低剂量雷公藤甲素抗颞叶癫痫作用的神经环路机制研究

Temporal lobe epilepsy (TLE) is easily resistant to antiepileptic drugs for the particularity and complexity of its underlying neural circuits, which is an important issue for the development of antiepileptic drugs and the clinical treatment of epilepsy. Funding by the National Natural Science Foundation of China, we found a novel “glutamatergic-GABAergic” antiepileptic circuit that mediated by entorhinal principal neuron in TLE mice, which indicate that it is necessary to study TLE and its treatments in a neuronal circuit level. On the other hand, the symptoms of TLE are similar as the “Feng-Xian” or “wind-epilepsy” according to traditional Chinese medicine theory, which is associated with “wind evil attacking the brain” and “stasis in the cerebral collaterals”. Triptolide is a major active component of extracts from the medicinal plant Tripterygium wilfordii Hook F. It can disperse the “wind evil” and “promoting blood circulation”, and hence it may be helpful to treatment of the “wind evil” and “promoting blood circulation” in TLE. In our pilot experiment, we found triptolide, at a very low dose, acted evident antiepileptic effect in mice and intractable rats TLE models. Moreover, by using electrophysiological recording, we found that triptolide adjusted hippocampal EEG rhythm, decreased the frequency and reduced the amplitude of epileptic discharges in TLE mice. However, triptolide did not affect the non-TLE seizures. These results suggest the anti-epileptic effect of triptolide may be related to the specific neuronal circuits in temporal lobe areas. Therefore, by using electrophysiology, optogenetics, genetic manipulation and other related technology methods, this project intends to illuminate the neuronal circuit mechanisms underlying the anti-epileptic effect of triptolide in TLE.

由于神经环路的特殊性，颞叶癫痫（TLE）极易对现有抗癫痫药物耐受，是癫痫临床治疗和药物研发的热点难题。申请人在青年基金资助下前期发现内嗅皮层与海马间存在一条由兴奋性谷氨酸能神经元介导的抗癫痫神经通路参与TLE发病，提示从神经环路水平研究TLE发病机制及其治疗的必要性。中医理论中TLE类似“风痫”，与“风邪上扰，脑络瘀阻”有关。雷公藤甲素是中药雷公藤的有效成分之一，具有祛风、活血通络等功效，或有助于干预“风邪”和“脑络瘀阻”。预实验发现低剂量雷公藤甲素在小鼠和耐药性大鼠TLE模型中具有良好的抗癫痫活性，电生理记录初步发现雷公藤甲素可以改善TLE小鼠海马脑电节律、降低海马痫样放电频率及幅度，但其对非TLE小鼠发作脑电没有明显作用，提示其作用可能具有神经环路特异性。因此，本项目拟利用电生理、光遗传学及基因干预等方法，阐明雷公藤甲素抗TLE作用及其调控神经环路机制。

颞叶癫痫易对抗癫痫药物耐受，其症状类似中医“风痫”，可能与“脑络瘀阻”有关。脑内炎症和脑神经环路的异化是颞叶癫痫的重要特征。雷公藤甲素(Triptolide)是中药材雷公藤中具有抗炎、免疫抑制的“祛风通络”功效的活性成分，可能兼具抗癫痫作用。本研究发现雷公藤甲素可以有效干预角膜点燃癫痫形成过程和大发作，并可以剂量依赖地干预红藻氨酸诱导的慢性颞叶癫痫小鼠自发发作和改善其认知功能，还可以降低海马炎症因子和抑制星形胶质细胞激活。但是，雷公藤甲素在正常小鼠最大电休克癫痫和戊四唑癫痫模型中没有急性抗癫痫作用。海马灶点内显微注射给予雷公藤甲素足以发挥抗颞叶癫痫作用，并且其抗癫痫作用特点为需一定的起效时间和存在长时程作用。在体微电极记录结合光遗传学发现，雷公藤甲素可以改善癫痫小鼠海马DG区的GABA能系统的“刹车”作用。利用膜片钳技术，初步还发现提高培养神经元动作电位阈值。但是，与抗癫痫作用类似，雷公藤甲素急性给药对海马DG区的GABA能系统的“刹车”作用和培养神经元动作电位阈值没有明显作用。利用网络药理学分析，进一步提示IL-1β可能是雷公藤甲素发挥抗癫痫作用的重要靶点，而直接海马内给予IL-1β确实可以削弱正常小鼠海马DG区的GABA能系统的“刹车”作用。同时，通过对相关临床研究和大样本人群数据的荟萃分析发现：（1）雷公藤甲素相关制剂在临床类风湿性关节炎治疗中具有良好的有效性和可接受的安全性；（2）类风湿性关节炎患者存在明显癫痫发病高风险。因此，本研究结果提示雷公藤甲素是一种潜在抗颞叶癫痫作用的活性中药单体。但出于安全性考虑，雷公藤甲素及相关制剂应谨慎使用，其可能更适于风湿病合并癫痫或难治性癫痫，后续可权衡利弊在类风湿性关节炎合并癫痫患者中开展临床研究进一步验证。