Objective: To compare the activities of cathepsin B (EC 3.4.22.1) and L (EC 3.4.22.15), calpain (EC 3.4.22.17), and dipeptidyl peptidase (EC 3.4.14.5 or DPP IV or CD26) in synovial membrane from patients with rheumatoid arthritis (RA), osteoarthritis (OA), and post-traumatic joint injury (PT).
Methods: Forty RA patients were divided into two groups on the basis of surgical procedure: the RAs group comprised 18 patients requiring surgical synovectomy; the RAr group comprised 22 patients requiring a total joint replacement or arthrodesis. A third group (the OA group) comprised 19 OA patients while six patients with post-traumatic joint injury were included in the fourth group (the PT group). Cathepsin and calpain activity was assessed using a Cobas Fara II centrifugal analyser. DPP IV activity was determined kinetically using a fluorogenic substrate.
Results: RAs patients were significantly younger than RAr patients, and the mean duration of RA was shorter in the RAs group than in the RAr group. Cathepsin and calpain activity in synovial membrane was higher in RA and OA patients than in the control group, but no statistical difference was observed between RA and OA. However, cathepsin, calpain, and DPP IV synovial activity was significantly higher in the RAs group than in either the OA or the PT group.
Conclusion: Our results show that proteinase activity tends to be higher in joints with early synovitis in RA, and suggest that these enzymes are not all involved at the same stage of the disease.