Staphylococcus aureus stimulates inducible nitric oxide synthase in articular cartilage.
OBJECTIVE
To determine if Staphylococcus aureus stimulates the L-arginine-nitric oxide (NO) synthase pathway in articular cartilage.


METHODS
A heat-killed and sonicated (denatured) S. aureus preparation was added to cultures of bovine articular cartilage. NO production was measured as accumulated nitrite in the culture medium and by the NO synthase-dependent conversion of 3H-L-arginine to 3H-L-citrulline in cartilage homogenates. Inducible NO synthase (iNOS) messenger RNA (mRNA) expression was analyzed by Northern blot. Proteoglycan synthesis was measured by 35SO4 incorporation into glycosaminoglycan.


RESULTS
Nitrite accumulation and 3H-L-citrulline formation in cartilage were elevated by denatured S. aureus (compared with unstimulated control cartilage) and inhibited by the NO synthase inhibitor N(G)-monomethyl-L-arginine. Northern blot analysis revealed increased iNOS mRNA expression in bovine chondrocytes in response to denatured S. aureus stimulation. Denatured S. aureus suppressed the accumulation of 35SO4-labeled macromolecules representing newly synthesized proteoglycans in bovine articular cartilage. The suppressed proteoglycan synthesis was due to the presence of NO.


CONCLUSIONS
These findings support the hypothesis that a component of S. aureus can stimulate iNOS in articular cartilage, and that NO generated from this enzyme down-regulates cartilage matrix proteoglycan synthesis.
Jang
D
D
University of New South Wales, St. George Hospital, Sydney, Australia.
Williams
R J
RJ
Wang
M X
MX
Wei
A Q
AQ
Murrell
G A
GA
D000818:Animals; D002358:Cartilage, Articular / Q000187:drug effects* / Q000201:enzymology; D002417:Cattle; D002457:Cell Extracts / Q000494:pharmacology; D002478:Cells, Cultured; D004789:Enzyme Activation; D066298:In Vitro Techniques; D008070:Lipopolysaccharides / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000187:drug effects / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D011509:Proteoglycans / Q000378:metabolism; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D013211:Staphylococcus aureus / Q000502:physiology*; D013431:Sulfates / Q000378:metabolism; D013462:Sulfur Radioisotopes; D013682:Teichoic Acids / Q000494:pharmacology
D002457:Cell Extracts; D008070:Lipopolysaccharides; D011509:Proteoglycans; D012333:RNA, Messenger; D013431:Sulfates; D013462:Sulfur Radioisotopes; D013682:Teichoic Acids; C009900:lipoteichoic acid; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II