Reverse-engineering the anti-MUC1 antibody 139H2 by mass spectrometry-based de novo sequencing

Mucin 1 (MUC1) is a transmembrane mucin expressed at the apical surface of epithelial cells at mucosal surfaces. MUC1 has a barrier function against bacterial invasion and is well known for its aberrant expression and glycosylation in adenocarcinomas. The MUC1 extracellular domain contains a variable number of tandem repeats (VNTR) of 20 amino acids, which are heavily O-linked glycosylated. Monoclonal antibodies against the MUC1 VNTR are powerful research tools with applications in the diagnosis and treatment of MUC1-expressing cancers. Here, we report direct mass spectrometry-based sequencing of anti-MUC1 hybridoma-derived 139H2 IgG, enabling reverse-engineering of the functional recombinant monoclonal antibody. The crystal structure of the 139H2 Fab fragment in complex with the MUC1 epitope was solved, revealing the molecular basis of 139H2 binding specificity to MUC1 and its tolerance to O-glycosylation of the VNTR. The available sequence of 139H2 will allow further development of MUC1-related diagnostic, targeting, and treatment strategies.

Lycium barbarum arabinogalactan alleviates intestinal mucosal damage in mice by restoring intestinal microbes and mucin O-glycans

Structurally defined arabinogalactan (LBP-3) from Lycium barbarum have effect on improving intestinal barrier function. However, whether its intestinal barrier function depended on the changes of intestinal mucin O-glycans have not been investigated. A dextran sodium sulfate-induced acute colitis mouse model was employed to test prevention and treatment with LBP-3. The intestinal microbiota as well as colonic mucin O-glycan profiles were analyzed. Supplementation with LBP-3 inhibited harmful bacteria, including Desulfovibrionaceae, Enterobacteriaceae, and Helicobacteraceae while significantly increased the abundance of beneficial bacteria (e.g., Lachnospiraceae, Ruminococcaceae, and Lactobacillaceae). Notably, LBP-3 augmented the content of neutral O-glycans by stimulating the fucosylation glycoforms (F1H1N2 and F1H2N2), short-chain sulfated O-glycans (S1F1H1N2, S1H1N2, and S1H2N3), and sialylated medium- and long-chain O-glycans (F1H2N2A1, H2N3A1, and F1H3N2A1). In summary, we report that supplement LBP-3 significantly reduced pathological symptoms, restored the bacterial community, and promoted the expression of O-glycans to successfully prevent and alleviate colitis in a mouse model, especially in the LBP-3 prevention testing group. The underlying mechanism of action was investigated using glycomics to better clarify which the structurally defined LBP-3 were responsible for its beneficial effect against ulcerative colitis and assess its use as a functional food or pharmaceutical supplement.

The impact of indole and mucin on sporulation, biofilm formation, and enterotoxin production in foodborne Clostridium perfringens

AIMS

Indole and mucin are compounds found in the host environment as they are produced by the host or by the host-associated microbiota. This study investigated whether indole and mucin impact Clostridium perfringens growth and sporulation, as well as enterotoxin production and biofilm formation.

METHODS AND RESULTS

There was no impact on growth of Cl. perfringens for up to 400 µM indole and 240 mg/l mucin, and neither indole nor mucin affected sporulation. Reverse-transcriptase qPCR showed that mucin strongly upregulated the expression of Cl. perfringens enterotoxin (up to 121-fold increase), whereas indole had a much more modest effect (2-fold). This was also reflected in increased Cl. perfringens enterotoxin levels in mucin-treated Cl. perfringens (as assessed by a reversed passive latex agglutination assay). Finally, mucin and indole significantly increased biofilm formation of Cl. perfringens, although the effect size was relatively small (less than 1.5 fold).

CONCLUSION

These results indicate that Cl. perfringens can sense its presence in a host environment by responding to mucin, and thereby markedly increased enterotoxin production.

Analyzing the interaction of Helicobacter pylori GAPDH with host molecules and hemin: Inhibition of hemin binding

Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) is a moonlighting enzyme. Apart from its primary role in the glycolytic pathway, in many bacterial species it is found in the extracellular milieu and also on the bacterial surface. Positioning on the bacterial surface allows the GAPDH molecule to interact with many host molecules such as plasminogen, fibrinogen, fibronectin, laminin and mucin etc. This facilitates the bacterial colonization of the host. Helicobacter pylori is a major human pathogen that causes a number of gastrointestinal infections and is the main cause of gastric cancer. The binding analysis of H. pylori GAPDH (HpGAPDH) with host molecules has not been carried out. Hence, we studied the interaction of HpGAPDH with holo-transferrin, lactoferrin, haemoglobin, fibrinogen, fibronectin, catalase, plasminogen and mucin using biolayer interferometry. Highest and lowest binding affinity was observed with lactoferrin (4.83 ± 0.70 × 10-9 M) and holo-transferrin (4.27 ± 2.39 × 10-5 M). Previous studies established GAPDH as a heme chaperone involved in intracellular heme trafficking and delivery to downstream target proteins. Therefore, to get insights into heme binding, the interaction between HpGAPDH and hemin was analyzed. Hemin binds to HpGAPDH with an affinity of 2.10 μM while the hemin bound HpGAPDH does not exhibit activity. This suggests that hemin most likely binds at the active site of HpGAPDH, prohibiting substrate binding. Blind docking of hemin with HpGAPDH also supports positioning of hemin at the active site. Metal ions were found to inhibit the activity of HpGAPDH, suggesting that it also possibly occupies the substrate binding site. Furthermore, with metal-bound HpGAPDH, hemin binding was not observed, suggesting metal ions act as an inhibitor of hemin binding. Since GAPDH has been identified as a heme chaperone, it will be interesting to analyse the biological consequences of inhibition of heme binding to GAPDH by metal ions.

Polysaccharides screening for pulmonary mucus penetration by molecular dynamics simulation and in vitro verification

Mucus penetration is one of the physiologic barriers of inhalation and nanocarriers can effectively facilitate the permeation of drugs. The interactions between the nanocarriers and mucin are crucial for penetration across the mucus layer on the respiratory tract. In this study, we proposed a molecular dynamics (MD) simulation method for the screening of polysaccharides that acted as the surface modification materials for inhalable nano-preparations to facilitate mucus penetration. MD revealed all-atom interactions between the monomers of polysaccharides, including dextran (DEX)/hyaluronic acid (HA)/carboxymethyl chitosan (CMCS) and the human mucin protein MUC5AC (hMUC5AC). The obtained data showed that DEX formed stronger non-covalent bonds with hMUC5AC compared to HA and CMCS, which suggested that HA and CMCS had better mucus permeability than DEX. For the in vitro verification, HA/CMCS-coated liposomes and DEX/PEG-inserted liposomes were prepared. The results of mucin interactions and mucus penetration studies confirmed that HA and CMCS possessed the weakest interactions with mucin and facilitated the mucus penetration, which was in consistent with the data from MD simulation. This work may shed light on the MD simulation-based screening of surface modification materials for inhalable nano-preparations to facilitate mucus penetration.

Design of a mucin-selective protease for targeted degradation of cancer-associated mucins

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.

