title: Neuromelanin selectively induces apoptosis in dopaminergic SH-SY5Y cells by deglutathionylation in mitochondria: involvement of the protein and melanin component.
abstract: Parkinson's disease (PD) is characterized by selective depletion of nigral dopamine (DA) neurons containing neuromelanin (NM), suggesting the involvement of NM in the pathogenesis. This study reports induction of apoptosis by NM in SH-SY5Y cells, whereas protease-K-treated NM, synthesized DA- and cysteinyl dopamine melanin showed much less cytotoxicity. Cell death was mediated by mitochondria-mediated apoptotic pathway, namely collapse of mitochondrial membrane potential, release of cytochrome c, and activation of caspase 3, but Bcl-2 over-expression did not suppress apoptosis. NM increased sulfhydryl content in mitochondria, and a major part of it was identified as GSH, whereas dopamine melanin significantly reduced sulfhydryl levels. Western blot analysis for protein-bound GSH demonstrated that only NM reduced S-glutathionylated proteins in mitochondria and dissociated macromolecular structure of complex I. Reactive oxygen and nitrogen species were required for the deglutathionylation by NM, which antioxidants reduced significantly with prevention of apoptosis. These results suggest that NM may be related to cell death of DA neurons in PD and aging through regulation of mitochondrial redox state and S-glutathionylation, for which NM-associated protein is absolutely required. The novel function of NM is discussed in relation to the pathogenesis of PD.
authors.affiliation: Department of Neurosciences, Gifu International Institute of Biotechnology, Kakamigahara, Gifu, Japan. mnaoi@giib.or.jp
authors.forename: Makoto
authors.initials: M
authors.lastname: Naoi
authors.forename: Wakako
authors.initials: W
authors.lastname: Maruyama
authors.forename: Hong
authors.initials: H
authors.lastname: Yi
authors.forename: Yuriko
authors.initials: Y
authors.lastname: Yamaoka
authors.forename: Masayo
authors.initials: M
authors.lastname: Shamoto-Nagai
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Akao
authors.forename: Manfred
authors.initials: M
authors.lastname: Gerlach
authors.forename: Masashi
authors.initials: M
authors.lastname: Tanaka
authors.forename: Peter
authors.initials: P
authors.lastname: Riederer
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D045744:Cell Line, Tumor; D004298:Dopamine / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism*; D006801:Humans; D008543:Melanins / Q000378:metabolism / Q000502:physiology*; D053078:Membrane Potential, Mitochondrial / Q000502:physiology*; D008928:Mitochondria / Q000378:metabolism*; D010300:Parkinson Disease / Q000209:etiology / Q000378:metabolism / Q000473:pathology
chemical_list: D008543:Melanins; C014121:neuromelanin; D005978:Glutathione; D004298:Dopamine