ISSN:
1420-908X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Cathepsin B is a lysosomal cysteine proteinase, thought to be involved in the degradation of connective tissue breakdown products internalized by endocytosis. It has also been implicated in the extracellular matrix degradation of collagens and proteoglycans in disease states such as tumour invasion, rheumatoid arthritis and osteoarthritis. To date it is still unclear which factors can potentially modulate the release and/or activation of this enzyme. The aim of this study was to investigate the effect of interleukin-1β and transforming growth factor β on cathepsin B activity in both cell lysates and cell supernatants, using first passage cultures of human articular chondrocytes. Enzyme activity was determined using a specific synthetic substrate for cathepsin B, in a fluorimetric assay. After 24 h incubation, IL-1β (10–100 U/ml) significantly stimulated cathepsin B activity dose dependently in cell lysates whereas no activity could be detected in the media. Production of cathepsin B activity was unaffected by the presence of 1.4 μM indomethacin, which suggests that prostaglandins are not regulators of cathepsin B activity. TGFβ had no significant effect on basal intracellular cathepsin B levels and variable effects on IL-1β stimulated levels. In three of the five experiments carried out, TGFβ showed a down-regulation of IL-1β-induced enzyme activity. The other two experiments showed an additive effect when TGFβ and IL-1β were co-incubated. Basal and IL-1β-induced levels of cathepsin B activity in cell lysates were both abolished after E-64 (5 μM) was incorporated in the assay incubation medium, which established the specificity of the reaction. These results suggest that IL-1β and TGFβ may be involved in the regulation of cathepsin B activity and thus cartilage breakdown associated with rheumatic diseases.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01987636
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