The Effect of Amniotic Membrane Transplantation or Conjunctival Autografts on the Tear Mucins MUC5A and MUC2 After Pterygium Resection: A Six-Month Follow-Up.

Purpose: Pterygium is an ocular surface disease characterized by the invasion of fibrovascular tissue from the bulbar conjunctiva to the cornea and is associated with abnormal tear function caused by changes in tear composition and osmolarity. In this study, the effect of two different surgical techniques to remove primary pterygium: conjunctival autograft surgery (CAG) and amniotic membrane transplantation (AMT), on changes in MUC2 and MUC5AC tear mucins concentration were evaluated. Methods: Forty-four patients (>18 years old) with primary unilateral pterygium (> 1.0 mm long, measured from the limbus to the apex on the cornea) were randomly enrolled, and assigned to the AMT or CAG group by using the permuted block technique. Patients with systemic inflammatory diseases or other eye comorbidities were excluded from the study. Tear break-up time (TBUT) and best-corrected visual acuity (BCVA) assessments were performed before surgery and at 1, 3, and 6 months after surgery. Tears were collected concurrently with the clinical evaluations, and MUC2 and MUC5AC concentrations were subsequently measured by means of ELISA. Results: At 6 months after CAG or AMT, TBUT and BCVA were significantly lower (P < 0.05) in comparison with the baseline values in the study subjects. The tear mucin concentrations of both MUC2 and MUC5AC were significantly higher (P < 0.0001) in patients with pterygium before any surgical procedure than in healthy individuals. The concentration of MUC2 increased at 1 and 3 months after CAG surgery and decreased at 6 months; however, the MUC2 concentration decreased on the AMT group in all time point measurements. Interestingly, the MUC5AC concentration significantly increased at 1 month after AMT or CAG and then decreased at 3 and 6 months after surgery. Finally, an inverse correlation was found between both MUC2 and MUC5AC tear mucins concentration and the TBUT. Conclusions: These results suggest that pterygium excision via both CAG or AMT changes the concentrations of the tear mucins MUC2 and MUC5AC during the evaluated times, and these changes could affect tear film stability and clinical recovery after pterygium treatment. Translational Relevance: The tear film stability during pterygium excision was evaluated to determine adequate treatments.

Morphological and functional features of the colonic mucus barrier in patients with symptomatic uncomplicated diverticular disease and acute uncomplicated diverticulitis.

OBJECTIVE: Aim: The purpose was to identify the morphological and functional features of the colonic mucus barrier in patients with symptomatic uncomplicated diverticular disease and acute uncomplicated diverticulitis. PATIENTS AND METHODS: Materials and Methods: In the research, three groups were formed. Group 1 included fragments of the mucous membrane of the large intestine, which were collected from 12 people during autopsies. The results of autopsies and histological examination of the material did not reveal any gastrointestinal pathology. Group 2 included biopsies of the mucous membrane of the large intestine from the area of the diverticulum of 34 patients with symptomatic uncomplicated diverticular disease. Group 3 included biopsies of the mucous membrane of the large intestine of 26 patients with acute uncomplicated diverticulitis. Histological (hematoxylin and eosin staining), histochemical (PAS reaction) and immunohistochemical (mouse monoclonal antibodies to Mucin 2 (MUC2) and Mucin 4 (MUC4)) staining methods were used. A morphometric study was also carried out. RESULTS: Results: In patients with diverticular disease, the authors identified disturbances in the morphofunctional state of the mucus barrier of the colon, the structure and function of goblet cells contained in its mucous membrane, characterized by a decrease in the thickness of the mucus layer covering the surface of the mucous membrane; a decrease in the size and number of goblet cells with a decrease in their mucus-producing ability; a change in the mucin profile, characterized by a violation of the content of MUC2 and MUC4. These changes were greatest in patients with acute uncomplicated diverticulitis compared with patients with symptomatic uncomplicated diverticular disease. CONCLUSION: Conclusions: The identified disturbances in the morphofunctional state of the mucus barrier of the colon, structural and functional changes in goblet cells may be one of the mechanisms for the development of acute uncomplicated diverticulitis and symptomatic uncomplicated diverticular disease.

