Notch pathway and the effect of apotransferrin on remyelination.

EVANGELINA APARICIO; ANA M. ADAMO

Huerta Grande, Córdoba.

Congreso; First Joint Meeting of the Argentine Society for Neurosciences (SAN) and the Argentine Workshop in Neurosciences (TAN); 2009

Argentine Society for Neurosciences (SAN) and the Argentine Workshop in Neurosciences (TAN

We have previously demonstrated that a single intracranial injection of apotransferrin (aTf) in 3-day-old rats produces an increase in myelin constituents (Escobar Cabrera, E., 1994, 97). These promyelinating effects of aTf were clearly shown in animals suffering demyelination after cuprizone (CPZ) feeding.  ApoTf induced a marked increase in myelin deposition as compared to the spontaneous remyelination observed in control animals (Adamo et al., 2006). In this study we evaluated the effect of aTf and the possible participation of the Notch receptor pathway in the remyelination on lysolecithin (LPC)-induced focal demyelination in the corpus callosum (CC). Adult Wistar rats were anaesthetized with a Ketamine/Xylaxine cocktail and positioned in a stereotaxic frame in order to be injected 1 ul of 2% LPC in saline solution (SS). LPC was injected unilaterally into the CC using stereotaxic coordinates: 2mm anterior and 1 mm lateral to the bregma with 2.5 mm deep from the skull surface. Controls were injected with 1 ul SS. The day of LPC injection was designated as day 0 (0 DPL). Seven days after, animals were injected  a single dose of 350 ng of aTf (1ì) in the subventricular zone (SVZ) (coordinates: 3 mm posterior relative to bregma, 3 mm lateral and 3 mm dorsoventral from the skull surface). After aTf or SS injections, animals were sacrificed at different times (2, 6 and 24 h or 3 and 7 days depending on the experiments). A subgroup of animals received one intraventricular injection of the g-secretase inhibitor (DAPT, 1 mM ) 5 min before the injection of aTf. To evaluate whether the effects of aTf are due to the protein or iron, experiments were carried out in the presence of desferroxamine (DFX 10 ng).  We observed a significant demyelination in the injected area in the CC at 7 DPL and a spontaneous reversion of such process at 21 DPL. The injection of aTf induced remyelination 10 DPL. We observed an increase in the oligondendrocytes (OL) APC+ population in the CC and SVZ concomitantly with a decrease in the OL precursors NG2+ in the SVZ and CC. The injection of ã-secretase inhibitor 5 min before the aTf blocked its effect in the remyelination process. Experiments in presence of DFX did not show differences in the promyelinating effect of aTF. Thus indicating that this effect are due to the protein preferent than the Iron. In this model of toxic demyelination, results seem to indicate the involvement of Notch pathway in the aTf effect on the remyelination process.