Proteome of airway surface liquid and mucus in newborn wildtype and cystic fibrosis piglets.

BACKGROUND: The respiratory tract is protected from inhaled particles and microbes by mucociliary clearance, mediated by the mucus and the cilia creating a flow to move the mucus cephalad. Submucosal glands secrete linear MUC5B mucin polymers and because they pass through the gland duct before reaching the airway surface, bundled strands of 1000-5000 parallel molecules exit the glands. In contrast, the surface goblet cells secrete both MUC5AC and MUC5B. METHODS: We used mass-spectrometry based proteomic analysis of unstimulated and carbachol stimulated newborn wild-type (WT) and cystic fibrosis transmembrane conductance regulator (CFTR) null (CF) piglet airways to study proteins in the airway surface liquid and mucus, to investigate if levels of MUC5AC and MUC5B were affected by carbachol stimulation and whether the proteins clustered according to function. RESULTS: Proteins in the first four extracted fractions clustered together and the fifth fraction contained the mucus cluster, mucins and other proteins known to associate with mucins, whereas the traditional airway surface liquid proteins clustered to fraction 1-4 and were absent from the mucus fraction. Carbachol stimulation resulted in increased MUC5AC and MUC5B. CONCLUSIONS: These results indicate a distinct separation between proteins in the washable surface liquid and the mucus fraction. In fractions 1-4 from newborn CF piglets an additional cluster containing acute phase proteins was observed, suggesting an early inflammatory response in CF piglets. Alternatively, increased levels of these proteins could indicate altered lung development in the CF piglets. This observation suggests that CF airway disease is present at birth and thus, treatment should commence directly after diagnosis.

The protective role of conjunctival goblet cell mucin sialylation.

Gel-forming mucins secreted by conjunctival goblet cells have been implicated in the clearance of allergens, pathogens, and debris. However, their roles remain incompletely understood. Here we show that human and mouse conjunctival goblet cell mucins have Alcian blue-detectable sialic acids, but not sulfates in the steady state. Interestingly, Balb/c mouse strain lacks this sialylation due to a point mutation in a sialyltransferase gene, St6galnac1, which is responsible for sialyl-Tn synthesis. Introduction of intact St6galnac1 to Balb/c restores the sialylation of conjunctival goblet cell mucus. Sialylated mucus efficiently captures and encapsulates the allergen particles in an impenetrable layer, leading to the protection of mice from the development of allergic conjunctivitis. Expression of ST6GALNAC1 and sialyl-Tn is upregulated in humans under conditions with chronic stimuli. These results indicate that the sialylated glycans on the ocular mucins play an essential role in maintaining the conjunctival mucosa by protecting from the incoming foreign bodies such as allergen particles.

Epidermal threads reveal the origin of hagfish slime.

When attacked, hagfishes produce a soft, fibrous defensive slime within a fraction of a second by ejecting mucus and threads into seawater. The rapid setup and remarkable expansion of the slime make it a highly effective and unique form of defense. How this biomaterial evolved is unknown, although circumstantial evidence points to the epidermis as the origin of the thread- and mucus-producing cells in the slime glands. Here, we describe large intracellular threads within a putatively homologous cell type from hagfish epidermis. These epidermal threads averaged ~2 mm in length and ~0.5 µm in diameter. The entire hagfish body is covered by a dense layer of epidermal thread cells, with each square millimeter of skin storing a total of ~96 cm threads. Experimentally induced damage to a hagfish's skin caused the release of threads, which together with mucus, formed an adhesive epidermal slime that is more fibrous and less dilute than the defensive slime. Transcriptome analysis further suggests that epidermal threads are ancestral to the slime threads, with duplication and diversification of thread genes occurring in parallel with the evolution of slime glands. Our results support an epidermal origin of hagfish slime, which may have been driven by selection for stronger and more voluminous slime.

