Autoantibody modulation of cartilage turnover in rheumatoid arthritis

摘要 风湿性关节炎（RA）影响世界人口的0.5-1%。类风湿性关节炎以自身抗体为特征 产生，滑膜炎症和肿胀，以及软骨和骨的破坏， 进行性残疾目前尚不清楚早期反应性，如抗瓜氨酸蛋白抗体， （ACPAs）和类风湿因子（RF）是致病性的、调节性的，或仅是次要现象， 与发病机制有关。一种可能的情况是，RA发生时，自身免疫反应开关 涉及靶向关节，特别是软骨内或附着于软骨的蛋白质。II型胶原蛋白是 关节软骨，也是大多数已知的可诱导关节炎的自身抗体的靶点。我们有 获得的证据表明，对II型胶原的自身免疫反应通常发生在RA患者中， 是引发疾病的主要机制之一。本文所述的研究计划 着重于通过基质金属蛋白酶13（MMP-13）对II型胶原蛋白加工的抗体调节， 在关节炎期间负责关节软骨降解的主要胶原酶。我们假设 如下在正常情况下，MMP-13最初在Gly 775-Leu 776键处切割II型胶原， 随后进一步消化胶原片段。在RA中，II型胶原的自身抗体抑制 MMP-13在不同阶段的作用，导致胶原片段的稳定产生。胶原 片段可以激活免疫系统，使其更具致病性或调节性， 软骨细胞的功能，从而在RA的启动中发挥作用。这代表了一种新的范式， RA发作和进展。为了探索这一假设，具体的目的是检验（1）的影响。 精氨酸残基在MMP-13加工II型胶原蛋白过程中翻译后修饰为瓜氨酸，（2）RA 抗体对MMP-13加工II型胶原和随后的片段产生的影响，和（3）MMP-13 衍生的II型胶原片段对软骨细胞活性和RA的体内小鼠模型的影响。这些目标 将采用多种策略，包括三螺旋水解的酶动力学分析， 结构，II型胶原片段的蛋白质组学分析，以及增殖，qRT-PCR，FACS，和 软骨细胞的蛋白质印迹分析。本研究将对特异性抗- 胶原抗体在RA进展中的作用。

ABSTRACT Rheumatoid arthritis (RA) affects 0.5-1% of the world population. RA is characterized by autoantibody production, synovial inflammation and swelling, and destruction of cartilage and bone resulting in progressive disability. It is not known whether early reactivities, such as anti-citrullinated protein antibodies (ACPAs) and rheumatoid factor (RF), are pathogenic, regulatory, or only a secondary phenomenon not related to the pathogenesis. A possible scenario is that RA occurs when the autoimmune response switches to targeting joints, in particular proteins within or adhering to cartilage. Type II collagen the major protein in joint cartilage and is also the target of most known autoantibodies that can induce arthritis. We have obtained evidence that autoimmune reactivities to type II collagen commonly occur in RA patients and may be one of the major mechanisms whereby the disease is initiated. The research plan described herein focuses on antibody modulation of type II collagen processing by matrix metalloproteinase 13 (MMP-13), the main collagenase responsible for degradation of articular cartilage during arthritis. Our hypothesis is as follows. Under normal circumstances, MMP-13 cleaves type II collagen initially at the Gly775-Leu776 bond, followed by further digestion of collagen fragments. In RA, autoantibodies to type II collagen inhibit the action of MMP-13 at different stages, resulting in the stable production of collagen fragments. The collagen fragments could activate the immune system to be more pathogenic or regulatory as well as modify chondrocyte functions, and thereby play a role in the initiation of RA. This represents a novel paradigm for RA onset and progression. To explore this hypothesis, the specific aims are to examine the effects of (1) posttranslational modification of Arg residues to citrulline on MMP-13 processing of type II collagen, (2) RA antibodies on MMP-13 processing of type II collagen and subsequent fragment production, and (3) MMP-13 derived type II collagen fragments on chondrocyte activity and in in vivo mouse models of RA. These aims will incorporate a variety of strategies, including enzyme kinetic analysis of hydrolysis of triple-helical structures, proteomics analysis of type II collagen fragments, and proliferation, qRT-PCR, FACS, and western blot analysis of chondrocytes. The present study will shed new light on the roles of specific anti- collagen antibodies in RA progression.