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Mucins, the biomolecular components of mucus, are glycoproteins that form a thick physical barrier at all tissue-air interfaces, forming a first line of defense against pathogens. Structural features of mucins and their interactions with other biomolecules remain largely unexplored due to the challenges associated with their high-resolution characterization. Combining limited mass spectrometry glycomics and protein sequencing data, we present all-atom, explicitly solvated molecular dynamics simulations of a major respiratory mucin, MUC5B. We detail key forces and degrees of freedom imposed by the extensive O-glycosylation, which imbue the canonically observed bottlebrush-like structures to these otherwise intrinsically disordered protein backbones. We compare our simulation results to static structures observed in recent scanning tunneling microscopy experiments as well as other published experimental efforts. Our work represents the demonstration of a workflow applied to a mucin example, which we hope will be employed by other groups to investigate the dynamics and interactions of other mucins, which can inform on structural details currently inaccessible to experimental techniques.

Mucus plugs occlude airways to obstruct airflow in asthma. Studies in patients and in mouse models show that mucus plugs occur in the context of type 2 inflammation, and studies in human airway epithelial cells (HAECs) show that IL-13-activated cells generate pathologic mucus independently of immune cells. To determine how HAECs autonomously generate pathologic mucus, we used a magnetic microwire rheometer to characterize the viscoelastic properties of mucus secreted under varying conditions. We found that normal HAEC mucus exhibited viscoelastic liquid behavior and that mucus secreted by IL-13-activated HAECs exhibited solid-like behavior caused by mucin cross-linking. In addition, IL-13-activated HAECs shows increased peroxidase activity in apical secretions, and an overlaid thiolated polymer (thiomer) solution shows an increase in solid behavior that was prevented by peroxidase inhibition. Furthermore, gene expression for thyroid peroxidase (TPO), but not lactoperoxidase (LPO), was increased in IL-13-activated HAECs and both TPO and LPO catalyze the formation of oxidant acids that cross-link thiomer solutions. Finally, gene expression for TPO in airway epithelial brushings was increased in patients with asthma with high airway mucus plug scores. Together, our results show that IL-13-activated HAECs autonomously generated pathologic mucus via peroxidase-mediated cross-linking of mucin polymers.

Targeted protein degradation is an emerging strategy for the elimination of classically undruggable proteins. Here, to expand the landscape of targetable substrates, we designed degraders that achieve substrate selectivity via recognition of a discrete peptide and glycan motif and achieve cell-type selectivity via antigen-driven cell-surface binding. We applied this approach to mucins, O-glycosylated proteins that drive cancer progression through biophysical and immunological mechanisms. Engineering of a bacterial mucin-selective protease yielded a variant for fusion to a cancer antigen-binding nanobody. The resulting conjugate selectively degraded mucins on cancer cells, promoted cell death in culture models of mucin-driven growth and survival, and reduced tumor growth in mouse models of breast cancer progression. This work establishes a blueprint for the development of biologics that degrade specific protein glycoforms on target cells.

The mechanism that triggers the progressive dysregulation of cell functions, inflammation, and breakdown of tissues during aging is currently unknown. We propose here a previously unknown mechanism due to tissue autodigestion by the digestive enzymes. After synthesis in the pancreas, these powerful enzymes are activated and transported inside the lumen of the small intestine to which they are compartmentalized by the mucin/epithelial barrier. We hypothesize that this barrier leaks active digestive enzymes (e.g. during meals) and leads to their accumulation in tissues outside the gastrointestinal tract. Using immune-histochemistry we provide evidence in young (4 months) and old (24 months) rats for significant accumulation of pancreatic trypsin, elastase, lipase, and amylase in peripheral organs, including liver, lung, heart, kidney, brain, and skin. The mucin layer density on the small intestine barrier is attenuated in the old and trypsin leaks across the tip region of intestinal villi with depleted mucin. The accumulation of digestive enzymes is accompanied in the same tissues of the old by damage to collagen, as detected with collagen fragment hybridizing peptides. We provide evidence that the hyperglycemia in the old is accompanied by proteolytic cleavage of the extracellular domain of the insulin receptor. Blockade of pancreatic trypsin in the old by a two-week oral treatment with a serine protease inhibitor (tranexamic acid) serves to significantly reduce trypsin accumulation in organs outside the intestine, collagen damage, as well as hyperglycemia and insulin receptor cleavage. These results support the hypothesis that the breakdown of tissues in aging is due to autodigestion and a side-effect of the fundamental requirement for digestion.

Objectives: Gastric papillary adenocarcinoma (GPA), a well-differentiated gastric adenocarcinoma, is associated with a worse prognosis compared to other differentiated gastric adenocarcinomas. Therefore, there is an urgent need to characterize its endoscopic manifestations for guiding biopsy site selection and achieving accurate diagnosis. Methods: From January 1, 2016, to December 31, 2022, the data of 46 cases of early gastric papillary adenocarcinoma (EGPA) and 183 cases of early gastric differentiated tubular adenocarcinoma (EGDTA) diagnosed via pathological examination following endoscopic submucosal dissection (ESD) at the Second Hospital of Shandong University were collected. Propensity score matching (PSM) was employed to match 92 EGDTA patients at a ratio of 1:2, serving as the control group. Differences between the two groups were analyzed using multivariable logistic regression. Lastly, the relationship between vessels within epithelial circle (VEC) structures in EGPA and the degree of malignancy was assessed. Results: Compared with EGDTA, EGPA was more likely to infiltrate the submucosa, more frequently associated with poorly differentiated cancer components, and more prone to invading lymphatic and blood vessels. EGPA was primarily located in the lower stomach and manifested as a uniformly elevated pattern under endoscopy, while VEC structural positivity could be visualized under ME-NBI. Moreover, EGPA lesions had larger diameters and were characterized by high expression of gastric mucins, namely MUC5AC and MUC6. When EGPA infiltrated the submucosa or contained poorly differentiated cancer components, the VEC structures were smaller. Conclusions: The present study demonstrated that EGPA exhibits a higher degree of malignancy. Endoscopic findings of a raised lesion with a uniform color under endoscopy and the presence of VEC structures under ME-NBI suggest a high possibility of EGPA. Moreover, smaller VEC structures were associated with a higher degree of malignancy, which may assist in guiding the selection of biopsy sites under endoscopy. [ABSTRACT FROM AUTHOR]

Cnidarians are the first phylum of metazoans to exhibit a functional mucus layer. In evolution, mucous cells perform the classical secretory function of mucus and act as sentinels for external insults, particularly in mammals. However, this topic has not been much analysed in the lower metazoans. This study aims to investigate the role of mucous cells in Actinia equina (Anthozoa, Hexacorallia) (Linnaeus, 1758) by using confocal microscopy and bioinformatics. The results show colocalization of Toll‐like receptor 2 (TLR2) and Mucin2 (MUC2) on these cells, suggesting a crosstalk between defence response and mucus secretion in cnidarians. Furthermore, the presence of TLR2 on the surface of mucous cells suggests their involvement in host defence responses, as occurs in vertebrates. Moreover, through in silico analysis, we confirmed the presence of orthologous genes for the tested antibodies, providing additional evidence to support our results from an evolutionary perspective. These data suggest that mucous cells play a defensive role throughout evolution, helping us understand how these cells have developed and adapted across phylogenesis. This information also provides new insights into the defensive strategies of invertebrates and clarifies their evolutionary history. [ABSTRACT FROM AUTHOR]

Mucus is a hydrated, viscoelastic, and adhesive gel that lubricates and protects the body from pathogens; however, its protective function hinders drug/nanomedicine diffusion and treatment efficiency. Therefore, novel drug delivery strategies are required to overcome challenging mucosal barriers. Here, multi‐responsive nanogels (NGs) are developed and explored their interaction with mucus. Specific NG features (e.g., surface charge, temperature responsiveness, and redox response) are evaluated in a typical mucus‐associated environment (i.e., mucin proteins and high glutathione concentrations). The results demonstrate that biocompatibility and the capacity to deliver a protein through mucosal barriers in different in vitro and in vivo models highlight the importance of specific NG design elements. Disulfide bonds are highlighted as redox‐sensitive cross‐linkers within the NG structure as critical for drug delivery performance; they function as degradation points that enable NG degradation and subsequent drug release and anchoring points to adhere to mucin, thereby enhancing their residence time at the desired site of action. Additionally, it is confirmed that surface charges impact interactions with mucin; positively charged NGs exhibit improved interactions with mucin compared to negatively charged and neutral NGs. Overall, the findings underline the importance of redox response and surface charge in NG design for reaching efficient mucosal drug delivery. [ABSTRACT FROM AUTHOR]

