Valproic acid (VPA) is the primary mood-stabilizing drug to exert neuroprotective effects and to treat bipolar disorder in clinic. Fibroblast growth factor 1 (FGF1) has been shown to regulate cell proliferation, cell division and neurogenesis. Human FGF1 gene 1B promoter (-540 to +31)-driven green fluorescence (F1BGFP) has been shown to recapitulate endogenous FGF1 gene expression and facilitates the isolation of neural stem/progenitor cells (NSPCs) from developing and adult mouse brains. In this study, we provide several lines of evidence to demonstrate the underlying mechanisms of VPA in activating FGF-1B promoter activity: (i) VPA significantly increased the FGF-1B mRNA expression and the percentage of F1BGFP(+) cells; (ii) the increase of F1BGFP expression by VPA involves changes of RFX1-3 transcriptional complexes and the increase of histone H3 acetylation on the 18-bp cis-element of FGF-1B promoter; (iii) treatments of other HDAC inhibitors, sodium butyrate and trichostatin A, significantly increased the expression levels of FGF-1B, RFX2 and RFX3 transcripts; (iv) treatments of GSK-3 inhibitor, lithium, or GSK-3 siRNAs also significantly activated FGF-1B promoter; (v) VPA specifically enhanced neuronal differentiation in F1BGFP(+) embryonic stem cells and NSPCs rather than GFP(-) cells. This study suggested, for the first time, that VPA activates human FGF1 gene promoter through inhibiting HDAC and GSK-3 activities.
