Reduced alpha-defensin expression is associated with inflammation and not NOD2 mutation status in ileal Crohn's disease.
OBJECTIVE
Reduced ileal Paneth cell alpha-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, alpha-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 alpha-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 alpha-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.
Simms
L A
LA
Inflammatory Bowel Disease Laboratory, Royal Brisbane and Women's Hospital Foundation, Brisbane, Australia. Lisa.Simms@qimr.edu.au
Doecke
J D
JD
Walsh
M D
MD
Huang
N
N
Fowler
E V
EV
Radford-Smith
G L
GL
D000328:Adult; D000368:Aged; D003424:Crohn Disease / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D005260:Female; D015870:Gene Expression; D005838:Genotype; D054501:Group II Phospholipases A2 / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007082:Ileum / Q000378:metabolism*; D007124:Immunoenzyme Techniques; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism; D016209:Interleukin-8 / Q000235:genetics / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009113:Muramidase / Q000235:genetics / Q000378:metabolism; D053473:Nod2 Signaling Adaptor Protein / Q000235:genetics* / Q000378:metabolism; D019879:Paneth Cells / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D023084:alpha-Defensins / Q000235:genetics / Q000378:metabolism*
D015850:Interleukin-6; D016209:Interleukin-8; C429018:NOD2 protein, human; D053473:Nod2 Signaling Adaptor Protein; D012333:RNA, Messenger; D023084:alpha-Defensins; D054501:Group II Phospholipases A2; C516287:PLA2G2A protein, human; D009113:Muramidase