Paneth cells: their role in innate immunity and inflammatory disease

High-confidence calling of normal epithelial cells allows identification of a novel stem-like cell state in the colorectal cancer microenvironment

Single-cell analyses can be confounded by assigning unrelated groups of cells to common developmental trajectories. For instance, cancer cells and admixed normal epithelial cells could adopt similar cell states thus complicating analyses of their developmental potential. Here, we develop and benchmark CCISM (for Cancer Cell Identification using Somatic Mutations) to exploit genomic single nucleotide variants for the disambiguation of cancer cells from genomically normal non-cancer cells in single-cell data. We find that our method and others based on gene expression or allelic imbalances identify overlapping sets of colorectal cancer versus normal colon epithelial cells, depending on molecular characteristics of individual cancers. Further, we define consensus cell identities of normal and cancer epithelial cells with higher transcriptome cluster homogeneity than those derived using existing tools. Using the consensus identities, we identify significant shifts of cell state distributions in genomically normal epithelial cells developing in the cancer microenvironment, with immature states increased at the expense of terminal differentiation throughout the colon, and a novel stem-like cell state arising in the left colon. Trajectory analyses show that the new cell state extends the pseudo-time range of normal colon stem-like cells in a cancer context. We identify cancer-associated fibroblasts as sources of WNT and BMP ligands potentially contributing to increased plasticity of stem cells in the cancer microenvironment. Our analyses advocate careful interpretation of cell heterogeneity and plasticity in the cancer context and the consideration of genomic information in addition to gene expression data when possible.

Verzi M. KAT2A and KAT2B prevent double-stranded RNA accumulation and interferon signaling to maintain intestinal stem cell renewal

Histone acetyltransferases KAT2A and KAT2B are paralogs highly expressed in the intestinal epithelium, but their functions are not well understood. In this study, double knockout of murine Kat2 genes in the intestinal epithelium was lethal, resulting in robust activation of interferon signaling and interferon-associated phenotypes including the loss of intestinal stem cells. Use of pharmacological agents and sterile organoid cultures indicated a cell-intrinsic double-stranded RNA trigger for interferon signaling. Acetyl-proteomics and sequencing of immunoprecipitated double-stranded RNA were used to interrogate the mechanism behind this response, which identified mitochondria-encoded double-stranded RNA as the source of intrinsic interferon signaling. Kat2a and Kat2b therefore play an essential role in regulating mitochondrial functions and maintaining intestinal health.

Effect of acetylcholinesterase inhibition on immune cells in the murine intestinal mucosa

The gastrointestinal tract (GI) is the largest immune organ whose function is controlled by a complex network of neurons from the enteric nervous system (ENS) as well as the sympathetic and parasympathetic system. Evolving evidence indicates that cross-communication between gut-innervating neurons and immune cells regulates many essential physiological functions including protection against mucosal infections. We previously demonstrated that following paraoxon treatment, 70 % of the mice were able to survive an oral infection with S. typhimurium, a virulent strain of Salmonella enterica serovar Typhimurium. The present study aims to investigate the effect that rivastigmine, a reversible AChE inhibitor used for the treatment of neurodegenerative diseases, has on the murine immune defenses of the intestinal mucosa. Our findings show that, similar to what is observed with paraoxon, administration of rivastigmine promoted the release of secretory granules from goblet and Paneth cells, resulting in increased mucin layer. Surprisingly, however, and unlike paraoxon, rivastigmine treatment did not affect overall mortality of infected mice. In order to investigate the mechanistic basis for the differential effects observed between paraoxon and rivastigmine, we used multi-color flowcytometric analysis to characterize the immune cell landscape in the intraepithelial (IE) and lamina propria (LP) compartments of intestinal mucosa. Our data indicate that treatment with paraoxon, but not rivastigmine, led to an increase of resident CD3+CD8+ T lymphocytes in the ileal mucosa (epithelium and lamina propria) and CD11b- CD11c+ dendritic cells in the LP. Our findings indicate the requirement for persistent cholinergic pathway engagement to effect a change in the cellular landscape of the mucosal tissue that is necessary for protection against lethal bacterial infections. Moreover, optimal protection requires a collaboration between innate and adaptive mucosal immune responses in the intestine.

How the Western Diet Thwarts the Epigenetic Efforts of Gut Microbes in Ulcerative Colitis and Its Association with Colorectal Cancer

Ulcerative colitis (UC) is an autoimmune disease in which the immune system attacks the colon, leading to ulcer development, loss of colon function, and bloody diarrhea. The human gut ecosystem consists of almost 2000 different species of bacteria, forming a bioreactor fueled by dietary micronutrients to produce bioreactive compounds, which are absorbed by our body and signal to distant organs. Studies have shown that the Western diet, with fewer short-chain fatty acids (SCFAs), can alter the gut microbiome composition and cause the host's epigenetic reprogramming. Additionally, overproduction of H2S from the gut microbiome due to changes in diet patterns can further activate pro-inflammatory signaling pathways in UC. This review discusses how the Western diet affects the microbiome's function and alters the host's physiological homeostasis and susceptibility to UC. This article also covers the epidemiology, prognosis, pathophysiology, and current treatment strategies for UC, and how they are linked to colorectal cancer.

Spatial Proteomics Reveals Alcohol-Induced Damages to the Crypts and Villi of the Mouse Small Intestine

Alcohol consumption perturbs the gut immune barrier and ultimately results in alcoholic liver diseases, but little is known about how immune-related cells in the gut are perturbed in this process. In this study, we employed laser capture microdissection and a label-free proteomics approach to investigate the consequences of alcohol exposure to the proteomes of crypts and villi in the proximal small intestine. Intestinal tissues from alcohol-fed and pair-fed mice were microdissected to selectively capture cells in the crypts and villi regions, followed by one-pot protein digestion and data-independent LC-MS/MS analysis. We successfully identified over 3000 proteins from each of the crypt or villi regions equivalent to ∼3000 cells. Analysis of alcohol-treated tissues indicated an enhanced alcohol metabolism and reduced levels of α-defensins in crypts, alongside increased lipid metabolism and apoptosis in villi. Immunofluorescence imaging further corroborated the proteomic findings. Our work provides a detailed profiling of the proteomic changes in the compartments of the mouse small intestine and aids in molecular-level understanding of alcohol-induced tissue damage.

In Vitro Models for Investigating Intestinal Host-Pathogen Interactions

Infectious diseases are increasingly recognized as a major threat worldwide due to the rise of antimicrobial resistance and the emergence of novel pathogens. In vitro models that can adequately mimic in vivo gastrointestinal physiology are in high demand to elucidate mechanisms behind pathogen infectivity, and to aid the design of effective preventive and therapeutic interventions. There exists a trade-off between simple and high throughput models and those that are more complex and physiologically relevant. The complexity of the model used shall be guided by the biological question to be addressed. This review provides an overview of the structure and function of the intestine and the models that are developed to emulate this. Conventional models are discussed in addition to emerging models which employ engineering principles to equip them with necessary advanced monitoring capabilities for intestinal host-pathogen interrogation. Limitations of current models and future perspectives on the field are presented.

Dietary fiber pectin: challenges and potential anti-inflammatory benefits for preterms and newborns

Pectins, a class of dietary fibers abundant in vegetables and fruits, have drawn considerable interest due to their potential anti-inflammatory properties. Numerous studies have indicated that incorporating pectins into infant formula could be a safe strategy for alleviating infant regurgitation and diarrhea. Moreover, pectins have been shown to modulate cytokine production, macrophage activity, and NF-kB expression, all contributing to their anti-inflammatory effects. Despite this promising evidence, the exact mechanisms through which pectins exert these functions and how their structural characteristics influence these processes remain largely unexplored. This knowledge is particularly significant in the context of gut inflammation in developing preterm babies, a critical aspect of necrotizing enterocolitis (NEC), and in children and adults dealing with inflammatory bowel disease (IBD). Our mini review aims to provide an up-to-date compilation of relevant research on the effects of pectin on gut immune responses, specifically focusing on preterms and newborns. By shedding light on the underlying mechanisms and implications of pectin-mediated anti-inflammatory properties, this review seeks to advance our knowledge in this area and pave the way for future research and potential therapeutic interventions.

