Mouse models of inflammatory bowel disease for investigating mucosal immunity in the intestine

Anti-inflammatory effects of heat-killed Lactiplantibacillus argentoratensis BBLB001 on a gut inflammation co-culture cell model and dextran sulfate sodium-induced colitis mouse model

Dysbiosis caused by dietary changes can alter the intestinal bacterial species and is closely associated with inflammatory bowel disease (IBD). Among the possible treatment options, postbiotics, which act to balance the constituent intestinal microflora, have gained substantial attention. Herein, we investigated the anti-inflammatory effects of heat-killed Lactiplantibacillus argentoratensis (hk-LA) BBLB001 isolated from a marine environment using both cell (Caco2/RAW264.7 cell co-culture) and animal (dextran sodium sulfate [DSS]-induced colitis in mice) models. hk-LA BBLB001 markedly reduced IL-8 secretion in Caco-2 cell culture medium after lipopolysaccharide-mediated stimulation of RAW264.7 cells by enhancing the expression of cell adhesion factors.The body weight loss, reduced inflammatory cytokine levels in the serum and colon tissues, colon shortening, and myeloperoxidase activation caused by DSS in mice were alleviated by hk-LA BBLB001. Similar to that in the intestinal cell model, the gene and protein expressions of cell adhesion molecules in the colon tissue were increased upon hk-LA BBLB001 treatment in DSS-induced colitis mice. We observed increased mucin expression and secretory IgA concentration in colon tissues, suggesting that hk-LA BBLB001 intake may benefit pathogen defense and the regulation of intestinal commensal bacteria. Thus, hk-LA BBLB001 may serve as an instrumental postbiotic material in IBD treatment.

Microbiome- and Host Inflammasome-Targeting Inhibitor Nanoligomers Are Therapeutic in the Murine Colitis Model

Autoimmune and autoinflammatory diseases account for more than 80 chronic conditions affecting more than 24 million people in the US. Among these autoinflammatory diseases, noninfectious chronic inflammation of the gastrointestinal (GI) tract causes inflammatory bowel diseases (IBDs), primarily Crohn's and ulcerative colitis (UC). IBD is a complex disease, and one hypothesis is that these are either caused or worsened by compounds produced by bacteria in the gut. While traditional approaches have focused on pan immunosuppressive techniques (e.g., steroids), low remission rates, prolonged illnesses, and an increased frequency of surgical procedures have prompted the search for more targeted and precision therapeutic approaches. IBD is a complex disease resulting from both genetic and environmental factors, but several recent studies have highlighted the potential pivotal contribution of gut microbiota dysbiosis. Gut microbiota are known to modulate the immune status of the gut by producing metabolites that are encoded in biosynthetic gene clusters (BGCs) of the bacterial genome. Here, we show a targeted and high-throughput screening of more than 90 biosynthetic genes in 41 gut anaerobes, through downselection using available bioinformatics tools, targeted gene manipulation in these genetically intractable organisms using the Nanoligomer platform, and identification and synthesis of top microbiome targets as a Nanoligomer BGC cocktail (SB_BGC_CK1, abbreviated as CK1) as a feasible precision therapeutic approach. Further, we used a host-directed immune target screening to identify the NF-κB and NLRP3 cocktail SB_NI_112 (or NI112 for short) as a targeted inflammasome inhibitor. We used these top two microbe- and host-targeted Nanoligomer cocktails in acute and chronic dextran sulfate sodium (DSS) mouse colitis and in TNFΔARE/+ transgenic mice that develop spontaneous Crohn's like ileitis. The mouse microbiome was humanized to replicate that in human IBD through antibiotic treatment, followed by mixed fecal gavage from 10 human donors and spiked with IBD-inducing microbial species. Following colonization, colitis was induced in mice using 1 week of 3% DSS (acute) or 6 weeks of 3 rounds of 2.5% DSS induction for a week followed by 1 week of no DSS (chronic colitis model). Both Nanoligomer cocktails (CK1 and NI112) showed a strong reduction in disease severity, significant improvement in disease histopathology, and profound downregulation of disease biomarkers in colon tissue, as assessed by multiplexed ELISA. Further, we used two different formulations of intraperitoneal injections (IP) and Nanoligomer pills in the chronic DSS colitis model. Although both formulations were highly effective, the oral pill formulation demonstrated a greater reduction in biochemical markers compared to IP. A similar therapeutic effect was observed in the TNFΔARE/+ model. Overall, these results point to the potential for further development and testing of this inflammasome-targeting host-directed therapy (NI112) and more personalized microbiome cocktails (CK1) for patients with recalcitrant IBD.

