Reduced α-defensin expression is associated with inflammation and not NOD2 mutation status in ileal Crohn's disease. Issue 7 (27th February 2008)

• Record Type: Journal Article
• Authors: Simms, L A; Doecke, J D; Walsh, M D; Huang, N; Fowler, E V; Radford-Smith, G L
• Is Part Of: Gut. Volume 57:Issue 7(2008)
• Page Start: 903
• Page End: 910
• Publication Date: 2008-02-27
• Subjects: Gastroenterology -- Periodicals; 616.33
• DOI: 10.1136/gut.2007.142588
• Languages: English
• ISSNs: 0017-5749

Abstract

Abstract : Background and aims: Reduced ileal Paneth cell α-defensin expression has been reported to be associated with Crohn's disease, especially in patients carrying NOD2 mutations. The aim of this study was to independently assess whether NOD2, α-defensins and Crohn's disease are linked. Methods: Using quantitative real-time polymerase chain reaction (RT-PCR), we measured the mRNA expression levels of key Paneth cell antimicrobial peptides (DEFA5, DEFA6, LYZ, PLA2G2A), inflammatory cytokines [interkelukin 6 (IL6) and IL8], and a marker of epithelial cell content, villin (VIL1) in 106 samples from both affected ileum (inflamed Crohn's disease cases, n = 44) and unaffected ileum (non-inflamed; Crohn's disease cases, n = 51 and controls, n = 11). Anti-human defensin 5 (HD-5) and haematoxylin/eosin immunohistochemical staining was performed on parallel sections from NOD2 wild-type and NOD2 mutant ileal Crohn's disease tissue. Results: In Crohn's disease patients, DEFA5 and DEFA6 mRNA expression levels were 1.9- and 2.2-fold lower, respectively, in histologically confirmed inflamed ileal mucosa after adjustment for confounders (DEFA5, p<0.001; DEFA6, p = 0.001). In contrast to previous studies, we found no significant association between α-defensin expression and NOD2 genotype. HD-5 protein data supports these RNA findings. The reduction in HD-5 protein expression appears due to surface epithelial cell loss and reduced Paneth cell numbers as a consequence of tissue damage. Conclusions: Reduction in α-defensin expression is independent of NOD2 status and is due to loss of surface epithelium as a consequence of inflammatory changes rather than being the inciting event prior to inflammation in ileal Crohn's disease.