KAT2 paralogs prevent dsRNA accumulation and interferon signaling to maintain intestinal stem cells

Histone acetyltransferases KAT2A and KAT2B are paralogs highly expressed in the intestinal epithelium, but their functions are not well understood. In this study, double knockout of murine Kat2 genes in the intestinal epithelium was lethal, resulting in robust activation of interferon signaling and interferon-associated phenotypes including the loss of intestinal stem cells. Use of pharmacological agents and sterile organoid cultures indicated a cell-intrinsic double-stranded RNA trigger for interferon signaling. Acetyl-proteomics and dsRIP-seq were employed to interrogate the mechanism behind this response, which identified mitochondria-encoded double-stranded RNA as the source of intrinsic interferon signaling. Kat2a and Kat2b therefore play an essential role in regulating mitochondrial functions as well as maintaining intestinal health.

Paneth cell dysfunction in radiation injury and radio-mitigation by human α-defensin 5

Introduction

The mechanism underlying radiation-induced gut microbiota dysbiosis is undefined. This study examined the effect of radiation on the intestinal Paneth cell α-defensin expression and its impact on microbiota composition and mucosal tissue injury and evaluated the radio-mitigative effect of human α-defensin 5 (HD5).

Methods

Adult mice were subjected to total body irradiation, and Paneth cell α-defensin expression was evaluated by measuring α-defensin mRNA by RT-PCR and α-defensin peptide levels by mass spectrometry. Vascular-to-luminal flux of FITC-inulin was measured to evaluate intestinal mucosal permeability and endotoxemia by measuring plasma lipopolysaccharide. HD5 was administered in a liquid diet 24 hours before or after irradiation. Gut microbiota was analyzed by 16S rRNA sequencing. Intestinal epithelial junctions were analyzed by immunofluorescence confocal microscopy and mucosal inflammatory response by cytokine expression. Systemic inflammation was evaluated by measuring plasma cytokine levels.

Results

Ionizing radiation reduced the Paneth cell α-defensin expression and depleted α-defensin peptides in the intestinal lumen. α-Defensin down-regulation was associated with the time-dependent alteration of gut microbiota composition, increased gut permeability, and endotoxemia. Administration of human α-defensin 5 (HD5) in the diet 24 hours before irradiation (prophylactic) significantly blocked radiation-induced gut microbiota dysbiosis, disruption of intestinal epithelial tight junction and adherens junction, mucosal barrier dysfunction, and mucosal inflammatory response. HD5, administered 24 hours after irradiation (treatment), reversed radiation-induced microbiota dysbiosis, tight junction and adherens junction disruption, and barrier dysfunction. Furthermore, HD5 treatment also prevents and reverses radiation-induced endotoxemia and systemic inflammation.

Conclusion

These data demonstrate that radiation induces Paneth cell dysfunction in the intestine, and HD5 feeding prevents and mitigates radiation-induced intestinal mucosal injury, endotoxemia, and systemic inflammation.

An updated review on oral protein-based antigen vaccines efficiency and delivery approaches: a special attention to infectious diseases

Various infectious agents affect human health via the oral entrance. The majority of pathogens lack approved vaccines. Oral vaccination is a convenient, safe and cost-effective approach with the potential of provoking mucosal and systemic immunity and maintaining individual satisfaction. However, vaccines should overcome the intricate environment of the gastrointestinal tract (GIT). Oral protein-based antigen vaccines (OPAVs) are easier to administer than injectable vaccines and do not require trained healthcare professionals. Additionally, the risk of needle-related injuries, pain, and discomfort is eliminated. However, OPAVs stability at environmental and GIT conditions should be considered to enhance their stability and facilitate their transport and storage. These vaccines elicit the local immunity, protecting GIT, genital tract and respiratory epithelial surfaces, where numerous pathogens penetrate the body. OPAVs can also be manipulated (such as using specific incorporated ligand and receptors) to elicit targeted immune response. However, low bioavailability of OPAVs necessitates development of proper protein carriers and formulations to enhance their stability and efficacy. There are several strategies to improve their efficacy or protective effects, such as incorporation of adjuvants, enzyme inhibitors, mucoadhesive or penetrating devices and permeation enhancers. Hence, efficient delivery of OPAVs into GIT require proper delivery systems mainly including smart target systems, probiotics, muco-adhesive carriers, lipid- and plant-based delivery systems and nano- and microparticles.

Evaluation of gene expression related to immunity, apoptosis, and gut integrity that underlies Artemisia's therapeutic effects in necrotic enteritis-challenged broilers

The experiment was designed to validate the effect of Artemisia annua and its novel commercial product (Navy Cox) on the control of necrotic enteritis (NE). A total of one hundred forty broiler chicks were randomly distributed into seven equal groups: G1, control negative; G2, infected with Eimeria (day 15) and C. perfringens (day 19); G3, treated with Navy Cox before challenge; G4, treated with Artemisia before challenge; G5, infected and then treated with Navy Cox; G6, infected and then treated with Artemisia; and G7, infected and treated with amoxicillin. Chicken response and immune organ indicants were recorded during the observation period (4 weeks). Whole blood and serum samples were collected for immunological evaluation, and tissue samples were collected for bacterial counts and estimation of mRNA expression of genes encoding apoptosis, tight junctions, and immunity. Chickens in the infected group revealed a significant decrease in RBCS, HB, PCV% total protein, Lysozyme, and nitric oxide activity in addition to leukocytosis, heterophilia, monocytosis, increase in cortisol, interleukins, and malondialdehyde. Treated groups displayed lower lesions, colony-forming units, and no mortality. Concurrently, a complete blood profile, antioxidants, and immune markers showed significant improvements. The mRNA expression levels of CASP, CLDN-1, OCLN, TJPI, MUC2, and cell-mediated immune response genes (p < 0.0001) were significantly alleviated in the treated groups compared with the challenged counterpart. This is the first-ever report on the efficacy valuation of Navy Cox compared to standard antibiotic treatment of clostridial NE. Navy Cox proved remarkable capability to minimize C. perfringens colonization in broiler intestines, modulation of mucus production, gut health integrity, immune organs, and immune response when used as a prophylactic agent in this form or naturally as Artemisia.

Role of Bacteria in the Development of Colorectal Cancer

Colorectal cancer (CRC) is the second leading cause of cancer-related death in the United States. Once limited to older populations, the incidence of CRC in patients under the age of 50 years is increasing and the etiology for this is uncertain. One hypothesis lies on the impact of the intestinal microbiome. The intestinal microbiome, composed primarily of bacteria but also viruses, fungi, and archaea, has been shown to regulate CRC development and progression both in vitro and in vivo. In this review, the role and intersection of the bacterial microbiome in various stages of clinical CRC development and management are discussed beginning with CRC screening. Various mechanisms whereby the microbiome has been shown to modulate CRC development including the influence of diet on the microbiome, bacterial-induced injury to the colonic epithelium, bacterial-produced toxins, and alteration of normal cancer immunosurveillance by the microbiome are discussed. Finally, the influence of microbiome on the response of CRC to treatment is discussed while highlighting ongoing clinical trials. The complexities of the microbiome and its role in CRC development and progression have become apparent and will require ongoing commitment to translate laboratory findings into meaningful clinical results that will aid more than 150,000 patients that develop CRC every year.

Mucoadhesive drug delivery systems: a promising non-invasive approach to bioavailability enhancement. Part I: biophysical considerations

INTRODUCTION

Mucoadhesive drug delivery systems (MDDS) are specifically designed to interact and bind to the mucosal layer for localized, prolonged, and/or targeted drug delivery. Over the past 4 decades, different sites have been explored for mucoadhesion including the nasal, oral, and vaginal cavities, the gastrointestinal tract and ocular tissues.

AREAS COVERED

The present review aims to provide a comprehensive understanding of different aspects of MDDS development. Part I focuses on the anatomical and biological aspects of mucoadhesion, which include a detailed elucidation of the structure and anatomy of the mucosa, the properties of mucin, the different theories of mucoadhesion and evaluation techniques.

