Aspirin renders the oesophageal mucosa more permeable to acid and pepsin

Effect of Low-Dose Aspirin on Chronic Acid Reflux Esophagitis in Rats

BACKGROUND

Clinical role of low-dose aspirin (LDA) in pathogenesis of gastroesophageal reflux disease is by far controversial. This can be attributed to the paucity of basic research detailing the mechanism of LDA-induced esophageal mucosal injury (EI) on underlying chronic acid reflux esophagitis (RE).

AIM

The aim of this study was to clarify the effect of LDA on chronic RE in rats.

METHODS

Esophagitis was induced in 8-week-old male Wistar rats by ligating the border between forestomach and glandular portion with a 2-0 silk tie and covering the duodenum with a small piece of 18-Fr Nélaton catheter. Seventy-eight chronic RE rat models were divided into five treatment groups, consisting of orally administered vehicle (controls), and aspirin doses of 2, 5, 50 or 100 mg/kg once daily for 28 days. EI was assessed by gross area of macroscopic mucosal injury, severity grade of esophagitis and microscopic depth of infiltration by inflammatory cells.

RESULTS

Area of esophagitis in animals with aspirin dose of 100 mg/kg/day showed a 36.5% increase compared with controls, although it failed to achieve statistical significance (p = 0.812). Additionally, the rate of severe EI was increased in animals with aspirin dose of 100 mg/kg/day as compared with controls (p < 0.05). The grade of severity correlated with the depth of inflammation (r _s = 0.492, p < 0.001).

CONCLUSIONS

Maximal dose aspirin (100 mg/kg/day) contributed in exacerbating preexisting EI. LDA (2 and 5 mg/kg/day), on the other hand, did not affect chronic RE in this model. LDA seems to be safe for use in patients with chronic RE.

A weakly acidic solution containing deoxycholic acid induces esophageal epithelial apoptosis and impairs integrity in an in vivo perfusion rabbit model

Impaired esophageal mucosal integrity may be an important contributor in the pathophysiology of gastroesophageal reflux disease (GERD). Nevertheless, the effect of potentially harmful agents on epithelial integrity is mainly evaluated in vitro for a short period of time and the possible induction of epithelial apoptosis has been neglected. Our objective was to assess the effect of an acidic and weakly acidic solution containing deoxycholic acid (DCA) on the esophageal epithelium in an in vivo rabbit model of esophageal perfusion and to evaluate the role of the epithelial apoptosis. The esophagus of 55 anesthetized rabbits was perfused for 30 min with different solutions at pH 7.2, pH 5.0, pH 1.0, and pH 5.0 containing 200 and 500 μM DCA. Thereafter, animals were euthanized immediately or at 24 or 48 h after the perfusion. Transepithelial electrical resistance, epithelial dilated intercellular spaces, and apoptosis were assessed in Ussing chambers, by transmission electron microscopy, and by TUNEL staining, respectively. No macroscopic or major microscopic alterations were observed after the esophageal perfusions. The acidic and weakly acidic solution containing DCA induced similar long-lasting functional impairment of the epithelial integrity but different ultrastructural morphological changes. Only the solution containing DCA induced epithelial apoptosis in vivo and in vitro in rabbit and human tissue. In contrast to acid, a weakly acidic solution containing DCA induces epithelial apoptosis and a long-lasting impaired mucosal integrity. The presence of apoptotic cells in the esophageal epithelium may be used as a marker of impaired integrity and/or bile reflux exposure.

Managing the adverse effects of nonsteroidal anti-inflammatory drugs

Conventional medical treatment for rheumatoid arthritis and osteoarthritis includes the use of NSAIDs (traditional and selective inhibitors of cyclooxygenase [COX]-2), because they provide unmistakable and significant health benefits in the treatment of pain and inflammation. However, they are associated with an increased risk of serious gastrointestinal (GI) and cardiovascular (CV) adverse events. Both beneficial and adverse effects are due to the same mechanism of action, which is inhibition of COX-dependent prostanoids. Since CV and GI risk are related to drug exposure, a reduction in the administered dose is recommended. However, this strategy will not eliminate the hazard owing to a possible contribution of individual genetic background. Further studies will be necessary to develop genetic and/or biochemical markers predictive of the CV and GI risk of NSAIDs.