Effect of chronic stress on gel-forming mucins in the small intestine of BALB/c mice.

Intestinal homeostasis involves the collaboration of gut barrier components, such as goblet cells and IgA-microbiota complexes, that are under the control of stress that promotes inflammatory responses addressed primarily in the colon. The aim of this study was to evaluate the effect of stress on mucins, goblet cells, and proinflammatory parameters in the proximal and distal regions of the small intestine. A group (n = 6) of female 8-week-old BALB/c mice underwent board immobilization stress (2 h per day for 4 days) and were sacrificed with isoflurane. Samples from proximal and distal small segments were collected to analyze the following: 1) goblet cells stained with periodic acid-Schiff (PAS) and with alcian blue (AB) to visualize histologically neutral and acidic mucins, respectively; 2) IgA-microbiota complexes identified by flow cytometry in intestinal lavages; and 3) MUC2, MUC5AC, and IL-18 mRNA levels in whole mucosal scrapings by reverse transcription-qPCR. Regarding the unstressed group, in the proximal region of small intestine both PAS+ and AB+ goblet cells were unchanged; however, MUC5AC and IL-18 mRNA levels were increased, and the percentage of IgA-microbiota complexes was reduced. In the distal segment, the number of PAS+ goblet cells was increased, whereas the number of AB+ goblet cells was reduced and did not affect the remaining parameters. The data suggest that stress induces inflammation in the proximal small intestine; these findings may provide an experimental reference for human diseases that may affect the proximal small intestine, such as Crohn's disease, in which stress contributes to the progression of intestinal inflammation or relapse.

Urolithin A-mediated augmentation of intestinal barrier function through elevated secretory mucin synthesis.

Maintaining the mucus layer is crucial for the innate immune system. Urolithin A (Uro A) is a gut microbiota-derived metabolite; however, its effect on mucin production as a physical barrier remains unclear. This study aimed to elucidate the protective effects of Uro A on mucin production in the colon. In vivo experiments employing wild-type mice, NF-E2-related factor 2 (Nrf2)-deficient mice, and wild-type mice treated with an aryl hydrocarbon receptor (AhR) antagonist were conducted to investigate the physiological role of Uro A. Additionally, in vitro assays using mucin-producing cells (LS174T) were conducted to assess mucus production following Uro A treatment. We found that Uro A thickened murine colonic mucus via enhanced mucin 2 expression facilitated by Nrf2 and AhR signaling without altering tight junctions. Uro A reduced mucosal permeability in fluorescein isothiocyanate-dextran experiments and alleviated dextran sulfate sodium-induced colitis. Uro A treatment increased short-chain fatty acid-producing bacteria and propionic acid concentration. LS174T cell studies confirmed that Uro A promotes mucus production through the AhR and Nrf2 pathways. In conclusion, the enhanced intestinal mucus secretion induced by Uro A is mediated through the actions of Nrf-2 and AhR, which help maintain intestinal barrier function.

Teleost Muc2 and Muc5ac: Key guardians of mucosal immunity in flounder (Paralichthys olivaceus).

Mucins secreted by mucous cells constitute a core part of the defense line against the invasion of pathogens. However, mucins' structure and immunological functions remain largely unknown in teleost fish. In this study, two typical mucins, Muc2 and Muc5ac of flounder (Paralichthys olivaceus), were cloned and their physicochemical properties, structure and conservation were analyzed. Notably, specific antibodies against flounder Muc2 and Muc5ac were developed. It was verified at the gene and protein level that Muc2 was expressed in the hindgut and gills but not in the skin, while Muc5ac was expressed in the skin and gills but not in the hindgut. After flounders were immunized by immersion with inactivated Edwardsiella tarda, Muc2 and Muc5ac were significantly upregulated at both the gene expression and protein levels, and Muc2+/Muc5ac+ mucous cells proliferated and increased secretion of Muc2 and Muc5ac. Moreover, Muc2 and Muc5ac exerted retention and clearance effects on E. tarda in a short period (within 1 dpi). These results revealed the characterization of fish mucins Muc2 and Muc5ac at the protein level and clarified the role of mucins as key guardians to maintain the mucus barrier, which advanced our understanding of teleost mucosal barrier.

