CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-504, Coimbra, Portugal.
Institute for Interdisciplinary Research, University of Coimbra, 3030-789, Coimbra, Portugal.
Cell Death Dis. 2018 Feb 20;9(3):297. doi: 10.1038/s41419-018-0351-1.
Despite the characteristic etiologies and phenotypes, different brain disorders rely on common pathogenic events. Glutamate-induced neurotoxicity is a pathogenic event shared by different brain disorders. Another event occurring in different brain pathological conditions is the increase of the extracellular ATP levels, which is now recognized as a danger and harmful signal in the brain, as heralded by the ability of P2 receptors (P2Rs) to affect a wide range of brain disorders. Yet, how ATP and P2R contribute to neurodegeneration remains poorly defined. For that purpose, we now examined the contribution of extracellular ATP and P2Rs to glutamate-induced neurodegeneration. We found both in vitro and in vivo that ATP/ADP through the activation of P2Y1R contributes to glutamate-induced neuronal death in the rat hippocampus. We found in cultured rat hippocampal neurons that the exposure to glutamate (100 µM) for 30 min triggers a sustained increase of extracellular ATP levels, which contributes to NMDA receptor (NMDAR)-mediated hippocampal neuronal death through the activation of P2Y1R. We also determined that P2Y1R is involved in excitotoxicity in vivo as the blockade of P2Y1R significantly attenuated rat hippocampal neuronal death upon the systemic administration of kainic acid or upon the intrahippocampal injection of quinolinic acid. This contribution of P2Y1R fades with increasing intensity of excitotoxic conditions, which indicates that P2Y1R is not contributing directly to neurodegeneration, rather behaving as a catalyst decreasing the threshold from which glutamate becomes neurotoxic. Moreover, we unraveled that such excitotoxicity process began with an early synaptotoxicity that was also prevented/attenuated by the antagonism of P2Y1R, both in vitro and in vivo. This should rely on the observed glutamate-induced calpain-mediated axonal cytoskeleton damage, most likely favored by a P2Y1R-driven increase of NMDAR-mediated Ca entry selectively in axons. This may constitute a degenerative mechanism shared by different brain diseases, particularly relevant at initial pathogenic stages.
尽管具有特征性的病因和表型，但不同的脑部疾病依赖于共同的致病事件。谷氨酸诱导的神经毒性是不同脑部疾病的共同致病事件。另一个发生在不同脑病理条件下的事件是细胞外 ATP 水平的增加，现在被认为是大脑中的危险和有害信号，这预示着 P2 受体 (P2R) 能够影响广泛的脑部疾病。然而，ATP 和 P2R 如何导致神经退行性变仍未得到明确界定。为此，我们现在研究了细胞外 ATP 和 P2R 对谷氨酸诱导的神经退行性变的贡献。我们发现，无论是在体外还是体内，ATP/ADP 通过激活 P2Y1R 有助于大鼠海马区谷氨酸诱导的神经元死亡。我们发现，在培养的大鼠海马神经元中，暴露于谷氨酸（100µM）30 分钟会引发细胞外 ATP 水平的持续增加，这通过激活 P2Y1R 有助于 NMDA 受体（NMDAR）介导的海马神经元死亡。我们还确定 P2Y1R 参与体内的兴奋性毒性，因为 P2Y1R 的阻断显著减轻了系统给予海人酸或海马内注射喹啉酸后大鼠海马神经元的死亡。随着兴奋性毒性条件的强度增加，P2Y1R 的这种作用会逐渐减弱，这表明 P2Y1R 并非直接导致神经退行性变，而是作为一种催化剂降低谷氨酸变得神经毒性的阈值。此外，我们揭示了这种兴奋性毒性过程始于早期的突触毒性，这种毒性也可以通过 P2Y1R 的拮抗作用来预防/减轻，无论是在体外还是体内。这可能依赖于观察到的谷氨酸诱导的钙蛋白酶介导的轴突细胞骨架损伤，这很可能是由 P2Y1R 驱动的 NMDAR 介导的 Ca 内流选择性增加在轴突中引起的。这可能是不同脑部疾病共有的退行性机制，在初始发病阶段尤为重要。
