Regulation of human intestinal T-cell responses by type 1 interferon-STAT1 signaling is disrupted in inflammatory bowel disease

STATs, promising targets for the treatment of autoimmune and inflammatory diseases

Cytokines play a crucial role in the pathophysiology of autoimmune and inflammatory diseases, with over 50 cytokines undergoing signal transduction through the Signal Transducers and Activators of Transcription (STAT) signaling pathway. Recent studies have solidly confirmed the pivotal role of STATs in autoimmune and inflammatory diseases. Therefore, this review provides a detailed summary of the immunological functions of STATs, focusing on exploring their mechanisms in various autoimmune and inflammatory diseases. Additionally, with the rapid advancement of structural biology in the field of drug discovery, many STAT inhibitors have been identified using structure-based drug design strategies. In this review, we also examine the structures of STAT proteins and compile the latest research on STAT inhibitors currently being tested in animal models and clinical trials for the treatment of immunological diseases, which emphasizes the feasibility of STATs as promising therapeutic targets and provides insights into the design of the next generation of STAT inhibitors.

Monocytes and macrophages: Origin, homing, differentiation, and functionality during inflammation

Monocytes and macrophages are essential components of innate immune system and have versatile roles in homeostasis and immunity. These phenotypically distinguishable mononuclear phagocytes play distinct roles in different stages, contributing to the pathophysiology in various forms making them a potentially attractive therapeutic target in inflammatory conditions. Several pieces of evidence have supported the role of different cell surface receptors expressed on these cells and their downstream signaling molecules in initiating and perpetuating the inflammatory response. In this review, we discuss the current understanding of the monocyte and macrophage biology in inflammation, highlighting the role of chemoattractants, inflammasomes, and integrins in the function of monocytes and macrophages during events of inflammation. This review also covers the recent therapeutic interventions targeting these mononuclear phagocytes at the cellular and molecular levels.

Increased type-I interferon level is associated with liver damage and fibrosis in primary sclerosing cholangitis

BACKGROUND

The level of type-I interferons (IFNs) in primary sclerosing cholangitis (PSC) was investigated to evaluate its association with disease activity and progression.

METHODS

Bioactive type-I IFNs were evaluated in a murine model of PSC and human patients' sera using a cell-based reporter assay and ELISA techniques. In total, 57 healthy participants, 71 PSC, and 38 patients with primary biliary cholangitis were enrolled in this study.

RESULTS

Bioactive type-I IFNs were elevated in the liver and serum of multidrug resistance protein 2-deficient animals and showed a correlation with the presence of CD45+ immune cells and serum alanine transaminase levels. Concordantly, bioactive type-I IFNs were elevated in the sera of patients with PSC as compared to healthy controls (sensitivity of 84.51%, specificity of 63.16%, and AUROC value of 0.8267). Bioactive IFNs highly correlated with alkaline phosphatase (r=0.4179, p<0.001), alanine transaminase (r=0.4704, p<0.0001), and gamma-glutamyl transpeptidase activities (r=0.6629, p<0.0001) but not with serum bilirubin. In addition, patients with PSC with advanced fibrosis demonstrated significantly higher type-I IFN values. Among the type-I IFN subtypes IFNα, β and IFNω could be detected in patients with PSC with IFNω showing the highest concentration among the subtypes and being the most abundant among patients with PSC.

CONCLUSIONS

The selectively elevated bioactive type-I IFNs specifically the dominating IFNω could suggest a novel inflammatory pathway that might also have a hitherto unrecognized role in the pathomechanism of PSC.

Commensal bacteria promote type I interferon signaling to maintain immune tolerance in mice

Type I interferons (IFNs) exert a broad range of biological effects important in coordinating immune responses, which have classically been studied in the context of pathogen clearance. Yet, whether immunomodulatory bacteria operate through IFN pathways to support intestinal immune tolerance remains elusive. Here, we reveal that the commensal bacterium, Bacteroides fragilis, utilizes canonical antiviral pathways to modulate intestinal dendritic cells (DCs) and regulatory T cell (Treg) responses. Specifically, IFN signaling is required for commensal-induced tolerance as IFNAR1-deficient DCs display blunted IL-10 and IL-27 production in response to B. fragilis. We further establish that IFN-driven IL-27 in DCs is critical in shaping the ensuing Foxp3+ Treg via IL-27Rα signaling. Consistent with these findings, single-cell RNA sequencing of gut Tregs demonstrated that colonization with B. fragilis promotes a distinct IFN gene signature in Foxp3+ Tregs during intestinal inflammation. Altogether, our findings demonstrate a critical role of commensal-mediated immune tolerance via tonic type I IFN signaling.

