The gastrointestinal mucus system in health and disease

Development of a Caco-2-based intestinal mucosal model to study intestinal barrier properties and bacteria-mucus interactions

The intestinal mucosal barrier is a dynamic system that allows nutrient uptake, stimulates healthy microbe-host interactions, and prevents invasion by pathogens. The mucosa consists of epithelial cells connected by cellular junctions that regulate the passage of nutrients covered by a mucus layer that plays an important role in host-microbiome interactions. Mimicking the intestinal mucosa for in vitro assays, particularly the generation of a mucus layer, has proven to be challenging. The intestinal cell-line Caco-2 is widely used in academic and industrial laboratories due to its capacity to polarize, form an apical brush border, and reproducibly grow into confluent cell layers in different culture systems. However, under normal culture conditions, Caco-2 cultures lack a mucus layer. Here, we demonstrate for the first time that Caco-2 cultures can form a robust mucus layer when cultured under air-liquid interface (ALI) conditions on Transwell inserts with addition of vasointestinal peptide (VIP) in the basolateral compartment. We demonstrate that unique gene clusters are regulated in response to ALI and VIP single stimuli, but the ALI-VIP combination treatment resulted in a significant upregulation of multiple mucin genes and proteins, including secreted MUC2 and transmembrane mucins MUC13 and MUC17. Expression of tight junction proteins was significantly altered in the ALI-VIP condition, leading to increased permeability to small molecules. Commensal Lactiplantibacillus plantarum bacteria closely associated with the Caco-2 mucus layer and differentially colonized the surface of the ALI cultures. Pathogenic Salmonella enterica were capable of invading beyond the mucus layer and brush border. In conclusion, Caco-2 ALI-VIP cultures provide an accessible and straightforward way to culture an in vitro intestinal mucosal model with improved biomimetic features. This novel in vitro intestinal model can facilitate studies into mucus and epithelial barrier functions and in-depth molecular characterization of pathogenic and commensal microbe-mucus interactions.

Advances in the acting mechanism and treatment of gut microbiota in metabolic dysfunction-associated steatotic liver disease

Metabolic Dysfunction-Associated Steatotic Liver Disease(MASLD) is increasing in prevalence worldwide and has become the greatest potential risk for cirrhosis and hepatocellular liver cancer. Currently, the role of gut microbiota in the development of MASLD has become a research hotspot. The development of MASLD can affect the homeostasis of gut microbiota, and significant changes in the composition or abundance of gut microbiota and its metabolite abnormalities can influence disease progression. The regulation of gut microbiota is an important strategy and novel target for the treatment of MASLD with good prospects. In this paper, we summarize the role of gut microbiota and its metabolites in the pathogenesis of MASLD, and describe the potential preventive and therapeutic efficacy of gut microbiota as a noninvasive marker to regulate the pathogenesis of MASLD based on the "gut-hepatic axis", which will provide new therapeutic ideas for the clinic.

Effect of hypoxia on the mucus system and intragastric microecology in the gastrointestinal tract

Digestive diseases have a high incidence worldwide, with various geographic, age, and gender factors influencing the occurrence and development of the diseases. The main etiologic factors involve genetics, environment, lifestyle, and dietary habits. In a low-oxygen environment, however, the body's tissue cells activate hypoxia-inducible factor (HIF), which produces different inflammatory mediators. Hypoxia impacts health at the molecular level by modulating cellular stress responses, metabolic pathways, and immune functions. It also alters gene expression and cellular behavior, thereby affecting gastrointestinal function. Under normal physiological conditions, the gastrointestinal mucus system serves as a crucial protective barrier, defending against mechanical injury, pathogenic invasion, and exposure to harmful chemicals. The integrity and functionality of this barrier are dependent on the synthesis and regulation of mucins and mucus, which are influenced by multiple factors. Additionally, the composition and diversity of the gastric microbiota are shaped by factors such as Helicobacter pylori infection, diet, and lifestyle. A balanced gastric microbiota supports gastrointestinal health and fortifies the mucus barrier. However, hypoxia can disrupt this equilibrium, leading to inflammation, alterations in the mucus layer, and destabilization of the gastric microbiota. Understanding the interplay between hypoxia, the mucus system, and the gastric microbiota is essential for identifying novel therapeutic strategies. Future research should elucidate the mechanisms through which hypoxia influences these systems and develop interventions to mitigate its adverse effects on gastrointestinal health. We examined the impact of hypoxia on the gastrointestinal mucus system and gastric microbiota, highlighting its implications for human health and potential therapeutic approaches.

Clca1 deficiency exacerbates colitis susceptibility via impairment of mucus barrier integrity and gut microbiota homeostasis

The intestinal mucus barrier has emerged as a promising therapeutic target for inflammatory bowel disease. Understanding its regulatory mechanisms is critical for elucidating ulcerative colitis (UC) pathogenesis, improving diagnostics, guiding treatments, and preventing relapse. Chloride Channel Accessory 1 (Clca1), a constituent of the mucus layer, remains understudied in colitis. Here, we investigated Clca1's role in mucosal immunity and intestinal homeostasis using experimental colitis models. Clca1-deficient (Clca1-/-) mice displayed compromised mucus layer integrity, reduced neutrophil infiltration, and gut microbiota dysbiosis. Notably, Clca1-/- mice exhibited exacerbated colitis severity following dextran sulfate sodium (DSS) challenge, accompanied by a diminished goblet cell populations. Fecal microbiota transplantation (FMT) studies revealed that gut microbiota critically modulates divergent phenotypic outcomes between genotypes. Our findings establish Clca1 as a multifunctional regulator of mucus barrier integrity through mechanisms involving goblet cell maintenance, neutrophil-mediated immunity, and host-microbiota crosstalk. These results advance the understanding of UC pathogenesis and identify Clca1-associated pathways as potential targets for barrier restoration therapies.

Microrheology of gel-forming airway mucins isolated from porcine trachea

Mucus produced in the lungs has important protective barrier functions that strongly depend on its biomolecular composition, biopolymer network architecture, and viscoelastic properties. However, to date, there has yet to be a readily available source of reconstituted, gel-forming mucins from the lungs to model and study its biophysical properties. To address this, we established an in-house procedure to extract airway mucins from pig trachea with minimal DNA contamination consisting of ∼70% by weight protein. Particle tracking microrheology was used to evaluate the biophysical properties of porcine trachea mucins for comparison to other reconstituted mucin and native mucus gels. At an ionic strength and pH reflective of conditions in the lungs, we found that porcine tracheal mucins formed a tighter mesh network and possessed a significantly greater microviscosity compared to mucins extracted from the porcine small intestine. In comparison to mucus harvested from human airway tissue cultures, we found that porcine tracheal mucins also possessed a greater microviscosity, suggesting that these mucins can form into a gel at physiological total solid concentrations.

Mucosal immune responses and intestinal microbiome associations in wild spotted hyenas (Crocuta crocuta)

Little is known about host-gut microbiome interactions within natural populations at the intestinal mucosa, the primary interface. We investigate associations between the intestinal microbiome and mucosal immune measures while controlling for host, social and ecological factors in 199 samples of 158 wild spotted hyenas (Crocuta crocuta) in the Serengeti National Park, Tanzania. We profile the microbiome composition using a multi-amplicon approach and measure faecal immunoglobulin A and mucin. Probabilistic models indicate that both immune measures predicted microbiome similarity among individuals in an age-dependent manner. These associations are the strongest within bacteria, intermediate within parasites, and weakest within fungi communities. Machine learning models accurately predicted both immune measures and identify the taxa driving these associations: symbiotic bacteria reported in humans and laboratory mice, unclassified bacteria, parasitic hookworms and fungi. These findings improve our understanding of the gut microbiome, its drivers, and interactions in wild populations under natural selection.

Optimal Approaches to Treating and Preventing Acute and Chronic Pouchitis by Altering Microbial Profiles

Pouchitis is the most common complication after restorative proctocolectomy with ileal pouch-anal anastomosis for ulcerative colitis. The authors review the role of the microbiota in both the pathogenesis of pouchitis, primarily via dysbiosis, as well as the resultant treatment strategies focused on correcting dysbiosis among patients with pouchitis. These include the role of antibiotics, probiotics, and potentially metabolomics in both treatment and risk stratification.