Assessment of polymeric mucin-drug interactions.

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

Cassia alata's dual role in modulating MUC2 expression in Eimeria papillata-infected jejunum and assessing its anti-inflammatory effects.

Coccidiosis poses significant hazards to animals, particularly in terms of compromised health, reduced productivity, and economic losses in livestock farming. The conventional treatments for coccidiosis often involve synthetic drugs, contributing to concerns about drug resistance and environmental impact. The pressing need for eco-friendly alternatives is highlighted in this study, emphasizing the importance of exploring medicinal plants like Cassia alata leaf extracts (CAE) against Eimeria papillata-induced infection in mice. The CAE exhibited significant phenolic (2.17 ± 0.03 g/100 g) and flavonoid (0.14 ± 0.01 g/100 g) content and demonstrated notable antioxidant activity. In infected mice, the CAE treatment led to a substantial reduction in oocyst output (~6 fold), ameliorating necrotic enteritis and inflammatory changes in the jejunum. Additionally, CAE treatment increased goblet cell numbers (9.3 ± 0.1 / villus) and decreased macrophage infiltration in the intestinal villi. Molecular analyses revealed CAE's positive modulation of MUC2 gene and notably reduced the levels of pro-inflammatory cytokines (specifically IL-1ß, IL-10, and IFN-γ) when contrasted with the infected cohort. Furthermore, CAE treatment significantly reduced nitric oxide levels (44.03 ± 2.4 µmol/mg), showcasing its anti-inflammatory properties. The findings of this study not only contribute to the understanding of CAE's therapeutic potential but also underscore the importance of seeking eco-friendly alternatives in the face of coccidiosis challenges, addressing both the well-being of animals and the sustainability of agricultural practices. RESEARCH HIGHLIGHTS: Cassia alata extract (CAE) exhibited significant phenolic and flavonoid content, displaying notable antioxidant activity. In infected mice, CAE treatment led to a substantial reduction in oocyst output, ameliorating necrotic enteritis and inflammatory changes in the jejunum. CAE treatment increased goblet cell numbers and decreased macrophage infiltration in the intestinal villi, while molecular analyses revealed its positive modulation of the MUC2 gene and notable reduction in pro-inflammatory cytokine levels. Additionally, CAE treatment significantly reduced nitric oxide levels, showcasing its anti-inflammatory properties.

Bacteriophage defends murine gut from Escherichia coli invasion via mucosal adherence.

Bacteriophage are sophisticated cellular parasites that can not only parasitize bacteria but are increasingly recognized for their direct interactions with mammalian hosts. Phage adherence to mucus is known to mediate enhanced antimicrobial effects in vitro. However, little is known about the therapeutic efficacy of mucus-adherent phages in vivo. Here, using a combination of in vitro gastrointestinal cell lines, a gut-on-a-chip microfluidic model, and an in vivo murine gut model, we demonstrated that a E. coli phage, øPNJ-6, provided enhanced gastrointestinal persistence and antimicrobial effects. øPNJ-6 bound fucose residues, of the gut secreted glycoprotein MUC2, through domain 1 of its Hoc protein, which led to increased intestinal mucus production that was suggestive of a positive feedback loop mediated by the mucus-adherent phage. These findings extend the Bacteriophage Adherence to Mucus model into phage therapy, demonstrating that øPNJ-6 displays enhanced persistence within the murine gut, leading to targeted depletion of intestinal pathogenic bacteria.

[Identification of potential pathogenic genes of intestinal metaplasia based on transcriptomic sequencing and bioinformatics analysis].

