Interleukin 9 Alters Epithelial Barrier and E-cadherin in Eosinophilic Esophagitis.

BACKGROUND: Eosinophilic esophagitis (EoE) is a chronic TH2-assocated inflammatory condition accompanied by substantial impairments in epithelial barrier function and increased numbers of interleukin 9 (IL-9) expressing inflammatory cells. While IL-9 is known to affect barrier function in the intestine, the functional effects of IL-9 on the esophagus are unclear. Herein we aimed to understand the expression of the IL-9 receptor and effects of IL-9 on the epithelium in EoE. METHODS: We used esophageal biopsies from pediatric EoE patients with active and inactive disease to analyze the expression of the IL-9 receptor, the adherens junction protein E-cadherin and the tight junction protein claudin-1. We treated primary human esophageal epithelial cells with IL-9 to understand its effects on E-cadherin expression and function. RESULTS: Active EoE subjects had increased epithelial expression of IL-9 receptor mRNA and protein (P < 0.05) and decreased membrane bound E-cadherin (P < 0.01) and claudin-1 (P < 0.05) expression. IL-9 receptor expression and mislocalized claudin-1 positively correlated and while membrane bound E-cadherin expression negatively correlated with the degree of histologic epithelial remodeling (P < 0.05). IL-9 decreased epithelial resistance in stratified primary human esophageal epithelial cells (P < 0.01) and membrane bound E-cadherin in epithelial cell monolayers (P < 0.01). CONCLUSIONS: These data suggest that IL-9, its receptor, and its effects on E-cadherin may be important mechanisms for epithelial barrier disruption in EoE.

TGF-ß1-induced PAI-1 contributes to a profibrotic network in patients with eosinophilic esophagitis.

BACKGROUND: Eosinophilic esophagitis (EoE) is an allergic disease of increasing worldwide incidence. Complications are due to tissue remodeling and involve TGF-ß1-mediated fibrosis. Plasminogen activator inhibitor 1 (PAI-1/serpinE1) can be induced by TGF-ß1, but its role in EoE is not known. OBJECTIVE: We sought to understand the expression and role of PAI-1 in patients with EoE. METHODS: We used esophageal biopsy specimens and plasma samples from control subjects and patients with EoE, primary human esophageal epithelial cells, and fibroblasts from patients with EoE in immunohistochemistry, quantitative PCR, and immunoassay experiments to understand the induction of PAI-1 by TGF-ß1, the relationship between PAI-1 and esophageal fibrosis, and the role of PAI-1 in fibrotic gene expression. RESULTS: PAI-1 expression was significantly increased in epithelial cells of biopsy specimens from patients with active EoE compared with that seen in biopsy specimens from patients with inactive EoE or control subjects (P < .001). Treatment of primary esophageal epithelial cells with recombinant TGF-ß1 increased PAI-1 transcription, intracellular protein expression, and secretion. Esophageal PAI-1 expression correlated with basal zone hyperplasia, fibrosis, and markers of esophageal remodeling, including vimentin, TGF-ß1, collagen I, fibronectin, and matrix metalloproteases, and plasma PAI-1 levels correlated with plasma TGF-ß1 levels. PAI-1 inhibition significantly decreased baseline and TGF-ß1-induced fibrotic gene expression. CONCLUSIONS: PAI-1 expression is significantly increased in the epithelium in patients with EoE and reflects fibrosis, and its inhibition decreases TGF-ß1-induced gene expression. Epithelial PAI-1 might serve as a marker of EoE severity and form part of a TGF-ß1-induced profibrotic network.

Smad3-deficient mice have reduced esophageal fibrosis and angiogenesis in a model of egg-induced eosinophilic esophagitis.

OBJECTIVES: Eosinophilic esophagitis (EoE) is a food-triggered disease associated with esophageal fibrosis and stricture formation in a subset of patients. In the present study we used a murine model of egg (ovalbumin [OVA])-induced EoE to determine whether inhibiting transforming growth factor-ß1 (TGF-ß1) signaling through the Smad3 pathway would inhibit features of esophageal remodeling including fibrosis, angiogenesis, and basal zone hyperplasia. METHODS: Wild-type (WT) and Smad3-deficient (KO [knockout]) mice were sensitized intraperitoneally and then challenged chronically with intraesophageal OVA for 1 month. Levels of esophageal eosinophils, esophageal TGF-ß1+ and vascular endothelial growth factor (VEGF)+ cells, and features of esophageal remodeling (fibrosis, angiogenesis, basal zone hyperplasia) were quantitated by immunohistochemistry and image analysis. RESULTS: OVA challenge induced a similar increase in the levels of esophageal major basic protein (MBP)+ eosinophils and esophageal TGF-ß1+ cells in WT and Smad3 KO mice. Smad3 KO mice challenged with OVA had significantly less esophageal fibrosis and esophageal angiogenesis compared with OVA-challenged WT mice. The reduced esophageal angiogenesis in Smad3 KO mice was associated with reduced numbers of VEGF+ cells in the esophagus. There was a trend toward OVA-challenged Smad3 KO to have reduced basal zone hyperplasia, but this was not statistically significant. CONCLUSIONS: In a mouse model of egg-induced EoE, Smad3-deficient mice have significantly less esophageal remodeling, especially fibrosis and angiogenesis that is associated with reduced expression of VEGF. Targeting the TGF-ß1/Smad3 pathway may be a novel strategy to reduce esophageal fibrosis and its associated complications such as esophageal strictures in EoE.