RESUMO
Neuroblastoma cell lines are commonly used as a model to study neuronal differentiation as they retain the capacity to differentiate into a neuronal-like phenotype. It is of great medical interest to understand the signalling pathways biasing differentiation versus proliferation. Neuroblastoma cells differentiate in response to serum reduction or addition of the cholesterol synthesis inhibitor mevastatin. The responsible pathways are not well characterized. In Neuro2a neuroblastoma cells, we found that mevastatin and serum withdrawal triggered the production of nitric oxide (NO). In addition, the differentiation of Neuro2a cells and the activation of Akt/PKB triggered by serum withdrawal could be blocked by addition of the NO synthetase (NOS) inhibitor l-NAME. Moreover, mevastatin and serum withdrawal rapidly increased the expression of the neuronal NOS isoform nNOS. However, addition of an NO donor SNP per se did not trigger neurite outgrowth. Taken together, we report for the first time a role of NO in neurite outgrowth of neuroblastoma cells triggered by mevastatin or serum reduction.
Assuntos
Inibidores de Hidroximetilglutaril-CoA Redutases/farmacologia , Lovastatina/análogos & derivados , Neuritos/fisiologia , Óxido Nítrico/fisiologia , Animais , Diferenciação Celular , Linhagem Celular Tumoral , Meios de Cultura Livres de Soro , Ativação Enzimática , Lovastatina/farmacologia , Camundongos , NG-Nitroarginina Metil Éster/farmacologia , Neuritos/efeitos dos fármacos , Neuroblastoma , Neurônios/citologia , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Óxido Nítrico/biossíntese , Doadores de Óxido Nítrico/farmacologia , Óxido Nítrico Sintase Tipo I/antagonistas & inibidores , Óxido Nítrico Sintase Tipo I/biossíntese , Nitroprussiato/farmacologia , Proteínas Proto-Oncogênicas c-akt/metabolismoRESUMO
Neuroblastoma is the second most common pediatric malignancy, characterized by a high rate of unexplained spontaneous remissions. Much progress has been made in understanding neuroblastoma differentiation triggered by certain agents such as retinoic acid. However, little is known about the signalling pathways that lead to differentiation of neuroblastoma cells due to serum withdrawal. We found that in Neuro2a neuroblastoma cells, EGFR, ERK1/2 and Akt showed increased phosphorylation after serum withdrawal, and that the activation of EGFR was necessary for the activation of Akt and ERK1/2. Inhibition of EGFR, ERK1/2 and PI3K blocked neuroblastoma differentiation after serum withdrawal. Interestingly, addition of high-density lipoprotein (HDL) abrogated serum-withdrawal induced neuroblastoma differentiation, as well as the activation of EGFR. Our results demonstrate a novel role for serum-derived lipoproteins in the control of receptor tyrosine kinase activity.
