Preferential Secretion of Thymic Stromal Lymphopoietin (TSLP) by Terminally Differentiated Esophageal Epithelial Cells: Relevance to Eosinophilic Esophagitis (EoE)

Abstract

Eosinophilic esophagitis (EoE) is a chronic Th2 and food antigen-mediated disease characterized by esophageal eosinophilic infiltration. Thymic stromal lymphopoetin (TSLP), an epithelial derived cytokine which bridges innate and Th2-type adaptive immune responses in other allergic conditions, is overexpressed in esophageal biopsies of EoE subjects. However, the triggers of TSLP expression in the esophageal epithelium are unknown. The objective of the current study was to characterize TSLP expression in human esophageal epithelium in EoE in vivo and to determine the role of food antigens upon epithelial TSLP expression in vitro. Using immunohistochemistry (IHC), we localized TSLP in esophageal biopsies of active EoE (≥15 eos/hpf), inactive EoE (<15 eos/hpf) and non-EoE control subjects, and found that TSLP expression was restricted to the differentiated suprabasal layer of the epithelium in actively inflamed EoE biopsies. Consistent with these results in vivo, inducible TSLP protein secretion was higher in CaCl2 differentiated telomerase-immortalized esophageal epithelial cells (EPC2-hTERT) compared to undifferentiated cells of the basal phenotype, following stimulation with the TLR3 ligand poly(I:C). To determine whether food antigens could directly induce epithelial TSLP secretion, differentiated and undifferentiated primary esophageal epithelial cells from EoE and non-EoE subjects were challenged with food antigens clinically relevant to EoE: Chicken egg ovalbumin (OVA), wheat, and milk proteins beta-lactoglobulin (blg) and beta-casein. Food antigens failed to induce TSLP secretion by undifferentiated cells; in contrast, only OVA induced TSLP secretion in differentiated epithelial cells from both EoE and control cell lines, an effect abolished by budesonide and NF-κb inhibition. Together, our study shows that specific food antigens can trigger innate immune mediated esophageal TSLP secretion, suggesting that esophageal epithelial cells at the barrier surface may play a significant role in the pathogenesis of EoE by regulating TSLP expression.

Genetic variations in the TLR3 locus are associated with eosinophilic esophagitis

“…17,19 We found that different tSNPs were independently associated with aeroallergen and food sensitization (rs11721827 and rs5743303, respectively), which suggests that the two variants could act as markers of the etiological variants. The influence of the hypothetical etiological variants could be related to differences in the 3 0 UTR region, the post-transcriptional control, mRNA expression levels or alternative forms of the transduced protein, which would affect its function.…”

Food Allergen Triggers are Increased in Children with the TSLP Risk Allele and Eosinophilic Esophagitis

“…Several genome wide and single polymorphism genetic studies have shown that compared to the general population, multiple SNPs at the TSLP genomic locus are associated with increased asthma susceptibility [RS3806933 (−847C>T), RS1837253] 2,5,17-23 or protection (RS1837253, RS2289276) 2,5,15,18,19,23 , increase risk of AD TSLP-SNPs (RS1898671, RS11466749, RS10043985 and RS2289276) 24,25 and atopy in general in different ethnic backgrounds, gender or age 1,25,26 . In our EoE patient population we confirmed a very high prevalence of atopic diseases compared to the general population.…”

“…This locus has been confirmed in two subsequent independent studies as a significant risk factor for EoE 13,14 . It has also been previously shown that chicken egg ovalbumin (OVA) induces differentiated esophageal epithelial cells to secrete TSLP via unknown mechanisms, an effect abolished by budesonide and NF-κb inhibition 15,16 . Therefore, similar to other atopic allergic diseases such as asthma, OVA can be used as a model of an antigen-induced atopic inflammatory process in EoE (i.e., production of TSLP from differentiated epithelial cells) 15 .…”

“…It has also been previously shown that chicken egg ovalbumin (OVA) induces differentiated esophageal epithelial cells to secrete TSLP via unknown mechanisms, an effect abolished by budesonide and NF-κb inhibition 15,16 . Therefore, similar to other atopic allergic diseases such as asthma, OVA can be used as a model of an antigen-induced atopic inflammatory process in EoE (i.e., production of TSLP from differentiated epithelial cells) 15 . TSLP is a pro-inflammatory cytokine in the interleukin 7 family that is secreted by epithelial cells in response to stressors such as infection, damage or allergens, and specifically promotes a Th2 immune response 17 .…”

“…Recent studies showed that TSLP may promote Th2 inflammation in EoE through basophil infiltration 2,5 . TSLP is activated not only in EoE but also in several allergic diseases such as atopic dermatitis and asthma 15 . There are no large scale studies to date which correlate the TSLP genotype with phenotype in pediatric patients with EoE.…”