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

Insight into the role of IRF7 in skin and connective tissue diseases

Interferons (IFNs) are signalling proteins primarily involved in initiating innate immune responses against pathogens and promoting the maturation of immune cells. Interferon Regulatory Factor 7 (IRF7) plays a pivotal role in the IFNs signalling pathway. The activation process of IRF7 is incited by exogenous or abnormal nucleic acids, which is followed by the identification via pattern recognition receptors (PRRs) and the ensuing signalling cascades. Upon activation, IRF7 modulates the expression of both IFNs and inflammatory gene regulation. As a multifunctional transcription factor, IRF7 is mainly expressed in immune cells, yet its presence is also detected in keratinocytes, fibroblasts, and various dermal cell types. In these cells, IRF7 is critical for skin immunity, inflammation, and fibrosis. IRF7 dysregulation may lead to autoimmune and inflammatory skin conditions, including systemic scleroderma (SSc), systemic lupus erythematosus (SLE), Atopic dermatitis (AD) and Psoriasis. This comprehensive review aims to extensively elucidate the role of IRF7 and its signalling pathways in immune cells and keratinocytes, highlighting its significance in skin-related and connective tissue diseases.

Potential shared pathogenic mechanisms between endometriosis and inflammatory bowel disease indicate a strong initial effect of immune factors

Introduction

Over the past decades, immune dysregulation has been consistently demonstrated being common charactoristics of endometriosis (EM) and Inflammatory Bowel Disease (IBD) in numerous studies. However, the underlying pathological mechanisms remain unknown. In this study, bioinformatics techniques were used to screen large-scale gene expression data for plausible correlations at the molecular level in order to identify common pathogenic pathways between EM and IBD.

Methods

Based on the EM transcriptomic datasets GSE7305 and GSE23339, as well as the IBD transcriptomic datasets GSE87466 and GSE126124, differential gene analysis was performed using the limma package in the R environment. Co-expressed differentially expressed genes were identified, and a protein-protein interaction (PPI) network for the differentially expressed genes was constructed using the 11.5 version of the STRING database. The MCODE tool in Cytoscape facilitated filtering out protein interaction subnetworks. Key genes in the PPI network were identified through two topological analysis algorithms (MCC and Degree) from the CytoHubba plugin. Upset was used for visualization of these key genes. The diagnostic value of gene expression levels for these key genes was assessed using the Receiver Operating Characteristic (ROC) curve and Area Under the Curve (AUC) The CIBERSORT algorithm determined the infiltration status of 22 immune cell subtypes, exploring differences between EM and IBD patients in both control and disease groups. Finally, different gene expression trends shared by EM and IBD were input into CMap to identify small molecule compounds with potential therapeutic effects.

Results

113 differentially expressed genes (DEGs) that were co-expressed in EM and IBD have been identified, comprising 28 down-regulated genes and 86 up-regulated genes. The co-expression differential gene of EM and IBD in the functional enrichment analyses focused on immune response activation, circulating immunoglobulin-mediated humoral immune response and humoral immune response. Five hub genes (SERPING1、VCAM1、CLU、C3、CD55) were identified through the Protein-protein Interaction network and MCODE.High Area Under the Curve (AUC) values of Receiver Operating Characteristic (ROC) curves for 5hub genes indicate the predictive ability for disease occurrence.These hub genes could be used as potential biomarkers for the development of EM and IBD. Furthermore, the CMap database identified a total of 9 small molecule compounds (TTNPB、CAY-10577、PD-0325901 etc.) targeting therapeutic genes for EM and IBD.

Discussion

Our research revealed common pathogenic mechanisms between EM and IBD, particularly emphasizing immune regulation and cell signalling, indicating the significance of immune factors in the occurence and progression of both diseases. By elucidating shared mechanisms, our study provides novel avenues for the prevention and treatment of EM and IBD.

High-throughput omics technologies in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic, relapsing intestinal disease. Elucidation of the pathogenic mechanisms of IBD requires high-throughput technologies (HTTs) to effectively obtain and analyze large amounts of data. Recently, HTTs have been widely used in IBD, including genomics, transcriptomics, proteomics, microbiomics, metabolomics and single-cell sequencing. When combined with endoscopy, the application of these technologies can provide an in-depth understanding on the alterations of intestinal microbe diversity and abundance, the abnormalities of signaling pathway-mediated immune responses and functionality, and the evaluation of therapeutic effects, improving the accuracy of early diagnosis and treatment of IBD. This review comprehensively summarizes the development and advancement of HTTs, and also highlights the challenges and future directions of these technologies in IBD research. Although HTTs have made striking breakthrough in IBD, more standardized methods and large-scale dataset processing are still needed to achieve the goal of personalized medicine.

IL-20 controls resolution of experimental colitis by regulating epithelial IFN/STAT2 signalling

OBJECTIVE

We sought to investigate the role of interleukin (IL)-20 in IBD and experimental colitis.

DESIGN

Experimental colitis was induced in mice deficient in components of the IL-20 and signal transducer and activator of transcription (STAT)2 signalling pathways. In vivo imaging, high-resolution mini-endoscopy and histology were used to assess intestinal inflammation. We further used RNA-sequencing (RNA-Seq), RNAScope and Gene Ontology analysis, western blot analysis and co-immunoprecipitation, confocal microscopy and intestinal epithelial cell (IEC)-derived three-dimensional organoids to investigate the underlying molecular mechanisms. Results were validated using samples from patients with IBD and non-IBD control subjects by a combination of RNA-Seq, organoids and immunostainings.

RESULTS

In IBD, IL20 levels were induced during remission and were significantly higher in antitumour necrosis factor responders versus non-responders. IL-20RA and IL-20RB were present on IECs from patients with IBD and IL-20-induced STAT3 and suppressed interferon (IFN)-STAT2 signalling in these cells. In IBD, experimental dextran sulfate sodium (DSS)-induced colitis and mucosal healing, IECs were the main producers of IL-20. Compared with wildtype controls, Il20-/-, Il20ra-/- and Il20rb-/- mice were more susceptible to experimental DSS-induced colitis. IL-20 deficiency was associated with increased IFN/STAT2 activity in mice and IFN/STAT2-induced necroptotic cell death in IEC-derived organoids could be markedly blocked by IL-20. Moreover, newly generated Stat2ΔIEC mice, lacking STAT2 in IECs, were less susceptible to experimental colitis compared with wildtype controls and the administration of IL-20 suppressed colitis activity in wildtype animals.

CONCLUSION

IL-20 controls colitis and mucosal healing by interfering with the IFN/STAT2 death signalling pathway in IECs. These results indicate new directions for suppressing gut inflammation by modulating IL-20-controlled STAT2 signals.

Cytokines and Regulating Epithelial Cell Division

Physiologically, cytokines play an extremely important role in maintaining cellular and subcellular homeostasis, as they interact almost with every cell in the organism. Therefore, cytokines play a significantly critical role in the field of pathogenic pharmacological therapy of different types of pathologies. Cytokine is a large family containing many subfamilies and can be evaluated into groups according to their action on epithelial cell proliferation; stimulatory include transforming growth factor-α (TGF-α), Interlukine-22 (IL-22), IL-13, IL-6, IL-1RA and IL-17 and inhibitory include IL-1α, interferon type I (IFN type I), and TGF-β. The balance between stimulatory and inhibitory cytokines is essential for maintaining normal epithelial cell turnover and tissue homeostasis. Dysregulation of cytokine production can contribute to various pathological conditions, including inflammatory disorders, tissue damage, and cancer. Several cytokines have shown the ability to affect programmed cell death (apoptosis) and the capability to suppress non-purpose cell proliferation. Clinically, understanding the role of cytokines' role in epithelial tissue is crucial for evaluating a novel therapeutic target that can be of use as a new tactic in the management of carcinomas and tissue healing capacity. The review provides a comprehensive and up-to-date synthesis of current knowledge regarding the multifaceted effects of cytokines on epithelial cell proliferation, with a particular emphasis on the intestinal epithelium. Also, the paper will highlight the diverse signaling pathways activated by cytokines and their downstream consequences on epithelial cell division. It will also explore the potential therapeutic implications of targeting cytokine- epithelial cell interactions in the context of various diseases.

