Mechanisms of disease: defensins in gastrointestinal diseases

Lactic Acid Bacteria-Gut-Microbiota-Mediated Intervention towards Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), encompassing ulcerative colitis (UC) and Crohn's disease (CD), arises from intricate interactions involving genetics, environment, and pharmaceuticals with an ambiguous pathogenic mechanism. Recently, there has been an increasing utilization of lactic acid bacteria (LAB) in managing IBD, attributed to their ability to enhance intestinal barrier function, mitigate inflammatory responses, and modulate gut microbiota. This review initiates by elucidating the pathogenesis of IBD and its determinants, followed by an exploration of the mechanisms underlying LAB therapy in UC and CD. Special attention is directed towards their influence on intestinal barrier function and homeostasis regulated by gut microbiota. Furthermore, the review investigates the complex interplay among pivotal gut microbiota, metabolites, and pathways associated with inflammation. Moreover, it underscores the limitations of LAB in treating IBD, particularly in light of their varying roles in UC and CD. This comprehensive analysis endeavors to offer insights for the optimized application of LAB in IBD therapy.

Spirobenzofuran Mitigates Ochratoxin A-Mediated Intestinal Adverse Effects in Pigs through Regulation of Beta Defensin 1

Antimicrobial peptides (AMPs) function to extensively suppress various problematic factors and are considered a new alternative for improving livestock health and enhancing immunomodulation. In this study, we explored whether AMP regulation has positive influences on Ochratoxin A (OTA) exposure using a porcine intestinal epithelial cell line (IPEC-J2 cells). We constructed a beta-defensin 1 (DEFB1) expression vector and used it to transfection IPEC-J2 cells to construct AMP overexpression cell lines. The results showed that OTA induced cytotoxicity, decreased cell migration, and increased inflammatory markers mRNA in IPEC-J2 cells. In DEFB1 overexpressing cell lines, OTA-induced reduced cell migration and increased inflammatory markers mRNA were alleviated. Additionally, a natural product capable of inducing DEFB1 expression, which was selected through high-throughput screening, showed significant alleviation of cytotoxicity, cell migration, and inflammatory markers compared to OTA-treated IPEC-J2 cells. Our finding provides novel insights and clues for the porcine industry, which is affected by OTA exposure.

Host defense peptides human β defensin 2 and LL-37 ameliorate murine necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a leading cause of preterm infant morbidity and mortality. Treatment for NEC is limited and non-targeted, which makes new treatment and prevention strategies critical. Host defense peptides (HDPs) are essential components of the innate immune system and have multifactorial mechanisms in host defense. LL-37 and hBD2 are two HDPs that have been shown in prior literature to protect from neonatal sepsis-induced mortality or adult inflammatory bowel disease, respectively. Therefore, this article sought to understand if these two HDPs could influence NEC severity in murine preclinical models. NEC was induced in P14-16 C57Bl/6 mice and HDPs were provided as a pretreatment or treatment. Both LL-37 and hBD2 resulted in decreased NEC injury scores as a treatment and hBD2 as a pretreatment. Our data suggest LL-37 functions through antimicrobial properties, while hBD2 functions through decreases in inflammation and improvement of intestinal barrier integrity.

Single-Cell Transcriptomic and Targeted Genomic Profiling Adjusted for Inflammation and Therapy Bias Reveal CRTAM and PLCB1 as Novel Hub Genes for Anti-Tumor Necrosis Factor Alpha Therapy Response in Crohn's Disease

BACKGROUND

The lack of reliable biomarkers in response to anti-TNFα biologicals hinders personalized therapy for Crohn's disease (CD) patients. The motivation behind our study is to shift the paradigm of anti-TNFα biomarker discovery toward specific immune cell sub-populations using single-cell RNA sequencing and an innovative approach designed to uncover PBMCs gene expression signals, which may be masked due to the treatment or ongoing inflammation; Methods: The single-cell RNA sequencing was performed on PBMC samples from CD patients either naïve to biological therapy, in remission while on adalimumab, or while on ustekinumab but previously non-responsive to adalimumab. Sieves for stringent downstream gene selection consisted of gene ontology and independent cohort genomic profiling. Replication and meta-analyses were performed using publicly available raw RNA sequencing files of sorted immune cells and an association analysis summary. Machine learning, Mendelian randomization, and oligogenic risk score methods were deployed to validate DEGs highly relevant to anti-TNFα therapy response; Results: This study found PLCB1 in CD4+ T cells and CRTAM in double-negative T cells, which met the stringent statistical thresholds throughout the analyses. An additional assessment proved causal inference of both genes in response to anti-TNFα therapy; Conclusions: This study, jointly with an innovative design, uncovered novel candidate genes in the anti-TNFα response landscape of CD, potentially obscured by therapy or inflammation.

The traditional herb Sargentodoxa cuneata alleviates DSS-induced colitis by attenuating epithelial barrier damage via blocking necroptotic signaling

ETHNOPHARMACOLOGICAL RELEVANCE

The traditional Chinese herb, Sargentodoxa cuneata, is primarily utilized as a crucial herb for managing ulcerative colitis (UC), also known as "Da Xue Teng (DXT)" or "Hong Teng" in Chinese. Nevertheless, the chemical composition, prototype, and metabolite constituents of DXT and its pharmacological mechanism of treatment for UC remain unclear.

AIM OF THE STUDY

Necroptosis, a caspase-independent form of programmed cell death, plays a crucial role in the inflammatory pathogenesis of UC. The occurrence of necroptosis in intestinal epithelial cells triggers a robust inflammatory response and disrupts the integrity of both the mucinous barrier and tight junction construction. The objective of our study was to determine the chemical composition of DXT, identify its absorbed active ingredients and metabolites in rat serum, and investigate whether DXT possesses epithelial barrier protective effects by inhibiting necroptosis.

MATERIALS AND METHODS

First, the UPLC-Q-TOF/MS was applied to identify the chemical composition of DXT, as well as the absorption components and metabolites of DXT in rat serum. Second, the network pharmacology analysis was further investigated to elucidate the potential targets for treating UC. Finally, the mechanism of action was validated by necroptosis-based experiment in vitro and an in vivo model of colitis.

RESULTS

A comprehensive analysis revealed the presence of 31 phytochemicals derived from DXT herb, as well as a total of 39 components in rat serum. Network pharmacology analysis indicated that TNF, EGFR, HSP90, etc. are the potential targets. Experimental in vitro and in vivo verified that the DXT could improve disease activity index, body weight, colon length and intestinal barrier permeability in mice with colitis by inhibiting necroptosis of intestinal epithelial cells.

CONCLUSIONS

In this study, the phytochemicals derived from DXT herb and absorption active ingredients and metabolites of DXT in rat serum were analyzed. The biological mechanism of treatment for UC can be elucidated by combining network pharmacology investigation with experimental in vitro and in vivo studies. The findings offered a theoretical basis for comprehending the bioactive substances and the pharmacological process of DXT.

Infection and inflammation stimulate expansion of a CD74+ Paneth cell subset to regulate disease progression

Paneth cells (PCs), a specialized secretory cell type in the small intestine, are increasingly recognized as having an essential role in host responses to microbiome and environmental stresses. Whether and how commensal and pathogenic microbes modify PC composition to modulate inflammation remain unclear. Using newly developed PC-reporter mice under conventional and gnotobiotic conditions, we determined PC transcriptomic heterogeneity in response to commensal and invasive microbes at single cell level. Infection expands the pool of CD74+ PCs, whose number correlates with auto or allogeneic inflammatory disease progressions in mice. Similar correlation was found in human inflammatory disease tissues. Infection-stimulated cytokines increase production of reactive oxygen species (ROS) and expression of a PC-specific mucosal pentraxin (Mptx2) in activated PCs. A PC-specific ablation of MyD88 reduced CD74+ PC population, thus ameliorating pathogen-induced systemic disease. A similar phenotype was also observed in mice lacking Mptx2. Thus, infection stimulates expansion of a PC subset that influences disease progression.

