Antimicrobial proteins in intestine and inflammatory bowel diseases

Intestinal Epithelial Axin1 Deficiency Protects Against Colitis via Altered Gut Microbiota

Intestinal homeostasis is maintained by specialized host cells and the gut microbiota. Wnt/β-catenin signaling is essential for gastrointestinal development and homeostasis, and its dysregulation has been implicated in inflammation and colorectal cancer. Axin1 negatively regulates activated Wnt/β-catenin signaling, but little is known regarding its role in regulating host-microbial interactions in health and disease. Here, we aim to demonstrate that intestinal Axin1 determines gut homeostasis and host response to inflammation. Axin1 expression was analyzed in human inflammatory bowel disease datasets. To explore the effects and mechanism of intestinal Axin1 in regulating intestinal homeostasis and colitis, we generated new mouse models with Axin1 conditional knockout in intestinal epithelial cell (IEC; Axin1 ΔIEC) and Paneth cell (PC; Axin1 ΔPC) to compare with control (Axin1 LoxP; LoxP: locus of X-over, P1) mice. We found increased Axin1 expression in the colonic epithelium of human inflammatory bowel disease (IBD). Axin1 ΔIEC mice exhibited altered goblet cell spatial distribution, PC morphology, reduced lysozyme expression, and enriched Akkermansia muciniphila (A. muciniphila). The absence of intestinal epithelial and PC Axin1 decreased susceptibility to dextran sulfate sodium (DSS)-induced colitis in vivo. Axin1 ΔIEC and Axin1 ΔPC mice became more susceptible to DSS-colitis after cohousing with control mice. Treatment with A. muciniphila reduced DSS-colitis severity. Antibiotic treatment did not change the IEC proliferation in the Axin1 Loxp mice. However, the intestinal proliferative cells in Axin1 ΔIEC mice with antibiotic treatment were reduced compared with those in Axin1 ΔIEC mice without treatment. These data suggest non-colitogenic effects driven by the gut microbiome. In conclusion, we found that the loss of intestinal Axin1 protects against colitis, likely driven by epithelial Axin1 and Axin1-associated A. muciniphila. Our study demonstrates a novel role of Axin1 in mediating intestinal homeostasis and the microbiota. Further mechanistic studies using specific Axin1 mutations elucidating how Axin1 modulates the microbiome and host inflammatory response will provide new therapeutic strategies for human IBD.

Oral Delivery of Mouse β-Defensin 14 (mBD14)-Producing Lactococcus lactis NZ9000 Attenuates Experimental Colitis in Mice

Antimicrobial peptides (AMPs) play essential roles in maintaining intestinal health and have been suggested as possible therapeutic strategies against inflammatory bowel disease (IBD). However, the instability of AMPs in the process of transmission in vivo limits their application in the treatment of IBD. In this study, we constructed the mBD14-producing Lactococcus lactis NZ9000 (L. lactis/mBD14) to achieve enteric delivery of mBD14 and evaluated its protective effect on dextran sodium sulfate (DSS)-induced colitis. Mice treated with L. lactis/mBD14 exhibited milder symptoms of colitis (P < 0.01). Additionally, L. lactis/mBD14 treatment reversed DSS-induced epithelial dysfunction and reduced the production of pro-inflammatory cytokines in colon (P < 0.01). Mechanistically, L. lactis/mBD14 significantly inhibited NOD-like receptor pyrin domain containing three inflammasome-mediated pro-inflammatory response (P < 0.05) and regulated microbiota homeostasis by promoting the abundance of probiotic bacteria Akkermansia muciniphila and Faecalibacterium prausnitzii and decreasing the pathogenic Escherichia coli (P < 0.01). Taken together, this study demonstrates the protective effect of L. lactis/mBD14 in DSS-induced colitis, and suggests that oral administration of L. lactis/mBD14 may represent a potential therapeutic strategy for IBD.

Alterations in fecal β-defensin-3 secretion as a marker of instability of the gut microbiota

Compositional changes in the microbiota (dysbiosis) may be a basis for Irritable Bowel Syndrome (IBS), but biomarkers are currently unavailable to direct microbiota-directed therapy. We therefore examined whether changes in fecal β-defensin could be a marker of dysbiosis in a murine model. Experimental dysbiosis was induced using four interventions relevant to IBS: a mix of antimicrobials, westernized diets (high-fat/high-sugar and high salt diets), or mild restraint stress. Fecal mouse β-defensin-3 and 16S rRNA-based microbiome profiles were assessed at baseline and during and following these interventions. Each intervention, except for mild restraint stress, altered compositional and diversity profiles of the microbiota. Exposure to antimicrobials or a high-fat/high-sugar diet, but not mild restraint stress, resulted in decreased fecal β-defensin-3 compared to baseline. In contrast, exposure to the high salt diet increased β-defensin-3 compared to baseline. Mice exposed to the mix of antimicrobials showed the largest compositional changes and the most significant correlations between β-defensin-3 levels and bacterial diversity. The high salt diet was also associated with significant correlations between changes in β-defensin-3 and bacterial diversity, and this was not accompanied by discernible inflammatory changes in the host. Thus, dietary change or antimicrobial exposure, both recognized factors in IBS exacerbations, induced marked dysbiosis that was accompanied by changes in fecal β-defensin-3 levels. We propose that serial monitoring of fecal β-defensins may serve as a marker of dysbiosis and help identify those IBS patients who may benefit from microbiota-directed therapeutic interventions.

