Significant enhancement of esophageal pre-epithelial defense by tegaserod: implications for an esophagoprotective effect

The Mucoadhesive Nanoparticle-Based Delivery System in the Development of Mucosal Vaccines

Mucosal tissue constitutes the largest interface between the body and the external environment, regulating the entry of pathogens, particles, and molecules. Mucosal immunization is the most effective way to trigger a protective mucosal immune response. However, the majority of the currently licensed vaccines are recommended to be administered by intramuscular injection, which has obvious shortcomings, such as high production costs, low patient compliance, and lack of mucosal immune response. Strategies for eliciting mucosal and systemic immune responses are being developed, including appropriate vaccine adjuvant, delivery system, and bacterial or viral vectors. Biodegradable mucoadhesive nanoparticles (NPs) are the most promising candidate for vaccine delivery systems due to their inherent immune adjuvant property and the ability to protect the antigen from degradation, sustain the release of loaded antigen, and increase the residence time of antigen at the administration site. The current review outlined the complex structure of mucosa, the mechanism of interaction between NPs and mucosa, factors affecting the mucoadhesion of NPs, and the application of the delivery system based on mucoadhesive NPs in the field of vaccines. Moreover, this review demonstrated that the biodegradable and mucoadhesive NP-based delivery system has the potential for mucosal administration of vaccines.

The esophageal mucosal barrier in health and disease: mucosal pathophysiology and protective mechanisms

Diseases of the esophagus, such as gastroesophageal reflux (GER), can result in changes to mucosal integrity, neurological function, and the microbiome. Although poorly understood, both age and GER can lead to changes to the enteric nervous system. In addition, the esophagus has a distinct microbiome that can be altered in GER. Mucosal integrity is also at risk due to persistent damage from acid. Diagnostic tools, such as ambulatory pH/impedance testing and esophageal mucosal impedance, can assess short-term and longitudinal GER burden, which can also assess the risk for mucosal compromise. The quality of the mucosal barrier is determined by its intercellular spaces, tight junctions, and tight junction proteins, which are represented by claudins, occludins, and adhesion molecules. Fortunately, there are protective factors for mucosal integrity that are secreted by the esophageal submucosal mucous glands and within saliva that are augmented by mastication. These protective factors have potential as therapeutic targets for GER. In this article, we aim to review diagnostic tools used to predict mucosal integrity, aging, and microbiome changes to the esophagus and esophageal mucosal defense mechanisms.

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 immunophenotypic relationship between the submucosal gland unit, columnar metaplasia and squamous islands in the columnar-lined oesophagus

AIMS

To characterize the immunophenotypic relationship between the squamous and the glandular compartments in the oesophagus of patients with columnar-lined oesophagus (CLO).

METHODS AND RESULTS

Eight tissue blocks from three oesophageal resection specimens from patients who underwent oesophagectomy for adenocarcinoma of the oesophagus were selected for immunohistochemical analysis. The markers of intestinal differentiation [CK20, CDX2 and MUC2] were all expressed in the expected pattern, solely in the glandular compartment of the resection specimens. CK4, CK17 and lysozyme were expressed in both the glandular and the squamous compartments. In addition, CK17 expression was found on both the squamous and glandular margins of the squamocolumnar transformation zones and in the submucosal gland (SMG) intraglandular and excretory ducts.

CONCLUSIONS

There is an immunophenotypic relationship between the squamous and the glandular compartments of the CLO, with expression of lysozyme, CK4 and CK17 in both squamous and columnar cells. These overlapping immunophenotypes indicate similar differentiation paths, and link the SMG unit with the columnar metaplasia and the neosquamous islands in CLO. Our findings support the theory of a cellular origin of CLO and neosquamous islands from the SMG unit.

Medical treatments of GERD: the old and new

The mainstay of pharmacological therapy for GERD is gastric acid suppression with proton pump inhibitors (PPIs), which are superior to histamine-2 receptor antagonists for healing erosive esophagitis and achieving symptomatic relief. However, up to one-third of patients may not respond to PPI therapy, creating the need for alternative treatments. Potential approaches include transient lower esophageal sphincter relaxation inhibitors, augmentation esophageal defense mechanisms by improving esophageal clearance or enhancing epithelial repair, and modulation of sensory pathways responsible for GERD symptoms. This review discusses the effectiveness of acid suppression and the data on alternative pharmacological approaches for the treatment of GERD.

