A head-to-head comparison of polymer interaction with mucin from porcine stomach and bovine submaxillary glands.

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.

Exploring strain-level diversity in the gut microbiome through mucin particle adhesion.

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. IMPORTANCE: Metabolism of mucin glycans by gut bacteria represents a crucial strategy for accessing nutrient reservoirs. The efficacy of mucin glycan utilization among gut bacteria hinges on the metabolic capabilities of individual strains, necessitating meticulous strain-level characterization. In this investigation, we used glass beads chemically immobilized with mucins to selectively enrich bacteria from fecal fermentation cultures, based on their superior adhesion to and metabolism of mucin glycoproteins. These findings lend support to the hypothesis that the physical interactions between bacteria and mucin glycoprotein components directly correlate with their capacity to utilize mucins as nutrient sources. Furthermore, our study implies that physical proximity may significantly influence bacterial nutrient acquisition within the ecosystem, facilitating gut bacteria's access to carbohydrate components.

The role of gastric mucins and mucin-related glycans in gastric cancers.

Gastric mucins serve as a protective barrier on the stomach's surface, protecting from external stimuli including gastric acid and gut microbiota. Their composition typically changes in response to the metaplastic sequence triggered by Helicobacter pylori infection. This alteration in gastric mucins is also observed in cases of gastric cancer, although the precise connection between mucin expressions and gastric carcinogenesis remains uncertain. This review first introduces the relationship between mucin expressions and gastric metaplasia or cancer observed in humans and mice. Additionally, we discuss potential pathogenic mechanisms of how aberrant mucins and their glycans affect gastric carcinogenesis. Finally, we summarize challenges to target tumor-specific glycans by utilizing lectin-drug conjugates that can bind to specific glycans. Understanding the correlation and mechanism between these mucin expressions and gastric carcinogenesis could pave the way for new strategies in gastric cancer treatment.

Structural and tribological studies on the interaction of porcine gastric mucin with non- and cationic-modified ß-lactoglobulins.

ß-lactoglobulin (BLG) is the major whey protein with negative charges at neutral pH in aqueous media. Thus, the interaction with mucins, the major polyanionic component of mucus, is very weak due to the electrostatic repulsion between them. The present study postulates that cationization of BLG molecules may reverse the interaction characteristics between BLG and mucin from repulsive to associative. To this end, cationic-modified BLGs were prepared by grafting positively charged ethylenediamine (EDA) moieties into the negatively charged carboxyl groups on the aspartic and glutamic acid residues and compared with non-modified BLG upon mixing with porcine gastric mucin (PGM). To characterize the structural and conformational features of PGM, non/cationized BLGs, and their mixtures, various spectroscopic approaches, including zeta potential, dynamic light scattering (DLS), and circular dichroism (CD) spectroscopy were employed. Importantly, we have taken surface adsorption with optical waveguide lightmode spectroscopy (OWLS), and tribological properties with pin-on-disk tribometry at the sliding interface as the key approaches to determine the interaction nature between them as mixing PGM with polycations can lead to synergistic lubrication at the nonpolar substrate in neutral aqueous media as a result of an electrostatic association. All the spectroscopic studies and a substantial improvement in lubricity collectively supported a tenacious and associative interaction between PGM and cationized BLGs, but not between PGM and non-modified BLG. This study demonstrates a unique and successful approach to intensify the interaction between BLG and mucins, which is meaningful for a broad range of disciplines, including food science, macromolecular interactions, and biolubrication etc.

Impaired Glycosylation of Gastric Mucins Drives Gastric Tumorigenesis and Serves as a Novel Therapeutic Target.

