Non-hypoxic Stabilization of Hypoxia-Inducible Factor Alpha (HIF-α): Relevance in Neural Progenitor/Stem Cells

摘要

Hypoxia-inducible factor-1 (HIF-1) plays an important role in neural progenitor cell (NPC) propagation and dopaminergic differentiation. In the presence of oxygen and iron, hypoxia-inducible factor 1 alpha (HIF-1α) is rapidly degraded via the prolyl hydroxylase (PHD)/VHL pathway. In addition to hypoxia, various non-hypoxic stimuli can stabilize HIF-1α in NPCs and influence the transcription of HIF-regulated genes. Here, we investigate various hypoxia mimetics: deferoxamine (DFO), ciclopirox olamine (CPX), dimethyloxallyl glycine (DMOG), a novel HIF-PHD inhibitor (FG-4497) and cobalt chloride (CoCl2) with respect to their ability to enhance in vitro proliferation, neurogenesis and dopaminergic differentiation of human fetal mesencephalic NPCs (hmNPCs) in ambient oxygen (21%). Although able to stabilize HIF-1α, iron chelators (DFO and CPX) and DMOG were toxic to hmNPCs. CoCl2 was beneficial only towards neuronal and dopaminergic differentiation, while FG-4497 enhanced proliferation, neurogenesis and dopaminergic differentiation of hmNPCs. Both CoCl2 and FG-4497 were protective to human dopaminergic neurons. Finally, exposure to hyperbaric oxygen (HBO) also stabilized HIF-1α in hmNPCs and induced neurogenesis in vitro. These findings suggest that several HIF stabilizing agents or conditions can rescue impaired neurons and promote neurogenesis in vitro.