Simple and accessible methods for quantifying isolated mucins for further evaluation

In this study, we present a detailed workflow for the isolation, quantitation, and evaluation of mucin proteins. These methods are applicable to a variety of biological, mucin-containing samples from the airways and other mucosal organ systems. While this report focuses on the salivary MUC5B protein from the respiratory system, the presented methodologies can be applied to other mucins, contributing to a broader application of these techniques. We used a simplified isopycnic centrifugation to purify and enrich MUC5B from human saliva. Isolated MUC5B was then subjected to a Bradford protein assay using a bovine submaxillary mucin (BSM) standard, which more accurately reflects the mucin concentration in our samples compared to a bovine serum albumin (BSA) standard. Additionally, we compare the mucin levels following quantitation using agarose polyacrylamide gel electrophoresis. Our findings show a near 2-fold increase in quantitation from the more representative, BSM standard, suggesting its importance for mucin studies. These methods support a wide range of experimental applications looking to assess mucins, thereby contributing to the broader field of mucin studies and advancing our understanding of the implications of mucins in health and disease.•A streamlined, one-step isopycnic ultracentrifugation to isolate MUC5B from human saliva•A Mucin Bradford assay that is modified from existing Bradford assay techniques to better quantitate mucin for mucin studies•An agarose-polyacrylamide gel electrophoresis method used to visualize and confirm the isolation and quantitation of mucin.

Regulatory Mechanism of Intestinal Stem Cells Based on Hippo Pathway and Signaling Crosstalk in Chicken

Recently, there has been a gradual increase in the demand for chicken and eggs. The gut, as the vital place of nutrient digestion and absorption, is highly associated with the development of livestock and poultry and the quality of meat, eggs, and milk. Intestinal stem cells, as an important source of intestinal cell proliferation and renewal, exert a vital effect on repairing injured intestinal epithelial cells and keeping homeostasis. Intestinal stem cell-regulated intestinal epithelial balance is closely controlled and modulated by interlinked developmental loops that maintain cell proliferation and differentiation processes in balance. Some conservative signaling pathways, including the Wnt, Notch, hedgehog, and bone morphogenetic protein (BMP) loops, have been proved to modulate intestinal health in poultry. Meanwhile, studies have revealed the importance of the Hippo pathway in gastrointestinal tract physiology by regulating intestinal stem cells. Moreover, crosstalk between Hippo and other signaling pathways provides tight, yet versatile, regulation of tissue homeostasis. In this review, we summarize studies on the role of the Hippo pathway in the intestine in these physiological processes and the underlying mechanisms responsible via interacting with these signaling pathways and discuss future research directions and potential therapeutic strategies targeting Hippo signaling in intestinal disease. A comprehensive understanding of how these signaling pathways regulate stem cell proliferation, differentiation, and self-renewal will help to understand the regulation of intestinal homeostasis. In addition, it has the capacity for creative ways to govern intestinal damage, enteritis, and associated disorders induced by different factors.

Advancements and Challenges in Modeling Mechanobiology in Intestinal Host-Microbiota Interaction

The gastrointestinal tract is a dynamic biomechanical environment where physical forces, cellular processes, and microbial interactions converge to shape the gut health and disease. In this review, we examine the unique mechanical properties of the gut, including peristalsis, viscoelasticity, shear stress, and tissue stiffness, and their roles in modulating host mechanosignaling and microbial behavior under physiological and pathological conditions. We discuss how these mechanical forces regulate gut epithelial integrity, immune responses, and microbial colonization, leading to distinct ecological niches across different intestinal segments. Furthermore, we highlight recent advancements in 3D culture systems and gut-on-a-chip models that accurately recapitulate the complex interplay between biomechanics and gut microbiota. By elucidating the intricate relationship between mechanobiology and gut function, this review underscores the potential for mechanotherapeutic strategies to modulate host-microbe interactions, offering promising avenues for the prevention and treatment of disorders such as inflammatory bowel disease, irritable bowel syndrome, and colorectal cancer.

Low butyrate concentrations exert anti-inflammatory and high concentrations exert pro-inflammatory effects on macrophages

Butyrate is a four-carbon short-chain fatty acid produced from microbial fermentation of dietary fibers present at high millimolar concentrations in the colonic lumen. However, in an intact epithelium, macrophages residing in the lamina propria are exposed to only micromolar butyrate concentrations. Current studies show anti-inflammatory properties of butyrate and suggest that it might have therapeutic applications in inflammatory bowel disease and colonic cancer. We now show that the effect of butyrate on human macrophages is strongly concentration dependent: 0.1 mM butyrate suppresses LPS-induced production of the pro-inflammatory cytokine tumor necrosis factor (TNF)-α. Experiments with siRNA knockdown and small molecule inhibitors suggest that this is mediated by a mechanism involving PPAR-γ signaling, whereas we observed no or only a minor effect of histone acetylation. In contrast, 10 mM butyrate promotes macrophage cell death, does not inhibit LPS-induced production of TNF-α, and promotes production of IL-1β, while production of anti-inflammatory IL-10 is reduced in a mechanism involving G protein-coupled receptors, the lipid transporter CD36, and the kinase SRC. We propose that butyrate is a signaling molecule for intestinal integrity, since intestinal disruption exposes macrophages to high butyrate concentrations.

Advances in the application of hydrogel adhesives for wound closure and repair in abdominal digestive organs

The abdominal cavity houses the majority of the digestive system organs, which frequently suffer from diseases with limited responsiveness to pharmacological treatments, such as bleeding, perforation, cancer, and mechanical obstruction. Invasive procedures, including endoscopy and surgery, are typically employed to manage these conditions. Currently, sutures and staplers remain the gold standard for internal wound closure. However, these methods inevitably cause secondary tissue damage. Unlike superficial organs such as the skin, the abdominal cavity presents a relatively confined environment where postoperative complications tend to be more severe. To achieve wound closure and repair, hydrogel adhesives have garnered attention due to their minimal invasiveness, robust sealing, and ease of application. Nonetheless, the application of hydrogel adhesives within the abdominal cavity faces several challenges, including adhesion in moist environments, selective adhesion, and resistance to acids and digestive enzymes. To date, there has been no comprehensive review focused on the use of hydrogel adhesives for wound closure in abdominal digestive organs. This review introduces the design principles of hydrogel adhesives tailored for abdominal organs and provides a detailed overview of recent advances in their applications for esophageal endoscopic submucosal dissection, gastric perforation, hepatic bleeding, pancreatic leakage, and intestinal anastomotic leakage. Additionally, the current challenges and future directions of hydrogel adhesives are discussed. This review aims to provide valuable insights for the development of next-generation hydrogel adhesives for wound closure and repair in abdominal digestive organs.

Modulating the Protein Corona on Nanoparticles by Finely Tuning Cross-Linkers Improves Macrophage Targeting in Oral Small Interfering RNA Delivery

The protein corona (PC) plays an important role in regulating the in vivo fate of nanoparticles (NPs). Modulating the surface chemical properties of NPs to control PC formation provides an alternative impetus for the oral delivery of small interfering RNA (siRNA). Herein, using tripolyphosphate (TPP), hyaluronic acid, and poly-γ-glutamic acid as cross-linkers, three types of mannose-modified trimethyl chitosan-cysteine (MTC)-based NPs with distinct surface chemistries were prepared to encapsulate siRNA via ionic gelation. The MTC-based NPs that were cross-linked exclusively with TPP (MTC/TPP/siRNA NPs) exhibited greater thiol group accessibility on their surfaces, resulting in a stronger affinity for apolipoprotein (APO) B48 during translocation across intestinal epithelia. Moreover, intracellular transport of MTC/TPP/siRNA NPs via the endoplasmic reticulum and Golgi apparatus further increased adsorption of APOB48, a key component of chylomicrons, which follow a similar transport pathway. Benefiting from the elevated APOB48 levels within the PC, the orally delivered MTC/TPP/siRNA NPs showed higher uptake by hepatic macrophages and better therapeutic efficacy for acute liver injury. Our results elucidate the role of NP surface chemical characteristics and translocation mechanisms across intestinal epithelia in forming oral PC, providing valuable insights for designing NPs that achieve effective oral gene delivery by customizing PC formation in vivo.