EXPERT OPINION

The mucosal layer presents a unique opportunity for effective localization as well as systemic drug delivery via MDDS. Formulation of MDDS requires a thorough understanding of the anatomy of mucus tissue, the rate of mucus secretion and turnover, and the physicochemical properties of mucus. Further, the moisture content and the hydration of polymers are crucial for interaction with mucus. A confluence of different theories used to explain the mechanism of mucoadhesion is useful for understanding the mucoadhesion of different MDDS and their evaluation is subject to factors, such as the site of administration, type of dosage form, and duration of action. [Figure: see text].

Intestinal protein uptake and IgE-mediated food allergy

Food allergy is affecting 5-8% of young children and 2-4% of adults and seems to be increasing in prevalence. The cause of the increase in food allergy is largely unknown but proposed to be influenced by both environmental and lifestyle factors. Changes in intestinal barrier functions and increased uptake of dietary proteins have been suggested to have a great impact on food allergy. In this review, we aim to give an overview of the gastrointestinal digestion and intestinal barrier function and provide a more detailed description of intestinal protein uptake, including the various routes of epithelial transport, how it may be affected by both intrinsic and extrinsic factors, and the relation to food allergy. Further, we give an overview of in vitro, ex vivo and in vivo techniques available for evaluation of intestinal protein uptake and gut permeability in general. Proteins are digested by gastric, pancreatic and integral brush border enzymes in order to allow for sufficient nutritional uptake. Absorption and transport of dietary proteins across the epithelial layer is known to be dependent on the physicochemical properties of the proteins and their digestion fragments themselves, such as size, solubility and aggregation status. It is believed, that the greater an amount of intact protein or larger peptide fragments that is transported through the epithelial layer, and thus encountered by the mucosal immune system in the gut, the greater is the risk of inducing an adverse allergic response. Proteins may be absorbed across the epithelial barrier by means of various mechanisms, and studies have shown that a transcellular facilitated transport route unique for food allergic individuals are at play for transport of allergens, and that upon mediator release from mast cells an enhanced allergen transport via the paracellular route occurs. This is in contrast to healthy individuals where transcytosis through the enterocytes is the main route of protein uptake. Thus, knowledge on factors affecting intestinal barrier functions and methods for the determination of their impact on protein uptake may be useful in future allergenicity assessments and for development of future preventive and treatment strategies.

Mucosal vaccination: onward and upward

INTRODUCTION

The unique mucosal immune system allows the generation of robust protective immune responses at the front line of pathogen encounters. The needle-free delivery route and cold chain-free logistic requirements also provide additional advantages in ease and economy. However, the development of mucosal vaccines faces several challenges, and only a handful of mucosal vaccines are currently licensed. These vaccines are all in the form of live attenuated or inactivated whole organisms, whereas no subunit-based mucosal vaccine is available.

AREAS COVERED

The selection of antigen, delivery vehicle, route and adjuvants for mucosal vaccination are highly important. This is particularly crucial for subunit vaccines, as they often fail to elicit strong immune responses. Emerging research is providing new insights into the biological and immunological uniqueness of mucosal tissues. However, many aspects of the mucosal immunology still await to be investigated.

EXPERT OPINION

This article provides an overview of the current understanding of mucosal vaccination and discusses the remaining knowledge gaps. We emphasize that because of the potential benefits mucosal vaccines can bring from the biomedical, social and economic standpoints, the unmet goal to achieve mucosal vaccine success is worth the effort.

Differentiated Epithelial Cells of the Gut

The intestine is a prime example of self-renewal where stem cells give rise to progenitor cells called transit-amplifying cells which differentiate into more specialized cells. There are two intestinal lineages: the absorptive (enterocytes and microfold cells) and the secretory (Paneth cells, enteroendocrine, goblet cells, and tuft cells). Each of these differentiated cell types has a role in creating an "ecosystem" to maintain intestinal homeostasis. Here, we summarize the main roles of each cell type.

The immune response as a therapeutic target in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is a complex and heterogeneous disorder considered a liver-damaging manifestation of metabolic syndrome. Its prevalence has increased in the last decades due to modern-day lifestyle factors associated with overweight and obesity, making it a relevant public health problem worldwide. The clinical progression of NAFLD is associated with advanced forms of liver injury such as fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). As such, diverse pharmacological strategies have been implemented over the last few years, principally focused on metabolic pathways involved in NAFLD progression. However, a variable response rate has been observed in NAFLD patients, which is explained by the interindividual heterogeneity of susceptibility to liver damage. In this scenario, it is necessary to search for different therapeutic approaches. It is worth noting that chronic low-grade inflammation constitutes a central mechanism in the pathogenesis and progression of NAFLD, associated with abnormal composition of the intestinal microbiota, increased lymphocyte activation in the intestine and immune effector mechanisms in liver. This review aims to discuss the current knowledge about the role of the immune response in NAFLD development. We have focused mainly on the impact of altered gut-liver-microbiota axis communication on immune cell activation in the intestinal mucosa and the role of subsequent lymphocyte homing to the liver in NAFLD development. We further discuss novel clinical trials that addressed the control of the liver and intestinal immune response to complement current NAFLD therapies.

Risk Factors for Incident Inflammatory Bowel Disease According to Disease Phenotype

BACKGROUND & AIMS

We examined whether relationships between known risk factors for Crohn's disease (CD) and ulcerative colitis (UC) differ according to disease phenotype, defined by Montreal classification, at the time of diagnosis.

METHODS

We performed a prospective cohort study of 208,070 adults from the Nurses' Health Study (NHS), NHSII, and Health Professionals Follow-Up Study (HPFS). Dietary, lifestyle, and medical data were obtained at baseline and every 2-4 years. We confirmed cases of inflammatory bowel disease (IBD) and their phenotypes via medical record review. We tested for heterogeneity across CD subtypes using the likelihood ratio test and for linear heterogeneity across UC subtypes using the meta-regression method.

RESULTS

We ascertained 346 cases of CD and 456 cases of UC over 5,117,021 person-years of follow-up (1986-2016 for NHS and HPFS; 1991-2017 for NHSII). Fiber intake was associated with decreased risk for ileocolonic but not ileal or colonic CD (Pheterogeneity = .04). Physical activity was associated with decreased risk of nonstricturing and nonpenetrating CD but not of penetrating CD (Pheterogeneity = .02). Higher body mass index and current smoking were associated with decreased risk of proctitis and left-sided UC but not of pan-UC (Plinear heterogeneity= .004 and .02, respectively). The associations between other risk factors examined and risk of CD and UC did not differ by disease phenotype (all Pheterogeneity > .06).

CONCLUSIONS

In 3 large prospective cohorts, we observed that dietary and lifestyle risk factors for IBD may differ according to disease phenotype. These findings highlight the need for disease stratification in future epidemiologic studies.

Alterations in Intestinal Brush Border Membrane Functionality and Bacterial Populations Following Intra-Amniotic Administration (Gallus gallus) of Catechin and Its Derivatives

Catechin is a flavonoid naturally present in numerous dietary products and fruits (e.g., apples, berries, grape seeds, kiwis, green tea, red wine, etc.) and has previously been shown to be an antioxidant and beneficial for the gut microbiome. To further enhance the health benefits, bioavailability, and stability of catechin, we synthesized and characterized catechin pentaacetate and catechin pentabutanoate as two new ester derivatives of catechin. Catechin and its derivatives were assessed in vivo via intra-amniotic administration (Gallus gallus), with the following treatment groups: (1) non-injected (control); (2) deionized H2O (control); (3) Tween (0.004 mg/mL dose); (4) inulin (50 mg/mL dose); (5) Catechin (6.2 mg/mL dose); (6) Catechin pentaacetate (10 mg/mL dose); and (7) Catechin pentabutanoate (12.8 mg/mL dose). The effects on physiological markers associated with brush border membrane morphology, intestinal bacterial populations, and duodenal gene expression of key proteins were investigated. Compared to the controls, our results demonstrated a significant (p < 0.05) decrease in Clostridium genera and E. coli species density with catechin and its synthetic derivative exposure. Furthermore, catechin and its derivatives decreased iron and zinc transporter (Ferroportin and ZnT1, respectively) gene expression in the duodenum compared to the controls. In conclusion, catechin and its synthetic derivatives have the potential to improve intestinal morphology and functionality and positively modulate the microbiome.