Ant may well destroy a whole dam: glycans of colonic mucus barrier disintegrated by gut bacteria

The colonic mucus layer plays a critical role in maintaining the integrity of the colonic mucosal barrier, serving as the primary defense against colonic microorganisms. Predominantly composed of mucin 2 (MUC2), a glycosylation-rich protein, the mucus layer forms a gel-like coating that covers the colonic epithelium surface. This layer provides a habitat for intestinal microorganisms, which can utilize mucin glycans present in the mucus layer as a sustainable source of nutrients. Additionally, metabolites produced by the microbiota during the metabolism of mucus glycans have a profound impact on host health. Under normal conditions, the production and consumption of mucus maintain a dynamic balance. However, several studies have demonstrated that certain factors, such as dietary fiber deficiency, can enhance the metabolism of mucus glycans by gut bacteria, thereby disturbing this balance and weakening the mucus barrier function of the mucus layer. To better understand the occurrence and development of colon-related diseases, it is crucial to investigate the complex metabolic patterns of mucus glycosylation by intestinal microorganisms. Our objective was to comprehensively review these patterns in order to clarify the effects of mucus layer glycan metabolism by intestinal microorganisms on the host.

Ion mobility-tandem mass spectrometry of mucin-type O-glycans

The dense O-glycosylation of mucins plays an important role in the defensive properties of the mucus hydrogel. Aberrant glycosylation is often correlated with inflammation and pathology such as COPD, cancer, and Crohn's disease. The inherent complexity of glycans and the diversity in the O-core structure constitute fundamental challenges for the analysis of mucin-type O-glycans. Due to coexistence of multiple isomers, multidimensional workflows such as LC-MS are required. To separate the highly polar carbohydrates, porous graphitized carbon is often used as a stationary phase. However, LC-MS workflows are time-consuming and lack reproducibility. Here we present a rapid alternative for separating and identifying O-glycans released from mucins based on trapped ion mobility mass spectrometry. Compared to established LC-MS, the acquisition time is reduced from an hour to two minutes. To test the validity, the developed workflow was applied to sputum samples from cystic fibrosis patients to map O-glycosylation features associated with disease.

Sex drives colonic mucin sialylation in wild mice

Mucin protein glycosylation is important in determining biological properties of mucus gels, which form protective barriers at mucosal surfaces of the body such as the intestine. Ecological factors including: age, sex, and diet can change mucus barrier properties by modulating mucin glycosylation. However, as our understanding stems from controlled laboratory studies in house mice, the combined influence of ecological factors on mucin glycosylation in real-world contexts remains limited. In this study, we used histological staining with 'Alcian Blue, Periodic Acid, Schiff's' and 'High-Iron diamine' to assess the acidic nature of mucins stored within goblet cells of the intestine, in a wild mouse population (Mus musculus). Using statistical models, we identified sex as among the most influential ecological factors determining the acidity of intestinal mucin glycans in wild mice. Our data from wild mice and experiments using laboratory mice suggest estrogen signalling associates with an increase in the relative abundance of sialylated mucins. Thus, estrogen signalling may underpin sex differences observed in the colonic mucus of wild and laboratory mice. These findings highlight the significant influence of ecological parameters on mucosal barrier sites and the complementary role of wild populations in augmenting standard laboratory studies in the advancement of mucus biology.

Expressing Optogenetic Actuators Fused to N-terminal Mucin Motifs Delivers Targets to Specific Subcellular Compartments in Polarized Cells

Optogenetics is a powerful approach in neuroscience research. However, other tissues of the body may benefit from controlled ion currents and neuroscience may benefit from more precise optogenetic expression. The present work constructs three subcellularly-targeted optogenetic actuators based on the channelrhodopsin ChR2-XXL, utilizing 5, 10, or 15 tandem repeats (TR) from mucin as N-terminal targeting motifs and evaluates expression in several polarized and non-polarized cell types. The modified channelrhodopsin maintains its electrophysiological properties, which can be used to produce continuous membrane depolarization, despite the expected size of the repeats. This work then shows that these actuators are subcellularly localized in polarized cells. In polarized epithelial cells, all three actuators localize to just the lateral membrane. The TR-tagged constructs also express subcellularly in cortical neurons, where TR5-ChR2XXL and TR10-ChR2XXL mainly target the somatodendrites. Moreover, the transfection efficiencies are shown to be dependent on cell type and tandem repeat length. Overall, this work verifies that the targeting motifs from epithelial cells can be used to localize optogenetic actuators in both epithelia and neurons, opening epithelia processes to optogenetic manipulation and providing new possibilities to target optogenetic tools.

In vitro mucin degradation and paracellular permeability by fecal water from Crohn's disease patients

Aim: This study aimed to examine the impact of fecal water (FW) of active and remissive Crohn's disease (CD) patients on mucin degradation and epithelial barrier function. Methods: FW and bacterial membrane vesicles (MVs) were isolated from fresh fecal samples of six healthy controls (HCs) and 12 CD patients. Bacterial composition was determined by 16S rRNA gene amplicon sequencing. Results: In vitro FW-induced mucin degradation was higher in CD samples versus HC (p < 0.01), but not associated with specific bacterial genera. FW of three remissive samples decreased transepithelial electrical resistance in Caco-2 cells by 78-87% (p < 0.001). MVs did not induce barrier alterations. Conclusion: The higher mucin-degradation capacity of CD-derived FW might suggest contributions of microbial products to CD pathophysiology.

Immunoengineering can overcome the glycocalyx armour of cancer cells

Cancer cell glycocalyx is a major line of defence against immune surveillance. However, how specific physical properties of the glycocalyx are regulated on a molecular level, contribute to immune evasion and may be overcome through immunoengineering must be resolved. Here we report how cancer-associated mucins and their glycosylation contribute to the nanoscale material thickness of the glycocalyx and consequently modulate the functional interactions with cytotoxic immune cells. Natural-killer-cell-mediated cytotoxicity is inversely correlated with the glycocalyx thickness of the target cells. Changes in glycocalyx thickness of approximately 10 nm can alter the susceptibility to immune cell attack. Enhanced stimulation of natural killer and T cells through equipment with chimeric antigen receptors can improve the cytotoxicity against mucin-bearing target cells. Alternatively, cytotoxicity can be enhanced through engineering effector cells to display glycocalyx-editing enzymes, including mucinases and sialidases. Together, our results motivate the development of immunoengineering strategies that overcome the glycocalyx armour of cancer cells.

MUC13 negatively regulates tight junction proteins and intestinal epithelial barrier integrity via protein kinase C

Glycosylated mucin proteins contribute to the essential barrier function of the intestinal epithelium. The transmembrane mucin MUC13 is an abundant intestinal glycoprotein with important functions for mucosal maintenance that are not yet completely understood. We demonstrate that in human intestinal epithelial monolayers, MUC13 localized to both the apical surface and the tight junction (TJ) region on the lateral membrane. MUC13 deletion resulted in increased transepithelial resistance (TEER) and reduced translocation of small solutes. TEER buildup in ΔMUC13 cells could be prevented by addition of MLCK, ROCK or protein kinase C (PKC) inhibitors. The levels of TJ proteins including claudins and occludin were highly increased in membrane fractions of MUC13 knockout cells. Removal of the MUC13 cytoplasmic tail (CT) also altered TJ composition but did not affect TEER. The increased buildup of TJ complexes in ΔMUC13 and MUC13-ΔCT cells was dependent on PKC. The responsible PKC member might be PKCδ (or PRKCD) based on elevated protein levels in the absence of full-length MUC13. Our results demonstrate for the first time that a mucin protein can negatively regulate TJ function and stimulate intestinal barrier permeability.

