雌激素对去势MCAO雌性大鼠Wnt信号通路的影响

The Effects of Oestradiol on Wnt Signaling Pathway in Ovariectomized MCAO Female Rats Models

目的:研究外源性雌激素对去势雌性大鼠大脑中动脉阻塞(MCAO)模型经典Wnt信号通路的影响,探讨雌激素在局灶性脑缺血中发挥神经保护作用的机制。方法:选取SPF级3个月龄Wistar雌性大鼠60只,采用去势雌性大鼠脑缺血模型,随机分为3组,假手术组、模型组、雌激素组[(17β-雌二醇,皮下注射,300μg/(kg·d)],每组20只。2,3,5-三苯基四唑氮红(TTC)染色法评估脑梗死体积,免疫组织化学、蛋白质印迹法测定左侧大脑皮质结肠腺瘤样息肉病(APC)蛋白和β-连环蛋白的表达。结果:雌激素组梗死体积[(255.43±51.43)mm3]比模型组[(490.75±93.38)mm3]小,2组差异有统计学意义(t=5.565,P=0.001)。免疫组织化学结果提示模型组APC蛋白表达水平高于其他2组,差异有统计学意义(均P<0.05),雌激素组β-连环蛋白水平高于模型组(P<0.05),与假手术组比较差异无统计学意义(P>0.05)。蛋白质印迹法结果显示雌激素组APC蛋白表达低于模型组,β-连环蛋白的表达高于模型组,差异均有统计学意义(均P<0.05)。结论:补充外源性雌激素可以通过下调皮质区APC蛋白表达,激活经典Wnt信号通路,进而发挥在去势雌性大鼠局灶性脑缺血损伤中的神经保护作用,为绝经激素治疗降低围绝经期妇女缺血性脑损伤的临床应用提供参考依据。

Objective： To investigate the effects of oestradiol on the Wnt signaling pathway in the middle cerebral artery occlusion（MCAO） model of ovariectomized female Wistar rats, so as to explore the protective effect of estrogen on the central nervous system. Methods：Sixty female Wistar rats aged three months were randomly and equally divided as follows： sham operation group（without ovariectomy）, model group（ovariectomy）, estrogen-treated group [ovariectomy and estrogen replacement, 17β-estrogen, s.c. 300 μg/（kg·d）]. All rats were developed the model of MCAO with the previous protocol. The brain infarction area was measured with the TTC staining. The expressions of APC and β-catenin were evaluated by immunohistochemistry and western blot. Results：The estrogen-treated group had significantly less infarct volume than the model group [（255.43 ±51.43） mm^3versus（490.75±93.38） mm^3, t=5.565, P=0.001]. Immunohistochemical analysis showed that model group had an increased expression of APC compared with sham operation group and estrogen-treated group（P〈0.05）. The protein expression of β-catenin 24 h after MCAO in the cerebral cortex of estrogen-treated group was significantly increased compared with model group（P〈0.05）, and there was no significant difference compared with sham operation group（P0.05）. Western blotting analysis showed that the expression of APC was decreased in cortex of the estrogen-treated group, and that the expression of β-catenin was increased, when compared with the model group（P〈0.05）. Conclusions：Exogenous oestradiol decreased the APC level, and activate the Wnt/β-catenin signaling pathway, in the cortex of MCAO brain damage in those ovariectomized female rats, suggesting that the hormone replacement therapy plays a protective effect in the central nervous system of brain blood supply insufficiency.