Pro-gliogenic effect of IL-1α in the differentiation of embryonic neural precursor cells in vitro

Inflammation is regarded as a main obstacle to brain regeneration. Major detrimental effects are attributed to microglial/macrophagic products, such as TNF-α and interleukin (IL)-6. The role of cytokines of the IL-1 family, particularly of IL-1α, in the modulation of neural precursor cell (NPC) properties is less characterized. IL-1α is one of the most abundant cytokines released upon acute stimulation of microglia with lipopolysaccharide and is down-regulated upon chronic stimulation. As we recently demonstrated, acutely activated microglia reduces NPC survival, prevent neuronal differentiation and promote glial differentiation. Chronically activated microglia are instead permissive to NPC survival and neuronal differentiation, and less effective in promoting astrocytic differentiation. We thus investigated whether IL-1α could contribute to the effects of acutely activated microglia on NPC. We found that NPC express functional IL-1 receptors and that exposure to recombinant IL-1α strongly enhances NPC differentiation into astrocytes, without affecting cell viability and neuronal differentiation. In the same conditions, recombinant IL-1β has pro-gliogenic effects at concentrations 10-fold higher than those found in activated microglial conditioned media. Interestingly, immunodepletion of IL-1α in activated microglial conditioned media fails to revert microglial pro-gliogenic action and slightly enhances neuronal differentiation, revealing that other microglial-derived factors contribute to the modulation of NPC properties. © 2010 International Society for Neurochemistry.