An unusual dual sugar-binding lectin domain controls the substrate specificity of a mucin-type O-glycosyltransferase

N-acetylgalactosaminyl-transferases (GalNAc-Ts) initiate mucin-type O-glycosylation, an abundant and complex posttranslational modification that regulates host-microbe interactions, tissue development, and metabolism. GalNAc-Ts contain a lectin domain consisting of three homologous repeats (α, β, and γ), where α and β can potentially interact with O-GalNAc on substrates to enhance activity toward a nearby acceptor Thr/Ser. The ubiquitous isoenzyme GalNAc-T1 modulates heart development, immunity, and SARS-CoV-2 infectivity, but its substrates are largely unknown. Here, we show that both α and β in GalNAc-T1 uniquely orchestrate the O-glycosylation of various glycopeptide substrates. The α repeat directs O-glycosylation to acceptor sites carboxyl-terminal to an existing GalNAc, while the β repeat directs O-glycosylation to amino-terminal sites. In addition, GalNAc-T1 incorporates α and β into various substrate binding modes to cooperatively increase the specificity toward an acceptor site located between two existing O-glycans. Our studies highlight a unique mechanism by which dual lectin repeats expand substrate specificity and provide crucial information for identifying the biological substrates of GalNAc-T1.

Stable expression of mucin glycoproteins GP40 and GP15 of Cryptosporidium parvum in Toxoplasma gondii

BACKGROUND

Cryptosporidium spp. are common protozoa causing diarrhea in humans and animals. There are currently only one FDA-approved drug and no vaccines for cryptosporidiosis, largely due to the limited knowledge of the molecular mechanisms involved in the invasion of the pathogens. Previous studies have shown that GP60, which is cleaved into GP40 and GP15 after expression, is an immunodominant mucin protein involved in the invasion of Cryptosporidium. The protein is highly O-glycosylated, and recombinant proteins expressed in prokaryotic systems are non-functional. Therefore, few studies have investigated the function of GP40 and GP15.

METHODS

To obtain recombinant GP40 with correct post-translational modifications, we used CRISPR/Cas9 technology to insert GP40 and GP15 into the UPRT locus of Toxoplasma gondii, allowing heterologous expression of Cryptosporidium proteins. In addition, the Twin-Strep tag was inserted after GP40 for efficient purification of GP40.

RESULTS

Western blotting and immunofluorescent microscopic analyses both indicated that GP40 and GP15 were stably expressed in T. gondii mutants. GP40 localized not only in the cytoplasm of tachyzoites but also in the parasitophorous vacuoles, while GP15 without the GPI anchor was expressed only in the cytoplasm. In addition, a large amount of recTgGP40 was purified using Strep-TactinXT supported by a visible band of ~ 50 kDa in SDS-PAGE.

CONCLUSIONS

The establishment of a robust and efficient heterologous expression system of GP40 in T. gondii represents a novel approach and concept for investigating Cryptosporidium mucins, overcoming the limitations of previous studies that relied on unstable transient transfection, which involved complex steps and high costs.

Proximal and Distal Bronchioles Contribute to the Pathogenesis of Non-Cystic Fibrosis Bronchiectasis

Rationale: Non-cystic fibrosis bronchiectasis (NCFB) may originate in bronchiolar regions of the lung. Accordingly, there is a need to characterize the morphology and molecular characteristics of NCFB bronchioles. Objectives: Test the hypothesis that NCFB exhibits a major component of bronchiolar disease manifest by mucus plugging and ectasia. Methods: Morphologic criteria and region-specific epithelial gene expression, measured histologically and by RNA in situ hybridization and immunohistochemistry, identified proximal and distal bronchioles in excised NCFB lungs. RNA in situ hybridization and immunohistochemistry assessed bronchiolar mucus accumulation and mucin gene expression. CRISPR-Cas9-mediated IL-1R1 knockout in human bronchial epithelial cultures tested IL-1α and IL-1β contributions to mucin production. Spatial transcriptional profiling characterized NCFB distal bronchiolar gene expression. Measurements and Main Results: Bronchiolar perimeters and lumen areas per section area were increased in proximal, but not distal, bronchioles in NCFB versus control lungs, suggesting proximal bronchiolectasis. In NCFB, mucus plugging was observed in ectatic proximal bronchioles and associated nonectatic distal bronchioles in sections with disease. MUC5AC and MUC5B mucins were upregulated in NCFB proximal bronchioles, whereas MUC5B was selectively upregulated in distal bronchioles. Bronchiolar mucus plugs were populated by IL-1β-expressing macrophages. NCFB sterile sputum supernatants induced human bronchial epithelial MUC5B and MUC5AC expression that was >80% blocked by IL-1R1 ablation. Spatial transcriptional profiling identified upregulation of genes associated with secretory cells, hypoxia, interleukin pathways, and IL-1β-producing macrophages in mucus plugs and downregulation of epithelial ciliogenesis genes. Conclusions: NCFB exhibits distinctive proximal and distal bronchiolar disease. Both bronchiolar regions exhibit bronchiolar secretory cell features and mucus plugging but differ in mucin gene regulation and ectasia.

Different Forms of TFF3 in the Human Endocervix, including a Complex with IgG Fc Binding Protein (FCGBP), and Further Aspects of the Cervico-Vaginal Innate Immune Barrier

TFF3 is a typical secretory poplypeptide of mucous epithelia belonging to the trefoil factor family (TFF) of lectins. In the intestine, respiratory tract, and saliva, TFF3 mainly exists as a high-molecular-mass complex with IgG Fc binding protein (FCGBP), which is indicative of a role in mucosal innate immunity. For the first time, we identified different forms of TFF3 in the endocervix, i.e., monomeric and homodimeric TFF3, as well as a high-molecular-mass TFF3-FCGBP complex; the latter also exists in a hardly soluble form. Immunohistochemistry co-localized TFF3 and FCGBP. Expression analyses of endocervical and post-menopausal vaginal specimens revealed a lack of mucin and TFF3 transcripts in the vaginal specimens. In contrast, genes encoding other typical components of the innate immune defense were expressed in both the endocervix and vagina. Of note, FCGBP is possibly fucosylated. Endocervical specimens from transgender individuals after hormonal therapy showed diminished expression, particularly of FCGBP. Furthermore, mucus swabs from the endocervix and vagina were analyzed concerning TFF3, FCGBP, and lysozyme. It was the aim of this study to illuminate several aspects of the cervico-vaginal innate immune barrier, which is clinically relevant as bacterial and viral infections are also linked to infertility, pre-term birth and cervical cancer.

Abnormalities in microbiota/butyrate/FFAR3 signaling in aging gut impair brain function

Aging-related abnormalities in gut microbiota are associated with cognitive decline, depression, and anxiety, but underlying mechanisms remain unstudied. Here, our study demonstrated that transplanting old gut microbiota to young mice induced inflammation in the gut and brain coupled with cognitive decline, depression, and anxiety. We observed diminished mucin formation and increased gut permeability ("leaky gut") with a reduction in beneficial metabolites like butyrate because of decline in butyrate-producing bacteria in the aged gut microbiota. This led to suppressed expression of butyrate receptors, free fatty acid receptors 2 and 3 (FFAR2/3). Administering butyrate alleviated inflammation, restored mucin expression and gut barriers, and corrected brain dysfunction. Furthermore, young mice with intestine-specific loss of FFAR2/3 exhibited gut and brain abnormalities akin to those in older mice. Our results demonstrate that reduced butyrate-producing bacteria in aged gut microbiota result in low butyrate levels and reduced FFAR2/3 signaling, leading to suppressed mucin formation that increases gut permeability, inflammation, and brain abnormalities. These findings underscore the significance of butyrate-FFAR2/3 agonism as a potential strategy to mitigate aged gut microbiota-induced detrimental effects on gut and brain health in older adults.

