Activation of microglia by secreted amyloid precursor protein evokes release of glutamate by cystine exchange and attenuates synaptic function
Activation of microglia by secreted amyloid precursor protein evokes release of glutamate by cystine exchange and attenuates synaptic function
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DOI：
10.1046/j.1471-4159.2001.00075.x
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发表时间：
2001-02-01
影响因子：
4.7
通讯作者：
Basile, AS
中科院分区：
文献类型：
--
作者：
Barger, SW;Basile, AS
作为慢性炎症反应的一部分，小胶质细胞活化是阿尔茨海默病的重要组成部分。先前发现分泌形式的P-淀粉样前体蛋白（sAPP）激活小胶质细胞，提高其神经毒性潜力。为了探索神经毒性机制，我们分析了小胶质细胞条件培养基中可以激活谷氨酸受体的药物。由sAPP激活的原代大鼠小胶质细胞的条件培养基引起海马神经元中的钙升高，而未经处理的小胶质细胞的培养基则没有。这种反应是敏感的NMDA受体拮抗剂，氨基磷酸戊酸。通过HPLC对条件化的小胶质细胞的分析揭示了暴露于sAPP的培养物中显著更高浓度的谷氨酸。实际上，sAPP处理的培养物中的谷氨酸水平显著高于用淀粉样蛋白P-肽处理的培养物中的谷氨酸水平。这种sAPP诱发的谷氨酸释放被完全阻断抑制的胱氨酸谷氨酸逆向转运蛋白的α-氨基己二酸或使用胱氨酸的培养基。此外，亚致死浓度的sAPP损害小胶质细胞-神经元共培养物中的突触密度，如神经元连接测定所证明的。最后，通过神经元型一氧化氮合酶（N-G-丙基-L-精氨酸）或诱导型一氧化氮合酶（1400 W）的抑制剂，在小胶质细胞-神经元共培养物中由sAPP诱发的神经毒性被减弱。总之，这些数据表明，通过sAPP激活的小胶质细胞释放兴奋性毒性水平的谷氨酸，可能是由于小胶质细胞内的自保护性抗氧化剂谷胱甘肽产生，最终导致突触变性和神经元死亡。
Microglial activation as part of a chronic inflammatory response is a prominent component of Alzheimer's disease. Secreted forms of the P-amyloid precursor protein (sAPP) previously were found to activate microglia, elevating their neurotoxic potential. To explore neurotoxic mechanisms, we analyzed microglia-conditioned medium for agents that could activate glutamate receptors. Conditioned medium from primary rat microglia activated by sAPP caused a calcium elevation in hippocampal neurons, whereas medium from untreated microglia did not. This response was sensitive to the NMDA receptor antagonist, aminophosphonovaleric acid. Analysis of microglia-conditioned by HPLC revealed dramatically higher concentrations of glutamate in cultures exposed to sAPP. Indeed, the glutamate levels in sAPP-treated cultures were substantially higher than those in cultures treated with amyloid p-peptide. This sAPP-evoked glutamate release was completely blocked by inhibition of the cystineglutamate antiporter by alpha -aminoadipate or use of cystine-free medium. Furthermore, a sublethal concentration of sAPP compromised synaptic density in microglia-neuron cocultures, as evidenced by neuronal connectivity assay. Finally, the neurotoxicity evoked by sAPP in microglia-neuron cocultures was attenuated by inhibitors of either the neuronal nitric oxide synthase (N-G-propyl-L-arginine)or inducible nitric oxide synthase (1400 W). Together, these data indicate a scenario by which microglia activated by sAPP release excitotoxic levels of glutamate, probably as a consequence of autoprotective antioxidant glutathione production within the microglia, ultimately causing synaptic degeneration and neuronal death.