Detection of Marker Associated with CTC in Colorectal Cancer in Mononuclear Cells of Patients with Benign Inflammatory Intestinal Diseases

Simple Summary

Colorectal carcinoma (CRC) is one of the most frequent cancers in western countries, and non-invasive methods for early detection are still needed. Circulating tumor cells (CTC) in blood of CRC patients have been proven as prognostic and predictive biomarker; however, the suitability of CTC-associated markers for early CRC detection and discrimination from benign diseases has not been analyzed. Thus, this study investigated whether CTC-associated markers can also be detected in the blood of patients with benign inflammatory intestinal disease (IID) or whether they are specific for malignancy. The detection rate of CK20 and DEFA5 clearly differed in diseased patients and healthy controls, while LAD1 and PLS3 was found in all samples but with clear qualitative differences in gene expression. No association between inflammation severity and CTC marker expression was found in IID patients. Finally, PLS3 was identified to be a suitable marker for differentiation between malignant and non-malignant intestinal diseases or healthy controls.

Abstract

Colorectal carcinoma (CRC) belongs to the most common tumor entities in western countries. Circulating tumor cells (CTC) in blood of CRC patients are a powerful prognostic and predictive biomarker. However, whether CTC-associated markers can also be used for early CRC detection and discrimination from benign diseases is not known. This study investigated the presence of CTC-associated markers CK20, PLS3, LAD1, and DEFA5 in blood of patients with benign inflammatory intestinal disease (IID) and their correlation with malignancy. The detection rate of CK20 and DEFA5 significantly differed between diseased patients and healthy controls. LAD1 and PLS3 were detected in all samples with clear differences in gene expression. DEFA5 expression was higher in CRC and IID patients compared to healthy donors, while CK20 and PLS3 were lower in CRC compared to IID patients or healthy controls. Overall, all CTC-associated markers were detectable in blood of IID patients, but not correlating with inflammation severity. Finally, PLS3 emerged as a suitable marker for differentiation between malignant and non-malignant intestinal diseases or healthy controls, however its suitability for early CRC detection needs to be further validated.

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.

Protective effects of potential probiotic Lactobacillus rhamnosus (MTCC-5897) fermented whey on reinforcement of intestinal epithelial barrier function in a colitis-induced murine model

Fermented foods provide essential nutritional components and bioactive molecules that have beneficial effects on several gastrointestinal disorders. In the present investigation, the potential protective effects of whey fermented with probiotic Lactobacillus rhamnosus MTCC-5897 on gastrointestinal health in a murine ulcerative colitis model induced by dextran sulfate sodium (DSS) were evaluated. Pre-consumption of whey fermented with probiotic L. rhamnosus (PFW) before colitis induction significantly reduced (p < 0.01) the disease activity index and improved (p < 0.05) the hematological parameters and histological scores. The considerably diminished levels (p < 0.01) of pro-inflammatory markers (IL-4, TNF-α, CRP and MPO activity) and the enhanced (p < 0.05) levels of the anti-inflammatory cytokine TGF-β with IgA in the intestine upon feeding PFW appeared to prevent inflammation on colitis induction. Transcriptional modulations in pathogen recognition receptors (TLR-2/4) and tight junctional genes (ZO-1, occludin, claudin-1) along with localized distribution of junctional (claudin-1, occludin and ZO-1) and cytoskeleton (actin) proteins improved immune homeostasis and intestinal barrier integrity. Besides, significantly reduced (p < 0.05) levels of the FITC-dextran marker in serum upon consumption of PFW directly confirmed the healthy status of the host gut.

COVID-19 and its Therapeutics: Special Emphasis on Mesenchymal Stem Cells Based Therapy

The novel virus, Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) caused the Corona Virus Disease-2019 (COVID-19) outbreak in Wuhan, Hubei province of China. This virus disseminated rapidly and reached to an unprecedented pandemic proportion in more than 213 nations with a large number of fatalities. The hypersecretion of pro-inflammatory cytokines is the main cause of mortality and morbidity due to COVID-19, therefore strategies that avert the cytokine storm may play a crucial role in abating the severity of COVID-19. This review highlights the minute details of SARS-CoV-2, its genomic organization, genomic variations within structural and non-structural proteins and viral progression mechanism in human beings. The approaches like antiviral strategies are discussed, including drugs that obstruct viral propagation and suppress the pro-inflammatory cytokines. This compilation emphasizes Mesenchymal Stem Cells (MSCs) based therapy alone or in combination with other therapeutics as an attractive curative approach for COVID-19 pandemic. The MSCs and its secretome, including antimicrobial peptides (AMPs) have various capabilities, for instance, immunomodulation, regeneration, antimicrobial properties, potential for attenuating the cytokine storm and bare minimum chances of being infected with SARS-CoV-2 virus. The immunomodulatory property of MSCs affects inflammatory state and regulates immune response during SARS-CoV-2 infection. However, as of now, there is no WHO-approved MSCs based therapy for the treatment of COVID-19 infection.

