title: Reactive species and oxidative stress in optic nerve vulnerable to secondary degeneration.
abstract: Secondary degeneration contributes substantially to structural and functional deficits following traumatic injury to the CNS. While it has been proposed that oxidative stress is a feature of secondary degeneration, contributing reactive species and resultant oxidized products have not been clearly identified in vivo. The study is designed to identify contributors to, and consequences of, oxidative stress in a white matter tract vulnerable to secondary degeneration. Partial dorsal transection of the optic nerve (ON) was used to model secondary degeneration in ventral nerve unaffected by the primary injury. Reactive species were assessed using fluorescent labelling and liquid chromatography/tandem mass spectroscopy (LC/MS/MS). Antioxidant enzymes and oxidized products were semi-quantified immunohistochemically. Mitophagy was assessed by electron microscopy. Fluorescent indicators of reactive oxygen and/or nitrogen species increased at 1, 3 and 7days after injury, in ventral ON. LC/MS/MS confirmed increases in reactive species linked to infiltrating microglia/macrophages in dorsal ON. Similarly, immunoreactivity for glutathione peroxidase and haem oxygenase-1 increased in ventral ON at 3 and 7days after injury, respectively. Despite increased antioxidant immunoreactivity, DNA oxidation was evident from 1day, lipid oxidation at 3days, and protein nitration at 7days after injury. Nitrosative and oxidative damage was particularly evident in CC1-positive oligodendrocytes, at times after injury at which structural abnormalities of the Node of Ranvier/paranode complex have been reported. The incidence of mitochondrial autophagic profiles was also significantly increased from 3days. Despite modest increases in antioxidant enzymes, increased reactive species are accompanied by oxidative and nitrosative damage to DNA, lipid and protein, associated with increasing abnormal mitochondria, which together may contribute to the deficits of secondary degeneration.
authors.affiliation: Experimental and Regenerative Neurosciences, School of Animal Biology, The University of Western Australia, Crawley, Western Australia, Australia.
authors.forename: Ryan L
authors.initials: RL
authors.lastname: O'Hare Doig
authors.affiliation: Experimental and Regenerative Neurosciences, School of Animal Biology, The University of Western Australia, Crawley, Western Australia, Australia.
authors.forename: Carole A
authors.initials: CA
authors.lastname: Bartlett
authors.affiliation: Vascular Biology Division, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia; University of New South Wales, NSW, Australia.
authors.forename: Ghassan J
authors.initials: GJ
authors.lastname: Maghzal
authors.affiliation: Vascular Biology Division, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Lam
authors.affiliation: Experimental and Regenerative Neurosciences, School of Animal Biology, The University of Western Australia, Crawley, Western Australia, Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: Archer
authors.affiliation: Vascular Biology Division, Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia; University of New South Wales, NSW, Australia.
authors.forename: Roland
authors.initials: R
authors.lastname: Stocker
authors.affiliation: Experimental and Regenerative Neurosciences, School of Animal Biology, The University of Western Australia, Crawley, Western Australia, Australia. Electronic address: lindy.fitzgerald@uwa.edu.au.
authors.forename: Melinda
authors.initials: M
authors.lastname: Fitzgerald
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002853:Chromatography, Liquid; D004195:Disease Models, Animal; D053331:Ectodysplasins / Q000378:metabolism; D004996:Ethidium / Q000031:analogs & derivatives / Q000378:metabolism; D005260:Female; D005979:Glutathione Peroxidase / Q000378:metabolism; D006147:Guanine / Q000031:analogs & derivatives / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D008928:Mitochondria / Q000473:pathology / Q000648:ultrastructure; D004676:Myelin Basic Protein / Q000378:metabolism; D009410:Nerve Degeneration / Q000209:etiology* / Q000503:physiopathology; D020221:Optic Nerve Injuries / Q000150:complications*; D018384:Oxidative Stress / Q000502:physiology*; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*; D053719:Tandem Mass Spectrometry; D013997:Time Factors; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism; D000094765:Glutathione Peroxidase GPX1
chemical_list: D053331:Ectodysplasins; D004676:Myelin Basic Protein; D017382:Reactive Oxygen Species; C067883:dihydroethidium; C002744:3-nitrotyrosine; D014443:Tyrosine; C024829:8-hydroxyguanine; D006147:Guanine; D005979:Glutathione Peroxidase; D004996:Ethidium; D000094765:Glutathione Peroxidase GPX1; C000722069:Gpx1 protein, rat
keywords: Antioxidant enzymes; Mitophagy; Neurotrauma; Oxidative damage; Oxidative stress; Reactive species; Secondary degeneration