Background Neoadjuvant therapy leads to a clinical complete response in a considerable proportion of patients with locally advanced rectal cancer, allowing for possible nonoperative management. The presence of mucin on magnetic resonance imaging (MRI) after neoadjuvant therapy leads to uncertainty about residual disease and appropriateness of a watch-and-wait strategy in patients with no evidence of disease on proctoscopy (endoscopic clinical complete response). Methods MRI reports for locally advanced rectal cancer patients seen between July 2016 and January 2020 at Memorial Sloan Kettering Cancer Center were queried for presence of mucin in the tumor bed on MRI following neoadjuvant therapy. Clinicodemographic, pathologic, and outcome data were compiled and analyzed. Results Of 71 patients with mucin on posttreatment MRI, 20 had a clinical complete response, and 51 had abnormalities on endoscopy and/or physical exam. One patient with a clinical complete response opted out of watch-and-wait; thus, 19 (27%) patients entered watch-and-wait, and 52 (73%) patients were planned for surgery (non–watch-and-wait). Of the 19 watch-and-wait patients, 15 (79%) have had no local regrowth with median follow-up of 50 months (range = 29-76 months), while 4 (21%) experienced regrowth between 9 and 29 months after neoadjuvant therapy. Of the 52 patients who were planned to have surgery (non–watch-and-wait), 49 underwent resection while 3 developed metastatic disease that precluded curative-intent surgery. Of the 49 patients who underwent surgery, 5 (10%) had a pathologic complete response (including the patient with an endoscopic clinical complete response). Conclusions The presence of mucin after neoadjuvant therapy for locally advanced rectal cancer does not preclude watch-and-wait management in otherwise appropriate candidates who achieve an endoscopic clinical complete response. [ABSTRACT FROM AUTHOR]

This study evaluated the impact of mucin on supersaturation and permeation of BCS Class 2 basic drugs in a pH-shift, 2-stage model using three model compounds, dipyridamole, ricobendazole, and Compound A. The three compounds showed various degrees of supersaturation (DoS) in Stage 2 and modest to no increases in flux with the presence of mucin in the dissolution media. Mucin's impact on DoS and flux, if any, appeared to be compound specific and possibly related to its pKa and ionization state. Overall, the increases in supersaturation and permeation due to mucin ranged from modest to minimal for the three model compounds under the conditions tested. The pH-shift model using MacroFLUX was able to monitor gastric and intestinal dissolution and simultaneously assess the effect of intestinal mucin on supersaturation and flux. [ABSTRACT FROM AUTHOR]

Human respiratory mucus (HRM) is extremely soft, compelling passive microrheology for linear viscoelastic characterization. We focus this study on the use of passive microrheology to characterize HRM heterogeneity, a phenomenon in normal HRM that becomes extreme during cystic fibrosis (CF) disease. Specifically, a fraction of the mucin polymers comprising HRM phase-separate into insoluble structures, called flakes, dispersed in mucin-depleted solution. We first reconstitute HRM samples to the MUC5B:MUC5AC mucin ratios consistent with normal and CF clinical samples, which we show recapitulate progressive flake formation and heterogeneity. We then employ passive particle tracking with 200 nm and 1 μm diameter beads in each reconstituted sample. To robustly analyze the tracking data, we introduce statistical denoising methods for low signal-to-noise tracking data within flakes, tested and verified using model-generated synthetic data. These statistical methods provide a fractional Brownian motion classifier of all successfully denoised, tracked beads in flakes and the dilute solution. From the ensemble of classifier data, per bead diameter and mucus sample, we then employ clustering methods to learn and infer multiple levels of heterogeneity: (i) tracked bead data within vs. outside flakes and (ii) within-flake data buried within or distinguishable from the experimental noise floor. Simulated data consistent with experimental data (within and outside flakes) are used to explore form(s) of the generalized Stokes–Einstein relation (GSER) that recover the dynamic moduli of homogeneous and heterogeneous truth sets of purely flakelike, dilute solution, and mixture samples. The appropriate form of GSER is applied to experimental data to show (i) flakes are heterogeneous with gel and sol domains; (ii) dilute solutions are heterogeneous with only sol domains; and (iii) flake and dilute solution properties vary with probe diameter. [ABSTRACT FROM AUTHOR]

Meloidogyne incognita is one of the globally serious plant parasitic nematodes. New control measure is urgently needed to replace the common chemical control method. Ascarosides are pheromones regulating the nematodes' aggregation, avoidance, mating, dispersal and dauer recovery and formation. Ascr#9, one of the ascarosides, exhibits the potential to repel M. incognita. However, the nematode genes involved in the perception of ascr# 9 signal are totally unknown. In this study, the transcriptome of ascr#9-treated second stage M. incognita juveniles (J2s) was analyzed, 44 pathways were significantly affected, multiple ligand-receptor and mucin type O-glycan were induced, and olfactory transduction was disturbed. A total of 11 highly differentially expressed genes involved in neuroactive ligand-receptor interaction and FMRFamide-like peptide related process were identified and knocked down by RNAi. The dispersal rates of M. incognita with three knocked-down genes (flp-14, mgl-1 and ADOR-1) significantly decreased, respectively, when ascr#9 was present. The results demonstrate that flp-14, mgl-1, and ADOR-1 are involved in the dispersal behavior of M. incognita nematodes responding to ascr#9, which promotes the interaction study between ascarosides and M. incognita, and provides new ideas for the prevention and control of M. incognita by using pheromone ascarosides. [ABSTRACT FROM AUTHOR]

Aims: Ulcerative colitis‐associated neoplasia (UCAN) is characterised by multifocal tumourigenesis. A wide range of metachronous lesions have been reported to occur after endoscopic treatment of UCAN, which suggests the development of sporadic tumours in lesions treated as UCAN. Therefore, we aimed to evaluate differences of immunohistochemistry (IHC) in features and clinicopathological characteristics of intramucosal lesions in patients with ulcerative colitis (UC). Methods and results: We examined 35 intramucosal lesions resected for carcinoma or dysplasia by total colectomy from patients with UC and 71 sporadic adenomas (SAs) endoscopically resected from patients without UC. UC lesions were divided into the conventional UCAN group, defined as p53 mutant pattern and normal expression of β‐catenin, and the non‐conventional UCAN group, defined as the rest. Ki‐67 distribution, α‐methylacyl‐CoA racemase (AMACR) expression and mucin phenotypes were compared using IHC, and clinicopathological characteristics were investigated. Conventional and non‐conventional UCAN lesions were located in the left colon and rectum. Relative to the SA lesions, UCAN lesions occurred in much younger patients and exhibited more frequent basal distribution of Ki‐67 in tumour crypts. Conventional UCAN lesions tended to be non‐polyploid and exhibited a higher frequency of normal AMACR expression than SA lesions. UC lesions were heterogeneous—only two of the eight patients with multiple lesions had lesions (both non‐conventional UCAN lesions) exhibiting concordant IHC staining features. Conclusions: The basal pattern of Ki‐67 distribution, normal expression of AMACR and a non‐intestinal mucin phenotype were determined as characteristic features suggestive of UCAN. Non‐polypoid growth was another a key feature of UCAN. [ABSTRACT FROM AUTHOR]

