以SCA17基因轉殖小鼠及其小腦初級培養平台評估具有抗氧化作用之化合物及天然物

Abstract

脊髓小腦萎縮症第十七型(SCA17)是染色體顯性遺傳的神經退化性疾病，是由於在TATA box binding (TBP)蛋白基因上有CAA/CAG三核苷酸過度擴增，此擴增編碼結果產生多麩醯胺酸造成蛋白質不正常的堆積而引發小腦的退化，尤其以Purkinje cell之受損最嚴重。先前有許多研究指出在細胞模式或是動物模式，給予中草藥或是抗氧化的藥物，皆可有效的改善神經退化性疾病。我們以SCA17小鼠作為一個藥物篩選的模式，以SCA17基因轉殖小鼠小腦的初級培養及組織培養評估中草藥和抗氧化藥物對於SCA17的療效。在小腦初級培養中，使用抗體IP3R1免疫染色標定Purkinje cell，計算神經突延展長度以評估藥物的功效。在切片組織培養中，藉由神經突的密度、Purkinje cell的形態及TBP聚集程度作為評估的依據；再將具有潛力的藥物施於SCA17基因轉殖小鼠，進行活體的探討。藉由rotarod，及小鼠自主運動(locomotor)之行為測試探討藥物的功用，以組織免疫染色分析病理層次及分子機制。由SCA17小鼠的小腦初級培養和切片組織培養之篩選，得知兩項中草藥萃取物及三個合成的抗氧化化合物可以增加神經突的延展。活體內的藥物測試發現，小鼠的體重和自主運動並沒有受到化合物的影響，而rotarod測試結果指出，藥物的給予有使其運動協調能力獲得改善。並且我們發現化合物的給予可以減緩Purkinje cell退化和不正常蛋白TBP的堆積，並且增加伴護蛋白和超氧化物歧化酶的表現，並降低發炎反應。這些化合物可能有潛力發展成為SCA17治療藥物。

Spinocerebellar ataxia 17 (SCA17) is an autosomal dominant neurodegenerative disease caused by trinucleotide CAA/CAG repeat excessive expansion in TATA box Binding Protein (TBP) gene. Expanded CAA/CAG repeat encodes polyglutamine (polyQ) in TBP, which causes mutant polyQ proteins aggregate and the cerebellar Purkinje cell degeneration. Some effective treatments for neurodegenerative disease using Chinese herbs and anti-oxidants have been reported in cellular and animal studies. Our lab has generated SCA17 mouse model and used for potential therapeutic screening. We first used SCA17 transgenic mouse cerebellar primary to screen potential Chinese herbs and anti-oxidative compounds. Immunocytochemistry was conducted to stain Purkinje cell, and measured neurite outgrowth to evaluate the effect of treatment in cerebellar primary culture. The screening results showed two herbal extracts and three synthesized anti-oxidative compounds could increase neurite outgrowth on SCA17 cerebellar primary culture. In vivo treatment results showed that mouse body weight and spontaneous activity were unaffected under the treatment of anti-oxdative compounds. The motor coordination of mice on rotarod task was improved after treatment. We also found that heat shock proteins and superoxide dismutase were increased and Purkinje cell degeneration , mutant protein TBP aggregation and inflammation were attenuated after the treatment with these compounds. These anti-oxidative compounds have potential for SCA17 diseases treatment.