De-Differentiation of Schwann Cells ans iron uptake. A closer look.

MARTINEZ VIVOT ROCÍO; USACH VANINA; GOITIA BELEN; SALIS CAROLINA; SETTON-AVRUJ PATRICIA

Vancouver, Canada.

Congreso; 3rd Canadian School of Neurociencie. University of British Columbia, Vancouver, British Columbia, Canada.; 2009

DE-DIFFERENTIATION OF SCHWANN CELLS AND IRON UPTAKE. A CLOSER LOOK. Martínez Vivot Rocío, Usach Vanina, Goitia Belén, Salis Carolina, Setton-Avruj Patricia Cátedra de Química Biológica Patológica, FFyB, IQUIFIB, UBA-CONICET, IIMHNO-UBA Schwann cells (SCs) originate from the neural crest cell lineage and are responsible for the myelination of the peripheral nervous system. During SCs development, precursors migrate along with the growing axons and proliferate rapidly at postnatal 2-4 day in rats. Loss of axonal contact, such as occurs after nerve injury or in isolated SCs in vitro, leads to down regulation of myelin genes expression. We have previously described that cultured SCs incubated in a serum free medium become de-differentiated acquiring a phenotype similar to SCs precursors and non-myelin forming SCs. Holotransferrin (hTf) prevented the de-differentiation promoted by serum deprivation, while apotransferrin (aTf) was unable to avoid such effect. This prodifferentiating effect suggests that iron or hTf are involved in the axonal signal that occurs physiologically during the maturation of SCs and which enables their survival. Whereas Tf-mediated iron uptake is considered to be the primary route of iron uptake in most cells, there is also evidence for Tf independent mechanisms. In the present work we demonstrate the existence of an alternative iron uptake pathway in SCs. For this purpose we measured 59Fe uptake by liquid scintillation counting in cultured SCs deprived of serum and submitted them to different treatments, in addition we evaluated the cells intracellular iron content by atomic absorption. No uptake of 59Fe was detected in the cells incubated in the presence of serum or aTf. However, cells treated with iron or hTf showed an increase in the 59Fe uptake, in agreement with results referred to intracellular iron content. In addition, an iron chelant blocked the effects promoted by iron or hTf. We evaluated TfR and Tf intracellular levels by Western blot (wb) analysis and observed that the expression of TfR increased in SCs submitted to serum deprivation, aTf suplementation decreased TfR levels to 66% and hTf treatment decreased levels to 30%. Finally we chose DMT1/NRAMP among the iron transporters described in literature and evaluated its presence in SCs also by wb analysis. The presence of DMT1 was demonstrated in nerve homogenate, isolated adult-rat myelin and cultured SCs. These data allow us to confirm the existence of a Tf independent iron uptake mechanism in SCs, which would become more relevant after exposing the cells to a harsh environment.