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  • 學位論文

膽固醇誘導人類神經纖維母細胞凋亡與脂筏含量、TrkB 活性及 Cyp46 蛋白質表現量相關

Cholesterol exposure induced SH-SY5Y cell apoptosis is associated with lipid raft content, tyrosine kinase B (TrkB) activity and Cyp46 protein expression

指導教授 : 林士祥

摘要


背景:流行病學中指出,阿茲海默症(Alzheimer’s disease, AD) 與高膽固醇血症具有高度相關性,且腦部膽固醇代謝異常為 AD 危險因子之一。目的:觀察膽固醇是否藉由增加細胞脂筏含量、類澱粉樣蛋白(β-Amyloid, Aβ) 的生合成與改變 brain-derived neurotrophic factor (BDNF)/ tyrosine kinase B (TrkB) 蛋白質表現量及其下游訊息傳遞路徑而導致細胞凋亡。 方法:以人類神經纖維母細胞株 SH-SY5Y 作為細胞模式,給予膽固醇後,觀察膽固醇、24-Hydroxycholesterol (24-OHC) 與脂筏含量、AD 相關蛋白質表現量、BDNF/TrkB 訊息傳遞路徑的改變及細胞凋亡之情形。 結果:給予細胞高濃度而無法代謝之膽固醇時,細胞總膽固醇與 24-OHC 含量增加,造成脂筏與Aβ含量上升以及 BDNF 與 Full-length TrkB (TrkBfl) 蛋白質表現量降低、而Truncated TrkB (TrkBtc) 增加,使下游 Phosphatidylinositol 3-kinase (PI3K)/Akt 與 Glycogen synthase kinase-3β (GSK-3β) 磷酸化減少,造成 tau 蛋白磷酸化增加,最後導致細胞凋亡。 結論:膽固醇及其代謝物會藉由增加脂筏含量,引起 Aβ 生合成以及細胞內 ROS 產量上升,並影響 BDNF/TrkB 的蛋白質表現量,使下游 PI3K、Akt、GSK-3β 訊息傳遞路徑失調,而導致磷酸化 tau 蛋白質的增加以及細胞形態的改變與凋亡。

並列摘要


Background: In epidemiology, Alzheimer’s disease (AD) is one of the most common forms of neurodegenerative disease. It has been shown that the disturbances in brain cholesterol metabolism are associated with the major pathological features of AD. Purpose: Our purpose was to investigate the effects of cholesterol towards neurodegeneration. Methods: We examed the content of SH-SY5Y cellular cholesterol and 24-hydroxycholesterol (24-OHC) production after cholesterol was treated. We examed the effects of cholesterol on lipid raft conents, protein expressions of β-amyloid (Aβ), β-secretase (BACE), brain-derived neurotrophic factor (BDNF)/tyrosine kinase B (TrkB) and its’ downstream signaling transduction proteins, cell morphology, synaptic length and mechanisms of cell apoptosis in SH-SY5Y human neuroblastoma cell. Results: We found that high cholesterol increases the contents of lipid raft and decreases the protein expressions of BDNF, full-length TrkB (TrkBfl) and p-TrkB, but increases the protein expressions of truncated TrkB (TrkBtc). It could cause the dysfunction of the PI3K-Akt-GSK-3β cascade and lead to phosphorylation of tau at Ser396 and cell apoptosis. Furthermore, elevations of Aβ, BACE and reactive oxygen species (ROS) were also observed. Conclusion: These findings suggest that cholesterol induced neuronal cell apoptosis is associated with contents of lipid raft, activity of TrkB and protein expression of Cyp46.

參考文獻


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