Introduction: Mucins are polydisperse molecules created to perform a variety of functions at the mucosal surface of the adult gastrointestinal tract. Two main groups of mucins could be identified: the membrane-associated mucins (MUC1, MUC4, MUC13, and MUC16), those bound to the apical plasma membrane of epithelial cells, and the secreted mucins (MUC2, MUC5AC, MUC5B, and MUC6), those secreted from the goblet cells. Little is known about the types and distribution patterns of mucins in prenatal life. Methods: We detected mucin-secreting cells in the developing rabbit esophagus though these cells are absent in the adult one. In order to identify the content and possible functions of these cells, we investigated the histochemical and immunohistochemical characteristics of their mucins. Results: Starting at 16th day of pregnancy, periodic acid Schiff (PAS), alcian blue (AB) pH (2.5), and PAS-AB combination intensely stained the mucous content, demonstrating both acidic and neutral mucopolysaccharides. Some blebs could be recognized on the free surface of the esophageal epithelium. Also, the mucous cells and some basal cells strongly immunoreacted with MUC1, but not MUC2, nor MUC5AC antibodies. Conclusion: Collectively, these data suggest that surface mucous cells are modified epithelial cells, not goblet cells, and may originate from the basal layer of the epithelial cells. A possible regulatory role for these MUC1-positive mucins in esophageal epithelial and mesenchymal cell differentiation and late organogenesis is suggested. However, future functional studies are recommended. [ABSTRACT FROM AUTHOR]

Background/Objectives: For locally applied, locally acting generic drug products, comparison to an originator product based on systemic exposure is usually not feasible due to low plasma concentrations and inadequate reflection of local exposure at the site of action. Where a validated PD model exists, a comparative clinical study can be performed in healthy subjects; where no surrogate endpoint is available, patients with the relevant indication need to be enrolled, with all the associated factors which could result in lack of sensitivity. Even though the need for alternative in vitro approaches has been acknowledged by both industry and regulatory bodies, the complexity of in vivo drug delivery processes makes the development of guidance documents particularly difficult. Our objective was to present in vitro approaches less classically used and to address in vivo relevance of the selected tests. Methods: This article analyses current regulatory approaches in Europe and the U.S., and highlights the key advantages of in vitro tests in terms of their sensitivity, reliability, reproducibility and in vivo relevance using locally applied flurbiprofen in various formulations. Results: The in vitro esophageal retention (IVOR) model demonstrates that the first 6–10 min after application of different flurbiprofen formulations is important for their comparison and also offers the best correlation with in vivo data using the partial area under the concentration-time curves (pAUCs). Rheological evaluations further demonstrated that the mucoadhesive properties of the gel spray formulation are based on interaction with mucin. Conclusions: Designing a relevant in vitro test requires adequate evaluation of the complexity of the drug substance, drug product, dosing conditions and delivery processes. [ABSTRACT FROM AUTHOR]

The interaction between soy hull polysaccharide and intestinal mucus is influenced by different ions. This study investigates the effects of various concentrations of Na+/K+ on the stability, interfacial activity, and viscoelasticity of the microwave-assisted ammonium oxalate extraction of soy hull polysaccharide (MASP) in simulated intestinal fluids (SIFs) in terms of particle size, zeta potential, surface hydrophobicity, Fourier-transform infrared spectroscopy, shear rheology, and microstructure. Results showed that 1.5 % Na+/K+ causes MASP and mucin in SIFs to bind through physical adsorption; the average particle size of the MASP/SIF miscible system increases from 1,659 to 1,881 and 1,736 nm. When the ion strength is 0.5 %, MASP rapidly reduces the SIF interfacial tension. The addition of Na+/K+ causes a slight redshift in the protein amide I band and an increase in the α-helix content with respect to the decrease in the β-turn and β-sheet corner content. Furthermore, 0.5 % content of Na+ and K+ causes small MASP particles to adsorb onto the surface of mucin, while 1.5 % content of Na+ and K+ causes MASP particles to arrange above mucin after 12 h. These findings provide reference for a deeper understanding of the selection of macroelements (sodium and potassium) in the intake of polysaccharide. [ABSTRACT FROM AUTHOR]

To cope with the constraints of conventional drug delivery systems, site‐specific drug delivery systems are the major focus of researchers. The present research developed water‐swellable, pH‐responsive methacrylic acid‐based hydrogel scaffolds of Artemisia vulgaris seed mucilage with mucin and loaded with acyclovir sodium as a model drug. The developed hydrogel discs are evaluated for diverse parameters. Drug loading efficiency in all formulations ranges from 63% to 75%. The hydrogels exhibited pH‐dependent swelling, displaying optimum swelling in a phosphate buffer (pH 7.4), and insignificant swelling in an acidic buffer (pH 1.2), in addition, they responded well to electrolyte concentrations. The sol‐gel fraction is estimated ranging from 60 to 95%. Dissolution studies unveiled sustained drug release for 24 h in a phosphate buffer of pH 7.4, exhibiting zero‐order release kinetics. Moreover, FTIR spectra confirmed the drug‐excipient compatibility. SEM photomicrographs revealed a rough and porous surface of hydrogel discs with several pores and channels. The PXRD diffractograms exposed the amorphous nature of the polymeric blends. The findings of acute toxicity studies proved the developed hydrogel network is biocompatible. Therefore, these outcomes connote the newly created network as a smart delivery system, able to dispatch acyclovir sodium into the intestinal segment for a prolonged period. [ABSTRACT FROM AUTHOR]

Intracellular accumulation of misfolded proteins causes serious human proteinopathies. The transmembrane emp24 domain 9 (TMED9) cargo receptor promotes a general mechanism of cytotoxicity by entrapping misfolded protein cargos in the early secretory pathway. However, the molecular basis for this TMED9-mediated cargo retention remains elusive. Here, we report cryo-electron microscopy structures of TMED9, which reveal its unexpected self-oligomerization into octamers, dodecamers, and, by extension, even higher-order oligomers. The TMED9 oligomerization is driven by an intrinsic symmetry mismatch between the trimeric coiled coil domain and the tetrameric transmembrane domain. Using frameshifted Mucin 1 as an example of aggregated disease-related protein cargo, we implicate a mode of direct interaction with the TMED9 luminal Golgi-dynamics domain. The structures suggest and we confirm that TMED9 oligomerization favors the recruitment of coat protein I (COPI), but not COPII coatomers, facilitating retrograde transport and explaining the observed cargo entrapment. Our work thus reveals a molecular basis for TMED9-mediated misfolded protein retention in the early secretory pathway. [ABSTRACT FROM AUTHOR]

Native mucus is heterogeneous, displays high inter-individual variation and is prone to changes during harvesting and storage. To overcome the lack of reproducibility and availability of native mucus, commercially available purified mucins, porcine gastric mucin (PGM) and mucin from bovine submaxillary gland (BSM), have been widely used. However, the question is to which extent the choice of mucin matters in studies of their interaction with polymers as their composition, structure and hence physicochemical properties differ. Accordingly, the interactions between PGM or BSM with two widely used polymers in drug delivery, polyethylene oxide and chitosan, was studied with orthogonal methods: turbidity, dynamic light scattering, and quartz crystal microbalance with dissipation monitoring. Polymer binding and adsorption to the two commercially available and purified mucins, PGM and BSM, is different depending on the mucin type. PEO, known to interact weakly with mucin, only displayed limited interaction with both mucins as confirmed by all employed methods. In contrast, chitosan was able to bind to both PGM and BSM. Interestingly, the results suggest that chitosan interacts with BSM to a greater extent than with PGM indicating that the choice of mucin, PGM or BSM, can affect the outcome of studies of mucin interactions with polymers. [ABSTRACT FROM AUTHOR]

The chronic airway infections with Pseudomonas aeruginosa are the major comorbidity in people with cystic fibrosis (CF). Within CF lungs, P. aeruginosa persists in the conducting airways together with human mucins as the most abundant structural component of its microenvironment. We investigated the adhesion of 41 serial CF airway P. aeruginosa isolates to airway mucin preparations from CF sputa. Mucins and bacteria were retrieved from five modulator-naïve patients with advanced CF lung disease. The P. aeruginosa isolates from CF airways and non-CF reference strains showed a strain-specific signature in their adhesion to ovine, porcine and bovine submaxillary mucins and CF airway mucins ranging from no or low to moderate and strong binding. Serial CF clonal isolates and colony morphotypes from the same sputum sample were as heterogeneous in their affinity to mucin as representatives of other clones thus making 'mucin binding' one of the most variable intraclonal phenotypic traits of P. aeruginosa known to date. Most P. aeruginosa CF airway isolates did not adhere more strongly to CF airway mucins than to plastic surfaces. The strong binders, however, exhibited a strain-specific affinity gradient to O-glycans, CF airway and mammalian submaxillary mucins. [ABSTRACT FROM AUTHOR]