Therapeutic Effect of HDAC5 Binding and Cell Penetrating Peptide for the Treatment of Inflammatory Bowel Disease

BACKGROUND

Inflammatory bowel disease (IBD) is an incurable disease that negatively influences the quality of life of patients. Current and emerging therapies target proinflammatory cytokines and/or receptors to downregulate proinflammatory responses, but insufficient remission requires other therapeutic agents. Herein, we report that the synthetic anti-inflammatory peptide 15 (SAP15) is capable of cell penetration and anti-inflammatory activity in human macrophages.

METHODS

SAP15 was labeled with fluorescence and administered to human leukemia monocytic cells (THP-1) cells for cell penetration analysis. Using biolayer interferometry analysis, the binding affinity of SAP15 with histone deacetylase 5 (HDAC5) was measured. SAP15-treated THP-1 cells were analyzed by protein phosphorylation assay, flow cytometry, and enzyme-linked immunosorbent assay (ELISA). In addition, in vivo analysis of the therapeutic effect on IBD was observed in a dextran sulfate sodium (DSS)-induced model. Samples from SAP15-treated mice were analyzed at both the macroscopic and microscopic levels using ELISA, myeloperoxidase (MPO) assays, and histological evaluations.

RESULTS

SAP15 was internalized within the cytosol and nucleus of THP-1 cells and bound to the HDAC5 protein. SAP15-treated macrophages were assessed for protein phosphorylation and showed inhibited phosphorylation of HDAC5 and other immune-related proteins, which led to increased M2-like macrophage markers and decreased M1-like macrophage markers and tumor necrosis factor-α and interleukin-6 cytokine levels. The SAP15 treatment on IBD model showed significant recovery of colon length. Further histological analysis of colon demonstrated the therapeutic effect of SAP15 on mucosal layer. Moreover, proinflammatory cytokine levels and MPO activity from the plasma show that SAP15 is effective in reduced proinflammatory responses.

CONCLUSION

These findings suggest that SAP15 is a novel peptide with a novel cell-penetrating peptide with anti-inflammatory property that can be used as a therapeutic agent for IBD and other inflammatory diseases.

The antimicrobial peptide database is 20 years old: Recent developments and future directions

In 2023, the Antimicrobial Peptide Database (currently available at https://aps.unmc.edu) is 20-years-old. The timeline for the APD expansion in peptide entries, classification methods, search functions, post-translational modifications, binding targets, and mechanisms of action of antimicrobial peptides (AMPs) has been summarized in our previous Protein Science paper. This article highlights new database additions and findings. To facilitate antimicrobial development to combat drug-resistant pathogens, the APD has been re-annotating the data for antibacterial activity (active, inactive, and uncertain), toxicity (hemolytic and nonhemolytic AMPs), and salt tolerance (salt sensitive and insensitive). Comparison of the respective desired and undesired AMP groups produces new knowledge for peptide design. Our unification of AMPs from the six life kingdoms into "natural AMPs" enabled the first comparison with globular or transmembrane proteins. Due to the dominance of amphipathic helical and disulfide-linked peptides, cysteine, glycine, and lysine in natural AMPs are much more abundant than those in globular proteins. To include peptides predicted by machine learning, a new "predicted" group has been created. Remarkably, the averaged amino acid composition of predicted peptides is located between the lower bound of natural AMPs and the upper bound of synthetic peptides. Synthetic peptides in the current APD, with the highest cationic and hydrophobic amino acid percentages, are mostly designed with varying degrees of optimization. Hence, natural AMPs accumulated in the APD over 20 years have laid the foundation for machine learning prediction. We discuss future directions for peptide discovery. It is anticipated that the APD will continue to play a role in research and education.

Identification of Novel Loci Involved in Adalimumab Response in Crohn’s Disease Patients Using Integration of Genome Profiling and Isoform-Level Immune-Cell Deconvoluted Transcriptome Profiling of Colon Tissue

Crohn’s disease is a consequence of dysregulated inflammatory response to the host’s microbiota. Although anti-TNF treatment improves the quality of the patient’s life, a large proportion of patients lose response to the treatment. The past decade of research has led to a continuum of studies showcasing the heterogeneity of anti-TNF response; thus, the aim of the present study was to dissect transcriptome-wide findings to transcript isoform specific levels and combine the analyses with refined information of immune cell landscapes in colon tissue, and subsequently select promising candidates using gene ontology and genomic integration. We enrolled Slovenian Crohn’s disease patients who were naïve with respect to adalimumab treatment. We performed colon tissue RNA sequencing and peripheral blood mononuclear cell DNA genotyping with a subsequent contemporary integrative approach to combine immune cell deconvoluted isoform transcript specific transcriptome analysis, gene ontology layering and genomic data. We identified nine genes (MACF1, CTSE, HDLBP, HSPA9, HLA-DMB, TAP2, LGMN, ANAPC11, ACP5) with 15 transcripts and 16 variants involved in the adalimumab response. Our study identified loci, some of which were previously shown to contribute to inflammatory bowel disease susceptibility, as novel loci involved in adalimumab response in Crohn’s disease patients.

NF-κB-coupled IL17 mediates inflammatory signaling and intestinal inflammation in Artemia sinica

Nuclear factor-κB (NF-κB) plays a role as a rheostatic transcription factor in regulating intestinal inflammation, and its disruption or constitutive activation leads to inflammation and injury. However, the molecular mechanisms of NF-κB regulation remain largely unknown. In this study, the NF-κB-regulated host defenses against pathogen infections and facilitation of IL17 expression during stimulation with different bacteria were investigated. Intestinal inflammation was induced by dextran sulfate sodium, and NF-κB activity was inhibited in an intestinal injury model. Mannose receptor C type, ABF1/2, serpin B13, lysozyme, and β-arrestin were significantly controlled by NF-κB in the inflamed intestinal tissue. High levels of NF-κB activation resulted in less pervasive intestinal damage and the maintenance of intestinal barrier integrity. Intestinal injury robustly increased the expression of IL17. NF-κB activation was enhanced by IL17 deficiency in the intestinal injury model. IL17 inhibition aggravated intestinal inflammation, leading to loss of epithelial architecture and the infiltration of inflammatory cells. These data suggest that NF-κB and IL17 play key mediator roles in the maintenance of gut epithelial integrity and immune homeostasis.

Exosome-like nanoparticles from Mulberry bark prevent DSS-induced colitis via the AhR/COPS8 pathway

Bark protects the tree against environmental insults. Here, we analyzed whether this defensive strategy could be utilized to broadly enhance protection against colitis. As a proof of concept, we show that exosome-like nanoparticles (MBELNs) derived from edible mulberry bark confer protection against colitis in a mouse model by promoting heat shock protein family A (Hsp70) member 8 (HSPA8)-mediated activation of the AhR signaling pathway. Activation of this pathway in intestinal epithelial cells leads to the induction of COP9 Constitutive Photomorphogenic Homolog Subunit 8 (COPS8). Utilizing a gut epithelium-specific knockout of COPS8, we demonstrate that COPS8 acts downstream of the AhR pathway and is required for the protective effect of MBELNs by inducing an array of anti-microbial peptides. Our results indicate that MBELNs represent an undescribed mode of inter-kingdom communication in the mammalian intestine through an AhR-COPS8-mediated anti-inflammatory pathway. These data suggest that inflammatory pathways in a microbiota-enriched intestinal environment are regulated by COPS8 and that edible plant-derived ELNs may hold the potential as new agents for the prevention and treatment of gut-related inflammatory disease.