BACKGROUND & AIMS: Gastric cancer is often accompanied by a loss of mucin 6 (MUC6), but its pathogenic role in gastric carcinogenesis remains unclear. METHODS: Muc6 knockout (Muc6-/-) mice and Muc6-dsRED mice were newly generated. Tff1Cre, Golph3-/-, R26-Golgi-mCherry, Hes1flox/flox, Cosmcflox/flox, and A4gnt-/- mice were also used. Histology, DNA and RNA, proteins, and sugar chains were analyzed by whole-exon DNA sequence, RNA sequence, immunohistochemistry, lectin-binding assays, and liquid chromatography-mass spectrometry analysis. Gastric organoids and cell lines were used for in vitro assays and xenograft experiments. RESULTS: Deletion of Muc6 in mice spontaneously causes pan-gastritis and invasive gastric cancers. Muc6-deficient tumor growth was dependent on mitogen-activated protein kinase activation, mediated by Golgi stress-induced up-regulation of Golgi phosphoprotein 3. Glycomic profiling revealed aberrant expression of mannose-rich N-linked glycans in gastric tumors, detected with banana lectin in association with lack of MUC6 expression. We identified a precursor of clusterin as a binding partner of mannose glycans. Mitogen-activated protein kinase activation, Golgi stress responses, and aberrant mannose expression are found in separate Cosmc- and A4gnt-deficient mouse models that lack normal O-glycosylation. Banana lectin-drug conjugates proved an effective treatment for mannose-rich murine and human gastric cancer. CONCLUSIONS: We propose that Golgi stress responses and aberrant glycans are important drivers of and promising new therapeutic targets for gastric cancer.

Kinesin Family Member B18 Is Related to Gastric Mucin Phenotype and Contributes to Gastric Cancer Progression by Regulating Epithelial-Mesenchymal Transition.

INTRODUCTION: Gastric cancer (GC) remains a common health concern worldwide and is the third leading cause of death in Japan. It can be broadly classified into gastric and intestinal mucin phenotypes using immunohistochemistry. We previously reported numerous associations of kinesin family member (KIF) genes and mucin phenotypes with GC. However, no previous studies have reported on the importance of KIF18B in GC using immunostaining. Thus, in this study, we investigated the expression and functions of KIF18B, which is highly expressed in gastric mucin phenotype GC. METHODS: We performed RNA-seq of gastric and intestinal mucin type GCs, and clinicopathological studies of the KIF18B we found were performed using 96 GC cases. We also performed functional analysis using GC-derived cell lines. RESULT: RNA-seq showed the upregulation of matrisome-associated genes in gastric mucin phenotype GC and a high expression of KIF18B. KIF18B was detected in 52 of the 96 GC cases (54%) through immunohistochemistry. Low KIF18B expression was significantly associated with poor overall survival (p < 0.01). Other molecules that were significantly associated with KIF18B were MUC5AC and claudin 18; these were also significantly associated with the gastric mucin phenotype. KIF18B small interfering RNA (siRNA)-transfected GC cells showed greater growth and spheroid colony formation than the negative control siRNA-transfected cells. Furthermore, expression of snail family transcriptional repressor 1 and cadherin 2 was significantly increased and that of cadherin 1 was significantly decreased in KIF18B siRNA-transfected GC cells. CONCLUSION: These findings not only suggest that KIF18B may be a useful prognostic marker, but also provide insight into the pathogenesis of the GC phenotype.

A Complex Connection Between the Diversity of Human Gastric Mucin O-Glycans, Helicobacter pylori Binding, Helicobacter Infection and Fucosylation.

Helicobacter pylori colonizes the stomach of half of the human population. Most H. pylori are located in the mucus layer, which is mainly comprised by glycosylated mucins. Using mass spectrometry, we identified 631 glycans (whereof 145 were fully characterized and the remainder assigned as compositions) on mucins isolated from 14 Helicobacter spp.-infected and 14 Helicobacter spp.-noninfected stomachs. Only six identified glycans were common to all individuals, from a total of 60 to 189 glycans in each individual. An increased number of unique glycan structures together with an increased intraindividual diversity and larger interindividual variation were identified among O-glycans from Helicobacter spp.-infected stomachs compared with noninfected stomachs. H. pylori strain J99, which carries the blood group antigen-binding adhesin (BabA), the sialic acid-binding adhesin (SabA), and the LacdiNAc-binding adhesin, bound both to Lewis b (Leb)-positive and Leb-negative mucins. Among Leb-positive mucins, H. pylori J99 binding was higher to mucins from Helicobacter spp.-infected individuals than noninfected individuals. Statistical correlation analysis, binding experiments with J99 wt, and J99ΔbabAΔsabA and inhibition experiments using synthetic glycoconjugates demonstrated that the differences in H. pylori-binding ability among these four groups were governed by BabA-dependent binding to fucosylated structures. LacdiNAc levels were lower in mucins that bound to J99 lacking BabA and SabA than in mucins that did not, suggesting that LacdiNAc did not significantly contribute to the binding. We identified 24 O-glycans from Leb-negative mucins that correlated well with H. pylori binding whereof 23 contained α1,2-linked fucosylation. The large and diverse gastric glycan library identified, including structures that correlated with H. pylori binding, could be used to select glycodeterminants to experimentally investigate further for their importance in host-pathogen interactions and as candidates to develop glycan-based therapies.

