Esophageal Epithelial Barrier Function Research Articles

Proton pump inhibitors modulate esophageal epithelial barrier function and crosstalk with eosinophils.

Eosinophilic esophagitis (EoE) is a chronic allergic disease characterized by esophageal dysfunction, type-2 inflammation, and esophageal eosinophilic infiltrate. While proton pump inhibitor (PPI) therapy is commonly used for EoE management, the underlying mechanism of action remains unclear. Air-liquid interface culture of esophageal epithelial cells was employed to investigate the impact of the PPI omeprazole on barrier integrity in IL-13-treated cultures. Epithelial chemokine secretion was assessed following stimulation with IL-13 and omeprazole, and the migration of eosinophils from healthy human donors was evaluated using 3 μm pore-sized transwells. A co-culture system of epithelial cells and eosinophils was employed to study chemokine secretion and eosinophil adhesion and activation markers. Omeprazole treatment in the IL-13-treated air-liquid interface (ALI) model resulted in 186 differentially expressed genes and restored barrier integrity compared to ALI treated with IL-13 alone. Omeprazole treatment reduced STAT6 phosphorylation, downregulated calpain 14, and upregulated desmoglein-1 in the IL-13-treated air-liquid interface samples. IL-13-induced upregulation of Eotaxin-3, CXCL10, and periostin, but this was downregulated by omeprazole. Further, the expression of CD11b, CD18, and CD69 was lower on eosinophils from omeprazole-treated epithelial-eosinophil co-cultures, which also had lower levels of eotaxin-3, CXCL10, CCL2, and CCL4. Omeprazole reduced the effects of IL-13 in both the epithelial air-liquid interface model and eosinophil-epithelial co-cultures, reducing barrier dysfunction, chemokine expression, and upregulation of eosinophil adhesion markers.

Metabolic dysfunction mediated by HIF-1α contributes to epithelial differentiation defects in eosinophilic esophagitis

Investigating the contributory role that epithelial cell metabolism plays in allergic inflammation is a key factor to understanding what influences dysfunction and the pathogenesis of the allergic disease eosinophilic esophagitis (EoE). We previously highlighted the absence of hypoxia signaling through HIF-1α in EoE contributes to esophageal epithelial dysfunction. However, metabolic regulation by HIF-1α has not been explored in esophageal allergy. Herein, we sought to define the role of HIF-1α-mediated metabolic dysfunction in esophageal epithelial differentiation processes and barrier function in EoE. In RNA-sequencing derived from EoE patient biopsies, we observed the expression pattern of key genes involved in mitochondrial metabolism/oxidative phosphorylation (OXPHOS) and glycolysis. Bioenergetics analysis using Seahorse was performed on EPC2-hTERT cells to decipher the metabolic processes involved in epithelial differentiation processes. In addition, air-liquid interface cultures were employed to delineate metabolic dependency mechanisms required for epithelial differentiation. Transcriptomic analysis identified an increase in genes associated with OXPHOS in patients with EoE. Epithelial origin of this signature was confirmed by complex V immunofluorescence of patient biopsies. Bioenergetic analysis in vitro revealed that differentiated epithelium was less reliant on OXPHOS compared with undifferentiated epithelium. Increased OXPHOS potential and reduced glycolytic capacity was mirrored in HIF1A-knockdown EPC2-hTERT cells which portray a significant absence of terminal markers of epithelial differentiation, including involucrin. Pharmacological glucose transport inhibition phenocopied this, while rescue of the HIF-1α-deficient phenotype using the pan-prolyl hydroxylase inhibitor DMOG resulted in restored expression of epithelial differentiation markers. An OXPHOS-dominated metabolic pattern in EoE patients, brought about largely by the absence of HIF-1α-mediated glycolysis, is linked with the deficit in esophageal epithelial differentiation.

