Cruickshank Sheena-M, Wakenshaw Louise, Cardone John, Howdle Peter-D, Murray Peter-J, Carding Simon-R
The Institute of Food Research, Norwich Research Park, Norwich NR4 7UA, UK.
World J Gastroenterol. 2008 Oct 14;14(38):5834-41. doi: 10.3748/wjg.14.5834.
To investigate the function of NOD2 in colonic epithelial cells (CEC).
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.
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.
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.
研究NOD2在结肠上皮细胞（CEC）中的功能。
采用体内和体外相结合的分析方法，研究在有或没有功能性NOD2蛋白存在的情况下上皮细胞更新情况，以及对肠道鼠伤寒沙门氏菌感染的反应。还使用了短发夹RNA（shRNA）干扰来研究敲低NOD2基因表达对结肠癌细胞系生长和存活的影响。
在结肠黏膜中，NOD2表达水平最高的是增殖的隐窝上皮细胞。NOD2识别的胞壁酰二肽（MDP）在体外促进CEC生长。相比之下，缺乏NOD2的CEC生长受损。在体内，Nod2(-/-)小鼠的CEC增殖也减少，凋亡增加，这在肠道沙门氏菌感染后也很明显。此外，通过shRNA干扰中和人结肠癌细胞中的NOD2 mRNA表达，由于凋亡水平增加导致存活率降低。
这些发现与NOD2蛋白参与促进CEC生长和存活一致。克罗恩病（CD）患者中CEC增殖缺陷可能导致肠道稳态破坏和过度炎症的潜在病理变化。
