Hubbard Jacqueline A, Szu Jenny I, Yonan Jennifer M, Binder Devin K
Department of Biochemistry and Molecular Biology, University of California, Riverside, USA.
Neuroscience Graduate Program, University of California, Riverside, USA.
Exp Neurol. 2016 Sep;283(Pt A):85-96. doi: 10.1016/j.expneurol.2016.05.003. Epub 2016 May 4.
Astrocytes regulate extracellular glutamate and water homeostasis through the astrocyte-specific membrane proteins glutamate transporter-1 (GLT1) and aquaporin-4 (AQP4), respectively. The role of astrocytes and the regulation of GLT1 and AQP4 in epilepsy are not fully understood. In this study, we investigated the expression of GLT1 and AQP4 in the intrahippocampal kainic acid (IHKA) model of temporal lobe epilepsy (TLE). We used real-time polymerase chain reaction (RT-PCR), Western blot, and immunohistochemical analysis at 1, 4, 7, and 30days after kainic acid-induced status epilepticus (SE) to determine hippocampal glial fibrillary acidic protein (GFAP, a marker for reactive astrocytes), GLT1, and AQP4 expression changes during the development of epilepsy (epileptogenesis). Following IHKA, all mice had SE and progressive increases in GFAP immunoreactivity and GFAP protein expression out to 30days post-SE. A significant initial increase in dorsal hippocampal GLT1 immunoreactivity and protein levels were observed 1day post SE and followed by a marked downregulation at 4 and 7days post SE with a return to near control levels by 30days post SE. AQP4 dorsal hippocampal protein expression was significantly downregulated at 1day post SE and was followed by a gradual return to baseline levels with a significant increase in ipsilateral protein levels by 30days post SE. Transient increases in GFAP and AQP4 mRNA were also observed. Our findings suggest that specific molecular changes in astrocyte glutamate transporters and water channels occur during epileptogenesis in this model, and suggest the novel therapeutic strategy of restoring glutamate and water homeostasis.
星形胶质细胞分别通过星形胶质细胞特异性膜蛋白谷氨酸转运体-1（GLT1）和水通道蛋白4（AQP4）来调节细胞外谷氨酸和水平衡。星形胶质细胞的作用以及GLT1和AQP4在癫痫中的调节机制尚未完全明确。在本研究中，我们调查了颞叶癫痫（TLE）海马内注射 kainic 酸（IHKA）模型中GLT1和AQP4的表达情况。我们在 kainic 酸诱导的癫痫持续状态（SE）后1、4、7和30天，使用实时聚合酶链反应（RT-PCR）、蛋白质免疫印迹法和免疫组织化学分析，以确定癫痫发生（癫痫形成）过程中海马胶质纤维酸性蛋白（GFAP，反应性星形胶质细胞的标志物）、GLT1和AQP4的表达变化。IHKA后，所有小鼠均出现SE，且GFAP免疫反应性和GFAP蛋白表达在SE后30天内逐渐增加。SE后1天，背侧海马GLT1免疫反应性和蛋白水平显著初始增加，随后在SE后4天和7天显著下调，到SE后30天恢复至接近对照水平。SE后1天，背侧海马AQP4蛋白表达显著下调，随后逐渐恢复至基线水平，到SE后30天同侧蛋白水平显著增加。还观察到GFAP和AQP4 mRNA的短暂增加。我们的研究结果表明，在该模型的癫痫形成过程中，星形胶质细胞谷氨酸转运体和水通道发生了特定的分子变化，并提示了恢复谷氨酸和水平衡的新治疗策略。
