carboxypeptidase-b and Osteoarthritis

We previously demonstrated that carboxypeptidase B (CPB) protects against joint erosion in rheumatoid arthritis by inactivating complement component C5a. We also found that levels of CPB are abnormally high in the synovial fluid of individuals with another joint disease, osteoarthritis (OA). We undertook this study to investigate whether CPB plays a role in the pathogenesis of OA.. We compared the development of OA in CPB-deficient (Cpb2(-/-) ) mice and wild-type mice by subjecting them to medial meniscectomy and histologically assessing cartilage damage, osteophyte formation, and synovitis in the stifle joints 4 months later. We measured levels of proCPB, proinflammatory cytokines, and complement components in synovial fluid samples from patients with symptomatic and radiographic knee OA. Finally, we used enzyme-linked immunosorbent assay, flow cytometry, and hemolytic assays to assess the effect of CPB on formation of membrane attack complex (MAC)-a complement effector critical to OA pathogenesis.. Cpb2(-/-) mice developed dramatically greater cartilage damage than did wild-type mice (P < 0.01) and had a greater number of osteophytes (P < 0.05) and a greater degree of synovitis (P < 0.05). In synovial fluid samples from OA patients, high levels of proCPB were associated with high levels of proinflammatory cytokines and complement components, and levels of proCPB correlated positively with those of MAC. In in vitro complement activation assays, activated CPB suppressed the formation of MAC as well as MAC-induced hemolysis.. Our data suggest that CPB protects against inflammatory destruction of the joints in OA, at least in part by inhibiting complement activation.

Topics: Animals; Arthritis, Experimental; Carboxypeptidase B; Carboxypeptidase B2; Cartilage, Articular; Complement Membrane Attack Complex; Cytokines; Enzyme-Linked Immunosorbent Assay; Humans; Inflammation Mediators; Mice; Mice, Knockout; Middle Aged; Osteoarthritis; Osteoarthritis, Knee; Osteophyte; Synovial Fluid; Synovitis

Topics: Animals; Carboxypeptidase B; Cartilage; Complement System Proteins; Mice; Mice, Knockout; Osteoarthritis

Osteopontin (OPN) is a proinflammatory cytokine that plays an important role in the pathogenesis of rheumatoid arthritis (RA). OPN can be cleaved by thrombin, resulting in OPN-R and exposing the cryptic C-terminal alpha4beta1 and alpha9beta1 integrin-binding motif (SVVYGLR). Thrombin-activatable carboxypeptidase B (CPB), also called thrombin-activatable fibrinolysis inhibitor, removes the C-terminal arginine from OPN-R, generating OPN-L and abrogating its enhanced cell binding. We undertook this study to investigate the roles of OPN-R and OPN-L in synoviocyte adhesion, which contributes to the formation of invasive pannus, and in neutrophil survival, which affects inflammatory infiltrates in RA.. Using specifically developed enzyme-linked immunosorbent assays, we tested the synovial fluid of patients with RA, osteoarthritis (OA), and psoriatic arthritis (PsA) to determine OPN-R, OPN-L, and full-length OPN (OPN-FL) levels.. Elevated levels of OPN-R and OPN-L were found in synovial fluid samples from RA patients, but not in samples from OA or PsA patients. Increased levels of OPN-R and OPN-L correlated with increased levels of multiple inflammatory cytokines, including tumor necrosis factor alpha and interleukin-6. Immunohistochemical analyses revealed robust expression of OPN-FL, but only minimal expression of OPN-R, in RA synovium, suggesting that cleaved OPN is released into synovial fluid. In cellular assays, OPN-FL, and to a lesser extent OPN-R and OPN-L, had an antiapoptotic effect on neutrophils. OPN-R augmented RA fibroblast-like synoviocyte binding mediated by SVVYGLR binding to alpha4beta1, whereas OPN-L did not.. Thrombin activation of OPN (resulting in OPN-R) and its subsequent inactivation by thrombin-activatable CPB (generating OPN-L) occurs locally within inflamed joints in RA. Our data suggest that thrombin-activatable CPB plays a central homeostatic role in RA by regulating neutrophil viability and reducing synoviocyte adhesion.

Topics: Antibodies, Anti-Idiotypic; Apoptosis; Arthritis, Psoriatic; Arthritis, Rheumatoid; Carboxypeptidase B; Cell Adhesion; Cell Survival; Humans; Interleukin-6; Neutrophils; Osteoarthritis; Osteopontin; Synovial Membrane; Thrombin; Tumor Necrosis Factor-alpha

In a prospective study, thirty patients in whom a Charnley hip prosthesis was implanted with cement (methylmethacrylate) and fifteen who received a prosthesis without cement were studied. The activation of complement, as indicated by the release of anaphylatoxins (C3a and C5a), reduced activity of whole complement, and decreased levels of C3, C4, and C5 in plasma, was evaluated. Activation of complement was found when methylmethacrylate was used. In patients in whom components were fixed without cement, no formation of anaphylatoxins occurred, and only slightly reduced whole-complement activity and concentrations of C3, C4, and C5 in plasma were found. A dose-correlated release of the anaphylatoxins was found when monomethylmethacrylate was incubated in fresh serum. One explanation for the hemodynamic instability in these patients might be the biological effects of anaphylatoxins that are released in association with fixation by cement.

Topics: Adult; Aged; Anaphylatoxins; Bone Cements; Carboxypeptidase B; Carboxypeptidases; Complement Activation; Complement System Proteins; Female; Hip Prosthesis; Humans; Male; Methylmethacrylates; Middle Aged; Osteoarthritis; Peptides; Prospective Studies