Effect of erythropoietin on staurosporine-induced apoptosis and differentiation of SH-SY5Y neuroblastoma cells

Since apoptosis appeared to be related to neurodegenerative processes, neuroprotection has been involved in investigation of therapeutic approaches focused upon pharmacological agents to prevent neuronal programmed cell death. In this regard, erythropoietin (Epo) seems to play a critical role. The present work was focused on the study of the Epo protective effect upon human neuroblastoma SH-SY5Y cells subjected to differentiation by staurosporine. Under this condition, profuse neurite outgrowth was accompanied by programmed cell death (35% of apoptotic cells by Hoechst assay, showing characteristic DNA ladder pattern). A previous treatment with recombinant human Epo (rHuEpo) increased the expression of the specific receptor for Epo while prevented apoptosis. Simultaneously, morphological changes in neurite elongation and interconnection induced by staurosporine were blocked by Epo. These Epo effects proved to be associated to the induction of Bcl-xL at the mRNA and protein levels (RT-PCR and Western blot after immunoprecipitation) and were mediated by activation of pathways inhibited by wortmannin. In conclusion, the fact that both events induced by staurosporine, cell apoptosis and differentiation, were prevented in SH-SY5Y cells previously exposed to rHuEpo suggests interrelated signaling pathways triggered by the Epo/EpoR interaction. © 2005 Elsevier B.V. All rights reserved.Fil:Pregi, N. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Vittori, D. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Pérez, G. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Leirós, C.P. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Nesse, A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Aluminum exposure affects transferrin-dependent and -independent iron uptake by K562 cells

Aluminum (Al) and iron (Fe) share several physicochemical characteristics and they both bind to transferrin (Tf), entering the cell via Tf receptors (TfR). Previously, we found similar values of affinity constant for the binding of TfR to Tf carrying either Al or Fe. The competitive interaction between both metals prevented normal Fe incorporation into K562 cells and triggered the upregulation of Fe transport. In the present work we demonstrated that Al modified Fe uptake without affecting the expression of Tf receptors. Both TfR and TfR2 mRNA levels, evaluated by RT-PCR, and TfR antigenic sites, analyzed by flow cytometry, were found unchanged after Al exposure. In turn, Al did induce upregulation of non-Tf bound Fe (NTBI) uptake. This modulation was not due to intracellular Fe decrease since NTBI transport proved not to be regulated by Fe depletion. Unlike its behavior in the presence of Tf, Al was unable to compete with NTBI uptake, suggesting that both metals do not share the same alternative transport pathway. We propose that Al interference with TfR-mediated Fe incorporation might trigger the upregulation of NTBI uptake, an adaptation aimed at incorporating the essential metal required for cellular metabolism without allowing the simultaneous access of a potentially toxic metal. © 2004 Elsevier B.V. All rights reserved.Fil:Pérez, G. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Pregi, N. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Vittori, D. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Di Risio, C. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Garbossa, G. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Nesse, A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina