Functional oesophageal epithelial defense against acid

Lack of Association between Epidermal Growth Factor or Its Receptor and Reflux Esophagitis, Barrett’s Esophagus, and Esophageal Adenocarcinoma: A Case-Control Study

The epidermal growth factor (EGF) and its receptor (EGFR) gene-gene interactions were shown to increase the susceptibility to esophageal cancer. However, the role of the EGF/EGFR pathway in the development of gastroesophageal reflux disease (GERD) and its complications (reflux esophagitis (RE), Barrett's esophagus (BE), and esophageal adenocarcinoma (EAC)) remains unclear. This association study is aimed at investigating functional EGF and EGFR gene polymorphisms, their mRNA expression in esophageal tissues, and EGF plasma levels in relation to RE, BE, and EAC development in the Central European population. 301 patients with RE/BE/EAC (cases) as well as 98 patients with nonerosive reflux disease (NERD) and 8 healthy individuals (controls) were genotyped for +61 A>G EGF (rs4444903) and +142285 G>A EGFR (rs2227983) polymorphisms using the TaqMan quantitative polymerase chain reaction (qPCR). In random subgroups, the EGF and EGFR mRNA expressions were analyzed by reverse transcription qPCR in esophageal tissue with and without endoscopically visible pathological changes; and the EGF plasma levels were determined by enzyme-linked immunosorbent assay. None of the genotyped SNPs nor EGF-EGFR genotype interactions were associated with RE, BE, or EAC development (p > 0.05). Moreover, mRNA expression of neither EGF nor EGFR differed between samples of the esophageal tissue with and without endoscopically visible pathology (p > 0.05) nor between samples from patients with different diagnoses, i.e., RE, BE, or EAC (p > 0.05). Nevertheless, the lower EGF mRNA expression in carriers of combined genotypes AA +61 EGF (rs4444903) and GG +142285 EGFR (rs2227983; p < 0.05) suggests a possible direct/indirect effect of EGF-EGFR gene interactions on EGF gene expression. In conclusion, EGF and EGFR gene variants and their mRNA/protein expression were not associated with RE, BE or EAC development in the Central European population.

Inhibition of NHE-1 Increases Smoke-Induced Proliferative Activity of Barrett's Esophageal Cell Line

Several clinical studies indicate that smoking predisposes its consumers to esophageal inflammatory and malignant diseases, but the cellular mechanism is not clear. Ion transporters protect esophageal epithelial cells by maintaining intracellular pH at normal levels. In this study, we hypothesized that smoking affects the function of ion transporters, thus playing a role in the development of smoking-induced esophageal diseases. Esophageal cell lines were treated with cigarettesmoke extract (CSE), and the viability and proliferation of the cells, as well as the activity, mRNA and protein expression of the Na+/H+ exchanger-1 (NHE-1), were studied. NHE-1 expression was also investigated in human samples. For chronic treatment, guinea pigs were exposed to tobacco smoke, and NHE-1 activity was measured. Silencing of NHE-1 was performed by using specific siRNA. CSE treatment increased the activity and protein expression of NHE-1 in the metaplastic cells and decreased the rate of proliferation in a NHE-1-dependent manner. In contrast, CSE increased the proliferation of dysplastic cells independently of NHE-1. In the normal cells, the expression and activity of NHE-1 decreased due to in vitro and in vivo smoke exposure. Smoking enhances the function of NHE-1 in Barrett's esophagus, and this is presumably a compensatory mechanism against this toxic agent.

OEsophageal Ion Transport Mechanisms and Significance Under Pathological Conditions

Ion transporters play an important role in several physiological functions, such as cell volume regulation, pH homeostasis and secretion. In the oesophagus, ion transport proteins are part of the epithelial resistance, a mechanism which protects the oesophagus against reflux-induced damage. A change in the function or expression of ion transporters has significance in the development or neoplastic progression of Barrett’s oesophagus (BO). In this review, we discuss the physiological and pathophysiological roles of ion transporters in the oesophagus, highlighting transport proteins which serve as therapeutic targets or prognostic markers in eosinophilic oesophagitis, BO and esophageal cancer. We believe that this review highlights important relationships which might contribute to a better understanding of the pathomechanisms of esophageal diseases.

Local effects of epidermal growth factor on the wound healing in esophageal anastomosis: An experimental study

OBJECTIVE

In this study with the experimental model of primary repair of esophageal atresia(EA), we investigated the effects of the epidermal growth factor(EGF) on wound healing in the anastomosis of EA.