Distinct transcriptional signatures in purified circulating immune cells drive heterogeneity in disease location in IBD

OBJECTIVE

To infer potential mechanisms driving disease subtypes among patients with inflammatory bowel disease (IBD), we profiled the transcriptome of purified circulating monocytes and CD4 T-cells.

DESIGN

RNA extracted from purified monocytes and CD4 T-cells derived from the peripheral blood of 125 endoscopically active patients with IBD was sequenced using Illumina HiSeq 4000NGS. We used complementary supervised and unsupervised analytical methods to infer gene expression signatures associated with demographic/clinical features. Expression differences and specificity were validated by comparison with publicly available single cell datasets, tissue-specific expression and meta-analyses. Drug target information, druggability and adverse reaction records were used to prioritise disease subtype-specific therapeutic targets.

RESULTS

Unsupervised/supervised methods identified significant differences in the expression profiles of CD4 T-cells between patients with ileal Crohn's disease (CD) and ulcerative colitis (UC). Following a pathway-based classification (Area Under Receiver Operating Characteristic - AUROC=86%) between ileal-CD and UC patients, we identified MAPK and FOXO pathways to be downregulated in UC. Coexpression module/regulatory network analysis using systems-biology approaches revealed mediatory core transcription factors. We independently confirmed that a subset of the disease location-associated signature is characterised by T-cell-specific and location-specific expression. Integration of drug-target information resulted in the discovery of several new (BCL6, GPR183, TNFAIP3) and repurposable drug targets (TUBB2A, PRKCQ) for ileal CD as well as novel targets (NAPEPLD, SLC35A1) for UC.

CONCLUSIONS

Transcriptomic profiling of circulating CD4 T-cells in patients with IBD demonstrated marked molecular differences between the IBD-spectrum extremities (UC and predominantly ileal CD, sandwiching colonic CD), which could help in prioritising particular drug targets for IBD subtypes.

STAT1-mediated induction of Ly6c-expressing macrophages are involved in the pathogenesis of an acute colitis model

BACKGROUND

The development of inflammatory bowel diseases is thought to be multifactorial, but the exact steps in pathogenesis are poorly understood. In this study, we investigated involvement of the activation of STAT1 signal pathway in the pathogenesis of an acute colitis model.

METHODS

A dextran sulfate sodium-induced acute colitis model was established by using wild-type C57BL/6 mice and STAT1-deficient mice. Disease indicators such as body weight loss and clinical score, induction of cytokines, chemokines, and inflammatory cells were evaluated in the acute colitis model.

RESULTS

Disease state was significantly improved in the acute colitis model using STAT1-deficient mice compared with wild-type mice. The induction of Ly6c-highly expressing cells in colorectal tissues was attenuated in STAT1-deficient mice. IL-6, CCL2, and CCR2 gene expressions in Ly6c-highly expressing cells accumulated in the inflamed colon tissues and were significantly higher than in Ly6c-intermediate-expressing cells, whereas TNF-α and IFN-α/β gene expression was higher in Ly6c-intermediate-expressing cells. Blockade of CCR2-mediated signaling significantly reduced the disease state in the acute colitis model.

CONCLUSIONS

Two different types of Ly6c-expressing macrophages are induced in the inflamed tissues through the IFN-α/β-STAT1-mediated CCL2/CCR2 cascade and this is associated with the pathogenesis such as onset, exacerbation, and subsequent chronicity of acute colitis.

