Crosstalk between the intestinal microbiota and the innate immune system in intestinal homeostasis and inflammatory bowel disease

The science of exosomes: Understanding their formation, capture, and role in cellular communication

Extracellular vesicles (EVs) serve as a crucial method for transferring information among cells, which is vital in multicellular organisms. Among these vesicles, exosomes are notable for their small size, ranging from 20 to 150 nm, and their role in cell-to-cell communication. They carry lipids, proteins, and nucleic acids between cells. The creation of exosomes begins with the inward budding of the cell membrane, which then encapsulates various macromolecules as cargo. Once filled, exosomes are released into the extracellular space and taken up by target cells via endocytosis and similar processes. The composition of exosomal cargo varies, encompassing diverse macromolecules with specific functions. Because of their significant roles, exosomes have been isolated from various cell types, including cancer cells, endothelial cells, macrophages, and mesenchymal cells, with the aim of harnessing them for therapeutic applications. Exosomes influence cellular metabolism, and regulate lipid, glucose, and glutamine pathways. Their role in pathogenesis is determined by their cargo, which can manipulate processes such as apoptosis, proliferation, inflammation, migration, and other molecular pathways in recipient cells. Non-coding RNA transcripts, a common type of cargo, play a pivotal role in regulating disease progression. Exosomes are implicated in numerous biological and pathological processes, including inflammation, cancer, cardiovascular diseases, diabetes, wound healing, and ischemic-reperfusion injury. As a result, they hold significant potential in the treatment of both cancerous and non-cancerous conditions.

The Impact of Phenotype of Inflammatory Bowel Diseases, Inflammation Activity and Therapy on Mucosal Mature Cd83+ Dendritic Cell

Background: Crohn's disease (CD) and ulcerative colitis (UC) are well-defined phenotypes of chronic inflammatory bowel diseases (IBDs). A mechanism of inflammation in these diseases is partially controlled by the intestinal dendritic cell (DC). In this study, we observed a mature CD83+ DC in colonic bioptic samples, and its correlation with disease phenotype and activity. Methods: The study included 219 subjects: 100 with UC, 44 with CD and 75 healthy subjects. Colonic biopsy specimens were incubated with the primary antibody Anti-CD83. Intraepithelial CD83+ DCs were counted per 100 enterocytes. The presence of CD83+ DC was analysed according to the type of IBD, histopathologic inflammation activity and treatment outcome. Results: The presence of mature CD83+ DCs (0, ≥1) differed according to disease types of IBD (p = 0.001), histologic inflammation activity (p = 0.049) and applied therapy (p = 0.001). The odds for CD83+ DC presence were 5.2 times higher in the CD group than in the control/UC group. The odds for CD83+ DC presence were 2.6 times higher in subjects without inflammation or chronic inflammation than with acute inflammation. They were also 3.7 times higher in subjects without therapy. The cut-off value 0.5 CD83+ DC (Rock analysis area = 0.699; SE 0.046; p < 0.001; 95% CI: 0.609-0.788) had been assessed as a differentiation marker between UC and CD. Conclusion: Presence of CD83+ DC could be used as a possible parameter in distinction between UC and CD, as well as a predictor of inflammation activity and treatment outcome.

The TNF∆ARE Model of Crohn's Disease-like Ileitis

Crohn's disease (CD) is one of the 2 main phenotypes of inflammatory bowel diseases (IBDs); CD ischaracterized by a discontinuous, spontaneously recurring, transmural immunopathology that largely affects the terminal ileum. Crohn's disease exhibits both a relapsing and progressive course, and its prevalence is on the rise globally, mirroring the trends of industrialization. While the precise pathogenesis of CD remains unknown, various factors including immune cell dysregulation, microbial dysbiosis, genetic susceptibility, and environmental factors have been implicated in disease etiology. Animal models, particularly ileitis mouse models, have provided valuable tools for studying the specific mechanisms underlying CD, allowing longitudinal assessment and sampling in interventional preclinical studies. Furthermore, animal models assess to evaluate the distinct role that bacterial and dietary antigens play in causing inflammation, using germ-free animals, involving the introduction of individual bacteria (monoassociation studies), and experimenting with well-defined dietary components. An ideal animal model for studying IBD, specifically CD, should exhibit an inherent intestinal condition that arises spontaneously and closely mimics the distinct transmural inflammation observed in the human disease, particularly in the terminal ileum. We have recently characterized the impact of disease-relevant, noninfectious microbiota and specific bacteria in a mouse model that replicates CD-like ileitis, capturing the intricate nature of human CD, namely the TNF∆ARE mouse model. Using germ-free mice, we studied the impact of different diets on the expansion of disease-relevant pathobionts and on the severity of inflammation. In this review article, we review some of the currently available ileitis mouse models and discuss in detail the TNF∆ARE model of CD-like Ileitis.

Role of ER Stress Mediated Unfolded Protein Responses and ER Stress Inhibitors in the Pathogenesis of Inflammatory Bowel Disease

Previous investigations have increased the knowledge about the pathological processes of inflammatory bowel diseases. Besides the complex organization of immune reactions, the mucosal epithelial lining has been recognized as a crucial regulator in the commencement and persistence of intestinal inflammation. As the intestinal epithelium is exposed to various environmental factors, the intestinal epithelial cells are confronted with diverse cellular stress conditions. In eukaryotic cells, an imbalance in the endoplasmic reticulum (ER) might cause aggregation of unfolded or misfolded proteins in the lumen of ER, a condition known as endoplasmic reticulum stress. This cellular mechanism stimulates the unfolded protein response (UPR), which elevates the potential of the endoplasmic reticulum protein folding, improves protein production and its maturation, and also stimulates ER-associated protein degradation. Current analyses reported that in the epithelium, the ER stress might cause the pathogenesis of inflammatory bowel disease that affects the synthesis of protein, inducing the apoptosis of the epithelial cell and stimulating the proinflammatory reactions in the gut. There have been significant efforts to develop small molecules or molecular chaperones that will be potent in ameliorating ER stress. The restoration of UPR balance in the endoplasmic reticulum via pharmacological intervention might be a novel therapeutic approach for the treatment of inflammatory bowel diseases (IBDs). This review provides novel insights into the role of chemical chaperone UPR modulators to modify ER stress levels. We further discuss the future directions/challenges in the development of therapeutic strategies for IBDs by targeting the ER stress. Figure depicting the role of endoplasmic reticulum stress-mediated inflammatory bowel disease and the therapeutic role of endoplasmic reticulum stress inhibitors in alleviating the diseased condition.