MATERIALS AND METHODS

Forty rabbits that were performed a resection of a 1-cm segment of the cervical esophagus followed by the end-to-end anastomosis were divided into four groups. Group I (7-day group) and III (21-day group), the control groups, had no EGF applied to the anastomosis. In group II (7-day group) and group III (21-day group), all around the anastomoses were locally covered with 100 μg/kg EGF. Group 1, 2 and 3, 4 were sacrificed on the 7th and 21st day, respectively. We investigated and compared with bursting pressure, vascularization around the anastomotic line by histopathology, inflammation, and fibroblast granulation as well as hydroxyproline level by biochemical.

RESULTS

No significant difference was found at vascularization and inflammation between all of the groups (p > 0.05). Considering the critical parameters of the groups, at bursting pressure difference was found between group 1 and 2 as well as 3 and (p < 0.05). At fibroblast granulation and hydroxyproline level, no difference was found between group 1 and 2 (p > 0.05) but the difference between group 3 and 4 (p < 0.05).

CONCLUSION

EGF might be useful in preventing anastomotic leakage of esophageal atresia in primary anastomosis of esophageal atresia by accelerating wound healing process and increasing the stability of the anastomotic line.

Increased prevalence of airway reactivity in children with eosinophilic esophagitis

RATIONALE

Asthma is prevalent in children with eosinophilic esophagitis (EoE) estimated at 24-42% in prior studies versus 9% for the general population. However, pulmonary function and airway hyperresponsiveness (AHR) in children with EoE have not been previously defined.

METHODS

A cross-sectional prospective study was conducted of children ages 7-18 years with EoE and healthy controls. Methacholine bronchial challenge and exhaled nitric oxide were assessed. As measures of atopy and immune activation, peripheral blood was analyzed for total IgE, specific IgE to selected aeroallergens, eosinophil count, and serum cytokines including eotaxin.

RESULTS

EoE subjects (n = 33) and healthy controls (n = 37) demonstrated similar, normal baseline spirometry. AHR occurred in 33% of children with EoE and 11% of healthy controls (P = 0.04; 95% confidence intervals [19%, 52%] and [4%, 26%], respectively). The majority of EoE subjects with AHR had no prior diagnosis of asthma. Overall, 69.7% of EoE subjects had either asthma or AHR. For EoE subjects, total serum IgE was the only biomarker associated with a greater risk of AHR (OR = 9.643, 95%CI 1.633, 56.925). EoE subjects with and without asthma were similar to healthy controls in mean levels of serum cytokines (IL-5, IL-9, EGF, FGF-2, eotaxin). In exploratory analyses, the subgroup with EoE and asthma without asthma controller therapy had higher mean FGF-2 than EoE subjects without asthma (110 pg/ml vs. 65 pg/ml, P = 0.0426).

CONCLUSIONS

Asthma and AHR may be more prevalent than previous estimates in children with EoE. For subjects with EoE, elevation in serum IgE was associated with a greater risk of AHR.

Esophageal epithelial resistance

Besides its important role of digestion and absorption, esophageal tissue has an essential role as a major barrier against intraluminal pathogens like hostile microorganisms and toxins. This barrier function is achieved via various mechanical, chemical, and immunological mechanisms which are typically altered in inflammatory diseases, thereby causing subsequent damage of the mucosa. In this review we will focus on the main structural and functional barriers of host defense within the esophageal mucosa, including the epithelial layer, membrane-bound and secretory mucins, and different types of defensins. In addition, we will discuss the relevance of biofilm on esophageal tissue and will illustrate the importance of different regulators of intestinal permeability like zonulin and desmosomal components.

Endoscopic characteristics of short-segment Barrett's esophagus, focusing on squamous islands and mucosal folds

BACKGROUND AND AIM

Endoscopic definitions of Barrett's esophagus (BE) vary among countries, mainly because of the difficulty in diagnosing short-segment BE (SSBE) endoscopically. The aim of this study was to investigate whether the endoscopic identification of squamous islands and the specific position of columnar epithelium helps improve the diagnosis of SSBE.

METHODS

First, we prospectively enrolled 100 consecutive patients with SSBE and evaluated the number of identified squamous islands in the columnar epithelium with different modalities: white light (WL), narrow band imaging (NBI), and iodine chromoendoscopy. Second, in another group of 100 consecutive patients with tongue-like SSBE, the correlation of the location of Barrett's mucosa to the esophageal longitudinal folds (ridge or valley) was evaluated endoscopically.

RESULTS

It was possible to detect squamous islands in 48, 71, and 75 patients by WL, NBI, and iodine chromoendoscopy, respectively. The detection rate of squamous islands by NBI or iodine chromoendoscopy was significantly superior to that by WL. Tongue-like SSBEs were predominantly found on the ridge of mucosal folds (71%), similar to the location of mucosal breaks (84%).

