Role of nitric oxide in the inhibition of BMP-2-mediated stimulation of proteoglycan synthesis in articular cartilage.
OBJECTIVE
Bone morphogenetic protein-2 (BMP-2)-mediated stimulation of articular cartilage proteoglycan (PG) synthesis is suppressed in arthritic murine knee joints and by interleukin-1 (IL-1). The goal of this study was to investigate whether the gaseous mediator nitric oxide (NO) plays a crucial role in the inhibition of BMP-2 effects by IL-1.


METHODS
Bone morphogenetic protein-2 alone or in combination with IL-1 was injected into the right knee joint of wild-type and NOS2 deficient C57BI/6x129/Sv mice. Proteoglycan synthesis was measured ex vivo by incorporation of 35S-sulfate on day 1, 2 and 3 after injection. To study the role of NO in the inhibition BMP-2-mediated stimulation of PG synthesis in arthritic joints, BMP-2 was injected intra-articularly in the joints of wild-type and NOS2 deficient mice with zymosan-induced arthritis. To check for NOS2 deficiency, NO production was measured in conditioned medium after challenge of patellae with surrounding tissue with IL-1.


RESULTS
BMP-2 potently stimulated proteoglycan synthesis in articular cartilage of normal knees (up to 4-fold) but not in arthritic knees. Co-injection of BMP-2 with tumor necrosis factor alpha had no effect on BMP-2-mediated stimulation of PG synthesis but co-injection with IL-1 alpha resulted in a nearly total inhibition of BMP-2-mediated stimulation. In contrast, in NOS2 deficient mice IL-1 had no effect on BMP-2-mediated stimulation of PG synthesis. However, injection of BMP-2 into arthritic knee joints of NOS2 knock out mice did not result in significant stimulation of PG synthesis.


CONCLUSIONS
In this study we show that NO plays a role in the inhibition of BMP-2-mediated stimulation of PG synthesis by IL-1. However, NO, or at least NOS2, plays no dominant role in the inhibition of BMP-2 effects in arthritic knee joints.
van der Kraan
P M
PM
Department of Rheumatology, University Hospital Nijmegen, The Netherlands. P.vanderkraan@reuma.azn.nl
Vitters
E L
EL
van Beuningen
H M
HM
van de Loo
F A
FA
van den Berg
W B
WB
D000818:Animals; D001169:Arthritis, Experimental / Q000378:metabolism*; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology*; D002358:Cartilage, Articular / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007270:Injections, Intra-Articular; D007375:Interleukin-1 / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000172:deficiency / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D011509:Proteoglycans / Q000096:biosynthesis*; D011994:Recombinant Proteins / Q000494:pharmacology; D013268:Stimulation, Chemical; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
C525718:BMP2 protein, human; C525719:Bmp2 protein, mouse; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D007375:Interleukin-1; D011509:Proteoglycans; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha; C499469:recombinant human bone morphogenetic protein-2; D009569:Nitric Oxide; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse