Dieker Jürgen W, Fransen Justin H, van Bavel Casandra C, Briand Jean-Paul, Jacobs Cor W, Muller Sylviane, Berden Jo H, van der Vlag Johan
Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
Arthritis Rheum. 2007 Jun;56(6):1921-33. doi: 10.1002/art.22646.
In systemic lupus erythematosus (SLE), inadequate removal of apoptotic cells may lead to challenge of the immune system with immunogenic self antigens that have been modified during apoptosis. We undertook this study to evaluate whether apoptosis-induced histone modifications are targets for the immune system in SLE.
The epitope of KM-2, a monoclonal antihistone autoantibody derived from a lupus mouse, was mapped by random peptide phage display. The reactivity of KM-2 and plasma with (acetylated) histone H4 (H4) peptides and with nonapoptotic, apoptotic, and hyperacetylated histones was determined by immunofluorescence staining, enzyme-linked immunosorbent assay, and Western blotting.
KM-2 recognized apoptosis-induced acetylation of H4 at lysines 8, 12, and 16. The majority of plasma samples from SLE patients and lupus mice showed higher reactivity with triacetylated H4 peptide (residues 1-22) and with hyperacetylated and apoptotic histones than with nonacetylated H4 peptide and normal histones. Importantly, administration of triacetylated H4 peptide to lupus-prone mice before disease onset accelerated the disease by enhancing mortality and aggravating proteinuria, skin lesions, and glomerular IgG deposition, while the nonacetylated H4 peptide had no pathogenic effect. The delayed-type hypersensitivity response in lupus mice against the triacetylated H4 peptide was higher than that against the nonacetylated H4 peptide. Bone marrow-derived dendritic cells (DCs) cultured in the presence of hyperacetylated nucleosomes showed increased expression/production of CD40, CD86, interleukin-6 (IL-6), and tumor necrosis factor alpha compared with DCs cultured in the presence of normal nucleosomes. Finally, DCs cultured in the presence of hyperacetylated nucleosomes were able to activate syngeneic T cells, because IL-2 production increased.
Apoptosis-induced acetylation of nucleosomes may represent an important driving force in the development of lupus.
在系统性红斑狼疮（SLE）中，凋亡细胞清除不足可能导致免疫系统受到在凋亡过程中发生修饰的免疫原性自身抗原的挑战。我们开展本研究以评估凋亡诱导的组蛋白修饰是否为SLE中免疫系统的靶点。
通过随机肽噬菌体展示对源自狼疮小鼠的单克隆抗组蛋白自身抗体KM-2的表位进行定位。通过免疫荧光染色、酶联免疫吸附测定和蛋白质印迹法测定KM-2和血浆与（乙酰化的）组蛋白H4（H4）肽以及与非凋亡、凋亡和高乙酰化组蛋白的反应性。
KM-2识别凋亡诱导的H4赖氨酸8、12和16位点的乙酰化。来自SLE患者和狼疮小鼠的大多数血浆样本与三乙酰化H4肽（第1-22位氨基酸残基）以及与高乙酰化和凋亡组蛋白的反应性高于与非乙酰化H4肽和正常组蛋白的反应性。重要的是，在疾病发作前向狼疮易感小鼠施用三乙酰化H4肽通过提高死亡率以及加重蛋白尿、皮肤病变和肾小球IgG沉积而加速疾病进展，而非乙酰化H4肽没有致病作用。狼疮小鼠对三乙酰化H4肽的迟发型超敏反应高于对非乙酰化H4肽的反应。与在正常核小体存在下培养的骨髓来源的树突状细胞（DC）相比，在高乙酰化核小体存在下培养的DC显示出CD40、CD86、白细胞介素-6（IL-6）和肿瘤坏死因子α的表达/产生增加。最后，在高乙酰化核小体存在下培养的DC能够激活同基因T细胞，因为IL-2产生增加。
凋亡诱导的核小体乙酰化可能是狼疮发病的重要驱动力。