A novel cysteine-rich adaptor protein is required for mucin packaging and secretory granule stability in vivo

Mucins are large, highly glycosylated extracellular matrix proteins that line and protect epithelia of the respiratory, digestive, and urogenital tracts. Previous work has shown that mucins form large, interconnected polymeric networks that mediate their biological functions once secreted. However, how these large matrix molecules are compacted and packaged into much smaller secretory granules within cells prior to secretion is largely unknown. Here, we demonstrate that a small cysteine-rich adaptor protein is essential for proper packaging of a secretory mucin in vivo. This adaptor acts via cysteine bonding between itself and the cysteine-rich domain of the mucin. Loss of this adaptor protein disrupts mucin packaging in secretory granules, alters the mobile fraction within granules, and results in granules that are larger, more circular, and more fragile. Understanding the factors and mechanisms by which mucins and other highly glycosylated matrix proteins are properly packaged and secreted may provide insight into diseases characterized by aberrant mucin secretion.

Mucus Structure, Viscoelastic Properties, and Composition in Chronic Respiratory Diseases

The respiratory mucus, a viscoelastic gel, effectuates a primary line of the airway defense when operated by the mucociliary clearance. In chronic respiratory diseases (CRDs), such as asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis (CF), the mucus is overproduced and its solid content augments, changing its structure and viscoelastic properties and determining a derangement of essential defense mechanisms against opportunistic microbial (virus and bacteria) pathogens. This ensues in damaging of the airways, leading to a vicious cycle of obstruction and infection responsible for the harsh clinical evolution of these CRDs. Here, we review the essential features of normal and pathological mucus (i.e., sputum in CF, COPD, and asthma), i.e., mucin content, structure (mesh size), micro/macro-rheology, pH, and osmotic pressure, ending with the awareness that sputum biomarkers (mucins, inflammatory proteins and peptides, and metabolites) might serve to indicate acute exacerbation and response to therapies. There are some indications that old and novel treatments may change the structure, viscoelastic properties, and biomarker content of sputum; however, a wealth of work is still needed to embrace these measures as correlates of disease severity in association with (or even as substitutes of) pulmonary functional tests.

Mucin Expression Profiles in Ulcerative Colitis: New Insights on the Histological Mucosal Healing

A structural weakness of the mucus barrier (MB) is thought to be a cause of ulcerative colitis (UC). This study aims to investigate the mucin (MUC) composition of MB in normal mucosa and UC. Ileocolonic biopsies were taken at disease onset and after treatment in 40 patients, including 20 with relapsing and 20 with remitting UC. Ileocolonic biopsies from 10 non-IBD patients were included as controls. Gut-specific MUC1, MUC2, MUC4, MUC5B, MUC12, MUC13, MUC15, and MUC17 were evaluated immunohistochemically. The promoters of mucin genes were also examined. Normal mucosa showed MUC2, MUC5B, and MUC13 in terminal ileum and colon, MUC17 in ileum, and MUC1, MUC4, MUC12, and MUC15 in colon. Membranous, cytoplasmic and vacuolar expressions were highlighted. Overall, the mucin expression was abnormal in UC. Derangements in MUC1, MUC4, and MUC5B were detected both at onset and after treatment. MUC2 and MUC13 were unaffected. Sequence analysis revealed glucocorticoid-responsive elements in the MUC1 promoter, retinoic-acid-responsive elements in the MUC4 promoter, and butyrate-responsive elements in the MUC5B promoter. In conclusion, MUCs exhibited distinct expression patterns in the gut. Their expression was disrupted in UC, regardless of the treatment protocols. Abnormal MUC1, MUC4, and MUC5B expression marked the barrier dysfunction in UC.

Regional Conjunctival Differences in Glycocalyx Mucin Expression in Dry Eye and Normal Subjects

Purpose

To compare regional conjunctival expression of membrane-associated mucins (MAMs) MUC1, MUC4, and MUC16 in normal and dry eye (DE) subjects.

Methods

Adults with and without signs and symptoms of DE were recruited. Impression cytology was performed to collect MAMs from four bulbar and upper eyelid palpebral conjunctival regions of both eyes. After protein extraction, samples from both eyes of a single subject were pooled by region, and expression was analyzed using a capillary electrophoresis nano-immunoassay system. The chemiluminescence intensity of each antigen binding signal was calculated after normalization to the total protein amount. Statistical analyses were conducted using GraphPad Prime 9.

Results

Samples from thirteen to sixteen DE and seven to eleven normal subjects were analyzed. In normal samples, MUC1 expression from the nasal bulbar conjunctiva was significantly greater than superior (P = 0.004) and inferior (P = 0.005). In DE samples, MUC1 expression was highest superiorly. Significant differences in MUC4 and MUC16 expression were not seen in normal samples. MUC4 and MUC16 expression was upregulated superiorly (P < 0.0001) and inferiorly (P < 0.0001) in DE compared with those regions in normal samples.

Conclusions

Although MAMs form a hydrophilic barrier called the glycocalyx, each mucin may have unique functions that are currently unexplored. All MAMs were expressed in the upper palpebral conjunctiva. Increased MUC1 expression nasally in healthy subjects suggests a functional need for increased protection. When comparing DE with normal eyes, upregulation of MUC1 superiorly, and in both MUC4 and MUC16 both superiorly and inferiorly, may indicate a need to decrease eyelid friction during blinking, especially in DE.

The Rosetta Stone of interactions of mucosa and associated bacteria in the gastrointestinal tract

PURPOSE OF REVIEW

Gut microbiota-mucosa-epithelial cells co-exist in an intricate three-way relationship that underpins gut homeostasis, and ultimately influences health and disease conditions. The O-glycans of mucin glycoproteins have been uncovered as a centrepiece of this system, although understanding the phenomena at play at the molecular level has been challenging and subject to significant traction over the last years. The purpose of this review is to discuss the recent advances in the phenomena that mediate microbiota and mucus multidirectional interactions in the human gut.

RECENT FINDINGS

The mucus biosynthesis and degradation by both commensal and pathogenic bacteria is under tight regulation and involves hundreds of carbohydrate-active enzymes (CAZy) and transporters. The fucosylation of O-glycans from mucin-2 seems to dictate binding by pathogenic species and to influence their virulence. Less clear is the influence of O-glycans in quorum sensing and biofilm formation. We have reviewed the advances in the in vitro models available to recreate the phenomena that capture the physiological context of the intestinal environment, emphasising models that include mucus and other aspects relevant to the physiological context.

SUMMARY

The recent findings highlight the importance of merging advances in analytical (glycans analysis) and omics techniques along with original robust in vitro models that enable to deconstruct part of the high complexity of the living gut and expand our understanding of the microbes-mucosa relationships and their significance in health and disease.

Fabrication and Characterization of Mucin Nanoparticles for Drug Delivery Applications

Mucin glycoproteins are ideal biomacromolecules for drug delivery applications since they naturally offer a plethora of different functional groups that can engage in specific and unspecific binding interactions with cargo molecules. However, to fabricate drug carrier objects from mucins, suitable stabilization mechanisms have to be implemented into the nanoparticle preparation procedure that allow for drug release profiles that match the requirements of the selected cargo molecule and its particular mode of action. Here, we describe two different methods to prepare crosslinked mucin nanoparticles that can release their cargo either on-demand or in a sustained manner. This method chapter includes a description of the preparation and characterization of mucin nanoparticles (stabilized either with synthetic DNA strands or with covalent crosslinks generated by free radical polymerization), as well as protocols to quantify the release of a model drug from those nanoparticles.

Bacterial Enzyme Assay for Mucin Glycan Degradation

Bacterial sialidase and sulfoglycosidase may act on the acidic modifications of mucin O-glycans, producing sialic acid and 6-sulfated N-acetylglucosamine, respectively. Assays for these enzymes, using mucin as a substrate, are enabled by the detection and/or quantification of the free monosaccharides that are released by these enzymes. This chapter describes enzyme reactions with mucin, detection by thin-layer chromatography of sialic acid, and quantification of 6-sulfated N-acetylglucosamine by liquid chromatography-tandem mass spectrometry.

