title: Roles of autophagy in MPP+-induced neurotoxicity in vivo: the involvement of mitochondria and α-synuclein aggregation.
abstract: Macroautophagy (also known as autophagy) is an intracellular self-eating mechanism and has been proposed as both neuroprotective and neurodestructive in the central nervous system (CNS) neurodegenerative diseases. In the present study, the role of autophagy involving mitochondria and α-synuclein was investigated in MPP+ (1-methyl-4-phenylpyridinium)-induced oxidative injury in chloral hydrate-anesthetized rats in vivo. The oxidative mechanism underlying MPP+-induced neurotoxicity was identified by elevated lipid peroxidation and heme oxygenase-1 levels, a redox-regulated protein in MPP+-infused substantia nigra (SN). At the same time, MPP+ significantly increased LC3-II levels, a hallmark protein of autophagy. To block MPP+-induced autophagy in rat brain, Atg7siRNA was intranigrally infused 4 d prior to MPP+ infusion. Western blot assay showed that in vivo Atg7siRNA transfection not only reduced Atg7 levels in the MPP+-infused SN but attenuated MPP+-induced elevation in LC3-II levels, activation of caspase 9 and reduction in tyrosine hydroxylase levels, indicating that autophagy is pro-death. The immunostaining study demonstrated co-localization of LC3 and succinate dehydrogenase (a mitochondrial complex II) as well as LC3 and α-synuclein, suggesting that autophagy may engulf mitochondria and α-synuclein. Indeed, in vivo Atg7siRNA transfection mitigated MPP+-induced reduction in cytochrome c oxidase. In addition, MPP+-induced autophagy differentially altered the α-synuclein aggregates in the infused SN. In conclusion, autophagy plays a prodeath role in the MPP+-induced oxidative injury by sequestering mitochondria in the rat brain. Moreover, our data suggest that the benefits of autophagy depend on the levels of α-synuclein aggregates in the nigrostriatal dopaminergic system of the rat brain.
authors.affiliation: Department of Physiology, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Kai-Chih
authors.initials: KC
authors.lastname: Hung
authors.affiliation: Department of Medical Research and Education, Taipei Veterans General Hospital, Taipei, Taiwan.
authors.forename: Hui-Ju
authors.initials: HJ
authors.lastname: Huang
authors.affiliation: Institute of Public Health, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Ming-Wei
authors.initials: MW
authors.lastname: Lin
authors.affiliation: Department of Nursing, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Yen-Ping
authors.initials: YP
authors.lastname: Lei
authors.affiliation: Department of Medical Research and Education, Taipei Veterans General Hospital, Taipei, Taiwan; Department of Pharmacology, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Anya Maan-yuh
authors.initials: AM
authors.lastname: Lin
mesh_terms: D000818:Animals; D001343:Autophagy / Q000235:genetics*; D000071193:Autophagy-Related Protein 7; D053453:Caspase 9 / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism; D007276:Injections, Intraventricular; D015227:Lipid Peroxidation; D008297:Male; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D020258:Neurotoxicity Syndromes / Q000209:etiology / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D010880:Piperidines / Q000633:toxicity*; D066329:Protein Aggregates; D011720:Pyrazoles / Q000633:toxicity*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D013378:Substantia Nigra / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D014446:Tyrosine 3-Monooxygenase / Q000235:genetics / Q000378:metabolism; D044764:Ubiquitin-Activating Enzymes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051844:alpha-Synuclein / Q000235:genetics / Q000378:metabolism*
chemical_list: D000071193:Autophagy-Related Protein 7; D053453:Caspase 9; D051547:Heme Oxygenase-1; D008869:Microtubule-Associated Proteins; D010880:Piperidines; D066329:Protein Aggregates; D011720:Pyrazoles; D034741:RNA, Small Interfering; D014446:Tyrosine 3-Monooxygenase; D044764:Ubiquitin-Activating Enzymes; D051844:alpha-Synuclein; C524478:1,3-bis(4-hydroxyphenyl)-4-methyl-5-(4-(2-piperidinylethoxy)phenol)-1H-pyrazole; C561242:Atg7 protein, rat; C526109:Anxa3 protein, rat; C506435:Casp9 protein, rat