Selected Cytokines and Metalloproteinases in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a collective term for two diseases: ulcerative colitis (UC) and Crohn's disease (CD). There are many factors, e.g., genetic, environmental and immunological, that increase the likelihood of these diseases. Indicators of IBDs include extracellular matrix metalloproteinases (MMPs). The aim of this review is to present data on the role of selected cytokines and metalloproteinases in IBD. In recent years, more and more transcriptomic studies are emerging. These studies are improving the characterization of the cytokine microenvironment inside inflamed tissue. It is observed that the levels of several cytokines are consistently increased in inflamed tissue in IBD, both in UC and CD. This review shows that MMPs play a major role in the pathology of inflammatory processes, cancer, and IBD. IBD-associated inflammation is associated with increased expression of MMPs and reduced ability of tissue inhibitors of metalloproteinases (TIMPs) to inhibit their action. In IBD patients in tissues that are inflamed, MMPs are produced in excess and TIMP activity is not sufficient to block MMPs. This review is based on our personal selection of the literature that was retrieved by a selective search in PubMed using the terms "Inflammatory bowel disease" and "pathogenesis of Inflammatory bowel diseases" that includes systematic reviews, meta-analyses, and clinical trials. The involvement of the immune system in the pathophysiology of IBD is reviewed in terms of the role of the cytokines and metalloproteinases involved.

Different levels of healing in inflammatory bowel diseases: mucosal, histological, transmural, barrier and complete healing

Mucosal healing on endoscopy has emerged as a key prognostic parameter in the management of patients with IBD (Crohn's disease, ulcerative colitis/UC) and can predict sustained clinical remission and resection-free survival. The structural basis for this type of mucosal healing is a progressive resolution of intestinal inflammation with associated healing of ulcers and improved epithelial barrier function. However, in some cases with mucosal healing on endoscopy, evidence of histological activity in mucosal biopsies has been observed. Subsequently, in UC, a second, deeper type of mucosal healing, denoted histological healing, was defined which requires the absence of active inflammation in mucosal biopsies. Both levels of mucosal healing should be considered as initial events in the resolution of gut inflammation in IBD rather than as indicators of complete transmural healing. In this review, the effects of anti-inflammatory, biological or immunosuppressive agents as well as small molecules on mucosal healing in clinical studies are highlighted. In addition, we focus on the implications of mucosal healing for clinical management of patients with IBD. Moreover, emerging techniques for the analysis of mucosal healing as well as potentially deeper levels of mucosal healing such as transmural healing and functional barrier healing of the mucosa are discussed. Although none of these new levels of healing indicate a definitive cure of the diseases, they make an important contribution to the assessment of patients' prognosis. The ultimate level of healing in IBD would be a resolution of all aspects of intestinal and extraintestinal inflammation (complete healing).

An Engineered Probiotic Produces a Type III Interferon IFNL1 and Reduces Inflammations in in vitro Inflammatory Bowel Disease Models

The etiology of inflammatory bowel diseases (IBDs) frequently results in the uncontrolled inflammation of intestinal epithelial linings and the local environment. Here, we hypothesized that interferon-driven immunomodulation could promote anti-inflammatory effects. To test this hypothesis, we engineered probiotic Escherichia coli Nissle 1917 (EcN) to produce and secrete a type III interferon, interferon lambda 1 (IFNL1), in response to nitric oxide (NO), a well-known colorectal inflammation marker. We then validated the anti-inflammatory effects of the engineered EcN strains in two in vitro models: a Caco-2/Jurkat T cell coculture model and a scaffold-based 3D coculture IBD model that comprises intestinal epithelial cells, myofibroblasts, and T cells. The IFNL1-expressing EcN strains upregulated Foxp3 expression in T cells and thereafter reduced the production of pro-inflammatory cytokines such as IL-13 and -33, significantly ameliorating inflammation. The engineered strains also rescued the integrity of the inflamed epithelial cell monolayer, protecting epithelial barrier integrity even under inflammation. In the 3D coculture model, IFNL1-expressing EcN treatment enhanced the population of regulatory T cells and increased anti-inflammatory cytokine IL-10. Taken together, our study showed the anti-inflammatory effects of IFNL1-expressing probiotics in two in vitro IBD models, demonstrating their potential as live biotherapeutics for IBD immunotherapy.

Mucosal p-STAT1/3 correlates with histologic disease activity in Crohn's disease and is responsive to filgotinib

The validity and relevance of histologic disease activity in Crohn's disease (CD) is unclear, owing to disconnects with endoscopic pathology. Here, we explore relationships between endoscopic, histologic, and molecular activity. This post hoc analysis of the Phase 2 FITZROY trial (NCT02048618) assessed baseline and week 10 (W10) inflammation across matched ileal and colonic segments in CD patients receiving filgotinib 200 mg (n = 42) vs placebo (n = 18). Macroscopic and microscopic disease were assessed by Simple Endoscopic Score for CD ulceration subscore (uSES-CD) and Global Histologic Activity Score activity subscore (aGHAS), respectively. Molecular activity was quantified by phosphorylated signal transducer and activator of transcription (pSTAT)1 and pSTAT3 in epithelium and nonepithelium. Segments were classified as "low" or "high" activity; correlations and concordance were calculated. Logistic regression identified W10 outcome predictors. Overall, 300 segments in 60 patients were assessed. Baseline uSES-CD and aGHAS correlations were 0.72 and 0.53 in colon and ileum, respectively. pSTAT levels had poor-to-moderate concordance with uSES-CD (κ range, 0.11-0.49) but moderate-to-good concordance with aGHAS (0.43-0.77). With filgotinib vs placebo, uSES-CD and aGHAS decreased in significantly more segments with high baseline uSES-CD and aGHAS, and significantly more segments with high baseline pSTAT improved at W10. pSTAT1 was more sensitive to change than uSES-CD and aGHAS. Low baseline pSTAT3 in colon nonepithelium predicted W10 low uSES-CD (P = .044). There was better concordance between histologic and molecular disease activity associated with higher sensitivity to change vs endoscopic severity in ileocolonic CD. Our results suggest histologic activity be included in the assessment of CD inflammatory burden.

Functions of IFNλs in Anti-Bacterial Immunity at Mucosal Barriers

Type III interferons (IFNs), or IFNλs, are cytokines produced in response to microbial ligands. They signal through the IFNλ receptor complex (IFNLR), which is located on epithelial cells and select immune cells at barrier sites. As well as being induced during bacterial or viral infection, type III IFNs are produced in response to the microbiota in the lung and intestinal epithelium where they cultivate a resting antiviral state. While the multiple anti-viral activities of IFNλs have been extensively studied, their roles in immunity against bacteria are only recently emerging. Type III IFNs increase epithelial barrier integrity and protect from infection in the intestine but were shown to increase susceptibility to bacterial superinfections in the respiratory tract. Therefore, the effects of IFNλ can be beneficial or detrimental to the host during bacterial infections, depending on timing and biological contexts. This duality will affect the potential benefits of IFNλs as therapeutic agents. In this review, we summarize the current knowledge on IFNλ induction and signaling, as well as their roles at different barrier sites in the context of anti-bacterial immunity.

