背景:已经形成共识,大脑中的神经回路是颞叶癫痫(TLE)的发病机理。特别是,在TLE的发展过程中,突触兴奋/抑制平衡(E/I平衡)与向高兴奋的转变有关。
方法:SpragueDawley(SD)大鼠腹膜内接受海藻酸(KA),制备TLE模型。接下来,脑电图(EEG)记录用于验证大鼠自发性复发性癫痫(SRS)的稳定性和可检测性。此外,使用免疫荧光评估大鼠和颞叶内侧癫痫(mTLE)患者的海马切片,以确定兴奋性和抑制性突触以及小胶质细胞吞噬作用的改变。
结果:我们发现KA在癫痫持续状态(SE)发作后14天诱导稳定的SRSs。此外,我们发现在癫痫发生过程中兴奋性突触持续增加,在玉米1(CA1)的辐射层(SR)中,囊泡谷氨酸转运蛋白1(vGluT1)的总面积大大增加,CA3的透明层(SL)和齿状回(DG)的多态层(PML)。相比之下,抑制性突触显著减少,随着SL和PML中谷氨酸脱羧酶65(GAD65)的总面积大大减少。此外,小胶质细胞在SRS形成后进行了活跃的突触吞噬作用,特别是在SL和PML。最后,在大鼠和人海马切片的反复发作期间,小胶质细胞优先修剪抑制性突触,这有助于海马亚区的突触改变。
结论:我们的发现详细表征了神经回路的改变,并证明了小胶质细胞介导的突触吞噬作用的选择性,能加强对TLE发病机制的理解,为癫痫治疗提供潜在的治疗靶点。
A consensus has formed that neural circuits in the brain underlie the pathogenesis of temporal lobe epilepsy (TLE). In particular, the synaptic excitation/inhibition balance (E/I balance) has been implicated in shifting towards elevated excitation during the development of TLE.
Sprague Dawley (SD) rats were intraperitoneally subjected to kainic acid (KA) to generate a model of TLE. Next, electroencephalography (EEG) recording was applied to verify the stability and detectability of spontaneous recurrent seizures (SRS) in rats. Moreover, hippocampal slices from rats and patients with mesial temporal lobe epilepsy (mTLE) were assessed using immunofluorescence to determine the alterations of excitatory and inhibitory synapses and microglial phagocytosis.
We found that KA induced stable SRSs 14 days after status epilepticus (SE) onset. Furthermore, we discovered a continuous increase in excitatory synapses during epileptogenesis, where the total area of vesicular glutamate transporter 1 (vGluT1) rose considerably in the stratum radiatum (SR) of cornu ammonis 1 (CA1), the stratum lucidum (SL) of CA3, and the polymorphic layer (PML) of the dentate gyrus (DG). In contrast, inhibitory synapses decreased significantly, with the total area of glutamate decarboxylase 65 (GAD65) in the SL and PML diminishing enormously. Moreover, microglia conducted active synaptic phagocytosis after the formation of SRSs, especially in the SL and PML. Finally, microglia preferentially pruned inhibitory synapses during recurrent seizures in both rat and human hippocampal slices, which contributed to the synaptic alteration in hippocampal subregions.
Our findings elaborately characterize the alteration of neural circuits and demonstrate the selectivity of synaptic phagocytosis mediated by microglia in TLE, which could strengthen the comprehension of the pathogenesis of TLE and inspire potential therapeutic targets for epilepsy treatment.