A Notch/STAT3-driven Blimp-1/c-Maf-dependent molecular switch induces IL-10 expression in human CD4+ T cells and is defective in Crohn´s disease patients

Immunosuppressive Interleukin (IL)-10 production by pro-inflammatory CD4⁺ T cells is a central self-regulatory function to limit aberrant inflammation. Still, the molecular mediators controlling IL-10 expression in human CD4⁺ T cells are largely undefined. Here, we identify a Notch/STAT3 signaling-module as a universal molecular switch to induce IL-10 expression across human naïve and major effector CD4⁺ T cell subsets. IL-10 induction was transient, jointly controlled by the transcription factors Blimp-1/c-Maf and accompanied by upregulation of several co-inhibitory receptors, including LAG-3, CD49b, PD-1, TIM-3 and TIGIT. Consistent with a protective role of IL-10 in inflammatory bowel diseases (IBD), effector CD4⁺ T cells from Crohn's disease patients were defective in Notch/STAT3-induced IL-10 production and skewed towards an inflammatory Th1/17 cell phenotype. Collectively, our data identify a Notch/STAT3-Blimp-1/c-Maf axis as a common anti-inflammatory pathway in human CD4⁺ T cells, which is defective in IBD and thus may represent an attractive therapeutic target.

MicroRNAs in Colon Tissue of Pediatric Ulcerative Pancolitis Patients Allow Detection and Prognostic Stratification

Prevalence of inflammatory bowel disease has been on the rise in recent years, especially in pediatric populations. This study aimed to provide precise identification and stratification of pediatric patients with diagnosed ulcerative colitis (UC) according to the severity of their condition and the prediction for standard treatment according to the specific expression of candidate miRNAs. We enrolled consecutive, therapeutically naïve, pediatric UC patients with confirmed pancolitis. We examined formalin-fixed paraffin-embedded specimens of colonic tissue for the expression of 10 selected candidate miRNAs. We performed receiver operating characteristic curve analysis, using area under the curve and a logistic regression model to evaluate the diagnostic and predictive power of the miRNA panels. Sixty patients were included in the final analysis. As a control group, 18 children without macroscopic and microscopic signs of inflammatory bowel disease were examined. The combination of three candidate miRNAs (let-7i-5p, miR-223-3p and miR-4284) enabled accurate detection of pediatric UC patients and controls. A panel of four candidate miRNAs (miR-375-3p, miR-146a-5p, miR-223-3p and miR-200b-3p) was associated with severity of UC in pediatric patients and a combination of three miRNAs (miR-21-5p, miR-192-5p and miR-194-5p) was associated with early relapse of the disease. Nine patients out of the total were diagnosed with primary sclerosing cholangitis (PSC) simultaneously with ulcerative colitis. A panel of 6 candidate miRNAs (miR-142-3p, miR-146a-5p, miR-223-3p, let-7i-5p, miR-192-5p and miR-194-5p) identified those patients with PSC. Specific combinations of miRNAs are promising tools for potential use in precise disease identification and severity and prognostic stratification in pediatric patients with ulcerative pancolitis.

p300 Serine 89: A Critical Signaling Integrator and Its Effects on Intestinal Homeostasis and Repair

Simple Summary

Given their high degree of identity and even greater similarity at the amino acid level, Kat3 coactivators, CBP (Kat3A) and p300 (Kat3B), have long been considered redundant. We describe the generation of novel p300 S89A knock-in mice carrying a single site directed amino acid mutation in p300, changing the highly evolutionarily conserved serine 89 to alanine, thus enhancing Wnt/CBP/catenin signaling (at the expense of Wnt/p300/catenin signaling). p300 S89A knock-in mice exhibit multiple organ system, immunologic and metabolic differences, compared with their wild type counterparts. In particular, these p300 S89A knock-in mice are highly sensitive to intestinal injury resulting in colitis which is known to significantly predispose to colorectal cancer. Our results highlight the critical role of this region in p300 as a signaling nexus and provide further evidence that p300 and CBP are non-redundant, playing definite and distinctive roles in development and disease.

Abstract

Differential usage of Kat3 coactivators, CBP and p300, by β-catenin is a fundamental regulatory mechanism in stem cell maintenance and initiation of differentiation and repair. Based upon our earlier pharmacologic studies, p300 serine 89 (S89) is critical for controlling differential coactivator usage by β-catenin via post-translational phosphorylation in stem/progenitor populations, and appears to be a target for a number of kinase cascades. To further investigate mechanisms of signal integration effected by this domain, we generated p300 S89A knock-in mice. We show that S89A mice are extremely sensitive to intestinal insult resulting in colitis, which is known to significantly increase the risk of developing colorectal cancer. We demonstrate cell intrinsic differences, and microbiome compositional differences and differential immune responses, in intestine of S89A versus wild type mice. Genomic and proteomic analyses reveal pathway differences, including lipid metabolism, oxidative stress response, mitochondrial function and oxidative phosphorylation. The diverse effects on fundamental processes including epithelial differentiation, metabolism, immune response and microbiome colonization, all brought about by a single amino acid modification S89A, highlights the critical role of this region in p300 as a signaling nexus and the rationale for conservation of this residue and surrounding region for hundreds of million years of vertebrate evolution.