Activation of Gut Microbiota-HIF1α Axis Effectively Restores Resistance to Aeromonas veronii Caused by Improper Administration of AiiO-AIO6

BACKGROUND

Feeding adult zebrafish a diet supplemented with quenching enzyme AiiO-AIO6 (AIO6) for 3 wk improved the growth performance and disease resistance. However, when the feeding period was extended to 8 wk, zebrafish's disease resistance to Aeromonas veronii decreased.

OBJECTIVES

We investigated the mechanisms of the reduced disease resistance of zebrafish induced by feeding on an AIO6 supplemented diet for a long term (8 wk) and assessed the effectiveness of feed additives in restoring the low disease resistance.

METHODS

One-month-old (adult) zebrafish were fed with a basal diet and the basal diet supplemented with AIO6 (10 U/g) for 8 wk (experiment 1). Furthermore, the zebrafish larvae model (experiment 2) was developed and used to study the mechanisms of how AIO6 affected disease resistance (experiment 3). We also investigated the effectiveness of selected prebiotic tributyrin, β-glucan or mannan in activating gut microbiota- HIF1α to restore the low disease resistance of adult zebrafish fed with AIO6 for 8 wk (experiment 4). Lastly, the effects of Bacillus subtilis in activating the gut microbiota-HIF1α and improving the low disease resistance of zebrafish larvae induced by AIO6 were examined (experiment 5).

RESULTS

Feeding adult zebrafish with AIO6 for 8 wk promoted growth but disordered the gut microbiota and reduced disease resistance. The zebrafish larvae model confirmed that feeding AIO6 for 2 d increased disease resistance, whereas 7 d decreased the resistance by suppressing HIF1α. Using a germ-free zebrafish larvae model, we also demonstrated that AIO6-induced gut microbiota mediated inhibition of HIF1α. Furthermore, zebrafish fed on the AIO6-containing diet supplement with tributyrin, β-glucan, mannan, or Bacillus subtilis activated the gut microbiota-HIF1α axis to reverse the low resistance caused by AIO6.

CONCLUSIONS

Activating the gut microbiota-HIF1α axis has a vital role in improving intestinal health and restores the low resistance to Aeromonas veronii caused by improper administration of dietary AIO6 in zebrafish.

Potential applications and mechanisms of natural products in mucosal-related diseases

The mucosal barrier serves as a crucial defense against external pathogens and allergens, being widely distributed across the respiratory, gastrointestinal, urogenital tracts, and oral cavity. Its disruption can lead to various diseases, including inflammatory bowel disease, asthma, urinary tract infections, and oral inflammation. Current mainstream treatments for mucosa-associated diseases primarily involve glucocorticoids and immunosuppressants, but their long-term use may cause adverse effects. Therefore, the development of safer and more effective therapeutic strategies has become a focus of research. Natural products, with their multi-target and multi-system regulatory advantages, offer a promising avenue for the treatment of mucosal diseases. This review summarizes the potential applications of natural products in diseases of mucosal barrier dysfunction through mechanisms such as immune modulation, inflammation inhibition, tight junction protein restoration, and gut microbiota regulation, with the aim of providing insights for the exploration of novel therapeutic strategies.

Ketoprofen Lysine Salt vs. Ketoprofen Acid: Assessing the Evidence for Enhanced Safety and Efficacy

Endoscopic investigations reveal that a significant majority of individuals taking NSAIDs exhibit acute hemorrhages and mucosal erosions within the gastroduodenal lining. Ketoprofen acid (KA) is a potent NSAID with established efficacy and cardiovascular tolerability, but its gastric tolerability is a recognized limitation. To mitigate this, ketoprofen lysine salt (KLS) was developed. This review evaluates the pharmacological advantages of KLS over KA. While both KA and KLS maintain similar potency, KLS offers distinct advantages. Firstly, KLS demonstrates superior gastrointestinal protection through enhanced antioxidant properties and upregulation of mucosal defenses, as evidenced by both in vitro and in vivo studies. Secondly, KLS exhibits significantly faster absorption, leading to a more rapid onset of analgesic effects; this is attributed to its increased solubility and faster achievement of therapeutic concentrations. In essence, KLS addresses the gastric tolerability issues of KA while providing a quicker onset of action, making it a valuable alternative for patients requiring NSAID therapy, particularly those with gastric sensitivities or in need of rapid pain relief.

A Bacteroides thetaiotaomicron genetic locus encodes activities consistent with mucin O-glycoprotein processing and N-acetylgalactosamine metabolism

The gut microbiota is a key modulator of human health and the status of major diseases including cancer, diabetes and inflammatory bowel disease. Central to microbiota survival is the ability to metabolise complex dietary and host-derived glycans, including intestinal mucins. The prominent human gut microbe Bacteroides thetaiotaomicron (B. theta) is a versatile and highly efficient complex glycan degrader thanks to the expansion of gene clusters termed polysaccharide utilisation loci (PULs). While the mechanism of action for several singular dietary glycan-induced PULs have been elucidated, studies on the unusually high number of mucin-inducible PULs in B. theta significantly lag behind. Here we show that a mucin inducible PUL BT4240-50 encodes activities consistent with the processing and metabolism of mucin O-glycoproteins and their core sugar N-acetylgalactosamine (GalNAc). PUL BT4240-50 was also shown to be important for competitive growth on mucins in vitro, encoding a kinase (BT4240) critical for GalNAc metabolism. Additionally, BT4240-kinase was shown to be essential for glycosaminoglycan metabolism, extending the PULs function beyond mucins. These data advance our understanding of glycoprotein metabolism at mucosal surfaces, highlighting GalNAc as a key metabolite for competitive microbial survival in the human gut.

Transmembrane mucins in lung adenocarcinoma: understanding of current molecular mechanisms and clinical applications

The mucin family is a group of highly glycosylated macromolecules widely present in human epithelial cells and with subtypes of secreted and membrane-associated forms. The membrane-associated mucins, known as transmembrane mucins, are not only involved in the formation of mucus barrier but also regulate cell signal transduction in physiological and pathological status. Transmembrane mucins could contribute to lung adenocarcinoma (LUAD) proliferation, apoptosis, angiogenesis, invasion, and metastasis, and remodel the immune microenvironment involved in immune escape. Furthermore, transmembrane mucins have been explored as potential LUAD indicators for diagnosis and prognosis. The development of targeted therapy and immunotherapeutic drugs targeting transmembrane mucins has also provided broad application prospects for clinic. In the following review, we summarize the characteristic structures of diverse transmembrane mucins, regulatory roles in promoting the progression of LUAD, and the current situation of diagnosis, prognosis, and therapeutic strategies based on transmembrane mucins.

Morphological and Histological Analysis of the Gastrointestinal Systems in Triplophysa strauchii and Triplophysa tenuis: Insights into Digestive Adaptations

Fish are vital for material cycling and energy flow in aquatic ecosystems. The genus Triplophysa, with over 100 known species, is significant in the Central Asian highlands' freshwater ecosystems. T. strauchii and T. tenuis, as representatives, occupy distinct ecological niches and face challenges from climate change and human activities. There is a lack of research on Triplophysa fishes' digestive systems, especially comparative studies, so this research aims to fill this gap. In September 2024, 40 samples of T. strauchii were collected from Sayram Lake and 40 samples of T. tenuis were collected from the Muzat River in Xinjiang. After acclimation, morphological observations (measuring fish and digestive tract parameters) and histological analyses (paraffin sectioning, HE staining, and microscopy) were carried out. The data were sorted in Excel and analyzed with an independent samples t-test in SPSS 27.0. Morphologically, T. strauchii has an obtuse snout, terminal mouth, specific upper lip papillae, and an S-shaped intestine about (1.45 ± 0.11) times its body length, while T. tenuis has an arc-shaped subterminal mouth, fringed papillae, and a spiral-shaped intestine around (0.82 ± 0.09) times its body length. Both possess a digestive tract, glands, and a hepatopancreas attached to the mesentery. Histologically, a large number of club cells were found in the oropharyngeal cavities of both species; their secretions have an adhesive effect on food, aiding food selection. Their digestive systems vary in structure and cell composition: the oropharyngeal cavity has three layers; the esophagus has four layers with more goblet cells in T. strauchii; the stomach has three regions without goblet cells and a thicker muscular layer in T. strauchii; the intestinal wall has four layers with different villi and goblet cell distributions; the hepatopancreas has lobules; and T. strauchii has a typical portal area. In conclusion, this study systematically compared the gastrointestinal systems of T. strauchii and T. tenuis for the first time, revealing significant structural differences related to their niches and feeding patterns as adaptations to specific environments. It fills the research gap, provides a basis for exploring fish ecological adaptation and environmental impacts on digestion, offers new ideas for Triplophysa protection strategies, and guides fish evolutionary biology research and Triplophysa resource protection and utilization.