Qingre Jiangni formula improves esophageal epithelial barrier function in gastroesophageal reflux rats through male hormones and the p38/MAPK pathway

Qingre Jiangni formula improves esophageal epithelial barrier function in gastroesophageal reflux rats through male hormones and the p38/MAPK pathway

Mast cells disrupt the function of the esophageal epithelial barrier

Mast cells (MCs) accumulate in the epithelium of patients with eosinophilic esophagitis (EoE), an inflammatory disorder characterized by extensive esophageal eosinophilic infiltration. Esophageal barrier dysfunction plays an important role in the pathophysiology of EoE. We hypothesized that MCs contribute to the observed impaired esophageal epithelial barrier. Herein, we demonstrate that coculture of differentiated esophageal epithelial cells with immunoglobulin E-activated MCs significanly decreased epithelial resistance by 30% and increased permeability by 22% compared with non-activated MCs. These changes were associated with decreased messenger RNA expression of barrier proteins filaggrin, desmoglein-1 and involucrin, and antiprotease serine peptidase inhibitor kazal type 7. Using targeted proteomics, we detected various cytokines in coculture supernatants, most notably granulocyte-macrophage colony-stimulating factor and oncostatin M (OSM). OSM expression was increased by 12-fold in active EoE and associated with MC marker genes. Furthermore, OSM receptor-expressing esophageal epithelial cells were found in the esophageal tissue of patients with EoE, suggesting that the epithelial cells may respond to OSM. Stimulation of esophageal epithelial cells with OSM resulted in a dose-dependent decrease in barrier function and expression of filaggrin and desmoglein-1 and an increase in protease calpain-14. Taken together, these data suggest a role for MCs in decreasing esophageal epithelial barrier function in EoE, which may in part be mediated by OSM.

Correlation of Esophageal Mean Nocturnal Baseline Impedance With Markers of Laryngopharyngeal Reflux.

Mean nocturnal baseline impedance (MNBI) is a measure of the esophageal epithelial barrier function calculated via high-resolution impedance manometry and can be used as a diagnostic tool and treatment response predictor for gastroesophageal reflux disease (GERD). However, its utility for laryngopharyngeal reflux (LPR) has been minimally studied. We aimed to investigate the relationship of MNBI between patients with suspected LPR, healthy controls, and their 24-h multichannel intraluminal impedance-pH (MII-pH) study results. Retrospective patient series analysis was performed of patients with suspected LPR and healthy controls who underwent 24-h MII-pH monitoring. MNBI values were calculated from impedance channels at the level of the hypopharynx, proximal esophagus, and distal esophagus. We compared these MNBI values between the subject groups with secondary analysis on MII-pH results, reflux symptom index, reflux findings score, DeMeester score, and salivary pepsin levels. Twenty-three patients with suspected LPR and 14 healthy controls were enrolled. Decreased distal esophageal MNBI was found to be significantly decreased in patients with suspected LPR compared with healthy controls (p< 0.01) and in subjects with positive MII-pH studies compared to negative MII-pH studies (p< 0.01). There were no significant correlations of MNBI at the hypopharynx or proximal esophagus. Distal esophageal MNBI has significant correlations with many phenotypic and biological markers of LPR. These findings indicate that MNBI has the potential to be applied to LPR, similar to its emerging use as a diagnostic tool and treatment response predictor for GERD. 3 Laryngoscope, 133:1927-1932, 2023.

EZH2-mediated suppression of CLDN1 leads to barrier dysfunction in PPI-refractory gastroesophageal reflux disease.

