Background: Major role of oxidative stress in the pathogenesis of neurodegenerative diseases have been suggested, being mitochondria one of the main sources of ROS. Aim: In the present work, we have studied the antioxidant effect of fingolimod phosphate (FP) on neuronal mitochondrial function and morphology using a model of mitochondrial oxidative damage induced by menadione (Vitk3). Methods: SN4741 neuronal cells were grown (70-80% confluence) and used as control (nontreated cells) or treated cells with Vitk3 15 µM alone or in presence of FP 50 nM during 4 hours. Mitochondrial membrane potential (MMP), cytochrome c oxidase (COX) activity, mitochondrial oxygen consumption rate (OCR), mitochondrial distribution (MTG) and morphology (EM) were analysed. Statistical differences were determined using one-way ANOVA. Results: Vitk3 incubation produces a dramatical decrease in MMP compared to control (43.7 %); this can be almost totally reverted by the co-incubation of Vitk3 in presence of FP (p<0.05). A 20.7 % decrease in COX activity has been found after Vitk3 incubation, again this effect was counteracted when Vitk3 and FP are combined, restoring COX activity to control levels (p<0.05). Vitk3 incubation triggers initially an increase in OCR, decreasing dramatically (61%) after 4 hours. In experiments co-incubating Vitk3 in presence of FP, the OCR decrease found was reduced to only 17% (p<0.05). In experiments with MitoTracker™ Green, we found a change in the network pattern distribution after Vitk3 administration that partially disappears when co-incubated in presence of FP. Almost all the mitochondria treated with Vitk3 show ultrastructural alterations at the electron microscopy level while normal mitochondria can be found when Vitk3 and FP are combined. Conclusion: FP protects against the mitochondrial damage induced by Vitk3, as seen by the results obtained in mitochondrial functional markers, distribution and morphology.

Insulin-like growth factor-II (IGF-II) is a naturally occurring hormone that exerts neurotrophic and neuroprotective properties in a wide range of neurodegenerative diseases and ageing. Accumulating evidence suggests that the effects of IGF-II in the brain may be explained by its binding to the specific transmembrane receptor, IGFII/M6P receptor (IGF-IIR). However, relatively little is known regarding the role of IGF-II through IGF-IIR in neuroprotection. Here, using adult cortical neuronal cultures, we investigated whether IGF-II exhibits long-term antioxidant effects and neuroprotection at the synaptic level after oxidative damage induced by high and transient levels of corticosterone (CORT). Furthermore, the involvement of the IGF-IIR was also studied to elucidate its role in the neuroprotective actions of IGF-II. We found that neurons treated with IGF-II after CORT incubation showed reduced oxidative stress damage and recovered antioxidant status (normalized total antioxidant status, lipid hydroperoxides and NAD(P) H:quinone oxidoreductase activity). Similar results were obtained when mitochondria function was analysed (cytochrome c oxidase activity, mitochondrial membrane potential and subcellular mitochondrial distribution). Furthermore, neuronal impairment and degeneration were also assessed (synaptophysin and PSD-95 expression, presynaptic function and FluoroJade B® stain). IGF-II was also able to recover the long-lasting neuronal cell damage. Finally, the effects of IGF-II were not blocked by an IGF-IR antagonist, suggesting the involvement of IGF-IIR. Altogether these results suggest that, in or model, IGF-II through IGF-IIR is able to revert the oxidative damage induced by CORT. In accordance with the neuroprotective role of the IGF-II/IGF-IIR reported in our study, pharmacotherapy approaches targeting this pathway may be useful for the treatment of diseases associated with cognitive deficits (i.e., neurodegenerative disorders, depression, etc.).

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