Gut microbiota and intestinal immunity interaction in ulcerative colitis and its application in treatment

Ulcerative colitis (UC) is a chronic, non-specific inflammatory bowel disease characterized by inflammation and injury of the colonic mucosa, exhibiting an increasing global incidence. Although research into UC pathogenesis is ongoing, the precise mechanisms remain to be fully elucidated. Studies indicate that UC development results from a complex interplay of factors, including genetic predisposition, environmental exposures, gut microbial dysbiosis, and immune dysregulation. Specifically, UC pathogenesis involves aberrant immune responses triggered by interactions between the host and gut microbiota. A complex, dynamic relationship exists between the microbial community and the host immune system throughout UC pathogenesis. Accumulating evidence suggests that changes in microbiota composition significantly impact gut immunity. This review will examine the intricate balance between the gut microbiota and mucosal immunity in UC progression and discuss potential therapeutic applications, providing a reference for further clinical treatment of this patient population.

Unravelling the Glycan Code: Molecular Dynamics and Quantum Chemistry Reveal How O-Glycan Functional Groups Govern OgpA Selectivity in Mucin Degradation by Akkermansia muciniphila

Mucins, heavily O-glycosylated glycoproteins, are a key component of mucus, and certain gut microbiota, including Akkermansia muciniphila, can utilise mucin glycans as a carbon source. Akkermansia muciniphila produces the O-glycopeptidase enzyme OgpA, which cleaves peptide bonds at the N-terminus of serine (Ser) or threonine (Thr) residues carrying O-glycan substitutions, with selectivity influenced by the O-glycan functional groups. Using molecular dynamics (MD) simulations and quantum chemistry calculations, we explored how different O-glycan groups affect OgpA's selectivity. Our results show that peptides bind to the enzyme via hydrogen bonds, π-π interactions, van der Waals forces and electrostatic interactions, with key residues, including Tyr90, Val138, Gly176, Tyr210 and Glu91, playing important roles. The primary determinant of selectivity is the interaction between the peptide's functional group and the enzyme's binding cavity, while peptide-enzyme interface interactions are secondary. Quantum chemistry calculations reveal that OgpA prefers peptides with a lower electrophilic character. This study provides new insights into mucin degradation by gut microbiota enzymes, advancing our understanding of this critical biological process.

Dairy Foods: A Matrix for Human Health and Precision Nutrition-Effect of processing infant milk formula on protein digestion and gut barrier health (in vitro and preclinical)

The infant gut is immature and permeable with high gastric pH, low protease activities, and underdeveloped intestinal architecture. Protein digestion in the upper gastrointestinal tract of infants is slow and incomplete. During manufacture, infant milk formula (IMF) is typically heat-treated so it is safe for human consumption. This heat treatment causes denaturation and aggregation of milk proteins, and formation of undesirable Maillard reaction products. The aim of this review is to critically summarize the in vitro and preclinical data available on the effect of IMF thermal processing on protein digestion and gut barrier physiology in the immature infant gut. Recent research efforts have focused on reducing thermal loads during IMF manufacturing by sourcing ingredients with low thermal loads, by reducing temperatures during IMF processing itself, and by seeking alternative processing technologies. This review also aims to evaluate whether these thermal reductions have a knock-on effect on protein digestion and gut barrier health in the infant. The ultimate aim is to create a safe next-generation IMF product that more closely mimics human breast milk in its protein digestion kinetics and its ability to promote gut barrier maturity in the infant.

Role of declined electrogenic Na+/HCO3- cotransporter NBCe1 in mucus barrier impairment and colonic inflammation

BACKGROUND

Electrogenic Na+/HCO3- co-transporter 1 (NBCe1) plays a pivotal role in epithelial bicarbonate transport involved in the maintenance of the intestinal mucus barrier. However, the specific role of NBCe1 in colitis remains unknown.

METHODS

NBCe1 was identified by bioinformatics analysis methods including GO/KEGG/GSEA, protein-protein interaction (PPI) network analysis, immune infiltration analysis, and Mendelian randomization (MR) analysis. Expression level of NBCe1 was detected in patients with IBD and in DSS-induced colitis mice. The role of NBCe1 in intestinal mucus barrier and colitis was accessed by S0859 pretreatment in DSS model. The function of NBCe1 and related bicarbonate secretion were evaluated using short-circuit current (Isc) measurements in Ussing chamber system.

RESULTS

Bioinformatic analyses indicated that SLC4A4 (NBCe1) was a signature gene in bicarbonate transport implicated in ulcerative colitis (UC) development and was negatively associated with the risk of UC. NBCe1's expression was significantly diminished in colonic mucosa of UC patients and DSS-treated mice. More severe intestinal inflammation and impaired mucus barrier were observed in S0859-treated mice. Moreover, S0859 administration led a significant decrease in mucus secretion rate and an significant increase in Isc of colonic mucosa. The forskolin-induced ΔIsc was also suppressed by S0859 pretreatment.

CONCLUSION

NBCe1 has been identified as a valuable signature gene may have a protective effect against the onset of colitis. Function of NBCe1 is diminished in colitis, which is associated with impaired mucus barrier and declined HCO3- secretion both contributing to the development of IBD.

Ingestible Smart Capsules for Chemical Sensing in the Gut

The development of novel ingestible sensors can aid physicians and patients in obtaining precise data on the health status of the gut at a local level. This in turn can facilitate earlier and more accurate disease diagnosis, improve the delivery of point-of-care medicine, and allow monitoring of the gastrointestinal (GI) tract status. This Tutorial overviews characteristics of the gut for inexpert readers and reviews emerging chemical sensing technologies for the GI tract from an analytical chemistry viewpoint.

Post-stroke depression: exploring gut microbiota-mediated barrier dysfunction through immune regulation

Post-stroke depression (PSD) is one of the most common and devastating neuropsychiatric complications in stroke patients, affecting more than one-third of survivors of ischemic stroke (IS). Despite its high incidence, PSD is often overlooked or undertreated in clinical practice, and effective preventive measures and therapeutic interventions remain limited. Although the exact mechanisms of PSD are not fully understood, emerging evidence suggests that the gut microbiota plays a key role in regulating gut-brain communication. This has sparked great interest in the relationship between the microbiota-gut-brain axis (MGBA) and PSD, especially in the context of cerebral ischemia. In addition to the gut microbiota, another important factor is the gut barrier, which acts as a frontline sensor distinguishing between beneficial and harmful microbes, regulating inflammatory responses and immunomodulation. Based on this, this paper proposes a new approach, the microbiota-immune-barrier axis, which is not only closely related to the pathophysiology of IS but may also play a critical role in the occurrence and progression of PSD. This review aims to systematically analyze how the gut microbiota affects the integrity and function of the barrier after IS through inflammatory responses and immunomodulation, leading to the production or exacerbation of depressive symptoms in the context of cerebral ischemia. In addition, we will explore existing technologies that can assess the MGBA and potential therapeutic strategies for PSD, with the hope of providing new insights for future research and clinical interventions.

Model systems to study tumor-microbiome interactions in early-onset colorectal cancer

Colorectal cancer (CRC) is a major health problem, with an alarming increase of early-onset CRC (EO-CRC) cases among individuals under 50 years of age. This trend shows the urgent need for understanding the underlying mechanisms leading to EO-CRC development and progression. There is significant evidence that the gut microbiome acts as a key player in CRC by triggering molecular changes in the colon epithelium, leading to tumorigenesis. However, a comprehensive collection and comparison of methods to study such tumor-microbiome interactions in the context of EO-CRC is sparse. This review provides an overview of the available in vivo, ex vivo as well as in vitro approaches to model EO-CRC and assess the effect of gut microbes on tumor development and growth. By comparing the advantages and limitations of each model system, it highlights that, while no single model is perfect, each is suitable for studying specific aspects of microbiome-induced tumorigenesis. Taken together, multifaceted approaches can simulate the human body's complexity, aiding in the development of effective treatment and prevention strategies for EO-CRC.

