Role of acid and duodenogastric reflux in esophageal mucosal injury: a review of animal and human studies

The Saudi Gastroenterology Association consensus on the clinical care pathway for the diagnosis and treatment of GERD

ABSTRACT

Gastroesophageal reflux disease (GERD) is one of the most common problems encountered in outpatient general medicine and gastroenterology clinics. GERD may present with classic esophageal symptoms, extraesophageal symptoms, or mixed symptoms. The diagnosis and treatment of GERD are challenging due to the variety of symptoms and multifactorial pathophysiology. Since there is no consensus on the diagnosis and treatment of GERD in Saudi Arabia, the Saudi Gastroenterology Association established an expert group to formulate a consensus on the clinical care pathway for the diagnosis and treatment of GERD to update health-care providers in Saudi Arabia. The expert group reviewed the literature including recently published international guidelines, clinical trials, and expert opinion and conducted virtual and in-person meetings. A total of 22 statements on the definition, diagnosis, and treatment of GERD were formulated, and three algorithms for the clinical care of GERD were developed with a detailed description for each step. The expert group endorsed the new definition of GERD, the practical principles of interpretation of the diagnostic GERD evaluation, and the practical guidance for GERD treatment including medical, surgical, and endoscopic therapy. The expert group recommends further studies to investigate local data on the diagnosis and treatment of GERD.

Cholelithiasis and cholecystectomy increase the risk of gastroesophageal reflux disease and Barrett's esophagus

Background

Cholelithiasis or cholecystectomy may contribute to the development of gastroesophageal reflux disease (GERD), Barrett's esophagus (BE), and esophageal adenocarcinoma (EAC) through bile reflux; however, current observational studies yield inconsistent findings. We utilized a novel approach combining meta-analysis and Mendelian randomization (MR) analysis, to assess the association between them.

Methods

The literature search was done using PubMed, Web of Science, and Embase databases, up to 3 November 2023. A meta-analysis of observational studies assessing the correlations between cholelithiasis or cholecystectomy, and the risk factors for GERD, BE, and EACwas conducted. In addition, the MR analysis was employed to assess the causative impact of genetic pre-disposition for cholelithiasis or cholecystectomy on these esophageal diseases.

Results

The results of the meta-analysis indicated that cholelithiasis was significantly linked to an elevated risk in the incidence of BE (RR, 1.77; 95% CI, 1.37-2.29; p < 0.001) and cholecystectomy was a risk factor for GERD (RR, 1.37; 95%CI, 1.09-1.72; p = 0.008). We observed significant genetic associations between cholelithiasis and both GERD (OR, 1.06; 95% CI, 1.02-1.10; p < 0.001) and BE (OR, 1.21; 95% CI, 1.11-1.32; p < 0.001), and a correlation between cholecystectomy and both GERD (OR, 1.04; 95% CI, 1.02-1.06; p < 0.001) and BE (OR, 1.13; 95% CI, 1.06-1.19; p < 0.001). After adjusting for common risk factors, such as smoking, alcohol consumption, and BMI in multivariate analysis, the risk of GERD and BE still persisted.

Conclusion

Our study revealed that both cholelithiasis and cholecystectomy elevate the risk of GERD and BE. However, there is no observed increase in the risk of EAC, despite GERD and BE being the primary pathophysiological pathways leading to EAC. Therefore, patients with cholelithiasis and cholecystectomy should be vigilant regarding esophageal symptoms; however, invasive EAC cytology may not be necessary.

Role of bile acids and their receptors in gastrointestinal and hepatic pathophysiology

Bile acids (BAs) can regulate their own metabolism and transport as well as other key aspects of metabolic homeostasis via dedicated (nuclear and G protein-coupled) receptors. Disrupted BA transport and homeostasis results in the development of cholestatic disorders and contributes to a wide range of liver diseases, including nonalcoholic fatty liver disease and hepatocellular and cholangiocellular carcinoma. Furthermore, impaired BA homeostasis can also affect the intestine, contributing to the pathogenesis of irritable bowel syndrome, inflammatory bowel disease, and colorectal and oesophageal cancer. Here, we provide a summary of the role of BAs and their disrupted homeostasis in the development of gastrointestinal and hepatic disorders and present novel insights on how targeting BA pathways might contribute to novel treatment strategies for these disorders.

Differential Bile Acid Detection in Refractory GERD Patient Saliva Using a Simple and Sensitive Liquid Chromatography Tandem Mass Spectrometry Approach

GOALS

The aim was to measure bile acids in human saliva using a sensitive ultraperformance liquid chromatography tandem mass spectrometry analysis method to distinguish quantitative differences in refractory gastroesophageal reflux disease (GERD) patients as compared with proton pump inhibitor (PPI) controlled GERD patients and healthy volunteers.

STUDY

Human saliva samples were analyzed from 2 separate studies. The first a meal-controlled pilot, in which premeal and postmeal saliva samples were analyzed from 20 healthy subjects and 20 patients with GERD symptoms controlled by PPIs. In a subsequent exploratory study, saliva was collected from 34 patients with continuing GERD symptoms despite PPI treatment (refractory GERD), 30 healthy subjects, and 30 PPI-controlled GERD patients at ≥4 hours postmeal.

RESULTS

In the meal-controlled pilot study, both healthy subjects and patients with PPI-controlled GERD, had total saliva bile acid increase for the first hour after consumption of a meal and returned to baseline levels 4 hours later. There was no difference in bile acid levels between the 2 groups. In the exploratory study, the saliva from patients with refractory GERD had statistically significant higher levels of total bile acid concentration compared with those of healthy volunteers and patients with PPI-controlled GERD (P=0.0181).

