VA Palo Alto Health Care System, Palo Alto, CA 94304.
Division of Immunology and Rheumatology, Stanford University, Stanford, CA 94305.
Arthritis Rheumatol. 2014 Jan;66(1):101-106. doi: 10.1002/art.38213.
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.
我们之前的研究表明羧肽酶 B（CPB）通过使补体成分 C5a 失活来预防类风湿关节炎的关节侵蚀。我们还发现另一种关节疾病骨关节炎（OA）患者的滑液中 CPB 水平异常升高。我们进行这项研究是为了探讨 CPB 是否在 OA 的发病机制中起作用。
我们通过对 CPB 缺陷（Cpb2（-/-））小鼠和野生型小鼠进行内侧半月板切除术，并在 4 个月后对其膝关节进行组织学评估软骨损伤、骨赘形成和滑膜炎，比较它们在 OA 发展中的差异。我们测量了患有症状性和放射学膝 OA 的患者滑液样本中 proCPB、促炎细胞因子和补体成分的水平。最后，我们使用酶联免疫吸附试验、流式细胞术和溶血试验来评估 CPB 对膜攻击复合物（MAC）形成的影响，MAC 是 OA 发病机制中至关重要的补体效应物。
Cpb2（-/-）小鼠比野生型小鼠发展出更严重的软骨损伤（P < 0.01），并且有更多的骨赘（P < 0.05）和更严重的滑膜炎（P < 0.05）。在 OA 患者的滑液样本中，高水平的 proCPB 与高水平的促炎细胞因子和补体成分相关，并且 proCPB 的水平与 MAC 的水平呈正相关。在体外补体激活试验中，激活的 CPB 抑制了 MAC 的形成以及 MAC 诱导的溶血。
我们的数据表明 CPB 可保护 OA 关节免受炎症破坏，至少部分是通过抑制补体激活来实现的。