The Effect of the Gut Microbiota on Systemic and Anti-Tumor Immunity and Response to Systemic Therapy against Cancer

Gut microbiota can have opposing functions from pro-tumorigenic to anti-tumorigenic effects. Increasing preclinical and clinical evidence suggests that the intestinal microbiota affects cancer patients’ response to immune checkpoint inhibitors (ICIs) immunotherapy, such as anti-programmed cell death protein 1 (PD-1) and its ligand (PD-L1) and anti-cytotoxic T lymphocyte-associated protein 4 (CTLA-4). Microbiota-induced inflammation possibly contributes to tumor growth and cancer development. Microbiota-derived metabolites can also be converted to carcinogenic agents related to genetic mutations and DNA damage in organs such as the colon. However, other attributes of microbiota, such as greater diversity and specific bacterial species and their metabolites, are linked to better clinical outcomes and potentially improved anti-tumor immunity. In addition, the intratumoral microbial composition strongly affects T-cell-mediated cytotoxicity and anti-tumor immune surveillance, adding more complexity to the cancer-microbiome-immune axis. Despite the emerging clinical evidence for the activity of the gut microbiota in immuno-oncology, the fundamental mechanisms of such activity are not well understood. This review provides an overview of underlying mechanisms by which the gut microbiota and its metabolites enhance or suppress anti-tumor immune responses. Understanding such mechanisms allows for better design of microbiome-specific treatment strategies to improve the clinical outcome in cancer patients undergoing systemic therapy.

Meta-Analysis of IBD Gut Samples Gene Expression Identifies Specific Markers of Ileal and Colonic Diseases

BACKGROUND

Inflammatory bowel diseases (IBDs) are characterized by chronic inflammation and tissue damages in limited segments of the digestive tract. Pathogenesis in the tissue and mucosal inflammation probably differs according to disease location. Our aim was to further analyze transcriptomic profiles in different locations of IBD, differentiating ulcerative colitis (UC), colonic Crohn's disease (CD), ileal CD, and pouchitis, with respect to normal colonic and ileal mucosa. We thus performed a meta-analysis focusing on specific transcriptomic signatures of ileal and colonic diseases.

METHODS

We identified 5 cohorts with available transcriptomic data in ileal or colonic samples from active IBD and non-IBD control samples. The meta-analysis was performed on 1047 samples. In each cohort separately, we compared gene expression in CD ileitis and normal ileum; in CD colitis, UC, and normal colon; and finally in pouchitis and normal ileum.

RESULTS

We identified specific markers of ileal (FOLH1, CA2) and colonic (REG3A) inflammation and showed that, with disease, some cells from the ileum start to express colonic markers. We confirmed by immunohistochemistry that these markers were specifically present in ileal or colonic diseases. We highlighted that, overall, colonic CD resembles UC and is distinct from ileal CD, which is in turn closer to pouchitis.

CONCLUSIONS

We demonstrated that ileal and colonic diseases exhibit specific signatures, independent of their initial clinical classification. This supports molecular, rather than clinical, disease stratification, and may be used to design drugs specifically targeting ileal or colonic diseases.

Integrity of the Intestinal Barrier: The Involvement of Epithelial Cells and Microbiota-A Mutual Relationship

Simple Summary

The gastrointestinal tract is a complex organization of various types of epithelial cells forming a single layer of the mucosal barrier, the host mucosal immune system, and microorganisms termed as gut microbiota inhabiting this area. The mucosal barrier, including physical and chemical factors, spatially segregates gut microbiota and the host immune system preventing the development of immune response directed towards non-pathogenic commensals and dietary antigens. However, for the maintenance of the integrity of the mucosal surfaces, cross-talk between epithelial cells and microbiota is required. The microbiome and the intestinal epithelium developed a complex dependence necessary for sustaining intestinal homeostasis. In this review, we highlight the role of specific epithelial cell subtypes and their role in barrier arrangement, the mechanisms employed by them to control intestinal microbiota as well as the mechanisms utilized by the microbiome to regulate intestinal epithelial function. This review will provide information regarding the development of inflammatory disorders dependent on the loss of intestinal barrier function and composition of the intestinal microbiota.

Abstract

The gastrointestinal tract, which is constantly exposed to a multitude of stimuli, is considered responsible for maintaining the homeostasis of the host. It is inhabited by billions of microorganisms, the gut microbiota, which form a mutualistic relationship with the host. Although the microbiota is generally recognized as beneficial, at the same time, together with pathogens, they are a permanent threat to the host. Various populations of epithelial cells provide the first line of chemical and physical defense against external factors acting as the interface between luminal microorganisms and immunocompetent cells in lamina propria. In this review, we focus on some essential, innate mechanisms protecting mucosal integrity, thus responsible for maintaining intestine homeostasis. The characteristics of decisive cell populations involved in maintaining the barrier arrangement, based on mucus secretion, formation of intercellular junctions as well as production of antimicrobial peptides, responsible for shaping the gut microbiota, are presented. We emphasize the importance of cross-talk between gut microbiota and epithelial cells as a factor vital for the maintenance of the homeostasis of the GI tract. Finally, we discuss how the imbalance of these regulations leads to the compromised barrier integrity and dysbiosis considered to contribute to inflammatory disorders and metabolic diseases.

Intestinal Barrier in Human Health and Disease

The intestinal mucosa provides a selective permeable barrier for nutrient absorption and protection from external factors. It consists of epithelial cells, immune cells and their secretions. The gut microbiota participates in regulating the integrity and function of the intestinal barrier in a homeostatic balance. Pathogens, xenobiotics and food can disrupt the intestinal barrier, promoting systemic inflammation and tissue damage. Genetic and immune factors predispose individuals to gut barrier dysfunction, and changes in the composition and function of the gut microbiota are central to this process. The progressive identification of these changes has led to the development of the concept of ‘leaky gut syndrome’ and ‘gut dysbiosis’, which underlie the relationship between intestinal barrier impairment, metabolic diseases and autoimmunity. Understanding the mechanisms underlying this process is an intriguing subject of research for the diagnosis and treatment of various intestinal and extraintestinal diseases.

Visualizing transfer of microbial biomolecules by outer membrane vesicles in microbe-host-communication in vivo

The intestinal microbiota influences mammalian host physiology in health and disease locally in the gut but also in organs devoid of direct contact with bacteria such as the liver and brain. Extracellular vesicles (EVs) or outer membrane vesicles (OMVs) released by microbes are increasingly recognized for their potential role as biological shuttle systems for inter-kingdom communication. However, physiologically relevant evidence for the transfer of functional biomolecules from the intestinal microbiota to individual host cells by OMVs in vivo is scarce. By introducing Escherichia coli engineered to express Cre-recombinase (E. coliCre ) into mice with a Rosa26.tdTomato-reporter background, we leveraged the Cre-LoxP system to report the transfer of bacterial OMVs to recipient cells in vivo. Colonizing the intestine of these mice with E. coliCre , resulted in Cre-recombinase induced fluorescent reporter gene-expression in cells along the intestinal epithelium, including intestinal stem cells as well as mucosal immune cells such as macrophages. Furthermore, even far beyond the gut, bacterial-derived Cre induced extended marker gene expression in a wide range of host tissues, including the heart, liver, kidney, spleen, and brain. Together, our findings provide a method and proof of principle that OMVs can serve as a biological shuttle system for the horizontal transfer of functional biomolecules between bacteria and mammalian host cells.

Unraveling enterohemorrhagic Escherichia coli infection: the promising role of dietary compounds and probiotics in bacterial elimination and host innate immunity boosting

The innate immune system has developed sophisticated strategies to defense against infections. Host cells utilize the recognition machineries such as toll-like receptors and nucleotide binding and oligomerization domain-like receptors to identify the pathogens and alert immune system. However, some pathogens have developed tactics to evade host defenses, including manipulation of host inflammatory response, interference with cell death pathway, and highjack of phagocytosis signaling for a better survival and colonization in host. Enterohemorrhagic Escherichia coli (EHEC) is a notorious foodborne pathogen that causes severe tissue damages and gastrointestinal diseases, which has been reported to disturb host immune responses. Diverse bioactive compounds such as flavonoids, phenolic acids, alkaloids, saccharides, and terpenoids derived from food varieties and probiotics have been discovered and investigated for their capability of combating bacterial infections. Some of them serve as novel antimicrobial agents and act as immune boosters that harness host immune system. In this review, we will discuss how EHEC, specifically E. coli O157:H7, hijacks the host immune system and interferes with host signaling pathway; and highlight the promising role of food-derived bioactive compounds and probiotics in harnessing host innate immunity and eliminating E. coli O157:H7 infection with multiple strategies.

