IL-33 alleviates DSS-induced chronic colitis in C57BL/6 mice colon lamina propria by suppressing Th17 cell response as well as Th1 cell response

The role of Interleukin-38 in modulating T cells in chronic Colitis: A mouse model study

BACKGROUND

Interleukin (IL)-38 belongs to the IL-36 subfamily within the IL-1 family. Patients with inflammatory bowel diseases (IBD) exhibit higher levels of IL-38 in their intestinal tissue compared to healthy controls, suggesting that IL-38 may play a role in the pathogenesis of IBD. However, IL-38's impact on T cell-mediated immune responses in gastrointestinal inflammation has not been investigated. Therefore, the objective of this work was to elucidate the role of IL-38 in modulating T cells in a mouse model of dextran sulfate sodium (DSS)-induced chronic colitis.

METHODS

Recombinant IL-38 (rIL-38) was administered intraperitoneally (i.p.) to mice with chronic colitis induced by DSS. Clinical symptoms, length of colon, and histologic alterations were assessed. Cytokine production was quantified using ELISA, and helper T (Th) cell subsets were evaluated via flow cytometry.

RESULTS

Administration of recombinant IL-38 (rIL-38) alleviated DSS-induced chronic colitis. In addition, animals with chronic colitis treated with rIL-38 exhibited a significant decrease in the spontaneous production of inflammatory cytokines by neutrophils in the lamina propria. Furthermore, rIL-38 treatment increased the absolute numbers and percentages of regulatory T cells (Tregs) but decreased the absolute numbers and percentages of Th1 and Th17 cells. Moreover, rIL-38 treatment also decreased IL-17A-producing γδT cells substantially.

CONCLUSION

This study's results show that IL-38 reduces the effects of chronic colitis caused by DSS by boosting Treg reactions and reducing Th1/Th17 reactions and IL-17A-producing γδT cells in LPL. Therefore, we propose that IL-38 has the potential to be utilized as a biological therapy agent for IBD.

IL-33's role in the gut immune system: A comprehensive review of its crosstalk and regulation

The intestinal tract is the largest immune organ in the human body, comprising a complex network of immune cells and epithelial cells that perform a variety of functions such as nutrient absorption, digestion, and waste excretion. Maintenance of homeostasis and effective responses to injury in the colonic epithelium are crucial for maintaining homeostasis between these two cell types. The onset and perpetuation of gut inflammation, characterizing inflammatory bowel diseases (IBD), are triggered by constitutive dysregulation of cytokine production. IL-33 is a newly characterized cytokine that has emerged as a critical modulator of inflammatory disorders. IL-33 is constitutively expressed in the nuclei of different cell types such as endothelial, epithelial, and fibroblast-like cells. Upon tissue damage or pathogen encounter, IL-33 is released as an alarmin and signals through a heterodimer receptor that consists of serum Stimulation-2 (ST2) and IL-1 receptor accessory protein (IL-1RAcP). IL-33 has the ability to induce Th2 cytokine production and enhance both Th1 and Th2, as well as Th17 immune responses. Exogenous administration of IL-33 in mice caused pathological changes in most mucosal tissues such as the lung and the gastrointestinal (GI) tract associated with increased production of type 2 cytokines and chemokines. In vivo and in vitro, primary studies have exhibited that IL-33 can activate Th2 cells, mast cells, or basophils to produce type 2 cytokines such as IL-4, IL-5, and IL-13. Moreover, several novel cell populations, collectively referred to as "type 2 innate lymphoid cells," were identified as being IL-33 responsive and are thought to be important for initiating type 2 immunity. Nevertheless, the underlying mechanisms by which IL-33 promotes type 2 immunity in the GI tract remain to be fully understood. Recently, it has been discovered that IL-33 plays important roles in regulatory immune responses. Highly suppressive ST2 + FoxP3+ Tregs subsets regulated by IL-33 were identified in several tissues, including lymphoid organs, gut, lung, and adipose tissues. This review aims to comprehensively summarize the current knowledge on IL-33's role in the gut immune system, its crosstalk, and regulation. The article will provide insights into the potential applications of IL-33-based therapies in the treatment of gut inflammatory disorders.

CD4 T-Cell Subsets and the Pathophysiology of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is an umbrella term for the chronic immune-mediated idiopathic inflammation of the gastrointestinal tract, manifesting as Crohn's disease (CD) or ulcerative colitis (UC). IBD is characterized by exacerbated innate and adaptive immunity in the gut in association with microbiota dysbiosis and the disruption of the intestinal barrier, resulting in increased bacterial exposure. In response to signals from microorganisms and damaged tissue, innate immune cells produce inflammatory cytokines and factors that stimulate T and B cells of the adaptive immune system, and a prominent characteristic of IBD patients is the accumulation of inflammatory T-cells and their proinflammatory-associated cytokines in intestinal tissue. Upon antigen recognition and activation, CD4 T-cells differentiate towards a range of distinct phenotypes: T helper(h)1, Th2, Th9, Th17, Th22, T follicular helper (Tfh), and several types of T-regulatory cells (Treg). T-cells are generated according to and adapt to microenvironmental conditions and participate in a complex network of interactions among other immune cells that modulate the further progression of IBD. This review examines the role of the CD4 T-cells most relevant to IBD, highlighting how these cells adapt to the environment and interact with other cell populations to promote or inhibit the development of IBD.