Eosinophilic oesophagitis and other non-reflux inflammatory conditions of the oesophagus: diagnostic imaging and management

Non-reflux inflammatory conditions of the oesophagus are at present rarely encountered in routine clinical practice. However there has been a recent increase in their diagnosis notably due to heightened awareness of their existence and because of the emergence of a number of immunological diseases and deficiencies. Of all the non-reflux conditions, most interest and literature is emerging on the natural history, pathophysiology, endoscopic pattern and management of eosinophilic oesophagitis. This condition, which until five years ago was unknown to most physicians has now been studied worldwide and although the true prevalence remains unclear, the incidence is increasing annually. In this paper we discuss diagnostic imaging and management of non-reflux inflammatory disorders of the oesophagus with particular reference to eosinophilic oesophagitis and Crohn's disease, both conditions of probable over active immunology, to other conditions associated with immune deficiency such as infective oesophagitis (candida, CMV, HSV, HIV) and tuberculous oesophagitis, as well as drug induced oesophageal injury.

Laryngeal epithelial defenses against laryngopharyngeal reflux: investigations of E-cadherin, carbonic anhydrase isoenzyme III, and pepsin

OBJECTIVES

This is the third annual report of an international research network studying the cellular impact of laryngopharyngeal reflux (LPR) on laryngeal epithelium. The objective of this study was to investigate the presence of E-cadherin (epithelial cadherin; the intercellular junctional complex protein) in relation to the presence of (intracellular) pepsin and carbonic anhydrase isoenzyme III (CAIII).

METHODS

Fifty-four laryngeal biopsy specimens from 18 LPR patients were studied by immunohistochemistry and Western blotting for pepsin, E-cadherin, and CAIII. These data were compared to those from normal control subjects analyzed in another research study.

RESULTS

Intracellular pepsin was detected in LPR patients, but not in controls. E-cadherin expression was reduced in patients with LPR. Carbonic anhydrase III expression was not found in the vocal fold or in the majority of samples taken from the ventricle of LPR patients and was inversely associated with E-cadherin membranous expression.

CONCLUSIONS

The findings of depleted E-cadherin and CAIII and the presence of pepsin appear to correlate with LPR. The reduced protective response indicated by the reduced expression of CAIII may play an important role in the disruption of the intercellular barrier associated with the down-regulation of E-cadherin.

Characterisation of adherens and tight junctional molecules in normal animal larynx; determining a suitable model for studying molecular abnormalities in human laryngopharyngeal reflux

BACKGROUND

The disruption of intercellular junctions in the larynx is a pathological feature of laryngopharyngeal reflux (LPR). Good experimental models are necessary to gain greater insight into the molecular mechanisms and alterations that result from abnormal exposure of the laryngeal epithelium to acid refluxate.

AIMS

To characterise laryngeal tissues from different species to determine the most suitable for use in experimental studies of LPR.

METHODS

Human and non-human laryngeal tissues (mouse, rat, guinea pig, porcine, and rabbit) were studied. Histological characterisation was performed by light microscopy. The expression and subcellular localisation of adherens junctional molecules (E-cadherin and beta catenin) was evaluated by immunohistochemistry, and tight junction molecules (occludin and zonula occludens 1 (ZO-1)) by western blotting. The ultrastructural features of porcine and human tissue were assessed by electron microscopy.

RESULTS

Porcine tissue revealed both respiratory-type and stratified squamous epithelium, as seen in the human larynx. The expression and subcellular localisation of the E-cadherin-catenin complex was detected in all species except mouse and rat. The pattern of ZO-1 and occludin expression was preserved in all species.

CONCLUSION

The expression of intercellular junctional complexes in porcine epithelium is similar to that seen in humans. These results confirm the suitability of these species to study molecular mechanisms of LPR in an experimental system.

