Lipid signature associated with chronic colon inflammation reveals a dysregulation in colonocyte differentiation process

Abstract

Inflammatory Bowel Disease (IBD) comprises a heterogeneous group of chronic inflammatory conditions of the gastrointestinal tract that include ulcerative colitis (UC) and Crohn's disease. Although the etiology is not well understood, IBD is characterized by a loss of the normal epithelium homeostasis that disrupts the intestinal barrier of these patients. Previous work by our group demonstrated that epithelial homeostasis along the colonic crypts involves a tight regulation of lipid profiles. To evaluate whether lipidomic profiles conveyed the functional alterations observed in the colonic epithelium of IBD, we performed matrix-assisted laser desorption ionization-mass spectrometry imaging (MALDI-MSI) analyses of endoscopic biopsies from inflamed and non-inflamed segments obtained from UC patients. Our results indicated that lipid profiling of epithelial cells discriminated between healthy and UC patients. We also demonstrated that epithelial cells of the inflamed mucosa were characterized by a decrease in mono- and di-unsaturated fatty acid-containing phospholipids and higher levels of arachidonic acid-containing species, suggesting an alteration of the lipid gradients occurring concomitantly to the epithelial differentiation. This result was reinforced by the immunofluorescence analysis of EPHB2 and HPGD, markers of epithelial cell differentiation, sustaining that altered lipid profiles were at least partially due to a faulty differentiation process. Overall, our results showed that lipid profiling by MALDI-MSI faithfully conveys molecular and functional alterations associated with the inflamed epithelium, providing the foundation for a novel molecular characterization of UC patients.

Keywords: Inflammatory bowel diseases; Mass spectrometry imaging; Ulcerative colitis, lipid profile.