PPI-refractory gastroesophageal reflux disease (RGERD) is characterized as the existence of reflux symptoms resistant to optimized PPI treatment. Alleviated mucosal integrity has been regarded as one of the mechanisms of RGERD. RNA sequencing analysis and GSEA were performed. Human biopsy samples, cell lines, and rat models were recruited. Trans-epithelial electrical resistance (TEER) was tested and a FITC-dextran flux assay was performed to detect barrier permeability. Tissue morphology was evaluated using HE staining, while gene expression was measured by qRT-PCR, western blotting, flow cytometry, immunofluorescence, immunohistochemistry, and chromatin immunoprecipitation (ChIP) analysis. The tight junction protein Claudin-1 is significantly weakened in the RGERD epithelium, while levels of EZH2-mediated H3K27me3 were increased. Forced EZH2 expression in epithelial cells led to H3K27me3 accumulation and Claudin-1 suppression, which consequently caused epithelial barrier dysfunction. Notably, studies on esophagogastroduodenal anastomosis (EGDA) rat models showed the attenuation of Claudin-1 level and barrier function could be rescued by an Ezh2 inhibitor GSK126. ChIP analysis followed by qPCR (ChIP-qPCR) revealed H3K27me3 suppressed CLDN1 via accumulating at the TSS area. For the first time, we explored the attenuated tight junction of RGERD, demonstrating a potential underlying mechanism that EZH2-mediated H3K27me3 could impair esophageal epithelial barrier function by suppressing the transcription of CLDN1.

Butyrate and propionate restore interleukin 13-compromised esophageal epithelial barrier function.

BackgroundEosinophilic esophagitis (EoE) is a food allergen driven disease that is accompanied by interleukin (IL) 13 overexpression and esophageal barrier dysfunction allowing transepithelial food allergen permeation. Nutraceuticals, such as short‐chain fatty acids (SCFAs) that restore barrier function and increase immune fitness may be a promising tool in the management of EoE. Here, we investigated the effects of the SCFAs acetate, propionate, and butyrate on an IL‐13‐compromised human esophageal epithelial barrier, including the mechanisms involved.MethodsAn air‐liquid interface culture model of differentiated human EPC2‐hTERT (EPC2) was used to study whether SCFAs could restore barrier function after IL‐13‐induced impairment. Esophageal epithelial barrier function was monitored by transepithelial electrical resistance (TEER) and FITC‐dextran paracellular flux, and was further examined by qPCR and immunohistochemical analysis. G protein‐coupled receptor (GPR) GPR41, GPR43, GPR109a, or histone deacetylase (HDAC) (ant)agonists were used to assess mechanisms of action of SCFAs.ResultsIL‐13 stimulation decreased TEER and increased FITC flux, which was counteracted by butyrate and propionate, but not acetate treatment. Barrier proteins FLG and DSG1 mRNA expression was upregulated following butyrate and propionate treatment, whereas expression of eosinophil chemoattractant CCL26 and protease CAPN14 was downregulated. Similarly, butyrate and propionate restored FLG and DSG1 protein expression. Similar effects were observed with an HDAC antagonist but not with GPR agonists.ConclusionNutraceuticals butyrate and propionate restore the barrier function of esophageal epithelial cells after an inflammatory insult and may be of therapeutic benefit in the management of EoE.

Products of GEJ Fat of Obese Patients Cause Rapid and Reversible Impairment of Esophageal Epithelial Barrier Function

