The Notch pathway and the promyelinating effect of aTf in toxic models of demyelination/ remyelination

EVANGELINA APARICIO; M. FLORENCIA ALMEIRA-GUBIANI; V.L. MILLANOVICH; ANA M. ADAMO

San Diego, CA.

Congreso; Neuroscience 2010; 2010

Neuroscience Society

Previous studies demonstrate that a single intracranial injection of apotransferrin (aTf) in 3-day-old rats increases myelin constituents. These promyelinating effects of aTf were shown in cuprizone (CPZ)-demyelinated animals (Adamo et al., 2006) and lysolecithin (LPC)-induced focal demyelination in the corpus callosum (CC). Notch is a family of receptors that control the maturation of oligodendrocytes (OL) and myelination, among other processes. We evaluated the effect of aTf and the possible participation of the Notch pathway in remyelination in both non-immune toxic models of demyelination mentioned above. Twenty-one-day-old Wistar rats were fed a diet containing 0.6% CPZ during 2 weeks. After withdrawal of CPZ, animals were treated with either a single intraventricular injection (IVI) of aTf (350 ng) or saline solution (SS). On the other hand, adult rats were stereotaxically injected 2% LPC in SS into the CC; seven days later these animals received a single dose of aTf or SS. A subset of both groups received an IVI injection of the g-secretase inhibitor (DAPT 1mM) before the injection of aTf. Animals were sacrificed at different times after aTf injection depending on experiments; subventricular zone (SVZ) and CC were dissected for Western blot and brains for immunohistochemistry. We studied the activation of Notch pathway by measuring its intracellular domain (NICD) and the expression of downstream genes by RT-PCR. We observed an increase in Notch receptor expression and in NICD levels in SVZ of demyelinated rats, as compared to controls, concomitant with an increase in Jagged Notch ligand and no differences in F3 contactin. aTf induced an increase in F3 contactin after 24 h both in controls and in CPZ-treated animals and a decrease in Jagged in CPZ-treated animals.  According to the activation of Notch pathway, RT-PCR preliminary results show an increase in Hes5 6 h after aTf injection in CPZ animals. In both models, aTf generated an increase in OL APC+ population as well as a decrease in OL precursors NG2+ in SVZ and CC. The injection of DAPT blocked aTf effect on remyelination. Experiments with deferroxamine showed no differences in the promyelinating effects of aTF. In these models, results seem to indicate the participation of the Notch pathway both in demyelination/remyelination and in the promyelinating effect of aTF.