Inhibiting Interleukin 36 Receptor Signaling Reduces Fibrosis in Mice With Chronic Intestinal Inflammation

Macrophages-microenvironment crosstalk in fibrostenotic inflammatory bowel disease: from basic mechanisms to clinical applications

INTRODUCTION

Intestinal fibrosis is a common complication of Inflammatory Bowel Disease (IBD) with no available drugs. The current therapeutic principle is surgical intervention as the core. Intestinal macrophages contribute to both the progression of inflammation and fibrosis. Understanding the role of macrophages in the intestinal microenvironment could bring new hope for fibrosis prevention or even reversal.

AREAS COVERED

This article reviewed the most relevant reports on macrophage in the field of intestinal fibrosis. The authors discussed current opinions about how intestinal macrophages function and interact with surrounding mediators during inflammation resolution and fibrostenotic IBD. Based on biological mechanisms findings, authors summarized related clinical trial outcomes.

EXPERT OPINION

The plasticity of intestinal macrophages allows them to undergo dramatic alterations in their phenotypes or functions when exposed to gastrointestinal environmental stimuli. They exhibit distinct metabolic characteristics, secrete various cytokines, express unique surface markers, and transmit different signals. Nevertheless, the specific mechanism through which the intestinal macrophages contribute to intestinal fibrosis remains unclear. It should further elucidate a novel therapeutic approach by targeting macrophages, especially distinct mechanisms in specific subgroups of macrophages involved in the progression of fibrogenesis in IBD.

Human intestinal myofibroblasts deposited collagen VI enhances adhesiveness for T cells - A novel mechanism for maintenance of intestinal inflammation

OBJECTIVE

Inflammatory bowel diseases (IBD) cause chronic intestinal damage and extracellular matrix (ECM) remodeling. The ECM may play an active role in inflammation by modulating immune cell functions, including cell adhesion, but this hypothesis has not been tested in IBD.

DESIGN

Primary human intestinal myofibroblast (HIMF)-derived ECM from IBD and controls, 3D decellularized colon or ECM molecule-coated scaffolds were tested for their adhesiveness for T cells. Matrisome was analysed via proteomics. Functional integrin blockade was used to investigate the underlying mechanism. Analysis of the pediatric Crohn's disease (CD) RISK inception cohort was used to explore an altered ECM gene expression as a potential predictor for a future complicated disease course.

RESULTS

HIMF-derived ECM and 3D decellularized colonic ECM from IBD bound more T cells compared to control. Control HIMFs exposed to the pro-inflammatory cytokines Iinterleukin-1β (IL-1β) and tumor necrosis factor (TNF) increased, and to transforming growth factor-β1 (TGF-β1) decreased ECM adhesiveness to T cells. Matrisome analysis of the HIMF-derived ECM revealed collagen VI as a major culprit for differences in T cell adhesion. Collagen VI knockdown in HIMF reduced adhesion T cell as did the blockage of integrin αvβ1. Elevated gene expression of collagen VI in biopsies of pediatric CD patients was linked to risk for future stricturing disease.

CONCLUSION

HIMF-derived ECM in IBD binds a remarkably enhanced number of T cells, which is dependent on Collagen VI and integrin αvβ1. Collagen VI expression is a risk factor for a future complicated CD course. Blocking immune cells retention may represent a novel approach to treatment in IBD.

Macrophages in intestinal fibrosis and regression

Intestinal macrophages are heterogenous cell populations with different developmental ontogeny and tissue anatomy. The concerted actions of intestinal macrophage subsets are critical to maintaining tissue homeostasis. However, the dysregulation of macrophages following tissue injury or chronic inflammation could also lead to intestinal fibrosis, with few treatment options in the clinic. In this review, we will characterize the features of intestinal macrophages in light of the latest advances in lineage tracing and single-cell sequencing technology. The roles of macrophages in distinct stages of intestinal fibrosis would be also elaborated. Finally, based on the reciprocal interaction between macrophages and intestinal fibrosis, we will propose the potential macrophage targeting anti-intestinal fibrosis therapies.

Landscape of new drugs and targets in inflammatory bowel disease

Although the therapeutic armamentarium of Inflammatory bowel diseases (IBD) physicians has expanded rapidly in recent years, a proportion of patients remain with a suboptimal response to medical treatment due to primary no response, loss of response or intolerance to currently available drugs. Our growing knowledges of IBD pathophysiology has led to the development of a multitude of new therapies over time, which may, 1 day, be able to address this unmet medical need. This review aims to provide physicians an update of emerging therapies in IBD by focusing on drugs currently in phase 3 clinical trials. Among the most promising molecules are anti-IL-23, JAK-inhibitors, anti-integrins and S1P modulators. While the results in terms of efficacy and safety are fairly clear for some classes, the question of safety remains more uncertain for other classes. Molecules at a more preliminary stage of development (phase 1 and 2), one of which may 1 day offer an optimal benefit-risk ratio, will also be presented as well as their respective mechanisms of action.

Macrophages in the gut: Masters in multitasking

The gastrointestinal tract has the important task of absorbing nutrients, a complex process that requires an intact barrier allowing the passage of nutrients but that simultaneously protects the host against invading microorganisms. To maintain and regulate intestinal homeostasis, the gut is equipped with one of the largest populations of macrophages in the body. Here, we will discuss our current understanding of intestinal macrophage heterogeneity and describe their main functions in the different anatomical niches of the gut during steady state. In addition, their role in inflammatory conditions such as infection, inflammatory bowel disease, and postoperative ileus are discussed, highlighting the roles of macrophages in immune defense. To conclude, we describe the interaction between macrophages and the enteric nervous system during development and adulthood and highlight their contribution to neurodegeneration in the context of aging and diabetes.

The endoscopic prediction model of simple endoscopic score for Crohn’s disease (SES-CD) as an effective predictor of intestinal obstruction in Crohn’s disease: A multicenter long-term follow-up study

Background

The simple endoscopic score for Crohn's disease (SES-CD) is a widely used index to evaluate clinical and endoscopic activity. However, the association and predictive value of SES-CD for intestinal obstruction in Crohn's disease (CD) remains unclear. We aimed to establish the best cut-off indicators of SES-CD for early clinical intervention and subsequent prevention of intestinal obstruction in CD.

Methods

Data on patients with CD evaluated at our institute from January 2016 to January 2022 were retrospectively collected. The SES-CD and Crohn's Disease Activity Index scores used in the analysis indicated the results of the first clinical and colonoscopy evaluations after hospitalization. The primary outcome was the occurrence of intestinal obstruction during admission and follow-up.

Results

A total of 248 patients with a median follow-up time of 2 years [interquartile range: 1.0–4.0] were enrolled, of which 28.2% developed intestinal obstruction. An SES-CD score of 8 was the most significant threshold evaluation, and SES-CD ≥8 had the largest area under the receiver operating characteristic curve (0.705), with a sensitivity of 52.9% and specificity of 88.2% in predicting intestinal obstruction. Furthermore, SES-CD ≥8 had the greatest risk factor for intestinal obstruction (odds ratio: 7.731; 95% confidence interval: 3.901–15.322; p < 0.001) and significantly decreased the overall intestinal obstruction-free survival (p < 0.001).

Conclusion

The SES-CD endoscopic prediction model could be an effective predictor of intestinal obstruction in patients with CD. More frequent follow-up and colonoscopic surveillance should be considered in patients with SES-CD score ≥8 to prevent the development of intestinal obstruction.

