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Cell Mar 2022Intestinal mucus forms the first line of defense against bacterial invasion while providing nutrition to support microbial symbiosis. How the host controls mucus barrier...
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.
Topics: Animals; Gastrointestinal Microbiome; Homeostasis; Humans; Inflammatory Bowel Diseases; Intestinal Mucosa; Mice; Mucus; Sialyltransferases; Symbiosis
PubMed: 35303419
DOI: 10.1016/j.cell.2022.02.013 -
Physiological Reviews Oct 2022The mucus clearance system is the dominant mechanical host defense system of the human lung. Mucus is cleared from the lung by cilia and airflow, including both... (Review)
Review
The mucus clearance system is the dominant mechanical host defense system of the human lung. Mucus is cleared from the lung by cilia and airflow, including both two-phase gas-liquid pumping and cough-dependent mechanisms, and mucus transport rates are heavily dependent on mucus concentration. Importantly, mucus transport rates are accurately predicted by the gel-on-brush model of the mucociliary apparatus from the relative osmotic moduli of the mucus and periciliary-glycocalyceal (PCL-G) layers. The fluid available to hydrate mucus is generated by transepithelial fluid transport. Feedback interactions between mucus concentrations and cilia beating, via purinergic signaling, coordinate Na absorptive vs Cl secretory rates to maintain mucus hydration in health. In disease, mucus becomes hyperconcentrated (dehydrated). Multiple mechanisms derange the ion transport pathways that normally hydrate mucus in muco-obstructive lung diseases, e.g., cystic fibrosis (CF), chronic obstructive pulmonary disease (COPD), non-CF bronchiectasis (NCFB), and primary ciliary dyskinesia (PCD). A key step in muco-obstructive disease pathogenesis is the osmotic compression of the mucus layer onto the airway surface with the formation of adherent mucus plaques and plugs, particularly in distal airways. Mucus plaques create locally hypoxic conditions and produce airflow obstruction, inflammation, infection, and, ultimately, airway wall damage. Therapies to clear adherent mucus with hydrating and mucolytic agents are rational, and strategies to develop these agents are reviewed.
Topics: Cystic Fibrosis; Humans; Lung; Mucociliary Clearance; Mucus; Pulmonary Disease, Chronic Obstructive
PubMed: 35001665
DOI: 10.1152/physrev.00004.2021 -
Gut Dec 2020The gastrointestinal tract is often considered as a key organ involved in the digestion of food and providing nutrients to the body for proper maintenance. However, this... (Review)
Review
The gastrointestinal tract is often considered as a key organ involved in the digestion of food and providing nutrients to the body for proper maintenance. However, this system is composed of organs that are extremely complex. Among the different parts, the intestine is viewed as an incredible surface of contact with the environment and is colonised by hundreds of trillions of gut microbes. The role of the gut barrier has been studied for decades, but the exact mechanisms involved in the protection of the gut barrier are various and complementary. Among them, the integrity of the mucus barrier is one of the first lines of protection of the gastrointestinal tract. In the past, this 'slimy' partner was mostly considered a simple lubricant for facilitating the progression of the food bolus and the stools in the gut. Since then, different researchers have made important progress, and currently, the regulation of this mucus barrier is gaining increasing attention from the scientific community. Among the factors influencing the mucus barrier, the microbiome plays a major role in driving mucus changes. Additionally, our dietary habits (ie, high-fat diet, low-fibre/high-fibre diet, food additives, pre- probiotics) influence the mucus at different levels. Given that the mucus layer has been linked with the appearance of diseases, proper knowledge is highly warranted. Here, we debate different aspects of the mucus layer by focusing on its chemical composition, regulation of synthesis and degradation by the microbiota as well as some characteristics of the mucus layer in both physiological and pathological situations.
Topics: Diet; Gastrointestinal Microbiome; Gastrointestinal Tract; Host Microbial Interactions; Humans; Inflammatory Bowel Diseases; Intestinal Mucosa; Microbiota; Mucins; Mucus; Probiotics
PubMed: 32917747
DOI: 10.1136/gutjnl-2020-322260 -
Annual Review of Biochemistry Jun 2020Generating the barriers that protect our inner surfaces from bacteria and other challenges requires large glycoproteins called mucins. These come in two types,... (Review)
Review
Generating the barriers that protect our inner surfaces from bacteria and other challenges requires large glycoproteins called mucins. These come in two types, gel-forming and transmembrane, all characterized by large, highly -glycosylated mucin domains that are diversely decorated by Golgi glycosyltransferases to become extended rodlike structures. The general functions of mucins on internal epithelial surfaces are to wash away microorganisms and, even more importantly, to build protective barriers. The latter function is most evident in the large intestine, where the inner mucus layer separates the numerous commensal bacteria from the epithelial cells. The host's conversion of MUC2 to the outer mucus layer allows bacteria to degrade the mucin glycans and recover the energy content that is then shared with the host. The molecular nature of the mucins is complex, and how they construct the extracellular complex glycocalyx and mucus is poorly understood and a future biochemical challenge.