CONCLUSIONS

Bile acids can be detected and accurately quantitated in human saliva using a sensitive ultraperformance liquid chromatography tandem mass spectrometry assay. Increases above threshold could indicate an underlying disease.This method could potentially be used to evaluate biliary reflux as an underlying pathophysiology of refractory GERD.

Bile reflux and hypopharyngeal cancer (Review)

Laryngopharyngeal reflux, a variant of gastroesophageal reflux disease, has been considered a risk factor in the development of hypopharyngeal cancer. Bile acids are frequently present in the gastroesophageal refluxate and their effect has been associated with inflammatory and neoplastic changes in the upper aerodigestive tract. Recent in vitro and in vivo studies have provided direct evidence of the role of acidic bile refluxate in hypopharyngeal carcinogenesis and documented the crucial role of NF-κB as a key mediator of early oncogenic molecular events in this process and also suggested a contribution of STAT3. Acidic bile can cause premalignant changes and invasive squamous cell cancer in the affected hypopharynx accompanied by DNA damage, elevated p53 expression and oncogenic mRNA and microRNA alterations, previously linked to head and neck cancer. Weakly acidic bile can also increase the risk for hypopharyngeal carcinogenesis by inducing DNA damage, exerting anti-apoptotic effects and causing precancerous lesions. The most important findings that strongly support bile reflux as an independent risk factor for hypopharyngeal cancer are presented in the current review and the underlying mechanisms are provided.

Deoxycholic acid activates and sensitizes vagal nociceptive afferent C-fibers in guinea pig esophagus

Bile acid reflux in the esophagus plays a role in the pathogenesis of certain esophageal disorders, where it can induce esophageal pain and heartburn. The present study aimed to determine whether bile acid, deoxycholic acid (DCA), directly activates and sensitizes esophageal vagal nociceptive afferent C-fiber subtypes. DCA-elicited effects on vagal nodose and jugular neurons were studied by calcium imaging. Its effects on esophageal-labeled nodose and jugular neurons were then determined by patch-clamp recording. At nodose and jugular C-fiber nerve endings in the esophagus, DCA-evoked action potentials (APs) were compared by extracellular single-unit recordings in ex vivo esophageal-vagal preparations. DCA application induced calcium influxes in nodose and jugular neurons and elicited inward currents in esophageal-labeled nodose and jugular neurons. In the presence of DCA, the current densities elicited by capsaicin were enhanced in those labeled neurons. Consistently, DCA perfusion at nerve terminals in the esophagus evoked APs in about 50% of esophageal nodose and jugular C-fibers. In DCA-sensitive C-fibers, DCA perfusion also sensitized the fibers such that the subsequent response to capsaicin was amplified. Collectively, these results provide new evidence that DCA directly activates and sensitizes nociceptive nodose and jugular C-fibers in the esophagus. Such activation and sensitization effects may contribute to bile acid-induced esophageal nociceptive symptoms that are refractory to proton-pump inhibitor therapy.NEW & NOTEWORTHY Bile acid reflux in the esophagus can induce pain and heartburn in certain esophageal disorders, but the underlying neuronal mechanism is still unclear. The present study demonstrated that bile acid, deoxycholic acid (DCA), directly activates esophageal vagal afferent nodose and jugular nociceptive C-fibers and sensitizes their response to capsaicin. Such effects may contribute to bile acid-induced esophageal nociceptive symptoms that refractory to proton-pump inhibitors (PPIs) therapy.

Expression of Adhesion Molecules in a Gastroduodenal Reflux Murine Model

BACKGROUND

Various adhesion molecules including intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) have been shown to play a role in inflammation as well as contribute to tumor progression and prognosis. We hypothesized that gastroduodenal reflux upregulates ICAM-1 and VCAM-1 expression in the distal esophagus, serving as possible early markers of pathologic esophageal disease.

METHODS

Normal human esophageal epithelial cells (HET1A), Barrett's cells (CPB), and esophageal adenocarcinoma cells (FLO1 and OE33) were treated with deoxycholic acid (DCA) at increasing concentrations for 24 hours. Adhesion molecule expression was assessed using immunoblotting. A surgical mouse reflux model was generated by performing a side-to-side anastomosis between the gastroesophageal junction and the first portion of the duodenum (duodeno-gastroesophageal anastomosis, DGEA). Esophageal sections were evaluated using H&E staining, immunohistochemistry, and immunofluorescence.

RESULTS

DCA induced a significant increase in ICAM-1 and VCAM-1 expression in HET1A, CPB, FLO1, and OE33 cells. Animals undergoing DGEA demonstrated a significant increase in mucosal hyperplasia (p<0.0001) and cellular proliferation (p<0.0001) compared to control animals. Immunofluorescence and western blot analysis of the lower esophagus demonstrated significant upregulation of ICAM-1 (p=0.005), with no change in VCAM-1 expression (p=0.82).

CONCLUSIONS

Our results reveal that ICAM-1 and VCAM-1 are upregulated in response to in vitro reflux treatment of normal esophageal epithelial cells. However, upon investigation using a mouse reflux model, ICAM-1 is noticeably upregulated without a concomitant increase in VCAM-1. These findings identify ICAM-1, but not VCAM-1, as a potential player in early esophageal disease developing from chronic reflux exposure.

Esophageal Function Abnormalities in Patients With Barrett's Esophagus

Various esophageal functional abnormalities have been described in patients with Barrett's esophagus (BE). A significantly higher esophageal acid exposure especially in the supine position has been documented in BE, as compared with the other gastroesophageal reflux disease phenotypes. In addition, weakly acidic reflux and duodenogastroesophageal reflux are more common in BE patients. The presence of Barrett's mucosa reduces esophageal mucosal impedance, occasionally to a level that prevents detection of reflux episodes. Reduced amplitude contractions and lower esophageal sphincter basal pressure are more common in BE patients as compared with the other gastroesophageal reflux disease groups. Ineffective esophageal motility is the most commonly defined motor disorder in BE. Reduced chemoreceptor and mechanoreceptor sensitivity to acid and balloon distention, respectively, have been suggested to explain lack or significantly less reports of reflux-related symptoms by BE patients.