The Reparative Roles of IL-33

When discovered in the early 2000s, interleukin-33 (IL-33) was characterized as a potent driver of type 2 immunity and implicated in parasite clearance, as well as asthma, allergy, and lung fibrosis. Yet research in other models has since revealed that IL-33 is a highly pleiotropic molecule with diverse functions. These activities are supported by elusive release mechanisms and diverse expression of the IL-33 receptor, STimulation 2 (ST2), on both immune and stromal cells. Interestingly, IL-33 also supports type 1 immune responses during viral and tumor immunity and after allogeneic hematopoietic stem cell transplantation. Yet the IL-33-ST2 axis is also critical to the establishment of systemic homeostasis and tissue repair and regeneration. Despite these recent findings, the mechanisms by which IL-33 governs the balance between immunity and homeostasis or can support both effective repair and pathogenic fibrosis are poorly understood. As such, ongoing research is trying to understand the potential reparative and regulatory versus pro-inflammatory and pro-fibrotic roles for IL-33 in transplantation. This review provides an overview of the emerging regenerative role of IL-33 in organ homeostasis and tissue repair as it relates to transplantation immunology. It also outlines the known impacts of IL-33 in commonly transplanted solid organs and covers the envisioned roles for IL-33 in ischemia-reperfusion injury, rejection, and tolerance. Finally, we give a comprehensive summary of its effects on different cell populations involved in these processes, including ST2 + regulatory T cells, innate lymphoid cell type 2, as well as significant myeloid cell populations.

TDAG51 deficiency attenuates dextran sulfate sodium-induced colitis in mice

Inflammatory bowel disease (IBD), including ulcerative colitis and Crohn's disease, is a group of chronic inflammatory diseases of the gastrointestinal tract. Although the multifactorial etiology of IBD pathogenesis is relatively well documented, the regulatory factors that confer a risk of IBD pathogenesis remain less explored. In this study, we report that T-cell death-associated gene 51 (TDAG51/PHLDA1) is a novel regulator of the development of dextran sulfate sodium (DSS)-induced colitis in mice. TDAG51 expression was elevated in the colon tissues of DSS-induced experimental colitis mice. TDAG51 deficiency protected mice against acute DSS-induced lethality and body weight changes and disease severity. DSS-induced structural damage and mucus secretion in colon tissues were significantly reduced in TDAG51-deficient mice compared with wild-type mice. We observed similar results in a DSS-induced chronic colitis mouse model. Finally, we showed that the production of inflammatory mediators, including proinflammatory enzymes, molecules and cytokines, was decreased in DSS-treated TDAG51-deficient mice compared with DSS-treated wild-type mice. Thus, we demonstrated that TDAG51 deficiency plays a protective role against DSS-induced colitis by decreasing the production of inflammatory mediators in mice. These findings suggest that TDAG51 is a novel regulator of the development of DSS-induced colitis and is a potential therapeutic target for IBD.

Inducing vascular normalization: A promising strategy for immunotherapy

In solid tumors, the vasculature is highly abnormal in structure and function, resulting in the formation of an immunosuppressive tumor microenvironment by limiting immune cells infiltration into tumors. Vascular normalization is receiving much attention as an alternative strategy to anti-angiogenic therapy, and its potential therapeutic targets include signaling pathways, angiogenesis-related genes, and metabolic pathways. Endothelial cells play an important role in the formation of blood vessel structure and function, and their metabolic processes drive blood vessel sprouting in parallel with the control of genetic signals in cancer. The feedback loop between vascular normalization and immunotherapy has been discussed extensively in many reviews. In this review, we summarize the impact of aberrant tumor vascular structure and function on drug delivery, metastasis, and anti-tumor immune responses. In addition, we present evidences for the mutual regulation of immune vasculature. Based on the importance of endothelial metabolism in controlling angiogenesis, we elucidate the crosstalk between endothelial cells and immune cells from the perspective of metabolic pathways and propose that targeting abnormal endothelial metabolism to achieve vascular normalization can be an alternative strategy for cancer treatment, which provides a new theoretical basis for future research on the combination of vascular normalization and immunotherapy.

Early life administration of Bifidobacterium bifidum BD-1 alleviates long-term colitis by remodeling the gut microbiota and promoting intestinal barrier development

Inflammatory bowel disease (IBD) is a chronic intestinal disease characterized by microbiota disturbance and intestinal mucosal damage. The current study aimed to investigate the preventive effects of Bifidobacterium bifidum BD-1 (BD-1) against long-term IBD and possible mechanism by which it alters the gut microbiota, immune response, and mucosal barrier. Our study found that early treatment of BD-1 + Ceftri (ceftriaxone followed by BD-1) and BD-1 confers a certain protective effect against the occurrence of long-term Dextran sulfate sodium-induced colitis, which manifests as a decrease in inflammation scores and MPO activity levels, as well as a relatively intact intestinal epithelial structure. Moreover, compared to BD-1, Ceftri, and NS, early treatment with BD-1 + Ceftri promoted greater expression levels of mucosal barrier-related proteins [KI67, MUC2, ZO-1, secretory immunoglobulin A (slgA), Clauding-1, and Occludin], better local immune responses activation, and moderately better modulation of systemic immune responses during long-term colitis. This may be due to the fact that BD-1 + Ceftri can deliberately prolong the colonization time of some beneficial microbiota (e.g., Bifidobacterium) and reduce the relative abundance of inflammation-related microbiota (e.g., Escherichia/Shigella and Ruminococcus). Interestingly, we found that the changes in the gut barrier and immunity were already present immediately after early intervention with BD-1 + Ceftri, implying that early effects can persist with appropriate intervention. Furthermore, intervention with BD-1 alone in early life confers an anti-inflammatory effect to a certain degree in the long-term, which may be due to the interaction between BD-1 and the host’s native gut microbiota affecting intestinal metabolites. In conclusion, BD-1 was not as effective as BD-1 + Ceftri in early life, perhaps due to its failure to fully play the role of the strain itself under the influence of the host’s complex microbiota. Therefore, further research is needed to explore specific mechanisms for single strain and native microbiota or the combination between probiotics and antibiotics.

The Effects of Sishen Wan on T Cell Responses in Mice Models of Ulcerative Colitis Induced by Dextran Sodium Sulfate

Currently, it is unclear whether Sishen Wan (SSW) could modulate the balance of Th1 cells, Th17 cells, and Tregs and we evaluated the effects of SSW on T cell responses in mice models of ulcerative colitis (UC). The mice models of acute UC (4% dextran sodium sulfate (DSS), 8 days) and chronic UC (3% DSS, 16 days) with SSW were assayed. Colon tissues were collected for immunohistochemical analysis, enzyme linked immunosorbent assay (ELISA), and flow cytometry (FCM). The expressions of cytokines associated with Tregs, transcription factors of Th17 cells, the frequencies of Th1 cells, Th17 cells, and Tregs, and the functional plasticity of Th17 cells were detected. The frequency of IFN-γ⁺ T cells was not changed significantly with SSW treatment in acute DSS. In chronic models, the frequency of IFN-γ⁺ T cells was downregulated with SSW. Meanwhile, the levels of RORγt and the frequency of IL-17A⁺ Th17 cells showed no significant differences after SSW treatment. Despite no significant effect on the transdifferentiation of Th17 cells in chronic UC models, SSW transdifferentiated Th17 cells into IL-10⁺ Th17 cells and downregulated IFN-γ⁺ Th17 cells/IL-10⁺ Th17 cells in acute DSS. Moreover, there were no significant changes of cytokines secreted by Tregs in acute DSS after SSW treatment, but SSW facilitated the expressions of IL-10 and IL-35, as well as development of IL-10⁺ Tregs in chronic DSS. SSW showed depressive effects on the immunoreaction of Th17 cells and might promote the conversion of Th17 cells into IL-10⁺ Th17 cells in acute UC, while it inhibited the excessive reaction of Th1 cells, facilitated the development of Tregs, and enhanced the anti-inflammatory effects in chronic UC.

Detrimental role of IL-33/ST2 pathway sustaining a chronic eosinophil-dependent Th2 inflammatory response, tissue damage and parasite burden during Toxocara canis infection in mice

Toxocariasis is a neglected disease that affects people around the world. Humans become infected by accidental ingestion of eggs containing Toxocara canis infective larvae, which upon reaching the intestine, hatch, penetrate the mucosa and migrate to various tissues such as liver, lungs and brain. Studies have indicated that Th2 response is the main immune defense mechanism against toxocariasis, however, there are still few studies related to this response, mainly the IL-33/ST2 pathway. Some studies have reported an increase in IL-33 during helminth infections, including T. canis. By binding to its ST2 receptor, IL-33 stimulating the Th2 polarized immune cell and cytokine responses. Thus, we aimed to investigate the role of the IL-33/ST2 pathway in the context of T. canis larval migration and the immunological and pathophysiological aspects of the infection in the liver, lungs and brain from Wild-Type (WT) BALB/c background and genetically deficient mice for the ST2 receptor (ST2-/-). The most important findings revealed that the IL-33/ST2 pathway is involved in eosinophilia, hepatic and cerebral parasitic burden, and induces the formation of granulomas related to tissue damage and pulmonary dysfunction. However, ST2-/- mice, the immune response was skewed to Th1/Th17 type than Th2, that enhanced the control of parasite burden related to IgG2a levels, tissue macrophages infiltration and reduced lung dysfunction. Collectively, our results demonstrate that the Th2 immune response triggered by IL-33/ST2 pathway mediates susceptibility to T. canis, related to parasitic burden, eosinophilia and granuloma formation in which consequently contributes to tissue inflammation and injury.

IL-33 is produced by colon fibroblasts and differentially regulated in acute and chronic murine colitis

IL-33 is upregulated in ulcerative colitis and has a protective role in chemically-induced acute murine colitis. We aimed to determine whether IL-33 influences Il10-/- chronic colitis and its cellular source in health and during colitis. Il10-/-Il33-/- and Il10-/-Il33+/+ littermates developed colitis of similar severity. Colon Il33 was induced in WT and Il10-/- mice exposed to DSS, but not in unchallenged Il10-/- mice with colitis. Il33-citrine reporter mice showed that Il33-citrine colocalized with α-smooth muscle actin+ myofibroblasts and vimentin+ fibroblasts in WT mice. Citrine+CD74+CD90hi inflammatory fibroblasts were increased with DSS treatment. IL-1β induced Il33 expression in colon myofibroblasts, but colon Il33 expression did not differ between DSS-treated WT and Il1r1-/- mice. In conclusion, deficiency of IL-33 does not alter the severity of chronic colitis in Il10-/- mice. Induction of Il33 upon DSS exposure in WT and Il10-/- mice, but not in unchallenged Il10-/- mice, suggests epithelial injury induces colon IL-33. Fibroblasts are the primary colonic source of IL-33 and IL-33-expressing CD90hiCD74+ fibroblasts are increased during DSS-induced colitis. IL-1β induces Il33 in colon myofibroblasts in vitro, but signaling through the IL-1R1 is not necessary for induction of IL-33 in DSS-induced colitis.