STAT1 coordinates intestinal epithelial cell death during gastrointestinal infection upstream of Caspase-8

Intestinal homeostasis and the maintenance of the intestinal epithelial barrier are essential components of host defense during gastrointestinal Salmonella Typhimurium infection. Both require a strict regulation of cell death. However, the molecular pathways regulating epithelial cell death have not been completely understood. Here, we elucidated the contribution of central mechanisms of regulated cell death and upstream regulatory components during gastrointestinal infection. Mice lacking Caspase-8 in the intestinal epithelium are highly sensitive towards bacterial induced enteritis and intestinal inflammation, resulting in an enhanced lethality of these mice. This phenotype was associated with an increased STAT1 activation during Salmonella infection. Cell death, barrier breakdown and systemic infection were abrogated by an additional deletion of STAT1 in Casp8^ΔIEC mice. In the absence of epithelial STAT1, loss of epithelial cells was abolished which was accompanied by a reduced Caspase-8 activation. Mechanistically, we demonstrate that epithelial STAT1 acts upstream of Caspase-8-dependent as well as -independent cell death and thus might play a major role at the crossroad of several central cell death pathways in the intestinal epithelium. In summary, we uncovered that transcriptional control of STAT1 is an essential host response mechanism that is required for the maintenance of intestinal barrier function and host survival.

Type III Interferons: Emerging Roles in Autoimmunity

Type III interferons (IFNs) or the lambda IFNs (IFNLs or IFN-λs) are antimicrobial cytokines that play key roles in immune host defense at endothelial and epithelial barriers. IFNLs signal via their heterodimeric receptor, comprised of two subunits, IFNLR1 and interleukin (IL)10Rβ, which defines the cellular specificity of the responses to the cytokines. Recent studies show that IFNL signaling regulates CD4+ T cell differentiation, favoring Th1 cells, which has led to the identification of IFNL as a putative therapeutic target for autoimmune diseases. Here, we summarize the IFNL signaling pathways during antimicrobial immunity, IFNL-mediated immunomodulation of both innate and adaptive immune cells, and induction of autoimmunity.

Probiotics in Intestinal Mucosal Healing: A New Therapy or an Old Friend?

Inflammatory bowel disease (IBD), Crohn’s disease, and ulcerative colitis are characterized by chronic and relapsing inflammation, while their pathogenesis remains mostly unelucidated. Gut commensal microbiota seem to be one of the various implicated factors, as several studies have shown a significant decrease in the microbiome diversity of patients with IBD. Although the question of whether microbiota dysbiosis is a causal factor or the result of chronic inflammation remains unanswered, one fact is clear; active inflammation in IBD results in the disruption of the mucus layer structure, barrier function, and also, colonization sites. Recently, many studies on IBD have been focusing on the interplay between mucosal and luminal microbiota, underlining their possible beneficial effect on mucosal healing. Regarding this notion, it has now been shown that specific probiotic strains, when administrated, lead to significantly decreased inflammation, amelioration of colitis, and improved mucosal healing. Probiotics are live microorganisms exerting beneficial effects on the host’s health when administered in adequate quantity. The aim of this review was to present and discuss the current findings on the role of gut microbiota and their metabolites in intestinal wound healing and the effects of probiotics on intestinal mucosal wound closure.

Interferon Lambda in the Pathogenesis of Inflammatory Bowel Diseases

Interferon λ (IFN-λ) is critical for host viral defense at mucosal surfaces and stimulates immunomodulatory signals, acting on epithelial cells and few other cell types due to restricted IFN-λ receptor expression. Epithelial cells of the intestine play a critical role in the pathogenesis of Inflammatory Bowel Disease (IBD), and the related type II interferons (IFN-γ) have been extensively studied in the context of IBD. However, a role for IFN-λ in IBD onset and progression remains unclear. Recent investigations of IFN-λ in IBD are beginning to uncover complex and sometimes opposing actions, including pro-healing roles in colonic epithelial tissues and potentiation of epithelial cell death in the small intestine. Additionally, IFN-λ has been shown to act through non-epithelial cell types, such as neutrophils, to protect against excessive inflammation. In most cases IFN-λ demonstrates an ability to coordinate the host antiviral response without inducing collateral hyperinflammation, suggesting that IFN-λ signaling pathways could be a therapeutic target in IBD. This mini review discusses existing data on the role of IFN-λ in the pathogenesis of inflammatory bowel disease, current gaps in the research, and therapeutic potential of modulating the IFN-λ-stimulated response.

Host-Viral Interactions in the Pathogenesis of Ulcerative Colitis

Ulcerative colitis is characterized by relapsing and remitting colonic mucosal inflammation. During the early stages of viral infection, innate immune defenses are activated, leading to the rapid release of cytokines and the subsequent initiation of downstream responses including inflammation. Previously, intestinal viruses were thought to be either detrimental or neutral to the host. However, persisting viruses may have a role as resident commensals and confer protective immunity during inflammation. On the other hand, the dysregulation of gut mucosal immune responses to viruses can trigger excessive, pathogenic inflammation. The purpose of this review is to discuss virus-induced innate immune responses that are at play in ulcerative colitis.

Interfering with SARS-CoV-2: are interferons friends or foes in COVID-19?

Type I and type III interferons are among the most potent anti-viral cytokines produced by the immune system. The recent outbreak of SARS-CoV-2, which causes COVID-19, underscores the vital role of these cytokines in controlling the virus and dictating disease severity. Here we delineate the pathways that lead to interferon production in response to SARS-CoV-2 encounter, and elucidate how this virus hinders the production and action of these cytokines; we also highlight that these interferon families serve protective as well as detrimental roles in patients with COVID-19, and conclude that a better understanding of the time, dose, localization, and activity of specific members of the interferon families is imperative for designing more efficient therapeutic interventions against this disease.

Interferon lambda in inflammation and autoimmune rheumatic diseases

Interferons are potent antiviral cytokines that modulate immunity in response to infection or other danger signals. In addition to their antiviral functions, type I interferons (IFNα and IFNβ) are important in the pathogenesis of autoimmune diseases. Type III interferons (IFNλs) were initially described as a specialized system that inhibits viral replication at epithelial barrier surfaces while limiting inflammatory damage. However, evidence now suggests that type III interferons have complex effects on both innate and adaptive immune responses and might also be pathogenic in systemic autoimmune diseases. Concentrations of IFNλs are increased in blood and tissues in a number of autoimmune rheumatic diseases, including systemic lupus erythematosus, and are further associated with specific clinical and laboratory parameters. This Review is aimed at providing a critical evaluation of the current literature on IFNλ biology and how type III interferons might contribute to immune dysregulation and tissue damage in autoimmunity. The potential effects of type III interferons on treatment strategies for autoimmune rheumatic diseases, such as interferon blockade, are also considered.

An IFN-STAT Axis Augments Tissue Damage and Inflammation in a Mouse Model of Crohn's Disease

Blocking interferon-function by therapeutic intervention of the JAK-STAT-axis is a novel promising treatment option for inflammatory bowel disease (IBD). Although JAK inhibitors have proven efficacy in patients with active ulcerative colitis (UC), they failed to induce clinical remission in patients with Crohn's disease (CD). This finding strongly implicates a differential contribution of JAK signaling in both entities. Here, we dissected the contribution of different STAT members downstream of JAK to inflammation and barrier dysfunction in a mouse model of Crohn's disease like ileitis and colitis (Casp8^ΔIEC mice). Deletion of STAT1 in Casp8^ΔIEC mice was associated with reduced cell death and a partial rescue of Paneth cell function in the small intestine. Likewise, organoids derived from the small intestine of these mice were less sensitive to cell death triggered by IBD-key cytokines such as TNFα or IFNs. Further functional in vitro and in vivo analyses revealed the impairment of MLKL-mediated necrosis as a result of deficient STAT1 function, which was in turn associated with improved cell survival. However, a decrease in inflammatory cell death was still associated with mild inflammation in the small intestine. The impact of STAT1 signaling on gastrointestinal inflammation dependent on the localization of inflammation, as STAT1 is essential for intestinal epithelial cell death regulation in the small intestine, whereas it is not the key factor for intestinal epithelial cell death in the context of colitis. Of note, additional deletion of STAT2 was not sufficient to restore Paneth cell function but strongly ameliorated ileitis. In summary, we provide here compelling molecular evidence that STAT1 and STAT2, both contribute to intestinal homeostasis, but have non-redundant functions. Our results further demonstrate that STATs individually affect the distinct pathophysiology of inflammation in the ileum and colon, respectively, which might explain the diverse outcome of JAK inhibitors on inflammatory bowel diseases.

