Proteomic analyses of the two mucus layers of the colon barrier reveal that their main component, the Muc2 mucin, is strongly bound to the Fcgbp protein

Host-derived CEACAM-laden vesicles engage enterotoxigenic E. coli for elimination and toxin neutralization

Enterotoxigenic Escherichia coli (ETEC) cause hundreds of millions of diarrheal illnesses annually ranging from mildly symptomatic cases to severe, life-threatening cholera-like diarrhea. Although ETEC are associated with long-term sequelae including malnutrition, the acute diarrheal illness is largely self-limited. Recent studies indicate that in addition to causing diarrhea, the ETEC heat-labile toxin (LT) modulates the expression of many genes in intestinal epithelia, including carcinoembryonic cell adhesion molecules (CEACAMs) which ETEC exploit as receptors, enabling toxin delivery. Here however, we demonstrate that LT also enhances the expression of CEACAMs on extracellular vesicles (EV) shed by intestinal epithelia and that CEACAM-laden EV increase in abundance during human infections, mitigate pathogen-host interactions, scavenge free ETEC toxins, and accelerate ETEC clearance from the gastrointestinal tract. Collectively, these findings indicate that CEACAMs play a multifaceted role in ETEC pathogen-host interactions, transiently favoring the pathogen, but ultimately contributing to innate responses that extinguish these common infections.

Significance statement

Enterotoxigenic E. coli, characterized by the production of heat-labile (LT) and heat-stable (ST) toxins, are a very common cause of diarrhea in low-income regions responsible for hundreds of millions of infections each year, and the major cause of diarrhea in travelers to endemic areas. Although these infections may be severe and cholera-like, they are typically self-limited. These studies demonstrate that extracellular vesicles produced by host intestinal cells can capture the bacteria and its secreted toxins at a distance from the cell surface, potentially acting as molecular decoys to neutralize the enterotoxins and extinguish the infection.

Changes of intestinal barrier in the process of intestinal inflammation induced by Aeromonas hydrophila in snakehead (Channa argus)

Bacterial intestinal inflammation frequently occurs in cultured fish. Nevertheless, research on intestinal barrier dysfunction in the process of intestinal inflammation is deficient. In this study, we explored the changes of intestinal inflammation induced by Aeromonas hydrophila (A. hydrophila) in snakehead and the relationship between intestinal barrier and inflammation. Snakehead [(13.05 ± 2.39) g] were infected via anus with A. hydrophila. Specimens were collected for analysis at 0, 1, 3, 7 and 21 d post-injection. The results showed that with the increase of exposure time, the hindgut underwent stages of normal function, damage, damage deterioration, repair and recovery. Relative to 0 d, the levels of IL-1β and TNF-α in serum, and the expression of nod1, tlr1, tlr5, nf-κb, tnf-α and il-1β in intestine were significantly increased, and showed an upward then downward pattern over time. However, the expression of tlr2 and il-10 were markedly decreased, and showed the opposite trend. In addition, with the development of intestinal inflammation, the diversity and richness of species, and the levels of phylum and genus in intestine were obviously altered. The levels of trypsin, LPS, AMS, T-SOD, CAT, GPx, AKP, LZM and C3 in intestine were markedly reduced, and displayed a trend of first decreasing and then rebounding. The ultrastructure observation showed that the microvilli and tight junction structure of intestinal epithelial cells experienced normal function initially, then damage, and finally recovery over time. The expression of claudin-3 and zo-1 in intestine were significantly decreased, and showed a trend of first decreasing and then rebounding. Conversely, the expression of mhc-i, igm, igt and pigr in intestine were markedly increased, and displayed a trend of increasing first and then decreasing. The above results revealed the changes in intestinal barrier during the occurrence and development of intestinal inflammation, which provided a theoretical basis for explaining the relationship between the two.

Stress-induced mucin 13 reductions drive intestinal microbiome shifts and despair behaviors

Depression is a prevalent psychological condition with limited treatment options. While its etiology is multifactorial, both chronic stress and changes in microbiome composition are associated with disease pathology. Stress is known to induce microbiome dysbiosis, defined here as a change in microbial composition associated with a pathological condition. This state of dysbiosis is known to feedback on depressive symptoms. While studies have demonstrated that targeted restoration of the microbiome can alleviate depressive-like symptoms in mice, translating these findings to human patients has proven challenging due to the complexity of the human microbiome. As such, there is an urgent need to identify factors upstream of microbial dysbiosis. Here we investigate the role of mucin 13 as an upstream mediator of microbiome composition changes in the context of stress. Using a model of chronic stress, we show that the glycocalyx protein, mucin 13, is selectively reduced after psychological stress exposure. We further demonstrate that the reduction of Muc13 is mediated by the Hnf4 transcription factor family. Finally, we determine that deleting Muc13 is sufficient to drive microbiome shifts and despair behaviors. These findings shed light on the mechanisms behind stress-induced microbial changes and reveal a novel regulator of mucin 13 expression.

Reinforcement of the intestinal mucosal barrier via mucus-penetrating PEGylated bacteria

The breakdown of the gut's mucosal barrier that prevents the infiltration of microorganisms, inflammatory cytokines and toxins into bodily tissues can lead to inflammatory bowel disease and to metabolic and autoimmune diseases. Here we show that the intestinal mucosal barrier can be reinforced via the oral administration of commensal bacteria coated with poly(ethylene glycol) (PEG) to facilitate their penetration into mucus. In mice with intestinal homoeostatic imbalance, mucus-penetrating PEGylated bacteria preferentially localized in mucus at the lower gastrointestinal tract, inhibited the invasion of pathogenic bacteria, maintained homoeostasis of the gut microbiota, stimulated the secretion of mucus and the expression of tight junctions, and prevented the mice from developing colitis and diabetes. Orally delivered PEGylated bacteria may help prevent and treat gastrointestinal disorders.

Network and structural analysis of quail mucins with expression pattern of mucin 1 and mucin 4 in the intestines of the Iraqi common quail (Coturnix coturnix)

Background and Aim

In avian and other species, mucins (MUCs) play a crucial role in the gastrointestinal tract (GIT), and constitute a large group of O-glycosylated glycoproteins, are glycoconjugate proteins. MUCs present in two forms: (1) membrane-attached on cell surfaces to repel external threats and (2) detachable, gel-forming proteins in the soluble form. In quail GIT, the specific types of MUCs that are expressed remain largely unknown. We investigated the expression of MUC1 and MUC4 MUCs in the GIT of Iraqi common quails and conducted network and structural analyses of all known MUC types across quail breeds.

Materials and Methods

Histological and gene expression analyses of MUC1 and MUC4 were conducted using fresh small intestine and large intestine samples from 10 quails. Using the STRING Database, Chimera software, and PrankWeb-ligand binding site prediction tool, network and structural analyses of all reported types of quail MUCs were conducted.

Results

Most intestinal MUCs in quails were acidic, with few neutral MUCs detectable through Alcian blue and periodic acid-schiff stains. Acidic MUCs were more expressed in the duodenum, ileum, cecum, and colon, whereas neutral MUCs were more expressed in the jejunum. MUC1 and MUC4 messenger RNA expression was significantly higher in the jejunum and colon than in the duodenum and ileum. The analysis of the network revealed that MUC 1, 15, 16, and 24 formed homologous networks, while MUC 2, 4, 5, and 6 formed heterologous networks. Specific MUC combinations, including MUC5A-MUC6, MUC5A-MUC5B, and MUC5B-MUC6, show higher intermolecular hydrogen bond formation affinity. MUC15, MUC16, and MUC24 showed minimal interaction with other MUC types. Among the analyzed MUCs, MUC5B, and MUC6 had the highest probability for binding, while MUC2, MUC4, and MUC5A showed lower probabilities despite greater numbers of binding sites.

Conclusion

This study's results offer significant insights into quails' MUCs' composition, expression, network interactions, and binding sites, advancing knowledge of MUC-related processes in gastrointestinal physiology and their potential connection to gastrointestinal diseases.

Rab7-dependent regulation of goblet cell protein CLCA1 modulates gastrointestinal homeostasis

Inflammation in ulcerative colitis is typically restricted to the mucosal layer of distal gut. Disrupted mucus barrier, coupled with microbial dysbiosis, has been reported to occur prior to the onset of inflammation. Here, we show the involvement of vesicular trafficking protein Rab7 in regulating the colonic mucus system. We identified a lowered Rab7 expression in goblet cells of colon during human and murine colitis. In vivo Rab7 knocked down mice (Rab7KD) displayed a compromised mucus layer, increased microbial permeability, and depleted gut microbiota with enhanced susceptibility to dextran sodium-sulfate induced colitis. These abnormalities emerged owing to altered mucus composition, as revealed by mucus proteomics, with increased expression of mucin protease chloride channel accessory 1 (CLCA1). Mechanistically, Rab7 maintained optimal CLCA1 levels by controlling its lysosomal degradation, a process that was dysregulated during colitis. Overall, our work establishes a role for Rab7-dependent control of CLCA1 secretion required for maintaining mucosal homeostasis.