Hagfishes are deep-sea animals, and they represent one of the oldest living relatives of animals with backbones. To defend themselves against predators, they produce a remarkable slime that is reinforced with fibers and can clog a predator's gills, thwarting the attack. The slime deploys in less than half a second, exuding from specialized glands on the hagfish's body and expanding up to 10,000 times its ejected volume. The defensive slime is highly dilute, consisting mostly of sea water, with low concentrations of mucus and strong, silk-like threads that are approximately 20 centimeters long. Where and how hagfish slime evolved remains a mystery. Zeng et al. set out to answer where on the hagfish's body the slime glands originated, and how they may have evolved. First, Zeng et al. examined hagfishes and found that cells in the surface layer of their skin (the epidermis) produce threads roughly two millimeters in length that are released when the hagfish's skin is damaged. These threads mix with the mucus that is produced by ruptured skin cells to form a slime that likely adheres to predators' mouths. This slime could be a precursor of the slime produced by the specialized glands. To test this hypothesis, Zeng et al. analyzed which genes are turned on and off both in the hagfishes' skin and in their slime glands. The patterns they found are consistent with the slime glands originating from the epidermis. Based on these results, Zeng et al. propose that ancient hagfishes first evolved the ability to produce slime with anti-predator effects when their skin was damaged in attacks. Over time, hagfishes that could produce and store more slime and eject it actively into a predator's mouth likely had a better chance of surviving. This advantage may have led to the appearance of increasingly specialized glands that could carry out these functions. The findings of Zeng et al. will be of interest to evolutionary biologists, marine biologists, and those studying the ecology of predator-prey interactions. Because of its unique material properties, hagfish slime is also of interest to biophysicists, bioengineers and those engaged in biomimetic research. The origin of hagfish slime glands is an interesting example of how a new trait evolved, and may provide insight into the evolution of other adaptive traits.

Rosmarinic Acid Restores Colonic Mucus Secretion in Colitis Mice by Regulating Gut Microbiota-Derived Metabolites and the Activation of Inflammasomes.

Maintaining a steady state of mucus barrier is an important potential target for polyphenol to exert its anticolitis activity. This study elucidates the pivotal role of polyphenol rosmaric acid (RA) in regulating the mucus barrier function and alleviating inflammation by identifying its gut microbiota-derived metabolites and evaluating its inhibitory effect on inflammasomes in colitis mice. Results demonstrated that RA treatment promoted the proliferation of goblet cells and restored the level of mucus secretion, especially Muc2. RA reshaped the microbiota of colitis mice, particularly the boost of core probiotics, such as p. Bacteroidaceae, f. Muribaculaceae, g. Muribaculaceae, g. Alistipes, and g. Clostridia_UCG-014. Nontargeted metabonomics and targeted metabonomics confirmed a significant increase in the bile acids and their metabolites (7-sulfocholic acid, stercobilin, chenodeoxycholic acid 3-sulfate, chenodeoxycholic acid sulfate, and ursodeoxycholic acid 3-sulfate), indole metabolites ((R)-2,3-dihydro-3,5-dihydroxy-2-oxo-3-indoleacetic acid, frovatriptan, 3-formyl-6-hydroxyindole, and brassicanal A), and short-chain fatty acids (SCFAs) (acetic acid, butyric acid, isobutyric acid, isovaleric acid, and valeric acid) that contributed to the strengthened mucus barrier function. In addition, being absorbed mainly in the lower digestive tract, RA inhibited the overexpression of inflammasomes (especially NLRP6) that occurred in colitis mice to promote the mucus secretion of goblet cells. These data confirmed that RA, as a promising candidate to enhance gut health, restored colonic mucus secretion in colitis mice by mediating the production of gut microbiota-derived metabolites and the overexpression of inflammasomes. The presented study provides scientific evidence explaining the apparent paradox of low bioavailability and high bioactivity in polyphenols.

Mucus increases cell iron uptake to impact the release of pro-inflammatory mediators after particle exposure.

We tested the hypothesis that (1) mucus production can be included in the cell response to iron deficiency; (2) mucus binds iron and increases cell metal uptake; and subsequently (3) mucus impacts the inflammatory response to particle exposure. Using quantitative PCR, RNA for both MUC5B and MUC5AC in normal human bronchial epithelial (NHBE) cells decreased following exposures to ferric ammonium citrate (FAC). Incubation of mucus-containing material collected from the apical surface of NHBE cells grown at air-liquid interface (NHBE-MUC) and a commercially available mucin from porcine stomach (PORC-MUC) with iron demonstrated an in vitro capacity to bind metal. Inclusion of either NHBE-MUC or PORC-MUC in incubations of both BEAS-2B cells and THP1 cells increased iron uptake. Exposure to sugar acids (N-acetyl neuraminic acid, sodium alginate, sodium guluronate, and sodium hyaluronate) similarly increased cell iron uptake. Finally, increased metal transport associated with mucus was associated with a decreased release of interleukin-6 and -8, an anti-inflammatory effect, following silica exposure. We conclude that mucus production can be involved in the response to a functional iron deficiency following particle exposure and mucus can bind metal, increase cell uptake to subsequently diminish or reverse a functional iron deficiency and inflammatory response following particle exposure.