Critical role of interferons in gastrointestinal injury repair

The etiology of ulcerative colitis is poorly understood and is likely to involve perturbation of the complex interactions between the mucosal immune system and the commensal bacteria of the gut, with cytokines acting as important cross-regulators. Here we use IFN receptor-deficient mice in a dextran sulfate sodium (DSS) model of acute intestinal injury to study the contributions of type I and III interferons (IFN) to the initiation, progression and resolution of acute colitis. We find that mice lacking both types of IFN receptors exhibit enhanced barrier destruction, extensive loss of goblet cells and diminished proliferation of epithelial cells in the colon following DSS-induced damage. Impaired mucosal healing in double IFN receptor-deficient mice is driven by decreased amphiregulin expression, which IFN signaling can up-regulate in either the epithelial or hematopoietic compartment. Together, these data underscore the pleiotropic functions of IFNs and demonstrate that these critical antiviral cytokines also support epithelial regeneration following acute colonic injury.

Interleukin-28A induces epithelial barrier dysfunction in CD patient-derived intestinal organoids

Intestinal barrier dysfunction is a pathogenic hallmark in Crohn's disease (CD). Identifying key players that regulate intestinal barrier may provide novel leads for therapeutic intervention. Interleukin-28A (IL-28A) is a newly identified IL-10/interferon cytokine family member, with its most implicated function being antiviral and anti-proliferative properties. However, the role and underlying mechanisms of IL-28A in the regulation of epithelial barrier in CD remain so far unexplored. IL-28A levels were measured in the plasma and biopsies of CD patients and healthy subjects. CD patient-derived intestinal organoids were characterized by differentiation gene markers and then exposed to TNF-α, IFN-γ, IL-1β or LPS, or IL-28A with or without GLPG0634 (filgotinib). Epithelial permeability was assessed by FITC-D4 flux. Expression of junctional components was analyzed by qRT-PCR, immunofluorescence staining, or Western blotting. JAK-STAT activity was analyzed by Western blotting. IL-28A levels were significantly increased in the plasma and biopsies from active patients with CD as compared with healthy subjects. IL-28A and its receptor complex IL-28AR/IL-10R2 were detected in CD patient-derived intestinal organoids and showed a selective response to IFN-γ exposure. IL-28A triggered epithelial barrier disruption and accompanied by reduced ZO-1 and E-cadherin expression. This effect was mediated by JAK-STAT1 pathway. Pre-incubation with the JAK1 inhibitor filgotinib ameliorated the barrier dysfunction induced by IL-28A. These results identified IL-28A as a novel regulator of epithelial barrier function and could be a putative target for CD treatment. We provide novel basic evidence that restoring intestinal barrier is a potential mechanism that contributes to the clinical benefits of JAK1 inhibitor in patients with CD.NEW & NOTEWORTHY IL-28A levels were significantly increased in the plasma and biopsies from active patients with CD as compared with healthy subjects. IFN-γ exposure stimulated IL-28A expression in intestinal organoids. Partially mimicking the effect of IFN-γ, IL-28A impaired epithelial barrier function and disrupted junctional components through the activation of JAK-STAT1 signaling, whereas JAK1 inhibitor ameliorated the above-mentioned effects of IL-28A. These findings highlight the newly identified cytokine IL-28A as a novel contributor to CD pathogenesis and could be a putative target for CD treatment. We also provide new evidence for potential applications of JAK inhibition in CD therapy.

Regulation of Intestinal Inflammation by Soybean and Soy-Derived Compounds

Environmental factors, particularly diet, are considered central to the pathogenesis of the inflammatory bowel diseases (IBD), Crohn’s disease and ulcerative colitis. In particular, the Westernization of diet, characterized by high intake of animal protein, saturated fat, and refined carbohydrates, has been shown to contribute to the development and progression of IBD. During the last decade, soybean, as well as soy-derived bioactive compounds (e.g., isoflavones, phytosterols, Bowman-Birk inhibitors) have been increasingly investigated because of their anti-inflammatory properties in animal models of IBD. Herein we provide a scoping review of the most studied disease mechanisms associated with disease induction and progression in IBD rodent models after feeding of either the whole food or a bioactive present in soybean.

Interferon-λ3 Exacerbates the Inflammatory Response to Microbial Ligands: Implications for SARS-CoV-2 Pathogenesis

Introduction

Interferon lambdas (IFN-λs) are antiviral cytokines that restrict pathogen infection and dissemination at barrier surfaces. Controlled expression of IFN-λs efficiently eliminates acute infections by activating a suite of interferon stimulated genes that inhibit viral propagation and activate local immune cells. Excessive or prolonged production of IFN-λs can however mediate tissue inflammation and disrupt epithelial barriers in both viral and non-viral disease. The mechanism by which IFN-λs drive this disease pathogenesis is poorly understood but may be caused by IFN-λ-mediated amplification of other innate immune signaling pathways.

Methods

Monocyte-derived macrophages were differentiated ± IFN-λ3 and treated with KDO-lipid A, poly I:C or zymosan, representing bacterial, viral or fungal ligands, respectively. Transcriptome and protein expression were quantified by RNA sequencing/PCR and ELISA/bead array, respectively. Bioinformatic analysis was used to define transcription factor profiles and signaling pathways amplified by IFN-λ3. Finally, the SARS-CoV-2 dataset GSE152075 was queried to compare the effects of IFNL versus IFNA expression in relation to viral load and nasopharyngeal transcriptomes.

Results

IFN-λ3 exacerbated inflammatory and chemotactic responses unique to each microbial ligand, as measured by RNA sequencing and by ELISA/bead array. Functional annotation identified pathways amplified by IFN-λ3, including inflammasome activation. Inflammasome amplification was confirmed in vitro, as measured by caspase 1 activity and IL-1β cleavage. Lastly, SARS-CoV-2 infected nasopharyngeal transcriptomes expressing IFN-λs but not IFN-αs were implicated in myeloid cell-driven pathogenesis including neutrophil degranulation, complement and coagulation cascades.

Discussion

These data suggest that IFN-λs contribute to disease pathology by exacerbating innate immune responses during chronic or severe disease states. IFN-λs may contribute to SARS-CoV-2 disease severity, however further study is required to confirm true causation.

Intestinal Mucosal Wound Healing and Barrier Integrity in IBD-Crosstalk and Trafficking of Cellular Players

The intestinal epithelial barrier is carrying out two major functions: restricting the entry of potentially harmful substances while on the other hand allowing the selective passage of nutrients. Thus, an intact epithelial barrier is vital to preserve the integrity of the host and to prevent development of disease. Vice versa, an impaired intestinal epithelial barrier function is a hallmark in the development and perpetuation of inflammatory bowel disease (IBD). Besides a multitude of genetic, molecular and cellular alterations predisposing for or driving barrier dysintegrity in IBD, the appearance of intestinal mucosal wounds is a characteristic event of intestinal inflammation apparently inducing breakdown of the intestinal epithelial barrier. Upon injury, the intestinal mucosa undergoes a wound healing process counteracting this breakdown, which is controlled by complex mechanisms such as epithelial restitution, proliferation and differentiation, but also immune cells like macrophages, granulocytes and lymphocytes. Consequently, the repair of mucosal wounds is dependent on a series of events including coordinated trafficking of immune cells to dedicated sites and complex interactions among the cellular players and other mediators involved. Therefore, a better understanding of the crosstalk between epithelial and immune cells as well as cell trafficking during intestinal wound repair is necessary for the development of improved future therapies. In this review, we summarize current concepts on intestinal mucosal wound healing introducing the main cellular mediators and their interplay as well as their trafficking characteristics, before finally discussing the clinical relevance and translational approaches to therapeutically target this process in a clinical setting.