Cathelicidin - A Novel Potential Marker of Pediatric Inflammatory Bowel Disease

Introduction

Cathelicidin is a multifunctional host defense peptide which may also exert pro-inflammatory signals and contribute to the development of autoimmune disorders. We aimed to assess serum concentration of cathelicidin in children with inflammatory bowel disease (IBD) compared to healthy controls and to evaluate its relationship with disease activity and phenotype.

Patients and Methods

The study group included 68 children with IBD. The control group comprised 20 children with functional abdominal pain. All patients and controls were tested for complete blood count, C-reactive protein, erythrocyte sedimentation rate and cathelicidin. Stool samples were collected to assess calprotectin.

Results

Cathelicidin was significantly increased in patients with ulcerative colitis (1073.39±214.52 ng/mL) and Crohn’s disease (1057.63±176.03 ng/mL) patients compared to controls (890.56±129.37 ng/mL) (H=16.28; p=0.0003). Cathelicidin was significantly elevated in children with active IBD (1044.90±176.17 ng/mL) and IBD remission (1098.10±227.87 ng/mL) compared to controls (Z=3.21; p=0.001; Z=−4.12; p<0.0001, respectively). Negative correlation between cathelicidin and calprotectin in children with ulcerative colitis was found (R=−0.39; p=0.02). Cathelicidin exhibited AUC of 0.815 for differentiation children with ulcerative colitis from the control group.

Conclusion

Serum cathelicidin is increased in children with Crohn’s disease and ulcerative colitis regardless of clinical activity of the disease suggesting that it may be a potential biomarker of IBD. Inverse correlation between cathelicidin and fecal calprotectin may imply a disparate role of these molecules in the pathophysiology of pediatric ulcerative colitis.

Plasma elafin, cathelicidin, and α-defensins are increased in paediatric inflammatory Crohn's disease and reflect disease location

INTRODUCTION

The aim of our study was to assess antimicrobial peptides in children with Crohn's disease (CD).

METHODS

Plasma elafin, cathelicidin, and α- and β-defensins were assessed in 35 children with CD using immunoassays. Phenotype and location of CD were assessed based on the results of endoscopic and radiological studies.

RESULTS

We found increased elafin, cathelicidin, and α-defensins in children with inflammatory phenotype as compared to stricturing and penetrating phenotypes of CD. Additionally, we found increased elafin and cathelicidin in colonic location and α-defensins in ileal CD locations.

CONCLUSIONS

Assessing antimicrobial peptides may be helpful in estimating of phenotype and location of CD lesions.

Mesenchymal Stromal Cells as Potential Antimicrobial for Veterinary Use-A Comprehensive Review

The emergence of “superbugs” resistant to antimicrobial medications threatens populations both veterinary and human. The current crisis has come about from the widespread use of the limited number of antimicrobials available in the treatment of livestock, companion animal, and human patients. A different approach must be sought to find alternatives to or enhancements of present conventional antimicrobials. Mesenchymal stromal cells (MSC) have antimicrobial properties that may help solve this problem. In the first part of the review, we explore the various mechanisms at work across species that help explain how MSCs influence microbial survival. We then discuss the findings of recent equine, canine, and bovine studies examining MSC antimicrobial properties in which MSCs are found to have significant effects on a variety of bacterial species either alone or in combination with antibiotics. Finally, information on the influence that various antimicrobials may have on MSC function is reviewed. MSCs exert their effect directly through the secretion of various bioactive factors or indirectly through the recruitment and activation of host immune cells. MSCs may soon become a valuable tool for veterinarians treating antimicrobial resistant infections. However, a great deal of work remains for the development of optimal MSC production conditions and testing for efficacy on different indications and species.

Toxicomicrobiomics: The Human Microbiome vs. Pharmaceutical, Dietary, and Environmental Xenobiotics

The harmful impact of xenobiotics on the environment and human health is being more widely recognized; yet, inter- and intraindividual genetic variations among humans modulate the extent of harm, mostly through modulating the outcome of xenobiotic metabolism and detoxification. As the Human Genome Project revealed that host genetic, epigenetic, and regulatory variations could not sufficiently explain the complexity of interindividual variability in xenobiotics metabolism, its sequel, the Human Microbiome Project, is investigating how this variability may be influenced by human-associated microbial communities. Xenobiotic-microbiome relationships are mutual and dynamic. Not only does the human microbiome have a direct metabolizing potential on xenobiotics, but it can also influence the expression of the host metabolizing genes and the activity of host enzymes. On the other hand, xenobiotics may alter the microbiome composition, leading to a state of dysbiosis, which is linked to multiple diseases and adverse health outcomes, including increased toxicity of some xenobiotics. Toxicomicrobiomics studies these mutual influences between the ever-changing microbiome cloud and xenobiotics of various origins, with emphasis on their fate and toxicity, as well the various classes of microbial xenobiotic-modifying enzymes. This review article discusses classic and recent findings in toxicomicrobiomics, with examples of interactions between gut, skin, urogenital, and oral microbiomes with pharmaceutical, food-derived, and environmental xenobiotics. The current state and future prospects of toxicomicrobiomic research are discussed, and the tools and strategies for performing such studies are thoroughly and critically compared.

