Iron overload impairs the migratory ability of a model of immature and migratory GnRH neurons

Iron represents a micronutrient for cellular metabolism and aerobic respiration, and is essential for proper brain development in the fetal and early neonatal period. However, excess iron produces toxic build-up via free radical formation. In thalassaemic and juvenile hemochromatosis patients with pubertal failure, iron overload interferes with the correct function of the hypothalamic–pituitary axis, leading to hypogonadotrophic hypogonadism and growth failure, but the mechanisms are still unclear. Aim of this study was to investigate the mechanisms of iron toxicity in vitro in GN-11 cells, a model of immature and migratory GnRH neurons. Gene expression analysis by semi-quantitative PCR showed that GN-11 express the iron proteins ferritin (a primary intracellular iron-storage protein) and transferrin (iron-binding extracellular glycoprotein that controls the level of free Fe and deliver iron to cells), as well as hepcidin (an iron regulatory hormone). Exposure of GN11 cells to 150 μM ferric ammonium citrate (FAC) resulted in the inhibition (−35%, P<0.05) of fetal bovine serum (FBS)-induced chemo-migration, assessed by Boyden chamber assay. Pre-treatment with 100 μM deferoxamine, a specific iron chelator, reverted the above reported effect. Time-course experiments showed that 150 μM FAC was associated with induction of phosphorylation of both extracellular signal-regulated kinase (ERK) and 5′ adenosine monophosphate-activated protein kinase (AMPK) after 10 min treatment, as evaluated by Western blotting. Specific ERK and AMPK inhibitors, U0126 and Compound C, respectively, abolished FAC-mediated signaling. Moreover, U0126 and Compound C (both 10 μM) counteracted FAC-driven phosphorylation of acetyl-CoA carboxylase, an AMPK downstream protein. In conclusion, the present data, though preliminary, show that acute iron treatment negatively affects the migration of GN-11 neurons in vitro, and is associated with the activatio of ERK and AMPK signaling pathways. We hypothesize that iron overload may impair migration of GnRH neurons from the olfactory placode into forebrain and hypothalamus, where they promote reproductive competence.