Assessment of Mucin-Associated Gene Expression Levels on the Ocular Surface

The ocular surface is covered with a mucus layer. The mucin-associated genes expressed in the ocular surface cells include MUC1, MUC4, MUC5AC, and MUC16. Impression cytology is useful for collecting specimens from the ocular surface, their histological examination, and measuring mucin-associated gene expression levels. The expression of mucin-associated gene levels was assessed by quantitative polymerase chain reaction. The expression levels of these mucin-associated genes are potential biomarkers for ocular surface diseases, including dry eye disease.

Expression Analysis of Genes Corresponding to Mucins and Their Glycans from Cervical Tissue Using RNA Sequencing

In the female reproductive tract, mucin proteins are the main component of mucus secreted by cervical goblet cells and play an essential role in many biological functions. They act as a medium for lubrication and mainting a cervical mucosal barrier against ascending pathogens from the vagina while also allowing sperm migration. The expression of mucin genes as well as the levels of O-glycosylation changes across the oestrous cycle. Detection and characterization of mucins and their glycans is important to understand the interface between the external and the internal environment, as the cervical epithelium represents the first line of defense against infections of the upper reproductive tract. Advances in the field of molecular biology have made possible to study differences in mucin and glycan gene expression which can help to understand impeded sperm transport as well as variation in the susceptibility to infection. This chapter discusses procedures relevant for both animals and humans on how to recover cervical tissue and perform a gene expression analysis of genes corresponding to mucins and their glycans using RNA sequencing.

Quantitation of Mucin by Densitometry of an Alcian Blue-Stained Membrane

It is a challenging task to quantify mucin using conventional protein quantification methods due to the large number of glycans attached to the peptide, which make up approximately 50-90% of its molecular weight. To address this issue, we propose a simple quantification method that involves spotting mucins onto a membrane and staining them with Alcian blue.

Recombinant Production of Glycoengineered Mucins in HEK293-F Cells

Recombinant mucins are attractive polymeric building blocks for new biomaterials, biolubricants, and therapeutics. Advances in glycoengineered host cell systems now enable the recombinant production of mucins with tailored O-glycan side chains, offering new opportunities to tune the functionality of mucins and investigate the biology of specific O-glycan structures. Here, we provide a protocol for the scalable production of glycoengineered mucins and mucin-like glycoproteins in suspension-adapted HEK293-F cells. The protocol includes the preparation of engineered cell lines with homozygous knockout (KO) of glycosyltransferases using CRISPR/Cas9 and homology-directed repair (HDR) templates designed for efficient screening of clones. Strategies are provided for the stable introduction of mucin expression cassettes into the HEK293-F genome and the subsequent isolation of high-expressing cell populations. The high-titer production of recombinant mucins in conventional shaker flasks is described as an example production strategy using these cell lines.

Preparation of O-Glycans from Mucins Using Hydrazine Treatment

Mucin glycomic analysis is crucial owing to the participation of mucin O-glycans in several biological functions. Liquid chromatographic analysis of fluorescently labeled glycans is an effective tool for glycomic analysis. The first step of this analysis involves the release of O-glycans from mucins. As no enzyme is known to release all glycans, chemical methods are required for the process; therefore, hydrazine treatment is a commonly used chemical method. It enables the release of O-glycans from mucin while preserving the aldehyde group at the reducing end. This ensures that the reducing end can be modified using fluorescent reagents. However, it is also accompanied by the degradation of the glycans through a process called "peeling." Here, we describe a method for releasing glycans from mucins using hydrazine treatment with minimal "peeling."

Lixisenatide ameliorated lipopolysaccharide (LPS)-induced expression of mucin and inflammation in bronchial epithelial cells

Chronic obstructive pulmonary disease (COPD) induces serious social and economic burdens due to its high disability and mortality, the pathogenesis of which is highly involved with inflammation, oxidative stress (OS), and mechanism of mucin 5AC (MUC5AC) secretion. Lixisenatide is a selective glucagon-like peptide 1 receptor agonist recently reported to have anti-inflammatory properties. Our study will focus on the potential impact of lixisenatide on lipopolysaccharide (LPS)-induced mucin secretion and inflammation in 16 human bronchial epithelial (16HBE) cells to check its potential function in COPD. 16HBE cells were treated with LPS, with or without lixisenatide (10 and 20 nM) for 1 day. Remarkably declined cell viability, enhanced lactate dehydrogenase release, activated OS, and elevated release of inflammatory cytokines were observed in LPS-treated 16HBE cells, accompanied by the activation of nuclear factor-κB signaling, all of which were signally reversed by lixisenatide. Moreover, elevated expression and release of MUC5AC were observed in LPS-treated 16HBE cells but were markedly repressed by lixisenatide. Furthermore, the repressed nuclear factor erythroid 2-related factor 2 (Nrf2) level in LPS-treated 16HBE cells was notably rescued by lixisenatide. Lastly, following the knockdown of Nrf2, the protective function of lixisenatide on LPS-triggered MUC5AC release in 16HBE cells was significantly abrogated. Collectively, lixisenatide ameliorated LPS-induced expression of mucin and inflammation in bronchial epithelial cells by regulating Nrf2.

Analysis of the Interaction Between Mucin and Green Fluorescent Protein (GFP)-Tagged Galectin-2 Using a 96-Well Plate

Due to a significant proportion of glycans binding to the peptide (constituting approximately 50-90% of the molecular weight), analyzing the interaction between the entire mucin molecule and its recognition protein (lectin) can be challenging. To address this, we propose a semiquantitative approach for measuring the interaction between mucin and lectin, which involves immobilizing mucin in a 96-well plate and subsequently adding lectin tagged with green fluorescent protein.

Therapeutic effect of yinchenhao decoction on cholelithiasis via mucin in the gallbladder and intestine

Cholelithiasis is a common and frequently occurring disease worldwide that belongs to the category of jaundice in traditional Chinese medicine. Yinchenhao decoction (YD) consists of Artemisia capillaris Thunb., Gardenia jasminoides J.Ellis, and Rheum palmatum L., and is traditionally used to treat jaundice, which has a significant therapeutic effect on cholelithiasis. Our study aimed to investigate the pathological mechanism of cholelithiasis and the therapeutic mechanism of YD via mucin in the gallbladder and intestine. YD was prepared and analyzed using HPLC. The supersaturation stability experiment was designed by the solvent-shift method. The cell transport experiment was conducted by coculture monolayers. The animal experiment was performed using a cholelithiasis model with a high-cholesterol diet. The related indicators were detected by automatic biochemical analyzer, PCR, western blot, or ELISA. Statistics were analyzed using χ2-tests and t-tests. As the results, in cholelithiasis, MUC5AC highly expressed in the gallbladder shortened cholesterol supersaturation and promoted cholesterol crystallization via the inflammatory cytokine signaling pathway; MUC2 highly expressed in the small intestine prolonged cholesterol supersaturation and promoted cholesterol absorption via the inflammatory cytokine signaling pathway. YD inhibited mucin expression in the gallbladder and intestine in a concentration-dependent manner for cholelithiasis treatment by inhibiting the inflammatory cytokine signaling pathway, which was attributed to the active components, including chlorogenic acid, geniposide, and rhein.