High circulating elafin levels are associated with Crohn's disease-associated intestinal strictures

Background

Antimicrobial peptide expression is associated with disease activity in inflammatory bowel disease (IBD) patients. IBD patients have abnormal expression of elafin, a human elastase-specific protease inhibitor and antimicrobial peptide. We determined elafin expression in blood, intestine, and mesenteric fat of IBD and non-IBD patients.

Methods

Serum samples from normal and IBD patients were collected from two UCLA cohorts. Surgical resection samples of human colonic and mesenteric fat tissues from IBD and non-IBD (colon cancer) patients were collected from Cedars-Sinai Medical Center.

Results

High serum elafin levels were associated with a significantly elevated risk of intestinal stricture in Crohn’s disease (CD) patients. Microsoft Azure Machine learning algorithm using serum elafin levels and clinical data identified stricturing CD patients with high accuracy. Serum elafin levels had weak positive correlations with clinical disease activity (Partial Mayo Score and Harvey Bradshaw Index), but not endoscopic disease activity (Mayo Endoscopic Subscore and Simple Endoscopic Index for CD) in IBD patients. Ulcerative colitis (UC) patients had high serum elafin levels. Colonic elafin mRNA and protein expression were not associated with clinical disease activity and histological injury in IBD patients, but stricturing CD patients had lower colonic elafin expression than non-stricturing CD patients. Mesenteric fat in stricturing CD patients had significantly increased elafin mRNA and protein expression, which may contribute to high circulating elafin levels. Human mesenteric fat adipocytes secrete elafin protein.

Conclusions

High circulating elafin levels are associated with the presence of stricture in CD patients. Serum elafin levels may help identify intestinal strictures in CD patients.

Mucosal expression of defensin-5, soluble phospholipase A2 and lysozyme in the intestine in a rat model of acute liver failure and its relationship to intestinal bacterial translocation

INTRODUCTION

To study the expression of defensin-5 (RD-5), soluble phospholipase A2 (sPLA2) and lysozyme in the intestine in a rat model of acute liver failure and its relationship with intestinal bacterial translocation (BT).

PATIENTS AND METHODS

Sprague-Dawley (SD) rats were divided into two groups. The experimental group was divided into five subgroups according to the lapsing time after the model was established, which were designated accordingly as 8h, 16h, 24h, 48h, and 72h groups. Acute liver failure (ALF) model was induced by intraperitoneal injection of 10% d-galactosamine. The homogenates of mesenteric lymph nodes (MLNs), liver and spleen from each group were cultured in agar to determine the bacterial outgrowth. The mRNA expression of RD-5, sPLA2, lysozyme and the protein expression of sPLA2, lysozyme were determined.

RESULTS

No bacteria grew in the organ cultures from the control group while experimental groups had positive cultures. Expression of the RD-5 and sPLA2 mRNA in the experimental groups gradually increased at early time points and peaked 16h after induction of ALF, then progressively decreased. The mRNA expression of lysozyme in the experimental group peaked at 8h after ALF induction, then progressively decreased. Similar results were obtained with Western blot and immunohistochemical staining.

DISCUSSION

The immune barrier function of the ileal mucosa in the rat model of acute liver failure was compromised as demonstrated by the decreased expression of RD-5, sPLA2 and lysozyme in Paneth cells along with increased intestinal bacterial translocation.

Integrative Analysis of Transcriptomic and Proteomic Profiling in Inflammatory Bowel Disease Colon Biopsies

BACKGROUND

Crohn's disease (CD) and ulcerative colitis (UC) are intestinal chronic inflammatory conditions characterized by altered epithelial barrier function and tissue damage. Despite significant efforts to understanding the biological mechanisms responsible for gut inflammation, the pathophysiology of CD and UC remains poorly understood.

METHODS

To help elucidate the potential mechanisms responsible for gut inflammation in CD and UC, transcriptomic and proteomic profiling of human colon biopsy specimens was performed. Dysregulated genes and proteins in disease tissues compared with normal tissues were characterized from the expression profiles and further subjected to pathway analysis to identify altered biological processes and signaling pathways.

RESULTS

Sample analysis showed 4250 genes with matched protein expression and a wide range of correlation of RNA-protein abundance across samples. Pathway analysis of dysregulated genes and proteins in CD and UC showed alterations in immune and inflammatory responses, complement cascade, and the suppression of metabolic processes and PPAR signaling. In CD, increased T-helper cell differentiation and elevated toll-like receptor and JAK/STAT signaling were observed. Interestingly, increased MAPK signaling was only observed in UC. Weighted gene co-expression network analysis suggested a possible role of epigenetic regulation in UC. Of note, a large discrepancy between regulation of RNA and protein levels in inflamed colon samples was detected for previously identified biomarkers including MMP14 and LAMP1.

CONCLUSIONS

With the analysis of dysregulated genes and pathways, the present study unravels key mechanisms contributing to CD and UC pathogenesis and emphasizes that integrative analysis of multi-omics data sets can provide more insight into understanding complex disease mechanisms.