Innate Immunity in Helicobacter pylori Infection and Gastric Oncogenesis

Helicobacter pylori is an extremely common cause of gastritis that can lead to gastric adenocarcinoma over time. Approximately half of the world's population is infected with H. pylori, making gastric cancer the fourth leading cause of cancer-related deaths worldwide. Innate immunity significantly contributes to systemic and local immune responses, maintains homeostasis, and serves as the vital link to adaptive immunity, and in doing so, mediates H. pylori infection outcomes and consequent cancer risk and development. The gastric innate immune system, composed of gastric epithelial and myeloid cells, is uniquely challenged by its need to interact simultaneously and precisely with commensal microbiota, exogenous pathogens, ingested substances, and endogenous exfoliated cells. Additionally, innate immunity can be detrimental by promoting chronic infection and fibrosis, creating an environment conducive to tumor development. This review summarizes and discusses the complex role of innate immunity in H. pylori infection and subsequent gastric oncogenesis, and in doing so, provides insights into how these pathways can be exploited to improve prevention and treatment.

Dietary Iron Alleviates Dextran Sodium Sulfate-Induced Intestinal Injury by Regulating Regeneration of Intestinal Stem Cells in Weaned Mice

Iron deficiency is the most common comorbidity of inflammatory bowel disease (IBD), but the effect of iron supplementation on the repair processes of intestinal injury in weaned mice is unknown. This study aimed to evaluate the potential mechanism of dietary iron on intestinal injury and intestinal regeneration in the dextran sodium sulfate (DSS)-induced colitis of the weaned mouse model. The mice were fed either a control diet containing (45.00 mg/kg Fe) or iron supplemental (448.30 mg/kg Fe) diet for 14 days, followed by a 7-day oral administration of 2.5% DSS to all mice. The result showed that at day 0 of the recovery period (0 DRP), the impact of iron on the gut index and intestinal morphology was found to be more significant in weaned mice compared to adult mice. At 3 DRP, the iron diet alleviated inflammation-induced weight loss, shortening of colon length, thickening of the muscle layer, and disruption of gut morphology. At 0, 3, and 7 DRP, we found that an iron diet increased intestinal stem cell (ISC) viability and protected epithelial integrity. Furthermore, FeSO4 significantly enhanced organoid viability and increased mRNA expression of differentiation, ISC, and retinol metabolism-related marker genes in the organoids compared with the control group. Overall, this study demonstrates that the iron diet accelerates intestinal regeneration after intestinal injury in weaned mice by activating the retinol metabolic pathway to regulate the proliferation and differentiation of ISCs.

α2,6-linked sialylated oligosaccharides riched in goat milk alleviate food allergy by regulating the gut flora and mucin O-glycosylation

The nutritious goat milk has low allergenicity. Oligosaccharides represent one of the crucial functional constituents in goat milk, which are structurally similar to human milk oligosaccharides (HMOs). Currently, the anti-allergic activity of GMOs has not been reported. In this study, GMOs were efficiently separated into neutral (NGMOs) and sialylated (SGMOs) fractions, following by qualitative and quantitative analysis at the isomer level using online LC-MS/MS. Fifteen NGMOs and 28 SGMOs were detected in goat milk, with 10 SGMOs reported for the first time. Distinctly, α2,6-linked SGMOs were 3.9 times more abundant in goat milk than in bovine milk, with the total relative content of 6'SL, 3'SLN and 6'NGL in SGMOs approach to 60%, which is more similar to HMOs. Orally administering GMOs, especially α2,6-linked sialylated oligosaccharides, significantly alleviated food allergy in ovalbumin-induced BALB/c mice. SGMOs restored the balance of Lachnospiraceae, Erysipelotrichaceae, and Bacteroidaceae, reconstructed the intestinal mucosal barrier, especially restored the levels of fucosylation, sialylation, and sulfation of mucin O-glycans, increased the expression of four core type 2 O-glycans (F1H2N2, F2H2N2, S1F2H2N2, and A1F1H2N2) significantly. This is the first comprehensive study of the anti-allergic activity of GMOs, and the results lay the foundation for the development of GMOs-based natural anti-allergic components.

Advances in Oral Biomacromolecule Therapies for Metabolic Diseases

Metabolic diseases like obesity and diabetes are on the rise, and therapies with biomacromolecules (such as proteins, peptides, antibodies, and oligonucleotides) play a crucial role in their treatment. However, these drugs are traditionally injected. For patients with chronic diseases (e.g., metabolic diseases), long-term injections are accompanied by inconvenience and low compliance. Oral administration is preferred, but the delivery of biomacromolecules is challenging due to gastrointestinal barriers. In this article, we introduce the available biomacromolecule drugs for the treatment of metabolic diseases. The gastrointestinal barriers to oral drug delivery and strategies to overcome these barriers are also explored. We then discuss strategies for alleviating metabolic defects, including glucose metabolism, lipid metabolism, and energy metabolism, with oral biomacromolecules such as insulin, glucagon-like peptide-1 receptor agonists, proprotein convertase subtilisin/kexin type 9 inhibitors, fibroblast growth factor 21 analogues, and peptide YY analogues.

Efavirenz Repurposing Challenges: A Novel Nanomicelle-Based Antiviral Therapy Against Mosquito-Borne Flaviviruses

Background/Objective: World Health Organization latest statistics state that 17% of infectious diseases are transmitted by vectors, causing more than 700,000 deaths each year. Particularly, dengue (DENV), Zika (ZIKV) and yellow fever (YFV) viral infections have generated international awareness due to their epidemic proportion and risks of international spread. In this framework, the repositioning strategy of Efavirenz (EFV) represents a key clinical feature to improve different antiviral therapies. Therefore, the development of Soluplus®-based nanomicelles (NMs) loaded with EFV (10 mg/mL) for optimized oral pharmacotherapy against ZIKV, DENV and YFV infections was investigated. Methods: EFV-NMs were obtained by an acetone diffusion technique. Micellar size and in vitro micellar interaction with mucin were assessed by dynamic light scattering. In vitro cytocompatibility was investigated in A549 and Vero cells and micellar in vitro antiviral activity against ZIKV, DENV and YFV was evaluated. In vivo oral bioavailability and histological studies were assessed in Wistar rats. Results: EFV encapsulation within Soluplus® NMs increased the drug's apparent aqueous solubility up to 4803-fold with a unimodal micellar size distribution and a micellar size of ~90 nm at 25 and 37 °C. Micellar in vitro interaction with mucin was also assessed in a pH range of 1.2-7.5 and its storage micellar physicochemical stability at 4 °C was confirmed over 2 years. In vitro cytocompatibility assays in A549 and Vero cells confirmed that EFV micellar dispersions resulted in safe nanoformulations. Interestingly, EFV-loaded NMs exhibited significantly higher in vitro antiviral activity compared with EFV solution for all the tested flaviviruses. In addition, the selectivity index (SI) values reveal that EFV-loaded NMs exhibited considerably more biological efficacy compared to EFV solution in A549 and Vero cell lines and for each viral infection (SI > 10). Further, the drug pharmacokinetics parameters were enhanced after the oral administration of EFV-loaded NMs, being biocompatible by not causing damage in the gastrointestinal segments. Conclusions: Overall, our EFV nanoformulation highlighted its potential as a novel drug delivery platform for optimized ZIKV, DENV and YFV antiviral therapy.

Ligustilide improves functional constipation by non-covalently activating TRPA1 in colon tissue

ETHNOPHARMACOLOGICAL RELEVANCE

Angelica sinensis (Oliv.) Diels (AS), a medicinal plant renowned for its constipation-relieving properties, lacks comprehensive studies on its active pharmaceutical ingredients (APIs) and underlying mechanisms. In the gastrointestinal tract, TRP channels enhance colonic mucus secretion, expedite intestinal motility, and regulate gastrointestinal hormones; however, few reports have systematically established the relationship between TRPs and ligustilide (Lig), a key API of AS.

AIM OF THE STUDY

This study aimed to explore the pharmacodynamic properties of AS in alleviating functional constipation, assess the potential of Lig for activating TRPs, and elucidate its mechanism of action.