α1,4-Linked N-acetylglucosamine suppresses gastric cancer development by inhibiting Mucin-1-mediated signaling.

Gastric cancer is the second leading cause of cancer deaths worldwide, and more understanding of its molecular basis is urgently needed. Gastric gland mucin secreted from pyloric gland cells, mucous neck cells, and cardiac gland cells of the gastric mucosa harbors unique O-glycans carrying terminal α1,4-linked N-acetylglucosamine (αGlcNAc) residues. We previously reported that αGlcNAc loss correlated positively with poor outcomes for patients with differentiated-type gastric cancer. However, the molecular mechanisms underlying these outcomes remained poorly understood. Here, we examined the effects of upregulated αGlcNAc expression on malignant phenotypes of the differentiated-type gastric cancer cell lines, AGS and MKN7. Upregulation of αGlcNAc following ectopic expression of its biosynthetic enzyme attenuated cell proliferation, motility, and invasiveness of AGS and MKN7 cells in vitro. Moreover, AGS cell tumorigenicity was significantly suppressed by αGlcNAc overexpression in a xenograft model. To define the molecular mechanisms underlying these phenotypes, we investigated αGlcNAc binding proteins in AGS cells and identified Mucin-1 (MUC1) and podocalyxin. Both proteins were colocalized with αGlcNAc on human gastric cancer cells. We also found that αGlcNAc was bound to MUC1 in murine normal gastric mucosa. When we assessed the effects of αGlcNAc binding to MUC1, we found that αGlcNAc blocked galectin-3 binding to MUC1, phosphorylation of the MUC1 C-terminus, and recruitment of Src and ß-catenin to that C-terminus. These results suggest that αGlcNAc regulates cancer cell phenotypes by dampening MUC1 signal transduction.

MUC6 expression is a preferable prognostic marker for invasive mucinous adenocarcinoma of the lung.

Gastric gland mucin consists of core protein MUC6 with residues heavily glycosylated by unique O-glycans carrying α1,4-linked N-acetylglucosamine (αGlcNAc). αGlcNAc-glycosylated MUC6 protein is seen in normal gastric and duodenal glands. Decreased αGlcNAc glycosylation on MUC6-positive tumor cells is often observed in premalignant lesions of the stomach, pancreas, and bile duct, and decreased MUC6 expression is seen in invasive cancer of these organs. Lung cancer (LC) is the most common cause of cancer death worldwide. Recently, the adenocarcinoma subtype has become the most common histological subtype of LC, and one of its invasive forms is invasive mucinous adenocarcinoma (IMA). Currently, prognostic markers of LC IMA are unknown. Here, we analyzed MUC5AC, MUC6, and αGlcNAc expression in 54 IMA LC cases. MUC5AC was positively expressed in 50 (93%), MUC6 in 38 (70%), and αGlcNAc in 19 (35%). Each expression level was scored from 0 to 3. The αGlcNAc expression score was significantly decreased relative to MUC6 (P < 0.001). Interestingly, disease-free survival was significantly higher in MUC6-positive than MUC6-negative cases based on the log-rank test (P = 0.021). For in vitro analysis, we ectopically expressed MUC6 in A549 cells, derived from LC and harboring a KRAS mutation. MUC6-expressing A549 cells showed significantly lower proliferation, motility, and invasiveness than control cells. Finally, F-actin staining in MUC6-expressing cells revealed a decrease or loss of filopodia associated with decreased levels of FSCN transcripts, which encodes an actin-bundling protein fascin1 necessary for cell migration. We conclude that MUC6 expression is a preferable prognostic biomarker in IMA LC.