Regulation of Interleukin-36γ/IL-36R Signaling Axis by PIN1 in Epithelial Cell Transformation and Breast Tumorigenesis

Simple Summary

Members of the interleukin (IL)-1 cytokine family exhibit dual functions in the regulation of inflammation and cancer. Recent studies have shown the critical role of IL-36γ, the newly identified IL-1 family member, in the regulation of cellular processes implicated in the progression of cancer. Therefore, the underlying mechanism of IL-36γ in tumor development is of considerable interest. Here, we identified the pivotal role of IL-36γ in the proliferation of breast cancer cells. Consistently, IL-36γ was found to promote epithelial cell transformation via the activation of c-Fos, c-Jun, and AP-1 transcription factors, followed by the IL36R-mediated MEK/ERK and JNK/c-Jun cascades. Furthermore, our findings demonstrate the critical role of PIN1 in the regulation of IL-36γ-induced mammary gland tumorigenesis.

Abstract

Given the increasing recognition of the relationship between IL-1 cytokines, inflammation, and cancer, the significance of distinct members of the IL-1 cytokine family in the etiology of cancer has been widely researched. In the present study, we investigated the underlying mechanism of the IL-36γ/IL-36R axis during breast cancer progression, which has not yet been elucidated. Initially, we determined the effects of IL-36γ on the proliferation and epithelial cell transformation of JB6 Cl41 mouse epidermal and MCF7 human breast cancer cells using BrdU incorporation and anchorage-independent growth assays. We found that treatment with IL-36γ increased the proliferation and colony formation of JB6 Cl41 and MCF7 cells. Analysis of the mechanism underlying the neoplastic cell transformation revealed that IL-36γ induced IL-36R-mediated phosphorylation of MEK1/2, ERK1/2, JNK1/2, and c-Jun, resulting in increased c-Fos, c-Jun, and AP-1 activities in JB6 Cl41 and MCF7 cells. Furthermore, the IL-36γ-induced tumorigenic capacity of MCF7 cells was considerably enhanced by PIN1, following MEK/ERK and JNK/c-Jun signaling. Interestingly, blocking PIN1 activity using juglone suppressed the IL-36γ-induced increase in the anchorage-independent growth of 4T1 metastatic mouse breast cancer cells. Finally, in a syngeneic mouse model, IL-36γ-induced tumor growth in the breast mammary gland was significantly inhibited following PIN1 knockout.

CD147 Targeting by AC-73 Induces Autophagy and Reduces Intestinal Fibrosis Associated with TNBS Chronic Colitis

BACKGROUND AND AIMS

Intestinal fibrosis is a common complication of inflammatory bowel diseases. Medical treatment of intestinal fibrosis is an unmet therapeutic need. CD147 overexpression can induce myofibroblast differentiation associated with extracellular matrix deposition, favouring the development of fibrosis. To understand whether CD147 may promote intestinal fibrosis, we analysed its expression and blocked its function by using its specific inhibitor AC-73 [3-{2-[([1,1'-biphenyl]-4-ylmethyl) amino]-1-hydroxyethyl} phenol] in the murine TNBS [trinitrobenzenesulfonic acid]-chronic colitis model associated with intestinal fibrosis.

METHODS

TNBS chronic colitis was induced by weekly intrarectal administration of escalating doses of TNBS. Ethanol-treated and untreated mice were used as controls. Separated groups of TNBS, ethanol-treated or untreated mice received AC-73 or vehicle administered intraperitoneally from day 21 to day 49. At day 49, mice were killed, and colons collected for histological analysis, protein and RNA extraction. CD147, α-SMA and activated TGF-β1 protein levels, CD147/ERK/STAT3 signalling pathway and autophagy were assessed by Western blot, collagen and inflammatory/fibrogenic cytokines mRNA tissue content by quantitative PCR.

RESULTS

In mice with chronic TNBS colitis, CD147 protein level increased during fibrosis development in colonic tissue, as compared to control mice. CD147 inhibition by AC-73 treatment reduced intestinal fibrosis, collagen and cytokine mRNA tissue content, without significant modulation of activated TGF-β1 protein tissue content. AC-73 inhibited CD147/ERK1/2 and STAT3 signalling pathway activation and induced autophagy.

CONCLUSIONS

CD147 is a potential new target for controlling intestinal fibrosis and its inhibitor, AC-73, might represent a potential new anti-fibrotic therapeutic option in IBD.

IL-36 Cytokines: Their Roles in Asthma and Potential as a Therapeutic

Interleukin (IL)-36 cytokines are members of the IL-1 superfamily, which consists of three agonists (IL-36α, IL-36β and IL-36γ) and an IL-36 receptor antagonist (IL-36Ra). IL-36 cytokines are crucial for immune and inflammatory responses. Abnormal levels of IL-36 cytokine expression are involved in the pathogenesis of inflammation, autoimmunity, allergy and cancer. The present study provides a summary of recent reports on IL-36 cytokines that participate in the pathogenesis of inflammatory diseases, and the potential mechanisms underlying their roles in asthma. Abnormal levels of IL-36 cytokines are associated with the pathogenesis of different types of asthma through the regulation of the functions of different types of cells. Considering the important role of IL-36 cytokines in asthma, these may become a potential therapeutic target for asthma treatment. However, existing evidence is insufficient to fully elucidate the specific mechanism underlying the action of IL-36 cytokines during the pathological process of asthma. The possible mechanisms and functions of IL-36 cytokines in different types of asthma require further studies.

Imbalance between IL-36 receptor agonist and antagonist drives neutrophilic inflammation in COPD

Current treatments fail to modify the underlying pathophysiology and disease progression of chronic obstructive pulmonary disease (COPD), necessitating alternative therapies. Here, we show that COPD subjects have increased IL-36γ and decreased IL-36 receptor antagonist (IL-36Ra) in bronchoalveolar and nasal fluid compared to control subjects. IL-36γ is derived from small airway epithelial cells (SAEC) and further induced by a viral mimetic, whereas IL-36RA is derived from macrophages. IL-36γ stimulates release of the neutrophil chemoattractants CXCL1 and CXCL8, as well as elastolytic matrix metalloproteinases (MMPs) from small airway fibroblasts (SAF). Proteases released from COPD neutrophils cleave and activate IL-36γ thereby perpetuating IL-36 inflammation. Transfer of culture media from SAEC to SAF stimulated release of CXCL1, that was inhibited by exogenous IL-36RA. The use of a therapeutic antibody that inhibits binding to the IL-36 receptor (IL-36R) attenuated IL-36γ driven inflammation and cellular cross talk. We have demonstrated a mechanism for the amplification and propagation of neutrophilic inflammation in COPD and that blocking this cytokine family via a IL-36R neutralizing antibody could be a promising new therapeutic strategy in the treatment of COPD.

Label-Free Characterization and Quantification of Mucosal Inflammation in Common Murine Colitis Models With Multiphoton Imaging

BACKGROUND

Clinical challenges in inflammatory bowel diseases require microscopic in vivo evaluation of inflammation. Here, label-free imaging holds great potential, and recently, our group demonstrated the advantage of using in vivo multiphoton endomicroscopy for longitudinal animal studies. This article extends our previous work by in-depth analysis of label-free tissue features in common colitis models quantified by the multiphoton colitis score (MCS).

METHODS

Fresh mucosal tissues were evaluated from acute and chronic dextran sulfate sodium (DSS), TNBS, oxazolone, and transfer colitis. Label-free imaging was performed by using second harmonic generation and natural autofluorescence. Morphological changes in mucosal crypts, collagen fibers, and cellularity in the stroma were analyzed and graded.

RESULTS

Our approach discriminated between healthy (mean MCS = 2.5) and inflamed tissue (mean MCS > 5) in all models, and the MCS was validated by hematoxylin and eosin scoring of the same samples (85.2% agreement). Moreover, specific characteristics of each phenotype were identified. While TNBS, oxazolone, and transfer colitis showed high cellularity in stroma, epithelial damage seemed specific for chronic, acute DSS and transfer colitis. Crypt deformations were mostly observed in acute DSS.

