Induction of Akt by endogenous neurosteroids and calcium sequestration in P19 derived neurons.
Neuronal cell death caused by pathophysiological over-activation of glutamate receptors and the subsequent CaII overloading, has been implicated in neurodegeneration after stroke, cerebral trauma and epileptic seizures. Recent findings suggest that certain progesterone metabolites (neurosteroids) such as allopregnanolone and dehydroepiandrosterone can protect neuronal cells from such insults. In the present study, murine P19 cells were induced to differentiate into postmitotic neurons expressing specific neuronal markers, including GABA(A) and NMDA receptors. Activation of NMDA receptors in P19-N neurons resulted in excitotoxic cell death, which involved suppression of the phosphorylation of the survival kinase PKB/Akt. Allopregnanolone and DHEA induced a rapid and prolonged phosphorylation of the Akt kinase and they were able to reverse the NMDA-induced suppression of the PI3-K/Akt pathway. The specificity of the neuroprotective effects of these neurosteroids was confirmed by the phosphatidylinositol 3-kinase (PI3-K) inhibitor wortmannin, as well as by the GABA(A) receptor antagonist, bicuculline. The neurotoxic effect of NMDA on P19-N neurons was directly correlated with increased CaII entry, since the addition of EGTA or BAPTA-AM, significantly suppressed the NMDA-induced decrease of phospho-Akt and subsequent neuronal death. These results suggest that neurosteroids are able to act as survival factors on P19-N neurons, promoting the activation of the PI3-K/Akt pathway through a calcium-entry dependent mechanism.
Department of Animal and Human Physiology, School of Biology, Faculty of Sciences, University of Athens, Panepistimiopolis, 15784, Athens, Greece.
Maria
M
Xilouri
Panagiota
P
Papazafiri
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002277:Carcinoma / Q000473:pathology; D002454:Cell Differentiation / Q000187:drug effects; D045744:Cell Line, Tumor; D002614:Chelating Agents / Q000494:pharmacology; D003687:Dehydroepiandrosterone / Q000494:pharmacology*; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity; D018756:GABA Antagonists / Q000494:pharmacology; D051379:Mice; D016202:N-Methylaspartate / Q000633:toxicity; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D018696:Neuroprotective Agents / Q000494:pharmacology*; D051058:Oncogene Protein v-akt / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011280:Pregnanolone / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects; D000077191:Wortmannin
D000730:Androstadienes; D002614:Chelating Agents; D004791:Enzyme Inhibitors; D018690:Excitatory Amino Acid Agonists; D018756:GABA Antagonists; D018696:Neuroprotective Agents; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D003687:Dehydroepiandrosterone; D004533:Egtazic Acid; D016202:N-Methylaspartate; D011280:Pregnanolone; D051058:Oncogene Protein v-akt; D002118:Calcium; D000077191:Wortmannin; D001640:Bicuculline