Figure 1. H₂O₂ mimics the effects of RA on VEGF mRNA and protein secretion when combined with transcriptional activators of VEGF.

In A, HESC were cultured in 12-well culture plates in the absence (Con) or presence of TGF-β (5 ng ml⁻¹) or TPA (50 nm) and cotreated with 1 μm RA or vehicle control as indicated. In B, cells were treated with TPA (50 nm) alone or in combination with 200 μm H₂O₂ as indicated. VEGF mRNA was assessed by quantitative real-time RT-PCR after treatment for 6 h (circles). VEGF protein in the supernatant (bars) was evaluated by ELISA after 6 h (in experiments with TPA) or overnight treatment (in experiments with TGF-β). VEGF protein levels were only significantly increased in the supernatant of cultures co-treated with either RA or H₂O₂. By contrast, results showed significant increases in mRNA expression in the presence of TPA or TGF-β alone.