Interactions between microbiota and cervical epithelial, immune, and mucus barrier.

The female reproductive tract harbours hundreds of bacterial species and produces numerous metabolites. The uterine cervix is located between the upper and lower parts of the female genital tract. It allows sperm and birth passage and hinders the upward movement of microorganisms into a relatively sterile uterus. It is also the predicted site for sexually transmitted infection (STI), such as Chlamydia, human papilloma virus (HPV), and human immunodeficiency virus (HIV). The healthy cervicovaginal microbiota maintains cervical epithelial barrier integrity and modulates the mucosal immune system. Perturbations of the microbiota composition accompany changes in microbial metabolites that induce local inflammation, damage the cervical epithelial and immune barrier, and increase susceptibility to STI infection and relative disease progression. This review examined the intimate interactions between the cervicovaginal microbiota, relative metabolites, and the cervical epithelial-, immune-, and mucus barrier, and the potent effect of the host-microbiota interaction on specific STI infection. An improved understanding of cervicovaginal microbiota regulation on cervical microenvironment homeostasis might promote advances in diagnostic and therapeutic approaches for various STI diseases.

[Role of brown adipose tissue in phlegm-dampness metabolic syndrome based on infrared thermal imaging].

This study aimed to explore the infrared manifestation and role of brown adipose tissue(BAT) in phlegm-dampness me-tabolic syndrome(MS), and to provide objective basis for clinical diagnosis and treatment of phlegm-dampness MS. Subjects were selected from the department of endocrinology and ward in the South District of Guang'anmen Hospital, China Academy of Chinese Medical Sciences from August 2021 to April 2022, including 20 in healthy control group, 40 in non phlegm-dampness MS group and 40 in phlegm-dampness MS group. General information, height and weight of the subjects were collected and body mass index(BMI) was calculated. Waist circumference(WC), systolic blood pressure(SBP) and diastolic blood pressure(DBP) was measured. Triglyceride(TG), high density lipoprotein cholesterol(HDL-C), fasting blood glucose(FBG), fasting insulin(FINS), leptin(LP), adiponectin(ADP) and fibroblast growth factor-21(FGF-21) were detected. The infrared thermal image of the supraclavicular region(SCR) of the subjects before and after cold stimulation test was collected by infrared thermal imager and the changes of infrared thermal image in the three groups were observed. In addition, the differences in the average body surface temperature of SCR among the three groups were compared, and the changes of BAT in SCR were analyzed. The results showed compared with the conditions in healthy control group, the levels of WC, SBP, DBP, TG and FPG in MS groups were increased(P<0.01), and the HDL-C level was decreased(P<0.01). Compared with non phlegm-dampness MS group, phlegm-dampness MS group had higher conversion score of phlegm dampness physique(P<0.01). According to the infrared heat map, there was no difference in the average body surface temperature of SCR among the three groups before cold stimulation. while after cold stimulation, the average body surface temperature of SCR in MS groups was lower than that in healthy control group(P<0.05). After cold stimulation, the maximum temperature of SCR and its arrival time in the three groups were as follows: healthy control group(3 min)>non phlegm-dampness MS group(4 min)>phlegm-dampness MS group(5 min). The thermal deviation of SCR was increased and the average body surface temperature of left and right sides were higher(P<0.01) in healthy control group and non phlegm-dampness MS group, while the thermal deviation of SCR did not change significantly in the phlegm-dampness MS group. Compared with that in healthy control group, the elevated temperature between left and right sides was lower(P<0.01, P<0.05), and compared with that in non phlegm-dampness MS group, the elevated temperature of left side was lower(P<0.05). The changes of the average body surface temperature of SCR in the three groups were in the order of healthy control group>non phlegm-dampness MS group>phlegm-dampness MS group. Compared with the conditions in healthy control group and non phlegm-dampness MS group, FINS, BMI and FGF-21 levels were increased(P<0.01,P<0.05), while ADP level was decreased(P<0.01, P<0.05) in phlegm-dampness MS group. Moreover, the LP level in phlegm-dampness MS group was higher than that in non phlegm-dampness MS group(P<0.01). It was observed in clinical trials that after cold stimulation, the average body surface temperature of SCR in MS patients was lower than that of the healthy people; the thermal deviation of SCR did not change significantly in the phlegm-dampness MS patients, and the difference in their elevated temperature was lower than that in the other two groups. These characteristics provided objective basis for clinical diagnosis and treatment of phlegm-dampness MS. With abnormal BAT related indicators, it was inferred that the content or activity of BAT in SCR of phlegm-dampness MS patients were reduced. There was a high correlation between BAT and phlegm-dampness MS, and thus BAT might become an important potential target for the intervention in phlegm-dampness MS.