The role of cGAS/STING in intestinal immunity

The gastrointestinal tract is a highly complex microenvironment under constant interaction with potentially harmful pathogens. Inflammatory bowel disease (IBD) is an archetypical inflammatory disease, in which the intestinal epithelium, defective autophagy, endoplasmic reticulum stress and dysbiosis play a key role. Although no risk-mediating gene variants of STING (TMEM173) have been identified so far, several seminal findings have elucidated a novel understanding of STING in the context of acute and chronic inflammation. STING, an endoplasmic reticulum resident adaptor protein binding cyclic dinucleotides, is a main inducer of type I interferons and canonically involved in antiviral and antibacterial immunity. Recent research has shed light on additional features of STING signaling involved in regulating the microbiota, facilitating autophagy, cell death or ER stress. Importantly, an increasing amount of studies suggests a considerable overlap of IBD pathophysiology and features of STING signaling. Since compelling evidence shows dysregulated type I IFNs in IBD, it is prompting to speculate on the hypothetical role of cGAS/STING/type I IFN signaling in IBD. Here, we summarize recent findings about the origin and function of STING signaling in the gastrointestinal tract and evolve the hypothesis that disturbed STING signaling might be profoundly interconnected with the pathophysiology of IBD.

Disease Risk-Associated Genetic Variants in STAT1 and STAT4 Function in a Complementary Manner to Increase Pattern-Recognition Receptor-Induced Outcomes in Human Macrophages

STAT proteins can regulate both pro- and anti-inflammatory cytokine signaling. Therefore, identifying consequences of modulating expression of a given STAT is ultimately critical for determining its potential as a therapeutic target and for defining the mechanisms through which immune-mediated disease variants in STAT genes contribute to disease pathogenesis. Genetic variants in the STAT1/STAT4 region are associated with multiple immune-mediated diseases, including inflammatory bowel disease (IBD). These diseases are characterized by dysregulated cytokine secretion in response to pattern-recognition receptor (PRR) stimulation. We found that the common IBD-associated rs1517352 C risk allele increased both STAT1 and STAT4 expression in human monocyte-derived macrophages (MDMs). We therefore hypothesized that the STAT1/STAT4 variant might regulate PRR-initiated responses in a complementary and cooperative manner because of the important role of autocrine/paracrine cytokines in modulating PRR-initiated signaling. STAT1 and STAT4 were required for PRR- and live bacterial-induced secretion of multiple cytokines. These outcomes were particularly dependent on PRR-initiated autocrine/paracrine IL-12-induced STAT4 activation to generate IFN-γ, with autocrine IFN-γ then signaling through STAT1. STAT1 and STAT4 also promoted bacterial-induced cytokines in intestinal myeloid cells and PRR-enhanced antimicrobial pathways in MDMs. Importantly, MDMs from rs1517352 C IBD risk allele carriers demonstrated increased TLR4-, IFN-γ- and IL-12-induced STAT1 and STAT4 phosphorylation and cytokine secretion and increased TLR4-enhanced antimicrobial pathways. Taken together, STAT1 and STAT4 expression is coregulated by a shared genetic region, and STAT1 /STAT4-immune disease-associated variants modulate IFN-γ- and IL-12-associated outcomes, and in turn, PRR-induced outcomes, highlighting that these genes cooperate to regulate pathways relevant to disease pathogenesis.

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.

Evaluation of Intestinal Epithelial Barrier Function in Inflammatory Bowel Diseases Using Murine Intestinal Organoids

BACKGROUND

Intestinal organoids have evolved as potential molecular tools that could be used to study host-microbiome interactions, nutrient uptake, and drug screening. Gut epithelial barrier functions play a crucial role in health and diseases, especially in autoimmune diseases, such as inflammatory bowel diseases (IBDs), because they disrupt the epithelial mucosa and impair barrier function.

