Reduced  -defensin expression is associated with inflammation and not NOD2 mutation status in ileal Crohn's disease

Abstract

Background and aims: Reduced ileal Paneth cell adefensin 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, a-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 adefensin 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 a-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.Crohn's disease is one of two major forms of inflammatory bowel disease (IBD), and is a chronic, debilitating disorder with increasing incidence and prevalence globally.

Characteristic changes in microbial community composition and expression of innate immune genes in acute appendicitis

“…For the regulation of hBD-2 a role of NOD2 has been reported, 47 but for other AMPs only few data exist. 48 The observed regulation of the mRNA of AMPs, cytokines and PRR suggested the involvement of bacteria in the pathogenesis of appendicitis. To assess these microbial communities associated with appendicitis we applied phylogenetic taxonomy based on 16S rDNA sequencing and observed an overall decrease in richness and diversity of the microbial flora in the inflamed appendices that was especially visible in low abundance bacterial taxa.…”

Actin reorganization as the molecular basis for the regulation of apoptosis in gastrointestinal epithelial cells

“…Indeed, changes in villin expression are linked with several GI disorders associated with abnormal apoptosis. 30 Gelsolin levels are elevated in many senescent tissues where increased gelsolin expression is believed to be responsible for the resistance to apoptosis and to the increased susceptibility of these tissue to cancer. 31 Studies done in yeast have shown that actin functions as a sensor that links changes in the nutritional status with mitochondrial-dependent commitment to cell death.…”

Nod2 is required for the regulation of commensal microbiota in the intestine

“…Nod2 mutations associated with Crohn's disease primarily predispose the development of ileal lesions (18) corresponding to the location of Paneth cells. Ileal Crohn's disease is characterized by a decrease in antimicrobial ␣-defensins produced by Paneth cells (19,20). Studies comparing ␣-defensin levels in ileal Crohn's patients who did not have Nod2 mutation and in those who had any of the 3 major mutations (R702W, G908R, and 1007fs) associated with Crohn's disease showed no significant difference in ␣-defensin levels between the 2 groups (20).…”

“…Ileal Crohn's disease is characterized by a decrease in antimicrobial ␣-defensins produced by Paneth cells (19,20). Studies comparing ␣-defensin levels in ileal Crohn's patients who did not have Nod2 mutation and in those who had any of the 3 major mutations (R702W, G908R, and 1007fs) associated with Crohn's disease showed no significant difference in ␣-defensin levels between the 2 groups (20). However, studies of individual mutations in Nod2 showed that the 1007fs mutation in Nod2 causes a decrease in the expression of ␣-defensin (19,21).…”