Neuroprotective role of superoxide dismutase 1 in retinal ganglion cells and inner nuclear layer cells against N-methyl-d-aspartate-induced cytotoxicity

Exp Eye Res. 2013 Oct;115:230-8. doi: 10.1016/j.exer.2013.07.002. Epub 2013 Jul 13.


The N-methyl-d-aspartate (NMDA) receptor-induced apoptosis is implicated in the pathological mechanisms of neural tissues, increasing the release of reactive oxygen species (ROS), resulting in a type of apoptotic cell death called excitotoxicity. Although intrinsic mechanisms to remove ROS, such as antioxidant enzymes, are provided by the tissue, the association between NMDA-induced excitotoxicity and antioxidative enzymes is not well understood. In this study, we focused on superoxide dismutase 1 (SOD1), an antioxidant enzyme, and investigated the role of SOD1 in the NMDA-induced neuronal cell death in the retina. NMDA was intravitreally injected into wild-type (WT) and SOD1 total knock-out (SOD1-deficient) mice. The number of TUNEL-positive cells in the retinal ganglion cell layer (GCL) and inner nuclear layer (INL) counted in the retinal sections and flatmount retinas were significantly higher in the SOD1-deficient mice than the WT mice after NMDA injection. Visual function assessed by dark-adapted electroretinogram (ERG) showed that the amplitudes of a-wave, b-wave, and oscillatory potential 2 were significantly reduced in the NMDA-injected SOD1-deficient mice. The level of ROS in the GCL and INL, measured using dihydroethidium, and the number of positive cells for γ-H2AX, a marker for DNA double strand breaks, and 8-OHdG, a marker for DNA oxidation, in the GCL were significantly increased in the SOD1-deficient mice after NMDA injection. We also measured mRNA and protein levels of SOD1 and SOD2 in the retina of WT mice, to find that mRNA and protein levels of SOD1, but not SOD2, were significantly reduced after NMDA injection. SOD1 deficiency exacerbated NMDA-induced damage to the inner retinal neurons, and NMDA reduced SOD1 levels in the retina of WT mice. Therefore, SOD1 protected retinal neurons against NMDA-induced retinal neurotoxicity, and NMDA-induced SOD1 reduction may be involved in neuronal vulnerability to excitotoxicity.

Keywords: N-methyl-d-aspartate; electroretinogram; excitotoxicity; reactive oxygen species; retina; superoxide dismutase 1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amacrine Cells / drug effects
  • Amacrine Cells / enzymology*
  • Amacrine Cells / pathology
  • Animals
  • Apoptosis / drug effects
  • Aspartic Acid / metabolism
  • Dark Adaptation
  • Electroretinography
  • Excitatory Amino Acid Agonists / toxicity*
  • Fluorescent Antibody Technique, Indirect
  • Immunoblotting
  • In Situ Nick-End Labeling
  • Intravitreal Injections
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • N-Methylaspartate / toxicity*
  • RNA, Messenger / metabolism
  • Reactive Oxygen Species / metabolism
  • Real-Time Polymerase Chain Reaction
  • Retinal Bipolar Cells / drug effects
  • Retinal Bipolar Cells / enzymology*
  • Retinal Bipolar Cells / pathology
  • Retinal Ganglion Cells / drug effects
  • Retinal Ganglion Cells / enzymology*
  • Retinal Ganglion Cells / pathology
  • Retinal Horizontal Cells / drug effects
  • Retinal Horizontal Cells / enzymology*
  • Retinal Horizontal Cells / pathology
  • Superoxide Dismutase / physiology*
  • Superoxide Dismutase-1


  • Excitatory Amino Acid Agonists
  • RNA, Messenger
  • Reactive Oxygen Species
  • Aspartic Acid
  • N-Methylaspartate
  • Sod1 protein, mouse
  • Superoxide Dismutase
  • Superoxide Dismutase-1