Interactions of ß-Lactoglobulin with Bovine Submaxillary Mucin vs. Porcine Gastric Mucin: The Role of Hydrophobic and Hydrophilic Residues as Studied by Fluorescence Spectroscopy.

The aim of this study was to investigate binding interactions between ß-lactoglobulin (BLG) and two different mucins, bovine submaxillary mucins (BSM) and porcine gastric mucin (PGM), using intrinsic and extrinsic fluorescence spectroscopies. Intrinsic fluorescence spectra showed an enhanced decrease of fluorescence intensity of BLG at all pH conditions when BLG was mixed with PGM rather than with BSM. We propose that, unlike BSM, the tertiary structure of PGM changes and the hydrophobic regions are exposed at pH 3 due to protonation of negatively charged residues. Results suggest that PGM also facilitated the structural unfolding of BLG and its binding with PGM by a hydrophobic interaction, especially at acidic pH, which was further supported by extrinsic fluorescence spectroscopy. Hydrophobic interaction is suggested as the dominant interaction mechanism between BLG and PGM at pH 3, whereas electrostatic interaction is the dominant one between BLG and BSM.

A survival comparison of gastric mucin-producing adenocarcinoma to conventional adenocarcinoma: a SEER database analysis.

BACKGROUND: Compared to conventional adenocarcinoma (CA), mucin-producing adenocarcinoma (MPA) is an uncommon histological subtype and is usually separated from other histological types and has been evaluated separately. The objective was to compare the clinicopathological characteristics and survivals of MPA with CA. METHODS: We retrospectively analyzed 1515 MPA patients in SEER database. Log-rank tests and KM survival curves were applied to determine the differences in overall survival (OS) and cancer specific survival (CSS) time. RESULTS: No significant differences were noted in OS and CSS time. The MPA patients who were treated with surgery and chemotherapy exhibited longer OS and CSS time periods than those without treatment. MPA patients treated with radiotherapy exhibited similar OS and CSS time with those without radiotherapy. MPA was not a prognostic factor of survival. CONCLUSIONS: MPA was a rare histological type of gastric cancer. Patients with MPA exhibited similar prognosis with those with CA. Surgery and chemotherapy were effective treatments for patients with MPA.

Gastric mucin phenotype indicates aggressive biological behaviour in early differentiated gastric adenocarcinomas following endoscopic treatment.

BACKGROUND: The distribution of mucin phenotypes and their relationship with clinicopathological features in early differentiated gastric adenocarcinomas in a Chinese cohort are unknown. We aimed to investigate mucin phenotypes and analyse the relationship between mucin phenotypes and clinicopathological features, especially biological behaviours, in early differentiated gastric adenocarcinomas from endoscopic specimens in a Chinese cohort. METHODS: Immunohistochemical staining of CD10, MUC2, MUC5AC, and MUC6 was performed in 257 tissue samples from patients with early differentiated gastric adenocarcinomas. The tumour location, gross type, tumour size, histological type, depth of invasion, lymphovascular invasion, mucosal background and other clinicopathological parameters were evaluated. The relationship between mucin phenotypes and clinicopathological features was analysed with the chi-square test. RESULTS: The incidences of gastric, gastrointestinal, intestinal and null phenotypes were 21 %, 56 %, 20 and 3 %, respectively. The mucin phenotypes were related to histology classification (P < 0.05). The proportion of the gastric phenotype became greater during the transition from differentiated to undifferentiated (P < 0.05). Complete intestinal metaplasia was higher in the gastric and intestinal phenotypes than in the gastrointestinal phenotype (P < 0.05). Tumours with poorly differentiated adenocarcinoma were mainly of the gastric phenotype, which was significantly higher than that of purely differentiated tubular adenocarcinoma (P < 0.05), and the depth of invasion in the mixed type was deeper (P < 0.05). Neither recurrence nor metastasis was detected. CONCLUSIONS: The mucin phenotype of early-differentiated gastric adenocarcinoma has clinical implications, and the gastric phenotype has aggressive biological behaviour in early differentiated gastric cancers, especially in those with poorly differentiated adenocarcinoma or papillary adenocarcinoma components.

