Overexpression of copper/zinc superoxide dismutase in transgenic rats protects vulnerable neurons against ischemic damage by blocking the mitochondrial pathway of caspase activation

J Neurosci. 2002 Jan 1;22(1):209-17. doi: 10.1523/JNEUROSCI.22-01-00209.2002.

Abstract

Mitochondria are known to be involved in the early stage of apoptosis by releasing cytochrome c, caspase-9, and the second mitochondria-derived activator of caspases (Smac). We have reported that overexpression of copper/zinc superoxide dismutase (SOD1) reduced superoxide production and ameliorated neuronal injury in the hippocampal CA1 subregion after global ischemia. However, the role of oxygen free radicals produced after ischemia/reperfusion in the mitochondrial signaling pathway has not been clarified. Five minutes of global ischemia was induced in male SOD1-transgenic (Tg) and wild-type (Wt) littermate rats. Cytosolic expression of cytochrome c and Smac and activation of caspases were evaluated by immunohistochemistry, Western blot, and caspase activity assay. Apoptotic cell death was characterized by DNA nick end and single-stranded DNA labeling. In the Wt animals, early superoxide production, mitochondrial release of cytochrome c, Smac, and cleaved caspase-9 were observed after ischemia. Active caspase-3 was subsequently increased, and 85% of the hippocampal CA1 neurons showed apoptotic DNA damage 3 d after ischemia. Tg animals showed less superoxide production and cytochrome c and Smac release. Subsequent active caspase-3 expression was not evident, and only 45% of the neurons showed apoptotic DNA damage. A caspase-3 inhibitor (N-benzyloxycarbonyl-val-ala-asp-fluoromethyl ketone) reduced cell death only in Wt animals. These results suggest that overexpression of SOD1 reduced oxidative stress, thereby attenuating the mitochondrial release of cytochrome c and Smac, resulting in less caspase activation and apoptotic cell death. Oxygen free radicals may play a pivotal role in the mitochondrial signaling pathway of apoptotic cell death in hippocampal CA1 neurons after global ischemia.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Animals, Genetically Modified
  • Apoptosis / physiology
  • Apoptosis Regulatory Proteins
  • Brain Ischemia / enzymology*
  • Brain Ischemia / pathology
  • Carrier Proteins / metabolism
  • Caspase 3
  • Caspase 9
  • Caspase Inhibitors
  • Caspases / metabolism*
  • Cytochrome c Group / metabolism
  • Cytoprotection / physiology*
  • DNA Damage / physiology
  • Enzyme Inhibitors / pharmacology
  • Gene Expression
  • Hippocampus / blood supply
  • Hippocampus / enzymology
  • Hippocampus / pathology
  • Immunohistochemistry
  • Male
  • Mitochondria / enzymology*
  • Mitochondrial Proteins / metabolism
  • Neurons / enzymology*
  • Neurons / pathology
  • Rats
  • Rats, Sprague-Dawley
  • Signal Transduction / physiology
  • Superoxide Dismutase / biosynthesis*
  • Superoxide Dismutase / genetics
  • Superoxide Dismutase-1
  • Superoxides / metabolism

Substances

  • Apoptosis Regulatory Proteins
  • Carrier Proteins
  • Caspase Inhibitors
  • Cytochrome c Group
  • DIABLO protein, rat
  • Enzyme Inhibitors
  • Mitochondrial Proteins
  • Superoxides
  • Sod1 protein, rat
  • Superoxide Dismutase
  • Superoxide Dismutase-1
  • Casp3 protein, rat
  • Casp9 protein, rat
  • Caspase 3
  • Caspase 9
  • Caspases