Controlled enzymatic production of astrocytic hydrogen peroxide protects neurons from oxidative stress via an Nrf2-independent pathway
Controlled enzymatic production of astrocytic hydrogen peroxide protects neurons from oxidative stress via an Nrf2-independent pathway
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星形胶质细胞过氧化氢的可控酶生成可通过一种不依赖于 Nrf2 的途径保护神经元免受氧化应激影响
DOI：
10.1073/pnas.1003996107
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发表时间：
2010-10-05
影响因子：
11.1
通讯作者：
Ratan, Rajiv R.
中科院分区：
文献类型：
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作者：
Haskew-Layton, Renee E.;Payappilly, Jimmy B.;Ratan, Rajiv R.
神经元依赖于它们与星形胶质细胞的代谢偶联来对抗氧化应激。转录因子核因子红细胞2相关因子2（Nrf 2）似乎对星形胶质细胞依赖性神经保护免受氧化损伤很重要。事实上，Nrf 2激活剂在中风、帕金森病和亨廷顿病模型中是有效的。然而，在星形胶质细胞中启动适应性神经保护级联反应的关键内源性信号，包括Nrf 2介导的基因表达的激活，仍然不清楚。过氧化氢（H（2）O（2））在细胞信号转导中起着重要作用，是星形胶质细胞适应性反应的一个有吸引力的候选介质。在这里，我们确定（i）H（2）O（2）在促进星形胶质细胞依赖性神经保护免受氧化应激中的重要性，以及（ii）H（2）O（2）在诱导星形胶质细胞Nrf 2激活中的相关性。为了控制与神经元共培养的星形胶质细胞胞质H（2）O（2）产生的持续时间和水平，我们在星形胶质细胞中选择性异源表达H（2）O（2）产生酶纤细红酵母D-氨基酸氧化酶（rgDAAO）。rgDAAO-星形胶质细胞暴露于D-丙氨酸导致H（2）O（2）的浓度依赖性产生。星形胶质细胞中7小时低水平的H（2）O（2）产生（类似于3.7 nmol.min.mg蛋白质）保护神经元免受氧化应激，但较高水平（类似于130 nmol.min.mg蛋白质）具有神经毒性。在没有直接暴露于星形胶质细胞衍生的H2 O2的情况下，神经保护作用也发生了，这表明星形胶质细胞的细胞内信号传导是一种特异性机制。Nrf 2的激活模拟了星形胶质细胞H2 O 2的作用，但H2 O 2诱导的保护作用不依赖于Nrf 2。星形胶质细胞蛋白酪氨酸磷酸酶抑制也保护神经元免于氧化死亡，这代表了H2 O2诱导的神经保护的一种可能机制。这些发现证明了rgDAAO在空间和时间上控制细胞内H（2）O（2）浓度以揭示独特的星形胶质细胞依赖性神经保护机制的实用性。
Neurons rely on their metabolic coupling with astrocytes to combat oxidative stress. The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) appears important for astrocyte-dependent neuroprotection from oxidative insults. Indeed, Nrf2 activators are effective in stroke, Parkinson disease, and Huntington disease models. However, key endogenous signals that initiate adaptive neuroprotective cascades in astrocytes, including activation of Nrf2-mediated gene expression, remain unclear. Hydrogen peroxide (H(2)O(2)) plays an important role in cell signaling and is an attractive candidate mediator of adaptive responses in astrocytes. Here we determine (i) the significance of H(2)O(2) in promoting astrocyte-dependent neuroprotection from oxidative stress, and (ii) the relevance of H(2)O(2) in inducing astrocytic Nrf2 activation. To control the duration and level of cytoplasmic H(2)O(2) production in astrocytes cocultured with neurons, we heterologously expressed the H(2)O(2)-producing enzyme Rhodotorula gracilis D-amino acid oxidase (rgDAAO) selectively in astrocytes. Exposure of rgDAAO-astrocytes to D-alanine lead to the concentration-dependent generation of H(2)O(2). Seven hours of low-level H(2)O(2) production (similar to 3.7 nmol.min.mg protein) in astrocytes protected neurons from oxidative stress, but higher levels (similar to 130 nmol.min.mg protein) were neurotoxic. Neuroprotection occurred without direct neuronal exposure to astrocyte-derived H(2)O(2), suggesting a mechanism specific to astrocytic intracellular signaling. Nrf2 activation mimicked the effect of astrocytic H(2)O(2) yet H(2)O(2)-induced protection was independent of Nrf2. Astrocytic protein tyrosine phosphatase inhibition also protected neurons from oxidative death, representing a plausible mechanism for H(2)O(2)-induced neuroprotection. These findings demonstrate the utility of rgDAAO for spatially and temporally controlling intracellular H(2)O(2) concentrations to uncover unique astrocyte-dependent neuroprotective mechanisms.