Molecular and morphometric changes in the small intestine during hot and cold exposure in thermally manipulated broiler chickens

Background and Aim:

Thermal stress (hot or cold) is one of many environmental stressors that severely affects the health of broiler chickens. One negative effect of thermal stress is the disruption of the intestinal barrier function in broiler chickens. This study aimed to evaluate the effect of thermal manipulation (TM) on the small intestine in terms of histomorphometry as well as junctional, heat-shock, and immune response gene expression during post-hatch exposure to thermal stress.

Materials and Methods:

The experiment was conducted by dividing 928 fertile Ross eggs into three incubation groups: The control (C) group (incubated at 37.8°C and 56% relative humidity [RH] for the whole incubation period), the TM using low temperature TML group (incubated at 36°C and 56% RH for 18 h/day from embryonic days 7 to 16), and the TM using high temperature (TMH) group (incubated at 39°C and 65% RH for 18 h/day from embryonic days 7 to 16). On post-hatch day 21, 90 chicks were randomly selected from each incubation group and were equally subdivided into three subgroups for the post-hatch thermal stress experiment: The TN subgroup (room temperature maintained at 24°C), the heat stress (HS) subgroup (room temperature maintained at 35°C), and the cold stress (CS) subgroup (room temperature maintained at 16°C). After 1 day of thermal stress exposure (age 22 days), five birds from each subgroup were euthanized and ileum samples were collected to evaluate the transcription of the Claudin (CLDN1), CLDN-5, Occludin, Cadherin-1, heat shock factors (HSF1), HSF3, 70 kilodalton heat shock protein, 90 kilodalton heat shock protein, Interleukin6 (IL6), IL8, toll-like receptors-2 (TLR2), and TLR4 genes by Real-Time Quantitative Reverse Transcription polymerase chain reaction analysis. Finally, after 4 and 7 days of thermal stress (age 25 and 28 days, respectively), nine chicks were euthanized, and their jejunum and ileum were collected for histomorphometric analysis.

Results:

After exposure to 1 day of thermal stress, the C subgroups exposed to thermal stress (HS and CS) possessed significantly increased expression of junctional, heat-shock, and immune response genes compared to the C-TN subgroup, and similar results were observed for the TMH. In contrast, thermally stressed TMH subgroups had significantly lower expression of the studied genes compared to C subgroups exposed to thermal stress. Furthermore, no significant changes were detected between the TML subgroups exposed to thermal stress and TML-TN. Moreover, significant alterations in villus height (VH), villus surface area, crypt depth (CD), and VH to CD ratio were observed between the TML, TMH, and C subgroups exposed to CS.

Conclusion:

It might be suggested that TM may have a protective impact on the small intestine histomorphometry and epithelial integrity of broilers during post-hatch exposure to thermal stress.

Histopathological Characterization of Colitis in Captive Western Lowland Gorillas (Gorilla gorilla ssp gorilla)

In captive gorillas, ulcerative colitis is an important cause of morbidity and mortality with no established definitive aetiopathogenesis. The aim of the study was to characterize histopathologically colonic lesions in captive western lowland gorillas (Gorilla gorilla ssp gorilla) and to apply the Nancy index, a disease activity scoring system for ulcerative colitis in humans. Colon samples from 21 animals were evaluated on the basis of histopathological characteristics for the diagnosis of inflammatory bowel disease in humans and divided into acute or chronic changes. The most common acute changes included the presence of neutrophils in the lamina propria (17/18; 94%), mucosal and submucosal oedema (12/18; 67%) and crypt abscesses (8/18; 44%). The most common chronic changes were lamina proprial lymphoplasmacytic infiltrates (17/18; 94%) and crypt dilation or distortion (6/18; 33%). Based on the Nancy index, 4/21 (19%) cases were grade 4 (the highest grade), 2/21 (10%) were grade 3, 11/21 (52%) were grade 2 and 4/21 (19%) cases were grade 0. The colonic changes were comparable to the acute phase of ulcerative colitis in humans. No unifying aetiopathogenesis could be identified. The Nancy index proved to be a valuable tool for the standardization of disease grading and established a basis for future studies of gorilla colitis.

Stem Cell Impairment at the Host-Microbiota Interface in Colorectal Cancer

Colorectal cancer (CRC) initiation is believed to result from the conversion of normal intestinal stem cells (ISCs) into cancer stem cells (CSCs), also known as tumor-initiating cells (TICs). Hence, CRC evolves through the multiple acquisition of well-established genetic and epigenetic alterations with an adenoma-carcinoma sequence progression. Unlike other stem cells elsewhere in the body, ISCs cohabit with the intestinal microbiota, which consists of a diverse community of microorganisms, including bacteria, fungi, and viruses. The gut microbiota communicates closely with ISCs and mounting evidence suggests that there is significant crosstalk between host and microbiota at the ISC niche level. Metagenomic analyses have demonstrated that the host-microbiota mutually beneficial symbiosis existing under physiologic conditions is lost during a state of pathological microbial imbalance due to the alteration of microbiota composition (dysbiosis) and/or the genetic susceptibility of the host. The complex interaction between CRC and microbiota is at the forefront of the current CRC research, and there is growing attention on a possible role of the gut microbiome in the pathogenesis of CRC through ISC niche impairment. Here we primarily review the most recent findings on the molecular mechanism underlying the complex interplay between gut microbiota and ISCs, revealing a possible key role of microbiota in the aberrant reprogramming of CSCs in the initiation of CRC. We also discuss recent advances in OMICS approaches and single-cell analyses to explore the relationship between gut microbiota and ISC/CSC niche biology leading to a desirable implementation of the current precision medicine approaches.

Vertical transmission of gut microbiota: Points of action of environmental factors influencing brain development

Environmental factors in early life interact with genetics to exert a long-lasting and broad influence on health and disease. There has been a marked growth in the number of environmental factors studied in association with neurodevelopmental disorders. Colonization of the gut microbiota in the offspring uses the maternal resident flora as a primary source of bacteria during perinatal periods. Several lines of evidence have shown that various environmental factors including the mode of delivery, exposure to antibiotics, infection, stress, diet, quality of breast milk, and type of infant-feeding during the perinatal periods can perturb the gut microbiota colonization in the offspring, finally leading to disturbances in brain development. This study proposes that the gut microbiota seeded primarily by maternal microbiota, and the postnatal colonization of the microbiota in the offspring can be critical action points of environmental factors when deciphering the mechanisms of actions of environmental factors in brain development. This research reviews the inheritance and colonization of the microbiota during early life and the potential actions of the environmental factors influencing brain development in the offspring by modulating the vertical transmission of gut microbiota.

Development of a human primary gut-on-a-chip to model inflammatory processes

Inflammatory bowel disease (IBD) is a complex multi-factorial disease for which physiologically relevant in vitro models are lacking. Existing models are often a compromise between biological relevance and scalability. Here, we integrated intestinal epithelial cells (IEC) derived from human intestinal organoids with monocyte-derived macrophages, in a gut-on-a-chip platform to model the human intestine and key aspects of IBD. The microfluidic culture of IEC lead to an increased polarization and differentiation state that closely resembled the expression profile of human colon in vivo. Activation of the model resulted in the polarized secretion of CXCL10, IL-8 and CCL-20 by IEC and could efficiently be prevented by TPCA-1 exposure. Importantly, upregulated gene expression by the inflammatory trigger correlated with dysregulated pathways in IBD patients. Finally, integration of activated macrophages offers a first-step towards a multi-factorial amenable IBD platform that could be scaled up to assess compound efficacy at early stages of drug development or in personalized medicine.