Changes of gut microbiota in colorectal cancer patients with Pentatrichomonas hominis infection

Pentatrichomonas hominis is a parasitic trichomonads protozoa that parasitizes in the colon and cecum of humans and other animals. Our previous studies have demonstrated that infection with P. hominis is associated with the incidence of colon cancer (37.93%). However, the mechanism by which P. hominis infections increase the incidence of colon cancer remains unclear. Previous studies have suggested that certain parasites promote colon cancer by regulating gut microbiota. This study aimed to elucidate whether the association between P. hominis infections and the increased incidence of colon cancer is related to changes in gut microbiota. Therefore, the gut microbiota patients with colon cancer who were infected with P. hominis and uninfected patients with colon cancer were analyzed by 16S rRNA high-throughput sequencing. The results demonstrated that patients with colon cancer who were not infected with P. hominis showed increased gut bacterial diversity, a higher relative abundance of Alcaligenes sp., Leucobacter sp., Paraprevotella sp., Ruminococcaceae UCG-002, and a significant reduction in the abundance of Veillonella sp., compared to individuals without colon cancer. Additionally, the relative abundance of the Ruminococcaceae UCG-002 and the Eubacterium eligens groups was reduced, while the relative abundance of bacteria associated with colon cancer, including Flavonifractor sp., Lachnoclostridium sp., and the Ruminococcus gnavus group, increased significantly in patients with colon cancer who were infected with P. hominis, compared to those of uninfected patients with colon cancer. In conclusion, these results suggested that P. hominis infections may aggravate the development of colon cancer and the findings provide new insights for subsequent in-depth studies on the pathogenesis, diagnosis, and prevention of colon cancer.

Food as Treatment of Inflammatory Bowel Diseases

Inflammatory bowel diseases (IBD), namely, Crohn's disease (CD) and ulcerative colitis (UC), are lifelong and incurable chronic inflammatory diseases affecting 6.8 million people worldwide. By 2030, the prevalence of IBD is estimated to reach 1% of the population in Western countries, and thus there is an urgent need to develop effective therapies to reduce the burden of this disease. Microbiome dysbiosis is at the heart of the IBD pathophysiology, and current research and development efforts for IBD treatments have been focused on gut microbiome regulation. Diet can shape the intestinal microbiome. Diet is also preferred over medication, is safe, and has been proven to be an effective strategy for the management of IBD. Therefore, although often overlooked, dietary interventions targeting the microbiome represent ideal treatments for IBD. Here, I summarize the latest research on diet as a treatment for IBD from infancy to adulthood, compile evidence of the mechanisms of action behind diet as treatment, and, lastly, provide insights into future research focusing on culturally tailored diets for ethnic minority groups with increased incidence of IBD yet underrepresented in nutrition research.

Microbiomics Revealed the Disturbance of Intestinal Balance in Rabbits with Diarrhea Caused by Stopping the Use of an Antibiotic Diet

The harmful effects of diarrhea on the growth performance of rabbits have been well documented, but the details of the potential mechanism of intestinal diarrhea when antibiotics are stopped are still unclear. Here, PacBio sequencing technology was used to sequence the full length 16S rRNA gene of the microbiota of intestinal content samples, in order to characterize the bacterial communities in the small intestine (duodenum and jejunum) and large intestine (colon and cecum) in normal Hyplus rabbits and those with diarrhea. The histopathological examination showed that intestinal necrosis occurred in different degrees in the diarrhea group, and that the mucosal epithelium was shed and necrotic, forming erosion, and the clinical manifestation was necrosis. However, the intestinal tissue structure of the normal group was normal. The results revealed that there were significant differences in bacterial communities and structure between the diarrhea and normal groups of four intestinal segments (p < 0.05). In general, 16 bacterial phyla, 144 bacterial genera and 22 metabolic pathways were identified in the two groups. Tax4Fun functional prediction analysis showed that KEGG related to amino acid metabolism and energy metabolism was enriched in the large intestines of rabbits with diarrhea, whereas lipid metabolism was more abundant in the small intestine of rabbits with diarrhea. In conclusion, the change in the relative abundance of the identified dominant microbiota, which could deplete key anti-inflammatory metabolites and lead to bacterial imbalance and diarrhea, resulted in diarrhea in Hyplus rabbits that stopped using antibiotics.

Single-Cell Sequencing of Developing Human Gut Reveals Transcriptional Links to Childhood Crohn's Disease

Human gut development requires the orchestrated interaction of differentiating cell types. Here, we generate an in-depth single-cell map of the developing human intestine at 6–10 weeks post-conception. Our analysis reveals the transcriptional profile of cycling epithelial precursor cells; distinct from LGR5-expressing cells. We propose that these cells may contribute to differentiated cell subsets via the generation of LGR5-expressing stem cells and receive signals from surrounding mesenchymal cells. Furthermore, we draw parallels between the transcriptomes of ex vivo tissues and in vitro fetal organoids, revealing the maturation of organoid cultures in a dish. Lastly, we compare scRNA-seq profiles from pediatric Crohn’s disease epithelium alongside matched healthy controls to reveal disease-associated changes in the epithelial composition. Contrasting these with the fetal profiles reveals the re-activation of fetal transcription factors in Crohn’s disease. Our study provides a resource available at www.gutcellatlas.org, and underscores the importance of unraveling fetal development in understanding disease.

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Single-cell RNA-seq map of the developing and pediatric human intestine

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Cycling BEX5+ epithelial precursors are distinct from adult LGR5+ stem cells

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Human fetal intestinal organoids mature in culture

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Fetal transcription factors are reactivated in the Crohn’s disease epithelium

Quorum Sensing, Biofilm, and Intestinal Mucosal Barrier: Involvement the Role of Probiotic

The intestine is a particularly dynamic environment in which the host constantly interacts with trillions of symbiotic bacteria called the microbiota. Using quorum sensing (QS) communication, bacteria can coordinate their social behavior and influence host cell activities in a non-invasive manner. Nowadays, a large amount of research has greatly spurred the understanding of how bacterial QS communication regulates bacterial cooperative behaviors due to coexistence and host-microbe interactions. In this review, we discuss bacterial QS in the gut and its role in biofilm formation. As a biological barrier, the mucosal immune system can effectively prevent pathogenic microorganisms and other immunogenic components from entering the internal environment of the host. We focus on the relationship between biofilm and intestinal mucosal immunity, and how probiotic bacteria may regulate them. This review is to provide a theoretical basis for the development of new techniques including probiotics targeting the intestinal barrier function, thereby improving gut health.

Gut-organ axis: a microbial outreach and networking

Human gut microbiota (GM) includes a complex and dynamic population of microorganisms that are crucial for well-being and survival of the organism. It has been reported as diverse and relatively stable with shared core microbiota, including Bacteroidetes and Firmicutes as the major dominants. They are the key regulators of body homeostasis, involving both intestinal and extra-intestinal effects by influencing many physiological functions such as metabolism, maintenance of barrier homeostasis, inflammation and hematopoiesis. Any alteration in GM community structures not only trigger gut disorders but also influence other organs and cause associated diseases. In recent past, the GM has been defined as a 'vital organ' with its involvement with other organs; thus, establishing a link or a bi- or multidirectional communication axis between the organs via neural, endocrine, immune, humoral and metabolic pathways. Alterations in GM have been linked to several diseases known to humans; although the exact interaction mechanism between the gut and the organs is yet to be defined. In this review, the bidirectional relationship between the gut and the vital human organs was envisaged and discussed under several headings. Furthermore, several disease symptoms were also revisited to redefine the communication network between the gut microbes and the associated organs.