Extraction of Mucin from Rodent Feces and Determination of O-Linked Oligosaccharide Chain Equivalent Derived from Fecal Mucin

Since the core protein of mucin in the digesta of the stomach and small intestine, which is less affected by bacteria, remains intact, mucin content can be measured by enzyme-linked immunosorbent assay (ELISA). However, the mucin core protein in bacteria-rich colon digesta and feces is partially hydrolyzed by bacterial enzymes and not fully recognized by mucin antibodies, so mucin cannot be accurately quantified by ELISA. This method quantifies the glycan content linked to the mucin core protein and expresses mucin content in the colon digesta and feces as the equivalent of O-linked oligosaccharide chain. Although mucin glycans are also hydrolyzed by colonic bacteria, this method is a more accurate and simple way to measure mucin content in the digesta of the large intestine and feces than the ELISA method.

Isolation of Membrane Bound Mucins from Human Bronchial Epithelial Cells

Membrane-bound mucins constitute a large portion of the periciliary layer of lung epithelial surfaces, and thus play an important role in many aspects of innate defense. The biophysical and biochemical properties of the membrane-bound mucins have important implications for mucociliary clearance, viral penetration, and potential therapeutics delivered to the airway surface. Hence, isolating them and determining these properties is important in understanding airways disease and ultimately in developing treatments. Here, we describe a method using isopycnic centrifugation to enrich and isolate shed membrane-bound mucins from the washings of human bronchial epithelial cell cultures.

In vivo dynamics of pro-inflammatory factors, mucins, and polymorph nuclear neutrophils in the bovine oviduct during the follicular and luteal phase

Dynamic functional changes in the oviductal microenvironment are the prerequisite for the establishment of pregnancy. The objective of this study was to gain the first insights into oestrous cycle-dependent dynamics of polymorph nuclear neutrophils (PMN) and the mRNA abundance of selected genes and their correlations in the oviduct of living cows. Mini-cytobrush samples were taken from the oviducts of healthy heifers (n = 6) and cows (n = 7) during the follicular (FOL) and luteal phase (LUT) by transvaginal endoscopy. Total RNA was isolated from the samples and subjected to reverse transcription-quantitative PCR for selected pro-inflammatory factors, glycoproteins, and a metabolic marker. The percentage of PMN was determined by cytological examination. The mean PMN percentage was 2.8-fold greater during LUT than FOL. During LUT, significantly greater mRNA abundance of the pro-inflammatory factors IL1B, CXCL1, CXCL3, and CXCL8 was observed. The OVGP1 mRNA abundance was twice as high during FOL than in LUT. Pearson correlation, principal component analysis and heatmap analyses indicated characteristic functional patterns with strong correlations among investigated factors. Using this novel approach, we illustrate complex physiological dynamics and interactions of the mRNA expression of pro-inflammatory factors, mucins, OVGP1, and PMN in the oviduct during the oestrous cycle.

Impact of structurally diverse polysaccharides on colonic mucin O-glycosylation and gut microbiota

Understanding how dietary polysaccharides affect mucin O-glycosylation and gut microbiota could provide various nutrition-based treatments. Here, the O-glycan profile of the colonic mucosa and gut microbiome were investigated in C57BL/6J mice fed six structurally diverse dietary polysaccharides and a mixture of six fibers. Dietary polysaccharides increased total O-glycans, mainly by stimulating neutral glycans. Highly branched arabinogalactan promoted terminally fucosylated core 1 O-glycans; whereas linear polysaccharides, including pectin, konjac glucomannan, inulin, and the fiber mixture, favored terminally di-fucosylated O-glycans. The last three polysaccharides also lowered the level of sulfated O-glycans and sialylated mono-fucosylated O-glycans. Varied monosaccharide composition in mixed polysaccharides had a synergistic beneficial effect, boosting fucosylated neutral glycans, decreasing acidic glycans, and stimulating microbial richness and diversity. Dietary polysaccharides containing arabinose and sulfate groups enhanced the relative abundances of Akkermansia and Muribaculaceae, respectively. The present comparison reveals the relationship between dietary polysaccharide structure, mucin O-glycan composition, and intestinal microorganisms.

Protective effect of alpha-ketoglutarate against water-immersion restraint stress-induced gastric mucosal damage in mice

Gastric lesions have several aetiologies, among which stress is the most prominent. Therefore, identification of new therapies to prevent stress is of considerable importance. Alpha-ketoglutarate (α-kg) several beneficial effects and has shown promise in combating oxidative stress, inflammation, and premature aging. Thus, this study aimed to evaluate the protective effect of α-kg in a gastric damage model by water-immersion restraint stress (WIRS). Pretreatment with α-kg decreased stress-related histopathological scores of tissue oedema, cell loss, and inflammatory infiltration. The α-kg restored the percentage of type III collagen fibres. Mucin levels were preserved as well as the structure and area of the myenteric plexus ganglia were preserved after pretreatment with α-kg. Myeloperoxidase (MPO) levels and the expression of pro-inflammatory cytokines (TNF-α and IL-1β) were also reduced following α-kg pretreatment. Decreased levels of glutathione (GSH) in the stress group were restored by α-kg. The omeprazole group was used as standard drug e also demonstrated improve on some parameters after the exposition to WIRS as inflammatory indexes, GSH and mucin. Through this, was possible to observe that α-kg can protect the gastric mucosa exposed to WIRS, preserve tissue architecture, reduce direct damage to the mucosa and inflammatory factors, stimulate the production of type III collagen and mucin, preserve the myenteric plexus ganglia, and maintain antioxidant potential. Due to, we indicate that α-kg has protective activity of the gastric mucosa, demonstrating its ability to prevent damage associated with gastric lesions caused by stress.

The yielding behaviour of human mucus

Mucus is a viscoelastic material with non-linear rheological properties such as a yield stress of the order of a few hundreds of millipascals to a few tens of pascals, due to a complex network of mucins in water along with non-mucin proteins, DNA and cell debris. In this review, we discuss the origin of the yield stress in human mucus, the changes in the rheology of mucus with the occurrence of diseases, and possible clinical applications in disease detection as well as cure. We delve into the domain of mucus rheology, examining both macro- and microrheology. Macrorheology involves investigations conducted at larger length scales (∼ a few hundreds of μm or higher) using traditional rheometers, which probe properties on a bulk scale. It is significant in elucidating various mucosal functions within the human body. This includes rejecting unwanted irritants out of lungs through mucociliary and cough clearance, protecting the stomach wall from the acidic environment as well as biological entities, safeguarding cervical canal from infections and providing a swimming medium for sperms. Additionally, we explore microrheology, which encompasses studies performed at length scales ranging from a few tens of nm to a μm. These microscale studies find various applications, including the context of drug delivery. Finally, we employ scaling analysis to elucidate a few examples in lung, cervical, and gastric mucus, including settling of irritants in lung mucus, yielding of lung mucus in cough clearance and cilial beating, spreading of exogenous surfactants over yielding mucus, swimming of Helicobacter pylori through gastric mucus, and lining of protective mucus in the stomach. The scaling analyses employed on the applications mentioned above provide us with a deeper understanding of the link between the rheology and the physiology of mucus.

GALNT2, an O-glycosylating enzyme, is a critical regulator of radioresistance of non-small cell lung cancer: evidence from an integrated multi-omics analysis

Radioresistance is the primary reason for radiotherapy failure in non-small cell lung cancer (NSCLC) patients. Glycosylation-related alterations are critically involved in tumor radioresistance. However, the relationship between glycosylation and NSCLC radioresistance is unclear. Here, we generated radioresistant NSCLC cell models by using fractionated irradiation. The aberrant glycosylation involved in NSCLC-related radioresistance was elucidated by transcriptomic, proteomic, and glycomic analyses. We conducted in vitro and in vivo investigations for determining the biological functions of glycosylation. Additionally, its downstream pathways and upstream regulators were inferred and verified. We demonstrated that mucin-type O-glycosylation and the O-glycosylating enzyme GALNT2 were highly expressed in radioresistant NSCLC cells. GALNT2 was found to be elevated in NSCLC tissues; this elevated level showed a remarkable association with response to radiotherapy treatment as well as overall survival. Functional experiments showed that GALNT2 knockdown improved NSCLC radiosensitivity via inducing apoptosis. By using a lectin pull-down system, we revealed that mucin-type O-glycans on IGF1R were modified by GALNT2 and that IGF1R could affect the expression of apoptosis-related genes. Moreover, GALNT2 knockdown-mediated in vitro radiosensitization was enhanced by IGF1R inhibition. According to a miRNA array analysis and a luciferase reporter assay, miR-30a-5p negatively modulated GALNT2. In summary, our findings established GALNT2 as a key contributor to the radioresistance of NSCLC. Therefore, targeting GALNT2 may be a promising therapeutic strategy for NSCLC.

