Serdar Meray, Herz Josephine, Kempe Karina, Winterhager Elke, Jastrow Holger, Heumann Rolf, Felderhoff-Müser Ursula, Bendix Ivo
Department of Pediatrics I, Neonatology, University Hospital, University Duisburg-Essen, Essen, Germany.
Imaging Center Essen, EM Unit, University Hospital Essen, University Duisburg-Essen, Essen, Germany.
Front Neurol. 2018 Mar 21;9:175. doi: 10.3389/fneur.2018.00175. eCollection 2018.
Prematurely born infants are highly susceptible to various environmental factors, such as inflammation, drug exposure, and also high environmental oxygen concentrations. Hyperoxia induces perinatal brain injury affecting white and gray matter development. It is well known that mitogen-activated protein kinase signaling is involved in cell survival, proliferation, and differentiation. Therefore, we aim to elucidate cell-specific responses of neuronal overexpression of the small GTPase Ras on hyperoxia-mediated brain injury. Six-day-old (P6) Ras mice (neuronal Ras overexpression under the synapsin promoter) or wild-type littermates were kept under hyperoxia (80% oxygen) or room air (21% oxygen) for 24 h. Apoptosis was analyzed by Western blot of cleaved Caspase-3 and neuronal and oligodendrocyte degeneration immunohistochemistry. Short-term differentiation capacity of oligodendrocytes was assessed by quantification of myelin basic protein expression at P11. Long-lasting changes of hyperoxia-induced alteration of myelin structures were evaluated transmission electron microscopy in young adult animals (P42). Western blot analysis of active Caspase-3 demonstrates a significant upregulation in wild-type littermates exposed to hyperoxia whereas Ras mice did not show any marked alteration of cleaved Caspase-3 protein levels. Immunohistochemistry revealed a protective effect of neuronal Ras overexpression on neuron and oligodendrocyte survival. Hyperoxia-induced hypomyelination in wild-type littermates was restored in Ras mice. These short-term protective effects through promotion of neuronal survival translated into long-lasting improvement of ultrastructural alterations of myelin sheaths in mice with neuronal overexpression of Ras compared with hyperoxic wild-type mice. Our data suggest that transgenic increase of neuronal Ras activity in the immature brain results in secondary protection of oligodendrocytes from hyperoxia-induced white matter brain injury.
早产婴儿极易受到各种环境因素的影响，如炎症、药物暴露以及高环境氧浓度。高氧会导致围产期脑损伤，影响白质和灰质的发育。众所周知，丝裂原活化蛋白激酶信号通路参与细胞存活、增殖和分化。因此，我们旨在阐明小GTPase Ras在神经元中过表达对高氧介导的脑损伤的细胞特异性反应。将6日龄（P6）的Ras小鼠（在突触素启动子下神经元Ras过表达）或野生型同窝小鼠置于高氧（80%氧气）或室内空气（21%氧气）环境中24小时。通过裂解的Caspase-3的蛋白质印迹分析细胞凋亡，并通过免疫组织化学分析神经元和少突胶质细胞变性。通过定量P11时髓鞘碱性蛋白的表达来评估少突胶质细胞的短期分化能力。在年轻成年动物（P42）中，通过透射电子显微镜评估高氧诱导的髓鞘结构改变的长期变化。活性Caspase-3的蛋白质印迹分析表明，暴露于高氧的野生型同窝小鼠中其表达显著上调，而Ras小鼠中裂解的Caspase-3蛋白水平未显示任何明显变化。免疫组织化学显示神经元Ras过表达对神经元和少突胶质细胞的存活具有保护作用。Ras小鼠恢复了野生型同窝小鼠中高氧诱导的髓鞘形成不足。与高氧野生型小鼠相比，这些通过促进神经元存活产生的短期保护作用转化为Ras神经元过表达小鼠髓鞘超微结构改变的长期改善。我们的数据表明，未成熟大脑中神经元Ras活性的转基因增加可导致少突胶质细胞免受高氧诱导的白质脑损伤的继发性保护。