Difference in Presence and Number of CD83+ Dendritic Cells in Patients with Ulcerative Colitis and Crohn's Disease

Different pathophysiological models provide insight into the important role of CD83+ dendritic cells (DCs) in the pathogenesis of Crohn's disease (CD) and ulcerative colitis (UC). There were 154 subjects included in this study: 60 with UC, 19 with CD and 75 in the control group. Colonic biopsy was performed in all subjects. Specimens were incubated with a primary anti-CD83 antibody. Intraepithelial DCs per 100 enterocytes were counted. The results were analysed according to demographic data, type of IBD and histological inflammation pattern. The odds ratio for CD83+ DCs=0 in the UC group was 3.4 times higher than that in the control group (OR = 3.4; 95% CI: 1.63-7.14; p = 0.001), and the odds ratio for CD83+ DCs ≥1 in the CD group was 5.3 times higher than that in the UC group (OR = 5.3; 95% CI: 1.4-20.2; p = 0.014). The odds ratio for CD83+ DCs=0 in the acute inflammation group was 2.7 times higher than that in the group without inflammation (OR = 2.7; 95% CI: 1.2-5.9; p = 0.011). In the group of patients with CD and acute inflammation (n = 11), there was only one subject without CD83+ DCs (p = 0,024). These results suggest an association of CD83+ DCs with the type of IBD and the histological inflammation pattern.

Neural Control of Inflammation: Bioelectronic Medicine in Treatment of Chronic Inflammatory Disease

Inflammation is important for antimicrobial defense and for tissue repair after trauma. The inflammatory response and its resolution are both active processes that must be tightly regulated to maintain homeostasis. Excessive inflammation and nonresolving inflammation cause tissue damage and chronic disease, including autoinflammatory and cardiovascular diseases. An improved understanding of the cellular and molecular mechanisms that regulate inflammation has supported development of novel therapies for several inflammatory diseases, including rheumatoid arthritis and inflammatory bowel disease. Many of the specific anticytokine therapies carry a risk for excessive immunosuppression and serious side effects. The discovery of the inflammatory reflex and the increasingly detailed understanding of the molecular interactions between homeostatic neural reflexes and the immune system have laid the foundation for bioelectronic medicine in the field of inflammatory diseases. Neural interfaces and nerve stimulators are now being tested in human clinical trials and may, as the technology develops further, have advantages over conventional drugs in terms of better compliance, continuously adaptable control of dosing, better monitoring, and reduced risks for unwanted side effects. Here, we review the current mechanistic understanding of common autoinflammatory conditions, consider available therapies, and discuss the potential use of increasingly capable devices in the treatment of inflammatory disease.

Repair and regeneration of small intestine: A review of current engineering approaches

The small intestine (SI) is difficult to regenerate or reconstruct due to its complex structure and functions. Recent developments in stem cell research, advanced engineering technologies, and regenerative medicine strategies bring new hope of solving clinical problems of the SI. This review will first summarize the structure, function, development, cell types, and matrix components of the SI. Then, the major cell sources for SI regeneration are introduced, and state-of-the-art biofabrication technologies for generating engineered SI tissues or models are overviewed. Furthermore, in vitro models and in vivo transplantation, based on intestinal organoids and tissue engineering, are highlighted. Finally, current challenges and future perspectives are discussed to help direct future applications for SI repair and regeneration.

Review of the Isolation, Characterization, Biological Function, and Multifarious Therapeutic Approaches of Exosomes

Exosomes are extracellular vesicles that contain a specific composition of proteins, lipids, RNA, and DNA. They are derived from endocytic membranes and can transfer signals to recipient cells, thus mediating a novel mechanism of cell-to-cell communication. They are also thought to be involved in cellular waste disposal. Exosomes play significant roles in various biological functions, including the transfer of biomolecules such as RNA, proteins, enzymes, and lipids and the regulation of numerous physiological and pathological processes in various diseases. Because of these properties, they are considered to be promising biomarkers for the diagnosis and prognosis of various diseases and may contribute to the development of minimally invasive diagnostics and next generation therapies. The biocompatible nature of exosomes could enhance the stability and efficacy of imaging probes and therapeutics. Due to their potential use in clinical applications, exosomes have attracted much research attention on their roles in health and disease. To explore the use of exosomes in the biomedical arena, it is essential that the basic molecular mechanisms behind the transport and function of these vesicles are well-understood. Herein, we discuss the history, biogenesis, release, isolation, characterization, and biological functions of exosomes, as well as the factors influencing their biogenesis and their technical and biological challenges. We conclude this review with a discussion on the future perspectives of exosomes.

The impact of corticosteroid use on inpatients with inflammatory bowel disease and positive polymerase chain reaction for Clostridium difficile

BACKGROUND/AIMS

Optimal management of inflammatory bowel disease (IBD) with concomitant Clostridium difficile infection (CDI) is controversial, especially when CDI diagnosis is made by polymerase chain reaction (PCR) testing, which may reflect colonization without infection.

METHODS

We performed a multicenter review of all inpatients with IBD and PCR diagnosed CDI. Outcomes included length of stay, 30- and 90-day readmission, colectomy during admission and within 3 months, intensive care unit (ICU) admission, CDI relapse and death for patients who received corticosteroid (CS) after CDI diagnosis versus those that did not. Propensity-adjusted regression analysis of outcomes based on CS usage was performed.

RESULTS

We identified 177 IBD patients with CDI, 112 ulcerative colitis and 65 Crohn's disease. For IBD overall, CS after CDI diagnosis was associated with prolonged hospitalization (5.5 days: 95% confidence interval [CI], 1.5-9.6 days; P=0.008), higher colectomy rate within 3 months (odds ratio [OR], 5.5; 95% CI, 1.1-28.2; P=0.042) and more frequent ICU admissions (OR, 7.8; 95% CI, 1.5-41.6; P=0.017) versus no CS. CS use post-CDI diagnosis in UC patients was associated with prolonged hospitalization (6.2 days: 95% CI, 0.4- 12.0 days; P=0.036) and more frequent ICU admissions (OR, 7.4; 95% CI, 1.1-48.7; P=0.036).

CONCLUSIONS

CS use among IBD inpatients with CDI diagnosed by PCR is associated with poorer outcomes and would seem to reinforce the importance of C. difficile toxin assay to help distinguish colonization from infection. This adverse effect appears more prominent among those with UC.

Exosomes in inflammation and role as biomarkers

Exosomes are endosomal-derived nano-vesicles. They are considered vehicles through which donor cells transfer proteins, lipids and nucleic acids to target cells thus influencing their metabolism. Exosomes are involved in inflammatory processes that play a pivotal role in a large number of pathologic states including cancer, inflammatory bowel diseases, type 2 diabetes, obesity, rheumatoid arthritis and neurodegenerative diseases. The association between inflammation and change in nature or expression level of some exosomal cargos is the fundamental step for identifying possible novel biomarkers of inflammatory-based diseases. A novel interesting exosome cargo is the SLC22A5 transport protein whose level in exosomes is regulated by the pro-inflammatory cytokine INF-γ. The advantage of using exosomes as a biomarker vehicle consists of their ease of collection from body fluids such as urine and saliva as they may represent a non-invasive means for screening human pathology.

