Institute of Physiology, Academy of Sciences of the Czech Republic, (v.v.i),Vídeňská 1083, 142 20 Prague 4, Czech Republic.
Exp Neurol. 2012 Jan;233(1):421-9. doi: 10.1016/j.expneurol.2011.11.009. Epub 2011 Nov 11.
The widely-held assumption was that oxidative stress does not occur during seizures in the immature brain. The major finding of the present study concerns evidence of oxidative stress in the brain of immature rats during seizures induced by DL-homocysteic acid. Seizures were induced in 12-day-old rats by bilateral intracerebroventricular infusion of DL-homocysteic acid (DL-HCA, 600 nmol/side) and oxidative stress was evaluated by in situ detection of superoxide anion (O(2)·(-)). Using hydroethidine (Het) method, the fluorescent signal of the oxidized products of Het (reflecting O(2)·(-) production) significantly increased (by 50%-60%) following 60 min lasting seizures in all the studied structures, namely CA1, CA3 and dentate gyrus of the hippocampus, cerebral cortex and thalamus. The enhanced O(2)·(-) production was substantially attenuated or completely prevented by substances providing an anticonvulsant effect, namely by a competitive NMDA receptor antagonist AP7, a highly selective and potent group II metabotropic glutamate receptor (mGluR) agonist 2R,4R-APDC and highly selective group III mGluR, subtype 8 agonist (S)-3,4-DCPG. Complete protection was achieved by two SOD mimetics Tempol and MnTMPYP which strongly suggest that the increased fluorescent signal reflects O(2)·(-) formation. In addition, both scavengers provided a partial protection against brain damage associated with the present model of seizures. Signs of neuronal degeneration, as evaluated by Fluoro-Jade B staining, were detected at 4h following the onset of seizures. The present findings thus suggest that the increased superoxide generation precedes neuronal degeneration and may thus play a causative role in neuronal injury. Occurrence of oxidative stress in brain of immature rats during seizures, as demonstrated in the present study, can have a clinical relevance for a novel approach to the treatment of epilepsy in children, suggesting that substances with antioxidant properties combined with the conventional therapies might provide a beneficial effect.
人们普遍认为，氧化应激不会在未成熟大脑的癫痫发作中发生。本研究的主要发现涉及到在由 DL-高半胱氨酸酸（DL-HCA）诱导的癫痫发作期间，未成熟大鼠大脑中氧化应激的证据。通过双侧侧脑室输注 DL-高半胱氨酸酸（DL-HCA，600nmol/侧）在 12 天大的大鼠中诱导癫痫发作，并通过原位检测超氧阴离子（O(2)·(-)）来评估氧化应激。使用羟乙基噻吩（Het）方法，在所有研究结构（即海马 CA1、CA3 和齿状回、大脑皮层和丘脑）中，持续 60 分钟的癫痫发作后，Het 的氧化产物的荧光信号显著增加（增加 50%-60%），反映了 O(2)·(-)的产生。通过提供抗惊厥作用的物质，即竞争性 NMDA 受体拮抗剂 AP7、高度选择性和有效的组 II 代谢型谷氨酸受体（mGluR）激动剂 2R，4R-APDC 和高度选择性组 III mGluR 亚型 8 激动剂（S）-3，4-DCPG，可显著减弱或完全阻止增强的 O(2)·(-)产生。两种 SOD 模拟物 Tempol 和 MnTMPYP 实现了完全保护，这强烈表明增加的荧光信号反映了 O(2)·(-)的形成。此外，两种清除剂均提供了对与本癫痫发作模型相关的脑损伤的部分保护。在用 Fluoro-Jade B 染色评估神经元变性的迹象时，在癫痫发作开始后 4 小时即可检测到。因此，本研究结果表明，超氧化物的产生增加先于神经元变性，因此可能在神经元损伤中起因果作用。本研究表明，在癫痫发作期间，未成熟大鼠大脑中发生氧化应激，这可能与儿童癫痫治疗的新方法具有临床相关性，表明具有抗氧化特性的物质与传统疗法相结合可能会产生有益的效果。