METHODS

In this study, we generated an in vitro IBD model based on dextran sodium sulfate (DSS) and intestinal organoids that could potentially be used to assess barrier integrity. Intestinal organoids were long-term cultivated and characterized with several specific markers, and the key functionality of paracellular permeability was determined using FITC-dextran 4 kDa. Intestinal organoids that had been treated with 2 µM DSS for 3 h were developed and the intestinal epithelial barrier function was sequentially evaluated.

RESULTS

The results indicated that the paracellular permeability represented epithelial characteristics and their barrier function had declined when they were exposed to FITC-dextran 4 kDa after DSS treatment. In addition, we analyzed the endogenous mRNA expression of pro-inflammatory cytokines and their downstream effector genes. The results demonstrated that the inflammatory cytokines genes significantly increased in inflamed organoids compared to the control, leading to epithelial barrier damage and dysfunction.

CONCLUSION

The collective results showed that in vitro 3D organoids mimic in vivo tissue topology and functionality with minor limitations, and hence are helpful for testing disease models.

A class of γδ T cell receptors recognize the underside of the antigen-presenting molecule MR1

T cell receptors (TCRs) recognize antigens presented by major histocompatibility complex (MHC) and MHC class I-like molecules. We describe a diverse population of human γδ T cells isolated from peripheral blood and tissues that exhibit autoreactivity to the monomorphic MHC-related protein 1 (MR1). The crystal structure of a γδTCR-MR1-antigen complex starkly contrasts with all other TCR-MHC and TCR-MHC-I-like complex structures. Namely, the γδTCR binds underneath the MR1 antigen-binding cleft, where contacts are dominated by the MR1 α3 domain. A similar pattern of reactivity was observed for diverse MR1-restricted γδTCRs from multiple individuals. Accordingly, we simultaneously report MR1 as a ligand for human γδ T cells and redefine the parameters for TCR recognition.

Inflammatory bowel disease pathobiology: the role of the interferon signature

The pathogenesis of inflammatory bowel disease (IBD) is still unclear, but includes both inflammatory and autoimmune reactions. Current methodological approaches could better elucidate the cytokine pathways and the genetics involved in the etiopathogenesis of this disease. Interferons (IFNs) are cytokines that play a key role in autoimmune/inflammatory disorders because of their pro- and anti-inflammatory properties as well as their immunoregulatory functions. An increased expression of IFN-regulated genes, widely known as an IFN signature, has been reported in blood and tissue from patients with autoimmune disorders. In this review, we present the function as well as the clinical and therapeutic potential of the IFN signature. Current data demonstrate that the IFN signature can be used as a biomarker that defines disease activity in autoimmune diseases, although this has not been thoroughly studied in IBD. Consequently, further investigation of the IFN signature in IBD would be essential for a better understanding of its actions.

Loss of adenomatous polyposis coli function renders intestinal epithelial cells resistant to the cytokine IL-22

Interleukin-22 (IL-22) is a critical immune defence cytokine that maintains intestinal homeostasis and promotes wound healing and tissue regeneration, which can support the growth of colorectal tumours. Mutations in the adenomatous polyposis coli gene (Apc) are a major driver of familial colorectal cancers (CRCs). How IL-22 contributes to APC-mediated tumorigenesis is poorly understood. To investigate IL-22 signalling in wild-type (WT) and APC-mutant cells, we performed RNA sequencing (RNAseq) of IL-22-treated murine small intestinal epithelial organoids. In WT epithelia, antimicrobial defence and cellular stress response pathways were most strongly induced by IL-22. Surprisingly, although IL-22 activates signal transducer and activator of transcription 3 (STAT3) in APC-mutant cells, STAT3 target genes were not induced. Our analyses revealed that ApcMin/Min cells are resistant to IL-22 due to reduced expression of the IL-22 receptor, and increased expression of inhibitors of STAT3, particularly histone deacetylases (HDACs). We further show that IL-22 increases DNA damage and genomic instability, which can accelerate cellular transition from heterozygosity (ApcMin/+) to homozygosity (ApcMin/Min) to drive tumour formation. Our data reveal an unexpected role for IL-22 in promoting early tumorigenesis while excluding a function for IL-22 in transformed epithelial cells.