Novel therapeutics for gastro-esophageal reflux symptoms

Approximately 20-30% of patients with gastro-esophageal reflux symptoms report inadequate symptom relief while on proton-pump inhibitor therapy. The mechanisms involved are failure of the antireflux barrier (transient lower esophageal sphincter relaxations), high proximal extent of the refluxate, esophageal hypersensitivity and impaired mucosal integrity. Persisting acid or nonacid reflux can be demonstrated in 40-50% of cases, suggesting that there is room for antireflux therapy in these patients. New antireflux compounds have been shown to decrease the occurrence of transient lower esophageal sphincter relaxations. The most promising classes of compounds are GABA type B agonists and metabotropic glutamate receptor 5 antagonists, which can reduce both reflux episodes and symptoms, but the development of these compounds has been abandoned for either safety issues or lack of efficacy. Esophageal hypersensitivity and impaired mucosal integrity may prove to be relevant therapeutic targets in the future.

New pharmacologic approaches in gastroesophageal reflux disease

This article highlights current and emerging pharmacological treatments for gastroesophageal reflux disease (GERD), opportunities for improving medical treatment, the extent to which improvements may be achieved with current therapy, and where new therapies may be required. These issues are discussed in the context of current thinking on the pathogenesis of GERD and its various manifestations and on the pharmacologic basis of current treatments.

Medical treatment of GORD. Emerging therapeutic targets and concepts

Approximately 20-30% of patients with gastro-oesophageal reflux symptoms report inadequate symptom relief while on PPI therapy. Persisting acid or non-acid reflux can be demonstrated in 40-50% of them suggesting that there is room for anti-reflux therapy in these patients. New anti-reflux compounds aim at decreasing the occurrence of transient lower oesophageal sphincter relaxations (TLOSRs) which represent the main mechanism of all types of reflux. The most promising classes of compounds are GABA(B) agonists and mGluR5 antagonists which have been shown to reduce both reflux episodes and symptoms and are currently under evaluation in phase II and III clinical trials. Compounds that target TLOSR activity represent a promising new therapeutic option for patients who suffer from GORD symptoms. These drugs will probably be developed as add-on therapy in combination with PPIs provided the tolerability and safety issues are resolved.

New pharmacologic approaches in gastroesophageal reflux disease

This article highlights current and emerging pharmacological treatments for gastroesophageal reflux disease (GERD), opportunities for improving medical treatment, the extent to which improvements may be achieved with current therapy, and where new therapies may be required. These issues are discussed in the context of current thinking on the pathogenesis of GERD and its various manifestations and on the pharmacologic basis of current treatments.

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.

Intestinal hormones and growth factors: effects on the small intestine

There are various hormones and growth factors which may modify the intestinal absorption of nutrients, and which might thereby be useful in a therapeutic setting, such as in persons with short bowel syndrome. In part I, we focus first on insulin-like growth factors, epidermal and transferring growth factors, thyroid hormones and glucocorticosteroids. Part II will detail the effects of glucagon-like peptide (GLP)-2 on intestinal absorption and adaptation, and the potential for an additive effect of GLP2 plus steroids.

The effect of tegaserod on esophageal submucosal glands bicarbonate and mucin secretion

Tegaserod, a 5-HT4 partial agonist, was shown to reduce esophageal acid exposure in patients with gastroesophageal reflux disease; however, its mechanism of action is poorly understood. Therefore, we have examined the effect of tegaserod on luminal bicarbonate and mucin secretion in the isolated perfused pig esophagus. We also studied its role in esophageal protection using SMG-bearing pig esophagus in comparison to the rabbit esophagus, which is devoid of them. The tissues were mounted in Ussing chambers, and acid injury was replicated by exposing the lumen to acid (pH 1.6) or acid/pepsin (pH 2.5). In pig esophagus, tegaserod increased bicarbonate secretion, but had no effect on basal mucin secretion. In Ussing chambers, tegaserod reduced injury to pig, but not rabbit esophagus exposed to acid (pH 2.5) plus pepsin. These results indicate that tegaserod stimulates SMG bicarbonate secretion, an effect that likely accounts for the observed protection against acid-pepsin injury to pig, but not rabbit, esophagus.