Fecal-adherent mucus is a non-invasive source of primary human MUC2 for structural and functional characterization in health and disease

The O-glycoprotein Mucin-2 (MUC2) forms the protective colon mucus layer. While animal models have demonstrated the importance of Muc2, few studies have explored human MUC2 in similar depth. Recent studies have revealed that secreted MUC2 is bound to human feces. We hypothesized human fecal MUC2 (HF-MUC2) was accessible for purification and downstream structural and functional characterization. We tested this via histologic and quantitative imaging on human fecal sections; extraction from feces for proteomic and O-glycomic characterization; and functional studies via growth and metabolic assays in vitro. Quantitative imaging of solid fecal sections showed a continuous mucus layer of varying thickness along human fecal sections with barrier functions intact. Lectin profiling showed HF-MUC2 bound several lectins but was weak to absent for Ulex europaeus 1 (α1,2 fucose-binding) and Sambucus nigra agglutinin (α2,6 sialic acid-binding), and did not have obvious b1/b2 barrier layers. HF-MUC2 separated by electrophoresis showed high molecular weight glycoprotein bands (∼1-2 MDa). Proteomics and Western analysis confirmed the enrichment of MUC2 and potential MUC2-associated proteins in HF-MUC2 extracts. MUC2 O-glycomics revealed diverse fucosylation, moderate sialylation, and little sulfation versus porcine colonic MUC2 and murine fecal Muc2. O-glycans were functional and supported the growth of Bacteroides thetaiotaomicron (B. theta) and short-chain fatty acid (SCFA) production in vitro. MUC2 could be similarly analyzed from inflammatory bowel disease stools, which displayed an altered glycomic profile and differential growth and SCFA production by B. theta versus healthy samples. These studies describe a new non-invasive platform for human MUC2 characterization in health and disease.

Activation of goblet-cell stress sensor IRE1β is controlled by the mucin chaperone AGR2

Intestinal goblet cells are secretory cells specialized in the production of mucins, and as such are challenged by the need for efficient protein folding. Goblet cells express Inositol-Requiring Enzyme-1β (IRE1β), a unique sensor in the unfolded protein response (UPR), which is part of an adaptive mechanism that regulates the demands of mucin production and secretion. However, how IRE1β activity is tuned to mucus folding load remains unknown. We identified the disulfide isomerase and mucin chaperone AGR2 as a goblet cell-specific protein that crucially regulates IRE1β-, but not IRE1α-mediated signaling. AGR2 binding to IRE1β disrupts IRE1β oligomerization, thereby blocking its downstream endonuclease activity. Depletion of endogenous AGR2 from goblet cells induces spontaneous IRE1β activation, suggesting that alterations in AGR2 availability in the endoplasmic reticulum set the threshold for IRE1β activation. We found that AGR2 mutants lacking their catalytic cysteine, or displaying the disease-associated mutation H117Y, were no longer able to dampen IRE1β activity. Collectively, these results demonstrate that AGR2 is a central chaperone regulating the goblet cell UPR by acting as a rheostat of IRE1β endonuclease activity.

Rare disease research workflow using multilayer networks elucidates the molecular determinants of severity in Congenital Myasthenic Syndromes

Exploring the molecular basis of disease severity in rare disease scenarios is a challenging task provided the limitations on data availability. Causative genes have been described for Congenital Myasthenic Syndromes (CMS), a group of diverse minority neuromuscular junction (NMJ) disorders; yet a molecular explanation for the phenotypic severity differences remains unclear. Here, we present a workflow to explore the functional relationships between CMS causal genes and altered genes from each patient, based on multilayer network community detection analysis of complementary biomedical information provided by relevant data sources, namely protein-protein interactions, pathways and metabolomics. Our results show that CMS severity can be ascribed to the personalized impairment of extracellular matrix components and postsynaptic modulators of acetylcholine receptor (AChR) clustering. This work showcases how coupling multilayer network analysis with personalized -omics information provides molecular explanations to the varying severity of rare diseases; paving the way for sorting out similar cases in other rare diseases.

Hydrogen sulfide responsive nanoplatforms: Novel gas responsive drug delivery carriers for biomedical applications

Hydrogen sulfide (H2S) is a toxic, essential gas used in various biological and physical processes and has been the subject of many targeted studies on its role as a new gas transmitter. These studies have mainly focused on the production and pharmacological side effects caused by H2S. Therefore, effective strategies to remove H2S has become a key research topic. Furthermore, the development of novel nanoplatforms has provided new tools for the targeted removal of H2S. This paper was performed to review the association between H2S and disease, related H2S inhibitory drugs, as well as H2S responsive nanoplatforms (HRNs). This review first analyzed the role of H2S in multiple tissues and conditions. Second, common drugs used to eliminate H2S, as well as their potential for combination with anticancer agents, were summarized. Not only the existing studies on HRNs, but also the inhibition H2S combined with different therapeutic methods were both sorted out in this review. Furthermore, this review provided in-depth analysis of the potential of HRNs about treatment or detection in detail. Finally, potential challenges of HRNs were proposed. This study demonstrates the excellent potential of HRNs for biomedical applications.

The gut mucus network: A dynamic liaison between microbes and the immune system

A complex mucus network made up of large polymers of the mucin-family glycoprotein MUC2 exists between the large intestinal microbial mass and epithelial and immune cells. This has long been understood as an innate immune defense barrier against the microbiota and other luminal threats that reinforces the barrier function of the epithelium and limits microbiota contact with the tissues. However, past and recent studies have provided new evidence of how critical the mucus network is to act as a 'liaison' between host and microbe to mediate anti-inflammatory, mutualistic interactions with the microbiota and protection from pathogens. This review summarizes historical and recent insights into the formation of the gut mucus network, how the microbes and immune system influence mucus, and in turn, how the mucus influences immune responses to the microbiota.

Native gastrointestinal mucus: Critical features and techniques for studying interactions with drugs, drug carriers, and bacteria

Gastrointestinal mucus plays essential roles in modulating interactions between intestinal lumen contents, including orally delivered drug carriers and the gut microbiome, and underlying epithelial and immune tissues and cells. This review is focused on the properties of and methods for studying native gastrointestinal mucus and its interactions with intestinal lumen contents, including drug delivery systems, drugs, and bacteria. The properties of gastrointestinal mucus important to consider in its analysis are first presented, followed by a discussion of different experimental setups used to study gastrointestinal mucus. Applications of native intestinal mucus are then described, including experimental methods used to study mucus as a barrier to drug delivery and interactions with intestinal lumen contents that impact barrier properties. Given the significance of the microbiota in health and disease, its impact on drug delivery and drug metabolism, and the use of probiotics and microbe-based delivery systems, analysis of interactions of bacteria with native intestinal mucus is then reviewed. Specifically, bacteria adhesion to, motility within, and degradation of mucus is discussed. Literature noted is focused largely on applications of native intestinal mucus models as opposed to isolated mucins or reconstituted mucin gels.

Microbial experience through housing in a farmyard-type environment alters intestinal barrier properties in mouse colons

To close the gap between ultra-hygienic research mouse models and the much more environmentally exposed conditions of humans, we have established a system where laboratory mice are raised under a full set of environmental factors present in a naturalistic, farmyard-type habitat-a process we have called feralization. In previous studies we have shown that feralized (Fer) mice were protected against colorectal cancer when compared to conventionally reared laboratory mice (Lab). However, the protective mechanisms remain to be elucidated. Disruption of the protective intestinal barrier is an acknowledged player in colorectal carcinogenesis, and in the current study we assessed colonic mucosal barrier properties in healthy, feralized C57BL/6JRj male mice. While we found no effect of feralization on mucus layer properties, higher expression of genes encoding the mucus components Fcgbp and Clca1 still suggested mucus enforcement due to feralization. Genes encoding other proteins known to be involved in bacterial defense (Itln1, Ang1, Retnlb) and inflammatory mechanisms (Zbp1, Gsdmc2) were also higher expressed in feralized mice, further suggesting that the Fer mice have an altered intestinal mucosal barrier. These findings demonstrate that microbial experience conferred by housing in a farmyard-type environment alters the intestinal barrier properties in mice possibly leading to a more robust protection against disease. Future studies to unravel regulatory roles of feralization on intestinal barrier should aim to conduct proteomic analyses and in vivo performance of the feralized mice intestinal barrier.