Food-specific IgGs Are Highly Increased in the Sera of Patients with Inflammatory Bowel Disease and Are Clinically Relevant to the Pathogenesis

Objective Dietary antigens are common luminal antigens in the gastrointestinal tract and have been considered to contribute to the pathogenesis of inflammatory bowel disease (IBD). We analyzed the levels of food-specific IgGs against a variety of dietary antigens, explored the clinical relevance of food allergy to the pathogenesis of IBD, and investigated whether or not infliximab (IFX) treatment could regulate the immune responses induced by dietary antigens. Methods A total of 301 IBD patients, including 201 patients with Crohn's disease (CD) and 100 patients with ulcerative colitis (UC), were recruited, and their serum food-specific IgGs against 14 food antigens were detected by a semi-quantitative enzyme linked immunosorbent assay (ELISA). Total serum IgG and IgE levels were measured by immunonephelometry and fluorescent enzyme immunoassay, respectively. Simultaneously, the relevant medical records and clinical data were collected for further analyses. Results Food-specific IgGs against egg, milk, wheat, corn, rice, tomato, codfish, and soybean antigens were found to be significantly increased in the sera of CD patients compared with UC patients and healthy controls (p<0.01). The levels of total serum IgG and IgE were also significantly higher in CD patients than in healthy controls (p<0.01). The titers of corn- and tomato-specific IgGs were found to be significantly correlated with total serum IgG in CD patients (p<0.05), while the titers of egg-, milk-, and wheat-specific IgGs were correlated with total serum IgE (p<0.05). Interestingly, IFX therapy was able to down-regulate the food-specific IgG-mediated immune response markedly in active CD patients. Conclusion Food-specific IgGs against egg, milk, wheat, corn, rice, tomato, codfish, and soybean are highly increased in the sera of CD patients. IFX treatment was able to down-regulate the levels of food-specific IgGs by suppressing intestinal inflammation and promoting mucosal healing. Therefore, food-specific IgGs may serve as an important approach in the diagnosis and management of food allergy in IBD.

Inhibition of lncRNA NEAT1 suppresses the inflammatory response in IBD by modulating the intestinal epithelial barrier and by exosome-mediated polarization of macrophages

Inflammatory bowel disease (IBD) is a multifactorial inflammatory disease, and increasing evidence has demonstrated that the mechanism of the pathogenesis of IBD is associated with intestinal epithelial barrier injury. Long non‑coding RNAs (lncRNAs) are a class of transcripts >200 nucleotides in length with limited protein‑coding capability. Nuclear paraspeckle assembly transcript 1 (NEAT1) is a recently identified nuclear‑restricted lncRNA, which localizes in subnuclear structures, termed paraspeckles, and is involved in the immune response in a variety of ways. However, the function of NEAT1 in IBD remains to be fully elucidated. In the present study, reverse transcription‑quantitative polymerase chain reaction assays were performed to determine the expression levels of NEAT1 lncRNA in IBD serum samples and tissues. Furthermore, the effect of NEAT1 on the cell permeability of colon cells was investigated via determination of trans‑epithelial electrical resistance as well as performance of western blot and immunofluorescence assays. In addition, dextran sodium sulfate assays were performed to investigate the effect of downregulation of NEAT1 in IBD of mice. The present study detected the expression levels of NEAT1 in IBD cells and animal models to examine the changes in intestinal epithelial cell permeability following inhibition of the expression of NEAT1. In addition, phenotypic transformation was examined following different treatments in epithelial cells and macrophages. The results suggested that the expression of NEAT1 was high in IBD and was involved in the inflammatory response by regulating the intestinal epithelial barrier and through exosome‑mediated polarization of macrophages. The downregulation of NEAT1 suppressed the inflammatory response by modulating the intestinal epithelial barrier and through exosome‑mediated polarization of macrophages in IBD. The results of the present study revealed a potential strategy of targeting NEAT1 for IBD therapy.

Peptidoglycan Suppresses Phagocytic Activities and Apoptosis of Macrophages in Colonic Mucosa Tissues of Crohn's Disease Patients and In Vitro

Background

Rac1 signaling plays a crucial role in controlling macrophage functions in CD. Peptidoglycan triggers several intracellular signaling pathways, including activation of Rac1, to regulate the function of macrophage. Suppressed Rac1 signaling in non-inflamed colonic mucosa of Crohn’s disease patients has been shown to correlate with increased innate immunity.

Material/Methods

We examined the effect of peptidoglycan on Rac1 signaling in macrophages and mucosal tissue samples collected from 10 patients with active Crohn’s disease and further investigated the effects of peptidoglycan on apoptosis and phagocytic activities of macrophages in vitro.

Results

Macrophage infiltration and Rac1 signaling was increased in inflamed mucosal tissues of Crohn’s disease patients. Immunoblotting assays revealed that peptidoglycan dose- and time-dependently increased the expression of Rac1-GTP, phosphorylated VAV1, and phosphorylated PAK1in RAW264.7 macrophages, which, however, was attenuated by 6-thioguanine. Peptidoglycan also dose-dependently inhibited phagocytic activities of human peripheral blood monocytic cells (PBMCs), which were partially abated by 6-thioguanine or NSC23766. Flow cytometry showed that peptidoglycan (3 μg/mL) decreased the proportion of apoptotic human PBMCs versus controls. The addition of 6-thioguanine or NSC3766 to peptidoglycan led to a sharper rise in the proportion of apoptotic human PBMCs than 6-thioguanine or NSC3766 alone.

Conclusions

Our findings suggest that Rac1 signaling is a common molecular target shared by peptidoglycan and immunosuppressive treatment in intestinal macrophages. Inhibiting Rac1 activation may be crucial for optimizing macrophage immunity for treatment of Crohn’s disease.

Mice with Inflammatory Bowel Disease are Susceptible to Clostridium difficile Infection With Severe Disease Outcomes

BACKGROUND

Over the past several decades, there has been a significant increase in the incidence of Clostridium difficile infection (CDI) in patients suffering from inflammatory bowel disease (IBD). However, a wild-type animal model is not available to study these comorbid diseases.

METHODS

We evaluated the susceptibility to CDI of mice with dextran sulfate sodium salt (DSS)-induced colitis (IBD mice) with or without antibiotic exposure; we examined the histopathology and cytokine response in the concomitant diseases after the model was created.

RESULTS

No CDI occurs in healthy control mice, wherease the incidence of CDI in IBD mice is 40%; however, in IBD mice that received antibiotics, the incidence of CDI is 100% and the disease is accompanied by high levels of toxins in the mouse feces and sera. Compared to IBD and CDI alone, those IBD mice infected with C. difficile have more severe symptoms, toxemia, histopathological damage, and higher mortality. Moreover, several proinflammatory cytokines and chemokines are significantly elevated in the colon tissues from IBD mice infected with C. difficile.

CONCLUSIONS

We, for the first time, demonstrate in an animal model that mice with dextran sulfate sodium induced-inflammatory bowel disease are significantly more susceptible to C. difficile infection, and that the bacterial infection led to more severe disease and death. These findings are consistent with clinical observations, thus, the animal model will permit us to study the pathogenesis of these concurrent diseases and to develop therapeutic strategies against the comorbidity of IBD and CDI.

