title: Early events of target deprivation/axotomy-induced neuronal apoptosis in vivo: oxidative stress, DNA damage, p53 phosphorylation and subcellular redistribution of death proteins.
abstract: The mechanisms of injury- and disease-associated apoptosis of neurons within the CNS are not understood. We used a model of cortical injury in rat and mouse to induce retrograde neuronal apoptosis in thalamus. In this animal model, unilateral ablation of the occipital cortex induces apoptosis of corticopetal projection neurons in the dorsal lateral geniculate nucleus (LGN), by 7 days post-lesion, that is p53 modulated and Bax dependent. We tested the hypothesis that this degenerative process is initiated by oxidative stress and early formation of DNA damage and is accompanied by changes in the levels of pro-apoptotic mediators of cell death. Immunoblotting revealed that the protein profiles of Bax, Bak and Bad were different during the progression of neuronal apoptosis in the LGN. Bax underwent a subcellular redistribution by 1 day post-lesion, while Bak increased later. Bad showed an early sustained increase. Cleaved caspase-3 was elevated maximally at 5 and 6 days. Active caspase-3 underwent a subcellular translocation to the nucleus. A dramatic phosphorylation of p53 was detected at 4 days post-lesion. DNA damage was assessed immunocytochemically as hydroxyl radical adducts (8-hydroxy-2-deoxyguanosine) and single-stranded DNA. Both forms of DNA damage accumulated early in target-deprived LGN neurons. Transgenic overexpression of superoxide dismutase-1 provided significant protection against the apoptosis but antioxidant pharmacotreatments with trolox and ascorbate were ineffective. We conclude that overlapping and sequential signaling pathways are involved in the apoptosis of adult brain neurons and that DNA damage generated by superoxide derivatives is an upstream mechanism for p53-regulated, Bax-dependent apoptosis of target-deprived neurons.
authors.affiliation: Division of Neuropathology, Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA. martinl@jhmi.edu
authors.forename: Lee J
authors.initials: LJ
authors.lastname: Martin
authors.forename: Anne C
authors.initials: AC
authors.lastname: Price
authors.forename: Karen B
authors.initials: KB
authors.lastname: McClendon
authors.forename: Nael A
authors.initials: NA
authors.lastname: Al-Abdulla
authors.forename: Jamuna R
authors.initials: JR
authors.lastname: Subramaniam
authors.forename: Philip C
authors.initials: PC
authors.lastname: Wong
authors.forename: Zhiping
authors.initials: Z
authors.lastname: Liu
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism / Q000494:pharmacology; D017209:Apoptosis / Q000502:physiology*; D019771:Axotomy; D001930:Brain Injuries / Q000473:pathology / Q000503:physiopathology*; D002352:Carrier Proteins / Q000378:metabolism; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002541:Cerebral Decortication; D004249:DNA Damage / Q000502:physiology*; D004195:Disease Models, Animal; D005829:Geniculate Bodies / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D018384:Oxidative Stress / Q000502:physiology*; D010766:Phosphorylation; D021381:Protein Transport / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2; D051381:Rats; D017207:Rats, Sprague-Dawley; D013347:Subcellular Fractions / Q000737:chemistry; D013788:Thalamus / Q000473:pathology / Q000503:physiopathology; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D051025:bcl-Associated Death Protein
chemical_list: D000975:Antioxidants; C494820:Bad protein, mouse; C494821:Bad protein, rat; C494773:Bak1 protein, mouse; C494774:Bak1 protein, rat; C494827:Bax protein, mouse; C494828:Bax protein, rat; D002352:Carrier Proteins; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D051025:bcl-Associated Death Protein; C505409:Casp3 protein, mouse; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases