Lipidomic Analysis of Esophageal Epithelia Reveals a Distinctive Sphingolipid Profile in Eosinophilic Esophagitis.

Abstract

Lipids play an essential role in epithelial barrier integrity. Despite increasing evidence of epithelial barrier dysfunction in eosinophilic esophagitis (EoE), the lipid composition of the esophageal epithelium is not characterized and any disruptions in EoE are unknown. Esophageal brushings and biopsies were collected from patients (ages 1-19 years) who underwent clinically indicated esophagogastroduodenoscopy. Participants were classified based on the number of eosinophils per high-power field (eos/HPF) in esophageal biopsies into: an EoE group (> 15 eos/HPF) and a control group (0-1 eos/HPF). Brushing samples were analyzed by targeted lipidomics using liquid chromatography tandem-mass spectrometry. The expression of inflammatory mediators and lipid biosynthesis enzymes was quantified by RT-PCR in esophageal biopsies and in a primary human esophageal epithelial cell line treated with IL-4/IL-13. EoE group had a significant increase in non-hydroxy fatty acid sphingosine ceramides (NS-CER) (p < 0.01), and a decrease in non-hydroxy fatty acid phytoceramides (NP-CER) with 18-carbon sphingoid bases, resulting in selectively increased NS-CER/NP-CER ratios as compared to controls in esophageal brushes (Mean ± SD: 5.0 ± 1.9 vs. 1.6 ± 1.2 p < 0.01). EoE biopsies had significantly decreased expression of DEGS1 (p < 0.01) and DEGS2 (p < 0.05) mRNA, enzymes responsible for the biosynthesis of NS-CER and NP-CER. A significant inverse correlation between NS-CER/NP-CER and DEGS2/DEGS1 mRNA ratios (p < 0.01) was observed. Conversely, a positive correlation between the NS-CER/NP-CER ratio and CCL26, IL-5, and IL-13 mRNA expression (p < 0.05) was noted. IL-4/IL-13 significantly dysregulated the expression of DEGS1 and DEGS2 mRNA in a primary esophageal epithelial cell line. Distinctive abnormalities in esophageal epithelium sphingolipid composition and production were revealed in EoE. Mechanistic ex vivo data demonstrate dysregulation of lipid biosynthesis enzymes by IL-4/IL-13. The characteristic lipid profile in EoE has significant implications for epithelial barrier dysfunction and may serve as a biomarker of disease activity.