Department of Neuropsychiatry, Division of Neuroscience, Graduate School of Medicine, Mie University, Tsu, Mie 514-8507, Japan.
Biomed Pharmacother. 2021 Jun;138:111462. doi: 10.1016/j.biopha.2021.111462. Epub 2021 Mar 8.
The antiepileptic/anticonvulsive action of brivaracetam is considered to occur via modulation of synaptic vesicle protein 2A (SV2A); however, the pharmacological mechanisms of action have not been fully characterised. To explore the antiepileptic/anticonvulsive mechanism of brivaracetam associated with SV2A modulation, this study determined concentration-dependent effects of brivaracetam on astroglial L-glutamate release associated with connexin43 (Cx43), tumour-necrosis factor-α (TNFα) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/glutamate receptor of rat primary cultured astrocytes using ultra-high-performance liquid chromatography. Furthermore, interaction among TNFα, elevated extracellular K and brivaracetam on expression of SV2A and Cx43 was determined using capillary immunoblotting. TNFα and elevated extracellular K predominantly enhanced astroglial L-glutamate release associated with respective AMPA/glutamate receptor and hemichannel. These effects were enhanced by a synergistic effect of TNFα and elevated extracellular K in combination. The activation of astroglial L-glutamate release, and expression of SV2A and Cx43 in the plasma membrane was suppressed by subchronic brivaracetam administration but were unaffected by acute administration. These results suggest that migration of SV2A to the astroglial plasma membrane by hyperexcitability activates astroglial glutamatergic transmission, perhaps via hemichannel activation. Subchronic brivaracetam administration suppressed TNFα-induced activation of AMPA/glutamate receptor and hemichannel via inhibition of ectopic SV2A. These findings suggest that combined inhibition of vesicular and ectopic SV2A functions contribute to the antiepileptic/anticonvulsive mechanism of brivaracetam action.
布瓦西坦的抗癫痫/抗惊厥作用被认为是通过调节突触囊泡蛋白 2A（SV2A）发生的；然而，其作用机制尚未完全阐明。为了探讨与 SV2A 调节相关的布瓦西坦的抗癫痫/抗惊厥机制，本研究采用超高效液相色谱法，测定了布瓦西坦浓度依赖性对原代培养大鼠星形胶质细胞缝隙连接蛋白 43（Cx43）、肿瘤坏死因子-α（TNFα）和 α-氨基-3-羟基-5-甲基-4-异恶唑丙酸（AMPA）/谷氨酸受体相关的 L-谷氨酸释放的影响。此外，采用毛细管免疫印迹法测定了 TNFα、细胞外高 K 和布瓦西坦对 SV2A 和 Cx43 表达的相互作用。TNFα 和细胞外高 K 主要增强与各自的 AMPA/谷氨酸受体和半通道相关的星形胶质细胞 L-谷氨酸释放。这些作用通过 TNFα 和细胞外高 K 的协同作用得到增强。慢性布瓦西坦给药可抑制 SV2A 和 Cx43 向星形胶质细胞膜的易位及星形胶质细胞 L-谷氨酸释放，但对急性给药无影响。这些结果表明，通过兴奋使 SV2A 向星形胶质细胞膜易位激活星形胶质细胞谷氨酸能传递，可能通过半通道激活。慢性布瓦西坦给药通过抑制异位 SV2A 抑制 TNFα 诱导的 AMPA/谷氨酸受体和半通道的激活。这些发现表明，囊泡和异位 SV2A 功能的联合抑制有助于布瓦西坦作用的抗癫痫/抗惊厥机制。
