Pedersen W A, Kloczewiak M A, Blusztajn J K
Department of Pathology and Laboratory Medicine, Boston University School of Medicine, MA 02118, USA.
Proc Natl Acad Sci U S A. 1996 Jul 23;93(15):8068-71. doi: 10.1073/pnas.93.15.8068.
The characteristic features of a brain with Alzheimer disease (AD) include the presence of neuritic plaques composed of amyloid beta-protein (Abeta) and reductions in the levels of cholinergic markers. Neurotoxic responses to Abeta have been reported in vivo and in vitro, suggesting that the cholinergic deficit in AD brain may be secondary to the degeneration of cholinergic neurons caused by Abeta. However, it remains to be determined if Abeta contributes to the cholinergic deficit in AD brain by nontoxic effects. We examined the effects of synthetic Abeta peptides on the cholinergic properties of a mouse cell line, SN56, derived from basal forebrain cholinergic neurons. Abeta 1-42 and Abeta 1-28 reduced the acetylcholine (AcCho) content of the cells in a concentration-dependent fashion, whereas Abeta 1-16 was inactive. Maximal reductions of 43% and 33% were observed after a 48-h treatment with 100 nM of Abeta 1-42 and 50 pM of Abeta 1-28, respectively. Neither Abeta 1-28 nor Abeta 1-42 at a concentration of 100 nM and a treatment period of 2 weeks was toxic to the cells. Treatment of the cells with Abeta 25-28 (48 h; 100 nM) significantly decreased AcCho levels, suggesting that the sequence GSNK (aa 25-28) is responsible for the AcCho-reducing effect of Abeta. The reductions in AcCho levels caused by Abeta 1-42 and Abeta 1-28 were accompanied by proportional decreases in choline acetyltransferase activity. In contrast, acetylcholinesterase activity was unaltered, indicating that Abeta specifically reduces the synthesis of AcCho in SN56 cells. The reductions in AcCho content caused by Abeta 1-42 could be prevented by a cotreatment with all-trans-retinoic acid (10 nM), a compound previously shown to increase choline acetyltransferase mRNA expression in SN56 cells. These results demonstrate a nontoxic, suppressive effect of Abeta on AcCho synthesis, an action that may contribute to the cholinergic deficit in AD brain.
患有阿尔茨海默病（AD）的大脑的特征包括存在由β-淀粉样蛋白（Aβ）组成的神经炎性斑块以及胆碱能标志物水平降低。体内和体外均已报道了对Aβ的神经毒性反应，这表明AD大脑中的胆碱能缺陷可能继发于Aβ导致的胆碱能神经元变性。然而，Aβ是否通过无毒作用导致AD大脑中的胆碱能缺陷仍有待确定。我们研究了合成Aβ肽对源自基底前脑胆碱能神经元的小鼠细胞系SN56胆碱能特性的影响。Aβ1-42和Aβ1-28以浓度依赖性方式降低细胞中的乙酰胆碱（AcCho）含量，而Aβ1-16无活性。在用100 nM的Aβ1-42和50 pM的Aβ1-28处理48小时后，分别观察到最大降低率为43%和33%。浓度为100 nM且处理期为2周的Aβ1-28和Aβ1-42对细胞均无毒性。用Aβ25-28（48小时；100 nM）处理细胞可显著降低AcCho水平，表明序列GSNK（氨基酸25-28）是Aβ降低AcCho作用的原因。Aβ1-42和Aβ1-28导致的AcCho水平降低伴随着胆碱乙酰转移酶活性的相应降低。相比之下，乙酰胆碱酯酶活性未改变，表明Aβ特异性降低SN56细胞中AcCho的合成。全反式维甲酸（10 nM）先前已显示可增加SN56细胞中胆碱乙酰转移酶mRNA表达，与Aβ1-42共同处理可防止Aβ1-42导致的AcCho含量降低。这些结果证明了Aβ对AcCho合成具有无毒的抑制作用，这一作用可能导致AD大脑中的胆碱能缺陷。