Cytokine-Mediated Crosstalk between Immune Cells and Epithelial Cells in the Gut

Cytokines are small proteins that are secreted by a vast majority of cell types in the gut. They not only establish cell-to-cell interactions and facilitate cellular signaling, but also regulate both innate and adaptive immune responses, thereby playing a central role in genetic, inflammatory, and infectious diseases of the gut. Both, immune cells and gut epithelial cells, play important roles in intestinal disease development. The epithelium is located in between the mucosal immune system and the gut microbiome. It not only establishes an efficient barrier against gut microbes, but it also signals information from the gut lumen and its composition to the immune cell compartment. Communication across the epithelial cell layer also occurs in the other direction. Intestinal epithelial cells respond to immune cell cytokines and their response influences and shapes the microbial community within the gut lumen. Thus, the epithelium should be seen as a translator or a moderator between the microbiota and the mucosal immune system. Proper communication across the epithelium seems to be a key to gut homeostasis. Indeed, current genome-wide association studies for intestinal disorders have identified several disease susceptibility loci, which map cytokine signatures and their related signaling genes. A thorough understanding of this tightly regulated cytokine signaling network is crucial. The main objective of this review was to shed light on how cytokines can orchestrate epithelial functions such as proliferation, cell death, permeability, microbe interaction, and barrier maintenance, thereby safeguarding host health. In addition, cytokine-mediated therapy for inflammation and cancer are discussed.

The Contradictory Role of Interleukin-33 in Immune Cells and Tumor Immunity

Interleukin (IL)-33 is a member of the IL-1 superfamily and is a crucial cytokine playing the role of a dual-function molecule. IL-33 mediates its function by interacting with its receptor suppression of tumorigenicity 2 (ST2), which is constitutively expressed on T helper (Th)1 cells, Th2 cells, and other immune cells. Previously, we summarized findings on IL-33 and performed an intensive study of the correlation between IL-33 and tumor. IL-33 enables anti-tumor immune responses through Th1 cells and natural killer (NK) cells and plays a role in tumor immune escape in cancers via Th2 cells and regulatory T cells. Herein, we discuss the contradictory role of IL-33 in immune cells in different cancer, and our summaries may be helpful for better understanding of the development of research on IL-33 and tumor immunity.

ILC2 Proliferated by IL-33 Stimulation Alleviates Acute Colitis in Rag1-/- Mouse through Promoting M2 Macrophage Polarization

This study was to identify functions of ILC2, a newly found innate lymphoid cell which mainly locates in mucosa organs like lungs and intestines, in IBD. We injected rIL-33 protein to C57/BL6 mouse to explore how IL-33 induces ILC2 proliferation. The results showed that ILC2 reached a proliferation peak at day 5 and expressed multiple surface markers like CD127, C-kit, CD69, CD44, ST2, CD27, DR3, MHCII, and CD90.2. ILC2 also expressed high quantity of IL-13 and IL-5 and few IL-17A which indicates a potentially immunological function in IBD development. Afterwards, we transferred sort purified ILC2 to Rag1^−/− mouse given DSS to induce acute colitis in order to explore the innate function of ILC2. Data showed that ILC2 alleviates DSS-induced acute innate colitis by repairing epithelial barrier and restore body weight. Furthermore, we found that ILC2 can cause macrophages polarizing to M2 macrophages in the gut. Therefore, we concluded that ILC2 played a therapeutic role in mouse acute colitis.

Immunomodulation of Murine Chronic DSS-Induced Colitis by Tuftsin-Phosphorylcholine

Helminths or their products can immunomodulate the host immune system, and this phenomenon may be applied as the basis of new anti-inflammatory treatments. Previously, we have shown the efficacy of tuftsin-phosphorylcholine (TPC), based on a helminth product, in four animal models of autoimmune diseases: arthritis, colitis, systemic lupus erythematosus, and experimental autoimmune encephalomyelitis. We demonstrated that TPC reduced inflammatory process ex vivo in peripheral blood lymphocytes (PBLs) and in biopsies from giant-cell arteritis. In the present study, we assessed the therapeutic potential of TPC treatment on a chronic colitis murine model. C57BL/6 mice with chronic colitis were treated with TPC after the third cycle of 2% dextran sodium sulfate (DSS). Oral TPC treatment resulted in amelioration of the colitis clinical manifestations exemplified by reduced disease activity index (DAI) score, expansion of mesenteric lymph nodes (MLN) T regulatory cells (shown by Fluorescence Activated Cell Sorting (FACS)), significant reduction in the expression of pro-inflammatory cytokines (IL-1β, IL17, IL-6, TNFα), and elevation in the expression of anti-inflammatory cytokine IL-10 (shown by RT-PCR). This study demonstrated the potential immunomodulatory effects of oral administration of TPC in a chronic colitis murine model. Further clinical trials are needed in order to evaluate this novel approach for the treatment of patients with inflammatory bowel disease.

