Histochemical demonstration of desialation and desulphation of normal and inflammatory bowel disease rectal mucus by faecal extracts

Quercetin ameliorates ulcerative colitis by restoring the balance of M2/M1 and repairing the intestinal barrier via downregulating cGAS‒STING pathway

Macrophage polarization is closely associated with the pathogenesis of ulcerative colitis (UC). Quercetin, a flavonoid, has shown promise as a treatment for inflammatory diseases, but its specific mechanism of action remains unclear. This study investigates whether quercetin can regulate intestinal macrophage polarization and promote intestinal tissue repair via the cGAS-STING pathway for the treatment of UC. In vivo, mice with 3% DSS-induced UC were intraperitoneally injected with quercetin and RU.521 for 7 days, following which their general conditions and corresponding therapeutic effects were assessed. The impact of interferon-stimulated DNA (ISD) and quercetin on macrophage polarization and the cGAS-STING pathway was investigated using RAW264.7 cells and bone marrow-derived macrophages (BMDMs) in vitro. The results demonstrated that ISD induced M1 macrophage polarization and activated the cGAS-STING pathway in vitro, while quercetin reversed ISD's inflammatory effects. In vivo, quercetin suppressed the cGAS-STING pathway in the intestinal macrophages of DSS-induced UC mice, which reduced M1 macrophage polarization, increased M2 polarization, and facilitated intestinal barrier repair in UC. Taken together, these findings provide new insights into the mechanisms via which quercetin could be used to treat UC.

Morpho-histochemical adaptations of the digestive tract in Gangetic mud-eel Ophichthys cuchia (Hamilton 1822) support utilization of mud-dwelling prey

Freshwater mud-eel, Ophichthys cuchia is nocturnal, carnivorous and economically important fish, yet its digestive physiology is unknown. We therefore studied the gastrointestinal (GI) tract of O. cuchia using morphological, osteological, histological and histochemical approach to understand how the structural adequacy of GI tract helps in acquisition of bottom and mud-dwelling prey and supports utilization of uncommon food resources. Morphologically the GI tract showed typical features of carnivorous fishes in the form of sub-terminal mouth, short muscular esophagus, expendable stomach, short intestine and rectum. Osteological investigation clearly showed that the specialized arrangement of teeth in the oral cavity and pharyngeal region helps in digging and manipulation of bottom and mud-dwelling prey. Longitudinal mucosal folds, stratified squamous epithelium with numerous goblet cells of esophagus protect mucosa from mechanical harm and also allow easy transit of prey into the stomach. Large-sized rugae of stomach are complemented with numerous gastric glands which together increase the transit time of carnivorous food stuff and ensure its complete digestion. The pylorus specifically allows only digested and finely ground food stuff into the intestine and thus avoids the intestinal blockage due to entry of undigested food. The enterocytes and goblet cells of intestine are absorptive and lubricative in their functions respectively. A significant increase in the number of goblet cells and thickness of muscularis from the intestine to the rectum was evident which facilitates the easier transit of food, protection for the epithelium from abrasion, and helps in defecation. Histochemistry revealed that the mucins are secreted throughout the GI tract and thus catalyze faster digestion of carnivorous food stuff, providing protection to mucosal membrane from abrasion, acts as a co-factor to support digestion, absorption of proteins, ions, fluids and helps in defecation. The outcome of this study clearly supports the notion that structural adaptations in the digestive tract of fishes can be effectively used as a blueprint to understand why and how particular fish species feed and use unique food. Additionally, the structural and functional adequacy of the digestive tract helps the fishes to acquire and utilize novel habitats and food resources. The results presented in this study will serve as a reference point for future studies, which focus primarily on understanding the evolution of carnivory in Synbranchids.

Structural adequacy of the digestive tract supports dual feeding habit in catfish Pachypterus khavalchor (Siluriformes: Horabagridae)

Lepidophagy is comparatively rare amongst teleost fishes, yet our understanding of this specialization is lacking. Therefore we examined the digestive tract features of Pachypterus khavalchor using morphological, osteological, histological and histochemical techniques to comprehend and relate structural organization of digestive tract with scale eating habit. Morphologically, the alimentary canal is defined by a short and muscular esophagus, well-developed stomach and comparatively short intestine. Gut content analysis and intestinal coefficient value (0.53 ± 0.01) revealed that P. khavalchor exhibit both carnivory and lepidophagy. However, P. khavalchor primarily feeds on the scales (67.47%) and other chitin-rich material like aquatic insects (17.62%), aquatic larvae (8.66%) which affirms its solid association with chitinase producing endosymbionts in the gut. Lepidophagy is further supported by the osteological observations. The perfect segregation of the functions such as food capture, ingestion and processing amongst the different types of teeth located in the oral cavity and pharyngeal region thus could be taken as evolutionary adaptations in scale eaters to support lepidophagy. Specialized arrangement of the esophageal and stomach epithelial folds could be altogether taken as an adaptation with the end goal to frame the scale stacks and accordingly facilitate the handling and processing of chitin-rich bolus. The esophageal mucosa is simple squamous epithelium instead of stratified epithelium with numerous goblet cells to withstand the mechanical harm by hard-food stuff like scales. The cardiac and fundic regions exhibited large number tubular gastric glands with simple columnar epithelium. Surface cells of all three stomach regions stained positive for PAS staining. The intestine is without pyloric caeca and is divided into anterior and posterior region. Histologically it is characterized by simple columnar epithelium with brush border and numerous goblet cells throughout its length. Presence of large number microvilli on anterior and posterior intestine was noticeable. Intestinal goblet cells reacted positively to PAS, AB (pH 1) and AB (pH 2.5). Secretions of goblet cells are important for lubricating and protecting the epithelium. The results of present investigation improve the understanding of the digestive physiology of scale eaters in general and P. khavalchor in particular. Overall, our data indicates that though P. khavalchor predominantly feeds on scale, the digestive physiology is adapted to support dual feeding habit (lepidophagy and carnivory).

