Abstract
Astrocytes become reactive after central nervous system injury, re-expressing glial fibrillary acidic protein (GFAP), vascular endothelial growth factor (VEGF), and nestin. Hypoxia-inducible transcription factor alpha (HIF-1α) is an important transcription factor for several genes including the VEGF and nestin genes, the expression of which generate reactive astrocytes and cause gliosis after cerebral ischemia. To evaluate the role of HIF-1α in reactive astrocyte formation, we applied the potent HIF-1α inhibitor YC-1 to a focal cerebral ischemia model and analyzed the expression of HIF-1α, VEGF, nestin, and GFAP. Quantitative real-time reverse transcription polymerase chain reaction and western blot analyses demonstrated that the expression of HIF-1α and its downstream genes (VEGF and nestin) were markedly attenuated in the YC-1-treated group versus the control group (HIF-1α, VEGF: p < 0.01; nestin: p < 0.05). GFAP expression was also effectively inhibited in the YC-1-treated group (p < 0.05). Immunohistochemical evaluations showed that GFAP-positive (GFAP+) cells in the YC-1-treated group were sparse in the peri-infarct area, while an immunofluorescence assay revealed that the number of VEGF+/GFAP+ and nestin+/GFAP+ reactive astrocytes were decreased in the YC-1-treated group (p < 0.05). These results demonstrate that HIF-1α suppression decreases the formation of reactive astrocytes and gliosis that occur following focal ischemia.