Porcine Deltacoronavirus Infection Disrupts the Intestinal Mucosal Barrier and Inhibits Intestinal Stem Cell Differentiation to Goblet Cells via the Notch Signaling Pathway

Goblet cells and their secreted mucus are important elements of the intestinal mucosal barrier, which allows host cells to resist invasion by intestinal pathogens. Porcine deltacoronavirus (PDCoV) is an emerging swine enteric virus that causes severe diarrhea in pigs and causes large economic losses to pork producers worldwide. To date, the molecular mechanisms by which PDCoV regulates the function and differentiation of goblet cells and disrupts the intestinal mucosal barrier remain to be determined. Here, we report that in newborn piglets, PDCoV infection disrupts the intestinal barrier: specifically, there is intestinal villus atrophy, crypt depth increases, and tight junctions are disrupted. There is also a significant reduction in the number of goblet cells and the expression of MUC-2. In vitro, using intestinal monolayer organoids, we found that PDCoV infection activates the Notch signaling pathway, resulting in upregulated expression of HES-1 and downregulated expression of ATOH-1 and thereby inhibiting the differentiation of intestinal stem cells into goblet cells. Our study shows that PDCoV infection activates the Notch signaling pathway to inhibit the differentiation of goblet cells and their mucus secretion, resulting in disruption of the intestinal mucosal barrier. IMPORTANCE The intestinal mucosal barrier, mainly secreted by the intestinal goblet cells, is a crucial first line of defense against pathogenic microorganisms. PDCoV regulates the function and differentiation of goblet cells, thereby disrupting the mucosal barrier; however, the mechanism by which PDCoV disrupts the barrier is not known. Here, we report that in vivo, PDCoV infection decreases villus length, increases crypt depth, and disrupts tight junctions. Moreover, PDCoV activates the Notch signaling pathway, inhibiting goblet cell differentiation and mucus secretion in vivo and in vitro. Thus, our results provide a novel insight into the mechanism underlying intestinal mucosal barrier dysfunction caused by coronavirus infection.

Interaction between mucus layer and gut microbiota in non-alcoholic fatty liver disease: Soil and seeds

ABSTRACT

The intestinal mucus layer is a barrier that separates intestinal contents and epithelial cells, as well as acts as the "mucus layer-soil" for intestinal flora adhesion and colonization. Its structural and functional integrity is crucial to human health. Intestinal mucus is regulated by factors such as diet, living habits, hormones, neurotransmitters, cytokines, and intestinal flora. The mucus layer's thickness, viscosity, porosity, growth rate, and glycosylation status affect the structure of the gut flora colonized on it. The interaction between "mucus layer-soil" and "gut bacteria-seed" is an important factor leading to the pathogenesis of non-alcoholic fatty liver disease (NAFLD). Probiotics, prebiotics, fecal microbiota transplantation (FMT), and wash microbial transplantation are efficient methods for managing NAFLD, but their long-term efficacy is poor. FMT is focused on achieving the goal of treating diseases by enhancing the "gut bacteria-seed". However, a lack of effective repair and management of the "mucus layer-soil" may be a reason why "seeds" cannot be well colonized and grow in the host gut, as the thinning and destruction of the "mucus layer-soil" is an early symptom of NAFLD. This review summarizes the existing correlation between intestinal mucus and gut microbiota, as well as the pathogenesis of NAFLD, and proposes a new perspective that "mucus layer-soil" restoration combined with "gut bacteria-seed" FMT may be one of the most effective future strategies for enhancing the long-term efficacy of NAFLD treatment.

IgGFc-binding protein and MUC2 mucin produced by colonic goblet-like cells spatially interact non-covalently and regulate wound healing

The colonic mucus bilayer is the first line of innate host defense that at the same time houses and nourishes the commensal microbiota. The major components of mucus secreted by goblet cells are MUC2 mucin and the mucus-associated protein, FCGBP (IgGFc-binding protein). In this study, we determine if FCGBP and MUC2 mucin were biosynthesized and interacted together to spatially enhance the structural integrity of secreted mucus and its role in epithelial barrier function. MUC2 and FCGBP were coordinately regulated temporally in goblet-like cells and in response to a mucus secretagogue but not in CRISPR-Cas9 gene-edited MUC2 KO cells. Whereas ~85% of MUC2 was colocalized with FCGBP in mucin granules, ~50% of FCGBP was diffusely distributed in the cytoplasm of goblet-like cells. STRING-db v11 analysis of the mucin granule proteome revealed no protein-protein interaction between MUC2 and FCGBP. However, FCGBP interacted with other mucus-associated proteins. FCGBP and MUC2 interacted via N-linked glycans and were non-covalently bound in secreted mucus with cleaved low molecular weight FCGBP fragments. In MUC2 KO, cytoplasmic FCGBP was significantly increased and diffusely distributed in wounded cells that healed by enhanced proliferation and migration within 2 days, whereas, in WT cells, MUC2 and FCGBP were highly polarized at the wound margin which impeded wound closure by 6 days. In DSS colitis, restitution and healed lesions in Muc2^+/+ but not Muc2^-/- littermates, were accompanied by a rapid increase in Fcgbp mRNA and delayed protein expression at 12- and 15-days post DSS, implicating a potential novel endogenous protective role for FCGBP in wound healing to maintain epithelial barrier function.

HMGB1 acts as an agent of host defense at the gut mucosal barrier

Mucosal barriers provide the first line of defense between internal body surfaces and microbial threats from the outside world. ¹ In the colon, the barrier consists of two layers of mucus and a single layer of tightly interconnected epithelial cells supported by connective tissue and immune cells. ² Microbes colonize the loose, outer layer of colonic mucus, but are essentially excluded from the tight, epithelial-associated layer by host defenses. ³ The amount and composition of the mucus is calibrated based on microbial signals and loss of even a single component of this mixture can destabilize microbial biogeography and increase the risk of disease. ^4-7 However, the specific components of mucus, their molecular microbial targets, and how they work to contain the gut microbiota are still largely unknown. Here we show that high mobility group box 1 (HMGB1), the prototypical damage-associated molecular pattern molecule (DAMP), acts as an agent of host mucosal defense in the colon. HMGB1 in colonic mucus targets an evolutionarily conserved amino acid sequence found in bacterial adhesins, including the well-characterized Enterobacteriaceae adhesin FimH. HMGB1 aggregates bacteria and blocks adhesin-carbohydrate interactions, inhibiting invasion through colonic mucus and adhesion to host cells. Exposure to HMGB1 also suppresses bacterial expression of FimH. In ulcerative colitis, HMGB1 mucosal defense is compromised, leading to tissue-adherent bacteria expressing FimH. Our results demonstrate a new, physiologic role for extracellular HMGB1 that refines its functions as a DAMP to include direct, virulence limiting effects on bacteria. The amino acid sequence targeted by HMGB1 appears to be broadly utilized by bacterial adhesins, critical for virulence, and differentially expressed by bacteria in commensal versus pathogenic states. These characteristics suggest that this amino acid sequence is a novel microbial virulence determinant and could be used to develop new approaches to diagnosis and treatment of bacterial disease that precisely identify and target virulent microbes.

The postbiotic of hawthorn-probiotic ameliorating constipation caused by loperamide in elderly mice by regulating intestinal microecology

Background

Constipation is common gastrointestinal disorder with high prevalence and recurrence, making people suffering. However, the treatment for constipation remains ineffectual. We aimed to the study the effects and mechanisms of postbiotic of hawthorn-probiotic on loperamide modeled old KM mice.

Methods

Constipated mice were grouped and treated with 10% lactulose (Y), hawthorn group (S), probiotic group (F) and postbiotic of hawthorn-probiotic (FS). Fecal changes were observed. AQP3 and Enac-γ were measured by RT-qPCR and Western blotting, intestinal barrier by H&E and immunofluorescence staining, cell proliferation and apoptosis by CCK8 and flow cytometry. Gut microbiota was further determined by 16 s rRNA sequence of feces.

Results

Postbiotic of hawthorn-probiotic improved intestinal movement and pathomorphology, elevated AQP3, Enac-γ and mucin-2 expression, accompanied by decreased serum TNF-α and cell apoptosis, but increased proliferation. Furthermore, it modified the gut microbiota of constipated mice, featured by upregulation of Lactobacillaceae.

Conclusion

Postbiotic of hawthorn-probiotic relieved constipation by combined effects of regulating intestinal water and sodium metabolism, maintain intestinal barrier and gut microflora.

