title: Impairment of mitochondrial anti-oxidant defence in SOD1-related motor neuron injury and amelioration by ebselen.
abstract: There is now compelling evidence of mitochondrial dysfunction in motor neuron disease (MND), but the molecular basis of these abnormalities is unknown. It is also unclear whether the observed mitochondrial dysfunction plays a central role in disease pathogenesis, and if so, whether its amelioration might present therapeutic opportunities. We adopted a candidate generation approach using proteomics to screen for changes in mitochondrial protein expression in a well-validated cell-culture model of superoxide dismutase 1 (SOD1) related familial MND (fMND). Changed proteins were identified by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectroscopy. Protein candidates included apoptotic regulators, anti-oxidants and components of the electron transport chain. Confirmatory Western blotting was performed, and validated protein expression changes were further investigated. Peroxiredoxin 3 (Prx3), a mitochondrial thioredoxin-dependent hydroperoxidase, is downregulated in the presence of mutant SOD1 in both our cell-culture model and in the spinal cord mitochondria of mutant SOD1 transgenic mice. We confirm the expression of Prx3 within the mitochondria of spinal motor neurons in mouse and humans by immunohistochemistry. Using quantitative real-time PCR (Q-PCR), we show that Prx3 is also downregulated in spinal motor neurons from patients with both sporadic (sMND) and SOD1-related fMND. In a disease characterized by oxidative stress, this represents a potentially important deficit in mitochondrial anti-oxidant defence. Recent evidence suggests that oxidative stress from aberrant copper chemistry may not play a major part in the pathogenesis of SOD1-related fMND. From the results of this study we propose disruption of mitochondrial anti-oxidant defence as an alternative mechanism whereby mutant SOD1 may generate oxidative stress within motor neurons. We further demonstrate that ebselen, an anti-oxidant drug already safely used in human studies and that acts as a Prx mimic, is able to ameliorate the toxicity of mutant SOD1 in our cell-culture model. We conclude by showing that ebselen is capable of inducing transcription of the anti-oxidant response element (ARE) and postulate that ebselen may act both by the transcriptional upregulation of anti-oxidant proteins, and directly as an anti-oxidant in its own right.
authors.affiliation: Academic Neurology Unit, The University of Sheffield Medical School Sheffield, UK.
authors.forename: Clare A
authors.initials: CA
authors.lastname: Wood-Allum
authors.forename: Siân C
authors.initials: SC
authors.lastname: Barber
authors.forename: Janine
authors.initials: J
authors.lastname: Kirby
authors.forename: Paul
authors.initials: P
authors.lastname: Heath
authors.forename: Hazel
authors.initials: H
authors.lastname: Holden
authors.forename: Richard
authors.initials: R
authors.lastname: Mead
authors.forename: Adrian
authors.initials: A
authors.lastname: Higginbottom
authors.forename: Simon
authors.initials: S
authors.lastname: Allen
authors.forename: Tim
authors.initials: T
authors.lastname: Beaujeux
authors.forename: Stefan E
authors.initials: SE
authors.lastname: Alexson
authors.forename: Paul G
authors.initials: PG
authors.lastname: Ince
authors.forename: Pamela J
authors.initials: PJ
authors.lastname: Shaw
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism / Q000494:pharmacology*; D001393:Azoles / Q000494:pharmacology*; D015153:Blotting, Western / Q000379:methods; D016923:Cell Death / Q000187:drug effects; D002478:Cells, Cultured; D015536:Down-Regulation; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D006801:Humans; D054833:Isoindoles; D051379:Mice; D008822:Mice, Transgenic; D008928:Mitochondria / Q000378:metabolism; D028361:Mitochondrial Diseases / Q000235:genetics / Q000378:metabolism*; D016472:Motor Neuron Disease / Q000235:genetics / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000378:metabolism; D016566:Organoselenium Compounds / Q000494:pharmacology*; D018384:Oxidative Stress / Q000187:drug effects; D010544:Peroxidases / Q000378:metabolism; D061105:Peroxiredoxin III; D054464:Peroxiredoxins; D016133:Polymerase Chain Reaction / Q000379:methods; D040901:Proteomics; D020218:Response Elements / Q000187:drug effects; D013116:Spinal Cord / Q000378:metabolism; D013482:Superoxide Dismutase / Q000235:genetics* / Q000378:metabolism; D000072105:Superoxide Dismutase-1
chemical_list: D000975:Antioxidants; D001393:Azoles; D054833:Isoindoles; D009363:Neoplasm Proteins; D016566:Organoselenium Compounds; C516116:Prdx3 protein, mouse; C000606290:SOD1 protein, human; C042986:ebselen; D010544:Peroxidases; C516115:PRDX3 protein, human; D061105:Peroxiredoxin III; D054464:Peroxiredoxins; C000606291:Sod1 protein, mouse; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1