CONCLUSIONS

Quantification of label-free imaging is promising for in vivo endoscopy. In the future, this could be valuable for monitoring of inflammatory pathways in murine models, which is highly relevant for the development of new inflammatory bowel disease therapeutics.

Caveolin-1 Alleviates Crohn's Disease-induced Intestinal Fibrosis by Inhibiting Fibroblasts Autophagy Through Modulating Sequestosome 1

BACKGROUND

Intestinal fibrosis is a common complication of Crohn's disease (CD) and is characterized by the excessive accumulation of extracellular matrix produced by activated myofibroblasts. Caveolin-1 (CAV1) inhibits fibrosis. However, limited data show that CAV1 affects intestinal fibrosis.

METHODS

Human CD tissue samples were gained from patients with CD who underwent surgical resection of the intestine and were defined as stenotic or nonstenotic areas. A dextran sodium sulfate-induced mouse model of intestinal fibrosis was established. For in vitro experiments, we purchased CCD-18Co intestinal fibrosis cells and isolated and cultured human primary colonic fibroblasts. These fibroblasts were activated by transforming growth factor β administration for 48 hours. In the functional experiments, a specific small interfering RNA or overexpression plasmid was transfected into fibroblasts. The messenger RNA levels of fibrosis markers, such as α-smooth muscle actin, fibronectin, connective tissue growth factor, and collagen I1α, were determined using quantitative polymerase chain reaction. Western blot analysis was applied to detect the expression of CAV1, SQSTM1/p62 (sequestosome 1), and other fibrosis markers.

RESULTS

In human CD samples and the dextran sodium sulfate-induced mouse model of intestinal fibrosis, we observed a downregulation of CAV1 in fibrosis-activated areas. Mechanistically, CAV1 knockdown in both human primary colonic fibroblasts and CCD-18Co cells promoted fibroblast activation, while CAV1 overexpression inhibited fibroblast activation in vitro. We found that SQSTM1/p62 positively correlated with CAV1 expression levels in patients with CD and that it was indirectly modulated by CAV1 expression. Rescue experiments showed that CAV1 decreased primary human intestinal fibroblast activation by inhibiting fibroblast autophagy through the modulation of SQSTM1/p62.

CONCLUSIONS

Our data demonstrate that CAV1 deficiency induces fibroblast activation by indirectly regulating SQSTM1/p62 to promote fibroblast autophagy. CAV1 or SQSTM1/p62 may be potential therapeutic targets for intestinal fibrosis.

Interleukin-36α is elevated in diffuse systemic sclerosis and may potentiate fibrosis

Systemic sclerosis (SSc) is an autoimmune prototypical connective tissues disease that results in alterations in vasculature, inflammation and fibrosis of the skin. Interleukin-1 family cytokines has been implicated in the disease including IL-1. IL-36α is an IL-1 family member that is clearly implicated in psoriatic skin disease but its role in systemic sclerosis disease is not clear. The aim of this work is to evaluate the levels and role of IL-36α in systemic sclerosis. Early diffuse SSc patients sera was isolated along with healthy controls and IL-36 levels quantified by ELISA. In vitro analysis was also undertaken with primary dermal fibroblasts with recombinant IL-36α and keratinocyte cells were also incubated with IL-36α. Cytokines were measured by ELISA. Serum IL-36 was significantly elevated compared to healthy controls. Elevated neutrophil elastase was also elevated in the matched sera. IL-36 was not directly pro-fibrotic in dermal fibroblasts but did induce pro-inflammatory cytokines that were dependant on the MAPK pathway for their release. IL-36α also led to release of CCL20 and CCL2 in keratinocytes which may potentiate fibrosis. IL-36α is elevated in SSc serum and whilst not directly pro-fibrotic it may through keratinocytes, potentiate fibrosis through keratinocyte-immune fibroblast cross-talk.

Adiponectin Alleviates Intestinal Fibrosis by Enhancing AMP-Activated Protein Kinase Phosphorylation

BACKGROUND

Intestinal fibrosis is a common complication of Crohn's disease (CD). Adiponectin reportedly exerts anti-inflammatory effects in various disease models, including colitis models.

AIMS

In this study, we aimed to determine the effects of adiponectin on intestinal fibrosis and the underlying mechanisms.

METHODS

A murine model of intestinal fibrosis was established by administering increasing doses of 2,4,6-trinitrobenzene sulfonic acid to Balb/c mice via enema for 7 weeks. Primary human fibroblasts were isolated from the colon tissues of patients with CD. The fibroblasts were incubated with transforming growth factor (TGF)-β1 to establish a fibrosis model in vitro. Pathway inhibitors were used to verify the potential signaling pathways involved in the anti-fibrogenic effect of adiponectin.

RESULTS

Compared with the normal mesentery, adiponectin expression was significantly increased in the hypertrophic mesentery of patients with CD. Intraperitoneal injection of adiponectin significantly decreased the activity of myeloperoxidase and the expression of pro-inflammatory cytokines (tumor necrosis factor α and interleukin 6) in the colon of fibrosis model mice, whereas the expression of the anti-inflammatory cytokine interleukin 10 was substantially increased. Moreover, adiponectin treatment inhibited colon shortening, decreased colon weight, and reduced fibrotic protein deposition in the model mice. Adiponectin reduced the phosphorylation of Smad2 and collagen deposition induced by TGF-β1 in primary human intestinal fibroblasts, with an increase in AMP-activated protein kinase (AMPK) phosphorylation. Furthermore, this phenomenon was reversed by the AMPK inhibitor.

CONCLUSIONS

Adiponectin can protect against intestinal fibrosis by enhancing the phosphorylation of AMPK and inhibiting the activity of the TGF-β1/Smad signaling pathway.

Metformin Ameliorates Chronic Colitis-Related Intestinal Fibrosis via Inhibiting TGF-β1/Smad3 Signaling

Intestinal fibrosis is considered to be a chronic complication of inflammatory bowel disease (IBD) and seriously threatening human health. Effective medical therapies or preventive measures are desirable but currently unavailable. Metformin has been proved to have a satisfactory anti-inflammatory effects in ulcerative colitis (UC) patients. Whether metformin can ameliorate chronic colitis-related intestinal fibrosis and the possible mechanisms remain unclear. Here, we established colitis-related intestinal fibrosis in mice by repetitive administration of TNBS or DSS. Preventive and therapeutic administration of metformin to chronic TNBS or DSS colitis mice indicated that metformin significantly attenuated intestinal fibrosis by suppressing Smad3 phosphorylation. In vitro studies with human colon fibroblast cell line (CCD-18Co) and primary human intestinal fibroblast treated with TGF-β1 confirmed the anti-fibrotic function of metformin for fibroblast activation, proliferation and collagen production. Mechanistically, metformin particularly inhibited phosphorylation and nuclear translocation of Smad3 by blocking the interaction of Smad3 with TβRI. These findings suggest that metformin will be an attractive anti-fibrotic drug for intestinal fibrosis in future therapies.

Tissue Niches Formed by Intestinal Mesenchymal Stromal Cells in Mucosal Homeostasis and Immunity

The gastrointestinal tract is the largest mucosal surface in our body and accommodates the majority of the total lymphocyte population. Being continuously exposed to both harmless antigens and potentially threatening pathogens, the intestinal mucosa requires the integration of multiple signals for balancing immune responses. This integration is certainly supported by tissue-resident intestinal mesenchymal cells (IMCs), yet the molecular mechanisms whereby IMCs contribute to these events remain largely undefined. Recent studies using single-cell profiling technologies indicated a previously unappreciated heterogeneity of IMCs and provided further knowledge which will help to understand dynamic interactions between IMCs and hematopoietic cells of the intestinal mucosa. In this review, we focus on recent findings on the immunological functions of IMCs: On one hand, we discuss the steady-state interactions of IMCs with epithelial cells and hematopoietic cells. On the other hand, we summarize our current knowledge about the contribution of IMCs to the development of intestinal inflammatory conditions, such as infections, inflammatory bowel disease, and fibrosis. By providing a comprehensive list of cytokines and chemokines produced by IMCs under homeostatic and inflammatory conditions, we highlight the significant immunomodulatory and tissue niche forming capacities of IMCs.

