Altered localization and expression of tight-junction proteins in a rat model with chronic acid reflux esophagitis

Impairment of Esophageal Barrier Integrity: New Insights into Esophageal Symptoms in Post-COVID-19

BACKGROUND

The COVID-19 pandemic, caused by SARS-CoV-2, has unveiled a range of symptoms beyond the respiratory system, including significant gastrointestinal manifestations.

AIMS

This study explores the prevalence and intensity of gastroesophageal symptoms in post-COVID-19 patients and the integrity of the esophageal epithelial barrier.

METHODS

We conducted a prospective longitudinal cohort study with 55 patients hospitalized due to COVID-19 at a University Hospital. Patients were evaluated during hospitalization and between 3 and 6 months post-discharge, using validated questionnaires for gastrointestinal and gastroesophageal reflux symptoms. Additionally, 25 of these patients underwent upper digestive endoscopy, with esophageal mucosal biopsies analyzed for transepithelial electrical resistance (TER), permeability, and expression of inflammatory cytokines and cell junction proteins. Data expressed as mean EPM, inference by two-way ANOVA.

RESULTS

Results were considered statistically significant at p < 0.05. There were significant increases in heartburn and acid reflux symptoms in post-COVID-19 patients, as measured by the GSRS questionnaire. Biopsies from post-COVID patients revealed increased esophageal permeability when compared to non-COVID patients in acidic media (pH 2: non-COVID-19: 717.8 ± 168.2 vs. post-COVID-19: 1377.6 ± 316.4), suggesting compromised mucosal barrier. Furthermore, IL-8 levels and expression of Claudin-2 were elevated in these patients.

CONCLUSIONS

The data suggested that COVID-19 infection may cause lasting damage to the esophageal epithelial barrier, increasing its permeability and provoking an exacerbated inflammatory response. These changes may explain the prevalence of post-infection gastroesophageal symptoms. Our findings underscored the importance of continuous monitoring and the development of therapeutic strategies to mitigate gastroesophageal effects in patients recovering from COVID-19.

Molecular and Functional Recovery of Esophageal Barrier Integrity After Laparoscopic Anti-reflux Surgery

BACKGROUND

Patients undergoing laparoscopic anti-reflux surgery (LARS) often experience improved quality of life and reduced gastroesophageal reflux disease (GERD) symptoms. This study aimed to assess the impact of LARS on epithelial remodeling and repair in the esophageal mucosa.

METHODS

Upper gastrointestinal (GI) endoscopy was performed once on healthy controls (HC) and twice on GERD patients before and approximately 6 month after surgery, with esophageal biopsies collected. The expressions of E-cadherin (ECAD), Occludin (OCLN), Claudin 1 (CLDN1), Claudin 4 (CLDN4), Zonula Occludens -1 (ZO-1), and ZO-2 were analyzed in the biopsies, and dilated intercellular spaces (DIS) were examined under light microscopy.

RESULTS

The study included 22 GERD patients who were underwent for LARS, and 20 HCs. All patients had pathological reflux episodes. In the Post-LARS group, TEER increased significantly compared to Pre-LARS and HC (p < 0.05), while mucosal permeability decreased (p < 0.05). A significant negative correlation was found between TEER and permeability (p = 0.0002). DIS remained dilated in both Pre- and Post-LARS patients compared to HC (p < 0.05). Gene expression analysis revealed significant increases in ZO-1, OCLN, and ZO-2 Post-LARS (p < 0.05).

CONCLUSION

LARS improves mucosal integrity by enhancing TEER and reducing permeability in GERD patients, although DIS remains unchanged. The upregulation of tight junction genes such as ZO-1 and OCLN Post-LARS suggests that surgical intervention may support epithelial barrier restoration. DIS remains dilated after LARS; this might be reason that it is not an early marker in GERD pathogenesis. These findings enhance our understanding of GERD nature and may inform future target therapeutic strategies.

Alginates for Protection Against Pepsin-Acid Induced Aerodigestive Epithelial Barrier Disruption

OBJECTIVE

Gastroesophageal reflux disease (GERD) and laryngopharyngeal reflux (LPR) are chronic conditions caused by backflow of gastric and duodenal contents into the esophagus and proximal aerodigestive tract, respectively. Mucosal barrier dysfunction resultant from the synergistic actions of chemical injury and the mucosal inflammatory response during reflux contributes to symptom perception. Alginates effectively treat symptoms of mild to moderate GERD and have recently shown benefit for LPR. In addition to forming a "raft" over gastric contents to reduce acidic reflux episodes, alginates have been found to bind the esophageal mucosa thereby preserving functional barrier integrity measured by transepithelial electrical resistance. The aim of this study was to further examine the topical protective capacity of alginate-based Gaviscon Advance (GA) and Double Action (GDA) against pepsin-acid mediated aerodigestive epithelial barrier dysfunction in vitro.

STUDY DESIGN

Translational.

METHODS

Immortalized human esophageal and vocal cord epithelial cells cultured in transwells were pretreated with liquid formula GA, GDA, matched viscous placebo solution, or saline (control), then treated for 1 h with saline, acid (pH 3-6) or pepsin (0.1-1 mg/ml) at pH 3-6. Endpoint measure was taken of horseradish peroxidase (HRP) allowed to diffuse across monolayers for 2 h.

RESULTS

Pepsin (0.1-1 mg/ml) at pH 3-6 increased HRP flux through cultures pretreated with saline or placebo (p < 0.05); acid alone did not. GA and GDA prevented barrier dysfunction.

CONCLUSIONS

GA and GDA preserved epithelial barrier function during pepsin-acid insult better than placebo suggesting that protection was due to alginate. These data support topical protection as a therapeutic approach to GERD and LPR. Laryngoscope, 132:2327-2334, 2022.

NF-κB: A novel therapeutic pathway for gastroesophageal reflux disease?

Although gastroesophageal reflux disease (GERD), a common chronic disease in clinical practice, has been widely studied, its potential adverse impact on patients is still a significant clinical concern. It is necessary to understand the pathogenesis of the disease and choose appropriate treatment according to its mechanism. The pathogenesis of GERD is diverse and complex. As the traditional treatment methods are expensive and ineffective in alleviating symptoms in some patients, new treatment options need to be explored. Our previous study suggested that the activation of nuclear factor-kappa beta (NF-κB) in esophageal mucosa may be related to the injury of epithelial barrier function caused by reflux. Based on the literature and our previous study results, it is speculated that inhibition of NF-κB activation may block the insult of GERD on the esophageal mucosal barrier. NF-κB may play an important role in the development of GERD. This article reviews the pathogenesis of GERD and the relationship between NF-κB and GERD, in order to provide new strategies for the treatment of GERD.

Protective Mechanisms of Liquid Formulations for Gastro-Oesophageal Reflux Disease in a Human Reconstructed Oesophageal Epithelium Model

Purpose

A novel experimental design based on a human-reconstructed oesophageal epithelium (HO2E) model has been applied to quantitively assess the properties of a set of liquid formulations, Device A (Gerdoff^® Protection), Device B (Esoxx^® One), and Device C (Marial^® gel) developed to form a temporary physical barrier on the oesophageal epithelium and modify epithelial permeability so to protect the oesophageal mucosa from refluxate components.

Methods

The formulations were applied to a prewetted HO2E model for 15 min. Then, a 0.5% caffeine solution was applied, and its penetration kinetics was assessed at 1 h and 2 h in acidic environments (pH= 3.3) to mirror exposure of the oesophageal mucosa to acidic reflux in GORD patients. Caffeine permeated into the basolateral compartment (evaluated by HPLC-UV) and Lucifer yellow (LY) permeability were quantified 15 min after application of the caffeine in acidic environments.

Results

At the 15 min timepoint, Device A reduced caffeine permeation by 77.2% and LY flux by 30.4% compared to the untreated control and with a faster mode of action than that of the other liquid formulations. Transepithelial caffeine flux was reduced, albeit with different timing and efficiency, by all three compounds up to the end of the 2 hour experiment. At 1 h, Device A reduced the caffeine flux by 79.2%; Device B, by 67.2%; and Device C, by 37%.

Conclusion

These results confirm the ability of the medical devices tested to interact with the oesophageal epithelium and create a temporary physical protective film for up to 2 hours after their application. The results underline differences in the mechanism of action of the three medical devices, with Device A performing faster than the other formulations. The overall results support the relevance of the reconstructed mucosal model to investigate oesophageal epithelium–product interactions and precisely differentiate liquid formulation performance.

Pathophysiology of Pediatric Gastroesophageal Reflux Disease: Similarities and Differences With Adults

Gastroesophageal reflux (GOR) is defined as "the passage of gastric contents into the esophagus with or without regurgitation and vomiting" and gastroesophageal reflux disease (GORD) is defined "when GOR leads to troublesome symptoms affecting the daily functioning and/or complications." This definition was first developed in 2006 by the Montreal consensus group (1) and later on adopted by pediatric gastroenterology societies such as ESPGHAN and NASPGHAN in 2009 (2). The definition of gastroesophageal reflux reveals little about its pathophysiology and is focused on symptomatology. In this way, it acts as an umbrella term for the multifactorial causes of the disease and the various phenotypes encountered; from functional heartburn to hypersensitive esophagus and nonerosive reflux disease, to erosive esophagitis and Barrett's esophagus. This article is devoted to the pathophysiology of pediatric GORD in comparison to adult GORD and is divided in 2 parts. In the first part, we will systematically describe the different mechanisms for the generation and clearance of reflux events, while on the second part we will discuss the mechanisms involved in symptoms generation. Finally, we will discuss the similarities and differences between pediatric and adult GORD.