An operative framework to model mucus clearance in silico by coupling cilia motion with the liquid environment.

Mucociliary clearance is the first defense mechanism of the respiratory tract against inhaled particles. This mechanism is based on the collective beating motion of cilia at the surface of epithelial cells. Impaired clearance, either caused by malfunctioning or absent cilia, or mucus defects, is a symptom of many respiratory diseases. Here, by exploiting the lattice Boltzmann particle dynamics technique, we develop a model to simulate the dynamics of multiciliated cells in a two-layer fluid. First, we tuned our model to reproduce the characteristic length- and time-scales of the cilia beating. We then check for the emergence of the metachronal wave as a consequence of hydrodynamic mediated correlations between beating cilia. Finally, we tune the viscosity of the top fluid layer to simulate the mucus flow upon cilia beating, and evaluate the pushing efficiency of a carpet of cilia. With this work, we build a realistic framework that can be used to explore several important physiological aspects of mucociliary clearance.

Stressing out over mucus secretion.

In this issue of Cell Host & Microbe, Naama et al. show that autophagy controls mucus secretion in the colons of mice. They demonstrate that autophagy reduces ER stress in mucus-producing goblet cells to enhance mucus production, which shapes the gut microbial community and protects against colitis.

Comparative study between histochemical mucus volume, histopathological findings, and endocytoscopic scores in patients with ulcerative colitis.

Ulcerative colitis (UC) causes a reduction in goblet cells. However, there have been few reports on the relationship between endoscopic and pathological findings and mucus volume. In this study, we quantitatively evaluated histochemical colonic mucus volume by fixing biopsied tissue sections taken from patients with UC in Carnoy's solution and compared it with endoscopic and pathological findings to determine whether there is a correlation between them. Observational study. A single-center, university hospital in Japan. Twenty-seven patients with UC (male/female, 16/11; mean age, 48.4 years; disease median duration, 9 years) were included in the study. The colonic mucosa of the most inflamed area and the surrounding less inflamed area were evaluated separately by local MES and endocytoscopic (EC) classification. Two biopsies were taken from each area; one was fixed with formalin for histopathological evaluation, and the other was fixed with Carnoy's solution for the quantitative evaluation of mucus via histochemical Periodic Acid Schiff and Alcian Blue staining. The relative mucus volume was significantly reduced in the local MES 1-3 groups, with worsening findings in EC-A/B/C and in groups with severe mucosal inflammation, crypt abscess, and severe reduction in goblet cells. The severity of inflammatory findings in UC by EC classification correlated with the relative mucus volume suggesting functional mucosal healing. We found a correlation between the colonic mucus volume and endoscopic and histopathological findings in patients with UC, and a stepwise correlation with disease severity, particularly in EC classification.

Skin mucus metabolomics provides insights into the interplay between diet and wound in gilthead seabream (Sparus aurata).

The molecular processes underlying skin wound healing in several fish species have been elucidated in the last years, however, metabolomic insights are scarce. Here we report the skin mucus metabolome of wounded and non-wounded gilthead seabream (Sparus aurata) fed with silk fibroin microparticles, a functional additive considered to accelerate the wound healing process. The three experimental diets (commercial diet enriched with 0 mg (control), 50 mg or 100 mg of silk fibroin microparticles Kg-1) were administered for 30 days and thereafter, a skin wound was inflicted. Skin mucus was collected on day 30 of feeding and 7 days post-wounding and subjected to metabolomic analysis by Ultra Performance Liquid Chromatography coupled with a high-resolution quadrupole-orbitrap mass spectrometry. The most enriched metabolite class was amino acids and derivatives, followed by nucleotides, nucleosides and analogues and carbohydrates and their derivatives. Metabolomic profiles revealed that the diet had a more profound effect than wounding in skin mucus. Metabolic pathway analysis of significantly affected metabolites revealed perturbations in the aminoacyl t-RNA biosynthesis in the skin. In particular, skin wound resulted in a decreased methionine level in mucus. Further, silk fibroin supplementation increased methionine level in skin mucus, which correlated with several wound morphometric parameters that characterized the epithelial healing capacity in seabream. The results provided new insight into the physiological consequences of skin wounds and how these processes could be influenced by dietary manipulation.

