Alpha-defensins (α-Defs) in Crohn's disease: decrease of ileal α-Def 5 via permanent methylation and increase in plasma α-Def 1-3 concentrations offering biomarker utility

An impaired expression of alpha-defensins (alpha-Defs) in the ileal mucosa and, conversely, increased levels in plasma, have been reported in Crohn's disease (CD). However, the specificity and correlation of these findings with the degree of inflammation are unclear. We aimed to characterize the concentration and utility of ileal and plasma alpha-Defs in CD and to analyse a potential epigenetic mechanism of alpha-Def expression. Peripheral blood samples and ileal biopsies were obtained from patients at disease onset (aCD), from those who achieved remission (iCD) and from two control groups (healthy controls and non-CD-aetiology ileitis patients). Plasma alpha-Defs 1-3 and 4 were detected by enzyme-linked immunosorbent assay (ELISA); alpha-Def 5 by immunolocalization. Methylation analysis of the alpha-Def 5 gene was performed using the MassARRAY EpiTYPER system. Plasma alpha-Defs 1-3 concentrations were significantly higher in aCD with ileal involvement (L1, L3) versus iCD or the control groups. The alpha-Defs 1-3 concentrations were also similar to healthy controls in patients with non-CD ileitis. There was a significant positive correlation between plasma alpha-Defs 1-3 levels in aCD and the endoscopic index, as well as with C-reactive protein (CRP) levels. The immunopositivity scoring showed significantly reduced alpha-Def 5 expression in ileal inflamed (aCD) versus non-inflamed mucosa (iCD and healthy controls). The alpha-Def 5 gene showed a higher methylation status in CD patients than controls, regardless of the inflammation. Plasma alpha-Defs 1-3 concentrations correlate with the degree of inflammation and appear to be specific biomarkers of ileal-CD at diagnosis. Ileal alpha-Def 5 expression is down-regulated permanently by methylation.