Effect of epithelial-specific MyD88 signaling pathway on airway inflammatory response to organic dust exposure

The Toll-like receptor (TLR) adaptor protein MyD88 is integral to airway inflammatory response to microbial-enriched organic dust extract (ODE) exposures. ODE-induced airway neutrophil influx and release of pro-inflammatory cytokines was essentially abrogated in global MyD88-deficient mice, yet these mice demonstrate an increase in airway epithelial cell mucin expression. To further elucidate the role of MyD88-dependent responses specific to lung airway epithelial cells in response to ODE in vivo, the surfactant protein C protein (SPC) Cre+ embryologic expressing airway epithelial cells floxed for MyD88 to disrupt MyD88 signaling were utilized. The inducible club cell secretory protein (CCSP) Cre+, MyD88 floxed, were also developed. Using an established protocol, mice were intranasally instilled with ODE or saline once or daily up to 3 weeks. Mice with MyD88-deficient SPC+ lung epithelial cells exhibited decreased neutrophil influx following ODE exposure once and repetitively for 1 week without modulation of classic pro-inflammatory mediators including tumor necrosis factor (TNF)-α, interleukin (IL)-6, and neutrophil chemoattractants. This protective response was lost after 3 weeks of repetitive exposure. ODE-induced Muc5ac mucin expression at 1 week was also reduced in MyD88-deficient SPC+ cells. Acute ODE-induced IL-33 was reduced in MyD88-deficient SPC+ cells whereas serum IgE levels were increased at one week. In contrast, mice with inducible MyD88-deficient CCSP+ airway epithelial cells demonstrated no significant difference in experimental indices following ODE exposure. Collectively, these findings suggest that MyD88-dependent signaling targeted to all airway epithelial cells plays an important role in mediating neutrophil influx and mucin production in response to acute organic dust exposures.

[Improvement effect of Shegan Mahuang Decoction on rats with cold-induced asthma based on TRPV1/NRF-1/mtTFA pathway]

This study investigated the therapeutic effect of Shegan Mahuang Decoction(SGMHD) on cold-induced asthma in rats and explored its underlying mechanism. Seventy-two healthy male SD rats of specific pathogen free(SPF) grade were randomly divided into a blank group, a model group, a positive control group(dexamethasone, 0.4 mg·kg~(-1)), and low-, medium-, and high-dose SGMHD groups(3.2, 6.4, and 12.8 g·kg~(-1)). The blank group received saline, while the other groups were sensitized by intraperitoneal injection of ovalbumin(OVA) solution. Subsequently, the rats were placed in a cold chamber adjustable to 0-2 ℃, and OVA solution was ultrasonically nebulized to induce cold-induced asthma in rats. After three weeks of treatment, the general behaviors of rats were observed. Hematoxylin-eosin(HE) staining was used to evaluate pathological changes in lung tissues, periodic acid-Schiff(PAS) staining assessed mucin changes, and Masson staining was performed to examine collagen deposition. Enzyme-linked immunosorbent assay(ELISA) was used to measure the levels of the inflammatory factors interleukin-4(IL-4) and vascular endothelial growth factor(VEGF) in serum and bronchoalveolar lavage fluid(BALF). Real-time quantitative polymerase chain reaction(RT-PCR) was employed to assess the mRNA expression levels of transient receptor potential vanilloid subfamily member 1(TRPV1), nuclear respiratory factor 1(NRF-1), and mitochondrial transcription factor A(mtTFA) in lung tissues. Western blot was used to measure the protein expression levels of TRPV1, NRF-1, and mtTFA in lung tissues. Compared with the blank group, the model group exhibited signs of rapid respiration, increased frequency of defecation with looser stools, and disheveled and dull fur. Pathological results showed significant infiltration of inflammatory cells in lung tissues, narrowing of bronchial lumens, increased mucin secretion, and enhanced collagen deposition in the model group. Additionally, the levels of IL-4 and VEGF in serum and BALF were significantly elevated, and the mRNA and protein expression levels of TRPV1, NRF-1, and mtTFA in lung tissues were significantly increased. Compared with the model group, SGMHD improved the behaviors of rats, alleviated pathological changes in lung tissues, mucin production, and collagen deposition, significantly decreased the levels of IL-4 and VEGF in serum and BALF, and reduced the mRNA expression levels of TRPV1, NRF-1, and mtTFA in lung tissues, with the medium-dose SGMHD group showing the most significant effect. Moreover, the protein expression levels of TRPV1, NRF-1, and mtTFA in lung tissues were also reduced, with the medium-dose SGMHD group exhibiting the most significant effect. In conclusion, this study demonstrates that SGMHD can alleviate airway inflammation and inhibit airway remodeling in cold-induced asthma rats. These effects may be associated with the modulation of the TRPV1/NRF-1/mtTFA signaling pathway.

Intestinal changes in permeability, tight junction and mucin synthesis in a mouse model of Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the accumulation of amyloid‑β (Aβ) in the brain. The gut/brain axis may serve a role in AD pathogenesis. The present study investigated deposition of Aβ in the intestinal epithelium and its potential effects on intestinal barrier function in a transgenic mouse model of AD. To investigate alterations in the structure and functionality of the intestinal mucosal barrier in AD model mice, hematoxylin and eosin staining for Paneth cell count, Alcian blue‑periodic acid Schiff staining for goblet cells, immunohistochemistry and immunofluorescence for mucin (MUC)2 and wheat germ agglutin expression, transmission electron microscopy for mucosal ultrastructure, FITC‑labeled dextran assay for intestinal permeability, quantitative PCR for goblet cell precursor expression and western blot analysis for tight junction proteins, MUC2 and inflammatory cytokine detection were performed. The results showed that AD model mice exhibited excessive Aβ deposition in the intestinal epithelium, which was accompanied by increased intestinal permeability, inflammatory changes and decreased expression of tight junction proteins. These alterations in the intestinal barrier led to an increased proliferation of goblet and Paneth cells and increased mucus synthesis. Dysfunction of gut barrier occurs in AD and may contribute to its etiology. Future therapeutic strategies to reverse AD pathology may involve early manipulation of gut physiology and its microbiota.

The SIRT3 activator ganoderic acid D regulates airway mucin MUC5AC expression via the NRF2/GPX4 pathway

PURPOSE

The expression of MUC5AC, a highly prevalent airway mucin, is regulated by stimulatory factors such as oxidative stress. Ganoderic acid D (GAD) activates mitochondrial deacetylase SIRT3. SIRT3 regulates mitochondrial function through deacetylation of mitochondrial proteins, thereby playing a significant role in alleviating oxidative stress-related diseases. Therefore, this study aimed to investigate the mechanisms and rationale underlying the regulation of MUC5AC expression by GAD.