Cytochemical features of the digestive tract mucosa of Hemisorubim platyrhynchos (Siluriformes: Pimelodidae)

Membranous organelles, acid glycoconjugates and lipids were characterized in the digestive tract mucosa of Hemisorubim platyrhynchos by cytochemistry techniques. Two types of mucous-secreting cells were observed in the digestive tract epithelium: goblet cells in the oesophagus and intestine and epithelial cells in the stomach. These cells had a Golgi apparatus more developed than the other cell types. The cytochemical analysis revealed that secretory granules are reactive to acid glycoconjugates, varying in reaction intensity according to the region of the digestive tract. Acid glycoconjugate reactions were also observed in oesophageal epithelial cell microridges and in enterocyte microvilli. In the digestive tract, acid glycoconjugates act to protect the epithelial surface, increasing mucous viscosity, which facilitates the passage of food, prevents the binding of parasites and facilitates their removal. Through lipid staining, a coated membrane was observed around each secretory granule of the oesophageal and intestinal goblet cells, while gastric epithelial cells granules were fully reactive. Oxynticopeptic cells of the gastric glands showed lipid droplets in the cytoplasm and also in the mitochondrial matrix, which act as an energy reserve for these cells that have a high energy demand. Enterocytes showed a well-developed smooth endoplasmic reticulum, especially in the apical region of the cell, being related to absorption and resynthesis of lipids.

Mucin-Microbiota Interaction During Postnatal Maturation of the Intestinal Ecosystem: Clinical Implications

The mucus layer and gut microbiota interplay contributes to host homeostasis. The mucus layer serves as a scaffold and a carbon source for gut microorganisms; conversely, gut microorganisms, including mucin degraders, influence mucin gene expression, glycosylation, and secretion. Conjointly they shield the epithelium from luminal pathogens, antigens, and toxins. Importantly, the mucus layer and gut microbiota are established in parallel during early postnatal life. During this period, the development of gut microbiota and mucus layer is coupled with that of the immune system. Developmental changes of different mucin types can impact the age-dependent patterns of intestinal infection in terms of incidence and severity. Altered mucus layer, dysbiotic microbiota, and abnormal mucus-gut microbiota interaction have the potential for inducing systemic effects, and accompany several intestinal diseases such as inflammatory bowel disease, colorectal cancer, and radiation-induced mucositis. Early life provides a pivotal window of opportunity to favorably modulate the mucus-microbiota interaction. The support of a health-compatible mucin-microbiota maturation in early life is paramount for long-term health and serves as an important opportunity for clinical intervention.

Functional morphology of the esophagus of the tropical house gecko Hemidactylus mabouia (Squamata: Gekkonidae)

In order to understand the biology of species that easily establish themselves in new environments, morphological studies are essential. This study aimed to describe the esophageal functional morphology ofHemidactylus mabouia, indicating adaptations to food habits. Seventeen adult specimens were used for anatomical, topological, histological, and histochemical analyses. Histological sections were stained with toluidine blue or submitted to techniques for identification of argyrophil and argentaffin endocrine cells, proteins, and glycoconjugates. The esophagus ofH. mabouiais a tubular straight-lined organ, and its anterior portion is dilated, facilitating the swallowing of whole prey. The esophageal epithelium is pseudostratified, containing cells secreting neutral and acid mucins. At the esophagogastric transition, we found a mixture of this epithelium with a simple prismatic epithelium secreting neutral mucins. The esophagus lamina propria is thin and non-glandular. At the esophagogastric transition it becomes thick and filled by branched simple acinous glands, with cells secreting neutral mucins, zymogenic cells, and argentaffin endocrine cells, with no argyrophil cells. The mucins protect the esophageal mucosa and lubricate the channel to facilitate the passage of food, while pepsinogen in the stomach increases the levels of pepsin for proteolytic digestion. The muscular tunica is made up of smooth muscle cells. Ciliary action, in addition to muscle contractions, facilitates the swallowing of small prey.

Mucosal barrier, bacteria and inflammatory bowel disease: possibilities for therapy

The mucosal barrier has three major components, the mucus layer, the epithelial glycocalyx and the surface epithelium itself, whose integrity largely depends on tight junction function. In health, there is relatively little direct interaction between the luminal microbiota and the epithelium - the continuous mucus layer in the colon keeps the surface epithelium out of contact with bacteria and the ileo-caecal valve ensures that the distal small intestine is relatively microbe free. Most interaction takes place at the Peyer's patches in the distal ileum and their smaller colonic equivalents, the lymphoid follicles. Peyer's patches are overlain by a 'dome' epithelium, 5% of whose cells are specialised M (microfold) epithelial cells, which act as the major portal of entry for bacteria. There are no goblet cells in the dome epithelium and M cells have a very sparse glycocalyx allowing easy microbial interaction. It is intriguing that the typical age range for the onset of Crohn's disease (CD) is similar to the age at which the number of Peyer's patches is greatest. Peyer's patches are commonly the sites of the initial lesions in CD and the 'anti-pancreatic' antibody associated with CD has been shown to have as its epitope the glycoprotein 2 that is the receptor for type-1 bacterial fimbrial protein (fimH) on M cells. There are many reasons to believe that the mucosal barrier is critically important in the pathogenesis of inflammatory bowel disease (IBD). These include (i) associations between both CD and ulcerative colitis (UC) with genes that are relevant to the mucosal barrier; (ii) increased intestinal permeability in unaffected relatives of CD patients; (iii) increased immune reactivity against bacterial antigens, and (iv) animal models in which altered mucosal barrier, e.g. denudation of the mucus layer associated with oral dextran sulphate in rodents, induces colitis. Whilst some IBD patients may have genetic factors leading to weakening of the mucosal barrier, it is likely that environmental factors may be even more important. Some may be subtle and indirect, e.g. the effects of stress on the mucosa barrier, whilst others may be more obvious, e.g. the effect of pathogen-related gastroenteritis, known often to act as trigger for IBD relapse. We have also been very interested in the potentially harmful effects of ingested detergents - either by contamination of cutlery by inadequate rinsing or via ingestion of processed foods containing permitted emulsifiers. In vitro and ex vivo studies show that even very small trace amounts of these surfactants can greatly increase bacterial translocation. Implications for therapy are not yet so obvious. We advise our IBD patients to avoid processed foods containing emulsifiers and to rinse their dishes well - whilst accepting that there is no direct evidence yet to support this. Therapies that aim to enhance the mucosal barrier have yet to come to market, but trials of enteric-delivered phosphatidylcholine in UC are promising. The faecal concentration of mucus-degrading bacterial enzymes (particularly proteases, sulphatases and sialidases) correlates with disease activity in UC, and these represent good targets for therapy.