Graphical Abstract

Single-cell profiling reveals differences between human classical adenocarcinoma and mucinous adenocarcinoma

Colorectal cancer is a highly heterogeneous disease. Most colorectal cancers are classical adenocarcinoma, and mucinous adenocarcinoma is a unique histological subtype that is known to respond poorly to chemoradiotherapy. The difference in prognosis between mucinous adenocarcinoma and classical adenocarcinoma is controversial. Here, to gain insight into the differences between classical adenocarcinoma and mucinous adenocarcinoma, we analyse 7 surgical tumour samples from 4 classical adenocarcinoma and 3 mucinous adenocarcinoma patients by single-cell RNA sequencing. Our results indicate that mucinous adenocarcinoma cancer cells have goblet cell-like properties, and express high levels of goblet cell markers (REG4, SPINK4, FCGBP and MUC2) compared to classical adenocarcinoma cancer cells. TFF3 is essential for the transcriptional regulation of these molecules, and may cooperate with RPS4X to eventually lead to the mucinous adenocarcinoma mucus phenotype. The observed molecular characteristics may be critical in the specific biological behavior of mucinous adenocarcinoma.

Prebiotic oligofructose protects against high-fat diet-induced obesity by changing the gut microbiota, intestinal mucus production, glycosylation and secretion

Obesity is a major risk factor for the development of type 2 diabetes and cardiovascular diseases, and gut microbiota plays a key role in influencing the host energy homeostasis. Moreover, obese mice have a different gut microbiota composition, associated with an alteration of the intestinal mucus layer, which represents the interface between the bacteria and the host. We previously demonstrated that prebiotic treatment with oligofructose (FOS) counteracted the effects of diet-induced obesity, together with changes in the gut microbiota composition, but it is not known if the intestinal mucus layer could be involved. In this study, we found that, in addition to preventing high-fat diet (HFD) induced obesity in mice, the treatment with FOS increased the expression of numerous genes involved in mucus production, glycosylation and secretion, the expression of both secreted and transmembrane mucins, and the differentiation and number of goblet cells. These results were associated with significant changes in the gut microbiota composition, with FOS significantly increasing the relative and absolute abundance of the bacterial genera Odoribacter, Akkermansia, two unknown Muribaculaceae and an unknown Ruminococcaceae. Interestingly, all these bacterial genera had a negative association with metabolic parameters and a positive association with markers of the mucus layer. Our study shows that FOS treatment is able to prevent HFD-induced metabolic disorders, at least in part, by acting on all the processes of the mucus production. These data suggest that targeting the mucus and the gut microbiota by using prebiotics could help to prevent or mitigate obesity and related disorders.

Effect of In Ovo Trace Element Supplementation on Immune-Related Cells of the Small Intestine of Post-hatched Broiler Chicken

Pathological conditions and harmful drugs cause many gastrointestinal diseases in broiler chicken. The current study was conducted to investigate the effect of trace elements zinc (Zn) and selenium (Se) supplementation on histomorphology, immunological role, and functional activity of goblet cells (GCs) of the small intestine. The Alcian blue-periodic acid-Schiff (AB-PAS) was performed to assess the histomorphological changes in GCs, which revealed the regular dispersion with high electron density of GCs throughout the mucosal surface in the supplemented group. However, irregular dispersion with low electron density of GCs was present in the control group. The immunological functional role of GCs within the small intestine was examined by mucicarmine staining, immunohistochemistry, and immunofluorescence. The results showed a high mucin glycol protein secretion in the supplemented group, whereas limited mucin glycol protein secretion in the control group. Furthermore, the biological significance showed a high and low immunoreactivity of Muc2 and Muc13 in the supplemented and control groups, respectively. Immunofluorescence was used to confirm the immunosignaling of Muc2. Results revealed high immunosignaling of Muc2 at the apical part of the small intestine in the supplementation group, while low immunosignaling of Muc2 in the control group. Results suggest that trace element supplementation had significant effect on morphology and immunological role of GCs, which might be essential for immune function and health status of broiler chicken.

Reprogrammed fecal and mucosa-associated intestinal microbiota and weakened mucus layer in intestinal goblet cell- specific Piezo1-deficient mice

Dysfunction of the mucus layer allows commensal and pathogenic microorganisms to reach the intestinal epithelium, thereby leading to infection and inflammation. This barrier is synthesized and secreted by host goblet cells. Many factors that influence the function of goblet cells (GCs) have been studied. However, how the microenvironment surrounding GCs influences the mucus layer and microbiota of the colon is unclear. To explore the effect of GC Piezo1 on the mucus layer and microbiota in the colon, we generated an intestinal epithelial Piezo1 conditional knockout mouse model. The fecal-associated microbiota (FAM) and mucosa-associated microbiota (MAM) of the two groups were characterized based on amplicon sequencing of the 16S rRNA gene. Our results showed that GC Piezo1-/- mice developed decreased GC numbers, thinner mucus layer, and increased inflammatory cytokines (e.g., CXCL1, CXCL2, IL-6) on the 7th day. In addition, decreased Spdef and increased DOCK4 were discovered in KO mice. Meanwhile, the diversity and richness were increased in MAM and decreased in FAM in the GC Piezo1-/- group compared with the GC Piezo1+/+ group. We also observed increased abundances of Firmicutes and decreased abundances of Verrucomicrobiota and Actinobacteriota in the MAM of the GC Piezo1-/- group. Additionally, BugBase predicts that potentially pathogenic bacteria may have increased in the inner mucus layer, which is consistent with the higher abundance of Helicobacter hepaticus, Lactobacillus johnsonii, Escherichia-Shigella and Oscillospiraceae in MAM. These results further support the hypothesis that the role of Piezo1 in GCs is important for maintaining the function of the mucus layer and intestinal microbiota balance in the mouse colon.

Defects in the expression of colonic host defense factors associate with barrier dysfunction induced by a high-fat/high-cholesterol diet

The effect of Western diets in the gastrointestinal system is largely mediated by their ability to promote alterations in the immunity and physiology of the intestinal epithelium, and to affect the composition of the commensal microbiota. To investigate the response of the colonic epithelium to high-fat/high-cholesterol diets (HFHCDs), we evaluated the synthesis of host defense factors involved in the maintenance of the colonic homeostasis. C57BL/6 mice were fed an HFHCD for 3 weeks and their colons were evaluated for histopathology, gene expression, and microbiota composition. In addition, intestinal permeability and susceptibility to Citrobacter rodentium were also studied. HFHCD caused colonic hyperplasia, loss of goblet cells, thinning of the mucus layer, moderate changes in the composition of the intestinal microbiota, and an increase in intestinal permeability. Gene expression analyses revealed significant drops in the transcript levels of Muc1, Muc2, Agr2, Atoh1, Spdef, Ang4, Camp, Tff3, Dmbt1, Fcgbp, Saa3, and Retnlb. The goblet cell granules of HFHCD-fed mice were devoid of Relmβ and Tff3, indicating defective production of those two factors critical for intestinal epithelial defense and homeostasis. In correspondence with these defects, colonic bacteria were in close contact with, and invading the epithelium. Fecal shedding of C. rodentium showed an increased bacterial burden in HFHCD-fed animals accompanied by increased epithelial damage. Collectively, our results show that HFHCD perturbs the synthesis of colonic host defense factors, which associate with alterations in the commensal microbiota, the integrity of the intestinal barrier, and the host's susceptibility to enteric infections.

Evaluation of the Fecal Proteome in Healthy and Diseased Cheetahs (Acinonyx jubatus) Suffering from Gastrointestinal Disorders

Fecal proteomics allows for the identification of proteins and peptides present in stools and is useful in finding possible new biomarkers for diagnosing and/or monitoring gastrointestinal (GI) disorders. In the present study, we investigated the fecal proteome in healthy and diseased cheetahs (Acinonyx jubatus). Captive individuals of this species frequently show gastrointestinal disorders characterized by recurrent episodes of diarrhea, rare episodes of vomiting and weight loss, associated with Helicobacter spp. infection. Fecal proteomic evaluation has been performed by two-dimensional electrophoresis followed by liquid chromatography-tandem mass spectrometry. In healthy cheetahs, the results showed the presence of the following proteins: collagen alpha-1 (II) chain, transthyretin, IgG Fc-binding protein, titin, dystonin, isopentenyl-diphosphate Delta-isomerase 1, sodium/potassium-transporting ATPase subunit alpha-1 and protein disulfide-isomerase A6. The presence of albumin isoforms was found only in diseased cheetahs. The present paper reports the study of the fecal proteome in the cheetah, evidences some differences between healthy and diseased patients and confirms, once again, the potential of fecal proteomics for the study of the GI environment, with promising developments regarding the identification of new diagnostic/monitoring markers.

