What is the secretory potential of submucosal mucous glands within the human gullet in health and disease?

Chronic fibrosing esophagitis with diffuse esophageal intramural pseudo‐diverticulosis

Diffuse esophageal intramural pseudo‐diverticulosis (DEIPD) is a chronic fibrosing inflammation of the esophagus of unknown origin. Its name derives from the characteristic pseudo‐diverticula formed by dilated ducts of submucosal glands. With an assumed prevalence of approximately 5–50/100 000, DEIPD is more frequent than previously estimated. It preferentially affects men between 50 and 70 years of age with a history of alcohol and tobacco abuse. Key symptoms are chronic dysphagia and food impactions. Typical endoscopic findings are multiple small, longitudinally aligned pseudo‐diverticle openings and trachealization of the esophagus. Additionally, the usually gray mucosa may show a fine‐grained pattern of very small red dots that merge into a pink tint, called “faux uni pattern.” Once established, clinical symptoms and endoscopic changes persist throughout life. Although there is no known causal therapy, complications like bolus impactions, candida infections, or reflux can and should be treated.

Mucin Secretion in Cystic Fibrosis: A Systematic Review

BACKGROUND

Mucus protects the epithelium against invaders and toxic materials. Sticky and thick mucus is characteristic of CF.

OBJECTIVE

The aim of this systematic review is to characterize the specific mucins secreted in the lung and intestinal tract of CF patients.

METHODS

A systematic literature search was conducted up to December 31, 2019. The following terms were used: "cystic fibrosis" AND "mucin." Case-control studies comparing mucin expression in CF patients to healthy controls were included.

RESULTS

We found 741 eligible studies, 694 studies were rejected because they were performed in animals and not in full text, and 32 studies were excluded being editorials, duplications, review articles, meta-analysis, or not in English. Fifteen studies were eligible for our study, including 150 CF patients compared to 82 healthy controls, all fulfilled the inclusion criteria. The main mucin types expressed in the sinus submucosal glands, sputum, tracheobronchial surface epithelium, and lung submucosal glands were MUC5AC and MUC5B. Increase in the number of sinusoidal submucosal glands and expression of MUC5B was found in CF patients, but no such difference from healthy controls was found for the number of goblet cells in the surface epithelium nor in the expression of -MUC5AC. The opposite was found in the tracheobronchial surface epithelium and in the lungs.

CONCLUSIONS

Increased expression of MUC5AC in the surface epithelium and of MUC5B in the subepithelial glands may be the result of higher secretion rate of mucin into the lumen of the respiratory tract, causing mucus plaque, infection, and inflammation.

Clinical and endoscopic characteristics of diffuse esophageal intramural pseudo-diverticulosis

INTRODUCTION

With 250 published cases worldwide, diffuse esophageal intramural pseudo-diverticulosis (DEIPD) is a poorly understood disease. The aim of this study was to determine the prevalence of DEIPD in our own population, identify risk factors and clinical symptoms, and characterize its typical endoscopic signs.

METHODS

Retrospective search in our center's endoscopic and clinical database. Reviewing of all cases by re-examining stored endoscopic photographs. Reviewing of all cases regarding age, sex, risk factors, comorbidities, histology, and clinical symptoms.

RESULTS

In a population of 150.000 we found 21 cases of DEIPD. Mean age was 56 ± 10 years. 86% were males, 76% had alcohol abuse, 57% had nicotine abuse, 38% had arteriosclerosis, 33% had COPD, 29% had malignancies, 24% had liver cirrhosis, 19% had impaired kidney function, and 15% had diabetes. Dysphagia was present in 62% and food bolus impaction (single or repeated) in 48%. Endoscopically, 95% of patients had multiple (> 4), small (0.25-2.5 mm) pseudodiverticle openings in the esophageal wall. In 62%, openings were aligned longitudinally. 86% showed edematous swelling of mucosa ("frosted glass look"), 76% showed a fine-grained pattern of small (10-100 µm) red dots ("faux uni pattern"), and 76% had a rigid, narrow lumen with multiple rings ("trachealization").