Dominant genotypes in mucosa-associated Escherichia coli strains from pediatric patients with inflammatory bowel disease

BACKGROUND

Studies performed in adults with inflammatory bowel disease (IBD) have suggested that mucosa-associated Escherichia coli strains may be involved in its pathogenesis. The aim of this study was to characterize E. coli strains from the intestinal mucosa of pediatric IBD patients to investigate whether a particular subset of strains could be associated with the disease.

METHODS

We analyzed the genomic and phenotypic traits of 60 E. coli strains isolated from biopsies of pediatric patients with Crohn's disease (CD), ulcerative colitis (UC), and from age-matched controls.

RESULTS

No noteworthy differences were found in the distribution of phylogroups. The percentage of adhesive E. coli strains was similar in biopsies from patients and controls. However, the adhesion ability of E. coli strains differed between ileal and colonic or rectal areas, only in the strains from CD and UC patients. The percentage of E. coli possessing more than 1 of the adhesive/virulence determinants was significantly higher in strains from UC than from CD and controls. Interestingly, the genetic profile examination revealed 2 large clusters of genetically linked E. coli strains from IBD patients. Ninety-two percent of the strains isolated from CD patients were in the first cluster (A) and were distributed between 2 genetic subclusters (A1 and A2), while a second cluster (B) contained most of the strains isolated from UC (78%; subcluster B1), and control strains (77%; subcluster B2).

CONCLUSIONS

Genomic analysis of mucosa-associated E. coli strains found a close genetic association between strains isolated from CD and UC patients.

Histochemical characterization of glycoproteins in the buccal epithelium of the catfish, Rita rita

Glycoproteins (GPs) elaborated by the buccal epithelium of the catfish, Rita rita, were analysed by a range of histochemical methods. These included methods for the characterization and simultaneous visualization of GPs with oxidizable vicinal diols, with O-acyl sugars, with O-sulphate esters and with sialic acid residues with and without O-acyl substitution at C7, C8 or C9. GPs elaborated at the surface of the buccal epithelium are primarily from two sources, the epithelial cells and the mucous goblet cells. They include GPs with O-sulphate esters, GPs with sialic acid residues without O-acyl substitution and GPs with oxidizable vicinal diols. Different classes of GPs have been associated with specific functions and are discussed in relation to their physiological significance, with special reference to their roles in lubrication, alteration in viscosity, trapping of food particles, buffering of fluids at the epithelial surface, prevention of proteoloytic damage to the epithelium, antimicrobial activity and defence against pathogens. The epithelium shows specialized modifications in the form of the buccal glands. These have been considered to increase the secretory surface that allows profuse secretion of mucus in a very short period of time. The secretions of these glands have been associated with multiple functions similar to those of saliva.

Histochemical localization of complex carbohydrates in the nasolabial glands of the Japanese deer (Cervus nippon yakushimae)

The localization of complex glycoconjugates in the nasolabial glands of the Japanese deer (C. nippon yakushimae) was studied using various histochemical methods, including lectin histochemistry, viewed using both light and electron microscopy. The secretory epithelium and luminal secretion of the deer nasolabial glands exhibited neutral and acidic glycoconjugates with different saccharide residues (alpha-D-mannose, alpha-N-acetyl-D-galactosamine, beta-D-galactose, beta-N-acetyl-D-glucosamine and sialic acid). Additionally, O-acetylated sialic acids were detectable in the glandular acini. The results obtained are discussed with regard to the specific functions of the glandular secretion, which may particularly improve water retention on the skin surface and protect against physical damage as well as microbial contamination. Furthermore, our results support the view of a salivary nature of this gland type.

Reinforcing the mucus: a new therapeutic approach for ulcerative colitis?

Luminal delivery of phosphatidyl rich phospholipids appears to reduce mucosal inflammatory activity in a high proportion of patients with chronically active ulcerative colitis. The simplicity and apparent safety of this therapeutic approach offers new insights into the importance of the mucus barrier in the pathogenesis and treatment of ulcerative colitis.

Ultracytochemical Demonstration of Glycoproteins in the Eccrine Glands of the Digital Pads of the North American Raccoon (Procyon lotor)

In the eccrine glands of the digital pads of the North American raccoon (Procyon lotor), ultrastructural localization of glycoproteins with various saccharide residues was studied using preferably lectin cytochemical methods. Secretory granules observed in the dark cells exhibited glycoproteins with different terminal sugars (alpha-D-mannose, beta-D-galactose, beta-N-acetyl-D-glucosamine and sialic acid). The cytoplasm of the clear cells contained numerous glycogen particles. Several sugars were also detectable in the surface coat of the plasma membrane of the secretory cells. The results obtained could be helpful in understanding secretion production and cell related secretion functions of the eccrine glands of the raccoon digital foot pads.

Disease-dependent adhesion of lactic acid bacteria to the human intestinal mucosa

Their adhesion to the intestinal mucosa is considered one of the main reasons for the beneficial health effects of specific lactic acid bacteria (LAB). However, the influence of disease on the mucosal adhesion is largely unknown. Adhesion of selected LAB to resected colonic tissue and mucus was determined in patients with three major intestinal diseases (i.e., diverticulitis, rectal carcinoma, and inflammatory bowel disease) and compared to healthy control tissue. All strains were observed to adhere better to immobilized mucus than to whole intestinal tissue. Two strains (Lactobacillus rhamnosus strain GG and L. reuteri) were found to exhibit disease-specific adhesion to intestinal tissue. All tested strains, with the exception of L. rhamnosus strain GG, displayed disease-specific adhesion to intestinal mucus. These results suggest that strains with optimal binding characteristics for a particular intestinal disease can be selected.