Role of the mucin-like glycoprotein FCGBP in mucosal immunity and cancer

IgGFc-binding protein (FCGBP) is a mucin first detected in the intestinal epithelium. It plays an important role in innate mucosal epithelial defense, tumor metastasis, and tumor immunity. FCGBP forms disulfide-linked heterodimers with mucin-2 and members of the trefoil factor family. These formed complexes inhibit bacterial attachment to mucosal surfaces, affect the motility of pathogens, and support their clearance. Altered FCGBP expression levels may be important in the pathologic processes of Crohn’s disease and ulcerative colitis. FCGBP is also involved in regulating the infiltration of immune cells into tumor microenvironments. Thus, the molecule is a valuable marker of tumor prognosis. This review summarizes the functional relevance and role of FCGBP in immune responses and disease development, and highlights the potential role in diagnosis and predicting tumor prognosis.

Dietary Inclusion of Dried Chicory Root Affects Cecal Mucosa Proteome of Nursery Pigs

Simple Summary

A well-balanced diet seems to play a key role in disease prevention and health promotion in young animals. Therefore, many attempts have been made to supplement feeds with novel nutritional components, with potential prebiotic capacity. It seems that chicory root fulfils those criteria as it contains high amounts of inulin-type fructans. Hence, the aim of the study was to determine the effect of dietary supplementation with 4% dried chicory root on the cecal mucosa proteome of piglets. It is shown that this feed additive may affect cellular metabolism in the cecal epithelium and may be beneficial for gut health.

Abstract

Prebiotics are known to have many beneficial effects on intestinal health by modulating the gut microbiota composition, thereby affecting epithelial cell proliferation and metabolism. This study had two aims: (1) to identify the protein constituents in the cecal mucosa of 50-day-old healthy (PIC × Penarlan P76) barrows, and (2) to assess the effects of 4% inclusion of dried chicory root in a cereal-based diet on the cecal mucosa proteome changes. Pigs (eight per group) were randomly allotted to the groups and were fed a control diet from the tenth day of life (C) or a diet supplemented with 4% of died chicory root (CR), for 40 days. At the age of 50 days, animals were sacrificed and cecal tissue samples were collected. It was found that feeding a CR diet significantly decreased the expression of 16 cecal mucosa proteins. Among them, fifteen proteins were down-regulated, while only one (KRT20) was shown to be up-regulated when compared to the C group. Dietary supplementation with CR caused down-expression of metabolism-associated proteins including enzymes involved in the process of glycolysis (G6PD, TPI1, ALDH9A1, CKMT1 and AKR1A1) as well as those engaged in transcriptional and translational activity (PRPF19, EEF1G) and several structural proteins (ACTR3, KRT77, CAP1 and actin). From our findings, it is possible to conclude that dietary chicory root at 4% had beneficial effects on the gut health of pigs as indicated by a changed abundance of certain cecal proteins such as KRT20, SERPINB1, HSP27, ANAXA2 and ANAXA4.

The function of gut microbiota in immune-related neurological disorders: a review

This review provides an overview of the importance of microbiota in the regulation of gut–brain communication in immune-related neurological disorders. The gastrointestinal (GI) tract hosts a diverse abundance of microbiota, referred to as gut microbiota. The gut microbiota plays a role in the maintenance of GI tract homeostasis and is likely to have multiple effects on brain development and function. The bidirectional communication between the gut microbiota and the brain is termed the microbiota–gut–brain axis. This communication between the intestine and the brain appears to affect human health and behavior, as certain animal studies have demonstrated the association between alterations in the gut microbiota and neurological disorders. Most insights about the microbiota–gut–brain axis come from germ-free animal models, which reveal the importance of gut microbiota in neural function. To date, many studies have observed the impact of the gut microbiota in patients with neurological disorders. Although many studies have investigated the microbiota–gut–brain axis, there are still limitations in translating this research to humans given the complexities of the relationship between the gut microbiota and the brain. In this review, we discuss emerging evidence of how the microbiota–gut–brain axis regulates brain development and function through biological networks, as well as the possible contribution of the microbiota–gut–brain axis in immune-related neurological disorders.

An Unexpected Alteration Colonic Mucus Appearance in the Constipation Model via an Intestinal Microenvironment

Due to the lack of research between the inner layers in the structure of colonic mucous and the metabolism of fatty acid in the constipation model, we aim to determine the changes in the mucous phenotype of the colonic glycocalyx and the microbial community structure following treatment with Rhubarb extract in our research. The constipation and treatment models are generated using adult male C57BL/6N mice. We perform light microscopy and transmission electron microscopy (TEM) to detect a Muc2-rich inner mucus layer attached to mice colon under different conditions. In addition, 16S rDNA sequencing is performed to examine the intestinal flora. According to TEM images, we demonstrate that Rhubarb can promote mucin secretion and find direct evidence of dendritic structure-linked mucus structures with its assembly into a lamellar network in a pore size distribution in the isolated colon section. Moreover, the diversity of intestinal flora has noticeable changes in constipated mice. The present study characterizes a dendritic structure and persistent cross-links have significant changes accompanied by the alteration of intestinal flora in feces in models of constipation and pretreatment with Rhubarb extract.

Enhanced therapeutic effect on colitis with powder formulations of Painong San associated with the promotion of intestinal adhesion and absorption

ETHNOPHARMACOLOGICAL RELEVANCE

Painong San is a prescription composed of traditional Chinese medicine, which has been used to treat colitis. The Painong San's usage recorded in "Jingui Yaolve" by Zhongjing Zhang in the Later Han Dynasty is powder. However, the decoction is often used in reality. It's unclear which dosage form of Painong San is more suitable for colitis treatment and why?

AIM OF THE STUDY

This study aims to evaluate the different therapeutic effects of Painong San (a powder of Painong San) and Painong Decoction (a decoction of Painong San) on a dextran sulfate sodium salt-induced colitis model and the possible reasons of these different effects.

MATERIALS AND METHODS

The contents of paeoniflorin, naringin, heperidin and neohesperidin in Painong San and Painong decoction were determined by an ultra-performance liquid chromatography system. The therapeutic effect on colitis was evaluated by intragastric administration of Painong San or Painong Decoction in dextran sulfate sodium salt-induced mouse model. The accumulated release rate of Painong San in vitro was analyzed with artificial gastric juice, artificial intestinal juice, and artificial colon juice. The concentrations of four compounds in the blood, intestinal contents, and intestinal fluids were detected by an-ultra performance liquid chromatography-tandem quadrupole mass spectrometry system. In situ intestinal perfusion experiments were used to observe the adhesion of Painong San to the intestine's surface. The expression of Mucin-2 and Trefoil Factor 3 in the colon was studied by immunohistochemistry.

RESULTS

There was no significant difference in the contents of the four compounds in Painong San and Painong Decoction. In vivo, Painong San has a better therapeutic effect than Painong Decoction in the treatment of colitis. Painong San could be released slowly in the simulated human digestion environment in vitro, and more Painong San particles were released on the intestinal surface in the colitis state in the healthy state. Painong San could increase the bioavailability of hesperidin and neohesperidin, and their concentrations in local intestinal tissue, intestinal fluid and intestinal contents. The expression of trefoil Factor 3 protein on the surface of the colon tended to be in the intestinal cavity and overlapped with the expression of mucin-2. Trefoil Factor 3 accumulates in the intestinal cavity of the colon in the state of colitis, which may increase the adhesion of Painong San particles.

CONCLUSION

In conclusion, this experiment proved that Painong San is a more suitable dosage form for the treatment of dextran sulfate sodium salt-induced colitis than Painong Decoction, which may be related to the enhancement of Painong San particle adhesion to the intestine in colitis. This study provides a reference for the selection of clinical dosage forms for traditional Chinese medicine.

Mucus, commensals, and the immune system

The immune system in the large intestine is separated from commensal microbes and comparatively rare enteric pathogens by a monolayer of diverse epithelial cells overlaid with a compact and adherent inner mucus layer and a looser outer mucus layer. Microorganisms, collectively referred to as the mucus-associated (MA) microbiota, physically inhabit this mucus barrier, resulting in a dynamic and incessant dialog to maintain both spatial segregation and immune tolerance. Recent major findings reveal novel features of the crosstalk between the immune system and mucus-associated bacteria in health and disease, as well as disease-related peripheral immune signatures indicative of host responses to these organisms. In this brief review, we integrate these novel observations into our overall understanding of host-microbiota mutualism at the colonic mucosal border and speculate on the significance of this emerging knowledge for our understanding of the prevention, development, and progression of chronic intestinal inflammation.

