Mu-opioid receptor activation prevents apoptosis following serum withdrawal in differentiated SH-SY5Y cells and cortical neurons via phosphatidylinositol 3-kinase.
Opioid peptides and alkaloids exert their effects via G protein-coupled receptors (GPCRs). It has been shown that, in addition to trophic factors, some GPCRs are able to activate the phosphatidylinositol 3-kinase/Akt (PI 3-K/Akt) signal transduction pathway, thus leading to cell survival. The aim of this study was to test whether activation of mu-opioid receptors has protective effects on serum withdrawal-induced cell death and to study the possible implication of PI 3-K in this process. In SH-SY5Y neuroblastoma cells fully differentiated by exposure to retinoic acid for five days, the enkephalin derivative selective mu-agonist DAMGO (0.1-2 microM) and the alkaloid morphine (0.1-10 microM) promoted cell survival after serum deprivation (MTT and trypan blue exclusion assays), without inducing cell proliferation. These effects were fully reversed by naloxone, by the selective mu-antagonist beta-funaltrexamine (beta-FNA) and also by the specific PI 3-K inhibitor LY294002. The two agonists stimulated Akt phosphorylation and the effect was also abolished by beta-FNA and by LY294002. In mouse primary cortical neurons, DAMGO reduced the percentage of apoptosis after 6, 12, 24 and 48 h of serum withdrawal; as determined by Hoechst staining. This effect was blocked by beta-FNA, by pre-treatment with pertussis toxin and by LY294002. DAMGO also stimulated Akt phosphorylation via PI 3-K in this primary neuronal culture. Together, these results indicate that stimulation of the mu-opioid receptor promotes neuronal survival in a G(i/o)-linked, PI 3-K-dependent signaling cascade and suggest that Akt may be a key downstream kinase involved in this anti-apoptotic effect.
Iglesias
M
M
Grup de Neurobiologia Molecular, Departament de Ciències Mèdiques Bàsiques, Universitat de Lleida, Lleida, Spain.
Segura
M F
MF
Comella
J X
JX
Olmos
G
G
D017209:Apoptosis / Q000187:drug effects*; D002454:Cell Differentiation; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology*; D016895:Culture Media, Serum-Free; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)- / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D009020:Morphine / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D017450:Receptors, Opioid, mu / Q000819:agonists* / Q000037:antagonists & inhibitors; D015398:Signal Transduction / Q000187:drug effects; D014212:Tretinoin / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D016895:Culture Media, Serum-Free; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D009020:Morphine; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D017450:Receptors, Opioid, mu; D014212:Tretinoin; C494918:AKT1 protein, human