Pro-apoptotic function of GABA-related transcripts following stroke

Neurobiol Dis. 2014 Oct;70:237-44. doi: 10.1016/j.nbd.2014.06.015. Epub 2014 Jun 28.

Abstract

Following cerebral injuries such as stroke, a structural and functional reorganization of the impaired tissue occurs, which is often accompanied by a re-expression of developmental genes. During brain development, embryonic splice variants of the GABA-synthesizing GAD67 gene (collectively termed EGAD) participate in cell proliferation, migration, and neuronal differentiation. We thus hypothesized an involvement of EGAD in post-ischemic plasticity. EGAD transcripts were up-regulated at early reperfusion times in the injured area following transient middle cerebral artery occlusion (with a peak expression of 4.5-fold at 6h in C57BL/6 mice). Cell-specific analysis by a combination of radioactive in situ hybridization and immunolabeling revealed EGAD up-regulation in TUNEL-positive neurons. This unexpected cell death-associated expression of EGAD was confirmed in cell culture models of ischemia (combined oxygen-glucose deprivation) and apoptosis (staurosporine). Staurosporine-mediated cell death led to cleaved Caspase-3 activation, a key regulator of apoptosis following stroke. Blocking of staurosporine-associated EGAD expression via antisense RNA treatment reduced cleaved Caspase-3 activation by ~30%. In addition to the involvement of EGAD in proliferative processes during brain development, we found here that EGAD participates in cell death under pathophysiological conditions in the adult brain. Re-expression of EGAD in neurons following stroke may play a role in aberrant cell cycle activation, consequently being pro-apoptotic. Our observation of a new GABA related pro-apoptotic mechanism and its successful modification might be of significant clinical relevance.

Keywords: Apoptosis; EGAD; GABA; MCAO; Staurosporine.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / physiology*
  • Brain / physiopathology*
  • Brain Ischemia / physiopathology*
  • Caspase 3 / metabolism
  • Cell Hypoxia / physiology
  • Cells, Cultured
  • Disease Models, Animal
  • Glucose / deficiency
  • Glutamate Decarboxylase / genetics
  • Glutamate Decarboxylase / metabolism*
  • Infarction, Middle Cerebral Artery
  • Male
  • Mice, Inbred C57BL
  • Neurons / physiology*
  • Protein Isoforms
  • Rats, Wistar
  • Staurosporine / toxicity
  • Stroke / physiopathology*

Substances

  • Protein Isoforms
  • Casp3 protein, mouse
  • Caspase 3
  • Glutamate Decarboxylase
  • glutamate decarboxylase 1
  • Staurosporine
  • Glucose