Concurrent generation of nitric oxide and superoxide inhibits proteoglycan synthesis in bovine articular chondrocytes: involvement of peroxynitrite.
OBJECTIVE
Nitric oxide (NO), widely assumed to be a mediator of interleukin 1 (IL-1), inhibits proteoglycan synthesis in articular chondrocytes. IL-1 also produces superoxide anion. We hypothesized that the IL-1 inhibited proteoglycan synthesis is the result of peroxynitrite formed by the reaction of NO with superoxide.


METHODS
Bovine articular chondrocytes were cultured in the presence of SIN-1, which leads to simultaneous generation of both NO and superoxide. Proteoglycan synthesis was measured based on the incorporation of [35S] sulfate, and the presence of peroxynitrite was confirmed using immunohistochemistry.


RESULTS
SIN-1 inhibited proteoglycan synthesis and superoxide dismutase reversed SIN-1 inhibited proteoglycan synthesis, indicating the simultaneous generation of superoxide is essential to inhibit proteoglycan synthesis. IL-1 induced peroxynitrite in articular chondrocytes and addition of peroxynitrite inhibited proteoglycan synthesis.


CONCLUSIONS
The concurrent generation of superoxide anion and NO is required for the action of IL-1 to inhibit proteoglycan synthesis. Peroxynitrite is a candidate for this underlying mechanism.
Oh
M
M
Department of Orthopedic Surgery, Kinki University School of Medicine, Osaka, Japan.
Fukuda
K
K
Asada
S
S
Yasuda
Y
Y
Tanaka
S
S
D000818:Animals; D002358:Cartilage, Articular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D002417:Cattle; D019902:Chondrocytes / Q000187:drug effects / Q000378:metabolism*; D007150:Immunohistochemistry; D007375:Interleukin-1 / Q000494:pharmacology; D008981:Molsidomine / Q000031:analogs & derivatives / Q000494:pharmacology; D009566:Nitrates / Q000502:physiology*; D009569:Nitric Oxide / Q000096:biosynthesis* / Q000502:physiology; D011509:Proteoglycans / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D013481:Superoxides / Q000378:metabolism*
D007375:Interleukin-1; D009566:Nitrates; D011509:Proteoglycans; D013481:Superoxides; C039642:peroxynitric acid; D009569:Nitric Oxide; C002385:linsidomine; D008981:Molsidomine