In Vitro Modelling of Barrier Impairment Associated with Gastro-Oesophageal Reflux Disease (GERD)

Purpose

A novel experimental model based on a 3D reconstructed human oesophageal epithelium model (HO2E) has been developed to investigate the structural and functional changes of the oesophageal epithelium following exposure to a solution of HCl 0.1 N (pH = 1.2) mirroring GERD microenvironment condition.

Methods

The barrier structure modification after the exposure to the acid solution on HO2E tissues was investigated immediately after damage induction and after 1 hour post incubation and compared to HO2E tissues exposed to phosphate buffered saline solution. Immunofluorescence (IF) was applied to quantify the expression and localization of barrier function proteins: Claudin-1 (CLDN-1), Claudin-4 (CLDN-4), Zonulin-1 (ZO-1), E-Cadherin and Mucin-1 (MUC1). Barrier functionality was measured by TEER.

Results

In the acidic microenvironment, TEER measurement has shown some limitations and results were not applicable, whereas the evaluation of protein localization and quantification provided clear and robust evidence of the damage which occurred to the epithelium barrier structure. CLDN-4 expression significantly decreased after exposure to acid. ZO-1 protein appeared upregulated immediately after exposure to HCl and was mainly localized in the cytoplasm and not on the cell membrane. This different localization was also observed for CLND-1. CLDN-1, MUC1 and, to a lower extent, ZO-1 expression increased during the post-incubation period.

Conclusion

The relevant tissue biomarkers identified, CLDN-1 and MUC1, can be used to monitor TJ structure and epithelial barrier recovery after acid-induced damage which, in our experimental conditions, were non-destructive and suitable for recovery studies. The established model can be useful to investigate the mechanism of action of formulations acting on this specific pathophysiological condition and/or designed to potentiate the physiological defense mechanisms of oesophageal mucosa.

Laryngopharyngeal Reflux and Inflammatory Responses in Mucosal Barrier Dysfunction of the Upper Aerodigestive Tract

The upper aerodigestive tract (UAT) is the first line of defense against environmental stresses such as antigens, microbes, inhalants, foods, etc., and mucins, intracellular junctions, epithelial cells, and immune cells are the major constituents of this defensive mucosal barrier. Laryngopharyngeal reflux (LPR) is recognized as an independent risk factor for UAT mucosal disorders, and in this review, we describe the components and functions of the mucosal barrier and the results of LPR-induced mucosal inflammation in the UAT. We discuss the interactions between the refluxate and the mucosal components and the mechanisms through which these damaging events disrupt and alter the mucosal barriers. In addition, we discuss the dynamic alterations in the mucosal barrier that might be potential therapeutic targets for LPR-induced disorders.

Mucosal pathogenesis in gastro-esophageal reflux disease

BACKGROUND

Despite gastro-esophageal reflux disease affecting up to 20% of Western populations, relatively little is known about the molecular mechanisms underlying its most troublesome symptom: heartburn. Recent findings have unveiled the role of components of the esophageal mucosa in the pathogenesis of GERD including sensory nociceptive nerves and inflammatory mediators. Erosive esophagitis was long believed to develop as a result of acid injury at the esophageal lumen, but novel concepts suggest the generation of reflux-induced esophageal injury as a result of cytokine-mediated inflammation. Moreover, the localization and characterization of mucosal afferent nerves vary between GERD phenotypes and could explain the heterogeneity of symptom perception between patients who experience similar levels of acid reflux.

PURPOSE

The purpose of this review is to consider the crosstalk of different factors of the esophageal mucosa in the pathogenesis of GERD, with a particular focus on mucosal innervation and molecular basis of acid-induced cytokine response. We discuss the current understanding of the mucosal response to acid injury, the nociceptive role of acid-sensitive receptors expressed in the esophageal mucosa, and the role of esophageal epithelial cells in initiating the onset of erosive esophagitis.

Duodenal acidification induces gastric relaxation and alters epithelial barrier function by a mast cell independent mechanism

Duodenal hyperpermeability and low-grade inflammation in functional dyspepsia is potentially related to duodenal acid exposure. We aimed to evaluate in healthy volunteers the involvement of mast cell activation on the duodenogastric reflex and epithelial integrity during duodenal acidification. This study consisted of 2 parts: (1) Duodenal infusion of acid or saline during thirty minutes in a randomized, double-blind cross-over manner with measurement of intragastric pressure (IGP) using high resolution manometry and collection of duodenal biopsies to measure epithelial barrier function and the expression of cell-to-cell adhesion proteins. Mast cells and eosinophils were counted and activation and degranulation status were assessed. (2) Oral treatment with placebo or mast cell stabilizer disodiumcromoglycate (DSCG) prior to duodenal perfusion with acid, followed by the procedures described above. Compared with saline, acidification resulted in lower IGP (P < 0.01), increased duodenal permeability (P < 0.01) and lower protein expression of claudin-3 (P < 0.001). Protein expression of tryptase (P < 0.001) was increased after acid perfusion. Nevertheless, an ultrastructural examination did not reveal degranulation of mast cells. DSCG did not modify the drop in IGP and barrier dysfunction induced by acid. Duodenal acidification activates an inhibitory duodenogastric motor reflex and, impairs epithelial integrity in healthy volunteers. However, these acid mediated effects occur independently from mast cell activation.

Role of Clostridium perfringens Enterotoxin on YAP Activation in Colonic Sessile Serrated Adenoma/ Polyps with Dysplasia

Sessile serrated adenoma/polyp with dysplasia (SSA/P-D) is an SSA/P with cellular dysplasia and has a higher risk of progressing to colon carcinogenesis. Previously, we reported that tight junction impairment by Clostridiumperfringens enterotoxin (CPE) leads to activation of the transcriptional co-activator yes-associated protein (YAP) in oral squamous cell carcinoma. Here, we investigated whether CPE activates YAP to promote the malignant progression of SSA/P. E-cadherin expression was lower in the 12 cases with SSA/P-D examined than that in normal mucosa, SSA/P, or tubular adenoma (TA). Furthermore, intracellular translocation of claudin-4 (CLDN4) and nuclear translocation of YAP were observed. The CPE gene was detected in DNA extracted from SSA/P-D lesions, but not in SSA/P or TA. Treatment of the rat intestinal epithelial cell line IEC6 with low-dose CPE resulted in intracellular translocation of CLDN4 to the cytoplasmic membrane. Cytoplasmic CLDN4 showed co-precipitation with transcriptional co-activator with PDZ-binding motif, zonula occludens (ZO)-1, large tumor suppressor, and mammalian Ste20-like. Additionally, YAP co-precipitated with ZO-2 under CPE treatment led to decreased YAP phosphorylation and nuclear translocation. YAP activation promoted increase in nuclear TEA domain family member level, expression of cyclin D1, snail, vimentin, CD44, NS and decrease in E-cadherin levels, thereby inducing stemness and epithelial-mesenchymal-transition (EMT). The Hippo complex with the incorporation of CLDN4 increased stability. Upon low-dose CPE treatment, HT29 cells with BRAF^V600E gene mutation showed increased growth, enhanced invasive potential, stemness, and induced EMT phenotype, whereas HCT116 cells, which carry KRAS^G13D gene mutation, did not show such changes. In an examination of 10 colorectal cancers, an increase in EMT and stemness was observed in CPE (+) and BRAF mutation (+) cases. These findings suggest that C.perfringens might enhance the malignant transformation of SSA/P-D via YAP activation. Our findings further highlight the importance of controlling intestinal flora using probiotics or antibiotics.

Changing Pattern of Adenocarcinoma of the Esophagogastric Junction in Recent 10 Years: Experience at a Large Tertiary Medical Center in China

Aims and background

To investigate the changing pattern of adenocarcinoma of the esophagogastric junction subtypes and its time trend relationship with that of reflux esophagitis over 10 years at a tertiary medical center in China.

Methods and study design

The medical records of all patients who underwent gastroscopy from 2000 to 2009 were reviewed. Subtypes of adenocarcinoma of the esophagogastric junction according to Siewert's classification, gastric non-cardiac adenocarcinoma, esophageal squamous cell carcinoma, reflux esophagitis and Helicobacter pylori infection were diagnosed according to the results of gastroscopy and mucosal histopathology. All the patients were divided into three cohorts (cohort A [2000–2003], cohort B [2004–2006]), cohort C [2007–2009]), and the proportion of adenocarcinoma of the esophagogastric junction and its subtypes in all upper gastrointestinal tumors (adenocarcinoma of the esophagogastric junction, gastric non-cardiac adenocarcinoma and esophageal squamous cell carcinoma) in each cohort were compared. The annual percentages of adenocarcinoma of the esophagogastric junction, reflux esophagitis and H pylori in all patients were also compared.

Results

70,073 patients (cohort A, n = 20298, cohort B, n = 20443, cohort C, n = 29332) who underwent gastroscopy were reviewed. Totally there were 279 patients with adenocarcinoma of the esophagogastric junction (0.398%, M:F = 5.6:1), 794 gastric non-cardiac adenocarcinoma patients (1.133%, M:F = 2:1), 366 esophageal squamous cell carcinoma patients (0.522%, M:F = 3.4:1) and 4681 reflux esophagitis patients. Among the three subtypes of adenocarcinoma of the esophagogastric junction, only type I adenocarcinoma of the esophagogastric junction in upper GI tumors exhibited increasing trend over time (1.86%, 3.39% and 4.94% for cohort A, B and C, respectively, P = 0.009). According to the WHO classification of histological types, the tubular types of adenocarcinoma of the esophagogastric junction have decreased (P = 0.008), whereas papillary type (P = 0.001) increased. The annual detection rate of type I adenocarcinoma of the esophagogastric junction appeared to be positively correlated with reflux esophagitis (r = 0.846, P = 0.002) and negatively with H pylori infection (r = -0.785, P = 0.007) in time trend.

Conclusions

Over a recent 10-year period, the three subtypes of adenocarcinoma of the esophagogastric junction showed different changing trends, suggesting heterogeneous characteristics of the three Siewert types of adenocarcinoma of the esophagogastric junction.

Additive Effects of Rebamipide Plus Proton Pump Inhibitors on the Expression of Tight Junction Proteins in a Rat Model of Gastro-Esophageal Reflux Disease

BACKGROUND/AIMS

The aim of this study was to investigate the effects of rebamipide on tight junction proteins in the esophageal mucosa in a rat model of gastroesophageal reflux disease (GERD).

METHODS

GERD was created in rats by tying the proximal stomach. The rats were divided into a control group, a proton pump inhibitor (PPI) group, and a PPI plus rebamipide (PPI+R) group. Pantoprazole (5 mg/kg) was administered intraperitoneally to the PPI and PPI+R groups. An additional dose of rebamipide (100 mg/kg) was administered orally to the PPI+R group. Mucosal erosions, epithelial thickness, and leukocyte infiltration into the esophageal mucosa were measured in isolated esophagi 14 days after the procedure. A Western blot analysis was conducted to measure the expression of claudin-1, -3, and -4.

RESULTS

The mean surface area of mucosal erosions, epithelial thickness, and leukocyte infiltration were lower in the PPI group and the PPI+R group than in the control group. Western blot analysis revealed that the expression of claudin-3 and -4 was significantly higher in the PPI+R group than in the control group.

CONCLUSIONS

Rebamipide may exert an additive effect in combination with PPI to modify the tight junction proteins of the esophageal mucosa in a rat model of GERD. This treatment might be associated with the relief of GERD symptoms.

Deoxycholic acid promotes development of gastroesophageal reflux disease and Barrett's oesophagus by modulating integrin-αv trafficking

The fundamental mechanisms underlying erosive oesophagitis and subsequent development of Barrett's oesophagus (BO) are poorly understood. Here, we investigated the contribution of specific components of the gastric refluxate on adhesion molecules involved in epithelial barrier maintenance. Cell line models of squamous epithelium (HET‐1A) and BO (QH) were used to examine the effects of bile acids on cell adhesion to extracellular matrix proteins (Collagen, laminin, vitronectin, fibronectin) and expression of integrin ligands (α₃, α_4, α₅, α₆ and α_ν). Experimental findings were validated in human explant oesophageal biopsies, a rat model of gastroesophageal reflux disease (GORD) and in patient tissue microarrays. The bile acid deoxycholic acid (DCA) specifically reduced adhesion of HET‐1A cells to vitronectin and reduced cell‐surface expression of integrin‐α_νvia effects on endocytic recycling processes. Increased expression of integrin‐α_v was observed in ulcerated tissue in a rat model of GORD and in oesophagitis and Barrett's intestinal metaplasia patient tissue compared to normal squamous epithelium. Increased expression of integrin‐α_ν was observed in QH BO cells compared to HET‐1A cells. QH cells were resistant to DCA‐mediated loss of adhesion and reduction in cell‐surface expression of integrin‐α_ν. We demonstrated that a specific component of the gastric refluxate, DCA, affects the epithelial barrier through modulation of integrin α_ν expression, providing a novel mechanism for bile acid‐mediated erosion of oesophageal squamous epithelium and promotion of BO. Strategies aimed at preventing bile acid‐mediated erosion should be considered in the clinical management of patients with GORD.

Contribution of immunomodulators to gastroesophageal reflux disease and its complications: stromal cells, interleukin 4, and adiponectin

Gastroesophageal reflux disease (GERD) has become the most commonly seen gastrointestinal disorder in outpatient clinics. In the United States, around 20% of the general population experience heartburn on a weekly basis. Although clinical complaints can be mild or moderate, patients with GERD may develop further complications, such as peptic strictures, Barrett's esophagus (BE), and even esophageal adenocarcinoma. Pathologically, GERD is developed as a result of chronic and enhanced exposure of the esophageal epithelium to noxious gastric refluxate. In this review article, we provide an overview of GERD and then focus on the roles of stromal cells, interleukin 4, and adiponectin in GERD and BE. The importance of inflammation and immunomodulators in GERD pathogenesis is highlighted. Targeting the immunomodulators or inflammation in general may improve the therapeutic outcome of GERD, in particular, in those refractory to proton pump inhibitors.

Gastrointestinal mucosal barrier function and diseases

The gastrointestinal mucosal barrier plays an essential role in the separation of the inside of the body from the outside environment. Tight junctions (TJs) are the most important component for construction of a constitutive barrier of epithelial cells, and they regulate the permeability of the barrier by tightly sealing the cell-cell junctions. TJ proteins are represented by claudins, occludin, junctional adhesion molecules, and scaffold protein zonula occludens. Among these TJ proteins, claudins are the major components of TJs and are responsible for the barrier and the polarity of the epithelial cells. Gastrointestinal diseases including reflux esophagitis, inflammatory bowel disease, functional gastrointestinal disorders, and cancers may be regulated by these molecules, and disruption of their functions leads to chronic inflammatory conditions and chronic or progressive disease. Therefore, regulation of the barrier function of epithelial cells by regulating the expression and localization of TJ proteins is a potential new target for the treatment of these diseases. Treatment strategies for these diseases might thus be largely altered if symptom generation and/or immune dysfunction could be regulated through improvement of mucosal barrier function. Since TJ proteins may also modify tumor infiltration and metastasis, other important goals include finding a good TJ biomarker of cancer progression and patient prognosis, and developing TJ protein-targeted therapies that can modify patient prognosis. This review summarizes current understanding of gastrointestinal barrier function, TJ protein expression, and the mechanisms underlying epithelial barrier dysregulation in gastrointestinal diseases.

Estrogen Enhances Esophageal Barrier Function by Potentiating Occludin Expression

BACKGROUND

We recently demonstrated that a female sex hormone, estrogen, suppressed esophageal epithelial injury in a reflux esophagitis model of rat, suggesting that estrogen may play an important role in controlling the progress of the gastro-esophageal reflux disease spectrum. However, the precise mechanism of the action is unclear.

AIM

To investigate the potential role of estrogen in the esophageal barrier function.

METHODS

Male rabbits were pretreated with either continuous release 17β-estradiol or placebo, and the excised esophageal mucosa was subjected to Ussing chamber experiments after the 2-week pre-treatment. The mucosal side of the chamber was perfused with luminal irritants (HCl or acidified sodium nitrite), while the basal side was perfused by modified Krebs buffer. The epithelial barrier function was evaluated by the transmembrane resistance and the epithelial permeability. The intercellular space of the epithelium was investigated with transmission electron microscopy and the expression of tight junction protein, occludin, claudin-1, and claudin-4, with immunoblotting.

RESULTS

Estrogen pre-treatment significantly attenuated the decrease in the transmembrane resistance and the increase in the epithelial permeability induced by luminal irritants. Furthermore, the dilation of the intercellular space induced by luminal HCl was significantly alleviated by 17β-estradiol administration. The baseline occludin expression was significantly potentiated by 17β-estradiol administration.

CONCLUSIONS

This is the first study showing an enhancement of the esophageal barrier function by 17β-estradiol administration. The lack of the protective effect of estrogen could be responsible for the male predominance of erosive reflux esophagitis.

Current perspectives on reflux laryngitis

Laryngopharyngeal reflux (LPR) is an extraesophageal manifestation of gastroesophageal reflux disease (GERD). With the increase of GERD patients, the importance of LPR is acknowledged widely. However, the pathophysiology of LPR is not understood completely and the diagnostic criteria for LPR remain controversial. Unfortunately, a gold standard diagnostic test for reflux laryngitis is not available. Recently, an experimental animal model for reflux laryngitis was developed to investigate the pathophysiology of reflux laryngitis. An empirical trial of lifestyle modification and proton pump inhibitor therapy is a reasonable approach for LPR symptoms. Alternatives after failure with aggressive medical treatment are limited and multichannel intraluminal impedance and pH monitoring is currently the best alternative to detect nonacid reflux. Additional prospective and evidence-based research is anticipated.

Effects of topical steroids on tight junction proteins and spongiosis in esophageal epithelia of patients with eosinophilic esophagitis

BACKGROUND & AIMS

The allergic response associated with eosinophilic esophagitis (EoE) occurs when food antigens permeate tight junction-mediated epithelial dilated intercellular spaces. We assessed whether levels of tight junction proteins correlate with the dilation of intercellular spaces (spongiosis) and the effects of topical steroids on these parameters.

METHODS

We assessed esophageal biopsy samples from 10 patients with active EoE treated with topical fluticasone, 10 untreated patients, and 10 patients without esophageal disease (controls) for degree of spongiosis. Immunohistochemical assays were used to determine the levels of the tight junction proteins filaggrin, zonula occludens (ZO)-1, ZO-2, ZO-3, and claudin-1. Histology and immunohistochemistry results were assessed blindly, with levels of tight junction proteins and degree of spongiosis rated on scales of 0 to 3.

RESULTS

The mean degrees of spongiosis in untreated and treated patients with EoE were 1.3 and 0.4, respectively (P = .016). Esophageal epithelia did not stain significantly for ZO-1 or ZO-2. Filaggrin was observed in a predominant cytoplasmic pattern, compared with the cytoplasmic and membranous patterns of ZO-3 and claudin-1. In biopsy specimens from patients with active EoE, the mean staining intensities for filaggrin, ZO-3, and claudin-1 were 1.6, 1.4, and 0.7, respectively. In biopsy specimens from patients treated with fluticasone, levels of filaggrin, ZO-3, and claudin-1 were 2.8 (P = .002 compared with untreated patients), 1.7 (P = .46 compared with untreated patients), and 1.3 (P = .25 compared with untreated patients), respectively. The correlation between the level of filaggrin and the degree of spongiosis was r = 0.23, and between ZO-3 staining and the degree of spongiosis was r = .016 (P = .001 for filaggrin vs ZO-3 staining).

CONCLUSIONS

Filaggrin, ZO-3, and claudin-1 (but not ZO-1 or ZO-2) are detected in the esophageal mucosa of patients with EoE treated with steroids and individuals without esophageal disease. Without treatment, spongiosis increases, corresponding with reduced levels of filaggrin, ZO-3, and claudin-1. Loss of tight junction regulators and dilation of intercellular spaces appear to be involved in the pathophysiology of EoE and could be targets for treatment.

ERK1/2 participates in regulating the expression and distribution of tight junction proteins in the process of reflux esophagitis

OBJECTIVE

To investigate the alterations of esophageal epithelial barrier during the process of reflux esophagitis (RE).

METHODS

In total, 85 Sprague-Dawley rats were randomly divided into two groups, the sham-operation group (n = 25) and the RE group induced by incomplete pyloric ligation (n = 60). The establishment of RE model and the severity of esophagitis were evaluated by hematoxylin and eosin stain. Dilated intercellular spaces (DIS) in the esophageal epithelium were observed by transmission electron microscopy. The cellular distributions of ZO-1, occludin and claudin-1 were assessed by immunohistochemical stain. The expressions of these tight junction (TJ) proteins and the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), myosin light chain (MLC) and nonmuscular myosin light chain kinase (nmMLCK) were analyzed by Western blot.

RESULTS

DIS occurred gradually in the RE group. ZO-1, occludin and claudin-1 were incompletely or even not expressed in the RE group. TJ proteins were expressed in the membrane instead of the cytoplasm in many epithelial cells in RE. With Western, the expression of ZO-1, occludin and claudin-1 was increased gradually in the RE group (P < 0.05). The phosphorylation levels of nmMLCK, MLC and ERK1/2 were also increased (P < 0.05). There was no marked changes in the esophageal epithelium in the sham-operation group.

CONCLUSIONS

TJ proteins could be used as sensitive markers of RE instead of DIS. ERK1/2 may participate in regulating TJ proteins in esophageal epithelia in RE.

Increased immunoreactivity of cathepsins in the rat esophagus under chronic acid reflux esophagitis

We have designed a stable rat chronic acid reflux esophagitis (RE) model. In gastrointestinal lesions, several lysosomal cathepsins are known to participate in epithelial permeability in cell-cell connections, such as tight junctions in ulcerative colitis. However, very few studies have focused on the distribution of cathepsins in the esophageal multilayer squamous epithelium. Therefore to clarify the role of cathepsins in RE, we investigated their immunohistological localization in the esophageal epithelium under normal conditions and after RE. Of the cathepsins examined (cathepsins B, C, D, F, H, L, S, and X), granular immunoreactivity for cathepsins B, C, D and L was observed in the control esophageal epithelia; although, their distribution differed depending on the enzyme examined. In the RE model, immunoreactivity of these cathepsins was increased in esophageal epithelial cells and activated macrophages. The immunoreactivity for cathepsins F, H, S and X was barely detectable in the control esophageal epithelium. However, in the RE model, we noticed a slight increase in the expression of cathepsins H and X in the epithelial cells. Furthermore, activated macrophages of the RE model possessed intense immunoreactivity for these cathepsins, which may have been related to esophageal inflammatory mechanisms.

Esophageal baseline impedance levels in patients with pathophysiological characteristics of functional heartburn

BACKGROUND

Recently, it has been suggested that low esophageal basal impedance may reflect impaired mucosal integrity and increased acid sensitivity. We aimed to compare baseline impedance levels in patients with heartburn and pathophysiological characteristics related to functional heartburn (FH) divided into two groups on the basis of symptom relief after proton pump inhibitors (PPIs).

METHODS

Patients with heartburn and negative endoscopy were treated with esomeprazole or pantoprazole 40 mg daily for 8 weeks. According to MII-pH (off therapy) analysis, patients with normal acid exposure time (AET), normal reflux number, and lack of association between symptoms and refluxes were selected; of whom 30 patients with a symptom relief higher than 50% after PPIs composed Group A, and 30 patients, matched for sex and age, without symptom relief composed Group B. A group of 20 healthy volunteers (HVs) was enrolled. For each patient and HV, we evaluated the baseline impedance levels at channel 3, during the overnight rest, at three different times.

KEY RESULTS

Group A (vs Group B) showed an increase in the following parameters: mean AET (1.4 ± 0.8% vs 0.5 ± 0.6%), mean reflux number (30.4 ± 8.7 vs 24 ± 6.9), proximal reflux number (11.1 ± 5.2 vs 8.2 ± 3.6), acid reflux number (17.9 ± 6.1 vs 10.7 ± 6.9). Baseline impedance levels were lower in Group A than in Group B and in HVs (p < 0.001).

CONCLUSIONS & INFERENCES

Evaluating baseline impedance levels in patients with heartburn and normal AET could achieve a better understanding of pathophysiology in reflux disease patients, and could improve the distinction between FH and hypersensitive esophagus.

In vivo evaluation of acid-induced changes in oesophageal mucosa integrity and sensitivity in non-erosive reflux disease

OBJECTIVE

Patients with non-erosive reflux disease (NERD) have impaired oesophageal mucosal integrity (dilated intercellular spaces). Oesophageal mucosal integrity reflects the balance between repeated reflux damage and mucosal recovery. The relationship between mucosal integrity and acid sensitivity is unclear. Oesophageal impedance may be used for in vivo mucosal integrity measurement. We studied acid-induced changes in oesophageal mucosal integrity and acid perception in patients with heartburn.

DESIGN

50 patients with heartburn whithout oesophagitis underwent impedance monitoring before, during and after 10 min oesophageal perfusion with neutral (pH 6.5) and acid solutions (pH 1). Symptoms and impedance were recorded during perfusion. Impedance recovery was assessed for 2 h post-perfusion in ambulatory conditions followed by 24-h impedance-pH study.

RESULTS

Reflux monitoring discriminated 20 NERD and 30 functional heartburn (FH) patients. Neutral perfusion caused impedance fall that recovered within 10 min. Acid perfusion caused impedance fall with slow recovery: 6.5 Ω/min (IQR 3.3-12.0 Ω/min). Patients with slow recovery (< 25th percentile) had lower baseline impedance (1273 Ω ± 208 Ω vs. 3220 Ω ± 275 Ω ±, p < 0.01) and more frequent acid sensitivity (10/12 vs. 4/12, p = 0.04) than those with fast (> 75th percentile) recovery. Patients with NERD had lower baseline impedance (1669 ± 182 Ω vs. 2384 ± 211 Ω, p = 0.02) and slower impedance recovery (6.0 ± 0.9 Ω/min vs. 10.7 ± 1.6 Ω/min, p = 0.03) than patients with FH.

CONCLUSION

Impaired mucosal integrity might be the consequence of repeated reflux episodes with slow recovery. Mucosal integrity, recovery capacity and symptom perception are linked. Low basal impedance and slow recovery after acid challenge are associated with increased acid sensitivity.

Relevance of ultrastructural alterations of intercellular junction morphology in inflamed human esophagus

BACKGROUND/AIMS

Detailed characterization of the ultrastructural morphology of intercellular space in gastroesophageal reflux disease has not been fully studied. We aimed to investigate whether subtle alteration in intercellular space structure and tight junction proteins might differ among patients with gastroesophageal reflux disease.

METHODS

Esophageal biopsies at 5 cm above the gastroesophageal junction were obtained from 6 asymptomatic controls, 10 patients with reflux symptoms but without erosions, and 18 patients with erosions. The biopsies were morphologically evaluated by transmission electron microscopy, and by using immunohistochemistry for tight junction proteins (claudin-1 and claudin-2 proteins).

RESULTS

The expressions of tight junction proteins did not differ between asymptomatic controls and gastroesophageal reflux disease patients. In patients with gastroesophageal reflux disease, altered desmosomal junction morphology was only found in upper stratified squamous epithelium. Dilated intercellular space occurred only in upper stratified squamous epithelium and in patients with erosive esophagitis.

CONCLUSIONS

This study suggests that dilated intercellular space may not be uniformly present inside the esophageal mucosa and predominantly it is located in upper squamous epithelium. Presence of desmosomal junction alterations is associated with increased severity of gastroesophageal reflux disease. Besides dilated intercellular space, subtle changes in ultrastructural morphology of intercellular space allow better identification of inflamed esophageal mucosa relevant to acid reflux.