Medical, Endoscopic and Surgical Management of Stricturing Crohn's Disease: Current Clinical Practice

The development of fibrostenotic intestinal disease occurs in approximately one-third of patients with Crohn's disease and is associated with increased morbidity. Despite introducing new biologic agents, stricturing Crohn's disease remains a significant clinical challenge. Medical treatment is considered the first-line treatment for inflammatory strictures, and anti-TNF agents appear to provide the most considerable benefit among the available medical treatments. However, medical therapy is ineffective on strictures with a mainly fibrotic component, and a high proportion of patients under anti-TNF will require surgery. In fibrotic strictures or cases refractory to medical treatment, an endoscopic or surgical approach should be considered depending on the location, length, and severity of the stricture. Both endoscopic balloon dilatation and endoscopic stricturoplasty are minimally invasive and safe, associated with a small risk of complications. On the other hand, the surgical approach is indicated in patients not suitable for endoscopic therapy. This review aimed to present and analyze the currently available medical, endoscopic, and surgical management of stricturing Crohn's disease.

Surgical Management of Small Bowel Crohn's Disease

Crohn's disease in the small bowel could present itself as an inflammatory stricture, a fibrotic stricture as penetrating disease or a combination of both. It is pertinent to differentiate the disease process as well as its extent to effectively manage the disease. Currently, a combination of medical and surgical therapies forms part of the treatment plan while the debate of which therapy is better continues. In managing the strictures, identification of the disease process through imaging plays a pivotal role as inflammatory strictures respond to anti-tumor necrosis factor (TNF) and biological agents, while fibrotic strictures require endoscopic or surgical intervention. Recent evidence suggests a larger role for surgical excision, particularly in ileocolic disease, while achieving a balance between disease clearance and bowel preservation. Several adaptations to the surgical technique, such as wide mesenteric excision, side to side or Kono-S anastomosis, and long-term metronidazole therapy, are being undertaken even though their absolute benefit is yet to be determined. Penetrating disease requires a broader multidisciplinary approach with a particular focus on nutrition, skincare, and intestinal failure management. The current guidance directs toward early surgical intervention for penetrating disease when feasible. Accurate preoperative imaging, medical management of active diseases, and surgical decision-making based on experience and evidence play a key role in success.

IL-36γ and IL-36Ra Reciprocally Regulate Colon Inflammation and Tumorigenesis by Modulating the Cell-Matrix Adhesion Network and Wnt Signaling

Inflammatory bowel disease and colorectal cancer are associated with dysregulation of cytokine networks. However, it is challenging to target cytokines for effective intervention because of the overlapping functions and unpredictable interactions of cytokines in such diverse networks. Here, it is shown that IL-36γ and IL-36Ra, an agonist and an antagonist for IL-36R signaling respectively, reciprocally regulate the experimental colitis and the colon cancer development in mice. Knockout or neutralization of IL-36γ alleviates dextran sulfate sodium (DSS)-induced colitis and inhibits colon cancer development, whereas knockout of IL-36Ra exacerbates DSS-induced colitis and promotes colonic tumorigenesis in multiple colon cancer models in mice. Mechanistically, IL-36γ upregulates extracellular matrix and cell-matrix adhesion molecules and facilitates Wnt signaling, which is mitigated by IL-36Ra or IL-36γ neutralizing antibody. Consistently, IL-36γ levels are positively correlated with extracellular matrix levels and β-catenin levels in human colorectal tumor biopsies. These findings suggest the critical role of IL-36γ and IL-36Ra in gut inflammation and tumorigenesis and indicate that targeting the IL-36γ/IL-36Ra signal balance provides potential therapeutic strategy for inflammatory bowel disease and gastrointestinal cancers.

Revisiting fibrosis in inflammatory bowel disease: the gut thickens

Intestinal fibrosis, which is usually the consequence of chronic inflammation, is a common complication of inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis. In the past few years, substantial advances have been made in the areas of pathogenesis, diagnosis and management of intestinal fibrosis. Of particular interest have been inflammation-independent mechanisms behind the gut fibrotic process, genetic and environmental risk factors (such as the role of the microbiota), and the generation of new in vitro and in vivo systems to study fibrogenesis in the gut. A huge amount of work has also been done in the area of biomarkers to predict or detect intestinal fibrosis, including novel cross-sectional imaging techniques. In parallel, researchers are embarking on developing and validating clinical trial end points and protocols to test novel antifibrotic agents, although no antifibrotic therapies are currently available. This Review presents the state of the art on the most recently identified pathogenic mechanisms of this serious IBD-related complication, focusing on possible targets of antifibrotic therapies, management strategies, and factors that might predict fibrosis progression or response to treatment.

Interleukin-1 Receptor-Like 2: One Receptor, Three Agonists, and Many Implications

The interleukin (IL)-1 superfamily of cytokines comprises 11 pro- and anti-inflammatory cytokines, which play essential roles during the immune response. Several pathogenic pathways are initiated by IL-1RL2 (interleukin 1 receptor-like 2) signaling, also known as IL-36R, in the skin, lungs, and gut. IL-36 cytokines promote the secretion of proinflammatory cytokines and chemokines, upregulation of antimicrobial peptides, proliferation mediators, and adhesion molecules on endothelial cells. In addition, the IL-36-IL-1RL2 axis has an essential role against viral infections, including a potential role in COVID-19 pathology. The evidence presented in this review highlights the importance of the axis IL-36-IL-1RL2 in the development of several inflammation-related diseases and the healing process. It suggests that IL-1RL2 ligands have specific roles depending on the tissue or cell source. However, there is still much to discover about this cytokine family, their functions in other organs, and how they accomplish a dual effect in inflammation and healing.

The Protective Role of IL-36/IL-36R Signal in Con A-Induced Acute Hepatitis

The IL-36 family, including IL-36α, IL-36β, IL-36γ, and IL-36R antagonist, belong to the IL-1 superfamily. It was reported that IL-36 plays a role in immune diseases. However, it remains unclear how IL-36 regulates inflammation. To determine the role of IL-36/IL-36R signaling pathways, we established an acute hepatitis mouse model (C57BL/6) by i.v. injection of the plant lectin Con A. We found that the levels of IL-36 were increased in the liver after Con A injection. Our results demonstrated the infiltrated neutrophils, but not the hepatocytes, were the main source of IL-36 in the liver. Using the IL-36R-/- mouse model (H-2b), we surprisingly found that the absence of IL-36 signals led to aggravated liver injury, as evidenced by increased mortality, elevated serum alanine aminotransferase and aspartate aminotransferase levels, and severe liver pathological changes. Further investigations demonstrated that a lack of IL-36 signaling induced intrahepatic activation of CD4+ and CD8+ T lymphocytes and increased the production of inflammatory cytokines. In addition, IL-36R-/- mice had reduced T regulatory cell numbers and chemokines in the liver. Together, our results from the mouse model suggested a vital role of IL-36 in regulating T cell function and homeostasis during liver inflammation.

