大鼠MCAO再灌注后不同皮质区HMGB1、NF-κB的时程表达及其意义

Time-course of HMGB1 and NF-κB Expression in Different Cortical Regions after MCAO Reperfusion in Rats

目的探讨大鼠局灶性脑缺血再灌注后不同皮质区HMGB1、NF-κB的动态变化及其意义。方法雄性SD大鼠72只,随机分为缺血后2、6、24、48、72h组以及假手术组(Sham)。线栓法制备大脑中动脉闭塞(MACO)再灌注模型,缺血时间2h。各时间点处死动物取脑,免疫组化染色检测不同时间点皮质核心区(CI)和皮质半暗带区(IP)中HMGB1、NF-κB的蛋白水平,并对两者进行相关分析,RT-PCR法检测上述两区相应时间点的HMGB1mRNA表达。结果 Sham组HMGB1的表达主要位于胞核,而NF-κB主要位于胞质。早在缺血后2h CI区即可见部分HMGB1胞质阳性的神经元,HMGB1胞质阳性表达在IP区数量较多,CI区相对较少。随着再灌注时间的延长,IP区HMGB1mRNA、HMGB1胞质阳性表达和NF-κB胞核阳性表达均呈先上升后下降的趋势,于24h达峰,且HMGB1的胞质阳性表达和NF-κB的胞核阳性表达呈明显正相关(r=0.742,P<0.001)。但在CI区,HMGB1mRNA、HMGB的胞质阳性表达呈先下降再上升,于24h降至最低,而NF-κB的胞核阳性表达于脑缺血后6h达峰,之后逐渐下降,72h又有上升趋势。结论 HMGB1/NF-κB通路可能参与了局灶性脑缺血再灌注后早期炎症介导的脑组织损伤,特别是在IP区,而针对此通路的靶向性治疗有望挽救半暗带。

Objective To explore the dynamic changes of NF - κB and HMGB1 expression in different cortical regions and its sig- nificance following focal cerebral ischemia - reperfusion in rats. Methods Seventy two male Sprague - Dawley were randomly divided in- to 6 groups which included sham group, and group of 2h, 6h, 24h, 48h, 72h after ischemia. The middle cerebral artery of rats were oc- cluded for two hours by using the intraluminal suture method and then recirculated. The animals were sacrificed and brains were removed at the indicated time points. The expression of HMGB1 and NF - κB were detected by immunohistochemistry in the cortical infarction（CI） and cortical penumbra （IP） at different time points, and the correlation was calculated between two items. HMGB1 mRNA were also de- tected by RT-PCR technique. Results In the Sham group, HMGB1 staining was mainly localized in the nucleus, but NF - κB was massively detected in the cytoplasm. It could found cytoplasm localization of HMGB1 expression in neurons as early as 2h of ischemia in CI. The high positive cells ratio of HMGB1 in IP was found, and lower ratio in CI. HMGBlmRNA, HMGB1 cytoplasmic expression and NF - κB nuclear expression in IP firstly increased and reached a peak at 24h, then decreased. There was positive correlation between the expression of HMGB1 and NF - κB protein（ r = 0. 742, P 〈 0. 001 ）. But HMGBlmRNA and HMGB1 cytoplasmic expression in CI firstly declined and failed the lowest at 24h, then gradually climbed. However, NF - κB nuclear expression reached a peak at 6h, then de- creased gradually, and had an upward trend at 72h. Conclusion HMGB1/NF - κB signaling pathway may contribute to the inflammation - mediated brain tissue damage in the early stages following focal cerebral ischemia - reperfusion, especially in IP. Targeted therapies of this pathway would be possible to save the penumbra.