CONCLUSION

With a prevalence of approximately 5 to 50/100.000, DEIPD may be more frequent than previously estimated. It preferably affects middle-aged male alcoholics. Key symptoms are chronic dysphagia and food impaction. Typical endoscopic findings are multiple, small, longitudinally aligned pseudodiverticle openings, frosted glass look, faux uni pattern, and trachealization of the esophagus.

Mucin Expression in the Esophageal Malignant and Pre-malignant States: A Systematic Review and Meta-analysis

BACKGROUND

Mucins are heavily glycosylated glycoproteins, synthesized by mucosal surfaces and have an important role in healthy state and malignant diseases. Change in mucins synthesis or secretion may be primary event or secondary to inflammation or carcinogenesis.

AIM

The aim of this study is to assess the current knowledge about mucin expression in esophageal lesions, and to establish a role for different mucin expressions as prognostic markers.

METHOD

English Medical literature searches were conducted for "mucin" and "esophagus." Observational studies were included. Meta-analysis was performed using comprehensive meta-analysis software. Pooled odds ratios (OR) and 95% confidence intervals (CI) were calculated.

RESULTS

In the random-effect model, mucin expression was significantly higher in esophageal lesions than in normal esophageal mucosa with OR=5.456 (95% CI, 1.883-15.807, P=0.002). Measure of heterogeneity, demonstrated in the included studies, was high: Q=287.501, df (Q)=44.00, P<0.0001, I=84.696%. There is a gradient of mucin expression and complexity in esophageal premalignant to malignant lesions, lower in Barrett's mucosa with low grade dysplasia (LGD), increased in high grade dysplasia (HGD), and highest in esophageal adenocarcinoma (EAC). MUC2, MUC3, MUC5AC, and MUC6 expression was higher in EAC than HGD, and higher in HGD than in LGD mucosa. The opposite was found for MUC1 and MUC4.

CONCLUSION

Increased expression of certain mucin genes in esophageal mucosa may be further studied as a potential diagnostic tool, and this may add important information in the surveillance of Barrett's esophagus.

Does the healing of the esophageal mucosa improve the function of the esophageal submucosal and salivary glands?

The esophageal pre-epithelial barrier encompasses components of secretions from both the esophageal submucosal and salivary glands. We demonstrated, in patients with reflux esophagitis (RE), significantly diminished luminal release of esophageal epidermal growth factor (EGF). The rate of luminal release of esophageal prostaglandin E₂ (PGE₂ ) was significantly higher compared with controls and significantly declined after healing of RE. Patients with RE also exhibited significant declines in esophageal mucin secretion; however, after healing of RE with rabeprazole, this rate increased significantly. The rate of salivary EGF and bicarbonate secretion in patients with RE was significantly lower than in controls. We have demonstrated that mastication of tasteless parafilm, which could be substituted with sugarless chewing gum in the clinical scenario, resulted in profound and significant increases in the rate of secretion of salivary protective factors, such as bicarbonate, mucin, protein, EGF, and PGE₂ , in patients with RE. Our data clearly indicate that there is a relationship between the form or the structure of the esophageal mucosa and the secretory function of not only the esophageal submucosal glands but also the salivary glands. Application of masticatory stimulation in a clinical scenario may also have some therapeutic potential.

The role of mucin in GERD and its complications

Acid, pepsin and other noxious material reach the esophageal mucosa and interact with the luminal aspect of the squamous epithelium. The first protective barrier to these potentially injurious substances is the mucus buffer layer that covers the mucosa. In healthy people, the esophagus has a protective surface adherent mucus gel barrier. Levels of mucin glycoprotein are considerably increased in response to acid and pepsin. A wide spectrum of mucin genes are expressed in normal esophageal mucosa, squamous cell carcinoma of the esophagus, Barrett epithelium and esophageal adenocarcinoma. The mucins MUC5AC and MUC6 are expressed to a similar degree in Barrett metaplasia and gastric mucosa, as is MUC2 in Barrett intestinal metaplasia and small bowel mucosa. Increased expression of MUC1 is associated with progression from dysplasia to adenocarcinoma of the esophagus. Thus, mucins have an important role in the defense of esophageal mucosa against the acid, pepsin and bile that are present in the refluxate. Changes in the expression of mucins occur in patients with GERD, and might lead to the development of new drugs.

