Analyse der NOD2-abhängigen Transkriptomregulation und Hemmung der NOD2-Aktivität durch A20

NOD2 is an intracellular receptor for the bacterial cell wall component, muramyl dipeptide. Activation of NOD2 induces a complex inflammatory and antibacterial cellular program. Mutations in the leucine-rich repeat region of NOD2, which lead to an impaired recognition of muramyl-dipeptide (MDP), have been genetically associated with chronic inflammatory diseases of barrier organs such as Crohn disease, asthma and atopic eczema. The transcriptomal signature that defines the physiological innate immune responses downstream of NOD2 activation still remains unclear . Adressing this problem, we tested NOD2 and its Crohn´s disease associated mutant NOD2L1007fsinsC expressing cells for transcriptional activation following to stimulation with MDP. Affimetrix HG-U133 plus 2.0 chips have been charged for genomewide mRNA analysis. Significant effects of the NOD2-genotype could be observed on expression of 3378 genes, and expression of 294 genes was MDP responsive. The mutated NOD2 variant showed lower basal activation and was not responsive to MDP. Within the MDP-dependent genes in the NOD2wt cells was a group of inflammation mediating chemokines (CXCL8, CXCL2, CXCL3, CXCL6). A second noticeable group were genes involved in negativ regulation of NF-kB response (NFKBIA, IER3, TNFAIP3). For selected genes, these results were verified by using PBMCs of an L1007fsinsC homozygote patient and an wild-type control. Overexpressed TNFAIP3 (A20) showed a dose dependent negative regulatory effect on MDP elicited NF-kB activation. This is a evidence for the relevance of A20 regulatory effects in NOD2 signalling. As Morbus Crohn is characterised by elevated NF-kB activation, the detailed clarification of NF-kB regulation might contribute to the understanding of etiopathogenesis of Crohn´s disease.