Topics: Animals; Carbohydrate Conformation; Carbohydrate Sequence; Gastrointestinal Microbiome; Gene Expression; Glycocalyx; Glycosylation; Glycosyltransferases; Goblet Cells; Humans; Mucins; Mucus; Symbiosis
PubMed: 32243763
DOI: 10.1146/annurev-biochem-011520-105053 -
Cell Host & Microbe Jul 2023The colon mucus layer is organized with an inner colon mucus layer that is impenetrable to bacteria and an outer mucus layer that is expanded to allow microbiota... (Review)
Review
The colon mucus layer is organized with an inner colon mucus layer that is impenetrable to bacteria and an outer mucus layer that is expanded to allow microbiota colonization. A major component of mucus is MUC2, a glycoprotein that is extensively decorated, especially with O-glycans. In the intestine, goblet cells are specialized in controlling glycosylation and making mucus. Some microbiota members are known to encode multiple proteins that are predicted to bind and/or cleave mucin glycans. The interactions between commensal microbiota and host mucins drive intestinal colonization, while at the same time, the microbiota can utilize the glycans on mucins and affect the colonic mucus properties. This review will examine this interaction between commensal microbes and intestinal mucins and discuss how this interplay affects health and disease.
Topics: Intestinal Mucosa; Mucin-2; Intestines; Mucus; Mucins; Microbiota; Polysaccharides
PubMed: 37442097
DOI: 10.1016/j.chom.2023.05.026 -
Cell Oct 2022Neuroepithelial crosstalk is critical for gut physiology. However, the mechanisms by which sensory neurons communicate with epithelial cells to mediate gut barrier...
Neuroepithelial crosstalk is critical for gut physiology. However, the mechanisms by which sensory neurons communicate with epithelial cells to mediate gut barrier protection at homeostasis and during inflammation are not well understood. Here, we find that Nav1.8CGRP nociceptor neurons are juxtaposed with and signal to intestinal goblet cells to drive mucus secretion and gut protection. Nociceptor ablation led to decreased mucus thickness and dysbiosis, while chemogenetic nociceptor activation or capsaicin treatment induced mucus growth. Mouse and human goblet cells expressed Ramp1, receptor for the neuropeptide CGRP. Nociceptors signal via the CGRP-Ramp1 pathway to induce rapid goblet cell emptying and mucus secretion. Notably, commensal microbes activated nociceptors to control homeostatic CGRP release. In the absence of nociceptors or epithelial Ramp1, mice showed increased epithelial stress and susceptibility to colitis. Conversely, CGRP administration protected nociceptor-ablated mice against colitis. Our findings demonstrate a neuron-goblet cell axis that orchestrates gut mucosal barrier protection.
Topics: Mice; Humans; Animals; Goblet Cells; Nociceptors; Calcitonin Gene-Related Peptide; Colitis; Mucus; Receptor Activity-Modifying Protein 1
PubMed: 36243004
DOI: 10.1016/j.cell.2022.09.024 -
Annals of the American Thoracic Society Nov 2018The lung is continuously exposed to particles, toxicants, and microbial pathogens that are cleared by a complex mechanical, innate, and acquired immune system.... (Review)
Review
The lung is continuously exposed to particles, toxicants, and microbial pathogens that are cleared by a complex mechanical, innate, and acquired immune system. Mucociliary clearance, mediated by the actions of diverse conducting airway and submucosal gland epithelial cells, plays a critical role in a multilayered defense system by secreting fluids, electrolytes, antimicrobial and antiinflammatory proteins, and mucus onto airway surfaces. The mucociliary escalator removes particles and pathogens by the mechanical actions of cilia and cough. Abnormalities in mucociliary clearance, whether related to impaired fluid secretion, ciliary dysfunction, lack of cough, or the disruption of epithelial cells lining the respiratory tract, contribute to the pathogenesis of common chronic pulmonary disorders. Although mucus and other airway epithelial secretions play a critical role in protecting the lung during acute injury, impaired mucus clearance after chronic mucus hyperproduction causes airway obstruction and infection, which contribute to morbidity in common pulmonary disorders, including chronic obstructive pulmonary disease, asthma, idiopathic pulmonary fibrosis, cystic fibrosis, bronchiectasis, and primary ciliary dyskinesia. In this summary, the molecular and cellular mechanisms mediating airway mucociliary clearance, as well as the role of goblet cell metaplasia and mucus hyperproduction, in the pathogenesis of chronic respiratory diseases are considered.
