藻類多醣萃取物的抗氧化活性做為多麩醯胺小腦萎縮症的治療策略

Abstract

大多數與年齡相關的神經退化性疾病特點是異常蛋白於受影響之腦區域有不正常聚集、累積而致病。先前研究表示，細胞內氧化壓力增加可能參與神經退化性疾病發病的病程。許多報導指出藻類多醣物質具有抗氧化活性。本研究目標在探討褐藻多醣、葛仙米藻多醣與綠藻多醣的抗氧化活性，及其在多麩醯胺小腦萎縮症治療上的應用。首先檢測上述藻類多醣的DPPH與活性氧自由基補捉能力，結果顯示這三種藻類多醣皆具有活性氧自由基捕捉能力。其次藉由雙氧水處理人類HEK-293胚胎腎細胞與SH-SY5Y神經瘤母細胞後，以CellRox green 螢光染劑及流式細胞儀檢測細胞內活性氧分子，發現前處理此三種藻類多醣，皆可有效降低雙氧水誘發的細胞死亡及活性氧化物生成量。最後構築正常(ATXN3/Q14)及突變(ATXN3/Q75)的人類第三型小腦萎縮症全長cDNA，並短暫表現於HEK-293T細胞。三種藻類多醣的前處理皆可顯著降低ATXN3/Q14~75轉染細胞的活性氧化物，但僅褐藻多醣前處理有效增強ATXN3/Q75表現細胞中HMOX1基因的表現。

Most age-related neurodegenerative diseases are characterized by accumulation of aberrant protein aggregates/inclusions in the affected brain regions. Several lines of evidence suggest that increased oxidative stress may involve in the pathogenesis of neurodegenerative diseases. Studies have shown that polysaccharides from several algal species have antioxidant activity. This study investigated the antioxidant activities of polysaccharide extracts from brown seaweed (fucoidan, a sulfated polysaccharide), Nostoc sphaeroides (a nitrogen-fixing cyanobacterium) and Chlorella sorokiniana (a green alga) and their application in polyQ-mediated spinocerebellar ataxias (SCA). Firstly, the polysaccharides from these algae were examined for their 1,1-diphenyl-2-picrylhydrazyl (DPPH) and superoxide anion radicals scavenging potential. The polysaccharides of these algae exhibited an effective scavenging capability on superoxide anion radical. Then their antioxidative activity was evaluated by measuring cellular production of reactive oxidative species (ROS) using CellRox green fluorescent probe on a flow cytometry. Pretreatment with polysaccharides from these algae protected both human embryonic kidney HEK-293 and neuroblastoma SH-SY5Y cells against the H2O2-induced cell death and reduced ROS production. Lastly, human SCA type 3 full length cDNAs with normal (ATXN3/Q14) and expanded (ATXN3/Q75) polyQ were constructed and transiently expressed in HEK-293T cells. Pre-treatment with algae polysaccharides significantly reduced ROS production in ATXN3/Q14~75 transfected cells. However, only fucoidan effectively enhanced hemeoxygenase (decycling) 1 (HMOX1) expression in ATXN3/Q75 expressing cells.