METHODS

The therapeutic efficacy of AS was assessed in a mouse model of loperamide hydrochloride-induced functional constipation. The APIs were screened via integrated activity-based UPLC profiling through periodic acid-Schiff (PAS) staining of the colon and immunofluorescence staining of HT-29 cells. The potential target was identified via target fishing and colocalization imaging via an alkynyl-modified Lig probe (AM-Lig). Molecular docking, microscale thermophoresis (MST), fluorescence quenching (FQ), and Fluo-4/Ca2+ influx assays were employed to reveal the interaction mode between Lig and the target protein. Finally, we assessed the efficacy of Lig in alleviating constipation in an animal model.

RESULTS

The efficacy of AS in improving functional constipation was demonstrated in a mouse constipation model, with Lig identified as the primary constituent responsible for inducing colon mucus secretion. Lig specifically targets TRPA1 in the colon, leading to calcium influx and subsequent mucus secretion, ultimately ameliorating functional constipation. Furthermore, a binding mode study revealed that Lig attaches to Thr684, located in the pre-S1 region, triggering TRPA1 channel activation.

CONCLUSIONS

Our findings demonstrate that Lig, the API in AS for constipation treatment, activates TRPA1 through non-covalent interactions, increasing mucus secretion and improving functional constipation. These findings advance our understanding of the therapeutic mechanism of AS and Lig on constipation and suggest a new approach for developing TRPA1 agonists.

The essential role of prebiotics in restoring gut health in long COVID

The gut microbiota (GM) plays an essential role in human health, influencing not only digestive processes but also the immune system´s functionality. The COVID-19 pandemic has highlighted the complex interaction between viral infections and the GM. Emerging evidence has demonstrated that SARS-CoV-2 can disrupt microbial homeostasis, leading to dysbiosis and compromised immune responses. The severity of COVID-19 has been associated with a reduction in the abundance of several beneficial bacteria in the gut. It has been proposed that consuming probiotics may help to re-colonize the GM. Although probiotics are important, prebiotics are essential for their metabolism, growth, and re-colonization capabilities. This chapter delves into the critical role of prebiotics in restoring GM after COVID-19 disease. The mechanisms by which prebiotics enhance the metabolism of beneficial bacteria will be described, and how prebiotics mediate the re-colonization of the gut with beneficial bacteria, thereby restoring microbial diversity and promoting the resilience of the gut-associated immune system. The benefits of consuming prebiotics from natural sources are superior to those from chemically purified commercial products.

Development and assessment of an intestinal tri-cellular model to investigate the pro/anti-inflammatory potential of digested foods

Introduction

Immunonutrition, defined as the potential of foods, nutrients and dietary patterns to modulate the immune system activity, has been proposed as a strategy to enhance the immune response in both metabolic and immune-mediated diseases. However, the anti-/pro-inflammatory role of foods and diets is far to be fully ascertained, and thus there is a continued needed for appropriate in vitro cell-culture models to investigate the role of foods in modulating cell-mediated inflammatory processes. This study aims to develop and test an in vitro tri-culture model, simulating the complexity of the intestinal tract and its multiple cell interactions.

Methods

To achieve this, the intestinal epithelial barrier was established by co-culturing human Caco-2 enterocyte-like and HT29-MTX-E12 mucus producing goblet-like colon cells, then adding human monocyte THP-1 cells to the basolateral compartment. The integrity and stability of the epithelial barrier were monitored and the inflammatory response of the model was assessed using various stressors at different concentrations, both individually and in combination (phorbol-12- myristate-13-acetate or PMA, and lipopolysaccharide or LPS), in terms of cytokines production. To test the model, different concentrations of in vitro digested broccoli (BD) were added to the apical section of the model.

Results

Supernatants from the basolateral compartment were collected and analyzed for cytokines production (IL-6, TNF-α, IL-12p70, IL-18 and IL-8) using automated ELISA (ELLA). Additionally, ZO-1 protein from the tight junctions of epithelial cells was analyzed by flow cytometry. The results indicated that 100 nM PMA added to the whole model for 20 h was the best stressor to simulate a mild-inflammatory status of the gut. Following treatment with BD, IL-6, TNF-α, IL-8 and IL-18 were significantly reduced compared to the control group, while ZO-1 expression increased at the lowest BD concentration.

Conclusions

These findings confirm the feasibility of the model for assessing the effects of food digesta on specific cytokines and permeability markers, representing a valuable strategy for investigating the role of foods in modulating the inflammatory response. The results obtained may support dietary strategies aimed at promoting wellbeing and preventing inflammatory-related metabolic diseases.

The effect of microenvironmental viscosity on the emergence of colon cancer cell resistance to doxorubicin

The colon possesses a unique physiological environment among human organs, where there is a highly viscous body fluid layer called the mucus layer above colonic epithelial cells. Dysfunction of the mucus layer not only contributes to the occurrence of colorectal cancer (CRC) but also plays an important role in the development of chemoresistance in CRC. Although viscosity is an essential property of the mucus layer, it remains elusive how viscosity affects chemoresistance in colon cancer cells. In this study, the influence of viscosity on their chemoresistance was elucidated by culturing colon cancer cells in media of different viscosities supplemented with doxorubicin (DOX). The viscosity range was adjusted from 99.4 mPa s to 776.6 mPa s by adding polyethylene glycol of different molecular weights in culture medium. Cell viability in the high viscosity medium was higher than that in the low viscosity medium. Expression of chemoresistance-related genes such as ABCC2 and ABCG2 increased when cells were cultured in the high viscosity medium. Furthermore, cell migration increased while proliferation decreased when cells were cultured in the high viscosity medium. The colon cancer cells cultured in the high viscosity medium exhibited high expression of p21 mRNA. The results suggested that viscosity could affect the resistance of colon cancer cells to DOX by regulating the expression of chemoresistance-related and proliferation-related genes.

Targeting Helicobacter pylori Through the "Muco-Microbiotic Layer" Lens: The Challenge of Probiotics and Microbiota Nanovesicles

The muco-microbiotic layer represents a critical biological frontier in gastroenterology, emphasizing the intricate interplay between the protective mucus, its resident microbiota, and extracellular vesicles. This review explores the functional morphology of the gastric mucosa, focusing on the gastric muco-microbiotic layer, its role as a protective barrier, and its dynamic interaction with some of the most insidious pathogens such as Helicobacter pylori (H. pylori). Highlighting the multifaceted mechanisms of H. pylori pathogenesis, we have delved into bacterial virulence factors, host immune responses, and the microbiota's regulatory effects. Novel therapeutic strategies for H. pylori eradication, including traditional antibiotic therapies and emerging adjuvant treatments like probiotics and probiotic-derived extracellular vesicles, are critically examined. These findings underscore the potential of targeting nanovesicular interactions in the gastric mucosa, proposing a paradigm shift in the management of H. pylori infections to improve patient outcomes while mitigating antibiotic resistance.

Carbohydrate-active enzymes from Akkermansia muciniphila break down mucin O-glycans to completion

Akkermansia muciniphila is a human microbial symbiont residing in the mucosal layer of the large intestine. Its main carbon source is the highly heterogeneous mucin glycoprotein, and it uses an array of carbohydrate-active enzymes and sulfatases to access this complex energy source. Here we describe the biochemical characterization of 54 glycoside hydrolases, 11 sulfatases and 1 polysaccharide lyase from A. muciniphila to provide a holistic understanding of their carbohydrate-degrading activities. This was achieved using a variety of liquid chromatography techniques, mass spectrometry, enzyme kinetics and thin-layer chromatography. These results are supported with A. muciniphila growth and whole-cell assays. We find that these enzymes can act synergistically to degrade the O-glycans on the mucin polypeptide to completion, down to the core N-acetylgalactosaime. In addition, these enzymes can break down human breast milk oligosaccharide, ganglioside and globoside glycan structures, showing their capacity to target a variety of host glycans. These data provide a resource to understand the full degradative capability of the gut microbiome member A. muciniphila.