OBJECTIVE: To explore the potential pathogenic genes of intestinal metaplasia. METHODS: Twenty-one patients with intestinal metaplasia admitted to the Department of Gastroenterology at the Second Affiliated Hospital of Anhui University of Chinese Medicine from January, 2022 to June, 2022, and 21 healthy subjects undergoing gastroscopic examination during the same period were enrolled in this study. All the participants underwent gastroscopy and pathological examination, and gastric tissue samples were collected for transcriptome sequencing to screen for differentially expressed genes (DEGs). The biological functions of the DEGs were analyzed using bioinformatics analysis, and qRT-PCR was used to validate the results. RESULTS: Transcriptomic sequencing identified a total of 1373 DEGs, including 827 upregulated and 546 downregulated ones. The top 6 upregulated genes (AGMAT, CCL25, FABP1, CDX1, SPINK4, and MUC2), ranked based on their significance and average expression level, were selected for validation, and qRT-PCR showed significant upregulation of their mRNAs in the gastric tissues of patients with intestinal metaplasia (P < 0.05). CONCLUSION: AGMAT, CCL25, FABP1, CDX1, SPINK4, and MUC2 participate in the occurrence and development of intestinal metaplasia, and may serve as potential biomarkers for diagnosing intestinal metaplasia.

The structure of the second CysD domain of MUC2 and role in mucin organization by transglutaminase-based cross-linking.

The MUC2 mucin protects the colonic epithelium by a two-layered mucus with an inner attached bacteria-free layer and an outer layer harboring commensal bacteria. CysD domains are 100 amino-acid-long sequences containing 10 cysteines that separate highly O-glycosylated proline, threonine, serine (PTS) regions in mucins. The structure of the second CysD, CysD2, of MUC2 is now solved by nuclear magnetic resonance. CysD2 shows a stable stalk region predicted to be partly covered by adjacent O-glycans attached to neighboring PTS sequences, whereas the CysD2 tip with three flexible loops is suggested to be well exposed. It shows transient dimer interactions at acidic pH, weakened at physiological pH. This transient interaction can be stabilized in vitro and in vivo by transglutaminase 3-catalyzed isopeptide bonds, preferring a specific glutamine residue on one flexible loop. This covalent dimer is modeled suggesting that CysD domains act as connecting hubs for covalent stabilization of mucins to form a protective mucus.

Restoration of Lactobacillus johnsonii and Enterococcus faecalis Caused the Elimination of Tritrichomonas sp. in a Model of Antibiotic-Induced Dysbiosis.

Inflammatory bowel disease (IBD) is a multifactorial disease involving the interaction of the gut microbiota, genes, host immunity, and environmental factors. Dysbiosis in IBD is associated with pathobiont proliferation, so targeted antibiotic therapy is a rational strategy. When restoring the microbiota with probiotics, it is necessary to take into account the mutual influence of co-cultivated microorganisms, as the microbiota is a dynamic community of species that mediates homeostasis and physiological processes in the intestine. The aim of our study was to investigate the recovery efficacy of two potential probiotic bacteria, L. johnsonii and E. faecalis, in Muc2-/- mice with impaired mucosal layer. Two approaches were used to determine the efficacy of probiotic supplementation in mice with dysbiosis caused by mucin-2 deficiency: bacterial seeding on selective media and real-time PCR analysis. The recovery time and the type of probiotic bacteria relocated affected only the number of E. faecalis. A significant positive correlation was found between colony-forming unit (CFU) and the amount of E. faecalis DNA in the group that was replanted with probiotic E. faecalis. As for L. johnsonii, it could be restored to its original level even without any additional bacteria supplementation after two weeks. Interestingly, the treatment of mice with L. johnsonii caused a decrease in the amount of E. faecalis. Furthermore, either L. johnsonii or E. faecalis treatment eliminated protozoan overgrowth caused by antibiotic administration.