Retinoid acid induced 16 deficiency aggravates colitis and colitis-associated tumorigenesis in mice

Inflammatory bowel disease (IBD) and colitis-associated colorectal cancer (CAC) is a serious health issue, but etiopathological factors remain unclear. Although some studies reported the roles of Retinoid acid induced 16 (RAI16) in the tumorigenesis of hepatocellular carcinoma and PKA signaling, the roles of RAI16 in IBD and CRC are undressed. RAI16^−/− mice were generated and the roles of RAI16 were addressed in dextran sodium sulfate (DSS) or azoxymethane (AOM)-DSS induced IBD or CAC mouse models, respectively. At first, RAI16^−/− mice were viable, fertile with no apparent defects. Then, it was found that RAI16^−/− mice were more susceptibility to colitis induced by DSS than wild type (WT) littermates, which was evaluated by disease activity index and histological score. Furthermore, the expressions of tissues repair associated molecules Cox2, Ereg and MMP-10 were significantly decreased in RAI16^−/− colon under DSS treatment. Gut barrier related genes including antimicrobial peptides Reg3b and Reg3g and intestinal mucus genes Muc4, Muc6 and Muc20 were reduced in RAI16^−/− colon. These findings indicated that RAI16 may function to affect genes involved in intestinal barrier function and immunoprotective inflammation. Accordingly, RAI16^−/− mice displayed significantly increased tumor burden compared with WT mice assessed in CAC model induced by AOM/DSS. Much more Ki67 + nuclei were observed in RAI16^−/− tumors suggesting RAI16 to be critical in colonic cell proliferation during tumorigenesis. Conclusively, we demonstrate the roles of RAI16 in colonic inflammation and inflammation-associated tumorigenesis by using a novel RAI16^−/− mouse model for the first time.

Dual immune functions of IL-33 in inflammatory bowel disease

Interleukin-33 (IL-33) has emerged as a critical regulator in a variety of diseases, including inflammatory bowel disease (IBD). IL-33 can be produced by various tissues and cells, and typically induces Th2-type immune responses via binding to the receptor ST2. In addition, accumulated data have shown that IL-33 also plays a modulatory role in the function of regulatory T cells (Tregs), B cells, and innate immune cells such as macrophages and innate lymphoid cells (ILCs). IBD, including Crohn's disease and ulcerative colitis, are characterized by aberrant immunological responses leading to intestinal tissue injury and destruction. Although IL-33 expression is increased in IBD patients and correlates with the patients' disease activity index, mechanistic studies to date have demonstrated both pathogenic and protective roles in animal models of experimental colitis. In this review, we will summarize the roles and mechanisms of IL-33 in IBD, which is essential to understand the pathogenesis of IBD and determine potential therapies.

Interleukin-13 and interleukin-33 mRNA are underexpressed in the duodenal mucosa of German Shepherd dogs with chronic enteropathy

BACKGROUND

A recent genome-wide association study in German Shepherd dogs (GSDs) with chronic enteropathy (CE) has identified polymorphisms in the Th2 cytokine genes.

HYPOTHESIS/OBJECTIVE

To determine if the expression of the Th2 cytokines, interleukin-13 (IL-13) and interleukin-33 (IL-33), is altered in the duodenal mucosa of GSDs with CE compared to non-GSDs with CE and healthy dogs.

ANIMALS

Twenty client-owned dogs diagnosed with CE (10 GSDs and 10 non-GSDs) at the Bristol Veterinary School and 8 healthy Beagle dogs from the Iowa State University Service Colony.

METHODS

Retrospective study using archived paraffin-embedded duodenal biopsy samples. A novel RNA in situ hybridization technology (RNAscope) was used to hybridize IL-13 and IL-33 mRNA probes onto at least 10 sections from duodenal biopsy samples for each dog. RNAscope signals were visualized using a microscope and semi-quantitative assessment was performed by a single operator.

RESULTS

Based on duodenal villus, subvillus, epithelial, and lamina propria average expression scores, GSDs with CE had significantly lower IL-13 and IL-33 mRNA expression compared to non-GSDs with CE (IL-13, P < .04; IL-33, P < .02) and healthy Beagle dogs (IL-13, P < .02; IL-33, P < .004).

CONCLUSIONS AND CLINICAL IMPORTANCE

Similar to human patients with ulcerative colitis, a subtype of human inflammatory bowel disease, these data indicate that Th2 cytokines may be involved in the pathogenesis of CE in GSDs.

Chronic colitis induces meninges traffic of gut-derived T cells, unbalances M1 and M2 microglia/macrophage and increases ischemic brain injury in mice

Ischemic stroke is one of the most common diseases leading to death and is the primary cause of physical handicap. Recent studies have reported that chronic colitis increases the risk of ischemic stroke, but it is unknown whether chronic colitis participates in ischemic brain injury directly. A combined mouse model of chronic colitis induced by dextran sodium sulfate (DSS) and ischemic stroke induced by photochemical infarction was used in this study. We demonstrated that chronic colitis significantly increased the infarction volume, activated microglia/macrophage numbers, proliferation of M1 microglia/macrophage, non-gut-derived CD4+ T lymphocyte penetration and decreased neuron numbers in the peri-infarction at 7 d after stroke. Furthermore, gut-derived CD4+ T cell accumulation on the meninges was observed at 7 d after stroke. In addition, selective depletion of meningeal macrophages resulted in a reduction of infarction volume and the non-gut-derived CD4+ T lymphocyte penetration. We concluded that chronic colitis exacerbated ischemic stroke by promoting CD4+ T cell migration from the gut to the meninges and disequilibrium of M1 and M2 microglia/macrophages. We speculated that the gut-derived CD4+ T cells may interact with meningeal macrophages and result in non-gut-derived CD4+ T lymphocyte infiltration that aggravated brain injury in ischemic stroke.

IL-33 Protects Mice against DSS-Induced Chronic Colitis by Increasing Both Regulatory B Cell and Regulatory T Cell Responses as Well as Decreasing Th17 Cell Response

BACKGROUND

Previously, we have reported that IL-33 functioned as a protective modulator in dextran sulfate sodium- (DSS-) induced chronic colitis by suppressing Th17 cell response in colon lamina propria and IL-33 induced both regulatory B cells (Bregs) and regulatory T cells (Tregs) in mesenteric lymph nodes (MLNs) of mice with DSS-induced acute colitis. Moreover, we speculated that IL-33 would promote the Treg or Breg responses leading to the attenuation of DSS-induced chronic colitis. So, we investigated the role of IL-33 on Bregs and Tregs in the MLN of DSS-induced chronic colitis mice.