Comparison of two topical treatments of gastro-oesophageal regurgitation in dogs during general anaesthesia

OBJECTIVE

To determine whether suction, lavage and instillation of sodium bicarbonate, following a gastro-oesophageal regurgitation event under general anaesthesia, would alter oesophageal pH to a greater degree than when lavage was not used.

STUDY DESIGN

Prospective, randomised, clinical study.

ANIMALS

A group of 22 client-owned dogs.

METHODS

Dogs presenting with gastro-oesophageal regurgitation (GOReg) under general anaesthesia were randomised into groups: no lavage (G1) or lavage (G2). All dogs underwent oesophageal suctioning until no further regurgitant material was retrieved. Dogs in G2 had oesophageal lavage with tap water until the suctioned water was clear. All dogs then had 4.2% sodium bicarbonate (0.6 mL kg^-1) instilled into the oesophagus. An oesophageal pH probe was placed to record pH immediately after: GOReg (T1), suctioning (T2), lavage of the oesophagus (T3; G2 only) and sodium bicarbonate instillation (T4). Categorical data were analysed using Fisher's exact test, and continuous data were analysed using either the two-sample t-test or the Wilcoxon rank-sum test. Parametric data are reported as mean ± standard deviation and non-parametric data as median (interquartile range). A p value < 0.05 was considered significant.

RESULTS

Oesophageal pH was low in both groups immediately after GOReg [G1: 2.95 (2.20-4.18), G2: 3.29 (1.41-4.03)] but oesophageal pH was not significantly different between groups at T1, T2 and T4. Oesophageal lavage significantly increased pH but the overall change in pH following bicarbonate administration (T2-T4) was not significantly different between groups [G1: 3.16 ± 1.52, G2: 3.52 ± 1.47]. No adverse events following GOReg were recorded.

CONCLUSIONS AND CLINICAL RELEVANCE

Both groups had similar and clinically important increases in oesophageal pH. Although oesophageal lavage increased pH, this did not affect the final oesophageal pH when sodium bicarbonate was instilled and therefore may be an unnecessary step.

Reflux esophagitis, functional and non-functional

The pathogenesis of gastroesophageal reflux disease has been explained by acid-peptic model. However, related with the progress of the diagnostic modalities, another phenotypical group of patients were defined and called "functional disorders of the esophagus". These patients are important because diagnosis is particularly difficult, co-morbid disorders especially psychiatric diseases are common, proton pump inhibitor response is low, and surgical results are very poor. Simpler and translational science studies are required in functional groups in order to differentiate from acid-peptic disorders. New and more accurate diagnostic modalities as well as therapeutic approaches are strongly needed in this particularly new and exciting era, especially in the effect of neuromodulators. Current diagnostic modalities should also be evaluated and in fact, normal values should be established. New medications, especially acting at the level of esophageal epithelium and intercellular spaces, might shift the paradigm.

Revisiting Montreal: New Insights into Symptoms and Their Causes, and Implications for the Future of GERD

The Montreal definition of gastroesophageal reflux disease (GERD) provided a rationale for acid suppression medication without investigation, thus enhancing the management of the substantial symptom burden in these patients. Increased proton-pump inhibitor use has also highlighted their limitations, with one third of "typical" symptoms known to be refractory. Most refractory symptoms are ascribed to reflux hypersensitivity (RH) and functional heartburn (FH). RH may be caused by impaired esophageal mucosal barrier function and sensitization of peripheral esophageal receptors. Central sensitization may also contribute to the perception of non-pathologic reflux in RH, and the perception of physiological stimuli in FH. Importantly, mechanisms underlying GERD, RH, and FH are (in theory) not mutually exclusive, further complicating patient management. Methods used to distinguish GERD from RH and FH are impractical for use in epidemiological studies and pragmatic care and may have limited diagnostic accuracy. This is impeding accurate prevalence estimates and risk factor determination and the identification of new therapies. Direct assessment of mucosal barrier function by measuring impedance is a promising candidate for improved diagnosis. Ultimately though the concept of GERD as a composite, symptom-based entity needs re-evaluation, so that new understandings of upper GI symptoms can direct more precise management.

Pathophysiology of Gastroesophageal Reflux Disease

The pathogenesis of gastroesophageal reflux disease (GERD) is complex and involves changes in reflux exposure, epithelial resistance, and visceral sensitivity. The gastric refluxate is a noxious material that injures the esophagus and elicits symptoms. Esophageal exposure to gastric refluxate is the primary determinant of disease severity. This exposure arises via compromise of the anti-reflux barrier and reduced ability of the esophagus to clear and buffer the refluxate, leading to reflux disease. However, complications and symptoms also occur in the context of normal reflux burden, when there is either poor epithelial resistance or increased visceral sensitivity. Reflux therefore develops via alterations in the balance of aggressive and defensive forces.

Not All Children with Cystic Fibrosis Have Abnormal Esophageal Neutralization during Chemical Clearance of Acid Reflux

PURPOSE

Acid neutralization during chemical clearance is significantly prolonged in children with cystic fibrosis, compared to symptomatic children without cystic fibrosis. The absence of available reference values impeded identification of abnormal findings within individual patients with and without cystic fibrosis. The present study aimed to test the hypothesis that significantly more children with cystic fibrosis have acid neutralization durations during chemical clearance that fall outside the physiological range.