Objective Visceral obesity is associated with GERD and reflux esophagitis, and weight loss in obese GERD patients can result in resolution of GERD symptoms and esophagitis. Traditionally, it has been assumed that visceral fat predisposes to GERD primarily by increasing intra-abdominal pressure. However, in earlier studies, we found that substances secreted by mature adipocytes in visceral fat from obese patients impair esophageal epithelial barrier function, induce dilated intercellular spaces (DIS) and reduce transepithelial resistance (TER). We now devised an in vitro experiment to simulate the effects of weight loss on visceral fat to determine if this fat's adverse effects on esophageal epithelial barrier integrity are reversible. Methods We obtained tissue from the fat pad at the gastroesophageal junction (GEJ) that is in intimate contact with the distal esophagus of 2 obese (BMI 46, 74) and 2 non-obese (BMI 26, 27) patients having foregut surgery. Human esophageal squamous cells were seeded into transwells and grown to confluence for 3 days. On day 4, cells were raised to an air-liquid interface (ALI) to allow for differentiation, stratification, and esophageal barrier formation until day 8. At day 8, ALI cultures were exposed to conditioned media (CM) from GEJ fat tissue or to control medium. Initial time course studies revealed a significant drop in TER measured by the EVOM2 Epithelial Volt/Ohm Meter after 1 hour of treatment with CM from GEJ fat of obese patients; thus, 1 hour was selected for all further studies. ALI cultures were also treated with CM from GEJ fat of obese patients for 1 hour after which that CM was removed and replaced with CM from the GEJ fat of non-obese patients for 1 hour. ALI cultures were stained with H&E and imaged; barrier permeability was assessed by a biotinylation reagent applied to the ALI surface. Results CM from GEJ fat of obese patients significantly reduced TER of ALI cultures compared with controls, while CM from GEJ fat of non-obese patients had no significant effect on TER (Table 1). DIS were found only in ALI cultures treated with obese CM. In ALIs grown with CM from non-obese patients, the biotinylation reagent stopped at the superficial layers of esophageal cells, whereas the biotinylation reagent diffused through all cell layers in ALIs grown with obese patient CM. Interestingly, within one hour of replacing CM from GEJ fat of obese patients with CM from GEJ fat of non-obese patients, TER levels increased significantly, DIS resolved almost completely (Figure 1), and the biotinylation reagent stopped at the superficial layers of esophageal cells. Conclusion Substances produced by GEJ fat of obese patients impair esophageal barrier integrity and cause DIS through mechanisms that are rapid and reversible. This might explain why obese patients who lose weight experience resolution of GERD symptoms.

Gastroesophageal Junction Fat Pad Tissue from Obese Patients Impairs Esophageal Epithelial Barrier Function and Disrupts Cell‐to‐Cell Connections

Introduction Visceral obesity is associated with GERD and, traditionally, it has been assumed that visceral fat predisposes to GERD primarily by increasing intra-abdominal pressure. However, transmission electron microscopy (TEM) of esophageal biopsies from obese individuals without GERD exhibit dilated intercellular spaces (DIS) and, in earlier studies, we found that substances secreted by mature adipocytes in visceral fat from obese patients impair esophageal epithelial barrier function, induce DIS and reduce transepithelial resistance (TER). There is a fat pad at the gastroesophageal junction (GEJ) that is in intimate contact with the distal esophagus. We now explore whether whole GEJ fat tissue of obese individuals secretes substances that impair esophageal barrier function. Methods We obtained GEJ fat from 3 obese (BMI 46, 60, 74) and 3 non-obese (BMI 24, 26, 27) patients having foregut surgery. Human esophageal squamous cells were seeded into transwells and grown to confluence for 3 days. On day 4, cells were raised to an air-liquid interface (ALI) to allow for differentiation, stratification, and esophageal barrier formation. ALI cultures were exposed to conditioned media (CM) from GEJ fat or to control medium beginning at day 4. TER was measured on days 4, 6, and 8 using the EVOM2 Epithelial Volt/Ohm Meter. On day 8, ALI cultures were stained with H&E and Ki-67 and imaged; barrier permeability was assessed by a biotinylation reagent applied to the ALI surface. TEM of ALIs and of esophageal biopsies from 2 non-obese and 2 obese patients without GERD were assessed. Results CM from all 3 obese patients significantly reduced TER on days 6 and 8; CM from 2 non-obese patients did not reduce TER whereas CM from 1 non-obese patient induced a slight reduction in TER at day 8 (Table 1). Marked DIS were found only in ALI cultures grown with CM from obese patients. In ALIs grown with CM from non-obese patients, the biotinylation reagent stopped at the superficial layers of esophageal cells. In contrast, the biotinylation reagent diffused through all cell layers in ALIs grown with obese patient CM. Increases in basaloid cells and in Ki-67 were found in ALIs grown with obese patient CM. TEMs of ALIs grown with non-obese patient CM demonstrated well-oriented cell-cell junctions similar to TEMs of non-obese patient esophageal biopsies. In contrast, ALIs grown with obese patient CM demonstrated cell-cell junctional structures that were disorganized, aggregated, and floating within the DIS, similar in appearance to TEMs of the obese patients’ esophageal biopsies. Conclusion Substances produced by GEJ fat of obese patients impair esophageal epithelial barrier integrity, cause basal cell hyperplasia and DIS, and disrupt intercellular connections. These findings in ALI cultures recapitulate abnormalities seen by TEM in esophageal biopsies of obese patients.

