Significance of cathepsin B accumulation in synovial fluid of rheumatoid arthritis

We measured and compared the activities of various kinds of proteinases, su ch as cysteine, serine, aspartic, and metalloproteinases, in synovial fluid s of 16 patients with rheumatoid arthritis (RA) and 18 patients with osteoa rthritis (OA). More than 19-fold higher activity of cathepsin B and about 6 -fold higher activity of prolylendopeptidase, compared to those of OA, were accumulated in RA fluid. Moreover, levels of cathepsins B and S using the corresponding sandwich enzyme immunoassays were statistically higher in RA fluid than those in OA. Significant amounts of 41-kDa and 35-kDa procatheps in L mere detected in RA fluid using gelatin zymography, while 41-kDa enzym e alone was detected in OA. Cathepsin B in RA fluid could degrade collagen, and this degradation was suppressed by the addition of CA-074, a specific inhibitor of cathepsin B. Therefore, cathepsin B may participate in joint d estruction of RA, and its inhibitor may be effective for RA care. (C) 2001 Academic Press.