Paper
Abstract Background Recently, we have identified a dysregulated protein signature in the esophageal epithelium of eosinophilic esophagitis (EoE) patients including proteins associated with inflammation and epithelial barrier function; however, the effect of proton pump inhibitor (PPI) treatment on this signature is unknown. Herein, we used a proteomic approach to investigate: (1) whether PPI treatment alters the esophageal epithelium protein profile observed in EoE patients and (2) whether the protein signature at baseline predicts PPI response. Methods We evaluated the protein signature of esophageal biopsies using a cohort of adult EoE ( n = 25) patients and healthy controls (C) ( n = 10). In EoE patients, esophageal biopsies were taken before (pre) and after (post) an 8‐week PPI treatment, determining the histologic response. Eosinophil count PostPPI was used to classify the patients: ≥15 eosinophils/hpf as non‐responders (non‐responder) and < 15 eosinophils/hpf as responders (R). Protein signature was determined and differentially accumulated proteins were characterized to identify altered biological processes and signaling pathways. Results Comparative analysis of differentially accumulated proteins between groups revealed common signatures between three groups of patients with inflammation (responder‐PrePPI, non‐responder‐PrePPI, and non‐responder‐PostPPI) and without inflammation (controls and responder‐PostPPI). PPI therapy almost reversed the EoE specific esophageal protein signature, which is enriched in pathways associated with inflammation and epithelial barrier function, in responder‐PostPPI. Furthermore, we identified a set of candidate proteins to differentiate responder‐PrePPI and non‐responder‐PrePPI EoE patients before treatment. Conclusion These findings provide evidence that PPI therapy reverses the alterations in esophageal inflammatory and epithelial proteins characterizing EoE, thereby providing new insights into the mechanism of PPI clinical response. Interestingly, our results also suggest that PPI response could be predicted at baseline in EoE.