Significant increase of esophageal mucin secretion in patients with reflux esophagitis after healing with rabeprazole: its esophagoprotective potential

Esophageal mucin secretion in patients with reflux esophagitis (RE) is significantly impaired. Rabeprazole augments gastric mucin secretion. We have studied, therefore, the effect of rabeprazole on esophageal mucin secretion in patients with RE. The study was conducted in 15 patients with RE treated with rabeprazole (20 mg QD) for 8 weeks. Esophageal secretions were collected during consecutive infusions of initial NaCl, HCl/Pepsin (HCl/P), and a final NaCl, using a specially designed esophageal catheter, before and after therapy. Mucin was measured using standard methodology. After rabeprazole administration esophageal mucin concentration as well as secretion increased during perfusion with initial saline (P < 0.01), HCl/P (P < 0.02), and concluding saline (P < 0.001). Stimulation of esophageal mucin secretion by rabeprazole may indicate that the mechanisms governing its secretion are similar to those implicated in gastric mucin output. Enhancement of esophageal mucin secretion by rabeprazole may translate into esophagoprotective potential in patients with reflux esophagitis.

Protection of the gastrointestinal tract epithelium against damage from low pH beverages

Extensive consumption of low pH beverages such as citrus juices (pHs 2.3 to 4.3), alcoholic beverages (pHs 2.7 to 4.5), and soft drinks (pHs 2.3 to 4.2) has raised the question of whether exposure of the gastrointestinal (GI) tract to acidic beverages will cause damage to the epithelial lining. To evaluate the potential effects of low pH beverages on the GI tract epithelium, a detailed examination of the literature was undertaken. In some animal models, there is evidence of damage to GI epithelial cells following exposure to low pH beverages; however, in these studies there is no definitive relationship between acidity and the amount or severity of damage. Results from several other studies, conducted in both animals and humans, indicate a lack of adverse effects on epithelial cells. Furthermore, there is no evidence that damage is irreversible. Permanent damage from routine exposure to acidic beverages in humans would not be expected because of repair mechanisms that are available to maintain a healthy epithelium. Additionally, numerous physical, chemical, and biological mechanisms are in place to prevent damage to the epithelial cells. Finally, the safe history of consumption of low pH beverages, including various fruit juices, supports the conclusion that low pH beverage ingestion does not cause damage to the GI epithelium.

Oral manifestations in patients with gastro-oesophageal reflux disease: a single-center case-control study

OBJECTIVE

To assess the occurrence of oral pathological changes and symptoms in patients affected by gastro-oesophageal reflux disease (GERD).

PATIENTS AND METHODS

200 patients with GERD and 100 matched healthy controls were studied. Thorough visual examination of the dental and oral mucosal tissues was performed and medical history relevant to oral symptoms was collected. The primary outcome was defined as a statistically significant difference, between the study group and controls, in the presence of the following indicators: soft/hard palate and uvula erythema, tooth wear, xerostomia, oral acid/burning sensation, subjective halitosis and dental sensitivity. Statistical analysis included chi-squared test, and crude odds ratio with 95% CI.

RESULTS

Univariate analysis showed that xerostomia, oral acid/burning sensation, subjective halitosis, and soft and hard palate mucosa and uvula erythema were more common in patients with GERD than matched controls (P < 0.05).

CONCLUSIONS

This study failed to find any significant association between GERD and dental erosions, whereas some symptoms and other objective oral mucosal changes were found to be significantly associated with GERD.

Expression of proteinase-activated receptor 2 on human primary gastrointestinal myofibroblasts and stimulation of prostaglandin synthesis