Taxifolin and gastro-adhesive microparticles containing taxifolin promotes gastric healing in vivo, inhibits Helicobacter pylori in vitro and proton pump reversibly in silico.

Taxifolin (3,5,7,3,4-pentahydroxy flavanone or dihydroquercetin, Tax) was identified as a gastroprotective compound and a gastroadhesive formulation was recently developed to prolong its residence time and release in the stomach. So, the gastric healing effectiveness of Tax and gastro-mucoadhesive microparticles containing Tax (MPTax) against the acetic acid induced-gastric ulcer in rats was investigated in this study. Moreover, the interactions between Tax and H+/K+-ATPase were investigated in silico, and its anti- H. pylori activity was determined in vitro. The oral treatment with MPTax (81.37 mg/kg, containing 12.29% of Tax) twice a day for seven days reduced the ulcer area by 63%, compared to vehicle-treated group (Veh: 91.9 ± 10.3 mm2). Tax (10 mg/kg, p.o) reduced the ulcer by 40% but with a p = 0.07 versus Veh group. Histological analysis confirmed these effects. Tax and MPTax increased the gastric mucin amount, reduced the myeloperoxidase activity, and increased the glutathione reduced content at ulcer site. However, only MPTax decreased the lipoperoxide accumulation at ulcer site. Besides, Tax and MPTax normalize the catalase and glutathione S-transferase activity. Tax showed reversible interaction with H+/K+-ATPase in silico and its anti-H. pylori effects was confirmed (MIC = 625 µg/mL). These results suggest that the antiulcer property of Tax involves the strengthening of the gastric protective factors in parallel to its inhibitory interaction with H+/K+-ATPase and H. pylori. Considering that ulcer healing action displayed by Tax was favored by gastroadhesive microparticles, this approach seems to be promising for its oral delivery to treat acid-peptic diseases.

The gastroprotective effect of red propolis extract from Northeastern Brazil and the role of its isolated compounds.

ETHNOPHARMACOLOGICAL RELEVANCE: Propolis has been used in folk medicine to treat gastric disorders for centuries. However, although studies have been conducted to validate the gastroprotective and anti-ulcer activity of some types of propolis, red propolis activity remains unknown. AIM OF THE STUDY: The present study aimed to evaluate the gastroprotective effect of the hydroalcoholic extract of red propolis (HERP), its mode of action, and the main compounds involved in its activity, therefore contributing to validate the chemical and pharmacological potential of this product. MATERIAL AND METHODS: The effect of HERP (30, 100 and 300 mg/kg p.o. and 30 mg/kg i.p.), and the isolated compounds vestitol (VS), neovestitol (NV), methylvestitol (MV), medicarpin (MD), and oblongifolin AB (OB) (10 mg/kg p.o.) were evaluated on gastric ulcers induced by 60% ethanol/0.3 M HCl (5 mL/kg, p.o.) in mice. Histological changes and mucin levels were assessed by HE and PAS, respectively. Moreover, oxidative stress parameters and myeloperoxidase activity were analyzed on ulcerated tissue. The effect of HERP on gastric acid secretion was evaluated by pyloric ligature model and the mechanisms involved in its gastroprotective effect were investigated by pretreating mice with L-NAME (a non-selective nitric oxide synthase inhibitor, 70 mg/kg, i.p.), NEM (a sulfhydryl group chelator, 10 mg/kg, i.p.), yohimbine (an alpha-adrenergic receptor antagonist, 2 mg/kg, i.p.) and indomethacin (a non-selective cyclooxygenase inhibitor, 10 mg/kg, i.p.). RESULTS: HERP (300 mg/kg p.o. or 30 mg/kg i.p.), MV, and MD (10 mg/kg p.o.) protected gastric mucosa against the damage induced by ethanol/HCl. Histological changes were attenuated by the HERP, MV, and MD. Moreover, HERP and MV increased mucin levels. Besides, oxidative stress and MPO activity were reduced by the three treatments. HERP did not display anti-secretory action, but its effect was abolished by indomethacin treatment. CONCLUSIONS: HERP displays gastroprotective property against ethanol/HCl-induced damage. Its effect is dependent on prostaglandins and mucin production. The compounds MV and MD may have an essential role in the activity of HERP. Our data contribute to validate the traditional use of propolis for gastric disorders.

