title: Minocycline prevents glutamate-induced apoptosis of cerebellar granule neurons by differential regulation of p38 and Akt pathways.
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.
authors.affiliation: Department of Biochemistry, Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: Rongbiao
authors.initials: R
authors.lastname: Pi
authors.forename: Wenming
authors.initials: W
authors.lastname: Li
authors.forename: Nelson T K
authors.initials: NT
authors.lastname: Lee
authors.forename: Hugh H N
authors.initials: HH
authors.lastname: Chan
authors.forename: Yongmei
authors.initials: Y
authors.lastname: Pu
authors.forename: Ling Nga
authors.initials: LN
authors.lastname: Chan
authors.forename: Nikolaus J
authors.initials: NJ
authors.lastname: Sucher
authors.forename: Donald C
authors.initials: DC
authors.lastname: Chang
authors.forename: Mingtao
authors.initials: M
authors.lastname: Li
authors.forename: Yifan
authors.initials: Y
authors.lastname: Han
mesh_terms: D051698:Activating Transcription Factor 2; D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western / Q000379:methods; D002118:Calcium / Q000378:metabolism; D002452:Cell Count / Q000379:methods; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology*; D002843:Chromatin / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018698:Glutamic Acid / Q000494:pharmacology*; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D018613:Microscopy, Confocal / Q000379:methods; D008911:Minocycline / Q000494:pharmacology*; D016202:N-Methylaspartate / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects* / Q000473:pathology / Q000502:physiology; D018696:Neuroprotective Agents / Q000494:pharmacology; D018408:Patch-Clamp Techniques / Q000379:methods; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017207:Rats, Sprague-Dawley; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013778:Tetrazolium Salts / Q000378:metabolism; D013844:Thiazoles / Q000378:metabolism; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D051698:Activating Transcription Factor 2; D002843:Chromatin; D017362:Cyclic AMP Response Element-Binding Protein; D004791:Enzyme Inhibitors; D018696:Neuroprotective Agents; D011518:Proto-Oncogene Proteins; D013778:Tetrazolium Salts; D013844:Thiazoles; D014157:Transcription Factors; D018698:Glutamic Acid; D012694:Serine; D016202:N-Methylaspartate; D016291:Dizocilpine Maleate; C494918:AKT1 protein, human; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases; C022616:thiazolyl blue; D008911:Minocycline; D002118:Calcium