Differential expression of intestinal genes in necrotic enteritis challenged broiler chickens with 2 different Clostridium perfringens strains

The primary cause of necrotic enteritis (NE) disease in chickens is the NetB-positive Clostridium perfringens bacterium. Many factors are known to affect the severity of NE in the challenge models of broiler chickens, and one of these factors is the virulence of C. perfringens strain. This study was conducted to evaluate the effect of 2 pathogenic C. perfringens strains in a NE challenge model on gut health and mRNA expression of genes encoding apoptosis, tight junction, immunity, and nutrient transporters in broilers. Day-old Ross-308 male broilers (n = 468) were allocated in a 2 × 3 factorial arrangement of treatments with in-feed antibiotics (no or yes) and challenge (Non, C. perfringens strain NE18, and C. perfringens strain NE36) as the factors. The birds in the challenged groups were inoculated with Eimeria species on day 9 and with a fresh suspension of C. perfringens NE18 or NE36 on day 14 and 15. Sample collection was performed on 2 birds of each pen on day 16. Necrotic enteritis challenge, impaired feed conversion ratio during day 0 to 16 compared with the control group where the effect of the NE36 challenge was more severe than that with NE18 (P < 0.001). The mRNA expression of mucin-2, immunoglobulin-G, occludin (P < 0.001), and tight junction protein-1 (P < 0.05) genes were downregulated in both challenged groups compared with the nonchallenged counterparts. Antibiotic supplementation, on the other hand, increased weight gain, and feed intake in all challenged birds (P < 0.01), but upregulated mucin-5ac and alanine, serine, cysteine, and threonine transporter-1 (P < 0.05) only in the NE18 challenged birds. The challenge with NE36 significantly upregulated caspase-8 and claudin-1 (P < 0.001), but downregulated glucose transporter-2 (P < 0.001) compared with the NE18 challenge. These results suggest that NE challenge is detrimental to the performance of broilers through compromised intestinal health, and different C. perfringens strains can affect the severity of the disease through modulating the expression of intestinal genes encoding proteins responsible for apoptosis, gut integrity, immunity, mucus production, and nutrient transporters.

Mini-Review on Lipofuscin and Aging: Focusing on The Molecular Interface, The Biological Recycling Mechanism, Oxidative Stress, and The Gut-Brain Axis Functionality

Intra-lysosomal accumulation of the autofluorescent "residue" known as lipofuscin, which is found within postmitotic cells, remains controversial. Although it was considered a harmless hallmark of aging, its presence is detrimental as it continually accumulates. The latest evidence highlighted that lipofuscin strongly correlates with the excessive production of reactive oxygen species; however, despite this, lipofuscin cannot be removed by the biological recycling mechanisms. The antagonistic effects exerted at the DNA level culminate in a dysregulation of the cell cycle, by inducing a loss of the entire internal environment and abnormal gene(s) expression. Additionally, it appears that a crucial role in the production of reactive oxygen species can be attributed to gut microbiota, due to their ability to shape our behavior and neurodevelopment through their maintenance of the central nervous system.

Modulations of genes related to gut integrity, apoptosis, and immunity underlie the beneficial effects of Bacillus amyloliquefaciens CECT 5940 in broilers fed diets with different protein levels in a necrotic enteritis challenge model

Background

The ban of in-feed antimicrobial additives has negatively affected the poultry industry by causing necrotic enteritis (NE) to emerge in the flocks. Alternatives such as Bacillus probiotics have shown to be effective on eliminating the negative effects of this disease. Two experiments were conducted to investigate the effect of Bacillus amyloliquefaciens CECT 5940 (BA) in broiler chickens under NE challenge and/or fed diets with different protein levels.

Methods

In both experiments, 480 day-old mix-sexed Ross-308 broilers were arranged in a 2 × 2 factorial arrangement of treatments. In experiment 1, the factors were NE challenge (yes or no) and probiotic (yes or no). In experiment 2, the factors were dietary crude protein levels (standard or reduced) and probiotic (yes or no) and were used under NE challenge condition. Oral administration of Eimeria oocysts (day 9) followed by inoculation with Clostridium perfringens (day 14 and 15) was used to induce NE challenge. On day 16, two birds from each treatment were gavaged with fluorescein isothiocyanate-dextran (FITC-d) and blood samples were collected for gut integrity evaluation, and jejunal samples were collected for gene expression assay.

Results

In experiment 1, BA supplementation decreased caspase-3 (CASP3) (P < 0.001) and caspase-8 (CASP8) (P < 0.05) and increased occludin (OCLD) (P < 0.05) expression regardless of the challenge. Additionally, BA supplementation downregulated interfron-γ (IFN-γ) expression (P < 0.01) and upregulated immunoglobulin-G (IgG) (P < 0.01) and immunoglobulin-M (IgM) (P < 0.05) only in challenged birds. In experiment 2, the expression of genes encoding mucin-2 (MUC2) (P < 0.001), tight junction protein-1 (TJP1) (P < 0.05) and OCLD (P < 0.05) were upregulated by the addition of BA in the diet, regardless of the crude protein level. Further, BA supplementation downregulated INF-γ (P < 0.01) and upregulated immunoglobulin-A (IgA) (P < 0.05), IgM (P < 0.05) and IgG (P < 0.01) regardless of the crude protein level.

Conclusion

These findings suggest that supplementation of BA in broiler diets can improve gut health by modulation of genes related to the mucosal barrier, tight junction, and immunity in broilers challenged by unfavourable conditions such as NE challenge.

Prophylactic effect of physical exercise on Aβ1-40-induced depressive-like behavior and gut dysfunction in mice

Alzheimer's disease (AD) is a prevalent neurodegenerative disease that is highly comorbid with depression. Gut dysfunction has been proposed as a possible risk factor for both clinical conditions. In the present study, we investigated the ability of treadmill exercise for 4 weeks (5 days/week, 40 min/day) to counteract amyloid β_1-40 peptide (Aβ_1-40)-induced depressive-like behavior, alterations in morphological parameters of the duodenum, and the abundance of Firmicutes and Bacteroidetes phyla. Aβ_1-40 administration (400 pmol/mouse, i.c.v.) increased immobility time in the tail suspension test (TST) and reduced time spent sniffing in the female urine sniffing test (FUST), indicating behavioral despair and impairment in reward-seeking behavior. These behavioral alterations, indicative of depressive-like behavior, were accompanied by reduced villus width in the duodenum. Moreover, photomicrographs obtained by transmission electron microscopy revealed abnormal epithelial microvilli in the duodenum from sedentary Aβ_1-40-exposed mice, characterized by shorter microvilli and heterogeneity in the length of these structures that exhibit a disordered packing. Regarding the ultrastructure of Paneth cells, Aβ_1-40 administration caused a reduction in the secretory granule diameter, as well as an enlarged peripheral halo. These animals also presented reduced Firmicutes and increased Bacteroidetes abundance, and increased Bacteroidetes/Firmicutes ratio. Most of the alterations observed in Aβ_1-40-exposed mice were prevented by the practice of physical exercise. Altogether the results provide evidence of the prophylactic effect of physical exercise on Aβ_1-40-induced depressive-like behavior and gut dysfunction in mice, suggesting that physical exercise could be useful for preventing depression associated with AD.

Absence of neurotensin attenuates intestinal dysbiosis and inflammation by maintaining Mmp7/α-defensin axis in diet-induced obese mice

We previously reported that high levels of plasma neurotensin (NT), a gut hormone released from enteroendocrine cells of the small bowel, contribute to obesity and comorbid conditions. Gut microbiota has been implicated in the obesity development. Paneth cells are critical in maintaining gut microbiota composition and homeostasis by releasing antimicrobial proteins including α-defensins. The purpose of our current study was to determine the possible role of NT in gut microbiota composition and α-defensin gene expression associated with obesity. Here we show that the ratio of Firmicutes/Bacteroidetes (F/B ratio) and intestinal proinflammatory cytokines is significantly increased in NT+/+ mice fed with a high-fat diet (HFD) which were improved in NT-deficient mice. HFD disrupted the intestinal Mmp7/α-defensin axis, which was completely prevented in NT-/- mice. In addition, NT treatment inhibited DEFA5 expression and concurrent NF-κB activity, which was blocked by a pan PKC inhibitor (Gö6983) or an inhibitor for atypical PKCs (CRT0066854). More importantly, the shRNA-mediated knockdown of atypical PKCτ reversed NT-attenuated DEFA5 expression and increased NF-κB activity. NT contributes to the HFD-induced disruption of gut microbiota composition and α-defensin expression. PKCτ/λ plays a central role in NT-mediated α-defensin gene expression which might be mediated through the inhibition of NF-κB signaling pathways in Paneth cells.

