Departments of Biochemistry and Faculty of Medicine, Aligarh Muslim University , India.
Scand J Rheumatol. 2012;41(6):426-33. doi: 10.3109/03009742.2012.698300. Epub 2012 Sep 18.
Rheumatoid arthritis (RA) is an autoimmune disease of complex aetiology and pathogenesis. In recent years it has become evident that apoptotically modified histones exert a central role in the induction of autoimmunity, for example in systemic lupus erythematosus (SLE) and RA. Because nitric oxide (NO)-related species have been found in inflamed joints of arthritis patients, we investigated whether nitrotyrosine is present in sera of RA patients, and whether peroxynitrite-modified H2A histone is likely to be involved in the induction and progression of RA.
Commercially available H2A histone was modified in vitro by peroxynitrite. The RA patients were divided into three groups on the basis of CRP, nitrite, total protein and IgG level. Sera of RA patients with high-titre rheumatoid factor (RF) were analysed for autoantibodies against native DNA and native and peroxynitrite-modified H2A histone. Binding characteristics and specificity of the autoantibodies were analysed by direct binding, inhibition enzyme-linked immunosorbent assay (ELISA), and band shift assay.
Sera from control subjects contained almost negligible amounts of 3-nitrotyrosine (3-NT); lower levels were found in group 1 RA patients in comparison to group 2 and group 3 patients, where the level of nitrotyrosine was progressively higher. Enzyme immunoassay data showed preferential binding of RA autoantibodies to peroxynitrite-modified H2A histone in comparison with native H2A histone or native DNA. The results suggest that peroxynitrite modification of self-antigen(s) can generate neoepitopes capable of inducing RA characteristic autoantibodies.
The preferential binding of peroxynitrite-modified histones by autoantibodies derived from RA sera indicates a role for oxidatively modified and nitrated proteins in the initiation/progression of RA.
类风湿关节炎（RA）是一种病因和发病机制复杂的自身免疫性疾病。近年来，人们已经认识到凋亡修饰组蛋白在诱导自身免疫方面起着核心作用，例如在系统性红斑狼疮（SLE）和 RA 中。由于在关节炎患者的炎症关节中已经发现了与一氧化氮（NO）相关的物质，我们研究了硝基酪氨酸是否存在于 RA 患者的血清中，以及过氧亚硝酸盐修饰的 H2A 组蛋白是否可能参与 RA 的诱导和进展。
体外使用过氧亚硝酸盐修饰商业可得的 H2A 组蛋白。根据 CRP、亚硝酸盐、总蛋白和 IgG 水平，将 RA 患者分为三组。分析 RA 患者高滴度类风湿因子（RF）的血清中针对天然 DNA 以及天然和过氧亚硝酸盐修饰 H2A 组蛋白的自身抗体。通过直接结合、抑制酶联免疫吸附试验（ELISA）和带迁移试验分析自身抗体的结合特性和特异性。
来自对照者的血清几乎不含 3-硝基酪氨酸（3-NT）；与组 2 和组 3 患者相比，组 1 RA 患者的水平较低，而组 2 和组 3 患者的水平逐渐升高。酶免疫测定数据显示，RA 自身抗体优先与过氧亚硝酸盐修饰的 H2A 组蛋白结合，而不是与天然 H2A 组蛋白或天然 DNA 结合。结果表明，自身抗原的过氧亚硝酸盐修饰可以产生新的表位，能够诱导 RA 特征性的自身抗体。
RA 血清中的自身抗体优先与过氧亚硝酸盐修饰的组蛋白结合，表明氧化修饰和硝化蛋白在 RA 的起始/进展中起作用。