Mucin glycoproteins are a significant source of carbon for the gut bacteria. Various gut microbial species possess diverse hydrolytic enzymes and catabolic pathways for breaking down mucin glycans, resulting in competition for the limited nutrients within the gut environment. Adherence to mucin glycans represents a crucial strategy used by gut microbes to access nutrient reservoirs. Understanding these properties is pivotal for comprehending the survival mechanisms of bacteria in the gastrointestinal tract. However, characterization of individual strains within the vast array of coexisting bacteria in the microbiome is challenging. To investigate this, we developed mucin-immobilized particles by immobilizing porcine gastric mucin (PGM) onto glass beads chemically modified with boronic acid. These PGM-immobilized particles were then anaerobically cultured with human fecal microbiota, and the bacteria adhering to PGM were isolated. Interestingly, the microbiome composition remained largely unchanged irrespective of PGM immobilization. Nonetheless, bacteria isolated from PGM-immobilized glass particles exhibited notably higher N-acetylgalactosaminidase activity compared to the control beads. Furthermore, Bacteroides strains isolated from PGM-immobilized glass particles displayed enhanced adhesive and metabolic properties to PGM. These findings underscore the utility of PGM particles in enriching and isolating specific microbes. Moreover, they highlight substantial differences in microbial properties at the strain level. We anticipate that PGM-immobilized particles will advance culture-based microbiome research, emphasizing the significance of strain-level characterization. [ABSTRACT FROM AUTHOR]

Raw and cooked (autoclaved) green bananas are fed to rats for 4 weeks and their effects on cecal microbiota and biomarkers of fermentation are evaluated and compared with those of potato starch, which is rich in RS. Relative abundances of genera Lachnospiraceae_NK4A136_group and Roseburia, and species Bifidobacterium pseudolongum in rat cecum are higher in the raw green banana group with higher RS consumption than in the control group. The raw green banana group shows higher cecal acetate production and similarly high levels of cecal n‐butyrate production than that in the potato starch group. In the autoclaved green banana group, the cecal microbial composition is altered and the relative abundance of family Ruminococcaceae increased. Additionally, the molar proportion of n‐butyrate in the cecum of the autoclaved green banana group is higher than that in the control group. The levels of cecal mucin and IgA in the raw green banana and potato starch groups are found to be higher compared to those observed in the control and autoclaved green banana groups. Therefore, raw and autoclaved green bananas can alter cecal microbial composition and thus exhibit beneficial intestinal fermentation characteristics. [ABSTRACT FROM AUTHOR]

Colorectal clear cell adenocarcinomas are rare tumors. They can be divided into two types: intestinal- and Müllerian-type. Most intestinal-type clear cell adenocarcinomas show a composite morphology, and most early-stage (T1) intestinal-type clear cell adenocarcinomas have an adenoma component. We report an additional early-stage (T1) colonic clear cell adenocarcinoma that was a de novo adenocarcinoma without any adenoma component. It had a pure morphology and the smallest size (0.6 cm) ever reported. Immunohistochemical results demonstrated an intestinal phenotype (KRT20+, KRT7−, CEA+, and CDX2+). Periodic acid-schiff and alcian blue stains were both negative, which demonstrated decrease in mucin expression in the clear tumor cells. Enteroblastic differentiation was observed in a few colorectal clear cell adenocarcinomas in the literature, while it had not been observed in the present tumor. The tumor did not have deep submucosal invasion and cancer embolus, endoscopic submucosal dissection with regular follow-up was an appropriate treatment for the patient. Due to the rarity and diversity of primary colorectal clear cell adenocarcinomas, the cause of clear cytoplasm change and the impact on patient prognosis remain unknown. Accumulating evidence indicates that clear cell adenocarcinomas of intestinal-type is a histological variant of colorectal adenocarcinoma. [ABSTRACT FROM AUTHOR]

Background Cardiac mucinous deposits are a rare entity only previously described in the setting of scleromyxedema, a disorder characterized by cutaneous and systemic mucin deposits, fibroblastic proliferation, and monoclonal gammopathies. Case summary A 41-year-old woman was transferred to our hospital after a month-long hospitalization with worsening cardiogenic shock requiring ionotropic support. Cardiac magnetic resonance imaging revealed a left ventricular ejection fraction of 23%, prior right coronary artery infarct, full-thickness late gadolinium enhancement in the left ventricle basilar wall, global abnormal parametric mapping parameters of both native T1, T2, and extracellular volume, and severe biventricular dysfunction concerning for infiltrative cardiomyopathy. Endomyocardial biopsy demonstrated heavy deposits of interstitial mucin, confirmed by electron microscopy; a Congo red stain was negative for amyloid. She was treated with an aggressive decongestive strategy, oral guideline-directed medical therapy, and intravenous immunoglobulin (IVIg); she was discharged home off inotropic support. Subsequently, she had three additional hospitalizations for heart failure exacerbation in a span of 6 months, and her overall prognosis remains guarded. Discussion We report a first known case of isolated cardiac myxedematosus associated with a severe systolic and diastolic cardiomyopathy. Our patient did not have any clinical evidence of systemic scleromyxedema or paraproteinemia, both of which have been reported in association with cardiac mucin deposits. Mucinosus has been described in patients with systemic lupus erythematous; however, cardiac deposits have not been reported. While IVIg has been used as a treatment in previously reported cases of cardiac scleromyxedema, its clinical benefit remains unclear in isolated cardiac myxedematosus. [ABSTRACT FROM AUTHOR]

Mucin-domain glycoproteins are densely O-glycosylated and play critical roles in a host of biological functions. In particular, the T cell immunoglobulin and mucin-domain containing family of proteins (TIM-1, -3, -4) decorate immune cells and act as key regulators in cellular immunity. However, their dense O-glycosylation remains enigmatic, primarily due to the challenges associated with studying mucin domains. Here, we demonstrate that the mucinase SmE has a unique ability to cleave at residues bearing very complex glycans. SmE enables improved mass spectrometric analysis of several mucins, including the entire TIM family. With this information in-hand, we perform molecular dynamics (MD) simulations of TIM-3 and -4 to understand how glycosylation affects structural features of these proteins. Finally, we use these models to investigate the functional relevance of glycosylation for TIM-3 function and ligand binding. Overall, we present a powerful workflow to better understand the detailed molecular structures and functions of the mucinome.

The structure and composition of mantle tissue from red abalone Haliotis rufescens were studied in relation to pearl farming. Histological (hematoxylin-eosin) and histochemical (PAS AJcian Blue. Sudan Black. Dahl's) tools were used to determine variations in the glycogen index, lipid index, and calcium coverage index of mantle tissue as a function of seasonality (cold and warm period) and body region (dorsal, central, ventral). Anatomically, only two well-developed and functional mantle folds (inner and outer) were observed across the marginal zone, together with a poorly developed, and presumably, rudimentary fold with the same cellular morphology as the inner fold. The inner mantle epithelium stored significantly higher concentrations of glycogen and mucins, triglycerides, and calcium than the outer epithelium. This pattern occurred significantly more during the cold season than during the warm season. Mucins from mantle tissue not only regulate crystal nucleation and orientation during biomineralization, but also give the inner nacreous layer its luster and color. High concentrations of lipids in mantle tissue could help compensate for the energy loss caused by the wound-healing processes associated with mantle tissue removal and seeding, which are stressful and energetically costly. The absorption of calcium ions from the environment to integrate a mierolaminate of calcareous compounds gives the shell its structural properties of hardness and strength. An approach with molecularultrastructural tools is recommended to broaden the understanding of mantle tissue regionalization and its relationship to pearl sac formation, which may help increase pearl yield and quality in H. rufescens. KEY WORDS: abalone, calcium, lipids, mantle tissue, nacre, pearls, INTRODUCTION In most molluscan classes, mantle tissue is responsible for forming a hard calcareous shell from elements and ions taken from the environment. This process, known as biomineralization, provides the [...]