Antibiotics damage the colonic mucus barrier in a microbiota-independent manner

Antibiotic use is a risk factor for development of inflammatory bowel diseases (IBDs). IBDs are characterized by a damaged mucus layer, which does not separate the intestinal epithelium from the microbiota. Here, we hypothesized that antibiotics affect the integrity of the mucus barrier, which allows bacterial penetrance and predisposes to intestinal inflammation. We found that antibiotic treatment led to breakdown of the colonic mucus barrier and penetration of bacteria into the mucus layer. Using fecal microbiota transplant, RNA sequencing followed by machine learning, ex vivo mucus secretion measurements, and antibiotic treatment of germ-free mice, we determined that antibiotics induce endoplasmic reticulum stress in the colon that inhibits colonic mucus secretion in a microbiota-independent manner. This antibiotic-induced mucus secretion flaw led to penetration of bacteria into the colonic mucus layer, translocation of microbial antigens into circulation, and exacerbation of ulcerations in a mouse model of IBD. Thus, antibiotic use might predispose to intestinal inflammation by impeding mucus production.

High casein concentration induces diarrhea through mTOR signal pathway inhibition in post-weaning piglets

Weaning is one of the most challenging periods in a pig's life, during which piglets suffer from nutrition and other issues. Post-weaning diarrhea is one of the major health problems in the pig industry, leading to high morbidity and mortality rates. Previous studies have demonstrated that both the source and concentration of proteins are closely associated with post-weaning diarrhea in piglets. This study was conducted to prevent and control post-weaning diarrhea by selecting different dietary protein concentrations. To eliminate interference from other protein sources, casein was used as the only protein source in this study. Fourteen piglets (weighing 8.43 ± 0.3 kg, weaned on the 28th day) were randomly assigned to two dietary protein groups: a low-protein group (LP, containing 17% casein) and a high-protein group (HP, containing 30% casein). The experiment lasted 2 weeks, during which all piglets had ad libitum access to food and water. Diarrhea was scored on a scale from 1 to 3 (where 1 indicates normal stools and 3 indicates watery diarrhea), and growth performance measurements were recorded daily. The results showed that the piglets in the HP group had persistent diarrhea during the whole study, whereas no diarrhea was observed among piglets in the control group. The body weights and feed intake were significantly lower in piglets in the HP group compared to those in the LP group (p < 0.05). The gastrointestinal pH was significantly higher in piglets in the HP group than those in the LP group (p < 0.05). The intestinal tract microorganisms of the piglets in both groups were significantly affected by the protein concentration of the diet. A diet with high casein concentration significantly reduced the microbiota diversity. Compared to the LP group, the 30% casein diet decreased the abundance of Firmicutes, Bacteroidetes, and Actinobacteria at the phylum level and the relative abundance of Ruminococcus at the genus level. Diarrhea-related mRNA abundances were analyzed by the real-time polymerase chain reaction (PCR) in the intestine of piglets, and the results showed that the HP concentration markedly decreased the expression of solute carriers (SLC, p < 0.05). The mammalian target of rapamycin-mTOR signaling pathway (p < 0.01) was activated in the HP group. In conclusion, a high-protein diet induced post-weaning diarrhea, decreased growth performance, increased gastrointestinal pH, and reduced expression of solute carrier proteins. However, the relationship between high dietary casein feed and post-weaning diarrhea remains unclear and needs to be explored further.

The mucosal immunity in crustaceans: Inferences from other species

Crustaceans such as shrimps and crabs, hold significant ecological significance and substantial economic value within marine ecosystems. However, their susceptibility to disease outbreaks and pathogenic infections has posed major challenges to production in recent decades. As invertebrate, crustaceans primarily rely on their innate immune system for defense, lacking the adaptive immune system found in vertebrates. Mucosal immunity, acting as the frontline defense against a myriad of pathogenic microorganisms, is a crucial aspect of their immune repertoire. This review synthesizes insights from comparative immunology, highlighting parallels between mucosal immunity in vertebrates and innate immune mechanisms in invertebrates. Despite lacking classical adaptive immunity, invertebrates, including crustaceans, exhibit immune memory and rely on inherent "innate immunity factors" to combat invading pathogens. Drawing on parallels from mammalian and piscine systems, this paper meticulously explores the complex role of mucosal immunity in regulating immune responses in crustaceans. Through the extrapolation from well-studied models like mammals and fish, this review infers the potential mechanisms of mucosal immunity in crustaceans and provides insights for research on mucosal immunity in crustaceans.