Performance evaluation of antimicrobial peptide ll-37 and hepcidin and β-defensin-2 secreted by mesenchymal stem cells

Peptides are secreted by different cell types and are trendy therapeutic agents that have attracted attention for the treatment of several diseases such as infections. Antimicrobial peptides exert various mechanisms such as changing cell membrane permeability which leads to inhibition or death of bacterial cells. mesenchymal stem cells (MSCs) are key to produce antimicrobial peptides and to inhibit the growth of pathogens. These cells have been shown to be capable of producing antimicrobial peptides upon exposure to different bacteria. As a result, antimicrobial peptides can be considered as novel agents for the treatment of infectious diseases. The purpose of this review was to investigate the targets and mechanisms of antimicrobial peptides secreted by MSCs.

Gene and Mirna Regulatory Networks During Different Stages of Crohn's Disease

BACKGROUND AND AIMS

Early treatment of Crohn's disease [CD] is required in order to optimize patient outcomes. To this end, we need to gain a better understanding of the molecular changes at the onset of CD.

METHODS

As a model for the earliest mucosal CD lesions, we study post-operative recurrent CD [Rutgeerts score ≥ i2b]. We are the first to analyse gene and microRNA [miRNA] expression profiles in ileal biopsies from these patients, and compare them with those of newly diagnosed [≤18 months] and late-stage [>10 years after diagnosis] CD patients.

RESULTS

Except for one gene [WNT5A], there are no differential genes in CD patients without post-operative recurrence [i0], showing that previous disease did not influence gene expression in the neoterminal ileum, and that this model can be used to study early mucosal CD lesions. Gene expression and co-expression network dysregulation is more pronounced in newly diagnosed and late-stage CD than in post-operative recurrent CD, with most important modules associated with [a]granulocyte adhesion/diapedesis, and cholesterol biosynthesis. In contrast, we found a role for snoRNAs/miRNAs in recurrent CD, highlighting the potential importance of regulatory RNAs in early disease stages. Immunohistochemistry confirmed the expression of key dysregulated genes in damaged/regenerating epithelium and immune cells in recurrent CD.

CONCLUSIONS

Aside from regulatory RNAs, there are no clear gene signatures separating post-operative recurrent, newly diagnosed, and late-stage CD. The relative contribution of dysregulated genes and networks differs, and suggests that surgery may reset the disease at the mucosal site, and therefore post-operative recurrent CD might be a good model a good model to study to study early mucosal CD lesions.

Duodenal expression of antimicrobial peptides in dogs with idiopathic inflammatory bowel disease and intestinal lymphoma

Although antimicrobial peptides (AMPs) play an integral role in the regulation of intestinal microbiota and homeostasis, their expression in canine gastrointestinal diseases, including idiopathic inflammatory bowel disease (IBD) and intestinal lymphoma, remains unknown. The objective of this study was to investigate the intestinal expression of AMPs in dogs with IBD or intestinal lymphoma. IBD was diagnosed in 44 dogs, small cell intestinal lymphoma in 25 dogs, and large cell intestinal lymphoma in 19 dogs. Twenty healthy beagles were used as normal controls. Duodenal mRNA expression of six representative AMPs - lactoferrin, lysozyme, cathelicidin, secretory leukocyte peptidase inhibitor (SLPI), bactericidal/permeability increasing protein (BPI), and canine beta defensin (CBD103) - was quantified by real-time reverse transcription polymerase chain reaction. The relative expression of BPI, lactoferrin, and SLPI was significantly higher in dogs with IBD and intestinal lymphomas than in healthy controls. Interestingly, the expression patterns of AMPs differed between dogs with IBD and those with intestinal lymphomas, especially small cell lymphoma. Increased expression of BPI differentiated IBD from dogs with small cell intestinal lymphoma, with a sensitivity of 93.2%, a specificity of 100%, and an area under the curve of 0.955. These results suggest that the expression patterns of AMP aid in the diagnosis of canine IBD and intestinal lymphoma, although it remains uncertain whether the altered AMP expression is the cause or effect of mucosal inflammation.

Impact of the Food Additive Titanium Dioxide (E171) on Gut Microbiota-Host Interaction

The interaction between gut microbiota and host plays a central role in health. Dysbiosis, detrimental changes in gut microbiota and inflammation have been reported in non-communicable diseases. While diet has a profound impact on gut microbiota composition and function, the role of food additives such as titanium dioxide (TiO₂), prevalent in processed food, is less established. In this project, we investigated the impact of food grade TiO₂ on gut microbiota of mice when orally administered via drinking water. While TiO₂ had minimal impact on the composition of the microbiota in the small intestine and colon, we found that TiO₂ treatment could alter the release of bacterial metabolites in vivo and affect the spatial distribution of commensal bacteria in vitro by promoting biofilm formation. We also found reduced expression of the colonic mucin 2 gene, a key component of the intestinal mucus layer, and increased expression of the beta defensin gene, indicating that TiO₂ significantly impacts gut homeostasis. These changes were associated with colonic inflammation, as shown by decreased crypt length, infiltration of CD8⁺ T cells, increased macrophages as well as increased expression of inflammatory cytokines. These findings collectively show that TiO₂ is not inert, but rather impairs gut homeostasis which may in turn prime the host for disease development.