Rational design of a microbial consortium of mucosal sugar utilizers reduces Clostridiodes difficile colonization.

Many intestinal pathogens, including Clostridioides difficile, use mucus-derived sugars as crucial nutrients in the gut. Commensals that compete with pathogens for such nutrients are therefore ecological gatekeepers in healthy guts, and are attractive candidates for therapeutic interventions. Nevertheless, there is a poor understanding of which commensals use mucin-derived sugars in situ as well as their potential to impede pathogen colonization. Here, we identify mouse gut commensals that utilize mucus-derived monosaccharides within complex communities using single-cell stable isotope probing, Raman-activated cell sorting and mini-metagenomics. Sequencing of cell-sorted fractions reveals members of the underexplored family Muribaculaceae as major mucin monosaccharide foragers, followed by members of Lachnospiraceae, Rikenellaceae, and Bacteroidaceae families. Using this information, we assembled a five-member consortium of sialic acid and N-acetylglucosamine utilizers that impedes C. difficile's access to these mucosal sugars and impairs pathogen colonization in antibiotic-treated mice. Our findings underscore the value of targeted approaches to identify organisms utilizing key nutrients and to rationally design effective probiotic mixtures.

Smart drug delivery against Helicobacter pylori: pectin-coated, mucoadhesive liposomes with antiadhesive activity and antibiotic cargo.

The first step in the development of Helicobacter pylori pathogenicity is the receptor-mediated adhesion to the gastric epithelium. Inhibition of outer membrane proteins of H. pylori (e.g. BabA) by antiadhesive drugs will contribute to reduced recolonization and infection. Pectin from apple inhibits the BabA and LPS-mediated adhesion of H. pylori to human stomach cells. Pectin-coated liposomes with encapsulated amoxicillin were characterized for polydispersity, zeta potential, encapsulation efficiency, stability, and amoxicillin release. Coated liposomes did not influence the viability of AGS and HT29-MTX cells up to 100 µg/mL but exert cytotoxicity against H. pylori at 10 µg/mL. Pectin-coating of liposomes provoked direct interaction and subsequent binding of the particles to surface structures of H. pylori, and interaction with mucus from porcine stomach and mucus secreted by HT29-MTX cells. Laser scanning microscopy of H. pylori and AGS cells together with liposomes indicated co-aggregation. The mucoadhesive effect seems interesting as stomach cells are covered by a mucus layer. H. pylori is able to penetrate and cross the mucin rapidly to reach pH-neutral epithelium to escape the acidic environment, followed by interaction with epithelial cells. In summary, all experimental evidence is consistent with a specific interaction of pectin-coated liposomes with mucins and surface structures of H. pylori. As the coated liposomes show mucoadhesion to the negatively charged mucins, docking to stomach mucin, mucus penetration, and recognition of and adhesion to H. pylori, they can be considered a novel type of multifunctional drug carriers for local antibiotic therapy against H. pylori. KEY POINTS: • Smart, multifunctional mucoadhesive liposomes • Specific targeting against BabA/LPS of Helicobacter pylori • Inhibition of bacterial adhesion of H. pylori to human host cells • Release of antibiotic cargo.

The Gastroprotective Effect of Small Molecule Oligopeptides Isolated from Walnut (Juglans regia L.) against Ethanol-Induced Gastric Mucosal Injury in Rats.