METHODS

Published reference value for acid neutralization duration during chemical clearance (determined using combined impedance/pH monitoring) was used to assess esophageal acid neutralization efficiency during chemical clearance in 16 children with cystic fibrosis (3 to <18 years) and 16 age-matched children without cystic fibrosis.

RESULTS

Duration of acid neutralization during chemical clearance exceeded the upper end of the physiological range in 9 of 16 (56.3%) children with and in 3 of 16 (18.8%) children without cystic fibrosis (p=0.0412). The likelihood ratio for duration indicated that children with cystic fibrosis are 2.1-times more likely to have abnormal acid neutralization during chemical clearance, and children with abnormal acid neutralization during chemical clearance are 1.5-times more likely to have cystic fibrosis.

CONCLUSION

Significantly more (but not all) children with cystic fibrosis have abnormally prolonged esophageal clearance of acid. Children with cystic fibrosis are more likely to have abnormal acid neutralization during chemical clearance. Additional studies involving larger sample sizes are needed to address the importance of genotype, esophageal motility, composition and volume of saliva, and gastric acidity on acid neutralization efficiency in cystic fibrosis children.

Bile-Induced Laryngitis: Is There a Basis in Evidence?

Most agree that bile reflux occurs with regularity in an otherwise healthy population and that biliary and acid reflux may play a synergistic role in damaging esophageal mucosa. But to what extent is laryngeal mucosa at risk? We constructed a saline-controlled rat model (n = 40) in which active component solutions of bile — taurocholic acid and chenodeoxycholic acid — were applied to intact laryngeal mucosa at various pH levels. Histologic sampling of the laryngeal mucosa allowed inflammation scores to be generated by a pathologist blinded to the solutions used. Both taurocholic acid at acid pH and chenodeoxycholic acid at basic pH preferentially induced statistically greater inflammation scores than did the saline control, approaching or exceeding inflammation scores attributed to hydrochloric acid at pH 1.2. These observations may clarify reasons for failure to uniformly control laryngeal injury by adequate suppression of gastric acid alone and may further justify alternative methods of laryngeal protection in patients refractory to adequate acid control.

Endoscopic Ex Vivo Evaluation of Bile Concentrations by Narrow Band Imaging: A Pilot Study

Background. Bile juice plays a major role in duodenogastroesophageal reflux (DGERD). Several devices to directly measure the bile concentration have been proposed. We aimed to ex-vivo evaluate the bile concentration by narrow band imaging (NBI). Method. From six surgical cholecystectomies, the content of the gallbladders was aspirated and the total biliary acid (TBA) concentration was evaluated. 2 mL was employed for serial twofold dilutions. Each dilution was scoped. Images on white light (WL) and NBI were captured and grouped accordingly to NBI-appearance and TBA-concentration. Results. Nondiluted bile had a TBA-concentration of 61965 ± 32989 μmol/L. Final dilution (1 : 4096) had 1.16 μmol/L. NBI and correspondent WL images were grouped into seven groups, and an NBI/Bile scale was created. Conclusion. The scale showed that not only NBI scale but also white light scale could be useful to predict the bile concentration. This initial study shows that NBI has a potential role in the detection of DGERD and further investigation is warranted to distinguish the presence and the concentration of bile, especially at very low TBA concentrations.

Chemical clearance in infants and children with Acid reflux in the physiologic range

BACKGROUND AND AIM

We reported that chemical clearance (CC) of acid gastroesophageal reflux (AGER) is relatively prolonged in children with cystic fibrosis (CF). Disparity in CC values within our CF cohort sparked curiosity as to what CC looks like in infants and children with AGER in the physiologic range. The aim of the study was to assess CC in infants and children with normal AGER.

METHODS

Impedance-pH tracings from our database for infants (≤ 12 months) and children (>12 months-18 years) were manually scanned for 2-phase AGER episodes. Tracings were excluded for patients who had AGER Indices >3% (children) or >6% (infants), had positive GER-symptom associations, were on antireflux medications, had a fundoplication, or had impedance studies shorter than 18 hour. In addition to medians (25%-75% interquartile range), we calculated the 95th percentile for the CC duration and the fifth percentile for the CC rate.

RESULTS

Two-phase AGER episodes were detected in 44 infants and 60 children. The median CC duration was 64.3 seconds (51.0-91.6 seconds) for infants and 37.5 seconds (27.7-52.4 seconds) for children. The median CC rate was 0.0622 pH units/second (PU/second) (0.0354-0.0946 PU/second) for infants and 0.0928 PU/second (0.0631-0.2057 PU/second) for children. The CC duration at the 95th percentile was 148.5 seconds for infants and 114.4 seconds for children. The CC rate at the fifth percentile was 0.0088 PU/second for infants and 0.0465 PU/second for children.

CONCLUSIONS

We report reference values for CC in infants and children who have normal acid reflux. These values should not be used as "cutoff values" because they were derived from infant and children cohorts that did not include individuals with intermediate AGER.

[Determination of hyperregeneratory esophagopathy in dogs with clinical signs attributable to esophageal disease]

OBJECTIVE

It was hypothesized that typical characteristics of hyperregeneratory esophagopathy (HRE) in humans such as basal cell hyperplasia and elongation of stromal papillae are also histologically detectable in canine esophageal epithelium, and that these changes are associated with clinical signs and endoscopic findings suggesting gastroesophageal reflux (GER).

