Nucleotide-binding oligomerization domain 2 and Toll-like receptor 2 function independently in a murine model of arthritis triggered by intraarticular peptidoglycan.
OBJECTIVE
Blau syndrome is an autoinflammatory disease resulting from mutations in the NOD2 gene, wherein granulomatous arthritis, uveitis, and dermatitis develop. The mechanisms by which aberrant NOD2 causes joint inflammation are poorly understood. Indeed, very few studies have addressed the function of nucleotide-binding oligomerization domain 2 (NOD-2) in the joint. This study was undertaken to investigate NOD-2 function in an experimental model of arthritis and to explore the potential interplay between Toll-like receptor 2 (TLR-2) and NOD-2 in joint inflammation.


METHODS
Mice deficient in TLR-2, myeloid differentiation factor 88 (MyD88), or NOD-2 and their wild-type controls were given an intraarticular injection of muramyl dipeptide (MDP), peptidoglycan (PG; a metabolite of which is MDP), or palmitoyl-3-cysteine-serine-lysine-4 (Pam(3)CSK(4)), a synthetic TLR-2 agonist. Joint inflammation was assessed by near-infrared fluorescence imaging and histologic analysis.


RESULTS
Locally administered PG resulted in joint inflammation, which was markedly reduced in mice deficient in either TLR-2 or the TLR signaling mediator MyD88. In addition to TLR-2 signaling events, NOD-2 mediated joint inflammation, as evidenced by the fact that mice deficient in NOD-2 showed significantly reduced PG-induced arthritis. TLR-2 or MyD88 deficiency did not influence arthritis induced by the specific NOD-2 agonist MDP. In addition, NOD-2 deficiency did not alter the TLR-2-dependent joint inflammation elicited by the synthetic TLR-2 agonist Pam(3)CSK(4).


CONCLUSIONS
Whereas NOD-2 and TLR-2 are both critical for the development of PG-induced arthritis, they appear to elicit inflammation independently of each other. Our findings indicate that NOD-2 plays an inflammatory role in arthritis.
Rosenzweig
Holly L
HL
Oregon Health & Science University, Portland, OR 97239, USA. rosenzwh@ohsu.edu
Jann
Monica J
MJ
Vance
Emily E
EE
Planck
Stephen R
SR
Rosenbaum
James T
JT
Davey
Michael P
MP
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001169:Arthritis, Experimental / Q000139:chemically induced / Q000235:genetics / Q000473:pathology*; D005838:Genotype; D007596:Joints / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D053473:Nod2 Signaling Adaptor Protein / Q000172:deficiency* / Q000235:genetics; D010457:Peptidoglycan / Q000494:pharmacology*; D051381:Rats; D015398:Signal Transduction; D051195:Toll-Like Receptor 2 / Q000172:deficiency* / Q000235:genetics / Q000502:physiology
D000911:Antibodies, Monoclonal; D053473:Nod2 Signaling Adaptor Protein; C495945:Nod2 protein, mouse; D010457:Peptidoglycan; C493486:Tlr2 protein, mouse; D051195:Toll-Like Receptor 2