Horiguchi Takashi, Kis Bela, Rajapakse Nishadi, Shimizu Katsuyoshi, Busija David W
Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC 27157-1083, USA.
Stroke. 2003 Apr;34(4):1015-20. doi: 10.1161/01.STR.0000063404.27912.5B. Epub 2003 Mar 20.
The role of mitochondrial ATP-sensitive potassium channels (mitoK(ATP)) in ischemic tolerance has been well documented in heart, but little work has been done in brain. To investigate the involvement of mitoK(ATP) activation in chemical preconditioning in brain, we examined the effect of 5-hydroxydecanoate (5-HD), a selective mitoK(ATP) blocker, on neurotoxin 3-nitropropionic acid (3-NPA)-induced ischemic tolerance to transient focal cerebral ischemia in rats.
Male Wistar rats were administrated 3-NPA (20 mg/kg IP; n=16) or vehicle (saline; n=16) 3 days before temporary occlusion (120 minutes) of the middle cerebral artery; 5-HD (40 mg/kg IP; n=16) was injected 20 minutes before 3-NPA administration. Infarct volumes were measured 4 days after reperfusion. To directly investigate whether chemical preconditioning activates mitoK(ATP), we tested the effect of prior incubation with 1 mmol/L 5-HD on 300 micromol/L 3-NPA-induced alterations of mitochondrial membrane potential (Delta(Psi)m) in cultured neurons and astrocytes using the fluorescent dye tetramethylrhodamine ethyl ester.
Treatment with 3-NPA exhibited a 16% reduction (P<0.05) and 23% reduction in infarct volume (P<0.01) for total brain and cortex, respectively. Pretreatment with 5-HD completely abolished the neuroprotective effect of chemical preconditioning. In cultured cells, 3-NPA resulted in mitochondrial depolarization. This change of Delta(Psi)m was completely blocked by 5-HD pretreatment.
These results strongly suggest that opening of mitoK(ATP) plays a key role as the trigger in the development of 3-NPA-induced ischemic tolerance in brain.
线粒体ATP敏感性钾通道（mitoK(ATP)）在心脏缺血耐受中的作用已有充分记载，但在脑方面的研究较少。为了研究mitoK(ATP)激活在脑化学预处理中的作用，我们检测了选择性mitoK(ATP)阻滞剂5-羟基癸酸（5-HD）对神经毒素3-硝基丙酸（3-NPA）诱导的大鼠短暂局灶性脑缺血缺血耐受的影响。
雄性Wistar大鼠在大脑中动脉临时闭塞（120分钟）前3天给予3-NPA（20mg/kg腹腔注射；n = 16）或溶剂（生理盐水；n = 16）；在给予3-NPA前20分钟注射5-HD（40mg/kg腹腔注射；n = 16）。再灌注4天后测量梗死体积。为了直接研究化学预处理是否激活mitoK(ATP)，我们使用荧光染料四甲基罗丹明乙酯检测了预先用1mmol/L 5-HD孵育对300μmol/L 3-NPA诱导的培养神经元和星形胶质细胞线粒体膜电位（ΔΨm）变化的影响。
3-NPA处理使全脑梗死体积减少16%（P<0.05），皮质梗死体积减少23%（P<0.01）。5-HD预处理完全消除了化学预处理的神经保护作用。在培养细胞中，3-NPA导致线粒体去极化。5-HD预处理完全阻断了ΔΨm的这种变化。
这些结果强烈表明mitoK(ATP)开放在3-NPA诱导的脑缺血耐受发展中作为触发因素起关键作用。
