Unfolded protein response up-regulates VEGF mRNA. HUVECs were treated for 6 hours in medium 199/2% FCS containing (A) 130 μM OxPAPC, 1 mM dithiothreitol (DTT), 3 μg/mL tunicamycin, 1 μg/mL thapsigargin, or 6 μg/mL brefeldin A, or (B) with increasing concentrations of homocysteine dissolved in medium 199 containing 2% FCS. (C) HUVECs were preincubated overnight with or without 2.5 mM sodium PBA in full growth medium. On the next day, the cells were stimulated for 6 hours with 130 μM OxPAPC or 3 μg/mL tunicamycin in medium 199 containing 2% FCS with or without PBA. After mRNA isolation, levels of mRNA encoding for VEGF were quantified by RT-qPCR. (D) HUVECs were transfected with siRNA against HTJ1 or control siRNA. Forty-eight hours later, the cells were stimulated for 6 hours with 130 μM OxPAPC in medium 199 containing 2% FCS. The incubations were terminated by Trizol, followed by quantification of VEGF mRNA. The data are normalized to the levels of β₂-microglobulin mRNA. Error bars represent SD.