Effects of Central Obesity on Esophageal Epithelial Barrier Function.

We assessed if obesity perturbs the esophageal epithelial barrier function independent of promotion of gastroesophageal reflux (GER). Thirty-eight participants were divided into 4 groups: Obesity-/GER-, Obesity+/GER-, Obesity-/GER+, and Obesity+/GER+. Esophageal intercellular space and desmosome density (structural integrity) and fluorescein leak (functional integrity) were measured. The Obesity+/GER- group demonstrated increased intercellular space, reduced desmosome density, and increased fluorescein leak compared with control subjects. These changes were similar but not additive to findings seen in Obesity-/GER + and Obesity+/GER+ patients. Central obesity impairs structural and functional integrity of the esophageal barrier independent of GER, likely predisposing to esophageal injury.

S0362 Central Obesity Perturbs Esophageal Epithelial Barrier Function by Down-Regulating Desmosomes

S0362 Central Obesity Perturbs Esophageal Epithelial Barrier Function by Down-Regulating Desmosomes

Recent insights into the biology of Barrett's esophagus.

Barrett's esophagus (BE) is the only known precursor to esophageal adenocarcinoma (EAC), an aggressive cancer with a poor prognosis. Our understanding of the pathogenesis and Barrett's metaplasia is incomplete, and this has limited the development of new therapeutic targets and agents, risk stratification ability, and management strategies. This review outlines current insights into the biology of BE and addresses controversies surrounding cell of origin, cellular reprogramming theories, updates on esophageal epithelial barrier function, and the significance of goblet cell metaplasia and its association with malignant change. Further research into the basic biology of BE is vital as it will underpin novel therapies and improve our ability to predict malignant progression and help identify the minority of patients who will develop EAC.

Products of Mature Adipocytes in Visceral Fat of Obese Patients Impair Esophageal Epithelial Barrier Formation and Function

