Chromatin breakdown during necrosis by serum Dnase1 and the plasminogen system
Chromatin breakdown during necrosis by serum Dnase1 and the plasminogen system
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DOI：
10.1002/art.20267
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发表时间：
2004-06-01
影响因子：
--
通讯作者：
Mannherz, HG
中科院分区：
文献类型：
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作者：
Napirei, M;Wulf, S;Mannherz, HG
目标。具有129 X C57BL/6遗传背景的DNase1缺陷小鼠出现系统性红斑狼疮的症状，如针对核小体的高滴度抗核自身抗体。在这项研究中，我们通过研究血清中存在的细胞外DNase1对体外培养的坏死细胞染色质分解的影响，分析了导致这种自身免疫的一个潜在的分子病理机制。人乳腺腺癌细胞(MCF-7)和其他细胞系经过氧化氢、链球菌溶血素O或冻融处理后均发生坏死。随后，研究了DNase1基因缺失和野生型小鼠的血清以及培养液中存在的纯化酶对染色质坏死性分解过程的影响。坏死性染色质断裂类似于凋亡的DNA阶梯，并由血清DNase1和纤溶酶共同催化。在坏死过程中，DNase1和纤溶酶原穿透细胞，并在胞浆和胞核中积聚。组织型纤溶酶原激活剂和尿激酶型纤溶酶原激活剂均能激活与细胞骨架和核结构结合的纤溶酶原，并降解组蛋白H1，从而促进DNase1对核小体间DNA的切割。我们的结果表明，血清DNase1与纤溶酶原系统的协同作用保证了在坏死过程中，通过DNA和DNA结合蛋白的联合裂解，染色质可以快速有效地分解。这种清除机制的失败可能导致抗核自身免疫，类似于在DNase1缺陷小鼠中观察到的。
Objective. Dnase1-deficient mice with the 129 X C57BL/6 genetic background develop symptoms of systemic lupus erythematosus, such as high titers of antinuclear autoantibodies directed against nucleosomes. In this study we analyzed a potential molecular pathomechanism leading to this autoimmunity, by exploring the influence of extracellular Dnase1 present in serum on the breakdown of chromatin in necrotic cells in vitro.Methods. Human breast adenocarcinoma cells (MCF-7) and other cell lines were subjected to necrosis induced by hydrogen peroxide, streptolysin O, or freeze-thawing. Subsequently, the influence of sera from Dnase1-dericient and wild-type mice as well as the influence of purified enzymes present in the culture medium on the process of necrotic chromatin breakdown was investigated.Results. Necrotic chromatin breakdown resembled apoptotic DNA laddering and was catalyzed by serum Dnase1 in conjunction with plasmin. During necrosis, Dnase1 and plasminogen penetrated the cell and accumulated in the cytoplasm and nucleus. Plasminogen bound to the cytoskeleton and nuclear structures, was activated to plasmin by either tissue-type or urokinase-type plasminogen activator, and degraded histone H1, thereby facilitating internucleosomal DNA cleavage by Dnase1.Conclusion. Our results suggest that serum Dnase1 in cooperation with the plasminogen system guarantees a fast and effective breakdown of chromatin during necrosis by the combined cleavage of DNA as well as of DNA binding proteins. The failure of such a clearance mechanism might lead to antinuclear autoimmunity similar to that observed in the Dnase1-deficient mouse.