Mechanism of inhibition of endothelin-1-stimulated proteoglycan and collagen synthesis in rat articular chondrocytes.
The aim of this study was to determine the effects of endothelin-1 (ET-1) on proteoglycan (PG) and collagen synthesis by rat articular chondrocytes (RAC). PG and collagen synthesis was measured by [(35)S]-sulphate and [(3)H]-glycine incorporation, respectively into monolayers of confluent RAC exposed to ET-1 (10(-11) M-10(-7) M). ET-1 stimulated PG and collagen synthesis in these cells in a concentration-dependent manner during the first 24 h of incubation. Prolonged contact of the cells with ET-1 resulted in a gradual decrease, and finally, inhibition of ET-1 effects. This inhibition is mediated by nitric oxide (NO) released in response to ET-1 since: (1) nitric oxide synthase inhibitor, nitro-L-arginine-methyl ester (L-NAME), enhanced both basal and ET-1-induced [(35)S]-sulphate and [(3)H]-glycine incorporations; (2) sodium nitroprusside (SNP), which spontaneously releases NO, inhibited both basal and ET-1-induced incorporations, and was also able to suppress the effects of L-NAME; (3) NO levels in the culture media were also correlated with the inhibition of [(35)S]-sulphate and [(3)H]-glycine incorporation; and (4) SNP also inhibited aggrecan and collagen II transcriptions, probably via cGMP. This effect was mimicked with 8-bromo-cGMP. Interestingly, the LY83583, which blocks the NO-dependent production and release of cGMP, inhibited PG-collagen synthesis but had no effect on their mRNA expressions. Thus, normal levels of cGMP appeared to be necessary for PG-collagen synthesis, whereas decreased levels are detrimental. In conclusion, NO, produced by rat AC in response to ET-1, counteracts the stimulation and finally induces inhibition of PG-collagen synthesis by ET-1 in these cells but NO-induced cGMP is only partially responsible for this inhibition.
Khatib
A-M
AM
INSERM-Unit 349, Lariboisière Hospital, 75475 Paris, CEDEX 10, France.
Siegfried
G
G
Messai
H
H
Moldovan
F
F
Mitrovic
D R
DR
D000634:Aminoquinolines / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D019902:Chondrocytes / Q000378:metabolism*; D003094:Collagen / Q000096:biosynthesis* / Q000378:metabolism; D024043:Collagen Type II / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000378:metabolism*; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D009599:Nitroprusside / Q000494:pharmacology; D011453:Prostaglandins / Q000378:metabolism; D011509:Proteoglycans / Q000037:antagonists & inhibitors*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors
D000634:Aminoquinolines; D024043:Collagen Type II; D019332:Endothelin-1; D009573:Nitrites; D011453:Prostaglandins; D011509:Proteoglycans; D012333:RNA, Messenger; D009599:Nitroprusside; D009569:Nitric Oxide; D003094:Collagen; D004247:DNA; C041715:6-anilino-5,8-quinolinedione; D019331:NG-Nitroarginine Methyl Ester