MATERIAL AND METHODS

Sixty-five adult dogs with clinical signs attributable to esophageal disease underwent esophagoscopy and biopsy. Clinical signs suggesting GER (regurgitation, ptyalism, painful discomfort) were prospectively evaluated through a questionnaire. Endoscopic mucosal alterations suggesting GER such as minimal endoscopic changes and obvious mucosal defects were assessed via video endoscopy. Biopsy specimens obtained from the esophageal squamous epithelium were evaluated histologically. The squamous epithelium's substructures of esophageal biopsies were quantitatively assessed through microscopic morphometry.

RESULTS

Esophageal squamous epithelium was considered normal in 48 dogs, and HRE was detected histologically in 17 dogs; both pathognomonic changes (basal cell hyperplasia, elongation of stromal papillae) were consistently present. Morphometrically assessed stromal papillary length and basal cell layer thickness was significantly (each, p < 0.0001) higher in the 17 dogs with HRE than in the 48 dogs without HRE, respectively. Overall, clinical signs suggesting GER were significantly (p = 0.02) more frequently encountered and regurgitation was significantly (p = 0.009) more common in the 17 dogs with HRE than in the 48 dogs without HRE. Similarly, endoscopic changes were significantly (p = 0.002) more frequently observed and minimal endoscopic changes suggesting GER were significantly (p = 0.004) more common in 17 dogs with HRE than in the 48 dogs without HRE.

CONCLUSION AND CLINICAL RELEVANCE

Typical characteristics of hyperregeneratory esophagopathy in humans are also histologically detectable in canine esophageal epithelium. Histological changes are associated with clinical signs and endoscopic findings suggesting GER.

Treatment of GORD: Three decades of progress and disappointments

The treatment of GORD has been revolutionized by the introduction, in the 1980s, of proton-pump inhibitors as the mainstay of medical therapy and by the development of laparoscopic antireflux surgery which has definitively replaced open surgery. However, despite these major advances, many unmet therapeutic needs still persist and justify novel therapeutic approaches. The aim of this historical review is to recall the main discoveries in the treatment of GORD that have occurred during the last three decades and to discuss why some initially promising drugs or techniques have not translated into clinical applications. A careful analysis of these previous disappointing experiences should help to identify high priorities and better research programmes on the management of GORD.

LIM homeodomain transcription factor Isl1 directs normal pyloric development by targeting Gata3

Background

Abnormalities in pyloric development or in contractile function of the pylorus cause reflux of duodenal contents into the stomach and increase the risk of gastric metaplasia and cancer. Abnormalities of the pyloric region are also linked to congenital defects such as the relatively common neonatal hypertrophic pyloric stenosis, and primary duodenogastric reflux. Therefore, understanding pyloric development is of great clinical relevance. Here, we investigated the role of the LIM homeodomain transcription factor Isl1 in pyloric development.

Results

Examination of Isl1 expression in developing mouse stomach by immunohistochemistry, whole mount in situ hybridization and real-time quantitative PCR demonstrated that Isl1 is highly expressed in developing mouse stomach, principally in the smooth muscle layer of the pylorus. Isl1 expression was also examined by immunofluorescence in human hypertrophic pyloric stenosis where the majority of smooth muscle cells were found to express Isl1. Isl1 function in embryonic stomach development was investigated utilizing a tamoxifen-inducible Isl1 knockout mouse model. Isl1 deficiency led to nearly complete absence of the pyloric outer longitudinal muscle layer at embryonic day 18.5, which is consistent with Gata3 null mouse phenotype. Chromatin immunoprecipitation, luciferase assays, and electrophoretic mobility shift assays revealed that Isl1 ensures normal pyloric development by directly targeting Gata3.

Conclusions

This study demonstrates that the Isl1-Gata3 transcription regulatory axis is essential for normal pyloric development. These findings are highly clinically relevant and may help to better understand pathways leading to pyloric disease.

Pathophysiology of gastroesophageal reflux disease

Gastroesophageal reflux disease (GERD) is one of the most common digestive diseases in the Western world, with typical symptoms, such as heartburn, regurgitation, or retrosternal pain, reported by 15% to 20% of the general population. The pathophysiology of GERD is multifactorial. Our understanding of these factors has significantly improved in recent years, with increased understanding of the acid pocket and hiatal hernia and how these factors interact. Although our insight has significantly increased over the past years, more studies are required to better understand symptom generation in GERD, especially in patients with therapy-resistant symptoms.

Esophageal barrier function and tight junction expression in healthy subjects and patients with gastroesophageal reflux disease: functionality of esophageal mucosa exposed to bile salt and trypsin in vitro

BACKGROUND AND AIMS. Gastroesophageal reflux disease (GERD) is associated with impaired epithelial barrier function. However, the influence of acid and/or bile acids on human esophageal epithelial barrier function and the tight junction (TJ) proteins has not been fully elucidated. The aim of the study is to investigate the esophageal barrier function and TJ expression in healthy subjects and patients with GERD. The functionality of esophageal mucosa exposed to bile salt deoxycholic acid (DCA) and trypsin has been studied in vitro. MATERIAL AND METHODS. Endoscopic biopsies from healthy controls and patients with GERD-related symptom with endoscopic erosive signs, as well as esophageal mucosa taken from patients undergoing esophagectomy were evaluated in Ussing chambers and by western blot and immunohistochemistry. RESULTS. The esophageal epithelium from GERD patients had lower electrical resistance and higher epithelial currents than controls. Claudin-1 and -4 were significantly decreased in GERD patients. The bile salt DCA in the low concentration of 1.5 mM and trypsin increased the resistance and claudin-1 expression, while the higher concentration of 2.5 mM DCA and trypsin decreased the resistance and the claudin-3, -4 and E-cadherin expressions. CONCLUSION. In addition to acidic reflux, duodenal reflux components, such as bile salts and trypsin, have the potential to disrupt the esophageal barrier function, partly by modulating the TJ proteins. However, the expression of TJ is dependent on both the refluxed material as well as the concentration of the bile salt.

