Effects of membrane lipids on the incorporation of Alzheimer's β-amyloid protein into membranes and neurotoxicity

人们普遍认为β-淀粉样蛋白（a - β p）的神经毒性与阿尔茨海默病的病因有关。我们之前的研究表明，a - β p直接结合到膜中，形成阳离子选择性离子通道，并导致永生化下丘脑神经元细胞内钙水平的增加。我们假设通过不受调节的淀粉样蛋白通道破坏钙稳态可能是a - β p神经毒性的主要事件。本研究采用多位点荧光法研究了a β p引起原代培养大鼠海马神经元细胞内钙水平升高的详细特征。我们发现并报道了a β p引起长期（超过三周）培养的大鼠海马神经元细胞内钙水平的显著增加，但短期（少于2周）培养的神经元细胞内钙水平没有显著增加。神经元对a - β p的反应具有高度的异质性。免疫组化观察显示，一些受限制的神经元与a - β p有亲和关系。为了确定对a - β p的神经毒性具有保护作用的物质，我们预先给药脱氢表雄酮硫酸盐（DHEA-S），其在老年人血清中的水平降低，并发现显著抑制a - β p诱导的细胞内钙水平的增加。我们的研究结果表明，AβP形成淀粉样蛋白通道的能力可能是基于阿尔茨海默病的发病机制。DHEA-S等内源性物质也可能有助于预防a - β p的神经毒性。

It is widely accepted that the neurotoxicity of β-amyloid protein (AβP) is implicated in the etiology of Alzheimer's disease. We have previously shown that AβP is directly incorporated into membranes, forms cation-selective ion channels, and causes an increase in intracellular calcium levels of immortalized hypothalamic neurons. We hypothesize that the disruption of calcium homeostasis through the unregulated amyloid channels may be the primary event of neuro-toxicity of AβP. In this study, we investigated the detailed characteristics of the increase in intracellular calcium levels of primary cultured rat hippocampal neurons caused by AβP using a multisite fluorometry system. We found and report here that AβP caused a marked increase in intracellular calcium levels of long-term (more than three weeks)-cultured rat hippocampal neurons, but not in short-term (less than 2 weeks)-cultured neurons. The responses of neurons to AβP were highly heterogeneous. Immunohistochemical observation revealed that some restricted neurons have an affinity to the AP. To determine the substances that can confer protection against the neurotoxicity of AβP, we preadministerated dehydroepiandrosterone sul-phate (DHEA-S), whose levels in the serum of elderly are reduced, and found a significant inhibition of the increase in intracellular calcium levels induced by AβP. Our results suggest the implication of the ability of AβP to form amyloid channels may be based on the Alzheimer's pathogenesis. It is also possible that the endogenous substances such as DHEA-S may con-tribute to the prevention from the neurotoxicity of AβP.