Yao Zhi-Xing, Brown Rachel C, Teper Gary, Greeson Janet, Papadopoulos Vassilios
Division of Hormone Research, Departments of Cell Biology, Pharmacology and Neurosciences and Samaritan Research Laboratories, Georgetown University School of Medicine, Washington DC 20057, USA.
J Neurochem. 2002 Dec;83(5):1110-9. doi: 10.1046/j.1471-4159.2002.01202.x.
22R-hydroxycholesterol, a steroid intermediate in the pathway of pregnenolone formation from cholesterol, was found at lower levels in Alzheimer's disease (AD) hippocampus and frontal cortex tissue specimens compared to age-matched controls. beta-Amyloid (Abeta) peptide has been shown to be neurotoxic and its presence in brain has been linked to AD pathology. 22R-hydroxycholesterol was found to protect, in a dose-dependent manner, against Abeta-induced rat sympathetic nerve pheochromocytoma (PC12) and differentiated human Ntera2/D1 teratocarcinoma (NT2N) neuron cell death. Other steroids tested were either inactive or acted on rodent neurons only. The effect of 22R-hydroxycholesterol was found to be stereospecific because its enantiomer 22S-hydroxycholesterol failed to protect the neurons from Abeta-induced cell death. Moreover, the effect of 22R-hydroxycholesterol was specific for Abeta-induced cell death because it did not protect against glutamate-induced neurotoxicity. The neuroprotective effect of 22R-hydroxycholesterol was seen when using Abeta1-42 but not the Abeta25-35 peptide. To investigate the mechanism of action of 22R-hydroxycholesterol we examined the direct binding of this steroid to Abeta using a novel cholesterol-protein binding blot assay. Using this method the direct specific binding, under native conditions, of 22R-hydroxycholesterol to Abeta1-42 and Abeta17-40, but not Abeta25-35, was observed. These data suggest that 22R-hydroxycholesterol binds to Abeta and the formed 22R-hydroxycholesterol/Abeta complex is not toxic to rodent and human neurons. We propose that 22R-hydroxycholesterol offers a new means of neuroprotection against Abeta toxicity by inactivating the peptide.
22R-羟基胆固醇是胆固醇生成孕烯醇酮途径中的一种甾体中间体，与年龄匹配的对照组相比，在阿尔茨海默病（AD）海马体和额叶皮质组织标本中的含量较低。β-淀粉样蛋白（Aβ）肽已被证明具有神经毒性，其在大脑中的存在与AD病理学有关。研究发现，22R-羟基胆固醇以剂量依赖的方式保护大鼠交感神经嗜铬细胞瘤（PC12）和分化的人Ntera2/D1畸胎癌（NT2N）神经元免受Aβ诱导的细胞死亡。测试的其他甾体要么无活性，要么仅对啮齿动物神经元起作用。发现22R-羟基胆固醇的作用具有立体特异性，因为其对映体22S-羟基胆固醇不能保护神经元免受Aβ诱导的细胞死亡。此外，22R-羟基胆固醇的作用对Aβ诱导的细胞死亡具有特异性，因为它不能保护细胞免受谷氨酸诱导的神经毒性。使用Aβ1-42时可观察到22R-羟基胆固醇的神经保护作用，而使用Aβ25-35肽时则未观察到。为了研究22R-羟基胆固醇的作用机制，我们使用一种新型的胆固醇-蛋白质结合印迹分析法检测了这种甾体与Aβ的直接结合。使用这种方法，在天然条件下观察到22R-羟基胆固醇与Aβ1-42和Aβ17-40直接特异性结合，但与Aβ25-35不结合。这些数据表明，22R-羟基胆固醇与Aβ结合，形成的22R-羟基胆固醇/Aβ复合物对啮齿动物和人类神经元无毒。我们提出，22R-羟基胆固醇通过使该肽失活，提供了一种针对Aβ毒性的新的神经保护手段。