The role of IL-36 subfamily in intestinal disease

Interleukin (IL)-36 is a subfamily, of the IL-1 super-family and includes IL-36α, IL-36β, IL-36γ, IL-38 and IL-36Ra. IL-36 cytokines are involved in the pathology of multiple tissues, including skin, lung, oral cavity, intestine, kidneys and joints. Recent studies suggest that IL-36 signaling regulates autoimmune disease in addition to antibacterial and antiviral responses. Most research has focused on IL-36 in skin diseases such as psoriasis, however, studies on intestinal diseases are also underway. This review outlines what is known about the bioactivity of the IL-36 subfamily and its role in the pathogenesis of intestinal diseases such as inflammatory bowel disease, colorectal cancer, gut dysbacteriosis and infection, and proposes that IL-36 may be a target for novel therapeutic strategies to prevent or treat intestinal diseases.

Increased Levels of Interleukin-36 in Obesity and Type 2 Diabetes Fuel Adipose Tissue Inflammation by Inducing Its Own Expression and Release by Adipocytes and Macrophages

Interleukin (IL)-36 is a recently described cytokine with well-known functions in the regulation of multiple inflammatory diseases. Since no data exists on how this cytokine regulates adipose tissue (AT) homeostasis, we aimed to explore the function of a specific isoform, IL-36γ, an agonist, in human obesity and obesity-associated type 2 diabetes as well as in AT inflammation and fibrosis. Plasma IL-36γ was measured in 91 participants in a case-control study and the effect of weight loss was evaluated in 31 patients with severe obesity undergoing bariatric surgery. Gene expression levels of IL36G and its receptor were analyzed in relevant human metabolic tissues. The effect of inflammatory factors and IL-36γ was determined in vitro in human adipocytes and macrophages. We found, for the first time, that the increased (P<0.05) circulating levels of IL-36γ in patients with obesity decreased (P<0.001) after weight and fat loss achieved by Roux-en-Y gastric bypass and that gene expression levels of IL36G were upregulated in the visceral AT (P<0.05) and in the peripheral blood mononuclear cells (P<0.01) from patients with obesity. We also demonstrated increased (P<0.05) expression levels of Il36g in the epididymal AT from diet-induced obese mice. IL36G was significantly enhanced (P<0.001) by LPS in human adipocytes and monocyte-derived macrophages, while no changes were found after the incubation with anti-inflammatory cytokines. The addition of IL-36γ for 24 h strongly induced (P<0.01) its own expression as well as key inflammatory and chemoattractant factors with no changes in genes associated with fibrosis. Furthermore, adipocyte-conditioned media obtained from patients with obesity increased (P<0.01) the release of IL-36γ and the expression (P<0.05) of cathepsin G (CTSG) in monocyte-derived macrophages. These findings provide, for the first time, evidence about the properties of IL-36γ in the regulation of AT-chronic inflammation, emerging as a link between AT biology and the obesity-associated comorbidities.

The Attenuation of Chronic Ulcerative Colitis by (R)-salbutamol in Repeated DSS-Induced Mice

Racemic salbutamol ((RS)-sal), which consist of the same amount of (R)-sal and (S)-sal, has been used for asthma and COPD due to its bronchodilation effect. However, the effect of (R)-sal on repeated dextran sulfate sodium (DSS)-induced chronic colitis has not yet been investigated. In this study evaluated the potential effect of (R)-, (S)-, and (RS)-sal in mice with repeated DSS-induced chronic colitis and investigated the underlying mechanisms. Here, we verified that chronic colitis was significantly attenuated by (R)-sal, which was evidenced by notably mitigated body weight loss, disease activity index (DAI), splenomegaly, colonic lengths shortening, and histopathological scores. (R)-sal treatment noticeably diminished the levels of inflammatory cytokines (such as TNF-α, IL-6, IL-1β, and IFN-γ). Notably, the efficacy of (R)-sal was better than that of (RS)-sal. Further research revealed that (R)-sal mitigated colonic CD4 leukocyte infiltration, decreased NF-κB signaling pathway activation, improved the Nrf-2/HO-1 signaling pathway, and increased the expression of ZO-1 and occludin. In addition, (R)-sal suppressed the levels of TGF-β1, α-SMA, and collagen in mice with chronic colitis. Furthermore, the 16S rDNA sequences analyzed of the intestinal microbiome revealed that (R)-sal could mitigate the intestinal microbiome structure and made it more similar to the control group, which mainly by relieving the relative abundance of pathogens (such as Bacteroides) and increasing the relative abundance of probiotics (such as Akkermansia). Therefore, (R)-sal ameliorates repeated DSS-induced chronic colitis in mice by improving inflammation, suppressing oxidative stress, mitigating intestinal barrier function, relieving intestinal fibrosis, and regulating the intestinal microbiome community. These results indicate that (R)-sal maybe a novel treatment alternative for chronic colitis.

Therapeutic Targeting of Intestinal Fibrosis in Crohn's Disease

Intestinal fibrosis is one of the most threatening complications of Crohn’s disease. It occurs in more than a third of patients with this condition, is associated with increased morbidity and mortality, and surgery often represents the only available therapeutic option. The mechanisms underlying intestinal fibrosis are partly known. Studies conducted so far have shown a relevant pathogenetic role played by mesenchymal cells (especially myofibroblasts), cytokines (e.g., transforming growth factor-β), growth factors, microRNAs, intestinal microbiome, matrix stiffness, and mesenteric adipocytes. Further studies are still necessary to elucidate all the mechanisms involved in intestinal fibrosis, so that targeted therapies can be developed. Although several pre-clinical studies have been conducted so far, no anti-fibrotic therapy is yet available to prevent or reverse intestinal fibrosis. The aim of this review is to provide an overview of the main therapeutic targets currently identified and the most promising anti-fibrotic therapies, which may be available in the near future.

The anti-inflammatory and protective role of interleukin-38 in inflammatory bowel disease

Interleukin (IL)-38 exerts an anti-inflammatory function by binding to several cytokine receptors, including the IL-36 receptor. In this study, we evaluated IL-38 expression in the inflamed mucosa of patients with inflammatory bowel disease (IBD) and investigated its functions. IL-38 mRNA expression in endoscopic biopsy samples was evaluated using quantitative PCR. IL-38 protein expression was analyzed using immunohistochemical technique. Dextran sulfate sodium-induced colitis was induced in C57BL/6 background IL-38KO mice. The IL-38 mRNA and protein expression were enhanced in the active mucosa of ulcerative colitis, but not in Crohn's disease. The ratio of IL-36γ to IL-38 mRNA expression was significantly elevated in the active mucosa of UC patients. Immunofluorescence staining revealed that B cells are the major cellular source of IL-38 in the colonic mucosa. IL-38 dose-dependently suppressed the IL-36γ-induced mRNA expression of CXC chemokines (CXCL1, CXCL2, and CXCL8) in HT-29 and T84 cells. IL-38 inhibited the IL-36γ-induced activation of nuclear-factor kappa B (NF-κB) and mitogen-activated protein kinases in HT-29 cells. DSS-colitis was significantly exacerbated in IL-38KO mice compared to wild type mice. In conclusion, IL-38 may play an anti-inflammatory and protective role in the pathophysiology of IBD, in particular ulcerative colitis, through the suppression of IL-36-induced inflammatory responses.

Challenges in the Pathophysiology, Diagnosis, and Management of Intestinal Fibrosis in Inflammatory Bowel Disease

Intestinal fibrosis is a common complication of inflammatory bowel disease (IBD) that is usually the consequence of chronic inflammation. Although the currently available anti-inflammatory therapies have had little impact on intestinal fibrosis in Crohn’s disease (CD), increased understanding of the pathophysiology and the development of therapies targeting fibrogenic pathways hold promise for the future. One of the critical challenges is how reduction or reversal of intestinal fibrosis should be defined and measured in the setting of clinical trials and drug approval. The International Organization for Inflammatory Bowel Disease (IOIBD) organized a workshop in Amsterdam, The Netherlands, on December 19^th and 20^th, 2018 in an attempt to review the current knowledge of the biological background, diagnosis, treatment of intestinal fibrosis and clinical trial endpoints. Basic and clinical scientists discussed the pathophysiology of intestinal fibrosis, the current status of biomarkers and imaging modalities in stenosing CD, and recent clinical studies in this area. Researchers from outside of the IBD field presented advances in the understanding of fibrotic processes in other organs, such as the skin, liver and lungs. Lastly, the design of clinical trials with antifibrotic therapy for IBD was discussed, with priority on patient populations, patient reported outcomes (PROs) and imaging. This report summarizes the key findings, discussions and conclusions of the workshop.