Intestinal mucus barrier: A potential therapeutic target for IBD

Intestinal mucus, a viscoelastic medium with mucin2 (MUC2) as its main component, covers the surface of intestinal epithelial cells and protects the intestine from invasion, forming the first barrier of the intestinal tract. Unlike the small intestine, where the mucus layer is a single layer, the colonic mucus layer can be divided into a sterile inner layer and an outer layer with bacterial colonization. Many of the substances in the mucus layer have beneficial effects on the intestinal epithelium, but the mucus layer is often affected by a variety of factors, mainly microbiological, dietary, and immunological. Inflammatory bowel disease (IBD) is a disease of increasing morbidity worldwide, with a complex etiology and a high relapse rate. In recent years, the mucus barrier in IBD has received increasing attention and is considered a key factor in the pathogenesis of IBD. Loss of goblet cells (GCs) and changes in the composition and properties of the mucus layer material are commonly found in the colon of IBD patients. Damage to the mucus layer may make it easier for microorganisms to access the intestinal epithelium and cause inflammation. There are currently a number of herbs and other therapies that can be used to treat IBD and repair the damaged mucus barrier. This review highlights the important role of the mucus layer in IBD and the therapies that target the mucus layer in IBD.

Chitooligosaccharides suppress airway inflammation, fibrosis, and mucus hypersecretion in a house dust mite-induced allergy model

Background

Respiratory allergy is a serious respiratory disorder characterized by inflammation, mucus hypersecretion, and airway tissue sclerosis. Disruption of the T helper 1 (Th1) and T helper 2 (Th2) immune systems by stimuli induced by house dust mites (HDM) and fine particulate matter leads to the secretion of various inflammatory cytokines, resulting in immune respiratory diseases characterized by airway inflammation. Chitooligosaccharides (COS) are known for their antioxidant and anti-inflammatory properties.

Methods

Human airway epithelial cells (BEAS-2B) were cultured in DMEM/F12 medium containing COS at concentrations of 25-100 µg/ml for 24 h. No intracellular toxicity was observed up to 1,000 µg/ml. Cell experiments were conducted at COS concentrations below 100 µg/ml, while animal experiments were performed at concentrations below 100 mg/kg body weight for 4 weeks. Samples of right lung tissue obtained from the experimental animals were used for gene and protein expression analysis, whereas samples of contralateral lung tissue were used for immunohistochemical analysis.

Results

COS regulated Th1 immunity by inhibiting major cytokines, including inflammatory tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6), in BEAS-2B cells. In the HDM-induced allergic respiratory model, COS suppressed the infiltration of inflammatory cells around the airways and inhibited the mRNA expression of Th1 immune cytokines in lung tissues, while also reducing the expression of nuclear factor kappa B (NF-κB)-related proteins. Furthermore, the results confirmed the suppression of the levels of immunoglobulin E (IgE) in the blood secreted by mast cells activated by HDM, which led to a reduction in allergic mucus hypersecretion and airway sclerosis.

Conclusion

In summary, COS are thought to improve airway resistance by alleviating inflammatory allergic respiratory diseases caused by HDM and are regarded as substances that regulate the balance of the Th1 and Th2 immune systems in epithelial cells affected by mucus hypersecretion.

Multi-omics perspective: mechanisms of gastrointestinal injury repair

In this review, we examine the significance of multi-omics technologies in understanding the plethora of intricate processes that activate gastrointestinal (GI) injury repair. Multi-omics, which includes genomics, transcriptomics, proteomics, and metabolomics, allows intricate mapping of cellular responses and molecular pathways involved in GI repair. We highlight the potential of multi-omics to discover previously unknown therapeutic targets or elucidate the molecular basis of the pathogenesis of GI. Furthermore, we explore the possibilities of integrating omics data to improve prediction models, and summarize the state-of-the-art technological developments and persisting obstacles that hinder the translation of multi-omics into clinical practice. Finally, innovative multi-omics approaches that can improve patient outcomes and advance therapeutic strategies in GI medicine are discussed.

Transcytosis of T4 Bacteriophage Through Intestinal Cells Enhances Its Immune Activation

Interactions between bacteriophages with mammalian immune cells are of great interest and most phages possess at least one molecular pattern (nucleic acid, sugar residue, or protein structure) that is recognizable to the immune system through pathogen associated molecular pattern (PAMP) receptors (i.e., TLRs). Given that phages reside in the same body niches as bacteria, they share the propensity to stimulate or quench immune responses depending on the nature of their interactions with host immune cells. While most in vitro research focuses on the outcomes of direct application of phages to immune cells of interest, the potential impact of their transcytosis through the intestinal barrier has yet to be considered. As transcytosis through intestinal cells is a necessary step in healthy systems for access by phage to the underlying immune cell populations, it is imperative to understand how this step may play a role in immune activation. We compared the activation of macrophages (as measured by TNFα secretion) following direct phage application to those stimulated by incubation with phage transcytosed through a polarized Caco2 epithelial barrier model. Our results demonstrate that phages capable of activating TNFα secretion upon direct contact maintain the stimulatory capability following transcytosis. Furthermore, activation of macrophages by a transcytosed phage is enhanced as compared to that occurring with an equivalent multiplicity of directly applied phage.

Exploring the Link Between Mucin 2 and Weaning Stress-Related Diarrhoea in Piglets

To explore the relationship between intestinal mucin 2 (MUC2) and weaning-induced diarrhoea in piglets, we analysed Min and Landrace piglets. The piglets were divided into a healthy weaned group, a weaned diarrhoea group, and a healthy unweaned control group. Intestinal tissues were collected, and goblet cell numbers, sizes, and degrees of intestinal injury were observed and recorded. Intestinal tissue MUC2 mRNA and protein expression were analysed via quantitative real-time PCR (qRT-PCR) and Western blotting. Min pigs presented significantly lower diarrhoea rates and intestinal injury scores than Landrace pigs (p < 0.01). The intestinal injury scores in the weaned diarrhoea group were significantly greater than those in the unweaned groups (p < 0.05), with Min pigs consistently exhibiting lower injury scores than Landrace pigs. Specifically, unweaned Min pigs presented significantly greater duodenal MUC2 mRNA (p < 0.05), and weaned healthy Min pigs presented notably greater expression in both the duodenum and jejunum (p < 0.01). These findings reveal enhanced intestinal protection against weaning stress and diarrhoea in Min pigs, with elevated MUC2 levels likely contributing to lower injury scores and milder symptoms, thus highlighting the influence of genetic differences.

The oral-gut microbiota axis: a link in cardiometabolic diseases

The oral-gut microbiota axis plays a crucial role in cardiometabolic health. This review explores the interactions between these microbiomes through enteric, hematogenous, and immune pathways, resulting in disruptions in microbial balance and metabolic processes. These disruptions contribute to systemic inflammation, metabolic disorders, and endothelial dysfunction, which are closely associated with cardiometabolic diseases. Understanding these interactions provides insights for innovative therapeutic strategies to prevent and manage cardiometabolic diseases.

The role of morphological adaptability in Vibrio cholerae's motility

Vibrio cholerae, the causative agent of cholera, displays remarkable adaptability to diverse environmental conditions through morphological changes that enhance its pathogenicity and influence the global epidemiology of the disease. This study examines the motility differences between filamentous and comma-shaped forms of the V. cholerae O1 strain under various viscosity conditions. Utilizing the El Tor strain, we induced filamentous transformation and conducted a comparative analysis with the canonical comma-shaped morphology. Our methodology involved assessing motility patterns, swimming speeds, rotation rates, kinematics, and reversal frequencies using dark-field microscopy and high-speed imaging techniques. The results show that filamentous V. cholerae cells retain enhanced motility in viscous environments, indicating an evolutionary adaptation for survival in varied habitats, particularly the human gastrointestinal tract. Filamentous forms exhibited increased reversal behavior at mucin interfaces, suggesting an advantage in penetrating the mucus layer. Furthermore, the presence of filamentous cells in bile-supplemented medium underscores their relevance in natural infection scenarios.

IMPORTANCE

This study highlights the enhanced motility of filamentous Vibrio cholerae in viscous environments, an adaptation that may provide a survival advantage in the human gastrointestinal tract. By demonstrating increased reversal behavior at mucin interfaces, filamentous V. cholerae cells exhibit a superior ability to penetrate the mucus layer, which is crucial for effective colonization and infection. Filamentous cells in bile-supplemented media further underscores their potential role in disease pathogenesis. These findings offer critical insights into the morphological flexibility of V. cholerae and its potential implications for infection dynamics, paving the way for more effective strategies in managing and preventing cholera outbreaks.