Study on the Protective Effect and Mechanism of Umbilicaria esculenta Polysaccharide in DSS-Induced Mice Colitis and Secondary Liver Injury.

This study aimed to explore the ameliorative effects and potential mechanisms of Huangshan Umbilicaria esculenta polysaccharide (UEP) in dextran sulfate sodium-induced acute ulcerative colitis (UC) and UC secondary liver injury (SLI). Results showed that UEP could ameliorate both colon and liver pathologic injuries, upregulate mouse intestinal tight junction proteins (TJs) and MUC2 expression, and reduce LPS exposure, thereby attenuating the effects of the gut-liver axis. Importantly, UEP significantly downregulated the secretion levels of TNF-α, IL-1ß, and IL-6 through inhibition of the NF-κB pathway and activated the Nrf2 signaling pathway to increase the expression levels of SOD and GSH-Px. In vitro, UEP inhibited the LPS-induced phosphorylation of NF-κB P65 and promoted nuclear translocation of Nrf2 in RAW264.7 cells. These results revealed that UEP ameliorated UC and SLI through NF-κB and Nrf2-mediated inflammation and oxidative stress. The study first investigated the anticolitis effect of UEP, suggesting its potential for the treatment of colitis and colitis-associated liver disease.

Infant milk formula, produced by membrane filtration, promotes mucus production in the upper small intestine of young pigs.

Human breast milk promotes maturation of the infant gastrointestinal barrier, including the promotion of mucus production. In the quest to produce next generation infant milk formula (IMF), we have produced IMF by membrane filtration (MEM-IMF). With a higher quantity of native whey protein, MEM-IMF more closely mimics human breast milk than IMF produced using conventional heat treatment (HT-IMF). After a 4-week dietary intervention in young pigs, animals fed a MEM-IMF diet had a higher number of goblet cells, acidic mucus and mucin-2 in the jejunum compared to pigs fed HT-IMF (P < 0.05). In the duodenum, MEM-IMF fed pigs had increased trypsin activity in the gut lumen, increased mRNA transcript levels of claudin 1 in the mucosal scrapings and increased lactase activity in brush border membrane vesicles than those pigs fed HT-IMF (P < 0.05). In conclusion, MEM-IMF is superior to HT-IMF in the promotion of mucus production in the young gut.

Insights into the effects of chronic combined chromium-nickel exposure on colon damage in mice through transcriptomic analysis and in vitro gastrointestinal digestion assay.

Heavy metals interact with each other in a coexisting manner to produce complex combined toxicity to organisms. At present, the toxic effects of chronic co-exposure to heavy metals hexavalent chromium [Cr(VI)] and divalent nickel [Ni(II)] on organisms are seldom studied and the related mechanisms are poorly understood. In this study, we explored the mechanism of the colon injury in mice caused by chronic exposure to Cr or/and Ni. The results showed that, compared with the control group, Cr or/and Ni chronic exposure affected the body weight of mice, and led to infiltration of inflammatory cells in the colon, decreased the number of goblet cells, fusion of intracellular mucus particles and damaged cell structure of intestinal epithelial. In the Cr or/and Ni exposure group, the activity of nitric oxide synthase (iNOS) increased, the expression levels of MUC2 were significantly down-regulated, and those of ZO-1 and Occludin were significantly up-regulated. Interestingly, factorial analysis revealed an interaction between Cr and Ni, which was manifested as antagonistic effects on iNOS activity, ZO-1 and MUC2 mRNA expression levels. Transcriptome sequencing further revealed that the expression of genes-related to inflammation, intestinal mucus and tight junctions changed obviously. Moreover, the relative contents of Cr(VI) and Ni(II) in the Cr, Ni and Cr+Ni groups all changed with in-vitro gastrointestinal （IVG）digestion, especially in the Cr+Ni group. Our results indicated that the chronic exposure to Cr or/and Ni can lead to damage to the mice colon, and the relative content changes of Cr(VI) and Ni(II) might be the main reason for the antagonistic effect of Cr+Ni exposure on the colon damage.