Autophagy controls mucus secretion from intestinal goblet cells by alleviating ER stress.

Colonic goblet cells are specialized epithelial cells that secrete mucus to physically separate the host and its microbiota, thus preventing bacterial invasion and inflammation. How goblet cells control the amount of mucus they secrete is unclear. We found that constitutive activation of autophagy in mice via Beclin 1 enables the production of a thicker and less penetrable mucus layer by reducing endoplasmic reticulum (ER) stress. Accordingly, genetically inhibiting Beclin 1-induced autophagy impairs mucus secretion, while pharmacologically alleviating ER stress results in excessive mucus production. This ER-stress-mediated regulation of mucus secretion is microbiota dependent and requires the Crohn's-disease-risk gene Nod2. Overproduction of mucus alters the gut microbiome, specifically expanding mucus-utilizing bacteria, such as Akkermansia muciniphila, and protects against chemical and microbial-driven intestinal inflammation. Thus, ER stress is a cell-intrinsic switch that limits mucus secretion, whereas autophagy maintains intestinal homeostasis by relieving ER stress.

Compositional changes and ecological characteristics of earthworm mucus under different electrical stimuli.

Earthworm mucus is rich in nutrients that can initiate the mineralization and humification of organic matter and is of great importance for contaminated soil remediation and sludge reutilization. In this study, six voltage and current combinations were utilized to promote earthworm mucus production (5 V and 6 V at 10, 20 and 30 mA, respectively), to explore the compositional changes of the mucus produced under different electrical stimuli, and to propose the best electrical stimulation group and mucus fraction applicable to soil heavy metal pollution remediation and sludge reutilization. The results showed that the mucus produced by the six electrical stimuli was mainly composed of proteins, amino acids, carbohydrates, fatty acids, and polysaccharides, with small amounts of alcohol, phenol, and ester organic substances. Under different electrical stimuli, each component changed significantly (P < 0.05). pH and conductivity were higher at 6 V 20 mA, total nitrogen and phosphorus contents reached their maximum at 5 V 30 mA, and total potassium at 6 V 10 mA. Protein, amino acids, and carbohydrates were most abundant in the mucus produced at 5 V 10 mA, while trace metal elements reached their lowest values at 5 V 10 mA. Finally, based on principal component analysis and combined with previous studies, it was concluded that the mucus produced at 5 V 10 mA was weakly alkaline, high in amino acids and nutrients and low in trace metal elements, and most suitable for sludge and straw composting experiments, soil remediation and amendment experiments.

Comparison of Physicochemical Properties of Native Mucus and Reconstituted Mucin Gels.

Simulating native mucus with model systems such as gels made from reconstituted mucin or commercially available polymers presents experimental advantages including greater sample availability and reduced inter- and intradonor heterogeneity. Understanding whether these gels reproduce the complex physical and biochemical properties of native mucus at multiple length scales is critical to building relevant experimental models, but few systematic comparisons have been reported. Here, we compared bulk mechanical properties, microstructure, and biochemical responses of mucus from different niches, reconstituted mucin gels (with similar pH and polymer concentrations as native tissues), and commonly used commercially available polymers. To evaluate gel properties across these length scales, we used small-amplitude oscillatory shear, single-particle tracking, and microaffinity chromatography with small analytes. With the exception of human saliva, the mechanical response of mucin gels was qualitatively similar to that of native mucus. The transport behavior of charged peptides through native mucus gels was qualitatively reproduced in gels composed of corresponding isolated mucins. Compared to native mucus, we observed substantial differences in the physicochemical properties of gels reconstituted from commercially available mucins and the substitute carboxymethylcellulose, which is currently used in artificial tear and saliva treatments. Our study highlights the importance of selecting a mucus model system guided by the length scale relevant to the scientific investigation or disease application.

Active cycle of breathing technique for cystic fibrosis.