IL-36 cytokines imprint a colitogenic phenotype on CD4+ T helper cells

IL-36 cytokines are emerging as potent orchestrators of intestinal inflammation and are being implicated in the pathogenesis of inflammatory bowel diseases (IBD). However, the mechanisms through which these cytokines mediate these effects remain to be fully uncovered. Here, we report specifically elevated expression of IL-36α, and not IL-36β or IL-36γ in the serum of newly diagnosed, treatment naïve, paediatric IBD patients and identify T cells as primary cellular mediators of IL-36 responses in the inflamed gut. IL-36R expression on CD4⁺ T cells was found to promote intestinal pathology in a murine model of colitis. Consistent with these effects, IL-36R can act as a potent instructor of CD4⁺ T cell differentiation in vivo, enhancing Th1 responses, while inhibiting the generation of Tregs. In addition, loss of IL-36 responsiveness significantly reduced the migration of pathogenic CD4⁺ T cells towards intestinal tissues and IL-36 was found to act, uniquely among IL-1 family members, to induce the expression of gut homing receptors in proinflammatory murine and human CD4⁺ T cells. These data reveal an important role for IL-36 cytokines in driving the colitogenic potential of CD4⁺ T cells and identify a new mechanism through which they may contribute to disease pathogenesis.

Immunological Regulation of Intestinal Fibrosis in Inflammatory Bowel Disease

Intestinal fibrosis is a late-stage phenotype of inflammatory bowel disease (IBD), which underlies most of the long-term complications and surgical interventions in patients, particularly those with Crohn's disease. Despite these issues, antifibrotic therapies are still scarce, mainly due to the current lack of understanding concerning the pathogenetic mechanisms that mediate fibrogenesis in patients with chronic intestinal inflammation. In the current review, we summarize recent evidence regarding the cellular and molecular factors of innate and adaptive immunity that are considered critical for the initiation and amplification of extracellular matrix deposition and stricture formation. We focus on the role of cytokines by dissecting the pro- vs antifibrotic components of the immune response, while taking into consideration their temporal association to the progressive stages of the natural history of IBD. We critically present evidence from animal models of intestinal fibrosis and analyze inflammation-fibrosis interactions that occur under such experimental scenarios. In addition, we comment on recent findings from large-scale, single-cell profiling of fibrosis-relevant populations in IBD patients. Based on such evidence, we propose future potential targets for antifibrotic therapies to treat patients with IBD.

Pyroptosis: Mechanisms and Links with Fibrosis

Fibrosis is responsible for approximately 45% of deaths in the industrialized world and has been a major global healthcare burden. Excessive fibrosis is the primary cause of organ failure. However, there are currently no approved drugs available for the prevention or treatment of fibrosis-related diseases. It has become evident that fibrosis is characterized by inflammation. In a large number of studies of various organs in mice and humans, pyroptosis has been found to play a significant role in fibrosis. Pyroptosis is a form of programmed cell death mediated by the N-terminal fragment of cysteinyl aspartate-specific proteinase (caspase)-1-cleaved gasdermin D (GSDMD, producing GSDMD-N) that gives rise to inflammation via the release of some proinflammatory cytokines, including IL-1β, IL-18 and HMGB1. These cytokines can initiate the activation of fibroblasts. Inflammasomes, an important factor upstream of GSDMD, can activate caspase-1 to trigger the maturation of IL-1β and IL-18. Moreover, the inhibition of inflammasomes, proinflammatory cytokines and GSDMD can prevent the progression of fibrosis. This review summarizes the growing evidence indicating that pyroptosis triggers fibrosis, and highlights potential novel targets for antifibrotic therapies.

Interleukin-36 Cytokines in Infectious and Non-Infectious Lung Diseases

The IL-36 family of cytokines were identified in the early 2000’s as a new subfamily of the IL-1 cytokine family, and since then, the role of IL-36 cytokines during various inflammatory processes has been characterized. While most of the research has focused on the role of these cytokines in autoimmune skin diseases such as psoriasis and dermatitis, recent studies have also shown the importance of IL-36 cytokines in the lung inflammatory response during infectious and non-infectious diseases. In this review, we discuss the biology of IL-36 cytokines in terms of how they are produced and activated, as well as their effects on myeloid and lymphoid cells during inflammation. We also discuss the role of these cytokines during lung infectious diseases caused by bacteria and influenza virus, as well as other inflammatory conditions in the lungs such as allergic asthma, lung fibrosis, chronic obstructive pulmonary disease, cystic fibrosis and cancer. Finally, we discuss the current therapeutic advances that target the IL-36 pathway and the possibility to extend these tools to treat lung inflammatory diseases.

Current Topics of the Mechanism of Intestinal Fibrosis in Crohn’s Disease

Intestinal fibrosis is one of the most common intestinal complications observed in inflammatory bowel disease, especially Crohn’s disease (CD). Intestinal fibrosis in CD is associated with chronic inflammation resulting from immunologic abnormalities and occurs as a form of tissue repair during the anti-inflammatory process. Various types of immune cells and mesenchymal cells, including myofibroblasts, are intricately involved in causing intestinal fibrosis. It is often difficult to treat intestinal fibrosis as intestinal stricture may develop despite treatment aimed at controlling inflammation. Detailed analysis of the pathogenesis of intestinal fibrosis is critical towards advancing the development of future therapeutic applications.

Paediatric Ulcerative Colitis Is a Fibrotic Disease and Is Linked with Chronicity of Inflammation

BACKGROUND AND AIMS

Intestinal fibrosis has recently been characterised in adult ulcerative colitis and may affect motility, diarrhoea, and the symptom of urgency. We aimed to charactersze the presence of fibrosis in paediatric patients with ulcerative colitis, and its link to severity and chronicity of mucosal inflammation, as well as clinical factors of severity.

METHODS

We performed a single-centre cross-sectional study in children ages 1-18 years with ulcerative colitis, undergoing colectomy or proctocolectomy. Tissue cross-sections were derived from proximal, mid, and distal colon and rectum, and inflammation and fibrosis were graded based on previously developed scores. Clinical data were collected prospectively.

RESULTS

From 62 patients, 205 intestinal sections were evaluated. Median age at diagnosis was 13 years, 100% had extensive colitis, and all resections were done for refractory disease. The presence, chronicity, and degree of inflammation were linked with the presence of fibrosis. Thickness of the muscularis mucosa was also linked with presence and chronicity of inflammation. The overall submucosal fibrosis burden was associated with prior anti-tumour necrosis factor use.

CONCLUSIONS

Paediatric patients with ulcerative colitis exhibit colorectal submucosal fibrosis and muscularis mucosa thickening, which correlate with the presence, chronicity, and degree of mucosal inflammation. Fibrosis should be recognised as a complication of paediatric ulcerative colitis, and ulcerative colitis should be considered a progressive disease.

Is the Macrophage Phenotype Determinant for Fibrosis Development?

