title: n-Butylidenephthalide exhibits protection against neurotoxicity through regulation of tryptophan 2, 3 dioxygenase in spinocerebellar ataxia type 3.
abstract: Spinocerebellar ataxia type 3 or Machado-Joseph disease (SCA3/MJD) is characterized by the repetition of a CAG codon in the ataxin-3 gene (ATXN3), which leads to the formation of an elongated mutant ATXN3 protein that can neither be denatured nor undergo proteolysis in the normal manner. This abnormal proteolysis leads to the accumulation of cleaved fragments, which have been identified as toxic and further they act as a seed for more aggregate formation, thereby increasing toxicity in neuronal cells. To date, there have been few studies or treatment strategies that have focused on controlling toxic fragment formation. The aim of this study is to develop a potential treatment strategy for addressing the complications of toxic fragment formation and to provide an alternative treatment strategy for SCA3. Our preliminary data on anti-aggregation and toxic fragment formation using an HEK (human embryonic kidney cells) 293T-84Q-eGFP (green fluorescent protein) cell model identified n-butylidenephthalide (n-BP) as a potential drug treatment for SCA3. n-BP decreased toxic fragment formation in both SCA3 cell and animal models. Moreover, results showed that n-BP can improve gait, motor coordination, and activity in SCA3 mice. To comprehend the molecular basis behind the control of toxic fragment formation, we used microarray analysis to identify tryptophan metabolism as a major player in controlling the fate of mutant ATXN3 aggregates. We also demonstrated that n-BP functions by regulating the early part of the kynurenine pathway through the downregulation of tryptophan 2, 3-dioxygenase (TDO2), which decreases the downstream neurotoxic product, quinolinic acid (QA). In addition, through the control of TDO2, n-BP also decreases active calpain levels, an important enzyme involved in the proteolysis of mutant ATXN3, thereby decreasing toxic fragment formation and associated neurotoxicity. Collectively, these findings indicate a correlation between n-BP, TDO2, QA, calpain, and toxic fragment formation. Thus, this study contributes to a better understanding of the molecular interactions involved in SCA3, and provides a novel potential treatment strategy for this neurodegenerative disease.
authors.affiliation: Department of Life Science and Graduate Institute of Biotechnology, National Dong Hwa University, Hualien, Taiwan, ROC.
authors.forename: Karthyayani
authors.initials: K
authors.lastname: Rajamani
authors.affiliation: Department of Life Science and Graduate Institute of Biotechnology, National Dong Hwa University, Hualien, Taiwan, ROC; Everfront Biotech Inc., New Taipei City, Taiwan, ROC.
authors.forename: Jen-Wei
authors.initials: JW
authors.lastname: Liu
authors.affiliation: Department of Life Science and Graduate Institute of Biotechnology, National Dong Hwa University, Hualien, Taiwan, ROC.
authors.forename: Cheng-Han
authors.initials: CH
authors.lastname: Wu
authors.affiliation: Department of Life Science and Graduate Institute of Biotechnology, National Dong Hwa University, Hualien, Taiwan, ROC.
authors.forename: I-Tsang
authors.initials: IT
authors.lastname: Chiang
authors.affiliation: Department of Life Science and Graduate Institute of Biotechnology, National Dong Hwa University, Hualien, Taiwan, ROC.
authors.forename: Deng-Huwei
authors.initials: DH
authors.lastname: You
authors.affiliation: Department of Life Science and Graduate Institute of Biotechnology, National Dong Hwa University, Hualien, Taiwan, ROC.
authors.forename: Si-Yin
authors.initials: SY
authors.lastname: Lin
authors.affiliation: Department of Applied Chemistry, Chaoyang University of Technology, Taichung, Taiwan, ROC.
authors.forename: Dean-Kuo
authors.initials: DK
authors.lastname: Hsieh
authors.affiliation: Bioinnovation Center, Tzu Chi Foundation, Buddhist Tzu Chi General Hospital, Tzu Chi University, Hualien, Taiwan, ROC; Department of Neurosurgery, Buddhist Tzu Chi General Hospital, Tzu Chi University, Hualien, Taiwan, ROC.
authors.forename: Shinn-Zong
authors.initials: SZ
authors.lastname: Lin
authors.affiliation: Bioinnovation Center, Tzu Chi Foundation, Buddhist Tzu Chi General Hospital, Tzu Chi University, Hualien, Taiwan, ROC; Department of Pathology, Buddhist Tzu Chi General Hospital, Tzu Chi University, Hualien, Taiwan, ROC. Electronic address: duke_harn@yahoo.com.tw.
authors.forename: Horng-Jyh
authors.initials: HJ
authors.lastname: Harn
authors.affiliation: Department of Life Science and Graduate Institute of Biotechnology, National Dong Hwa University, Hualien, Taiwan, ROC. Electronic address: twchiou@gms.ndhu.edu.tw.
authors.forename: Tzyy-Wen
authors.initials: TW
authors.lastname: Chiou
mesh_terms: D000818:Animals; D000067699:Ataxin-3 / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002154:Calpain / Q000378:metabolism; D002531:Cerebellum / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D004195:Disease Models, Animal; D057809:HEK293 Cells; D006801:Humans; D017827:Machado-Joseph Disease / Q000188:drug therapy* / Q000201:enzymology* / Q000473:pathology; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D018696:Neuroprotective Agents / Q000494:pharmacology*; D010796:Phthalic Anhydrides / Q000494:pharmacology*; D017378:Quinolinic Acid / Q000008:administration & dosage / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D014364:Tryptophan / Q000378:metabolism; D014366:Tryptophan Oxygenase / Q000378:metabolism*
chemical_list: D018696:Neuroprotective Agents; D010796:Phthalic Anhydrides; D019837:Ryanodine Receptor Calcium Release Channel; D014364:Tryptophan; D014366:Tryptophan Oxygenase; D000067699:Ataxin-3; C511594:Atxn3 protein, mouse; D002154:Calpain; D017378:Quinolinic Acid; C026105:butylidenephthalide; D002118:Calcium
keywords: Machado-Joseph disease; Polyglutamine disease; Spinocerebellar ataxia; Tryptophan 2, 3-dioxygenase; Tryptophan metabolism