Acid challenge to the esophageal mucosa: effects on local nitric oxide formation and its relation to epithelial functions

Expression of inducible nitric oxide synthase, nitrotyrosine, eosinophilic peroxidase, eotaxin-3, and galectin-3 in patients with gastroesophageal reflux disease, eosinophilic esophagitis, and in healthy controls: a semiquantitative image analysis of 3,3'-diaminobenzidine-stained esophageal biopsies

Eosinophilic esophagitis (EoE) and gastroesophageal reflux disease (GERD) share many histopathological features; therefore, markers for differentiation are of diagnostic interest and may add to the understanding of the underlying mechanisms. The nitrergic system is upregulated in GERD and probably also in EoE. Esophageal biopsies of patients with EoE (n = 20), GERD (n = 20), and healthy volunteers (HVs) (n = 15) were exposed to antibodies against inducible nitric oxide synthase (iNOS), nitrotyrosine, eosinophilic peroxidase, eotaxin-3, and galectin-3. The stained object glasses were randomized, digitized, and blindly analyzed regarding the expression of DAB (3,3'-diaminobenzidine) by a protocol developed in QuPath software. A statistically significant overexpression of iNOS was observed in patients with any of the two inflammatory diseases compared with that in HVs. Eotaxin-3 could differentiate HVs versus inflammatory states. Gastroesophageal reflux patients displayed the highest levels of nitrotyrosine. Neither iNOS nor nitrotyrosine alone were able to differentiate between the two diseases. For that purpose, eosinophil peroxidase was a better candidate, as the mean levels increased stepwise from HVs via GERD to EoE. iNOS and nitrotyrosine are significantly overexpressed in patients with EoE and GERD compared with healthy controls, but only eosinophil peroxidase could differentiate the two types of esophagitis. The implications of the finding of the highest levels of nitrotyrosine among gastroesophageal reflux patients are discussed.

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.

Adam, Eve and the reflux enigma: age and sex differences across the gastro-oesophageal reflux spectrum

INTRODUCTION

We present demographic differences across the gastro-oesophageal reflux disease (GORD) spectrum in a UK District General Hospital.

PATIENTS AND METHODS

Data were prospectively collected over 37 years. At endoscopy patients were categorized as: erosive oesophagitis (EO), Barrett's oesophagus (BO) or nonerosive reflux disease (NER). Analysis 1: comparison of EO, BO and NER 1977-2001 when the database for GORD without BO closed. Analysis 2: demographic differences in oesophageal adenocarcinoma (OAC) in total BO population diagnosed 1977-2011.

RESULTS

GORD 1977-2001 (n=11 944): sex, male predominance in EO and BO but not NER; male : female ratios, 1.81, 1.65, 0.87, respectively (P<0.0001); mean age at presentation, EO 54 years, BO 62 years, NER 50 years; women were older than men by 10, 7 and 6 years, respectively.BO 1977-2011: prevalent OAC, 87/1468 (6%); male : female ratio, 4.1 (P<0.0001); incident OAC, 54/1381 (3.9%); male : female ratio, 3.5 (P<0.0001). Among all BO, more men developed OAC (3 vs. 0.9%). Within each sex, proportion of OAC higher among men (4.9 vs. 2.3%); at OAC diagnosis women were slightly but not significantly older (69.9 vs. 72.3 years, P=0.322).

CONCLUSION

Two views may explain our findings. First, women have either milder reflux, or reduced mucosal sensitivity hence reflux remains silent for longer. Alternatively, women genuinely develop reflux later, that is, are more protected and for longer from developing GORD and its complications. Early evidence is emerging that female sex hormones may indeed have a protective role in GORD during the reproductive period. We suggest reflux and its consequences may be an example of 'protection' conferred on Eve.

Barrett's, blood groups and progression to oesophageal cancer: is nitric oxide the link?

INTRODUCTION

Incidence of oesophageal adenocarcinoma (OAC) is increasing rapidly. OAC arises in columnar-lined oesophagus (CLO), a metaplastic change affecting some patients with gastro-oesophageal reflux disease (GORD). As yet there is no reliable method of identifying those at highest risk. Our earlier observation of an association between OAC and blood group O Rhesus negative, if confirmed, may help identify those at greatest risk.