CONCLUSIONS

Squamous islands in the columnar epithelium were efficiently observed by NBI or iodine chromoendoscopy. SSBE was found more frequently on the ridges but not in the valleys of esophageal longitudinal mucosal folds. NBI endoscopic observation focusing on columnar epithelium with squamous islands on the ridges of distal esophageal folds may improve endoscopic detection of SSBE.

Functional single-nucleotide polymorphism of epidermal growth factor is associated with the development of Barrett's esophagus and esophageal adenocarcinoma

Reflux esophagitis (RO) and Barrett's esophagus (BO) can cause esophageal adenocarcinoma (OAC). The esophageal mucosa in the RO-BO-OAC cascade is chronically exposed to gastro-esophageal reflux. Epidermal growth factor (EGF) has an important role in the protection and repair of mucosal damage, and non-physiologic levels are associated with gastrointestinal tumors. The aim is to determine the functional effect of EGF gene polymorphisms on RO, BO and OAC development. A cohort of 871 unrelated Dutch Caucasians consisted of 198 healthy controls, 298 RO patients, 246 BO patients and 129 OAC patients. The frequency of the EGF-production-associated 5'UTR A+61G polymorphism was determined in these four groups. EGF immunohistochemistry was performed on BO biopsies. EGF expression was significantly lower in the G/G genotype compared with the A/G (P=0.008) and A/A (P=0.002) group. The G/G genotype was significantly more prevalent in RO (odds ratios (OR)=2.6; 95% confidence intervals (95% CI): 1.3-5.2), BO (OR=3.0; 95% CI: 1.5-6.2) and OAC (OR=4.1; 95% CI: 1.8-9.7) than in controls. The G allele is associated with reduced EGF expression and increased risk for RO, BO and OAC development. This indicates that reduced mucosal protection resulting from genetically decreased EGF expression enhances esophageal tumor development.

Epithelial Na+ channel delta subunit is an acid sensor in the human oesophagus

Gastro-oesophageal reflux disease is caused by the reflux of gastric contents into the oesophagus, and thus the oesophageal lumen is damaged by gastric acid. The acid sensor involved in oesophageal epithelial defense is still unclear. Recently, we described that the epithelial Na(+) channel delta subunit (ENaCdelta) is a candidate molecule for a pH sensor in the human brain. Here, using reverse transcription-polymerase chain reaction and in situ hybridization methods, we showed that the proton-sensitive ENaCdelta was strongly expressed in the epithelial layer of the human oesophagus, representative peripheral tissue that can be exposed to an acidic environment. Other ENaC subunits (alpha, beta, and gamma) were also localized there. Based on the expression pattern, human oesophageal ENaC complex was mimicked in the Xenopus oocyte expression system and the response to acidic pH was recorded using a two-electrode voltage-clamp technique. The human oesophageal-mimicking ENaCdeltabetagammaalpha complex generated an amiloride-sensitive inward current at the holding potential of -60 mV. The ENaCdeltabetagammaalpha current was significantly activated by acidic pH (pH 4.0), approximately equal to the luminal value when gastric acid refluxes into the oesophagus. In conclusion, ENaCdelta is a candidate molecule for pH sensing in the gastrointestinal system in humans, providing a novel therapeutic target for gastro-oesophageal reflux disease.

Cyclo-oxygenase-independent inhibition of apoptosis and stimulation of proliferation by leptin in human colon cancer cells

Obesity increases the risk of colon cancer. Hyperleptinemia is characteristic of obesity and leptin has been reported to be a colonic growth factor. We have examined the involvement of the cyclo-oxygenase (COX) pathways in the proliferation and anti-apoptotic effects of leptin. Leptin stimulated proliferation in HT-29 colon cancer cells: this was unaffected by inhibition of COX-1, COX-2, protein kinase C, or the epidermal growth factor receptor. Leptin did not increase COX-2 mRNA or COX-derived prostaglandin E2 production. Celecoxib induced apoptosis in a COX-independent manner. Leptin reduced both serum starvation- and celecoxib-induced apoptosis. Inhibition of ERK, p38 MAP kinase, and nuclear factor (NF)-kappaB abolished the growth-promoting and anti-apoptotic effects of leptin. Treatment of HT-29 cells with leptin stimulated phosphorylation of ERK and p38 MAP kinase and nuclear translocation of active NF-kappaB. We conclude that leptin stimulates colon cancer proliferation via COX-independent pathways and reduces celecoxib-induced apoptosis via ERK, p38 MAP kinase, and NF-kappaB pathways.