Mucin family members play an indispensable role in immunity against pathogen invasion. Currently, there are very few studies on members of the mucin family in Japanese flounder Paralichthys olivaceus. In this regard, we characterized the mucin members in Japanese flounder as well as their involvement in response to pathogen infection. In our results, a total of 9 mucin genes were identified based on the whole genome database of flounder. Among them, MUC2-1, MUC2-2, MUC5AC-1, MUC5AC-2 and MUC5B are secreted mucins, while MUC3A, MUC3B, MUC13 and MUC15 are membrane binding mucins. The collinearity results showed that the adjacent MUC genes of flounder had collinearity relationship with many other teleosts. Phylogenetic tree results showed that the mucin gene of flounder was divided into several subfamilies. In addition, the expression patterns of flounder mucin family members were examined in 11 healthy tissues. The expression changes of mucin gene were also detected in six immune tissues (gill, intestine, skin, liver, kidney, spleen) after pathogen infection, revealing their role in disease resistance. Collinear analysis indicates the adjacent mucin genes. According to the protein interaction network (PPI) results, the mucin genes interact with the galnt genes. The results provide a solid foundation for further research on the function of mucins in mucosal immunity of flounder. [ABSTRACT FROM AUTHOR]

Abstract Ovarian cancer stands as the deadliest gynecologic malignancy, responsible for nearly 65% of all gynecologic cancer-related deaths. The challenges in early detection and diagnosis, coupled with the widespread intraperitoneal spread of cancer cells and resistance to chemotherapy, contribute significantly to the high mortality rate of this disease. Due to the absence of specific symptoms and the lack of effective screening methods, most ovarian cancer cases are diagnosed at advanced stages. While chemotherapy is a common treatment, it often leads to tumor recurrence, necessitating further interventions. In recent years, antibody-drug conjugates (ADCs) have emerged as a valuable tool in targeted cancer therapy. These complex biotherapeutics combine an antibody that specifically targets tumor specific/associated antigen(s) with a high potency anti-cancer drug through a linker, offering a promising approach for ovarian cancer treatment. The identification of molecular targets in various human tumors has paved the way for the development of targeted therapies, with ADCs being at the forefront of this innovation. By delivering cytotoxic agents directly to tumors and metastatic lesions, ADCs show potential in managing chemo-resistant ovarian cancers. Mucins such as MUC16, MUC13, and MUC1 have shown significantly higher expression in ovarian tumors as compared to normal and/or benign samples, thus have become promising targets for ADC generation. While traditional markers are limited by their elevated levels in non-cancerous conditions, mucins offer a new possibility for targeted treatment in ovarian cancer. This review comprehensively described the potential of mucins for the generation of ADC therapy, highlighting their importance in the quest to improve the outcome of ovarian cancer patients.

Specific molecular and inflammatory endotypes have been identified for chronic respiratory disorders, including asthma and COPD (chronic obstructive pulmonary disease). These endotypes correspond with clinical aspects of disease, enabling targeted medicines to address certain pathophysiologic pathways, often referred to as “precision medicine”. With respect to bronchiectasis, many comorbidities and underlying causes have been identified. Inflammatory endotypes have also been widely studied and reported. Additionally, several genes have been shown to affect disease progression. However, the lack of a clear classification has also hampered our understanding of the disease’s natural course. The aim of this review is, thus, to summarize the current knowledge on biomarkers and actionable targets of this complex pathologic condition and to point out unmet needs, which are required in the design of effective diagnostic and therapeutic trials.

Current prophylactic and disease control measures in aquaculture highlight the need of alternative strategies to prevent disease and reduce antibiotic use. Mucus covered mucosal surfaces are the first barriers pathogens encounter. Mucus, which is mainly composed of highly glycosylated mucins, has the potential to contribute to disease prevention if we can strengthen this barrier. Therefore, aim of this study was to develop and characterize fish in vitro mucosal surface models based on commercially available cell lines that are functionally relevant for studies on mucin regulation and host-pathogen interactions. The rainbow trout (Oncorhynchus mykiss) gill epithelial cell line RTgill-W1 and the embryonic cell line from Chinook salmon (Oncorhynchus tshawytscha) CHSE-214 were grown on polycarbonate membrane inserts and chemically treated to differentiate the cells into mucus producing cells. RTGill-W1 and CHSE-214 formed an adherent layer at two weeks post-confluence, which further responded to treatment with the γ-secretase inhibitor DAPT and prolonged culture by increasing the mucin production. Mucins were metabolically labelled with N-azidoacetylgalactosamine 6 h post addition to the in vitro membranes. The level of incorporated label was relatively similar between membranes based on RTgill-W1, while larger interindividual variation was observed among the CHSE in vitro membranes. Furthermore, O-glycomics of RTgill-W1 cell lysates identified three sialylated O-glycans, namely Galβ1-3(NeuAcα2–6)GalNAcol, NeuAcα-Galβ1-3GalNAcol and NeuAcα-Galβ1-3(NeuAcα2–6)GalNAcol, resembling the glycosylation present in rainbow trout gill mucin. These glycans were also present in CHSE-214. Additionally, we demonstrated binding of the fish pathogen A. salmonicida to RTgill-W1 and CHSE-214 cell lysates. Thus, these models have similarities to in vivo mucosal surfaces and can be used to investigate the effect of pathogens and modulatory components on mucin production. [ABSTRACT FROM AUTHOR]

Anti-cancer therapy is crucial in cancer prevention and anti-cancer, and thus, highly sensitive methods for detecting cancer biomarkers are essential for cancer early diagnosis. Herein, an electrochemical aptamer biosensor based on the CRISPR-Cas12a system was constructed for the detection of cancer tumor biomarker MUC1 mucin. The sensitivity was significantly prompted by enzyme-catalyzed signal amplification, and the selectivity was improved by the dual recognition of the aptamer to MUC1 and crRNA-Cas12a system to the aptamer. Glucose oxidase (GOD) was loaded on the surface of magnetic Fe3O4@Au (MGNP) via probe single-stranded DNA (pDNA) with the terminal modification of mercapto (–SH) to form GOD-pDNA/MGNP. The corresponding aptamer of MUC1 (MUC1 Apt) binds to its complementary ssDNA (cDNA) to form the activator Apt/cDNA, which is specifically recognized by crRNA-Cas12a and excites the trans-cleavage function of Cas12a, thus in turn trans-cleaves pDNA and detaches GOD from the magnetic particles. The magnetic beads were separated and transferred into a glucose solution, and the oxidation current of H2O2 produced by the catalytic reaction of GOD was measured on a Pt-modified magnetically-controlled glassy carbon electrode, resulting in an indirect determination of MUC1. The current change was linear with the logarithm of MUC1 concentration in the range from 1.0 × 10−17 g mL−1 to 1.0 × 10−10 g mL−1. The detection limit was as low as 7.01 × 10−18 g mL−1. The method was applied for the detection of MUC1 in medical samples. [ABSTRACT FROM AUTHOR]

Ovarian cancer stands as the deadliest gynecologic malignancy, responsible for nearly 65% of all gynecologic cancer-related deaths. The challenges in early detection and diagnosis, coupled with the widespread intraperitoneal spread of cancer cells and resistance to chemotherapy, contribute significantly to the high mortality rate of this disease. Due to the absence of specific symptoms and the lack of effective screening methods, most ovarian cancer cases are diagnosed at advanced stages. While chemotherapy is a common treatment, it often leads to tumor recurrence, necessitating further interventions. In recent years, antibody-drug conjugates (ADCs) have emerged as a valuable tool in targeted cancer therapy. These complex biotherapeutics combine an antibody that specifically targets tumor specific/associated antigen(s) with a high potency anti-cancer drug through a linker, offering a promising approach for ovarian cancer treatment. The identification of molecular targets in various human tumors has paved the way for the development of targeted therapies, with ADCs being at the forefront of this innovation. By delivering cytotoxic agents directly to tumors and metastatic lesions, ADCs show potential in managing chemo-resistant ovarian cancers. Mucins such as MUC16, MUC13, and MUC1 have shown significantly higher expression in ovarian tumors as compared to normal and/or benign samples, thus have become promising targets for ADC generation. While traditional markers are limited by their elevated levels in non-cancerous conditions, mucins offer a new possibility for targeted treatment in ovarian cancer. This review comprehensively described the potential of mucins for the generation of ADC therapy, highlighting their importance in the quest to improve the outcome of ovarian cancer patients. [ABSTRACT FROM AUTHOR]