Impact of Food-Derived Bioactive Compounds on Intestinal Immunity

The gastrointestinal system is responsible for the digestion and the absorption of nutrients. At the same time, it is essentially involved in the maintenance of immune homeostasis. The strongest antigen contact in an organism takes place in the digestive system showing the importance of a host to develop mechanisms allowing to discriminate between harmful and harmless antigens. An efficient intestinal barrier and the presence of a large and complex part of the immune system in the gut support the host to implement this task. The continuous ingestion of harmless antigens via the diet requires an efficient immune response to reliably identify them as safe. However, in some cases the immune system accidentally identifies harmless antigens as dangerous leading to various diseases such as celiac disease, inflammatory bowel diseases and allergies. It has been shown that the intestinal immune function can be affected by bioactive compounds derived from the diet. The present review provides an overview on the mucosal immune reactions in the gut and how bioactive food ingredients including secondary plant metabolites and probiotics mediate its health promoting effects with regard to the intestinal immune homeostasis.

Human β-Defensin 2 and Its Postulated Role in Modulation of the Immune Response

Studies described so far suggest that human β-defensin 2 is an important protein of innate immune response which provides protection for the human organism against invading pathogens of bacterial, viral, fungal, as well as parasitical origin. Its pivotal role in enhancing immunity was proved in infants. It may also be considered a marker of inflammation. Its therapeutic administration has been suggested for maintenance of the balance of systemic homeostasis based on the appropriate composition of the microbiota. It has been suggested that it may be an important therapeutic tool for modulating the response of the immune system in many inflammatory diseases, offering new treatment modalities. For this reason, its properties and role in the human body discussed in this review should be studied in more detail.

The Safety, Tolerability and Efficacy of Probiotic Bacteria for Equine Use

Probiotic bacteria are used widely as nutritional supplements and treatment interventions in the management of livestock and companion animals. The aim of this review is to summarize the current evidence reporting on the safety, tolerability and efficacy of probiotic bacteria use in horses. An online search of five databases for studies reporting on the use of probiotic bacteria use in horses which were either healthy or had a gastrointestinal or extraintestinal disease was conducted. A total of 18 articles were eligible for full review. No clear benefits were identified to support supplementation of equids with probiotic bacteria to improve starch and fiber digestion, nor for the treatment of colic or prevention of salmonellosis. Conflicting results were seen with the management of scouring in neonatal foals. Exacerbation of diarrhea and additional adverse events were reported in response to the administration of high doses of novel probiotic bacterial species. Probiotic bacteria given to exercising horses, improved aerobic fitness and stamina. The majority of probiotic bacterial species used in equine studies are bacterial species commonly used for human consumption and indigenous to the human gastrointestinal microbiota. There is a paucity of evidence to support the use of probiotic bacteria in the health maintenance and disease management of horses. While there are unclear and conflicting results associated with probiotic bacteria use for gastrointestinal conditions in both horses and foals, the administration of multistrain bacterial formulations to increase stamina in exercising horses shows promise.

Application of Polymeric Nano-Materials in Management of Inflammatory Bowel Disease

Inflammatory Bowel Disease (IBD) is an umbrella term used to describe disorders that involve Crohn's disease (CD), ulcerative colitis (UC) and pouchitis. The disease occurrence is more prevalent in the working group population which not only hampers the well being of an individual but also has negative economical impact on society. The current drug regime used therapy is very costly owing to the chronic nature of the disease leading to several side effects. The condition gets more aggravated due to the lower concentration of drug at the desired site. Therefore, in the present scenario, a therapy is needed which can maximize efficacy, adhere to quality of life, minimize toxicity and doses, be helpful in maintaining and stimulating physical growth of mucosa with minimum disease complications. In this aspect, nanotechnology intervention is one promising field as it can act as a carrier to reduce toxicity, doses and frequency which in turn help in faster recovery. Moreover, nanomedicine and nanodiagnostic techniques will further open a new window for treatment in understanding pathogenesis along with better diagnosis which is poorly understood till now. Therefore the present review is more focused on recent advancements in IBD in the application of nanotechnology.

Recent advances: peptides and self-assembled peptide-nanosystems for antimicrobial therapy and diagnosis

Bacterial infections, especially the refractory treatment of drug-resistant bacteria, are one of the greatest threats to human health. Self-assembling peptide-based strategies can specifically detect the bacteria at the site of infection in the body and kill it.

Gastric Microbiota Alteration in Klebsiella pneumoniae-Caused Liver Abscesses Mice

Gastric microbiota provides a biological barrier against the invasion of foreign pathogens from the oral cavity, playing a vital role in maintaining gastrointestinal health. Klebsiella spp. of oral origin causes various infections not only in gastrointestinal tract but also in other organs, with Klebsiella pneumoniae serotype K1 resulting in a liver abscess (KLA) through oral inoculation in mice. However, the relationship between gastric microbiota and the extra-gastrointestinal KLA infection is not clear. In our study, a 454 pyrosequencing analysis of the bacterial 16S rRNA gene shows that the composition of gastric mucosal microbiota in mice with or without KLA infection varies greatly after oral inoculation with K. pneumoniae serotype K1 isolate. Interestingly, only several bacteria taxa show a significant change in gastric mucosal microbiota of KLA mice, including the decreased abundance of Bacteroides, Alisptipes and increased abundance of Streptococcus. It is worth noting that the abundance of Klebsiella exhibits an obvious increase in KLA mice, which might be closely related to KLA infection. At the same time, the endogenous antibiotics, defensins, involved in the regulation of the bacterial microbiota also show an increase in stomach and intestine. All these findings indicate that liver abscess caused by K. pneumoniae oral inoculation has a close relationship with gastric microbiota, which might provide important information for future clinical treatment.

The Microbiome in Visceral Medicine: Inflammatory Bowel Disease, Obesity and Beyond

It has become increasingly evident over the past two decades that the microbiota plays a nurturing role in the development of the immune system. This appears to be important since the amplitude of immune responses has a crucial regulatory function in homeostasis and the prevention of unwanted inflammation. Hence, a malfunctioning gut flora has been shown to play a key role in visceral medicine. Strong evidence demonstrates for example that intestinal inflammation can develop as a result of a dysregulated microbiota, deficient antimicrobial responses, and aberrant bacterial translocation into the bowel wall. In healthy individuals, the bacterial translocation is blocked by a single layer of highly specialized intestinal epithelial cells which forms a strong barrier that lines the gut wall. This structure is responsible for an efficient absorption of nutrients while keeping the luminal flora at bay. In susceptible individuals, for yet incompletely understood reasons, either defective epithelial barrier function or dysregulated microbial composition or microbial pathogens drive intestinal inflammation. Many therapeutic strategies focusing on the modulation of the microbiota have been proposed recently but future research including prospective human studies and gnotobiotic mouse models are still needed to evaluate the contribution and potential therapeutic value of individual bacteria to human health.

Inflammatory Bowel Disease

BACKGROUND

Inflammatory bowel diseases are common in Europe, with prevalences as high as 1 in 198 persons (ulcerative colitis) and 1 in 310 persons (Crohn's disease).

METHODS

This review is based on pertinent articles retrieved by a search in PubMed and in German and European guidelines and Cochrane reviews of controlled trials.

