Platelet-activating factor enhances the expression of vascular endothelial growth factor in normal human astrocytes.

Vascular endothelial growth factor (VEGF) is a potent and specific mitogen for vascular endothelial cells. To examine whether platelet-activating factor (PAF) induces the expression of VEGF in human astrocytes, we stimulated cultured normal astrocytes with PAF and performed semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) or real-time quantitative PCR for VEGF mRNA and enzyme-linked immunosorbent assay for VEGF protein. PAF increased the expression of VEGF in astrocytes in time- and dose-dependent manners. After 24-h stimulation, 10 nM PAF increased the levels of VEGF protein in astrocyte-conditioned medium by 1.3-fold. When the cells were subjected to hypoxia, the PAF-induced production of VEGF was enhanced by 6.7-fold as compared to the unstimulated cells incubated under normoxia. Dexamethasone was found to inhibit the enhanced VEGF production in response to the stimulation with PAF under hypoxia. We conclude that PAF induces VEGF gene expression in human astrocytes, and the PAF-induced increase in the expression of VEGF may modulate nervous tissue injury due to hypoxia.