Evidence that brain-derived neurotrophic factor neuroprotection is linked to its ability to reverse the NMDA-induced inactivation of protein kinase C in cortical neurons.
Several lines of evidence indicate that a rapid loss of neuronal protein kinase C (PKC) activity is a characteristic feature of cerebral ischemia and is a necessary step in the NMDA-induced death of cultured neurons. Exposing embryonic day 18 primary rat cortical neurons to 50 microM NMDA or 50 microM glutamate for 10 min caused approximately 80% cell death over the next 24 h, but excitotoxic death was largely averted, i.e., by 70-80%, in cells pretreated with brain-derived neurotrophic factor (BDNF). An 8-h preexposure to BDNF (50-100 ng/ml) maximally protected cortical cells from the effects of NMDA and glutamate, although the transient application of BDNF between 8 and 4 h before NMDA was equally protective. These effects of BDNF were abolished at supralethal, i.e., >100 microM, NMDA concentrations. It is significant that BDNF pretreatment prevented the inactivation of PKC in cortical cells normally seen 30 min to 2 h following lethal NMDA or glutamate exposure. This BDNF effect did not arise from changes in NMDA channel activity because neither whole-cell NMDA current amplitudes nor increases in intracellular free Ca2+ concentration were altered by the 8-h BDNF pretreatment. Furthermore, BDNF offered no neuroprotection to cells treated with the PKC inhibitors staurosporine (10-20 nM), calphostin C (1-2.5 microM), or GF-109203X (100 nM) at the time of NMDA addition. These results underscore the importance of PKC inactivation in glutamate-induced neuronal death. They also suggest that BDNF neuroprotection arises, at least in part, via its ability to block the mechanism by which pathophysiological Ca2+ influx through the NMDA receptor causes membrane PKC inactivation.
Tremblay
R
R
Cellular Neurobiology Group, Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario.
Hewitt
K
K
Lesiuk
H
H
Mealing
G
G
Morley
P
P
Durkin
J P
JP
D000818:Animals; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002540:Cerebral Cortex / Q000166:cytology; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D005260:Female; D018698:Glutamic Acid / Q000633:toxicity; D007211:Indoles / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D008301:Maleimides / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008565:Membrane Proteins; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D016202:N-Methylaspartate / Q000494:pharmacology; D009474:Neurons / Q000737:chemistry / Q000187:drug effects / Q000201:enzymology*; D018696:Neuroprotective Agents / Q000494:pharmacology*; D009498:Neurotoxins / Q000378:metabolism; D010766:Phosphorylation; D011247:Pregnancy; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology*; D019311:Staurosporine / Q000494:pharmacology
D019208:Brain-Derived Neurotrophic Factor; D004791:Enzyme Inhibitors; D018690:Excitatory Amino Acid Agonists; D007211:Indoles; D047908:Intracellular Signaling Peptides and Proteins; D008301:Maleimides; D008565:Membrane Proteins; D018696:Neuroprotective Agents; D009498:Neurotoxins; D011506:Proteins; D016194:Receptors, N-Methyl-D-Aspartate; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D018698:Glutamic Acid; D016202:N-Methylaspartate; D011493:Protein Kinase C; D019311:Staurosporine; C070515:bisindolylmaleimide I; D002118:Calcium