Acidic deoxycholic acid and chenodeoxycholic acid induce interleukin-8 production through p38 mitogen-activated protein kinase and protein kinase A in a squamous epithelial model

BACKGROUND AND AIM

Immune-mediated mucosal inflammation characterized by the production of interleukin (IL)-8 is associated with the development of gastroesophageal reflux disease. The effects of bile acids, which are major components of reflux fluid, on the production of IL-8 and related mechanisms remain unclear. This study aimed to address these questions using an esophageal stratified squamous epithelial model.

METHODS

Normal human esophageal epithelial cells were seeded on the Transwell inserts and cultured with the air-liquid interface system to establish the model. Bile acids under different pH conditions were added to the apical compartment to examine their effects on IL-8 production and the underlying cellular signaling.

RESULTS

Conjugated bile acids under a neutral or acidic condition did not induce IL-8 production, and unconjugated bile acids, deoxycholic acid (DCA), and chenodeoxycholic acid (CDCA) all significantly induced IL-8 production, dose- and time-dependently, only under weakly acid conditions. Inhibition of p38 mitogen-activated protein kinase (p38 MAPK) and protein kinase A (PKA) attenuated the production of IL-8 induced by acidic DCA and CDCA. Inhibition of PKA did not block the bile acid-induced p38 MAPK activation.

CONCLUSIONS

Compared with conjugated bile acids, the unconjugated bile acids DCA and CDCA are more likely to induce IL-8 production in vivo, especially under weakly acid conditions. This process involves two independent signaling pathways, p38 MAPK and PKA.

Novel therapeutics for gastro-esophageal reflux symptoms

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

Hiatal hernia and the risk of Barrett's esophagus

BACKGROUND AND AIM

Barrett's esophagus has been associated with the presence of hiatal hernia; however, to date no meta-analysis of the relationship has been performed. We aimed to conduct a systematic review and meta-analysis, providing a quantitative estimate of the increased risk of Barrett's esophagus associated with hiatal hernia.

METHODS

A search was conducted through four electronic databases (Medline, PubMed, Embase, and Current Contents Connect) to 4 April 2012, for observational studies of Barrett's esophagus patients. We calculated pooled odds ratios and 95% confidence intervals using a random effects model for the association of hiatal hernia with any length Barrett's esophagus, as well as with short segment Barrett's esophagus and long segment Barrett's esophagus. 33 studies comprising 4390 Barrett's esophagus patients were eligible for the meta-analysis.

RESULTS

Hiatal hernia was associated with an increased risk of Barrett's esophagus of any length (odds ratio 3.94; 95% confidence interval 3.02-5.13). Heterogeneity was present (I2 = 82.03%, P < 0.001), and the Egger test for publication bias was significant (P = 0.0005). The short segment Barrett's esophagus subgroup analysis likewise showed an increased risk (odds ratio 2.87; 95% confidence interval 1.75-4.70). The strongest association was between hiatal hernia and long segment Barrett's esophagus (odds ratio 12.67; 95% confidence interval 8.33-19.25). The increased risk was present even after adjusting for reflux and body mass index.

CONCLUSIONS

 The presence of hiatal hernia was associated with an increased risk of Barrett's esophagus, even after adjusting for clinically significant confounders. The strongest association was found between hiatal hernia and long segment Barrett's esophagus.

Effect of proton pump inhibition on acid, weakly acid and weakly alkaline gastro-esophageal reflux in children

BACKGROUND

The effect of proton pump inhibitors on the characteristics of gastroesophageal reflux (GER) in children and adolescents was evaluated.

METHODS

Twenty-one children and adolescents with symptoms suggesting GER disease (GERD) underwent upper endoscopy and a 24-hour multichannel intraluminal impedance/pH (MII-pH) monitoring before and at the end of 2 months of therapy with proton pump inhibitors (PPIs).

RESULTS

Fourteen (67%) patients reported clinically relevant symptom improvement after 2 months of PPIs intake. At the first endoscopy, 8 (38%) patients had macroscopic signs of reflux esophagitis; after two months of therapy, 6/8 (75%) patients had a complete mucosal recovery. There was a significant reduction in the total percentage of mean acid reflux time (from 13.1% to 3.8%), and the De Meester score dropped to normal (from 46.4 to 13.1). The mean number of acid refluxes decreased significantly from 48 to 15 per 24 hours, while inversely, the mean number of weakly acid refluxes increased significantly from 26 to 64 per 24 hours. PPI therapy did not affect the total number of reflux episodes, the number of liquid and mixed refluxes, the duration of esophageal bolus exposure and proximal extent of the reflux.

CONCLUSIONS

In children and adolescents with GERD, PPIs do not affect the total number of reflux episodes. PPIs only decrease the acidity of refluxate. Nevertheless, the majority of patients with typical reflux symptoms may report symptom improvement. Esophagitis can be healed after PPI treatment. The treatment of weakly acid and weakly alkaline reflux remains a challenge for physicians in the future.

Analysis of the protective biochemical and pathologic effects of aminoguanidine on an experimental aspiration pneumonitis model induced by bile acids

BACKGROUND

Gastroesophageal reflux (GER) is a common clinical pathology detected in childhood. Bile acids (BAs) are present in reflux and cause various pathologies in the esophagus, the larynx, and the lungs.

OBJECTIVE

We aimed to show if aminoguanidine (AG) contributes to the biochemical and histopathologic treatment of experimental aspiration pneumonitis induced by BAs.