METHODS

IL-33 was administered by intraperitoneal injection to mice with DSS-induced chronic colitis. Clinical symptoms, colon length, and histological changes were determined. The production of cytokines was measured by ELISA. The T and B cell subsets were measured by flow cytometry. The expression of mRNA of transcription factors was measured by quantitative real-time PCR.

RESULTS

We show that IL-33 treatment increases both Breg and Treg responses in the MLN of mice with DSS-induced chronic colitis. Moreover, IL-33 treatment also decreases Th17 cell response in the MLN of mice with DSS-induced chronic colitis.

CONCLUSION

Our data provide clear evidence that IL-33 plays a protective role in DSS-induced chronic colitis, which is closely related to increasing Breg and Treg responses in the MLN of mice as well as suppressing Th17 cell responses.

Can We Target Endogenous Anti-inflammatory Responses as a Therapeutic Strategy for Inflammatory Bowel Disease?

Inflammatory bowel disease (IBD) describes chronic relapsing remitting inflammation of the gastrointestinal tract including ulcerative colitis and Crohn's disease. The prevalence of IBD is rising across the globe. Despite a growing therapeutic arsenal, current medical treatments are not universally effective, do not induce lasting remission in all, or are accompanied by short- and long-term adverse effects. Therefore, there is a clinical need for novel therapeutic strategies for IBD. Current treatments for IBD mainly manipulate the immune system for therapeutic gain by inhibiting pro-inflammatory activity. There is a robust endogenous immunoregulatory capacity within the repertoire of both innate and adaptive immune responses. An alternative treatment strategy for IBD is to hijack and bolster this endogenous capability for therapeutic gain. This review explores this hypothesis and presents current evidence for this therapeutic direction in immune cell function, cytokine biology, and alternative mechanisms of immunoregulation such as microRNA, oligonucleotides, and the endocannabinoid system.

IL-33 promotes recovery from acute colitis by inducing miR-320 to stimulate epithelial restitution and repair

Defective and/or delayed wound healing has been implicated in the pathogenesis of several chronic inflammatory disorders, including inflammatory bowel disease (IBD). The resolution of inflammation is particularly important in mucosal organs, such as the gut, where restoration of epithelial barrier function is critical to reestablish homeostasis with the interfacing microenvironment. Although IL-33 and its receptor ST2/ILRL1 are known to be increased and associated with IBD, studies using animal models of colitis to address the mechanism have yielded ambiguous results, suggesting both pathogenic and protective functions. Unlike those previously published studies, we focused on the functional role of IL-33/ST2 during an extended (2-wk) recovery period after initial challenge in dextran sodium sulfate (DSS)-induced colitic mice. Our results show that during acute, resolving colitis the normal function of endogenous IL-33 is protection, and the lack of either IL-33 or ST2 impedes the overall recovery process, while exogenous IL-33 administration during recovery dramatically accelerates epithelial restitution and repair, with concomitant improvement of colonic inflammation. Mechanistically, we show that IL-33 stimulates the expression of a network of microRNAs (miRs) in the Caco2 colonic intestinal epithelial cell (IEC) line, especially miR-320, which is increased by >16-fold in IECs isolated from IL-33-treated vs. vehicle-treated DSS colitic mice. Finally, IL-33-dependent in vitro proliferation and wound closure of Caco-2 IECs is significantly abrogated after specific inhibition of miR-320A. Together, our data indicate that during acute, resolving colitis, IL-33/ST2 plays a crucial role in gut mucosal healing by inducing epithelial-derived miR-320 that promotes epithelial repair/restitution and the resolution of inflammation.

Suppression of Th17 Cell Response in the Alleviation of Dextran Sulfate Sodium-Induced Colitis by Ganoderma lucidum Polysaccharides

Background

Ganoderma lucidum polysaccharides (GLP) has anti-inflammatory and immunomodulatory effects. Dysregulated immune responses are involved in the pathogenesis of dextran sulfate sodium (DSS)-induced colitis. The aim of this study was to assess the therapeutic potential of GLP to alleviate DSS-induced colitis.

Methods

The mice were administered with GLP by intragastric gavage daily for two weeks prior to the DSS treatment. Mice were orally administered with 2.5% DSS dissolved in drinking water with GLP or water treatment for 6 days. The mice were killed on day 7 after induction of colitis. Survival rates, body weight loss, colon lengths, histological changes, and disease activity index scores (DAI) were evaluated.

Results

GLP significantly improved survival rates, colon length shortening, body weight loss, histopathological score, and DAI scores in mice with DSS-induced colitis. GLP markedly suppressed the secretions of TNF-α, IL-1β, IL-6, IL-17A, and IL-4 and significantly affected populations of Th17 cells, B cells, NK cells, and NKT cells in the lamina propria lymphocytes.

Conclusions

GLP prevented inflammation, maintained intestinal homeostasis, and regulated the intestinal immunological barrier functions in mice with DSS-induced colitis.