The Role and Function of Mucins and Its Relationship to Inflammatory Bowel Disease

Mucus is present throughout the gastrointestinal tract and is essential for regulating gut microbiota homeostasis and preventing disease by protecting the gastrointestinal barrier from microorganisms, pathogens and toxins or other irritants. Mucin (MUC)-2 is a secreted protein produced by epithelial goblet cells as the main component of mucus. Defects in the gastrointestinal tract, such as inflammation and ulcers, cause damage to the mucus barrier, which can worsen mucus quality and reduce mucus production. Therefore, we would like to review the characteristics of MUC2 and its role in intestinal disorders and highlight the importance of further studies. We also investigated whether the role of MUC2 differs between children and adults, ulcerative colitis (UC) and Crohn's disease (CD).

EPA and DHA differentially coordinate the crosstalk between host and gut microbiota and block DSS-induced colitis in mice by a reinforced colonic mucus barrier

Background: Ulcerative colitis (UC) is a chronic inflammatory disorder of the colon with a continuously remitting and relapsing course. Its etiology is closely related to abnormal interactions between host and gut microbiota. The mucus barrier lining the gastrointestinal tract is necessary to coordinate host and gut microbiota interaction by nourishing and modulating the microbiota. Differential effects of the anti-inflammatory fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) on UC progression in mice were firstly addressed by our previous work; here, the mechanism for their respective effects were further uncovered from host-microbiome crosstalk based on mucus barrier modulation to pave the way for UC therapy. Methods: Assessment of the disease activity index and histopathology score was conducted in mice with dextran sodium sulfate (DSS)-induced colitis pre-treated with different doses of EPA and DHA. Mucin generation, glycosylation and secretion were evaluated by a combination of electron microscopy, specific mucous staining, and qPCR. Western blotting was used to analyze the underlying molecular events. Fecal short chain fatty acids were detected using gas chromatography, and the gut microbial composition was analyzed using 16S rRNA sequencing. Results: Compared with DHA, the more potent inhibitory effect of high dose EPA on DSS-induced colitis was reconfirmed, which was underlain by a reinforced mucus layer as indicated by increased mucin granule release, mucus layer stratification and markedly upregulated expression of the key modulators involved in goblet cell differentiation. In turn a remarkably enhanced mucus barrier in the EPA group functioned to modulate the gut microbiome, as demonstrated by the enriched abundance of the phylum Bacteroidetes and mucin-degrading bacterium Akkermansia muciniphila producing acetic and propionic acids. Conclusions: EPA and DHA differentially coordinate the interaction between the host and the gut microbiota and relieve mucus barrier disruption in DSS-induced colitis. EPA may develop into a promising adjunctive therapy for UC.

The barrier and beyond: Roles of intestinal mucus and mucin-type O-glycosylation in resistance and tolerance defense strategies guiding host-microbe symbiosis

Over the past two decades, our appreciation of the gut mucus has moved from a static lubricant to a dynamic and essential component of the gut ecosystem that not only mediates the interface between host tissues and vast microbiota, but regulates how this ecosystem functions to promote mutualistic symbioses and protect from microbe-driven diseases. By delving into the complex chemistry and biology of the mucus, combined with innovative in vivo and ex vivo approaches, recent studies have revealed novel insights into the formation and function of the mucus system, the O-glycans that make up this system, and how they mediate two major host-defense strategies - resistance and tolerance - to reduce damage caused by indigenous microbes and opportunistic pathogens. This current review summarizes these findings by highlighting the emerging roles of mucus and mucin-type O-glycans in influencing host and microbial physiology with an emphasis on host defense strategies against bacteria in the gastrointestinal tract.

Mucus sialylation determines intestinal host-commensal homeostasis

Intestinal mucus forms the first line of defense against bacterial invasion while providing nutrition to support microbial symbiosis. How the host controls mucus barrier integrity and commensalism is unclear. We show that terminal sialylation of glycans on intestinal mucus by ST6GALNAC1 (ST6), the dominant sialyltransferase specifically expressed in goblet cells and induced by microbial pathogen-associated molecular patterns, is essential for mucus integrity and protecting against excessive bacterial proteolytic degradation. Glycoproteomic profiling and biochemical analysis of ST6 mutations identified in patients show that decreased sialylation causes defective mucus proteins and congenital inflammatory bowel disease (IBD). Mice harboring a patient ST6 mutation have compromised mucus barriers, dysbiosis, and susceptibility to intestinal inflammation. Based on our understanding of the ST6 regulatory network, we show that treatment with sialylated mucin or a Foxo3 inhibitor can ameliorate IBD.

Assessment of source material for human intestinal organoid culture for research and clinical use

Objective

Human intestinal organoids (hIOs) have potential as a model for investigating intestinal diseases. The hIO system faces logistic challenges including limited access to biopsies or low expression of epithelial cell types. Previous research identified the feasibility of tissue from the transverse (TC) or sigmoid colon (SC), or from cryopreserved biopsies from regions of the gastrointestinal tract. We aimed to create a protocol for robust hIO generation that could be implemented across multiple centres, allowing for development of a consistent biobank of hIOs from diverse patients.

Results

TC and SC hIOs were expanded from fresh or frozen biopsies with standard or refined media. The expression of epithelial cells was evaluated via PCR. Growth of TC and SC hIO from healthy donors was reproducible from freshly acquired and frozen biopsies. A refined media including insulin-like growth factor (IGF)-1 and fibroblast growth factor (FGF)-2 enabled the expression of epithelial cells, including higher expression of goblet cells and enterocytes compared to standard organoid media. We identified a consistent time point where hIOs generated from frozen biopsies reflect similar hIO composition from freshly acquired samples. Feasibility of hIOs as a tool for research and clinical use, including the use of frozen biopsies, was demonstrated.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-022-05925-4.

GPR120 prevents colorectal adenocarcinoma progression by sustaining the mucosal barrier integrity

GPR120 (encoded by FFAR4 gene) is a receptor for long chain fatty acids, activated by ω-3 Polyunsaturated Fatty Acids (PUFAs), and expressed in many cell types. Its role in the context of colorectal cancer (CRC) is still puzzling with many controversial evidences. Here, we explored the involvement of epithelial GPR120 in the CRC development. Both in vitro and in vivo experiments were conducted to mimic the conditional deletion of the receptor from gut epithelium. Intestinal permeability and integrity of mucus layer were assessed by using Evans blue dye and immunofluorescence for MUC-2 protein, respectively. Microbiota composition, presence of lipid mediators and short chain fatty acids were analyzed in the stools of conditional GPR120 and wild type (WT) mice. Incidence and grade of tumors were evaluated in all groups of mice before and after colitis-associated cancer. Finally, GPR120 expression was analyzed in 9 human normal tissues, 9 adenomas, and 17 primary adenocarcinomas. Our work for the first time highlights the role of the receptor in the progression of colorectal cancer. We observed that the loss of epithelial GPR120 in the gut results into increased intestinal permeability, microbiota translocation and dysbiosis, which turns into hyperproliferation of epithelial cells, likely through the activation of β -catenin signaling. Therefore, the loss of GPR120 represents an early event of CRC, but avoid its progression as invasive cancer. these results demonstrate that the epithelial GPR120 receptor is essential to maintain the mucosal barrier integrity and to prevent CRC developing. Therefore, our data pave the way to GPR120 as an useful marker for the phenotypic characterization of CRC lesions and as new potential target for CRC prevention.

Mucin-Type O-Glycans: Barrier, Microbiota, and Immune Anchors in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), which affects about 7 million people globally, is a chronic inflammatory condition of the gastrointestinal tract caused by gut microbiota alterations, immune dysregulation, and genetic and environmental factors. The association of microbial and immune molecules with mucin-type O-glycans has been increasingly noticed by researchers. Mucin is the main component of mucus, which forms a protective barrier between the microbiota and immune cells in the colon. Mucin-type O-glycans alter the diversity of gastrointestinal microorganisms, which in turn increases the level of O-glycosylation of host intestinal proteins via the utilization of glycans. Additionally, alterations in mucin-type O-glycans not only increase the activity and stability of immune cells but are also involved in the maintenance of intestinal mucosal immune tolerance. Although there is accumulating evidence indicating that mucin-type O-glycans play an important role in IBD, there is limited literature that integrates available data to present a complete picture of exactly how O-glycans affect IBD. This review emphasizes the roles of the mucin-type O-glycans in IBD. This seeks to provide a better understanding and encourages future studies on IBD glycosylation and the design of novel glycan-inspired therapies for IBD.