Glucose promotes regulatory T cell differentiation to maintain intestinal homeostasis

Glucose, the critical energy source in the human body, is considered a potential risk factor in various autoimmune diseases when consumed in high amounts. However, the roles of glucose at moderate doses in the regulation of autoimmune inflammatory diseases and CD4+ T cell responses are controversial. Here, we show that while glucose at a high concentration (20% w/v) promotes intestinal inflammation, it suppresses colitis at a moderate dose (6% w/v), which increases the proportion of intestinal regulatory T (Treg) cells but does not affect effector CD4+ T cells. Glucose treatment promotes Treg cell differentiation but it does not affect Treg stability. Feeding glucose alters gut microbiota compositions, which are not involved in the glucose induction of Treg cells. Glucose promotes aryl hydrocarbon receptor (AhR) activation to induce Treg polarization. These findings reveal the different effects of glucose at different doses on the intestinal immune response.

Protective Effects of Aminooxyacetic Acid on Colitis Induced in Mice with Dextran Sulfate Sodium

As a known inhibitor of pyridoxal phosphate-dependent transaminase glutamic-oxaloacetic transaminase 1 (GOT1), aminooxyacetic acid (AOAA) has been pointed out to have potential pharmacological effects in antiepileptic, anticonvulsant, antibacterial, cancer cell proliferation inhibition, and acute myocardial infarction (MI) relief. However, its role in inflammatory bowel disease (IBD) has not been reported. Through the in vivo experiment of dextran sulfate sodium- (DSS-) induced colitis in mice, it was found that AOAA significantly attenuated the symptoms, signs, and pathological changes of colitis. In addition, AOAA treatment prevented gut barrier damages by enhancing the expression of zona occludens- (ZO-) 1, occludin, claudin-1, and E-cadherin and recovering the upregulation of the most abundant intermediate filament protein (vimentin). Moreover, the release of interleukin- (IL-) 1β, IL-6, and tumour necrosis factor- (TNF-) α was suppressed, yet the level of IL-10 was upregulated by AOAA treatment compared to the model group. Furthermore, it was shown that AOAA administration boosted M2-like phenotype and effectively reduced M1 macrophage phenotype in the lamina propria of mouse colonic epithelium. Similarly, the effect of AOAA was verified in vitro. AOAA effectively inhibited the classically activated M1 macrophage phenotype and proinflammatory cytokine (IL-1β, TNF-α, and IL-6) expression induced by lipopolysaccharide (LPS) and promoted M2-like phenotype. Collectively, this study reveals for the first time that short-term treatment of AOAA can significantly alleviate DSS-induced acute colitis by regulating intestinal barrier function and macrophage polarization, which provides a theoretical basis for the potential use of AOAA in the treatment of IBD.

A Preliminary Metabolomic Study of Yorkshire Terrier Enteropathy

Perturbations of metabolite profiles in human and canine enteropathies have been reported before. However, data in dogs are scarce and inconsistent. Currently, the metabolite profile in Yorkshire Terrier enteropathy (YTE) and the impact of treatment is unknown. The objective of this study was to investigate the plasma metabolome of 13 Yorkshire Terriers with YTE and compare it to 20 healthy Yorkshire Terriers. Furthermore, we studied the impact of treatment on the metabolome. In this prospective observational study, plasma metabolite profiles were analyzed by flow injection analysis-tandem mass spectrometry (FIA-MS/MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) using a targeted metabolomics kit. Metabolite analysis revealed that YTE is accompanied by changes in lipid and bile acid metabolism. YTE was associated with a significant decrease of long-chain fatty acids (octadecenoic acid, eicosadienoic acid, eicosatrienoic acid) and lower levels of long-chain acylcarnitines (tetradecanoylcarnitine, hexadecanoylcarnitine, hexadecenoylcarnitine, octadecenoylcarnitine) compared with healthy controls. Furthermore, taurodeoxycholic acid, a secondary bile acid, was decreased in plasma from YTE patients. These changes might be breed-specific and might be involved in the pathogenesis of YTE. Interestingly, changes in metabolite levels were not recovered after treatment and differed considerably from healthy controls.

Analyzing the Role of Gut Microbiota on the Onset of Autoimmune Diseases Using TNFΔARE Murine Model