Histochemical analysis of glycoconjugates in the ceruminous glands of the North American raccoon (Procyon lotor)

The distribution and selectivities of glycoconjugates in the ceruminous glands of the North American raccoon (Procyon lotor) were studied by light and electron microscopic histochemical methods, particularly lectin histochemistry. In the modified apocrine glands present, the apocrine secretion mode was combined with exocytosis, whereby the secretory epithelium and the luminal secretion of the ceruminous glands exhibited considerable amounts of complex carbohydrates with various terminal sugars (alpha-D-mannose, beta-D-galactose, alpha-L-fucose, alpha-N-acetyl-galactosamine, beta-N-acetyl-D-glucosamine, N-acetyl-neuraminic acid). Alpha-L-fucose and N-acetyl-neuraminic acid were distinctly prominent in secretory granules or within the free surface coat of the plasma membrane of the glandular cells, as well as in the luminal secretion. Several free sugars (alpha-D-mannose, alpha-L-fucose, beta-D-galactose, beta-N-acetyl-D-glucosamine) were also detectable in the secretion of associated sebaceous glands. The ceruminous gland secretion may control viscoelasticity and/or bacterial degradation of the glandular secretion mixture to improve the protection of the external auditory canal against physical damage or microbial contamination.

Characterization of glycoproteins in the epithelial cells of human and other mammalian gallbladder. A review

The mammalian gallbladder mucosa is lined by a simple columnar epithelium. Typical surface epithelial cells (principal cells) contain short microvilli, secretory granules, dense bodies, mitochondria and Golgi apparatus. Dense bodies are thought to be lysosomes. Secretory granules contain mucous glycoproteins which are released to the lumen by exocytosis. Oligosaccharide side chains of mucous glycoproteins may provide a favorable environment for nucleation of cholesterol in gallstone formation; therefore they have been studied during the past decades. Histochemical techniques allow the in situ identification of carbohydrates at both the cellular and subcellular levels. The oligosaccharide chains of principal cell mucous glycoproteins have been studied by classical histochemical techniques (PAS, alcian blue, HID, etc). These techniques indicate that mammalian gallbladder mucous glycoproteins are heavily sulphated, whereas sialic acid residues are scarce. Neutral mucins have not been described in the mammalian gallbladder. Electron microscopic studies have located the oligosaccharide chains in secretory granules and Golgi apparatus. More recently, lectins (molecules which specifically recognize and bind with different saccharides or saccharide sequences) have been applied for the intracellular localization of carbohydrate residues. Lectin histochemistry has detected fucose, galactose, N-acetylglucosamine, N-acetylgalactosamine and N-acetylneuraminic acid residues in mucous granules, Golgi apparatus and apical membrane of human principal cells. Mannose residues were observed only in dense bodies. The combined use of deglycosylation procedures and lectin histochemistry has revealed a variety of terminal sequences in oligosaccharide chains of gallbladder mucous glycoproteins: Neu5Ac(alpha 2-3)Gal(beta 1-3)GalNAc, Neu5Ac(alpha 2-3)Gal(beta 1-4)GlcNAc and Gal(beta 1-4)GlcNAc. This technology also suggested the occurrence of N-linked oligosaccharides in the dense bodies of principal cells. Mucous granules mainly contained mucin-type O-linked oligosaccharides although some N-linked chains have also been detected. Gallstone formation is probably a complex process depending on multiple factors. Mucous glycoproteins are one of the factors involved in this process. Histochemical methods offer an excellent research tool for the characterization of glycoproteins in the epithelial cells of the gallbladder, thus contributing to the elucidation of the pathophysiology of gallstone formation.

Altered expression of mucins throughout the colon in ulcerative colitis

BACKGROUND/AIMS

Regional differences in the biology of the colonic epithelium may determine the extent of involvement by ulcerative colitis. Novel monoclonal antibodies (MAbs) were used in this study to investigate regional heterogeneity in the colonic mucosa.

METHODS

MAbs generated using a method of tolerisation against common antigens in the proximal colon and distal colon were used for immunoperoxidase staining, comparative histochemistry, immunoblotting, and slot-blot analysis.

RESULTS

The colon specific MAbs 5F1 (IgG3) and 6G4 (IgM) stained goblet cell contents throughout the normal distal colon but staining was markedly reduced in the proximal colon (p < 0.0001). In the distal colon of patients with ulcerative colitis, whether quiescent or actively inflamed, reactivity was reduced compared with controls (p < 0.05, p < 0.001 respectively). By contrast, an overall increase in staining was seen in the uninflamed proximal colon in ulcerative colitis compared with controls (p < 0.02). Comparative staining with high iron diamine and biochemical analyses indicated that MAb 6G4 was reactive with mucin bearing sulphate or O-acetylated sialic acid groups, or both.

CONCLUSIONS

Regional differences in the staining characteristics of normal colonic mucin have been shown using novel monoclonal antibodies. The pattern of mucin expression throughout the colon in ulcerative colitis is altered even in the absence of histological changes.

Mucus glycoproteins and their role in colorectal disease

In this review, the nature and impact of progress in the study of mucins is outlined, emphasizing the current understanding of the structure and physiological function of these molecules in the colorectum. The use of new methods for preparation and separation has led to improvements in the analysis of mucins; these are detailed, as are their difficulties and pitfalls. Results obtained with these methods are correlated with long-established histochemical techniques and the use of chemical, lectin, and antibody reagents for general and specific detection of mucins in all procedures is described. Improvements in the detection and analysis of mucins in biopsy-size tissue samples and in larger numbers of individual clinical cases have now permitted a much wider approach to the pathological evaluation of mucin biology and progress with these techniques is outlined. The significance of the discovery of a family of mucin genes is presented and new concepts of mucin structure resulting from these studies are described. Bacterial degradation of the mucus layer at the surface of the colorectal mucosa is considered in line with the homeostatic relationship with mucosal mucin synthesis. Finally, the implications of abnormal mucins in colorectal disease are considered in the light of recent methodological advances.

