評估SAHA及L-BMX對SCA17小鼠之治療潛力

Abstract

脊隨小腦萎縮症第十七型(SCA17)是一種晚發型的神經退化性疾病，造成疾病的原因是因為人類第六對染色體上面TATA-box binding protein (TBP) 這個基因有不正常CAG/CAA三核甘酸擴增的現象，進而導致轉譯出對於細胞有毒的polyQ蛋白，而使得中樞神經性統的細胞死亡。SCA17臨床上的病症類似於漢丁頓是舞蹈症(HD)，病人會有運動失調、肌張力不足、認知障礙、精神疾病、失智症及舞蹈症等等。 目前有一些治療的方針是針對基因的調控做標的，像是核染色質的乙烯化，就廣泛的被應用在癌症的研究上。在先前的研究中，不管是在動物體或是細胞研究中，組蛋白去乙烯酶的抑制物(HDACi)被發現具有神經保護的功效，因此我們想研究這個治療方式是否也是有利於SCA17的治療，我們選用了兩支抑制物，SHAH是臨床上已經在使用的藥物，以及另一支新穎的HDAC抑制物L-BMX。 在我們的結果中顯示，長期投予這兩支HDAC抑制物，對於SCA17皆有輕微的治療成效，在病理組織切片的分析中，我們發現投予藥物後，小鼠腦部發炎的情況有顯著的改善，而小鼠運動行為分析上，在比較和緩的分析實驗中，我們可以看到小鼠的步伐以及平衡木上的平衡測試，也都有輕微改善的結果。因此，這兩支藥物確實對於SCA17小鼠的治療有輕微的成效。 此外，我們也另外做了SACA17小鼠早期的病理分析以及小腦中各種細胞的超微結構觀察，發現Purkinje cell細胞除了細胞核有不規則萎縮的情況外，在軸突的部分也有明顯的結構鬆脫，可能會進而導致訊號傳遞的失常及細胞死亡；另外我們也發現早期小鼠腦部發炎的狀況，也可能引起神經細胞的壓力而導致其死亡。Spinocerebellar ataxias (SCA) 17, is a late onset neurodegenerative disease caused by abnormal CAG/CAA overexpansion in the coding region of the TATA-box binding protein (TBP) gene on chromosome 6q27. The N-terminal polyglutamine (polyQ) overexpansion of TBP leads to intercellular toxicity in central nervous system. The symptoms of SCA17 patients are similar to that of Huntington’s disease (HD), including ataxia, seizure, cognitive dysfunctions, psychiatric symptoms, dystonia, and chorea. The epigenetic regulation of chromatin modification, such as histone acetylation, is widely used in cancer therapy. In recently study, histone deacetylase inhibitors (HDACi) was shown to play a role in neuron protection both in vivo and in vitro. In this study, we applied a widely-used HDACi, suberoylanilide hydroxamic acid (SAHA), and a novel HDACi, L-BMX, on the hTBP-109Q transgenic (TG) mice to assess their therapeutic potential on SCA17. Our preliminary result showed these two HDACi treatment have mild therapeutic effect on cerebella pathology of transgenic mice through immunostaining analyses. Behavior test with rotarod showed that animals could not benefit from the long-term treatment of these two HDACi compounds. However, under the low strength behavior tests, footprint and beam test, mice showed better performance with SAHA or L-BMX treatment than the non-treated TG control mice. These results revealed that SAHA and L-BMX might have mild beneficial effect on SCA17 mice. In addition, to further elucidate the neuropathology of the hTBP-109Q transgenic mice, we used immunofluorescent staining and electron microscope (EM) analyses to study the pathological profile of mouse cerebellum and Purkinje cells, respectively. These data should provide us more information for the pathogenesis and therapeutic design for SCA17.