亨廷頓舞蹈症 (Huntington’s disease)是一種顯性遺傳的神經退化性疾病，主要的成因為huntingtin(Htt)基因exon1中的CAG三核甘酸重複序列異常擴增所導致，會導致錯誤折疊的亨廷頓蛋白形成聚集體並堆積在神經細胞中。亨廷頓相關蛋白40是一個會與亨廷頓蛋白結合的蛋白，目前對於亨廷頓相關蛋白40詳細作用機制仍不清楚，在亨廷頓舞蹈症患者腦中與帶有突變型亨廷頓蛋白的小鼠紋狀體細胞STHdhQ111/Q111中發現表現量會異常上升。之前有研究顯示突變型亨廷頓蛋白會抑制神經元的核蛋白輸入粒線體，也有研究指出突變型亨廷頓蛋白會抑制PGC-1α，一種調控粒線體新生的轉錄激活因子，進而損害粒線體，而當粒線體受損時，會產生過多的活性氧(Reactive oxygen species)，使細胞的氧化壓力增加，而在R6/2轉基因亨廷頓舞蹈症模式小鼠的血漿還有紋狀體的透析液中也都能發現DNA氧化損傷的標記OH8dG濃度增加。超氧化物歧化酶(Superoxide dismutase)是細胞中對抗氧化壓力的酵素之一，能夠將細胞中過多的超氧化物轉化為氧氣與雙氧水，再藉由細胞中其他抗氧化酵素達到清除細胞中的ROS。在細胞產生氧化壓力時會啟動多條訊息傳遞路徑進而對細胞內過多的ROS做出應對，其中像是Nrf2 pathway或是MAPK pathway，其中活化Nrf2之後會轉譯轉錄出下游抗氧化酵素來清除過多的ROS。當細胞中的ROS失衡時會對粒線體造成損壞，粒線體遭到氧化損壞時回藉由一系列的分裂(fission)和融合(fusion)相互作用，來回復或是移除受損的胞器，或是維持粒線體原本的功能與型態。我們發現在STHdhQ7/Q7細胞中過度表現亨廷頓相關蛋白40時會使細胞中的SOD表現量降低，並會使粒線體的型態傾向片斷化，且如果在STHdhQ7/Q7細胞中過度表現亨廷頓相關蛋白40再過度表現SOD就能使粒線體分裂情況改善。橄欖苦苷(Oleuropein)是一種天然多酚化合物，由橄欖、橄欖葉、橄欖油中萃取而出，其具有非常好的抗氧化能力，先前有研究顯示橄欖苦苷也能藉由活化細胞中抗氧化酵素來達到細胞抗氧化的功效。普羅布考(Probucol)是一種具有抗氧化能力的降血脂藥物，先前的研究發現，Probucol可以減緩由QA或是3-NP所誘發的氧化壓力徵狀。我們也試著使用Oleuropein與Probucol去治療過度表現亨廷頓相關蛋白40時所引發的氧化壓力徵狀，結果發現Probucol能夠回復因為過度表現亨廷頓相關蛋白40而降低的SOD1的表現量。STHdhQ111/Q111是亨廷頓舞蹈症的小鼠紋狀體模式細胞，我們也試著使用Oleuropein與Probucol治療來改善STHdhQ111/Q111的病徵，結果發現在STHdhQ111/Q111細胞中，SOD2的表現量也是顯著較低的，而過氧化氫酶(catalase)則是顯著增加，且Probucol在STHdhQ7/Q7細胞中都會降低Glutathione peroxidase和Glutathione reductase的表現量。我們也在STHdhQ7/Q7細胞中過度表現突變型亨廷頓蛋白，並試著以Oleuropein與Probucol來改善其氧化壓力的徵狀，我們發現過度表現突變型亨廷頓蛋白會使HO1顯著下降。在最近的研究中發現在Hdh140Q/140Q亨廷頓舞蹈症模式小鼠中發現亨廷頓相關蛋白40蛋白表現量會顯著下降，在實驗室先前研究發現STHdhQ111/Q111中，亨廷頓相關蛋白40蛋白表現量也都是顯著降低的。所以我們也使用knockdown shRNAs來降低細胞中內生性亨廷頓相關蛋白40，發現當內生性亨廷頓相關蛋白40降低時，SOD的表現量也會顯著降低，且Nrf2也有被活化的現象。泛素-蛋白酶體降解系統(Ubiquitin Proteasome System)是細胞中清除錯誤摺疊蛋白的機制之一，其中PA28γ能活化蛋白酶體，我們也發現在STHdhQ7/Q7細胞中過度表現亨廷頓相關蛋白40再過度表現PA28γ也能使粒線體分裂情況改善。

Huntington's disease is a dominant inherited neurodegenerative disease, caused by an abnormal amplification of CAG trinucleotide repeats in the exon1 of huntingtin gene. The mutation leads to formation and accumulation of misfolding huntingtin protein in the nerve cells. HAP40 is a 40-kDa protein that interacts with the COOH-terminal part of huntingtin. Thus far, the cellular function of theHAP40 is still unclear. Expression of HAP40 is abnormally increased in the brains of HD patients and STHdhQ111/Q111 cell line. Previous studies have shown mutant huntingtin can impair mitochondrial functions. When damaged, the mitochondria produce more reactive oxygen species, thereby increasing cellular oxidation pressure. In HD mice, plasma and striatal microdialysates had high levels of OH8dG, a well-established marker of oxidative damage to DNA. Superoxide dismutase is an enzyme that alternately catalyzes the dismutation of the superoxide radical into ordinary molecular oxygen and hydrogen peroxide. It can remove excess reactive oxygen species in cells and mitigates oxidative stress. Oleuropein is a natural polyphenolic compound with high antioxidant capacity. Here, We assessed effects of Superoxide dismutase、oleuropein on antioxidant defense system in cellular oxidative stresses. Our data revealed that Increase of HAP40 decreases superoxide dismutase protein levels. We found that increasing HAP40 level increased mitochondrial fragmentation in STHdhQ7/Q7 cells. On the other hand, an increase of superoxide dismutase expression decreased mitochondrial fragmentation in HAP40 overexpressing STHdhQ7/Q7 cells. Therefore, we tested wether depletion of HAP40 affect superoxide dismutase protein levels. Results indicated that deplation of HAP40 also decreases superoxide dismutase protein levels. Ubiquitin proteasome system is one of the mechanisms to remove the wrong folding protein in the cells. PA28γ can activate the proteasome. We also found that increase of PA28γ decrease mitochondrial fragmentation in HAP40 overexpressing STHdhQ7/Q7 cells.

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