IL-13 promoted the phosphorylation of STAT3 and STAT6 on colonic epithelial cells with the secretion of TSLP and CCL26

Abstract

Food allergy prevalence is increasing worldwide. Eosinophilic inflammatory responses can be associated with food allergy and the underlying mechanisms in human colonic mucosa are poorly understood. We previously reported that allergic sensitized pediatric patients with juvenile polyps showed local IgE class-switch recombination with high levels of TSLP, IL-33 and CCL26 (main chemoattractant for eosinophils), that might be related with the hypereosinophilia. This study aimed to investigate the intestinal epithelial cells as a source for these soluble mediators under different inflammatory settings.Caco-2 cells were stimulated with IL-13 (10 ng/ml) or IFN-γ (10 ng/ml) and CCL26, TSLP and IL-33 were evaluated by ELISA in culture supernatants. Cell activation was analyzed with a tyrosine-kinase phosphorylation array and finally, kinase activation was confirmed by immunoblotting. Comparison between groups was made using Student´s t-test.We found that TSLP and CCL26 levels were significantly increased in Caco-2 cells in response to IL-13 (p<0.1 in 3 independent experiments), whereas it remained unchanged following the stimulation with IFN-γ. Cell activation was also demonstrated by analyzing the tyrosine-kinase activation, and we found that STAT-3, STAT-6, Lck, Akt, IGF-IR were higher phosphorylated upon IL-13 stimulus than cells exposed to IFN-γ or medium (p<0,1). No effect was observed on IL-33 secretion under the conditions studied.In conclusion, our findings show that colonic epithelial cells respond to a Th2 environment by secreting TSLP, which may promote mucosal type-2 inflammation through ILC2 activation, and CCL26, which is probably involved in the eosinophil chemoattraction. The IL-13-driven cell activation involves the STAT3, STAT6 pathways, and other kinases. These findings may pave the way to identify the mucosal epithelial cells as the triggers of inflammation and eosinophil-rich cell infiltration, and the tyrosine phosphorylation as a therapeutic target.