Kinboshi Masato, Mukai Takahiro, Nagao Yuki, Matsuba Yusuke, Tsuji Yoshimi, Tanaka Shiho, Tokudome Kentaro, Shimizu Saki, Ito Hidefumi, Ikeda Akio, Inanobe Atsushi, Kurachi Yoshihisa, Inoue Seiji, Ohno Yukihiro
Laboratory of Pharmacology, Osaka University of Pharmaceutical Sciences, Osaka, Japan.
Department of Neurology, Wakayama Medical University, Wakayama, Japan.
Front Mol Neurosci. 2017 Dec 7;10:408. doi: 10.3389/fnmol.2017.00408. eCollection 2017.
Inwardly rectifying potassium (Kir) 4.1 channels in astrocytes regulate neuronal excitability by mediating spatial potassium buffering. Although dysfunction of astrocytic Kir4.1 channels is implicated in the development of epileptic seizures, the functional mechanisms of Kir4.1 channels in modulating epileptogenesis remain unknown. We herein evaluated the effects of Kir4.1 inhibition (blockade and knockdown) on expression of brain-derived neurotrophic factor (BDNF), a key modulator of epileptogenesis, in the primary cultures of mouse astrocytes. For blockade of Kir4.1 channels, we tested several antidepressant agents which reportedly bound to and blocked Kir4.1 channels in a subunit-specific manner. Treatment of astrocytes with fluoxetine enhanced BDNF mRNA expression in a concentration-dependent manner and increased the BDNF protein level. Other antidepressants (e.g., sertraline and imipramine) also increased the expression of BDNF mRNA with relative potencies similar to those for inhibition of Kir4.1 channels. In addition, suppression of Kir4.1 expression by the transfection of small interfering RNA (siRNA) targeting Kir4.1 significantly increased the mRNA and protein levels of BDNF. The BDNF induction by Kir4.1 siRNA transfection was suppressed by the MEK1/2 inhibitor U0126, but not by the p38 MAPK inhibitor SB202190 or the JNK inhibitor SP600125. The present results demonstrated that inhibition of Kir4.1 channels facilitates BDNF expression in astrocytes primarily by activating the Ras/Raf/MEK/ERK pathway, which may be linked to the development of epilepsy and other neuropsychiatric disorders.
星形胶质细胞中的内向整流钾通道（Kir）4.1通过介导空间钾缓冲来调节神经元兴奋性。尽管星形胶质细胞Kir4.1通道功能障碍与癫痫发作的发生有关，但Kir4.1通道在调节癫痫发生中的功能机制仍不清楚。我们在此评估了Kir4.1抑制（阻断和敲低）对小鼠星形胶质细胞原代培养物中脑源性神经营养因子（BDNF）表达的影响，BDNF是癫痫发生的关键调节因子。为了阻断Kir4.1通道，我们测试了几种据报道以亚基特异性方式结合并阻断Kir4.1通道的抗抑郁药。用氟西汀处理星形胶质细胞以浓度依赖性方式增强了BDNF mRNA表达并增加了BDNF蛋白水平。其他抗抑郁药（如舍曲林和丙咪嗪）也增加了BDNF mRNA的表达，其相对效力与抑制Kir4.1通道的效力相似。此外，通过转染靶向Kir4.1的小干扰RNA（siRNA）抑制Kir4.1表达显著增加了BDNF的mRNA和蛋白水平。Kir4.1 siRNA转染诱导的BDNF被MEK1/2抑制剂U0126抑制，但未被p38 MAPK抑制剂SB202190或JNK抑制剂SP600125抑制。目前的结果表明，抑制Kir4.1通道主要通过激活Ras/Raf/MEK/ERK途径促进星形胶质细胞中BDNF的表达，这可能与癫痫和其他神经精神疾病的发生有关。