IL-33-induced alternatively activated macrophage attenuates the development of TNBS-induced colitis

Accumulated data have shown that alternatively activated macrophage exerts a modulatory role in many diseases, including colitis. Interleukin-33 (IL-33), a critical modulator in adaptive and innate immune, has been implicated in autoimmunity and inflammation. Previously, we have reported that IL-33 functions as a protective modulator in TNBS-induced colitis, which is closely related to a Th1-to-Th2/Treg switch. Here, we present novel evidence suggesting that IL-33 primes macrophage into alternatively activated macrophages (AAM) in TNBS-induced colitis. The strong polarized effect of IL-33 was tightly associated with the markedly increased induction of Th2-type cytokines. To confirm the beneficial effects of AAM induced by IL-33, peritoneal AAMs isolated from IL-33-treated mice were transferred to recipient mice with TNBS colitis. The adoptive transfer resulted in prominent inhibition of disease activity and inflammatory cytokines in the TNBS-treated mice. In conclusion, our data provide clear evidence that IL-33 plays a protective role in TNBS-induced colitis, which is closely related to AAM polarization.

Angiogenesis for tumor vascular normalization of Endostar on hepatoma 22 tumor-bearing mice is involved in the immune response

Tumor vascular normalization involved in immune response is beneficial to the chemotherapy of tumors. Recombinant human endostatin (Endostar), an angiogenesis inhibitor, has been demonstrated to be effective in hepatocellular cancer (HCC). However, its vascular normalization in HCC and the role of the immune response in angiogenesis were unclear. In the present study, effects of Endostar on tumor vascular normalization were evaluated in hepatoma 22 (H22) tumor-bearing mice. Endostar was able to inhibit the proliferation and infiltration of tumor cells and improve α-fetoprotein, tumor necrosis factor-α and cyclic adenosine 5′-phosphate levels in the serum of H22-bearing mice, as well as the protein expression levels of the immune factors interferon-γ and cluster of differentiation (CD)86 in liver tissue. Endostar also exhibited more marked downregulation of the levels of vascular endothelial growth factor, CD31, matrix metalloproteinase (MMP)-2, MMP-9 and interleukin-17 during day 3–9 treatment, resulting in short-term normalization of tumor blood vessels. The period of vascular normalization was 3–9 days. The results of the present study demonstrated that Endostar was able to induce the period of vascular normalization, contributing to a more efficacious means of HCC treatment combined with other chemotherapy, and this effect was associated with the immune response. It may be concluded that Endostar inhibited immunity-associated angiogenesis behaviors of vascular endothelial cells in response to HCC. The results of the present study provided more reasonable possibility for the combination therapy of Endostar for the treatment of HCC.

Pretreatment with bacterial components promotes DSS-injured colonic epithelial repair through the activation of STAT-3

Bacterial protection and epithelial repair are important against inflammatory bowel disease (IBD). The present study was designed to examine the effects of different bacterial components on the repair of normal and dextran sodium sulfate (DSS)‑treated colonic epithelial cells and the corresponding mechanisms. Human colonic epithelial cells (HT‑29) were pretreated with various doses of LPS or CpG‑dsDNA for 24 h and then treated with or without DSS for another 24 h. The epithelial repair was assessed by video analyses following mechanical injury. The epithelial expression of cluster of differentiation (CD)40 was assayed using flow cytometeric analysis. The production of interleukin (IL)‑6 and tumor necrosis factor (TNF) in the cell culture medium were measured using ELISA. The expression of p38 mitogen‑activated protein kinase (MAPK) and signal transducer and activator of transcription (STAT)‑3 were examined using western blot analysis and reverse transcription‑quantitative polymerase chain reaction analysis. MAPK and STAT‑3 inhibitors were also administrated to observe signaling‑mediated repair. The results showed that pretreatment with lipopolysaccharide (LPS) or CpG‑dsDNA promoted epithelial repair of the DSS‑treated cells. The promoting effects were associated with the downregulation of CD40 molecules, inhibition of the p38 MAPK/TNFα pathway and activation of the STAT3/IL‑6 pathway. The STAT3 inhibitor abrogated the protective effects of LPS and CpG‑dsDNA on wound repair. These results demonstrated that LPS and CpG‑dsDNA induced preadaptation to DSS injury. This preadaptation was accompanied by the activation of STAT‑3. Thus, bacterial components may be used as a strategy for the therapeutic prevention of IBD.

Crosstalk between intestinal epithelial cell and adaptive immune cell in intestinal mucosal immunity

Constantly challenged by luminal bacteria, intestinal epithelium forms both a physical and biochemical defense against pathogens. Besides, intestinal epithelium senses dynamic and continuous changes in luminal environment and transmits signals to subjacent immune cells accordingly. It has been long accepted that adaptive immune cells fulfill their roles partly by modulating function of intestinal epithelial cells. Recent studies have brought up the proposal that intestinal epithelial cells also actively participate in the regulation of adaptive immunity, especially CD4+ adaptive T cells, which indicates that there is reciprocal crosstalk between intestinal epithelial cells and adaptive immune cells, and the crosstalk may play important role in intestinal mucosal immunity. This Review makes a comprehensive summary about crosstalk between intestinal epithelial cells and CD4+ adaptive T cells in intestinal immunity. Special attention would be given to their implications in inflammatory bowel disease pathogenesis and potential therapeutic targets.

Disruption of the TWEAK/Fn14 pathway prevents 5-fluorouracil-induced diarrhea in mice

AIM

To clarify the roles of TWEAK and its receptor Fn14 in 5-fluorouracil (5-FU)-induced diarrhea.

METHODS

Diarrhea was induced in wild-type (WT), Fn14 knockout (KO), and IL-13 receptor (IL-13R)α1 KO BALB/c mice using a single injection of 5-FU. Histological analysis, cytokine analysis, and flow cytometry was performed on ileal tissues and cells. Murine colon carcinoma-bearing mice were co-treated with an anti-TWEAK antibody and 5-FU. Embryonic fibroblast response to cytokines was also analyzed.