RESULTS

Typically, the main clinical features of inflammatory bowel diseases are diarrhea, abdominal pain, and, in the case of ulcerative colitis, peranal bleeding. These diseases are due to a complex immunological disturbance with both genetic and environmental causes. A defective mucosal barrier against commensal bowel flora plays a major role in their pathogenesis. The diagnosis is based on laboratory testing, ultrasonography, imaging studies, and, above all, gastrointestinal endoscopy. Most patients with Crohn's disease respond to budesonide or systemic steroids; aminosalicylates are less effective. Refractory exacerbations may be treated with antibodies against tumor necrosis factor (TNF) or, more recently, antibodies against integrin, a protein of the cell membrane. In ulcerative colitis, aminosalicylates are given first; if necessary, steroids or antibodies against TNF-α or integrin are added. Maintenance therapy to prevent further relapses often involves immunosuppression with thiopurines and/or antibodies. Once all conservative treatment options have been exhausted, surgery may be necessary.

CONCLUSION

The treatment of chronic inflammatory bowel diseases requires individually designed therapeutic strategies and the close interdisciplinary collaboration of internists and surgeons.

Vitamin D Signaling through Induction of Paneth Cell Defensins Maintains Gut Microbiota and Improves Metabolic Disorders and Hepatic Steatosis in Animal Models

Metabolic syndrome (MetS), characterized as obesity, insulin resistance, and non-alcoholic fatty liver diseases (NAFLD), is associated with vitamin D insufficiency/deficiency in epidemiological studies, while the underlying mechanism is poorly addressed. On the other hand, disorder of gut microbiota, namely dysbiosis, is known to cause MetS and NAFLD. It is also known that systemic inflammation blocks insulin signaling pathways, leading to insulin resistance and glucose intolerance, which are the driving force for hepatic steatosis. Vitamin D receptor (VDR) is highly expressed in the ileum of the small intestine, which prompted us to test a hypothesis that vitamin D signaling may determine the enterotype of gut microbiota through regulating the intestinal interface. Here, we demonstrate that high-fat-diet feeding (HFD) is necessary but not sufficient, while additional vitamin D deficiency (VDD) as a second hit is needed, to induce robust insulin resistance and fatty liver. Under the two hits (HFD+VDD), the Paneth cell-specific alpha-defensins including α-defensin 5 (DEFA5), MMP7 which activates the pro-defensins, as well as tight junction genes, and MUC2 are all suppressed in the ileum, resulting in mucosal collapse, increased gut permeability, dysbiosis, endotoxemia, systemic inflammation which underlie insulin resistance and hepatic steatosis. Moreover, under the vitamin D deficient high fat feeding (HFD+VDD), Helicobacter hepaticus, a known murine hepatic-pathogen, is substantially amplified in the ileum, while Akkermansia muciniphila, a beneficial symbiotic, is diminished. Likewise, the VD receptor (VDR) knockout mice exhibit similar phenotypes, showing down regulation of alpha-defensins and MMP7 in the ileum, increased Helicobacter hepaticus and suppressed Akkermansia muciniphila. Remarkably, oral administration of DEFA5 restored eubiosys, showing suppression of Helicobacter hepaticus and increase of Akkermansia muciniphila in association with resolving metabolic disorders and fatty liver in the HFD+VDD mice. An in vitro analysis showed that DEFA5 peptide could directly suppress Helicobacter hepaticus. Thus, the results of this study reveal critical roles of a vitamin D/VDR axis in optimal expression of defensins and tight junction genes in support of intestinal integrity and eubiosis to suppress NAFLD and metabolic disorders.

Gastrointestinal organoids: How they gut it out

The gastrointestinal tract is characterized by a self-renewing epithelium fueled by adult stem cells residing at the bottom of the intestinal crypt and gastric glands. Their activity and proliferation is strongly dependent on complex signaling pathways involving other crypt/gland cells as well as surrounding stromal cells. In recent years organoids are becoming increasingly popular as a new and powerful tool to study developmental or other biological processes. Organoids retain morphological and molecular patterns of the tissue they are derived from, are self-organizing, relatively simple to handle and accessible to genetic engineering. This review focuses on the developmental processes and signaling molecules involved in epithelial homeostasis and how a profound knowledge of these mechanisms allowed the establishment of a three dimensional organoid culture derived from adult gastrointestinal stem cells.

Coculture with Low-Dose SWCNT Attenuates Bacterial Invasion and Inflammation in Human Enterocyte-like Caco-2 Cells

Single walled carbon nanotubes (SWCNTs) have been shown to be highly effective against a wide range of bacteria. Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) infection is a well-known mediator to prolong hospitalization and initiate chronic inflammation, yet the biological effects of SWCNTs on the pathogen-infected enterocytes remain unclear. Herein, it is shown that the low-dose SWCNT treatment attenuates the human enterocyte-like Caco-2 cells from the damage of E. coli and S. aureus infection by suppressing NLRP3 inflammasome activation. The relatively low-dose (1 and 10 μg mL(-1) ) SWCNT treatments reduce the adhesion and invasion of E. coli and S. aureus to Caco-2 cells, increase the cell viability and proliferation, reduce the tight junction permeability, and restitute the integrity of cell surface microvilli structure, meanwhile has low cytotoxicity to the host cells. The low-dose SWCNT treatment further reduces the NLRP3-mediated IL-1β secretion in the infected cells. The results identify that a low-dose SWCNT treatment serves a protective function for the E. coli- and S. aureus-infected Caco-2 cells by negatively regulating mitochondrial reactive oxygen species-mediated NLRP3 inflammasome activation.

Fecal microbiota transplantation and bacterial consortium transplantation have comparable effects on the re-establishment of mucosal barrier function in mice with intestinal dysbiosis

Fecal microbiota transplantation (FMT) is a promising therapy, despite some reports of adverse side effects. Bacterial consortia transplantation (BCT) for targeted restoration of the intestinal ecosystem is considered a relatively safe and simple procedure. However, no systematic research has assessed the effects of FMT and BCT on immune responses of intestinal mucosal barrier in patients. We conducted complementary studies in animal models on the effects of FMT and BCT, and provide recommendations for improving the clinical outcomes of these treatments. To establish the dysbiosis model, male BALB/c mice were treated with ceftriaxone intra-gastrically for 7 days. After that, FMT and BCT were performed on ceftriaxone-treated mice for 3 consecutive days to rebuild the intestinal ecosystem. Post-FMT and post-BCT changes of the intestinal microbial community and mucosal barrier functions were investigated and compared. Disruption of intestinal microbial homeostasis impacted the integrity of mucosal epithelial layer, resulting in increased intestinal permeability. These outcomes were accompanied by overexpression of Muc2, significant decrease of SIgA secretion, and overproduction of defensins and inflammatory cytokines. After FMT and BCT, the intestinal microbiota recovered quickly, this was associated with better reconstruction of mucosal barriers and re-establishment of immune networks compared with spontaneous recovery (SR). Although based on a short-term study, our results suggest that FMT and BCT promote the re-establishment of intestinal microbial communities in mice with antibiotic-induced dysbiosis, and contribute to the temporal and spatial interactions between microbiota and mucosal barriers. The effects of BCT are comparable to that of FMT, especially in normalizing the intestinal levels of Muc2, SIgA, and defensins.

ClC-3 chloride channel/antiporter defect contributes to inflammatory bowel disease in humans and mice

BACKGROUND

ClC-3 channel/antiporter plays a critical role in a variety of cellular activities. ClC-3 has been detected in the ileum and colon.

