calpastatin and Osteoarthritis

To develop a quantitative method of measuring autoantibodies against human calpastatin in rheumatoid arthritis (RA) and to determine their diagnostic value compared with other autoimmune and articular diseases.. We performed a highly sensitive ELISA for IgG and IgM anticalpastatin autoantibodies in human sera using human erythrocyte calpastatin as an antigen. Samples were diluted 1:2000 for the measurement of IgG and 1:400 for IgM.. IgG anticalpastatin antibodies were found in the sera of 48 of 58 patients (82.8%) with RA. In contrast, IgG anticalpastatin antibodies were found in the sera of only 2 of 11 (8.3%) patients with osteoarthritis (OA). Compared to sera from patients with other autoimmune diseases, anticalpastatin antibody sensitivity for RA was better than that of systemic lupus erythematosus (5.6%), systemic sclerosis (0%), mixed connective tissue disease (0%), and Sjögren's syndrome (20%). IgG anticalpastatin antibodies also showed high specificity (96.1%) for RA. Almost 90% of patients with RA were positive for IgG or IgM anticalpastatin antibodies.. We have developed a simple, sensitive, specific, and quantitative ELISA for anticalpastatin antibodies that may have a high diagnostic value for RA.

Topics: Adult; Aged; Arthritis, Rheumatoid; Autoantibodies; Autoantigens; Blotting, Western; Calcium-Binding Proteins; Enzyme-Linked Immunosorbent Assay; Erythrocytes; Female; Humans; Immunoglobulin G; Immunoglobulin M; Male; Middle Aged; Osteoarthritis; Sensitivity and Specificity

Our previous reports revealed that calpain has proteoglycanase activity and exists in synovial fluid in osteoarthritis and rheumatoid arthritis. We examined the effects of cytokines on expression of the calpain-calpastatin system 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 mRNAs expressed were determined by Northern blotting. Northern blots were subjected to computerized densitometer and band intensities were determined. Interleukin-1 (IL-1) down-regulated m-calpain and tissue-type calpastatin mRNA expression in OA and RA FLS. In RA FLS, although IL-6 did not alter m-calpain mRNA expression, IL-1 + tumor necrosis factor (TNF) and IL-1 + transforming growth factor (TGF) down-regulated m-calpain mRNA expression. These results provide new information about the effects of inflammatory cytokines on calpain and calpastatin system in OA and RA pathology.

Topics: Arthritis, Rheumatoid; Calcium-Binding Proteins; Calpain; Cells, Cultured; Cytokines; Down-Regulation; Gene Expression Regulation, Enzymologic; Humans; Interleukin-1; Kinetics; Osteoarthritis; RNA, Messenger; Synovial Fluid; Transforming Growth Factors; Tumor Necrosis Factor-alpha

Calpains (calcium-dependent cysteine proteinases; optimum pH 7.0-7.5) have been regarded as intracellular proteinases. We examined the cell-free components of synovial fluid from 14 patients with osteoarthritis and demonstrated the existence of calpains, as the caseinolytic activities of chromatographic fractions, together with calpastatin, the specific endogenous inhibitor of calpains. The presence of these calpains and calpastatin was verified by immunoblotting with their respective specific antibodies. Calpain fractions showed proteoglycan-degrading activity. The results suggest that the calpain-calpastatin system may contribute to the turnover of cartilage matrix components.

Topics: Aged; Aged, 80 and over; Animals; Calcium-Binding Proteins; Calpain; Cartilage, Articular; Drug Stability; Endopeptidases; Hot Temperature; Humans; Immunoelectrophoresis; Metalloendopeptidases; Middle Aged; Osteoarthritis; Proteoglycans; Swine; Synovial Fluid