Interferons at the crossroad of cell death pathways during gastrointestinal inflammation and infection

Interferons (IFNs) are pleiotropic immune-modulatory cytokines that are well known for their essential role in host defense against viruses, bacteria, and other pathogenic microorganisms. They can exert both, protective or destructive functions depending on the microorganism, the targeted tissue and the cellular context. Interferon signaling results in the induction of IFN-stimulated genes (ISGs) influencing different cellular pathways including direct anti-viral/anti-bacterial response, immune-modulation or cell death. Multiple pathways leading to host cell death have been described, and it is becoming clear that depending on the cellular context, IFN-induced cell death can be beneficial for both: host and pathogen. Accordingly, activation or repression of corresponding signaling mechanisms occurs during various types of infection but is also an important pathway for gastrointestinal inflammation and tissue damage. In this review, we summarize the role of interferons at the crossroad of various cell death pathways in the gut during inflammation and infection.

Biological Behavior and Lipid Metabolism of Colon Cancer Cells are Regulated by a Combination of Sterol Regulatory Element-Binding Protein 1 and ATP Citrate Lyase

Purpose

To research the effects of ATP citrate lyase (ACLY) and Sterol-regulatory element binding protein 1 (SREBP1) on the biology and lipid metabolism of colorectal cancer cells.

Methods

Colorectal cancer cells Caco-2 and Lovo were transfected with ACLY or SREBP1 gene knockdown lentiviruses. Four groups were set: ACLY knockdown, SREBP1 knockdown group, empty vector-transfected (negative control), and untreated cells (blank control). Cell proliferation was measured using CCK-8, colony formation, and EdU labeling assays. Apoptosis was detected using Annexin V-APC/7- AAD and JC-1 assay. Transwell migration and wound healing assays analyzed cell migration and invasion. A triglyceride test kit and oil red O stain assessed cell lipid production. Key factors related to lipid metabolism were detected.

Results

ACLY and SREBP1 promoted cell proliferation at 48 and 120 h, but there was no significant difference in Caco-2 cells at 24 h, at which point the effect of SREBP1 was more important. ACLY's effect on cell proliferation was more obvious at 120 h. Colony formation assays in Caco-2 showed similar results to the CCK-8 assay at 120 h, but ACLY knockdown had no effect in Lovo cells. EDU assays showed that ACLY or SREBP1 facilitated DNA reproduction in the two cell lines, in which SREBP1 was more significant. Knockdown of the two genes showed significant differences in Lovo cells. However, ALCY knockdown promoted apoptosis to a greater extent than SREBP1 knockdown in Caco-2 cells. In addition, ACLY and SREBP1 enhanced migration, invasion, and lipid production in both cell lines. Knockdown of ACLY or SREBP1 reduced lipid metabolism pathway gene expression in the two cell lines.

Conclusion

Knockdown of ACLY and SREBP1 genes inhibit the proliferation, migration, and invasion of colorectal cancer cells, while promoting their apoptosis. Our results identified potential new targets to treat colorectal cancer via lipid synthesis modulation in cancer cells.

Interleukin-28A maintains the intestinal epithelial barrier function through regulation of claudin-1

Background

Interleukin-28A (IL-28A or interferon-λ2) is reported to maintain intestinal mucosal homeostasis. However, the effects and mechanisms of IL-28A on intestinal ischemia reperfusion (I/R) have not yet been studied.

Methods

Adult C57BL/6 mice were randomly divided into three groups: sham, I/R, and I/R+IL-28A (n=5 in each group). The I/R+IL-28A group mice were injected with recombinant mouse IL-28A 12 hours before the operation. Mice were sacrificed 6 hours after reperfusion. The mucosal permeability was investigated, and histology analyses were performed. Additionally, a hypoxic Caco-2 cell culture model was established. Fludarabine was used to inhibit phosphorylated signal transducer and activator of transcription 1 (pSTAT1). The expression of IL-28A, tight junctions (TJs), and pSTAT1 was assessed by western blot, immunohistochemical (IHC) staining, or immunofluorescence staining. Epithelial permeability was measured by transepithelial electrical resistance (TER).

Results

The expression of IL-28A was decreased in intestinal lamina propria in the I/R group compared with the control group. Administration of IL-28A significantly alleviated the I/R-induced increase in intestinal permeability and tissue damage. Treatment with IL-28A significantly attenuated intestinal I/R-induced disruption of TJ proteins, including zonula occludens-1 (ZO-1), occludin, and claudin-1. In vitro, IL-28A treatment reversed the decrease in TER of Caco-2 monolayers exposed to hypoxic environments. IL-28A led to the activation of STAT1 and the upregulation of claudin-1 expression both in vivo and in vitro. Also, inhibiting phosphorylation of STAT1 reversed the effects of IL-28A on the expression and distribution of claudin-1 in Caco-2 cells.

Conclusions

Intestinal epithelial barrier dysfunction caused by intestinal I/R is ameliorated by IL-28A via the regulation of claudin-1.

Interferon lambda 4 genotype and pathway in alcoholic hepatitis

OBJECTIVES

Single nucleotide polymorphisms within the interferon lambda 4 (IFNL4) gene influence liver inflammation and fibrosis in chronic liver disease. We investigated whether this is also the case during acute liver disease, alcoholic hepatitis. We, therefore, related variants within the IFNL4 gene to the clinical course of acute alcoholic hepatitis, and characterized the activation state of the IFN lambda system in these patients.

METHODS

In this pilot study, 58 patients with alcoholic hepatitis were genotyped for the rs368234815IFNL4 single nucleotide polymorphism (deltaG, deltaG/TT: IFN lambda 4 positive, TT/TT: IFN lambda 4 negative). The genotypes were related to mortality, infection and inflammation and expression of the IFNL receptor 1 and IFN inducible genes were measured in liver and peripheral leukocytes.

RESULTS

Amongst the alcoholic hepatitis patients who died, the IFN negative patients live longer after diagnosis, and also the IFN negative patients tended to have an overall short-term survival benefit compared to IFN lambda positive patients (p = .058). The IFN lambda 4 negative patients at diagnosis had fewer circulating monocytes and lower plasma soluble CD163. The patients with alcoholic hepatitis had reduced expression of the IFNL receptor 1in both liver and blood compared with healthy controls. In blood, the expression of IFN stimulated genes was lower than in healthy controls and most so in the patients, who died.

CONCLUSIONS

The IFN lambda 4 pathway seems involved in the acute disease processes of alcoholic hepatitis and patients without IFN lambda expression seem to have a short-term survival benefit.

PRKAR2A deficiency protects mice from experimental colitis by increasing IFN-stimulated gene expression and modulating the intestinal microbiota

Protein kinase A (PKA) plays an important role in regulating inflammation via its catalytic subunits. Recently, PKA regulatory subunits have been reported to directly modulate some signaling pathways and alleviate inflammation. However, the role of PKA regulatory subunits in colonic inflammation remains unclear. Therefore, we conducted this study to investigate the role of the PKA regulatory subunit PRKAR2A in colitis. We observed that PRKAR2A deficiency protected mice from dextran sulfate sodium (DSS)-induced experimental colitis. Our experiments revealed that the intestinal epithelial cell-specific deletion of Prkar2a contributed to this protection. Mechanistically, the loss of PRKAR2A in Prkar2a^-/- mice resulted in an increased IFN-stimulated gene (ISG) expression and altered gut microbiota. Inhibition of ISGs partially reversed the protective effects against DSS-induced colitis in Prkar2a^-/- mice. Antibiotic treatment and cross-fostering experiments demonstrated that the protection against DSS-induced colitis in Prkar2a^-/- mice was largely dependent on the gut microflora. Altogether, our work demonstrates a previously unidentified function of PRKAR2A in promoting DSS-induced colitis.

The impact of parturition induction with cloprostenol on immunological parameters in the sow colostrum

BACKGROUND

Farrowing induction with prostaglandin F2 analogue cloprostenol is commonly used on commercial farms to manage the timing of farrowing. When labour induction is applied, the questions arise about possible side effects of such a hormonal intervention on physiological processes connected with labour and lactation, including colostral immunity.