The assessment of the mucoadhesive properties peak mucoadhesive force (F max) and work of mucoadhesion (W muc) with texture analyzers is a common in vitro method for analyzing formulation capabilities. Challenges arise in selecting and standardizing experimental conditions due to various variables influencing mucoadhesion. This complexity hampers direct product performance comparisons. In our study, we explored factors (contact force and time, probe speed and mucin in artificial saliva) impacting a model formulation's mucoadhesive capacity. Using Omcilon-A®Orabase on porcine buccal mucosa, we systematically varied experimental conditions, employing a statistical approach (Central Composite Design - CCD). Three variables (contact force, contact time, probe speed) and their interactions were assessed for their impact on F max and W muc. Results showed that contact time and force positively affected F max , while only contact time influenced W muc. In the mucin artificial saliva test, a force of 0.5 N, time of 600 s, and speed of 1 mm/s yielded optimal F max (0.587 N) and W muc (0.468 N.s). These conditions serve as a reference for comparing mucoadhesive properties of formulations for topical oral use. [Display omitted] [ABSTRACT FROM AUTHOR]

Rheological properties of gastric contents depend on the food ingested, and on the volume and composition of secretions from the host, which may vary. This study investigates the impact of saliva regular incorporation in the stomach after a meal on the rheological properties of gastric contents, considering two levels of salivary flow (low = 0.5 and high = 1.5 mL/min). In vitro chymes were obtained by mixing sour cream, simulated gastric fluid, two different volumes of oral fluid (at‐rest human saliva, SSF for Simulated Salivary Fluid or water) and adjusting pH at 3. Chymes samples were characterized at 37°C for their particle size and rheological properties. Overall, particle size distribution was not different between samples: incorporating a larger volume of saliva resulted in more heterogeneity, but the surface area moment D[3,2] and volume moment D[4,3] did not differ significantly with the oral fluid type. Shear viscosity of chyme samples was higher when saliva was incorporated, in comparison with water or SSF. In addition, as shown from data extracted at γ̇$$ \dot{\gamma} $$ = 20 s−1 the higher the fluid volume the lower the shear viscosity, which is attributed to a dilution effect. However, this dilution effect was attenuated in the case of saliva, most likely due to its composition in organic compounds (e.g., mucins) contributing to the rheological properties of this biological fluid. In these in vitro conditions, both saliva and the salivation rate had a significant but slight impact on the rheological properties of gastric contents (of the order of 1–5 mPa s at γ̇$$ \dot{\gamma} $$ = 20 s−1). [ABSTRACT FROM AUTHOR]

Mucins are major components of the mucus. Besides the highly O‐glycosylated tandem repeat domains, mucins contain Cys domains (CysDs). CysDs contain conserved disulfide‐forming cysteine residues as well as a WxxW motif. Since this is the consensus sequence for tryptophan C‐mannosylation, mucin CysDs have been suggested to be targets for C‐mannosyltransferases, but this has never been directly shown. Here, we recombinantly expressed human mucin CysDs in Chinese hamster ovary (CHO) cells and analyzed the C‐mannosylation status. Mass spectrometric analysis revealed that the putative C‐mannose site is not or only barely C‐mannosylated. However, mutation of the adjacent cysteine residues enabled C‐mannosylation to occur. In contrast to mucin CysDs, the homologous CysD of human cartilage intermediate layer protein 1 (CILP1) lacks these cysteine residues preceding the WxxW motif. We show that CILP1 CysD is C‐mannosylated, but introducing a cysteine at the −2 position causes this modification to be lost. We thus conclude that the presence of cysteine residues prevents the modification of the WxxW motif in CysDs. [ABSTRACT FROM AUTHOR]

The flagellar MS‐ring, uniquely constituted by FliF, is essential for flagellar biogenesis and functionality in several bacteria. The aim of this study was to dissect the role of FliF in the Gram‐positive and peritrichously flagellated Bacillus cereus. We demonstrate that fliF forms an operon with the upstream gene fliE. In silico analysis of B. cereus ATCC 14579 FliF identifies functional domains and amino acid residues that are essential for protein functioning. The analysis of a ΔfliF mutant of B. cereus, constructed in this study using an in frame markerless gene replacement method, reveals that the mutant is unexpectedly able to assemble flagella, although in reduced amounts compared to the parental strain. Nevertheless, motility is completely abolished by fliF deletion. FliF deprivation causes the production of submerged biofilms and affects the ability of B. cereus to adhere to gastrointestinal mucins. We additionally show that the fliF deletion does not compromise the secretion of the three components of hemolysin BL, a toxin secreted through the flagellar type III secretion system. Overall, our findings highlight the important role of B. cereus FliF in flagella‐related functions, being the protein required for complete flagellation, motility, mucin adhesion, and pellicle biofilms. [ABSTRACT FROM AUTHOR]

• Novel in vitro methods are necessary to substitute costly, slow, and highly complex in vivo models to evaluate ophthalmic formulations. • The efficacy of topical ophthalmic drug products depends directly on formulation residence time in the eye, which must be sufficient for the drug to penetrate the cornea to reach the site of action at therapeutic levels. • A new in vitro alternative method that mimics the in vivo dynamic barriers of the eye by using a dynamic tear flow system and a synthetic barrier to simulate the cornea is presented. • The OphtalMimic is a promising tool for comparing the performance of ophthalmic formulations regarding their residence time. The necessity of animal-free performance tests for novel ophthalmic formulation screening is challenging. For this, we developed and validated a new device to simulate the dynamics and physical–chemical barriers of the eye for in vitro performance tests of topic ophthalmic formulations. The OphthalMimic is a 3D-printed device with an artificial lacrimal flow, a cul-de-sac area, a support base, and a simulated cornea comprised of a polymeric membrane containing poly-vinyl alcohol 10 % (w/v), gelatin 2.5 % (w/v), and different proportions of mucin and poloxamer, i.e., 1:1 (M1), 1:2 (M2), and 2:1 (M3) w/v, respectively. The support base is designed to move between 0° and 50° to replicate the movement of an eyelid. We challenged the model by testing the residence performance of poloxamer®407 16 % and poloxamer®407 16 % + chitosan 1 % (PLX16CS10) gels containing fluconazole. The test was conducted with a simulated tear flow of 1.0 mL.min−1 for 5 min. The OphthalMimic successfully distinguished PLX16 and PLX16C10 formulations based on their fluconazole drainage (M1: 65 ± 14 % and 27 ± 10 %; M2: 58 ± 6 % and 38 ± 9 %; M3: 56 ± 5 % and 38 ± 18 %). In conclusion, the OphthalMimic is a promising tool for comparing the animal-free performance of ophthalmic formulations. [ABSTRACT FROM AUTHOR]

Mucus stasis is a pathologic hallmark of muco-obstructive diseases, including cystic fibrosis (CF). Mucins, the principal component of mucus, are extensively modified with hydroxyl (O)-linked glycans, which are largely terminated by sialic acid. Sialic acid is a negatively charged monosaccharide and contributes to the biochemical/biophysical properties of mucins. Reports suggest that mucin sialylation may be altered in CF; however, the consequences of reduced sialylation on mucus clearance have not been fully determined. Here, we investigated the consequences of reduced sialylation on the charge state and conformation of the most prominent airway mucin, MUC5B, and defined the functional consequences of reduced sialylation on mucociliary transport (MCT). Reduced sialylation contributed to a lower charged MUC5B form and decreased polymer expansion. The inhibition of total mucin sialylation de novo impaired MCT in primary human bronchial epithelial cells and rat airways, and specific α-2,3 sialylation blockade was sufficient to recapitulate these findings. Finally, we show that ST3 beta-galactoside alpha-2,3-sialyltransferase (ST3Gal1) expression is downregulated in CF and partially restored by correcting CFTR via Elexacaftor/Tezacaftor/Ivacaftor treatment. Overall, this study demonstrates the importance of mucin sialylation in mucus clearance and identifies decreased sialylation by ST3Gal1 as a possible therapeutic target in CF and potentially other muco-obstructive diseases. [ABSTRACT FROM AUTHOR]

