Modulation of the catabolic effects of interleukin-1 beta on human articular chondrocytes by transforming growth factor-beta.
The effects of IL-1 beta and TGF-beta on the biosynthesis of extracellular matrix structural components relative to the metalloproteinases and their inhibitor TIMP1 in human articular chondrocytes were investigated. It has been proposed that TGF-beta, acting as a positive regulator of matrix accretion, can counteract the increased loss of cartilage matrix induced by IL-1 beta. To allow a comparison of their effects on mRNA levels for these different components, quantitation by competitive RT/PCR was employed. This method was found to give reproducible estimates of mRNA levels and the observed effects of IL-1 beta and TGF-beta on individual components of this system agree with qualitative data obtained by northern blotting. IL-1 beta had a more pronounced effect on aggrecan mRNA levels than on those for type II collagen. Similar quantitative differences were observed between collagenase and stromelysin mRNA levels. TGF-beta generally counteracted the effects of IL-1 beta, and new steady state levels were attained within 24 h. However, the reversal of IL-1 beta induced suppression of matrix protein mRNA levels appeared more effective than its suppression of the increase in stromelysin and collagenase mRNA levels. Similarly TGF-beta did not reduce the extent of IL-1 beta induced secretion of stromelysin at the protein level. TIMP1 mRNA levels were only slightly reduced by IL-1 beta; however this cytokine effectively suppressed its induction by TGF-beta. The higher concentrations of TGF-beta and longer exposure times required to overcome the suppressive effects of IL-1 beta suggest that the interaction between IL-1 beta and TGF-beta in the regulation of TIMP1 expression follows a different mechanism to that operating for the metalloproteinases and matrix proteins. Thus the overall potential of TGF-beta to inhibit proteolysis is attenuated by its much slower effect on TIMP1 mRNA levels.
Lum
Z P
ZP
Department of Surgery, McGill University, Montreal, Québec, Canada.
Hakala
B E
BE
Mort
J S
JS
Recklies
A D
AD
D053674:Aggrecans; D001483:Base Sequence; D002358:Cartilage, Articular / Q000166:cytology / Q000378:metabolism*; D002478:Cells, Cultured; D003094:Collagen / Q000096:biosynthesis / Q000235:genetics; D017364:Collagenases / Q000235:genetics; D016326:Extracellular Matrix Proteins; D006023:Glycoproteins / Q000096:biosynthesis* / Q000235:genetics; D006706:Homeostasis; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology*; D037181:Lectins, C-Type; D019278:Matrix Metalloproteinase 3; D008666:Metalloendopeptidases / Q000096:biosynthesis* / Q000235:genetics; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes / Q000235:genetics; D016133:Polymerase Chain Reaction; D011509:Proteoglycans / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D019714:Tissue Inhibitor of Metalloproteinases; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D053674:Aggrecans; D016326:Extracellular Matrix Proteins; D006023:Glycoproteins; D007375:Interleukin-1; D037181:Lectins, C-Type; D015345:Oligonucleotide Probes; D011509:Proteoglycans; D012333:RNA, Messenger; D019714:Tissue Inhibitor of Metalloproteinases; D016212:Transforming Growth Factor beta; D003094:Collagen; D017364:Collagenases; D008666:Metalloendopeptidases; D019278:Matrix Metalloproteinase 3