探討β類澱粉蛋白對於α-Synuclein所導致神經毒性之分子機轉研究

Investigation of the Molecular Mechanisms on Amyloid β Mediating α-Synuclein-induced Neurotoxicity

鄭毓仕(Yu-Shih Cheng)

指導教授 ： 林志立 ； 賴德仁

中山醫學大學/醫學院/醫學研究所/碩士(2014年)

https://doi.org/10.6834/CSMU.2014.00134

摘要

在所有失智症患者中，路易氏體失智症 (Dementia with Lewy bodies, DLB) 患者的人數，僅次於阿滋海默症 (Alzheimer’s disease, AD) 患者，占失智症當中相當大人數。且此兩個常見的失智症當中，α-Synuclein與β類澱粉蛋白 (beta-Amyloid, Aβ) 分別為前後兩者患者腦部中的主要病理特徵，其機制皆為該蛋白質不正常摺疊堆積在神經細胞當中。此外其中一類的DLB患者腦部出現的路易氏體除了α-Synuclein之外，也有Aβ不正常折疊蛋白質堆積在腦部中，且這些病人的病程進行要比AD病患的病程要來的快很多。據此，本研究的目的便是希望瞭解在DLB的病理發展過程中，Aβ是否影響α-Synuclein的聚集並產生神經毒性。我們利用transfection的方法，讓α-Synuclein在SK-N-MC細胞株中overexpression，接著再處理Aβ來模擬DLB患者腦部的情況，藉此這個模式來研究有可能造成DLB的分子機制；此外我們也與臨床醫師合作，收集DLB患者的周邊血液，並抽取血液中leukocytes的mRNA，來與AD患者及正常人進行比較。本研究結果發現，首先α-Synuclein會增強Aβ所產生的細胞凋亡，然後以西方墨點法及螢光染色發現，此增強的現象可能是透過透過抑制細胞自我清除的功能，包括細胞自噬、ubiquitin proteasome system (UPS)，並且增強老化造成降低Sirt1、Foxo3a及代謝氧化壓力的酵素SOD1表現，接著產生的氧化壓力可能造成粒線體功能障礙 (mitochondrial dysfunction)。最後在患者leukocyte中發現Sirt1、SOD1以及BDNF的mRNA表現量似乎比阿茲海默症患者與正常人來的低。本研究認為Aβ很有可能是在DLB的形成過程中扮演一個很重要的角色，並且其致病機轉為透過抑制細胞本身的自我清除能力，誘發細胞老化的現象，來造成更嚴重的細胞凋亡，在未來或許可以透過活化細胞自噬的藥物，或是利用治療阿茲海默症中，減緩Aβ形成的相關的藥物，來達到延緩DLB患者的病程與臨床病狀，有效幫助DLB的治療。

關鍵字

路易氏體失智症 ； α-synuclein ； 細胞自噬 ； β類澱粉蛋白 ； 老化

並列摘要

In all dementia patient, the percentage of Dementia with Lewy bodies (DLB) patients is very high, and just less than Alzheimer’s disease (AD) patients. In these two common dementia, α-Synuclein and Aβ are two major pathological features in the brain of patients, respectively. The mechanism of these features is that these abnormal folding protein accumulated in the neuron cells. Additionally, there are one type of DLB patients have been found not only α-Synuclein but also Aβ abnormal accumulated in the brain, and the progress of these DLB patients are more fast than AD patients. Accordingly, the aim of this study is to investigate whether Aβ affects the accumulation of α-Synuclein, and induced more neuron toxicity in pathological development process of DLB. We overexpressed α-Synuclein in SK-N-MC cell line by transfection, and treated with Aβ to mimic the brain environment of DLB patients. We studied some molecular mechanism which may cause DLB by this model. Besides, we had a cooperation with clinical doctors to collect the peripheral blood of patients, and purified the mRNA form leukocytes in blood, and compared it with AD patients and normal person. In this study, we first investigated that α-Synuclein increased Aβ induced cell apoptosis. Then we found this phenomenon may through inhibiting cell self-clearance system including autophagy and ubiquitin proteasome system (UPS), and increasing aging resulted in inhibition of Sirt1, Foxo3a and SOD1, the enzyme which can clean up ROS by western blot and fluorescence stain. Next the ROS increased may result in mitochondria dysfunction. Last, we observed the Sirt1, SOD1 and BDNF mRNA level of leukocyte from DLB patients are less than AD and human normal control. In conclusion, We suggested that Aβ may play an important role in the progression of DLB. The molecular mechanism of DLB was inhibiting cell self-clearance, and induced the phenomenon of aging, and finally led to more apoptosis. In the future, maybe we can use some drugs which can induce cell autophagy, or decrease the formation of Aβ to slow down the progression and the symptom of DLB, and to help the treatment of DLB effectively.

並列關鍵字

Dementia with Lewy bodies (DLB) ； α-synuclein, Autophagy ； beta-Amyloid (Aβ) ； Aging

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