Human Intestinal Microbiota: Interaction Between Parasites and the Host Immune Response

The human gut is a highly complex ecosystem with an extensive microbial community, and the influence of the intestinal microbiota reaches the entire host organism. For example, the microbiome regulates fat storage, stimulates or renews epithelial cells, and influences the development and maturation of the brain and the immune system. Intestinal microbes can protect against infection by pathogenic bacteria, viruses, fungi and parasites. Hence, the maintenance of homeostasis between the gut microbiota and the rest of the body is crucial for health, with dysbiosis affecting disease. This review focuses on intestinal protozoa, especially those still representing a public health problem in Mexico, and their interactions with the microbiome and the host. The decrease in prevalence of intestinal helminthes in humans left a vacant ecological niche that was quickly occupied by protozoa. Although the mechanisms governing the interaction between intestinal microbiota and protozoa are poorly understood, it is known that the composition of the intestinal bacterial populations modulates the progression of protozoan infection and the outcome of parasitic disease. Most reports on the complex interactions between intestinal bacteria, protozoa and the immune system emphasize the protective role of the microbiota against protozoan infection. Insights into such protection may facilitate the manipulation of microbiota components to prevent and treat intestinal protozoan infections. Here we discuss recent findings about the immunoregulatory effect of intestinal microbiota with regards to intestinal colonization by protozoa, focusing on infections by Entamoeba histolytica, Blastocystis spp, Giardia duodenalis, Toxoplasma gondii and Cryptosporidium parvum. The possible consequences of the microbiota on parasitic, allergic and autoimmune disorders are also considered.

Expression of CD200R1 and its Ligand CD200 on T-helper Lymphocytes of Pediatric Patients with Ulcerative Colitis and Crohn's Disease

BACKGROUND

CD200 and its receptor CD200R are both type I membrane glycoproteins that modulate the activity of myeloid and lymphoid cells, and their interaction is functionally important in the suppression of effector T-cell responses by regulatory T-cells. We aimed to investigate the extent of expression of CD200 and CD200R1 on CD4+ T-cells in blood of children with ulcerative colitis (UC) and Crohn's disease (CD) and to explore their correlations with effector T cell subsets, regulatory T cells (Treg), and routine clinical and serological markers.

METHODS

The frequencies of blood CD4+ expressing CD200 and CD200R1 as well as T-helper CD4+CD25+Foxp3+ Treg, CD4+ IL-17+ (Th17), CD4+ IFN-γ + (Th1), and CD4+IL-4+ (Th2) were estimated by flow cytometry in 23 patients with CD, 14 with UC, and 14 healthy volunteers (HCs). The clinical and inflammatory markers were also investigated.

RESULTS

IBD patients showed decreased CD4+CD200R1+ T-cells, whereas, CD4+CD200+ T-cells were significantly higher in patient groups compared with healthy controls. Treg cells were found significantly decreased in the patients with UC and CD compared with healthy controls (both at p < 0.01). The percentage of Th17 was found significantly increased in CD (p < 0.05) compared with UC patients and healthy subjects (p = 0.014). CD200+CD4+ T-cells showed significant positive correlations with ESR, Th1, and Th17 (r = 0.438, p < 0.05; r = 0.411, p < 0.05; r = 0.492, p < 0.01, respectively). CD200R1+CD4+ T-cells correlated positively with Th2 and Treg (r = 0.482, p < 0.01, and r = 0.457, p < 0.01, respectively) and negatively with ESR (r = -0.387, p < 0.01).

CONCLUSIONS

Our study demonstrates an aberrant expression of CD200/CD200R1 on CD4+ T-cells in IBD patients and these data may have potent pathological significance in IBD pathophysiology.

Orally administered sodium 4-phenylbutyrate suppresses the development of dextran sulfate sodium-induced colitis in mice

Sodium 4-phenylbutyrate (PBA) exerts therapeutic effects in a wide range of pathologies. A previous study by the present authors revealed that intraperitoneal administration of PBA suppresses the onset of dextran sulfate sodium (DSS)-induced colitis in mice. In the present study, the effects of orally administered PBA are investigated, as this route of administration is more clinically relevant. The therapeutic efficacy of PBA (10 mg/12 h) in mice with experimental colitis was assessed based on the disease activity index, production of inflammatory cytokines, colon length and histopathological investigations. The results of the present study demonstrated a significantly higher survival rate in the PBA-treated group compared with the PBA-untreated (DSS control) group (P=0.0156). PBA treatment improved pathological indices of experimental colitis (P<0.05). Furthermore, the oral administration of PBA significantly inhibited the DSS-induced shortening of the colon (P<0.05) and overproduction of interleukin (IL)-1β and IL-6 (both P<0.05) as measured in colonic lavage fluids. A marked attenuation of the DSS-induced overproduction of tumor necrosis factor was also observed. For histopathological analysis, a marked decrease in mature goblet cells and increase in enlarged nuclei of the absorptive cells was observed in colon lesions of DSS control mice as compared with normal untreated mice. However, in the PBA-treated mice, no such lesions were observed and the mucosa resembled that of DSS-untreated mice. The results of the present study, combined with those results of a previous study, suggest that oral and intraperitoneal administration of PBA have similar preventative effects on DSS-induced colitis, achieved by suppressing its pathogenesis.

Inflammation-associated DNA methylation patterns in epithelium of ulcerative colitis

Aberrant DNA methylation patterns have been reported in inflamed tissues and may play a role in disease. We studied DNA methylation and gene expression profiles of purified intestinal epithelial cells from ulcerative colitis patients, comparing inflamed and non-inflamed areas of the colon. We identified 577 differentially methylated sites (false discovery rate <0.2) mapping to 210 genes. From gene expression data from the same epithelial cells, we identified 62 differentially expressed genes with increased expression in the presence of inflammation at prostate cancer susceptibility genes PRAC1 and PRAC2. Four genes showed inverse correlation between methylation and gene expression; ROR1, GXYLT2, FOXA2, and, notably, RARB, a gene previously identified as a tumor suppressor in colorectal adenocarcinoma as well as breast, lung and prostate cancer. We highlight targeted and specific patterns of DNA methylation and gene expression in epithelial cells from inflamed colon, while challenging the importance of epithelial cells in the pathogenesis of chronic inflammation.

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

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

Clostridium difficile infection in inflammatory bowel disease: challenges in diagnosis and treatment

The problem of Clostridium difficile infection (CDI) has reached epidemic proportions, particularly in industrialized nations. The pathophysiology, disease course and the potential complications are well appreciated in the general hospitalized patient. However, when CDI occurs in the setting of inflammatory bowel disease (IBD), a number of distinct differences in the diagnosis and clinical management of the infection in this population should be appreciated by gastroenterologists, hospitalists and other care providers. This review highlights the unique aspects of CDI when it occurs in IBD patients with an emphasis on the challenge of distinguishing persistent infection from exacerbation of underlying chronic colitis. An understanding of how CDI may differ in presentation and how management should be altered can prevent serious and life-threatening complications.

