脑组织缺血耐受性与凋亡相关基因NF-κB和caspase-3的表达研究

Study on the tolerance to cerebral ischemia and the expression of NF- κB and caspase-3

目的探讨脑缺血预处理引起的脑保护机制，为临床缺血性脑血管病的防治提供理论依据。方法48只健康雄性Sprague-Dawley（SD）大鼠（体重200～250g）随机分成3组：假手术组（n=16）、脑缺血预处理组（n=16）、脑缺血组（n=16）。假手术组：颈部正中切口暴露右侧颈总动脉后缝合皮肤。脑缺血预处理组：按Koizumi线栓法改良制成局灶-局灶脑缺血模型，先阻断大脑中动脉血流30min后恢复血流，再灌注24h，之后再阻断同侧大脑中动脉血流24h。脑缺血组：阻断大脑中动脉血流24h。分别观察3组动物的以下指标：按Bederson法进行神经功能评分；以干湿重法计算脑含水量，脑含水量（％）=（湿重-干重）／湿重；用免疫组织化学方法检测大鼠海马组织NF—κB和caspase-3的表达。结果（1）神经功能评分：假手术组、预处理组和脑缺血组分别为0分、（1．13±0．99）分和（2．25±0．89）分。各组间比较差异明显（P〈0．05）。（2）脑含水量测定：假手术组、预处理组和脑缺血组分别为（69．9±0．38）％、（75．5±0．54）％和（81．9±0．55）％，各组间比较差异明显（P〈0．05）。（3）基因表达检测（个／高倍视野）：假手术组、预处理组和脑缺血组NF-κB表达分别为11．2±2．59、25．4±3．78和38．6±7．67；假手术组、预处理组和脑缺血组caspase-3表达分别为0．8±0．84、27．2±3．42和37．8±4．49。预处理组NF—κB和caspase-3的表达均低于脑缺血组，而高于假手术组，各组间比较差异有显著性意义（P〈0．05）。结论脑缺血预处理后对再次缺血有保护作用，凋亡相关基因NF—κB和caspase-3表达的减少在这种脑保护机制中可能起重要作用。

Objective To investigate the brain protecting mechanism produced by ischemia preconditioning. Methods Forty - eight healthy male Sprague - Dawley （SD） rats （ weight 200 - 250 g） were randomly divided into 3 groups ： false operation group （n =16）, ischemia preconditioning group （n = 16）, and ischemia group （n = 16）. False operation group： sewing up the skin after exposing the common carotid artery （CCA） in the right side. Ischemia preconditioning group： a focal - focal cerebral ischemic model, adopting the thread embolism method according to Koizumi. Occluding middle cerebral artery（MCA） blood flow for 30 minutes, then reperfusing for 24 hours, after that, occluding MCA again for 24 hours. Ischemia group： occluding MCA directly for 24 hours. The following indexes in 3 groups were observed respectively： neurological function （according to Bederson method） ; the water content of brain （wet weight and dry weight method）, and the expression of NF - κB and caspase - 3 in hippocampal tissue of rats （ immunohistochemistry method）. Results （ 1 ） Thenerve functional scoring： false operation group, ischemia preconditioning group and ischemia group is respectively 0 point, （ 1.13 ± 0.99） points and （2.25 ± 0.89） points, the difference was significant （ P 〈 0.05）. （2） The water content of brain ： false operation group, ischemia preconditioning group and ischemia group is respectively （69.9 ± 0.38 ） %, （75.5 ± 0.54） % and （81.9 ± 0.55 ） %, the difference was significant （ P 〈 0.05 ）. （ 3 ） Detection of gene expression （ unit ： number/high power field ） ： the NF - κB expression in false operation group, ischemia preconditioning group and ischemia group is respectively 11.2 ± 2.59,25.4 ± 3.78 and 38.6 ± 7.67 ; the caspase - 3 expression in false operation group, ischemia preconditioning group and ischemia group is respectively 0.8 ± 0.84,27.2 ± 3.42 and 37.8 ± 4.49. The expressions of NF - κB and caspase - 3 in ischemia preconditioning group were lower than those in ischemia group, but higher than those in false operation group, the difference was significant （P 〈 0.05 ）. Conclusion Ischemia preconditioning could increase the tolerance obviously to severe ischemia injury later. The decreasing expression of genes related to apoptosis such as NF - κB and caspase - 3 might play an important role in this protecting mechanism of brain.