Activation of ERK and Akt signaling in focal cerebral ischemia: modulation by TGF-alpha and involvement of NMDA receptor

Neurobiol Dis. 2002 Dec;11(3):443-56. doi: 10.1006/nbdi.2002.0553.

Abstract

Cerebral ischemia activates ERK and Akt pathways. We studied whether these activations were affected by treatment with the protective growth factor transforming growth factor-alpha (TGF-alpha), and whether they were mediated through N-methyl D-aspartate (NMDA) receptors. The middle cerebral artery was occluded in rats and signaling was studied 1 h later. Noncompetitive NMDA receptor antagonist MK-801 was injected i.p. before the occlusion, whereas in other rats TGF-alpha was given intraventricularly before and after occlusion. Ischemia caused ERK phosphorylation in the nucleus, localized in the endothelium and neurons. Phosphorylation of ERK was prevented by TGF-alpha, but it was enhanced in the nucleus and cytoplasm by MK-801. Also, MK-801 but not TGF-alpha increased p-Akt. Results suggest that preventing ERK activation is related to the protective effect of TGF-alpha, whereas the protective effect of MK-801 is associated with activation of pro-survival Akt. While results support that NMDA receptor signaling precludes Akt activation, we did not find evidence to support that it underlies ischemia-induced ERK phosphorylation. This study illustrates that neuroprotection results from a fine balance between death and survival signaling pathways.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blotting, Western
  • Brain Ischemia / drug therapy
  • Brain Ischemia / metabolism*
  • Densitometry
  • Dizocilpine Maleate / pharmacology
  • Excitatory Amino Acid Antagonists / pharmacology
  • Immunohistochemistry
  • Male
  • Mitogen-Activated Protein Kinases / metabolism*
  • Neuroprotective Agents / metabolism
  • Neuroprotective Agents / pharmacology*
  • Protein Serine-Threonine Kinases*
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-akt
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, N-Methyl-D-Aspartate / metabolism*
  • Signal Transduction* / drug effects
  • Transforming Growth Factor alpha / administration & dosage
  • Transforming Growth Factor alpha / metabolism*

Substances

  • Excitatory Amino Acid Antagonists
  • Neuroprotective Agents
  • Proto-Oncogene Proteins
  • Receptors, N-Methyl-D-Aspartate
  • Transforming Growth Factor alpha
  • Dizocilpine Maleate
  • Akt1 protein, rat
  • Protein Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • Mitogen-Activated Protein Kinases