Very little is known about disease transmission via the gut microbiome. We hypothesized that certain inflammatory features could be transmitted via the gut microbiome and tested this hypothesis using an animal model of inflammatory diseases. Twelve-week-old healthy C57 Bl/6 and Germ-Free (GF) female and male mice were fecal matter transplanted (FMT) under anaerobic conditions with TNFΔARE-/+ donors exhibiting spontaneous Rheumatoid Arthritis (RA) and Inflammatory Bowel Disease (IBD) or with conventional healthy mice control donors. The gut microbiome analysis was performed using 16S rRNA sequencing amplification and bioinformatics analysis with the HIVE bioinformatics platform. Histology, immunohistochemistry, ELISA Multiplex analysis, and flow cytometry were conducted to confirm the inflammatory transmission status. We observed RA and IBD features transmitted in the GF mice cohort, with gut tissue disruption, cartilage alteration, elevated inflammatory mediators in the tissues, activation of CD4/CD8+ T cells, and colonization and transmission of the gut microbiome similar to the donors' profile. We did not observe a change or transmission when conventional healthy mice were FMT with TNFΔARE-/+ donors, suggesting that a healthy microbiome might withstand an unhealthy transplant. These findings show the potential involvement of the gut microbiome in inflammatory diseases. We identified a cluster of bacteria playing a role in this mechanism.

Rhein regulates redox-mediated Nlrp3 inflammasome activation in intestinal inflammation through macrophage-activated crosstalk

BACKGROUND AND PURPOSE

Macrophage infiltration and activation is a critical step during acute colitis. Redox-mediated Nlrp3 inflammasome activation in macrophages plays a critical role in mediating colonic inflammatory responses. Rhein isolated from the rhizome of rhubarb exhibits anti-inflammatory effects in various diseases. However, its role in regulating acute colonic inflammation is unexplored. This study was designed to investigate the protective mechanisms of rhein during acute gut inflammation and its regulation in macrophage activation.

EXPERIMENTAL APPROACH

The inhibitory effect of rhein on Nlrp3 inflammasome was evaluated in activated macrophages and colitic mice. The expressions of inflammatory mediators, inflammasome complex and redox-related signaling were analyzed by ELISA kits, western blots, immunofluorescence staining and qRT-PCR. Besides, the phenotype of macrophages was also assessed by flow cytometry. Colonic inflammation was evaluated by histological analysis.

KEY RESULTS

Rhein significantly decreased IL-1β secretion via Nlrp3 inflammasome by disturbing its complex assembly in macrophages. Rhein also activated Nrf2-HO1-NQO1 pathway, inhibited Nox2 subunits expression and translocation to regulate redox balance. Moreover, rhein attenuated inflammatory responses by mediating macrophage polarization from M1 to M2 phenotype. NF-κB, AP-1 and MAPK signalings were also involved in improving inflammatory conditions by rhein. In mice with acute intestinal inflammation, rhein treatment attenuated clinical features, reduced macrophage infiltration into the damaged lesions to alleviate colonic inflammation.

CONCLUSION AND IMPLICATIONS

Rhein regulated redox-mediated Nlrp3 inflammasome activation to protect against acute colitis, by interfering with macrophage accumulation and polarization. These findings provide a promising strategy of novel compounds for regulating mucosal inflammation in gastrointestinal disorders.

Immunological Aspect in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic inflammation in the alimentary tract due to improper immune response toward external and internal antigens. The disease consists of 2 entities: ulcerative colitis (UC) and Crohn’s disease (CD). The disease’s prevalence is increasing worldwide due to westernization and industrialization. Europe still holds the highest prevalence of IBD in the world. There are 2 peaks of disease incidence. The first is in the third decade of life and the second is in the fourth decade. Slight male predominance is observed in IBD. Internal and external risk factors play important role in the occurrence of IBD including genetic, smoking, reduced fibre intake, less or absent breastfeeding, sedentary occupation, pollution exposure, and medications. The disease carries heavy economic burden and hampers patient’s quality of life. The immune concept of IBD was hypothesized in 1950s since the symptoms resolved with the administration of steroid. Innate and adaptive immune systems are involved in the pathogenesis of IBD. Antigen presenting cells are found hyperactive, intestinal barrier is disrupted, and autophagy activity is increased. Molecular mimicry occurs between foreign and self antigen. The activity of T helper (Th)1, Th2, and Th17 is amplified while regulatory T cell’s activity is suppressed. Pro-inflammatory cytokine production is elevated but anti-inflammatory cytokines is lowered. Finally, there is increased immunoglobulin G level in intestinal mucosa and imbalance of gut microorganism. All the above immune disturbances lead to chronic inflammation in IBD.

Distinct roles of interleukin-17 and T helper 17 cells among autoimmune diseases

Background

Interleukin (IL)-17 and T helper 17 (T_H17) cells, a distinct subset of CD4⁺ T cells which promotes the expression of IL-17, mediate host defensive mechanisms to various infections and are involved in the pathogenesis of autoimmune diseases including inflammatory bowel disease (IBD), psoriasis, and rheumatic diseases. IL-17 inhibitors have shown to be effective in psoriasis, but failed to demonstrate response in IBD. Further, clinical trials of IL-17 inhibitors reported some cases of new onset IBD. We aim to discuss the roles of IL-17 and T_H17 cells among autoimmune diseases and the possible immunological mechanisms of new onset IBD in patients undergoing IL-17 inhibitors.

