Neuroprotective effect of cyosporinA. (Study for mitochordrial permeability transition pore and cytochromeC)

本研究采用mdrla基因敲除（KO）小鼠局灶缺血模型研究环孢素A （CsA）对脑缺血的治疗作用，该模型缺乏p糖蛋白导致CsA容易通过血脑屏障（BBB）。首先建立FVB小鼠（野生型mdria基因敲除小鼠）局灶性缺血模型，再灌注时给予10mg/kg CsA可减小模型梗死面积。这是CsA对小鼠脑缺血的神经保护作用的第一个证据。在mdrla KO小鼠中，我们证明在再灌注后给予2mg/kg甚至1mg/kg CsA可显著减少梗死面积。这些结果表明，如果CsA到达脑实质，则具有强大的神经保护作用。有趣的是，10mg/kg CsA给药对mdrla KO小鼠局灶性缺血模型无效。10mg/kg CsA对mdala KO小鼠可能过高，因为CsA在大脑中的浓度可能异常高。然而，CsA对缺血再灌注损伤的保护机制尚不明确。采用CsA模型，用Western blot法检测再灌注时脑内细胞浆细胞色素C的变化。CsA 1mg/kg给药KO小鼠脑内胞浆细胞色素C低于对照小鼠。这一结果表明，CsA可以阻止线粒体的通透性、过渡孔的打开和细胞色素C的释放。

We investigated the efficacy of cyclosporin A (CsA) for brain ischemia using focal ischemic model of mdrla knockout (KO) mice which lacks p-glycoprotein resulting CsA easily pass through blood brain bomer (BBB). At first, we made focal ischemic model of FVB mice (wild type of mdria knockout mice), then 10mg/kg CsA administered during reperfusion, diminishes infarct size in the model. This result is the first evidence of CsA's neuroprotective effect in mice brain ischemia. In mdrla KO mice, we demonstrate 2mg/kg and even 1mg/kg CsA significantly reduce infarct size when administered after reperfusion. These results suggest that CsA has potent neuroprotective effect, if it reaches brain parenchyma. Interestingly, 10mg/kg CsA administration is not effective in focal ischemic model of mdrla KO mice. 10mg/kg CsA may be too much for mdala KO mice because CsA concentration in the brain is possibly unusually high. The mechanism whereby CsA is protective in ischemia-reperfusion damage is however equivocal. Using our CsA model of mdria KO mice, cytosolic cytochrome C in the brain was analyzed by Western blot during reperfusion. Cytosolic cytochrome C in CsA 1mg/kg administrated KO mice brain was lower than that of vehicle administrated mice. This result suggests that CsA prevents mitochondrial permeability transition pore opening, and release of cytochrome C from the pore.