title: Methylpyridinium (MPP(+))- and nerve growth factor-induced changes in pro- and anti-apoptotic signaling pathways in SH-SY5Y neuroblastoma cells.
abstract: The parkinsonian neurotoxin methylpyridinium (MPP(+)) mimics the neuropathology of Parkinson's disease (PD) and likely kills neurons by inhibiting complex I of the electron transport chain and increasing oxidative stress. We examined the time course of activation/inactivation of multiple pro- and anti-apoptotic signaling pathways in MPP(+)-induced apoptotic death of SH-SY5Y neuroblastoma cells. We found an early increase and later decrease of transcriptional activity of the generally anti-apoptotic nuclear factor kappa-beta (NF-kappa B) and early increases in activating phosphorylation of the anti-apoptotic upstream kinase protein kinase B (PKB, also known as AKT). Sequestration-inducing phosphorylation of pro-apoptotic BAD protein increased early then declined. A small biphasic increase in the generally pro-apoptotic p38 kinase activity paralleled the biphasic rise in NF-kappa B-mediated transcription. Inhibition of p38 kinase with 5 micro M SB203540, inhibition of MEK-ERK with 50 micro M U0126, or inhibition of phosphatidylinositol-3-kinase (PI3K) with 10 micro M LY294002 reduced cell viability by 4, 18 or 37%, respectively, after 24 h. All three kinase inhibitors increased cell death in response to 24 h of MPP(+), with the greatest effect shown by LY294002. Nerve growth factor (NGF) caused an early increase in activating phosphorylation of PKB/AKT and MEK-ERK and increased cell survival during MPP(+) exposure. We found that acute MPP(+) exposure activates multiple interacting death- and survival-promoting pathways. Survival-promoting MEK-ERK and PI3K pathways contribute to viability during MPP(+) exposure, both are activated by NGF, and loss of PI3K-mediated signaling and NF-kappa B-mediated transcription may commit cells irreversibly to apoptosis in this model. It remains unknown to what extent these signaling pathways modulate dopamine neuronal death in PD.
mesh_terms: D015655:1-Methyl-4-phenylpyridinium / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D002352:Carrier Proteins / Q000378:metabolism; D004347:Drug Interactions; D006801:Humans; D048728:MAP Kinase Kinase Kinase 1; D020935:MAP Kinase Signaling System / Q000187:drug effects; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D020932:Nerve Growth Factor / Q000494:pharmacology*; D009447:Neuroblastoma; D009474:Neurons / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D009498:Neurotoxins / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D014407:Tumor Cells, Cultured; D051025:bcl-Associated Death Protein; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: C494819:BAD protein, human; D002352:Carrier Proteins; D016328:NF-kappa B; D009498:Neurotoxins; D011518:Proto-Oncogene Proteins; D051025:bcl-Associated Death Protein; D020932:Nerve Growth Factor; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048728:MAP Kinase Kinase Kinase 1; C482576:MAP3K1 protein, human; D015655:1-Methyl-4-phenylpyridinium