Methods

A non-systematic literature review using PubMed/Medline.

Results

IL-17 inhibitors, which either target IL-17 A (secukinumab and ixekizumab) or the IL-17 receptor (brodalumab), have demonstrated clinical benefits in plaque psoriasis, psoriatic arthritis, or axial spondyloarthritis. However, secukinumab and brodalumab have shown no clinical benefit in Crohn's disease and led to frequent serious adverse events including worsening of Crohn's disease. Further, some cases of new onset IBD were reported in clinical trials of IL-17 inhibitors. Consistently, an animal model of colitis has demonstrated that IL-17 can directly inhibit the development of T helper 1 (T_H1) cells and T_H1 cells can induce aggressive colitis in the absence of IL-17 signaling.

Conclusions

IL-17 and T_H17 cells might have protective rather than pro-inflammatory roles in the intestine. IL-17 inhibition may induce inflammation in the intestine by favoring T_H1 pathways, which explain the lack of response to IL-17 inhibitors in IBD.

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IL-17 and T_H17 cells play important roles in the pathologies of autoimmune diseases.

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Monoclonal antibodies targeting IL-17 have demonstrated clinical benefits.

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Clinical trials of IL-17 inhibitors reported new onset inflammatory bowel disease.

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IL-17 can directly inhibit the development of T_H1 cells.

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T_H1 cells may induce aggressive colitis in the absence of IL-17 signaling.

Modeling microbe-host interaction in the pathogenesis of Crohn's disease

Alterations in the gut microbiota structure and function are thought to play an important role in the pathogenesis of Crohn's disease (CD). The rapid advancement of high-throughput sequencing technologies led to the identification of microbiome risk signatures associated with distinct disease phenotypes and progressing disease entities. Functional validation of the identified microbiome signatures is essential to understand the underlying mechanisms of microbe-host interactions. Germfree mouse models are available to study the functional role of disease-conditioning complex gut microbial ecosystems (dysbiosis) or pathobionts (single bacteria) in the pathogenesis of CD-like inflammation. Here, we discuss the clinical and mechanistic relevance and limitations of gnotobiotic mouse models in the context of CD. In addition, we will address the role of diet as an essential external factor modulating microbiome changes, potentially underlying disease initiation and development.

Diet and Inflammatory Bowel Disease: What Quality Standards Should Be Applied in Clinical and Laboratory Studies?

Many patients suffering from inflammatory bowel disease (IBD) follow restrictive diets, as many respective recommendations circulate. Efforts are made to evaluate and summarize the published information, for example, in a recent consensus manuscript by the International Organization for the Study of IBD (IOIBD). However, the standards that should be applied to make claims about dietary effects are poorly defined. In this manuscript, the scientific basis of recommendations for nutritional interventions in IBD is analyzed. Epidemiological evidence on diet in IBD is always biased by numerous factors, and the number of robust dietary intervention studies is limited due to methodological difficulties. Therefore, animal models are used to test hypotheses with respect to dietary factors and intestinal inflammation. Naturally, animal models have limitations, and knowledge of key characteristics of colitis animal models is crucial to understand their advantages and disadvantages. In recent years the important role of the microbiota for IBD and dietary factors has been discovered. Microbiota data are added to many publications on IBD and nutrition. The quality of those data varies largely. Subsequently, quality standards for microbiota analyses also are discussed. Finally, quality requirements to be applied on recommendations for dietary changes in patients with IBD are suggested.

Mucosal immunity and tRNA, tRF, and tiRNA

Mucosal immunity has crucial roles in human diseases such as respiratory tract infection, inflammatory bowel diseases (IBD), and colorectal cancer (CRC). Recent studies suggest that the mononuclear phagocyte system, cancer cells, bacteria, and viruses induce the mucosal immune reaction by various pathways, and can be major factors in the pathogenesis of these diseases. Transfer RNA (tRNA) and its fragments, including tRNA-derived RNA fragments (tRFs) and tRNA-derived stress-induced RNAs (tiRNAs), have emerged as a hot topic in recent years. They not only are verified as essential for transcription and translation but also play roles in cellular homeostasis and functions, such as cell metastasis, proliferation, and apoptosis. However, the specific relationship between their biological regulation and mucosal immunity remains unclear to date. In the present review, we carry out a comprehensive discussion on the specific roles of tRNA, tRFs, and tiRNAs relevant to mucosal immunity and related diseases.

