title: On the neurotoxicity mechanism of leukoaminochrome o-semiquinone radical derived from dopamine oxidation: mitochondria damage, necrosis, and hydroxyl radical formation.
abstract: Leukoaminochrome o-semiquinone radical is generated during one-electron reduction of dopamine oxidation product aminochrome when DT-diaphorase is inhibited. Incubation of 100 microM aminochrome with 100 microM dicoumarol, an inhibitor of DT-diaphorase during 2 h, induces 56% cell death (P < 0.001) with concomitant formation of (i) intracellular hydroperoxides (4.2-fold increase compared to control; P < 0.001); (ii) hydroxyl radicals, detected with ESR and spin trapping agents (2.4-fold increase when cells were incubated with aminochrome in the presence of dicoumarol compared to aminochrome alone); (iii) intracellular edema, and cell membrane deterioration determined by transmission electron microscopy; (iv) absence of apoptosis, supported by using anexin-V with flow cytometry; (v) a strong decrease of mitochondrial membrane potential determined by the fluorescent dye 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolylcarbocyanineiodide (P < 0.01); (vi) swelling and disruption of outer and inner mitochondrial membranes determined by transmission electron microscopy. These results support the proposed role of leukoaminochrome o-semiquinone radical as neurotoxin in Parkinson's disease neurodegeneration and DT-diaphorase as neuroprotective enzyme.
authors.affiliation: Morphology, ICBM, Faculty of Medicine, Casilla 70000, Santiago-7, Chile.
authors.forename: Christian
authors.initials: C
authors.lastname: Arriagada
authors.forename: Irmgard
authors.initials: I
authors.lastname: Paris
authors.forename: Maria Jose
authors.initials: MJ
authors.lastname: Sanchez de las Matas
authors.forename: Pedro
authors.initials: P
authors.lastname: Martinez-Alvarado
authors.forename: Sergio
authors.initials: S
authors.lastname: Cardenas
authors.forename: Patricia
authors.initials: P
authors.lastname: Castañeda
authors.forename: Rebecca
authors.initials: R
authors.lastname: Graumann
authors.forename: Carolina
authors.initials: C
authors.lastname: Perez-Pastene
authors.forename: Claudio
authors.initials: C
authors.lastname: Olea-Azar
authors.forename: Eduardo
authors.initials: E
authors.lastname: Couve
authors.forename: Maria T
authors.initials: MT
authors.lastname: Herrero
authors.forename: Pablo
authors.initials: P
authors.lastname: Caviedes
authors.forename: Juan
authors.initials: J
authors.lastname: Segura-Aguilar
mesh_terms: D000818:Animals; D016227:Benzoquinones / Q000378:metabolism*; D002460:Cell Line; D004298:Dopamine / Q000378:metabolism*; D017665:Hydroxyl Radical / Q000378:metabolism; D008564:Membrane Potentials / Q000502:physiology; D008928:Mitochondria / Q000378:metabolism*; D009336:Necrosis; D009410:Nerve Degeneration / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism* / Q000473:pathology / Q000502:physiology; D009498:Neurotoxins / Q000378:metabolism*; D010084:Oxidation-Reduction; D051381:Rats; D011916:Rats, Inbred F344; D013378:Substantia Nigra / Q000166:cytology; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D016227:Benzoquinones; D009498:Neurotoxins; C025232:semiquinone radicals; D017665:Hydroxyl Radical; D013482:Superoxide Dismutase; D004298:Dopamine