Faecal mucinase activity assessed in inflammatory bowel disease using 14C threonine labelled mucin substrate

Previous studies have shown the presence in faeces of sulphatases, sialidases, glycosidases, and proteases relevant to mucus degradation, but the relative role of these enzymes in the degradation of colonic mucus has been unclear. A total mucinase assay using 14C threonine biologically labelled human colonic mucin as substrate was therefore developed in this study. Faecal mucinase activity of a pooled normal faecal filtrate was capable of removing 80% of the 14C threonine label from mucin within eight hours incubation, but 20% remained intact despite prolonged incubation. The pH profile of mucinase activity is broad (pH 4.5-9.5) suggesting contribution from multiple enzymes. Mucinase activity was reduced by preincubation with 100 micrograms/ml chymostatin (82.8%), 0.5 mg/ml EDTA (91.6%), and 4 g/l bismuth subsalicylate (72.0%). All 55 faecal samples studied contained detectable mucinase activity, measured as dpm release/micrograms protein/hour, which was greater in samples from patients with ulcerative colitis (n = 17, median 52.7, interquartile range 32.9-66.9), than controls (n = 26, 34.4, 26.8-40.4, p < 0.02) or patients with Crohn's disease (n = 12, 35.5, 17.5-55.7, p < 0.05). There was, however, no significant difference in faecal mucinase activity between inactive and active ulcerative colitis. These results suggest that faecal mucinase activity is one factor contributing to the thin mucus layer in ulcerative colitis and represents a potential target for drug treatment.

South Asian and European colitics show characteristic differences in colonic mucus glycoprotein type and turnover

South Asians in Britain have a high incidence of ulcerative colitis and a low incidence of colorectal cancer. The pattern of mucus production in 12 South Asian and 16 European colitics and a control group of 19 South Asians was studied. Three types of mucin were identified after organ culture of colonic biopsy specimens with a dual label of [3H]-glucosamine and sodium [35S]-sulphate: type A had a high [35S]:[3H] ratio and high incorporation ([3H] dpm/micrograms DNA > 500); type B had a low ratio and high incorporation; and type C had low incorporation but with either high (C1) or low (C2) ratios. European colitic mucins show a significant reduction in the level of sulphation detected by mucin histochemistry with high iron diamine/Alcian blue staining, together with predominantly type B or C2 mucins (low sulphation). South Asian colitics showed histochemically normal patterns of high sulphation and largely type A and C1 mucins (high sulphation). There was no correlation of mucin type with disease activity index in either ethnic group. The appearance of apparently normal mucin in patients with ulcerative colitis may be a useful marker for the identification of a subgroup at low risk of colorectal cancer.

Increased faecal mucin sulphatase activity in ulcerative colitis: a potential target for treatment

Colonic mucin is heavily sulphated and it has been shown that enzymatic desulphation by faecal bacterial sulphatases greatly increases its susceptibility to degradation by faecal glycosidases. A possible role for faecal mucin sulphatase in the pathogenesis of inflammatory bowel disease has therefore been explored. Faecal mucin sulphatase activity assayed using 35S mucin as substrate was increased in ulcerative colitis (median 80.2 units/g pellet weight (range 6.9-1063; 95% confidence intervals (CI): 45.2 to 293.8, n = 22) compared with 11.3 units/g (range 3.0-53.5; 95% CI: 8.7 to 29.8, n = 17) in healthy controls (p < 0.01), where one unit released 1000 dpm free sulphate/hour from 35S mucin (1680 dpm/microgram). Patients with active ulcerative colitis had higher sulphatase activity (median 146; 95% CI: 98 to 253 units/g, n = 10) than those with inactive ulcerative colitis (median 42.2; CI: 22.5 to 81.6 units/g, n = 12) (p < 0.05). Longitudinal studies in patients with ulcerative colitis show fluctuations of faecal mucin sulphatase activity corresponding to clinical disease activity in six of seven patients. Faecal mucin sulphatase activity was not significantly increased in Crohn's disease (median 36.6, range 5.7-106.6; 95% CI: 22.9 to 65.3 units/g, n = 14). The bismuth salts, bismuth subcitrate and bismuth subsalicylate were found to inhibit faecal mucin sulphatase activity at concentrations achievable therapeutically. The increased faecal mucin sulphatase activity in ulcerative colitis could be the result of greater intraluminal substrate (mucin) availability leading to bacterial enzyme induction, but would probably result in more rapid degradation of secreted mucin and represents a potential target for treatment.

Effect of nicotine on rectal mucus and mucosal eicosanoids

Because ulcerative colitis is largely a disease of non-smokers and nicotine may have a beneficial effect on the disease, the effect of nicotine on rectal mucosa in rabbits was examined. Nicotine was given subcutaneously by an Alzet mini-pump in doses of 0.5, 1.25, and 2 mg/kg/day for 14 days to three groups of eight animals and compared with eight controls. Mean (SD) serum nicotine concentrations (ng/ml) were 3.5 (1.1), 8.8 (2.3), and 16.2 (5.2) respectively in the treated groups. The thickness of adherent mucus on rectal mucosa in controls (median 36 microns) was significantly reduced by low dose (22 microns, p = 0.0011), and increased by high dose nicotine (48 microns, p = 0.035). Incorporation of radioactive glucosamine into papain resistant glycoconjugates was unchanged, indicating that mucin synthesis was unaltered. Prostaglandins (PG) were reduced, in some cases significantly (6-keto PGF1 alpha, PGF2 alpha, and hydroxy-eicosatetraenoic acid), by nicotine, which showed an inverse dose dependence--with greatest inhibition in relation to the lowest dose. Nicotine, and possibly smoking, may affect colitis by an action on mucosal eicosanoids and on adherent surface mucus secretion in the rectum and large bowel.

