Visualization of calcium signals in acute thromboembolic model of stroke

细胞内钙离子的增加在生命功能的处理中起着关键作用。细胞的坏死和凋亡都是由钙离子通过质膜内流引起的。缺血和创伤等刺激可增加钙离子通过质膜的通透性。细胞内钙离子的升高激活了各种蛋白水解酶和半胱氨酸氨基转移酶。如果钙离子水平高到足以导致细胞功能障碍，就可能发生细胞凋亡或坏死。人们可以推测，细胞死亡可以通过抑制钙超载来防止。然而，脑缺血时钙信号的分布尚未被证实。我们开发了一种新的方法来检测血栓栓塞性缺血后大鼠大脑皮层的钙信号。暴露大鼠大脑皮层预先负载Fra-2 AM，然后静脉注射Rose Bengal。用540 nm波长绿光照射大脑中动脉近端，形成血栓。然后，用340和380 nm光交替照射缺血大脑皮层发出化学发光。化学发光强度在交替照射后60min达到峰值。病理检查证实，缺血中心区钙信号最强。缺血半暗带钙信号中等。正常大脑皮质未见钙信号。缺血半暗区被认为是从细胞死亡中拯救出来的治疗靶点。综上所述，我们首次在体内证实了缺血大脑皮层中的钙信号。

The increase in intracellular calcium ion plays a pivotal in processing vital function. Both necrosis and apoptosis are triggered by the influx of calcium ion via plasma membrane. The stimuli, such as ischemia and trauma, enhance permeability of calcium ion through plasma membrane. The elevation of intracellular calcium ion activates various proteolytic enzymes and caspases. If the calcium ion level reaches high enough to cause cell dysfunction, either apoptosis or necrosis may be programmed. One can surmise that cell death may be prevented by the inhibition of calcium overload. However, distribution of calcium signals during cerebral ischemia has not yet been demonstrated. We developed a novel method to detect calcium signals in the rat cerebral cortex after thromboembolic ischemia. Exposed rat cerebral cortex was preloaded with fra-2 AM, then Rose Bengal was injected intravenously. The proximal middle cerebral artery was irradiated producing thrombosis with 540 nm wavelength green light. Thereafter, ischemic cerebral cortex was alternatively irradiated with 340 and 380 nm light to emit chemiluminescence. The intensity of chemiluminescence took a peak at 60 minutes after the alternative irradiation. The highest calcium signals occurred in ischemic core which was proved by the pathological examination. In ischemic penumbra calcium signal was moderate. No calcium signal was demonstrated in normal cortex. The region of ischemic penumbra deemed a therapeutic target of rescue from cell death. In conclusion, we demonstrated for the first time calcium signals in the ischemic cerebral cortex in vivo.