RESULTS

5-FU induced high Fn14 expression in epithelial cells. The severity of 5-FU-induced diarrhea was lower in Fn14 KO mice compared with WT mice. Administration of anti-TWEAK antibody reduced 5-FU-induced diarrhea without affecting the antitumor effects of 5-FU in vivo. 5-FU-induced expression of IL-13, IL-17A, TNF-α, and IFN-γ in the ileum was Fn14 dependent. The severity of 5-FU-induced diarrhea was lower in IL-13Rα1 KO mice, indicating major role for IL-13 signaling via IL-13Rα1 in pathogenesis. We found that IL-13Rα2, an IL-13 neutralizing/cell protective receptor, was strongly induced by IL-33 in vitro and in vivo. IL-13Rα2 was upregulated in the ileum of 5-FU-treated Fn14 KO mice. Thus, the deletion of Fn14 upregulated IL-13Rα2 expression, which reduced IL-13 expression and activity.

CONCLUSION

Disruption of the TWEAK/Fn14 pathway affects several interconnected pathways, including those associated with IL-13, IL-33, and IL-13Rα2, to attenuate 5-FU-induced intestinal side effects.

Recent Advances: The Imbalance of Cytokines in the Pathogenesis of Inflammatory Bowel Disease

Cytokines play an important role in the immunopathogenesis of inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis, where they drive and regulate multiple aspects of intestinal inflammation. The imbalance between proinflammatory and anti-inflammatory cytokines that occurs in IBD results in disease progression and tissue damage and limits the resolution of inflammation. Targeting cytokines have been novel strategies in the treatment of IBD. Recent studies show the beneficial effects of anticytokine treatments to IBD patients, and multiple novel cytokines are found to be involved in the pathogenesis of IBD. In this review, we will discuss the recent advances of novel biologics in clinics and clinical trials, and novel proinflammatory and anti-inflammatory cytokines found in IBD with focusing on IL-12 family and IL-1 family members as well as their relevance to the potential therapy of IBD.

Cytokines and intestinal inflammation

PURPOSE OF REVIEW

Cytokines of the intestinal microenvironment largely dictate immunological responses after mucosal insults and the dominance of homeostatic or proinflammatory pathways. This review presents important recent studies on the role of specific cytokines in the pathogenesis of intestinal inflammation.

RECENT FINDINGS

The particular mucosal effects of cytokines depend on their inherent properties but also the cellular origin, type of stimulatory antigens, intermolecular interactions, and the particular immunological milieu. Novel cytokines of the interleukin-1 (IL-1) family, including IL-33 and IL-36, have dominant roles in mucosal immunity, whereas more established ones such as IL-18 are constantly enriched with unique properties. Th17 cells are important mucosal constituents, although their profound plasticity, makes the specific set of cytokines they secrete more important than their mere numbers. Finally, various cytokines, such as tumor necrosis factor-α, IL-6, tumor necrosis factor-like cytokine 1A, and death receptor, 3 demonstrate dichotomous roles with mucosa-protective function in acute injury but proinflammatory effects during chronic inflammation.

SUMMARY

The role of cytokines in mucosal health and disease is increasingly revealed. Such information not only will advance our understanding of the pathogenesis of gut inflammation, but also set the background for development of reliable diagnostic and prognostic biomarkers and cytokine-specific therapies.

Wounds that heal and wounds that don't - The role of the IL-33/ST2 pathway in tissue repair and tumorigenesis

IL-33 is a member of the IL-1 family of cytokines. IL-33 is predominantly located within the nucleus of cells where it plays a role in gene regulation. Given the right combination of signals and cellular damage, stored IL-33 is released from the cell where it can interact with its receptor ST2, triggering danger-associated responses and act as a cellular "alarmin". Whilst IL-33/ST2 signalling has been shown to induce potent pro-inflammatory responses that can be detrimental in certain disease states, a dichotomous, protective role of IL-33 in promoting wound healing has also emerged in multiple tissues types. This review will explore the current literature concerning this homeostatic role of IL-33/ST2 in tissue repair and also review its role in uncontrolled wound responses as seen in both fibrosis and tumorigenesis.

Apigenin supplementation protects the development of dextran sulfate sodium-induced murine experimental colitis by inhibiting canonical and non-canonical inflammasome signaling pathways

The present study was designed to elucidate the protective effects of dietary apigenin (API) enrichment in a chronic colitis model induced by DSS in mice. Inflammatory mediators and the possible role of canonical and non-canonical NLRP3 inflammasome signaling pathways in the beneficial effects of API under chronic inflammatory conditions were also explored. Six-week-old mice were randomized in four dietary groups: sham and control groups received standard diet (SD), and other two groups were fed with API at 0.1%. After 30days, all groups except sham received 3% DSS in drinking water for 5days followed by a regime of 21days of water. Our results revealed that dietary API supplementation decreased the macroscopic and microscopic damage signs of colitis; also, it was capable to down-regulate mPGES, COX-2 and iNOS enzyme colonic expressions and to decrease serum matrix metalloproteinase (MMP-3) levels. Similarly, API diet reduced IL-1β and TNF-α proinflammatory cytokine secretions in primary LPS-stimulated splenocytes. Furthermore, we demonstrated that API anti-inflammatory activity was related with an inhibition of both canonical and non-canonical NLRP3 inflammasome pathways by decreasing proinflammatory IL-1β and IL-18 cytokine levels as a consequence of regulation of cleaved caspase-1 and caspase-11 enzymes. We conclude that API supplement might provide a basis for developing a new dietary strategy for the prevention of chronic ulcerative colitis.