Evidence for the involvement of NOD2 in regulating colonic epithelial cell growth and survival.
OBJECTIVE
To investigate the function of NOD2 in colonic epithelial cells (CEC).


METHODS
A combination of in vivo and in vitro analyses of epithelial cell turnover in the presence and absence of a functional NOD2 protein and, in response to enteric Salmonella typhimurium infection, were used. shRNA interference was also used to investigate the consequences of knocking down NOD2 gene expression on the growth and survival of colorectal carcinoma cell lines.


RESULTS
In the colonic mucosa the highest levels of NOD2 expression were in proliferating crypt epithelial cells. Muramyl dipeptide (MDP), that is recognized by NOD2, promoted CEC growth in vitro. By contrast, the growth of NOD2-deficient CECs was impaired. In vivo CEC proliferation was also reduced and apoptosis increased in Nod2(-/-) mice, which were also evident following enteric Salmonella infection. Furthermore, neutralization of NOD2 mRNA expression in human colonic carcinoma cells by shRNA interference resulted in decreased survival due to increased levels of apoptosis.


CONCLUSIONS
These findings are consistent with the involvement of NOD2 protein in promoting CEC growth and survival. Defects in proliferation by CECs in cases of CD may contribute to the underlying pathology of disrupted intestinal homeostasis and excessive inflammation.
The Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, UK.
Sheena-M
SM
Cruickshank
Louise
L
Wakenshaw
John
J
Cardone
Peter-D
PD
Howdle
Peter-J
PJ
Murray
Simon-R
SR
Carding
D000119:Acetylmuramyl-Alanyl-Isoglutamine / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival; D003106:Colon / Q000187:drug effects / Q000378:metabolism* / Q000382:microbiology / Q000473:pathology; D004195:Disease Models, Animal; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism* / Q000382:microbiology / Q000473:pathology; D006801:Humans; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism* / Q000382:microbiology / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D053473:Nod2 Signaling Adaptor Protein / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D012480:Salmonella Infections / Q000378:metabolism* / Q000382:microbiology / Q000473:pathology; D012486:Salmonella typhimurium; D013997:Time Factors
C429018:NOD2 protein, human; D053473:Nod2 Signaling Adaptor Protein; C495945:Nod2 protein, mouse; D034741:RNA, Small Interfering; D000119:Acetylmuramyl-Alanyl-Isoglutamine