Genistein alleviates dextran sulfate sodium-induced colitis in mice through modulation of intestinal microbiota and macrophage polarization.

OBJECTIVES: Ulcerative colitis (UC) is a colonic immune system disorder, manifested with long duration and easy relapse. Genistein has been reported to possess various biological activities. However, it remains unclear whether genistein can ameliorate UC by modulating the homeostasis of the intestinal bacterial community. METHODS: The dextran sodium sulfate (DSS)-induced UC mice were administrated with genistein (20 mg/kg/day) or genistein (40 mg/kg/day) for ten days. The general physical condition of the mice was monitored. After sacrifice, the changes in colon length and colonic pathological morphology were observed. The expression of intestinal barrier proteins, inflammatory cytokines, and macrophage markers in the colon was detected. The composition and metabolic products of the intestinal microbiota were analyzed. RESULTS: Genistein treatment visibly improved body weight change and disease activity index in DSS-induced mice. Genistein treatment ameliorated colonic pathological alterations and promoted the expression of mucin-2 and tight junction proteins. Genistein administration inhibited myeloperoxidase activity and colonic inflammatory cytokines. Furthermore, genistein administration improved the structure of the intestinal microbial community, promoted the production of short-chain fatty acids, and modulated macrophage polarization. CONCLUSIONS: These results revealed that genistein mediated macrophage polarization balance by improving intestinal microbiota and its metabolites, thereby alleviating DSS-induced colitis.

Colon-available mango (poly)phenols exhibit mitigating effects on the intestinal barrier function in human intestinal cell monolayers under inflammatory conditions.

This study investigated the impact of in vivo available colon-mango (poly)phenols on stress-induced impairment of intestinal barrier function. Caco-2/HT29-MTX cells were incubated with six extracts of ileal fluid collected pre- and 4-8 h post-mango consumption before being subjected to inflammatory stress. (Poly)phenols in ileal fluids were analysed by UHPLC-HR-MS. Epithelial barrier function was monitored by measurement of trans-epithelial electrical resistance (TEER) and the production of selected inflammatory markers (interleukin-8 (IL-8) and nitric oxide (NO)) and the major mucin of the mucosal layer (MUC2). Post-mango intake ileal fluids contained principally benzoic acids, hydroxybenzenes and galloyl derivatives. There was a high interindividual variability in the levels of these compounds, which was reflected by the degree of variability in the protective effects of individual ileal extracts on inflammatory changes in the treated cell cultures. The 24 h treatment with non-cytotoxic doses of extracts of 4-8 h post-mango intake ileal fluid significantly reduced the TEER decrease in monolayers treated with the inflammatory cytomix. This effect was not associated with changes in IL-8 expression and secretion or claudine-7 expression. The mango derived-ileal fluid extract (IFE) also mitigated cytomix-dependent nitrite secretion, as a proxy of NO production, and the MUC2 reduction observed upon the inflammatory challenge. These insights shed light on the potential protective effect of mango (poly)phenols on the intestinal barrier exposed to inflammatory conditions.

Sishen Wan enhances intestinal barrier function via regulating endoplasmic reticulum stress to improve mice with diarrheal irritable bowel syndrome.