METHODS

Twenty-eight female Sprague Dawley rats were used. There were 4 groups in the study: (1) group aspirated with 0.9% saline (n = 7), (2) group aspirated with 0.9% saline and treated with AG (n = 7), (3) group aspirated with a solution of 10 mg/kg taurocholic acid and 5 mg/kg taurochenodeoxycholate (n = 7), and (4) group aspirated with BA and treated with AG (n = 7). The saline and BA solutions were administered as 1 mL/kg intratracheally. The AG was administered intraperitoneally twice a day at a 150 mg/kg dose for 7 days. The different histopathologic and biochemical parameters were analyzed.

RESULTS

Clara cell protein 16 and malondialdehyde levels were found to be significantly higher in the BA group than in the group where saline was administered; however, they were significantly lower in the BA + AG group than in the BA group. The total superoxide dismutase activity decreased significantly in the BA group compared with the group where saline was administered. A significant increase in superoxide dismutase activity was observed in the BA + AG group when compared with the group where only BA was administered. When the group where BA was administered solely was compared with the group where saline was administered, peribronchial inflammatory cell infiltration, alveolar septal infiltration, alveolar histiocytes, interstitial fibrosis, and granuloma were significantly higher in the BA group than in the saline group. When the BA + AG group was compared with the BA group, peribronchial inflammatory cell infiltration, alveolar septal infiltration, alveolar histiocytes, interstitial fibrosis, and granuloma were found to be significantly lower.

CONCLUSIONS

Oxidant stress increases and antioxidant capacity decreases in pneumonitis induced by BAs. AG administration as an antioxidant helps in recovery, both biochemically and histopathologically. Consequently, AG seems to be an alternative that should be considered in a conservative approach to treating aspiration pneumonitis.

Conditional expression of Wnt9b in Six2-positive cells disrupts stomach and kidney function

During kidney development, canonical Wnt signaling activates differentiation, while the transcription factor Six2 maintains the progenitor pool. These opposing signals help to regulate nephron formation and ensure the full complement of nephrons are formed. Since these two factors control differing fates in kidney mesenchyme, we hypothesized that overexpression of Wnt9b in Six2-expressing cells would disrupt kidney formation and may alter cell differentiation decisions in other tissues. We created a transgenic mouse that conditionally expressed the canonical Wnt ligand in the developing kidney, Wnt9b. The transgene is activated by cre recombinase and expresses GFP. We first tested its biological activity using Hoxb7-cre and found that transgenic Wnt9b was capable of inducing differentiation genes and of rescuing kidney development in Wnt9b^−/− homozygous deficient mice. In contrast, expression of Wnt9b in cells using Six2-cre caused gastrointestinal distress and severe renal failure in adult mice. Transgenic kidneys had numerous cystic tubules and elevated creatinine values (0.652±0.044) compared to wild-type mice (0.119±0.002). These animals also exhibited a malformed pyloric sphincter, duodenogastric reflux, and a transformation of the distal stomach into proximal fate. The gene expression changes observed for the Wnt9b:EGFP transgene were compared to a stabilized β-catenin allele to determine that Wnt9b is activating the canonical Wnt pathway in the tissues analyzed. These results demonstrate that expression of Wnt9b in Six2-positive cells disrupts cell fate decisions in the kidney and the gastrointestinal tract.

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.

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.

Effect of low-proof alcoholic beverages on duodenogastro-esophageal reflux in health and GERD

BACKGROUND

Alcoholic beverages are known to increase acidic gastro-esophageal reflux (GER) and the risk of esophagitis. Moreover, duodenogastro-esophageal reflux (DGER), containing bile acids, was shown to harmfully alter the esophageal mucosa, alone and synergistically with HCl and pepsin. However, studies directly addressing potential effects of different low proof alcoholic beverages on DGER in health and disease are missing.

METHODS

Bilitec readings for beer and white, rose, and red wine were obtained in vitro from pure and from mixtures with bile. One-hour DGER monitoring and pH-metry were performed in 12 healthy subjects and nine reflux patients with DGER after ingestion of a standardized liquid meal together with 300 mL of water, white wine, and in the volunteers, beer and rose wine.

KEY RESULTS

Bilitec measurement was found to be feasible in the presence of beer, white wine, and using a threshold of 0.25, rose wine. However, the presence of red wine resulted in extinction values above this threshold. The consumption of all investigated alcoholic beverages, especially of white wine, triggered increased acidic GER, both in healthy participants and patients with reflux disease. In contrast, no relevant DGER was found after intake of alcoholic beverages.

CONCLUSIONS & INFERENCES

Fiber-optic bilirubin monitoring can be used for DGER monitoring in combination with alcoholic beverages, except with red wine. Low-proof alcoholic beverages are a strong trigger of GER, but not of DGER, both in healthy subjects and patients with reflux disease.

Epidemiology of symptom-defined gastroesophageal reflux disease and reflux esophagitis: the systematic investigation of gastrointestinal diseases in China (SILC)

OBJECTIVE

Gastroesophageal reflux disease (GERD) is thought to be less prevalent in China than in Western countries. However, essential population-based endoscopy data are lacking for this country.

MATERIAL AND METHODS

As part of a wider study, 3600 individuals selected randomly from the Shanghai region were asked to undergo endoscopy. Participants completed a general information questionnaire and a Chinese version of the Reflux Disease Questionnaire. When sufficient numbers were available, associations were assessed using multiple logistic regression or the Wilcoxon rank-sum test.

