Effects of hypoxic preconditioning on the expression of iron influx and efflux proteins in primary neuron culture.

The mechanisms of neuroprotection induced by hypoxic preconditioning (HP) and the effects of HP on iron metabolism proteins in the brain have not been fully elucidated. Based on the accumulated information, we hypothesized that HP would be able to affect the expression of iron metabolism proteins in the brain and that the changes in the expression of these proteins induced by HP might be partly associated with the HP-induced neuroprotection. Here, we demonstrated for the first time that HP could induce a significant increase in the expression of HIF-1alpha as well as iron uptake (TfR1 and DMT1) and release (Fpn1) proteins and thus increase transferrin-bound iron (Tf-Fe) and non-transferrin-bound iron (NTBI) uptake and iron release, and also a progressive increase in cellular iron content in the cultured neurons. We concluded that HP has the ability to speed iron transport rate and proposed that the increase in iron transport rate and cellular iron in neurons might be one of the mechanisms involved in neuroprotection in the HP neurons. We also demonstrated that Fpn1 expression was significantly affected by HIF-1alpha, implying that the gene encoding this iron efflux protein is hypoxia-inducible.