Gut bacteria signaling to mitochondria in intestinal inflammation and cancer

The gastrointestinal microbiome plays a pivotal role in physiological homeostasis of the intestine as well as in the pathophysiology of diseases including inflammatory bowel diseases (IBD) and colorectal cancer (CRC). Emerging evidence suggests that gut microbiota signal to the mitochondria of mucosal cells, including epithelial cells and immune cells. Gut microbiota signaling to mitochondria has been shown to alter mitochondrial metabolism, activate immune cells, induce inflammasome signaling, and alter epithelial barrier function. Both dysbiosis of the gut microbiota and mitochondrial dysfunction are associated with chronic intestinal inflammation and CRC. This review discusses mitochondrial metabolism of gut mucosal cells, mitochondrial dysfunction, and known gut microbiota-mediated mitochondrial alterations during IBD and CRC.

Intestinal enteroids recapitulate the effects of short-chain fatty acids on the intestinal epithelium

Enteroids are cultured primary intestinal epithelial cells that recapitulate epithelial lineage development allowing for a more complex and physiologically relevant model for scientific study. The large presence of intestinal stem cells (ISC) in these enteroids allows for the study of metabolite effects on cellular processes and resulting progeny cells. Short-chain fatty acids (SCFA) such as butyrate (BUT) are bacterial metabolites produced in the gastrointestinal tract that are considered to be beneficial to host cells. Therefore, the objective was to study the effects of SCFAs on biomarkers of ISC activity, differentiation, barrier function and epithelial defense in the intestine using mouse and human enteroid models. Enteroids were treated with two concentrations of acetate (ACET), propionate (PROP), or BUT for 24 h. Enteroids treated with BUT or PROP showed a decrease in proliferation via EdU uptake relative to the controls in both mouse and human models. Gene expression of Lgr5 was shown to decrease with BUT and PROP treatments, but increased with ACET. As a result of BUT and PROP treatments, there was an increase in differentiation markers for enterocyte, Paneth, goblet, and enteroendocrine cells. Gene expression of antimicrobial proteins Reg3β, Reg3γ, and Defb1 were stimulated by BUT and PROP, but not by ACET which had a greater effect on expression of tight junction genes Cldn3 and Ocln in 3D enteroids. Similar results were obtained with human enteroids treated with 10 mM SCFAs and grown in either 3D or Transwell™ model cultures, although tight junctions were influenced by BUT and PROP, but not ACET in monolayer format. Furthermore, BUT and PROP treatments increased transepithelial electrical resistance after 24 h compared to ACET or control. Overall, individual SCFAs are potent stimulators of cellular gene expression, however, PROP and especially BUT show great efficacy for driving cell differentiation and gene expression.

Immunology-Guided Biomaterial Design for Mucosal Cancer Vaccines

Cancer of mucosal tissues is a major cause of worldwide mortality for which only palliative treatments are available for patients with late-stage disease. Engineered cancer vaccines offer a promising approach for inducing antitumor immunity. The route of vaccination plays a major role in dictating the migratory pattern of lymphocytes, and thus vaccine efficacy in mucosal tissues. Parenteral immunization, specifically subcutaneous and intramuscular, is the most common vaccination route. However, this induces marginal mucosal protection in the absence of tissue-specific imprinting signals. To circumvent this, the mucosal route can be utilized, however degradative mucosal barriers must be overcome. Hence, vaccine administration route and selection of materials able to surmount transport barriers are important considerations in mucosal cancer vaccine design. Here, an overview of mucosal immunity in the context of cancer and mucosal cancer clinical trials is provided. Key considerations are described regarding the design of biomaterial-based vaccines that will afford antitumor immune protection at mucosal surfaces, despite limited knowledge surrounding mucosal vaccination, particularly aided by biomaterials and mechanistic immune-material interactions. Finally, an outlook is given of how future biomaterial-based mucosal cancer vaccines will be shaped by new discoveries in mucosal vaccinology, tumor immunology, immuno-therapeutic screens, and material-immune system interplay.

Gut commensal bacteria, Paneth cells and their relations to radiation enteropathy

In steady state, the intestinal epithelium forms an important part of the gut barrier to defend against luminal bacterial attack. However, the intestinal epithelium is compromised by ionizing irradiation due to its inherent self-renewing capacity. In this process, small intestinal bacterial overgrowth is a critical event that reciprocally alters the immune milieu. In other words, intestinal bacterial dysbiosis induces inflammation in response to intestinal injuries, thus influencing the repair process of irradiated lesions. In fact, it is accepted that commensal bacteria can generally enhance the host radiation sensitivity. To address the determination of radiation sensitivity, we hypothesize that Paneth cells press a critical "button" because these cells are central to intestinal health and disease by using their peptides, which are responsible for controlling stem cell development in the small intestine and luminal bacterial diversity. Herein, the most important question is whether Paneth cells alter their secretion profiles in the situation of ionizing irradiation. On this basis, the tolerance of Paneth cells to ionizing radiation and related mechanisms by which radiation affects Paneth cell survival and death will be discussed in this review. We hope that the relevant results will be helpful in developing new approaches against radiation enteropathy.

Lactobacillus reuteri Promotes Intestinal Development and Regulates Mucosal Immune Function in Newborn Piglets

Intestinal microbiota is necessary for the guarantee of intestinal mucosal barrier. However, the detailed effect of probiotics on porcine intestinal development, especially in the early life, is still unclear. In this study, we treated 3-day-old newborn piglets with Lactobacillus reuteri (L. reuteri) D8 and observed its beneficial effect on piglets. The body weights, villus height, and crypt depth of jejunum were all significantly increased after L. reuteri treatment in piglets. L. reuteri also significantly increased the proliferation index of PCNA⁺ cells in the crypt, as well as c-Myc and Tcf4 expressions. Furthermore, L. reuteri also enhanced intestinal mucosal barrier with the increase of goblet cells and antimicrobial peptides (AMPs) expressions of Muc2, Lyz1, and pBD1. The well development of Peyer's patches and increased number of CD3⁺ T cells, combined with increased expression of IL-4 and IFN-γ, also demonstrated the immune stimulation effect of L. reuteri D8. This study demonstrated that L. reuteri promotes the development of intestine mucosal system and maintains intestinal mucosal barrier in newborn piglets.

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

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

Herpesviruses and the Unfolded Protein Response

Herpesviruses usurp cellular stress responses to promote viral replication and avoid immune surveillance. The unfolded protein response (UPR) is a conserved stress response that is activated when the protein load in the ER exceeds folding capacity and misfolded proteins accumulate. The UPR aims to restore protein homeostasis through translational and transcriptional reprogramming; if homeostasis cannot be restored, the UPR switches from "helper" to "executioner", triggering apoptosis. It is thought that the burst of herpesvirus glycoprotein synthesis during lytic replication causes ER stress, and that these viruses may have evolved mechanisms to manage UPR signaling to create an optimal niche for replication. The past decade has seen considerable progress in understanding how herpesviruses reprogram the UPR. Here we provide an overview of the molecular events of UPR activation, signaling and transcriptional outputs, and highlight key evidence that herpesviruses hijack the UPR to aid infection.

Functional Changes of Paneth Cells in the Intestinal Epithelium of Mice with Obstructive Jaundice and After Internal and External Biliary Drainage

OBJECTIVE

To investigate the functional changes of Paneth cells in the intestinal epithelium of mice with obstructive jaundice (OJ) and after internal biliary drainage (ID) and external biliary drainage (ED).

METHODS

The experiment was divided into two stages. First stage: Mice were randomly assigned to two groups: (I) sham operation (SH); (II) OJ. The mice were sacrificed before the operation and on the 1st, 3rd, 5th and 7th day after the operation to collect specimens. Second stage: Mice were randomly assigned to four groups: (I) SH; (II) OJ; (III) OJ and ED; and (IV) OJ and ID. They were reoperated on day 5 for biliary drainage procedure. The specimens were collected on day 10.