OBJECTIVE

To determine the functions of ClC-3 in the gastrointestinal tract.

DESIGN

After administration of dextran sulfate sodium (DSS) or 2,4,6-trinitrobenzenesulfonic acid (TNBS), intestines from ClC-3-/- and wild-type mice were examined by histological, cellular, molecular and biochemical approaches. ClC-3 expression was determined by western blot and immunostaining.

RESULTS

ClC-3 expression was reduced in intestinal tissues from patients with UC or Crohn's disease and from mice treated with DSS. Genetic deletion of ClC-3 increased the susceptibility of mice to DSS- or TNBS-induced experimental colitis and prevented intestinal recovery. ClC-3 deficiency promoted DSS-induced apoptosis of intestinal epithelial cells through the mitochondria pathway. ClC-3 interacts with voltage-dependent anion channel 1, a key player in regulation of mitochondria cytochrome c release, but DSS treatment decreased this interaction. In addition, lack of ClC-3 reduced the numbers of Paneth cells and impaired the expression of antimicrobial peptides. These alterations led to dysfunction of the epithelial barrier and invasion of commensal bacteria into the mucosa.

CONCLUSIONS

A defect in ClC-3 may contribute to the pathogenesis of IBD by promoting intestinal epithelial cell apoptosis and Paneth cell loss, suggesting that modulation of ClC-3 expression might be a new strategy for the treatment of IBD.

Genomic ATG16L1 risk allele-restricted Paneth cell ER stress in quiescent Crohn's disease

OBJECTIVE

Although genome wide association studies have partly uncovered the genetic basis of Crohn's disease (CD), it remains a challenge to link genetic polymorphisms to functional intestinal phenotypes. Paneth cells are specialised antimicrobial epithelial cells localised to the small-intestinal crypt-base. Here, we investigate whether genomic variations in ATG16L1 affect Paneth cell function.

DESIGN

Genomic variation of ATG16L1 (T300A, rs2241880) was determined in DNA from 78 patients with CD and 12 healthy controls. Paraffin-embedded ileal biopsies from patients with genotype AA (n=17), GA (n=38) and patients with the GG allele (n=23) were stained for GRP78, phospho-EIF2α, lysozyme, cleaved-caspase 3, phosphohistone H3, phospho-IκB, p65, phospho-p38MAPK and PHLDA1. Microbial composition of biopsies was assessed by PCR. Disease phenotype was scored.

RESULTS

In patients with quiescent disease but with an ATG16L1 risk allele, the endoplasmic reticulum (ER) stress markers GRP78 and pEIF2α were highly expressed in Paneth cells. Other CD risk gene variations did not correlate with Paneth cell ER stress. Functionally, patients with ER-stressed Paneth cells showed no changes in intestinal epithelial cells proliferation or apoptosis, Paneth cell or stem cell numbers, p65, phospho-IκB and phospho-p38 staining. However, a significantly increased presence of adherent-invasive Escherichia coli was observed in biopsies from patients with ER-stressed Paneth cells. Phenotypically, patients with GRP78 positive Paneth cells have relatively less colonic disease over ileal disease (-21%, p=0.04), more fistulas (+21%, p=0.05) and an increased need for intestinal surgery (+38%, p=0.002).

CONCLUSIONS

The ATG16L1 T300A polymorphism defines a specific subtype of patients with CD, characterised by Paneth cell ER stress even during quiescent disease. Paneth cell ER stress correlates with bacterial persistence, and is thus likely to modulate antimicrobial functionality of this cell type in patients with CD.

High-level expression, purification and characterisation of porcine β-defensin 2 in Pichia pastoris and its potential as a cost-efficient growth promoter in porcine feed

Porcine β-defensin 2 (pBD2), a recently discovered porcine defensin that is produced by the intestine, exerts antimicrobial activities and innate immune effects that are linked to intestinal diseases in pigs. Here, we report a codon-optimised protein corresponding to mature pBD2 cDNA that was expressed and purified in Pichia pastoris yeast. The highest amount of secreted protein (3,694.0 mg/L) was reached 144 h into a 150-h induction during high-density cultivation. Precipitation followed by gel exclusion chromatography yielded 383.7 mg/L purified recombinant pBD2 (rpBD2) with a purity of ~93.7 %. Two recombinant proteins of 5,458.5 and 5,258.4 Da were detected in the mass spectrum due to variation in the amino-terminus. The rpBD2 exhibited high antimicrobial activity against a broad range of pig pathogenic bacteria (minimal inhibitory concentration [MIC] 32-128 μg/mL); the highest activity was observed against Salmonella choleraesuis, Staphylococcus aureus and Streptococcus suis (MIC 32-64 μg/mL). However, rpBD2 also inhibited the growth of probiotics such as Lactobacillus plantarum, Bacillus subtilis and Saccharomyces cerevisiae, but at lower efficacies than the pathogens. Purified or unpurified rpBD2 also maintained high activity over a wide range of pH values (2.0-10.0), a high thermal stability at 100 °C for 40 min and significant resistance to papain, pepsin and trypsin. In addition, the activity of rpBD2 towards S. aureus was unaffected by 10 mM dithiothreitol (DTT) and 20 % dimethyl sulphoxide (DMSO). Our results suggest that pBD2 could be produced efficiently in large quantities in P. pastoris and be a substitute for traditional antibiotics for growth promotion in the porcine industry.

Genetic variants synthesize to produce paneth cell phenotypes that define subtypes of Crohn's disease

BACKGROUND & AIMS

Genetic susceptibility loci for Crohn's disease (CD) are numerous, complex, and likely interact with undefined components of the environment. It has been a challenge to link the effects of particular loci to phenotypes of cells associated with pathogenesis of CD, such as Paneth cells. We investigated whether specific phenotypes of Paneth cells associated with particular genetic susceptibility loci can be used to define specific subtypes of CD.

METHODS

We performed a retrospective analysis of 119 resection specimens collected from patients with CD at 2 separate medical centers. Paneth cell phenotypes were classified as normal or abnormal (with disordered, diminished, diffuse, or excluded granule phenotypes) based on lysozyme-positive secretory granule morphology. To uncover the molecular basis of the Paneth cell phenotypes, we developed methods to determine transcriptional profiles from whole-thickness and laser-capture microdissected, formalin-fixed, paraffin-embedded tissue sections.

RESULTS

The proportion of abnormal Paneth cells was associated with the number of CD-associated NOD2 risk alleles. The cumulative number of NOD2 and ATG16L1 risk alleles had an additive effect on the proportion of abnormal Paneth cells. Unsupervised clustering analysis of demographic and Paneth cell data divided patients into 2 principal subgroups, defined by high and low proportions of abnormal Paneth cells. The disordered and diffuse abnormal Paneth cell phenotypes were associated with an altered transcriptional signature of immune system activation. We observed an inverse correlation between abnormal Paneth cells and presence of granuloma. In addition, high proportions of abnormal Paneth cells were associated with shorter time to disease recurrence after surgery.

CONCLUSIONS

Histologic analysis of Paneth cell phenotypes can be used to divide patients with CD into subgroups with distinct pathognomonic and clinical features.