A glycosulphatase that removes sulphate from mucus glycoprotein

A novel glycosulphatase has been purified from a mucus glycopeptide-degrading Prevotella from the colon. The purified enzyme removed inorganic [35S]sulphate from 35S-labelled native rat gastric mucus glycoprotein. Desulphation of mucus glycoprotein was initially rapid (19% complete after 10 min) but then plateaued, reaching only 33% after 3 h. Crude periplasmic extracts could remove 79% of the radioactivity as inorganic sulphate. These results suggest that steric hindrance may limit the access of the purified glycosulphatase to the mucus glycoprotein oligosaccharide chains in the absence of glycosidases, and/or that the enzyme may have the wrong specificity for some of the remaining sulphated sugars in the chains. The apparent molecular mass of the enzyme was 111 kDa as judged from gel exclusion chromatography, and it appeared to be composed of two identical subunits. The enzyme was localized in the periplasm of the bacterium, and using pig gastric mucus glycopeptide as a growth substrate markedly increased enzyme levels. Enzymic activity increased at the end of the growth phase. The substrate specificity of the enzyme was tested against low-molecular-mass sulphated molecules. The monosaccharides glucose 6-sulphate and N-acetylglucosamine 6-sulphate were rapidly desulphated, the latter being the major sulphated sugar in some mucus glycoproteins. Lactose 6-sulphate, galactose 6-sulphate, sulphated steroids and unsaturated disaccharide sulphate breakdown products from chondroitin sulphate were not desulphated. Glycosulphatases which can remove sulphate from mucus glycoproteins may play an important role in the degradation of highly sulphated mucus glycoproteins in the digestive tract, and could modify the effectiveness of mucus glycoproteins in mucosal protection.

Hirschsprung's disease: clinical and experimental observations

Hirschsprung's disease (HD) is a relatively common cause of intestinal obstruction in the newborn. It is characterized by an absence of ganglion cells in the distal bowel beginning at the internal sphincter and extending proximally for varying distances. The etiology of HD-associated enterocolitis remains a complex issue. This study has provided further support for a possible infectious etiology of enterocolitis complicating HD.

Mucin degradation in the human colon: production of sialidase, sialate O-acetylesterase, N-acetylneuraminate lyase, arylesterase, and glycosulfatase activities by strains of fecal bacteria

Oligosaccharide side chains of human colonic mucins contain O-acetylated sialic acids and glycosulfate esters. Although these substituents are considered to protect the chains against degradation by bacterial glycosidases, sialate O-acetylesterase, N-acetylneuraminate lyase, and glycosulfatase activities have been found in fecal extracts. To better define the source of these activities, we measured extracellular and cell-bound sialidase, sialate O-acetylesterase, N-acetylneuraminate lyase, arylesterase, and glycosulfatase activities produced by 23 isolates of human fecal bacteria grown anaerobically in a hog gastric mucin culture medium; these represented dominant populations of fecal anaerobes, facultative anaerobes, and the subset of mucin oligosaccharide-degrading bacteria. Every strain produced sialidase and high levels of arylesterase, and all but five facultative anaerobes produced sialate O-acetylesterase. Sialic acids containing 2 mol or more of O-acetyl ester per mol of sialic acid were cleaved from mucin glycoproteins more slowly by sialidases of mucin oligosaccharide-degrading stains than were sialic acids containing 1 or 0 mol, and only N-acetyl- and mono-O-acetylated sialic acids were recovered from enzyme digests of a mucin containing di-O-acetylated sialic acids. No detectable N-acetylneuraminate lyase activity was produced by any strain, but low activity was induced by increasing the glycoprotein-bound sialic acid concentration in the culture medium of six Escherichia coli strains. Using lactitol-6-sulfate as a substrate, we found weak glycosulfatase activity in the partially purified, concentrated enzyme mixture in the culture supernatants of four mucin oligosaccharide-degrading strains but in none of the unconcentrated culture fractions. We conclude that the presence of two or more O-acetyl groups on sialic acids inhibits enteric bacterial sialidases but that production of sialate O-acetylesterases by several populations of enteric bacteria lessens the likelihood that mucin oligosaccharide chains terminating in O-acetylated sialic acids are protected from degradation. Sialate O-acetylesterases have a role in bacterial degradation of mucin glycoproteins in the human colon.

Acidification of the colonic mucins following polyvalent colonization of the germ-free rat

Colonic mucins of germ-free (GF) and conventional rats (CV) were compared. After isolation by gel filtration on Sepharose CL-4B and purification by density gradient centrifugation, the content of isolated colonic mucins was estimated by determination of PAS positive carbohydrates. Purified mucins were subjected to carbohydrate and amino acid analysis and separated into mucin subclasses by ion exchange chromatography. While the total amount of colonic mucins was not statistically different in GF and CV animals, analysis of carbohydrate composition demonstrated an increased amount of sialic acid in CV rat mucin. This was in accordance with results of ion exchange chromatography, revealing a significant higher amount of negative charged mucin subclasses in CV mucin, compared to the germ-free counterpart. The results of amino acid analysis were similar in both groups. The compositional differences in carbohydrate moieties are attributed to modulations by the intestinal flora. A selective bacterial degradation of the neutral mucin subclasses and modifications in the mucin composition due to a stimulated synthesis are discussed.