Enteroids Generated from Patients with Severe Inflammation in Crohn's Disease Maintain Alterations of Junctional Proteins

BACKGROUND

The mechanisms underlying loss of intestinal epithelial barrier [IEB] function in Crohn's disease [CD] are poorly understood. We tested whether human enteroids generated from isolated intestinal crypts of CD patients serve as an appropriate in vitro model to analyse changes of IEB proteins observed in patients' specimens.

METHODS

Gut samples from CD patients and healthy individuals who underwent surgery were collected. Enteroids were generated from intestinal crypts and analyses of junctional proteins in comparison to full wall samples were performed.

RESULTS

Histopathology confirmed the presence of CD and the extent of inflammation in intestinal full wall sections. As revealed by immunostaining and Western blot analysis, profound changes in expression patterns of tight junction, adherens junction and desmosomal proteins were observed in full wall specimens when CD was present. Unexpectedly, when enteroids were generated from specimens of CD patients with severe inflammation, alterations of most tight junction proteins and the majority of changes in desmosomal proteins but not E-cadherin were maintained under culture conditions. Importantly, these changes were maintained without any additional stimulation of cytokines. Interestingly, qRT-PCR demonstrated that mRNA levels of junctional proteins were not different when enteroids from CD patients were compared to enteroids from healthy controls.

CONCLUSIONS

These data indicate that enteroids generated from patients with severe inflammation in CD maintain some characteristics of intestinal barrier protein changes on a post-transcriptional level. The enteroid in vitro model represents an appropriate tool to gain further cellular and molecular insights into the pathogenesis of barrier dysfunction in CD.

Single-cell atlas of colonic CD8+ T cells in ulcerative colitis

Colonic antigen-experienced lymphocytes such as tissue-resident memory CD8+ T cells can respond rapidly to repeated antigen exposure. However, their cellular phenotypes and the mechanisms by which they drive immune regulation and inflammation remain unclear. Here we compiled an unbiased atlas of human colonic CD8+ T cells in health and ulcerative colitis (UC) using single-cell transcriptomics with T-cell receptor repertoire analysis and mass cytometry. We reveal extensive heterogeneity in CD8+ T-cell composition, including expanded effector and post-effector terminally differentiated CD8+ T cells. While UC-associated CD8+ effector T cells can trigger tissue destruction and produce tumor necrosis factor (TNF)-α, post-effector cells acquire innate signatures to adopt regulatory functions that may mitigate excessive inflammation. Thus, we identify colonic CD8+ T-cell phenotypes in health and UC, define their clonal relationships and characterize terminally differentiated dysfunctional UC CD8+ T cells expressing IL-26, which attenuate acute colitis in a humanized IL-26 transgenic mouse model.

Improving translational research in sex-specific effects of comorbidities and risk factors in ischaemic heart disease and cardioprotection: position paper and recommendations of the ESC Working Group on Cellular Biology of the Heart

Ischaemic heart disease (IHD) is a complex disorder and a leading cause of death and morbidity in both men and women. Sex, however, affects several aspects of IHD, including pathophysiology, incidence, clinical presentation, diagnosis as well as treatment and outcome. Several diseases or risk factors frequently associated with IHD can modify cellular signalling cascades, thus affecting ischaemia/reperfusion injury as well as responses to cardioprotective interventions. Importantly, the prevalence and impact of risk factors and several comorbidities differ between males and females, and their effects on IHD development and prognosis might differ according to sex. The cellular and molecular mechanisms underlying these differences are still poorly understood, and their identification might have important translational implications in the prediction or prevention of risk of IHD in men and women. Despite this, most experimental studies on IHD are still undertaken in animal models in the absence of risk factors and comorbidities, and assessment of potential sex-specific differences are largely missing. This ESC WG Position Paper will discuss: (i) the importance of sex as a biological variable in cardiovascular research, (ii) major biological mechanisms underlying sex-related differences relevant to IHD risk factors and comorbidities, (iii) prospects and pitfalls of preclinical models to investigate these associations, and finally (iv) will provide recommendations to guide future research. Although gender differences also affect IHD risk in the clinical setting, they will not be discussed in detail here.