Tight Junction Proteins and Signaling Pathways in Cancer and Inflammation: A Functional Crosstalk

The ability of epithelial cells to organize through cell–cell adhesion into a functioning epithelium serves the purpose of a tight epithelial protective barrier. Contacts between adjacent cells are made up of tight junctions (TJ), adherens junctions (AJ), and desmosomes with unique cellular functions and a complex molecular composition. These proteins mediate firm mechanical stability, serves as a gatekeeper for the paracellular pathway, and helps in preserving tissue homeostasis. TJ proteins are involved in maintaining cell polarity, in establishing organ-specific apical domains and also in recruiting signaling proteins involved in the regulation of various important cellular functions including proliferation, differentiation, and migration. As a vital component of the epithelial barrier, TJs are under a constant threat from proinflammatory mediators, pathogenic viruses and bacteria, aiding inflammation and the development of disease. Inflammatory bowel disease (IBD) patients reveal loss of TJ barrier function, increased levels of proinflammatory cytokines, and immune dysregulation; yet, the relationship between these events is partly understood. Although TJ barrier defects are inadequate to cause experimental IBD, mucosal immune activation is changed in response to augmented epithelial permeability. Thus, the current studies suggest that altered barrier function may predispose or increase disease progression and therapies targeted to specifically restore the barrier function may provide a substitute or supplement to immunologic-based therapies. This review provides a brief introduction about the TJs, AJs, structure and function of TJ proteins. The link between TJ proteins and key signaling pathways in cell proliferation, transformation, and metastasis is discussed thoroughly. We also discuss the compromised intestinal TJ integrity under inflammatory conditions, and the signaling mechanisms involved that bridge inflammation and cancer.

Growth characteristics of Chlamydia trachomatis in human intestinal epithelial Caco-2 cells

Chlamydia trachomatis is an obligate intracellular bacterium causing infections of the eyes, urogenital and respiratory tracts. Asymptomatic, repeat and chronic infections with C. trachomatis are common in the urogenital tract potentially causing severe reproductive pathology. Animal models of infection and epidemiological studies suggested the gastrointestinal tract as a reservoir of chlamydiae and as a source of repeat urogenital infections. Thus, we investigated the growth characteristics of C. trachomatis in human intestinal epithelial Caco-2 cells and the infection-induced defensin production. Immunofluorescence staining and transmission electron microscopy showed the presence of chlamydial inclusions in the cells. Chlamydial DNA and viable C. trachomatis were recovered from Caco-2 cells in similar quantity compared to that detected in the usual in vitro host cell of this bacterium. The kinetics of expression of selected C. trachomatis genes in Caco-2 cells indicated prolonged replication with persisting high expression level of late genes and of heat shock protein gene groEL. Replication of C. trachomatis induced moderate level of β-defensin-2 production by Caco-2 cells, which might contribute to avoidance of immune recognition in the intestine. According to our results, Caco-2 cells support C. trachomatis replication, suggesting that the gastrointestinal tract is a site of residence for these bacteria.

The DH31/CGRP enteroendocrine peptide triggers intestinal contractions favoring the elimination of opportunistic bacteria

The digestive tract is the first organ affected by the ingestion of foodborne bacteria. While commensal bacteria become resident, opportunistic or virulent bacteria are eliminated from the gut by the local innate immune system. Here we characterize a new mechanism of defense, independent of the immune system, in Drosophila melanogaster. We observed strong contractions of longitudinal visceral muscle fibers for the first 2 hours following bacterial ingestion. We showed that these visceral muscle contractions are induced by immune reactive oxygen species (ROS) that accumulate in the lumen and depend on the ROS-sensing TRPA1 receptor. We then demonstrate that both ROS and TRPA1 are required in a subset of anterior enteroendocrine cells for the release of the DH31 neuropeptide which activates its receptor in the neighboring visceral muscles. The resulting contractions of the visceral muscles favors quick expulsion of the bacteria, limiting their presence in the gut. Our results unveil a precocious mechanism of defense against ingested opportunistic bacteria, whether they are Gram-positive like Bacillus thuringiensis or Gram-negative like Erwinia carotovora carotovora. Finally, we found that the human homolog of DH31, CGRP, has a conserved function in Drosophila.

The intestine is the first barrier to fight non-commensal bacteria ingested along with the food. The innate immune system is the main mean mounted by the gut lining in response to ill-causing bacteria to avoid detrimental impact. Intestinal cells produce chlorine bleach and antimicrobial peptides that destroy exogenous bacteria. Here, we identified and characterized a new mechanism of gut defense that occurs rapidly after ingestion of exogenous bacteria. We found that the enteroendocrine cells perceive the presence of chlorine bleach in the lumen thanks to a sensor. This sensor promotes a calcium flux within enteroendocrine cells that allows the release of a hormone. This hormone acts locally on the visceral muscle surrounding the intestine by provoking its strong contractions (or spasms). We show that these strong but brief visceral contractions are helping to the quick expulsion of the ingested bacteria thus limiting their potential detrimental impact on the intestine. Markedly, the bleach-sensor is well known to be involved in pain. Therefore we have deciphered in this study a biological mechanism that has so far been described only empirically by medicine, potentially explaining intestinal pain and visceral spasms upon food poisoning.