METHODS

Human airway epithelial cells (NCI-H292) were exposed to pyocyanin (PCN) to establish an in vitro cell model of airway mucus hypersecretion. The expression of SIRT3, MUC5AC, and NRF2 pathway proteins in cells was assessed. Cellular mitochondrial morphology and oxidative stress markers were analyzed. C57BL/6 mice were induced with Pseudomonas aeruginosa (PA) to establish an in vivo mouse model of airway mucus hypersecretion. The expression of SIRT3 and MUC5AC in the airways was examined. In addition, the differential expression of target genes in the airway epithelial tissues of patients with chronic obstructive pulmonary disease (COPD) was analyzed using publicly available databases.

RESULTS

The results revealed a significant upregulation of MUC5AC expression and a significant downregulation of SIRT3 expression in relation to airway mucus hypersecretion. GAD inhibited the overexpression of MUC5AC in PCN-induced NCI-H292 cells and PA-induced mouse airways by upregulating SIRT3. GAD activated the NRF2/GPX4 pathway and inhibited PCN-induced oxidative stress and mitochondrial morphological changes in NCI-H292 cells. However, ML385 inhibited the regulatory effects of GAD on MUC5AC expression.

CONCLUSION

The SIRT3 activator GAD downregulated MUC5AC expression, potentially through activation of the NRF2/GPX4 pathway. Accordingly, GAD may be a potential treatment approach for airway mucus hypersecretions.

Estradiol mediates colonic epithelial protection in aged mice after stroke and is associated with shifts in the gut microbiome

The gut is a major source of bacteria and antigens that contribute to neuroinflammation after brain injury. Colonic epithelial cells (ECs) are responsible for secreting major cellular components of the innate defense system, including antimicrobial proteins (AMP) and mucins. These cells serve as a critical regulator of gut barrier function and maintain host-microbe homeostasis. In this study, we determined post-stroke host defense responses at the colonic epithelial surface in mice. We then tested if the enhancement of these epithelial protective mechanisms is beneficial in young and aged mice after stroke. AMPs were significantly increased in the colonic ECs of young males, but not in young females after experimental stroke. In contrast, mucin-related genes were enhanced in young females and contributed to mucus formation that maintains the distance between the host and gut bacteria. Bacterial community profiling was done using universal amplification of 16S rRNA gene sequences. The sex-specific colonic epithelial defense responses after stroke in young females were reversed with ovariectomy and led to a shift from a predominately mucin response to the enhanced AMP expression seen in males after stroke. Estradiol (E2) replacement prior to stroke in aged females increased mucin gene expression in the colonic ECs. Interestingly, we found that E2 treatment reduced stroke-associated neuronal hyperactivity in the insular cortex, a brain region that interacts with visceral organs such as the gut, in parallel to an increase in the composition of Lactobacillus and Bifidobacterium in the gut microbiota. This is the first study demonstrating sex differences in host defense mechanisms in the gut after brain injury.

Effects and Mechanisms of Resveratrol on the Adhesion of Lactobacillus acidophilus NCFM

Based on the adhesion and surface properties of Lactobacillus acidophilus NCFM, five common polyphenols in fruits and vegetables, including resveratrol, epicatechin, quercetin, hesperidin, and caffeic acid, were screened, and the reasons for resveratrol promoting adhesion were systematically explained. The results showed that resveratrol could significantly enhance NCFM adhesion to mucin (1.73 fold), followed by epicatechin (1.47 fold), caffeic acid (1.30 fold), and hesperidin (0.99 fold), while quercetin had a certain degree of inhibition (0.84 fold). The effects of these polyphenols on surface hydrophobicity and auto-aggregation of NCFM were consistent with adhesion results. Then, how resveratrol promotes NCFM adhesion was further explored. The results of the proteomic analysis showed that resveratrol changed the surface layer proteins of NCFM, involving 4 up-regulated proteins and 12 down-regulated proteins. In addition, resveratrol promoted the expression of mucin genes and the glycosylation of mucins on the HT-29 cell surface. Our results indicate that resveratrol changes the surface layer proteins of NCFM to modify surface properties and adhere to mucins. Meanwhile, resveratrol promotes expression and glycosylation of mucins in HT-29 cells. Our findings provide theoretical support for an in-depth explanation of the interaction among resveratrol, NCFM, and the HT-29 cells.

MUC13 drives cancer aggressiveness and metastasis through the YAP1-dependent pathway

Anchorage-independent survival after intravasation of cancer cells from the primary tumor site represents a critical step in metastasis. Here, we reveal new insights into how MUC13-mediated anoikis resistance, coupled with survival of colorectal tumor cells, leads to distant metastasis. We found that MUC13 targets a potent transcriptional coactivator, YAP1, and drives its nuclear translocation via forming a novel survival complex, which in turn augments the levels of pro-survival and metastasis-associated genes. High expression of MUC13 is correlated well with extensive macrometastasis of colon cancer cells with elevated nuclear YAP1 in physiologically relevant whole animal model systems. Interestingly, a positive correlation of MUC13 and YAP1 expression was observed in human colorectal cancer tissues. In brief, the results presented here broaden the significance of MCU13 in cancer metastasis via targeting YAP1 for the first time and provide new avenues for developing novel strategies for targeting cancer metastasis.

Rhubarb extract rebuilding the mucus homeostasis and regulating mucin-associated flora to relieve constipation

In clinical trials, rhubarb extract (Rb) was demonstrated to efficiently alleviate constipation. We would like to find out the underlying mechanism of rhubarb relieving constipation. However, there are few studies on the effects of rhubarb on colonic mucus secretion and constipation. The aim of this study was to investigate the effects of rhubarb on colonic mucus secretion and its underlying mechanism. The mice were randomly divided into four groups. Group I was the control group and Group II was the rhubarb control group, with Rb (24 g/kg body weight [b.w.]) administered through intragastric administration for three days. Group III mice were given diphenoxylate (20 mg/kg b.w.) for five days via gavage to induce constipation. Group IV received diphenoxylate lasting five days before undergoing Rb administration for three days. The condition of the colon was evaluated using an endoscope. Particularly, the diameter of blood vessels in the colonic mucosa expanded considerably in constipation mice along with diminishing mucus output, which was in line with the observation via scanning electron microscope (SEM) and transmission electron microscope (TEM). We also performed metagenomic analysis to reveal the microbiome related to mucin gene expression level referring to mucin secretion. In conclusion, Rb relieves constipation by rebuilding mucus homeostasis and regulating the microbiome.

Association between neuropeptides and mucins in Crohn's disease mucous cells

Crohn's disease (CD) and ulcerative colitis (UC) are both inflammatory bowel diseases (IBD). Unlike UC, which is limited to the mucosa of the colon, CD inflammation is characterized by chronic mucosal ulcerations affecting the entire gastrointestinal tract. Goblet cells (GCs) can be found in some lining epithelia, particularly in the respiratory and digestive tracts. GCs represent the main source of mucin that are the significant components of the mucus layer; hypertrophy of GCs and an increase in mucin production are observed in many enteric infections. The cytoplasm of goblet cells may also contain neuropeptides, such as serotonin, that can be altered in inflammatory bowel disease (IBD). The defense system of the gut is represented by the intestinal mucosal barrier, its protective function is strictly connected to the regulation of the mucus layer and the coordination of the neuro-immune response. Paraformaldehyde-fixed intestinal tissues, obtained from fifteen patients with Crohn's disease, were analyzed by immunostaining for MUC2, MUC4, 5-HT, and VAChT. This study aims to define the link between neuropeptides and mucins in mucous cells and their involvement in the inflammation process. Our results showed in mucous cells of Crohn's disease (CD) patients a high expression of MUC4 and a decrease in the expression of vesicular acetylcholine transporter (VAChT) demonstrating the presence of an inflammatory state.