Gastroesophageal reflux activates the NF-κB pathway and impairs esophageal barrier function in mice

The barrier function of the esophageal epithelium is a major defense against gastroesophageal reflux disease. Previous studies have shown that reflux damage is reflected in a decrease in transepithelial electrical resistance associated with tight junction alterations in the esophageal epithelium. To develop novel therapies, it is critical to understand the molecular mechanisms whereby contact with a refluxate impairs esophageal barrier function. In this study, surgical models of duodenal and mixed reflux were developed in mice. Mouse esophageal epithelium was analyzed by gene microarray. Gene set enrichment analysis showed upregulation of inflammation-related gene sets and the NF-κB pathway due to reflux. Significance analysis of microarrays revealed upregulation of NF-κB target genes. Overexpression of NF-κB subunits (p50 and p65) and NF-κB target genes (matrix metalloproteinases-3 and -9, IL-1β, IL-6, and IL-8) confirmed activation of the NF-κB pathway in the esophageal epithelium. In addition, real-time PCR, Western blotting, and immunohistochemical staining also showed downregulation and mislocalization of claudins-1 and -4. In a second animal experiment, treatment with an NF-κB inhibitor, BAY 11-7085 (20 mg·kg⁻¹·day⁻¹ ip for 10 days), counteracted the effects of duodenal and mixed reflux on epithelial resistance and NF-κB-regulated cytokines. We conclude that gastroesophageal reflux activates the NF-κB pathway and impairs esophageal barrier function in mice and that targeting the NF-κB pathway may strengthen esophageal barrier function against reflux.

Gastroesophageal reflux activates the NF-κB pathway and impairs esophageal barrier function in mice

The barrier function of the esophageal epithelium is a major defense against gastroesophageal reflux disease. Previous studies have shown that reflux damage is reflected in a decrease in transepithelial electrical resistance associated with tight junction alterations in the esophageal epithelium. To develop novel therapies, it is critical to understand the molecular mechanisms whereby contact with a refluxate impairs esophageal barrier function. In this study, surgical models of duodenal and mixed reflux were developed in mice. Mouse esophageal epithelium was analyzed by gene microarray. Gene set enrichment analysis showed upregulation of inflammation-related gene sets and the NF-κB pathway due to reflux. Significance analysis of microarrays revealed upregulation of NF-κB target genes. Overexpression of NF-κB subunits (p50 and p65) and NF-κB target genes (matrix metalloproteinases-3 and -9, IL-1β, IL-6, and IL-8) confirmed activation of the NF-κB pathway in the esophageal epithelium. In addition, real-time PCR, Western blotting, and immunohistochemical staining also showed downregulation and mislocalization of claudins-1 and -4. In a second animal experiment, treatment with an NF-κB inhibitor, BAY 11-7085 (20 mg·kg⁻¹·day⁻¹ ip for 10 days), counteracted the effects of duodenal and mixed reflux on epithelial resistance and NF-κB-regulated cytokines. We conclude that gastroesophageal reflux activates the NF-κB pathway and impairs esophageal barrier function in mice and that targeting the NF-κB pathway may strengthen esophageal barrier function against reflux.

Esophageal intraluminal baseline impedance is associated with severity of acid reflux and epithelial structural abnormalities in patients with gastroesophageal reflux disease

BACKGROUND

The esophageal intraluminal baseline impedance may be used to evaluate the status of mucosa integrity. Esophageal acid exposure decreases the baseline impedance. We aimed to compare baseline impedance in patients with various reflux events and with different acid-related parameters, and investigate the relationships between epithelial histopathologic abnormalities and baseline impedance.

METHODS

A total of 229 GERD patients and 34 controls underwent 24-h multichannel intraluminal impedance and pH monitoring (MII-pH monitoring), gastroendoscopy, and completed a GERD questionnaire (GerdQ). We quantified epithelial intercellular spaces (ICSs) and expression of tight junction (TJ) proteins by histologic techniques.

RESULTS

Mean baseline values in reflux esophagitis (RE) (1752 ± 1018 Ω) and non-erosive reflux disease (NERD) (2640 ± 1143 Ω) were significantly lower than in controls (3360 ± 1258 Ω; p < 0.001 and p = 0.001, respectively). Among NERD subgroups, mean baselines in the acid reflux group (2510 ± 1239 Ω) and mixed acid/weakly acidic reflux group (2393 ± 1009 Ω) were much lower than in controls (3360 ± 1258 Ω; p = 0.020 and p < 0.001, respectively). The mean baseline in severe RE patients was significantly lower than in mild RE patients (LA-C/D vs. LA-A/B: 970 ± 505 Ω vs. 1921 ± 1024 Ω, p < 0.001). There was a significant negative correlation between baseline value and acid exposure time (AET) (r = -0.41, p < 0.001), and a weak but significant correlation (r = -0.20, p = 0.007) between baseline value and weakly AET. Negative correlations were observed between ICS and the baseline impedance (r = -0.637, p < 0.001) and claudin-1 and the baseline impedance (r = -0.648, p < 0.001).

CONCLUSIONS

Patients with dominant acid reflux events and with longer AET have low baseline impedance. Baseline values are correlated with esophageal mucosal histopathologic changes such as dilated ICS and TJ alteration.

Role of tight junction proteins in gastroesophageal reflux disease

BACKGROUND

Gastroesophageal reflux disease (GERD) is associated with impaired epithelial barrier function that is regulated by cell-cell contacts. The aim of the study was to investigate the expression pattern of selected components involved in the formation of tight junctions in relation to GERD.

METHODS

Eighty-four patients with GERD-related symptoms with endoscopic signs (erosive: n = 47) or without them (non-erosive: n = 37) as well as 26 patients lacking GERD-specific symptoms as controls were included. Endoscopic and histological characterization of esophagitis was performed according to the Los Angeles and adapted Ismeil-Beigi criteria, respectively. Mucosal biopsies from distal esophagus were taken for analysis by histopathology, immunohistochemistry and quantitative reverse-transcription polymerase chain reaction (RT-PCR) of five genes encoding tight junction components [Occludin, Claudin-1, -2, Zona occludens (ZO-1, -2)].

RESULTS

Histopathology confirmed GERD-specific alterations as dilated intercellular spaces in the esophageal mucosa of patients with GERD compared to controls (P < 0.05). Claudin-1 and -2 were 2- to 6-fold upregulation on transcript (P < 0.01) and in part on protein level (P < 0.015) in GERD, while subgroup analysis of revealed this upregulation for ERD only. In both erosive and non-erosive reflux disease, expression levels of Occludin and ZO-1,-2 were not significantly affected. Notably, the induced expression of both claudins did not correlate with histopathological parameters (basal cell hyperplasia, dilated intercellular spaces) in patients with GERD.

CONCLUSIONS

Taken together, the missing correlation between the expression of tight junction-related components and histomorphological GERD-specific alterations does not support a major role of the five proteins studied in the pathogenesis of GERD.

Bile salts disrupt human esophageal squamous epithelial barrier function by modulating tight junction proteins

Reflux of acid and bile acids contributes to epithelial tissue injury in gastro-esophageal reflux disease. However, the influence of refluxed material on human esophageal stratified epithelial barrier function and tight junction (TJ) proteins has not been fully elucidated. Here, we investigated the influence of acid and bile acids on barrier function and TJ protein distribution using a newly developed air-liquid interface (ALI) in vitro culture model of stratified squamous epithelium based on primary human esophageal epithelial cells (HEECs). Under ALI conditions, HEECs formed distinct epithelial layers on Transwell inserts after 7 days of culture. The epithelial layers formed TJ, and the presence of claudin-1, claudin-4, and occludin were detected by immunofluorescent staining. The NP-40-insoluble fraction of these TJ proteins was significantly higher by day 7 of ALI culture. Exposure of HEECs to pH 2, and taurocholic acid (TCA) and glycocholic acid (GCA) at pH 3, but not pH 4, for 1 h decreased transepithelial electrical resistance (TEER) and increased paracellular permeability. Exposure of cell layers to GCA (pH 3) and TCA (pH 3) for 1 h also markedly reduced the insoluble fractions of claudin-1 and -4. We found that deoxycholic acid (pH 7.4 or 6, 1 h) and pepsin (pH 3, 24 h) significantly decreased TEER and increased permeability. Based on these findings, ALI-cultured HEECs represent a new in vitro model of human esophageal stratified epithelium and are suitable for studying esophageal epithelial barrier functions. Using this model, we demonstrated that acid, bile acids, and pepsin disrupt squamous epithelial barrier function partly by modulating TJ proteins. These results provide new insights into understanding the role of TJ proteins in esophagitis.

Gastro-oesophageal reflux disease is associated with up-regulation of desmosomal components in oesophageal mucosa

AIMS

Gastro-oesophageal reflux disease (GERD) is associated with impaired epithelial barrier function. This study was aimed at investigating the role of desmosomal proteins in relation to GERD.

METHODS AND RESULTS

Ninety-five patients with GERD-related symptoms (erosive, n = 51; non-erosive, n = 44) and 27 patients lacking those symptoms were included. Endoscopic and histological characterization of oesophagitis was performed according to the Los Angeles and Ismeil-Beigi criteria, respectively. Multiple biopsies were taken from the oesophageal mucosa of each patient. Gene expression analysis of plakoglobin, desmoglein-1, desmoglein-2 and desmoglein-3 was performed by quantitative real time (RT)-polymerase chain reaction and immunohistochemistry in the oesophageal mucosa. Routine histology revealed specific GERD-related alterations, such as dilatation of intercellular spaces (DIS), basal cell hyperplasia (BCH), and elongation of the papillae, in the oesophageal mucosa of patients with GERD, as compared with controls (all parameters: P < 0.05). All four genes and corresponding proteins were found to be up-regulated by between 1.7 and 8.1-fold (transcript level, P < 0.05; protein level, P < 0.05). Induced gene expression levels of plakoglobin, desmoglein-1 and desmoglein-2 correlated significantly with DIS and BCH.

CONCLUSIONS

Taken together, the uniform up-regulation of desmosomal genes/proteins in the oesophageal mucosa of patients with GERD supports the concept of architectural and molecular changes in the desmosomal compartment in the pathogenesis of GERD.

Esophageal disease: updated information on inflammation

The following on esophageal disease provides updated information the mucosal defense against acid and acid-pepsin injury; the roles of platelet activating factor, mast cells, proinflammatory cytokines, and chemokines in inflammation; differences and similarities in erosive and nonerosive esophagitis; acid and vanilloid receptors in esophageal mucosa; and bile acid receptors in esophageal epithelium.

Acidic bile salts modulate the squamous epithelial barrier function by modulating tight junction proteins

Experimental models for esophageal epithelium in vitro either suffer from poor differentiation or complicated culture systems. An air-liquid interface system with normal human bronchial epithelial cells can serve as a model of esophageal-like squamous epithelial cell layers. Here, we explore the influence of bile acids on barrier function and tight junction (TJ) proteins. The cells were treated with taurocholic acid (TCA), glycocholic acid (GCA), or deoxycholic acid (DCA) at different pH values, or with pepsin. Barrier function was measured by transepithelial electrical resistance (TEER) and the diffusion of paracellular tracers (permeability). The expression of TJ proteins, including claudin-1 and claudin-4, was examined by Western blotting of 1% Nonidet P-40-soluble and -insoluble fractions. TCA and GCA dose-dependently decreased TEER and increased paracellular permeability at pH 3 after 1 h. TCA (4 mM) or GCA (4 mM) did not change TEER and permeability at pH 7.4 or pH 4. The combination of TCA and GCA at pH 3 significantly decreased TEER and increased permeability at lower concentrations (2 mM). Pepsin (4 mg/ml, pH 3) did not have any effect on barrier function. DCA significantly decreased the TEER and increased permeability at pH 6, a weakly acidic condition. TCA (4 mM) and GCA (4 mM) significantly decreased the insoluble fractions of claudin-1 and claudin-4 at pH 3. In conclusion, acidic bile salts disrupted the squamous epithelial barrier function partly by modulating the amounts of claudin-1 and claudin-4. These results provide new insights for understanding the role of TJ proteins in esophagitis.

Establishment of a reflux esophago-laryngitis model in rats

BACKGROUND

To investigate the pathophysiology of reflux laryngitis, an experimental model is required.

AIM

The aim of this study is to establish an animal model of reflux esophago-laryngitis, modifying our previously reported model of chronic acid reflux esophagitis.

METHODS

The modified chronic acid reflux esophagitis (m-RE) group (n = 10), in which the duodenum was wrapped with 2.5 mm of Nelaton catheter, was not treated with any drugs. Also postoperatively, two treatment groups (n = 10 in each) received different dosages of rabeprazole (RPZ): 1.0 mg/kg/day (RPZ 1.0 group) or 10.0 mg/kg/day (RPZ 10.0 group). As a control group (n = 5), other rats underwent sham operation. The esophagus and larynx were resected on day 14 after the operation, and ulcer score of the esophagus was assessed. The epithelial thickness and leukocyte infiltration of the supraglottic and subglottic laryngeal mucosae were investigated. The number of interleukin (IL)-1β-positive cells was also counted and defined as the IL-1β labeling index.

RESULTS

In the m-RE group, the epithelial thickness, leukocyte infiltration, and IL-1β labeling index of the supraglottic and subglottic laryngeal mucosae were increased compared with controls (P < 0.01). In the RPZ groups, not only the ulcer score of esophagus but also the epithelial thickness, leukocyte infiltration, and IL-1β labeling index of both the supraglottic and subglottic laryngeal mucosae were decreased dose-dependently relative to the m-RE group (P < 0.05).

CONCLUSIONS

Our modified chronic acid reflux esophagitis model proved useful in establishing a rat reflux esophago-laryngitis model, with both pathological laryngeal findings and reflux esophagitis shown to be improved by administration of a proton pump inhibitor.

Dissociation and dispersion of claudin-3 from the tight junction could be one of the most sensitive indicators of reflux esophagitis in a rat model of the disease

BACKGROUND

The aim of this study was to characterize pathological lesions of the esophageal epithelial tight junction (TJ) complex in a rat reflux esophagitis (RE) model in a search for a reliable diagnostic indicator.

METHODS

Rats underwent an operation to induce RE, with or without rabeprazole treatment (1.0 and 10.0 mg/kg/day). Sham-operated rats served as a control. Fourteen days after the operation, esophagi were isolated from the rats and submitted to double-label confocal immunofluorescence microscopy, and biochemical analyses.

RESULTS

Immunofluorescence microscopy revealed that claudins-1, -3, and -4 were located on the surfaces of epithelial cells in the normal esophagus of the control group, although there were differences in the distribution patterns between claudin-3 and claudins-1 and -4 in the epithelial layer. However, in RE, the immunoreactivity of claudin-3 on the cell surface was decreased, and it appeared instead as a faint granular pattern within the epithelial cytoplasm. Claudin-3 expression in the entire esophageal epithelium was also decreased. The expression and location of claudins-1 and -4 in epithelial cells were basically unaffected in RE. Gastric acid-induced dissociation of claudin-3 elicited instability of the epithelial TJ complex, which was confirmed by sedimentation analysis using centrifugation in a sucrose density gradient. Rabeprazole (10.0 mg/kg/day) attenuated these alterations.

CONCLUSIONS

Our data indicate that the dispersion of claudin-3 from esophageal epithelial plasma membranes to cytoplasm and the resulting instability of the TJ complex could be one of the most specific and sensitive indicators for monitoring inflammatory and recovery processes in RE.

The integrity of the esophageal mucosa. Balance between offensive and defensive mechanisms

Heartburn is the most common and characteristic symptom of gastroesophageal reflux disease. It ultimately results from contact of refluxed gastric acid with nociceptors within the esophageal mucosa and transmission of this peripheral signal to the central nervous system for cognition. Healthy esophageal epithelium provides an effective barrier between refluxed gastric acid and esophageal nociceptors; but this barrier is vulnerable to attack and damage, particularly by acidic gastric contents. How gastric acid is countered by defensive elements within the esophageal mucosa is a major focus of this discussion. When the defense is successful, the subject is asymptomatic and when unsuccessful, the subject experiences heartburn. Those with heartburn commonly fall into one of three endoscopic types: nonerosive reflux disease, erosive esophagitis and Barrett's esophagus. Although what determines endoscopic type remains unknown; it is proposed herein that inflammation plays a key, modulating role.

Protons released during pancreatic acinar cell secretion acidify the lumen and contribute to pancreatitis in mice

BACKGROUND & AIMS

Secretory granules are acidic; cell secretion will therefore lead to extracellular acidification. We propose that during secretion, protons co-released with proteins from secretory granules of pancreatic acinar cells acidify the restricted extracellular space of the pancreatic lumen to regulate normal physiological and pathophysiological functions in this organ

METHODS

Extracellular changes in pH were quantified in real time using 2-photon microscopy analysis of pancreatic tissue fragments from mouse models of acute pancreatitis (mice given physiological concentrations [10 -20 pM] of cholecystokinin or high concentrations of [100 nM] cerulein). The effects of extracellular changes in pH on cell behavior and structures were measured.

RESULTS

With physiological stimulation, secretory granule fusion (exocytosis) caused acidification of the pancreatic lumen. Acidifications specifically affected intracellular calcium responses and accelerated the rate of recovery from agonist-evoked calcium signals. Protons therefore appear to function as negative-feedback, extracellular messengers during coupling of cell stimuli with secretion. At high concentrations of cerulein, large increases in secretory activity were associated with extreme, prolonged acidification of the luminal space. These pathological changes in pH led to disruption of intercellular junctional coupling, measured by movement of occludin and E-cadherin.

CONCLUSIONS

By measuring changes in extracellular pH in pancreas of mice, we observed that luminal acidification resulted from exocytosis of zymogen granules from acinar cells. This process is part of normal organ function but could contribute to the tissue damage in cases of acute pancreatitis.

Esophageal sensation and esophageal hypersensitivity - overview from bench to bedside

Noxious stimuli in the esophagus activate nociceptive receptors on esophageal mucosa, such as transient receptor potential, acid-sensing ion channel and the P2X family, a family of ligand-gated ion channels responsive to ATP, and this generates signals that are transmitted to the central nervous system via either spinal nerves or vagal nerves, resulting in esophageal sensation. Among the noxious stimuli, gastric acid and other gastric contents are clinically most important, causing typical reflux symptoms such as heartburn and regurgitation. A conventional acid penetration theory has been used to explain the mechanism of heartburn, but much recent evidence does not support this theory. Therefore, it may be necessary to approach the causes of heartburn symptoms from a new conceptual framework. Hypersensitivity of the esophagus, like that of other visceral organs, includes peripheral, central and probably psychosocial factor-mediated hypersensitivity, and is known to play crucial roles in the pathoegenesis of nonerosive reflux disease, functional heartburn and non-cardiac chest pain. There also are esophagitis patients who do not perceive typical symptoms. This condition is known as silent gastroesophageal reflux disease. Although the pathogenesis of silent gastroesophageal reflux disease is still not known, hyposensitivity to reflux of acid may possibly explain the condition.

Rikkunshito, a traditional Japanese medicine, may relieve abdominal symptoms in rats with experimental esophagitis by improving the barrier function of epithelial cells in esophageal mucosa

BACKGROUND

A traditional Japanese medicine, rikkunshito, has been reported to relieve dyspepsia symptoms. We investigated the effect of rikkunshito on RE-induced abdominal dyspepsia, and performed experiments to elucidate the mechanism of that effect.