Characteristic changes in microbial community composition and expression of innate immune genes in acute appendicitis

Appendicitis represents a common and severe gastrointestinal illness in younger individuals worldwide. The disease is characterized by an excessive inflammatory response and it is believed that bacterial overgrowth due to blockage of the appendix lumen might be involved. Despite the high incidence, only limited data on the pathophysiological changes exist; in particular, the innate immune responses involved are largely unknown. Real-time PCR analysis of tissue samples from inflamed and normal appendices demonstrated differentially regulated expression patterns of epithelial-derived antimicrobial peptides (AMP). The α-defensins human neutrophil peptides 1–3, HD5 and HD6, as well as the two β-defensins, human β-defensins (hBD)-2 and hBD-3, were up-regulated, whereas hBD-1 was down-regulated in acute appendicitis. Expression of upstream regulators of AMP expression, NOD-2 and TLRs 1, 2, 4, 5, 7, 8 and 10 was significantly increased as detected by real-time PCR. Finally, we confirmed the involvement of the pro-inflammatory cytokines IL-1β and IL-8, and detected characteristic changes in microbial community composition in appendicitis tissue specimens by 16S rDNA based detection techniques. In this study, we demonstrate a differential regulation of the innate immune system along with an altered bacterial diversity in acute appendicitis.

Human colonic mucus is a reservoir for antimicrobial peptides

BACKGROUND AND AIMS

To prevent bacterial adherence and translocation, the colonic mucosa is covered by a protecting mucus layer and the epithelium synthesizes antimicrobial peptides. The present qualitative study investigated the contents and interaction of these peptides in and with rectal mucus.

METHODS

Rectal mucus extracts were analyzed for antimicrobial activity and screened with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, Dot blot and immunohistochemistry for antimicrobial peptides. In addition, binding of AMPs to mucins was investigated by Western blot and enzyme-linked lectin assays.

RESULTS

In functional tests the mucus layer exhibited a strong antimicrobial activity. We detected 11 antimicrobial peptides in mucus extracts from healthy persons including the defensins HBD-1 and -3, the cathelicidin LL-37, ubiquitin, lysozyme, histones, high mobility group nucleosome-binding domain-containing protein 2, ubiquicidin and other ribosomal proteins. AMPs were bound by mucins but this was demonstrated to be reversible and inhibition of antibacterial activity was limited.

CONCLUSION

These findings indicate that epithelial antimicrobial peptides are retained in the intestinal mucus layer without losing their efficacy. Thus, the mucus layer and its composition provide an attractive drug target to restore antimicrobial barrier function in intestinal diseases.

Innate immune functions of α-defensins in the small intestine

The intestinal mucosa interfaces with a complex, dense community of microorganisms, including hundreds of species of resident microbiota and many transient microbes entering from food- and water-borne sources. In the small intestine, Paneth cells (specialized secretory epithelial cells) produce abundant quantities of α-defensins and several other antibiotic peptides. Human Paneth cells make two α-defensins: HD5 and HD6. Data from in vivo models indicate that Paneth cell α-defensins play a pivotal role in defense from food- and water-borne pathogens in the intestine. The mechanism by which these two α-defensins protect from enteric pathogens is quite distinct. HD5 is a potent antimicrobial that kills target microbes by membrane disruption, whereas HD6 is newly discovered to self-assemble to form fibrils and nanonets that surround and entangle bacteria. Recent data suggest that HD5 also serves to help shape the composition of the colonizing microbiota. Studies in humans suggest that reduced expression of HD5 and HD6 is a fundamental feature of ileal Crohn's disease. Mechanistically, the link between reduced Paneth cell α-defensin expression and ileal Crohn's disease pathogenesis may be a result of the weakened mucosal antimicrobial defense and/or alterations in the composition of commensal microbiota.

Defective antibacterial barrier in inflammatory bowel disease

The pathogenesis of inflammatory bowel disease (IBD) is very complex, including a variety of genetic and environmental contributing factors. In this context, over the past few years, a picture of IBD as a primary defect of the innate immune system rather than the adaptive immune system has evolved. The intestinal antimicrobial barrier morphologically consists of a single layer of epithelial cells and the mucus and constitutes the first defense mechanism against the microbial burden of the gut. From a more mechanistic point of view, this barrier additionally depends on a crucial interplay between the mucus and antimicrobial peptides like for instance defensins. Disturbances in this system are in the pathophysiological center stage of IBD genesis and progression. In this article we will give a short overview about some of the key mechanisms in this context with special attention on defensins and the mucus layer.

Antimicrobial peptides and gut microbiota in homeostasis and pathology

We survive because we adapted to a world of microorganisms. All our epithelial surfaces participate in keeping up an effective barrier against microbes while not initiating ongoing inflammatory processes and risking collateral damage to the host. Major players in this scenario are antimicrobial peptides (AMPs). Such broad-spectrum innate antibiotics are in part produced by specialized cells but also widely sourced from all epithelia as well as circulating inflammatory cells. AMPs belong to an ancient defense system found in all organisms and participated in a preservative co-evolution with a complex microbiome. Particularly interesting interactions between host barrier and microbiota can be found in the gut. The intestinal cell lining not only has to maintain a tightly regulated homeostasis during its high-throughput regeneration, but also a balanced relationship towards an extreme number of mutualistic or commensal inhabitants. Recent research suggests that advancing our understanding of the circumstances of such balanced and sometimes imbalanced interactions between gut microbiota and host AMPs should have therapeutic implications for different intestinal disorders.

Helicobacter pylori and Crohn’s disease: A retrospective single-center study from China

AIM: To investigate the association between Helicobacter pylori (H. pylori) infection and the prevalence of Crohn’s disease (CD).

METHODS: Subjects were selected from patients admitted the gastrointestinal (GI) department at The First Affiliated Hospital School of Medicine (Zhejiang University) for abdominal pain, hematochezia, diarrhea and other GI symptoms between January 2008 and September 2012. CD was diagnosed by endoscopy and biopsy. H. pylori infection was detected by a ¹⁴C-urea breath test and culturing of the biopsy sample. Demographic, anthropometric and serologic data were collected for each patient. H. pylori infection rate was compared between CD and control groups, followed by a subgroup analysis based on extent and severity of CD. Student’s t, Mann-Whiney U, and χ² tests were used to analyze the data.

RESULTS: A total of 447 patients were analyzed, including 229 in the CD group and 248 in the control group. There were no significant differences in age, sex, and rates of hypertension or diabetes. However, the CD group showed significantly higher rates of smoking history (34.9% vs 18.1%), alcohol intake (17.4% vs 8.1%), white blood cell count (9.7 ± 2.9 × 10⁹/L vs 4.3 ± 0.9 × 10⁹/L), and C-reactive protein (36.3 ± 20.8 mg/L vs 5.5 ± 2.3 mg/L) but lower body mass index (24.5 ± 2.0 kg/m²vs 26.0 ± 2.2 kg/m²) than the control group. The H. pylori infection rate in the CD group was 27.1%, significantly lower than that of 47.9% in the control group. Furthermore, the H. pylori infection rates in patients with colonic, small intestine, ileocolonic and extensive CD were 31.1%, 28.9%, 26.8% and 25.9% respectively, all of which were significantly lower than in the control group. Finally, the H. pylori infection rates in patients with remission, moderate and severe CD were 34.3%, 30.7% and 22.0% respectively, which were also significantly lower than in the control group.

CONCLUSION: Lower H. pylori infection in CD patients suggests a correlation between bacterial infection and CD, suggesting caution when considering H. pylori eradication in CD patients.

