Gu Yan-ting, Xue Yi-xue, Wang Yan-feng, Wang Jin-hui, Chen Xia, ShangGuan Qian-ru, Lian Yan, Zhong Lei, Meng Ying-nan
Department of Physiology, Life Science and Biology Pharmacopedia Institution, Shenyang Pharmaceutical University, Shenyang 110016, Liaoning Province, PR China.
Department of Neurobiology, College Basic of Medicine, China Medical University, Shenyang 110001, Liaoning Province, PR China.
Neuropharmacology. 2013 Dec;75:407-15. doi: 10.1016/j.neuropharm.2013.08.004. Epub 2013 Aug 23.
Adenosine 5'-triphosphate-sensitive potassium channel (KATP channel) activator, minoxidil sulfate (MS), can selectively increase the permeability of the blood-tumor barrier (BTB); however, the mechanism by which this occurs is still under investigation. Using a rat brain glioma (C6) model, we first examined the expression levels of occludin and claudin-5 at different time points after intracarotid infusion of MS (30 μg/kg/min) by western blotting. Compared to MS treatment for 0 min group, the protein expression levels of occludin and claudin-5 in brain tumor tissue of rats showed no changes within 1 h and began to decrease significantly after 2 h of MS infusion. Based on these findings, we then used an in vitro BTB model and selective inhibitors of diverse signaling pathways to investigate whether reactive oxygen species (ROS)/RhoA/PI3K/PKB pathway play a key role in the process of the increase of BTB permeability induced by MS. The inhibitor of ROS or RhoA or PI3K or PKB significantly attenuated the expression of tight junction (TJ) protein and the increase of the BTB permeability after 2 h of MS treatment. In addition, the significant increases in RhoA activity and PKB phosphorylation after MS administration were observed, which were partly inhibited by N-2-mercaptopropionyl glycine (MPG) or C3 exoenzyme or LY294002 pretreatment. The present study indicates that the activation of signaling cascades involving ROS/RhoA/PI3K/PKB in BTB was required for the increase of BTB permeability induced by MS. Taken together, all of these results suggested that MS might increase BTB permeability in a time-dependent manner by down-regulating TJ protein expression and this effect could be related to ROS/RhoA/PI3K/PKB signal pathway.
5'-三磷酸腺苷敏感性钾通道（KATP通道）激活剂硫酸米诺地尔（MS）可选择性增加血脑肿瘤屏障（BTB）的通透性；然而，其发生机制仍在研究中。我们使用大鼠脑胶质瘤（C6）模型，首先通过蛋白质印迹法检测颈内动脉输注MS（30μg/kg/min）后不同时间点紧密连接蛋白occludin和claudin-5的表达水平。与MS处理0分钟组相比，大鼠脑肿瘤组织中occludin和claudin-5的蛋白表达水平在1小时内无变化，MS输注2小时后开始显著下降。基于这些发现，我们随后使用体外BTB模型和多种信号通路的选择性抑制剂，研究活性氧（ROS）/RhoA/PI3K/PKB通路是否在MS诱导的BTB通透性增加过程中起关键作用。ROS或RhoA或PI3K或PKB的抑制剂显著减弱了MS处理2小时后紧密连接（TJ）蛋白的表达和BTB通透性的增加。此外，观察到MS给药后RhoA活性和PKB磷酸化显著增加，N-2-巯基丙酰甘氨酸（MPG）或C3外切酶或LY294002预处理可部分抑制这种增加。本研究表明，BTB中涉及ROS/RhoA/PI3K/PKB的信号级联激活是MS诱导BTB通透性增加所必需的。综上所述，所有这些结果表明，MS可能通过下调TJ蛋白表达以时间依赖性方式增加BTB通透性，且这种作用可能与ROS/RhoA/PI3K/PKB信号通路有关。
