Roles of autophagy in MPP+-induced neurotoxicity in vivo: the involvement of mitochondria and α-synuclein aggregation

• Published in: PloS one 2014-03, Vol.9 (3), p.e91074
• Main Authors: Hung, Kai-Chih, Huang, Hui-Ju, Lin, Ming-Wei, Lei, Yen-Ping, Lin, Anya Maan-yuh
• Format: Article
• Language: English
• Subjects: Aggregates; alpha-Synuclein - genetics; alpha-Synuclein - metabolism; Animals; Apoptosis; Autophagy; Autophagy - genetics; Autophagy-Related Protein 7; Biology and Life Sciences; Brain; Brain research; Caspase; Caspase 9 - genetics; Caspase 9 - metabolism; Caspase-9; Cell death; Central nervous system; Chloral; Chloral hydrate; Cytochrome; Cytochrome-c oxidase; Dopamine receptors; Electron transport; Gene Expression Regulation; Heme; Heme oxygenase (decyclizing); Heme Oxygenase-1 - genetics; Heme Oxygenase-1 - metabolism; Hospitals; Hydroxylase; Injections, Intraventricular; Laboratory animals; Lipid Peroxidation; Localization; Male; Medical research; Medicine and Health Sciences; Microtubule-Associated Proteins - genetics; Microtubule-Associated Proteins - metabolism; Mitochondria; Mitochondria - drug effects; Mitochondria - genetics; Mitochondria - metabolism; Mitochondrial DNA; MPP; Neurodegeneration; Neurodegenerative diseases; Neurological diseases; Neuroprotection; Neurotoxicity; Neurotoxicity Syndromes - etiology; Neurotoxicity Syndromes - genetics; Neurotoxicity Syndromes - metabolism; Neurotoxicity Syndromes - pathology; Oxidative stress; Oxygenase; Parkinson's disease; Peroxidation; Phagocytosis; Piperidines - toxicity; Protein Aggregates; Proteins; Pyrazoles - toxicity; Rats; Rats, Sprague-Dawley; Reduction; Research and Analysis Methods; RNA, Small Interfering - genetics; RNA, Small Interfering - metabolism; Rodents; Sequestering; Signal Transduction; Studies; Substantia nigra; Substantia Nigra - drug effects; Substantia Nigra - metabolism; Substantia Nigra - pathology; Succinate dehydrogenase; Synuclein; Transfection; Tyrosine; Tyrosine 3-monooxygenase; Tyrosine 3-Monooxygenase - genetics; Tyrosine 3-Monooxygenase - metabolism; Ubiquitin-Activating Enzymes - antagonists & inhibitors; Ubiquitin-Activating Enzymes - genetics; Ubiquitin-Activating Enzymes - metabolism
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0091074

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.