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.
Henrotin
Y E
YE
Bone and Cartilage Metabolism Research Unit, Institute of Pathology, University of Liège, Belgium.
Zheng
S X
SX
Deby
G P
GP
Labasse
A H
AH
Crielaard
J M
JM
Reginster
J Y
JY
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