AIM AND METHODS

To assess the distribution of blood group and Rhesus D (RhD) factor in patients with GORD compared with the blood donating general population. GORD was categorized as nonerosive reflux (NER), erosive oesophagitis, CLO and OAC. The Rotherham Hospital database holds details of all GORD, CLO and OAC patients seen in the Gastroenterology Unit. Blood group information for patients with GORD was obtained from patients' records and the hospital's blood transfusion service. The blood group distribution in the general population was obtained from the National Blood Transfusion Service. The number of expected to observed patients in each blood group for each subtype was compared.

RESULTS

Two thousand six hundred and ten NER, 2813 erosive oesophagitis, 568 CLO and 73 OAC patients had a recorded blood group. For RhD positive patients observed proportions in each blood group were similar to expected. The most striking difference was the marked excess of OAC in blood group O, Rhesus negative (P=0.002).

CONCLUSION

CLO patients with blood group O, RhD negative carry a disproportionately higher risk of developing OAC. The mechanism is unknown but the finding has practical application in guiding risk stratification and intensity of surveillance.

Contribution of histology to the diagnosis of reflux disease

Histology in reflux disease is still regarded as having low sensitivity and specificity. During the last three decades several histological parameters have been developed, including thickness of basal cell layer, length of epithelial papillae, intraepithelial inflammatory cells and dilation of intercellular spaces. Unfortunately classification of these parameters was often not related to the clinical symptoms of the reflux affected individuals, proper control subjects were often missing and often no interobserver variation was given. Another reason for the proposed low value of biopsies is the fact that biopsies were often taken in a non-standardised way. Recent studies point towards an area of predominantly epithelial damage close to the lesser curvature or around the right oesophageal wall. In parallel, some large, careful studies carried out recently showed a good correlation with the clinical picture of reflux disease due to a standardised biopsy protocol and proper controls. But biopsies are not recommended in all routine classical cases of reflux disease since it is believed that little further information in addition to endoscopy can be obtained. However, histology can deliver much more information than the diagnosis of reflux induced lesions (e.g. the exclusion of malignancy or other oesophageal diseases).

Circumferential and axial distribution of esophageal mucosal damage in reflux disease

The aim of this study was to evaluate the axial and radial distribution of histological markers including hyperplasia of the basal cell layer, elongation of the papillae and dilatation of the intercellular spaces of the squamous epithelium in patients with nonerosive reflux disease compared to controls and to relate this to the macroscopic topography in erosive reflux disease. Two different study populations were included in this report. Endoscopic esophageal biopsies were taken from 21 healthy control subjects and 21 nonerosive reflux disease patients before and after 4 weeks of esomeprazole therapy. Endoscopic still images from 50 erosive reflux disease patients were reviewed for the radial orientation of LA grade A and/or B esophagitis (Los Angeles criteria for grading of reflux esophagitis). The 3 o'clock position of the squamocolumnar junction showed significantly thicker basal cell layer (P=0.011) and more intercellular space dilatation (P=0.01) in nonerosive reflux disease patients compared to the 9 o'clock position. Only a significant difference in dilatation of the intercellular spaces (P=0.018) between nonerosive reflux disease patients and controls were observed in the 3 o'clock region at the squamocolumnar junction, whereas 1-2 cm orally, all three histological criteria differed significantly (P<or=0.01). After treatment, on the contrary, papillary length was significantly less pronounced at the squamocolumnar junction (P<0.01). Endoscopically, erosions were predominantly visualized in the 3 o'clock region (P<0.05). Histological mucosal changes in nonerosive reflux disease patients and visible mucosal erosions in erosive reflux disease patients occur most frequently at the same position, namely in the 3 o'clock quadrant in the distal esophagus. The histological difference between nonerosive reflux disease patients and controls are more distinct 1-2 cm oral to rather than at the squamocolumnar junction. However the effect of therapy is most pronounced at the squamocolumnar junction.