Integrative Analyses of Long Non-coding RNA and mRNA Involved in Piglet Ileum Immune Response to Clostridium perfringens Type C Infection

Long non-coding RNAs (lncRNAs) have been shown to play important roles in regulating host immune and inflammatory responses to bacterial infection. Infection with Clostridium perfringens (C. perfringens), a food-borne zoonotic pathogen, can lead to a series of inflammatory diseases in human and piglet, greatly challenging the healthy development of global pig industry. However, the roles of lncRNAs involved in piglet immune response against C. perfringens type C infection remain unknown. In this study, the regulatory functions of ileum lncRNAs and mRNAs were investigated in piglet immune response to C. perfringens type C infection among resistance (IR), susceptibility (IS) and sham-inoculation (control, IC) groups. A total of 480 lncRNAs and 3,669 mRNAs were significantly differentially expressed, the differentially expressed lncRNAs and mRNAs in the IR and IS groups were enriched in various pathways of ABC transporters, olfactory transduction, PPAR signaling pathway, chemokine signaling pathway and Toll-like receptor signaling pathway, involving in regulating piglet immune responses and resistance during infection. There were 212 lncRNAs and 505 target mRNAs found to have important association with C. perfringens infectious diseases, furthermore, 25 dysregulated lncRNAs corresponding to 13 immune-related target mRNAs were identified to play potential roles in defense against bacterial infection. In conclusion, the results improve our understanding on the characteristics of lncRNAs and mRNAs on regulating host immune response against C. perfringens type C infection, which will provide a reference for future research into exploring C. perfringens-related diseases in human.

Impact of Autophagy of Innate Immune Cells on Inflammatory Bowel Disease

Autophagy, an intracellular degradation mechanism, has many immunological functions and is a constitutive process necessary for maintaining cellular homeostasis and organ structure. One of the functions of autophagy is to control the innate immune response. Many studies conducted in recent years have revealed the contribution of autophagy to the innate immune response, and relationships between this process and various diseases have been reported. Inflammatory bowel disease is an intractable disorder with unknown etiology; however, immunological abnormalities in the intestines are known to be involved in the pathology of inflammatory bowel disease, as is dysfunction of autophagy. In Crohn's disease, many associations with autophagy-related genes, such as ATG16L1, IRGM, NOD2, and others, have been reported. Abnormalities in the ATG16L1 gene, in particular, have been reported to cause autophagic dysfunction, resulting in enhanced production of inflammatory cytokines by macrophages as well as abnormal function of Paneth cells, which are important in intestinal innate immunity. In this review, we provide an overview of the autophagy mechanism in innate immune cells in inflammatory bowel disease.

mPGES-1-Mediated Production of PGE2 and EP4 Receptor Sensing Regulate T Cell Colonic Inflammation

PGE₂ is a lipid mediator of the initiation and resolution phases of inflammation, as well as a regulator of immune system responses to inflammatory events. PGE₂ is produced and sensed by T cells, and autocrine or paracrine PGE₂ can affect T cell phenotype and function. In this study, we use a T cell-dependent model of colitis to evaluate the role of PGE₂ on pathological outcome and T-cell phenotypes. CD4⁺ T effector cells either deficient in mPGES-1 or the PGE₂ receptor EP4 are less colitogenic. Absence of T cell autocrine mPGES1-dependent PGE₂ reduces colitogenicity in association with an increase in CD4⁺RORγt⁺ cells in the lamina propria. In contrast, recipient mice deficient in mPGES-1 exhibit more severe colitis that corresponds with a reduced capacity to generate FoxP3⁺ T cells, especially in mesenteric lymph nodes. Thus, our research defines how mPGES-1-driven production of PGE₂ by different cell types in distinct intestinal locations impacts T cell function during colitis. We conclude that PGE₂ has profound effects on T cell phenotype that are dependent on the microenvironment.

Transcriptional Regulation of Macrophages Polarization by MicroRNAs

Diversity and plasticity are the hallmarks of cells from the monocyte-macrophage lineage. Macrophages undergo classical M1 or alternative M2 activation in response to the microenvironment signals. Several transcription factors, such as peroxisome proliferator-activated receptors, signal transducers and activators of transcription, CCAAT-enhancer-binding proteins, interferon regulatory factors, Kruppel-like factors, GATA binding protein 3, nuclear transcription factor-κB, and c-MYC, were found to promote the expression of specific genes, which dictate the functional polarization of macrophages. Importantly, these transcription factors can be regulated by microRNAs (miRNAs), a group of small non-coding RNAs, which regulate gene expression through translation repression or mRNA degradation. Recent studies have also revealed that miRNAs control macrophage polarization by regulating transcription factors in response to the microenvironment signals. This review will summarize recent progress of miRNAs in the transcriptional regulation of macrophage polarization and provide the insights into the development of macrophage-centered diagnostic and therapeutic strategies.

