STIMULATION OF THE SECRETION OF LATENT CYSTEINE PROTEINASE ACTIVITY BY TUMOR-NECROSIS-FACTOR-ALPHA AND INTERLEUKIN-1

Objective. Cultured synovial fibroblast-like cells from 3 patients wit h rheumatoid arthritis (RA) and 3 patients with osteoarthritis (OA) we re evaluated for their potential to secrete cysteine proteinases spont aneously and after stimulation by tumor necrosis factor alpha (TNFalph a) or interleukin-1 (IL-1). Methods. Culture media and cell lysates we re analyzed before and after high performance liquid chromatography (H PLC) using the enzymatic substrate, Z-Phe-Arg-AMC, and by immunoblotti ng with anti-cathepsin B antiserum. Immunolocalization of cathepsin B was studied on cell monolayers. Results. Latent cysteine proteinase ac tivity was found to be secreted spontaneously by cultured synovial fib roblast-like cells. This activity was increased after treatment with e ither TNFalpha or IL-1. Stimulated protease activity was eluted by HPL C at a peak coincident with that of purified cathepsin B. By immunoblo t, cell supernatants contained a 43-kd form of cathepsin B, while cell lysates contained a 30-kd form, consistent, respectively, with cathep sin B before and after cleavage of its propeptide. An intracellular in crease in cathepsin B after treatment with TNFalpha was also seen with immunohistochemical studies. Conclusion. TNFalpha (in the 6 cases stu died) and IL-1 (in 4 cases) stimulated the secretion of a latent cyste ine proteinase activity from synovial fibroblast-like cells, which app ears to represent primarily cathepsin B.