Topics: Cell Differentiation; Cilia; Epithelial Cells; Humans; Lung Diseases; Mucins; Mucociliary Clearance; Mucus
PubMed: 30431340
DOI: 10.1513/AnnalsATS.201802-128AW -
Immunological Reviews Jul 2014The gastrointestinal tract is covered by mucus that has different properties in the stomach, small intestine, and colon. The large highly glycosylated gel-forming mucins... (Review)
Review
The gastrointestinal tract is covered by mucus that has different properties in the stomach, small intestine, and colon. The large highly glycosylated gel-forming mucins MUC2 and MUC5AC are the major components of the mucus in the intestine and stomach, respectively. In the small intestine, mucus limits the number of bacteria that can reach the epithelium and the Peyer's patches. In the large intestine, the inner mucus layer separates the commensal bacteria from the host epithelium. The outer colonic mucus layer is the natural habitat for the commensal bacteria. The intestinal goblet cells secrete not only the MUC2 mucin but also a number of typical mucus components: CLCA1, FCGBP, AGR2, ZG16, and TFF3. The goblet cells have recently been shown to have a novel gate-keeping role for the presentation of oral antigens to the immune system. Goblet cells deliver small intestinal luminal material to the lamina propria dendritic cells of the tolerogenic CD103(+) type. In addition to the gel-forming mucins, the transmembrane mucins MUC3, MUC12, and MUC17 form the enterocyte glycocalyx that can reach about a micrometer out from the brush border. The MUC17 mucin can shuttle from a surface to an intracellular vesicle localization, suggesting that enterocytes might control and report epithelial microbial challenge. There is communication not only from the epithelial cells to the immune system but also in the opposite direction. One example of this is IL10 that can affect and improve the properties of the inner colonic mucus layer. The mucus and epithelial cells of the gastrointestinal tract are the primary gate keepers and controllers of bacterial interactions with the host immune system, but our understanding of this relationship is still in its infancy.
Topics: Animals; Enterocytes; Gastrointestinal Tract; Goblet Cells; Humans; Immune System; Mucins; Mucous Membrane; Mucus; Peyer's Patches
PubMed: 24942678
DOI: 10.1111/imr.12182 -
Annual Review of Pathology Jan 2023Despite the advent of sophisticated and efficient new biologics to treat inflammation in asthma, the disease persists. Even following treatment, many patients still... (Review)
Review
Despite the advent of sophisticated and efficient new biologics to treat inflammation in asthma, the disease persists. Even following treatment, many patients still experience the well-known symptoms of wheezing, shortness of breath, and coughing. What are we missing? Here we examine the evidence that mucus plugs contribute to a substantial portion of disease, not only by physically obstructing the airways but also by perpetuating inflammation. In this way, mucus plugs may act as an immunogenic stimulus even in the absence of allergen or with the use of current therapeutics. The alterations of several parameters of mucus biology, driven by type 2 inflammation, result in sticky and tenacious sputum, which represents a potent threat, first due to the difficulties in expectoration and second by acting as a platform for viral, bacterial, or fungal colonization that allows exacerbations. Therefore, in this way, mucus plugs are an overlooked but critical feature of asthmatic airway disease.
Topics: Humans; Asthma; Mucus; Sputum; Inflammation
PubMed: 36270294
DOI: 10.1146/annurev-pathol-042220-015902 -
American Journal of Respiratory and... May 2022Cross-sectional analysis of mucus plugs in computed tomography (CT) lung scans in the Severe Asthma Research Program (SARP)-3 showed a high mucus plug phenotype. To...
Cross-sectional analysis of mucus plugs in computed tomography (CT) lung scans in the Severe Asthma Research Program (SARP)-3 showed a high mucus plug phenotype. To determine if mucus plugs are a persistent asthma phenotype and if changes in mucus plugs over time associate with changes in lung function. In a longitudinal analysis of baseline and Year 3 CT lung scans in SARP-3 participants, radiologists generated mucus plug scores to assess mucus plug persistence over time. Changes in mucus plug score were analyzed in relation to changes in lung function and CT air trapping measures. In 164 participants, the mean (range) mucus plug score was similar at baseline and Year 3 (3.4 [0-20] vs. 3.8 [0-20]). Participants and bronchopulmonary segments with a baseline plug were more likely to have plugs at Year 3 than those without baseline plugs (risk ratio, 2.8; 95% confidence interval [CI], 2.0-4.1; < 0.001; and risk ratio, 5.0; 95% CI, 4.5-5.6; < 0.001, respectively). The change in mucus plug score from baseline to Year 3 was significantly negatively correlated with change in FEV% predicted ( = -0.35; < 0.001) and with changes in CT air trapping measures (all values < 0.05). Mucus plugs identify a persistent asthma phenotype, and susceptibility to mucus plugs occurs at the subject and the bronchopulmonary segment level. The association between change in mucus plug score and change in airflow over time supports a causal role for mucus plugs in mechanisms of airflow obstruction in asthma.
Topics: Asthma; Cross-Sectional Studies; Humans; Lung; Mucus; Respiratory Function Tests
PubMed: 35104436
DOI: 10.1164/rccm.202110-2265OC