Hypoxia induces complex I inhibition and ultrastructural damage by increasing mitochondrial nitric oxide in developing CNS.
NO-mediated toxicity contributes to neuronal damage after hypoxia; however, the molecular mechanisms involved are still a matter of controversy. Since mitochondria play a key role in signalling neuronal death, we aimed to determine the role of nitrative stress in hypoxia-induced mitochondrial damage. Therefore, we analysed the biochemical and ultrastructural impairment of these organelles in the optic lobe of chick embryos after in vivo hypoxia-reoxygenation. Also, we studied the NO-dependence of damage and examined modulation of mitochondrial nitric oxide synthase (mtNOS) after the hypoxic event. A transient but substantial increase in mtNOS content and activity was observed at 0-2 h posthypoxia, resulting in accumulation of nitrated mitochondrial proteins measured by immunoblotting. However, no variations in nNOS content were observed in the homogenates, suggesting an increased translocation to mitochondria and not a general de novo synthesis. In parallel with mtNOS kinetics, mitochondria exhibited prolonged inhibition of maximal complex I activity and ultrastructural phenotypes associated with swelling, namely, fading of cristae, intracristal dilations and membrane disruption. Administration of the selective nNOS inhibitor 7-nitroindazole 20 min before hypoxia prevented complex I inhibition and most ultrastructural damage. In conclusion, we show here for the first time that hypoxia induces NO-dependent complex I inhibition and ultrastructural damage by increasing mitochondrial NO in the developing brain.
Giusti
Sebastián
S
Institute of Cell Biology and Neuroscience 'Prof. E De Robertis', School of Medicine, University of Buenos Aires, Paraguay 2155, 1121 Buenos Aires, Argentina.
Converso
Daniela P
DP
Poderoso
Juan J
JJ
Fiszer de Plazas
Sara
S
D000818:Animals; D002490:Central Nervous System / Q000196:embryology* / Q000378:metabolism / Q000648:ultrastructure*; D002642:Chick Embryo; D004305:Dose-Response Relationship, Drug; D042967:Electron Transport Complex I / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D000860:Hypoxia / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D007191:Indazoles / Q000494:pharmacology; D046529:Microscopy, Electron, Transmission; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology* / Q000648:ultrastructure; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D013997:Time Factors
D004791:Enzyme Inhibitors; D007191:Indazoles; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D042967:Electron Transport Complex I; C080122:7-nitroindazole; D019331:NG-Nitroarginine Methyl Ester