RESULTS

Of 3153 (87.6%) individuals who completed the survey, 1030 (32.7%) agreed to endoscopy and 1029 endoscopies were suitable for analysis. Symptom-defined GERD was more prevalent in the endoscopy group (4.7%) than in the non-endoscopy group (1.7%). Prevalence estimates were 6.4% for reflux esophagitis, 1.8% for endoscopically suspected esophageal metaplasia and 0.7% for hiatus hernia. Reflux esophagitis was more prevalent in patients with symptom-defined GERD than in those without (12.5% [6/48] vs. 6.1% [60/981]), and was significantly associated with reflux symptoms of any frequency or severity (OR = 2.10, 95% CI 1.13-3.89) and with negative Helicobacter pylori infection (OR = 0.44, 95% CI 0.25-0.80). Only 28.8% of participants with reflux esophagitis had heartburn and/or regurgitation symptoms. Epigastric burning was significantly more severe and frequent in participants with reflux esophagitis than in those without (p = 0.05).

CONCLUSIONS

Reflux esophagitis is less prevalent in China than reported in Western countries. Further work is needed to establish why reflux esophagitis appears less symptomatic in China than in Western countries.

Weakly acidic reflux

The advent of multichannel intraluminal impedance-pH (MII-pH) monitoring has generated interest in the role of weakly acidic reflux in persistent symptoms in patients with gastroesophageal reflux disease (GERD). Emerging evidence suggests that MII-pH may be superior to conventional pH testing under certain circumstances in the detection of reflux and expert opinions have been put forth advocating a central role for pH impedance monitoring in the detection of GERD. However the clinical relevance of an impedance-based diagnosis of reflux and its impact on clinically relevant outcomes is less clear. This review appraises the role of weakly acidic reflux in health and in GERD patients and the clinical utility of detecting weakly acidic reflux in the management of GERD.

Medical treatment of GORD. Emerging therapeutic targets and concepts

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

Efficacy, tolerability and pharmacokinetics of a modified release formulation of ADX10059, a negative allosteric modulator of metabotropic glutamate receptor 5: an esophageal pH-impedance study in healthy subjects

BACKGROUND

Animal studies show metabotropic glutamate receptor 5 inhibition reduces transient lower esophageal sphincter relaxations and increases lower esophageal sphincter tone. A preliminary, single-day study, demonstrated oral ADX10059 reduced 24-h esophageal acid exposure and clinical symptoms in gastro-esophageal reflux disease (GERD) patients, but had suboptimal tolerability, ascribable to the compound's rapid absorption. This study evaluated ADX10059 modified-release (MR) formulation pharmacokinetics, tolerability, and pharmacodynamics.

METHODS

Randomized, double-blind placebo-controlled study. Three groups of eight healthy, male subjects received placebo (n = 2) or ADX10059 (n = 6) 50, 125 or 250 mg b.i.d. for 6 days. Esophageal pH-impedance was performed on day 1 and day 6 of treatment, for 1-h fasting and for 4 h post refluxogenic meal. Treatment effect was determined by Kruskall-Wallis test and placebo comparison by Wilcoxon rank sum.

KEY RESULTS

Following placebo, reflux episodes increased from day 1 to day 6. Significant treatment effect was seen for total esophageal acid exposure (P = 0.048) and postprandial number of weakly acidic reflux episodes (P = 0.041). Significant differences from placebo were seen for 125 mg b.i.d.; 250 mg b.i.d. was not more effective than 125 mg b.i.d. Twice daily ADX10059 MR gave satisfactory 24-h exposure and good tolerability.

CONCLUSIONS & INFERENCES

ADX10059 decreased reflux episodes in healthy subjects. The MR formulation is suitable for longer-term treatment to evaluate symptom control in GERD patients.

Emerging concepts of bile reflux in the constellation of gastroesophageal reflux disease

RATIONALE

Reflux of gastric and duodenal contents in patients with gastroesophageal reflux disease (GERD) has been postulated as a major cause of complications, such as Barrett's esophagus or malignant degeneration.

FINDINGS

We present a summary of experimental, clinical, and immunohistochemical studies that show that acid and bile reflux are increased in patients who suffer from GERD, are the key factor in the pathogenesis of Barrett's esophagus, and are possibly related to the development of esophageal adenocarcinoma.

Six2 activity is required for the formation of the mammalian pyloric sphincter

The functional activity of Six2, a member of the so/Six family of homeodomain-containing transcription factors, is required during mammalian kidney organogenesis. We have now determined that Six2 activity is also necessary for the formation of the pyloric sphincter, the functional gate at the stomach-duodenum junction that inhibits duodenogastric reflux. Our data reveal that several genes known to be important for pyloric sphincter formation in the chick (e.g., Bmp4, Bmpr1b, Nkx2.5, Sox9, and Gremlin) also appear to be required for the formation of this structure in mammals. Thus, we propose that Six2 activity regulates this gene network during the genesis of the pyloric sphincter in the mouse.

Significant increase of esophageal mucin secretion in patients with reflux esophagitis after healing with rabeprazole: its esophagoprotective potential

Esophageal mucin secretion in patients with reflux esophagitis (RE) is significantly impaired. Rabeprazole augments gastric mucin secretion. We have studied, therefore, the effect of rabeprazole on esophageal mucin secretion in patients with RE. The study was conducted in 15 patients with RE treated with rabeprazole (20 mg QD) for 8 weeks. Esophageal secretions were collected during consecutive infusions of initial NaCl, HCl/Pepsin (HCl/P), and a final NaCl, using a specially designed esophageal catheter, before and after therapy. Mucin was measured using standard methodology. After rabeprazole administration esophageal mucin concentration as well as secretion increased during perfusion with initial saline (P < 0.01), HCl/P (P < 0.02), and concluding saline (P < 0.001). Stimulation of esophageal mucin secretion by rabeprazole may indicate that the mechanisms governing its secretion are similar to those implicated in gastric mucin output. Enhancement of esophageal mucin secretion by rabeprazole may translate into esophagoprotective potential in patients with reflux esophagitis.