Ion exchange chromatography of purified colonic mucus glycoproteins in inflammatory bowel disease: absence of a selective subclass defect

Previous reports of a selective mucin subclass defect in ulcerative colitis have been reassessed using high performance chromatography (Superose 6 and Mono Q) for mucin purification and fractionation coupled with analysis of the fractions obtained using a combination of enzyme linked lectin and mucin antibody assays. Mucin samples purified from snap frozen rectal biopsy specimens obtained from patients with ulcerative colitis (n = 12), Crohn's disease (n = 5), and non-inflammatory bowel disease control subjects (n = 9) were subject to ion exchange chromatography using a continuous 0-0.35 mol/l NaCl salt gradient with a final 2.5 mol/l NaCl step. In all samples the major proportion (mean (SD) 86.7 (8.9)%) of the mucin detectable by wheat germ agglutinin binding eluted between 0.15 and 0.35 mol/l NaCl with no significant difference in elution profile between ulcerative colitis and control subjects. Significant elution of glycoprotein at less than 0.15 mol/l NaCl did occur, however, when a lower molecular weight mucin containing fraction which contained concanavalin A positive (glucose or mannose containing) material was analysed similarly. Similar ion exchange profiles were obtained when (3H)N-acetylglucosamine labelled mucins were studied after tissue culture of rectal biopsy specimens. No significant alteration in the ion exchange profile of purified mucins in ulcerative colitis has been shown in these studies. It is possible that the previously reported relative depletion of mucin subclass IV (eluting with 0.20 mol/l NaCl) may simply have reflected mucin depletion.

Colonic glycoproteins in monozygotic twins with inflammatory bowel disease

Colonic glycoprotein composition was evaluated in monozygotic twins with inflammatory bowel disease using ion-exchange chromatography. Fifty-three individuals, 12 pairs and 1 single twin with ulcerative colitis and 14 pairs with Crohn's disease, were evaluated. Seven twin pairs were concordant for the presence of ulcerative colitis or Crohn's disease, whereas twin siblings of 10 ulcerative colitis probands and 9 Crohn's disease probands were not known to have inflammatory bowel disease. Content of one chromatographically defined component of colonic mucin, designated HCM species IV, was reduced in both patients with ulcerative colitis (1040 +/- 300 cpm/10,000 cpm total HCM) and their apparently healthy twins (1340 +/- 540 cpm/10,000 cpm total HCM) compared with control subjects (4030 +/- 1,000 cpm/10,000 cpm total HCM). Composition of mucin in Crohn's disease patients and their nonaffected twins was not significantly different than in controls. These observations suggest that altered profiles of mucin glycoprotein may be present before the onset of ulcerative colitis and may be genetically defined. Conversely, it appears that alterations in glycoproteins only are not sufficient to initiate mucosal inflammation.

Impaired sulphation of phenol by the colonic mucosa in quiescent and active ulcerative colitis

Substantial amounts of phenols are produced in the human colon by bacterial fermentation of protein. In the colonic mucosa of animals, phenols are inactivated predominantly by conjugation with sulphate. The purpose of this study was to confirm sulphation of phenols by isolated colonocytes from man and to evaluate mucosal sulphation in inflammatory bowel disease using the phenol, paracetamol, in rectal dialysis bags. The incubation of paracetamol with colonocytes isolated from resected colon specimens (n = 7) yielded a mean (SE) value of 7.0 (0.9) mumols/g dry weight of paracetamol sulphate after 60 minutes but virtually undetectable values of paracetamol glucuronide. Paracetamol sulphate was detected in rectal dialysates from all control subjects, with a mean (SE) value of 4.2 (0.8) nmol/hour. Sulphation was significantly impaired (p less than 0.01) in 19 patients with active ulcerative colitis (0.6 (0.2) nmol/hour) and in 17 patients with ulcerative colitis in remission (1.1 (0.4) nmol/hour). Sulphation in eight patients with Crohn's colitis (4.3 (2.1) nmol/hour) was similar to that in control subjects. Impairment of the capacity of the mucosa to sulphate phenols in quiescent and active ulcerative colitis may pose a metabolic burden on colonic epithelial cells, which are continuously exposed to endogenous phenols from the colonic lumen.

Rectal bismuth subsalicylate as therapy for ulcerative colitis

In a prospective open study, 15 patients with ulcerative colitis which was unresponsive to conventional therapy were treated with enemas containing bismuth subsalicylate (700 or 800 mg b.d.). Nine out of the 15 patients showed a significant clinical response, and 6 had gone into complete clinical remission after 8 weeks treatment. Sigmoidoscopoic appearances of the rectal mucosa showed improvement in 9 out of 15 patients at 2 weeks, and 11 out of 15 at 8 weeks. The mucosa appeared sigmoidoscopically normal in 6 out of 15 at 8 weeks. It proved possible to reduce the oral prednisolone dosage from a median of 15 mg/day (range 10 to 35 mg/day) to 6 mg/day (range 0 to 18 mg/day) after 8 weeks of treatment; 5 patients were no longer taking oral steroids at this time. Rectal bismuth subsalicylate appears likely to be an effective therapy in ulcerative colitis and controlled trials are now required.

Influence of mucin on glycosidase, protease and arylamidase activities of human gut bacteria grown in a 3-stage continuous culture system

Human intestinal bacteria were grown in a 3-stage continuous culture system on a medium containing complex polysaccharides and proteins as carbon and nitrogen sources. Selected bacterial populations were enumerated and glycosidase, protease and arylamidase activities measured. Comparison of arylamidase and glycosidase activities in the multichamber system (MCS) and faeces showed that the predominant faecal enzymes were also produced by bacteria growing in the MCS. After 48 d operation, porcine gastric mucin (5.8 g/d) was independently fed to vessel 1. Elevated levels of volatile fatty acid (VFA) formation showed that the glycoprotein was actively fermented. The increase in carbohydrate availability as a result of breakdown of the mucin oligosaccharides stimulated bacterial growth and activities. The enzymological measurements showed that mucin increased production of both cell-bound and extracellular glycosidases, such as beta-galactosidase, alpha-glucosidase and N-acetyl-beta-glucosaminidase. Protease activities were profoundly influenced by mucin. These were largely cell-bound in non-mucin cultures but were predominantly extracellular and collagenolytic when mucin was present. Experiments with protease inhibitors showed that cysteine proteases were the major cell-bound and extracellular enzymes in both mucin and non-mucin cultures, but that serine and metalloproteases were also present. The effect of mucin on arylamidase formation was less marked, although there was increased production of these enzymes in vessels 1 and 2 of the MCS. These results suggest that host-produced substances such as mucin glycoprotein may play a role in modulating the growth and activity of bacteria growing in the human large intestine.

