols provide complementary experimental platforms to test the effectiveness of therapeutic compounds shown to be well tolerated by mice.

Preconditioning with intravenous colitic cell-free DNA prevents DSS-colitis by altering TLR9-associated gene expression profile

BACKGROUND

Presence of cell-free-circulating DNA (fcDNA) sequences in sera of patients with inflammatory bowel diseases (IBD) is a well-established phenomenon. Potential roles of fcDNA in diagnosis, prognosis and therapy monitoring of chronic inflammatory colonic disorders have already been examined, albeit its actual biological function still remains unclear.

AIMS AND METHODS

In the present experiment, we studied the immunobiological effects of isolated fcDNA of normal and inflammatory origin administered intravenously to mice prior to induction of dextran sulfate sodium (DSS)-colitis. In addition to evaluate the current disease and histological activity, changes of the gene expression profile in isolated lamina propria cells upon TLR9 ligation were assayed.

RESULTS

A single intravenous dose of fcDNA pretreatment with colitic fcDNA exhibited beneficial response concerning the clinical and histological severity of DSS-colitis as compared to effects of normal fcDNA. Pretreatment with colitic fcDNA substantially altered the expression of several TLR9-related and inflammatory cytokine genes in a clinically favorable manner.

CONCLUSIONS

During the process of acute colitis, the subsequent inflammatory environment presumably results in changes of fcDNA with the potential to facilitate the downregulation of inflammation and improvement of regeneration. Thus, preconditioning of mice with colitis-derived fcDNA via TLR9 signaling could exert a tissue-protective effect and influence beneficially the course of DSS-colitis. Elucidating mechanisms of immune response alterations by nucleic acids may provide further insight into the etiology of IBD and develop the basis of novel immunotherapies.

Cyclooxygenase-2 silencing for the treatment of colitis: a combined in vivo strategy based on RNA interference and engineered Escherichia coli

Nonpathogenic-invasive Escherichia coli (InvColi) bacteria are suitable for genetic transfer into mammalian cells and may act as a vehicle for RNA Interference (RNAi) in vivo. Cyclooxygenase-2 (COX-2) is overexpressed in ulcerative colitis (UC) and Crohn's disease (CD), two inflammatory conditions of the colon and small intestine grouped as inflammatory bowel disease (IBD). We engineered InvColi strains for anti-COX-2 RNAi (InvColi(shCOX2)), aiming to investigate the in vivo feasibility of a novel COX-2 silencing strategy in a murine model of colitis induced by dextran sulfate sodium (DSS). Enema administrations of InvColi(shCOX2) in DSS-treated mice led to COX-2 downregulation, colonic mucosa preservation, reduced colitis disease activity index (DAI) and increased mice survival. Moreover, DSS/InvColi(shCOX2)-treated mice showed lower levels of circulating pro-inflammatory cytokines and a reduced colitis-associated shift of gut microbiota. Considering its effectiveness and safety, we propose our InvColi(shCOX2) strategy as a promising tool for molecular therapy in intestinal inflammatory diseases.

The role of CXCR3 in DSS-induced colitis

Inflammatory bowel disease (IBD) is a group of disorders that are characterized by chronic, uncontrolled inflammation in the intestinal mucosa. Although the aetiopathogenesis is poorly understood, it is widely believed that IBD stems from a dysregulated immune response towards otherwise harmless commensal bacteria. Chemokines induce and enhance inflammation through their involvement in cellular trafficking. Reducing or limiting the influx of these proinflammatory cells has previously been demonstrated to attenuate inflammation. CXCR3, a chemokine receptor in the CXC family that binds to CXCL9, CXCL10 and CXCL11, is strongly overexpressed in the intestinal mucosa of IBD patients. We hypothesised that CXCR3 KO mice would have impaired cellular trafficking, thereby reducing the inflammatory insult by proinflammatory cell and attenuating the course of colitis. To investigate the role of CXCR3 in the progression of colitis, the development of dextran sulfate sodium (DSS)-induced colitis was investigated in CXCR3^−/− mice over 9 days. This study demonstrated attenuated DSS-induced colitis in CXCR3^−/− mice at both the macroscopic and microscopic level. Reduced colitis correlated with lower recruitment of neutrophils (p = 0.0018), as well as decreased production of IL-6 (p<0.0001), TNF (p = 0.0038), and IFN-γ (p = 0.0478). Overall, our results suggest that CXCR3 plays an important role in recruiting proinflammatory cells to the colon during colitis and that CXCR3 may be a therapeutic target to reduce the influx of proinflammatory cells in the inflamed colon.

Longitudinal analysis of inflammation and microbiota dynamics in a model of mild chronic dextran sulfate sodium-induced colitis in mice

AIM: To characterize longitudinally the inflammation and the gut microbiota dynamics in a mouse model of dextran sulfate sodium (DSS)-induced colitis.