The study investigated the protective effect of walnut oligopeptides (WOPs) against ethanol-induced gastric injury using Sprague-Dawley (SD) rats. Rats were randomly divided into seven groups based on body weight (10/group), normal group, ethanol group, whey protein group (220 mg/kg body weight), omeprazole group (20 mg/kg body weight), and three WOPs groups (220, 440, 880 mg/kg body weight). After 30 days of treatment with WOPs, rats were given 5 ml/kg absolute ethanol by gavage to induce gastric mucosal injury. Gastric ulcer index (GUI) were determined and the following measured; gastric content pH, gastric mucin, endogenous pepsinogens (PG), prostaglandin E2 (PGE2), inflammatory cytokines, oxidative stress indicators, and the expression of apoptosis-related proteins were measured to evaluate the gastroprotective effect of WOPs. The results showed that the administration with WOPs markedly mitigated the hemorrhagic gastric lesions caused by ethanol in rats, and decreased the GUI, the gastric content pH, PG1, PG2, and NO levels, enhanced mucin and PGE2. Also, WOPs repressed gastric inflammation through the reduction of TNF-α, IL-6, IL-1ß and increase IL-10 levels, and revealed antioxidant properties with the enhancement of superoxide dismutase, glutathione, and catalase activity, while reduction of malondialdehyde. Moreover, WOPs treatment significantly down-regulated Bax, caspase-3 and nuclear factor-κB p65 (NF-κB p65) expression, while up-regulating the expression of Bcl-2 and inhibitor kappa Bα (IκBα) protein. These results indicated that WOPs have protective effects against ethanol-induced gastric mucosal injury in rats through anti-inflammatory, anti-oxidation, and anti-apoptosis mechanisms.

Response to lubiprostone in chronic constipation is associated with increased mucus and mucin output: a randomized clinical trial.

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The Interaction of Helicobacter pylori with TFF1 and Its Role in Mediating the Tropism of the Bacteria Within the Stomach.

Helicobacter pylori colonises the human stomach and has tropism for the gastric mucin, MUC5AC. The majority of organisms live in the adherent mucus layer within their preferred location, close to the epithelial surface where the pH is near neutral. Trefoil factor 1 (TFF1) is a small trefoil protein co-expressed with the gastric mucin MUC5AC in surface foveolar cells and co-secreted with MUC5AC into gastric mucus. Helicobacter pylori binds with greater avidity to TFF1 dimer, which is present in gastric mucus, than to TFF1 monomer. Binding of H. pylori to TFF1 is mediated by the core oligosaccharide subunit of H. pylori lipopolysaccharide at pH 5.0-6.0. Treatment of H. pylori lipopolysaccharide with mannosidase or glucosidase inhibits its interaction with TFF1. Both TFF1 and H. pylori have a propensity for binding to mucins with terminal non-reducing α- or ß-linked N-acetyl-d-glucosamine or α-(2,3) linked sialic acid or Gal-3-SO42-. These findings are strong evidence that TFF1 has carbohydrate-binding properties that may involve a conserved patch of aromatic hydrophobic residues on the surface of its trefoil domain. The pH-dependent lectin properties of TFF1 may serve to locate H. pylori deep in the gastric mucus layer close to the epithelium rather than at the epithelial surface. This restricted localisation could limit the interaction of H. pylori with epithelial cells and the subsequent host signalling events that promote inflammation.

Carbohydrate-Dependent and Antimicrobial Peptide Defence Mechanisms Against Helicobacter pylori Infections.

The human stomach is a harsh and fluctuating environment for bacteria with hazards such as gastric acid and flow through of gastric contents into the intestine. H. pylori gains admission to a stable niche with nutrient access from exudates when attached to the epithelial cells under the mucus layer, whereof adherence to glycolipids and other factors provides stable and intimate attachment. To reach this niche, H. pylori must overcome mucosal defence mechanisms including the continuously secreted mucus layer, which provides several layers of defence: (1) mucins in the mucus layer can bind H. pylori and transport it away from the gastric niche with the gastric emptying, (2) mucins can inhibit H. pylori growth, both via glycans that can have antibiotic like function and via an aggregation-dependent mechanism, (3) antimicrobial peptides (AMPs) have antimicrobial activity and are retained in a strategic position in the mucus layer and (4) underneath the mucus layer, the membrane-bound mucins provide a second barrier, and can function as releasable decoys. Many of these functions are dependent on H. pylori interactions with host glycan structures, and both the host glycosylation and concentration of antimicrobial peptides change with infection and inflammation, making these interactions dynamic. Here, we review our current understanding of mucin glycan and antimicrobial peptide-dependent host defence mechanisms against H. pylori infection.