ObjectiveVisceral obesity is associated with GERD and its complications of reflux esophagitis, Barrett’s esophagus and esophageal adenocarcinoma. A traditional explanation for these associations is that visceral fat causes pathological acid reflux by increasing intra‐abdominal pressure. However, for unknown reasons, the esophagus of obese patients who have normal esophageal acid exposure can exhibit evidence of impaired epithelial barrier function including dilated intercellular spaces (DIS) and reduced transepithelial resistance (TER). In this study, we explored our hypothesis that the visceral fat of obese individuals secretes substances that impair esophageal barrier function, thus predisposing to injury by GERD.MethodsWe obtained subcutaneous (SQ) and visceral (VIS) fat from 1 non‐obese (BMI 18) and 2 obese (BMIs 51&amp; 42) patients having foregut surgery; VIS included both mesenteric fat and gastroesophageal junction (GEJ) fat pad. Fat contains both mature adipocytes (MAs) and adipocyte derived stem cells (ADSCs), which were isolated from adipocyte tissues by collagenase digestion and differential centrifugation; immunofluorescence (CD90+, CD44+, CD31−, CD45−) was used to confirm ADSC isolation. Telomerase‐immortalized normal, human esophageal squamous cells (NES‐B10T) were seeded into transwells and grown to confluence for 3 days. On day 4, the cells were raised to an air‐liquid interface (ALI) to allow for differentiation, stratification, and formation of an esophageal epithelial barrier. ALI cultures were exposed to conditioned media (CM) from MAs or ADSCs, or to control NES medium beginning at day 4. TER was measured (in Ω·cm2) on days 4, 6, and 8 using the EVOM2 Epithelial Volt/Ohm Meter (World Precision Instruments, Sarasota, FL). On day 10, ALI cultures were stained with H&amp;E and imaged.ResultsCM from ADSCs of SQ and VIS fat from an obese patient did not reduce the TER of NES ALI cultures at any time point; CM from MAs of SQ fat from all 3 patients also did not reduce TER. In contrast, CM from MAs of VIS fat from both obese patients significantly reduced TER on day 6 compared with control medium; TER also remained lower than control on day 8 (Table 1). CM from MAs of VIS fat from the non‐obese patient did not reduce TER of NES ALI cultures at any time point (Table 1). H&amp;E staining demonstrated DIS only in those ALI cultures grown with the CM from MAs of VIS fat from the obese patients.ConclusionsSubstances produced by MAs, but not by ADSCs, in the VIS fat of obese patients impair esophageal epithelial barrier integrity and cause morphologic changes of DIS. No such effects were found for substances produced by MAs in the SQ fat of any patient, or from those produced by MAs in VIS fat of the non‐obese patient. Moreover, VIS fat in the mesentery and at the GEJ exert similar functional and morphologic effects on esophageal barrier formation. We are conducting further investigations to identify the mechanisms underlying the impairment of esophageal barrier formation caused by visceral adiposity, specifically for the GEJ fat pad that surrounds the distal esophagus.Support or Funding InformationBaylor Scott &amp; White Research Institute Transepithelial Resistance (Ω·cm2 ±SEM) of NES on Day 6 and Day 8 of ALI Culture Exposed to Conditioned Media from Mature Adipocytes from Subcutaneous (SQ), Mesenteric, and GEJ Adipocyte Tissues BMI Control Day 6 SQ Day 6 Mesenteric Day 6 GEJ Day 6 Control Day 8 SQ Day 8 Mesenteric Day 8 GEJ Day 8 18 241±2.1 242±2.0 234±2.0 235±2.5 245±3.8 256±2.2 243±4.2 248±7.2 51 212±2.0 204±3.5 194±3.0 * 192±0.5 ** 235±8.5 233±1.0 209±6.5 207±8.0 42 264±3.6 263±5.5 236±2.3 ** 239±3.3 ** 251±2.4 296±45 249±0.9 237±2.6 * *p≤0.05; **p≤0.01 compared with control

Toll-like receptor 2 stimulation augments esophageal barrier integrity.

Germline-encoded innate immune pattern recognition receptors (PRR) are expressed at epithelial surfaces and modulate epithelial defenses. Evidence suggests that stimulation of the Toll-like receptor (TLR) family of PRR may regulate epithelial barrier integrity by upregulating tight junction (TJ) complex protein expression, but it is not known whether this mechanism is utilized in esophageal epithelial cells. TJ complex proteins maintain intact barrier function and are dysregulated in atopic disorders including eosinophilic esophagitis. Pattern recognition receptors expression was assessed in EoE and control primary esophageal epithelial cells, demonstrating robust expression of TLR2 and TLR3. The three-dimensional air-liquid interface culture (ALI) model was used to test whether TLR2 or TLR3 stimulation alters epithelial barrier function using an in vitro model of human epithelium. Transepithelial electrical resistance (TEER) and FITC-Dextran permeability were evaluated to assess membrane permeability. ALI cultures were evaluated by histology, immunohistochemistry, Western blotting, and chromatin immunoprecipitation (ChIP). TLR3 stimulation did not change TEER in the ALI model. TLR2 stimulation increased TEER (1.28- to 1.31-fold) and decreased paracellular permeability to FITC-Dextran, and this effect was abolished by treatment with anti-TLR2 blocking antibody. TJ complex proteins claudin-1 and zonula occludens-1 were upregulated following TLR2 stimulation, and ChIP assay demonstrated altered histone 4 acetyl binding at the TJP1 enhancer and CLDN1 enhancer and promoter following zymosan treatment, implying the occurrence of durable chromatin changes. Our findings implicate the TLR2 pathway as a potential regulator of esophageal epithelial barrier function and suggest that downstream chromatin modifications are associated with this effect.