BACKGROUND: People with cystic fibrosis (CF) experience chronic airway infections as a result of mucus buildup within the lungs. Repeated infections often cause lung damage and disease. Airway clearance therapies aim to improve mucus clearance, increase sputum production, and improve airway function. The active cycle of breathing technique (ACBT) is an airway clearance method that uses a cycle of techniques to loosen airway secretions including breathing control, thoracic expansion exercises, and the forced expiration technique. This is an update of a previously published review. OBJECTIVES: To compare the clinical effectiveness of ACBT with other airway clearance therapies in CF. SEARCH METHODS: We searched the Cochrane Cystic Fibrosis Trials Register, compiled from electronic database searches and handsearching of journals and conference abstract books. We also searched clinical trials registries and the reference lists of relevant articles and reviews. Date of last search: 29 March 2021. SELECTION CRITERIA: We included randomised or quasi-randomised controlled clinical studies, including cross-over studies, comparing ACBT with other airway clearance therapies in CF. DATA COLLECTION AND ANALYSIS: Two review authors independently screened each article, abstracted data and assessed the risk of bias of each study. We used GRADE to assess our confidence in the evidence assessing quality of life, participant preference, adverse events, forced expiratory volume in one second (FEV1) % predicted, forced vital capacity (FVC) % predicted, sputum weight, and number of pulmonary exacerbations. MAIN RESULTS: Our search identified 99 studies, of which 22 (559 participants) met the inclusion criteria. Eight randomised controlled studies (259 participants) were included in the analysis; five were of cross-over design. The 14 remaining studies were cross-over studies with inadequate reports for complete assessment. The study size ranged from seven to 65 participants. The age of the participants ranged from six to 63 years (mean age 18.7 years). In 13 studies follow up lasted a single day. However, there were two long-term randomised controlled studies with follow up of one to three years. Most of the studies did not report on key quality items, and therefore, have an unclear risk of bias in terms of random sequence generation, allocation concealment, and outcome assessor blinding. Due to the nature of the intervention, none of the studies blinded participants or the personnel applying the interventions. However, most of the studies reported on all planned outcomes, had adequate follow up, assessed compliance, and used an intention-to-treat analysis. Included studies compared ACBT with autogenic drainage, airway oscillating devices (AOD), high-frequency chest compression devices, conventional chest physiotherapy (CCPT), positive expiratory pressure (PEP), and exercise. We found no difference in quality of life between ACBT and PEP mask therapy, AOD, other breathing techniques, or exercise (very low-certainty evidence). There was no difference in individual preference between ACBT and other breathing techniques (very low-certainty evidence). One study comparing ACBT with ACBT plus postural exercise reported no deaths and no adverse events (very low-certainty evidence). We found no differences in lung function (forced expiratory volume in one second (FEV1) % predicted and forced vital capacity (FVC) % predicted), oxygen saturation or expectorated sputum between ACBT and any other technique (very low-certainty evidence). There were no differences in the number of pulmonary exacerbations between people using ACBT and people using CCPT (low-certainty evidence) or ACBT with exercise (very low-certainty evidence), the only comparisons to report this outcome. AUTHORS' CONCLUSIONS: There is little evidence to support or reject the use of the ACBT over any other airway clearance therapy and ACBT is comparable with other therapies in outcomes such as participant preference, quality of life, exercise tolerance, lung function, sputum weight, oxygen saturation, and number of pulmonary exacerbations. Longer-term studies are needed to more adequately assess the effects of ACBT on outcomes important for people with cystic fibrosis such as quality of life and preference.

Mucin networks: Dynamic structural assemblies controlling mucus function.

Contrary to first appearances, mucus structural biology is not an oxymoron. Though mucus hydrogels derive their characteristics largely from intrinsically disordered, heavily glycosylated polypeptide segments, the secreted mucin glycoproteins that constitute mucus undergo an orderly assembly process controlled by folded domains at their termini. Recent structural studies revealed how mucin complexes promote disulphide-mediated polymerization to produce the mucus gel scaffold. Additional protein-protein and protein-glycan interactions likely tune the mesoscale properties, stability, and activities of mucins. Evidence is emerging that even intrinsically disordered glycosylated segments have specific structural roles in the production and properties of mucus. Though soft-matter biophysical approaches to understanding mucus remain highly relevant, high-resolution structural studies of mucins and other mucus components are providing new perspectives on these vital, protective hydrogels.