Recent advances in the treatment of GERD in the elderly: focus on proton pump inhibitors

The prevalence of gastroesophageal reflux disease (GERD) increases with age, and older people are more likely to develop severe disease. Studies of elderly patients with GERD indicate differences in presentation and diagnosis, compared with GERD in younger adults. Indeed, an older patient with GERD may present with atypical symptoms such as dysphagia, vomiting, weight loss, anaemia and anorexia, and less frequently with typical symptoms such as heartburn or acid regurgitation. These findings are attributed to pathophysiological changes in esophageal function that occur with age. Therefore, GERD in elderly patients is more likely to be poorly diagnosed or undiagnosed. Although few studies have concentrated specifically on elderly patients, the proton pump inhibitors (PPIs) have been shown to be more effective than histamine receptor antagonists for healing reflux esophagitis and for preventing its recurrence when they are given as maintenance therapy. In addition, the PPIs seem to be safe both in short- and in long-term therapy of elderly patients with GERD.

Functional oesophageal epithelial defense against acid

Functional oesophageal epithelial defense, including cell proliferation, restitution, buffers and ion transporters, plays a significant role in maintaining mucosal integrity and enabling rapid repair after injury. Growth factors such as epidermal growth factor (EGF), transforming growth factor-alpha (TGF-alpha), hepatocyte growth factor (HGF) and keratinocyte growth factor (KGF) are associated with oesophageal epithelial proliferation or restitution. Na+/H+ exchanger-1, an ion transporter, regulates intracellular pH and cell volume, and may have roles in cell proliferation, migration and survival. Cytokine, adhesion molecules, cyclooxygenase-2 and free radicals are associated with oesophageal inflammation and breach of the functional epithelial defense. Although the oesophagus does not have strong functional epithelial defense against acid, this defensive mechanisms may be involved in the pathogenesis of non-erosive gastro-oesophageal reflux disease. Medical therapy may be developed in future to enhance functional oesophageal epithelial defense.

[Esophageal complications of non steroidal antiinflammatory drugs]

The effect of non steroidal anti-inflammatory drugs (NSAIDs) on esophageal mucosa is not well known. NSAIDs do not provoke gastro-esophageal reflux disease in healthy subjects but can worsen a preexistant non symptomatic reflux. Mechanism of action is not determined; NSAIDs do not modify the motility of lower esophagus sphincter or of esophageal body. A significant increase of symptoms of GERD (hearthburn and acid regurgitation) is observed in patients treated with NSAIDs. Relative risk of GERD symptoms with NSAIDs is about 2. Erosive esophagitis is common in elderly patients taking NSAIDs but it is not proven that an increased risk of esophagitis exists with NSAID therapy. Case-control studies favored an association between NSAIDs consumption and benign esophageal stricture. NSAIDs can provoke a pill-induced esophagitis, specially if the drugs are absorbed without water and in case of preexistant acid reflux.

Mechanisms of gastroesophageal reflux and gastroesophageal reflux disease

Gastroesophageal reflux is a physiological phenomenon, occurring with different severity and duration in different individuals. Reflux occurs when this normal event results in the occurrence of symptoms/signs or complications. The pathophysiology of gastroesophageal reflux is complex and diverse, since it is influenced by factors that are genetic, environmental (e.g., diet smoking), anatomic, hormonal, and neurogenic. However, many mechanisms remain incompletely understood. Future research should focus on a better understanding of the physiology of the upper and lower esophageal sphincters, and of gastric motility. The afferent and efferent neural pathways and neuropharmacologic mediators of transient lower esophageal sphincter relaxations and gastric dysmotility require further study. The role of anatomic malformations such as hiatal hernia in children has been underestimated. While therapeutic possibilities are greater in number and largely improved, the outcomes of some treatments are far from satisfactory in many cases. In addition to development of new forms of treatment, research should address better use of currently available medical and surgical treatments.

