NOD2 transgenic mice exhibit enhanced MDP-mediated down-regulation of TLR2 responses and resistance to colitis induction.
OBJECTIVE
Mutations in the CARD15 gene encoding NOD2 are susceptibility factors in Crohn's disease. We explored the mechanism of this susceptibility using mice that over express NOD2.


METHODS
Cellular and molecular responses of mice bearing an NOD2 transgene or administered plasmids that express wild-type and mutated NOD2 constructs were examined.


RESULTS
In initial studies, we showed that splenocytes from NOD2 transgenic mice as compared with littermate controls exhibit decreased interleukin (IL)-12p70 responses to peptidoglycan (PGN), a TLR2 ligand that contains muramyl dipeptide, but not other TLR ligands; in contrast, IL-12 responses to PAM(3)CSK(4), a TLR2 ligand that does not contain muramyl dipeptide, were normal. Similarly, transgenic mice as compared with controls exhibited greatly decreased IL-12p40 responses to intraperitoneal administration of PGN but not to lipopolysaccharide. In further studies, we showed using electrophoretic mobility shift assay that PGN-stimulated cells from transgenic mice exhibited decreased activation of nuclear factor kappaB. Finally, in a series of studies on the effect of the NOD2 on susceptibility to induced colitis, we found that (1) transgenic mice were highly resistant to induction of PGN colitis and partially resistant to induction of trinitrobenzene sulfonic acid (TNBS) colitis and (2) mice administered a plasmid expressing a wild-type NOD2 gene were completely resistant to TNBS colitis whereas mice administered a plasmid expressing an NOD2 gene with the Crohn's disease frameshift mutation were only slightly resistant to TNBS colitis.


CONCLUSIONS
These data offer new evidence that NOD2 mutations contribute to inflammatory bowel disease by causing excessive TLR2 cytokine responses.
Yang
Zhiqiong
Z
Mucosal Immunity Section, Laboratory of Host Defenses, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland, USA.
Fuss
Ivan J
IJ
Watanabe
Tomohiro
T
Asano
Naoki
N
Davey
Michael P
MP
Rosenbaum
James T
JT
Strober
Warren
W
Kitani
Atsushi
A
D000119:Acetylmuramyl-Alanyl-Isoglutamine / Q000494:pharmacology*; D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D000818:Animals; D002478:Cells, Cultured; D003092:Colitis / Q000139:chemically induced / Q000235:genetics* / Q000276:immunology; D015536:Down-Regulation / Q000187:drug effects*; D016368:Frameshift Mutation / Q000235:genetics; D007113:Immunity, Innate / Q000187:drug effects; D018664:Interleukin-12 / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009000:Monocytes / Q000166:cytology / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D053473:Nod2 Signaling Adaptor Protein / Q000235:genetics* / Q000502:physiology*; D010457:Peptidoglycan; D010957:Plasmids / Q000235:genetics; D013154:Spleen / Q000166:cytology / Q000378:metabolism; D051195:Toll-Like Receptor 2 / Q000235:genetics* / Q000378:metabolism; D014302:Trinitrobenzenesulfonic Acid
D000276:Adjuvants, Immunologic; D016328:NF-kappa B; D053473:Nod2 Signaling Adaptor Protein; C495945:Nod2 protein, mouse; D010457:Peptidoglycan; C493486:Tlr2 protein, mouse; D051195:Toll-Like Receptor 2; D018664:Interleukin-12; D000119:Acetylmuramyl-Alanyl-Isoglutamine; D014302:Trinitrobenzenesulfonic Acid