METHODS

RE model rats were prepared using 8-week-old male Wistar rats, and rikkunshito was administered in drinking water. Voluntary movement was used as an index of RE-induced abdominal dyspepsia, which was monitored by an infrared sensor. On the tenth day after surgery, the total area of esophageal erosion was measured, and samples of nonerosive mucosa were collected. Using those samples, intercellular spaces of epithelial mucosa were examined by transmission electron microscopy, and the NP-40-soluble and -insoluble levels of the tight junction proteins claudin-1, -3 and -4 and their mRNAs were determined.

RESULTS

Rikkunshito did not reduce the average total area of erosive lesions in the esophageal mucosa of RE model rats. On day 10, voluntary movement was significantly decreased in the RE model rats and rikkunshito significantly increased it. Nonerosive esophageal mucosa from RE rats showed dilation of intercellular spaces in epithelium, and significantly decreased claudin-3 mRNA and protein levels. Rikkunshito significantly suppressed intercellular space dilation and significantly increased the level of NP-40-insoluble claudin-3, but it did not affect the mRNA level, suggesting that it promoted tight junction formation by facilitating the translocation of proteins.

CONCLUSION

Rikkunshito increased voluntary movement in RE model rats. This may have been because rikkunshito ameliorated the symptoms of RE by improving the barrier function of esophageal mucosa.

Reactive nitrogen oxide species induce dilatation of the intercellular space of rat esophagus

OBJECTIVE

Dilatation of the intercellular space (DIS) of the esophageal epithelium is recognized as one of the earliest histological changes in gastroesophageal reflux disease patients. At the human gastroesophageal junction, reactive nitrogen oxide species (RNOS) are generated luminally through the entero-salivary re-circulation of dietary nitrate. In cases with gastroesophageal reflux, the site of luminal RNOS generation may shift to the distal esophagus. The aim of this study was to investigate whether luminal RNOS exposure could be involved in the pathogenesis of DIS.

MATERIAL AND METHODS

Rat esophageal mucosa was studied with an Ussing chamber model. On the luminal side of the chamber, RNOS were generated by the acidification of physiologic concentrations of sodium nitrite (1.0 or 5.0 mM). Esophageal barrier function was assessed by means of electrophysiological transmembrane resistance and membrane permeability by means of (3)H-mannitol flux. The dimensions of the intercellular spaces were assessed by using transmission electron microscopy.

RESULTS

Administration of acid plus sodium nitrite induced DIS of the esophageal epithelium, and this ultrastructural morphological change was accompanied by a concomitant decrease in the transmembrane resistance and an increase in the epithelial permeability. The DIS induced by luminal RNOS was also confirmed in an in vivo exposure model.

CONCLUSIONS

The present animal study indicates that the RNOS generated by the acidification of salivary nitrite in the presence of refluxed gastric acid in the esophagus could be a luminal factor that is responsible for the induction of DIS. Further studies are warranted to investigate the clinical relevance of the present findings to the human situation.

Expression of tight junction protein occludin and changes in intercellular space in the esophageal epithelium in patients with gastroesophageal reflux disease

AIM: To investigate the distribution and expression of tight junction protein occludin and observe changes in intercellular space in the esophageal epithelium in patients with gastroesophageal reflux disease (GERD).

METHODS: Sixty-two GERD patients (30 cases of reflux esophagitis (RE) and 32 cases of nonerosive reflux disease (NERD) and 10 non-GERD patients were included in the study. Immunohistochemistry was used to examine the distribution and expression of occludin in the esophageal epithelium in these patients. The stained sections were observed and photographed under light microscopy. The intercellular space in the esophageal epithelium was measured by computer-assisted morphometry. One hundred measurements were performed in each case to calculate the mean intercellular space diameter.

RESULTS: Occludin was distributed continuously in the cell membrane in normal esophageal epithelium. Of 32 NERD patients, 4 showed normal occludin expression, and 28 showed varying degrees of aberrant occludin expression (e.g., incomplete membrane expression, cytoplasmic expression and expression loss). In contrast, all RE patients showed aberrant occludin expression. The rates of aberrant occludin expression in NERD and RE patients were significantly higher than that in non- GERD patients (both P < 0.01). No significant difference was observed in the rate of aberrant occludin expression between RE and NERD patients (P > 0.05). The mean intercellular space diameters in NERD and RE patients were significantly higher than that in non- GERD patients (1.38 ± 0.26 µm and 1.51 ± 0.31 µm vs 0.77 ± 0.12 µm, respectively; both P < 0.01). No significant difference was noted in the mean intercellular space diameter between RE and NERD patients (P > 0.05).

CONCLUSION: Occludin shows diminished expression and altered distribution in the esophageal epithelium in patients with gastroesophageal reflux disease. Aberrant expression of occludin may result in dilated intercellular space and impair the integrity of mucosal epithelial barrier, which may partly explain the pathogenesis of GERD.

Interleukin-6, desmosome and tight junction protein expression levels in reflux esophagitis-affected mucosa

AIM: To investigate the correlation between the expression levels of interleukin (IL)-6 and proteins in tight junctions (TJs) in the esophageal mucosa of rats modeling different types of reflux esophagitis (RE), and the ability of aluminum phosphate to protect against RE-induced mucosal damage via these proteins.

METHODS: Male SPF Wistar rats aged 56 d were divided randomly into acid RE, alkaline RE, mixed RE, and control groups. Various surgical procedures were performed to establish rat models of acid RE. At 14 d after the procedure, some of the rats started aluminum phosphate treatment. Transmission electron microscopy (TEM) was used to observe the morphological features of TJs and desmosomes in the esophageal epithelium. Immunohistochemical methods and Western blotting were used to measure expression of claudin 1, occludin, ZO-1, JAM-1, DSG-1 and IL-6; reverse transcription polymerase chain reaction (RT-PCR) was used to measure expression of mRNA of claudin 1, occludin, ZO-1, JAM-1, DSG-1 and IL-6.

RESULTS: At day 14 after the procedures, an RE model was established in all subsequently sacrificed rats of groups A, B and C. By both gross and microscopic observation, the mucosa was damaged and thickened as the disease progressed. With TEM observation, a widened intercellular space was noticed, with significantly fewer desmosomes. Immunohistochemistry showed significantly higher levels of all proteins in all RE models compared to control rats at 3 d after operation (65.5% ± 25.6% vs 20.5% ± 2.1%, P < 0.05, respectively). At 14 d after operation, along with continuing hyperplasia in the basal layer, the expression of TJ proteins in individual cells gradually decreased (12.4% ± 2.1% vs 20.5% ± 2.1%, P < 0.05, respectively). Western blottings and RT-PCR showed a directly proportional increase in IL-6 levels in relation to TJ proteins, as compared to controls (0.878 ± 0.024 vs 0.205 ± 0.021 and 0.898 ± 0.022 vs 0.205 ± 0.021, P < 0.05, respectively). Upon treatment with aluminum phosphate, however, these protein levels were restored to normal gradually over 30-60 d in rats with acid RE (30.4% ± 2.1% vs 20.5% ± 2.1%, P > 0.05, treated vs untreated, respectively). These levels increased in the rat with alkaline RE, and this increase was accompanied by continued hyperplasia in comparison with controls (85.5% ± 25.6% vs 20.5% ± 2.1%, P < 0.05, respectively). Furthermore, the expression of TJ proteins was not correlated significantly with that of IL-6 in this group.

CONCLUSION: These findings indicate that TJ proteins are highly expressed as an early molecular event involved in RE development, and that IL-6 is an inflammatory factor in this process.

Characteristic pathological findings and effects of ecabet sodium in rat reflux esophagitis

AIM: To explore the pathological findings in the entire esophagus in rats with reflux esophagitis, and the effects of ecabet sodium (ES).

METHODS: A rat model of chronic acid reflux esophagitis was used. In the treatment group, ES was administered after surgery (n = 16). No drug was administered postoperatively to the esophagitis group (n = 9). Sham-operated rats were used as a control group (n = 5). Rats were sacrificed on day 7 after the operation. The epithelial thickness and leukocyte infiltration were examined in the upper, middle and lower areas of the esophagus. The survival rate, incidence of esophageal ulcer, and mean surface area and number of esophageal ulcers were determined in the esophagitis and ES groups. Esophageal histology was assessed in all three groups.

RESULTS: Leukocyte infiltration in the esophagitis group was 26.3 ± 22.0 in the middle esophagus and 8.2 ± 4.9 in the upper esophagus, which was significantly greater than that in the controls (1.3 ± 1.1 and 1.4 ± 1.0, respectively) (P < 0.05). The thickness of the epithelium in the esophagitis group was 210.8 ± 47.7 &mgr;m in the lower esophagus and 204.2 ± 60.1 &mgr;m in the middle esophagus, which was significantly greater than that in the controls (26.0 ± 5.5 and 21.0 ± 6.5 &mgr;m, respectively) (P < 0.05). The mean number of ulcers per animal in the ES group in the entire esophagus was 5.4 ± 2.5, which was significantly less than that in the esophagitis group (9.0 ± 3.5) (P < 0.05). The epithelial thickness in the ES group was 97.5 ± 32.2 &mgr;m in the lower esophagus, which was decreased compared with that in the esophagitis group (210.8 ± 47.7 &mgr;m) (P < 0.05).

CONCLUSION: Mucosal inflammation extended to the upper esophagus close to the hypopharynx. Our study suggested that ES may have a useful defensive role in reflux esophagitis.

