bromochloroacetic-acid and calpastatin

Topics: Acute-Phase Proteins; Antibodies, Antinuclear; Arthritis, Rheumatoid; Autoantibodies; Biomarkers; Calcium-Binding Proteins; Disease Progression; Filaggrin Proteins; Humans; Interleukin-1; Intermediate Filament Proteins; Keratins; Matrix Metalloproteinase 3; Peptides, Cyclic; Predictive Value of Tests; Prognosis

STATEMENT OF FINDINGS: An inception cohort of 238 patients having peripheral joint synovitis of less than 12 months duration was evaluated clinically and followed prospectively for 1 year to determine the clinical significance of a number of rheumatoid arthritis (RA) associated autoantibodies. Serum samples collected at the time of the initial evaluation were tested for rheumatoid factor (RF) and antibodies to Sa (anti-Sa), RA-33, (pro)filaggrin [antifilaggrin antibody (AFA)], cyclic citrullinated peptide (anti-CCP), calpastatin, and keratin [antikeratin antibody (AKA)]. RF had a sensitivity of 66% and a specificity of 87% for RA. Anti-Sa, AFA, and anti-CCP all had a specificity of more than 90%, but a sensitivity of less than 50% for this diagnosis. Overall, there was a high degree of correlation between AFA, AKA, anti-Sa or anti-CCP, this being highest between anti-Sa and anti-CCP (odds ratio, 13.3; P < 0.001). Of the 101 patients who were positive for at least one of these four autoantibodies, 57% were positive for only one. Finally, anti-SA identified a subset of predominantly male RA patients with severe, erosive disease. Anti-SA, AFA and anti-CCP are all specific for early RA but, overall, have little additional diagnostic value over RF alone. Although these antibodies may preferentially recognize citrullinated antigens, the modest degree of concordance between them in individual patient sera suggests that it is unlikely a single antigen is involved in generating these responses.

Topics: Acute Disease; Adult; Antibody Specificity; Arthritis, Rheumatoid; Autoantibodies; Calcium-Binding Proteins; Citrulline; Coenzyme A Ligases; Cohort Studies; Epitopes; Female; Filaggrin Proteins; Histocompatibility Testing; Humans; Intermediate Filament Proteins; Keratins; Male; Middle Aged; Peptides, Cyclic; Predictive Value of Tests; Proteins; Rheumatoid Factor; Seroepidemiologic Studies; Synovitis

Two forms of Ca++-dependent cysteine proteinases, calpain I, requiring low Ca++ (microM concentration), and calpain II, requiring high Ca++ (mM concentration), were purified from the cytosolic fraction of pig epidermis. Calpains I and II were separated on DEAE-cellulose chromatography, and thereafter they were purified by separate but almost identical procedures, which included chromatographies on Sephacryl S-300, Blue Sepharose CL-6B, and DEAE Bio-Gel A. Purified calpains I and II required 10 and 450 microM Ca++ for half-maximal activation, respectively, and had an optimal pH of 7.0 to 8.0. Both enzymes were heterodimers and composed of one heavy subunit (83 kDa for calpain I and 80 kDa for calpain II) and one light subunit (29 kDa for both enzymes). The action of calpains I and II on keratin extracted from the same tissue was studied. Both enzymes rapidly cleaved keratin into small fragments. The cleavage depends on Ca++ and could be blocked by leupeptin and calpastation, an endogenous calpain-specific inhibitor, which was also found in the cytosolic fraction of pig epidermis and partially purified.

Topics: Animals; Calcium-Binding Proteins; Calpain; Chromatography; Epidermis; In Vitro Techniques; Keratins; Swine