Exosome in intestinal mucosal immunity

Intercellular communication of immune cells is critical to elicit efficient inflammatory responses. In intestinal mucosa, imbalance in pro-inflammatory and anti-inflammatory mediators, especially cytokines and chemokines, characterizes the underlying immune mechanisms of inflammatory bowel disease. Exosomes, small membrane vesicles secreted into the extracellular environment, are emerging as another important intercellular messenger in immune responses. A major recent breakthrough in this field unveils the capacity of exosomes to mediate the functional transfer of genetic materials (mRNAs and miRNAs) between immune cells. RAB27A and RAB27B are two small GTPases involved in exosome secretion. With respect to intestinal mucosal immunity, increased number of RAB27A-positive immune cells and RAB27B-positive immune cells are demonstrated in the colonic mucosa of patients with active ulcerative colitis as compared with that of healthy controls. This indicates the important role of exosome-mediated immune responses in the pathogenesis of inflammatory bowel disease. Here, we will discuss the immune properties of exosomes and recent advances in their function with a special focus on intestinal mucosal immunity.

Intestinal FoxO signaling is required to survive oral infection in Drosophila

The intestinal immune system is tailored to fight pathogens effectively while tolerating the indigenous microbiota. Impairments of this homeostatic interaction may contribute to the etiology of various diseases including inflammatory bowel diseases. However, the molecular architecture underlying this complex regulatory interaction is not well understood. Here, we show that the fruit fly Drosophila melanogaster has a multilayered intestinal immune system that ensures strictly localized antimicrobial responses. Enterocytes, a major cell population of the intestine, produced antimicrobial peptides (AMPs) in a FoxO- but not NF-κB-dependent manner. Consequently, animals impaired in FoxO-mediated signaling had a significantly lowered resistance to intestinal infections; they were unable to increase the expression of AMP genes and males showed an increased bacterial load in response to an infection. Conventional innate immune signaling converging onto NF-κB activation was operative in only a few regions of the intestine, comprising the proventriculus, copper cells, and intestinal stem cells. Taken together, our results imply that danger-mediated as well as conventional innate immune signaling constitute modules that contribute to the fruit fly's intestinal immune system. We propose that this special architecture ensures localized and efficient antimicrobial responses against invasive pathogens while preserving the microbiota.

Assessing DNA methylation in the developing human intestinal epithelium: potential link to inflammatory bowel disease

DNA methylation is one of the major epigenetic mechanisms implicated in regulating cellular development and cell-type-specific gene expression. Here we performed simultaneous genome-wide DNA methylation and gene expression analysis on purified intestinal epithelial cells derived from human fetal gut, healthy pediatric biopsies, and children newly diagnosed with inflammatory bowel disease (IBD). Results were validated using pyrosequencing, real-time PCR, and immunostaining. The functional impact of DNA methylation changes on gene expression was assessed by employing in-vitro assays in intestinal cell lines. DNA methylation analyses allowed identification of 214 genes for which expression is regulated via DNA methylation, i.e. regulatory differentially methylated regions (rDMRs). Pathway and functional analysis of rDMRs suggested a critical role for DNA methylation in regulating gene expression and functional development of the human intestinal epithelium. Moreover, analysis performed on intestinal epithelium of children newly diagnosed with IBD revealed alterations in DNA methylation within genomic loci, which were found to overlap significantly with those undergoing methylation changes during intestinal development. Our study provides novel insights into the physiological role of DNA methylation in regulating functional maturation of the human intestinal epithelium. Moreover, we provide data linking developmentally acquired alterations in the DNA methylation profile to changes seen in pediatric IBD.

Oral immune therapy: targeting the systemic immune system via the gut immune system for the treatment of inflammatory bowel disease

Inflammatory bowel diseases (IBD) are associated with an altered systemic immune response leading to inflammation-mediated damage to the gut and other organs. Oral immune therapy is a method of systemic immune modulation via alteration of the gut immune system. It uses the inherit ability of the innate system of the gut to redirect the systemic innate and adaptive immune responses. Oral immune therapy is an attractive clinical approach to treat autoimmune and inflammatory disorders. It can induce immune modulation without immune suppression, has minimal toxicity and is easily administered. Targeting the systemic immune system via the gut immune system can serve as an attractive novel therapeutic method for IBD. This review summarizes the current data and discusses several examples of oral immune therapeutic methods for using the gut immune system to generate signals to reset systemic immunity as a treatment for IBD.

A critical role for cellular inhibitor of protein 2 (cIAP2) in colitis-associated colorectal cancer and intestinal homeostasis mediated by the inflammasome and survival pathways

Cellular inhibitors of apoptosis proteins (cIAPs) are critical arbiters of cell death and key mediators of inflammation and innate immunity. cIAP2 is frequently overexpressed in colorectal cancer and in regenerating crypts of ulcerative colitis patients. However, its corresponding functions in intestinal homeostasis and underlying mechanisms in disease pathogenesis are poorly understood. We found that mice deficient in cIAP2 exhibited reduced colitis-associated colorectal cancer tumor burden but, surprisingly, enhanced susceptibility to acute and chronic colitis. The exacerbated colitis phenotype of cIAP2-deficient mice was mediated by increased cell death and impaired activation of the regenerative inflammasome-interleukin-18 (IL-18) pathway required for tissue repair following injury. Accordingly, administration of recombinant IL-18 or pharmacological inhibition of caspases or the kinase RIPK1 protected cIAP2-deficient mice from colitis and restored intestinal epithelial barrier architecture. Thus, cIAP2 orchestrates intestinal homeostasis by exerting a dual function in suppressing cell death and promoting intestinal epithelial cell proliferation and crypt regeneration.

Mitochondrial dysfunction in inflammatory bowel disease

Inflammatory Bowel Disease (IBD) represents a group of idiopathic disorders characterized by chronic or recurring inflammation of the gastrointestinal tract. While the exact etiology of disease is unknown, IBD is recognized to be a complex, multifactorial disease that results from an intricate interplay of genetic predisposition, an altered immune response, changes in the intestinal microbiota, and environmental factors. Together, these contribute to a destruction of the intestinal epithelial barrier, increased gut permeability, and an influx of immune cells. Given that most cellular functions as well as maintenance of the epithelial barrier is energy-dependent, it is logical to assume that mitochondrial dysfunction may play a key role in both the onset and recurrence of disease. Indeed several studies have demonstrated evidence of mitochondrial stress and alterations in mitochondrial function within the intestinal epithelium of patients with IBD and mice undergoing experimental colitis. Although the hallmarks of mitochondrial dysfunction, including oxidative stress and impaired ATP production are known to be evident in the intestines of patients with IBD, it is as yet unclear whether these processes occur as a cause of consequence of disease. We provide a current review of mitochondrial function in the setting of intestinal inflammation during IBD.

Intestinal Microbiota and the Innate Immune System - A Crosstalk in Crohn's Disease Pathogenesis

Crohn's disease (CD) is a chronic, relapsing inflammatory disorder that can occur anywhere along the gastrointestinal tract. The precise etiology of CD is still unclear but it is widely accepted that a complex series of interactions between susceptibility genes, the immune system and environmental factors are implicated in the onset and perpetuation of the disease. Increasing evidence from experimental and clinical studies implies the intestinal microbiota in disease pathogenesis, thereby supporting the hypothesis that chronic intestinal inflammation arises from an abnormal immune response against the microorganisms of the intestinal flora in genetically susceptible individuals. Given that CD patients display changes in their gut microbiota composition, collectively termed "dysbiosis," the question raises whether the altered microbiota composition is a cause of disease or rather a consequence of the inflammatory state of the intestinal environment. This review will focus on the crosstalk between the gut microbiota and the innate immune system during intestinal inflammation, thereby unraveling the role of the microbiota in CD pathogenesis.