METHODS: In animal models, the most common method used to trigger colitis is based on the oral administration of the sulfated polysaccharides DSS. The murine DSS colitis model has been widely adopted to induce severe acute, chronic or semi-chronic colitis, and has been validated as an important model for the translation of mice data to human inflammatory bowel disease (IBD). However, it is now clear that models characterized by mild intestinal damage are more accurate for studying the effects of therapeutic agents. For this reason, we have developed a murine model of mild colitis to study longitudinally the inflammation and microbiota dynamics during the intestinal repair processes, and to obtain data suitable to support the recovery of gut microbiota-host homeostasis.

RESULTS: All plasma cytokines evaluated, except IL-17, began to increase (P < 0.05), after 7 d of DSS administration. IL-17 only began to increase 4 d after DSS withdrawal. IL-1β and IL-17 continue to increase during the recovery phase, even when clinical signs of colitis had disappeared. IL-6, IL-10 and IFN-γ reached their maxima 4 d after DSS withdrawal and decreased during the late recovery phase. TNFα reached a peak (a three- fold increase, P < 0.05), after which it slightly decreased, only to increase again close to the end of the recovery phase. DSS administration induced profound and rapid changes in the mice gut microbiota. After 3 d of DSS administration, we observed a major reduction in Bacteroidetes/Prevotella and a corresponding increase in Bacillaceae, with respect to control mice. In particular, Bacteroidetes/Prevotella decreased from a relative abundance of 59.42%-33.05%, while Bacillaceae showed a concomitant increase from 2.77% to 10.52%. Gut microbiota rapidly shifted toward a healthy profile during the recovery phase and returned normal 4 d after DSS withdrawal. Cyclooxygenase 2 expression started to increase 4 d after DSS withdrawal (P < 0.05), when dysbiosis had recovered, and continued to increase during the recovery phase. Taken together, these data indicated that a chronic phase of intestinal inflammation, characterized by the absence of dysbiosis, could be obtained in mice using a single DSS cycle.

CONCLUSION: Dysbiosis contributes to the local and systemic inflammation that occurs in the DSS model of colitis; however, chronic bowel inflammation is maintained even after recovery from dysbiosis.

Pregnane X receptor agonists enhance intestinal epithelial wound healing and repair of the intestinal barrier following the induction of experimental colitis

The intestinal epithelial barrier plays a key role in the maintenance of homeostasis within the gastrointestinal tract. Barrier dysfunction leading to increased epithelial permeability is associated with a number of gastrointestinal disorders including the inflammatory bowel diseases (IBD) - Crohn's disease and ulcerative colitis. It is thought that the increased permeability in patients with IBD may be driven by alterations in the epithelial wound healing response. To this end considerable study has been undertaken to identify signaling pathways that may accelerate intestinal epithelial wound healing and normalize the barrier dysfunction observed in IBD. In the current study we examined the role of the pregnane X receptor (PXR) in modulating the intestinal epithelial wound healing response. Mutations and reduced mucosal expression of the PXR are associated with IBD, and others have reported that PXR agonists can dampen intestinal inflammation. Furthermore, stimulation of the PXR has been associated with increased cell migration and proliferation, two of the key processes involved in wound healing. We hypothesized that PXR agonists would enhance intestinal epithelial repair. Stimulation of Caco-2 intestinal epithelial cells with rifaximin, rifampicin and SR12813, all potent agonists of the PXR, significantly increased wound closure. This effect was driven by p38 MAP kinase-dependent cell migration, and occurred in the absence of cell proliferation. Treating mice with a rodent specific PXR agonist, pregnenolone 16α-carbonitrile (PCN), attenuated the intestinal barrier dysfunction observed in the dextran sulphate sodium (DSS) model of experimental colitis, an effect that occurred independent of the known anti-inflammatory effects of PCN. Taken together our data indicate that the activation of the PXR can enhance intestinal epithelial repair and suggest that targeting the PXR may help to normalize intestinal barrier dysfunction observed in patients with IBD. Furthermore, our data provide additional insight into the potential mechanisms through which rifaximin elicits its clinical efficacy in the treatment of IBD.

Oleuropein protects against dextran sodium sulfate-induced chronic colitis in mice

The anti-inflammatory effect of oleuropein (1), the major phenolic secoiridoid in Olea europaea, was evaluated in an experimental model of chronic colitis in mice. Animals were exposed to four repeated cycles of dextran sodium sulfate in drinking water followed by a 7-day rest period. Animals receiving a standard diet supplemented with 0.25% of 1 (equivalent to 500 mg/kg/day) for 56 days exhibited a decrease of inflammatory symptoms, as reflected by improvement of disease activity index and histopathological changes. It was found that 1 decreased inflammatory cell recruitment and the release of inflammatory cytokines interleukin (IL)-1β and IL-6 with increased IL-10 levels in colon tissue. Colon expression of cyclooxygenase-2 and inducible nitric oxide synthase was reduced significantly by 1. The anti-inflammatory molecular mechanism of 1 was associated with the suppression of the phosphorylation of p38 mitogen-activated protein kinase and might be mediated by up-regulation of annexin A1. In addition, 1 ameliorated intestinal wound healing in IEC-18 monolayers. Therefore, oleuropein seems to be a promising active molecule in experimental ulcerative colitis.