Lee T H, Kato H, Chen S T, Kogure K, Itoyama Y
Second Department of Neurology, Chang Gung Memorial Hospital, Taipei, Taiwan.
Stroke. 1998 Aug;29(8):1687-96; discussion 1697. doi: 10.1161/01.str.29.8.1687.
In vitro studies have shown that nerve growth factor (NGF) is protective to cortical neurons against various insults. However, the role of NGF in relation to its high-affinity trkA receptor in the cortical neurons has not been well discussed. In this experiment, we studied the possible involvement of the NGF/receptor system in the ischemic injury of cortical neurons after focal cerebral ischemia in rats.
Male Wistar rats received right middle cerebral artery occlusion of 90 minutes' duration. The rats were decapitated at different reperfusion time points: hour 4 and days 1, 3, 7, and 14 of recirculation. Brain sections at the level of striatum were immunostained against NGF, trkA, glial fibrillary acidic protein (GFAP), and stress protein HSP70. Double immunostaining against NGF and GFAP was also performed. Optical density of NGF immunoreactivity in the ischemic and nonischemic cortexes was compared between sham-control and ischemic animals.
In the sham-control rats, NGF immunoreactivity was present in the cortical and striatal neurons. However, beginning at hour 4 after recirculation, there was a significant decrease of NGF in the ischemic cortex and striatum. Beginning at day 1, NGF was absent completely in the infarcted striatum and cortex. However, in the peri-infarct penumbra area, despite a decrease in NGF at hour 4 and day 1, NGF recovered beginning at day 3 and returned almost to the sham-control level at day 14. In the nonischemic cortex, NGF increased beginning at hour 4, peaked at day 7, and returned almost to the sham-control level at day 14. The trkA and HSP70 immunoreactivities were not present in the sham-control cortex. However, trkA was induced at hour 4 in the ischemic cortex and at days 1 and 3 in the peri-infarct penumbra cortex. The HSP70 was induced at days 1 and 3 in the peri-infarct penumbra area. Double immunostaining showed that the number of GFAP-positive cells increased gradually, and NGF immunoreactivity in the GFAP-positive cells became gradually intense after ischemia.
Our study demonstrated a temporal profile of NGF and trkA in the ischemic cortex and NGF expression by reactive astrocytes. Our data suggest that the NGF/receptor system may play a role in the astrocyte/neuron interaction under certain pathological conditions, such as focal cerebral ischemia.
体外研究表明，神经生长因子（NGF）对皮质神经元免受各种损伤具有保护作用。然而，NGF及其高亲和力trkA受体在皮质神经元中的作用尚未得到充分讨论。在本实验中，我们研究了NGF/受体系统在大鼠局灶性脑缺血后皮质神经元缺血性损伤中的可能作用。
雄性Wistar大鼠接受右侧大脑中动脉90分钟的闭塞。在不同的再灌注时间点（再循环4小时及再循环后第1、3、7和14天）将大鼠断头。对纹状体水平的脑切片进行针对NGF、trkA、胶质纤维酸性蛋白（GFAP）和应激蛋白HSP70的免疫染色。还进行了针对NGF和GFAP的双重免疫染色。比较假手术对照组和缺血动物的缺血和非缺血皮质中NGF免疫反应性的光密度。
在假手术对照组大鼠中，皮质和纹状体神经元中存在NGF免疫反应性。然而，再循环后4小时开始，缺血皮质和纹状体中的NGF显著减少。从第1天开始，梗死纹状体和皮质中NGF完全缺失。然而，在梗死周围半暗带区域，尽管在4小时和第1天NGF减少，但从第3天开始NGF恢复，并在第14天几乎恢复到假手术对照组水平。在非缺血皮质中，NGF从4小时开始增加，在第7天达到峰值，并在第14天几乎恢复到假手术对照组水平。假手术对照组皮质中不存在trkA和HSP70免疫反应性。然而，缺血皮质在4小时诱导出trkA，梗死周围半暗带皮质在第1天和第3天诱导出trkA。梗死周围半暗带区域在第1天和第3天诱导出HSP70。双重免疫染色显示，缺血后GFAP阳性细胞数量逐渐增加，GFAP阳性细胞中的NGF免疫反应性逐渐增强。
我们的研究证明了缺血皮质中NGF和trkA的时间变化情况以及反应性星形胶质细胞对NGF的表达。我们的数据表明，NGF/受体系统可能在某些病理条件下，如局灶性脑缺血，在星形胶质细胞/神经元相互作用中发挥作用。
