Rau Shane W, Dubal Dena B, Böttner Martina, Wise Phyllis M
Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky 40536, USA.
J Neurosci. 2003 Nov 19;23(33):10487-94. doi: 10.1523/JNEUROSCI.23-33-10487.2003.
Estrogen replacement therapy enhances mood, delays cognitive decline, and reduces the risk of neurodegeneration. Our laboratory has shown previously that pretreatment with low physiological levels of estradiol protects against middle cerebral artery occlusion (MCAO)-induced brain injury during late phases of neuronal cell death. Immediate early genes (IEGs) are induced by various forms of brain injury, and their induction is known to be a critical step in programmed cell death. The current study tested the hypothesis that the ability of estradiol to reduce MCAO-induced cell death involves attenuation of expression of one or more IEGs. We examined the effects of MCAO on the temporospatial pattern of IEG expression and the modulation of this pattern by estradiol replacement. Rats were ovariectomized and treated with either vehicle or low physiological concentrations of estradiol. One week later, rats underwent MCAO and brains were collected 1, 4, 8, 16, and 24 hr later. We assessed IEG mRNAs in discrete regions of brain by RT-PCR at 24 hr. We examined expression of c-Fos mRNA and protein in greater detail using in situ hybridization and immunohistochemistry to delineate the time course and specific regions of cortex in which estradiol influenced its expression. Our results reveal that c-fos, fosB, c-jun, and junB levels were upregulated at 24 hr. Furthermore, estradiol selectively affected the expression of c-Fos mRNA and protein by attenuating the injury-induced increase in a time- and region-specific manner. Our findings strongly suggest that the ability of estradiol to protect against MCAO-induced cell death involves attenuation of c-Fos induction.
雌激素替代疗法可改善情绪、延缓认知衰退并降低神经退行性变的风险。我们实验室先前已表明，用低生理水平的雌二醇进行预处理可在神经元细胞死亡的后期阶段预防大脑中动脉闭塞（MCAO）诱导的脑损伤。即刻早期基因（IEGs）可由多种形式的脑损伤诱导产生，并且已知它们的诱导是程序性细胞死亡中的关键步骤。当前研究检验了这样一个假设，即雌二醇减少MCAO诱导的细胞死亡的能力涉及一种或多种即刻早期基因表达的减弱。我们研究了MCAO对即刻早期基因表达的时空模式的影响以及雌二醇替代对这种模式的调节作用。将大鼠去卵巢，并用赋形剂或低生理浓度的雌二醇进行处理。一周后，对大鼠进行大脑中动脉闭塞手术，并在术后1、4、8、16和24小时收集大脑。我们在24小时时通过逆转录聚合酶链反应（RT-PCR）评估大脑离散区域中的即刻早期基因信使核糖核酸（mRNAs）。我们使用原位杂交和免疫组织化学更详细地研究了c-Fos信使核糖核酸和蛋白质的表达，以描绘雌二醇影响其表达的时间进程和皮质的特定区域。我们的结果显示，在24小时时c-fos、fosB、c-jun和junB水平上调。此外，雌二醇通过以时间和区域特异性方式减弱损伤诱导的增加，选择性地影响c-Fos信使核糖核酸和蛋白质的表达。我们的研究结果强烈表明，雌二醇预防MCAO诱导的细胞死亡的能力涉及c-Fos诱导的减弱。