It is known that subepithelial myofibroblast-derived prostaglandin (PG)E2 can regulate intestinal epithelial cell functions, and that proteinase-activated receptor-2 (PAR2) is abundantly expressed in the gastrointestinal tract. Since PAR2 activation has previously been associated with stimulation of PGE2 synthesis, we hypothesized that PAR2 expressed on primary human gastrointestinal myofibroblasts regulates PGE2 synthesis via cyclooxygenase (COX)-1 and (or) COX-2, and associated PGE synthases. Primary human myofibroblasts were isolated from the resection tissue of the esophagus, small intestine, and colon. Expression of functional PAR2 was determined by RT-PCR and by calcium mobilization in Fura-2/AM-loaded cells. Trypsin and the selective PAR2-activating peptide (PAR2-AP) SLIGRL-NH2 stimulated PGE2 synthesis in a concentration-dependent manner, as measured by enzyme immunoassay. Selective COX inhibition showed PAR2-induced PGE2 synthesis to be COX-1 dependent in esophageal myofibroblasts and both COX-1 and COX-2 dependent in colonic cells, consistent with the distribution of COX-1 and COX-2 expression. Although both cytosolic and microsomal PGE synthases were expressed in cells from all tissues, microsomal PGE synthases were expressed at highest levels in the colonic myofibroblasts. Activation of PAR2 on gastrointestinal myofibroblasts stimulates PGE2 synthesis via different pathways in the colon than in the esophagus and small intestine.

Esophageal mucin: an adherent mucus gel barrier is absent in the normal esophagus but present in columnar-lined Barrett's esophagus

OBJECTIVES

The presence of a protective adherent mucus gel barrier against gastric reflux in the healthy esophagus is uncertain. The aim was to characterize the surface mucin composition and determine the extent of any adherent mucus gel layer on the normal esophagus, and compare this with that in Barrett's esophagus.

METHODS

Isolated surface mucins were characterized by density centrifugation, gel filtration chromatography, and chemical composition. Adherent surface mucus was visualized in situ on unfixed and cryostat sections of mucosa and biopsies using a method that preserves mucus layer thickness.

RESULTS

There was a complete absence of adherent mucus gel layers on normal human, pig, and rat esophagi. This was in contrast to the thick adherent mucous layer (median thickness = 100-200 microm) seen on the corresponding gastric mucosa. Small quantities of glycoprotein with a composition characteristic of a secretory mucin were isolated from the pig esophagus surface. The mucin, density range between 1.44 and 1.48 g x ml(-1), contained 80% carbohydrate and was rich in serine, threonine, and proline. The mucin fragmented into smaller glycoprotein units on proteolysis and partially on reduction. Cryostat sections from columnar-lined esophageal biopsies had a substantial adherent surface mucous layer (median thickness = 90 microm, interquartile range = 84-94 microm) staining for neutral mucins (gastric-type epithelium) and acidic mucins (intestinal metaplasia).

CONCLUSIONS

A secretory mucin, with an analysis distinct from that of gastric or salivary mucin, is present in very small quantities on the esophageal mucosa and in amounts insufficient to form an adherent gel layer. It is unlikely that mucus has a role in protecting the normal esophagus against reflux. However, an adherent mucous layer was observed over columnar-lined esophagus, and this may protect against reflux.

Mechanisms of oesophageal mucosal defence

The integrity of the oesophageal mucosa depends upon an equilibrium between aggressive factors, predominantly acid and pepsin, and protective mechanisms. Protective mechanisms operate within the oesophageal mucosa as pre-epithelial, epithelial and post-epithelial defences. Only the protective components of the oesophageal pre-epithelial defence can be tested in vivo in humans. It has been recently demonstrated that human oesophageal submucosal glands elaborate mucous secretion rich in bicarbonate and non-bicarbonate buffers, mucin, prostaglandin E(2), epidermal growth factor (EGF) and transforming growth factor alpha (TGFalpha). This oesophageal secretion, accompanied by similarly protective factors within the swallowed saliva, defines the protective potential of the oesophageal pre-epithelial defence that exists in the form of a mucus-buffer layer covering the oesophageal mucosa and which retards the back-diffusion of hydrogen ions. It has also been demonstrated that patients with severe erosive reflux oesophagitis exhibit qualitative impairment in both the salivary and oesophageal components of the oesophageal pre-epithelial defence. Furthermore, patients with endoscopically negative gastro-oesophageal reflux disease have a significantly stronger oesophageal pre-epithelial defence than patients with erosive reflux oesophagitis. On the other hand, African-Americans, who are less likely to develop erosive reflux oesophagitis, have a stronger oesophageal pre-epithelial defence than do Caucasians. The salivary component of the oesophageal pre-epithelial defence can be enhanced by mastication and the administration of cisapride, whereas oesophageal secretion can only be significantly augmented by cisapride.