Potential role of heat shock protein 90 in regulation of hyperthermia-driven differentiation of neural stem cells

ObjectiveOur previous studies indicated that hyperthermia may play a role in differentiation of neural stem cells and that hypoxia inducible factor-1(HIF-1) was critical in this process. Heat shock protein 90 (Hsp90) is one of the most common heat-related proteins and involved in HIF-1 expression by regulating its activity and stabilization. Here, we hypothesized that HSP90 may be involved in regulation of hyperthermia-driven differentiation of neural stem cells(NSCs). We also investigated whether the HSP90 activity exert its regulatory action via HIF-1 pathway and the transcriptional level of the target genes of HIF-1.\n\nMethodThe cultured NSCs were divided into three groups: an hyperthermic treatment group(40NSC) which NSCs was induced under 40{degrees}C temperature; a control group(37NSC) which NSCs was induced under 37{degrees}C temperature; an hyperthermic treatment and HSP90-inhibited group(40NSC+GA) which NSCs was induced with 0.5M HSP90 inhibitor Geldanamycin(GA) under 40{degrees}C temperature. We examined cells HSPa and HIF-1a expression during a time window of 5 days(12h, 1d, 3d, 5d) post-differentiation. The expression HSP, HIF-1, VEGF (vascular endothelial growth factor) and erythmpoietin(EPO) of during a time window was evaluated by RT-qPCR. The proportion of Tuj-1 positive differentiated cells were observed by flow cytometry.\n\nResultHyperthermia promoted neuronal differentiation of NSC, and this effect could be blocked by HSP90 inhibitor GA. We observed the up-regulation of HSP90 during hyperthermia treatment, and that the protein levels of HIF-1 changed depending of the GA treatment. GA could not inhibited HSP90 expression but suppressed HSP activity and decreased the expression HIF-1 protein. Inhibition of HIF-1 expression by GA could consequently affect expression of its targeted genes such as VEGF and EPO.\n\nConclusionHyperthermia promote differentiation of NSCs into neurons. HSP90 involved in the regulation of hyperthermia-driven differentiation of NSC, and the mechanism is related to HIF-1 and its downstream gene activation.