Food allergy among Iranian children with inflammatory bowel disease: A preliminary report

BACKGROUND

Evidence has shown a link between allergic disease and inflammatory bowel diseases (IBDs). We investigated food allergy in Iranian pediatric IBD patients.

MATERIALS AND METHODS

A cross-sectional study was conducted on a consecutive sample of children with newly diagnosed IBD referring to Mofid Children's University Hospital in Tehran (Iran) between November 2013 and March 2015. Data on age, gender, history of cow's milk allergy (CMA), IBD type, routine laboratory tests, and colonoscopic and histopathological findings were gathered. Food allergy was assessed with the skin prick test (SPT).

RESULTS

A total of 28 patients including 19 ulcerative colitis (UC), 7 Cronh's disease (CD), and two with unclassified colitis with a mean age of 8.3 ± 4.4 years. (57.1% females, 42.9% were studied. History of CMA was present in eight patients (28.6%). Seventeen patients (60.7%) had at least one food allergy (68.4% of UC vs. 42.9% of CD, P = 0.230). Ten patients (35.7%) had multiple food allergies (36.8% of UC vs. 42.9% of CD, P > 0.999). Common allergic foods were cow's milk (28.6%), beef, seafood, albumen, wheat, and walnuts (each 10.7%), and peanuts and chestnuts (each 7.1%). The SPT showed CMA in 68.4% (8/17) of UC but none of the CD patients (P = 0.077).

CONCLUSION

Food allergy is frequent in Iranian pediatric IBD patients with CMA being the most common observed allergy. The CMA seems to be more frequent in UC than in CD patients.

Th17 Cells as Potential Probiotic Therapeutic Targets in Inflammatory Bowel Diseases

Inflammatory bowel diseases (IBD) are characterized by wasting and chronic intestinal inflammation triggered by various cytokine-mediated pathways. In recent years, it was shown that T helper 17 (Th17) cells are involved in the pathogenesis of IBD, which makes them an attractive therapeutic target. Th17 cells preferentially produce interleukin (IL)-17A–F as signature cytokines. The role of the interplay between host genetics and intestinal microbiota in the pathogenesis of IBD was demonstrated. Probiotics are live microorganisms that when orally ingested in adequate amounts, confer a health benefit to the host by modulating the enteric flora or by stimulating the local immune system. Several studies indicated the effectiveness of probiotics in preventing and treating IBD (ulcerative colitis, and Crohn’s disease). Furthermore, there is mounting evidence of probiotics selectively targeting the Th17 lineage in the prevention and management of inflammatory and autoimmune diseases such as IBD. This review highlights critical roles of Th17 cells in the pathogenesis of IBD and the rationale for using probiotics as a novel therapeutic approach for IBD through manipulation of Th17 cells. The potential molecular mechanisms by which probiotics modulate Th17 cells differentiation and production are also discussed.

Risk factors and clinical implication of superimposed Campylobacter jejuni infection in patients with underlying ulcerative colitis

Background and aims: Superimposed Campylobacter jejuni infection (CJI) has been described in patients with ulcerative colitis (UC). Its risk factors and impact on the disease course of UC are not known. Our aims were to evaluate the risk factors for CJI in UC patients and the impact of the bacterial infection on outcomes of UC.

Methods: Out of a total of 918 UC patients tested, 21 (2.3%) of patients were found to be positive for CJI (the study group). The control group comprised 84 age-matched UC patients who had tested negative for CJI. Risk factors for CJI and UC-related outcomes at 1 year after diagnosis of CJI were compared between the two groups.

Results: Ten patients (47.6%) with CJI required hospital admission at the time of diagnosis, including eight for the management of “UC flare”. Treatment with antibiotics resulted in improvement in symptoms in 13 patients (61.9%). On multivariate analysis, hospital admission in the preceding year was found to be an independent risk factor for CJI [odds ratio (OR): 3.9; 95% confidence interval (CI): 1.1–14.1] and there was a trend for chronic liver disease as a strong risk factor (OR: 5.0; 95% CI: 0.9–28.3). At 1-year follow up, there was a trend for higher rates of UC-related colectomy (28.8% vs. 14.3%; P = 0.11), and mortality (9.5% vs. 1.2%; P = 0.096) in the study group.

Conclusion: Recent hospitalization within 1 year was found to be associated with increased risk for CJI in UC patients. There was a trend for worse clinical outcomes of UC with in patients with superimposed CJI, which was frequently associated with UC flare requiring hospital admission.

Lactobacillus acidophilus suppresses colitis-associated activation of the IL-23/Th17 axis

The aim of this paper is to determine the modulatory effects of Lactobacillus acidophilus on the IL-23/Th17 immune axis in experimental colitis. DSS-induced mouse models of UC were to be saline, hormones, and different concentrations of Lactobacillus acidophilus intervention. The expression of interleukin- (IL-) 17, tumor necrosis factor α (TNFα), IL-23, transforming growth factor β1 (TGFβ1), signal transducer and activator of transcription 3 (STAT3), and phosphorylated (p)-STAT3 was examined by RT-PCR, Western blotting, and immunohistochemical analysis. And the results showed that administration of L. acidophilus suppressed Th17 cell-mediated secretion of proinflammatory cytokine IL-17 through downregulation of IL-23 and TGFβ1 expression and downstream phosphorylation of p-STAT3.

The histone deacetylase Hdac1 regulates inflammatory signalling in intestinal epithelial cells

Background

It has recently been found that both nuclear epithelial-expressed histone deacetylases Hdac1 and Hdac2 are important to insure intestinal homeostasis and control the mucosal inflammatory response in vivo. In addition, HDAC inhibitors modulate epithelial cell inflammatory responses in cancer cells. However, little is known of the specific role of different HDAC, notably Hdac1, in the regulation of inflammatory gene expression in intestinal epithelial cells (IEC).

Methods

We investigated the role of Hdac1 in non-transformed IEC-6 rat cells infected with lentiviral vectors expressing specific Hdac1 shRNAs, to suppress Hdac1 expression. Proliferation was assessed by cell counting. Deacetylase activity was measured with a colorimetric HDAC assay. Cells were treated with IL-1β and/or the JQ1 bromodomain acetyl-binding inhibitor. Nuclear protein levels of Hdac1, Hdac2, phosphorylated or unphosphorylated NF-κB p65 or C/EBPβ, and NF-κB p50 and actin were determined by Western blot. Chemokine and acute phase protein expression was assessed by semi-quantitative RT-PCR analysis. Secreted cytokine and chemokine levels were assessed with a protein array. Chromatin immunoprecipitation experiments were done to assess RNA polymerase II recruitment.

