Inflammatory cytokines induced down-regulation of m-calpain mRNA expression in fibroblastic synoviocytes from patients with osteoarthritis and rheumatoid arthritis

Our previous reports revealed that calpain has proteoglycanase activity and exists in synovial fluid in osteoarthritis and rheumatoid arthritis. We ex amined the effects of cytokines on expression of the calpain-calpastatin sy stem in fibroblastic synoviocytes (FLS). Primary cultures of human FLS from osteoarthritis (OA) and rheumatoid arthritis (RA) patients were stimulated with inflammatory cytokines and the amounts of m-calpain and calpastatin m RNAs expressed were determined by Northern blotting. Northern blots were su bjected to computerized densitometer and band intensities were determined. Interleukin-1 (IL-1) down-regulated m-calpain and tissue-type calpastatin m RNA expression in OA and RA FLS. In RA FLS, although IL-6 did not alter m-c alpain mRNA expression, IL-1 + tumor necrosis factor (TNF) and IL-1 + trans forming growth factor (TGF) down-regulated m-calpain mRNA expression. These results provide new information about the effects of inflammatory cytokine s on calpain and calpastatin system in OA and RA pathology. (C) 1999 Academ ic Press.