A serine proteinase inactivator inhibits chondrocyte-mediated cartilage proteoglycan breakdown occurring in response to proinflammatory cytokines.
The role played by serine proteinases with trypsin-like specificity in chondrocyte-mediated cartilage proteoglycan breakdown was investigated by use of a selective proteinase inactivator, 7-amino-4-chloro-3-(-3-isothiureidopropoxy)isocoumarin, in explant culture systems. This compound was a rapid inactivator of urokinase-type plasminogen activator. It potently inhibited interleukin 1- and tumor necrosis factor-stimulated proteoglycan release from both nasal and articular cartilage. Its less potent inhibition of basal and retinoic acid-stimulated release appeared to be due to cytotoxic effects. The functional half-life of the inactivator in culture medium was 95 min, and its concentration in cartilage was 2.5-fold higher than in the surrounding medium. Following spontaneous hydrolysis the breakdown products of the inactivator were unable to inhibit proteoglycan release. Trypsin-like activity was demonstrated by enzyme histochemistry to be chondrocyte-associated and inhibited by the serine proteinase inactivator. Cell-associated and secreted plasminogen activator activity was detected by zymography. These results suggest the involvement of a serine proteinase(s) with trypsin-like specificity, possibly urokinase-type plasminogen activator, in chondrocyte-mediated cartilage proteoglycan breakdown occurring as a result of stimulation with proinflammatory cytokines. Basal proteoglycan breakdown may occur via a different pathway. Our findings point to a pathological role for serine proteinase(s) in the development of cartilage diseases such as arthritis, possibly in a cascade which results in the activation of the enzyme(s) directly responsible for proteoglycan breakdown. It remains to be shown whether the target serine proteinase is urokinase-type plasminogen activator.
Bryson
H
H
Division of Biochemical & Musculoskeletal Medicine, Section of Human Metabolism & Clinical Biochemistry, University of Sheffield Medical School, Beech Hill Road, Sheffield, S10 2RX, United Kingdom.
Bunning
R A
RA
Feltell
R
R
Kam
C M
CM
Kerrigan
J
J
Powers
J C
JC
Buttle
D J
DJ
D000818:Animals; D002356:Cartilage / Q000187:drug effects* / Q000378:metabolism*; D002417:Cattle; D019902:Chondrocytes / Q000187:drug effects* / Q000378:metabolism*; D003374:Coumarins / Q000494:pharmacology; D003470:Culture Media; D046508:Culture Techniques; D016207:Cytokines / Q000494:pharmacology; D006801:Humans; D018836:Inflammation Mediators / Q000494:pharmacology; D049934:Isocoumarins; D007700:Kinetics; D011509:Proteoglycans / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000378:metabolism; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology*; D014568:Urokinase-Type Plasminogen Activator / Q000037:antagonists & inhibitors
D003374:Coumarins; D003470:Culture Media; D016207:Cytokines; D018836:Inflammation Mediators; D049934:Isocoumarins; D011509:Proteoglycans; D015842:Serine Proteinase Inhibitors; C064440:7-amino-4-chloro-3-(3-isothiureidopropoxy)isocoumarin; D012697:Serine Endopeptidases; D014568:Urokinase-Type Plasminogen Activator