RESULTS

In this study, immune cells composition, lysozyme concentration, complement bacteriolytic activity and proinflamatory (GM-CSF2, IL-1β, IL-6, a TNFα) and anti-inflammatory (IL-4, IL-10, TGFβ1 a TGFβ2) cytokines were measured in colostrum samples from sows farrowing naturally (NP) and from sows with farrowing induced using cloprostenol administration on day 113 of gestation (IP). A significantly higher proportion of lymphocytes was found in colostrum of induced sows compared to colostrum of non-induced sows. No significant differences between NP and IP were found in complement activity, in the proportions of granulocytes, macrophages and lymphocyte subpopulations. Lower lysozyme concentration and higher IL-1β, IL-6, TGFβ1 and TNFα concentrations were found in IP sow colostrum compared to colostrum from NP sows.

CONCLUSIONS

An increased proportion of colostral lymphocytes can positively influence the cellular immunity transmission from sow to her offspring. On the other hand, a lower lysozyme concentration can adversely affect newborn's intestinal immunity, as well as changes in cytokine concentrations can have an adverse effect on newborn piglet intestinal epithelium development and its defence function.

Resolution of Inflammation and Gut Repair in IBD: Translational Steps Towards Complete Mucosal Healing

Despite significant recent therapeutic advances, complete mucosal healing remains a difficult treatment target for many patients with inflammatory bowel diseases (IBD) to achieve. Our review focuses on the translational concept of promoting resolution of inflammation and repair as a necessary adjunctive step to reach this goal. We explore the roles of inflammatory cell apoptosis and efferocytosis to promote resolution, the new knowledge of gut monocyte-macrophage populations and their secreted prorepair mediators, and the processes of gut epithelial repair and regeneration to bridge this gap. We discuss the need and rationale for this vision and the tangible steps toward integrating proresolution therapies in IBD.

Intestinal Epithelial Cells Express Immunomodulatory ISG15 During Active Ulcerative Colitis and Crohn's Disease

BACKGROUND AND AIMS

Intestinal epithelial cells [IECs] secrete cytokines that recruit immune cells to the mucosa and regulate immune responses that drive inflammation in inflammatory bowel disease [IBD]. However, experiments in patient-derived IEC models are still scarce. Here, we aimed to investigate how innate immunity and IEC-specific pattern recognition receptor [PRR] signalling can be involved in an enhanced type I interferon [IFN] gene signature observed in colon epithelium of patients with active IBD, with a special focus on secreted ubiquitin-like protein ISG15.

METHODS

Gene and protein expression in whole mucosa biopsies and in microdissected human colonic epithelial lining, in HT29 human intestinal epithelial cells and primary 3D colonoids treated with PRR-ligands and cytokines, were detected by transcriptomics, in situ hybridisation, immunohistochemistry, western blots, and enzyme-linked immunosorbent assay [ELISA]. Effects of IEC-secreted cytokines were examined in human peripheral blood mononuclear cells [PBMCs] by multiplex chemokine profiling and ELISA.

RESULTS

The type I IFN gene signature in human mucosal biopsies was mimicked in Toll-like receptor TLR3 and to some extent tumour necrosis factor [TNF]-treated human IECs. In intestinal biopsies, ISG15 expression correlated with expression of the newly identified receptor for extracellular ISG15, LFA-1 integrin. ISG15 was expressed and secreted from HT29 cells and primary 3D colonoids through both JAK1-pSTAT-IRF9-dependent and independent pathways. In experiments using PBMCs, we show that ISG15 releases IBD-relevant proinflammatory cytokines such as CXCL1, CXCL5, CXCL8, CCL20, IL1, IL6, TNF, and IFNγ.

CONCLUSIONS

ISG15 is secreted from primary IECs upon extracellular stimulation, and mucosal ISG15 emerges as an intriguing candidate for immunotherapy in IBD.

Interferon-λ Receptor Expression: Novel Reporter Mouse Reveals Within- and Cross-Tissue Heterogeneity

Interferon-λ (IFN-λ) plays an important role in mucosal immunity, but reliable information regarding the expression of the IFN-λ receptor in individual cells is still missing. One reason for this knowledge gap is the lack of antibodies that specifically recognize the unique IFNLR1 subunit of the dimeric IFN-λ receptor complex. In this study, we investigated whether a reporter mouse carrying a bacterial β-galactosidase gene inserted into the Ifnlr1 locus could be used to visualize IFN-λ receptor-expressing cells in whole organs. First we confirmed that insertion of the reporter cassette inactivated the Ifnlr1 gene, and that gene function could be restored by removing the β-galactosidase insert by site-specific recombination. When whole tissues were analyzed, prominent β-galactosidase activity was confined to the intestinal tract of reporter mice. However, only the snout expressed β-galactosidase at levels high enough for reliable detection in whole tissue extracts. Interestingly, individual epithelial cells in the upper airways expressed β-galactosidase activity to variable degrees as determined by flow cytometry and histology, suggesting a remarkable heterogeneity in IFNLR1 expression levels. Taken together, our results demonstrate a surprisingly strong within- and cross-tissue heterogeneity of IFNLR1 expression that may have physiological implications.

Cytokines in inflammatory bowel diseases - Update 2020

Inflammatory Bowel Diseases (IBD), namely Crohn's Disease and Ulcerative Colitis, cause a significant disease burden in modern civilization. Ever since the introduction of anti-TNF-directed therapies 20 years ago, cytokines have attracted a lot of research attention and several cytokine-directed therapies have been implemented in the clinical treatment of these diseases. The research progress in these past years has underlined the importance of both myeloid and lymphoid elements of the immune system in the pathogenesis of IBD and their cytokine-mediated interplay. The conceptual framework of the mucosal cytokine network has shifted during these years from a T helper (Th) dichotomy (Th1/Th2) to the effector/regulatory T cell balance, while nowadays, the importance of myeloid cell instruction of lymphocytes, namely by IL-12 and IL-23, is increasingly recognized. Anti-IL-12p40 agents, like ustekinumab, groundbreakingly changed patient care, and anti-IL23p19-directed approaches are on the verge of grand success. In this review we present a modular approach to understand the cytokine network and put it into the context of the pathogenesis of IBD with a special focus on publications since 2014.

In-vivo Activity of IFN-λ and IFN-α Against Bovine-Viral-Diarrhea Virus in a Mouse Model

Bovine-viral-diarrhea virus (BVDV) can cause significant economic losses in livestock. The disease is controlled with vaccination and bovines are susceptible until vaccine immunity develops and may remain vulnerable if a persistently infected animal is left on the farm; therefore, an antiviral agent that reduces virus infectivity can be a useful tool in control programs. Although many compounds with promising in-vitro efficacy have been identified, the lack of laboratory-animal models limited their potential for further clinical development. Recently, we described the activity of type I and III interferons, IFN-α and IFN-λ respectively, against several BVDV strains in-vitro. In this study, we analyzed the in-vivo efficacy of both IFNs using a BALB/c-mouse model. Mice infected with two type-2 BVDV field strains developed a viremia with different kinetics, depending on the infecting strain's virulence, that persisted for 56 days post-infection (dpi). Mice infected with the low-virulence strain elicited high systemic TNF-α levels at 2 dpi. IFNs were first applied subcutaneously 1 day before or after infection. The two IFNs reduced viremia with different kinetics, depending on whether either one was applied before or after infection. In a second experiment, we increased the number of applications of both IFNs. All the treatments reduced viremia compared to untreated mice. The application of IFN-λ pre- and post-infection reduced viremia over time. This study is the first proof of the concept of the antiviral potency of IFN-λ against BVDV in-vivo, thus encouraging further trails for a potential use of this cytokine in cattle.