Results

Reduced Hdac1 protein levels led to Hdac2 protein increases and decreased cell proliferation. Hdac1 depletion prolonged nuclear IL-1β-induced phosphorylation of NF-κB p65 protein on Ser536 as opposed to total p65, and of C/EBPβ on Ser105. In addition, semi-quantitative RT-PCR analysis revealed three patterns of expression caused by Hdac1 depletion, namely increased basal and IL-1β-stimulated levels (Hp, Kng1), increased IL-1β-stimulated levels (Cxcl2) and decreased basal levels with normal IL-1β induction levels (Ccl2, Ccl5, Cxcl1, C3). Secreted cytokine and chemokine measurements confirmed that Hdac1 played roles both as an IL-1β signalling repressor and activator. Hdac1 depletion did not alter the JQ1 dependent inhibition of basal and IL-1β-induced inflammatory gene expression. Hdac1 depletion led to decreased basal levels of RNA polymerase II enrichment on the Ccl2 promoter, as opposed to the Gapdh promoter, correlating with decreased Ccl2 basal mRNA expression.

Conclusions

Hdac1 is a major nuclear HDAC controlling IL-1β-dependent inflammatory response in IEC, notably by regulating gene-specific transcriptional responses. Hdac1 may be important in restricting basal and inflammatory-induced gene levels to defined ranges of expression.

Electronic supplementary material

The online version of this article (doi:10.1186/s12950-014-0043-2) contains supplementary material, which is available to authorized users.

Role of programmed necrosis and cell death in intestinal inflammation

PURPOSE OF REVIEW

To critically review recent advances on the role of programmed necrosis and other cell death modalities in intestinal health and inflammatory bowel disease.

RECENT FINDINGS

Tight regulation of intestinal epithelial cell proliferation and cell death is required for intestinal physiology, and to maintain an integral barrier that restricts microbiota translocation and ensures immune tolerance. Apoptosis has long been considered as a normal part of intestinal epithelial cell turnover. However, recent studies have demonstrated that excessive cell death leads to deleterious intestinal inflammation, as is observed in inflammatory bowel disease. Additionally, a novel form of cell death dubbed programmed necrosis, or necroptosis, has been recently shown to be pathological in the gut.

SUMMARY

The role of cell death in the intestine is complex and its potential implication in intestinal diseases, and inflammatory bowel disease in particular, needs to be reevaluated.

Intestinal epithelium in inflammatory bowel disease

The intestinal epithelium has a strategic position as a protective physical barrier to luminal microbiota and actively contributes to the mucosal immune system. This barrier is mainly formed by a monolayer of specialized intestinal epithelial cells (IECs) that are crucial in maintaining intestinal homeostasis. Therefore, dysregulation within the epithelial layer can increase intestinal permeability, lead to abnormalities in interactions between IECs and immune cells in underlying lamina propria, and disturb the intestinal immune homeostasis, all of which are linked to the clinical disease course of inflammatory bowel disease (IBD). Understanding the role of the intestinal epithelium in IBD pathogenesis might contribute to an improved knowledge of the inflammatory processes and the identification of potential therapeutic targets.

Influences of the colonic microbiome on the mucous gel layer in ulcerative colitis

The colonic mucus gel layer (MGL) is a critical component of the innate immune system acting as a physical barrier to microbes, luminal insults, and toxins. Mucins are the major component of the MGL. Selected microbes have the potential to interact with, bind to, and metabolize mucins. The tolerance of the host to the presence of these microbes is critical to maintaining MGL homeostasis. In disease states such as ulcerative colitis (UC), both the mucosa associated microbes and the constituent MGL mucins have been shown to be altered. Evidence is accumulating that implicates the potential for mucin degrading bacteria to negatively impact the MGL and its stasis. These effects appear more pronounced in UC.   This review is focused on the host-microbiome interactions within the setting of the MGL. Special focus is given to the mucolytic potential of microbes and their interactions in the setting of the colitic colon.

The acetylome regulators Hdac1 and Hdac2 differently modulate intestinal epithelial cell dependent homeostatic responses in experimental colitis

Histone deacetylases (Hdac) remove acetyl groups from proteins, influencing global and specific gene expression. Hdacs control inflammation, as shown by Hdac inhibitor-dependent protection from dextran sulfate sodium (DSS)-induced murine colitis. Although tissue-specific Hdac knockouts show redundant and specific functions, little is known of their intestinal epithelial cell (IEC) role. We have shown previously that dual Hdac1/Hdac2 IEC-specific loss disrupts cell proliferation and determination, with decreased secretory cell numbers and altered barrier function. We thus investigated how compound Hdac1/Hdac2 or Hdac2 IEC-specific deficiency alters the inflammatory response. Floxed Hdac1 and Hdac2 and villin-Cre mice were interbred. Compound Hdac1/Hdac2 IEC-deficient mice showed chronic basal inflammation, with increased basal disease activity index (DAI) and deregulated Reg gene colonic expression. DSS-treated dual Hdac1/Hdac2 IEC-deficient mice displayed increased DAI, histological score, intestinal permeability, and inflammatory gene expression. In contrast to double knockouts, Hdac2 IEC-specific loss did not affect IEC determination and growth, nor result in chronic inflammation. However, Hdac2 disruption protected against DSS colitis, as shown by decreased DAI, intestinal permeability and caspase-3 cleavage. Hdac2 IEC-specific deficient mice displayed increased expression of IEC gene subsets, such as colonic antimicrobial Reg3b and Reg3g mRNAs, and decreased expression of immune cell function-related genes. Our data show that Hdac1 and Hdac2 are essential IEC homeostasis regulators. IEC-specific Hdac1 and Hdac2 may act as epigenetic sensors and transmitters of environmental cues and regulate IEC-mediated mucosal homeostatic and inflammatory responses. Different levels of IEC Hdac activity may lead to positive or negative outcomes on intestinal homeostasis during inflammation.

Clostridium difficile and inflammatory bowel disease: Role in pathogenesis and implications in treatment

Clostridium difficile (C. difficile) is the leading cause of antibiotic associated colitis and nosocomial diarrhea. Patients with inflammatory bowel disease (IBD) are at increased risk of developing C. difficile infection (CDI), have worse outcomes of CDI-including higher rates of colectomy and death, and experience higher rates of recurrence. However, it is still not clear whether C. difficile is a cause of IBD or a consequence of the inflammatory state in the intestinal environment. The burden of CDI has increased dramatically over the past decade, with severe outbreaks described in many countries, which have been attributed to a new and more virulent strain. A parallel rise in the incidence of CDI has been noted in patients with IBD. IBD patients with CDI tend be younger, have less prior antibiotic exposure, and most cases of CDI in these patients represent outpatient acquired infections. The clinical presentation of CDI in these patients can be unique-including diversion colitis, enteritis and pouchitis, and typical findings on colonoscopy are often absent. Due to the high prevalence of CDI in patients hospitalized with an IBD exacerbation, and the prognostic implications of CDI in these patients, it is recommended to test all IBD patients hospitalized with a disease flare for C. difficile. Treatment includes general measures such as supportive care and infection control measures. Antibiotic therapy with either oral metronidazole, vancomycin, or the novel antibiotic-fidaxomicin, should be initiated as soon as possible. Fecal macrobiota transplantation constitutes another optional treatment for severe/recurrent CDI. The aim of this paper is to review recent data on CDI in IBD: role in pathogenesis, diagnostic methods, optional treatments, and outcomes of these patients.