Fibrosis is a pathophysiological process of wound repair that leads to the deposit of connective tissue in the extracellular matrix. This complication is mainly associated with different pathologies affecting several organs such as lung, liver, heart, kidney, and intestine. In this fibrotic process, macrophages play an important role since they can modulate fibrosis due to their high plasticity, being able to adopt different phenotypes depending on the microenvironment in which they are found. In this review, we will try to discuss whether the macrophage phenotype exerts a pivotal role in the fibrosis development in the most important fibrotic scenarios.

Serum Levels of Interleukin-36 Alpha and Interleukin-36 Receptor Antagonist In Behcet’s Syndrome

Background Behcet’s syndrome (BS) is a systemic vasculitic disorder. This study aimed to investigate the levels of serum IL-36α and IL-36Ra in patients with BS.

Material and Methods A total of 80 subjects (60 BS patients and 20 healthy controls [HC]) were included.

Results The median IL-36α level was 0.11 ng/ml in the BS group and 0.09 ng/ml in the HC group (p=0.058). The mean IL-36Ra level was 13.62 pg/ml in the BS group and 13.26 pg/ml in the HC group (p=0.348). Serum IL-36Ra levels of the active group were significantly higher (p=0.037). Patients with oral ulcers and central nervous system involvement had higher serum IL36Ra levels. In the BS group, a positive correlation was found between serum IL-36Ra and CRP. In a multivariate analysis, the IL-36Ra level (OR=1.067; 95% CI=1.001–1.137; p=0.045) was independently associated with disease activity.

Conclusion According to these findings, it is not clear whether such a slight difference is clinically significant, but they suggest that the IL-36 cytokine family may play a role in the course of the disease.

IL-36γ and IL-36Ra Reciprocally Regulate NSCLC Progression by Modulating GSH Homeostasis and Oxidative Stress-Induced Cell Death

The balance between antioxidants and reactive oxygen species (ROS) critically regulates tumor initiation and progression. However, whether and how the tumor-favoring redox status is controlled by cytokine networks remain poorly defined. Here, it is shown that IL-36γ and IL-36Ra reciprocally regulate the progression of non-small cell lung cancer (NSCLC) by modulating glutathione metabolism and ROS resolution. Knockout, inhibition, or neutralization of IL-36γ significantly inhibits NSCLC progression and prolongs survival of the KrasLSL-G12D/+ Tp53fl/fl and KrasLSL-G12D/+ Lkb1fl/fl mice after tumor induction, whereas knockout of IL-36Ra exacerbates tumorigenesis in these NSCLC mouse models and accelerates death of mice. Mechanistically, IL-36γ directly upregulates an array of genes involved in glutathione homeostasis to reduce ROS and prevent oxidative stress-induced cell death, which is mitigated by IL-36Ra or IL-36γ neutralizing antibody. Consistently, IL-36γ staining is positively and negatively correlated with glutathione biosynthesis and ROS in human NSCLC tumor biopsies, respectively. These findings highlight essential roles of cytokine networks in redox for tumorigenesis and provide potential therapeutic strategy for NSCLC.

Development of Anti-fibrotic Therapy in Stricturing Crohn's Disease: Lessons from Randomized Trials in Other Fibrotic Diseases

Intestinal fibrosis is considered an inevitable complication of Crohn's disease (CD) that results in symptoms of obstruction and stricture formation. Endoscopic or surgical treatment is required to treat the majority of patients. Progress in the management of stricturing CD is hampered by the lack of effective anti-fibrotic therapy; however, this situation is likely to change because of recent advances in other fibrotic diseases of the lung, liver and skin. In this review, we summarized data from randomized controlled trials (RCT) of anti-fibrotic therapies in these conditions. Multiple compounds have been tested for the anti-fibrotic effects in other organs. According to their mechanisms, they were categorized into growth factor modulators, inflammation modulators, 5-hydroxy-3-methylgultaryl-coenzyme A (HMG-CoA) reductase inhibitors, intracellular enzymes and kinases, renin-angiotensin system (RAS) modulators and others. From our review of the results from the clinical trials and discussion of their implications in the gastrointestinal tract, we have identified several molecular candidates that could serve as potential therapies for intestinal fibrosis in CD.

IL-36 in chronic inflammation and fibrosis - bridging the gap?

IL-36 is a member of the IL-1 superfamily and consists of three agonists and one receptor antagonist (IL-36Ra). The three endogenous agonists, IL-36α, -β, and -γ, act primarily as proinflammatory cytokines, and their signaling through the IL-36 receptor (IL-36R) promotes immune cell infiltration and secretion of inflammatory and chemotactic molecules. However, IL-36 signaling also fosters secretion of profibrotic soluble mediators, suggesting a role in fibrotic disorders. IL-36 isoforms and IL-36 have been implicated in inflammatory diseases including psoriasis, arthritis, inflammatory bowel diseases, and allergic rhinitis. Moreover, IL-36 has been connected to fibrotic disorders affecting the kidney, lung, and intestines. This review summarizes the expression, cellular source, and function of IL-36 in inflammation and fibrosis in various organs, and proposes that IL-36 modulation may prove valuable in preventing or treating inflammatory and fibrotic diseases and may reveal a mechanistic link between inflammation and fibrosis.

Inositol-Requiring Kinase 1 Regulates Apoptosis via Inducing Endoplasmic Reticulum Stress in Colitis Epithelial Cells

BACKGROUND

Endoplasmic reticulum stress (ERS) has been studied as critical factor during occurrence and development of ulcerative colitis (UC). However, the role of ERS in inflamed UC remains unclear.

AIMS

The purpose of this study was to analyze the role of inositol-requiring kinase 1 (IRE-1), a major regulator of ER, in regulating ERS and cell viability.

METHODS

In UC mucosa tissue, IRE-1, BiP, XBP-1s, CHOP caspase-12 and GADD34 mRNA were assayed by qRT-PCR. Then, human normal colon epithelial cell line (NCM-460) and colon fibroblast cell line (CCD-33Co) were cultured, and downregulated or upregulated IRE-1 expression. ERS was induced with 100 ng/mL of Interleukin 6 (IL-6). CCK8 assay was performed to analyze cell proliferation. Flow cytometry analysis was conducted to detect the apoptosis. Western blot assay was used to examine ERS markers.

RESULTS

IRE-1, BiP, XBP-1s, caspase-12 and CHOP mRNA were highly expressed in UC mucosa tissue, and the expression of GADD34 mRNA significantly decreased. These results show that ERS-induced unfolded protein response was enhanced in UC mucosa tissue. In cells, silencing the expression of IRE-1 could suppress cell proliferation and promote apoptosis through activating unfolded protein response, while the over-expression of IRE-1 had the opposite effect. IL-6 could induce ERS and cells apoptosis. Furthermore, we demonstrated that shRNA IRE-1 could enhance the inhibition of IL-6 on cells viability.

CONCLUSIONS

Inhibition of IRE-1 enhanced unfolded protein response and cells apoptosis and IL-6-induced ERS and suggested that IRE-1 might be a potential target of UC.

The Potential Immunomodulatory Properties of Levornidazole Contribute to Improvement in Experimental Ulcerative Colitis

The use of an antibiotic with immunomodulatory properties could be fascinating in treating multifactorial inflammatory conditions such as ulcerative colitis (UC). We report our investigations into the immunomodulatory properties of levornidazole, the S-enantiomer of ornidazole, which displayed a tremendous therapeutic potential in UC induced by dextran sodium sulfate (DSS). Levornidazole administration to DSS-colitic mice attenuated the intestinal inflammatory process, with an efficacy better than that shown by 5-amino salicylic acid. This was evidenced by decreased disease activity index, ameliorated macroscopic and microscopic colon damages, and reduced expression of inflammatory cytokines. Additionally, levornidazole displayed anti-inflammatory activity through Caveolin-1-dependent reducing IL-1β and IL-18 secretion by macrophages contributing to its improvement of the intestinal inflammation, as confirmed in vitro and in vivo. In conclusion, these results pointed out that the immunomodulatory effects of levornidazole played a vital role in ameliorating the intestinal inflammatory process, which would be crucial for the translation of its use into clinical settings.