Type III Interferons (Lambda Interferons) in Rheumatic Autoimmune Diseases

The last 2 decades have witnessed the discovery and characterization of a new family of cytokines with immunological characteristics similar to those described for type I interferons, type III or lambda interferons. Unraveling the molecular mechanisms underlying each type of interferon has allowed us to understand how some autoimmune diseases can be considered as interferonopathies. Under normal conditions, type III interferons play a key role in the defense against viruses by modulating the functioning of several types of innate and adaptive immune cells. These effects include upregulation of major histocompatibility complex molecules by myeloid dendritic cells, increased functioning of pattern recognition receptors by plasmacytoid dendritic cells, decreased activity of regulatory T cells, enhanced production of antibodies by plasmatic cells and increased expression of chemokines and adhesion molecules by leukocytes and endothelial cells. Notably, all these mechanisms have been described to boost autoimmunity, and type III interferons pathway activation has been related to the pathogenesis of autoimmune conditions such as systemic lupus erythematosus, systemic sclerosis and Sjögren's syndrome. This review provides an overview of the current evidence on the contribution of type III interferons in the pathogenesis of rheumatic autoimmune diseases in humans.

Interferon Lambda Promotes Paneth Cell Death Via STAT1 Signaling in Mice and Is Increased in Inflamed Ileal Tissues of Patients With Crohn's Disease

BACKGROUND & AIMS

Interferon lambda (IFNL) is expressed at high levels by intestinal epithelial cells (IECs) and mucosal immune cells in response to infection and inflammation. We investigated whether IFNL might contribute to pathogenesis of Crohn's disease (CD).

METHODS

We obtained serum samples and terminal ileum biopsies from 47 patients with CD and 16 healthy individuals (controls). We measured levels of IFNL by enzyme-linked immunosorbent assay and immunohistochemistry and location of expression by confocal microscopy. Activation of IFNL signaling via STAT1 was measured in areas of no, mild, moderate, and severe inflammation and correlated with Paneth cell homeostasis and inflammation. IFNL expression and function were studied in wild-type mice and mice with intestinal epithelial cell-specific (ΔIEC) disruption or full-body disruption of specific genes (Mlkl^-/-, Stat1^ΔIEC, Casp8^ΔIEC, Casp8^ΔIECRipk3^-/-, Casp8^ΔIECTnfr^-/-, Casp8^ΔIECMlkl^-/-, and Nod2^-/- mice). Some mice were given tail vein injections of a vector encoding a secreted form of IFNL. Intestinal tissues were collected from mice and analyzed by immunohistochemistry and immunoblots. We generated 3-dimensional small intestinal organoids from mice and studied the effects of IFNL and inhibitors of STAT-signaling pathway.

RESULTS

Patients with CD had significant increases in serum and ileal levels of IFNL compared with controls. Levels of IFNL were highest in ileum tissues with severe inflammation. High levels of IFNL associated with a reduced number of Paneth cells and increased cell death at the crypt bottom in inflamed ileum samples. Intestinal tissues from the ileum of wild-type mice injected with a vector expressing IFNL had reduced numbers of Paneth cells. IFNL-induced death of Paneth cells in mice did not occur via apoptosis, but required Mixed Lineage Kinase Domain Like (MLKL) and activation of Signal transducer and activator of transcription 1 (STAT1). In organoids, inhibitors of Janus kinase (JAK) signaling via STAT1 (glucocorticoids, tofacitinib, or filgotinib) reduced expression of proteins that mediate cell death and prevented Paneth cell death.

CONCLUSIONS

Levels of IFNL are increased in serum and inflamed ileal tissues from patients with CD and associated with a loss of Paneth cells. Expression of a secreted form of IFNL in mice results in loss of Paneth cells from intestinal tissues, via STAT1 and MLKL, controlled by caspase 8. Strategies to reduce IFNL or block its effects might be developed for treatment of patients with CD affecting the terminal ileum.

Resolution of Crohn's disease

Crohn's disease (CD) is characterized by chronic inflammation of the gastrointestinal tract and represents one of the main inflammatory bowel disease (IBD) forms. The infiltration of immune cells into the mucosa and uncontrolled production of pro-inflammatory cytokines and other mediators trigger the chronic inflammatory reaction in the intestine [1]. The inflammatory setting consists of subsequent events that comprise an induction phase, the peak of inflammation which is subsequently followed by the resolution phase. The induction phase, which represents the first phase of inflammation, is important for the rapid and efficient activation of the immune system for sufficient host defense. The permanent sensing of exogenous or endogenous danger signals enables the fast initiation of the inflammatory reaction. The immune cell infiltrate initiates an inflammatory cascade where released lipid and protein mediators play an indispensable role [2, 3]. The last decades of research strongly suggest that resolution of inflammation is similarly a tightly coordinated and active process. The basic concept that resolution of inflammation has to be regarded as an active process has been thoroughly described by others [4-6]. The following review focuses on mechanisms, pathways, and specific mediators that are actively involved in the resolution of inflammation in CD.

SARI attenuates colon inflammation by promoting STAT1 degradation in intestinal epithelial cells

SARI functions as a suppressor of colon cancer and predicts survival of colon cancer patients, but its role in regulating colitis has not been characterized. Here we show that SARI^-/- mice were highly susceptible to colitis, which was associated with enhanced macrophage infiltration and inflammatory cytokine production. Bone marrow reconstitution experiments demonstrated that disease susceptibility was not dependent on the deficiency of SARI in the immune compartment but on the protective role of SARI in the intestinal epithelial cells (IECs). Furthermore, SARI deficiency enhanced Chemokine (C-C motif) Ligand 2 (CCL2) production and knockout of CCR2 blocks the promoting role of SARI deficiency on colitis. Mechanistically, SARI directly targets and promotes signal transducer and activator of transcription 1 (STAT1) degradation in IECs, followed by persistent inactivation of the STAT1/CCL2 transcription complex. In summary, SARI attenuated colitis in mice by impairing colitis-dependent STAT1/CCL2 transcriptional activation in IECs and macrophages recruitment in colon tissue.

Differential Activation of the Transcription Factor IRF1 Underlies the Distinct Immune Responses Elicited by Type I and Type III Interferons

Type I and III interferons (IFNs) activate similar downstream signaling cascades, but unlike type I IFNs, type III IFNs (IFNλ) do not elicit strong inflammatory responses in vivo. Here, we examined the molecular mechanisms underlying this disparity. Type I and III IFNs displayed kinetic differences in expression of IFN-stimulated genes and proinflammatory responses, with type I IFNs preferentially stimulating expression of the transcription factor IRF1. Type III IFNs failed to induce IRF1 expression because of low IFNλ receptor abundance and insufficient STAT1 activation on epithelial cells and thus did not activate the IRF1 proinflammatory gene program. Rather, IFNλ stimulation preferentially induced factors implicated in tissue repair. Our findings suggest that IFN receptor compartmentalization and abundance confer a spatiotemporal division of labor where type III IFNs control viral spread at the site of the infection while restricting tissue damage; the transient induction of inflammatory responses by type I IFNs recruits immune effectors to promote protective immunity.

Targeting immune cell circuits and trafficking in inflammatory bowel disease

Inflammatory bowel diseases (IBDs) such as Crohn's disease and ulcerative colitis are characterized by uncontrolled activation of intestinal immune cells in a genetically susceptible host. Due to the progressive and destructive nature of the inflammatory process in IBD, complications such as fibrosis, stenosis or cancer are frequently observed, which highlights the need for effective anti-inflammatory therapy. Studies have identified altered trafficking of immune cells and pathogenic immune cell circuits as crucial drivers of mucosal inflammation and tissue destruction in IBD. A defective gut barrier and microbial dysbiosis induce such accumulation and local activation of immune cells, which results in a pro-inflammatory cytokine loop that overrides anti-inflammatory signals and causes chronic intestinal inflammation. This Review discusses pathogenic cytokine responses of immune cells as well as immune cell trafficking as a rational basis for new translational therapies in IBD.