View from the Biological Property: Insight into the Functional Diversity and Complexity of the Gut Mucus.

Due to mucin's important protective effect on epithelial tissue, it has garnered extensive attention. The role played by mucus in the digestive tract is undeniable. On the one hand, mucus forms "biofilm" structures that insulate harmful substances from direct contact with epithelial cells. On the other hand, a variety of immune molecules in mucus play a crucial role in the immune regulation of the digestive tract. Due to the enormous number of microorganisms in the gut, the biological properties of mucus and its protective actions are more complicated. Numerous pieces of research have hinted that the aberrant expression of intestinal mucus is closely related to impaired intestinal function. Therefore, this purposeful review aims to provide the highlights of the biological characteristics and functional categorization of mucus synthesis and secretion. In addition, we highlight a variety of the regulatory factors for mucus. Most importantly, we also summarize some of the changes and possible molecular mechanisms of mucus during certain disease processes. All these are beneficial to clinical practice, diagnosis, and treatment and can provide some potential theoretical bases. Admittedly, there are still some deficiencies or contradictory results in the current research on mucus, but none of this diminishes the importance of mucus in protective impacts.

Novel food drug interaction mechanism involving acyclovir, chitosan and endogenous mucus.

Drug absorption from drug products may be affected by pharmaceutical excipients and/or food additives through different mechanisms. Chitosan is a recognized nutraceutical, with potential as an excipient due to its permeability enhancer properties. While chitosan properties have been evaluated in in vitro and pre-clinical models, studies in humans are scarce. Unexpectedly, a controlled clinical trial showed chitosan actually reduced acyclovir bioavailability. The effect seems to be related to an interaction with gastrointestinal mucus that prevents further absorption, although more in depth research is needed to unravel the mechanism. In this paper, we propose a mechanism underlying this excipient effect. The mucus - chitosan interaction was characterized and its effect on acyclovir diffusion, permeation and bioaccessibility was investigated. Further, pharmacokinetic modeling was used to assess the clinical relevance of our findings. Results suggest that in situ coacervation between endogenous mucus and chitosan rapidly entrap 20-30% of acyclovir dissolved dose in the intestinal lumen. This local reduction of acyclovir concentration together with its short absorption window in the small intestine would explain the reduction in acyclovir Cmax and AUC. This study highlights the importance of considering mucus in any biorelevant absorption model attempting to anticipate the effect of chitosan on drug absorption.

Shaoyao decoction restores the mucus layer in mice with DSS-induced colitis by regulating Notch signaling pathway.

ETHNOPHARMACOLOGICAL RELEVANCE: Restoring the mucus layer is a potential strategy for treating ulcerative colitis (UC). Previous studies reported that a Chinese medicine formula Shaoyao Decoction (SYD) effectively improved UC. However, the role and mechanism of SYD in restoring the mucus layer are still vague. AIM OF THE STUDY: This study aimed to research the therapeutical effects and unravel the involved mechanism of SYD on DSS-evoked UC. MATERIALS AND METHODS: First, the constituents of SYD were detected by UPLC-QTOF-MS/MS. Then, the DSS-induced UC model was introduced to investigate the pharmacologic action and molecular mechanism of SYD on UC. Pharmacodynamic indicators were assessed including body weight, colon length, ulcerations, disease activity index (DAI), inflammatory cytokines and histological parameters. To investigate the integrality and functions of the mucous layer, AB-PAS stain and UEA-1 stain were used to evaluate the completeness of mucous layer, as well as the maturation of goblet cells (GCs). The bacterial invasion was detected by fluorescence in situ hybridization. As to mechanism exploration, the expressions of Notch/Hes1 pathway were investigated by using agonists in lipopolysaccharides (LPS) -stimulated LS174T cell. RESULTS: After modeling in mice, SYD remarkedly ameliorated the symptoms of mouse colitis, the expression of pro-inflammatory factors declined, and increased IL-10 expression was observed in SYD-treated mice. Besides, SYD repaired the structure of the mucus layer and prevented bacterial invasion. Mechanism investigation discovered that SYD promoted GCs differentiation by inhibiting the Notch pathway, which was consistent with the results in LPS-challenged LS174 cell. CONCLUSIONS: These findings demonstrated that SYD could restore the mucus layer to prevent UC via suppressing the Notch signaling pathway, which provided evidences for the UC treatment of SYD in the clinic.