Lu Kwok-Tung, Huang Tai-Chun, Tsai Ya-Hsin, Yang Yi-Ling
Department of Life Science, National Taiwan Normal University, Taipei, Taiwan.
Institute of Biochemical Science and Technology, National Chia-Yi University, Chia-Yi, Taiwan.
J Neurochem. 2017 Mar;140(5):718-727. doi: 10.1111/jnc.13920.
Na -K -2Cl co-transporter (NKCC1) plays an important role in traumatic brain injury (TBI)-induced brain edema via the MAPK cascade. The transient receptor potential vanilloid type 4 (TRPV4) channel participates in neurogenic inflammation, pain transmission, and edema. In this study, we investigated the relationship between NKCC1 and TRPV4 and the related signaling pathways in TBI-induced brain edema and neuronal damage. TBI was induced by the calibrated weight-drop device. Adult male Wistar rats were randomly assigned into sham and experimental groups for time-course studies of TRPV4 expression after TBI. Hippocampal TRPV4, NKCC1, MAPK, and PI-3K cascades were analyzed by western blot, and brain edema was also evaluated among the different groups. Expression of hippocampal TRPV4 peaked at 8 h after TBI, and phosphorylation of the MAPK cascade and Akt was significantly elevated. Administration of either the TRPV4 antagonist, RN1734, or NKCC1 antagonist, bumetanide, significantly attenuated TBI-induced brain edema through decreasing the phosphorylation of MEK, ERK, and Akt proteins. Bumetanide injection inhibited TRPV4 expression, which suggests NKCC1 activation is critical to TRPV4 activation. Our results showed that hippocampal NKCC1 activation increased TRPV4 expression after TBI and then induced severe brain edema and neuronal damage through activation of the MAPK cascade and Akt-related signaling pathway.
钠-钾-2氯共转运体（NKCC1）通过丝裂原活化蛋白激酶（MAPK）级联反应在创伤性脑损伤（TBI）诱导的脑水肿中起重要作用。瞬时受体电位香草酸亚型4（TRPV4）通道参与神经源性炎症、疼痛传递和水肿形成。在本研究中，我们调查了TBI诱导的脑水肿和神经元损伤中NKCC1与TRPV4之间的关系以及相关信号通路。采用校准的重物坠落装置诱导TBI。成年雄性Wistar大鼠被随机分为假手术组和实验组，用于研究TBI后TRPV4表达的时间进程。通过蛋白质免疫印迹法分析海马TRPV4、NKCC1、MAPK和PI-3K级联反应，并评估不同组之间的脑水肿情况。海马TRPV4的表达在TBI后8小时达到峰值，MAPK级联反应和Akt的磷酸化显著升高。给予TRPV4拮抗剂RN1734或NKCC1拮抗剂布美他尼，通过降低MEK、ERK和Akt蛋白的磷酸化，显著减轻TBI诱导的脑水肿。注射布美他尼可抑制TRPV4表达，这表明NKCC1的激活对TRPV4的激活至关重要。我们的结果表明，海马NKCC1的激活在TBI后增加了TRPV4的表达，然后通过激活MAPK级联反应和Akt相关信号通路诱导严重的脑水肿和神经元损伤。