Zonulin is not increased in the cardiac and esophageal mucosa of patients with gastroesophageal reflux disease

Human Zonulin, related to the Zonula occludens toxin of Vibrio cholerae, regulates intestinal permeability and is induced in inflammatory disorders of the lower GI tract. Gastroesophageal reflux disease (GERD) is associated with an impairment of epithelial barrier function. Here, we studied expression of zonulin in the gastroesophageal mucosa of 58 patients with typical reflux symptoms and 27 asymptomatic controls. During endoscopy, multiple biopsies from gastroesophageal mucosa were obtained for routine histopathology (Helicobacter pylori-status, inflammation) and gene expression analysis (immunohistochemistry, ELISA). Patients with GERD presented with typical histopathological alterations like elongation of papillae (P=0.015), basal cell hyperplasia (P<0.001) and dilatation of intercellular spaces (P=0.002). Zonulin was found to be expressed ubiquitously in gastroesophageal mucosa. Mucosal levels in controls ranged between 2.2 and 3.7 ng/microg total protein. Mean values were significantly higher in antrum (3.3+/-1.7 ng/microg) than cardia (2.7+/-1.2n g/microg) and esophagus (2.2+/-1.3 ng/microg) (P<0.001), but did not differ between GERD and controls for cardia and esophageal mucosa. Immunohistochemistry revealed that predominantly epithelial cells but not stromal cells contribute to the zonulin expression in gastroesophageal mucosa. In conclusion, despite its established role for intestinal permeability, Zonulin seems not to be involved in the regulation of epithelial barrier function in relation to GERD.

Experimental oesophagitis in the rat is associated with decreased voluntary movement

Growing interest has arisen regarding the mechanism of dyspeptic symptom generation. However, no evaluation system of these symptoms in animals has been developed. In this study, we examined whether voluntary movement of rats could be a measure to assess visceral symptoms of reflux oesophagitis. A chronic acid reflux oesophagitis model was made using rats, and the size of erosions was measured. Omeprazole was administered to the oesophagitis rats for 10 days. The amount of voluntary movement was measured by an infrared sensor. Intracellular spaces in oesophageal epithelium were also measured using a emission electron microscope. NP-40 soluble and insoluble fractions of claudins were examined by Western blot. Voluntary movement was significantly lower in the oesophagitis model rats than in the sham-operated rats (P < 0.01). Although omeprazole reduced the size of erosions, it did not significantly affect the total amount of voluntary movement (r = -0.033, P = 0.916). Intracellular spaces were significantly dilated in the oesophagitis model rats and claudin-3 showed a significantly lower relative quantity in the NP-40 insoluble fraction. Omeprazole significantly increased voluntary movement of oesophagitis model rats and the relative quantity of claudin-3 in the insoluble fraction (P < 0.05). Dilated intercellular spaces and the lower level of claudin-3 may relate to the voluntary movement of oesophagitis model rats. Decreases in voluntary movement of oesophagitis model rats may reflect visceral symptoms and be able to serve as an index of chronic abdominal symptoms.

Nonerosive reflux disease: a pathophysiologic perspective

Nonerosive reflux disease (NERD) is the most common phenotype of gastroesophageal reflux disease. By definition, patients with NERD have typical reflux symptoms caused by the intraesophageal reflux of gastric contents but have no visible esophageal mucosal injury. This is in contrast to patients with reflux esophagitis, also known as erosive reflux disease, and Barrett's esophagus, who have obvious esophageal mucosal injury on endoscopy. Only 50% of patients with NERD have pathologic esophageal acid contact time (ACT) as detected on 24-hour pH monitoring (ie, NERD-positive). NERD patients with physiologic esophageal ACT and good temporal correlation of symptoms with reflux events (symptom index > 50% or symptom-association probability > 95%) are considered to have esophageal hypersensitivity (ie, NERD-negative). Finally, patients with physiologic esophageal ACT but poor symptom-reflux correlation are now considered to have functional heartburn and not NERD. NERD-positive patients have motor dysfunction and acidic reflux abnormalities that are similar to patients with reflux esophagitis and Barrett's esophagus, whereas NERD-negative patients have minimal abnormalities that are not much different than healthy controls. The histopathologic feature most indicative of NERD is the presence of dilated intercellular spaces within squamous epithelium, an ultrastructural abnormality readily identified on transmission electron microscopy and on light microscopy.

Effects of the concentration and frequency of acid infusion on the development and maintenance of esophageal hyperalgesia in a human volunteer model

Previous studies have demonstrated that a single 30-min distal esophageal infusion of concentrated (0.15 M, pH 0.8) hydrochloric acid (HCl) induces hyperalgesia to an electrical stimulus in a human model. The aim of this study was to refine this model using physiological acid concentrations (pH 1.8-4) in repeated short exposures. Two different cohorts of 10 volunteers underwent two studies. Study 1: randomization to four 5-min distal esophageal infusions of acid (0.15 M) or saline, 1 h apart. Double-blind measurements of baseline and postexposure proximal esophageal and chest wall pain thresholds (PTs) were performed to electrical stimulation at 30-min intervals throughout the study. Study 2: randomization to four 15-min infusions of 0.15, 0.075, and 0.01 M HCl and saline. In study 1, with multiple acid infusions, a significant progressive drop in PTs was observed in both areas tested (P < or = 0.0001). In study 2, increasing acid concentrations had a significant effect over multiple time points, P < or = 0.0001. Similar initial reductions in PTs were observed for all acid concentrations compared with saline; however, hypersensitivity was shorter lasting with 0.01 M acid. In healthy subjects, esophageal hypersensitivity can be induced and maintained up to 4 h by repeated short-duration acid infusion and at physiological pH levels. This has implications for future model design and pathophysiological understanding of acid-related esophageal hypersensitivity.

Electrophysiological characterization of vagal afferents relevant to mucosal nociception in the rat upper oesophagus

Emerging evidence indicates a nociceptive role of vagal afferents. A distinct oesophageal innervation in the rat, with muscular and mucosal afferents travelling predominantly in the recurrent (RLN) and superior laryngeal nerve (SLN), respectively, enabled characterization of mucosal afferents with nociceptive properties, using novel isolated oesophagus-nerve preparations. SLN and RLN single-fibre recordings identified 55 and 14 units, respectively, with none conducting faster than 8.7 m s(-1). Mucosal response characteristics in the SLN distinguished mechanosensors (n = 13), mechanosensors with heat sensitivity (18) from those with cold sensitivity (19) and a mechanoinsensitive group (5). The mechanosensitive fibres, all slowly adapting, showed a unimodal distribution of mechanical thresholds (1.4-128 mN, peak approximately 5.7 mN). No difference in response characteristics of C and Adelta fibres was encountered. Mucosal proton stimulation (pH 5.4 for 3 min), mimicking gastro-oesophageal reflux disease (GORD), revealed in 31% of units a desensitizing response that peaked around 20 s and faded within 60 s. Cold stimulation (15 degrees C) was proportionally encoded but the response showed slow adaptation. In contrast, the noxious heat (48 degrees C) response showed no obvious adaptation with discharge rates reflecting the temperature's time course. Polymodal (69%) mucosal units, > 30% proton sensitive, were found in each fibre category and were considered nociceptors; they are tentatively attributed to vagal nerve endings type I, IV and V, previously morphologically described. All receptive fields were mapped and the distribution indicates that the posterior upper oesophagus may serve as a 'cutbank', detecting noxious matters, ingested or regurgitated, and triggering nocifensive reflexes such as bronchoconstriction in GORD.

Metabolic syndrome and gastrointestinal diseases

Metabolic syndrome is a cluster of metabolic abnormalities consisting essentially of obesity, especially abdominal obesity. Metabolic syndrome has been highlighted as a risk factor for cardiovascular and other chronic diseases. Obesity has been implicated in various gastrointestinal diseases such as gastroesophageal reflux diseases and colorectal cancer. Recently, abdominal obesity has been shown to be more important than obesity as expressed by an elevated body mass index as a causative factor for the development of these diseases. In addition to the mechanical effects of obesity, such as an increase in intra-abdominal pressure from large amounts of adipose tissue, substances that adipose tissues secrete, such as tumor necrosis factor-alpha, interleukin-6, leptin, and insulin-like growth factor-1, have been proposed to be pathogenic links to these diseases. In this review, we discuss the association of metabolic syndrome or the individual components of metabolic syndrome, focusing on obesity and abdominal obesity, with gastrointestinal diseases.

Molecular defense mechanisms of Barrett's metaplasia estimated by an integrative genomics

Barrett's esophagus is characterized by the replacement of squamous epithelium with specialized intestinal metaplastic mucosa. The exact mechanisms of initiation and development of Barrett's metaplasia remain unknown, but a hypothesis of "successful adaptation" against noxious reflux components has been proposed. To search for the repertoire of adaptation mechanisms of Barrett's metaplasia, we employed high-throughput functional genomic and proteomic methods that defined the molecular background of metaplastic mucosa resistance to reflux. Transcriptional profiling was established for 23 pairs of esophageal squamous epithelium and Barrett's metaplasia tissue samples using Affymetrix U133A 2.0 GeneChips and validated by quantitative real-time polymerase chain reaction. Differences in protein composition were assessed by electrophoretic and mass-spectrometry-based methods. Among 2,822 genes differentially expressed between Barrett's metaplasia and squamous epithelium, we observed significantly overexpressed metaplastic mucosa genes that encode cytokines and growth factors, constituents of extracellular matrix, basement membrane and tight junctions, and proteins involved in prostaglandin and phosphoinositol metabolism, nitric oxide production, and bioenergetics. Their expression likely reflects defense and repair responses of metaplastic mucosa, whereas overexpression of genes encoding heat shock proteins and several protein kinases in squamous epithelium may reflect lower resistance of normal esophageal epithelium than Barrett's metaplasia to reflux components. Despite the methodological and interpretative difficulties in data analyses discussed in this paper, our studies confirm that Barrett's metaplasia may be regarded as a specific microevolution allowing for accumulation of mucosal morphological and physiological changes that better protect against reflux injury.