Department of Neuroscience, Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy.
Neurobiol Dis. 2013 Oct;58:102-14. doi: 10.1016/j.nbd.2013.03.006. Epub 2013 Mar 21.
Toll-like receptor 4 (TLR4) activation in neuron and astrocytes by High Mobility Group Box 1 (HMGB1) protein is a key mechanism of seizure generation. HMGB1 also activates the Receptor for Advanced Glycation Endproducts (RAGE), but it was unknown whether RAGE activation contributes to seizures or to HMGB1 proictogenic effects. We found that acute EEG seizures induced by 7ng intrahippocampal kainic acid (KA) were significantly reduced in Rage-/- mice relative to wild type (Wt) mice. The proictogenic effect of HMGB1 was decreased in Rage-/- mice, but less so, than in Tlr4-/- mice. In a mouse mesial temporal lobe epilepsy (mTLE) model, status epilepticus induced by 200ng intrahippocampal KA and the onset of the spontaneous epileptic activity were similar in Rage-/-, Tlr4-/- and Wt mice. However, the number of hippocampal paroxysmal episodes and their duration were both decreased in epileptic Rage-/- and Tlr4-/- mice vs Wt mice. All strains of epileptic mice displayed similar cognitive deficits in the novel object recognition test vs the corresponding control mice. CA1 neuronal cell loss was increased in epileptic Rage-/- vs epileptic Wt mice, while granule cell dispersion and doublecortin (DCX)-positive neurons were similarly affected. Notably, DCX neurons were preserved in epileptic Tlr4-/- mice. We did not find compensatory changes in HMGB1-related inflammatory signaling nor in glutamate receptor subunits in Rage-/- and Tlr4-/- naïve mice, except for ~20% NR2B subunit reduction in Rage-/- mice. RAGE was induced in neurons, astrocytes and microvessels in human and experimental mTLE hippocampi. We conclude that RAGE contributes to hyperexcitability underlying acute and chronic seizures, as well as to the proictogenic effects of HMGB1. RAGE and TLR4 play different roles in the neuropathologic sequelae developing after status epilepticus. These findings reveal new molecular mechanisms underlying seizures, cell loss and neurogenesis which involve inflammatory pathways upregulated in human epilepsy.
高迁移率族蛋白 B1（HMGB1）蛋白通过 Toll 样受体 4（TLR4）激活神经元和星形胶质细胞是引发癫痫发作的关键机制。HMGB1 还激活晚期糖基化终产物受体（RAGE），但尚不清楚 RAGE 激活是否与癫痫发作或 HMGB1 的致痫作用有关。我们发现，与野生型（Wt）小鼠相比，海马内注射 7ng 海人酸（KA）引起的急性 EEG 癫痫发作，在 Rage-/- 小鼠中明显减少。HMGB1 的致痫作用在 Rage-/- 小鼠中降低，但不如在 Tlr4-/- 小鼠中降低。在小鼠内侧颞叶癫痫（mTLE）模型中，海马内注射 200ng KA 诱导的癫痫持续状态和自发性癫痫活动的发作在 Rage-/-、Tlr4-/-和 Wt 小鼠中相似。然而，与 Wt 小鼠相比，癫痫发作的 Rage-/-和 Tlr4-/- 小鼠的海马阵发性发作次数及其持续时间均减少。所有癫痫发作的小鼠在新物体识别测试中与相应的对照小鼠相比均表现出相似的认知缺陷。与癫痫发作的 Wt 小鼠相比，癫痫发作的 Rage-/- 小鼠中 CA1 神经元细胞丢失增加，而颗粒细胞弥散和双皮质素（DCX）阳性神经元受到类似影响。值得注意的是，癫痫发作的 Tlr4-/- 小鼠中保留了 DCX 神经元。我们没有发现 Rage-/- 和 Tlr4-/- 未处理小鼠中与 HMGB1 相关的炎症信号或谷氨酸受体亚基发生代偿性变化，除了 Rage-/- 小鼠中 NR2B 亚基减少约 20%。在人类和实验性 mTLE 海马中，神经元、星形胶质细胞和微血管中均诱导了 RAGE。我们得出结论，RAGE 有助于急性和慢性癫痫发作下的过度兴奋，以及 HMGB1 的致痫作用。RAGE 和 TLR4 在癫痫持续状态后发展的神经病理学后果中发挥不同的作用。这些发现揭示了涉及人类癫痫中上调的炎症途径的癫痫发作、细胞丢失和神经发生的新分子机制。