Modulation of porcine β-defensins 1 and 2 upon individual and combined Fusarium toxin exposure in a swine jejunal epithelial cell line

Defensins are small antimicrobial peptides (AMPs) that play an important role in the innate immune system of mammals. Since the effect of mycotoxin contamination of food and feed on the secretion of intestinal AMPs is poorly understood, the aim of this study was to elucidate the individual and combined effects of four common Fusarium toxins, deoxynivalenol (DON), nivalenol (NIV), zearalenone (ZEA), and fumonisin B1 (FB1), on the mRNA expression, protein secretion, and corresponding antimicrobial effects of porcine β-defensins 1 and 2 (pBD-1 and pBD-2) using a porcine jejunal epithelial cell line, IPEC-J2. In general, upregulation of pBD-1 and pBD-2 mRNA expression occurred following exposure to Fusarium toxins, individually and in mixtures (P < 0.05). However, no significant increase in secreted pBD-1 and pBD-2 protein levels was observed, as measured by enzyme-linked immunosorbent assay (ELISA). Supernatants from IPEC-J2 cells exposed to toxins, singly or in combination, however, possessed significantly less antimicrobial activity against Escherichia coli than untreated supernatants. When single toxins and two-toxin combinations were assessed, toxicity effects were shown to be nonadditive (including synergism, potentiation, and antagonism), suggesting interactive toxin effects when cells are exposed to mycotoxin combinations. The results show that Fusarium toxins, individually and in mixtures, activate distinct antimicrobial defense mechanisms possessing the potential to alter the intestinal microbiota through diminished antimicrobial effects. Moreover, by evaluating toxin mixtures, this improved understanding of toxin effects will enable more effective risk assessments for common mycotoxin combinations observed in contaminated food and feed.

Association between Helicobacter Pylori infection and ulcerative colitis--a case control study from China

AIMS

To investigate the association between H. pylori infection and UC prevalence in China.

MATERIALS AND METHODS

Subjects were selected from patients admitted in Department of Gastroenterology for abdominal pain, hematochezia, diarrhea and other GI symptoms during 2009-2012. UC diagnosis was based on both colonoscopy and biopsy. H. pylori detection was based on (14)C urea breath test (UBT) and biopsy sample culture. Patients' demographic, anthropometric and serologic data were selected. H. pylori infection rate was compared between UC and control groups, followed by a subgroup analysis on the association between H. pylori infection and extent and severity degree of UC.

RESULTS

Totally, 153 and 121 patients were selected and divided into UC and control groups. There were no significant differences in age, gender, BMI, hypertension and diabetes. However, smoking history was significantly lower while WBC and CRP levels were significantly higher in UC group. The H. pylori infection rate in UC group was 30.5%, significantly lower than that of 57.0% in control group. The H. pylori infection rate in UC of left colon and whole colon were 33,9% and 24.2% (p<0.05 between them), both significantly lower than that in control group. In addition, the H. pylori infection rates in mild, moderate and severe UC subgroups were 37.8%, 32.3% and 22.2% (p>0.05 among them), all of which were significantly lower than that in control group.

CONCLUSION

We reported a significantly lower H. pylori infection rate in UC patients with different extent and severity degree, which provides evidence for bacteria involvement in UC pathogenesis and reminder clinicians to keep cautious in considering H. pylori eradication in UC patients.

Recombinant human beta 2-defensin fusion proteins as a tool to investigate defensin structure and function in small human intestinal tissue samples

OBJECTIVE

Effects of immune cells on the beta 2 (β2)-defensin (HBD2) expression and its antibacterial activity in the intestinal mucosa of patients with inflammatory bowel diseases remains unclear. The small size of these proteins presents a major challenge in localizing antibacterial activities in human intestinal tissue. In this study, we evaluated the detection limits at mRNA and protein level by approaching HBD2 from small tissue samples.

METHODS

HT-29 colonic epithelial cells were incubated with proinflammatory cytokines before HBD2 mRNA was investigated by quantitative polymerase chain reaction. The HBD2 protein was assessed by Western blot analysis using HBD2 fused with enhanced green fluorescent protein (HBD2-EGFP). Purified HBD2 fused with the glutathione-S-transferase (GST-HBD2) was used to detect antibacterial activity in a densitometric assay.

RESULTS

Interleukin (IL)-1β induced HBD2 mRNA in HT-29 cells; however, tumor necrosis factor-α, IL-6 and IL-17 did not. The Western blot had a sensitivity of 1.5 pmol to detect recombinant HBD2, but did not detect HBD2 in either human intestinal or IL-1β-treated HT-29 cells. HBD2-EGFP was detected by HBD2-specific Western blot within cell lysates and culture supernants of transfected HT-29 and primary cells. In nanomolar ranges, GST-HBD2 reduced bacterial growth. The HBD2 bioactivity depended on solution conditions, but not on the size of the fusion partner.

CONCLUSION

The established fusion proteins provide excellent tools to evaluate expression patterns and antibacterial effects of HBD2 in human intestinal tissue samples.

Antimicrobial peptides: clinical relevance and therapeutic implications

Antimicrobial peptides (AMPs) are molecules that provide protection against environmental pathogens, acting against a large number of microorganisms, including bacteria, fungi, yeast, virus and others. Two major groups of antimicrobial peptides are found in humans: cathelicidins and defensins. Recently, several studies have furnished information that besides their role in infection diseases, antimicrobial peptides play a role in diseases as diverse as inflammatory disorders, autoimmunity and cancer. Here, we discuss the role of antimicrobial peptides and vitamin D have in such complex diseases and propose their use should be more explored in the diagnosis and treatment of such conditions.

Cholinergic signalling in gut immunity

The gut immune system shares many signalling molecules and receptors with the autonomic nervous system. A good example is the vagal neurotransmitter acetylcholine (ACh), for which many immune cell types express cholinergic receptors (AChR). In the last decade the vagal nerve has emerged as an integral part of an immune regulation network via its release of ACh; a system coined "the cholinergic anti-inflammatory reflex". The perspective of cholinergic immune regulation in the gut mucosa has been widened by the recent discovery of populations of ACh producing immune cells in the spleen and other organs. As such, ACh, classically referred to as neurotransmitter, may serve a much broader function as bi-directional signalling molecule between neurons and non-neuronal cell types of the immune system.

Autophagy in the intestinal epithelium regulates Citrobacter rodentium infection

Autophagy, a ubiquitous degradation pathway, is important for the survival and homeostasis of cells. Previous studies have demonstrated the role of autophagy in host defense against bacterial infection, but the importance of autophagy in the intestinal epithelium for the regulation of bacterial infection has not been fully elucidated. In this study, we showed that the essential autophagy protein Atg7 is required for resistance to Citrobacter rodentium infection in the intestinal epithelium. Infected mice in which Atg7 had been conditionally deleted from the intestinal epithelium exhibited greater clinical evidence of disease and higher expression levels of pro-inflammatory cytokine mRNA in the large intestine. Moreover, C. rodentium clearance was reduced in the Atg7 conditional knockout mice. These results demonstrate that autophagy in intestinal epithelial cells plays an important role in host defense against C. rodentium infection and the regulation of C. rodentium infectious colitis.