Uncovering potential single nucleotide polymorphisms, copy number variations and related signaling pathways in primary Sjogren's syndrome

Primary Sjogren’s syndrome (pSS) is a complex systemic autoimmune disease, which is difficult to accurately diagnose due to symptom diversity in patients, especially at earlier stages. We tried to find potential single nucleotide polymorphisms (SNPs), copy number variations (CNVs) and related signaling pathways. Genomic DNA was extracted from peripheral blood of 12 individuals (7 individuals from 3 pSS pedigrees and 5 sporadic cases) for whole-exome sequencing (WES) analysis. SNPs and CNVs were identified, followed by functional annotation of genes with SNPs and CNVs. Gene expression profile (involving 64 normal controls and 166 cases) was downloaded from the Gene Expression Omnibus database (GEO) dataset for differentially expression analysis. Sanger sequencing and in vitro validation was used to validate the identified SNPs and differentially expressed genes, respectively. A total of 5 SNPs were identified in both pedigrees and sporadic cases, such as FES, PPM1J, and TRAPPC9. A total of 3402 and 19 CNVs were identified in pedigrees and sporadic cases, respectively. Fifty-one differentially expressed genes were associated with immunity, such as BATF3, LAP3, BATF2, PARP9, and IL15RA. AMPK signaling pathway and cell adhesion molecules (CAMs) were the most significantly enriched signaling pathways of identified SNPs. Identified CNVs were associated with systemic lupus erythematosus, mineral absorption, and HTLV-I infection. IL2-STAT5 signaling, interferon-gamma response, and interferon-alpha response were significantly enriched immune related signaling pathways of identified differentially expressed genes. In conclusion, our study found some potential SNPs, CNVs, and related signaling pathways, which could be useful in understanding the pathological mechanism of pSS.

Akkermansia muciniphila and host interaction within the intestinal tract

In the modern world, metabolic syndrome is one of the major health problems. Heredity, overeating, and a sedentary lifestyle are believed to be the main predisposing factors for its development. However, recent data indicate that gut microbiota plays a significant role in metabolic profile formation. In 2004, Derrien et al. isolated and characterized the bacterium Akkermansia muciniphila, which lives mainly in the human intestine and has the ability to utilize intestinal mucin. It proved to be a good candidate for the role of a new-generation probiotic due to its ability to improve the laboratory and physical indicators associated with metabolic syndrome and type 2 diabetes in mice and humans. In this review, we describe the basic microbiological characteristics of this bacterium, its main habitats, clinical effects after oral administration, and different ways of influencing the digestive tract. All these data allow us to understand the mechanism of its beneficial effects, which is important for its future introduction into the treatment of the metabolic syndrome.

Intestinal goblet cells sample and deliver lumenal antigens by regulated endocytic uptake and transcytosis

Intestinal goblet cells maintain the protective epithelial barrier through mucus secretion and yet sample lumenal substances for immune processing through formation of goblet cell associated antigen passages (GAPs). The cellular biology of GAPs and how these divergent processes are balanced and regulated by goblet cells remains unknown. Using high-resolution light and electron microscopy, we found that in mice, GAPs were formed by an acetylcholine (ACh)-dependent endocytic event remarkable for delivery of fluid-phase cargo retrograde into the trans-golgi network and across the cell by transcytosis - in addition to the expected transport of fluid-phase cargo by endosomes to multi-vesicular bodies and lysosomes. While ACh also induced goblet cells to secrete mucins, ACh-induced GAP formation and mucin secretion were functionally independent and mediated by different receptors and signaling pathways, enabling goblet cells to differentially regulate these processes to accommodate the dynamically changing demands of the mucosal environment for barrier maintenance and sampling of lumenal substances.

Clinicopathological and Fecal Proteome Evaluations in 16 Dogs Presenting Chronic Diarrhea Associated with Lymphangiectasia

Canine intestinal lymphangiectasia (IL) is a condition characterized by variably severe gastrointestinal signs, frequently associated with laboratory abnormalities; the research for markers allowing a better understanding of the severity degree and/or obtaining an early diagnosis and/or monitoring is continuously progressing. In the present study, we investigated possible new diagnostic/follow-up markers in IL dogs, namely, serum C-reactive protein, serum bacterial lipopolysaccharide, serum cleaved cytokeratin 18, serum citrulline, and zonulin (in both serum and feces). A fecal proteomic study looking for possible confirmation and/or new marker candidates was also performed. All markers in both substrates, with the exception of serum citrulline, significantly differed between diseased and control dogs. Fecal proteomics allowed the retrieval of three proteins in IL dogs (Fc fragment of IgG-binding protein; transthyretin; proproteinase E) that were not previously found in clinically healthy subjects. Although further studies are needed, C-reactive protein, bacterial lipopolysaccharide, cleaved cytokeratin 18, and zonulin (in both serum and feces) resulted as promising markers for canine IL; similarly, fecal proteomics represents a road worthy of being pursued in the search for candidate biomarkers.

Neglected roles of IgG Fc-binding protein secreted from airway mucin-producing cells in protecting against SARS-CoV-2 infection

Both innate immunity and acquired immunity are involved in severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. The induction of Abs that neutralize the virus has been described, and certain Abs against endemic coronaviruses may cross-react with SARS-CoV-2. Detailed mechanisms to protect against the pandemic of SARS-CoV-2 remain unresolved. We previously reported that IgG Fc-binding protein (Fcγbp), a unique, large molecular weight, and mucin-like secretory Fc receptor protein, secreted from goblet cells of human small and large intestine, mediates the transportation of serum IgG onto the mucosal surface. In this review, we show that mucous bronchial gland cells and some goblet cells are immunoreactive for Fcγbp. Fcγbp traps the cross-reactive (both neutralizing and non-neutralizing) IgG bound to the virus and can consequently eliminate the virus from the mucosal surface to decrease viral loads. Fcγbp can also suppress immune overreaction by interfering with Fc-binding by macrophages and competing with complement fixation. Fcγbp secreted from mucin-producing cells of the airway functions as an important anti-infection mucosal defense. The Fcγbp-mediated mechanism can be a key factor in explaining why SARS-CoV-2 is less infective/lethal in children, and may also be involved in the unique Ab response, recurrent infection, and effects of serum therapy and vaccination.

High-resolution serum proteome trajectories in COVID-19 reveal patient-specific seroconversion

A deeper understanding of COVID-19 on human molecular pathophysiology is urgently needed as a foundation for the discovery of new biomarkers and therapeutic targets. Here we applied mass spectrometry (MS)-based proteomics to measure serum proteomes of COVID-19 patients and symptomatic, but PCR-negative controls, in a time-resolved manner. In 262 controls and 458 longitudinal samples of 31 patients, hospitalized for COVID-19, a remarkable 26% of proteins changed significantly. Bioinformatics analyses revealed co-regulated groups and shared biological functions. Proteins of the innate immune system such as CRP, SAA1, CD14, LBP, and LGALS3BP decreased early in the time course. Regulators of coagulation (APOH, FN1, HRG, KNG1, PLG) and lipid homeostasis (APOA1, APOC1, APOC2, APOC3, PON1) increased over the course of the disease. A global correlation map provides a system-wide functional association between proteins, biological processes, and clinical chemistry parameters. Importantly, five SARS-CoV-2 immunoassays against antibodies revealed excellent correlations with an extensive range of immunoglobulin regions, which were quantified by MS-based proteomics. The high-resolution profile of all immunoglobulin regions showed individual-specific differences and commonalities of potential pathophysiological relevance.

Expression profiling of ileal mucosa in asthma reveals upregulation of innate immunity and genes characteristic of Paneth and goblet cells

Background

The expression profiles of the intestinal mucosa have not been comprehensively investigated in asthma. We aimed to explore this in the Correlated Expression and Disease Association Research (CEDAR) patient cohort.

Methods

Differential expression analysis of ileal, transverse colon, and rectal biopsies were supplemented by a comparison of transcriptomes from platelets and leukocytes subsets, including CD4+, CD8+, CD14+, CD15+, and CD19+ cells. Asthma patients (n = 15) and controls (n = 15) had similar age (p = 0.967), body mass index (p = 0.870), similar numbers of females (80%) and smoking rates (13.3%).

