Marin R, Guerra B, Hernández-Jiménez J-G, Kang X-L, Fraser J D, López F J, Alonso R
Laboratory of Cellular Neurobiology, Department of Physiology, University of La Laguna, School of Medicine, 38071 Santa Cruz de Tenerife, Spain.
Neuroscience. 2003;121(4):917-26. doi: 10.1016/s0306-4522(03)00464-0.
The pathology of Alzheimer's disease includes amyloid-beta peptide aggregation that contributes to degeneration of cholinergic neurons. Even though the underlying molecular mechanisms remain unclear, recent in vitro evidence supports a protective role for estrogens against several neurotoxic agents. Here we report that, in a murine cholinergic cell line (SN56), the massive cell death induced by 1-40 fragment of amyloid-beta peptide was prevented by 17beta-estradiol through a mechanism that may involve estrogen receptor activation. The protective effect of estradiol was observed in a dose-dependent manner, and was completely blocked by the pure antiestrogen ICI 182,780. In contrast, the inactive isomer 17alpha-estradiol consistently showed weaker neuroprotection than the native hormone that was unaffected by ICI 182,780 treatment. In addition, equivalent concentrations of 17beta-estradiol enhanced luciferase activity in cells transfected with a luciferase reporter gene driven by tandem estrogen response elements. Estrogen-induced luciferase activity was blocked by ICI 182,780, indicating estrogen receptor-dependent transcriptional activity. We also observed by reverse transcription-polymerase chain reaction, Western blot and immunocytochemistry that increasing concentrations of 17beta-estradiol enhanced the expression of estrogen receptor alpha mRNA and protein during amyloid-beta-induced toxicity. Under these conditions, it was found by confocal microscopy that the localization of estrogen receptor alpha in the absence of hormone was mainly extranuclear. However, the receptor was consistently observed also at the nuclear region after estrogen exposure. Overall, these data suggest that estrogen may exert neuroprotective effects against amyloid-beta-induced toxicity by activation of estrogen receptor-mediated pathways. In addition, intracellular estrogen receptors are up-regulated by their cognate hormone even during exposure to neurotoxic agents.
阿尔茨海默病的病理学包括β-淀粉样肽聚集，这会导致胆碱能神经元变性。尽管潜在的分子机制仍不清楚，但最近的体外证据支持雌激素对几种神经毒性剂具有保护作用。在此我们报告，在小鼠胆碱能细胞系（SN56）中，17β-雌二醇通过一种可能涉及雌激素受体激活的机制，阻止了由β-淀粉样肽1-40片段诱导的大量细胞死亡。观察到雌二醇的保护作用呈剂量依赖性，并且被纯抗雌激素ICI 182,780完全阻断。相比之下，无活性的异构体17α-雌二醇始终显示出比天然激素弱的神经保护作用，且不受ICI 182,780处理的影响。此外，等效浓度的17β-雌二醇增强了用由串联雌激素反应元件驱动的荧光素酶报告基因转染的细胞中的荧光素酶活性。雌激素诱导的荧光素酶活性被ICI 182,780阻断，表明雌激素受体依赖性转录活性。我们还通过逆转录-聚合酶链反应、蛋白质印迹和免疫细胞化学观察到，在β-淀粉样肽诱导毒性期间，17β-雌二醇浓度的增加增强了雌激素受体α mRNA和蛋白质的表达。在这些条件下，通过共聚焦显微镜发现，在没有激素的情况下，雌激素受体α的定位主要在核外。然而，在雌激素暴露后，在核区域也始终观察到该受体。总体而言，这些数据表明雌激素可能通过激活雌激素受体介导的途径对β-淀粉样肽诱导的毒性发挥神经保护作用。此外，即使在暴露于神经毒性剂期间，细胞内雌激素受体也会被其同源激素上调。
