Nielsen Marianne, Lambertsen K L, Clausen B H, Meldgaard M, Diemer N H, Zimmer J, Finsen B
Institute of Medical Biology, Anatomy and Neurobiology, University of Southern Denmark, Winsloewparken 21, 5000, Odense C, Denmark.
Exp Brain Res. 2009 Mar;194(1):17-27. doi: 10.1007/s00221-008-1665-5. Epub 2009 Jan 13.
Endonuclease G (EndoG) is a mitochondrial enzyme, known to be involved in caspase-independent cell death following translocation to the cellular nucleus. Nuclear translocation of EndoG has been observed in the ischemic area following transient occlusion of the middle cerebral artery (MCA) in mice, but not after permanent MCA occlusion. In this study we investigated the cellular and temporal expression of EndoG in infarcted cortex during the first 24 h after permanent MCA occlusion in mice, using immunohistochemistry, quantitative rt-PCR and cell specific immunoflourescence markers. EndoG translocated from the cytoplasm to the nucleus as early as 4 h and with a significant increase in the number of EndoG positive nuclei at 12 and 24 h after MCA occlusion. Nuclear translocation of EndoG was observed in degenerating NeuN positive neurons that were evenly distributed throughout the developing infarct. Translocation of EndoG was supported by unaltered EndoG mRNA levels. EndoG was neither expressed in GFAP positive astrocytes nor in CD11b positive microglia/macrophages. In contrast, CD11b positive microglia, but not infiltrating CD11b positive bone marrow-derived macrophages, were shown to express activated caspase-3. The translocation of EndoG to the nucleus of neurons in the infarct implicates EndoG in ischemic neuronal degeneration after permanent MCA occlusion in mice. Increased knowledge about EndoG involvement in ischemic neuronal cell death in mice might offer a promise to control processes involved in neuronal cell death pathways in stroke.
核酸内切酶G（EndoG）是一种线粒体酶，已知在易位至细胞核后参与不依赖于半胱天冬酶的细胞死亡过程。在小鼠大脑中动脉（MCA）短暂闭塞后的缺血区域观察到了EndoG的核易位，但在MCA永久性闭塞后未观察到。在本研究中，我们使用免疫组织化学、定量逆转录聚合酶链反应（rt-PCR）和细胞特异性免疫荧光标记物，研究了小鼠MCA永久性闭塞后最初24小时内梗死皮层中EndoG的细胞和时间表达情况。EndoG最早在4小时就从细胞质易位至细胞核，在MCA闭塞后12小时和24小时，EndoG阳性细胞核的数量显著增加。在整个梗死灶中均匀分布的正在退化的NeuN阳性神经元中观察到了EndoG的核易位。EndoG mRNA水平未改变支持了EndoG的易位。EndoG在GFAP阳性星形胶质细胞和CD11b阳性小胶质细胞/巨噬细胞中均未表达。相反，CD11b阳性小胶质细胞而非浸润性CD11b阳性骨髓来源巨噬细胞显示表达活化的半胱天冬酶-3。EndoG易位至梗死灶中神经元的细胞核表明EndoG参与了小鼠MCA永久性闭塞后的缺血性神经元变性。对EndoG参与小鼠缺血性神经元细胞死亡的了解增加，可能为控制中风中神经元细胞死亡途径所涉及的过程带来希望。
