Immunoregulatory Defects In Inflammatory Bowel Disease

本研究探讨了在抗原呈递细胞中表达NOD2转基因的小鼠，通过MDP刺激NOD2调控TLR2反应的可能性。在最初的研究中，我们发现，与对照组相比，刺激nod2转基因小鼠的脾细胞，IL-12p70对肽聚糖（PGN）的反应大大降低，PGN是一种含有MDP的TLR2配体，但不含其他TLR配体；相比之下，IL-12对不含MDP的TLR2配体PAM 3CSK4的反应正常。同样，与对照组相比，转基因小鼠对IP给药PGN的IL-12p40反应显著降低，而对LPS则没有。在进一步的研究中，我们使用EMSA发现，来自NOD2-Tg小鼠的pgni刺激细胞显示出p65和c-Rel超移位大大减少，表明这些成分向细胞核的易位减少。然后，在一系列体内研究中，我们确定了NOD2过表达对诱导结肠炎易感性的影响。在最初的研究中，我们发现携带NOD2基因的转基因小鼠对诱导pgnn -结肠炎具有高度抗性，对诱导tnbs -结肠炎具有部分抗性。然后，在补充研究中，我们发现给予表达野生型NOD2基因的质粒的小鼠对tnbs -结肠炎完全耐药，而给予表达带有克罗恩病框架移位突变的NOD2基因的质粒的小鼠对tnbs -结肠炎只有轻微耐药。

The present study explores the possibility that muramyl dipeptide (MDP) stimulation of NOD2 regulates TLR2 responses using mice expressing a NOD2 transgene in antigen-presenting cells. In initial studies we showed that stimulation of splenocytes from NOD2-transgenic mice as compared to littermate-controls (controls) exhibited greatly decreased IL-12p70 responses to peptidoglycan (PGN) a TLR2 ligand that contains MDP, but not other TLR ligands; in contrast, IL-12 responses to PAM 3CSK4, a TLR2 ligand that does not contain MDP, were normal. Similarly, transgenic mice as compared to controls exhibited greatly decreased IL-12p40 responses to IP administration of PGN but not to LPS. In further studies we showed using EMSA that PGNstimulated cells from NOD2-Tg mice exhibited greatly decreased p65 and c-Rel super-shifts, indicating decreased translocation of these components to the nucleus. Then, in a series of in vivo studies we determined the effect of NOD2 over-expression on susceptibility to induced colitis. In initial studies we found that transgenic mice bearing the NOD2 transgene were highly resistant to induction of PGN-colitis and partially resistant to induction of TNBS-colitis. Then, in complementary studies we showed that mice administered a plasmid expressing a wild-type NOD2 gene was completely resistant to TNBS-colitis whereas mice administered a plasmid expressing a NOD2 gene with the Crohns disease frame-shift mutation was only slightly resistant to TNBS-colitis. These data buttress previous evidence that wild-type NOD2 functions as an inhibitor of TLR2-induced IL-12 production whereas NOD2 resulting from a mutated NOD2 gene is a poor inhibitor of such production. As such, they provide support for the thesis that NOD2 mutations contribute to IBD by leading to excessive TLR2 cytokine responses.