Metallo-endopeptidase activity in mouse and rat urine.

Bovine articular cartilage explants were maintained in culture for 4 days in the presence of 25 units o f IL-1 with 0 (m), 50 ( m ) and 200 ( m ) pg/ml naproxen, and the media were analysed to determine proteoglycan ( a ) and collagenase activity (h). cultures, and this was maintained for subsequent days. Gelatinase activity showed no significant change with 1L-l at any time. TIMP activity showed a dose-independent increase up to 210'56 over control values. Removal of IL-l from the cultures showed a reduction of metalloproteinase activity within 24 h. In contrast, naproxen caused a doseand time-dependent decrease of proteoglycan release from the articular cartilage explants into the media. During 4 days of culture proteoglycan release was reduced by 37% in the presence of 200 pg of naproxen/ml. Naproxen also caused a doseand timcdependent decrease of collagenase activity that was released from the articular cartilage matrix. During 4 days of culture in the presence of 0.1, 1, 10, 20 or 200 pg of naproxen/ml, collagenase activity was reduced by 22"/0, 25%, 28%, 42% and 54%, respectively. In cultures of articular cartilage incubated with both IL-1 and naproxen, the NSAlD was found to reduce, but not eliminate, IL-1's augmentation of proteoglycan release and collagenase activity in a dosedependent fashion (Fig. 1 ). In summary, these results show that 1L-1-induced proteoglycan breakdown correlates with the 1L1-induced incrcase of the expression of MMP activities associated with matrix turnover and breakdown. However, the responses observed for the different MMPs and TIMP varied with time and dose, indicating the expression of MMP activities may be independently controlled. In contrast, naproxen reduced the proteoglycan release from the cartilage, and this corresponded to a reduction of metalloproteinase activity. Naproxen was also able to reduce the stimulation of the proteoglycan breakdown rate and MMP activity induced by IL-1, although at the concentrations used it was unable t o eliminate the IL1 response.