Results

Significant differential expression was found in the ileum alone, and not in any other cell/tissue types. More genes were found to be overexpressed (1,150) than under-expressed (380). The most overexpressed genes included Fc Fragment of IgG Binding Protein (FCGBP, logFC = 3.01, pFDR = 0.015), Mucin 2 (MUC2, logFC = 2.78, pFDR = 0.015), and Alpha 1B Defensin (DEFA1B, logFC = 2.73, pFDR = 0.024). Gene ontology implicated the immune system, including interleukins 4 and 13, as well as antimicrobial peptides in this overexpression. There was concordance of gene over- (STAT1, XBP1) and underexpression (NELF, RARA) in asthma and Crohn’s disease ileum when our results were compared to another dataset (p = 3.66 × 10^–7).

Conclusion

Ileal mucosa in asthma exhibits a specific transcriptomic profile, which includes the overexpression of innate immune genes, mostly characteristic of Paneth and goblet cells, in addition to other changes that may resemble Crohn’s disease.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13223-021-00584-9.

Proteomics study of Mycoplasma pneumoniae pneumonia reveals the Fc fragment of the IgG-binding protein as a serum biomarker and implicates potential therapeutic targets

Macrolide and corticosteroid resistance has been reported in patients with Mycoplasma pneumoniae (MP) pneumonia (MPP). MP clearance is difficult to achieve through antibiotic treatment in sensitive patients with severe MPP (SMPP). SMPP in children might progress to airway remodeling and even bronchiolitis/bronchitis obliterans. Therefore, identifying serum biomarkers that indicate MPP progression and exploring new targeted drugs for SMPP treatment require urgency. In this study, serum samples were collected from patients with general MPP (GMPP) and SMPP to conduct proteomics profiling. The Fc fragment of the IgG-binding protein (FCGBP) was identified as the most promising indicator of SMPP. Biological enrichment analysis indicated uncontrolled inflammation in SMPP. ELISA results proved that the FCGBP level in patients with SMPP was substantially higher than that in patients with GMPP. Furthermore, the FCGBP levels showed a decreasing trend in patients with GMPP but the opposite trend in patients with SMPP during disease progression. Connectivity map analyses identified 25 possible targeted drugs for SMPP treatment. Among them, a mechanistic target of rapamycin kinase (mTOR) inhibitor, which is a macrolide compound and a cell proliferation inhibitor, was the most promising candidate for targeting SMPP. To our knowledge, this study was the first proteomics-based characterization of patients with SMPP and GMPP.

At the right time in the right place: How do luminal gradients position the microbiota along the gut?

The gastrointestinal system is highly compartmentalized, where individual segments perform separate tasks to achieve common physiological goals. The gut luminal content, chyme, changes its chemical and physical properties as it passes through different intestinal segments. Together, the chyme composition, mucus, pH and oxygen gradients along the gut create a variety of highly distinct ecological niches that form, maintain and reinforce the symbiosis with the particular microbiota. Hosting different microbiota members at specific locations creates one of the most complex and sophisticated gradient - gradient of the local ecosystems that live and interact with each other, providing advantages and challenges to the host and creating our microbial self. Here, we discuss how intestinal luminal gradients are created and maintained in homeostasis, their role in a correct microbiota positioning, and their change upon inflammation and cancer.

The IgGFc-binding protein FCGBP is secreted with all GDPH sequences cleaved but maintained by interfragment disulfide bonds

Mucus forms an important protective barrier that minimizes bacterial contact with the colonic epithelium. Intestinal mucus is organized in a complex network with several specific proteins, including the mucin-2 (MUC2) and the abundant IgGFc-binding protein, FCGBP. FCGBP is expressed in all intestinal goblet cells and is secreted into the mucus. It is comprised of repeated von Willebrand D (vWD) domain assemblies, most of which have a GDPH amino acid sequence that can be autocatalytically cleaved, as previously observed in the mucins MUC2 and mucin-5AC. However, the functions of FCGBP in the mucus are not understood. We show that all vWD domains of FCGBP with a GDPH sequence are cleaved and that these cleavages occur early during biosynthesis in the endoplasmic reticulum. All cleaved fragments, however, remain connected via a disulfide bond within each vWD domain. This cleavage generates a C-terminal-reactive Asp-anhydride that could react with other molecules, such as MUC2, but this was not observed. Quantitative analyses by MS showed that FCGBP was mainly soluble in chaotropic solutions, whereas MUC2 was insoluble, and most of the secreted FCGBP was not covalently bound to MUC2. Although FCGBP has been suggested to bind immunoglobulin G, we were unable to reproduce this binding in vitro using purified proteins. In conclusion, while the function of FCGBP is still unknown, our results suggest that it does not contribute to covalent crosslinking in the mucus, nor incorporate immunoglobulin G into mucus, instead the single disulfide bond linking each fragment could mediate controlled dissociation.

Hydrogen Sulfide Oxidation by Sulfide Quinone Oxidoreductase

Hydrogen sulfide (H2 S) is an environmental toxin and a heritage of ancient microbial metabolism that has stimulated new interest following its discovery as a neuromodulator. While many physiological responses have been attributed to low H2 S levels, higher levels inhibit complex IV in the electron transport chain. To prevent respiratory poisoning, a dedicated set of enzymes that make up the mitochondrial sulfide oxidation pathway exists to clear H2 S. The committed step in this pathway is catalyzed by sulfide quinone oxidoreductase (SQOR), which couples sulfide oxidation to coenzyme Q10 reduction in the electron transport chain. The SQOR reaction prevents H2 S accumulation and generates highly reactive persulfide species as products; these can be further oxidized or can modify cysteine residues in proteins by persulfidation. Here, we review the kinetic and structural characteristics of human SQOR, and how its unconventional redox cofactor configuration and substrate promiscuity lead to sulfide clearance and potentially expand the signaling potential of H2 S. This dual role of SQOR makes it a promising target for H2 S-based therapeutics.

Features of intestinal microbiota disorders in the development of metabolic disorders in non-alcoholic fatty liver disease

We discussed about the term intestinal permeability like as the mucosal barrier a single structural and functional conception that includes the layer of mucus, the indigenous microbiota and the epithelium of the mucosa in this publication. Information was presented about the role of the microbiota, the composition of intestinal mucus, epithelial cells and proteins of tight junctions which lead to various metabolic diseases. The complex pathogenetic interactions are formed between the intestinal mucosal barrier, metabolic disorders such as non-alcoholic fatty liver disease and cardiovascular diseases. The complex researches and modification of this interactions will allow to create personalized approaches and to prevent of these diseases.

IgG Fc Binding Protein (FCGBP) is Down-Regulated in Metastatic Lesions and Predicts Survival in Metastatic Colorectal Cancer Patients

Background

The liver is the most frequent site for metastatic spread in colorectal cancer (CRC) patients, and these patients have much poorer prognosis than those without metastasis. Previous studies have shown that IgG Fc binding protein (FCGBP) plays important roles in tumorigenesis, progression, and prognosis, but its role in CRC metastasis remains unclear.

Purpose

In this study, we are aimed to explore the significance of FCGBP in liver metastatic CRC (LMCRC) patients.

Methods

We analyzed the expression of FCGBP RNA between CRC primary samples and liver metastatic samples in the Gene Expression Omnibus (GEO) database and The Cancer Genome Atlas (TCGA). Next, we assessed the expression of FCGBP protein in 135 paired primary CRC (PC) samples and LMCRC samples. Finally, we explored the relationship between the expression features and clinicopathological characteristics.

Results

The expression data of FCGBP were obtained from the GEO and TCGA databases. FCGBP RNA expression was evaluated between primary lesions (PC) and liver metastatic lesions (LM). FCGBP RNA was down-regulated in PC and LM, and especially lower in LM (p<0.001). Next, the expression of FCGBP protein was evaluated by an immunohistochemistry array in 135 paired primary tumor tissues and metastatic tissues. We found that FCGBP protein was down-regulated in primary lesions and metastatic lesions, especially in metastatic lesions. According to the immunohistochemistry score (SI), each cohort was divided into FCGBP-positive (SI=4–12) and FCGBP-negative (SI=0–3) groups. In both groups, the levels of CEA (PC group, 3.880 vs 77.049, p<0.001; LM group, 3.890 vs 14.239, p=0.008) and CA19-9 (PC group, 8.610 vs 111.700, p<0.001; LM group, 7.660 vs 19.380, p=0.037) were lower than those in the FCGBP-negative group. FCGBP positivity in the LM cohort was an independent risk factor in both overall survival (HR 1.573, 95% Cl [1.017–2.433], p=0.042) and disease-free survival (HR 1.869, 95% Cl [1.256–2.781], p=0.002).

Conclusion

This study found a relationship between FCGBP expression and clinical information of LMCRC patients, and found that FCGBP expression decreased with disease development. The expression of FCGBP in liver metastasis is associated with both the overall and progression-free survival. Our results show that FCGBP could be a promising prognostic factor for LMCRC.