The optimal performance of drug delivery formulations, including polymeric nanoparticles, relies on particle distribution throughout the body and the interactions with biological barriers, particularly mucosal layers, which often limit their potential. A systematic and comprehensive study is presented through a multidisciplinary approach combining conventional and novel techniques for in vitro studies to understand the key molecular interactions between polymeric micelles and mucin. The results shows that polymeric micelles are integrates within the mucin layer, mirroring its viscoelastic properties, evidenced as a dissipation difference of 0.1 ± 0.44, measured by quartz crystal microbalance with dissipation. Surface‐enhanced Raman scattering reveals predominant hydrogen bonding within the mucin's hydrophilic core, while the isothermal titration calorimetry method confirms multiple non‐specific binding sites on the protein backbone. By performing the periodic acid‐Schiff stain assay, a binding amount of 0.20 mg of mucin per milligram of nanoparticles is quantified. Furthermore, motility studies show the surface binding of mucin on the polymeric nanoparticles influencing their Brownian motion. This study sheds light toward the improvement for a better drug delivery formulation and fabrication of optimal nanoparticle colloidal systems, which can advance translational drug delivery technologies into clinical application while enriching the field of surface and colloidal chemistry. [ABSTRACT FROM AUTHOR]

Lupus erythematosus tumidus is an uncommon disorder characterized by erythematous urticarial non-scarring plaques. It has high photosensitivity and a clinical course with relapses and spontaneous remission. Histologic features include perivascular and periadnexal lymphocytic infiltration and interstitial mucin deposition, with the absence of changes on the epidermal surface. We present the case of a 55-year-old male who presented with an erythematous urticarial plaque on the forehead. Initially, we consider Hansen's disease due to its prevalence and regional epidemiology. [ABSTRACT FROM AUTHOR]

• Expression of Muc13 is decreased in the intestines of stressed animals. • Mice lacking Muc13 show microbiome signatures like those found in stressed mice. • Muc13 deletion can induce despair and anxiety-like behaviors in mice. • The transcription factor HNF4 binds to and regulates Muc13 gene expression. Depression is a prevalent psychological condition with limited treatment options. While its etiology is multifactorial, both chronic stress and changes in microbiome composition are associated with disease pathology. Stress is known to induce microbiome dysbiosis, defined here as a change in microbial composition associated with a pathological condition. This state of dysbiosis is known to feedback on depressive symptoms. While studies have demonstrated that targeted restoration of the microbiome can alleviate depressive-like symptoms in mice, translating these findings to human patients has proven challenging due to the complexity of the human microbiome. As such, there is an urgent need to identify factors upstream of microbial dysbiosis. Here we investigate the role of mucin 13 as an upstream mediator of microbiome composition changes in the context of stress. Using a model of chronic stress, we show that the glycocalyx protein, mucin 13, is selectively reduced after psychological stress exposure. We further demonstrate that the reduction of Muc13 is mediated by the Hnf4 transcription factor family. Finally, we determine that deleting Muc13 is sufficient to drive microbiome shifts and despair behaviors. These findings shed light on the mechanisms behind stress-induced microbial changes and reveal a novel regulator of mucin 13 expression. [ABSTRACT FROM AUTHOR]

Recent studies have demonstrated the ability of mucin O‐glycans to attenuate virulence in diverse, cross‐kingdom pathogens, sparking interest in their development as a novel therapeutic approach against infection. Although their virulence attenuating activity is evident, mucin glycans obtained from native sources comprise mixtures of several hundred distinct structures, and therefore the specific active glycan epitopes and molecular mechanisms of virulence attenuation remain unclear. Individual mucin glycan structures cannot be purified from native sources and are not amenable to automated synthesis; therefore, to further investigate the phenomena of virulence attenuation we have been developing convergent and scalable methods (>30 mg per target glycan) to assemble a mucin O‐glycan library in sufficient scale and purity to facilitate biological studies. Previously we described a method to obtain core 1 & core 2‐type mucin glycan derivatives that have since been used to identify active epitopes in Candida albicans and Vibrio cholerae. In the current study, we describe the expansion of our glycan library to include core 3 & core 4‐type derivatives, increasing the structural diversity of our platform for biological evaluation. [ABSTRACT FROM AUTHOR]

Mucin is a glycoprotein secreted throughout the mammalian gastrointestinal tract that can support endogenous microorganisms in the absence of complex polysaccharides. While several mucin-degrading bacteria have been identified, the interindividual differences in microbial communities capable of metabolizing this complex polymer are not well described. To determine whether community assembly on mucin is deterministic across individuals or whether taxonomically distinct but functionally similar mucin-degrading communities are selected across fecal inocula, we used a 10-day in vitro sequential batch culture fermentation from three human donors with mucin as the sole carbon source. For each donor, 16S rRNA gene amplicon sequencing was used to characterize microbial community succession, and the short-chain fatty acid profile was determined from the final community. All three communities reached a steady-state by day 7 in which the community composition stabilized. Taxonomic comparisons amongst communities revealed that one of the final communities had Desulfovibrio , another had Akkermansia , and all three shared other members, such as Bacteroides. Metabolic output differences were most notable for one of the donor's communities, with significantly less production of acetate and propionate than the other two communities. These findings demonstrate the feasibility of developing stable mucin-degrading communities with shared and unique taxa. Furthermore, the mechanisms and efficiencies of mucin degradation across individuals are important for understanding how this community-level process impacts human health. [ABSTRACT FROM AUTHOR]

Gastric ulceration is a common gastrointestinal ailment with serious consequences that can lead to serious illness or even death. This study aimed to examine the efficacy of tadalafil (TAD) and dexlansoprazole (DLP) in treating stomach ulcers caused by dexamethasone (DEX) in male albino Wister rats. Thirty male albino Wister rats were divided into 5 groups (6 rats each): control group received normal saline, positive control group received DEX 5 mg/kg/day intraperitoneal (i.p.) for 7 days, the third group received DLP 30 mg/kg/day orally after DEX, the fourth group received TAD 5 mg/kg/day orally after DEX, and the fifth group received DLP and TAD orally after DEX. Persistence and prevention of ulcers, pepsin activity, mucin content, and histopathological changes were evaluated after each trial. Reduced glutathione (GSH), nitric oxide (NO), and malondialdehyde (MDA) levels were measured in gastric homogenates. Serum levels of prostaglandin E2 (PGE2), tumor necrosis factor-α (TNF-α), and interleukin-10 (IL-10) were also measured. Treatment with either TAD or DLP alone significantly reduced ulcer index (U.I.), pepsin activity, TNF-α, IL-10 and MDA with significant rise in mucin content, PGE2, NO, GSH, and improved the histological alteration compared to DEX group. When TAD and DLP were administered together, there was a more notable decrease in U.I., pepsin activity, gastric MDA, TNF-α, and IL-10 with concomitant more significant increase in mucin content, NO content, and PGE2 production compared to the TAD or DLP groups alone. Compared to each medicine alone, TAD and DLP together have promising therapeutic potential in preventing stomach ulcers caused by DEX. [ABSTRACT FROM AUTHOR]

