title: Superoxide is an associated signal for apoptosis in axonal injury.
abstract: Optic neuropathy is the leading cause of irreversible blindness, and a paradigm for central nervous system axonal disease. The primary event is damage to retinal ganglion cell axons, with subsequent death of the cell body by apoptosis. Trials of neuroprotection for these and other neuronal diseases have mostly failed, primarily because mechanisms of neuroprotection in animals do not necessarily translate to humans. We developed a methodology for imaging an intracellular transduction pathway that signals neuronal death in the living animal. Using longitudinal confocal scanning multilaser ophthalmoscopy, we identified the production of superoxide within retrograde-labelled rat retinal ganglion cells after optic nerve transection. Superoxide was visualized by real-time imaging of its reaction product with intravitreally administered hydroethidine and confirmed by differential spectroscopy of the specific product 2-hydroxyethidium. Retinal ganglion cell superoxide increased within 24 h after axotomy, peaking at 4 days, and was not observed in contralateral untransected eyes. The superoxide signal preceded phosphatidylserine externalization, indicating that superoxide generation was an early event and preceded apoptosis. Intravitreal pegylated superoxide dismutase blocked superoxide generation after axotomy and delayed retinal ganglion cell death. Together, these results are consistent with superoxide being an upstream signal for retinal ganglion cell apoptosis after optic nerve injury. Early detection of axonal injury with superoxide could serve as a predictive biomarker for patients with optic neuropathy.
authors.affiliation: Maisonneuve-Rosemont Hospital Research Centre and Department of Ophthalmology, University of Montreal, 5415 boul. de l'Assomption, Montréal, Quebec, Canada.
authors.forename: Akiyasu
authors.initials: A
authors.lastname: Kanamori
authors.forename: Maria-Magdalena
authors.initials: MM
authors.lastname: Catrinescu
authors.forename: Noriko
authors.initials: N
authors.lastname: Kanamori
authors.forename: Katrina A
authors.initials: KA
authors.lastname: Mears
authors.forename: Rachel
authors.initials: R
authors.lastname: Beaubien
authors.forename: Leonard A
authors.initials: LA
authors.lastname: Levin
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001369:Axons / Q000473:pathology*; D002452:Cell Count / Q000379:methods; D002461:Cell Line, Transformed; D003911:Dextrans; D004195:Disease Models, Animal; D004996:Ethidium / Q000031:analogs & derivatives / Q000378:metabolism; D005260:Female; D018613:Microscopy, Confocal / Q000379:methods; D020221:Optic Nerve Injuries / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D010617:Phenanthridines / Q000737:chemistry / Q000627:therapeutic use; D011092:Polyethylene Glycols / Q000378:metabolism; D051381:Rats; D020318:Rats, Long-Evans; D012165:Retinal Ganglion Cells / Q000187:drug effects / Q000473:pathology*; D015398:Signal Transduction / Q000502:physiology*; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism*; D013997:Time Factors
chemical_list: C506392:2-hydroxyethidium; D017304:Annexin A5; D003911:Dextrans; D010617:Phenanthridines; D013481:Superoxides; C058428:hydroethidine; D011092:Polyethylene Glycols; D013482:Superoxide Dismutase; C063471:polyethylene glycol-superoxide dismutase; D004996:Ethidium