Walnut phenolic extract inhibits nuclear factor kappaB signaling in intestinal epithelial cells, and ameliorates experimental colitis and colitis-associated colon cancer in mice

PURPOSE

Walnuts (Juglans regia) are known to have anti-cancer and immunomodulatory effects. However, little information is available on the effects of walnut phenolic extract (WPE) on intestinal inflammation and colitis-associated colon cancer.

METHODS

COLO205 cells were pretreated with WPE and then stimulated with tumor necrosis factor (TNF)-α. In the acute colitis model, wild type mice (C57BL/6) were administered 4% dextran sulfate sodium (DSS) for 5 days. In the chronic colitis model, interleukin (IL)-10^-/- mice were administered with either the vehicle or WPE (20 mg/kg) by oral gavage daily for 2 weeks. In an inflammation-associated tumor model, wild type mice were administered a single intraperitoneal injection of azoxymethane followed by three cycles of 2% DSS for 5 days and 2 weeks of free water consumption.

RESULTS

WPE significantly inhibited IL-8 and IL-1α expression in COLO205 cells. WPE attenuated both the TNF-α-induced IκB phosphorylation/degradation and NF-κB DNA binding activity. The administration of oral WPE significantly reduced the severity of colitis in both acute and chronic colitis models, including the IL-10^-/- mice. In immunohistochemical staining, WPE attenuated NF-κB signaling in the colons of both colitis models. Finally, WPE also significantly reduced tumor development in a murine model of colitis-associated colon cancer (CAC).

CONCLUSIONS

WPE ameliorates acute and chronic colitis and CAC in mice, suggesting that WPE may have potentials for the treatment of inflammatory bowel disease.

P17, an Original Host Defense Peptide from Ant Venom, Promotes Antifungal Activities of Macrophages through the Induction of C-Type Lectin Receptors Dependent on LTB4-Mediated PPARγ Activation

Despite the growing knowledge with regard to the immunomodulatory properties of host defense peptides, their impact on macrophage differentiation and on its associated microbicidal functions is still poorly understood. Here, we demonstrated that the P17, a new cationic antimicrobial peptide from ant venom, induces an alternative phenotype of human monocyte-derived macrophages (h-MDMs). This phenotype is characterized by a C-type lectin receptors (CLRs) signature composed of mannose receptor (MR) and Dectin-1 expression. Concomitantly, this activation is associated to an inflammatory profile characterized by reactive oxygen species (ROS), interleukin (IL)-1β, and TNF-α release. P17-activated h-MDMs exhibit an improved capacity to recognize and to engulf Candida albicans through the overexpression both of MR and Dectin-1. This upregulation requires arachidonic acid (AA) mobilization and the activation of peroxisome proliferator-activated receptor gamma (PPARγ) nuclear receptor through the leukotriene B4 (LTB4) production. AA/LTB4/PPARγ/Dectin-1-MR signaling pathway is crucial for P17-mediated anti-fungal activity of h-MDMs, as indicated by the fact that the activation of this axis by P17 triggered ROS production and inflammasome-dependent IL-1β release. Moreover, we showed that the increased anti-fungal immune response of h-MDMs by P17 was dependent on intracellular calcium mobilization triggered by the interaction of P17 with pertussis toxin-sensitive G-protein-coupled receptors on h-MDMs. Finally, we also demonstrated that P17-treated mice infected with C. albicans develop less severe gastrointestinal infection related to a higher efficiency of their macrophages to engulf Candida, to produce ROS and IL-1β and to kill the yeasts. Altogether, these results identify P17 as an original activator of the fungicidal response of macrophages that acts upstream PPARγ/CLRs axis and offer new immunomodulatory therapeutic perspectives in the field of infectious diseases.

Cxcr2 signaling and the microbiome suppress inflammation, bile duct injury, and the phenotype of experimental biliary atresia

Biliary atresia is progressive fibro-inflammatory cholangiopathy of young children. Central to pathogenic mechanisms of injury is the tissue targeting by the innate and adaptive immune cells. Among these cells, neutrophils and the IL-8/Cxcl-8 signaling via its Cxcr2 receptor have been linked to bile duct injury. Here, we aimed to investigate whether the intestinal microbiome modulates Cxcr2-dependent bile duct injury and obstruction. Adult wild-type (WT) and Cxcr2^-/- mice were fed a diet supplemented with sulfamethoxazole/trimethoprim (SMZ/TMP) during pregnancy and lactation, and their pups were injected intraperitoneally with rhesus rotavirus (RRV) within 24 hours of life to induce experimental biliary atresia. The maternal exposure to SMZ/TMP significantly lowered the incidence of jaundice and bile duct obstruction and resulted in improved survival, especially in Cxcr2^-/- mice. Analyses of the microbiome by deep sequencing of 16S rRNA of the neonatal colon showed a delay in bacterial colonization of WT mice induced by SMZ/TMP, with a notable switch from Proteobacteria to Firmicutes. Interestingly, the genetic inactivation of Cxcr2 alone produced a similar bacterial shift. When treated with SMZ/TMP, Cxcr2^-/- mice infected with RRV to induce experimental biliary atresia showed further enrichment of Corynebacterium, Anaerococcus and Streptococcus. Among these, Anaerococcus lactolyticus was significantly associated with a suppression of biliary injury, cholestasis, and survivability. These results suggest that the postnatal development of the intestinal microbiota is an important susceptibility factor for experimental biliary atresia.