IL-36 cytokines in inflammatory and malignant diseases: not the new kid on the block anymore

The IL-36 family of cytokines were first identified in 2000 based on their sequence homology to IL-1 cytokines. Over subsequent years, the ability of these cytokines to either agonise or antagonise an IL-1R homologue, now known as the IL-36 Receptor (IL-36R), was identified and these cytokines went through several cycles of renaming with the current nomenclature being proposed in 2010. Despite being identified over 20 years ago, it is only during the last decade that the function of these cytokines in health and disease has really begun to be appreciated, with both homeostatic functions in wound healing and response to infection, as well as pathological functions now ascribed. In the disease context, over activation of IL-36 has now been associated with many inflammatory diseases including Psoriasis and inflammatory bowel diseases, with roles in cancer also now being investigated. This review summarises the current knowledge of IL-36 biology, its role in inflammatory diseases and focuses on an emerging role for IL-36 in cancer.

Endotrophin and C6Ma3, serological biomarkers of type VI collagen remodelling, reflect endoscopic and clinical disease activity in IBD

In inflammatory bowel disease (IBD), the chronic inflammation deeply affects the intestinal extracellular matrix. The aim of this study was to investigate if remodeling of the intestinal basement membrane type VI collagen was associated with pathophysiological changes in Crohn’s disease (CD) and ulcerative colitis (UC). Serum from IBD patients (CD: n = 65; UC: n = 107; irritable bowel syndrome: n = 18; healthy subjects: n = 20) was investigated in this study. The serological biomarkers C6Ma3 (a matrix metalloproteinase (MMP) generated fragment of the type VI collagen α3 chain) and PRO-C6, also called endotrophin (the C-terminus of the released C5 domain of the type VI collagen α3 chain) were measured by ELISAs. Serum C6Ma3 was increased in CD patients with moderate to severe and mild endoscopically active disease compared to endoscopic remission (p = 0.002, p = 0.0048), respectively, and could distinguish endoscopically active disease from remission with an AUC of 1.0 (sensitivity: 100%, specificity: 100%) (p < 0.0001), which was superior to CRP. C6Ma3 was increased in CD patients with moderate to severe clinical disease compared to mild and remission (p = 0.04; p = 0.009). Serum PRO-C6, endotrophin, was increased in CD patients in clinically remission compared to mild disease (p = 0.04) and moderate to severe disease (p = 0.065). In UC, fecal calprotectin was the only marker that alone could distinguish both clinical and endoscopic active and inactive disease. Type VI collagen degradation of the α3 chain mediated by MMPs was increased in CD patients with endoscopically active disease, measured by the serological biomarker C6Ma3, which was able to distinguish endoscopically active from inactive CD.

E-type prostanoid receptor 4 drives resolution of intestinal inflammation by blocking epithelial necroptosis

Inflammatory bowel diseases present with elevated levels of intestinal epithelial cell (IEC) death, which compromises the gut barrier, activating immune cells and triggering more IEC death. The endogenous signals that prevent IEC death and break this vicious cycle, allowing resolution of intestinal inflammation, remain largely unknown. Here we show that prostaglandin E2 signalling via the E-type prostanoid receptor 4 (EP4) on IECs represses epithelial necroptosis and induces resolution of colitis. We found that EP4 expression correlates with an improved IBD outcome and that EP4 activation induces a transcriptional signature consistent with resolution of intestinal inflammation. We further show that dysregulated necroptosis prevents resolution, and EP4 agonism suppresses necroptosis in human and mouse IECs. Mechanistically, EP4 signalling on IECs converges on receptor-interacting protein kinase 1 to suppress tumour necrosis factor-induced activation and membrane translocation of the necroptosis effector mixed-lineage kinase domain-like pseudokinase. In summary, our study indicates that EP4 promotes the resolution of colitis by suppressing IEC necroptosis.

Effect and Mechanism of TL1A Expression on Epithelial-Mesenchymal Transition during Chronic Colitis-Related Intestinal Fibrosis

BACKGROUND AND AIMS

Recent evidences reveal that epithelial to mesenchymal transition (EMT) exacerbates the process of intestinal fibrosis. Tumor necrosis factor-like ligand 1A (TL1A) is a member of the tumor necrosis family (TNF), which can take part in the development of colonic inflammation and fibrosis by regulating immune response or inflammatory factors. The purpose of this study was to elucidate the possible contribution of TL1A in onset and progression of intestinal inflammation and fibrosis through EMT.

METHODS

Colonic specimens were obtained from patients with inflammatory bowel disease (IBD) and control individuals. The expression levels of TL1A and EMT-related markers in intestinal tissues were evaluated. Furthermore, the human colorectal adenocarcinoma cell line, HT-29, was stimulated with TL1A, anti-TL1A antibody, or BMP-7 to assess EMT process. In addition, transgenic mice expressing high levels of TL1A in lymphoid cells were used to further investigate the mechanism of TL1A in intestinal fibrosis.

RESULTS

High levels of TL1A expression were detected in the intestinal specimens of patients with ulcerative colitis and Crohn's disease and were negatively associated with the expression of an epithelial marker (E-cadherin), while it was positively associated with the expression of interstitial markers (FSP1 and α-SMA). Transgenic mice with high expression of TL1A were more sensitive to dextran sodium sulfate and exhibited severe intestinal inflammation and fibrosis. Additionally, the TGF-β1/Smad3 pathway may be involved in TL1A-induced EMT, and the expression of IL-13 and EMT-related transcriptional molecules (e.g., ZEB1 and Snail1) was increased in the intestinal specimens of the transgenic mice. Furthermore, TL1A-induced EMT can be influenced by anti-TL1A antibody or BMP-7 in vitro.

CONCLUSIONS

TL1A participates in the formation and process of EMT in intestinal fibrosis. This new knowledge enables us to better understand the pathogenesis of intestinal fibrosis and identify new therapeutic targets for its treatment.

Noncoding RNAs as Promising Diagnostic Biomarkers and Therapeutic Targets in Intestinal Fibrosis of Crohn's Disease: The Path From Bench to Bedside

Fibrosis is a major pathway to organ injury and failure, accounting for more than one-third of deaths worldwide. Intestinal fibrosis causes irreversible and serious clinical complications, such as strictures and obstruction, secondary to a complex pathogenesis. Under the stimulation of profibrotic soluble factors, excessive activation of mesenchymal cells causes extracellular matrix deposition via canonical transforming growth factor-β/Smads signaling or other pathways (eg, epithelial-to-mesenchymal transition and endothelial-to-mesenchymal transition) in intestinal fibrogenesis. In recent studies, the importance of noncoding RNAs (ncRNAs) stands out in fibrotic diseases in that ncRNAs exhibit a remarkable variety of biological functions in modulating the aforementioned fibrogenic responses. In this review, we summarize the role of ncRNAs, including the emerging long ncRNAs and circular RNAs, in intestinal fibrogenesis. Notably, the translational potential of ncRNAs as diagnostic biomarkers and therapeutic targets in the management of intestinal fibrosis is discussed based on clinical trials from fibrotic diseases in other organs. The main points of this review include the following: • Characteristics of ncRNAs and mechanisms of intestinal fibrogenesis • Wide participation of ncRNAs (especially the emerging long ncRNAs and circular RNAs) in intestinal fibrosis, including transforming growth factor-β signaling, epithelial-to-mesenchymal transition/endothelial-to-mesenchymal transition, and extracellular matrix remodeling • Translational potential of ncRNAs in the diagnosis and treatment of intestinal fibrosis based on clinical trials from fibrotic diseases in other organs.