Semaphorin 3E regulates apoptosis in the intestinal epithelium during the development of colitis

Semaphorin 3E (SEMA3E) has emerged as an axon-guiding molecule that regulates various biological processes including the immune responses and apoptosis. However, its role in the pathophysiology of colitis remains elusive. We investigated the role of SEMA3E in intestinal epithelial cells (IECs) activation, using biopsies from patients with active ulcerative colitis (UC), a mouse model of UC, and an in-vitro model of intestinal mucosal healing. In this study, we confirmed that the mRNA level of SEMA3E is reduced significantly in patients with UC and demonstrated a negative linear association between SEMA3E mRNA and p53-associated genes. In mice, genetic deletion of Sema3e resulted in an increase onset and severity of colitis, p53-associated genes, apoptosis, and IL-1beta production. Recombinant SEMA3E treatment protected against colitis and decreased these effects. Furthermore, in stimulated epithelial cells, recombinant SEMA3E treatment enhanced wound healing, resistance to oxidative stress and decreased apoptosis and p53-associated genes. Together, these findings identify SEMA3E as a novel regulator in intestinal inflammation that regulates IECs apoptosis and suggest a potential novel approach to treat UC.

Systems biology in inflammatory bowel diseases: on the way to precision medicine

Inflammatory bowel diseases (IBD) are chronic and recurrent inflammatory disorders of the gastrointestinal tract. The elucidation of their etiopathology requires complex and multiple approaches. Systems biology has come to fulfill this need in approaching the pathogenetic mechanisms of IBD and its etiopathology, in a comprehensive way, by combining data from different scientific sources. In combination with bioinformatics and network medicine, it uses principles from computer science, mathematics, physics, chemistry, biology, medicine and computational tools to achieve its purposes. Systems biology utilizes scientific sources that provide data from omics studies (e.g., genomics, transcriptomics, etc.) and clinical observations, whose combined analysis leads to network formation and ultimately to a more integrative image of disease etiopathogenesis. In this review, we analyze the current literature on the methods and the tools utilized by systems biology in order to cover an innovative and exciting field: IBD-omics.

Deficiency in intestinal epithelial O-GlcNAcylation predisposes to gut inflammation

Post-translational modifications in intestinal epithelial cells (IECs) allow for precise control in intestinal homeostasis, the breakdown of which may precipitate the pathological damage and inflammation in inflammatory bowel disease. The O-linked β-N-acetylglucosamine (O-GlcNAc) modification on intracellular proteins controls diverse biological processes; however, its roles in intestinal homeostasis are still largely unexplored. Here, we found that levels of protein O-GlcNAcylation and the expression of O-GlcNAc transferase (OGT), the enzyme adding the O-GlcNAc moiety, were reduced in IECs in human IBD patients. Deletion of OGT specifically in IECs resulted in disrupted epithelial barrier, microbial dysbiosis, Paneth cell dysfunction, and intestinal inflammation in mice. Using fecal microbiota transplantation in mice, we demonstrated that microbial dysbiosis although was insufficient to induce spontaneous inflammation but exacerbated chemical-induced colitis. Paneth cell-specific deletion of OGT led to Paneth cell dysfunction, which might predispose mice to chemical-induced colitis. On the other hand, the augmentation of O-GlcNAc signaling by inhibiting O-GlcNAcase, the enzyme removing O-GlcNAcylation, alleviated chemical-induced colitis. Our data reveal that protein O-GlcNAcylation in IECs controls key regulatory mechanisms to maintain mucosal homeostasis.

Contribution of Wound-Associated Cells and Mediators in Orchestrating Gastrointestinal Mucosal Wound Repair

The gastrointestinal mucosa, structurally formed by the epithelium and lamina propria, serves as a selective barrier that separates luminal contents from the underlying tissues. Gastrointestinal mucosal wound repair is orchestrated by a series of spatial and temporal events that involve the epithelium, recruited immune cells, resident stromal cells, and the microbiota present in the wound bed. Upon injury, repair of the gastrointestinal barrier is mediated by collective migration, proliferation, and subsequent differentiation of epithelial cells. Epithelial repair is intimately regulated by a number of wound-associated cells that include immune cells and stromal cells in addition to mediators released by luminal microbiota. The highly regulated interaction of these cell types is perturbed in chronic inflammatory diseases that are associated with impaired wound healing. An improved understanding of prorepair mechanisms in the gastrointestinal mucosa will aid in the development of novel therapeutics that promote mucosal healing and reestablish the critical epithelial barrier function.

Engulfment and Cell Motility Protein 1 Protects Against DSS-induced Colonic Injury in Mice via Rac1 Activation

BACKGROUND AND AIMS

Mucosal healing is an emerging therapeutic goal that could result in clinical remission of inflammatory bowel disease [IBD]. We sought to determine the role of engulfment and cell motility protein 1 [ELMO1] in wound healing in vitro and in vivo and to investigate the underlying pathways.

METHODS

RNA transcriptome sequencing was performed to detect the expression profiles of mRNA between inflamed tissues and corresponding non-inflamed tissues of IBD patients, followed by Gene Expression Omnibus [GEO] datasets and western blot analysis. The effects of ELMO1 overexpression or knockdown on cell migration and proliferation were determined. The dependence of these effects on Rac1 was assessed using a Rac1 inhibitor [NSC23766] and a Rac1 pull-down assay. We identified the underlying pathways involved by Gene Ontology [GO] analysis. A dextran sulphate sodium [DSS]-induced colitis model was established to evaluate the role of ELMO1 in colonic mucosal healing.

RESULTS

ELMO1 was upregulated in inflamed tissues compared with corresponding non-inflamed tissues. ELMO1 overexpression increased cell migration in a Rac1-dependent manner. Depletion of ELMO1, or NSC23766 administration, abolished this effect. GO analysis revealed that ELMO1 overexpression preferentially affected pathways involved in cytoskeletal regulation and wound healing, which was demonstrated by enhanced F-actin staining and increased numbers of extending lamellipodia in cells overexpressing ELMO1. In DSS-induced colitis, systemic delivery of pSin-EF2-ELMO1-Pur attenuated colonic inflammation and promoted recovery from colonic injury. The protective effect of ELMO1 was dependent on Rac1 activation.

CONCLUSIONS

ELMO1 protects against DSS-induced colonic injury in mice through its effect on epithelial migration via Rac1 activation.

Exclusive dependence of IL-10Rα signalling on intestinal microbiota homeostasis and control of whipworm infection

The whipworm Trichuris trichiura is a soil-transmitted helminth that dwells in the epithelium of the caecum and proximal colon of their hosts causing the human disease, trichuriasis. Trichuriasis is characterized by colitis attributed to the inflammatory response elicited by the parasite while tunnelling through intestinal epithelial cells (IECs). The IL-10 family of receptors, comprising combinations of subunits IL-10Rα, IL-10Rβ, IL-22Rα and IL-28Rα, modulates intestinal inflammatory responses. Here we carefully dissected the role of these subunits in the resistance of mice to infection with T. muris, a mouse model of the human whipworm T. trichiura. Our findings demonstrate that whilst IL-22Rα and IL-28Rα are dispensable in the host response to whipworms, IL-10 signalling through IL-10Rα and IL-10Rβ is essential to control caecal pathology, worm expulsion and survival during T. muris infections. We show that deficiency of IL-10, IL-10Rα and IL-10Rβ results in dysbiosis of the caecal microbiota characterised by expanded populations of opportunistic bacteria of the families Enterococcaceae and Enterobacteriaceae. Moreover, breakdown of the epithelial barrier after whipworm infection in IL-10, IL-10Rα and IL-10Rβ-deficient mice, allows the translocation of these opportunistic pathogens or their excretory products to the liver causing organ failure and lethal disease. Importantly, bone marrow chimera experiments indicate that signalling through IL-10Rα and IL-10Rβ in haematopoietic cells, but not IECs, is crucial to control worm expulsion and immunopathology. These findings are supported by worm expulsion upon infection of conditional mutant mice for the IL-10Rα on IECs. Our findings emphasize the pivotal and complex role of systemic IL-10Rα signalling on immune cells in promoting microbiota homeostasis and maintaining the intestinal epithelial barrier, thus preventing immunopathology during whipworm infections.