Mo1166 – Disruption of Esophageal Epithelial Barrier Function and Its Correlation with Eosinophil Infiltration in Eosinophilic Esophagitis

Mo1166 – Disruption of Esophageal Epithelial Barrier Function and Its Correlation with Eosinophil Infiltration in Eosinophilic Esophagitis

17β-Estradiol protects the esophageal epithelium from IL-13–induced barrier dysfunction and remodeling

The incidence of eosinophilic esophagitis (EoE) is greater in male than female subjects, and the underlying molecular basis for this sex bias remains unclear. We sought to delineate the contribution of the sex hormone estrogen to the EoE phenotype and esophageal epithelial barrier function and remodeling. We performed demographic and incidence analyses of EoE in male and female subjects from a single-center pediatric cohort. Estrogen-responsive gene expression analyses and estrogen receptor (ESR) immunofluorescence staining of esophageal biopsy specimens from patients with EoE and control subjects were performed. The effect of 17β-estradiol (E2) on IL-13-induced signaling pathways, gene expression, and esophageal epithelial architecture and barrier function in a primary human esophageal keratinocyte cell (EPC2) culture system (EPC2-air-liquid interface) was examined. We observed a male predominance in patients with EoE. Analyses of RNA sequencing data sets revealed a significant dysregulation of the estrogen-responsive gene network and expression of ESR1 and ESR2 in esophageal biopsy specimens from patients with EoE compared with control subjects. IL-13 stimulation of EPC2-air-liquid interface cells led to altered cellular architecture with induced dilation of intercellular spaces and barrier dysfunction. Pretreatment of EPC2s with E2 prior to IL-13 exposure abrogated IL-13-induced architectural changes and esophageal barrier dysfunction. Mechanistically, E2-protective effects were dependent on ESR2 and associated with diminishing of IL-13-induced tyrosine kinase 2 and signal transducer and activator of transcription 6 phosphorylation and EoE-dysregulated gene expression. Estrogen-responsive genes are modified in patients with EoE compared with control subjects. E2 attenuated IL-13-induced architectural changes and esophageal epithelial barrier dysfunction through inhibition of the IL-13/tyrosine kinase 2/signal transducer and activator of transcription 6 pathway via ESR2-dependent process. Estrogen hormone signaling may protect against development of EoE in female subjects.

TGF-β1 alters esophageal epithelial barrier function by attenuation of claudin-7 in eosinophilic esophagitis.

Barrier dysfunction has been implicated in the pathophysiology of eosinophilic esophagitis (EoE). TGF-β1, a potent pleiotropic molecule, is increased in EoE, however, no study has evaluated its influence on esophageal epithelial barrier. We hypothesized that TGF-β1 regulates barrier dysfunction in EoE. We aimed to determine the role of TGF-β1 in epithelial barrier in models of EoE. To examine the impact of TGF-β1 on esophageal barrier, immortalized human esophageal epithelial (EPC2-hTERT) cells were exposed to TGF-β1 during the 3-dimensional air liquid interface (3D-ALI) model in vitro. TGF-β1 exposure diminished EPC2-hTERT barrier function as measured by transepithelial electrical resistance (TEER) and 3kDa FITC dextran paracellular flux (FITC Flux) and H&E assessment revealed prominent cellular separation. In analysis of epithelial barrier molecules, TGF-β1 led to the specific reduction in expression of the tight-junction molecule, claudin-7 and this was prevented by TGF-β receptor I inhibitor. shRNA mediated claudin-7 knockdown diminished epithelial barrier function, while claudin-7 overexpression resulted in protection from TGF-β1-mediated barrier dysfunction. In analysis of pediatric EoE biopsies claudin-7 expression was decreased, altered localization was observed by immunofluorescence analysis and the TGF-β1 downstream transcription factor phosphorylated SMAD2/3 (pSMAD2/3) was increased. Our data suggest that TGF-β1 participates in esophageal epithelial barrier dysfunction through claudin-7 dysregulation.