Metronidazole-induced encephalopathy in a patient with Crohn's disease

Metronidazole is a widely used antibiotic for the treatment of anaerobic bacterial infections. Metronidazole-induced encephalopathy (MIEP) is a rare but potentially reversible disease. The mechanism of MIEP remains unclear, and differences in the neurotoxic effects of oral versus intravenous (IV) metronidazole administration have not yet been determined. We report the case of a Crohn's disease (CD) patient who experienced encephalopathy immediately after a single IV dose of metronidazole following long-term exposure to the oral form of the drug. The 64-year-old man with intractable CD experienced a sudden change in mental status, aphasia, and muscle weakness after IV administration of metronidazole. He had previously taken metronidazole orally for 13 years and received intermittent IV metronidazole treatments for CD exacerbation. Brain magnetic resonance imaging (MRI) showed high-intensity signals in the bilateral medial thalamus and the midbrain and pontine tegmentum on fluid-attenuated inversion recovery images. After discontinuation of metronidazole, the high-intensity brain MRI signals resolved and the patient's mental status dramatically improved; however, the patient exhibited mild cognitive dysfunction 2 months after the onset of encephalopathy.

The Roles of Cathelicidin LL-37 in Inflammatory Bowel Disease

Human cathelicidin LL-37, the only member of the cathelicidin family of host defense peptides expressed in humans, plays a crucial role in host defense against pathogen invasion, as well as in regulating the functions of anti-inflammation, antitumorigenesis, and tissue repair. It is primarily produced by phagocytic leukocytes and epithelial cells, and mediates a wide range of biological responses. Emerging evidence from several studies indicates that LL-37 plays a prominent and complex role in inflammatory bowel disease (IBD). Although overexpression of LL-37 has been implicated in the inflamed and noninflamed colon mucosa in patients with ulcerative colitis, LL-37 expression was not changed in the inflamed or noninflamed colon or ileal mucosa in patients with Crohn's disease. Furthermore, studies in animal models and human patients further characterized the protective effect of cathelicidins both in ulcerative colitis and Crohn's disease. These data suggest the intricate functions of LL-37 in IBD. They will also create many strategies and opportunities for therapeutic intervention in IBD in the future. This review aims to elucidate the structure and bioactivity of LL-37 and also discuss the recent progress in understanding the relationship between LL-37 and IBD.

Antimicrobial peptides and wound healing: biological and therapeutic considerations

Repair of tissue wounds is a fundamental process to re-establish tissue integrity and regular function. Importantly, infection is a major factor that hinders wound healing. Multicellular organisms have evolved an arsenal of host-defense molecules, including antimicrobial peptides (AMPs), aimed at controlling microbial proliferation and at modulating the host's immune response to a variety of biological or physical insults. In this brief review, we provide the evidence for a role of AMPs as endogenous mediators of wound healing and their promising therapeutic potential for the treatment of non-life-threatening skin and other epithelial injuries.

Intestinal stem cells and intestinal homeostasis in health and in inflammation: A review

BACKGROUND

The human intestine is a complex group of organs, highly specialized in processing food and providing nutrients to the body. It is under constant threat from microbials and toxins and has therefore developed a number of protective mechanisms. One important mechanism is the constant shedding of epithelial cells into the lumen; another is the production and maintenance of a double-layered mucous boundary in which there is continuous sampling of the luminal microbiota and a persistent presence of antimicrobial enzymes. However, the gut needs commensal bacteria to effectively break down food into absorbable nutrients, which necessitates constant communication between the luminal bacteria and the intestinal immune cells in homeostasis. Disruption of homeostasis, for whatever reason, will give rise to (chronic) inflammation.

DISCUSSION

Both medical and surgical management of this disruption is discussed.

Epigenetic alterations in inflammatory bowel disease and cancer

Overwhelming evidences supports the idea that inflammatory bowel disease (IBD) is caused by a complex interplay between genetic alterations of multiple genes and an aberrant interaction with environmental factors. There is growing evidence that epigenetic factors can play a significant part in the pathogenesis of IBD. Significant effort has been invested in uncovering genetic and epigenetic factors, which may increase the risk of IBD, but progress has been slow, and few IBD-specific factors have been detected so far. It has been known for decades that DNA methylation is the most well studied epigenetic modification, and analysis of DNA methylation is leading to a new generation of cancer biomarkers. Therefore, in this review, we summarize the role of DNA methylation alteration in IBD pathogenesis, and discuss specific genes or genetic loci using recent molecular technology advances. Here, we suggest that DNA methylation should be studied in depth to understand the molecular pathways of IBD pathogenesis, and discuss epigenetic studies of IBD that may have a significant impact on the field of IBD research.