Mucosal immune response in biology, disease prevention and treatment

The mucosal immune system, as the most extensive peripheral immune network, serves as the frontline defense against a myriad of microbial and dietary antigens. It is crucial in preventing pathogen invasion and establishing immune tolerance. A comprehensive understanding of mucosal immunity is essential for developing treatments that can effectively target diseases at their entry points, thereby minimizing the overall impact on the body. Despite its importance, our knowledge of mucosal immunity remains incomplete, necessitating further research. The outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has underscored the critical role of mucosal immunity in disease prevention and treatment. This systematic review focuses on the dynamic interactions between mucosa-associated lymphoid structures and related diseases. We delve into the basic structures and functions of these lymphoid tissues during disease processes and explore the intricate regulatory networks and mechanisms involved. Additionally, we summarize novel therapies and clinical research advances in the prevention of mucosal immunity-related diseases. The review also addresses the challenges in developing mucosal vaccines, which aim to induce specific immune responses while maintaining tolerance to non-pathogenic microbes. Innovative therapies, such as nanoparticle vaccines and inhalable antibodies, show promise in enhancing mucosal immunity and offer potential for improved disease prevention and treatment.

The MYO1B and MYO5B motor proteins and the sorting nexin SNX27 regulate apical targeting of membrane mucin MUC17 in enterocytes

A dense glycocalyx, composed of the megaDalton-sized membrane mucin MUC17, coats the microvilli in the apical brush border of transporting intestinal epithelial cells, called enterocytes. The formation of the MUC17-based glycocalyx in the mouse small intestine occurs at the critical suckling-weaning transition. The glycocalyx extends 1 µm into the intestinal lumen and prevents the gut bacteria from directly attaching to the enterocytes. To date, the mechanism behind the positioning of MUC17 to the brush border is not known. Here, we show that the actin-based motor proteins MYO1B and MYO5B, and the sorting nexin SNX27, regulate apical targeting of MUC17 in enterocytes. We demonstrate that MUC17 turnover at the brush border is slow and controlled by MYO1B and SNX27. Furthermore, we report that MYO1B regulates MUC17 protein levels in enterocytes, whereas MYO5B specifically governs MUC17 levels at the brush border. Together, our results extend our understanding of the apical targeting of membrane mucins and provide mechanistic insights into how defective positioning of MUC17 renders enterocytes sensitive to bacterial challenges.

Mucus-on-a-chip: investigating the barrier properties of mucus with organic bioelectronics

Gastrointestinal (GI) mucus is a biologically complex hydrogel that acts as a partially permeable barrier between the contents of the GI tract and the mucosal epithelial lining. Its structural integrity is essential for the lubrication of the tract thereby aiding smooth transit of contents, and the protection of the epithelium from pathogens that seek to colonise and invade. Understanding its physical response to drugs and the microbiome is essential for treating many gastrointestinal infectious diseases. Given this, a static in vitro model of a GI mucus-on-a-chip has been developed with integrated electronics to monitor the barrier properties of mucus hydrogels. Its application for investigating the effect of drugs and biofilm formation on the mucus structure is validated using rheological techniques, confocal microscopy and electrochemical impedance spectroscopy (EIS).

Role of Akkermansia muciniphila in insulin resistance

Insulin resistance (IR) is a pathogenic factor in numerous metabolic diseases. The gut microbiota plays a crucial role in maintaining the function of the intestinal barrier and overall human health, thereby influencing IR. Dysbiosis of the gut microbiota can contribute to the development of IR. Therefore, it is essential to maintain a balanced and diverse gut microbiota for optimal health. Akkermansia muciniphila, a widely present microorganism in the human intestine, has been shown to regulate gastrointestinal mucosal barrier integrity, reduce endotoxin penetration, decrease systemic inflammation levels, and improve insulin sensitivity. Reduced abundance of A. muciniphila is associated with an increased risk of IR and other metabolic diseases, highlighting its correlation with IR. Understanding the role and regulatory mechanism of A. muciniphila is crucial for comprehending IR pathogenesis and developing novel strategies for preventing and treating related metabolic disorders. Individual variations may exist in both the gut microbiota composition and its impact on IR among different individuals. Further investigation into individual differences between A. muciniphila and IR will facilitate advancements in personalized medicine by promoting tailored interventions based on the gut microbiota composition, which is a potential future direction that would optimize insulin sensitivity while preventing metabolic disease occurrence. In this review, we describe the physiological characteristics of A. muciniphila, emphasize its roles in underlying mechanisms contributing to IR pathology, and summarize how alterations in its abundance affect IR development, thereby providing valuable insights for further research on A. muciniphila, as well as new drug development targeting diabetes.

Nanoencapsulation of vitamin B2 using chitosan-modified poly(lactic-co-glycolic acid) nanoparticles: Synthesis, characterization, and in vitro studies on simulated gastrointestinal stability and delivery

Vitamin B2, or riboflavin, is essential for maintaining healthy cellular metabolism and function. However, its light sensitivity, poor water solubility, and gastrointestinal barriers limit its storage, delivery, and absorption. Selecting suitable nanomaterials for encapsulating vitamin B2 is crucial to overcoming these challenges. This study employed chitosan-coated poly(lactic-co-glycolic acid) nanoparticles (CS-PLGA NPs) as a novel delivery system to enhance the bioavailability of vitamin B2 for food fortification and nutraceutical applications. The nanoparticles, with sizes below 200 nm, exhibited greater stability than PLGA NPs after freeze-drying and in simulated body fluids. Encapsulation improved the photostability of vitamin B2 under ultraviolet light and prolonged its release in simulated body fluids compared to non-encapsulated vitamin B2. Furthermore, CS-PLGA NPs demonstrated higher uptake in intestinal epithelial cells (Caco-2), indicating enhanced transport and potential for use in fortified food systems. These findings underscore the promise of CS-PLGA NPs for delivering vitamin B2 in food, nutraceutical, and pharmaceutical applications. PRACTICAL APPLICATION: The use of chitosan-coated PLGA NPs for encapsulating vitamin B2 offers a promising solution to enhance its bioavailability, especially for individuals with gastrointestinal absorption issues. This formulation improves stability, controlled release, and cellular uptake, which can lead to more effective supplementation strategies in nutraceutical and pharmaceutical applications. It could benefit patients with vitamin B2 deficiencies, such as those with malabsorption disorders, by ensuring efficient delivery through the gastrointestinal tract. Additionally, this approach can be applied to other water-soluble vitamins or bioactive compounds, offering a versatile platform for improving the efficacy of oral supplements.

Potential and challenges in application of physiologically based pharmacokinetic modeling in predicting diarrheal disease impact on oral drug pharmacokinetics

Physiologically based pharmacokinetic (PBPK) modeling is a physiologically relevant approach that integrates drug-specific and system parameters to generate pharmacokinetic predictions for target populations. It has gained immense popularity for drug-drug interaction, organ impairment, and special population studies over the past 2 decades. However, an application of PBPK modeling with great potential remains rather overlooked-prediction of diarrheal disease impact on oral drug pharmacokinetics. Oral drug absorption is a complex process involving the interplay between physicochemical characteristics of the drug and physiological conditions in the gastrointestinal tract. Diarrhea, a condition common to numerous diseases impacting many worldwide, is associated with physiological changes in many processes critical to oral drug absorption. In this Minireview, we outline key processes governing oral drug absorption, provide a high-level overview of key parameters for modeling oral drug absorption in PBPK models, examine how diarrheal diseases may impact these processes based on literature findings, illustrate the clinical relevance of diarrheal disease impact on oral drug absorption, and discuss the potential and challenges of applying PBPK modeling in predicting disease impacts. SIGNIFICANCE STATEMENT: Pathophysiological changes resulting from diarrheal diseases can alter important factors governing oral drug absorption, contributing to suboptimal drug exposure and treatment failure. Physiologically based pharmacokinetic (PBPK) modeling is an in silico approach that has been increasingly adopted for drug-drug interaction potential, organ impairment, and special population assessment. This Minireview highlights the potential and challenges of using physiologically based pharmacokinetic modeling as a tool to improve our understanding of how diarrheal diseases impact oral drug pharmacokinetics.