Mucosal-delivered drugs have to pass through the mucus layer before absorption through the epithelial cell membrane. Although there has been increasing interest in polymeric mucins, a major structural component of mucus, potentially acting as important physiological regulators of mucosal drug absorption, there are no reports that have systematically evaluated the interaction between mucins and drugs. In this study, we assessed the potential interaction between human polymeric mucins (MUC2, MUC5B, and MUC5AC) and various drugs with different chemical profiles by simple centrifugal method and fluorescence analysis. We found that paclitaxel, rifampicin, and theophylline likely induce the aggregation of MUC5B and/or MUC2. In addition, we showed that the binding affinity of drugs for polymeric mucins varied, not only between individual drugs but also among mucin subtypes. Furthermore, we demonstrated that deletion of MUC5AC and MUC5B in A549 cells increased the cytotoxic effects of cyclosporin A and paclitaxel, likely due to loss of mucin-drug interaction. In conclusion, our results indicate the necessity to determine the binding of drugs to mucins and their potential impact on the mucin network property. [ABSTRACT FROM AUTHOR]

Background: B3GNT7, a glycosyltransferase of significant importance that is highly expressed in intestinal epithelial cells, plays a pivotal role in intestinal physiological processes. This study elucidates novel insights into the potential role and underlying mechanisms of B3GNT7 in ulcerative colitis (UC). Methods: An experimental colitis model was induced using DSS in mice to investigate B3GNT7 expression in the colon via transcriptomics and immunohistochemistry. Bioinformatics analysis was employed to delineate the biological functions of B3GNT7. Additionally, the correlation between the transcription levels of B3GNT7 in colonic tissues from patients with UC, sourced from the IBDMDB database, and the severity of colonic inflammation was analyzed to elucidate potential mechanisms. Results: The DSS-induced colitis model was successfully established, and transcriptomic analysis identified a marked downregulation of B3GNT7 expression in the colonic tissues compared to the controls. Functional enrichment analysis indicated B3GNT7's predominant role in mucin O-glycosylation. Protein interaction analysis revealed that B3GNT7 predominantly interacts with members of the mucin MUC family, including MUC2, MUC3, and MUC6. In patients with UC, B3GNT7 transcription levels were significantly reduced, particularly in those with moderate to severe disease activity. The expression level of B3GNT7 exhibited a negative correlation with the endoscopic severity of UC. Gene set enrichment analysis (GSEA) further demonstrated significant enrichment of B3GNT7 in the mucin O-glycosylation synthesis pathway. Conclusion: The downregulation of B3GNT7 expression in the colonic tissues of UC patients may contribute to the compromised mucin barrier function and the exacerbation of colitis. [ABSTRACT FROM AUTHOR]

MUC2 mucin, the primary gel-forming component of intestinal mucus, is well researched and a model of polymerisation and post-secretory organisation has been published previously. Recently, several significant developments have been made which either introduce new ideas or challenge previous theories. New ideas include an overhaul of the MUC2 C-terminal globular structure which is proposed to harbour several previously unobserved domains, and include a site for an extra intermolecular disulphide bridge dimer between the cysteine 4379 of adjacent MUC2 C-termini. MUC2 polymers are also now thought to be secreted attached to the epithelial surface of goblet cells in the small intestine and removed following secretion via a metalloprotease meprin β-mediated cleavage of the von Willebrand D2 domain of the N-terminus. It remains unclear whether MUC2 forms intermolecular dimers, trimers, or both, at the N-termini during polymerisation, with several articles supporting either trimer or dimer formation. The presence of a firm inner mucus layer in the small intestine is similarly unclear. Considering this recent research, this review proposes an update to the previous model of MUC2 polymerisation and secretion, considers conflicting theories and data, and highlights the importance of this research to the understanding of MUC2 mucus layers in health and disease. [ABSTRACT FROM AUTHOR]

The erosion of the colonic mucus layer by a dietary fiber-deprived gut microbiota results in heightened susceptibility to an attaching and effacing pathogen, Citrobacter rodentium. Nevertheless, the questions of whether and how specific mucolytic bacteria aid in the increased pathogen susceptibility remain unexplored. Here, we leverage a functionally characterized, 14-member synthetic human microbiota in gnotobiotic mice to deduce which bacteria and functions are responsible for the pathogen susceptibility. Using strain dropouts of mucolytic bacteria from the community, we show that Akkermansia muciniphila renders the host more vulnerable to the mucosal pathogen during fiber deprivation. However, the presence of A. muciniphila reduces pathogen load on a fiber-sufficient diet, highlighting the context-dependent beneficial effects of this mucin specialist. The enhanced pathogen susceptibility is not owing to altered host immune or pathogen responses, but is driven by a combination of increased mucus penetrability and altered activities of A. muciniphila and other community members. Our study provides novel insights into the mechanisms of how discrete functional responses of the same mucolytic bacterium either resist or enhance enteric pathogen susceptibility. Synopsis: Susceptibility to a mucosal pathogen is both microbiome- and diet-dependent, with mucin specialist Akkermansia muciniphila increasing susceptibility on a fiber-free diet, whereas a fiber-rich diet allows the same commensal to confer resistance. Variations of a 14-member synthetic human gut microbiota show the key role of dietary fiber in determining the severity of Citrobacter rodentium infection through specific members of the microbiome. Combined action of increased mucus barrier permeability and altered community networks underlie the increased pathogen susceptibility in the Akkermansia muciniphila-containing communities fed a fiber-free diet. Exclusion of Akkermansia muciniphila from the synthetic microbiota or consumption of a fiber-rich diet is sufficient to prevent severe infection. Dietary context is key, with the presence of Akkermansia muciniphila protecting against severe infection under fiber-rich conditions. Susceptibility to a mucosal pathogen is both microbiome- and diet-dependent, with mucin specialist Akkermansia muciniphila increasing susceptibility on a fiber-free diet, whereas a fiber-rich diet allows the same commensal to confer resistance. [ABSTRACT FROM AUTHOR]

Cholelithiasis is a common biliary tract disease. However, the exact mechanism underlying gallstone formation remains unclear. Mucin plays a vital role in the nuclear formation and growth of cholesterol and pigment stones. Excessive mucin secretion can result in cholestasis and decreased gallbladder activity, further facilitating stone formation and growth. Moreover, gallstones may result in inflammation and the secretion of inflammatory factors, which can further increase mucin expression and secretion to promote the growth of gallstones. This review systematically summarises and analyses the role of mucins in gallstone occurrence and development and its related mechanisms to explore new ideas for interventions in stone formation or recurrence. [ABSTRACT FROM AUTHOR]

Background and Aim: In avian and other species, mucins (MUCs) play a crucial role in the gastrointestinal tract (GIT), and constitute a large group of O-glycosylated glycoproteins, are glycoconjugate proteins. MUCs present in two forms: (1) membrane-attached on cell surfaces to repel external threats and (2) detachable, gel-forming proteins in the soluble form. In quail GIT, the specific types of MUCs that are expressed remain largely unknown. We investigated the expression of MUC1 and MUC4 MUCs in the GIT of Iraqi common quails and conducted network and structural analyses of all known MUC types across quail breeds. Materials and Methods: Histological and gene expression analyses of MUC1 and MUC4 were conducted using fresh small intestine and large intestine samples from 10 quails. Using the STRING Database, Chimera software, and PrankWeb-ligand binding site prediction tool, network and structural analyses of all reported types of quail MUCs were conducted. Results: Most intestinal MUCs in quails were acidic, with few neutral MUCs detectable through Alcian blue and periodic acid-schiff stains. Acidic MUCs were more expressed in the duodenum, ileum, cecum, and colon, whereas neutral MUCs were more expressed in the jejunum. MUC1 and MUC4 messenger RNA expression was significantly higher in the jejunum and colon than in the duodenum and ileum. The analysis of the network revealed that MUC 1, 15, 16, and 24 formed homologous networks, while MUC 2, 4, 5, and 6 formed heterologous networks. Specific MUC combinations, including MUC5A-MUC6, MUC5A-MUC5B, and MUC5B-MUC6, show higher intermolecular hydrogen bond formation affinity. MUC15, MUC16, and MUC24 showed minimal interaction with other MUC types. Among the analyzed MUCs, MUC5B, and MUC6 had the highest probability for binding, while MUC2, MUC4, and MUC5A showed lower probabilities despite greater numbers of binding sites. Conclusion: This study's results offer significant insights into quails' MUCs' composition, expression, network interactions, and binding sites, advancing knowledge of MUC-related processes in gastrointestinal physiology and their potential connection to gastrointestinal diseases. [ABSTRACT FROM AUTHOR]