Genotoxic effects of myosmine in a human esophageal adenocarcinoma cell line

The incidence of esophageal adenocarcinoma is rapidly rising in Western populations. Gastroesophageal reflux disease (GERD) is thought to be one of the most important risk factors. However, the mechanisms by which GERD enhances tumor formation at the gastroesophageal junction are not well understood. Myosmine is a tobacco alkaloid which has also a wide spread occurrence in human diet. It is readily activated by nitrosation and peroxidation giving rise to the same hydroxypyridylbutanone-releasing DNA adducts as the esophageal carcinogen N'-nitrosonornicotine. Therefore, the genotoxicity of myosmine was tested in a human esophageal adenocarcinoma cell line (OE33). DNA damage was assessed by single-cell gel electrophoresis (Comet assay). DNA strand breaks, alkali labile sites and incomplete excision repair were expressed using the Olive tail moment (OTM). The Fapy glycosylase (Fpg) enzyme was incorporated into the assay to reveal additional oxidative DNA damage. DNA migration was determined after incubation of the cells for 1-24h. Under neutral conditions high myosmine concentrations of 25-50mM were necessary to elicit a weak genotoxic effect. At pH 6 genotoxicity was clearly enhanced giving a significant increase of OTM values at 5mM myosmine. Lower pH values could not be tested because of massive cytotoxicity even in the absence of myosmine. Co-incubation of 25 mM myosmine with 1mM H(2)O(2) for 1h significantly enhanced the genotoxicity of H(2)O(2) but not the oxidative lesions additionally detected with the Fpg enzyme. In the presence of the peroxynitrite donor 3-morpholinosydnonimine (SIN-1) a dose-dependent significant genotoxic effect was obtained with 1-10mM myosmine after 4h incubation. NS-398, a selective inhibitor of cyclooxygenase 2, did not affect the SIN-1 stimulated genotoxicity of myosmine. Finally, the 23 h repair of N-methyl-N'-nitro-N-nitrosoguanidine-induced DNA lesions was significantly inhibited in the presence of 10mM myosmine. In conclusion, myosmine exerts significant genotoxic effects in esophageal cells under conditions which may prevail in GERD such as increased oxidative and nitrosative stress resulting from chronic inflammation.

Pharyngeal reflux episodes at pH 5 in healthy volunteers

OBJECTIVE

The clinically used cut-off limit in reflux disease is pH 4. Yet, earlier studies have shown a poor correlation between pharyngeal reflux episodes and symptoms or laryngeal findings, and treatment results have been suboptimal. Moreover, recent data suggest that pepsin is still active at pH 5. The aim of this study was to evaluate the occurrence of pharyngeal pH 5 reflux episodes in healthy controls and to correlate these to the pH monitoring results with a cut-off limit of pH 4.

MATERIAL AND METHODS

The results of double-probe 24-h pH monitoring from 35 healthy controls were reanalysed concerning the occurrence of pH decreases to pH 5.

RESULTS

Pharyngeal pH 5 reflux episodes occurred in 32 healthy controls (91%). The median number of pharyngeal reflux episodes at pH 5 was 4.0. The vast majority of these reflux episodes (92%) occurred in the upright position, especially in the postprandial period. The median time pH < 5 in the pharynx was 0.1% while the upper limit of normality was 1.5%. Pharyngeal pH 5 reflux episodes were 5 times more common than pH 4 reflux episodes. There was a significant positive correlation between hypopharyngeal and oesophageal acid exposure time at both pH 4 and 5 (p<0.01).

CONCLUSIONS

Pharyngeal pH 5 reflux episodes are present in most healthy adults, mainly in upright position and in the postprandial period. The importance of these episodes for the occurrence of laryngeal symptoms and signs and for treatment response needs to be prospectively assessed.

Acid challenge to the human esophageal mucosa: effects on epithelial architecture in health and disease

The histological changes that occur in the squamous epithelium in response to acute acid challenge was examined in healthy controls and proton pump inhibitor-treated gastroesophageal reflux disease (GERD) patients and related to the state of untreated erosive GERD in a saline-controlled, randomized perfusion study. In the basal state a stepwise significant increase in the thickness of the basal cell layer, papillary length, and dilatation of intercellular spaces (DIS) was seen when the three groups were compared. Acid perfusion induced a slight increase in the height of the basal cell layer mainly in healthy volunteers; this layer appears to be reactive to acute acid challenge as well as to acid suppressive therapy. DIS increases promptly in response to acute acid exposure in the healthy epithelium but no changes were seen in the lengths of the papillae or regarding DIS in the GERD patients. A protective effect of luminal nitric oxide on DIS development is suggested.