Association of a functional variant in the Wnt co-receptor LRP6 with early onset ileal Crohn's disease

Ileal Crohn's Disease (CD), a chronic small intestinal inflammatory disorder, is characterized by reduced levels of the antimicrobial peptides DEFA5 (HD-5) and DEFA6 (HD-6). Both of these α-defensins are exclusively produced in Paneth cells (PCs) at small intestinal crypt bases. Different ileal CD-associated genes including NOD2, ATG16L1, and recently the β-catenin-dependant Wnt transcription factor TCF7L2 have been linked to impaired PC antimicrobial function. The Wnt pathway influences gut mucosal homeostasis and PC maturation, besides directly controlling HD-5/6 gene expression. The herein reported candidate gene study focuses on another crucial Wnt factor, the co-receptor low density lipoprotein receptor-related protein 6 (LRP6). We analysed exonic single nucleotide polymorphisms (SNPs) in a large cohort (Oxford: n = 1,893) and prospectively tested 2 additional European sample sets (Leuven: n = 688, Vienna: n = 1,628). We revealed an association of a non-synonymous SNP (rs2302685; Ile1062Val) with early onset ileal CD (OR 1.8; p = 0.00034; for homozygous carriers: OR 4.1; p = 0.00004) and additionally with penetrating ileal CD behaviour (OR 1.3; p = 0.00917). In contrast, it was not linked to adult onset ileal CD, colonic CD, or ulcerative colitis. Since the rare variant is known to impair LRP6 activity, we investigated its role in patient mucosa. Overall, LRP6 mRNA was diminished in patients independently from the genotype. Analysing the mRNA levels of PC product in biopsies from genotyped individuals (15 controls, 32 ileal, and 12 exclusively colonic CD), we found particularly low defensin levels in ileal CD patients who were carrying the variant. In addition, we confirmed a direct relationship between LRP6 activity and the transcriptional expression of HD-5 using transient transfection. Taken together, we identified LRP6 as a new candidate gene in ileal CD. Impairments in Wnt signalling and Paneth cell biology seem to represent pathophysiological hallmarks in small intestinal inflammation and should therefore be considered as interesting targets for new therapeutic approaches.

Proteomics at the interface of psychology, gut physiology and dysfunction: an underexploited approach that deserves expansion

Gut functions such as digestion and absorption are essential to life and the emerging insights into the gut-brain axis - that is, the cross talk between the enteric and CNS - point towards critical links between (eating) behavior, psychology, whole body and gut physiology, and digestive and overall health. While proteomics is ideally positioned to shed more light on these interactions, be it applied to the periphery (e.g., blood) or the locus of action (i.e., the gut), it is to date largely underexploited, mainly because of challenging sampling and tissue complexity. In view of the contrast between potential and current delivery of proteomics in the context of intestinal health, this article briefs the reader on the state-of-the-art of molecular intestinal research, reviews current proteomic studies (explicitly focusing on the most recent ones that target inflammatory bowel disease patient samples) and argues for an expansion of this research field.

Gene-environment interaction in chronic disease: a European Science Foundation Forward Look

Over the last half century, a dramatic increase in the incidence of chronic inflammatory diseases, such as asthma, allergy, and irritable bowel syndrome, has rightfully led to concern about how the modern lifestyle might inappropriately trigger innate physiologic defense mechanisms. Health care research in the Western world is faced with a significant challenge if it is to meet the needs of its populations in the decades ahead. The tools with which we hope to advance our understanding of the intrinsic and extrinsic mechanisms of chronic inflammatory diseases must therefore be adequately exploited and further developed to identify treatment and prevention strategies. There is an urgent need to prioritize resources and identify the most efficient scientific and societal initiatives to be adopted within this area. In this context national collaboration within Europe and beyond to establish state-of-the-art practices with an interdisciplinary perspective and promote an efficient exchange of best practices is essential. Such an approach likely represents the most efficient manner in which strategies for amelioration of the increase of chronic inflammatory diseases in the Western world can be achieved. The present report is based on a Forward Look initiative conducted by the European Medical Research Councils under the European Science Foundation. Experts from industry and academia, as well as relevant interest organizations, have been consulted in the process of conducting this initiative and have, based on this work, developed a set of final recommendations that target academic research, science funders, and policy makers.

Gut microbiota and probiotics in colon tumorigenesis

The human gastrointestinal tract harbors a complex and abundant microbial community reaching as high as 10(13)-10(14) microorganisms in the colon. This endogenous microbiota forms a symbiotic relationship with their eukaryotic host and this close partnership helps maintain homeostasis by performing essential and non-redundant tasks (e.g. nutrition/energy and, immune system balance, pathogen exclusion). Although this relationship is essential and beneficial to the host, various events (e.g. infection, diet, stress, inflammation) may impact microbial composition, leading to the formation of a dysbiotic microbiota, further impacting on health and disease states. For example, Crohn's disease and ulcerative colitis, collectively termed inflammatory bowel diseases (IBD), have been associated with the establishment of a dysbiotic microbiota. In addition, extra-intestinal disorders such as obesity and metabolic syndrome are also associated with the development of a dysbiotic microbiota. Consequently, there is an increasing interest in harnessing the power of the microbiome and modulating its composition as a means to alleviate intestinal pathologies/disorders and maintain health status. In this review, we will discuss the emerging relationship between the microbiota and development of colorectal cancer as well as present evidence that microbial manipulation (probiotic, prebiotic) impacts disease development.

Nod2: a key regulator linking microbiota to intestinal mucosal immunity

The human intestine harbors a large number of bacteria that are constantly interacting with the intestinal immune system, eliciting non-pathological basal level immune responses. Increasing evidence points to dysbiosis of microbiota in the intestine as an underlying factor in inflammatory bowel disease susceptibility. Loss-of-function mutations in NOD2 are among the stronger genetic factors linked to ileal Crohn's disease. Indeed, Nod2 is a key regulator of microbiota in the intestine, as microflora in the terminal ileum is dysregulated in Nod2-deficient mice. Nod2 is highly expressed in Paneth cells, which are responsible for the regulation of ileal microflora by anti-microbial compounds, and Nod2-deficient ileal intestinal epithelia are unable to kill bacteria efficiently. It is therefore likely that NOD2 mutations in Crohn's disease may increase disease susceptibility by altering interactions between ileal microbiota and mucosal immunity.

Probiotics, nuclear receptor signaling, and anti-inflammatory pathways

There is increased investigation of the human microbiome as it relates to health and disease. Dysbiosis is implicated in various clinical conditions including inflammatory bowel disease (IBD). Probiotics have been explored as a potential treatment for IBD and other diseases. The mechanism of action for probiotics has yet to be fully elucidated. This paper discusses novel mechanisms of action for probiotics involving anti-inflammatory signaling pathways. We highlight recent progress in probiotics and nuclear receptor signaling, such as peroxisome-proliferator-activated receptor gamma (PPARγ) and vitamin D receptor (VDR). We also discuss future areas of investigation.

Food allergies

Food incompatibilities affect approximately 20% of the general population in Western countries. In about one quarter of the affected children and one tenth of affected adults, the incompatibility is based on an allergy, that is, on an immunologically generated incompatibility reaction. Gastrointestinal symptoms occur in a third of these cases. Food allergies are caused by IgE-dependent or IgE-independent immunologic reactions, which lead to an inflammatory reaction, in which mast cells, eosinophilic granulocytes, and other cells are involved. Both genetic and environmental causes are under consideration. New findings concerning the interaction between the innate immune system and intestinal microflora have generated innovative therapeutic concepts, including the use of probiotics to prevent food allergies. The development of recombinant allergens and varieties of allergens will improve diagnostic possibilities and bring new therapeutic options, such as hyposensitization and induction of immunologic tolerance. Food intolerances (nonimmunologic food incompatibilities often caused by specific enzyme deficiencies) must be diagnostically differentiated from food allergies.

Innate antimicrobial immunity in inflammatory bowel diseases

Inflammatory bowel diseases are characterized by chronic intestinal inflammation at different sites. Data from animal models as well as human patients including gene-association studies suggest that different components of the innate barrier function are primarily defective. These recent advances support the evolving hypothesis that intestinal bacteria induce inflammation predominantly as a result of a weakened innate mucosal barrier in genetically predisposed individuals. This article discusses our current understanding of the primary events of disease. Together, these findings should result in new therapeutic avenues aimed at restoring antimicrobial barrier function to prevent a bacterial-triggered inflammatory response.