Translational Potential of Metabolomics on Animal Models of Inflammatory Bowel Disease-A Systematic Critical Review

In the development of inflammatory bowel disease (IBD), the gut microbiota has been established as a key factor. Recently, metabolomics has become important for understanding the functional relevance of gut microbial changes in disease. Animal models for IBD enable the study of factors involved in disease development. However, results from animal studies may not represent the human situation. The aim of this study was to investigate whether results from metabolomics studies on animal models for IBD were similar to those from studies on IBD patients. Medline and Embase were searched for relevant studies up to May 2017. The Covidence systematic review software was used for study screening, and quality assessment was conducted for all included studies. Data showed a convergence of ~17% for metabolites differentiated between IBD and controls in human and animal studies with amino acids being the most differentiated metabolite subclass. The acute dextran sodium sulfate model appeared as a good model for analysis of systemic metabolites in IBD, but analytical platform, age, and biological sample type did not show clear correlations with any significant metabolites. In conclusion, this systematic review highlights the variation in metabolomics results, and emphasizes the importance of expanding the applied detection methods to ensure greater coverage and convergence between the various different patient phenotypes and animal models of inflammatory bowel disease.

Obacunone Protects Against Ulcerative Colitis in Mice by Modulating Gut Microbiota, Attenuating TLR4/NF-κB Signaling Cascades, and Improving Disrupted Epithelial Barriers

Obacunone, a natural limonoid compound abundantly distributed in citrus fruits, possesses various biological properties, such as antitumor, antioxidant, and antiviral activities. Recent studies suggested an anti-inflammatory activity of obacunone in vitro, but its efficacy on intestinal inflammation remains unknown. This study was designed to evaluate the effects and mechanisms of obacunone in ameliorating intestinal inflammation in a mouse model of ulcerative colitis (UC). We found that obacunone efficiently alleviated the severity of dextran sulfate sodium (DSS)-induced mouse UC by modulating the abnormal composition of the gut microbiota and attenuating the excessive activation of toll-like receptor 4 (TLR4)/nuclear factor-kappa B (NF-κB) signaling. The intestinal epithelial barrier was disrupted in DSS colitis mice, which was associated with activation of inflammatory signaling cascades. However, obacunone promoted the expression of tight junction proteins (TJP1 and occludin) and repressed the activation of inflammatory signaling cascades. In summary, our findings demonstrated that obacunone attenuated the symptoms of experimental UC in mice through modulation of the gut microbiota, attenuation of TLR4/NF-κB signaling cascades, and restoration of intestinal epithelial barrier integrity.

Environmental Microbial Factors Determine the Pattern of Inflammatory Lesions in a Murine Model of Crohn's Disease-Like Inflammation

Crohn's disease (CD) patients can be grouped into patients suffering from ileitis, ileocolitis, jejunoileitis, and colitis. The pathophysiological mechanism underlying this regional inflammation is still unknown. Although most murine models of inflammatory bowel disease (IBD) develop inflammation in the colon, there is an unmet need for novel models that recapitulate the spontaneous and fluctuating nature of inflammation as seen in CD. Recently, mice with an intestinal epithelial cell-specific deletion for Caspase-8 (Casp8ΔIEC mice), which are characterized by cell death-driven ileitis and disrupted Paneth cell homeostasis, have been identified as a novel model of CD-like ileitis. Here we uncovered that genetic susceptibility alone is sufficient to drive ileitis in Casp8ΔIEC mice. In sharp contrast, environmental factors, such as a disease-relevant microbial flora, determine colonic inflammation. Accordingly, depending on the microbial environment, isogenic Casp8ΔIEC mice either exclusively developed ileitis or suffered from pathologies in several parts of the gastrointestinal tract. Colitis in these mice was characterized by massive epithelial cell death, leading to spread of commensal gut microbes to the extra-intestinal space and hence an aberrant activation of the systemic immunity. We further uncovered that Casp8ΔIEC mice show qualitative and quantitative changes in the intestinal microbiome associated with an altered mucosal and systemic immune response. In summary, we identified that inflammation in this murine model of CD-like inflammation is characterized by an immune reaction, presumably directed against a disease-relevant microbiota in a genetically susceptible host, with impaired mucosal barrier function and bacterial clearance at the epithelial interface.

Immunological mechanisms underpinning faecal microbiota transplantation for the treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic gastrointestinal disease that results from a dysregulated immune response against specific environmental triggers in a genetically predisposed individual. Increasing evidence has indicated a causal role for changes in gut microbiota (dysbiosis) contributing to this immune-mediated intestinal inflammation. These mechanisms involve dysregulation of multiple facets of the host immune pathways that are potentially reversible. Faecal microbiota transplantation (FMT) is the transfer of processed stool from a healthy donor into an individual with an illness. FMT has shown promising results in both animal model experiments and clinical studies in IBD in the resolution of intestinal inflammation. The underlying mechanisms, however, are unclear. Insights from these studies have shown interactions between modulation of dysbiosis via changes in abundances of specific members of the gut microbial community and changes in host immunological pathways. Unravelling these causal relationships has promising potential for a translational therapy role to develop targeted microbial therapies and understand the mechanisms that underpin IBD aetiopathogenesis. In this review, we discuss current evidence for the contribution of gut microbiota in the disruption of intestinal immune homeostasis and immunoregulatory mechanisms that are associated with the resolution of inflammation through FMT in IBD.