RESULTS

The expressions of lysozyme and cryptdin-4 increased first and then decreased over time in group OJ, and the number of Paneth cells decreased gradually with the extension of OJ time（p<0.05. After the secondary operation on the mice to relieve OJ, the number of Paneth cells and expressions of lysozyme and cryptdin-4 in group ID increased more significantly than those in group ED（p<0.05）.

CONCLUSION

OJ could cause intestinal Paneth cells to dysfunction in mice. ID was more significant than ED in restoring the function of Paneth cells. It might be one of the mechanisms that make ID superior to ED.

TLR4 Agonist Monophosphoryl Lipid A Alleviated Radiation-Induced Intestinal Injury

The small intestine is one of the most sensitive organs to irradiation injury, and the development of high effective radioprotectants especially with low toxicity for intestinal radiation sickness is urgently needed. Monophosphoryl lipid A (MPLA) was found to be radioprotective in our previous study, while its effect against the intestinal radiation injury remained unknown. In the present study, we firstly determined the intestinal apoptosis after irradiation injury according to the TUNEL assay. Subsequently, we adopted the immunofluorescence technique to assess the expression levels of different biomarkers including Ki67, γ-H2AX, and defensin 1 in vivo. Additionally, the inflammatory cytokines were detected by RT-PCR. Our data indicated that MPLA could protect the intestine from ionizing radiation (IR) damage through activating TLR4 signal pathway and regulating the inflammatory cytokines. This research shed new light on the protective effect of the novel TLR4 agonist MPLA against intestine detriment induced by IR.

Gut microbiota in ALS: possible role in pathogenesis?

Introduction: The gut microbiota has important roles in maintaining human health. The microbiota and its metabolic byproducts could play a role in the pathogenesis of neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). Areas covered: The authors evaluate the methods of assessing the gut microbiota, and also review how the gut microbiota affects the various physiological functions of the gut. The authors then consider how gut dysbiosis could theoretically affect the pathogenesis of ALS. They present the current evidence regarding the composition of the gut microbiota in ALS and in rodent models of ALS. Finally, the authors review therapies that could improve gut dysbiosis in the context of ALS. Expert opinion: Currently reported studies suggest some instances of gut dysbiosis in ALS patients and mouse models; however, these studies are limited, and more information with well-controlled larger datasets is required to make a definitive judgment about the role of the gut microbiota in ALS pathogenesis. Overall this is an emerging field that is worthy of further investigation. The authors advocate for larger studies using modern metagenomic techniques to address the current knowledge gaps.

Challenge to the Intestinal Mucosa During Sepsis

Sepsis is a complex of life-threating organ dysfunction in critically ill patients, with a primary infectious cause or through secondary infection of damaged tissues. The systemic consequences of sepsis have been intensively examined and evidences of local alterations and repercussions in the intestinal mucosal compartment is gradually defining gut-associated changes during sepsis. In the present review, we focus on sepsis-induced dysfunction of the intestinal barrier, consisting of an increased permeability of the epithelial lining, which may facilitate bacterial translocation. We discuss disturbances in intestinal vascular tonus and perfusion and coagulopathies with respect to their proposed underlying molecular mechanisms. The consequences of enzymatic responses by pancreatic proteases, intestinal alkaline phosphatases, and several matrix metalloproteases are also described. We conclude our insight with a discussion on novel therapeutic interventions derived from crucial aspects of the gut mucosal dynamics during sepsis.

Associations of Gut Microbiota With Heat Stress-Induced Changes of Growth, Fat Deposition, Intestinal Morphology, and Antioxidant Capacity in Ducks

Accumulating evidence has revealed the dysbiosis of gut/fecal microbiota induced by heat stress (HS) in mammals and poultry. However, the effects of HS on microbiota communities in different intestinal segments of Cherry-Valley ducks (a widely used meat-type breed) and their potential associations with growth performances, fat deposition, intestinal morphology, and antioxidant capacity have not been well evaluated yet. In this study, room temperature (RT) of 25°C was considered as control, and RT at 32°C for 8 h per day was set as the HS treatment. After 3 weeks, the intestinal contents of jejunum, ileum, and cecum were harvested to investigate the microbiota composition variations by 16S ribosomal RNA amplicon sequencing. And the weight gain, adipose indices, intestinal morphology, and a certain number of serum biochemical parameters were also measured and analyzed. The results showed the microbial species at different levels differentially enriched in duck jejunum and cecum under HS, while no significant data were observed in ileum. HS also caused the intestinal morphological changes (villus height and the ratio of villus height to crypt depth) and the reductions of growth speed (daily gain), levels of serum triglyceride (TG) and total cholesterol, and antioxidant activity (higher malondialdehyde (MDA) content and lower total antioxidant). The higher abdominal fat content and serum glucose level were also observed in HS ducks. The Spearman correlation analysis indicated that in jejunum the phyla Firmicutes and Proteobacteria were associated with average daily gain, feed/gain, serum TG and MDA levels, and villus height/crypt depth (P < 0.05). The phylum Firmicutes and genus Acinetobacter were significantly associated with fat deposition and serum glucose level (P < 0.05). The genus Lactobacillus was positively associated with serum total antioxidant (P < 0.05), while some other microbial species were found negatively associated, including order Pseudomonadales, genera Acinetobacter, and unidentified_Mitochondria. However, no significant correlations were observed in cecum. These findings imply the potential roles of duck gut microbiota in the intestinal injuries, fat deposition, and reductions of growth speed and antioxidant capacity caused by HS, although the molecular mechanisms requires further investigation.

Interactions Between the Gut Microbiota and the Host Innate Immune Response Against Pathogens

The mammalian intestine is colonized by over a trillion microbes that comprise the "gut microbiota," a microbial community which has co-evolved with the host to form a mutually beneficial relationship. Accumulating evidence indicates that the gut microbiota participates in immune system maturation and also plays a central role in host defense against pathogens. Here we review some of the mechanisms employed by the gut microbiota to boost the innate immune response against pathogens present on epithelial mucosal surfaces. Antimicrobial peptide secretion, inflammasome activation and induction of host IL-22, IL-17, and IL-10 production are the most commonly observed strategies employed by the gut microbiota for host anti-pathogen defense. Taken together, the body of evidence suggests that the host gut microbiota can elicit innate immunity against pathogens.

Effect of stocking density and sex on growth performance, meat quality, and intestinal barrier function in broiler chickens

The objective of the current experiment was to investigate the effect of stocking density and sex on growth performance, meat quality, and intestinal barrier function in broiler chickens. The experiment was conducted in a completely randomized design with a 2 × 4 factorial arrangement consisting of sex and four different stocking densities in battery cages. A total of 540 1-d-old Ross 308 broiler chickens were allotted to one of eight treatments with five replicates. Within each sex, birds were raised at four different stocking densities of 15.2, 20.2, 25.3, or 30.4 birds/m2 from 1 to 28 d of age. Different stocking densities were achieved by raising a different number of birds per battery cage with identical floor size (0.76 m × 0.78 m). At the end of the experiment, two birds per replicate were euthanized by CO2 asphyxiation to collect tissue samples for further analyses. Results indicated that no interactions between sex and stocking density were observed for all measurements except for serum lipopolysaccharide (LPS) concentrations. Increasing stocking density decreased (linear, P < 0.01) body weight gain and feed intake, but had no negative effects on meat quality. Trans-epithelial electrical resistance values, a measure of intestinal permeability, were decreased (linear, P < 0.01) with increasing stocking density, regardless of sex. Accordingly, serum LPS concentrations were increased (linear, P < 0.01) with increasing stocking density. However, increasing stocking density increased serum LPS concentrations in male broiler chickens, but had no effects on female broiler chickens, showing an interaction (P < 0.01). The expression of zonula occludens-1 (ZO-1) and junctional adhesion molecule B (JAM-2) was decreased (linear, P < 0.05) with increasing stocking density. In conclusion, increasing stocking density decreases broiler performance regardless of sex and this negative effect is likely associated with decreased intestinal barrier function.