Minocycline prevents glutamate-induced apoptosis of cerebellar granule neurons by differential regulation of p38 and Akt pathways

J Neurochem. 2004 Dec;91(5):1219-30. doi: 10.1111/j.1471-4159.2004.02796.x.

Abstract

Minocycline has been shown to have remarkably neuroprotective qualities, but underlying mechanisms remain elusive. We reported here the robust neuroprotection by minocycline against glutamate-induced apoptosis through regulations of p38 and Akt pathways. Pre-treatment of cerebellar granule neurons (CGNs) with minocycline (10-100 microm) elicited a dose-dependent reduction of glutamate excitotoxicity and blocked glutamate-induced nuclear condensation and DNA fragmentations. Using patch-clamping and fluorescence Ca2+ imaging techniques, it was found that minocycline neither blocked NMDA receptors, nor reduced glutamate-caused rises in intracellular Ca2+. Instead, confirmed by immunoblots, minocycline in vivo and in vitro was shown to directly inhibit the activation of p38 caused by glutamate. A p38-specific inhibitor, SB203580, also attenuated glutamate excitotoxicity. Furthermore, the neuroprotective effects of minocycline were blocked by phosphatidylinositol 3-kinase (PI3-K) inhibitors LY294002 and wortmannin, while pharmacologic inhibition of glycogen synthase kinase 3beta (GSK3beta) attenuated glutamate-induced apoptosis. In addition, immunoblots revealed that minocycline reversed the suppression of phosphorylated Akt and GSK3beta caused by glutamate, as were abolished by PI3-K inhibitors. These results demonstrate that minocycline prevents glutamate-induced apoptosis in CGNs by directly inhibiting p38 activity and maintaining the activation of PI3-K/Akt pathway, which offers a novel modality as to how the drug exerts protective effects.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Activating Transcription Factor 2
  • Animals
  • Animals, Newborn
  • Apoptosis / drug effects*
  • Blotting, Western / methods
  • Calcium / metabolism
  • Cell Count / methods
  • Cell Survival / drug effects
  • Cells, Cultured
  • Cerebellum / cytology*
  • Chromatin / metabolism
  • Cyclic AMP Response Element-Binding Protein / metabolism
  • DNA Fragmentation / drug effects
  • Dizocilpine Maleate / pharmacology
  • Dose-Response Relationship, Drug
  • Drug Interactions
  • Enzyme Inhibitors / pharmacology
  • Glutamic Acid / pharmacology*
  • Humans
  • Membrane Potentials / drug effects
  • Microscopy, Confocal / methods
  • Minocycline / pharmacology*
  • N-Methylaspartate / pharmacology
  • Neurons / drug effects*
  • Neurons / pathology
  • Neurons / physiology
  • Neuroprotective Agents / pharmacology
  • Patch-Clamp Techniques / methods
  • Protein-Serine-Threonine Kinases / metabolism*
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-akt
  • Rats
  • Rats, Sprague-Dawley
  • Serine / metabolism
  • Signal Transduction / drug effects
  • Tetrazolium Salts / metabolism
  • Thiazoles / metabolism
  • Time Factors
  • Transcription Factors / metabolism
  • p38 Mitogen-Activated Protein Kinases / metabolism*

Substances

  • Activating Transcription Factor 2
  • Chromatin
  • Cyclic AMP Response Element-Binding Protein
  • Enzyme Inhibitors
  • Neuroprotective Agents
  • Proto-Oncogene Proteins
  • Tetrazolium Salts
  • Thiazoles
  • Transcription Factors
  • Glutamic Acid
  • Serine
  • N-Methylaspartate
  • Dizocilpine Maleate
  • AKT1 protein, human
  • Akt1 protein, rat
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • p38 Mitogen-Activated Protein Kinases
  • thiazolyl blue
  • Minocycline
  • Calcium