Bryostatin-1 ameliorated experimental colitis in Il-10-/- Mice by protecting the intestinal barrier and limiting immune dysfunction

Bryostatin‐1 (Bry‐1) has been proven to be effective and safe in clinical trials of a variety of immune‐related diseases. However, little is known about its effect on Crohn's disease (CD). We aimed to investigate the impact of Bry‐1 on CD‐like colitis and determine the mechanism underlying this effect. In the present study, 15‐week‐old male Il‐10^−/− mice with spontaneous colitis were divided into positive control and Bry‐1‐treated (Bry‐1, 30 μg/kg every other day, injected intraperitoneally for 4 weeks) groups. Age‐matched, male wild‐type (WT) mice were used as a negative control. The effects of Bry‐1 on colitis, intestinal barrier function and T cell responses as well as the potential regulatory mechanisms were evaluated. We found that the systemic delivery of Bry‐1 significantly ameliorated colitis in Il‐10^−/− mice, as demonstrated by decreases in the disease activity index (DAI), inflammatory score and proinflammatory mediator levels. The protective effects of Bry‐1 on CD‐like colitis included the maintenance of intestinal barrier integrity and the helper T cell (Th)/regulatory T cell (Treg) balance. These effects of Bry‐1 may act in part through nuclear factor erythroid 2‐related factor 2 (Nrf2) signalling activation and STAT3/4 signalling inhibition. The protective effect of Bry‐1 on CD‐like colitis suggests Bry‐1 has therapeutic potential in human CD, particularly given the established clinical safety of Bry‐1.

Intestinal Organoids as a Novel Complementary Model to Dissect Inflammatory Bowel Disease

Inflammatory bowel diseases (IBDs) include colitis ulcerosa and Crohn's disease, besides the rare microscopic colitis. Both diseases show a long-lasting, relapsing-remitting, or even chronic active course with tremendous impact on quality of life. IBDs frequently cause disability, surgical interventions, and high costs; as in other autoimmune diseases, their prevalent occurrence at an early phase of life raises the burden on health care systems. Unfortunately, our understanding of the pathogenesis is still incomplete and treatment therefore largely focuses on suppressing the resulting excessive inflammation. One obstacle for deciphering the causative processes is the scarcity of models that parallel the development of the disease, since intestinal inflammation is mostly induced artificially; moreover, the intestinal epithelium, which strongly contributes to IBD pathogenesis, is difficult to assess. Recently, the development of intestinal epithelial organoids has overcome many of those problems. Here, we give an overview on the current understanding of the pathogenesis of IBDs with reference to the limitations of previous well-established experimental models. We highlight the advantages and detriments of recent organoid-based experimental setups within the IBD field and suggest possible future applications.

Reproducing the human mucosal environment ex vivo: inflammatory bowel disease as a paradigm

PURPOSE OF REVIEW

The medical management of inflammatory bowel disease (IBD) remains problematic with a pressing need for innovation in drug development as well as delivery of personalized therapies. Both the disease's inherent pathophysiologic complexity and heterogeneity in its etiology conspire in making it difficult to accurately model for either the purposes of basic research or drug development. Multiple attempts at creating meaningful experimental models have fallen short of adequately recapitulating the disease and most do not capture any aspect of the cause or the effects of patient heterogeneity that underlays most of the difficulties faced by physicians and their patients. In vivo animal models, tissue culture systems, and more recent synthetic biology approaches are all too simplistically reductionist for the task. However, ex vivo culture platforms utilizing patient biopsies offer a system that more closely mimics end-stage disease processes that can be studied in detail and subjected to experimental manipulations.

RECENT FINDINGS

Recent studies describe further optimization of mucosal explant cultures in order to increase tissue viability and maintain a polarized epithelial layer. Current applications of the platform include studies of the interplay between the epithelial, immune and stromal compartment of the intestinal tissue, investigation of host-microbial interactions, preclinical evaluation of candidate drugs and uncovering mechanisms of action of established or emerging treatments for IBD.

SUMMARY

Patient explant-based assays offer an advanced biological system in IBD that recapitulates disease complexity and reflects the heterogeneity of the patient population. In its current stage of development, the system can be utilized for drug testing prior to the costlier and time-consuming evaluation by clinical trials. Further refinement of the technology and establishment of assay readouts that correlate with therapeutic outcomes will yield a powerful tool for personalized medicine approaches in which individual patient responses to available treatments are assessed a priori, thus reducing the need for trial and error within the clinical setting.