The Esophageal Epithelial Barrier in Health and Disease

Dysfunction in the esophageal epithelial barrier function is a major source for morbidity. To better understand the pathophysiologic pathways of the diseases associated with barrier dysfunction, including gastroesophageal reflux disease, eosinophilic esophagitis, Barrett's esophagus, and obesity, it is important to understand the esophageal epithelial embryologic development, microscopic anatomy with a special focus on the barrier structure and function, extraepithelial defense mechanisms, and how these change in the diseased state. In recent years, significant progress has been made in elucidating the esophageal barrier structure and function both invitro and invivo. This has enhanced the understanding of mechanisms of disease, and may also allow identification of therapeutic targets that can help in the management of these diseases. This review provides a detailed discussion regarding the esophageal epithelial barrier structure and function, the current and historical techniques used to study the barrier, and how it is affected by common esophageal diseases.

Serotonin disrupts esophageal mucosal integrity: an investigation using a stratified squamous epithelial model.

Serotonin regulates gastrointestinal function, and mast cells are a potential nonneuronal source of serotonin in the esophagus. Tight junction (TJ) proteins in the esophageal epithelium contribute to the barrier function, and the serotonin signaling pathway may contribute to epithelial leakage in gastroesophageal reflux disease. Therefore, the aim of this study was to investigate the role of serotonin on barrier function, TJ proteins, and related signaling pathways. Normal primary human esophageal epithelial cells were cultured with use of an air-liquid interface system. Serotonin was added to the basolateral compartment, and transepithelial electrical resistance (TEER) was measured. The expression of TJ proteins and serotonin receptor 7 (5-HT7) was assessed by Western blotting. The involvement of 5-HT7 was assessed with use of an antagonist and an agonist. The underlying cellular signaling pathways were examined with use of specific blockers. Serotonin decreased TEER and reduced the expression of TJ proteins ZO-1, occludin, and claudin1, but not claudin4. A 5-HT7 antagonist blocked the serotonin-induced decrease in TEER, and a 5-HT7 agonist decreased TEER. Inhibition of p38 mitogen-activated protein kinase (MAPK) reduced the serotonin-induced decrease in TEER. Inhibition of p38 MAPK blocked the decrease of ZO-1 levels, whereas extracellular-signal-regulated kinase (ERK) inhibition blocked the decrease in occludin levels. Cell signaling pathway inhibitors had no effect on serotonin-induced alterations in claudin1 and claudin4 levels. Serotonin induced phosphorylation of p38 MAPK and ERK, and a 5-HT7 antagonist partially blocked serotonin-induced phosphorylation of p38 MAPK but not that of ERK. Serotonin disrupted esophageal squamous epithelial barrier function by modulating the levels of TJ proteins. Serotonin signaling pathways may mediate the pathogenesis of gastroesophageal reflux disease.

Recent advances in understanding/managing eosinophilic esophagitis in adults

It is an exciting time for research in eosinophilic esophagitis (EoE). As a new and increasingly prevalent disease, it is receiving considerable attention in the medical world, resulting in a flood of new insights. Clearly, a genetic predisposition seems likely with the identification of abnormalities in thymic stromal lymphopoietin (TSLP), calpain14, and eotaxin-3 genes. There are also well-defined abnormalities described in esophageal epithelial barrier function in these patients. The relationship between gastroesophageal reflux disease (GERD) and EoE remains unclear, but emerging data suggest that the concept of proton pump inhibitor responsive esophageal eosinophilia (PPIREE) may retain less importance, as this subset of patients becomes a likely subset of EoE in general. Finally, we approach the looming issue of long-term maintenance therapy. Although we lack adequate specific data on how to provide long-term pharmacologic treatment, studies clearly show that for most patients, this is a progressive disease that warrants such consideration.