Nitric oxide downregulates interleukin 1beta (IL-1beta) stimulated IL-6, IL-8, and prostaglandin E2 production by human chondrocytes.
OBJECTIVE
To investigate the effects of endogenously produced nitric oxide (NO) on interleukin 6 (IL-6), IL-8, prostaglandin E2 (PGE2), and proteoglycan production by human chondrocytes.


METHODS
Human articular chondrocytes were isolated from their extracellular matrix by triple successive enzymatic digestion of the cartilage and cultured 48 h in a well defined culture medium. IL-6 and IL-8 were directly assayed into culture media by specific enzyme amplified sensitivity immunoassays. Proteoglycans and PGE2 were quantified by specific radioimmunoassays. Cell culture media were assayed for NO2 using a spectrophotometric assay based upon the Griess reaction.


RESULTS
Unstimulated chondrocytes produced low levels of NO, IL-6, IL-8, and PGE2. Production was significantly stimulated by IL-1beta and lipopolysaccharide (LPS). As well, proteoglycan synthesis was profoundly inhibited by IL-1beta and LPS. Inhibition of NO synthesis with the competitive inhibitor NG-monomethyl-L-arginine (L-NMMA) led to enhancement of IL-6, IL-8, and PGE2 production stimulated by either IL-1beta alone or in combination with LPS, whereas the inhibition of proteoglycan production by IL-1beta was not modified by L-NMMA.


CONCLUSIONS
LPS and IL-1beta stimulated IL-6, IL-8, and PGE2 production are downregulated by endogenously produced NO, which could limit the inflammatory reaction occurring in arthritis.
Bone and Cartilage Metabolism Research Unit, Institute of Pathology, University of Liège, Belgium.
Y E
YE
Henrotin
S X
SX
Zheng
G P
GP
Deby
A H
AH
Labasse
J M
JM
Crielaard
J Y
JY
Reginster
D000328:Adult; D000368:Aged; D002478:Cells, Cultured; D019902:Chondrocytes / Q000187:drug effects* / Q000378:metabolism; D015232:Dinoprostone / Q000096:biosynthesis*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007375:Interleukin-1 / Q000378:metabolism / Q000494:pharmacology*; D015850:Interleukin-6 / Q000096:biosynthesis*; D016209:Interleukin-8 / Q000096:biosynthesis*; D008875:Middle Aged; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors
D004791:Enzyme Inhibitors; D007375:Interleukin-1; D015850:Interleukin-6; D016209:Interleukin-8; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D015232:Dinoprostone; D019331:NG-Nitroarginine Methyl Ester