Han Jun, Xu Hang-Hang, Chen Xiao-Long, Hu Hao-Ran, Hu Kun-Mei, Chen Zhi-Wu, He Guo-Wei
Drug Research and Development Center, School of Pharmacy, Third-Grade Pharmacology Laboratory of State, Administration of Traditional Chinese Medicine, Anhui Provincial Engineering Research Center for Polysaccharide Drugs, Wannan Medical College, Wuhu, Anhui, China.
Department of Pharmacology, School of Basic Medicine, Anhui Medical University, Hefei, Anhui 230031, China.
Evid Based Complement Alternat Med. 2018 Oct 11;2018:8919867. doi: 10.1155/2018/8919867. eCollection 2018.
Total flavonoids of Rhododendron (TFR) is extracted from Rhododendron, a herbal medicine widely used in China. The main components are flavone compounds such as warfarin, rutin, quercetin, and hyperoside. We investigated the role of TRPV4 channel in the TFR induced endothelium-dependent hyperpolarizing factor- (EDHF-) mediated responses against ischemia/reperfusion injury (IR) in cerebral IR (CIR) rats.
The morphological changes of cerebral cortex, the relaxation of cerebral basal artery (CBA), and cell membrane potential recording were studied in CIR rats. The outward potassium current in smooth muscle cell was recorded by whole-cell patch clamp recording. The protein expression of TRPV4, SKca, and IKca was determined. Confocal laser was used to measure the Ca fluorescence intensity.
After treatment with TFR, the number of pyramidal cells in brain tissue increased and the number of empty or lightly stained cells decreased and these effects were eliminated by using HC-067047, Apamin, or TRAM-34. TFR induced and EDHF-mediated dilatation and hyperpolarization in CBA were also attenuated by using these inhibitors. The increased outward current density elicited by TFR in acutely isolated CBA smooth muscle cells was abolished by using TRAM-34 and Apamin. TFR upregulated the protein expression of TRPV4, SKca, and IKca that was also eliminated by these inhibitors. Laser scanning showed that the increased mean fluorescence intensity of Ca by CIR was decreased by using TFR and that this effect was again eliminated by the above inhibitors.
We conclude that in the CBA of the CIR rats the protective effect of TFR on ischemic cerebrovascular injury may be related to the activation of the TRPV4 in both endothelium and smooth muscle by increasing its expression and activity. The activation of TRPV4 channel in the endothelium may be linked to the opening of endothelial IKca/SKca channels that induces EDHF-mediated relaxation and hyperpolarization in the smooth muscle cell. In addition, the activation of TRPV4 in the smooth muscle cell in CBA may be linked with the activation of BK channel through a TRPV4-dependent pathway, reduce Ca concentration in the cell, and relaxes the vessel. These findings may form a new therapeutic target for protection of ischemic brain injury and facilitate the use of Chinese medicine in brain protection.
杜鹃花总黄酮（TFR）是从杜鹃花中提取的，杜鹃花是中国广泛使用的一种草药。其主要成分是黄酮类化合物，如华法林、芦丁、槲皮素和金丝桃苷。我们研究了瞬时受体电位香草酸亚型4（TRPV4）通道在TFR诱导的内皮依赖性超极化因子（EDHF）介导的对脑缺血/再灌注损伤（IR）的反应中的作用，该损伤发生在脑缺血再灌注（CIR）大鼠中。
研究了CIR大鼠大脑皮质的形态变化、脑基底动脉（CBA）的舒张以及细胞膜电位记录。通过全细胞膜片钳记录平滑肌细胞的外向钾电流。测定TRPV4、小电导钙激活钾通道（SKca）和大电导钙激活钾通道（IKca）的蛋白表达。使用共聚焦激光测量钙荧光强度。
用TFR处理后，脑组织中锥体细胞数量增加，空泡或淡染细胞数量减少，而使用HC-067047、蜂毒明肽或TRAM-34可消除这些作用。使用这些抑制剂也减弱了TFR诱导的CBA中EDHF介导的舒张和超极化。使用TRAM-34和蜂毒明肽消除了TFR在急性分离的CBA平滑肌细胞中引起的外向电流密度增加。TFR上调了TRPV4、SKca和IKca的蛋白表达，而这些抑制剂也消除了这种上调。激光扫描显示，CIR引起的钙平均荧光强度增加通过使用TFR而降低，并且这种作用再次被上述抑制剂消除。
我们得出结论，在CIR大鼠的CBA中，TFR对缺血性脑血管损伤的保护作用可能与通过增加其表达和活性激活内皮细胞和平滑肌细胞中的TRPV4有关。内皮细胞中TRPV4通道的激活可能与内皮IKca/SKca通道的开放有关，后者诱导平滑肌细胞中EDHF介导的舒张和超极化。此外，CBA中平滑肌细胞中TRPV4的激活可能通过TRPV4依赖性途径与BK通道的激活有关，降低细胞内钙浓度并使血管舒张。这些发现可能形成保护缺血性脑损伤的新治疗靶点，并促进中药在脑保护中的应用。