Impact of Paneth Cell Autophagy on Inflammatory Bowel Disease

Intestinal mucosal barrier, mainly consisting of the mucus layer and epithelium, functions in absorbing nutrition as well as prevention of the invasion of pathogenic microorganisms. Paneth cell, an important component of mucosal barrier, plays a vital role in maintaining the intestinal homeostasis by producing antimicrobial materials and controlling the host-commensal balance. Current evidence shows that the dysfunction of intestinal mucosal barrier, especially Paneth cell, participates in the onset and progression of inflammatory bowel disease (IBD). Autophagy, a cellular stress response, involves various physiological processes, such as secretion of proteins, production of antimicrobial peptides, and degradation of aberrant organelles or proteins. In the recent years, the roles of autophagy in the pathogenesis of IBD have been increasingly studied. Here in this review, we mainly focus on describing the roles of Paneth cell autophagy in IBD as well as several popular autophagy-related genetic variants in Penath cell and the related therapeutic strategies against IBD.

Type 1 Interferon in the Human Intestine-A Co-ordinator of the Immune Response to the Microbiota

The human gut is in constant complex interaction with the external environment. Although much is understood about the composition and function of the microbiota, much remains to be learnt about the mechanisms by which these organisms interact with the immune system in health and disease. Type 1 interferon (T1IFN), a ubiquitous and pleiotropic family of cytokines, is a critical mediator of the response to viral, bacterial, and other antigens sampled in the intestine. Although inflammation is enhanced in mouse model of colitis when T1IFN signaling is lost, the action of T1IFN is context specific and can be pro- or anti-inflammatory. In humans, T1IFN has been used to treat inflammatory diseases, including multiple sclerosis and inflammatory bowel disease but intestinal inflammation can also develop after the administration of T1IFN. Recent findings indicate that "tonic" or "endogenous" T1IFN, induced by signals from the commensal microbiota, modulates the local signaling environment to prime the intestinal mucosal immune system to determine later responses to pathogens and commensal organisms. This review will summarize the complex immunological effects of T1IFN and recent the role of T1IFN as a mediator between the microbiota and the mucosal immune system, highlighting human data wherever possible. It will discuss what we can learn from clinical experiences with T1IFN and how the T1IFN pathway may be manipulated in the future to maintain mucosal homeostasis.

Type I and III Interferon in the Gut: Tight Balance between Host Protection and Immunopathology

The intestinal mucosa forms an active interface to the outside word, facilitating nutrient and water uptake and at the same time acts as a barrier toward the highly colonized intestinal lumen. A tight balance of the mucosal immune system is essential to tolerate harmless antigens derived from food or commensals and to effectively defend against potentially dangerous pathogens. Interferons (IFN) provide a first line of host defense when cells detect an invading organism. Whereas type I IFN were discovered almost 60 years ago, type III IFN were only identified in the early 2000s. It was initially thought that type I IFN and type III IFN performed largely redundant functions. However, it is becoming increasingly clear that type III IFN exert distinct and non-redundant functions compared to type I IFN, especially in mucosal tissues. Here, we review recent progress made in unraveling the role of type I/III IFN in intestinal mucosal tissue in the steady state, in response to mucosal pathogens and during inflammation.

Intestinal Autophagy and Its Pharmacological Control in Inflammatory Bowel Disease

Intestinal mucosal barrier, mainly composed of the intestinal mucus layer and the epithelium, plays a critical role in nutrient absorption as well as protection from pathogenic microorganisms. It is widely acknowledged that the damage of intestinal mucosal barrier or the disturbance of microorganism balance in the intestinal tract contributes greatly to the pathogenesis and progression of inflammatory bowel disease (IBD), which mainly includes Crohn’s disease and ulcerative colitis. Autophagy is an evolutionarily conserved catabolic process that involves degradation of protein aggregates and damaged organelles for recycling. The roles of autophagy in the pathogenesis and progression of IBD have been increasingly studied. This present review mainly describes the roles of autophagy of Paneth cells, macrophages, and goblet cells in IBD, and finally, several potential therapeutic strategies for IBD taking advantage of autophagy.