BACKGROUND: Diarrheal irritable bowel syndrome (IBS-D), characterized primarily by the presence of diarrhea and abdominal pain, is a clinical manifestation resulting from a multitude of causative factors. Furthermore, Sishen Wan (SSW) has demonstrated efficacy in treating IBS-D. Nevertheless, its mechanism of action remains unclear. METHODS: A model of IBS-D was induced by a diet containing 45 % lactose and chronic unpredictable mild stress. Additionally, the impact of SSW was assessed by measuring body weight, visceral sensitivity, defecation parameters, intestinal transport velocity, intestinal neurotransmitter levels, immunohistochemistry, and transmission electron microscopy analysis. Immunofluorescent staining was used to detect the expression of Mucin 2 (MUC2) and Occludin in the colon. Western blotting was used to detect changes in proteins related to tight junction (TJ), autophagy, and endoplasmic reticulum (ER) stress in the colon. Finally, 16S rRNA amplicon sequencing was used to monitor the alteration of gut microbiota after SSW treatment. RESULTS: Our study revealed that SSW administration resulted in reduced visceral sensitivity, improved defecation parameters, decreased intestinal transport velocity, and reduced intestinal permeability in IBS-D mice. Furthermore, SSW promotes the secretion of colonic mucus by enhancing autophagy and inhibiting ER stress. SSW treatment caused remodeling of the gut microbiome by increasing the abundance of Blautia, Muribaculum and Ruminococcus torques group. CONCLUSION: SSW can improve intestinal barrier function by promoting autophagy and inhibiting ER stress, thus exerting a therapeutic effect on IBS-D.

Biochanin a ameliorates DSS-induced ulcerative colitis by improving colonic barrier function and protects against the development of spontaneous colitis in the Muc2 deficient mice.

There is an increasing appreciation that colonic barrier function is closely related to the development and progression of colitis. The mucus layer is a crucial component of the colonic barrier, responsible for preventing harmful bacteria from invading the intestinal epithelium and causing inflammation. Furthermore, a defective mucus barrier is also a significant characteristic of ulcerative colitis (UC). Biochanin A (BCA), an isoflavonoid, has garnered increasing interest due to its significant biological activities. However, the impact of BCA on UC has not been reported yet. In this study, we used a dextran sodium sulfate (DSS)-induced ulcerative colitis model and the Muc2 deficient (Muc2-/-) mice spontaneous colitis model to explore the mechanisms of BCA in the treatment of UC. Here, we verified that DSS-induced UC was observably attenuated and spontaneous colitis in Muc2-/- mice was relieved by BCA. Treatment with BCA improved colitis-related symptoms and reduced intestinal permeability by upregulating the levels of goblet cells and tight junction (TJ) proteins. In addition, we confirmed that BCA promotes autophagy through the AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR)/Unc-51-like kinase 1 (ULK1) pathway, thereby alleviating DSS-induced UC. In addition, the administration of BCA was able to reduce apoptosis and promote proliferation by suppressing Cleaved Caspase-3 (Cleaved Cas-3) expression, and increasing PCNA and Ki67 levels. Further research revealed that BCA treatment ameliorated spontaneous colitis and alleviated epithelial damage in Muc2-/- mice by restoring the intestinal barrier and promoting autophagy. Our results demonstrated that BCA alleviated UC by enhancing intestinal barrier function and promoting autophagy. These findings indicate that BCA may be a novel treatment alternative for UC.

Coarse-grained modeling and dynamics tracking of nanoparticles diffusion in human gut mucus.

The gastrointestinal (GI) tract's mucus layer serves as a critical barrier and a mediator in drug nanoparticle delivery. The mucus layer's diverse molecular structures and spatial complexity complicates the mechanistic study of the diffusion dynamics of particulate materials. In response, we developed a bi-component coarse-grained mucus model, specifically tailored for the colorectal cancer environment, that contained the two most abundant glycoproteins in GI mucus: Muc2 and Muc5AC. This model demonstrated the effects of molecular composition and concentration on mucus pore size, a key determinant in the permeability of nanoparticles. Using this computational model, we investigated the diffusion rate of polyethylene glycol (PEG) coated nanoparticles, a widely used muco-penetrating nanoparticle. We validated our model with experimentally characterized mucus pore sizes and the diffusional coefficients of PEG-coated nanoparticles in the mucus collected from cultured human colorectal goblet cells. Machine learning fingerprints were then employed to provide a mechanistic understanding of nanoparticle diffusional behavior. We found that larger nanoparticles tended to be trapped in mucus over longer durations but exhibited more ballistic diffusion over shorter time spans. Through these discoveries, our model provides a promising platform to study pharmacokinetics in the GI mucus layer.