Distribution of mucins in the mucosa of the digestive tract of reptiles: a histochemical study

In the present study, the distribution and characteristics of mucins in the digestive tract of 3 reptiles (Lacerta lepida, Mauremys caspica and Testudo graeca) are investigated. In the esophagus of Testudo graeca, both the glands and the mucous cells of the surface epithelium contained sulphosialo-mucins. In Lacerta lepida, esophageal mucous cells contained either-sialo-mucins or sulphosialo-mucins. The esophageal mucous cells of Mauremys caspica contained acidic mucosubstances. The stomach of the species studied revealed a small amount of acidic mucosubstances; in Lacerta lepida and Testudo graeca, abundant neutral mucins were detected. In the intestine, the amount of acidic mucosubstances was increased in a caudal direction, the sulphosialo-mucins being predominant. In conclusion, acid mucins were more abundant in the esophagus and intestine than in the stomach. This may be related to cytoprotective roles in the esophagus and protection against potential pathogens in the intestine.

Altered lectin binding by colonic epithelial glycoconjugates in ulcerative colitis and Crohn's disease

Evidence is accumulating that colonic mucin glycoconjugates are altered in ulcerative colitis. In order to investigate this further, the lectin-binding properties of rectal glycoconjugates have been studied in ulcerative colitis, Crohn's disease, and controls using lectin-peroxidase histochemistry. Ten lectins were used including peanut agglutinin (PNA) which is known to bind to malignant and adenomatous but not normal colonic mucins. Eight of 21 ulcerative colitis rectal biopsies and 10 of 17 Crohn's disease rectal biopsies showed PNA positivity, particularly in the supranuclear region of surface epithelial cells. There was no correlation between PNA positivity and duration of disease or inflammation, and none of the biopsies showed evidence of dysplasia. This abnormality in epithelial cell glycoconjugates seems to be commonly present in nondysplastic mucosa and occurs in both ulcerative colitis and Crohn's disease. It may reflect a fundamental abnormality in mucus glycoprotein synthesis in inflammatory bowel disease.

What sequence of pathogenetic events leads to acute ulcerative colitis?

The etiology of ulcerative colitis remains unresolved despite new immunologic, biochemical, and microbiologic observations made in this disease. A sequence of pathogenetic events has been adduced from abnormalities reported from human and experimental colitis with the express purpose of establishing priority of factors that may lead to an attack of acute ulcerative colitis. The presence of undefined bacterial metabolites in the colonic lumen causing specific breakdown of fatty acid oxidation in colonic epithelial cells is proposed to be the initiating event of the disease process that leads to an immune response and eicosanoid response perpetuating epithelial cell damage. The proposals embody the thesis that primary metabolic damage to colonocytes determines the clinical and pathologic manifestations of ulcerative colitis.

Basis of sialic acid heterogeneity in ulcerative colitis

To test the suggestion that an inherited defect in colonic mucus rendering it susceptible to degradation by bacterial enzymes may be an important factor in the aetiology of ulcerative colitis, 650 colonoscopic and rectal biopsy specimens from 166 patients with colitis were stained by mild periodic acid Schiff (mPAS), which shows sialic acid that is deficient in O-acetyl substituents. There was an excess of mPAS positive sialic acid in patients with chronic ulcerative colitis, but the increased expression was patchy and coincided with a morphological change in the form of epithelial hyperplasia (metaplasia). Hyperplasia was more common in the rectum and in women and was associated with, and presumably secondary to, active inflammation. It is concluded that variation in the structure of sialic acid is acquired and is therefore unlikely to be implicated in the aetiology of ulcerative colitis.

Natural history and pathophysiology of enterocolitis in the piebald lethal mouse model of Hirschsprung's disease

A breeding colony of piebald lethal mice was established in order to study the natural history of congenital megacolon in a mouse model of Hirschsprung's disease and to investigate mucosal defense mechanisms and secretory functions in enterocolitis complicating congenital megacolon. In experiment 1, 214 mice were studied, 53 of which had congenital megacolon. All piebald lethal mice with congenital megacolon (S1/S1) died at 3 to 11 weeks of age. Two distinct patterns of mortality were identified. A majority of mice (64%) became acutely ill at 3 to 4 weeks of age and died, whereas the remainder died between 9 and 11 weeks of age. The former group of mice exhibited clinical and histologic evidence of severe enterocolitis while the latter group had massive abdominal distension and classical megacolon. In experiment 2, piebald mice with congenital megacolon were killed at the time of acute illness. Significant histologic and immunohistochemical differences were seen in the ganglionic colon between piebald mice with early clinical onset of acute illness and piebald mice with the classical clinical picture of congenital megacolon. In the former group of mice the number of immunocytes in the lamina propria was significantly higher than in control mice (P less than .001), immunoglobulin-producing cells were equally distributed throughout the lamina propria and IgA-containing cells were by far the most abundant cell type identified in the colon. In the latter group of mice, immunocyte responses were significantly low and the distribution of immunocytes markedly different, with the immunoglobulin-producing cells being located only at the deep layer of lamina propria.(ABSTRACT TRUNCATED AT 250 WORDS)

A histochemical study of the mucins in the digestive tract of the chicken

Little is known about the distribution of glycoproteins in the digestive tube of birds. In the present study, the localization and distribution of mucins in the digestive tract of the chicken are reported. Sialo- and sulpho-mucins were widely distributed throughout the chicken digestive tube. Some of the mucous cells of the proximal segment of the proventriculus presented neutral glycoproteins; in the medial segment, surface cells containing only sialo-mucins were observed. Surface cells of the gizzard contained both sialo- and sulpho-mucins while PAS-positive material was localized in the lumen of the glands. 2 types of mucous cells were observed in the small intestine; 1 type contained only sialo-mucins and the other contained both sialo- and sulpho-mucins. In the large intestine and caecum, both types of acid mucins were present in the mucous cells. In conclusion, the distribution of glycoproteins in the chicken reported in the present study show marked differences with that reported in other avian species.