Eicosanoids and the esophagus

Eicosanoids are products of arachidonic acid metabolism. Among the products produced are the prostaglandins and leukotrienes, products which are known to play important roles in health and disease of many gastrointestinal tissues. Here, we review current knowledge about eicosanoids in the esophagus, including production in healthy and diseased tissues and potential physiologic and pathophysiologic effects in two important esophageal mucosal disorders, reflux esophagitis and esophageal cancer.

Experimental esophagitis induced by acid and pepsin in rabbits mimicking human reflux esophagitis

BACKGROUND & AIMS

The lack of appropriate animal models might explain the paucity of information on the mechanisms of mucosal damage and defense in reflux esophagitis. The aim of this study was to develop a model of esophagitis in rabbits mimicking human reflux esophagitis.

METHODS

New Zealand white rabbits underwent surgery for placement of a plastic tube into the cervical esophagus. Acidified pepsin (AP) was intermittently perfused for different periods. Esophageal injury was assessed by macroscopic and microscopic examination, including the cell proliferation immunohistochemical parameter mib1.

RESULTS

Rabbit losses (20%) were attributable mostly to postsurgical mortality and tube displacement. Perfusion of AP for 60 min/12 h or 45 min/12 h induced high-grade esophagitis by days 3 and 5, respectively, characterized by diffuse erosion/ulceration, inflammation, bleeding, and reactive epithelial changes. Perfusion of acidified pepsin for 60 min/day, especially at 30 min/12 h, induced low-grade esophagitis characterized by superficial epithelial loss, mild/absent inflammation, and epithelial reactive changes including increased cell proliferation, basal hyperplasia, and papillomatosis, which reached maximal expression by day 7. This perfusion regimen induced mucosal adaptation to damage.

CONCLUSIONS

Different and highly reproducible esophageal mucosal lesions mimicking human reflux esophagitis can be induced in rabbits with repetitive acid and pepsin exposure.

Esophageal motility and intraesophageal pH patterns in patients with esophagitis and chronic nonsteroidal anti-inflammatory drug use

Clinical reports suggest that nonsteroidal anti-inflammatory drugs (NSAIDs) use might induce esophageal symptoms and damage, including esophagitis, but experimental data are conflicting, and some indicate that NSAIDs improve mucosal damage. It is not known whether patients with endoscopically diagnosed esophagitis during NSAID use have different baseline reflux patterns from patients with reflux esophagitis and no NSAID use. Two groups of patients with and without chronic NSAID use and esophagitis were prospectively studied. Twenty-four-hour pH monitoring and esophageal manometry were performed in all patients who were free of NSAID and any other drug use during tests. Esophageal motility and reflux patterns did not differ in patients with esophagitis regardless of the presence or absence of NSAID use. However, the subgroup of patients with grades II and III esophagitis and chronic NSAID use had a significantly greater lower esophageal sphincter (LES) pressure and a less severe intraesophageal pH profile than patients without NSAID use. In agreement with clinical reports, these results suggest that NSAID use may aggravate an otherwise milder acid-related esophageal disease in a subgroup of patients.

Prostaglandin E2 is the major arachidonic acid metabolite secreted by esophageal mucosal cells in rabbits

Unlike gastric mucosa, it has been considered that lipoxygenase metabolites protect the esophageal mucosa and that prostaglandins are only secreted in the presence of esophageal inflammation. The aim of this study was to determine the profile of arachidonic acid metabolites and their response to regulatory compounds in rabbit esophageal mucosal cells in culture. Eicosanoids secreted into the medium were extracted and identified by HPLC and RIA. Esophageal mucosal cells in culture metabolized arachidonic acid mainly through the cycloxygenase pathway and PGE2 was the major arachidonic acid metabolite secreted. The addition of IL-1 beta and A23187 (calcium ionophore) stimulated PGE2 synthesis. In basal conditions neither leukotrienes nor HETEs were detected. However, the addition of the NDGA induced the secretion of lipoxygenase metabolites identified as 12-15 HETEs. In conclusion, rabbit esophageal epithelial cells in culture metabolize arachidonic acid via both cycloxygenase and lipoxygenase pathways. In our system, PGE2 was the main arachidonic acid metabolite.